The N-terminal fragment of osteocalcin is released during osteoclastic bone resorption in vitro

Kurihara, Noriyoshi; Hosoda, Kei; Tatsumi, Junichi; Yamaji, Takayuki; Hoshihara, Eiyoshi; Arai, Fumio; Ikeda, Katsumi

doi:10.1007/s007740050022

Cited by 6 publications

(5 citation statements)

References 21 publications

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“…The immunoassay results and microscopic data together support a concept for the release of immunodetectable osteocalcin during bone resorption. In agreement with our results, Kurihara et al (46) have provided evidence for osteocalcin immunoreactivity in the supernatant of human bone particle-derived osteoclasts cultured on human bone slices a Because ␥-carboxylation is destroyed in MALDI-MS and not included in observed ions (51,52), all calculations of theoretical molecular masses were performed using the sequence of bovine osteocalcin (average molecular masses) with glutamic acid at positions 17, 21, and 24 instead of ␥-carboxyglutamic acid.…”

Section: Discussionsupporting

confidence: 90%

Release of Intact and Fragmented Osteocalcin Molecules from Bone Matrix during Bone Resorption in Vitro

Ivaska

Hentunen

Vääräniemi

et al. 2004

Journal of Biological Chemistry

175

114

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Osteocalcin detected from serum samples is considered a specific marker of osteoblast activity and bone formation rate. However, osteocalcin embedded in bone matrix must also be released during bone resorption. To understand the contribution of each type of bone cell in circulating osteocalcin levels, we used immunoassays detecting different molecular forms of osteocalcin to monitor bone resorption in vitro. Osteoclasts were obtained from rat long bones and cultured on bovine bone slices using osteocalcin-depleted fetal bovine serum. In addition, human osteoclasts differentiated from peripheral blood mononuclear cells were used. Both rat and human osteoclasts released osteocalcin from bovine bone into medium. The amount of osteocalcin increased in the presence of parathyroid hormone, a stimulator of resorption, and decreased in the presence of bafilomycin A1, an inhibitor of resorption. The amount of osteocalcin in the medium correlated with a well characterized marker of bone resorption, the C-terminal telopeptide of type I collagen (r > 0.9, p < 0.0001). The heterogeneity of released osteocalcin was determined using reverse phase high performance liquid chromatography, and several molecular forms of osteocalcin, including intact molecule, were identified in the culture medium. In conclusion, osteocalcin is released from the bone matrix during bone resorption as intact molecules and fragments. In addition to the conventional use as a marker of bone formation, osteocalcin can be used as a marker of bone resorption in vitro. Furthermore, bone matrix-derived osteocalcin may contribute to circulating osteocalcin levels, suggesting that serum osteocalcin should be considered as a marker of bone turnover rather than bone formation. Osteocalcin (OC)1 is a 6-kDa noncollagenous protein produced by osteoblasts (1), osteocytes (2), and odontoblasts (3).Osteocalcin messenger RNA has also been detected in tissues other than bone, but it appears to be processed properly only in the bone microenvironment (4, 5). The structure of osteocalcin is characterized by three glutamic acid residues, which undergo a vitamin K-dependent carboxylation. The ␥-carboxyglutamic acid residues (Gla) provide osteocalcin with the ability to bind bone hydroxyapatite with a high affinity (6, 7). Osteocalcin is the second most abundant protein in the bone matrix, and it is highly conserved among all vertebrate species (8). The biological function of osteocalcin is probably related to the regulation of bone turnover and/or mineralization (9, 10).The expression of osteocalcin is a marker of late osteoblast differentiation and is induced only after the expression of other osteoblastic markers such as alkaline phosphatase and type I collagen (11,12). Newly synthesized osteocalcin is mostly (60 -90%) adsorbed to the bone hydroxyapatite via the Gla residues, but a part of it leaks into the circulation where it can be detected (13,14). Although osteoblasts synthesize only intact osteocalcin (15), osteocalcin may further undergo intracellular processing or ...

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Section: Discussionsupporting

confidence: 90%

Release of Intact and Fragmented Osteocalcin Molecules from Bone Matrix during Bone Resorption in Vitro

Ivaska

Hentunen

Vääräniemi

et al. 2004

Journal of Biological Chemistry

175

114

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“…Potentially, this might be attributed to the different phases of osteoblast differentiation and activation, reflected by these markers [30]. The significant increase in OC (a marker of bone formation and potentially resorption [31]) and a tendency towards an increase in CTX β and u DPD/Cr in the Gambian subjects may be attributed to their more pronounced increase in PTH.…”

Section: Discussionmentioning

confidence: 99%

Ethnic differences in parathyroid hormone secretion and mineral metabolism in response to oral phosphate administration

Yan

Schoenmakers

Zhou

et al. 2009

Bone

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Ethnic differences in bone metabolism have been reported and it has been suggested that these may be partly due to prolonged exposure to an elevated plasma parathyroid hormone (PTH) concentration or a decreased sensitivity to PTH. We explored ethnic differences in bone and mineral metabolism by 5 days of oral phosphate (P) loading to stimulate PTH secretion. Healthy older people from UK (B), The Gambia (G) and China (C), 15 individuals from each sex and ethnic group, were studied. Blood and urine samples were collected before and 2 h after P dose on days 1, 4 and 5 and on a control day. The induced changes (%) in PTH and markers of mineral and bone metabolism after 2 h and over 5 days were examined.At baseline, PTH, 1,25(OH)2D and bone turnover markers were higher in Gambian subjects than in British and Chinese subjects (P ≤ 0.01).2 h after P loading, ionized calcium (iCa) decreased and PTH and plasma P (P) increased in all groups (P ≤ 0.01, n.s. between groups). Urinary P to creatinine ratio (uP/Cr) increased, the increase being greater in Chinese subjects than in British and Gambian subjects on days 4 and 5 (P ≤ 0.01). By day 5, fasting iCa was decreased and P increased in British and Gambian (P ≤ 0.01) but not in Chinese subjects. Fasting PTH and uP/Cr increased in all groups. There were ethnic differences in changes in bone markers, but the relationship with changes in PTH was comparable between groups.In conclusion, ethnic differences in mineral metabolism in response to 5-day P loading were found. Chinese subjects showed a more rapid renal clearance of P than British and Gambian counterparts and there were differences between the groups in the skeletal response to P loading, but no evidence was found for resistance to the resorbing effects of PTH.

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“…In Vitro Osteoclast Formation Assay-Primary bone marrow macrophages (BMMs) were isolated as described previously (25) and were plated in 96-well plates (1.3 ϫ 10 5 /well) in ␣-minimum Eagle's medium containing 10% FCS, M-CSF (50 ng/ml), and RANKL (10 ng/ml). After 3 days medium was changed to medium devoid of RANKL with or without CpG-ODN (100 nM), and osteoclast formation (tartrate-resistant acid phosphatase-positive cells with three or more nuclei) was evaluated 30 h later.…”

Section: Methodsmentioning

confidence: 99%

Toll-like Receptor 9 Regulates Tumor Necrosis Factor-α Expression by Different Mechanisms

Amcheslavsky

Zou

Bar‐Shavit

2004

Journal of Biological Chemistry

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The N-terminal fragment of osteocalcin is released during osteoclastic bone resorption in vitro

Cited by 6 publications

References 21 publications

Release of Intact and Fragmented Osteocalcin Molecules from Bone Matrix during Bone Resorption in Vitro

Release of Intact and Fragmented Osteocalcin Molecules from Bone Matrix during Bone Resorption in Vitro

Ethnic differences in parathyroid hormone secretion and mineral metabolism in response to oral phosphate administration

Toll-like Receptor 9 Regulates Tumor Necrosis Factor-α Expression by Different Mechanisms

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