Lipid peroxidation and antioxidant enzyme activities in erythrocytes of type 2 diabetic patients.

BACKGROUND AND OBJECTIVE: Although diabetes mellitus (DM) patients are claimed to be under oxidative stress because of prolonged exposure to hyperglycemia, the influence of glycemic control and cardiovascular complication in diabetes on oxidative stress parameters has not been fully studied. The present study aimed to investigate lipid peroxidation end product (malondialdehyde, MDA) and antioxidant enzymes in fairly controlled type 2 DM (fasting plasma glucose [FPG] < or = 180 mg/dl) or type 2 DM complicated with coronary heart disease (CHD) and poorly controlled type 2 DM (FPG > 180 mg/dl) in comparison to a normal healthy group (FPG < 110 mg/dl).

MATERIAL AND METHOD: MDA and antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) were determined in the red cell of 19 subjects with poorly controlled type 2 DM, 26 subjects with fairly controlled type 2 DM and 20 subjects with type 2 DM complicated with CHD who were matched for age and gender. Twenty healthy subjects with normal plasma glucose level and matched for age and gender were served as a control group. In all groups of DM these oxidative stress parameters were compared to a control group by one-way ANOVA test. Pearson rank correlation coefficient was used to compare the relationship between FPG and oxidative stress status in type 2 DM and normal controls.

RESULTS: The red cell MDA levels were significantly higher in all types of diabetes compared to age-matched normal controls. The mean of red cell MDA level was highest in type 2 DM complicated with CHD. Red cell antioxidant enzyme activities were also significantly increased except for SOD and GPx activities in fairly controlled type 2 DM. The significant positive correlation between oxidative stress status (as MDA and CAT) and FPG was found in poorly controlled type 2 DM and type 2 DM complicated with CHD whereas in fairly controlled type 2 DM the significant positive correlation between CAT and FPG was only observed.

CONCLUSION: These findings strongly confirmed the evidence that diabetic patients were susceptible to oxidative stress and higher blood glucose level had an association with free radical-mediated lipid peroxidation. The highest level of MDA in type 2 DM complicated with CHD suggested that oxidative stress played an important role in the pathogenesis of cardiovascular complication. The results also showed the increase in antioxidant enzymes. These could probably be due to adaptive response to pro-oxidant in diabetic state. Hence, there seems to be imbalance between oxidant and antioxidant systems in type 2 diabetic patients.