Posted for Mico Tatalovic

It seems counterintuitive, but a paper published in Nature raises the possibility of losing weight by injecting fat cells.

In the paper American researchers describe using a molecular switch – two proteins PRDM16-C/EBP-beta – to turn mouse and human skin cells into brown fat cells (paper, press release).

White fat cells store fat, while brown fat cells use those stores to produce heat. Heavier people seem to have more white fat but less brown fat than slim people, so one idea for treating obese people is to increase stores of the energy-burning fat. Until now this could not be done since making brown fat was a mystery.

“Brown fat is one of the body’s natural defenses against obesity,” said cell biologist Bruce Spiegelman of Harvard Medical School, who co-authored the paper. “We’re trying to tap into a natural pathway involved in this kind of biology.” (Wired.)

Spiegelman’s team managed not only to use the molecular switch to convert skin cells brown fat cells but also transplanted them into mice, where there seem to be working as normal brown fat cells, with one difference: the implanted cells are ‘on’ all the time.

“They’re basically in the on position all the time.” Spiegelman told Wired, but this might be a good thing – it might mean that smaller amount of brown fat tissue would be needed to treat obesity in people if that tissue is burning fat stores all the time.

Although the engineered and transplanted brown fat cells work in mice, it is still not clear if they actually make them any slimmer. Spiegelman is now working on transplanting these cells into obese mice to see if they lose weight.

Sven Enerbacktold, a medical geneticist from University of Gothenburg in Sweden says the paper is a “really important step” in elucidating the basic biology of brown fat cells and suggested that according to his calculations, inserting 50 to 100 grams of brown fat cells into a person would enable them to burn off more than 10 pounds of white fat tissue a year (New York Times).

But others are less convinced. Endocrinologist Francesco Celi of the National Institutes of Health, says that even if there was a safe way to administer extra brown fat tissue to people, the body might still compensate for lost energy by demanding more food or slowing down other aspects of metabolism.

“It’s a very sound and solid study,” he said (Wired again). “In the long run, this could be a strategy. But from this data to the clinic, there is a long, long time.”

Image: engineered brown fat cells from mouse skin / Shingo Kajimura