Polymorphisms in the transforming growth factor-β1 gene and the risk of asthma: A meta-analysis

Background and objective: Polymorphisms in the transforming growth factor-beta 1 (TGF-beta 1) gene have been implicated in susceptibility to asthma, but a large number of studies have reported inconclusive results. Ameta-analysis was performed to investigate the association between polymorphisms in the TGF-beta 1 gene and asthma susceptibility. Methods: Searches were performed of Medline (Ovid), PubMed, the Chinese Biological Medicine Database (CBM), the Chinese Journals Full-text Database (CNKI), the Cochrane Library Database and the Web of Science, covering all papers published up to 30 April 2009. Statistical analysis was performed using Revman4.2.8 and STATA10.0 software. Results: Two polymorphisms (-509C/T and 915G/C(G25C)) were investigated in 14 studies, involving 2979 asthma patients and 4941 control subjects. The results showed that individuals carrying the -509T allele (TT+TC) had a 36% increased risk of asthma, when compared with homozygotes (-509CC) (OR 1.36, 95% CI: 1.12-1.65). However, there was no significant association with risk of asthma in carriers of the 915C allele (GC+CC) compared with 915GG homozygotes (OR 1.05, 95% CI: 0.65-1.70). In a subgroup analysis by ethnicity, the risk of asthma associated with the -509T allele was significantly elevated among Asians (OR 1.50, 95% CI: 1.04-2.17) but not Caucasians (OR 1.16, 95% CI: 1.00-1.36). In a subgroup analysis by age, the -509T allele was associated with a significantly elevated risk of asthma among adults (OR 1.45, 95% CI: 1.09-1.92) but not children (OR 1.19, 95% CI: 0.96-1.46). Conclusions: This meta-analysis suggested that the -509C/T polymorphism in the TGF-beta 1 gene may be a risk factor for asthma. To further evaluate gene-gene and gene-environment interactions between polymorphisms in the TGF-beta 1 gene and asthma susceptibility, more studies involving thousands of patients are required.