Reduced Antioxidant Potential of LDL Is Associated With Increased Susceptibility to LDL Peroxidation in Type II Diabetic Patients

BACKGROUND: Type II diabetes mellitus is a complex heterogeneous group of metabolic conditions characterized by an increased level of blood glucose, due to impairment in insulin action and/or insulin secretion. Hyperglycemia is a major factor in the pathogenesis of atherosclerosis in diabetes. Oxidative modification of low density lipoprotein (LDL) is recognized as one of the major processes involved in the early stages of atherosclerosis in type II diabetes. LDL contains different antioxidants, which increase LDL resistance against oxidative modification, this is known as its antioxidant potential (AOP). OBJECTIVES: The present study has been carried out to investigate the sensitivity of LDL to oxidation, AOP of LDL and to assess whether hyperglycemia in diabetes mellitus is associated with increased LDL oxidizability, and whether these relationships are related to diabetic complications. PATIENTS AND METHODS: This study was carried out on 100 diabetic subjects, divided into two groups according to their glycosylated hemoglobin (HbA1c) values, either regulated ( < 0.50 M hexose/ M Hb) or unregulated ( > 0.50 M hexose/ M Hb.) A further 50 healthy subjects were included to determine the sensitivity of LDL oxidation and measurement of LDL AOP. LDL from the serum sample was precipitated by the heparin-citrate precipitation method. The LDL fractions were exposed to oxidation with copper sulphate and their sensitivity to oxidation was evaluated. AOP was measured by taking measurements from 30 subjects in each group. RESULTS: The sensitivity of LDL oxidation was significantly higher in both diabetic groups compared to the control group. AOP was significantly decreased in all diabetic groups compared to the control group. CONCLUSIONS: In type II diabetes, the increased susceptibility of LDL to oxidation is related to hyperglycemia and low AOP.