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Puente Ruiz N, Valero Díaz de Lamadrid MC, Riancho JA. Etiology of hypophosphatemia in adults. Med Clin (Barc) 2025; 164:30-37. [PMID: 39025772 DOI: 10.1016/j.medcli.2024.05.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 05/13/2024] [Accepted: 05/15/2024] [Indexed: 07/20/2024]
Abstract
Long-term hypophosphatemia, defined by serum phosphorus (P) levels <2.5mg/dL, impairs the development and quality of mineralized tissue of the skeletal, dental, and auditory systems. P homeostasis depends mainly on intestinal absorption and renal excretion. Hypophosphatemia may be due to the redistribution of P to the intracellular space, increased renal losses, or decreased intestinal absorption. Hypophosphatemia can be categorized as acute or chronic, depending on the time course. Most cases, either acute or chronic, are due to acquired causes. However, some chronic cases may have a genetic origin. Accurate and early diagnosis, followed by adequate treatment, is essential to limit its negative effects on the body.
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Affiliation(s)
- Nuria Puente Ruiz
- Servicio de Medicina Interna, Hospital Universitario Marqués de Valdecilla; Departamento de Medicina y Psiquiatría, Universidad de Cantabria; Instituto de Investigación Marqués de Valdecilla (IDIVAL), Santander, España; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER, ISCIII), Madrid, España.
| | - M Carmen Valero Díaz de Lamadrid
- Servicio de Medicina Interna, Hospital Universitario Marqués de Valdecilla; Departamento de Medicina y Psiquiatría, Universidad de Cantabria; Instituto de Investigación Marqués de Valdecilla (IDIVAL), Santander, España
| | - José A Riancho
- Servicio de Medicina Interna, Hospital Universitario Marqués de Valdecilla; Departamento de Medicina y Psiquiatría, Universidad de Cantabria; Instituto de Investigación Marqués de Valdecilla (IDIVAL), Santander, España; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER, ISCIII), Madrid, España
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2
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Salera D, Bellasi A, Del Vecchio L, Locatelli F. Update on current and emerging treatment paradigms for hyperphosphatemia in chronic kidney disease. Expert Opin Pharmacother 2025; 26:85-100. [PMID: 39676576 DOI: 10.1080/14656566.2024.2441328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2024] [Accepted: 12/09/2024] [Indexed: 12/17/2024]
Abstract
INTRODUCTION Hyperphosphatemia in advanced CKD often accompanies high PTH and FGF23 levels, impaired bone mineralization, ectopic calcifications, and increased cardiovascular risks. Novel treatments are now available to lower serum phosphorus effectively. However, safety, tolerability, and patient adherence must be evaluated to determine the best therapeutic option for hyperphosphatemia. AREAS COVERED This review examines available treatment strategies for hyperphosphatemia in CKD patients and new emerging treatments, emphasizing the latest inhibitors of active phosphate absorption. EXPERT OPINION Despite the numerous compounds available, managing hyperphosphatemia in CKD remains challenging. While many phosphate binders exist, they often have limitations and side effects. Aluminum carries significant toxicity risks. Calcium-based binders are effective but can cause hypercalcemia and vascular calcification. Lanthanum is absorbed in the gut, but its long-term tissue deposition appears clinically irrelevant. Sevelamer reduces vascular calcification but has inconclusive data and gastrointestinal side effects. Iron-based binders are effective but may cause gastrointestinal discomfort and lack long-term outcome data. New inhibitors of intestinal phosphate absorption show promise with low pill burden but need more clinical validation. Although these newer compounds might eventually improve phosphate management in CKD patients, enhancing adherence and reducing pill burden, future studies are required to elucidate the best treatment for hyperphosphatemia.
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Affiliation(s)
- Davide Salera
- Service of Nephrology, Ospedale Regionale di Lugano, Ospedale Civico, Ente Ospedaliero Cantonale, Lugano, Switzerland
| | - Antonio Bellasi
- Service of Nephrology, Ospedale Regionale di Lugano, Ospedale Civico, Ente Ospedaliero Cantonale, Lugano, Switzerland
- Faculty of Biomedical Sciences, Università della Svizzera italiana (USi), Lugano, Switzerland
| | - Lucia Del Vecchio
- Department of Nephrology and Dialysis, Sant'Anna Hospital, ASST Lariana, Como, Italy
| | - Francesco Locatelli
- Department of Nephrology and Dialysis, Past Director, Alessandro Manzoni Hospital, ASST Lecco, Lecco, Italy
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3
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Radványi Z, Schnitzbauer U, Pastor-Arroyo EM, Hölker S, Himmerkus N, Bleich M, Müller D, Breiderhoff T, Hernando N, Wagner CA. Absence of claudin-3 does not alter intestinal absorption of phosphate in mice. Pflugers Arch 2024; 476:1597-1612. [PMID: 39115555 PMCID: PMC11381482 DOI: 10.1007/s00424-024-02998-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2024] [Revised: 07/04/2024] [Accepted: 07/23/2024] [Indexed: 09/10/2024]
Abstract
Intestinal absorption of phosphate is bimodal, consisting of a transcellular pathway and a poorly characterized paracellular mode, even though the latter one contributes to the bulk of absorption under normal dietary conditions. Claudin-3 (Cldn3), a tight junction protein present along the whole intestine in mice, has been proposed to tighten the paracellular pathway for phosphate. The aim of this work was to characterize the phosphate-related phenotype of Cldn3-deficient mice. Cldn3-deficient mice and wildtype littermates were fed standard diet or challenged for 3 days with high dietary phosphate. Feces, urine, blood, intestinal segments and kidneys were collected. Measurements included fecal, urinary, and plasma concentrations of phosphate and calcium, plasma levels of phosphate-regulating hormones, evaluation of trans- and paracellular phosphate transport across jejunum and ileum, and analysis of intestinal phosphate and calcium permeabilities. Fecal and urinary excretion of phosphate as well as its plasma concentration was similar in both genotypes, under standard and high-phosphate diet. However, Cldn3-deficient mice challenged with high dietary phosphate had a reduced urinary calcium excretion and increased plasma levels of calcitriol. Intact FGF23 concentration was also similar in both groups, regardless of the dietary conditions. We found no differences either in intestinal phosphate transport (trans- or paracellular) and phosphate and calcium permeabilities between genotypes. The intestinal expression of claudin-7 remained unaltered in Cldn3-deficient mice. Our data do not provide evidence for a decisive role of Cldn3 for intestinal phosphate absorption and phosphate homeostasis. In addition, our data suggest a novel role of Cldn3 in regulating calcitriol levels.
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Affiliation(s)
- Zsuzsa Radványi
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Udo Schnitzbauer
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | - Simone Hölker
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | | | - Markus Bleich
- Institute of Physiology, Kiel University, Kiel, Germany
| | - Dominik Müller
- Department of Pediatrics, Division of Gastroenterology, Nephrology and Metabolic Diseases, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Tilman Breiderhoff
- Department of Pediatrics, Division of Gastroenterology, Nephrology and Metabolic Diseases, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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4
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Wang SZ, Wang MD, Wang JY, Yuan M, Li YD, Luo PT, Xiao F, Li H. Genome-wide association study of growth curve parameters reveals novel genomic regions and candidate genes associated with metatarsal bone traits in chickens. Animal 2024; 18:101129. [PMID: 38574453 DOI: 10.1016/j.animal.2024.101129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 03/02/2024] [Accepted: 03/05/2024] [Indexed: 04/06/2024] Open
Abstract
The growth and development of chicken bones have an enormous impact on the health and production performance of chickens. However, the development pattern and genetic regulation of the chicken skeleton are poorly understood. This study aimed to evaluate metatarsal bone growth and development patterns in chickens via non-linear models, and to identify the genetic determinants of metatarsal bone traits using a genome-wide association study (GWAS) based on growth curve parameters. Data on metatarsal length (MeL) and metatarsal circumference (MeC) were obtained from 471 F2 chickens (generated by crossing broiler sires, derived from a line selected for high abdominal fat, with Baier layer dams) at 4, 6, 8, 10, and 12 weeks of age. Four non-linear models (Gompertz, Logistic, von Bertalanffy, and Brody) were used to fit the MeL and MeC growth curves. Subsequently, the estimated growth curve parameters of the mature MeL or MeC (A), time-scale parameter (b), and maturity rate (K) from the non-linear models were utilized as substitutes for the original bone data in GWAS. The Logistic and Brody models displayed the best goodness-of-fit for MeL and MeC, respectively. Single-trait and multi-trait GWASs based on the growth curve parameters of the Logistic and Brody models revealed 4 618 significant single nucleotide polymorphisms (SNPs), annotated to 332 genes, associated with metatarsal bone traits. The majority of these significant SNPs were located on Gallus gallus chromosome (GGA) 1 (167.433-176.318 Mb), GGA2 (96.791-103.543 Mb), GGA4 (65.003-83.104 Mb) and GGA6 (64.685-95.285 Mb). Notably, we identified 12 novel GWAS loci associated with chicken metatarsal bone traits, encompassing 35 candidate genes. In summary, the combination of single-trait and multi-trait GWASs based on growth curve parameters uncovered numerous genomic regions and candidate genes associated with chicken bone traits. The findings benefit an in-depth understanding of the genetic architecture underlying metatarsal growth and development in chickens.
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Affiliation(s)
- S Z Wang
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture and Rural Affairs, Harbin 150030, PR China; Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin 150030, PR China; College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR China
| | - M D Wang
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture and Rural Affairs, Harbin 150030, PR China; Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin 150030, PR China; College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR China
| | - J Y Wang
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture and Rural Affairs, Harbin 150030, PR China; Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin 150030, PR China; College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR China
| | - M Yuan
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture and Rural Affairs, Harbin 150030, PR China; Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin 150030, PR China; College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR China
| | - Y D Li
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture and Rural Affairs, Harbin 150030, PR China; Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin 150030, PR China; College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR China
| | - P T Luo
- Fujian Sunnzer Biotechnology Development Co. Ltd, Guangze, Fujian Province 354100, PR China
| | - F Xiao
- Fujian Sunnzer Biotechnology Development Co. Ltd, Guangze, Fujian Province 354100, PR China
| | - H Li
- Key Laboratory of Chicken Genetics and Breeding, Ministry of Agriculture and Rural Affairs, Harbin 150030, PR China; Key Laboratory of Animal Genetics, Breeding and Reproduction, Education Department of Heilongjiang Province, Harbin 150030, PR China; College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, PR China.
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5
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Abstract
Phosphorus is an essential mineral that is, in the form of inorganic phosphate (Pi), required for building cell membranes, DNA and RNA molecules, energy metabolism, signal transduction and pH buffering. In bone, Pi is essential for bone stability in the form of apatite. Intestinal absorption of dietary Pi depends on its bioavailability and has two distinct modes of active transcellular and passive paracellular absorption. Active transport is transporter mediated and partly regulated, while passive absorption depends mostly on bioavailability. Renal excretion controls systemic Pi levels, depends on transporters in the proximal tubule and is highly regulated. Deposition and release of Pi into and from soft tissues and bone has to be tightly controlled. The endocrine network coordinating intestinal absorption, renal excretion and bone turnover integrates dietary intake and metabolic requirements with renal excretion and is critical for bone stability and cardiovascular health during states of hypophosphataemia or hyperphosphataemia as evident from inborn or acquired diseases. This review provides an integrated overview of the biology of phosphate and Pi in mammals.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
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6
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Abstract
Inorganic phosphate (Pi) is an essential component of many biologically important molecules such as DNA, RNA, ATP, phospholipids, or apatite. It is required for intracellular phosphorylation signaling events and acts as pH buffer in intra- and extracellular compartments. Intestinal absorption, uptake into cells, and renal reabsorption depend on a set of different phosphate transporters from the SLC20 (PiT transporters) and SLC34 (NaPi transporters) gene families. The physiological relevance of these transporters is evident from rare monogenic disorders in humans affecting SLC20A2 (Fahr's disease, basal ganglia calcification), SLC34A1 (idiopathic infantile hypercalcemia), SLC34A2 (pulmonary alveolar microlithiasis), and SLC34A3 (hereditary hypophosphatemic rickets with hypercalciuria). SLC34 transporters are inhibited by millimolar concentrations of phosphonoformic acid or arsenate while SLC20 are relatively resistant to these compounds. More recently, a series of more specific and potent drugs have been developed to target SLC34A2 to reduce intestinal Pi absorption and to inhibit SLC34A1 and/or SLC34A3 to increase renal Pi excretion in patients with renal disease and incipient hyperphosphatemia. Also, SLC20 inhibitors have been developed with the same intention. Some of these substances are currently undergoing preclinical and clinical testing. Tenapanor, a non-absorbable Na+/H+-exchanger isoform 3 inhibitor, reduces intestinal Pi absorption likely by indirectly acting on the paracellular pathway for Pi and has been tested in several phase III trials for reducing Pi overload in patients with renal insufficiency and dialysis.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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7
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Borghi F, Saiardi A. Evolutionary perspective on mammalian inorganic polyphosphate (polyP) biology. Biochem Soc Trans 2023; 51:1947-1956. [PMID: 37844192 PMCID: PMC10657179 DOI: 10.1042/bst20230483] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/06/2023] [Accepted: 10/10/2023] [Indexed: 10/18/2023]
Abstract
Inorganic polyphosphate (polyP), the polymeric form of phosphate, is attracting ever-growing attention due to the many functions it appears to perform within mammalian cells. This essay does not aim to systematically review the copious mammalian polyP literature. Instead, we examined polyP synthesis and functions in various microorganisms and used an evolutionary perspective to theorise key issues of this field and propose solutions. By highlighting the presence of VTC4 in distinct species of very divergent eucaryote clades (Opisthokonta, Viridiplantae, Discoba, and the SAR), we propose that whilst polyP synthesising machinery was present in the ancestral eukaryote, most lineages subsequently lost it during evolution. The analysis of the bacteria-acquired amoeba PPK1 and its unique polyP physiology suggests that eukaryote cells must have developed mechanisms to limit cytosolic polyP accumulation. We reviewed the literature on polyP in the mitochondria from the perspective of its endosymbiotic origin from bacteria, highlighting how mitochondria could possess a polyP physiology reminiscent of their 'bacterial' beginning that is not yet investigated. Finally, we emphasised the similarities that the anionic polyP shares with the better-understood negatively charged polymers DNA and RNA, postulating that the nucleus offers an ideal environment where polyP physiology might thrive.
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Affiliation(s)
- Filipy Borghi
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, U.K
| | - Adolfo Saiardi
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, U.K
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8
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Garneau AP, Slimani S, Haydock L, Nsimba-Batomene TR, Préfontaine FCM, Lavoie MM, Tremblay LE, Fiola MJ, Mac-Way F, Isenring P. Molecular mechanisms, physiological roles, and therapeutic implications of ion fluxes in bone cells: Emphasis on the cation-Cl - cotransporters. J Cell Physiol 2022; 237:4356-4368. [PMID: 36125923 PMCID: PMC10087713 DOI: 10.1002/jcp.30879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 08/25/2022] [Accepted: 09/01/2022] [Indexed: 11/11/2022]
Abstract
Bone turnover diseases are exceptionally prevalent in human and come with a high burden on physical health. While these diseases are associated with a variety of risk factors and causes, they are all characterized by common denominators, that is, abnormalities in the function or number of osteoblasts, osteoclasts, and/or osteocytes. As such, much effort has been deployed in the recent years to understand the signaling mechanisms of bone cell proliferation and differentiation with the objectives of exploiting the intermediates involved as therapeutic preys. Ion transport systems at the external and in the intracellular membranes of osteoblasts and osteoclasts also play an important role in bone turnover by coordinating the movement of Ca2+ , PO4 2- , and H+ ions in and out of the osseous matrix. Even if they sustain the terminal steps of osteoformation and osteoresorption, they have been the object of very little attention in the last several years. Members of the cation-Cl- cotransporter (CCC) family are among the systems at work as they are expressed in bone cells, are known to affect the activity of Ca2+ -, PO4 2- -, and H+ -dependent transport systems and have been linked to bone mass density variation in human. In this review, the roles played by the CCCs in bone remodeling will be discussed in light of recent developments and their potential relevance in the treatment of skeletal disorders.
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Affiliation(s)
- Alexandre P Garneau
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada.,Service de Néphrologie-Transplantation Rénale Adultes, Hôpital Necker-Enfants Malades, AP-HP, Inserm U1151, Université Paris Cité, rue de Sèvres, Paris, France
| | - Samira Slimani
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Ludwig Haydock
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | | | | | - Mathilde M Lavoie
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Laurence E Tremblay
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Marie-Jeanne Fiola
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Fabrice Mac-Way
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
| | - Paul Isenring
- Department of Medicine, Nephrology Research Group, Laval University, Québec, Québec, Canada
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9
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Abstract
Phosphate homeostasis is dependent on the interaction and coordination of four main organ systems: thyroid/parathyroids, gastrointestinal tract, bone and kidneys, and three key hormonal regulators, 1,25-hydroxyvitamin D3, parathyroid hormone and FGF23 with its co- factor klotho. Phosphorus is a critical nutritional element for normal cellular function, but in excess can be toxic to tissues, particularly the vasculature. As phosphate, it also has an important interaction and inter-dependence with calcium and calcium homeostasis sharing some of the same controlling hormones, although this is not covered in our article. We have chosen to provide a current overview of phosphate homeostasis only, focusing on the role of two major organ systems, the gastrointestinal tract and kidneys, and their contribution to the control of phosphate balance. We describe in some detail the mechanisms of intestinal and renal phosphate transport, and compare and contrast their regulation. We also consider a significant example of phosphate imbalance, with phosphate retention, which is chronic kidney disease; why consequent hyperphosphatemia is important, and some of the newer means of managing it.
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Affiliation(s)
- Joanne Marks
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom
| | - Robert J Unwin
- Department of Neuroscience, Physiology & Pharmacology, University College London, London, United Kingdom; Department of Renal Medicine, University College London, London, United Kingdom.
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10
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Jönsson ÅLM, Hernando N, Knöpfel T, Mogensen S, Bendstrup E, Hilberg O, Christensen JH, Simonsen U, Wagner CA. Impaired phosphate transport in SLC34A2 variants in patients with pulmonary alveolar microlithiasis. Hum Genomics 2022; 16:13. [PMID: 35443721 PMCID: PMC9019944 DOI: 10.1186/s40246-022-00387-y] [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: 12/31/2021] [Accepted: 03/23/2022] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Variants in SLC34A2 encoding the sodium-dependent phosphate transport protein 2b (NaPi-IIb) cause the rare lung disease pulmonary alveolar microlithiasis (PAM). PAM is characterised by the deposition of calcium-phosphate concretions in the alveoli usually progressing over time. No effective treatment is available. So far, 30 allelic variants in patients have been reported but only a few have been functionally characterised. This study aimed to determine the impact of selected SLC34A2 variants on transporter expression and phosphate uptake in cellular studies. METHODS Two nonsense variants (c.910A > T and c.1456C > T), one frameshift (c.1328delT), and one in-frame deletion (c.1402_1404delACC) previously reported in patients with PAM were selected for investigation. Wild-type and mutant c-Myc-tagged human NaPi-IIb constructs were expressed in Xenopus laevis oocytes. The transport function was investigated with a 32Pi uptake assay. NaPi-IIb protein expression and localisation were determined with immunoblotting and immunohistochemistry, respectively. RESULTS Oocytes injected with the wild-type human NaPi-IIb construct had significant 32Pi transport compared to water-injected oocytes. In addition, the protein had a molecular weight as expected for the glycosylated form, and it was readily detectable in the oocyte membrane. Although the protein from the Thr468del construct was synthesised and expressed in the oocyte membrane, phosphate transport was similar to non-injected control oocytes. All other mutants were non-functional and not expressed in the membrane, consistent with the expected impact of the truncations caused by premature stop codons. CONCLUSIONS Of four analysed SLC34A2 variants, only the Thr468del showed similar protein expression as the wild-type cotransporter in the oocyte membrane. All mutant transporters were non-functional, supporting that dysfunction of NaPi-IIb underlies the pathology of PAM.
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Affiliation(s)
- Åsa Lina M. Jönsson
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Clinical Genetics, Aarhus University Hospital, Aarhus, Denmark
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Swiss National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Thomas Knöpfel
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Swiss National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
| | - Susie Mogensen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Elisabeth Bendstrup
- Centre for Rare Lung Diseases, Department of Respiratory Diseases and Allergy, Aarhus University Hospital, Aarhus, Denmark
| | - Ole Hilberg
- Medical Department, Vejle Hospital, Vejle, Denmark
| | | | - Ulf Simonsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Carsten A. Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
- Swiss National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland
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11
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Wang X, Xu Y, Yu X, Dey A, Zhang HY, Zink CM, Wodka D, Porter G, Matter WF, Porras L, Reidy CA, Peterson JA, Mattioni BE, Haas JV, Kowala MC, Wetterau JR. Effects of pharmacological inhibition of the sodium-dependent phosphate cotransporter 2b (NPT2b) on intestinal phosphate absorption in mouse and rat models. Pharmacol Res Perspect 2022; 10:e00938. [PMID: 35194979 PMCID: PMC8863579 DOI: 10.1002/prp2.938] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 01/25/2022] [Accepted: 01/27/2022] [Indexed: 11/08/2022] Open
Abstract
An excess phosphate burden in renal disease has pathological consequences for bone, kidney, and heart. Therapies to decrease intestinal phosphate absorption have been used to address the problem, but with limited success. Here, we describe the in vivo effects of a novel potent inhibitor of the intestinal sodium-dependent phosphate cotransporter NPT2b, LY3358966. Following treatment with LY3358966, phosphate uptake into plasma 15 min following an oral dose of radiolabeled phosphate was decreased 74% and 22% in mice and rats, respectively, indicating NPT2b plays a much more dominant role in mice than rats. Following the treatment with LY3358966 and radiolabeled phosphate, mouse feces were collected for 48 h to determine the ability of LY3358966 to inhibit phosphate absorption. Compared to vehicle-treated animals, there was a significant increase in radiolabeled phosphate recovered in feces (8.6% of the dose, p < .0001). Similar studies performed in rats also increased phosphate recovered in feces (5.3% of the dose, p < .05). When used in combination with the phosphate binder sevelamer in rats, there was a further small, but not significant, increase in fecal phosphate. In conclusion, LY3358966 revealed a more prominent role for NPT2b on acute intestinal phosphate uptake into plasma in mice than rats. However, the modest effects on total intestinal phosphate absorption observed in mice and rats with LY3359866 when used alone or in combination with sevelamer highlights the challenge to identify new more effective therapeutic targets and/or drug combinations to treat the phosphate burden in patients with renal disease.
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Affiliation(s)
- Xiaojun Wang
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Yanping Xu
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Xiaohong Yu
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Asim Dey
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Hong Y. Zhang
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Charity M. Zink
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Derek Wodka
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Gina Porter
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - William F. Matter
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Leah Porras
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Charles A. Reidy
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | | | - Brian E. Mattioni
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Joseph V. Haas
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - Mark C. Kowala
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
| | - John R. Wetterau
- Lilly Research LaboratoriesEli Lilly and CompanyIndianapolisIndianaUSA
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12
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Irsik DL, Bollag WB, Isales CM. Renal Contributions to Age-Related Changes in Mineral Metabolism. JBMR Plus 2021; 5:e10517. [PMID: 34693188 PMCID: PMC8520061 DOI: 10.1002/jbm4.10517] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/28/2021] [Accepted: 05/09/2021] [Indexed: 11/10/2022] Open
Abstract
Aging results in a general decline in function in most systems. This is particularly true with respect to the skeleton and renal systems, impacting mineral homeostasis. Calcium and phosphate regulation requires tight coordination among the intestine, bone, parathyroid gland, and kidney. The role of the intestine is to absorb calcium and phosphate from the diet. The bone stores or releases calcium and phosphate depending on the body's needs. In response to low plasma ionized calcium concentration, the parathyroid gland produces parathyroid hormone, which modulates bone turnover. The kidney reabsorbs or excretes the minerals and serves as the final regulator of plasma concentration. Many hormones are involved in this process in addition to parathyroid hormone, including fibroblast growth factor 23 produced by the bone and calcitriol synthesized by the kidney. Sclerostin, calcitonin, osteoprotegerin, and receptor activator of nuclear factor‐κB ligand also contribute to tissue‐specific regulation. Changes in the function of organs due to aging or disease can perturb this balance. During aging, the intestine cannot absorb calcium efficiently due to decreased expression of key proteins. In the bone, the balance between bone formation and bone resorption tends toward the latter in older individuals. The kidney may not filter blood as efficiently in the later decades of life, and the expression of certain proteins necessary for mineral homeostasis declines with age. These changes often lead to dysregulation of organismal mineral homeostasis. This review will focus on how mineral homeostasis is impacted by aging with a particular emphasis on the kidney's role in this process. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Debra L Irsik
- Charlie Norwood VA Medical Center Augusta GA USA.,Department of Neuroscience and Regenerative Medicine Augusta University Augusta GA USA
| | - Wendy B Bollag
- Charlie Norwood VA Medical Center Augusta GA USA.,Department of Physiology Augusta University Augusta GA USA
| | - Carlos M Isales
- Department of Neuroscience and Regenerative Medicine Augusta University Augusta GA USA.,Division of Endocrinology, Department of Medicine Augusta University Augusta GA USA
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13
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Abdrabbo M, Birch CM, Brandt M, Cicigoi KA, Coffey SJ, Dolan CC, Dvorak H, Gehrke AC, Gerzema AEL, Hansen A, Henseler EJ, Huelsbeck AC, LaBerge B, Leavens CM, Le CN, Lindquist AC, Ludwig RK, Reynolds JH, Severson NJ, Sherman BA, Sillman HW, Smith MA, Smith MA, Snortheim MJ, Svaren LM, Vanderpas EC, Wackett MJ, Wozney AJ, Bhattacharyya S, Hati S. Vitamin D and COVID-19: A review on the role of vitamin D in preventing and reducing the severity of COVID-19 infection. Protein Sci 2021; 30:2206-2220. [PMID: 34558135 PMCID: PMC8521296 DOI: 10.1002/pro.4190] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 09/18/2021] [Accepted: 09/21/2021] [Indexed: 12/12/2022]
Abstract
Severe Acute Respiratory Syndrome Coronavirus‐2 (SARS‐CoV‐2) is a pathogenic coronavirus causing COVID‐19 infection. The interaction between the SARS‐CoV‐2 spike protein and the human receptor angiotensin‐converting enzyme 2, both of which contain several cysteine residues, is impacted by the disulfide‐thiol balance in the host cell. The host cell redox status is affected by oxidative stress due to the imbalance between the reactive oxygen/nitrogen species and antioxidants. Recent studies have shown that Vitamin D supplementation could reduce oxidative stress. It has also been proposed that vitamin D at physiological concentration has preventive effects on many viral infections, including COVID‐19. However, the molecular‐level picture of the interplay of vitamin D deficiency, oxidative stress, and the severity of COVID‐19 has remained unclear. Herein, we present a thorough review focusing on the possible molecular mechanism by which vitamin D could alter host cell redox status and block viral entry, thereby preventing COVID‐19 infection or reducing the severity of the disease.
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Affiliation(s)
- Mobeen Abdrabbo
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Cole M Birch
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Michael Brandt
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Kelsey A Cicigoi
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Stephen J Coffey
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Connor C Dolan
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Hannah Dvorak
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Ava C Gehrke
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Audrey E L Gerzema
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Abby Hansen
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Ethan J Henseler
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Alyssa C Huelsbeck
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Ben LaBerge
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Caterra M Leavens
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Christine N Le
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Allison C Lindquist
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Rickaela K Ludwig
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Jacob H Reynolds
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Nathaniel J Severson
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Brandon A Sherman
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Hunter W Sillman
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Michael A Smith
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Macey A Smith
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Marissa J Snortheim
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Levi M Svaren
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Emily C Vanderpas
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Miles J Wackett
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Alec J Wozney
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Sudeep Bhattacharyya
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
| | - Sanchita Hati
- Department of Chemistry and Biochemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin, USA
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14
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Wagner CA. Coming out of the PiTs-novel strategies for controlling intestinal phosphate absorption in patients with CKD. Kidney Int 2021; 98:273-275. [PMID: 32709284 DOI: 10.1016/j.kint.2020.04.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 03/27/2020] [Accepted: 04/02/2020] [Indexed: 12/15/2022]
Abstract
The kidneys are the gatekeepers of phosphate balance, and loss of kidney function causes a profound disturbance of mineral metabolism. Patients with chronic kidney disease suffer from an excessive cardiovascular disease risk with a high morbidity and mortality. Current therapies aimed at reducing total phosphate body load are insufficient, and novel strategies are urgently needed. In this issue, Tsuboi and colleagues provide evidence for the use of a novel phosphate transporter inhibitor to reduce intestinal phosphate absorption.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland; National Center of Competence in Research (NCCR) Kidney Control of Homeostasis (Kidney.CH), University of Zurich, Zurich, Switzerland.
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15
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Tang X, Liu X, Liu H. Mechanisms of Epidermal Growth Factor Effect on Animal Intestinal Phosphate Absorption: A Review. Front Vet Sci 2021; 8:670140. [PMID: 34195248 PMCID: PMC8236626 DOI: 10.3389/fvets.2021.670140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 05/03/2021] [Indexed: 01/15/2023] Open
Abstract
Phosphorus is one of the essential mineral elements of animals that plays an important role in animal growth and development, bone formation, energy metabolism, nucleic acid synthesis, cell signal transduction, and blood acid–base balance. It has been established that the Type IIb sodium-dependent phosphate cotransporters (NaPi-IIb) protein is the major sodium-dependent phosphate (Pi) transporter, which plays an important role in Pi uptake across the apical membrane of epithelial cells in the small intestine. Previous studies have demonstrated that epidermal growth factor (EGF) is involved in regulating intestinal Pi absorption. Here we summarize the effects of EGF on active Pi transport of NaPi-IIb under different conditions. Under normal conditions, EGF inhibits the active transport of Pi by inhibiting the expression of NaPi-IIb, while, under intestinal injury condition, EGF promotes the active absorption of Pi through upregulating the expression of NaPi-IIb. This review provides a reference for information about EGF-regulatory functions in Pi absorption in the animal intestine.
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Affiliation(s)
- Xiaopeng Tang
- State Engineering Technology Institute for Karst Desertfication Control, School of Karst Science, Guizhou Normal University, Guiyang, China
| | - Xuguang Liu
- State Engineering Technology Institute for Karst Desertfication Control, School of Karst Science, Guizhou Normal University, Guiyang, China
| | - Hu Liu
- State Key Laboratory of Grassland Agro-Ecosystems, International Centre for Tibetan Plateau Ecosystem Management, Engineering Research Center of Arid Agriculture and Ecological Remediation of Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, China
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16
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Pastor-Arroyo EM, Rodriguez JMM, Pellegrini G, Bettoni C, Levi M, Hernando N, Wagner CA. Constitutive depletion of Slc34a2/NaPi-IIb in rats causes perinatal mortality. Sci Rep 2021; 11:7943. [PMID: 33846411 PMCID: PMC8042035 DOI: 10.1038/s41598-021-86874-z] [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: 12/10/2020] [Accepted: 03/15/2021] [Indexed: 11/23/2022] Open
Abstract
Absorption of dietary phosphate (Pi) across intestinal epithelia is a regulated process mediated by transcellular and paracellular pathways. Although hyperphosphatemia is a risk factor for the development of cardiovascular disease, the amount of ingested Pi in a typical Western diet is above physiological needs. While blocking intestinal absorption has been suggested as a therapeutic approach to prevent hyperphosphatemia, a complete picture regarding the identity and regulation of the mechanism(s) responsible for intestinal absorption of Pi is missing. The Na+/Pi cotransporter NaPi-IIb is a secondary active transporter encoded by the Slc34a2 gene. This transporter has a wide tissue distribution and within the intestinal tract is located at the apical membrane of epithelial cells. Based on mouse models deficient in NaPi-IIb, this cotransporter is assumed to mediate the bulk of active intestinal absorption of Pi. However, whether or not this is also applicable to humans is unknown, since human patients with inactivating mutations in SLC34A2 have not been reported to suffer from Pi depletion. Thus, mice may not be the most appropriate experimental model for the translation of intestinal Pi handling to humans. Here, we describe the generation of a rat model with Crispr/Cas-driven constitutive depletion of Slc34a2. Slc34a2 heterozygous rats were indistinguishable from wild type animals under standard dietary conditions as well as upon 3 days feeding on low Pi. However, unlike in humans, homozygosity resulted in perinatal lethality.
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Affiliation(s)
- Eva Maria Pastor-Arroyo
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Josep M Monné Rodriguez
- Laboratory for Animal Model Pathology (LAMP), Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 268, 8057, Zurich, Switzerland
| | - Giovanni Pellegrini
- Laboratory for Animal Model Pathology (LAMP), Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 268, 8057, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Moshe Levi
- Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, DC, USA
| | - Nati Hernando
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
| | - Carsten A Wagner
- Institute of Physiology, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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17
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Filipska I, Winiarska A, Knysak M, Stompór T. Contribution of Gut Microbiota-Derived Uremic Toxins to the Cardiovascular System Mineralization. Toxins (Basel) 2021; 13:toxins13040274. [PMID: 33920096 PMCID: PMC8070663 DOI: 10.3390/toxins13040274] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 02/07/2023] Open
Abstract
Chronic kidney disease (CKD) affects more than 10% of the world population and leads to excess morbidity and mortality (with cardiovascular disease as a leading cause of death). Vascular calcification (VC) is a phenomenon of disseminated deposition of mineral content within the media layer of arteries preceded by phenotypic changes in vascular smooth muscle cells (VSMC) and/or accumulation of mineral content within the atherosclerotic lesions. Medial VC results in vascular stiffness and significantly contributes to increased cardio-vascular (CV) morbidity, whereas VC of plaques may rather increase their stability. Mineral and bone disorders of CKD (CKD-MBD) contribute to VC, which is further aggravated by accumulation of uremic toxins. Both CKD-MBD and uremic toxin accumulation affect not only patients with advanced CKD (glomerular filtration rate (GFR) less than 15 mL/min/1.72 m2, end-stage kidney disease) but also those on earlier stages of a disease. The key uremic toxins that contribute to VC, i.e., p-cresyl sulphate (PCS), indoxyl sulphate (IS) and trimethylamine-N-oxide (TMAO) originate from bacterial metabolism of gut microbiota. All mentioned toxins promote VC by several mechanisms, including: Transdifferentiation and apoptosis of VSMC, dysfunction of endothelial cells, oxidative stress, interaction with local renin–angiotensin–aldosterone system or miRNA profile modification. Several attractive methods of gut microbiota manipulations have been proposed in order to modify their metabolism and to limit vascular damage (and VC) triggered by uremic toxins. Unfortunately, to date no such method was demonstrated to be effective at the level of “hard” patient-oriented or even clinically relevant surrogate endpoints.
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18
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Winiarska A, Filipska I, Knysak M, Stompór T. Dietary Phosphorus as a Marker of Mineral Metabolism and Progression of Diabetic Kidney Disease. Nutrients 2021; 13:789. [PMID: 33673618 PMCID: PMC7997399 DOI: 10.3390/nu13030789] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 02/22/2021] [Accepted: 02/24/2021] [Indexed: 12/31/2022] Open
Abstract
Phosphorus is an essential nutrient that is critically important in the control of cell and tissue function and body homeostasis. Phosphorus excess may result in severe adverse medical consequences. The most apparent is an impact on cardiovascular (CV) disease, mainly through the ability of phosphate to change the phenotype of vascular smooth muscle cells and its contribution to pathologic vascular, valvular and other soft tissue calcification. Chronic kidney disease (CKD) is the most prevalent chronic disease manifesting with the persistent derangement of phosphate homeostasis. Diabetes and resulting diabetic kidney disease (DKD) remain the leading causes of CKD and end-stage kidney disease (ESRD) worldwide. Mineral and bone disorders of CKD (CKD-MBD), profound derangement of mineral metabolism, develop in the course of the disease and adversely impact on bone health and the CV system. In this review we aimed to discuss the data concerning CKD-MBD in patients with diabetes and to analyze the possible link between hyperphosphatemia, certain biomarkers of CKD-MBD and high dietary phosphate intake on prognosis in patients with diabetes and DKD. We also attempted to clarify if hyperphosphatemia and high phosphorus intake may impact the onset and progression of DKD. Careful analysis of the available literature brings us to the conclusion that, as for today, no clear recommendations based on the firm clinical data can be provided in terms of phosphorus intake aiming to prevent the incidence or progression of diabetic kidney disease.
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Affiliation(s)
| | | | | | - Tomasz Stompór
- Department of Nephrology, Hypertension and Internal Medicine, University of Warmia and Mazury in Olsztyn, 10561 Olsztyn, Poland; (A.W.); (I.F.); (M.K.)
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19
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King AJ, Kohler J, Fung C, Jiang Z, Quach A, Kumaraswamy P, Chertow GM, Rosenbaum DP. Combination treatment with tenapanor and sevelamer synergistically reduces urinary phosphorus excretion in rats. Am J Physiol Renal Physiol 2021; 320:F133-F144. [PMID: 33283643 DOI: 10.1152/ajprenal.00137.2020] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 11/06/2020] [Accepted: 11/16/2020] [Indexed: 12/22/2022] Open
Abstract
The majority of patients with chronic kidney disease (CKD) receiving dialysis do not achieve target serum phosphorus concentrations, despite treatment with phosphate binders. Tenapanor is a nonbinder, sodium/hydrogen exchanger isoform 3 (NHE3) inhibitor that reduces paracellular intestinal phosphate absorption. This preclinical study evaluated the effect of tenapanor and varying doses of sevelamer carbonate on urinary phosphorus excretion, a direct reflection of intestinal phosphate absorption. We measured 24-h urinary phosphorus excretion in male rats assigned to groups dosed orally with vehicle or tenapanor (0.3 mg/kg/day) and provided a diet containing varying amounts of sevelamer [0-3% (wt/wt)]. We also evaluated the effect of the addition of tenapanor or vehicle on 24-h urinary phosphorus excretion to rats on a stable dose of sevelamer [1.5% (wt/wt)]. When administered together, tenapanor and sevelamer decreased urinary phosphorus excretion significantly more than either tenapanor or sevelamer alone across all sevelamer dose levels. The Bliss statistical model of independence indicated that the combination was synergistic. A stable sevelamer dose [1.5% (wt/wt)] reduced mean ± SE urinary phosphorus excretion by 42 ± 3% compared with vehicle; together, tenapanor and sevelamer reduced residual urinary phosphorus excretion by an additional 37 ± 6% (P < 0.05). Although both tenapanor and sevelamer reduce intestinal phosphate absorption individually, administration of tenapanor and sevelamer together results in more pronounced reductions in intestinal phosphate absorption than if either agent is administered alone. Further evaluation of combination tenapanor plus phosphate binder treatment in patients receiving dialysis with hyperphosphatemia is warranted.
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Affiliation(s)
| | | | - Cyra Fung
- Ardelyx, Incorporated, Fremont, California
| | | | | | | | - Glenn M Chertow
- Division of Nephrology, Stanford University School of Medicine, Stanford, California
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20
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Li S, De La Cruz J, Hutchens S, Mukhopadhyay S, Criss ZK, Aita R, Pellon-Cardenas O, Hur J, Soteropoulos P, Husain S, Dhawan P, Verlinden L, Carmeliet G, Fleet JC, Shroyer NF, Verzi MP, Christakos S. Analysis of 1,25-Dihydroxyvitamin D 3 Genomic Action Reveals Calcium-Regulating and Calcium-Independent Effects in Mouse Intestine and Human Enteroids. Mol Cell Biol 2020; 41:e00372-20. [PMID: 33139494 PMCID: PMC7849401 DOI: 10.1128/mcb.00372-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 10/05/2020] [Accepted: 10/24/2020] [Indexed: 01/27/2023] Open
Abstract
Although vitamin D is critical for the function of the intestine, most studies have focused on the duodenum. We show that transgenic expression of the vitamin D receptor (VDR) only in the distal intestine of VDR null mice (KO/TG mice) results in the normalization of serum calcium and rescue of rickets. Although it had been suggested that calcium transport in the distal intestine involves a paracellular process, we found that the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-activated genes in the proximal intestine associated with active calcium transport (Trpv6, S100g, and Atp2b1) are also induced by 1,25(OH)2D3 in the distal intestine of KO/TG mice. In addition, Slc30a10, encoding a manganese efflux transporter, was one of the genes most induced by 1,25(OH)2D3 in both proximal and distal intestine. Both villus and crypt were found to express Vdr and VDR target genes. RNA sequence (RNA-seq) analysis of human enteroids indicated that the effects of 1,25(OH)2D3 observed in mice are conserved in humans. Using Slc30a10-/- mice, a loss of cortical bone and a marked decrease in S100g and Trpv6 in the intestine was observed. Our findings suggest an interrelationship between vitamin D and intestinal Mn efflux and indicate the importance of distal intestinal segments to vitamin D action.
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Affiliation(s)
- Shanshan Li
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
| | - Jessica De La Cruz
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
| | - Steven Hutchens
- Division of Pharmacology and Toxicology, College of Pharmacy, Institute for Cellular and Molecular Biology and Institute for Neuroscience, The University of Texas at Austin, Austin, Texas, USA
| | - Somshuvra Mukhopadhyay
- Division of Pharmacology and Toxicology, College of Pharmacy, Institute for Cellular and Molecular Biology and Institute for Neuroscience, The University of Texas at Austin, Austin, Texas, USA
| | - Zachary K Criss
- Integrative Molecular and Biomedical Sciences Graduate Program, Division of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Rohit Aita
- Department of Genetics, Rutgers University, New Brunswick, New Jersey, USA
| | | | - Joseph Hur
- Department of Genetics, Rutgers University, New Brunswick, New Jersey, USA
| | - Patricia Soteropoulos
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
- Genomics Center, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
| | - Seema Husain
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
- Genomics Center, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
| | - Puneet Dhawan
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
- Genomics Center, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
| | - Lieve Verlinden
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, Leuven, Belgium
| | - Geert Carmeliet
- Laboratory of Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, Leuven, Belgium
| | - James C Fleet
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana, USA
| | - Noah F Shroyer
- Integrative Molecular and Biomedical Sciences Graduate Program, Division of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Michael P Verzi
- Department of Genetics, Rutgers University, New Brunswick, New Jersey, USA
| | - Sylvia Christakos
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, New Jersey, USA
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21
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Pastor‐Arroyo EM, Knöpfel T, Imenez Silva PH, Schnitzbauer U, Poncet N, Biber J, Wagner CA, Hernando N. Intestinal epithelial ablation of Pit-2/Slc20a2 in mice leads to sustained elevation of vitamin D 3 upon dietary restriction of phosphate. Acta Physiol (Oxf) 2020; 230:e13526. [PMID: 32564464 DOI: 10.1111/apha.13526] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/27/2020] [Accepted: 06/15/2020] [Indexed: 12/31/2022]
Abstract
AIM Several Na+ -dependent phosphate cotransporters, namely NaPi-IIb/SLC34A2, Pit-1/SLC20A1 and Pit-2/SLC20A2, are expressed at the apical membrane of enterocytes but their contribution to active absorption of phosphate is unclear. The aim of this study was to compare their pattern of mRNA expression along the small and large intestine and to analyse the effect of intestinal depletion of Pit-2 on phosphate homeostasis. METHODS Intestinal epithelial Pit-2-deficient mice were generated by crossing floxed Pit-2 with villin-Cre mice. Mice were fed 2 weeks standard or low phosphate diets. Stool, urine, plasma and intestinal and renal tissue were collected. Concentration of electrolytes and hormones, expression of mRNAs and proteins and intestinal transport of tracers were analysed. RESULTS Intestinal mRNA expression of NaPi-IIb and Pit-1 is segment-specific, whereas the abundance of Pit-2 mRNA is more homogeneous. In ileum, NaPi-IIb mRNA expression is restricted to enterocytes, whereas Pit-2 mRNA is found in epithelial and non-epithelial cells. Overall, their mRNA expression is not regulated by dietary phosphate. The absence of Pit-2 from intestinal epithelial cells does not affect systemic phosphate homeostasis under normal dietary conditions. However, in response to dietary phosphate restriction, Pit-2-deficient mice showed exacerbated hypercalciuria and sustained elevation of 1,25(OH)2 vitamin D3 . CONCLUSIONS In mice, the intestinal Na+ /phosphate cotransporters are not coexpressed in all segments. NaPi-IIb but not Pit-2 mRNA is restricted to epithelial cells. Intestinal epithelial Pit-2 does not contribute significantly to absorption of phosphate under normal dietary conditions. However, it may play a more significant role upon dietary phosphate restriction.
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Affiliation(s)
| | - Thomas Knöpfel
- Institute of Physiology University of Zürich Zürich Switzerland
| | | | | | - Nadège Poncet
- Institute of Physiology University of Zürich Zürich Switzerland
| | - Jürg Biber
- Institute of Physiology University of Zürich Zürich Switzerland
| | | | - Nati Hernando
- Institute of Physiology University of Zürich Zürich Switzerland
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22
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Abstract
Phosphate is an essential nutrient for life and is a critical component of bone formation, a major signaling molecule, and structural component of cell walls. Phosphate is also a component of high-energy compounds (i.e., AMP, ADP, and ATP) and essential for nucleic acid helical structure (i.e., RNA and DNA). Phosphate plays a central role in the process of mineralization, normal serum levels being associated with appropriate bone mineralization, while high and low serum levels are associated with soft tissue calcification. The serum concentration of phosphate and the total body content of phosphate are highly regulated, a process that is accomplished by the coordinated effort of two families of sodium-dependent transporter proteins. The three isoforms of the SLC34 family (SLC34A1-A3) show very restricted tissue expression and regulate intestinal absorption and renal excretion of phosphate. SLC34A2 also regulates the phosphate concentration in multiple lumen fluids including milk, saliva, pancreatic fluid, and surfactant. Both isoforms of the SLC20 family exhibit ubiquitous expression (with some variation as to which one or both are expressed), are regulated by ambient phosphate, and likely serve the phosphate needs of the individual cell. These proteins exhibit similarities to phosphate transporters in nonmammalian organisms. The proteins are nonredundant as mutations in each yield unique clinical presentations. Further research is essential to understand the function, regulation, and coordination of the various phosphate transporters, both the ones described in this review and the phosphate transporters involved in intracellular transport.
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Affiliation(s)
- Nati Hernando
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Kenneth Gagnon
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
| | - Eleanor Lederer
- University of Zurich-Irchel, Institute of Physiology, Zurich, Switzerland; Department of Medicine, University of Louisville School of Medicine, Louisville, Kentucky; and Robley Rex VA Medical Center, Louisville, Kentucky
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Tay-Zar AC, Srichana P, Sadiq MB, Anal AK. Restriction of dietary non-phytate phosphorus on growth performance and expression of intestinal phosphate cotransporter genes in broilers. Poult Sci 2019; 98:4685-4693. [PMID: 30982064 DOI: 10.3382/ps/pez171] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 03/13/2019] [Indexed: 11/20/2022] Open
Abstract
Effects of dietary non-phytate phosphorus (nPP) restriction on growth and duodenal type IIb sodium-dependent phosphate cotransporter (NaPi-IIb) genes were observed. A total of 432 one-day old Cobb500 male broiler chickens in 36 cage pens were divided into 6 groups with each group containing 6 pens. Each group was treated with one of the diets containing 0.33, 0.37, 0.41, 0.45, 0.49, and 0.53% of nPP up to 14 D. During 15 to 31 D, birds were treated with one of the diets containing 0.23, 0.27, 0.31, 0.35, 0.39, and 0.43% of nPP. Level of Ca was kept the same across all treatments. Dietary nPP level influenced (P < 0.001) weight gain and feed intake in both growth phases, whereas effect on feed per gain ratio was seen only in the second phase. Toe ash, tibia ash, and tibia breaking strength responded to treatments (P < 0.01) at 14 D. Only tibia ash content was significantly improved (P < 0.001) at 31 D. Growth and bone parameters linearly improved with an increase in dietary nPP content (P < 0.05). Above dietary nPP 0.41% and 0.31% for first phase and second phase, respectively, no significant improvement was seen. Duodenal NaPi-IIb mRNA overexpressed with a decrease in dietary nPP in both phases (P < 0.05). Relative expression of NaPi-IIb in lowest nPP group were 2.2 folds higher in the first phase and 3.6 folds higher in the second phase compared to respective highest nPP groups of each phase. No significant change in NaPi-IIb expression was seen above 0.37% of dietary nPP for 14 D and 0.31% of dietary nPP for 31 D. Dietary requirements of nPP 0.41% for 0 to 14 D and 0.31% for 15 to 31 D were adequate for optimal growth and bone parameters. This study fills the gap in understanding of intestinal NaPi-IIb expression in response to dietary nPP restriction in broilers older than 21 D of age.
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Affiliation(s)
- Aye Cho Tay-Zar
- Department of Food, Agriculture and BioResources, Asian Institute of Technology, Klong Luang 12120, Thailand
| | - Pairat Srichana
- Feed Technology Department, Charoen Pokphand Group, Bangrak, Bangkok 10500, Thailand
| | - Muhammad Bilal Sadiq
- Department of Food, Agriculture and BioResources, Asian Institute of Technology, Klong Luang 12120, Thailand
| | - Anil Kumar Anal
- Department of Food, Agriculture and BioResources, Asian Institute of Technology, Klong Luang 12120, Thailand
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Daryadel A, Natale L, Seebeck P, Bettoni C, Schnitzbauer U, Gassmann M, Wagner CA. Elevated FGF23 and disordered renal mineral handling with reduced bone mineralization in chronically erythropoietin over-expressing transgenic mice. Sci Rep 2019; 9:14989. [PMID: 31628396 PMCID: PMC6802194 DOI: 10.1038/s41598-019-51577-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 09/09/2019] [Indexed: 12/22/2022] Open
Abstract
Fibroblast Growth Factor 23 (FGF23) is a phosphaturic factor causing increased renal phosphate excretion as well as suppression of 1,25 (OH)2-vitamin D3. Highly elevated FGF23 can promote development of rickets and osteomalacia. We and others previously reported that acute application of erythropoietin (EPO) stimulates FGF23 production. Considering that EPO is clinically used as chronic treatment against anemia, we used here the Tg6 mouse model that constitutively overexpresses human EPO in an oxygen-independent manner, to examine the consequences of long-term EPO therapy on mineral and bone metabolism. Six to eight weeks old female Tg6 mice showed elevated intact and C-terminal fragment of FGF23 but normal plasma levels of PTH, calcitriol, calcium and phosphate. Renal function showed moderate alterations with higher urea and creatinine clearance and mild albuminuria. Renal phosphate excretion was normal whereas mild hypercalciuria was found. Renal expression of the key proteins TRPV5 and calbindin D28k involved in active calcium reabsorption was reduced in Tg6 mice. Plasma levels of the bone turnover marker osteocalcin were comparable between groups. However, urinary excretion of deoxypyridinoline (DPD) was lower in Tg6 mice. MicroCT analysis showed reduced total, cortical, and trabecular bone mineral density in femora from Tg6 mice. Our data reveal that chronic elevation of EPO is associated with high FGF23 levels and disturbed mineral homeostasis resulting in reduced bone mineral density. These observations imply the need to study the impact of therapeutically applied EPO on bone mineralization in patients, especially those suffering from chronic kidney disease.
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Affiliation(s)
- Arezoo Daryadel
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,National Centre for Competence in Research NCCR "Kidney.CH", Zurich, Switzerland
| | - Luciano Natale
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Petra Seebeck
- Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,Zurich Integrative Rodent Physiology (ZIRP), University of Zurich, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,National Centre for Competence in Research NCCR "Kidney.CH", Zurich, Switzerland
| | - Udo Schnitzbauer
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,National Centre for Competence in Research NCCR "Kidney.CH", Zurich, Switzerland
| | - Max Gassmann
- Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland.,Universidad Peruana Cayetano Heredia (UPCH), Lima, Peru
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland. .,Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland. .,National Centre for Competence in Research NCCR "Kidney.CH", Zurich, Switzerland.
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Knöpfel T, Himmerkus N, Günzel D, Bleich M, Hernando N, Wagner CA. Paracellular transport of phosphate along the intestine. Am J Physiol Gastrointest Liver Physiol 2019; 317:G233-G241. [PMID: 31169994 DOI: 10.1152/ajpgi.00032.2019] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Inorganic phosphate (Pi) is crucial for many biological functions, such as energy metabolism, signal transduction, and pH buffering. Efficient systems must exist to ensure sufficient supply for the body of Pi from diet. Previous experiments in humans and rodents suggest that two pathways for the absorption of Pi exist, an active transcellular Pi transport and a second paracellular pathway. Whereas the identity, role, and regulation of active Pi transport have been extensively studied, much less is known about the properties of the paracellular pathway. In Ussing chamber experiments, we characterized paracellular intestinal Pi permeabilities and fluxes. Dilution potential measurements in intestinal cell culture models demonstrated that the tight junction is permeable to Pi, with monovalent Pi having a higher permeability than divalent Pi. These findings were confirmed in rat and mouse intestinal segments by use of Ussing chambers and a combination of dilution potential measurements and fluxes of radiolabeled 32Pi. Both techniques yielded very similar results, showing that paracellular Pi fluxes were bidirectional and that Pi permeability was ~50% of the permeability for Na+ or Cl-. Pi fluxes were a function of the concentration gradient and Pi species (mono- vs. divalent Pi). In mice lacking the active transcellular Pi transport component sodium-dependent Pi transporter NaPi-IIb, the paracellular pathway was not upregulated. In summary, the small and large intestines have a very high paracellular Pi permeability, which may favor monovalent Pi fluxes and allow efficient uptake of Pi even in the absence of active transcellular Pi uptake.NEW & NOTEWORTHY The paracellular permeability for phosphate is high along the entire axis of the small and large intestine. There is a slight preference for monovalent phosphate. Paracellular phosphate fluxes do not increase when transcellular phosphate transport is genetically abolished. Paracellular phosphate transport may be an important target for therapies aiming to reduce intestinal phosphate absorption.
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Affiliation(s)
- Thomas Knöpfel
- University of Zürich, Institute of Physiology, Zürich, Switzerland
| | - Nina Himmerkus
- Christian-Albrechts-Universität zu Kiel, Physiologisches Institut, Kiel, Germany
| | - Dorothee Günzel
- Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Institut für Klinische Physiologie, Berlin, Germany
| | - Markus Bleich
- Christian-Albrechts-Universität zu Kiel, Physiologisches Institut, Kiel, Germany
| | - Nati Hernando
- University of Zürich, Institute of Physiology, Zürich, Switzerland
| | - Carsten A Wagner
- University of Zürich, Institute of Physiology, Zürich, Switzerland
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Wagner CA, Rubio-Aliaga I, Hernando N. Renal phosphate handling and inherited disorders of phosphate reabsorption: an update. Pediatr Nephrol 2019; 34:549-559. [PMID: 29275531 DOI: 10.1007/s00467-017-3873-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 12/08/2017] [Accepted: 12/12/2017] [Indexed: 01/12/2023]
Abstract
Renal phosphate handling critically determines plasma phosphate and whole body phosphate levels. Filtered phosphate is mostly reabsorbed by Na+-dependent phosphate transporters located in the brush border membrane of the proximal tubule: NaPi-IIa (SLC34A1), NaPi-IIc (SLC34A3), and Pit-2 (SLC20A2). Here we review new evidence for the role and relevance of these transporters in inherited disorders of renal phosphate handling. The importance of NaPi-IIa and NaPi-IIc for renal phosphate reabsorption and mineral homeostasis has been highlighted by the identification of mutations in these transporters in a subset of patients with infantile idiopathic hypercalcemia and patients with hereditary hypophosphatemic rickets with hypercalciuria. Both diseases are characterized by disturbed calcium homeostasis secondary to elevated 1,25-(OH)2 vitamin D3 as a consequence of hypophosphatemia. In vitro analysis of mutated NaPi-IIa or NaPi-IIc transporters suggests defective trafficking underlying disease in most cases. Monoallelic pathogenic mutations in both SLC34A1 and SLC34A3 appear to be very frequent in the general population and have been associated with kidney stones. Consistent with these findings, results from genome-wide association studies indicate that variants in SLC34A1 are associated with a higher risk to develop kidney stones and chronic kidney disease, but underlying mechanisms have not been addressed to date.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. .,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland.
| | - Isabel Rubio-Aliaga
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.,National Center for Competence in Research (NCCR) Kidney.CH, Zurich, Switzerland
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Lederer E, Wagner CA. Clinical aspects of the phosphate transporters NaPi-IIa and NaPi-IIb: mutations and disease associations. Pflugers Arch 2018; 471:137-148. [DOI: 10.1007/s00424-018-2246-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 12/05/2018] [Indexed: 12/12/2022]
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Abstract
Inorganic phosphate (Pi) is essential for signal transduction and cell metabolism, and is also an essential structural component of the extracellular matrix of the skeleton. Pi is sensed in bacteria and yeast at the plasma membrane, which activates intracellular signal transduction to control the expression of Pi transporters and other genes that control intracellular Pi levels. In multicellular organisms, Pi homeostasis must be maintained in the organism and at the cellular level, requiring an endocrine and metabolic Pi-sensing mechanism, about which little is currently known. This Review will discuss the metabolic effects of Pi, which are mediated by Pi transporters, inositol pyrophosphates and SYG1-Pho81-XPR1 (SPX)-domain proteins to maintain cellular phosphate homeostasis in the musculoskeletal system. In addition, we will discuss how Pi is sensed by the human body to regulate the production of fibroblast growth factor 23 (FGF23), parathyroid hormone and calcitriol to maintain serum levels of Pi in a narrow range. New findings on the crosstalk between iron and Pi homeostasis in the regulation of FGF23 expression will also be outlined. Mutations in components of these metabolic and endocrine phosphate sensors result in genetic disorders of phosphate homeostasis, cardiomyopathy and familial basal ganglial calcifications, highlighting the importance of this newly emerging area of research.
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Affiliation(s)
- Sampada Chande
- Section of Endocrinology and Metabolism, Yale University School of Medicine, New Haven, CT, USA
| | - Clemens Bergwitz
- Section of Endocrinology and Metabolism, Yale University School of Medicine, New Haven, CT, USA.
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Marks J. The role of SLC34A2 in intestinal phosphate absorption and phosphate homeostasis. Pflugers Arch 2018; 471:165-173. [PMID: 30343332 PMCID: PMC6325986 DOI: 10.1007/s00424-018-2221-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 12/13/2022]
Abstract
There has recently been significant interest in the concept of directly targeting intestinal phosphate transport to control hyperphosphatemia in patients with chronic kidney disease. However, we do not have a complete understanding of the cellular mechanisms that govern dietary phosphate absorption. Studies in the 1970s documented both active and passive pathways for intestinal phosphate absorption. However, following the cloning of the intestinal SLC34 cotransporter, NaPi-IIb, much of the research focused on the role of this protein in active transcellular phosphate absorption and the factors involved in its regulation. Generation of a conditional NaPi-IIb knockout mouse has demonstrated that this protein is critical for the maintenance of skeletal integrity during periods of phosphate restriction and that under normal physiological conditions, the passive sodium-independent pathway is likely be the more dominant pathway for intestinal phosphate absorption. The review aims to summarise the most recent developments in our understanding of the role of the intestine in phosphate homeostasis, including the acute and chronic renal adaptations that occur in response to dietary phosphate intake. Evidence regarding the overall contribution of the transcellular and paracellular pathways for phosphate absorption will be discussed, together with the clinical benefit of inhibiting these pathways for the treatment of hyperphosphatemia in chronic kidney disease.
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Affiliation(s)
- Joanne Marks
- Department of Neuroscience, Physiology and Pharmacology, Royal Free Campus, University College London, Rowland Hill Street, London, NW3 2PF, UK.
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Hernando N, Wagner CA. Mechanisms and Regulation of Intestinal Phosphate Absorption. Compr Physiol 2018; 8:1065-1090. [PMID: 29978897 DOI: 10.1002/cphy.c170024] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
States of hypo- and hyperphosphatemia have deleterious consequences including rickets/osteomalacia and renal/cardiovascular disease, respectively. Therefore, the maintenance of appropriate plasma levels of phosphate is an essential requirement for health. This control is executed by the collaborative action of intestine and kidney whose capacities to (re)absorb phosphate are regulated by a number of hormonal and metabolic factors, among them parathyroid hormone, fibroblast growth factor 23, 1,25(OH)2 vitamin D3 , and dietary phosphate. The molecular mechanisms responsible for the transepithelial transport of phosphate across enterocytes are only partially understood. Indeed, whereas renal reabsorption entirely relies on well-characterized active transport mechanisms of phosphate across the renal proximal epithelia, intestinal absorption proceeds via active and passive mechanisms, with the molecular identity of the passive component still unknown. The active absorption of phosphate depends mostly on the activity and expression of the sodium-dependent phosphate cotransporter NaPi-IIb (SLC34A2), which is highly regulated by many of the factors, mentioned earlier. Physiologically, the contribution of NaPi-IIb to the maintenance of phosphate balance appears to be mostly relevant during periods of low phosphate availability. Therefore, its role in individuals living in industrialized societies with high phosphate intake is probably less relevant. Importantly, small increases in plasma phosphate, even within normal range, associate with higher risk of cardiovascular disease. Therefore, therapeutic approaches to treat hyperphosphatemia, including dietary phosphate restriction and phosphate binders, aim at reducing intestinal absorption. Here we review the current state of research in the field. © 2017 American Physiological Society. Compr Physiol 8:1065-1090, 2018.
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Affiliation(s)
- Nati Hernando
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
| | - Carsten A Wagner
- National Center for Competence in Research NCCR Kidney.CH, Institute of Physiology, University Zurich-Irchel, Zurich, Switzerland
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Patent Highlights February-March 2018. Pharm Pat Anal 2018; 7:147-154. [PMID: 29882729 DOI: 10.4155/ppa-2018-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research development.
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