Association of Vitamin D binding protein polymorphism with risk of type 2 diabetes mellitus in a Pakistani urban population: A case control study.

Objective: To assess if genotypes/diplotypes of vitamin D binding protein have any association with type 2 diabetes mellitus. Methods: This case-control study was conducted from January 2013 to July 2015 at the endocrinology clinics of the Aga Khan University Hospital, Karachi, and comprised adult patients with type 2 diabetes and their age-and gender-matched healthy controls. Venous blood was obtained and assessed for serum/plasma 25 hydroxyvitamin D, parathyroid hormone, calcium, alkaline phosphatase and creatinine. Deoxyribonucleic acid was isolated and genotyping was done by polymerase chain reaction-restriction fragment length polymorphism procedures. Results: Of the 330 participants, there were 165(50%) cases and as many controls. There were 116(70.3%) males and 49(29.7%) females in each group. The mean age of the patients was 48.82 +/- 9.23 years and that of the controls was 46.27 +/- 8.77 years (range: 22-70 years) (p=0.010) Mean serum concentration of 25 hydroxy vitamin D was significantly higher among the patients compared to the controls (p<0.001), but not significantly different by genotypes or diplotypes (p>0.05). Multiple conditional logistic regression revealed an association of group-specific 1-2 genotype with patients when adjusted for age, body mass index, and serum levels of 25 hydroxy vitamin D with matched adjusted odds ratio (95% confidence interval) being 3.1(1.22-7.88). Conclusion: Group-specific 1-2 genotype of vitamin D binding protein gene was associated with the risk of type 2 diabetes.