Association between the vitamin D receptor gene polymorphisms and diabetic nephropathy risk: a meta-analysis

Aims Diabetic nephropathy (DN) is a severe microvascular complication frequently associated with type 1 and type 2 diabetes mellitus. The objective of this study was to estimate the effect between Apa I, Bsm I, Fok I and Taq I polymorphisms of the vitamin D receptor (VDR) gene and DN susceptibility. Methods Eligible case–control studies published updated to March 2017 were searched. The odds ratio (OR) and 95% confident intervals (CI) were employed to calculate the strength of effect. Results 12 articles were finally screened out, including 3954 diabetic patients and 1248 healthy controls. When compared with the diabetic patients without nephropathy, our results found that only the Bsm I polymorphism was associated with increased risk of DN under the allelic model (B vs. b: OR = 1.51, 95% CI = 1.03-2.20, P = 0.04) and dominant model (BB + Bb vs. bb: OR = 1.52, 95% CI = 1.00-2.31, P = 0.05). When compared with the healthy controls, our results showed that the Bsm I polymorphism was associated with the DN susceptibility under the allelic model (B vs. b: OR = 1.80, 95% CI = 1.12-2.91, P = 0.02), the homogeneous model (BB vs. bb: OR = 1.43, 95% CI = 1.03-1.98, P = 0.03), and the domain model (BB + Bb vs. bb: OR = 1.80, 95% CI = 1.06-3.05, P = 0.03); the Taq I variant was associated with increased risk of DN only under the heterogeneous model (Tt vs. tt: OR = 2.29, 95% CI = 1.04-5.03, P = 0.04). Conclusions Our results suggested that B allele, and BB + Bb genotypes of Bsm I variant, Tt genotype of Taq I variant might be risk factors for DN. Future researches are still needed to identify our results.