1
|
Abstract
Calcium and phosphorus are the most abundant minerals in the body. An adult body contains over 1 kg of calcium and it has various functions throughout the body. The average plasma concentration of calcium is about 2.5 mmol/l. The intracellular concentration of calcium is approximately 100 nmol/ml. The control of both intracellular and extracellular calcium concentrations is vital.
Collapse
|
2
|
Omara II, Mou CT, Persia ME, Wong EA. Effects of available phosphorus source and concentration on performance and expression of sodium phosphate type IIb cotransporter, vitamin D-1α-hydroxylase, and vitamin D-24-hydroxylase mRNA in broiler chicks. Poult Sci 2020; 99:1822-1831. [PMID: 32241462 PMCID: PMC7587676 DOI: 10.1016/j.psj.2019.12.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/26/2019] [Accepted: 12/10/2019] [Indexed: 11/17/2022] Open
Abstract
This experiment was conducted to examine the effect of 2 phosphorus (P) sources on broiler performance to day 14. The P bioavailability was estimated using bird performance and tibia ash measurements, whereas P digestibility, intestinal P transporter, kidney vitamin D-1α-hydroxylase, and vitamin D-24-hydroxylase mRNA abundances were also determined. Slope regression analysis was used to determine the bioavailability of dicalcium phosphate (Dical P) and nanocalcium phosphate (Nano P) with dietary available P (AvP) set to 0.20% P (control) using AvP from the major ingredients and Dical P. The experimental treatments were achieved by supplementation with either Dical P or Nano P to generate 0.24, 0.28, 0.32, and 0.36% AvP. A total of 648-day-old unsexed broiler chicks were divided into 72 birds per treatment (8 replicate cages of 9 birds). Slope regression analysis showed positive linear relationships between BW, feed intake (FI), tibia ash weight (TAW), and tibia ash percentage (TAP) with dietary Dical P and Nano P levels. Comparisons between regression slopes for Dical P and Nano P fed birds were not significantly different for BW, feed intake, tibia ash weight, and tibia ash percentage, indicating similar P bioavailability from Dical P and Nano P. There were interactions between P source and AvP for feed efficiency (FE) and apparent ileal P digestibility (AIPD). Dicalcium phosphate had greater FE than Nano P at 0.28% AvP and greater AIPD than Nano P at 0.24% AvP. The addition of AvP from Dical P and Nano P resulted in reduced sodium phosphate cotransporter mRNA abundance in the duodenum in a dose–dependent response. In the kidney, vitamin D-1α-hydroxylase mRNA abundance was greater at 0.36% Nano P compared with control, but there was no difference with Dical P. There was no difference in vitamin D-24-hydroxylase mRNA abundance between control and supplementation with Nano P or Dical P. In conclusion, Nano P and Dical P had the same bioavailability but had different effects on gene expression.
Collapse
Affiliation(s)
- I I Omara
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24060, USA; Animal Production Department, Faculty of Agriculture, Cairo University, Giza 12613, Egypt
| | - C T Mou
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24060, USA
| | - M E Persia
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24060, USA
| | - E A Wong
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA 24060, USA.
| |
Collapse
|
3
|
Tatsumi S, Katai K, Kaneko I, Segawa H, Miyamoto KI. NAD metabolism and the SLC34 family: evidence for a liver-kidney axis regulating inorganic phosphate. Pflugers Arch 2018; 471:109-122. [PMID: 30218374 DOI: 10.1007/s00424-018-2204-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 08/29/2018] [Accepted: 09/06/2018] [Indexed: 12/18/2022]
Abstract
The solute carrier 34 (SLC34) family of membrane transporters is a major contributor to Pi homeostasis. Many factors are involved in regulating the SLC34 family. The roles of the bone mineral metabolism factors parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF23) in Pi homeostasis are well studied. Intracellular Pi is thought to be involved in energy metabolism, such as ATP production. Under certain conditions of altered energy metabolism, plasma Pi concentrations are affected by the regulation of a Pi shift into cells or release from the tissues. We recently investigated the mechanism of hepatectomy-related hypophosphatemia, which is thought to involve an unknown phosphaturic factor. Hepatectomy-related hypophosphatemia is due to impaired nicotinamide adenine dinucleotide (NAD) metabolism through its effects on the SLC34 family in the liver-kidney axis. The oxidized form of NAD, NAD+, is an essential cofactor in various cellular biochemical reactions. Levels of NAD+ and its reduced form NADH vary with the availability of dietary energy and nutrients. Nicotinamide phosphoribosyltransferase (Nampt) generates a key NAD+ intermediate, nicotinamide mononucleotide, from nicotinamide and 5-phosphoribosyl 1-pyrophosphate. The liver, an important organ of NAD metabolism, is thought to release metabolic products such as nicotinamide and may control NAD metabolism in other organs. Moreover, NAD is an important regulator of the circadian rhythm. Liver-specific Nampt-deficient mice and heterozygous Nampt mice have abnormal daily plasma Pi concentration oscillations. These data indicate that NAD metabolism in the intestine, liver, and kidney is closely related to Pi metabolism through the SLC34 family. Here, we review the relationship between the SLC34 family and NAD metabolism based on our recent studies.
Collapse
Affiliation(s)
- Sawako Tatsumi
- Department of Molecular Nutrition, Institution of Biomedical Science, Tokushima University Graduate School, 3-18-15 Kuramoto, Tokushima, 770-8503, Japan.,Department of Food Science and Nutrition, School of Human Cultures, The University of Shiga Prefecture, Hikone, Japan
| | - Kanako Katai
- Faculty of Human Life and Science, Department of Food Science and Nutrition, Doshisha Women's College of Liberal Arts, Kyoto, Japan
| | - Ichiro Kaneko
- Department of Molecular Nutrition, Institution of Biomedical Science, Tokushima University Graduate School, 3-18-15 Kuramoto, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institution of Biomedical Science, Tokushima University Graduate School, 3-18-15 Kuramoto, Tokushima, 770-8503, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institution of Biomedical Science, Tokushima University Graduate School, 3-18-15 Kuramoto, Tokushima, 770-8503, Japan.
| |
Collapse
|
4
|
Chen P, Huang Y, Bayir A, Wang C. Characterization of the isoforms of type IIb sodium-dependent phosphate cotransporter (Slc34a2) in yellow catfish, Pelteobagrus fulvidraco, and their vitamin D 3-regulated expression under low-phosphate conditions. FISH PHYSIOLOGY AND BIOCHEMISTRY 2017; 43:229-244. [PMID: 27620186 DOI: 10.1007/s10695-016-0282-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 08/27/2016] [Indexed: 06/06/2023]
Abstract
In this study, two isoforms slc34a2 genes (type IIb sodium-dependent phosphate cotransporter), slc34a2a2 and slc34a2b, were cloned from intestine and kidney of yellow catfish (Pelteobagrus fulvidraco), with rapid amplification of cDNA ends. The structure differences and the regulation effects of dietary VD3 under low phosphorus were compared among three isoforms of slc34a2 in yellow catfish. The predicted Slc34a2a2 and Slc34a2b proteins match 65 % and 53.8 % sequence identity, with Slc34a2a1, respectively. The membrane-spanning domains were different among these three isoforms. Intestinal Slc34a2a1 and Slc34a2a2 proteins had eight and eleven transmembrane domains, while renal Slc34a2b protein had nine. The tissue distribution study showed that same as slc34a2a1, slc34a2a2 mRNA was mainly distributed in intestine and slc34a2b mRNA in kidney. The effect of vitamin D3 (VD3) level on slc34a2 subfamily expression under low-phosphate conditions, induced by the addition of 0 (VD0), 324 (VD1), 1243 (VD2), 3621 (VD3), 8040 (VD4), or 22700 (VD5) IU VD3/kg feed, was assessed by qPCR. The dose-responsive expression of intestinal slc34a2a2 and high expression of intestinal slc34a2a2 in VD5 together with peak expression of kidney slc34a2b in VD3 coincided with the accumulation of body phosphate content. These data suggested that appropriate level of dietary VD3 up-regulated slc34a2a1, slc34a2a2, and slc34a2b mRNA levels, which increased phosphate retention. In conclusion, the current study provided another possible approach to improve dietary phosphate utilization by adding appropriate level of VD3 to a low-phosphate diet to regulate intestinal and renal slc34a2 gene expression and thus minimize the excretion of phosphorus in yellow catfish.
Collapse
Affiliation(s)
- Pei Chen
- The College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
- Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, People's Republic of China
- Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, People's Republic of China
| | - Yanqing Huang
- East China Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Shanghai, 200090, People's Republic of China
| | - Abdulkadir Bayir
- Department of Aquaculture, Faculty of Fisheries, Atatürk University, 25240, Erzurum, Turkey
| | - Chunfang Wang
- The College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
- Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, People's Republic of China.
- Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, People's Republic of China.
| |
Collapse
|
5
|
Saito A, Nikolaidis NM, Amlal H, Uehara Y, Gardner JC, LaSance K, Pitstick LB, Bridges JP, Wikenheiser-Brokamp KA, McGraw DW, Woods JC, Sabbagh Y, Schiavi SC, Altinişik G, Jakopović M, Inoue Y, McCormack FX. Modeling pulmonary alveolar microlithiasis by epithelial deletion of the Npt2b sodium phosphate cotransporter reveals putative biomarkers and strategies for treatment. Sci Transl Med 2016; 7:313ra181. [PMID: 26560359 DOI: 10.1126/scitranslmed.aac8577] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pulmonary alveolar microlithiasis (PAM) is a rare, autosomal recessive lung disorder associated with progressive accumulation of calcium phosphate microliths. Inactivating mutations in SLC34A2, which encodes the NPT2b sodium-dependent phosphate cotransporter, has been proposed as a cause of PAM. We show that epithelial deletion of Npt2b in mice results in a progressive pulmonary process characterized by diffuse alveolar microlith accumulation, radiographic opacification, restrictive physiology, inflammation, fibrosis, and an unexpected alveolar phospholipidosis. Cytokine and surfactant protein elevations in the alveolar lavage and serum of PAM mice and confirmed in serum from PAM patients identify serum MCP-1 (monocyte chemotactic protein 1) and SP-D (surfactant protein D) as potential biomarkers. Microliths introduced by adoptive transfer into the lungs of wild-type mice produce marked macrophage-rich inflammation and elevation of serum MCP-1 that peaks at 1 week and resolves at 1 month, concomitant with clearance of stones. Microliths isolated by bronchoalveolar lavage readily dissolve in EDTA, and therapeutic whole-lung EDTA lavage reduces the burden of stones in the lungs. A low-phosphate diet prevents microlith formation in young animals and reduces lung injury on the basis of reduction in serum SP-D. The burden of pulmonary calcium deposits in established PAM is also diminished within 4 weeks by a low-phosphate diet challenge. These data support a causative role for Npt2b in the pathogenesis of PAM and the use of the PAM mouse model as a preclinical platform for the development of biomarkers and therapeutic strategies.
Collapse
Affiliation(s)
- Atsushi Saito
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - Nikolaos M Nikolaidis
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - Hassane Amlal
- Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Yasuaki Uehara
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - Jason C Gardner
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - Kathleen LaSance
- Vontz Core Imaging Laboratory, Vontz Center for Molecular Studies, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - Lori B Pitstick
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - James P Bridges
- Perinatal Institute, Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | | | - Dennis W McGraw
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA
| | - Jason C Woods
- Pulmonary Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Yves Sabbagh
- The Sanofi-Genzyme R&D Center, Genzyme, a Sanofi company, Framingham, MA 01701, USA
| | - Susan C Schiavi
- The Sanofi-Genzyme R&D Center, Genzyme, a Sanofi company, Framingham, MA 01701, USA
| | - Göksel Altinişik
- Department of Chest Diseases, Faculty of Medicine, Pamukkale University, Denizli 20160, Turkey
| | - Marko Jakopović
- Department for Respiratory Diseases, University Hospital Centre Zagreb, University of Zagreb School of Medicine, 10000 Zagreb, Croatia
| | - Yoshikazu Inoue
- Department of Diffuse Lung Diseases and Respiratory Failure, Clinical Research Center, National Hospital Organization Kinki-Chuo Chest Medical Center, Osaka 5918555, Japan
| | - Francis X McCormack
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, The University of Cincinnati, Cincinnati, OH 45267, USA.
| |
Collapse
|
6
|
Fatima S, Yusufi ANK, Mahmood R. Effect of cisplatin on renal brush border membrane enzymes and phosphate transport. Hum Exp Toxicol 2016; 23:547-54. [PMID: 15688982 DOI: 10.1191/0960327104ht491oa] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cisplatin (CDDP) is widely used in the treatment of various cancers but its clinical use is associated with dose limiting nephrotoxicity. The present work was carried out to study the effect of administration of CDDP on rat renal brush border membrane (BBM) marker enzymes and inorganic phosphate (Pi) transport across BBM vesicles (BBMV). Animals were administered a single intraperitoneal dose of CDDP (6 mg/kg body weight) or normal saline and then sacrificed 2, 4, 8 and 16 days after this treatment. The administration of CDDP resulted in increased serum creatinine and blood urea nitrogen levels and decreased activity of BBM marker enzymes in the BBM as well as in the homogenates of cortex and medulla. Kinetic studies showed that the Vmaxof the enzymes was decreased in BBM from CDDP treated rats while the Kmremained unchanged. The Na+-gradient dependent transport of Pi across BBMV was also significantly reduced after CDDP treatment. These results strongly suggest that the administration of a single nephrotoxic dose of CDDP results in impairment of the functions of renal BBM.
Collapse
Affiliation(s)
- Sabiha Fatima
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, UP, India
| | | | | |
Collapse
|
7
|
Chen P, Tang Q, Wang C. Characterizing and evaluating the expression of the type IIb sodium-dependent phosphate cotransporter (slc34a2) gene and its potential influence on phosphorus utilization efficiency in yellow catfish (Pelteobagrus fulvidraco). FISH PHYSIOLOGY AND BIOCHEMISTRY 2016; 42:51-64. [PMID: 26298316 DOI: 10.1007/s10695-015-0116-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 08/17/2015] [Indexed: 06/04/2023]
Abstract
A sodium-dependent phosphate cotransporter gene, NaPi-IIb (slc34a2), was isolated from yellow catfish (Pelteobagrus fulvidraco) intestine through homology cloning and the rapid amplification of cDNA ends. The full-length cDNA of slc34a2 consisted of 2326 bp with an open reading frame encoding 621 amino acids, a 160-bp 5' untranslated region, and a 300-bp 3' untranslated region. The deduced amino acid sequence showed 79.0 and 70.9% sequence identity to Astyanax mexicanus and Pundamilia nyererei, respectively. The membrane-spanning domains based on the hydrophilic and hydrophobic properties of the deduced amino acids were predicted, and results showed that the putative protein had eight transmembrane domains, with the intracellular NH2 and COOH termini. Two functional regions including first intracellular loop and third extracellular loop as well as the six N-glycosylation sites in second extracellular loop were found. The slc34a2 mRNA in the tested tissues was examined through semiquantitative reverse transcription polymerase chain reaction and quantitative real-time PCR, with the highest level found in the anterior intestine, followed by the posterior and middle intestines. The slc34a2 mRNA expression in the whole intestine under different dietary phosphorus (P) treatments was detected using qPCR. The results showed that the slc34a2 expression levels in the low-P groups (0.33 and 0.56%) were significantly higher (p < 0.05) than levels in the sufficient-P (0.81%) and high-P (1.15, 1.31, and 1.57%) groups. High expression of slc34a2 mRNA in low-P groups stimulated P utilization efficiency, indicating the close relationship between genotype and phenotype in yellow catfish. In contrast with conventional strategies (formula and feeding strategies), this study provided another possible approach by using molecular techniques to increase the P utilization in yellow catfish.
Collapse
Affiliation(s)
- Pei Chen
- The College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
- Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, People's Republic of China
| | - Qin Tang
- The College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China
| | - Chunfang Wang
- The College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China.
- Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, People's Republic of China.
- Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, People's Republic of China.
| |
Collapse
|
8
|
Tatsumi S, Miyagawa A, Kaneko I, Shiozaki Y, Segawa H, Miyamoto KI. Regulation of renal phosphate handling: inter-organ communication in health and disease. J Bone Miner Metab 2016; 34:1-10. [PMID: 26296817 DOI: 10.1007/s00774-015-0705-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 07/16/2015] [Indexed: 01/18/2023]
Abstract
In this review, we focus on the interconnection of inorganic phosphate (Pi) homeostasis in the network of the bone-kidney, parathyroid-kidney, intestine-kidney, and liver-kidney axes. Such a network of organ communication is important for body Pi homeostasis. Normalization of serum Pi levels is a clinical target in patients with chronic kidney disease (CKD). Particularly, disorders of the fibroblast growth factor 23/klotho system are observed in early CKD. Identification of phosphaturic factors from the intestine and liver may enhance our understanding of body Pi homeostasis and Pi metabolism disturbances in CKD patients.
Collapse
Affiliation(s)
- Sawako Tatsumi
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Atsumi Miyagawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ichiro Kaneko
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Yuji Shiozaki
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Hiroko Segawa
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan
| | - Ken-Ichi Miyamoto
- Department of Molecular Nutrition, Institute of Biomedical Sciences, Tokushima University Graduate School, 3-18-15 Kuramoto-cho, Tokushima, 770-8503, Japan.
| |
Collapse
|
9
|
Yamada Y, Harada M, Yamaguchi A, Sugiyama M, Kanno T, Hashimoto K, Ehara T, Shimojo H, Shigematsu H, Kamijo Y. Acute Phosphate Nephropathy with Diffuse Tubular Injury Despite Limited Calcium Phosphate Deposition. Intern Med 2016; 55:2229-35. [PMID: 27523000 DOI: 10.2169/internalmedicine.55.5864] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An 86-year-old woman developed acute kidney injury after colonoscopy. A renal biopsy showed diffuse tubular injury with minimal calcium phosphate deposits (CPDs), which were thought to be caused by an oral sodium phosphate bowel purgative before colonoscopy. According to these findings, she was diagnosed with acute phosphate nephropathy (APhN). In contrast to previous reports of diffuse tubular injury associated with tubular CPDs in APhN, this case demonstrated diffuse tubular injury despite a limited distribution of CPDs, suggesting that calcium phosphate can cause tubular injury without deposition. This case thus supports the hypothesis that urinary calcium phosphate crystals may cause tubular injury via other mechanisms, including inflammatory cytokines.
Collapse
Affiliation(s)
- Yosuke Yamada
- Department of Nephrology, Shinshu University School of Medicine, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Huber K, Zeller E, Rodehutscord M. Modulation of small intestinal phosphate transporter by dietary supplements of mineral phosphorus and phytase in broilers. Poult Sci 2015; 94:1009-17. [PMID: 25834252 DOI: 10.3382/ps/pev065] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2015] [Indexed: 01/01/2023] Open
Abstract
Dietary phosphorus (P) is known as a main modulator of phosphate (Pi) transporter expression. The effect of supplemented mineral P with or without phytase on protein expression of two sodium-dependent Pi (NaPi) transporters and a calcium channel was studied in the small intestine of broilers. Thirty-six broilers were randomly assigned to six different diets at 15 days of age. Two levels of total P (tP, adjusted by monocalcium phosphate (MCP) supplementation), 0.39% (BD-) and 0.47% (BD+) were fed until day 25; and at each tP level, three levels of phytase were used with 0, 500, and 12,500 FTU/kg of an E. coli phytase. Mucosa samples from jejunum and ileum were taken and apical membranes were isolated by MgCl2 precipitation. Protein expression of NaPi IIb, NaPi type III (PiT1) and the calcium channel TRPV6 were semiquantitatively measured by Western blotting and jejunal mucosal phytase activity by measurement of Pi release. The jejunal NaPi IIb transporter was expressed with two distinct bands, which were modulated differently by diet. NaPi IIb Band1 increased (P < 0.05) and Band2 decreased (P < 0.05) with phytase supplementation but was not affected by MCP supplementation. This inverse modulation of Band1 and Band2 was significantly related to the amount of net absorbed P with higher expression of Band1 at higher amounts of net absorbed P. In addition, a second Pi transporter, PiT1, was detected in which ileal expression decreased (P < 0.05) in response to higher phytase supplementation. The expression of the calcium channel TRPV6 was increased in BD+ groups. A trend for an interaction between MCP and phytase supplementation on mucosal phytase activity was observed (P = 0.079) with a decrease in activity when BD+ with 12,500 FTU/kg phytase was fed. Chicken intestinal epithelial cells responded to dietary supplemented phytase and MCP by changing the Pi transporter expression in apical membranes. In conclusion, availability of Pi is most likely the key modulator of transporter protein expression. However, a contribution of lower inositol phosphates generated by phytases and other phosphatases may also be relevant.
Collapse
Affiliation(s)
- Korinna Huber
- Physiologisches Institut, Tierärztliche Hochschule, 30173 Hannover, Germany
| | - Ellen Zeller
- Institut für Tierernährung, Universität Hohenheim, 70599 Stuttgart, Germany
| | | |
Collapse
|
11
|
Abstract
Recent studies of inherited disorders of phosphate metabolism have shed new light on the understanding of phosphate metabolism. Phosphate has important functions in the body and several mechanisms have evolved to regulate phosphate balance including vitamin D, parathyroid hormone and phosphatonins such as fibroblast growth factor-23 (FGF23). Disorders of phosphate homeostasis leading to hypo- and hyperphosphataemia are common and have clinical and biochemical consequences. Notably, recent studies have linked hyperphosphataemia with an increased risk of cardiovascular disease. This review outlines the recent advances in the understanding of phosphate homeostasis and describes the causes, investigation and management of hypo- and hyperphosphataemia.
Collapse
Affiliation(s)
- P Manghat
- Department of Chemical Pathology, Darent Valley Hospital, Dartford, UK
| | - R Sodi
- Department of Biochemistry, NHS Lanarkshire, East Kilbride, UK
| | - R Swaminathan
- Department of Chemical Pathology, St. Thomas Hospital, London, UK
| |
Collapse
|
12
|
Tang Y, Zhou L. Characterization of Adenosine A1 Receptors in Human Proximal Tubule Epithelial (HK-2) Cells. ACTA ACUST UNITED AC 2011. [DOI: 10.3109/10606820308250] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
13
|
Ohi A, Hanabusa E, Ueda O, Segawa H, Horiba N, Kaneko I, Kuwahara S, Mukai T, Sasaki S, Tominaga R, Furutani J, Aranami F, Ohtomo S, Oikawa Y, Kawase Y, Wada NA, Tachibe T, Kakefuda M, Tateishi H, Matsumoto K, Tatsumi S, Kido S, Fukushima N, Jishage KI, Miyamoto KI. Inorganic phosphate homeostasis in sodium-dependent phosphate cotransporter Npt2b⁺/⁻ mice. Am J Physiol Renal Physiol 2011; 301:F1105-13. [PMID: 21816756 DOI: 10.1152/ajprenal.00663.2010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An inorganic phosphate (P(i))-restricted diet is important for patients with chronic kidney disease and patients on hemodialysis. Phosphate binders are essential for preventing hyperphosphatemia and ectopic calcification. The sodium-dependent P(i) (Na/P(i)) transport system is involved in intestinal P(i) absorption and is regulated by several factors. The type II sodium-dependent P(i) transporter Npt2b is expressed in the brush-border membrane in intestinal epithelial cells and transports P(i). In the present study, we analyzed the phenotype of Npt2b(-/-) and hetero(+/-) mice. Npt2b(-/-) mice died in utero soon after implantation, indicating that Npt2b is essential for early embryonic development. At 4 wk of age, Npt2b(+/-) mice showed hypophosphatemia and low urinary P(i) excretion. Plasma fibroblast growth factor 23 levels were significantly decreased and 1,25(OH)(2)D(3) levels were significantly increased in Npt2b(+/-) mice compared with Npt2b(+/+) mice. Npt2b mRNA levels were reduced to 50% that in Npt2b(+/+) mice. In contrast, renal Npt2a and Npt2c transporter protein levels were significantly increased in Npt2b(+/-) mice. At 20 wk of age, Npt2b(+/-) mice showed hypophosphaturia and reduced Na/P(i) cotransport activity in the distal intestine. Npt2b(+/+) mice with adenine-induced renal failure had hyperphosphatemia and high plasma creatinine levels. Npt2b(+/-) mice treated with adenine had significantly reduced plasma P(i) levels compared with Npt2b(+/+) mice. Intestinal Npt2b protein and Na(+)/P(i) transport activity levels were significantly lower in Npt2b(+/-) mice than in the Npt2b(+/+) mice. The findings of the present studies suggest that Npt2b is an important target for the prevention of hyperphosphatemia.
Collapse
Affiliation(s)
- Akiko Ohi
- Department of Molecular Nutrition Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima City, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Marks J, Debnam ES, Unwin RJ. Phosphate homeostasis and the renal-gastrointestinal axis. Am J Physiol Renal Physiol 2010; 299:F285-96. [PMID: 20534868 DOI: 10.1152/ajprenal.00508.2009] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Transport of phosphate across intestinal and renal epithelia is essential for normal phosphate balance, yet we know less about the mechanisms and regulation of intestinal phosphate absorption than we do about phosphate handling by the kidney. Recent studies have provided strong evidence that the sodium-phosphate cotransporter NaPi-IIb is responsible for sodium-dependent phosphate absorption by the small intestine, and it might be that this protein can link changes in dietary phosphate to altered renal phosphate excretion to maintain phosphate balance. Evidence is also emerging that specific regions of the small intestine adapt differently to acute or chronic changes in dietary phosphate load and that phosphatonins inhibit both renal and intestinal phosphate transport. This review summarizes our current understanding of the mechanisms and control of intestinal phosphate absorption and how it may be related to renal phosphate reabsorption; it also considers the ways in which the gut could be targeted to prevent, or limit, hyperphosphatemia in chronic and end-stage renal failure.
Collapse
Affiliation(s)
- Joanne Marks
- Dept. of Neuroscience, Physiology, and Pharmacology, Univ. College London Medical School, UK.
| | | | | |
Collapse
|
15
|
Morales E, Gutierrez E, Andres A. Treatment with calcimimetics in kidney transplantation. Transplant Rev (Orlando) 2010; 24:79-88. [DOI: 10.1016/j.trre.2010.01.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 01/18/2010] [Indexed: 11/26/2022]
|
16
|
Riquier-Brison ADM, Leong PKK, Pihakaski-Maunsbach K, McDonough AA. Angiotensin II stimulates trafficking of NHE3, NaPi2, and associated proteins into the proximal tubule microvilli. Am J Physiol Renal Physiol 2009; 298:F177-86. [PMID: 19864301 DOI: 10.1152/ajprenal.00464.2009] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Angiotensin II (ANG II) stimulates proximal tubule (PT) sodium and water reabsorption. We showed that treating rats acutely with the angiotensin-converting enzyme inhibitor captopril decreases PT salt and water reabsorption and provokes rapid redistribution of the Na(+)/H(+) exchanger isoform 3 (NHE3), Na(+)/Pi cotransporter 2 (NaPi2), and associated proteins out of the microvilli. The aim of the present study was to determine whether acute ANG II infusion increases the abundance of PT NHE3, NaPi2, and associated proteins in the microvilli available for reabsorbing NaCl. Male Sprague-Dawley rats were infused with a dose of captopril (12 microg/min for 20 min) that increased PT flow rate approximately 20% with no change in blood pressure (BP) or glomerular filtration rate (GFR). When ANG II (20 ng x kg(-1) x min(-1) for 20 min) was added to the captopril infusate, PT volume flow rate returned to baseline without changing BP or GFR. After captopril, NHE3 was localized to the base of the microvilli and NaPi2 to subapical cytoplasmic vesicles; after 20 min ANG II, both NHE3 and NaPi2 redistributed into the microvilli, assayed by confocal microscopy and density gradient fractionation. Additional PT proteins that redistributed into low-density microvilli-enriched membranes in response to ANG II included myosin VI, DPPIV, NHERF-1, ezrin, megalin, vacuolar H(+)-ATPase, aminopeptidase N, and clathrin. In summary, in response to 20 min ANG II in the absence of a change in BP or GFR, multiple proteins traffic into the PT brush-border microvilli where they likely contribute to the rapid increase in PT salt and water reabsorption.
Collapse
Affiliation(s)
- Anne D M Riquier-Brison
- Department of Cell and Neurobiology, University of Southern California Keck School of Medicine, Los Angeles, California 90089, USA
| | | | | | | |
Collapse
|
17
|
Abstract
Acute phosphate nephropathy (APhN) is a clinical pathological entity characterized by acute and subsequent chronic renal failure following exposure to oral sodium phosphate (OSP) bowel purgatives. Renal biopsy findings include acute and chronic tubular injury with prominent tubular and interstitial calcium phosphate deposits. Risk factors for APhN include older age, female gender, hypertension, chronic kidney disease (CKD), and treatment with angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and diuretics. The pathomechanism of APhN involves hypovolemia-induced avid proximal salt and water reabsorption, delivery of a large phosphate load to the distal nephron, and precipitation of calcium phosphate in the distal tubule and collecting duct. To date, 37 cases of biopsy-proven APhN have been reported, and epidemiologic studies have produced inconsistent results regarding the incidence of acute kidney injury (AKI) following the use of OSP purgatives. OSP solution was withdrawn from the market in December of 2008, but OSP tablets, offered by prescription only, remain available. Prevention of APhN is best achieved by avoiding OSP in high-risk patients, aggressive hydration before, during, and after OSP administration, minimizing the dose of OSP, and maintaining a minimum of a 12 h interval between OSP administrations.
Collapse
|
18
|
Kiyamova R, Gryshkova V, Ovcharenko G, Lituyev D, Malyuchik S, Usenko V, Khozhayenko Y, Gurtovyy V, Yin B, Ritter G, Old L, Filonenko V, Gout I. Development of monoclonal antibodies specific for the human sodium-dependent phosphate co-transporter NaPi2b. Hybridoma (Larchmt) 2008; 27:277-84. [PMID: 18724815 DOI: 10.1089/hyb.2008.0015] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Homeostasis of inorganic phosphate in the human body is maintained by regulated absorption, metabolism, and excretion. Sodium-dependent phosphate transporters (NaPi) mediate the transport of inorganic phosphate (P(i)) in cells in response to dietary phosphate consumption, hormones, and growth factors. NaPi2b is a member of the sodium-dependent phosphate transporter family, with a distinct pattern of expression and regulation. Signaling pathways activated by mitogens, glucocorticoids, and metabolic factors have been implicated in regulating P(i) transport via NaPi2b. Inactivation of NaPi2b function by mutations has been linked to human pathologies, such as pulmonary alveolar microlithiasis. In this study, we describe the generation and characterization of monoclonal antibodies against human NaPi2b. The monoclonal antibodies were shown to recognize specifically transiently overexpressed and endogenous NaPi2b in commonly used immunoassays, including Western blotting, immunoprecipitation, and immunohistochemistry. These properties make them particularly valuable reagents for elucidating NaPi2b function in health and disease.
Collapse
Affiliation(s)
- Ramziya Kiyamova
- Department of Cell Signaling, Institute of Molecular Biology and Genetics, NAS of Ukraine, Kyiv, Ukraine
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Marks J, Churchill LJ, Debnam ES, Unwin RJ. Matrix extracellular phosphoglycoprotein inhibits phosphate transport. J Am Soc Nephrol 2008; 19:2313-20. [PMID: 19005008 DOI: 10.1681/asn.2008030315] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The role of putative humoral factors, known as phosphatonins, in phosphate homeostasis and the relationship between phosphate handling by the kidney and gastrointestinal tract are incompletely understood. Matrix extracellular phosphoglycoprotein (MEPE), one of several candidate phosphatonins, promotes phosphaturia, but whether it also affects intestinal phosphate absorption is unknown. Here, using the in situ intestinal loop technique, we demonstrated that short-term infusion of MEPE inhibits phosphate absorption in the jejunum but not the duodenum. Simultaneous measurement of urinary phosphate excretion suggests that the phosphaturic action of MEPE correlates with a significant reduction in the protein levels of the renal sodium-phosphate co-transporter NaPi-IIa in the proximal convoluted tubules of the outer renal cortex, assessed by Western blotting and immunohistochemistry. This short-term inhibitory effect of MEPE on renal and intestinal phosphate handling occurred without any changes in circulating levels of parathyroid hormone, 1,25-dihydroxyvitamin D(3), or fibroblast growth factor 23. Taken together, these findings suggest that MEPE is a candidate phosphatonin involved in phosphate homeostasis, acting in both the kidney and the gastrointestinal tract.
Collapse
Affiliation(s)
- Joanne Marks
- Department of Physiology, University College London Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF.
| | | | | | | |
Collapse
|
20
|
Marcucci G, Masi L, Brandi ML. Phosphatonins: new hormones that control phosphorus homeostasis. Expert Rev Endocrinol Metab 2008; 3:513-526. [PMID: 30290433 DOI: 10.1586/17446651.3.4.513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Phosphorus (Pi) plays an important role in nucleic acid synthesis, energy metabolism, bone mineralization and cell signaling, and is also present in sugars, phospholipids and phosphoproteins. Phosphate homeostasis is controlled by processes that regulate the intestinal absorption and renal excretion of Pi, and bone turnover. These processes are influenced by peptide and sterol hormones, such as parathyroid hormone and 1α,25-dihydroxyvitamin D (1α,25[OH]2D3). Recently, a new class of phosphate-regulating peptides has been discovered: phosphatonins. These factors, such as FGF-23, secreted frizzled-related protein-4, matrix extracellular phosphoglycoprotein and FGF-7, are circulating peptides with potent phosphaturic activity. These peptides inhibit Na/Pi transporters in renal epithelial cells and, therefore, increase renal Pi excretion. In addition, FGF-23 and secreted frizzled-related protein-4 inhibit 25-hydroxyvitamin D 1α-hydroxylase activity, reducing 1α,25(OH)2D3 synthesis and, thus, intestinal Pi absorption. Phosphatonins have been associated with hypophosphatemic diseases, such as tumor-induced osteomalacia, X-linked hypophosphatemic rickets, autosomal dominant hypophosphatemic rickets, autosomal recessive hypophosphatemic rickets and hyperphosphatemic disease (e.g., tumoral calcinosis). The aim of this article is to review the role of phosphatonins in Pi metabolism in normal and pathologic conditions and also to investigate the correlations among the various phosphatonins.
Collapse
Affiliation(s)
- Gemma Marcucci
- a Department of Internal Medicine and # De Gene Spin-off, University of Florence, Medical School, Florence, Italy
| | - Laura Masi
- a Department of Internal Medicine and # De Gene Spin-off, University of Florence, Medical School, Florence, Italy
| | - Maria Luisa Brandi
- b Department of Internal Medicine, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy.
| |
Collapse
|
21
|
Kirchner S, Muduli A, Casirola D, Prum K, Douard V, Ferraris RP. Luminal fructose inhibits rat intestinal sodium-phosphate cotransporter gene expression and phosphate uptake. Am J Clin Nutr 2008; 87:1028-38. [PMID: 18400728 PMCID: PMC2430509 DOI: 10.1093/ajcn/87.4.1028] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND While searching by microarray for sugar-responsive genes, we inadvertently discovered that sodium-phosphate cotransporter 2B (NaPi-2b) mRNA concentrations were much lower in fructose-perfused than in glucose-perfused intestines of neonatal rats. Changes in NaPi-2b mRNA abundance by sugars were accompanied by similar changes in NaPi-2b protein abundance and in rates of inorganic phosphate (Pi) uptake. OBJECTIVE We tested the hypothesis that luminal fructose regulates NaPi-2b. DESIGN We perfused into the intestine fructose, glucose, and nonmetabolizable or poorly transported glucose analogs as well as phlorizin. RESULTS NaPi-2b mRNA concentrations and Pi uptake rates in fructose-perfused intestines were approximately 30% of those in glucose and its analogs. NaPi-2b inhibition by fructose is specific because the mRNA abundance and activity of the fructose transporter GLUT5 (glucose transporter 5) increased with fructose perfusion, whereas those of other transporters were independent of the perfusate. Plasma Pi after 4 h of perfusion was independent of the perfusate, probably because normal kidneys can maintain normophosphatemia. Inhibiting glucose-6-phosphatase, another fructose-responsive gene, with tungstate or vanadate nonspecifically inhibited NaPi-2b mRNA expression and Pi uptake in both glucose- or fructose-perfused intestines. The AMP kinase (AMPK)-activator AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside) enhanced and the fatty acid synthase-AMPK inhibitor C75 (3-carboxy-4-octyl-2-methylenebutyrolactone trans-4-carboxy-5-octyl-3-methylenebutyrolactone) prevented fructose inhibition of NaPi-2b but had no effect on expression of other transporters. NaPi-2b expression decreased markedly with age and was inhibited by fructose in all age groups. CONCLUSIONS Energy levels in enterocytes may play a role in NaPi-2b inhibition by luminal fructose. Consumption of fructose that supplies approximately 10% of caloric intake by Americans clearly affects absorption of Pi and may promote Pi homeostasis in patients with impaired renal function.
Collapse
Affiliation(s)
- Séverine Kirchner
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103-2714, USA
| | | | | | | | | | | |
Collapse
|
22
|
Khundmiri SJ, Ahmad A, Bennett RE, Weinman EJ, Steplock D, Cole J, Baumann PD, Lewis J, Singh S, Clark BJ, Lederer ED. Novel regulatory function for NHERF-1 in Npt2a transcription. Am J Physiol Renal Physiol 2008; 294:F840-9. [PMID: 18216150 DOI: 10.1152/ajprenal.00180.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Several lines of evidence show that sodium/hydrogen exchanger regulatory factor 1 (NHERF-1) regulates the expression and activity of the type IIa sodium-dependent phosphate transporter (Npt2a) in renal proximal tubules. We have previously demonstrated that expression of a COOH-terminal ezrin binding domain-deficient NHERF-1 in opossum kidney (OK) cells decreased expression of Npt2a in apical membranes but did not affect responses to parathyroid hormone. We hypothesized that NHERF-1 regulates apical membrane expression of Npt2a in renal proximal tubule cells. To address this hypothesis, we compared regulation of Npt2a expression and function in NHERF-deficient OK cells (OK-H) and wild-type cells (OK-WT). In OK-H cells, phosphate uptake and expression of Npt2a protein in apical membranes were significantly lower than in OK-WT cells. Transient transfection of green fluorescent protein-tagged Npt2a cDNA into OK-H cells resulted in aberrant localization of an Npt2a fragment to the cytosol but not to the apical membrane. OK-H cells also exhibited a marked decrease in Npt2a mRNA expression. As demonstrated by luciferase assay, Npt2a promoter activity was significantly decreased in OK-H cells compared with that shown in OK-WT cells. Transfection of OK-H cells with human NHERF-1 restored Npt2a expression at both the protein and mRNA levels and regulation by parathyroid hormone. Expression of NHERF-1 constructs with mutations in the PDZ domains or the ezrin binding domain in OK-H cells suggested that the PDZ2 domain is critical for apical translocation of Npt2a and for expression at the mRNA level. Our data demonstrate for the first time that NHERF-1 regulates Npt2a transcription and membrane insertion.
Collapse
Affiliation(s)
- Syed Jalal Khundmiri
- Department of Medicine, Univ. of Louisville, Kidney Disease Program, 570 S. Preston St, Suite 102, Louisville, KY 40202, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Marks J, Churchill LJ, Srai SK, Biber J, Murer H, Jaeger P, Debnam ES, Unwin RJ. Intestinal phosphate absorption in a model of chronic renal failure. Kidney Int 2007; 72:166-73. [PMID: 17457376 DOI: 10.1038/sj.ki.5002292] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hyperphosphatemia is an important consequence of chronic renal failure (CRF). Lowering of the plasma phosphate concentration is believed to be critical in the management of patients with CRF, especially those on dialysis. Reports of the effect of CRF on the intestinal handling of phosphate in vitro have been conflicting; but what happens in vivo has not been studied. What effect a reduction in the dietary phosphate intake has on intestinal phosphate absorption in CRF in vivo is unclear. In this study, we have used the in situ intestine loop technique to determine intestinal phosphate absorption in the 5/6-nephrectomy rat model of CRF under conditions of normal and restricted dietary phosphate intake. In this model of renal disease, we found that there is no significant change in the phosphate absorption in either the duodenum or jejunum regardless of the dietary phosphate intake. There was also no change in the expression of the messenger RNA of the major intestinal phosphate carrier the sodium-dependent-IIb transporter. Furthermore, we found no change in the intestinal villus length or in the location of phosphate uptake along the villus. Our results indicate that in CRF, unlike the kidney, there is no reduction in phosphate transport across the small intestine. This makes intestinal phosphate absorption a potential target in the prevention and treatment of hyperphosphatemia.
Collapse
Affiliation(s)
- J Marks
- Department of Physiology, Royal Free and University College Medical School, London, UK.
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Ghanekar H, Welch BJ, Moe OW, Sakhaee K. Post-renal transplantation hypophosphatemia: a review and novel insights. Curr Opin Nephrol Hypertens 2006; 15:97-104. [PMID: 16481873 DOI: 10.1097/01.mnh.0000203187.49890.cc] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE OF REVIEW This review intends to elucidate the pathophysiologic mechanism of renal phosphorus loss in the post-renal transplantation population. This review will provide new insight in to the pathophysiologic mechanism(s) responsible for the development of this phenomenon and will also explore the pathogenetic role of persistent phosphorus wasting in the development of post-renal transplantation osteodystrophy. RECENT FINDINGS Recently, the phosphaturic hormone, fibroblast growth factor-23, has been ascertain to be increased in the sera of patients with chronic kidney and end-stage renal disease. There is new evidence that a non-PTH humoral factor is persistently present in post-renal transplantation patients that is likely responsible for the observed persistent renal phosphorus loss. We offer that fibroblast growth factor-23 (and/or other phosphatonins) is the culprit factor responsible for the phenomenon of persistent hypophosphatemia in post-renal transplantation patients. Moreover, we believe that the phenomenon of persistent renal phosphorus wasting is an important but overlooked cause of osteodystrophy and increased fracture risk in this patient population. SUMMARY The pathophysiology of post-renal transplantation phosphorus wasting is complex and to date is still not fully recognized. Further studies of the regulatory mechanism of fibroblast growth factor-23 and its metabolism may offer additional insights into phosphorus homeostasis and its clinical application in the post-renal transplantation population.
Collapse
Affiliation(s)
- Hrishikesh Ghanekar
- Department of Internal Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | | | | | | |
Collapse
|
25
|
Pande S, Ritter CS, Rothstein M, Wiesen K, Vassiliadis J, Kumar R, Schiavi SC, Slatapolsky E, Brown AJ. FGF-23 and sFRP-4 in chronic kidney disease and post-renal transplantation. Nephron Clin Pract 2006; 104:p23-32. [PMID: 16691036 PMCID: PMC4446726 DOI: 10.1159/000093277] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 02/02/2006] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The phosphatonins fibroblast growth factor-23 (FGF-23) and FRP-4 are inhibitors of tubular phosphate reabsorption that may play a role in the hyperphosphatemia associated with chronic kidney disease (CKD) or in the hypophosphatemia associated with renal transplants. METHODS Plasma FGF-23, FRP-4, phosphorus and parathyroid hormone were measured in patients at all stages of CKD. Phosphate regulation of FGF-23 and secreted frizzled related protein-4 (sFRP-4) was examined in end-stage renal disease patients in the presence and absence of therapeutic phosphate binder usage. In renal transplant patients, plasma FGF-23, sFRP-4 and phosphorus concentrations were determined before and 4-5 days after transplantation. RESULTS Plasma FGF-23 correlated with creatinine clearance (r2 = -0.584, p < 0.0001) and plasma phosphorus (r2 = 0.347, p < 0.001) in CKD patients and with plasma phosphorus (r2 = 0.448, p < 0.001) in end-stage renal disease patients. Phosphate binder withdrawal increased FGF-23 levels. In kidney transplant patients, dramatic decreases in FGF-23 (-88.8 +/- 5.4%) and phosphorus (-64 +/- 10.2%) were observed by 4-5 days post-transplantation. In patients with post-transplant hypophosphatemia, FGF-23 levels correlated inversely with plasma phosphorus (r2 = 0.661, p < 0.05). sFRP-4 levels did not change with creatinine clearance or hyperphosphatemia in CKD or end-stage renal disease patients, and no relation was noted between post-transplant sFRP-4 levels and hypophosphatemia. CONCLUSIONS In CKD, FGF-23 levels rose with decreasing creatinine clearance rates and increasing plasma phosphorus levels, and rapidly decreased post-transplantation suggesting FGF-23 is cleared by the kidney. Residual FGF-23 may contribute to the hypophosphatemia in post-transplant patients.
Collapse
Affiliation(s)
- Sangeeta Pande
- Renal Division, Washington University School of Medicine, St Louis, MO
| | - Cynthia S. Ritter
- Renal Division, Washington University School of Medicine, St Louis, MO
| | - Marcos Rothstein
- Renal Division, Washington University School of Medicine, St Louis, MO
| | - Karen Wiesen
- Renal Division, Washington University School of Medicine, St Louis, MO
| | | | - Rajiv Kumar
- Mayo Clinic and Foundation, Rochester, Minnesota
| | | | | | - Alex J. Brown
- Renal Division, Washington University School of Medicine, St Louis, MO
| |
Collapse
|
26
|
Marks J, Srai SK, Biber J, Murer H, Unwin RJ, Debnam ES. Intestinal phosphate absorption and the effect of vitamin D: a comparison of rats with mice. Exp Physiol 2006; 91:531-7. [PMID: 16431934 DOI: 10.1113/expphysiol.2005.032516] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Previously, it was thought that intestinal phosphate transport occurred exclusively in the proximal small intestine of rodents and humans. However, a recent study has demonstrated that the ileum of mice contributes significantly to the absorption of dietary phosphate, but it is not known whether this region is also an important site of phosphate absorption in the rat. In the present study, we have investigated the mRNA and protein levels of the sodium-phosphate cotransporter, NaPi-IIb, in three regions of rat and mouse small intestine, and related its expression levels to the rate of net phosphate absorption, as measured using the in situ intestinal loop technique. 1,25-Dihydroxyvitamin D3 is an important physiological regulator of intestinal phosphate absorption that increases phosphate transport in both the duodenum and jejunum of the rat. Based on the recently proposed regional profile of phosphate absorption along the mouse small intestine, we have re-evaluated the effects of 1,25-dihydroxyvitamin D3 using three distinct regions of the mouse and rat small intestine. Our studies have revealed important differences in the intestinal handling of phosphate between mice and rats. In mice, maximal phosphate absorption occurs in the ileum, which is paralleled by the highest expression levels of NaPi-IIb mRNA and protein. In contrast, in rats maximal absorption occurs in the duodenum with very little absorption occurring in the ileum, which is similar to the pattern reported in humans. However, in both rodent species only the jejunum shows an increase in phosphate absorption in response to treatment with 1,25-dihydroxyvitamin D3.
Collapse
Affiliation(s)
- Joanne Marks
- Department of Physiology, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, UK.
| | | | | | | | | | | |
Collapse
|
27
|
Berndt TJ, Bielesz B, Craig TA, Tebben PJ, Bacic D, Wagner CA, O'Brien S, Schiavi S, Biber J, Murer H, Kumar R. Secreted frizzled-related protein-4 reduces sodium-phosphate co-transporter abundance and activity in proximal tubule cells. Pflugers Arch 2005; 451:579-87. [PMID: 16151791 DOI: 10.1007/s00424-005-1495-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Accepted: 07/11/2005] [Indexed: 01/23/2023]
Abstract
The phosphatonin, secreted frizzled-related protein-4 (sFRP-4), induces phosphaturia and inhibits 25-hydroxyvitamin D 1alpha-hydroxylase activity normally induced in response to hypophosphatemia. To determine the mechanism by which sFRP-4 alters renal phosphate (P(i)) transport, we examined the effect of sFRP-4 on renal brush border membrane (BBMV) Na(+)-dependent P(i) uptake, and the abundance and localization of the major Na(+)-P(i)-IIa co-transporter in proximal tubules and opossum kidney (OK) cells. Infusion of sFRP-4 increased renal fractional excretion of P(i) and decreased renal beta-catenin concentrations. The increase in renal P(i) excretion with sFRP-4 infusion was associated with a 21.9 +/- 3.4% decrease in BBMV Na(+)-dependent P(i) uptake (P < 0.001) compared with a 39.5 +/- 2.1% inhibition of Na(+)-dependent P(i) transport in renal BBMV induced by PTH (P < 0.001). sFRP-4 infusion was associated with a 30.7 +/- 4.8% decrease in Na(+)-P(i)-IIa co-transporter protein abundance (P < 0.01) assessed by immunoblotting methods compared to a 45.4 +/- 8.8% decrease induced by PTH (P < 0.001). In OK cells, sFRP-4 reduced surface expression of a heterologous Na(+)-P(i)-IIa co-transporter. We conclude that sFRP-4 increases renal P(i) excretion by reducing Na(+)-P(i)-IIa transporter abundance in the brush border of the proximal tubule through enhanced internalization of the protein.
Collapse
Affiliation(s)
- Theresa J Berndt
- Division of Nephrology and Hypertension, Departments of Medicine and Biochemistry and Molecular Biology, Mayo Clinic Rochester, Mayo College of Medicine, MN, 55905, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Yan X, Yokote H, Jing X, Yao L, Sawada T, Zhang Y, Liang S, Sakaguchi K. Fibroblast growth factor 23 reduces expression of type IIa Na+/Pi co-transporter by signaling through a receptor functionally distinct from the known FGFRs in opossum kidney cells. Genes Cells 2005; 10:489-502. [PMID: 15836777 DOI: 10.1111/j.1365-2443.2005.00853.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Fibroblast growth factor (FGF) 23 is an important phosphaturic factor that inhibits inorganic phosphate (Pi) reabsorption from the renal proximal tubule. Its overproduction and proteolysis-resistant mutation such as R179Q cause tumor-induced osteomalacia and autosomal dominant hypophosphatemic rickets, respectively. To clarify the signaling mechanisms of FGF23 that mediate the reduction of Pi reabsorption, we inhibited the function of the known FGFRs in opossum kidney (OK-E) cells by expressing a dominant-negative (DN) form of FGFR. OK-E cells, which represent the renal proximal tubular cells, expressed all four known FGFRs. FGF23(R179Q) bound to and activated FGFR2, a prominent FGFR expressed in OK-E cells. The activated receptor transmitted a signal to increase the expression of type IIa Na(+)/Pi co-transporter and the Pi uptake. Expression of FGFR2(DN), which suppresses the major FGFR-mediated signal through the FRS2alpha-ERK pathway, reversed the function of FGF23(R179Q). When FGF23(R179Q) was applied to the basolateral side of polarized OK-E cells, regardless of the FGFR2(DN) expression, the apical Pi uptake decreased significantly. The apical application of FGF23(R179Q) in the polarized cells did not show such decrease but increase. The exogenously expressed FGFR2 was detectable only at the apical membrane. These results suggest that an FGF23 receptor, which is functionally distinct from the known FGFRs, is expressed at the basolateral membrane of OK-E cells.
Collapse
Affiliation(s)
- Xiaomei Yan
- Department of Molecular Cell Biology, Institute of Advanced Medicine, Wakayama Medical University, 811-1 Kimiidera, Wakayama 641-8509, Japan
| | | | | | | | | | | | | | | |
Collapse
|
29
|
Kruse AE, Eisenberger U, Frey FJ, Mohaupt MG. The calcimimetic cinacalcet normalizes serum calcium in renal transplant patients with persistent hyperparathyroidism. Nephrol Dial Transplant 2005; 20:1311-4. [PMID: 15941846 DOI: 10.1093/ndt/gfh924] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Treatment of persistent hyperparathyroidism in renal transplant patients resistant to calcium and vitamin D sterols is limited and often requires parathyroidectomy. Given the potential hazards linked to surgery, an alternative approach to manage excess parathyroid hormone (PTH) secretion is needed. Calcimimetics inhibit PTH secretion by modulating the calcium-sensing receptor in the parathyroid. Lowering of the serum calcium concentration with the calcimimetic cinacalcet has previously been demonstrated in patients with primary hyperparathyroidism or with secondary hyperparathyroidism on dialysis. Here we present the first clinical observations of a calcimimetic in patients with persistent hyperparathyroidism. METHODS A 30 mg dose of cinacalcet was prescribed once daily for 3 months to seven female and seven male stable renal transplant patients, aged 23-65 years, 7 months to 14 years after transplantation, with a serum creatinine ranging from 89 to 229 micromol/l and persistent hyperparathyroidism. Concomitant medication included cyclosporin and low-dose prednisone in all patients. RESULTS On cinacalcet, serum calcium decreased and normalized in all but two patients (baseline 2.72+/-0.03 mmol/l; 1 month 2.42+/-0.04 mmol/l, P<0.001), whereas serum PTH and phosphate levels did not change significantly. A slight reduction in renal function, as assessed by serum creatinine concentration, was observed at months 2 and 3 (P<0.05). An immunoglobulin-deficient patient developed colitis after 1 week of treatment and cinacalcet was withdrawn. No patient stopped cinacalcet because of other presumed side effects. CONCLUSION Calcimimetics are a promising therapy in renal transplant patients with persistent hyperparathyroidism. Prospective controlled studies must now be designed focusing on functionally relevant musculo-skeletal end-points and allowing the exclusion of negative effects on long-term renal and general outcome of such patients.
Collapse
Affiliation(s)
- Anja E Kruse
- Department of Nephrology and Hypertension, University Hospital Berne, Inselspital, Freiburgstrasse, CH-3010 Bern, Switzerland
| | | | | | | |
Collapse
|
30
|
Stauber A, Radanovic T, Stange G, Murer H, Wagner CA, Biber J. Regulation of intestinal phosphate transport. II. Metabolic acidosis stimulates Na(+)-dependent phosphate absorption and expression of the Na(+)-P(i) cotransporter NaPi-IIb in small intestine. Am J Physiol Gastrointest Liver Physiol 2005; 288:G501-6. [PMID: 15701624 DOI: 10.1152/ajpgi.00168.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
During metabolic acidosis, P(i) serves as an important buffer to remove protons from the body. P(i) is released from bone together with carbonate buffering protons in blood. In addition, in the kidney, the fractional excretion of phosphate is increased allowing for the excretion of more acid equivalents in urine. The role of intestinal P(i) absorption in providing P(i) to buffer protons and compensating for loss from bone during metabolic acidosis has not been clarified yet. Inducing metabolic acidosis (NH(4)Cl in drinking water) for 2 or 7 days in mice increased urinary fractional P(i) excretion twofold, whereas serum P(i) levels were not altered. Na(+)-dependent P(i) transport in the small intestine, however, was stimulated from 1.89 +/- 3.22 to 40.72 +/- 11.98 pmol/mg protein (2 days of NH(4)Cl) in brush-border membrane vesicles prepared from total small intestine. Similarly, the protein abundance of the Na(+)-dependent phosphate cotransporter NaPi-IIb in the brush-border membrane was increased 5.3-fold, whereas mRNA levels remained stable. According to immunohistochemistry and real-time PCR NaPi-IIb expression was found to be mainly confined to the ileum in the small intestine, and this distribution was not altered during metabolic acidosis. These results suggest that the stimulation of intestinal P(i) absorption during metabolic acidosis may contribute to the buffering of acid equivalents by providing phosphate and may also help to prevent excessive liberation of phosphate from bone.
Collapse
Affiliation(s)
- Annina Stauber
- Institute of Physiology, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland
| | | | | | | | | | | |
Collapse
|
31
|
Capuano P, Bacic D, Stange G, Hernando N, Kaissling B, Pal R, Kocher O, Biber J, Wagner CA, Murer H. Expression and regulation of the renal Na/phosphate cotransporter NaPi-IIa in a mouse model deficient for the PDZ protein PDZK1. Pflugers Arch 2004; 449:392-402. [PMID: 15517343 DOI: 10.1007/s00424-004-1351-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Accepted: 09/16/2004] [Indexed: 10/26/2022]
Abstract
Inorganic phosphate (P(i)) is reabsorbed in the renal proximal tubule mainly via the type-IIa sodium-phosphate cotransporter (NaPi-IIa). This protein is regulated tightly by different factors, among them dietary P(i) intake and parathyroid hormone (PTH). A number of PDZ-domain-containing proteins have been shown to interact with NaPi-IIa in vitro, such as Na(+)/H(+) exchanger-3 regulatory factor-1 (NHERF1) and PDZK1. PDZK1 is highly abundant in kidney and co-localizes with NaPi-IIa in the brush border membrane of proximal tubules. Recently, a knock-out mouse model for PDZK1 (Pdzk1(-/-)) has been generated, allowing the role of PDZK1 in the expression and regulation of the NaPi-IIa cotransporter to be examined in in vivo and in ex vivo preparations. The localization of NaPi-IIa and other proteins interacting with PDZK1 in vitro [Na(+)/H(+) exchanger (NHE3), chloride-formate exchanger (CFEX)/putative anion transporter-1 (PAT1), NHERF1] was not altered in Pdzk1(-/-) mice. The abundance of NaPi-IIa adapted to acute and chronic changes in dietary P(i) intake, but steady-state levels of NaPi-IIa were reduced in Pdzk1(-/-) under a P(i) rich diet. This was paralleled by a higher urinary fractional P(i) excretion. The abundance of the anion exchanger CFEX/PAT1 (SLC26A6) was also reduced. In contrast, NHERF1 abundance increased in the brush border membrane of Pdzk1(-/-) mice fed a high-P(i) diet. Acute regulation of NaPi-IIa by PTH in vivo and by PTH and activators of protein kinases A, C and G (PKA, PKC and PKG) in vitro (kidney slice preparation) was not altered in Pdzk1(-/-) mice. In conclusion, loss of PDZK1 did not result in major changes in proximal tubule function or NaPi-IIa regulation. However, under a P(i)-rich diet, loss of PDZK1 reduced NaPi-IIa abundance indicating that PDZK1 may play a role in the trafficking or stability of NaPi-IIa under these conditions.
Collapse
Affiliation(s)
- Paola Capuano
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Steffansen B, Nielsen CU, Brodin B, Eriksson AH, Andersen R, Frokjaer S. Intestinal solute carriers: an overview of trends and strategies for improving oral drug absorption. Eur J Pharm Sci 2004; 21:3-16. [PMID: 14706808 DOI: 10.1016/j.ejps.2003.10.010] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A large amount of absorptive intestinal membrane transporters play an important part in absorption and distribution of several nutrients, drugs and prodrugs. The present paper gives a general overview on intestinal solute carriers as well as on trends and strategies for targeting drugs and/or prodrugs to these carriers in order to increasing oral bioavailability and distribution. A number of absorptive intestinal transporters are described in terms of gene and protein classification, driving forces, substrate specificities and cellular localization. When targeting absorptive large capacity membrane transporters in the small intestine in order to increase oral bioavailabilities of drug or prodrug, the major influence on in vivo pharmacokinetics is suggested to be dose-dependent increase in bioavailability as well as prolonged blood circulation due to large capacity facilitated absorption, and renal re-absorption, respectively. In contrast, when targeting low-capacity transporters such as vitamin transporters, dose independent saturable absorption kinetics are suggested. We thus believe that targeting drug substrates for absorptive intestinal membrane transporters could be a feasible strategy for optimizing drug bioavailability and distribution.
Collapse
Affiliation(s)
- Bente Steffansen
- Department of Pharmaceutics, The Danish University of Pharmaceutical Sciences, 2 Universitetsparken, DK-2100 Copenhagen, Denmark.
| | | | | | | | | | | |
Collapse
|
33
|
Sugiura SH, Ferraris RP. Contributions of different NaPi cotransporter isoforms to dietary regulation of P transport in the pyloric caeca and intestine of rainbow trout. ACTA ACUST UNITED AC 2004; 207:2055-64. [PMID: 15143139 DOI: 10.1242/jeb.00971] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The anatomical proximity and embryological relationship of the pyloric caeca (PC) and small intestine of rainbow trout has led to the frequent assumption, on little evidence, that they have the same enzymes and transporters. In trout, the PC is an important absorptive organ for dietary nutrients, but its role in dietary P absorption has not been reported. We found that apical inorganic phosphate (Pi) transport in PC comprises carrier-mediated and diffusive components. Carrier-mediated uptake was energy- and temperature-dependent, competitively inhibited and Na(+)-independent, and greater than the Na(+)-dependent intestinal uptake. Pi uptake in PC was pH-sensitive in the presence of Na(+). Despite the active Pi transport system in PC, high postprandial luminal Pi concentrations ( approximately 20 mmol l(-1)) indicate that diffusive uptake represents approximately 92% of total Pi uptake in PC of fed fish. The nucleotide sequence of a sodium-phosphate cotransporter (NaPi-II) isoform isolated from PC was approximately 8% different from the intestinal NaPi cotransporter. PC-NaPi mRNA was abundant in PC but rare in the intestine, whereas intestinal NaPi mRNA was abundant in the intestine but scarce in PC. Dietary P restriction reduced serum and bone P concentrations, increased intestine-type, but not PC-type, NaPi mRNA in PC, and increased Pi uptake in intestine but not in PC. Intestine-type NaPi expression may be useful for predicting dietary P deficiency.
Collapse
Affiliation(s)
- Shozo H Sugiura
- New Jersey Medical School, Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103, USA
| | | |
Collapse
|
34
|
Wright SH, Dantzler WH. Molecular and cellular physiology of renal organic cation and anion transport. Physiol Rev 2004; 84:987-1049. [PMID: 15269342 DOI: 10.1152/physrev.00040.2003] [Citation(s) in RCA: 342] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Organic cations and anions (OCs and OAs, respectively) constitute an extraordinarily diverse array of compounds of physiological, pharmacological, and toxicological importance. Renal secretion of these compounds, which occurs principally along the proximal portion of the nephron, plays a critical role in regulating their plasma concentrations and in clearing the body of potentially toxic xenobiotics agents. The transepithelial transport involves separate entry and exit steps at the basolateral and luminal aspects of renal tubular cells. It is increasingly apparent that basolateral and luminal OC and OA transport reflects the concerted activity of a suite of separate transport processes arranged in parallel in each pole of proximal tubule cells. The cloning of multiple members of several distinct transport families, the subsequent characterization of their activity, and their subcellular localization within distinct regions of the kidney now allows the development of models describing the molecular basis of the renal secretion of OCs and OAs. This review examines recent work on this issue, with particular emphasis on attempts to integrate information concerning the activity of cloned transporters in heterologous expression systems to that observed in studies of physiologically intact renal systems.
Collapse
Affiliation(s)
- Stephen H Wright
- Dept. of Physiology, College of Medicine, Univ. of Arizona, Tucson, AZ 85724, USA.
| | | |
Collapse
|
35
|
Sugiura SH, Ferraris RP. Dietary phosphorus-responsive genes in the intestine, pyloric ceca, and kidney of rainbow trout. Am J Physiol Regul Integr Comp Physiol 2004; 287:R541-50. [PMID: 15166007 DOI: 10.1152/ajpregu.00225.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Identification of phosphorus (P)-responsive genes is important in diagnosing the adequacy of dietary P intake well before clinical symptoms arise. The mRNA abundance of selected genes was determined in the intestine, pyloric ceca, and kidney of rainbow trout fed low-P (LP) or sufficient-P (SP) diet for 2, 5, and 20 days. The LP-to-SP ratio (LP/SP) of mRNA abundance was used to evaluate the difference in gene expression between LP and SP fish, and to compare the response with bone and serum P, which are conventional indicators of P status. The LP/SP of intestinal, cecal, and renal type II sodium-phosphate cotransporter (NaPi-II) mRNA abundance changed from approximately 1-2 (day 2) to approximately 1.4-4 (day 5) and to approximately 2-10 (day 20). The LP/SP of renal NaPi-II, vitamin D 24-hydroxylase, and vitamin D receptor mRNA abundance correlated inversely with serum P on day 5 but not on day 2 and day 20. In another study, differentially expressed genes between LP and SP fish were examined by subtractive hybridization, confirmed by Northern blot, and evaluated by t-test and correlation with serum and bone P concentrations. About 30 genes were identified as dietary P responsive at day 20, including intestinal meprin and cysteinesulfinic acid decarboxylase, renal S100 calcium-binding protein and mitochondrial P(i) carrier, and cecal apolipoprotein E, somatomedin B-related protein, and NaPi-II. The LP/SP of mRNA abundance of renal mitochondrial P(i) carrier and intestinal cysteinesulfinic acid decarboxylase changed significantly by day 2, and intestinal meprin by day 5. Hence, these genes and NaPi-II are among the earliest steady-response genes capable of predicting P deficiency well before the onset of clinical deficiency.
Collapse
Affiliation(s)
- Shozo H Sugiura
- Department of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, 185 S. Orange Ave., Newark, NJ 07101-1709, USA
| | | |
Collapse
|
36
|
Abstract
Serum phosphate concentrations are maintained within a defined range by processes that regulate the intestinal absorption and renal excretion of inorganic phosphate. The hormones currently believed to influence these processes are parathyroid hormone (PTH) and the active metabolite of vitamin D, 1alpha,25-dihydroxyvitamin D (1alpha,25(OH)2D). A new class of phosphate-regulating factors, collectively known as the phosphatonins, have been shown to be associated with the hypophosphatemic diseases, tumor-induced osteomalacia (TIO), X-linked hypophosphatemic rickets (XLH), and autosomal-dominant hypophosphatemic rickets (ADHR). These factors, which include fibroblast growth factor 23 (FGF23) and secreted frizzled-related protein 4 (FRP4), decrease extracellular fluid phosphate concentrations by directly reducing renal phosphate reabsorption and by suppressing 1alpha,25(OH)2D formation through the inhibition of 25-hydroxyvitamin D 1alpha-hydroxylase. The role of these substances under normal or pathologic conditions is not yet clear. For example, it is unknown whether any of the phosphatonins are directly responsible for the decreased concentrations of 1alpha,25(OH)2D observed in chronic and end-stage kidney disease or whether they are induced in an attempt to correct the hyperphosphatemia seen in late stages of chronic renal failure. Future experiments should clarify their physiologic and pathologic roles in phosphate metabolism.
Collapse
Affiliation(s)
- Susan C Schiavi
- Genzyme Corporation, Framingham, Massachusetts 01701-9322, USA.
| | | |
Collapse
|
37
|
Coloso RM, King K, Fletcher JW, Weis P, Werner A, Ferraris RP. Dietary P regulates phosphate transporter expression, phosphatase activity, and effluent P partitioning in trout culture. J Comp Physiol B 2003; 173:519-30. [PMID: 12851780 DOI: 10.1007/s00360-003-0360-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2003] [Indexed: 11/26/2022]
Abstract
Phosphate utilization by fish is an important issue because of its critical roles in fish growth and aquatic environmental pollution. High dietary phosphorus (P) levels typically decrease the efficiency of P utilization, thereby increasing the amount of P excreted as metabolic waste in effluents emanating from rainbow trout aquaculture. In mammals, vitamin D3 is a known regulator of P utilization but in fish, its regulatory role is unclear. Moreover, the effects of dietary P and vitamin D3 on expression of enzymatic and transport systems potentially involved in phosphate utilization are little known. We therefore monitored production of effluent P, levels of plasma vitamin D3 metabolites, as well as expression of phosphatases and the sodium phosphate cotransporter (NaPi2) in trout fed semipu diets that varied in dietary P and vitamin D3 levels. Mean soluble P concentrations varied markedly with dietary P but not with vitamin D3, and constituted 40-70% of total effluent P production by trout. Particulate P concentrations accounted for 25-50% of effluent P production, but did not vary with dietary P or vitamin D3. P in settleable wastes accounted for <10% of effluent P. The stronger effect of dietary P on effluent P levels is paralleled by its striking effects on phosphatases and NaPi2. The mRNA abundance of the intestinal and renal sodium phosphate transporters increased in fish fed low dietary P; vitamin D3 had no effect. Low-P diets reduced plasma phosphate concentrations. Intracellular phytase activity increased but brushborder alkaline phosphatase activity decreased in the intestine, pyloric caeca, and gills of trout fed diets containing low dietary P. Vitamin D3 had no effect on enzyme activities. Moreover, plasma concentrations of 25-hydroxyvitamin D3 and of 1,25-dihydroxyvitamin D3 were unaffected by dietary P and vitamin D3 levels. The major regulator of P metabolism, and ultimately of levels of P in the effluent from trout culture, is dietary P.
Collapse
Affiliation(s)
- R M Coloso
- Department of Pharmacology and Physiology, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103-2714, USA
| | | | | | | | | | | |
Collapse
|
38
|
Lederer ED, Khundmiri SJ, Weinman EJ. Role of NHERF-1 in regulation of the activity of Na-K ATPase and sodium-phosphate co-transport in epithelial cells. J Am Soc Nephrol 2003; 14:1711-9. [PMID: 12819230 DOI: 10.1097/01.asn.0000072744.67971.21] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Parathyroid hormone (PTH), acting at least in part through a cAMP signaling pathway, regulates three important transporters in the renal proximal convoluted tubule, namely Na-H exchanger 3, Na-K ATPase, and type IIa sodium phosphate cotransporter (NaPi IIa). The regulation of Na-H exchanger 3 by protein kinase A requires a protein co-factor from the sodium-hydrogen exchanger regulatory factor (NHERF) family of proteins (NHERF-1 and NHERF-2). However, the role of NHERF in PTH regulation of Na-K ATPase and NaPi IIa has not been explored. For studying the role of NHERF-1 on PTH regulation of these transporters, wild-type mNHERF-1 (1-355) or mNHERF-1 (1-325) lacking the ezrin-binding domain were expressed in proximal tubule-derived opossum kidney cells. PTH inhibited Na-K ATPase activity in cells expressing wild-type NHERF-1 associated with increased serine phosphorylation of the alpha subunit of the transporter. By contrast, in cells expressing mNHERF (1-325), the phosphorylation of the alpha subunit of Na-K ATPase was blunted and the activity of the transporter was stimulated in response to PTH. Basal sodium-dependent phosphate transport was lower in cells expressing mNHERF-1 (1-325) as compared with cells expressing mNHERF-1 (1-355). Nonetheless, there were no differences in PTH-associated inhibition of the activity or the decrease in membrane expression of the NaPi IIa in any of the cell lines. These experiments document for the first time an association between NHERF-1 and PTH regulation of Na-K ATPase in epithelial cells. These experiments also suggest that the mechanism for retrieval of NaPi IIa transporters from the apical membrane in response to cAMP does not require NHERF.
Collapse
|
39
|
Moz Y, Silver J, Naveh-Many T. Characterization of cis-acting element in renal NaPi-2 cotransporter mRNA that determines mRNA stability. Am J Physiol Renal Physiol 2003; 284:F663-70. [PMID: 12475748 DOI: 10.1152/ajprenal.00332.2002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypophosphatemia leads to an increase in Na(+)-P(i) cotransporter (NaPi-2) mRNA levels. This increase is posttranscriptional and correlates with a more stable transcript mediated by the terminal 698 nt of the NaPi-2 mRNA. A 71-nt binding element was identified with renal proteins from rats fed control and low-P(i) (-P(i)) diet. The binding of -P(i) renal proteins to this transcript was increased compared with control proteins. The functionality of the cis element was demonstrated by an in vitro degradation assay. -P(i) renal proteins stabilized transcripts that included the cis element compared with control renal extracts. The full-length NaPi-2 transcript, but not control transcripts, was stabilized by -P(i) extracts. Insertion of the binding element into green fluorescent protein (GFP) as a reporter gene decreased chimeric GFP mRNA levels in transfection experiments. Our results suggest that the protein-binding region of the NaPi-2 mRNA functions as a cis-acting instability element. In hypophosphatemia there is increased binding to the cis-acting element and subsequent stabilization of NaPi-2 mRNA.
Collapse
Affiliation(s)
- Yulia Moz
- Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hadassah University Hospital, Jerusalem, Israel 91120
| | | | | |
Collapse
|
40
|
Marounek M, Dusková D, Skrivanová V. Hydrolysis of phytic acid and its availability in rabbits. Br J Nutr 2003; 89:287-94. [PMID: 12628024 DOI: 10.1079/bjn2002785] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Twenty weaned rabbits were fed ad libitum two granulated feeds containing lucerne meal, barley, oats, wheat bran, oilseed meals and sugarbeet pulp in different proportions. Phytate P in these feeds represented 28.6 and 29.3 % of the total P. Digestibility trials were carried out in rabbits 7 and 10 weeks old. Digestibility of phytate P was 82.1 %, on average. Apparent digestibility of total P was 48.1 and 35.5 % in rabbits aged 7 and 10 weeks, respectively. Concentration of P in the faecal DM of these rabbits averaged 11.9 and 14.7 mg/g. Most of the faecal P was phosphates P (68.1 %). Proportion of phytate P in total faecal P was 9.0 %. Age effect on total P digestibility and faecal P concentration was significant (P<0.05). In five in vitro experiments twenty-four rabbits were killed at the age of 11 weeks, digesta samples diluted with physiological saline containing phytic acid and incubated anaerobically. Calculations of phytase activity in segments of the digestive tract were based on the estimation of phytic acid hydrolysed during the first 2 h of incubation. The caecum contained 58.6 % of the phytase activity of the digestive tract. Corresponding relative values for the phytase activity in the stomach, small intestine and colon were 22.3, 7.7 and 11.4 %, respectively. In incubations of the caecal contents, phytic acid was hydrolysed more rapidly at pH 5-6 than in the neutral pH region. The hydrolysis was inhibited by Ca cations, and to a small extent also by phosphate anions. Commercial fungal phytase (Natupho) was highly active in incubations of the contents of the stomach at pH 1.9. It can be concluded that phytic acid is hydrolysed quite efficiently in the digestive tract of rabbits. This hydrolysis occurred mainly in the caecum. Absorption of soluble inorganic phosphates in the gut is incomplete.
Collapse
Affiliation(s)
- M Marounek
- Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Prague 10, Uhríneves, CZ-104 00, Czech Republic.
| | | | | |
Collapse
|
41
|
Yang LE, Leong PKK, Ye S, Campese VM, McDonough AA. Responses of proximal tubule sodium transporters to acute injury-induced hypertension. Am J Physiol Renal Physiol 2003; 284:F313-22. [PMID: 12388425 DOI: 10.1152/ajprenal.00134.2002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal injury-induced by phenol injection activates renal sympathetic afferent pathways, increases norepinephrine release from the posterior hypothalamus, activates renal efferent pathways, and provokes a rapid and persistent hypertension. This study aimed to determine whether phenol injury provoked a redistribution of proximal Na(+) transporters from internal stores to the apical cell surface mediated by sympathetic activation, a response that could contribute to generation or maintenance of hypertension. Anesthetized rats were cannulated for arterial blood pressure tracing and saline infusion and then 50 microl 10% phenol or saline was injected into one renal cortex (n = 7 each). Fifty minutes after injection, kidneys were removed and renal cortex membranes from injected kidneys were fractionated on sorbitol gradients and pooled into three windows (WI-WIII) that contained enriched apical brush border (WI); mixed apical, intermicrovillar cleft and dense apical tubules (WII); and intracellular membranes (WIII). Na(+) transporter distributions were determined by immunoblot and expressed as percentage of total in gradient. Acute phenol injury increased blood pressure 20-30 mmHg and led to redistribution of Na(+)/H(+) exchanger type 3 (NHE3) out of WIII (from 22.79 +/- 4.75 to 10.79 +/- 2.01% of total) to WI (13.07 +/- 1.97 to 27.15 +/- 4.08%), Na(+)-P(i) cotransporter 2 out of WII (68.72 +/- 1.95 to 59.76 +/- 2.21%) into WI (9.5 +/- 1.62 to 18.7 +/- 1.45%), and a similar realignment of dipeptidyl-peptidase IV immunoreactivity and alkaline phosphatase activity to WI. Renal denervation before phenol injection prevented the NHE3 redistribution. By confocal microscopy, NHE3 localized to the brush border after phenol injection. The results indicate that phenol injury provokes redistribution of Na(+) transporters from intermicrovillar cleft/intracellular membrane pools to apical membranes associated with sympathetic nervous system activation, which may contribute to phenol injury-induced hypertension.
Collapse
Affiliation(s)
- Li E Yang
- Department of Physiology and Biophysics, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9142, USA
| | | | | | | | | |
Collapse
|
42
|
Abstract
Phosphate (Pi) retention is a common problem in patients with chronic kidney disease, particularly in those who have reached end-stage renal disease (ESRD). In addition to causing secondary hyperparathyroidism and renal osteodystrophy, recent evidence suggests that, in ESRD patients, high serum phosphorus concentration and increased calcium and phosphorous (Ca x P) product are associated with vascular and cardiac calcifications and increased mortality. Dietary phosphorus restriction and Pi removal by dialysis are not sufficient to restore Pi homeostasis. Reduction of intestinal Pi absorption with the use of Pi binders is currently the primary treatment for Pi retention in patients with ESRD. The use of large doses of calcium-containing Pi binders along with calcitriol administration may contribute to over-suppression of parathyroid hormone secretion and adynamic bone disease as well as to a high incidence of vascular calcifications. When used in patients with impaired renal function, aluminium salts were found to accumulate in bone and other tissues, resulting in osteomalacia and encephalopathy.Sevelamer, an aluminium- and calcium-free Pi binder can reduce serum phosphorus concentration and is associated with a significantly lower incidence of hypercalcaemia, while maintaining the ability to suppress parathyroid hormone production. An additional benefit of sevelamer is its ability to lower low density lipoprotein-cholesterol and total cholesterol levels. Sevelamer attenuates the progression of vascular calcifications in haemodialysis patients, which may lead to lower mortality. The use of sevelamer in non-dialysed patients might aggravate metabolic acidosis, common in these patients. Several other calcium-free Pi binders are in development. Lanthanum carbonate has shown significant promise in clinical trials in ESRD patients. Magnesium salts do not offer a significant advantage over currently available Pi binders. Their use is restricted to patients receiving dialysis since excess magnesium must be removed by dialysis. Iron-based compounds have shown variable efficacy in short-term clinical trials in small numbers of haemodialysis patients. Mixed metal hydroxyl carbonate compounds have shown efficacy in animals but have not been studied in humans. Major safety issues include absorption of the metal component with possible tissue accumulation and toxicity.
Collapse
|
43
|
Zhuang L, Peng JB, Tou L, Takanaga H, Adam RM, Hediger MA, Freeman MR. Calcium-selective ion channel, CaT1, is apically localized in gastrointestinal tract epithelia and is aberrantly expressed in human malignancies. J Transl Med 2002; 82:1755-64. [PMID: 12480925 DOI: 10.1097/01.lab.0000043910.41414.e7] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
CaT1 is a highly selective calcium entry channel that has been proposed to be responsible for apical calcium entry in the vitamin D-regulated transcellular pathway of Ca(2+) absorption; however, the lack of a CaT1 antibody suitable for immunohistochemistry has prevented the direct testing of this hypothesis by the localization of CaT1 protein in the gastrointestinal tract and other tissues. In this study, we developed two CaT1 antibodies and have used them to establish for the first time that CaT1 localizes to the apical membrane of intestinal absorptive cells, thereby providing the first direct evidence that this protein is in fact an apical entry channel in the gastrointestinal tract. In addition, we found that CaT1 protein is highly expressed in a number of exocrine organs including pancreas, prostate, and mammary gland, suggesting an, as yet, unrecognized role in secretory epithelia. Finally, we found CaT1 protein to be present at elevated levels in comparison with normal tissues in a series of prostate, breast, thyroid, colon, and ovarian carcinomas, consistent with previous reports of up-regulation of CaT1 mRNA in prostate cancer tissues. Our findings indicate that CaT1 is likely to serve as a component of transcellular calcium transport mechanisms in many tissues and epithelial cancers.
Collapse
Affiliation(s)
- Liyan Zhuang
- The Urologic Laboratory, Department of Urology, Children's Hospital Boston, Massachusetts 02115, USA
| | | | | | | | | | | | | |
Collapse
|
44
|
Swiatecka-Urban A, Duhaime M, Coutermarsh B, Karlson KH, Collawn J, Milewski M, Cutting GR, Guggino WB, Langford G, Stanton BA. PDZ domain interaction controls the endocytic recycling of the cystic fibrosis transmembrane conductance regulator. J Biol Chem 2002; 277:40099-105. [PMID: 12167629 DOI: 10.1074/jbc.m206964200] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The C terminus of CFTR contains a PDZ interacting domain that is required for the polarized expression of cystic fibrosis transmembrane conductance regulator (CFTR) in the apical plasma membrane of polarized epithelial cells. To elucidate the mechanism whereby the PDZ interacting domain mediates the polarized expression of CFTR, Madin-Darby canine kidney cells were stably transfected with wild type (wt-CFTR) or C-terminally truncated human CFTR (CFTR-DeltaTRL). We tested the hypothesis that the PDZ interacting domain regulates sorting of CFTR from the Golgi to the apical plasma membrane. Pulse-chase studies in combination with domain-selective cell surface biotinylation revealed that newly synthesized wt-CFTR and CFTR-DeltaTRL were targeted equally to the apical and basolateral membranes in a nonpolarized fashion. Thus, the PDZ interacting domain is not an apical sorting motif. Deletion of the PDZ interacting domain reduced the half-life of CFTR in the apical membrane from approximately 24 to approximately 13 h but had no effect on the half-life of CFTR in the basolateral membrane. Thus, the PDZ interacting domain is an apical membrane retention motif. Next, we examined the hypothesis that the PDZ interacting domain affects the apical membrane half-life of CFTR by altering its endocytosis and/or endocytic recycling. Endocytosis of wt-CFTR and CFTR-DeltaTRL did not differ. However, endocytic recycling of CFTR-DeltaTRL was decreased when compared with wt-CFTR. Thus, deletion of the PDZ interacting domain reduced the half-life of CFTR in the apical membrane by decreasing CFTR endocytic recycling. Our results identify a new role for PDZ proteins in regulating the endocytic recycling of CFTR in polarized epithelial cells.
Collapse
|
45
|
|