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Cladis DP, Burstad KM, Biruete A, Jannasch AH, Cooper BR, Hill Gallant KM. Dietary Phosphorus Levels Influence Protein-Derived Uremic Toxin Production in Nephrectomized Male Rats. Nutrients 2024; 16:1807. [PMID: 38931160 PMCID: PMC11207110 DOI: 10.3390/nu16121807] [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: 05/20/2024] [Revised: 06/05/2024] [Accepted: 06/06/2024] [Indexed: 06/28/2024] Open
Abstract
Gut microbiota-derived uremic toxins (UT) accumulate in patients with chronic kidney disease (CKD). Dietary phosphorus and protein restriction are common in CKD treatment, but the relationship between dietary phosphorus, a key nutrient for the gut microbiota, and protein-derived UT is poorly studied. Thus, we explored the relationship between dietary phosphorus and serum UT in CKD rats. For this exploratory study, we used serum samples from a larger study on the effects of dietary phosphorus on intestinal phosphorus absorption in nephrectomized (Nx, n = 22) or sham-operated (sham, n = 18) male Sprague Dawley rats. Rats were randomized to diet treatment groups of low or high phosphorus (0.1% or 1.2% w/w, respectively) for 1 week, with serum trimethylamine oxide (TMAO), indoxyl sulfate (IS), and p-cresol sulfate (pCS) analyzed by LC-MS. Nx rats had significantly higher levels of serum TMAO, IS, and pCS compared to sham rats (all p < 0.0001). IS showed a significant interaction between diet and CKD status, where serum IS was higher with the high-phosphorus diet in both Nx and sham rats, but to a greater extent in the Nx rats. Serum TMAO (p = 0.24) and pCS (p = 0.34) were not affected by dietary phosphorus levels. High dietary phosphorus intake for 1 week results in higher serum IS in both Nx and sham rats. The results of this exploratory study indicate that reducing dietary phosphorus intake in CKD may have beneficial effects on UT accumulation.
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Affiliation(s)
- Dennis P. Cladis
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA; (D.P.C.); (K.M.B.)
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA;
- Department of Food Science and Technology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA
| | - Kendal M. Burstad
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA; (D.P.C.); (K.M.B.)
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA;
| | - Annabel Biruete
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA;
- Department of Nutrition and Dietetics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
- Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Amber H. Jannasch
- Bindley Bioscience Center, Purdue University, West Lafayette, IN 47906, USA; (A.H.J.); (B.R.C.)
| | - Bruce R. Cooper
- Bindley Bioscience Center, Purdue University, West Lafayette, IN 47906, USA; (A.H.J.); (B.R.C.)
| | - Kathleen M. Hill Gallant
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA; (D.P.C.); (K.M.B.)
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA;
- Division of Nephrology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Saito T, Ichimura Y, Oda M, Saitoh H. Preferential meropenem absorption activated by 1α,25-dihydroxyvitamin D 3 and shared with foscarnet, a phosphate transporter substrate, in the rat ileum. Drug Metab Pharmacokinet 2024; 55:100997. [PMID: 38367298 DOI: 10.1016/j.dmpk.2024.100997] [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: 10/03/2023] [Revised: 12/24/2023] [Accepted: 01/09/2024] [Indexed: 02/19/2024]
Abstract
Meropenem (MEPM) is used for the treatment of serious infectious diseases solely as. INJECTABLE: Therefore, the development of an oral formulation would expand its clinical utility. To this end, an exact understanding of the absorption characteristics of MEPM is essential. In this study, MEPM absorption in the rat small intestine was investigated using an in situ loop technique and an in vitro diffusion chamber method. The disappearance ratios of MEPM (0.1 mM) were in the order of ileum > duodenum > jejunum. The extensive MEPM disappearance in the ileum was significantly reduced in the presence of foscarnet, a Na+-dependent phosphate transporter (NaPi-T) substrate, whereas glycylsarcosine, thiamine, taurocholic acid, and biapenem had no effects. The mucosal-to-serosal (M-to-S) permeation of MEPM across the rat ileal segments was very small under normal experimental conditions. However, on addition of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) to the experimental medium, the M-to-S permeation of MEPM markedly increased, showing a more than 7-fold greater apparent permeation coefficient. The present results suggest that MEPM is preferentially absorbed in the rat ileum, sharing with foscarnet, and that 1,25(OH)2D3 potentially activates the absorption of MEPM there. A likely candidate for involvement in MEPM absorption was NaPi-T or a related transporter.
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Affiliation(s)
- Toshihide Saito
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari, Tobetsu, Hokkaido, 061-0293, Japan
| | - Yuichi Ichimura
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari, Tobetsu, Hokkaido, 061-0293, Japan
| | - Masako Oda
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari, Tobetsu, Hokkaido, 061-0293, Japan
| | - Hiroshi Saitoh
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari, Tobetsu, Hokkaido, 061-0293, Japan.
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Turner ME, Beck L, Hill Gallant KM, Chen Y, Moe OW, Kuro-o M, Moe S, Aikawa E. Phosphate in Cardiovascular Disease: From New Insights Into Molecular Mechanisms to Clinical Implications. Arterioscler Thromb Vasc Biol 2024; 44:584-602. [PMID: 38205639 PMCID: PMC10922848 DOI: 10.1161/atvbaha.123.319198] [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] [Indexed: 01/12/2024]
Abstract
Hyperphosphatemia is a common feature in patients with impaired kidney function and is associated with increased risk of cardiovascular disease. This phenomenon extends to the general population, whereby elevations of serum phosphate within the normal range increase risk; however, the mechanism by which this occurs is multifaceted, and many aspects are poorly understood. Less than 1% of total body phosphate is found in the circulation and extracellular space, and its regulation involves multiple organ cross talk and hormones to coordinate absorption from the small intestine and excretion by the kidneys. For phosphate to be regulated, it must be sensed. While mostly enigmatic, various phosphate sensors have been elucidated in recent years. Phosphate in the circulation can be buffered, either through regulated exchange between extracellular and cellular spaces or through chelation by circulating proteins (ie, fetuin-A) to form calciprotein particles, which in themselves serve a function for bulk mineral transport and signaling. Either through direct signaling or through mediators like hormones, calciprotein particles, or calcifying extracellular vesicles, phosphate can induce various cardiovascular disease pathologies: most notably, ectopic cardiovascular calcification but also left ventricular hypertrophy, as well as bone and kidney diseases, which then propagate phosphate dysregulation further. Therapies targeting phosphate have mostly focused on intestinal binding, of which appreciation and understanding of paracellular transport has greatly advanced the field. However, pharmacotherapies that target cardiovascular consequences of phosphate directly, such as vascular calcification, are still an area of great unmet medical need.
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Affiliation(s)
- Mandy E. Turner
- Division of Cardiovascular Medicine, Department of Medicine, Center for Interdisciplinary Cardiovascular Sciences, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Laurent Beck
- Nantes Université, CNRS, Inserm, l’institut du thorax, F-44000 Nantes, France
| | - Kathleen M Hill Gallant
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota, USA
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Yabing Chen
- Department of Pathology, University of Alabama at Birmingham
- Research Department, Veterans Affairs Birmingham Medical Center, Birmingham, AL, USA
| | - Orson W Moe
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Makoto Kuro-o
- Division of Anti-aging Medicine, Center for Molecular Medicine, Jichi Medical University 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan
| | - Sharon Moe
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Elena Aikawa
- Division of Cardiovascular Medicine, Department of Medicine, Center for Interdisciplinary Cardiovascular Sciences, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
- Division of Cardiovascular Medicine, Department of Medicine, Center for Excellence in Vascular Biology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
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Wang X, Yu X, Gavardinas K, Dey A, Zhang HY, Porter G, Porras L, Yu L, Guo H, Reidy CA, Haas JV, Xu Y, Kowala MC, Jadhav PK, Wetterau JR. Effect of an NHE3 inhibitor in combination with an NPT2b inhibitor on gastrointestinal phosphate absorption in Rodent models. PLoS One 2024; 19:e0292091. [PMID: 38277356 PMCID: PMC10817170 DOI: 10.1371/journal.pone.0292091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 09/12/2023] [Indexed: 01/28/2024] Open
Abstract
Many of the pathological consequences of chronic kidney disease can be attributed to an elevation in serum phosphate levels. Current therapies focused on decreasing intestinal phosphate absorption to treat hyperphosphatemia are inadequate. The most effective therapeutic strategy may be to target multiple absorptive pathways. In this study, the ability of a novel inhibitor of the intestinal sodium hydrogen exchanger 3 (NHE3), LY3304000, which inhibits paracellular, diffusional uptake of phosphate, to work in combination with an inhibitor of the active transporter, sodium dependent phosphate cotransporter 2b (NPT2b), LY3358966, was explored. LY3304000 modestly inhibited the acute uptake of phosphate into plasma of rats, while surprisingly, it doubled the rate of phosphate uptake in mice, an animal model dominated by NPT2b mediated acute phosphate uptake. In rats, LY3004000 and LY3358966 work in concert to inhibit acute phosphate uptake. On top of LY3358966, LY3304000 further decreased the acute uptake of phosphate into plasma. Studies measuring the recovery of radiolabeled phosphate in the intestine demonstrated LY3304000 and LY3358966 synergistically inhibited the absorption of phosphate in rats. We hypothesize the synergism is because the NHE3 inhibitor, LY3304000, has two opposing effects on intestinal phosphate absorption in rats, first it decreases diffusion mediated paracellular phosphate absorption, while second, it simultaneously increases phosphate absorption through the NPT2b pathway. NHE3 inhibition decreases proton export from enterocytes and raises the cell surface pH. In vitro, NPT2b mediated phosphate transport is increased at higher pHs. The increased NPT2b mediated transport induced by NHE3 inhibition is masked in rats which have relatively low levels of NPT2b mediated phosphate transport, by the more robust inhibition of diffusion mediated phosphate absorption. Thus, the inhibition of NPT2b mediated phosphate transport in rats in the presence of NHE3 inhibition has an effect that exceeds its effect in the absence of NHE3 inhibition, leading to the observed synergism on phosphate absorption between NPT2b and NHE3 inhibition.
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Affiliation(s)
- Xiaojun Wang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Xiaohong Yu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Kostas Gavardinas
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Asim Dey
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Hong Y. Zhang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Gina Porter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Leah Porras
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Lan Yu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Haihong Guo
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Charles A. Reidy
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Joseph V. Haas
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Yanping Xu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Mark C. Kowala
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - Prabhakar K. Jadhav
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
| | - John R. Wetterau
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, United States of America
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5
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Lucea S, Chopo-Escuin G, Guillén N, Sosa C, Sorribas V. Intestinal and Renal Adaptations to Changes of Dietary Phosphate Concentrations in Rat. FUNCTION 2023; 5:zqad063. [PMID: 38033458 PMCID: PMC10686248 DOI: 10.1093/function/zqad063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 11/05/2023] [Accepted: 11/07/2023] [Indexed: 12/02/2023] Open
Abstract
We have studied the role of the intestine, kidney, and several hormones when adapting to changes in dietary P concentration. Normal and parathyroidectomized (PTX) rats were fed pH-matched diets containing 0.1%, 0.6%, and 1.2% P concentrations. 32Pi uptake was determined in the jejunum and kidney cortex brush border membrane vesicles. Several hormone and ion concentrations were determined in the blood and urine of rats. Both jejunum and kidney cortex Pi transport was regulated with 5 d of chronic feeding of P diets in normal rats. Acute adaptation was determined by switching foods on day 6, which was only clearly observed in the kidney cortex of normal rats, with more statistical variability in the jejunum. However, no paradoxical increase of Pi uptake in the jejunum was reproduced after the acute switch to the 1.2% P diet. Pi uptake in the jejunum was parathyroid hormone (PTH)-independent, but in the kidney, the chronic adaptation was reduced, and no acute dietary adaptations were observed. The NaPi2a protein was more abundant in the PTX than the sham kidneys, but contrary to the modest or absent changes in Pi uptake adaptation, the transporter was similarly regulated by dietary P, as in the sham rats. PTH and fibroblast growth factor 23 (FGF23) were the only hormones regulated by all diet changes, even in fasting animals, which exhibited regulated Pi transport despite similar phosphatemia. Evidence of Pi appetite effects was also observed. In brief, our results show new characteristics of Pi adaptations, including a lack of correlation between Pi transport, NaPi2a expression, and PTH/FGF23 concentrations.
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Affiliation(s)
- Susana Lucea
- Laboratory of Molecular Toxicology, Department of Biochemistry and Cell and Molecular Biology, University of Zaragoza, E50013 Zaragoza, Spain
| | - Gema Chopo-Escuin
- Laboratory of Molecular Toxicology, Department of Biochemistry and Cell and Molecular Biology, University of Zaragoza, E50013 Zaragoza, Spain
| | - Natalia Guillén
- Laboratory of Molecular Toxicology, Department of Biochemistry and Cell and Molecular Biology, University of Zaragoza, E50013 Zaragoza, Spain
| | - Cecilia Sosa
- Laboratory of Molecular Toxicology, Department of Biochemistry and Cell and Molecular Biology, University of Zaragoza, E50013 Zaragoza, Spain
| | - Víctor Sorribas
- Laboratory of Molecular Toxicology, Department of Biochemistry and Cell and Molecular Biology, University of Zaragoza, E50013 Zaragoza, Spain
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6
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Burstad KM, Cladis DP, Vorland CJ, Wastney ME, Biruete A, Dominguez JM, O'Neill KD, Chen NX, Moe SM, Hill Gallant KM. Acute High Dietary Phosphorus Following Low-Phosphorus Diet Acclimation Does Not Enhance Intestinal Fractional Phosphorus Absorption in Nephrectomized Male Rats. JBMR Plus 2022; 6:e10698. [PMID: 36530183 PMCID: PMC9751657 DOI: 10.1002/jbm4.10698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 10/05/2022] [Accepted: 10/27/2022] [Indexed: 05/21/2024] Open
Abstract
Dietary phosphorus restriction and phosphorus binders are commonly prescribed for patients with chronic kidney disease (CKD). However, occurrences of non-adherence to these interventions are common. As low-phosphorus (LP) diets have been consistently experimentally shown in vitro to increase intestinal phosphorus absorption efficiency, a bout of non-adherence to diet or binders may cause an unintended consequence of enhanced intestinal phosphorus absorption. Thus, we aimed to determine the effect of a single bout of high-phosphorus (HP) intake after acclimation to a LP diet. Male Sprague Dawley rats with 5/6 nephrectomy (n = 36) or sham operation (n = 36) were block-randomized to 1 of 3 diets: LP (0.1% P w/w), HP (1.2%), or LP followed by acute HP (LPHP 0.1% then 1.2%). Phosphorus absorption tests were conducted using 33P radioisotope administrated by oral gavage or intravenously (iv). Although the overall two-way ANCOVA model for intestinal fractional phosphorus absorption was non-significant, exploratory comparisons showed intestinal fractional phosphorus absorption efficiency tended to be higher in rats in the LP compared with HP or LPHP groups. Rats in the HP or LPHP groups had higher plasma phosphorus compared with rats in the LP group, but the LPHP group was not different from the HP group. Gene expression of the major intestinal phosphate transporter, NaPi-2b, was lower in the jejunum of rats in the LPHP group compared with rats in the HP group but not different in the duodenum. These results demonstrate that an acute HP load after acclimation to a LP diet does not lead to enhanced intestinal fractional phosphorus absorption efficiency in 5/6 nephrectomized male rats. These data provide evidence against the notion that dietary phosphorus restriction or binder use adversely increases absorption efficiency after a single instance of dietary or binder non-adherence. However, other adverse consequences of fluctuating dietary phosphorus intake cannot be ruled out. © 2022 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)
- Kendal M Burstad
- Department of Food Science and NutritionUniversity of MinnesotaSaint PaulMNUSA
- Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA
| | - Dennis P Cladis
- Department of Food Science and NutritionUniversity of MinnesotaSaint PaulMNUSA
- Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA
| | - Colby J Vorland
- Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA
- Department of Applied Health ScienceIndiana University School of Public Health‐BloomingtonBloomingtonINUSA
| | - Meryl E Wastney
- Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA
| | - Annabel Biruete
- Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA
- Department of Medicine‐Division of NephrologyIndiana University School of MedicineIndianapolisINUSA
- Department of Nutrition and DieteticsIndiana University‐Purdue University IndianapolisIndianapolisINUSA
| | - James M Dominguez
- Department of Medicine‐Division of NephrologyIndiana University School of MedicineIndianapolisINUSA
| | - Kalisha D O'Neill
- Department of Medicine‐Division of NephrologyIndiana University School of MedicineIndianapolisINUSA
| | - Neal X Chen
- Department of Medicine‐Division of NephrologyIndiana University School of MedicineIndianapolisINUSA
| | - Sharon M Moe
- Department of Medicine‐Division of NephrologyIndiana University School of MedicineIndianapolisINUSA
- Department of Anatomy and Cell BiologyIndiana University School of MedicineIndianapolisINUSA
- Department of MedicineRoudebush Veterans Affairs Medicine CenterIndianapolisINUSA
| | - Kathleen M Hill Gallant
- Department of Food Science and NutritionUniversity of MinnesotaSaint PaulMNUSA
- Department of Nutrition SciencePurdue UniversityWest LafayetteINUSA
- Department of Medicine‐Division of NephrologyIndiana University School of MedicineIndianapolisINUSA
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Li C, Cai H, Li S, Liu G, Deng X, Bryden WL, Zheng A. Comparing the potential of Bacillus amyloliquefaciens CGMCC18230 with antimicrobial growth promoters for growth performance, bone development, expression of phosphorus transporters, and excreta microbiome in broiler chickens. Poult Sci 2022; 101:102126. [PMID: 36099660 PMCID: PMC9474562 DOI: 10.1016/j.psj.2022.102126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 07/21/2022] [Accepted: 08/03/2022] [Indexed: 11/09/2022] Open
Abstract
Bone health of broiler chickens is essential for welfare and production. In this study, the probiotic Bacillus amyloliquefaciens (BA) CGMCC18230 was compared with antimicrobial growth promoters (AGPs) for its ability to promote growth and bone health. To address this, a total of 180 Arbor Acres (AA) 1-day-old, male, broiler chicks were randomly allocated into 3 treatment groups, with 6 replicates, containing 10 chicks in each replicate. The treatment groups were: control group (CON) fed a corn-soybean based diet; BA treatment group fed the basal diet supplemented with 2.5 × 1010 CFU/kg BA CGMCC18230; AGPs treatment group was fed the basal diet containing the antibiotics aureomycin (75 mg/kg), flavomycin (5 mg/kg) and kitasamycin (20 mg/kg). Over the 42 d experiment, broilers fed BA and AGPs diets both had higher BW, and the ADG was significantly (P < 0.05) higher than that of the CON group both in the grower phase (22–42 d) and overall. Moreover, with BA birds had higher (P < 0.05) serum concentrations of phosphorus (P, day 42) and alkaline phosphatase (ALP, days 21 and 42). Conversely, the content of P in excreta decreased significantly (P < 0.05) on days 21 and 42. Tibia bone mineralization was improved in BA, and the mRNA of P transport related genes PiT-1,2 in the duodenum and jejunum were significantly up-regulated in the BA group than in the CON group (P < 0.05). 16S rRNA gene sequencing revealed that dietary BA supplementation increased the relative abundance of butyrate-producing bacteria (Ruminococcaceae) and polyamine-producing bacteria (Akkermansia and Alistipes), which had a positive effect on bone development. These data show that dietary supplementation of BA CGMCC18320 improves broiler growth performance and bone health similar to supplementation with AGPs through up-regulation of intestinal P transporters, microbial modulation and increase P retention. However, no significant influence of BA CGMCC18320 supplementation on the retention of Ca was found.
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Rubio-Aliaga I, Krapf R. Phosphate intake, hyperphosphatemia, and kidney function. Pflugers Arch 2022; 474:935-947. [PMID: 35511366 PMCID: PMC9338892 DOI: 10.1007/s00424-022-02691-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/11/2022] [Accepted: 04/12/2022] [Indexed: 12/25/2022]
Abstract
Phosphate is essential in living organisms and its blood levels are regulated by a complex network involving the kidneys, intestine, parathyroid glands, and the skeleton. The crosstalk between these organs is executed primarily by three hormones, calcitriol, parathyroid hormone, and fibroblast growth factor 23. Largely due to a higher intake of ultraprocessed foods, dietary phosphate intake has increased in the last decades. The average intake is now about twice the recommended dietary allowance. Studies investigating the side effect of chronic high dietary phosphate intake suffer from incomplete dietary phosphate assessment and, therefore, often make data interpretation difficult. Renal excretion is quickly adapted to acute and chronic phosphate intake. However, at the high ends of dietary intake, renal adaptation, even in pre-existing normal kidney function, apparently is not perfect. Experimental intervention studies suggest that chronic excess of dietary phosphate can result in sustained higher blood phosphate leading to hyperphosphatemia. Evidence exists that the price of the homeostatic response (phosphaturia in response to phosphate loading/hyperphosphatemia) is an increased risk for declining kidney function, partly due by intraluminal/tubular calcium phosphate particles that provoke renal inflammation. High dietary phosphate intake and hyperphosphatemia are progression factors for declining kidney function and are associated with higher cardiovascular disease and mortality risk. This is best established for pre-existing chronic kidney disease, but epidemiological and experimental data strongly suggest that this holds true for subjects with normal renal function as well. Here, we review the latest advances in phosphate intake and kidney function decline.
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Affiliation(s)
- Isabel Rubio-Aliaga
- Institute of Physiology, National Center of Competence in Research NCCR Kidney.CH, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
| | - Reto Krapf
- Synlab Suisse, 6002, Lucerne, Switzerland
- Department of Medicine, University of Basel, 4056, Basel, Switzerland
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9
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Shi H, Wang J, Teng PY, Tompkins YH, Jordan B, Kim WK. Effects of phytase and coccidial vaccine on growth performance, nutrient digestibility, bone mineralization, and intestinal gene expression of broilers. Poult Sci 2022; 101:102124. [PMID: 36130448 PMCID: PMC9489506 DOI: 10.1016/j.psj.2022.102124] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/26/2022] [Accepted: 08/03/2022] [Indexed: 11/08/2022] Open
Abstract
A study was conducted to evaluate effects of phytase and coccidial vaccine on growth performance, bone mineralization, nutrient digestibility, and intestinal gene expression of broiler chickens. The experiment was conducted in a 2 × 4 completely randomized factorial arrangement with 6 replicates per treatment and 10 birds each. Applications of coccidiosis vaccine and different dietary treatments were the 2 main factors in the current study. The dietary treatments included 1) a positive control (PC; 0.90% Ca and 0.45% available P: avP); 2) a negative control (NC; 0.75% Ca and 0.30% AvP); 3) NC + 500 FTU/kg of phytase (NC + 500PHY); and 4) NC + 1500 FTU/kg of phytase (NC + 1500PHY). Data were analyzed using SAS by 2-way ANOVA via GLM procedure. The statistical significance was set at P ≤ 0.05, and means were further separated using Tukey's Test. The results indicated that vaccination had no effect on growth performance except for feed intake from 0 to 14 d but negatively (P < 0.05) regulated bone ash and Ca digestibility. Birds fed with the Ca and P-reduced diet (NC) showed a lower BWG and bone ash compared to birds fed with the normal diet (PC), but supplementing phytase mitigated the negative effects on those birds. Broilers fed the NC diet had higher (P < 0.05) total Ca and P digestibility, and phytate degradation; supplementing phytase further increased P digestibility and phytate degradation of the broilers. A significant interaction (P < 0.05) between phytase and vaccination was observed, suggesting the vaccinated birds fed the PC diet and the unvaccinated birds fed the NC + 1500PHY increased calcium-sensing receptor gene expression compared with the unvaccinated birds fed the PC diet. In conclusion, in spite of coccidiosis vaccine, supplementing phytase at 1,500 FTU/kg alleviated the negative effects on growth performance, bone mineralization, and apparent ileal digestibility of P and phytate.
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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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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: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [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 Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Yanping Xu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Xiaohong Yu
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Asim Dey
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Hong Y Zhang
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Charity M Zink
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Derek Wodka
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Gina Porter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - William F Matter
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Leah Porras
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Charles A Reidy
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Jeffrey A Peterson
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Brian E Mattioni
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Joseph V Haas
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - Mark C Kowala
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
| | - John R Wetterau
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana, USA
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12
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Lucea S, Guillén N, Sosa C, Sorribas V. Inhibition of epithelial phosphate transport by NAD +/NADH. Am J Physiol Cell Physiol 2022; 322:C803-C813. [PMID: 35264014 DOI: 10.1152/ajpcell.00404.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nicotinamide is an important regulator of Pi homeostasis after conversion into NAD+/NADH. In this work, we have studied the classical inhibition of Pi transport by these compounds in the brush border membrane vesicles (BBMV) of rat kidney and rat intestine, and we examined the effects in Opossum Kidney (OK) cells and in phosphate transporter-expressing Xenopus laevis oocytes. In BBMV, NAD+ required preincubation at either room temperature or on ice to inhibit Pi uptake in BBMV. However, no effects were observed in the known Slc34 or Slc20 Pi transporters expressed in Xenopus oocytes, in OK cells, or in isolated rat cortical nephron segments. In BBMV from jejunum or kidney cortex, the inhibition of Pi transport was specific, dose-related, and followed a competitive inhibition pattern, as shown by linear transformation and non-linear regression analyses. A Ki value of 538 µM NAD+ in kidney BBMV was obtained. Ribosylation inhibitors and ribosylation assays revealed no evidence that this reaction was responsible for inhibiting Pi transport. An analysis of the persistence of NAD+/NADH revealed a half-life of just 2 minutes during preincubation. Out of several metabolites of NAD degradation, only ADP-ribose was able to inhibit Pi uptake. Pi concentration also increased during 30 minutes of preincubation, up to 0.67mM, most likely as a metabolic end-product. In conclusion, the classical inhibition of Pi transport by NAD+/NADH in BBMV seems to be caused by the degradation metabolites of these compounds during the preincubation time.
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Affiliation(s)
- Susana Lucea
- Group of Molecular Toxicology, Department of Biochemistry and Molecular and Cell Biology, University of Zaragoza, Veterinary Faculty, Zaragoza, Spain
| | - Natalia Guillén
- Group of Molecular Toxicology, Department of Biochemistry and Molecular and Cell Biology, University of Zaragoza, Veterinary Faculty, Zaragoza, Spain
| | - Cecilia Sosa
- Group of Molecular Toxicology, Department of Biochemistry and Molecular and Cell Biology, University of Zaragoza, Veterinary Faculty, Zaragoza, Spain
| | - Victor Sorribas
- Group of Molecular Toxicology, Department of Biochemistry and Molecular and Cell Biology, University of Zaragoza, Veterinary Faculty, Zaragoza, Spain
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13
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Ogata H, Takeshima A, Ito H. An update on phosphate binders for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis: a review of safety profiles. Expert Opin Drug Saf 2022; 21:947-955. [PMID: 35180026 DOI: 10.1080/14740338.2022.2044472] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Hyperphosphatemia is an inevitable complication for patients undergoing dialysis, as is the resulting need for treatment with phosphate binders. Currently, various phosphate binders are clinically available. In addition to their phosphate-lowering activity, individual phosphate binders have differing safety profiles and off-target actions. AREAS COVERED This paper reviews the safety of phosphate binders and issues to be resolved. EXPERT OPINION Calcium-based phosphate binders are well tolerated but may increase calcium overload risk. Sevelamer reduces serum cholesterol levels and exerts anti-inflammatory effects. Compared to sevelamer, bixalomer is associated with fewer gastrointestinal symptoms. Aluminum-containing binders, lanthanum carbonate, and sucroferric oxyhydroxide exhibit strong phosphate-lowering activity. Although ferric citrate reduces erythropoiesis-stimulating agents and intravenous iron doses, its use requires monitoring of iron metabolic markers to avoid overload. Occasionally, combined use of multiple phosphate binders can offer the advantages of each phosphate binder while minimizing their drawbacks; thus, this may be desirable according to individual patients' conditions and comorbidities. However, increased pill burden and nonadherence to phosphate binders emerge as new problems. We expect that novel therapeutic strategies will be developed to resolve these issues.
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Affiliation(s)
- Hiroaki Ogata
- Division of Nephrology, Department of Internal Medicine, Showa University, Northern Yokohama Hospital, Chigasaki-chuo 35-1, Tsuzuki, Yokohama 2248503, JAPAN
| | - Akiko Takeshima
- Division of Nephrology, Department of Internal Medicine, Showa University, Northern Yokohama Hospital, Chigasaki-chuo 35-1, Tsuzuki, Yokohama 2248503, JAPAN
| | - Hidetoshi Ito
- Division of Nephrology, Department of Internal Medicine, Showa University, Northern Yokohama Hospital, Chigasaki-chuo 35-1, Tsuzuki, Yokohama 2248503, JAPAN
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14
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Lu A, Pu M, Mo S, Su J, Hu J, Li C, Wang W, Yang T. (Pro)renin Receptor Regulates Phosphate Homeostasis in Rats via Releasing Fibroblast Growth Factor-23. Front Physiol 2022; 13:784521. [PMID: 35222071 PMCID: PMC8874195 DOI: 10.3389/fphys.2022.784521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 01/14/2022] [Indexed: 11/13/2022] Open
Abstract
Phosphate (Pi) is one of the basic necessities required for sustenance of life and its metabolism largely relies on excretory function of the kidney, a process chiefly under the endocrine control of bone-derived fibroblast growth factor 23 (FGF23). However, knowledge gap exists in understanding the regulatory loop responsible for eliciting phophaturic response to Pi treatment. Here, we reported a novel role of (pro)renin receptor (PRR) in mediating phosphaturic response to Pi treatment via upregulation of FGF23 production. Male Sprague-Dawley rats were pretreated for 5 days via osmotic pump-driven infusion of a PRR antagonist PRO20 or vehicle, and then treated with high Pi (HP) solution as drinking fluid for the last 24 h. PRO20 reduced HP-induced Pi excretion by 42%, accompanied by blunted upregulation of circulating FGF23 and parathyroid hormone (PTH) and downregulation of renal Na/Pi-IIa expression. In cultured osteoblast cells, exposure to HP induced a 1.56-fold increase in FGF23 expression, which was blunted by PRO20 or siRNA against PRR. Together, these results suggest that activation of PRR promotes phosphaturic response through stimulation of FGF23 production and subsequent downregulation of renal Na/Pi-IIa expression.
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Affiliation(s)
- Aihua Lu
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Min Pu
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Shiqi Mo
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Jiahui Su
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Jiajia Hu
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Chunling Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Weidong Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Tianxin Yang
- Department of Internal Medicine, University of Utah and Veterans Affairs Medical Center, Salt Lake City, UT, United States
- *Correspondence: Tianxin Yang,
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15
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Xue J, Thomas L, Murali SK, Levi M, Fenton RA, Dominguez Rieg JA, Rieg T. Enhanced phosphate absorption in intestinal epithelial cell-specific NHE3 knockout mice. Acta Physiol (Oxf) 2022; 234:e13756. [PMID: 34978760 PMCID: PMC9286053 DOI: 10.1111/apha.13756] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 11/16/2021] [Accepted: 01/01/2022] [Indexed: 12/11/2022]
Abstract
Aims The kidneys play a major role in maintaining Pi homeostasis. Patients in later stages of CKD develop hyperphosphatemia. One novel treatment option is tenapanor, an intestinal‐specific NHE3 inhibitor. To gain mechanistic insight into the role of intestinal NHE3 in Pi homeostasis, we studied tamoxifen‐inducible intestinal epithelial cell‐specific NHE3 knockout (NHE3IEC‐KO) mice. Methods Mice underwent dietary Pi challenges, and hormones as well as urinary/plasma Pi were determined. Intestinal 33P uptake studies were conducted in vivo to compare the effects of tenapanor and NHE3IEC‐KO. Ex vivo Pi transport was measured in everted gut sacs and brush border membrane vesicles. Intestinal and renal protein expression of Pi transporters were determined. Results On the control diet, NHE3IEC‐KO mice had similar Pi homeostasis, but a ~25% reduction in FGF23 compared with control mice. Everted gut sacs and brush border membrane vesicles showed enhanced Pi uptake associated with increased Npt2b expression in NHE3IEC‐KO mice. Acute oral Pi loading resulted in higher plasma Pi in NHE3IEC‐KO mice. Tenapanor inhibited intestinal 33P uptake acutely but then led to hyper‐absorption at later time points compared to vehicle. In response to high dietary Pi, plasma Pi and FGF23 increased to higher levels in NHE3IEC‐KO mice which was associated with greater Npt2b expression. Reduced renal Npt2c and a trend for reduced Npt2a expression were unable to correct for higher plasma Pi. Conclusion Intestinal NHE3 has a significant contribution to Pi homeostasis. In contrast to effects described for tenapanor on Pi homeostasis, NHE3IEC‐KO mice show enhanced, rather than reduced, intestinal Pi uptake.
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Affiliation(s)
- Jianxiang Xue
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
| | - Linto Thomas
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
| | | | - Moshe Levi
- Department of Biochemistry and Molecular & Cellular Biology Georgetown University Washington District of Columbia USA
| | | | - Jessica A. Dominguez Rieg
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
- James A. Haley Veterans' Hospital Tampa Florida USA
| | - Timo Rieg
- Department of Molecular Pharmacology and Physiology Morsani College of Medicine University of South Florida Tampa Florida USA
- James A. Haley Veterans' Hospital Tampa Florida USA
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16
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Brescia V, Fontana A, Lovero R, Capobianco C, Marsico SV, De Chirico T, Pinto C, Varraso L, Cazzolla AP, Di Serio F. Determination of iFGF23 Upper Reference Limits (URL) in healthy pediatric population, for its better correct use. Front Endocrinol (Lausanne) 2022; 13:1018523. [PMID: 36440231 PMCID: PMC9681906 DOI: 10.3389/fendo.2022.1018523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Accepted: 10/12/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The measurement of Fibroblast growth factor 23 (FGF23) may be useful in the diagnosis and management of abnormal phosphate metabolism in both patients with preserved renal function or with chronic kidney disease (CKD). FGF-23 tests differ considerably by molecule assayed (iFGF23 or cFGF23), analytical performance and reference ranges. We establish iFGF23 Upper Reference Limits (URL) in apparently healthy pediatric individuals using automated immunochemiluminescent assay. METHODS We measured the levels of plasma iFGF23 from 115 samples from apparently healthy pediatric subjects [59 (51.3%) individuals were male; median age 10 years (range 1-18)] included in an observational study conducted at Policlinico University Hospital of Bari. The method used for the iFGF23 assay was immunochemiluminescent sandwich assay developed by DiaSorin on the Liaison XL platform. Statistical calculation of 95% reference interval, right-sided (CLSI C28-A3) and verification of age and sex covariables was performed for the calculation of the URL. RESULTS The URL concentration of iFGF23 was 61.21 pg/mL (58.63 to 63.71, 90% CI). No significant differences were found between the median concentrations of iFGF23 differentiated by sex and age. CONCLUSIONS The dosage of iFGF23 is important both for the differential diagnosis of the various forms of rickets, and for the subsequent monitoring of the effectiveness of drug treatment. We have established the URL for the iFGF23 Liaison test in apparently healthy pediatric subjects. The availability of iFGF23 pediatric reference values will allow a better clinical use of the test.
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Affiliation(s)
- Vincenzo Brescia
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Antonietta Fontana
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Roberto Lovero
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
- *Correspondence: Roberto Lovero,
| | - Carmela Capobianco
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Stella Vita Marsico
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Tiziana De Chirico
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Carla Pinto
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Lucia Varraso
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
| | - Angela Pia Cazzolla
- Department of Clinical and Experimental Medicine, Università degli Studi di Foggia, Foggia, Italy
| | - Francesca Di Serio
- Clinical Pathology Unit, Azienda Ospedaliero-Universitaria (AOU) Policlinico Consorziale di Bari - Ospedale Giovanni XXIII, Bari, Italy
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A 5-year-old girl with bony deformities and disproportionate short stature: Answers. Pediatr Nephrol 2021; 36:3117-3121. [PMID: 33730275 DOI: 10.1007/s00467-021-05038-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 02/19/2021] [Accepted: 02/26/2021] [Indexed: 10/21/2022]
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18
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Sprague SM, Martin KJ, Coyne DW. Phosphate Balance and CKD-Mineral Bone Disease. Kidney Int Rep 2021; 6:2049-2058. [PMID: 34386654 PMCID: PMC8343779 DOI: 10.1016/j.ekir.2021.05.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 05/10/2021] [Indexed: 12/29/2022] Open
Abstract
Chronic kidney disease-mineral bone disorder (CKD-MBD) is a common comorbidity in patients with CKD. Characterized by laboratory abnormalities, bone abnormality, and vascular calcification, CKD-MBD encompasses a group of mineral and hormone disturbances that are strongly associated with increased cardiovascular (CV) morbidity and mortality. Abnormal serum phosphate concentrations are an independent risk factor for CV morbidity and mortality, and overall mortality. Phosphate retention plays a central role in initiating and driving many other disturbances in CKD-MBD (e.g., increased parathyroid hormone and fibroblast growth factor 23 concentrations, hypocalcemia, low vitamin D) that are also linked to increased CV risk. Thus, effective phosphate control is a logical therapeutic target for CKD-MBD treatment. Current phosphate management strategies (dietary restrictions, dialysis, phosphate binders) are insufficient to consistently achieve and maintain target phosphate concentrations in patients on dialysis. Phosphate binders reduce available phosphate for intestinal absorption but do not impair the dominant phosphate absorption pathway. Novel therapies that consider new mechanistic understandings of intestinal phosphate absorption are needed. One such therapy is tenapanor, a targeted sodium-hydrogen exchanger isoform 3 inhibitor that has been shown to reduce serum phosphate concentrations in multiple clinical trials. Tenapanor has a novel mechanism of action that reduces intestinal phosphate absorption in the primary paracellular phosphate absorption pathway.
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Affiliation(s)
- Stuart M. Sprague
- Division of Nephrology and Hypertension, NorthShore University Health System, Evanston, IL, USA
| | | | - Daniel W. Coyne
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
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19
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Stremke ER, Wiese GN, Moe SM, Wastney ME, Moorthi RN, Hill Gallant KM. Intestinal Phosphorus Absorption in Moderate CKD and Healthy Adults Determined Using a Radioisotopic Tracer. J Am Soc Nephrol 2021; 32:2057-2069. [PMID: 34244325 PMCID: PMC8455256 DOI: 10.1681/asn.2020091340] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 03/15/2021] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Reducing intestinal phosphorus absorption is a cornerstone in CKD-MBD management. Yet, knowledge gaps include how CKD pathophysiology affects intestinal phosphorus absorption. In vivo rodent studies suggest that intestinal phosphorus absorption remains inappropriately normal in early-moderate CKD, despite declining 1,25-dihydroxyvitamin D (1,25D). We measured intestinal phosphorus absorption in patients with moderate CKD versus healthy adults using a direct radiotracer method. METHODS Patients with CKD and healthy adults matched for age, sex, and race were enrolled in this 8-day controlled diet study: the first 6 days outpatient and the final 2 days inpatient. Oral and intravenous doses of 33P and serial blood and urine sampling determined intestinal phosphorus absorption during the final 2 days. Secondary outcomes included fasting biochemistries and 24-hour urine phosphorus (uP). RESULTS In total, n=8 patients with CKD (eGFR=29-55 ml/min per 1.73 m2) and n=8 matched healthy controls completed the study. On a controlled diet, no difference in fractional intestinal phosphorus absorption was detected between patients with CKD and healthy adults (0.69 versus 0.62, respectively; P=0.52), and this was similar for 24-hour uP (884 versus 935 mg/d, respectively; P=0.70). Fractional intestinal phosphorus absorption was not significantly related to 24-hour uP. Patients with CKD had higher serum intact PTH and intact FGF23 and lower 1,25D. The relationship between 1,25D and fractional intestinal phosphorus absorption was not statistically significant. CONCLUSIONS Intestinal phosphorus absorption with typical dietary intake did not differ in patients with moderate CKD compared with controls, despite lower serum 1,25D levels. In this setting, a relationship between 24-hour uP and fractional or absolute intestinal absorption was not evident. Further investigation is needed to determine what factors influence intestinal phosphorus absorption in CKD and the apparent lack of compensation by the intestine to limit phosphorus absorption in the face of declining kidney function and reduced 1,25D. Whether this is evident across a range of dietary phosphorus intakes, as well as CKD severity, also needs to be determined. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER Phosphorus Absorption in Healthy Adults and in Patients with Moderate Chronic Kidney Disease, NCT03108222.
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Affiliation(s)
- Elizabeth R. Stremke
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
- Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, Minnesota
| | - Gretchen N. Wiese
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
| | - Sharon M. Moe
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Medicine, Roudebush Veterans Administration Medical Center, Indianapolis, Indiana
| | - Meryl E. Wastney
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
- Metabolic Modeling Services, West Lafayette, Indiana
| | - Ranjani N. Moorthi
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Kathleen M. Hill Gallant
- Department of Nutrition Science, Purdue University, West Lafayette, Indiana
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota
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20
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Stanczyk M, Chrul S, Wyka K, Tkaczyk M. Serum intact fibroblast growth factor 23 in healthy paediatric population. Open Med (Wars) 2021; 16:1022-1027. [PMID: 34258392 PMCID: PMC8262519 DOI: 10.1515/med-2021-0288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 03/28/2021] [Accepted: 04/20/2021] [Indexed: 11/25/2022] Open
Abstract
Introduction It is believed that fibroblast growth factor 23 (FGF23) can become an early biomarker of chronic kidney disease progression. Data on FGF23 age dependency are inconsistent. We present the results of the cross-sectional study concerning FGF23 levels in healthy Polish children. Material and methods This study was conducted in 121 children aged 0–18 years. Kidney function and intact FGF23 levels in serum were assessed. Differences between age groups and according to gender were analysed. Results The difference in FGF23 between age groups and according to gender was statistically insignificant. In the youngest and the oldest group, a trend to higher FGF23 levels was observed. FGF23 level in girls tended to be higher than boys, apart from the age group between 1 and 4 years. There was a negative correlation between eGFR and FGF23 (r = −0.26, p < 0.05) – strong in girls (r = −0.38, p < 0.05), but not in boys. In each age group, we found no significant correlation between eGFR and FGF23. Conclusions Our study supports the evidence that the FGF23 level in paediatric population is not age or sex dependent. The results can serve as a reference point under clinical conditions and for other studies on the topic.
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Affiliation(s)
- Malgorzata Stanczyk
- Department of Pediatrics, Immunology and Nephrology, Polish Mother's Memorial Hospital Research Institute, Rzgowska 281/289, Lodz 93-338, Poland.,Department of Pediatrics, Preventive Cardiology and Immunology of Developmental Age, Medical University of Lodz, Poland
| | - Slawomir Chrul
- Department of Pediatrics, Immunology and Nephrology, Polish Mother's Memorial Hospital Research Institute, Lodz 93-338, Poland
| | - Krystyna Wyka
- Department of Pediatrics, Oncology and Hematology, Medical University of Lodz, Lodz, Poland
| | - Marcin Tkaczyk
- Department of Pediatrics, Immunology and Nephrology, Polish Mother's Memorial Hospital Research Institute, Lodz 93-338, Poland.,Department of Pediatrics, Preventive Cardiology and Immunology of Developmental Age, Medical University of Lodz, Poland
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21
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Asowata EO, Olusanya O, Abaakil K, Chichger H, Srai SKS, Unwin RJ, Marks J. Diet-induced iron deficiency in rats impacts small intestinal calcium and phosphate absorption. Acta Physiol (Oxf) 2021; 232:e13650. [PMID: 33749990 DOI: 10.1111/apha.13650] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 02/26/2021] [Accepted: 03/17/2021] [Indexed: 12/31/2022]
Abstract
AIMS Recent reports suggest that iron deficiency impacts both intestinal calcium and phosphate absorption, although the exact transport pathways and intestinal segment responsible have not been determined. Therefore, we aimed to systematically investigate the impact of iron deficiency on the cellular mechanisms of transcellular and paracellular calcium and phosphate transport in different regions of the rat small intestine. METHODS Adult, male Sprague-Dawley rats were maintained on a control or iron-deficient diet for 2 weeks and changes in intestinal calcium and phosphate uptake were determined using the in situ intestinal loop technique. The circulating levels of the hormonal regulators of calcium and phosphate were determined by ELISA, while the expression of transcellular calcium and phosphate transporters, and intestinal claudins were determined using qPCR and western blotting. RESULTS Diet-induced iron deficiency significantly increased calcium absorption in the duodenum but had no impact in the jejunum and ileum. In contrast, phosphate absorption was significantly inhibited in the duodenum and to a lesser extent the jejunum, but remained unchanged in the ileum. The changes in duodenal calcium and phosphate absorption in the iron-deficient animals were associated with increased claudin 2 and 3 mRNA and protein levels, while levels of parathyroid hormone, fibroblast growth factor-23 and 1,25-dihydroxy vitamin D3 were unchanged. CONCLUSION We propose that iron deficiency alters calcium and phosphate transport in the duodenum. This occurs via changes to the paracellular pathway, whereby upregulation of claudin 2 increases calcium absorption and upregulation of claudin 3 inhibits phosphate absorption.
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Affiliation(s)
- Evans O. Asowata
- Department of Neuroscience, Physiology & Pharmacology University College London London UK
| | - Oluwatobi Olusanya
- Department of Neuroscience, Physiology & Pharmacology University College London London UK
| | - Kaoutar Abaakil
- Department of Neuroscience, Physiology & Pharmacology University College London London UK
| | - Havovi Chichger
- Biomedical Research Group School of Life Sciences Anglia Ruskin University Cambridge UK
| | - Surjit K. S. Srai
- Institute of Structural and Molecular Biology University College London London UK
| | - Robert J. Unwin
- Department of Renal Medicine University College London London UK
| | - Joanne Marks
- Department of Neuroscience, Physiology & Pharmacology University College London London UK
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22
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Figueres L, Beck-Cormier S, Beck L, Marks J. The Complexities of Organ Crosstalk in Phosphate Homeostasis: Time to Put Phosphate Sensing Back in the Limelight. Int J Mol Sci 2021; 22:5701. [PMID: 34071837 PMCID: PMC8199323 DOI: 10.3390/ijms22115701] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 05/13/2021] [Accepted: 05/21/2021] [Indexed: 12/16/2022] Open
Abstract
Phosphate homeostasis is essential for health and is achieved via interaction between the bone, kidney, small intestine, and parathyroid glands and via intricate processes involving phosphate transporters, phosphate sensors, and circulating hormones. Numerous genetic and acquired disorders are associated with disruption in these processes and can lead to significant morbidity and mortality. The role of the kidney in phosphate homeostasis is well known, although it is recognized that the cellular mechanisms in murine models and humans are different. Intestinal phosphate transport also appears to differ in humans and rodents, with recent studies demonstrating a dominant role for the paracellular pathway. The existence of phosphate sensing has been acknowledged for decades; however, the underlying molecular mechanisms are poorly understood. At least three phosphate sensors have emerged. PiT2 and FGFR1c both act as phosphate sensors controlling Fibroblast Growth Factor 23 secretion in bone, whereas the calcium-sensing receptor controls parathyroid hormone secretion in response to extracellular phosphate. All three of the proposed sensors are expressed in the kidney and intestine but their exact function in these organs is unknown. Understanding organ interactions and the mechanisms involved in phosphate sensing requires significant research to develop novel approaches for the treatment of phosphate homeostasis disorders.
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Affiliation(s)
- Lucile Figueres
- Department of Neuroscience, Physiology and Pharmacology, Royal Free Campus, University College London, London NW3 2PF, UK;
- CHU de Nantes, Université de Nantes, F-44042 Nantes, France
| | - Sarah Beck-Cormier
- Inserm, UMR 1229, RMeS Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, F-44042 Nantes, France; (S.B.-C.); (L.B.)
| | - Laurent Beck
- Inserm, UMR 1229, RMeS Regenerative Medicine and Skeleton, Université de Nantes, ONIRIS, F-44042 Nantes, France; (S.B.-C.); (L.B.)
| | - Joanne Marks
- Department of Neuroscience, Physiology and Pharmacology, Royal Free Campus, University College London, London NW3 2PF, UK;
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Chande S, Dijk F, Fetene J, Yannicelli S, Carpenter TO, van Helvoort A, Bergwitz C. Phosphorus bioaccessibility measured in four amino acid-based formulas using in-vitro batch digestion translates well into phosphorus bioavailability in mice. Nutrition 2021; 89:111291. [PMID: 34111672 DOI: 10.1016/j.nut.2021.111291] [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: 10/18/2020] [Revised: 04/07/2021] [Accepted: 04/18/2021] [Indexed: 10/21/2022]
Abstract
OBJECTIVE The aim of this study was to quantify the bioaccessibility of phosphorus from amino acid-based formulas (AAFs) under different digestive conditions. METHODS We developed in-vitro batch digestion models with stomach digestion at different pH mimicking the normal digestive condition and conditions representing use of acid-suppressive medication. To validate bioaccessibility findings, we devised a low phosphorus murine model to test phosphorus bioavailability under compromised digestive conditions using proton pump inhibitors (PPIs) to neutralize stomach pH. RESULTS In vitro phosphorus bioaccessibility of AAFs Neocate® Infant and Neocate Junior ranged between 57% and 65% under normal digestive conditions for infants (stomach pH 3.5) and between 38% and 46% under conditions that simulated bypass of stomach acidification, which is comparable to control diet and two EleCare® AAFs. In vivo bioavailability analysis showed that both Neocate formulas were able to normalize plasma phosphorus levels when administered to low phosphorus mice along with PPIs (control diet + PPI 8 ± 0.4; Neocate Infant 10.1 ± 0.9; Neocate Junior 9.2 ± 0.6; EleCare Infant 8.6 ± 0.4; EleCare Junior 8.7 ± 0.5; n = 8-10; P < 0.0001 versus baseline 3.4 ± 0.2 mg/dL). In comparison, plasma phosphorus levels remained lower on the low phosphorus diet (5.7 ± 0.2 mg/dL). Furthermore, urinary phosphorus/creatinine and intact fibroblast growth factor 23 were significantly lowered by low phosphorus diet. In contrast, intact parathyroid hormone and 1,25-dihydroxy vitamin D decreased and increased, respectively, and these parameters likewise normalized in mice administered AAFs. CONCLUSION The present findings indicated that phosphorus bioaccessibility in the in-vitro batch digestion model translates well into phosphorus bioavailability in mice even under compromised digestive conditions that bypass gastric acidification.
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Affiliation(s)
- Sampada Chande
- Yale University School of Medicine, Section of Endocrinology and Metabolism, New Haven, Connecticut, USA
| | | | - Jonathan Fetene
- Yale University School of Medicine, Section of Endocrinology and Metabolism, New Haven, Connecticut, USA
| | | | - Thomas O Carpenter
- Yale University School of Medicine, Department of Pediatrics, New Haven, Connecticut, USA
| | - Ardy van Helvoort
- Danone Nutricia Research, Utrecht, The Netherlands; School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands
| | - Clemens Bergwitz
- Yale University School of Medicine, Section of Endocrinology and Metabolism, New Haven, Connecticut, USA.
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24
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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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25
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Ichida Y, Ohtomo S, Yamamoto T, Murao N, Tsuboi Y, Kawabe Y, Segawa H, Horiba N, Miyamoto KI, Floege J. Evidence of an intestinal phosphate transporter alternative to type IIb sodium-dependent phosphate transporter in rats with chronic kidney disease. Nephrol Dial Transplant 2021; 36:68-75. [PMID: 32879980 PMCID: PMC7771979 DOI: 10.1093/ndt/gfaa156] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Indexed: 12/14/2022] Open
Abstract
Background Phosphate is absorbed in the small intestine via passive flow and active transport.NaPi-IIb, a type II sodium-dependent phosphate transporter, is considered to mediate active phosphate transport in rodents. To study the regulation of intestinal phosphate transport in chronic kidney disease (CKD), we analyzed the expression levels of NaPi-IIb, pituitary-specific transcription factor 1 (PiT-1) and PiT-2 and the kinetics of intestinal phosphate transport using two CKD models. Methods CKD was induced in rats via adenine orThy1 antibody injection. Phosphate uptake by intestinal brush border membrane vesicles (BBMV) and the messenger RNA (mRNA) expression of NaPi-IIb, PiT-1 and PiT-2 were analyzed. The protein expression level of NaPi-IIb was measured by mass spectrometry (e.g. liquid chromatography tandem mass spectrometry). Results In normal rats, phosphate uptake into BBMV consisted of a single saturable component and its Michaelis constant (Km) was comparable to that of NaPi-IIb. The maximum velocity (Vmax) correlated with mRNA and protein levels of NaPi-IIb. In the CKD models, intestinal phosphate uptake consisted of two saturable components. The Vmax of the higher-affinity transport, which is thought to be responsible for NaPi-IIb, significantly decreased and the decrease correlated with reduced NaPi-IIb expression. The Km of the lower-affinity transport was comparable to that of PiT-1 and -2. PiT-1 mRNA expression was much higher than that of PiT-2, suggesting that PiT-1 was mostly responsible for phosphate transport. Conclusions This study suggests that the contribution of NaPi-IIb to intestinal phosphate absorption dramatically decreases in rats with CKD and that a low-affinity alternative to NaPi-IIb, in particular PiT-1, is upregulated in a compensatory manner in CKD.
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Affiliation(s)
- Yasuhiro Ichida
- Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Shuichi Ohtomo
- Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Tessai Yamamoto
- Translational Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Naoaki Murao
- Translational Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Yoshinori Tsuboi
- Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Yoshiki Kawabe
- Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Naoshi Horiba
- Research Division, Chugai Pharmaceutical Co., Ltd, Shizuoka, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Jürgen Floege
- Division of Nephrology and Clinical Immunology, RWTH Aachen University Hospital, Aachen, Germany
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Ketteler M, Wiecek A, Rosenkranz AR, Pasch A, Rekowski J, Hellmann B, Karus M, Ammer R. Efficacy and Safety of a Novel Nicotinamide Modified-Release Formulation in the Treatment of Refractory Hyperphosphatemia in Patients Receiving Hemodialysis-A Randomized Clinical Trial. Kidney Int Rep 2021; 6:594-604. [PMID: 33732974 PMCID: PMC7938065 DOI: 10.1016/j.ekir.2020.12.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 12/08/2020] [Indexed: 01/19/2023] Open
Abstract
INTRODUCTION Despite widespread use of phosphate binders (PBs), phosphate control is insufficient in many hemodialysis patients. Preliminary clinical observations suggest that nicotinamide may act synergistically with PBs to improve phosphate control. METHODS This multinational, randomized, double-blind, placebo-controlled study evaluated the efficacy and safety of nicotinamide modified release (NAMR) in combination with oral PB in a large cohort of hemodialysis patients with abnormal serum phosphate concentration (>4.5 mg/dl) despite treatment with PB. Patients entered a proof-of-efficacy phase (12 weeks [W12]) in which adjustments of relevant comedication were not permitted, followed by a safety extension phase for up to 52 weeks. Here, we report the results of the first phase. RESULTS The intention-to-treat (ITT) population consisted of 539 patients in the NAMR and 183 patients in the placebo group. NAMR and placebo were orally administered once daily (250-1500 mg/d). Mean age of patients was 61.8 years, and 63.0% were men. In the confirmatory analysis that estimated the difference in serum phosphate concentration after 12 weeks, NAMR proved superior over placebo with a significant difference of -0.51 mg/dl (95% confidence interval [CI] -0.72, -0.29; P < 0.0001). This effect was associated with significantly lower intact parathyroid hormone (iPTH) values (NAMR: 292.4±300.4 pg/ml vs. placebo: 337.0±302.7 pg/ml; P = 0.04) and an improved calcification propensity (T50 time; NAMR: 23.8±97.1 minutes vs. placebo: 2.3±100.7 minutes; P = 0.02). Diarrhea and pruritus were more frequent in the NAMR group. CONCLUSION NAMR combined with oral PB significantly improved phosphate control in hemodialysis patients.
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Affiliation(s)
- Markus Ketteler
- Robert Bosch Hospital, Department of General Internal Medicine and Nephrology, Stuttgart, Germany
- University of Split, School of Medicine, Split, Croatia
| | - Andrzej Wiecek
- Department of Nephrology, Transplantation and Internal Medicine, Medical University of Silesia in Katowice, Poland
| | - Alexander R. Rosenkranz
- Division of Nephrology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Andreas Pasch
- Calciscon AG, Nidau, Switzerland
- Institute of Physiology and Pathophysiology, Johannes Kepler University Linz, Linz, Austria
- Nierenpraxis Bern, Bern, Switzerland
- Department of Nephrology, Lindenhofspital, Bern, Switzerland
| | - Jan Rekowski
- Institute for Medical Informatics, Biometry and Epidemiology, Essen University Hospital, Essen, Germany
- Center for Clinical Studies, University Hospital Essen, Essen, Germany
| | - Burkhard Hellmann
- Medical Department, MEDICE Arzneimittel Pütter GmbH & Co KG, Iserlohn, Germany
| | - Michael Karus
- Medical Department, MEDICE Arzneimittel Pütter GmbH & Co KG, Iserlohn, Germany
| | - Richard Ammer
- Medical Department, MEDICE Arzneimittel Pütter GmbH & Co KG, Iserlohn, Germany
- Department of Nephrology, University Hospital Münster, Münster, Germany
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27
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Yi G, Ma Y, Chen Y, Yang X, Yang B, Tian W. A Review of the Functions of Matrix Vesicles in Periodontal Tissues. Stem Cells Dev 2021; 30:165-176. [PMID: 33349125 DOI: 10.1089/scd.2020.0155] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Periodontal tissues consist of cementum, periodontal ligaments, and alveolar bone, which provide indispensable support for physiological activities involving mastication, swallowing, and pronunciation. The formation of periodontal tissues requires a complex process, during which a close relationship with biomineralization is noticeable. Alveolar bone and cementum are physically hard, both of which are generated from biomineralization and possess the exact mechanical properties resembling other hard tissues. However, when periodontitis, congenital abnormalities, periapical diseases, and other pathological conditions affect the organism, the most common symptom, alveolar bone defect, is always unavoidable, which results in difficulties for current clinical treatment. Thus, exploring effective therapies to improve the prognosis is important. Matrix vesicles (MVs), a special subtype of extracellular vesicles related to histogenesis, are widely produced by the stem cells of developing hard tissues. With the assistance of the enzymes and transporters contained within them, MVs can construct the extracellular matrix and an adequate microenvironment, thus promoting biomineralization and periodontal development. Presently, MVs can be effectively extracted and delivered by scaffolds and generate hard tissues in vitro and in vivo, which are expected to be translated into therapies for alveolar bone defects. In this review, we generalize recent research progress on MV morphology, molecular composition, biological mechanism, and, in particular, the biological functions in periodontal development. In addition to the above unique roles of MVs, we further describe the available MV-related biotechnologies and achievements that make them promising for coping with existing problems and improving the treatment of alveolar bone defects.
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Affiliation(s)
- Genzheng Yi
- Engineering Research Center of Oral Translational Medicine, Ministry of Education, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Yue Ma
- Engineering Research Center of Oral Translational Medicine, Ministry of Education, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Yan Chen
- Engineering Research Center of Oral Translational Medicine, Ministry of Education, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Xueting Yang
- Engineering Research Center of Oral Translational Medicine, Ministry of Education, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Bo Yang
- Engineering Research Center of Oral Translational Medicine, Ministry of Education, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Weidong Tian
- Engineering Research Center of Oral Translational Medicine, Ministry of Education, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China
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28
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Behrens JL, Schnepel N, Hansen K, Hustedt K, Burmester M, Klinger S, Breves G, Muscher-Banse AS. Modulation of Intestinal Phosphate Transport in Young Goats Fed a Low Phosphorus Diet. Int J Mol Sci 2021; 22:ijms22020866. [PMID: 33467106 PMCID: PMC7831023 DOI: 10.3390/ijms22020866] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 01/07/2021] [Accepted: 01/13/2021] [Indexed: 12/03/2022] Open
Abstract
The intestinal absorption of phosphate (Pi) takes place transcellularly through the active NaPi-cotransporters type IIb (NaPiIIb) and III (PiT1 and PiT2) and paracellularly by diffusion through tight junction (TJ) proteins. The localisation along the intestines and the regulation of Pi absorption differ between species and are not fully understood. It is known that 1,25-dihydroxy-vitamin D3 (1,25-(OH)2D3) and phosphorus (P) depletion modulate intestinal Pi absorption in vertebrates in different ways. In addition to the apical uptake into the enterocytes, there are uncertainties regarding the basolateral excretion of Pi. Functional ex vivo experiments in Ussing chambers and molecular studies of small intestinal epithelia were carried out on P-deficient goats in order to elucidate the transepithelial Pi route in the intestine as well as the underlying mechanisms of its regulation and the proteins, which may be involved. The dietary P reduction had no effect on the duodenal and ileal Pi transport rate in growing goats. The ileal PiT1 and PiT2 mRNA expressions increased significantly, while the ileal PiT1 protein expression, the mid jejunal claudin-2 mRNA expression and the serum 1,25-(OH)2D3 levels were significantly reduced. These results advance the state of knowledge concerning the complex mechanisms of the Pi homeostasis in vertebrates.
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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: 1.3] [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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30
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Hernando N, Pastor-Arroyo EM, Marks J, Schnitzbauer U, Knöpfel T, Bürki M, Bettoni C, Wagner CA. 1,25(OH) 2 vitamin D 3 stimulates active phosphate transport but not paracellular phosphate absorption in mouse intestine. J Physiol 2020; 599:1131-1150. [PMID: 33200827 DOI: 10.1113/jp280345] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/02/2020] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Intestinal absorption of phosphate proceeds via an active/transcellular route mostly mediated by NaPi-IIb/Slc34a2 and a poorly characterized passive/paracellular pathway. Intestinal phosphate absorption and expression of NaPi-IIb are stimulated by 1,25(OH)2 vitamin D3 but whether NaPi-IIb is the only target under hormonal control remains unknown. We report that administration of 1,25(OH)2 vitamin D3 to wild-type mice resulted in the expected increase in active transport of phosphate in jejunum, without changing paracellular fluxes. Instead, the same treatment failed to alter phosphate transport in intestinal-depleted Slc34a2-deficient mice. In both genotypes, 1,25(OH)2 vitamin D3 induced similar hyperphosphaturic responses and changes in the plasma levels of FGF23 and PTH. While urinary phosphate loss induced by administration of 1,25(OH)2 vitamin D3 did not alter plasma phosphate, further studies should investigate whether chronic administration would lead to phosphate imbalance in mice with reduced active intestinal absorption. ABSTRACT Intestinal absorption of phosphate is stimulated by 1,25(OH)2 vitamin D3. At least two distinct mechanisms underlie phosphate absorption in the gut, an active transcellular transport requiring the Na+ /phosphate cotransporter NaPi-IIb/Slc34a2, and a poorly characterized paracellular passive pathway. 1,25(OH)2 vitamin D3 stimulates NaPi-IIb expression and function, and loss of NaPi-IIb reduces intestinal phosphate absorption. However, it is remains unknown whether NaPi-IIb is the only target for hormonal regulation by 1,25(OH)2 vitamin D3 . Here we compared the effects of intraperitoneal administration of 1,25(OH)2 vitamin D3 (2 days, once per day) in wild-type and intestinal-specific Slc34a2-deficient mice, and analysed trans- vs. paracellular routes of phosphate absorption. We found that treatment stimulated active transport of phosphate only in jejunum of wild-type mice, though NaPi-IIb protein expression was upregulated in jejunum and ileum. In contrast, 1,25(OH)2 vitamin D3 administration had no effect in Slc34a2-deficient mice, suggesting that the hormone specifically regulates NaPi-IIb expression. In both groups, 1,25(OH)2 vitamin D3 elicited the expected increase of plasma fibroblast growth factor 23 (FGF23) and reduction of parathyroid hormone (PTH). Treatment resulted in hyperphosphaturia (and hypercalciuria) in both genotypes, though mice remained normophosphataemic. While increased intestinal absorption and higher FGF23 can trigger the hyperphosphaturic response in wild types, only higher FGF23 can explain the renal response in Slc34a2-deficient mice. Thus, 1,25(OH)2 vitamin D3 stimulates intestinal phosphate absorption by acting on the active transcellular pathway mostly mediated by NaPi-IIb while the paracellular pathway appears not to be affected.
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Affiliation(s)
- Nati Hernando
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | | | - Joanne Marks
- University College London, Gower St, London, WC1E 6BT, UK
| | - Udo Schnitzbauer
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Thomas Knöpfel
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Matthias Bürki
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, University of Zürich, Zürich, Switzerland
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Ichida Y, Hosokawa N, Takemoto R, Koike T, Nakatogawa T, Hiranuma M, Arakawa H, Miura Y, Azabu H, Ohtomo S, Horiba N. Significant Species Differences in Intestinal Phosphate Absorption between Dogs, Rats, and Monkeys. J Nutr Sci Vitaminol (Tokyo) 2020; 66:60-67. [PMID: 32115455 DOI: 10.3177/jnsv.66.60] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A treatment for hyperphosphatemia would be expected to reduce mortality rates for CKD and dialysis patients. Although rodent studies have suggested sodium-dependent phosphate transporter type IIb (NaPi-IIb) as a potential target for hyperphosphatemia, NaPi-IIb selective inhibitors failed to achieve efficacy in human clinical trials. In this study, we analyzed phosphate metabolism in rats, dogs, and monkeys to confirm the species differences. Factors related to phosphate metabolism were measured and intestinal phosphate absorption rate was calculated from fecal excretion in each species. Phosphate uptake by intestinal brush border membrane vesicles (BBMV) and the mRNA expression of NaPi-IIb, PiT-1, and PiT-2 were analyzed. In addition, alkaline phosphatase (ALP) activity was evaluated. The intestinal phosphate absorption rate, including phosphate uptake by BBMV and NaPi-IIb expression, was the highest in dogs. Notably, urinary phosphate excretion was the lowest in monkeys, and their intestinal phosphate absorption rate was by far the lowest. Dogs and rats showed positive correlations between Vmax/Km of phosphate uptake in BBMV and NaPi-IIb expression. Although phosphate uptake was observed in the BBMV of monkeys, NaPi-IIb expression was not detected and ALP activity was low. This study revealed significant species differences in intestinal phosphate absorption. NaPi-IIb contributes to intestinal phosphate uptake in rats and dogs. However, in monkeys, phosphate is poorly absorbed due to the slight degradation of organic phosphate in the intestine.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Hiroko Azabu
- Chugai Research Institute for Medical Science, Inc
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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: 4.0] [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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Serna J, Bergwitz C. Importance of Dietary Phosphorus for Bone Metabolism and Healthy Aging. Nutrients 2020; 12:E3001. [PMID: 33007883 PMCID: PMC7599912 DOI: 10.3390/nu12103001] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 09/25/2020] [Accepted: 09/26/2020] [Indexed: 12/13/2022] Open
Abstract
Inorganic phosphate (Pi) plays a critical function in many tissues of the body: for example, as part of the hydroxyapatite in the skeleton and as a substrate for ATP synthesis. Pi is the main source of dietary phosphorus. Reduced bioavailability of Pi or excessive losses in the urine causes rickets and osteomalacia. While critical for health in normal amounts, dietary phosphorus is plentiful in the Western diet and is often added to foods as a preservative. This abundance of phosphorus may reduce longevity due to metabolic changes and tissue calcifications. In this review, we examine how dietary phosphorus is absorbed in the gut, current knowledge about Pi sensing, and endocrine regulation of Pi levels. Moreover, we also examine the roles of Pi in different tissues, the consequences of low and high dietary phosphorus in these tissues, and the implications for healthy aging.
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Affiliation(s)
- Juan Serna
- Yale College, Yale University, New Haven, CT 06511, USA;
| | - Clemens Bergwitz
- Section of Endocrinology and Metabolism, Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06519, USA
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All-trans retinoic acid reduces the transcriptional regulation of intestinal sodium-dependent phosphate co-transporter gene (Npt2b). Biochem J 2020; 477:817-831. [PMID: 32016357 DOI: 10.1042/bcj20190716] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 01/13/2020] [Accepted: 02/03/2020] [Indexed: 01/03/2023]
Abstract
Inorganic phosphate (Pi) homeostasis is regulated by intestinal absorption via type II sodium-dependent co-transporter (Npt2b) and by renal reabsorption via Npt2a and Npt2c. Although we previously reported that vitamin A-deficient (VAD) rats had increased urine Pi excretion through the decreased renal expression of Npt2a and Npt2c, the effect of vitamin A on the intestinal Npt2b expression remains unclear. In this study, we investigated the effects of treatment with all-trans retinoic acid (ATRA), a metabolite of vitamin A, on the Pi absorption and the Npt2b expression in the intestine of VAD rats, as well as and the underlying molecular mechanisms. In VAD rats, the intestinal Pi uptake activity and the expression of Npt2b were increased, but were reduced by the administration of ATRA. The transcriptional activity of reporter plasmid containing the promoter region of the rat Npt2b gene was reduced by ATRA in NIH3T3 cells overexpressing retinoic acid receptor (RAR) and retinoid X receptor (RXR). On the other hand, CCAAT/enhancer-binding proteins (C/EBP) induced transcriptional activity of the Npt2b gene. Knockdown of the C/EBP gene and a mutation analysis of the C/EBP responsible element in the Npt2b gene promoter indicated that C/EBP plays a pivotal role in the regulation of Npt2b gene transcriptional activity by ATRA. EMSA revealed that the RAR/RXR complex inhibits binding of C/EBP to Npt2b gene promoter. Together, these results suggest that ATRA may reduce the intestinal Pi uptake by preventing C/EBP activation of the intestinal Npt2b gene.
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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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36
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Law JP, Price AM, Pickup L, Radhakrishnan A, Weston C, Jones AM, McGettrick HM, Chua W, Steeds RP, Fabritz L, Kirchhof P, Pavlovic D, Townend JN, Ferro CJ. Clinical Potential of Targeting Fibroblast Growth Factor-23 and αKlotho in the Treatment of Uremic Cardiomyopathy. J Am Heart Assoc 2020; 9:e016041. [PMID: 32212912 PMCID: PMC7428638 DOI: 10.1161/jaha.120.016041] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Chronic kidney disease is highly prevalent, affecting 10% to 15% of the adult population worldwide and is associated with increased cardiovascular morbidity and mortality. As chronic kidney disease worsens, a unique cardiovascular phenotype develops characterized by heart muscle disease, increased arterial stiffness, atherosclerosis, and hypertension. Cardiovascular risk is multifaceted, but most cardiovascular deaths in patients with advanced chronic kidney disease are caused by heart failure and sudden cardiac death. While the exact drivers of these deaths are unknown, they are believed to be caused by uremic cardiomyopathy: a specific pattern of myocardial hypertrophy, fibrosis, with both diastolic and systolic dysfunction. Although the pathogenesis of uremic cardiomyopathy is likely to be multifactorial, accumulating evidence suggests increased production of fibroblast growth factor-23 and αKlotho deficiency as potential major drivers of cardiac remodeling in patients with uremic cardiomyopathy. In this article we review the increasing understanding of the physiology and clinical aspects of uremic cardiomyopathy and the rapidly increasing knowledge of the biology of both fibroblast growth factor-23 and αKlotho. Finally, we discuss how dissection of these pathological processes is aiding the development of therapeutic options, including small molecules and antibodies, directly aimed at improving the cardiovascular outcomes of patients with chronic kidney disease and end-stage renal disease.
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Affiliation(s)
- Jonathan P. Law
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
- Department of NephrologyUniversity Hospitals Birmingham NHS Foundation TrustBirminghamUnited Kingdom
| | - Anna M. Price
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
- Department of NephrologyUniversity Hospitals Birmingham NHS Foundation TrustBirminghamUnited Kingdom
| | - Luke Pickup
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
| | - Ashwin Radhakrishnan
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
| | - Chris Weston
- Institute of Immunology and ImmunotherapyUniversity of BirminghamUnited Kingdom
- NIHR Birmingham Biomedical Research CentreUniversity Hospitals Birmingham NHS Foundation Trust and University of BirminghamUnited Kingdom
| | - Alan M. Jones
- School of PharmacyUniversity of BirminghamUnited Kingdom
| | | | - Winnie Chua
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
| | - Richard P. Steeds
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
- Department of CardiologyUniversity Hospitals Birmingham NHS Foundation TrustBirminghamUnited Kingdom
| | - Larissa Fabritz
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
- Department of CardiologyUniversity Hospitals Birmingham NHS Foundation TrustBirminghamUnited Kingdom
| | - Paulus Kirchhof
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
| | - Davor Pavlovic
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
| | - Jonathan N. Townend
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
- Department of CardiologyUniversity Hospitals Birmingham NHS Foundation TrustBirminghamUnited Kingdom
| | - Charles J. Ferro
- Birmingham Cardio‐Renal GroupUniversity Hospitals BirminghamUniversity of BirminghamUnited Kingdom
- Institute of Cardiovascular SciencesUniversity of BirminghamUnited Kingdom
- Department of NephrologyUniversity Hospitals Birmingham NHS Foundation TrustBirminghamUnited Kingdom
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Motta SE, Imenez Silva PH, Daryadel A, Haykir B, Pastor-Arroyo EM, Bettoni C, Hernando N, Wagner CA. Expression of NaPi-IIb in rodent and human kidney and upregulation in a model of chronic kidney disease. Pflugers Arch 2020; 472:449-460. [PMID: 32219532 DOI: 10.1007/s00424-020-02370-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 02/29/2020] [Accepted: 03/20/2020] [Indexed: 01/07/2023]
Abstract
Na+-coupled phosphate cotransporters from the SLC34 and SLC20 families of solute carriers mediate transepithelial transport of inorganic phosphate (Pi). NaPi-IIa/Slc34a1, NaPi-IIc/Slc34a3, and Pit-2/Slc20a2 are all expressed at the apical membrane of renal proximal tubules and therefore contribute to renal Pi reabsorption. Unlike NaPi-IIa and NaPi-IIc, which are rather kidney-specific, NaPi-IIb/Slc34a2 is expressed in several epithelial tissues, including the intestine, lung, testis, and mammary glands. Recently, the expression of NaPi-IIb was also reported in kidneys from rats fed on high Pi. Here, we systematically quantified the mRNA expression of SLC34 and SLC20 cotransporters in kidneys from mice, rats, and humans. In all three species, NaPi-IIa mRNA was by far the most abundant renal transcript. Low and comparable mRNA levels of the other four transporters, including NaPi-IIb, were detected in kidneys from rodents and humans. In mice, the renal expression of NaPi-IIa transcripts was restricted to the cortex, whereas NaPi-IIb mRNA was observed in medullary segments. Consistently, NaPi-IIb protein colocalized with uromodulin at the luminal membrane of thick ascending limbs of the loop of Henle segments. The abundance of NaPi-IIb transcripts in kidneys from mice was neither affected by dietary Pi, the absence of renal NaPi-IIc, nor the depletion of intestinal NaPi-IIb. In contrast, it was highly upregulated in a model of oxalate-induced kidney disease where all other SLC34 phosphate transporters were downregulated. Thus, NaPi-IIb may contribute to renal phosphate reabsorption, and its upregulation in kidney disease might promote hyperphosphatemia.
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Affiliation(s)
- Sarah E Motta
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Pedro Henrique Imenez Silva
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Arezoo Daryadel
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Betül Haykir
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Eva Maria Pastor-Arroyo
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carla Bettoni
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Nati Hernando
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Carsten A Wagner
- Institute of Physiology, Switzerland and National Center of Competence in Research NCCR Kidney, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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38
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Cozzolino M, Ketteler M, Wagner CA. An expert update on novel therapeutic targets for hyperphosphatemia in chronic kidney disease: preclinical and clinical innovations. Expert Opin Ther Targets 2020; 24:477-488. [PMID: 32191548 DOI: 10.1080/14728222.2020.1743680] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Introduction: The management of hyperphosphatemia in patients with chronic kidney disease (CKD) is complicated, requiring a multidisciplinary approach that includes dietary phosphate restriction, dialysis, and phosphate binders.Areas covered: We describe key players involved in regulating inorganic phosphate homeostasis and their differential role in healthy people and different stages of CKD. The contribution of paracellular and transcellular intestinal absorptive mechanisms are also examined. Finally, we illuminate recent therapeutic approaches for hyperphosphatemia in CKD. We searched PubMed/Medline (up to November 2019) using the following terms: chronic kidney disease, dialysis, diet, hyperphosphatemia, NaPi2b, nicotinamide, phosphate binder, secondary hyperparathyroidism, tenapanor and vascular calcification.Expert opinion: The precise mechanisms regulating intestinal phosphate absorption in humans is not completely understood. However, it is now established that this process involves two independent pathways: a) active transport (i.e. transcellular route, via specific ion transporters) and inactive transport (i.e. paracellular route across tight junctions). Dietary phosphate restriction and phosphate-binder use can lead to an undesirable maladaptive increase in phosphate uptake and promote active phosphate transport by increased expression of the gastrointestinal sodium-dependent phosphate transporter, NaPi2b. Nicotinamide may overcome these limitations through the inhibition of NaPi2b, by improved efficacy and reduced phosphate binder use and better compliance.
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Affiliation(s)
- Mario Cozzolino
- Renal Division, ASST Santi Paolo E Carlo, Department of Health Sciences, University of Milan, Milan, Italy
| | - Markus Ketteler
- Department of General Internal Medicine and Nephrology, Robert-Bosch-Krankenhaus, Stuttgart, Germany
| | - Carsten Alexander Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland.,National Center of Competence in Research, NCCR Kidney. CH, Zurich, Switzerland
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Yaguchi A, Akahane K, Tsuchioka K, Yonekubo S, Yamamoto S, Tamai Y, Tatemichi S, Takeda H. A comparison between the combined effect of calcium carbonate with sucroferric oxyhydroxide and other phosphate binders: an in vitro and in vivo experimental study. BMC Nephrol 2019; 20:465. [PMID: 31830936 PMCID: PMC6909506 DOI: 10.1186/s12882-019-1655-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 12/03/2019] [Indexed: 02/06/2023] Open
Abstract
Background Approximately 30% of patients on dialysis received combination therapy for their phosphate binder prescription; however, few studies for combined effects of phosphate binders are reported. For the purpose of evaluating the efficacy of combination therapy, we compared the efficacy of sucroferric oxyhydroxide (PA21) combined with calcium carbonate with that of lanthanum carbonate hydrate, sevelamer hydrochloride, and ferric citrate hydrate combined with calcium carbonate. Methods For in vitro studies, calcium carbonate and the other phosphate binders alone or in combination were stirred in phosphate solution at pH 2–8 for 2 h. After centrifuging the suspension, the phosphorus level in the supernatant was determined. For in vivo studies, rats were orally administered calcium carbonate and the other phosphate binders (except for sevelamer hydrochloride) alone or in combination, followed by oral administration of phosphate solution adjusted to pH 2 or 7. Serum samples were collected from the rats at predetermined timepoints and the serum phosphorus levels were determined and analyzed using a two-way analysis of variance. Results In the in vitro study, the measured phosphate-binding capacity of combining sevelamer hydrochloride, PA21, and lanthanum carbonate hydrate with calcium carbonate was approximately equal to or greater than the theoretical values under most conditions. Furthermore, these combined effects were insensitive to pH in that order. The measured phosphate-binding capacity of ferric citrate hydrate combined with calcium carbonate was smaller than the theoretical values, and the combination did not exhibit efficacy under any of the tested conditions. In the in vivo study, the combined effect of PA21 and calcium carbonate at both pH values and that of lanthanum carbonate hydrate and calcium carbonate at pH 2 were additive. In contrast, the combined effect of lanthanum carbonate hydrate and calcium carbonate at pH 7 and that of ferric citrate hydrate and calcium carbonate at pH 2 were antagonistic. Conclusions These results suggest that coadministration of PA21 and calcium carbonate showed good and relatively stable efficacy throughout the range of the gastrointestinal pH and that combining lanthanum carbonate hydrate and ferric citrate hydrate with calcium carbonate may not produce the expected efficacy under certain conditions.
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Affiliation(s)
- Atsushi Yaguchi
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan.
| | - Kenji Akahane
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
| | - Kumi Tsuchioka
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
| | - Saori Yonekubo
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
| | - Shota Yamamoto
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
| | - Yasuaki Tamai
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
| | - Satoshi Tatemichi
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
| | - Hiroo Takeda
- Pharmacology Research Group, Pharmacology and Pharmacokinetics Research Laboratory, R&D, Kissei Pharmaceutical Co., Ltd., 4365-1 Kashiwabara, Hotaka, Azumino, Nagano, 399-8304, Japan
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40
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Cao S, Zhang S, Liu G, Zhang L, Lu L, Zhang R, Liao X, Luo X. Kinetics of phosphorus absorption and expressions of related transporters in primary cultured duodenal epithelial cells of chick embryos. J Anim Physiol Anim Nutr (Berl) 2019; 104:237-244. [PMID: 31808203 DOI: 10.1111/jpn.13260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 10/21/2019] [Accepted: 11/02/2019] [Indexed: 01/21/2023]
Abstract
Two experiments were conducted to investigate the kinetics of phosphorus (P) absorption and expressions of type IIb sodium-dependent phosphate cotransporter (NaP-IIb), inorganic phosphate transporters 1 and 2 (PiT-1 and PiT-2) in primary cultured duodenal epithelial cells of chick embryos. In experiment 1, the P absorptions across duodenal epithelial cell monolayers at different incubation time points (0, 10, 20, 40, 60, 80, 100 and 120 min) were compared. In experiment 2, the kinetics of P absorption was performed at 40 min after incubation of duodenal epithelial cells with the media containing 0, 0.75, 1.5, 3.0, 6.0, 12.0, 24.0 and 48.0 mmol P/L as KH2 PO4 , and the mRNA and protein expression levels of NaP-IIb, PiT-1 and PiT-2 in duodenal epithelial cells with the media containing 0, 6.0 and 48.0 mmol P/L were determined at 87 min after incubation. The results from experiment 1 showed that the P absorption increased linearly (p < .0001) from 0 to 80 min and the fastest increase occurred at 40 min; the asymptotic model was shown to have the best fit degree, and the optimal incubation time for saturable P absorption was determined to be 87 min. The kinetic curves of P absorption from experiment 2 demonstrated that P absorption was a mixed process of a non-saturable diffusion plus a saturable carrier-mediated transport across the duodenal epithelial cells. The high P concentration (48.0 mmol/L) decreased (p < .05) NaP-IIb and PiT-1 mRNA and protein levels and increased (p < .0001) PiT-2 mRNA level. These results indicated that the P absorption across primary cultured duodenal epithelial cell monolayers of chick embryos was a mixed process of a non-saturable diffusion plus a saturable carrier-mediated transport and could be restricted by reducing the NaP-IIb and PiT-1 expressions while increasing the PiT-2 expression at a high P concentration.
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Affiliation(s)
- Sumei Cao
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China.,Laboratory of Feed Biotechnology, State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, P. R. China
| | - Shumin Zhang
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China
| | - Guoqing Liu
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China
| | - Liyang Zhang
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China
| | - Lin Lu
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China
| | - Rijun Zhang
- Laboratory of Feed Biotechnology, State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, P. R. China
| | - Xiudong Liao
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China
| | - Xugang Luo
- Mineral Nutrition Research Division, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, P. R. China
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41
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Phosphorus absorption and gene expression levels of related transporters in the small intestine of broilers. Br J Nutr 2019; 119:1346-1354. [PMID: 29845902 DOI: 10.1017/s0007114518000934] [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] [Indexed: 11/06/2022]
Abstract
To investigate the P absorption and gene expression levels of related co-transporters, type IIb sodium-dependent phosphate co-transporter (NaPi-IIb), inorganic phosphate transporter 1 (PiT-1) and inorganic phosphate transporter 2 (PiT-2) in the small intestine of broilers, 450 1-d-old Arbor Acres male broilers were randomly allocated to one of three treatments with ten replicate cages of fifteen birds per cage for each treatment in a completely randomised design. Chickens were fed a diet with no added inorganic P (containing 0·06 % non-phytate P (NPP)) or with either 0·21 or 0·44 % NPP for 21 d. Plasma P concentration in the hepatic portal vein, mRNA and protein expression levels of NaPi-IIb, PiT-1 and PiT-2 were determined at 7, 14 and 21 d of age. The results showed that the concentration of P in plasma in the hepatic portal vein increased as dietary NPP increased (P<0·0001). At 14 and 21 d of age, the increase in dietary NPP inhibited (P<0·003) NaPi-IIb mRNA expression level in the duodenum, as well as PiT-1 mRNA and protein expression levels in the ileum, but promoted NaPi-IIb protein expression level (P<0·002) and PiT-2 mRNA and protein expression levels (P<0·04) in the duodenum. These results suggest that NaPi-IIb, PiT-1 and PiT-2 might be important P transporters in the small intestine of broilers. Higher intestinal P absorption may be achieved by up-regulating the protein expression levels of NaPi-IIb and PiT-2 and down-regulating the protein expression of PiT-1.
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Saurette M, Alexander RT. Intestinal phosphate absorption: The paracellular pathway predominates? Exp Biol Med (Maywood) 2019; 244:646-654. [PMID: 30764666 DOI: 10.1177/1535370219831220] [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] [Indexed: 01/28/2023] Open
Abstract
IMPACT STATEMENT This review summarizes the work on transcellular intestinal phosphate absorption, arguing why this pathway is not the predominant pathway in humans consuming a "Western" diet. We then highlight the recent evidence which is strongly consistent with paracellular intestinal phosphate absorption mediating the bulk of intestinal phosphate absorption in humans.
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Affiliation(s)
- Matthew Saurette
- 1 Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2R7, Canada.,2 The Women's & Children's Health Research Institute, Edmonton, Alberta T6G 1C9, Canada
| | - R Todd Alexander
- 1 Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2R7, Canada.,2 The Women's & Children's Health Research Institute, Edmonton, Alberta T6G 1C9, Canada.,3 Department of Pediatrics, University of Alberta, Edmonton, Alberta T6G 2R7, Canada
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Abstract
Calcium kidney stones are common worldwide. Most are idiopathic and composed of calcium oxalate. Calcium phosphate is present in around 80% and may initiate stone formation. Stone production is multifactorial with a polygenic genetic contribution. Phosphaturia is found frequently among stone formers but until recently received scant attention. This review examines possible mechanisms for the phosphaturia and its relevance to stone formation from a wide angle. There is a striking lack of clinical data. Phosphaturia is associated, but not correlated, with hypercalciuria, increased 1,25 dihydroxy-vitamin D [1,25 (OH)2D], and sometimes evidence of disturbances in proximal renal tubular function. Phosphate reabsorption in the proximal renal tubules requires tightly regulated interaction of many proteins. Paracellular flow through intercellular tight junctions is the major route of phosphate absorption from the intestine and can be reduced therapeutically in hyperphosphatemic patients. In monogenic defects stones develop when phosphaturia is associated with hypercalciuria, generally explained by increased 1,25 (OH)2D production in response to hypophosphatemia. Calcification does not occur in disorders with increased FGF23 when phosphaturia occurs in isolation and 1,25 (OH)2D is suppressed. Candidate gene studies have identified mutations in the phosphate transporters, but in few individuals. One genome-wide study identified a polymorphism of the phosphate transporter gene SLC34A4 associated with stones. Others did not find mutations obviously linked to phosphate reabsorption. Future genetic studies should have a wide trawl and should focus initially on groups of patients with clearly defined phenotypes. The global data should be pooled.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
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Jacquillet G, Unwin RJ. Physiological regulation of phosphate by vitamin D, parathyroid hormone (PTH) and phosphate (Pi). Pflugers Arch 2019; 471:83-98. [PMID: 30393837 PMCID: PMC6326012 DOI: 10.1007/s00424-018-2231-z] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/20/2018] [Accepted: 10/25/2018] [Indexed: 01/05/2023]
Abstract
Inorganic phosphate (Pi) is an abundant element in the body and is essential for a wide variety of key biological processes. It plays an essential role in cellular energy metabolism and cell signalling, e.g. adenosine and guanosine triphosphates (ATP, GTP), and in the composition of phospholipid membranes and bone, and is an integral part of DNA and RNA. It is an important buffer in blood and urine and contributes to normal acid-base balance. Given its widespread role in almost every molecular and cellular function, changes in serum Pi levels and balance can have important and untoward effects. Pi homoeostasis is maintained by a counterbalance between dietary Pi absorption by the gut, mobilisation from bone and renal excretion. Approximately 85% of total body Pi is present in bone and only 1% is present as free Pi in extracellular fluids. In humans, extracellular concentrations of inorganic Pi vary between 0.8 and 1.2 mM, and in plasma or serum Pi exists in both its monovalent and divalent forms (H2PO4- and HPO42-). In the intestine, approximately 30% of Pi absorption is vitamin D regulated and dependent. To help maintain Pi balance, reabsorption of filtered Pi along the renal proximal tubule (PT) is via the NaPi-IIa and NaPi-IIc Na+-coupled Pi cotransporters, with a smaller contribution from the PiT-2 transporters. Endocrine factors, including, vitamin D and parathyroid hormone (PTH), as well as newer factors such as fibroblast growth factor (FGF)-23 and its coreceptor α-klotho, are intimately involved in the control of Pi homeostasis. A tight regulation of Pi is critical, since hyperphosphataemia is associated with increased cardiovascular morbidity in chronic kidney disease (CKD) and hypophosphataemia with rickets and growth retardation. This short review considers the control of Pi balance by vitamin D, PTH and Pi itself, with an emphasis on the insights gained from human genetic disorders and genetically modified mouse models.
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Affiliation(s)
- Grégory Jacquillet
- Centre for Nephrology, University College London (UCL), Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK
| | - Robert J Unwin
- Centre for Nephrology, University College London (UCL), Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK.
- AstraZeneca IMED ECD CVRM R&D, Gothenburg, Sweden.
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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: 3.2] [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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Vorland CJ, Lachcik PJ, Aromeh LO, Moe SM, Chen NX, Hill Gallant KM. Effect of dietary phosphorus intake and age on intestinal phosphorus absorption efficiency and phosphorus balance in male rats. PLoS One 2018; 13:e0207601. [PMID: 30452474 PMCID: PMC6242370 DOI: 10.1371/journal.pone.0207601] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 10/26/2018] [Indexed: 12/31/2022] Open
Abstract
Intestinal phosphorus absorption is an important component of whole-body phosphorus metabolism, and limiting dietary phosphorus absorption is particularly of interest as a therapeutic target in patients with chronic kidney disease to manage mineral bone disorders. Yet, mechanisms and regulation of intestinal phosphorus absorption have not been adequately studied and discrepancies in findings exist based on the absorption assessment technique used. In vitro techniques show rather consistent effects of dietary phosphorus intake level and age on intestinal sodium-dependent phosphate transport. But, the few studies that have used in vivo techniques conflict with these in vitro studies. Therefore, we aimed to investigate the effects of dietary phosphorus intake level on phosphorus absorption using the in situ ligated loop technique in three different aged rats. Male Sprague-Dawley rats (n = 72), were studied at 10-, 20-, and 30-weeks-of-age on a low (0.1%), normal (0.6%), or high (1.2%) phosphorus diet in a 3x3 factorial design (n = 8/group). Rats were fed their assigned diet for 2-weeks prior to absorption testing by jejunal ligated loop as a non-survival procedure, utilizing 33P radioisotope. Metabolic cages were used for determination of calcium and phosphorus balance over the final four days prior to sacrifice, and blood was collected at the time of sacrifice for biochemistries. Our results show that phosphorus absorption was higher in 10-week-old rats compared with 20- and 30-week-olds and this corresponded to higher gene expression of the major phosphate transporter, NaPi-2b, as well as higher whole-body phosphorus balance and net phosphorus absorption. Dietary phosphorus intake level did not affect jejunal phosphorus absorption or NaPi-2b gene expression. Our results contrast with studies utilizing in vitro techniques, but corroborate results of other rodent studies utilizing in situ or in vivo methods. Thus, there is need for additional studies that employ more physiological methods of phosphorus absorption assessment.
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Affiliation(s)
- Colby J. Vorland
- Department of Nutrition Science, Purdue University, West Lafayette, IN, United States of America
| | - Pamela J. Lachcik
- Department of Nutrition Science, Purdue University, West Lafayette, IN, United States of America
| | - Loretta O. Aromeh
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Sharon M. Moe
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, United States of America
- Department of Medicine, Roudebush Veterans Affairs Medicine Center, Indianapolis, IN, United States of America
| | - Neal X. Chen
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, United States of America
| | - Kathleen M. Hill Gallant
- Department of Nutrition Science, Purdue University, West Lafayette, IN, United States of America
- * E-mail:
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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: 25] [Impact Index Per Article: 4.2] [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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Stremke ER, Hill Gallant KM. Intestinal Phosphorus Absorption in Chronic Kidney Disease. Nutrients 2018; 10:E1364. [PMID: 30249044 PMCID: PMC6213936 DOI: 10.3390/nu10101364] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 09/17/2018] [Accepted: 09/19/2018] [Indexed: 02/06/2023] Open
Abstract
Chronic kidney disease (CKD) affects approximately 10% of adults worldwide. Dysregulation of phosphorus homeostasis which occurs in CKD leads to development of CKD-Mineral Bone Disorder (CKD-MBD) and contributes to increased morbidity and mortality in these patients. Phosphorus is regulated by multiple hormones (parathyroid hormone (PTH), 1,25-dihyxdroxyvitamin D (1,25D), and fibroblast growth factor 23 (FGF23)) and tissues (kidney, intestine, parathyroid glands, and bone) to maintain homeostasis. In health, the kidneys are the major site of regulation for phosphorus homeostasis. However, as kidney function declines, the ability of the kidneys to adequately excrete phosphorus is reduced. The hormonal changes that occur with CKD would suggest that the intestine should compensate for impaired renal phosphorus excretion by reducing fractional intestinal phosphorus absorption. However, limited studies in CKD animal models and patients with CKD suggest that there may be a break in this homeostatic response where the intestine fails to compensate. As many existing therapies for phosphate management in CKD are aimed at reducing absolute intestinal phosphorus absorption, better understanding of the factors that influence fractional and absolute absorption, the mechanism by which intestinal phosphate absorption occurs, and how CKD modifies these is a much-needed area of study.
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Affiliation(s)
- Elizabeth R Stremke
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA.
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Fouque D, Vervloet M, Ketteler M. Targeting Gastrointestinal Transport Proteins to Control Hyperphosphatemia in Chronic Kidney Disease. Drugs 2018; 78:1171-1186. [PMID: 30022383 PMCID: PMC6132443 DOI: 10.1007/s40265-018-0950-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Management of hyperphosphatemia in patients with dialysis-dependent chronic kidney disease remains a major challenge, requiring a multifaceted approach that includes dietary phosphate restriction, dialysis, and phosphate binders. However, these treatments fail to meet serum phosphate targets in many patients, potentially further exacerbating the significant morbidity and mortality burden associated with the disease. Recent advances in our understanding of the mechanisms underlying phosphate homeostasis have shed new light on the issue and suggest that gastrointestinal transport proteins may be promising targets for new hyperphosphatemia treatments. Drugs that inhibit or downregulate these transport proteins, and thus reduce phosphate uptake from the gut, may overcome some of the limitations of existing phosphate-lowering strategies, such as interdialytic rises in serum phosphate levels, poor adherence to dietary and phosphate-binder regimens, and maladaptive responses that can increase gastrointestinal phosphate absorption. Here, we review the latest preclinical and clinical data for two candidates in this novel drug class: tenapanor, a small-molecule inhibitor of the sodium/hydrogen ion-exchanger isoform 3, and nicotinamide, an inhibitor of sodium-phosphate-2b cotransporters. We also discuss how potential synergies in their mechanisms of action suggest that coadministering phosphate binders with sodium-phosphate-2b cotransporter inhibitors may yield additive benefits over traditional phosphate-binder therapy.
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Affiliation(s)
- Denis Fouque
- Department of Nephrology, Centre Hospitalier Lyon-Sud, Université de Lyon, Carmen, 165 Chemin du Grand Revoyet, 69495, Pierre-Bénite, France
| | - Marc Vervloet
- Department of Nephrology and Amsterdam Cardiovascular Sciences (ACS), VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, Netherlands
| | - Markus Ketteler
- Division of Nephrology, Klinikum Coburg GmbH, Ketschendorfer Str. 33, D-96450, Coburg, Germany.
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50
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Ren ZZ, Bütz DE, Wahhab AN, Piepenburg AJ, Cook ME. Additive effects of fibroblast growth factor 23 neutralization and dietary phytase on chick calcium and phosphorus metabolism. Poult Sci 2018; 96:1167-1173. [PMID: 27665015 DOI: 10.3382/ps/pew339] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Accepted: 08/11/2016] [Indexed: 01/01/2023] Open
Abstract
Phytase hydrolyzes phytate rendering phosphorus available for intestinal absorption, while systemic neutralization of fibroblast growth factor 23 (FGF-23), using anti-FGF-23 antibody, has been shown to increase phosphate retention. Hence, neutralization of FGF-23 should be additive with phytase in reducing dietary non-phytate phosphorus (nPP) needs in chickens fed plant-based diets rich in phytic acid. This study was designed to test the additive effects of maternally derived anti-FGF-23 antibody and dietary phytase on the performance of chicks fed a low nPP diet from one to 14 d. Single Comb White Leghorn laying hens were vaccinated with either an adjuvant control or a synthetic FGF-23 peptide (GMNPPPYS). Chicks from vaccinated hens with control or anti-FGF-23 maternal antibodies were fed either a diet containing 0.2% nPP and 0.9% calcium with or without 500 unit phytase per kg of diet (2 × 2 factorial with main effects of antibody type and phytase addition, n = 15 pens of chicks/treatment). A significant interaction between dietary phytase and maternally derived anti-FGF-23 antibody on growth and feed efficiency was observed (P ≤ 0.05), in which chicks receiving either phytase or maternally derived anti-FGF-23 antibody had improved body weight gain (21 or 15%, respectively) and feed efficiency (16 or 18%, respectively) as compared to chicks with control antibody and not fed phytase. Both phytase and maternally derived anti-FGF-23 antibody independently increased (P ≤ 0.05) plasma phosphate (11 and 11%, respectively) and percent tibiotarsus ash (13 and 11%, respectively). Significant main effects and the lack of an interaction supported an additive effect of phytase and anti-FGF-23 antibody on plasma phosphate and percent tibiotarsus ash. Feeding phytase to chicks fed 0.2% nPP increased plasma FGF-23 levels by 22% (P ≤ 0.05); however, no effects of anti-FGF-23 antibody on plasma FGF-23 levels were observed. In conclusion, dietary phytase and presence of anti-FGF-23 antibody have an additive effect on plasma phosphate and tibiotarsus ash in chicks fed low nPP diets. Data support that phytase and anti-FGF-23 antibody increase phosphate utilization by different mechanisms.
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Affiliation(s)
- Z Z Ren
- Department of Animal Sciences, 1675 Observatory Drive, University of Wisconsin-Madison 53706.,Institute of Animal Nutrition, 211 Huimin Road, Sichuan Agricultural University, Chengdu, Sichuan 611130, China
| | - D E Bütz
- Department of Animal Sciences, 1675 Observatory Drive, University of Wisconsin-Madison 53706
| | - A N Wahhab
- Department of Animal Sciences, 1675 Observatory Drive, University of Wisconsin-Madison 53706
| | - A J Piepenburg
- Department of Animal Sciences, 1675 Observatory Drive, University of Wisconsin-Madison 53706
| | - M E Cook
- Department of Animal Sciences, 1675 Observatory Drive, University of Wisconsin-Madison 53706
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