The association between vitamin D receptor gene polymorphisms and asthma: a systematic review and meta-analysis

Abstract

Background: Numerous studies have reported on the genetic factors related to asthma. In recent years, the vitamin D receptor (VDR) has been identified as one of the asthma susceptibility genes that is closely associated with the pathogenesis of asthma. Methods: Randomized controlled trials (RCTs) related to asthma and the VDR were identified from the Chinese and English databases. The following keywords were used as search terms: “asthma”, “vitamin D receptor”, “VDR”, “polymorphism”, and “mutation”. Meta-analysis was performed using RevMan 5.3 and Stata 13 software provided by the Cochrane system. Results: A total of 7 RCTs were included in this meta-analysis, 6 of which described the correct random allocation methods, 6 described the allocation plan in detail, and 4 used the blinding method. The frequency of the CC + CA dominant genotype at the Apa I locus and the GG + GA genotype frequency at the Bsm I locus of the VDR gene were significantly higher in asthmatic patients compared to control healthy patients [odds ratio (OR) =0.81, 95% confidence interval (CI): 0.68 to 0.98, P=0.03<0.05; and OR =2.05, 95% CI: 1.23 to 3.41, P=0.006<0.05, respectively]. There were no significant differences between the CC, CT, and TT genotype frequencies at the Fok I site of the VDR gene in the experimental group and the CC, CT, TT genotype frequencies at the Taq I site and the control group (P>0.05). There was no significant difference between the genotype frequencies. Discussion: Meta-analysis confirmed that VDR gene polymorphisms are closely related to the onset of asthma, and the gene expression of the Fok I, Bsm I, Apa I, and Taq I loci directly affects the incidence of asthma.