Osteocalcin

Endocrine Actions of Osteocalcin

Osteocalcin is the most abundant noncollagenous protein of bone matrix. Once transcribed, this protein undergoes posttranslational modifications within osteoblastic cells before its secretion, including the carboxylation of three glutamic residues in glutamic acid, which is essential for hydroxyapatite binding and deposition in the extracellular matrix of bone. Recent provocative data from expe...

Six osteocalcin assays compared.

We evaluated comparatively six commercially available osteocalcin kits: ELSA-OST-NAT IRMA (CIS), ELSA-Osteo IRMA (CIS), Osteocalcin IRMA (Nichols), OSTK-PR RIA (CIS), OSCA Test Osteocalcin RIA (Henning), and Osteocalcin RIA (Nichols). All of them presented acceptable values of variance, sensitivity, and serial dilutions. However, only the ELSA-OST-NAT, ELSA-Osteo, and OSCA Test kits had analyti...

Imaging using osteocalcin-luciferase.

Osteocalcin, energy and glucose metabolism.

Osteocalcin is a bone matrix protein that has been associated with several hormonal actions on energy and glucose metabolism. Animal and experimental models have shown that osteocalcin is released into the bloodstream and exerts biological effects on pancreatic beta cells and adipose tissue. Undercarboxylated osteocalcin is the hormonally active isoform and stimulates insulin secretion and enha...

Gamma-carboxylation regulates osteocalcin function

The only well described function of vitamin K (VK) is to serve as a co-factor for the γ-carboxylation of particular proteins to convert specific glutamic acid (Glu) residues to γ-carboxyglutamic acid (Gla) residues. This process involves two enzymes, γ-glutamyl carboxylase (γ-carboxylase or GGCX) and vitamin K epoxide reductase (VKORC1), which together constitute the vitamin K cycle [1]. Physio...