Fat-burning hormone may be key to weight loss

Brown fat has been a hot topic in obesity research in recent years. So has a hormone produced in the brain called orexin. Now scientists have linked these two concepts in a theory that may lead to new weight-loss therapies.

Brown fat is a healthy substance that contains blood vessels and helps burn fat. People who are obese are thought to have less-active brown fat. Orexin is a hormone that is known to play a role in controlling appetite. In a paper published Tuesday, scientists have shown that orexin also activates brown fat to burn calories.

The study used mice who were genetically engineered to lack orexin. These mice were obese even though they ate less than other mice. When scientists looked at the brown fat composition, they found that fat cells didn’t develop properly when the mice were embryos. That defect caused a lifelong predisposition to gain weight.

The research supports the theory that obesity can have its roots in the fetal environment and raises the stakes on understanding prenatal brown fat development.

“Without orexin, mice are permanently programmed to be obese,” the lead author of the study, Dr. Devanjan Sikder of the Sanford-Burnham Medical Research Institute in Orlando, Fla., said in a news release. “We’re now taking the next steps in determining how orexin -- or a chemical that has the same effect -- might be used in humans to therapeutically prevent or treat obesity.”

The study appears in the journal CellMetabolism.

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