Abstract 18904: High-denisty Lipoprotein Distribution in Obesity Favors Apolipoprotein E and C-III-containing Subfractions Associated with Risk for Future Coronary Heart Disease

Abstract

Human high-density lipoprotein (HDL) particles are highly heterogeneous in composition. Both the plasma concentration of HDL with apoC-III and the concentration of apoE in HDL predict higher incidence of coronary heart disease (CHD). Little is known about the concentration of HDL apoA-I associated with apoE or apoC-III, whether apoE and apoC-III are present in smaller or larger cholesterol ester-rich HDL, and whether the distribution is affected in obesity. We studied 20 normal weight subjects (BMI 23-25) and 20 obese subjects (BMI 30-35) matched by age (mean age, 51 years). Sixteen distinct HDL subpopulations were separated from plasma samples by first using anti-apoAI, anti-apoE and anti-apoC-III immunoaffinity chromatography in sequence followed by size separation using nondenaturing electrophoresis. The mean HDL-cholesterol and plasma apoA-I concentrations in the normal weight group were 65 and 179mg/dL respectively, compared to 50 and 170mg/dL in the obese group. Mean apoA-I concentrations of HDL fractions without apoE or apoC-III was 160mg/dL in the normal weight group, compared to 136mg/dL in the obese; with apoE only 9 and 12mg/dL respectively; with apoC-III only 7.4 and 14.7 mg/dL; and with both apoE and apoC-III 2.6 and 7.5mg/dL (p<0.01 for a difference in apoA-I concentration and distribution across HDL types). All told, about 10% of HDL apoA-I in normal weight subjects contained apoE, apoC-III or both, compared to 20% in obese subjects. The concentrations of apoE and apoC-III in HDL in the obese were about double that of the normal weight group (p<0.01). In the obese group, the high concentration of HDL with apoE was distributed to small HDL. More so, obese had a higher percent of large HDL containing apoC-III and no apoE. In conclusion, despite similar plasma total apoA-I levels in obese and normal weight groups, the obese had higher concentrations of HDL containing apoE or apoC-III, subfractions which are associated with CHD, whereas the normal weight group had higher concentration of HDL without apoE or apoC-III, a subtraction with protective association against CHD. Mechanistically, the increased presence of apoC-III in large size HDL and apoE in small size HDL in obese may indicate a reduced capacity of HDL for RCT.