N ⁶-methyladenosine (m⁶A) modification plays a fundamental role in the epigenetic regulation of the mammalian transcriptome. m⁶A can be demethylated by fat mass- and obesity-associated (FTO) protein and α-ketoglutarate-dependent dioxygenase alkB homolog 5 (ALKBH5) protein. However, the importance of m⁶A alteration in type 2 diabetes mellitus (T2DM) has not been explored.

The objective of the study was to investigate whether m⁶A content was reduced in T2DM patients and whether m⁶A content was correlated with the mRNA expression levels of the FTO and ALKBH5 genes.

In this case-control study, peripheral blood samples were obtained from 88 T2DM patients and 92 healthy controls. For the diabetic animal model experiment, blood samples were obtained from seven diabetic and eight nondiabetic rats. A sensitive liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed for the determination of the m⁶A content in RNA, quantitative real-time PCR was used to examine the mRNA expression levels of the FTO and ALKBH5 genes, and high-resolution melting and DNA sequencing were used to detect FTO single-nucleotide polymorphisms.

Our results showed that the m⁶A contents in the RNA from T2DM patients and diabetic rats were significantly lower compared with the control groups (P = 2.6 × 10⁻²⁴ for T2DM patients; P = .001 for diabetic rats, respectively), and T2DM can be characterized by the content of m⁶A. The mRNA expression level of FTO was significantly higher in T2DM patients than that of the controls (P = .0007) and was associated with the risk of T2DM (odds ratio 2.797, 95% confidence interval 1.452–5.389, P = .002). Moreover, the m⁶A contents were correlated with FTO mRNA expression.

These data suggest that the increased mRNA expression of FTO could be responsible for the reduction of m⁶A in T2DM, which may further increase the risk of complications of T2DM. Low m⁶A should be investigated further as a novel potential biomarker of T2DM.