Another Molecular Clue About Exercise's Power to Combat Obesity and Type 2 Diabetes

During the past 14 years, researchers have identified an important biochemical pathway in energy metabolism. At the center of this pathway is a molecule called PGC1-α, a transcription factor that stimulates the coordinated activation of many other genes. Exercise triggers muscle cells to produce PGC1-α; as a result, white fat cells develop into brown fat cells (which burn rather than store calories; JW Gen Med Sep 30 2008), and insulin resistance is reduced. But how does muscle-derived PGC1-α elicit its effects in distant tissues?

These investigators now report that PGC1-α stimulates muscle cells to produce and secrete a hormone, which they call irisin. This hormone transforms subcutaneous white fat cells into brown fat cells. Even without e…