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Ginsberg C, Hoofnagle AN, Katz R, Hughes-Austin J, Miller LM, Becker JO, Kritchevsky SB, Shlipak MG, Sarnak MJ, Ix JH. The Vitamin D Metabolite Ratio Is Associated With Changes in Bone Density and Fracture Risk in Older Adults. J Bone Miner Res 2021; 36:2343-2350. [PMID: 34423858 PMCID: PMC8688212 DOI: 10.1002/jbmr.4426] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 08/03/2021] [Accepted: 08/11/2021] [Indexed: 12/15/2022]
Abstract
Recent studies have suggested that 25-hydroxyvitamin D (25(OH)D) may be a poor biomarker of bone health, in part because measured levels incorporate both protein-bound and free vitamin D. The ratio of its catabolic product (24,25-dihydroxyvitamin D [24,25(OH)2 D]) to 25(OH)D (the vitamin D metabolite ratio [VMR]) may provide more information on sufficient vitamin D stores and is not influenced by vitamin D-binding protein concentrations. We evaluated whether the VMR or 25(OH)D are more strongly associated with bone loss and fracture risk in older adults. We performed a retrospective cohort study of 786 community-dwelling adults aged 70 to 79 years who participated in the Health Aging and Body Composition study. Our primary outcomes were annual changes in bone density and incident fracture. The mean age of these participants was 75 ± 3 years, 49% were female, 42% were Black, and 23% had an estimated glomerular filtration rate (eGFR) <60 mL/mL/1.73m2 . In fully adjusted models, a 50% lower VMR was associated with 0.3% (0.2%, 0.6%) more rapid decline in total hip bone mineral density (BMD). We found similar relationships with thoracic and lumbar spine BMD. In contrast, 25(OH)D3 concentrations were not associated with longitudinal change in BMD. There were 178 fractures during a mean follow-up of 10 years. Each 50% lower VMR was associated with a 49% (95% confidence interval [CI] 1.06, 2.08) greater fracture risk, whereas lower 25(OH)D3 concentrations were not significantly associated with fracture risk (hazard ratio [HR] per 50% lower 1.07 [0.80, 1.43]). In conclusion, among a diverse cohort of community-dwelling older adults, a lower VMR was more strongly associated with both loss of BMD and fracture risk compared with 25(OH)D3 . Trials are needed to evaluate the VMR as a therapeutic target in persons at risk for worsening BMD and fracture. © 2021 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Charles Ginsberg
- Nephrology Section, Veterans Affairs San Diego Healthcare System, San Diego, CA and Division of Nephrology-Hypertension, University of California, San Diego, San Diego, CA
| | - Andrew N Hoofnagle
- Departments of Laboratory Medicine and Medicine and the Kidney Research Institute, University of Washington, Seattle, WA
| | - Ronit Katz
- Department of Obstetrics & Gynecology, University of Washington, Seattle, WA
| | - Jan Hughes-Austin
- Nephrology Section, Veterans Affairs San Diego Healthcare System, San Diego, CA and Division of Nephrology-Hypertension, University of California, San Diego, San Diego, CA
| | - Lindsay M. Miller
- Nephrology Section, Veterans Affairs San Diego Healthcare System, San Diego, CA and Division of Nephrology-Hypertension, University of California, San Diego, San Diego, CA
| | - Jessica O. Becker
- Departments of Laboratory Medicine and Medicine and the Kidney Research Institute, University of Washington, Seattle, WA
| | - Stephen B. Kritchevsky
- Department of Internal Medicine, Section of Gerontology and Geriatric Medicine, Wake Forest School of Medicine, Winston-Salem, NC
| | - Michael G. Shlipak
- Kidney Health Research Collaborative, Veterans Affairs Medical Center, San Francisco, CA and University of California, San Francisco, CA
| | - Mark J. Sarnak
- Department of Medicine, Division of Nephrology, Tufts Medical Center, Boston, Massachusetts
| | - Joachim H. Ix
- Nephrology Section, Veterans Affairs San Diego Healthcare System, San Diego, CA and Division of Nephrology-Hypertension, University of California, San Diego, San Diego, CA
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Sonneveld R, Hoenderop JG, Stavenuiter AW, Ferrantelli E, Baltissen MP, Dijkman HB, Florquin S, Rops AL, Wetzels JF, Berden JH, van der Vlag J, Nijenhuis T. 1,25-Vitamin D3 Deficiency Induces Albuminuria. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:794-804. [DOI: 10.1016/j.ajpath.2015.11.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 10/22/2015] [Accepted: 11/19/2015] [Indexed: 12/19/2022]
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Christakos S, Dhawan P, Verstuyf A, Verlinden L, Carmeliet G. Vitamin D: Metabolism, Molecular Mechanism of Action, and Pleiotropic Effects. Physiol Rev 2016; 96:365-408. [PMID: 26681795 PMCID: PMC4839493 DOI: 10.1152/physrev.00014.2015] [Citation(s) in RCA: 1071] [Impact Index Per Article: 133.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
1,25-Dihydroxvitamin D3 [1,25(OH)2D3] is the hormonally active form of vitamin D. The genomic mechanism of 1,25(OH)2D3 action involves the direct binding of the 1,25(OH)2D3 activated vitamin D receptor/retinoic X receptor (VDR/RXR) heterodimeric complex to specific DNA sequences. Numerous VDR co-regulatory proteins have been identified, and genome-wide studies have shown that the actions of 1,25(OH)2D3 involve regulation of gene activity at a range of locations many kilobases from the transcription start site. The structure of the liganded VDR/RXR complex was recently characterized using cryoelectron microscopy, X-ray scattering, and hydrogen deuterium exchange. These recent technological advances will result in a more complete understanding of VDR coactivator interactions, thus facilitating cell and gene specific clinical applications. Although the identification of mechanisms mediating VDR-regulated transcription has been one focus of recent research in the field, other topics of fundamental importance include the identification and functional significance of proteins involved in the metabolism of vitamin D. CYP2R1 has been identified as the most important 25-hydroxylase, and a critical role for CYP24A1 in humans was noted in studies showing that inactivating mutations in CYP24A1 are a probable cause of idiopathic infantile hypercalcemia. In addition, studies using knockout and transgenic mice have provided new insight on the physiological role of vitamin D in classical target tissues as well as evidence of extraskeletal effects of 1,25(OH)2D3 including inhibition of cancer progression, effects on the cardiovascular system, and immunomodulatory effects in certain autoimmune diseases. Some of the mechanistic findings in mouse models have also been observed in humans. The identification of similar pathways in humans could lead to the development of new therapies to prevent and treat disease.
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Affiliation(s)
- Sylvia Christakos
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey; and Laboratory of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium
| | - Puneet Dhawan
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey; and Laboratory of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium
| | - Annemieke Verstuyf
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey; and Laboratory of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium
| | - Lieve Verlinden
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey; and Laboratory of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium
| | - Geert Carmeliet
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey; and Laboratory of Clinical and Experimental Endocrinology, KU Leuven, Leuven, Belgium
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Christakos S, Seth T, Hirsch J, Porta A, Moulas A, Dhawan P. Vitamin D Biology Revealed Through the Study of Knockout and Transgenic Mouse Models. Annu Rev Nutr 2013; 33:71-85. [DOI: 10.1146/annurev-nutr-071812-161249] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sylvia Christakos
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103;
| | - Tanya Seth
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103;
| | - Jennifer Hirsch
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103;
| | - Angela Porta
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103;
| | - Anargyros Moulas
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103;
| | - Puneet Dhawan
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07103;
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Lin Y, Ubels JL, Schotanus MP, Yin Z, Pintea V, Hammock BD, Watsky MA. Enhancement of vitamin D metabolites in the eye following vitamin D3 supplementation and UV-B irradiation. Curr Eye Res 2012; 37:871-8. [PMID: 22632164 DOI: 10.3109/02713683.2012.688235] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE This study was designed to measure vitamin D metabolites in the aqueous and vitreous humor and in tear fluid, and to determine if dietary vitamin D3 supplementation affects these levels. We also determined if the corneal epithelium can synthesize vitamin D following UV-B exposure. METHODS Rabbits were fed a control or vitamin D3 supplemented diet. Pilocarpine-stimulated tear fluid was collected and aqueous and vitreous humor were drawn from enucleated eyes. Plasma vitamin D was also measured. To test for epithelial vitamin D synthesis, a human corneal limbal epithelial cell line was irradiated with two doses of UV-B (10 and 20 mJ/cm(2)/day for 3 days) and vitamin D was measured in control or 7-dehydrocholesterol treated culture medium. Measurements were made using mass spectroscopy. RESULTS 25(OH)-vitamin D3 and 24,25(OH)(2)-vitamin D3 increased significantly following D3 supplementation in all samples except vitreous humor. Tear fluid and aqueous humor had small but detectable 1,25(OH)(2)-vitamin D3 levels. Vitamin D2 metabolites were observed in all samples. Vitamin D3 levels were below the detection limit for all samples. Minimal vitamin D3 metabolites were observed in control and UV-B-irradiated epithelial culture medium except following 7-dehydrocholesterol treatment, which resulted in a UV-B-dose dependent increase in vitamin D3, 25(OH)-vitamin D3 and 24,25(OH)(2)-vitamin D3. CONCLUSIONS There are measurable concentrations of vitamin D metabolites in tear fluid and aqueous and vitreous humor, and oral vitamin D supplementation affects vitamin D metabolite concentrations in the anterior segment of the eye. In addition, the UV exposure results lead us to conclude that corneal epithelial cells are likely capable of synthesizing vitamin D3 metabolites in the presence of 7-dehydrocholesterol following UV-B exposure.
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Affiliation(s)
- Yanping Lin
- Department of Entomology & Cancer Center, University of California, Davis, CA, USA
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Taskapan H. Is 24,25(OH)D level really high in dialysis patients with high FGF23 levels? Int Urol Nephrol 2012; 44:1135-44. [PMID: 22467088 DOI: 10.1007/s11255-012-0157-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 03/05/2012] [Indexed: 12/20/2022]
Abstract
Deficiency of 1,25-dihydroxyvitamin D [1,25(OH)(2)D] and excessive fibroblast growth factor (FGF23) are suggested to be associated with increased mortality in patients with chronic kidney disease (CKD). Generally, 24-hydroxylation has been considered the first step in the degradation pathway of 1,25(OH)(2)D and 25(OH)D. 24,25-dihydroxyvitamin D [24,25(OH)(2)D] was believed to be a degradation product, with no important biological effects. However, some data have accumulated showing that 24,25(OH)(2)D has biological effects on its own. Under conditions of eucalcemia, the synthesis of 24,25(OH)(2)D is increased, and the synthesis of 1,25(OH)(2)D is decreased. In patients with CKD, both high parathyroid hormone levels, which decrease the activity of enzyme CYP24A1 (24-hydroxylase), and high FGF23 levels, which increase the activity of enzyme CYP24A1, were often detected. However, information about 24,25(OH)(2)D levels in these patients is very limited. Whether compensatory changes in levels of FGF23 and 24,25(OH)(2)D in CKD patients are protective or harmful remain unknown issues. Therefore, more studies are needed to identify the nature of the interactions between these molecules and to fully elucidate their clinical significance.
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Affiliation(s)
- Hulya Taskapan
- Nephrology Department, Inonu University Medical Faculty, 4400 Malatya, Turkey.
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Wagner D, Hanwell HE, Schnabl K, Yazdanpanah M, Kimball S, Fu L, Sidhom G, Rousseau D, Cole DEC, Vieth R. The ratio of serum 24,25-dihydroxyvitamin D(3) to 25-hydroxyvitamin D(3) is predictive of 25-hydroxyvitamin D(3) response to vitamin D(3) supplementation. J Steroid Biochem Mol Biol 2011; 126:72-7. [PMID: 21605672 DOI: 10.1016/j.jsbmb.2011.05.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2011] [Revised: 04/21/2011] [Accepted: 05/05/2011] [Indexed: 11/24/2022]
Abstract
24,25-Dihydroxyvitamin D (24,25VD) is a major catabolite of 25-hydroxyvitamin D (25VD) metabolism, and may be physiologically active. Our objectives were to: (1) characterize the response of serum 24,25VD(3) to vitamin D(3) (VD(3)) supplementation; (2) test the hypothesis that a higher 24,25VD(3) to 25VD(3) ratio (24,25:25VD(3)) predicts 25VD(3) response. Serum samples (n=160) from wk 2 and wk 6 of a placebo-controlled, randomized clinical trial of VD(3) (28,000IU/wk) were analyzed for serum 24,25VD(3) and 25VD(3) by mass spectrometry. Serum 24,25VD(3) was highly correlated with 25VD(3) in placebo- and VD(3)-treated subjects at each time point (p<0.0001). At wk 2, the 24,25:25VD(3) ratio was lower with VD(3) than with placebo (p=0.035). From wk 2 to wk 6, the 24,25:25VD(3) ratio increased with the VD(3) supplement (p<0.001) but not with placebo, such that at wk 6 this ratio did not significantly differ between groups. After correcting for potential confounders, we found that 24,25:25VD(3) at wk 2 was inversely correlated to the 25VD(3) increment by wk 6 in the supplemented group (r=-0.32, p=0.02) but not the controls. There is a strong correlation between 24,25VD(3) and 25VD(3) that is only modestly affected by VD(3) supplementation. This indicates that the catabolism of 25VD(3) to 24,25VD(3) rises with increasing 25VD(3). Furthermore, the initial ratio of serum 24,25VD(3) to 25VD(3) predicted the increase in 25VD(3). The 24,25:25VD(3) ratio may therefore have clinical utility as a marker for VD(3) catabolism and a predictor of serum 25VD(3) response to VD(3) supplementation.
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Affiliation(s)
- Dennis Wagner
- Department of Nutritional Sciences, University of Toronto, Canada.
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Brandi M. Indications on the use of vitamin D and vitamin D metabolites in clinical phenotypes. CLINICAL CASES IN MINERAL AND BONE METABOLISM : THE OFFICIAL JOURNAL OF THE ITALIAN SOCIETY OF OSTEOPOROSIS, MINERAL METABOLISM, AND SKELETAL DISEASES 2010; 7:243-250. [PMID: 22460535 PMCID: PMC3213838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Affiliation(s)
- M.L. Brandi
- Address for correspondence: Maria Luisa Brandi, MD, PhD, Bone and Mineral Metabolism Unit, Department of Internal Medicine, Viale Pieraccini 6 - 50139 Florence, Italy, Ph. 39 055 4271012, Fax 39 055 2337867, E-mail:
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9
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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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10
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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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St-Arnaud R, Arabian A, Travers R, Barletta F, Raval-Pandya M, Chapin K, Depovere J, Mathieu C, Christakos S, Demay MB, Glorieux FH. Deficient mineralization of intramembranous bone in vitamin D-24-hydroxylase-ablated mice is due to elevated 1,25-dihydroxyvitamin D and not to the absence of 24,25-dihydroxyvitamin D. Endocrinology 2000; 141:2658-66. [PMID: 10875271 DOI: 10.1210/endo.141.7.7579] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The 25-hydroxyvitamin D-24-hydroxylase enzyme (24-OHase) is responsible for the catabolic breakdown of 1,25-dihydroxyvitamin D [1,25(OH)2D], the active form of vitamin D. The 24-OHase enzyme can also act on the 25-hydroxyvitamin D substrate to generate 24,25-dihydroxyvitamin D, a metabolite whose physiological importance remains unclear. We report that mice with a targeted inactivating mutation of the 24-OHase gene had impaired 1,25(OH)2D catabolism. Surprisingly, complete absence of 24-OHase activity during development leads to impaired intramembranous bone mineralization. This phenotype was rescued by crossing the 24-OHase mutant mice to mice harboring a targeted mutation in the vitamin D receptor gene, confirming that the elevated 1,25(OH)2D levels, acting through the vitamin D receptor, were responsible for the observed accumulation of osteoid. Our results confirm the physiological importance of the 24-OHase enzyme for maintaining vitamin D homeostasis, and they reveal that 24,25-dihydroxyvitamin D is a dispensable metabolite during bone development.
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Affiliation(s)
- R St-Arnaud
- Genetics Unit, Shriners Hospital for Children, Montréal, Québec, Canada.
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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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Abstract
Vitamin D undergoes a first hydroxylation in the liver to generate 25-hydroxyvitamin D, then this metabolite is further hydroxylated in the kidney to yield either 1alpha,25-dihydroxyvitamin D [1alpha,25(OH)2D], or 24R,25-dihydroxyvitamin D[24,25(OH)2D]. The production of 1alpha,25(OH)2D is catalyzed by the enzyme 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-OHase), while the synthesis of 24,25(OH)2D is catalyzed by the enzyme 25-hydroxyvitamin D-24-hydroxylase (24-OHase). To determine the role of each of these enzymes in vivo and their putative role during development, we have inactivated each gene by homologous recombination in embryonic stem cells. The targeting vector for the 1alpha-OHase gene was constructed to allow tissue-specific gene inactivation in order to study the hypothesized paracrine/autocrine roles of the 1alpha-OHase enzyme in particular target tissues such as skin, brain, or macrophages. The targeting vector for the 24-OHase gene utilized standard methodology, and analysis of the phenotype of 24-OHase-deficient mice confirmed the role of the 24-OHase enzyme in the catabolism of 1alpha,25(OH)2D. The phenotype of the second generation 24-OHase-null mice also suggests a key role for 24,25(OH)2D in intramembranous bone formation during development.
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Affiliation(s)
- R St-Arnaud
- Shriners Hospital for Children, and Department of Surgery, McGill University, Montreal, Quebec, Canada.
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15
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Sims NA, White CP, Sunn KL, Thomas GP, Drummond ML, Morrison NA, Eisman JA, Gardiner EM. Human and murine osteocalcin gene expression: conserved tissue restricted expression and divergent responses to 1,25-dihydroxyvitamin D3 in vivo. Mol Endocrinol 1997; 11:1695-708. [PMID: 9328351 DOI: 10.1210/mend.11.11.0008] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Human and murine osteocalcin genes demonstrate similar cell-specific expression patterns despite significant differences in gene locus organization and sequence variations in cis-acting regulatory elements. To investigate whether differences in these regulatory regions result in an altered response to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in vivo, we compared the response of the endogenous mouse osteocalcin gene to a bacterial reporter gene directed by flanking regions of the human osteocalcin gene in transgenic mice. Transgene expression colocalized with endogenous osteocalcin expression in serial sections, being detected in osteoblasts, osteocytes and hypertrophic chondrocytes. In calvarial cell culture lysates from transgenic and nontransgenic mice, the endogenous mouse osteocalcin gene did not respond to 1,25-(OH)2D3 treatment. Despite this, transgene activity was significantly increased in the same cells. Similarly, Northern blots of total cellular RNA and in situ hybridization studies of transgenic animals demonstrated a maximal increase in transgene expression at 6 h after 1,25-(OH)2D3 injection (23.6+/-3.6-fold) with a return to levels equivalent to uninjected animals by 24 h (1.2+/-0.1-fold). This increase in transgene expression was also observed at 6 h after 1,25-(OH)2D3 treatment in animals on a low calcium diet (25.2+/-7.7-fold) as well as in transgenic mice fed a vitamin D-deficient diet containing strontium chloride to block endogenous 1,25-(OH)2D3 production (7.5+/-0.9-fold). In contrast to the increased transgene expression levels, neither endogenous mouse osteocalcin mRNA levels nor serum osteocalcin levels were significantly altered after 1,25-(OH)2D3 injection in transgenic or nontransgenic mice, regardless of dietary manipulations, supporting evidence for different mechanisms regulating the response of human and mouse osteocalcin genes to 1,25-(OH)2D3. Although the cis- and trans-acting mechanisms directing cell-specific gene expression appear to be conserved in the mouse and human osteocalcin genes, responsiveness to 1,25-(OH)2D3 is not. The mouse osteocalcin genes do not respond to 1,25-(OH)2D3 treatment, but the human osteocalcin-directed transgene is markedly upregulated under the same conditions and in the same cells. The divergent responses of these homologous genes to 1,25-(OH)2D3 are therefore likely to be due to differences in mouse and human osteocalcin-regulatory sequences rather than to variation in the complement of trans-acting factors present in mouse osteoblastic cells. Increased understanding of these murine-human differences in osteocalcin regulation may shed light on the function of osteocalcin and its regulation by vitamin D in bone physiology.
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Affiliation(s)
- N A Sims
- Bone and Mineral Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales, Australia
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Bikle DD. ROLE OF VITAMIN D, ITS METABOLITES, AND ANALOGS IN THE MANAGEMENT OF OSTEOPOROSIS. Rheum Dis Clin North Am 1994. [DOI: 10.1016/s0889-857x(21)00359-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Yamato H, Okazaki R, Ishii T, Ogata E, Sato T, Kumegawa M, Akaogi K, Taniguchi N, Matsumoto T. Effect of 24R,25-dihydroxyvitamin D3 on the formation and function of osteoclastic cells. Calcif Tissue Int 1993; 52:255-60. [PMID: 8481842 DOI: 10.1007/bf00298729] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Previous reports demonstrated that the administration of large doses of 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] to animals with normal vitamin D supply causes an increase in bone volume with reduced bone resorption and decreased osteoclast number. The present study was undertaken to clarify if 24R,25(OH)2D3 has any inhibitor effect on the formation and function of osteoclasts. The effect of 24R,25(OH)2D3 on the formation of osteoclastic cells was examined by measuring the number of tartrate-resistant acid phosphatase-positive multinucleated cells (MNCs) formed from hemopoietic progenitor cells obtained from spleens of 5-fluorouracil-treated mice. Treatment with 1,25(OH)2D3 or parathyroid hormone fragment 1-34 [PTH(1-34)] stimulated osteoclast-like MNC formation in a dose-dependent manner. Addition of 24R,25(OH)2D3 alone showed a weak stimulatory effect on MNC formation at 10(-6) M, which appeared to be due to its binding to 1,25(OH)2D3 receptors. In contrast, when 24R,25(OH)2D3 was added together with 1,25(OH)2D3 or PTH(1-34), it inhibited osteoclast-like MNC formation stimulated by these hormones. A significant inhibition of MNC formation was observed with 10(-7) M 24R,25(OH)2D3, and the stimulatory effect of 1,25(OH)2D3 or PTH(1-34) was almost completely eliminated with 10(-6) M 24R,25(OH)2D3. Neither 24S,25(OH)2D3 nor 25(OH)D3 exhibited a similar inhibitory effect. The effect of 24R,25(OH)2D3 on the resorptive function of osteoclasts was examined by measuring the formation of resorption pits by mouse bone cells on dentine slices. Treatment with 24R,25(OH)2D3 also inhibited the resorption pit formation stimulated by 1,25(OH)2D3 or PTH(1-34) with similar dose response.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H Yamato
- Fourth Department of Internal Medicine, University of Tokyo School of Medicine, Japan
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18
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Abstract
Parenteral nutrition (PN)-related bone disease remains a problem in patients of all ages. Understanding of the pathogenesis of PN-related bone disease is complicated by the effect of underlying illnesses, therapeutic interventions, and pre-existing nutrition deficiencies before the initiation of PN therapy. Interrelation of various nutrients, for example, calcium, phosphorus, and vitamin D, in their effects on bone mineralization, demands simultaneous assessment of the role of multiple nutrients and increases the difficulty in defining the role of a single nutrient in the development of bone disease. However, recent reports indicate that there exist a number of factors important in the development of PN-related bone disease and some factors such as increased mineral requirement are unique to growing infants whereas other factors such as aluminum toxicity may be common to both adult and pediatric populations. Nonnutritional factors, including chronic use of potent loop diuretics and altered acid-base status, can affect urine mineral loss, cell metabolism, and bone mineralization, particularly in small, preterm infants. Current evidence indicates that the cause of PN-related bone disease is multifactorial, and the prevention of PN-related bone disease awaits better delineation of the exact sequence of pathogenic events.
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Affiliation(s)
- W W Koo
- Department of Pediatrics, University of Tennessee, Memphis
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19
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Erben RG, Weiser H, Sinowatz F, Rambeck WA, Zucker H. Vitamin D metabolites prevent vertebral osteopenia in ovariectomized rats. Calcif Tissue Int 1992; 50:228-36. [PMID: 1617497 DOI: 10.1007/bf00296287] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The present study investigated the prophylactic effects of vitamin D metabolites and vitamin D metabolite combinations on static and dynamic, tetracycline-based, histomorphometric parameters in the axial skeleton of ovariectomized rats. Forty-three Fischer-344 rats (10 weeks old, 130 g each body weight, BW) were either bilaterally ovariectomized (OVX) or sham-operated (SHAM). The rats were allocated into the following groups: SHAM; OVX; OVX + 7.5 ng 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]/rat/day; OVX + 15 ng 1 alpha,24R,25-trihydroxyvitamin D3 [1,24,25-(OH)3D3]/rat/day; OVX + 75 ng 24R,25-dihydroxyvitamin D3 [24,25(OH)2D3]/rat/day; OVX + 7.5 ng 1,25(OH)2D3/rat/day + 15 ng 1,24,25(OH)3D3/rat/day; OVX + 7.5 ng 1,25(OH)2D3/rat/day + 75 ng 24,25(OH)2D3/rat/day. The vitamin D metabolites were fed orally starting 4 weeks after surgery. Urine and blood samples were collected 12 and 16 weeks postovariectomy, respectively. Sixteen weeks after surgery, all rats were sacrificed, and the first lumbar vertebrae were processed undecalcified for histomorphometric analysis. Ovariectomy induced a highly significant reduction (P less than 0.001) of cancellous bone mass in the secondary spongiosa of the lumbar vertebral body. The bone loss in OVX rats was accompanied by a distinct elevation of all histomorphometric parameters of bone formation and resorption. 1,25(OH)2D3 and both vitamin D metabolite combinations significantly raised serum calcium levels and prevented the bone loss by inhibiting the increased bone resorption in OVX rats. In the applied dosage, 1,24,25(OH)3D3 and 24,25(OH)2D3 alone were ineffective in preserving the cancellous bone of the lumbar vertebra in OVX rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R G Erben
- Institute of Physiology, Veterinary Faculty, Ludwig-Maximilians-University, Munich, Federal Republic of Germany
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20
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Nakamura T, Suzuki K, Hirai T, Kurokawa T, Orimo H. Increased bone volume and reduced bone turnover in vitamin D-replete rabbits by the administration of 24R,25-dihydroxyvitamin D3. Bone 1992; 13:229-36. [PMID: 1637569 DOI: 10.1016/8756-3282(92)90202-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
To study the effect of a large dose of 24R,25(OH)2D3 on bone metabolism, we treated vitamin D-replete rabbits with the agent for eight weeks. Fifteen rabbits 20 weeks of age were divided into three groups of five animals each. Group I received only the vehicle; groups II and III were given the agent at doses of 10 micrograms/kg/d, and 100 micrograms/kg/d, respectively. Through the dosing period, serum calcium, phosphorus, alkaline phosphatase, and creatinine levels were not altered. By the end of the experiment, serum 1,25(OH)2D or serum 25(OH)D levels did not change, nor did the PTH level. Serum 24,25(OH)2D levels for groups I, II, and III were 5.25 +/- 3.40, 76.16 +/- 19.90 (p less than .01), and 199.0 +/- 30.90 (p less than .01) ng/ml, respectively. The bone mineral content (BMC) significantly increased in group III. The percentages of BMC increase in group III over group I were 14.5% on the femur, 34.1% (p less than .01) on the sixth lumbar vertebra, and 23.3% (p less than .05) on the seventh lumbar vertebra. A marked increase of bone mineral densities in the cancellous bone-rich regions was seen in group III. Bone histomorphometry on the seventh lumbar vertebra demonstrated that both the eroded surface and the osteoclast number were reduced and the surfaces indicating bone formation such as the osteoid surface and the tetracycline double labeled surface were also reduced. However, both the osteoid thickness and the mineral apposition rate increased and the mineral formation rate at the tissue level remained approximately equal to that in the control.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- T Nakamura
- Department of Orthopedics, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
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21
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Matsumoto T, Igarashi C, Takeuchi Y, Harada S, Kikuchi T, Yamato H, Ogata E. Stimulation by 1,25-dihydroxyvitamin D3 of in vitro mineralization induced by osteoblast-like MC3T3-E1 cells. Bone 1991; 12:27-32. [PMID: 2054233 DOI: 10.1016/8756-3282(91)90051-j] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Although vitamin D is essential for mineralization of bone, it is as yet unclear whether vitamin D has a direct stimulatory effect on the bone mineralization process. In the present study, the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on in vitro mineralization mediated by osteoblast-like MC3T3-E1 cells was examined. MC3T3-E1 cells continued to grow after they reached confluency, and DNA content and alkaline phosphatase activity increased linearly until about 16 days of culture, whereas 45Ca accumulation into cell and matrix layer remained low. After this period, DNA content plateaued, and 45Ca accumulation increased sharply. Histological examination by von Kossa staining revealed that calcium was accumulated into extracellular matrix. In addition, needle-shaped mineral crystals similar to hydroxyapatite crystals could be demonstrated in between collagen fibrils by electron microscopy. Thus, MC3T3-E1 cells differentiate in vitro into cells with osteoblastic phenotype and exhibit mineralization. When MC3T3-E1 cells were treated with 1,25(OH)2D3 at this stage of culture, there was a dose-dependent stimulation of 45Ca accumulation by 1,25(OH)2D3, and a significant stimulation of 45Ca accumulation was observed with 3 x 10(-10) M 1,25(OH)2D3. Although 1,25(OH)2D3 enhanced alkaline phosphatase activity and collagen synthesis at the early phase of culture, it did not affect any of these parameters at the late phase when 1,25(OH)2D3 stimulated mineralization. Neither 24,25-dihydroxyvitamin D3 nor human PTH(1-34) affected mineralization in the presence or absence of 1,25(OH)2D3. These results demonstrate that 1,25(OH)2D3 stimulates matrix mineralization induced by osteoblastic MC3T3-E1 cells, and are consistent with the possibility that 1,25(OH)2D3 has a direct stimulatory effect on bone mineralization process.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- T Matsumoto
- Fourth Department of Internal Medicine, University of Tokyo School of Medicine, Japan
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22
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Bikle DD, Halloran BP, McGalliard-Cone C, Morey-Holton E. Different responses of trabecular and cortical bone to 1,25(OH)2D3 infusion. THE AMERICAN JOURNAL OF PHYSIOLOGY 1990; 259:E715-22. [PMID: 2240210 DOI: 10.1152/ajpendo.1990.259.5.e715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Previous studies regarding the effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on bone have suggested that 1,25(OH)2D3 increases bone mass and calcium. Many of these studies have focused on trabecular or total bone without examining cortical bone per se. To determine whether the response of trabecular bone to 1,25(OH)2D3 differed from the response of cortical bone, we infused 1,25(OH)2D3 into rats and examined bone mass, 45Ca accumulation, and the density distribution of bone particles (as a measure of bone maturation) in both the proximal tibia and shaft. In the proximal tibia 1,25(OH)2D3 decreased 45Ca accumulation, yet increased bone mass and shifted the particle distribution to more mineralized fractions. In the shaft there was a redistribution of bone to less mineralized fractions that was not accompanied by a change in total bone mass or a decrease in 45Ca accumulation. Thus 1,25(OH)2D3 may retard bone maturation and mineralization throughout the tibia, but this effect in the proximal tibia appears to be overshadowed by a reduction in bone resorption resulting in an accumulation of well-mineralized bone in that region. Bone resorption, however, was not measured directly. The net result is an increase in bone mass and density of trabecular bone not seen in cortical bone.
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Affiliation(s)
- D D Bikle
- Veterans Administration Medical Center, San Francisco, California 94121
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23
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Koo WW, Sherman R, Succop P, Ho M, Buckley D, Tsang RC. Serum vitamin D metabolites in very low birth weight infants with and without rickets and fractures. J Pediatr 1989; 114:1017-22. [PMID: 2498490 DOI: 10.1016/s0022-3476(89)80455-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Seventy-one very low birth weight (less than or equal to 1500 gm) infants were studied to determine the sequential changes in serum vitamin D metabolite concentrations between infants with and without radiographically documented rickets, fractures, or both (R/F). Usual intake of vitamin D included 20 IU/kg/day from parenteral nutrition or 400 IU/day supplementation with enteral feeding. Radiographs of both forearms and serum samples were obtained at 3, 6, 9, and 12 months. Twenty-two infants had R/F. At 3 months, significantly lower mean (+/- SEM) serum phosphorus levels (4.5 +/- 0.4 vs 6.1 +/- 0.2 mg/dl), higher 1,25-dihydroxyvitamin D (1,25-[OH]2D) concentrations (96 +/- 5 vs 77 +/- 4 pg/ml), and higher free 1,25-(OH)2D index (1,25-[OH]2D:vitamin D binding protein ratio; 5.2 +/- 0.3 x 10(5) vs 4.0 +/- 0.2 x 10(5] were found in the R/F group. These values returned to normal and were similar between groups on subsequent measurements. Serum calcium, magnesium, and 25-hydroxyvitamin D (25-OHD) concentrations were normal and similar between groups. In both groups, serum vitamin D binding concentrations increased initially but remained stable and normal beyond 6 months. We conclude that in very low birth weight infants with R/F, the vitamin D status (as indicated by serum 25-OHD concentrations) is normal, and that lowered serum phosphorus levels, higher serum 1,25-(OH)2D levels, and a higher free 1,25-(OH)2D index support the thesis that mineral deficiency (especially of phosphorus) may be important in the pathogenesis of R/F in small preterm infants.
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Affiliation(s)
- W W Koo
- Department of Pediatrics, University of Cincinnati, Children's Hospital Research Foundation, Ohio
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24
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Popoff SN, McGuire JL, Zerwekh JE, Marks SC. Treatment of congenital osteopetrosis in the rabbit with high-dose 1,25-dihydroxyvitamin D. J Bone Miner Res 1989; 4:57-67. [PMID: 2718779 DOI: 10.1002/jbmr.5650040109] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Osteopetrosis is a congenital metabolic bone disease characterized by skeletal sclerosis resulting from defective osteoclast-mediated bone resorption. Osteopetrosis has been described in several animal species (mouse, rat, and rabbit) and in children. Bone marrow transplantation, originally shown to reverse the skeletal sclerosis in some animal mutations, has been effective in curing osteopetrosis in some children. Unfortunately, not all children with osteopetrosis are candidates for or respond to bone marrow transplantation. Recent studies have shown that several animal mutations and some children inheriting osteopetrosis have significantly elevated serum levels of 1,25-(OH)2D. Based on the possibility that there may be a resistance to 1,25-(OH)2D, high-dose calcitriol therapy has been used to treat some children and stimulated some parameters of resorption. In this study, we have examined the effects of high-dose calcitriol therapy on various serum and skeletal parameters in the osteopetrotic rabbit. Mutant rabbits and normal littermates were given continuous infusions of calcitriol via subcutaneously implanted osmotic minipumps for 2 weeks at a dose of 0.5, 2.5, or 25 micrograms/kg/per day. Untreated mutant rabbits are hypocalcemic and hypophosphatemic in the presence of elevated serum 1,25-(OH)2 levels in comparison with their normal littermates. Calcitriol infusions resulted in dose-dependent increases in circulating 1,25-(OH)2D levels in both normal and mutant rabbits. However, evaluation of other serum parameters and the skeletal response demonstrated significant differences between osteopetrotic and normal rabbits. At the highest dose, normal animals rapidly became hypercalcemic and osteoporotic, accompanied by weight loss and a failure to thrive; mutants remained hypocalcemic and osteopetrotic but did not exhibit the deleterious physical effects seen in treated normal littermates. Although the number of osteoclasts increased in both mutants and normals, osteoclast phenotype in the former remained abnormal. These data indicate that although very high levels of circulating 1,25-(OH)2D were achieved in osteopetrotic mutants, activation of osteoclast-mediated bone resorption with subsequent improvement of skeletal sclerosis was not observed.
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Affiliation(s)
- S N Popoff
- Department of Cell Biology, University of Massachusetts Medical School, Worcester
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25
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Affiliation(s)
- A M Parfitt
- Bone and Mineral Research Laboratory, Henry Ford Hospital, Detroit, Michigan
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26
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Nakamura T, Kurokawa T, Orimo H. Increase of bone volume in vitamin D-repleted rats by massive administration of 24R,25(OH)2D3. Calcif Tissue Int 1988; 43:235-43. [PMID: 3145129 DOI: 10.1007/bf02555140] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A large dose of 24R,25(OH)2D3 was administered to the vitamin D-repleted rat to examine its effect on the bone. Male Wistar rats were fed a diet containing 0, 0.025, 1.25, 4.0, and 12.5 ppm 24R, 25(OH)2D3 for 2 years starting at age 6 weeks. The estimated amounts of daily intake of 24R,25(OH)2D3 were 0, 93, 4640, 14680, and 49580 ng/100 g body weight, respectively. No notable difference was found in either the weight or the death rate of the animal. The long-term administration of massive doses of 24R,25(OH)2D3 did not lead to hypercalcemia nor did it affect the blood phosphorus, alkaline-phosphatase, or creatinine levels. Radiographs revealed a striking increase in the bone density on the bones from the animals treated with 1.25 ppm or more 24R,25(OH)2D3. Direct single photon absorptiometry revealed a dose-dependent increase in total bone minerals of both the femur and coccyx. Histological examination revealed a marked increase in the cortical thickness of the femur as well as in the cancellous bone volume of the coccyx. Polarizing microscopy demonstrated the lamellar structure of the bone, and undecalcified sections confirmed the increase of mineralized bone. Ash weight, calcium, phosphorus, and magnesium contents on the tibia and fibula also indicated the ascending dose-dependent increase up to 150% of the control. The parameters of bone size were not altered in any group. These results clearly suggest that 24R,25(OH)2D3 given in massive doses has the pharmacological action of increasing bone volume in the rat without causing remarkable hypercalcemia.
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Affiliation(s)
- T Nakamura
- Department of Orthopaedic Surgery, Faculty of Medicine, University of Tokyo, Japan
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27
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Marks SC, Popoff SN. Bone cell biology: the regulation of development, structure, and function in the skeleton. THE AMERICAN JOURNAL OF ANATOMY 1988; 183:1-44. [PMID: 3055928 DOI: 10.1002/aja.1001830102] [Citation(s) in RCA: 267] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Bone cells compose a population of cells of heterogeneous origin but restricted function with respect to matrix formation, mineralization, and resorption. The local, mesenchymal origin of the cells which form the skeleton contrasts with their extraskeletal, hemopoietic relatives under which bone resorption takes place. However, the functions of these two diverse populations are remarkably related and interdependent. Bone cell regulation, presently in its infancy, is a complicated cascade involving a plethora of local and systemic factors, including some components of the skeletal matrices and other organ systems. Thus, any understanding of bone cell regulation is a key ingredient in understanding not only the development, maintenance, and repair of the skeleton but also the prevention and treatment of skeletal disorders.
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Affiliation(s)
- S C Marks
- Department of Anatomy, University of Massachusetts Medical School, Worcester 01655
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28
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Jones G, DeLuca HF. High-performance liquid chromatography of vitamin D and its application to endocrinology. MONOGRAPHS ON ENDOCRINOLOGY 1988; 30:95-139. [PMID: 3068529 DOI: 10.1007/978-3-642-83467-7_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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29
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DeLuca HF, Ostrem V. The relationship between the vitamin D system and cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1986; 206:413-29. [PMID: 3035900 DOI: 10.1007/978-1-4613-1835-4_30] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The classic function of 1,25-dihydroxyvitamin D3, the hormonally active form of vitamin D, is the maintenance of normal levels of calcium and phosphorus in the blood. 1,25-Dihydroxyvitamin D3 binds to a specific receptor protein and exerts its biologic action by a mechanism analogous to that proposed for other steroid hormones, that is, the receptor-ligand complex acts on the chromatin to induce transcription of specific genes. Intracellular receptors that bind 1,25-dihydroxyvitamin D3 with high affinity have been found in a large number of tumor cell lines examined as melanoma, osteosarcoma, and human breast and colonic carcinoma cells. The 1,25-dihydroxyvitamin D3 receptor in these cells has characteristics similar to the receptor in bone and intestine, the known target tissues of the hormone. In fact, 1,25-dihydroxyvitamin D3 inhibits the proliferation of melanoma, osteosarcoma, and breast carcinoma cells. More recently, 1,25-dihydroxyvitamin D3 has been shown to suppress the growth and induce monocytic differentiation of murine and human myeloid leukemia cells in vitro. These results point to a previously unsuspected involvement of vitamin D in cell proliferation and differentiation and suggest that analogs of the vitamin D hormone may be of interest as possible therapeutic agents in the treatment of malignancy.
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30
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Jarnagin K, Zeng SY, Phelps M, DeLuca HF. Metabolism and pharmacokinetics of 24,25-dihydroxyvitamin D3 in the vitamin D3-replete rat. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)38771-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Abstract
1,25-dihydroxyvitamin D3 [1,25(OH)2D3] is essential for normal growth and mineralization, but its direct effects on various aspects of bone formation remain controversial. 1,25(OH)2D3 was studied for its effects on DNA, collagen and noncollagen protein synthesis, and alkaline phosphatase activity (APA) in the periosteum and periosteum-free bone from 21-day fetal rat calvariae. 1,25(OH)2D3 (0.01 to 10 nM) inhibited the incorporation of 3H-proline into collagenase-digestible protein (CDP) and the percent of collagen synthesized, and, at 10 nM, APA in the periosteum-free bone. 1,25(OH)2D3 inhibited type I collagen without affecting other collagen types. In contrast, 1,25(OH)2D3 at 10 nM caused a small but significant stimulation of the incorporation of 3H-thymidine into acid-insoluble residues (DNA) and on DNA content; both effects were exclusively observed in the periosteum. Hydroxyurea did not modify the inhibitory effect of 1,25(OH)2D3 on 3H-proline incorporation into CDP. These studies indicate that 1,25(OH)2D3 stimulates periosteal DNA synthesis but inhibits type I collagen synthesis and APA in the periosteum-free bone.
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32
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Vitamin D and Kidney Disease. Nephrology (Carlton) 1984. [DOI: 10.1007/978-1-4612-5284-9_115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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