Bones play important role in regulating blood sugar, shows study

16 August, 2007:

In a discovery that may be described as very surprising, an international team of scientists has found that bone plays an important role in controlling sugar metabolism, energy balance, and weight.

The finding, which suggests that the skeleton is actually a member of the endocrine system, adds immensely to the understanding of metabolism and may lead to new ways to prevent and treat Type 2 diabetes.

The study – published in the August 10, 2007, issue of the journal Cell – was carried out on laboratory mice by researchers in New York, Chicago and Hershey, Pennsylvania (the United States), Seoul (Korea), Lyon (France), Cambridge (the United Kingdom) and Montreal (Canada).

It is generally believed that the skeleton is an inert calcified structure that just stops the body from collapsing inside the skin.

Dr Gerard Karsenty and Paul Marks at Columbia University Medical Center, main authors of the paper, said: “The discovery that our bones are responsible for regulating blood sugar in ways that were not known before completely changes our understanding of the function of the skeleton and uncovers a crucial aspect of energy metabolism.”

Karsenty and colleagues had suspected that bone might be involved in metabolism because leptin, a hormone released by fat cells, is also involved in the control of bone formation. So they decided to look for other molecules that might be communicating between bone-forming cells and the endocrine system.

Using laboratory mice, they discovered metabolic processes, previously unknown, where a hormone called osteocalcin – that is known to regulate mineralisation and is released in bone-forming cells known as osteoblasts – also regulates glucose (blood sugar) and the deposition of fat.

The scientists showed that an increase in osteocalcin effectively prevents the development of Type 2 diabetes and obesity in the laboratory mice.

The finding is exciting because it suggests that increasing the levels of osteocalcin in patients with Type 2 diabetes could be a promising treatment route, especially since such patients tend to have low levels of the hormone.

Osteocalcin was thought only to be involved in bone development, but it seems it has a second crucial role in the endocrine system, that is, increasing the secretion of insulin and also increasing sensitivity to insulin. Osteocalcin also boosts production of pancreatic beta cells that make insulin (a much sought but currently unattainable path in new treatment research for Type 2 diabetes) and reduces fat deposits by interacting with fat cells.

When mice that did not have osteocalcin were examined, it was found that they had Type 2 diabetes, an increase in fat deposits, a decrease in insulin, a decrease in adiponectin expression (a protein that regulates fat deposits), and a much lower count of beta cells in the pancreas.

It came as a complete surprise to the research team to discover that endocrine processes in the pancreas and fat cells were also being controlled by signals from the skeleton.