LncRNA H19 promoted alcohol-associated liver disease through dysregulation of alternative splicing and methionine metabolism

Long non-coding RNAs (lncRNAs) constitute a significant portion of the human genome. LncRNA H19 is among the first identified lncRNAs and is highly expressed during fetal development but decreases in the liver shortly after birth. H19 is reactivated during the development of various liver diseases; however, the role of H19 in the pathogenesis of alcohol-associated liver disease (ALD) remains elusive. Elevated levels of H19 were observed in human peripheral blood and livers of patients with alcohol-associated cirrhosis and alcohol-associated hepatitis. Similar observations were also seen in the livers of ethanol-fed mice. Hepatic overexpression of H19 promoted ethanol-induced liver steatosis and injury. Metabolomics analysis revealed a significant decrease in methionine levels in H19-overexpressed mouse livers. H19 was found to inhibit Betaine-homocysteine methyltransferase (BHMT), a key enzyme in methionine synthesis. H19 regulated the alternative splicing process of Bhmt through Polypyrimidine tract-binding protein 1 (PTBP1), resulting in a decrease in the Bhmt protein-coding variant. Maternally specific knockout of H19 (H19Mat+/-) or liver-specific knockout of the H19 differentially methylation domain (H19DMDHep-/-) in ethanol-fed mice led to an increase in BHMT expression and improvement in hepatic steatosis. Additionally, restoration of BHMT rescued H19 overexpression-mediated ethanol-induced fatty liver. In summary, we identified a novel mechanism of H19 regulating BHMT alternative splicing and methionine metabolism through PTBP1 in ALD. Targeting the H19-PTBP1-BHMT pathway could be a potential therapeutic intervention in patients with ALD.