January 13, 2011

New Cholesterol Measurement

(Ivanhoe Newswire) -- It has been well-known that high levels of high-density lipoprotein (HDL) cholesterol, the "good" kind, are associated with a lower risk of heart disease. Recent studies have asked if pharmacologic increases in HDL cholesterol levels are beneficial to the patient. A new study shows that a different metric, a measure of HDL function called cholesterol efflux capacity, is more closely associated with protection against heart disease than HDL cholesterol levels themselves.

Atherosclerosis typically occurs with a build-up of cholesterol along the artery wall. Cholesterol efflux capacity, an integrated measure of HDL function, is a direct calculation of the efficiency by which a person's HDL removes cholesterol from cholesterol-loaded macrophages (a type of white blood cell) -- the sort that accumulate in arterial plaque.

"Recent scientific findings have directed increasing interest toward the concept that measures of the function of HDL, rather than simply its level in the blood, might be more important to assessing cardiovascular risk and evaluating new HDL-targeted therapies," Daniel J. Rader, M.D., director of Preventive Cardiology at Penn., was quoted as saying. "Our study is the first to relate a measure of HDL function -- its ability to remove cholesterol from macrophages -- to measures of cardiovascular disease in a large number of people."

In this study, Rader and colleagues at Penn measured cholesterol efflux capacity in 203 healthy volunteers who underwent assessment of carotid artery intima-media thickness, which is a measure of arthrosclerosis. There were 442 patients with confirmed coronary artery disease and 351 patients without such confirmed disease.

An inverse relationship was seen between cholesterol efflux capacity and carotid intima-media thickness both before and after adjustment for the HDL cholesterol level. After an age- and gender-adjusted analysis, increasing efflux capacity conferred decreased likelihood of having coronary artery disease. This relationship remained after the addition of traditional cardiovascular risk factors, including HDL cholesterol levels, as covariates. Additionally, men and current smokers had decreased efflux capacity.

"The findings from this study support the concept that measurement of HDL function provides information beyond that of HDL level and suggests the potential for wider use of this measure of HDL function in the assessment of new HDL therapies," Rader said. "Future studies may prove fruitful in elucidating additional HDL components that determine cholesterol efflux capacity."

SOURCE: New England Journal of Medicine, published online January 11, 2011