Project description:Purpose: To determine how STAT1 activity in white adipocytes affects insulin sensitivity. Methods: Adipocyte specific (ADIPOQ-Cre) STAT1 fl/fl mice (STAT1 fKO) and littermate controls (STAT1 fl/fl) were placed on 60% HFD for 18 weeks, followed by metabolic phenoptying and tissue harvest for RNA-seq Results: STAT1 expression in WAT inversely correlated with fasting plasma glucose in both obese mice and humans. Metabolomic and gene expression profiling established STAT1 deletion in adipocytes (STAT1 fKO) enhanced mitochondrial function and accelerated TCA cycle flux coupled with subcutaneous WAT hyperplasia. STAT1 fKO reduced WAT inflammation, but insulin resistance persisted in obese mice. Rather, elimination of type I cytokine interferon gamma (IFNg) activity enhanced insulin sensitivity in diet-induced obesity. Conclusions: Our findings reveal a permissive mechanism that bridges WAT inflammation to whole-body insulin sensitivity.
Project description:Insulin resistance is the hallmark of obese and type 2 diabetes patients. Defective insulin sensitivity in the liver results in increased glucsoe production, which is the major cause of hyperglycemia in diabetic patients. Increased lipopolysaccharide (LPS) leakage from the gut of diet-induced obesity causes insulin resisitance; moreover, activation of deacetylase Sirtuin1 restore insulin sensitivity in obesity. However, the mechanism resulting in insulin resistance by LPS remains poorly understood. Here, we show that Ep300 (P300) harboring an intrinsic acetyltransferase activity was rapidly induced in the liver of animals fed a high-fat diet, and the induction of Ep300 is through LPS-stimulated activation of ER stress. Induced Ep300 impairs insulin signaling by acetylating mediators in insulin signaling. Inhibition of P300 acetyltransferase activity improves insulin signaling. Thus, Ep300 acetyltransferase activity is a therapeutic target.
Project description:Cytokines of the IL-1 family are important modulators of obesity-induced inflammation and the development of systemic insulin resistance. Here, we report that IL-37, a newly-described antiinflammatory member of the IL-1 family, affects obesity-induced inflammation and insulin resistance. IL-37 transgenic mice (IL-37tg) did not develop an obese phenotype in response to a high-fat diet (HFD). Unlike WT mice, IL-37tg mice exhibited reduced numbers of adipose tissue macrophages and preserved glucose tolerance and insulin sensitivity after 16 weeks of HFD. A short-term HFD intervention revealed that the IL-37-mediated improvement in glucose tolerance is independent of bodyweight. IL-37tg mice manifested a beneficial metabolic profile with higher circulating levels of the anti-inflammatory adipokine adiponectin. In vitro treatment of differentiating adipocytes with recombinant IL-37 reduced adipogenesis. The beneficial effects of recombinant IL-37 involved activation of AMPK signaling. In humans, steady-state IL-37 adipose tissue mRNA levels were positively correlated with insulin sensitivity, lower adipose tissue levels of leptin and a lower inflammatory status of the adipose tissue. These findings reveal IL-37 as an important anti-inflammatory modulator during obesity-induced inflammation and insulin resistance in both mice and humans and suggest that IL-37 is a potential target for the treatment of obesity-induced insulin resistance and type 2 diabetes. Gene arrays were performed on epidydimal white adipose tissue samples from wild type and human IL37-overexpressing transgenic mice fed a high fat diet for 16 weeks.
Project description:We screened intronic microRNAs dysregulated in liver of obese mouse models to identify previously uncharacterized coding host genes that may contribute to the pathogenesis of obesity-associated insulin resistance and type 2 diabetes mellitus. Our approach identified the expression of Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) was strongly increased in liver of obese mouse models both in rodents and humans.Eda expression in murine liver is controlled via PPARγ activation, increases in circulation and promotes JNK activation and inhibitory serine phosphorylation of IRS1 in skeletal muscle. Consistently, bi-directional modulation of hepatic Eda expression in mouse models affects systemic glucose metabolism with alterations of muscle insulin signaling, revealing a novel role of EDA as an obesity-associated hepatokine, which impairs insulin sensitivity in skeletal muscle.
Project description:Background and Aims: Insulin resistance is a key factor in the pathogenesis of NAFLD. We evaluated the importance of subcutaneous abdominal adipose tissue (SAAT) inflammation and both plasma and SAAT-derived exosomes in regulating insulin sensitivity in people with obesity and NAFLD. Methods: Adipose tissue inflammation (macrophage and T cell content and gene expression of proinflammatory cytokines), liver and whole-body insulin sensitivity (assessed by a hyperinsulinemic-euglycemic clamp and glucose tracer infusion), and 24-hour serial plasma cytokine concentrations were evaluated in three groups stratified by adiposity, insulin sensitivity and intrahepatic triglyceride (IHTG) content: 1) metabolically-healthy lean (LEAN; n=14); 2) metabolically-healthy obese with normal IHTG content (OB-NL; n=28); and 3) metabolically-unhealthy obese with NAFLD (OB-NAFLD; n=28). The effect of plasma and SAAT-derived exosomes on insulin action (insulin-stimulated Akt phosphorylation) in human skeletal muscle myotubes was assessed in a subset of participants. Results: Proinflammatory macrophages, proinflammatory CD4 and CD8 T cell populations, and gene expression of several cytokines in SAAT were greater in the OB-NAFLD than the OB-NL and LEAN groups. However, with the exception of PAI-1, which was greater in the OB-NAFLD than the LEAN and OB-NL groups, 24-hour plasma cytokine concentration areas-under-the-curve (AUC) were not different between groups. The percentage of proinflammatory macrophages and plasma PAI-1 concentration AUC were inversely correlated with both hepatic and whole-body insulin sensitivity. Compared with exosomes from OB-NL participants, plasma and SAAT-derived exosomes obtained from the OB-NAFLD group impaired insulin action in myotubes. Conclusion: These results suggest SAAT-derived exosomes and PAI-1 are involved in the pathogenesis of systemic insulin resistance in people with obesity and NAFLD. ClinicalTrials.gov number: NCT02706262.
Project description:Cytokines of the IL-1 family are important modulators of obesity-induced inflammation and the development of systemic insulin resistance. Here, we report that IL-37, a newly-described antiinflammatory member of the IL-1 family, affects obesity-induced inflammation and insulin resistance. IL-37 transgenic mice (IL-37tg) did not develop an obese phenotype in response to a high-fat diet (HFD). Unlike WT mice, IL-37tg mice exhibited reduced numbers of adipose tissue macrophages and preserved glucose tolerance and insulin sensitivity after 16 weeks of HFD. A short-term HFD intervention revealed that the IL-37-mediated improvement in glucose tolerance is independent of bodyweight. IL-37tg mice manifested a beneficial metabolic profile with higher circulating levels of the anti-inflammatory adipokine adiponectin. In vitro treatment of differentiating adipocytes with recombinant IL-37 reduced adipogenesis. The beneficial effects of recombinant IL-37 involved activation of AMPK signaling. In humans, steady-state IL-37 adipose tissue mRNA levels were positively correlated with insulin sensitivity, lower adipose tissue levels of leptin and a lower inflammatory status of the adipose tissue. These findings reveal IL-37 as an important anti-inflammatory modulator during obesity-induced inflammation and insulin resistance in both mice and humans and suggest that IL-37 is a potential target for the treatment of obesity-induced insulin resistance and type 2 diabetes.
Project description:The aim of this study was to detect and functionally investigate miRNAs linked to insulin sensitivity in human subcutaneous white adipose tissue (scWAT). Subjects were selected based on the insulin-stimulated lipogenesis response of subcutaneous adipocytes. Eleven miRNAs displayed differential expression between OIR and OIS states. Overexpression of miR-143-3p and miR-652-3p increased insulin-stimulated lipogenesis in human in vitro-differentiated adipocytes. MicroRNAs-143-3p and -652-3p are linked to scWAT insulin resistance independently of obesity.
Project description:The BCL-2 family are crucial regulators of the mitochondrial pathway of apoptosis in normal physiology and disease. Besides their role in cell death, BCL-2 proteins have been implicated in the regulation of mitochondrial oxidative phosphorylation and cellular metabolism. However, it remains unclear whether these proteins have a physiological role in glucose homeostasis and metabolism in vivo. Here we report that fat accumulation in the liver increases JNK-dependent BIM expression in hepatocytes. We generated liver-specific BIM knockout (BLKO) mice to determine the consequences of hepatic BIM deficiency in diet-induced obesity. BLKO mice had lower hepatic lipid content, increased insulin signalling and improved global glucose metabolism. Consistent with this, lipogenic and lipid uptake genes were downregulated and lipid oxidation enhanced in obese BLKO mice. Moreover, oxidative stress, oxidation of protein tyrosine phosphatases and activation of PPAR-g/STAT1/CD36 were decreased in livers/hepatocytes from BLKO mice, suggesting a mechanism for their metabolic phenotype. Importantly, adenovirus-mediated knockdown of BIM reduced fat accumulation and improved insulin sensitivity in high fat fed mice. Our data postulate BIM as a novel therapeutic target regulating mitochondrial bioenergetics and liver function in obesity.
Project description:We evaluated the potential importance of adipose tissue (AT) oxygenation on AT biology and insulin sensitivity in people. AT oxygen partial pressure (pO2), branched chain amino acid (BCAA) catabolism and marker of inflammation were determined in three groups stratified by adiposity and insulin sensitivity: 1) metabolically-healthy lean (MHL); 2) metabolically-healthy obese (MHO); and 3) metabolically-unhealthy obese (MUO). AT pO2 progressively declined from the MHL to the MHO to the MUO group, and was positively associated with hepatic and whole-body insulin sensitivity. AT pO2 was positively associated with AT expression of genes involved in BCAA catabolism and negatively associated with plasma BCAA concentrations. Although AT pO2 was negatively associated with AT markers of inflammation, it was not associated with plasma adipokine concentrations. These results support the notion that reduced AT pO2 in people with obesity contributes to insulin resistance by decreasing AT BCAA catabolism and thereby increasing plasma BCAA concentrations.