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Koo B, Lee J, Nyachoti CM. Diet complexity and l-threonine supplementation: effects on nutrient digestibility, nitrogen and energy balance, and body composition in nursery pigs. J Anim Sci 2020; 98:skaa124. [PMID: 32307532 PMCID: PMC7216776 DOI: 10.1093/jas/skaa124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 04/16/2020] [Indexed: 01/13/2023] Open
Abstract
This study was conducted to investigate the effects of dietary complexity and l-Thr supplementation on energy and nutrient utilization in nursery pigs. Thirty-two nursery pigs (7.23 ± 0.48 kg) were randomly assigned to a 2 × 2 factorial treatment arrangement based on diet complexity (complex vs. simple) with different levels of l-Thr supplementation. The complex diet contained animal protein sources (e.g., fish meal and plasma) and a dairy product (e.g., dried whey) to mimic a conventional nursery diet. The simple diet was formulated with corn, wheat, and soybean meal. Both diets were supplemented with l-Thr to contain either 100% or 115% (SUP Thr) of the estimated standardized ileal digestible Thr requirement for 9 kg body weight pigs (NRC, 2012). The pigs were individually housed in metabolism crates and fed an experimental diet ad libitum for a 7-d adaptation period and 5 d of total but separate urine and fecal collection. On day 14, all pigs were euthanized to determine body composition. The diet complexity, l-Thr supplementation, and their interactions were considered main effects. Pigs fed the complex diet tended to exhibit greater (P < 0.10) apparent total tract digestibility (ATTD) of ash and urinary energy output than those fed the simple diet. The complex diet had greater (P < 0.05) digestible energy and net energy contents than the simple diet. Furthermore, the complex diet-fed pigs had lower (P < 0.05) plasma urea nitrogen concentration on day 14 than simple diet-fed pigs. The SUP Thr decreased (P < 0.05) ATTD of acid detergent fiber but trended (P < 0.10) toward a decrease in urinary nitrogen (N) output and an increase in N retention and body N mass. In conclusion, the simple diet for nursery pigs had lower digestible and net energy contents than a complex diet. The SUP Thr can improve N utilization and body protein deposition, irrespective of diet complexity.
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Affiliation(s)
- Bonjin Koo
- Department of Animal Science, University of Manitoba, Winnipeg, MB, Canada
| | - Jinyoung Lee
- Department of Animal Science, University of Manitoba, Winnipeg, MB, Canada
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2
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Singh S, Arthur S, Sundaram U. Mechanisms of Regulation of Transporters of Amino Acid Absorption in Inflammatory Bowel Diseases. Compr Physiol 2020; 10:673-686. [PMID: 32163200 DOI: 10.1002/cphy.c190016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Intestinal absorption of dietary amino acids/peptides is essential for protein homeostasis, which in turn is crucial for maintaining health as well as restoration of health from significant diseases. Dietary amino acids/peptides are absorbed by unique transporter processes present in the brush border membrane of absorptive villus cells, which line the entire length of the intestine. To date, the only nutrient absorptive system described in the secretory crypt cells in the mammalian intestine is the one that absorbs the amino acid glutamine. Majority of the amino acid transporters are sodium dependent and therefore require basolateral membrane Na-K-ATPase to maintain an efficient transcellular Na gradient for their activity. These transport processes are tightly regulated by various cellular and molecular mechanisms that facilitate their optimal activity during normal physiological processes. Malabsorption of amino acids, recently described in pathophysiological states such as in inflammatory bowel disease (IBD), is undoubtedly responsible for the debilitating symptoms of IBD such as malnutrition, weight loss and ultimately a failure to thrive. Also recently, in vivo models of IBD and in vitro studies have demonstrated that specific immune-inflammatory mediators/pathways regulate specific amino acid transporters. This provides possibilities to derive novel nutrition and immune-based treatment options for conditions such as IBD. © 2020 American Physiological Society. Compr Physiol 10:673-686, 2020.
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Affiliation(s)
- Soudamani Singh
- Department of Clinical and Translational Sciences and Appalachian Clinical and Translational Science Institute, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, USA
| | - Subha Arthur
- Department of Clinical and Translational Sciences and Appalachian Clinical and Translational Science Institute, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, USA
| | - Uma Sundaram
- Department of Clinical and Translational Sciences and Appalachian Clinical and Translational Science Institute, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia, USA
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3
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Abstract
The small intestine mediates the absorption of amino acids after ingestion of protein and sustains the supply of amino acids to all tissues. The small intestine is an important contributor to plasma amino acid homeostasis, while amino acid transport in the large intestine is more relevant for bacterial metabolites and fluid secretion. A number of rare inherited disorders have contributed to the identification of amino acid transporters in epithelial cells of the small intestine, in particular cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, and dicarboxylic aminoaciduria. These are most readily detected by analysis of urine amino acids, but typically also affect intestinal transport. The genes underlying these disorders have all been identified. The remaining transporters were identified through molecular cloning techniques to the extent that a comprehensive portrait of functional cooperation among transporters of intestinal epithelial cells is now available for both the basolateral and apical membranes. Mouse models of most intestinal transporters illustrate their contribution to amino acid homeostasis and systemic physiology. Intestinal amino acid transport activities can vary between species, but these can now be explained as differences of amino acid transporter distribution along the intestine. © 2019 American Physiological Society. Compr Physiol 9:343-373, 2019.
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Affiliation(s)
- Stefan Bröer
- Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia
| | - Stephen J Fairweather
- Research School of Biology, The Australian National University, Canberra, ACT 2601, Australia
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4
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Mastrototaro L, Sponder G, Saremi B, Aschenbach JR. Gastrointestinal methionine shuttle: Priority handling of precious goods. IUBMB Life 2016; 68:924-934. [DOI: 10.1002/iub.1571] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 09/22/2016] [Indexed: 01/05/2023]
Affiliation(s)
- Lucia Mastrototaro
- Institute of Veterinary Physiology, Department of Veterinary Medicine, Free University of Berlin; Berlin Germany
| | - Gerhard Sponder
- Institute of Veterinary Physiology, Department of Veterinary Medicine, Free University of Berlin; Berlin Germany
| | - Behnam Saremi
- Evonik Nutrition & Care GmbH; Animal Nutrition-Animal Nutrition Services; Hanau Germany
| | - Jörg R. Aschenbach
- Institute of Veterinary Physiology, Department of Veterinary Medicine, Free University of Berlin; Berlin Germany
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5
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Yang C, Yang X, Lackeyram D, Rideout TC, Wang Z, Stoll B, Yin Y, Burrin DG, Fan MZ. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula. Amino Acids 2016; 48:1491-508. [PMID: 26984322 DOI: 10.1007/s00726-016-2210-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 02/29/2016] [Indexed: 01/11/2023]
Abstract
Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA co-transporter (B(0)AT1, encoded by the SLC6A19 gene) plays a dominant role for apical uptake of large neutral AA including L-Gln, we hypothesized that high apical Na(+)-Gln co-transport activity, and B(0)AT1 (SLC6A19) in co-expression with angiotensin-converting enzyme 2 (ACE2) were expressed along the entire small intestinal crypt-villus axis in young animals via unique control mechanisms. Kinetics of Na(+)-Gln co-transport activity in the apical membrane vesicles, prepared from epithelial cells sequentially isolated along the jejunal crypt-villus axis from liquid formula-fed young pigs, were measured with the membrane potential being clamped to zero using thiocyanate. Apical maximal Na(+)-Gln co-transport activity was much higher (p < 0.05) in the upper villus cells than in the middle villus (by 29 %) and the crypt (by 30 %) cells, whereas Na(+)-Gln co-transport affinity was lower (p < 0.05) in the upper villus cells than in the middle villus and the crypt cells. The B(0)AT1 (SLC6A19) mRNA abundance was lower (p < 0.05) in the crypt (by 40-47 %) than in the villus cells. There were no significant differences in B(0)AT1 and ACE2 protein abundances on the apical membrane among the upper villus, the middle villus and the crypt cells. Our study suggests that piglet fast growth is associated with very high intestinal apical Na(+)-neutral AA uptake activities via abundantly co-expressing B(0)AT1 and ACE2 proteins in the apical membrane and by transcribing the B(0)AT1 (SLC6A19) gene in the epithelia along the entire crypt-villus axis.
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Affiliation(s)
- Chengbo Yang
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada. .,Department of Animal Science, Faculty of Agricultural and Food Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
| | - Xiaojian Yang
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.,Southern Research and Outreach Center, University of Minnesota, Waseca, MN, 56093, USA
| | - Dale Lackeyram
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Todd C Rideout
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.,Department of Exercise and Nutrition Sciences, the State University of New York at Buffalo, New York, 14214, USA
| | - Zirong Wang
- College of Animal Science, Xinjiang Agricultural University, Urumqi, 830052, Xinjiang, China
| | - Barbara Stoll
- US Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Yulong Yin
- Institute of Subtropical Agriculture, The Chinese Academy of Sciences, Changsha, 410125, Hunan, China
| | - Douglas G Burrin
- US Department of Agriculture/Agricultural Research Service, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Ming Z Fan
- Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
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6
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Miao ZG, Wang LJ, Fei-Zhu F, Li GW, Xu ZR. Developmental changes of jejunal brush-border enzyme activity in growing Jinhua gilts. ITALIAN JOURNAL OF ANIMAL SCIENCE 2016. [DOI: 10.4081/ijas.2009.143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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7
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Sjögren E, Abrahamsson B, Augustijns P, Becker D, Bolger MB, Brewster M, Brouwers J, Flanagan T, Harwood M, Heinen C, Holm R, Juretschke HP, Kubbinga M, Lindahl A, Lukacova V, Münster U, Neuhoff S, Nguyen MA, Peer AV, Reppas C, Hodjegan AR, Tannergren C, Weitschies W, Wilson C, Zane P, Lennernäs H, Langguth P. In vivo methods for drug absorption – Comparative physiologies, model selection, correlations with in vitro methods (IVIVC), and applications for formulation/API/excipient characterization including food effects. Eur J Pharm Sci 2014; 57:99-151. [DOI: 10.1016/j.ejps.2014.02.010] [Citation(s) in RCA: 196] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 02/15/2014] [Accepted: 02/17/2014] [Indexed: 01/11/2023]
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8
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van Vliet D, Derks TGJ, van Rijn M, de Groot MJ, MacDonald A, Heiner-Fokkema MR, van Spronsen FJ. Single amino acid supplementation in aminoacidopathies: a systematic review. Orphanet J Rare Dis 2014; 9:7. [PMID: 24422943 PMCID: PMC3895659 DOI: 10.1186/1750-1172-9-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 12/27/2013] [Indexed: 12/15/2022] Open
Abstract
Aminoacidopathies are a group of rare and diverse disorders, caused by the deficiency of an enzyme or transporter involved in amino acid metabolism. For most aminoacidopathies, dietary management is the mainstay of treatment. Such treatment includes severe natural protein restriction, combined with protein substitution with all amino acids except the amino acids prior to the metabolic block and enriched with the amino acid that has become essential by the enzymatic defect. For some aminoacidopathies, supplementation of one or two amino acids, that have not become essential by the enzymatic defect, has been suggested. This so-called single amino acid supplementation can serve different treatment objectives, but evidence is limited. The aim of the present article is to provide a systematic review on the reasons for applications of single amino acid supplementation in aminoacidopathies treated with natural protein restriction and synthetic amino acid mixtures.
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Affiliation(s)
| | | | | | | | | | | | - Francjan J van Spronsen
- Department of Metabolic Diseases, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
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9
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Cervantes-Ramírez M, Mendez-Trujillo V, Araiza-Piña B, Barrera-Silva M, González-Mendoza D, Morales-Trejo A. Supplemental leucine and isoleucine affect expression of cationic amino acid transporters and myosin, serum concentration of amino acids, and growth performance of pigs. GENETICS AND MOLECULAR RESEARCH 2013; 12:115-26. [DOI: 10.4238/2013.january.24.3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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10
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Woodward AD, Fan MZ, Geor RJ, McCutcheon LJ, Taylor NP, Trottier NL. Characterization of L-lysine transport across equine and porcine jejunal and colonic brush border membrane. J Anim Sci 2012; 90:853-62. [DOI: 10.2527/jas.2011-4210] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- A. D. Woodward
- Department of Animal Science, Michigan State University, East Lansing 48824
| | - M. Z. Fan
- Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - R. J. Geor
- Department of Large Animal Clinical Science, Michigan State University, East Lansing 48824
| | - L. J. McCutcheon
- Department of Large Animal Clinical Science, Michigan State University, East Lansing 48824
| | - N. P. Taylor
- Department of Animal Science, Michigan State University, East Lansing 48824
| | - N. L. Trottier
- Department of Animal Science, Michigan State University, East Lansing 48824
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11
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Bröer S. The role of the neutral amino acid transporter B0AT1 (SLC6A19) in Hartnup disorder and protein nutrition. IUBMB Life 2009; 61:591-9. [PMID: 19472175 PMCID: PMC7165679 DOI: 10.1002/iub.210] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Hartnup disorder (OMIM 234500) is an autosomal recessive disorder, which was first described in 1956 as an aminoaciduria of neutral amino acids accompanied by a variety of symptoms, such as a photo‐sensitive skin‐rash and cerebellar ataxia. The disorder is caused by mutations in the neutral amino acid transporter B0AT1 (SLC6A19)1. To date 21 mutations have been identified in more than twenty families. SLC6A19 requires either collectrin or angiotensin‐converting enzyme 2 for surface expression in the kidney and intestine, respectively. This ties SLC6A19 together with more complex functions such as blood‐pressure control, glomerular structure, and exocytosis. © 2009 IUBMB IUBMB Life, 61(6): 591–599, 2009
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Affiliation(s)
- Stefan Bröer
- School of Biology, College of Medicine, Biology and Environment, Australian National University, Canberra, Australian Capital Territory, Australia.
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12
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Schaart MW, de Bruijn ACJM, Schierbeek H, Tibboel D, Renes IB, van Goudoever JB. Small intestinal MUC2 synthesis in human preterm infants. Am J Physiol Gastrointest Liver Physiol 2009; 296:G1085-90. [PMID: 19246635 DOI: 10.1152/ajpgi.90444.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Mucin 2 (MUC2) is the structural component of the intestinal protective mucus layer, which contains high amounts of threonine in its peptide backbone. MUC2 synthesis rate might be a potential parameter for intestinal barrier function. In this study, we aimed to determine whether systemic threonine was used for small intestinal MUC2 synthesis and to calculate the MUC2 fractional synthetic rate (FSR) in human preterm infants. Seven preterm infants with an enterostomy following bowel resection for necrotizing enterocolitis received intravenous infusion of [U-(13)C]threonine to determine incorporation of systemic threonine into secreted MUC2 in intestinal outflow fluid. Small intestinal MUC2 was isolated using cesium chloride gradient ultracentrifugation and gravity gel filtration chromatography. MUC2-containing fractions were identified by SDS-PAGE/periodic acid-Schiff staining and Western blot analysis and were subsequently pooled. Isotopic enrichment of threonine, measured in MUC2 using gas chromatography isotopic ratio mass spectrometry, was used to calculate the FSR of MUC2. Systemically derived threonine was indeed incorporated into small intestinal MUC2. Median FSR of small intestinal MUC2 was 67.2 (44.3-103.9)% per day. Systemic threonine is rapidly incorporated into MUC2 in the small intestine of preterm infants, and thereby MUC2 has a very high synthesis rate.
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Affiliation(s)
- Maaike W Schaart
- Erasmus Medical Center, Sophia Children's Hospital, Department of Pediatrics, Division of Neonatology, Rotterdam, the Netherlands
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13
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Martín-Venegas R, Rodríguez-Lagunas MJ, Mercier Y, Geraert PA, Ferrer R. Effect of pH onl- andd-methionine uptake across the apical membrane of Caco-2 cells. Am J Physiol Cell Physiol 2009; 296:C632-8. [DOI: 10.1152/ajpcell.00478.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The transport systems involved in intestinal methionine (Met) absorption are described as Na+-dependent and Na+-independent mechanisms. However, since recent studies have suggested the importance of the H+gradient as a driving force for intestinal nutrient absorption, the aim of the present work was to test whether Met transport across the apical membrane of Caco-2 cells is affected by extracellular pH. The results show that l- and d-Met uptake was increased by lowering extracellular pH from 7.4 to 5.5, in both the presence and absence of Na+. Cis-inhibition experiments revealed that inhibition of l-Met transport by 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) or l-lysine (l-Lys) was higher at a pH of 5.5. Moreover, the BCH-insensitive component was not affected by pH, whereas the l-Lys-insensitive component was increased by lowering extracellular pH, thus suggesting the participation of system L. The contribution of another mechanism, sensitive to both BCH and l-Lys, was also considered. The inhibition obtained with taurine (Tau) was also higher at a pH of 5.5, thus suggesting the involvement of system B0,+on pH-stimulated component. As for d-Met uptake, the results showed higher inhibition with l-Lys and Tau at a pH of 5.5 and no effect on the l-Lys- or Tau-insensitive component. In conclusion, Met transport across the apical membrane of Caco-2 cells is increased by low extracellular pH as the result of the stimulation of two transport systems functionally identified with systems L and B0,+for l-Met and with system B0,+for d-Met.
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Talukder JR, Kekuda R, Saha P, Arthur S, Sundaram U. Identification and characterization of rabbit small intestinal villus cell brush border membrane Na-glutamine cotransporter. Am J Physiol Gastrointest Liver Physiol 2008; 295:G7-G15. [PMID: 18436625 PMCID: PMC2494716 DOI: 10.1152/ajpgi.00606.2007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glutamine, the primary metabolic fuel for the mammalian small intestinal enterocytes, is primarily assimilated by Na-amino acid cotransporters. Although Na-solute cotransport has been shown to exist in the brush border membrane (BBM) of the absorptive villus cells, the identity of Na-glutamine cotransport in rabbit small intestinal villus cells was unknown. Na-dependent glutamine uptake is present in villus BBM vesicles. An intravesicular proton gradient did not stimulate this Na-dependent glutamine uptake, whereas Li+ did not significantly suppress this uptake. These observations in concert with amino acid substitution studies suggested that Na-glutamine cotransporter in the villus cell BBM was the newly identified cotransporter B0AT1 (SLC6A19). Quantitative real-time PCR identified the message for this cotransporter in villus cells. Thus a full-length cDNA of B0AT1 was cloned and expressed in MDA-MB-231 cells. This expressed cotransporter exhibited characteristics similar to those observed in villus cells from the rabbit small intestine. Antibody was generated for B0AT1 that demonstrated the presence of this cotransporter protein in the villus cell BBM. Kinetic studies defined the kinetic parameters of this cotransporter. Thus this study describes the identification, cloning, and characterization of the Na-amino acid cotransporter responsible for the assimilation of a critical amino acid by the absorptive villus cells in the mammalian small intestine.
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Affiliation(s)
- Jamilur R. Talukder
- Section of Digestive Diseases, Department of Medicine, West Virginia University, School of Medicine
| | - Ramesh Kekuda
- Section of Digestive Diseases, Department of Medicine, West Virginia University, School of Medicine
| | - Prosenjit Saha
- Section of Digestive Diseases, Department of Medicine, West Virginia University, School of Medicine
| | - Subha Arthur
- Section of Digestive Diseases, Department of Medicine, West Virginia University, School of Medicine
| | - Uma Sundaram
- Section of Digestive Diseases, Department of Medicine, West Virginia University, School of Medicine
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15
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Bröer S. Apical transporters for neutral amino acids: physiology and pathophysiology. Physiology (Bethesda) 2008; 23:95-103. [PMID: 18400692 DOI: 10.1152/physiol.00045.2007] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Absorption of amino acids in kidney and intestine involves a variety of transporters for different groups of amino acids. This is illustrated by inherited disorders of amino acid absorption, such as Hartnup disorder, cystinuria, iminoglycinuria, dicarboxylic aminoaciduria, and lysinuric protein intolerance, affecting separate groups of amino acids. Recent advances in the molecular identification of apical neutral amino acid transporters has shed a light on the molecular basis of Hartnup disorder and iminoglycinuria.
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Affiliation(s)
- Stefan Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, Australia.
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16
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Bröer S. Amino acid transport across mammalian intestinal and renal epithelia. Physiol Rev 2008; 88:249-86. [PMID: 18195088 DOI: 10.1152/physrev.00018.2006] [Citation(s) in RCA: 614] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The transport of amino acids in kidney and intestine is critical for the supply of amino acids to all tissues and the homeostasis of plasma amino acid levels. This is illustrated by a number of inherited disorders affecting amino acid transport in epithelial cells, such as cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, dicarboxylic aminoaciduria, and some other less well-described disturbances of amino acid transport. The identification of most epithelial amino acid transporters over the past 15 years allows the definition of these disorders at the molecular level and provides a clear picture of the functional cooperation between transporters in the apical and basolateral membranes of mammalian epithelial cells. Transport of amino acids across the apical membrane not only makes use of sodium-dependent symporters, but also uses the proton-motive force and the gradient of other amino acids to efficiently absorb amino acids from the lumen. In the basolateral membrane, antiporters cooperate with facilitators to release amino acids without depleting cells of valuable nutrients. With very few exceptions, individual amino acids are transported by more than one transporter, providing backup capacity for absorption in the case of mutational inactivation of a transport system.
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Affiliation(s)
- Stefan Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
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18
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Cottrell JJ, Stoll B, Buddington RK, Stephens JE, Cui L, Chang X, Burrin DG. Glucagon-like peptide-2 protects against TPN-induced intestinal hexose malabsorption in enterally refed piglets. Am J Physiol Gastrointest Liver Physiol 2006; 290:G293-300. [PMID: 16166344 DOI: 10.1152/ajpgi.00275.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Premature infants receiving chronic total parenteral nutrition (TPN) due to feeding intolerance develop intestinal atrophy and reduced nutrient absorption. Although providing the intestinal trophic hormone glucagon-like peptide-2 (GLP-2) during chronic TPN improves intestinal growth and morphology, it is uncertain whether GLP-2 enhances absorptive function. We placed catheters in the carotid artery, jugular and portal veins, duodenum, and a portal vein flow probe in piglets before providing either enteral formula (ENT), TPN or a coinfusion of TPN plus GLP-2 for 6 days. On postoperative day 7, all piglets were fed enterally and digestive functions were evaluated in vivo using dual infusion of enteral ((13)C) and intravenous ((2)H) glucose, in vitro by measuring mucosal lactase activity and rates of apical glucose transport, and by assessing the abundances of sodium glucose transporter-1 (SGLT-1) and glucose transporter-2 (GLUT2). Both ENT and GLP-2 pigs had larger intestine weights, longer villi, and higher lactose digestive capacity and in vivo net glucose and galactose absorption compared with TPN alone. These endpoints were similar in ENT and GLP-2 pigs except for a lower intestinal weight and net glucose absorption in GLP-2 compared with ENT pigs. The enhanced hexose absorption in GLP-2 compared with TPN pigs corresponded with higher lactose digestive and apical glucose transport capacities, increased abundance of SGLT-1, but not GLUT-2, and lower intestinal metabolism of [(13)C]glucose to [(13)C]lactate. Our findings indicate that GLP-2 treatment during chronic TPN maintains intestinal structure and lactose digestive and hexose absorptive capacities, reduces intestinal hexose metabolism, and may facilitate the transition to enteral feeding in TPN-fed infants.
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Affiliation(s)
- J J Cottrell
- USDA-ARS, Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
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Adeola O, King DE. Developmental changes in morphometry of the small intestine and jejunal sucrase activity during the first nine weeks of postnatal growth in pigs1. J Anim Sci 2006; 84:112-8. [PMID: 16361497 DOI: 10.2527/2006.841112x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The objective of this study was to investigate the development of small intestinal size and digestive capacity of the jejunum in growing pigs. The weight, length, surface area, and mucosa weight of the small intestine were measured when pigs were 1, 3, 5, and 9 wk of age. Sucrase and alkaline phosphatase (ALP) activities of the jejunal brush-border membrane, prepared by differential centrifugation and Mg2+ precipitation, were determined at the respective postnatal stages. Body weights increased 7-fold from 2.7 kg at 1 wk to 23.32 kg at 9 wk postnatal. Body weight gains were greater (P < 0.05) from wk 3 to 5 than from wk 1 to 3. Weights of the small intestine and of the intestinal mucosa increased faster (P < 0.05) from 3 to 5 wk than from 1 to 3 wk; the slowest increase occurred from 5 to 9 wk. Weights of the duodenum, jejunum, and ileum, and mucosa from the respective sections increased (P < 0.05) as pigs grew from 3 to 9 wk. Mucosa weight relative to the weight of the section was greater (P < 0.05) for the duodenum and jejunum than for the ileum at 9 wk of age. Between the ages of 3 and 9 wk, the increase in mucosa weight was highest for the jejunum followed by the duodenum and the ileum. The increase was greatest for the duodenum followed by the jejunum and the ileum when mucosal weight was expressed per unit of appropriate intestinal section weight. There was a 55-fold increase in jejunal sucrase activity from 1 to 9 wk; the greatest rate of increase occurred between 5 and 9 wk. Total jejunal ALP activities in pigs at 9 wk was greater (P < 0.05) than at 5 wk, which in turn was greater than at 1 wk of age. In summary, increases in BW during the first 9 wk of postnatal growth in pigs are accompanied by significant developmental changes in digestive capacity including intestinal weights, length, and area as well as jejunal brush-border sucrase and ALP activities.
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Affiliation(s)
- O Adeola
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907-2054, USA.
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Böhmer C, Bröer A, Munzinger M, Kowalczuk S, Rasko J, Lang F, Bröer S. Characterization of mouse amino acid transporter B0AT1 (slc6a19). Biochem J 2005; 389:745-51. [PMID: 15804236 PMCID: PMC1180725 DOI: 10.1042/bj20050083] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Revised: 03/16/2005] [Accepted: 04/01/2005] [Indexed: 12/31/2022]
Abstract
The mechanism of the mouse (m)B0AT1 (slc6a19) transporter was studied in detail using two electrode voltage-clamp techniques and tracer studies in the Xenopus oocyte expression system. All neutral amino acids induced inward currents at physiological potentials, but large neutral non-aromatic amino acids were the preferred substrates of mB0AT1. Substrates were transported with K0.5 values ranging from approx. 1 mM to approx. 10 mM. The transporter mediates Na+-amino acid co-transport with a stoichiometry of 1:1. No other ions were involved in the transport mechanism. An increase in the extracellular Na+ concentration reduced the K0.5 for leucine, and vice versa. Moreover, the K0.5 values and Vmax values of both substrates varied with the membrane potential. As a result, K0.5 and Vmax values are a complex function of the concentration of substrate and co-substrate and the membrane potential. A model is presented assuming random binding order and a positive charge associated with the ternary [Na+-substrate-transporter] complex, which is consistent with the experimental data.
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Affiliation(s)
- Christoph Böhmer
- *Physiologisches Institut, Universität Tübingen, 72076 Tübingen, Germany
| | - Angelika Bröer
- †School of Biochemistry & Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Michael Munzinger
- †School of Biochemistry & Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Sonja Kowalczuk
- †School of Biochemistry & Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
| | - John E. J. Rasko
- ‡Gene Therapy, Centenary Institute of Cancer Medicine and Cell Biology, University of Sydney & Sydney Cancer Centre, Locked Bag No 6, Newtown, NSW 2042, Australia
| | - Florian Lang
- *Physiologisches Institut, Universität Tübingen, 72076 Tübingen, Germany
| | - Stefan Bröer
- †School of Biochemistry & Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
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Bröer A, Cavanaugh JA, Rasko JEJ, Bröer S. The molecular basis of neutral aminoacidurias. Pflugers Arch 2005; 451:511-7. [PMID: 16052352 DOI: 10.1007/s00424-005-1481-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2005] [Accepted: 06/09/2005] [Indexed: 10/25/2022]
Abstract
Recent success in the molecular cloning and identification of apical neutral amino acid transporters has shed a new light on inherited neutral amino acidurias, such as Hartnup disorder and Iminoglycinuria. Hartnup disorder is caused by mutations in the neutral amino acid transporter B(0) AT1 (SLC6A19). The transporter is found in kidney and intestine, where it is involved in the resorption of all neutral amino acids. The molecular defect underlying Iminoglycinuria has not yet been identified. However, two transporters, the proton amino acid transporter PAT1 (SLC36A1) and the IMINO transporter (SLC6A20) appear to play key roles in the resorption of glycine and proline. A model is presented, involving all three transporters that can explain the phenotypic variability of iminoglycinuria.
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Affiliation(s)
- Angelika Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra
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22
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Bröer S, Cavanaugh JA, Rasko JEJ. Neutral amino acid transport in epithelial cells and its malfunction in Hartnup disorder. Biochem Soc Trans 2005; 33:233-6. [PMID: 15667315 DOI: 10.1042/bst0330233] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hartnup disorder is an autosomal recessive abnormality of renal and gastrointestinal neutral amino acid transport. A corresponding transport activity has been characterized in kidney and intestinal cells and named system B(0). The failure to resorb amino acids in this disorder is thought to be compensated by a protein-rich diet. However, in combination with a poor diet and other factors, more severe symptoms can develop in Hartnup patients, including a photosensitive pellagra-like skin rash, cerebellar ataxia and other neurological symptoms. Homozygosity mapping in a Japanese family and linkage analysis on six Australian pedigrees placed the Hartnup disorder gene at a locus on chromosome 5p15. This fine mapping facilitated a candidate gene approach within the interval, which resulted in the cloning and characterization of a novel member of the sodium-dependent neurotransmitter transporter family (B(0)AT1, SLC6A19) from mouse and human kidney, which shows all properties of system B(0). Flux experiments and electrophysiological recording showed that the transporter is Na(+) dependent and Cl(-) independent, electrogenic and actively transports most neutral amino acids. In situ hybridization showed strong expression in intestinal villi and in the proximal tubule of the kidney. Expression of B(0)AT1 was restricted to kidney, intestine and skin. A total of ten mutations have been identified in SLC6A19 that co-segregate with disease in the predicted recessive manner, with the majority of affected individuals being compound heterozygotes. These mutations lead to altered neutral amino acid transport function compared to the wild-type allele in vitro. One of the mutations occurs in members of the original Hartnup family described in 1956, thereby defining SLC6A19 as the 'Hartnup'-gene.
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Affiliation(s)
- S Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia.
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23
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Fan MZ, Matthews JC, Etienne NMP, Stoll B, Lackeyram D, Burrin DG. Expression of apical membrane L-glutamate transporters in neonatal porcine epithelial cells along the small intestinal crypt-villus axis. Am J Physiol Gastrointest Liver Physiol 2004; 287:G385-98. [PMID: 15044176 DOI: 10.1152/ajpgi.00232.2003] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Enteral l-glutamate is extensively utilized as an oxidative fuel by the gut mucosa in the neonate. To identify major uptake pathways and to understand uptake regulation, we examined transport kinetics and molecular identities of apical membrane l-glutamate transporters in epithelial cells sequentially isolated along the small intestinal crypt-villus axis from milk protein-fed, 16-day-old pigs. The distended intestinal sac method was used to isolate 12 sequential cell fractions from the tip villus to the bottom crypt. Initial rates and kinetics of l-glutamate uptake were measured with l-[G-(3)H]glutamate by fast filtration in apical membrane vesicles prepared by Mg(2+) precipitation and differential centrifugation, with membrane potential clamped by SCN(-). Initial l-glutamate uptake results suggested the presence of B(o) and X(AG)(-) transport systems, but the X(AG)(-) system was predominant for uptake across the apical membrane. Kinetic data suggested that l-glutamate uptake through the X(AG)(-) system was associated with higher maximal transport activity but lower transporter affinity in crypt than in villus cells. Molecular identity of the X(AG)(-) glutamate transporter, based on immunoblot and RT-PCR analysis, was primarily the defined excitatory amino acid carrier (EAAC)-1. EAAC-1 expression was increased with cell differentiation and regulated at transcription and translation levels from crypt to upper villus cells. In conclusion, efficiency and capacity of luminal l-glutamate uptake across the apical membrane are regulated by changing expression of the X(AG)(-) system transporter gene EAAC-1 at transcription and translation levels as well as maximal uptake activity and transporter affinity along the intestinal crypt-villus axis in the neonate.
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Affiliation(s)
- Ming Z Fan
- USDA/ARS Children's Nutrition Research Center, Dept. of Pediatrics, Baylor College of Medicine, 1100 Bates St., Houston, TX 77030, USA
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Shikano N, Kawai K, Nakajima S, Kubodera A, Kubota N, Ishikawa N, Saji H. Transcellular transport of 4-iodo-L-meta-tyrosine via system L across monolayers of kidney epithelial cell line LLC-PK1. Nucl Med Biol 2004; 31:477-82. [PMID: 15093818 DOI: 10.1016/j.nucmedbio.2003.12.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2003] [Revised: 12/11/2003] [Accepted: 12/19/2003] [Indexed: 10/26/2022]
Abstract
The substance 4-[(125)I]iodo-L-meta-tyrosin (4-[(125)I]mTyr) is a radioiodinated amino acid that exhibits high in vivo stability and rapid renal elimination in vivo. We investigated transport of 4-[(125)I]mTyr in LLC-PK(1) (porcine kidney epithelial cell line) monolayers grown on collagen-coated, micro-porous membrane filters. We found that 4-[(125)I]mTyr transport in LLC-PK(1) cells was carrier-mediated and sodium-independent, and that 4-[(125)I]mTyr transport was similar to that of L-Tyr and 3-iodo-alpha-methyl-L-tyrosine. The results of the inhibition experiments suggest that 4-[(125)I]mTyr transport is predominantly mediated by a L-type amino acid transporter 1-like porcine homologue (a component of system L) in both basolateral and apical membrane.
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Affiliation(s)
- Naoto Shikano
- Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan.
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25
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Shikano N, Kawai K, Nakajima S, Kubodera A, Kubota N, Ishikawa N, Saji H. Transcellular transport of radioiodinated 3-iodo-α-methyl-L-tyrosine across monolayers of kidney epithelial cell line LLC-PK1. Ann Nucl Med 2004; 18:227-34. [PMID: 15233284 DOI: 10.1007/bf02985004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVE 3-[123I]iodo-alpha-methyl-L-tyrosine ([123I]IMT) is an imaging agent for amino acid transport. In order to obtain fundamental data related to tumor imaging with [123I]IMT and renal physiological accumulation of [123I]IMT, we investigated the transport characteristics of [125I]IMT in porcine kidney epithelial cell line LLC-PK1 using cell monolayers grown on microporous membrane filters. METHODS LLC-PK1 monolayers were created on a collagen-coated microporous (3 microm) membrane (4.7 cm2). To examine transcellular transport (secretion and reabsorption) and accumulation, the monolayers were incubated for up to 90 min at 37 degrees C with 18.5 kBq [125I]IMT in Dulbecco's phosphate-buffered saline (pH 7.4) as an uptake solution. After incubation, transcellular transport was assessed by quantifying the radioactivity of the solutions on each side of the monolayer. For the accumulation experiment, the cells were solubilized in NaOH solution, and the radioactivity was quantified. For the inhibition experiment, the inhibitor was added at a final concentration of 1 mM. For the pH dependence experiment, the pH of the apical-side uptake solution was varied from pH 5 to pH 8. Transport of [14C]Tyr was examined for comparison. RESULTS Bi-directional transcellular transport of [125I]IMT was observed, corresponding to secretion and reabsorption in proximal tubule. Accumulation of [125I]IMT from the basolateral side (1.62 +/- 0.15%) and the apical side (2.62 +/- 0.35%) was observed at 90 min. 2-Amino-bicyclo[2,2,1]heptane-2-carboxylic acid (a specific inhibitor of system L), L-Tyr (mother compound of [125I]IMT) and 2-aminoisobutyric acid (an inhibitor of system L and A) inhibited both directional transport (p < 0.01) and accumulation (p < 0.01). 2-(Methylamino)isobutyric acid (a specific inhibitor of system A) appeared to inhibit transport and accumulation, but the results were not significant. Decreasing apical pH significantly enhanced accumulation of [125I]IMT from both sides (p < 0.001), whereas accumulation of mother L-Tyr was significantly suppressed. CONCLUSIONS The inhibition experiments suggest that the main contributor to [125I]IMT transport is system L, rather than Na+ -dependent transport, in both apical and basolateral membrane. [125I]IMT was transported by the system that transported L-Tyr, but the observed pH dependence of transport suggests that different mechanisms are involved in accumulation of [125I]IMT and [14C]Tyr.
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Affiliation(s)
- Naoto Shikano
- Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Inashiki-gun, Ibaraki, Japan.
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26
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Bröer A, Klingel K, Kowalczuk S, Rasko JEJ, Cavanaugh J, Bröer S. Molecular cloning of mouse amino acid transport system B0, a neutral amino acid transporter related to Hartnup disorder. J Biol Chem 2004; 279:24467-76. [PMID: 15044460 DOI: 10.1074/jbc.m400904200] [Citation(s) in RCA: 185] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Resorption of amino acids in kidney and intestine is mediated by transporters, which prefer groups of amino acids with similar physico-chemical properties. It is generally assumed that most neutral amino acids are transported across the apical membrane of epithelial cells by system B(0). Here we have characterized a novel member of the Na(+)-dependent neurotransmitter transporter family (B(0)AT1) isolated from mouse kidney, which shows all properties of system B(0). Flux experiments showed that the transporter is Na(+)-dependent, electrogenic, and actively transports most neutral amino acids but not anionic or cationic amino acids. Superfusion of mB(0)AT1-expressing oocytes with neutral amino acids generated inward currents, which were proportional to the fluxes observed with labeled amino acids. In situ hybridization showed strong expression in intestinal microvilli and in the proximal tubule of the kidney. Expression of mouse B(0)AT1 was restricted to kidney, intestine, and skin. It is generally assumed that mutations of the system B(0) transporter underlie autosomal recessive Hartnup disorder. In support of this notion mB(0)AT1 is located on mouse chromosome 13 in a region syntenic to human chromosome 5p15, the locus of Hartnup disorder. Thus, the human homologue of this transporter is an excellent functional and positional candidate for Hartnup disorder.
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MESH Headings
- Amino Acid Sequence
- Amino Acid Transport Systems/genetics
- Amino Acid Transport Systems, Neutral/genetics
- Amino Acids/chemistry
- Animals
- Anions
- Base Sequence
- Biological Transport
- Cations
- Cloning, Molecular
- DNA, Complementary/metabolism
- Electrophysiology
- Hartnup Disease/metabolism
- Hydrogen-Ion Concentration
- In Situ Hybridization
- Intestinal Mucosa/metabolism
- Ions
- Kidney/metabolism
- Leucine/chemistry
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Models, Biological
- Models, Genetic
- Molecular Sequence Data
- Mutation
- Oocytes/metabolism
- Peptides/chemistry
- Phylogeny
- Plasmids/metabolism
- Protein Structure, Tertiary
- RNA, Complementary/metabolism
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Skin/metabolism
- Substrate Specificity
- Time Factors
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Affiliation(s)
- Angelika Bröer
- School of Biochemistry and Molecular Biology, Australian National University, Canberra ACT 0200, Australia
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Sanjurjo P, Aldamiz L, Georgi G, Jelinek J, Ruiz JI, Boehm G. Dietary threonine reduces plasma phenylalanine levels in patients with hyperphenylalaninemia. J Pediatr Gastroenterol Nutr 2003; 36:23-6. [PMID: 12499992 DOI: 10.1097/00005176-200301000-00007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
BACKGROUND In order to achieve normal intellectual development, the plasma phe-nylalanine (PHE) levels of patients with hyperphenylalaninemia should not exceed toxic levels. This goal is usually accomplished by employing special diets in which the patient's protein intake is in the form of PHE-free mixtures of amino acids. There is evidence from our own observations in animals and a preliminary observation in patients with hyperphenylalaninemia that supplemental dietary threonine (THR) might decrease plasma PHE concentrations. METHODS In this placebo-controlled crossover study, the effect of supplemental oral THR on the plasma amino acid concentrations of 12 patients with hyperphenylalaninemia was investigated. Before starting the first treatment period of this cross-over study, the patients were randomly assigned to one of two groups supplemented either with approximately 50 mg THR/kg per day or with a similar amount of maltodextrin as placebo. After a feeding period of 8 weeks and a wash-out period of 8 weeks, the supplements were crossed over and the study continued for an additional 8 weeks. Blood was obtained at the start and the end of each supplementation period. RESULTS Dietary THR supplementation of approximately 50 mg/kg per day resulted in a significant decrease of plasma PHE levels ( P = 0.0234). There was a close positive correlation between plasma and urinary PHE concentrations ( P < 0.001) indicating that the lower plasma PHE levels in the THR supplemented patients were not caused by higher urinary excretion of PHE. CONCLUSIONS The data of the present study show that oral THR supplementation has a clear plasma-PHE-reducing effect but they do not allow any conclusion about the mechanisms responsible for the observed effect. Although it seems attractive on the basis of the present data to use THR supplementation in patients with hyperphenylalaninemia, the mechanism of the observed effect should be clarified before introduction of such a treatment in these patients.
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Affiliation(s)
- P Sanjurjo
- Department of Paediatrics Cruces Hospital, Baracaldo, Spain
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Potter SJ, Lu A, Wilcken B, Green K, Rasko JEJ. Hartnup disorder: polymorphisms identified in the neutral amino acid transporter SLC1A5. J Inherit Metab Dis 2002; 25:437-48. [PMID: 12555937 DOI: 10.1023/a:1021286714582] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Hartnup disorder is an inborn error of renal and gastrointestinal neutral amino acid transport. The cloning and functional characterization of the 'system B0' neutral amino acid transporter SLC1A5 led to it being proposed as a candidate gene for Hartnup disorder. Linkage analysis performed at 19q13.3, the chromosomal position of SLC1A5, was suggestive of an association with the Hartnup phenotype in some families. However, SLC1A5 was not linked to the Hartnup phenotype in other families. Linkage analysis also excluded an alternative candidate region at 11q13 implicated by a putative mouse model for Hartnup disorder. Sequencing of the coding region of SLC1A5 in Hartnup patients revealed two coding region polymorphisms. These mutations did not alter the predicted amino acid sequence of SLC1A5 and were considered unlikely to play a role in Hartnup disorder. There were no mutations in splice sites flanking each exon. Quantitative RT-PCR of SLC1A5 messenger RNA in affected and unaffected subjects did not support systemic differences in expression as an explanation for Hartnup disorder. In the six unrelated Hartnup pedigrees studied, examination of linkage at 19q13.3, polymorphisms in the coding sequence and quantitation of expression of SLC1A5 did not suffice to explain the defect in neutral amino acid transport.
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Affiliation(s)
- S J Potter
- Gene Therapy Research Unit, Centenary Institute of Cancer Medicine and Cell Biology, NSW, Australia
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Medina V, Lorenzo A, Díaz M. Electrogenic Na(+)-dependent L-alanine transport in the lizard duodenum. Involvement of systems A and ASC. Am J Physiol Regul Integr Comp Physiol 2001; 280:R612-22. [PMID: 11171637 DOI: 10.1152/ajpregu.2001.280.3.r612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
L-Alanine transport across the isolated duodenal mucosa of the lizard Gallotia galloti has been studied in Ussing chambers under short-circuit conditions. Net L-alanine fluxes, transepithelial potential difference (PD), and short-circuit current (Isc) showed concentration-dependent relationships. Na(+)-dependent L-alanine transport was substantially inhibited by the analog alpha-methyl aminoisobutyric acid (MeAIB). Likewise, MeAIB fluxes were completely inhibited by L-alanine, indicating the presence of system A for neutral amino acid transport. System A transport activity was electrogenic and exhibited hyperbolic relationships for net MeAIB fluxes, PD, and Isc, which displayed similar apparent K(m) values. Na(+)-dependent L-alanine transport, but not MeAIB transport, was partially inhibited by L-serine and L-cysteine, indicating the participation of system ASC. This transport activity represents the major pathway for L-alanine absorption and seemed to operate in an electroneutral mode with a negligible contribution to the L-alanine-induced electrogenicity. It is concluded from the present study that the active Na(+)-dependent L-alanine transport across the isolated duodenal mucosa of Gallotia galloti results from the independent activity of systems A and ASC for neutral amino acid transport.
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Affiliation(s)
- V Medina
- Laboratorio de Fisiología Animal, Departamento de Biología Animal, Universidad de La Laguna, 38206 Tenerife, Spain
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Munck LK, Grondahl ML, Thorboll JE, Skadhauge E, Munck BG. Transport of neutral, cationic and anionic amino acids by systems B, b(o,+), X(AG), and ASC in swine small intestine. Comp Biochem Physiol A Mol Integr Physiol 2000; 126:527-37. [PMID: 10989343 DOI: 10.1016/s1095-6433(00)00227-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Amino acid influx across the brush border membrane of the intact pig ileal epithelium was studied. It was examine whether in addition to system B, systems ASC and b(o,+) were involved in transport of bipolar amino acids. The kinetics of interactions between lysine and leucine demonstrates that system b(o,+) is present and accessible also to L-glutamine. D-aspartate (K(1/2) 0.3 mM) and L-glutamate (K(i) 0.5 mM) share a high affinity transporter with a maximum rate of 1.3 micromol cm(-2) h(-1), while only L-glutamate with a K(1/2) of 14.4 mM uses a low affinity transporter with a maximum rate of 2. 7 micromol cm(-2) h(-1), system ASC, against which serine has a K(i) of 1.6 mM. In the presence of 100 mM lysine, L-glutamine (A), leucine (B), and methionine (C) fulfilled the criteria of the ABC test for transport by one and the same transporter. However, serine inhibits not only transport of L-glutamate but also of glutamine (K(i) 0.5 mM), and L-glutamate inhibits part of the transport of glutamine. The test does, therefore, only indicate that the three bipolar amino acids have similar affinities for transport by systems B and ASC. Further study of the function of system B must be carried out under full inhibition by lysine and glutamate.
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Affiliation(s)
- L K Munck
- Department of Internal Medicine, Koge Hospital, DK-4600, Koge, Denmark.
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31
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A new assay for functional lectins: the brush border lectin agglutination assay (BBLAA). Anim Feed Sci Technol 1999. [DOI: 10.1016/s0377-8401(98)00214-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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32
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Fan MZ, Adeola O, McBurney MI, Cheeseman CI. Kinetic analysis of L-glutamine transport into porcine jejunal enterocyte brush-border membrane vesicles. Comp Biochem Physiol A Mol Integr Physiol 1998; 121:411-22. [PMID: 10048191 DOI: 10.1016/s1095-6433(98)10152-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
L-Glutamine transport into porcine jejunal enterocyte brush border membrane vesicles was studied. Uptake was mediated by a Na(+)-dependent and a Na(+)-independent pathway as well as by diffusion. The initial rates of glutamine uptake over a range of concentrations is both Na(+)-gradient and Na(+)-free conditions were analyzed and kinetic parameters were obtained. Na(+)-dependent glutamine transport had a K(m) of 0.77 +/- 0.16 mM and a Jmax of 70.7 +/- 5.8 pmol mg protein-1 s-1; Na(+)-independent glutamine transport had a K(m) of 3.55 +/- 0.78 mM and a Jmax of 55.1 +/- 6.6 pmol mg protein-1 s-1. The non-saturable component measured with HgCl2-poisoned brush border membrane vesicles in the Na(+)-free condition contained passive diffusion and non-specific membrane binding and was defined to be apparent glutamine diffusion and the glutamine permeability coefficient (Kdiff) was estimated to be Kdiff = 3.78 +/- 0.06 pmol 1 mg protein-1 mmol-1 s-1. Results of inhibition experiments showed that Na(+)-dependent glutamine uptake occurred primarily through the brush border system-B degree transporters, whereas Na(+)-independent glutamine uptake occurred via the system-L transporters. Furthermore, the kinetics of L-leucine and L-cysteine inhibition of L-glutamine uptake demonstrated that neutral amino acids sharing the same brush border transporters can effectively inhibit each other in their transport.
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Affiliation(s)
- M Z Fan
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
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33
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Soriano-García JF, Torras-Llort M, Ferrer R, Moreto M. Multiple pathways for L-methionine transport in brush-border membrane vesicles from chicken jejunum. J Physiol 1998; 509 ( Pt 2):527-39. [PMID: 9575301 PMCID: PMC2230979 DOI: 10.1111/j.1469-7793.1998.527bn.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
1. The intestinal transport of L-methionine has been investigated in brush-border membrane vesicles isolated from the jejunum of 6-week-old chickens. L-Methionine influx is mediated by passive diffusion and by Na+-dependent and Na+-independent carrier-mediated mechanisms. 2. In the absence of Na+, cis-inhibition experiments with neutral and cationic amino acids indicate that two transport components are involved in L-methionine influx: one sensitive to L-lysine and the other sensitive to 2-aminobicyclo[2.2. 1]heptane-2-carboxylic acid (BCH). The L-lysine-sensitive flux is strongly inhibited by L-phenylalanine and can be broken down into two pathways, one sensitive to N-ethylmaleimide (NEM) and the other to L-glutamine and L-cystine. 3. The kinetics of L-methionine influx in Na+-free conditions is described by a model involving three transport systems, here called a, b and c: systems a and b are able to interact with cationic amino acids but differ in their kinetic characteristics (system a: Km = 2.2 +/- 0.3 microM and Vmax = 0.13 +/- 0.005 pmol (mg protein)-1 (2 s)-1; system b: Km = 3.0 +/- 0.3 mM and Vmax = 465 +/- 4.3 pmol (mg protein)-1 (2 s)-1); system c is specific for neutral amino acids, has a Km of 1.29 +/- 0.08 mM and a Vmax of 229 +/- 5.0 pmol (mg protein)-1 (2 s)-1 and is sensitive to BCH inhibition. 4. The Na+-dependent component can be inhibited by BCH and L-phenylalanine but cannot interact either with cationic amino acids or with alpha-(methylamino)isobutyrate (MeAIB). 5. The kinetic analysis of L-methionine influx under a Na+ gradient confirms the activity of the above described transport systems a and b. System a is not affected by the presence of Na+ while system b shows a 3-fold decrease in the Michaelis constant and a 1.4-fold increase in Vmax. In the presence of Na+, the BCH-sensitive component can be subdivided into two pathways: one corresponds to system c and the other is Na+ dependent and has a Km of 0.64 +/- 0. 013 mM and a Vmax of 391 +/- 2.3 pmol (mg protein)-1 (2 s)-1. 6. It is concluded that L-methionine is transported in the chicken jejunum by four transport systems, one with functional characteristics similar to those of system bo, + (system a); a second (system b) similar to system y+, which we suggest naming y+m to account for its high Vmax for L-methionine transport in the absence of Na+; a third (system c) which is Na+ independent and has similar properties to system L; and a fourth showing Na+ dependence and tentatively identified with system B.
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Affiliation(s)
- J F Soriano-García
- Departament de Fisiologia-Divisio IV, Facultat de Farmàcia, Universitat de Barcelona, E-08028 Barcelona, Spain
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Torras-Llort M, Soriano-García JF, Ferrer R, Moretó M. Effect of a lysine-enriched diet on L-lysine transport by the brush-border membrane of the chicken jejunum. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:R69-75. [PMID: 9458900 DOI: 10.1152/ajpregu.1998.274.1.r69] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The influx of L-lysine into apical vesicles from the chicken jejunum occurs through two systems, one with low Michaelis constant (K(m)) and features of system b0,+ and the other with relatively high K(m) for L-lysine and with properties of system y+. In the present study the effect of a lysine-enriched diet (Lys, containing 68 g L-lysine/kg dietary protein, control animals 48 g/kg) on L-lysine uptake through both transport systems was investigated. Results show that 1) lysine enrichment had no effect on either body weight or the efficiency of food utilization. 2) In Lys-fed animals, the mediated L-lysine influx was best fitted to the two-system model with y+ and b0,+ activity. 3) In the presence of an Na+ gradient, total L-lysine uptake is significantly higher in Lys-fed animals than in control birds (about 40% increase). 4) Lys diet increases K(m)b0,+ 6-fold (KSCN gradient) and 12-fold (NaSCN gradient) and maximum velocity (Vmax) by 6- and 20-fold, respectively. The effects of Lys enrichment on the y(+)-like system are only observed on the Vmax and in the presence of a Na+ gradient (30% increase). 5) Na+ is involved in the activation of the transport process in the Lys-fed chickens, but there is no correlation between external Na+ concentration and L-lysine influx. In conclusion, both b(0,+)- and y(+)-like transport systems are upregulated by dietary lysine but with different kinetic profiles; the high-capacity y(+)-like carrier shows a Vmax increase without changes in K(m), whereas the low-capacity b(0,+)-like system shows an increase in Vmax as well as in the K(m).
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Affiliation(s)
- M Torras-Llort
- Unitat de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona, Spain
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Kekuda R, Prasad PD, Fei YJ, Torres-Zamorano V, Sinha S, Yang-Feng TL, Leibach FH, Ganapathy V. Cloning of the sodium-dependent, broad-scope, neutral amino acid transporter Bo from a human placental choriocarcinoma cell line. J Biol Chem 1996; 271:18657-61. [PMID: 8702519 DOI: 10.1074/jbc.271.31.18657] [Citation(s) in RCA: 199] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We have isolated a cDNA from a human placental choriocarcinoma cell cDNA library which, when expressed in HeLa cells, induces a Na+-dependent amino acid transport system with preference for zwitterionic amino acids. Anionic amino acids, cationic amino acids, imino acids, and N-methylated amino acids are excluded by this system. These characteristics are identical to those described for the amino acid transporter Bo. When expressed in Xenopus laevis oocytes that do not have detectable endogenous activity of the amino acid transporter Bo, the cloned transporter increases alanine transport in the oocytes severalfold and induces alanine-evoked inward currents in the presence of Na+. The cDNA codes for a polypeptide containing 541 amino acids with 10 putative transmembrane domains. Amino acid sequence homology predicts this transporter (hATBo) to be a member of a superfamily consisting of the glutamate transporters, the neutral amino acid transport system ASCT, and the insulin-activable neutral/anionic amino acid transporter. Chromosomal assignment studies with somatic cell hybrid analysis and fluorescent in situ hybridization have located the ATBo gene to human chromosome 19q13.3.
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Affiliation(s)
- R Kekuda
- Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30912, USA
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Mesonero JE, Rodriguez Yoldi MC, Rodriguez Yoldi MJ. Inhibition of L-threonine intestinal absorption in rabbits by cadmium. Biol Trace Elem Res 1996; 52:133-42. [PMID: 8773754 DOI: 10.1007/bf02789455] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cadmium compounds are widely spread in the environment. Animal exposure to cadmium compounds occurs mainly through foods or drinks contaminated by this metal. Cadmium has been shown to produce several negative effects on the gastrointestinal tract such as inhibition on sugars and amino acids absorption. The aim of the present work was to study the inhibitory characteristics of cadmium on L-threonine intestinal absorption in rabbits in order to understand about this malabsorption of nutrients. Our results show that L-threonine tissue accumulation as well as mucosal to serosal transepithelial fluxes are decreased in a dose-dependent manner in rabbit jejunum. Amino acid diffusion across the intestinal epithelium was not affected by cadmium. A noncompetitive mechanism and a partial reversion by dithioerythritol (thiol groups protector) is described for this inhibition.
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Affiliation(s)
- J E Mesonero
- Departamento de Farmacología y Fisiología, Facultad de Veterinaria, Zaragoza, Spain
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Munck LK, Grøndahl ML, Skadhauge E. beta-Amino acid transport in pig small intestine in vitro by a high-affinity, chloride-dependent carrier. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1238:49-56. [PMID: 7654750 DOI: 10.1016/0005-2736(95)00107-e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This study describes unidirectional influx of amino acids and D-glucose across the small intestinal brush-border membrane of fully weaned eight week old pigs. Influx is minimal in the duodenum and maximal in the distal and/or mid small intestine. Influx of beta-alanine, taurine and N-methyl-aminoisobutyric acid is chloride-dependent. The activation stoichiometry for taurine influx is 1.0 +/- 0.2 chloride/2.4 +/- 0.3 sodium/1 taurine. Influx of D-glucose, lysine, glycine and glutamate is chloride-independent. An ABC test demonstrates a common beta-amino acid carrier: (a) the apparent affinity constant K1/2Taurine is 44 +/- 13 microM (means +/- S.D.) and the inhibitory constant (KiTaurine) against beta-alanine influx is 41 +/- 5 microM (means +/- S.E.). (b) K1/2beta-alanine is 97 +/- 23 microM and Kibeta-alanine against taurine influx is 160 +/- 22 microM. (c) KiHypotaurine against taurine and beta-alanine influx is 43 +/- 4 (n = 7) and 22 +/- 5 microM (n = 7), respectively. In conclusion, a high affinity, low capacity, sodium- and chloride-dependent carrier of beta-amino acids is present in pig small intestine.
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Affiliation(s)
- L K Munck
- Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark
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Pan M, Stevens BR. Differentiation- and protein kinase C-dependent regulation of alanine transport via system B. J Biol Chem 1995; 270:3582-7. [PMID: 7876094 DOI: 10.1074/jbc.270.8.3582] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The regulation of sodium-dependent L-alanine transport is described for the first time in intestinal cells. Substrate analogue inhibition patterns and Dixon analyses indicated that uptake occurred via transport system B, an epithelial cell variant of systems B0,+ and ASC. System B served > 95% of the Na(+)-dependent alanine uptake in both undifferentiated (2 days postpassaging) and differentiated (> 9 days postpassaging) states of the human Caco-2 cultured intestinal cell line. (Methylamino)isobutyric acid-inhibitable system A transport accounted for < 5% of total alanine uptake. System B activity was greater in undifferentiated cells compared with the differentiated state, and activity at any differentiation state was stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA). The maximal stimulation, determined by TPA dose-response/exposure time data, was attributable to a change in cell transport capacity (Vmax), with Km unaffected. The Vmax of system B was greater in 2-day-old cells (2.79 +/- 0.21 nmol min-1 mg of protein-1; Km = 164 +/- 26 microM alanine), decreasing to Vmax = 0.51 +/- 0.03 nmol min-1 mg of protein-1 (Km = 159 +/- 14 microM) in 9-day-old cells. Regardless of differentiation status, the sodium-activation Hill coefficient was 1.06 +/- 0.10, and the alanine passive diffusion permeability coefficient was 0.53 +/- 0.08 microliter min-1 mg of protein-1. Phorbol ester up-regulated the Vmax of system B in 2-day-old cells to Vmax = 6.32 +/- 0.37 nmol min-1 mg of protein-1 (Km = 169 +/- 18 microM), and in 9-day-old cells to Vmax = 1.42 +/- 0.05 nmole min-1 mg of protein-1 (Km = 180 +/- 10 microM). Phorbol ester stimulation of transport occurred after at least 6 h of continual exposure, and was blocked by the protein kinase C inhibitors chelerythrine or photoactivated calphostin C. Protein synthesis inhibitors cycloheximide and actinomycin D each blocked the phorbol ester up-regulation of system B activity. It is concluded that Caco-2 cells regulate carrier-mediated sodium-dependent transport of L-alanine by changing the membrane capacity to transport alanine via system B and that this regulation involves de novo protein synthesis under the control of protein kinase C.
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Affiliation(s)
- M Pan
- Department of Physiology, College of Medicine, University of Florida, Gainesville 32610
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Nakanishi M, Kagawa Y, Narita Y, Hirata H. Purification and reconstitution of an intestinal Na(+)-dependent neutral L-alpha-amino acid transporter. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37111-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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