METTL14-induced m6A methylation increases G6pc biosynthesis, hepatic glucose production and metabolic disorders in obesity
RNA N6-methyladenosine (m6A) modification emerges as a pivotal mechanism underpinning numerous intracellular processes. METTL14 dimerizes with METTL3 as a m6A writer to install m6A on mRNA. Subsequently, m6A readers bind to m6A-marked RNAs to influence their metabolism/fate. However, there is a knowledge gap in m6A writers and readers governing liver metabolism. Glucose-6-phosphatase catalytic subunit (G6pc) is the gatekeeper of glycogenolysis and gluconeogenesis, determining hepatic glucose production (HGP); however, posttranscriptional regulation of G6pc is poorly understood. Here, we identify METTL14 as a posttranscriptional regulator of G6pc synthesis. Deletion of Mettl14 decreased, whereas overexpression of METTL14 increased, G6pc mRNA m6A methylation in hepatocytes. We mapped five m6A sites, and mutating the 5 sites (G6pc?5A) blocked METTL14-induced m6A methylation of G6pc?5A mRNA. METTL14 increased G6pc but not G6pc?5A mRNA stability and translation. YTHDF1 and YTHDF3 acted as m6A readers for G6pc mRNA to increase G6pc synthesis. Deletion of Mettl14 decreased gluconeogenesis in primary hepatocytes,  liver slices, and mice. Liver METTL14, METTL3, and m6A-methylated G6pc mRNA were upregulated in mice with diet-induced obesity. Deletion of hepatic Mettl14 decreased HGP and mitigated diet-induced metabolic disorders. Collectively, these results unveil a previously-unrecognized METTL14/G6pc mRNA m6A/G6pc biosynthesis/HGP axis guiding glucose metabolism in health and disease. Overall design: Mettl14f/f mice (8 weeks) were fed HFD for 10 weeks and injected with AAV8-TBG-Cre or AAV8-TBG-GFP (control) vector via tail vein. Eight weeks later, total RNA was extracted by RNeasy Mini Kit for RNA-seq.