Glutathione S-Transferase T1 (GSTT1) Null Polymorphism, Smoking, and Their Interaction in Coronary Heart Disease: A Comprehensive Meta-Analysis

Background The association between glutathione S-transferase T1 (GSTT1) null polymorphism and coronary heart disease (CHD) is inconsistent among studies, and data on the GSTT1 null genotype-smoking interplay in CHD is lacking. We conducted this meta-analysis to investigate the relationship between GSTT1 null polymorphism and CHD and to assess the potential interaction between GSTT1 null genotype and smoking. Methods PubMed and EMBASE databases were searched up to 27 January 2016 using the appropriate terms. Odds ratios were pooled using either fixed-effects or random-effects models. Results Twenty-nine articles including 31 studies with 15,004 cases and 35,597 controls were eligible. The randomeffects model showed that the GSTT1 null genotype was associated with increased CHD risk (OR = 1.213, 95% CI: 1.004-1.467; I-2 = 90.4%). After excluding 10 studies detected by Galbraith plot, the fixed effects summary estimate also showed an increased risk of CHD (OR = 1.14, 95% CI: 1.06-1.22; I-2 = 27.7%). A case-only analysis including eight studies showed a statistically significant positive interaction between GSTT1 null polymorphism and smoking status on CHD (OR = 1.34, 95% CI: 1.09-1.64; I-2 = 0%). Sensitivity analyses further supported the associations. No publication bias was observed. Conclusions This meta-analysis suggests that GSTT1 null polymorphism is associated with the risk of CHD. To our knowledge, this is the first meta-analysis to prove a positive effect of the interaction between GSTT1 null genotype and smoking status on the risk of CHD. Future studies with detailed individual information are needed to confirm our findings.