TORONTO — The skeleton has long been seen as an inert scaffolding that gives the body shape and stability. But now researchers say bones appear to secrete a hormone that helps regulate sugar and fat — and that could have major implications for preventing or treating Type 2 diabetes.
Researchers at Columbia University in New York have discovered that certain bone cells produce a hormone called osteocalcin, which controls the metabolism of blood sugar (glucose) and fat deposits through previously unknown mechanisms.
“It is very exciting conceptually because it's a new function for an organ,” senior author Dr. Gerard Karsenty said Thursday from La Eaule, France, where he was vacationing. “It's also very exciting potentially from a medical point of view because it could be a treatment for Type 2 diabetes.”
In work in laboratory mice, the scientists show that bone-forming cells called osteoblasts release osteocalcin, which in turn increases both the secretion of insulin and insulin sensitivity. It also boosts the number of insulin-producing cells in the pancreas while reducing stores of fat.
All in all, that means the collection of femurs, ribs, clavicles and other bones that make up our skeleton aren't merely a framework for our various tissues, but an endocrine organ that helps control energy metabolism, said Dr. Karsenty, head of genetics at Columbia's school of medicine.
“These results uncover an important aspect of endocrinology that was unappreciated until now,” he said.
Dr. Karsenty and his colleagues, whose work is published in Friday's edition of the journal Cell, studied lab rats that had been genetically altered so their bodies did not produce osteocalcin.
“We realized that in the absence of osteocalcin, the mice were developing Type 2 diabetes and were overweight — not obese, but with increased fat mass — on a normal diet, which is rather unusual,” he said.
Most treatments for diabetes bump up insulin secretion to regulate blood sugar, but the problem is they also decrease insulin sensitivity, defined as the degree to which cells respond to a particular dose of insulin by lowering blood glucose levels.
While osteocalcin raises insulin production, it also bolsters insulin sensitivity at the same time, making it a potentially ideal treatment, said Dr. Karsenty, whose team is testing out injections of the hormone on different species to see if it could prevent or eliminate Type 2 diabetes.
“If it were (to work), the next species after that would be human beings.”
Source : theglobeandmail
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