Silibinin ameliorates fructose-induced lipid accumulation and activates autophagy in HepG2 Cells.

BACKGROUND: Autophagy was recently regarded as a potential mechanism in nonalcoholic fatty liver disease. Silibinin (SIL), a natural flavonoid, has been used to prevent nonalcoholic fatty liver disease, however, the underlying mechanism is unclear. The aim of the present study was to explore the effect of SIL on hepatic steatosis and the possible link with autophagy.

METHODS: The degree of hepatic steatosis in HepG2 cells was observed by oil-red O staining and triglyceride content. The effect of SIL on autophagy was tested by the Autophagy Detection Kit, and the expression of sterol regulatory element binding protein 1 (srebp-1), fatty acid synthase (Fas), light chain 3, beclin-1, p62, AMP-activated kinase (AMPK), and mammalian target of rapamycin (mTOR) were examined by western blots.

RESULTS: The lipid accumulation of HepG2 cells increased significantly in the high-fructose group compared to the control group. After SIL intervention, lipid accumulation was decreased. Using a fluorescence microscope, SIL was found to induce autophagy. Compared to control, the expressions of srebp-1, Fas, and phosphorylated-mTOR were increased by high-fructose, while the expressions of light chain 3 and beclin-1 were decreased and srebp-1, Fas, and p62 were increased by autophagy inhibition. In contrast, opposite results were found in the SIL intervention group. The protein content of phosphorylated-mTOR was decreased, while phosphorylated-AMPK was increased in the SIL group compared to the high-fructose group.

CONCLUSION: SIL can reduce lipid accumulation in HepG2 cells exposed to high-fructose by inducing autophagy. The AMPK/mTOR signaling pathway could be one of the underlying molecular mechanisms.