Association between Val66Met polymorphisms in brain-derived neurotrophic factor gene and asthma risk: a meta-analysis.

Abstract

The Val66Met polymorphisms in brain-derived neurotrophic factor (BDNF) gene have been reported to be associated with asthma risk, while the results are inconclusive. Considering a single study may lack the power to provide reliable conclusion, we performed a meta-analysis to investigate the association between the Val66Met polymorphisms and asthma susceptibility. A comprehensive literature search of PubMed, Embase, China National Knowledge Infrastructure (CNKI) and Wanfang databases was conducted before February 12, 2015. The pooled odds ratio (OR) with 95% confidence intervals (CIs) were calculated. Six eligible studies with a total of 3501 subjects were finally included in this meta-analysis. Overall, a significantly increased risk was detected in the Val66Met G allele (G vs. A: OR 1.33, 95% CI 1.19-1.49, P=5.61E-07; GG vs. GA+AA: OR 1.48, 95% CI 1.20-1.83, P=3.14E-04; GG vs. GA: OR 1.48, 95% CI 1.17-1.89, P=0.001; GG vs. AA: OR 1.62, 95% CI 1.20-2.19, P=0.002). Moreover, stratification by ethnicity indicated marked association between the Val66Met G allele and asthma risk in Caucasians (G vs. A: OR 1.29, 95% CI 1.12-1.49, P=0.001; GG+GA vs. AA: OR 1.59, 95% CI 1.03-2.46, P=0.039; GG vs. GA+AA: OR 1.32, 95% CI 1.11-1.57, P=0.001; GG vs. GA: OR 1.28, 95% CI 1.07-1.53, P=0.007; GG vs. AA: OR 1.72, 95% CI 1.11-2.68, P=0.015). Our present meta-analysis suggests that the Val66Met polymorphisms in BDNF gene are potentially associated with asthma risk in Caucasians. Further well-designed case-control studies with larger sample size and more ethnic groups are needed to confirm these conclusions.