Your average gym goer is under the false assumption that your skeleton is merely a coat rack for your flesh. Those of us who have a little more education understand that bones are living tissue and, not unlike how our flesh displays to the world our activity and fitness (or total lack thereof), our bones are now showing us just how fit you are.
I’m not talking just about density. While total bone density is certainly something all of us should strive for (men get osteoperosis too), our bones are constantly remodeling due to our activity. Stronger muscles not only increase the density of bone, due to the fact that your bones actually bend when you’re training and remodel to not bend as much, but bone is also an endocrine organ, secreting various proteins that provide a marker of bone health and, as recent research suggests, rate of muscular usage.
Osteocalcin is a protein found in bone and dentin, secreted solely by the osteoblasts, and is used as a serum signal of bone growth. This nifty little protein also functions as a hormone in the body, telling the beta cells to release more insulin and adipose tissue to release more adiponectin, increasing insulin sensitivity.
While doing some fun researchy-type stuff yesterday, I got nose-deep in reading about how osteocalcin is inversely related to fat mass and plasma glucose in elderly men. And if you dig into the research, there’s a whole boatload of other studies showing just how serum osteocalcin is associated with metabolic syndrome and fat mass. Inversely related in fact.
Now understand that this isn’t some “new leptin,” which is to say a magic bullet: no amount of osteoblast infusions are going to decrease fat mass and metabolic syndrome. Rather, reference what I was talking about earlier that osteocalcin is secreted during bone remodeling and it’s not a far leap to make that this is a serum maker of significant physical activity. If you’re doing something strenuous enough to increase bone remodeling, even if it’s not exercise but an active life, you’re less likely to have metabolic syndrome. You’re using more of the glucose you’re taking in. You’re not storing as much as fat.
Your bones are not a tissue rack and osteocalcin is another indicator of not only how active an organ it is but also of how active an animal you are.