July 30th, 2009

Reports the New York Times:

A new approach to treating obesity has been opened up by a discovery about how the body creates brown fat, the cells that burn white fat and turn it into body heat.

Researchers led by Bruce M. Spiegelman of Harvard Medical School report their discovery in Thursday’s issue of the journal Nature. Their paper describes the natural system by which brown fat cells are generated from their precursors.

Dr. Spiegelman has used this system — a pair of proteins that switch on the brown fat cell’s distinctive genes — to convert both mouse and human skin cells into brown fat cells.

Brown fat cells have a very different role from the better-known white fat cells. The white cells store fat; the brown cells burn it off as heat.

Babies have lots of brown fat to help keep warm. Until April 2009, biologists believed that the brown fat quickly disappeared and was not found in adults. Dr. Sven Enerback of the University of Goteborg in Sweden and others then reported that some brown fat tissue persisted in adults, raising the possibility that if the cells could be made more active, a person might burn off more fat.

…

A key element in making brown fat cells seemed to be a kind of protein called a zinc finger (because it reaches into the spiral of a DNA molecule to switch on particular genes). Dr. Spiegelman figured that if he inactivated all the relevant zinc finger proteins in brown fat cells, they should turn back into their precursors, the white fat cells.

The experiment worked. The brown fat cells did revert, but not into white fat cells. They turned into muscle cells.

“It was the most bizarre experiment my lab ever did,” Dr. Spiegelman said Wednesday.

Find out more at the NYT.