Researchers at Harvard University say they have identified two chemical compounds that could replace "bad" fat cells in the human body with healthy fat-burning cells, in what may be the first step toward the development of an effective medical treatment – which could even take the form of a pill – to help control weight gain.

Not all fat is created equal. While white fat cells store energy as lipids and contribute to obesity, heart disease and type 2 diabetes, the less common brown fat cells pack energy in iron-rich mitochondria, have been shown to lower triglyceride levels and insulin resistance in mice, and appear to be correlated with lower body weight in humans. Brown fat makes up about five percent of the body mass of healthy newborns, helping them keep warm, and is still present in lower quantities in our neck and shoulders as adults, where it helps burn the white fat cells.

Associate professor Chad Cowan and colleagues at Harvard say they have developed a way to identify the chemical compounds that induce fat stem cells to produce "good" brown-like fat cells instead of the "bad" white ones. The scientists say they have already used their system to pinpoint two such compounds that can accomplish this in humans.

Other drugs (viagra included) have been known to be able to turn white fat cells into brown, but their effect is only temporary. This new method, however, is reportedly showing a stable conversion of fat cells over time, which has an exciting potential for long-term health improvement.

But turning these two chemicals into a practical treatment is not going to be a straightforward process. Aside from the lengthy medical trials still to come, the two compounds identified so far both target the same molecule  –  a molecule that contributes to the inflammatory response. The concern here is that tinkering with it by using the compounds over the long term and without modifications could end up compromising the immune system.

Cowan’s team achieved this result by screening a catalog of only about one thousand compounds. But now, as the first two are being tested on mice to investigate the long-term effects on metabolism and immune system, the researchers are approaching pharmaceutical companies to gain access to a much larger database of over a million compounds, with the hope of finding a candidate that doesn't have the potential adverse effects of the first two.

A paper describing the advance was published on the journal Nature Cell Biology.

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