Treating obesity with brown fat in the body

Researchers have shown that they can produce brown fat, a natural energy-burning type of fat that counteracts obesity. If such a strategy can be developed for use in people, it could open a novel approach to treating obesity and diabetes.

Dana-Farber Cancer Institute researchers published their findings in the journal Nature.

A team led by Bruce Spiegelman, PhD, has identified both parts of a molecular switch that normally causes some immature muscle cells in the embryo to become brown fat cells. With this switch in hand, the scientists showed they could manipulate it to force other types of cells in the laboratory to produce brown fat, known as Brown Adipose Tissue (BAT).

The scientists then transplanted these synthetic brown fat precursors, known as eBAT (engineered BAT), into adult mice to augment their innate stores of brown fat. Tests showed that the brown fat transplants were burning caloric energy at a high rate — energy that otherwise would have been stored as fat in white adipose tissue.

“Since brown fat cells have very high capacity to dissipate excess energy and counteract obesity, eBAT has a very high potential for treating obesity,” said Shingo Kajimura, PhD, lead author of the paper. “We are currently working on this.”

Excess caloric energy in the diet is stored in white fat calls that pile up in the body, particularly in the thighs and abdomen. The accumulated fat content in overweight people puts stress on these cells, which give out signals that cause inflammation in body organs and the circulatory system, creating risks of heart disease and diabetes.

Brown fat, by contrast, works in an opposite fashion; it evolved to protect animals from cold conditions and prevent obesity. Brown fat cells are equipped with a large supply of mitochondria — tiny organelles that use oxygen to burn sugar from the diet to generate heat, rather than store the energy as fat.

Scientists have long thought that brown fat was present in young animals and human newborns but virtually absent in human adults. Recently, however, researchers have used modern PET (positron emission tomography) scanners — which detect tissue that is actively absorbing sugar — to search for deposits of brown fat in adults. Such experiments have revealed unexpectedly large amounts of brown fat scattered through the neck and chest areas.

A more conventional possibility, Spiegelman said, would be to administer a drug to the patient that would ramp up the production of brown fat without the need for a transplant. “If we can find a hormone that does that, it’s reasonable to think that it might provide a direct anti-obesity treatment.”

Source: Dana-Farber Cancer Institute, USA



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