Publications
TOP 10
Loft A, Alfaro A J, Schmidt S F, Pedersen F B, Terkelsen M K, Puglia M, Chow K K, Feuchtinger A, Troullinaki M, Maida A, Wolff G, Sakurai M, Berutti R, Ekim Üstünel B, Nawroth P P, Ravnskjaer K, Diaz M B, Blagoev B, Herzig S: Liver-fibrosis-activated transcriptional networks govern hepatocyte reprogramming and intra-hepatic communication. Cell Metab 33, 1685-1700.e9.
DOI: 10.1016/j.cmet.2021.06.005
Seitz S, Kwon Y, Hartleben G, Jülg J, Sekar R, Krahmer N, Najafi B, Loft A, Gancheva S, Stemmer K, Feuchtinger A, Hrabe de Angelis M, Müller T D, Mann M, Blüher M, Roden M, Berriel Diaz M, Behrends C, Gilleron J, Herzig S & Zeigerer A: Hepatic Rab24 controls blood glucose homeostasis via improving mitochondrial plasticity. Nature Metabolism 2019; 1009–1026.
DOI: 10.1038/s42255-019-0124-x
Rios Garcia M, Steinbauer B, Kshitij S, Singhal M, Mattijssen F, Maida A, Christian S, Hess-Stumpp H, Augustin HG, Müller-Decker K, Nawroth PP, Herzig S, Berriel Diaz M: Acetyl-CoA Carboxylase 1-Dependent Protein Acetylation Controls Breast Cancer Metastasis and Recurrence. Cell Metabolism 2017; 26(6):842-855.e5.
DOI: 10.1016/j.cmet.2017.09.018
Rohm M, Schäfer M, Laurent V, Ekim Üstünel B, Niopek K, Algire C, Hautzinger O, Sijmonsma TP, Zota A, Medrikova D, Pellegata NS, Ryden M, Kulyte A, Dahlman I, Arner P, Petrovic N, Cannon B, Amri EZ, Kemp BE, Steinberg GR, Janovska P, Kopecky J, Wolfrum C, Blüher M, Berriel Diaz M, Herzig S: An AMP-activated protein kinase–stabilizing peptide ameliorates adipose tissue wasting in cancer cachexia in mice. Nature Medicine 2016; 22(10):1120-1130.
DOI: 10.1038/nm.4171
Rohm M, Sommerfeld A, Strzoda D, Jones A, Sijmonsma TP, Rudofsky G, Wolfrum C, Sticht C, Gretz N, Zeyda M, Leitner L, Nawroth PP, Stulnig TM, Berriel Diaz M, Vegiopoulos A, Herzig S: Transcriptional cofactor TBLR1 controls lipid mobilization in white adipose tissue. Cell Metabolism 2013; 17(4):575-585.
DOI: 10.1016/j.cmet.2013.02.010
Rose AJ, Berriel Diaz M, Reimann A, Klement J, Walcher T, Krones-Herzig A, Strobel O, Werner J, Peters A, Kleyman A, Tuckermann JP, Vegiopoulos A, Herzig S: Molecular control of systemic bile acid homeostasis by the liver glucocorticoid receptor. Cell Metabolism 2011 ; 14(1):123-130.
DOI: 10.1016/j.cmet.2011.04.010
Vegiopoulos A, Müller-Decker K, Strzoda D, Schmitt I, Chichelnitskiy E, Ostertag A, Berriel Diaz M, Rozman J, Hrabe de Angelis M, Nüsing RM, Meyer CW, Wahli W, Klingenspor M, Herzig S: Cyclooxygenase-2 controls energy homeostasis in mice by de novo recruitment of brown adipocytes. Science 2010; 328(5982):1158-1161.
DOI: 10.1126/science.1186034
Lemke U, Krones-Herzig A, Berriel Diaz M, Narvekar P, Ziegler A, Vegiopoulos A, Cato ACB, Bohl S, Klingmüller U, Screaton RA, Müller-Decker K, Kersten S, Herzig S: The glucocorticoid receptor controls hepatic dyslipidemia through Hes1. Cell Metabolism 2008; 8(3):212-223.
DOI: 10.1016/j.cmet.2008.08.001
Herzig S, Hedrick S, Morantte I, Koo SH, Galimi F, Montminy M: CREB controls hepatic lipid metabolism through nuclear hormone receptor PPAR-gamma. Nature 2003; 426(6963):190-193.
DOI: 10.1038/nature02110
Herzig S, Long F, Jhala US, Hedrick S, Quinn R, Bauer A, Rudolph D, Schutz G, Yoon C, Puigserver P, Spiegelman B, Montminy M: CREB regulates hepatic gluconeogenesis through the coactivator PGC-1. Nature 2001; 413(6852):179-183.
DOI: 10.1038/35093131
2022
Adv. Exp. Med. Biol. 1390, 61-82 (2022)
Nuclear receptors are master regulators of energy metabolism through the conversion of extracellular signals into gene expression signatures. The function of the respective nuclear receptor is tissue specific, signal and co-factor dependent. While normal nuclear receptor function is central to metabolic physiology, aberrant nuclear receptor signaling is linked to various metabolic diseases such as type 2 diabetes mellitus, obesity, or hepatic steatosis. Thus, the tissue specific manipulation of nuclear receptors is a major field in biomedical research and represents a treatment approach for metabolic syndrome. This chapter focuses on key nuclear receptors involved in regulating the metabolic function of liver, adipose tissue, skeletal muscle, and pancreatic β-cells. It also addresses the importance of nuclear co-factors for fine-tuning of nuclear receptor function. The mode of action, role in energy metabolism, and therapeutic potential of prominent nuclear receptors is outlined.
Wissenschaftlicher Artikel
Scientific Article
Mol. Metab. 62:101518 (2022)
OBJECTIVE: Regulation of proteasomal activity is an essential component of cellular proteostasis and function. This is evident in patients with mutations in proteasome subunits and associated regulators, who suffer from proteasome-associated autoinflammatory syndromes (PRAAS). These patients display lipodystrophy and fevers, which may be partly related to adipocyte malfunction and abnormal thermogenesis in adipose tissue. However, the cell-intrinsic pathways that could underlie these symptoms are unclear. Here, we investigate the impact of two proteasome subunits implicated in PRAAS, Psmb4 and Psmb8, on differentiation, function and proteostasis of brown adipocytes. METHODS: In immortalized mouse brown pre-adipocytes, levels of Psmb4, Psmb8, and downstream effectors genes were downregulated through reverse transfection with siRNA. Adipocytes were differentiated and analyzed with various assays of adipogenesis, lipogenesis, lipolysis, inflammation, and respiration. RESULTS: Loss of Psmb4, but not Psmb8, disrupted proteostasis and adipogenesis. Proteasome function was reduced upon Psmb4 loss, but partly recovered by the activation of Nuclear factor, erythroid-2, like-1 (Nfe2l1). In addition, cells displayed higher levels of surrogate inflammation and stress markers, including Activating transcription factor-3 (Atf3). Simultaneous silencing of Psmb4 and Atf3 lowered inflammation and restored adipogenesis. CONCLUSIONS: Our study shows that Psmb4 is required for adipocyte development and function in cultured adipocytes. These results imply that in humans with PSMB4 mutations, PRAAS-associated lipodystrophy is partly caused by disturbed adipogenesis. While we uncover a role for Nfe2l1 in the maintenance of proteostasis under these conditions, Atf3 is a key effector of inflammation and blocking adipogenesis. In conclusion, our work highlights how proteasome dysfunction is sensed and mitigated by the integrated stress response in adipocytes with potential relevance for PRAAS patients and beyond.
Wissenschaftlicher Artikel
Scientific Article
Eur. J. Neurol. 29, 3081-3091 (2022)
BACKGROUND: Diabetic sensorimotor peripheral neuropathy (DSPN) is usually considered to affect predominantly the lower limbs (LL-N), while the impact of upper limb neuropathy (UL-N) on hand functional performance and quality of life (QoL) has not been evaluated systematically. This study aims to investigate the prevalence and characteristics of UL-N and its functional and psychosocial consequences in type 2 diabetes. METHODS: Individuals with type 2 diabetes (n=141) and an age- and sex-matched control group (n=73) underwent comprehensive assessment of neuropathy, hand functional performance and psychosocial status. RESULTS: The prevalence of UL-N was 30.5% in patients with diabetes and that of LL-N 49.6%, with 25.5% exhibiting both. Patients with diabetes showed similar sensory phenotype regarding both large and small fiber functions in hands and feet. Patients with UL-N showed reduced manual dexterity, but normal hand grip force. Additionally, there was a correlation between reduced dexterity and sensory deficits. Patients with UL-N had reduced estimates of psychosocial health including health-related QoL compared to control subjects and patients without UL-N. UL-N correlated with the severity of LL-N, but not with duration of diabetes, glycaemia, age, or sex. CONCLUSIONS: This study points to a substantial prevalence of UL-N in type 2 diabetes. The sensory phenotype of patients with UL-N was similar to LL-N and was characterized by loss of sensory function. Our study demonstrated an association of UL-N with impaired manual dexterity and reduced health-related QoL. Thus, upper limb sensorimotor functions should be assessed early in patients with diabetes.
Wissenschaftlicher Artikel
Scientific Article
Life Sci. 303:120601 (2022)
The gut microbiome influences cognition and behavior in mammals, yet its metabolic impact on the brain is only starting to be defined. Using metabolite profiling of antibiotics-treated mice, we reveal the microbiome as a key input controlling circadian metabolic cycles in the brain. Intra and inter-region analyses characterise the influence of the microbiome on the suprachiasmatic nucleus, containing the central clockwork, as well as the hippocampus and cortex, regions involved in learning and behavior.
Wissenschaftlicher Artikel
Scientific Article
Nature 608, 778-783 (2022)
Ferroptosis, a non-apoptotic form of cell death marked by iron-dependent lipid peroxidation1, has a key role in organ injury, degenerative disease and vulnerability of therapy-resistant cancers2. Although substantial progress has been made in understanding the molecular processes relevant to ferroptosis, additional cell-extrinsic and cell-intrinsic processes that determine cell sensitivity toward ferroptosis remain unknown. Here we show that the fully reduced forms of vitamin K—a group of naphthoquinones that includes menaquinone and phylloquinone3—confer a strong anti-ferroptotic function, in addition to the conventional function linked to blood clotting by acting as a cofactor for γ-glutamyl carboxylase. Ferroptosis suppressor protein 1 (FSP1), a NAD(P)H-ubiquinone reductase and the second mainstay of ferroptosis control after glutathione peroxidase-44,5, was found to efficiently reduce vitamin K to its hydroquinone, a potent radical-trapping antioxidant and inhibitor of (phospho)lipid peroxidation. The FSP1-mediated reduction of vitamin K was also responsible for the antidotal effect of vitamin K against warfarin poisoning. It follows that FSP1 is the enzyme mediating warfarin-resistant vitamin K reduction in the canonical vitamin K cycle6. The FSP1-dependent non-canonical vitamin K cycle can act to protect cells against detrimental lipid peroxidation and ferroptosis.
Wissenschaftlicher Artikel
Scientific Article
Endocr. Relat. Cancer 29, 285-306 (2022)
Aggressive pheochromocytomas and paragangliomas (PPGLs) are difficult to treat, and molecular targeting is being increasingly considered, but with variable results. This study investigates established and novel molecular-targeted drugs and chemotherapeutic agents for the treatment of PPGLs in human primary cultures and murine cell line spheroids. In PPGLs from 33 patients, including 7 metastatic PPGLs, we identified germline or somatic driver-mutations in 79% of cases, allowing us to assess potential differences in drug responsivity between pseudohypoxia-associated cluster 1- (n=10) and kinase signaling-associated cluster 2-related (n=14) PPGL primary cultures. Single anti-cancer drugs were either more effective in cluster 1 (cabozantinib, selpercatinib, 5-FU) or similarly effective in both clusters (everolimus, sunitinib, alpelisib, trametinib, niraparib, entinostat, gemcitabine, AR-A014418, high-dose zoledronic acid). High-dose estrogen and low-dose zoledronic acid were the only single substances more effective in cluster 2. Neither cluster 1- nor cluster 2-related patient primary cultures responded to HIF-2α inhibitors, temozolomide, dabrafenib, or octreotide. We showed particular efficacy of targeted combination treatments (cabozantinib/everolimus, alpelisib/everolimus, alpelisib/trametinib) in both clusters, with higher efficacy of some targeted combinations in cluster 2 and overall synergistic effects (cabozantinib/everolimus, alpelisib/trametinib) or synergistic effects in cluster 2 (alpelisib/everolimus). Cabozantinib/everolimus combination therapy, gemcitabine, and high-dose zoledronic acid appear to be promising treatment options with particularly high efficacy in SDHB-mutant and metastatic tumors. In conclusion, only minor differences regarding drug responsivity were found between cluster 1 and cluster 2: some single anti-cancer drugs were more effective in cluster 1 and some targeted combination treatments were more effective in cluster 2.
Wissenschaftlicher Artikel
Scientific Article
Mol. Metab. 60:101497 (2022)
Brown adipose tissue (BAT) burns fatty acids (FAs) to produce heat, and shows diurnal oscillation in glucose and triglyceride (TG)-derived FA-uptake, peaking around wakening. To gain insight in the diurnal regulation of metabolic BAT activity, we employed RNA-sequencing and lipidomics in murine BAT and identified pronounced enrichment of oscillating genes involved in extracellular lipolysis accompanied by oscillations of FA and monoacylglycerol content. This coincided with peak lipoprotein lipase (Lpl) expression, and was predicted to be driven by peroxisome proliferator-activated receptor gamma (PPARγ) activity. Chromatin immunoprecipitation (ChIP)-sequencing for PPARγ confirmed oscillation in binding of PPARγ to Lpl. Of the known LPL-modulators, angiopoietin-like 4 (Angptl4) showed the largest diurnal amplitude opposite to Lpl, and both Angptl4 knockout and overexpression attenuated oscillations of LPL and TG-derived FA-uptake by BAT. Our findings highlight involvement of PPARγ and a crucial role of ANGPTL4 in mediating the diurnal oscillation of TG-derived FA-uptake by BAT, and imply that time of day is essential when targeting LPL activity in BAT to improve metabolic health.
Wissenschaftlicher Artikel
Scientific Article
Mol. Metab. 60:101487 (2022)
Objective: Fibrotic organ responses have recently been identified as long-term complications in diabetes. Indeed, insulin resistance and aberrant hepatic lipid accumulation represent driving features of progressive non-alcoholic fatty liver disease (NAFLD), ranging from simple steatosis and non-alcoholic steatohepatitis (NASH) to fibrosis. Effective pharmacological regimens to stop progressive liver disease are still lacking to-date. Methods: Based on our previous discovery of transforming growth factor beta-like stimulated clone (TSC)22D4 as a key driver of insulin resistance and glucose intolerance in obesity and type 2 diabetes, we generated a TSC22D4-hepatocyte specific knockout line (TSC22D4-HepaKO) and exposed mice to control or NASH diet models. Mechanistic insights were generated by metabolic phenotyping and single-nuclei RNA sequencing. Results: Hepatic TSC22D4 expression was significantly correlated with markers of liver disease progression and fibrosis in both murine and human livers. Indeed, hepatic TSC22D4 levels were elevated in human NASH patients as well as in several murine NASH models. Specific genetic deletion of TSC22D4 in hepatocytes led to reduced liver lipid accumulation, improvements in steatosis and inflammation scores and decreased apoptosis in mice fed a lipogenic MCD diet. Single-nuclei RNA sequencing revealed a distinct TSC22D4-dependent gene signature identifying an upregulation of mitochondrial-related processes in hepatocytes upon loss of TSC22D4. An enrichment of genes involved in the TCA cycle, mitochondrial organization, and triglyceride metabolism underscored the hepatocyte-protective phenotype and overall decreased liver damage as seen in mouse models of hepatocyte-selective TSC22D4 loss-of-function. Conclusions: Together, our data uncover a new connection between targeted depletion of TSC22D4 and intrinsic metabolic processes in progressive liver disease. Hepatocyte-specific reduction of TSC22D4 improves hepatic steatosis and promotes hepatocyte survival via mitochondrial-related mechanisms thus paving the way for targeted therapies.
Wissenschaftlicher Artikel
Scientific Article
Non-coding RNA 8:32 (2022)
Cold and nutrient‐activated brown adipose tissue (BAT) is capable of increasing systemic energy expenditure via the uncoupled respiration and secretion of endocrine factors, thereby protecting mice against diet‐induced obesity and improving insulin response and glucose tolerance in men. Long non‐coding RNAs (lncRNAs) have recently been identified as fine‐tuning regulators of cellular function. While certain lncRNAs have been functionally characterised in adipose tissue, their overall contribution in the activation of BAT remains elusive. We identified lncRNAs correlating to interscapular brown adipose tissue (iBAT) function in a high fat diet (HFD) and cold stressed mice. We focused on Gm15551, which has an adipose tissue specific expression profile, is highly upregulated during adipogenesis, and downregulated by β‐adrenergic activation in mature adipocytes. Although we performed comprehensive transcriptional and adipocyte physiology profiling in vitro and in vivo, we could not detect an effect of gain or loss of function of Gm15551.
Wissenschaftlicher Artikel
Scientific Article
FEBS Lett. 596, 1434-1444 (2022)
Adipose tissue regulates whole-body energy homeostasis. Both lipodystrophy and obesity, the extreme and opposite aspects of adipose tissue dysfunction, result in metabolic disorders: insulin resistance and hepatic steatosis. Cyclin-dependent kinases (CDKs) have been reported to be involved in adipose tissue development and functions. Using adipose tissue-specific knockout mice, here we demonstrate that the deletion of CDK7 in adipose tissue results in progressive lipodystrophy, insulin resistance, impaired adipokine secretion and down-regulation of fat-specific genes, which are aggravated on high-fat diet and during aging. Our studies suggest that CDK7 is a key regulatory component of adipose tissue maintenance and systemic energy homeostasis.
Wissenschaftlicher Artikel
Scientific Article
Cell Rep. 39:110910 (2022)
In hepatocytes, peroxisome proliferator-activated receptor α (PPARα) orchestrates a genomic and metabolic response required for homeostasis during fasting. This includes the biosynthesis of ketone bodies and of fibroblast growth factor 21 (FGF21). Here we show that in the absence of adipose triglyceride lipase (ATGL) in adipocytes, ketone body and FGF21 production is impaired upon fasting. Liver gene expression analysis highlights a set of fasting-induced genes sensitive to both ATGL deletion in adipocytes and PPARα deletion in hepatocytes. Adipose tissue lipolysis induced by activation of the β3-adrenergic receptor also triggers such PPARα-dependent responses not only in the liver but also in brown adipose tissue (BAT). Intact PPARα activity in hepatocytes is required for the cross-talk between adipose tissues and the liver during fat mobilization.
Wissenschaftlicher Artikel
Scientific Article
J. Clin. Endocrinol. Metab. 107, 2167-2181 (2022)
CONTEXT: Novel fasting interventions have gained scientific and public attention. Periodic fasting has emerged as a dietary modification promoting beneficial effects on metabolic syndrome. OBJECTIVE: Assess whether periodic fasting reduces albuminuria and activates nephropathy-driven pathways. DESIGN/PARTICIPANTS: Proof-of-concept study where individuals with type 2 diabetes (n = 40) and increased albumin-to-creatinine ratio (ACR) were randomly assigned to receive a monthly fasting-mimicking diet (FMD) or a Mediterranean diet for 6 months with 3-month follow-up. MAIN OUTCOMES MEASURES: Change in ACR was assessed by analysis of covariance adjusted for age, sex, weight loss, and baseline value. Prespecified subgroup analysis for patients with micro- vs macroalbuminuria at baseline was performed. Change in homeostatic model assessment for insulin resistance (HOMA-IR), circulating markers of dicarbonyl detoxification (methylglyoxal-derived hydroimidazolone 1, glyoxalase-1, and hydroxyacetone), DNA-damage/repair (phosphorylated histone H2AX), lipid oxidation (acylcarnitines), and senescence (soluble urokinase plasminogen activator receptor) were assessed as exploratory endpoints. RESULTS: FMD was well tolerated with 71% to 95% of the participants reporting no adverse effects. After 6 months, change in ACR was comparable between study groups [110.3 (99.2, 121.5) mg/g; P = 0.45]. FMD led to a reduction of ACR in patients with microalbuminuria levels at baseline [-30.3 (-35.7, -24.9) mg/g; P ≤ 0.05] but not in those with macroalbuminuria [434.0 (404.7, 463.4) mg/g; P = 0.23]. FMD reduced HOMA-IR [-3.8 (-5.6, -2.0); P ≤ 0.05] and soluble urokinase plasminogen activator receptor [-156.6 (-172.9, -140.4) pg/mL; P ≤ 0.05], while no change was observed in markers of dicarbonyl detoxification or DNA-damage/repair. Change in acylcarnitines was related to patient responsiveness to ACR improvement. At follow-up only HOMA-IR reduction [-1.9 (-3.7, -0.1), P ≤ 0.05]) was sustained. CONCLUSIONS: Improvement of microalbuminuria and of markers of insulin resistance, lipid oxidation, and senescence suggest the potential beneficial effects of periodic fasting in type 2 diabetes.
Wissenschaftlicher Artikel
Scientific Article
Front. Neurosci. 15:811085 (2022)
Objective: It is controversially discussed in how far smoking contributes to diabetic polyneuropathy (DPN) in type 2 diabetes (T2D). Diffusion-weighted magnetic resonance neurography (MRN) at 3 Tesla has been shown to provide objective values for structural nerve integrity in patients with T2D. The aim of this study was to investigate the contribution of cigarette smoking on structural nerve integrity in T2D. Methods: This cross-sectional prospective cohort study investigated the structural integrity of the sciatic nerve in 10 smokers, 40 never-smokers, and 20 ex-smokers with T2D and 10 healthy control subjects, using diffusion tensor imaging MRN at 3 Tesla and semi-automated nerve fiber tracking. Results were correlated with clinical, electrophysiological, and serological data. Results: The sciatic nerve's fractional anisotropy (FA), a parameter for structural nerve integrity, was significantly lower in smokers with T2D when compared to controls (p = 0.002) and never-smokers (p = 0.015), and lower in ex-smokers when compared to controls (p = 0.015). In addition, sciatic nerve radial diffusivity, a marker of myelin damage, was increased in smokers versus controls and never-smokers (p = 0.048, p = 0.049, respectively). Furthermore, FA in T2D patients was negatively correlated with clinical and electrophysiological markers of DPN. FA also showed negative correlations with the pulse wave velocity, a marker of arterial stiffness and associated microangiopathy, in controls (r = -0.70; p = 0.037), never-smokers (r = -0.45; p = 0.004), ex-smokers (r = -0.55; p = 0.009), and a similar trend in smokers (r = -0.63; p = 0.076). Negative correlations were found between FA and skin auto-fluorescence, a marker of tissue advanced glycation end product accumulation and therefore long-term glycemic stress in T2D, in never-smokers (r = -0.39; p = 0.020) and smokers (r = -0.84; p = 0.004), but not in ex-smokers (r = -0.07; p = 0.765). Conclusion: The findings indicate that smoking contributes to sciatic nerve damage in T2D, potentially worsening DPN due to glycemic stress and less microangiopathy-associated myelin damage in active smokers, while angiopathic effects predominate in ex-smokers. To stop smoking may therefore pose a promising preventive measure to slow the progression of DPN in T2D.
Wissenschaftlicher Artikel
Scientific Article
FEBS Lett., DOI: 10.1002/1873-3468.14409 (2022)
Glucocorticoids (GCs) are widely used therapeutic agents to treat a broad range of inflammatory conditions. Their functional effects are elicited by binding to the glucocorticoid receptor (GR), which regulates transcription of distinct gene networks in response to ligand. However, the mechanisms governing various aspects of undesired side effects versus beneficial immunomodulation upon GR activation remain complex and incompletely understood. In this review, we discuss emerging models of inflammatory gene regulation by GR, highlighting GR's regulatory specificity conferred by context-dependent changes in chromatin architecture and transcription factor or co-regulator dynamics. GR controls both gene activation and repression, with the repression mechanism being central to favourable clinical outcomes. We describe current knowledge about 3D genome organisation and its role in spatiotemporal transcriptional control by GR. Looking beyond, we summarise the evidence for dynamics in gene regulation by GR through cooperative convergence of epigenetic modifications, transcription factor crosstalk, molecular condensate formation and chromatin looping. Further characterising these genomic events will reframe our understanding of mechanisms of transcriptional repression by GR.
Review
Review
Biochem. Biophys. Res. Commun. 618, 46-53 (2022)
Non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH) and liver fibrosis emerge as progressive liver diseases that accompany metabolic syndrome usually characterized by obesity, insulin resistance and type 2 diabetes. Currently no FDA approved treatments exist for the treatment of NASH and liver fibrosis, which requires a better knowledge of the underlying molecular mechanisms. TSC22D4 belongs to the TSC-22 protein family, the members of which are regulated by inflammatory and stress signals. Interestingly, patients with type 2 diabetes, with NAFLD as well as with NASH all have elevated levels of hepatic TSC22D4 expression. Previous studies with targeted deletion of TSC22D4 specifically in hepatocytes showed that TSC22D4 not only acts as a critical controller of diabetic hyperglycemia, but also contributes to NAFLD/NASH progression. To gain better insight into the development of progressive liver diseases, here we studied the function of TSC22D4 in hepatic stellate cells (HSCs), which play a key role in the pathogenesis of liver fibrosis. Our results indicated that TSC22D4 contributes to TGFβ1-mediated activation of HSCs and promotes their proliferation and migration. RNA-Sequencing analysis revealed that TSC22D4 initiates transcriptional events associated with HSC activation. Overall, our findings establish TSC22D4 as a key hub in the development of liver fibrosis, acting across different cellular compartments. Combinatorial TSC22D4 targeting in both hepatocytes and HSC may thus show superior efficacy against progressive liver disease.
Wissenschaftlicher Artikel
Scientific Article
Metabolites 12:99 (2022)
Naturally occurring substances are valuable resources for drug development. In this respect, chalcones are known to be antiproliferative agents against prostate cancer cell lines through various mechanisms or targets. Based on the literature and preliminary results, we aimed to study and optimise the efficiency of a series of chalcones to inhibit androgen-converting AKR1C3, known to promote prostate cancer. A total of 12 chalcones with different substitution patterns were synthesised. Structure–activity relationships associated with these modifications on AKR1C3 inhibition were analysed by performing enzymatic assays and docking simulations. In addition, the selectivity and cytotoxicity of the compounds were assessed. In enzymatic assays, C-6′ hydroxylated derivatives were more active than C-6′ methoxylated derivatives. In contrast, C-4 methylation increased activity over C-4 hydroxylation. Docking results supported these findings with the most active compounds fitting nicely in the binding site and exhibiting strong interactions with key amino acid residues. The most effective inhibitors were not cytotoxic for HEK293T cells and selective for 17β-hydroxysteroid dehydrogenases not primarily involved in steroid hormone metabolism. Nevertheless, they inhibited several enzymes of the steroid metabolism pathways. Favourable substitutions that enhanced AKR1C3 inhibition of chalcones were identified. This study paves the way to further develop compounds from this series or related flavonoids with improved inhibitory activity against AKR1C3.
Wissenschaftlicher Artikel
Scientific Article
Cells 11:560 (2022)
Continuous activation of hypoxia pathways in pheochromocytomas and paragangliomas (PPGLs) is associated with higher disease aggressiveness, for which effective treatment strategies are still missing. Most of the commonly used in vitro models lack characteristics of these pseudohypoxic tumors, including elevated expression of hypoxia-inducible factor (HIF) 2α. To address this shortcoming, we investigated whether recurrent hypoxia cycles lead to continuous activation of hypoxia pathways under normoxic conditions and whether this pseudohypoxia is associated with increased cellular aggressiveness. Rat pheochromocytoma cells (PC12) were incubated under hypoxia for 24 h every 3–4 days, up to 20 hypoxia–reoxygenation cycles, resulting in PC12 Z20 cells. PC12 Z20 control cells were obtained by synchronous cultivation under normoxia. RNA sequencing revealed upregulation of HIF2α in PC12 Z20 cells and a pseudohypoxic gene signature that overlapped with the gene signature of pseudohypoxic PPGLs. PC12 Z20 cells showed a higher growth rate, and the migration and adhesion capacity were significantly increased compared with control cells. Changes in global methylation, together with the pseudohypoxic conditions, may be responsible for the increased aggressiveness of this new model. The established sub-cell line with characteristics of pseudohypoxic PPGLs represent a complementary model for further investigations, for example, with regard to new therapeutic approaches.
Wissenschaftlicher Artikel
Scientific Article
Metabolites 12:445 (2022)
Resistance training promotes metabolic health and stimulates muscle
hypertrophy, but the precise routes by which resistance exercise (RE)
conveys these health benefits are largely unknown. Aim: To investigate
how acute RE affects human skeletal muscle metabolism. Methods: We
collected vastus lateralis biopsies from six healthy male untrained
volunteers at rest, before the first of 13 RE training sessions, and 45
min after the first and last bouts of RE. Biopsies were analysed using
untargeted mass spectrometry-based metabolomics. Results: We measured
617 metabolites covering a broad range of metabolic pathways. In the
untrained state RE altered 33 metabolites, including increased
3-methylhistidine and N-lactoylvaline, suggesting increased protein
breakdown, as well as metabolites linked to ATP (xanthosine) and NAD
(N1-methyl-2-pyridone-5-carboxamide) metabolism; the bile acid
chenodeoxycholate also increased in response to RE in muscle opposing
previous findings in blood. Resistance training led to muscle
hypertrophy, with slow type I and fast/intermediate type II muscle fibre
diameter increasing by 10.7% and 10.4%, respectively. Comparison of
post-exercise metabolite levels between trained and untrained state
revealed alterations of 46 metabolites, including decreased N-acetylated
ketogenic amino acids and increased beta-citrylglutamate which might
support growth. Only five of the metabolites that changed after acute
exercise in the untrained state were altered after chronic training,
indicating that training induces multiple metabolic changes not directly
related to the acute exercise response. Conclusion: The human skeletal
muscle metabolome is sensitive towards acute RE in the trained and
untrained states and reflects a broad range of adaptive processes in
response to repeated stimulation.
Wissenschaftlicher Artikel
Scientific Article
Front. Neurosci. 15:741494 (2022)
BackgroundRecent studies have found that troponin T parallels the structural and functional decay of peripheral nerves at the level of the lower limbs in patients with type 2 diabetes (T2D). The aim of this study was to determine whether this finding can also be reproduced at the level of the upper limbs.MethodsTen patients with fasting glucose levels >100 mg/dl (five with prediabetes and five with T2D) underwent magnetic resonance neurography of the right upper arm comprising T2-weighted and diffusion weighted sequences. The fractional anisotropy (FA), an indicator for the structural integrity of peripheral nerves, was calculated in an automated approach for the median, ulnar, and radial nerve. All participants underwent additional clinical, serological, and electrophysiological assessments.ResultsHigh sensitivity Troponin T (hsTNT) and HbA1c were negatively correlated with the average FA of the median, ulnar and radial nerve (r = -0.84; p = 0.002 and r = -0.68; p = 0.032). Both FA and hsTNT further showed correlations with items of the Michigan Hand Outcome Questionnaire (r = -0.76; p = 0.010 and r = 0.87; p = 0.001, respectively). A negative correlation was found for hsTNT and HbA1c with the total Purdue Pegboard Test Score (r = -0.87; p = 0.001 and r = -0.68; p = 0.031).ConclusionThis study is the first to find that hsTNT and HbA1c are associated with functional and structural parameters of the nerves at the level of the upper limbs in patients with impaired glucose tolerance and T2D. Our results support the hypothesis that hyperglycemia-related microangiopathy, represented by elevated hsTNT levels, is a contributor to nerve damage in diabetic polyneuropathy.
Wissenschaftlicher Artikel
Scientific Article
Mol. Metab. 57:101436 (2022)
OBJECTIVE: Ferroptosis continues to emerge as a novel modality of cell death with important therapeutic implications for a variety of diseases, most notably cancer and degenerative diseases. While susceptibility, initiation, and execution of ferroptosis have been linked to reprogramming of cellular lipid metabolism, imbalances in iron-redox homeostasis, and aberrant mitochondrial respiration, the detailed mechanisms of ferroptosis are still insufficiently well understood. METHODS AND RESULTS: Here we show that diminished proteasome function is a new mechanistic feature of ferroptosis. The transcription factor nuclear factor erythroid-2, like-1 (NFE2L1) protects from ferroptosis by sustaining proteasomal activity. In cellular systems, loss of NFE2L1 reduced cellular viability after the induction of both chemically and genetically induced ferroptosis, which was linked to the regulation of proteasomal activity under these conditions. Importantly, this was reproduced in a Sedaghatian-type Spondylometaphyseal Dysplasia (SSMD) patient-derived cell line carrying mutated glutathione peroxidase-4 (GPX4), a critical regulator of ferroptosis. Also, reduced proteasomal activity was associated with ferroptosis in Gpx4-deficient mice. In a mouse model for genetic Nfe2l1 deficiency, we observed brown adipose tissue (BAT) involution, hyperubiquitination of ferroptosis regulators, including the GPX4 pathway, and other hallmarks of ferroptosis. CONCLUSION: Our data highlight the relevance of the NFE2L1-proteasome pathway in ferroptosis. Manipulation of NFE2L1 activity might enhance ferroptosis-inducing cancer therapies as well as protect from aberrant ferroptosis in neurodegeneration, general metabolism, and beyond.
Wissenschaftlicher Artikel
Scientific Article
EMBO Mol. Med.:e14364 (2022)
Invasive nonfunctioning (NF) pituitary neuroendocrine tumors (PitNETs) are non-resectable neoplasms associated with frequent relapses and significant comorbidities. As the current therapies of NF-PitNETs often fail, new therapeutic targets are needed. The observation that circulating angiopoietin-2 (ANGPT2) is elevated in patients with NF-PitNET and correlates with tumor aggressiveness prompted us to investigate the ANGPT2/TIE2 axis in NF-PitNETs in the GH3 PitNET cell line, primary human NF-PitNET cells, xenografts in zebrafish and mice, and in MENX rats, the only autochthonous NF-PitNET model. We show that PitNET cells express a functional TIE2 receptor and secrete bioactive ANGPT2, which promotes, besides angiogenesis, tumor cell growth in an autocrine and paracrine fashion. ANGPT2 stimulation of TIE2 in tumor cells activates downstream cell proliferation signals, as previously demonstrated in endothelial cells (ECs). Tie2 gene deletion blunts PitNETs growth in xenograft models, and pharmacological inhibition of Angpt2/Tie2 signaling antagonizes PitNETs in primary cell cultures, tumor xenografts in mice, and in MENX rats. Thus, the ANGPT2/TIE2 axis provides an exploitable therapeutic target in NF-PitNETs and possibly in other tumors expressing ANGPT2/TIE2. The ability of tumor cells to coopt angiogenic signals classically viewed as EC-specific expands our view on the microenvironmental cues that are essential for tumor progression.
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Scientific Article
Proc. Natl. Acad. Sci. U.S.A. 119:e2200083119 (2022)
SignificanceWhile increasing evidence associates the disruption of circadian rhythms with pathologic conditions, including obesity, type 2 diabetes, and nonalcoholic fatty liver diseases (NAFLD), the involved mechanisms are still poorly described. Here, we show that, in both humans and mice, the pathogenesis of NAFLD is associated with the disruption of the circadian clock combined with perturbations of the growth hormone and sex hormone pathways. However, while this condition protects mice from the development of fibrosis and insulin resistance, it correlates with increased fibrosis in humans. This suggests that the perturbation of the circadian clock and its associated disruption of the growth hormone and sex hormone pathways are critical for the pathogenesis of metabolic and liver diseases.
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Scientific Article
Cell Metab. 34, 473-486.e9 (2022)
Fasting metabolism and immunity are tightly linked; however, it is largely unknown how immune cells contribute to metabolic homeostasis during fasting in healthy subjects. Here, we combined cell-type-resolved genomics and computational approaches to map crosstalk between hepatocytes and liver macrophages during fasting. We identified the glucocorticoid receptor (GR) as a key driver of fasting-induced reprogramming of the macrophage secretome including fasting-suppressed cytokines and showed that lack of macrophage GR impaired induction of ketogenesis during fasting as well as endotoxemia. Mechanistically, macrophage GR suppressed the expression of tumor necrosis factor (TNF) and promoted nuclear translocation of hepatocyte GR to activate a fat oxidation/ketogenesis-related gene program, cooperatively induced by GR and peroxisome proliferator-activated receptor alpha (PPARα) in hepatocytes. Together, our results demonstrate how resident liver macrophages directly influence ketogenesis in hepatocytes, thereby also outlining a strategy by which the immune system can set the metabolic tone during inflammatory disease and infection.
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Scientific Article
Cardiovasc. Res., DOI: 10.1093/cvr/cvac022 (2022)
AIMS: Atherosclerosis is a chronic inflammatory disease of the arteries leading to the formation of atheromatous plaques. Human mesenchymal stem cells (hMSCs) are recruited from the circulation into plaques where in response to their environment they adopt a phenotype with immunomodulatory properties. However, the mechanisms underlying hMSC function in these processes are unclear. Recently, we described that miRNA let-7f controls hMSC invasion guided by inflammatory cytokines and chemokines. Here, we investigated the role of let-7f in hMSC tropism to human atheromas and the effects of the plaque microenvironment on cell fate and release of soluble factors. METHODS AND RESULTS: Incubation of hMSCs with LL-37, an antimicrobial peptide abundantly found in plaques, increased biosynthesis of let-7f and N-formyl peptide receptor 2 (FPR2), enabling chemotactic invasion of the cells towards LL-37, as determined by qRT-PCR, flow cytometry, and cell invasion assay analysis. In an Apoe -/- mouse model of atherosclerosis, circulating hMSCs preferentially adhered to athero-prone endothelium. This property was facilitated by elevated levels of let-7f in the hMSCs, as assayed by ex vivo artery perfusion and 2-photon laser scanning microscopy. Exposure of hMSCs to homogenized human atheromatous plaque material considerably induced the production of various cytokines, chemokines, matrix metalloproteinases, and tissue inhibitors of metalloproteinases, as studied by PCR array and Western blot analysis. Moreover, exposure to human plaque extracts elicited differentiation of hMSCs into cells of the myogenic lineage, suggesting a potentially plaque-stabilizing effect. CONCLUSIONS: Our findings indicate that let-7f promotes hMSC tropism toward atheromas through the LL-37/FPR2 axis and demonstrate that hMSCs upon contact with human plaque environment develop a potentially athero-protective signature impacting the pathophysiology of atherosclerosis. TRANSLATIONAL PERSPECTIVE: Human mesenchymal stem cells (hMSCs) represent a promising therapeutic approach in various pathophysiological processes associated with inflammation including atherosclerosis. The current knowledge about the mechanisms of hMSC tropism towards human atherosclerotic plaques and their beneficial effects at the site is poor. Bridging this gap is essential for clinical application of hMSCs. Our work provides insight into the contribution of microRNA let-7f in hMSC recruitment to atheroprone areas, where hMSCs display athero-protective potential by releasing immunomodulatory factors and differentiating towards plaque-stabilizing cells. Our findings highlight circulating hMSCs as a possible therapeutic strategy for the stabilization of atherosclerotic plaques.
Wissenschaftlicher Artikel
Scientific Article
Lancet Diabet. Endocrinol. 10, 221-230 (2022)
Current evidence suggests that severity and mortality of COVID-19 is higher in men than in women, whereas women might be at increased risk of COVID-19 reinfection and development of long COVID. Differences between sexes have been observed in other infectious diseases and in the response to vaccines. Sex-specific expression patterns of proteins mediating virus binding and entry, and divergent reactions of the immune and endocrine system, in particular the hypothalamic-pituitary-adrenal axis, in response to acute stress might explain the higher severity of COVID-19 in men. In this Personal View, we discuss how sex hormones, comorbidities, and the sex chromosome complement influence these mechanisms in the context of COVID-19. Due to its role in the severity and progression of SARS-CoV-2 infections, we argue that sexual dimorphism has potential implications for disease treatment, public health measures, and follow-up of patients predisposed to the development of long COVID. We suggest that sex differences could be considered in future pandemic surveillance and treatment of patients with COVID-19 to help to achieve better disease stratification and improved outcomes.
Review
Review
Cell Metab. 34, 329-345.e8 (2022)
Tissue sensitivity and response to exercise vary according to the time of day and alignment of circadian clocks, but the optimal exercise time to elicit a desired metabolic outcome is not fully defined. To understand how tissues independently and collectively respond to timed exercise, we applied a systems biology approach. We mapped and compared global metabolite responses of seven different mouse tissues and serum after an acute exercise bout performed at different times of the day. Comparative analyses of intra- and inter-tissue metabolite dynamics, including temporal profiling and blood sampling across liver and hindlimb muscles, uncovered an unbiased view of local and systemic metabolic responses to exercise unique to time of day. This comprehensive atlas of exercise metabolism provides clarity and physiological context regarding the production and distribution of canonical and novel time-dependent exerkine metabolites, such as 2-hydroxybutyrate (2-HB), and reveals insight into the health-promoting benefits of exercise on metabolism.
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Scientific Article
Adv. Drug Deliv. Rev. 181:114110 (2022)
Despite the increasing prevalence of obesity and diabetes, there is no efficient treatment to combat these epidemics. The adipose organ is the main site for energy storage and plays a pivotal role in whole body lipid metabolism and energy homeostasis, including remodeling and dysfunction of adipocytes and adipose tissues in obesity and diabetes. Thus, restoring and balancing metabolic functions in the adipose organ is in demand. MiRNAs represent a novel class of drugs and drug targets, as they are heavily involved in the regulation of many cellular and metabolic processes and diseases, likewise in adipocytes. In this review, we summarize key regulatory activities of miRNAs in the adipose organ, discuss various miRNA replacement and inhibition strategies, promising delivery systems for miRNAs and reflect the future of novel miRNA-based therapeutics to target adipose tissues with the ultimate goal to combat metabolic disorders.
Review
Review
Cancers 14:90 (2022)
Background: Cancer is primarily a disease of high age in humans, yet most mouse studies on cancer cachexia are conducted using young adolescent mice. Given that metabolism and muscle function change with age, we hypothesized that aging may affect cachexia progression in mouse models. Methods: We compare tumor and cachexia development in young and old mice of three different strains (C57BL/6J, C57BL/6N, BALB/c) and with two different tumor cell lines (Lewis Lung Cancer, Colon26). Tumor size, body and organ weights, fiber cross-sectional area, circulating cachexia biomarkers, and molecular markers of muscle atrophy and adipose tissue wasting are shown. We correlate inflammatory markers and body weight dependent on age in patients with cancer. Results: We note fundamental differences between mouse strains. Aging aggravates weight loss in LLC-injected C57BL/6J mice, drives it in C57BL/6N mice, and does not influence weight loss in C26-injected BALB/c mice. Glucose tolerance is unchanged in cachectic young and old mice. The stress marker GDF15 is elevated in cachectic BALB/c mice independent of age and increased in old C57BL/6N and J mice. Inflammatory markers correlate significantly with weight loss only in young mice and patients. Conclusions: Aging affects cachexia development and progression in mice in a strain-dependent manner and influences the inflammatory profile in both mice and patients. Age is an important factor to consider for future cachexia studies.
Wissenschaftlicher Artikel
Scientific Article
Cells 11:28 (2022)
Glucocorticoids are potent anti-inflammatory drugs; however, their molecular mode of action remains complex and elusive. They bind to the glucocorticoid receptor (GR), a nuclear receptor that controls gene expression in almost all tissues in a cell type-specific manner. While GR’s transcriptional targets mediate beneficial reactions in immune cells, they also harbor the potential of adverse metabolic effects in other cell types such as hepatocytes. Here, we have profiled nascent transcription upon glucocorticoid stimulation in LPS-activated primary murine macrophages using 4sU-seq. We compared our results to publicly available nascent transcriptomics data from murine liver and bioinformatically identified non-coding RNAs transcribed from intergenic GR binding sites in a tissue-specific fashion. These tissue-specific enhancer RNAs (eRNAs) correlate with target gene expression, reflecting cell type-specific glucocorticoid responses. We further associate GRmediated eRNA expression with changes in H3K27 acetylation and BRD4 recruitment in inflammatory macrophages upon glucocorticoid treatment. In summary, we propose a common mechanism by which GR-bound enhancers regulate target gene expression by changes in histone acetylation, BRD4 recruitment and eRNA expression. We argue that local eRNAs are potential therapeutic targets downstream of GR signaling which may modulate glucocorticoid response in a cell type-specific way.
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Scientific Article
Clin. Cancer Res. 28, 1038-1052 (2022)
PURPOSE: The genetic relatedness between primary and recurrent head and neck squamous cell carcinomas (HNSCC) reflects the extent of heterogeneity and therapy-driven selection of tumor subpopulations. Yet, current treatment of recurrent HNSCC ignores the molecular characteristics of therapy-resistant tumor populations. EXPERIMENTAL DESIGN: From 150 tumors, 74 primary HNSCCs were RNA-sequenced and 38 matched primary/recurrent tumor pairs were both, whole-exome and RNA-sequenced. Transcriptome analysis determined the predominant classical (CL), basal (BA) and inflamed-mesenchymal (IMS) transcriptional subtypes according to an established classification. Genomic alterations and clonal compositions of tumors were evaluated from whole-exome data. RESULTS: While CL and IMS subtypes were more common in primary HNSCC with low recurrence rates, the BA subtype was more prevalent and stable in recurrent tumors. The BA subtype was associated with a transcriptional signature of partial epithelial-to-mesenchymal transition (p-emt) and early recurrence. In 44% of matched cases, the dominant subtype changed from primary to recurrent tumors, preferably from IMS to BA or CL. Gene set enrichment analysis identified upregulation of Hypoxia, p-emt and radiation resistance signatures and downregulation of tumor inflammation in recurrences compared to index tumors. A relevant subset of primary/recurrent tumor pairs presented no evidence for a common clonal origin. CONCLUSIONS: Our study showed a high degree of genetic and transcriptional heterogeneity between primary/recurrent tumors, suggesting therapy-related selection of a transcriptional subtype with characteristics unfavorable for therapy. We conclude that therapy decisions should be based on genetic and transcriptional characteristics of recurrences rather than primary tumors to enable optimally tailored treatment strategies.
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Scientific Article
2021
Front. Endocrin. 12:765201 (2021)
Patients with diabetes are over-represented among the total cases reported with "idiopathic" pulmonary fibrosis (IPF). This raises the question, whether this is an association only or whether diabetes itself can cause pulmonary fibrosis. Recent studies in mouse models of type 1 and type 2 diabetes demonstrated that diabetes causes pulmonary fibrosis. Both types of diabetes trigger a cascade, starting with increased DNA damage, an impaired DNA repair, and leading to persistent DNA damage signaling. This response, in turn, induces senescence, a senescence-associated-secretory phenotype (SASP), marked by the release of pro-inflammatory cytokines and growth factors, finally resulting in fibrosis. Restoring DNA repair drives fibrosis into remission, thus proving causality. These data can be translated clinically to patients with type 2 diabetes, characterized by long-term diabetes and albuminuria. Hence there are several arguments, to substitute the term "idiopathic" pulmonary fibrosis (IPF) in patients with diabetes (and exclusion of other causes of lung diseases) by the term "diabetes-induced pulmonary fibrosis" (DiPF). However, future studies are required to establish this term and to study whether patients with diabetes respond to the established therapies similar to non-diabetic patients.
Review
Review
EJNMMI Res. 11:121 (2021)
Pheochromocytomas (PCCs) and paragangliomas (PGLs), together referred to as PPGLs, are rare chromaffin cell-derived tumors. They require timely diagnosis as this is the only way to achieve a cure through surgery and because of the potentially serious cardiovascular complications and sometimes life-threatening comorbidities that can occur if left untreated. The biochemical diagnosis of PPGLs has improved over the last decades, and the knowledge of the underlying genetics has dramatically increased. In addition to conventional anatomical imaging by CT and MRI for PPGL detection, new functional imaging modalities have emerged as very useful for patient surveillance and stratification for therapy. The availability of validated and predictive animal models of cancer is essential for translating molecular, imaging and therapy response findings from the bench to the bedside. This is especially true for rare tumors, such as PPGLs, for which access to large cohorts of patients is limited. There are few animal models of PPGLs that have been instrumental in refining imaging modalities for early tumor detection, as well as in identifying and evaluating novel imaging tracers holding promise for the detection and/or treatment of human PPGLs. The in vivo PPGL models mainly include xenografts/allografts generated by engrafting rat or mouse cell lines, as no representative human cell line is available. In addition, there is a model of endogenous PCCs (i.e., MENX rats) that was characterized in our laboratory. In this review, we will summarize the contribution that various representative models of PPGL have given to the visualization of these tumors in vivo and we present an example of a tracer first evaluated in MENX rats, and then translated to the detection of these tumors in human patients. In addition, we will illustrate briefly the potential of ex vivo biological imaging of intact adrenal glands in MENX rats.
Review
Review
Mol. Metab. 56:101412 (2021)
OBJECTIVE: Multiple GWAS have identified SNPs in the 8q24 locus near TRIB1 that significantly associate with plasma lipids and other markers of cardiometabolic health, and prior studies have uncovered roles for hepatic and myeloid Trib1 in plasma lipid regulation and atherosclerosis. The same 8q24 SNPs additionally associate with plasma adiponectin levels in humans, implicating TRIB1 in adipocyte biology. Here, we hypothesize that TRIB1 in adipose tissue regulates plasma adiponectin, lipids, and metabolic health. METHODS: We investigate the metabolic phenotype of adipocyte-specific Trib1 knockout mice (Trib1_ASKO) on chow and high fat diet. Through secretomics of adipose tissue explants and RNA-seq of adipocytes and livers from these mice, we further investigate the mechanism of TRIB1 in adipose tissue. RESULTS: Trib1_ASKO mice have an improved metabolic phenotype with increased plasma adiponectin levels, improved glucose tolerance, and decreased plasma lipids. Trib1_ASKO adipocytes have increased adiponectin production and secretion independent of the known TRIB1 function of regulating proteasomal degradation. RNA-seq analysis of adipocytes and livers from Trib1_ASKO mice suggests that alterations in adipocyte function underlie the observed plasma lipid changes. Adipose tissue explant secretomics further reveals that Trib1_ASKO adipose tissue has decreased ANGPTL4 production, and we demonstrate an accompanying increase in LPL activity that likely underlies the triglyceride phenotype. CONCLUSION: Adipocyte Trib1 regulates multiple aspects of metabolic health, confirming previously observed genetic associations in humans and shedding light on further mechanisms by which TRIB1 regulates plasma lipids and metabolic health.
Wissenschaftlicher Artikel
Scientific Article
Int. J. Mol. Sci. 22:12695 (2021)
Palmitoleic acid (C16:1n7) has been identified as a regulator of physiological cardiac hypertrophy. In the present study, we aimed to investigate the molecular pathways involved in C16:1n7 responses in primary murine cardiomyocytes (PCM) and a mouse model of isoproterenol (ISO)-induced cardiac damage. PCMs were stimulated with C16:1n7 or a vehicle. Afterwards, RNA sequencing was performed using an Illumina HiSeq sequencer. Confirmatory analysis was performed in PCMs and HL-1 cardiomyocytes. For an in vivo study, 129 sv mice were orally treated with a vehicle or C16:1n7 for 22 days. After 5 days of pre-treatment, the mice were injected with ISO (25 mg/kg/d s. c.) for 4 consecutive days. Cardiac phenotyping was performed using echocardiography. In total, 129 genes were differentially expressed in PCMs stimulated with C16:1n7, including Angiopoietin-like factor 4 (Angptl4) and Pyruvate Dehydrogenase Kinase 4 (Pdk4). Both Angptl4 and Pdk4 are proxisome proliferator-activated receptor α/δ (PPARα/δ) target genes. Our in vivo results indicated cardioprotective and anti-fibrotic effects of C16:1n7 application in mice. This was associated with the C16:1n7-dependent regulation of the cardiac PPAR-specific signaling pathways. In conclusion, our experiments demonstrated that C16:1n7 might have protective effects on cardiac fibrosis and inflammation. Our study may help to develop future lipid-based therapies for catecholamine-induced cardiac damage.
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Scientific Article
Cell Rep. Med. 2:100434 (2021)
miRNAs have crucial functions in many biological processes and are candidate biomarkers of disease. Here, we show that miR-216a is a conserved, pancreas-specific miRNA with important roles in pancreatic islet and acinar cells. Deletion of miR-216a in mice leads to a reduction in islet size, β-cell mass, and insulin levels. Single-cell RNA sequencing reveals a subpopulation of β-cells with upregulated acinar cell markers under a high-fat diet. miR-216a is induced by TGF-β signaling, and inhibition of miR-216a increases apoptosis and decreases cell proliferation in pancreatic cells. Deletion of miR-216a in the pancreatic cancer-prone mouse line KrasG12D;Ptf1aCreER reduces the propensity of pancreatic cancer precursor lesions. Notably, circulating miR-216a levels are elevated in both mice and humans with pancreatic cancer. Collectively, our study gives insights into how β-cell mass and acinar cell growth are modulated by a pancreas-specific miRNA and also suggests miR-216a as a potential biomarker for diagnosis of pancreatic diseases.
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Scientific Article
Nat. Commun. 12:6883 (2021)
In female mammals, the cessation of ovarian functions is associated with significant metabolic alterations, weight gain, and increased susceptibility to a number of pathologies associated with ageing. The molecular mechanisms triggering these systemic events are unknown because most tissues are responsive to lowered circulating sex steroids. As it has been demonstrated that isoform alpha of the estrogen receptor (ERα) may be activated by both estrogens and amino acids, we test the metabolic effects of a diet enriched in specific amino acids in ovariectomized (OVX) mice. This diet is able to block the OVX-induced weight gain and fat deposition in the liver. The use of liver-specific ERα KO mice demonstrates that the hepatic ERα, through the control of liver lipid metabolism, has a key role in the systemic response to OVX. The study suggests that the liver ERα might be a valuable target for dietary treatments for the post-menopause.
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Scientific Article
Cell Rep. 37:110003 (2021)
Brown adipose tissue (BAT) thermogenic activity is tightly regulated by cellular redox status, but the underlying molecular mechanisms are incompletely understood. Protein S-nitrosylation, the nitric-oxide-mediated cysteine thiol protein modification, plays important roles in cellular redox regulation. Here we show that diet-induced obesity (DIO) and acute cold exposure elevate BAT protein S-nitrosylation, including UCP1. This thermogenic-induced nitric oxide bioactivity is regulated by S-nitrosoglutathione reductase (GSNOR; alcohol dehydrogenase 5 [ADH5]), a denitrosylase that balances the intracellular nitroso-redox status. Loss of ADH5 in BAT impairs cold-induced UCP1-dependent thermogenesis and worsens obesity-associated metabolic dysfunction. Mechanistically, we demonstrate that Adh5 expression is induced by the transcription factor heat shock factor 1 (HSF1), and administration of an HSF1 activator to BAT of DIO mice increases Adh5 expression and significantly improves UCP1-mediated respiration. Together, these data indicate that ADH5 controls BAT nitroso-redox homeostasis to regulate adipose thermogenesis, which may be therapeutically targeted to improve metabolic health.
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Scientific Article
Peptides 146:170677 (2021)
Calcitonin Gene-Related Peptide (CGRP) is a potent vasodilator peptide widely distributed in the central nervous system and various peripheral tissues, including cardiac muscle. However, its role in heart protein metabolism remains unknown. We examined the acute effects of CGRP on autophagy and the related signaling pathways in the heart mice and cultured neonatal cardiomyocytes. CGRP (100 μg kg−1; s.c.) or 0.9 % saline was injected in awake male C57B16 mice, and the metabolic profile was determined up to 60 min. In fed mice, CGRP drastically increased glycemia and reduced insulinemia, an effect that was accompanied by reduced cardiac phosphorylation levels of Akt at Ser473 without affecting FoxO. Despite these catabolic effects, CGRP acutely inhibited autophagy as estimated by the decrease in LC3II:LC3I and autophagic flux. In addition, the fasting-induced autophagic flux in mice hearts was entirely abrogated by one single injection of CGRP. In parallel, CGRP stimulated PKA/CREB and mTORC1 signaling and increased the phosphorylation of Unc51-like kinase-1 (ULK1), an essential protein in autophagy initiation. Similar effects were observed in cardiomyocytes, in which CGRP also inhibited autophagic flux and stimulated Akt and FoxO phosphorylation. These findings suggest that CGRP in vivo acutely suppresses autophagy in the heart of fed and fasted mice, most likely through the activation of PKA/mTORC1 signaling but independent of Akt.
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Scientific Article
Front. Endocrin. 12:739021 (2021)
The acclimatization of brown adipose tissue (BAT) to sustained cold exposure requires an adaptive increase in proteasomal protein quality control. Ubiquilins represent a recently identified family of shuttle proteins with versatile functions in protein degradation, such as facilitating substrate targeting and proteasomal degradation. However, whether ubiquilins participate in brown adipocyte function has not been investigated so far. Here, we determine the role of ubiquilins for proteostasis and non-shivering thermogenesis in brown adipocytes. We found that Ubqln1, 2 and 4 are highly expressed in BAT and their expression was induced by cold and proteasomal inhibition. Surprisingly, silencing of ubiquilin gene expression (one or multiple in combinations) did not lead to aggravated ER stress or inflammation. Moreover, ubiquitin level and proteasomal activity under basal conditions were not impacted by loss of ubiquilins. Also, non-shivering thermogenesis measured by norepinephrine-induced respiration remained intact after loss of ubiquilins. In conclusion, ubiquilin proteins are highly abundant in BAT and regulated by cold, but they are dispensable for brown adipocyte proteostasis and thermogenesis.
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Scientific Article
Cell Tissue Res., DOI: 10.1007/s00441-021-03539-z (2021)
Stroke is the leading cause of adult disability. Endogenous neural stem/progenitor cells (NSPCs) originating from the subventricular zone (SVZ) contribute to the brain repair process. However, molecular mechanisms underlying CNS disease-induced SVZ NSPC-redirected migration to the lesion area are poorly understood. Here, we show that genetic depletion of the p75 neurotrophin receptor (p75NTR−/−) in mice reduced SVZ NSPC migration towards the lesion area after cortical injury and that p75NTR−/− NSPCs failed to migrate upon BDNF stimulation in vitro. Cortical injury rapidly increased p75NTR abundance in SVZ NSPCs via bone morphogenetic protein (BMP) receptor signaling. SVZ-derived p75NTR−/− NSPCs revealed an altered cytoskeletal network- and small GTPase family-related gene and protein expression. In accordance, BMP-treated non-migrating p75NTR−/− NSPCs revealed an altered morphology and α-tubulin expression compared to BMP-treated migrating wild-type NSPCs. We propose that BMP-induced p75NTR abundance in NSPCs is a regulator of SVZ NSPC migration to the lesion area via regulation of the cytoskeleton following cortical injury.
Review
Review
EJNMMI Res. 11:94 (2021)
Cachexia, a multifactorial wasting syndrome, is highly prevalent among advanced-stage cancer patients. Unlike weight loss in healthy humans, the progressive loss of body weight in cancer cachexia primarily implicates lean body mass, caused by an aberrant metabolism and systemic inflammation. This may lead to disease aggravation, poorer quality of life, and increased mortality. Timely detection is, therefore, crucial, as is the careful monitoring of cancer progression, in an effort to improve management, facilitate individual treatment and minimize disease complications. A detailed analysis of body composition and tissue changes using imaging modalities-that is, computed tomography, magnetic resonance imaging, (18F) fluoro-2-deoxy-D-glucose (18FDG) PET and dual-energy X-ray absorptiometry-shows great premise for charting the course of cachexia. Quantitative and qualitative changes to adipose tissue, organs, and muscle compartments, particularly of the trunk and extremities, could present important biomarkers for phenotyping cachexia and determining its onset in patients. In this review, we present and compare the imaging techniques that have been used in the setting of cancer cachexia. Their individual limitations, drawbacks in the face of clinical routine care, and relevance in oncology are also discussed.
Review
Review
J. Physiol.-London, DOI: 10.1113/JP281979 (2021)
KEY POINTS: Obesity and the associated adipocyte pathology are risk factors for cardiovascular disease Translational research is possible but strongly depends on the mouse model used White adipose tissue inflammation contributes to metabolic and vascular dysfunction Brown adipose tissue thermogenesis supports metabolic and vascular function ABSTRACT: Obesity is a medical disorder caused by multiple mechanisms of dysregulated energy balance. A major consequence of obesity is an increased risk to develop diabetes, diabetic complications, and cardiovascular disease. While a better understanding of the molecular mechanisms linking obesity, insulin resistance, and cardiovascular disease is needed, translational research of the human pathology is hampered by the available cellular and rodent model systems. Major barriers are the species-specific differences in energy balance, vascular biology, and adipose tissue physiology, especially related to white and brown adipocytes, and adipose tissue browning. In rodents, non-shivering thermogenesis is responsible for a large part of energy expenditure, but humans possess much less thermogenic fat, which makes temperature is an important variable in translational research. Mouse models with predisposition to dyslipidaemia housed at thermoneutrality and fed a high-fat diet more closely reflect human physiology. Also, adipocytes play a key role in the endocrine regulation of cardiovascular function. Adipocytes secrete a variety of hormones, lipid mediators, and other metabolites that directly influence the local microenvironment as well as distant tissues. This is specifically apparent in perivascular depots, where adipocytes modulate vascular function and inflammation. Altogether, these mechanisms highlight the critical role of adipocytes in the development of cardiometabolic disease. Abstract figure legend While cardiometabolic health is associated with adipose tissue browning and beneficial adipokine profiles, obesity leads to adipose tissue whitening, inflammation, and atherosclerosis. This article is protected by copyright. All rights reserved.
Review
Review
Nat. Rev. Endocrinol., DOI: 10.1038/s41574-021-00577-z (2021)
An emerging feature of type 1 diabetes mellitus and type 2 diabetes mellitus is their association with pulmonary fibrosis, which negatively affects the prognosis of patients. Here, we provide a brief update of the field and the remaining open questions.
Review
Review
Radiology 302, 153-161 (2021)
Background Diffusion-weighted imaging (DWI) provides specific in vivo information about tissue microstructure, which is increasingly recognized for various applications outside the central nervous system. However, standard sequence parameters are commonly adopted from optimized central nervous system protocols, thus potentially neglecting differences in tissue-specific diffusional behavior. Purpose To characterize the optimal tissue-specific diffusion imaging weighting scheme over the b domain in peripheral nerves under physiologic and pathologic conditions. Materials and Methods In this prospective cross-sectional study, 3-T MR neurography of the sciatic nerve was performed in healthy volunteers (n = 16) and participants with type 2 diabetes (n = 12). For DWI, 16 b values in the range of 0-1500 sec/mm2 were acquired in axial and radial diffusion directions of the nerve. With a region of interest-based approach, diffusion-weighted signal behavior as a function of b was estimated using standard monoexponential, biexponential, and kurtosis fitting. Goodness of fit was assessed to determine the optimal b value for two-point DWI/diffusion tensor imaging (DTI). Results Non-Gaussian diffusional behavior was observed beyond b values of 600 sec/mm2 in the axial and 800 sec/mm2 in the radial diffusion direction in both participants with diabetes and healthy volunteers. Accordingly, the biexponential and kurtosis models achieved a better curve fit compared with the standard monoexponential model (Akaike information criterion >99.9% in all models), but the kurtosis model was preferred in the majority of cases. Significant differences between healthy volunteers and participants with diabetes were found in the kurtosis-derived parameters Dk and K. The results suggest an upper bound b value of approximately 700 sec/mm2 for optimal standard DWI/DTI in peripheral nerve applications. Conclusion In MR neurography, an ideal standard diffusion-weighted imaging/diffusion tensor imaging protocol with b = 700 sec/mm2 is suggested. This is substantially lower than in the central nervous system due to early-occurring non-Gaussian diffusion behavior and emphasizes the need for tissue-specific b value optimization. Including higher b values, kurtosis-derived parameters may represent promising novel imaging markers of peripheral nerve disease. ©RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Jang and Du in this issue.
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Scientific Article
STAR Protoc. 2:100805 (2021)
Isolation of nuclei tagged in specific cell types (INTACT) allows for stress-free and high-throughput analyses of cellular subpopulations. Here, we present an improved protocol for isolation of pure and high-quality GFP-labeled nuclei from frozen livers of INTACT mice, as well as protocols for downstream sequencing analyses. The adaptation to frozen tissue provides a pause point that allows sampling at multiple time points and/or phenotypic characterization of livers prior to nuclei isolation and downstream analyses. For complete details on the use of this protocol, please refer to Loft et al. (2021).
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Scientific Article
Int. J. Mol. Sci. 22:9979 (2021)
Background: Amino acids have a central role in cell metabolism, and intracellular changes contribute to the pathogenesis of various diseases, while the role and specific organ distribution of dipeptides is largely unknown. Method: We established a sensitive, rapid and reliable UPLC-MS/MS method for quantification of 36 dipeptides. Dipeptide patterns were analyzed in brown and white adipose tissues, brain, eye, heart, kidney, liver, lung, muscle, sciatic nerve, pancreas, spleen and thymus, serum and urine of C57BL/6N wildtype mice and related to the corresponding amino acid profiles. Results: A total of 30 out of the 36 investigated dipeptides were detected with organ-specific distribution patterns. Carnosine and anserine were most abundant in all organs, with the highest concentrations in muscles. In liver, Asp-Gln and Ala-Gln concentrations were high, in the spleen and thymus, Glu-Ser and Gly-Asp. In serum, dipeptide concentrations were several magnitudes lower than in organ tissues. In all organs, dipeptides with C-terminal proline (Gly-Pro and Leu-Pro) were present at higher concentrations than dipeptides with N-terminal proline (Pro-Gly and Pro-Leu). Organ-specific amino acid profiles were related to the dipeptide profile with several amino acid concentrations being related to the isomeric form of the dipeptides. Aspartate, histidine, proline and serine tissue concentrations correlated with dipeptide concentrations, when the amino acids were present at the C-but not at the N-terminus. Conclusion: Our multi-dipeptide quantification approach demonstrates organ-specific dipeptide distribution. This method allows us to understand more about the dipeptide metabolism in disease or in healthy state.
Wissenschaftlicher Artikel
Scientific Article
ESC Heart Fail., DOI: 10.1002/ehf2.13607 (2021)
AIMS: Acute cellular rejection (ACR) following heart transplantation (HTX) is associated with long-term graft loss and increased mortality. Disturbed mitochondrial bioenergetics have been identified as pathophysiological drivers in heart failure, but their role in ACR remains unclear. We aimed to prove functional disturbances of myocardial bioenergetics in human heart transplant recipients with mild ACR by assessing myocardial mitochondrial respiration using high-resolution respirometry, digital image analysis of myocardial inflammatory cell infiltration, and clinical assessment of HTX patients. We hypothesized that (i) mild ACR is associated with impaired myocardial mitochondrial respiration and (ii) myocardial inflammation, systemic oxidative stress, and myocardial oedema relate to impaired mitochondrial respiration and myocardial dysfunction. METHODS AND RESULTS: We classified 35 HTX recipients undergoing endomyocardial biopsy according International Society for Heart and Lung Transplantation criteria to have no (0R) or mild (1R) ACR. Additionally, we quantified immune cell infiltration by immunohistochemistry and digital image analysis. We analysed mitochondrial substrate utilization in myocardial fibres by high-resolution respirometry and performed cardiovascular magnetic resonance (CMR). ACR (1R) was diagnosed in 12 patients (34%), while the remaining 23 patients revealed no signs of ACR (0R). Underlying cardiomyopathies (dilated cardiomyopathy 50% vs. 65%; P = 0.77), comorbidities (type 2 diabetes mellitus: 50% vs. 35%, P = 0.57; chronic kidney disease stage 5: 8% vs. 9%, P > 0.99; arterial hypertension: 59% vs. 30%, P = 0.35), medications (tacrolimus: 100% vs. 91%, P = 0.54; mycophenolate mofetil: 92% vs. 91%, P > 0.99; prednisolone: 92% vs. 96%, P > 0.99) and time post-transplantation (21.5 ± 26.0 months vs. 29.4 ± 26.4 months, P = 0.40) were similar between groups. Mitochondrial respiration was reduced by 40% in ACR (1R) compared with ACR (0R) (77.8 ± 23.0 vs. 128.0 ± 33.0; P < 0.0001). Quantitative assessment of myocardial CD3+ -lymphocyte infiltration identified ACR (1R) with a cut-off of >14 CD3+ -lymphocytes/mm2 (100% sensitivity, 82% specificity; P < 0.0001). Myocardial CD3+ infiltration (r = -0.41, P < 0.05), systemic oxidative stress (thiobarbituric acid reactive substances; r = -0.42, P < 0.01) and myocardial oedema depicted by global CMR derived T2 time (r = -0.62, P < 0.01) correlated with lower oxidative capacity and overt cardiac dysfunction (global longitudinal strain; r = -0.63, P < 0.01). CONCLUSIONS: Mild ACR with inflammatory cell infiltration associates with impaired mitochondrial bioenergetics in cardiomyocytes. Our findings may help to identify novel checkpoints in cardiac immune metabolism as potential therapeutic targets in post-transplant care.
Wissenschaftlicher Artikel
Scientific Article
Cancers 13:4433 (2021)
Purpose: To evaluate the suitability of psoas and erector spinae muscle proton density fat fraction (PDFF) and fat volume as biomarkers for monitoring cachexia severity in an oncological cohort, and to evaluate regional variances in muscle parameters over time. Methods: In this prospective study, 58 oncological patients were examined by a 3 T MRI receiving between one and five scans. Muscle volume and PDFF were measured, segmentation masks were divided into proximal, middle and distal muscle section. Results: A regional variation of fat distribution in erector spinae muscle at baseline was found (p < 0.01). During follow‐ups significant relative change of muscle parameters was observed. Relative maximum change of erector spinae muscle showed a significant regional variation. Correlation testing with age as a covariate revealed significant correlations for baseline psoas fat volume (r = −0.55, p < 0.01) and baseline psoas PDFF (r = −0.52, p = 0.02) with maximum BMI change during the course of the disease. Conclusion: In erector spinae muscles, a regional variation of fat distribution at baseline and relative maximum change of muscle parameters was observed. Our results indicate that psoas muscle PDFF and fat volume could serve as MRI-determined biomarkers for early risk stratification and disease monitoring regarding progression and severity of weight loss in cancer cachexia.
Wissenschaftlicher Artikel
Scientific Article
Diabetologia, DOI: 10.1007/s00125-021-05557-6 (2021)
Aims/hypothesis: The individual risk of progression of diabetic peripheral neuropathy is difficult to predict for each individual. Mutations in proteins that are responsible for the process of myelination are known to cause neurodegeneration and display alteration in experimental models of diabetic neuropathy. In a prospective observational human pilot study, we investigated myelin-specific circulating mRNA targets, which have been identified in vitro, for their capacity in the diagnosis and prediction of diabetic neuropathy. The most promising candidate was tested against the recently established biomarker of neural damage, neurofilament light chain protein. Methods: Schwann cells were cultured under high-glucose conditions and mRNAs of various myelin-specific genes were screened intra- and extracellularly. Ninety-two participants with type 2 diabetes and 30 control participants were enrolled and evaluated for peripheral neuropathy using neuropathy deficit scores, neuropathy symptom scores and nerve conduction studies as well as quantitative sensory testing at baseline and after 12/24 months of a follow-up period. Magnetic resonance neurography of the sciatic nerve was performed in 37 individuals. Neurofilament light chain protein and four myelin-specific mRNA transcripts derived from in vitro screenings were measured in the serum of all participants. The results were tested for associations with specific neuropathic deficits, fractional anisotropy and the progression of neuropathic deficits at baseline and after 12 and 24 months. Results: In neuronal Schwann cells and human nerve sections, myelin protein zero was identified as the strongest candidate for a biomarker study. Circulating mRNA of myelin protein zero was decreased significantly in participants with diabetic neuropathy (p < 0.001), whereas neurofilament light chain protein showed increased levels in participants with diabetic neuropathy (p < 0.05). Both variables were linked to altered electrophysiology, fractional anisotropy and quantitative sensory testing. In a receiver-operating characteristic curve analysis myelin protein zero improved the diagnostic performance significantly in combination with a standard model (diabetes duration, age, BMI, HbA1c) from an AUC of 0.681 to 0.836 for the detection of diabetic peripheral neuropathy. A follow-up study revealed that increased neurofilament light chain was associated with the development of a hyperalgesic phenotype (p < 0.05), whereas decreased myelin protein zero predicted hypoalgesia (p < 0.001) and progressive loss of nerve function 24 months in advance (HR of 6.519). Conclusions/interpretation: This study introduces a dynamic and non-invasive assessment strategy for the underlying pathogenesis of diabetic peripheral neuropathy. The diagnosis of axonal degeneration, associated with hyperalgesia, and demyelination, linked to hypoalgesia, could benefit from the usage of neurofilament light chain protein and circulating mRNA of myelin protein zero as potential biomarkers. Graphical abstract: [Figure not available: see fulltext.]
Wissenschaftlicher Artikel
Scientific Article
Life Sci. All. 4:e202101037 (2021)
Various forms of fasting and ketogenic diet have shown promise in (pre-)clinical studies to normalize body weight, improve metabolic health, and protect against disease. Recent studies suggest that β-hydroxybutyrate (βOHB), a fasting-characteristic ketone body, potentially acts as a signaling molecule mediating its beneficial effects via histone deacetylase inhibition. Here, we have investigated whether βOHB, in comparison to the well-established histone deacetylase inhibitor butyrate, influences cellular differentiation and gene expression. In various cell lines and primary cell types, millimolar concentrations of βOHB did not alter differentiation in vitro, as determined by gene expression and histological assessment, whereas equimolar concentrations of butyrate consistently impaired differentiation. RNA sequencing revealed that unlike butyrate, βOHB minimally impacted gene expression in primary adipocytes, macrophages, and hepatocytes. However, in myocytes, βOHB up-regulated genes involved in the TCA cycle and oxidative phosphorylation, while down-regulating genes belonging to cytokine and chemokine signal transduction. Overall, our data do not support the notion that βOHB serves as a powerful signaling molecule regulating gene expression but suggest that βOHB may act as a niche signaling molecule in myocytes.
Wissenschaftlicher Artikel
Scientific Article
STAR Protoc. 2:100700 (2021)
With the advancement of laser-based microscopy tools, it is now possible to explore mechano-kinetic processes occurring inside the cell. Here, we describe the advanced protocol for studying the DNA repair kinetics in real time using the laser to induce the DNA damage. This protocol can be used for inducing, testing, and studying the repair mechanisms associated with DNA double-strand breaks, interstrand cross-link repair, and single-strand break repair. For complete details on the use and execution of this protocol, please refer to Kumar et al. (2017, 2020).
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Scientific Article
J. Cachexia Sarcopenia Muscle, DOI: 10.1002/jcsm.12758 (2021)
BACKGROUND: Cancer cachexia (CCx) is a multifactorial wasting disorder characterized by involuntary loss of body weight that affects many cancer patients and implies a poor prognosis, reducing both tolerance to and efficiency of anticancer therapies. Actual challenges in management of CCx remain in the identification of tumour-derived and host-derived mediators involved in systemic inflammation and tissue wasting and in the discovery of biomarkers that would allow for an earlier and personalized care of cancer patients. The aim of this study was to identify new markers of CCx across different species and tumour entities. METHODS: Quantitative secretome analysis was performed to identify specific factors characteristic of cachexia-inducing cancer cell lines. To establish the subsequently identified phospholipase PLA2G7 as a marker of CCx, plasma PLA2G7 activity and/or protein levels were measured in well-established mouse models of CCx and in different cohorts of weight-stable and weight-losing cancer patients with different tumour entities. Genetic PLA2G7 knock-down in tumours and pharmacological treatment using the well-studied PLA2G7 inhibitor darapladib were performed to assess its implication in the pathogenesis of CCx in C26 tumour-bearing mice. RESULTS: High expression and secretion of PLA2G7 were hallmarks of cachexia-inducing cancer cell lines. Circulating PLA2G7 activity was increased in different mouse models of CCx with various tumour entities and was associated with the severity of body wasting. Circulating PLA2G7 levels gradually rose during cachexia development. Genetic PLA2G7 knock-down in C26 tumours only partially reduced plasma PLA2G7 levels, suggesting that the host is also an important contributor. Chronic treatment with darapladib was not sufficient to counteract inflammation and tissue wasting despite a strong inhibition of the circulating PLA2G7 activity. Importantly, PLA2G7 levels were also increased in colorectal and pancreatic cancer patients with CCx. CONCLUSIONS: Overall, our data show that despite no immediate pathogenic role, at least when targeted as a single entity, PLA2G7 is a consistent marker of CCx in both mice and humans. The early increase in circulating PLA2G7 levels in pre-cachectic mice supports future prospective studies to assess its potential as biomarker for cancer patients.
Wissenschaftlicher Artikel
Scientific Article
Nat. Commun. 12:5068 (2021)
p53 regulates several signaling pathways to maintain the metabolic homeostasis of cells and modulates the cellular response to stress. Deficiency or excess of nutrients causes cellular metabolic stress, and we hypothesized that p53 could be linked to glucose maintenance. We show here that upon starvation hepatic p53 is stabilized by O-GlcNAcylation and plays an essential role in the physiological regulation of glucose homeostasis. More specifically, p53 binds to PCK1 promoter and regulates its transcriptional activation, thereby controlling hepatic glucose production. Mice lacking p53 in the liver show a reduced gluconeogenic response during calorie restriction. Glucagon, adrenaline and glucocorticoids augment protein levels of p53, and administration of these hormones to p53 deficient human hepatocytes and to liver-specific p53 deficient mice fails to increase glucose levels. Moreover, insulin decreases p53 levels, and over-expression of p53 impairs insulin sensitivity. Finally, protein levels of p53, as well as genes responsible of O-GlcNAcylation are elevated in the liver of type 2 diabetic patients and positively correlate with glucose and HOMA-IR. Overall these results indicate that the O-GlcNAcylation of p53 plays an unsuspected key role regulating in vivo glucose homeostasis.
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Scientific Article
Diabetes 70, 2785-2795:2785-2795 (2021)
Lifestyle intervention (LI) can prevent type 2 diabetes, but response to LI varies depending on risk subphenotypes. We tested if prediabetic individuals with low risk benefit from conventional LI and individuals with high risk benefit from an intensification of LI in a multi-center randomized controlled intervention over 12 months with 2 years follow up. 1105 prediabetic individuals based on ADA glucose criteria were stratified into a high- and low-risk phenotype, based on previously described thresholds of insulin secretion, insulin sensitivity and liver fat content. Low-risk individuals were randomly assigned to conventional LI according to the DPP protocol or control (1:1), high-risk individuals to conventional or intensified LI with doubling of required exercise (1:1). A total of 908 (82%) participants completed the study. In high-risk individuals, the difference between conventional and intensified LI in post-challenge glucose change was -0.29 mmol/l [CI:-0.54;-0.04], p=0.025. Liver fat (-1.34 percentage points [CI:-2.17;-0.50], p=0.002) and cardiovascular risk (-1.82[CI:-3.13-0.50],p=0.007) underwent larger reductions with intensified than with conventional LI. During a follow up of 3 years, intensified compared to conventional LI had a higher probability to normalize glucose tolerance (p=0.008). In conclusion, it is possible in high-risk individuals with prediabetes to improve glycemic and cardiometabolic outcomes by intensification of LI. Individualized, risk-phenotype-based LI may be beneficial for the prevention of diabetes.
Wissenschaftlicher Artikel
Scientific Article
Int. J. Mol. Sci. 22:7958 (2021)
Biological aging research is expected to reveal modifiable molecular mechanisms that can be harnessed to slow or possibly reverse unhealthy trajectories. However, there is first an urgent need to define consensus molecular markers of healthy and unhealthy aging. Established aging hallmarks are all linked to metabolism, and a ‘rewired’ metabolic circuitry has been shown to accelerate or delay biological aging. To identify metabolic signatures distinguishing healthy from unhealthy aging trajectories, we performed nontargeted metabolomics on skeletal muscles from 2-month-old and 21-month-old mice, and after dietary and lifestyle interventions known to impact biological aging. We hypothesized that common metabolic signatures would highlight specific pathways and processes promoting healthy aging, while revealing the molecular underpinnings of unhealthy aging. Here, we report 50 metabolites that commonly distinguished aging trajectories in all cohorts, including 18 commonly reduced under unhealthy aging and 32 increased. We stratified these metabolites according to known relationships with various aging hallmarks and found the greatest associations with oxidative stress and nutrient sensing. Collectively, our data suggest interventions aimed at maintaining skeletal muscle arginine and lysine may be useful therapeutic strategies to minimize biological aging and maintain skeletal muscle health, function, and regenerative capacity in old age.
Wissenschaftlicher Artikel
Scientific Article
Adv. Sci., e2100275 (2021)
Type 2 diabetes is a metabolic, chronic disorder characterized by insulin resistance and elevated blood glucose levels. Although a large drug portfolio exists to keep the blood glucose levels under control, these medications are not without side effects. More importantly, once diagnosed diabetes is rarely reversible. Dysfunctions in the kidney, retina, cardiovascular system, neurons, and liver represent the common complications of diabetes, which again lack effective therapies that can reverse organ injury. Overall, the molecular mechanisms of how type 2 diabetes develops and leads to irreparable organ damage remain elusive. This review particularly focuses on novel targets that may play role in pathogenesis of type 2 diabetes. Further research on these targets may eventually pave the way to novel therapies for the treatment—or even the prevention—of type 2 diabetes along with its complications.
Review
Review
Cell Metab. 33, 1685-1700.e9 (2021)
Liver fibrosis is a strong predictor of long-term mortality in individuals with metabolic-associated fatty liver disease; yet, the mechanisms underlying the progression from the comparatively benign fatty liver state to advanced non-alcoholic steatohepatitis (NASH) and liver fibrosis are incompletely understood. Using cell-type-resolved genomics, we show that comprehensive alterations in hepatocyte genomic and transcriptional settings during NASH progression, led to a loss of hepatocyte identity. The hepatocyte reprogramming was under tight cooperative control of a network of fibrosis-activated transcription factors, as exemplified by the transcription factor Elf-3 (ELF3) and zinc finger protein GLIS2 (GLIS2). Indeed, ELF3- and GLIS2-controlled fibrosis-dependent hepatokine genes targeting disease-associated hepatic stellate cell gene programs. Thus, interconnected transcription factor networks not only promoted hepatocyte dysfunction but also directed the intra-hepatic crosstalk necessary for NASH and fibrosis progression, implying that molecular "hub-centered" targeting strategies are superior to existing mono-target approaches as currently used in NASH therapy.
Wissenschaftlicher Artikel
Scientific Article
Adv. Sci., DOI: 10.1002/advs.202101281:e2101281 (2021)
Increased acrolein (ACR), a toxic metabolite derived from energy consumption, is associated with diabetes and its complications. However, the molecular mechanisms are mostly unknown, and a suitable animal model with internal increased ACR does not exist for in vivo studying so far. Several enzyme systems are responsible for acrolein detoxification, such as Aldehyde Dehydrogenase (ALDH), Aldo-Keto Reductase (AKR), and Glutathione S-Transferase (GST). To evaluate the function of ACR in glucose homeostasis and diabetes, akr1a1a-/- zebrafish mutants are generated using CRISPR/Cas9 technology. Accumulated endogenous acrolein is confirmed in akr1a1a-/- larvae and livers of adults. Moreover, a series of experiments are performed regarding organic alterations, the glucose homeostasis, transcriptome, and metabolomics in Tg(fli1:EGFP) zebrafish. Akr1a1a-/- larvae display impaired glucose homeostasis and angiogenic retina hyaloid vasculature, which are caused by reduced acrolein detoxification ability and increased internal ACR concentration. The effects of acrolein on hyaloid vasculature can be reversed by acrolein-scavenger l-carnosine treatment. In adult akr1a1a-/- mutants, impaired glucose tolerance accompanied by angiogenic retina vessels and glomerular basement membrane thickening, consistent with an early pathological appearance in diabetic retinopathy and nephropathy, are observed. Thus, the data strongly suggest impaired ACR detoxification and elevated ACR concentration as biomarkers and inducers for diabetes and diabetic complications.
Wissenschaftlicher Artikel
Scientific Article
Cancers 13:3097 (2021)
Invasive nonfunctioning pituitary tumors (NFPTs) are non-resectable neoplasms associated with frequent relapse and significant comorbidities. Current treatments, including somatostatin receptor 2 (SSTR2)-directed somatostatin analogs (SSAs), often fail against NFPTs. Thus, identifying effective therapies is clinically relevant. As NFPTs express SSTR3 at high levels, pasireotide, a multireceptor-targeted SSA, might be beneficial. Here we evaluated pasireotide in the only representative model of spontaneous NFPTs (MENX rats) in vivo. Octreotide long-acting release (LAR), pasireotide LAR, or placebo, were administered to age-matched, tumor-bearing MENX rats of both sexes for 28 d or 56 d. Longitudinal high-resolution magnetic resonance imaging monitored tumor growth. While tumors in placebo-treated rats increased in volume over time, PTs in drug-treated rats displayed significant growth suppression, and occasional tumor shrinkage. Pasireotide elicited stronger growth inhibition. Radiological responses correlated with tumors’ proliferation rates. Both SSAs, but especially pasireotide, were more effective in female vs. male rats. Basal Sstr3 expression was significantly higher in the former group. It is noteworthy that female human NFPTs patients also have a trend towards higher SSTR3 expression. Altogether, our studies provide the rationale for testing pasireotide in patients with residual/recurrent NFPTs. If confirmed, the sex-related SSTR3 expression might be used as criteria to stratify NFPTs patients for treatment with pasireotide.
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Scientific Article
Cancers 13:2843 (2021)
Small cell lung carcinoma (SCLC) is a highly aggressive malignancy with a very high mortality rate. A prominent part of this is because these carcinomas are refractory to chemotherapies, such as etoposide or cisplatin, making effective treatment almost impossible. Here, we report that elevated expression of the RAGE variant-V in SCLC promotes homology-directed DNA DSBs repair when challenged with anti-cancer drugs. This variant exclusively localizes to the nucleus, interacts with members of the double-strand break (DSB) repair machinery and thus promotes the recruitment of DSBs repair factors at the site of damage. Increased expression of this variant thus, promotes timely DNA repair. Congruently, the tumor cells expressing high levels of variant-V can tolerate chemotherapeutic drug treatment better than the RAGE depleted cells. Our findings reveal a yet undisclosed role of the RAGE variant-V in the homology-directed DNA repair. This variant thus can be a potential target to be considered for future therapeutic approaches in advanced SSLC.
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Scientific Article
Cell Death Dis. 12:516 (2021)
Bone marrow-derived human mesenchymal stem cells (hMSCs) are recruited to damaged or inflamed tissues where they contribute to tissue repair. This multi-step process involves chemokine-directed invasion of hMSCs and on-site release of factors that influence target cells or tumor tissues. However, the underlying molecular mechanisms are largely unclear. Previously, we described that microRNA let-7f controls hMSC differentiation. Here, we investigated the role of let-7f in chemotactic invasion and paracrine anti-tumor effects. Incubation with stromal cell-derived factor-1α (SDF-1α) or inflammatory cytokines upregulated let-7f expression in hMSCs. Transfection of hMSCs with let-7f mimics enhanced CXCR4-dependent invasion by augmentation of pericellular proteolysis and release of matrix metalloproteinase-9. Hypoxia-induced stabilization of the hypoxia-inducible factor 1 alpha in hMSCs promoted cell invasion via let-7f and activation of autophagy. Dependent on its endogenous level, let-7f facilitated hMSC motility and invasion through regulation of the autophagic flux in these cells. In addition, secreted let-7f encapsulated in exosomes was increased upon upregulation of endogenous let-7f by treatment of the cells with SDF-1α, hypoxia, or induction of autophagy. In recipient 4T1 tumor cells, hMSC-derived exosomal let-7f attenuated proliferation and invasion. Moreover, implantation of 3D spheroids composed of hMSCs and 4T1 cells into a breast cancer mouse model demonstrated that hMSCs overexpressing let-7f inhibited tumor growth in vivo. Our findings provide evidence that let-7f is pivotal in the regulation of hMSC invasion in response to inflammation and hypoxia, suggesting that exosomal let-7f exhibits paracrine anti-tumor effects.
Wissenschaftlicher Artikel
Scientific Article
STAR Protoc. 2:100609 (2021)
Quantifying differential genome occupancy by chromatin immunoprecipitation (ChIP) remains challenging due to variation in chromatin fragmentation, immunoprecipitation efficiencies, and intertube variability. In this protocol, we add heterologous spike-ins from Drosophila chromatin as an internal control to the mice chromatin before immunoprecipitation to normalize for technical variation in ChIP-qPCR or ChIP-seq. The choice of spike-in depends on the evolutionary conservation of the protein of interest and the antibody used. For complete details on the use and execution of this protocol, please refer to Greulich et al. (2021).
Wissenschaftlicher Artikel
Scientific Article
Diabetes akt. 19, 82-85 (2021)
Diabetes kann zu verschiedenen schwerwiegenden Komplikationen führen wie
kardiovaskuläre Komorbiditäten, Neuropathie, Retinopathie,
Nephropathie, nicht-alkoholische Fettlebererkrankungen (NAFLD) und auch
Krebs. Um solche Folgen künftig vermeiden bzw. hinauszögern zu können,
gilt es zu erkennen, welche Patienten ein besonders hohes Risiko für
Komplikationen haben. Ziel des Forschungsschwerpunkts „Folgeerkrankungen
des Diabetes“ ist es, neue Wege zur Prävention, zur verbesserten
Behandlung oder sogar zur Heilung von Folgeerkrankungen von Typ-1- und
Typ-2-Diabetes zu erforschen. Die DZD-Forschenden vermuten, dass häufige
diabetische Langzeitkomplikationen auf einer dysfunktionalen
Verstoffwechslung von Glukose und Lipiden in den frühen Stadien der
Krankheitsmanifestation beruhen, was zur Bildung toxischer Metabolite
und oxidativem Stress, Carbonyl-Stress und Entzündungsreaktionen führt.
Dies kann wiederum die DNA schädigen und langfristig die Organfunktion
beeinträchtigen.
Wissenschaftlicher Artikel
Scientific Article
Nat. Commun. 12:2999 (2021)
The proper functional interaction between different tissues represents a key component in systemic metabolic control. Indeed, disruption of endocrine inter-tissue communication is a hallmark of severe metabolic dysfunction in obesity and diabetes. Here, we show that the FNDC4-GPR116, liver-white adipose tissue endocrine axis controls glucose homeostasis. We found that the liver primarily controlled the circulating levels of soluble FNDC4 (sFNDC4) and lowering of the hepatokine FNDC4 led to prediabetes in mice. Further, we identified the orphan adhesion GPCR GPR116 as a receptor of sFNDC4 in the white adipose tissue. Upon direct and high affinity binding of sFNDC4 to GPR116, sFNDC4 promoted insulin signaling and insulin-mediated glucose uptake in white adipocytes. Indeed, supplementation with FcsFNDC4 in prediabetic mice improved glucose tolerance and inflammatory markers in a white-adipocyte selective and GPR116-dependent manner. Of note, the sFNDC4-GPR116, liver-adipose tissue axis was dampened in (pre) diabetic human patients. Thus our findings will now allow for harnessing this endocrine circuit for alternative therapeutic strategies in obesity-related pre-diabetes.
Wissenschaftlicher Artikel
Scientific Article
Diabetologia 64, 1850-1865 (2021)
Aims/hypothesis: Adipocytes are critical cornerstones of energy metabolism. While obesity-induced adipocyte dysfunction is associated with insulin resistance and systemic metabolic disturbances, adipogenesis, the formation of new adipocytes and healthy adipose tissue expansion are associated with metabolic benefits. Understanding the molecular mechanisms governing adipogenesis is of great clinical potential to efficiently restore metabolic health in obesity. Here we investigate the role of heart and neural crest derivatives-expressed 2 (HAND2) in adipogenesis. Methods: Human white adipose tissue (WAT) was collected from two cross-sectional studies of 318 and 96 individuals. In vitro, for mechanistic experiments we used primary adipocytes from humans and mice as well as human multipotent adipose-derived stem (hMADS) cells. Gene silencing was performed using siRNA or genetic inactivation in primary adipocytes from loxP and or tamoxifen-inducible Cre-ERT2 mouse models with Cre-encoding mRNA or tamoxifen, respectively. Adipogenesis and adipocyte metabolism were measured by Oil Red O staining, quantitative PCR (qPCR), microarray, glucose uptake assay, western blot and lipolysis assay. A combinatorial RNA sequencing (RNAseq) and ChIP qPCR approach was used to identify target genes regulated by HAND2. In vivo, we created a conditional adipocyte Hand2 deletion mouse model using Cre under control of the Adipoq promoter (Hand2 ) and performed a large panel of metabolic tests. Results: We found that HAND2 is an obesity-linked white adipocyte transcription factor regulated by glucocorticoids that was necessary but insufficient for adipocyte differentiation in vitro. In a large cohort of humans, WAT HAND2 expression was correlated to BMI. The HAND2 gene was enriched in white adipocytes compared with brown, induced early in differentiation and responded to dexamethasone (DEX), a typical glucocorticoid receptor (GR, encoded by NR3C1) agonist. Silencing of NR3C1 in hMADS cells or deletion of GR in a transgenic conditional mouse model results in diminished HAND2 expression, establishing that adipocyte HAND2 is regulated by glucocorticoids via GR in vitro and in vivo. Furthermore, we identified gene clusters indirectly regulated by the GR–HAND2 pathway. Interestingly, silencing of HAND2 impaired adipocyte differentiation in hMADS and primary mouse adipocytes. However, a conditional adipocyte Hand2 deletion mouse model using Cre under control of the Adipoq promoter did not mirror these effects on adipose tissue differentiation, indicating that HAND2 was required at stages prior to Adipoq expression. Conclusions/interpretation: In summary, our study identifies HAND2 as a novel obesity-linked adipocyte transcription factor, highlighting new mechanisms of GR-dependent adipogenesis in humans and mice. Data availability: Array data have been submitted to the GEO database at NCBI (GSE148699). Graphical abstract: [Figure not available: see fulltext.] AdipoqCre
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Scientific Article
Cell Metab. 33, 1155-1170.e10 (2021)
Pathologies of the micro- and macrovascular systems are a hallmark of the metabolic syndrome, which can lead to chronically elevated blood pressure. However, the underlying pathomechanisms involved still need to be clarified. Here, we report that an obesity-associated increase in serum leptin triggers the select expansion of the micro-angioarchitecture in pre-autonomic brain centers that regulate hemodynamic homeostasis. By using a series of cell- and region-specific loss- and gain-of-function models, we show that this pathophysiological process depends on hypothalamic astroglial hypoxia-inducible factor 1α-vascular endothelial growth factor (HIF1α-VEGF) signaling downstream of leptin signaling. Importantly, several distinct models of HIF1α-VEGF pathway disruption in astrocytes are protected not only from obesity-induced hypothalamic angiopathy but also from sympathetic hyperactivity or arterial hypertension. These results suggest that hyperleptinemia promotes obesity-induced hypertension via a HIF1α-VEGF signaling cascade in hypothalamic astrocytes while establishing a novel mechanistic link that connects hypothalamic micro-angioarchitecture with control over systemic blood pressure.
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Scientific Article
Mol. Metab. 51:101235 (2021)
OBJECTIVE: The molecular pathogenesis of late complications associated with type 2 diabetes mellitus (T2DM) is not yet fully understood. While high glucose levels indicated by increased HbA1c only poorly explain disease progression and late complications, a pro-inflammatory status, oxidative stress and reactive metabolites generated by metabolic processes were postulated to be involved. Individuals with metabolic syndrome (MetS) frequently progress to T2DM, whereby 70% of T2DM patients show non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of MetS, and insulin resistance (IR). Epidemiological studies have shown that T2DM and steatosis are associated with alterations in iron metabolism and hepatic iron accumulation. Excess free iron triggers oxidative stress and a switch towards a macrophage pro-inflammatory status. However, so far it remains unclear if hepatic iron accumulation plays a causative role in the generation of IR and T2DM or whether it is merely a manifestation of altered hepatic metabolism. To address this open question, we have generated and characterized a mouse model of T2DM with IR, steatosis and iron overload. METHODS: Leprdb/db mice hallmarked by T2DM, IR and steatosis were crossed with Fpnwt/C326S mice with systemic iron overload to generate Leprdb/db/Fpnwt/C326S mice. The resulting progeny was characterized for major diabetic and iron-related parameters. RESULTS: We show that features associated with T2DM in Leprdb/db mice, such as obesity, steatosis or insulin resistance reduce the degree of tissue iron overload in Fpnwt/C326S mice, suggesting an 'iron resistance' phenotype. By contrast, we observe increased serum iron levels that strongly exceed those in the iron-overloaded Fpnwt/C326S mice. Increased hepatic iron levels induce oxidative stress and lipid peroxidation and aggravate insulin resistance, as indicated by diminished IRS1 phosphorylation and AKT activation. Additionally, in the liver we observe gene response patterns indicative of de novo lipogenesis and increased gluconeogenesis as well as elevated free glucose levels. Finally, we show that iron overload in Leprdb/db/Fpnwt/C326S mice enhances microvascular complications observed in retinopathy, suggesting that iron accumulation can enhance diabetic late complications associated with the liver and the eye. CONCLUSION: Taken together, our data show that iron causes the worsening of symptoms associated with the metabolic syndrome and T2DM. These findings imply that iron depletion strategies together with anti-diabetic drugs may ameliorate insulin resistance and diabetic late complications.
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Scientific Article
Compr. Physiol. 11, 1759-1783 (2021)
Discovered almost simultaneously with insulin, glucagon is a pleiotropic hormone with metabolic action that goes far beyond its classical role to increase blood glucose. Albeit best known for its ability to directly act on the liver to increase de novo glucose production and to inhibit glycogen breakdown, glucagon lowers body weight by decreasing food intake and by increasing metabolic rate. Glucagon further promotes lipolysis and lipid oxidation and has positive chronotropic and inotropic effects in the heart. Interestingly, recent decades have witnessed a remarkable renaissance of glucagon's biology with the acknowledgment that glucagon has pharmacological value beyond its classical use as rescue medication to treat severe hypoglycemia. In this article, we summarize the multifaceted nature of glucagon with a special focus on its hepatic action and discuss the pharmacological potential of either agonizing or antagonizing the glucagon receptor for health and disease.
Wissenschaftlicher Artikel
Scientific Article
Thromb. Haemost. 121, 1464-1475 (2021)
Metabolic complications in diabetic patients are driven by a combination of increased levels of nutrients and the presence of a proinflammatory environment. Methylglyoxal (MG) is a toxic byproduct of catabolism and has been strongly associated with the development of such complications. Macrophages are key mediators of inflammatory processes and their contribution to the development of metabolic complications has been demonstrated. However, a direct link between reactive metabolites and macrophage activation has not been demonstrated yet. Here, we show that acute MG treatment activated components of the p38 MAPK pathway and enhanced glycolysis in primary murine macrophages. MG induced a distinct gene expression profile sharing similarities with classically activated proinflammatory macrophages as well as metabolically activated macrophages usually found in obese patients. Transcriptomic analysis revealed a set of 15 surface markers specifically upregulated in MG-treated macrophages, thereby establishing a new set of targets for diagnostic or therapeutic purposes under high MG conditions, including diabetes. Overall, our study defines a new polarization state of macrophages that may specifically link aberrant macrophage activation to reactive metabolites in diabetes.
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Scientific Article
Front. Neurosci. 15:642589 (2021)
Background: Nerve damage in diabetic neuropathy (DN) is assumed to begin in the distal legs with a subsequent progression to hands and arms at later stages. In contrast, recent studies have found that lower limb nerve lesions in DN predominate at the proximal sciatic nerve and that, in the upper limb, nerve functions can be impaired at early stages of DN. Materials and Methods: In this prospective, single-center cross-sectional study, participants underwent diffusion-weighted 3 Tesla magnetic resonance neurography in order to calculate the sciatic nerve’s fractional anisotropy (FA), a surrogate parameter for structural nerve integrity. Results were correlated with clinical and electrophysiological assessments of the lower limb and an examination of hand function derived from the Purdue Pegboard Test. Results: Overall, 71 patients with diabetes, 11 patients with prediabetes and 25 age-matched control subjects took part in this study. In patients with diabetes, the sciatic nerve’s FA showed positive correlations with tibial and peroneal nerve conduction velocities (r = 0.62; p < 0.001 and r = 0.56; p < 0.001, respectively), and tibial and peroneal nerve compound motor action potentials (r = 0.62; p < 0.001 and r = 0.63; p < 0.001, respectively). Moreover, the sciatic nerve’s FA was correlated with the Pegboard Test results in patients with diabetes (r = 0.52; p < 0.001), prediabetes (r = 0.76; p < 0.001) and in controls (r = 0.79; p = 0.007). Conclusion: This study is the first to show that the sciatic nerve’s FA is a surrogate marker for functional and electrophysiological parameters of both upper and lower limbs in patients with diabetes and prediabetes, suggesting that nerve damage in these patients is not restricted to the level of the symptomatic limbs but rather affects the entire peripheral nervous system.
Wissenschaftlicher Artikel
Scientific Article
Nat. Commun. 12:1588 (2021)
Adipose tissue expansion, as seen in obesity, is often metabolically detrimental causing insulin resistance and the metabolic syndrome. However, white adipose tissue expansion at early ages is essential to establish a functional metabolism. To understand the differences between adolescent and adult adipose tissue expansion, we studied the cellular composition of the stromal vascular fraction of subcutaneous adipose tissue of two and eight weeks old mice using single cell RNA sequencing. We identified a subset of adolescent preadipocytes expressing the mature white adipocyte marker Asc-1 that showed a low ability to differentiate into beige adipocytes compared to Asc-1 negative cells in vitro. Loss of Asc-1 in subcutaneous preadipocytes resulted in spontaneous differentiation of beige adipocytes in vitro and in vivo. Mechanistically, this was mediated by a function of the amino acid transporter ASC-1 specifically in proliferating preadipocytes involving the intracellular accumulation of the ASC-1 cargo D-serine.
Wissenschaftlicher Artikel
Scientific Article
Nat. Rev. Endocrinol. 17, 276-295 (2021)
In mammals, the white adipocyte is a cell type that is specialized for storage of energy (in the form of triacylglycerols) and for energy mobilization (as fatty acids). White adipocyte metabolism confers an essential role to adipose tissue in whole-body homeostasis. Dysfunction in white adipocyte metabolism is a cardinal event in the development of insulin resistance and associated disorders. This Review focuses on our current understanding of lipid and glucose metabolic pathways in the white adipocyte. We survey recent advances in humans on the importance of adipocyte hypertrophy and on the in vivo turnover of adipocytes and stored lipids. At the molecular level, the identification of novel regulators and of the interplay between metabolic pathways explains the fine-tuning between the anabolic and catabolic fates of fatty acids and glucose in different physiological states. We also examine the metabolic alterations involved in the genesis of obesity-associated metabolic disorders, lipodystrophic states, cancers and cancer-associated cachexia. New challenges include defining the heterogeneity of white adipocytes in different anatomical locations throughout the lifespan and investigating the importance of rhythmic processes. Targeting white fat metabolism offers opportunities for improved patient stratification and a wide, yet unexploited, range of therapeutic opportunities.
Review
Review
Cell Rep. 34:108742 (2021)
The Authors Glucocorticoids such as dexamethasone are widely used immunomodulators. Combining proteomics, ChIP-seq, RNA-seq, and genetic loss-of-function studies in murine macrophages, Greulich et al. show that recruitment of the SETD1A/COMPASS complex to cis-regulatory elements by the glucocorticoid receptor mediates some of their anti-inflammatory actions.
Wissenschaftlicher Artikel
Scientific Article
Mol. Metab. 49:101181 (2021)
OBJECTIVE: We aimed to assess the spatiotemporal GLP-1 and GIP receptor signaling, trafficking and recycling dynamics of GIPR mono-agonists, GLP-1R mono-agonists including semaglutide, and GLP-1/GIP dual-agonists MAR709 and tirzepatide. METHODS: Receptor G protein recruitment and internalization/trafficking dynamics were assessed using bioluminescence resonance energy transfer (BRET)-based technology and live cell HILO microscopy. RESULTS: Relative to the native and acylated GLP-1 agonists, MAR709 and tirzepatide show preserved maximal cAMP production despite partial Gαs recruitment paralleled by diminished ligand-induced receptor internalization at both target receptors. Despite MAR709's lower internalization rate, GLP-1R co-localization with Rab11-associated recycling endosomes was not different between MAR709 and GLP-1R specific mono-agonists. CONCLUSIONS: Our data indicate that MAR709 and tirzepatide induce unique spatiotemporal GLP-1 and GIP receptor signaling, trafficking and recycling dynamics relative to the native peptides, semaglutide and matched mono-agonist controls. These findings support the hypothesis that the structure of the GLP-1/GIP dual-agonists confer a biased agonism that, in addition to its influence on intracellular signaling, uniquely modulates receptor trafficking.
Wissenschaftlicher Artikel
Scientific Article
Mol. Metab. 47:101169 (2021)
BACKGROUND: The global rise of metabolic disorders, such as obesity, diabetes type 2 and cardiovascular disease, demands a thorough molecular understanding of the cellular mechanisms that govern health or disease. The endoplasmic reticulum (ER) is a key organelle for cellular function and metabolic adaptation and, therefore, disturbed ER function, "ER stress", is a key feature of metabolic disorders. SCOPE OF REVIEW: As ER stress remains an ill-defined phenomenon, this review provides a general guide to understanding the nature, aetiology and consequences of ER stress in metabolic disorders. We define ER stress by its type of stressor, which is driven by proteotoxicity, lipotoxicity, and/or glucotoxicity. We discuss the implications of ER stress in metabolic disorders by reviewing evidence implicating ER phenotypes and organelle communication, protein quality control, calcium homeostasis, lipid and carbohydrate metabolism, and inflammation as key mechanisms in the development of ER stress and metabolic dysfunction. MAJOR CONCLUSIONS: In mammalian biology, ER is a phenotypically and functionally diverse platform for nutrient sensing, which is critical for cell-type specific metabolic control by e.g. hepatocytes, adipocytes, muscle cells, and neurons. In these cells, ER stress is a distinct, transient state of functional imbalance, which is usually resolved by the activation of adaptive programs such as the unfolded protein response (UPR), ER-associated protein degradation (ERAD), or autophagy. However, challenges to proteostasis also impact lipid and glucose metabolism and vice versa. In the ER, both sensing and adaptive measures are integrated and failure of the ER to adapt leads to aberrant metabolism, organelle dysfunction, insulin resistance, and inflammation. In conclusion, the ER is intricately linked to a wide spectrum of cellular functions and is a critical component in maintaining and restoring metabolic health.
Review
Review
Cell Rep. 34:108624 (2021)
Thermoneutral conditions typical for standard human living environments result in brown adipose tissue (BAT) involution, characterized by decreased mitochondrial mass and increased lipid deposition. Low BAT activity is associated with poor metabolic health, and BAT reactivation may confer therapeutic potential. However, the molecular drivers of this BAT adaptive process in response to thermoneutrality remain enigmatic. Using metabolic and lipidomic approaches, we show that endogenous fatty acid synthesis, regulated by carbohydrate-response element-binding protein (ChREBP), is the central regulator of BAT involution. By transcriptional control of lipogenesis-related enzymes, ChREBP determines the abundance and composition of both storage and membrane lipids known to regulate organelle turnover and function. Notably, ChREBP deficiency and pharmacological inhibition of lipogenesis during thermoneutral adaptation preserved mitochondrial mass and thermogenic capacity of BAT independently of mitochondrial biogenesis. In conclusion, we establish lipogenesis as a potential therapeutic target to prevent loss of BAT thermogenic capacity as seen in adult humans.
Wissenschaftlicher Artikel
Scientific Article
Cancers 13:126 (2021)
BACKGROUND: Pseudohypoxic tumors activate pro-oncogenic pathways typically associated with severe hypoxia even when sufficient oxygen is present, leading to highly aggressive tumors. Prime examples are pseudohypoxic pheochromocytomas and paragangliomas (p-PPGLs), neuroendendocrine tumors currently lacking effective therapy. Previous attempts to generate mouse models for p-PPGLs all failed. Here, we describe that the rat MENX line, carrying a Cdkn1b (p27) frameshift-mutation, spontaneously develops pseudohypoxic pheochromocytoma (p-PCC). METHODS: We compared rat p-PCCs with their cognate human tumors at different levels: histology, immunohistochemistry, catecholamine profiling, electron microscopy, transcriptome and metabolome. The vessel architecture and angiogenic potential of pheochromocytomas (PCCs) was analyzed by light-sheet fluorescence microscopy ex vivo and multi-spectral optoacoustic tomography (MSOT) in vivo. RESULTS: The analysis of tissues at various stages, from hyperplasia to advanced grades, allowed us to correlate tumor characteristics with progression. Pathological changes affecting the mitochrondrial ultrastructure where present already in hyperplasias. Rat PCCs secreted high levels of norepinephrine and dopamine. Transcriptomic and metabolomic analysis revealed changes in oxidative phosphorylation that aggravated over time, leading to an accumulation of the oncometabolite 2-hydroxyglutarate, and to hypermethylation, evident by the loss of the epigenetic mark 5-hmC. While rat PCC xenografts showed high oxygenation, induced by massive neoangiogenesis, rat primary PCC transcriptomes possessed a pseudohypoxic signature of high Hif2a, Vegfa, and low Pnmt expression, thereby clustering with human p-PPGL. CONCLUSION: Endogenous rat PCCs recapitulate key phenotypic features of human p-PPGLs. Thus, MENX rats emerge as the best available animal model of these aggressive tumors. Our study provides evidence of a link between cell cycle dysregulation and pseudohypoxia.
Wissenschaftlicher Artikel
Scientific Article
Nat. Metab. 3, 394–409 (2021)
Both obesity and sarcopenia are frequently associated in ageing, and
together may promote the progression of related conditions such as
diabetes and frailty. However, little is known about the
pathophysiological mechanisms underpinning this association. Here we
uncover dysregulated systemic alanine metabolism and hyper-expression of
the alanine transaminases (ALT) in the liver of obese/diabetic mice and
humans. Hepatocyte-selective silencing of both ALT enzymes revealed a
clear role in systemic alanine clearance which related to glycemic
control. In obese/diabetic mice, not only did silencing both ALT enzymes
retard hyperglycemia, but also reversed skeletal muscle atrophy. This
was due to a rescue of depressed skeletal muscle protein synthesis, with
a liver-skeletal muscle amino acid metabolic crosstalk exemplified by
ex vivo experiments. Mechanistically, chronic liver glucocorticoid and
glucagon signaling driven liver alanine catabolism promoted
hyperglycemia and skeletal muscle wasting. Taken together, here we
reveal an endocrine-hepato-muscular metabolic cycle linking
hyperglycemia and skeletal muscle atrophy in type 2 diabetes.
Wissenschaftlicher Artikel
Scientific Article
Front. Cell Dev. Biol. 9:641410 (2021)
TBL1XR1 gene is associated with multiple developmental disorders presenting several neurological aspects. The relative protein is involved in the modulation of important cellular pathways and master regulators of transcriptional output, including nuclear receptor repressors, Wnt signaling, and MECP2 protein. However, TBL1XR1 mutations (including complete loss of its functions) have not been experimentally studied in a neurological context, leaving a knowledge gap in the mechanisms at the basis of the diseases. Here, we show that Tbl1xr1 knock-out mice exhibit behavioral and neuronal abnormalities. Either the absence of TBL1XR1 or its point mutations interfering with stability/regulation of NCOR complex induced decreased proliferation and increased differentiation in neural progenitors. We suggest that this developmental unbalance is due to a failure in the regulation of the MAPK cascade. Taken together, our results broaden the molecular and functional aftermath of TBL1XR1 deficiency associated with human disorders.
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Scientific Article
Life Sci. All. 4:e202000898 (2021)
Members of the lipocalin protein family serve as biomarkers for kidney disease and acute phase inflammatory reactions, and are under preclinical development for the diagnosis and therapy of allergies. However, none of the lipocalin family members has made the step into clinical development, mostly due to their complex biological activity and the lack of in-depth mechanistic knowledge. Here, we show that the hepatokine lipocalin 13 (LCN13) triggers glucose-dependent insulin secretion and cell proliferation of primary mouse islets. However, inhibition of endogenous LCN13 expression in lean mice did not alter glucose and lipid homeostasis. Enhanced hepatic secretion of LCN13 in either diet-induced or genetic obesity led to no discernible impact on systemic glucose and lipid metabolism, neither in preventive nor therapeutic setting. Of note, loss or forced LCN13 hepatic secretion did not trigger any compensatory regulation of related lipocalin family members. Together, these data are in stark contrast to the suggested gluco-regulatory and therapeutic role of LCN13 in obesity, and imply complex regulatory steps in LCN13 biology at the organismic level mitigating its principal insulinotropic effects.
Wissenschaftlicher Artikel
Scientific Article
Cell Metab. 33, 833-844.e5 (2021)
Uncertainty exists as to whether the glucose-dependent insulinotropic polypeptide receptor (GIPR) should be activated or inhibited for the treatment of obesity. Gipr was recently demonstrated in hypothalamic feeding centers, but the physiological relevance of CNS Gipr remains unknown. Here we show that HFD-fed CNS-Gipr KO mice and humanized (h)GIPR knockin mice with CNS-hGIPR deletion show decreased body weight and improved glucose metabolism. In DIO mice, acute central and peripheral administration of acyl-GIP increases cFos neuronal activity in hypothalamic feeding centers, and this coincides with decreased body weight and food intake and improved glucose handling. Chronic central and peripheral administration of acyl-GIP lowers body weight and food intake in wild-type mice, but shows blunted/absent efficacy in CNS-Gipr KO mice. Also, the superior metabolic effect of GLP-1/GIP co-agonism relative to GLP-1 is extinguished in CNS-Gipr KO mice. Our data hence establish a key role of CNS Gipr for control of energy metabolism.
Wissenschaftlicher Artikel
Scientific Article
EMBO Mol. Med.:e12461 (2021)
By accentuating drug efficacy and impeding resistance mechanisms, combinatorial, multi-agent therapies have emerged as key approaches in the treatment of complex diseases, most notably cancer. Using high-throughput drug screens, we uncovered distinct metabolic vulnerabilities and thereby identified drug combinations synergistically causing a starvation-like lethal catabolic response in tumor cells from different cancer entities. Domperidone, a dopamine receptor antagonist, as well as several tricyclic antidepressants (TCAs), including imipramine, induced cancer cell death in combination with the mitochondrial uncoupler niclosamide ethanolamine (NEN) through activation of the integrated stress response pathway and the catabolic CLEAR network. Using transcriptome and metabolome analyses, we characterized a combinatorial response, mainly driven by the transcription factors CHOP and TFE3, which resulted in cell death through enhanced pyrimidine catabolism as well as reduced pyrimidine synthesis. Remarkably, the drug combinations sensitized human organoid cultures to the standard-of-care chemotherapy paclitaxel. Thus, our combinatorial approach could be clinically implemented into established treatment regimen, which would be further facilitated by the advantages of drug repurposing.
Wissenschaftlicher Artikel
Scientific Article
Nat. Commun. 12:426 (2021)
Painful neuropathy is a frequent complication in diabetes. Proopiomelanocortin (POMC) is an endogenous opioid precursor peptide, which plays a protective role against pain. Here, we report dysfunctional POMC-mediated antinociception in sensory neurons in diabetes. In streptozotocin-induced diabetic mice the Pomc promoter is repressed due to increased binding of NF-kB p50 subunit, leading to a loss in basal POMC level in peripheral nerves. Decreased POMC levels are also observed in peripheral nervous system tissue from diabetic patients. The antinociceptive pathway mediated by POMC is further impaired due to lysosomal degradation of μ-opioid receptor (MOR). Importantly, the neuropathic phenotype of the diabetic mice is rescued upon viral overexpression of POMC and MOR in the sensory ganglia. This study identifies an antinociceptive mechanism in the sensory ganglia that paves a way for a potential therapy for diabetic neuropathic pain.
Wissenschaftlicher Artikel
Scientific Article
J. Steroid Biochem. Mol. Biol. 206:105790 (2021)
17β-Hydroxysteroid dehydrogenase type 2 (17β-HSD2) catalyzes the conversion of highly active estrogens and androgens into their less active forms using NAD+ as cofactor. Substrate and cofactor specificities of 17β-HSD2 have been reported and potent 17β-HSD2 inhibitors have been discovered in a ligand-based approach. However, the molecular basis and the amino acids involved in the enzymatic functionality are poorly understood, as no crystal structure of the membrane-associated 17β-HSD2 exists. The functional properties of only few amino acids are known. The lack of topological information impedes structure-based drug design studies and limits the design of biochemical experiments. The aim of this work was the determination of the 17β-HSD2 topology. For this, the first homology model of 17β-HSD2 in complex with NAD+ and 17β-estradiol was built, using a multi-fragment “patchwork” approach. To confirm the quality of the model, fifteen selected amino acids were exchanged one by one using site directed mutagenesis. The mutants’ functional behavior demonstrated that the generated model was of very good quality and allowed the identification of several key amino acids involved in either ligand or internal structure stabilization. The final model is an optimal basis for further experiments like, for example, lead optimization.
Wissenschaftlicher Artikel
Scientific Article
Diabetes 70, 616-626 (2021)
Type 2 diabetes has become a pandemic and leads to late diabetic complications of organs including kidney and eye. Lowering hyperglycemia is the typical therapeutic goal in clinical medicine. However, hyperglycemia may only be a symptom of diabetes but not the sole cause of late diabetic complications, Instead, other diabetes-related alterations could be causative. Here, we studied the role of CaM Kinase II δ (CaMKIIδ) that is known to be activated through diabetic metabolism. CaMKIIδ is expressed ubiquitously and might therefore affect several different organ systems. We crossed diabetic leptin receptor mutant mice to mice lacking CaMKIIδ globally. Remarkably, CaMKIIδ-deficient diabetic mice did not develop hyperglycemia. As potential underlying mechanisms, we provide evidence for improved insulin sensing with increased glucose transport into skeletal muscle but also reduced hepatic glucose production. Despite normoglycemia, CaMKIIδ-deficient diabetic mice developed the full picture of diabetic nephropathy but diabetic retinopathy was prevented. We also unmasked a retina-specific gene expression signature that might contribute to CaMKII-dependent retinal diabetic complications. These data challenge the clinical concept of normalizing hyperglycemia in diabetes as a causative treatment strategy for late diabetic complications and call for a more detailed analysis of intracellular metabolic signals in different diabetic organs.
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Scientific Article
Prog. Biophys. Mol. Biol. 159, 86-104 (2021)
Aims: After summarizing current concepts for the role of TRPC cation channels in cardiac cells and in processes triggered by mechanical stimuli arising e.g. during pressure overload, we analysed the role of TRPC1 and TRPC4 for background Ca2+ entry (BGCE) and for cardiac pressure overload induced transcriptional remodelling. Methods and results: Mn2+-quench analysis in cardiomyocytes from several Trpc-deficient mice revealed that both TRPC1 and TRPC4 are required for BGCE. Electrically-evoked cell shortening of cardiomyocytes from TRPC1/C4-DKO mice was reduced, whereas parameters of cardiac contractility and relaxation assessed in vivo were unaltered. As pathological cardiac remodelling in mice depends on their genetic background, and the development of cardiac remodelling was found to be reduced in TRPC1/C4-DKO mice on a mixed genetic background, we studied TRPC1/C4-DKO mice on a C57BL6/N genetic background. Cardiac hypertrophy was reduced in those mice after chronic isoproterenol infusion (−51.4%) or after one week of transverse aortic constriction (TAC; −73.0%). This last manoeuvre was preceded by changes in the pressure overload induced transcriptional program as analysed by RNA sequencing. Genes encoding specific collagens, the Mef2 target myomaxin and the gene encoding the mechanosensitive channel Piezo2 were up-regulated after TAC in wild type but not in TRPC1/C4-DKO hearts. Conclusions: Deletion of the TRPC1 and TRPC4 channel proteins protects against development of pathological cardiac hypertrophy independently of the genetic background. To determine if the TRPC1/C4-dependent changes in the pressure overload induced alterations in the transcriptional program causally contribute to cardio-protection needs to be elaborated in future studies.
Wissenschaftlicher Artikel
Scientific Article
2020
Laryngoscope, DOI: 10.1002/lary.29300 (2020)
Objectives/Hypothesis: Injection laryngoplasty of materials for unilateral vocal-fold paralysis has shown various results regarding the long-term stability of the injected material. We evaluated a fibrin-gel based cell suspension with autologous chondrocytes in-vitro and in-vivo as long-term-stable vocal-fold augmentation material in an animal model. Study Design: This study compises an in vitro cell-culture part as well as an in vivo animal study with New Zealand White Rabbits. Methods: In in-vitro experiments, auricular chondrocytes harvested from 24 New Zealand White Rabbits cadavers were cultivated in pellet cultures to evaluate cartilage formation for 4 weeks using long-term-stable fibrin gel as carrier. Injectability and injection volume for the laryngoplasty was determined in-vitro using harvested cadaveric larynxes. In-vivo 24 Rabbits were biopsied for elastic cartilage of the ear and autologous P1 cells were injected lateral of one vocal cord into the paraglottic space suspended in a long-term-stable fibrin gel. Histologic evaluation was performed after 2, 4, 12, and 24 weeks. Results: During 12-week pellet culture, we found extracellular matrix formation and weight-stable cartilage of mature appearance. In-vivo, mature cartilage was found in two larynxes (n = 6) at 4 weeks, in four (n = 6) at 12 weeks, and in five (n = 6) at 24 weeks mostly located in the paraglottic space and sometimes with spurs into the vocalis muscle. Surrounding tissue was often infiltrated with inflammatory cells. Material tended to dislocate through the cricothyroid space into the extraglottic surrounding tissue. Conclusions: A cell-based approach with chondrocytes for permanent vocal-fold augmentation has not previously been reported. We have achieved the formation of structurally mature cartilage in the paraglottic space, but this is accompanied by difficulties with dislocated material, deformation of the augmentation, and inflammation. Level of Evidence: N/A Laryngoscope, 2020.
Wissenschaftlicher Artikel
Scientific Article
Front. Immunol. 11:574046 (2020)
The pseudokinase TRIB1 controls cell function in a range of contexts, by regulating MAP kinase activation and mediating protein degradation via the COP1 ubiquitin ligase. TRIB1 regulates polarization of macrophages and dysregulated Trib1 expression in murine models has been shown to alter atherosclerosis burden and adipose homeostasis. Recently, TRIB1 has also been implicated in the pathogenesis of prostate cancer, where it is often overexpressed, even in the absence of genetic amplification. Well described TRIB1 effectors include MAP kinases and C/EBP transcription factors, both in immune cells and in carcinogenesis. However, the mechanisms that regulate TRIB1 itself remain elusive. Here, we show that the long and conserved 3’untranslated region (3’UTR) of TRIB1 is targeted by miRNAs in macrophage and prostate cancer models. By using a systematic in silico analysis, we identified multiple “high confidence” miRNAs potentially binding to the 3’UTR of TRIB1 and report that miR-101-3p and miR-132-3p are direct regulators of TRIB1 expression and function. Binding of miR-101-3p and miR-132-3p to the 3’UTR of TRIB1 mRNA leads to an increased transcription and secretion of interleukin-8. Our data demonstrate that modulation of TRIB1 by miRNAs alters the inflammatory profile of both human macrophages and prostate cancer cells.
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Scientific Article
Redox Biol. 37:101723 (2020)
Increased methylglyoxal (MG) formation is associated with diabetes and its complications. In zebrafish, knockout of the main MG detoxifying system Glyoxalase 1, led to limited MG elevation but significantly elevated aldehyde dehydrogenases (ALDH) activity and aldh3a1 expression, suggesting the compensatory role of Aldh3a1 in diabetes. To evaluate the function of Aldh3a1 in glucose homeostasis and diabetes, aldh3a1(-/-) zebrafish mutants were generated using CRISPR-Cas9. Vasculature and pancreas morphology were analysed by zebrafish transgenic reporter lines. Corresponding reactive carbonyl species (RCS), glucose, transcriptome and metabolomics screenings were performed and ALDH activity was measured for further verification. Aldh3a1(-/-) zebrafish larvae displayed retinal vasodilatory alterations, impaired glucose homeostasis, which can be aggravated via pdx1 silencing induced hyperglycaemia. Unexpectedly, MG was not altered, but 4-hydroxynonenal (4-HNE), another prominent lipid peroxidation RCS exhibited high affinity with Aldh3a1, was increased in aldh3a1 mutants. 4-HNE was responsible for the retinal phenotype via pancreas disruption induced hyperglycaemia and can be rescued via L-Carnosine treatment. Furthermore, in type 2 diabetic patients, serum 4-HNE was increased and correlated with disease progression. Thus, our data suggest impaired 4-HNE detoxification and elevated 4-HNE concentration as biomarkers but also the possible inducers for diabetes, from genetic susceptibility to the pathological progression.
Wissenschaftlicher Artikel
Scientific Article
iScience 23:101763 (2020)
Regulation of glucose homeostasis is a fundamental process to maintain blood glucose at a physiological level, and its dysregulation is associated with the development of several metabolic diseases. Here, we report on a zebrafish mutant for Aldo-keto-reductase 1a1b (akr1a1b) as a regulator of gluconeogenesis. Adult akr1a1b
-/-
mutant zebrafish developed fasting hypoglycemia, which was caused by inhibiting phosphoenolpyruvate carboxykinase (PEPCK) expression as rate-limiting enzyme of gluconeogenesis. Subsequently, glucogenic amino acid glutamate as substrate for gluconeogenesis accumulated in the kidneys, but not in livers, and induced structural and functional pronephros alterations in 48-hpf akr1a1b
-/-
embryos. Akr1a1b
-/-
mutants displayed increased nitrosative stress as indicated by increased nitrotyrosine, and increased protein-S-nitrosylation. Inhibition of nitrosative stress using the NO synthase inhibitor L-NAME prevented kidney damage and normalized PEPCK expression in akr1a1b
-/-
mutants. Thus, the data have identified Akr1a1b as a regulator of gluconeogenesis in zebrafish and thereby controlling glucose homeostasis.
Wissenschaftlicher Artikel
Scientific Article
Front. Neurosci. 14:570744 (2020)
Diabetic neuropathy (DPN) is one of the most severe and yet most poorly understood complications of diabetes mellitus.In vivoimaging of dorsal root ganglia (DRG), a key structure for the understanding of DPN, has been restricted to animal studies. These have shown a correlation of decreased DRG volume with neuropathic symptom severity. Our objective was to investigate correlations of DRG morphology and signal characteristics at 3 Tesla (3T) magnetic resonance neurography (MRN) with clinical and serological data in diabetic patients with and without DPN. In this cross-sectional study, participants underwent 3T MRN of both L5 DRG using an isotropic 3D T2-weighted, fat-suppressed sequence with subsequent segmentation of DRG volume and analysis of normalized signal properties. Overall, 55 diabetes patients (66 +/- 9 years; 32 men; 30 with DPN) took part in this study. DRG volume was smaller in patients with severe DPN when compared to patients with mild or moderate DPN (134.7 +/- 21.86 vs 170.1 +/- 49.22;p= 0.040). In DPN patients, DRG volume was negatively correlated with the neuropathy disability score (r= -0.43; 95%CI = -0.66 to -0.14;p= 0.02), a measure of neuropathy severity. DRG volume showed negative correlations with triglycerides (r= -0.40; 95%CI = -0.57 to -0.19;p= 0.006), and LDL cholesterol (r= -0.33; 95%CI = -0.51 to -0.11;p= 0.04). There was a strong positive correlation of normalized MR signal intensity (SI) with the neuropathy symptom score in the subgroup of patients with painful DPN (r= 0.80; 95%CI = 0.46 to 0.93;p= 0.005). DRG SI was positively correlated with HbA1c levels (r= 0.30; 95%CI = 0.09 to 0.50;p= 0.03) and the triglyceride/HDL ratio (r= 0.40; 95%CI = 0.19 to 0.57;p= 0.007). In this firstin vivostudy, we found DRG morphological degeneration and signal increase in correlation with neuropathy severity. This elucidates the potential importance of MR-based DRG assessments in studying structural and functional changes in DPN.
Wissenschaftlicher Artikel
Scientific Article
Antioxidants 9:939 (2020)
The glyoxalase system was discovered over a hundred years ago and since then it has been claimed to provide the role of an indispensable enzyme system in order to protect cells from a toxic byproduct of glycolysis. This review gives a broad overview of what has been postulated in the last 30 years of glyoxalase research, but within this context it also challenges the concept that the glyoxalase system is an exclusive tool of detoxification and that its substrate, methylglyoxal, is solely a detrimental burden for every living cell due to its toxicity. An overview of consequences of a complete loss of the glyoxalase system in various model organisms is presented with an emphasis on the role of alternative detoxification pathways of methylglyoxal. Furthermore, this review focuses on the overlooked posttranslational modification of Glyoxalase 1 and its possible implications for cellular maintenance under various (patho-)physiological conditions. As a final note, an intriguing point of view for the substrate methylglyoxal is offered, the concept of methylglyoxal (MG)-mediated hormesis.
Review
Review
J. Cachexia Sarcopenia Muscle 11, 1459-1475 (2020)
Background Cancer cachexia (CCx) is a multifactorial energy-wasting syndrome reducing the efficiency of anti-cancer therapies, quality of life, and survival of cancer patients. In the past years, most studies focused on the identification of tumour and host-derived proteins contributing to CCx. However, there is still a lack of studies addressing the changes in bioactive lipids. The aim of this study was to identify specific lipid species as a hallmark of CCx by performing a broad range lipid analysis of plasma from well-established CCx mouse models as well as cachectic and weight stable cancer patients. Methods Plasma from non-cachectic (PBS-injected mice, NC26 tumour-bearing mice), pre-cachectic and cachectic mice (C26 and LLC tumour-bearing mice, Apc(Min/+)mutant mice), and plasma from weight stable and cachectic patients with gastrointestinal cancer, were analysed using the Lipidyzer (TM) platform. In total, 13 lipid classes and more than 1100 lipid species, including sphingolipids, neutral and polar glycerolipids, were covered by the analysis. Correlation analysis between specific lipid species and readouts of CCx were performed. Lipidomics data were confirmed by gene expression analysis of metabolic organs to analyse enzymes involved in sphingolipid synthesis and degradation. Results A decrease in several lysophosphatidylcholine (LPC) species and an increase in numerous sphingolipids including sphingomyelins (SMs), ceramides (CERs), hexosyl-ceramides (HCERs) and lactosyl-ceramides (LCERs), were mutual features of CCx in both mice and cancer patients. Notably, sphingolipid levels gradually increased during cachexia development. Key enzymes involved in ceramide synthesis were elevated in liver but not in adipose, muscle, or tumour tissues, suggesting that ceramide turnover in the liver is a major contributor to elevated sphingolipid levels in CCx. LPC(16:1), LPC(20:3), SM(16:0), SM(24:1), CER(16:0), CER(24:1), HCER(16:0), and HCER(24:1) were the most consistently affected lipid species between mice and humans and correlated negatively (LPCs) or positively (SMs, CERs and HCERs) with the severity of body weight loss. Conclusions High levels of sphingolipids, specifically ceramides and modified ceramides, are a defining feature of murine and human CCx and may contribute to tissue wasting and skeletal muscle atrophy through the inhibition of anabolic signals. The progressive increase in sphingolipids during cachexia development supports their potential as early biomarkers for CCx.
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Scientific Article
Curr. Opin. Pharmacol. 53, 101-116 (2020)
Obesity and cancer cachexia are diseases at opposite ends of the BMI. However, despite the apparent dichotomy, these pathologies share some common underlying mechanisms that lead to profound metabolic perturbations. Insulin resistance, adipose tissue lipolysis, skeletal muscle atrophy and systemic inflammation are key players in both diseases. Several strategies for pharmacological treatments have been employed in obesity and cancer cachexia but demonstrated only limited effects. Therefore, there is still a need to develop novel, more effective strategies. In this review we summarize existing therapies and discuss potential novel strategies that could arise by bridging common aspects between obesity and cachexia. We discuss the potential role of macrophage manipulation and the modulation of inflammation by targeting Nuclear Receptors (NRs) as potential novel therapeutic strategies.
Review
Review
Int. J. Cancer 147, 3523-3538 (2020)
Pituitary adenomas (PAs) are intracranial tumors associated with significant morbidity due to hormonal dysregulation, mass effects and have a heavy treatment burden. Growth hormone (GH)-secreting PAs (somatotropinomas) cause acromegaly-gigantism. Genetic forms of somatotropinomas due to germlineAIPmutations (AIPmut+) have an early onset and are aggressive and resistant to treatment with somatostatin analogs (SSAs), including octreotide. The molecular underpinnings of these clinical features remain unclear. We investigated the role of miRNA dysregulation inAIPmut+ vsAIPmut- PA samples by array analysis. miR-34a and miR-145 were highly expressed inAIPmut+ vsAIPmut- somatotropinomas. Ectopic expression ofAIPmut (p.R271W) inAip(-/-)mouse embryonic fibroblasts (MEFs) upregulated miR-34a and miR-145, establishing a causal link betweenAIPmut and miRNA expression. In PA cells (GH3), miR-34a overexpression promoted proliferation, clonogenicity, migration and suppressed apoptosis, whereas miR-145 moderately affected proliferation and apoptosis. Moreover, high miR-34a expression increased intracellular cAMP, a critical mitogenic factor in PAs. Crucially, high miR-34a expression significantly blunted octreotide-mediated GH inhibition and antiproliferative effects. miR-34a directly targetsGnai2encoding G alpha i2, a G protein subunit inhibiting cAMP production. Accordingly, G alpha i2 levels were significantly lower inAIPmut+ vsAIPmut- PA. Taken together, somatotropinomas withAIPmutations overexpress miR-34a, which in turn downregulates G alpha i2 expression, increases cAMP concentration and ultimately promotes cell growth. Upregulation of miR-34a also impairs the hormonal and antiproliferative response of PA cells to octreotide. Thus, miR-34a is a novel downstream target of mutantAIPthat promotes a cellular phenotype mirroring the aggressive clinical features ofAIPmut+ acromegaly.
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Scientific Article
FASEB J. 34, 12946-12962 (2020)
Although we have shown that catecholamines suppress the activity of the Ubiquitin-Proteasome System (UPS) and atrophy-related genes expression through a cAMP-dependent manner in skeletal muscle from rodents, the underlying mechanisms remain unclear. Here, we report that a single injection of norepinephrine (NE; 1 mg kg(-1); s.c) attenuated the fasting-induced up-regulation of FoxO-target genes in tibialis anterior (TA) muscles by the stimulation of PKA/CREB and Akt/FoxO1 signaling pathways. In addition, muscle-specific activation of PKA by the overexpression of PKA catalytic subunit (PKAcat) suppressed FoxO reporter activity induced by (1) a wild-type; (2) a non-phosphorylatable; (3) a non-phosphorylatable and non-acetylatable forms of FoxO1 and FoxO3; (4) downregulation of FoxO protein content, and probably by (5) PGC-1 alpha up-regulation. Consistently, the overexpression of the PKAcat inhibitor (PKI) up-regulated FoxO activity and the content of Atrogin-1 and MuRF1, as well as induced muscle fiber atrophy, the latter effect being prevented by the overexpression of a dominant negative (d. n.) form of FoxO (d.n.FoxO). The sustained overexpression of PKAcat induced fiber-type transition toward a smaller, slower, and more oxidative phenotype and improved muscle resistance to fatigue. Taken together, our data provide the first evidence that endogenous PKA activity is required to restrain the basal activity of FoxO and physiologically important to maintain skeletal muscle mass.
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Scientific Article
Nutrients 12:2124 (2020)
The bile acid receptor, TGR5, is a key regulator of glucose homeostasis, but the mechanisms by which TGR5 signaling improves glucose regulation are incompletely defined. In particular, TGR5 has an increasingly appreciated role in liver physiology and pathobiology; however, whether TGR5 signaling within the liver contributes to its glucoregulatory effects is unknown. Therefore, we investigated the role of hepatocyte TGR5 signaling on glucose regulation using a hepatocyte-specific TGR5 knockout mouse model. Hepatocyte-specificTgr5(Hep+/+)andTgr5(Hep-/-)mice were fed a high fat diet (HFD) for 7 weeks and then orally gavaged with three doses of a highly potent, TGR5-specific agonist, Compound 18 (10 mg/kg), or vehicle, over 72 h and underwent an oral glucose tolerance test (OGTT) after the last dose. Herein, we report that TGR5 mRNA and protein is present in mouse hepatocytes. Cumulative food intake, body weight, and adiposity do not differ betweenTgr5(Hep+/+)andTgr5(Hep-/-)mice with or without treatment with Compound 18. However, administration of Compound 18 improves glucose tolerance inTgr5(HEP+/+)mice, but not inTgr5(Hep-/-)mice. Further, this effect occurred independent of body weight and GLP-1 secretion. Together, these data demonstrate that TGR5 is expressed in hepatocytes, where it functions as a key regulator of whole-body glucose homeostasis.
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Scientific Article
Liver Int. 40, 2982-2997 (2020)
Background and aims Non-alcoholic fatty liver disease (NAFLD) is becoming increasingly prevalent and nutrition intervention remains the most important therapeutic approach for NAFLD. Our aim was to investigate whether low- (LP) or high-protein (HP) diets are more effective in reducing liver fat and reversing NAFLD and which mechanisms are involved. Methods 19 participants with morbid obesity undergoing bariatric surgery were randomized into two hypocaloric (1500-1600 kcal/day) diet groups, a low protein (10E% protein) and a high protein (30E% protein), for three weeks prior to surgery. Intrahepatic lipid levels (IHL) and serum fibroblast growth factor 21 (FGF21) were measured before and after the dietary intervention. Autophagy flux, histology, mitochondrial activity and gene expression analyses were performed in liver samples collected during surgery. Results IHL levels decreased by 42.6% in the HP group, but were not significantly changed in the LP group despite similar weight loss. Hepatic autophagy flux and serum FGF21 increased by 66.7% and 42.2%, respectively, after 3 weeks in the LP group only. Expression levels of fat uptake and lipid biosynthesis genes were lower in the HP group compared with those in the LP group. RNA-seq analysis revealed lower activity of inflammatory pathways upon HP diet. Hepatic mitochondrial activity and expression of beta-oxidation genes did not increase in the HP group. Conclusions HP diet more effectively reduces hepatic fat than LP diet despite of lower autophagy and FGF21. Our data suggest that liver fat reduction upon HP diets result primarily from suppression of fat uptake and lipid biosynthesis.
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Scientific Article
Mol. Metab. 40:101026 (2020)
Objective: Increasing energy expenditure through activation of brown adipose tissue (BAT) thermogenesis is an attractive approach to counteract obesity. It is therefore essential to understand the molecular mechanisms that control BAT functions. Until now several members of the Janus kinase (JAK) - signal transducer and activator of transcription (STAT) pathway have been implicated as being relevant for BAT physiology. However, whether the STAT family member STAT5 is important for the thermogenic property of adipose tissues is unknown. Therefore, we have investigated the role of STAT5 in thermogenic fat in this paper.Methods: We performed metabolic and molecular analyses using mice that harbor an adipocyte-specific deletion of Stat5a/b alleles.Results: We found that STAT5 is necessary for acute cold-induced temperature maintenance and the induction of lipid mobilization in BAT following beta(3)-adrenergic stimulation. Moreover, mitochondrial respiration of primary differentiated brown adipocytes lacking STAT5 was diminished. Increased sensitivity to cold stress upon STAT5 deficiency was associated with reduced expression of thermogenic markers including uncoupling protein 1 (UCP1), while decreased stimulated lipolysis was linked to decreased protein kinase A (PKA) activity. Additionally, brown remodeling of white adipose tissue was diminished following chronic beta(3)-adrenergic stimulation, which was accompanied by a decrease in mitochondrial performance.Conclusion: We conclude that STAT5 is essential for the functionality and the beta-adrenergic responsiveness of thermogenic adipose tissue.
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Scientific Article
Mol. Metab. 39:101044 (2020)
Background: Individuals with diabetes are at a greater risk of hospitalization and mortality resulting from viral, bacterial, and fungal infections. The coronavirus disease-2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has spread quickly to more than 213 countries and claimed 395,779 lives as of June 7, 2020. Notably, in several studies, diabetes is one of the most reported comorbidities in patients with severe COVID-19.Scope of review: In this review, I summarize the clinical data on the risk for infectious diseases in individuals with diabetes while highlighting the mechanisms for altered immune regulation. The focus is on coronaviruses. Based on the new clinical data obtained from COVID-19 patients, a discussion of mechanisms, such as cytokine storm, pulmonary and endothelial dysfunction, and hypercoagulation, that may render individuals with diabetes more vulnerable to COVID-19 is provided.Major conclusions: Epidemiological studies show that poorly controlled diabetes is a risk factor for various infectious diseases. Given the global burden of diabetes and the pandemic nature of coronaviruses, understanding how diabetes affects COVID-19 severity is critical to designing tailored treatments and clinical management of individuals affected by diabetes.
Review
Review
Nucleic Acids Res. 48, 8393-8407 (2020)
The glucocorticoid receptor is an important immunosuppressive drug target and metabolic regulator that acts as a ligand-gated transcription factor. Generally, GR's anti-inflammatory effects are attributed to the silencing of inflammatory genes, while its adverse effects are ascribed to the upregulation of metabolic targets. GR binding directly to DNA is proposed to activate, whereas GR tethering to pro-inflammatory transcription factors is thought to repress transcription. Usingmice with a point mutation in GR's zinc finger, that still tether via protein-protein interactions while being unable to recognize DNA, we demonstrate that DNA binding is essential for both transcriptional activation and repression. Performing ChIP-Seq, RNA-Seq and proteomics under inflammatory conditions, we show that DNA recognition is required for the assembly of a functional co-regulator complex to mediate glucocorticoid responses. Our findings may contribute to the development of safer immunomodulators with fewer side effects.
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Scientific Article
Comp. Struc. Biotech. J. 18, 1330-1341 (2020)
Advancements in the field of next generation sequencing lead to the
generation of ever-more data, with the challenge often being how to
combine and reconcile results from different OMICs studies such as
genome, epigenome and transcriptome. Here we provide an overview of the
standard processing pipelines for ChIP-seq and RNA-seq as well as common
downstream analyses. We describe popular multi-omics data integration
approaches used to identify target genes and co-factors, and we discuss
how machine learning techniques may predict transcriptional regulators
and gene expression.
Review
Review
J. Diab. Complic. 34:107648 (2020)
Aims: Cathepsin D (CTSD) and L (CTSL) are lysosomal proteases which degrade and detoxify advanced glycation end product (AGE)-modified proteins which are predictive of the development of diabetic nephropathy. We aimed to quantify cathepsin levels in urine from patients with type 2 diabetes and to relate these to the amount of urinary free AGES at baseline and with kidney function after four years of follow-up in this closed cohort study.Methods: We established and validated a LC MS/MS method for the quantification of CTSD and CTSL in urine. Patients with type 2 diabetes were screened for diabetic kidney disease and 141 patients were seen at baseline and after four years. CTSD and CTSL and free AGEs were quantified in urine by LC MS/MS at baseline in these patients.Results: The detection limit of CTSD and CTSL in urine was 2.4 ng/l and 19.1 ng/l, respectively. CTSD (p < 0.0001, r = 0.555) and CTSL (p < 0.0001, r= 0.608) correlated positively with albuminuria at time of recruitment. In addition levels of the proteases but not albuminuria correlated with urinary levels of the major cross-linking AGE glucosepane (CTSD: p = 0.012, r = 0.225; CTSL: p < 0.001, r = 0376). A strong non-linear association between CTSD (r = 0.568), CTSL (r = 0.588) and change in albuminuria over four years was present. High levels of CTSL (p = 0.007, beta = -0.366) were associated with an improvement of albuminuria after four years.Conclusions: A sensitive LC MS/MS assay for the quantification of CTSD and CTSL in urine was established. High CTSL baseline levels were associated with an improvement in albuminuria at follow-up. An increased excretion and thus detoxification of the free form of the pathogenic cross-linking AGE glucosepane could explain the positive predictive value of high CTSL levels on albuminuria.
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Scientific Article
Semin. Cell Dev. Biol. 108, 72-81 (2020)
In cells, lipids are stored in lipid droplets, dynamic organelles that adapt their size, abundance, lipid and protein composition and organelle interactions to metabolic changes. Lipid droplet accumulation in the liver is the hallmark of non-alcoholic fatty liver disease (NAFLD). Due to the prevalence of obesity, the strongest risk factor for steatosis, NAFLD and its associated complications are currently affecting more than 1 billion people worldwide. Here, we review how triglyceride and phospholipid homeostasis are regulated in hepatocytes and how imbalances between lipid storage, degradation and lipoprotein secretion lead to NAFLD. We discuss how organelle interactions are altered in NAFLD and provide insights how NAFLD progression is associated with changes in hepatocellular signaling and organ-crosstalk. Finally, we highlight unsolved questions in hepatic LD and lipoprotein biology and give an outlook on therapeutic options counteracting hepatic lipid accumulation.
Review
Review
Sci. Rep. 10:7593 (2020)
In light of the limited treatment options of diabetic polyneuropathy (DPN) available, suitable animal models are essential to investigate pathophysiological mechanisms and to identify potential therapeutic targets. In vivo evaluation with current techniques, however, often provides only restricted information about disease evolution. In the study of patients with DPN, magnetic resonance neurography (MRN) has been introduced as an innovative diagnostic tool detecting characteristic lesions within peripheral nerves. We developed a novel multicontrast ultra high field MRN strategy to examine major peripheral nerve segments in diabetic mice non-invasively. It was first validated in a cross-platform approach on human nerve tissue and then applied to the popular streptozotocin(STZ)-induced mouse model of DPN. In the absence of gross morphologic alterations, a distinct MR-signature within the sciatic nerve was observed mirroring subtle changes of the nerves' fibre composition and ultrastructure, potentially indicating early re-arrangements of DPN. Interestingly, these signal alterations differed from previously reported typical nerve lesions of patients with DPN. The capacity of our approach to non-invasively assess sciatic nerve tissue structure and function within a given mouse model provides a powerful tool for direct translational comparison to human disease hallmarks not only in diabetes but also in other peripheral neuropathic conditions.
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Scientific Article
Mol. Metab. 36:100953 (2020)
Background: Imaging mass spectrometry enables in situ label-free detection of thousands of metabolites from intact tissue samples. However, automated steps for multi-omics analyses and interpretation of histological images have not yet been implemented in mass spectrometry data analysis workflows. The characterization of molecular properties within cellular and histological features is done via time-consuming, nonobjective, and irreproducible definitions of regions of interest, which are often accompanied by a loss of spatial resolution due to mass spectra averaging.Methods: We developed a new imaging pipeline called Spatial Correlation Image Analysis (SPACiAL), which is a computational multimodal workflow designed to combine molecular imaging data with multiplex immunohistochemistry (IHC). SPACiAL allows comprehensive and spatially resolved in situ correlation analyses on a cellular resolution. To demonstrate the method, matrix-assisted laser desorption-ionization (MALDI) Fourier-transform ion cyclotron resonance (FTICR) imaging mass spectrometry of metabolites and multiplex IHC staining were performed on the very same tissue section of mouse pancreatic islets and on human gastric cancer tissue specimens. The SPACiAL pipeline was used to perform an automatic, semantic-based, functional tissue annotation of histological and cellular features to identify metabolic profiles. Spatial correlation networks were generated to analyze metabolic heterogeneity associated with cellular features.Results: To demonstrate the new method, the SPACiAL pipeline was used to identify metabolic signatures of alpha and beta cells within islets of Langerhans, which are cell types that are not distinguishable via morphology alone. The semantic-based, functional tissue annotation allows an unprecedented analysis of metabolic heterogeneity via the generation of spatial correlation networks. Additionally, we demonstrated intra- and intertumoral metabolic heterogeneity within HER2/neu-positive and -negative gastric tumor cells.Conclusions: We developed the SPACiAL workflow to provide IHC-guided in situ metabolomics on intact tissue sections. Diminishing the workload by automated recognition of histological and functional features, the pipeline allows comprehensive analyses of metabolic heterogeneity. The multimodality of immunohistochemical staining and extensive molecular information from imaging mass spectrometry has the advantage of increasing both the efficiency and precision for spatially resolved analyses of specific cell types. The SPACiAL method is a stepping stone for the objective analysis of high-throughput, multi-omics data from clinical research and practice that is required for diagnostics, biomarker discovery, or therapy response prediction.
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Scientific Article
Curr. Opin. Pharmacol. 53, 35-44 (2020)
Glucocorticoids (GCs) are widely used immunomodulators. They regulate gene expression by binding and activating the Glucocorticoid Receptor (GR), but underlying transcriptional mechanisms remain enigmatic. This review summarizes recent findings identifyingspecific GR-bound DNA sequences whose configuration may affect transcriptional output. Additional factors affecting GR's anti-inflammatory actions, including different chromatin states such as DNAse hypersensitive regions and histone marks will be discussed, together with the relevant transcriptional co-regulators and promoter/enhancer features. Furthermore, the involvement of non-coding RNAs such as lncRNAs, miRNAs and eRNAs adds another level of regulation to the GR's transcriptional activity. Characterizing and understanding these multiple mechanisms will be crucial for developing more targeted immunomodulatory therapies with reduced adverse effects such as obesity, diabetes and osteoporosis.
Review
Review
Acta Physiol. 230:e13496 (2020)
Aim Resistance exercise increases muscle mass over time. However, the early signalling events leading to muscle growth are not yet well-defined. Here, we aim to identify new signalling pathways important for muscle remodelling after exercise.Methods We performed a phosphoproteomics screen after a single bout of exercise in mice. As an exercise model we used unilateral electrical stimulation in vivo and treadmill running. We analysed muscle biopsies from human subjects to verify if our findings in murine muscle also translate to exercise in humans.Results We identified a new phosphorylation site on Myocardin-Related Transcription Factor B (MRTF-B), a co-activator of serum response factor (SRF). Phosphorylation of MRTF-B is required for its nuclear translocation after exercise and is accompanied by the transcription of the SRF target gene Fos. In addition, high-intensity exercise also remodels chromatin at specific SRF target gene loci through the phosphorylation of histone 3 on serine 10 in myonuclei of both mice and humans. Ablation of the MAP kinase member MSK1/2 is sufficient to prevent this histone phosphorylation, reduce induction of SRF-target genes, and prevent increases in protein synthesis after exercise.Conclusion Our results identify a new exercise signalling fingerprint in vivo, instrumental for exercise-induced protein synthesis and potentially muscle growth.
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Scientific Article
Cell 181, 1189-1193 (2020)
Researchers around the globe have been mounting, accelerating, and redeploying efforts across disciplines and organizations to tackle the SARS-CoV-2 outbreak. However, humankind continues to be afflicted by numerous other devastating diseases in increasing numbers. Here, we outline considerations and opportunities toward striking a good balance between maintaining and redefining research priorities.
Review
Review
EMBO J. 39:e103477 (2020)
Diabetes-associated organ fibrosis, marked by elevated cellular senescence, is a growing health concern. Intriguingly, the mechanism underlying this association remained unknown. Moreover, insulin alone can neither reverse organ fibrosis nor the associated secretory phenotype, favoring the exciting notion that thus far unknown mechanisms must be operative. Here, we show that experimental type 1 and type 2 diabetes impairs DNA repair, leading to senescence, inflammatory phenotypes, and ultimately fibrosis. Carbohydrates were found to trigger this cascade by decreasing the NAD(+)/NADH ratio and NHEJ-repair in vitro and in diabetes mouse models. Restoring DNA repair by nuclear over-expression of phosphomimetic RAGE reduces DNA damage, inflammation, and fibrosis, thereby restoring organ function. Our study provides a novel conceptual framework for understanding diabetic fibrosis on the basis of persistent DNA damage signaling and points to unprecedented approaches to restore DNA repair capacity for resolution of fibrosis in patients with diabetes.
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Scientific Article
EMBO Mol. Med. 12:e09271 (2020)
The role of the endothelium is not just limited to acting as an inert barrier for facilitating blood transport. Endothelial cells (ECs), through expression of a repertoire of angiocrine molecules, regulate metabolic demands in an organ-specific manner. Insulin flux across the endothelium to muscle cells is a rate-limiting process influencing insulin-mediated lowering of blood glucose. Here, we demonstrate that Notch signaling in ECs regulates insulin transport to muscle. Notch signaling activity was higher in ECs isolated from obese mice compared to non-obese. Sustained Notch signaling in ECs lowered insulin sensitivity and increased blood glucose levels. On the contrary, EC-specific inhibition of Notch signaling increased insulin sensitivity and improved glucose tolerance and glucose uptake in muscle in a high-fat diet-induced insulin resistance model. This was associated with increased transcription of Cav1, Cav2, and Cavin1, higher number of caveolae in ECs, and insulin uptake rates, as well as increased microvessel density. These data imply that Notch signaling in the endothelium actively controls insulin sensitivity and glucose homeostasis and may therefore represent a therapeutic target for diabetes.
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Scientific Article
Biol. Chem. 401, 1019-1030 (2020)
The proper production, degradation, folding and activity of proteins, proteostasis, is essential for any cellular function. From single cell organisms to humans, selective pressures have led to the evolution of adaptive programs that ensure proteins are properly produced and disposed of when necessary. Environmental factors such as temperature, nutrient availability, pathogens as well as predators have greatly influenced the development of mechanisms such as the unfolded protein response, endoplasmic reticulum-associated protein degradation and autophagy, working together in concert to secure cellular proteostasis. In our modern society, the metabolic systems of the human body face the distinct challenge of changed diets, chronic overnutrition and sedentary lifestyles. Obesity and excess white adipose tissue accumulation are linked to a cluster of metabolic diseases and disturbed proteostasis is a common feature. Conversely, processes that promote energy expenditure such as exercise, shivering as well as non-shivering thermogenesis by brown adipose tissue (BAT) and beige adipocytes counter-act metabolic dysfunction. Here we review the basic concepts of proteostasis in obesity-linked metabolic diseases and focus on adipocytes, which are critical regulators of mammalian energy metabolism.
Review
Review
Diabetes 69, 713-723 (2020)
Clinical studies have suggested that changes in peripheral nerve microcirculation may contribute to nerve damage in diabetic polyneuropathy (DN). High-sensitivity troponin T (hsTNT) assays have been recently shown to provide predictive values for both cardiac and peripheral microangiopathy in type 2 diabetes (T2D). This study investigated the association of sciatic nerve structural damage in 3 Tesla (3T) magnetic resonance neurography (MRN) with hsTNT and N-terminal pro-brain natriuretic peptide serum levels in patients with T2D. MRN at 3T was performed in 51 patients with T2D (23 without DN, 28 with DN) and 10 control subjects without diabetes. The sciatic nerve's fractional anisotropy (FA), a marker of structural nerve integrity, was correlated with clinical, electrophysiological, and serological data. In patients with T2D, hsTNT showed a negative correlation with the sciatic nerve's FA (r = -0.52, P < 0.001), with a closer correlation in DN patients (r = -0.66, P < 0.001). hsTNT further correlated positively with the neuropathy disability score (r = 0.39, P = 0.005). Negative correlations were found with sural nerve conduction velocities (NCVs) (r = -0.65, P < 0.001) and tibial NCVs (r = -0.44, P = 0.002) and amplitudes (r = -0.53, P < 0.001). This study is the first to show that hsTNT is a potential indicator for structural nerve damage in T2D. Our results indirectly support the hypothesis that microangiopathy contributes to structural nerve damage in T2D.
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Scientific Article
FASEB J. 34, 3336-3346 (2020)
In Type 1 Diabetes Mellitus (T1DM), leukocyte infiltration of the pancreatic islets and the resulting immune-mediated destruction of beta cells precede hyperglycemia and clinical disease symptoms. In this context, the role of the pancreatic endothelium as a barrier for autoimmunity- and inflammation-related destruction of the islets is not well studied. Here, we identified Robo4, expressed on endothelial cells, as a regulator of pancreatic vascular endothelial permeability during autoimmune diabetes. Circulating levels of Robo4 were upregulated in mice subjected to the Multiple Low-Dose Streptozotocin (MLDS) model of diabetes. Upon MLDS induction, Robo4-deficiency resulted in increased pancreatic vascular permeability, leukocyte infiltration to the islets and islet apoptosis, associated with reduced insulin levels and faster diabetes development. On the contrary, in vivo administration of Slit2 in mice modestly delayed the emergence of hyperglycaemia and ameliorated islet inflammation in MLDS-induced diabetes. Thus, Robo4-mediated endothelial barrier integrity reduces insulitis and islet destruction in autoimmune diabetes. Our findings highlight the importance of the endothelium as gatekeeper of pancreatic inflammation during T1DM development and may pave the way for novel Robo4-related therapeutic approaches for autoimmune diabetes.
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Scientific Article
Radiology 294, 405-414 (2020)
Background: The pathophysiologic mechanisms underlying painful symptoms in diabetic polyneuropathy (DPN) are poorly understood.They may be associated with MRI characteristics, which have not yet been investigated.Purpose: To investigate correlations between nerve structure, load and spatial distribution of nerve lesions, and pain in patients with DPN.Materials and Methods: In this prospective single-center cross-sectional study, participants with type 1 or 2 diabetes volunteered between June 2015 and March 2018. Participants underwent 3-T MR neurography of the sciatic nerve with a T2-weighed fat-suppressed sequence, which was preceded by clinical and electrophysiologic tests. For group comparisons, analysis of variance or the Kruskal-Wall is test was performed depending on Gaussian or non-Gaussian distribution of data. Spearman correlation coefficients were calculated for correlation analysis.Results: A total of 131 participants (mean age, 62 years +/- 11 [standard deviation]; 82 men) with either type 1 (n = 45) or type 2 (n = 86) diabetes were evaluated with painful (n = 64), painless (n = 37), or no (n = 30) DPN. Participants who had painful diabetic neuropathy had a higher percentage of nerve lesions in the full nerve volume (15.2% +/- 1.6) than did participants with nonpainful DPN (10.4% +/- 1.7, P = .03) or no DPN (8.3% +/- 1.7; P<.001). The amount and extension of T2-weighted hyperintense nerve lesions correlated positively with the neuropathy disability score (r = 0.37; 95% confidence interval [CI]: 0.21, 0.52; r = 0.37; 95% CI: 0.20, 0.52, respectively) and the neuropathy symptom score (r = 0.41; 95% CI: 0.25, 0.55; r = 0.34; 95% CI: 0.17,0.49, respectively). Negative correlations were found for the tibial nerve conduction velocity (r = -0.23; 95% CI: -0.44, -0.01; r = 20.37; 95% CI: 20.55, 20.15, respectively). The cross-sectional area of the nerve was positively correlated with the neuropathy disability score (r = 0.23; 95% CI: 0.03, 0.36). Negative correlations were found for the tibial nerve conduction velocity (r = 20.24; 95% CI: -0.45, -0.01).Conclusion: The amount and extension of T2-weighted hyperintense fascicular nerve lesions were greater in patients with painful diabetic neuropathy than in those with painless diabetic neuropathy. These results suggest that proximal fascicular damage is associated with the evolution of painful sensory symptoms in diabetic polyneuropathy.
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Scientific Article
EMBO Rep. 21:e48354 (2020)
Pluripotent stem cells are thought of as a surrogate of early developmental stages that sustain the capacity to generate all cell types in the body, thereby constituting an invaluable tool to address the mechanisms underlying cellular plasticity. In the mouse, cells resembling totipotent 2-cell-stage embryos (2-cell-like cells) arise at a very low frequency in embryonic stem cell (ESC) cultures. However, the extent to which these early-embryonic-like cells recapitulate the molecular features of the early embryo is unclear. Here, we have undertaken a characterization of some of the metabolic features of early-embryonic-like cells in culture. Our data indicate that early-embryonic-like cells exhibit decreased glycolytic and respiratory activity, lower levels of reactive oxygen species and increased glucose uptake, suggesting a shift of the metabolic programme during 2-cell-like cell reprogramming. Accordingly, we find that 2-cell-like cells can be induced by defined metabolites. Thus, in addition to their transcriptional and chromatin features, 2-cell-like cells recapitulate some of the metabolic features of their in vivo counterpart. Altogether, our work underscores a distinct metabolic state of early-embryonic-like cells and identifies compounds that can induce their emergence in vitro.
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Nat. Biotechnol. 38, 293-296 (2020)
We develop mid-infrared optoacoustic microscopy (MiROM) for label-free, bond-selective, live-cell metabolic imaging, enabling spatiotemporal monitoring of carbohydrates, lipids and proteins in cells and tissues. Using acoustic detection of optical absorption, MiROM converts mid-infrared sensing into a positive-contrast imaging modality with negligible photodamage and high sensitivity. We use MiROM to observe changes in intrinsic carbohydrate distribution from a diffusive spatial pattern to tight co-localization with lipid droplets during adipogenesis.Mid-infrared optoacoustic microscopy enables label-free, bond-selective imaging in living cells
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Scientific Article
Chem. Phys. Lipids 226, DOI: 10.1016/j.chemphyslip.2019.104837 (2020)
Non-coding RNAs (ncRNAs) like microRNAs (miRNAs) or small interference RNAs (siRNAs) with their power to selectively silence any gene of interest enable the targeting of so far 'undruggable' proteins and diseases. Such RNA molecules have gained much attention from biotech and pharmaceutical companies, which led to the first Food and Drug Administration (FDA) approved ncRNA therapeutic in 2018.However, the main barrier in clinical practice of ncRNAs is the lack of an effective delivery system that can protect the RNA molecules from nuclease degradation, deliver them to specific tissues and cell types, and release them into the cytoplasm of the targeted cells, all without inducing adverse effects.For that reason, drug delivery approaches, formulations, technologies and systems for transporting pharmacological ncRNA compounds to achieve a diagnostic or therapeutic effect in the human body are in demand.Here, we review the development of therapeutic lipid -based nanoparticles for delivery of miRNAs, one class of endogenous ncRNAs with specific regulatory functions. We outline challenges and opportunities for advanced miRNA-based therapies, and discuss the complexity associated with the delivery of functional miRNAs. Novel strategies are addressed how to deal with the most critical points in miRNA delivery, such as toxicity, specific targeting of disease sites, proper cellular uptake and endosomal escape of miRNAs. Current fields of application and various preclinical settings involving miRNA therapeutics are discussed, providing an outlook to future clinical approaches.Following the current trends and technological developments in nanomedicine exciting new delivery systems for ncRNA-based therapeutics can be expected in upcoming years.
Review
Review
2019
Diabetes 69, 436-447 (2019)
Studies on magnetic resonance neurography (MRN) in diabetic polyneuropathy (DPN) have found proximal sciatic nerve lesions. The aim of this study was to evaluate the functional relevance of sciatic nerve lesions in DPN, expecting correlations with the impairment of large fiber function. 61 patients with diabetes mellitus type 2 (48 with, 13 without DPN) and 12 controls were enrolled, undergoing MRN, quantitative sensory testing, and electrophysiological examinations. There were differences in mechanical detection (Aβ fibers) and mechanical pain (Aδ fibers), but not in thermal pain and thermal detection clusters (C fibers) between the groups. Lesion load correlated with lower Aα, Aβ, and Aδ fiber, but not C fiber function in all participants. Patients with lower function showed a higher load of nerve lesions than patients with elevated function or no measurable deficit despite apparent DPN. Longer diabetes duration was associated with higher lesion load in patients with DPN, suggesting that nerve lesions in DPN may accumulate over time and become clinically relevant once a critical amount of nerve fascicles is affected. Moreover, MRN is an objective method for determining lower function mainly in medium and large fibers in DPN.
Wissenschaftlicher Artikel
Scientific Article
Nat. Commun. 10:5686 (2019)
Diabetes mellitus affects one in eleven adults worldwide. Most suffer from Type 2 Diabetes which features elevated blood glucose levels and an inability to adequately secrete or respond to insulin. Insulin producing beta-cells have primary cilia which are implicated in the regulation of glucose metabolism, insulin signaling and secretion. To better understand how beta-cell cilia affect glucose handling, we ablate cilia from mature beta-cells by deleting key cilia component Ift88. Here we report that glucose homeostasis and insulin secretion deteriorate over 12 weeks post-induction. Cilia/basal body components are required to suppress spontaneous auto-activation of EphA3 and hyper-phosphorylation of EphA receptors inhibits insulin secretion. In beta-cells, loss of cilia/basal body function leads to polarity defects and epithelial-to-mesenchymal transition. Defective insulin secretion from IFT88-depleted human islets and elevated pEPHA3 in islets from diabetic donors both point to a role for cilia/basal body proteins in human glucose homeostasis.
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Scientific Article
Mol. Cell 76, 531-545.e5 (2019)
The glucocorticoid receptor (GR) is a potent metabolic regulator and a major drug target. While GR is known to play integral roles in circadian biology, its rhythmic genomic actions have never been characterized. Here we mapped GR's chromatin occupancy in mouse livers throughout the day and night cycle. We show how GR partitions metabolic processes by time-dependent target gene regulation and controls circulating glucose and triglycerides differentially during feeding and fasting. Highlighting the dominant role GR plays in synchronizing circadian amplitudes, we find that the majority of oscillating genes are bound by and depend on GR. This rhythmic pattern is altered by high-fat diet in a ligand-independent manner. We find that the remodeling of oscillatory gene expression and postprandial GR binding results from a concomitant increase of STAT5 co-occupancy in obese mice. Altogether, our findings highlight GR's fundamental role in the rhythmic orchestration of hepatic metabolism.
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Scientific Article
Nat. Metab. 1, 1009-1026 (2019)
Non-alcoholic fatty liver disease (NAFLD) represents a key feature of obesity-related type 2 diabetes with increasing prevalence worldwide. To our knowledge, no treatment options are available to date, paving the way for more severe liver damage, including cirrhosis and hepatocellular carcinoma. Here, we show an unexpected function for an intracellular trafficking regulator, the small Rab GTPase Rab24, in mitochondrial fission and activation, which has an immediate impact on hepatic and systemic energy homeostasis. RAB24 is highly upregulated in the livers of obese patients with NAFLD and positively correlates with increased body fat in humans. Liver-selective inhibition of Rab24 increases autophagic flux and mitochondrial connectivity, leading to a strong improvement in hepatic steatosis and a reduction in serum glucose and cholesterol levels in obese mice. Our study highlights a potential therapeutic application of trafficking regulators, such as RAB24, for NAFLD and establishes a conceptual functional connection between intracellular transport and systemic metabolic dysfunction.
Wissenschaftlicher Artikel
Scientific Article
EMBO Rep. 20:e48552 (2019)
Aberrant activity of the glucocorticoid (GC)/glucocorticoid receptor (GR) endocrine system has been linked to obesity-related metabolic dysfunction. Traditionally, the GC/GR axis has been believed to play a crucial role in adipose tissue formation and function in both, white (WAT) and brown adipose tissue (BAT). While recent studies have challenged this notion for WAT, the contribution of GC/GR signaling to BAT-dependent energy homeostasis remained unknown. Here, we have generated and characterized a BAT-specific GR-knockout mouse (GR(BATKO)), for the first time allowing to genetically interrogate the metabolic impact of BAT-GR. The HPA axis in GR(BATKO) mice was intact, as was the ability of mice to adapt to cold. BAT-GR was dispensable for the adaptation to fasting-feeding cycles and the development of diet-induced obesity. In obesity, glucose and lipid metabolism, insulin sensitivity, and food intake remained unchanged, aligning with the absence of changes in thermogenic gene expression. Together, we demonstrate that the GR in UCP1-positive BAT adipocytes plays a negligible role in systemic metabolism and BAT function, thereby opposing a long-standing paradigm in the field.
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Scientific Article
JCI insight 4:e126154 (2019)
The increased formation of methylglyoxal (MG) under hyperglycemia is associated with the development of microvascular complications in patients with diabetes mellitus; however, the effects of elevated MG levels in vivo are poorly understood. In zebrafish, a transient knockdown of glyoxalase 1, the main MG detoxifying system, led to the elevation of endogenous MG levels and blood vessel alterations. To evaluate effects of a permanent knockout of glyoxalase 1 in vivo, glo1-/- zebrafish mutants were generated using CRISPR/Cas9. In addition, a diet-induced-obesity zebrafish model was used to analyze glo1-/- zebrafish under high nutrient intake. Glo1-/- zebrafish survived until adulthood without growth deficit and showed increased tissue MG concentrations. Impaired glucose tolerance developed in adult glo1-/- zebrafish and was indicated by increased postprandial blood glucose levels and postprandial S6 kinase activation. Challenged by an overfeeding period, fasting blood glucose levels in glo1-/- zebrafish were increased which translated into retinal blood vessel alterations. Thus, the data have identified a defective MG detoxification as a metabolic prerequisite and glyoxalase 1 alterations as a genetic susceptibility to the development of type 2 diabetes mellitus under high nutrition intake.
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Scientific Article
PLoS ONE 14:e0222771 (2019)
Asprosin is a counter-regulatory hormone to insulin which plays a role in fasting. It may therefore also play a role in hypoglycaemia unawareness, which has been subsequently examined in this pilot study. Intravenous glucose tolerance test was used to induce controlled hyperglycemia whereas a hyperinsulinemic clamp test was used to induce a controlled hypoglycaemia in 15 patients with diabetes type 1, with and without hypoglycaemia unawareness. Changes in asprosin plasma levels did not differ between patients with and without hypoglycaemia unawareness. However, nine patients with insulin resistance as well as higher liver stiffness values and low-density lipoprotein but lower high-density lipoprotein levels did not show the expected increase in asprosin plasma levels during hypoglycemia. Therefore, insulin resistance and alterations in liver structure, most likely early stages of non-alcoholic fatty liver disease, seem to be relevant in type 1 diabetes and do not only lead to elevated plasma levels of asprosin, but also to a blunted asprosin response in hypoglycemia.
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Scientific Article
Front. Immunol. 10:1859 (2019)
For many decades, glucocorticoids have been widely used as the gold standard treatment for inflammatory conditions. Unfortunately, their clinical use is limited by severe adverse effects such as insulin resistance, cardiometabolic diseases, muscle and skin atrophies, osteoporosis, and depression. Glucocorticoids exert their effects by binding to the Glucocorticoid Receptor (GR), a ligand-activated transcription factor which both positively, and negatively regulates gene expression. Extensive research during the past several years has uncovered novel mechanisms by which the GR activates and represses its target genes. Genome-wide studies and mouse models have provided valuable insight into the molecular mechanisms of inflammatory gene regulation by GR. This review focusses on newly identified target genes and GR co-regulators that are important for its anti-inflammatory effects in innate immune cells, as well as mutations within the GR itself that shed light on its transcriptional activity. This research progress will hopefully serve as the basis for the development of safer immune suppressants with reduced side effect profiles.
Review
Review
Mol. Metab. 28, 91-106 (2019)
Objective: Although it is well established that a-calcitonin gene-related peptide (CGRP) stabilizes muscle-type cholinergic receptors nicotinic subunits (AChR), the underlying mechanism by which this neuropeptide regulates muscle protein metabolism and neuromuscular junction (NMJ) morphology is unclear.Methods: To elucidate the mechanisms how CGRP controls NMJ stability in denervated mice skeletal muscles, we carried out physiological, pharmacological, and molecular analyses of atrophic muscles induced by sciatic nerve transection.Results: Here, we report that CGRP treatment in vivo abrogated the deleterious effects on NMJ upon denervation (DEN), an effect that was associated with suppression of skeletal muscle proteolysis, but not stimulation of protein synthesis. CGRP also blocked the DEN-induced increase in endocytic AChR vesicles and the elevation of autophagosomes per NMJ area. The treatment of denervated animals with rapamycin blocked the stimulatory effects of CGRP on mTORC1 and its inhibitory actions on autophagic flux and NMJ degeneration. Furthermore, CGRP inhibited the DEN-induced hyperactivation of Ca2+-dependent proteolysis, a degradative system that has been shown to destabilize NMJ. Consistently, calpain was found to be activated by cholinergic stimulation in myotubes leading to the dispersal of AChR clusters, an effect that was abolished by CGRP.Conclusion: Taken together, these data suggest that the inhibitory effect of CGRP on autophagy and calpain may represent an important mechanism for the preservation of synapse morphology when degradative machinery is exacerbated upon denervation conditions.
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Scientific Article
Mol. Aspects Med. 68, 90-100 (2019)
For the past decade, brown adipose tissue (BAT) has been extensively studied as a potential therapy for obesity and metabolic diseases due to its thermogenic and glucose-consuming properties. It is now clear that the function of BAT goes beyond heat production, as it also plays an important endocrine role by secreting the so-called batokines to communicate with other metabolic tissues and regulate systemic energy homeostasis. However, despite numerous studies showing the benefits of BAT in rodents, it is still not clear whether recruitment of BAT can be utilized to treat human patients. Here, we review the advances on understanding the role of BAT in metabolism and its benefits on glucose and lipid homeostasis in both humans and rodents. Moreover, we discuss the latest methodological approaches to assess the contribution of BAT to human metabolism as well as the possibility to target BAT, pharmacologically or by lifestyle adaptations, to treat metabolic disorders.
Review
Review
Arch. Toxicol. 93, 1609-1637 (2019)
Drug-induced liver injury (DILI) cannot be accurately predicted by animal models. In addition, currently available in vitro methods do not allow for the estimation of hepatotoxic doses or the determination of an acceptable daily intake (ADI). To overcome this limitation, an in vitro/in silico method was established that predicts the risk of human DILI in relation to oral doses and blood concentrations. This method can be used to estimate DILI risk if the maximal blood concentration (Cmax) of the test compound is known. Moreover, an ADI can be estimated even for compounds without information on blood concentrations. To systematically optimize the in vitro system, two novel test performance metrics were introduced, the toxicity separation index (TSI) which quantifies how well a test differentiates between hepatotoxic and non-hepatotoxic compounds, and the toxicity estimation index (TEI) which measures how well hepatotoxic blood concentrations in vivo can be estimated. In vitro test performance was optimized for a training set of 28 compounds, based on TSI and TEI, demonstrating that (1) concentrations where cytotoxicity first becomes evident in vitro (EC10) yielded better metrics than higher toxicity thresholds (EC50); (2) compound incubation for 48 h was better than 24 h, with no further improvement of TSI after 7 days incubation; (3) metrics were moderately improved by adding gene expression to the test battery; (4) evaluation of pharmacokinetic parameters demonstrated that total blood compound concentrations and the 95%-population-based percentile of Cmax were best suited to estimate human toxicity. With a support vector machine-based classifier, using EC10 and Cmax as variables, the cross-validated sensitivity, specificity and accuracy for hepatotoxicity prediction were 100, 88 and 93%, respectively. Concentrations in the culture medium allowed extrapolation to blood concentrations in vivo that are associated with a specific probability of hepatotoxicity and the corresponding oral doses were obtained by reverse modeling. Application of this in vitro/in silico method to the rat hepatotoxicant pulegone resulted in an ADI that was similar to values previously established based on animal experiments. In conclusion, the proposed method links oral doses and blood concentrations of test compounds to the probability of hepatotoxicity.
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Scientific Article
Identification of the fructose transporter GLUT5 (SLC2A5) as a novel target of nuclear receptor LXR.
Sci. Rep. 9:9299 (2019)
Fructose has become a major constituent of our modern diet and is implicated as an underlying cause in the development of metabolic diseases. The fructose transporter GLUT5 (SLC2A5) is required for intestinal fructose absorption. GLUT5 expression is induced in the intestine and skeletal muscle of type 2 diabetes (T2D) patients and in certain cancers that are dependent on fructose metabolism, indicating that modulation of GLUT5 levels could have potential in the treatment of these diseases. Using an unbiased screen for transcriptional control of the human GLUT5 promoter we identified a strong and specific regulation by liver X receptor alpha (LXR alpha, NR1H3). Using promoter truncations and site-directed mutagenesis we identified a functional LXR response element (LXRE) in the human GLUT5 promoter, located at -385 bp relative to the transcriptional start site (TSS). Finally, mice treated with LXR agonist T0901317 showed an increase in Glut5 mRNA and protein levels in duodenum and adipose tissue, underscoring the in vivo relevance of its regulation by LXR. Together, our findings show that LXR alpha regulates GLUT5 in mice and humans. As a ligand-activated transcription factor, LXR alpha might provide novel pharmacologic strategies for the selective modulation of GLUT5 activity in the treatment of metabolic disease as well as cancer.
Wissenschaftlicher Artikel
Scientific Article
Nat. Commun. 10:2474 (2019)
Diabetes is a global health problem caused primarily by the inability of pancreatic beta-cells to secrete adequate levels of insulin. The molecular mechanisms underlying the progressive failure of beta-cells to respond to glucose in type-2 diabetes remain unresolved. Using a combination of transcriptomics and proteomics, we find significant dysregulation of major metabolic pathways in islets of diabetic beta V59M mice, a non-obese, eulipidaemic diabetes model. Multiple genes/proteins involved in glycolysis/gluconeogenesis are upregulated, whereas those involved in oxidative phosphorylation are downregulated. In isolated islets, glucose-induced increases in NADH and ATP are impaired and both oxidative and glycolytic glucose metabolism are reduced. INS-1 beta-cells cultured chronically at high glucose show similar changes in protein expression and reduced glucose-stimulated oxygen consumption: targeted metabolomics reveals impaired metabolism. These data indicate hyperglycaemia induces metabolic changes in beta-cells that markedly reduce mitochondrial metabolism and ATP synthesis. We propose this underlies the progressive failure of beta-cells in diabetes.
Wissenschaftlicher Artikel
Scientific Article
Traffic 20, 552-570 (2019)
The endosomal system plays an essential role in cell homeostasis by controlling cellular signaling, nutrient sensing, cell polarity and cell migration. However, its place in the regulation of tissue, organ and whole body physiology is less well understood. Recent studies have revealed an important role for the endosomal system in regulating glucose and lipid homeostasis, with implications for metabolic disorders such as type 2 diabetes, hypercholesterolemia and non-alcoholic fatty liver disease. By taking insights from in vitro studies of endocytosis and exploring their effects on metabolism, we can begin to connect the fields of endosomal transport and metabolic homeostasis. In this review, we explore current understanding of how the endosomal system influences the systemic regulation of glucose and lipid metabolism in mice and humans. We highlight exciting new insights that help translate findings from single cells to a wider physiological level and open up new directions for endosomal research.
Review
Review
JAMA net. open 2:e194798 (2019)
Importance: Lowering serum cholesterol levels is a well-established treatment for dyslipidemia in patients with type 2 diabetes (T2D). However, nerve lesions in patients with T2D increase with lower serum cholesterol levels, suggesting that lowering serum cholesterol levels is associated with diabetic polyneuropathy (DPN) in patients with T2D. Objective: To investigate whether there is an association between serum cholesterol levels and peripheral nerve lesions in patients with T2D with and without DPN. Design, Setting, and Participants: This single-center, cross-sectional, prospective cohort study was performed from June 1, 2015, to March 31, 2018. Observers were blinded to clinical data. A total of 256 participants were approached, of whom 156 were excluded. A total of 100 participants consented to undergo magnetic resonance neurography of the right leg at the Department of Neuroradiology and clinical, serologic, and electrophysiologic assessment at the Department of Endocrinology, Heidelberg University Hospital, Heidelberg, Germany. Exposures: Quantification of the nerve's diameter and lipid equivalent lesion (LEL) load with a subsequent analysis of all acquired clinical and serologic data with use of 3.0-T magnetic resonance neurography of the right leg with 3-dimensional reconstruction of the sciatic nerve. Main Outcomes and Measures: The primary outcome was lesion load and extension. Secondary outcomes were clinical, serologic, and electrophysiologic findings. Results: A total of 100 participants with T2D (mean [SD] age, 64.6 [0.9] years; 68 [68.0%] male) participated in the study. The LEL load correlated positively with the nerve's mean cross-sectional area (r = 0.44; P < .001) and the maximum length of a lesion (r = 0.71; P < .001). The LEL load was negatively associated with total serum cholesterol level (r = -0.41; P < .001), high-density lipoprotein cholesterol level (r = -0.30; P = .006), low-density lipoprotein cholesterol level (r = -0.33; P = .003), nerve conduction velocities of the tibial (r = -0.33; P = .01) and peroneal (r = -0.51; P < .001) nerves, and nerve conduction amplitudes of the tibial (r = -0.31; P = .02) and peroneal (r = -0.28; P = .03) nerves. Conclusions and Relevance: The findings suggest that lowering serum cholesterol levels in patients with T2D and DPN is associated with a higher amount of nerve lesions and declining nerve conduction velocities and amplitudes. These findings may be relevant to emerging therapies that promote an aggressive lowering of serum cholesterol levels in patients with T2D.
Wissenschaftlicher Artikel
Scientific Article
Cell. Mol. Life Sci. 76, 4551-4568 (2019)
The gene CNDP1 was associated with the development of diabetic nephropathy. Its enzyme carnosinase 1 (CN1) primarily hydrolyzes the histidine-containing dipeptide carnosine but other organ and metabolic functions are mainly unknown. In our study we generated CNDP1 knockout zebrafish, which showed strongly decreased CN1 activity and increased intracellular carnosine levels. Vasculature and kidneys of CNDP1 −/− zebrafish were not affected, except for a transient glomerular alteration. Amino acid profiling showed a decrease of certain amino acids in CNDP1 −/− zebrafish, suggesting a specific function for CN1 in the amino acid metabolisms. Indeed, we identified a CN1 activity for Ala–His and Ser–His. Under diabetic conditions increased carnosine levels in CNDP1 −/− embryos could not protect from respective organ alterations. Although, weight gain through overfeeding was restrained by CNDP1 loss. Together, zebrafish exhibits CN1 functions, while CNDP1 knockout alters the amino acid metabolism, attenuates weight gain but cannot protect organs from diabetic complications.
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Scientific Article
Vasa 48, 186-192 (2019)
BACKGROUND: The enzyme glyoxalase1 (GLO1) is the main opponent in the degradation of the reactive metabolite methylglyoxal (MG), which by glycation of macromolecules is involved in atherogenesis. Reduced GLO1-activity in atherosclerotic tissue is known to be associated with diabetes. It has been shown that treatment of patients with type 2 diabetes with metformin leads to increased GLO1-activity in peripheral-blood-cells. The aim of this study was to evaluate whether metformin treatment increases GLO1-activity in atherosclerotic lesions of patients with type 2 diabetes. PATIENTS AND METHODS: Patients with type 2 diabetes and carotid artery disease were included into the study prospectively. Type of diabetes-medication was documented upon admission along with demographic and clinical history. Using shock frozen endarterectomy-derived carotid artery plaques, GLO1-activity as well as protein expression was measured by a spectophotometric assay and western-blotting respectively. RESULTS: 33 patients (76 % male, mean age 71 years) were included into the study and were divided according to treatment with metformin or not (15 vs. 18 patients). GLO1-activity was increased by the factor 1.36 when treated with metformin - however, not significantly (0.86 vs. 0.63 U/mg, p = 0.056). Normalisation of GLO1-activity onto GLO1-expression level lead to a significant increase by more than twofold (8.48 vs. 3.85, p = 0.044) while GLO1-protein levels did not differ significantly. GLO1-activity correlated positively with increasing HbA1c, especially under metformin treatment. CONCLUSIONS: Treatment with metformin in patients with type 2 diabetes is associated with enhanced GLO1-activity in atherosclerotic lesions. Regarding the macro- and microvascular complications in these patients further studies are needed to gain more insight into the effect of metformin on the GLO/MG system.
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Scientific Article
J. Biophotonics 12:e201800439 (2019)
Detection and monitoring of esophageal cancer severity require an imaging technique sensitive enough to detect early pathological changes in the esophagus and capable of analyzing the esophagus over 360 degrees in a non-invasive manner. Optoacoustic endoscopy (COE) has been shown to resolve superficial vascular structure of the esophageal lumen in rats and rabbits using catheter-type probes. Although these systems can work well in small animals, they are unsuitable for larger lumens with thicker walls as required for human esophageal screening, due to their lack of position stability along the full organ circumference, sub-optimal acoustic coupling and limited signal-to-noise ratio (SNR). In this work, we introduce a novel capsule COE system that provides high-quality 360 degrees images of the entire lumen, specifically designed for typical dimensions of human esophagus. The pill-shaped encapsulated probe consists of a novel and highly sensitive ultrasound transducer fitted with an integrated miniature pre-amplifier, which increases SNR of 10 dB by minimizing artifacts during signal transmission compared to the configuration without the preamplifier. The scanner rotates helically around the central axis of the probe to capture three-dimensional images with uniform quality. We demonstrate for the first time ex vivo volumetric vascular network images to a depth of 2 mm in swine esophageal lining using COE. Vascular information can be resolved within the mucosa and submucosa layers as confirmed by histology of samples stained with hematoxylin and eosin and with antibody against vascular marker CD31. COE creates new opportunities for optoacoustic screening of esophageal cancer in humans.
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Scientific Article
Handb. Exp. Pharmacol. 251, 215-237 (2019)
Brite/brown adipose tissue (BAT) is a thermogenic tissue able to dissipate energy via non-shivering thermogenesis. It is naturally activated by cold and has been demonstrated to increase thermogenic capacity, elevate energy expenditure, and to ultimately contribute to fat mass reduction. Thus, it emerges as novel therapeutic concept for pharmacological intervention in obesity and other metabolic disorders. Therefore, the comprehensive understanding of the regulatory network in thermogenic adipocytes is in demand.The surprising findings that (1) all human protein-coding genes make up not more than 2% of our genome, (2) organismal complexity goes well along with the percentage of nonprotein-coding sequences, and that (3) three quarters of our genome are pervasively transcribed, provide evidence that noncoding RNAs (ncRNAs) are not junk, but a significant and even predominant part of our transcriptome representing a treasure chest worth retrieving regulatory determinants in biological processes and diseases.In this chapter, the impact of regulatory small and long ncRNAs (lncRNAs) in particular microRNAs and lncRNAs on BAT formation and metabolic function and their involvement in physiological and pathological conditions has been reviewed.
Review
Review
Thromb. Haemost. 119, 567-575 (2019)
Endocannabinoids are a group of arachidonic acid-derived lipid mediators binding to cannabinoid receptors CB1 and CB2. An overactivity of the endocannabinoid system plays a pathophysiological role in the development of visceral obesity and insulin resistance. Moreover, elevated circulating endocannabinoid levels are also prevalent in atherosclerosis. The pathophysiological increase of endocannabinoid levels is due to an altered expression of endocannabinoid synthesizing and degrading enzymes induced by inflammatory mediators such as cytokines or lipids. Emerging experimental evidence suggests that enhanced endocannabinoid signalling affects atherosclerosis via multiple effects, including a modulation of vascular inflammation, leukocyte recruitment, macrophage cholesterol metabolism and consequently atherosclerotic plaque stability. In addition, recent findings in various metabolic disease models highlight the relevance of peripheral CB1 cannabinoid receptors in adipose tissue, liver and pancreas, which crucially regulate lipid and glucose metabolism as well as macrophage properties in these organs. This suggests that targeting the endocannabinoid system in the vasculature and peripheral organs might have a therapeutic potential for atherosclerosis by inhibiting vascular inflammation and improving metabolic risk factors. This review will provide a brief update on the effects of endocannabinoid signalling in atherosclerosis and related metabolic complications.
Review
Review
Acta Pharm. Sin. B 9, 443-454 (2019)
The Tribbles (TRIB) family of pseudokinase proteins has been shown to play key roles in cell cycle, metabolic diseases, chronic inflammatory disease, and cancer development. A better understanding of the mechanisms of TRIB pseudokinases could provide new insights for disease development and help promote TRIB proteins as novel therapeutic targets for drug discovery. At the 2nd International Symposium on Tribbles and Diseases held on May 7-9, 2018 in Beijing, China, a group of leading Tribbles scientists reported their findings and ongoing studies about the effects of the different TRIB proteins in the areas of immunity, metabolism, fundamental cell biology and cancer. Here, we summarize important and insightful overviews from 4 keynote lectures, 13 plenary lectures and 8 short talks that took place during this meeting. These findings may offer new insights for the understanding of the roles of TRIB pseudokinases in the development of various diseases.
Review
Review
Endocr. Connect. 8, 367–377 (2019)
Acromegaly is a rare disease due to chronic excess growth hormone (GH) and IGF-1. Aryl hydrocarbon receptor interacting protein (AIP) mutations are associated with an aggressive, inheritable form of acromegaly that responds poorly to SST2-specific somatostatin analogs (SSA). The role of pasireotide, an SSA with affinity for multiple SSTs, in patients with AIP mutations has not been reported. We studied two AIP mutation positive acromegaly patients with early-onset, invasive macroadenomas and inoperable residues after neurosurgery. Patient 1 came from a FIPA kindred and had uncontrolled GH/IGF-1 throughout 10 years of octreotide/lanreotide treatment. When switched to pasireotide LAR, he rapidly experienced hormonal control which was associated with marked regression of his tumor residue. Pasireotide LAR was stopped after >10 years due to low IGF-1 and he maintained hormonal control without tumor regrowth for >18 months off pasireotide LAR. Patient 2 had a pituitary adenoma diagnosed when aged 17 that was not cured by surgery. Chronic pasireotide LAR therapy produced hormonal control and marked tumor shrinkage but control was lost when switched to octreotide. Tumor immunohistochemistry showed absent AIP and SST2 staining and positive SST5. Her AIP mutation positive sister developed a 2.5 cm follicular thyroid carcinoma aged 21 with tumoral loss of heterozygosity at the AIP locus and absent AIP staining. Patients 1 and 2 required multi-modal therapy to control diabetes. On stopping pasireotide LAR after >10 years of treatment, Patient 1’s glucose metabolism returned to baseline levels. Long-term pasireotide LAR therapy can be beneficial in some AIP mutation positive acromegaly patients that are resistant to first-generation SSA.
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Scientific Article
EMBO Rep. 20:e47258 (2019)
Cachexia is a wasting disorder that accompanies many chronic diseases including cancer and results from an imbalance of energy requirements and energy uptake. In cancer cachexia, tumor-secreted factors and/or tumor-host interactions cause this imbalance, leading to loss of adipose tissue and skeletal and cardiac muscle, which weakens the body. In this review, we discuss how energy enters the body and is utilized by the different organs, including the gut, liver, adipose tissue, and muscle, and how these organs contribute to the energy wasting observed in cachexia. We also discuss futile cycles both between the organs and within the cells, which are often used to fine-tune energy supply under physiologic conditions. Ultimately, understanding the complex interplay of pathologic energy-wasting circuits in cachexia can bring us closer to identifying effective treatment strategies for this devastating wasting disease.
Review
Review
Neurobiol. Dis. 127, 76-86 (2019)
Painful diabetic neuropathy (PDN) is a devastating neurological complication of diabetes. Methylglyoxal (MG) is a reactive metabolite whose elevation in the plasma corresponds to PDN in patients and pain-like behavior in rodent models of type 1 and type 2 diabetes. Here, we addressed the MG-related spinal mechanisms of PDN in type 2 diabetes using db/db mice, an established model of type 2 diabetes, and intrathecal injection of MG in conventional C57BL/6J mice. Administration of either a MG scavenger (GERP10) or a vector overexpressing glyoxalase 1, the catabolic enzyme for MG, attenuated heat hypersensitivity in db/db mice. In C57BL/6J mice, intrathecal administration of MG produced signs of both evoked (heat and mechanical hypersensitivity) and affective (conditioned place avoidance) pain. MG-induced Ca2+ mobilization in lamina II dorsal horn neurons of C57BL/6J mice was exacerbated in db/db, suggestive of MG-evoked central sensitization. Pharmacological and/or genetic inhibition of transient receptor potential ankyrin subtype 1 (TRPA1), adenylyl cyclase type 1 (AC1), protein kinase A (PKA), or exchange protein directly activated by cyclic adenosine monophosphate (Epac) blocked MG-evoked hypersensitivity in C57BL/6J mice. Similarly, intrathecal administration of GERP10, or inhibitors of TRPA1 (HC030031), AC1 (NB001), or Epac (HJC-0197) attenuated hypersensitivity in db/db mice. We conclude that MG and sensitization of a spinal TRPAl-AC1-Epac signaling cascade facilitate PDN in db/db mice. Our results warrant clinical investigation of MG scavengers, glyoxalase inducers, and spinally-directed pharmacological inhibitors of a MG-TRPAl-AC1-Epac pathway for the treatment of PDN in type 2 diabetes.
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Scientific Article
Cell. Signal. 57, 45-57 (2019)
AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis, acting as a sensor of energy and nutrient status. As such, AMPK is considered a promising drug target for treatment of medical conditions particularly associated with metabolic dysfunctions. To better understand the downstream effectors and physiological consequences of AMPK activation, we have employed a chemical genetic screen in mouse primary hepatocytes in an attempt to identify novel AMPK targets. Treatment of hepatocytes with a potent and specific AMPK activator 991 resulted in identification of 65 proteins phosphorylated upon AMPK activation, which are involved in a variety of cellular processes such as lipid/glycogen metabolism, vesicle trafficking, and cytoskeleton organisation. Further characterisation and validation using mass spectrometry followed by immunoblotting analysis with phosphorylation site-specific antibodies identified AMPK-dependent phosphorylation of Gapex-5 (also known as GTPase-activating protein and VPS9 domain-containing protein 1 (GAPVD1)) on Ser902 in hepatocytes and starch-binding domain 1 (STBD1) on Ser175 in multiple cells/tissues. As new promising roles of AMPK as a key metabolic regulator continue to emerge, the substrates we identified could provide new mechanistic and therapeutic insights into AMPK-activating drugs in the liver.
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Scientific Article
Plant Signal. Behav. 14:e1581561 (2019)
Subcellular localization of trafficking proteins in a single cell affects the assembly of trafficking machinery between organelles and vesicles throughout the targeting pathway. RabGTPase is one of the regulators to direct specific targeting of cargo molecules depending on GDP/GTP bound status. We have recently determined the crystal structures of GDP-bound inactive and both GTP- and GppNHp-bound active forms of Arabidopsis RabA1a. It is notable that the switch regions of RabA1a exhibit conformational changes derived by GDP or GTP binding. However, it was not clear that where the GDP- or GTP-bound RabA1a is localized at the subcellular level in a cell. Here we demonstrate that the distinct proportion of subcellular localization of RabA1a depends on its site-specific mutation as the GDP- or GTP-bound form. RabA1a proteins located at the plasma membrane, endosomes, and cytosol. While the GDP-bound form of RabA1a(S27N) located more at endosomes than the plasma membrane compared to the proportions of RabA1a wild-type, and the GTP-bound RabA1a(Q72L) located mainly at the plasma membrane in comparison to RabA1a wild-type and RabA1a(S27N). These distinct proportional localizations of RabA1a enable a cognate interaction between inactive/active RabA1 and effector molecules to direct specific targeting of its cargo molecules.
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Scientific Article
FASEB J. 33, 5924-5941 (2019)
The glucocorticoid receptor (GR) represents the crucial molecular mediator of key endocrine, glucocorticoid hormone-dependent regulatory circuits, including control of glucose, protein, and lipid homeostasis. Consequently, aberrant glucocorticoid signaling is linked to severe metabolic disorders, including insulin resistance, obesity, and hyperglycemia, all of which also appear upon chronic glucocorticoid therapy for the treatment of inflammatory conditions. Of note, long-term glucocorticoid exposure under these therapeutic conditions typically induces glucocorticoid resistance, requiring higher doses and consequently triggering more severe metabolic phenotypes. However, the molecular basis of acquired glucocorticoid resistance remains unknown. In a screen of differential microRNA expression during glucocorticoid-dependent adipogenic differentiation of human multipotent adipose stem cells, we identified microRNA 29a (miR-29a) as one of the most down-regulated transcripts. Overexpression of miR-29a impaired adipogenesis. We found that miR-29a represses GR in human adipogenesis by directly targeting its mRNA, and downstream analyses revealed that GR mediates most of miR-29a's anti-adipogenic effects. Conversely, miR-29a expression depends on GR activation, creating a novel miR-29-driven feedback loop. miR-29a and GR expression were inversely correlated both in murine adipose tissue and in adipose tissue samples obtained from human patients. In the latter, miR-29a levels were additionally strongly negatively correlated with body mass index and adipocyte size. Importantly, inhibition of miR-29 in mice partially rescued the down-regulation of GR during dexamethasone treatment. We discovered that, in addition to modulating GR function under physiologic conditions, pharmacologic glucocorticoid application in inflammatory disease also induced miR-29a expression, correlating with reduced GR levels. This effect was abolished in mice with impaired GR function. In summary, we uncovered a novel GR-miR-29a negative feedback loop conserved between mice and humans, in health and disease. For the first time, we elucidate a microRNA-related mechanism that might contribute to GR dysregulation and resistance in peripheral tissues.-Glantschnig, C., Koenen, M., Gil-Lozano, M., Karbiener, M., Pickrahn, I., Williams-Dautovich, J., Patel, R., Cummins, C. L., Giroud, M., Hartleben, G., Vogl, E., Blüher, M., Tuckermann, J., Uhlenhaut, H., Herzig, S., Scheideler, M. A miR-29a-driven negative feedback loop regulates peripheral glucocorticoid receptor signaling.
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Scientific Article
Nat. Commun. 10:306 (2019)
Glucocorticoids (GCs) are effective drugs, but their clinical use is compromised by severe side effects including hyperglycemia, hyperlipidemia and obesity. They bind to the Glucocorticoid Receptor (GR), which acts as a transcription factor. The activation of metabolic genes by GR is thought to underlie these adverse effects. We identify the bHLH factor E47 as a modulator of GR target genes. Using mouse genetics, we find that E47 is required for the regulation of hepatic glucose and lipid metabolism by GR, and that loss of E47 prevents the development of hyperglycemia and hepatic steatosis in response to GCs. Here we show that E47 and GR co-occupy metabolic promoters and enhancers. E47 is needed for the efficient recruitment of GR and coregulators such as Mediator to chromatin. Altogether, our results illustrate how GR and E47 regulate hepatic metabolism, and might provide an entry point for novel therapies with reduced side effects.
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Scientific Article
Diabetes Ther. 10, 229-243 (2019)
Introduction: Treatment options and decisions are often based on the results of clinical trials. We have evaluated the public availability of results from completed, registered phase III clinical trials on diabetic nephropathy and current treatment options. Methods: This was a cross-sectional analysis in which STrengthening the Reporting of OBservational studies in Epidemiology criteria were applied for design and analysis. In June 2017, 34 completed phase III clinical trials on diabetic nephropathy in the ClinicalTrials. gov registry were identified and matched to publications in the ClinicalTrials.gov registry and to those in the PubMed and Google Scholar databases. If no publication was identified, the principal investigator was contacted. The ratio of published and non-published studies was calculated. Various parameters, including study design, drugs, and comparators provided, were analyzed. Results: Drugs/supplements belonged to 26 different categories of medications, with the main ones being angiotensin-converting enzyme inhibitors, angiotensin-II receptors blockers, and dipeptidyl-peptidase-4-inhibitors. Among the trials completed before 2016 (n = 32), 22 (69%) were published, and ten (31%) remained unpublished. Thus, data on 11 different interventions and more than 1000 patients remained undisclosed. Mean time to publication was 26.5 months, which is longer than the time constrictions imposed by the U.S. Food and Drug Administration Amendments Act. Most trials only showed weak effects on micro- and macroalbuminuria, with an absolute risk reduction of 1.0 and 0.3%, respectively, and the number needed to treat varied between 91 and 333, without any relevant effect on end-stage-renal disease by intensive glucose-lowering treatment. Comparison of the results, however, was difficult since study design, interventions, and the renal outcome parameters vary greatly between the studies. Conclusion: Despite the financial and human resources involved and the relevance for therapeutic guidelines and clinical decisions, about one-third of phase III clinical trials on diabetic nephropathy remain unpublished. Interventions used in published trials showed a low efficacy on renal outcome. Funding: Deutsche Forschungsgemeinschaft (DFG): SFB 1118.
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Scientific Article
Mol. Metab. 19, 97-106 (2019)
Objective: Extracellular matrix remodeling is required for adipose expansion under increased caloric intake. In turn, inhibited expandability due to aberrant collagen deposition promotes insulin resistance and progression towards the metabolic syndrome. An emerging role for the small leucine-rich proteoglycan Lumican in metabolically driven nonalcoholic fatty liver disease sparks an interest in further understanding its role in diet-induced obesity and metabolic complications.Methods: Whole body ablation of Lumican (Lum(-/-)) gene and adeno-associated virus-mediated over-expression were used in combination with control or high fat diet to assess energy balance, glucose homeostasis as well as adipose tissue health and remodeling.Results: Lumican was found to be particularly enriched in the stromal cells isolated from murine gonadal white adipose tissue. Likewise murine and human visceral fat showed a robust increase in Lumican as compared to fat from the subcutaneous depot. Lumican null female mice exhibited moderately increased fat mass, decreased insulin sensitivity and increased liver triglycerides in a diet-dependent manner. These changes coincided with inflammation in adipose tissue and no overt effects in adipose expandability, i.e. adipocyte formation and hypertrophy. Lumican over-expression in visceral fat and liver resulted in improved insulin sensitivity and glucose clearance.Conclusions: These data indicate that Lumican may represent a functional link between the extracellular matrix, glucose homeostasis, and features of the metabolic syndrome. (C) 2018 The Authors. Published by Elsevier GmbH.
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Scientific Article
Gastroenterology 156, 203-217.e20 (2019)
BACKGROUND AND AIMS: Cells in pancreatic ductal adenocarcinoma (PDAC) undergo autophagy, but its effects vary with tumor stage and genetic factors. We investigated the consequences of varying levels of the autophagy related 5 (Atg5) protein on pancreatic tumor formation and progression. METHODS: We generated mice that express oncogenic Kras in primary pancreatic cancer cells and have homozygous disruption of Atg5 (A5; Kras) or heterozygous disruption of Atg5 (A5(+/-); Kras), and compared them with mice with only oncogenic Kras (controls). Pancreata were analyzed by histology and immunohistochemistry. Primary tumor cells were isolated and used to perform transcriptome, metabolome, intracellular calcium, extracellular cathepsin activity, and cell migration and invasion analyses. The cells were injected into wild-type littermates, and orthotopic tumor growth and metastasis were monitored. Atg5 was knocked down in pancreatic cancer cell lines using small hairpin RNAs; cell migration and invasion were measured, and cells were injected into wild-type littermates. PDAC samples were obtained from independent cohorts of patients and protein levels were measured on immunoblot and immunohistochemistry; we tested the correlation of protein levels with metastasis and patient survival times. RESULTS: A5(+/-); Kras mice, with reduced Atg5 levels, developed more tumors and metastases, than control mice, whereas A5; Kras mice did not develop any tumors. Cultured A5(+/-); Kras primary tumor cells were resistant to induction and inhibition of autophagy, had altered mitochondrial morphology, compromised mitochondrial function, changes in intracellular Ca2thorn oscillations, and increased activity of extracellular cathepsin L and D. The tumors that formed in A5(+/-); Kras mice contained greater numbers of type 2 macrophages than control mice, and primary A5(+/-); Kras tumor cells had up-regulated expression of cytokines that regulate macrophage chemoattraction and differentiation into M2 macrophage. Knockdown of Atg5 in pancreatic cancer cell lines increased their migratory and invasive capabilities, and formation of metastases following injection into mice. In human PDAC samples, lower levels of ATG5 associated with tumor metastasis and shorter survival time. CONCLUSIONS: In mice that express oncogenic Kras in pancreatic cells, heterozygous disruption of Atg5 and reduced protein levels promotes tumor development, whereas homozygous disruption of Atg5 blocks tumorigenesis. Therapeutic strategies to alter autophagy in PDAC should consider the effects of ATG5 levels to avoid the expansion of resistant and highly aggressive cells.
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Scientific Article
Clin. Cancer Res. 25, 1505-1516 (2019)
Purpose: Human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) is associated with unfavorable prognosis, while independent prognostic markers remain to be defined.Experimental Design: We retrospectively performed miRNA expression profiling. Patients were operated for locally advanced HPV-negative HNSCC and had received radiochemotherapy in eight different hospitals (DKTK-ROG; n = 85). Selection fulfilled comparable demographic, treatment, and follow-up characteristics. Findings were validated in an independent single-center patient sample (LMU-KKG; n = 77). A prognostic miRNA signature was developed for freedom from recurrence and tested for other endpoints. Recursivepartitioning analysis was performed on the miRNA signature, tumor and nodal stage, and extracapsular nodal spread. Technical validation used qRT-PCR. An miRNA-mRNA target network was generated and analyzed.Results: For DKTK-ROG and LMU-KKG patients, the median follow-up was 5.1 and 5.3 years, and the 5-year freedom from recurrence rate was 63.5% and 75.3%, respectively. A five-miRNA signature (hsa-let-7g-3p, hsamiR- 6508-5p, hsa-miR-210-5p, hsa-miR-4306, and hsa-miR-7161-3p) predicted freedom from recurrence in DKTK-ROG [hazard ratio (HR) 4.42; 95% confidence interval (CI), 1.98-9.88, P < 0.001], which was confirmed in LMU-KKG (HR 4.24; 95% CI, 1.40-12.81, P = 0.005). The signature also predicted overall survival (HR 3.03; 95% CI, 1.50-6.12, P = 0.001), recurrence-free survival (HR 3.16; 95% CI, 1.65-6.04, P < 0.001), and disease-specific survival (HR 5.12; 95% CI, 1.88-13.92, P < 0.001), all confirmed in LMU-KKG data. Adjustment for relevant covariates maintained the miRNA signature predicting all endpoints. Recursive- partitioning analysis of both samples combined classified patients into low (n = 17), low-intermediate (n = 80), high-intermediate (n = 48), or high risk (n = 17) for recurrence (P < 0.001).Conclusions: The five-miRNA signature is a strong and independent prognostic factor for disease recurrence and survival of patients with HPV-negative HNSCC.
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Scientific Article
Exp. Clin. Endocrinol. Diabet. 127, 203-214 (2019)
Levels of reactive metabolites such as reactive carbonyl and oxygen species are increased in patients with diabetes mellitus. The most important reactive dicarbonyl species, methylglyoxal (MG), formed as by-product during glucose metabolism, is more and more recognized as a trigger for the development and progression of diabetic complications. Although it is clear that MG provokes toxic effects, it is currently not well understood what cellular changes MG induces on a molecular level that may lead to pathophysiological conditions found in long-term diabetic complications. Here we review the current knowledge about the molecular effects that MG can induce in a cell. Within the mammalian system, we will focus mostly on the metabolic effects MG exerts when applied systemically to rodents or when applied in vitro to pancreatic beta-cells and adipocytes. Due to the common limitations associated with complex model organisms, we then summarize how yeast as a very simple model organism can help to gain valuable comprehensive information on general defence pathways cells exert in response to MG stress. Pioneering studies in additional rather simple eukaryotic model organisms suggest that many cellular reactions in response to MG are highly conserved throughout evolution.
Review
Review
2018
npj Aging Mech. Dis. 4:4 (2018)
There is increasing evidence that senescent cells are a driving force behind many age-related pathologies and that their selective elimination increases the life- and healthspan of mice. Senescent cells negatively affect their surrounding tissue by losing their cell specific functionality and by secreting a pro-tumorigenic and pro-inflammatory mixture of growth hormones, chemokines, cytokines and proteases, termed the senescence-associated secretory phenotype (SASP). Here we identified an extract from the plant subsp. , which exhibited weak senolytic activity, delayed the acquisition of a senescent phenotype and induced a papillary phenotype with improved functionality in human dermal fibroblasts. When administered to stress-induced premature senescent fibroblasts, this extract changed their global mRNA expression profile and particularly reduced the expression of various SASP components, thereby ameliorating the negative influence on nearby cells. Thus, the investigated plant extract represents a promising possibility to block age-related loss of tissue functionality.
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Scientific Article
BMC Genomics 19:794 (2018)
Background: Norepinephrine (NE) signaling has a key role in white adipose tissue (WAT) functions, including lipolysis, free fatty acid liberation and, under certain conditions, conversion of white into brite (brown-in-white) adipocytes. However, acute effects of NE stimulation have not been described at the transcriptional network level.Results: We used RNA-seq to uncover a broad transcriptional response. The inference of protein-protein and protein-DNA interaction networks allowed us to identify a set of immediate-early genes (IEGs) with high betweenness, validating our approach and suggesting a hierarchical control of transcriptional regulation. In addition, we identified a transcriptional regulatory network with IEGs as master regulators, including HSF1 and NFIL3 as novel NE-induced IEG candidates. Moreover, a functional enrichment analysis and gene clustering into functional modules suggest a crosstalk between metabolic, signaling, and immune responses.Conclusions: Altogether, our network biology approach explores for the first time the immediate-early systems level response of human adipocytes to acute sympathetic activation, thereby providing a first network basis of early cell fate programs and crosstalks between metabolic and transcriptional networks required for proper WAT function.
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Scientific Article
Molecules 23:2823 (2018)
Skin cancer is currently diagnosed as one in every three cancers. Melanoma, the most aggressive form of skin cancer, is responsible for 79% of skin cancer deaths and the incidence is rising faster than in any other solid tumor type. Previously, we have demonstrated that dimethylacrylshikonin (DMAS), isolated from the roots of Onosma paniculata (Boraginaceae), exhibited the lowest IC50 values against different tumor types out of several isolated shikonin derivatives. DMAS was especially cytotoxic towards melanoma cells and led to apoptosis and cell cycle arrest. In this study, we performed a comprehensive gene expression study to investigate the mechanism of action in more detail. Gene expression signature was compared to vehicle-treated WM164 control cells after 24 h of DMAS treatment; where 1192 distinct mRNAs could be identified as expressed in all replicates and 89 were at least 2-fold differentially expressed. DMAS favored catabolic processes and led in particular to p62 increase which is involved in cell growth, survival, and autophagy. More in-depth experiments revealed that DMAS led to autophagy, ROS generation, and loss of mitochondrial membrane potential in different melanoma cells. It has been reported that the induction of an autophagic cell death represents a highly effective approach in melanoma therapy.
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Scientific Article
Trends Cancer 4, 849-860 (2018)
Cancer cachexia is a multifactorial condition characterized by body weight loss that negatively affects quality of life and survival of patients with cancer. Despite the clinical relevance, there is currently no defined standard of care to effectively counteract cancer-associated progressive tissue wasting. Skeletal muscle atrophy represents the main manifestation of cancer cachexia. However, cancer cachexia is increasingly seen as a systemic phenomenon affecting and/or influenced by various organs. Here, we describe recent developments elucidating the roles of different tissues as well as tissue crosstalk in this wasting syndrome, including potential links to other cancer-associated morbidities. A more comprehensive understanding of cancer cachexia etiology and heterogeneity may enable the development of intervention strategies to prevent or reverse this devastating condition.
Review
Review
Dev. Cell 47, 205-221.e7 (2018)
Lipid metabolism is highly compartmentalized between cellular organelles that dynamically adapt their compositions and interactions in response to metabolic challenges. Here, we investigate how diet-induced hepatic lipid accumulation, observed in non-alcoholic fatty liver disease (NAFLD), affects protein localization, organelle organization, and protein phosphorylation in vivo. We develop a mass spectrometric workflow for protein and phosphopeptide correlation profiling to monitor levels and cellular distributions of similar to 6,000 liver proteins and similar to 16,000 phosphopeptides during development of steatosis. Several organelle contact site proteins are targeted to lipid droplets (LDs) in steatotic liver, tethering organelles orchestrating lipid metabolism. Proteins of the secretory pathway dramatically redistribute, including the mis-localization of the COPI complex and sequestration of the Golgi apparatus at LDs. This correlates with reduced hepatic protein secretion. Our systematic in vivo analysis of subcellular rearrangements and organelle-specific phosphorylation reveals how nutrient overload leads to organellar reorganization and cellular dysfunction.
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Scientific Article
Mol. Metab. 18, 143-152 (2018)
Objectives: The deficit of Glyoxalase I (Glo1) and the subsequent increase in methylglyoxal (MG) has been reported to be one the five mechanisms by which hyperglycemia causes diabetic late complications. Aldo-keto reductases (AKR) have been shown to metabolize MG; however, the relative contribution of this superfamily to the detoxification of MG in vivo, particularly within the diabetic state, remains unknown.Methods: CRISPR/Cas9-mediated genome editing was used to generate a Glo1 knock-out (Glo1(-/-)) mouse line. Streptozotocin was then applied to investigate metabolic changes under hyperglycemic conditions.Results: Glo1(-/-) mice were viable and showed no elevated MG or MG-H1 levels under hyperglycemic conditions. It was subsequently found that the enzymatic efficiency of various oxidoreductases in the liver and kidney towards MG were increased in the Glo1(-/-) mice. The functional relevance of this was supported by the altered distribution of alternative detoxification products. Furthermore, it was shown that MG-dependent AKR activity is a potentially clinical relevant pathway in human patients suffering from diabetes.Conclusions: These data suggest that in the absence of GLO1, AKR can effectively compensate to prevent the accumulation of MG. The combination of metabolic, enzymatic, and genetic factors, therefore, may provide a better means of identifying patients who are at risk for the development of late complications caused by elevated levels of MG. (C) 2018 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license.
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Scientific Article
World J. Gastroenterol. 24, 4028-4035 (2018)
AIMTo investigate whether the adipocytes derived hormone adiponectin (ADPN) affects the mechanical responses in strips from the mouse gastric fundus.METHODSFor functional experiments, gastric strips from the fundal region were cut in the direction of the longitudinal muscle layer and placed in organ baths containing Krebs-Henseleit solution. Mechanical responses were recorded via force-displacement transducers, which were coupled to a polygraph for continuous recording of isometric tension. Electrical field stimulation (EFS) was applied via two platinum wire rings through which the preparation was threaded. The effects of ADPN were investigated on the neurally-induced contractile and relaxant responses elicited by EFS. The expression of ADPN receptors, Adipo-R1 and Adipo-R2, was also evaluated by touchdown-PCR analysis.RESULTSIn the functional experiments, EFS (4-16 Hz) elicited tetrodotoxin (TTX)-sensitive contractile responses. Addition of ADPN to the bath medium caused a reduction in amplitude of the neurally-induced contractile responses (P < 0.05). The effects of ADPN were no longer observed in the presence of the nitric oxide (NO) synthesis inhibitor L-N-G-nitro arginine (L-NNA) (P > 0.05). The direct smooth muscle response to methacholine was not influenced by ADPN (P > 0.05). In carbachol precontracted strips and in the presence of guanethidine, EFS induced relaxant responses. Addition of ADPN to the bath medium, other than causing a slight and progressive decay of the basal tension, increased the amplitude of the neurally-induced relaxant responses (P < 0.05). Touchdown-PCR analysis revealed the expression of both Adipo-R1 and Adipo-R2 in the gastric fundus.CONCLUSIONThe results indicate for the first time that ADPN is able to influence the mechanical responses in strips from the mouse gastric fundus.
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Scientific Article
Comparative secretome analyses of primary murine white and brown adipocytes reveal novel adipokines.
Mol. Cell. Proteomics 17, 2358-2370 (2018)
The adipose organ, including white and brown adipose tissues, is an important player in systemic energy homeostasis, storing excess energy in form of lipids while releasing energy upon various energy demands. Recent studies have demonstrated that white and brown adipocytes also function as endocrine cells and regulate systemic metabolism by secreting factors that act locally and systemically. However, a comparative proteomic analysis of secreted factors from white and brown adipocytes and their responsiveness to adrenergic stimulation has not been reported yet. Therefore, we studied and compared the secretome of white and brown adipocytes, with and without norepinephrine (NE) stimulation. Our results reveal that carbohydrate-metabolism-regulating proteins are preferably secreted from white adipocytes, while brown adipocytes predominantly secrete a large variety of proteins. Upon NE stimulation, an increased secretion of known adipokines is favored by white adipocytes while brown adipocytes secreted higher amounts of novel adipokines. Furthermore, the secretory response between NE-stimulated and basal state was multifaceted addressing lipid and glucose metabolism, adipogenesis, and antioxidative reactions. Intriguingly, NE stimulation drastically changed the secretome in brown adipocytes. In conclusion, our study provides a comprehensive catalogue of novel adipokine candidates secreted from white and brown adipocytes with many of them responsive to NE. Given the beneficial effects of brown adipose tissue activation on its endocrine function and systemic metabolism, this study provides an archive of novel batokine candidates and biomarkers for activated brown adipose tissue.
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Scientific Article
Nat. Commun. 9:3129 (2018)
Since modern foods are unnaturally enriched in single metabolites, it is important to understand which metabolites are sensed by the human body and which are not. We previously showed that the fatty acid stearic acid (C18:0) signals via a dedicated pathway to regulate mitofusin activity and thereby mitochondrial morphology and function in cell culture. Whether this pathway is poised to sense changes in dietary intake of C18:0 in humans is not known. We show here that C18:0 ingestion rapidly and robustly causes mitochondrial fusion in people within 3 h after ingestion. C18:0 intake also causes a drop in circulating long-chain acylcarnitines, suggesting increased fatty acid beta-oxidation in vivo. This work thereby identifies C18:0 as a dietary metabolite that is sensed by our bodies to control our mitochondria. This could explain part of the epidemiological differences between C16:0 and C18:0, whereby C16:0 increases cardiovascular and cancer risk whereas C18:0 decreases both.
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Scientific Article
Respiration 96, 29-40 (2018)
Background: Diabetes mellitus is a significant comorbidity of interstitial lung disease (ILD). Objectives: The aim of this study was to investigate the incidence of restrictive lung disease (RLD) and ILD in patients with prediabetes and type 2 diabetes (T2D). Methods: Forty-eight nondiabetics, 68 patients with prediabetes, 29 newly diagnosed T2D, and 110 patients with long-term T2D were examined for metabolic control, diabetes-related complications, breathlessness, and lung function. Five participants with T2D, breathlessness, and RLD underwent multidetector computed tomography (MDCT) and a Six-Minute Walk Test (6MWT). Lung tissue from 4 patients without diabetes and from 3 patients with T2D was histologically examined for presence of pulmonary fibrosis. Results: Breathlessness in combination with RLD was significantly increased in patients with prediabetes and T2D (p < 0.01). RLD was found in 9% of patients with prediabetes, in 20% of patients with newly diagnosed T2D, and in 27% of patients with long-term T2D. Thus, patients with long-term T2D had an increased risk of RLD (OR 5.82 [95% CI 1.71-20.5], p < 0.01). RLD was significantly associated with glucose metabolism and albuminuria (p < 0.01); furthermore, presence of nephropathy increased the risk of RLD (OR 8.57 [95% CI 3.4-21.9], p < 0.01) compared to nondiabetics. MDCT revealed ILD in 4 patients, the 6MWT correlated with the extent of ILD, and histological analysis showed fibrosing ILD in patients with T2D. Conclusions: This study demonstrates increased breathlessness and a high prevalence of RLD in patients with T2D, indicating an association between diabetes and fibrosing ILD.
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Scientific Article
Cell. Physiol. Biochem. 46, 713-726 (2018)
Background/Aims: Reactive dicarbonyl compounds, such as methylglyoxal (MG), contribute to diabetic complications. MG-scavenging capacities of carnosine and anserine, which have been shown to mitigate diabetic nephropathy, were evaluated in vitro and in vivo. Methods: MG-induced cell toxicity was characterized by MTT and MG-H1-formation, scavenging abilities by Western Blot and NMR spectroscopies, cellular carnosine transport by qPCR and microplate luminescence and carnosine concentration by HPLC. Results: In vitro, carnosine and anserine dose-dependently reduced N-carboxyethyl lysine (CEL) and advanced glycation end products (AGEs) formation. NMR studies revealed the formation of oligo/polymeric products of MG catalyzed by carnosine or anserine. MG toxicity (0.3-1 mM) was dose-dependent for podocytes, tubular and mesangial cells whereas low MG levels (0.2 mM) resulted in increased cell viability in podocytes (143±13%, p<0.001) and tubular cells (129±3%, p<0.001). Incubation with carnosine/anserine did not reduce MG-induced toxicity, independent of incubation times and across large ranges of MG to carnosine/anserine ratios. Cellular carnosine uptake was low (<0.1% in 20 hours) and cellular carnosine concentrations remained unaffected. The putative carnosine transporter PHT1 along with the taurine transporter (TauT) was expressed in all cell types while PEPT1, PEPT2 and PHT2, also belonging to the proton-coupled oligopeptide transporter (POT) family, were only expressed in tubular cells. Conclusion: While carnosine and anserine catalyze the formation of MG oligo/polymers, the molar ratios required for protection from MG-induced cellular toxicity are not achievable in renal cells. The effect of carnosine in vivo, to mitigate diabetic nephropathy may therefore be independent upon its ability to scavenge MG and/or carnosine is mainly acting extracellularly.
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Scientific Article
EMBO Mol. Med. 10:e8613 (2018)
Most antidiabetic drugs treat disease symptoms rather than adipose tissue dysfunction as a key pathogenic cause in the metabolic syndrome and type 2 diabetes. Pharmacological targeting of adipose tissue through the nuclear receptor PPARg, as exemplified by glitazone treatments, mediates efficacious insulin sensitization. However, a better understanding of the context-specific PPARg responses is required for the development of novel approaches with reduced side effects. Here, we identified the transcriptional cofactor Cited4 as a target and mediator of rosiglitazone in human and murine adipocyte progenitor cells, where it promoted specific sets of the rosiglitazone-dependent transcriptional program. In mice, Cited4 was required for the proper induction of thermogenic expression by Rosi specifically in subcutaneous fat. This phenotype had high penetrance in females only and was not evident in beta-adrenergically stimulated browning. Intriguingly, this specific defect was associated with reduced capacity for systemic thermogenesis and compromised insulin sensitization upon therapeutic rosiglitazone treatment in female but not male mice. Our findings on Cited4 function reveal novel unexpected aspects of the pharmacological targeting of PPARg.
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Scientific Article
Transpl. Int. 31, 751-760 (2018)
Steunstichting ESOT A prolonged cold ischaemia time (CIT) is suspected to be associated with an increased ischaemia and reperfusion injury (IRI) resulting in an increased damage to the graft. In total, 91 patients were evaluated for a delayed graft function within 7 days after kidney transplantation (48 deceased, 43 living donors). Blood and urine samples were collected before, immediately after the operation, and 1, 3, 5, 7 and 10 days later. Plasma and/or urine levels of total keratin 18 (total K18), caspase-cleaved keratin 18 (cc K18), the soluble receptor for advanced glycation end products (sRAGE), tissue inhibitor of metalloproteinase-2 (TIMP-2) and insulin-like growth factor-binding protein-7 (IGFBP7) were measured. As a result of prolonged CIT and increased IRI, deceased donor transplantations were shown to suffer from a more distinct cell cycle arrest and necrotic cell death. Plasmatic total K18 and urinary TIMP-2 and IGFBP7 were therefore demonstrated to be of value for the detection of a delayed graft function (DGF), as they improved the diagnostic performance of a routinely used clinical scoring system. Plasmatic total K18 and urinary TIMP-2 and IGFBP7 measurements are potentially suitable for early identification of patients at high risk for a DGF following kidney transplantation from deceased or living donors.
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Scientific Article
Sci. Signal. 11:eaai7838 (2018)
Purpose of Review Advances in technology have expanded telemedicine opportunities covering medical practice, research, and education. This is of particular importance in movement disorders (MDs), where the combination of disease progression, mobility limitations, and the sparse distribution of MD specialists increase the difficulty to access. In this review, we discuss the prospects, challenges, and strategies for telemedicine in MDs.Recent Findings Telemedicine for MDs has been mainly evaluated in Parkinson's disease (PD) and compared to in-office care is cost-effective with similar clinical care, despite the barriers to engagement. However, particular groups including pediatric patients, rare MDs, and the use of telemedicine in underserved areas need further research.Summary Interdisciplinary telemedicine and tele-education for MDs are feasible, provide similar care, and reduce travel costs and travel time compared to in-person visits. These benefits have been mainly demonstrated for PD but serve as a model for further validation in other movement disorders.
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Scientific Article
J. Nutr. Biochem. 57, 189-196 (2018)
Recent studies have demonstrated that dietary protein dilution (PD) can promote metabolic inefficiency and improve glucose metabolism. However, whether PD can promote other aspects of metabolic health, such as improve systemic lipid metabolism, and mechanisms therein remains unknown. Mouse models of obesity, such as high-fat-diet-fed C57B1/6 N mice, and New Zealand Obese mice were fed normal (i.e., 20%P) and protein-dilute (i.e., 5%EP) diets. FGF21 -/-and Cd36-/-and corresponding littermate +/+ controls were also studied to examine gene-diet interactions. Here, we show that chronic PD retards the development of hypertrigylceridemia and fatty liver in obesity and that this relies on the induction of the hepatokine fibroblast growth factor 21 (FGF21). Furthermore, PD greatly enhances systemic lipid homeostasis, the mechanisms by which include FGF21-stimulated, and cluster of differentiation 36 (CD36) mediated, fatty acid clearance by oxidative tissues, such as heart and brown adipose tissue. Taken together, our preclinical studies demonstrate a novel nutritional strategy, as well as highlight a role for FGF21-stimulated systemic lipid metabolism, in combating obesity-related dyslipidemia.
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Scientific Article
Aging 10, 1103-1132 (2018)
Loss of functionality during aging of cells and organisms is caused and accompanied by altered cell-to-cell communication and signalling. One factor thereby is the chronic accumulation of senescent cells and the concomitant senescence-associated secretory phenotype (SASP) that contributes to microenvironment remodelling and a pro-inflammatory status. While protein based SASP factors have been well characterized, little is known about small extracellular vesicles (sEVs) and their miRNA cargo. Therefore, we analysed secretion of sEVs from senescent human dermal fibroblasts and catalogued the therein contained miRNAs. We observed a four-fold increase of sEVs, with a concomitant increase of > 80% of all cargo miRNAs. The most abundantly secreted miRNAs were predicted to collectively target mRNAs of pro-apoptotic proteins, and indeed, senescent cell derived sEVs exerted anti-apoptotic activity. In addition, we identified senescencespecific differences in miRNA composition of sEVs, with an increase of miR-23a-5p and miR-137 and a decrease of miR-625-3p, miR-766-3p, miR-199b-5p, miR-381-3p, miR-17-3p. By correlating intracellular and sEV-miRNAs, we identified miRNAs selectively retained in senescent cells (miR-21-3p and miR-17-3p) or packaged specifically into senescent cell derived sEVs (miR-15b-5p and miR-30a-3p). Therefore, we suggest sEVs and their miRNA cargo to be novel, members of the SASP that are selectively secreted or retained in cellular senescence.
Wissenschaftlicher Artikel
Scientific Article
J. Lipid Res. 59, 452-461 (2018)
The recent characterization of functional brown adipose tissue in adult humans has opened new perspectives for regulation of energy expenditure with respect to obesity and diabetes. Furthermore, dietary recommendations have taken into account the insufficient dietary intake of ω3 PUFAs and the concomitant excessive intake of ω6 PUFA associated with the occurrence of overweight/obesity. We aimed to study whether ω3 PUFAs could play a role in the recruitment and function of energy-dissipating brown/brite adipocytes. We show that ω3 PUFA supplementation has a beneficial effect on the thermogenic function of adipocytes. In vivo, a low dietary ω6:ω3 ratio improved the thermogenic response of brown and white adipose tissues to β3-adrenergic stimulation. This effect was recapitulated in vitro by PUFA treatment of hMADS adipocytes. We pinpointed the ω6- derived eicosanoid prostaglandin (PG)F2α as the molecular origin because the effects were mimicked with a specific PGF2α receptor agonist. PGF2α level in hMADS adipocytes was reduced in response to ω3 PUFA supplementation. The recruitment of thermogenic adipocytes is influenced by the local quantity of individual oxylipins, which is controlled by the ω6:ω3 ratio of available lipids. In human nutrition, energy homeostasis may thus benefit from the implementation of a more balanced dietary ω6:ω3 ratio.
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Scientific Article
Diabetes Care 41, 1068-1075 (2018)
OBJECTIVE: To study incident diabetic polyneuropathy (DPN) prospectively during the first 13 years after a screening-based diagnosis of type 2 diabetes and determine the associated risk factors for the development of DPN. RESEARCH DESIGN AND METHODS: We assessed DPN longitudinally in the Danish arm of the Anglo-Danish-Dutch study of Intensive Treatment of Diabetes in Primary Care (ADDITION) using the Michigan Neuropathy Screening Instrument questionnaire (MNSIQ), defining DPN with scores ≥4. Risk factors present at the diabetes diagnosis associated with the risk of incident DPN were estimated using Cox proportional hazard models adjusted for trial randomization group, sex, and age. RESULTS: Of the total cohort of 1,533 people, 1,445 completed the MNSIQ at baseline and 189 (13.1%) had DPN at baseline. The remaining 1,256 without DPN entered this study (median age 60.8 years [interquartile range 55.6; 65.6], 59% of whom were men). The cumulative incidence of DPN was 10% during 13 years of diabetes. Age (hazard ratio [HR] 1.03 [95% CI 1.00; 1.07]) (unit = 1 year), weight (HR 1.09 [95% CI 1.03; 1.16]) (unit = 5 kg), waist circumference (HR 1.14 [95% CI 1.05; 1.24]) (unit = 5 cm), BMI (HR 1.14 [95% CI 1.06; 1.23]) (unit = 2 kg/m2), log2 methylglyoxal (HR 1.45 [95% CI 1.12; 1.89]) (unit = doubling), HDL cholesterol (HR 0.82 [95% CI 0.69; 0.99]) (unit = 0.25 mmol/L), and LDL cholesterol (HR 0.92 [95% CI 0.86; 0.98]) (unit = 0.25 mmol/L) at baseline were significantly associated with the risk of incident DPN. CONCLUSIONS: This study provides further epidemiological evidence for obesity as a risk factor for DPN. Moreover, low HDL cholesterol levels and higher levels of methylglyoxal, a markerofdicarbonyl stress, are identifiedasrisk factors for the developmentofDPN.
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Scientific Article
Ann. Neurol. 83, 588-598 (2018)
ObjectiveTo visualize and quantify differences of microstructural nerve damage in distal symmetric diabetic neuropathy (DPN) between type 1 diabetes (T1D) and type 2 diabetes (T2D), and to detect correlations between neuropathic symptoms and serological risk factors. MethodsThree-tesla magnetic resonance neurography of the sciatic nerve was performed in 120 patients (T1D, n=35; T2D, n=85) with either DPN (n=84) or no DPN (n=36). Results were subsequently correlated with clinical, serological, and electrophysiological patient data. ResultsT2-weighted (T2w)-hyperintense lesions correlated negatively with tibial compound motor action potential (r=-0.58, p<0.0001) and peroneal nerve conduction (r=0.51, p=0.0002), and positively with neuropathy disability score (NDS; r=-0.54, p<0.0001), neuropathy symptom score (NSS; r=0.52, p<0.0001), and HbA1c level (r=0.23, p=0.014). T2w-hypointense lesions correlated positively with NDS (r=0.28, p=0.002), NSS (r=0.36, p<0.0001), and serum triglycerides (r=0.34, p=0.0003), and negatively with serum high-density lipoprotein (HDL; r=-0.48, p<0.0001). For DPN in T1D, elevated values of T2w-hyperintense lesions (19.674.13% vs 12.49 +/- 1.23%, p=0.027) and HbA1c (8.74 +/- 0.29% vs 7.11 +/- 0.16%, p<0.0001) were found when compared to T2D. For DPN in T2D, elevated T2w-hypointense lesions (23.41 +/- 2.69mm(3) vs 11.43 +/- 1.74mm(3), p=0.046) and triglycerides (220.70 +/- 23.70mg/dl vs 106.60 +/- 14.51mg/dl, p<0.0001), and lower serum HDL (51.29 +/- 3.02mg/dl vs 70.79 +/- 4.65mg/dl, p<0.0001) were found when compared to T1D. InterpretationThe predominant type of nerve lesion in DPN differs between T1D and T2D. Correlations found between lesion type and serological parameters indicate that predominant nerve lesions in T1D are associated with poor glycemic control and loss of nerve conduction, whereas predominant lesions in T2D are associated with changes in lipid metabolism. These findings may be helpful for future studies on the underlying pathophysiological pathways and possible treatments for DPN in T1D and T2D. Ann Neurol 2018;83:588-598
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Scientific Article
Acta Diabetol. 55, 585-592 (2018)
Aromatic hydrocarbons belong to the most abundant contaminants in groundwater systems. They can serve as carbon and energy source for a multitude of indigenous microorganisms. Predictions of contaminant biodegradation and microbial growth in contaminated aquifers are often vague because the parameters of microbial activity in the mathematical models used for predictions are typically derived from batch experiments, which don't represent conditions in the field. In order to improve our understanding of key drivers of natural attenuation and the accuracy of predictive models, we conducted comparative experiments in batch and sediment flow-through systems with varying concentrations of contaminant in the inflow and flow velocities applying the aerobic Pseudomonas putida strain F1 and the denitrifying Aromatoleum aromaticum strain EbN1. We followed toluene degradation and bacterial growth by measuring toluene and oxygen concentrations and by direct cell counts. In the sediment columns, the total amount of toluene degraded by P. putida F1 increased with increasing source concentration and flow velocity, while toluene removal efficiency gradually decreased. Results point at mass transfer limitation being an important process controlling toluene biodegradation that cannot be assessed with batch experiments. We also observed a decrease in the maximum specific growth rate with increasing source concentration and flow velocity. At low toluene concentrations, the efficiencies in carbon assimilation within the flow-through systems exceeded those in the batch systems. In all column experiments the number of attached cells plateaued after an initial growth phase indicating a specific "carrying capacity" depending on contaminant concentration and flow velocity. Moreover, in all cases, cells attached to the sediment dominated over those in suspension, and toluene degradation was performed practically by attached cells only. The observed effects of varying contaminant inflow concentration and flow velocity on biodegradation could be captured by a reactive-transport model. By monitoring both attached and suspended cells we could quantify the release of new-grown cells from the sediments to the mobile aqueous phase. Studying flow velocity and contaminant concentrations as key drivers of contaminant transformation in sediment flow-through microcosms improves our system understanding and eventually the prediction of microbial biodegradation at contaminated sites.
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Scientific Article
Cell Metab. 27, 926-934.e8 (2018)
The molecular causes of type 2 diabetes (T2D) are not well understood. Both type 1 diabetes (T1D) and T2D are characterized by impaired insulin signaling and hyperglycemia. From analogy to T1D, insulin resistance and hyperglycemia are thought to also play causal roles in T2D. Recent clinical studies, however, found that T2D patients treated to maintain glycemia below the diabetes definition threshold (HbA(1c) < 6.5%) still develop diabetic complications. This suggests additional insulin-and glucose-independent mechanisms could be involved in T2D progression and/or initiation. T2D patients have elevated levels of the metabolite methylglyoxal (MG). We show here, using Drosophila glyoxalase 1 knockouts, that animals with elevated methylglyoxal recapitulate several core aspects of T2D: insulin resistance, obesity, and hyperglycemia. Thus elevated MG could constitute one root cause of T2D, suggesting that the molecular causes of elevated MG warrant further study.
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Scientific Article
J. Biol. Chem. 293, 4845-4859 (2018)
The enzyme AICAR-transformylase/IMP cyclohydrolase (ATIC) catalyzes the last two steps of purine de novo synthesis. It metabolizes 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), which is an AMP analogue, leading to activation of AMP-activated kinase (AMPK). We investigated whether the AICAR-ATIC pathway plays a role in the high glucose (HG)-mediated DNA damage response and AICAR-mediated AMPK activation, explaining the detrimental effects of glucose on neuronal damage and shortening of the lifespan. HG up-regulated the expression and activity of the Caenorhabditis elegans homologue of ATIC, C55F2.1 (atic-1), and increased the levels of reactive oxygen species and methylglyoxal-derived advanced glycation end products. Overexpression of atic-1 decreased the lifespan and head motility and increased neuronal damage under both standard and HG conditions. Inhibition of atic-1 expression, by RNAi, under HG was associated with increased lifespan and head motility and reduced neuronal damage, reactive oxygen species, and methylglyoxal-derived advanced glycation end product accumulation. This effect was independent of an effect on DNA damage or antioxidant defense pathways, such as superoxide dismutase (sod-3) or glyoxalase-1 (glod-4), but was dependent on AMPK and accumulation of AICAR. Through AMPK, AICAR treatment also reduced the negative effects of HG. The mitochondrial inhibitor rotenone abolished the AICAR/AMPK-induced amelioration of HG effects, pointing to mitochondria as a prime target of the glucotoxic effects in C. elegans. We conclude that atic-1 is involved in glucotoxic effects under HG conditions, either by blocked atic-1 expression or via AICAR and AMPK induction.
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Scientific Article
Circulation 137, 2592-2608 (2018)
Skin affections after sulfur mustard (SM) exposure include erythema, blister formation and severe inflammation. An antidote or specific therapy does not exist. Anti-inflammatory compounds as well as substances counteracting SM-induced cell death are under investigation. In this study, we investigated the benzylisoquinoline alkaloide berberine (BER), a metabolite in plants like berberis vulgaris, which is used as herbal pharmaceutical in Asian countries, against SM toxicity using a well-established in vitro approach. Keratinocyte (HaCaT) mono-cultures (MoC) or HaCaT/THP-1 co-cultures (CoC) were challenged with 100, 200 or 300 mM SM for 1 h. Post-exposure, both MoC and CoC were treated with 10, 30 or 50 mu M BER for 24 h. At that time, supernatants were collected and analyzed both for interleukine (IL) 6 and 8 levels and for content of adenylate-kinase (AK) as surrogate marker for cell necrosis. Cells were lysed and nucleosome formation as marker for late apoptosis was assessed. In parallel, AK in cells was determined for normalization purposes. BER treatment did not influence necrosis, but significantly decreased apoptosis. Anti-inflammatory effects were moderate, but also significant, primarily in CoC. Overall, BER has protective effects against SM toxicity in vitro. Whether this holds true should be evaluated in future in vivo studies.
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Scientific Article
Mol. Metab. 9, 156-167 (2018)
Objective: Diabetic retinopathy (DR) is induced by an accumulation of reactive metabolites such as ROS, RNS, and RCS species, which were reported to modulate the activity of cation channels of the TRPC family. In this study, we use Trpc1/4/5/6(-/-) compound knockout mice to analyze the contribution of these TRPC proteins to diabetic retinopathy. Methods: We used Nanostring- and qPCR-based analysis to determine mRNA levels of TRPC channels in control and diabetic retinae and retinal cell types. Chronic hyperglycemia was induced by Streptozotocin (STZ) treatment. To assess the development of diabetic retinopathy, vaso-regression, pericyte loss, and thickness of individual retinal layers were analyzed. Plasma and cellular methylglyoxal (MG) levels, as well as Glyoxalase 1 (GL01) enzyme activity and protein expression, were measured in WT and Trpc1/4/5/6(-/-) cells or tissues. MG-evoked toxicity in cells of both genotypes was compared by MTT assay. Results: We find that Trpc1/4/5/6(-/-) mice are protected from hyperglycemia-evoked vasoregression determined by the formation of acellular capillaries and pericyte drop-out. In addition, Trpc1/4/5/6(-/-) mice are resistant to the STZ-induced reduction in retinal layer thickness. The RCS metabolite methylglyoxal, which represents a key mediator for the development of diabetic retinopathy, was significantly reduced in plasma and red blood cells (RBCs) of STZ-treated Trpc1/4/5/6(-/-) mice compared to controls. GLO1 is the major MG detoxifying enzyme, and its activity and protein expression were significantly elevated in Trpc1/4/5/6-deficient cells, which led to significantly increased resistance to MG toxicity. GLO1 activity was also increased in retinal extracts from Trpc1/4/5/6(-/-) mice. The TRPCs investigated here are expressed at different levels in endothelial and glial cells of the retina. Conclusion: The protective phenotype in diabetic retinopathy observed in Trpc1/4/5/6(-/-) mice is suggestive of a predominant action of TRPCs in Muller cells and microglia because of their central position in the retention of a proper homoeostasis of the neurovascular unit. (C) 2018 The Authors. Published by Elsevier GmbH.
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Scientific Article
Redox Biol. 15, 12-21 (2018)
NADPH oxidases are important sources of reactive oxygen species (ROS). Several Nox homologues are present together in the vascular system but whether they exhibit crosstalk at the activity level is unknown. To address this, vessel function of knockout mice for the cytosolic Nox organizer proteins p47phox, NoxO1 and a p47phox-NoxO1-double knockout were studied under normal condition and during streptozotocin-induced diabetes.
RESULTS:
In the mouse aorta, mRNA expression for NoxO1 was predominant in smooth muscle and endothelial cells, whereas p47phox was markedly expressed in adventitial cells comprising leukocytes and tissue resident macrophages. Knockout of either NoxO1 or p47phox resulted in lower basal blood pressure. Deletion of any of the two subunits also prevented diabetes-induced vascular dysfunction. mRNA expression analysis by MACE (Massive Analysis of cDNA ends) identified substantial gene expression differences between the mouse lines and in response to diabetes. Deletion of p47phox induced inflammatory activation with increased markers of myeloid cells and cytokine and chemokine induction. In contrast, deletion of NoxO1 resulted in an attenuated interferon gamma signature and reduced expression of genes related to antigen presentation. This aspect was also reflected by a reduced number of circulating lymphocytes in NoxO1-/- mice.
INNOVATION AND CONCLUSION:
ROS production stimulated by NoxO1 and p47phox limit endothelium-dependent relaxation and maintain blood pressure in mice. However, NoxO1 and p47phox cannot substitute each other despite their similar effect on vascular function. Deletion of NoxO1 induced an anti-inflammatory phenotype, whereas p47phox deletion rather elicited a hyper-inflammatory response.
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Scientific Article
Nat. Med. 24, 62-72 (2018)
The stress-responsive epigenetic repressor histone deacetylase 4 (HDAC4) regulates cardiac gene expression. Here we show that the levels of an N-terminal proteolytically derived fragment of HDAC4, termed HDAC4-NT, are lower in failing mouse hearts than in healthy control hearts. Virus-mediated transfer of the portion of the Hdac4 gene encoding HDAC4-NT into the mouse myocardium protected the heart from remodeling and failure; this was associated with decreased expression of Nr4a1, which encodes a nuclear orphan receptor, and decreased NR4A1-dependent activation of the hexosamine biosynthetic pathway (HBP). Conversely, exercise enhanced HDAC4-NT levels, and mice with a cardiomyocyte-specific deletion of Hdac4 show reduced exercise capacity, which was characterized by cardiac fatigue and increased expression of Nr4a1. Mechanistically, we found that NR4A1 negatively regulated contractile function in a manner that depended on the HBP and the calcium sensor STIM1. Our work describes a new regulatory axis in which epigenetic regulation of a metabolic pathway affects calcium handling. Activation of this axis during intermittent physiological stress promotes cardiac function, whereas its impairment in sustained pathological cardiac stress leads to heart failure.
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Scientific Article
J. Diab. Complic. 32, 130-138 (2018)
Aims: Low levels of reactive oxygen species and resulting oxidative protein modifications may play a beneficial role in cellular function under stress conditions. Here we studied the influence of age-dependent protein carbonylation on expression and activity of the anti-oxidative selenoenzyme glutathione peroxidase(GPx) in insulin-deficient Ins2(Akita) mice and type 2 diabetic obese db/db mice in context of diabetic nephropathy. Methods: Protein carbonylation, GPx expression and activity were examined in kidney tissue and lysates by common histological and protein biochemical methods. Results: In kidneys of Ins2(Akita) mice, carbonylated proteins, GPx-1 and GPx-4 expression were mainly detected in podocytes and mesangial cells. GPx activity was increased in kidney cortex homogenates of these mice. Remarkably, young animals did not show a concomitant increase in GPx expression but enhanced GPx carbonylation. No carbonylation-dependent modification of GPx activity was detected in db/db mice. In cultured podocytes hyperglycemia induced an increase in GPx expression but had no effect on activity or carbonylation. In kidney tissue sections of type 1 or type 2 diabetes patients, GPx-1 and GPx-4 expression but not overall protein carbonylation was significantly decreased. Conclusions: These results indicate the existence of a threshold for beneficial carbonylation-dependent redox signaling during the progression of diabetic nephropathy. (C) 2017 Elsevier Inc. All rights reserved.
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Scientific Article
Gerontology, DOI: 10.1159/000485183 (2018)
Aging is a time-related process of functional decline at organelle, cellular, tissue, and organismal level that ultimately limits life. Cellular senescence is a state of permanent growth arrest in response to stress and one of the major drivers of aging and age-related disorders. Senescent cells accumulate with age, and removal of these cells delays age-related disorders in different tissues and prolongs healthy lifespan. One of the most studied aging mechanisms is the accumulation of reactive oxygen species damage in cells, organs, and organisms over time. Elevated oxidative stress is also found in metabolic diseases such as obesity, metabolic syndrome and associated disorders. Moreover, dysregulation of the energy homeostasis is also associated with aging, and many age-related genes also control energy metabolism, with the adipose organ, comprising white, brite, and brown adipocytes, as an important metabolic player in the regulation of whole-body energy homeostasis. This review summarizes transformations in the adipose organ upon aging and cellular senescence and sheds light on the reallocation of fat mass between adipose depots, on the metabolism of white and brown adipose tissue, on the regenerative potential and adipogenic differentiation capacity of preadipocytes, and on alterations in mitochondria and bioenergetics. In conclusion, the aging process is a lifelong, creeping process with gradual decline in (pre-)adipocyte function over time. Thus, slowing down the accumulation of (pre-)adipocyte damage and dysfunction, removal of senescent preadipocytes as well as blocking deleterious compounds of the senescent secretome are protective measures to maintain a lasting state of health at old age.
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Scientific Article
Endocr. Relat. Cancer 25, 145-162 (2018)
Rats affected by the MENX syndrome spontaneously develop multiple neuroendocrine tumors (NETs) including adrenal, pituitary and thyroid gland neoplasms. MENX was initially reported to be inherited as a recessive trait and affected rats were found to be homozygous for the predisposing Cdkn1b mutation encoding p27. We here report that heterozygous MENX-mutant rats (p27+/mut) develop the same spectrum of NETs seen in the homozygous (p27mut/mut) animals but with slower progression. Consequently, p27+/mut rats have a significantly shorter lifespan compared with their wild-type (p27+/+) littermates. In the tumors of p27+/mut rats, the wild-type Cdkn1b allele is neither lost nor silenced, implying that p27 is haploinsufficient for tumor suppression in this model. Transcriptome profiling of rat adrenal (pheochromocytoma) and pituitary tumors having different p27 dosages revealed a tissue-specific, dose-dependent effect of p27 on gene expression. In p27+/mut rats, thyroid neoplasms progress to invasive and metastatic medullary thyroid carcinomas (MTCs) accompanied by increased calcitonin levels, as in humans. Comparison of expression signatures of late-stage vs early-stage MTCs from p27+/mut rats identified genes potentially involved in tumor aggressiveness. The expression of a subset of these genes was evaluated in human MTCs and found to be associated with aggressive RET-M918T-positive tumors. Altogether, p27 haploinsufficiency in MENX rats uncovered a novel, representative model of invasive and metastatic MTC exploitable for translational studies of this often aggressive and incurable cancer.
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Scientific Article
2017
Int. J. Mol. Sci. 18:2578 (2017)
Single cell organisms can surprisingly exceed the number of human protein-coding genes, which are thus not at the origin of the complexity of an organism. In contrast, the relative amount of non-protein-coding sequences increases consistently with organismal complexity. Moreover, the mammalian transcriptome predominantly comprises non-(protein)-coding RNAs (ncRNA), of which the long ncRNAs (lncRNAs) constitute the most abundant part. lncRNAs are highly species- and tissue-specific with very versatile modes of action in accordance with their binding to a large spectrum of molecules and their diverse localization. lncRNAs are transcriptional regulators adding an additional regulatory layer in biological processes and pathophysiological conditions. Here, we review lncRNAs affecting metabolic organs with a focus on the liver, pancreas, skeletal muscle, cardiac muscle, brain, and adipose organ. In addition, we will discuss the impact of lncRNAs on metabolic diseases such as obesity and diabetes. In contrast to the substantial number of lncRNA loci in the human genome, the functionally characterized lncRNAs are just the tip of the iceberg. So far, our knowledge concerning lncRNAs in energy homeostasis is still in its infancy, meaning that the rest of the iceberg is a treasure chest yet to be discovered.
Review
Review
Front. Physiol. 8:968 (2017)
Skeletal muscle mass is a result of the balance between protein breakdown and protein synthesis. It has been shown that multiple conditions of muscle atrophy are characterized by the common regulation of a specific set of genes, termed atrogenes. It is not known whether various models of muscle hypertrophy are similarly regulated by a common transcriptional program. Here, we characterized gene expression changes in three different conditions of muscle growth, examining each condition during acute and chronic phases. Specifically, we compared the transcriptome of Extensor Digitorum Longus (EDL) muscles collected (1) during the rapid phase of postnatal growth at 2 and 4 weeks of age, (2) 24 h or 3 weeks after constitutive activation of AKT, and (3) 24 h or 3 weeks after overload hypertrophy caused by tenotomy of the Tibialis Anterior muscle. We observed an important overlap between significantly regulated genes when comparing each single condition at the two different timepoints. Furthermore, examining the transcriptional changes occurring 24 h after a hypertrophic stimulus, we identify an important role for genes linked to a stress response, despite the absence of muscle damage in the AKT model. However, when we compared all different growth conditions, we did not find a common transcriptional fingerprint. On the other hand, all conditions showed a marked increase in mTORC1 signaling and increased ribosome biogenesis, suggesting that muscle growth is characterized more by translational, than transcriptional regulation.
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Scientific Article
J. Vis. Exp. 2017:e56538 (2017)
Nerve-resident immune cells in the peripheral nervous system (PNS) are essential to maintaining neuronal integrity in a healthy nerve. The immune cells of the PNS are affected by injury and disease, affecting the nerve function and the capacity for regeneration. Neuronal immune cells are commonly analyzed by immunofluorescence (IF). While IF is essential for determining the location of the immune cells in the nerve, IF is only semi-quantitative and the method is limited to the number of markers that can be analyzed simultaneously and the degree of surface expression. In this study, flow cytometry was used for quantitative analysis of leukocyte infiltration into sciatic nerves or dorsal root ganglions (DRGs) of individual mice. Single cell analysis was performed using DAPI and several proteins were analyzed simultaneously for either surface or intracellular expression. Both sciatic nerves from one mouse that were treated according to this protocol generated >= 30,000 single nucleated events. The proportion of leukocytes in the sciatic nerves, determined by expression of CD45, was approximately 5% of total cell content in the sciatic nerve and approximately 5-10% in the DRG. Although this protocol focuses primarily on the immune cell population within the PNS, the flexibility of flow cytometry to measure a number of markers simultaneously means that the other cells populations present within the nerve, such as Schwann cells, pericytes, fibroblasts, and endothelial cells, can also be analyzed using this method. This method therefore provides a new means for studying systemic effects on the PNS, such as neurotoxicology and genetic models of neuropathy or in chronic diseases, such as diabetes.
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Scientific Article
J. Am. Soc. Nephrol. 28, 3182-3189 (2017)
Established therapies for diabetic nephropathy (dNP) delay but do not prevent its progression. The shortage of established therapiesmay reflect the inability to target the tubular compartment. The chemical chaperone tauroursodeoxycholic acid (TUDCA) ameliorates maladaptive endoplasmic reticulum (ER) stress signaling and experimental dNP. Additionally, TUDCA activates the farnesoid X receptor (FXR), which is highly expressed in tubular cells.We hypothesized that TUDCA ameliorates maladaptive ER signaling via FXR agonism specifically in tubular cells. Indeed, TUDCA induced expression of FXR-dependent genes (SOCS3 and DDAH1) in tubular cells but not in other renal cells. In vivo, TUDCA reduced glomerular and tubular injury in db/db and diabetic endothelial nitric oxide synthase-deficient mice. FXR inhibition with Z-guggulsterone or vivo-morpholino targeting of FXR diminished the ER-stabilizing and renoprotective effects of TUDCA. Notably, these in vivo approaches abolished tubular but not glomerular protection by TUDCA. Combined intervention with TUDCA and the angiotensin-converting enzyme inhibitor enalapril in 16-week-old db/db mice reduced albuminuria more efficiently than did either treatment alone. Although both therapies reduced glomerular damage, only TUDCA ameliorated tubular damage. Thus, interventions that specifically protect the tubular compartment in dNP, such as FXR agonism, may provide renoprotective effects on top of those achieved by inhibiting angiotensin-converting enzyme.
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Scientific Article
Nucleic Acids Res. 45, 10595-10613 (2017)
The integrity of genome is a prerequisite for healthy life. Indeed, defects in DNA repair have been associated with several human diseases, including tissue-fibrosis, neurodegeneration and cancer. Despite decades of extensive research, the spatio-mechanical processes of double-strand break (DSB)repair, especially the auxiliary factor(s) that can stimulate accurate and timely repair, have remained elusive. Here, we report an ATM-kinase dependent, unforeseen function of the nuclear isoform of the Receptor for Advanced Glycation End-products (nRAGE) in DSB-repair. RAGE is phosphorylated at Serine(376) and Serine(389) by the ATM kinase and is recruited to the site of DNA-DSBs via an early DNA damage response. nRAGE preferentially colocalized with the MRE11 nuclease subunit of the MRN complex and orchestrates its nucleolytic activity to the ATR kinase signaling. This promotes efficient RPA2(S4-S8) and CHK1(S345) phosphorylation and thereby prevents cellular senescence, IPF and carcinoma formation. Accordingly, loss of RAGE causatively linked to perpetual DSBs signaling, cellular senescence and fibrosis. Importantly, in a mouse model of idiopathic pulmonary fibrosis (RAGE(-/-)), reconstitution of RAGE efficiently restored DSB-repair and reversed pathological anomalies. Collectively, this study identifies nRAGE as a master regulator of DSB-repair, the absence of which orchestrates persistent DSB signaling to senescence, tissue-fibrosis and oncogenesis.
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Scientific Article
Cell Metab. 26, 1–14.e1–e5 (2017)
Breast tumor recurrence and metastasis represent the main causes of cancer-related death in women, and treatments are still lacking. Here, we define the lipogenic enzyme acetyl-CoA carboxylase (ACC) 1 as a key player in breast cancer metastasis. ACC1 phosphorylation was increased in invading cells both in murine and human breast cancer, serving as a point of convergence for leptin and transforming growth factor (TGF) β signaling. ACC1 phosphorylation was mediated by TGFβ-activated kinase (TAK) 1, and ACC1 inhibition was indispensable for the elevation of cellular acetyl-CoA, the subsequent increase in Smad2 transcription factor acetylation and activation, and ultimately epithelial-mesenchymal transition and metastasis induction. ACC1 deficiency worsened tumor recurrence upon primary tumor resection in mice, and ACC1 phosphorylation levels correlated with metastatic potential in breast and lung cancer patients. Given the demonstrated effectiveness of anti-leptin receptor antibody treatment in halting ACC1-dependent tumor invasiveness, our work defines a "metabolocentric" approach in metastatic breast cancer therapy.
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Scientific Article
Horm. Mol. Biol. Clin. Investig. 31:0043 (2017)
The dramatically increasing world-wide prevalence of obesity is recognized as a risk factor for the development of various diseases. The growing research on the role of adipose tissue in controlling energy homeostasis and insulin sensitivity has revealed that the promotion of brown adipose tissue (BAT) activity and the browning of white adipose tissue (WAT) leads to multiple health benefits and prevents obesity and type 2 diabetes (T2D). Inducible thermogenic adipocytes do exist in adult humans and are linked with increased energy combustion and lower body fat mass. Thus brown adipocytes are currently placed at the center of attention for novel therapeutic strategies against metabolic diseases such as obesity and diabetes. Besides the classical, norepinephrine-mediated sympathetic recruitment and activation of thermogenic adipocytes, a number of novel circulating factors have been recently identified to have a positive or negative impact on thermogenic adipocyte formation and activity. In this review their mechanism of action and the plausible therapeutic applications will be summarized and discussed.
Review
Review
Neuroscience, DOI: 10.1016/j.neuroscience.2017.09.023 (2017)
IBRO. A 62-year-old diabetologist diagnosed himself to have diabetes type-2, with an HbA1c of 9.5. Five months after lifestyle intervention and a multi-drug approach, HbA1c was 6.3, systolic blood pressure was below 135. mmHg and BMI reduced to 27. But he suffered from severe painful diabetic neuropathy. Therefore he decided to visit his friend, a famous neuroscientist at an even more famous university. He asked him several plain questions: 1. What is the natural course of painful diabetic neuropathy? 2. Why do I have, despite almost normalizing HbA1c, more problems than before? 3. Are you sure my problems are due to diabetes or should we do a nerve biopsy? 4. Are there imaging techniques helpful for the diagnosis of this diabetic complication, starting in the distal nerve endings of the foot and slowly moving ahead? 5. Can you suggest any drug, specific and effective, for relieving painful diabetic neuropathy?This review will use the experts' answers to the questions of the diabetologist, not only to give a summary of the current knowledge, but even more to highlight areas of research needed for improving the fate of patients with painful diabetic neuropathy. Based on the unknowns, which exceed the knowns in diabetic neuropathy, a quest for more public support of research is made.
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Scientific Article
Nucleic Acids Res. 45, 11121-11130 (2017)
Transcription comprises a highly regulated sequence of intrinsically stochastic processes, resulting in bursts of transcription intermitted by quiescence. In transcription activation or repression, a transcription factor binds dynamically to DNA, with a residence time unique to each factor. Whether the DNA residence time is important in the transcription process is unclear. Here, we designed a series of transcription repressors differing in their DNA residence time by utilizing the modular DNA binding domain of transcription activator-like effectors (TALEs) and varying the number of nucleotide-recognizing repeat domains. We characterized the DNA residence times of our repressors in living cells using single molecule tracking. The residence times depended non-linearly on the number of repeat domains and differed by more than a factor of six. The factors provoked a residence time-dependent decrease in transcript level of the glucocorticoid receptor-activated gene SGK1. Down regulation of transcription was due to a lower burst frequency in the presence of long binding repressors and is in accordance with a model of competitive inhibition of endogenous activator binding. Our single molecule experiments reveal transcription factor DNA residence time as a regulatory factor controlling transcription repression and establish TALE-DNA binding domains as tools for the temporal dissection of transcription regulation.
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Scientific Article
Exp. Clin. Endocrinol. Diabet. 126, 141-147 (2017)
The receptor for advanced glycation end-products (RAGE) is a multi-ligand receptor which belongs to the pattern recognition receptor family and can bind to various ligands such as advanced glycation end-products (AGEs), members of the S100 protein family, glycosaminoglycans, amyloid beta peptides, high-mobility group box-1 (HMGB1) and nucleic acids through its extracellular domain. The RAGE-ligand interaction leads to the activation of MAP kinase and NF-kB signaling pathways. Further ligand-induced up-regulation of RAGE is involved in various patho-physiological situations including late diabetic complications, Alzheimer disease and several other neurodegenerative diseases. A secreted soluble isoform of RAGE (sRAGE), corresponding to the extracellular domain only, has the ability to block RAGE-associated cellular activation and signaling. Further application of recombinant sRAGE has been shown to block RAGE-mediated pathophysiological conditions in various models of cancer or multiple sclerosis. These finding demonstrates sRAGE as a therapeutic tool to block RAGE-associated inflammatory signaling. In this manuscript, we describe a two-step simple, novel and convenient method for expressing and purifying scalable quantities of biologically active murine form of sRAGE by using E. coli as an expression host. The method we propose has several advantages over the current available methods particularly in terms of yield and quality of preparation. The sRAGE produced by this expression system retains all the secondary structural properties as analyzed by the ligand binding affinities. The produced protein also retains all the DNA-RAGE binding functional properties and thus can be a valuable tool for studying dynamics of this novel RAGE ligand. Moreover this method can be utilized by researchers to generate biologically active endotoxin-free sRAGE for in vivo applications to study and treat RAGE-associated pathologies.
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Scientific Article
Development 144, 3917-3931 (2017)
During corticogenesis, distinct classes of neurons are born from progenitor cells located in the ventricular and subventricular zones, from where they migrate towards the pial surface to assemble into highly organized layer-specific circuits. However, the precise and coordinated transcriptional network activity defining neuronal identity is still not understood. Here, we show that genetic depletion of the basic helix-loop-helix (bHLH) transcription factor E2A splice variant E47 increased the number of Tbr1-positive deep layer and Satb2-positive upper layer neurons at E14.5, while depletion of the alternatively spliced E12 variant did not affect layer-specific neurogenesis. While ChIP-Seq identified a big overlap for E12- and E47-specific binding sites in embryonic NSCs, including sites at the cyclin-dependent kinase inhibitor (CDKI) Cdkn1c gene locus, RNA-Seq revealed a unique transcriptional regulation by each splice variant. E47 activated the expression of the CDKI Cdkn1c through binding to a distal enhancer. Finally, overexpression of E47 in embryonic NSCs in vitro impaired neurite outgrowth and E47 overexpression in vivo by in utero electroporation disturbed proper layer-specific neurogenesis and upregulated p57(KIP2) expression. Overall, this study identified E2A target genes in embryonic NSCs and demonstrates that E47 regulates neuronal differentiation via p57(KIP2).
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Scientific Article
Redox Biol. 13, 674-686 (2017)
Energy production is inevitably linked to the generation of toxic metabolites, such as reactive oxygen and carbonyl species, known as major contributors to ageing and degenerative diseases. It remains unclear how cells can adapt to elevated energy flux accompanied by accumulating harmful by-products without taking any damage. Therefore, effects of a sudden rise in glucose concentrations were studied in yeast cells. This revealed a feedback mechanism initiated by the reactive dicarbonyl methylglyoxal, which is formed non-enzymatically during glycolysis. Low levels of methylglyoxal activate a multi-layered defence response against toxic metabolites composed of prevention, detoxification and damage remission. The latter is mediated by the protein quality control system and requires inducible Hsp70 and Btn2, the aggregase that sequesters misfolded proteins. This glycohormetic mechanism enables cells to pre-adapt to rising energy flux and directly links metabolic to proteotoxic stress. Further data suggest the existence of a similar response in endothelial cells.
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Scientific Article
Front. Neurosci. 11:369 (2017)
Circadian rhythms are widely known to govern human health and disease, but specific pathogenic mechanisms linking circadian disruption to metabolic diseases are just beginning to come to light. This is thanks in part to the development and application of various "omics"-based tools in biology and medicine. Current high-throughput technologies allow for the simultaneous monitoring of multiple dynamic cellular events over time, ranging from gene expression to metabolite abundance and sub-cellular localization. These fundamental temporal and spatial perspectives have allowed for a more comprehensive understanding of how various dynamic cellular events and biochemical processes are related in health and disease. With advances in technology, metabolomics has become a more routine "omics" approach for studying metabolism, and "circadian metabolomics" (i.e., studying the 24-h metabolome) has recently been undertaken by several groups. To date, circadian metabolomes have been reported for human serum, saliva, breath, and urine, as well as tissues from several species under specific disease or mutagenesis conditions. Importantly, these studies have consistently revealed that 24-h rhythms are prevalent in almost every tissue and metabolic pathway. Furthermore, these circadian rhythms in tissue metabolism are ultimately linked to and directed by internal 24-h biological clocks. In this review, we will attempt to put these data-rich circadian metabolomics experiments into perspective to find out what they can tell us about metabolic health and disease, and what additional biomarker potential they may reveal.
Review
Review
Cell Rep. 20, 1422-1434 (2017)
Increased pro-inflammatory signaling is a hallmark of metabolic dysfunction in obesity and diabetes. Although both inflammatory and energy substrate handling processes represent critical layers of metabolic control, their molecular integration sites remain largely unknown. Here, we identify the heterodimerization interface between the α and β subunits of transcription factor GA-binding protein (GAbp) as a negative target of tumor necrosis factor alpha (TNF-α) signaling. TNF-α prevented GAbpα and β complex formation via reactive oxygen species (ROS), leading to the non-energy-dependent transcriptional inactivation of AMP-activated kinase (AMPK) β1, which was identified as a direct hepatic GAbp target. Impairment of AMPKβ1, in turn, elevated downstream cellular cholesterol biosynthesis, and hepatocyte-specific ablation of GAbpα induced systemic hypercholesterolemia and early macro-vascular lesion formation in mice. As GAbpα and AMPKβ1 levels were also found to correlate in obese human patients, the ROS-GAbp-AMPK pathway may represent a key component of a hepato-vascular axis in diabetic long-term complications.
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Scientific Article
Endocr. Relat. Cancer 24, T161-T177 (2017)
Animal models of cancer have been instrumental in advancing our understanding of the biology of tumor initiation and progression, in studying gene function and in performing preclinical studies aimed at testing novel therapies. Several animal models of the MEN1 syndrome have been generated in different organisms by introducing loss-of-function mutations in the orthologues of the human MEN1 gene. In this review, we will discuss MEN1 and MEN1-like models in Drosophila, mice and rats. These model systems with their specific advantages and limitations have contributed to elucidate the function of Menin in tumorigenesis, which turned out to be remarkably conserved from flies to mammals, as well as the biology of the disease. Mouse models of MEN1 closely resemble the human disease in terms of tumor spectrum and associated hormonal changes, although individual tumor frequencies are variable. Rats affected by the MENX (MEN1-like) syndrome share some features with MEN1 patients albeit they bear a germline mutation in Cdkn1b (p27) and not in Men1 Both Men1-knockout mice and MENX rats have been exploited for therapy-response studies testing novel drugs for efficacy against neuroendocrine tumors (NETs) and have provided promising leads for novel therapies. In addition to presenting well-established models of MEN1, we also discuss potential models which, if implemented, might broaden even further our knowledge of neuroendocrine tumorigenesis. In the future, patient-derived xenografts in zebrafish or mice might allow us to expand the tool-box currently available for preclinical studies of MEN1-associated tumors.
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Mol. Metab. 6, 873-881 (2017)
Objective: Dietary protein dilution (PD) has been associated with metabolic advantages such as improved glucose homeostasis and increased energy expenditure. This phenotype involves liver-induced release of FGF21 in response to amino acid insufficiency; however, it has remained unclear whether dietary dilution of specific amino acids (AAs) is also required. Circulating branched chain amino acids (BCAAs) are sensitive to protein intake, elevated in the serum of obese humans and mice and thought to promote insulin resistance. We tested whether replenishment of dietary BCAAs to an AA-diluted (AAD) diet is sufficient to reverse the glucoregulatory benefits of dietary PD. Methods: We conducted AA profiling of serum from healthy humans and lean and high fat-fed or New Zealand obese (NZO) mice following dietary PD. We fed wildtype and NZO mice one of three amino acid defined diets: control, total AAD, or the same diet with complete levels of BCAAs (AAD + BCAA). We quantified serum AAs and characterized mice in terms of metabolic efficiency, body composition, glucose homeostasis, serum FGF21, and tissue markers of the integrated stress response (ISR) and mTORC1 signaling. Results: Serum BCAAs, while elevated in serum from hyperphagic NZO, were consistently reduced by dietary PD in humans and murine models. Repletion of dietary BCAAs modestly attenuated insulin sensitivity and metabolic efficiency in wildtype mice but did not restore hyperglycemia in NZO mice. While hepatic markers of the ISR such as P-eIF2α and FGF21 were unabated by dietary BCAA repletion, hepatic and peripheral mTORC1 signaling were fully or partially restored, independent of changes in circulating glucose or insulin. Conclusions: Repletion of BCAAs in dietary PD is sufficient to oppose changes in somatic mTORC1 signaling but does not reverse the hepatic ISR nor induce insulin resistance in type 2 diabetes during dietary PD.
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Scientific Article
EMBO J. 36, 1999-2017 (2017)
Adipose tissue represents a critical component in healthy energy homeostasis. It fulfills important roles in whole-body lipid handling, serves as the body's major energy storage compartment and insulation barrier, and secretes numerous endocrine mediators such as adipokines or lipokines. As a consequence, dysfunction of these processes in adipose tissue compartments is tightly linked to severe metabolic disorders, including obesity, metabolic syndrome, lipodystrophy, and cachexia. While numerous studies have addressed causes and consequences of obesity-related adipose tissue hypertrophy and hyperplasia for health, critical pathways and mechanisms in (involuntary) adipose tissue loss as well as its systemic metabolic consequences are far less understood. In this review, we discuss the current understanding of conditions of adipose tissue wasting and review microenvironmental determinants of adipocyte (dys)function in related pathophysiologies.
Review
Review
Clin. Ther. 39, 1132-1144.e2 (2017)
PURPOSE: External electric muscle stimulation (EMS) of the thigh muscles was found to reduce pain resulting from diabetic neuropathy (DN), a vascular complication of diabetes. This study investigated circulating hematopoietic stem cells (HSCs) after EMS treatment. Impaired function of HSCs and the subpopulation endothelial progenitor cells (EPCs), important for neovascularization and endothelial repair, has been associated with DN. METHODS: Twenty-four patients with painful DN were treated 3 times with EMS over a period of 1 week. Blood samples were collected before and after the first EMS treatment. Before a fourth treatment, neuropathic pain was evaluated and a third blood sample was collected. Cells were used for flow cytometry. FINDINGS: Patients with painful DN reported that the pain decreased after 3 times of 1-hour treatments with EMS (Neuropathy Symptom Score: from 8 to 6, P = 0.001; Neuropathy Disability Score: from 5.5 to 5, P = 0.027, n = 24). At the end of the study, diastolic blood pressure had decreased from 80 to 70 mm Hg (P = 0.043), and plasma adrenaline and noradrenaline metabolites metanephrine and normetanephrine were reduced (both P ≤ 0.01; n = 21). A single EMS treatment caused an immediate and transient decrease in the frequency of CD34(+) HSCs in circulation (-20%; P < 0.001; n = 27). In 9 of the patients with DN, the proportion of HSCs expressing vascular endothelial growth factor receptor 2 (VEGFR2; defining the HSCs as EPCs) increased by 36% (P = 0.011) after EMS treatment. Proteins required for binding to endothelium (junctional adhesion molecule A and CD31), homing toward hypoxic tissue (C-X-C chemokine receptor type 4), and endothelial differentiation (CD31) were increased on HSCs immediately after EMS treatment. An increased frequency of VEGFR2 expression was also observed on HSCs of 6 healthy control volunteers (34%; P = 0.046) after EMS treatment, but not after sham treatment. IMPLICATIONS: Three EMS treatments decreased symptoms of pain caused by DN and reduced diastolic blood pressure and biomarkers of stress. A single EMS treatment increased molecules mediating attachment and differentiation on the surface of HSCs in circulation. We hypothesize that the EMS-induced increase in surface attachment molecules on the HSCs caused the HSCs to leave circulation and that EMS treatment improves the function of HSCs and EPCs in vivo.
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Scientific Article
Sci. Rep. 7:4023 (2017)
Liver cells communicate with the extracellular environment to take up nutrients via endocytosis. Iron uptake is essential for metabolic activities and cell homeostasis. Here, we investigated the role of the endocytic system for maintaining iron homeostasis. We specifically depleted the small GTPase Rab5 in the mouse liver, causing a transient loss of the entire endo-lysosomal system. Strikingly, endosome depletion led to a fast reduction of hepatic iron levels, which was preceded by an increased abundance of the iron exporter ferroportin. Compensatory changes in livers of Rab5-depleted mice include increased expression of transferrin receptor 1 as well as reduced expression of the iron-regulatory hormone hepcidin. Serum iron indices (serum iron, free iron binding capacity and total iron binding capacity) in Rab5-KD mice were increased, consistent with an elevated splenic and hepatic iron export. Our data emphasize the critical importance of the endosomal compartments in hepatocytes to maintain hepatic and systemic iron homeostasis in vivo. The short time period (between day four and five) upon which these changes occur underscore the fast dynamics of the liver iron pool.
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Scientific Article
Cell Rep. 19, 643-654 (2017)
Activation of immune cells results in rapid functional changes, but how such fast changes are accomplished remains enigmatic. By combining time courses of 4sU-seq, RNA-seq, ribosome profiling (RP), and RNA polymerase II (RNA Pol II) ChIP-seq during T cell activation, we illustrate genome-wide temporal dynamics for ∼10,000 genes. This approach reveals not only immediate-early and posttranscriptionally regulated genes but also coupled changes in transcription and translation for >90% of genes. Recruitment, rather than release of paused RNA Pol II, primarily mediates transcriptional changes. This coincides with a genome-wide temporary slowdown in cotranscriptional splicing, even for polyadenylated mRNAs that are localized at the chromatin. Subsequent splicing optimization correlates with increasing Ser-2 phosphorylation of the RNA Pol II carboxy-terminal domain (CTD) and activation of the positive transcription elongation factor (pTEFb). Thus, rapid de novo recruitment of RNA Pol II dictates the course of events during T cell activation, particularly transcription, splicing, and consequently translation.
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Scientific Article
Int. J. Mol. Sci. 18:984 (2017)
Advanced glycation end-products (AGEs) are non-enzymatic protein and amino acid adducts as well as DNA adducts which form from dicarbonyls and glucose. AGE formation is enhanced in diabetes and is associated with the development of diabetic complications. In the current review, we discuss mechanisms that lead to enhanced AGE levels in the context of diabetes and diabetic complications. The methylglyoxal-detoxifying glyoxalase system as well as alternative pathways of AGE detoxification are summarized. Therapeutic approaches to interfere with different pathways of AGE formation are presented.
Review
Review
J. Neuroimmunol. 306, 76-82 (2017)
Streptozotocin (STZ) treatment, a common model for inducing diabetes in rodent models, induces thermal hyperalgesia and neuronal toxicity independently of hyperglycemia by oxidizing and activating TRPA1 and TRPV1. Following treatment with STZ, CD45+ immune cells were found to be depleted in sciatic nerve (SN) and DRG in mice, prior to hyperglycemia. Macrophages were also lost in DRG and NFκB-p65-activation was increased in SN macrophages. Immune cells were significantly reduced in both SN and DRG up to three weeks, post-treatment. Loss of PNS-resident macrophages in response to STZ-mediated toxicity may affect the regenerative capacity of the nerve in response to further injury caused by diabetes.
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Scientific Article
Proc. Natl. Acad. Sci. U.S.A. 114, 5265-5270 (2017)
Aging is accompanied by major changes in adipose tissue distribution and function. In particular, with time, thermogenic-competent beige adipocytes progressively gain a white adipocyte morphology. However, the mechanisms controlling the age-related transition of beige adipocytes to white adipocytes remain unclear. Lysine-specific demethylase 1 (Lsd1) is an epigenetic eraser enzyme positively regulating differentiation and function of adipocytes. Here we show that Lsd1 levels decrease in aging inguinal white adipose tissue concomitantly with beige fat cell decline. Accordingly, adipocyte-specific increase of Lsd1 expression is sufficient to rescue the age-related transition of beige adipocytes to white adipocytes in vivo, whereas loss of Lsd1 precipitates it. Lsd1 maintains beige adipocytes by controlling the expression of peroxisome proliferator-activated receptor a (Ppara), and treatment with a Ppara agonist is sufficient to rescue the loss of beige adipocytes caused by Lsd1 ablation. In summary, our data provide insights into the mechanism controlling the age-related beige-to-white adipocyte transition and identify Lsd1 as a regulator of beige fat cell maintenance.
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Scientific Article
J. Diab. Complic. 31, 1058-1065 (2017)
BACKGROUND & AIM: Activated leukocyte cell adhesion molecule (ALCAM/CD166) functions analogue to the receptor of advanced glycation end products, which has been implicated in the development of diabetic nephropathy (DN). We investigated the expression of ALCAM and its ligand S100B in patients with DN. METHODS: A total of 34 non-diabetic patients, 29 patients with type 2 diabetes and normal albuminuria and 107 patients with type 2 diabetes complicated with DN were assessed for serum concentration of soluble ALCAM (sALCAM) by ELISA. Expression of ALCAM and S100B in kidney histology from patients with DN was determined by immunohistochemistry. Cell expression of ALCAM and S100B was analyzed through confocal immunofluorescence microscopy. RESULTS: Serum concentration of sALCAM was increased in diabetic patients with DN compared to non-diabetic (59.85±14.99ng/ml vs. 126.88±66.45ng/ml, P<0.0001). Moreover sALCAM correlated positively with HbA1c (R=0.31, P<0.0001), as well as with the stages of chronic kidney disease and negatively correlated with eGFR (R=-0.20, P<0.05). In diabetic patients with normal albuminuria sALCAM was increased compared to patients with DN (126.88±66.45ng/ml vs. 197.50±37.17ng/ml, P<0.0001). In diabetic patients, ALCAM expression was significantly upregulated in both the glomeruli and tubules (P<0.001). ALCAM expression in the glomeruli correlated with presence of sclerosis (R=0.25, P<0.001) and localized mainly in the podocytes supporting the hypothesis that membrane bound ALCAM drives diabetic nephropathy and thus explaining sALCAM decrease in diabetic patients with DN. The expression of S100B was increased significantly in the glomeruli of diabetic patients (P<0.001), but not in the tubules. S100B was as well localized in the podocytes. CONCLUSIONS: This study identifies for the first time ALCAM as a potential mediator in the late complications of diabetes in the kidney.
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Scientific Article
Mol. Cell. Endocrinol. 456, 87-94 (2017)
Obesity has reached epidemic proportions world-wide and constitutes a substantial risk factor for hypertension, type 2 diabetes, cardiovascular diseases and certain cancers. So far, regulation of energy intake by dietary and pharmacological treatments has met limited success. The main interest of current research is focused on understanding the role of different pathways involved in adipose tissue function and modulation of its mass. Whole-genome sequencing studies revealed that the majority of the human genome is transcribed, with thousands of non-protein-coding RNAs (ncRNA), which comprise small and long ncRNAs. ncRNAs regulate gene expression at the transcriptional and post-transcriptional level. Numerous studies described the involvement of ncRNAs in the pathogenesis of many diseases including obesity and associated metabolic disorders. ncRNAs represent potential diagnostic biomarkers and promising therapeutic targets. In this review, we focused on small ncRNAs involved in the formation and function of adipocytes and obesity.
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Scientific Article
Nat. Med. 23, 623-630 (2017)
Adaptive thermogenesis is the process of heat generation in response to cold stimulation. It is under the control of the sympathetic nervous system, whose chief effector is the catecholamine norepinephrine (NE). NE enhances thermogenesis through β3-adrenergic receptors to activate brown adipose tissue and by 'browning' white adipose tissue. Recent studies have reported that alternative activation of macrophages in response to interleukin (IL)-4 stimulation induces the expression of tyrosine hydroxylase (TH), a key enzyme in the catecholamine synthesis pathway, and that this activation provides an alternative source of locally produced catecholamines during the thermogenic process. Here we report that the deletion of Th in hematopoietic cells of adult mice neither alters energy expenditure upon cold exposure nor reduces browning in inguinal adipose tissue. Bone marrow-derived macrophages did not release NE in response to stimulation with IL-4, and conditioned media from IL-4-stimulated macrophages failed to induce expression of thermogenic genes, such as uncoupling protein 1 (Ucp1), in adipocytes cultured with the conditioned media. Furthermore, chronic treatment with IL-4 failed to increase energy expenditure in wild-type, Ucp1(-/-) and interleukin-4 receptor-α double-negative (Il4ra(-/-)) mice. In agreement with these findings, adipose-tissue-resident macrophages did not express TH. Thus, we conclude that alternatively activated macrophages do not synthesize relevant amounts of catecholamines, and hence, are not likely to have a direct role in adipocyte metabolism or adaptive thermogenesis.
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Exp. Clin. Endocrinol. Diabet., DOI: 10.1055/s-0042-123036 (2017)
Diabetes mellitus and bone metabolism affect mesenchymal tissues and have numerous epidemiological and pathophysiological associations in common. Diabetes mellitus affects bone metabolism and increases fracture risk. The pathophysiological mechanims how type 1 and type 2 diabetes impair bone metabolism and bone strength may differ which is outlined in this review. Direct metabolic effects in additon to centrally controlled endocrine loops exert suppressive effects on bone formation and may also stimulate bone Resorption. Decreased bone formation in combination with increased bone resorption strongly increases fracture risk.
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Scientific Article
Biochim. Biophys. Acta 1863, 654-662 (2017)
The reactive metabolite methylglyoxal (MG) has been identified as mediator of pain. Scavenging of free MG and the prevention of MG-derived post-translational modifications may provide a useful therapeutic treatment. An arginine-rich, fatty acid coupled, cyclic peptide (CycK(Myr)R4E) with high proteolytic stability and prolonged circulation was developed for the scavenging of MG. It was shown to reduce the formation of albumin-MG adducts in vitro and prevented MG-induced pain by reducing plasma MG levels through the formation of peptide-MG adducts in vivo. CycK(Myr)R4E therefore presents a promising option for the treatment of pain and other diabetic complications associated with high MG levels.
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Scientific Article
Stem Cell Rep. 8, 21-29 (2017)
Aging is accompanied by loss of subcutaneous adipose tissue. This may be due to reduced differentiation capacity or deficiency in DNA damage repair (DDR) factors. Here we investigated the role of SNEVhPrp19/hPso4, which was implicated in DDR and senescence evasion, in adipogenic differentiation of human adipose stromal cells (hASCs). We showed that SNEV is induced during adipogenesis and localized both in the nucleus and in the cytoplasm. Knockdown of SNEV perturbed adipogenic differentiation and led to accumulation of DNA damage in hASCs upon oxidative stress. In addition, we demonstrated that SNEV is required for fat deposition in Caenorhabditis elegans. Consequently, we tested other DDR factors and found that WRN is also required for adipogenesis in both models. These results demonstrate that SNEV regulates adipogenesis in hASCs and indicate that DDR capacity in general might be a pre-requisite for this process.
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Trends Endocrinol. Metab. 28, 104-120 (2017)
Brown and brown-like adipocytes are specialized adipocytes with a high capacity to convert metabolic energy to heat. This function is not only eminent in supporting organismal thermogenesis, but may also have potential in the fight against obesity. The latter has spurred a massive interest in understanding the development and regulation of these thermogenic adipocytes. Here, we review how genome-wide studies based on next-generation sequencing have provided insight into how the chromatin and transcriptional landscapes are established in thermogenic adipocytes and how thermogenic signals can change the genomic programming of white adipocytes. Furthermore, we discuss how the integration of genomic data can be used to discover novel transcriptional pathways that may be modulated as part of therapeutic strategies for the treatment of obesity. The development and thermogenic functions of brown adipocytes are regulated by coordinated actions of many different transcription factors, cofactors, noncoding RNAs, and histone modifiers.Activation of thermogenic transcriptional regulators can change the genomic programming of white adipocytes and lead to the formation of brown-like adipocytes.Integrative genomic approaches allow deciphering of the transcriptional networks that control the development and specialized functions of thermogenic adipocytes.Integrative genomic approaches may reveal novel transcriptional pathways that can be targeted to increase the thermogenic capacity of adipocytes.
Review
Review
J. Biol. Chem. 292, 685-690 (2017)
Methylglyoxal (MG) is a reactive metabolite that forms adducts on cysteine, lysine and arginine residues of proteins, thereby affecting their function. Methylglyoxal is detoxified by the Glyoxalase system, consisting of two enzymes, Glo1 and Glo2, that act sequentially to convert MG into D-lactate. Recently, the Parkinsonism-associated protein DJ-1 was described in vitro to have glyoxalase activity, thereby detoxifying the MG metabolite, or deglycase activity, thereby removing the adduct formed by MG on proteins. Since Drosophila is an established model system to study signaling, neurodegeneration, and metabolic regulation in vivo, we asked whether DJ-1 contributes to MG detoxification in vivo. Using both DJ-1 knockdown in Drosophila cells in culture, and DJ-1 β knock-out flies, we could detect no contribution of DJ-1 to survival to MG challenge or to accumulation of MG protein adducts. Furthermore, we provide data suggesting that the previously reported deglycation activity of DJ- 1 can be ascribed to a TRIS buffer artifact.
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Scientific Article
Exp. Cell Res. 350, 242-252 (2017)
Exploring the cell biology of hepatocytes in vitro could be a powerful strategy to dissect the molecular mechanisms underlying the structure and function of the liver in vivo. However, this approach relies on appropriate in vitro cell culture systems that can recapitulate the cell biological and metabolic features of the hepatocytes in the liver whilst being accessible to experimental manipulations. Here, we adapted protocols for high-resolution fluorescence microscopy and quantitative image analysis to compare two primary hepatocyte culture systems, monolayer and collagen sandwich, with respect to the distribution of two distinct populations of early endosomes (APPL1 and EEA1-positive), endocytic capacity, metabolic and signaling activities. In addition to the re-acquisition of hepatocellular polarity, primary hepatocytes grown in collagen sandwich but not in monolayer culture recapitulated the apico-basal distribution of EEA1 endosomes observed in liver tissue. We found that such distribution correlated with the organization of the actin cytoskeleton in vitro and, surprisingly, was dependent on the nutritional state in vivo. Hepatocytes in collagen sandwich also exhibited faster kinetics of low-density lipoprotein (LDL) and epidermal growth factor (EGF) internalization, showed improved insulin sensitivity and preserved their ability for glucose production, compared to hepatocytes in monolayer cultures. Although no in vitro culture system can reproduce the exquisite structural features of liver tissue, our data nevertheless highlight the ability of the collagen sandwich system to recapitulate key structural and functional properties of the hepatocytes in the liver and, therefore, support the usage of this system to study aspects of hepatocellular biology in vitro.
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Scientific Article
Endocr. Relat. Cancer 24, 1-15 (2017)
Pheochromocytomas (PCCs) are mostly benign tumors, amenable to complete surgical resection. However, 10–17% of cases can become malignant, and once metastasized, there is no curative treatment for this disease. Given the need to identify the effective therapeutic approaches for PCC, we evaluated the antitumor potential of the dual-PI3K/mTOR inhibitor BEZ235 against these tumors. We employed an in vivo model of endogenous PCCs (MENX mutant rats), which closely recapitulate the human tumors. Mutant rats with PCCs were treated with 2 doses of BEZ235 (20 and 30 mg/kg), or with placebo, for 2 weeks. Treatment with BEZ235 induced cytostatic and cytotoxic effects on rat PCCs, which could be appreciated by both staining the tumors ex vivo with appropriate markers and non-invasively by functional imaging (diffusion-weighted magnetic resonance imaging) in vivo. Transcriptomic analyses of tumors from rats treated with BEZ235 or placebo-identified potential mediators of therapy response were performed. Slc6a2, encoding the norepinephrine transporter (NET), was downregulated in a dose-dependent manner by BEZ235 in rat PCCs. Moreover, BEZ235 reduced Slc6a2/NET expression in PCC cell lines (MPC) also. Studies of a BEZ235-resistant derivative of the MPC cell line confirmed that the reduction of NET expression associates with the response to the drug. Reduction of NET expression after BEZ235 treatment in vivo could be monitored by positron emission tomography (PET) using a tracer targeting NET. Altogether, here we demonstrate the efficacy of BEZ235 against PCC in vivo, and show that functional imaging can be employed to monitor the response of PCC to PI3K/mTOR inhibition therapy.
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Scientific Article
J. Diab. Complic. 31, 304-310 (2017)
BACKGROUND: Glucose derived metabolism generates reactive metabolites affecting the neuronal system and lifespan in C. elegans. Here, the role of the insulin homologue ins-7 and its downstream effectors in the generation of high glucose induced neuronal damage and shortening of lifespan was studied. RESULTS: In C. elegans high glucose conditions induced the expression of the insulin homologue ins-7. Abrogating ins-7 under high glucose conditions in non-neuronal cells decreased reactive oxygen species (ROS)-formation and accumulation of methylglyoxal derived advanced glycation endproducts (AGEs), prevented structural neuronal damage and normalised head motility and lifespan. The restoration of lifespan by decreased ins-7 expression was dependent on the concerted action of sod-3 and glod-4 coding for the homologues of iron-manganese superoxide dismutase and glyoxalase 1, respectively. CONCLUSIONS: Under high glucose conditions mitochondria-mediated oxidative stress and glycation are downstream targets of ins-7. This impairs the neuronal system and longevity via a non-neuronal/neuronal crosstalk by affecting sod-3 and glod-4, thus giving further insight into the pathophysiology of diabetic complications.
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Scientific Article
J. Magn. Reson. Imaging 45, 369-380 (2017)
PURPOSE: To evaluate the volume and changes of human brown adipose tissue (BAT) in vivo following exposure to cold using magnetic resonance imaging (MRI). MATERIALS AND METHODS: The clavicular region of 10 healthy volunteers was examined with a 3T MRI system. One volunteer participated twice. A cooling vest that was circulated with temperature-controlled water was used to expose each volunteer to a cold environment. Three different water temperature phases were employed: baseline (23°C, 20 min), cooling (12°C, 90 min), and a final warming phase (37°C, 30 min). Temperatures of the water in the circuit, of the body, and at the back skin of the volunteers were monitored with fiberoptic temperature probes. Applying the 2-point DIXON pulse sequence every 5 minutes, fat fraction (FF) maps were determined and evaluated over time to distinguish between brown and white adipose tissue. RESULTS: Temperature measurements showed a decrease of 3.8 ± 1.0°C of the back skin temperature, while the body temperature stayed constant at 37.2 ± 0.9°C. Focusing on the two interscapular BAT depots, a mean FF decrease of -2.9 ± 2.0%/h (P < 0.001) was detected during cold stimulation in a mean absolute volume of 1.31 ± 1.43 ml. Also, a correlation of FF decrease to back skin temperature decrease was observed in all volunteers (correlation coefficients: |r| = [0.51; 0.99]). CONCLUSION: We found that FF decreases in BAT begin immediately with mild cooling of the body and continue during long-time cooling.
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Scientific Article
Endocrine 55, 386-397 (2017)
MEN1 is the main gene responsible for tumorigenesis of syndromic and sporadic primary hyperparathyroidism (PHPT). Germline mutations of the CDKN1B/p27(Kip) gene have been associated with multiple endocrine tumors in rats and humans. To evaluate the involvement of the CDKN1B gene and its relationship with MEN1 in sporadic PHPT, we carried out sequencing and loss of heterozygosity analyses of the CDKN1B gene in 147 sporadic parathyroid adenomas. p27 immunohistochemistry and genetic screening of the MEN1 gene were performed in 50 cases. Three germline CDKN1B variants (c.-80C>T, c.-29_-26delAGAG, c.397C>A) were identified in 3/147 patients. Reduction of CDKN1B gene transcription rate was demonstrated in vitro for the novel c.-80C>T and the c.-29_-26delAGAG variants. Loss of p27 expression was detected in the tumor carrying the c.-29_-26delAGAG variant. Two tumors carrying the CDKN1B variants also harbored a MEN1 mutation. Fifty-four percent of 50 CDKN1B mutation-negative tumors had a reduction of p27 nuclear staining. Somatic MEN1 mutations, identified in 15/50 samples, significantly segregated in tumors negative for nuclear and cytoplasmic p27 staining. The germline nature of the CDKN1B mutations suggests that they might predispose to PHPT. The lack of somatic CDKN1B mutations in our samples points to a rare involvement in parathyroid adenomas, despite the frequent loss of nuclear p27 expression. MEN1 biallelic inactivation seems to be directly related to down-regulation of p27 expression through the inhibition of CDKN1B gene transcription.
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Scientific Article
2016
J. Biol. Chem. 292, 3224-3238 (2016)
The glyoxalase system is a highly specific enzyme system existing in all mammalian cells which is responsible for the detoxification of dicarbonyl species, primarily methylglyoxal (MG). It has been implicated to play an essential role in preventing the increased formation of advanced glycation endproducts under certain pathological conditions. We have established the first glyoxalase 1 knock-out model (GLO1-/-) in mammalian Schwann cells using CRISPR/Cas9 technique to investigate compensatory mechanisms. Neither elevated concentrations of MG nor associated protein modifications were observed in GLO1-/- cells. Alternative detoxification of MG in GLO1-/- is achieved by increased catalytic efficiency of aldose reductase towards hemithioacetal (product of glutathione and MG), most likely caused by S-nitrosylation of aldose reductase. The hemithioacetal is mainly converted into lactaldehyde, which is paralleled by a loss of reduced glutathione. Inhibition of aldose reductase in GLO1-/- cells is associated with an increased sensitivity against MG, elevated intracellular MG levels and associated modifications, as well as increased oxidative stress. Our data suggest that aldose reductase can compensate the loss of GLO1. This might be of clinical importance within the context of neuronal diseases caused by an impaired glyoxalase system and elevated levels of dicarbonyl species, such as MG.
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Scientific Article
Int. J. Mol. Sci. 17:2011 (2016)
MicroRNAs (miRNAs) are master regulators of drug resistance and have been previously proposed as potential biomarkers for the prediction of therapeutic response in colorectal cancer (CRC). Sorafenib, a multi-kinase inhibitor which has been approved for the treatment of liver, renal and thyroid cancer, is currently being studied as a monotherapy in selected molecular subtypes or in combination with other drugs in metastatic CRC. In this study, we explored sorafenib-induced cellular effects in Kirsten rat sarcoma viral oncogene homolog olog (KRAS) wild-type and KRAS-mutated CRC cell lines (Caco-2 and HRT-18), and finally profiled expression changes of specific miRNAs within the miRNome (>1000 human miRNAs) after exposure to sorafenib. Overall, sorafenib induced a time- and dose-dependent growth-inhibitory effect through S-phase cell cycle arrest in KRAS wild-type and KRAS-mutated CRC cells. In HRT-18 cells, two human miRNAs (hsa-miR-597 and hsa-miR-720) and two small RNAs (SNORD 13 and hsa-miR-3182) were identified as specifically sorafenib-induced. In Caco-2 cells, nine human miRNAs (hsa-miR-3142, hsa-miR-20a, hsa-miR-4301, hsa-miR-1290, hsa-miR-4286, hsa-miR-3182, hsa-miR-3142, hsa-miR-1246 and hsa-miR-720) were identified to be differentially regulated post sorafenib treatment. In conclusion, we confirmed sorafenib as a potential anti-neoplastic treatment strategy for CRC cells by demonstrating a growth-inhibitory and cell cycle-arresting effect of this drug. Changes in the miRNome indicate that some specific miRNAs might be relevant as indicators for sorafenib response, drug resistance and potential targets for combinatorial miRNA-based drug strategies.
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Scientific Article
Recent Results Cancer Res. 208, 219-242 (2016)
Multiple epidemiological studies demonstrated that overweight and obesity significantly increase the risk of several types of cancer. As the prevalence of obesity is dramatically rising, it is expected that it will represent one of the major lifestyle-associated risk factors for cancer development in the near future. Numerous recent studies expanded knowledge about key players and pathways, which are deregulated in the obese state and potentially promote cancer initiation, progression and aggressiveness via remote and local effects. These players include (but are not limited to) insulin/IGF, adipokines and inflammatory signaling molecules as well as metabolites. Nevertheless, the detailed mechanisms linking obesity and malignant transformation at the systemic, cellular and molecular level still demand further investigation. Additionally, dysfunctional molecular metabolic pathways appear to be specific for distinct cancer entities, thereby yet precluding definition of a common principle. This chapter will present an overview of the current knowledge of molecular nodes linking obesity and cancer and will briefly touch upon potential therapy options addressing metabolic cancer etiologies.
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Scientific Article
Best Pract. Res. Clin. Endocrinol. Metab. 30, 653-664 (2016)
The worldwide epidemic of obesity demands novel and more effective therapeutic approaches. Fat cells are at the core of energy metabolism trying either to cope with a positive energy balance by hypertrophy and hyperplasia of energy storing white adipocytes or to counteract obesity by the induction of non-shivering thermogenesis in energy combusting brite/brown adipocytes. However, the comprehensive regulatory network of adipocyte formation remains to be elucidated. MicroRNAs are an emerging class of important regulatory determinants in many biological processes and diseases, including adipocyte formation and obesity. In this review, microRNAs governing the formation of white, brite and brown adipocytes as well as candidates with impact on obesity are overviewed, concluded with recommendations for further research that considers prerequisites for successful therapeutic applications.
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Scientific Article
Nat. Commun. 7:13267 (2016)
Obesity-related insulin resistance represents the core component of the metabolic syndrome, promoting glucose intolerance, pancreatic beta cell failure and type 2 diabetes. Efficient and safe insulin sensitization and glucose control remain critical therapeutic aims to prevent diabetic late complications Here, we identify transforming growth factor beta-like stimulated clone (TSC) 22 D4 as a molecular determinant of insulin signalling and glucose handling. Hepatic TSC22D4 inhibition both prevents and reverses hyperglycaemia, glucose intolerance and insulin resistance in diabetes mouse models. TSC22D4 exerts its effects on systemic glucose homeostasis - at least in part - through the direct transcriptional regulation of the small secretory protein lipocalin 13 (LCN13). Human diabetic patients display elevated hepatic TSC22D4 expression, which correlates with decreased insulin sensitivity, hyperglycaemia and LCN13 serum levels. Our results establish TSC22D4 as a checkpoint in systemic glucose metabolism in both mice and humans, and propose TSC22D4 inhibition as an insulin sensitizing option in diabetes therapy.
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Scientific Article
BMC Endocr. Disord. 16:56 (2016)
Background: The aim of this study was to investigate the effect of a lifestyle intervention in obesity on the soluble form of the activated leukocyte cell adhesion molecule (sALCAM) and its association with metabolic parameters. Methods: Twenty-nine obese subjects selected from the OPTIFAST (R) 52 program. This program consisted into 2 crucial phases: an initial 12-week active weight reduction phase, followed by a 40-week weight maintenance phase. At baseline, after 12 weeks and at the end of the program, fasting glucose and insulin, total cholesterol, LDL-C, HDL-C, triglycerides, adiponectin, leptin, high sensitivity CRP, sALCAM, homeostasis model assessment-estimated insulin resistance (HOMA-IR) and leptin-to-adiponectin-ratio were determined. Oral glucose tolerance test (OGTT) was performed when indicated. Results: At baseline, the serum concentration of sALCAM was increased and correlated positively with HOMA-IR and negatively with age. At the end of the program, sALCAM concentrations decreased significantly. Multivariate analysis showed that sALCAM significantly correlated with age, glucose concentration after 2 h OGTT and the HOMA-IR. A higher decrease of HOMA-IR during the study was observed in subjects with higher concentration of sALCAM at baseline. Conclusions: sALCAM might be a novel biomarker in obesity that correlates and predicts insulin sensitivity improvement and that can be affected by lifestyle intervention.
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Scientific Article
Skelet. Muscle 6:33 (2016)
The circadian oscillations of muscle genes are controlled either directly by the intrinsic muscle clock or by extrinsic factors, such as feeding, hormonal signals, or neural influences, which are in turn regulated by the central pacemaker, the suprachiasmatic nucleus of the hypothalamus. A unique feature of circadian rhythms in skeletal muscle is motor neuron-dependent contractile activity, which can affect the oscillation of a number of muscle genes independently of the muscle clock. The role of the intrinsic muscle clock has been investigated using different Bmal1 knockout (KO) models. A comparative analysis of these models reveals that the dramatic muscle wasting and premature aging caused by global conventional KO are not present in muscle-specific Bmal1 KO or in global Bmal1 KO induced in the adult, therefore must reflect the loss of Bmal1 function during development in non-muscle tissues. On the other hand, muscle-specific Bmal1 knockout causes impaired muscle glucose uptake and metabolism, supporting a major role of the muscle clock in anticipating the sleep-to-wake transition, when glucose becomes the predominant fuel for the skeletal muscle.
Review
Review
Mol. Metab. 5, 615-25 (2016)
OBJECTIVE: In rodents and humans, besides brown adipose tissue (BAT), islands of thermogenic adipocytes, termed "brite" (brown-in-white) or beige adipocytes, emerge within white adipose tissue (WAT) after cold exposure or β3-adrenoceptor stimulation, which may protect from obesity and associated diseases. microRNAs are novel modulators of adipose tissue development and function. The purpose of this work was to characterize the role of microRNAs in the control of brite adipocyte formation. METHODS/RESULTS: Using human multipotent adipose derived stem cells, we identified miR-125b-5p as downregulated upon brite adipocyte formation. In humans and rodents, miR-125b-5p expression was lower in BAT than in WAT. In vitro, overexpression and knockdown of miR-125b-5p decreased and increased mitochondrial biogenesis, respectively. In vivo, miR-125b-5p levels were downregulated in subcutaneous WAT and interscapular BAT upon β3-adrenergic receptor stimulation. Injections of an miR-125b-5p mimic and LNA inhibitor directly into WAT inhibited and increased β3-adrenoceptor-mediated induction of UCP1, respectively, and mitochondrial brite adipocyte marker expression and mitochondriogenesis. CONCLUSION: Collectively, our results demonstrate that miR-125b-5p plays an important role in the repression of brite adipocyte function by modulating oxygen consumption and mitochondrial gene expression.
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Scientific Article
BioTechniques 61, 137-148 (2016)
Protein aggregation is both a hallmark of and a driving force for a number of diseases. It is therefore important to identify the nature of these aggregates and the mechanism(s) by which the cell counteracts their detrimental properties. Currently, the study of aggregation in vivo is performed primarily using fluorescently tagged versions of proteins and analyzing the aggregates by fluorescence microscopy. While this strategy is considered the gold standard, it has several limitations, particularly with respect to its suitability for high-throughput screening (HTS). Here, using a GFP fusion of the well-characterized yeast prion amyloid protein [PSI+], we demonstrate that flow cytometry, which utilizes the same physical principles as fluorescence microscopy, can be used to determine the aggregate load and pattern in live and fixed yeast cells. Furthermore, our approach can easily be applied to high-throughput analyses such as screenings with a yeast deletion library.
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Scientific Article
BMC Cancer 16:680 (2016)
Background: Galectin-7 (Gal-7) is negatively regulated in cervical cancer, and appears to be a link between the apoptotic response triggered by cancer and the anti-tumoral activity of the immune system. Our understanding of how cervical cancer cells and their molecular networks adapt in response to the expression of Gal-7 remains limited. Methods: Meta-analysis of Gal-7 expression was conducted in three cervical cancer cohort studies and TCGA. In silico prediction and bisulfite sequencing were performed to inquire epigenetic alterations. To study the effect of Gal-7 on cervical cancer, we ectopically re-expressed it in the HeLa and SiHa cervical cancer cell lines, and analyzed their transcriptome and SILAC-based proteome. We also examined the tumor and microenvironment host cell transcriptomes after xenotransplantation into immunocompromised mice. Differences between samples were assessed with the Kruskall-Wallis, Dunn's Multiple Comparison and T tests. Kaplan-Meier and log-rank tests were used to determine overall survival. Results: Gal-7 was constantly downregulated in our meta-analysis (p < 0.0001). Tumors with combined high Gal-7 and low galectin-1 expression (p = 0.0001) presented significantly better prognoses (p = 0.005). In silico and bisulfite sequencing assays showed de novo methylation in the Gal-7 promoter and first intron. Cells re-expressing Gal-7 showed a high apoptosis ratio (p < 0.05) and their xenografts displayed strong growth retardation (p < 0.001). Multiple gene modules and transcriptional regulators were modulated in response to Gal-7 reconstitution, both in cervical cancer cells and their microenvironments (FDR < 0.05 %). Most of these genes and modules were associated with tissue morphogenesis, metabolism, transport, chemokine activity, and immune response. These functional modules could exert the same effects in vitro and in vivo, even despite different compositions between HeLa and SiHa samples. Conclusions: Gal-7 re-expression affects the regulation of molecular networks in cervical cancer that are involved in diverse cancer hallmarks, such as metabolism, growth control, invasion and evasion of apoptosis. The effect of Gal-7 extends to the microenvironment, where networks involved in its configuration and in immune surveillance are particularly affected.
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Scientific Article
J. Clin. Invest. 126, 3263-3278 (2016)
Dietary protein intake is linked to an increased incidence of type 2 diabetes (T2D). Although dietary protein dilution (DPD) can slow the progression of some aging-related disorders, whether this strategy affects the development and risk for obesity-associated metabolic disease such as T2D is unclear. Here, we determined that DPD in mice and humans increases serum markers of metabolic health. In lean mice, DPD promoted metabolic inefficiency by increasing carbohydrate and fat oxidation. In nutritional and polygenic murine models of obesity, DPD prevented and curtailed the development of impaired glucose homeostasis independently of obesity and food intake. DPD-mediated metabolic inefficiency and improvement of glucose homeostasis were independent of uncoupling protein 1 (UCP1), but required expression of liver-derived fibroblast growth factor 21 (FGF21) in both lean and obese mice. FGF21 expression and secretion as well as the associated metabolic remodeling induced by DPD also required induction of liver-integrated stress response-driven nuclear protein 1 (NUPR1). Insufficiency of select nonessential amino acids (NEAAs) was necessary and adequate for NUPR1 and subsequent FGF21 induction and secretion in hepatocytes in vitro and in vivo. Taken together, these data indicate that DPD promotes improved glucose homeostasis through an NEAA insufficiency-induced liver NUPR1/FGF21 axis.
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Scientific Article
J. Nat. Med. 22, 1120-1130 (2016)
Cachexia represents a fatal energy-wasting syndrome in a large number of patients with cancer that mostly results in a pathological loss of skeletal muscle and adipose tissue. Here we show that tumor cell exposure and tumor growth in mice triggered a futile energy-wasting cycle in cultured white adipocytes and white adipose tissue (WAT), respectively. Although uncoupling protein 1 (Ucp1)-dependent thermogenesis was dispensable for tumor-induced body wasting, WAT from cachectic mice and tumor-cell-supernatant-treated adipocytes were consistently characterized by the simultaneous induction of both lipolytic and lipogenic pathways. Paradoxically, this was accompanied by an inactivated AMP-activated protein kinase (Ampk), which is normally activated in peripheral tissues during states of low cellular energy. Ampk inactivation correlated with its degradation and with upregulation of the Ampk-interacting protein Cidea. Therefore, we developed an Ampk-stabilizing peptide, ACIP, which was able to ameliorate WAT wasting in vitro and in vivo by shielding the Cidea-targeted interaction surface on Ampk. Thus, our data establish the Ucp1-independent remodeling of adipocyte lipid homeostasis as a key event in tumor-induced WAT wasting, and we propose the ACIP-dependent preservation of Ampk integrity in the WAT as a concept in future therapies for cachexia.
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Scientific Article
Nat. Commun. 7:12397 (2016)
The myogenic regulatory factor MRF4 is highly expressed in adult skeletal muscle but its function is unknown. Here we show that Mrf4 knockdown in adult muscle induces hypertrophy and prevents denervation-induced atrophy. This effect is accompanied by increased protein synthesis and widespread activation of muscle-specific genes, many of which are targets of MEF2 transcription factors. MEF2-dependent genes represent the top-ranking gene set enriched after Mrf4 RNAi and a MEF2 reporter is inhibited by co-transfected MRF4 and activated by Mrf4 RNAi. The Mrf4 RNAi-dependent increase in fibre size is prevented by dominant negative MEF2, while constitutively active MEF2 is able to induce myofibre hypertrophy. The nuclear localization of the MEF2 corepressor HDAC4 is impaired by Mrf4 knockdown, suggesting that MRF4 acts by stabilizing a repressor complex that controls MEF2 activity. These findings open new perspectives in the search for therapeutic targets to prevent muscle wasting, in particular sarcopenia and cachexia.
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Scientific Article
J. Vasc. Surg. 64, 990-994 (2016)
Objective: Glyoxalase 1 (GLO1) is ubiquitously expressed in the cytosol of the cell and is the major opponent against the reactive metabolite methylglyoxal, which is involved in the development of atherosclerosis. Nondiabetic individuals with an increased hemoglobin A1c (HbA1c) level are at higher risk for development of cardiovascular diseases. As such, this study investigated whether there was an association between reduced GLO1 activity in atherosclerotic lesions of nondiabetic patients with an increased HbA1c level. Methods: HbA1c level was determined in venous blood of patients with carotid artery disease. Protein level of GLO1 was measured in endarterectomy-derived carotid artery plaques by Western blotting. Activity was measured by spectrophotometric assay in the plaques as well as in the erythrocytes; GLO1 activity in erythrocytes was compared with that in a cohort of healthy individuals (n = 15; 33% men; average age, 60 years). Results: There were 36 patients with carotid artery disease (69% men; average age, 69 years) included in this study and divided into two equal groups: group I, HbA1c < 5.7% (<39 mmol/mol); and group II, 5.7% ≤ HbA1c < 6.5% (39 mmol/mol ≤ HbA1c < 48 mmol/mol). GLO1 activity in carotid plaques was reduced by 29% in group II compared with group I (P = .048), whereas protein expression was unchanged (P = .25). Analysis of GLO1 activity in erythrocytes revealed no difference between the groups (P = .36) or in comparison to healthy controls (P = .15). Examination of clinical parameters showed an increased amount of patients with concomitant peripheral arterial disease in group II (44% vs 10%; P = .020). Conclusions: Reduction of GLO1 activity in atherosclerotic lesions of nondiabetic patients with increased HbA1c is associated with a functional involvement of this protective enzyme in atherogenesis. Systemic GLO1 activity seems to be independent of both HbA1c and localized atherosclerosis as it was unchanged between group I and group II as well as compared with healthy controls, respectively.
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Scientific Article
Sci. Rep. 6:28613 (2016)
In response to cold or β3-adrenoreceptor stimulation brown adipose tissue (BAT) promotes non-shivering thermogenesis, leading to energy dissipation. BAT has long been thought to be absent or scarce in adult humans. The recent discovery of thermogenic brite/beige adipocytes has opened the way to development of novel innovative strategies to combat overweight/obesity and associated diseases. Thus it is of great interest to identify regulatory factors that govern the brite adipogenic program. Here, we carried out global microRNA (miRNA) expression profiling on human adipocytes to identify miRNAs that are regulated upon the conversion from white to brite adipocytes. Among the miRNAs that were differentially expressed, we found that Let-7i-5p was down regulated in brite adipocytes. A detailed analysis of the Let-7i-5p levels showed an inverse expression of UCP1 in murine and human brite adipocytes both in vivo and in vitro. Functional studies with Let-7i-5p mimic in human brite adipocytes in vitro revealed a decrease in the expression of UCP1 and in the oxygen consumption rate. Moreover, the Let-7i-5p mimic when injected into murine sub-cutaneous white adipose tissue inhibited partially β3-adrenergic activation of the browning process. These results suggest that the miRNAs Let-7i-5p participates in the recruitment and the function of brite adipocytes.
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Scientific Article
J. Biotechnol. 235, 150-161 (2016)
As Chinese Hamster Ovary (CHO) cells are the cell line of choice for the production of human-like recombinant proteins, there is interest in genetic optimization of host cell lines to overcome certain limitations in their growth rate and protein secretion. At the same time, a detailed understanding of these processes could be used to advantage by identification of marker transcripts that characterize states of performance.In this context, microRNAs (miRNAs) that exhibit a robust correlation to the growth rate of CHO cells were determined by analyzing miRNA expression profiles in a comprehensive collection of 46 samples including CHO-K1, CHO-S and CHO-DUKXB11, which were adapted to various culture conditions, and analyzed in different growth stages using microarrays. By applying Spearman or Pearson correlation coefficient criteria of. >. |0.6|, miRNAs with high correlation to the overall growth, or growth rates observed in exponential, serum-free, and serum-free exponential phase were identified. An overlap of twelve miRNAs common for all sample sets was revealed, with nine positively and three negatively correlating miRNAs.The here identified panel of miRNAs can help to understand growth regulation in CHO cells and contains putative engineering targets as well as biomarkers for cell lines with advantageous growth characteristics.
Review
Review
Nat. Commun. 7:11869 (2016)
Receptor-interacting protein kinase 3 (RIPK3) mediates necroptosis, a form of programmed cell death that promotes inflammation in various pathological conditions, suggesting that it might be a privileged pharmacological target. However, its function in glucose homeostasis and obesity has been unknown. Here we show that RIPK3 is over expressed in the white adipose tissue (WAT) of obese mice fed with a choline-deficient high-fat diet. Genetic inactivation of Ripk3 promotes increased Caspase-8-dependent adipocyte apoptosis and WAT inflammation, associated with impaired insulin signalling in WAT as the basis for glucose intolerance. Similarly to mice, in visceral WAT of obese humans, RIPK3 is overexpressed and correlates with the body mass index and metabolic serum markers. Together, these findings provide evidence that RIPK3 in WAT maintains tissue homeostasis and suppresses inflammation and adipocyte apoptosis, suggesting that systemic targeting of necroptosis might be associated with the risk of promoting insulin resistance in obese patients.
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Scientific Article
Thyroid 26, 1131-1140 (2016)
BACKGROUND: Cell models are key instruments for in vitro studies of the thyroid. Permanent thyroid cell lines that are widely used in laboratory research typically originate from tumors. For many purposes it is desirable to compare tumor cells with cells originating from normal tissue. However, such cultures grow slowly, have a highly limited lifespan and are known to lose their thyroid characteristics. The aim of the present study was to type coding and noncoding thyroid markers in different culture systems in an attempt to determine the optimal conditions for in vitro experimentation. METHODS: Human primary thyroid cells were isolated from histologically nontumorous tissues. Two alternative media (6H and H7h) were used. The morphology and behavior of the ensuing monolayer (2-dimensional) cultures was monitored by microscopy. The expression of key thyroid-related genes (n=9) was monitored by RT-PCR on Days 8, 21 and 43 after initiation. As a pilot study the same markers were studied in a 3-dimensional hanging-drop culture system. RESULTS: In the cultures with 6H or H7h medium, the primary thyroid cells displayed growth in numbers and size. Most cells retained the main morphological characteristics of thyroid cells throughout the first two weeks of culture and fibroblast-like cells appeared around Day 19. By Day 21, most thyroid gene markers were retained but by Day 43 several markers were no longer present. The lncRNA transcripts PTCSC2 (spliced) and PTCSC3 were the first to disappear. There were no fundamental differences between the two media in the early period of culture. In the 3-dimensional system most thyroid markers were retained by Day 21. CONCLUSION: Cultures of thyroid cells retain many thyroid characteristics up to Day 21 whereafter fibroblast-like dedifferentiated cells begin to dominate.
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Scientific Article
Endocrinology 157, 3157-3166 (2016)
Pheochromocytomas (PCCs) are tumors arising from neural crest-derived chromaffin cells. There are currently few animal models of PCC that recapitulate the key features of human tumors. Since such models may be useful for investigations of molecular pathomechanisms and development of novel therapeutic interventions, we characterized a spontaneous animal model (MENX rats) that develops endogenous PCCs with complete penetrance. Urine was longitudinally collected from wild-type (wt) and MENX-affected (mutant) rats and outputs of catecholamines and their O-methylated metabolites determined by mass spectrometry. Adrenal catecholamine contents, cellular ultrastructure and expression of phenylethanolamine N-methyltransferase (PNMT), which converts norepinephrine to epinephrine, were also determined in wt and mutant rats. Blood pressure was longitudinally measured and end-organ pathology assessed. Compared to wt rats, mutant animals showed age-dependent increases in urinary outputs of norepinephrine (P=0.0079) and normetanephrine (P=0.0014) that correlated in time with development of tumor nodules, increases in blood pressure and development of hypertension-related end-organ pathology. Development of tumor nodules, which lacked expression of PNMT, occurred on a background of adrenal medullary morphological and biochemical changes occurring as early as 1 month of age and involving increased adrenal medullary concentrations of dense cored vesicles, tissue contents of both norepinephrine and epinephrine and urinary outputs of metanephrine, the metabolite of epinephrine. Taken together, MENX-affected rats share several biochemical and pathophysiological features with PCC patients. This model thus provides a suitable platform to study the pathogenesis of PCC for preclinical translational studies aimed at development of novel therapies for aggressive forms of human tumors.
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Cancer Res. 76, 3644-3654 (2016)
RAF kinase inhibitor protein (RKIP) is a seminal regulator of intracellular signaling and exhibits both anti-metastatic and anti-tumorigenic properties. Decreased expression of RKIP has been described in several human malignancies, including acute myeloid leukemia (AML). As the mechanisms leading to RKIP loss in AML are still unclear, we aimed to analyze the potential involvement of micro-RNAs (miRNAs) within this study. miRNA microarray and qPCR data of more than 400 AML patient specimens revealed correlation between decreased expression of RKIP and increased expression of miR-23a, a member of the miR-23a/27a/24-2 cluster. In functional experiments, overexpression of miR-23a decreased RKIP mRNA and protein expression, whereas miR-23a inhibition caused the opposite effect. By employing an RKIP 3'UTR luciferase reporter construct with and without mutation or deletion of the putative miR-23a binding site, we could show that RKIP modulation by miR-23a is mediated via direct binding to this region. Importantly, miR-23a overexpression induced a significant increase of proliferation in hematopoietic cells. Simultaneous transfection of an RKIP expression construct lacking the miR-23a binding sites reversed this phenotype, indicating that this effect is truly mediated via downregulation of RKIP. Finally, by analyzing more than 4300 primary patient specimens via database retrieval from The Cancer Genome Atlas (TCGA), we could highlight the importance of the miR-23a/RKIP axis in a broad range of human cancer entities. In conclusion, we have identified miR-23a as a negative regulator of RKIP expression in AML and have provided data that suggest the importance of our observation beyond this tumor entity.
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Steroids 114, 7-15 (2016)
Glucocorticoids (GCs), as ligands for the glucocorticoid receptor (GR), represent one of the most effective and frequently used classes of drugs for anti-inflammatory and immunosuppressive therapy. In addition, its role in physiological and pathophysiological processes makes the GR an important research target. The past decades have yielded a wealth of insight into the physiological and pharmacological effects of GCs. Today's era of next generation sequencing techniques is now beginning to elucidate the molecular and genomic circuits underlying GR's cell type-specific actions. This review focuses on the concepts and insights gained from recent studies in two of the most important tissues for GC action: the liver (mediating GR's metabolic effects) and macrophages (as the main target of anti-inflammatory GC therapy). We summarize results obtained from transgenic mouse models, molecular and genome-wide studies to illustrate GR's complex interactions with DNA, chromatin, co-regulators and other transcription factors. Characterizing the cell type-specific transcriptional complexes assembled around GR will pave the road for the development of new anti-inflammatory and metabolic therapies in the future.
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EMBO Mol. Med. 8, 654-669 (2016)
Recent studies have demonstrated that repeated short-term nutrient withdrawal (i.e. fasting) has pleiotropic actions to promote organismal health and longevity. Despite this, the molecular physiological mechanisms by which fasting is protective against metabolic disease are largely unknown. Here, we show that, metabolic control, particularly systemic and liver lipid metabolism, is aberrantly regulated in the fasted state in mouse models of metabolic dysfunction. Liver transcript assays between lean/healthy and obese/diabetic mice in fasted and fed states uncovered "growth arrest and DNA damage-inducible" GADD45β as a dysregulated gene transcript during fasting in several models of metabolic dysfunction including ageing, obesity/pre-diabetes and type 2 diabetes, in both mice and humans. Using whole-body knockout mice as well as liver/hepatocyte-specific gain- and loss-of-function strategies, we revealed a role for liver GADD45β in the coordination of liver fatty acid uptake, through cytoplasmic retention of FABP1, ultimately impacting obesity-driven hyperglycaemia. In summary, fasting stress-induced GADD45β represents a liver-specific molecular event promoting adaptive metabolic function.
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Cell Rep. 15, 360-371 (2016)
Lipoprotein synthesis is controlled by estrogens, but the exact mechanisms underpinning this regulation and the role of the hepatic estrogen receptor α (ERα) in cholesterol physiology are unclear. Utilizing a mouse model involving selective ablation of ERα in the liver, we demonstrate that hepatic ERα couples lipid metabolism to the reproductive cycle. We show that this receptor regulates the synthesis of cholesterol transport proteins, enzymes for lipoprotein remodeling, and receptors for cholesterol uptake. Additionally, ERα is indispensable during proestrus for the generation of high-density lipoproteins efficient in eliciting cholesterol efflux from macrophages. We propose that a specific interaction with liver X receptor α (LXRα) mediates the broad effects of ERα on the hepatic lipid metabolism.
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Sci. Signal. 9:rs1 (2016)
Mapping the in vivo distribution of endogenous oxidants in animal tissues is of substantial biomedical interest. Numerous health-related factors, including diet, physical activity, infection, aging, toxins, or pharmacological intervention, may cause redox changes. Tools are needed to pinpoint redox state changes to particular organs, tissues, cell types, and subcellular organelles. We describe a procedure that preserves the in vivo redox state of genetically encoded redox biosensors within histological tissue sections, thus providing "redox maps" for any tissue and comparison of interest. We demonstrate the utility of the technique by visualizing endogenous redox differences and changes in the context of tumor growth, inflammation, embryonic development, and nutrient starvation.
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Nat. Commun. 7:10782 (2016)
Hypothalamic leptin signalling has a key role in food intake and energy-balance control and is often impaired in obese individuals. Here we identify histone deacetylase 5 (HDAC5) as a regulator of leptin signalling and organismal energy balance. Global HDAC5 KO mice have increased food intake and greater diet-induced obesity when fed high-fat diet. Pharmacological and genetic inhibition of HDAC5 activity in the mediobasal hypothalamus increases food intake and modulates pathways implicated in leptin signalling. We show HDAC5 directly regulates STAT3 localization and transcriptional activity via reciprocal STAT3 deacetylation at Lys685 and phosphorylation at Tyr705. In vivo, leptin sensitivity is substantially impaired in HDAC5 loss-of-function mice. Hypothalamic HDAC5 overexpression improves leptin action and partially protects against HFD-induced leptin resistance and obesity. Overall, our data suggest that hypothalamic HDAC5 activity is a regulator of leptin signalling that adapts food intake and body weight to our dietary environment.
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Scientific Article
Biochim. Biophys. Acta-Mol. Cell Biol. Lipids 1861, 285-293 (2016)
Brite adipocytes recently discovered in humans are of considerable importance in energy expenditure by converting energy excess into heat. This property could be useful in the treatment of obesity, and nutritional aspects are relevant to this important issue. Using hMADS cells as a human cell model which undergoes a white to a brite adipocyte conversion, we had shown previously that arachidonic acid, the major metabolite of the essential nutrient Ω6-linoleic acid, plays a major role in this process. Its metabolites PGE2 and PGF2 alpha inhibit this process via a calcium-dependent pathway, whereas in contrast carbaprostacyclin (cPGI2), a stable analog of prostacyclin, activates white to brite adipocyte conversion. Herein, we show that cPGI2 generates via its cognate cell-surface receptor IP-R, a cyclic AMP-signaling pathway involving PKA activity which in turn induces the expression of UCP1. In addition, cPGI2 activates the pathway of nuclear receptors of the PPAR family, i.e. PPARα and PPARγ, which act separately from IP-R to up-regulate the expression of key genes involved in the function of brite adipocytes. Thus dual pathways are playing in concert for the occurrence of a browning process of human white adipocytes. These results make prostacyclin analogs as a new class of interesting molecules to treat obesity and associated diseases.
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Scientific Article
Mol. Metab. 5, 67-78 (2016)
Objectives Cancer cachexia affects the majority of tumor patients and significantly contributes to high mortality rates in these subjects. Despite its clinical importance, the identity of tumor-borne signals and their impact on specific peripheral organ systems, particularly the heart, remain mostly unknown. Methods and Results By combining differential colon cancer cell secretome profiling with large-scale cardiomyocyte phenotyping, we identified a signature panel of seven “cachexokines”, including Bridging integrator 1, Syntaxin 7, Multiple inositol-polyphosphate phosphatase 1, Glucosidase alpha acid, Chemokine ligand 2, Adamts like 4, and Ataxin-10, which were both sufficient and necessary to trigger cardiac atrophy and aberrant fatty acid metabolism in cardiomyocytes. As a prototypical example, engineered secretion of Ataxin-10 from non-cachexia-inducing cells was sufficient to induce cachexia phenotypes in cardiomyocytes, correlating with elevated Ataxin-10 serum levels in murine and human cancer cachexia models. Conclusions As Ataxin-10 serum levels were also found to be elevated in human cachectic cancer patients, the identification of Ataxin-10 as part of a cachexokine cocktail now provides a rational approach towards personalized predictive, diagnostic and therapeutic measures in cancer cachexia.
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Scientific Article
2015
Mol. Metab. 4, 406-417 (2015)
OBJECTIVE: Type 2 diabetes arises from insulin resistance of peripheral tissues followed by dysfunction of β-cells in the pancreas due to metabolic stress. Both depletion and supplementation of neutral amino acids have been discussed as strategies to improve insulin sensitivity. Here we characterise mice lacking the intestinal and renal neutral amino acid transporter B(0)AT1 (Slc6a19) as a model to study the consequences of selective depletion of neutral amino acids. METHODS: Metabolic tests, analysis of metabolite levels and signalling pathways were used to characterise mice lacking the intestinal and renal neutral amino acid transporter B(0)AT1 (Slc6a19). RESULTS: Reduced uptake of neutral amino acids in the intestine and loss of neutral amino acids in the urine causes an overload of amino acids in the lumen of the intestine and reduced systemic amino acid availability. As a result, higher levels of glucagon-like peptide 1 (GLP-1) are produced by the intestine after a meal, while the liver releases the starvation hormone fibroblast growth factor 21 (FGF21). The combination of these hormones generates a metabolic phenotype that is characterised by efficient removal of glucose, particularly by the heart, reduced adipose tissue mass, browning of subcutaneous white adipose tissue, enhanced production of ketone bodies and reduced hepatic glucose output. CONCLUSIONS: Reduced neutral amino acid availability improves glycaemic control. The epithelial neutral amino acid transporter B(0)AT1 could be a suitable target to treat type 2 diabetes.
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Scientific Article
J. Diabetes Res.:842584 (2015)
Objective. Glyoxalase-1 is an enzyme detoxifying methylglyoxal (MG). MG is a potent precursor of advanced glycation endproducts which are regarded to be a key player in micro- and macrovascular damage. Yet, the role of Glo1 in atherosclerosis remains unclear. In this study, the effect of Glo1 on mouse metabolism and atherosclerosis is evaluated. Methods. Glo1 knockdown mice were fed a high fat or a standard diet for 10 weeks. Body weight and composition were investigated by Echo MRI. The PhenoMaster system was used to measure the energy expenditure. To evaluate the impact of Glo1 on atherosclerosis, Glo1KD mice were crossed with ApoE-knockout mice and fed a high fat diet for 14 weeks. Results. Glo1 activity was significantly reduced in heart, liver, and kidney lysates derived from Glo1KD mice. Yet, there was no increase in methylglyoxal-derived AGEs in all organs analyzed. The Glo1 knockdown did not affect body weight or body composition. Metabolic studies via indirect calorimetry did not show significant effects on energy expenditure. Glo1KD mice crossed to ApoE−/− mice did not show enhanced formation of atherosclerosis. Conclusion. A Glo1 knockdown does not have major short term effects on the energy expenditure or the formation of atherosclerotic plaques.
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Scientific Article
PLoS Genet. 11:e1005561 (2015)
In mammals, the liver plays a central role in maintaining carbohydrate and lipid homeostasis by acting both as a major source and a major sink of glucose and lipids. In particular, when dietary carbohydrates are in excess, the liver converts them to lipids via de novo lipogenesis. The molecular checkpoints regulating the balance between carbohydrate and lipid homeostasis, however, are not fully understood. Here we identify PPP2R5C, a regulatory subunit of PP2A, as a novel modulator of liver metabolism in postprandial physiology. Inactivation of PPP2R5C in isolated hepatocytes leads to increased glucose uptake and increased de novo lipogenesis. These phenotypes are reiterated in vivo, where hepatocyte specific PPP2R5C knockdown yields mice with improved systemic glucose tolerance and insulin sensitivity, but elevated circulating triglyceride levels. We show that modulation of PPP2R5C levels leads to alterations in AMPK and SREBP-1 activity. We find that hepatic levels of PPP2R5C are elevated in human diabetic patients, and correlate with obesity and insulin resistance in these subjects. In sum, our data suggest that hepatic PPP2R5C represents an important factor in the functional wiring of energy metabolism and the maintenance of a metabolically healthy state.
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Scientific Article
Mol. Metab. 4, 823-833 (2015)
Objective: Physical activity and circadian rhythms are well-established determinants of human health and disease, but the relationship between muscle activity and the circadian regulation of muscle genes is a relatively new area of research. It is unknown whether muscle activity and muscle clock rhythms are coupled together, nor whether activity rhythms can drive circadian gene expression in skeletal muscle. Methods: We compared the circadian transcriptomes of two mouse hindlimb muscles with vastly different circadian activity patterns, the continuously active slow soleus and the sporadically active fast tibialis anterior, in the presence or absence of a functional skeletal muscle clock (skeletal muscle-specific Bmal1 KO). In addition, we compared the effect of denervation on muscle circadian gene expression. Results: We found that different skeletal muscles exhibit major differences in their circadian transcriptomes, yet core clock gene oscillations were essentially identical in fast and slow muscles. Furthermore, denervation caused relatively minor changes in circadian expression of most core clock genes, yet major differences in expression level, phase and amplitude of many muscle circadian genes. Conclusions: We report that activity controls the oscillation of around 15% of skeletal muscle circadian genes independently of the core muscle clock, and we have identified the Ca2+-dependent calcineurin-NFAT pathway as an important mediator of activity-dependent circadian gene expression, showing that circadian locomotor activity rhythms drive circadian rhythms of NFAT nuclear translocation and target gene expression.
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Scientific Article
Front. Endocrin. 6:129 (2015)
De novo formation of beige/brite adipocytes from progenitor cells contributes to the thermogenic adaptation of adipose tissue and holds great potential for the therapeutic remodeling of fat as a treatment for obesity. Despite the recent identification of several factors regulating browning of white fat, there is a lack of physiological cell models for the mechanistic investigation of progenitor-mediated beige/brite differentiation. We have previously revealed prostacyclin (PGI2) as one of the few known endogenous extracellular mediators promoting de novo beige/brite formation by relaying β-adrenergic stimulation to the progenitor level. Here, we present a cell model based on murine primary progenitor cells defined by markers previously shown to be relevant for in vivo browning, including a simplified isolation procedure. We demonstrate the specific and broad induction of thermogenic gene expression by PGI2 signaling in the absence of lineage conversion, and reveal the previously unidentified nuclear relocalization of the Ucp1 gene locus in association with transcriptional activation. By profiling the time course of the progenitor response, we show that PGI2 signaling promoted progenitor cell activation through cell cycle and adhesion pathways prior to metabolic maturation toward an oxidative cell phenotype. Our results highlight the importance of core progenitor activation pathways for the recruitment of thermogenic cells and provide a resource for further mechanistic investigation.
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Scientific Article
Mol. Metab. 4, 732-740 (2015)
Objective: One of the major side effects of glucocorticoid (GC) treatment is lean tissue wasting, indicating a prominent role in systemic amino acid metabolism. In order to uncover a novel aspect of GCs and their intracellular-receptor, the glucocorticoid receptor (GR), on metabolic control, we conducted amino acid and acylcarnitine profiling in human and mouse models of GC/GR gain- and loss-of-function. Methods: Blood serum and tissue metabolite levels were determined in Human Addison's disease (AD) patients as well as in mouse models of systemic and liver-specific GR loss-of-function (AAV-miR-GR) with or without dexamethasone (DEX) treatments. Body composition and neuromuscular and metabolic function tests were conducted invivo and exvivo, the latter using precision cut liver slices. Results: A serum metabolite signature of impaired urea cycle function (i.e. higher [ARG]:[ORN+CIT]) was observed in human (CTRL: 0.45±0.03, AD: 1.29±0.04; p<0.001) and mouse (AAV-miR-NC: 0.97±0.13, AAV-miR-GR: 2.20±0.19; p<0.001) GC/GR loss-of-function, with similar patterns also observed in liver. Serum urea levels were consistently affected by GC/GR gain- (~+32%) and loss (~-30%) -of-function. Combined liver-specific GR loss-of-function with DEX treatment revealed a tissue-autonomous role for the GR to coordinate an upregulation of liver urea production rate invivo and exvivo, and prevent hyperammonaemia and associated neuromuscular dysfunction invivo. Liver mRNA expression profiling and GR-cistrome mining identified Arginase I (ARG1) a urea cycle gene targeted by the liver GR. Conclusions: The liver GR controls systemic and liver urea cycle function by transcriptional regulation of ARG1 expression.
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Scientific Article
Nat. Commun. 6:7796 (2015)
Acute lung injury (ALI) is a severe inflammatory disease for which no specific treatment exists. As glucocorticoids have potent immunosuppressive effects, their application in ALI is currently being tested in clinical trials. However, the benefits of this type of regimen remain unclear. Here we identify a mechanism of glucocorticoid action that challenges the long-standing dogma of cytokine repression by the glucocorticoid receptor. Contrarily, synergistic gene induction of sphingosine kinase 1 (SphK1) by glucocorticoids and pro-inflammatory stimuli via the glucocorticoid receptor in macrophages increases circulating sphingosine 1-phosphate levels, which proves essential for the inhibition of inflammation. Chemical or genetic inhibition of SphK1 abrogates the therapeutic effects of glucocorticoids. Inflammatory p38 MAPK- and mitogen- and stress-activated protein kinase 1 (MSK1)-dependent pathways cooperate with glucocorticoids to upregulate SphK1 expression. Our findings support a critical role for SphK1 induction in the suppression of lung inflammation by glucocorticoids, and therefore provide rationales for effective anti-inflammatory therapies.
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Scientific Article
Int. J. Obes. 39, 1733-1741 (2015)
BackgroundA growing body of evidence suggests that many downstream pathologies of obesity are amplified or even initiated by molecular changes within white adipose tissue (WAT). Such changes are the result of an excessive expansion of individual white adipocytes and could potentially be ameliorated via an increase in de novo adipocyte recruitment (adipogenesis). Mesoderm specific transcript (MEST) is a protein with a putative yet unidentified enzymatic function and has previously been shown to correlate with adiposity and adipocyte size in mouse.ObjectivesThis study analysed WAT samples and employed a cell model of adipogenesis to characterise MEST expression and function in human.Methods and ResultsMEST mRNA and protein levels increased during adipocyte differentiation of human Multipotent Adipose-Derived Stem (hMADS) cells. Further, obese individuals displayed significantly higher MEST levels in WAT compared to normal weight subjects, and MEST was significantly correlated with adipocyte volume. In striking contrast to previous mouse studies, knockdown of MEST enhanced human adipocyte differentiation, most likely via a significant promotion of peroxisome proliferator-activated receptor (PPAR) signaling, glycolysis and fatty acid biosynthesis pathways at early stages. Correspondingly, overexpression of MEST impaired adipogenesis. We further found that silencing of MEST fully substitutes for the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) as inducer of adipogenesis. Accordingly, phosphorylation of the pro-adipogenic transcription factors cAMP response element-binding protein (CREB) and activating transcription factor 1 (ATF1) were highly increased upon MEST knockdown.ConclusionsWhile we found a similar association between MEST and adiposity as previously described for mouse, our functional analyses suggest that MEST acts as an inhibitor of human adipogenesis, contrary to previous murine studies. We have further established a novel link between MEST and CREB/ATF1 that could be of general relevance in regulation of metabolism, particularly obesity-associated diseases.
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EMBO Mol. Med. 7, 1048-1062 (2015)
Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer fatalities in Western societies, characterized by high metastatic potential and resistance to chemotherapy. Critical molecular mechanisms of these phenotypical features still remain unknown, thus hampering the development of effective prognostic and therapeutic measures in PDAC. Here, we show that transcriptional co-factor Transducin beta-like (TBL) 1 was over-expressed in both human and murine PDAC. Inactivation of TBL1 in human and mouse pancreatic cancer cells reduced cellular proliferation and invasiveness, correlating with diminished glucose uptake, glycolytic flux, and oncogenic PI3 kinase signaling which in turn could rescue TBL1 deficiency-dependent phenotypes. TBL1 deficiency both prevented and reversed pancreatic tumor growth, mediated transcriptional PI3 kinase inhibition, and increased chemosensitivity of PDAC cells in vivo. As TBL1 mRNA levels were also found to correlate with PI3 kinase levels and overall survival in a cohort of human PDAC patients, TBL1 was identified as a checkpoint in the malignant behavior of pancreatic cancer and its expression may serve as a novel molecular target in the treatment of human PDAC.
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Scientific Article
Front. Endocrin. 6:81 (2015)
The increase of life expectancy has led to the increase of age-related diseases such as osteoporosis. Osteoporosis is characterized by bone weakening promoting the occurrence of fractures with defective bone regeneration. Men aged over 50 have a prevalence for osteoporosis of 20%, which is related to a decline in sex hormones occurring during andropause or surgical orchidectomy. As we previously demonstrated in a mouse model for menopause in women that treatment with the neurohypophyseal peptide hormone oxytocin (OT) normalizes body weight and prevents the development of osteoporosis, herein we addressed the effects of OT in male osteoporosis. Thus, we treated orchidectomized mice, an animal model suitable for the study of male osteoporosis, for 8 weeks with OT and then analyzed trabecular and cortical bone parameters as well as fat mass using micro-computed tomography. Orchidectomized mice displayed severe bone loss, muscle atrophy accompanied by fat mass gain as expected in andropause. Interestingly, OT treatment in male mice normalized fat mass as it did in female mice. However, although OT treatment led to a normalization of bone parameters in ovariectomized mice, this did not happen in orchidectomized mice. Moreover, loss of muscle mass was not reversed in orchidectomized mice upon OT treatment. All of these observations indicate that OT acts on fat physiology in both sexes, but in a sex specific manner with regard to bone physiology.
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Scientific Article
Genome Res. 25, 836-844 (2015)
Glucocorticoids (GCs) are commonly prescribed drugs, but their anti-inflammatory benefits are mitigated by metabolic side effects. Their transcriptional effects, including tissue-specific gene activation and repression, are mediated by the glucocorticoid receptor (GR), which is known to bind as a homodimer to a palindromic DNA sequence. Using ChIP-exo in mouse liver under endogenous corticosterone exposure, we report here that monomeric GR interaction with a half-site motif is more prevalent than homodimer binding. Monomers colocalize with lineage-determining transcription factors in both liver and primary macrophages, and the GR half-site motif drives transcription, suggesting that monomeric binding is fundamental to GR's tissue-specific functions. In response to exogenous GC in vivo, GR dimers assemble on chromatin near ligand-activated genes, concomitant with monomer evacuation of sites near repressed genes. Thus, pharmacological GCs mediate gene expression by favoring GR homodimer occupancy at classic palindromic sites at the expense of monomeric binding. The findings have important implications for improving therapies that target GR.
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Cell Metab. 21, 678-691 (2015)
Obesity, insulin resistance, and related pathologies are associated with immune-mediated chronic inflammation. Kit mutant mice are protected from diet-induced obesity and associated co-morbidities, and this phenotype has previously been attributed to their lack of mast cells. We performed a comprehensive metabolic analysis of Kit-dependent Kit(W/Wv) and Kit-independent Cpa3(Cre/+) mast-cell-deficient mouse strains, employing diet-induced or genetic (Lep(Ob/Ob) background) models of obesity. Our results show that mast cell deficiency, in the absence of Kit mutations, plays no role in the regulation of weight gain or insulin resistance. Moreover, we provide evidence that the metabolic phenotype observed in Kit mutant mice, while independent of mast cells, is immune regulated. Our data underscore the value of definitive mast cell deficiency models to conclusively test the involvement of this enigmatic cell in immune-mediated pathologies and identify Kit as a key hematopoietic factor in the pathogenesis of metabolic syndrome.
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Methods Mol. Biol. 1296, 161-171 (2015)
Microarray technology has evolved to efficiently profile the expression of RNAs. However, analysis of small non-coding RNAs (ncRNAs) is challenging due to their short length and highly divergent sequences with large variation in GC content leading to very different hybridization properties. To overcome these challenges, LNA-modified oligonucleotides have been used to enhance and normalize the melting temperature (Tm) of capture probes, which allows sensitive profiling of small ncRNAs regardless of their sequence. Here, we describe the isolation and labeling of small non-coding RNAs, as well as their hybridization to microarrays with LNA-modified oligonucleotide probes using a semi-automated hybridization device.
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PLoS ONE 10:e0118534 (2015)
Regulatory T (Treg) cells are critical determinants of both immune responses and metabolic control. Here we show that systemic ablation of Treg cells compromised the adaptation of whole-body energy expenditure to cold exposure, correlating with impairment in thermogenic marker gene expression and massive invasion of pro-inflammatory macrophages in brown adipose tissue (BAT). Indeed, BAT harbored a unique sub-set of Treg cells characterized by a unique gene signature. As these Treg cells respond to BAT activation upon cold exposure, this study defines a BAT-specific Treg sub-set with direct implications for the regulation of energy homeostasis in response to environmental stress.
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Scientific Article
PLoS ONE 10:e0118534 (2015)
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Scientific Article
Methods Mol. Biol. 1296, 161-171 (2015)
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Scientific Article
EMBO J. 34, 344-360 (2015)
In mammals, glucocorticoids (GCs) and their intracellular receptor, the glucocorticoid receptor (GR), represent critical checkpoints in the endocrine control of energy homeostasis. Indeed, aberrant GC action is linked to severe metabolic stress conditions as seen in Cushing's syndrome, GC therapy and certain components of the Metabolic Syndrome, including obesity and insulin resistance. Here, we identify the hepatic induction of the mammalian conserved microRNA (miR)-379/410 genomic cluster as a key component of GC/GR-driven metabolic dysfunction. Particularly, miR-379 was up-regulated in mouse models of hyperglucocorticoidemia and obesity as well as human liver in a GC/GR-dependent manner. Hepatocyte-specific silencing of miR-379 substantially reduced circulating very-low-density lipoprotein (VLDL)-associated triglyceride (TG) levels in healthy mice and normalized aberrant lipid profiles in metabolically challenged animals, mediated through miR-379 effects on key receptors in hepatic TG re-uptake. As hepatic miR-379 levels were also correlated with GC and TG levels in human obese patients, the identification of a GC/GR-controlled miRNA cluster not only defines a novel layer of hormone-dependent metabolic control but also paves the way to alternative miRNA-based therapeutic approaches in metabolic dysfunction.
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Endocr. Connect. 4, 1-8 (2015)
Inactivating germline mutations of the CDKN1B gene, encoding for the nuclear cyclin-dependent kinase inhibitor p27kip1 protein, have been reported in patients with multiple endocrine neoplasia type 4 (MEN4), a MEN1-like phenotype without MEN1 mutations. The aim of this study was to in vitro characterize the germline CDKN1B mutation c.374_375delCT (S125X) we detected in a patient with MEN4. The proband was affected by multiglandular primary hyperparathyroidism and gastro-entero-pancreatic tumors. We carried out subcellular localization experiments transfecting into eukaryotic HeLa and GH3 cell lines plasmid vectors expressing the CDKN1B wild type (wt) or mutant cDNA. Western blot studies showed that fusion proteins were expressed at equal levels. The mutated protein was shorter compared to the wt protein and lacked the highly conserved C-terminal domain, which includes the bipartite nuclear localization signal at amino acids 152/153 and 166/168. In HeLa and GH3 cells wt p27 localized in the nucleus whereas the p27_S125X protein was retained in the cytoplasm predicting the loss of tumor suppressive function. The proband's tumoral parathyroid tissue did not show allelic loss, since wt and mutant alleles were both present by sequencing the somatic DNA. Immunohistochemistry showed a complete loss of nuclear p27 expression in the parathyroid adenoma removed by the patient at the second surgery. In conclusion, our study confirms the pathogenic role of the c.374_375delCT CDKN1B germline mutation in a patient with MEN4.
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