The role of NOS2A −954G/C and vascular endothelial growth factor +936C/T polymorphisms in type 2 diabetes mellitus and diabetic nonproliferative retinopathy risk management

Type 2 diabetes mellitus (T2DM) remains one of the major health problems in Europe. Retinopathy is one of the major causes of morbidity in T2DM, strongly influencing the evolution and prognosis of these patients. In the last 2 decades, several studies have been conducted to identify the possible genetic susceptibility factors involved in the pathogenesis of the disease. However, there is little data related to the involvement of vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) gene polymorphisms in the T2DM Caucasian population. The objective of this study was to identify a possible connection between NOS2A -954G/C (rs2297518) and VEGF +936C/T (rs3025039) polymorphisms and the risk of developing T2DM and nonproliferative diabetic retinopathy in a Caucasian population group. We investigated 200 patients diagnosed with T2DM and 208 controls. Genotypes were determined by multiplex polymerase chain reaction-restriction fragment length polymorphism. Statistical and comparative analyses (Fisher's exact test) for dominant and recessive models of NOS2A -954G/C and VEGF +936C/T polymorphisms revealed an increased risk of T2DM (χ (2)=8.14, phi =0.141, P=0.004, odds ratio [OR] =2.795, 95% confidence interval [CI] =1.347-5.801; χ (2)=18.814, phi =0.215, P<0.001, OR =2.59, 95% CI =1.675-4.006, respectively). Also, comparative analysis for the recessive model (using Pearson's chi-square test [χ (2)] and the phi coefficient [phi]) reveals that the variant CC genotype of NOS2A gene is more frequently associated with T2DM without retinopathy (χ (2)=3.835, phi =-0.138, P=0.05, OR =0.447, 95% CI =0.197-1.015). In conclusion, the results of the study place VEGF +936C/T polymorphisms among the genetic risk factor for T2DM, whereas NOS2A -954G/C polymorphisms act like a protective individual factor for nonproliferative retinopathy.