Osteocalcin (1-49) is a non-collagenous peptide that is secreted by osteoblasts and odontoblasts and comprises 1-2% of the total protein in bone. Secretion of osteocalcin (1-49) is stimulated by 1,25-dihydroxy vitamin D and plasma levels increase in diseases that induce dysregulated bone turnover such as osteoporosis, Paget's disease, and primary hyperparathyroidism. Osteocalcin (1-49) is positively correlated with insulin sensitivity and negatively correlated with high blood glucose levels in women. In vitro, osteocalcin induces chemotaxis of MDA-MB-231 breast cancer cells, human peripheral blood monocytes, and rat osteosarcoma cells with osteoblast-like characteristics. It is also expressed by vascular smooth muscle cells (VSMCs) displaying an osteoblast-like phenotype and has been positively associated with calcification of aortic tissue and heart valves in humans.