Study Suggests That Too Much Good Cholesterol Could Be Bad

LEXINGTON, Ky. (AP) - University of Kentucky biochemist Eric J.
Smart thinks for diabetics, having high level of high-density
lipoprotein - commonly known as good cholesterol - could be too
much of a good thing.
Smart, who led a team doing research on high-density
lipoprotein, said having high levels of it in the bloodstream might
increase the risk of cardiovascular disease.
"In fact, it appears that for a person with diabetes, having
high levels of HDL could be counterproductive," Smart said. "It
was an outcome that we completely didn't expect. But I think it's
really profound, because it says that HDL doesn't always have to be
good for you."
That seems to fly in the face of more than 20 years of medical
wisdom, which has held generally that HDL helps protect us from
heart problems.
Reams of medical advice have been written, diets have been
devised, and drugs have been developed around the proposition that
high levels of "good" HDL are desirable, and that levels of
"bad" LDL, or low density lipoprotein, should be kept low.
The University of Kentucky research, reported recently in the
American Journal of Physiology, suggests that scientists have more
work to do on HDL.
Despite his findings, Smart said, people should not try to lower
their HDL levels. Smart directs the Kentucky Pediatric Research
Institute and holds the Barnstable-Brown endowed chair for diabetes
research at the University of Kentucky.
Smart and his team made their discovery while researching HDL
and diabetes over the past year. They found that in people with
diabetes, HDL molecules bind with a natural compound called
myristic acid, which causes the HDL to inhibit the body's natural
production of nitric oxide, a substance known to protect against
cardiovascular disease.
Myristic acid is a long-chain fatty acid suspected of increasing
cardiovascular risk, Smart said.
Smart's team reported that the effect was seen in both men and
women with diabetes. In effect, HDL in diabetics may reverse its
usual role, becoming a potential threat rather than a protector,
the study indicates.
It is still unclear why HDL and myristic acid latch onto each
other in people with diabetes, or exactly how that inhibits nitric
oxide production.
"What we found was that all of the HDL we looked at, whether it
came from people or mice with diabetes, inhibited nitric oxide,"
Smart said. "It was a major surprise to find that it worked the
same way in mice and humans."
Judith Berliner, a professor of medicine and pathology at UCLA,
said the study could help researchers find a way to make HDL work
for diabetics.
"It's a novel finding that this particular fatty acid might be
doing this to HDL," Berliner said. "They don't know what to do
about that now, but I it might allow for some kind of targeting or
intervention to make the HDL more protective."
HDL, along with LDL and triglycerides, are the three lipids that
together make up one's overall cholesterol reading. Scientists say
that HDL gathers up cholesterol in the blood and carries it to the
liver, where it can be excreted from the body.
That helps keep cholesterol levels under control, and it's why
HDL is considered "good." But LDL is thought to deposit
cholesterol in arteries, where it can build up to form plaques that
impede blood flow and may lead to strokes or heart attacks. It's
why LDL has a "bad" reputation.
Next for the researchers, Smart said, is to find out why and how
myristic acid attaches to HDL molecules in diabetics, and where the
compound comes from. Smart says myristic acid is found in many
foods, but said he suspects the body also manufactures it.
"Unfortunately, the way HDL and LDL are presented as good and
bad in the media may give people the impression that we understand
everything, and that if you just lower your LDL you'll be safe. But
we need to know a lot more," Smart said.
Information from: Lexington Herald-Leader,

(Copyright 2007 by The Associated Press. All Rights Reserved.)

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