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Kamenický P, Briot K, Munns CF, Linglart A. X-linked hypophosphataemia. Lancet 2024:S0140-6736(24)01305-9. [PMID: 39181153 DOI: 10.1016/s0140-6736(24)01305-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 06/17/2024] [Accepted: 06/18/2024] [Indexed: 08/27/2024]
Abstract
X-linked hypophosphataemia is a genetic disease caused by defects in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene and is characterised by X-linked dominant inheritance. The main consequence of PHEX deficiency is increased production of the phosphaturic hormone fibroblast growth factor 23 (FGF23) in osteoblasts and osteocytes. Chronic exposure to circulating FGF23 is responsible for renal phosphate wasting and decreased synthesis of calcitriol, which decreases intestinal phosphate absorption. These mechanisms result in lifelong hypophosphataemia, impaired growth plate and bone matrix mineralisation, and diverse manifestations in affected children and adults, including some debilitating morbidities and possibly increased mortality. Important progress has been made in disease knowledge and management over the past decade; in particular, targeting FGF23 is a therapeutic approach that has substantially improved outcomes. However, patients affected by this complex disease need lifelong care and innovative treatment strategies, such as gene repair of PHEX, are necessary to further limit the disease burden.
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Affiliation(s)
- Peter Kamenický
- Université Paris-Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France; Centre de Référence des Maladies du Métabolisme du Calcium et du Phosphate, Service d'Endocrinologie et des Maladies de la Reproduction, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, Le Kremlin-Bicêtre, France.
| | - Karine Briot
- Centre de Référence des Maladies du Métabolisme du Calcium et du Phosphate, Service de Rhumatologie, Hôpital Cochin, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Craig F Munns
- Department of Endocrinology and Diabetes, Queensland Children's Hospital and Child Health Research Centre and Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - Agnès Linglart
- Université Paris-Saclay, Inserm, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France; Service d'Endocrinologie et du Diabète de l'Enfant, Hôpital Bicêtre, Assistance Publique-Hôpitaux de Paris, Le Kremlin-Bicêtre, France
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Gędaj A, Gregorczyk P, Żukowska D, Chorążewska A, Ciura K, Kalka M, Porębska N, Opaliński Ł. Glycosylation of FGF/FGFR: An underrated sweet code regulating cellular signaling programs. Cytokine Growth Factor Rev 2024; 77:39-55. [PMID: 38719671 DOI: 10.1016/j.cytogfr.2024.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 06/22/2024]
Abstract
Fibroblast growth factors (FGFs) and their receptors (FGFRs) constitute plasma-membrane localized signaling hubs that transmit signals from the extracellular environment to the cell interior, governing pivotal cellular processes like motility, metabolism, differentiation, division and death. FGF/FGFR signaling is critical for human body development and homeostasis; dysregulation of FGF/FGFR units is observed in numerous developmental diseases and in about 10% of human cancers. Glycosylation is a highly abundant posttranslational modification that is critical for physiological and pathological functions of the cell. Glycosylation is also very common within FGF/FGFR signaling hubs. Vast majority of FGFs (15 out of 22 members) are N-glycosylated and few FGFs are O-glycosylated. Glycosylation is even more abundant within FGFRs; all FGFRs are heavily N-glycosylated in numerous positions within their extracellular domains. A growing number of studies points on the multiple roles of glycosylation in fine-tuning FGF/FGFR signaling. Glycosylation modifies secretion of FGFs, determines their stability and affects interaction with FGFRs and co-receptors. Glycosylation of FGFRs determines their intracellular sorting, constitutes autoinhibitory mechanism within FGFRs and adjusts FGF and co-receptor recognition. Sugar chains attached to FGFs and FGFRs constitute also a form of code that is differentially decrypted by extracellular lectins, galectins, which transform FGF/FGFR signaling at multiple levels. This review focuses on the identified functions of glycosylation within FGFs and FGFRs and discusses their relevance for the cell physiology in health and disease.
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Affiliation(s)
- Aleksandra Gędaj
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Paulina Gregorczyk
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Dominika Żukowska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Aleksandra Chorążewska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Krzysztof Ciura
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Marta Kalka
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Natalia Porębska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Łukasz Opaliński
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland.
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Nakanishi T, Yamazaki M, Tachikawa K, Ueta A, Kawai M, Ozono K, Michigami T. Complex intrinsic abnormalities in osteoblast lineage cells of X-linked hypophosphatemia: Analysis of human iPS cell models generated by CRISPR/Cas9-mediated gene ablation. Bone 2024; 181:117044. [PMID: 38331306 DOI: 10.1016/j.bone.2024.117044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/04/2024] [Accepted: 02/05/2024] [Indexed: 02/10/2024]
Abstract
X-linked hypophosphatemia (XLH) is caused by inactivating variants of the phosphate regulating endopeptidase homolog X-linked (PHEX) gene. Although the overproduction of fibroblast growth factor 23 (FGF23) is responsible for hypophosphatemia and impaired vitamin D metabolism, the pathogenesis of XLH remains unclear. We herein generated PHEX-knockout (KO) human induced pluripotent stem (iPS) cells by applying CRISPR/Cas9-mediated gene ablation to an iPS clone derived from a healthy male, and analyzed PHEX-KO iPS cells with deletions extending from exons 1 to 3 and frameshifts by inducing them to differentiate into the osteoblast lineage. We confirmed the increased production of FGF23 in osteoblast lineage cells differentiated from PHEX-KO iPS cells. In vitro mineralization was enhanced in osteoblast lineage cells from PHEX-KO iPS cells than in those from isogenic control iPS cells, which reminded us of high bone mineral density and enthesopathy in patients with XLH. The extracellular level of pyrophosphate (PPi), an inhibitor of mineralization, was elevated, and this increase appeared to be partly due to the reduced activity of tissue non-specific alkaline phosphatase (TNSALP). Osteoblast lineage cells derived from PHEX-KO iPS cells also showed the increased expression of multiple molecules such as dentine matrix protein 1, osteopontin, RUNX2, FGF receptor 1 and early growth response 1. This gene dysregulation was similar to that in the osteoblasts/osteocytes of Phex-deficient Hyp mice, suggesting that common pathogenic mechanisms are shared between human XLH and Hyp mice. Moreover, we found that the phosphorylation of CREB was markedly enhanced in osteoblast lineage cells derived from PHEX-KO iPS cells, which appeared to be associated with the up-regulation of the parathyroid hormone related protein gene. PHEX deficiency also affected the response of the ALPL gene encoding TNSALP to extracellular Pi. Collectively, these results indicate that complex intrinsic abnormalities in osteoblasts/osteocytes underlie the pathogenesis of human XLH.
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Affiliation(s)
- Tatsuro Nakanishi
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan; Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - Miwa Yamazaki
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan
| | - Kanako Tachikawa
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan
| | - Ayu Ueta
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan; 1st Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita, Osaka 565-0871, Japan
| | - Masanobu Kawai
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan
| | | | - Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka Prefectural Hospital Organization, Izumi, Osaka 594-1101, Japan.
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Perumal NL, Padidela R. Phosphate Homeostasis and Disorders of Phosphate Metabolism. Curr Pediatr Rev 2024; 20:412-425. [PMID: 36545737 DOI: 10.2174/1573396319666221221121350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 11/25/2022] [Accepted: 11/28/2022] [Indexed: 12/24/2022]
Abstract
Phosphate is indispensable for human life and evolutionary changes over several millions of years have established tightly regulated mechanisms to ensure phosphate homeostasis. In this process, calcium and phosphate metabolism have come to be intricately linked together. Three hormones (PTH, FGF23 and Calcitriol) maintain the fine balance of calcium and phosphate metabolism through their actions at three sites (the gut, the kidneys and the skeleton). Disorders that disrupt this balance can have serious clinical consequences. Acute changes in serum phosphate levels can result in life threatening complications like respiratory failure and cardiac arrythmias. Chronic hypophosphataemia predominantly affects the musculoskeletal system and presents as impaired linear growth, rickets, osteomalacia and dental problems. Hyperphosphataemia is very common in the setting of chronic kidney disease and can be difficult to manage. A thorough understanding of calcium and phosphate homeostasis is essential to diagnose and treat conditions associated with hypo and hyperphosphataemia. In this review, we will discuss the calcium and phosphate metabolism, aetiologies and management of hypo and hyperphosphataemia.
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Affiliation(s)
| | - Raja Padidela
- Department of Endocrinology, Royal Manchester Children's Hospital, Manchester, United Kingdom
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Portales-Castillo I, Rieg T, Khalid SB, Nigwekar SU, Neyra JA. Physiopathology of Phosphate Disorders. ADVANCES IN KIDNEY DISEASE AND HEALTH 2023; 30:177-188. [PMID: 36868732 PMCID: PMC10565570 DOI: 10.1053/j.akdh.2022.12.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 12/24/2022] [Accepted: 12/29/2022] [Indexed: 03/05/2023]
Abstract
Intracellular phosphate is critical for cellular processes such as signaling, nucleic acid synthesis, and membrane function. Extracellular phosphate (Pi) is an important component of the skeleton. Normal levels of serum phosphate are maintained by the coordinated actions of 1,25-dihydroxyvitamin D3, parathyroid hormone and fibroblast growth factor-23, which intersect in the proximal tubule to control the reabsorption of phosphate via the sodium-phosphate cotransporters Npt2a and Npt2c. Furthermore, 1,25-dihydroxyvitamin D3 participates in the regulation of dietary phosphate absorption in the small intestine. Clinical manifestations associated with abnormal serum phosphate levels are common and occur as a result of genetic or acquired conditions affecting phosphate homeostasis. For example, chronic hypophosphatemia leads to osteomalacia in adults and rickets in children. Acute severe hypophosphatemia can affect multiple organs leading to rhabdomyolysis, respiratory dysfunction, and hemolysis. Patients with impaired kidney function, such as those with advanced CKD, have high prevalence of hyperphosphatemia, with approximately two-thirds of patients on chronic hemodialysis in the United States having serum phosphate levels above the recommended goal of 5.5 mg/dL, a cutoff associated with excess risk of cardiovascular complications. Furthermore, patients with advanced kidney disease and hyperphosphatemia (>6.5 mg/dL) have almost one-third excess risk of death than those with phosphate levels between 2.4 and 6.5 mg/dL. Given the complex mechanisms that regulate phosphate levels, the interventions to treat the various diseases associated with hypophosphatemia or hyperphosphatemia rely on the understanding of the underlying pathobiological mechanisms governing each patient condition.
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Affiliation(s)
- Ignacio Portales-Castillo
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, and Harvard Medical School, Boston, MA; Endocrine Unit, Massachusetts General Hospital, and Harvard Medical School, Boston, MA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL; James A. Haley Veterans' Hospital, Tampa, FL; Center for Hypertension and Kidney Research, University of South Florida, Tampa, FL
| | - Sheikh B Khalid
- Department of Internal Medicine, The Indus Hospital, Lahore Pakistan
| | - Sagar U Nigwekar
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, and Harvard Medical School, Boston, MA
| | - Javier A Neyra
- Department of Internal Medicine, Division of Nephrology, University of Alabama at Birmingham, Birmingham, AL.
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Heijboer AC, Cavalier E. The Measurement and Interpretation of Fibroblast Growth Factor 23 (FGF23) Concentrations. Calcif Tissue Int 2023; 112:258-270. [PMID: 35665817 PMCID: PMC9859838 DOI: 10.1007/s00223-022-00987-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 05/06/2022] [Indexed: 02/05/2023]
Abstract
Two decades after the discovery of the hormone FGF23, we know more about phosphate homeostasis as it turned out that FGF23 is the central hormone that regulates this. Hereditary hypophosphatemic rickets and tumor-induced osteomalacia could by then be explained, by autonomous FGF23 production, and the nephrology field was excited by this new marker as it turned out to be independently associated with mortality in people treated by hemodialysis. This led to the development of several immunoassays to be able to measure FGF23 in blood. In the past years we learned that FGF23 is a rather stable peptide, the precision of the assays is acceptable but assays are not standardized and therefore not comparable. This means that reference values and cutoff values need to be assay specific. For several assays reference values have been established and gender and age did not seem of high importance. The phosphate content of the diet, which can be culturally dependent, however, should be taken into account when interpreting results, but to what extent is not totally clear. Currently, clinical application of the immunoassays is established in the diagnosis of hereditary hypophosphatemic rickets and diagnosis and follow-up of tumor-induced osteomalacia. Definite conclusions on the usefulness of the FGF23 measurement in people with CKD either as a marker for risk prediction or a as target for treatment remains to be determined. The latter applications would require dedicated prospective clinical trials, which may take years, before providing answers. To improve the standardization of the FGF23 assays and to shed light on the biological functions that fragments might have we might aim for an LC-MS/MS-based method to quantify both intact and fragmented FGF23. In this literature review we will summarize the current knowledge on the physiological role of FGF23, its quantification, and the clinical usefulness of its determination.
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Affiliation(s)
- Annemieke C Heijboer
- Endocrine Laboratory, Department of Clinical Chemistry, Amsterdam Gastroenterology Endocrinology & Metabolism, Amsterdam UMC, Vrije Universiteit Amsterdam and University of Amsterdam, de Boelelaan 1117 and Meibergdreef 9, Amsterdam, The Netherlands.
| | - Etienne Cavalier
- Department of Clinical Chemistry, CHU de Liège, University of Liège, 4000, Liège, Belgium
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Liu C, Ni X, Zhao Z, Qi W, Jiang Y, Li M, Wang O, Xing X, Xia W. Bone characteristics of autosomal dominant hypophosphatemic rickets patients. Bone 2023; 167:116602. [PMID: 36347435 DOI: 10.1016/j.bone.2022.116602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 10/10/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Autosomal dominant hypophosphatemic rickets (ADHR) is a rare disease caused by activating mutations in fibroblast growth factor 23 (FGF23) gene. With FGF23 activation, ADHR is a good model to explore the effects of FGF23 on skeletal development and mineralization. However, the bone microarchitecture of ADHR patients is poorly investigated. This study aims to illustrate the bone properties of ADHR patients and clarify the effect of FGF23 on load bearing and non-load bearing bone. METHODS Bone microarchitectures of 11 ADHR subjects and sex- and age-matched healthy controls were analyzed by HR-pQCT. The effect of FGF23 mutations on load bearing and non-load bearing bone was explored by comparison of bone microarchitecture in distal radius and distal tibia. The BMD, bone microarchitecture and bone strength were compared between 7 ADHR patients and 7 age- and sex-matched XLH patients. RESULTS Among 11 subjects with FGF23 mutations, 10 patients presented with obvious symptoms, five of which had received 1-3 years of iron supplement, neutral phosphate, and calcitriol treatments. The symptomatic patients presented with low bone density and fractures in X rays, with decreased Z score of aBMD (L1-L4: -1.3 ± 1.4, femoral neck: -2.1 ± 1.8, total hip: -1.85 ± 1.6). Compared with controls, HR-pQCT analysis of 5 untreated ADHR patients showed increased total area (+61.6 %, p = 0.03) and cortical perimeter (+17.2 %, p = 0.03) in distal radius. No significant differences were found in other parameters in distal radius. In distal tibia, the patients presented obvious defects in cancellous bone, with decreased trabecular vBMD (-62.9 %, p = 0.003), trabecular BV/TV (-48.7 %, p = 0.003) and trabecular number (-42.2 %, p = 0.001). The trabecular separation (+113.3 %, p = 0.007) and trabecular network inhomogeneity (+226.7 %, p = 0.001) were accordingly increased. In addition to another 5 treated patients, the bone microarchitecture changes revealed similar pattern, but the increase of total area and cortical perimeter in distal radius was no longer statistically significant. The non-symptomatic ADHR patient demonstrated slightly decreased total vBMD, trabecular vBMD and trabecular BV/TV in distal tibia. The changing pattern of bone geometry and microarchitecture of ADHR patients were similar to XLH patients but showed less deficit and stronger bone strength. CONCLUSION ADHR patients presented increased total area and cortical perimeter in distal radius, and obvious defect in cancellous bone in distal tibia. FGF23 have impairment effect on trabecular bone especially in weight bearing site.
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Affiliation(s)
- Chang Liu
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China; Department of Endocrinology, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Xiaolin Ni
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Zhen Zhao
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China; Department of Geriatrics, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Wenting Qi
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Yan Jiang
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Mei Li
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Ou Wang
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Xiaoping Xing
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Weibo Xia
- Department of Endocrinology, NHC Key Laboratory of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
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Cipriani C, Minisola S, Colangelo L, DE Martino V, Ferrone F, Biamonte F, Danese V, Sonato C, Santori R, Occhiuto M, Pepe J. FGF23 functions and disease. Minerva Endocrinol (Torino) 2022; 47:437-448. [PMID: 33792238 DOI: 10.23736/s2724-6507.21.03378-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The main function of fibroblast growth factor 23 (FGF23) is the regulation of phosphate metabolism through its action on the sodium-dependent phosphate cotransporters in the proximal renal tubules. Additionally, FGF23 interacts with vitamin D and parathyroid hormone in a complex metabolic pathway whose detailed mechanisms are still not clear in human physiology and disease. More recently, research has also focused on the understanding of mechanisms of FGF23 action on organs and system other than the kidneys and bone, as well as on its interaction with other metabolic pathways. Collectively, the new evidence are successfully used for the clinical evaluation and management of FGF23-related disorders, for which new therapies with many potential applications are now available.
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Affiliation(s)
- Cristiana Cipriani
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy -
| | - Salvatore Minisola
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Luciano Colangelo
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Viviana DE Martino
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Federica Ferrone
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Federica Biamonte
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Vittoria Danese
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Chiara Sonato
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Rachele Santori
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Marco Occhiuto
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
| | - Jessica Pepe
- Department of Clinical, Internal, Anesthesiological and Cardiovascular Sciences, Sapienza University, Rome, Italy
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Abstract
Inorganic phosphate (Pi) in the mammalian body is balanced by its influx and efflux through the intestines, kidneys, bones, and soft tissues, at which several sodium/Pi co-transporters mediate its active transport. Pi homeostasis is achieved through the complex counter-regulatory feedback balance between fibroblast growth factor 23 (FGF23), 1,25-dihydroxyvitamin D (1,25(OH)2D), and parathyroid hormone. FGF23, which is mainly produced by osteocytes in bone, plays a central role in Pi homeostasis and exerts its effects by binding to the FGF receptor (FGFR) and αKlotho in distant target organs. In the kidneys, the main target, FGF23 promotes the excretion of Pi and suppresses the production of 1,25(OH)2D. Deficient and excess FGF23 result in hyperphosphatemia and hypophosphatemia, respectively. FGF23-related hypophosphatemic rickets/osteomalacia include tumor-induced osteomalacia and various genetic diseases, such as X-linked hypophosphatemic rickets. Coverage by the national health insurance system in Japan for the measurement of FGF23 and the approval of burosumab, an FGF23-neutralizing antibody, have had a significant impact on the diagnosis and treatment of FGF23-related hypophosphatemic rickets/osteomalacia. Some of the molecules responsible for genetic hypophosphatemic rickets/osteomalacia are highly expressed in osteocytes and function as local regulators of FGF23 production. A number of systemic factors also regulate FGF23 levels. Although the mechanisms responsible for Pi sensing in mammals have not yet been elucidated in detail, recent studies have suggested the involvement of FGFR1. The further clarification of the mechanisms by which osteocytes detect Pi levels and regulate FGF23 production will lead to the development of better strategies to treat hyperphosphatemic and hypophosphatemic conditions.
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Affiliation(s)
- Toshimi Michigami
- Department of Bone and Mineral Research, Research Institute, Osaka Women's and Children's Hospital, Osaka 594-1101, Japan
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Pathogenic Variants of the PHEX Gene. ENDOCRINES 2022. [DOI: 10.3390/endocrines3030040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Twenty-five years ago, a pathogenic variant of the phosphate-regulating endopeptidase homolog X-linked (PHEX) gene was identified as the cause of X-linked hypophosphatemic rickets (XLH). Subsequently, the overproduction of fibroblast growth factor 23 (FGF23) due to PHEX defects has been found to be associated with XLH pathophysiology. However, the mechanism by which PHEX deficiency contributes to the upregulation of FGF23 and the function of PHEX itself remain unclear. To date, over 700 pathogenic variants have been identified in patients with XLH, and functional assays and genotype–phenotype correlation analyses based on pathogenic variant data derived from XLH patients have been reported. Genetic testing for XLH is useful for the diagnosis. Not only have single-nucleotide variants causing missense, nonsense, and splicing variants and small deletion/insertion variants causing frameshift/non-frameshift alterations been observed, but also gross deletion/duplication variants causing copy number variants have been reported as pathogenic variants in PHEX. With the development of new technologies including next generation sequencing, it is expected that an increasing number of pathogenic variants will be identified. This chapter aimed to summarize the genotype of PHEX and related analyses and discusses the pathophysiology of PHEX defects to seek clues on unsolved questions.
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PHEXL222P Mutation Increases Phex Expression in a New ENU Mouse Model for XLH Disease. Genes (Basel) 2022; 13:genes13081356. [PMID: 36011266 PMCID: PMC9407253 DOI: 10.3390/genes13081356] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 02/02/2023] Open
Abstract
PhexL222P mouse is a new ENU mouse model for XLH disease due to Leu to Pro amino acid modification at position 222. PhexL222P mouse is characterized by growth retardation, hypophosphatemia, hypocalcemia, reduced body bone length, and increased epiphyseal growth plate thickness and femur diameter despite the increase in PHEXL222P expression. Actually, PhexL222P mice show an increase in Fgf23, Dmp1, and Mepe and Slc34a1 (Na-Pi IIa cotransporter) mRNA expression similar to those observed in Hyp mice. Femoral osteocalcin and sclerostin and Slc34a1 do not show any significant variation in PhexL222P mice. Molecular dynamics simulations support the experimental data. P222 might locally break the E217-Q224 β-sheet, which in turn might disrupt inter-β-sheet interactions. We can thus expect local protein misfolding, which might be responsible for the experimentally observed PHEXL222P loss of function. This model could be a valuable addition to the existing XLH model for further comprehension of the disease occurrence and testing of new therapies.
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Function of PHEX mutations p.Glu145* and p.Trp749Arg in families with X-linked hypophosphatemic rickets by the negative regulation mechanism on FGF23 promoter transcription. Cell Death Dis 2022; 13:518. [PMID: 35654784 PMCID: PMC9163062 DOI: 10.1038/s41419-022-04969-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 01/21/2023]
Abstract
X-linked hypophosphatemic rickets (XLH) is characterized by increased circulating fibroblast growth factor 23 (FGF23) concentration caused by PHEX (NM_000444.5) mutations. Renal tubular resorption of phosphate is impaired, resulting in rickets and impaired bone mineralization. By phenotypic-genetic linkage analysis, two PHEX pathogenic mutations were found in two XLH families: c.433 G > T, p.Glu145* in exon 4 and c.2245 T > C, p.Trp749Arg in exon 22. Immunofluorescence showed that the localization of p.Glu145* and p.Trp749Arg mutant and secretory PHEX (secPHEX) changed, with decreased expression. In a HEK293T cell model co-transfected with PHEX, secPHEX, and FGF23, wild-type PHEX, secPHEX, and FGF23 proteins were distributed in the cell membrane or endoplasmic reticulum, while the mutant was located in the nuclear membrane and cytoplasm. qPCR of p.Glu145* revealed decreased PHEX and secPHEX mRNA expression in cells, with no difference in mRNA expression of p.Trp749Arg. Both mutations decreased intracellular PHEX endopeptidase activity. Western blot analysis showed decrease in mutant and secPHEX protein expression and no FGF23 protein expression in single-transfected PHEX and secPHEX cells. In cells co-transfected with FGF23, PHEX and secPHEX mutation promoted FGF23 expression. Dual-luciferase reporter gene was used to detect the effect of PHEX on FGF23 promoter. The dual-luciferase reporter gene showed that after PHEX overexpression, the activity of mutant firefly luciferase was significantly higher than that of wild type. The regulatory mechanism between PHEX and FGF23 is still unclear, but we found that PHEX is a direct transcriptional inhibitor of FGF23 and affects the expression of FGF23. This study verified the pathogenicity of the two variants and revealed the possible regulatory mechanism between PHEX and FGF23.
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Pathogenesis of FGF23-Related Hypophosphatemic Diseases Including X-linked Hypophosphatemia. ENDOCRINES 2022. [DOI: 10.3390/endocrines3020025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Since phosphate is indispensable for skeletal mineralization, chronic hypophosphatemia causes rickets and osteomalacia. Fibroblast growth factor 23 (FGF23), which is mainly produced by osteocytes in bone, functions as the central regulator of phosphate metabolism by increasing the renal excretion of phosphate and suppressing the production of 1,25-dihydroxyvitamin D. The excessive action of FGF23 results in hypophosphatemic diseases, which include a number of genetic disorders such as X-linked hypophosphatemic rickets (XLH) and tumor-induced osteomalacia (TIO). Phosphate-regulating gene homologous to endopeptidase on the X chromosome (PHEX), dentin matrix protein 1 (DMP1), ectonucleotide pyrophosphatase phosphodiesterase-1, and family with sequence similarity 20c, the inactivating variants of which are responsible for FGF23-related hereditary rickets/osteomalacia, are highly expressed in osteocytes, similar to FGF23, suggesting that they are local negative regulators of FGF23. Autosomal dominant hypophosphatemic rickets (ADHR) is caused by cleavage-resistant variants of FGF23, and iron deficiency increases serum levels of FGF23 and the manifestation of symptoms in ADHR. Enhanced FGF receptor (FGFR) signaling in osteocytes is suggested to be involved in the overproduction of FGF23 in XLH and autosomal recessive hypophosphatemic rickets type 1, which are caused by the inactivation of PHEX and DMP1, respectively. TIO is caused by the overproduction of FGF23 by phosphaturic tumors, which are often positive for FGFR. FGF23-related hypophosphatemia may also be associated with McCune-Albright syndrome, linear sebaceous nevus syndrome, and the intravenous administration of iron. This review summarizes current knowledge on the pathogenesis of FGF23-related hypophosphatemic diseases.
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Trombetti A, Al-Daghri N, Brandi ML, Cannata-Andía JB, Cavalier E, Chandran M, Chaussain C, Cipullo L, Cooper C, Haffner D, Harvengt P, Harvey NC, Javaid MK, Jiwa F, Kanis JA, Laslop A, Laurent MR, Linglart A, Marques A, Mindler GT, Minisola S, Yerro MCP, Rosa MM, Seefried L, Vlaskovska M, Zanchetta MB, Rizzoli R. Interdisciplinary management of FGF23-related phosphate wasting syndromes: a Consensus Statement on the evaluation, diagnosis and care of patients with X-linked hypophosphataemia. Nat Rev Endocrinol 2022; 18:366-384. [PMID: 35484227 DOI: 10.1038/s41574-022-00662-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/10/2022] [Indexed: 12/17/2022]
Abstract
X-linked hypophosphataemia (XLH) is the most frequent cause of hypophosphataemia-associated rickets of genetic origin and is associated with high levels of the phosphaturic hormone fibroblast growth factor 23 (FGF23). In addition to rickets and osteomalacia, patients with XLH have a heavy disease burden with enthesopathies, osteoarthritis, pseudofractures and dental complications, all of which contribute to reduced quality of life. This Consensus Statement presents the outcomes of a working group of the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases, and provides robust clinical evidence on management in XLH, with an emphasis on patients' experiences and needs. During growth, conventional treatment with phosphate supplements and active vitamin D metabolites (such as calcitriol) improves growth, ameliorates leg deformities and dental manifestations, and reduces pain. The continuation of conventional treatment in symptom-free adults is still debated. A novel therapeutic approach is the monoclonal anti-FGF23 antibody burosumab. Although promising, further studies are required to clarify its long-term efficacy, particularly in adults. Given the diversity of symptoms and complications, an interdisciplinary approach to management is of paramount importance. The focus of treatment should be not only on the physical manifestations and challenges associated with XLH and other FGF23-mediated hypophosphataemia syndromes, but also on the major psychological and social impact of the disease.
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Affiliation(s)
- Andrea Trombetti
- Division of Bone Diseases, Department of Medicine, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
- Division of Geriatrics, Department of Rehabilitation and Geriatrics, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland
| | - Nasser Al-Daghri
- Chair for Biomarkers of Chronic Diseases, Biochemistry Department, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | | | - Jorge B Cannata-Andía
- Hospital Universitario Central de Asturias (HUCA), Oviedo, Spain
- Universidad de Oviedo, Oviedo, Spain
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Oviedo, Spain
- Retic REDinREN-RICORS, 2040-ISCIII, Madrid, Spain
| | - Etienne Cavalier
- Department of Clinical Chemistry, University of Liege, CHU de Liège, Liège, Belgium
| | - Manju Chandran
- Complicated Metabolic Bone Disorders Clinic, Osteoporosis and Bone Metabolism Unit, Department of Endocrinology, Singapore General Hospital, Singapore, Singapore
| | - Catherine Chaussain
- Université de Paris, Institut des maladies musculo-squelettiques, URP2496, UFR Odontologie, Montrouge, France
- AP-HP, FHU DDS-Net, Centre de Référence des Maladies Rares du Métabolisme du Calcium et du Phosphore, Service médecine bucco-dentaire, Hôpital Bretonneau, GH Paris Nord Université de Paris, Paris, France
| | - Lucia Cipullo
- Patient representative with XLH, Geneva, Switzerland
| | - Cyrus Cooper
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
- NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, UK
| | - Dieter Haffner
- Department of Paediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Pol Harvengt
- XLH Belgium, Belgian association of patients with XLH (a member of the International XLH Alliance), Waterloo, Belgium
| | - Nicholas C Harvey
- MRC Lifecourse Epidemiology Centre, University of Southampton, Southampton, UK
- NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | | | - Famida Jiwa
- Chair of the Committee of Patients Societies at the International Osteoporosis Foundation, Osteoporosis Canada, Toronto, Canada
| | - John A Kanis
- Mary McKillop Institute for Health Research, Australian Catholic University, Melbourne, Australia
- Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Sheffield, UK
| | - Andrea Laslop
- Scientific Office, Federal Office for Safety in Health Care, Vienna, Austria
| | - Michaël R Laurent
- Centre for Metabolic Bone Diseases, University Hospitals Leuven, Leuven, Belgium
| | - Agnès Linglart
- Paris-Saclay University, INSERM U1185, Le Kremlin-Bicêtre, France
- AP-HP, endocrinology and diabetes for children, Reference centre for rare diseases of calcium and phosphate metabolism, OSCAR network, Platform of expertise for rare diseases of Paris Saclay Hospital, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France
| | - Andréa Marques
- Rheumatology Department, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal
- Health Sciences Research Unit: Nursing (UICiSA:E), Nursing School of Coimbra, Coimbra, Portugal
| | - Gabriel T Mindler
- Department of Paediatric Orthopaedics, Orthopaedic Hospital Speising, Vienna, Austria
- Vienna Bone and Growth Center, Vienna, Austria
| | - Salvatore Minisola
- Department of Clinical, Internal, Anaesthesiologic and Cardiovascular Sciences, 'Sapienza', Rome University, Rome, Italy
| | | | - Mario Miguel Rosa
- Departamento de Neurociências, Laboratório de Farmacologia Clínica E Terapêutica Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
| | - Lothar Seefried
- Orthopedic Department, University of Würzburg, Würzburg, Germany
| | - Mila Vlaskovska
- Medical Faculty, Department of Pharmacology, Medical University Sofia, Sofia, Bulgaria
| | - María Belén Zanchetta
- Instituto de Investigaciones Metabólicas (IDIM), Universidad del Salvador, Buenos Aires, Argentina
| | - René Rizzoli
- Division of Bone Diseases, Department of Medicine, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland.
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Fuente R, García-Bengoa M, Fernández-Iglesias Á, Gil-Peña H, Santos F, López JM. Cellular and Molecular Alterations Underlying Abnormal Bone Growth in X-Linked Hypophosphatemia. Int J Mol Sci 2022; 23:ijms23020934. [PMID: 35055123 PMCID: PMC8778463 DOI: 10.3390/ijms23020934] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/12/2022] [Accepted: 01/13/2022] [Indexed: 12/21/2022] Open
Abstract
X-linked hypophosphatemia (XLH), the most common form of hereditary hypophosphatemic rickets, is caused by inactivating mutations of the phosphate-regulating endopeptidase gene (PHEX). XLH is mainly characterized by short stature, bone deformities and rickets, while in hypophosphatemia, normal or low vitamin D levels and low renal phosphate reabsorption are the principal biochemical aspects. The cause of growth impairment in patients with XLH is not completely understood yet, thus making the study of the growth plate (GP) alterations necessary. New treatment strategies targeting FGF23 have shown promising results in normalizing the growth velocity and improving the skeletal effects of XLH patients. However, further studies are necessary to evaluate how this treatment affects the GP as well as its long-term effects and the impact on adult height.
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Affiliation(s)
- Rocío Fuente
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, 33006 Oviedo, Spain; (R.F.); (M.G.-B.); (Á.F.-I.); (H.G.-P.); (F.S.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33011 Oviedo, Spain
- Institute of Physiology, Center for Integrative Human Physiology (ZIHP), University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - María García-Bengoa
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, 33006 Oviedo, Spain; (R.F.); (M.G.-B.); (Á.F.-I.); (H.G.-P.); (F.S.)
- Research Center for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine Hannover, 30559 Hanover, Germany
| | - Ángela Fernández-Iglesias
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, 33006 Oviedo, Spain; (R.F.); (M.G.-B.); (Á.F.-I.); (H.G.-P.); (F.S.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33011 Oviedo, Spain
| | - Helena Gil-Peña
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, 33006 Oviedo, Spain; (R.F.); (M.G.-B.); (Á.F.-I.); (H.G.-P.); (F.S.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33011 Oviedo, Spain
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), 33011 Oviedo, Spain
| | - Fernando Santos
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, 33006 Oviedo, Spain; (R.F.); (M.G.-B.); (Á.F.-I.); (H.G.-P.); (F.S.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), 33011 Oviedo, Spain
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), 33011 Oviedo, Spain
| | - José Manuel López
- Department of Morphology and Cellular Biology, Faculty of Medicine, University of Oviedo, 33006 Oviedo, Spain
- Correspondence:
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Abstract
Osteocytes are dendritic cells in the mineralized bone matrix that descend from osteoblasts. They play critical roles in controlling bone mass through the production of sclerostin, an inhibitor of bone formation, and receptor activator of nuclear factor κ B ligand, an inducer of osteoblastic bone resorption. Osteocytes also govern phosphate homeostasis through the production of fibroblast growth factor 23 (FGF23), which lowers serum phosphate levels by increasing renal phosphate excretion and reducing the synthesis of 1,25-dihydroxyvitamin D (1,25(OH)2D), an active metabolite of vitamin D. The production of FGF23 in osteocytes is regulated by various local and systemic factors. Phosphate-regulating gene homologous to endopeptidase on X chromosome (PHEX), dentin matrix protein 1 (DMP1), and family with sequence similarity 20, member C function as local negative regulators of FGF23 production in osteocytes, and their inactivation causes the overproduction of FGF23 and hypophosphatemia. Sclerostin has been suggested to regulate the production of FGF23, which may link the two functions of osteocytes, namely, the control of bone mass and regulation of phosphate homeostasis. Systemic regulators of FGF23 production include 1,25(OH)2D, phosphate, parathyroid hormone, insulin, iron, and inflammation. Therefore, the regulation of FGF23 in osteocytes is complex and multifactorial. Recent mouse studies have suggested that decreases in serum phosphate levels from youth to adulthood are caused by growth-related increases in FGF23 production by osteocytes, which are associated with the down-regulation of Phex and Dmp1.
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17
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Ishihara Y, Ohata Y, Takeyari S, Kitaoka T, Fujiwara M, Nakano Y, Yamamoto K, Yamada C, Yamamoto K, Michigami T, Mabe H, Yamaguchi T, Matsui K, Tamada I, Namba N, Yamamoto A, Etoh J, Kawaguchi A, Kosugi R, Ozono K, Kubota T. Genotype-phenotype analysis, and assessment of the importance of the zinc-binding site in PHEX in Japanese patients with X-linked hypophosphatemic rickets using 3D structure modeling. Bone 2021; 153:116135. [PMID: 34333162 DOI: 10.1016/j.bone.2021.116135] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 07/09/2021] [Accepted: 07/26/2021] [Indexed: 11/25/2022]
Abstract
X-linked hypophosphatemic rickets (XLH) is an inheritable type of rickets caused by inactivating variants in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene, which results in the overproduction of fibroblast growth factor 23 (FGF23). The mechanism by which PHEX impairment leads to FGF23 overproduction is unknown. Because little is known regarding the genotype-phenotype correlation in Japanese XLH, we summarized the available clinical and genetic data and analyzed the genotype-phenotype relationships using 3-dimensional (3D) structure modeling to clarify the XLH pathophysiology. We retrospectively reviewed the clinical features and performed genetic analysis of 39 Japanese patients with XLH from 28 unrelated pedigrees carrying any known or novel PHEX variant. To predict changes in the 3D structure of mutant PHEX, we constructed a putative 3D model of each mutant and evaluated the effect of structural alteration by genotype-phenotype correlation analysis. Genetic analysis revealed 23 PHEX variants, including eight novel variants. They were associated with high i-FGF23 levels, hypophosphatemia, phosphaturia, high alkaline phosphatase levels, and short stature. No gene dosage effect or genotype-phenotype correlation was observed when truncating and non-truncating variants were compared. However, the conservation of the zinc-binding site and cavity in PHEX had an impact on the elevation of i-FGF23 levels. Via genotype-phenotype relationship analysis using 3D modeling, we showed that the zinc-binding site and cavity in PHEX can play a critical role in its function. These findings provide new genetic clues for investigating the function of PHEX and the pathogenesis of XLH.
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Affiliation(s)
- Yasuki Ishihara
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan; The 1st. Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita, Japan; Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yasuhisa Ohata
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Shinji Takeyari
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Taichi Kitaoka
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Makoto Fujiwara
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan; The 1st. Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita, Japan
| | - Yukako Nakano
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Kenichi Yamamoto
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan; Department of Statistical Genetics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Chieko Yamada
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Katsusuke Yamamoto
- Department of Pediatric Nephrology and Metabolism, Osaka Women's and Children's Hospital, Izumi, Japan
| | - Toshimi Michigami
- Department of Bone and Mineral Research, Osaka Women's and Children's Hospital, Izumi, Japan
| | - Hiroyo Mabe
- Department of Pediatrics, Kumamoto University Hospital, Kumamoto, Japan
| | - Takeshi Yamaguchi
- Department of Pediatrics, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Katsuyuki Matsui
- Department of Pediatrics, Shiga University of Medical Science, Otsu, Japan
| | - Izumi Tamada
- Department of Pediatrics, Imakiire General Hospital, Kagoshima, Japan
| | - Noriyuki Namba
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan; Division of Pediatrics and Perinatology, Faculty of Medicine, Tottori University, Tottori, Japan
| | - Akiko Yamamoto
- Department of Pediatrics, Kumamoto Chuo Hospital, Kumamoto, Japan
| | - Junya Etoh
- Department of Pediatrics, Saga-Ken Medical Centre Koseikan, Saga, Japan
| | - Azusa Kawaguchi
- Department of Pediatrics, National Hospital Organization Hokkaido Medical Center, Sapporo, Japan
| | - Rieko Kosugi
- Department of Diabetes and Endocrinology, Shizuoka General Hospital, Shizuoka, Japan
| | - Keiichi Ozono
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan
| | - Takuo Kubota
- Department of Pediatrics, Osaka University Graduate School of Medicine, Suita, Japan.
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18
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Generation of two multipotent mesenchymal progenitor cell lines capable of osteogenic, mature osteocyte, adipogenic, and chondrogenic differentiation. Sci Rep 2021; 11:22593. [PMID: 34799645 PMCID: PMC8605002 DOI: 10.1038/s41598-021-02060-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 11/09/2021] [Indexed: 01/04/2023] Open
Abstract
Mesenchymal progenitors differentiate into several tissues including bone, cartilage, and adipose. Targeting these cells in vivo is challenging, making mesenchymal progenitor cell lines valuable tools to study tissue development. Mesenchymal stem cells (MSCs) can be isolated from humans and animals; however, obtaining homogenous, responsive cells in a reproducible fashion is challenging. As such, we developed two mesenchymal progenitor cell (MPC) lines, MPC1 and MPC2, generated from bone marrow of male C57BL/6 mice. These cells were immortalized using the temperature sensitive large T-antigen, allowing for thermal control of proliferation and differentiation. Both MPC1 and MPC2 cells are capable of osteogenic, adipogenic, and chondrogenic differentiation. Under osteogenic conditions, both lines formed mineralized nodules, and stained for alizarin red and alkaline phosphatase, while expressing osteogenic genes including Sost, Fgf23, and Dmp1. Sost and Dmp1 mRNA levels were drastically reduced with addition of parathyroid hormone, thus recapitulating in vivo responses. MPC cells secreted intact (iFGF23) and C-terminal (cFGF23) forms of the endocrine hormone FGF23, which was upregulated by 1,25 dihydroxy vitamin D (1,25D). Both lines also rapidly entered the adipogenic lineage, expressing adipose markers after 4 days in adipogenic media. MPC cells were also capable of chondrogenic differentiation, displaying increased expression of cartilaginous genes including aggrecan, Sox9, and Comp. With the ability to differentiate into multiple mesenchymal lineages and mimic in vivo responses of key regulatory genes/proteins, MPC cells are a valuable model to study factors that regulate mesenchymal lineage allocation as well as the mechanisms that dictate transcription, protein modification, and secretion of these factors.
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A 5-year-old girl with bony deformities and disproportionate short stature: Answers. Pediatr Nephrol 2021; 36:3117-3121. [PMID: 33730275 DOI: 10.1007/s00467-021-05038-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 02/19/2021] [Accepted: 02/26/2021] [Indexed: 10/21/2022]
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20
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Jaschke N, Sipos W, Hofbauer LC, Rachner TD, Rauner M. Skeletal endocrinology: where evolutionary advantage meets disease. Bone Res 2021; 9:28. [PMID: 34050126 PMCID: PMC8163738 DOI: 10.1038/s41413-021-00149-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 02/16/2021] [Accepted: 02/23/2021] [Indexed: 02/06/2023] Open
Abstract
The regulation of whole-body homeostasis by the skeleton is mediated by its capacity to secrete endocrine signaling molecules. Although bone-derived hormones confer several adaptive benefits, their physiological functions also involve trade-offs, thus eventually contributing to disease. In this manuscript, we discuss the origins and functions of two of the best-studied skeletal mediators, fibroblast growth factor 23 and osteocalcin, in an evolutionary context. Moreover, we provide a theoretical framework seeking to explain the broad involvement of these two hormones in amniote physiology as well as their potential to fuel the development and progression of diseases. Vice versa, we outline which perturbations might be amenable to manipulation of these systems and discuss limitations and ongoing challenges in skeletal endocrine research. Finally, we summarize unresolved questions and potential future studies in this thriving field.
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Affiliation(s)
- Nikolai Jaschke
- Department of Medicine III & Center for Healthy Aging, Technische Universität Dresden, Dresden, Germany
| | - Wolfgang Sipos
- Clinical Department for Farm Animals, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Lorenz C Hofbauer
- Department of Medicine III & Center for Healthy Aging, Technische Universität Dresden, Dresden, Germany
| | - Tilman D Rachner
- Department of Medicine III & Center for Healthy Aging, Technische Universität Dresden, Dresden, Germany
| | - Martina Rauner
- Department of Medicine III & Center for Healthy Aging, Technische Universität Dresden, Dresden, Germany.
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21
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Chu C, Elitok S, Zeng S, Xiong Y, Hocher CF, Hasan AA, Krämer BK, Hocher B. C-terminal and intact FGF23 in kidney transplant recipients and their associations with overall graft survival. BMC Nephrol 2021; 22:125. [PMID: 33832449 PMCID: PMC8033679 DOI: 10.1186/s12882-021-02329-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 03/30/2021] [Indexed: 12/31/2022] Open
Abstract
Background Increased fibroblast growth factor 23 (FGF23) is a risk factor for mortality, cardiovascular disease, and progression of chronic kidney disease. Limited data exist comparing the association of either c-terminal FGF23 (cFGF23) or intact FGF23 (iFGF23) in kidney transplant recipients (KTRs) with overall (all-cause) graft loss. Methods We conducted a prospective observational cohort study in 562 stable kidney transplant recipients. Patients were followed for graft loss and all-cause mortality for a median follow-up of 48 months. Results During a median follow-up of 48 months, 94 patients had overall graft loss (primary graft loss or death with functioning graft). Both cFGF23 and iFGF23 concentrations were significantly higher in patients with overall graft loss than those without (24.59 [11.43–87.82] versus 10.67 [5.99–22.73] pg/ml; p < 0.0001 and 45.24 [18.63–159.00] versus 29.04 [15.23–60.65] pg/ml; p = 0.002 for cFGF23 and iFGF23, respectively). Time-dependent ROC analysis showed that cFGF23 concentrations had a better discriminatory ability than iFGF23 concentrations in predicting overall (all-cause) graft loss. Cox regression analyses adjusted for risk factors showed that cFGF23 (HR for one unit increase of log transformed cFGF23: 1.35; 95% CI, 1.01–1.79; p = 0.043) but not iFGF23 (HR for one unit increase of log transformed iFGF23: 0.97; 95% CI, 0.75–1.25; p = 0.794) was associated with the overall graft loss. Conclusion Elevated cFGF23 concentrations at baseline are independently associated with an increased risk of overall graft loss. iFGF23 measurements were not independently associated with overall graft loss. The cFGF23 ELISA might detect bioactive FGF23 fragments that are not detected by the iFGF23 ELISA. Supplementary Information The online version contains supplementary material available at 10.1186/s12882-021-02329-7.
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Affiliation(s)
- Chang Chu
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany.,Department of Nephrology, Charité - Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany
| | - Saban Elitok
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany.,Clinic for Nephrology and Endocrinology, Klinikum Ernst von Bergmann, Potsdam, Germany
| | - Shufei Zeng
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany.,Department of Nephrology, Charité - Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany
| | - Yingquan Xiong
- Department of Nephrology, Charité - Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany.,Institute of Pharmacy, Free University of Berlin, Berlin, Germany
| | - Carl-Friedrich Hocher
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Ahmed A Hasan
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany.,Institute of Pharmacy, Free University of Berlin, Berlin, Germany.,Department of Biochemistry, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Bernhard K Krämer
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany.,European Center for Angioscience, Medical Faculty Mannheim of the University of Heidelberg, Heidelberg, Germany.,Mannheim Institute for Innate Immunoscience, Medical Faculty Mannheim of the University of Heidelberg, Mannheim, Germany
| | - Berthold Hocher
- Fifth Department of Medicine (Nephrology/ Endocrinology/ Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany. .,Key Laboratory of Study and Discovery of Small Targeted Molecules of Hunan Province, School of Medicine, Hunan Normal University, Changsha, China. .,Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China. .,IMD Institut für Medizinische Diagnostik Berlin-Potsdam GbR, Berlin, Germany.
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22
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Koumakis E, Cormier C, Roux C, Briot K. The Causes of Hypo- and Hyperphosphatemia in Humans. Calcif Tissue Int 2021; 108:41-73. [PMID: 32285168 DOI: 10.1007/s00223-020-00664-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 01/20/2020] [Indexed: 12/11/2022]
Abstract
Phosphate homeostasis involves several major organs that are the skeleton, the intestine, the kidney, and parathyroid glands. Major regulators of phosphate homeostasis are parathormone, fibroblast growth factor 23, 1,25-dihydroxyvitamin D, which respond to variations of serum phosphate levels and act to increase or decrease intestinal absorption and renal tubular reabsorption, through the modulation of expression of transcellular transporters at the intestinal and/or renal tubular level. Any acquired or genetic dysfunction in these major organs or regulators may induce hypo- or hyperphosphatemia. The causes of hypo- and hyperphosphatemia are numerous. This review develops the main causes of acquired and genetic hypo- and hyperphosphatemia.
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Affiliation(s)
- Eugénie Koumakis
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France.
| | - Catherine Cormier
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France
| | - Christian Roux
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France
| | - Karine Briot
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France
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23
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Athonvarangkul D, Insogna KL. New Therapies for Hypophosphatemia-Related to FGF23 Excess. Calcif Tissue Int 2021; 108:143-157. [PMID: 32504139 DOI: 10.1007/s00223-020-00705-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 05/12/2020] [Indexed: 12/12/2022]
Abstract
FGF23 is a hormone produced by osteocytes in response to an elevation in the concentration of extracellular phosphate. Excess production of FGF23 by bone cells, or rarely by tumors, is the hormonal basis for several musculoskeletal syndromes characterized by hypophosphatemia due to renal phosphate wasting. FGF23-dependent chronic hypophosphatemia causes rickets and osteomalacia, as well as other skeletal complications. Genetic disorders of FGF23-mediated hypophosphatemia include X-linked hypophosphatemia (XLH), autosomal dominant hypophosphatemic rickets (ADHR), autosomal recessive hypophosphatemic rickets (ARHR), fibrous dysplasia of bone, McCune-Albright syndrome, and epidermal nevus syndrome (ENS), also known as cutaneous skeletal hypophosphatemia syndrome (CSHS). The principle acquired form of FGF23-mediated hypophosphatemia is tumor-induced osteomalacia (TIO). This review summarizes current knowledge about the pathophysiology and clinical presentation of the most common FGF23-mediated conditions, with a focus on new treatment modalities. For many decades, calcitriol and phosphate supplements were the mainstay of therapy. Recently, burosumab, a monoclonal blocking antibody to FGF23, has been approved for treatment of XLH in children and adults, and an active comparator trial in children has shown good efficacy and safety for this drug. The remainder of FGF23-mediated hypophosphatemic disorders continue to be treated with phosphate and calcitriol, although ongoing trials with burosumab for treatment of tumor-induced osteomalacia show early promise. Burosumab may be an effective treatment for the remainder of FGF23-mediated disorders, but clinical trials to support that possibility are at present not available.
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Affiliation(s)
- Diana Athonvarangkul
- Department of Medicine Section of Endocrinology, Yale School of Medicine, PO Box 802080, New Haven, CT, 06520, USA.
| | - Karl L Insogna
- Department of Medicine Section of Endocrinology, Yale School of Medicine, PO Box 802080, New Haven, CT, 06520, USA
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24
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Hoac B, Østergaard M, Wittig NK, Boukpessi T, Buss DJ, Chaussain C, Birkedal H, Murshed M, McKee MD. Genetic Ablation of Osteopontin in Osteomalacic Hyp Mice Partially Rescues the Deficient Mineralization Without Correcting Hypophosphatemia. J Bone Miner Res 2020; 35:2032-2048. [PMID: 32501585 DOI: 10.1002/jbmr.4101] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 05/24/2020] [Accepted: 06/01/2020] [Indexed: 11/09/2022]
Abstract
PHEX is predominantly expressed by bone and tooth-forming cells, and its inactivating mutations in X-linked hypophosphatemia (XLH) lead to renal phosphate wasting and severe hypomineralization of bones and teeth. Also present in XLH are hallmark hypomineralized periosteocytic lesions (POLs, halos) that persist despite stable correction of serum phosphate (Pi ) that improves bulk bone mineralization. In XLH, mineralization-inhibiting osteopontin (OPN, a substrate for PHEX) accumulates in the extracellular matrix of bone. To investigate how OPN functions in Hyp mice (a model for XLH), double-null (Hyp;Opn-/- ) mice were generated. Undecalcified histomorphometry performed on lumbar vertebrae revealed that Hyp;Opn-/- mice had significantly reduced osteoid area/bone area (OV/BV) and osteoid thickness of trabecular bone as compared to Hyp mice, despite being as hypophosphatemic as Hyp littermate controls. However, tibias examined by synchrotron radiation micro-CT showed that mineral lacunar volumes remained abnormally enlarged in these double-null mice. When Hyp;Opn-/- mice were fed a high-Pi diet, serum Pi concentration increased, and OV/BV and osteoid thickness normalized, yet mineral lacunar area remained abnormally enlarged. Enpp1 and Ankh gene expression were increased in double-null mice fed a high-Pi diet, potentially indicating a role for elevated inhibitory pyrophosphate (PPi ) in the absence of OPN. To further investigate the persistence of POLs in Hyp mice despite stable correction of serum Pi , immunohistochemistry for OPN on Hyp mice fed a high-Pi diet showed elevated OPN in the osteocyte pericellular lacunar matrix as compared to Hyp mice fed a control diet. This suggests that POLs persisting in Hyp mice despite correction of serum Pi may be attributable to the well-known upregulation of mineralization-inhibiting OPN by Pi , and its accumulation in the osteocyte pericellular matrix. This study shows that OPN contributes to osteomalacia in Hyp mice, and that genetic ablation of OPN in Hyp mice improves the mineralization phenotype independent of systemic Pi -regulating factors. © 2020 American Society for Bone and Mineral Research.
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Affiliation(s)
- Betty Hoac
- Faculty of Dentistry, McGill University, Montreal, QC, Canada
| | - Maja Østergaard
- Department of Chemistry and the Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
| | - Nina K Wittig
- Department of Chemistry and the Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
| | - Tchilalo Boukpessi
- Faculty of Dentistry, McGill University, Montreal, QC, Canada.,EA 2496, Laboratory Orofacial Pathologies, Imaging and Biotherapies, School of Dentistry Université de Paris, Paris, France.,Assistance Publique-Hôpitaux de Paris (AP-HP) Department of Odontology, Charles Foix and Bretonneau Hospitals and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism, Paris, France
| | - Daniel J Buss
- Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, QC, Canada
| | - Catherine Chaussain
- EA 2496, Laboratory Orofacial Pathologies, Imaging and Biotherapies, School of Dentistry Université de Paris, Paris, France.,Assistance Publique-Hôpitaux de Paris (AP-HP) Department of Odontology, Charles Foix and Bretonneau Hospitals and Reference Center for Rare Diseases of Calcium and Phosphorus Metabolism, Paris, France
| | - Henrik Birkedal
- Department of Chemistry and the Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus, Denmark
| | - Monzur Murshed
- Faculty of Dentistry, McGill University, Montreal, QC, Canada.,Department of Medicine, Faculty of Medicine, McGill University, Montreal, QC, Canada.,Shriners Hospital for Children, Montreal, QC, Canada
| | - Marc D McKee
- Faculty of Dentistry, McGill University, Montreal, QC, Canada.,Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, QC, Canada
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25
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Genome-wide association study for circulating fibroblast growth factor 21 and 23. Sci Rep 2020; 10:14578. [PMID: 32884031 PMCID: PMC7471933 DOI: 10.1038/s41598-020-71569-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Accepted: 08/06/2020] [Indexed: 11/09/2022] Open
Abstract
Fibroblast growth factors (FGFs) 21 and 23 are recently identified hormones regulating metabolism of glucose, lipid, phosphate and vitamin D. Here we conducted a genome-wide association study (GWAS) for circulating FGF21 and FGF23 concentrations to identify their genetic determinants. We enrolled 5,000 participants from Taiwan Biobank for this GWAS. After excluding participants with diabetes mellitus and quality control, association of single nucleotide polymorphisms (SNPs) with log-transformed FGF21 and FGF23 serum concentrations adjusted for age, sex and principal components of ancestry were analyzed. A second model additionally adjusted for body mass index (BMI) and a third model additionally adjusted for BMI and estimated glomerular filtration rate (eGFR) were used. A total of 4,201 participants underwent GWAS analysis. rs67327215, located within RGS6 (a gene involved in fatty acid synthesis), and two other SNPs (rs12565114 and rs9520257, located between PHC2-ZSCAN20 and ARGLU1-FAM155A respectively) showed suggestive associations with serum FGF21 level (P = 6.66 × 10–7, 6.00 × 10–7 and 6.11 × 10–7 respectively). The SNPs rs17111495 and rs17843626 were significantly associated with FGF23 level, with the former near PCSK9 gene and the latter near HLA-DQA1 gene (P = 1.04 × 10–10 and 1.80 × 10–8 respectively). SNP rs2798631, located within the TGFB2 gene, was suggestively associated with serum FGF23 level (P = 4.97 × 10–7). Additional adjustment for BMI yielded similar results. For FGF23, further adjustment for eGFR had similar results. We conducted the first GWAS of circulating FGF21 levels to date. Novel candidate genetic loci associated with circulating FGF21 or FGF23 levels were found. Further replication and functional studies are needed to support our findings.
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26
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Reznikov N, Hoac B, Buss DJ, Addison WN, Barros NMT, McKee MD. Biological stenciling of mineralization in the skeleton: Local enzymatic removal of inhibitors in the extracellular matrix. Bone 2020; 138:115447. [PMID: 32454257 DOI: 10.1016/j.bone.2020.115447] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/14/2020] [Accepted: 05/20/2020] [Indexed: 12/12/2022]
Abstract
Biomineralization is remarkably diverse and provides myriad functions across many organismal systems. Biomineralization processes typically produce hardened, hierarchically organized structures usually having nanostructured mineral assemblies that are formed through inorganic-organic (usually protein) interactions. Calcium‑carbonate biomineral predominates in structures of small invertebrate organisms abundant in marine environments, particularly in shells (remarkably it is also found in the inner ear otoconia of vertebrates), whereas calcium-phosphate biomineral predominates in the skeletons and dentitions of both marine and terrestrial vertebrates, including humans. Reconciliation of the interplay between organic moieties and inorganic crystals in bones and teeth is a cornerstone of biomineralization research. Key molecular determinants of skeletal and dental mineralization have been identified in health and disease, and in pathologic ectopic calcification, ranging from small molecules such as pyrophosphate, to small membrane-bounded matrix vesicles shed from cells, and to noncollagenous extracellular matrix proteins such as osteopontin and their derived bioactive peptides. Beyond partly knowing the regulatory role of the direct actions of inhibitors on vertebrate mineralization, more recently the importance of their enzymatic removal from the extracellular matrix has become increasingly understood. Great progress has been made in deciphering the relationship between mineralization inhibitors and the enzymes that degrade them, and how adverse changes in this physiologic pathway (such as gene mutations causing disease) result in mineralization defects. Two examples of this are rare skeletal diseases having osteomalacia/odontomalacia (soft bones and teeth) - namely hypophosphatasia (HPP) and X-linked hypophosphatemia (XLH) - where inactivating mutations occur in the gene for the enzymes tissue-nonspecific alkaline phosphatase (TNAP, TNSALP, ALPL) and phosphate-regulating endopeptidase homolog X-linked (PHEX), respectively. Here, we review and provide a concept for how existing and new information now comes together to describe the dual nature of regulation of mineralization - through systemic mineral ion homeostasis involving circulating factors, coupled with molecular determinants operating at the local level in the extracellular matrix. For the local mineralization events in the extracellular matrix, we present a focused concept in skeletal mineralization biology called the Stenciling Principle - a principle (building upon seminal work by Neuman and Fleisch) describing how the action of enzymes to remove tissue-resident inhibitors defines with precision the location and progression of mineralization.
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Affiliation(s)
- N Reznikov
- Object Research Systems Inc., 760 St. Paul West, Montreal, Quebec H3C 1M4, Canada.
| | - B Hoac
- Faculty of Dentistry, McGill University, 3640 University St., Montreal, Quebec H3A 0C7, Canada
| | - D J Buss
- Department of Anatomy and Cell Biology, McGill University, 3640 University St., Montreal, Quebec H3A 0C7, Canada
| | - W N Addison
- Department of Molecular Signaling and Biochemistry, Kyushu Dental University, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu, Fukuoka, Japan
| | - N M T Barros
- Departamento de Biofísica, São Paulo, Departamento de Ciências Biológicas, Universidade Federal de São Paulo, Diadema, Brazil
| | - M D McKee
- Faculty of Dentistry, McGill University, 3640 University St., Montreal, Quebec H3A 0C7, Canada; Department of Anatomy and Cell Biology, McGill University, 3640 University St., Montreal, Quebec H3A 0C7, Canada.
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27
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Padidela R, Nilsson O, Makitie O, Beck-Nielsen S, Ariceta G, Schnabel D, Brandi ML, Boot A, Levtchenko E, Smyth M, Jandhyala R, Mughal Z. The international X-linked hypophosphataemia (XLH) registry (NCT03193476): rationale for and description of an international, observational study. Orphanet J Rare Dis 2020; 15:172. [PMID: 32605590 PMCID: PMC7329472 DOI: 10.1186/s13023-020-01434-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 06/04/2020] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND X-linked hypophosphataemia (XLH) is a rare, hereditary, progressive and lifelong phosphate wasting disorder characterised by pathological elevations in fibroblast growth factor (FGF) 23 concentration and activity; XLH has an incidence of approximately 1 in 20-25,000 individuals. Excess FGF23 activity leads to increased phosphate excretion in the kidneys - mediated by downregulation of renal tubular phosphate transporters - and reduced phosphate absorption in the intestines - due to impaired vitamin D activation. This results in impaired bone growth and mineralisation, short and disproportionate stature, leg bowing, musculoskeletal pain, spontaneous dental abscesses, rickets, and osteomalacia. The spectrum of manifestations differs between paediatric and adult patients. Those involved in the treatment of this condition face many challenges, including a lack of robust natural history and demographic data. This multicentre, international, rare-disease patient registry (XLH Registry) was established to address the paucity of data in XLH and to help inform future clinical practice. RESULTS The XLH Registry collects standard diagnostic and monitoring practice data, including (where applicable) diagnosis and disease progression history, treatment regimens and family history; the protocol does not mandate any interventions or clinical assessments. The XLH Registry aims to recruit 1200 paediatric and adult patients with XLH over 10 years, and several data analyses and peer-reviewed publications are expected to be generated throughout this period. A post-authorisation safety study for Bburosumab, for which the registry Sponsor is the marketing authorisation holder, will be nested as a sub-study within the XLH Registry via a subsequent protocol amendment. CONCLUSION The data collected within this rare-disease patient registry will be utilised to synthesise real-world evidence to inform the management of XLH, to improve the quality of life and standard of care of patients living with this rare debilitating disease.
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Affiliation(s)
- Raja Padidela
- Royal Manchester Children's Hospital and Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Ola Nilsson
- Karolinska Institutet, Stockholm, Sweden
- Örebro University, Örebro, Sweden
| | - Outi Makitie
- Children's Hospital, Pediatric Research Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | | | - Gema Ariceta
- Hospital Vall d'Hebron, Universitat Autonoma Barcelona, Barcelona, Spain
| | - Dirk Schnabel
- Center for Chronic Sick Children, Pediatric Endocrinology, Charité, University Medicine Berlin, Berlin, Germany
| | | | | | | | | | | | - Zulf Mughal
- Royal Manchester Children's Hospital and Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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28
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Menon LP, Weinstein RS. Iron replacement ameliorates hypophosphatemia in autosomal dominant hypophosphatemic rickets: A review of the role of iron. Bone 2020; 131:115137. [PMID: 31756522 DOI: 10.1016/j.bone.2019.115137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 10/14/2019] [Accepted: 11/01/2019] [Indexed: 01/08/2023]
Abstract
Autosomal dominant hypophosphatemic rickets (ADHR) is remarkable among the hypophosphatemic rickets syndromes for its variable age of presentation and periods of quiescence during which serum phosphate and fibroblast growth factor 23 (FGF 23) levels are normal without therapy. In contrast, hypophosphatemia in X-linked hypophosphatemic rickets (XLH) manifests soon after birth and requires lifelong therapy. This suggests that there are environmental factors which can alter FGF 23 activity in ADHR but not in XLH. We present an adult with ADHR in whom resolution of hypophosphatemia was achieved by correcting iron deficiency without the need for phosphate supplementation. Serial iron and FGF 23 levels revealed an inverse relationship (r=-0.79, p<0.04). All patients with ADHR who present with hypophosphatemia and worsening symptoms should be screened for iron deficiency. If iron deficiency is detected, therapy with a combination of calcitriol and iron supplementation should be considered without phosphate supplementation.
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Affiliation(s)
- Lakshmi P Menon
- Division of Endocrinology and Metabolism, Center for Osteoporosis and Metabolic Bone Diseases, Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America
| | - Robert S Weinstein
- Division of Endocrinology and Metabolism, Center for Osteoporosis and Metabolic Bone Diseases, Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, United States of America.
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29
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Abstract
The term uraemic cardiomyopathy refers to the cardiac abnormalities that are seen in patients with chronic kidney disease (CKD). Historically, this term was used to describe a severe cardiomyopathy that was associated with end-stage renal disease and characterized by severe functional abnormalities that could be reversed following renal transplantation. In a modern context, uraemic cardiomyopathy describes the clinical phenotype of cardiac disease that accompanies CKD and is perhaps best characterized as diastolic dysfunction seen in conjunction with left ventricular hypertrophy and fibrosis. A multitude of factors may contribute to the pathogenesis of uraemic cardiomyopathy, and current treatments only modestly improve outcomes. In this Review, we focus on evolving concepts regarding the roles of fibroblast growth factor 23 (FGF23), inflammation and systemic oxidant stress and their interactions with more established mechanisms such as pressure and volume overload resulting from hypertension and anaemia, respectively, activation of the renin-angiotensin and sympathetic nervous systems, activation of the transforming growth factor-β (TGFβ) pathway, abnormal mineral metabolism and increased levels of endogenous cardiotonic steroids.
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Affiliation(s)
- Xiaoliang Wang
- Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, USA
| | - Joseph I Shapiro
- Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, USA.
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30
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Abstract
Chronic kidney disease (CKD) is a global health epidemic that accelerates cardiovascular disease, increases risk of infection, and causes anemia and bone disease, among other complications that collectively increase risk of premature death. Alterations in calcium and phosphate homeostasis have long been considered nontraditional risk factors for many of the most morbid outcomes of CKD. The discovery of fibroblast growth factor 23 (FGF23), which revolutionized the diagnosis and treatment of rare hereditary disorders of FGF23 excess that cause hypophosphatemic rickets, has also driven major paradigm shifts in our understanding of the pathophysiology and downstream end-organ complications of disordered mineral metabolism in CKD. As research of FGF23 in CKD has rapidly advanced, major new questions about its regulation and effects continuously emerge. These are promoting exciting innovations in laboratory, patient-oriented, and epidemiological research and stimulating clinical trials of new therapies and repurposing of existing ones to target FGF23.
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Affiliation(s)
- John Musgrove
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina 27710, USA;
| | - Myles Wolf
- Division of Nephrology, Department of Medicine, Duke University School of Medicine, Durham, North Carolina 27710, USA; .,Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina 27710, USA
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31
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Liu C, Zhao Z, Wang O, Li M, Xing X, Hsieh E, Fukumoto S, Jiang Y, Xia W. Earlier Onset in Autosomal Dominant Hypophosphatemic Rickets of R179 than R176 Mutations in Fibroblast Growth Factor 23: Report of 20 Chinese Cases and Review of the Literature. Calcif Tissue Int 2019; 105:476-486. [PMID: 31486862 DOI: 10.1007/s00223-019-00597-y] [Citation(s) in RCA: 10] [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: 09/24/2018] [Accepted: 08/10/2019] [Indexed: 01/20/2023]
Abstract
Autosomal dominant hypophosphatemic rickets (ADHR) is a rare hereditary disorder characterized by variant onset ages and diverse phenotypes. Our aim is to explore the genotype-phenotype correlations between ADHR patients with R176 and R179 mutations in FGF23 gene. Clinical manifestations, laboratory examinations, and genetic analyses were collected from 20 patients in six Chinese ADHR kindreds in our hospital. Previously published ADHR literatures were reviewed. Among 20 Chinese ADHR mutation carriers, 11 patients revealed overt symptoms. 10/11 (90.9%) of which were females. Patients with R179 mutations presented with earlier onset than those with R176 mutation [1.3 (1.0, 37.0) years vs. 28.5 (19.0, 44.0) years]. More patients with R179 mutations had a history of rickets with lower extremity deformity [3/4 (75%) vs. 1/7 (14.3%), p < 0.05]. The serum phosphate, i-FGF23 and c-FGF23 levels of patients with R179 and R176 mutations were 0.47 ± 0.14 mmol/L versus 0.57 ± 0.17 mmol/L, 79.6 ± 87.0 pg/mL versus 79.9 ± 107.4 pg/mL, and 33.4 ± 3.0 RU/mL versus 121.3 ± 177.6 RU/mL, respectively. 7/11 of patients had iron deficiency at onset of disease. When combined with previously reported seven ADHR families, difference was observed in the age of onset among symptomatic patients with R179 and R176 mutations [1.0 (0.9, 37.0) years vs. 24.5 (1.2, 57.0) years, p < 0.05]. Patients with R179 mutation were more likely to have rickets than R176 mutation (11/13, 84.6% vs. 5/20, 25.0%, p < 0.01) and lower extremity deformity (10/13, 76.9% vs. 6/19, 31.6%, p < 0.01). ADHR patients with R179 mutations had earlier onset age and more rickets compared to those with mutations in R176, which partially explained the clinical heterogeneity of ADHR.
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Affiliation(s)
- Chang Liu
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Zhen Zhao
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Ou Wang
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Mei Li
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Xiaoping Xing
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China
| | - Evelyn Hsieh
- Section of Rheumatology, Department of Internal Medicine, Yale School of Medicine, New Haven, USA
| | - Seiji Fukumoto
- Fujii Memorial Institute of Medical Sciences, Tokushima, Japan
| | - Yan Jiang
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China.
| | - Weibo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, 100730, China.
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32
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Lerch C, Shroff R, Wan M, Rees L, Aitkenhead H, Kaplan Bulut I, Thurn D, Karabay Bayazit A, Niemirska A, Canpolat N, Duzova A, Azukaitis K, Yilmaz E, Yalcinkaya F, Harambat J, Kiyak A, Alpay H, Habbig S, Zaloszyc A, Soylemezoglu O, Candan C, Rosales A, Melk A, Querfeld U, Leifheit-Nestler M, Sander A, Schaefer F, Haffner D. Effects of nutritional vitamin D supplementation on markers of bone and mineral metabolism in children with chronic kidney disease. Nephrol Dial Transplant 2019; 33:2208-2217. [PMID: 29481636 DOI: 10.1093/ndt/gfy012] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 12/14/2017] [Indexed: 12/13/2022] Open
Abstract
Background We investigated the effects of nutritional vitamin D supplementation on markers of bone and mineral metabolism, i.e. serum levels of fibroblast growth factor 23 (FGF23), Klotho, bone alkaline phosphatase (BAP) and sclerostin, in two cohorts with chronic kidney disease (CKD). Methods In all, 80 vitamin D-deficient children were selected: 40 with mild to moderate CKD from the ERGO study, a randomized trial of ergocalciferol supplementation [estimated glomerular filtration rate (eGFR) 55 mL/min/1.73 m2], and 40 with advanced CKD from the observational Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) study (eGFR 24 mL/min/1.73 m2). In each study, vitamin D supplementation was started in 20 children and 20 matched children not receiving vitamin D served as controls. Measures were taken at baseline and after a median period of 8 months. Age- and gender-related standard deviation scores (SDSs) were calculated. Results Before vitamin D supplementation, children in the ERGO study had normal FGF23 (median 0.31 SDS) and BAP (-0.10 SDS) but decreased Klotho and sclerostin (-0.77 and -1.04 SDS, respectively), whereas 4C patients had increased FGF23 (3.87 SDS), BAP (0.78 SDS) and sclerostin (0.76 SDS) but normal Klotho (-0.27 SDS) levels. Vitamin D supplementation further increased FGF23 in 4C but not in ERGO patients. Serum Klotho and sclerostin normalized with vitamin D supplementation in ERGO but remained unchanged in 4C patients. BAP levels were unchanged in all patients. In the total cohort, significant effects of vitamin D supplementation were noted for Klotho at eGFR 40-70 mL/min/1.73 m2. Conclusions Vitamin D supplementation normalized Klotho and sclerostin in children with mild to moderate CKD but further increased FGF23 in advanced CKD.
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Affiliation(s)
- Christian Lerch
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School Children's Hospital, Hannover, Germany
| | - Rukshana Shroff
- Renal Unit, Great Ormond Street Hospital for Children, London, UK
| | - Mandy Wan
- Renal Unit, Great Ormond Street Hospital for Children, London, UK
| | - Lesley Rees
- Renal Unit, Great Ormond Street Hospital for Children, London, UK
| | - Helen Aitkenhead
- Department of Chemical Pathology, Great Ormond Street Hospital for Children, London, UK
| | - Ipek Kaplan Bulut
- Department of Pediatric Nephrology, Ege University, Bornova, Izmir, Turkey
| | - Daniela Thurn
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School Children's Hospital, Hannover, Germany
| | - Aysun Karabay Bayazit
- Department of Pediatric Nephrology, Faculty of Medicine, Cukurova University, Adana, Turkey
| | - Anna Niemirska
- Department of Nephrology, Kidney Transplantation and Arterial Hypertension, Children's Memorial Health Institute, Warsaw, Poland
| | - Nur Canpolat
- Department of Pediatrics, Istanbul University Cerrahpasa Faculty of Medicine, Istanbul, Turkey
| | - Ali Duzova
- Division of Pediatric Nephrology, Hacettepe University, Faculty of Medicine, Ankara, Turkey
| | - Karolis Azukaitis
- Clinic of Pediatrics, Faculty of Medicine, Vilnius University, Vilnius, Lithuania
| | - Ebru Yilmaz
- Department of Pediatric Nephrology, Sanliurfa Children's Hospital, Sanliurfa, Turkey
| | - Fatos Yalcinkaya
- Department of Pediatric Nephrology, School of Medicine, Ankara University, Ankara, Turkey
| | - Jerome Harambat
- Department of Pediatrics, Bordeaux University Hospital, Bordeaux, France
| | - Aysel Kiyak
- Department of Pediatric Nephrology, Yenimahalle Egitim ve Arastirma Hastanesi Bakirkoy, Istanbul, Turkey
| | - Harika Alpay
- Department of Pediatric Nephrology, Marmara University School of Medicine, Istanbul, Turkey
| | - Sandra Habbig
- Division of Pediatric Nephrology, University Children's and Adolescent's Hospital, Cologne, Germany
| | - Ariane Zaloszyc
- Pole Médico-Chirurgical de Pédiatrie, Service de Pédiatrie I, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Oguz Soylemezoglu
- Department of Pediatric Nephrology, Gazi University Hospital, Ankara, Turkey
| | - Cengiz Candan
- Department of Pediatric Nephrology, Göztepe Egitim ve Arastirma Hastanesi, Cocuk Klinigi, Göztepe, Istanbul, Turkey
| | - Alejandra Rosales
- Department of Pediatrics, Innsbruck Medical University, Innsbruck, Austria
| | - Anette Melk
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School Children's Hospital, Hannover, Germany
| | - Uwe Querfeld
- Clinic of Pediatric Nephrology, Charite Children's Hospital, Berlin, Germany
| | - Maren Leifheit-Nestler
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School Children's Hospital, Hannover, Germany
| | - Anja Sander
- Institute of Medical Biometry and Informatics, University Heidelberg, Heidelberg, Germany
| | | | - Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School Children's Hospital, Hannover, Germany
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Huang J, Bao X, Xia W, Zhu L, Zhang J, Ma J, Jiang N, Yang J, Chen Q, Jing T, Liu J, Ma D, Xu G. Functional analysis of a de novo mutation c.1692 del A of the PHEX gene in a Chinese family with X-linked hypophosphataemic rickets. Bone Joint Res 2019; 8:405-413. [PMID: 31537998 PMCID: PMC6719531 DOI: 10.1302/2046-3758.88.bjr-2018-0276.r1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Objectives X-linked hypophosphataemic rickets (XLHR) is a disease of impaired bone mineralization characterized by hypophosphataemia caused by renal phosphate wasting. The main clinical manifestations of the disorder are O-shaped legs, X-shaped legs, delayed growth, and bone pain. XLHR is the most common inheritable form of rickets, with an incidence of 1/20 000 in humans. It accounts for approximately 80% of familial cases of hypophosphataemia and serves as the prototype of defective tubular phosphate (PO43+) transport, due to extra renal defects resulting in unregulated FGF23 activity. XLHR is caused by loss-of-function mutations in the PHEX gene. The aim of this research was to identify the genetic defect responsible for familial hypophosphataemic rickets in a four-generation Chinese Han pedigree and to analyze the function of this mutation. Methods The genome DNA samples of all members in the pedigree were extracted from whole blood. We sequenced all exons of the PHEX and FGF23 genes, as well as the adjacent splice site sequence with Sanger sequencing. Next, we analyzed the de novo mutation c.1692 del A of the PHEX gene with an online digital service and investigated the mutant PHEX with SWISS-MODEL, immunofluorescence, and protein stability detection. Results Through Sanger sequencing, we found a de novo mutation, c.1692 del A, in exon 16 of the PHEX gene in this pedigree. This mutation can make the PHEX protein become unstable and decay rapidly, which results in familial XLHR. Conclusion We have found a de novo loss-of-function mutation, c.1692 del A, in exon 16 of the PHEX gene that can cause XLHR. Cite this article: J. Huang, X. Bao, W. Xia, L. Zhu, J. Zhang, J. Ma, N. Jiang, J. Yang, Q. Chen, T. Jing, J. Liu, D. Ma, G. Xu. Functional analysis of a de novo mutation c.1692 del A of the PHEX gene in a Chinese family with X-linked hypophosphataemic rickets. Bone Joint Res 2019;8:405–413. DOI: 10.1302/2046-3758.88.BJR-2018-0276.R1.
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Affiliation(s)
- Jianbo Huang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Xiaogang Bao
- Department of Orthopedic Surgery, The Spine Surgical Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Wenjun Xia
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Lingjun Zhu
- Department of Orthopedic Surgery, The Spine Surgical Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Jin Zhang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Jing Ma
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Nan Jiang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Jichun Yang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Qing Chen
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Tianrui Jing
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Jia Liu
- Department of Orthopedic Surgery, The Spine Surgical Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Duan Ma
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China; Research Center for Birth Defects, Institutes of Biomedical Sciences, Fudan University, Shanghai, China
| | - Guohua Xu
- Department of Orthopedic Surgery, The Spine Surgical Center, Changzheng Hospital, Second Military Medical University, Shanghai, China
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Abstract
Fibroblast growth factor 23 (FGF23), one of the endocrine fibroblast growth factors, is a principal regulator in the maintenance of serum phosphorus concentration. Binding to its cofactor αKlotho and a fibroblast growth factor receptor is essential for its activity. Its regulation and interaction with other factors in the bone-parathyroid-kidney axis is complex. FGF23 reduces serum phosphorus concentration through decreased reabsorption of phosphorus in the kidney and by decreasing 1,25 dihydroxyvitamin D (1,25(OH)2D) concentrations. Various FGF23-mediated disorders of renal phosphate wasting share similar clinical and biochemical features. The most common of these is X-linked hypophosphatemia (XLH). Additional disorders of FGF23 excess include autosomal dominant hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets, fibrous dysplasia, and tumor-induced osteomalacia. Treatment is challenging, requiring careful monitoring and titration of dosages to optimize effectiveness and to balance side effects. Conventional therapy for XLH and other disorders of FGF23-mediated hypophosphatemia involves multiple daily doses of oral phosphate salts and active vitamin D analogs, such as calcitriol or alfacalcidol. Additional treatments may be used to help address side effects of conventional therapy such as thiazides to address hypercalciuria or nephrocalcinosis, and calcimimetics to manage hyperparathyroidism. The recent development and approval of an anti-FGF23 antibody, burosumab, for use in XLH provides a novel treatment option.
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Affiliation(s)
- Anisha Gohil
- Indiana University School of Medicine, Riley Hospital for Children, Fellow, Endocrinology and Diabetes, 705 Riley Hospital Drive, Room 5960, Indianapolis, IN 46202, USA, E-mail:
| | - Erik A Imel
- Indiana University School of Medicine, Riley Hospital for Children, Associate Professor of Medicine and Pediatrics, 1120 West Michigan Street, CL 459, Indianapolis, IN 46202, USA
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Czaya B, Faul C. The Role of Fibroblast Growth Factor 23 in Inflammation and Anemia. Int J Mol Sci 2019; 20:E4195. [PMID: 31461904 PMCID: PMC6747522 DOI: 10.3390/ijms20174195] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 02/07/2023] Open
Abstract
In patients with chronic kidney disease (CKD), adverse outcomes such as systemic inflammation and anemia are contributing pathologies which increase the risks for cardiovascular mortality. Amongst these complications, abnormalities in mineral metabolism and the metabolic milieu are associated with chronic inflammation and iron dysregulation, and fibroblast growth factor 23 (FGF23) is a risk factor in this context. FGF23 is a bone-derived hormone that is essential for regulating vitamin D and phosphate homeostasis. In the early stages of CKD, serum FGF23 levels rise 1000-fold above normal values in an attempt to maintain normal phosphate levels. Despite this compensatory action, clinical CKD studies have demonstrated powerful and dose-dependent associations between FGF23 levels and higher risks for mortality. A prospective pathomechanism coupling elevated serum FGF23 levels with CKD-associated anemia and cardiovascular injury is its strong association with chronic inflammation. In this review, we will examine the current experimental and clinical evidence regarding the role of FGF23 in renal physiology as well as in the pathophysiology of CKD with an emphasis on chronic inflammation and anemia.
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Affiliation(s)
- Brian Czaya
- Division of Nephrology, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Christian Faul
- Division of Nephrology, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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Barnes JW, Duncan D, Helton S, Hutcheson S, Kurundkar D, Logsdon NJ, Locy M, Garth J, Denson R, Farver C, Vo HT, King G, Kentrup D, Faul C, Kulkarni T, De Andrade JA, Yu Z, Matalon S, Thannickal VJ, Krick S. Role of fibroblast growth factor 23 and klotho cross talk in idiopathic pulmonary fibrosis. Am J Physiol Lung Cell Mol Physiol 2019; 317:L141-L154. [PMID: 31042083 PMCID: PMC6689746 DOI: 10.1152/ajplung.00246.2018] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 04/10/2019] [Accepted: 04/28/2019] [Indexed: 01/24/2023] Open
Abstract
Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing interstitial pneumonia that mainly affects the elderly. Several reports have demonstrated that aging is involved in the underlying pathogenic mechanisms of IPF. α-Klotho (KL) has been well characterized as an "age-suppressing" hormone and can provide protection against cellular senescence and oxidative stress. In this study, KL levels were assessed in human plasma and primary lung fibroblasts from patients with idiopathic pulmonary fibrosis (IPF-FB) and in lung tissue from mice exposed to bleomycin, which showed significant downregulation when compared with controls. Conversely, transgenic mice overexpressing KL were protected against bleomycin-induced lung fibrosis. Treatment of human lung fibroblasts with recombinant KL alone was not sufficient to inhibit transforming growth factor-β (TGF-β)-induced collagen deposition and inflammatory marker expression. Interestingly, fibroblast growth factor 23 (FGF23), a proinflammatory circulating protein for which KL is a coreceptor, was upregulated in IPF and bleomycin lungs. To our surprise, FGF23 and KL coadministration led to a significant reduction in fibrosis and inflammation in IPF-FB; FGF23 administration alone or in combination with KL stimulated KL upregulation. We conclude that in IPF downregulation of KL may contribute to fibrosis and inflammation and FGF23 may act as a compensatory antifibrotic and anti-inflammatory mediator via inhibition of TGF-β signaling. Upon restoration of KL levels, the combination of FGF23 and KL leads to resolution of inflammation and fibrosis. Altogether, these data provide novel insight into the FGF23/KL axis and its antifibrotic/anti-inflammatory properties, which opens new avenues for potential therapies in aging-related diseases like IPF.
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Affiliation(s)
- Jarrod W Barnes
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Dawn Duncan
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Scott Helton
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Samuel Hutcheson
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Deepali Kurundkar
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Naomi J Logsdon
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Morgan Locy
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Jaleesa Garth
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Rebecca Denson
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Carol Farver
- Department of Pathology, Cleveland Clinic , Cleveland, Ohio
| | - Hai T Vo
- Department of Neurobiology, The University of Alabama at Birmingham , Birmingham, Alabama
| | - Gwendalyn King
- Department of Neurobiology, The University of Alabama at Birmingham , Birmingham, Alabama
| | - Dominik Kentrup
- Division of Nephrology and Hypertension, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Christian Faul
- Division of Nephrology and Hypertension, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Tejaswini Kulkarni
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Joao A De Andrade
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
- Birmingham VA Medical Center , Birmingham, Alabama
| | - Zhihong Yu
- Department of Anesthesiology and Perioperative Medicine (Molecular and Translational Biomedicine), University of Alabama , Birmingham, Alabama
| | - Sadis Matalon
- Department of Anesthesiology and Perioperative Medicine (Molecular and Translational Biomedicine), University of Alabama , Birmingham, Alabama
| | - Victor J Thannickal
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
| | - Stefanie Krick
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama , Birmingham, Alabama
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van Vuren AJ, Gaillard CAJM, Eisenga MF, van Wijk R, van Beers EJ. The EPO-FGF23 Signaling Pathway in Erythroid Progenitor Cells: Opening a New Area of Research. Front Physiol 2019; 10:304. [PMID: 30971944 PMCID: PMC6443968 DOI: 10.3389/fphys.2019.00304] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/07/2019] [Indexed: 12/14/2022] Open
Abstract
We provide an overview of the evidence for an erythropoietin-fibroblast growth factor 23 (FGF23) signaling pathway directly influencing erythroid cells in the bone marrow. We outline its importance for red blood cell production, which might add, among others, to the understanding of bone marrow responses to endogenous erythropoietin in rare hereditary anemias. FGF23 is a hormone that is mainly known as the core regulator of phosphate and vitamin D metabolism and it has been recognized as an important regulator of bone mineralization. Osseous tissue has been regarded as the major source of FGF23. Interestingly, erythroid progenitor cells highly express FGF23 protein and carry the FGF receptor. This implies that erythroid progenitor cells could be a prime target in FGF23 biology. FGF23 is formed as an intact, biologically active protein (iFGF23) and proteolytic cleavage results in the formation of the presumed inactive C-terminal tail of FGF23 (cFGF23). FGF23-knockout or injection of an iFGF23 blocking peptide in mice results in increased erythropoiesis, reduced erythroid cell apoptosis and elevated renal and bone marrow erythropoietin mRNA expression with increased levels of circulating erythropoietin. By competitive inhibition, a relative increase in cFGF23 compared to iFGF23 results in reduced FGF23 receptor signaling and mimics the positive effects of FGF23-knockout or iFGF23 blocking peptide. Injection of recombinant erythropoietin increases FGF23 mRNA expression in the bone marrow with a concomitant increase in circulating FGF23 protein. However, erythropoietin also augments iFGF23 cleavage, thereby decreasing the iFGF23 to cFGF23 ratio. Therefore, the net result of erythropoietin is a reduction of iFGF23 to cFGF23 ratio, which inhibits the effects of iFGF23 on erythropoiesis and erythropoietin production. Elucidation of the EPO-FGF23 signaling pathway and its downstream signaling in hereditary anemias with chronic hemolysis or ineffective erythropoiesis adds to the understanding of the pathophysiology of these diseases and its complications; in addition, it provides promising new targets for treatment downstream of erythropoietin in the signaling cascade.
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Affiliation(s)
- Annelies J van Vuren
- Van Creveldkliniek, Department of Internal Medicine and Dermatology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Carlo A J M Gaillard
- Department of Internal Medicine and Dermatology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Michele F Eisenga
- Department of Internal Medicine, Division of Nephrology, University Medical Center Groningen, University of Groningen, Groningen, Netherlands
| | - Richard van Wijk
- Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Eduard J van Beers
- Van Creveldkliniek, Department of Internal Medicine and Dermatology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
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Fauconnier C, Roy T, Gillerot G, Roy C, Pouleur AC, Gruson D. FGF23: Clinical usefulness and analytical evolution. Clin Biochem 2019; 66:1-12. [PMID: 30853324 DOI: 10.1016/j.clinbiochem.2019.03.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 02/05/2019] [Accepted: 03/05/2019] [Indexed: 12/16/2022]
Abstract
Fibroblast Growth Factor 23 (FGF23) is a key hormone for the regulation of phosphate homeostasis. Over the past decades, FGF23 was the subject of intense research in the fields of nephrology and the cardiology. It presents a remarkable correlation with well-established biomarkers of cardiovascular disorders in both chronic kidney disease (CKD) and heart failure (HF) patients. The interest of FGF23 lies in its early-onset in the primary course of CKD as well as in the incremental prognosis information it conveys in both CKD and HF. Different types of assays of FGF-23 testing exist, those targeting the intact form (iFGF23), the other one detecting terminal fragments (cFGF23). The issue is still pending which assay suits best for clinical use. Recently, the implementation of this biomarker on multianalyzer platforms, on which other markers of phospho-calcic balance are set up, allows a rapid turn-around-time and a potential financial gain. However, despite the good analytical performances of the automated methods, there is a poor harmonization between assays. The introduction of an international certified reference material should standardize the measurement and improve the harmonization of results from different laboratories. A deeper understanding of physio-pathological mechanisms and processing of FGF-23 should reinforce its clinical indications and might also identify new therapeutic targets for the treatment of CKD and HF.
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Affiliation(s)
- Charlotte Fauconnier
- Department of Laboratory Medicine, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Tatiana Roy
- Department of Laboratory Medicine, Clinique Saint-Pierre Ottignies, Belgium
| | - Gaëlle Gillerot
- Nephrology Department, Clinique Saint-Pierre Ottignies, Belgium
| | - Clotilde Roy
- Division of Cardiology, Department of Cardiovascular Diseases, Cliniques Universitaires St. Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Anne-Catherine Pouleur
- Division of Cardiology, Department of Cardiovascular Diseases, Cliniques Universitaires St. Luc, Université Catholique de Louvain, Brussels, Belgium
| | - Damien Gruson
- Department of Laboratory Medicine, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Brussels, Belgium; Pôle de recherche en endocrinologie, diabète et nutrition, Institut de recherche expérimentale et clinique, Cliniques universitaires Saint-Luc et Université catholique de Louvain, Bruxelles, Belgium.
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Beck-Nielsen SS, Mughal Z, Haffner D, Nilsson O, Levtchenko E, Ariceta G, de Lucas Collantes C, Schnabel D, Jandhyala R, Mäkitie O. FGF23 and its role in X-linked hypophosphatemia-related morbidity. Orphanet J Rare Dis 2019; 14:58. [PMID: 30808384 PMCID: PMC6390548 DOI: 10.1186/s13023-019-1014-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 01/30/2019] [Indexed: 12/29/2022] Open
Abstract
Background X-linked hypophosphatemia (XLH) is an inherited disease of phosphate metabolism in which inactivating mutations of the Phosphate Regulating Endopeptidase Homolog, X-Linked (PHEX) gene lead to local and systemic effects including impaired growth, rickets, osteomalacia, bone abnormalities, bone pain, spontaneous dental abscesses, hearing difficulties, enthesopathy, osteoarthritis, and muscular dysfunction. Patients with XLH present with elevated levels of fibroblast growth factor 23 (FGF23), which is thought to mediate many of the aforementioned manifestations of the disease. Elevated FGF23 has also been observed in many other diseases of hypophosphatemia, and a range of animal models have been developed to study these diseases, yet the role of FGF23 in the pathophysiology of XLH is incompletely understood. Methods The role of FGF23 in the pathophysiology of XLH is here reviewed by describing what is known about phenotypes associated with various PHEX mutations, animal models of XLH, and non-nutritional diseases of hypophosphatemia, and by presenting molecular pathways that have been proposed to contribute to manifestations of XLH. Results The pathophysiology of XLH is complex, involving a range of molecular pathways that variously contribute to different manifestations of the disease. Hypophosphatemia due to elevated FGF23 is the most obvious contributor, however localised fluctuations in tissue non-specific alkaline phosphatase (TNAP), pyrophosphate, calcitriol and direct effects of FGF23 have been observed to be associated with certain manifestations. Conclusions By describing what is known about these pathways, this review highlights key areas for future research that would contribute to the understanding and clinical treatment of non-nutritional diseases of hypophosphatemia, particularly XLH.
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Affiliation(s)
| | - Zulf Mughal
- Royal Manchester Children's Hospital, Manchester, UK
| | | | - Ola Nilsson
- Karolinska Institutet, Stockholm, Sweden and Örebro University, Örebro, Sweden
| | | | - Gema Ariceta
- Hospital Universitario Materno-Infantil Vall d'Hebron, Universitat Autonoma de Barcelona, Barcelona, Spain
| | | | - Dirk Schnabel
- University Children's Hospital of Berlin, Berlin, Germany
| | | | - Outi Mäkitie
- Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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Weber TJ, Quarles LD. Molecular Control of Phosphorus Homeostasis and Precision Treatment of Hypophosphatemic Disorders. ACTA ACUST UNITED AC 2019; 5:75-85. [PMID: 31871877 DOI: 10.1007/s40610-019-0118-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Purpose of Review Serum phosphorus is maintained in a narrow range by balancing dietary phosphate absorption, influx and efflux of phosphorus from bone and intracellular stores, and renal reabsorption of filtered phosphate. Acute hypophosphatemia, typically caused by transient increases in cellular uptake, can lead to severe complications such as cardiopulmonary dysfunction and rhabdomyolysis that can warrant parenteral phosphate repletion. Chronic hypophosphatemia, however, generally represents true phosphate deficiency and may result in long-term metabolic and skeletal complications, particularly in children due to the critical importance of phosphorus to skeletal mineralization and longitudinal growth. Recent Findings In addition to the well characterized roles of vitamin D and parathyroid hormone (PTH), a new bone-kidney axis has been discovered that regulates phosphate homeostasis through the bone-derived hormone Fibroblast Growth Factor 23 (FGF23) and its phosphaturic actions that are mediated by activation of fibroblast growth factor receptors (FGFRs) complexed with α-Klotho in renal tubules. Chronic hypophosphatemia can now be classified as FGF23 dependent or independent. Summary In cases of FGF23 dependent hypophosphatemia, traditional non-specific treatments with elemental phosphorus and 1,25(OH)2 vitamin D (calcitriol) can now be replaced with a targeted approach by using an FGF-23 blocking antibody (Burosumab).
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Affiliation(s)
- Thomas J Weber
- Department of Medicine, Division of Endocrinology, Metabolism and Nutrition, 303 Baker House, DUMC 3470, Duke University Medical Center, Durham, NC 27710
| | - L Darryl Quarles
- Department of Medicine, Division of Nephrology 956 Court Ave, Suite B266, University of Tennessee Health Sciences Center, Memphis, TN 38163
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Abstract
Our understanding of the regulation of phosphate balance has benefited tremendously from the molecular identification and characterization of genetic defects leading to a number of rare inherited or acquired disorders affecting phosphate homeostasis. The identification of the key phosphate-regulating hormone, fibroblast growth factor 23 (FGF23), as well as other molecules that control its production, such as the glycosyltransferase GALNT3, the endopeptidase PHEX, and the matrix protein DMP1, and molecules that function as downstream effectors of FGF23 such as the longevity factor Klotho and the phosphate transporters NPT2a and NPT2c, has permitted us to understand the complex interplay that exists between the kidneys, bone, parathyroid, and gut. Such insights from genetic disorders have allowed not only the design of potent targeted treatment of FGF23-dependent hypophosphatemic conditions, but also provide clinically relevant observations related to the dysregulation of mineral ion homeostasis in health and disease.
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Affiliation(s)
- Marta Christov
- Division of Nephrology, Department of Medicine, New York Medical College, Valhalla, NY, USA
| | - Harald Jüppner
- Endocrine Unit and Pediatric Nephrology Unit, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
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Abstract
Rickets refers to deficient mineralization at the growth plate and is usually associated with abnormal serum calcium and/or phosphate. There are several subtypes of rickets, including hypophosphatemic rickets (vitamin-D-resistant rickets secondary to renal phosphate wasting), vitamin D-dependent rickets (defects of vitamin D metabolism) and nutritional rickets (caused by dietary deficiency of vitamin D, and/or calcium, and/or phosphate). Most rickets manifest as bone deformities, bone pain, and impaired growth velocity. Diagnosis of rickets is established through the medical history, physical examination, biochemical tests and radiographs. It is of crucial importance to determine the cause of rickets, including the molecular characterization in case of vitamin D resistant rickets, and initiate rapidly the appropriate therapy. In this review, we describe the different causes and therapies of genetic and nutritional rickets, supported by the recent progress in genetics and development of novel molecules such as anti-FGF23 antibody.
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Affiliation(s)
- A S Lambert
- APHP, Department of Pediatric Endocrinology and Diabetology for Children, Bicêtre Paris-Sud, Le Kremlin-Bicêtre, France; APHP, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Filière OSCAR and Plateforme D'Expertise Maladies Rares Paris-Sud, Bicêtre Paris-Sud, Le Kremlin Bicêtre, France.
| | - A Linglart
- APHP, Department of Pediatric Endocrinology and Diabetology for Children, Bicêtre Paris-Sud, Le Kremlin-Bicêtre, France; APHP, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Filière OSCAR and Plateforme D'Expertise Maladies Rares Paris-Sud, Bicêtre Paris-Sud, Le Kremlin Bicêtre, France
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Krick S, Grabner A, Baumlin N, Yanucil C, Helton S, Grosche A, Sailland J, Geraghty P, Viera L, Russell DW, Wells JM, Xu X, Gaggar A, Barnes J, King GD, Campos M, Faul C, Salathe M. Fibroblast growth factor 23 and Klotho contribute to airway inflammation. Eur Respir J 2018; 52:1800236. [PMID: 29748308 PMCID: PMC6044452 DOI: 10.1183/13993003.00236-2018] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Accepted: 04/27/2018] [Indexed: 01/20/2023]
Abstract
Circulating levels of fibroblast growth factor (FGF)23 are associated with systemic inflammation and increased mortality in chronic kidney disease. α-Klotho, a co-receptor for FGF23, is downregulated in chronic obstructive pulmonary disease (COPD). However, whether FGF23 and Klotho-mediated FGF receptor (FGFR) activation delineates a pathophysiological mechanism in COPD remains unclear. We hypothesised that FGF23 can potentiate airway inflammation via Klotho-independent FGFR4 activation.FGF23 and its effect were studied using plasma and transbronchial biopsies from COPD and control patients, and primary human bronchial epithelial cells isolated from COPD patients as well as a murine COPD model.Plasma FGF23 levels were significantly elevated in COPD patients. Exposure of airway epithelial cells to cigarette smoke and FGF23 led to a significant increase in interleukin-1β release via Klotho-independent FGFR4-mediated activation of phospholipase Cγ/nuclear factor of activated T-cells signalling. In addition, Klotho knockout mice developed COPD and showed airway inflammation and elevated FGFR4 expression in their lungs, whereas overexpression of Klotho led to an attenuation of airway inflammation.Cigarette smoke induces airway inflammation by downregulation of Klotho and activation of FGFR4 in the airway epithelium in COPD. Inhibition of FGF23 or FGFR4 might serve as a novel anti-inflammatory strategy in COPD.
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Affiliation(s)
- Stefanie Krick
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Alexander Grabner
- Division of Nephrology, Department of Medicine, Duke University Medical Center, Duke University, Durham, USA
| | - Nathalie Baumlin
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL 33136, USA
| | - Christopher Yanucil
- Division of Nephrology, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Scott Helton
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Astrid Grosche
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL 33136, USA
| | - Juliette Sailland
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL 33136, USA
| | - Patrick Geraghty
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, State University of New York Downstate Medical Center, Brooklyn, NY, USA
| | - Liliana Viera
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Derek W. Russell
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - J. Michael Wells
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
- UAB Lung Health Center, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Xin Xu
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Amit Gaggar
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jarrod Barnes
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Gwendalyn D. King
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Michael Campos
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL 33136, USA
| | - Christian Faul
- Division of Nephrology, Department of Medicine, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Matthias Salathe
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL 33136, USA
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Leifheit-Nestler M, Grabner A, Hermann L, Richter B, Schmitz K, Fischer DC, Yanucil C, Faul C, Haffner D. Vitamin D treatment attenuates cardiac FGF23/FGFR4 signaling and hypertrophy in uremic rats. Nephrol Dial Transplant 2018; 32:1493-1503. [PMID: 28339837 DOI: 10.1093/ndt/gfw454] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 12/06/2016] [Indexed: 11/13/2022] Open
Abstract
Background Vitamin D deficiency and excess of circulating fibroblast growth factor 23 (FGF23) contribute to cardiovascular mortality in patients with chronic kidney disease (CKD). FGF23 activates FGF receptor 4 and (FGFR4) calcineurin/nuclear factor of activated T cells (NFAT) signaling in cardiac myocytes, thereby causing left ventricular hypertrophy (LVH). Here, we determined if 1,25-dihydroxyvitamin D (calcitriol) inhibits FGF23-induced cardiac signaling and LVH. Methods 5/6 nephrectomized (5/6 Nx) rats were treated with different doses of calcitriol for 4 or 10 weeks and cardiac expression of FGF23/FGFR4 and activation of calcineurin/NFAT as well as LVH were analyzed. FGFR4 activation and hypertrophic cell growth were studied in cultured cardiac myocytes that were co-treated with FGF23 and calcitriol. Results In 5/6Nx rats with LVH, we detected elevated FGF23 expression in bone and myocardium, increased cardiac expression of FGFR4 and elevated cardiac activation of calcineurin/NFAT signaling. Cardiac expression levels of FGF23 and FGFR4 significantly correlated with the presence of LVH in uremic rats. Treatment with calcitriol reduced LVH as well as cardiac FGFR4 expression and calcineurin/NFAT activation. Bone and cardiac FGF23 expression were further stimulated by calcitriol in a dose-dependent manner, but levels of intact cardiac FGF23 protein were suppressed by high-dose calcitriol. In cultured cardiac myocytes, co-treatment with calcitriol blocked FGF23-induced activation of FGFR4 and hypertrophic cell growth. Conclusions Our data suggest that in CKD, cardioprotective effects of calcitriol stem from its inhibitory actions on the cardiac FGF23/FGFR4 system, and based on their counterbalancing effects on cardiac myocytes, high FGF23 and low calcitriol synergistically contribute to cardiac hypertrophy.
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Affiliation(s)
- Maren Leifheit-Nestler
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Alexander Grabner
- Department of Medicine, Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Laura Hermann
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Beatrice Richter
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Karin Schmitz
- Department of Pediatrics, University Hospital Rostock, Rostock, Germany
| | | | - Christopher Yanucil
- Department of Medicine, Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, FL, USA.,Department of Cell Biology and Anatomy, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - Christian Faul
- Department of Medicine, Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, FL, USA.,Department of Cell Biology and Anatomy, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
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Maia MLDA, Abreu ALS, Nogueira PCK, Val MLDMD, Carvalhaes JTDA, Andrade MCD. HYPOPHOSPHATEMIC RICKETS: CASE REPORT. ACTA ACUST UNITED AC 2018; 36:242-247. [PMID: 29617471 PMCID: PMC6038795 DOI: 10.1590/1984-0462/;2018;36;2;00009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 05/16/2017] [Indexed: 11/22/2022]
Abstract
OBJECTIVE Early diagnosis and immediate treatment of hypophosphatemic rickets is of utmost importance as it may prevent subsequent sequelae. This report aims at warning pediatricians to consider the presence of the disease. CASE DESCRIPTION Description of the metabolic profile, creatinine clearance, nutritional status, weight and body structure of a patient who presented the clinical-laboratorial characteristics of hypophosphatemic rickets and was followed in an outpatient clinic for tubulopathies over the period of 12 months. The patient had been bedridden for some time, was dependent on mechanical ventilation and presented an altered metabolic bone condition. Treatment was phosphate (initial: 65 mg/kg/day and final: 24,2 mg/kg/day), calcium (initial: 127 mg/kg/day, final: 48,4 mg/kg/day) and calcitriol (initial: 0.06 mcg/kg/day, final: 0.03 mcg/kg/day). The patient improved, evolving into spontaneous breathing and walking unaided. Laboratory results: calcium (mg/dL) initial 7.1, final 10.1; phosphate (mg/dL) initial 1.7 final 3.2; magnesium (mg/dL) initial 1.5 final 2.1, parathyroid hormone (pg/l) initial 85.8, final 52.7, alkaline phosphatase (UI/l) initial 12660, final 938; there was also improvement in weight/structural development (Z score: H/A initial: -6.05, final -3.64; W/A: initial -2.92, final -1.57) with presence of transitory gallstones. Creatinine clearance (mL/min/1.73m2bsa) was constant. The medication improved his laboratory results and nutritional status, but the patient did not return for two years for follow-up and, during this period, his condition has noticeably deteriorated. COMMENTS Early diagnosis and follow-up are essential in dealing with this pathology.
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Shanbhogue VV, Hansen S, Jørgensen NR, Beck-Nielsen SS. Impact of Conventional Medical Therapy on Bone Mineral Density and Bone Turnover in Adult Patients with X-Linked Hypophosphatemia: A 6-Year Prospective Cohort Study. Calcif Tissue Int 2018; 102:321-328. [PMID: 29143140 DOI: 10.1007/s00223-017-0363-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 11/09/2017] [Indexed: 12/24/2022]
Abstract
X-linked hypophosphatemia (XLH) is a rare, inheritable disorder manifesting as rickets in children and osteomalacia in adults. While conventional medical treatment with oral phosphate and alfacalcidol is recommended in childhood, it is undecided whether adults should continue therapy. The aim of this 6-year prospective study was to determine the impact of conventional medical treatment on areal bone mineral density (aBMD), bone turnover markers (BTMs) and measures of calcium homeostasis in 27 adult patients with XLH, 11 of whom received medical treatment. Lumbar spine and total hip aBMD, as assessed by DXA, and biochemical measures of calcium, phosphate, PTH, 1,25 dihydroxyvitamin D2+3 (1,25(OH)2D), fibroblast growth factor 23 (FGF23), P1NP and CTX were measured at baseline and at follow-up. The renal tubular reabsorption of PO4 (TmPO4/GFR) was calculated at both time points. Multilevel mixed-effects linear regression models were used for analyses. During the study period, spine and hip aBMD did not change significantly between treated and non-treated XLH patients. There was a trend towards a decrease in calcium, phosphate and TmPO4/GFR in the treatment group (p = 0.057, p = 0.080 and p = 0.063, respectively), whereas PTH, FGF23, 1,25(OH)2D and P1NP did not change significantly in either groups. However, CTX increased significantly in the treated compared to non-treated group (p = 0.044). Continuing conventional medical therapy in adulthood, although associated with increased bone resorption, does not promote or prevent loss of bone mass as evidenced from the stable aBMD of the hip and spine in XLH patients.
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Affiliation(s)
- Vikram Vinod Shanbhogue
- Department of Endocrinology, Odense University Hospital, Odense, Denmark
- Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Stinus Hansen
- Department of Endocrinology, Odense University Hospital, Odense, Denmark
- Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Niklas Rye Jørgensen
- Department of Clinical Biochemistry, Rigshospitalet, Glostrup, Denmark
- OPEN, Odense Patient data Explorative Network, Odense University Hospital/Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Signe Sparre Beck-Nielsen
- Department of Pediatrics, Kolding Hospital at Lillebaelt Hospital, Sygehusvej 24, DK-6000, Kolding, Denmark.
- Institute of Regional Health Research, University of Southern Denmark, Odense, Denmark.
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Hoac B, Susan-Resiga D, Essalmani R, Marcinkiweicz E, Seidah NG, McKee MD. Osteopontin as a novel substrate for the proprotein convertase 5/6 (PCSK5) in bone. Bone 2018; 107:45-55. [PMID: 29126984 DOI: 10.1016/j.bone.2017.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 11/05/2017] [Accepted: 11/06/2017] [Indexed: 12/30/2022]
Abstract
Seven proprotein convertases cleave the basic amino acid consensus sequence K/R-Xn-K/R↓ (where n=0, 2, 4 or 6 variable amino acids) to activate precursor proteins. Despite similarities in substrate specificity, basic amino acid-specific proprotein convertases have a distinct tissue distribution allowing for enzymatic actions on tissue-resident substrates. Proprotein convertase 5/6 (PC5/6) has two splice variants - soluble PC5/6A and membrane-bound PC5/6B - and is expressed during mouse development in many tissues including bone and tooth, but little is known about the substrates for PC5/6 therein. Osteopontin (OPN) is an abundant bone extracellular matrix protein with roles in mineralization, cell adhesion and cell migration, and it has putative consensus sequence sites for cleavage by PC5/6, which may modify its function in bone. Since PC5/6-knockout mouse embryos show developmental abnormalities, and reduced overall mineralization, we designed this study to determine whether OPN is a substrate of PC5/6. In silico analysis of OPN protein sequences identified four potential PC5/6 consensus cleavage sites in human OPN, and three sites - including a noncanonical sequence - in mouse OPN. Ex vivo co-transfections with human OPN revealed complete OPN cleavage reducing full-length OPN (~70kDa) to an N-terminal fragment migrating at ~50kDa and two C-terminal fragments at ~18kDa and ~16kDa. Direct cleavage of OPN by PC5/6A - the predominant isoform expressed in human osteoblast cells - was confirmed by cell-free enzyme-substrate assays and by mass spectrometry. The latter was also used to investigate potential cleavage sites. Co-transfections of PC5/6 and mouse OPN showed partial cleavage of OPN into a C-terminal OPN fragment migrating at ~30kDa and an N-terminal fragment migrating at ~29kDa. Micro-computed tomography of PC5/6-knockout embryos at E18.5 confirmed a reduction in mineralized bone, and in situ hybridization performed on cryo-sections of normal mouse bone using Pcsk5 and Opn anti-sense and control-sense cRNA probes indicated the co-localization of the expression of these genes in bone cells. This mRNA expression profile was supported by semi-quantitative RT-PCR using osteoblast primary cultures, and cultured MC3T3-E1 osteoblast and MLO-Y4 osteocyte cell lines. Immunoblotting for OPN from mouse bone extracts showed altered OPN processing in PC5/6-knockout mice compared to wildtype mice. OPN fragments migrated at ~25kDa and ~16kDa in wildtype bone and were not present in PC5/6-deficient bone. In conclusion, this study demonstrates that Pcsk5 is expressed in bone-forming cells, and that OPN is a novel substrate for PC5/6. Cleavage of OPN by PC5/6 may modify the function of OPN in bone and/or modulate other enzymatic cleavages of OPN, leading to alterations in the bone phenotype.
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Affiliation(s)
- Betty Hoac
- Faculty of Dentistry, McGill University, Montreal, QC, Canada
| | - Delia Susan-Resiga
- Laboratory of Biochemical Neuroendocrinology, Montreal Clinical Research Institute, Affiliated with the University of Montreal, Montreal, QC, Canada
| | - Rachid Essalmani
- Laboratory of Biochemical Neuroendocrinology, Montreal Clinical Research Institute, Affiliated with the University of Montreal, Montreal, QC, Canada
| | - Edwige Marcinkiweicz
- Laboratory of Biochemical Neuroendocrinology, Montreal Clinical Research Institute, Affiliated with the University of Montreal, Montreal, QC, Canada
| | - Nabil G Seidah
- Laboratory of Biochemical Neuroendocrinology, Montreal Clinical Research Institute, Affiliated with the University of Montreal, Montreal, QC, Canada
| | - Marc D McKee
- Faculty of Dentistry, McGill University, Montreal, QC, Canada; Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, QC, Canada.
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The role of fibroblast growth factor 23 and Klotho in uremic cardiomyopathy. Curr Opin Nephrol Hypertens 2018; 25:314-24. [PMID: 27219043 DOI: 10.1097/mnh.0000000000000231] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW In chronic kidney disease (CKD), multiple factors contribute to the development of cardiac hypertrophy by directly targeting the heart or indirectly by inducing systemic changes such as hypertension, anemia, and inflammation. Furthermore, disturbances in phosphate metabolism have been identified as nonclassical risk factors for cardiovascular mortality in these patients. With declining kidney function, the physiologic regulators of phosphate homeostasis undergo changes in their activity as well as their circulating levels, thus potentially contributing to cardiac hypertrophy once they are out of balance. Recently, two of these phosphate regulators, fibroblast growth factor 23 (FGF23) and Klotho, have been shown to affect cardiac remodeling, thereby unveiling a novel pathomechanism of cardiac hypertrophy in CKD. Here we discuss the potential direct versus indirect effects of FGF23 and the soluble form of Klotho on the heart, and their crosstalk in the regulation of cardiac hypertrophy. RECENT FINDINGS In models of CKD, FGF23 can directly target cardiac myocytes via FGF receptor 4 and induce cardiac hypertrophy in a blood pressure-independent manner. Soluble Klotho may directly target the heart via an unknown receptor thereby protecting the myocardium from pathologic stress stimuli that are associated with CKD, such as uremic toxins or FGF23. SUMMARY Elevated serum levels of FGF23 and reduced serum levels of soluble Klotho contribute to uremic cardiomyopathy in a synergistic manner.
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Richter B, Faul C. FGF23 Actions on Target Tissues-With and Without Klotho. Front Endocrinol (Lausanne) 2018; 9:189. [PMID: 29770125 PMCID: PMC5940753 DOI: 10.3389/fendo.2018.00189] [Citation(s) in RCA: 127] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 04/06/2018] [Indexed: 12/11/2022] Open
Abstract
Fibroblast growth factor (FGF) 23 is a phosphaturic hormone whose physiologic actions on target tissues are mediated by FGF receptors (FGFR) and klotho, which functions as a co-receptor that increases the binding affinity of FGF23 for FGFRs. By stimulating FGFR/klotho complexes in the kidney and parathyroid gland, FGF23 reduces renal phosphate uptake and secretion of parathyroid hormone, respectively, thereby acting as a key regulator of phosphate metabolism. Recently, it has been shown that FGF23 can also target cell types that lack klotho. This unconventional signaling event occurs in an FGFR-dependent manner, but involves other downstream signaling pathways than in "classic" klotho-expressing target organs. It appears that klotho-independent signaling mechanisms are only activated in the presence of high FGF23 concentrations and result in pathologic cellular changes. Therefore, it has been postulated that massive elevations in circulating levels of FGF23, as found in patients with chronic kidney disease, contribute to associated pathologies by targeting cells and tissues that lack klotho. This includes the induction of cardiac hypertrophy and fibrosis, the elevation of inflammatory cytokine expression in the liver, and the inhibition of neutrophil recruitment. Here, we describe the signaling and cellular events that are caused by FGF23 in tissues lacking klotho, and we discuss FGF23's potential role as a hormone with widespread pathologic actions. Since the soluble form of klotho can function as a circulating co-receptor for FGF23, we also discuss the potential inhibitory effects of soluble klotho on FGF23-mediated signaling which might-at least partially-underlie the pleiotropic tissue-protective functions of klotho.
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50
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Eren M, Place AT, Thomas PM, Flevaris P, Miyata T, Vaughan DE. PAI-1 is a critical regulator of FGF23 homeostasis. SCIENCE ADVANCES 2017; 3:e1603259. [PMID: 28924605 PMCID: PMC5597312 DOI: 10.1126/sciadv.1603259] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 08/11/2017] [Indexed: 05/29/2023]
Abstract
Elevated levels of fibroblast growth factor 23 (FGF23), a bone-derived phosphaturic hormone, are associated with a number of pathologic conditions including chronic kidney disease, cardiac hypertrophy, and congestive heart failure. Currently, there are no specific treatments available to lower plasma FGF23 levels. We have recently reported that genetic plasminogen activator inhibitor-1 (PAI-1) deficiency provided a significant reduction in circulating FGF23 levels while simultaneously prolonging the life span of Klotho-deficient mice. We extend our investigations into the effect of PAI-1 on FGF23 homeostasis. Transgenic overexpression of PAI-1 resulted in threefold increase in FGF23 levels compared to wild-type littermates. Moreover, pharmacological modulation of PAI-1 activity with the small-molecule PAI-1 antagonist TM5441 significantly reduced FGF23 levels in PAI-1 transgenic and Klotho-deficient mice. In addition, TM5441 treatment or PAI-1 deficiency significantly accelerated the clearance of endogenous FGF23 and recombinant human FGF23 from circulation in mice with acute kidney injury. On the basis of these observations, we studied the effects of plasminogen activators (PAs), tissue-type PA (tPA) and urokinase-type PA (uPA), on FGF23. We demonstrate that both PAs directly cleave FGF23; however, it is not known whether the PA-generated FGF23 peptides retain or acquire functions that affect binding and/or signaling properties of intact FGF23. PAI-1 inhibits the PA-dependent cleavage of FGF23, and TM5441 inhibition of PAI-1 restores the proteolysis of FGF23. Furthermore, top-down proteomic analysis indicates that tPA cleaves FGF23 at multiple arginines including the proconvertase sensitive site R176. In summary, our results indicate that PAI-1 prevents the PA-driven proteolysis of FGF23 and PAI-1 inhibition provides a novel therapeutic approach to prevent the pathologic consequences of increased FGF23.
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Affiliation(s)
- Mesut Eren
- Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Aaron T. Place
- Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Paul M. Thomas
- Proteomics Center of Excellence, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Panagiotis Flevaris
- Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Toshio Miyata
- United Centers for Advanced Research and Translational Medicine, Tohoku University Graduate School of Medicine, Miyagi, Japan
| | - Douglas E. Vaughan
- Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
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