Plant sterol ester of α-linolenic acid alleviates hepatic steatosis associated with improving lysosomal function and promoting autophagy via inhibiting mTORC1

The modulation of lysosome-dependent autophagy as a critical protective mechanism affecting the pathogenesis of the non-alcoholic fatty liver disease (NAFLD) is becoming a growing area of concern. The current research was designed to evaluate the effect of plant sterol ester of α-linolenic acid (PS-ALA) on lysosomal function and autophagy in preventing the occurrence of hepatic steatosis using in vivo and in vitro models. Our result showed that treatment with PS-ALA significantly alleviated lipid and free cholesterol (FC) accumulation in a high-fat and high-cholesterol diet (HFCD) feeding mice and reduced the levels of FC, free fatty acid, and triglyceride by 66.7%, 70.4%, and 58.3% in oleic acid/cholesterol (OA/Cho)-treated HepG2 cells. In addition, we found that HFCD or OA/Cho damaged lysosomal function and blocked autophagy characteristics by increased LC3II and p62 accumulation. Administration of PS-ALA significantly promoted lysosome biogenesis, alleviated the damage of lysosomes, activated autophagy, and accelerate lysosome-dependent lipid degradation in OA/Cho-induced cells. Further molecular mechanism study revealed that PS-ALA intervention reduced the expression level of phosphorylation mTORC1 by 34% in the liver and induced subsequent nuclear translocation of TFEB. Activation of mTORC1 by MHY1485 markedly abolished PS-ALA-induced lysosome biogenesis and autophagy in OA/Cho-induced cells, leading to lipid accumulation. Our findings support the suitability of PS-ALA as a therapeutic strategy for NAFLD upon its beneficial effect on lysosomal function and autophagy via inhibiting mTORC1 signaling.