Virus shown to cause obesity
Researchers now have proof that a virus may be involved in human obesity, according to a paper just published in the International Journal of Obesity. A virus had been shown to cause obesity in animal subjects, but the link between the virus and humans remained unproven.
Dr Richard L. Atkinson (Obetech Obesity Research Center, Richmond, VA) and other researchers tested both obese and thin volunteers for antibodies to adenovirus-36—the suspected agent—as well as three other viruses not believed to be linked to obesity. They not only searched for antibodies to the virus, but checked serum lipid (cholesterol and triglyceride) levels as well. They also measured the body mass index (BMI) of the individuals and their percentage body fat.
The researchers also included 89 pairs of twins in their study, enabling them to compare differences between twins who tested differently for exposure to Ad-36.
Animal experiments had shown that when infected with Ad-36, stem cells turned into fat cells. It is well known that increasing the number of fat cells in the body enhances the likelihood that the individual will be overweight.
The present study was designed to test for an effect of the virus on humans.
When all the data were analyzed, the scientists found that 30% of the obese versus 11% of the thin subjects had been exposed to the adenovirus. Among twin pairs in which one twin had been exposed to the adenovirus and one had not, the exposed twins showed higher percentage body fat and BMI.
Perhaps the most surprising effect of the adenovirus confirmed in this study is that while it increases fat accumulation, it lowers serum triglyceride and cholesterol levels.
As expected, the study showed no correlation between human obesity, cholesterol or triglyceride levels and exposure to the adenoviruses known as Ad-2, Ad-31, and Ad-37. Heretofore, this class of viruses has been associated primarily with minor infections such as colds, respiratory infections, and pink eye.
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