The joint effect of the endothelin receptor B gene (EDNRB) polymorphism rs10507875 and nitric oxide synthase 3 gene (NOS3) polymorphism rs869109213 in Slovenian patients with type 2 diabetes mellitus and diabetic retinopathy

Increasing evidence suggests that endothelin and nitric oxide synthase genes and their products exert biological effects on the vasculature via the nitric oxide or endothelin pathway. The aim of the study was to evaluate the association of rs10507875 and rs869109213 (alone or in interaction) with diabetic retinopathy (DR) in subjects with type 2 diabetes mellitus (T2DM). We genotyped the single nucleotide polymorphism rs10507875 of the endothelin receptor B gene (EDNRB) and variable number tandem repeats rs869109213 of the nitric oxide synthase 3 gene (NOS3) in 270 Slovenian patients with DR and T2DM and 256 controls with T2DM without clinical signs of DR. The genotyping was performed using either real-time polymerase chain reaction (PCR) or standard PCR. We found a significant association between the genotypes of NOS3 rs869109213 polymorphism and the risk of DR in the co-dominant model (4a4b genotype; 1.99-fold increased risk [1.09-3.65]; 95% confidence interval [CI]; p = 0.02), co-dominant model (4a4a genotype; 4.16-fold increased risk [1.03-16.74]; 95% CI; p = 0.04), and dominant model (4a4a and 4a4b genotypes; 2.22-fold increased risk [1.26-3.92]; 95% CI; p = 0.01) compared to the 4b4b genotype. Moreover, the joint effect of the two polymorphisms on DR risk was greater than the individual effect of each polymorphism in the analyzed genetic models. Additionally, adjusted odds ratio showed an increased risk in dominant × dominant (4.15-fold [1.40-12.26]; 95% CI; p = 0.01) and recessive × dominant (2.24-fold [1.25-4.01]; 95% CI; p = 0.02) genotype combinations of the two polymorphisms. In conclusion, our results indicate that NOS3 rs869109213 polymorphism alone or in a combination with EDNRB rs10507875 polymorphism may be associated with DR in Slovenian patients with T2DM.