Human relaxin-2 attenuates hepatic steatosis and fibrosis in mice with non-alcoholic fatty liver disease

Human relaxin-2 reduces hepatic fibrosis in mice. However, the effects of relaxin-2 on hepatic steatosis and fibrosis in animals with non-alcoholic fatty liver disease (NAFLD) remain to be elucidated. C57BL/6 mice fed a high-fat diet (HFD) or methionine–choline-deficient (MCD) diet were randomly assigned to receive recombinant human relaxin-2 (25 or 75 μg/kg/day) or vehicle for 4 weeks. In HFD-fed mice, relaxin-2 decreased systemic insulin resistance and reduced body weight, epididymal fat mass and serum leptin and insulin concentrations. In livers of HFD-fed mice, relaxin-2 attenuated steatosis and increased phosphorylation of insulin receptor substrate-1, Akt and endothelial nitric oxide synthase (eNOS), and activated genes that regulate fatty acid oxidation and suppressed acetyl-CoA carboxylase. Relaxin-2 had no direct anti-steatotic effect on primary mouse hepatocytes, but S-nitroso-N-acetylpenicillamine attenuated palmitic acid-induced steatosis and activated genes regulating fatty acid oxidation in hepatocytes. In mice fed an MCD diet, relaxin-2 attenuated steatosis, inflammation and fibrosis. Relaxin-2 increased eNOS and Akt phosphorylation and transcript levels of cytochrome P450-4a10 and decreased acetyl-CoA carboxylase in MCD-fed mouse livers. Moreover, expression levels of Kupffer cell activation, hepatic stellate cell activation and hepatocyte apoptosis were decreased in MCD diet-fed mice receiving relaxin-2. In conclusion, relaxin-2 reduces hepatic steatosis by activating intrahepatic eNOS in HFD-fed mice and further attenuates liver fibrosis in MCD diet-fed mice. Therefore, human relaxin-2 is a potential therapeutic treatment for NAFLD. Relaxin-2 reduces liver steatosis in mice with high-fat diet (HFD)-induced non-alcoholic fatty liver disease with simple steatosis or methionine-choline-deficient (MCD) diet-induced non-alcoholic steatohepatitis by activating the eNOS/NO pathway. Additionally, relaxin-2 improves insulin resistance and obesity in HFD mice. In MCD mice, relaxin-2 further attenuates hepatic inflammation and fibrosis with reduction in levels of hepatocyte apoptosis and hepatic stellate cell activation.