Liraglutide induces autophagy through AMPK / mTOR signaling pathway and improves hepatocyte steatosis

ObjectiveTo investigate the role and possible mechanism of adenylate activated protein kinase(AMPK)/rapamycin target protein(mTOR) pathway in the improvement of liraglutide(LG) on hepatocyte steatosis.

MethodsIn animal experiment, the mice were randomly divided into control group, model group and LG group, with 10 mice in each group.The mice in the control group were fed with ordinary diet, and the mice in other groups were fed with high-fat diet to construct hepatic steatosis model.In the LG group, the mice were injected with LG at 0.6 mg·kg^-1·d^-1 intraperitoneally, and in the other two groups, the mice were treated with the same amount of 0.9% sodium chloride solution for 4 weeks.The levels of serum alanine aminotransferase(ALT), aspartate aminotransferase(AST), low density lipoprotein(LDL), cholesterol(TC) and triglyceride(TG) were detected; the changes of morphology, steatosis and lipid droplets of hepatocytes were observed through HE and oil red O staining methods.The expressions of p-AMPK, p-mTOR, autophagy-related proteins LC3B and Beclin1 were detected by Western blotting.In cell experiment, the palmitic acid(PA) induced steatosis model in HepG2 hepatocytes was established, the cells were equally divided into model group(PA), LG Group(PA+LG) and AMPK inhibitor group(PA+LG+compound C).The expression of autophagy-related protein LC3B was detected by immunofluorescence; the protein expressions of p- AMPK, p-mTOR, LC3B and Beclin1 were detected by Western blotting.

ResultsIn contrast to control group, the levels of ALT, AST, LDL, TC and TG in model group were increased significantly, and decreased significantly after LG treatment (P < 0.05 to P < 0.01);HE and oil red O staining showed that in the model group, there had large areas of steatosis and a large number of fused lipid droplets.The steatosis and lipid droplets content was decreased significantly in the LG group.Western blotting results showed that the protein expressions of p-AMPK, LC3B and Beclin1 were decreased significantly in model group, but increased in LG group, p-mTOR was increased in model group, and decreased in LG group(P < 0.05 to P < 0.01).Cell experiment: immunofluorescence staining showed that LC3B expression in LG group was significantly higher than that in model group, while LC3B expression was inhibited in AMPK inhibitor group.Western blotting results showed that compared with the model group, the protein expressions of p-AMPK, LC3B and Beclin1 in LG group were significantly increased, but the expressions were inhibited after the application of AMPK inhibitor, while p-mTOR expression was on the contrary, which had statistically significance(P < 0.05 to P < 0.01).

ConclusionsLiraglutide improved hepatocyte steatosis through AMPK/mTOR pathway, and autophagy may be involved.