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Yu W, Zeng C, Wang C, Jia S, Liu C, Zeng Y, Cheng J. N1F(Improved-Nephropathy 1 Formula) Ameliorates Renal Interstitial Fibrosis via Inhibiting Extracellular Matrix Deposition and Regulating the FGF23/P38MAPK/Wnt Pathway. Cell Biochem Biophys 2024; 82:927-943. [PMID: 38722471 DOI: 10.1007/s12013-024-01244-6] [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] [Accepted: 02/24/2024] [Indexed: 08/25/2024]
Abstract
BACKGROUND Renal fibrosis is the primary pathway in the progression of chronic kidney disease (CKD) towards end-stage renal failure. The currently used drugs currently are ineffective, and their mechanisms of action remain unclear. This study aims to investigate the nephroprotective effect of Improved-Nephropathy 1 Formula (N1F) in a rat model of unilateral ureteral obstruction (UUO) and explore the potential mechanisms of N1F-containing serum in treating TGF-ß1-induced human renal tubular epithelial cells (HK-2). METHODS SD rats received 2-week continuous N1F gavage starting on day 2 after UUO. HK-2 cells were pretreated with a P38MAPK inhibitor for 1 h in vitro, followed by induction of the cells with TGF-ß1 and treatment with N1F 48 h later. The chemical composition of N1F was analyzed using high-performance liquid chromatography-Q-Orbitrap high-resolution liquid mass spectrometry. Renal function was assessed by measuring serum creatinine (Scr), blood urea nitrogen (BUN) and urine protein (Upro) levels. Hematoxylin and eosin (HE) and Masson's trichrome (Masson) staining were used to evaluate the extent of renal tissue damage and fibrosis. Western blotting, immunohistochemistry, and immunofluorescence were used to detect the protein levels of relevant indices. The RNA levels of the relevant indices were detected using real-time fluorescence quantitative PCR (RT-qPCR). RESULTS We identified 361 chemical components in the water extract of N1F. These chemical components of N1F significantly reduced the area associated with interstitial fibrosis in the kidneys of UUO rats and the levels of serum creatinine, urea nitrogen, and urinary protein. Additionally, N1F decreased the protein levels of FGF23, Wnt1, ß-catenin and p-P38MAPK/P38MAPK, along with the expression of renalfibrosis-associated proteins, α-SMA, FN, Collagen III, and Vimentin in the renal tissues of the UUO rats, while enhancing klotho and DKK1 protein levels. In vitro experiments revealed that inhibition of P38MAPK signaling significantly suppressed the expression of proteins related to the Wnt signaling pathway, with a concomitant decrease in the expression of FGF23 and an increase in the expression of Klotho. Notably, the P38MAPK inhibitor (SB203580) had similar effects to N1F in altering the above-mentioned indices in vitro. CONCLUSIONS N1F may exhibit potential therapeutic efficacy against renal fibrosis by inhibiting the FGF23/P38MAPK/Wnt signaling pathway, consequently inhibiting extracellular matrix deposition due to renal injury.
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Affiliation(s)
- Wenxiu Yu
- The Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China
- The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China
| | - Congcong Zeng
- The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China
| | - Chenggong Wang
- School of Pharmacy, Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China
| | - Sining Jia
- School of Pharmacy, Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China
| | - Chen Liu
- Zhejiang Chinese Medical University, Hangzhou, 310026, Zhejiang, PR China
| | - Yini Zeng
- The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China
| | - Jinguo Cheng
- The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, PR China.
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Xiao L, Clarke K, Hurley MM. Fibroblast Growth Factor 23 Neutralizing Antibody Ameliorates Abnormal Renal Phosphate Handling in Sickle Cell Disease Mice. Endocrinology 2023; 164:bqad173. [PMID: 37972265 PMCID: PMC11032245 DOI: 10.1210/endocr/bqad173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 11/08/2023] [Accepted: 11/09/2023] [Indexed: 11/19/2023]
Abstract
We assessed the involvement of fibroblast growth factor 23 (FGF23) in phosphaturia in sickle cell disease (SCD) mice. Control and SCD mice were treated with FGF23 neutralizing antibody (FGF23Ab) for 24 hours. Serum ferritin was significantly increased in SCD mice and was significantly reduced in female but not male SCD mice by FGF23Ab. FGF23Ab significantly reduced increased erythropoietin in SCD kidneys. Serum intact FGF23 was significantly increased in SCD female mice and was markedly increased in SCD male mice; however, FGF23Ab significantly reduced serum intact FGF23 in both genotypes and sexes. Serum carboxy-terminal-fragment FGF23 (cFGF23) was significantly reduced in SCD IgG male mice and was markedly but not significantly reduced in SCD IgG female mice. FGF23Ab significantly increased cFGF23 in both sexes and genotypes. Serum 1,25-dihydroxyvitamin D3 was significantly increased in SCD IgG and was further significantly increased by FGF23Ab in both sexes and genotypes. Significantly increased blood urea nitrogen in SCD was not reduced by FGF23Ab. The urine phosphate (Pi)/creatinine ratio was significantly increased in SCD in both sexes and was significantly reduced by FGF23Ab. Increased SCD kidney damage marker kidney injury molecule 1 was rescued, but sclerotic glomeruli, increased macrophages, and lymphocytes were not rescued by short-term FGF23Ab. FGF23Ab significantly reduced increased phospho-fibroblast growth factor receptor 1, αKlotho, phosphorylated extracellular signal-regulated kinase, phosphorylated serum/glucocorticoid-regulated kinase 1, phosphorylated sodium-hydrogen exchanger regulatory factor-1, phosphorylated janus kinase 3, and phosphorylated transducer and activator of transcription-3 in SCD kidneys. The type II sodium Pi cotransporter (NPT2a) and sodium-dependent Pi transporter PiT-2 proteins were significantly reduced in SCD kidneys and were increased by FGF23Ab. We conclude that increased FGF23/FGF receptor 1/αKlotho signaling promotes Pi wasting in SCD by downregulating NPT2a and PIT2 via modulation of multiple signaling pathways that could be rescued by FGF23Ab.
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Affiliation(s)
- Liping Xiao
- Department of Medicine, Division of Endocrinology and Metabolism, UConn Health School of Medicine, Farmington, CT, 06030, USA
| | - Kai Clarke
- Department of Medicine, Division of Endocrinology and Metabolism, UConn Health School of Medicine, Farmington, CT, 06030, USA
| | - Marja M Hurley
- Department of Medicine, Division of Endocrinology and Metabolism, UConn Health School of Medicine, Farmington, CT, 06030, USA
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Agoro R, White KE. Anemia and fibroblast growth factor 23 elevation in chronic kidney disease: homeostatic interactions and emerging therapeutics. Curr Opin Nephrol Hypertens 2022; 31:320-325. [PMID: 35703246 PMCID: PMC9307122 DOI: 10.1097/mnh.0000000000000797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE OF REVIEW Chronic kidney disease (CKD) is a progressive disorder that is associated with development of elevated fibroblast growth factor 23 (FGF23) levels and anemia. Here, we review recent literature that extends our current knowledge on the interactions between FGF23 and anemia in CKD and the impact of anemia-targeting therapeutics on FGF23 elevation in CKD. RECENT FINDINGS The anemia of CKD is primarily driven by a lack of erythropoietin (EPO) and iron deficiency. In addition to EPO and iron replacement, novel drug classes to treat anemia have been approved or are in clinical development. A recent observational study provides supportive evidence for the hypothesis that FGF23 elevation in CKD mediates adverse effects of iron deficiency on the cardiovascular system in patients with CKD. Preclinical and clinical studies revealed that ferric citrate (FC), and hypoxia-induced factor-prolyl hydroxylase inhibitor (HIF-PHI) treatment may reduce elevated FGF23 levels in CKD, suggesting that correcting anemia in CKD could potentially lower FGF23 levels. However, as we describe, HIF-PHI have context-dependent effects. Moreover, whether a reduction in FGF23 will improve patient outcomes in patients with CKD remains to be determined. SUMMARY With the emergence of novel therapeutics to treat oxygen and iron utilization deficits in CKD, studies have investigated the impact of these new drugs on FGF23. Several of these drugs, including FC and HIF-PHIs, alleviate iron homeostasis alterations in CKD and are associated with FGF23 reduction. Herein, we review the relationships between oxygen/iron sensing and FGF23 in CKD, recent findings which link FGF23 with cardiac dysfunction, as well as future translational and clinical avenues.
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Affiliation(s)
- Rafiou Agoro
- Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA 46202
| | - Kenneth E. White
- Department of Medical & Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA 46202
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN, USA 46202
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Liesen MP, Noonan ML, Ni P, Agoro R, Hum JM, Clinkenbeard EL, Damrath JG, Wallace JM, Swallow EA, Allen MR, White KE. Segregating the effects of ferric citrate-mediated iron utilization and FGF23 in a mouse model of CKD. Physiol Rep 2022; 10:e15307. [PMID: 35656701 PMCID: PMC9163801 DOI: 10.14814/phy2.15307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 05/03/2022] [Indexed: 11/24/2022] Open
Abstract
Ferric citrate (FC) is an approved therapy for chronic kidney disease (CKD) patients as a phosphate (Pi) binder for dialysis-dependent CKD, and for iron deficiency anemia (IDA) in non-dialysis CKD. Elevated Pi and IDA both lead to increased FGF23, however, the roles of iron and FGF23 during CKD remain unclear. To this end, iron and Pi metabolism were tested in a mouse model of CKD (0.2% adenine) ± 0.5% FC for 6 weeks, with and without osteocyte deletion of Fgf23 (flox-Fgf23/Dmp1-Cre). Intact FGF23 (iFGF23) increased in all CKD mice but was lower in Cre+ mice with or without FC, thus the Dmp1-Cre effectively reduced FGF23. Cre+ mice fed AD-only had higher serum Pi than Cre- pre- and post-diet, and the Cre+ mice had higher BUN regardless of FC treatment. Total serum iron was higher in all mice receiving FC, and liver Tfrc, Bmp6, and hepcidin mRNAs were increased regardless of genotype; liver IL-6 showed decreased mRNA in FC-fed mice. The renal 1,25-dihydroxyvitamin D (1,25D) anabolic enzyme Cyp27b1 had higher mRNA and the catabolic Cyp24a1 showed lower mRNA in FC-fed mice. Finally, mice with loss of FGF23 had higher bone cortical porosity, whereas Raman spectroscopy showed no changes in matrix mineral parameters. Thus, FC- and FGF23-dependent and -independent actions were identified in CKD; loss of FGF23 was associated with higher serum Pi and BUN, demonstrating that FGF23 was protective of mineral metabolism. In contrast, FC maintained serum iron and corrected inflammation mediators, potentially providing ancillary benefit.
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Affiliation(s)
- Michael P. Liesen
- Department of Medical & Molecular GeneticsIndiana University School of MedicineIndianapolisIndianaUSA
- Department of PhysiologyMarian UniversityIndianapolisIndianaUSA
| | - Megan L. Noonan
- Department of Medical & Molecular GeneticsIndiana University School of MedicineIndianapolisIndianaUSA
| | - Pu Ni
- Department of Medical & Molecular GeneticsIndiana University School of MedicineIndianapolisIndianaUSA
| | - Rafiou Agoro
- Department of Medical & Molecular GeneticsIndiana University School of MedicineIndianapolisIndianaUSA
| | - Julia M. Hum
- Department of PhysiologyMarian UniversityIndianapolisIndianaUSA
| | - Erica L. Clinkenbeard
- Department of Medical & Molecular GeneticsIndiana University School of MedicineIndianapolisIndianaUSA
| | - John G. Damrath
- Purdue University Weldon School of Biomedical EngineeringWest LafayetteIndianaUSA
| | - Joseph M. Wallace
- Department of Biomedical EngineeringIndiana University‐Purdue University at IndianapolisIndianapolisIndianaUSA
| | - Elizabeth A. Swallow
- Department of Anatomy, Cell Biology, and PhysiologyIndiana University School of MedicineIndianapolisIndianaUSA
| | - Matthew R. Allen
- Department of Biomedical EngineeringIndiana University‐Purdue University at IndianapolisIndianapolisIndianaUSA
- Department of Anatomy, Cell Biology, and PhysiologyIndiana University School of MedicineIndianapolisIndianaUSA
- Department of MedicineDivision of NephrologyIndiana University School of MedicineIndianapolisIndianaUSA
| | - Kenneth E. White
- Department of Medical & Molecular GeneticsIndiana University School of MedicineIndianapolisIndianaUSA
- Department of MedicineDivision of NephrologyIndiana University School of MedicineIndianapolisIndianaUSA
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Franco ML, Beyerstedt S, Rangel ÉB. Klotho and Mesenchymal Stem Cells: A Review on Cell and Gene Therapy for Chronic Kidney Disease and Acute Kidney Disease. Pharmaceutics 2021; 14:pharmaceutics14010011. [PMID: 35056905 PMCID: PMC8778857 DOI: 10.3390/pharmaceutics14010011] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 12/16/2021] [Accepted: 12/17/2021] [Indexed: 02/07/2023] Open
Abstract
Chronic kidney disease (CKD) and acute kidney injury (AKI) are public health problems, and their prevalence rates have increased with the aging of the population. They are associated with the presence of comorbidities, in particular diabetes mellitus and hypertension, resulting in a high financial burden for the health system. Studies have indicated Klotho as a promising therapeutic approach for these conditions. Klotho reduces inflammation, oxidative stress and fibrosis and counter-regulates the renin-angiotensin-aldosterone system. In CKD and AKI, Klotho expression is downregulated from early stages and correlates with disease progression. Therefore, the restoration of its levels, through exogenous or endogenous pathways, has renoprotective effects. An important strategy for administering Klotho is through mesenchymal stem cells (MSCs). In summary, this review comprises in vitro and in vivo studies on the therapeutic potential of Klotho for the treatment of CKD and AKI through the administration of MSCs.
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Affiliation(s)
- Marcella Liciani Franco
- Albert Einstein Research and Education Institute, Hospital Israelita Albert Einstein, Sao Paulo 05652-900, Brazil; (M.L.F.); (S.B.)
| | - Stephany Beyerstedt
- Albert Einstein Research and Education Institute, Hospital Israelita Albert Einstein, Sao Paulo 05652-900, Brazil; (M.L.F.); (S.B.)
| | - Érika Bevilaqua Rangel
- Albert Einstein Research and Education Institute, Hospital Israelita Albert Einstein, Sao Paulo 05652-900, Brazil; (M.L.F.); (S.B.)
- Nephrology Division, Federal University of São Paulo, Sao Paulo 04038-901, Brazil
- Correspondence: ; Tel.: +55-11-2151-2148
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Ni P, Clinkenbeard EL, Noonan ML, Richardville JM, McClintick J, Hato T, Janosevic D, Cheng YH, El-Achkar TM, Eadon MT, Dagher PC, White KE. Targeting fibroblast growth factor 23-responsive pathways uncovers controlling genes in kidney mineral metabolism. Kidney Int 2020; 99:598-608. [PMID: 33159963 DOI: 10.1016/j.kint.2020.10.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 09/21/2020] [Accepted: 10/09/2020] [Indexed: 12/17/2022]
Abstract
Fibroblast Growth Factor 23 (FGF23) is a bone-derived hormone that reduces kidney phosphate reabsorption and 1,25(OH)2 vitamin D synthesis via its required co-receptor alpha-Klotho. To identify novel genes that could serve as targets to control FGF23-mediated mineral metabolism, gene array and single-cell RNA sequencing were performed in wild type mouse kidneys. Gene array demonstrated that heparin-binding EGF-like growth factor (HBEGF) was significantly up-regulated following one-hour FGF23 treatment of wild type mice. Mice injected with HBEGF had phenotypes consistent with partial FGF23-mimetic activity including robust induction of Egr1, and increased Cyp24a1 mRNAs. Single cell RNA sequencing showed overlapping HBEGF and EGF-receptor expression mostly in the proximal tubule, and alpha-Klotho expression in proximal and distal tubule segments. In alpha-Klotho-null mice devoid of canonical FGF23 signaling, HBEGF injections significantly increased Egr1 and Cyp24a1 with correction of basally elevated Cyp27b1. Additionally, mice placed on a phosphate deficient diet to suppress FGF23 had endogenously increased Cyp27b1 mRNA, which was rescued in mice receiving HBEGF. In HEK293 cells with stable alpha-Klotho expression, FGF23 and HBEGF increased CYP24A1 mRNA expression. HBEGF, but not FGF23 bioactivity was blocked with EGF-receptor inhibition. Thus, our findings support that the paracrine/autocrine factor HBEGF could play novel roles in controlling genes downstream of FGF23 via targeting common signaling pathways.
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Affiliation(s)
- Pu Ni
- Department of Medical and Molecular Genetics, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Erica L Clinkenbeard
- Department of Medical and Molecular Genetics, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Megan L Noonan
- Department of Medical and Molecular Genetics, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Joseph M Richardville
- Department of Medical and Molecular Genetics, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Jeanette McClintick
- Department of Biochemistry and Molecular Biology, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Takashi Hato
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Danielle Janosevic
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Ying-Hua Cheng
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Tarek M El-Achkar
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael T Eadon
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Pierre C Dagher
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
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Köhler OM, Grünberg W, Schnepel N, Muscher-Banse AS, Rajaeerad A, Hummel J, Breves G, Wilkens MR. Dietary phosphorus restriction affects bone metabolism, vitamin D metabolism and rumen fermentation traits in sheep. J Anim Physiol Anim Nutr (Berl) 2020; 105:35-50. [PMID: 33001513 DOI: 10.1111/jpn.13449] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 07/04/2020] [Accepted: 08/24/2020] [Indexed: 12/12/2022]
Abstract
Homeostasis of calcium (Ca) and phosphate (Pi ) is maintained by a concerted interplay of absorption and reabsorption via the gastrointestinal tract and the kidney and by storage and mobilization from the bone regulated mainly by parathyroid hormone (PTH), 1,25-dihydroxycholecalciferol and calcitonin. The present study aimed at characterizing the effects of dietary P restriction on bone, vitamin D metabolism and rumen fermentation traits reflecting the endogenous P cycle maintaining the ruminal P supply for microbial metabolism. The experiments were done in eleven female, non-pregnant, non-lactating four- to nine-year-old Black Headed Mutton sheep allotted to two feeding groups: "P-restricted" (0.11% P/kg DM and 0.88% Ca/kg DM) and "Control" (0.38% P/kg DM and 0.88% Ca/kg DM). Dietary P restriction did not lead to hypophosphataemia, probably due to a compensation by bone mobilization, demonstrated by increased serum concentrations of a resorption marker and altered gene expression in bone tissue. In addition, the RNA expression of fibroblast growth factor 23, a bone-derived factor involved in the regulation of vitamin D metabolism, was significantly reduced with dietary P restriction. Furthermore, several genes related to vitamin D metabolism and plasma concentrations of 1,25-(OH)2 D were associated with serum concentrations of phosphate (Pi ). In the parotid gland, the expression of the Pi transporter NaPi2b was negatively associated with serum Pi and positively with parathyroid PTH expression. Although Pi concentrations in saliva and the gastrointestinal tract were significantly reduced, we found no adverse effects of the P-restricted ration on the production of short chain fatty acids, but slight differences in the production of butyrate as well as its relationship to rumen Pi and ammonia concentrations that might indicate an impact on ruminal fermentation.
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Affiliation(s)
- Oriana M Köhler
- Department of Animal Sciences, Faculty of Agricultural Sciences, University of Goettingen, Goettingen, Germany
| | - Walter Grünberg
- Clinic for Cattle, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany
| | - Nadine Schnepel
- Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany
| | - Alexandra S Muscher-Banse
- Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany
| | - Abbas Rajaeerad
- Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
| | - Jürgen Hummel
- Department of Animal Sciences, Faculty of Agricultural Sciences, University of Goettingen, Goettingen, Germany
| | - Gerhard Breves
- Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany
| | - Mirja R Wilkens
- Department of Animal Sciences, Faculty of Agricultural Sciences, University of Goettingen, Goettingen, Germany.,Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Foundation, Hanover, Germany
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Martins JS, Liu ES, Sneddon WB, Friedman PA, Demay MB. 1,25-Dihydroxyvitamin D Maintains Brush Border Membrane NaPi2a and Attenuates Phosphaturia in Hyp Mice. Endocrinology 2019; 160:2204-2214. [PMID: 31237611 PMCID: PMC6735734 DOI: 10.1210/en.2019-00186] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Accepted: 06/19/2019] [Indexed: 12/21/2022]
Abstract
Phosphate homeostasis is critical for many cellular processes and is tightly regulated. The sodium-dependent phosphate cotransporter, NaPi2a, is the major regulator of urinary phosphate reabsorption in the renal proximal tubule. Its activity is dependent upon its brush border localization that is regulated by fibroblast growth factor 23 (FGF23) and PTH. High levels of FGF23, as are seen in the Hyp mouse model of human X-linked hypophosphatemia, lead to renal phosphate wasting. Long-term treatment of Hyp mice with 1,25-dihydroxyvitamin D (1,25D) or 1,25D analogues has been shown to improve renal phosphate wasting in the setting of increased FGF23 mRNA expression. Studies were undertaken to define the cellular and molecular basis for this apparent FGF23 resistance. 1,25D increased FGF23 protein levels in the cortical bone and circulation of Hyp mice but did not impair FGF23 cleavage. 1,25D attenuated urinary phosphate wasting as early as one hour postadministration, without suppressing FGF23 receptor/coreceptor expression. Although 1,25D treatment induced expression of early growth response 1, an early FGF23 responsive gene required for its phosphaturic effects, it paradoxically enhanced renal phosphate reabsorption and NaPi2a protein expression in renal brush border membranes (BBMs) within one hour. The Na-H+ exchange regulatory factor 1 (NHERF1) is a scaffolding protein thought to anchor NaPi2a to the BBM. Although 1,25D did not alter NHERF1 protein levels acutely, it enhanced NHERF1-NaPi2a interactions in Hyp mice. 1,25D also prevented the decrease in NHERF1/NaPi2a interactions in PTH-treated wild-type mice. Thus, these investigations identify a novel role for 1,25D in the hormonal regulation of renal phosphate handling.
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Affiliation(s)
- Janaina S Martins
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Eva S Liu
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
- Division of Endocrinology Diabetes and Hypertension, Brigham and Women’s Hospital, Boston, Massachusetts
| | - W Bruce Sneddon
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Peter A Friedman
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Marie B Demay
- Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
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Wheeler JA, Clinkenbeard EL. Regulation of Fibroblast Growth Factor 23 by Iron, EPO, and HIF. ACTA ACUST UNITED AC 2019; 5:8-17. [PMID: 31218207 DOI: 10.1007/s40610-019-0110-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Purpose of review Fibroblast growth factor-23 (FGF23) is the key hormone produced in bone critical for phosphate homeostasis. Elevated serum phosphorus and 1,25dihydroxyvitaminD stimulates FGF23 production to promote renal phosphate excretion and decrease 1,25dihydroxyvitaminD synthesis. Thus completing the feedback loop and suppressing FGF23. Unexpectedly, studies of common and rare heritable disorders of phosphate handling identified links between iron and FGF23 demonstrating novel regulation outside the phosphate pathway. Recent Findings Iron deficiency combined with an FGF23 cleavage mutation was found to induce the autosomal dominant hypophosphatemic rickets phenotype. Physiological responses to iron deficiency, such as erythropoietin production as well as hypoxia inducible factor activation, have been indicated in regulating FGF23. Additionally, specific iron formulations, used to treat iron deficiency, alter post-translational processing thereby shifting FGF23 protein secretion. Summary Molecular and clinical studies revealed that iron deficiency, through several mechanisms, alters FGF23 at the transcriptional and post-translational level. This review will focus upon the novel discoveries elucidated between iron, its regulators, and their influence on FGF23 bioactivity.
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Affiliation(s)
- Jonathan A Wheeler
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Erica L Clinkenbeard
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
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The elevation of circulating fibroblast growth factor 23 without kidney disease does not increase cardiovascular disease risk. Kidney Int 2018; 94:49-59. [DOI: 10.1016/j.kint.2018.02.017] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 01/24/2018] [Accepted: 02/01/2018] [Indexed: 11/23/2022]
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Schiavi SC, Moysés RMA. Turning over renal osteodystrophy dogma: direct actions of FGF23 on osteoblast β-catenin pathway. Kidney Int 2017; 90:17-20. [PMID: 27312441 DOI: 10.1016/j.kint.2016.03.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 03/01/2016] [Accepted: 03/09/2016] [Indexed: 01/08/2023]
Abstract
Although recognized as a major complication of chronic kidney disease (CKD), the pathophysiology of the CKD-related mineral and bone disorder (CKD-MBD) is not completely understood. Recently, the inhibition of Wnt/β-catenin pathway in osteocytes by sclerostin has been shown to play a role in CKD-MBD. The study by Carrilo-Lopez et al. confirms this inhibition in an experimental model of CKD. Moreover, they describe direct actions of FGF23-Klotho on osteoblasts, increasing the expression of DKK1, another Wnt/β-catenin pathway inhibitor.
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Affiliation(s)
| | - Rosa M A Moysés
- Medicine Master Degree Program, Universidade Nove de Julho, Universidade Nove de Julho, São Paulo, Brazil; Nephrology Division, Universidade de São Paulo, São Paulo, Brazil.
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Leifheit-Nestler M, Kucka J, Yoshizawa E, Behets G, D'Haese P, Bergen C, Meier M, Fischer DC, Haffner D. Comparison of calcimimetic R568 and calcitriol in mineral homeostasis in the Hyp mouse, a murine homolog of X-linked hypophosphatemia. Bone 2017; 103:224-232. [PMID: 28728941 DOI: 10.1016/j.bone.2017.06.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 06/02/2017] [Accepted: 06/23/2017] [Indexed: 12/28/2022]
Abstract
X-linked hypophosphatemia (XLH) caused by mutations in the Phex gene is the most common human inherited phosphate wasting disorder characterized by enhanced synthesis of fibroblast growth factor 23 (FGF23) in bone, renal phosphate wasting, 1,25(OH)2D3 (1,25D) deficiency, rickets and osteomalacia. Here we studied the effects of calcimimetic R568 and calcitriol treatment in the Hyp mouse, a murine homolog of XLH. We hypothesized that mineral homeostasis is differentially affected by R568 and 1,25D with respect to the PTH-vitamin D-FGF23-Klotho axis and bone health. Four-week-old male Hyp mice received R568 in different doses, 1,25D or vehicle for 28days. Vehicle-treated wild-type mice served as controls. Both R568 and 1,25D reduced PTH levels, yet only 1,25D raised serum phosphate levels in Hyp mice. 1,25D increased calciuria and further enhanced FGF23 synthesis in bone and circulating FGF23 levels. By contrast, R568 reduced bone FGF23 expression and serum total but not intact FGF23 concentrations. Renal 1,25D metabolism was further impaired by 1,25D and improved although not normalized by R568. Hyp mice showed reduced renal Klotho levels, which were increased by 1,25D and high dose R568. 1,25D, but not R568, significantly improved femur growth, and weight gain, and partially restored growth plate morphology and bone mineralization. Although a significant improvement of trabecular bone was noted by μCT, compared to 1,25D the effects of R568 on bone histomophometric parameters were marginal. Our data indicate that monotherapy with R568 reduced PTH and FGF23 synthesis in bone, but failed to restore vitamin D and phosphate metabolism and skeletal abnormalities in Hyp mice. By contrast, 1,25D improved body growth, and defective mineralization despite further enhancement of skeletal FGF23 synthesis thereby highlighting the importance of vitamin D in bone mineralization in Hyp mice.
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Affiliation(s)
- Maren Leifheit-Nestler
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany.
| | - Julia Kucka
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Emi Yoshizawa
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Geert Behets
- Laboratory of Pathophysiology, University of Antwerp, Wilrijk, Belgium
| | - Patrick D'Haese
- Laboratory of Pathophysiology, University of Antwerp, Wilrijk, Belgium
| | - Christian Bergen
- Institute for Laboratory Animal Science, Small Animal Imaging Center, Hannover Medical School, Hannover, Germany
| | - Martin Meier
- Institute for Laboratory Animal Science, Small Animal Imaging Center, Hannover Medical School, Hannover, Germany
| | | | - Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
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13
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Hum JM, O'Bryan L, Smith RC, White KE. Novel functions of circulating Klotho. Bone 2017; 100:36-40. [PMID: 27890549 PMCID: PMC5441975 DOI: 10.1016/j.bone.2016.11.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Revised: 11/21/2016] [Accepted: 11/21/2016] [Indexed: 01/08/2023]
Abstract
A significant portion of the key biological functions of αKlotho (αKL) and its cognate ligand Fibroblast growth factor-23 (FGF23) have been revealed through the study of rare diseases of mineral metabolism. These findings have far reaching implications for common disorders such as chronic kidney disease-mineral bone disorder (CKD-MBD). αKL's predominant effect on mineral homeostasis is through its actions in the kidney as a co-receptor for FGF23, however emerging data has shed light on its capacity to act as a circulating factor through the cleavage of the transmembrane form of αKL ('mKL') to produce 'cleaved KL' or 'cKL'. This review summarizes new findings from studies using extended delivery of cKL to mouse models with phenotypes reflecting those arising in CKD-MBD.
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Affiliation(s)
- Julia M Hum
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Division of Biomedical Science, Marian University School of Osteopathic Medicine, Indianapolis, IN 46222, USA
| | - Linda O'Bryan
- Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Rosamund C Smith
- Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN 46285, USA
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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14
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Erben RG, Andrukhova O. FGF23-Klotho signaling axis in the kidney. Bone 2017; 100:62-68. [PMID: 27622885 DOI: 10.1016/j.bone.2016.09.010] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 09/08/2016] [Accepted: 09/09/2016] [Indexed: 01/04/2023]
Abstract
Fibroblast growth factor-23 (FGF23) is a bone-derived hormone protecting against the potentially deleterious effects of hyperphosphatemia by suppression of phosphate reabsorption and of active vitamin D hormone synthesis in the kidney. The kidney is one of the main target organs of FGF23 signaling. The purpose of this review is to highlight the recent advances in the area of FGF23-Klotho signaling in the kidney. During recent years, it has become clear that FGF23 acts independently on proximal and distal tubular epithelium. In proximal renal tubules, FGF23 suppresses phosphate reabsorption by a Klotho dependent activation of extracellular signal-regulated kinase-1/2 (ERK1/2) and of serum/glucocorticoid-regulated kinase-1 (SGK1), leading to phosphorylation of the scaffolding protein Na+/H+ exchange regulatory cofactor (NHERF)-1 and subsequent internalization and degradation of sodium-phosphate cotransporters. In distal renal tubules, FGF23 augments calcium and sodium reabsorption by increasing the apical membrane expression of the epithelial calcium channel TRPV5 and of the sodium-chloride cotransporter NCC through a Klotho dependent activation of with-no-lysine kinase-4 (WNK4). In proximal and distal renal tubules, FGF receptor-1 is probably the dominant FGF receptor mediating the effects of FGF23 by forming a complex with membrane-bound Klotho in the basolateral membrane. The newly described sodium- and calcium-conserving functions of FGF23 may have major implications for the pathophysiology of diseases characterized by chronically increased circulating FGF23 concentrations such as chronic kidney disease.
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15
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α-Klotho expression determines nitric oxide synthesis in response to FGF-23 in human aortic endothelial cells. PLoS One 2017; 12:e0176817. [PMID: 28463984 PMCID: PMC5413063 DOI: 10.1371/journal.pone.0176817] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 04/18/2017] [Indexed: 01/03/2023] Open
Abstract
Endothelial cells (ECs) express fibroblast growth factor (FGF) receptors and are metabolically active after treatment with FGF-23. It is not known if this effect is α-Klotho independent or mediated by humoral or endogenous endothelial α-Klotho. In the present study, we aimed to characterize EC α-Klotho expression within the human vascular tree and to investigate the potential role of α-Klotho in determining FGF-23 mediated EC regulation. Human tissue and ECs from various organs were used for immunohistochemistry and Western blot. Primary cultures of human aortic endothelial cells (HAECs) and human brain microvascular endothelial cells (HBMECs) were used to generate in vitro cell models. We found endogenous α-Klotho expression in ECs from various organs except in microvascular ECs from human brain. Furthermore, FGF-23 stimulated endothelial nitric oxide synthase (eNOS) expression, nitric oxide (NO) production, and cell proliferation in HAECs. Interestingly, these effects were not observed in our HBMEC model in vitro. High phosphate treatment and endothelial α-Klotho knockdown mitigated FGF-23 mediated eNOS induction, NO production, and cell proliferation in HAECs. Rescue treatment with soluble α-Klotho did not reverse endothelial FGF-23 resistance caused by reduced or absent α-Klotho expression in HAECs. These novel observations provide evidence for differential α-Klotho functional expression in the human endothelium and its presence may play a role in determining the response to FGF-23 in the vascular tree. α-Klotho was not detected in cerebral microvascular ECs and its absence may render these cells nonresponsive to FGF-23.
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16
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Fuente R, Gil-Peña H, Claramunt-Taberner D, Hernández O, Fernández-Iglesias A, Alonso-Durán L, Rodríguez-Rubio E, Santos F. X-linked hypophosphatemia and growth. Rev Endocr Metab Disord 2017; 18:107-115. [PMID: 28130634 DOI: 10.1007/s11154-017-9408-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
X-Linked hypophosphatemia (XLH) is the most common form of hereditary rickets caused by loss-of function mutations in the PHEX gene. XLH is characterized by hypophosphatemia secondary to renal phosphate wasting, inappropriately low concentrations of 1,25 dihydroxyvitamin D and high circulating levels of fibroblast growth factor 23 (FGF23). Short stature and rachitic osseous lesions are characteristic phenotypic findings of XLH although the severity of these manifestations is highly variable among patients. The degree of growth impairment is not dependent on the magnitude of hypophosphatemia or the extent of legs´ bowing and height is not normalized by chronic administration of phosphate supplements and 1α hydroxyvitamin D derivatives. Treatment with growth hormone accelerates longitudinal growth rate but there is still controversy regarding the potential risk of increasing bone deformities and body disproportion. Treatments aimed at blocking FGF23 action are promising, but information is lacking on the consequences of counteracting FGF23 during the growing period. This review summarizes current knowledge on phosphorus metabolism in XLH, presents updated information on XLH and growth, including the effects of FGF23 on epiphyseal growth plate of the Hyp mouse, an animal model of the disease, and discusses growth hormone and novel FGF23 related therapies.
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Affiliation(s)
- R Fuente
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - H Gil-Peña
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | - D Claramunt-Taberner
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - O Hernández
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - A Fernández-Iglesias
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - L Alonso-Durán
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - E Rodríguez-Rubio
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - F Santos
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain.
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.
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17
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Abstract
Fibroblast growth factor-23 (FGF23) is a bone-derived hormone known to suppress phosphate reabsorption and vitamin D hormone production in the kidney. Klotho was originally discovered as an anti-aging factor, but the functional role of Klotho is still a controversial issue. Three major functions have been proposed, a hormonal function of soluble Klotho, an enzymatic function as glycosidase, and the function as an obligatory co-receptor for FGF23 signaling. The purpose of this review is to highlight the recent advances in the area of FGF23 and Klotho signaling in the kidney, in the parathyroid gland, in the cardiovascular system, in bone, and in the central nervous system. During recent years, major new functions of FGF23 and Klotho have been discovered in these organ systems. Based on these novel findings, FGF23 has emerged as a pleiotropic endocrine and auto-/paracrine factor influencing not only mineral metabolism but also cardiovascular function.
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18
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Du E, Xiao L, Hurley MM. FGF23 Neutralizing Antibody Ameliorates Hypophosphatemia and Impaired FGF Receptor Signaling in Kidneys of HMWFGF2 Transgenic Mice. J Cell Physiol 2016; 232:610-616. [PMID: 27306296 DOI: 10.1002/jcp.25458] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 06/14/2016] [Indexed: 01/15/2023]
Abstract
High molecular weight FGF2 transgenic mice (HMWTg) phenocopy the Hyp mouse, homolog of human X-linked hypophosphatemic rickets with phosphate wasting and abnormal fibroblast growth factor (FGF23), fibroblast growth factor receptor (FGFR), Klotho and mitogen activated protein kinases (MAPK) signaling in kidney. In this study, we assessed whether short-term (24 h) in vivo administration of FGF23 neutralizing antibody (FGF23Ab) could rescue hypophosphatemia and impaired FGFR signaling in kidneys of HMWTg male mice. Bone mineral density and bone mineral content in 1-month-old HMWTg mice were significantly reduced compared with Control/VectorTg mice. Serum FGF23 was significantly increased in HMWTg compared with VectorTg. Serum phosphate was significantly reduced in HMWTg and was rescued by FGF23Ab. Serum parathyroid hormone (PTH) was significantly increased in HMWTg but was not reduced by FGF23Ab. 1, 25(OH)2 D was inappropriately normal in serum of HMWTg and was significantly increased in both Vector and HMWTg by FGF23Ab. Analysis of HMWTg kidneys revealed significantly increased mRNA expression of the FGF23 co-receptor Klotho, transcription factor mRNAs for early growth response-1 transcription factor (Egr-1), and c-fos were all significantly decreased by FGF23Ab. A significant reduction in the phosphate transporter Npt2a mRNA was also observed in HMWTg kidneys, which was increased by FGF23Ab. FGF23Ab reduced p-FGFR1, p-FGFR3, KLOTHO, p-ERK1/2, C-FOS, and increased NPT2A protein in HMWTg kidneys. We conclude that FGF23 blockade rescued hypophosphatemia by regulating FGF23/FGFR downstream signaling in HMWTg kidneys. Furthermore, HMWFGF2 isoforms regulate PTH expression independent of FGF23/FGFR signaling. J. Cell. Physiol. 232: 610-616, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- E Du
- Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut
| | - L Xiao
- Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut
| | - M M Hurley
- Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut
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19
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Clinkenbeard EL, Cass TA, Ni P, Hum JM, Bellido T, Allen MR, White KE. Conditional Deletion of Murine Fgf23: Interruption of the Normal Skeletal Responses to Phosphate Challenge and Rescue of Genetic Hypophosphatemia. J Bone Miner Res 2016; 31:1247-57. [PMID: 26792657 PMCID: PMC4891276 DOI: 10.1002/jbmr.2792] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 01/14/2016] [Accepted: 01/20/2016] [Indexed: 01/12/2023]
Abstract
The transgenic and knockout (KO) animals involving Fgf23 have been highly informative in defining novel aspects of mineral metabolism, but are limited by shortened lifespan, inability of spatial/temporal FGF23 control, and infertility of the global KO. To more finely test the role of systemic and genetic influences in FGF23 production, a mouse was developed that carried a floxed ("f")-Fgf23 allele (exon 2 floxed) which demonstrated in vivo recombination when bred to global-Cre transgenic mice (eIIa-cre). Mice homozygous for the recombined allele ("Δ") had undetectable serum intact FGF23, elevated serum phosphate (p < 0.05), and increased kidney Cyp27b1 mRNA (p < 0.05), similar to global Fgf23-KO mice. To isolate cellular FGF23 responses during phosphate challenge, Fgf23(Δ/f) mice were mated with early osteoblast type Iα1 collagen 2.3-kb promoter-cre mice (Col2.3-cre) and the late osteoblast/early osteocyte Dentin matrix protein-1-cre (Dmp1-cre). Fgf23(Δ/f) /Col2.3-cre(+) and Fgf23(Δ/f) /Dmp1-cre(+) exhibited reduced baseline serum intact FGF23 versus controls. After challenge with high-phosphate diet Cre(-) mice had 2.1-fold to 2.5-fold increased serum FGF23 (p < 0.01), but Col2.3-cre(+) mice had no significant increase, and Dmp1-cre(+) mice had only a 37% increase (p < 0.01) despite prevailing hyperphosphatemia in both models. The Fgf23(Δ/f) /Col2.3-cre was bred onto the Hyp (murine X-linked hypophosphatemia [XLH] model) genetic background to test the contribution of osteoblasts and osteocytes to elevated FGF23 and Hyp disease phenotypes. Whereas Hyp mice maintained inappropriately elevated FGF23 considering their marked hypophosphatemia, Hyp/Fgf23(Δ/f) /Col2.3-cre(+) mice had serum FGF23 <4% of Hyp (p < 0.01), and this targeted restriction normalized serum phosphorus and ricketic bone disease. In summary, deleting FGF23 within early osteoblasts and osteocytes demonstrated that both cell types contribute to baseline circulating FGF23 concentrations, and that targeting osteoblasts/osteocytes for FGF23 production can modify systemic responses to changes in serum phosphate concentrations and rescue the Hyp genetic syndrome. © 2016 American Society for Bone and Mineral Research.
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Affiliation(s)
- Erica L. Clinkenbeard
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Taryn A. Cass
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Pu Ni
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Julia M. Hum
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Teresita Bellido
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Matthew R. Allen
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kenneth E. White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, USA
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20
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Kinoshita S, Kawai M. The FGF23/KLOTHO Regulatory Network and Its Roles in Human Disorders. VITAMINS AND HORMONES 2016; 101:151-74. [PMID: 27125741 DOI: 10.1016/bs.vh.2016.02.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The functions of Klotho (KL) are multifaceted and include the regulation of aging and mineral metabolism. It was originally identified as the gene responsible for premature aging-like symptoms in mice and was subsequently shown to function as a coreceptor in the fibroblast growth factor (FGF) 23 signaling pathway. The discovery of KL as a partner for FGF23 led to significant advances in understanding of the molecular mechanisms underlying phosphate and vitamin D metabolism, and simultaneously clarified the pathogenic roles of the FGF23 signaling pathway in human diseases. These novel insights led to the development of new strategies to combat disorders associated with the dysregulated metabolism of phosphate and vitamin D, and clinical trials on the blockade of FGF23 signaling in X-linked hypophosphatemic rickets are ongoing. Molecular and functional insights on KL and FGF23 have been discussed in this review and were extended to how dysregulation of the FGF23/KL axis causes human disorders associated with abnormal mineral metabolism.
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Affiliation(s)
- S Kinoshita
- Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan
| | - M Kawai
- Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan.
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21
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Abstract
The regulation of phosphate metabolism as an influence on bone homeostasis is profound. Recent advances in understanding the systemic control of Fibroblast growth factor-23 (FGF23) has uncovered novel effectors of endocrine feedback loops for calcium, phosphate, and vitamin D balance that interact with 'traditional' feedback loops for mineral metabolism. Not only are these findings re-shaping research studying phosphate handling and skeletal interactions, they have provided new therapeutic interventions. Emerging data support that the control of FGF23 production in bone and its circulating concentrations is a multi-layered process, with some influences affecting FGF23 transcription and some post-translational modification of the secreted, bioactive protein. Additionally, the actions of FGF23 on its target tissues via its co-receptor αKlotho, are subject to regulatory events just coming to light. The recent findings of systemic influences on circulating FGF23 and the downstream manifestations on bone homeostasis will be reviewed herein.
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Affiliation(s)
- Erica L Clinkenbeard
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Kenneth E White
- Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, IN 46202
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22
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Du E, Xiao L, Hurley MM. FGFR Inhibitor Ameliorates Hypophosphatemia and Impaired Engrailed-1/Wnt Signaling in FGF2 High Molecular Weight Isoform Transgenic Mice. J Cell Biochem 2016; 117:1991-2000. [PMID: 26762209 DOI: 10.1002/jcb.25493] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 01/11/2016] [Indexed: 12/26/2022]
Abstract
High molecular weight FGF2 transgenic (HMWTg) mouse phenocopies the Hyp mouse, homolog of human X-linked hypophosphatemic rickets with hypophosphatemis, and abnormal FGF23, FGFR, Klotho signaling in kidney. Since abnormal Wnt signaling was reported in Hyp mice we assessed whether Wnt signaling was impaired in HMWTg kidneys and the effect of blocking FGF receptor (FGFR) signaling. Bone mineral density and bone mineral content in female HMWTg mice were significantly reduced. HMWTg mice were gavaged with FGFR inhibitor NVP-BGJ398, or vehicle and were euthanized 24 h post treatment. Serum phosphate was significantly reduced and urine phosphate was significantly increased in HMWTg and was rescued by NVP-BGJ398. Analysis of kidneys revealed a significant reduction in Npt2a mRNA in HMWTg that was significantly increased by NVP-BGJ398. Increased FGFR1, KLOTHO, P-ERK1/2, and decreased NPT2a protein in HMWTg were rescued by NVP-BGJ398. Wnt inhibitor Engrailed-1 mRNA and protein was increased in HMWTg and was decreased by BGJ398. Akt mRNA and protein was decreased in HMWTg and was increased by NVP-BGJ398. The active form of glycogen synthase 3 beta (pGSK3-β) and phosphor-β-catenin were increased in HMWTg and were both decreased by NVP-BGJ398 while decreased active-β-catenin in HMWTg was increased by NVP-BGJ398. We conclude that FGFR blockade rescued hypophosphatemia by regulating FGF and WNT signaling in HMWTg kidneys. J. Cell. Biochem. 117: 1991-2000, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Erxia Du
- Department of Medicine, UCONN Health, Farmington, 06030, Connecticut
| | - Liping Xiao
- Department of Medicine, UCONN Health, Farmington, 06030, Connecticut
| | - Marja M Hurley
- Department of Medicine, UCONN Health, Farmington, 06030, Connecticut
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23
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Abstract
The decrease in bone mass and strength during aging has multiple causes. Osteocytes are long-lived cells within the bone matrix that perform a variety of functions, including the control of bone remodeling. Because of their longevity, osteocytes are more likely than osteoclasts or osteoblasts to accumulate molecular damage over time. Osteocytes utilize quality-control pathways like autophagy to remove damaged organelles and macromolecules, and thereby maintain function. When the damage is excessive, cell death pathways such as apoptosis minimize the impact of potential osteocyte dysfunction on the skeleton. The goal of this review is to discuss how dysregulation of these pathways in osteocytes may contribute to the decline in bone mass and strength with age.
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Affiliation(s)
- Robert L Jilka
- Center for Osteoporosis and Metabolic Bone Diseases, Central Arkansas Veterans Healthcare System, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
| | - Charles A O'Brien
- Center for Osteoporosis and Metabolic Bone Diseases, Central Arkansas Veterans Healthcare System, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
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24
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Kawai M. The FGF23/Klotho axis in the regulation of mineral and metabolic homeostasis. Horm Mol Biol Clin Investig 2016; 28:55-67. [DOI: 10.1515/hmbci-2015-0068] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 01/07/2016] [Indexed: 11/15/2022]
Abstract
AbstractThe function of fibroblast growth factor (FGF) 23 has been suggested to be multifaceted beyond its canonical function as a regulator of mineral metabolism. FGF23 was originally shown to play a central role in phosphate (Pi) and vitamin D metabolism, and a number of diseases associated with dysregulated Pi metabolism have been attributed to abnormal FGF23 signaling activities. The discovery of Klotho as a co-receptor for FGF23 signaling has also accelerated understanding on the molecular mechanisms underlying Pi and vitamin D metabolism. In addition to these canonical functions, FGF23 has recently been implicated in a number of metabolic diseases including chronic kidney disease-associated complications, cardiovascular diseases, and obesity-related disorders; however, the physiological significance and molecular mechanisms of these emerging roles of FGF23 remain largely unknown. Molecular and functional insights into the FGF23 pathway will be discussed in the present review, with an emphasis on its role in human disorders related to dysregulated Pi metabolism as well as metabolic disorders.
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25
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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.
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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.
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Diener S, Schorpp K, Strom TM, Hadian K, Lorenz-Depiereux B. Development of A Cell-Based Assay to Identify Small Molecule Inhibitors of FGF23 Signaling. Assay Drug Dev Technol 2015; 13:476-87. [DOI: 10.1089/adt.2015.653] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Affiliation(s)
- Susanne Diener
- German Research Center for Environmental Health, Institute of Human Genetics, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
| | - Kenji Schorpp
- Assay Development and Screening Platform, German Research Center for Environmental Health, Institute of Molecular Toxicology and Pharmacology, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
| | - Tim-Matthias Strom
- German Research Center for Environmental Health, Institute of Human Genetics, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
- Institute of Human Genetics, Klinikum rechts der Isar der Technischen Universität München, Munich, Bavaria, Germany
| | - Kamyar Hadian
- Assay Development and Screening Platform, German Research Center for Environmental Health, Institute of Molecular Toxicology and Pharmacology, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
| | - Bettina Lorenz-Depiereux
- German Research Center for Environmental Health, Institute of Human Genetics, HelmholtzZentrum München, Neuherberg, Bavaria, Germany
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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.
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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
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Zelenchuk LV, Hedge AM, Rowe PSN. SPR4-peptide alters bone metabolism of normal and HYP mice. Bone 2015; 72:23-33. [PMID: 25460577 PMCID: PMC4342984 DOI: 10.1016/j.bone.2014.11.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 11/06/2014] [Accepted: 11/14/2014] [Indexed: 11/13/2022]
Abstract
CONTEXT ASARM-peptides are substrates and ligands for PHEX, the gene responsible for X-linked hypophosphatemic rickets (HYP). PHEX binds to the DMP1-ASARM-motif to form a trimeric-complex with α5β3-integrin on the osteocyte surface and this suppresses FGF23 expression. ASARM-peptide disruption of this complex increases FGF23 expression. We used a 4.2kDa peptide (SPR4) that binds to ASARM-peptide and ASARM-motif to study DMP1-PHEX interactions and to assess SPR4 for treating inherited hypophosphatemic rickets. DESIGN Subcutaneously transplanted osmotic pumps were used to infuse SPR4-peptide or vehicle into wild-type mice (WT) and HYP-mice for 4 weeks. RESULTS Asymmetrically distributed mineralization defects occurred with WT-SPR4 femurs. Specifically, SPR4 induced negative effects on trabecular bone and increased bone volume and mineralization in cortical-bone. Markedly increased sclerostin and reduced active β-catenin occurred with HYP mice. SPR4-infusion suppressed sclerostin and increased active β-catenin in WT and HYP mice and improved HYP-mice trabecular mineralization defects but not cortical mineralization defects. CONCLUSIONS SPR4-peptide has bimodal activity and acts by: (1) preventing DMP1 binding to PHEX and (2) sequestering an inhibitor of DMP1-PHEX binding, ASARM-peptide. In PHEX defective HYP-mice the second pathway predominates. Although SPR4-peptide improved trabecular calcification defects, decreased sclerostin and increased active β-catenin it did not correct HYP-mice cortical mineralization defects on a normal phosphate diet. Thus, for inherited hypophosphatemic rickets patients on a normal phosphate diet, SPR4-peptide is not a useful therapeutic.
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Affiliation(s)
- Lesya V Zelenchuk
- The Kidney Institute, Kansas University Medical Center, Kansas City, KS, USA
| | - Anne-Marie Hedge
- The Kidney Institute, Kansas University Medical Center, Kansas City, KS, USA
| | - Peter S N Rowe
- The Kidney Institute, Kansas University Medical Center, Kansas City, KS, USA.
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Fenton RA, Murray F, Dominguez Rieg JA, Tang T, Levi M, Rieg T. Renal phosphate wasting in the absence of adenylyl cyclase 6. J Am Soc Nephrol 2014; 25:2822-34. [PMID: 24854272 PMCID: PMC4243352 DOI: 10.1681/asn.2013101102] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 03/31/2014] [Indexed: 11/03/2022] Open
Abstract
Parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) enhance phosphate excretion by the proximal tubule of the kidney by retrieval of the sodium-dependent phosphate transporters (Npt2a and Npt2c) from the apical plasma membrane. PTH activates adenylyl cyclase (AC) through PTH 1 receptors and stimulates the cAMP/PKA signaling pathway. However, the precise role and isoform(s) of AC in phosphate homeostasis are not known. We report here that mice lacking AC6 (AC6(-/-)) have increased plasma PTH and FGF-23 levels compared with wild-type (WT) mice but comparable plasma phosphate concentrations. Acute activation of the calcium-sensing receptor or feeding a zero phosphate diet almost completely suppressed plasma PTH levels in both AC6(-/-) and WT mice, indicating a secondary cause for hyperparathyroidism. Pharmacologic blockade of FGF receptors resulted in a comparable increase in plasma phosphate between genotypes, whereas urinary phosphate remained significantly higher in AC6(-/-) mice. Compared with WT mice, AC6(-/-) mice had reduced renal Npt2a and Npt2c protein abundance, with approximately 80% of Npt2a residing in lysosomes. WT mice responded to exogenous PTH with redistribution of Npt2a from proximal tubule microvilli to intracellular compartments and lysosomes alongside a PTH-induced dose-response relationship for fractional phosphate excretion and urinary cAMP excretion. These responses were absent in AC6(-/-) mice. In conclusion, AC6 in the proximal tubule modulates cAMP formation, Npt2a trafficking, and urinary phosphate excretion, which are highlighted by renal phosphate wasting in AC6(-/-) mice.
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Affiliation(s)
- Robert A Fenton
- Interactions of Proteins in Epithelial Transport Center, Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Fiona Murray
- Department of Medicine, University of California San Diego, La Jolla, California
| | | | - Tong Tang
- Veterans Affairs San Diego Healthcare System, San Diego, California; and
| | - Moshe Levi
- Department of Medicine, University of Colorado Denver, Aurora, Colorado
| | - Timo Rieg
- Department of Medicine, University of California San Diego, La Jolla, California; Veterans Affairs San Diego Healthcare System, San Diego, California; and
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30
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Wang N, Robaye B, Gossiel F, Boeynaems JM, Gartland A. The P2Y13 receptor regulates phosphate metabolism and FGF-23 secretion with effects on skeletal development. FASEB J 2014; 28:2249-59. [PMID: 24487286 DOI: 10.1096/fj.13-243626] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Purinergic signaling mediates many cellular processes, including embryonic development and regulation of endocrine signaling. The ADP P2Y13 receptor is known to regulate bone and stem cells activities, although relatively little is known about its role in bone development. In this study we demonstrate, using contemporary techniques, that deletion of the P2Y13 receptor results in an age-dependent skeletal phenotype that is governed by changes in phosphate metabolism and hormone levels. Neonatal and postnatal (2 wk) P2Y13 receptor-knockout (KO) mice were indistinguishable from their wild-type (WT) littermate controls. A clear bone phenotype was observed in young (4-wk-old) KO mice compared WT controls, with 14% more trabecular bone, 35% more osteoblasts, 73% fewer osteoclasts, and a 17% thicker growth plate. Mature (>10 wk of age) KO mice showed the opposite bone phenotype, with 14% less trabecular bone, 22% fewer osteoblasts, and 10% thinner growth plate. This age-dependent phenotype correlated with serum fibroblast growth factor-23 (FGF-23) and phosphorus levels that were 65 and 16% higher, respectively, in young KO mice but remained unchanged in mature mice. These findings provide novel insights for the role of the P2Y13 receptor in skeletal development via coordination with hormonal regulators of phosphate homeostasis.
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Affiliation(s)
- Ning Wang
- 1The Mellanby Centre for Bone Research, Department of Human Metabolism, The University of Sheffield, Beech Hill Rd., Sheffield, S10 2RX, UK.
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31
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Andrukhova O, Smorodchenko A, Egerbacher M, Streicher C, Zeitz U, Goetz R, Shalhoub V, Mohammadi M, Pohl EE, Lanske B, Erben RG. FGF23 promotes renal calcium reabsorption through the TRPV5 channel. EMBO J 2014; 33:229-46. [PMID: 24434184 PMCID: PMC3983685 DOI: 10.1002/embj.201284188] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
αKlotho is thought to activate the epithelial calcium channel Transient Receptor Potential Vanilloid-5 (TRPV5) in distal renal tubules through its putative glucuronidase/sialidase activity, thereby preventing renal calcium loss. However, αKlotho also functions as the obligatory co-receptor for fibroblast growth factor-23 (FGF23), a bone-derived phosphaturic hormone. Here, we show that renal calcium reabsorption and renal membrane abundance of TRPV5 are reduced in Fgf23 knockout mice, similar to what is seen in αKlotho knockout mice. We further demonstrate that αKlotho neither co-localizes with TRPV5 nor is regulated by FGF23. Rather, apical membrane abundance of TRPV5 in renal distal tubules and thus renal calcium reabsorption are regulated by FGF23, which binds the FGF receptor-αKlotho complex and activates a signaling cascade involving ERK1/2, SGK1, and WNK4. Our data thereby identify FGF23, not αKlotho, as a calcium-conserving hormone in the kidney.
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32
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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.
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33
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Lee JY, Imel EA. The changing face of hypophosphatemic disorders in the FGF-23 era. PEDIATRIC ENDOCRINOLOGY REVIEWS : PER 2013; 10 Suppl 2:367-379. [PMID: 23858620 PMCID: PMC4170520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In the past decade, research in genetic disorders of hypophosphatemia has significantly expanded our understanding of phosphate metabolism. X-linked hypophosphatemia (XLH) is the most common inherited form of rickets due to renal phosphate wasting. Recent understanding of the mechanisms of disease and role of fibroblast growth factor 23 (FGF-23) in XLH and other hypophosphatemic disorders have opened new potential therapeutic avenues. We will discuss the current standard of treatment for XLH as well as promising future directions under study.
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Affiliation(s)
- Janet Y Lee
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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34
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Uchihashi K, Nakatani T, Goetz R, Mohammadi M, He X, Razzaque MS. FGF23-induced hypophosphatemia persists in Hyp mice deficient in the WNT coreceptor Lrp6. CONTRIBUTIONS TO NEPHROLOGY 2013; 180:124-37. [PMID: 23652555 DOI: 10.1159/000346792] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Deregulated phosphate homeostasis can lead to a wide range of disorders, including myopathy, cardiac dysfunction, and skeletal abnormalities. Therefore, characterization of the molecular regulation of phosphate metabolism is of pathophysiological and clinical significance. Hyp mouse is the model for human X-linked hypophosphatemia which is due to mutations that inactivate the endopeptidases of the X chromosome (PHEX). PHEX inactivation leads to increased serum levels of fibroblast growth factor 23 (FGF23), a phosphaturic hormone that induces excessive renal phosphate excretion and severe hypophosphatemia. The expression of WNT signaling components is increased in Hyp mice. To determine the potential role of WNT signaling in FGF23-mediated hypophosphatemia, we cross-bred Hyp mice with mice deficient in the WNT coreceptor low-density lipoprotein receptor-related protein 6 (Lrp6) to generate Hyp and Lrp6 double mutant mice (Hyp/Lrp6). Like Hyp mice, Hyp/Lrp6 double mutants maintained high serum levels of FGF23, and accordingly exhibited hypophosphatemia to the same degree as the Hyp mice did, indicating that genetically reducing WNT signaling does not impact FGF23-induced phosphaturia. Moreover, similar to Hyp mice, the Hyp/Lrp6 double mutants also exhibited reduced mineralization of the bone, further supporting that reduced WNT signaling does not affect the chronic phosphate wasting caused by excess FGF23 in these mice. In further support of our finding, injection of bioactive FGF23 protein into Lrp6 mutant mice reduced serum phosphate levels to a similar degree as FGF23 injection into wild-type mice. Our in vivo studies provide genetic and pharmacological evidence for a WNT-independent function of FGF23 in the regulation of phosphate homeostasis.
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Affiliation(s)
- Kazuyoshi Uchihashi
- Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA 02115, USA
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35
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Abstract
Over the last decade the discovery of fibroblast growth factor 23 (FGF23) and the progressive and ongoing clarification of its role in phosphate and mineral metabolism have led to expansion of the diagnostic spectrum of primary hypophosphatemic syndromes. This article focuses on the impairment of growth in these syndromes. Growth retardation is a common, but not constant, feature and it presents with large variability. As a result of the very low prevalence of other forms of primary hypophosphatemic syndromes, the description of longitudinal growth and the pathogenesis of its impairment have been mostly studied in X-linked hypophosphatemia (XLH) patients and in Hyp mice, the animal model of this disease. In general, children with XLH have short stature with greater shortness of lower limbs than trunk. Treatment with phosphate supplements and 1α vitamin D derivatives heals active lesions of rickets, but does not normalize growth of XLH patients. Patients might benefit from recombinant human growth hormone (rhGH) therapy, which may accelerate the growth rate without increasing body disproportion or correcting hypophosphatemia. These clinical data as well as research findings obtained in Hyp mice suggest that the pathogenesis of defective growth in XLH and other hypophosphatemic syndromes is not entirely dependent on the mineralization disorder and point to other effects of hypophosphatemia itself or FGF23 on the metabolism of bone and growth plate.
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Affiliation(s)
- Fernando Santos
- Hospital Universitario Central de Asturias & University of Oviedo, Oviedo, Asturias, Spain.
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36
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Smith RC, O'Bryan LM, Farrow EG, Summers LJ, Clinkenbeard EL, Roberts JL, Cass TA, Saha J, Broderick C, Ma YL, Zeng QQ, Kharitonenkov A, Wilson JM, Guo Q, Sun H, Allen MR, Burr DB, Breyer MD, White KE. Circulating αKlotho influences phosphate handling by controlling FGF23 production. J Clin Invest 2012. [PMID: 23187128 DOI: 10.1172/jci64986] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The FGF23 coreceptor αKlotho (αKL) is expressed as a membrane-bound protein (mKL) that forms heteromeric complexes with FGF receptors (FGFRs) to initiate intracellular signaling. It also circulates as an endoproteolytic cleavage product of mKL (cKL). Previously, a patient with increased plasma cKL as the result of a translocation [t(9;13)] in the αKLOTHO (KL) gene presented with rickets and a complex endocrine profile, including paradoxically elevated plasma FGF23, despite hypophosphatemia. The goal of this study was to test whether cKL regulates phosphate handling through control of FGF23 expression. To increase cKL levels, mice were treated with an adeno-associated virus producing cKL. The treated groups exhibited dose-dependent hypophosphatemia and hypocalcemia, with markedly elevated FGF23 (38 to 456 fold). The animals also manifested fractures, reduced bone mineral content, expanded growth plates, and severe osteomalacia, with highly increased bone Fgf23 mRNA (>150 fold). cKL activity in vitro was specific for interactions with FGF23 and was FGFR dependent. These results demonstrate that cKL potently stimulates FGF23 production in vivo, which phenocopies the KL translocation patient and metabolic bone syndromes associated with elevated FGF23. These findings have important implications for the regulation of αKL and FGF23 in disorders of phosphate handling and biomineralization.
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Affiliation(s)
- Rosamund C Smith
- Biotechnology Discovery Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
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37
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Andrukhova O, Zeitz U, Goetz R, Mohammadi M, Lanske B, Erben RG. FGF23 acts directly on renal proximal tubules to induce phosphaturia through activation of the ERK1/2-SGK1 signaling pathway. Bone 2012; 51:621-8. [PMID: 22647968 PMCID: PMC3419258 DOI: 10.1016/j.bone.2012.05.015] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 04/09/2012] [Accepted: 05/22/2012] [Indexed: 12/17/2022]
Abstract
Fibroblast growth factor-23 (FGF23) is a bone-derived endocrine regulator of phosphate homeostasis which inhibits renal tubular phosphate reabsorption. Binding of circulating FGF23 to FGF receptors in the cell membrane requires the concurrent presence of the co-receptor αKlotho. It is still controversial whether αKlotho is expressed in the kidney proximal tubule, the principal site of phosphate reabsorption. Hence, it has remained an enigma as to how FGF23 downregulates renal phosphate reabsorption. Here, we show that renal proximal tubular cells do express the co-receptor αKlotho together with cognate FGF receptors, and that FGF23 directly downregulates membrane expression of the sodium-phosphate cotransporter NaPi-2a by serine phosphorylation of the scaffolding protein Na(+)/H(+) exchange regulatory cofactor (NHERF)-1 through ERK1/2 and serum/glucocorticoid-regulated kinase-1 signaling.
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Affiliation(s)
| | - Ute Zeitz
- University of Veterinary Medicine Vienna, Vienna, Austria
| | - Regina Goetz
- New York University School of Medicine, New York, USA
| | | | | | - Reinhold G. Erben
- University of Veterinary Medicine Vienna, Vienna, Austria
- Corresponding author at: Institute of Physiology, Pathophysiology and Biophysics, Dept. of Biomedical Sciences, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria. Fax: + 43 1 250 77 4599.
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38
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Zhang MYH, Ranch D, Pereira RC, Armbrecht HJ, Portale AA, Perwad F. Chronic inhibition of ERK1/2 signaling improves disordered bone and mineral metabolism in hypophosphatemic (Hyp) mice. Endocrinology 2012; 153:1806-16. [PMID: 22334725 PMCID: PMC3320256 DOI: 10.1210/en.2011-1831] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The X-linked hypophosphatemic (Hyp) mouse carries a loss-of-function mutation in the phex gene and is characterized by hypophosphatemia due to renal phosphate (Pi) wasting, inappropriately suppressed 1,25-dihydroxyvitamin D [1,25(OH)₂D] production, and rachitic bone disease. Increased serum fibroblast growth factor-23 concentration is responsible for the disordered metabolism of Pi and 1,25(OH)₂D. In the present study, we tested the hypothesis that chronic inhibition of fibroblast growth factor-23-induced activation of MAPK signaling in Hyp mice can reverse their metabolic derangements and rachitic bone disease. Hyp mice were administered the MAPK inhibitor, PD0325901 orally for 4 wk. PD0325901 induced a 15-fold and 2-fold increase in renal 1α-hydroxylase mRNA and protein abundance, respectively, and thereby higher serum 1,25(OH)₂D concentrations (115 ± 13 vs. 70 ± 16 pg/ml, P < 0.05), compared with values in vehicle-treated Hyp mice. With PD0325901, serum Pi levels were higher (5.1 ± 0.5 vs. 3 ± 0.2 mg/dl, P < 0.05), and the protein abundance of sodium-dependent phosphate cotransporter Npt2a, was greater than in vehicle-treated mice. The rachitic bone disease in Hyp mice is characterized by abundant unmineralized osteoid bone volume, widened epiphyses, and disorganized growth plates. In PD0325901-treated Hyp mice, mineralization of cortical and trabecular bone increased significantly, accompanied by a decrease in unmineralized osteoid volume and thickness, as determined by histomorphometric analysis. The improvement in mineralization in PD0325901-treated Hyp mice was confirmed by microcomputed tomography analysis, which showed an increase in cortical bone volume and thickness. These findings provide evidence that in Hyp mice, chronic MAPK inhibition improves disordered Pi and 1,25(OH)₂D metabolism and bone mineralization.
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Affiliation(s)
- Martin Y H Zhang
- Department of Pediatrics, University of California San Francisco, San Francisco, California 94143-0748, USA
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39
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Iron deficiency drives an autosomal dominant hypophosphatemic rickets (ADHR) phenotype in fibroblast growth factor-23 (Fgf23) knock-in mice. Proc Natl Acad Sci U S A 2011; 108:E1146-55. [PMID: 22006328 DOI: 10.1073/pnas.1110905108] [Citation(s) in RCA: 271] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Autosomal dominant hypophosphatemic rickets (ADHR) is unique among the disorders involving Fibroblast growth factor 23 (FGF23) because individuals with R176Q/W and R179Q/W mutations in the FGF23 (176)RXXR(179)/S(180) proteolytic cleavage motif can cycle from unaffected status to delayed onset of disease. This onset may occur in physiological states associated with iron deficiency, including puberty and pregnancy. To test the role of iron status in development of the ADHR phenotype, WT and R176Q-Fgf23 knock-in (ADHR) mice were placed on control or low-iron diets. Both the WT and ADHR mice receiving low-iron diet had significantly elevated bone Fgf23 mRNA. WT mice on a low-iron diet maintained normal serum intact Fgf23 and phosphate metabolism, with elevated serum C-terminal Fgf23 fragments. In contrast, the ADHR mice on the low-iron diet had elevated intact and C-terminal Fgf23 with hypophosphatemic osteomalacia. We used in vitro iron chelation to isolate the effects of iron deficiency on Fgf23 expression. We found that iron chelation in vitro resulted in a significant increase in Fgf23 mRNA that was dependent upon Mapk. Thus, unlike other syndromes of elevated FGF23, our findings support the concept that late-onset ADHR is the product of gene-environment interactions whereby the combined presence of an Fgf23-stabilizing mutation and iron deficiency can lead to ADHR.
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40
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Farrow EG, Imel EA, White KE. Miscellaneous non-inflammatory musculoskeletal conditions. Hyperphosphatemic familial tumoral calcinosis (FGF23, GALNT3 and αKlotho). Best Pract Res Clin Rheumatol 2011; 25:735-47. [PMID: 22142751 PMCID: PMC3233725 DOI: 10.1016/j.berh.2011.10.020] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 10/13/2011] [Indexed: 11/18/2022]
Abstract
Familial tumoral calcinosis (TC) is a rare disorder distinguished by the development of ectopic and vascular calcified masses that occur in settings of hyperphosphatemia (hFTC) and normophosphatemia (nFTC). Serum phosphorus concentrations are relatively tightly controlled by interconnected endocrine activity at the level of the intestine, kidney, and skeleton. Discovering the molecular causes for heritable forms of hFTC has shed new light on the regulation of serum phosphate balance. This review will focus upon the genetic basis and clinical approaches for hFTC, due to genes that are related to the phosphaturic hormone fibroblast growth factor-23 (FGF23). These include FGF23 itself, an FGF23-glycosylating enzyme (GALNT3), and the FGF23 co-receptor α-Klotho (αKL). Our understanding of the molecular basis of hFTC will, in the short term, aid in understanding normal phosphate balance, and in the future, provide potential insight into the design of novel therapeutic strategies for both rare and common disorders of phosphate metabolism.
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Affiliation(s)
- Emily G. Farrow
- Departments of Medical and Molecular Genetics, IN, 46202 USA
| | - Erik A. Imel
- Medicine Indiana University School of Medicine Indianapolis, IN, 46202 USA
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41
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Rhee Y, Bivi N, Farrow E, Lezcano V, Plotkin LI, White KE, Bellido T. Parathyroid hormone receptor signaling in osteocytes increases the expression of fibroblast growth factor-23 in vitro and in vivo. Bone 2011; 49:636-43. [PMID: 21726676 PMCID: PMC3167030 DOI: 10.1016/j.bone.2011.06.025] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 06/17/2011] [Accepted: 06/19/2011] [Indexed: 12/14/2022]
Abstract
Mice with constitutive activation of parathyroid hormone (PTH) receptor signaling in osteocytes (DMP1-caPTHR1 transgenic mice) exhibit increased bone mass and remodeling, two of the recognized skeletal actions of PTH. Moreover, similar to PTH administration, DMP1-caPTHR1 mice exhibit decreased expression of the osteocyte-derived Wnt antagonist Sost/sclerostin. We now report that PTH receptor activation also regulates in vivo and in vitro the expression of fibroblast growth factor 23 (FGF23), an osteocyte product involved in inorganic phosphate (Pi) homeostasis and bone mineralization. Whole bones and osteocytes, but not osteoblasts, from DMP1-caPTHR1 mice exhibit elevated FGF23 expression, which is corrected in double transgenic mice overexpressing Sost in osteocytes. PTH, PTH related protein (PTHrP), or a cAMP stable analog, increase FGF23 transcripts in a time- and dose-dependent manner in osteocyte-containing calvarial cell cultures. Circulating FGF23 is also elevated in DMP1-caPTHR1 mice; however, plasma Pi or renal Pi reabsorption is not altered. Furthermore, the FGF23 receptor complex comprising FGFR1 and KLOTHO is expressed in osteoblastic cells; and FGFR1, GALNT3, as well as downstream targets of FGF23 signaling, are increased in osteocytes but not in osteoblasts from DMP1-caPTHR1 mice. Thus, PTH receptor signaling has the potential to modulate the endocrine and auto/paracrine functions of osteocytes by regulating FGF23 through cAMP- and Wnt-dependent mechanisms.
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Affiliation(s)
- Yumie Rhee
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46022, USA.
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Christov M, Koren S, Yuan Q, Baron R, Lanske B. Genetic ablation of sfrp4 in mice does not affect serum phosphate homeostasis. Endocrinology 2011; 152:2031-6. [PMID: 21427221 PMCID: PMC3075942 DOI: 10.1210/en.2010-1351] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 02/28/2011] [Indexed: 11/19/2022]
Abstract
Serum phosphate levels are regulated by PTH and the fibroblast growth factor 23 (Fgf23)/Klotho endocrine system, which both affect expression of Npt2a and thus the apical reabsorption of phosphate in the proximal renal tubules. In addition to Fgf23, secreted frizzled-related protein 4 (Sfrp4) has recently been implicated as an additional phosphate regulator in vivo and in vitro. Here we demonstrate that ablation of the Sfrp4 gene in mice does not lead to altered serum or urine phosphate levels. Furthermore, Sfrp4 is unable to compensate for the absence of Fgf23 or Klotho because double knockouts have a similar biochemical profile and phenotype as animals with ablation of Fgf23 or Klotho alone. Taken together, our data suggest that Sfrp4 does not contribute to the long-term regulation of serum phosphate levels in mice.
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Affiliation(s)
- Marta Christov
- Department of Medicine, Harvard School of Dental Medicine, Boston, Massachusetts 02115, USA.
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