Researchers at Columbia University in New York have discovered that certain bone cells produce a hormone called osteocalcin, which influences beta-cell proliferation and controls the metabolism of blood sugar (glucose) and fat deposits through previously unknown mechanisms. 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.
“It is very exciting conceptually because it’s a new function for an organ,” senior author Dr. Gerard Karsenty said.. “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, 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.”
Published in August 10th edition of the journal Cell
Poll Results Not So Sweet for Diabetes Drug Avandia: A majority of healthcare professionals responding to an online survey, said that they will not prescribe rosiglitazone (Avandia) for their patients with type 2 diabetes, and one in four believe that the drug should be pulled off the market. Although 36% of the respondents say they will continue to prescribe rosiglitazone for select patients, in accordance with the FDA panel’s recommendation, 55% said they will no longer prescribe the drug. And 23% said that it should be taken off the market entirely. The spring 2007 publication of a meta-analysis showing that rosiglitazone carries a 43% increase in the relative risk of heart attack in patients with type 2 diabetes touched off the firestorm that resulted in the special FDA hearing. The beleaguered drug held 37% of the US oral anti-diabetic market in 2006. It is possible, however, that clinicians may soften their current negative stance on rosiglitazone over time.
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