Bone hormone spurs insulin production
A hormone involved in bone repair can also induce insulin production and control diabetes, says a new report compiled by researchers at the Columbia University Medical Center, New York.
Studies on mice suggests that osteocalcin, which is released during the breakdown and regrowth of bone tissue, also triggers insulin secretion and helps cells of the body take up glucose.
As production of insulin and absorption and utilisation of glucose by the cells are two major impairments occur in diabetic patients, this new discovery could lead to new diabetes drugs.
The finding strengthens the idea that diabetes can be treated by regulating levels of osteocalcin in the body, says Dr. Gerard Karsenty from the Columbia University Medical Center, who headed a team that conducted the research. The study reported has since been published in the journal Cell.
The insulin receptor appears at several places within the human body, including osteoblasts – the mono-nucleate cells that are responsible for bone formation. These release osteocalcin, which Karsenty and his team first linked with glucose regulation in 2007.
Researchers found that once uncarboxylated, the osteocalcin switches on insulin production in the pancreas and improves the ability of cells in the whole body to take in glucose activating a mechanism which is impaired in diabetes.
As bone making cells begin the resorption process, the cell environment becomes more acidic which favours decarboxylation and thereby activates more osteocalcin, which in turn stimulates insulin production. Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in the transfer of calcium from bone fluid to blood.
But they also found that insulin favored bone resorption, so the process appears to be a "feed-forward" loop where insulin signals osteoblasts to start resorption, which in turn releases more osteocalcin and causes the release of more insulin.
"Insulin is a street-smart molecule that takes advantage of the functional interplay between bone resorption and osteocalcin, to turn-on the secretion and synthesis of more insulin," says Karsenty, who believes that the findings will have important implications for both diabetes and osteoporosis patients.
For starters, the study shows that osteocalcin is involved in diabetes onset. In addition, it could result in bone becoming a new target in the treatment of type-2 diabetes, as it appears to contribute strongly to glucose intolerance. And most importantly, osteocalcin could become a treatment option for patients suffering from type-2 diabetes.