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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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Rios-Leyvraz M, Thacher TD, Dabas A, Elsedfy HH, Baroncelli GI, Cashman KD. Serum 25-hydroxyvitamin D threshold and risk of rickets in young children: a systematic review and individual participant data meta-analysis to inform the development of dietary requirements for vitamin D. Eur J Nutr 2024; 63:673-695. [PMID: 38280944 PMCID: PMC10948504 DOI: 10.1007/s00394-023-03299-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 11/28/2023] [Indexed: 01/29/2024]
Abstract
PURPOSE The objective of this systematic review was to determine a minimum serum 25-hydroxyvitamin D (25OHD) threshold based on the risk of having rickets in young children. This work was commissioned by the WHO and FAO within the framework of the update of the vitamin D requirements for children 0-3 years old. METHODS A systematic search of Embase was conducted to identify studies involving children below 4 years of age with serum 25OHD levels and radiologically confirmed rickets, without any restriction related to the geographical location or language. Study-level and individual participant data (IPD)-level random effects multi-level meta-analyses were conducted. The odds, sensitivity and specificity for rickets at different serum 25OHD thresholds were calculated for all children as well as for children with adequate calcium intakes only. RESULTS A total of 120 studies with 5412 participants were included. At the study-level, children with rickets had a mean serum 25OHD of 23 nmol/L (95% CI 19-27). At the IPD level, children with rickets had a median and mean serum 25OHD of 23 and 29 nmol/L, respectively. More than half (55%) of the children with rickets had serum 25OHD below 25 nmol/L, 62% below 30 nmol/L, and 79% below 40 nmol/L. Analysis of odds, sensitivities and specificities for nutritional rickets at different serum 25OHD thresholds suggested a minimal risk threshold of around 28 nmol/L for children with adequate calcium intakes and 40 nmol/L for children with low calcium intakes. CONCLUSION This systematic review and IPD meta-analysis suggests that from a public health perspective and to inform the development of dietary requirements for vitamin D, a minimum serum 25OHD threshold of around 28 nmol/L and above would represent a low risk of nutritional rickets for the majority of children with an adequate calcium intake.
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Affiliation(s)
- Magali Rios-Leyvraz
- Department of Nutrition and Food Safety, World Health Organization, Geneva, Switzerland.
| | - Tom D Thacher
- Department of Family Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Aashima Dabas
- Department of Pediatrics, Maulana Azad Medical College, New Delhi, India
| | | | - Giampiero I Baroncelli
- Pediatric and Adolescent Endocrinology, Division of Pediatrics, Department of Obstetrics, Gynecology and Pediatrics, University Hospital, Pisa, Italy
| | - Kevin D Cashman
- Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences, and Department of Medicine, University College Cork, Cork, Ireland
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Raimann A, Misof BM, Fratzl P, Fratzl-Zelman N. Bone Material Properties in Bone Diseases Affecting Children. Curr Osteoporos Rep 2023; 21:787-805. [PMID: 37897675 DOI: 10.1007/s11914-023-00822-6] [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] [Accepted: 09/12/2023] [Indexed: 10/30/2023]
Abstract
PURPOSE OF REVIEW Metabolic and genetic bone disorders affect not only bone mass but often also the bone material, including degree of mineralization, matrix organization, and lacunar porosity. The quality of juvenile bone is moreover highly influenced by skeletal growth. This review aims to provide a compact summary of the present knowledge on the complex interplay between bone modeling and remodeling during skeletal growth and to alert the reader to the complexity of bone tissue characteristics in children with bone disorders. RECENT FINDINGS We describe cellular events together with the characteristics of the different tissues and organic matrix organization (cartilage, woven and lamellar bone) occurring during linear growth. Subsequently, we present typical alterations thereof in disorders leading to over-mineralized bone matrix compared to those associated with low or normal mineral content based on bone biopsy studies. Growth spurts or growth retardation might amplify or mask disease-related alterations in bone material, which makes the interpretation of bone tissue findings in children complex and challenging.
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Affiliation(s)
- Adalbert Raimann
- Department of Pediatrics and Adolescent Medicine, Division of Pediatric Pulmonology, Allergology and Endocrinology, Medical University of Vienna, Vienna, Austria
- Vienna Bone and Growth Center, Vienna, Austria
| | - Barbara M Misof
- Vienna Bone and Growth Center, Vienna, Austria
- Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of OEGK and AUVA Trauma Center Meidling, 1st Medical Department, Hanusch Hospital, Vienna, Austria
| | - Peter Fratzl
- Max Planck Institute of Colloids and Interfaces, Department of Biomaterials, Research Campus Golm, Potsdam, Germany
| | - Nadja Fratzl-Zelman
- Vienna Bone and Growth Center, Vienna, Austria.
- Ludwig Boltzmann Institute of Osteology at the Hanusch Hospital of OEGK and AUVA Trauma Center Meidling, 1st Medical Department, Hanusch Hospital, Vienna, Austria.
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Fischer PR, Sempos CT, Pettifor JM, Fraser DR, Munns CF, Durazo-Arvizu RA, Thacher TD. Serum 1,25-dihydroxyvitamin D levels in the diagnosis and pathogenesis of nutritional rickets - a multivariable re-analysis of a case-control study. Am J Clin Nutr 2023; 117:998-1004. [PMID: 36801463 DOI: 10.1016/j.ajcnut.2023.02.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 02/08/2023] [Accepted: 02/13/2023] [Indexed: 02/21/2023] Open
Abstract
BACKGROUND A multivariable logistic regression model resulting from a case-control study of nutritional rickets in Nigerian children suggested that higher levels of serum 25(OH)D may be required to prevent nutritional rickets in populations with low-calcium intakes. OBJECTIVES This current study evaluates if adding serum 1,25-dihydroxyvitamin D [1,25(OH)2D] to that model shows that increased levels of serum 1,25(OH)2D are independently associated with risk of children on low-calcium diets having nutritional rickets. METHODS Multivariable logistic regression analysis was used to model the association between serum 1,25(OH)2D and risk of having nutritional rickets in cases (n = 108) and controls (n = 115) after adjusting for age, sex, weight-for age z-score, religion, phosphorus intake and age began walking and the interaction between serum 25(OH)D and dietary calcium intake (Full Model). RESULTS Serum 1,25(OH)2D levels were significantly higher (320 pmol/L vs. 280 pmol/L) (P = 0.002), and 25(OH)D levels were lower (33 nmol/L vs. 52 nmol/L) (P < 0.0001) in children with rickets than in control children. Serum calcium levels were lower in children with rickets (1.9 mmol/L) than in control children (2.2 mmol/L) (P < 0.001). Dietary calcium intakes were similarly low in both groups (212 mg/d) (P = 0.973). In the multivariable logistic model, 1,25(OH)2D was independently associated with risk of having rickets [coefficient = 0.007 (95% confidence limits: 0.002-0.011)] after adjusting for all variables in the Full Model. CONCLUSIONS Results confirmed theoretical models that in children with low dietary calcium intake, 1,25(OH)2D serum concentrations are higher in children with rickets than in children without rickets. The difference in 1,25(OH)2D levels is consistent with the hypothesis that children with rickets have lower serum calcium concentrations which prompt the elevation of PTH levels resulting in an elevation of 1,25(OH)2D levels. These results support the need for additional studies to identify dietary and environmental risks for nutritional rickets.
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Affiliation(s)
- Philip R Fischer
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN, United States, Department of Pediatrics, Sheikh Shakhbout Medical City, Abu Dhabi, United Arab Emirates and Khalifa University College of Medicine and Health Sciences, Abu Dhabi, United Arab Emirates.
| | | | - John M Pettifor
- Department of Pediatrics, SAMRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa
| | - David R Fraser
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, Australia
| | - Craig F Munns
- Child Health Research Centre, The University of Queensland, Brisbane, Queensland, Australia and Department of Endocrinology and Diabetes, Queensland Children's Hospital, Brisbane, Queensland, Australia
| | - Ramon A Durazo-Arvizu
- Biostatistical Core, The Sabin Research Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States
| | - Tom D Thacher
- Department of Family Medicine, Jos University Teaching Hospital, Jos, Nigeria
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Vlok M, Snoddy AME, Ramesh N, Wheeler BJ, Standen VG, Arriaza BT. The role of dietary calcium in the etiology of childhood rickets in the past and the present. Am J Hum Biol 2023; 35:e23819. [PMID: 36251616 DOI: 10.1002/ajhb.23819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 09/06/2022] [Accepted: 09/27/2022] [Indexed: 11/11/2022] Open
Abstract
For more than two centuries, lack of sunlight has been understood to cause vitamin D deficiency and documented as a primary cause of rickets. As such, evidence of rickets in the archeological record has been used as a proxy for vitamin D status in past individuals and populations. In the last decade, a clinical global consensus has emerged wherein it is recognized that dietary calcium deficiency also plays a role in the manifestation of rickets and classic skeletal deformities may not form if dietary calcium is normal even if vitamin D is deficient. This disease is now clinically called "nutritional rickets" to reflect the fact that rickets can take calcium deficiency-predominant or vitamin D deficiency-predominant forms. However, there are currently no paleopathological studies wherein dietary calcium deficiency is critically considered a primary etiology of the disease. We review here the interplay of calcium, vitamin D, and phosphorous in bone homeostasis, examine the role of dietary calcium in human health, and critically explore the clinical literature on calcium deficiency-predominant rickets. Finally, we report a case of rickets from the late Formative Period (~2500-1500 years ago) of the Atacama Desert and argue the disease in this infant is likely an example of calcium deficiency-predominant rickets. We conclude that most archeological cases of rickets are the result of multiple micronutrient deficiencies that compound to manifest in macroscopic skeletal lesions. For clinicians, these factors are important for implementing best treatment practice, and for paleopathologists they are necessary for appropriate interpretation of health in past communities.
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Affiliation(s)
- Melandri Vlok
- Sydney Southeast Asia Centre, The University of Sydney, Camperdown, Australia.,Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Anne Marie E Snoddy
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Niranjan Ramesh
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Benjamin J Wheeler
- Department of Women and Children's Health, Otago Medical School, University of Otago, Dunedin, New Zealand
| | - Vivien G Standen
- Departamento de Antropología, Universidad de Tarapacá, Arica, Chile
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Windswept Deformity a Disease or a Symptom? A Systematic Review on the Aetiologies and Hypotheses of Simultaneous Genu Valgum and Varum in Children. CHILDREN 2022; 9:children9050703. [PMID: 35626880 PMCID: PMC9140164 DOI: 10.3390/children9050703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 05/01/2022] [Accepted: 05/03/2022] [Indexed: 11/17/2022]
Abstract
Objective: The objective of this study is to create an overview of the possible aetiologies of windswept deformity and to emphasize the points of attention when presented with a case. Methods: A systematic search according to the PRISMA statement was conducted using PubMed, African Journals Online, Cochrane, Embase, Google Scholar, and Web of Science. Articles investigating the aetiology of windswept deformity at the knee in children, and articles with windswept deformity as an ancillary finding were included. The bibliographic search was limited to English-language articles only. The level of evidence and methodological appraisal were assessed. Results: Forty-five articles discussing the aetiology of windswept deformity were included. A variety of aetiologies can be brought forward. These can be divided into the following groups: ‘Rickets and other metabolic disorders’, ‘skeletal dysplasias and other genetic disorders’, ‘trauma’ and ‘descriptive articles without specific underlying disorder’. With rickets being the largest group. Interestingly, in the group without a specific underlying disorder, all patients were from African descent, being otherwise healthy and presented with windswept deformity between two and three years of age. Conclusion: We have presented an overview that may help identify the underlying disorder in children with windswept deformity. A step-by-step guide for clinicians who see a child with windswept deformity is provided. Even though, according to the Oxford level of evidence, most articles have a low level of evidence.
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Mays S, Brickley MB. Is dietary deficiency of calcium a factor in rickets? Use of current evidence for our understanding of the disease in the past. INTERNATIONAL JOURNAL OF PALEOPATHOLOGY 2022; 36:36-44. [PMID: 35139469 DOI: 10.1016/j.ijpp.2021.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 11/01/2021] [Accepted: 11/25/2021] [Indexed: 06/14/2023]
Abstract
OBJECTIVE Rickets is considered an indicator of vitamin D deficiency in palaeopathology, but a strand of biomedical thought maintains that dietary calcium deficiency may sometimes play a part in its causation. Our aim is to evaluate the extent to which low calcium intake should be considered as a factor in biocultural interpretations of rickets. METHODS We assess published modern epidemiological studies that provide primary data to support claims for a role for dietary calcium deficiency in rickets. We also consider how we might identify, via indicators of calcium intake, populations at risk of calcium deficiency in the past. RESULTS Support for dietary calcium deficiency as a cause of rickets is equivocal. Direct measurement of dietary calcium in the past is not possible, but exposure to risk factors for low calcium intake can to some extent be identified. CONCLUSION Whilst there is little evidence to alter the view that rickets is essentially an indicator of a population's vitamin D status, occasionally, in very low calcium intake groups, dietary calcium deficiency may play a synergistic role by accentuating the need for vitamin D. SIGNIFICANCE The notion that dietary calcium deficiency may be a cause of rickets appears to be gaining currency in bioarchaeological studies. This paper shows that it is unusual for this to be the case, and even then the role of vitamin D remains crucial. LIMITATIONS This paper attempts to summarise the current state of biomedical study in an area that is subject to continuing investigation.
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Affiliation(s)
- S Mays
- Research Department, Historic England, UK; Department of Archaeology, University of Southampton, UK; School of History, Classics and Archaeology, University of Edinburgh, UK.
| | - M B Brickley
- Department of Anthropology, McMaster University, Canada
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Abstract
Policy decisions and the practice of public health nutrition need to be based on solid evidence, developed through rigorous research studies where objective measures are used and results that run counter to dogma are not dismissed but investigated. In recent years, enhancements in study designs, and methodologies for systematic reviews and meta-analysis, have improved the evidence-base for nutrition policy and practice. However, these still rely on a full appreciation of the strengths and limitations of the measures on which conclusions are drawn and on the thorough investigation of outcomes that do not fit expectations or prevailing convictions. The importance of ‘hard facts’ and ‘misfits’ in research designed to advance knowledge and improve public health nutrition is illustrated in this paper through a selection of studies from different stages in my research career, focused on the nutritional requirements of resource-poor populations in Africa and Asia.
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Braithwaite VS, Mwangi MN, Jones KS, Demir AY, Prentice A, Prentice AM, Andang'o PEA, Verhoef H. Antenatal iron supplementation, FGF23, and bone metabolism in Kenyan women and their offspring: secondary analysis of a randomized controlled trial. Am J Clin Nutr 2021; 113:1104-1114. [PMID: 33675347 PMCID: PMC8106766 DOI: 10.1093/ajcn/nqaa417] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 12/10/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Fibroblast growth factor-23 (FGF23) regulates body phosphate homeostasis primarily by increasing phosphaturia. It also acts as a vitamin D-regulating hormone. Maternal iron deficiency is associated with perturbed expression and/or regulation of FGF23 and hence might be implicated in the pathogenesis of hypophosphatemia-driven rickets in their offspring. OBJECTIVES We aimed to determine the effect of antenatal oral iron supplementation on FGF23 concentration and maternal and infant markers of bone-mineral regulation. METHODS We performed a secondary analysis of a trial in which 470 rural Kenyan women with singleton pregnancies and hemoglobin concentrations ≥ 90 g/L were randomly allocated to daily, supervised supplementation with 60 mg elemental iron as ferrous fumarate or placebo from 13-23 weeks of gestation until 1 mo postpartum. As previously reported, iron supplementation improved iron status in mothers and neonates. For the present study, we reanalyzed all available plasma samples collected in mothers and neonates at birth, with primary outcomes being concentrations of FGF23, measured by 2 assays: 1 that detects intact hormone and C-terminal cleavage products (total-FGF23) and another that detects the intact hormone only (intact-FGF23). RESULTS Analysis was performed on 433 women (n = 216, iron group; n = 217, placebo group) and 414 neonates (n = 207, iron group; n = 207, placebo group). Antenatal iron supplementation reduced geometric mean total-FGF23 concentrations in mothers and neonates by 62.6% (95% CI: 53.0%, 70.3%) and 15.2% (95% CI: -0.3%, 28.4%, P = 0.06), respectively. In addition, it increased geometric mean neonatal intact-FGF23 concentrations by 21.6% (95% CI: 1.2%, 46.1%), increased geometric mean maternal hepcidin concentrations by 136.4% (95% CI: 86.1%, 200.3%), and decreased mean maternal 25-hydroxyvitamin D concentrations by 6.1 nmol/L (95% CI: -11.0, -1.2 nmol/L). CONCLUSIONS Analysis of this randomized trial confirms that iron supplementation can reverse elevated FGF23 production caused by iron deficiency in iron-deficient mothers and their neonates. Further investigations are warranted to assess to what extent iron supplementation can prevent FGF23-mediated hypophosphatemic rickets or osteomalacia.
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Affiliation(s)
| | - Martin N Mwangi
- Wageningen University, Division of Human Nutrition and Health, P.O. Box 17, 6700 AA Wageningen, The Netherlands,University of Malawi, College of Medicine, Training and Research Unit of Excellence, Private Bag 360, BT 3, Chichiri, Blantyre, Malawi
| | - Kerry S Jones
- National Institute for Health Research (NIHR) Biomedical Research Centre Nutritional Biomarker Laboratory, MRC Epidemiology Unit, University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0AH, United Kingdom
| | - Ayşe Y Demir
- Meander Medical Centre, Laboratory for Clinical Chemistry and Hematology, P.O. Box 1502, 3800 BM Amersfoort, The Netherlands
| | - Ann Prentice
- Medical Research Council (MRC) Nutrition and Bone Health Research Group, Clifford Allbutt Building, University of Cambridge, Cambridge Biomedical Campus, Cambridge, CB2 0AH, United Kingdom (formerly the MRC Elsie Widdowson Laboratory, 120 Fulbourn Road, Cambridge, CB1 9NL, United Kingdom),Medical Research Council (MRC) Unit The Gambia at London School of Hygiene & Tropical Medicine, Atlantic Boulevard, Fajara, Banjul, The Gambia
| | - Andrew M Prentice
- Medical Research Council (MRC) Unit The Gambia at London School of Hygiene & Tropical Medicine, Atlantic Boulevard, Fajara, Banjul, The Gambia
| | - Pauline E A Andang'o
- Maseno University, School of Public Health and Community Development, Maseno, Kenya
| | - Hans Verhoef
- Wageningen University, Division of Human Nutrition and Health, P.O. Box 17, 6700 AA Wageningen, The Netherlands,Wageningen University, Cell Biology and Immunology Group, P.O. Box 338, 6708 WD Wageningen, The Netherlands
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Ahmed S, Goldberg GR, Raqib R, Roy SK, Haque S, Braithwaite VS, Pettifor JM, Prentice A. Aetiology of nutritional rickets in rural Bangladeshi children. Bone 2020; 136:115357. [PMID: 32276153 PMCID: PMC7262584 DOI: 10.1016/j.bone.2020.115357] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/01/2020] [Accepted: 04/03/2020] [Indexed: 01/26/2023]
Abstract
OBJECTIVES A high prevalence of rickets of unknown aetiology has been reported in Chakaria, Bangladesh. Classically, rickets is caused by vitamin D deficiency but increasing evidence from Africa and Asia points towards other nutritional deficiencies or excessive exposure to some metals. The aim of this study was to investigate the aetiology of rickets in rural Bangladeshi children. METHODS 64 cases with rickets-like deformities were recruited at first presentation together with age-sex-village matched controls. Data and sample acquisition included anthropometry, radiographs, fasted plasma and urinary samples, 24 h weighed dietary intake together with a 24 h urine collection, and 13C-breath tests to detect Helicobacter (H.) pylori infection. RESULTS One child had active rickets and frank hypovitaminosis D (F, n = 1) and one had deformities with radiological features of Blount disease (M, n = 1). The remaining cases were grouped into those with active rickets, defined as a radiographic Thacher score ≥1.5 (Group A, n = 24, 12M, 12F) and rickets-like bone deformities but not active rickets (Group B, n = 38, 28M, 10F). All children had a low dietary calcium intake, but this was lower in Group A than their controls (mean (SD): 156 (80) versus 323 (249) mg/day, p = 0.005). Plasma 25-hydroxyvitamin D (25OHD) was lower in Group A compared to controls; 63% of Group A and 8% of controls had a concentration <25 nmol/L (p ≤ 0.0001). There was, however, no evidence of differences in skin sunshine exposure. Group A had lower plasma calcium and phosphate and higher 1,25-dihydroxyvitamin D (1,25(OH)2D) and parathyroid hormone (PTH). 88% of Group A and 0% of controls had undetectable plasma intact fibroblast growth factor (iFGF23), with c-terminal FGF23 (cFGF23) concentrations in the normal range. Urinary phosphate and daily outputs of environmental metals relative to creatinine were higher and tubular maximal phosphate reabsorption per unit glomerular filtration rate (TmP/GFR) was lower in Group A compared to controls. Although less pronounced than Group A, Group B had higher alkaline phosphatase, 1,25(OH)2D and PTH concentrations than controls but similar calcium intake, TmP/GFR, iFGF23 and cFGF23 concentrations. Mean 25OHD concentrations were also similar to controls and there was no significant difference in the percentage <25 nmol/L (Group B: 13%, controls: 5%, p = 0.2) No group differences were seen in prevalence of anaemia, iron deficiency or H. pylori infection. CONCLUSION Nutritional rickets in this region is likely to be predominantly due to low calcium intake in the context of poor vitamin D status and exposure to environmental metals, but not H. pylori infection, anaemia or iron deficiency.
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Affiliation(s)
- Sonia Ahmed
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK; International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), Dhaka 1000, Bangladesh.
| | - Gail R Goldberg
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK
| | - Rubhana Raqib
- International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), Dhaka 1000, Bangladesh
| | - Swapan Kumar Roy
- International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), Dhaka 1000, Bangladesh
| | - Shahidul Haque
- Social Assistance and Rehabilitation for the Physically Vulnerable (SARPV), Dhaka 1207, Bangladesh
| | - Vickie S Braithwaite
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK; MRC Epidemiology Unit, University of Cambridge School of Clinical Medicine, Cambridge CB2 0SL, UK
| | - John M Pettifor
- SAMRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, University of the Witwatersrand, Johannesburg, South Africa
| | - Ann Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK
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11
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Bouillon R, Antonio L. Nutritional rickets: Historic overview and plan for worldwide eradication. J Steroid Biochem Mol Biol 2020; 198:105563. [PMID: 31809867 DOI: 10.1016/j.jsbmb.2019.105563] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 11/10/2019] [Accepted: 12/02/2019] [Indexed: 02/01/2023]
Abstract
Rickets was first described in great detail in the mid 17th century and was affecting a great number of children in major European cities. The disease, however, existed already in the Roman times. The etiology of this disease remained enigmatic until the 1920s when two different mechanisms, lack of exposure to sunlight and lack of a dietary factor were finally solved by the discovery of vitamin D and its dual origin. Soon thereafter, the implementation of vitamin D supplementation for all infants and small children largely eliminated nutritional rickets in Europe and North America. It took nearly a century to elucidate the complex chemistry, metabolism, mode and spectrum of activity of the vitamin D endocrine system. Nutritional rickets, whether due to simple vitamin D or calcium deficiency or both, remains widely ravaging many infants and children around the world. Asian countries and the Middle East are mainly confronted with vitamin D deficiency whereas many African and some Asian countries face calcium deficiency rickets. Immigrants and refugees or in general people with a darker skin living in moderate climate zone are also confronted with this disease. There is great consensus how this disease could be prevented or cured. In collaboration with most international professional societies, we prepare a memorandum, in line with the successful battle against iodine deficiency disorders, to convince the World Health Organization and its member states to start an implementation program to eradicate nutritional rickets by 2030.
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Affiliation(s)
- Roger Bouillon
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases, Metabolism and Ageing, KU, Leuven, Belgium.
| | - Leen Antonio
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases, Metabolism and Ageing, KU, Leuven, Belgium
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12
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Bharati J, Bhatia D, Khandelwal P, Gupta N, Sinha A, Khadgawat R, Hari P, Bagga A. C-Terminal Fibroblast Growth Factor-23 Levels in Non-Nutritional Hypophosphatemic Rickets. Indian J Pediatr 2019; 86:555-557. [PMID: 30835073 DOI: 10.1007/s12098-019-02909-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 02/14/2019] [Indexed: 01/08/2023]
Abstract
Fibroblast growth factor-23 (FGF23) is central to phosphate homeostasis. The author examined if blood levels of FGF23 allow discrimination of classic hypophosphatemic rickets from other causes of non-nutritional rickets with hypophosphatemia. Forty-two children (median age: 102 mo) with non-nutritional rickets and hypophosphatemia were clinically classified as having distal renal tubular acidosis (RTA, n = 12), Fanconi syndrome (n = 8), classic hypophosphatemic rickets (n = 11), vitamin D dependent rickets (n = 7) and Dent disease (n = 4). Median blood FGF23 (measured by C-terminal ELISA) concentrations were similar in all groups (P = 0.24). These levels did not correlate with phosphate, tubular maximum for phosphate, calcium, 25-hydroxyvitamin D, creatinine, and parathormone levels. Patients with distal RTA showed variable degree of proximal tubular dysfunction that resolved following alkali supplements. Blood FGF23 levels did not satisfactorily differentiate classic hypophosphatemic rickets from other causes of hypophosphatemic rickets.
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Affiliation(s)
- Joyita Bharati
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Divya Bhatia
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Priyanka Khandelwal
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Nandita Gupta
- Department of Endocrinology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Aditi Sinha
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Rajesh Khadgawat
- Department of Endocrinology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
| | - Pankaj Hari
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
| | - Arvind Bagga
- Division of Nephrology, Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India.
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13
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Thandrayen K, Pettifor JM. The roles of vitamin D and dietary calcium in nutritional rickets. Bone Rep 2018; 8:81-89. [PMID: 29955625 PMCID: PMC6019962 DOI: 10.1016/j.bonr.2018.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/04/2018] [Accepted: 01/25/2018] [Indexed: 01/31/2023] Open
Abstract
The etiology and pathogenesis of nutritional rickets are becoming progressively clearer. Vitamin D deficiency has generally been considered the major or only player in the pathogenesis of nutritional rickets. However, recent research into calcium deficiency has now provided clinicians with reasons to investigate and manage patients with nutritional rickets more appropriately. The important question when assessing cases of nutritional rickets is: “Is it calcium or vitamin D deficiency or both that play a major role in the pathogenesis of the disease?” The case presentation in this review highlights the risk factors, clinical presentation and pathophysiology of nutritional rickets in a young South African black child from a semi-urban area in Johannesburg, a city with abundant sunshine throughout the year. Vitamin D and calcium deficiencies play synergistic roles in nutritional rickets. Dietary calcium intake of <300 mg/day increases the risk of nutritional rickets. Vitamin D status is worsened by dietary calcium deficiency itself. Marked elevation of 1,25-dihydroxyvitamin D is characteristic of calcium deficiency. Preventative strategies needed to decrease the prevalence of nutritional rickets.
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Affiliation(s)
- Kebashni Thandrayen
- Department of Paediatrics, Chris Hani Baragwanath Academic Hospital, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - John M Pettifor
- Department of Paediatrics, MRC/Wits Developmental Pathways for Health Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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14
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Abstract
Rickets is a bone disease associated with abnormal serum calcium and phosphate levels. The clinical presentation is heterogeneous and depends on the age of onset and pathogenesis but includes bowing deformities of the legs, short stature and widening of joints. The disorder can be caused by nutritional deficiencies or genetic defects. Mutations in genes encoding proteins involved in vitamin D metabolism or action, fibroblast growth factor 23 (FGF23) production or degradation, renal phosphate handling or bone mineralization have been identified. The prevalence of nutritional rickets has substantially declined compared with the prevalence 200 years ago, but the condition has been re-emerging even in some well-resourced countries; prematurely born infants or breastfed infants who have dark skin types are particularly at risk. Diagnosis is usually established by medical history, physical examination, biochemical tests and radiography. Prevention is possible only for nutritional rickets and includes supplementation or food fortification with calcium and vitamin D either alone or in combination with sunlight exposure. Treatment of typical nutritional rickets includes calcium and/or vitamin D supplementation, although instances infrequently occur in which phosphate repletion may be necessary. Management of heritable types of rickets associated with defects in vitamin D metabolism or activation involves the administration of vitamin D metabolites. Oral phosphate supplementation is usually indicated for FGF23-independent phosphopenic rickets, whereas the conventional treatment of FGF23-dependent types of rickets includes a combination of phosphate and activated vitamin D; an anti-FGF23 antibody has shown promising results and is under further study.
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15
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Abstract
Twin studies indicate that genetic factors may explain about 50% of the variation of serum 25-hydroxyvitamin D (25OHD). Polymorphisms of 3 genes, delta-7-sterol-reductase, CYP2R1, and DBP/GC (and maybe CYP24A1) combined, can explain about 5% to 10% of the variation in serum 25OHD. These polymorphisms are found in nearly all populations. The variation in serum 25OHD found in different areas and populations in the world is mainly due to environmental and lifestyle factors, not truly dependent on racial differences. One genetic variant of DBP, (GC2), is associated with a modest (∼10%) decrease in serum DBP and 25OHD concentrations for unexplained reasons.
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Affiliation(s)
- Roger Bouillon
- Clinical and Experimental Endocrinology, KU Leuven, Herestraat 49 ON1 Box 902, Leuven 3000, Belgium.
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16
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Jones KDJ, Hachmeister CU, Khasira M, Cox L, Schoenmakers I, Munyi C, Nassir HS, Hünten-Kirsch B, Prentice A, Berkley JA. Vitamin D deficiency causes rickets in an urban informal settlement in Kenya and is associated with malnutrition. MATERNAL AND CHILD NUTRITION 2017; 14. [PMID: 28470840 PMCID: PMC5763407 DOI: 10.1111/mcn.12452] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 02/28/2017] [Accepted: 03/01/2017] [Indexed: 11/29/2022]
Abstract
The commonest cause of rickets worldwide is vitamin D deficiency, but studies from sub-Saharan Africa describe an endemic vitamin D-independent form that responds to dietary calcium enrichment. The extent to which calcium-deficiency rickets is the dominant form across sub-Saharan Africa and in other low-latitude areas is unknown. We aimed to characterise the clinical and biochemical features of young children with rickets in a densely populated urban informal settlement in Kenya. Because malnutrition may mask the clinical features of rickets, we also looked for biochemical indices of risk in children with varying degrees of acute malnutrition. Twenty one children with rickets, aged 3 to 24 months, were identified on the basis of clinical and radiologic features, along with 22 community controls, and 41 children with either severe or moderate acute malnutrition. Most children with rickets had wrist widening (100%) and rachitic rosary (90%), as opposed to lower limb features (19%). Developmental delay (52%), acute malnutrition (71%), and stunting (62%) were common. Compared to controls, there were no differences in calcium intake, but most (71%) had serum 25-hydroxyvitamin D levels below 30 nmol/L. These results suggest that rickets in young children in urban Kenya is usually driven by vitamin D deficiency, and vitamin D supplementation is likely to be required for full recovery. Wasting was associated with lower calcium (p = .001), phosphate (p < .001), 25-hydroxyvitamin D (p = .049), and 1,25-dihydroxyvitamin D (p = 0.022) levels, the clinical significance of which remain unclear.
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Affiliation(s)
- Kelsey D J Jones
- KEMRI-Wellcome Trust Research Programme, Kenya.,Section of Paediatrics and Centre for Global Health Research, Imperial College, London, UK
| | | | | | - Lorna Cox
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK
| | - Inez Schoenmakers
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.,Department of Medicine, Faculty of Medicine and Health Science, University of East Anglia, Norwich, UK
| | - Caroline Munyi
- Baraka Health Centre, German Doctors Nairobi, Nairobi, Kenya
| | - H Samira Nassir
- Baraka Health Centre, German Doctors Nairobi, Nairobi, Kenya
| | | | - Ann Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.,MRC Keneba, The Gambia
| | - James A Berkley
- KEMRI-Wellcome Trust Research Programme, Kenya.,Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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Creo AL, Thacher TD, Pettifor JM, Strand MA, Fischer PR. Nutritional rickets around the world: an update. Paediatr Int Child Health 2017; 37:84-98. [PMID: 27922335 DOI: 10.1080/20469047.2016.1248170] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Worldwide, nutritional rickets continues to be an evolving problem with several causes. This paper provides an updated literature review characterising the prevalence, aetiology, pathophysiology and treatment of nutritional rickets worldwide. A systematic review of articles on nutritional rickets from various geographical regions was undertaken. For each region, key information was extracted, including prevalence, cause of rickets specific to the region, methods of confirming the diagnosis and current treatment and preventive measures. Calcium deficiency continues to be a major cause of rickets in Africa and Asia. Vitamin D deficiency rickets is perhaps increasing in the Americas, Europe and parts of the Middle East. There continues to be a distinct presentation of calcium-predominant versus vitamin D predominant rickets, although there are overlapping features. More careful diagnosis of rickets and reporting of 25-OHD concentrations has improved accurate knowledge of rickets prevalence and better delineated the cause. Nutritional rickets continues to be an evolving and multi-factorial problem worldwide. It is on a spectrum, ranging from isolated vitamin D deficiency to isolated calcium deficiency. Specific areas which require emphasis include a consistent community approach to screening and diagnosis, vitamin D supplementation of infants and at-risk children, prevention of maternal vitamin D deficiency and the provision of calcium in areas with low calcium diets.
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Affiliation(s)
- Ana L Creo
- a Department of Pediatric and Adolescent Medicine , Mayo Clinic , Rochester , MN , USA
| | - Tom D Thacher
- b Department of Family Medicine , Mayo Clinic , Rochester , MN , USA
| | - John M Pettifor
- c Wits/SAMRC Developmental Pathways for Health Research Unit, Department of Paediatrics , University of the Witwatersrand , Johannesburg , South Africa
| | - Mark A Strand
- d Pharmacy Practice, Department of Public Health , North Dakota State University , Fargo , ND , USA
| | - Philip R Fischer
- a Department of Pediatric and Adolescent Medicine , Mayo Clinic , Rochester , MN , USA
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18
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Mitchell DM, Jüppner H, Burnett-Bowie SAM. FGF23 Is Not Associated With Age-Related Changes in Phosphate, but Enhances Renal Calcium Reabsorption in Girls. J Clin Endocrinol Metab 2017; 102:1151-1160. [PMID: 28323960 PMCID: PMC5460726 DOI: 10.1210/jc.2016-4038] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 01/25/2017] [Indexed: 02/06/2023]
Abstract
CONTEXT Fibroblast growth factor (FGF)23 is a critical determinant of phosphate homeostasis. The role of FGF23, however, in regulating physiologic changes in serum phosphate and renal phosphate handling across childhood is not well described. In addition, animal models have suggested a role for FGF23 in regulating renal calcium excretion. OBJECTIVE To assess changes in FGF23 concentrations across childhood in relation to changes in mineral ions and hormones of mineral ion homeostasis. DESIGN This was a cross-sectional study. SETTING The study was conducted at a Clinical Research Center at a tertiary care hospital. PATIENTS OR OTHER PARTICIPANTS Ninety healthy girls ages 9 to 18 years were recruited from the surrounding community. MAIN OUTCOME MEASURES The associations of intact and C-terminal FGF23 concentrations with measures of mineral ion homeostasis were determined by univariable and multivariable linear regression. RESULTS Serum phosphate and renal phosphate excretion varied with age, as expected (R = -0.49, P < 0.001 and R = -0.48, P < 0.001, respectively). Neither intact nor C-terminal FGF23 varied with age, and FGF23 was not correlated with serum or urinary phosphate. Intact FGF23 was positively correlated with serum calcium (R = 0.39, P < 0.001) and negatively correlated with urinary calcium/creatinine ratio (R = -0.27, P = 0.011). CONCLUSIONS The changes in serum and urinary phosphate handling across childhood do not appear to be determined by alterations in FGF23 concentrations. These data may point to a role for FGF23 in calcium regulation in human physiology.
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Affiliation(s)
| | - Harald Jüppner
- Endocrine Unit,
- Pediatric Nephrology Unit, Massachusetts General Hospital, Boston, Massachusetts 02114
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19
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Goto S, Fujii H, Kono K, Watanabe K, Nakai K, Nishi S. Serum FGF23 levels may not be associated with serum phosphate and 1,25-dihydroxyvitamin D levels in patients with Fanconi syndrome-induced hypophosphatemia. Clin Kidney J 2016; 9:677-81. [PMID: 27679714 PMCID: PMC5036911 DOI: 10.1093/ckj/sfw086] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 06/23/2016] [Indexed: 12/20/2022] Open
Abstract
Fibroblast growth factor 23 (FGF23) is regulated by sustained phosphate supplementation and restriction. However, few studies have investigated FGF23 levels in patients with Fanconi syndrome. Therefore, we evaluated intact and C-terminal FGF23 and FGF23-associated parameters in four patients with Fanconi syndrome. Serum intact and C-terminal FGF23 levels were extremely low. Although serum phosphate and 1,25-dihydroxyvitamin D levels improved to or above the normal range within 1 year of treatment with oral phosphate and calcitriol, serum FGF23 levels remained low. Serum FGF23 levels in patients with Fanconi syndrome might be regulated by novel factors other than serum phosphate and 1,25-dihydroxyvitamin D levels.
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Affiliation(s)
- Shunsuke Goto
- Division of Nephrology and Kidney Center , Kobe University Graduate School of Medicine , 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 , Japan
| | - Hideki Fujii
- Division of Nephrology and Kidney Center , Kobe University Graduate School of Medicine , 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 , Japan
| | - Keiji Kono
- Division of Nephrology and Kidney Center , Kobe University Graduate School of Medicine , 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 , Japan
| | - Kentaro Watanabe
- Division of Nephrology and Kidney Center , Kobe University Graduate School of Medicine , 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 , Japan
| | - Kentaro Nakai
- Division of Nephrology and Kidney Center , Kobe University Graduate School of Medicine , 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 , Japan
| | - Shinichi Nishi
- Division of Nephrology and Kidney Center , Kobe University Graduate School of Medicine , 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017 , Japan
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20
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Braithwaite VS, Freeman R, Greenwood CL, Summers DM, Nigdikar S, Lavy CBD, Offiah AC, Bishop NJ, Cashman J, Prentice A. The aetiology of rickets-like lower limb deformities in Malawian children. Osteoporos Int 2016; 27:2367-2372. [PMID: 27059923 PMCID: PMC4901102 DOI: 10.1007/s00198-016-3541-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 02/08/2016] [Indexed: 01/23/2023]
Abstract
UNLABELLED Debilitating rickets-like lower limb deformities are common in children throughout the world, particularly in Malawi, Africa where the causes are unknown. We have identified that Blount disease and calcium deficiency rickets are the likely causes of these deformities and propose calcium supplementation as a potential treatment of Malawian rickets. INTRODUCTION Surgical correction of rickets-like lower limb deformities is the most common paediatric operation performed at Beit Cure Orthopaedic Hospital, Malawi. The aim of this study was to investigate the aetiology of these deformities. METHODS Children with a tibio-femoral angle of deformity >20° were enrolled (n = 42, 3.0-15.0 years). Anthropometric and early life and well-being data were collected. Early morning serum and urine samples were collected on the morning of the operation for markers of calcium and phosphate homeostasis. Knee radiographs were obtained, and the children were diagnosed with either Blount (BD, n = 22) or evidence of rickets disease (RD, n = 20). As BD is a mechanical rather than metabolic disease, BD were assumed to be biochemically representative of the local population and thus used as a local reference for RD. RESULTS There were no differences in anthropometry or early life experiences between BD and RD. Parathyroid hormone (PTH), 1,25-dihydroxyvitamin D, total alkaline phosphatase and urinary phosphate were significantly higher and serum phosphate, 25-hydroxyvitamin D (25OHD) and tubular maximal reabsorption of phosphate significantly lower in RD than BD. There was no difference in serum calcium, fibroblast growth factor 23 or markers of iron status between groups. All children had 25OHD > 25 nmol/L. CONCLUSIONS Vitamin D deficiency is not implicated in the aetiology of RD or BD in Malawian children. The cause of RD in Malawi is likely to be dietary calcium deficiency leading to elevated PTH resulting in increased losses of phosphate from the bone and glomerular filtrate. The causes of BD remain unclear; there was no evidence in support of previously suggested risk factors such as being overweight or starting to walk early. Prior to surgical intervention, supplementation with calcium should be considered for children with RD.
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Affiliation(s)
- V S Braithwaite
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, UK.
| | - R Freeman
- Department of Paediatric Orthopaedics, Robert Jones Agnes Hunt NHS Foundation Trust, Oswestry, Shropshire, UK
| | - C L Greenwood
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, UK
| | - D M Summers
- Department of Surgery, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - S Nigdikar
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, UK
| | - C B D Lavy
- Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Science, University of Oxford, Oxford, UK
| | - A C Offiah
- Department of Oncology and Metabolism, Academic Unit of Child Health, University of Sheffield, Sheffield, UK
| | - N J Bishop
- Department of Oncology and Metabolism, Academic Unit of Child Health, University of Sheffield, Sheffield, UK
| | - J Cashman
- Beit Cure Orthopaedic Hospital, Blantyre, Malawi
| | - A Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, UK
- MRC Keneba, Keneba, The Gambia
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Braithwaite VS, Prentice A, Darboe MK, Prentice AM, Moore SE. The effects of maternal iron deficiency on infant fibroblast growth factor-23 and mineral metabolism. Bone 2016; 83:1-8. [PMID: 26453792 PMCID: PMC4720219 DOI: 10.1016/j.bone.2015.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 09/25/2015] [Accepted: 10/05/2015] [Indexed: 12/16/2022]
Abstract
Fibroblast growth factor-23 (FGF23), a phosphate(Phos)-regulating hormone, is abnormally elevated in hypophosphataemic syndromes and an elevated FGF23 is a predictor of mortality in kidney disease. Recent findings suggest iron deficiency as a potential mediator of FGF23 expression and murine studies have shown in utero effects of maternal iron deficiency on offspring FGF23 and phosphate metabolism. Our aim was to investigate the impact of maternal iron status on infant FGF23 and mineral metabolites over the first 2years of life. Infants born to mothers with normal (NIn=25,) and low (LIn=25) iron status during pregnancy, from a mother-infant trial (ISRCTN49285450) in rural Gambia, West Africa, had blood and plasma samples analysed at 12, 24, 52, 78 and 104weeks (wk) of age. Circulating intact-FGF23 (I-FGF23), Phos, total alkaline phosphatase (TALP) and haemoglobin (Hb) decreased and estimated glomerular filtration rate increased over time [all P≤0.0001)]. C-terminal-FGF23 (C-FGF23) and TALP were significantly higher in LI compared with NI, from 52wk for C-FGF23 [Beta coefficient (SE) 18.1 (0.04) %, P=0.04] and from 24wk for TALP [44.7 (29.6) U/L, P=0.04]. Infant Hb was the strongest negative predictor of C-FGF23 concentration [-21% (4%) RU/mL, P≤0.0001], Phos was the strongest positive predictor of I-FGF23 [32.0(3.9) pg/mL, P≤0.0001] and I-FGF23 did not predict C-FGF23 over time [-0.5% (0.5%), P=0.3]. In conclusion, this study suggests that poor maternal iron status is associated with a higher infant C-FGF23 and TALP but similar I-FGF23 concentrations in infants and young children. These findings further highlight the likely public health importance of preventing iron deficiency during pregnancy. Whether or not children who are born to iron deficient mothers have persistently high concentrations of these metabolites and are more likely to be at risk of impaired bone development and pre-disposed to rickets requires further research.
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Affiliation(s)
- V S Braithwaite
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK and MRC Unit, The Gambia.
| | - A Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK and MRC Unit, The Gambia
| | - M K Darboe
- MRC International Nutrition Group at London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UK and MRC Unit, The Gambia
| | - A M Prentice
- MRC International Nutrition Group at London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UK and MRC Unit, The Gambia
| | - S E Moore
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge CB1 9NL, UK and MRC Unit, The Gambia; MRC International Nutrition Group at London School of Hygiene & Tropical Medicine, Keppel St, London WC1E 7HT, UK and MRC Unit, The Gambia
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22
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Silanikove N, Leitner G, Merin U. The Interrelationships between Lactose Intolerance and the Modern Dairy Industry: Global Perspectives in Evolutional and Historical Backgrounds. Nutrients 2015; 7:7312-31. [PMID: 26404364 PMCID: PMC4586535 DOI: 10.3390/nu7095340] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/23/2015] [Accepted: 08/26/2015] [Indexed: 02/07/2023] Open
Abstract
Humans learned to exploit ruminants as a source of milk about 10,000 years ago. Since then, the use of domesticated ruminants as a source of milk and dairy products has expanded until today when the dairy industry has become one of the largest sectors in the modern food industry, including the spread at the present time to countries such as China and Japan. This review analyzes the reasons for this expansion and flourishing. As reviewed in detail, milk has numerous nutritional advantages, most important being almost an irreplaceable source of dietary calcium, hence justifying the effort required to increase its consumption. On the other hand, widespread lactose intolerance among the adult population is a considerable drawback to dairy-based foods consumption. Over the centuries, three factors allowed humans to overcome limitations imposed by lactose intolerance: (i) mutations, which occurred in particular populations, most notably in the north European Celtic societies and African nomads, in which carriers of the lactose intolerance gene converted from being lactose intolerant to lactose tolerant; (ii) the ability to develop low-lactose products such as cheese and yogurt; and (iii) colon microbiome adaptation, which allow lactose intolerant individuals to overcome its intolerance. However, in a few examples in the last decade, modern dairy products, such as the popular and widespread bio-cultured yogurts, were suspected to be unsuitable for lactose intolerant peoples. In addition, the use of lactose and milk-derived products containing lactose in non-dairy products has become widespread. For these reasons, it is concluded that it might be important and helpful to label food that may contain lactose because such information will allow lactose intolerant groups to control lactose intake within the physiological limitations of ~12 g per a single meal.
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Affiliation(s)
- Nissim Silanikove
- Biology of Lactation Laboratory, Institute of Animal Science, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel.
| | - Gabriel Leitner
- National Mastitis Reference Center, Kimron Veterinary Institute, P.O. Box 12, Bet Dagan 50250, Israel.
| | - Uzi Merin
- Department of Food Quality and Safety, Agricultural Research Organization, The Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel.
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Jones HL, Jammeh L, Owens S, Fulford AJ, Moore SE, Pettifor JM, Prentice A. Prevalence of rickets-like bone deformities in rural Gambian children. Bone 2015; 77:1-5. [PMID: 25871880 PMCID: PMC4456426 DOI: 10.1016/j.bone.2015.04.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 04/01/2015] [Accepted: 04/06/2015] [Indexed: 11/20/2022]
Abstract
The aim of this study was to estimate the burden of childhood rickets-like bone deformity in a rural region of West Africa where rickets has been reported in association with a low calcium intake. A population-based survey of children aged 0.5-17.9 years living in the province of West Kiang, The Gambia was conducted in 2007. 6221 children, 92% of those recorded in a recent census, were screened for physical signs of rickets by a trained survey team with clinical referral of suspected cases. Several objective measures were tested as potential screening tools. The prevalence of bone deformity in children <18.0 years was 3.3%. The prevalence was greater in males (M = 4.3%, F = 2.3%, p < 0.001) and in children <5.0 years (5.7%, M = 8.3%, F = 2.9%). Knock-knee was more common (58%) than bow-leg (31%) or windswept deformity (9%). Of the 196 examined clinically, 36 were confirmed to have a deformity outside normal variation (47% knock-knee, 53% bow-leg), resulting in more conservative prevalence estimates of bone deformity: 0.6% for children <18.0 years (M = 0.9%, F = 0.2%), 1.5% for children < 5.0 years (M = 2.3%, F = 0.6%). Three of these children (9% of those with clinically-confirmed deformity, 0.05% of those screened) had active rickets on X-ray at the time of medical examination. This emphasises the difficulties in comparing prevalence estimates of rickets-like bone deformities from population surveys and clinic-based studies. Interpopliteal distance showed promise as an objective screening measure for bow-leg deformity. In conclusion, this population survey in a rural region of West Africa with a low calcium diet has demonstrated a significant burden of rickets-like bone deformity, whether based on physical signs under survey conditions or after clinical examination, especially in boys < 5.0 years.
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Affiliation(s)
- Helen L Jones
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK; MRC Keneba, The Gambia
| | | | - Stephen Owens
- MRC Keneba, The Gambia; Northumbria Healthcare NHS Foundation Trust, UK
| | - Anthony J Fulford
- MRC Keneba, The Gambia; MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Sophie E Moore
- MRC Keneba, The Gambia; MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, UK
| | - John M Pettifor
- MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Ann Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK; MRC Keneba, The Gambia.
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Glorieux FH, Pettifor JM. Vitamin D/dietary calcium deficiency rickets and pseudo-vitamin D deficiency rickets. BONEKEY REPORTS 2014; 3:524. [PMID: 24818008 DOI: 10.1038/bonekey.2014.19] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 02/24/2014] [Indexed: 11/09/2022]
Abstract
This review describes the pathogenesis, clinical presentation and biochemical perturbations found in privational (nutritional) rickets and pseudo-vitamin D deficiency rickets (PDDR), an autosomal recessive condition with loss of function mutations in CYP27B1. It may seem strange to combine a discussion on privational rickets and PDDR as a single topic, but privational rickets and PDDR present with similar clinical signs and symptoms and with similar perturbations in bone and mineral metabolism. Of interest is the characteristic lack of features of rickets at birth in infants with PDDR, a finding which has also been reported in infants born to vitamin D-deficient mothers. This highlights the independence of the fetus and neonate from the need for vitamin D to maintain calcium homeostasis during this period. The variable roles of vitamin D deficiency and dietary calcium deficiency in the pathogenesis of privational rickets are discussed and the associated alterations in vitamin D metabolism highlighted. Although PDDR is a rare autosomal recessive disorder, results of long-term follow-up are now available on the effect of treatment with calcitriol, and these are discussed. Areas of uncertainty, such as should affected mothers breastfeed their infants, are emphasized.
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Affiliation(s)
- Francis H Glorieux
- Genetics Unit, Shriners Hospital for Children-Canada and McGill University , Montreal, Quebec, Canada
| | - John M Pettifor
- MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand , Parktown, South Africa
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25
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Osteocyte Communication with the Kidney Via the Production of FGF23: Remote Control of Phosphate Homeostasis. Clin Rev Bone Miner Metab 2014. [DOI: 10.1007/s12018-014-9155-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Braithwaite V, Jones KS, Assar S, Schoenmakers I, Prentice A. Predictors of intact and C-terminal fibroblast growth factor 23 in Gambian children. Endocr Connect 2013; 3:1-10. [PMID: 24258305 PMCID: PMC3869962 DOI: 10.1530/ec-13-0070] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Accepted: 11/20/2013] [Indexed: 12/16/2022]
Abstract
Elevated C-terminal fibroblast growth factor 23 (C-FGF23) concentrations have been reported in Gambian children with and without putative Ca-deficiency rickets. The aims of this study were to investigate whether i) elevated C-FGF23 concentrations in Gambian children persist long term; ii) they are associated with higher intact FGF23 concentrations (I-FGF23), poor iron status and shorter 25-hydroxyvitamin D half-life (25OHD-t1/2); and iii) the persistence and predictors of elevated FGF23 concentrations differ between children with and without a history of rickets. Children (8-16 years, n=64) with a history of rickets and a C-FGF23 concentration >125 RU/ml (bone deformity (BD), n=20) and local community children with a previously measured elevated C-FGF23 concentration (LC+, n=20) or a previously measured C-FGF23 concentration within the normal range (LC-, n=24) participated. BD children had no remaining signs of bone deformities. C-FGF23 concentration had normalised in BD children, but remained elevated in LC+ children. All the children had I-FGF23 concentration within the normal range, but I-FGF23 concentration was higher and iron status poorer in LC+ children. 1,25-dihydroxyvitamin D was the strongest negative predictor of I-FGF23 concentration (R(2)=18%; P=0.0006) and soluble transferrin receptor was the strongest positive predictor of C-FGF23 concentration (R(2)=33%; P≤0.0001). C-FGF23 and I-FGF23 concentrations were poorly correlated with each other (R(2)=5.3%; P=0.07). 25OHD-t1/2 was shorter in BD children than in LC- children (mean (s.d.): 24.5 (6.1) and 31.5 (11.5) days respectively; P=0.05). This study demonstrated that elevated C-FGF23 concentrations normalised over time in Gambian children with a history of rickets but not in local children, suggesting a different aetiology; that children with resolved rickets had a shorter 25OHD-t1/2, suggesting a long-standing increased expenditure of 25OHD, and that iron deficiency is a predictor of elevated C-FGF23 concentrations in both groups of Gambian children.
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Affiliation(s)
- Vickie Braithwaite
- Medical Research Council (MRC) Human Nutrition ResearchElsie Widdowson LaboratoriesFulbourn Road, Cambridge, CB1 9NLUK
| | - Kerry S Jones
- Medical Research Council (MRC) Human Nutrition ResearchElsie Widdowson LaboratoriesFulbourn Road, Cambridge, CB1 9NLUK
- MRC Keneba, KenebaWest KiangThe Gambia
| | - Shima Assar
- Medical Research Council (MRC) Human Nutrition ResearchElsie Widdowson LaboratoriesFulbourn Road, Cambridge, CB1 9NLUK
| | - Inez Schoenmakers
- Medical Research Council (MRC) Human Nutrition ResearchElsie Widdowson LaboratoriesFulbourn Road, Cambridge, CB1 9NLUK
| | - Ann Prentice
- Medical Research Council (MRC) Human Nutrition ResearchElsie Widdowson LaboratoriesFulbourn Road, Cambridge, CB1 9NLUK
- MRC Keneba, KenebaWest KiangThe Gambia
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27
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Prentice A. Standing on the shoulders of giants: Understanding calcium and vitamin D requirements. NUTR BULL 2013. [DOI: 10.1111/nbu.12043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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28
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Bouillon R, Van Schoor NM, Gielen E, Boonen S, Mathieu C, Vanderschueren D, Lips P. Optimal vitamin D status: a critical analysis on the basis of evidence-based medicine. J Clin Endocrinol Metab 2013; 98:E1283-304. [PMID: 23922354 DOI: 10.1210/jc.2013-1195] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
CONTEXT Public health authorities around the world recommend widely variable supplementation strategies for adults, whereas several professional organizations, including The Endocrine Society, recommend higher supplementation. METHODS We analyzed published randomized controlled clinical trials to define the optimal intake or vitamin D status for bone and extraskeletal health. CONCLUSIONS The extraskeletal effects of vitamin D are plausible as based on preclinical data and observational studies. However, apart from the beneficial effects of 800 IU/d of vitamin D3 for reduction of falls in the elderly, causality remains yet unproven in randomized controlled trials (RCTs). The greatest risk for cancer, infections, cardiovascular and metabolic diseases is associated with 25-hydroxyvitamin D (25OHD) levels below 20 ng/mL. There is ample evidence from RCTs that calcium and bone homeostasis, estimated from serum 1,25-dihydroxyvitamin D and PTH, calcium absorption, or bone mass, can be normalized by 25OHD levels above 20 ng/mL. Moreover, vitamin D supplementation (800 IU/d) in combination with calcium can reduce fracture incidence by about 20%. Such a dose will bring serum levels of 25OHD above 20 ng/mL in nearly all postmenopausal women. Based on calculations of the metabolic clearance of 25OHD, a daily intake of 500-700 IU of vitamin D3 is sufficient to maintain serum 25OHD levels of 20 ng/mL. Therefore, the recommendations for a daily intake of 1500-2000 IU/d or serum 25OHD levels of 30 ng or higher for all adults or elderly subjects, as suggested by The Endocrine Society Task Force, are premature. Fortunately, ongoing RCTs will help to guide us to solve this important public health question.
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Affiliation(s)
- Roger Bouillon
- Clinical and Experimental Endocrinology, KU Leuven, Department of Endocrinology, Herestraat 49 ON1, Box 902, 3000 Leuven, Belgium.
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Prentice A. Nutritional rickets around the world. J Steroid Biochem Mol Biol 2013; 136:201-6. [PMID: 23220549 DOI: 10.1016/j.jsbmb.2012.11.018] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 11/16/2012] [Accepted: 11/28/2012] [Indexed: 10/27/2022]
Abstract
Nutritional rickets is a major public health problem in many countries of the world. The disease is characterized by deformities of the long bones, enlargement of the wrists and costochondral junctions, hypotonia and, in infants, craniotabes and delayed fontanelle closure. Predominantly caused by severe vitamin D deficiency, rickets can also be associated with hypocalcemic seizures and cardiac failure. First presentation is typically at 6-24 months of age, although hypocalcemia may be evident in younger infants. In many affluent industrialized countries, the prevalence of rickets in the general population diminished after the introduction of clean-air legislation and dietary supplementation. However, in such countries, vitamin-D deficiency rickets has re-emerged in recent years, particularly among groups with limited exposure to UVB-containing sunshine. Infants at risk of rickets tend to be those whose mothers had poor vitamin D status during pregnancy and those exclusively breast-fed for a prolonged period with little skin exposure to UVB. In other countries of the world, the prevalence of rickets can be high, even in regions with abundant year-round UVB-containing sunshine. In general, this is also due to vitamin D deficiency related to limited sun exposure. However, reports from Africa and Asia suggest that there may be other etiological factors involved. Studies in South Africa, Nigeria, The Gambia and Bangladesh have identified rickets in children, typically 3-5 years old at first presentation, in whom plasma 25-hydroxyvitamin D concentrations are higher than those characteristic of primary vitamin D deficiency. Calcium deficiency has been implicated, and in some, but not all, disturbances of phosphate metabolism, renal compromise and iron deficiency may also be involved. Continuing studies of the etiology of nutritional rickets will provide evidence to underpin guidelines for the prevention and treatment of rickets world-wide. This article is part of a Special Issue entitled 'Vitamin D Workshop'.
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Affiliation(s)
- Ann Prentice
- MRC Human Nutrition Research, Cambridge, United Kingdom.
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30
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Braithwaite V, Pettifor JM, Prentice A. Novel SLC34A3 mutation causing hereditary hypophosphataemic rickets with hypercalciuria in a Gambian family. Bone 2013; 53:216-20. [PMID: 23246670 PMCID: PMC3557384 DOI: 10.1016/j.bone.2012.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 10/25/2012] [Accepted: 12/04/2012] [Indexed: 01/28/2023]
Abstract
Three siblings, aged 12, 4 and 2 years, presented at a Gambian clinic with bone deformities. Radiographs of knees and wrists confirmed the presence of florid rickets. The family (including 2 unaffected siblings and the mother) were investigated for hereditary rickets. The three affected siblings had biochemical features of hereditary hypophosphataemic rickets with hypercalciuria (HHRH) with normal plasma calcium and 25-hydroxyvitamin D concentrations, elevated 1,25-dihydroxyvitamin D, hypophosphataemia, hyperphosphaturia and hypercalciuria. At presentation, two of the three affected siblings had an elevated fibroblast growth factor-23 (FGF23) concentration. The mother and clinically unaffected siblings had largely normal biochemistry. Genetic analysis of the SLC34A3 gene, encoding the type IIc sodium-phosphate cotransporter, in DNA samples from the siblings and their mother was conducted. Three single nucleotide polymorphisms (SNPs) S168F, E513V and L599L were identified. E513V and L599L had been previously identified as benign polymorphisms. S168F however, is a previously unreported variant. In silico mutation evaluation predicted that the S168F mutation causes changes in the protein product which are damaging to its function. In addition, the three clinically affected siblings were homozygous in the S168F variant whereas the unaffected family members were carriers. This study describes a biochemical profile and complementary gene data consistent with a rare genetic hypophosphataemic rickets disease in a family from rural Gambia. To our knowledge, this study reports the first cases of HHRH in Africa and describes a novel causal mutation within the SLC34A3 gene.
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Affiliation(s)
- Vickie Braithwaite
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.
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31
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Braithwaite V, Bruggraber SFA, Prentice A. Intact fibroblast growth factor 23 and fragments in plasma from Gambian children. Osteoporos Int 2013; 24:1121-4. [PMID: 22648001 PMCID: PMC3572374 DOI: 10.1007/s00198-012-2029-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 04/25/2012] [Indexed: 12/23/2022]
Abstract
UNLABELLED Fibroblast growth factor 23 (FGF23) is grossly elevated in Gambian children with rickets and, at a lower prevalence, in those without bone deformities. We used western blotting to mimic the detection capabilities of the C-terminal FGF23 enzyme-linked immunosorbent assay (ELISA). Only intact FGF23 hormone was present in Gambian plasma samples from children with and without rickets. INTRODUCTION Elevated circulating FGF23 concentrations have been detected in plasma samples from Gambian children using the C-terminal Immutopics ELISA. The Immutopics ELISA detects both the intact FGF23 hormone and the C-terminal fragment. The aim of this study was to determine whether the elevated FGF23 concentrations as detected by the ELISA were predominantly due to a high proportion of intact FGF23 hormone and/or C-terminal FGF23 fragments. METHODS Stored, frozen plasma samples from previous studies of Gambian children with known concentrations of FGF23 as determined by C-terminal Immutopics ELISA assay, were selected for western blotting analysis: from children with rickets-like bone deformities (n = 4) and local controls (n = 4), with elevated >900 RU/ml (n = 2) and normal <30 RU/ml (n = 2; from each group). The anti-FGF23 polyclonal antibody that recognizes the C-terminal of FGF23 (as used in the Immutopics kit) was used as the primary antibody and the anti-IgG polyclonal antibody conjugated to horseradish peroxidase (HRP) was used as the secondary antibody. RESULTS Firstly, C-terminal FGF23 fragments, although detectable in standards from the Immutopics ELISA kit, were not in the Gambian plasma samples. Secondly, there was no difference in the size of FGF23 molecules present in plasma from children with rickets-like bone deformities and children from the local community. CONCLUSIONS Western blotting has provided evidence that elevated FGF23 concentrations, as determined by the C-terminal Immutopics ELISA, measured in Gambian children with and without rickets-like bone deformities was not caused by an increased proportion of circulating inactive C-terminal fragments.
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Affiliation(s)
- V Braithwaite
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge CB1 9NL, United Kingdom.
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32
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Pettifor JM, Thandrayen K. Hypophosphatemic rickets: unraveling the role of FGF23. Calcif Tissue Int 2012; 91:297-306. [PMID: 23001439 DOI: 10.1007/s00223-012-9651-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 09/06/2012] [Indexed: 12/29/2022]
Abstract
The classification of the various forms of hypophosphatemic rickets has been rationalized by the discovery of the central role that fibroblast growth factor 23 (FGF23) plays in the pathogenesis of a number of genetic and acquired forms of the disease. Although the details of the interaction of FGF23 with other osteoblast/osteocyte-derived proteins remain unclear at present, the measurement of circulating levels of FGF23 appears to be a useful biochemical test in determining the various causes of hypophosphatemic rickets. Furthermore, animal studies suggest that agents interfering in the action of FGF23 might play important roles in the future management of the FGF23-mediated forms of rickets. Phase 1 and phase 2 trials in humans with X-linked hypophosphatemic rickets are currently under way.
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Affiliation(s)
- John M Pettifor
- MRC/Wits Developmental Pathways for Health Research Unit, Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand, 7 York Rd, Parktown, Johannesburg 2193, South Africa.
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Klassen K, Martineau AR, Wilkinson RJ, Cooke G, Courtney AP, Hickson M. The effect of tenofovir on vitamin D metabolism in HIV-infected adults is dependent on sex and ethnicity. PLoS One 2012; 7:e44845. [PMID: 22984574 PMCID: PMC3440360 DOI: 10.1371/journal.pone.0044845] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 08/08/2012] [Indexed: 11/19/2022] Open
Abstract
Background Tenofovir has been associated with renal phosphate wasting, reduced bone mineral density, and higher parathyroid hormone levels. The aim of this study was to carry out a detailed comparison of the effects of tenofovir versus non-tenofovir use on calcium, phosphate and, vitamin D, parathyroid hormone (PTH), and bone mineral density. Methods A cohort study of 56 HIV-1 infected adults at a single centre in the UK on stable antiretroviral regimes comparing biochemical and bone mineral density parameters between patients receiving either tenofovir or another nucleoside reverse transcriptase inhibitor. Principal Findings In the unadjusted analysis, there was no significant difference between the two groups in PTH levels (tenofovir mean 5.9 pmol/L, 95% confidence intervals 5.0 to 6.8, versus non-tenofovir; 5.9, 4.9 to 6.9; p = 0.98). Patients on tenofovir had significantly reduced urinary calcium excretion (median 3.01 mmol/24 hours) compared to non-tenofovir users (4.56; p<0.0001). Stratification of the analysis by age and ethnicity revealed that non-white men but not women, on tenofovir had higher PTH levels than non-white men not on tenofovir (mean difference 3.1 pmol/L, 95% CI 5.3 to 0.9; p = 0.007). Those patients with optimal 25-hydroxyvitamin D (>75 nmol/L) on tenofovir had higher 1,25-dihydroxyvitamin D [1,25(OH)2D] (median 48 pg/mL versus 31; p = 0.012), fractional excretion of phosphate (median 26.1%, versus 14.6; p = 0.025) and lower serum phosphate (median 0.79 mmol/L versus 1.02; p = 0.040) than those not taking tenofovir. Conclusions The effects of tenofovir on PTH levels were modified by sex and ethnicity in this cohort. Vitamin D status also modified the effects of tenofovir on serum concentrations of 1,25(OH)2D and phosphate.
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Affiliation(s)
- Karen Klassen
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
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34
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Braithwaite V, Jarjou LMA, Goldberg GR, Prentice A. Iron status and fibroblast growth factor-23 in Gambian children. Bone 2012; 50:1351-6. [PMID: 22465847 PMCID: PMC3360160 DOI: 10.1016/j.bone.2012.03.010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 02/17/2012] [Accepted: 03/09/2012] [Indexed: 11/19/2022]
Abstract
A relationship between iron and fibroblast growth factor-23 (FGF23) metabolic pathways has been proposed. Iron deficiency anaemia is prevalent in The Gambia and concentrations of fibroblast growth factor-23 FGF23 are elevated in a large percentage of Gambian children with rickets-like bone deformity. We speculate that low iron status may be involved in the aetiology of Gambian rickets. The aim of this study was to determine if there was a relationship between haemoglobin, as a marker of iron status, and FGF23 in samples from children with and without a history of rickets-like bone deformities in The Gambia. We conducted a retrospective analysis of studies carried out from 2006 to 2008 in children from a rural community in The Gambia where iron deficiency anaemia is endemic and where elevated circulating concentrations of FGF23 have been found. To investigate the relationship between circulating FGF23 and haemoglobin concentrations we used an age-adjusted linear regression model on data from children <18y of age with a family or personal history of rickets-like bone deformity (BD) (n=108) and from the local community (LC) (n=382). We found that circulating concentration of FGF23 was inversely correlated with haemoglobin concentration. This effect was more pronounced in BD children compared with LC children (interaction: P≤0.0001). Anaemia and elevated FGF23 were more prevalent in BD children compared to LC children (P=0.0003 and P=0.0001 respectively). In conclusion, there is a stronger relationship between FGF23 and haemoglobin in Gambian children with a history of rickets compared to local community children. This study provides support for the contention that iron may be involved in FGF23 metabolic pathways.
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35
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Braithwaite V, Jarjou LM, Goldberg GR, Jones H, Pettifor JM, Prentice A. Follow-up study of Gambian children with rickets-like bone deformities and elevated plasma FGF23: possible aetiological factors. Bone 2012; 50:218-25. [PMID: 22023931 PMCID: PMC3459093 DOI: 10.1016/j.bone.2011.10.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Revised: 10/06/2011] [Accepted: 10/07/2011] [Indexed: 11/25/2022]
Abstract
We have previously reported on a case-series of children (n=46) with suspected calcium-deficiency rickets who presented in The Gambia with rickets-like bone deformities. Biochemical analyses discounted vitamin D-deficiency as an aetiological factor but indicated a perturbation of Ca-P metabolism involving low plasma phosphate and high circulating fibroblast growth factor-23 (FGF23) concentrations. A follow-up study was conducted 5 years after presentation to investigate possible associated factors and characterise recovery. 35 children were investigated at follow-up (RFU). Clinical assessment of bone deformities, overnight fasted 2 h urine and blood samples, 2-day weighed dietary records and 24 h urine collections were obtained. Age- and season-matched data from children from the local community (LC) were used to calculate standard deviation scores (SDS) for RFU children. None of the RFU children had radiological signs of active rickets. However, over half had residual leg deformities consistent with rickets. Dietary Ca intake (SDS-Ca=-0.52 (0.98) p=0.04), dietary Ca/P ratio (SDS-Ca/P=-0.80 (0.82) p=0.0008) and TmP:GFR (SDS-TmP:GFR=-0.48 (0.81) p=0.04) were significantly lower in RFU children compared with LC children and circulating FGF23 concentration was elevated in 19% of RFU children. Furthermore an inverse relationship was seen between haemoglobin and FGF23 (R(2)=25.8, p=0.004). This study has shown differences in biochemical and dietary profiles between Gambian children with a history of rickets-like bone deformities and children from the local community. This study provided evidence in support of the calcium deficiency hypothesis leading to urinary phosphate wasting and rickets and identified glomerular filtration rate and iron status as possible modulators of FGF23 metabolic pathways.
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Affiliation(s)
| | | | - Gail R. Goldberg
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK
- MRC Keneba, The Gambia
| | - Helen Jones
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK
| | - John M. Pettifor
- Department of Paediatrics, Faculty of Health Sciences, University of the Witwatersrand and Chris Hani Baragwaneth Hospital, Johannesburg, South Africa
| | - Ann Prentice
- MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK
- MRC Keneba, The Gambia
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36
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Martin A, Quarles LD. Evidence for FGF23 involvement in a bone-kidney axis regulating bone mineralization and systemic phosphate and vitamin D homeostasis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 728:65-83. [PMID: 22396162 PMCID: PMC6350529 DOI: 10.1007/978-1-4614-0887-1_4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Bone is involved in the maintenance of phosphate and vitamin D homeostasis via its production and secretion of FGF23 and serves as a reservoir for the storage and release of calcium and phosphate into the circulation. Alterations in mineralization of extracellular matrix and the remodeling activities of the skeleton are coupled to the kidney conservation of phosphate and production of 1,25(OH)2D via the regulation of FGF23 production by osteocytes through yet-to-be defined locally derived factors. In addition, FGF23 production is regulated by 1,25(OH)2D in a feedback loop where FGF23 stimulate Cyp24 mediated degradation of 1,25(OH)2D that serves to protect the organism from the toxic effects of vitamin D excess. In this chapter, we will review the regulation and function of FGF23.
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Affiliation(s)
- Aline Martin
- University of Tennessee Health Science Center, Department of Medicine, Memphis, Tennessee, USA
| | - L. Darryl Quarles
- University of Tennessee Health Science Center, Department of Medicine, Memphis, Tennessee, USA
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Abstract
Calcium (Ca(2+)) and phosphate (PO(4)(3-)) homeostasis are coordinated by systemic and local factors that regulate intestinal absorption, influx and efflux from bone, and kidney excretion and reabsorption of these ions through a complex hormonal network. Traditionally, the parathyroid hormone (PTH)/vitamin D axis provided the conceptual framework to understand mineral metabolism. PTH secreted by the parathyroid gland in response to hypocalcemia functions to maintain serum Ca(2+) levels by increasing Ca(2+) reabsorption and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] production by the kidney, enhancing Ca(2+) and PO(4)(3-) intestinal absorption and increasing Ca(2+) and PO(4)(3-) efflux from bone, while maintaining neutral phosphate balance through phosphaturic effects. FGF23 is a recently discovered hormone, predominately produced by osteoblasts/osteocytes, whose major functions are to inhibit renal tubular phosphate reabsorption and suppress circulating 1,25(OH)(2)D levels by decreasing Cyp27b1-mediated formation and stimulating Cyp24-mediated catabolism of 1,25(OH)(2)D. FGF23 participates in a new bone/kidney axis that protects the organism from excess vitamin D and coordinates renal PO(4)(3-) handling with bone mineralization/turnover. Abnormalities of FGF23 production underlie many inherited and acquired disorders of phosphate homeostasis. This review discusses the known and emerging functions of FGF23, its regulation in response to systemic and local signals, as well as the implications of FGF23 in different pathological and physiological contexts.
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Affiliation(s)
- Aline Martin
- University of Tennessee Health Science Center, Memphis, Tennessee, USA
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38
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Samadfam R, Richard C, Nguyen-Yamamoto L, Bolivar I, Goltzman D. Bone formation regulates circulating concentrations of fibroblast growth factor 23. Endocrinology 2009; 150:4835-45. [PMID: 19819968 DOI: 10.1210/en.2009-0472] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We examined the role of bone remodeling in the regulation of circulating concentrations of FGF23 using mouse models manifesting differing degrees of coupled and uncoupled bone turnover. Administration of the antiresorptive agent osteoprotegerin produced a profound reduction in bone resorption and formation in male and oophorectomized female mice, accompanied by an increase in serum levels of fibroblast growth factor 23 (FGF23) and a reduction in circulating 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. In contrast, exogenous PTH(1-34) administration increased bone turnover and reduced circulating FGF23. In 1,25(OH)(2)D-deficient, 25-hydroxyvitamin D 1alpha-hydroxylase null mice on a high-calcium diet, endogenous PTH was elevated, bone formation but not resorption was increased, and serum FGF23 was virtually undetectable; on a rescue diet, serum calcium was normalized, PTH levels were reduced, bone formation was reduced, and serum FGF23 levels increased. After PTH treatment of wild-type mice, gene expression of dentin matrix protein 1 (DMP1) in bone was increased, whereas gene expression of FGF23 was reduced. In vitro studies in the osteoblastic cell line UMR-106 showed that externally added DMP1 could inhibit FGF23 gene expression and production stimulated by 1,25(OH)(2)D(3). The results show that osteoblastic bone formation is a potent modulator of FGF23 production and release into the circulation, suggest that the biological consequences on mineral homeostasis of circulating FGF23 may also be dependent on the prevailing rate of bone turnover, and provide evidence that DMP1 may be a direct negative regulator of FGF23 production in osteoblastic cells.
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Affiliation(s)
- Rana Samadfam
- Calcium Research Laboratory, Royal Victoria Hospital, 687 Pine Avenue, Room H4.67, Montreal, Quebec, Canada H3A 1A1
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Chaplin G, Jablonski NG. Vitamin D and the evolution of human depigmentation. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2009; 139:451-61. [PMID: 19425101 DOI: 10.1002/ajpa.21079] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- George Chaplin
- Department of Anthropology, The Pennsylvania State University, University Park, PA 16802, USA.
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Abstract
Africa is heterogeneous in latitude, geography, climate, food availability, religious and cultural practices, and skin pigmentation. It is expected, therefore, that prevalence of vitamin D deficiency varies widely, in line with influences on skin exposure to UVB sunshine. Furthermore, low calcium intakes and heavy burden of infectious disease common in many countries may increase vitamin D utilization and turnover. Studies of plasma 25OHD concentration indicate a spectrum from clinical deficiency to values at the high end of the physiological range; however, data are limited. Representative studies of status in different countries, using comparable analytical techniques, and of relationships between vitamin D status and risk of infectious and chronic diseases relevant to the African context are needed. Public health measures to secure vitamin D adequacy cannot encompass the whole continent and need to be developed locally.
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41
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Abstract
The prevalence of clinical vitamin D deficiency (rickets and osteomalacia) is high in many parts of the world, and there is a resurgence of rickets among children of ethnic minority groups in Europe and Australasia. Plasma 25-hydroxyvitamin D concentration (25OHD) is a useful risk marker of clinical vitamin D deficiency. This review summarizes the factors that contribute to differences in 25OHD among populations and provides an overview of the prevalence of low vitamin D status worldwide. It discusses the controversies that surround the interpretation of 25OHD, other proposed indices of vitamin D adequacy and dietary reference values for vitamin D, and describes the emerging evidence that a very low calcium intake may contribute to the etiology of rickets in Africa and Asia. There is an urgent need for action to address the global burden of rickets and osteomalacia.
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Affiliation(s)
- Ann Prentice
- The Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, United Kingdom and Medical Research Council Keneba, Keneba, The Gambia.
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Abstract
Given the dramatic increase in skeletal size during growth, the need to preserve skeletal mass during adulthood, and the large capacity of bone to store calcium and phosphate, juxtaposed with the essential role of phosphate in energy metabolism and the adverse effects of hyperphosphatemia, it is not surprising that a complex systems biology has evolved that permits cross-talk between bone and other organs to adjust phosphate balance and bone mineralization in response to changing physiological requirements. This review examines the newly discovered signaling pathways involved in the endocrine functions of bone, such as those mediated by the phosphaturic and 1,25(OH)2D-regulating hormone FGF23, and the broader systemic effects associated with abnormalities of calcium and phosphate homeostasis.
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Affiliation(s)
- L Darryl Quarles
- The Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
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