Exendin-4 improves glucose metabolism in insulin-resistant cells by upregulating the phosphorylative AMPK

Abstract

Glucagon-like peptide-1 (GLP-1) is a peptide with multiple functions in regulating blood glucose with the mechnism still not throughly understand. AMP-activated protein kinase (AMPK) plays an important role in glucose and energy homeostasis, especially in type 2 diabetes mellitus (T2DM) pathophysiology. This study explores GLP-1 analogue exendin-4 (Ex-4) regulating glucose balance by activating AMPK and regulation gluconeogenesis in insulin-resistant cell model (IR/ HepG2). IR/HepG2 cells were treated with Ex-4, AMPK activator or Ex-4 pretreated with AMPK inhibitor Compound C. The change of cell morphology, glucose consumption and lipid content in IR/HepG2 cells were examined. The expression of AMPK and p-AMPK in IR/HepG2 treated by Ex-4 were determined by Western blot and immunochemisthistology (IHC) assay. Key enzymes of glucose metabolism, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G-6-Pase) in IR/HepG2 cells treated by Ex-4 were detected by Western blot, immunohistochemistry and qRT-PCR. The results showed that Ex-4 treatment increased the expression of p-AMPK and reduced the expression of G-6-Pase and PEPCK in IR/HepG2 cells. Pretreatment with AMPK inhibitor Compound C counteracts the effect of Ex-4. These findings suggest that Ex-4 fulfilled it glucose regulation effect by phosphorylation of AMPK and decreased the expression of enzymes involving gluconeogenesis.