Association of Vitamin D receptor gene TaqI polymorphisms with tuberculosis susceptibility: a meta-analysis

Vitamin D receptor (VDR) is a receptor of vitamin D3, which plays a pivotal role in regulating cell proliferation and differentiation, lymphocyte activation and cytokine production, and is associated with TB susceptibility. Growing studies explored the association of TaqI polymorphism of VDR with tuberculosis (TB) susceptibility. However, the results were inconsistent and conflicting. To assess the relationship between the VDR TaqI gene polymorphism and the risk of TB, a meta-analysis was performed. Databases including PubMed and EMbase were systematically searched for genetic association studies of TaqI polymorphism of VDR and tuberculosis until February 15, 2015. Data were extracted by two independent authors and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated to assess the strength of the association between VDR TaqI gene polymorphism and TB risk, meta-regression and subgroup analyses were performed to identify the source of heterogeneity. Thirty-eight studies with a total of 6881 cases and 7511 controls were reviewed in the present meta-analysis. A statistically significant correlations were observed between VDR TaqI gene polymorphism and TB risk in South and West Asians (t vs. T: OR=1.27, 95% CI=1.07-1.51, P=0.007; tt vs. TT: OR=1.59, 95% CI=1.11-2.26, P=0.011; tt vs. Tt + TT: OR=1.43, 95% CI=1.17-1.73, P=0.000; tt + Tt vs. TT: OR=1.32, 95% CI=1.05-1.67, P=0.019). Heterogeneity between studies was not pronounced, and meta-regression found no source contributed to heterogeneity. However, after stratified analysis with respect to genotyping methods and sample size, significant association was found in "small" studies (<500 participants) and studies with "PCR-RFLP" methods. Synthesis of the available studies suggests that t allele of the VDR TaqI polymorphism is significantly associated with an increased TB risk in South and West Asians.