Move Dem Bones

October 15, 2007

Move Dem Bones 

 Competency # 4 Activity                          Reference: Karsenty et al, Cell, August 2007 

 Those old dry bones of yours may have a very interesting role to play in keeping you healthy.  You thought your bones were all about holding your body together.  Well, just this week we find out that your bones are now all about holding your metabolism together.  

Your bones are actually an endocrine organ.  They secrete hormones!  This is a fascinating story. A researcher at Columbia Univesity, Gerald Karsenty found that fat cells secrete a hormone that influences bone forming cells called osteoblasts.  Osteoblasts are responsible for forming new bone.  They are active in remodeling and shaping your bones in response to fractures, but also in response to daily use.   The more you use a bone, the more it gets stronger in response to the strains you put on it.  Follow me?  

For years now, we have known that osteoblasts make a protein called osteocalcin.  Only osteoblasts make it.  We just didn't know exactly what it did. Now, Dr. Karsenty developed a line of mice genetically engineered to make more or less osteocalcin.  The deficient mice had low levels of insulin and very poor response to insulin in their fat cells.  The mice with extra osteocalcin were skinny, even on a high calorie diet.  And their tissues were very sensitive to insulin.  

The osteocalcin made the pancreas ramp up and make lots of extra insulin producing cells.  And, it made fat cells put out a hormone called adiponectin.  Adiponectin makes you insulin sensitive. Why is all this important?  Actually, it’s not just important, it’s huge.  It unlocks a major key to understanding diabetes.   Sixty percent of us are overweight, and at risk of getting diabetes.  The hallmark of “metabolic syndrome”, or prediabetes, is the gradual decline in our sensitivity to insulin.  And humans, with pre-diabetes, or metabolic syndrome, are known to have low levels of osteocalcin.  That was chalked off to coincidence. 

 Now, osteocalcin could be a treatment for diabetes, if one could make it and purify it, because it would be a great way to use the natural mechanisms of your body to make you more insulin sensitive and thereby control your blood sugar better.  That’s a great idea, if you want to spend $ 200 a month buying an expensive medicine.

 Let’s go down a different road.  This is conjecture, as the science hasn’t been established yet, but the pieces all fit.  When you exercise, you move blood through your body, including your bone marrow.  You flush out more osteocalcin from your marrow spaces where your osteoblasts are.  The normal use of your bones makes them remodel and reshape themselves in response to your usage, and put out more osteocalcin.  We’ve known that exercise controls your blood sugar, more than just the calories you use.  Now we know why…  And we know that exercise, of any kind, helps diabetes.  And exercise is the key to losing weight and keeping it off.  

Conjecture: exercise is the key to weight control because you flush osteocalcin out of your bones with all that extra blood flow.  It makes your fat cells store less fat and release more adiponectin.  You burn some calories.  But your metabolism gets better because osteocalcin ramps up the good stuff.  Your health improves.   Your bones are “glands” and make hormones.  Fascinating. 

 WWW.  What will work for me?  Exercise is where it’s at.  I am walking around the new pond in our village every night we can, except when the mosquitoes get too monstrous.  Can I use that as an excuse to get my treadmill greased up?  I’m moving into Stage 3 of change.  (Remember: Stage 1 of change is DENIAL.  Stage 2 is THINKING.  I’m PLANNING to exercise.   That’s three.   By trying a little, sooner or later, I’ll move into Stage 4, and actually start exercising.   Just not yet.  How about you?  Next week.  How much should I exercise?  The new standards have just been published.  Move them bones.  There's evidence!

The column is written by Dr. John E. Whitcomb, MD, Brookfield Longevity, Brookfield, WI (262-784-5300)