Glucosamine Promotes Autophagy and Attenuates Hepatic Steatosis Via O-GlcNAcylation-Mediated Mechanisms

Autophagy is a key cellular process regulating lipid turnover and maintaining hepatic homeostasis, and its impairment is closely associated with the pathogenesis of nonalcoholic fatty liver disease (NAFLD). In this study, we examined the effects of glucosamine (GlcN), a hexosamine biosynthetic pathway intermediate, on autophagy and lipid accumulation using both human hepatocellular carcinoma (HepG2) cells and a high-fat diet (HFD)-induced NAFLD mouse model. GlcN treatment led to a dose- and time-dependent increase in the expression of autophagy-related markers LC3 and p62 at both mRNA and protein levels. Pharmacological inhibition of O-GlcNAcase (OGA) further enhanced autophagic activity, whereas inhibition of O-GlcNAc transferase (OGT) abrogated GlcN-induced autophagic responses, implicating O-GlcNAcylation as a key mediator of GlcN-driven autophagy induction. Functionally, GlcN significantly reduced palmitic acid (PA)-induced lipid accumulation in HepG2 cells and alleviated hepatic steatosis in HFD-fed mice, likely through enhancement of autophagic flux. These findings demonstrate that GlcN promotes lipid clearance in hepatocytes via O-GlcNAc-dependent autophagy and highlight its potential as a therapeutic agent for NAFLD and related metabolic disorders.