Association of MTHFR C677T polymorphism and type 2 diabetes mellitus (T2DM) susceptibility

Methylenetetrahydrofolate reductase (MTHFR) is essential in mediating folate metabolism, and thus plays an important role in diabetes and diabetic complications. MTHFR C677T (rs1801133 C>T) polymorphism has been proposed to be linked with type 2 diabetes mellitus (T2DM) susceptibility. However, the conclusions are inconsistent. Therefore, we rechecked their linkage aiming to obtain a more reliable estimation by performing an updated meta-analysis.

We searched electronic databases PubMed, EMBASE, CNKI, and Wanfang to obtain studies updated to October 2019.

After carefully screening, we finally incorporated 68 studies with 10,812 cases and 8,745 controls. The genotype frequency of C677T polymorphism was analyzed pooled to generate odds ratios (ORs) and 95% confidence intervals (CIs). Pooled results presented that MTHFR C677T polymorphism was significantly associated with T2DM under homozygous (OR = 1.64, 95% CI = 1.39-1.94), heterozygous (OR = 1.38, 95% CI = 1.20-1.59), recessive (OR = 1.41, 95% CI = 1.23-1.61), dominant (OR = 1.47, 95% CI = 1.27-1.70), and allele (OR = 1.37, 95% CI = 1.23-1.52) genetic models. Stratified analysis demonstrated that C677T genotype was associated with T2DM in Asian populations, but not Caucasian and African populations.

Our results indicated that MTHFR C677T polymorphism confers to T2DM, especially in Asian populations. Much more large-scale case-control studies are needed to strengthen such conclusion in the future.