Human adenovirus-36 (AD-36) is an unwelcome visitor already because it causes colds, infections like pink-eye, and small intestine inflammation.

Now Dr. Magdalena Pasarica of Louisiana State University has found a peculiar reason to dislike it even more: it also provokes adult stem cells to develop into pre-fat cells. Her research builds upon the findings of her colleague, Dr. Nikhil Dhurandhar, who coined the term "infectobesity" to describe virus-caused weight gain.

It's a topic that drew his attention when he noticed that chickens infected with a deadly avian adenovirus became paradoxically fatter before they died.

Dr. Pasarica obtained adult stem cells from fatty tissue extracted from liposuction patients. In a test tube, she infected half of the cells with AD-36. By the end of a week, the uninfected cells were unchanged, but most of the infected cells had developed into pre-fat cells.

The more virus inserted into the cells, the greater the fat cell growth that was observed. Moreover, the exposed cells collected fat faster than normal, so that the infected tissue ended up with not only more, but also fatter, fat cells.

A previous study found AD-36 in thirty percent of obese people, but only eleven percent of lean people. It's already known that fat secretes hormones and signaling proteins and that inflammation is associated with fat.

Given the extensive interaction between the immune system and fat tissue, the researchers believe that viral infection, like environment and genetics, could be a significant factor in obesity.

Dr. Parisca has found a particular gene in AD-36 that appears to be directly responsible for the virus's promotion of fat. More research is called for, however, before anti-obesity therapies targeting the virus can be considered. Meanwhile, it's back to the old tried and true: exercise and diet.

Source: Medline Plus; Journal of Nutrition, 2001; WebMD