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van der Meijden K, Bravenboer N, Dirks NF, Heijboer AC, den Heijer M, de Wit GMJ, Offringa C, Lips P, Jaspers RT. Effects of 1,25(OH)2 D3 and 25(OH)D3 on C2C12 Myoblast Proliferation, Differentiation, and Myotube Hypertrophy. J Cell Physiol 2016; 231:2517-28. [PMID: 27018098 PMCID: PMC5111790 DOI: 10.1002/jcp.25388] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 03/23/2016] [Indexed: 12/14/2022]
Abstract
An adequate vitamin D status is essential to optimize muscle strength. However, whether vitamin D directly reduces muscle fiber atrophy or stimulates muscle fiber hypertrophy remains subject of debate. A mechanism that may affect the role of vitamin D in the regulation of muscle fiber size is the local conversion of 25(OH)D to 1,25(OH)2 D by 1α-hydroxylase. Therefore, we investigated in a murine C2C12 myoblast culture whether both 1,25(OH)2 D3 and 25(OH)D3 affect myoblast proliferation, differentiation, and myotube size and whether these cells are able to metabolize 25(OH)D3 and 1,25(OH)2 D3 . We show that myoblasts not only responded to 1,25(OH)2 D3 , but also to the precursor 25(OH)D3 by increasing their VDR mRNA expression and reducing their proliferation. In differentiating myoblasts and myotubes 1,25(OH)2 D3 as well as 25(OH)D3 stimulated VDR mRNA expression and in myotubes 1,25(OH)2 D3 also stimulated MHC mRNA expression. However, this occurred without notable effects on myotube size. Moreover, no effects on the Akt/mTOR signaling pathway as well as MyoD and myogenin mRNA levels were observed. Interestingly, both myoblasts and myotubes expressed CYP27B1 and CYP24 mRNA which are required for vitamin D3 metabolism. Although 1α-hydroxylase activity could not be shown in myotubes, after treatment with 1,25(OH)2 D3 or 25(OH)D3 myotubes showed strongly elevated CYP24 mRNA levels compared to untreated cells. Moreover, myotubes were able to convert 25(OH)D3 to 24R,25(OH)2 D3 which may play a role in myoblast proliferation and differentiation. These data suggest that skeletal muscle is not only a direct target for vitamin D3 metabolites, but is also able to metabolize 25(OH)D3 and 1,25(OH)2 D3 . J. Cell. Physiol. 231: 2517-2528, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.
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Affiliation(s)
- K van der Meijden
- Department of Internal Medicine/Endocrinology, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - N Bravenboer
- Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - N F Dirks
- Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - A C Heijboer
- Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - M den Heijer
- Department of Internal Medicine/Endocrinology, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - G M J de Wit
- Laboratory for Myology, MOVE Research Institute Amsterdam, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - C Offringa
- Laboratory for Myology, MOVE Research Institute Amsterdam, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - P Lips
- Department of Clinical Chemistry, VU University Medical Center, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands
| | - R T Jaspers
- Laboratory for Myology, MOVE Research Institute Amsterdam, Department of Human Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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van der Meijden K, Lips P, van Driel M, Heijboer AC, Schulten EAJM, den Heijer M, Bravenboer N. Primary human osteoblasts in response to 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and 24R,25-dihydroxyvitamin D3. PLoS One 2014; 9:e110283. [PMID: 25329305 PMCID: PMC4201491 DOI: 10.1371/journal.pone.0110283] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 09/15/2014] [Indexed: 11/18/2022] Open
Abstract
The most biologically active metabolite 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has well known direct effects on osteoblast growth and differentiation in vitro. The precursor 25-hydroxyvitamin D3 (25(OH)D3) can affect osteoblast function via conversion to 1,25(OH)2D3, however, it is largely unknown whether 25(OH)D3 can affect primary osteoblast function on its own. Furthermore, 25(OH)D3 is not only converted to 1,25(OH)2D3, but also to 24R,25-dihydroxyvitamin D3 (24R,25(OH)2D3) which may have bioactivity as well. Therefore we used a primary human osteoblast model to examine whether 25(OH)D3 itself can affect osteoblast function using CYP27B1 silencing and to investigate whether 24R,25(OH)2D3 can affect osteoblast function. We showed that primary human osteoblasts responded to both 25(OH)D3 and 1,25(OH)2D3 by reducing their proliferation and enhancing their differentiation by the increase of alkaline phosphatase, osteocalcin and osteopontin expression. Osteoblasts expressed CYP27B1 and CYP24 and synthesized 1,25(OH)2D3 and 24R,25(OH)2D3 dose-dependently. Silencing of CYP27B1 resulted in a decline of 1,25(OH)2D3 synthesis, but we observed no significant differences in mRNA levels of differentiation markers in CYP27B1-silenced cells compared to control cells after treatment with 25(OH)D3. We demonstrated that 24R,25(OH)2D3 increased mRNA levels of alkaline phosphatase, osteocalcin and osteopontin. In addition, 24R,25(OH)2D3 strongly increased CYP24 mRNA. In conclusion, the vitamin D metabolites 25(OH)D3, 1,25(OH)2D3 and 24R,25(OH)2D3 can affect osteoblast differentiation directly or indirectly. We showed that primary human osteoblasts not only respond to 1,25(OH)2D3, but also to 24R,25(OH)2D3 by enhancing osteoblast differentiation. This suggests that 25(OH)D3 can affect osteoblast differentiation via conversion to the active metabolite 1,25(OH)2D3, but also via conversion to 24R,25(OH)2D3. Whether 25(OH)D3 has direct actions on osteoblast function needs further investigation.
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Affiliation(s)
- Karen van der Meijden
- Department of Internal Medicine/Endocrinology, VU University Medical Center, Research Institute MOVE, Amsterdam, The Netherlands
| | - Paul Lips
- Department of Internal Medicine/Endocrinology, VU University Medical Center, Research Institute MOVE, Amsterdam, The Netherlands
| | - Marjolein van Driel
- Department of Internal Medicine/Endocrinology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Annemieke C. Heijboer
- Department of Clinical Chemistry, VU University Medical Center, Research Institute MOVE, Amsterdam, The Netherlands
| | - Engelbert A. J. M. Schulten
- Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands
| | - Martin den Heijer
- Department of Internal Medicine/Endocrinology, VU University Medical Center, Research Institute MOVE, Amsterdam, The Netherlands
| | - Nathalie Bravenboer
- Department of Clinical Chemistry, VU University Medical Center, Research Institute MOVE, Amsterdam, The Netherlands
- * E-mail:
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Lancaster ST, Blackburn J, Blom A, Makishima M, Ishizawa M, Mansell JP. 24,25-Dihydroxyvitamin D3 cooperates with a stable, fluoromethylene LPA receptor agonist to secure human (MG63) osteoblast maturation. Steroids 2014; 83:52-61. [PMID: 24513053 DOI: 10.1016/j.steroids.2014.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 12/18/2013] [Accepted: 01/27/2014] [Indexed: 12/29/2022]
Abstract
Vitamin D receptor (VDR) agonists supporting human osteoblast (hOB) differentiation in the absence of bone resorption are attractive agents in a bone regenerative setting. One potential candidate fulfilling these roles is 24,25-dihydroxy vitamin D3 (24,25D). Over forty years ago it was reported that supraphysiological levels of 24,25D could stimulate intestinal calcium uptake and aid bone repair without causing bone calcium mobilisation. VDR agonists co-operate with certain growth factors to enhance hOB differentiation but whether 24,25D might act similarly in promoting cellular maturation has not been described. Given our discovery that lysophosphatidic acid (LPA) co-operated with VDR agonists to enhance hOB maturation, we co-treated MG63 hOBs with 24,25D and a phosphatase-resistant LPA analog. In isolation 24,25D inhibited proliferation and stimulated osteocalcin expression. When co-administered with the LPA analog there were synergistic increases in alkaline phosphatase (ALP). These are encouraging findings which may help realise the future application of 24,25D in promoting osseous repair.
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Affiliation(s)
- Sarah Tamar Lancaster
- Musculoskeletal Research Unit, Avon Orthopaedic Centre, Southmead Hospital, Bristol BS10 5NB, UK
| | - Julia Blackburn
- Musculoskeletal Research Unit, Avon Orthopaedic Centre, Southmead Hospital, Bristol BS10 5NB, UK
| | - Ashley Blom
- Musculoskeletal Research Unit, Avon Orthopaedic Centre, Southmead Hospital, Bristol BS10 5NB, UK
| | - Makoto Makishima
- Division of Biochemistry, Department of Biomedical Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, Japan
| | - Michiyasu Ishizawa
- Division of Biochemistry, Department of Biomedical Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, Japan
| | - Jason Peter Mansell
- Department of Biological, Biomedical & Analytical Sciences, University of the West of England, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
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Lancaster S, Mansell JP. The role of lysophosphatidic acid on human osteoblast formation, maturation and the implications for bone health and disease. ACTA ACUST UNITED AC 2013. [DOI: 10.2217/clp.12.86] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Edouard T, Husseini A, Glorieux FH, Rauch F. Serum 24,25-dihydroxyvitamin D concentrations in osteogenesis imperfecta: relationship to bone parameters. J Clin Endocrinol Metab 2012; 97:1243-9. [PMID: 22319032 DOI: 10.1210/jc.2011-3015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Several studies suggest that 24,25-dihydroxyvitamin D [24,25(OH)₂D] may have an effect on bone mass and metabolism. OBJECTIVE We evaluated the relationship between serum 24,25(OH)₂D levels and bone density and bone metabolism in children with a primary bone disorder-osteogenesis imperfecta (OI). MATERIALS AND METHODS The study included 132 patients (age, 1.1 to 17.9 yr; 67 girls) with OI types I, III, or IV who had not received bisphosphonate treatment at the time of analysis. RESULTS Serum 24,25(OH)₂D levels were significantly higher in OI type III than in OI type I or IV. Serum 24,25(OH)₂D concentrations were positively correlated with serum 25-hydroxyvitamin D (25OHD) levels and negatively correlated with serum PTH levels, and were not correlated with serum 1α,25-dihydroxyvitamin D [1,25(OH)₂D]. The ratio between serum 24,25(OH)₂D and 25OHD was negatively correlated with age and was independent of serum 25OHD concentrations. Regression analysis revealed that OI severity (P = 0.04), serum 25OHD levels (P < 0.001), and serum PTH concentrations (P = 0.045), but not age, gender, or serum 1,25(OH)₂D, were independent predictors of serum 24,25(OH)₂D levels. No correlation was found between serum 24,25(OH)₂D levels or the ratio between serum 24,25(OH)₂D and 25OHD and lumbar spine bone mineral density z-scores or bone marker levels (serum osteocalcin and urinary collagen type I N-telopeptide) after adjusting for OI type, age, and gender. CONCLUSION Patients with more severe OI type had higher 24,25(OH)₂D serum levels and higher serum 24,25(OH)₂D to 25OHD ratios, suggesting an increased 25OHD-24-hydroxylase activity.
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Affiliation(s)
- Thomas Edouard
- Genetics Unit, Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec, Canada H3G 1A6
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Kurajoh M, Inaba M, Yamada S, Imanishi Y, Tsuchida T, Ishimura E, Nishizawa Y. Association of increased active PTH(1-84) fraction with decreased GFR and serum Ca in predialysis CRF patients: modulation by serum 25-OH-D. Osteoporos Int 2008; 19:709-16. [PMID: 18239958 DOI: 10.1007/s00198-007-0554-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 08/24/2007] [Indexed: 10/22/2022]
Abstract
UNLABELLED As the serum calcium and glomerular filtration rate decreased, the proportion of active PTH(1-84) molecules in PTH immunoreactivity increased in serum from predialysis uremic patients, particularly those with vitamin D insufficiency. INTRODUCTION The PTH(1-84) fraction was altered in predialysis patients with chronic renal failure (CRF). METHODS Serum PTH in predialysis CRF patients without any medication was measured by PTH(1-84)-specific whole PTH assay and intact PTH assay cross-reacting with N-truncated PTH. RESULTS In CRF patients, the glomerular filtration rate (GFR) correlated positively with serum Ca and 1,25-dihydroxyvitamin D (1,25(OH)(2)D), and inversely with serum Pi, log intact PTH, and log whole PTH. In multiple regression analysis, including age, gender, body mass index, GFR, Ca, and Pi and 1,25(OH)(2)D as independent variables, serum Ca and GFR associated significantly with serum log whole PTH and intact PTH. Serum log whole PTH/intact PTH ratio, which increased as serum Ca and GFR decreased, retained a negative correlation in those with serum 25-hydroxyvitamin D levels below 20 ng/ml, but not in those above 20 ng/ml. The ratio also correlated positively with serum log tartrate-resistant acid-phosphatase-5b, log cross-linked N-telopeptide of type-I collagen, and log bone alkaline-phosphatase. CONCLUSION As GFR declined with suppression of serum Ca, the proportion of active PTH molecules increased in predialysis CRF patients, particularly those with vitamin D insufficiency.
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Affiliation(s)
- M Kurajoh
- Department of Metabolism, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, 545-8585, Japan
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Sosroseno W, Sugiatno E, Samsudin AR, Ibrahim MF. The effect of nitric oxide on the production of cyclic AMP by a human osteoblast (HOS) cell line stimulated with hydroxyapatite. Biomed Pharmacother 2007; 62:328-32. [PMID: 17988826 DOI: 10.1016/j.biopha.2007.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Accepted: 10/03/2007] [Indexed: 11/29/2022] Open
Abstract
The aim of the present study was to determine the effect of nitric oxide (NO) on the production of cyclic AMP (cAMP) by a human osteoblast cell line (HOS cells) stimulated with hydroxyapatite. Cells were cultured on the HA surfaces with or without the presence of NO donors (SNAP and NAP) for 3 days. The effect of adenylyl cyclase inhibitor (SQ22536), NO scavenger (carboxy PTIO) or endothelial nitric oxide synthase (eNOS) inhibitor (L-NIO), was assessed by adding these to the cultures of HA-stimulated HOS cells with or without the presence of SNAP. Furthermore, HOS cells were pre-treated with anti-human integrin alphaV antibody prior to culturing on HA surfaces with or without the presence of SNAP. The levels of cAMP and cGMP were determined from the 3-day culture supernatants. The results showed that the production of cAMP but not cGMP by HA-stimulated HOS cells was augmented by SNAP. SQ22536 and carboxy PTIO suppressed but L-NIO only partially inhibited the production of cAMP by HA-stimulated HOS cells with or without the presence of exogenous NO. Pre-treatment of the cells with anti-human integrin alphaV antibody suppressed the production of cAMP by HA-stimulated HOS cells with or without the presence of NO. Therefore, the results of the present study suggest that NO may up-regulate the production of cAMP, perhaps, by augmenting adenylyl cyclase activity initiated by the binding between HOS cell-derived integrin alphaV and HA surface.
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Affiliation(s)
- Wihaskoro Sosroseno
- School of Dentistry, AIMST University, Amanjaya Campus, 2 Persiaran Cempaka, Sungai Petani 08000, Kedah Darul Aman, Malaysia.
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van Driel M, Koedam M, Buurman CJ, Roelse M, Weyts F, Chiba H, Uitterlinden AG, Pols HAP, van Leeuwen JPTM. Evidence that both 1α,25-dihydroxyvitamin D3 and 24-hydroxylated D3 enhance human osteoblast differentiation and mineralization. J Cell Biochem 2006; 99:922-35. [PMID: 16741965 DOI: 10.1002/jcb.20875] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Vitamin D plays a major role in the regulation of mineral homeostasis and affects bone metabolism. So far, detailed knowledge on the vitamin D endocrine system in human bone cells is limited. Here we investigated the direct effects of 1alpha,25-(OH)2D3 on osteoblast differentiation and mineralization. Also, we studied the impact of 24-hydroxylation, generally considered as the first step in the degradation pathway of vitamin D, as well as the role of the nuclear and presumed membrane vitamin D receptor (VDR). For this we used a human osteoblast cell line (SV-HFO) that has the potency to differentiate during culture forming a mineralized extracellular matrix in a 3-week period. Transcriptional analyses demonstrated that both 1alpha,25-(OH)2D3 and the 24-hydroxylated metabolites 24R,25-(OH)2D3 and 1alpha,24R,25-(OH)3D3 induced gene transcription. All metabolites dose-dependently increased alkaline phosphatase (ALP) activity and osteocalcin (OC) production (protein and RNA), and directly enhanced mineralization. 1Alpha,24R,25-(OH)3D3 stimulated ALP activity and OC production most potently, while for mineralization it was equipotent to 1alpha,25-(OH)2D3. The nuclear VDR antagonist ZK159222 almost completely blocked the effects of all metabolites. Interestingly, 1beta,25-(OH)2D3, an inhibitor of membrane effects of 1alpha,25-(OH)2D3 in the intestine, induced gene transcription and increased ALP activity, OC expression and mineralization. In conclusion, not only 1alpha,25-(OH)2D3, but also the presumed 24-hydroxylated "degradation" products stimulate differentiation of human osteoblasts. 1Alpha,25-(OH)2D3 as well as the 24-hydroxylated metabolites directly enhance mineralization, with the nuclear VDR playing a central role. The intestinal antagonist 1beta,25-(OH)2D3 acts in bone as an agonist and directly stimulates mineralization in a nuclear VDR-dependent way.
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Affiliation(s)
- M van Driel
- Department of Internal Medicine, Erasmus MC, 3015 GE Rotterdam, The Netherlands
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Boyan BD, Bonewald LF, Sylvia VL, Nemere I, Larsson D, Norman AW, Rosser J, Dean DD, Schwartz Z. Evidence for distinct membrane receptors for 1 alpha,25-(OH)(2)D(3) and 24R,25-(OH)(2)D(3) in osteoblasts. Steroids 2002; 67:235-46. [PMID: 11856547 DOI: 10.1016/s0039-128x(01)00160-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1 alpha,25-(OH)(2)D(3) exerts its effects on chondrocytes and enterocytes via nuclear receptors (1,25-nVDR) and a separate membrane receptor (1,25-mVDR) that activates protein kinase C (PKC). 24R,25-(OH)(2)D(3) also stimulates PKC in chondrocytes, but through other membrane mechanisms. This study examined the hypothesis that osteoblasts possess distinct membrane receptors for 1 alpha,25-(OH)(2)D(3) and 24R,25-(OH)(2)D(3) that are involved in the activation of PKC and that receptor expression varies as a function of cell maturation state. 1 alpha,25-(OH)(2)D(3) stimulated PKC in well differentiated (UMR-106, MC-3T3-E1) and moderately differentiated (ROS 17/2.8) osteoblast-like cells, and in cultures of fetal rat calvarial (FRC) cells and 2T3 cells treated with rhBMP-2 to promote differentiation. 24R,25-(OH)(2)D(3) stimulated PKC in FRC and 2T3 cultures that had not been treated to induce differentiation, and in ROS 17/2.8 cells. MG63 cells, a relatively undifferentiated osteoblast-like cell line, had no response to either metabolite. Ab99, a polyclonal antibody generated to the chick enterocyte 1,25-mVDR, but not a specific antibody to the 1,25-nVDR, inhibited response to 1 alpha,25-(OH)(2)D(3). 1 alpha,25-(OH)(2)D(3) exhibited specific binding to plasma membrane preparations from cells demonstrating a PKC response to this metabolite that is typical of positive cooperativity. Western blots of these membrane proteins reacted with Ab99, and the Ab99-positive protein had an Mr of 64 kDa. There was no cross-reaction with antibodies to the C- or N-terminus of annexin II. The effect of 24,25-(OH)(2)D(3) on PKC was stereospecific; 24S,25-(OH)(2)D(3) had no effect. These results demonstrate that response to 1 alpha,25-(OH)(2)D(3) and 24R,25-(OH)(2)D(3) depends on osteoblast maturation state and suggest that specific and distinct membrane receptors are involved.
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Affiliation(s)
- Barbara D Boyan
- Department of Orthopaedics, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
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Thierry-Palmer M, Tewolde TK, Forté C, Wang M, Bayorh MA, Emmett NL, White J, Griffin K. Plasma 24,25-dihydroxyvitamin D concentration of Dahl salt-sensitive rats decreases during high salt intake. J Steroid Biochem Mol Biol 2002; 80:315-21. [PMID: 11948016 DOI: 10.1016/s0960-0760(02)00029-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Dahl salt-sensitive rats, but not salt-resistant rats, develop hypertension in response to high salt intake. We have previously shown an inverse relationship between plasma 25-hydroxyvitamin D (25-OHD) concentration and blood pressure of Dahl salt-sensitive rats during high salt intake. In this study, we report on the relationship between high salt intake and plasma 24,25-dihydroxyvitamin D (24,25-(OH)(2)D) concentration of Dahl salt-sensitive and salt-resistant rats. Rats were fed a high salt diet (8%) and sacrificed at day 2, 7, 14, 21, and 28. Plasma 24,25-(OH)(2)D concentrations of salt-sensitive rats were reduced to 50% of that at baseline at day 2-when blood pressure and plasma 25-OHD concentration were unchanged, but 25-OHD content in the kidney was 81% of that at baseline. Plasma 24,25-(OH)(2)D concentration was reduced further to 10% of that at baseline from day 7 to 14 of high salt intake, a reduction that was prevented in rats switched to a low salt (0.3%) diet at day 7. Exogenous 24,25-dihydroxycholecalciferol (24,25-(OH)(2)D(3)), administered at a level that increased plasma 24,25-(OH)(2)D concentration to five times normal, did not attenuate the salt-induced hypertension of salt-sensitive rats. Plasma 24,25-(OH)(2)D concentration of salt-resistant rats was gradually reduced to 50% of that at baseline at day 14 and returned to baseline value at day 28 of high salt intake. We conclude that the decrease in plasma 24,25-(OH)(2)D concentration in salt-sensitive rats during high salt intake is caused by decreased 25-OHD content in the kidney and also by another unidentified mechanism.
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Affiliation(s)
- Myrtle Thierry-Palmer
- Department of Biochemistry, Morehouse School of Medicine, 720 Westview Drive, SW, Atlanta, GA 30310-1495, USA.
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Abstract
The 1alpha-hydroxylated metabolite of 25-hydroxyvitamin D(3), 1,25-dihydroxyvitamin D(3), is the biologically most active metabolite of vitamin D. The 24-hydroxylated metabolites were generally considered as degradation products of a catabolic pathway finally leading to excretion of calcitroic acid. Studies with analogues fluorinated at the C-24 position did not indicate a physiological function for 24R,25(OH)(2)D(3). Nevertheless throughout the years various studies showed biologic effects of other metabolites than 1alpha,25(OH)(2)D(3). In particular the metabolite 24R,25(OH)(2)D(3) has been functionally analyzed, e.g. with respect to a role in normal chicken egg hatchability and effects on chondrocytes in the resting zone of cartilage. Numerous studies have shown the presence of the vitamin D receptor in bone cells and effects of 1alpha,25(OH)(2)D(3) on bone and bone cells. Also for 24R,25(OH)(2)D(3) studies have been performed focusing on effects on bone and bone cells. The purpose of this review is to summarize the data regarding 24R,25(OH)(2)D(3) and bone and to evaluate its role in bone biology.
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Affiliation(s)
- J P van Leeuwen
- Department of Internal Medicine, Erasmus Medical Center Rotterdam, Dr. Molewaterplein 40, 3015 GD, Rotterdam, The Netherlands.
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Abstract
The physiological role of 24,25-dihydroxyvitamin D remains controversial. Recent results suggest that 24,25-dihydroxyvitamin D is essential for fracture healing, and binding sites for 24,25-dihydroxyvitamin D have been identified in fracture callus tissue. Mice deficient in the 25-hydroxyvitamin D-24-hydroxylase enzyme provide novel genetic tools in which to study the role of 24,25-dihydroxyvitamin D in bone development and fracture repair.
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Affiliation(s)
- R St-Arnaud
- Genetics Unit, Shriners Hospital for Children, Montréal, Québec, Canada.
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