Cellular cholesterol efflux mediated by HDL isolated from subjects with low HDL levels and coronary artery disease

Abstract

Objective - The aim of this study was to verify whether HDL particles isolated from patients with coronary artery disease (CAD) and low HDL-C had diminished ability to promote cholesterol efflux from cultured cells compared with HDL isolated from subjects without CAD and with normal HDL-C. Methods - Smooth muscle cells isolated from human aortas cultured and radiolabeled with 3H-cholesterol were loaded with cholesterol and incubated with increasing concentrations of HDL isolated from 13 CAD patients with low HDL-C (CAD group) or from 5 controls without CAD (C group). Efflux of cellular cholesterol was measured by cellular depletion of radiolabeled cholesterol and by the appearance of 3H-cholesterol into experimental medium expressed as a percentage of total labeled cholesterol. Results - Cholesterol efflux increased with the amount of HDL present in the medium, and no difference was found between groups at various HDL protein concentrations: efflux was 28 ± 6.3% (C) and 25.5 ± 8.9% (CAD) with 25 μg/mL; 34 ± 4.3% (C) and 31.9 ± 6.6% (CD) with 50 μg/mL and 39.5 ± 3.5% (C) and 37.1 ± 4.4% (CAD) with 100 μg/mL, HDL. Conclusion - Because the HDL fraction of CAD patients with low HDL-C have normal ability to extract cholesterol from cells of the vessel wall, it is suggested that low HDL-C atherogenicity should be ascribed to diminished concentrations of HDL particles rather than to the qualitative properties of the HDL fraction.