Abstract 436: Macrophage-Specific Cholesterol Efflux Capacity as a Biomarker for High-Density Lipoprotein Function: Comparison of Isotopic Versus Fluorometric Methods for High-Throughput Assessment

Abstract

Background: Cholesterol efflux capacity (CEC) is emerging as a novel cardiovascular biomarker of HDL function. To facilitate large-scale human studies, we analyzed analytical performance of CEC and compared a high-throughput fluorometric method with the standard isotopic method. Methods: CEC was assessed in J774 cells with either 3 H-cholesterol (isotopic) or BODIPY-cholesterol (fluorometric) to 2.8% apo B-depleted plasma over 4h. Three cohorts were studied: 22 healthy men and women, 38 patients with premature coronary heart disease (CHD) and 196 subjects selected from the Dallas Heart Study (DHS), a population-based study of Dallas county residents. All samples were stored greater than 1 year prior to measurement. Results: In healthy subjects (A-B), CEC by both methods did not show diurnal or weekly variation or changes with prandial status, or one freeze/thaw cycle. However, storage at -20 o C resulted in lower CEC compared to storage at -80 o C (p=0.02). CEC by both methods was similarly decreased in patients with CHD compared to healthy controls (p=0.06). In 212 DHS subjects, CEC for the two methods were correlated with each other (r=0.54, p<0.0001) but had differential correlations with HDL-C and HDL-P (figure). Conclusions: CEC to apo B-depleted human plasma is not influenced by timing of sampling or storage conditions, with the exception of storage at -20 o C. A 96-well high-throughput fluorometric method using BODIPY-cholesterol exhibited similar performance characteristics as the standard isotopic method with differing correlations with HDL composition and may therefore be advantageous in large scale human studies.