A hormone produced in the bones appears to play a role in protecting humans and other animals from obesity and diabetes, according to a report published today in the journal Cell.
The study is the first to identify a regulatory role for the skeleton and may solve a half-century-old mystery by showing that the hormone, osteocalcin, controls sugar metabolism.
Its existence has been known for 50 years, "but its function was never understood," said senior author Dr. Gerard Karsenty, a geneticist at Columbia University Medical Center.
"It's always exciting when two fields that seem totally unconnected turn out to be possibly interrelated," said Richard N. Bergman, director of the Metabolic Research Laboratory at USC's Keck School of Medicine, who was not involved with the study.
Type 2 diabetes occurs when the body becomes resistant to insulin, the hormone that regulates sugar metabolism. Osteocalcin offers some protection against diabetes because it boosts insulin sensitivity.
The scientists knocked out the osteocalcin gene in mice and found that the mice got fat and developed diabetes, even with a normal diet.
Treating the mice with osteocalcin helped to better regulate their blood sugar and insulin.
Growing cells in a dish, the researchers also determined that osteocalcin causes the pancreas to make more insulin and prompts fat cells to make more of a protein that boosts insulin activity.
People with untreated type 2 diabetes have low osteocalcin levels, Karsenty said, making the hormone an appealing target for potential therapies. "The goal will be to see if we could treat type 2 diabetes in mice, and eventually in bigger animals, with osteocalcin," he said.