More HDL questions.
The HDL ("good") cholesterol story isn't as simple as researchers had thought.
Numerous studies have found a higher risk of heart disease in people with low HDL levels (under 40 in men or under 50 in women). However, last year, a trial that raised HDL levels with niacin (2,000 mg a day) failed to lower the risk of heart disease in people who had low HDL and were also taking statins to lower their LDL ("bad") cholesterol (see Jul./Aug. 2011, p. 8).
And in May, Roche Pharmaceuticals halted a trial testing an HDL-raising drug called dalcetrapib after it found no evidence that the drug was curbing the risk of heart attacks. Two other HDL-raising drugs--fenofibrate and torcetrapib--also failed to protect the heart in earlier studies. (Torcetrapib never reached the market.)
Now two new studies suggest that people who have versions of genes that raise their HDL have no lower risk of heart disease than people with other versions of those genes.
Researchers at Harvard University found no lower risk of heart disease in people with HDL-raising versions of an endothelial lipase gene. And Danish researchers found no lower risk in people with HDL-raising versions of the lecithin-cholesterol acyltransferase gene.
"This may suggest that low HDL cholesterol levels per se do not cause" heart attacks, said the Danish scientists. But not everyone is convinced.
"There may be ways of changing HDL that may be protective that we don't know about yet," suggests Frank Sacks, professor of cardiovascular disease prevention at Harvard Medical School. "For example, making the liver produce more HDL might be better than drugs like dalcetrapib and torcetrapib, which keep cholesterol in HDL," he explains.
"That creates a big, overstuffed HDL that may not be able to move cholesterol from cells and tissues to the liver for excretion." Sacks' bottom line: "We don't know much about HDL metabolism in humans."
What to do: Losing excess weight and getting more exercise can raise HDL. HDL or not, there's plenty of reason to do both.
Lancet DOI: 10.1016/S0140-6736(12)60312-2. J. Clin. Endocrinol. Metab. 97: E248, 2012.
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|Title Annotation:||QUICK STUDIES; high density lipoproteins|
|Publication:||Nutrition Action Healthletter|
|Date:||Jul 1, 2012|
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