Not all HDL cholesterol ‘good’ for your heart
MedWire News: High-density lipoprotein (HDL) cholesterol is composed of two subtypes that have opposite associations with coronary heart disease (CHD), show US researchers.
The major subtype of HDL cholesterol, which lacks surface apolipoprotein (apo) C-III, has a protective association with CHD, while the smaller subfraction, which does display surface apoC-III, tends to be associated with increased CHD risk, they report.
"This finding… could lead to better evaluation of risk of heart disease in individuals and to more precise targeting of treatments to raise the protective HDL or lower the unfavorable HDL with apoC-III," said lead author Frank Sacks, from the Harvard School of Public Health, Boston, Massachusetts, in a press statement.
The researchers have previously shown that apoC-III provokes inflammatory and atherogenic responses in cells involved in atherosclerosis. However, although particles exist both with and without apoC-III, little is known about the role of apoC-III in relation to HDL function or CHD risk, they explain.
For the current research, Sacks and colleagues therefore compared plasma concentrations of total HDL, HDL with apoC-III, and HDL without apoC-III as predictors for CHD risk in two prospective studies of men and women who were initially free of CHD.
They measured HDL cholesterol in the plasma of 572 participants from the Nurses' Health Study and 699 participants from the Health Professionals Follow-Up Study. Plasma HDL cholesterol was then separated according to the presence or absence of apoC-III.
Baseline blood samples were obtained between 1990 and 1995 and participants were followed up for incident CHD, defined as a diagnosis of nonfatal myocardial infarction or fatal CHD, for 10-14 years.
The researchers report that total HDL cholesterol was inversely associated with risk for CHD among the participants. There was a 22% decrease in CHD risk per standard deviation (SD) in total HDL cholesterol
However, individuals who developed CHD had significantly lower levels of HDL cholesterol that lacked apoC-III than those who did not develop CHD, at mean baseline concentrations of 1.52 mmol/L versus 1.64 mmol/L, respectively.
As reported in the Journal of the American Heart Association, multivariate analysis revealed that the two HDL cholesterol subtypes had opposing associations with CHD risk.
Each SD increase in HDL without apoC-III (0.53 mmol/L) was associated with a significant 34% decrease in risk for incident CHD while each SD increase in HDL with apoC-III (0.07 mmol/L) was associated with an 18% increase in risk for incident CHD.
"Our findings highlight that HDL comprises a group of particles that may be more or less closely linked with atherosclerosis," write Sacks et al.
"This may have implications for future development of novel therapeutic interventions aimed at HDL elevation as the cardioprotective benefits may differ depending on the affected HDL subfraction," they conclude.
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By Sally Robertson