Bones secrete a hormone that helps regulate sugar and fat, a scientific breakthrough that could one day lead to the prevention and treatment of Type 2 diabetes, U.S. researchers report.
The scientists have discovered that certain bone cells produce osteocalcin, which controls the metabolism of blood sugar (glucose) and fat deposits through previously unknown channels.
Osteoblasts release the hormone osteocalcin, which in turn increases both the secretion of insulin and insulin sensitivity, researchers report.
(CBC)
"What this study shows is that [the skeleton] is a lively organ that has a function to regulate the biology of the other organs in the body, such as the pancreas and insulin secretion, and fat and insulin sensitivity," Dr. Gerard Karsenty, chair of the department of genetics and development at Columbia University Medical Center and the study's lead author, told CBC News.
"It is the first time the skeleton has shown to reach out to other organs in the body."
In studies on mice, scientists showed 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.
Bones an endocrine organ
That means the collection of femurs, ribs, clavicles and other bones that make up the skeleton aren't merely a framework for various tissues, but an endocrine organ that helps control metabolism, said Karsenty.
"These results uncover an important aspect of endocrinology that was unappreciated until now," he said.
Karsenty and his colleagues, whose work is published in Friday's edition of the journal Cell, studied lab mice that had been genetically altered so their bodies did not produce osteocalcin. In the absence of the hormone, the mice developed Type 2 diabetes and were overweight — not obese, but with increased fat mass — on a normal diet.
Most treatments for diabetes increase insulin secretion to better regulate blood sugar. However, 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 Karsenty, whose team is testing injections of the hormone on different species to see if it could prevent or eliminate Type 2 diabetes.
Study confirms diabetes-bone link
Why has it taken so long to discover that bones have a hormonal link? Karsenty said scientists have largely focused their research on bone composition.
"It has not been discovered before because people have focused their studies on the biology of bone cells," he said.
He said the next step is to conduct studies on humans to see how the bone-hormone link can lead to obesity and diabetes. Researchers suspect age-related weight gain may be caused by how bones function, Karsenty said.
"Certainly, as we age, we eat less than when we were 20 years old, yet we gain weight. And this occurs at a time when bone mass decreases."
Karsenty feels osteocalcin holds promise for diabetics.
"Osteocalcin could be viewed in the future as a treatment for Type 2 diabetes."
Dr. Robert Hegele, an endocrinologist at the University of Western Ontario's school of medicine, said it would likely be 10 to 15 years before scientists will know whether such hormone injections would be effective and safe for humans.
In the meantime, Karsenty advises, people should take care of their bones, given their newly discovered role.
"There is a lot to be gained and nothing to be lost by taking care of our bones."
With files from the Canadian PressRelated
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