Isolation of LDL Subfractions and Their Susceptibility to Oxidation as a Risk Factor for Coronary Artery Diseases

Abstract

Background and Objectives: Oxidation of low-density lipoprotein (LDL) is now widely accepted as a key event in the development of atherosclerosis. Oxidative modification of LDL leads to enhanced uptake by the macrophage receptor in the arterial wall, resulting in an accumulation of lipid within the cytoplasm of the cell. The resulting foam cell formation is a perquisite step in the development of the atherosclerotic plaque. Human plasma LDL comprises mainly three subfractions, varying in size and density and chemical composition. The aim of present study was to evaluate and compare of susceptibility to oxidation of three LDL subfractions in coronary heart disease (CHD) patients and control group as risk factor in diagnosis of CHD. Material and Methods: The study group consisted of 60 men [mean age (477)] with suspected CHD undergoing coronary angiography and the control group consisted of 60 men [mean age (449)] that had no any history for atherosclerosis or CHD. Cholesterol and triglyceride concentration were measured by enzymatic methods. LDL subfractions were isolated by density gradient ultracentrifugation and susceptibility to oxidation were studied by Cu2+ in the 234 nm absorbing oxidation products. Results: Three LDL subfractions were isolated from plasma by density gradient ultracentrifugation. The kinetics of the oxidation of subfractions were preformed in the presence of Cu2+ in the 234nm absorption. Comparing of lag time in study groups were showed that the lag time of LDL1 (p(0.0001), LDL2 (p<0.0001) and LDL3 (p<0.0001) were significantly reduced in patients group, and a significant correlation between cholesterol with LDL2, LDL3 lag time in control and patient groups (r=-0.329, p<0.05 and r=0.453, p<0.01 respectively) and also triglyceride in both groups were found (r=-0.407, p<0.001 and r=-0.830, p<0.01 respectively). Conclusion: These finding could be explain of the arising atherogenesity from LDL1 to LDL3 in both patient and control groups and also indicate that susceptivility to oxidation in patients group is more talented than control group. These results suggest that measurment of susceptibility to oxidation of LDL subfractions could be a useful laboratory technique for predicate of premature CHD.