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Abstract
Rickets is a bone disease associated with abnormal serum calcium and phosphate levels. The clinical presentation is heterogeneous and depends on the age of onset and pathogenesis but includes bowing deformities of the legs, short stature and widening of joints. The disorder can be caused by nutritional deficiencies or genetic defects. Mutations in genes encoding proteins involved in vitamin D metabolism or action, fibroblast growth factor 23 (FGF23) production or degradation, renal phosphate handling or bone mineralization have been identified. The prevalence of nutritional rickets has substantially declined compared with the prevalence 200 years ago, but the condition has been re-emerging even in some well-resourced countries; prematurely born infants or breastfed infants who have dark skin types are particularly at risk. Diagnosis is usually established by medical history, physical examination, biochemical tests and radiography. Prevention is possible only for nutritional rickets and includes supplementation or food fortification with calcium and vitamin D either alone or in combination with sunlight exposure. Treatment of typical nutritional rickets includes calcium and/or vitamin D supplementation, although instances infrequently occur in which phosphate repletion may be necessary. Management of heritable types of rickets associated with defects in vitamin D metabolism or activation involves the administration of vitamin D metabolites. Oral phosphate supplementation is usually indicated for FGF23-independent phosphopenic rickets, whereas the conventional treatment of FGF23-dependent types of rickets includes a combination of phosphate and activated vitamin D; an anti-FGF23 antibody has shown promising results and is under further study.
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152
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Souberbielle JC, Prié D, Piketty ML, Rothenbuhler A, Delanaye P, Chanson P, Cavalier E. Evaluation of a New Fully Automated Assay for Plasma Intact FGF23. Calcif Tissue Int 2017; 101:510-518. [PMID: 28761972 DOI: 10.1007/s00223-017-0307-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 07/15/2017] [Indexed: 02/05/2023]
Abstract
Several FGF23 immunoassays are available. However, they are reserved for research purposes as none have been approved for clinical use. We evaluated the performances of a new automated assay for intact FGF23 on the DiaSorin Liaison platform which is approved for clinical use. We established reference values in 908 healthy French subjects aged 18-89 years, and measured iFGF23 in patients with disorders of phosphate metabolism and in patients with chronic kidney disease (CKD). Intra-assay CV was 1.04-2.86% and inter-assay CV was 4.01-6.3%. The limit of quantification was <10 ng/L. Serum iFGF23 concentrations were considerably lower than EDTA values highlighting the importance of using exclusively EDTA plasma. Liaison iFGF23 values were approximately 25% higher than Immutopics values. In the 908 healthy subjects, distribution of the Liaison iFGF23 values was Gaussian with a mean ± 2SD interval of 22.7-93.1 ng/L. Men had a slightly higher level than women (60.3 ± 17.6 and 55.2 ± 17.2 ng/L, respectively). Plasma iFGF23 concentration in 11 patients with tumour-induced osteomalacia, 8 patients with X-linked hypophosphatemic rickets, 43 stage 3a, 43 stage 3b, 43 stage 4, 44 stage 5 CKD patients, and 44 dialysis patients were 217.2 ± 144.0, 150.9 ± 28.6, 98.5 ± 42.0, 130.8 ± 88.6, 130.8 ± 88.6, 331.7 ± 468.2, 788.8 ± 1306.6 and 6103.9 ± 11,178.8 ng/L, respectively. This new iFGF23 assay available on a platform that already allows the measurement of other important parameters of the mineral metabolism is a real improvement for the laboratories and clinicians/researchers involved in this field.
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Affiliation(s)
- Jean-Claude Souberbielle
- Service des Explorations Fonctionnelles, G.H. Necker Enfants Malades, 149 rue de Sèvres, 75743, Paris cedex 15, France
| | - Dominique Prié
- Service des Explorations Fonctionnelles, G.H. Necker Enfants Malades, 149 rue de Sèvres, 75743, Paris cedex 15, France
| | - Marie-Liesse Piketty
- Service des Explorations Fonctionnelles, G.H. Necker Enfants Malades, 149 rue de Sèvres, 75743, Paris cedex 15, France
| | - Anya Rothenbuhler
- Service d'Endocrinologie pédiatrique, French Reference Center for Rare Disorders of the Mineral Metabolism, Department of Endocrinology and Diabetology for Children, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, 78 rue du Général Leclerc, 94270, Le Kremlin Bicêtre, France
| | - Pierre Delanaye
- Department of Nephrology-Dialysis-Transplantation, University of Liège, CHU de Liège, 4000, Liège, Belgium
| | - Philippe Chanson
- Service d'Endocrinologie et des Maladies de la Reproduction, Assistance Publique-Hôpitaux de Paris, Hôpitaux Universitaires Paris-Sud, Hôpital de Bicêtre, 94275, Le Kremlin Bicêtre, France
- INSERM 1185, Fac Med Paris Sud, Univ Paris-Sud, Université Paris-Saclay, 94276, Le Kremlin Bicêtre, France
| | - Etienne Cavalier
- Department of Clinical Chemistry, University of Liège, CHU de Liège, 4000, Liège, Belgium.
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153
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Leifheit-Nestler M, Kucka J, Yoshizawa E, Behets G, D'Haese P, Bergen C, Meier M, Fischer DC, Haffner D. Comparison of calcimimetic R568 and calcitriol in mineral homeostasis in the Hyp mouse, a murine homolog of X-linked hypophosphatemia. Bone 2017; 103:224-232. [PMID: 28728941 DOI: 10.1016/j.bone.2017.06.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 06/02/2017] [Accepted: 06/23/2017] [Indexed: 12/28/2022]
Abstract
X-linked hypophosphatemia (XLH) caused by mutations in the Phex gene is the most common human inherited phosphate wasting disorder characterized by enhanced synthesis of fibroblast growth factor 23 (FGF23) in bone, renal phosphate wasting, 1,25(OH)2D3 (1,25D) deficiency, rickets and osteomalacia. Here we studied the effects of calcimimetic R568 and calcitriol treatment in the Hyp mouse, a murine homolog of XLH. We hypothesized that mineral homeostasis is differentially affected by R568 and 1,25D with respect to the PTH-vitamin D-FGF23-Klotho axis and bone health. Four-week-old male Hyp mice received R568 in different doses, 1,25D or vehicle for 28days. Vehicle-treated wild-type mice served as controls. Both R568 and 1,25D reduced PTH levels, yet only 1,25D raised serum phosphate levels in Hyp mice. 1,25D increased calciuria and further enhanced FGF23 synthesis in bone and circulating FGF23 levels. By contrast, R568 reduced bone FGF23 expression and serum total but not intact FGF23 concentrations. Renal 1,25D metabolism was further impaired by 1,25D and improved although not normalized by R568. Hyp mice showed reduced renal Klotho levels, which were increased by 1,25D and high dose R568. 1,25D, but not R568, significantly improved femur growth, and weight gain, and partially restored growth plate morphology and bone mineralization. Although a significant improvement of trabecular bone was noted by μCT, compared to 1,25D the effects of R568 on bone histomophometric parameters were marginal. Our data indicate that monotherapy with R568 reduced PTH and FGF23 synthesis in bone, but failed to restore vitamin D and phosphate metabolism and skeletal abnormalities in Hyp mice. By contrast, 1,25D improved body growth, and defective mineralization despite further enhancement of skeletal FGF23 synthesis thereby highlighting the importance of vitamin D in bone mineralization in Hyp mice.
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Affiliation(s)
- Maren Leifheit-Nestler
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany.
| | - Julia Kucka
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Emi Yoshizawa
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Geert Behets
- Laboratory of Pathophysiology, University of Antwerp, Wilrijk, Belgium
| | - Patrick D'Haese
- Laboratory of Pathophysiology, University of Antwerp, Wilrijk, Belgium
| | - Christian Bergen
- Institute for Laboratory Animal Science, Small Animal Imaging Center, Hannover Medical School, Hannover, Germany
| | - Martin Meier
- Institute for Laboratory Animal Science, Small Animal Imaging Center, Hannover Medical School, Hannover, Germany
| | | | - Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
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154
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Johnson K, Levine K, Sergi J, Chamoun J, Roach R, Vekich J, Favis M, Horn M, Cao X, Miller B, Snyder W, Aivazian D, Reagan W, Berryman E, Colangelo J, Markiewicz V, Bagi CM, Brown TP, Coyle A, Mohammadi M, Magram J. Therapeutic Effects of FGF23 c-tail Fc in a Murine Preclinical Model of X-Linked Hypophosphatemia Via the Selective Modulation of Phosphate Reabsorption. J Bone Miner Res 2017; 32:2062-2073. [PMID: 28600887 PMCID: PMC5816679 DOI: 10.1002/jbmr.3197] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 05/30/2017] [Accepted: 06/09/2017] [Indexed: 01/13/2023]
Abstract
Fibroblast growth factor 23 (FGF23) is the causative factor of X-linked hypophosphatemia (XLH), a genetic disorder effecting 1:20,000 that is characterized by excessive phosphate excretion, elevated FGF23 levels and a rickets/osteomalacia phenotype. FGF23 inhibits phosphate reabsorption and suppresses 1α,25-dihydroxyvitamin D (1,25D) biosynthesis, analytes that differentially contribute to bone integrity and deleterious soft-tissue mineralization. As inhibition of ligand broadly modulates downstream targets, balancing efficacy and unwanted toxicity is difficult when targeting the FGF23 pathway. We demonstrate that a FGF23 c-tail-Fc fusion molecule selectively modulates the phosphate pathway in vivo by competitive antagonism of FGF23 binding to the FGFR/α klotho receptor complex. Repeated injection of FGF23 c-tail Fc in Hyp mice, a preclinical model of XLH, increases cell surface abundance of kidney NaPi transporters, normalizes phosphate excretion, and significantly improves bone architecture in the absence of soft-tissue mineralization. Repeated injection does not modulate either 1,25D or calcium in a physiologically relevant manner in either a wild-type or disease setting. These data suggest that bone integrity can be improved in models of XLH via the exclusive modulation of phosphate. We posit that the selective modulation of the phosphate pathway will increase the window between efficacy and safety risks, allowing increased efficacy to be achieved in the treatment of this chronic disease. © 2017 American Society for Bone and Mineral Research.
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Affiliation(s)
- Kristen Johnson
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Kymberly Levine
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Joseph Sergi
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Jean Chamoun
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Rachel Roach
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | | | - Mike Favis
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Mark Horn
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Xianjun Cao
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Brian Miller
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - William Snyder
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Dikran Aivazian
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - William Reagan
- Drug Safety Research and Development, Pfizer, Groton, CT, USA
| | | | | | | | - Cedo M Bagi
- Comparative Medicine, Pfizer, Groton, CT, USA
| | - Thomas P Brown
- Drug Safety Research and Development, Pfizer, Groton, CT, USA
| | - Anthony Coyle
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
| | - Moosa Mohammadi
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Jeanne Magram
- Center for Therapeutic Innovation, Pfizer, New York, NY, USA
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155
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Clinkenbeard EL, White KE. Heritable and acquired disorders of phosphate metabolism: Etiologies involving FGF23 and current therapeutics. Bone 2017; 102:31-39. [PMID: 28159712 PMCID: PMC5537045 DOI: 10.1016/j.bone.2017.01.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 01/20/2017] [Accepted: 01/29/2017] [Indexed: 10/20/2022]
Abstract
Phosphate is critical for many cellular processes and structural functions, including as a key molecule for nucleic acid synthesis and energy metabolism, as well as hydroxyapatite formation in bone. Therefore it is critical to maintain tight regulation of systemic phosphate levels. Based upon its broad biological importance, disruption of normal phosphate homeostasis has detrimental effects on skeletal integrity and overall health. Investigating heritable diseases of altered phosphate metabolism has led to key discoveries underlying the regulation and systemic actions of the phosphaturic hormone Fibroblast growth factor-23 (FGF23). Both molecular and clinical studies have revealed novel targets for the development and optimization of therapies for disorders of phosphate handling. This review will focus upon the bridge between genetic discoveries involving disorders of altered FGF23 bioactivity, as well as describe how these findings have translated into pharmacologic application.
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Affiliation(s)
- Erica L Clinkenbeard
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA.
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156
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Eisenga MF, van Londen M, Leaf DE, Nolte IM, Navis G, Bakker SJL, de Borst MH, Gaillard CAJM. C-Terminal Fibroblast Growth Factor 23, Iron Deficiency, and Mortality in Renal Transplant Recipients. J Am Soc Nephrol 2017; 28:3639-3646. [PMID: 28774998 DOI: 10.1681/asn.2016121350] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 06/16/2017] [Indexed: 02/06/2023] Open
Abstract
Iron deficiency (ID) is independently associated with an increased risk of death in renal transplant recipients (RTRs). ID promotes production and cleavage of intact fibroblast growth factor 23 (iFGF23) into C-terminal fibroblast growth factor 23 (cFGF23), elevated levels of which are also prospectively associated with adverse outcomes. We hypothesized that in RTRs, the relationship between ID and mortality is mediated by FGF23. We measured plasma iFGF23 and cFGF23 levels in 700 stable RTRs at a median of 5.4 years after transplant. RTRs with ID had median (interquartile range) cFGF23 concentrations higher than those of RTRs without ID (223 [131-361] versus 124 [88-180] RU/ml; P<0.001), whereas iFGF23 concentrations were similar between groups. In multivariable-adjusted Cox regression analyses, ID associated with increased mortality (81 events; hazard ratio, 1.95; 95% confidence interval, 1.22 to 3.10; P<0.01). However, this association lost significance after additional adjustment for cFGF23 levels (hazard ratio, 1.45; 95% confidence interval, 0.87 to 2.51; P=0.15). In further mediation analysis, cFGF23 explained 46% of the association between ID and mortality, whereas iFGF23 did not mediate this association. In conclusion, we found that cFGF23 levels are increased in iron-deficient RTRs and that the underlying biologic process driving production and cleavage of iFGF23, or alternatively the increased level of cFGF23 fragments, probably is an important mediator of the association between ID and mortality. Our results underline the strong relationship between iron and FGF23 physiology, and provide a potential mechanism explaining the relationship between ID and adverse outcome in RTRs.
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Affiliation(s)
| | | | - David E Leaf
- Division of Renal Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Ilja M Nolte
- Department of Epidemiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; and
| | - Gerjan Navis
- Division of Nephrology, Department of Internal Medicine, and
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157
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Minisola S, Peacock M, Fukumoto S, Cipriani C, Pepe J, Tella SH, Collins MT. Tumour-induced osteomalacia. Nat Rev Dis Primers 2017; 3:17044. [PMID: 28703220 DOI: 10.1038/nrdp.2017.44] [Citation(s) in RCA: 169] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tumour-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is a rare paraneoplastic disorder caused by tumours that secrete fibroblast growth factor 23 (FGF23). Owing to the role of FGF23 in renal phosphate handling and vitamin D synthesis, TIO is characterized by decreased renal tubular reabsorption of phosphate, by hypophosphataemia and by low levels of active vitamin D. Chronic hypophosphataemia ultimately results in osteomalacia (that is, inadequate bone mineralization). The diagnosis of TIO is usually suspected when serum phosphate levels are chronically low in the setting of bone pain, fragility fractures and muscle weakness. Locating the offending tumour can be very difficult, as the tumour is often very small and can be anywhere in the body. Surgical removal of the tumour is the only definitive treatment. When the tumour cannot be located or when complete resection is not possible, medical treatment with phosphate salts or active vitamin D is necessary. One of the most promising emerging treatments for unresectable tumours that cause TIO is the anti-FGF23 monoclonal antibody KRN23. The recent identification of a fusion of fibronectin and fibroblast growth factor receptor 1 (FGFR1) as a molecular driver in some tumours not only sheds light on the pathophysiology of TIO but also opens the door to a better understanding of the transcription, translocation, post-translational modification and secretion of FGF23, as well as suggesting approaches to targeted therapy. Further study will reveal if the FGFR1 pathway is also involved in tumours that do not harbour the translocation.
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Affiliation(s)
- Salvatore Minisola
- Department of Internal Medicine and Medical Disciplines, Sapienza University of Rome, Viale del Policlinico 155, 00161 Rome, Italy
| | - Munro Peacock
- Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Seijii Fukumoto
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| | - Cristiana Cipriani
- Department of Internal Medicine and Medical Disciplines, Sapienza University of Rome, Viale del Policlinico 155, 00161 Rome, Italy
| | - Jessica Pepe
- Department of Internal Medicine and Medical Disciplines, Sapienza University of Rome, Viale del Policlinico 155, 00161 Rome, Italy
| | - Sri Harsha Tella
- Section on Skeletal Disorders and Mineral Homeostasis, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, USA.,Endocrinology and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Michael T Collins
- Section on Skeletal Disorders and Mineral Homeostasis, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland, USA
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158
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Hum JM, O'Bryan L, Smith RC, White KE. Novel functions of circulating Klotho. Bone 2017; 100:36-40. [PMID: 27890549 PMCID: PMC5441975 DOI: 10.1016/j.bone.2016.11.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Revised: 11/21/2016] [Accepted: 11/21/2016] [Indexed: 01/08/2023]
Abstract
A significant portion of the key biological functions of αKlotho (αKL) and its cognate ligand Fibroblast growth factor-23 (FGF23) have been revealed through the study of rare diseases of mineral metabolism. These findings have far reaching implications for common disorders such as chronic kidney disease-mineral bone disorder (CKD-MBD). αKL's predominant effect on mineral homeostasis is through its actions in the kidney as a co-receptor for FGF23, however emerging data has shed light on its capacity to act as a circulating factor through the cleavage of the transmembrane form of αKL ('mKL') to produce 'cleaved KL' or 'cKL'. This review summarizes new findings from studies using extended delivery of cKL to mouse models with phenotypes reflecting those arising in CKD-MBD.
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Affiliation(s)
- Julia M Hum
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Division of Biomedical Science, Marian University School of Osteopathic Medicine, Indianapolis, IN 46222, USA
| | - Linda O'Bryan
- Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Rosamund C Smith
- Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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159
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FGF23 is synthesised locally by renal tubules and activates injury-primed fibroblasts. Sci Rep 2017; 7:3345. [PMID: 28611350 PMCID: PMC5469734 DOI: 10.1038/s41598-017-02709-w] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022] Open
Abstract
In kidney disease, higher circulating levels of the mineral-regulating hormone fibroblast growth factor (FGF)-23 are predictive of disease progression but direct pathogenic effects on the kidney are unknown. We sought evidence of local renal synthesis in response to unilateral ureteric obstruction in the mouse, and pro-fibrotic actions of FGF23 on the fibroblast in vitro. Acute tubulointerstitial injury due to unilateral ureteric obstruction stimulated renal FGF23 synthesis by tubules, and downregulated inactivating proprotein convertases, without effects on systemic mineral metabolism. In vitro, FGF23 had divergent effects on fibroblast activation in cells derived from normal and obstructed kidneys. While FGF23 failed to stimulate fibrogenesis in normal fibroblasts, in those primed by injury, FGF23 induced pro-fibrotic signalling cascades via activation of TGF-β pathways. Effects were independent of α-klotho. Tubule-derived FGF23 may amplify myofibroblast activation in acute renal injury, and might provide a novel therapeutic target in renal fibrosis.
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160
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Kim SJ, Cheresh P, Eren M, Jablonski RP, Yeldandi A, Ridge KM, Budinger GRS, Kim DH, Wolf M, Vaughan DE, Kamp DW. Klotho, an antiaging molecule, attenuates oxidant-induced alveolar epithelial cell mtDNA damage and apoptosis. Am J Physiol Lung Cell Mol Physiol 2017; 313:L16-L26. [PMID: 28428174 DOI: 10.1152/ajplung.00063.2017] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 04/03/2017] [Accepted: 04/16/2017] [Indexed: 11/22/2022] Open
Abstract
Alveolar epithelial cell (AEC) apoptosis and inadequate repair resulting from "exaggerated" lung aging and mitochondrial dysfunction are critical determinants promoting lung fibrosis. α-Klotho, which is an antiaging molecule that is expressed predominantly in the kidney and secreted in the blood, can protect lung epithelial cells against hyperoxia-induced apoptosis. We reasoned that Klotho protects AEC exposed to oxidative stress in part by maintaining mitochondrial DNA (mtDNA) integrity and mitigating apoptosis. We find that Klotho levels are decreased in both serum and alveolar type II (AT2) cells from asbestos-exposed mice. We show that oxidative stress reduces AEC Klotho mRNA and protein expression, whereas Klotho overexpression is protective while Klotho silencing augments AEC mtDNA damage. Compared with wild-type, Klotho heterozygous hypomorphic allele (kl/+) mice have increased asbestos-induced lung fibrosis due in part to increased AT2 cell mtDNA damage. Notably, we demonstrate that serum Klotho levels are reduced in wild-type but not mitochondrial catalase overexpressing (MCAT) mice 3 wk following exposure to asbestos and that EUK-134, a MnSOD/catalase mimetic, mitigates oxidant-induced reductions in AEC Klotho expression. Using pharmacologic and genetic silencing studies, we show that Klotho attenuates oxidant-induced AEC mtDNA damage and apoptosis via mechanisms dependent on AKT activation arising from upstream fibroblast growth factor receptor 1 activation. Our findings suggest that Klotho preserves AEC mtDNA integrity in the setting of oxidative stress necessary for preventing apoptosis and asbestos-induced lung fibrosis. We reason that strategies aimed at augmenting AEC Klotho levels may be an innovative approach for mitigating age-related lung diseases.
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Affiliation(s)
- Seok-Jo Kim
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois.,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Paul Cheresh
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois.,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Mesut Eren
- Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Renea P Jablonski
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois.,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Anjana Yeldandi
- Department of Pathology, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Karen M Ridge
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois.,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - G R Scott Budinger
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois.,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - Dong-Hyun Kim
- Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois; and
| | - Myles Wolf
- Department of Medicine, Duke University School of Medicine, Durham, North Carolina
| | - Douglas E Vaughan
- Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
| | - David W Kamp
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; .,Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois
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161
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Ramadan AR, Shawar SM, Alghamdi MA. Development and Validation of a Simple Diagnostic Method to Detect Gain and Loss of Function Defects in Fibroblast Growth Factor-23. Horm Res Paediatr 2017; 86:45-52. [PMID: 27355663 DOI: 10.1159/000447113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/26/2016] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Fibroblast growth factor-23 (FGF23) is a bone-derived hormone that regulates the homeostasis of phosphate and vitamin D. Three substitutions in the hormone are reported to cause autosomal dominant hypophosphatemic rickets and seven substitutions to cause autosomal recessive hyperphosphatemic familial tumoral calcinosis (HFTC). Both disorders are rare in the general population and occur most often in the Eastern Mediterranean region and Africa. None of the mutations could be identified using standard restriction fragment length polymorphism. The only technique currently available to confirm the clinical diagnosis is DNA sequencing. METHODS Using a tri-primer ARMS-PCR, in vitro site-directed mutagenesis and DNA sequencing, we developed, verified and validated a rapid and reliable diagnostic test for the ten mutations in FGF23. RESULTS We generated a test for all ten mutations and confirmed each test by DNA sequencing. We increased the specificity of the test by introducing a mismatch at position -2 in the 3'-terminus of the reverse primer of the normal and the mutant sequences. Finally, using DNA sequencing, we validated the technique for FGF23/S129F substitution by testing samples from 80 individuals from two unrelated Arab families harboring HFTC. CONCLUSIONS This inexpensive and specific method could be adopted where DNA sequencing is not available or affordable.
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Affiliation(s)
- Ahmad R Ramadan
- Department of Life Sciences, Medical Biotechnology, Arabian Gulf University, Manama, Bahrain
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162
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Holmlund-Suila E, Viljakainen H, Ljunggren Ö, Hytinantti T, Andersson S, Mäkitie O. Fibroblast Growth Factor 23 Concentrations Reflect Sex Differences in Mineral Metabolism and Growth in Early Infancy. Horm Res Paediatr 2017; 85:232-41. [PMID: 26943634 DOI: 10.1159/000443988] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 01/11/2016] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The role of fibroblast growth factor 23 (FGF23) in the regulation of mineral homeostasis in early life is inadequately understood. We aimed to explore the effects of vitamin D supplementation on serum FGF23 and to elucidate longitudinal changes in FGF23, in addition to studying its association with mineral metabolism in early infancy. METHODS Altogether 113 healthy infants received vitamin D3 10, 30 or 40 µg/day from age 0.5 to 3.0 months. Cord blood at birth and capillary blood samples at 3 months were analyzed for serum 25-hydroxyvitamin D, parathyroid hormone, phosphate, calcium and intact and C-terminal FGF23. RESULTS In repeated-measures ANCOVA, intact FGF23 concentration increased with time (p < 0.001) and C-terminal FGF23 decreased (p < 0.001). At 3 months, girls had a higher concentration of intact FGF23 (51 vs. 26 pg/ml, p < 0.001) and a greater increase over time (x0394;FGF23 intact 45 vs. 16 pg/ml, p = 0.001) than boys. Vitamin D did not affect serum intact or C-terminal FGF23 concentrations. Girls showed a positive correlation between phosphate and intact FGF23 (p = 0.004), whereas in boys phosphate and C-terminal FGF23 correlated inversely (p = 0.006). CONCLUSIONS A substantial sex-related difference in intact FGF23 concentration exists during early infancy, possibly related to differences in skeletal growth between boys and girls.
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Affiliation(s)
- Elisa Holmlund-Suila
- Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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163
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Hum JM, O'Bryan LM, Tatiparthi AK, Cass TA, Clinkenbeard EL, Cramer MS, Bhaskaran M, Johnson RL, Wilson JM, Smith RC, White KE. Chronic Hyperphosphatemia and Vascular Calcification Are Reduced by Stable Delivery of Soluble Klotho. J Am Soc Nephrol 2017; 28:1162-1174. [PMID: 27837149 PMCID: PMC5373441 DOI: 10.1681/asn.2015111266] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 10/01/2016] [Indexed: 12/22/2022] Open
Abstract
αKlotho (αKL) regulates mineral metabolism, and diseases associated with αKL deficiency are characterized by hyperphosphatemia and vascular calcification (VC). αKL is expressed as a membrane-bound protein (mKL) and recognized as the coreceptor for fibroblast growth factor-23 (FGF23) and a circulating soluble form (cKL) created by endoproteolytic cleavage of mKL. The functions of cKL with regard to phosphate metabolism are unclear. We tested the ability of cKL to regulate pathways and phenotypes associated with hyperphosphatemia in a mouse model of CKD-mineral bone disorder and αKL-null mice. Stable delivery of adeno-associated virus (AAV) expressing cKL to diabetic endothelial nitric oxide synthase-deficient mice or αKL-null mice reduced serum phosphate levels. Acute injection of recombinant cKL downregulated the renal sodium-phosphate cotransporter Npt2a in αKL-null mice supporting direct actions of cKL in the absence of mKL. αKL-null mice with sustained AAV-cKL expression had a 74%-78% reduction in aorta mineral content and a 72%-77% reduction in mineral volume compared with control-treated counterparts (P<0.01). Treatment of UMR-106 osteoblastic cells with cKL + FGF23 increased the phosphorylation of extracellular signal-regulated kinase 1/2 and induced Fgf23 expression. CRISPR/Cas9-mediated deletion of fibroblast growth factor receptor 1 (FGFR1) or pretreatment with inhibitors of mitogen-activated kinase kinase 1 or FGFR ablated these responses. In summary, sustained cKL treatment reduced hyperphosphatemia in a mouse model of CKD-mineral bone disorder, and it reduced hyperphosphatemia and prevented VC in mice without endogenous αKL. Furthermore, cKL stimulated Fgf23 in an FGFR1-dependent manner in bone cells. Collectively, these findings indicate that cKL has mKL-independent activity and suggest the potential for enhancing cKL activity in diseases of hyperphosphatemia with associated VC.
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Affiliation(s)
- Julia M Hum
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana
| | - Linda M O'Bryan
- Biotechnology Discovery Research, Lilly Research Laboratories
| | - Arun K Tatiparthi
- Lead Optimization Toxicology and Pharmacology, Covance Inc., Greenfield, Indiana
| | - Taryn A Cass
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana
| | - Erica L Clinkenbeard
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana
| | - Martin S Cramer
- Biotechnology Discovery Research, Lilly Research Laboratories
| | | | | | - Jonathan M Wilson
- Tailored Therapeutics, Eli Lilly and Company, Indianapolis, Indiana; and
| | | | - Kenneth E White
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana;
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164
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Song L, Linstedt AD. Inhibitor of ppGalNAc-T3-mediated O-glycosylation blocks cancer cell invasiveness and lowers FGF23 levels. eLife 2017; 6:e24051. [PMID: 28362263 PMCID: PMC5407854 DOI: 10.7554/elife.24051] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 03/30/2017] [Indexed: 01/12/2023] Open
Abstract
Small molecule inhibitors of site-specific O-glycosylation by the polypeptide N-acetylgalactosaminyltransferase (ppGalNAc-T) family are currently unavailable but hold promise as therapeutics, especially if selective against individual ppGalNAc-T isozymes. To identify a compound targeting the ppGalNAc-T3 isozyme, we screened libraries to find compounds that act on a cell-based fluorescence sensor of ppGalNAc-T3 but not on a sensor of ppGalNAc-T2. This identified a hit that subsequent in vitro analysis showed directly binds and inhibits purified ppGalNAc-T3 with no detectable activity against either ppGalNAc-T2 or ppGalNAc-T6. Remarkably, the inhibitor was active in two medically relevant contexts. In cell culture, it opposed increased cancer cell invasiveness driven by upregulated ppGalNAc-T3 suggesting the inhibitor might be anti-metastatic. In cells and mice, it blocked ppGalNAc-T3-mediated glycan-masking of FGF23 thereby increasing its cleavage, a possible treatment of chronic kidney disease. These findings establish a pharmacological approach for the ppGalNAc-transferase family and suggest that targeting specific ppGalNAc-transferases will yield new therapeutics.
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Affiliation(s)
- Lina Song
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States
| | - Adam D Linstedt
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, United States
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165
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Sharaf El Din UA, Salem MM, Abdulazim DO. Is Fibroblast growth factor 23 the leading cause of increased mortality among chronic kidney disease patients? A narrative review. J Adv Res 2017; 8:271-278. [PMID: 28337344 PMCID: PMC5347517 DOI: 10.1016/j.jare.2017.02.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/20/2017] [Accepted: 02/20/2017] [Indexed: 12/16/2022] Open
Abstract
The death rate among chronic kidney disease patients is the highest compared to other chronic diseases. 60% of these fatalities are cardiovascular. Cardiovascular calcifications and chronic inflammation affect almost all chronic kidney disease patients and are associated with cardiovascular mortality. Fibroblast growth factor 23 is associated with vascular calcification. Systemic inflammation in chronic kidney disease patients is multifactorial. The role of systemic inflammation in the pathogenesis of vascular calcification was recently reappraised. Fibroblast growth factor 23 was accused as a direct stimulus of left ventricular hypertrophy, uremic inflammation, and impaired neutrophil function. This review will discuss the underlying mechanisms that underlie the link between Fibroblast growth factor 23 and increased mortality encountered among chronic kidney disease patients.
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Affiliation(s)
- Usama A.A. Sharaf El Din
- Nephrology Unit, Internal Medicine Department, School of Medicine, Cairo University, Egypt
- Corresponding author.
| | - Mona M. Salem
- Endocrinology Unit, Internal Medicine Department, School of Medicine, Cairo University, Egypt
| | - Dina O. Abdulazim
- Rheumatology and Rehabilitation Department, School of Medicine, Cairo University, Egypt
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166
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Shawar SM, Ramadan AR, Ali BR, Alghamdi MA, John A, Hudaib FM. FGF23-S129F mutant bypasses ER/Golgi to the circulation of hyperphosphatemic familial tumoral calcinosis patients. Bone 2016; 93:187-195. [PMID: 26620085 DOI: 10.1016/j.bone.2015.11.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 11/15/2015] [Accepted: 11/21/2015] [Indexed: 02/05/2023]
Abstract
FGF23 is essential for the homeostasis of phosphate, and vitamin D. Loss-of-function mutations in this hormone cause hyperphosphatemic familial tumoral calcinosis (HFTC). Earlier reports suggested that intact FGF23 from loss of function mutants such as FGF23/S129F (iFGF23/S129F) is retained intracellularly while the carboxy-terminal fragment is secreted. We sought to investigate the fate of iFGF23/S129F mutant hormone in vivo and in vitro. Five patients clinically diagnosed with HFTC and confirmed by DNA sequencing to carry the c.386 C>T; p.S129F mutation in the homozygous state were studied. Healthy and heterozygous individuals were used as controls in the study. Using ELISA assays, we showed that iFGF23/S129F was 2-5 folds higher in patients' plasma, compared to heterozygous or healthy controls. Importantly, the mutant hormone could not be detected in the patients' sera. However, using proteinase inhibition profiling, we found that a serum metalloproteinase degraded the iFGF23/S129F explaining our failure to detect it in sera. The serum metalloproteinase degrades the WT and the mutant at different rates. Also, confocal microscopy imaging using wild-type (WT) FGF23 or FGF23/S129F mutant in transiently transfected HEK293 and HeLa cells showed weak staining of the Golgi complex with some vesicular staining resembling the ER. Additionally, FGF23 variants (FGF23/WT, FGF23/S129F, FGF23/S71G, and FGF23/R176Q) from stably transfected HEK293 cells secreted high levels into a serum-free medium that can be detected by ELISA and Western blot. Our results suggest that iFGF23/S129F mutant bypasses the ER/Golgi quality control system to the circulation of HFTC patients by an unknown pathway. Finally, we hypothesize that either the mutant hormone is unable to bind α-Klotho-FGFR1c, or it binds the dyad receptor with low affinity and, therefore, incapable of initiating maximal intracellular signaling. Our findings raise the potential use of the WT hormone in therapies of some HFTC patients.
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Affiliation(s)
- Said M Shawar
- Life Sciences Department, Medical Biotechnology, Arabian Gulf University, Manama, Bahrain.
| | - Ahmad R Ramadan
- Life Sciences Department, Medical Biotechnology, Arabian Gulf University, Manama, Bahrain
| | - Bassam R Ali
- Pathology Department, College of Medicine and Health Sciences, United Arab Emirates University, Al-Ain, United Arab Emirates
| | - Manal A Alghamdi
- Life Sciences Department, Medical Biotechnology, Arabian Gulf University, Manama, Bahrain
| | - Anne John
- Pathology Department, College of Medicine and Health Sciences, United Arab Emirates University, Al-Ain, United Arab Emirates
| | - Ferial M Hudaib
- Life Sciences Department, Medical Biotechnology, Arabian Gulf University, Manama, Bahrain
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167
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Nakashima Y, Mima T, Yashiro M, Sonou T, Ohya M, Masumoto A, Yamanaka S, Koreeda D, Tatsuta K, Hanba Y, Moribata M, Negi S, Shigematsu T. Expression and localization of fibroblast growth factor (FGF)23 and Klotho in the spleen: its physiological and functional implications. Growth Factors 2016; 34:196-202. [PMID: 28095739 DOI: 10.1080/08977194.2016.1273222] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The FGF23-Klotho signaling axis is known to exert anti-aging effects via calcium-phosphorus metabolism. In mice deficient in FGF23-Klotho signaling, however, the number of splenocytes is reduced. FGF23 is expressed in both bone and spleen, with regulation of its production differing in these organs. As FGF23-Klotho signaling may play an immunological role in the spleen, splenocytes in male C57BL/6J mice were assayed for expression of Klotho or FGF23 by flow cytometry and immunohistochemistry. Cells that expressed Klotho included CD45R/B220+ CD21/CD35+ CD1d+ CD43- marginal zone B cells. These cells also expressed FGF receptor 1, indicating that Klotho-positive B cells could respond to FGF23. Plasmacytoid dendritic cells (pDCs) with CD11c+ CD45R/B220+ CD11b- CD8α- were found to produce FGF23. Klotho-positive cells and FGF23-producing cells were present in close proximity to each other, suggesting that FGF23 produced by pDCs may act within a limited area. These findings indicate that FGF23-Klotho signaling could play a biological or immunological role in the spleen.
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Affiliation(s)
- Yuri Nakashima
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Toru Mima
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Mitsuru Yashiro
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Tomohiro Sonou
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Masaki Ohya
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Asuka Masumoto
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Shintaro Yamanaka
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Daisuke Koreeda
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Koichi Tatsuta
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Yoshiyuki Hanba
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Mari Moribata
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Shigeo Negi
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
| | - Takashi Shigematsu
- a Department of Nephrology , Wakayama Medical University , Wakayama , Japan
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168
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Xiao Z, Riccardi D, Velazquez HA, Chin AL, Yates CR, Carrick JD, Smith JC, Baudry J, Quarles LD. A computationally identified compound antagonizes excess FGF-23 signaling in renal tubules and a mouse model of hypophosphatemia. Sci Signal 2016; 9:ra113. [PMID: 27879395 PMCID: PMC6544179 DOI: 10.1126/scisignal.aaf5034] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Fibroblast growth factor-23 (FGF-23) interacts with a binary receptor complex composed of α-Klotho (α-KL) and FGF receptors (FGFRs) to regulate phosphate and vitamin D metabolism in the kidney. Excess FGF-23 production, which causes hypophosphatemia, is genetically inherited or occurs with chronic kidney disease. Among other symptoms, hypophosphatemia causes vitamin D deficiency and the bone-softening disorder rickets. Current therapeutics that target the receptor complex have limited utility clinically. Using a computationally driven, structure-based, ensemble docking and virtual high-throughput screening approach, we identified four novel compounds predicted to selectively inhibit FGF-23-induced activation of the FGFR/α-KL complex. Additional modeling and functional analysis found that Zinc13407541 bound to FGF-23 and disrupted its interaction with the FGFR1/α-KL complex; experiments in a heterologous cell expression system showed that Zinc13407541 selectivity inhibited α-KL-dependent FGF-23 signaling. Zinc13407541 also inhibited FGF-23 signaling in isolated renal tubules ex vivo and partially reversed the hypophosphatemic effects of excess FGF-23 in a mouse model. These chemical probes provide a platform to develop lead compounds to treat disorders caused by excess FGF-23.
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Affiliation(s)
- Zhousheng Xiao
- Department of Medicine, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38165, USA
| | - Demian Riccardi
- Department of Chemistry, Earlham College, 801 National Road West, Richmond, IN 47374, USA
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Hector A Velazquez
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
- Department of Chemistry, Tennessee Technological University, 55 University Drive, Cookeville, TN 38501, USA
| | - Ai L Chin
- University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830, USA
| | - Charles R Yates
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Jesse D Carrick
- University of Tennessee/Oak Ridge National Laboratory Center for Molecular Biophysics, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830, USA
| | - Jeremy C Smith
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
- Department of Chemistry, Tennessee Technological University, 55 University Drive, Cookeville, TN 38501, USA
| | - Jerome Baudry
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
- Department of Chemistry, Tennessee Technological University, 55 University Drive, Cookeville, TN 38501, USA
| | - L Darryl Quarles
- Department of Medicine, College of Medicine, University of Tennessee Health Science Center, Memphis, TN 38165, USA.
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169
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Lu X, Hu MC. Klotho/FGF23 Axis in Chronic Kidney Disease and Cardiovascular Disease. KIDNEY DISEASES 2016; 3:15-23. [PMID: 28785560 DOI: 10.1159/000452880] [Citation(s) in RCA: 123] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 10/26/2016] [Indexed: 12/26/2022]
Abstract
BACKGROUND Membrane αKlotho (hereinafter called Klotho) is highly expressed in the kidney and functions as a coreceptor of FGF receptors (FGFRs) to activate specific fibroblast growth factor 23 (FGF23) signal pathway. FGF23 is produced in bones and participates in the maintenance of mineral homeostasis. The extracellular domain of transmembrane Klotho can be cleaved by secretases and released into the circulation as soluble Klotho. Soluble Klotho does not only weakly activate FGFRs to transduce the FGF23 signaling pathway, but also functions as an enzyme and hormonal substance to play a variety of biological functions. FGF23 exerts its biological effects through activation of FGFRs in a Klotho-dependent manner. However, extremely high FGF23 can exert its pathological action in a Klotho-independent manner. SUMMARY The decline in serum and urinary Klotho followed by a rise in serum FGF23 at an early stage of chronic kidney disease (CKD) functions as an early biomarker for kidney dysfunction and can also serve as a predictor for risk of cardiovascular disease (CVD) and mortality in both CKD patients and the general population. Moreover, Klotho deficiency is a pathogenic factor for CKD progression and CVD. FGF23 may also contribute to CVD. Prevention of Klotho decline, reactivation of endogenous Klotho production, or supplementation of exogenous Klotho attenuate renal fibrosis, retard CKD progression, improve mineral metabolism, ameliorate cardiomyopathy, and alleviate vascular calcification in CKD. However, the poor CVD outcome after depletion of FGF23 with FGF23 antibody stimulates the generation of a more specific inhibitor of FGF23 for CKD treatment. KEY MESSAGE Klotho/FGF23 may not only be diagnostic and/or prognostic biomarkers for CKD and CVD, but are also pathogenic contributors to CKD progression and CVD development. The Klotho/FGF23 axis should be a novel target for renal clinics.
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Affiliation(s)
- Xiang Lu
- Department of Geriatrics, Sir Run Run Hospital, Nanjing Medical University, Nanjing, PR China
| | - Ming Chang Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
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170
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Tan SJ, Satake S, Smith ER, Toussaint ND, Hewitson TD, Holt SG. Parenteral iron polymaltose changes i:c-terminal FGF23 ratios in iron deficiency, but not in dialysis patients. Eur J Clin Nutr 2016; 71:180-184. [DOI: 10.1038/ejcn.2016.217] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 09/22/2016] [Accepted: 09/27/2016] [Indexed: 12/17/2022]
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171
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Courbebaisse M, Mehel H, Petit-Hoang C, Ribeil JA, Sabbah L, Tuloup-Minguez V, Bergerat D, Arlet JB, Stanislas A, Souberbielle JC, Le Clésiau H, Fischmeister R, Friedlander G, Prié D. Carboxy-terminal fragment of fibroblast growth factor 23 induces heart hypertrophy in sickle cell disease. Haematologica 2016; 102:e33-e35. [PMID: 27789679 DOI: 10.3324/haematol.2016.150987] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Marie Courbebaisse
- Université Paris Descartes, Sorbonne-Paris-Cité, Faculté de Médecine, Paris.,INSERM U1151-CNRS UMR8253, Paris.,Service de Physiologie Explorations Fonctionnelles Hôpital Necker-Enfants Malades Assistance Publique-Hôpitaux de Paris.,Service de Physiologie Explorations Fonctionnelles Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris
| | | | | | - Jean-Antoine Ribeil
- Département de Biothérapie, Hôpital Necker-Enfants Malades Assistance Publique-Hôpitaux de Paris
| | - Laurent Sabbah
- Unité Fonctionnelle de Cardiologie Adultes, Hôpital Necker-Enfants Malades Assistance Publique-Hôpitaux de Paris
| | | | | | - Jean-Benoit Arlet
- Service de Médecine Interne, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris.,INSERM U1163, CNRS 8254, Institut IMAGINE, Paris
| | - Aurélie Stanislas
- Département de Biothérapie, Hôpital Necker-Enfants Malades Assistance Publique-Hôpitaux de Paris
| | - Jean-Claude Souberbielle
- INSERM U1151-CNRS UMR8253, Paris.,Service de Physiologie Explorations Fonctionnelles Hôpital Necker-Enfants Malades Assistance Publique-Hôpitaux de Paris
| | - Hervé Le Clésiau
- Centre de Santé et d'Assurance Maladie Agence de Seine-Saint-Denis, Bobigny, France
| | - Rodolphe Fischmeister
- INSERM UMR-S 1180 Université Paris-Sud, Université Paris-Saclay, Châtenay-Malabry, France
| | - Gérard Friedlander
- Université Paris Descartes, Sorbonne-Paris-Cité, Faculté de Médecine, Paris.,INSERM U1151-CNRS UMR8253, Paris.,Service de Physiologie Explorations Fonctionnelles Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris
| | - Dominique Prié
- Université Paris Descartes, Sorbonne-Paris-Cité, Faculté de Médecine, Paris .,INSERM U1151-CNRS UMR8253, Paris.,Service de Physiologie Explorations Fonctionnelles Hôpital Necker-Enfants Malades Assistance Publique-Hôpitaux de Paris
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172
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Chen J, Lin Y, Sun Z. Deficiency in the anti-aging gene Klotho promotes aortic valve fibrosis through AMPKα-mediated activation of RUNX2. Aging Cell 2016; 15:853-60. [PMID: 27242197 PMCID: PMC5013020 DOI: 10.1111/acel.12494] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/29/2016] [Indexed: 01/14/2023] Open
Abstract
Fibrotic aortic valve disease (FAVD) is an important cause of aortic stenosis, yet currently there is no effective treatment for FAVD due to its unknown etiology. The purpose of this study was to investigate whether deficiency in the anti‐aging Klotho gene (KL) promotes high‐fat‐diet‐induced FAVD and to explore the underlying molecular mechanism. Heterozygous Klotho‐deficient (KL+/−) mice and WT littermates were fed with a high‐fat diet (HFD) or normal diet for 13 weeks, followed by treatment with the AMPKα activator (AICAR) for an additional 2 weeks. A HFD caused a greater increase in collagen levels in the aortic valves of KL+/− mice than of WT mice, indicating that Klotho deficiency promotes HFD‐induced aortic valve fibrosis (AVF). AMPKα activity (pAMPKα) was decreased, while protein expression of collagen I and RUNX2 was increased in the aortic valves of KL+/− mice fed with a HFD. Treatment with AICAR markedly attenuated HFD‐induced AVF in KL+/− mice. AICAR not only abolished the downregulation of pAMPKα but also eliminated the upregulation of collagen I and RUNX2 in the aortic valves of KL+/− mice fed with HFD. In cultured porcine aortic valve interstitial cells, Klotho‐deficient serum plus cholesterol increased RUNX2 and collagen I protein expression, which were attenuated by activation of AMPKα by AICAR. Interestingly, silencing of RUNX2 abolished the stimulatory effect of Klotho deficiency on cholesterol‐induced upregulation of matrix proteins, including collagen I and osteocalcin. In conclusion, Klotho gene deficiency promotes HFD‐induced fibrosis in aortic valves, likely through the AMPKα–RUNX2 pathway.
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Affiliation(s)
- Jianglei Chen
- Department of Physiology College of Medicine University of Oklahoma Health Sciences Center Oklahoma City OK 73104 USA
| | - Yi Lin
- Department of Physiology College of Medicine University of Oklahoma Health Sciences Center Oklahoma City OK 73104 USA
| | - Zhongjie Sun
- Department of Physiology College of Medicine University of Oklahoma Health Sciences Center Oklahoma City OK 73104 USA
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173
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Ramnitz MS, Gourh P, Goldbach-Mansky R, Wodajo F, Ichikawa S, Econs MJ, White KE, Molinolo A, Chen MY, Heller T, Del Rivero J, Seo-Mayer P, Arabshahi B, Jackson MB, Hatab S, McCarthy E, Guthrie LC, Brillante BA, Gafni RI, Collins MT. Phenotypic and Genotypic Characterization and Treatment of a Cohort With Familial Tumoral Calcinosis/Hyperostosis-Hyperphosphatemia Syndrome. J Bone Miner Res 2016; 31:1845-1854. [PMID: 27164190 PMCID: PMC5071128 DOI: 10.1002/jbmr.2870] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 04/22/2016] [Accepted: 05/09/2016] [Indexed: 01/05/2023]
Abstract
Familial tumoral calcinosis (FTC)/hyperostosis-hyperphosphatemia syndrome (HHS) is a rare disorder caused by mutations in the genes encoding fibroblast growth factor-23 (FGF23), N-acetylgalactosaminyltransferase 3 (GALNT3), or KLOTHO. The result is functional deficiency of, or resistance to, intact FGF23 (iFGF23), causing hyperphosphatemia, increased renal tubular reabsorption of phosphorus (TRP), elevated or inappropriately normal 1,25-dihydroxyvitamin D3 (1,25D), ectopic calcifications, and/or diaphyseal hyperostosis. Eight subjects with FTC/HHS were studied and treated. Clinical manifestations varied, even within families, ranging from asymptomatic to large, disabling calcifications. All subjects had hyperphosphatemia, increased TRP, and elevated or inappropriately normal 1,25D. C-terminal FGF23 was markedly elevated whereas iFGF23 was comparatively low, consistent with increased FGF23 cleavage. Radiographs ranged from diaphyseal hyperostosis to massive calcification. Two subjects with severe calcifications also had overwhelming systemic inflammation and elevated C-reactive protein (CRP). GALNT3 mutations were identified in seven subjects; no causative mutation was found in the eighth. Biopsies from four subjects showed ectopic calcification and chronic inflammation, with areas of heterotopic ossification observed in one subject. Treatment with low phosphate diet, phosphate binders, and phosphaturia-inducing therapies was prescribed with variable response. One subject experienced complete resolution of a calcific mass after 13 months of medical treatment. In the two subjects with systemic inflammation, interleukin-1 (IL-1) antagonists significantly decreased CRP levels with resolution of calcinosis cutis and perilesional inflammation in one subject and improvement of overall well-being in both subjects. This cohort expands the phenotype and genotype of FTC/HHS and demonstrates the range of clinical manifestations despite similar biochemical profiles and genetic mutations. Overwhelming systemic inflammation has not been described previously in FTC/HHS; the response to IL-1 antagonists suggests that anti-inflammatory drugs may be useful adjuvants. In addition, this is the first description of heterotopic ossification reported in FTC/HHS, possibly mediated by the adjacent inflammation. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Mary Scott Ramnitz
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Pravitt Gourh
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Raphaela Goldbach-Mansky
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Felasfa Wodajo
- Musculoskeletal Tumor Surgery, Virginia Cancer Specialists, Fairfax, VA, USA
| | - Shoji Ichikawa
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michael J Econs
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Alfredo Molinolo
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Marcus Y Chen
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Theo Heller
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Jaydira Del Rivero
- National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Patricia Seo-Mayer
- Division of Nephrology and Hypertension, Pediatric Specialists of Virginia and Georgetown University School of Medicine, Fairfax, VA, USA
| | - Bita Arabshahi
- Department of Rheumatology, Pediatric Specialists of Virginia, Fairfax, VA, USA
| | - Malaka B Jackson
- Department of Pediatric Endocrinology, University of South Carolina School of Medicine, Columbia, SC, USA
| | - Sarah Hatab
- Department of Pediatric Endocrinology, Emory University School of Medicine, Atlanta, GA, USA
| | - Edward McCarthy
- Department of Pathology, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Lori C Guthrie
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Beth A Brillante
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Rachel I Gafni
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Michael T Collins
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
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174
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Sneddon WB, Ruiz GW, Gallo LI, Xiao K, Zhang Q, Rbaibi Y, Weisz OA, Apodaca GL, Friedman PA. Convergent Signaling Pathways Regulate Parathyroid Hormone and Fibroblast Growth Factor-23 Action on NPT2A-mediated Phosphate Transport. J Biol Chem 2016; 291:18632-42. [PMID: 27432882 PMCID: PMC5009241 DOI: 10.1074/jbc.m116.744052] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Indexed: 12/18/2022] Open
Abstract
Parathyroid hormone (PTH) and FGF23 are the primary hormones regulating acute phosphate homeostasis. Human renal proximal tubule cells (RPTECs) were used to characterize the mechanism and signaling pathways of PTH and FGF23 on phosphate transport and the role of the PDZ protein NHERF1 in mediating PTH and FGF23 effects. RPTECs express the NPT2A phosphate transporter, αKlotho, FGFR1, FGFR3, FGFR4, and the PTH receptor. FGFR1 isoforms are formed from alternate splicing of exon 3 and of exon 8 or 9 in Ir-like loop 3. Exon 3 was absent, but mRNA containing both exons 8 and 9 is present in cytoplasm. Using an FGFR1c-specific antibody together with mass spectrometry analysis, we show that RPTECs express FGFR-β1C. The data are consistent with regulated FGFR1 splicing involving a novel cytoplasmic mechanism. PTH and FGF23 inhibited phosphate transport in a concentration-dependent manner. At maximally effective concentrations, PTH and FGF23 equivalently decreased phosphate uptake and were not additive, suggesting a shared mechanism of action. Protein kinase A or C blockade prevented PTH but not FGF23 actions. Conversely, inhibiting SGK1, blocking FGFR dimerization, or knocking down Klotho expression disrupted FGF23 actions but did not interfere with PTH effects. C-terminal FGF23(180-251) competitively and selectively blocked FGF23 action without disrupting PTH effects. However, both PTH and FGF23-sensitive phosphate transport were abolished by NHERF1 shRNA knockdown. Extended treatment with PTH or FGF23 down-regulated NPT2A without affecting NHERF1. We conclude that FGFR1c and PTHR signaling pathways converge on NHERF1 to inhibit PTH- and FGF23-sensitive phosphate transport and down-regulate NPT2A.
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MESH Headings
- Cell Line, Transformed
- Fibroblast Growth Factor-23
- Fibroblast Growth Factors/genetics
- Fibroblast Growth Factors/metabolism
- Glucuronidase/biosynthesis
- Glucuronidase/genetics
- Humans
- Klotho Proteins
- Parathyroid Hormone/genetics
- Parathyroid Hormone/metabolism
- Phosphates/metabolism
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Receptor, Fibroblast Growth Factor, Type 1/genetics
- Receptor, Fibroblast Growth Factor, Type 1/metabolism
- Receptor, Fibroblast Growth Factor, Type 3/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 3/genetics
- Receptor, Fibroblast Growth Factor, Type 4/biosynthesis
- Receptor, Fibroblast Growth Factor, Type 4/genetics
- Receptor, Parathyroid Hormone, Type 1/genetics
- Receptor, Parathyroid Hormone, Type 1/metabolism
- Signal Transduction/physiology
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/metabolism
- Sodium-Phosphate Cotransporter Proteins, Type IIa/genetics
- Sodium-Phosphate Cotransporter Proteins, Type IIa/metabolism
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Affiliation(s)
- W Bruce Sneddon
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Giovanni W Ruiz
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Luciana I Gallo
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Kunhong Xiao
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Qiangmin Zhang
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and
| | - Youssef Rbaibi
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Ora A Weisz
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 Cell Biology, and
| | - Gerard L Apodaca
- Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 Cell Biology, and
| | - Peter A Friedman
- From the Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology and the Departments of Structural Biology,
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175
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Suvannasankha A, Tompkins DR, Edwards DF, Petyaykina KV, Crean CD, Fournier PG, Parker JM, Sandusky GE, Ichikawa S, Imel EA, Chirgwin JM. FGF23 is elevated in multiple myeloma and increases heparanase expression by tumor cells. Oncotarget 2016; 6:19647-60. [PMID: 25944690 PMCID: PMC4637311 DOI: 10.18632/oncotarget.3794] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 03/10/2015] [Indexed: 01/09/2023] Open
Abstract
Multiply myeloma (MM) grows in and destroys bone, where osteocytes secrete FGF23, a hormone which affects phosphate homeostasis and aging. We report that multiple myeloma (MM) cells express receptors for and respond to FGF23. FGF23 increased mRNA for EGR1 and its target heparanase, a pro-osteolytic factor in MM. FGF23 signals through a complex of klotho and a classical FGF receptor (FGFR); both were expressed by MM cell lines and patient samples. Bone marrow plasma cells from 42 MM patients stained positively for klotho, while plasma cells from 8 patients with monoclonal gammopathy of undetermined significance (MGUS) and 6 controls were negative. Intact, active FGF23 was increased 2.9X in sera of MM patients compared to controls. FGF23 was not expressed by human MM cells, but co-culture with mouse bone increased its mRNA. The FGFR inhibitor NVP-BGJ398 blocked the heparanase response to FGF23. NVP-BGJ398 did not inhibit 8226 growth in vitro but significantly suppressed growth in bone and induction of the osteoclast regulator RANK ligand, while decreasing heparanase mRNA. The bone microenvironment provides resistance to some anti-tumor drugs but increased the activity of NVP-BGJ398 against 8226 cells. The FGF23/klotho/heparanase signaling axis may offer targets for treatment of MM in bone.
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Affiliation(s)
- Attaya Suvannasankha
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Richard L. Roudebush VA Medical Center, Indianapolis, IN, USA
| | - Douglas R Tompkins
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Daniel F Edwards
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Katarina V Petyaykina
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Colin D Crean
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Pierrick G Fournier
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Jamie M Parker
- Department of Pathology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - George E Sandusky
- Department of Pathology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Shoji Ichikawa
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Erik A Imel
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - John M Chirgwin
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Richard L. Roudebush VA Medical Center, Indianapolis, IN, USA
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176
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Liu ES, Martins JS, Raimann A, Chae BT, Brooks DJ, Jorgetti V, Bouxsein ML, Demay MB. 1,25-Dihydroxyvitamin D Alone Improves Skeletal Growth, Microarchitecture, and Strength in a Murine Model of XLH, Despite Enhanced FGF23 Expression. J Bone Miner Res 2016; 31:929-39. [PMID: 26751835 PMCID: PMC4862933 DOI: 10.1002/jbmr.2783] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 01/05/2016] [Accepted: 01/07/2016] [Indexed: 01/24/2023]
Abstract
X-linked hypophosphatemia (XLH) is characterized by impaired renal tubular reabsorption of phosphate owing to increased circulating FGF23 levels, resulting in rickets in growing children and impaired bone mineralization. Increased FGF23 decreases renal brush border membrane sodium-dependent phosphate transporter IIa (Npt2a) causing renal phosphate wasting, impairs 1-α hydroxylation of 25-hydroxyvitamin D, and induces the vitamin D 24-hydroxylase, leading to inappropriately low circulating levels of 1,25-dihydroxyvitamin D (1,25D). The goal of therapy is prevention of rickets and improvement of growth in children by phosphate and 1,25D supplementation. However, this therapy is often complicated by hypercalcemia and nephrocalcinosis and does not always prevent hyperparathyroidism. To determine if 1,25D or blocking FGF23 action can improve the skeletal phenotype without phosphate supplementation, mice with XLH (Hyp) were treated with daily 1,25D repletion, FGF23 antibodies (FGF23Ab), or biweekly high-dose 1,25D from d2 to d75 without supplemental phosphate. All treatments maintained normocalcemia, increased serum phosphate, and normalized parathyroid hormone levels. They also prevented the loss of Npt2a, α-Klotho, and pERK1/2 immunoreactivity observed in the kidneys of untreated Hyp mice. Daily treatment with 1,25D decreased urine phosphate losses despite a marked increase in bone FGF23 mRNA and in circulating FGF23 levels. Daily 1,25D was more effective than other treatments in normalizing the growth plate and metaphyseal organization. In addition to being the only therapy that normalized lumbar vertebral height and body weight, daily 1,25D therapy normalized bone geometry and was more effective than FGF23Ab in improving trabecular bone structure. Daily 1,25D and FGF23Ab improved cortical microarchitecture and whole-bone biomechanical properties more so than biweekly 1,25D. Thus, monotherapy with 1,25D improves growth, skeletal microarchitecture, and bone strength in the absence of phosphate supplementation despite enhancing FGF23 expression, demonstrating that 1,25D has direct beneficial effects on the skeleton in XLH, independent of its role in phosphate homeostasis. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Eva S Liu
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Boston, MA, USA.,Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Division of Nephrology, Universidade de São Paulo, São Paulo, Brazil
| | - Adalbert Raimann
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Department of Pediatrics and Adolescent Medicine, Medical University Vienna, Vienna, Austria
| | | | - Daniel J Brooks
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Department of Orthopedics, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Vanda Jorgetti
- Division of Nephrology, Universidade de São Paulo, São Paulo, Brazil
| | - Mary L Bouxsein
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA.,Department of Orthopedics, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, MA, USA.,Harvard Medical School, Boston, MA, USA
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177
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Zhang J, Li Y. Therapeutic uses of FGFs. Semin Cell Dev Biol 2016; 53:144-54. [DOI: 10.1016/j.semcdb.2015.09.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 09/07/2015] [Indexed: 01/23/2023]
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178
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Fukumoto S. FGF23-FGF Receptor/Klotho Pathway as a New Drug Target for Disorders of Bone and Mineral Metabolism. Calcif Tissue Int 2016; 98:334-40. [PMID: 26126937 DOI: 10.1007/s00223-015-0029-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 06/19/2015] [Indexed: 10/23/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is a phosphaturic hormone produced by bone and works by binding to Klotho-FGF receptor complex. Excessive and deficient actions of FGF23 result in hypophosphatemic and hyperphosphatemic diseases, respectively. Therefore, it is reasonable to think that modulating FGF23 activities may be a novel therapeutic measure for these diseases. Several preclinical reports indicate that the inhibition of FGF23 activities ameliorates hypophosphatemic rickets/osteomalacia caused by excessive actions of FGF23. In addition, phase I-II clinical trials of anti-FGF23 antibody in adult patients with X-linked hypophosphatemia rickets, the most prevalent cause of genetic FGF23-related hypophosphatemic rickets, indicated that the antibody enhances renal tubular phosphate reabsorption and increases serum phosphate. However, it is not known whether the inhibition of FGF23 activities actually brings clinical improvement of rickets and osteomalacia. Available data indicate that FGF23-FGF receptor/Klotho pathway can be a new drug target for disorders of phosphate and bone metabolism.
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Affiliation(s)
- Seiji Fukumoto
- Department of Nuclear Receptor Ligands and Vitamins Research, Fujii Memorial Institute of Medical Sciences, Tokushima University, 3-18-15 Kuramoto-cho, Tokushima-shi, Tokushima, 770-8503, Japan.
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179
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Abstract
Alpha-Klotho (αKlotho) protein is encoded by the gene, Klotho, and functions as a coreceptor for endocrine fibroblast growth factor-23. The extracellular domain of αKlotho is cleaved by secretases and released into the circulation where it is called soluble αKlotho. Soluble αKlotho in the circulation starts to decline in chronic kidney disease (CKD) stage 2 and urinary αKlotho in even earlier CKD stage 1. Therefore soluble αKlotho is an early and sensitive marker of decline in kidney function. Preclinical data from numerous animal experiments support αKlotho deficiency as a pathogenic factor for CKD progression and extrarenal CKD complications including cardiac and vascular disease, hyperparathyroidism, and disturbed mineral metabolism. αKlotho deficiency induces cell senescence and renders cells susceptible to apoptosis induced by a variety of cellular insults including oxidative stress. αKlotho deficiency also leads to defective autophagy and angiogenesis and promotes fibrosis in the kidney and heart. Most importantly, prevention of αKlotho decline, upregulation of endogenous αKlotho production, or direct supplementation of soluble αKlotho are all associated with attenuation of renal fibrosis, retardation of CKD progression, improvement of mineral metabolism, amelioration of cardiac function and morphometry, and alleviation of vascular calcification in CKD. Therefore in rodents, αKlotho is not only a diagnostic and prognostic marker for CKD but the enhancement of endogenous or supplement of exogenous αKlotho are promising therapeutic strategies to prevent, retard, and decrease the comorbidity burden of CKD.
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Affiliation(s)
- J A Neyra
- University of Texas Southwestern Medical Center, Dallas, TX, United States; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - M C Hu
- University of Texas Southwestern Medical Center, Dallas, TX, United States; Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, United States.
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180
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Chia J, Goh G, Bard F. Short O-GalNAc glycans: regulation and role in tumor development and clinical perspectives. Biochim Biophys Acta Gen Subj 2016; 1860:1623-39. [PMID: 26968459 DOI: 10.1016/j.bbagen.2016.03.008] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 03/03/2016] [Accepted: 03/03/2016] [Indexed: 12/12/2022]
Abstract
BACKGROUND While the underlying causes of cancer are genetic modifications, changes in cellular states mediate cancer development. Tumor cells display markedly changed glycosylation states, of which the O-GalNAc glycans called the Tn and TF antigens are particularly common. How these antigens get over-expressed is not clear. The expression levels of glycosylation enzymes fail to explain it. SCOPE OF REVIEW We describe the regulation of O-GalNAc glycosylation initiation and extension with emphasis on the initiating enzymes ppGalNAcTs (GALNTs), and introduce the GALA pathway--a change in GALNTs compartmentation within the secretory pathway that regulates Tn levels. We discuss the roles of O-GalNAc glycans and GALNTs in tumorigenic processes and finally consider diagnostic and therapeutic perspectives. MAJOR CONCLUSIONS Contrary to a common hypothesis, short O-glycans in tumors are not the result of an incomplete glycosylation process but rather reveal the activation of regulatory pathways. Surprisingly, high Tn levels reveal a major shift in the O-glycoproteome rather than a shortening of O-glycans. These changes are driven by membrane trafficking events. GENERAL SIGNIFICANCE Many attempts to use O-glycans for biomarker, antibody and therapeutic vaccine development have been made, but suffer limitations including poor sensitivity and/or specificity that may in part derive from lack of a mechanistic understanding. Deciphering how short O-GalNAc glycans are regulated would open new perspectives to exploit this biology for therapeutic usage. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.
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Affiliation(s)
- Joanne Chia
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, 138673, Singapore
| | - Germaine Goh
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, 138673, Singapore
| | - Frederic Bard
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, 138673, Singapore; Department of Biochemistry, National University of Singapore, 21 Lower Kent Ridge, Road, 119077, Singapore.
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181
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Kinoshita S, Kawai M. The FGF23/KLOTHO Regulatory Network and Its Roles in Human Disorders. VITAMINS AND HORMONES 2016; 101:151-74. [PMID: 27125741 DOI: 10.1016/bs.vh.2016.02.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The functions of Klotho (KL) are multifaceted and include the regulation of aging and mineral metabolism. It was originally identified as the gene responsible for premature aging-like symptoms in mice and was subsequently shown to function as a coreceptor in the fibroblast growth factor (FGF) 23 signaling pathway. The discovery of KL as a partner for FGF23 led to significant advances in understanding of the molecular mechanisms underlying phosphate and vitamin D metabolism, and simultaneously clarified the pathogenic roles of the FGF23 signaling pathway in human diseases. These novel insights led to the development of new strategies to combat disorders associated with the dysregulated metabolism of phosphate and vitamin D, and clinical trials on the blockade of FGF23 signaling in X-linked hypophosphatemic rickets are ongoing. Molecular and functional insights on KL and FGF23 have been discussed in this review and were extended to how dysregulation of the FGF23/KL axis causes human disorders associated with abnormal mineral metabolism.
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Affiliation(s)
- S Kinoshita
- Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan
| | - M Kawai
- Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan.
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182
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Kovesdy CP, Quarles LD. FGF23 from bench to bedside. Am J Physiol Renal Physiol 2016; 310:F1168-74. [PMID: 26864938 DOI: 10.1152/ajprenal.00606.2015] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 02/04/2016] [Indexed: 12/31/2022] Open
Abstract
There is a strong association between elevated circulating fibroblast growth factor-23 (FGF23) levels and adverse outcomes in patients with chronic kidney disease (CKD) of all stages. Initially discovered as a regulator of phosphate and vitamin D homeostasis, FGF23 has now been implicated in several pathophysiological mechanisms that may negatively impact the cardiovascular and renal systems. FGF23 is purported to have direct (off-target) effects in the myocardium, as well as canonical effects on FGF receptor/α-klotho receptor complexes in the kidney to activate the renin-angiotensin-aldosterone system, modulate soluble α-klotho levels, and increase sodium retention, to cause left ventricular hypertrophy (LVH). Conversely, FGF23 could be an innocent bystander produced in response to chronic inflammation or other processes associated with CKD that cause LVH and adverse cardiovascular outcomes. Further exploration of these complex mechanisms is needed before modulation of FGF23 can become a legitimate clinical target in CKD.
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Affiliation(s)
- Csaba P Kovesdy
- University of Tennessee Health Science Center, Memphis, Tennessee; and Memphis Veterans Affairs Medical Center, Memphis, Tennessee
| | - L Darryl Quarles
- University of Tennessee Health Science Center, Memphis, Tennessee; and
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183
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Abstract
The regulation of phosphate metabolism as an influence on bone homeostasis is profound. Recent advances in understanding the systemic control of Fibroblast growth factor-23 (FGF23) has uncovered novel effectors of endocrine feedback loops for calcium, phosphate, and vitamin D balance that interact with 'traditional' feedback loops for mineral metabolism. Not only are these findings re-shaping research studying phosphate handling and skeletal interactions, they have provided new therapeutic interventions. Emerging data support that the control of FGF23 production in bone and its circulating concentrations is a multi-layered process, with some influences affecting FGF23 transcription and some post-translational modification of the secreted, bioactive protein. Additionally, the actions of FGF23 on its target tissues via its co-receptor αKlotho, are subject to regulatory events just coming to light. The recent findings of systemic influences on circulating FGF23 and the downstream manifestations on bone homeostasis will be reviewed herein.
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Affiliation(s)
- Erica L Clinkenbeard
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202
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184
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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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185
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Li X, Wang C, Xiao J, McKeehan WL, Wang F. Fibroblast growth factors, old kids on the new block. Semin Cell Dev Biol 2016; 53:155-67. [PMID: 26768548 DOI: 10.1016/j.semcdb.2015.12.014] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 12/18/2015] [Indexed: 01/08/2023]
Abstract
The fibroblast growth factors (FGFs) are a family of cell intrinsic regulatory peptides that control a broad spectrum of cellular activities. The family includes canonic FGFs that elicit their activities by activating the FGF receptor (FGFR) tyrosine kinase and non-canonic members that elicit their activities intracellularly and via FGFR-independent mechanisms. The FGF signaling axis is highly complex due to the existence of multiple isoforms of both ligands and receptors, as well as cofactors that include the chemically heterogeneous heparan sulfate (HS) cofactors, and in the case of endocrine FGFs, the Klotho coreceptors. Resident FGF signaling controls embryonic development, maintains tissue homeostasis, promotes wound healing and tissue regeneration, and regulates functions of multiple organs. However, ectopic or aberrant FGF signaling is a culprit for various diseases, including congenital birth defects, metabolic disorder, and cancer. The molecular mechanisms by which the specificity of FGF signaling is achieved remain incompletely understood. Since its application as a druggable target has been gradually recognized by pharmaceutical companies and translational researchers, understanding the determinants of FGF signaling specificity has become even more important in order to get into the position to selectively suppress a particular pathway without affecting others to minimize side effects.
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Affiliation(s)
- Xiaokun Li
- College of Pharmacy, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Cong Wang
- College of Pharmacy, Wenzhou Medical University, Wenzhou, Zhejiang, China.
| | - Jian Xiao
- College of Pharmacy, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Wallace L McKeehan
- Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX 77030-3303, United States
| | - Fen Wang
- Institute of Biosciences and Technology, Texas A&M University Health Science Center, Houston, TX 77030-3303, United States.
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186
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Inflammation and functional iron deficiency regulate fibroblast growth factor 23 production. Kidney Int 2016; 89:135-46. [PMID: 26535997 PMCID: PMC4854810 DOI: 10.1038/ki.2015.290] [Citation(s) in RCA: 342] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 08/11/2015] [Accepted: 08/13/2015] [Indexed: 12/11/2022]
Abstract
Circulating levels of fibroblast growth factor 23 (FGF23) are elevated in patients with chronic kidney disease (CKD), but the mechanisms are poorly understood. Here we tested whether inflammation and iron deficiency regulate FGF23. In wild-type mice, acute inflammation induced by single injections of heat-killed Brucella abortus or interleukin-1β (IL-1β) decreased serum iron within 6 h, and was accompanied by significant increases in osseous Fgf23 mRNA expression and serum levels of C-terminal FGF23, but no changes in intact FGF23. Chronic inflammation induced by repeated bacteria or IL-1β injections decreased serum iron, increased osseous Fgf23 mRNA, and serum C-terminal FGF23, but modestly increased biologically active, intact FGF23 serum levels. Chronic iron deficiency mimicked chronic inflammation. Increased osseous FGF23 cleavage rather than a prolonged half-life of C-terminal FGF23 fragments accounted for the elevated C-terminal FGF23 but near-normal intact FGF23 levels in inflammation. IL-1β injection increased Fgf23 mRNA and C-terminal FGF23 levels similarly in wildtype and Col4a3(ko) mice with CKD but markedly increased intact FGF23 levels only in the CKD mice. Inflammation increased Fgf23 transcription by activating Hif1α signaling. Thus, inflammation and iron deficiency stimulate FGF23 production. Simultaneous upregulation of FGF23 cleavage in osteocytes maintains near-normal levels of biologically active, intact circulating FGF23, whereas downregulated or impaired FGF23 cleavage may contribute to elevated intact serum FGF23 in CKD.
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187
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Kawai M. The FGF23/Klotho axis in the regulation of mineral and metabolic homeostasis. Horm Mol Biol Clin Investig 2016; 28:55-67. [DOI: 10.1515/hmbci-2015-0068] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 01/07/2016] [Indexed: 11/15/2022]
Abstract
AbstractThe function of fibroblast growth factor (FGF) 23 has been suggested to be multifaceted beyond its canonical function as a regulator of mineral metabolism. FGF23 was originally shown to play a central role in phosphate (Pi) and vitamin D metabolism, and a number of diseases associated with dysregulated Pi metabolism have been attributed to abnormal FGF23 signaling activities. The discovery of Klotho as a co-receptor for FGF23 signaling has also accelerated understanding on the molecular mechanisms underlying Pi and vitamin D metabolism. In addition to these canonical functions, FGF23 has recently been implicated in a number of metabolic diseases including chronic kidney disease-associated complications, cardiovascular diseases, and obesity-related disorders; however, the physiological significance and molecular mechanisms of these emerging roles of FGF23 remain largely unknown. Molecular and functional insights into the FGF23 pathway will be discussed in the present review, with an emphasis on its role in human disorders related to dysregulated Pi metabolism as well as metabolic disorders.
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188
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Hu MC, Shi M, Zhang J, Addo T, Cho HJ, Barker SL, Ravikumar P, Gillings N, Bian A, Sidhu SS, Kuro-o M, Moe OW. Renal Production, Uptake, and Handling of Circulating αKlotho. J Am Soc Nephrol 2016; 27:79-90. [PMID: 25977312 PMCID: PMC4696570 DOI: 10.1681/asn.2014101030] [Citation(s) in RCA: 183] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 03/14/2015] [Indexed: 01/13/2023] Open
Abstract
αKlotho is a multifunctional protein highly expressed in the kidney. Soluble αKlotho is released through cleavage of the extracellular domain from membrane αKlotho by secretases to function as an endocrine/paracrine substance. The role of the kidney in circulating αKlotho production and handling is incompletely understood, however. Here, we found higher αKlotho concentration in suprarenal compared with infrarenal inferior vena cava in both rats and humans. In rats, serum αKlotho concentration dropped precipitously after bilateral nephrectomy or upon treatment with inhibitors of αKlotho extracellular domain shedding. Furthermore, the serum half-life of exogenous αKlotho in anephric rats was four- to five-fold longer than that in normal rats, and exogenously injected labeled recombinant αKlotho was detected in the kidney and in urine of rats. Both in vivo (micropuncture) and in vitro (proximal tubule cell line) studies showed that αKlotho traffics from the basal to the apical side of the proximal tubule via transcytosis. Thus, we conclude that the kidney has dual roles in αKlotho homeostasis, producing and releasing αKlotho into the circulation and clearing αKlotho from the blood into the urinary lumen.
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Affiliation(s)
- Ming Chang Hu
- Departments of Internal Medicine, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas;
| | - Mingjun Shi
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | | | | | - Han Ju Cho
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Sarah L Barker
- Banting and Best Department of Medical Research and Department of Molecular Genetics, The Donnelly Centre, University of Toronto, Toronto, Ontario, Canada; and
| | - Priya Ravikumar
- Departments of Internal Medicine, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Nancy Gillings
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ao Bian
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Sachdev S Sidhu
- Banting and Best Department of Medical Research and Department of Molecular Genetics, The Donnelly Centre, University of Toronto, Toronto, Ontario, Canada; and
| | - Makoto Kuro-o
- Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas; Pathology, Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan
| | - Orson W Moe
- Departments of Internal Medicine, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas; Physiology, and
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189
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Abstract
Bone-derived fibroblast growth factor-23 (FGF23) plays an important role in systemic phosphate turnover. Increased FGF23 activity results in hypophosphatemic disorders, while reduced activity is linked to hyperphosphatemic disorders. FGF23, together with klotho as co-factor, can activate FGF receptors in its target tissues to exert its functions. However, the molecular regulation of FGF23 synthesis is not clearly defined, and recent studies have found that parathyroid hormone (PTH) can activate the nuclear receptor-associated protein-1 (Nurr1) to induce FGF23 transcription in bone cells.
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190
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Neyra JA, Moe OW, Hu MC. Fibroblast growth factor 23 and acute kidney injury. Pediatr Nephrol 2015; 30:1909-18. [PMID: 25480729 PMCID: PMC4458234 DOI: 10.1007/s00467-014-3006-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 02/07/2023]
Abstract
Fibroblast growth factor 23 (FGF23), which is produced in bone, participates in the maintenance of phosphate metabolism and can serve as a biomarker for adverse cardiovascular outcomes in patients with chronic kidney disease and end-stage renal disease. Circulating FGF23 rapidly increases after acute kidney injury (AKI), preceding other known markers such as neutrophil gelatinase-associated lipocalin and serum creatinine. The increase in FGF23 in AKI appears to be independent of parathyroid hormone, vitamin D signaling pathways, and dietary phosphate. The potential mechanisms include: (1) increased production of FGF23 in the bone by yet-to-be-identified factors; (2) ectopic production of FGF23 by injured renal tubules; and (3) decreased renal clearance of circulating FGF23. Circulating FGF23 determined by intact FGF23 enzyme-linked immunosorbent assay (ELISA) is a more reliable biomarker of AKI than FGF23 C-terminal ELISA (a mixed readout of C-terminal fragment and intact FGF23). Given that FGF23 can be ectopically expressed in differentiated renal tubules and iron modulates FGF23 metabolism, an effect of iron on FGF23 expression in renal tubules is conceivable but remains to be confirmed. More clinical and experimental studies are required to validate the use of circulating FGF23 as a biomarker for the early identification of AKI and prediction of short- and long-term adverse outcomes post-AKI. More importantly, the biologic effect of increased FGF23 in AKI needs to be defined.
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Affiliation(s)
- Javier A Neyra
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-885, USA
| | - Orson W Moe
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-885, USA
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-885, USA
| | - Ming Chang Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-885, USA.
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX, 75390-885, USA.
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191
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Przybylowski P, Wasilewski G, Janik L, Kozlowska S, Nowak E, Malyszko J. Fibroblast growth factor 23 and Klotho as cardiovascular risk factors in heart transplant recipients. Transplant Proc 2015; 46:2848-51. [PMID: 25380933 DOI: 10.1016/j.transproceed.2014.09.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
BACKGROUND Fibroblast growth factor (FGF) 23 is one of the most recently discovered FGFs. This phosphaturic hormone produced in bones is a risk factor for cardiovascular diseases and thus mortality. Klotho is an essential coreceptor for FGF23 and at the same time it is known as a "longevity" hormone. There are no data considering FGF23 and Klotho roles in heart transplant (HT) recipients. The aim of this study was to assess Klotho and FGF23 serum concentration in heart transplant recipients depending on immunosuppressive therapy regimen and comorbidities. METHODS Eighty-four stable heart transplant recipients were enrolled in the study; 22 healthy volunteers served as control subjects. FGF23 and Klotho protein concentration, markers of renal function, such as cystatin C and neutrophil gelatinase-associated lipocalin (NGAL), and heart failure markers, such as copeptine and N-termiinal pro-B-type natriuretic peptide (NT-proBNP), were evaluated. RESULTS FGF23 concentration was significantly higher in the HT group whereas Klotho protein was significantly lower. FGF23 correlated with creatinine level (r = 0.72; P < .001), estimated glomerular filtration rate (eGFR; r = -0.32; P < .01), cystatin C (r = 0.36; P < .01), NGAL (r = 0.51; P < .001), hemoglobin (r = -0.39; P < .001), NT-proBNP (r = 0.51; P < .001), high-density lipoprotein (HDL; r = 0.27; P < .05), intraventricular septum thickness (r = 0.42; P < .01) and right ventricular systolic pressure (r = 0.34; P < .05). Klotho protein correlated only with age (r = -0.21; P < .05), creatinine (r = -0.21; P < .05), and eGFR (r = -0.31; P < .01). FGF23 concentration was significantly higher in patients with eGFR <60 mL/min whereas Klotho protein was significantly lower. FGF23 predictors were renal function (creatinine concentration; β = 0.45; P = .0001), HDL (β = 0.33; P = .003), intraventricular septum thickness (β = 0.38; P = .0003), and right ventricular systolic pressure (β = 0.34; P = .003), explaining 70% of FGF23 variability. CONCLUSIONS FGF23/Klotho system disorders in HT recipients are related to cardiovascular system function and kidney failure and could cause increased risk of cardiovascular disease.
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Affiliation(s)
- P Przybylowski
- Department of Cardiovascular Surgery and Transplantology, Medical College, Jagiellonian University Medical College, John Paul II Hospital, Cracow, Poland.
| | - G Wasilewski
- Department of Cardiovascular Surgery and Transplantology, Medical College, Jagiellonian University Medical College, John Paul II Hospital, Cracow, Poland
| | - L Janik
- Department of Cardiovascular Surgery and Transplantology, Medical College, Jagiellonian University Medical College, John Paul II Hospital, Cracow, Poland
| | - S Kozlowska
- Department of Cardiovascular Surgery and Transplantology, Medical College, Jagiellonian University Medical College, John Paul II Hospital, Cracow, Poland
| | - E Nowak
- Department of Internal Medicine and Angiology, Brothers Hospitallers' of St John of God Hospital, Cracow, Poland
| | - J Malyszko
- 2nd Department of Nephrology, Medical University of Bialystok, Poland
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192
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Diener S, Schorpp K, Strom TM, Hadian K, Lorenz-Depiereux B. Development of A Cell-Based Assay to Identify Small Molecule Inhibitors of FGF23 Signaling. Assay Drug Dev Technol 2015; 13:476-87. [DOI: 10.1089/adt.2015.653] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- Susanne Diener
- German Research Center for Environmental Health, Institute of Human Genetics, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
| | - Kenji Schorpp
- Assay Development and Screening Platform, German Research Center for Environmental Health, Institute of Molecular Toxicology and Pharmacology, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
| | - Tim-Matthias Strom
- German Research Center for Environmental Health, Institute of Human Genetics, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
- Institute of Human Genetics, Klinikum rechts der Isar der Technischen Universität München, Munich, Bavaria, Germany
| | - Kamyar Hadian
- Assay Development and Screening Platform, German Research Center for Environmental Health, Institute of Molecular Toxicology and Pharmacology, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
| | - Bettina Lorenz-Depiereux
- German Research Center for Environmental Health, Institute of Human Genetics, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
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193
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Abstract
Aging is an inevitable and progressive biological process involving dysfunction and eventually destruction of every tissue and organ. This process is driven by a tightly regulated and complex interplay between genetic and acquired factors. Klotho is an antiaging gene encoding a single-pass transmembrane protein, klotho, which serves as an aging suppressor through a wide variety of mechanisms, such as antioxidation, antisenescence, antiautophagy, and modulation of many signaling pathways, including insulin-like growth factor and Wnt. Klotho deficiency activates Wnt expression and activity contributing to senescence and depletion of stem cells, which consequently triggers tissue atrophy and fibrosis. In contrast, the klotho protein was shown to suppress Wnt-signaling transduction, and inhibit cell senescence and preserve stem cells. A better understanding of the potential effects of klotho on stem cells could offer novel insights into the cellular and molecular mechanisms of klotho deficiency-related aging and disease. The klotho protein may be a promising therapeutic agent for aging and aging-related disorders.
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Affiliation(s)
- Ao Bian
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA ; Department of Nephrology, First Affiliated Hospital of Nanjing Medical University, Nanjing, People's Republic of China
| | - Javier A Neyra
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, USA
| | - Ming Zhan
- Methodist Hospital Research Institute, Weill Cornell Medical College, Houston, TX, USA
| | - Ming Chang Hu
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA ; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, USA
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194
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Olauson H, Vervloet MG, Cozzolino M, Massy ZA, Ureña Torres P, Larsson TE. New insights into the FGF23-Klotho axis. Semin Nephrol 2015; 34:586-97. [PMID: 25498378 DOI: 10.1016/j.semnephrol.2014.09.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Abnormal mineral metabolism is a hallmark in patients with advanced chronic kidney disease (CKD). Hyperphosphatemia, and the homeostatic mechanisms controlling phosphate metabolism, have received particular attention over the past decade. The phosphate-regulating hormone fibroblast growth factor-23 (FGF23) was discovered through studies of rare hypophosphatemic disorders, whereas Klotho, which subsequently turned out to be a co-receptor for FGF23, was identified in a mouse model showing hyperphosphatemia and multiple aging-like traits. The FGF23-Klotho endocrine axis is a pivotal regulator of mineral metabolism. In CKD, early onset of Klotho deficiency contributes to renal FGF23 resistance and a maladaptive increase in circulating FGF23. FGF23 is an early biomarker of renal injury and increased FGF23 predicts adverse clinical outcomes, in particular cardiovascular disease. A paradigm of FGF23 excess and Klotho deficiency is proposed, in which FGF23 preferentially stimulates left ventricular hypertrophy, and loss of Klotho augments fibrosis, endothelial dysfunction, and vascular calcification. The clinical benefit of FGF23 and Klotho measurements remain uncertain, nevertheless, the FGF23-Klotho axis is a solid candidate for a novel diagnostic and therapeutic target in CKD.
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Affiliation(s)
- Hannes Olauson
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Marc G Vervloet
- Department of Nephrology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Mario Cozzolino
- Department of Health Sciences, University of Milan, Renal Division, San Paolo Hospital, Milan, Italy
| | - Ziad A Massy
- Inserm U-1088, Université de Picardie Jules Verne (UPJV), Amiens, France; Division of Nephrology, Ambroise Paré Hospital, Paris-Ile-de-France-Ouest University (Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)), Paris-Boulogne Billancourt, France
| | - Pablo Ureña Torres
- Service of Nephrology and Dialysis, Clinique du Landy and Department of Renal Physiology, Necker Hospital, University of Paris Descartes, Paris, France
| | - Tobias E Larsson
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden; Department of Nephrology, Karolinska University Hospital, Stockholm, Sweden.
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195
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Richter M, Lautze HJ, Walther T, Braun T, Kostin S, Kubin T. The failing heart is a major source of circulating FGF23 via oncostatin M receptor activation. J Heart Lung Transplant 2015; 34:1211-4. [PMID: 26267742 DOI: 10.1016/j.healun.2015.06.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 05/06/2015] [Accepted: 06/09/2015] [Indexed: 10/23/2022] Open
Affiliation(s)
| | | | | | - Thomas Braun
- Department of Cardiac Development and Remodeling, Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Sawa Kostin
- Department of Cardiac Development and Remodeling, Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Thomas Kubin
- Department of Cardiac Development and Remodeling, Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
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196
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van Breda F, Emans ME, van der Putten K, Braam B, van Ittersum FJ, Kraaijenhagen RJ, de Borst MH, Vervloet M, Gaillard CAJM. Relation between Red Cell Distribution Width and Fibroblast Growth Factor 23 Cleaving in Patients with Chronic Kidney Disease and Heart Failure. PLoS One 2015; 10:e0128994. [PMID: 26079688 PMCID: PMC4469605 DOI: 10.1371/journal.pone.0128994] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 05/04/2015] [Indexed: 12/19/2022] Open
Abstract
OBJECTIVE In chronic kidney disease (CKD), both anemia and deregulated phosphate metabolism are common and predictive of adverse outcome. Previous studies suggest that iron status influences phosphate metabolism by modulating proteolytic cleavage of FGF23 into C-terminal fragments. Red cell distribution width (RDW) was recently identified as a strong prognostic determinant for cardiovascular morbidity and mortality, independently of iron status. We assessed whether RDW is associated with FGF23 cleaving in CKD patients with heart failure. MATERIALS AND METHODS The associations between RDW and either intact FGF23 (iFGF23), C-terminal FGF23 (cFGF23, reflecting iFGF23 and C-terminal fragments together) and the iFGF23/cFGF23 ratio were analyzed in 52 patients with CKD (eGFR 34,9 ± 13.9 ml/min/1.73m2) and chronic heart failure (CHF). Associations between RDW and FGF23 forms were studied by linear regression analysis adjusted for parameters of renal function, iron metabolism, phosphate metabolism and inflammation. RESULTS Median cFGF23 levels were 197.5 [110-408.5] RU/ml, median iFGF23 levels were 107.3 [65.1-162.2] pg/ml and median FGF23 ratio was 0.80 [0.37-0.86]. Mean RDW was 14.1 ± 1.2%. cFGF23 and RDW were associated (β = 1.63 x 10(-3), P < 0.001), whereas iFGF23 and RDW were not (β = -1.38 x 10(-3), P = 0.336). The iFGF23/cFGF23 ratio was inversely associated with RDW. The difference between cFGF23 and iFGF23 (cFGF23- iFGF23) was positively associated with RDW (β = 1.74 x 10(-3), P < 0.001). The association between cFGF23 and RDW persisted upon multivariable linear regression analysis, adjusted for parameters of renal function, phosphate metabolism, iron metabolism and inflammation (β = 0.97 x 10(-3), P = 0.047). CONCLUSION RDW is associated with cFGF23 but not with iFGF23 levels in patients with CKD and CHF. This suggests a connection between RDW and FGF23 catabolism, independent of iron status and inflammation. Future studies are needed to unravel underlying mechanisms and whether these pertain to the link between RDW and outcome.
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Affiliation(s)
- Fenna van Breda
- Department of Nephrology and ICaR-VU, VUMC, Amsterdam, the Netherlands
- * E-mail:
| | - Mireille E. Emans
- Department of Cardiology, Ikazia Hospital, Rotterdam, the Netherlands
| | | | - Branko Braam
- Department of Medicine, division of Nephrology and Immunology, University of Alberta, Edmonton, Canada
| | | | - Rob J. Kraaijenhagen
- Department of Clinical Chemistry, Meander Medical Center, Amersfoort, the Netherlands
| | | | - Marc Vervloet
- Department of Nephrology and ICaR-VU, VUMC, Amsterdam, the Netherlands
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Brown RB, Razzaque MS. Dysregulation of phosphate metabolism and conditions associated with phosphate toxicity. BONEKEY REPORTS 2015; 4:705. [PMID: 26131357 PMCID: PMC4455690 DOI: 10.1038/bonekey.2015.74] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 03/25/2015] [Indexed: 02/07/2023]
Abstract
Phosphate homeostasis is coordinated and regulated by complex cross-organ talk through delicate hormonal networks. Parathyroid hormone (PTH), secreted in response to low serum calcium, has an important role in maintaining phosphate homeostasis by influencing renal synthesis of 1,25-dihydroxyvitamin D, thereby increasing intestinal phosphate absorption. Moreover, PTH can increase phosphate efflux from bone and contribute to renal phosphate homeostasis through phosphaturic effects. In addition, PTH can induce skeletal synthesis of another potent phosphaturic hormone, fibroblast growth factor 23 (FGF23), which is able to inhibit renal tubular phosphate reabsorption, thereby increasing urinary phosphate excretion. FGF23 can also fine-tune vitamin D homeostasis by suppressing renal expression of 1-alpha hydroxylase (1α(OH)ase). This review briefly discusses how FGF23, by forming a bone-kidney axis, regulates phosphate homeostasis, and how its dysregulation can lead to phosphate toxicity that induces widespread tissue injury. We also provide evidence to explain how phosphate toxicity related to dietary phosphorus overload may facilitate incidence of noncommunicable diseases including kidney disease, cardiovascular disease, cancers and skeletal disorders.
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Affiliation(s)
- Ronald B Brown
- Department of Hospitality Management and Dietetics, College of Human Ecology, Kansas State University, Manhattan, KS, USA
| | - Mohammed S Razzaque
- Department of Applied Oral Sciences, Forsyth Institute, Cambridge, MA, USA
- Division of Research & Development, VPS Healthcare, Abu Dhabi, UAE
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Abstract
Adding to its well-known roles in locomotion and calcium balance, the skeleton has recently been appreciated as a true endocrine organ. Bone remodeling, a highly dynamic process, requires synchronized activities and crosstalk between bone cells. Discovery and characterization of the Wnt/β catenin pathway in bone formation, FGF23 regulation of phosphate homeostasis and osteocalcin in energy and glucose homeostasis have reframed our view of the skeleton from simply a target tissue of the endocrine system to an endocrine tissue itself. This comprehensive review provides an overview of these complex pathways, their application to human bone disorders and implications for developing diagnostic and therapeutic targets.
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Affiliation(s)
- Anda Gonciulea
- Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Esapa CT, Hannan FM, Babinsky VN, Potter P, Thomas GP, Croucher PI, Brown MA, Brown SDM, Cox RD, Thakker RV. N-ethyl-N-Nitrosourea (ENU) induced mutations within the klotho gene lead to ectopic calcification and reduced lifespan in mouse models. PLoS One 2015; 10:e0122650. [PMID: 25860694 PMCID: PMC4393098 DOI: 10.1371/journal.pone.0122650] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 02/11/2015] [Indexed: 11/18/2022] Open
Abstract
Ectopic calcification (EC), which is the pathological deposition of calcium and phosphate in extra-skeletal tissues, may be associated with hypercalcaemic and hyperphosphataemic disorders, or it may occur in the absence of metabolic abnormalities. In addition, EC may be inherited as part of several monogenic disorders and studies of these have provided valuable insights into the metabolic pathways regulating mineral metabolism. For example, studies of tumoural calcinosis, a disorder characterised by hyperphosphataemia and progressive EC, have revealed mutations of fibroblast growth factor 23 (FGF23), polypeptide N-acetyl galactosaminyltransferase 3 (GALNT3) and klotho (KL), which are all part of a phosphate-regulating pathway. However, such studies in humans are limited by the lack of available large families with EC, and to facilitate such studies we assessed the progeny of mice treated with the chemical mutagen N-ethyl-N-nitrosourea (ENU) for EC. This identified two mutants with autosomal recessive forms of EC, and reduced lifespan, designated Ecalc1 and Ecalc2. Genetic mapping localized the Ecalc1 and Ecalc2 loci to a 11.0 Mb region on chromosome 5 that contained the klotho gene (Kl), and DNA sequence analysis identified nonsense (Gln203Stop) and missense (Ile604Asn) Kl mutations in Ecalc1 and Ecalc2 mice, respectively. The Gln203Stop mutation, located in KL1 domain, was severely hypomorphic and led to a 17-fold reduction of renal Kl expression. The Ile604Asn mutation, located in KL2 domain, was predicted to impair klotho protein stability and in vitro expression studies in COS-7 cells revealed endoplasmic reticulum retention of the Ile604Asn mutant. Further phenotype studies undertaken in Ecalc1 (kl203X/203X) mice demonstrated elevations in plasma concentrations of phosphate, FGF23 and 1,25-dihydroxyvitamin D. Thus, two allelic variants of Kl that develop EC and represent mouse models for tumoural calcinosis have been established.
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Affiliation(s)
- Christopher T. Esapa
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford, United Kingdom
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell, Harwell Science and Innovation Campus, Harwell, United Kingdom
| | - Fadil M. Hannan
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford, United Kingdom
- Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Valerie N. Babinsky
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford, United Kingdom
| | - Paul Potter
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell, Harwell Science and Innovation Campus, Harwell, United Kingdom
| | - Gethin P. Thomas
- University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, University of Queensland, Brisbane, Australia
| | | | - Matthew A. Brown
- University of Queensland Diamantina Institute, Translational Research Institute, Princess Alexandra Hospital, University of Queensland, Brisbane, Australia
| | - Steve D. M. Brown
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell, Harwell Science and Innovation Campus, Harwell, United Kingdom
| | - Roger D. Cox
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell, Harwell Science and Innovation Campus, Harwell, United Kingdom
| | - Rajesh V. Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford, United Kingdom
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200
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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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