June 10, 2009
Overlooked Form Of Cholesterol Linked To Heart Attack Risk
Danish scientists reported the strongest evidence yet that an often-ignored form of cholesterol can cause heart attacks, Reuters reported.
They found that heart attacks are more common in people with higher levels of a little-understood form of cholesterol called lipoprotein (a), which varies up to a thousand fold from one person to another.
While millions of people take statins to cut heart attack and stroke risk, it does not affect lipoprotein (a).
But Borge Nordestgaard of Copenhagen University Hospital, who led the study, said the findings might encourage the development of new cholesterol-lowering drugs.
People with the highest lipoprotein (a) levels were two to three times more likely to have a heart attack than those with the lowest levels, according to the research published in the Journal of the American Medical Association.
Nordestgaard said the study has shown that lipoprotein (a) is causing heart attacks.
Lipoprotein (a) is one of several forms of cholesterol found in the blood, with levels determined almost entirely by genetics.
Low-density lipoprotein, commonly known as "bad" cholesterol, can be lowered with the use of statins such as top-selling brands like Pfizer's Lipitor, known chemically as atorvastatin, and AstraZeneca's Crestor, or rosuvastatin.
Nordestgaard said the study might explain why statins don't work for some people.
The Danish team analyzed the genes of 45,000 men and women who gave blood samples for a large national survey starting in 1976. They tested their lipoprotein (a) levels and then followed them until 2007 in order to gain more perspective into lipoprotein (a)'s role in heart attacks.
The study found that people with the highest levels of this cholesterol had the most heart attacks, and one specific genetic variation accounted for about a quarter of the cases of high lipoprotein (a).
Nordestgaard said lipoprotein (a) has been around for a long time as a risk factor, but many people never took it too seriously because they didn't think it caused heart attacks.
"Now we show that, like LDL, it is causing heart attacks," he added.
He noted one problem was that people have little control over the cholesterol, in which levels can vary up to a thousand-fold among certain people.
The vitamin niacin is often prescribed generically in order to lower cholesterol, but it also lowers lipoprotein (a) levels. However, it can cause uncomfortable flushing. Aspirin is also said to lower lipoprotein (a) levels.
A drug called Tredaptive that is marketed in Europe by Merck & Co combines niacin with an anti-flushing agent, but U.S. health regulators have rejected the drug.
Hopefully, the study will spur drugmakers to begin work on a new drug specifically aimed at lipoprotein (a) levels, Nordestgaard said.
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