Mammalian Ste20-Like Kinase 1 Regulates AMPK to Mitigate the Progression of Non-Alcoholic Fatty Liver Disease

Non-alcoholic steatohepatitis (NASH) escalates adverse liver-related outcomes, with its progression linked to hepatic lipotoxicity induced by excess hepatic free cholesterol (FC) MST1 has been identified as a potential regulator of hepatic lipid metabolism, potentially ameliorating NAFLD. This study aims to delineate the role of MST1 in the progression of NASH. Wild-type (WT) and MST1 gene knockout (MST1 KO) mice were induced into NASH using a high-fat, high-sugar, high-cholesterol Western diet (WD). In vivo overexpression of MST1 was conducted using lentivirus in WD-fed WT mice. In vitro, HepG2 cells were subjected to MST1 knockdown and overexpression treatments, cultured in a medium induced by a mixture of palmitic acid and oleic acid as free fatty acids (FFA). The NASH model activates the hepatic cholesterol synthesis pathway, leading to an overload of hepatic free cholesterol and downregulation of MST1 expression. Knocking out MST1 exacerbates hepatic FC accumulation and inflammatory damage, activating the cholesterol synthesis pathway. Conversely, upregulating MST1 expression improves hepatic FC deposition, alleviating hepatic damage and inflammation. We found that AMPKα is a substrate of MST1, and MST1 can phosphorylate AMPKα at Thr172. Phosphorylation of AMPKα at Thr172 inhibits the cholesterol synthesis pathway, significantly reversing hepatic FC overload and inflammation caused by MST1 deficiency. Further mechanistic studies indicate that MST1 inhibits cholesterol synthesis by targeting the AMPK/SREBP2 pathway, thereby improving hepatic inflammatory damage caused by FC overload. MST1 targeting AMPK in regulating hepatic cholesterol synthesis metabolism serves as an attractive therapeutic target for preventing the progression of NASH-associated inflammation and fibrosis.