A population association study of vitamin D receptor gene polymorphisms and haplotypes with the risk of systemic lupus erythematosus in a Chinese population

The aim of the study is to investigate the association of vitamin D receptor (VDR) gene polymorphism, additional gene–gene interaction, and haplotype combination with systemic lupus erythematosus (SLE) risk. Pairwise linkage disequilibrium (LD) analysis was conducted using SNPstats. The association between four SNPs within VDR gene and SLE risk was investigated by logistic regression. Generalized multifactor dimensionality reduction (GMDR) was used to analyze the interaction among four SNPs. Four SNPs within VDR gene were selected for genotyping in this study, including rs2228570, rs1544410, rs7975232, and rs731236. The T allele of rs2228570 and the G allele of the rs1544410 were associated with increased MM risk, adjusted ORs (95%CI) were 1.61(1.25–2.11) and 1.78 (1.34–2.23), respectively. GMDR analysis suggested a significant two-locus model (P = 0.0010) involving rs1544410 and rs2228570, and in this model, the cross-validation consistency was 10/10, and the testing accuracy was 62.70%. The haplotype analysis indicated that the most common haplotype was rs1544410-A and rs7975232-G haplotype, the frequencies of which were 0.4701 and 0.5467 in case and control group. Haplotype containing the rs1544410-G and rs7975232-T alleles were associated with increased SLE risk, OR (95%CI) = 2.08 (1.47–2.72), P < 0.001. We found that rs2228570 and rs1544410 within VDR gene, their interaction and haplotype containing the rs1544410-G and rs7975232-T alleles were all associated with increased SLE risk.