Correlation analysis of plasma high-density lipoprotein subfractions and coronary heart disease in the elderly with type 2 diatetes mellitus

Objective To evaluate whether one or both of the major high-density lipoprotein(HDL) subfractions(HDL_2,HDL_3) is strongly associated with the risk of coronary heart disease(CHD) in the elderly with type 2 diabetes mellitus(DM). Methods The separation of HDL subfractions was carried out by ultracentrifugation in a Beckman Airfuge.HDL_3 subclass was isolated from the supernatant and its cholesterol content was measured by dextran sulfate-magnesium chloride technique.Plasma HDL_2 cholesterol was calculated as the difference between the results for total HDL cholesterol and HDL_3 cholesterol. Results Type 2 DM patients with CHD had significantly lower HDL_3 cholesterol levels comparing to either the control [(0.32±0.17) mmol/L versus(0.54±0.25) mmol/L,P0.001] or CHD patients without DM [(0.32±0.17) mmol/L versus(0.42(±0.16)) mmol/L,P0.05],while HDL_2 cholesterol levels were not significantly reduced.In the diabetic patients with CHD,there were statistically significant decrease in HDL cholesterol [(1.04±0.30) mmol/L versus(1.24(±0.32)) mmol/L,P0.05] and HDL_3 cholesterol [(0.32±0.17) mmol/L versus(0.47±0.16) mmol/L,P(0.01)] in comparison to the diabetic patients without CHD,while HDL_2 cholesterol levels were [(0.72(±0.30) mmol/L) versus(0.77±0.28) mmol/L,P0.05] unaltered.The partial correlation analysis indicated that CHD correlated significantly with HDL_3 cholesterol(r=-0.301,P=0.030),but not with HDL cholesterol(r=(-0.154),P=0.274) and HDL_2 cholesterol(r=-0.014,P=0.924). Conclusions HDL_3 is the more variable subclass and reflects changes in HDL.This suggests that the protective role of total HDL against coronary artery disease is mainly mediated through HDL_3 fraction.Therefore,HDL_3 might be a better predictor of coronary heart disease than the total HDL and HDL_2 in the elderly with type 2 diatetes mellitus.