First we find out that our belly fat is an endocrine organ, and now it's our bones. Dr. Gerard Karsenty of Columbia University has discovered that bone-building cells (osteoblasts) secrete a hormone called osteocalcin that not only tells the beta cells to secrete more insulin, but also causes the number of beta cells themselves to increase.

Of course, beta cell proliferation is the holy grail of diabetes cure research, so this finding has exciting potential for further study.

Osteocalcin also tells your fat to increase its release of adiponectin, a hormone that improves insulin sensitivity. While your bones are using osteocalcin to talk to your fat, your fat is using the hormone leptin to talk to your bones. This synergistic hormonal conversation makes sense, given that your bones need to grow stronger to hold up all that extra weight. It's leptin that tells your bones they'd better bulk up.

What's really amazing is that your bones have a big effect on blood sugar as well. Dr. Karsenty found that higher levels of osteocalcin prevented not only obesity, but also insulin insensitivity and type 2 diabetes in mice. Mice engineered to lack osteocalcin got fat, developed type 2 diabetes, and had reduced levels of insulin and adiponectin, as well as decreased beta cell proliferation.

Dr. Karsenty is currently looking into whether giving diabetic mice osteocalcin will cure their diabetes. Previous research has shown that people with type 2 diabetes have lower levels of osteocalcin, so the future of research into this hormone is promising.

Sources: EurekAlert; Time; Cell, August 2007