Insulin promotes the expression of the gluconeogenic rate-limiting enzymes phosphoenolpyruvate carboxykinase (Pepck) and glucose 6-phosphatase (G6pase) through PI3k/Akt/mTOR signaling pathway in goose hepatocytes

ABSTRACT

To identify what makes insulin have an activating or inhibiting role in gluconeogenesis in goose hepatocytes and whether insulin regulates PEPCK and G6Pase through the PI3k/Akt/mTOR pathway or not, goose primary hepatocytes were isolated and cultured in vitro. After 12h cultured in serum-free medium, hepatocytes were incubated for 24 h in the medium with no addition (control) or with the addition of 50, 100, and 150 nM of insulin, 1000 nM NVP-BEZ235, or co-addition of 150nM insulin and 1000nM NVP-BEZ235. Glucose concentration and PEPCK and G6Pase expression were determined. The results showed that PEPCK and G6Pase mRNA levels and activities were up regulated in the 50, 100, and 150nM insulin treatments, while glucose concentration was not significantly altered (p > 0.05). Compared with the activation role of 150nM insulin alone, the co-treatment with1000nM NVP-BEZ235 and 150nM insulin significantly down regulated PEPCK mRNA level and G6Pase protein activity (p < 0.05). However, there is a different result on mRNA level of G6Pase. In conclusion, G6Pase and PEPCK are up regulated by insulin through PI3k/Akt/mTOR pathway in goose hepatocytes. However, G6Pase mRNA and protein levels may be regulated by insulin through different signaling pathways.(AU)