Oxidative stress and proteolytic activity in erythrocytes of diabetic patients

Background: High blood glucose levels induce oxidative stress and decrease antioxidant defenses. Objectives: The present study aims to assess the association, if any, between increase in proteolytic enzyme activities and oxidative stress in diabetic subjects. Patients and Methods: Fifty-one non diabetic patients (33 men, 18 women, mean age 54.47 year) and 53 diabetic patients (39 men, 14 women, mean age 52.92year) were included in the study. Diabetic status was assessed by the fasting blood sugar (FBS) using glucose oxidase method. Oxidant stress was measured by estimating erythrocyte malondialdehyde (MDA) in terms of thiobarbituric acid reacting substance (TBARS). Proteolytic activity was estimated by the amount of amino groups released by the erythrocyte lysate of the diabetic individual using phenylhydrazine treated hemoglobin. Results: Erythrocyte MDA was higher in diabetics (cases) (4.7±1.7 nmoles/gHb) than in controls (3.3±2.2 nmoles/gHb) (p=0.001). Erythrocyte proteolytic activity was also higher in cases (167.2±648 nmoles/gHb) than the controls (27.9±31.7 nmoles/gHb). Conclusions: Both erythrocyte lipid peroxidation and the proteolytic activity in the erythrocyte lysates of diabetic patients was significantly higher in cases than in controls. Diabetes is associated with a significant increase in TBARS, an index of oxidant stress. Proteolytic enzymes degrade many oxidatively altered proteins preventing the accumulation of altered and damaged proteins in the cell.