Osteocalcin
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[edit] Biology
Osteocalcin is a noncollagenous protein found in bone and dentin. It is secreted by osteoblasts and thought to play a role in mineralization and calcium ion homeostasis. It has been stipulated that osteocalcin may also function as a negative regulator of bone formation, although its exact role is unknown.
[edit] Use as a biochemical marker for bone formation
As osteocalcin is manufactured by osteoblasts, it is often used as a biochemical marker, or biomarker, for the bone formation process. It has been routinely observed that higher serum-osteocalcin levels are relatively well correlated with increases in bone mineral density (BMD) during treatment with anabolic bone formation drugs for osteoporosis, such as forteo. In many studies, Osteocalcin is used as a preliminary biomarker on the effectiveness of a given drug on bone formation.
There is some controversy over the efficacy of using osteocalcin as a reliable biomarker for the bone formation process. While osteocalcin is found in the body during bone formation because it is manufactured by active osteoblasts, the protein may also tightly bind to the newly formed bone structure during this process. Thus, when existing bone is resorbed during osteoclast activity, any osteocalcin that was bound in the bone is released, which may cause an additional rise in serum-osteocalcin levels in the body. Therefore, it is claimed that osteocalcin is more appropriatly a marker for bone turnover than bone formation. However, the amount of osteocalcin freely released into the body during osteoblast activity is disproportionately larger than any released during osteoclast resorption.
Other biomarkers for bone formation are Bone Specific alkaline phosphatase (BSAP), Carboxy-terminal propeptide of type 1 collagen (PICP), and Amino-terminal propeptide of type 1 collagen (PINP).de:Osteocalcin
