Aims/hypothesis: In obesity oxidative stress is thought to contribute to the development of insulin resistance, non-alcoholic fatty liver disease and the progression to non-alcoholic steatohepatitis. Our aim was to examine the precise contributions of hepatocyte-derived H2O2 to liver pathophysiology.
Methods: Glutathione peroxidase (GPX) 1 is an antioxidant enzyme that is abundant in the liver and converts H2O2 to water. We generated Gpx1 lox/lox mice to conditionally delete Gpx1 in hepatocytes (Alb-Cre;Gpx1 lox/lox) and characterised mice fed chow, high-fat or choline-deficient amino-acid-defined (CDAA) diets.
Results: Chow-fed Alb-Cre;Gpx1 lox/lox mice did not exhibit any alterations in body composition or energy expenditure, but had improved insulin sensitivity and reduced fasting blood glucose. This was accompanied by decreased gluconeogenic and increased glycolytic gene expression as well as increased hepatic glycogen. Hepatic insulin receptor Y1163/Y1163 phosphorylation and Akt Ser-473 phosphorylation were increased in fasted chow-fed Alb-Cre;Gpx1 lox/lox mice, associated with increased H2O2 production and insulin signalling in isolated hepatocytes. The enhanced insulin signalling was accompanied by the increased oxidation of hepatic protein tyrosine phosphatases previously implicated in the attenuation of insulin signalling. High-fat-fed Alb-Cre;Gpx1 lox/lox mice did not exhibit alterations in weight gain or hepatosteatosis, but exhibited decreased hepatic inflammation, decreased gluconeogenic gene expression and increased insulin signalling in the liver. Alb-Cre;Gpx1 lox/lox mice fed a CDAA diet that promotes non-alcoholic steatohepatitis exhibited decreased hepatic lymphocytic infiltrates, inflammation and liver fibrosis.
Conclusions/interpretation: Increased hepatocyte-derived H2O2 enhances hepatic insulin signalling, improves glucose control and protects mice from the development of non-alcoholic steatohepatitis.
Keywords: Fibrosis; Glutathione peroxidase-1; Hepatocyte; Inflammation; Insulin resistance; Non-alcoholic fatty liver disease; Non-alcoholic steatohepatitis; Protein tyrosine phosphatase; Reactive oxygen species; Type 2 diabetes.