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Baroncelli GI, Comberiati P, Aversa T, Baronio F, Cassio A, Chiarito M, Cosci o di Coscio M, De Sanctis L, Di Iorgi N, Faienza MF, Fintini D, Franceschi R, Kalapurackal M, Longhi S, Mariani M, Pitea M, Secco A, Tessaris D, Vierucci F, Wasniewska M, Weber G, Mora S. Diagnosis, treatment, and management of rickets: a position statement from the Bone and Mineral Metabolism Group of the Italian Society of Pediatric Endocrinology and Diabetology. Front Endocrinol (Lausanne) 2024; 15:1383681. [PMID: 38706696 PMCID: PMC11066174 DOI: 10.3389/fendo.2024.1383681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Accepted: 04/03/2024] [Indexed: 05/07/2024] Open
Abstract
Rickets results from impaired mineralization of growing bone due to alterations in calcium and phosphate homeostasis. Clinical signs of rickets are related to the age of the patient, the duration of the disease, and the underlying disorder. The most common signs of rickets are swelling of the wrists, knees or ankles, bowing of the legs (knock-knees, outward bowing, or both) and inability to walk. However, clinical features alone cannot differentiate between the various forms of rickets. Rickets includes a heterogeneous group of acquired and inherited diseases. Nutritional rickets is due to a deficiency of vitamin D, dietary calcium or phosphate. Mutations in genes responsible for vitamin D metabolism or function, the production or breakdown of fibroblast growth factor 23, renal phosphate regulation, or bone mineralization can lead to the hereditary form of rickets. This position paper reviews the relevant literature and presents the expertise of the Bone and Mineral Metabolism Group of the Italian Society of Pediatric Endocrinology and Diabetology (SIEDP). The aim of this document is to provide practical guidance to specialists and healthcare professionals on the main criteria for diagnosis, treatment, and management of patients with rickets. The various forms of rickets are discussed, and detailed references for the discussion of each form are provided. Algorithms to guide the diagnostic approach and recommendations to manage patients with rare forms of hereditary rickets are proposed.
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Affiliation(s)
- Giampiero I. Baroncelli
- Pediatric and Adolescent Endocrinology, Division of Pediatrics, Department of Obstetrics, Gynecology and Pediatrics, University Hospital, Pisa, Italy
| | - Pasquale Comberiati
- Pediatric and Adolescent Endocrinology, Division of Pediatrics, Department of Obstetrics, Gynecology and Pediatrics, University Hospital, Pisa, Italy
- Department of Clinical and Experimental Medicine, Section of Paediatrics, University of Pisa, Pisa, Italy
| | - Tommaso Aversa
- Department of Human Pathology of Adulthood and Childhood, University of Messina, Messina, Italy
- Pediatric Unit, University Hospital “G. Martino”, Messina, Italy
| | - Federico Baronio
- Pediatric Unit, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy
| | - Alessandra Cassio
- Pediatric Unit, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy
- Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy
| | - Mariangela Chiarito
- Pediatric Unit, Department of Precision and Regenerative Medicine and Ionian Area, University “A. Moro” of Bari, Bari, Italy
| | - Mirna Cosci o di Coscio
- Pediatric and Adolescent Endocrinology, Division of Pediatrics, Department of Obstetrics, Gynecology and Pediatrics, University Hospital, Pisa, Italy
| | - Luisa De Sanctis
- Division of Pediatric Endocrinology, Department of Public Health and Pediatrics, University of Turin, Regina Margherita Children’s Hospital, Turin, Italy
| | - Natascia Di Iorgi
- Department of Pediatrics, IRCCS Istituto Giannina Gaslini, Genova, Italy
- Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genova, Genova, Italy
| | - Maria Felicia Faienza
- Pediatric Unit, Department of Precision and Regenerative Medicine and Ionian Area, University “A. Moro” of Bari, Bari, Italy
| | - Danilo Fintini
- Endocrinology and Diabetology Unit, Bambino Gesù Children Hospital, IRCCS, Rome, Italy
| | - Roberto Franceschi
- Department of Pediatrics, Santa Chiara Hospital of Trento, APSS, Trento, Italy
| | - Mila Kalapurackal
- Department of Pediatrics, Hospital of Bolzano (SABES-ASDAA), Teaching Hospital of Paracelsus Medical University (PMU), Bolzano, Italy
| | - Silvia Longhi
- Department of Pediatrics, Hospital of Bolzano (SABES-ASDAA), Teaching Hospital of Paracelsus Medical University (PMU), Bolzano, Italy
| | - Michela Mariani
- Endocrinology and Diabetology Unit, Bambino Gesù Children Hospital, IRCCS, Rome, Italy
| | - Marco Pitea
- Pediatric Endocrinology Unit, Department of Pediatrics, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Andrea Secco
- Pediatric and Pediatric Emergency Unit, Children Hospital, Azienda Ospedaliera SS Antonio e Biagio e C. Arrigo, Alessandria, Italy
| | - Daniele Tessaris
- Division of Pediatric Endocrinology, Department of Public Health and Pediatrics, University of Turin, Regina Margherita Children’s Hospital, Turin, Italy
| | | | - Malgorzata Wasniewska
- Department of Human Pathology of Adulthood and Childhood, University of Messina, Messina, Italy
| | - Giovanna Weber
- Pediatric Endocrinology Unit, Department of Pediatrics, IRCCS Ospedale San Raffaele, Milan, Italy
| | - Stefano Mora
- Laboratory of Pediatric Endocrinology, Department of Pediatrics, IRCCS Ospedale San Raffaele, Milan, Italy
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Cao Y, You Y, Wang Q, Ren X, Li S, Li L, Xia W, Guan X, Yang T, Ikegawa S, Wang Z, Zhao X. Identification of six novel variants from nine Chinese families with hypophosphatemic rickets. BMC Med Genomics 2022; 15:161. [PMID: 35842615 PMCID: PMC9287957 DOI: 10.1186/s12920-022-01305-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 06/27/2022] [Indexed: 11/25/2022] Open
Abstract
Background Hypophosphatemic rickets (HR) is a rare genetic disorder associated with renal phosphate wasting and characterized by bone defects. Inactivating mutations in the phosphate regulating endopeptidase homolog X‑linked gene (PHEX) account for most cases of HR. The aim of this study was to identify causative variants in nine unrelated Chinese families associated with HR, and to determine potential pathogenicity of the identified variants. Methods Genomic DNA was isolated from the peripheral blood of HR patients and their healthy relatives, followed by next-generation sequencing and/or Sanger sequencing. In silico prediction combined with conservation analysis was performed to assess the effects of the variants, and 3D protein modeling was conducted to predict the functional effects on the encoded protein. Results All HR patients recruited in this study displayed bone deformities and tooth agenesis, as well as reduced serum phosphate levels and elevated urine phosphate levels. Nine PHEX variants were identified in eight families, including four novel variants (c.1661_1726del, c.980A > G, c.1078A > T, and c.1017_1051dup). Of the nine identified PHEX variants, five caused a truncated protein, two caused an altered amino acid, and the other two were the canonical splicing variants. Novel variants c.1336G > A and c.1364 T > C in SLC34A3 were also found in one family. Conservation analysis showed that all the amino acids corresponding to the missense variants were highly conserved. In silico analysis and 3D protein structure modeling confirmed the pathogenicity of these variants. Conclusions This study identified four novel variants in PHEX and two novel variants in SLC34A3 in a Chinese cohort with HR. Our findings highlight the dominant role of PHEX in HR, and expand the genotypic and phenotypic spectra of this disorder. Supplementary Information The online version contains supplementary material available at 10.1186/s12920-022-01305-w.
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Affiliation(s)
- Yixuan Cao
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Yi You
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Qiong Wang
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Xiuzhi Ren
- The People's Hospital of Wuqing District, Tianjin, 301700, China
| | - Shan Li
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Lulu Li
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Weibo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology of the Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, 100730, China
| | - Xin Guan
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Tao Yang
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China
| | - Shiro Ikegawa
- Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences (IMS), Tokyo, 108-8639, Japan
| | - Zheng Wang
- Laboratory for Bone and Joint Diseases, RIKEN Center for Integrative Medical Sciences (IMS), Tokyo, 108-8639, Japan
| | - Xiuli Zhao
- Department of Medical Genetics, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and School of Basic Medicine, Peking Union Medical College, Beijing, 100005, China.
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Yang Y, Wang Y, Shen Y, Liu M, Dai S, Wang X, Liu H. Identification of a Novel Missense Mutation of the PHEX Gene in a Large Chinese Family with X-Linked Hypophosphataemia. Front Genet 2022; 13:792183. [PMID: 35251124 PMCID: PMC8891598 DOI: 10.3389/fgene.2022.792183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 01/18/2022] [Indexed: 11/13/2022] Open
Abstract
X-linked hypophosphataemia (XLH) is an X-linked dominant rare disease that refers to the most common hereditary hypophosphatemia (HH) caused by mutations in the phosphate-regulating endopeptidase homolog X-linked gene (PHEX; OMIM: * 300550). However, mutations that have already been reported cannot account for all cases of XLH. Extensive genetic analysis can thus be helpful for arriving at the diagnosis of XLH. Herein, we identified a novel heterozygous mutation of PHEX (NM_000444.5: c.1768G > A) in a large Chinese family with XLH by whole-exome sequencing (WES). In addition, the negative effect of this mutation in PHEX was confirmed by both bioinformatics analysis and in vitro experimentation. The three-dimensional protein-model analysis predicted that this mutation might impair normal zinc binding. Immunofluorescence staining, qPCR, and western blotting analysis confirmed that the mutation we detected attenuated PHEX protein expression. The heterozygous mutation of PHEX (NM_000444.5: c.1768G > A) identified in this study by genetic and functional experiments constitutes a novel genetic cause of XLH, but further study will be required to expand its use in clinical and molecular diagnoses of XLH.
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Affiliation(s)
- Yanting Yang
- Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Chengdu, China
- Medical Genetics Department/Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Chengdu, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Sichuan University, Chengdu, China
| | - Yuanda Wang
- State Key Laboratory of Biotherapy and Cancer Center, Sichuan University, Chengdu, China
| | - Ying Shen
- Department of Obstetrics/Gynecology, Joint Laboratory of Reproductive Medicine (SCU-CUHK), Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu, China
| | - Mohan Liu
- State Key Laboratory of Biotherapy and Cancer Center, Sichuan University, Chengdu, China
| | - Siyu Dai
- Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Chengdu, China
- Medical Genetics Department/Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Chengdu, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Sichuan University, Chengdu, China
| | - Xiaodong Wang
- Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Chengdu, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Sichuan University, Chengdu, China
- *Correspondence: Xiaodong Wang, ; Hongqian Liu,
| | - Hongqian Liu
- Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Chengdu, China
- Medical Genetics Department/Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Chengdu, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Sichuan University, Chengdu, China
- *Correspondence: Xiaodong Wang, ; Hongqian Liu,
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Hereditary Hypophosphatemic Rickets with Hypercalciuria (HHRH) Presenting with Genu Valgum Deformity: Treatment with Phosphate Supplementation and Surgical Correction. Case Rep Endocrinol 2020; 2020:1047327. [PMID: 32695531 PMCID: PMC7368196 DOI: 10.1155/2020/1047327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/18/2020] [Indexed: 11/17/2022] Open
Abstract
We describe a case of hereditary hypophosphatemic rickets with hypercalciuria (HHRH) in a 32-year-old female with short stature, chronic pathologic genu valgum deformity, and knee pain who was referred to endocrinology clinic after previous inconclusive workups. We present imaging spanning 10 years of untreated disease. Biochemical studies showed hypophosphatemia with undetectable fibroblast growth factor 23 (FGF23.) Renal ultrasound revealed bilateral medullary nephrocalcinosis despite no apparent hypercalciuria. Due to concern for HHRH, genetic testing was performed that determined this patient to be homozygous in the SLC34A3 gene for a previously described missense variant (c.1402C > T, p.Arg468Trp). There was no known family history of rickets. A bone biopsy with metabolic studies was performed for diagnostic and prognostic reasons. The histopathological findings along with tetracycline uptake studies were consistent with a diagnosis of HHRH. Treatment with phosphorous supplementation and surgical correction of her valgum deformity resulted in resolution of pain, but no change in bone histomorphometry.
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Abstract
Hypophosphatemic rickets, mostly of the X-linked dominant form caused by pathogenic variants of the PHEX gene, poses therapeutic challenges with consequences for growth and bone development and portends a high risk of fractions and poor bone healing, dental problems and nephrolithiasis/nephrocalcinosis. Conventional treatment consists of PO4 supplements and calcitriol requiring monitoring for treatment-emergent adverse effects. FGF23 measurement, where available, has implications for the differential diagnosis of hypophosphatemia syndromes and, potentially, treatment monitoring. Newer therapeutic modalities include calcium sensing receptor modulation (cinacalcet) and biological molecules targeting FGF23 or its receptors. Their long-term effects must be compared with those of conventional treatments.
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Affiliation(s)
- Martin Bitzan
- Department of Pediatrics, The Montreal Children's Hospital, McGill University Health Centre, 1001 Boulevard Décarie, Room B RC.6164, Montreal, Quebec H4A 3J1, Canada.
| | - Paul R Goodyer
- The Research Institute of the McGill University Health Centre, 1001 Boulevard Décarie, Room EM1.2232, Montreal, Quebec H4A3J1, Canada
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Barbieri AM, Chiodini I, Ragni E, Colaianni G, Gadda F, Locatelli M, Lampertico P, Spada A, Eller‐Vainicher C. Suppressive effects of tenofovir disoproxil fumarate, an antiretroviral prodrug, on mineralization and type II and type III sodium‐dependent phosphate transporters expression in primary human osteoblasts. J Cell Biochem 2018; 119:4855-4866. [DOI: 10.1002/jcb.26696] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 01/22/2018] [Indexed: 01/22/2023]
Affiliation(s)
- Anna Maria Barbieri
- Unit of Endocrinology and Metabolic DiseasesFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
- Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoUniversity of MilanMilanItaly
| | - Iacopo Chiodini
- Unit of Endocrinology and Metabolic DiseasesFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Enrico Ragni
- Cell Factory, Unit of Cell Therapy and CryobiologyFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Graziana Colaianni
- Department of Basic and Medical Sciences, Neurosciences and Sense Organs, section of Human Anatomy and HistologyUniversity of BariBariItaly
| | - Franco Gadda
- Department of UrologyFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Marco Locatelli
- Unit of NeurosurgeryFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
| | - Pietro Lampertico
- ‘A. M. and A. Migliavacca’ Center for Liver Disease, Division of Gastroenterology and Hepatology, Fondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoUniversity of MilanMilanItaly
| | - Anna Spada
- Unit of Endocrinology and Metabolic DiseasesFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
- Department of Clinical Sciences and Community Health, Fondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoUniversity of MilanMilanItaly
| | - Cristina Eller‐Vainicher
- Unit of Endocrinology and Metabolic DiseasesFondazione IRCCS Ca′ Granda Ospedale Maggiore PoliclinicoMilanItaly
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Acar S, BinEssa HA, Demir K, Al-Rijjal RA, Zou M, Çatli G, Anık A, Al-Enezi AF, Özışık S, Al-Faham MSA, Abacı A, Dündar B, Kattan WE, Alsagob M, Kavukçu S, Tamimi HE, Meyer BF, Böber E, Shi Y. Clinical and genetic characteristics of 15 families with hereditary hypophosphatemia: Novel Mutations in PHEX and SLC34A3. PLoS One 2018; 13:e0193388. [PMID: 29505567 PMCID: PMC5837132 DOI: 10.1371/journal.pone.0193388] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 02/11/2018] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Hereditary hypophosphatemia is a group of rare renal phosphate wasting disorders. The diagnosis is based on clinical, radiological, and biochemical features, and may require genetic testing to be confirmed. METHODOLOGY Clinical features and mutation spectrum were investigated in patients with hereditary hypophosphatemia. Genomic DNA of 23 patients from 15 unrelated families were screened sequentially by PCR-sequencing analysis for mutations in the following genes: PHEX, FGF23, DMP1, ENPP1, CLCN5, SLC34A3 and SLC34A1. CytoScan HD Array was used to identify large deletions. RESULTS Genetic evaluation resulted in the identification of an additional asymptomatic but intermittent hypophosphatemic subject. Mutations were detected in 21 patients and an asymptomatic sibling from 13 families (86.6%, 13/15). PHEX mutations were identified in 20 patients from 12 families. Six of them were novel mutations present in 9 patients: c.983_987dupCTACC, c.1586+2T>G, c.1206delA, c.436+1G>T, c.1217G>T, and g.22,215,887-22,395,767del (179880 bp deletion including exon 16-22 and ZNF645). Six previously reported mutations were found in 11 patients. Among 12 different PHEX mutations, 6 were de novo mutations. Patients with de novo PHEX mutations often had delayed diagnosis and significantly shorter in height than those who had inherited PHEX mutations. Novel compound heterozygous mutations in SLC34A3 were found in one patient and his asymptomatic sister: c.1335+2T>A and c.1639_1652del14. No mutation was detected in two families. CONCLUSIONS This is the largest familial study on Turkish patients with hereditary hypophosphatemia. PHEX mutations, including various novel and de novo variants, are the most common genetic defect. More attention should be paid to hypophosphatemia by clinicians since some cases remain undiagnosed both during childhood and adulthood.
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Affiliation(s)
- Sezer Acar
- Division of Pediatric Endocrinology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Huda A. BinEssa
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Korcan Demir
- Division of Pediatric Endocrinology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Roua A. Al-Rijjal
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Minjing Zou
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Gönül Çatli
- Division of Pediatric Endocrinology, Katip Çelebi University School of Medicine, Izmir, Turkey
| | - Ahmet Anık
- Division of Pediatric Endocrinology, Adnan Menderes University School of Medicine, Izmir, Turkey
| | - Anwar F. Al-Enezi
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Seçil Özışık
- Department of Endocrinology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Manar S. A. Al-Faham
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Ayhan Abacı
- Division of Pediatric Endocrinology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Bumin Dündar
- Division of Pediatric Endocrinology, Katip Çelebi University School of Medicine, Izmir, Turkey
| | - Walaa E. Kattan
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Maysoon Alsagob
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Salih Kavukçu
- Division of Pediatric Nephrology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Hamdi E. Tamimi
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Brian F. Meyer
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Ece Böber
- Division of Pediatric Endocrinology, Dokuz Eylul University School of Medicine, Izmir, Turkey
| | - Yufei Shi
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
- * E-mail:
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Guven A, Al-Rijjal RA, BinEssa HA, Dogan D, Kor Y, Zou M, Kaya N, Alenezi AF, Hancili S, Tarım Ö, Baitei EY, Kattan WE, Meyer BF, Shi Y. Mutational analysis of PHEX, FGF23 and CLCN5 in patients with hypophosphataemic rickets. Clin Endocrinol (Oxf) 2017; 87:103-112. [PMID: 28383812 DOI: 10.1111/cen.13347] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 03/30/2017] [Accepted: 04/03/2017] [Indexed: 12/30/2022]
Abstract
CONTEXT Hypophosphataemic rickets (HR) is a group of rare hereditary renal phosphate wasting disorders caused by mutations in PHEX, FGF23, DMP1, ENPP1, CLCN5 or SLC34A3. OBJECTIVE To investigate underlying genetic defects in patients with hypophosphataemic rickets. METHODS We analysed genomic DNA from nine unrelated families for mutations in the entire coding region of PHEX, FGF23, DMP1, ENPP1, CLCN5 or SLC34A3 by PCR sequencing and copy number analysis. RESULTS A total of 14 patients were studied. PHEX mutations were identified in 12 patients from seven families. Five of them were novel mutations present in eight patients: c.154G>T (p.E52*), c.401_402insGCCAAA (p.Q134_K135insPK), c.1600C>T (p.P534S), g.22016715_22056805del (40-kb deletion including promoter and exons 1-3) and c.2242_2243delCT (p.L748 fs*48). Four patients had previously reported mutations: c.1768+1G>A and c.1807G>A (p.W602*). Novel CLCN5 (c.1205G>A, p.W402*) and FGF23 (c.526C>G, p.R176G) mutations were found in two patients from the remaining two families. Many of the mutations were de novo: c.154G>T and c.2242_2243delCT in PHEX and c.526C>G in FGF23. Furthermore, we characterized the breakpoint of the novel PHEX g.22016715_22056805del and the c.2242_2243delCT, which is 6 bp from the stop codon, resulting in a frameshift and extension of the reading frame by 42 amino acids. CONCLUSIONS Novel and de novo mutations are frequent and PHEX mutations are still the most common genetic defects in the Turkish population. Gene copy number analysis should be considered in patients with negative results by conventional PCR-based sequencing analysis. The current study further expands the mutation spectrum underlying HR.
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Affiliation(s)
- Ayla Guven
- Department of Pediatric, Amasya University Medical Faculty, Amasya, Turkey
- Pediatric Endocrinology Clinic, Goztepe Educational and Research Hospital, Istanbul, Turkey
| | - Roua A Al-Rijjal
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Huda A BinEssa
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Durmuş Dogan
- Department of Pediatrics, Division of Pediatric Endocrinology, Uludag University Faculty of Medicine, Bursa, Turkey
| | - Yılmaz Kor
- Pediatric Endocrinology Division, Adana Numune Training and Research Hospital, Adana, Turkey
| | - Minjing Zou
- Pediatric Endocrinology Clinic, Goztepe Educational and Research Hospital, Istanbul, Turkey
| | - Namik Kaya
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Anwar F Alenezi
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Suna Hancili
- Department of Pediatric, Amasya University Medical Faculty, Amasya, Turkey
- Pediatric Endocrinology Clinic, Goztepe Educational and Research Hospital, Istanbul, Turkey
| | - Ömer Tarım
- Department of Pediatrics, Division of Pediatric Endocrinology, Uludag University Faculty of Medicine, Bursa, Turkey
| | - Essa Y Baitei
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Walaa E Kattan
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Brian F Meyer
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
| | - Yufei Shi
- Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
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Lu X, Hu MC. Klotho/FGF23 Axis in Chronic Kidney Disease and Cardiovascular Disease. KIDNEY DISEASES 2016; 3:15-23. [PMID: 28785560 DOI: 10.1159/000452880] [Citation(s) in RCA: 123] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2016] [Accepted: 10/26/2016] [Indexed: 12/26/2022]
Abstract
BACKGROUND Membrane αKlotho (hereinafter called Klotho) is highly expressed in the kidney and functions as a coreceptor of FGF receptors (FGFRs) to activate specific fibroblast growth factor 23 (FGF23) signal pathway. FGF23 is produced in bones and participates in the maintenance of mineral homeostasis. The extracellular domain of transmembrane Klotho can be cleaved by secretases and released into the circulation as soluble Klotho. Soluble Klotho does not only weakly activate FGFRs to transduce the FGF23 signaling pathway, but also functions as an enzyme and hormonal substance to play a variety of biological functions. FGF23 exerts its biological effects through activation of FGFRs in a Klotho-dependent manner. However, extremely high FGF23 can exert its pathological action in a Klotho-independent manner. SUMMARY The decline in serum and urinary Klotho followed by a rise in serum FGF23 at an early stage of chronic kidney disease (CKD) functions as an early biomarker for kidney dysfunction and can also serve as a predictor for risk of cardiovascular disease (CVD) and mortality in both CKD patients and the general population. Moreover, Klotho deficiency is a pathogenic factor for CKD progression and CVD. FGF23 may also contribute to CVD. Prevention of Klotho decline, reactivation of endogenous Klotho production, or supplementation of exogenous Klotho attenuate renal fibrosis, retard CKD progression, improve mineral metabolism, ameliorate cardiomyopathy, and alleviate vascular calcification in CKD. However, the poor CVD outcome after depletion of FGF23 with FGF23 antibody stimulates the generation of a more specific inhibitor of FGF23 for CKD treatment. KEY MESSAGE Klotho/FGF23 may not only be diagnostic and/or prognostic biomarkers for CKD and CVD, but are also pathogenic contributors to CKD progression and CVD development. The Klotho/FGF23 axis should be a novel target for renal clinics.
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Affiliation(s)
- Xiang Lu
- Department of Geriatrics, Sir Run Run Hospital, Nanjing Medical University, Nanjing, PR China
| | - Ming Chang Hu
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Cheng CY, Chang SY, Lin MH, Ku SY, Sun NL, Cheng SH. Tenofovir disoproxil fumarate-associated hypophosphatemia as determined by fractional excretion of filtered phosphate in HIV-infected patients. J Infect Chemother 2016; 22:744-747. [PMID: 27613487 DOI: 10.1016/j.jiac.2016.08.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 08/04/2016] [Accepted: 08/08/2016] [Indexed: 01/18/2023]
Abstract
INTRODUCTION Tenofovir disoproxil fumarate (TDF) -containing regimens have been associated with nephrotoxicity and hypophosphatemia in HIV-infected patients. The objective of this study was to assess the possible risk factors for hypophosphatemia and evaluate the relationship between fractional excretion of filtered phosphate (FePi) and hypophosphatemia in TDF users. PATIENT AND METHODS Patients were enrolled in a prospective cohort study between January 2011 and December 2014. We classified experienced HIV-infected patients (individuals maintained on antiretroviral therapy (ART) for 6 months or more) and naïve patients into 3 treatment groups: TDF-containing ART (group 1), non-TDF-containing ART (never received TDF or had not received TDF in the past 6 months; group 2) and naive to antiretroviral therapy (group 3). Specimens from each individual were assessed for serum phosphate, serum creatinine, urine phosphate, and urine creatinine. Multivariable logistic regression was performed to control for the following variables measured at baseline: eGFR, age, sex, sexual orientation, injection drug use (IDUs), HIV-RNA viral load, and CD4 cell count. RESULTS The frequency of hypophosphatemia in groups 1, 2, and 3 was 20.2%, 7.2%, and 14.6%, respectively (P = 0.002). FePi above 10% also was significantly associated with hypophosphatemia (P = 0.003; adjusted odds ratio = 2.54). Patients with elevated CD4 cell counts (>500 cells/μL) exhibited a lower risk of hypophosphatemia (P = 0.002; adjusted odds ratio = 0.35). CONCLUSIONS Hypophosphatemia is a multifactorial etiology; FePi was confirmed as a suggested method to predict the risk of hypophosphatemia in TDF users. Clinical Trial Number: TYGH103011.
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Affiliation(s)
- Chien-Yu Cheng
- Department of Internal Medicine, Division of Infectious Diseases, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan City, Taiwan.
| | - Shu-Yin Chang
- AIDS Care Center, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan City, Taiwan.
| | - Mei-Hui Lin
- AIDS Care Center, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan City, Taiwan.
| | - Shin-Yen Ku
- AIDS Care Center, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan City, Taiwan.
| | - Na-Lee Sun
- AIDS Care Center, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan City, Taiwan.
| | - Shu-Hsing Cheng
- Department of Internal Medicine, Division of Infectious Diseases, Taoyuan General Hospital, Ministry of Health and Welfare, Taoyuan City, Taiwan.
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What is nephrocalcinosis? Kidney Int 2015; 88:35-43. [PMID: 25807034 DOI: 10.1038/ki.2015.76] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Revised: 01/18/2015] [Accepted: 01/22/2015] [Indexed: 12/24/2022]
Abstract
The available publications on nephrocalcinosis are wide-ranging and have documented multiple causes and associations of macroscopic or radiological nephrocalcinosis, most often located in the renal medulla, with various metabolic and genetic disorders; in fact, so many and various are these that it is difficult to define a common underlying mechanism. We have reviewed nephrocalcinosis in relation to its definition, genetic associations, animal models, and putative mechanisms. We have concluded, and hypothesized, that nephrocalcinosis is primarily a renal interstitial process, resembling metastatic calcification, and that it may have some features in common with, and pathogenic links to, vascular calcification.
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Zou M, Buluş D, Al-Rijjal RA, Andıran N, BinEssa H, Kattan WE, Meyer B, Shi Y. Hypophosphatemic rickets caused by a novel splice donor site mutation and activation of two cryptic splice donor sites in the PHEX gene. J Pediatr Endocrinol Metab 2015; 28:211-6. [PMID: 25153221 DOI: 10.1515/jpem-2014-0103] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 06/19/2014] [Indexed: 11/15/2022]
Abstract
X-linked hypophosphatemic rickets (XLH) is the most common inherited form of rickets. XLH is caused by inactivating mutations in the PHEX gene and is transmitted as an X-linked dominant disorder. We investigated PHEX mutation in a sporadic Turkish girl with hypophosphatemic rickets. The patient was 2 years of age with a complaint of inability to walk. She had bowing of legs and growth retardation. Laboratory data showed normal calcium, low phosphate with markedly elevated ALP, and low phosphate renal tubular reabsorption. She was treated with Calcitriol 0.5 mg/kg/day and oral phosphate supplement with good response. The entire coding region of PHEX gene was sequenced from patient's peripheral leukocyte DNA and a novel 13 bp deletion at the donor splice site of exon5 was found (c.663+12del). Instead of using the donor splice site of intron 4 to splice out exon 5 and intron 5, the spliceosome utilized two nearby cryptic donor splice sites (5' splice site) to splice out intron 4, resulting in two smaller transcripts. Both of them could not translate into functional proteins due to frameshift. Her parents did not carry the mutation, indicating that this is a de novo PHEX mutation likely resulting from mutagenesis of X chromosome in paternal germ cells. We conclude that c.663+12del is a novel mutation that can activate nearby cryptic 5' splice sites. The selection of cryptic 5' splice sites adds the complexity of cell's splicing mechanisms. The current study extends the database of PHEX mutation and cryptic 5' splice sites.
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Biber J, Murer H, Mohebbi N, Wagner C. Renal Handling of Phosphate and Sulfate. Compr Physiol 2014; 4:771-92. [DOI: 10.1002/cphy.c120031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Phosphate metabolism and vitamin D. BONEKEY REPORTS 2014; 3:497. [PMID: 24605214 DOI: 10.1038/bonekey.2013.231] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 09/18/2013] [Indexed: 01/09/2023]
Abstract
Phosphate plays many essential roles in our body. To accomplish these functions, serum phosphate needs to be maintained in a certain range. Serum phosphate level is regulated by intestinal phosphate absorption, renal phosphate handling and equilibrium of extracellular phosphate with that in bone or intracellular fluid. Several hormones such as parathyroid hormone, 1,25-dihydroxyvitamin D (1,25(OH)2D) and fibroblast growth factor 23 (FGF23) regulate serum phosphate by modulating intestinal phosphate absorption, renal phosphate reabsorption and/or bone metabolism. In addition, dietary phosphate rapidly enhances renal phosphate excretion, although detailed mechanisms of this adaptation remain to be clarified. Physiologically, extracellular concentrations of phosphate and these hormones are maintained by several negative feedback loops. For example, 1,25(OH)2D enhances FGF23 production and FGF23 reduces 1,25(OH)2D level. In addition, phosphate affects 1,25(OH)2D and FGF23 levels. Dysfunction of these negative feedback loops results in several diseases with abnormal phosphate and 1,25(OH)2D levels. Especially, excess actions of FGF23 cause several hypophosphatemic rickets/osteomalacia with relatively low level of 1,25(OH)2D that had been classified as vitamin D-resistant rickets/osteomalacia. In contrast, deficient actions of FGF23 cause hyperphosphatemic familial tumoral calcinosis. However, there still remain several unanswered questions regarding phosphate and vitamin D metabolism.
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Durmaz E, Zou M, Al-Rijjal RA, Baitei EY, Hammami S, Bircan I, Akçurin S, Meyer B, Shi Y. Novel and de novo PHEX mutations in patients with hypophosphatemic rickets. Bone 2013; 52:286-91. [PMID: 23079138 DOI: 10.1016/j.bone.2012.10.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 10/07/2012] [Accepted: 10/08/2012] [Indexed: 01/18/2023]
Abstract
X-linked hypophosphatemic rickets (XLH) is the most common inherited rickets. XLH is caused by inactivating mutations in the PHEX gene and is transmitted as an X-linked dominant disorder. We investigated PHEX mutation in 10 patients from 6 unrelated Turkish families by PCR-sequence analysis. Six different PHEX mutations were detected in the patients. Four of them were novel: c.1217G>A (p.C406Y) in exon 11, c.2078G>T (p.C693F) in exon 21, a splice donor site mutation in intron 13 (IVS13+1G>T), and a splice acceptor site mutation in intron 13 (IVS13-2A>G). De novo PHEX mutations were found exclusively in female patients from 4 families and inherited mutations were detected from remaining two families. The patients' phenotype was consistent with the loss of PHEX function. Literature review of 78 sporadic cases shows that de novo mutations are present in 83% female patients and female/male ratio is 5 to 1. One patient had biallilic PHEX mutations at c.1735G>A (p.G579R) whereas her mother and two siblings carried a monoallelic mutation. The clinical and laboratory findings of the patient with biallilic PHEX mutation were similar to those with monoallelic mutation. The study shows that PHEX mutation is a common cause of either familial or sporadic hypophosphatemic rickets in Turkish population. Gene dosage effect is not observed. The frequent de novo mutations found in the female patients are likely resulting from mutagenesis of X chromosome in paternal germ cells.
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Affiliation(s)
- Erdem Durmaz
- Department of Pediatric Endocrinology, Akdeniz University School of Medicine, Antalya, Turkey
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Lederer E, Miyamoto KI. Clinical consequences of mutations in sodium phosphate cotransporters. Clin J Am Soc Nephrol 2012; 7:1179-87. [PMID: 22516291 DOI: 10.2215/cjn.09090911] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Three families of sodium phosphate cotransporters have been described. Their specific roles in human health and disease have not been defined. Review of the literature reveals that the type II sodium phosphate cotransporters play a significant role in transepithelial transport in a number of tissues including kidney, intestine, salivary gland, mammary gland, and lung. The type I transporters seem to play a major role in renal urate handling and mutations in these proteins have been implicated in susceptibility to gout. The ubiquitously expressed type III transporters play a lesser role in phosphate homeostasis but contribute to cellular phosphate uptake, mineralization, and inflammation. The recognition of species differences in the expression, regulation, and function of these transport proteins suggests an urgent need to find ways to study them in humans.
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Affiliation(s)
- Eleanor Lederer
- University of Louisville School of Medicine, Louisville, KY 40202, USA.
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Pathar G, Föller M, Daryadel A, Mutig K, Bogatikov E, Fajol A, Almilaji A, Michael D, Stange G, Voelkl J, Wagner CA, Bachmann S, Lang F. OSR1-Sensitive Renal Tubular Phosphate Reabsorption. ACTA ACUST UNITED AC 2012; 36:149-61. [DOI: 10.1159/000343405] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2012] [Indexed: 02/06/2023]
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Pathare G, Föller M, Michael D, Walker B, Hierlmeier M, Mannheim JG, Pichler BJ, Lang F. Enhanced FGF23 Serum Concentrations and Phosphaturia in Gene Targeted Mice Expressing WNK-Resistant Spak. ACTA ACUST UNITED AC 2012; 36:355-64. [DOI: 10.1159/000343393] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2012] [Indexed: 12/20/2022]
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Bacchetta J, Cochat P, Salusky IB. [FGF23 and Klotho: the new cornerstones of phosphate/calcium metabolism]. Arch Pediatr 2011; 18:686-95. [PMID: 21497493 PMCID: PMC4292917 DOI: 10.1016/j.arcped.2011.03.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 01/21/2011] [Accepted: 03/08/2011] [Indexed: 12/18/2022]
Abstract
Since its first description as a phosphaturic agent in the early 2000s, fibroblast growth factor 23 (FGF23) has rapidly become the third key player of phosphate/calcium metabolism after PTH and vitamin D. FGF23 is a protein synthesized by osteocytes that acts mainly as a phosphaturic factor and a suppressor of 1α hydroxylase activity in the kidney. It inhibits the expression of type IIa and IIc sodium-phosphate cotransporters on the apical membrane of proximal tubular cells, thus leading to inhibition of phosphate reabsorption. Moreover, it also inhibits 1α hydroxylase activity. These two renal pathways account together for the hypophosphatemic effect of FGF23, but FGF23 has also been recently described as an inhibiting factor for PTH synthesis. Its exact role in bone remains to be defined. A transmembrane protein, Klotho, is an essential cofactor for FGF23 biological activity, but it can also act by itself for calcium and PTH regulation. This paper gives an overview of these recent data of phosphate/calcium physiology, as well as a description of clinical conditions associated with FGF23 deregulation (genetic diseases and chronic kidney disease). As a conclusion, future therapeutic consequences of the FGF23/Klotho axis are discussed.
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Affiliation(s)
- J Bacchetta
- Centre de référence des maladies rénales rares, hôpital Femme-Mère-Enfant, boulevard Pinel, 69677 Bron cedex, France
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Saito A, Kaseda R, Hosojima M, Sato H. Proximal tubule cell hypothesis for cardiorenal syndrome in diabetes. Int J Nephrol 2010; 2011:957164. [PMID: 21197105 PMCID: PMC3005801 DOI: 10.4061/2011/957164] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 11/05/2010] [Indexed: 12/23/2022] Open
Abstract
Incidence of cardiovascular disease (CVD) is remarkably high among patients with chronic kidney disease (CKD), even in the early microalbuminuric stages with normal glomerular filtration rates. Proximal tubule cells (PTCs) mediate metabolism and urinary excretion of vasculotoxic substances via apical and basolateral receptors and transporters. These cells also retrieve vasculoprotective substances from circulation or synthesize them for release into the circulation. PTCs are also involved in the uptake of sodium and phosphate, which are critical for hemodynamic regulation and maintaining the mineral balance, respectively. Dysregulation of PTC functions in CKD is likely to be associated with the development of CVD and is linked to the progression to end-stage renal disease. In particular, PTC dysfunction occurs early in diabetic nephropathy, a leading cause of CKD. It is therefore important to elucidate the mechanisms of PTC dysfunction to develop therapeutic strategies for treating cardiorenal syndrome in diabetes.
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Affiliation(s)
- Akihiko Saito
- Department of Applied Molecular Medicine and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan
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