Not All 'Good' Cholesterol is Beneficial

Some HDL cholesterol does not protect against cardiovascular disease

(RxWiki News) Most patients are aware that "good" HDL cholesterol can protect against coronary heart disease. However, scientists have found that not all HDL cholesterol benefits the heart, and some may even be harmful.

Harvard School of Public Health researchers have successfully shown that a small protein called apolipoprotein C-III (apoC-III), that at times resides on the surface of high-density lipoprotein (HDL) cholesterol, may increase the risk of heart disease.

HDL cholesterol without the protein may be particularly beneficial, on the other hand.

"Eat oatmeal, beans and other fiber sources to reduce cholesterol."

Frank Sacks, professor of cardiovascular disease prevention at the Harvard School of Public Health and senior author of the study, said that if the finding is confirmed in larger studies, it could lead to a better risk evaluation for heart disease. It also could contribute to finding targets for treatment to increase protective HDL or decrease the unfavorable HDL.

A high level of HDL cholesterol has been shown to indicate a low risk of cardiovascular disease. However, drug trials that attempted to increase HDL have shown mixed results.

Several companies, most recently Roche, have scrapped plans for a drug to boost HDL because trial results did not indicate a benefit.

This has lead investigators to suggest that HDL cholesterol may contain components that are both protective and harmful.

Investigators collected blood samples from 32,826 women in the Brigham and Women's Hospital-based Nurses' Health Study between 1989 and 1990, and 18,225 men in the Health Professionals Follow-up Study between 1993 and 1995.

During a follow-up period that ranged from 10 to 14 years, 634 cases of coronary heart disease were documented. Those patients were compared to others of a similar age, smoking status and blood draw date who did not have heart disease.

Researchers also compared plasma concentrations of total HDL, HDL that has apoC-III, and HDL without apoC-III as predictors of the risk of coronary heart disease. After adjustments for various factors, they found two subclasses of HDL in apparently healthy men and women.

The main type of HDL that does not contain apoC-III was found to be protective against coronary heart disease. But about 13 percent of HDL cholesterol with apoC-III on its surface was linked to a higher risk of heart disease.

Those men and women with the highest concentrations of HDL apoC-III, among the top 20 percent of the population, had a 60 percent increased risk of coronary heart disease.

Researchers said measuring HDL apoC-III and HDL without apoC-III may be the best gauge of heart disease risk or HDL protection.

The study, funded by The National Institutes of Health and the Villum Kann Rasmussen Foundation, was recently published in the Journal of the American Heart Association.

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Review Date: 
May 8, 2012