We think of bones as inanimate cement, supporting our body. In fact, it’s still this wrong impression of bone as structure only that infects modern orthopedic surgery. For example, as I’ve blogged before, bone is living tissue that reacts. So many bone spurs are evidence that your body is trying to fix itself rather than an indication that’s it’s broken. Now a scientist at Columbia University has again expanded this understanding of bone as “alive” by showing that a hormone produced by bone can impact everything from your brain to your genitals.
The hormone is called Osteocalcin. What’s interesting about this messenger chemical is that it’s only secreted by ostoblast cells. When a bone stem cell wants to make more bone, it becomes an osteoblast cell. This cell can produce new bone components like a master mason laying brick. Up until recently, while we knew that osteocalcin was produced by osteoblasts and told their kind to make more bone, we didn’t know what else it did. Then a researcher at Columbia noticed that mice bred to not produce osteocalcin were diabetic, so he confirmed through additional experiments that osteocalcin also regulated blood sugar in both mice and humans. Think of this for a second. Your bone health may be one of the things that determines if you’ll become a diabetic or not! In fact he later discovered that your pancreas produces insulin that talks to your bone osteoblasts which in turn talk back through osteocalcin to help keep blood sugar in check.
So if this major discovery had stayed at bones control blood sugar, it would have been freaky enough, however how about the concept that bones control your sex drive? Yes Columbia later discovered that Osteocalcin also controls testosterone production. This actually makes some sense, as we know that men on testosterone have thicker bones, so that testosterone makes osteoblasts build more bone. However, now we know that the bone cells produce a hormone that tells your genitals to make more testosterone! If you think of this one from an evolutionary standpoint, strong males have strong bones who live to procreate, so it makes sense that strong muscles, strong bones, and sex drive would be somehow associated. In fact this group’s most recent publication shows that male fertility itself is regulated through a bone-pancreas-testis axis.
The upshot? Mom was right about milk and bones! Drink your milk to build strong bones because good bones may have a lot more to do with your overall health than we ever imagined! In addition, because of these discoveries, we may have to be really careful with how we use drugs to impact bone. For example, one of our main therapeutic strategies for helping female osteoporosis is by using chemicals to poison the ostoclasts (the opposite cell type from ostoblasts that break down bone). The most common osteoporosis drug class called Bisphosphonates works this way. We already know that these drugs can lead to osteonecrois (bone death) in certain patients. What’s happening in these patients to their testosterone or insulin levels? For example, one recent study suggested that patients with diabetic complications were at higher risk for bone osteonecrosis by taking bisphosphonates. Is the drug impact on osteocalcin levels the missing link between those two issues? Looks like we need more research in this area.