Basal serum nitric oxide levels in patients with type 2 diabetes mellitus and different stages of retinopathy

Abstract

Purpose: To compare the basal serum levels of nitric oxide (NO) in patients with type 2 diabetes mellitus and different stages of diabetic retinopathy (DR) with the levels in nondiabetic control subjects. Methods: The 39 patients with type 2 diabetes included in this study were divided by stage of DR into 3 groups: group A, those without DR; group B, those with background/preproliferative DR; and group C, those with proliferative DR. Eleven non-diabetic subjects made up the control group (group D). The NO concentration was determined indirectly by measuring the serum level of nitrite (NO2 -) plus nitrate (NO3 -) (NO x = NO2 - plus NO3 -) using a spectrophotometric method based on the Griess reaction. Results: The patients with type 2 diabetes had significantly higher levels of serum NO x than the nondiabetic controls (p = 0.0001). In addition, the levels in the patients with proliferative DR were significantly higher (p = 0.002) than the levels in the patients with nonproliferative or no DR. Conclusion: Our study demonstrated both elevated levels of serum NOx in diabetic patients as compared with nondiabetic controls and a relationship between NOx and DR severity. Hence, abnormal NO metabolism may have a role in the pathogenesis of DR.