METTL14-Induced M6A Methylation Increases G6pc Biosynthesis, Hepatic Glucose Production and Metabolic Disorders in Obesity.

METTL14 dimerizes with METTL3 to install N6-methyladenosine (m6A) on mRNA (m6A writers). Subsequently, m6A readers bind to m6A-marked RNA to influence its metabolism. RNA m6A emerges to critically regulate multiple intracellular processes; however, there is a gap in our understanding of m6A in liver metabolism. Glucose-6-phosphatase catalytic subunit (G6pc) mediates hepatic glucose production (HGP) and serves as the gatekeeper for glycogenolysis and gluconeogenesis; however, G6pc regulation is not fully understood. Here, METTL14 is identified as a posttranscriptional regulator of G6pc. Liver METTL14, METTL3, and m6A-methylated G6pc mRNA are upregulated in mice with diet-induced obesity. Deletion of Mettl14 decreases, whereas overexpression of METTL14 increases, G6pc mRNA m6A in hepatocytes in vitro and in vivo. Five m6A sites are identified, and disruption of them (G6pcΔ 5A) blocks METTL14-induced m6A methylation of G6pcΔ 5A mRNA. METTL14 increases both stability and translation of G6pc but not G6pcΔ 5A mRNA. YTHDF1 and YTHDF3 but not YTHDF2 (m6A readers) bind to m6A-marked G6pc mRNA to increase its synthesis. Deletion of hepatic Mettl14 decreases gluconeogenesis in primary hepatocytes, liver slices, and mice. Hepatocyte-specific restoration of G6pc reverses defective HGP in Mettl14 knockout mice. These results unveil a METTL14/G6pc mRNA m6A/G6pc biosynthesis/HGP axis governing glucose metabolism in health and metabolic disease.