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

Abstract

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.

Ghrelin‐insulin‐like growth factor‐1 axis is activated via autonomic neural circuits in the non‐alcoholic fatty liver disease

“…In animal models of NASH and hepatic cirrhosis, IGF‐1 replacement therapy was effective in reducing inflammation and fibrosis . These therapeutic effects of GH and IGF‐1 supplementation include the mechanisms of inhibition of hepatic fat synthesis, inhibition of Kupffer's cell function, reduction of oxidative stress in hepatocytes, induction of senescence to hepatic Kupffer's cells, hepatocyte proliferation, and stimulation of autophagy . Apart from the liver, these effects were also observed in the heart, increasing the muscle mass and improving cardiac function .…”

G protein‐coupled receptors can control the Hippo/YAP pathway through Gq signaling

“…The ghrelin receptor is mainly expressed in the hypothalamus and the gastrointestinal tract and is involved in a broad range of physiological functions 58 . Ghrelin is known to drive proliferation and differentiation and inhibiting apoptosis in several cellular models 59–61 . While several studies suggest that Ghrelin promotes cancer such as colorectal malignancies 62 or renal cell carcinoma metastasis, 63 neither Ghrelin nor Anamorelin, used as GHS‐R1a agonist for the treatment of cancer cachexia encouraged tumor growth in xenograft models 64 or in humans with NSLC (non‐small lung cell carcinoma) in a short‐term phase 3 safety extension study 65 .…”

High-Fat Diet Induced Gut Microbiota Alterations Associating With Ghrelin/Jak2/Stat3 Up-Regulation to Promote Benign Prostatic Hyperplasia Development

“…All cells were incubated at 37°C in an atmosphere with 5% CO 2 . Before treatment, cells were starved for 12 h. The cell lines were treated with 1 μmol/L of Ghrelin referring to previous reports ( Abdanipour et al, 2018 ; Wang Q. et al, 2018 ) and 1 μM Jak2/STAT3 inhibitor WP1066 (Sigma, United States).…”