Polymorphisms in the vitamin D receptor gene and risk of primary biliary cirrhosis: A meta-analysis

Background and AimPrimary biliary cirrhosis (PBC) is a chronic and progressive cholestatic autoimmune liver disease. Although many studies have evaluated the association between many functional polymorphisms in the vitamin D receptor (VDR) gene and PBC risk, debates still exist. Our aim is to evaluate the association between VDR gene polymorphisms, including TaqI (rs731236), BsmI (rs1544410), and ApaI (rs7975232), and the risk of PBC by a systematic review. MethodsWe searched literatures in PubMed, SCOPUS, and EMBASE until July 2013. We calculated pooled odds ratios (OR) and 95% confidence intervals (CIs) using a fixed effects model or a random effects model for the risk to PBC associated with different VDR gene polymorphisms. And the heterogeneity assumption decided the effect model. ResultsA total of six relevant studies, with 1322 PBC cases and 2264 controls, were included in this meta-analysis. The results indicated that TaqI (rs731236) polymorphism was significantly associated with PBC risk (for T vs t OR=0.75, 95% CI 0.63, 0.89, Pz=0.001; TT+Tt vs tt OR=0.62, 95% CI 0.44, 0.86, Pz =0.005; OR=0.74, 95% CI 0.58, 0.94, Pz =0.016 for recessive model), while ApaI (rs7975232) or BsmI (rs1544410) polymorphism did not. ConclusionBased on current evidences from published studies, the cumulative effect of TaqI polymorphism in VDR was significantly associated with PBC. Larger studies with mixed ethnicity subjects and stratified by clinical and sub clinical characteristics are needed to validate our findings.