It was too good to be true. Cholesterol was "Bad" once upon a time and
then it became "Bad" LDL cholesteroland "Good" HDL cholesterol.
Then it was determined that not all LDL was equally "Bad", it depended
on more chemical details than previously considered.
Now, Not all "GOOD" HDL cholesterol is actually "GOOD". It depends on
more chemical details than previously considered.
Good science strives to be as simple as possible, but the constant
caution is to not become overly simple.
The story of Cholesterol appears to be constantly fighting drastic
oversimplifications, as well as other forms of politicized science.
Eventually, researchers will get it right.
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http://www.eurekalert.org/pub_releases/2007-08/cfta-nrs081407.php
New review suggests caution on drugs to raise 'good' cholesterol
Public release date: 14-Aug-2007
With 40 percent of all heart attacks and related cardiovascular problems
occurring in people who have low levels of so-called �good� cholesterol,
researchers have long sought medications to increase the amount of this
type of cholesterol in the body�s circulation.
But a new review of 31 randomized controlled trials published in the
Journal of the American Medical Association suggests that so far, only
modest evidence supports the use of most medications to raise levels of
high-density lipoprotein (HDL) � good cholesterol. Some are even harmful.
The authors concluded that while efforts to lower low-density
lipoprotein (LDL or �bad cholesterol�) �have consistently reduced
cardiovascular disease risk, HDL-based approaches are much more complex
and sometimes disappointing.� As a result, �the primary focus should be
on LDL,� said review co-author Mehdi Shishehbor, D.O., of the Cleveland
Clinic.
�The news is that not everything that raises HDL will be beneficial,�
said Ronald Krauss, M.D., spokesman for the American Heart Association
and director of atherosclerosis research at Children's Hospital Oakland
Research Institute in California.
�HDL is a much more complicated issue than LDL,� said Prediman Shah,
M.D., director of the Atherosclerosis Research Center at Cedars-Sinai
Medical Center in Los Angeles. �It�s not only important how much HDL
there is, but what kind it is. Quality is as important as quantity. Is
the function good or is it [a form of HDL] that doesn�t do the job
properly"�
There are many types of HDL, not all of which nurture the heart and
blood vessels. The good kinds seem to carry fat out of arteries to the
liver and perform functions in cell membranes and elsewhere. However,
HDLs vary considerably in size, density and other chemical properties
that change their ability to sustain health.
Certain kinds of HDL could even increase inflammation, clogging arteries
rather than clearing them, and doctors currently do not have a simple
way to tell this �bad� type of �good� cholesterol from the genuinely
beneficial kind in their patients. Right now, only expensive tests used
in research settings can sort this out.
Fortunately, lifestyle changes can help without negative side effects,
according to the review. �The safest way to raise HDL is by weight loss,
exercise and smoking cessation,� Shishehbor said.
The review also found support for moderate alcohol use � one or two
drinks a day for men, one for women � although physicians do not
recommend that nondrinkers take up drinking to protect their hearts.
Raising HDL by eating fish or taking fish oil to increase intake of
omega-3 fatty acids is another effective strategy, the review suggested.
As for pharmacological approaches, the review found that the most
effective currently available drug to raise HDL is the vitamin niacin,
taken in high doses. �Statins, niacin and fibrates are available
pharmacologic agents that increase HDL; however, they may be associated
with adverse side effects,� said Shishehbor, who recommended close
medical supervision.
At least one-third of patients cannot tolerate high-dose niacin,
according to Shah. �The most common side effect is flushing and itching
that drives some people nuts.� He said methods exist to minimize the
problem, but they do not work for everyone.
Meanwhile, new medications have proved disappointing. Trials of one
drug, torcetrapib, ended abruptly because the drug increased mortality
risk and raised blood pressure. The class of diabetes drugs called
thiazolidinediones (which include Avandia and Actos) increase HDL, but
also seem to raise the risk of cardiovascular problems.
The once highly touted weight-loss drug rimonabant, which blocks the
brain receptors activated by marijuana, does raise HDL; however, the
U.S. Food and Drug Administration recently refused to approve it because
it also seems to elevate risk for psychiatric problems like depression.
�I�m much more excited about the prospect of what�s coming in this area
in the next three to five years,� said Shah, who is studying approaches
to boosting HDL that use different mechanisms from those that have been
associated with problems. Clinical trials of a gene therapy based on his
research are currently under way.
�Despite the recent negative HDL trials, this field is extremely
exciting and the pace of discovery is unbelievably fast,� Shishehbor
said. At least one other drug with a novel mechanism of action is also
in trials � and at least three other approaches have led to new drugs in
the pipeline.
People with blood levels of HDL lower than 35 mg/dL have eight times the
risk of heart disease compared to those with 65mg/dL or more. Some 16
percent to 18 percent of men have low levels, compared with 3 percent to
6 percent of women.
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Contact: Lisa Esposito
[email hidden]
Center for the Advancement of Health