Vaccine may target obesity in the future: researchers
- From: "Tiger Lily" <me@xxxxxxxxxxx>
- Date: Fri, 21 Oct 2005 15:32:38 -0600
Vaccine may target obesity in the future:
researchers
Oct 18 2:34 PM US/Eastern
When babies receive shots against diseases like
polio and measles, their vaccinations may in the
future include protection against getting fat,
according to researchers.
Infection by certain pathogens triggers rapid
increases in fatty tissue in animals, Nikhil
Dhurnadha told the annual meeting of NAASO, the
Obesity Society, in this western Canadian city.
At the same time, the discovery that many more
obese people than normal-weight people have been
exposed to a certain virus suggests a link between
obesity and viral infection.
"Not all obesity can be explained by infection,"
said Dhurandhar, of the Pennington Biomedial
Research Center at Louisiana State University in
Baton Rouge. "Infections can be one of the
causes."
Popular opinion has long held that most obesity is
caused simply by overeating, underexercise and a
lack of will power. But viruses are just one of
many contributing factors that scientists have
recently discovered.
Researchers are reporting at the conference on
other fat triggers that include a genetic tendency
to store fat among groups whose ancestors survived
famines, medications such as treatments for
psychotic mental disorders, toxins in the
environment like organochlorines, and infectious
agents like bacteria, viruses and prions.
"Obesity is multifactoral," Dhurandhar told
scientists at the conference.
In an interview with AFP, he said there is proof
that at least 10 different pathogens cause obesity
in animals. They include canine distemper virus,
RAV7 and MAM1 avian viruses, the Borna virus in
rats -- which is also linked with depression in
humans, types of scrapie, three adeno viruses
including AD5, AD36 and AD37 which cause fat gain
in several species, and chlamydia pneumonae
bacteria.
Scientists have also found that when mice are
infected by general bacteria from the guts of
other mice, the recipients body fat increases.
Dhurandhar became interested in viral causes of
obesity while working as a family physician in
Bombay in the 1980s, during a severe outbreak of
SMAM1, an adeno virus that kills chickens.
A friend noticed that the dead chickens were
unusually fat, with enlarged livers, kidneys, low
cholesterol levels and an atrophied thymus gland.
Dhurandhar wondered how the virus affected people.
He tested his own patients, and found 20 per cent
of his obese patients had been exposed to SMAM1,
and that those people were significantly heavier
with lower cholesterol levels.
He moved to the United States to conduct more
research, and started working with Richard
Atkinson at the University of Wisconsin. Because
US authorities refused permission to import the
Indian avian virus, the pair decided to work with
adeno virus AD36.
First, they infected laboratory chickens, mice and
monkeys, all of which grew significantly fatter
and had lower cholesterol.
Then, because they could not test the virus on
humans, they examined stored blood from 500 people
in Wisconsin, Florida and New York. They found
antibodies for AD36 in 30 per cent of the obese
people, but only in 11 per cent of people with
normal body weight.
And, just as Dhurandhar earlier discovered among
his Indian patients, the obese who had been
exposed to the virus were 20 per cent heavier than
other overweight people.
Further tests on tissue from lab monkeys taken
over a nine-year period showed that healthy
monkeys newly infected by AD36 "gained 15 per cent
body weight in six months, and dropped their
cholesterol by 30 per cent."
The scientists also studied 26 pairs of twins, and
found that in cases where one twin had been
exposed to AD36, in all cases their weight was
significantly greater.
"In 10 years, people may be able to walk into a
clinic and be told that their obesity is due to X
cause, such as genes, the endocrine system, or
pathogens. That may have a more productive outcome
than a blanket treatment right now, (which) is not
very successful," said Dhurandhar.
And because viruses are hard or impossible to
treat, he said, prevention through vaccines will
be key.
.
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