Shao, Baohai

Rationale: Coronary endothelial dysfunction (ED)—an early marker of atherosclerosis—increases the risk of cardiovascular events. Objective: We tested the hypothesis that cholesterol efflux capacity and high-density lipoprotein (HDL) particle concentration predict coronary ED better than HDL-cholesterol (HDL-C). Methods and Results: We studied 80 subjects with nonobstructive (<30% stenosis) coronary artery disease. ED was defined as <50% change in coronary blood flow in response to intracoronary infusions of acetylcholine during diagnostic coronary angiography. Cholesterol efflux capacity and HDL particle concentration (HDL-P IMA ) were assessed with validated assays. Cholesterol efflux capacity and HDL-P IMA were both strong, inverse predictors of ED ( P <0.001 and 0.005, respectively). In contrast, HDL-C and other traditional lipid risk factors did not differ significantly between control and ED subjects. Large HDL particles were markedly decreased in ED subjects (33%; P =0.005). After correction for HDL-C, both efflux capacity and HDL-P IMA remained significant predictors of ED status. HDL-P IMA explained cholesterol efflux capacity more effectively than HDL-C ( r =0.54 and 0.36, respectively). The efflux capacities of isolated HDL and serum HDL correlated strongly ( r =0.49). Conclusions: Cholesterol efflux capacity and HDL-P IMA are reduced in subjects with coronary ED, independently of HDL-C. Alterations in HDL-P IMA and HDL itself account for a much larger fraction of the variation in cholesterol efflux capacity than does HDL-C. A selective decrease in large HDL particles may contribute to impaired cholesterol efflux capacity in ED subjects. These observations support a role for HDL size, concentration, and function as markers—and perhaps mediators—of coronary atherosclerosis in humans.