Newly isolated 'beige fat' cells may help fight obesity

Washington, July 13 (ANI): Scientists have isolated a new type of energy-burning fat cell in adult humans, which they say may have therapeutic potential for treating obesity.

Called "beige fat," the cells are found in scattered pea-sized deposits beneath the skin near the collarbone and along the spine in adult humans.

Because this type of fat can burn off calories - rather than store them, as "white fat" cells do - beige fat cells might spawn new therapies for obesity and diabetes, according to researchers led by Bruce Spiegelman, PhD, of Dana-Farber.

The study at Dana-Farber Cancer Institute found that beige fat is genetically distinct from "brown fat," which also burns calories to generate heat. Brown fat is found in small mammals and human infants, where it protects against harm from cold. White fat, on the other hand, stores calories, and excess white fat contributes to obesity.

Existence of this third type of fat (in addition to white and brown) had been proposed in a paper by Spiegelman's lab in 2008, but the Dana-Farber team is the first to isolate them and to determine their unique genetic profile.

In the new report, Spiegelman's team, led by first author, Jun Wu, PhD, also found that beige cells are specifically targeted by the hormone irisin, which muscle cells express during exercise.

In 2009, three research groups reported that the deposits found in adult humans contained brown fat, but the new research has identified them as beige fat by their genetic makeup.

"Going forward, it means that what you want to study for potential therapies are the beige fat cells in these 'hotspots' we're all walking around with," said Spiegelman, senior author of a report detailing the study.

Even in small amounts, brown and beige fat can burn large amounts of calories.

"The therapeutic potential of both kinds of brown fat cells is clear," the researchers said, "as genetic manipulations in mice that create more brown or beige fat have strong anti- obesity and anti-diabetic actions."

Researchers are already seeking ways to exploit human brown fat for human benefits.

Both types of fat contain energy-burning organelles called mitochondria, which contain iron and are the cause of the brown and beige hues.

A key difference is that brown fat cells express high levels of UCP1 - a protein required by mitochondria to burn calories and generate heat - while beige cells normally express low levels of it. Beige cells can, however, turn on high levels of UCP1 in response to cold or certain hormones like irisin, enabling beige fat to burn calories nearly as effectively as brown fat.

The journal Cell published the study online and the print issue of Cell will publish on July 20. (ANI)