Antagonic effect of ghrelin and LEAP-2 on hepatic stellate cell activation and liver fibrosis in obesity-associated nonalcoholic fatty liver disease.

Abstract

Growing evidence suggests the key role of ghrelin in the onset and progression of nonalcoholic fatty liver disease (NAFLD). The potential participation of ghrelin and the ghrelin receptor antagonist, LEAP-2, in the onset of liver fibrosis in patients with severe obesity and NAFLD through the regulation of TGF-β1-induced hepatic stellate cell (HSC) activation was investigated. Circulating (n = 179) and hepatic expression (n = 95) of ghrelin and LEAP-2 were measured in patients with severe obesity and available liver pathology analysis undergoing Roux-en-Y gastric bypass (RYGB). The effect of ghrelin isoforms and LEAP-2 on TGF-β1-induced HSC activation, fibrogenic response, and contractile properties was evaluated in vitro in human LX-2 cells. Plasma and hepatic ghrelin were negatively associated, while LEAP-2 exhibited a positive association with liver fibrosis in patients with obesity and NAFLD. Six months after RYGB, hepatic function was improved and, although acylated ghrelin and LEAP-2 concentrations remained unchanged, both hormones were inversely related to post-surgical levels of profibrogenic factors TGF-β1 and TIMP-1. Acylated ghrelin treatment reversed TGF-β1-induced myofibroblast-like phenotype, collagen contractile properties, and the upregulation of factors involved in HSC activation and fibrogenesis via PI3K/Akt/mTOR pathway. Moreover, acylated ghrelin inhibited the mild HSC activation induced by LEAP-2. Ghrelin is an anti-fibrogenic factor blocking HSC activation induced by the most potent fibrogenic cytokine, TGF-β1, and LEAP-2. The imbalance between acylated ghrelin and ghrelin receptor antagonist LEAP-2 might contribute to maintain liver fibrosis in patients with obesity and NAFLD.