Sestrin1 Alleviates Metabolic Dysfunction-Associated Steatohepatitis by Inhibiting the mTORC1 Signaling Pathway

MASLD is the most prevalent chronic liver disease globally. Its advanced stage MASH causes end-stage liver disease featuring injury, inflammation, and fibrosis. Over 1000 MASH drug trials exist, yet most exhibit side effects. Sestrin1—a leucine sensor in mTORC1 signaling—regulates diseases including cancer, atherosclerosis, and metabolic disorders. Its role in MASH remains unexplored. We aim to study the role of Sestrin1 in the progression of MASH and its potential molecular mechanisms. Male wild-type and Sestrin1 KO mice (C57BL/6J) received choline-deficient high-fat (CDAHFD, 6 weeks) or high-fat/high-cholesterol diet (HFHC, 16 weeks) to induce MASH, with normal chow controls. Fasting weight/glucose were monitored periodically. Post-16 weeks, serum lipids (TG, TC) and liver enzymes (ALT, AST) were analyzed. Histopathology (H&E, Oil Red O, PicroSirius Red, CD11b IF) evaluated steatosis, inflammation, and fibrosis. Primary hepatocytes underwent adenoviral Sestrin1 knockdown/overexpression, PO ± rapamycin treatment, Nile Red staining, and TG quantification. Expression of genes associated with metabolic/inflammatory/fibrotic was assessed by RT-qPCR; Western blotting analyzed Sestrin1 and mTORC1 pathway proteins. Sestrin1 was upregulated in MASH models. Its depletion exacerbated HFHC diet-induced steatosis, inflammation, and fibrosis. Knockdown aggravated hepatocyte lipid accumulation/inflammation, while overexpression alleviated these effects. Mechanistically, Sestrin1 inhibited mTORC1 signaling, and mTORC1 blockade rescued Sestrin1 knockdown-mediated promotion of PO-induced lipid/inflammatory responses. These results suggest that Sestrin1 can inhibit the progression of MASH by inhibiting the mTORC1 signaling pathway, and may be a potential new target for the treatment of MASH.