Methionine Adenosyltransferase 1A and S-Adenosylmethionine in Alcohol-Associated Liver Disease.

Alcohol-associated liver disease (ALD) is a leading cause of liver-related morbidity, mortality, and premature death worldwide. Its pathogenesis is complex and incompletely understood, with disrupted methionine metabolism as a key contributor. This pathway converts methionine into S-adenosylmethionine (SAM or SAMe), the principal methyl donor, a precursor of glutathione (GSH), and a critical regulator of hepatocellular function. Alterations in methionine metabolism are primarily driven by downregulation of methionine adenosyltransferase 1A (MAT1A), the liver-specific gene encoding the MATα1 subunit responsible for SAMe biosynthesis. Reduced MAT1A expression and activity lead to hepatic SAMe and GSH deficiency, resulting in global hypomethylation, mitochondrial dysfunction, impaired lipid metabolism, and progressive liver injury, hallmarks of ALD. Recent studies show that MATα1 also localizes to hepatocyte mitochondria, where its selective depletion contributes to mitochondrial dysfunction in ALD. Experimental models demonstrate that SAMe supplementation restores methylation capacity, replenishes GSH, reduces oxidative stress, and improves mitochondrial function and liver histology. Preservation of mitochondrial MATα1 also protects against ALD, underscoring its importance in hepatocellular health. Clinical exploration of SAMe in early-stage ALD suggests potential benefit and motivates continued investigation into treatment strategies that build on and extend beyond supplementation. This review summarizes current knowledge on the role of the MAT1A/SAMe axis in ALD pathophysiology, emphasizing molecular functions and critically evaluating preclinical and clinical evidence for potential therapy.