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 H-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 H-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 microg/mL; 34 +/- 4.3% (C) and 31.9 +/- 6.6% (CD) with 50 micro g/mL and 39.5 +/- 3.5% (C) and 37.1 +/- 4.4% (CAD) with 100 micro g/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.