Regulation of brown adipose tissue recruitment, metabolism and thermogenic function by peroxisome proliferator-activated receptor γ.
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ABSTRACT:
SUBMITTER: Bolsoni-Lopes A
PROVIDER: S-EPMC4843924 | biostudies-other | 2015 Oct-Dec
REPOSITORIES: biostudies-other
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Project description:Objective- Perivascular adipose tissue (PVAT) contributes to vascular homeostasis by producing paracrine factors. Previously, we reported that selective deletion of PPAR? (peroxisome proliferator-activated receptor ?) in vascular smooth muscle cells resulted in concurrent loss of PVAT and enhanced atherosclerosis in mice. To address the causal relationship between loss of PVAT and atherosclerosis, we used BA-PPAR?-KO (brown adipocyte-specific PPAR? knockout) mice. Approach and Results- Deletion of PPAR? in brown adipocytes did not affect PPAR? in white adipocytes or vascular smooth muscle cells or PPAR? and PPAR? expression in brown adipocytes. However, development of PVAT and interscapular brown adipose tissue was remarkably impaired, associated with reduced expression of genes encoding lipogenic enzymes in the BA-PPAR?-KO mice. Thermogenesis in brown adipose tissue was significantly impaired with reduced expression of thermogenesis genes in brown adipose tissue and compensatory increase in subcutaneous and gonadal white adipose tissues. Remarkably, basal expression of inflammatory genes and macrophage infiltration in PVAT and brown adipose tissue were significantly increased in the BA-PPAR?-KO mice. BA-PPAR?-KO mice were crossbred with ApoE KO (apolipoprotein E knockout) mice to investigate the development of atherosclerosis. Flow cytometry analysis confirmed increased systemic and PVAT inflammation. Consequently, atherosclerotic lesions were significantly increased in mice with impaired PVAT development, thus indicating that the lack of normal PVAT is sufficient to drive increased atherosclerosis. Conclusions- PPAR? is required for functional PVAT development. PPAR? deficiency in PVAT, while still expressed in vascular smooth muscle cell, enhances atherosclerosis and results in vascular and systemic inflammation, providing new insights on the specific roles of PVAT in atherosclerosis and cardiovascular disease at large.
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Project description:Peroxisome proliferator-activated receptor gamma agonists have been proposed as breast cancer preventives. Individuals who carry a mutated copy of BRCA1, DNA repair-associated gene, are at increased risk for development of breast cancer. Published data in the field suggest there could be interactions between peroxisome proliferator-activated receptor gamma and BRCA1 that could influence the activity of peroxisome proliferator-activated receptor gamma agonists for prevention. This review explores these possible interactions between peroxisome proliferator-activated receptor gamma, peroxisome proliferator-activated receptor gamma agonists and BRCA1 and discusses feasible experimental directions to provide more definitive information on the potential connections.
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Project description:Peroxisome proliferator‑activated receptors (PPARs) have been suggested as the master regulators of adipose tissue formation, however their role in regulating brown fat functionality has not been resolved. To address this question, we generated inducible brown fat specific mouse models for PPARa, b/d and g, respectively. Interestingly, we found that both PPARa and b/d are dispensable for brown fat function. In contrast, we could show that ablation of PPARg in vitro as well in vivo led to a reduced thermogenic capacity accompanied by a loss of inducibility by β-adrenergic signaling, as well as a shift from oxidative fatty acid metabolism to glucose utilization. We identified glycerol kinase (Gyk) as a partial mediator of PPARgfunction, and could show that Gyk expression correlates with brown fat thermogenic capacity in human brown fat biopsies. Thus, Gyk might constitute the link between PPARg mediated regulation of brown fat function and activation by β-adrenergic signaling.
2018-01-16 | GSE103474 | GEO
Project description:PURPOSE: Obesity is a risk factor for asthma and type II diabetes. Peroxisome proliferator- activated receptor (PPAR)-? has been suggested to regulate inflammatory responses in diabetes and asthma. We investigated whether PPAR-?, PPAR-?, adiponectin receptors (AdipoR1, AdipoR2), leptin, and tumor necrosis factor (TNF)-? are expressed in rat lung tissues and whether the expression differs between obese Otsuka Long-Evans Tokushima Fatty (OLETF) and lean Long Evans Tokushima Otsuka (LETO) rats. MATERIALS AND METHODS: Obese and lean rats were given with a high fat diet or a 30% restricted diet for 32 weeks, and their blood glucose levels and weights were monitored. After 32 weeks, mRNA levels of PPAR-?, PPAR-?, AdipoR1, AdipoR2, leptin, and TNF-? in lung tissues were measured using real time PCR. RESULTS: PPAR-?, PPAR-?, AdipoR1, AdipoR2, leptin, and TNF-? were expressed in both obese and lean rat lung tissues. Increased serum glucose levels on intraperitoneal glucose tolerance testing and a higher weight gain at 32 weeks were observed in OLETF control rats compared to OLETF diet restricted rats. PPAR-? expression was markedly elevated in obese control and diet restricted rats compared to lean rats, although PPAR-? expression in obese rats was not affected by diet restriction. Leptin was highly expressed in OLETF rats compared to LETO rats. TNF-? expression was enhanced in OLETF control rats compared LETO diet restricted rats, and decreased by diet restriction. PPAR-?, AdipoR1, and AdipoR2 expression were not significantly different between obese and lean rats. CONCLUSION: PPAR-? was highly expressed in the lung tissues of obese rats and may be a novel treatment target for regulating lung inflammation associated with obesity.
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Project description:BackgroundThe peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors and members of the nuclear receptor superfamily. The PPAR family consists of three members: PPARalpha, PPARgamma, and PPARdelta. PPARdelta controls the transcription of genes involved in multiple physiological pathways, including cellular differentiation, lipid metabolism and energy homeostasis. The receptor is expressed almost ubiquitously, with high expression in liver and skeletal muscle. Although the physiological ligands of PPARdelta remain undefined, a number of high affinity synthetic ligands have been developed for the receptor as a therapeutic target for type 2 diabetes mellitus, dyslipidemia and the metabolic syndrome.MethodsIn this study, the metabolic role of PPARdelta activation has been investigated in liver, skeletal muscle, blood serum and white adipose tissue from ob/ob mice using a high affinity synthetic ligand and contrasted with PPARgamma activation. To maximize the analytical coverage of the metabolome, (1)H-nuclear magnetic resonance ((1)H-NMR) spectroscopy, gas chromatography-mass spectrometry (GC-MS) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) were used to examine metabolites from tissue extracts.ResultsAnalysis by multivariate statistics demonstrated that PPARdelta activation profoundly affected glycolysis, gluconeogenesis, the TCA cycle and linoleic acid and alpha-linolenic acid essential fatty acid pathways.ConclusionsAlthough activation of both PPARdelta and PPARgamma lead to increased insulin sensitivity and glucose tolerance, PPARdelta activation was functionally distinct from PPARgamma activation, and was characterized by increased hepatic and peripheral fatty acid oxidative metabolism, demonstrating the distinctive catabolic role of this receptor compared with PPARgamma.
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Project description:ObjectiveForkhead box O (FoxO) transcription factors represent evolutionarily conserved targets of insulin signaling, regulating metabolism and cellular differentiation in response to changes in nutrient availability. Although the FoxO1 isoform is known to play a key role in adipogenesis, its physiological role in differentiated adipose tissue remains unclear.Research design and methodsIn this study, we analyzed the phenotype of FoxO1 haploinsufficient mice to investigate the role of FoxO1 in high-fat diet-induced obesity and adipose tissue metabolism.ResultsWe showed that reduced FoxO1 expression protects mice against obesity-related insulin resistance with marked improvement not only in hepatic insulin sensitivity but also in skeletal muscle insulin action. FoxO1 haploinsufficiency also resulted in increased peroxisome proliferator-activated receptor (PPAR)gamma gene expression in adipose tissue, with enhanced expression of PPARgamma target genes known to influence metabolism. Moreover, treatment of mice with the PPARgamma agonist rosiglitazone caused a greater improvement in in vivo insulin sensitivity in FoxO1 haploinsufficient animals, including reductions in circulating proinflammatory cytokines.ConclusionsThese findings indicate that FoxO1 proteins negatively regulate insulin action and that their effect may be explained, at least in part, by inhibition of PPARgamma function.
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Project description:ObjectiveNuclear receptor Peroxisome Proliferator-Activated Receptor γ (PPARγ) is a promising target for the treatment of type 2 diabetes. The antidiabetic drug thiazolidinediones (TZDs) are potent insulin sensitizers as full agonists of PPARγ, but cause unwanted side effects. Recent discoveries have shown that TZDs improve insulin sensitivity by blocking PPARγ phosphorylation at S273, which decouples the full agonism-associated side effects. PPARγ ligands that act through the blockage of PPARγ phosphorylation but lack the full agonist activity would be expected to improve insulin sensitivity without TZD-associated side effects, however, chemicals that carry such traits and bind to PPARγ with high-affinity are lacking. Moreover, TZDs are known to promote white-to-brown adipocyte conversion and energy expenditure and appear to require their full agonism on PPARγ for this activity. It is unknown whether a partial or non-TZD agonist of PPARγ is capable of promoting browning effect. In this study, we developed a novel non-TZD partial agonist of PPARγ and investigated its function on insulin sensitivity and white-to-brown conversion and energy expenditure in diet-induced obese mice.MethodsA novel indole-based chemical WO95E was designed via medicinal chemistry and tested for PPARγ binding and activity and for the effect on PPARγ phosphorylation. Diet-induced obese mice were administered with WO95E for 4 weeks. Insulin sensitivity, glucose tolerance, body weight, fat tissue weight, adipocyte size, morphology, energy expenditure, and expression levels of genes involved in PPARγ activity, thermogenesis/browning, and TZD-related side effects were evaluated.ResultsWO95E binds to PPARγ with high affinity and acts as a PPARγ partial agonist. WO95E inhibits PPARγ phosphorylation and regulates PPARγ phosphorylation-dependent genes. WO95E ameliorates insulin resistance and glucose tolerance in mice of diet-induced obesity, with minimal TZD use-associated side effects. We found that WO95E promotes white-to-brown adipocyte conversion and energy expenditure and hence protects against diet-induced obesity. WO95E decreases the size of adipocytes and suppresses adipose tissue inflammation. WO95E also suppresses obesity-associated liver steatosis.ConclusionsWO95E improves insulin sensitivity and glucose homeostasis and promotes browning and energy expenditure by acting as a novel PPARγ phosphorylation inhibitor/partial agonist. Our findings suggest the potential of this compound or its derivative for the therapeutic treatment of insulin resistance and obesity.
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