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Ay B, Cyr SM, Klovdahl K, Zhou W, Tognoni CM, Iwasaki Y, Rhee EP, Dedeoglu A, Simic P, Bastepe M. Gα11 deficiency increases fibroblast growth factor 23 levels in a mouse model of familial hypocalciuric hypercalcemia. JCI Insight 2024; 9:e178993. [PMID: 38530370 PMCID: PMC11141917 DOI: 10.1172/jci.insight.178993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 03/14/2024] [Indexed: 03/28/2024] Open
Abstract
Fibroblast growth factor 23 (FGF23) production has recently been shown to increase downstream of Gαq/11-PKC signaling in osteocytes. Inactivating mutations in the gene encoding Gα11 (GNA11) cause familial hypocalciuric hypercalcemia (FHH) due to impaired calcium-sensing receptor signaling. We explored the effect of Gα11 deficiency on FGF23 production in mice with heterozygous (Gna11+/-) or homozygous (Gna11-/-) ablation of Gna11. Both Gna11+/- and Gna11-/- mice demonstrated hypercalcemia and mildly raised parathyroid hormone levels, consistent with FHH. Strikingly, these mice also displayed increased serum levels of total and intact FGF23 and hypophosphatemia. Gna11-/- mice showed augmented Fgf23 mRNA levels in the liver and heart, but not in bone or bone marrow, and also showed evidence of systemic inflammation with elevated serum IL-1β levels. Furin gene expression was significantly increased in the Gna11-/- liver, suggesting enhanced FGF23 cleavage despite the observed rise in circulating intact FGF23 levels. Gna11-/- mice had normal renal function and reduced serum levels of glycerol-3-phosphate, excluding kidney injury as the primary cause of elevated intact FGF23 levels. Thus, Gα11 ablation caused systemic inflammation and excess serum FGF23 in mice, suggesting that patients with FHH - at least those with GNA11 mutations - may be at risk for these complications.
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Affiliation(s)
- Birol Ay
- Endocrine Unit, Department of Medicine, and
| | | | | | - Wen Zhou
- Endocrine Unit, Department of Medicine, and
- Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Christina M. Tognoni
- Department of Veterans Affairs, VA Boston Healthcare System, Boston, Massachusetts, USA
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA
| | | | - Eugene P Rhee
- Endocrine Unit, Department of Medicine, and
- Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Alpaslan Dedeoglu
- Department of Veterans Affairs, VA Boston Healthcare System, Boston, Massachusetts, USA
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA
- Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Massachusetts, USA
| | - Petra Simic
- Endocrine Unit, Department of Medicine, and
- Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
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2
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Abstract
Inorganic phosphate (Pi) is an essential component of many biologically important molecules such as DNA, RNA, ATP, phospholipids, or apatite. It is required for intracellular phosphorylation signaling events and acts as pH buffer in intra- and extracellular compartments. Intestinal absorption, uptake into cells, and renal reabsorption depend on a set of different phosphate transporters from the SLC20 (PiT transporters) and SLC34 (NaPi transporters) gene families. The physiological relevance of these transporters is evident from rare monogenic disorders in humans affecting SLC20A2 (Fahr's disease, basal ganglia calcification), SLC34A1 (idiopathic infantile hypercalcemia), SLC34A2 (pulmonary alveolar microlithiasis), and SLC34A3 (hereditary hypophosphatemic rickets with hypercalciuria). SLC34 transporters are inhibited by millimolar concentrations of phosphonoformic acid or arsenate while SLC20 are relatively resistant to these compounds. More recently, a series of more specific and potent drugs have been developed to target SLC34A2 to reduce intestinal Pi absorption and to inhibit SLC34A1 and/or SLC34A3 to increase renal Pi excretion in patients with renal disease and incipient hyperphosphatemia. Also, SLC20 inhibitors have been developed with the same intention. Some of these substances are currently undergoing preclinical and clinical testing. Tenapanor, a non-absorbable Na+/H+-exchanger isoform 3 inhibitor, reduces intestinal Pi absorption likely by indirectly acting on the paracellular pathway for Pi and has been tested in several phase III trials for reducing Pi overload in patients with renal insufficiency and dialysis.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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3
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Zhu Z, Liu M, Zhang Y, Wu J, Gao M, Lei T, Huang F, Chen H, Wu M. Risk factors for the comorbidity of osteoporosis/osteopenia and kidney stones: a cross-sectional study. Arch Osteoporos 2023; 18:128. [PMID: 37857823 DOI: 10.1007/s11657-023-01338-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Accepted: 10/09/2023] [Indexed: 10/21/2023]
Abstract
Low femoral neck bone mineral density (BMD) was associated with the increased risk of kidney stones. Low dietary magnesium intake and increased serum alkaline phosphatase were associated with the increased risk of low femoral neck BMD in kidney stone formers. PURPOSE To evaluate whether low femoral neck bone mineral density (BMD) was associated with a higher risk of kidney stones, and identify risk factors for the comorbidity of osteoporosis/osteopenia and kidney stones. METHODS We analyzed individuals aged ≥ 20 years from National Health and Nutrition Examination Survey 2007-2020 data. Osteoporosis/osteopenia is defined as any T-score < -1.0 of femoral neck, total femoral, and mean lumbar spine (L1-L4) BMD. Dietary intakes (sodium, potassium, magnesium, calcium, phosphorus, calcium/phosphorus, vitamin D (25OHD2+25OHD3)) and serum parameters (sodium, potassium, calcium, phosphorus, bicarbonate, vitamin D, alkaline phosphatase (ALP)) were screened for identifying risk factors for the comorbidity. RESULTS The prevalence of comorbidity of osteoporosis/osteopenia and kidney stones was 4.82%. Femoral neck BMD T-score was negatively associated with the prevalence of kidney stones (n=11,864). Dietary magnesium intake, serum phosphorus, and bicarbonate were negatively associated with the comorbidity prevalence, and serum ALP was positively associated with the comorbidity prevalence (n=6978). Additionally, there remain significant associations of dietary magnesium intake, serum ALP, and bicarbonate with not only femoral neck BMD T-score (n=11331), but also the prevalence of kidney stones (n=23,111) in general population. Furthermore, dietary magnesium intake was positively correlated to femoral neck BMD T-score in stone formers (SFs), while serum ALP was negatively correlated to femoral neck BMD T-score in SFs (n=1163). CONCLUSION Low femoral neck BMD was closely associated with an increased risk of kidney stones. Low magnesium intake and increased serum ALP were associated with the increased risk of the comorbidity, as well as indicative of low femoral neck BMD T-score in SFs, which offered a clue to further clarify the mechanism leading to paradoxical calcification of bone resorption and kidney stones, and had the potential to perform personalized diagnostic workup for low BMD in SFs.
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Affiliation(s)
- Zewu Zhu
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Department of Internal Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, CT, USA
| | - Minghui Liu
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Youjie Zhang
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Jian Wu
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Meng Gao
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Ting Lei
- Department of Orthopedics, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Fang Huang
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Hequn Chen
- Department of Urology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Maolan Wu
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, Hunan, China.
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China.
- Division of Allergy and Clinical Immunology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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4
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Xie H, Bastepe I, Zhou W, Ay B, Ceraj Z, Portales-Castillo IA, Liu ES, Burnett-Bowie SAM, Jüppner H, Rhee EP, Bastepe M, Simic P. 1,25-Dihydroxyvitamin D3 regulates furin-mediated FGF23 cleavage. JCI Insight 2023; 8:e168957. [PMID: 37681408 PMCID: PMC10544208 DOI: 10.1172/jci.insight.168957] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 07/17/2023] [Indexed: 09/09/2023] Open
Abstract
Intact fibroblast growth factor 23 (iFGF23) is a phosphaturic hormone that is cleaved by furin into N-terminal and C-terminal fragments. Several studies have implicated vitamin D in regulating furin in infections. Thus, we investigated the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D] and the vitamin D receptor (VDR) on furin-mediated iFGF23 cleavage. Mice lacking VDR (Vdr-/-) had a 25-fold increase in iFGF23 cleavage, with increased furin levels and activity compared with wild-type (WT) littermates. Inhibition of furin activity blocked the increase in iFGF23 cleavage in Vdr-/- animals and in a Vdr-knockdown osteocyte OCY454 cell line. Chromatin immunoprecipitation revealed VDR binding to DNA upstream of the Furin gene, with more transcription in the absence of VDR. In WT mice, furin inhibition reduced iFGF23 cleavage, increased iFGF23, and reduced serum phosphate levels. Similarly, 1,25(OH)2D reduced furin activity, decreased iFGF23 cleavage, and increased total FGF23. In a post hoc analysis of a randomized clinical trial, we found that ergocalciferol treatment, which increased serum 1,25(OH)2D, significantly decreased serum furin activity and iFGF23 cleavage, compared with placebo. Thus, 1,25(OH)2D inhibits iFGF23 cleavage via VDR-mediated suppression of Furin expression, thereby providing a mechanism by which vitamin D can augment phosphaturic iFGF23 levels.
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Affiliation(s)
- Han Xie
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Isinsu Bastepe
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Wen Zhou
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Birol Ay
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Zara Ceraj
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Ignacio A. Portales-Castillo
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Eva S. Liu
- Endocrine Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | | | - Harald Jüppner
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
- Pediatric Nephrology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Eugene P. Rhee
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Murat Bastepe
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Petra Simic
- Nephrology Division and
- Endocrine Division, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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5
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Ramos P, Larson B, Ashrafzadeh-Kian S, Ito N, Kato H, Bornhorst JA, Algeciras-Schimnich A. Intact Fibroblast Growth Factor 23 Concentrations in Hypophosphatemic Disorders. Endocr Pract 2023; 29:193-198. [PMID: 36627024 DOI: 10.1016/j.eprac.2023.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/23/2022] [Accepted: 01/03/2023] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Evaluation of circulating fibroblast growth factor 23 (FGF23) concentrations plays a key role in the differential diagnosis of patients presenting with hypophosphatemia. FGF23 concentrations obtained by different immunoassays are not comparable and subsequently, differences in the clinical performance of the assays might arise. In this study, we evaluated the clinical performance of the Medfrontier FGF23 Intact immunoassay (MedFrontier, Minaris Medical Co, Ltd, Tokyo, Japan) in clinically relevant hypophosphatemic conditions. METHODS Intact FGF23 (iFGF23) was measured in serum samples from 61 patients with FGF23-dependent hypophosphatemia (42-tumor induced osteomalacia [TIO] and 19-X-linked hypophosphatemia [XLH]); 8 patients with FGF23-independent hypophosphatemia (6-Fanconi Syndrome and 2-Vitamin D dependent rickets); 10 normophosphatemic patients; 15 chronic kidney disease (CKD) stage-2/3 and 20 CKD stage-4/5 patients; and a healthy control population. Disease-specific differences in measured iFGF23 concentrations and FGF23 concentration association with phosphate concentrations were reported. RESULTS iFGF23 concentrations were significantly elevated in 90% and 84% of TIO and XLH hypophosphatemia patients as compared to healthy controls (both TIO and XLH, P = .0001). There was no significant correlation between iFGF23 and phosphate concentrations (P = .74 and P = .86) for TIO and XLH, respectively. Patients with CKD showed a significant increase in serum iFGF23 as the estimated glomerular filtration rate decreased (ρ = -0.79, P ≤ 0.0001). CONCLUSIONS This study evaluated the clinical performance of the MedFrontier iFGF23 assay in a large cohort of XLH and TIO Caucasian and Asian patients. The clinical sensitivity of this iFGF23 assay is appropriate for clinical use.
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Affiliation(s)
- Paola Ramos
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | - Bethany Larson
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
| | | | - Nobuaki Ito
- Division of Nephrology and Endocrinology, The University of Tokyo Hospital, Tokyo, Japan; Osteoporosis Center, The University of Tokyo Hospital, Tokyo, Japan
| | - Hajime Kato
- Division of Nephrology and Endocrinology, The University of Tokyo Hospital, Tokyo, Japan; Osteoporosis Center, The University of Tokyo Hospital, Tokyo, Japan
| | - Joshua A Bornhorst
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
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6
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Jan de Beur SM, Minisola S, Xia WB, Abrahamsen B, Body JJ, Brandi ML, Clifton-Bligh R, Collins M, Florenzano P, Houillier P, Imanishi Y, Imel EA, Khan AA, Zillikens MC, Fukumoto S. Global guidance for the recognition, diagnosis, and management of tumor-induced osteomalacia. J Intern Med 2023; 293:309-328. [PMID: 36511653 PMCID: PMC10108006 DOI: 10.1111/joim.13593] [Citation(s) in RCA: 20] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused by mesenchymal tumors that secrete fibroblast growth factor 23 (FGF23). Patients present with progressive bone pain, muscle weakness, and fragility fractures. TIO is characterized by hypophosphatemia, excess renal phosphate excretion, and low/inappropriately normal 1,25-dihydroxyvitamin D (1,25(OH)2 D) levels. Rarity and enigmatic clinical presentation of TIO contribute to limited awareness among the medical community. Accordingly, appropriate diagnostic tests may not be requested, leading to delayed diagnosis and poorer patient outcomes. We have developed a global guidance document to improve the knowledge of TIO in the medical community, enabling the recognition of patients with TIO and appropriate referral. We provide recommendations aiding diagnosis, referral, and treatment, helping promote a global standard of patient management. We reviewed the literature and conducted a three-round Delphi survey of TIO experts. Statements were drafted based on published evidence and expert opinions (≥70% consensus required for final recommendations). Serum phosphate should be measured in patients presenting with chronic muscle pain or weakness, fragility fractures, or bone pain. Physical examination should establish features of myopathy and identify masses that could be causative tumors. Priority laboratory evaluations should include urine/serum phosphate and creatinine to assess renal tubular reabsorption of phosphate and TmP/GFR, alkaline phosphatase, parathyroid hormone, 25-hydroxyvitamin D, 1,25(OH)2 D, and FGF23. Patients with the clinical/biochemical suspicion of TIO should be referred to a specialist for diagnosis confirmation, and functional imaging should be used to localize causative tumor(s). Recommended treatment is tumor resection or, with unresectable/unidentifiable tumors, phosphate salts plus active vitamin D, or burosumab.
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Affiliation(s)
- Suzanne M Jan de Beur
- Division of Endocrinology and Metabolism, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Salvatore Minisola
- Department of Clinical, Internal, Anesthesiology and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Wei-Bo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology, State Key Laboratory of Complex Severe and Rare Diseases, NHC, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Bo Abrahamsen
- Open Patient data Explorative Network (OPEN), Department of Clinical Research, University of Southern Denmark and Odense University Hospital, Odense, Denmark.,Department of Medicine, Holbaek Hospital, Holbaek, Denmark.,Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
| | - Jean-Jacques Body
- Department of Medicine, CHU Brugmann, Université Libre de Bruxelles, Brussels, Belgium
| | - Maria Luisa Brandi
- Department of Surgery and Translational Medicine, University of Florence, University Hospital of Florence, Florence, Italy
| | - Roderick Clifton-Bligh
- Department of Endocrinology and Diabetes, Royal North Shore Hospital, Sydney, Australia.,Cancer Genetics Unit, Kolling Institute, Sydney, Australia.,Sydney Medical School, University of Sydney, Sydney, Australia
| | - Michael Collins
- Skeletal Diseases and Mineral Homeostasis Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, USA
| | - Pablo Florenzano
- Centro Traslacional de Endocrinología UC (CETREN-UC), Endocrinology Department, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pascal Houillier
- Centre de Recherche des Cordeliers, INSERM, Sorbonne Université, Université de Paris, Département des Maladies Rénales et Métaboliques, Hôpital Européen Georges-Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Yasuo Imanishi
- Department of Metabolism, Endocrinology, and Molecular Medicine, Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan
| | - Erik A Imel
- Division of Endocrinology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Aliya A Khan
- Division of Endocrinology and Metabolism, Calcium Disorders Clinic, Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - M Carola Zillikens
- Department of Internal Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Seiji Fukumoto
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
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7
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Histological Assessment of Endochondral Ossification and Bone Mineralization. ENDOCRINES 2023. [DOI: 10.3390/endocrines4010006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Finely tuned cartilage mineralization, endochondral ossification, and normal bone formation are necessary for normal bone growth. Hypertrophic chondrocytes in the epiphyseal cartilage secrete matrix vesicles, which are small extracellular vesicles initiating mineralization, into the intercolumnar septa but not the transverse partitions of the cartilage columns. Bone-specific blood vessels invade the unmineralized transverse septum, exposing the mineralized cartilage cores. Many osteoblast precursors migrate to the cartilage cores, where they synthesize abundant bone matrices, and mineralize them in a process of matrix vesicle-mediated bone mineralization. Matrix vesicle-mediated mineralization concentrates calcium (Ca) and inorganic phosphates (Pi), which are converted into hydroxyapatite crystals. These crystals grow radially and are eventually get out of the vesicles to form spherical mineralized nodules, leading to collagen mineralization. The influx of Ca and Pi into the matrix vesicle is regulated by several enzymes and transporters such as TNAP, ENPP1, PiT1, PHOSPHO1, annexins, and others. Such matrix vesicle-mediated mineralization is regulated by osteoblastic activities, synchronizing the synthesis of organic bone material. However, osteocytes reportedly regulate peripheral mineralization, e.g., osteocytic osteolysis. The interplay between cartilage mineralization and vascular invasion during endochondral ossification, as well as that of osteoblasts and osteocytes for normal mineralization, appears to be crucial for normal bone growth.
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8
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Bone Turnover Markers and Bone Mineral Density in Children with Hypophosphatemic Rickets. J Clin Med 2022; 11:jcm11154622. [PMID: 35956239 PMCID: PMC9369845 DOI: 10.3390/jcm11154622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Revised: 08/01/2022] [Accepted: 08/05/2022] [Indexed: 11/29/2022] Open
Abstract
Hypophosphatemic rickets is a rare disease that results in bone deformities. However, little is known about bone turnover and bone mass disorders in this disease. This retrospective study included 12 children aged 1–16 years diagnosed with hypophosphatemic rickets. Parameters of calcium-phosphate metabolism and bone turnover markers were analysed. Bone mineral density was assessed with the use of dual-energy X-ray absorptiometry, and indices of quantitative ultrasound examination of tibiae and radial bones were analysed. In the majority of patients, hypophosphatemia and hyperphosphaturia were present. The assessed bone turnover markers showed increased bone formation. Increased pyridinoline levels were found in 5 out of 12 patients. Bone mineral density was decreased only in one patient. Decreased values of quantitative ultrasound examination were observed in all the analysed patients. Conclusions: (1) Bone metabolism disturbances, reflected in the increased values of bone turnover markers and worse bone quality, were found in the group of patients with hypophosphatemic rickets. (2) It is crucial to determine bone turnover markers, dual-energy X-ray absorptiometry findings and indices of quantitative ultrasound examination in order to monitor progress of the disease, as well as treatment effects.
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9
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Sasaki S, Shiozaki Y, Hanazaki A, Koike M, Tanifuji K, Uga M, Kawahara K, Kaneko I, Kawamoto Y, Wiriyasermkul P, Hasegawa T, Amizuka N, Miyamoto KI, Nagamori S, Kanai Y, Segawa H. Tmem174, a regulator of phosphate transporter prevents hyperphosphatemia. Sci Rep 2022; 12:6353. [PMID: 35428804 PMCID: PMC9012787 DOI: 10.1038/s41598-022-10409-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 04/05/2022] [Indexed: 11/23/2022] Open
Abstract
Renal type II sodium-dependent inorganic phosphate (Pi) transporters NaPi2a and NaPi2c cooperate with other organs to strictly regulate the plasma Pi concentration. A high Pi load induces expression and secretion of the phosphaturic hormones parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) that enhance urinary Pi excretion and prevent the onset of hyperphosphatemia. How FGF23 secretion from bone is increased by a high Pi load and the setpoint of the plasma Pi concentration, however, are unclear. Here, we investigated the role of Transmembrane protein 174 (Tmem174) and observed evidence for gene co-expression networks in NaPi2a and NaPi2c function. Tmem174 is localized in the renal proximal tubules and interacts with NaPi2a, but not NaPi2c. In Tmem174-knockout (KO) mice, the serum FGF23 concentration was markedly increased but increased Pi excretion and hypophosphatemia were not observed. In addition, Tmem174-KO mice exhibit reduced NaPi2a responsiveness to FGF23 and PTH administration. Furthermore, a dietary Pi load causes marked hyperphosphatemia and abnormal NaPi2a regulation in Tmem174-KO mice. Thus, Tmem174 is thought to be associated with FGF23 induction in bones and the regulation of NaPi2a to prevent an increase in the plasma Pi concentration due to a high Pi load and kidney injury.
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Affiliation(s)
- Sumire Sasaki
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Yuji Shiozaki
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Ai Hanazaki
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Megumi Koike
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Kazuya Tanifuji
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Minori Uga
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Kota Kawahara
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Ichiro Kaneko
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Yasuharu Kawamoto
- Department of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Pattama Wiriyasermkul
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan
| | - Tomoka Hasegawa
- Developmental Biology of Hard Tissue, Faculty of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Norio Amizuka
- Developmental Biology of Hard Tissue, Faculty of Dental Medicine, Hokkaido University, Sapporo, Japan
| | - Ken-Ichi Miyamoto
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan.,Graduate School of Agriculture, Ryukoku University, Ohtsu, Japan
| | - Shushi Nagamori
- Department of Laboratory Medicine, The Jikei University School of Medicine, Tokyo, Japan.
| | - Yoshikatsu Kanai
- Department of Bio-System Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Hiroko Segawa
- Department of Applied Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan.
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10
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Abstract
PURPOSE OF REVIEW Fibroblast growth factor 23 (FGF23) is a bone- and bone marrow-derived hormone that is critical to maintain phosphate homeostasis. The principal actions of FGF23 are to reduce serum phosphate levels by decreasing kidney phosphate reabsorption and 1,25-dihydroxyvitamin D synthesis. FGF23 deficiency causes hyperphosphatemia and ectopic calcifications, while FGF23 excess causes hypophosphatemia and skeletal defects. Excess FGF23 also correlates with kidney disease, where it is associated with increased morbidity and mortality. Accordingly, FGF23 levels are tightly regulated, but the mechanisms remain incompletely understood. RECENT FINDINGS In addition to bone mineral factors, additional factors including iron, erythropoietin, inflammation, energy, and metabolism regulate FGF23. All these factors affect Fgf23 expression, while some also regulate FGF23 protein cleavage. Conversely, FGF23 may have a functional role in regulating these biologic processes. Understanding the bi-directional relationship between FGF23 and non-bone mineral factors is providing new insights into FGF23 regulation and function.
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Affiliation(s)
- Petra Simic
- Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
- Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Jodie L Babitt
- Nephrology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
- Program in Membrane Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
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11
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Ito N, Fukumoto S. Congenital Hyperphosphatemic Conditions Caused by the Deficient Activity of FGF23. Calcif Tissue Int 2021; 108:104-115. [PMID: 31965220 DOI: 10.1007/s00223-020-00659-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 01/09/2020] [Indexed: 02/07/2023]
Abstract
Congenital diseases that could result in hyperphosphatemia at an early age include hyperphosphatemic familial tumoral calcinosis (HFTC)/hyperostosis-hyperphosphatemia syndrome (HHS) and congenital hypoparathyroidism/pseudohypoparathyroidism due to the insufficient activity of fibroblast growth factor (FGF) 23 and parathyroid hormone. HFTC/HHS is a rare autosomal recessive disease caused by inactivating mutations in the FGF23, UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3), or Klotho (KL) genes, resulting in the excessive cleavage of active intact FGF23 (FGF23, GALNT3) or increased resistance to the action of FGF23 (KL). Massive ectopic calcification, known as tumoral calcinosis (TC), is seen in periarticular soft tissues, typically in the hip, elbow, and shoulder in HFTC/HHS, reducing the range of motion. However, other regions, such as the eye, intestine, vasculature, and testis, are also targets of ectopic calcification. The other symptoms of HFTC/HHS are painful hyperostosis of the lower legs, dental abnormalities, and systemic inflammation. Low phosphate diets, phosphate binders, and phosphaturic reagents such as acetazolamide are the treatment options for HFTC/HHS and have various consequences, which warrant the development of novel therapeutics involving recombinant FGF23.
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Affiliation(s)
- Nobuaki Ito
- Division of Nephrology and Endocrinology, The University of Tokyo Hospital, Tokyo, Japan.
| | - Seiji Fukumoto
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
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12
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Smith PS, Gottesman GS, Zhang F, Cook F, Ramirez B, Wenkert D, Wollberg V, Huskey M, Mumm S, Whyte MP. X-Linked Hypophosphatemia: Uniquely Mild Disease Associated With PHEX 3'-UTR Mutation c.*231A>G (A Retrospective Case-Control Study). J Bone Miner Res 2020; 35:920-931. [PMID: 31910300 DOI: 10.1002/jbmr.3955] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 12/17/2019] [Accepted: 12/30/2019] [Indexed: 12/27/2022]
Abstract
X-linked hypophosphatemia (XLH), the most prevalent heritable renal phosphate (Pi) wasting disorder, is caused by deactivating mutations of PHEX. Consequently, circulating phosphatonin FGF23 becomes elevated and hypophosphatemia in affected children leads to rickets with skeletal deformity and reduced linear growth while affected adults suffer from osteomalacia and forms of ectopic mineralization. In 2015, we reported uniquely mild XLH in six children and four of their mothers carrying the non-coding PHEX 3'-UTR mutation c.*231A>G. Herein, we characterize this mild XLH variant by comparing its features in 30 individuals to 30 age- and sex-matched patients with XLH but without the 3'-UTR mutation. The "UTR" and "XLH" groups, both comprising 17 children (2 to 17 years, 3 girls) and 13 adults (23 to 63 years, 10 women), had mean ages of 23 years. Only 43% of the UTR group versus 90% of the XLH group had received medical treatment for their disorder, including 0% versus 85% of the females, respectively (ps < .0001). The UTR group was taller: mean ± SD height Z-score (HZ) -1.0 ± 1.0 versus -2.0 ± 1.4 (p = .0034), with significantly greater height for females (-0.9 ± 0.7 versus -2.3 ± 1.4; p = .0050) but not males (-1.2 ± 1.1 versus -1.9 ± 1.5; p = .1541), respectively. Mean ± SD "arm span Z-score" (AZ) did not differ between the UTR -0.8 ± 1.3 versus XLH -1.3 ± 1.8 groups (p = .2269). Consequently, the UTR group was more proportionate with a mean ∆Z (AZ - HZ) of 0.1 ± 0.6 versus 0.7 ± 1.0 (p = .0158), respectively. Compared to the XLH group, the UTR group had significantly higher fasting serum Pi and renal tubular threshold maximum for phosphorus per glomerular filtration rate (TmP/GFR) (ps ≤ .0060), serum FGF23 concentrations within the reference range (p = .0068), and similar serum alkaline phosphatase levels (p = .6513). UTR lumbar spine bone mineral density Z-score was higher (p = .0343). Thus, the 3'-UTR variant of XLH is distinctly mild, especially in girls and women, posing challenges for its recognition and management. © 2020 American Society for Bone and Mineral Research.
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Affiliation(s)
- Pamela S Smith
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA.,Division of Pediatric Endocrinology and Diabetes, Department of Pediatrics, Washington University School of Medicine at St. Louis Children's Hospital, St. Louis, MO, USA
| | - Gary S Gottesman
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA
| | - Fan Zhang
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA
| | - Fiona Cook
- Divsion of Endocrinology, Department of Internal Medicine, Brody School of Medicine, Greenville, NC, USA
| | - Beatriz Ramirez
- Divsion of Endocrinology, Department of Internal Medicine, Brody School of Medicine, Greenville, NC, USA
| | - Deborah Wenkert
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA
| | - Valerie Wollberg
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA
| | - Margaret Huskey
- Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, MO, USA
| | - Steven Mumm
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA.,Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, MO, USA
| | - Michael P Whyte
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children - St. Louis, St. Louis, MO, USA.,Division of Pediatric Endocrinology and Diabetes, Department of Pediatrics, Washington University School of Medicine at St. Louis Children's Hospital, St. Louis, MO, USA.,Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, MO, USA
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13
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14
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Rose E, Lee D, Xiao E, Zhao W, Wee M, Cohen J, Bergwitz C. Endocrine regulation of MFS2 by branchless controls phosphate excretion and stone formation in Drosophila renal tubules. Sci Rep 2019; 9:8798. [PMID: 31217461 PMCID: PMC6584732 DOI: 10.1038/s41598-019-45269-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 04/16/2019] [Indexed: 12/15/2022] Open
Abstract
How inorganic phosphate (Pi) homeostasis is regulated in Drosophila is currently unknown. We here identify MFS2 as a key Pi transporter in fly renal (Malpighian) tubules. Consistent with its role in Pi excretion, we found that dietary Pi induces MFS2 expression. This results in the formation of Malpighian calcium-Pi stones, while RNAi-mediated knockdown of MFS2 increases blood (hemolymph) Pi and decreases formation of Malpighian tubule stones in flies cultured on high Pi medium. Conversely, microinjection of adults with the phosphaturic human hormone fibroblast growth factor 23 (FGF23) induces tubule expression of MFS2 and decreases blood Pi. This action of FGF23 is blocked by genetic ablation of MFS2. Furthermore, genetic overexpression of the fly FGF branchless (bnl) in the tubules induces expression of MFS2 and increases Malpighian tubule stones suggesting that bnl is the endogenous phosphaturic hormone in adult flies. Finally, genetic ablation of MFS2 increased fly life span, suggesting that Malpighian tubule stones are a key element whereby high Pi diet reduces fly longevity previously reported by us. In conclusion, MFS2 mediates excretion of Pi in Drosophila, which is as in higher species under the hormonal control of FGF-signaling.
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Affiliation(s)
- Emily Rose
- Section Endocrinology, Yale School of Medicine, New Haven, CT, USA
| | - Daniela Lee
- Section Endocrinology, Yale School of Medicine, New Haven, CT, USA
| | - Emily Xiao
- Section Endocrinology, Yale School of Medicine, New Haven, CT, USA
| | - Wenzhen Zhao
- Section Endocrinology, Yale School of Medicine, New Haven, CT, USA
| | - Mark Wee
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA
| | - Jonathan Cohen
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA
| | - Clemens Bergwitz
- Section Endocrinology, Yale School of Medicine, New Haven, CT, USA.
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15
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Wagner CA, Rubio-Aliaga I, Hernando N. Renal phosphate handling and inherited disorders of phosphate reabsorption: an update. Pediatr Nephrol 2019; 34:549-559. [PMID: 29275531 DOI: 10.1007/s00467-017-3873-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 12/08/2017] [Accepted: 12/12/2017] [Indexed: 01/12/2023]
Abstract
Renal phosphate handling critically determines plasma phosphate and whole body phosphate levels. Filtered phosphate is mostly reabsorbed by Na+-dependent phosphate transporters located in the brush border membrane of the proximal tubule: NaPi-IIa (SLC34A1), NaPi-IIc (SLC34A3), and Pit-2 (SLC20A2). Here we review new evidence for the role and relevance of these transporters in inherited disorders of renal phosphate handling. The importance of NaPi-IIa and NaPi-IIc for renal phosphate reabsorption and mineral homeostasis has been highlighted by the identification of mutations in these transporters in a subset of patients with infantile idiopathic hypercalcemia and patients with hereditary hypophosphatemic rickets with hypercalciuria. Both diseases are characterized by disturbed calcium homeostasis secondary to elevated 1,25-(OH)2 vitamin D3 as a consequence of hypophosphatemia. In vitro analysis of mutated NaPi-IIa or NaPi-IIc transporters suggests defective trafficking underlying disease in most cases. Monoallelic pathogenic mutations in both SLC34A1 and SLC34A3 appear to be very frequent in the general population and have been associated with kidney stones. Consistent with these findings, results from genome-wide association studies indicate that variants in SLC34A1 are associated with a higher risk to develop kidney stones and chronic kidney disease, but underlying mechanisms have not been addressed to date.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. .,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland.
| | - Isabel Rubio-Aliaga
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
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16
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Beck-Nielsen SS, Mughal Z, Haffner D, Nilsson O, Levtchenko E, Ariceta G, de Lucas Collantes C, Schnabel D, Jandhyala R, Mäkitie O. FGF23 and its role in X-linked hypophosphatemia-related morbidity. Orphanet J Rare Dis 2019; 14:58. [PMID: 30808384 PMCID: PMC6390548 DOI: 10.1186/s13023-019-1014-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 01/30/2019] [Indexed: 12/29/2022] Open
Abstract
Background X-linked hypophosphatemia (XLH) is an inherited disease of phosphate metabolism in which inactivating mutations of the Phosphate Regulating Endopeptidase Homolog, X-Linked (PHEX) gene lead to local and systemic effects including impaired growth, rickets, osteomalacia, bone abnormalities, bone pain, spontaneous dental abscesses, hearing difficulties, enthesopathy, osteoarthritis, and muscular dysfunction. Patients with XLH present with elevated levels of fibroblast growth factor 23 (FGF23), which is thought to mediate many of the aforementioned manifestations of the disease. Elevated FGF23 has also been observed in many other diseases of hypophosphatemia, and a range of animal models have been developed to study these diseases, yet the role of FGF23 in the pathophysiology of XLH is incompletely understood. Methods The role of FGF23 in the pathophysiology of XLH is here reviewed by describing what is known about phenotypes associated with various PHEX mutations, animal models of XLH, and non-nutritional diseases of hypophosphatemia, and by presenting molecular pathways that have been proposed to contribute to manifestations of XLH. Results The pathophysiology of XLH is complex, involving a range of molecular pathways that variously contribute to different manifestations of the disease. Hypophosphatemia due to elevated FGF23 is the most obvious contributor, however localised fluctuations in tissue non-specific alkaline phosphatase (TNAP), pyrophosphate, calcitriol and direct effects of FGF23 have been observed to be associated with certain manifestations. Conclusions By describing what is known about these pathways, this review highlights key areas for future research that would contribute to the understanding and clinical treatment of non-nutritional diseases of hypophosphatemia, particularly XLH.
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Affiliation(s)
| | - Zulf Mughal
- Royal Manchester Children's Hospital, Manchester, UK
| | | | - Ola Nilsson
- Karolinska Institutet, Stockholm, Sweden and Örebro University, Örebro, Sweden
| | | | - Gema Ariceta
- Hospital Universitario Materno-Infantil Vall d'Hebron, Universitat Autonoma de Barcelona, Barcelona, Spain
| | | | - Dirk Schnabel
- University Children's Hospital of Berlin, Berlin, Germany
| | | | - Outi Mäkitie
- Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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Gooi JH, Chia LY, Vrahnas C, Sims NA. Isolation, Purification, Generation, and Culture of Osteocytes. Methods Mol Biol 2019; 1914:39-51. [PMID: 30729459 DOI: 10.1007/978-1-4939-8997-3_3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Osteocytes reside within bone matrix and produce both paracrine and endocrine factors that influence the skeleton and other tissues. Despite their abundance and physiological importance, osteocytes have been difficult to study in vitro because they are difficult to extract and purify, and do not retain their phenotype in standard culture conditions. However, new techniques for this purpose are emerging. This chapter will describe three methods we use to study osteocytes: (1) isolating and purifying primary osteocytes from murine bone, with and without hematopoietic-lineage depletion, (2) differentiating cultured osteoblasts (or osteoblast cell lines) until they reach a stage of osteocytic gene expression, and (3) using the Ocy454 osteocyte-like cell line.
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Affiliation(s)
- Jonathan H Gooi
- Department of Medicine, St. Vincent's Hospital Melbourne, The University of Melbourne, Melbourne, VIC, Australia
| | - Ling Yeong Chia
- Department of Medicine, St. Vincent's Hospital Melbourne, The University of Melbourne, Melbourne, VIC, Australia
- St. Vincent's Institute of Medical Research, Melbourne, VIC, Australia
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Clayton, VIC, Australia
| | - Christina Vrahnas
- Department of Medicine, St. Vincent's Hospital Melbourne, The University of Melbourne, Melbourne, VIC, Australia
- St. Vincent's Institute of Medical Research, Melbourne, VIC, Australia
- MRC Protein Phosphorylation & Ubiquitylation Unit, University of Dundee, Sir James Black Centre, Dundee, UK
| | - Natalie A Sims
- Department of Medicine, St. Vincent's Hospital Melbourne, The University of Melbourne, Melbourne, VIC, Australia.
- St. Vincent's Institute of Medical Research, Melbourne, VIC, Australia.
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18
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Hu Y, Feng J, Wu F. The Multiplicity of Polypeptide GalNAc-Transferase: Assays, Inhibitors, and Structures. Chembiochem 2018; 19:2503-2521. [PMID: 30152088 DOI: 10.1002/cbic.201800303] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/27/2018] [Indexed: 12/18/2022]
Abstract
Mucin-type O-glycosylation is the dominant form of glycosylation in eukaryotes and plays an important role in various physiological processes. The polypeptide GalNAc-transferase (GalNAc-T) catalyzes the first step in the attachment of mucin-type O-glycosylation. GalNAc-T was recently uncovered to be linked with cancer, atherogenic dyslipidemia, and X-linked hypophosphatemic rickets. Therefore, it has attracted increasing interest as a new target for exploring the underlying mechanism and developing new treatments for related diseases. Decades of studies on GalNAc-T have laid a stable foundation for understanding the catalytic mechanism, determining atom-resolution three-dimensional structures, and developing various types of biochemical assays as well as small-molecule inhibitor leads. Here, we systematically summarize this invaluable knowledge on GalNAc-T and cultivate new perspectives to foster breakthrough points for mucin-type O-glycosylation.
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Affiliation(s)
- Youtian Hu
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Juan Feng
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Fang Wu
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, 200240, China
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19
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Lederer E, Wagner CA. Clinical aspects of the phosphate transporters NaPi-IIa and NaPi-IIb: mutations and disease associations. Pflugers Arch 2018; 471:137-148. [DOI: 10.1007/s00424-018-2246-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 12/05/2018] [Indexed: 12/12/2022]
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20
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Michałus I, Rusińska A. Rare, genetically conditioned forms of rickets: Differential diagnosis and advances in diagnostics and treatment. Clin Genet 2018; 94:103-114. [DOI: 10.1111/cge.13229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 02/01/2018] [Accepted: 02/02/2018] [Indexed: 12/21/2022]
Affiliation(s)
- I. Michałus
- Department of Propedeutics Pediatrics and Bone Metabolic Diseases; Medical University of Lodz; Lodz Poland
| | - A. Rusińska
- Department of Propedeutics Pediatrics and Bone Metabolic Diseases; Medical University of Lodz; Lodz Poland
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21
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Linglart A, Chaussain C. [Endocrine control of serum phosphate: from the discoveries of phosphatonins to novel therapies]. ANNALES D'ENDOCRINOLOGIE 2018. [PMID: 28645356 DOI: 10.1016/s0003-4266(17)30076-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Phosphate is absorbed through the gut, stored in the bone and reabsorbed through the proximal renal tubule. More importantly, PTH and FGF23 have been identified as the main phosphaturic factors that control the expression of the phosphate co-transporters NaPi-IIa et IIc. By allowing the adjustment of the urinary phosphate reabsorption, these two phosphatonins play a major role in bone and tooth mineralization and growth. Recently, novel therapies have successfully targeted the FGF23 signaling pathway to treat the hypophosphatemia in patients affected with molecular defects of this pathway (mutations in the PHEX gene).
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Affiliation(s)
- A Linglart
- APHP, Department of Pediatric Endocrinology, Bicêtre Paris Sud Hospital, Reference center for Rare Disorders of the Mineral Metabolism and Plateforme d'Expertise Paris Sud Maladies Rares, Bicêtre Paris Sud Hospital, 78 Rue du Général Leclerc, 94270 Le Kremlin Bicêtre, France.
| | - C Chaussain
- AP-HP Department of Odontology, Bretonneau Hospital, and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism, and EA 2496, Laboratory Orofacial Pathologies, Imaging and Biotherapies, School of Dentistry University Paris Descartes Sorbonne, 12 Rue de l'École de Médecine, 75006 Paris, France
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Gizard A, Rothenbuhler A, Pejin Z, Finidori G, Glorion C, de Billy B, Linglart A, Wicart P. Outcomes of orthopedic surgery in a cohort of 49 patients with X-linked hypophosphatemic rickets (XLHR). Endocr Connect 2017; 6:566-573. [PMID: 28954742 PMCID: PMC5633063 DOI: 10.1530/ec-17-0154] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 09/07/2017] [Indexed: 01/18/2023]
Abstract
BACKGROUND X-linked hypophosphatemic rickets (XLHR) is due to mutations in PHEX leading to unregulated production of FGF23 and hypophosphatemia. XLHR is characterized by leg bowing of variable severity. Phosphate supplements and oral vitamin analogs, partially or, in some cases, fully restore the limb straightness. Surgery is the alternative for severe or residual limb deformities. OBJECTIVE To retrospectively assess the results of surgical limb correction in XLHR (osteotomies and bone alignment except for 3 transient hemiepiphysiodesis). METHODS We analyzed the incidence of recurrence and post-surgical complications in 49 XLHR patients (29F, 20M) (mean age at diagnosis 6.0 years (± 7.1)). RESULTS At first surgery, the mean age was 13.4 years (± 5.0). Recurrence was observed in 14/49 (29%) patients. The number of additional operations significantly decreased with age (2.0 (± 0.9), 1.7 (± 1.0) and 1.2 (± 0.4) in children <11 years, between 11 and 15, and >15 years; P < 0.001). Incidence of recurrence seemed to be lower in patients with good metabolic control of the rickets (25% vs 33%). Complications were observed in 57% of patients. CONCLUSION We report a large series of surgical procedures in XLHR. Our results confirm that phosphate supplements and vitamin D analog therapy is the first line of treatment to correct leg bowing. Surgery before puberty is associated with a high risk of recurrence of the limb deformity. Such procedures should only be recommended, following multidisciplinary discussions, in patients with severe distortion leading to mechanical joint and ligament complications, or for residual deformities once growth plates have fused.
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Affiliation(s)
- A Gizard
- Department of Pediatric Orthopedic SurgeryBesançon University Hospital, Paris, France
| | - A Rothenbuhler
- APHPDepartment of Pediatric Endocrinology, Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- Reference Center for Rare Disorders of Calcium and Phosphate MetabolismLe Kremlin Bicêtre, France
- Plateforme d'Expertise Paris Sud Maladies Rares and Filière OSCARBicêtre Paris Sud, Le Kremlin Bicêtre, France
| | - Z Pejin
- APHPDepartment of Pediatric Orthopedic Surgery, Necker Hospital, Paris, France
| | - G Finidori
- APHPDepartment of Pediatric Orthopedic Surgery, Necker Hospital, Paris, France
| | - C Glorion
- APHPDepartment of Pediatric Orthopedic Surgery, Necker Hospital, Paris, France
| | - B de Billy
- Department of Pediatric Orthopedic SurgeryBesançon University Hospital, Paris, France
| | - A Linglart
- APHPDepartment of Pediatric Endocrinology, Bicêtre Paris Sud, Le Kremlin Bicêtre, France
- Reference Center for Rare Disorders of Calcium and Phosphate MetabolismLe Kremlin Bicêtre, France
- Plateforme d'Expertise Paris Sud Maladies Rares and Filière OSCARBicêtre Paris Sud, Le Kremlin Bicêtre, France
- INSERM U1169Hôpital Bicêtre, Le Kremlin Bicêtre, et Université Paris-Saclay, Le Kremlin Bicêtre, France
| | - P Wicart
- Reference Center for Rare Disorders of Calcium and Phosphate MetabolismLe Kremlin Bicêtre, France
- APHPDepartment of Pediatric Orthopedic Surgery, Necker Hospital, Paris, France
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23
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Dhir G, Li D, Hakonarson H, Levine MA. Late-onset hereditary hypophosphatemic rickets with hypercalciuria (HHRH) due to mutation of SLC34A3/NPT2c. Bone 2017; 97:15-19. [PMID: 27939817 PMCID: PMC5367968 DOI: 10.1016/j.bone.2016.12.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/01/2016] [Accepted: 12/05/2016] [Indexed: 12/19/2022]
Abstract
OBJECTIVE To identify a genetic basis for markedly reduced bone density and multiple fractures in an adult patient with hypophosphatemia and hypercalciuria. SUBJECTS A 54-year-old Vietnamese man, his unaffected two daughters and wife. METHODS We performed biochemical studies and sequenced the SLC34A3 gene using genomic DNA from peripheral blood mononuclear cells. RESULTS Biochemical evaluation of the proband revealed hypophosphatemia with increased renal phosphate wasting, hypercalciuria, low serum parathyroid hormone (PTH) and an elevated serum 1,25(OH)2D level. Mutation analysis of SLC34A3 gene revealed that the patient was a compound heterozygote for two nonsynonymous nucleotide substitutions: a novel c.571G>A (p.G191S) damaging mutation and the previously reported c.200G>A (p.R67H) polymorphism, consistent with the clinical diagnosis of late-onset hereditary hypophosphatemic rickets with hypercalciuria (HHRH). His wife and older daughter both carried the p.R67H polymorphism, while his younger daughter was compound heterozygous for p.R67H and p.G191S. CONCLUSIONS HHRH is an uncommon autosomal recessive disease that generally manifests in childhood as rickets or nephrolithiasis, but an adult onset phenotype may occur in heterozygous carriers of SLC34A3 mutations. The severe presentation of this proband in adulthood with marked nephrolithiasis, multiple fractures and low bone density emphasizes the importance of measuring the serum phosphorus level in patients with suspected but unexplained osteoporosis and/or recurrent renal stones. The recognition of late-onset HHRH facilitates timely institution of appropriate therapy.
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Affiliation(s)
- Gauri Dhir
- Division of Endocrinology Diabetes and Metabolism, Cooper Medical School of Rowan University, Camden, NJ 08103, USA
| | - Dong Li
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - Michael A Levine
- Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA; Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
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Cuervo C, Abitbol CL, Zilleruelo GE, Freundlich M. Fibroblast growth factor-23 and renin-angiotensin system levels in vitamin-D-dependent rickets type I. Pediatr Nephrol 2016; 31:1189-93. [PMID: 26939683 DOI: 10.1007/s00467-016-3356-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 02/12/2016] [Accepted: 02/13/2016] [Indexed: 12/20/2022]
Abstract
BACKGROUND As 1,25(OH)2D3 vitamin D3 induces fibroblast growth factor-23 (FGF-23) production and suppresses the renin-angiotensin-aldosterone system (RAAS), its absence in vitamin-D-dependent rickets type I (VDDR-I) may have adverse health consequences. CASE DESCRIPTION An infant presented at age 8 months with hypocalcemia and rickets and very low 1,25(OH)2D3 levels. Genetic analysis confirmed VDRR-I, and calcitriol therapy was initiated. During periods of nonadherence to therapy, chemical measurements revealed detectable FGF-23 levels, with undetectable 1,25(OH)2D3, hypophosphatemia, low tubular reabsorption of phosphate, hypocalcemia, and very elevated parathyroid hormone (PTH) levels. These changes, in addition to elevated RAAS levels, normalized during calcitriol therapy despite elevated FGF-23 levels. At age 12 years, all rachitic manifestations were absent, and bone mineral density (BMD) and the echocardiogram were normal. CONCLUSIONS Whereas 1,25(OH)2D3 is not indispensable for FGF-23 production, PTH in the absence of vitamin D may maintain FGF-23 secretion despite hypocalcemia. Normalization of urinary phosphate losses despite elevated FGF-23 during calcitriol-mediated suppression of secondary hyperparathyroidism points to a cardinal role of PTH as a cause of the phosphaturia in VDRR-I. Normalization of RAAS by calcitriol may conceivably prevent adverse cardiovascular outcomes.
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Affiliation(s)
- Carlos Cuervo
- Division of Pediatric Nephrology, University of Miami Miller School of Medicine, PO Box 016960(M-714), Miami, FL, 33101, USA
| | - Carolyn L Abitbol
- Division of Pediatric Nephrology, University of Miami Miller School of Medicine, PO Box 016960(M-714), Miami, FL, 33101, USA
| | - Gaston E Zilleruelo
- Division of Pediatric Nephrology, University of Miami Miller School of Medicine, PO Box 016960(M-714), Miami, FL, 33101, USA
| | - Michael Freundlich
- Division of Pediatric Nephrology, University of Miami Miller School of Medicine, PO Box 016960(M-714), Miami, FL, 33101, USA.
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Braithwaite VS, Prentice A, Darboe MK, Prentice AM, Moore SE. The effects of maternal iron deficiency on infant fibroblast growth factor-23 and mineral metabolism. Bone 2016; 83:1-8. [PMID: 26453792 PMCID: PMC4720219 DOI: 10.1016/j.bone.2015.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 09/25/2015] [Accepted: 10/05/2015] [Indexed: 12/16/2022]
Abstract
Fibroblast growth factor-23 (FGF23), a phosphate(Phos)-regulating hormone, is abnormally elevated in hypophosphataemic syndromes and an elevated FGF23 is a predictor of mortality in kidney disease. Recent findings suggest iron deficiency as a potential mediator of FGF23 expression and murine studies have shown in utero effects of maternal iron deficiency on offspring FGF23 and phosphate metabolism. Our aim was to investigate the impact of maternal iron status on infant FGF23 and mineral metabolites over the first 2years of life. Infants born to mothers with normal (NIn=25,) and low (LIn=25) iron status during pregnancy, from a mother-infant trial (ISRCTN49285450) in rural Gambia, West Africa, had blood and plasma samples analysed at 12, 24, 52, 78 and 104weeks (wk) of age. Circulating intact-FGF23 (I-FGF23), Phos, total alkaline phosphatase (TALP) and haemoglobin (Hb) decreased and estimated glomerular filtration rate increased over time [all P≤0.0001)]. C-terminal-FGF23 (C-FGF23) and TALP were significantly higher in LI compared with NI, from 52wk for C-FGF23 [Beta coefficient (SE) 18.1 (0.04) %, P=0.04] and from 24wk for TALP [44.7 (29.6) U/L, P=0.04]. Infant Hb was the strongest negative predictor of C-FGF23 concentration [-21% (4%) RU/mL, P≤0.0001], Phos was the strongest positive predictor of I-FGF23 [32.0(3.9) pg/mL, P≤0.0001] and I-FGF23 did not predict C-FGF23 over time [-0.5% (0.5%), P=0.3]. In conclusion, this study suggests that poor maternal iron status is associated with a higher infant C-FGF23 and TALP but similar I-FGF23 concentrations in infants and young children. These findings further highlight the likely public health importance of preventing iron deficiency during pregnancy. Whether or not children who are born to iron deficient mothers have persistently high concentrations of these metabolites and are more likely to be at risk of impaired bone development and pre-disposed to rickets requires further research.
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Affiliation(s)
- V S Braithwaite
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK and MRC Unit, The Gambia.
| | - A Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK and MRC Unit, The Gambia
| | - M K Darboe
- MRC International Nutrition Group at London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UK and MRC Unit, The Gambia
| | - A M Prentice
- MRC International Nutrition Group at London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UK and MRC Unit, The Gambia
| | - S E Moore
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK and MRC Unit, The Gambia; MRC International Nutrition Group at London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UK and MRC Unit, The Gambia
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Bai X, Miao D, Xiao S, Qiu D, St-Arnaud R, Petkovich M, Gupta A, Goltzman D, Karaplis AC. CYP24 inhibition as a therapeutic target in FGF23-mediated renal phosphate wasting disorders. J Clin Invest 2016; 126:667-80. [PMID: 26784541 DOI: 10.1172/jci81928] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 11/25/2015] [Indexed: 12/13/2022] Open
Abstract
CYP24A1 (hereafter referred to as CYP24) enzymatic activity is pivotal in the inactivation of vitamin D metabolites. Basal renal and extrarenal CYP24 is usually low but is highly induced by its substrate 1,25-dihydroxyvitamin D. Unbalanced high and/or long-lasting CYP24 expression has been proposed to underlie diseases like chronic kidney disease, cancers, and psoriasis that otherwise should favorably respond to supplemental vitamin D. Using genetically modified mice, we have shown that renal phosphate wasting hypophosphatemic states arising from high levels of fibroblast growth factor 23 (FGF23) are also associated with increased renal Cyp24 expression, suggesting that elevated CYP24 activity is pivotal to the pathophysiology of these disorders. We therefore crossed 2 mouse strains, each with distinct etiology for high levels of circulating FGF23, onto a Cyp24-null background. Specifically, we evaluated Cyp24 deficiency in Hyp mice, the murine homolog of X-linked dominant hypophosphatemic rickets, and transgenic mice that overexpress a mutant FGF23 (FGF23R176Q) that is associated with the autosomal dominant form of hypophosphatemic rickets. Loss of Cyp24 in these murine models of human disease resulted in near-complete recovery of rachitic/osteomalacic bony abnormalities in the absence of any improvement in the serum biochemical profile. Moreover, treatment of Hyp and FGF23R1760-transgenic mice with the CYP24 inhibitor CTA102 also ameliorated their rachitic bones. Our results link CYP24 activity to the pathophysiology of FGF23-dependent renal phosphate wasting states and implicate pharmacologic CYP24 inhibition as a therapeutic adjunct for their treatment.
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Abstract
The discovery of the Klotho (KL) gene, which was originally identified as a putative aging-suppressor gene, has generated tremendous interest and has advanced understanding of the aging process. In mice, the overexpression of the KL gene extends the life span, whereas mutations to the KL gene shorten the life span. The human KL gene encodes the α-Klotho protein, which is a multifunctional protein that regulates the metabolism of phosphate, calcium, and vitamin D. α-Klotho also may function as a hormone, although the α-Klotho receptor(s) has not been found. Point mutations of the KL gene in humans are associated with hypertension and kidney disease, which suggests that α-Klotho may be essential to the maintenance of normal renal function. Three α-Klotho protein types with potentially different functions have been identified: a full-length transmembrane α-Klotho, a truncated soluble α-Klotho, and a secreted α-Klotho. Recent evidence suggests that α-Klotho suppresses the insulin and Wnt signaling pathways, inhibits oxidative stress, and regulates phosphatase and calcium absorption. In this review, we provide an update on recent advances in the understanding of the molecular, genetic, biochemical, and physiological properties of the KL gene. Specifically, this review focuses on the structure of the KL gene and the factors that regulate KL gene transcription, the key sites in the regulation of α-Klotho enzyme activity, the α-Klotho signaling pathways, and the molecular mechanisms that underlie α-Klotho function. This current understanding of the molecular biology of the α-Klotho protein may offer new insights into its function and role in aging.
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Affiliation(s)
- Yuechi Xu
- Department of Physiology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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28
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Chia LY, Walsh NC, Martin TJ, Sims NA. Isolation and gene expression of haematopoietic-cell-free preparations of highly purified murine osteocytes. Bone 2015; 72:34-42. [PMID: 25460578 DOI: 10.1016/j.bone.2014.11.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 10/14/2014] [Accepted: 11/11/2014] [Indexed: 10/24/2022]
Abstract
To define their gene expression and function, osteocytes are commonly isolated and purified by fluorescence-activated cell sorting (FACS) from mice expressing GFP directed by the dentin matrix protein 1 (Dmp1) promoter (DMP1-GFP). These cells express mRNA for osteocyte genes, including sclerostin (Sost) and Dmp1, and genes associated with the osteoclast phenotype: Dcstamp, Oscar, Cathepsin K (Ctsk), tartrate resistant acid phosphatase (TRAP/Acp5) and calcitonin receptor (Calcr). This suggests either that osteoclasts and osteocytes share genes and functions or that DMP1-GFP(+) preparations contain haematopoietic osteoclasts. To resolve this we stained DMP1-GFP cells for haematopoietic lineage (Lin) surface markers (CD2, CD3e, CD4, CD45, CD5, CD8, CD11b, B220, Gr1, Ter119) and CD31. Lin(-)CD31(-) (Lin(-)) and Lin(+)CD31(+) (Lin(+)) populations were analysed for GFP, and the four resulting populations assessed by quantitative real-time PCR. Lin(-)GFP(+) cells expressed mRNAs for Sost, Dmp1, and Mepe, confirming their osteocyte identity. Dcstamp and Oscar mRNAs were restricted to haematopoietic (Lin(+)) cells, but Calcr, Ctsk and Acp5 were readily detected in purified osteocytes (Lin(-)GFP(+)). The capacity of these purified osteocytes to support osteoclastogenesis was assessed: no TRAP+ cells with >2 nuclei were formed when purified osteocytes were cultured with bone marrow macrophages and stimulated with 1,25-dihydroxyvitamin-D3/prostaglandin E2. Lin(-)GFP(+) osteocytes also expressed lower levels of Tnfsf11 (RANKL) mRNA than the osteoblast-enriched population (Lin(-)GFP(-)). This demonstrates the importance of haematopoietic depletion in generating highly purified osteocytes and shows that osteocytes express Acp5, Ctsk and Calcr, but not other osteoclast markers, and do not fully support osteoclast formation in vitro.
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Affiliation(s)
- Ling Yeong Chia
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia
| | - Nicole C Walsh
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia
| | - T John Martin
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia
| | - Natalie A Sims
- St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia.
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29
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Umbach AT, Zhang B, Daniel C, Fajol A, Velic A, Hosseinzadeh Z, Bhavsar SK, Bock CT, Kandolf R, Pichler BJ, Amann KU, Föller M, Lang F. Janus kinase 3 regulates renal 25-hydroxyvitamin D 1α-hydroxylase expression, calcitriol formation, and phosphate metabolism. Kidney Int 2014; 87:728-37. [PMID: 25493954 DOI: 10.1038/ki.2014.371] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 08/21/2014] [Accepted: 09/11/2014] [Indexed: 01/26/2023]
Abstract
Calcitriol, a powerful regulator of phosphate metabolism and immune response, is generated by 25-hydroxyvitamin D 1α-hydroxylase in the kidney and macrophages. Renal 1α-hydroxylase expression is suppressed by Klotho and FGF23, the expression of which is stimulated by calcitriol. Interferon γ (INFγ) regulates 1α-hydroxylase expression in macrophages through transcription factor interferon regulatory factor-1. INFγ-signaling includes Janus kinase 3 (JAK3) but a role of JAK3 in the regulation of 1α-hydroxylase expression and mineral metabolism has not been shown. Thus, the impact of JAK3 deficiency on calcitriol formation and phosphate metabolism was measured. Renal interferon regulatory factor-1 and 1α-hydroxylase transcript levels, serum calcitriol and FGF23 levels, intestinal phosphate absorption as well as absolute and fractional renal phosphate excretion were significantly higher in jak3 knockout than in wild-type mice. Coexpression of JAK3 increased the phosphate-induced current in renal sodium-phosphate cotransporter-expressing Xenopus oocytes. Thus, JAK3 is a powerful regulator of 1α-hydroxylase expression and phosphate transport. Its deficiency leads to marked derangement of phosphate metabolism.
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Affiliation(s)
- Anja T Umbach
- Department of Physiology, University of Tübingen, Tübingen, Germany
| | - Bingbing Zhang
- 1] Department of Physiology, University of Tübingen, Tübingen, Germany [2] Department of Molecular Pathology, University of Tübingen, Tübingen, Germany
| | - Christoph Daniel
- Department of Nephropathology, University Hospital Erlangen, Erlangen, Germany
| | - Abul Fajol
- Department of Physiology, University of Tübingen, Tübingen, Germany
| | - Ana Velic
- Proteome Center, University of Tübingen, Tübingen, Germany
| | | | - Shefalee K Bhavsar
- 1] Department of Physiology, University of Tübingen, Tübingen, Germany [2] Novartis Oncology, Novartis International AG, Hyderabad, India
| | - C-Thomas Bock
- Department of Molecular Pathology, University of Tübingen, Tübingen, Germany
| | - Reinhard Kandolf
- Department of Molecular Pathology, University of Tübingen, Tübingen, Germany
| | - Bernd J Pichler
- Department of Radiology, University of Tübingen, Tübingen, Germany
| | - Kerstin U Amann
- Department of Nephropathology, University Hospital Erlangen, Erlangen, Germany
| | - Michael Föller
- Department of Physiology, University of Tübingen, Tübingen, Germany
| | - Florian Lang
- Department of Physiology, University of Tübingen, Tübingen, Germany
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30
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Fabbri S, Ciuffi S, Nardone V, Gomes AR, Mavilia C, Zonefrati R, Galli G, Luzi E, Tanini A, Brandi ML. PTH-C1: a rat continuous cell line expressing the parathyroid phenotype. Endocrine 2014; 47:90-9. [PMID: 24627164 DOI: 10.1007/s12020-014-0229-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 02/26/2014] [Indexed: 01/17/2023]
Abstract
The lack of a continuous cell line of epithelial parathyroid cells able to produce parathyroid hormone (PTH) has hampered the studies on in vitro evaluation of the mechanisms involved in the control of parathyroid cell function and proliferation. The PT-r cell line was first established from rat parathyroid tissue in 1987, but these cells were known to express the parathyroid hormone-related peptide (Pthrp) gene, but not the Pth gene. In an attempt to subclone the PT-r cell line, a rat parathyroid cell strain was isolated and named PTH-C1. During 3 years, in culture, PTH-C1 cells maintained an epithelioid morphology, displaying a diploid chromosome number, a doubling time around 15 h during the exponential phase of growth, and parathyroid functional features. PTH-C1 cell line produces PTH and expresses the calcium sensing receptor (Casr) gene and other genes known to be involved in parathyroid function. Most importantly, the PTH-C1 cells also exhibit an in vitro secretory response to calcium. Altogether these findings indicate the uniqueness of the PTH-C1 cell line as an in vitro model for cellular and molecular studies on parathyroid physiopathology.
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Affiliation(s)
- Sergio Fabbri
- Department of Surgery and Translational Medicine, University of Florence, Largo Brambilla 3, 50134, Florence, Italy
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31
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Gkentzi D, Efthymiadou A, Kritikou D, Chrysis D. Fibroblast growth factor 23 and Klotho serum levels in healthy children. Bone 2014; 66:8-14. [PMID: 24880094 DOI: 10.1016/j.bone.2014.05.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 05/13/2014] [Accepted: 05/22/2014] [Indexed: 12/18/2022]
Abstract
Data for fibroblast growth factor 23 (FGF23) and particularly for Klotho in healthy children are limited. We aimed to investigate the relationship between FGF23 and Klotho with age and TmP/GFR and to evaluate parameters that might affect FGF23 and Klotho. In 159 healthy children (82 boys) with a mean±SD age of 8.78±3.47years we measured FGF23 (intact FGF23/iFGF23 and C-terminal FGF23/cFGF23) and soluble aKlotho serum levels by ELISA. Mean±SD value for cFGF23, was 51.14±12.79 RU/ml whereas median (range) values for iFGF23 and Klotho were 35 (8.8, 120) pg/ml and 1945 (372, 5866) pg/ml respectively. Neither FGF23 nor Klotho were significantly associated with age. Pubertal children had higher Klotho than prepubertal (p<0.05), and girls had higher levels of cFGF23 (p<0.05) and Klotho (p<0.001) than boys. Serum phosphate and TmP/GFR were positively associated with cFGF23 (p<0.01 and p<0.001), iFGF23 (p<0.05 and p<0.001) and Klotho (p<0.05 and p<0.01). Klotho was positively correlated with IGF-I (p<0.0001) and 1,25 (OH)2 vitamin D (p<0.05). In this study we provide data on cFGF23, iFGF23, and Klotho measured simultaneously in healthy children. The positive association of serum phosphate and TmP/GFR with FGF23 and Klotho suggests that they have a counterregulatory effect on phosphate homeostasis. The strong association of Klotho with IGF-I could indicate a role of Klotho in linear growth through phosphate regulation, but further studies are required.
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Affiliation(s)
- Despoina Gkentzi
- Department of Pediatrics, Medical School, University of Patras, Rio, Greece.
| | - Alexandra Efthymiadou
- Pediatric Endocrine Unit, Department of Pediatrics, Medical School, University of Patras, Rio, Greece
| | - Dimitra Kritikou
- Pediatric Endocrine Unit, Department of Pediatrics, Medical School, University of Patras, Rio, Greece
| | - Dionisios Chrysis
- Pediatric Endocrine Unit, Department of Pediatrics, Medical School, University of Patras, Rio, Greece
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Kuzynski M, Goss M, Bottini M, Yadav MC, Mobley C, Winters T, Poliard A, Kellermann O, Lee B, Millan JL, Napierala D. Dual role of the Trps1 transcription factor in dentin mineralization. J Biol Chem 2014; 289:27481-93. [PMID: 25128529 DOI: 10.1074/jbc.m114.550129] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
TRPS1 (tricho-rhino-phalangeal syndrome) is a unique GATA-type transcription factor that acts as a transcriptional repressor. TRPS1 deficiency and dysregulated TRPS1 expression result in skeletal and dental abnormalities implicating TRPS1 in endochondral bone formation and tooth development. Moreover, patients with tricho-rhino-phalangeal syndrome frequently present with low bone mass indicating TRPS1 involvement in bone homeostasis. In addition, our previous data demonstrated accelerated mineralization of the perichondrium in Trps1 mutant mice and impaired dentin mineralization in Col1a1-Trps1 transgenic mice, implicating Trps1 in the mineralization process. To understand the role of Trps1 in the differentiation and function of cells producing mineralized matrix, we used a preodontoblastic cell line as a model of dentin mineralization. We generated both Trps1-deficient and Trps1-overexpressing stable cell lines and analyzed the progression of mineralization by alkaline phosphatase and alizarin red staining. As predicted, based on our previous in vivo data, delayed and decreased mineralization of Trps1-overexpressing odontoblastic cells was observed when compared with control cells. This was associated with down-regulation of genes regulating phosphate homeostasis. Interestingly, Trps1-deficient cells lost the ability to mineralize and demonstrated decreased expression of several genes critical for initiating the mineralization process, including Alpl and Phospho1. Based on these data, we have concluded that Trps1 serves two critical and context-dependent functions in odontoblast-regulated mineralization as follows: 1) Trps1 is required for odontoblast maturation by supporting expression of genes crucial for initiating the mineralization process, and 2) Trps1 represses the function of mature cells and, consequently, restricts the extent of extracellular matrix mineralization.
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Affiliation(s)
- Maria Kuzynski
- From the Institute of Oral Health Research, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Morgan Goss
- From the Institute of Oral Health Research, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Massimo Bottini
- the Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, California 92037, the Department of Experimental Medicine and Surgery, University of Rome Tor Vergata, 00133Rome, Italy
| | - Manisha C Yadav
- the Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, California 92037
| | - Callie Mobley
- From the Institute of Oral Health Research, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Tony Winters
- From the Institute of Oral Health Research, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Anne Poliard
- the EA2496 UFR d'Odontologie, Université Paris Descartes, 92120 Montrouge, France
| | - Odile Kellermann
- INSERM UMR-S 1124, Université René Descartes Paris 5, Centre Universitaire des Saints-Pères, 75270 Paris Cedex 06, France
| | - Brendan Lee
- the Department of Molecular and Human Genetics, Baylor College of Medicine, and the Howard Hughes Medical Institute, Houston, Texas 77030
| | - Jose Luis Millan
- the Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, California 92037
| | - Dobrawa Napierala
- From the Institute of Oral Health Research, Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Alabama at Birmingham, Birmingham, Alabama 35294,
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33
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Rendenbach C, Yorgan TA, Heckt T, Otto B, Baldauf C, Jeschke A, Streichert T, David JP, Amling M, Schinke T. Effects of extracellular phosphate on gene expression in murine osteoblasts. Calcif Tissue Int 2014; 94:474-83. [PMID: 24366459 DOI: 10.1007/s00223-013-9831-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 12/01/2013] [Indexed: 02/07/2023]
Abstract
That phosphate homeostasis is tightly linked to skeletal mineralization is probably best underscored by the fact that the phosphaturic hormone FGF23 is primarily expressed by terminally differentiated osteoblasts/osteocytes and that increased circulating FGF23 levels are causative for different types of hypophosphatemic rickets. In contrast, FGF23 inactivation results in hyperphosphatemia, and unexpectedly this phenotype is associated with severe osteomalacia in Fgf23-deficient mice. In this context it is interesting that different cell types have been shown to respond to extracellular phosphate, thereby raising the concept that phosphate can act as a signaling molecule. To identify phosphate-responsive genes in primary murine osteoblasts we performed genome wide expression analysis with cells maintained in medium containing either 1 or 4 mM sodium phosphate for 6 h. As confirmed by qRT-PCR, this analysis revealed that several known osteoblast differentiation markers (Bglap, Ibsp, and Phex) were unaffected by raising extracellular phosphate levels. In contrast, we found that the expression of Enpp1 and Ank, two genes encoding inhibitors of matrix mineralization, was induced by extracellular phosphate, while the expression of Sost and Dkk1, two genes encoding inhibitors of bone formation, was negatively regulated. The ability of osteoblasts to respond to extracellular phosphate was dependent on their differentiation state, and shRNA-dependent repression of the phosphate transporter Slc20a1 in MC3T3-E1 cells partially abolished their molecular response to phosphate. Taken together, our results provide further evidence for a role of extracellular phosphate as a signaling molecule and raise the possibility that severe hyperphosphatemia can negatively affect skeletal mineralization.
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Affiliation(s)
- C Rendenbach
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, 20246, Hamburg, Germany
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34
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Shindyapina AV, Mkrtchyan GV, Gneteeva T, Buiucli S, Tancowny B, Kulka M, Aliper A, Zhavoronkov A. Mineralization of the Connective Tissue: A Complex Molecular Process Leading to Age-Related Loss of Function. Rejuvenation Res 2014; 17:116-33. [DOI: 10.1089/rej.2013.1475] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Anastasia V. Shindyapina
- Lomonosov Moscow State University, Moscow, Russian Federation
- Bioinformatics and Medical Information Technology Laboratory. Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation
- Moscow Institute of Physics and Technology, Moscow, Russian Federation
- First Open Institute for Regenerative Medicine for Young Scientists, Moscow, Russia
| | - Garik V. Mkrtchyan
- Lomonosov Moscow State University, Moscow, Russian Federation
- Bioinformatics and Medical Information Technology Laboratory. Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation
- First Open Institute for Regenerative Medicine for Young Scientists, Moscow, Russia
| | - Tatiana Gneteeva
- First Open Institute for Regenerative Medicine for Young Scientists, Moscow, Russia
- I.M. Sechenov First Moscow State Medical University, Moscow, Russia
| | - Sveatoslav Buiucli
- Moscow Institute of Physics and Technology, Moscow, Russian Federation
- First Open Institute for Regenerative Medicine for Young Scientists, Moscow, Russia
| | - B. Tancowny
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
- National Institute for Nanotechnology, National Research Council, Edmonton, Alberta, Canada
| | - M. Kulka
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
- National Institute for Nanotechnology, National Research Council, Edmonton, Alberta, Canada
| | - Alexander Aliper
- Bioinformatics and Medical Information Technology Laboratory. Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation
- Moscow Institute of Physics and Technology, Moscow, Russian Federation
- First Open Institute for Regenerative Medicine for Young Scientists, Moscow, Russia
| | - Alexander Zhavoronkov
- Bioinformatics and Medical Information Technology Laboratory. Center for Pediatric Hematology, Oncology and Immunology, Moscow, Russian Federation
- Moscow Institute of Physics and Technology, Moscow, Russian Federation
- First Open Institute for Regenerative Medicine for Young Scientists, Moscow, Russia
- The Biogerontology Research Foundation, Reading, United Kingdom
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Abstract
Teeth are mineralized organs composed of three unique hard tissues, enamel, dentin, and cementum, and supported by the surrounding alveolar bone. Although odontogenesis differs from osteogenesis in several respects, tooth mineralization is susceptible to similar developmental failures as bone. Here we discuss conditions fitting under the umbrella of rickets, which traditionally referred to skeletal disease associated with vitamin D deficiency but has been more recently expanded to include newly identified factors involved in endocrine regulation of vitamin D, phosphate, and calcium, including phosphate-regulating endopeptidase homolog, X-linked, fibroblast growth factor 23, and dentin matrix protein 1. Systemic mineral metabolism intersects with local regulation of mineralization, and factors including tissue nonspecific alkaline phosphatase are necessary for proper mineralization, where rickets can result from loss of activity of tissue nonspecific alkaline phosphatase. Individuals suffering from rickets often bear the additional burden of a defective dentition, and transgenic mouse models have aided in understanding the nature and mechanisms involved in tooth defects, which may or may not parallel rachitic bone defects. This report reviews dental effects of the range of rachitic disorders, including discussion of etiologies of hereditary forms of rickets, a survey of resulting bone and tooth mineralization disorders, and a discussion of mechanisms, known and hypothesized, involved in the observed dental pathologies. Descriptions of human pathology are augmented by analysis of transgenic mouse models, and new interpretations are brought to bear on questions of how teeth are affected under conditions of rickets. In short, the rachitic tooth will be revealed.
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Affiliation(s)
- Brian L Foster
- National Institute for Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
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Schaffler MB, Cheung WY, Majeska R, Kennedy O. Osteocytes: master orchestrators of bone. Calcif Tissue Int 2014; 94:5-24. [PMID: 24042263 PMCID: PMC3947191 DOI: 10.1007/s00223-013-9790-y] [Citation(s) in RCA: 305] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 08/22/2013] [Indexed: 12/12/2022]
Abstract
Osteocytes comprise the overwhelming majority of cells in bone and are its only true "permanent" resident cell population. In recent years, conceptual and technological advances on many fronts have helped to clarify the role osteocytes play in skeletal metabolism and the mechanisms they use to perform them. The osteocyte is now recognized as a major orchestrator of skeletal activity, capable of sensing and integrating mechanical and chemical signals from their environment to regulate both bone formation and resorption. Recent studies have established that the mechanisms osteocytes use to sense stimuli and regulate effector cells (e.g., osteoblasts and osteoclasts) are directly coupled to the environment they inhabit-entombed within the mineralized matrix of bone and connected to each other in multicellular networks. Communication within these networks is both direct (via cell-cell contacts at gap junctions) and indirect (via paracrine signaling by secreted signals). Moreover, the movement of paracrine signals is dependent on the movement of both solutes and fluid through the space immediately surrounding the osteocytes (i.e., the lacunar-canalicular system). Finally, recent studies have also shown that the regulatory capabilities of osteocytes extend beyond bone to include a role in the endocrine control of systemic phosphate metabolism. This review will discuss how a highly productive combination of experimental and theoretical approaches has managed to unearth these unique features of osteocytes and bring to light novel insights into the regulatory mechanisms operating in bone.
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Affiliation(s)
- Mitchell B. Schaffler
- University: City College of New York, Department: Biomedical Engineering, Phone: 212-650-5070, Fax: 212-650-6727
| | - Wing-Yee Cheung
- University: City College of New York, Department: Biomedical Engineering
| | - Robert Majeska
- University: City College of New York, Department: Biomedical Engineering
| | - Oran Kennedy
- University: New York University, Department: Orthopaedic Surgery
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The SLC34 family of sodium-dependent phosphate transporters. Pflugers Arch 2013; 466:139-53. [PMID: 24352629 DOI: 10.1007/s00424-013-1418-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 12/01/2013] [Accepted: 12/02/2013] [Indexed: 12/27/2022]
Abstract
The SLC34 family of sodium-driven phosphate cotransporters comprises three members: NaPi-IIa (SLC34A1), NaPi-IIb (SLC34A2), and NaPi-IIc (SLC34A3). These transporters mediate the translocation of divalent inorganic phosphate (HPO4 (2-)) together with two (NaPi-IIc) or three sodium ions (NaPi-IIa and NaPi-IIb), respectively. Consequently, phosphate transport by NaPi-IIa and NaPi-IIb is electrogenic. NaPi-IIa and NaPi-IIc are predominantly expressed in the brush border membrane of the proximal tubule, whereas NaPi-IIb is found in many more organs including the small intestine, lung, liver, and testis. The abundance and activity of these transporters are mostly regulated by changes in their expression at the cell surface and are determined by interactions with proteins involved in scaffolding, trafficking, or intracellular signaling. All three transporters are highly regulated by factors including dietary phosphate status, hormones like parathyroid hormone, 1,25-OH2 vitamin D3 or FGF23, electrolyte, and acid-base status. The physiological relevance of the three members of the SLC34 family is underlined by rare Mendelian disorders causing phosphaturia, hypophosphatemia, or ectopic organ calcifications.
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Abstract
PURPOSE OF REVIEW The purpose of this study is to review the regulation of phosphate and recent progress in fibroblast growth factor-23 (FGF-23), a key phosphate regulatory hormone. RECENT FINDINGS Phosphate is required for mineralization of bone, muscle strength and a host of biologic functions. Phosphate is sensed by bone that responds with secretion of FGF-23. The major action of FGF-23 is to stimulate phosphaturia. Feedback loops between FGF-23, 1,25-dihydroxyvitamin D3 and parathyroid hormone maintain phosphate homeostasis. Information about FGF-23 has accumulated from studies in patients with oncogenic osteomalacia and inherited disorders of phosphate wasting rickets that explains the pathophysiology. Exciting new discoveries have highlighted FGF-23 as an independent risk factor for cardiovascular disease in patients with chronic kidney disease. The phosphate sensor triggering FGF-23 production remains to be identified. SUMMARY Derangements in FGF-23 production, half-life or downstream response are responsible for several disorders of phosphate wasting, rickets and oncogenic osteomalacia. Very high levels of FGF-23 in renal failure are an independent risk for cardiovascular disease.
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Affiliation(s)
- Mark S Nanes
- Department of Medicine, Atlanta VA Medical Center and Division of Endocrinology, Lipids, and Metabolism, Emory University School of Medicine, Atlanta, Georgia, USA
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Abstract
The last decade has seen an exponential increase in our understanding of osteocytes function and biology. These cells, once considered inert by-standers trapped into the mineralized bone, has now risen to be key regulators of skeletal metabolism, mineral homeostasis, and hematopoiesis. As tools and techniques to study osteocytes improved and expanded, it has become evident that there is more to these cells than initially thought. Osteocytes are now recognized not only as the key responders to mechanical forces but also as orchestrators of bone remodeling and mineral homeostasis. These cells are the primary source of several important proteins, such as sclerostin and fibroblast growth factor 23, that are currently target as novel therapies for bone loss (as the case for antisclerostin antibodies) or phosphate disorders. Better understanding of the intricate cellular and molecular mechanisms that govern osteocyte biology will open new avenue of research and ultimately indentify novel therapeutics to treat bone and mineral disorders. This review summarizes novel findings and discusses future avenues of research.
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Affiliation(s)
- Paola Divieti Pajevic
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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Yorgan T, Rendenbach C, Jeschke A, Amling M, Cheah KSE, Schinke T. Increased Col10a1 expression is not causative for the phenotype of Phex-deficient Hyp mice. Biochem Biophys Res Commun 2013; 442:209-13. [PMID: 24269824 DOI: 10.1016/j.bbrc.2013.11.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 11/07/2013] [Indexed: 12/25/2022]
Abstract
X-linked hypophosphatemic rickets (XLHR) is a severe disorder of phosphate homeostasis and skeletal mineralization caused by mutations of PHEX, encoding a bone-specific endopeptidase. Phex-deficient Hyp mice have been extensively studied to understand the molecular bases of XLHR, and here it was found that Fgf23, encoding a major phosphaturic hormone, was transcriptionally activated in bone-forming osteoblasts. We and others could additionally show that Col10a1 expression is increased in Hyp osteoblasts and bones, thereby raising the possibility that ectopic production of type X collagen could contribute to the impaired mineralization of the Hyp bone matrix. Here we show that an additional deficiency of the Col10a1 gene does not overtly affect the skeletal phenotype of Hyp mice. More specifically, Col10a1-deficient Hyp mice displayed severe disturbances of skeletal growth, bone mass acquisition and bone matrix mineralization, and they were essentially indistinguishable from Hyp littermates. This was confirmed by non-decalcified histology and bone-specific histomorphometry quantifying all relevant parameters of growth plate maturation, trabecular bone architecture and osteoid accumulation. Taken together, our results show that increased Col10a1 expression in Phex-deficient osteoblasts is not a major cause of the XLHR phenotype, which was an important issue to address based on the previous findings.
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Affiliation(s)
- Timur Yorgan
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany
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Rafaelsen SH, Raeder H, Fagerheim AK, Knappskog P, Carpenter TO, Johansson S, Bjerknes R. Exome sequencing reveals FAM20c mutations associated with fibroblast growth factor 23-related hypophosphatemia, dental anomalies, and ectopic calcification. J Bone Miner Res 2013; 28:1378-85. [PMID: 23325605 DOI: 10.1002/jbmr.1850] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/27/2012] [Accepted: 12/05/2012] [Indexed: 01/06/2023]
Abstract
Fibroblast growth factor 23 (FGF23) plays a crucial role in renal phosphate regulation, exemplified by the causal role of PHEX and DMP1 mutations in X-linked hypophosphatemic rickets and autosomal recessive rickets type 1, respectively. Using whole exome sequencing we identified compound heterozygous mutations in family with sequence similarity 20, member C (FAM20C) in two siblings referred for hypophosphatemia and severe dental demineralization disease. FAM20C mutations were not found in other undiagnosed probands of a national Norwegian population of familial hypophosphatemia. Our results demonstrate that mutations in FAM20C provide a putative new mechanism in human subjects leading to dysregulated FGF23 levels, hypophosphatemia, hyperphosphaturia, dental anomalies, intracerebral calcifications and osteosclerosis of the long bones in the absence of rickets.
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Wöhrle S, Henninger C, Bonny O, Thuery A, Beluch N, Hynes NE, Guagnano V, Sellers WR, Hofmann F, Kneissel M, Graus Porta D. Pharmacological inhibition of fibroblast growth factor (FGF) receptor signaling ameliorates FGF23-mediated hypophosphatemic rickets. J Bone Miner Res 2013; 28:899-911. [PMID: 23129509 DOI: 10.1002/jbmr.1810] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 10/18/2012] [Accepted: 10/23/2012] [Indexed: 12/11/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is a circulating factor secreted by osteocytes that is essential for phosphate homeostasis. In kidney proximal tubular cells FGF23 inhibits phosphate reabsorption and leads to decreased synthesis and enhanced catabolism of 1,25-dihydroxyvitamin D3 (1,25[OH]2 D3 ). Excess levels of FGF23 cause renal phosphate wasting and suppression of circulating 1,25(OH)2 D3 levels and are associated with several hereditary hypophosphatemic disorders with skeletal abnormalities, including X-linked hypophosphatemic rickets (XLH) and autosomal recessive hypophosphatemic rickets (ARHR). Currently, therapeutic approaches to these diseases are limited to treatment with activated vitamin D analogues and phosphate supplementation, often merely resulting in partial correction of the skeletal aberrations. In this study, we evaluate the use of FGFR inhibitors for the treatment of FGF23-mediated hypophosphatemic disorders using NVP-BGJ398, a novel selective, pan-specific FGFR inhibitor currently in Phase I clinical trials for cancer therapy. In two different hypophosphatemic mouse models, Hyp and Dmp1-null mice, resembling the human diseases XLH and ARHR, we find that pharmacological inhibition of FGFRs efficiently abrogates aberrant FGF23 signaling and normalizes the hypophosphatemic and hypocalcemic conditions of these mice. Correspondingly, long-term FGFR inhibition in Hyp mice leads to enhanced bone growth, increased mineralization, and reorganization of the disturbed growth plate structure. We therefore propose NVP-BGJ398 treatment as a novel approach for the therapy of FGF23-mediated hypophosphatemic diseases.
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Affiliation(s)
- Simon Wöhrle
- Novartis Institutes for BioMedical Research, Basel, Switzerland
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Abstract
Recently, fibroblast growth factor 23 (FGF23) has sparked widespread interest because of its potential role in regulating phosphate and vitamin D metabolism. In this review, we summarized the FGF superfamily, the mechanism of FGF23 on phosphate and vitamin D metabolism, and the FGF23 related bone disease.
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Affiliation(s)
- Eryuan Liao
- Institute of Metabolism and Endocrinology, the Second Xiangya Hospital, Central South University, Changsha, 410011, China.
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Seitz S, Rendenbach C, Barvencik F, Streichert T, Jeschke A, Schulze J, Amling M, Schinke T. Retinol deprivation partially rescues the skeletal mineralization defects of Phex-deficient Hyp mice. Bone 2013; 53:231-8. [PMID: 23266491 DOI: 10.1016/j.bone.2012.12.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 12/10/2012] [Accepted: 12/12/2012] [Indexed: 12/24/2022]
Abstract
X-linked hypophosphatemic rickets (XLH) is a genetic disorder caused by mutational inactivation of the PHEX gene, encoding a transmembrane endopeptidase expressed in osteoblasts. Since several experiments involving Phex-deficient Hyp mice have demonstrated that an increased expression of Fgf23 in osteoblasts is causative for the renal phosphate loss characteristic of XLH, we performed genome-wide expression analysis to compare differentiated osteoblasts from wildtype and Hyp mice. Here we did not only observe the expected increase of Fgf23 expression in the latter ones, but also a differential expression of genes that are either induced by or involved in retinoic acid signaling, which led us to analyze whether dietary retinol deprivation would influence the phenotype of Hyp mice. Unexpectedly, feeding a retinol-free diet resulted in a partial rescue of the growth plate and bone mineralization defects in 6 weeks old Hyp mice. When we fed the same diet for 24 weeks the amount of non-mineralized bone matrix (osteoid) was reduced by more than 70%, although phosphate homeostasis was unaffected. In contrast, a dietary normalization of serum phosphate levels in Hyp mice reduced the osteoid amount by less than 30%, thereby demonstrating a previously unknown impact of retinol on the cell-autonomous mineralization defect of Phex-deficient osteoblasts.
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Affiliation(s)
- Sebastian Seitz
- Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg 20246, Germany
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Chiam P, Tan HC, Bee YM, Chandran M. Oncogenic osteomalacia -- hypophosphataemic spectrum from "benignancy" to "malignancy". Bone 2013; 53:182-7. [PMID: 23220596 DOI: 10.1016/j.bone.2012.11.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 11/27/2012] [Accepted: 11/29/2012] [Indexed: 12/24/2022]
Abstract
Though case reports and case series about oncogenic osteomalacia due to benign mesenchymal tumours and much more rarely, secondary to malignant ones exist in the literature, there has not been any series reported from a single department spanning the gamut of causes from benign to malignant. We present 3 patients who were seen at the department of endocrinology of our hospital between 2010 and 2012 with hypophosphataemia and severe skeletal complications. All of them were found to have oncogenic osteomalacia otherwise known as tumour induced osteomalacia (TIO) - a paraneoplastic syndrome characterised by renal phosphate wasting and severe hypophosphataemia. The implicating tumours in our patients ranged from a subcutaneous mesenchymal tumour in the heel to a mixed connective tissue variant within the nasal cavity to metastatic prostate cancer. All our patients had protracted periods before the diagnosis was made, during which time the burden of their metabolic and skeletal pathology had increased. A timely recognition of the clinical features and biochemical findings of this rare but potentially debilitating disease is critical. Physicians should be cognizant of the presence of the disease and its localising and treatment strategies.
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Affiliation(s)
- P Chiam
- Department of Endocrinology, Singapore General Hospital, Outram Road, Singapore
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46
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Abstract
PURPOSE OF REVIEW Description of the recent advances on the regulation of phosphate metabolism, gene mutations, and new approaches to treatment in patients with hypophosphatemic rickets. RECENT FINDINGS Fibroblast growth factor 23 (FGF23) overproduction may be a primary cause of hypophosphatemic rickets. Inactivating mutations of phosphate-regulating gene with homologies to endopeptidases on the X chromosome, dentin matrix acidic phosphoprotein 1, and ectonucleotide pyrophosphatase/phosphodiesterase 1 are associated with X-linked hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets 1, and autosomal recessive hypophosphatemic rickets 2, respectively. Activating mutations of FGF23 gene is the cause of autosomal dominant hypophosphatemic rickets. Iron deficiency may affect autosomal dominant hypophosphatemic rickets phenotype by regulating FGF23 production.Current treatment with activated vitamin D metabolites and oral inorganic phosphate salts may partially correct skeletal lesions and linear growth in patients with hypophosphatemic rickets. However, some patients have poor improvement by the current treatment. SUMMARY Identification of the causative mutation in patients with hypophosphatemic rickets may be useful to confirm the diagnosis and probably for prognosis. Inhibition of FGF23 overproduction by anti-FGF23 neutralizing antibodies could be a future approach for treatment of patients with FGF23-dependent hypophosphatemic rickets.
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Affiliation(s)
- Giampiero I Baroncelli
- Pediatric Unit I, Department of Obstetrics, Gynecology and Pediatrics, University-Hospital, Pisa, Italy.
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