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Liver key to
extending life
ABC Net, March 18, 2002
Holes in blood vessel walls
deplete: Sample A is from the blood vessel of the liver of a young
rat; Sample B is from an old rat and has few holes. (Pic: D. Le Couteur)
Professor David Le Couteur, of the Centre for Education and Research
in Ageing at Concord Hospital, presented his case at a symposium at Sydney
University on Saturday.
There are many wonderful things about getting older, said Dr Le Couteur,
a geriatrician with a background in clinical pharmacology and toxicology.
"Your mortgage is paid off, your children have moved out, you're not
embarrassed about who you are, and you have the benefit of wisdom and
resilience," he said.
"It would be fine if it wasn't for dementia, arthritis, heart
disease, cancer, and pneumonia. This is why we are actively investigating
new ways to prevent age-related disease."
Professor Le Couteur said that many age-related illnesses were caused
by toxins and fats and that this is where his interest in the liver came
from.
The liver's role in the body is to process blood coming from the gut by
absorbing nutrients, metabolising fats, and processing toxins.
"Previous to our research, the liver was not thought to change much
during ageing, except for shrinking in size," he said.
However Professor Le Couteur and colleague Allan McLean of the
National Ageing Research Institute in Melbourne have discovered that as
the liver ages, its blood vessels also change.
The blood vessels in a healthy liver have tiny holes in their walls to
allow blood going from the gut into the liver to be processed.
Professor Le Couteur and team have found that in rats, baboons, and
humans these tiny holes seem to clog up or disappear as the liver ages.
"This means that fats and toxins can't get processed properly,"
he said. "And it explains a lot of problems."
For example, he said, the fats involved in atherosclerosis — the
build-up on blood vessel walls — float around in the blood because they
are unable to be processed properly in the liver.
In an article due to appear in medical journal The Lancet next
month, Professor Le Couteur argues that the age-related increase in
atherosclerosis is due to these age-related changes in the liver.
Previous research has shown that toxins such as alcohol and
bacteria-derived toxins damage the holes in the blood vessels, but this is
the first time this type of process has been related to diseases of
ageing.
"Rather than simply using drugs to treat Alzheimer's and heart
disease, we could be using a broader range of interventions targeted at
the liver instead," Professor Le Couteur said.
His team is exploring avenues such as reducing food intake, using
antioxidants designed to work specifically in the liver at time of
digestion, improving blood flow to the liver, and using substances that
return the healthy holes in liver blood vessels.
Interestingly, alcohol is one such substance that helps to punch holes in
the liver blood vessels — which could explain the so-called 'wine
paradox'. Alcohol in moderation is beneficial to health but too much is
bad.
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