GCSH promotes MASH progression by regulating cuproptosis through the glycine-GSH metabolic pathway.

BACKGROUND AND OBJECTIVES: Cuproptosis, a recently identified form of programmed cell death, has an unclear role in the context of metabolic dysfunction-associated steatohepatitis (MASH). This study aims to elucidate the role of cuproptosis in the early stages of MASH progression, identify its primary regulatory factors, and delineate the associated molecular mechanisms.

METHODS: Liver specimens from MASH patients were evaluated to characterize hepatic cuproptosis and its correlation with clinical indices. MASH cell models were established using free fatty acid (FFA)-treated primary hepatocytes and HepG2 cells, while an in vivo MASH model was induced by feeding mice a high-fat, high-fructose, high-cholesterol (HFFC) diet. The copper chelator tetrathiomolybdate (TTM) was administered to verify the causal role of cuproptosis. Bioinformatic analyses were conducted to identify core genes related to cuproptosis. Following shRNA-mediated gene knockdown, rescue experiments were performed using exogenous glycine supplementation and the GSH synthesis inhibitor buthionine sulfoximine (BSO). Comprehensive assessments were performed on cuproptosis markers, mitochondrial function, lipid metabolism, and inflammatory indicators.

RESULTS: Hepatic cuproptosis was significantly activated in early-stage MASH patients and HFFC-fed mice, characterized by the depletion of Fe-S cluster proteins alongside robust DLAT oligomerization. These cuproptosis hallmarks showed positive associations with Non-Alcoholic Fatty Liver Disease Activity Scores (NAS) and metabolic dysfunction. Intervention with TTM substantially attenuated these changes and simultaneously improved mitochondrial respiratory chain function, reduced steatosis, and diminished inflammatory responses, thereby indicating that cuproptosis is a key driver of MASH pathology. Bioinformatic analysis identified the glycine cleavage system H protein (GCSH) as the core regulatory gene, which was significantly upregulated in liver tissues from both early-stage MASH patients and mouse models. Knockdown of Gcsh effectively suppressed cuproptosis and ameliorated MASH phenotypes. Mechanistically, we observed reduced hepatic glycine levels and decreased GSH/GSSG ratios in MASH. The upregulation of GCSH expression was observed to enhance glycine catabolism, consequently depleting the substrates necessary for GSH synthesis. Notably, rescue experiments mediated by BSO markedly diminished the protective effects of Gcsh knockdown, thereby corroborating the role of GSH as a pivotal downstream effector of GCSH within the glycine-GSH metabolic pathway.

CONCLUSIONS: This study identifies cuproptosis as a critical pathogenic driver in the progression of early-stage MASH. We elucidate a novel GCSH-glycine-GSH-cuproptosis regulatory axis, wherein GCSH acts as an upstream metabolic regulator, rather than merely a passive substrate, exacerbating disease pathology through glycine catabolism-mediated GSH depletion. These findings suggest that GCSH and the glycine-GSH axis represent promising therapeutic targets for MASH intervention.