Boston researchers discover a new type of energy-burning fat

By Carolyn Y. Johnson, Globe Staff

An international team led by Dana-Farber Cancer Institute scientists has described in detail a new kind of fat, called “beige fat,” that burns calories, rather than stores them. They have also shown that this energy-burning fat exists in adult humans, and are searching for ways to turn on such fat cells to combat obesity and diabetes.

“What we learn here may teach us to activate it,” said Bruce Spiegelman, a professor of cell biology at Harvard Medical School and Dana-Farber Cancer Institute who led the work published on Thursday in the journal Cell.

Over the past decade, interest in a type of energy-burning fat called brown fat has exploded. That type of fat had been known to exist in infants but had been thought to disappear with age, until in 2009 three independent teams of scientists found evidence that adults, too, had small deposits of such energy-burning brown fat near their spines and collarbones. The discovery fueled interest in the possible role this type of fat could play in human health and whether it could be exploited by drug developers to help people lose weight.

The new work reveals that what researchers had called brown fat in adult humans is actually beige, genetically different from classical brown fat. The ability to deeply understand the cellular identity of this type of fat will help scientists measure how much there is in the body and search for ways to turn it on.

Spiegelman’s laboratory reported earlier this year that it had discovered a new hormone, which they called irisin, which is released by muscles and could stimulate normal, energy-storing white fat to transform it, to act more like brown fat. Now, they’ve discovered that the brown fat-like tissue is actually beige fat, and is sensitive to the hormone.

That earlier research is also being pursued by a Boston startup company, Ember Therapeutics, co-founded by Spiegelman.

He said that his hope is that the new detailed characterization of beige fat would provide a powerful research tool for the entire scientific community, and that he would make the cells available for distribution to other laboratories.

Dr. C. Ronald Kahn, chief academic officer at the Joslin Diabetes Center, who has worked on brown fat, including detecting the tissue in adult humans, said the new work is important because it provides a detailed look at the molecular characteristics of this new type of brown fat cell.

It “also suggests that stimulating brown fat in humans, which might be useful for weight loss or control of metabolic disease, may be possible, just like stimulated beige fat in mice,” Kahn wrote in an e-mail.