METTL1-mediated m7G methylation of FoxO1 regulates lipid metabolism in metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MASLD) is characterized by the accumulation and degeneration of lipids in hepatocytes, presenting a complex pathogenesis that complicates drug development. In this study, we found that methyltransferase-like 1 (METTL1) is upregulated in the livers of both MASLD mice and clinical samples. Hepatocyte-specific depletion of METTL1 inhibits lipid synthesis and promotes lipid oxidation, alleviating metabolic disorders in high-fat diet (HFD)-induced MASLD mice. Conversely, overexpression of METTL1 enhances lipid synthesis while suppressing lipid oxidation. Mechanistically, METTL1 regulates the stability and protein expression levels of FoxO1 mRNA by methylating the Exon1 region of FoxO1, as demonstrated by m7G sequencing. Additionally, we found that overexpression of FoxO1 counteracts the protective effects of METTL1 deficiency on metabolic disorders in MASLD mice. Moreover, we identified a potent small-molecule inhibitor of METTL1, specifically Homatropine Methylbromide (HtMBm), which significantly ameliorated HFD-induced MASLD. Overall, our study suggests that METTL1 plays a crucial role in the progression of MASLD and highlights the therapeutic potential of targeting METTL1 to modulate fatty acid metabolism in this condition.