Abstract 16815: Cholesterol Efflux Capcity in Genetic Forms of HDL Deficiency
Objective: High-density lipoprotein cholesterol (HDL-C) deficiency is the most frequent lipoprotein abnormality in patients with premature coronary artery disease. In order to determine the functionality of HDL particles in genetically defined HDL deficiency (<5th percentile), we employed a cell-based assay to examine ABCA1-dependent cholesterol efflux capacity in apoB-depleted plasma isolated from 19 probands of French Canadian descent. First degree relatives with normal HDL levels served as controls.
Methods and Results: We determined the ability of apoB-depleted plasma to promote cholesterol efflux from [3H] cholesterol-labeled, cAMP-stimulated J774 macrophages. Cases consisted of 16 ABCA1 heterozygotes, and three APOA1 E136X heterozygotes. We obtained evidence that ApoB-depleted plasma isolated from subjects with genetic forms of HDL deficiency had significantly reduced levels of ABCA1-mediated cholesterol efflux as compared to sibling controls (72.33 %). Conversely, when normalized to apoA-I levels, the efflux capacity of apoB-depleted plasma from subjects was attenuated as compared to sibling controls.
Linear regression was used to determine which biochemical measurement (apoA-I concentration, HDL-C level and HDL subfractions quantified by 2DPAGGE) best explained the cholesterol efflux results. A strong, positive correlation was found between cholesterol efflux measurements and apoA-I levels, HDL-C levels, alpha-2 HDL levels, and alpha-3 HDL levels (all p< 0.05). However, HDL-C levels only explained approximately 27% of the variability in cellular cholesterol efflux, suggesting that efflux capacity may help better understand HDL functionality.
Conclusion: While HDL obtained from subjects with ABCA1 or APOA1 gene defects had decreased cellular cholesterol efflux compared with sibling controls, this difference was markedly attenuated when corrected for apoA-I mass, suggesting that such particles remain functional in cholesterol efflux through ABCA1.
- © 2011 by American Heart Association, Inc.