Viruses may be fattening

Sterlingdog

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« on: January 30, 2006, 11:54:26 PM »

Viruses May Be Fattening

Scientists find evidence to suggest viral infection may be cause of human obesity.
January 30, 2006

For years, scientists have wondered whether viruses should shoulder some responsibility for the wave of obesity sweeping the planet. On Monday, a U.S. medical journal released a study establishing such a link in chickens.

In all of human history, obesity stands alone among chronic diseases for the rapidity of its spread. In fact, the pattern of its quick rise looks very much like that of an infectious disease epidemic.

Six viruses have already been shown to produce obesity in animals, but University of Wisconsin, Madison scientists have now shown that a human virus can cause obesity in chickens, a strong suggestion that it could make people fat, too.

The findings, which implicated a type of adenovirus, were released by the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, which published the study.

?The nearly simultaneous increase in the prevalence of obesity in most countries of the world is difficult to explain by changes in food intake and exercise alone, and suggests that adenoviruses could have contributed,? reads the study.

Potential Vaccine?

With the idea that obesity might be at least in part caused by a virus comes the theoretical potential for a highly lucrative vaccine of great benefit to public health.

About 127 million adults in the United States alone are overweight, with 60 million of these defined as obese, according to the American Obesity Association. The total cost of obesity to the U.S. economy, in 1998 dollars, may have been as much as $78.5 billion, according to the CDC.

The problem also is prevalent in the developing world, where obesity is frequently found alongside starvation. Worldwide there are more than 1 billion overweight adults, of whom at least 300 million of them are obese, according to the World Health Organization.

?There has been an alarming worldwide increase in the prevalence of obesity in the past 30 years,? said Richard L. Atkinson, Professor of Medicine and Nutritional Sciences at the University of Wisconsin.

The prevalence of obesity increased by 30 percent between 1980 and 1990, and by 61 percent between 1990 and 2000.

?This increase is the type of pattern that might occur with a new infectious disease, as has been seen with the AIDS virus,? Dr. Atkinson added.

Chicken Fat

In the study, scientists inoculated three-week-old chickens with three types of human adenovirus. They found that a virus called Ad-37 caused obesity in chickens even though the birds did not eat more.

Another adenovirus, Ad-36, has been linked to obesity in chickens, mice, and primates, and blood samples from obese people show they are much more likely than slim people to carry antibodies for the virus.

?When human twins are discordant for antibodies to Ad-36 antibodies, the antibody-positive twin has a higher body mass index,? reads the journal?s editorial.

The scientists warn that much more research is required in the field, and suggest the ?daunting task? of testing all 50-odd human adenoviruses for their role in obesity would be the first step toward developing a vaccine.


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