1
|
Gędaj A, Gregorczyk P, Żukowska D, Chorążewska A, Ciura K, Kalka M, Porębska N, Opaliński Ł. Glycosylation of FGF/FGFR: An underrated sweet code regulating cellular signaling programs. Cytokine Growth Factor Rev 2024; 77:39-55. [PMID: 38719671 DOI: 10.1016/j.cytogfr.2024.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 04/23/2024] [Accepted: 04/23/2024] [Indexed: 06/22/2024]
Abstract
Fibroblast growth factors (FGFs) and their receptors (FGFRs) constitute plasma-membrane localized signaling hubs that transmit signals from the extracellular environment to the cell interior, governing pivotal cellular processes like motility, metabolism, differentiation, division and death. FGF/FGFR signaling is critical for human body development and homeostasis; dysregulation of FGF/FGFR units is observed in numerous developmental diseases and in about 10% of human cancers. Glycosylation is a highly abundant posttranslational modification that is critical for physiological and pathological functions of the cell. Glycosylation is also very common within FGF/FGFR signaling hubs. Vast majority of FGFs (15 out of 22 members) are N-glycosylated and few FGFs are O-glycosylated. Glycosylation is even more abundant within FGFRs; all FGFRs are heavily N-glycosylated in numerous positions within their extracellular domains. A growing number of studies points on the multiple roles of glycosylation in fine-tuning FGF/FGFR signaling. Glycosylation modifies secretion of FGFs, determines their stability and affects interaction with FGFRs and co-receptors. Glycosylation of FGFRs determines their intracellular sorting, constitutes autoinhibitory mechanism within FGFRs and adjusts FGF and co-receptor recognition. Sugar chains attached to FGFs and FGFRs constitute also a form of code that is differentially decrypted by extracellular lectins, galectins, which transform FGF/FGFR signaling at multiple levels. This review focuses on the identified functions of glycosylation within FGFs and FGFRs and discusses their relevance for the cell physiology in health and disease.
Collapse
Affiliation(s)
- Aleksandra Gędaj
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Paulina Gregorczyk
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Dominika Żukowska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Aleksandra Chorążewska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Krzysztof Ciura
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Marta Kalka
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Natalia Porębska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland
| | - Łukasz Opaliński
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Joliot-Curie 14a, Wroclaw 50-383, Poland.
| |
Collapse
|
2
|
Chen J, Kuang S, Cen J, Zhang Y, Shen Z, Qin W, Huang Q, Wang Z, Gao X, Huang F, Lin Z. Multiomics profiling reveals VDR as a central regulator of mesenchymal stem cell senescence with a known association with osteoporosis after high-fat diet exposure. Int J Oral Sci 2024; 16:41. [PMID: 38777841 PMCID: PMC11111693 DOI: 10.1038/s41368-024-00309-9] [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: 10/20/2023] [Revised: 04/24/2024] [Accepted: 04/28/2024] [Indexed: 05/25/2024] Open
Abstract
The consumption of a high-fat diet (HFD) has been linked to osteoporosis and an increased risk of fragility fractures. However, the specific mechanisms of HFD-induced osteoporosis are not fully understood. Our study shows that exposure to an HFD induces premature senescence in bone marrow mesenchymal stem cells (BMSCs), diminishing their proliferation and osteogenic capability, and thereby contributes to osteoporosis. Transcriptomic and chromatin accessibility analyses revealed the decreased chromatin accessibility of vitamin D receptor (VDR)-binding sequences and decreased VDR signaling in BMSCs from HFD-fed mice, suggesting that VDR is a key regulator of BMSC senescence. Notably, the administration of a VDR activator to HFD-fed mice rescued BMSC senescence and significantly improved osteogenesis, bone mass, and other bone parameters. Mechanistically, VDR activation reduced BMSC senescence by decreasing intracellular reactive oxygen species (ROS) levels and preserving mitochondrial function. Our findings not only elucidate the mechanisms by which an HFD induces BMSC senescence and associated osteoporosis but also offer new insights into treating HFD-induced osteoporosis by targeting the VDR-superoxide dismutase 2 (SOD2)-ROS axis.
Collapse
Affiliation(s)
- Jiayao Chen
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Shuhong Kuang
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Jietao Cen
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Yong Zhang
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Zongshan Shen
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Wei Qin
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Qiting Huang
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Zifeng Wang
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, China
| | - Xianling Gao
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China
| | - Fang Huang
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China.
| | - Zhengmei Lin
- Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China.
- Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
- Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China.
| |
Collapse
|
3
|
Courbon G, Kentrup D, Thomas JJ, Wang X, Tsai HH, Spindler J, Von Drasek J, Ndjonko LM, Martinez-Calle M, Lynch S, Hivert L, Wang X, Chang W, Feng JQ, David V, Martin A. FGF23 directly inhibits osteoprogenitor differentiation in Dmp1-knockout mice. JCI Insight 2023; 8:e156850. [PMID: 37943605 PMCID: PMC10807721 DOI: 10.1172/jci.insight.156850] [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: 11/18/2021] [Accepted: 11/01/2023] [Indexed: 11/12/2023] Open
Abstract
Fibroblast growth factor 23 (FGF23) is a phosphate-regulating (Pi-regulating) hormone produced by bone. Hereditary hypophosphatemic disorders are associated with FGF23 excess, impaired skeletal growth, and osteomalacia. Blocking FGF23 became an effective therapeutic strategy in X-linked hypophosphatemia, but testing remains limited in autosomal recessive hypophosphatemic rickets (ARHR). This study investigates the effects of Pi repletion and bone-specific deletion of Fgf23 on bone and mineral metabolism in the dentin matrix protein 1-knockout (Dmp1KO) mouse model of ARHR. At 12 weeks, Dmp1KO mice showed increased serum FGF23 and parathyroid hormone levels, hypophosphatemia, impaired growth, rickets, and osteomalacia. Six weeks of dietary Pi supplementation exacerbated FGF23 production, hyperparathyroidism, renal Pi excretion, and osteomalacia. In contrast, osteocyte-specific deletion of Fgf23 resulted in a partial correction of FGF23 excess, which was sufficient to fully restore serum Pi levels but only partially corrected the bone phenotype. In vitro, we show that FGF23 directly impaired osteoprogenitors' differentiation and that DMP1 deficiency contributed to impaired mineralization independent of FGF23 or Pi levels. In conclusion, FGF23-induced hypophosphatemia is only partially responsible for the bone defects observed in Dmp1KO mice. Our data suggest that combined DMP1 repletion and FGF23 blockade could effectively correct ARHR-associated mineral and bone disorders.
Collapse
Affiliation(s)
- Guillaume Courbon
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Dominik Kentrup
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Jane Joy Thomas
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Xueyan Wang
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Hao-Hsuan Tsai
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Jadeah Spindler
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - John Von Drasek
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Laura Mazudie Ndjonko
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Marta Martinez-Calle
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Sana Lynch
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Lauriane Hivert
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Xiaofang Wang
- Texas A&M School of Dentistry, Texas A&M University, Dallas, Texas, USA
| | - Wenhan Chang
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Jian Q. Feng
- Shanxi Medical University School and Hospital of Stomatology, Clinical Medical Research Center of Oral Diseases of Shanxi Province, Taiyuan, China
| | - Valentin David
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Aline Martin
- Division of Nephrology and Hypertension, Center for Translational Metabolism and Health, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| |
Collapse
|
4
|
Courbon G, Thomas JJ, Martinez-Calle M, Wang X, Spindler J, Von Drasek J, Hunt-Tobey B, Mehta R, Isakova T, Chang W, Creemers JWM, Ji P, Martin A, David V. Bone-derived C-terminal FGF23 cleaved peptides increase iron availability in acute inflammation. Blood 2023; 142:106-118. [PMID: 37053547 PMCID: PMC10356820 DOI: 10.1182/blood.2022018475] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 03/24/2023] [Accepted: 04/06/2023] [Indexed: 04/15/2023] Open
Abstract
Inflammation leads to functional iron deficiency by increasing the expression of the hepatic iron regulatory peptide hepcidin. Inflammation also stimulates fibroblast growth factor 23 (FGF23) production by increasing both Fgf23 transcription and FGF23 cleavage, which paradoxically leads to excess in C-terminal FGF23 peptides (Cter-FGF23), rather than intact FGF23 (iFGF23) hormone. We determined that the major source of Cter-FGF23 is osteocytes and investigated whether Cter-FGF23 peptides play a direct role in the regulation of hepcidin and iron metabolism in response to acute inflammation. Mice harboring an osteocyte-specific deletion of Fgf23 showed a ∼90% reduction in Cter-FGF23 levels during acute inflammation. Reduction in Cter-FGF23 led to a further decrease in circulating iron in inflamed mice owing to excessive hepcidin production. We observed similar results in mice showing impaired FGF23 cleavage owing to osteocyte-specific deletion of Furin. We next showed that Cter-FGF23 peptides bind members of the bone morphogenetic protein (BMP) family, BMP2 and BMP9, which are established inducers of hepcidin. Coadministration of Cter-FGF23 and BMP2 or BMP9 prevented the increase in Hamp messenger RNA and circulating hepcidin levels induced by BMP2/9, resulting in normal serum iron levels. Finally, injection of Cter-FGF23 in inflamed Fgf23KO mice and genetic overexpression of Cter-Fgf23 in wild type mice also resulted in lower hepcidin and higher circulating iron levels. In conclusion, during inflammation, bone is the major source of Cter-FGF23 secretion, and independently of iFGF23, Cter-FGF23 reduces BMP-induced hepcidin secretion in the liver.
Collapse
Affiliation(s)
- Guillaume Courbon
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Jane Joy Thomas
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Marta Martinez-Calle
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Xueyan Wang
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Jadeah Spindler
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - John Von Drasek
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Bridget Hunt-Tobey
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Rupal Mehta
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Tamara Isakova
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Wenhan Chang
- Endocrine Research Unit, San Francisco Veterans Affairs Medical Center, University of California San Francisco, San Francisco, CA
| | | | - Peng Ji
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Aline Martin
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| | - Valentin David
- Division of Nephrology and Hypertension, Department of Medicine, Center for Translational Metabolism and Health, Institute for Public Health and Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL
| |
Collapse
|
5
|
Kritmetapak K, Kumar R. Phosphatonins: From Discovery to Therapeutics. Endocr Pract 2023; 29:69-79. [PMID: 36210014 DOI: 10.1016/j.eprac.2022.09.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 01/11/2023]
Abstract
OBJECTIVE Phosphate is crucial for cell signaling, energy metabolism, nucleotide synthesis, and bone mineralization. The gut-bone-parathyroid-kidney axis is influenced by parathyroid hormone, 1,25-dihydroxyvitamin D, and phosphatonins, especially fibroblast growth factor 23 (FGF23). These hormones facilitate maintenance of phosphate homeostasis. This review summarizes current knowledge regarding the phosphate homeostasis, phosphatonin pathophysiology, and clinical implications of FGF23-related hypophosphatemic disorders, with specific focus on burosumab treatment. METHOD A focused literature search of PubMed was conducted. RESULTS Phosphatonins including FGF23, secreted frizzled-related protein 4, matrix extracellular phosphoglycoprotein, and fibroblast growth factor 7 play a pathogenic role in several hypophosphatemic disorders. Excess FGF23 inhibits sodium-dependent phosphate cotransporters (NaPi-2a and NaPi-2c), resulting in hyperphosphaturia and hypophosphatemia. Additionally, FGF23 suppresses 1,25-dihydroxyvitamin D synthesis in the proximal renal tubule, and thus, it indirectly inhibits intestinal phosphate absorption. Disorders of FGF23-related hypophosphatemia include X-linked hypophosphatemia (XLH), autosomal dominant hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets, fibrous dysplasia/McCune-Albright syndrome, and tumor-induced osteomalacia (TIO). Complications of conventional therapy with oral phosphate and vitamin D analogs comprise gastrointestinal distress, hypercalcemia, nephrocalcinosis, and secondary/tertiary hyperparathyroidism. In both children and adults with XLH and TIO, the anti-FGF23 antibody burosumab exhibits a favorable safety profile and is associated with healing of rickets in affected children and improvement of osteomalacia in both children and adults. CONCLUSION The treatment paradigm for XLH and TIO is changing based on data from recent clinical trials. Research suggest that burosumab is effective and safe for pediatric and adult patients with XLH or TIO.
Collapse
Affiliation(s)
| | - Rajiv Kumar
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota.
| |
Collapse
|
6
|
PHEXL222P Mutation Increases Phex Expression in a New ENU Mouse Model for XLH Disease. Genes (Basel) 2022; 13:genes13081356. [PMID: 36011266 PMCID: PMC9407253 DOI: 10.3390/genes13081356] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 02/02/2023] Open
Abstract
PhexL222P mouse is a new ENU mouse model for XLH disease due to Leu to Pro amino acid modification at position 222. PhexL222P mouse is characterized by growth retardation, hypophosphatemia, hypocalcemia, reduced body bone length, and increased epiphyseal growth plate thickness and femur diameter despite the increase in PHEXL222P expression. Actually, PhexL222P mice show an increase in Fgf23, Dmp1, and Mepe and Slc34a1 (Na-Pi IIa cotransporter) mRNA expression similar to those observed in Hyp mice. Femoral osteocalcin and sclerostin and Slc34a1 do not show any significant variation in PhexL222P mice. Molecular dynamics simulations support the experimental data. P222 might locally break the E217-Q224 β-sheet, which in turn might disrupt inter-β-sheet interactions. We can thus expect local protein misfolding, which might be responsible for the experimentally observed PHEXL222P loss of function. This model could be a valuable addition to the existing XLH model for further comprehension of the disease occurrence and testing of new therapies.
Collapse
|
7
|
Function of PHEX mutations p.Glu145* and p.Trp749Arg in families with X-linked hypophosphatemic rickets by the negative regulation mechanism on FGF23 promoter transcription. Cell Death Dis 2022; 13:518. [PMID: 35654784 PMCID: PMC9163062 DOI: 10.1038/s41419-022-04969-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 01/21/2023]
Abstract
X-linked hypophosphatemic rickets (XLH) is characterized by increased circulating fibroblast growth factor 23 (FGF23) concentration caused by PHEX (NM_000444.5) mutations. Renal tubular resorption of phosphate is impaired, resulting in rickets and impaired bone mineralization. By phenotypic-genetic linkage analysis, two PHEX pathogenic mutations were found in two XLH families: c.433 G > T, p.Glu145* in exon 4 and c.2245 T > C, p.Trp749Arg in exon 22. Immunofluorescence showed that the localization of p.Glu145* and p.Trp749Arg mutant and secretory PHEX (secPHEX) changed, with decreased expression. In a HEK293T cell model co-transfected with PHEX, secPHEX, and FGF23, wild-type PHEX, secPHEX, and FGF23 proteins were distributed in the cell membrane or endoplasmic reticulum, while the mutant was located in the nuclear membrane and cytoplasm. qPCR of p.Glu145* revealed decreased PHEX and secPHEX mRNA expression in cells, with no difference in mRNA expression of p.Trp749Arg. Both mutations decreased intracellular PHEX endopeptidase activity. Western blot analysis showed decrease in mutant and secPHEX protein expression and no FGF23 protein expression in single-transfected PHEX and secPHEX cells. In cells co-transfected with FGF23, PHEX and secPHEX mutation promoted FGF23 expression. Dual-luciferase reporter gene was used to detect the effect of PHEX on FGF23 promoter. The dual-luciferase reporter gene showed that after PHEX overexpression, the activity of mutant firefly luciferase was significantly higher than that of wild type. The regulatory mechanism between PHEX and FGF23 is still unclear, but we found that PHEX is a direct transcriptional inhibitor of FGF23 and affects the expression of FGF23. This study verified the pathogenicity of the two variants and revealed the possible regulatory mechanism between PHEX and FGF23.
Collapse
|
8
|
The regulation of FGF23 under physiological and pathophysiological conditions. Pflugers Arch 2022; 474:281-292. [PMID: 35084563 PMCID: PMC8837506 DOI: 10.1007/s00424-022-02668-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 12/18/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is an important bone hormone that regulates phosphate homeostasis in the kidney along with active vitamin D (1,25(OH)2D3) and parathyroid hormone (PTH). Endocrine effects of FGF23 depend, at least in part, on αKlotho functioning as a co-receptor whereas further paracrine effects in other tissues are αKlotho-independent. Regulation of FGF23 production is complex under both, physiological and pathophysiological conditions. Physiological regulators of FGF23 include, but are not limited to, 1,25(OH)2D3, PTH, dietary phosphorus intake, and further intracellular and extracellular factors, kinases, cytokines, and hormones. Moreover, several acute and chronic diseases including chronic kidney disease (CKD) or further cardiovascular disorders are characterized by early rises in the plasma FGF23 level pointing to further mechanisms effective in the regulation of FGF23 under pathophysiological conditions. Therefore, FGF23 also serves as a prognostic marker in several diseases. Our review aims to comprehensively summarize the regulation of FGF23 in health and disease.
Collapse
|
9
|
Ratsma DMA, Zillikens MC, van der Eerden BCJ. Upstream Regulators of Fibroblast Growth Factor 23. Front Endocrinol (Lausanne) 2021; 12:588096. [PMID: 33716961 PMCID: PMC7952762 DOI: 10.3389/fendo.2021.588096] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 01/11/2021] [Indexed: 12/11/2022] Open
Abstract
Fibroblast growth factor 23 (FGF23) has been described as an important regulator of mineral homeostasis, but has lately also been linked to iron deficiency, inflammation, and erythropoiesis. FGF23 is essential for the maintenance of phosphate homeostasis in the body and activating mutations in the gene itself or inactivating mutations in its upstream regulators can result in severe chronic hypophosphatemia, where an unbalanced mineral homeostasis often leads to rickets in children and osteomalacia in adults. FGF23 can be regulated by changes in transcriptional activity or by changes at the post-translational level. The balance between O-glycosylation and phosphorylation is an important determinant of how much active intact or inactive cleaved FGF23 will be released in the circulation. In the past years, it has become evident that iron deficiency and inflammation regulate FGF23 in a way that is not associated with its classical role in mineral metabolism. These conditions will not only result in an upregulation of FGF23 transcription, but also in increased cleavage, leaving the levels of active intact FGF23 unchanged. The exact mechanisms behind and function of this process are still unclear. However, a deeper understanding of FGF23 regulation in both the classical and non-classical way is important to develop better treatment options for diseases associated with disturbed FGF23 biology. In this review, we describe how the currently known upstream regulators of FGF23 change FGF23 transcription and affect its post-translational modifications at the molecular level.
Collapse
|
10
|
Koumakis E, Cormier C, Roux C, Briot K. The Causes of Hypo- and Hyperphosphatemia in Humans. Calcif Tissue Int 2021; 108:41-73. [PMID: 32285168 DOI: 10.1007/s00223-020-00664-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 01/20/2020] [Indexed: 12/11/2022]
Abstract
Phosphate homeostasis involves several major organs that are the skeleton, the intestine, the kidney, and parathyroid glands. Major regulators of phosphate homeostasis are parathormone, fibroblast growth factor 23, 1,25-dihydroxyvitamin D, which respond to variations of serum phosphate levels and act to increase or decrease intestinal absorption and renal tubular reabsorption, through the modulation of expression of transcellular transporters at the intestinal and/or renal tubular level. Any acquired or genetic dysfunction in these major organs or regulators may induce hypo- or hyperphosphatemia. The causes of hypo- and hyperphosphatemia are numerous. This review develops the main causes of acquired and genetic hypo- and hyperphosphatemia.
Collapse
Affiliation(s)
- Eugénie Koumakis
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France.
| | - Catherine Cormier
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France
| | - Christian Roux
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France
| | - Karine Briot
- Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, Reference Center for Rare Genetic Bone Disorders, OSCAR Filière, Rheumatology Department, Cochin Hospital, AP-HP Centre-Paris University, 27 Rue du Faubourg Saint-Jacques, 75014, Paris, France
| |
Collapse
|
11
|
Abstract
FGF23 is a phosphotropic hormone produced by the bone. FGF23 works by binding to the FGF receptor-Klotho complex. Klotho is expressed in several limited tissues including the kidney and parathyroid glands. This tissue-restricted expression of Klotho is believed to determine the target organs of FGF23. FGF23 reduces serum phosphate by suppressing the expression of type 2a and 2c sodium-phosphate cotransporters in renal proximal tubules. FGF23 also decreases 1,25-dihydroxyvitamin D levels by regulating the expression of vitamin D-metabolizing enzymes, which results in reduced intestinal phosphate absorption. Excessive actions of FGF23 cause several types of hypophosphatemic rickets/osteomalacia characterized by impaired mineralization of bone matrix. In contrast, deficient actions of FGF23 result in hyperphosphatemic tumoral calcinosis with high 1,25-dihydroxyvitamin D levels. These results indicate that FGF23 is a physiological regulator of phosphate and vitamin D metabolism and indispensable for the maintenance of serum phosphate levels.
Collapse
|
12
|
Abstract
Over the past 25 years, successive cloning of SLC34A1, SLC34A2 and SLC34A3, which encode the sodium-dependent inorganic phosphate (Pi) cotransport proteins 2a-2c, has facilitated the identification of molecular mechanisms that underlie the regulation of renal and intestinal Pi transport. Pi and various hormones, including parathyroid hormone and phosphatonins, such as fibroblast growth factor 23, regulate the activity of these Pi transporters through transcriptional, translational and post-translational mechanisms involving interactions with PDZ domain-containing proteins, lipid microdomains and acute trafficking of the transporters via endocytosis and exocytosis. In humans and rodents, mutations in any of the three transporters lead to dysregulation of epithelial Pi transport with effects on serum Pi levels and can cause cardiovascular and musculoskeletal damage, illustrating the importance of these transporters in the maintenance of local and systemic Pi homeostasis. Functional and structural studies have provided insights into the mechanism by which these proteins transport Pi, whereas in vivo and ex vivo cell culture studies have identified several small molecules that can modify their transport function. These small molecules represent potential new drugs to help maintain Pi homeostasis in patients with chronic kidney disease - a condition that is associated with hyperphosphataemia and severe cardiovascular and skeletal consequences.
Collapse
|
13
|
Lecoq AL, Brandi ML, Linglart A, Kamenický P. Management of X-linked hypophosphatemia in adults. Metabolism 2020; 103S:154049. [PMID: 31863781 DOI: 10.1016/j.metabol.2019.154049] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/23/2019] [Accepted: 11/25/2019] [Indexed: 11/27/2022]
Abstract
X-linked hypophosphatemia (XLH) is caused by mutations in the PHEX gene which result in Fibroblast Growth Factor-23 (FG-F23) excess and phosphate wasting. Clinically, XLH children present with rickets, bone deformities and short stature. In adulthood, patients may still be symptomatic with bone and joint pain, osteomalacia-related fractures or pseudofractures, precocious osteoarthrosis, enthesopathy, muscle weakness and severe dental anomalies. Besides these musculoskeletal and dental manifestations, adult XLH patients are also prone to secondary and tertiary hyperparathyroidism, cardiovascular and metabolic disorders. Pathophysiology of hyperparathyroidism is only partially understood but FGF23 excess and deficient production of calcitriol likely contributes to its development. Similarly, the pathophysiological mechanisms of potential cardiovascular and metabolic involvements are not clear, but FGF-23 excess may play an essential role. Treatment should be considered in symptomatic patients, patients undergoing orthopedic or dental surgery and women during pregnancy and lactation. Treatment with oral phosphate salts and active vitamin D analogs has incomplete efficacy and potential risks. Burosumab, a recombinant human monoclonal antibody against FGF-23, has proven its efficacy in phase 2 and phase 3 clinical trials in adult patients with XLH, but currently its position as first line or second line treatment differ among the countries.
Collapse
Affiliation(s)
- Anne-Lise Lecoq
- AP-HP, Department of Endocrinology and Reproductive Diseases, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, and Platform of Expertise for Rare Disorders, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France
| | - Maria Luisa Brandi
- Department of Surgery and Translational Medicine, University of Florence, University Hospital of Florence, Florence, Italy
| | - Agnès Linglart
- AP-HP, Endocrinology and Diabetes for Children, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, and Platform of Expertise for Rare Disorders, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France; Université Paris-Saclay, INSERM, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France
| | - Peter Kamenický
- AP-HP, Department of Endocrinology and Reproductive Diseases, Reference Center for Rare Disorders of Calcium and Phosphate Metabolism, filière OSCAR, and Platform of Expertise for Rare Disorders, Bicêtre Paris Saclay Hospital, Le Kremlin-Bicêtre, France; Université Paris-Saclay, INSERM, Physiologie et Physiopathologie Endocriniennes, Le Kremlin-Bicêtre, France.
| |
Collapse
|
14
|
Imel EA, Biggin A, Schindeler A, Munns CF. FGF23, Hypophosphatemia, and Emerging Treatments. JBMR Plus 2019; 3:e10190. [PMID: 31485552 PMCID: PMC6715782 DOI: 10.1002/jbm4.10190] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2018] [Revised: 02/13/2019] [Accepted: 02/26/2019] [Indexed: 01/03/2023] Open
Abstract
FGF23 is an important hormonal regulator of phosphate homeostasis. Together with its co-receptor Klotho, it modulates phosphate reabsorption and both 1α-hydroxylation and 24-hydroxylation in the renal proximal tubules. The most common FGF23-mediated hypophosphatemia is X-linked hypophosphatemia (XLH), caused by mutations in the PHEX gene. FGF23-mediated forms of hypophosphatemia are characterized by phosphaturia and low or low-normal calcitriol concentrations, and unlike nutritional rickets, these cannot be cured with nutritional vitamin D supplementation. Autosomal dominant and autosomal recessive forms of FGF23-mediated hypophosphatemias show a similar pathophysiology, despite a variety of different underlying genetic causes. An excess of FGF23 activity has also been associated with a number of other conditions causing hypophosphatemia, including tumor-induced osteomalacia, fibrous dysplasia of the bone, and cutaneous skeletal hypophosphatemia syndrome. Historically phosphate supplementation and therapy using analogs of highly active vitamin D (eg, calcitriol, alfacalcidol, paricalcitol, eldecalcitol) have been used to manage conditions involving hypophosphatemia; however, recently a neutralizing antibody for FGF23 (burosumab) has emerged as a promising treatment agent for FGF23-mediated disorders. This review discusses the progression of clinical trials for burosumab for the treatment of XLH and its recent availability for clinical use. Burosumab may have potential for treating other conditions associated with FGF23 overactivity, but these are not yet supported by trial data. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
Collapse
Affiliation(s)
- Erik A Imel
- Division of EndocrinologyIndiana University School of Medicine, Indianapolis, INUSA
| | - Andrew Biggin
- The University of Sydney Children's Hospital Westmead Clinical School, University of SydneySydneyAustralia
- Department of EndocrinologyThe Children's Hospital at WestmeadWestmeadAustralia
| | - Aaron Schindeler
- The University of Sydney Children's Hospital Westmead Clinical School, University of SydneySydneyAustralia
- Orthopaedic Research Unit, The Children's Hospital at WestmeadWestmeadAustralia
| | - Craig F Munns
- The University of Sydney Children's Hospital Westmead Clinical School, University of SydneySydneyAustralia
- Department of EndocrinologyThe Children's Hospital at WestmeadWestmeadAustralia
| |
Collapse
|
15
|
Bär L, Stournaras C, Lang F, Föller M. Regulation of fibroblast growth factor 23 (FGF23) in health and disease. FEBS Lett 2019; 593:1879-1900. [PMID: 31199502 DOI: 10.1002/1873-3468.13494] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/26/2019] [Accepted: 03/27/2019] [Indexed: 12/19/2022]
Abstract
Fibroblast growth factor 23 (FGF23) is mainly produced in the bone and, upon secretion, forms a complex with a FGF receptor and coreceptor αKlotho. FGF23 can exert several endocrine functions, such as inhibiting renal phosphate reabsorption and 1,25-dihydroxyvitamin D3 production. Moreover, it has paracrine activities on several cell types, including neutrophils and hepatocytes. Klotho and Fgf23 deficiencies result in pathologies otherwise encountered in age-associated diseases, mainly as a result of hyperphosphataemia-dependent calcification. FGF23 levels are also perturbed in the plasma of patients with several disorders, including kidney or cardiovascular diseases. Here, we review mechanisms controlling FGF23 production and discuss how FGF23 regulation is perturbed in disease.
Collapse
Affiliation(s)
- Ludmilla Bär
- Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Christos Stournaras
- Institute of Biochemistry, University of Crete Medical School, Heraklion, Greece
| | - Florian Lang
- Institute of Physiology, University of Tübingen, Germany
| | - Michael Föller
- Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| |
Collapse
|
16
|
Haffner D, Emma F, Eastwood DM, Duplan MB, Bacchetta J, Schnabel D, Wicart P, Bockenhauer D, Santos F, Levtchenko E, Harvengt P, Kirchhoff M, Di Rocco F, Chaussain C, Brandi ML, Savendahl L, Briot K, Kamenicky P, Rejnmark L, Linglart A. Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia. Nat Rev Nephrol 2019; 15:435-455. [PMID: 31068690 PMCID: PMC7136170 DOI: 10.1038/s41581-019-0152-5] [Citation(s) in RCA: 271] [Impact Index Per Article: 54.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.
Collapse
Affiliation(s)
- Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany.
- Center for Congenital Kidney Diseases, Center for Rare Diseases, Hannover Medical School, Hannover, Germany.
| | - Francesco Emma
- Department of Pediatric Subspecialties, Division of Nephrology, Children's Hospital Bambino Gesù - IRCCS, Rome, Italy
| | - Deborah M Eastwood
- Department of Orthopaedics, Great Ormond St Hospital for Children, Orthopaedics, London, UK
- The Catterall Unit Royal National Orthopaedic Hospital NHS Trust, Stanmore, UK
| | - Martin Biosse Duplan
- Dental School, Université Paris Descartes Sorbonne Paris Cité, Montrouge, France
- APHP, Department of Odontology, Bretonneau Hospital, Paris, France
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
| | - Justine Bacchetta
- Department of Pediatric Nephrology, Rheumatology and Dermatology, University Children's Hospital, Lyon, France
| | - Dirk Schnabel
- Center for Chronic Sick Children, Pediatric Endocrinology, Charitè, University Medicine, Berlin, Germany
| | - Philippe Wicart
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
- APHP, Department of Pediatric Orthopedic Surgery, Necker - Enfants Malades University Hospital, Paris, France
- Paris Descartes University, Paris, France
| | - Detlef Bockenhauer
- University College London, Centre for Nephrology and Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Fernando Santos
- Hospital Universitario Central de Asturias (HUCA), University of Oviedo, Oviedo, Spain
| | - Elena Levtchenko
- Department of Pediatric Nephrology and Development and Regeneration, University Hospitals Leuven, University of Leuven, Leuven, Belgium
| | - Pol Harvengt
- RVRH-XLH, French Patient Association for XLH, Suresnes, France
| | - Martha Kirchhoff
- Phosphatdiabetes e.V., German Patient Association for XLH, Lippstadt, Germany
| | - Federico Di Rocco
- Pediatric Neurosurgery, Hôpital Femme Mère Enfant, Centre de Référence Craniosténoses, Université de Lyon, Lyon, France
| | - Catherine Chaussain
- Dental School, Université Paris Descartes Sorbonne Paris Cité, Montrouge, France
- APHP, Department of Odontology, Bretonneau Hospital, Paris, France
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
| | - Maria Louisa Brandi
- Metabolic Bone Diseases Unit, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
| | - Lars Savendahl
- Pediatric Endocrinology Unit, Karolinska University Hospital, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - Karine Briot
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
- Paris Descartes University, Paris, France
- APHP, Department of Rheumatology, Cochin Hospital, Paris, France
- INSERM UMR-1153, Paris, France
| | - Peter Kamenicky
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
- APHP, Department of Endocrinology and Reproductive Diseases, Bicêtre Paris-Sud Hospital, Paris, France
- INSERM U1185, Bicêtre Paris-Sud, Paris-Sud - Paris Saclay University, Le Kremlin-Bicêtre, France
| | - Lars Rejnmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Agnès Linglart
- APHP, Reference Center for Rare Diseases of Calcium and Phosphate Metabolism, and Filière OSCAR, Paris, France
- INSERM U1185, Bicêtre Paris-Sud, Paris-Sud - Paris Saclay University, Le Kremlin-Bicêtre, France
- APHP, Platform of Expertise of Paris-Sud for Rare Diseases and Filière OSCAR, Bicêtre Paris-Sud Hospital (HUPS), Le Kremlin-Bicêtre, France
- APHP, Endocrinology and Diabetes for Children, Bicêtre Paris-Sud Hospital, Le Kremlin-Bicêtre, France
| |
Collapse
|
17
|
Beck-Nielsen SS, Mughal Z, Haffner D, Nilsson O, Levtchenko E, Ariceta G, de Lucas Collantes C, Schnabel D, Jandhyala R, Mäkitie O. FGF23 and its role in X-linked hypophosphatemia-related morbidity. Orphanet J Rare Dis 2019; 14:58. [PMID: 30808384 PMCID: PMC6390548 DOI: 10.1186/s13023-019-1014-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 01/30/2019] [Indexed: 12/29/2022] Open
Abstract
Background X-linked hypophosphatemia (XLH) is an inherited disease of phosphate metabolism in which inactivating mutations of the Phosphate Regulating Endopeptidase Homolog, X-Linked (PHEX) gene lead to local and systemic effects including impaired growth, rickets, osteomalacia, bone abnormalities, bone pain, spontaneous dental abscesses, hearing difficulties, enthesopathy, osteoarthritis, and muscular dysfunction. Patients with XLH present with elevated levels of fibroblast growth factor 23 (FGF23), which is thought to mediate many of the aforementioned manifestations of the disease. Elevated FGF23 has also been observed in many other diseases of hypophosphatemia, and a range of animal models have been developed to study these diseases, yet the role of FGF23 in the pathophysiology of XLH is incompletely understood. Methods The role of FGF23 in the pathophysiology of XLH is here reviewed by describing what is known about phenotypes associated with various PHEX mutations, animal models of XLH, and non-nutritional diseases of hypophosphatemia, and by presenting molecular pathways that have been proposed to contribute to manifestations of XLH. Results The pathophysiology of XLH is complex, involving a range of molecular pathways that variously contribute to different manifestations of the disease. Hypophosphatemia due to elevated FGF23 is the most obvious contributor, however localised fluctuations in tissue non-specific alkaline phosphatase (TNAP), pyrophosphate, calcitriol and direct effects of FGF23 have been observed to be associated with certain manifestations. Conclusions By describing what is known about these pathways, this review highlights key areas for future research that would contribute to the understanding and clinical treatment of non-nutritional diseases of hypophosphatemia, particularly XLH.
Collapse
Affiliation(s)
| | - Zulf Mughal
- Royal Manchester Children's Hospital, Manchester, UK
| | | | - Ola Nilsson
- Karolinska Institutet, Stockholm, Sweden and Örebro University, Örebro, Sweden
| | | | - Gema Ariceta
- Hospital Universitario Materno-Infantil Vall d'Hebron, Universitat Autonoma de Barcelona, Barcelona, Spain
| | | | - Dirk Schnabel
- University Children's Hospital of Berlin, Berlin, Germany
| | | | - Outi Mäkitie
- Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| |
Collapse
|
18
|
Hernando N, Wagner CA. Mechanisms and Regulation of Intestinal Phosphate Absorption. Compr Physiol 2018; 8:1065-1090. [PMID: 29978897 DOI: 10.1002/cphy.c170024] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
States of hypo- and hyperphosphatemia have deleterious consequences including rickets/osteomalacia and renal/cardiovascular disease, respectively. Therefore, the maintenance of appropriate plasma levels of phosphate is an essential requirement for health. This control is executed by the collaborative action of intestine and kidney whose capacities to (re)absorb phosphate are regulated by a number of hormonal and metabolic factors, among them parathyroid hormone, fibroblast growth factor 23, 1,25(OH)2 vitamin D3 , and dietary phosphate. The molecular mechanisms responsible for the transepithelial transport of phosphate across enterocytes are only partially understood. Indeed, whereas renal reabsorption entirely relies on well-characterized active transport mechanisms of phosphate across the renal proximal epithelia, intestinal absorption proceeds via active and passive mechanisms, with the molecular identity of the passive component still unknown. The active absorption of phosphate depends mostly on the activity and expression of the sodium-dependent phosphate cotransporter NaPi-IIb (SLC34A2), which is highly regulated by many of the factors, mentioned earlier. Physiologically, the contribution of NaPi-IIb to the maintenance of phosphate balance appears to be mostly relevant during periods of low phosphate availability. Therefore, its role in individuals living in industrialized societies with high phosphate intake is probably less relevant. Importantly, small increases in plasma phosphate, even within normal range, associate with higher risk of cardiovascular disease. Therefore, therapeutic approaches to treat hyperphosphatemia, including dietary phosphate restriction and phosphate binders, aim at reducing intestinal absorption. Here we review the current state of research in the field. © 2017 American Physiological Society. Compr Physiol 8:1065-1090, 2018.
Collapse
Affiliation(s)
- Nati Hernando
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
| | - Carsten A Wagner
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
| |
Collapse
|
19
|
Kinoshita Y, Fukumoto S. X-Linked Hypophosphatemia and FGF23-Related Hypophosphatemic Diseases: Prospect for New Treatment. Endocr Rev 2018; 39:274-291. [PMID: 29381780 DOI: 10.1210/er.2017-00220] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 01/23/2018] [Indexed: 12/21/2022]
Abstract
Phosphate plays essential roles in many biological processes, and the serum phosphate level is tightly controlled. Chronic hypophosphatemia causes impaired mineralization of the bone matrix and results in rickets and osteomalacia. Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphate metabolism. FGF23 excess induces hypophosphatemia via impaired phosphate reabsorption in the renal proximal tubules and decreased phosphate absorption in the intestines. There are several types of genetic and acquired FGF23-related hypophosphatemic diseases. Among these diseases, X-linked hypophosphatemia (XLH), which is caused by inactivating mutations in the phosphate-regulating endopeptidase homolog, X-linked (PHEX) gene, is the most prevalent form of genetic FGF23-related hypophosphatemic rickets. Another clinically relevant form of FGF23-related hypophosphatemic disease is tumor-induced osteomalacia (TIO), a paraneoplastic syndrome associated with FGF23-producing tumors. A combination of active vitamin D and phosphate salts is the current medical therapy used to treat patients with XLH and inoperative TIO. However, this therapy has certain efficacy- and safety-associated limitations. Several measures to inhibit FGF23 activity have been considered as possible new treatments for FGF23-related hypophosphatemic diseases. In particular, a humanized monoclonal antibody for FGF23 (burosumab) is a promising treatment in patients with XLH and TIO. This review will focus on the phosphate metabolism and the pathogenesis and treatment of FGF23-related hypophosphatemic diseases.
Collapse
Affiliation(s)
- Yuka Kinoshita
- Division of Nephrology and Endocrinology, Department of Medicine, The University of Tokyo Hospital, Tokyo, Japan
| | - Seiji Fukumoto
- Fujii Memorial Institute of Medical Sciences, Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
| |
Collapse
|
20
|
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.
Collapse
|
21
|
Lv K, Huang H, Yi X, Chertoff ME, Li C, Yuan B, Hinton RJ, Feng JQ. A novel auditory ossicles membrane and the development of conductive hearing loss in Dmp1-null mice. Bone 2017; 103:39-46. [PMID: 28603080 PMCID: PMC5568469 DOI: 10.1016/j.bone.2017.06.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 06/07/2017] [Accepted: 06/07/2017] [Indexed: 10/19/2022]
Abstract
Genetic mouse models are widely used for understanding human diseases but we know much less about the anatomical structure of the auditory ossicles in the mouse than we do about human ossicles. Furthermore, current studies have mainly focused on disease conditions such as osteomalacia and rickets in patients with hypophosphatemia rickets, although the reason that these patients develop late-onset hearing loss is unknown. In this study, we first analyzed Dmp1 lac Z knock-in auditory ossicles (in which the blue reporter is used to trace DMP1 expression in osteocytes) using X-gal staining and discovered a novel bony membrane surrounding the mouse malleus. This finding was further confirmed by 3-D micro-CT, X-ray, and alizarin red stained images. We speculate that this unique structure amplifies and facilitates sound wave transmissions in two ways: increasing the contact surface between the eardrum and malleus and accelerating the sound transmission due to its mineral content. Next, we documented a progressive deterioration in the Dmp1-null auditory ossicle structures using multiple imaging techniques. The auditory brainstem response test demonstrated a conductive hearing loss in the adult Dmp1-null mice. This finding may help to explain in part why patients with DMP1 mutations develop late-onset hearing loss, and supports the critical role of DMP1 in maintaining the integrity of the auditory ossicles and its bony membrane.
Collapse
Affiliation(s)
- Kun Lv
- Biomedical Sciences, Texas A&M College of Dentistry, Dallas, TX 75246, USA; The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan 430079, China
| | - Haiyang Huang
- Biomedical Sciences, Texas A&M College of Dentistry, Dallas, TX 75246, USA
| | - Xing Yi
- Department of Hearing and Speech, KU Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 6616, USA
| | - Mark E Chertoff
- Department of Hearing and Speech, KU Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 6616, USA
| | - Chaoyuan Li
- Biomedical Sciences, Texas A&M College of Dentistry, Dallas, TX 75246, USA
| | - Baozhi Yuan
- Department of Medicine, School of Medicine and Public Health, Univ. Wisconsin, Madison, WI 53726, USA
| | - Robert J Hinton
- Biomedical Sciences, Texas A&M College of Dentistry, Dallas, TX 75246, USA
| | - Jian Q Feng
- Biomedical Sciences, Texas A&M College of Dentistry, Dallas, TX 75246, USA.
| |
Collapse
|
22
|
FGF23 is synthesised locally by renal tubules and activates injury-primed fibroblasts. Sci Rep 2017; 7:3345. [PMID: 28611350 PMCID: PMC5469734 DOI: 10.1038/s41598-017-02709-w] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022] Open
Abstract
In kidney disease, higher circulating levels of the mineral-regulating hormone fibroblast growth factor (FGF)-23 are predictive of disease progression but direct pathogenic effects on the kidney are unknown. We sought evidence of local renal synthesis in response to unilateral ureteric obstruction in the mouse, and pro-fibrotic actions of FGF23 on the fibroblast in vitro. Acute tubulointerstitial injury due to unilateral ureteric obstruction stimulated renal FGF23 synthesis by tubules, and downregulated inactivating proprotein convertases, without effects on systemic mineral metabolism. In vitro, FGF23 had divergent effects on fibroblast activation in cells derived from normal and obstructed kidneys. While FGF23 failed to stimulate fibrogenesis in normal fibroblasts, in those primed by injury, FGF23 induced pro-fibrotic signalling cascades via activation of TGF-β pathways. Effects were independent of α-klotho. Tubule-derived FGF23 may amplify myofibroblast activation in acute renal injury, and might provide a novel therapeutic target in renal fibrosis.
Collapse
|
23
|
Nakamura Y, Takagi M, Takeda R, Miyai K, Hasegawa Y. Hypertension is a characteristic complication of X-linked hypophosphatemia. Endocr J 2017; 64:283-289. [PMID: 28025445 DOI: 10.1507/endocrj.ej16-0199] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
X-linked hypophosphatemia (XLH) is a group of rare disorders caused by defective proximal tubular reabsorption of phosphate. Mutations in the PHEX gene are responsible for the majority of cases. There are very few reports of long-term complications of XLH other than skeletal and dental diseases. The aim of this study was to identify the phenotypic presentation of XLH during adulthood including complications other than skeletal and dental diseases. The clinical and biochemical phenotype of 22 adult patients with a PHEX gene mutation were examined retrospectively from their medical records. 6 patients had hypertension. The average age of hypertension onset was 29.0 years. Secondary hyperparathyroidism preceded the development of hypertension in 5 patients. 1 patient developed tertiary hyperparathyroidism. 15 patients had nephrocalcinosis. 2 patients had chronic renal dysfunction. Patients with hypertension had a significantly lower eGFR (p=0.010) compared to patients without hypertension. No significant difference was found in any other parameters. To examine the genotype-phenotype correlation, 10 adult males were chosen for analysis. No significant genotype-phenotype correlation analysis was revealed in any of the complications. However, there was a possibility that the age at nephrocalcinosis onset was younger in the non-missense mutation group than in the missense mutation group (p=0.063). This study corroborated the view that early-onset hypertension could be one of the characteristic complications seen in XLH patients. Considering the limited number of our patients, further study is necessary to address a potential cause of hypertension. XLH patients require careful lifelong treatment.
Collapse
Affiliation(s)
- Yoshie Nakamura
- Division of Genetic Research, Tokyo Metropolitan Children's Medical Center, Tokyo 183-8561, Japan
| | | | | | | | | |
Collapse
|
24
|
Abstract
Fibroblast growth factor 23 (FGF23) is an important regulator of phosphate and vitamin D metabolism and its excessive or insufficient production leads to a wide variety of skeletal disorders. This article reviews the FGF23-α-Klotho signaling pathway, highlighting the latest developments in FGF23 regulation and action, and describes the disorders associated with FGF23 excess or deficiency.
Collapse
Affiliation(s)
- Anda R Gonciulea
- Division of Endocrinology, Diabetes and Metabolism, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Suzanne M Jan De Beur
- Division of Endocrinology, Diabetes and Metabolism, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| |
Collapse
|
25
|
Yamamoto H, Ramos-Molina B, Lick AN, Prideaux M, Albornoz V, Bonewald L, Lindberg I. Posttranslational processing of FGF23 in osteocytes during the osteoblast to osteocyte transition. Bone 2016; 84:120-130. [PMID: 26746780 PMCID: PMC4755901 DOI: 10.1016/j.bone.2015.12.055] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/04/2015] [Accepted: 12/09/2015] [Indexed: 11/29/2022]
Abstract
FGF23 is an O-glycosylated circulating peptide hormone with a critical role in phosphate homeostasis; it is inactivated by cellular proprotein convertases in a pre-release degradative pathway. We have here examined the metabolism of FGF23 in a model bone cell line, IDG-SW3, prior to and following differentiation, as well as in regulated secretory cells. Labeling experiments showed that the majority of (35)S-labeled FGF23 was cleaved to smaller fragments which were constitutively secreted by all cell types. Intact FGF23 was much more efficiently stored in differentiated than in undifferentiated IDG-SW3 cells. The prohormone convertase PC2 has recently been implicated in FGF23 degradation; however, FGF23 was not targeted to forskolin-stimulatable secretory vesicles in a regulated cell line, suggesting that it lacks a targeting signal to PC2-containing compartments. In vitro, PC1/3 and PC2, but not furin, efficiently cleaved glycosylated FGF23; surprisingly, PC5/6 accomplished a small amount of conversion. FGF23 has recently been shown to be phosphorylated by the kinase FAM20C, a process which was shown to reduce FGF23 glycosylation and promote its cleavage; our in vitro data, however, show that phosphorylation does not directly impact cleavage, as both PC5/6 and furin were able to efficiently cleave unglycosylated, phosphorylated FGF23. Using qPCR, we found that the expression of FGF23 and PC5/6, but not PC2 or furin, increased substantially following osteoblast to osteocyte differentiation. Western blotting confirmed the large increase in PC5/6 expression upon differentiation. FGF23 has been linked to a variety of bone disorders ranging from autosomal dominant hypophosphatemic rickets to chronic kidney disease. A better understanding of the biosynthetic pathway of this hormone may lead to new treatments for these diseases.
Collapse
Affiliation(s)
- Hiroyuki Yamamoto
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Bruno Ramos-Molina
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Adam N Lick
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Matthew Prideaux
- School of Dentistry, Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City, Kansas City, MO 64108, USA
| | - Valeria Albornoz
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Lynda Bonewald
- School of Dentistry, Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City, Kansas City, MO 64108, USA
| | - Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
| |
Collapse
|
26
|
Ren Y, Han X, Jing Y, Yuan B, Ke H, Liu M, Feng JQ. Sclerostin antibody (Scl-Ab) improves osteomalacia phenotype in dentin matrix protein 1(Dmp1) knockout mice with little impact on serum levels of phosphorus and FGF23. Matrix Biol 2015; 52-54:151-161. [PMID: 26721590 DOI: 10.1016/j.matbio.2015.12.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/15/2015] [Accepted: 12/16/2015] [Indexed: 02/05/2023]
Abstract
Unlike treatments for most rickets, the treatment using 1,25-(OH)2 vitamin D3 has little efficacy on patients with hypophosphatemic rickets, a set of rare genetic diseases. Thus, understanding the local cause for osteomalacia in hypophosphatemic rickets and developing an effective treatment to restore mineralization in this rare disease has been a longstanding goal in medicine. Here, we used Dmp1 knockout (KO) mice (whose mutations led to the same type of autosomal recessive hypophosphatemic rickets in humans) as the model in which the monoclonal antibody of sclerostin (Scl-Ab) was tested in two age groups for 8weeks: the prevention group (starting at age 4weeks) and the treatment group (starting at age 12weeks). Applications of Scl-Ab greatly improved the osteomalacia phenotype (>15%) and the biomechanical properties (3-point bending, ~60%) in the treated long-bone group. Our studies not only showed improvement of the osteomalacia in the alveolar bone, which has the highest bone metabolism rate, as well as the long bone phenotypes in treated mice. All these improvements attributed to the use of Scl-Ab are independent of the change in serum levels of phosphorus and FGF23, since Scl-Ab had little efficacy on those parameters. Finally, we propose a model to explain how Scl-Ab can improve the Dmp1 KO osteomalacia phenotype, in which the sclerostin level is already low.
Collapse
Affiliation(s)
- Yinshi Ren
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, TX, USA
| | - Xianglong Han
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, TX, USA; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, China
| | - Yan Jing
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, TX, USA
| | - Baozhi Yuan
- Department of Medicine, University of Wisconsin-Madison and Geriatric Research and Education Center, Madison, WI, USA
| | - Huazhu Ke
- Department of Metabolic Disorders, Amgen Inc., Thousand Oaks, CA, USA
| | - Min Liu
- Department of Metabolic Disorders, Amgen Inc., Thousand Oaks, CA, USA
| | - Jian Q Feng
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry, Dallas, TX, USA.
| |
Collapse
|
27
|
Hernando N, Myakala K, Simona F, Knöpfel T, Thomas L, Murer H, Wagner CA, Biber J. Intestinal Depletion of NaPi-IIb/Slc34a2 in Mice: Renal and Hormonal Adaptation. J Bone Miner Res 2015; 30:1925-37. [PMID: 25827490 DOI: 10.1002/jbmr.2523] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 03/26/2015] [Accepted: 03/27/2015] [Indexed: 11/10/2022]
Abstract
The Na(+) -dependent phosphate-cotransporter NaPi-IIb (SLC34A2) is widely expressed, with intestine, lung, and testis among the organs with highest levels of mRNA abundance. In mice, the intestinal expression of NaPi-IIb is restricted to the ileum, where the cotransporter localizes specifically at the brush border membrane (BBM) and mediates the active transport of inorganic phosphate (Pi). Constitutive full ablation of NaPi-IIb is embryonically lethal whereas the global but inducible removal of the transporter in young mice leads to intestinal loss of Pi and lung calcifications. Here we report the generation of a constitutive but intestinal-specific NaPi-IIb/Slc34a2-deficient mouse model. Constitutive intestinal ablation of NaPi-IIb results in viable pups with normal growth. Homozygous mice are characterized by fecal wasting of Pi and complete absence of Na/Pi cotransport activity in BBM vesicles (BBMVs) isolated from ileum. In contrast, the urinary excretion of Pi is reduced in these animals. The plasma levels of Pi are similar in wild-type and NaPi-IIb-deficient mice. In females, the reduced phosphaturia associates with higher expression of NaPi-IIa and higher Na/Pi cotransport activity in renal BBMVs, as well as with reduced plasma levels of intact FGF-23. A similar trend is found in males. Thus, NaPi-IIb is the only luminal Na(+) -dependent Pi transporter in the murine ileum and its absence is fully compensated for in adult females by a mechanism involving the bone-kidney axis. The contribution of this mechanism to the adaptive response is less apparent in adult males.
Collapse
Affiliation(s)
- Nati Hernando
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Komuraiah Myakala
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Fabia Simona
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Thomas Knöpfel
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Linto Thomas
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Heini Murer
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| | - Jürg Biber
- Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP). University of Zurich, Zurich, Switzerland
| |
Collapse
|
28
|
Yang X, Yan W, Tian Y, Ma P, Opperman LA, Wang X. Family with sequence similarity member 20C is the primary but not the only kinase for the small-integrin-binding ligand N-linked glycoproteins in bone. FASEB J 2015; 30:121-8. [PMID: 26324849 DOI: 10.1096/fj.15-273607] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 08/17/2015] [Indexed: 12/27/2022]
Abstract
Recent studies have identified family with sequence similarity member 20C (FAM20C) as a kinase that phosphorylates the Ser in Ser-X-Glu/phospho-Ser (pSer) motifs in the small-integrin-binding ligand N-linked glycoproteins (SIBLINGs). There is no in vivo evidence that validates this finding, and it is unclear whether FAM20C is the only kinase for SIBLINGs. We extracted bone noncollagenous proteins (NCPs) from Fam20C-knockout (KO) mice and analyzed the phosphorylation levels. The total NCPs were separated into osteopontin-, bone sialoprotein-, and dentin matrix protein-1-enriched fractions by anion-exchange chromatography and analyzed by SDS-PAGE, native PAGE, and Western immunoblot analysis. The NCP phosphorylation level in the KO mice was lower than that in the wild-type (WT). On the native gel, the SIBLINGs from KO mice showed a lower migration rate (Mr) than those from the WT. Calf intestine phosphatase treatment shifted SIBLINGs from the WT mice to the level adjacent to the KO, but failed to shift the latter, suggesting a phosphorylation loss of SIBLINGs in the KO mice. Mass spectrometry identified less pSers in the SIBLINGs from the KO mice [including the region of the acidic Ser- and aspartate-rich motif (ASARM) peptides]. In an intriguing finding, several pSers in the Ser-X-Glu motifs in the KO mice maintained their phosphorylation, whereas several others in non-Ser-X-Glu motifs did not. Phospho-Tyrs and phospho-Thrs in the SIBLINGs did not appear to be associated with FAM20C. Our results indicate that FAM20C is the primary, but not the only, kinase for the SIBLINGs.-Yang, X., Yan, W., Tian, Y., Ma, P., Opperman, L. A., Wang, X. Family with sequence similarity member 20C is the primary but not the only kinase for the small-integrin-binding ligand N-linked glycoproteins in bone.
Collapse
Affiliation(s)
- Xiudong Yang
- *Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; Southern Medical University, Guangdong, People's Republic of China; Sichuan University, Sichuan, People's Republic of China; and Capital Medical University, Beijing, People's Republic of China
| | - Wenjuan Yan
- *Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; Southern Medical University, Guangdong, People's Republic of China; Sichuan University, Sichuan, People's Republic of China; and Capital Medical University, Beijing, People's Republic of China
| | - Ye Tian
- *Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; Southern Medical University, Guangdong, People's Republic of China; Sichuan University, Sichuan, People's Republic of China; and Capital Medical University, Beijing, People's Republic of China
| | - Pan Ma
- *Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; Southern Medical University, Guangdong, People's Republic of China; Sichuan University, Sichuan, People's Republic of China; and Capital Medical University, Beijing, People's Republic of China
| | - Lynne A Opperman
- *Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; Southern Medical University, Guangdong, People's Republic of China; Sichuan University, Sichuan, People's Republic of China; and Capital Medical University, Beijing, People's Republic of China
| | - Xiaofang Wang
- *Department of Biomedical Sciences and Center for Craniofacial Research and Diagnosis, Texas A&M University Baylor College of Dentistry, Dallas, Texas, USA; Southern Medical University, Guangdong, People's Republic of China; Sichuan University, Sichuan, People's Republic of China; and Capital Medical University, Beijing, People's Republic of China
| |
Collapse
|
29
|
Abstract
Traditionally, control of phosphorus in the body has been considered secondary to the tighter control of calcium by parathyroid hormone and vitamin D. However, over the past decade, substantial advances have been made in understanding the control of phosphorus by the so-called phosphatonin system, the lynchpin of which is fibroblast growth factor 23 (FGF23). FGF23 binds to the klotho/FGFR1c receptor complex in renal tubular epithelial cells, leading to upregulation of Na/Pi cotransporters and subsequent excretion of phosphorus from the body. In addition, FGF23 inhibits parathyroid hormone and the renal 1α-hydroxylase enzyme, while it stimulates 24-hydroxylase, leading to decreased 1,25-dihydroxyvitamin D3. FGF23 is intimately involved in the pathogenesis of a number of diseases, particularly the hereditary hypophosphatemic rickets group and chronic kidney disease, and is a target for the development of new treatments in human medicine. Little work has been done on FGF23 or the other phosphatonins in veterinary medicine, but increases in FGF23 are seen with chronic kidney disease in cats, and increased FGF23 expression has been found in soft tissue sarcomas in dogs.
Collapse
Affiliation(s)
- M. R. Hardcastle
- Gribbles Veterinary Pathology Ltd, Mt Wellington, Auckland, New Zealand
| | - K. E. Dittmer
- Animal and Biomedical Sciences, Institute of Veterinary, Massey University, Palmerston North, New Zealand
| |
Collapse
|
30
|
A unified model for bone-renal mineral and energy metabolism. Curr Opin Pharmacol 2015; 22:64-71. [PMID: 25880364 DOI: 10.1016/j.coph.2015.03.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 03/27/2015] [Accepted: 03/30/2015] [Indexed: 01/09/2023]
Abstract
The beginning of the millennium saw the discovery of a new bone-matrix protein, Matrix Extracellular PhosphoglycoprotEin (MEPE) and an associated C-terminal motif called ASARM. This motif and other distinguishing features occur in a group of proteins called SIBLINGs. These proteins include dentin matrix protein 1 (DMP1), osteopontin, dentin-sialophosphoprotein (DSPP), statherin, bone sialoprotein (BSP) and MEPE. MEPE, DMP1 and ASARM-motifs regulate expression of a phosphate regulating cytokine FGF23. Further, a trimeric interaction between phosphate regulating endopeptidase homolog X-linked (PHEX), DMP1, and α5β3-integrin that occurs on the plasma-membrane of the osteocyte mediates FGF23 regulation (FAP pathway). ASARM-peptides competitively inhibit the trimeric complex and increase FGF23. A second pathway involves specialized structures, matrix vesicles pathway (MVP). This review will discuss the FAP and MVP pathways and present a unified model for mineral and energy metabolism.
Collapse
|
31
|
Lindberg I, Pang HW, Stains JP, Clark D, Yang AJ, Bonewald L, Li KZ. FGF23 is endogenously phosphorylated in bone cells. J Bone Miner Res 2015; 30:449-54. [PMID: 25195776 PMCID: PMC4750499 DOI: 10.1002/jbmr.2354] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 08/28/2014] [Accepted: 09/03/2014] [Indexed: 01/22/2023]
Abstract
Levels of serum phosphate are controlled by the peptide hormone FGF23, secreted from bone osteocytes. Elevated levels of circulating FGF23 are a key factor in several hypophosphatemic disorders and play a role in chronic kidney disease. Posttranslational processing of FGF23 includes multi-site O-glycosylation, which reduces intracellular cleavage by proprotein convertases. The FGF23 protein also contains four serine phosphorylation consensus sequences (S-X-D/E); in this work, we asked whether FGF23 is a substrate for secretory phosphorylation. Both HEK cells as well as IDG-SW3 cells, an osteocyte model, incorporated radiolabeled orthophosphate into intact FGF23, as well as into the 14-kDa carboxy-terminal-but not the 17-kDa N-terminal-fragment. Sequential serine-to-alanine site-directed mutagenesis of four kinase consensus sites showed that labeling occurred on three serines within the carboxy-terminal fragment, Ser180 (adjacent to the cleavage site), Ser207, and Ser212. Liquid chromatography-coupled mass spectroscopy indicated the presence of phosphate at Ser212 in recombinant R&D mouse FGF23(R179Q) , confirming labeling results. A phosphopeptide-specific antibody was raised against phospho-Ser212 and exhibited immunoreactivity in osteocytes present in mouse long bone, providing further evidence that FGF23 is naturally phosphorylated in bone. Bone SIBLING proteins are serine-phosphorylated by the ubiquitous Golgi secretory kinase FAM20C. Cotransfection of HEK and MC3T3 cells with FGF23 and active, but not inactive, FAM20C kinase increased the storage and release of FGF23 in radiolabeling experiments, indicating potential effects of phosphorylation on FGF23 stability. Collectively, these data point to an important role for phosphorylation of FGF23 in bone.
Collapse
Affiliation(s)
- Iris Lindberg
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | | | | | | | | | | | | |
Collapse
|
32
|
Abstract
PURPOSE OF REVIEW To review the emerging literature on changes in fibroblast growth factor 23 (FGF23) levels in the setting of acute kidney injury (AKI). RECENT FINDINGS Studies suggest that FGF23 levels are elevated in patients with AKI and correlate with increased risk of death or need for dialysis in adults, or prolonged ventilation time and higher fluid gain in children. Animal studies have shown that the cause behind this FGF23 increase is multifactorial and includes increased production in bone and decreased clearance, but not vitamin D or parathyroid hormone (PTH) activated pathways. Interestingly, FGF23 levels are found to be mildly elevated even in hospitalized patients without kidney injury, although this observation may be limited to only c-terminal FGF23 fragments. The prognostic implications of an elevated FGF23 value in patients with AKI need to be confirmed in larger cohorts and evaluated for long-term outcomes such as the development of new chronic kidney disease (CKD) or CKD progression, as well as cardiovascular disease, similar to the studies of FGF23 in the prevalent CKD population. SUMMARY FGF23 levels are elevated in patients with AKI and are associated with morbidity and mortality in small human studies. Mechanistic work in animals suggests that the elevation is independent of PTH or vitamin D signaling pathways. Much work remains to understand the physiology behind FGF23 elevation and the long-term effects of FGF23 in AKI.
Collapse
|
33
|
Abstract
Rapid and somewhat surprising advances have recently been made toward understanding the molecular mechanisms causing heritable disorders of hypophosphatemia. The results of clinical, genetic, and translational studies have interwoven novel concepts underlying the endocrine control of phosphate metabolism, with far-reaching implications for treatment of both rare Mendelian diseases as well as common disorders of blood phosphate excess such as chronic kidney disease (CKD). In particular, diseases caused by changes in the expression and proteolytic control of the phosphaturic hormone fibroblast growth factor-23 (FGF23) have come to the forefront in terms of directing new models explaining mineral metabolism. These hypophosphatemic disorders as well as others resulting from independent defects in phosphate transport or metabolism will be reviewed herein, and implications for emerging therapeutic strategies based upon these new findings will be discussed.
Collapse
Affiliation(s)
- Kenneth E. White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202
- Correspondence to: Kenneth E. White, Ph.D., Department of Medical & Molecular Genetics, Indiana University School of Medicine, 975 West Walnut St., IB130, Indianapolis, IN 46202, Office phone: (317) 278-1775, Fax: (317) 274-2293,
| | - Julia M. Hum
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Michael J. Econs
- Division of Endocrinology and Metabolism, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202
| |
Collapse
|
34
|
Abstract
Increases in fibroblastic growth factor 23 (FGF23 or Fgf23) production by osteocytes result in hypophosphatemia and rickets in the Hyp mouse homologue of X-linked hypophosphatemia (XLH). Fibroblastic growth factor (FGF) signaling has been implicated in the pathogenesis of Hyp. Here, we conditionally deleted FGF receptor 1 (FGFR1 or Fgfr1) in osteocytes of Hyp mice to investigate the role of autocrine/paracrine FGFR signaling in regulating FGF23 production by osteocytes. Crossing dentin matrix protein 1 (Dmp1)-Cre;Fgfr1null/+ mice with female Hyp;Fgfr1flox/flox mice created Hyp and Fgfr1 (Fgfr1Dmp1-cKO)-null mice (Hyp;Fgfr1Dmp1-cKO) with a 70% decrease in bone Fgfr1 transcripts. Fgfr1Dmp1-cKO-null mice exhibited a 50% reduction in FGF23 expression in bone and 3-fold reduction in serum FGF23 concentrations, as well as reductions in sclerostin (Sost), phosphate regulating endopeptidase on X chromosome (PHEX or Phex), matrix extracellular phosphoglycoprotein (Mepe), and Dmp1 transcripts, but had no demonstrable alterations in phosphate or vitamin D homeostasis or skeletal morphology. Hyp mice had hypophosphatemia, reductions in 1,25(OH)2D levels, rickets/osteomalacia and elevated FGF2 expression in bone. Compared to Hyp mice, compound Hyp;Fgfr1Dmp1-cKO-null mice had significant improvement in rickets and osteomalacia in association with a decrease in serum FGF23 (3607 to 1099 pg/ml), an increase in serum phosphate (6.0 mg/dl to 9.3 mg/dl) and 1,25(OH)2D (121±23 to 192±34 pg/ml) levels, but only a 30% reduction in bone FGF23 mRNA expression. FGF23 promoter activity in osteoblasts was stimulated by FGFR1 activation and inhibited by overexpression of a dominant negative FGFR1(TK−), PLCγ and MAPK inhibitors. FGF2 also stimulated the translation of an FGF23 cDNA transfected into osteoblasts via a FGFR1 and PI3K/Akt-dependent mechanism. Thus, activation of autocrine/paracrine FGF pathways is involved in the pathogenesis of Hyp through FGFR1-dependent regulation of FGF23 by both transcriptional and post-transcriptional mechanisms. This may serve to link local bone metabolism with systemic phosphate and vitamin D homeostasis.
Collapse
|
35
|
Christov M, Jüppner H. Dietary phosphate: the challenges of exploring its role in FGF23 regulation. Kidney Int 2014; 84:639-41. [PMID: 24080872 DOI: 10.1038/ki.2013.198] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Fibroblast growth factor 23 (FGF23) is an important regulator of phosphate homeostasis, yet efforts to control its circulating levels by manipulating dietary phosphate intake in humans and animals with normal or impaired kidney function have yielded conflicting results. In the study by Zhang et al., severe phosphate restriction in a genetic mouse model of progressive kidney dysfunction failed to cause a uniform FGF23 reduction, again highlighting the complexity of FGF23 regulation.
Collapse
Affiliation(s)
- Marta Christov
- 1] Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA [2] Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | | |
Collapse
|
36
|
Zelenchuk LV, Hedge AM, Rowe PSN. PHEX mimetic (SPR4-peptide) corrects and improves HYP and wild type mice energy-metabolism. PLoS One 2014; 9:e97326. [PMID: 24839967 PMCID: PMC4026222 DOI: 10.1371/journal.pone.0097326] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 04/17/2014] [Indexed: 12/19/2022] Open
Abstract
CONTEXT PHEX or DMP1 mutations cause hypophosphatemic-rickets and altered energy metabolism. PHEX binds to DMP1-ASARM-motif to form a complex with α5β3 integrin that suppresses FGF23 expression. ASARM-peptides increase FGF23 by disrupting the PHEX-DMP1-Integrin complex. We used a 4.2 kDa peptide (SPR4) that binds to ASARM-peptide/motif to study the DMP1-PHEX interaction and to assess SPR4 for the treatment of energy metabolism defects in HYP and potentially other bone-mineral disorders. DESIGN Subcutaneously transplanted osmotic pumps were used to infuse SPR4-peptide or vehicle (VE) into wild-type mice (WT) and HYP-mice (PHEX mutation) for 4 weeks. RESULTS SPR4 partially corrected HYP mice hypophosphatemia and increased serum 1.25(OH)2D3. Serum FGF23 remained high and PTH was unaffected. WT-SPR4 mice developed hypophosphatemia and hypercalcemia with increased PTH, FGF23 and 1.25(OH)2D3. SPR4 increased GAPDH HYP-bone expression 60× and corrected HYP-mice hyperglycemia and hypoinsulinemia. HYP-VE serum uric-acid (UA) levels were reduced and SPR4 infusion suppressed UA levels in WT-mice but not HYP-mice. SPR4 altered leptin, adiponectin, and sympathetic-tone and increased the fat mass/weight ratio for HYP and WT mice. Expression of perlipin-2 a gene involved in obesity was reduced in HYP-VE and WT-SPR4 mice but increased in HYP-SPR4 mice. Also, increased expression of two genes that inhibit insulin-signaling, ENPP1 and ESP, occurred with HYP-VE mice. In contrast, SPR4 reduced expression of both ENPP1 and ESP in WT mice and suppressed ENPP1 in HYP mice. Increased expression of FAM20C and sclerostin occurred with HYP-VE mice. SPR4 suppressed expression of FAM20C and sclerostin in HYP and WT mice. CONCLUSIONS ASARM peptides and motifs are physiological substrates for PHEX and modulate osteocyte PHEX-DMP1-α5β3-integrin interactions and thereby FGF23 expression. These interactions also provide a nexus that regulates bone and energy metabolism. SPR4 suppression of sclerostin and/or sequestration of ASARM-peptides improves energy metabolism and may have utility for treating familial rickets, osteoporosis, obesity and diabetes.
Collapse
Affiliation(s)
- Lesya V. Zelenchuk
- Internal Medicine, The Kidney Institute, Kansas University Medical Center (KUMC), Kansas City, Kansas, United States of America
| | - Anne-Marie Hedge
- Internal Medicine, The Kidney Institute, Kansas University Medical Center (KUMC), Kansas City, Kansas, United States of America
| | - Peter S. N. Rowe
- Internal Medicine, The Kidney Institute, Kansas University Medical Center (KUMC), Kansas City, Kansas, United States of America
| |
Collapse
|
37
|
Dysregulated gene expression in the primary osteoblasts and osteocytes isolated from hypophosphatemic Hyp mice. PLoS One 2014; 9:e93840. [PMID: 24710520 PMCID: PMC3977859 DOI: 10.1371/journal.pone.0093840] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 03/07/2014] [Indexed: 12/27/2022] Open
Abstract
Osteocytes express multiple genes involved in mineral metabolism including PHEX, FGF23, DMP1 and FAM20C. In Hyp mice, a murine model for X-linked hypophosphatemia (XLH), Phex deficiency results in the overproduction of FGF23 in osteocytes, which leads to hypophosphatemia and impaired vitamin D metabolism. In this study, to further clarify the abnormality in osteocytes of Hyp mice, we obtained detailed gene expression profiles in osteoblasts and osteocytes isolated from the long bones of 20-week-old Hyp mice and wild-type (WT) control mice. The expression of Fgf23, Dmp1, and Fam20c was higher in osteocytic cells than in osteoblastic cells in both genotypes, and was up-regulated in Hyp cells. Interestingly, the up-regulation of these genes in Hyp bones began before birth. On the other hand, the expression of Slc20a1 encoding the sodium/phosphate (Na+/Pi) co-transporter Pit1 was increased in osteoblasts and osteocytes from adult Hyp mice, but not in Hyp fetal bones. The direct effects of extracellular Pi and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on isolated osteoblastic and osteocytic cells were also investigated. Twenty-four-hour treatment with 10−8 M 1,25(OH)2D3 increased the expression of Fgf23 in WT osteoblastic cells but not in osteocytic cells. Dmp1 expression in osteocytic cells was increased due to the 24-hour treatment with 10 mM Pi and was suppressed by 10−8 M 1,25(OH)2D3 in WT osteocytic cells. We also found the up-regulation of the genes for FGF1, FGF2, their receptors, and Egr-1 which is a target of FGF signaling, in Hyp osteocytic cells, suggesting the activation of FGF/FGFR signaling. These results implicate the complex gene dysregulation in osteoblasts and osteocytes of Hyp mice, which might contribute to the pathogenesis.
Collapse
|
38
|
Imel EA, Gray AK, Padgett LR, Econs MJ. Iron and fibroblast growth factor 23 in X-linked hypophosphatemia. Bone 2014; 60:87-92. [PMID: 24325979 PMCID: PMC3928787 DOI: 10.1016/j.bone.2013.12.001] [Citation(s) in RCA: 28] [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: 06/20/2013] [Revised: 11/23/2013] [Accepted: 12/03/2013] [Indexed: 02/03/2023]
Abstract
BACKGROUND Excess fibroblast growth factor 23 (FGF23) causes hypophosphatemia in autosomal dominant hypophosphatemic rickets (ADHR) and X-linked hypophosphatemia (XLH). Iron status influences C-terminal FGF23 (incorporating fragments plus intact FGF23) in ADHR and healthy subjects, and intact FGF23 in ADHR. We hypothesized that in XLH serum iron would inversely correlate to C-terminal FGF23, but not to intact FGF23, mirroring the relationships in normal controls. METHODS Subjects included 25 untreated outpatients with XLH at a tertiary medical center and 158 healthy adult controls. Serum iron and plasma intact FGF23 and C-terminal FGF23 were measured in stored samples. RESULTS Intact FGF23 was greater than the control mean in 100% of XLH patients, and >2SD above the control mean in 88%, compared to 71% and 21% respectively for C-terminal FGF23. In XLH, iron correlated negatively to log-C-terminal FGF23 (r=-0.523, p<0.01), with a steeper slope than in controls (p<0.001). Iron was not related to log-intact FGF23 in either group. The log-ratio of intact FGF23 to C-terminal FGF23 was higher in XLH (0.00±0.44) than controls (-0.28±0.21, p<0.01), and correlated positively to serum iron (controls r=0.276, p<0.001; XLH r=0.428, p<0.05), with a steeper slope in XLH (p<0.01). CONCLUSION Like controls, serum iron in XLH is inversely related to C-terminal FGF23 but not intact FGF23. XLH patients are more likely to have elevated intact FGF23 than C-terminal FGF23. The relationships of iron to FGF23 in XLH suggest that altered regulation of FGF23 cleaving may contribute to maintaining hypophosphatemia around an abnormal set-point.
Collapse
Affiliation(s)
- Erik A Imel
- Indiana University School of Medicine, Department of Medicine, USA; Indiana University School of Medicine, Department of Pediatrics, USA.
| | - Amie K Gray
- Indiana University School of Medicine, Department of Medicine, USA
| | - Leah R Padgett
- Indiana University School of Medicine, Department of Medicine, USA
| | - Michael J Econs
- Indiana University School of Medicine, Department of Medicine, USA
| |
Collapse
|
39
|
Penido MGMG, Alon US. Hypophosphatemic rickets due to perturbations in renal tubular function. Pediatr Nephrol 2014; 29:361-73. [PMID: 23636577 DOI: 10.1007/s00467-013-2466-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2012] [Revised: 03/03/2013] [Accepted: 03/04/2013] [Indexed: 12/13/2022]
Abstract
The common denominator for all types of rickets is hypophosphatemia, leading to inadequate supply of the mineral to the growing bone. Hypophosphatemia can result from insufficient uptake of the mineral from the gut or its disproportionate losses in the kidney, the latter being caused by either tubular abnormalities per se or the effect on the tubule of circulating factors like fibroblast growth factor-23 and parathyroid hormone (PTH). High serum levels of the latter result in most cases from abnormalities in vitamin D metabolism which lead to decreased calcium absorption in the gut and hypocalcemia, triggering PTH secretion. Rickets is a disorder of the growth plate and hence pediatric by definition. However, it is important to recognize that the effect of hypophosphatemia on other parts of the skeleton results in osteomalacia in both children and adults. This review addresses the etiology, pathophysiologic mechanisms, clinical manifestations and treatment of entities associated with hypophosphatemic rickets due to perturbations in renal tubular function.
Collapse
Affiliation(s)
- Maria Goretti M G Penido
- Pediatric Nephrology Unit, Clinics Hospital, School of Medicine, Federal University of Minas Gerais, Av. Professor Alfredo Balena, 190, CEP, 30130100, Belo Horizonte, MG, Brazil,
| | | |
Collapse
|
40
|
Abstract
Teeth are mineralized organs composed of three unique hard tissues, enamel, dentin, and cementum, and supported by the surrounding alveolar bone. Although odontogenesis differs from osteogenesis in several respects, tooth mineralization is susceptible to similar developmental failures as bone. Here we discuss conditions fitting under the umbrella of rickets, which traditionally referred to skeletal disease associated with vitamin D deficiency but has been more recently expanded to include newly identified factors involved in endocrine regulation of vitamin D, phosphate, and calcium, including phosphate-regulating endopeptidase homolog, X-linked, fibroblast growth factor 23, and dentin matrix protein 1. Systemic mineral metabolism intersects with local regulation of mineralization, and factors including tissue nonspecific alkaline phosphatase are necessary for proper mineralization, where rickets can result from loss of activity of tissue nonspecific alkaline phosphatase. Individuals suffering from rickets often bear the additional burden of a defective dentition, and transgenic mouse models have aided in understanding the nature and mechanisms involved in tooth defects, which may or may not parallel rachitic bone defects. This report reviews dental effects of the range of rachitic disorders, including discussion of etiologies of hereditary forms of rickets, a survey of resulting bone and tooth mineralization disorders, and a discussion of mechanisms, known and hypothesized, involved in the observed dental pathologies. Descriptions of human pathology are augmented by analysis of transgenic mouse models, and new interpretations are brought to bear on questions of how teeth are affected under conditions of rickets. In short, the rachitic tooth will be revealed.
Collapse
Affiliation(s)
- Brian L Foster
- National Institute for Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | | | | |
Collapse
|
41
|
Linglart A, Biosse-Duplan M, Briot K, Chaussain C, Esterle L, Guillaume-Czitrom S, Kamenicky P, Nevoux J, Prié D, Rothenbuhler A, Wicart P, Harvengt P. Therapeutic management of hypophosphatemic rickets from infancy to adulthood. Endocr Connect 2014; 3:R13-30. [PMID: 24550322 PMCID: PMC3959730 DOI: 10.1530/ec-13-0103] [Citation(s) in RCA: 207] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In children, hypophosphatemic rickets (HR) is revealed by delayed walking, waddling gait, leg bowing, enlarged cartilages, bone pain, craniostenosis, spontaneous dental abscesses, and growth failure. If undiagnosed during childhood, patients with hypophosphatemia present with bone and/or joint pain, fractures, mineralization defects such as osteomalacia, entesopathy, severe dental anomalies, hearing loss, and fatigue. Healing rickets is the initial endpoint of treatment in children. Therapy aims at counteracting consequences of FGF23 excess, i.e. oral phosphorus supplementation with multiple daily intakes to compensate for renal phosphate wasting and active vitamin D analogs (alfacalcidol or calcitriol) to counter the 1,25-diOH-vitamin D deficiency. Corrective surgeries for residual leg bowing at the end of growth are occasionally performed. In absence of consensus regarding indications of the treatment in adults, it is generally accepted that medical treatment should be reinitiated (or maintained) in symptomatic patients to reduce pain, which may be due to bone microfractures and/or osteomalacia. In addition to the conventional treatment, optimal care of symptomatic patients requires pharmacological and non-pharmacological management of pain and joint stiffness, through appropriated rehabilitation. Much attention should be given to the dental and periodontal manifestations of HR. Besides vitamin D analogs and phosphate supplements that improve tooth mineralization, rigorous oral hygiene, active endodontic treatment of root abscesses and preventive protection of teeth surfaces are recommended. Current outcomes of this therapy are still not optimal, and therapies targeting the pathophysiology of the disease, i.e. FGF23 excess, are desirable. In this review, medical, dental, surgical, and contributions of various expertises to the treatment of HR are described, with an effort to highlight the importance of coordinated care.
Collapse
Affiliation(s)
- Agnès Linglart
- Service d'Endocrinologie et Diabétologie de l'EnfantHôpital Bicêtre, APHP78 rue du Général Leclerc , Le Kremlin Bicêtre, 94270France
- Université Paris 11 faculté de Médecine, Hôpital Bicêtre70 rue du général Leclerc, Le Kremlin-Bicêtre, 94270France
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
- Correspondence should be addressed to A Linglart
| | - Martin Biosse-Duplan
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
- Service d'Odontologie-Maladies Rares Hôpital Bretonneau 2 rue Carpeaux Paris, 75018France
- Université Paris Descartes 12 Rue de l'École de MédecineParis, 75006France
| | - Karine Briot
- Université Paris Descartes 12 Rue de l'École de MédecineParis, 75006France
- Service Rhumatologie B Hôpital Cochin, APHP27, rue du Faubourg Saint-Jacques, Paris, 75014France
| | - Catherine Chaussain
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
- Service d'Odontologie-Maladies Rares Hôpital Bretonneau 2 rue Carpeaux Paris, 75018France
- Université Paris Descartes 12 Rue de l'École de MédecineParis, 75006France
| | - Laure Esterle
- Service d'Endocrinologie et Diabétologie de l'EnfantHôpital Bicêtre, APHP78 rue du Général Leclerc , Le Kremlin Bicêtre, 94270France
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
| | - Séverine Guillaume-Czitrom
- Service de Pédiatrie générale – Consultation de rhumatologieHôpital Bicêtre, APHP78 rue du Général Leclerc , Le Kremlin Bicêtre, 94270France
- Centre de Référence des Maladies Rares des Maladies Auto-Inflammatoires Rares de l'EnfantLe Kremlin BicêtreFrance
| | - Peter Kamenicky
- Service d'Endocrinologie et des Maladies de la ReproductionHôpital Bicêtre, APHP78 rue du Général Leclerc , Le Kremlin Bicêtre, 94270France
- Université Paris 11 faculté de Médecine, Hôpital Bicêtre70 rue du général Leclerc, Le Kremlin-Bicêtre, 94270France
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
| | - Jerome Nevoux
- Service d'ORL et chirurgie cervico-maxillo-facialeHôpital Bicêtre, APHP78 rue du Général Leclerc , Le Kremlin Bicêtre, 94270France
- Université Paris 11 faculté de Médecine, Hôpital Bicêtre70 rue du général Leclerc, Le Kremlin-Bicêtre, 94270France
| | - Dominique Prié
- Université Paris Descartes 12 Rue de l'École de MédecineParis, 75006France
- Service d'explorations fonctionnelles rénales, Hôpital Necker-Enfants Malades149 rue de Sèvres, Paris, 75015France
| | - Anya Rothenbuhler
- Service d'Endocrinologie et Diabétologie de l'EnfantHôpital Bicêtre, APHP78 rue du Général Leclerc , Le Kremlin Bicêtre, 94270France
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
| | - Philippe Wicart
- Centre de Référence des Maladies Rares du Métabolisme du Calcium et du PhosphoreLe Kremlin-BicêtreFrance
- Université Paris Descartes 12 Rue de l'École de MédecineParis, 75006France
- Service de Chirurgie infantile orthopédiqueHôpital Necker-Enfants Malades149 rue de Sèvres, Paris, 75015 France
| | - Pol Harvengt
- Association de patients RVRH-XLH20 rue Merlin de Thionville, Suresnes , 92150France
| |
Collapse
|
42
|
Abstract
There is growing interest in the role of fibroblast growth factor 23 (FGF23) in various diseases of disordered mineral metabolism. In chronic kidney disease (CKD), where biochemical evidence of mineral disturbances is especially common, FGF23 measurement has been advocated as an early and sensitive marker for CKD-related bone disease. In this setting, FGF23 analysis may also improve the discrimination of risk of adverse renal and cardiovascular outcomes and aid targeting of those patients that are likely to benefit from interventions. Nonetheless, while the physiological relevance of FGF23 in the control of mineral metabolism is now firmly established, relatively little attention has been paid to important preanalytical and analytical aspects of FGF23 measurement that may impact on its clinical utility. Here we review these issues and discuss the suitability of FGF23 testing strategies for routine clinical practice. The current ‘state-of-the-art’ enzyme-linked immunosorbent assay methods for FGF23 measurement show poor agreement due to differences in FGF23 fragment detection, antibody specificity and calibration. Such analytical variability does not permit direct comparison of FGF23 measurements made with different assays and is likely to at least in part account for some of the inconsistencies noted between observational studies. From a clinical perspective, the lack of concordance has implications for the development of standardized reference intervals and clinical decision limits. Finally, the inherent assay-dependent biological variability of plasma FGF23 concentration can further complicate the interpretation of results and the design of FGF23-based testing protocols. Currently, it would be premature to consider incorporating FGF23 measurements into standard testing repertoires.
Collapse
Affiliation(s)
- Edward R Smith
- Department of Renal Medicine, Eastern Health Clinical School, Faculty of Medicine Nursing and Health Sciences, Monash University, Box Hill, Victoria, Australia
| | - Lawrence P McMahon
- Department of Renal Medicine, Eastern Health Clinical School, Faculty of Medicine Nursing and Health Sciences, Monash University, Box Hill, Victoria, Australia
| | - Stephen G Holt
- Department of Renal Medicine, Eastern Health Clinical School, Faculty of Medicine Nursing and Health Sciences, Monash University, Box Hill, Victoria, Australia
- Department of Nephrology, The Royal Melbourne Hospital, Parkville, Victoria, Australia
| |
Collapse
|
43
|
McKee MD, Hoac B, Addison WN, Barros NM, Millán JL, Chaussain C. Extracellular matrix mineralization in periodontal tissues: Noncollagenous matrix proteins, enzymes, and relationship to hypophosphatasia and X-linked hypophosphatemia. Periodontol 2000 2013; 63:102-22. [PMID: 23931057 PMCID: PMC3766584 DOI: 10.1111/prd.12029] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2012] [Indexed: 12/26/2022]
Abstract
As broadly demonstrated for the formation of a functional skeleton, proper mineralization of periodontal alveolar bone and teeth - where calcium phosphate crystals are deposited and grow within an extracellular matrix - is essential for dental function. Mineralization defects in tooth dentin and cementum of the periodontium invariably lead to a weak (soft or brittle) dentition in which teeth become loose and prone to infection and are lost prematurely. Mineralization of the extremities of periodontal ligament fibers (Sharpey's fibers) where they insert into tooth cementum and alveolar bone is also essential for the function of the tooth-suspensory apparatus in occlusion and mastication. Molecular determinants of mineralization in these tissues include mineral ion concentrations (phosphate and calcium), pyrophosphate, small integrin-binding ligand N-linked glycoproteins and matrix vesicles. Amongst the enzymes important in regulating these mineralization determinants, two are discussed at length here, with clinical examples given, namely tissue-nonspecific alkaline phosphatase and phosphate-regulating gene with homologies to endopeptidases on the X chromosome. Inactivating mutations in these enzymes in humans and in mouse models lead to the soft bones and teeth characteristic of hypophosphatasia and X-linked hypophosphatemia, respectively, where the levels of local and systemic circulating mineralization determinants are perturbed. In X-linked hypophosphatemia, in addition to renal phosphate wasting causing low circulating phosphate levels, phosphorylated mineralization-regulating small integrin-binding ligand N-linked glycoproteins, such as matrix extracellular phosphoglycoprotein and osteopontin, and the phosphorylated peptides proteolytically released from them, such as the acidic serine- and aspartate-rich-motif peptide, may accumulate locally to impair mineralization in this disease.
Collapse
Affiliation(s)
- Marc D. McKee
- Faculty of Dentistry, McGill University, Montreal, QC, Canada
- Department of Anatomy and Cell Biology, Faculty of Dentistry, McGill University, Montreal, QC, Canada
| | - Betty Hoac
- Faculty of Dentistry, McGill University, Montreal, QC, Canada
| | - William N. Addison
- Department of Oral Medicine, Infection and Immunity, Harvard University School of Dental Medicine, Boston, MA, USA
| | - Nilana M.T. Barros
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brasil, and Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Diadema, SP, Brasil
| | - José Luis Millán
- Sanford Children's Health Research Center, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA
| | - Catherine Chaussain
- EA 2496, UFR Odontologie, University Paris Descartes PRES Sorbonne Paris Cité; AP-HP: Odontology Department Bretonneau, Paris and Centre de Référence des Maladies Rares du Métabolisme du Phosphore et du Calcium, Kremlin Bicêtre, France
| |
Collapse
|
44
|
Abstract
The molecular identification and characterization of genetic defects leading to a number of rare inherited or acquired disorders affecting phosphate homeostasis has added tremendous detail to our understanding of the regulation of phosphate balance. The identification of the key phosphate-regulating hormone, fibroblast growth factor 23 (FGF23), as well as other molecules that control its production, such as the N-acetylgalactosaminyltransferase 3 GALNT3, the endopeptidase phosphate-regulating protein with homologies to endopeptidases on the X chromosome, and the matrix protein dentin matrix protein 1, and molecules that function as downstream effectors of FGF23, such as the longevity factor Klotho and the phosphate transporters NPT2a and NPT2c, has permitted us to understand the elegant and complex interplay that exists between the kidneys, bone, parathyroid, and gut. Such insights from genetic disorders have allowed not only the design of potent targeted therapies for some of these rare genetic disorders, such as using anti-FGF23 antibodies for treatment of X-linked hypophosphatemic rickets, but also have led to clinically relevant observations related to the dysregulation of mineral ion homeostasis in chronic kidney disease. Thus, we are able to leverage our knowledge of rare human disorders affecting only a few individuals, to understand and potentially treat disease processes that affect millions of patients.
Collapse
|
45
|
Abstract
Fibrous dysplasia (FD) is a skeletal disorder caused by activating mutations in Gsα that result in elevations in cAMP. A feature of FD is elevated blood levels of the bone cell-derived phosphaturic hormone, fibroblast growth factor-23 (FGF23). FGF23 regulates serum phosphorus and active vitamin D levels by action on proximal renal tubule cells. An essential step in the production of biologically active FGF23 is glycosylation by the UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyl transferase (ppGalNAc-T3). In the absence of glycosylation, FGF23 is processed into inactive N- and C-terminal proteins by a subtilisin proprotein convertase, probably furin. Normally, most if not all circulating FGF23 is intact. In FD, C-terminal levels are elevated, suggesting altered FGF23 processing. Altered processing in FD is the result of a cAMP-dependent, coordinated decrease in ppGalNAc-T3 and an increase in furin enzyme activity. These findings, and emerging data from other diseases, suggest regulation of FGF23 processing may be a physiologically important process.
Collapse
Affiliation(s)
- Alison M Boyce
- Bone Health Program, Division of Orthopaedics and Sports Medicine, Children’s National Medical Center, Washington, DC 20010
- Division of Endocrinology and Diabetes, Children’s National Medical Center, Washington, D.C. 20010
| | - Nisan Bhattacharyya
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20910
| | - Michael T Collins
- Skeletal Clinical Studies Unit, Craniofacial and Skeletal Diseases Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, 20910
| |
Collapse
|
46
|
Feng JQ, Clinkenbeard EL, Yuan B, White KE, Drezner MK. Osteocyte regulation of phosphate homeostasis and bone mineralization underlies the pathophysiology of the heritable disorders of rickets and osteomalacia. Bone 2013; 54:213-21. [PMID: 23403405 PMCID: PMC3672228 DOI: 10.1016/j.bone.2013.01.046] [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: 01/15/2013] [Revised: 01/30/2013] [Accepted: 01/31/2013] [Indexed: 12/13/2022]
Abstract
Although recent studies have established that osteocytes function as secretory cells that regulate phosphate metabolism, the biomolecular mechanism(s) underlying these effects remain incompletely defined. However, investigations focusing on the pathogenesis of X-linked hypophosphatemia (XLH), autosomal dominant hypophosphatemic rickets (ADHR), and autosomal recessive hypophosphatemic rickets (ARHR), heritable disorders characterized by abnormal renal phosphate wasting and bone mineralization, have clearly implicated FGF23 as a central factor in osteocytes underlying renal phosphate wasting, documented new molecular pathways regulating FGF23 production, and revealed complementary abnormalities in osteocytes that regulate bone mineralization. The seminal observations leading to these discoveries were the following: 1) mutations in FGF23 cause ADHR by limiting cleavage of the bioactive intact molecule, at a subtilisin-like protein convertase (SPC) site, resulting in increased circulating FGF23 levels and hypophosphatemia; 2) mutations in DMP1 cause ARHR, not only by increasing serum FGF23, albeit by enhanced production and not limited cleavage, but also by limiting production of the active DMP1 component, the C-terminal fragment, resulting in dysregulated production of DKK1 and β-catenin, which contributes to impaired bone mineralization; and 3) mutations in PHEX cause XLH both by altering FGF23 proteolysis and production and causing dysregulated production of DKK1 and β-catenin, similar to abnormalities in ADHR and ARHR, but secondary to different central pathophysiological events. These discoveries indicate that ADHR, XLH, and ARHR represent three related heritable hypophosphatemic diseases that arise from mutations in, or dysregulation of, a single common gene product, FGF23 and, in ARHR and XLH, complimentary DMP1 and PHEX directed events that contribute to abnormal bone mineralization.
Collapse
Affiliation(s)
- Jian Q Feng
- Department of Biomedical Sciences, Baylor College of Dentistry, Texas A&M Health Science Center, Dallas, TX 75246, USA
| | | | | | | | | |
Collapse
|