PHILADELPHIA — Scientists are learning how they might stoke the body’s fat-burning furnace by turning up a molecular thermostat.
Mice lacking a protein that responds to the hunger-promoting hormone ghrelin burn more energy in their brown fat than other mice, Yuxiang Sun of Baylor College of Medicine in Houston reported December 13 at the American Society for Cell Biology’s annual meeting. This revved-up brown fat helps keep mice lean and energetic into middle age. The finding could eventually lead to a way to help people fight obesity.
Brown fat burns energy instead of just storing it the way white fat does. This metabolically active fat is important in helping rodents and other animals maintain their body temperature. Recently researchers learned that adult humans have brown fat, and that the amount of energy burned by brown fat decreases with age and weight. The discovery has spurred interest in learning how to turn brown fat on.
Sun and her colleagues didn’t start out trying to rev up brown fat. Because the hormone ghrelin has been shown to make animals eat more, the researchers reasoned that blocking the molecule’s activity might reduce appetite and help animals and people lose weight. Sun and her colleagues genetically engineered mice to completely lack either ghrelin or the ghrelin receptor, a protein that interacts with ghrelin and sets off a series of biological reactions in cells that leads to the hormone’s effect.