Therapeutic effects of isosteviol sodium on non-alcoholic fatty liver disease by regulating autophagy via Sirt1/AMPK pathway

Isosteviol sodium (STVNa) is a beyerane diterpene synthesized via acid hydrolysis of stevioside, which can improve glucose and lipid metabolism in animals with diabetes. However, it remains unknown whether STVNa can exhibit a therapeutic effect on nonalcoholic fatty liver disease (NAFLD) and its underlying mechanism. We hypothesize that autophagic initiation may play a key role in mediating the development of NAFLD. Herein, we assessed the effects of STVNa on NAFLD and its underlying mechanisms. The results demonstrated that STVNa treatment effectively ameliorated NAFLD in rats fed high-fat diet (HFD). Moreover, STVNa decreased the expression of inflammation-related genes and maintained a balance of pro-inflammatory cytokines in NAFLD rats. STVNa also reduced lipid accumulation in free fatty acid (FFA)-exposed LO2 cells. In addition, STVNa attenuated hepatic oxidative stress and fibrosis in NAFLD rats. Furthermore, STVNa enhanced autophagy and activated Sirtuin 1/adenosine monophosphate-activated protein kinase (Sirt1/AMPK) pathway both in vivo and in vitro, thus attenuating intracellular lipid accumulation. In summary, STVNa could improve lipid metabolism in NAFLD by initiating autophagy via Sirt1/AMPK pathway. Therefore, STVNa may be an alternative therapeutic agent for treatment of NAFLD.