Ghrelin Stimulates Hepatocyte Proliferation via Regulating Cell Cycle Through GSK3β/Β-Catenin Signaling Pathway

BACKGROUND/AIMS: Obesity is associated with a reduction in ghrelin, a 28 aa gastric hormone. Whether reduced ghrelin contributes to the impaired proliferation of hepatocytes associated with obesity-related steatosis remains largely unknown. Here we examined the effects of ghrelin on the proliferation of hepatocytes derived from lean and obese mice. METHODS: AML 12 cells or hepatocytes isolated from mice fed normal chow diet (NCD) or high fat diet (HFD) were used. Effects of ghrelin on hepatocyte proliferation were detected with CCK8 assay and EdU staining. Cell cycle was analyzed by flow cytometry. Levels of proliferation markers was examined by Western blot. RESULTS: Growth hormone secretagogue receptor 1a (GHS-R1a) mRNA and protein were present in hepatocytes. Levels of GHS-R1a were increased upon ghrelin treatment. Ghrelin significantly increased hepatocyte proliferation measured by Cell Counting Kit-8(CCK8) assay and EdU staining in a dose- and time-dependent manner. Proportion of cells in S phase was markedly increased upon treatment with ghrelin. Ghrelin significantly increased levels of proliferating cell nuclear antigen (PCNA) and cyclin D1, while reducing p27 in hepatocytes from mice fed NCD or HFD. Deletion of GHS-R1a completely abolished the effects of ghrelin in cultured hepatocytes. Ghrelin stimulated the phosphorylation of glycogen synthase kinase 3 beta (GSK3β), leading to subsequent increase of nuclear β-catenin in hepatocytes derived from lean and obese mice. This effect was dependent on the GHS-R1a. CONCLUSION: Ghrelin activates GHS-R1a to stimulate hepatocyte proliferation via GSK3/β-catenin signaling pathway.