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Obesity in Some People There is new evidence that infection with a common virus may be a contributing factor to the obesity epidemic sweeping through many countries. In laboratory experiments, scientists showed that infection with human adenovirus-36 (Ad-36), long recognized as a cause of respiratory and eye infections in humans, transforms adult stem cells obtained from fat tissue into fat cells. Stem cells not exposed to the virus, in contrast, were unchanged. In addition, the study reported identification of a specific gene in the virus that appears to be involved in this obesity-promoting effect. The findings, which could lead to a vaccine or antiviral medication to help fight viral obesity in the future, were presented at the 234th national meeting of the American Chemical Society. “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,” said study presenter Magdalena Pasarica. “Not all infected people will develop obesity,” she said. “We would ultimately like to identify the underlying factors that predispose some obese people to develop this virus and eventually find a way to treat it.” Pasarica was part of the original research group which demonstrated that the Ad- 36 virus was capable of causing animals infected with it to accumulate fat. The group also conducted an epidemiologic study — the first to associate a virus with human obesity — showing 30 percent of obese people were infected with the Ad-36 virus in comparison to 11 percent of lean individuals. But evidence that the virus could actually cause fat levels to increase in human cells was lacking until now, Pasarica said. In the current study, Pasarica and her associates obtained adult stem cells from fatty tissue from a broad cross-section of patients who had undergone liposuction. Half of the stem cells were exposed to the virus. After about a week of growth in tissue culture, most of the virus-infected adult stem cells developed into fat cells, whereas the stem cells which were not exposed to the virus did not, the researchers say. Researchers recently identified a gene in the Ad-36 virus that appears to be involved in causing fat accumulation observed in infected animals. That gene, called E4Orfl, is now emerging as a promising target for future human therapies, such as vaccines and anti-viral medicines, aimed at preventing or inhibiting the obesity virus, Pasarica said. The exact mechanism by which the virus might cause obesity in people is currently unknown. Researchers also do not know how long the virus remains in the body of obese individuals or how long its fat-enhancing effect lasts once the virus is gone. However, a recent study demonstrated that animals that developed the virus remained obese up to six months after their infection was gone. More studies are needed, especially in humans, she adds. The researchers are not ruling out the possibility that other human viruses may also contribute to obesity. (Source: American Chemical Society) |
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