Diabetic Retinopathy is Associated with Oxidative Stress and Mitigation of Gene Expression of Antioxidant Enzymes

Abstract
Type 2 diabetes is a metabolic disease associated with serious complications, including diabetic retinopathy (DR). The authors' main aim was to investigate biochemical parameters and the oxidative stress associated with the type 2 DR patients and to study gene expression of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) among patients with DR [DR(+)] compared with a control nondiabetic group. In all, 67 patients with DR included in this study were diabetic for more than 10 years. Among them, 22 patients were DR(+), and 45 patients did not have DR [DR(-)]. The subjects' age range was 14 years to 80 years old with diabetes duration range between 2 and 45 years. Body mass index (BMI) was 31.43 ± 5.94 and 32.33 ± 6.54, systolic blood pressure was 117.15 ± 18.16 mmHg and 126.15 ± 20.26 mmHg, diastolic blood pressure was 81.11 ± 10.55 mmHg and 82.77 ± 10.85 mmHg, HbA1c was 7.2 ± 1.1 and 8.19 ± 1.95, serum total cholesterol was 6.61 ± 1.11 and 4.11 ± 0.31, serum triglycerides were 3.52 ± 0.89 and 3.42 ± 0.79, serum low-density lipoprotein (LDL) was 2.12 ± 0.10 and 2.42 ± 0.15, high-density lipoprotein (HDL) was 2.66 ± 0.30 and 2.55 ± 0.21, SOD was 3.12 ± 0.87 and 1.53 ± 0.14, GPx was 11.14 ± 2.21 and 8.2 ± 1.84, CAT was 26.43 ± 3.34 and 9.60 ± 2.14, for DR(-) and DR(+) patients, respectively. SOD, GPx and CAT polymerase chain reaction (PCR) products of the DR(+) patients revealed the diminished expression of CAT gene followed by GPx and SOD genes. All were significant compared with the normal controls, P < 0.05. Linear regression analysis revealed a strong significant positive correlation between the retinopathy grade and the diastolic blood pressure, diabetes duration, hemoglobin A1c (HA1c)%, and fasting blood glucose (P < 0.001). A marginally significant positive correlation between the retinopathy grade and LDL-cholesterol was observed (P < 0.05), and a significant negative correlation between the retinopathy grade and total cholesterol was observed (P < 0.05). Poor glycemic control and alteration in mRNA gene expression of antioxidant enzymes are strongly associated with development of DR and the regular screening is mandatory for early detection and treatment.

This article was published online in the International Journal of General Medicine and is free to access.