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

ABSTRACT 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.