An Updated Meta-Analysis of the Effects of the Endothelial Nitric Oxide synthase Gene G894T Polymorphism and Erectile...

Erectile dysfunction (ED) is a common disorder leading to a serious and negative impact on the patient's quality of life. The gene encoding endothelial nitric oxide synthase (eNOS) is an interesting candidate gene for understanding the physiopathology of ED. However, an association between eNOS G894T polymorphism and ED risk is uncertain and should be updated. Therefore, a meta-analysis of the current literature was necessary to clarify this relationship. We searched Pubmed and China National Knowledge Infrastructure (CNKI) (last search updated on Dec 12, 2013) using 'nitric oxide synthase,' 'polymorphism or variant,' 'genotype,' and 'ED' as keywords. We also searched reference lists of studies corresponding to the inclusion criteria for the meta-analysis. These studies involved the total number of 1,445 ED men and 1,459 healthy control men subjects. Odds ratio (OR) and 95 % confidence intervals (CIs) were used to evaluate this relationship. Statistical analysis was performed with STATA10.0. In the overall analysis, significantly decreased associations between ED risk and eNOS G894T polymorphism were found. Moreover, in the subgroup analysis based on ethnicity, similar significant associations were detected in both Caucasians (such as GG+GT vs. TT: OR 0.92, 95 %CI 0.86-0.97) and Asians (such as GG+GT vs. TT: OR 0.24, 95 % CI 0.07-0.85). The Egger's test did not reveal the presence of a publication bias. Our investigations demonstrate that eNOS G894T polymorphism might protect men against ED risk. Further studies based on larger sample size and gene-environment interactions should be conducted.