Abstract 274: HDL-Mediated Cellular Cholesterol Efflux in Patients with Severe Carotid Atherosclerosis
The objective of this study was to examine the function of high-density lipoproteins (HDL) in patients with severe carotid atherosclerosis undergoing carotid endarterectomy (CEA) and in patients with coronary artery disease (CAD).
We examined clinical, biochemical and lipoprotein profiles and HDL cholesterol efflux capacity (CEC) in 155 patients undergoing CEA and compared the results with patients with an acute coronary syndrome (ACS time 0 n=26) measured within 48 hours of the event, and again at 12 weeks (ACS recovery, n=26), in patients with chronic, stable CAD (sCAD) n=27 and in healthy controls. There were 110 men (71%) and 45 women (29%) with a mean age 69±10 years in the CEA group. Mean HDL-C was 0.96±0.26 mmol/L (38±10 mg/dL). There were no significant differences in HDL-C between CEA, ACS and sCAD subjects.
HDL was obtained after depletion of apo B-containing lipoproteins with PEG precipitation. Cellular efflux capacity was determined by incubating HDL in cAMP-stimulated J774 mouse peritoneal macrophages for 6 hours. Specific cholesterol efflux was obtained by subtracting total efflux from efflux in non-cAMP stimulated cells. The procedure was standardized to enable medium throughput. Coefficient of variability was approximately 5%.
HDL from CEA patients differ in its ability to promote cholesterol efflux. The range of CEC observed was: min 14.7%, max 34.0% mean 22.4±0.6%; (IQR 18.9-27.3% median 22.0). We found a weak correlation between HDL-C and CEC in patients CEA (r= 0.20, P=0.012); a significant correlation was found between apo A-I and CEC (r=0.23, P=0.005). Subjects with similar HDL-C or apoA-I differed in their ability to promote cellular cholesterol efflux, suggesting that the HDL-C mass does not reflect functionality. We found similar CEC in patients with CAD and ACS recovery.
Here, we report that patients with severe carotid atherosclerosis have low HDL-C and a CEC similar to that observed in CAD patients. The function of HDL to promote cellular cholesterol efflux, as determined by CEC, varied over a wide range and was only weakly correlated with HDL-C. The significant correlation between apo AI and CEC suggests that HDL particle size -and composition may also be an important determinant of the ability to promote cellular cholesterol efflux.
- © 2013 by American Heart Association, Inc.