Skeleton Key: Bone Cells May Play a Part in Regulating the
Body's Metabolism  Two new studies suggest that the sugar-
regulating hormone insulin may play a role in bone health, and
implicate the skeleton as a major regulator of energy metabolism
Insulin, the well-known blood sugar hormone, may have a newly
discovered function in the body that will rattle your
bones—regulating skeletal growth and breakdown.  Two new studies
published online July 22 in Cell show that insulin stimulates
both bone building and breakdown in mice through the hormone's
effects on two types of bone cells: bone-building osteoblasts
and bone-resorbing osteoclasts. What's more, these cells are
involved in an intricate hormonal loop that in turn regulates
not only insulin production, but also blood sugar levels and
energy metabolism. The studies suggest that the skeleton may be
an important regulator of whole-body energy metabolism, joining
the ranks of known metabolic regulators such as muscle and fat.
The authors conclude that their f