[acb-diabetics] bone growth and insulin production

[Patricia LaFrance-Wolf]

Breakdown of Bone Keeps Blood Sugar in Check

 

The human skeleton plays an important role in regulating blood sugar and
researchers, led by Columbia University Medical Center, have further
illuminated

how bone controls this process.... 

 

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The finding is important because it may lead to more targeted drugs for Type
2 diabetes. Led by Gerard Karsenty, MD, PhD, chair of the Department of
Genetics

and Development at Columbia University Medical Center, NY,, researchers
found that the destruction of old bone during normal skeletal regrowth -- a
process

known as resorption -- is necessary to maintain a healthy level of glucose
in the blood. 

 

While resorption is a process that occurs throughout life to make way for
new bone, Dr. Karsenty's team discovered that it also acts to stimulate the
release

of insulin into the bloodstream and improve the uptake of glucose by cells
in the entire body.

 

The findings suggest that, for some people, diabetes may develop from
changes in the skeleton, and that drugs designed to stimulate the
bone-insulin pathway

may lead to better drugs for Type 2 diabetes. 

 

The first clue that the skeleton may have an important role in regulating
blood glucose came in 2007 when Dr. Karsenty discovered that a hormone
released

by bone -- known as osteocalcin -- can regulate glucose levels. Osteocalcin
turns on the production of insulin in the pancreas and improves the ability

of other cells to take in glucose. Both of these processes are impaired in
Type 2 diabetes.

 

The new paper reveals that osteocalcin cannot work until cells that degrade
bone start working and begin the resorption process. As the cells degrade
bone,

inactive osteocalcin is converted to its active form by the increase in
acidity around the bone. 

 

"Remarkably, insulin was discovered to favor bone resorption. Hence, in a
feed-forward loop it favors the activation of osteocalcin, which in turn
favors

insulin synthesis and secretion," said Dr. Karsenty.

 

"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."

 

By identifying the tight connection existing between energy metabolism and
skeleton physiology -- in this case between insulin and osteocalcin -- this
new

study further underscores the wealth of physiological function exerted by
the skeleton. The finding further strengthens the idea that diabetes could
be

treated by increasing the level of osteocalcin in the body. In addition, the
researchers suggested that since most drugs to treat another condition --

osteoporosis -- work by inhibiting bone resorption, the drugs may decrease
the activation of osteocalcin and cause glucose intolerance in some
patients.

 

"This research has important implications for both diabetes and osteoporosis
patients," said Dr. Karsenty. "First, this research shows that osteocalcin

is involved in diabetes onset; secondly, bone may become a new target in the
treatment of Type 2 diabetes, the most frequent form of diabetes, as it
appears

to contribute strongly to glucose intolerance; and, finally, osteocalcin
could become a treatment for Type 2 diabetes."

 

"And for people with osteoporosis, the concern is that a common treatment,
bisphosphonates -- which work by inhibiting bone resorption and therefore
may

increase glucose intolerance, could push someone with borderline glucose
intolerance into full-fledged disease onset. Although, more research is
needed

to study this further," said Dr. Karsenty.

 

Ferron M, et al "Insulin signaling in osteoblasts integrates bone remodeling
and energy metabolism" Cell 2010; 142: 296-308. 

 

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