Although best known for promoting erections, sildenafil may also serve as a weight loss aid by coaxing our bodies to store more healthy "brown fat" relative to unhealthy "white fat" than it would otherwise do on its own, a new study suggests.

According to the research, this is because sildenafil inhibits the breakdown of cyclic GMP, which has been well known as a messenger molecule used by the body to control blood pressure and flow, and has now been shown to play an important role determining which type of fat-white or brown-the body stores.

"There is a growing need for novel treatments against obesity," Alexander Pfeifer, M.D., Ph.D., a researcher involved in the work from the Institute of Pharmacology and Toxicology at the University of Bonn, Biomedical Center in Bonn, Germany said.

"Finding new positive effects of existing drugs, such as sildenafil, in adipose tissue might help to bridge the period until novel drugs against obesity have been developed," he said.

To make this discovery, Pfeifer and colleagues used mice to show that cyclic GMP reduced the secretion of pro-inflammatory hormones, which, in turn, shifted the "color code" of fat from white to brown.

Mice treated with sildenafil showed browning of the white fat after just a few days of treatment, which is believed to be the result of high cyclic GMP levels.

Then the researchers used isolated fat cells and treated the cells directly with cyclic GMP and identified a "browning" effect as well.
The study is published online in The FASEB Journal.