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Sampath TK, Simic P, Sendak R, Draca N, Bowe AE, O'Brien S, Schiavi SC, McPherson JM, Vukicevic S. Thyroid-stimulating hormone restores bone volume, microarchitecture, and strength in aged ovariectomized rats. J Bone Miner Res 2007; 22:849-59. [PMID: 17352644 DOI: 10.1359/jbmr.070302] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED We show the systemic administration of low levels of TSH increases bone volume and improves bone microarchitecture and strength in aged OVX rats. TSH's actions are mediated by its inhibitory effects on RANKL-induced osteoclast formation and bone resorption coupled with stimulatory effects on osteoblast differentiation and bone formation, suggesting TSH directly affects bone remodeling in vivo. INTRODUCTION Thyroid-stimulating hormone (TSH) receptor haploinsufficient mice with normal circulating thyroid hormone levels have reduced bone mass, suggesting that TSH directly affects bone remodeling. We examined whether systemic TSH administration restored bone volume in aged ovariectomized (OVX) rats and influenced osteoclast formation and osteoblast differentiation in vitro. MATERIALS AND METHODS Sprague-Dawley rats were OVX at 6 months, and TSH therapy was started immediately after surgery (prevention mode; n = 80) or 7 mo later (restoration mode; n = 152). Hind limbs and lumbar spine BMD was measured at 2- or 4-wk intervals in vivo and ex vivo on termination at 8-16 wk. Long bones were subjected to microCT, histomorphometric, and biomechanical analyses. The direct effect of TSH was examined in osteoclast and osteoblast progenitor cultures and established rat osteosarcoma-derived osteoblastic cells. Data were analyzed by ANOVA Dunnett test. RESULTS In the prevention mode, low doses (0.1 and 0.3 microg) of native rat TSH prevented the progressive bone loss, and importantly, did not increase serum triiodothyroxine (T3) and thyroxine (T4) levels in aged OVX rats. In restoration mode, animals receiving 0.1 and 0.3 microg TSH had increased BMD (10-11%), trabecular bone volume (100-130%), trabecular number (25-40%), trabecular thickness (45-60%), cortical thickness (5-16%), mineral apposition and bone formation rate (200-300%), and enhanced mechanical strength of the femur (51-60%) compared with control OVX rats. In vitro studies suggest that TSH's action is mediated by its inhibitory effects on RANKL-induced osteoclast formation, as shown in hematopoietic stem cells cultivated from TSH-treated OVX rats. TSH also stimulates osteoblast differentiation, as shown by effects on alkaline phosphatase activity, osteocalcin expression, and mineralization rate. CONCLUSIONS These results show for the first time that systemically administered TSH prevents bone loss and restores bone mass in aged OVX rats through both antiresorptive and anabolic effects on bone remodeling.
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Affiliation(s)
- T Kuber Sampath
- Genzyme Corporation, Framingham, Massachusetts 01701-9322, USA.
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Berndt TJ, Craig TA, McCormick DJ, Lanske B, Sitara D, Razzaque MS, Pragnell M, Bowe AE, O’Brien SP, Schiavi SC, Kumar R. Biological activity of FGF-23 fragments. Pflugers Arch 2007; 454:615-23. [PMID: 17333246 PMCID: PMC3818792 DOI: 10.1007/s00424-007-0231-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Accepted: 02/06/2007] [Indexed: 12/14/2022]
Abstract
The phosphaturic activity of intact, full-length, fibroblast growth factor-23 (FGF-23) is well documented. FGF-23 circulates as the intact protein and as fragments generated as the result of proteolysis of the full-length protein. To assess whether short fragments of FGF-23 are phosphaturic, we compared the effect of acute, equimolar infusions of full-length FGF-23 and various FGF-23 fragments carboxyl-terminal to amino acid 176. In rats, intravenous infusions of full-length FGF-23 and FGF-23 176-251 significantly and equivalently increased fractional phosphate excretion (FE Pi) from 14 +/- 3 to 32 +/- 5% and 15 +/- 2 to 33 +/- 2% (p < 0.001), respectively. Chronic administration of FGF-23 176-251 reduced serum Pi and serum concentrations of 1alpha,25-dihydroxyvitamin D. Shorter forms of FGF-23 (FGF-23 180-251 and FGF-23 184-251) retained phosphaturic activity. Further shortening of the FGF-23 carboxyl-terminal domain, however, abolished phosphaturic activity, as infusion of FGF-23 206-251 did not increase urinary phosphate excretion. Infusion of a short fragment of the FGF-23 molecule, FGF-23 180-205, significantly increased FE Pi in rats and reduced serum Pi in hyperphosphatemic Fgf-23 ( -/- ) knockout mice. The activity of FGF-23 180-251 was confirmed in opossum kidney cells in which the peptide reduced Na(+)-dependent Pi uptake and enhanced internalization of the Na(+)-Pi IIa co-transporter. We conclude that carboxyl terminal fragments of FGF-23 are phosphaturic and that a short, 26-amino acid fragment of FGF-23 retains significant phosphaturic activity.
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Affiliation(s)
- Theresa J. Berndt
- Department of Internal Medicine, Mayo Clinic College of Medicine, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
| | - Theodore A. Craig
- Department of Internal Medicine, Mayo Clinic College of Medicine, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
| | - Daniel J. McCormick
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
| | - Beate Lanske
- Department of Developmental Biology, Harvard School of Dental Medicine, 188 Longwood Ave., Boston, MA 02115
| | - Despina Sitara
- Department of Developmental Biology, Harvard School of Dental Medicine, 188 Longwood Ave., Boston, MA 02115
| | - Mohammed S. Razzaque
- Department of Developmental Biology, Harvard School of Dental Medicine, 188 Longwood Ave., Boston, MA 02115
| | - Marlon Pragnell
- Receptor Ligand Therapeutics, Endocrine and Renal Sciences, Genzyme Corp., 1 Mountain Rd, Framingham, Massachusetts 01701, USA
| | - Ann E. Bowe
- Receptor Ligand Therapeutics, Endocrine and Renal Sciences, Genzyme Corp., 1 Mountain Rd, Framingham, Massachusetts 01701, USA
| | - Stephen P. O’Brien
- Receptor Ligand Therapeutics, Endocrine and Renal Sciences, Genzyme Corp., 1 Mountain Rd, Framingham, Massachusetts 01701, USA
| | - Susan C. Schiavi
- Receptor Ligand Therapeutics, Endocrine and Renal Sciences, Genzyme Corp., 1 Mountain Rd, Framingham, Massachusetts 01701, USA
| | - Rajiv Kumar
- Department of Internal Medicine, Mayo Clinic College of Medicine, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
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Berndt T, Craig TA, Bowe AE, Vassiliadis J, Reczek D, Finnegan R, Jan De Beur SM, Schiavi SC, Kumar R. Secreted frizzled-related protein 4 is a potent tumor-derived phosphaturic agent. J Clin Invest 2003; 112:785-94. [PMID: 12952927 PMCID: PMC182208 DOI: 10.1172/jci18563] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Tumors associated with osteomalacia elaborate the novel factor(s), phosphatonin(s), which causes phosphaturia and hypophosphatemia by cAMP-independent pathways. We show that secreted frizzled-related protein-4 (sFRP-4), a protein highly expressed in such tumors, is a circulating phosphaturic factor that antagonizes renal Wnt-signaling. In cultured opossum renal epithelial cells, sFRP-4 specifically inhibited sodium-dependent phosphate transport. Infusions of sFRP-4 in normal rats over 2 hours specifically increased renal fractional excretion of inorganic phosphate (FEPi) from 14% +/- 2% to 34% +/- 5% (mean +/- SEM, P < 0.01). Urinary cAMP and calcium excretion were unchanged. In thyro-parathyroidectomized rats, sFRP-4 increased FEPi from 0.7% +/- 0.2% to 3.8% +/- 1.2% (P < 0.05), demonstrating that sFRP-4 inhibits renal inorganic phosphate reabsorption by PTH-independent mechanisms. Administration of sFRP-4 to intact rats over 8 hours increased FEPi, decreased serum phosphate (1.95 +/- 0.1 to 1.53 +/- 0.09 mmol/l, P < 0.05) but did not alter serum 1alpha, 25-dihydroxyvitamin D, renal 25-hydroxyvitamin D 1alpha-hydroxylase cytochrome P450, and sodium-phosphate cotransporter mRNA concentrations. Infusion of sFRP-4 antagonizes Wnt action as demonstrated by reduced renal beta-catenin and increased phosphorylated beta-catenin concentrations. The sFRP-4 is detectable in normal human serum and in the serum of a patient with tumor-induced osteomalacia. Thus, sFRP-4 displays phosphatonin-like properties, because it is a circulating protein that promotes phosphaturia and hypophosphatemia and blunts compensatory increases in 1alpha, 25-dihydroxyvitamin D.
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Affiliation(s)
- Theresa Berndt
- Department of Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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Bowe AE, Finnegan R, Jan de Beur SM, Cho J, Levine MA, Kumar R, Schiavi SC. FGF-23 inhibits renal tubular phosphate transport and is a PHEX substrate. Biochem Biophys Res Commun 2001; 284:977-81. [PMID: 11409890 DOI: 10.1006/bbrc.2001.5084] [Citation(s) in RCA: 276] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Oncogenic osteomalacia (OOM), X-linked hypophosphatemia (XLH), and autosomal dominant hypophosphatemic rickets (ADHR) are phenotypically similar disorders characterized by hypophosphatemia, decreased renal phosphate reabsorption, normal or low serum calcitriol concentrations, normal serum concentrations of calcium and parathyroid hormone, and defective skeletal mineralization. XLH results from mutations in the PHEX gene, encoding a membrane-bound endopeptidase, whereas ADHR is associated with mutations of the gene encoding FGF-23. Recent evidence that FGF-23 is expressed in mesenchymal tumors associated with OOM suggests that FGF-23 is responsible for the phosphaturic activity previously termed "phosphatonin." Here we show that both wild-type FGF-23 and the ADHR mutant, FGF-23(R179Q), inhibit phosphate uptake in renal epithelial cells. We further show that the endopeptidase, PHEX, degrades native FGF-23 but not the mutant form. Our results suggest that FGF-23 is involved in the pathogenesis of these three hypophosphatemic disorders and directly link PHEX and FGF-23 within the same biochemical pathway.
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Affiliation(s)
- A E Bowe
- Applied Genomics, Genzyme, Framingham, Massachusetts 01701-9322, USA
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Dackowski WR, Connors TD, Bowe AE, Stanton V, Housman D, Doggett NA, Landes GM, Klinger KW. The region surrounding the PKD1 gene: a 700-kb P1 contig from a YAC-deficient interval. Genome Res 1996; 6:515-24. [PMID: 8828040 DOI: 10.1101/gr.6.6.515] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
As part of an effort to identify the gene responsible for the predominant form of polycystic kidney disease (PKD1), we used a gridded human P1 library for contig assembly. The interval of interest, a 700-kb segment on chromosome 16p13.3, can be physically delineated by the genetic markers D16S125 and D16S84 and chromosomally characterized as a GC-rich isochore enriched for CpG islands, genes, and Alu-like repeats. Our attempts to recover CEPH YACs that encode this region of chromosome 16 were unsuccessful. However, we screened an arrayed P1 library using 15 distinct probes from the D16S125-D16S84 interval and identified 56 independent P1 clones. Only one probe from the interval was unsuccessful in identifying a P1 clone. Forty-four P1 clones were determined to be unique based on restriction enzyme analysis, and 42 of these were found to originate from chromosome 16p13.3, based on FISH to metaphase chromosomes. The 700-kb interval could be defined by a single sequence-ready contig comprised of 12 P1 clones and 1 cosmid clone. Our studies support the use of multiple libraries to generate the requisite physical reagents for positional cloning and encourage the use of Escherichia coli-based large-insert cloning systems to recover clones from YAC-deficient chromosomal intervals.
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Affiliation(s)
- W R Dackowski
- Department of Human Genetics, Integrated Genetics, Framingham, Massachusetts 01701, USA
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Yunis JJ, Soreng AL, Bowe AE. Fragile sites are targets of diverse mutagens and carcinogens. Oncogene 1987; 1:59-69. [PMID: 3438083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Using a high-resolution chromosome banding technique with cultured human lymphocytes and caffeine as a mutagen enhancer, 16 different mutagens and carcinogens were found to induce 110 recurrent fragile sites. All agents produced chromosome breaks and the majority of the 110 recurrent break sites involved were elicited by at least half of all agents, even though they act through different molecular mechanisms. Two of the agents used are known to induce hypersensitive chromatin sites in regulatory regions of active genes. Of the 110 mutagen-sensitive fragile sites, 50 coincide with the location of 50 of 75 specific cancer chromosome breakpoints (67%) and 21 with the location of 26 of 36 oncogenes (72%). The expression of so many similar fragile sites following exposure of cultured cells to diverse mutagens, and the high correlation of these sites with cancer chromosome breakpoints and oncogenes, suggests that they can be general targets of mutagenic action.
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Affiliation(s)
- J J Yunis
- Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455
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