Association Between TGF-β1 Polymorphisms and Asthma Susceptibility Among the Chinese: A Meta-Analysis

Objective: Asthma is the most common chronic pulmonary disease in China and is characterized by airway inflammation and episodic airflow obstruction. The aim of this meta-analysis was to evaluate the relation of two transforming growth factor-1 (TGF-1) polymorphisms with asthma risk in Chinese population. Methods: PubMed, Springer, EMBASE, MEDLINE, CNKI (China National Knowledge Infrastructure), and Wanfang databases were used to search and retrieve relevant eligible case-control studies published through December 2017. The odds ratios (OR) and 95% confidence intervals (CI) were used to evaluate the effect. Results: A total of 2040 asthma patients and 1952 controls from 12 studies were analyzed. Two polymorphic sites of TGF-1 gene were identified: -509C/T and +869T/C. We found that the -509C/T polymorphism was associated with increased asthma risk under the heterozygous model (CT vs. CC: OR=1.40, 95% CI=1.03-1.90, p=0.03) and the dominant model (TT+CT vs. CC: OR=1.41, 95% CI=1.05-1.90, p=0.02). Subgroup analyses by age suggested that -509C/T variant was associated with childhood asthma. Analysis of disease severity indicated that this variant was associated with both mild-to-moderate asthma and severe asthma. However, the +869T/C polymorphism was not associated with asthma susceptibility in subgroup analysis by age or disease severity. Conclusions: This study demonstrated that the -509C/T polymorphism of the TGF-1 gene might be a risk factor for asthma in the Chinese population, especially in Chinese children. Further large-scale case-control studies are still required.