Hepatic Lipid Stress Drives Metabolic Dysfunction-Associated Steatohepatitis Progression through FTO O-GlcNAcylation-Induced m6A Demethylation of HRAS.

Metabolic dysfunction-associated steatohepatitis (MASH) is driven by nutrient stress through incompletely defined epigenetic mechanisms. This study demonstrates that lipid stress activates the hexosamine biosynthesis pathway (HBP), elevating O-linked β-N-acetylglucosamine (O-GlcNAc) modification of the N6-methyladenosine (m6A) demethylase fat mass and obesity-associated protein (FTO) at Ser195. This post-translational modification recruits the deubiquitinase ubiquitin-specific peptidase 20 (USP20), displaces the E3 ligase F-box and WD repeat domain containing 7 (FBXW7), and enhances FTO protein stability and m6A demethylase activity. O-GlcNAc-dependent FTO activation removes m6A from Harvey rat sarcoma viral oncogene homolog (HRAS) mRNA, evades YTH N6‑methyladenosine RNA binding protein 2 (YTHDF2)‑mediated degradation, and prolongs transcript half-life. Subsequent HRAS upregulation activates the PI3K/AKT signaling pathway, driving hepatic steatosis and inflammation. Administration of a novel cell-penetrating peptide (CPP) designed to block FTO O-GlcNAcylation at Ser195 effectively ameliorates MASH progression in vitro and in vivo. These findings establish FTO O-GlcNAcylation as a druggable metabolic-epigenetic checkpoint in MASH pathogenesis, revealing a promising therapeutic strategy for this increasingly prevalent liver disease.