Nitric oxide synthase 3 (NOS3) 4b/a, T-786C and G894T polymorphisms in association with diabetic retinopathy susceptibility: A meta-analysis

Aims: To assess the association between the NOS3 4b/a, T-786C and G894T polymorphisms and diabetic retinopathy (DR) susceptibility.Materials and Methods: Twenty-one studies covering 8,111 subjects were included. The fixed or random effect model used was based on heterogeneity.Results: A significant association of the intron 4a allele in the NOS3 4b/a polymorphism with reduced risk of DR was found in dominant (OR 0.778, 95% CI 0.654–0.926) and additive (OR 0.809, 95% CI 0.698–0.937) models. Subgroup analysis revealed that the intron 4a allele additive model (OR 0.807, 95% CI 0.697–0.935) was associated with DR risk in type 2 diabetic patients. We also found a marginally significant association of the C allele in the T-786C polymorphism with reduced risk of proliferative DR. In contrast, no statistically significant association was observed between the G894T polymorphism and DR risk, either in the overall or subgroup analyses.Conclusions: The intron 4a allele of the 4b/a polymorphism in the eNOS gene has protective effects against DR, especially in type 2 diabetic patients. The C allele of the T-786C polymorphism may be a protective factor for proliferative DR. However, the G894T polymorphism does not appear to influence the development of DR. This conclusion warrants confirmation by further studies.