August 20, 2007 / 7:54 PM / 12 years ago

Too fat? Common virus may be to blame: study

CHICAGO (Reuters) - A common virus caused human adult stem cells to turn into fat cells and could explain why some people become obese, U.S. researchers said on Monday.

An overweight pedestrian sits on a wall outside the Houses of Parliament in London in this March 31, 2004 file photo. A common virus caused human adult stem cells to turn into fat cells and could explain why some people become obese, U.S. researchers said on Monday. REUTERS/Toby Melville/Files

The research builds on prior studies of adenovirus-36 — a common cause of respiratory and eye infections — and it may lead to an obesity vaccine, they said.

“We’re not talking about preventing all types of obesity, but if it is caused by this virus in humans, we want a vaccine to prevent this,” said Nikhil Dhurandhar, an associate professor at Pennington Biomedical Research Center at Louisiana State University System.

The virus adenovirus-36 or Ad-36, caused animals to pack on the pounds in lab experiments. “These animals accumulated a lot of fat,” Dhurandhar said in a telephone interview.

Dhurandhar also has shown that obese people were three times more likely to have been infected with Ad-36 than thin people in a large study of humans.

Now, researchers in Dhurandhar’s lab have shown that exposure to the virus caused adult human stem cells to turn into fat-storing cells.

Dr. Magdalena Pasarica, who led the study, obtained adult stem cells from fat tissue of people who had undergone liposuction. Stem cells are a type of master cell that exist in an immature form and give rise to more specialized cells.

Half of the stem cells were exposed to the virus Ad-36. After a week, most of the infected stem cells developed into fat cells, while the uninfected cells were unchanged.

Pasarica presented her findings at a meeting of the American Chemical Society in Boston.

“The virus appears to change their commitment to a fat storing cell,” Dhurandhar said, adding that Ad-36 is just one of 10 pathogens linked to obesity and that more may be out there.

He acknowledged that some people might find it hard to believe that a virus could be responsible for obesity.

“Certainly overeating has something to do with gaining weight. No doubt about that. But that is not the whole truth,” Dhurandhar said. “There are multiple causes of obesity. They range from simple overeating to genes to metabolism and perhaps viruses and infections.”

Long term, he said he hoped to develop a vaccine and perhaps treatments for the virus. But first, he and colleagues need to better understand the role of Ad-36 in human obesity, he said.

Globally, around 400 million people are obese, including 20 million children under age 5, according to the World Health Organization.

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