Obesity Virus: More, Bigger Fat Cells

adenovirus-36 or Ad-36 --
to human obesity.

Previous
research B showed that nearly 30% of obese people, but only 11% of lean
people, have been infected with Ad-36. Monkeys experimentally infected with
Ad-36 gain significant weight.

Now Dhurandhar's team finds evidence that Ad-36 has a direct effect on human
fat cells. Infection of adult stem cells from human fat triggers their
transition into pre-fat cells. And these virus-infected cells hold much more
fat than normal pre-fat cells.

The end result: more, fatter fat cells.

Dhurandhar colleague Magdalena Pasarica, MD, PhD, presented the findings at
the 234th national meeting of the American Chemical Society, held Aug. 19-23 in
Boston.

"We're not saying that a virus is the only cause of obesity, but this
study provides stronger evidence that some obesity cases may involve viral
infections," Pasarica says in a news release. "We would ultimately like
to identify the underlying factors that predispose some obese people to [the
effects of] this virus and eventually find a way to treat it."

It's not entirely clear how the virus acts on fat stem cells. But Pasarica
reported a major clue: One specific Ad-36 gene, called E4Orfl, is responsible
for the virus's obesity-related effects.

The researchers are now trying to figure out why some people seem to become
obese after Ad-36 infection while others don't.

There are some 50 adenovirus strains. Various strains cause some 5% of
respiratory infections every year, ranging from mild colds to serious
pneumonia. Some of these viruses also cause eye infections. Ad-36 was
originally isolated from a German girl with diabetes; however, it has not been
linked to any specific disease.

A vaccine, used by the military, can prevent some types of adenovirus
infection. However, the adenovirus strains used in this vaccine are very
different from the Ad-36 strain.

Dhurandhar first became interested in obesity-related viruses while working
in India. There he investigated a peculiar phenomenon: Chickens infected with a
deadly avian adenovirus became fatter, not thinner, before they died.

When Dhurandhar moved to the U.S. to pursue his studies, he found that
agriculture authorities were not going to allow him to import the chicken
virus. So he began looking for human adenovirus strains that might have the
same effect. That led to the discovery of the obesity-related effects of
Ad-36.

Interestingly, other researchers have implicated another human adenovirus --
Ad-37 -- in human obesity.

By Daniel DeNoon
Reviewed by Louise Chang
B)2005-2006 WebMD, Inc. All rights reserved