[Exendin-4 promotes autophagy to relieve lipid deposition in a NAFLD cell model by activating AKT/mTOR signaling pathway].

OBJECTIVE: To investigate the effect of exendin-4 on lipid deposition in hepatocytes and explore its possible mechanism for treatment of nonalcoholic fatty liver disease (NAFLD). METHODS: Human normal hepatocyte line LO2 and hepatoma cell line HepG2 were treated with palmitic acid (PA) to mimic hepatocyte steatosis or with combined treatments with PA+exendin-4 or PA+exendin-4+3BDO. Lipid deposition and proliferation of the two cell lines following treatment with PA or PA+exendin-4 were detected using Oil Red O staining and CCK8 assay, and the expression of p-mTOR, m-TOR, p-AKT, AKT and autophagy-related proteins LC3-Ⅰ/Ⅱ and p62 were detected with Western blotting; the expression of GLP-1R was detected with both Western blotting and immunofluorescence assay. The expression of LC3-Ⅰ/Ⅱ and p62 in the cells following treatment with PA+exendin-4 and PA+exendin-4+3BDO was detected with Western blotting. RESULTS: Lipid deposition in the two cell lines increased significantly after PA treatment, but was alleviated by co-treatment with exendin-4. PA treatment significantly inhibited the proliferation of the two cell lines ( < 0.01), and this inhibitory effect was obviously attenuated by exendin-4 ( < 0.05). Immunofluorescence assay showed that both LO2 and HepG2 cells expressed GLP-1R. The expression of p-mTOR was significantly lower and that of p-AKT was higher in cells treated with PA+exendin-4 than in PA-treated cells. Exendin-4 also down-regulated the autophagy-associated protein p62 and up-regulated the expression of LC3-Ⅱ in PA-treated cells, and this effect was obviously reversed by 3BDO. CONCLUSION: Exendin-4 may activate the AKT-mTOR signal pathway to promote autophagy its direct action on GLP-1R. Exendin-4 can also alleviate lipid deposition and promote proliferation of PA-treated hepatocytes, suggesting its important role in PA-induced lipid deposition in hepatocytes.