Adipose deficiency of Nrf2 in ob/ob mice results in severe metabolic syndrome.
ABSTRACT: Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor that functions as a master regulator of the cellular adaptive response to oxidative stress. Our previous studies showed that Nrf2 plays a critical role in adipogenesis by regulating expression of CCAAT/enhancer-binding protein ? and peroxisome proliferator-activated receptor ?. To determine the role of Nrf2 in the development of obesity and associated metabolic disorders, the incidence of metabolic syndrome was assessed in whole-body or adipocyte-specific Nrf2-knockout mice on a leptin-deficient ob/ob background, a model with an extremely positive energy balance. On the ob/ob background, ablation of Nrf2, globally or specifically in adipocytes, led to reduced white adipose tissue (WAT) mass, but resulted in an even more severe metabolic syndrome with aggravated insulin resistance, hyperglycemia, and hypertriglyceridemia. Compared with wild-type mice, WAT of ob/ob mice expressed substantially higher levels of many genes related to antioxidant response, inflammation, adipogenesis, lipogenesis, glucose uptake, and lipid transport. Absence of Nrf2 in WAT resulted in reduced expression of most of these factors at mRNA or protein levels. Our findings support a novel role for Nrf2 in regulating adipose development and function, by which Nrf2 controls the capacity of WAT expansion and insulin sensitivity and maintains glucose and lipid homeostasis.
Project description:Intermittent fasting (IF) is an effective dietary intervention to counteract obesity-associated metabolic abnormalities. Previously, we and others have highlighted white adipose tissue (WAT) browning as the main underlying mechanism of IF-mediated metabolic benefits. However, whether IF retains its efficacy in different models, such as genetically obese/diabetic animals, is unknown. Here, leptin-deficient ob/ob mice were subjected to 16 weeks of isocaloric IF, and comprehensive metabolic phenotyping was conducted to assess the metabolic effects of IF. Unlike our previous study, isocaloric IF-subjected ob/ob animals failed to exhibit reduced body weight gain, lower fat mass, or decreased liver lipid accumulation. Moreover, isocaloric IF did not result in increased thermogenesis nor induce WAT browning in ob/ob mice. These findings indicate that isocaloric IF may not be an effective approach for regulating body weight in ob/ob animals, posing the possible limitations of IF to treat obesity. However, despite the lack of improvement in insulin sensitivity, isocaloric IF-subjected ob/ob animals displayed improved glucose tolerance as well as higher postprandial insulin level, with elevated incretin expression, suggesting that isocaloric IF is effective in improving nutrient-stimulated insulin secretion. Together, this study uncovers the insulinotropic effect of isocaloric IF, independent of adipose thermogenesis, which is potentially complementary for the treatment of type 2 diabetes.
Project description:To evaluate whether Nrf2 deficiency impacts insulin resistance and lipid accumulation in liver and white adipose tissue.Lep(ob/ob) mice (OB) with targeted Nrf2 deletion (OB-Nrf2KO) were generated. Pathogenesis of obesity and type 2 diabetes was measured in C57BL/6J, Nrf2KO, OB, and OB-Nrf2KO mice. Hepatic lipid content, lipid clearance, and very low-density lipoprotein (VLDL) secretion were determined between OB and OB-Nrf2KO mice.OB-Nrf2KO mice exhibited decreased white adipose tissue mass and decreased adipogenic and lipogenic gene expression compared with OB mice. Nrf2 deficiency prolonged hyperglycemia in response to glucose challenge, which was paralleled by reduced insulin-stimulated Akt phosphorylation. In OB mice, Nrf2 deficiency decreased hepatic lipid accumulation, decreased peroxisome proliferator-activated receptor ? expression and nicotinamide adenine dinucleotide phosphate (NADPH) content, and enhanced VLDL secretion. However, this observation was opposite in lean mice. Additionally, OB-Nrf2KO mice exhibited increased plasma triglyceride content, decreased HDL-cholesterol content, and enhanced apolipoprotein B expression, suggesting Nrf2 deficiency caused dyslipidemia in these mice.Nrf2 deficiency in Lep(ob/ob) mice reduced white adipose tissue mass and prevented hepatic lipid accumulation but induced insulin resistance and dyslipidemia. This study indicates a dual role of Nrf2 during metabolic dysregulation-increasing lipid accumulation in liver and white adipose tissue but preventing lipid accumulation in obese mice.
Project description:ob/ob mice is an obese mice. CIDE family proteins including Cidea, Cideb and Cidec play important role in lipid metabolism. Cidea is mainly expressed in the brown adipose tissue (BAT). Cidec is mainly expressed in the BAT and white adipose tissue (WAT). We generated ob/ob/Cidea-/-/Cidec-/- mice to investigate the phenotype of fat tissue. ob/ob/Cidea-/-/Cidec-/- mice are lean when compared with ob/ob mice. The tissue weight and TAG content of BAT and WAT was extreamly decreased in ob/ob/Cidea-/-/Cidec-/- mice compared with that in ob/ob mice. We next extract the total RNA from the BAT and WAT of ob/ob and ob/ob/Cidea-/-/Cidec-/- mice, to perform microarray analysis using Mouse Gene 1.0 ST array system, Affymetrix. We then analysised the up-regulated and down regulated pathways. Overall design: We extract the RNA of BAT and WAT from 4 month old mice and hybridization on Affymetrix microarrays. We then analysis the data.
Project description:Glycerol is an important metabolite for the control of lipid accumulation in white adipose tissue (WAT) and liver. We aimed to investigate whether exogenous administration of leptin improves features of non-alcoholic fatty liver disease (NAFLD) in leptin-deficient ob/ob mice via the regulation of AQP3 and AQP7 (glycerol channels mediating glycerol efflux in adipocytes) and AQP9 (aquaglyceroporin facilitating glycerol influx in hepatocytes). Twelve-week-old male wild type and ob/ob mice were divided in three groups as follows: control, leptin-treated (1 mg/kg/d) and pair-fed. Leptin deficiency was associated with obesity and NAFLD exhibiting an AQP3 and AQP7 increase in WAT, without changes in hepatic AQP9. Adipose Aqp3 and hepatic Aqp9 transcripts positively correlated with markers of adiposity and hepatic steatosis. Chronic leptin administration (4-weeks) was associated with improved body weight, whole-body adiposity, and hepatosteatosis of ob/ob mice and to a down-regulation of AQP3, AQP7 in WAT and an up-regulation of hepatic AQP9. Acute leptin stimulation in vitro (4-h) induced the mobilization of aquaglyceroporins towards lipid droplets (AQP3) and the plasma membrane (AQP7) in murine adipocytes. Our results show that leptin restores the coordinated regulation of fat-specific AQP7 and liver-specific AQP9, a step which might prevent lipid overaccumulation in WAT and liver in obesity.
Project description:To identify new genes that are important in fat metabolism, we utilized the Lexicon-Genentech knockout database of genes encoding transmembrane and secreted factors and whole murine genome transcriptional profiling data that we generated for 3T3-L1 in vitro adipogenesis. Cross-referencing null models evidencing metabolic phenotypes with genes induced in adipogenesis led to identification of a new gene, which we named RIFL (refeeding induced fat and liver). RIFL-null mice have serum triglyceride levels approximately one-third of wild type. RIFL transcript is induced >100-fold during 3T3-L1 adipogenesis and is also increased markedly during adipogenesis of murine and human primary preadipocytes. siRNA-mediated knockdown of RIFL during 3T3-L1 adipogenesis results in an ~35% decrease in adipocyte triglyceride content. Murine RIFL transcript is highly enriched in white and brown adipose tissue and liver. Fractionation of WAT reveals that RIFL transcript is exclusive to adipocytes with a lack of expression in stromal-vascular cells. Nutritional and hormonal studies are consistent with a prolipogenic function for RIFL. There is evidence of an approximately eightfold increase in RIFL transcript level in WAT in ob/ob mice compared with wild-type mice. RIFL transcript level in WAT and liver is increased ~80- and 12-fold, respectively, following refeeding of fasted mice. Treatment of 3T3-L1 adipocytes with insulin increases RIFL transcript ?35-fold, whereas agents that stimulate lipolysis downregulate RIFL. Interestingly, the 198-amino acid RIFL protein is predicted to be secreted and shows ~30% overall conservation with the NH(2)-terminal half of angiopoietin-like 3, a liver-secreted protein that impacts lipid metabolism. In summary, our data suggest that RIFL is an important new regulator of lipid metabolism.
Project description:Leptin-deficient ob/ob mice are overweight, develop insulin resistance, and serve as a model for type 2 diabetes (T2D). Studies suggest that inflammatory pathways are linked to the development of insulin resistance and T2D both in animals and humans. We asked whether the induction of regulatory T cells (Tregs) could alleviate the pathological and metabolic abnormalities in ob/ob mice. We induced TGF-beta-dependent CD4(+) latency-associated peptide (LAP)-positive Tregs by oral administration of anti-CD3 antibody plus beta-glucosylceramide. We found a decrease in pancreatic islet cell hyperplasia, fat accumulation in the liver, and inflammation in adipose tissue, accompanied by lower blood glucose and liver enzymes. In addition, treated animals had decreased CD11b(+)F4/80(+) macrophages and TNF-alpha in adipose tissue. Adoptive transfer of orally induced CD4(+)LAP(+) Tregs ameliorated metabolic and cytokine abnormalities. Our results demonstrate the importance of inflammation in T2D and identify a unique immunological approach for treatment of T2D by the induction of Tregs.
Project description:Obesity is closely associated with various metabolic disorders. However, little is known about abnormalities in the metabolic change of obese adipose tissue. Here we use static metabolic analysis and <i>in vivo</i> metabolic turnover analysis to assess metabolic dynamics in obese mice. The static metabolic analyses showed that glutamate and constitutive metabolites of the TCA cycle were increased in the white adipose tissue (WAT) of ob/ob and diet-induced obesity mice but not in the liver or skeletal muscle of these obese mice. Moreover, <i>in vivo</i> metabolic turnover analyses demonstrated that these glucose-derived metabolites were dynamically and specifically produced in obese WAT compared with lean WAT. Glutamate rise in obese WAT was associated with down-regulation of glutamate aspartate transporter (GLAST), a major glutamate transporter for adipocytes, and low uptake of glutamate into adipose tissue. In adipocytes, glutamate treatment reduced adiponectin secretion and insulin-mediated glucose uptake and phosphorylation of Akt. These data suggest that a high intra-adipocyte glutamate level potentially relates to adipocyte dysfunction in obesity. This study provides novel insights into metabolic dysfunction in obesity through comprehensive application of <i>in vivo</i> metabolic turnover analysis in two obese animal models.
Project description:The risk of obesity (OB) in adulthood is strongly influenced by maternal body composition. Here we examined the hypothesis that maternal OB influences white adipose tissue (WAT) transcriptome and increases propensity for adipogenesis in the offspring, prior to the development of OB, using an established model of long-term metabolic programming. Employing an overfeeding-based rat model, in which exposure to OB is limited to preconception and gestation alone, we conducted global transcriptomic profiling in WAT, and gene/protein expression analysis of lipogenic and adipogenic pathways and examined adipogenic differentiation of WAT stromal-vascular cells ex vivo. Using reduced representation bisulfite sequencing we also evaluated genome-scale changes in DNA methylation in offspring WAT. Maternal OB led to extensive changes in expression of genes (± 1.8-fold, P ? .05), revealing a distinct up-regulation of lipogenic pathways in WAT. mRNA expression of a battery of sterol regulatory element-binding protein-1-regulated genes was increased in OB-dam offspring, which were confirmed by immunoblotting. In conjunction with lipogenic gene expression, OB-dam offspring showed increased glucose transporter-4 mRNA/protein expression and greater AKT phosphorylation following acute insulin challenge, suggesting sensitization of insulin signaling in WAT. Offspring of OB dams also exhibited increased in vivo expression of adipogenic regulators (peroxisome proliferator-activated receptor-?, CCAAT enhancer binding protein ? [C/EBP-?] and C/EBP-?), associated with greater ex vivo differentiation of WAT stromal-vascular cells. These transcriptomic changes were associated with alterations in DNA methylation of CpG sites and CGI shores, proximal to developmentally important genes, including key pro-adipogenic factors (Zfp423 and C/EBP-?). Our findings strongly suggest that the maternal OB in utero alters adipocyte commitment and differentiation via epigenetic mechanisms.
Project description:Obesity and its metabolic complications are associated with increased expression/activity of stearoyl-CoA desaturase-1 (SCD1), a major regulator of lipid metabolism. Reduction or ablation of this enzyme is associated with an improved metabolic profile and has gained attention as a target for pharmaceutical development. Sterculic oil (SO) is a known inhibitor of SCD1 and may provide a natural approach for treating obesity and/or insulin resistance. The purpose of this study was to evaluate the effects of SO consumption in leptin-deficient ob/ob mice, a model of obesity and insulin resistance. Five-week-old male mice received either an AIN-93G (control) or an AIN-93G diet containing 0.5% SO. After 9 weeks, SO supplementation did not alter food intake or body weight; however, the desaturase indices, a proxy of SCD1 activity, were reduced in liver and adipose tissue of SO-supplemented animals. This reduction was associated with improved glucose and insulin tolerance and attenuated hepatic inflammation in obese ob/ob mice, while no appreciable changes were observed in lean control mice receiving SO. Future studies are needed to better understand the mechanism(s) by which SO is functioning to improve glucose metabolism and to further explore the nutraceutical potential and health implications of SO supplementation.
Project description:Females are, in general, more insulin sensitive than males. To investigate whether this is a direct effect of sex-steroids (SS) in white adipose tissue (WAT), we developed a male mouse model overexpressing the aromatase enzyme, converting testosterone (T) to estradiol (E2), specifically in WAT (Ap2-arom mice). Adipose tissue E2 levels were increased while circulating SS levels were unaffected in male Ap2-arom mice. Importantly, male Ap2-arom mice were more insulin sensitive compared with WT mice and exhibited increased serum adiponectin levels and upregulated expression of Glut4 and Irs1 in WAT. The expression of markers of macrophages and immune cell infiltration was markedly decreased in WAT of male Ap2-arom mice. The adipogenesis was enhanced in male Ap2-arom mice, supported by elevated Pparg expression in WAT and enhanced differentiation of preadipocyte into mature adipocytes. In summary, increased adipose tissue aromatase activity reduces adipose tissue inflammation and improves insulin sensitivity in male mice. We propose that estrogen increases insulin sensitivity via a local effect in WAT on adiponectin expression, adipose tissue inflammation, and adipogenesis.