Role of redox metals, oxidative protein products and antioxidant potentials of thiols in diabetic retinopathy

Oxidative stress has been proved in the pathogenesis of diabetes mellitus (DM) and diabetic retinopathy (DR) not only by the reactive oxygen species (ROS) but also due to non-enzymatic protein glycosylation, auto-oxidation of glucose, impaired glutathione metabolism, alteration in the antioxidants and advanced oxidative protein product formation. The current study was undertaken to establish the relationship between iron, copper and antioxidants like reduced glutathione (GSH), total thiols, and advanced oxidation protein products (AOPP) as well as total protein and albumin. The study group consisted of a total of 90 subjects which included non-diabetic healthy controls (n=30), diabetes mellitus patients (n=30), and diabetic retinopathy patients (n=30). All the parameters were measured using spectrophotometric methods. AOPP levels showed a very highly significant increase in DR patients and in DM patients compared to normal controls, the AOPP levels being higher in the DR compared to the DM patients (p= 0.001). The levels of thiols showed a very highly significant decrease in DR and DM as compared to normal subjects. The total proteins level showed a very highly significant decrease (P = 0.001) in DR and DM compared to normal. There was no change in the level of albumin. A significant increase in the levels of iron was observed in DR when compared to DM and control. The levels of copper in DR showed a very highly significant increase when compared to DM and controls (p = 0.001). Our study indicates a possible increase in the copper and iron-mediated generation of ROS thereby leading to increased consumption of antioxidants in the body.