Diabetic retinopathy is associated with oxidative stress and mitigation of gene expression of antioxidant enzymes

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.