Here's another way to get rid of cholesterol
Reported August 17, 2010
Good news for cholesterol fearing people— there is more than one way to get rid
Mark Brown of Wake Forest University School of Medicine said that "cholesterol
really can't be broken down.”
To get rid of it, it must be excreted, and now Brown and his colleagues have new
evidence for an alternate way to deliver cholesterol into the faeces.
The findings revise scientific dogma about cholesterol loss that goes back
almost 40 years.
Textbooks say that white blood cells known as macrophages gobble up cholesterol
from artery walls.
That cholesterol is then delivered to high-density lipoprotein [HDL, aka good
cholesterol], which takes it back to the liver where it goes into bile.
"Bile is necessary under the model to deliver cholesterol to the intestine,"
In fact, studies in dogs unable to get cholesterol into bile showed that the
animals actually experienced an increase in cholesterol loss.
And recent studies in mice showed a similar thing.
Researchers said that an alternative pathway has largely been ignored, and thus
scientists have made very little progress in defining the molecular pathways and
Now, Brown and his colleagues offer new evidence that helps support and clarify
this alternate path for cholesterol.
They report that mice made unable to secrete cholesterol into bile through
genetic manipulation or surgery still lose cholesterol through the faeces at a
Macrophages in those animals also continued to take up cholesterol from blood
The researchers believe that alternate path delivers cholesterol from the liver
to the intestine directly through the bloodstream.
"The classic view of reverse cholesterol transport involved the delivery of
peripheral cholesterol via HDL to the liver for secretion into bile. In
parallel, we believe that the liver also plays a gatekeeper role for nonbiliary
fecal sterol loss by repackaging peripheral cholesterol into nascent plasma
lipoproteins that are destined for subsequent intestinal delivery," wrote the
For the purposes of cholesterol-lowering drug discovery, it may prove fruitful
to consider those two pathways as "separate and complementary," said Brown.
The study is published in the July issue of Cell Metabolism.