Acute exercise reduces hepatic glucose production through inhibition of the Foxo1/HNF-4α pathway in insulin resistant mice

摘要

Protein hepatocyte nuclear factor 4α (HNF-4α) is atypically activated in the liver of diabetic rodents and contributes to hepatic glucose production. HNF-4α and Foxo1 can physically interact with each other and represent an important signal transduction pathway that regulates the synthesis of glucose in the liver. Foxo1 and HNF-4α interact with their own binding sites in the phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) promoters, and this binding is required for their effects on those promoters. However, the effect of physical activity on the HNF-4α/Foxo1 pathway is currently unknown. Here, we investigate the protein levels of HNF-4α and the HNF-4α/Foxo1 pathway in the liver of leptin-deficient (ob/ob) and diet-induced obese Swiss (DIO) mice after acute exercise. The ob/ob and DIO mice swam for four 30 min periods, with 5 min rest intervals for a total swimming time of 2 h. Eight hours after the acute exercise protocol, the mice were submitted to an insulin tolerance test (ITT) and determination of biochemical and molecular parameters. Acute exercise improved insulin signalling, increasing insulin-stimulated Akt and Foxo1 phosphorylation and decreasing HNF-4α protein levels in the liver of DIO and ob/ob mice under fasting conditions. These phenomena were accompanied by a reduction in the expression of gluconeogenesis genes, such as PEPCK and G6Pase. Importantly, the PI3K inhibitor reversed the acute effect of exercise on fasting hyperglycaemia, confirming the involvement of the PI3K pathway. The present study shows that exercise acutely improves the action of insulin in the liver of animal models of obesity and diabetes, resulting in increased phosphorylation and nuclear exclusion of Foxo1, and a reduction in the Foxo1/HNF-4α pathway. Since nuclear localization and the association of these proteins is involved in the activation of PEPCK and G6Pase, we believe that the regulation of Foxo1 and HNF-4α activities are important mechanisms involved in exercise-induced improvement of glucose homeostasis in insulin resistant states.