Osteocalcin
- OMIM: 112260
- UniProt: P02818
Osteocalcin (synonym: "bone γ - carboxylglutamic acid- containing protein " or " BGP ", the gene: BGLAP ) is a peptide hormone discovered in 1975 in the body of most vertebrates. It is formed in the bone by osteoblasts and odontoblasts in tooth by and binds to hydroxyapatite and calcium. It is part ( one or two percent) of non-collagenous extracellular bone matrix. Osteocalcin is a bone structure of the marker, and to inhibit bone mineralization. Osteocalcin was extracted in the form of completely preserved from the bones of Neanderthals. In mice, small amounts osteocalcin already stimulate insulin secretion and the breakdown of fat cells.
Design and function
The osteocalcin in humans consists of 49 amino acids. Osteocalcin is encoded in humans by a gene on chromosome 1q25 - q31. Its synthesis is induced in osteoblasts by 1,25 (OH) VitD3. The elimination of the gene results in the experiment in mice to an abnormally increased bone mineralization and growth of bone at a simultaneously reduced breaking strength and narrowing of the medullary cavity, a feature of osteopetrosis (marble bone disease).
Osteocalcin contains glutamyl residues which vitamin K and the enzyme Γ - γ - carboxylated Glutamylcarboxylase must be using the cofactor before osteocalcin can actively bind calcium in the bones. The bone matrix contains about 2% of osteocalcin. The calcium-binding property has osteocalcin with other calcium -binding proteins (eg, calbindin or specific clotting factors ) together.
Latest for man nor corroborating research findings point to the osteocalcin to a blood sugar -lowering and fat loss promoting function. Osteocalcin acts on glucose metabolism apparently a) directly: by stimulating the production of insulin in the β - cells of the islets of Langerhans of the pancreas; and possibly b) indirect: by promoting the release of adiponectin which increases the effectiveness of insulin. Osteocalcin apparently causes increased fat loss in the body fat stores. In animal experiments proved mice with high serum Osteocalcinwerten equally resistant to diabetes and obesity, diseased mice in return with missing serum osteocalcin in diabetes and obesity. The newly discovered metabolic functions of the osteocalcin may require new approaches to diabetes II treatment.
In February 2011, an American research group published the results of studies that indicate that osteocalcin promotes fertility of male mice. By binding to a G -protein coupled receptor in the Leydig cells of the testis, it regulates in CREB - dependent manner the expression of enzymes necessary for the production of testosterone. This caused osteocalcin survival of male germ cells. On the other hand, it seems but no influence on the estrogen production in females to have. For the first time a regulating influence of the skeleton has been demonstrated on fertility.
Laboratory values
Osteocalcin is a marker of bone formation with a good diagnostic specificity. Osteocalcin can be detected in blood and urine. The determination method used for this purpose is a chemiluminescent immunoassay. We determined the osteocalcin to assess bone turnover in osteoporosis or multiple myeloma. With the osteocalcin can also check the effectiveness of calcitriol therapy. Osteocalcin has a plasma half -life of 4 minutes. It is excreted by the kidney. At a reduced renal function increased osteocalcin may be used only conditionally. Likewise, ( variants of the vitamin D receptor ) may be responsible for altered values in some individuals genetic factors.
- Primary and secondary hyperparathyroidism,
- High - turnover osteoporosis,
- Bone metastases in malignancies,
- Osteitis deformans,
- Osteomalacia,
- Hyperthyroidism,
- Renal failure
- Hypoparathyroidism,
- Low- turnover osteoporosis,
- Prolonged cortisone therapy,
- Rheumatoid arthritis
The normal range in children and adolescents aged 2 to 17 years is 2.8 to 41 ug / L, with a strong increase has been seen during the pubertal growth spurt. In adults, the normal range is from 3 to 14 g / L.