To most dieters, no fat is good fat. But in work published this week in Nature, an insight into the origin of a special class of calorie-burning fat cells could lead to new ways of boosting metabolism and combating obesity, researchers said.
But less known brown fat, made up of heat-producing cells have been found to possess fat and energy, generating structures called mitochondria.
Ronald Kahn of the Joslin Diabetes Centre at Harvard Medical School in Boston, Massachusetts who is one of the researchers involved in the latest study pointed out that brown fat burns a tremendous amount of energy. According to Kahn, about 50 grams of brown fat could burn up 20 percent of a person’s daily caloric intake.
Brown-fat pads between the shoulder blades are thought to help newborns stay warm, but precisely what purpose the cells serve in adults is still unclear.
"It’s a very efficient tissue at wasting energy," agrees Bruce Spiegelman of the Dana-Farber Cancer Institute and Harvard Medical School, another member of the team.
That would seem to prompt a simple solution to the growing obesity problem, according to the researchers.
Meanwhile, Kahn, Yu-Hua Tseng and their colleagues have identified another protein, called bone morphogenic protein 7 or BMP7, that is crucial to the generation of brown fat cells. When researchers over-expressed the protein, mice developed slightly more brown fat, slightly higher body temperatures and exhibited slightly lower weight gain than untreated mice after just five days.
The work could open new therapeutic avenues, Dominique Langin said, a clinical biochemist at the National Institute of Health and Medical Research (INSERM), Toulouse, France. But it will be important, he added, to characterise the process further in humans. In large mammals such as humans, the brown fat present at birth disappears and then reforms in other locations, and the contribution that brown fat makes to overall metabolism is unclear. In mice, brown fat does not undergo the same shift, and it plays a clear role in regulating body temperature.