Vitamin D receptor gene (VDR) polymorphisms and the urolithiasis risk: an updated meta-analysis based on 20 case-control studies

Vitamin D receptor (VDR) plays a key role in calcium metabolism, and is closely related to urinary stone formation (urolithiasis). Previous studies have investigated the associations between VDR single nucleotide polymorphisms (SNPs) (polymorphisms at BsmI, ApaI, FokI, or TaqI cutting sites) and urolithiasis in different populations. However, the results remain inconsistent and controversial. Therefore, meta-analysis was performed to evaluate these associations. Twenty studies that investigated the associations between VDR SNPs and urolithiasis were retrieved. Odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated under the most appropriate genetic model. The TaqI polymorphism was associated with an increased risk of urolithiasis (tt + Tt vs. TT: OR = 1.253; 95 % CI = 1.033-1.520, p = 0.022, I (2) = 0), whereas the ApaI, BsmI, and FokI polymorphisms were not. Stratifying for ethnicity, a slightly increased risk was found among Asians as compared to Whites (OR 1.263, 1.232, respectively, p < 0.01). Deviation from Hardy-Weinberg equilibrium (HWE) was the major source of heterogeneity. In summary, this updated meta-analysis suggests the TaqI polymorphism is associated with urolithiasis risk, whereas BsmI, ApaI, and FokI polymorphisms are not.