N-nitrosodimethylamine increased glucose production by promoting hyperglycemia in hepatocyte via AMPK signaling pathway in vivo and in vitro

N-nitrosodimethylamine (NDMA), as a disinfection by-product of drinking water, has been detected in various water. Epidemiological investigations have found that exposure to NDMA can exacerbate the development of diseases related to Insulin resistance. In this study, male C57BL/6 mice were exposed to 0.5 and 12.5 mg/L NDMA by drinking water for 12 weeks. The mice in 12.5 mg/L NDMA group appeared fasting blood glucose elevation, and glucose tolerance and Insulin sensitivity decreased. NDMA exposure enhanced hepatic gluconeogenesis and suppressed glycolysis of mice, but not affecting glycogen synthesis. In addition, NDMA exposure inhibited the phosphorylation of AMPK and FOXO1 as well as GLUT2 protein expression, and increased PGC-1α protein levels. GLUT2 protein decreasing could reduce glucose uptake of hepatocyte and enhance blood glucose concentration. Dephosphorylated FOXO1 might translocate to the nucleus, binding promoters of gluconeogenesis key Enzymes PEPCK and G6Pase to upregulate their expression and promote gluconeogenesis. PGC-1α could also stimulate the expression of PEPCK and G6Pase. Furthermore, human normal liver cells (MIHA) were treated with NDMA for 24 hours. AMPK as a central energy sensor, regulates hepatic glucose production, uptake, and the process of glycolmetabolism. Therefore, AMPK agonist AICAR was used to explore the mechanism of NDMA causing hyperglycemia. AICAR reversed p-FoxO1, PGC-1α, GLUT2, PEPCK and G6Pase proteins expression and improved the glycolysis and glucose uptake capacity in NDMA treated MIHA cells. In conclusion, NDMA in drinking water led to fasting blood glucose enhancing, impairment of glucose tolerance and Insulin sensitivity, increasing hepatic gluconeogenesis via AMPK signaling.

AMPK; N-nitrosodimethylamine; PGC-1α; blood glucose; gluconeogenesis.