Are Vitamin D Receptor Gene Polymorphisms Associated with Metabolic Syndrome and Type 2 Diabetes? Results of a Case-control Study

The possible role of vitamin D receptor (VDR) genotypes in association with metabolic syndrome (MetS) and type 2 diabetes (T2D) is still unclear. This study aimed to investigate the associations between MetS and T2D with the presence of single nucleotide polymorphisms (SNPs) of the vitamin D receptor (VDR) gene in Iranian subjects with T2D.
730 Iranian subjects (372 T2D and 358 controls) were enrolled in this case-control study. FokI, BsmI, ApaI and TaqI SNPs of the VDR gene were genotyped using the restriction fragment length polymorphism method. The statistical difference in genotype distribution among the groups was assessed by the χ2 test. Logistic regression was performed to calculate odds ratios for the association of the genotype frequencies between different groups with risk of MetS and T2D.
The most common genotypes for the BsmI, ApaI, and TaqI SNPs were Bb, Aa, and TT, respectively, whereas for FokI, they were FF. Adjusted χ2 test revealed no difference between the groups in the genotypes frequencies of 4 VDR polymorphisms in T2D subjects. T2D patients with Tt genotype presented a significantly higher FBS (p=0.009) than those with TT and tt genotypes in TaqI polymorphism. Logistic regression showed no association between MetS risk and VDR genotypes.
In conclusion, no evidence was found showing that VDR gene polymorphisms have a role in the risk of T2D and MetS in Iranian subjects. Further examination should be carried out on large prospective cohort studies, which apply genome wide association to evaluate the direct effect of these polymorphisms on T2D.