Targeting xCT-mediated amino acid metabolism: A novel mechanism of silymarin in ameliorating MAFLD-associated ferroptosis.

Metabolic dysfunction-associated fatty liver disease (MAFLD) affected approximately 25% of the global population, resulting in a huge economic burden. Silymarin, a traditional European herbal remedy with known hepatoprotective properties, has not been fully explored for its therapeutic potential in MAFLD. MAFLD mice fed with high-fat diet (HFD) and palmitic acid (PA)-induced HepG2 cells were used to investigate the mechanism of silymarin in vivo and in vitro. HE and Oil Red were utilized to determine the lipotoxic injury in liver. The levels of glutathione (GSH), Malondialdehyde (MDA), iron, and reactive oxygen species (ROS) were measured via corresponding kits to verify the status of ferroptosis. The target of silymarin was validated through western blot, qPCR, immunohistochemistry and immunofluorescence. Targeted amino acid metabolomics was applied to detect the amino acid alteration in liver by LC-MS/MS. Silymarin reduced the weight and fat accumulation in MAFLD mice. The decreased levels of MDA and ROS and the increased level of GSH indicated that silymarin diminished hepatic ferroptosis. xCT is the potent target of silymarin in MAFLD. Cystine deprivation experiment indicated that cystine played a critical role in silymarin therapy. And silymarin treatment also resulted in amino acid reprogramming in liver. These results suggested that silymarin alleviated MAFLD by targeting xCT and inhibiting ferroptosis. The alteration in amino acid by silymarin provided new clues for MAFLD therapy.