Glucose Is Involved in the Dynamic Regulation of m6A in Patients With Type 2 Diabetes

Context: N-6-methyladenosine (m(6)A) in mRNA is the most abundant and reversible modification. However, the mechanism behind the decrease in m(6)A in patients with type 2 diabetes (T2D) has not yet been thoroughly investigated. Objective: To clarify whether glucose is involved in the dynamic regulation of m(6)A in T2D and to identify a possible underlying mechanism. Methods: Liquid chromatography/electrospray ionization/tandem mass spectrometry and quantitative PCR were performed to determine the m(6)A content and the mRNA expression of target genes in 102 patients with T2D and 107 controls. An additional 12 patients with normal fasting blood glucose, emergency hyperglycemia, or emergency hypoglycemia, as well as HepG2 cells with high-glucose treatment and FTO knockout or overexpression were used to confirm the initial observations in patients. Results: In patients with T2D, the m(6)A content was decreased, and mRNA expression levels of FTO, METTL3, METTL14, and WTAP were increased. Interestingly, the m(6)A content was negatively associated with mRNA expression levels of METTL3, METTL14, and FTO. Moreover, FTO was positively correlated with serum glucose. In HepG2 cells, high glucose upregulated FTO protein, whereas it had no significant effect on METTL3 or METTL14. Additionally, mRNA expression levels of FOXO1, G6PC, and DGAT2 were significantly increased and positively correlated with FTO and serum glucose in patients. Conclusions: Our data revealed that in patients with T2D, high-glucose-enhanced FTO mRNA expression resulted in a decrease in m(6)A. The lower m(6)A content might be responsible for the upregulation of methyltransferases. Additionally, FTO induced mRNA expression of FOXO1, G6PC, and DGAT2 and was closely associated with glucose metabolism.