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Dual role of vitamin D-binding protein 1F allele in chronic obstructive pulmonary disease susceptibility: a meta-analysis.

Vitamin D-binding protein (DBP), a highly polymorphic serum protein, encoded by GC gene, is important in the development of chronic obstructive pulmonary disease (COPD). This meta-analysis was performed to assess the association between GC polymorphisms (1F, 1S, and 2 alleles) and COPD susceptibility. Published case-control studies were retrieved from the Pubmed, Embase, and China National Knowledge Infrastructure databases. After data extraction, pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Seven case-control studies were included. Pooled effect size showed that GC polymorphisms were not significantly associated with COPD susceptibility. According to ethnicity, the 1F allele was significantly correlated with COPD susceptibility in Asians (1F vs 1S, OR: 1.52, 95%CI: 1.16-2.00 and 1F vs 2, OR: 1.87, 95%CI: 1.42-2.44), indicating that individuals with the 1F allele have an increased risk of COPD compared to those with the 1S or 2 allele. However, the 1F allele was associated with a lower, insignificant risk of COPD than the 1S and 2 alleles in Caucasians (1F vs 1S, OR: 0.83, 95%CI: 0.64-1.08 and 1F vs 2, OR: 0.73, 95%CI: 0.54-0.98). Moreover, no significant association was found for the 1S and 2 alleles in Asians (OR: 1.23, 95%CI: 0.90- 1.69) and Caucasians (OR: 0.89, 95%CI: 0.70-1.13). After excluding each study, the pooled results were robust and no publication bias was observed. We found that the GC 1F allele confers a risk of COPD in Asians, whereas the 1F allele may protect against COPD in Caucasians.