Association of genetic polymorphisms in vitamin D receptor (ApaI, TaqI and FokI) with vitamin D and glycemic status in type 2 diabetes patients from Southern India

Objectives: To evaluate the association of VDR polymorphisms (FokI, TaqI and ApaI) with vitamin D levels and glycemic status in type 2 diabetes patients from Southern India.

Methods: In this observational study, genotype frequencies and vitamin D levels of 200 cases (type 2 diabetes patients) were compared with 300 controls (unrelated anonymised stored samples of healthy volunteers) from south India. Serum 25 (OH) D levels were measured by immunoassay technique, glycated hemoglobin (HbA_1c) was measured using HPLC and genotyping of VDR polymorphisms were carried out using Real time Polymerase Chain Reaction (RT PCR).

Results: About 69.2% of type 2 diabetes patients were found to have vitamin D deficiency. FokI polymorphism showed variations in serum 25 (OH) D levels, with AA and AG genotypes having significantly lower serum 25 (OH) D levels as compared to GG [13.24 (8.4) ng/ml, 15.02 (7.07) ng/ml and 20.67 (13.64) ng/ml respectively]. There was no difference in HbA_1c levels with respect to the vitamin D levels and VDR polymorphisms.

Conclusions: AA and AG genotypes of FokI polymorphisms are associated with low serum 25 (OH) D levels. However there was no association between VDR polymorphisms and glycemic status in south Indian type 2 diabetes patients.