Osteocalcin as a hormone regulating glucose metabolism

Figure 5 Schematic representation of the mechanisms regulating glucose metabolism by bone. Undercarboxylated osteocalcin (ucOC) secreted from bone directly stimulates insulin secretion from pancreas and indirectly through increasing the secretion of glucagon-like peptide-1 (GLP-1) from small intestine. UcOC stimulates the expression of adiponectin in adipose tissue, resulting in increasing insulin sensitivity. UcOC also enhances insulin signaling in muscle. G-protein coupled receptor family C group 6 member A (GPRC6A) is a receptor for ucOC and expressed in pancreas β-cells, epithelial cells of small intestine, adipocytes, and myotubes.