Project description:Obesity and insulin resistance are associated with oxidative stress, which may be implicated in their progression. The kinase JNK1 emerged as a promising drug target for the treatment of obesity and type-2 diabetes. However, JNK1 is a key mediator of the oxidative stress response, promoting either cell dead or survival depending on magnitude and context of its activation. Furthermore, JNK inactivation shortens lifespan in drosophila and c. elegans. To learn on the safety and efficacy of long-term JNK inhibition in vertebrates, we investigated mice lacking JNK1 (JNK1-/-) exposed over a long period to an obesogenic high-fat diet (HFD). JNK1-/- mice chronically fed an HFD developed more skin oxidative damage because of reduced catalase expression, but also showed sustained protection from obesity, adipose tissue inflammation, steatosis, and insulin resistance, paralleled by decreased oxidative damage in fat and liver. We conclude that JNK1 is a relatively safe drug target for obesity-related diseases. RNA was collected from liver, skin and epididymal fat tissues from JNK1 KO mice and WT mice fed in high fat diet. Each condition was run in quadruplicate
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:Obesity and insulin resistance are associated with oxidative stress, which may be implicated in their progression. The kinase JNK1 emerged as a promising drug target for the treatment of obesity and type-2 diabetes. However, JNK1 is a key mediator of the oxidative stress response, promoting either cell dead or survival depending on magnitude and context of its activation. Furthermore, JNK inactivation shortens lifespan in drosophila and c. elegans. To learn on the safety and efficacy of long-term JNK inhibition in vertebrates, we investigated mice lacking JNK1 (JNK1-/-) exposed over a long period to an obesogenic high-fat diet (HFD). JNK1-/- mice chronically fed an HFD developed more skin oxidative damage because of reduced catalase expression, but also showed sustained protection from obesity, adipose tissue inflammation, steatosis, and insulin resistance, paralleled by decreased oxidative damage in fat and liver. We conclude that JNK1 is a relatively safe drug target for obesity-related diseases.
Project description:Nutrigenomics analysis was used to investigate the molecular responses to dietary Cu deficiency independently and in combination with 30% (w/w) sucrose in a mature rat model of NAFLD. Low Cu significantly decreased hepatic and serum Cu, and induced NAFLD-like histopathology, mild steatosis, up-regulated transcripts in inflammation and hepatic stellate cell activation, and significantly increased oxidative stress. Rats fed low Cu together with 30% sucrose also developed insulin resistance, increased ATP citrate lyase and FASN expression, and greater oxidative stress. High sucrose with adequate Cu also promoted inflammation and fibrosis, but not steatosis. This study indicates that low dietary Cu and sucrose consumption are singular and synergistic dietary factors in promotion of NAFLD and NASH that act independently of obesity or severe steatosis, likely by promoting oxidative stress and activation of inflammation and fibrosis.
Project description:Over 40 % of microRNAs are located in introns of coding genes, and many intronic microRNAs are co-regulated with their host genes. In such cases of co-regulation, the products of host genes and their intronic microRNAs can cooperate to coordinately regulate biologically important pathways. Therefore, 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 that expression of both Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) and its intronic microRNA, miR-676, was strongly increased in liver of obese mouse models. Moreover, hepatic EDA expression is increased in obese human subjects, reduced upon weight loss, and its hepatic expression correlates with systemic insulin resistance. Eda expression in murine liver is controlled via PPARg 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:We demonstrate that the ketogenic diet a low carbohydrate diet can induce fibrosis and NASH regardless of body weight loss compared to high-fat diet (HFD) fed mice. KD-fed mice develop severe hepatic injury, inflammation, and steatosis. In addition, KD increases IL-6-JNK signaling and aggravates diet induced-glucose intolerance and hepatic insulin resistance compared to HFD. Notably, pharmacological inhibition of IL-6 and JNK reverses KD‐induced glucose intolerance and restores insulin sensitivity.
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:Nutrigenomics analysis was used to investigate the molecular responses to dietary Cu deficiency independently and in combination with 30% (w/w) sucrose in a mature rat model of NAFLD. Low Cu significantly decreased hepatic and serum Cu, and induced NAFLD-like histopathology, mild steatosis, up-regulated transcripts in inflammation and hepatic stellate cell activation, and significantly increased oxidative stress. Rats fed low Cu together with 30% sucrose also developed insulin resistance, increased ATP citrate lyase and FASN expression, and greater oxidative stress. High sucrose with adequate Cu also promoted inflammation and fibrosis, but not steatosis. This study indicates that low dietary Cu and sucrose consumption are singular and synergistic dietary factors in promotion of NAFLD and NASH that act independently of obesity or severe steatosis, likely by promoting oxidative stress and activation of inflammation and fibrosis. Mature (6 months old) male Wistar Rats that had been allowed ad libitum access to Mazuri rodent pellets were used in the study. Twenty-four rats were divided into four groups and fed for 12 weeks with diets based on the Purified AIN76A formulation, modified for target sucrose and Cu content (Custom Animal Diets, Bangor, NJ). Sucrose and copper content in diets were as follows: ‘A’ CuD/30%- Cu deficient (<0.3 mg Cu/kg)/30% sucrose, ‘B’ CuA/30%- Cu adequate (125 mg/kg)/30% sucrose, ‘C’ CuD/10%- <0.3 mg/kg Cu/10% sucrose, and ‘D’ CuA (125 mg/kg Cu)/10% sucrose (control). Starch and dextrin were used to equalize carbohydrates.
Project description:Mice overexpressing reverse tetracycline-transactivator (rtTA) exhibited all four sequelae of metabolic syndrome (visceral obesity insulin resistance, dyslipidemia, and hypertension), a pro-inflammatory state and marked hepatic steatosis. Gene expression profiling of the adipose tissue, muscle and liver revealed changes in gene expression of key factors involved in lipid metabolism, insulin resistance, and inflammation.
Project description:Obesity is tightly linked to hepatic steatosis and insulin resistance. One feature of this association is the paradox of selective insulin resistance: insulin fails to suppress hepatic gluconeogenesis but activates lipid synthesis in the liver. How lipid accumulation interferes selectively with some branches of hepatic insulin signaling is not well understood. Here we provide a resource, based on unbiased approaches and established in a simple cell culture system, to enable investigations of the phenomenon of selective insulin resistance. We analyzed the phosphoproteome of insulin-treated human hepatoma cells and identified sites in which palmitate selectively impairs insulin signaling. As an example, we show that palmitate interferes with insulin signaling to FoxO1, a key transcription factor regulating gluconeogenesis, and identify a possible mechanism. This model system, together with our comprehensive characterization of the proteome, phosphoproteome, and lipidome changes in response to palmitate treatment, provides a novel and useful resource for unraveling the mechanisms underlying selective insulin resistance.