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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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Brown MN, Walters DC, Schmidt MA, Hill J, McConnell A, Jansen EEW, Salomons GS, Arning E, Bottiglieri T, Gibson KM, Roullet JB. Maternal glutamine supplementation in murine succinic semialdehyde dehydrogenase deficiency, a disorder of γ-aminobutyric acid metabolism. J Inherit Metab Dis 2019; 42:1030-1039. [PMID: 31032972 DOI: 10.1002/jimd.12107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 03/29/2019] [Accepted: 04/25/2019] [Indexed: 11/09/2022]
Abstract
Murine succinic semialdehyde dehydrogenase deficiency (SSADHD) manifests with high concentrations of γ-aminobutyric acid (GABA) and γ-hydroxybutyrate (GHB) and low glutamine in the brain. To understand the pathogenic contribution of central glutamine deficiency, we exposed aldh5a1-/- (SSADHD) mice and their genetic controls (aldh5a1+/+ ) to either a 4% (w/w) glutamine-containing diet or a glutamine-free diet from conception until postnatal day 30. Endpoints included brain, liver and blood amino acids, brain GHB, ataxia scores, and open field testing. Glutamine supplementation did not improve aldh5a1-/- brain glutamine deficiency nor brain GABA and GHB. It decreased brain glutamate but did not change the ratio of excitatory (glutamate) to inhibitory (GABA) neurotransmitters. In contrast, glutamine supplementation significantly increased brain arginine (30% for aldh5a1+/+ and 18% for aldh5a1-/- mice), and leucine (12% and 18%). Glutamine deficiency was confirmed in the liver. The test diet increased hepatic glutamate in both genotypes, decreased glutamine in aldh5a1+/+ but not in aldh5a1-/- , but had no effect on GABA. Dried bloodspot analyses showed significantly elevated GABA in mutants (approximately 800% above controls) and decreased glutamate (approximately 25%), but no glutamine difference with controls. Glutamine supplementation did not impact blood GABA but significantly increased glutamine and glutamate in both genotypes indicating systemic exposure to dietary glutamine. Ataxia and pronounced hyperactivity were observed in aldh5a1-/- mice but remained unchanged by the diet intervention. The study suggests that glutamine supplementation improves peripheral but not central glutamine deficiency in experimental SSADHD. Future studies are needed to fully understand the pathogenic role of brain glutamine deficiency in SSADHD.
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Affiliation(s)
- Madalyn N Brown
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington
| | - Dana C Walters
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington
| | - Michelle A Schmidt
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, Washington
| | | | | | - Erwin E W Jansen
- Department of Clinical Chemistry, Metabolic Unit, VU University Medical Center & Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - Gajja S Salomons
- Department of Clinical Chemistry, Metabolic Unit, VU University Medical Center & Amsterdam Neuroscience, Amsterdam, the Netherlands
| | - Erland Arning
- Baylor Scott and White Research Institute, Institute of Metabolic Disease, Dallas, Texas
| | - Teodoro Bottiglieri
- Baylor Scott and White Research Institute, Institute of Metabolic Disease, Dallas, Texas
| | - K Michael Gibson
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington
| | - Jean-Baptiste Roullet
- Department of Pharmacotherapy, College of Pharmacy and Pharmaceutical Sciences, Washington State University, Spokane, Washington
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Yang X, Wang G, Gong X, Huang C, Mao Q, Zeng L, Zheng P, Qin Y, Ye F, Lian B, Zhou C, Wang H, Zhou W, Xie P. Effects of chronic stress on intestinal amino acid pathways. Physiol Behav 2019; 204:199-209. [PMID: 30831184 DOI: 10.1016/j.physbeh.2019.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 02/22/2019] [Accepted: 03/01/2019] [Indexed: 01/23/2023]
Abstract
Major depressive disorder (MDD) is a debilitating mental disorder with a high prevalence and severe impacts on quality of life. However, the pathophysiological mechanisms underlying MDD remain poorly understood. Here, we used high-performance liquid chromatography with ultraviolet detection-based targeted metabolomics to identify amino acid changes in the small intestine, in a rat model of chronic unpredictable mild stress (CUMS). Pearson's correlation analysis was conducted to investigate the correlations between amino acid changes and behavioral outcomes. Western blot analysis was employed to verify intestinal amino acid transport function. Moreover, we performed an integrated analysis of related differential amino acids in the hippocampus, peripheral blood mononuclear cells (PBMCs), urine and cerebellum identified in our previous studies using the CUMS rat model to further our understanding of amino acid metabolism in depression. Decreased concentrations of glutamine and glycine and upregulation of aspartic acid were found in CUMS model rats. These changes were significantly correlated with depressive-like behaviors. Western blot analysis revealed that CUMS rats exhibited a reduction in the expression levels of amino acid transporters ASCT2 and B0AT1, as well as an increase in LAT1 expression. Impaired transport of glycine and glutamine into the small intestine may contribute to a central deficiency. The current findings suggest that the glycine and glutamine uptake systems may be potential therapeutic targets for depression. The integrated analysis strategy used in the current study may provide new insight into the cellular and molecular mechanisms underlying the gut-brain axis, and help to elucidate the pathophysiological changes in central and peripheral systems in depression.
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Affiliation(s)
- Xun Yang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China; Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Guowei Wang
- Ning Xia Medical University, Yin Chuan, Ning Xia 750004, China
| | - Xue Gong
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China; Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Cheng Huang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China; Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Qiang Mao
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; The Second Affiliated Hospital of Chongqing Medical University, Department of Pharmacy, Chongqing, China
| | - Li Zeng
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Nephrology, Second Affiliated Hospital, Chongqing Medical University, Chongqing 400010, China
| | - Peng Zheng
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China; Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Yinhua Qin
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Fei Ye
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China; Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Bin Lian
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Chanjuan Zhou
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, Yongchuan Hospital, Chongqing Medical University, Chongqing 402460, China
| | - Haiyang Wang
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Wei Zhou
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Peng Xie
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China; Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China.
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Jando J, Camargo SMR, Herzog B, Verrey F. Expression and regulation of the neutral amino acid transporter B0AT1 in rat small intestine. PLoS One 2017; 12:e0184845. [PMID: 28915252 PMCID: PMC5600382 DOI: 10.1371/journal.pone.0184845] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 08/24/2017] [Indexed: 01/11/2023] Open
Abstract
Absorption of neutral amino acids across the luminal membrane of intestinal enterocytes is mediated by the broad neutral amino acid transporter B0AT1 (SLC6A19). Its intestinal expression depends on co-expression of the membrane-anchored peptidase angiotensin converting enzyme 2 (ACE2) and is additionally enhanced by aminopeptidase N (CD13). We investigated in this study the expression of B0AT1 and its auxiliary peptidases as well as its transport function along the rat small intestine. Additionally, we tested its possible short- and long-term regulation by dietary proteins and amino acids. We showed by immunofluorescence that B0AT1, ACE2 and CD13 co-localize on the luminal membrane of small intestinal villi and by Western blotting that their protein expression increases in distal direction. Furthermore, we observed an elevated transport activity of the neutral amino acid L-isoleucine during the nocturnal active phase compared to the inactive one. Gastric emptying was delayed by intragastric application of an amino acid cocktail but we observed no acute dietary regulation of B0AT1 protein expression and L-isoleucine transport. Investigation of the chronic dietary regulation of B0AT1, ACE2 and CD13 by different diets revealed an increased B0AT1 protein expression under amino acid-supplemented diet in the proximal section but not in the distal one and for ACE2 protein expression a reverse localization of the effect. Dietary regulation for CD13 protein expression was not as distinct as for the two other proteins. Ring uptake experiments showed a tendency for increased L-isoleucine uptake under amino acid-supplemented diet and in vivo L-isoleucine absorption was more efficient under high protein and amino acid-supplemented diet. Additionally, plasma levels of branched-chain amino acids were elevated under high protein and amino acid diet. Taken together, our experiments did not reveal an acute amino acid-induced regulation of B0AT1 but revealed a chronic dietary adaptation mainly restricted to the proximal segment of the small intestine.
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Affiliation(s)
- Julia Jando
- Institute of Physiology, Zurich Center of Integrative Human Physiology and NCCR Kidney.CH, University of Zurich, Zurich, Switzerland
| | - Simone M. R. Camargo
- Institute of Physiology, Zurich Center of Integrative Human Physiology and NCCR Kidney.CH, University of Zurich, Zurich, Switzerland
| | - Brigitte Herzog
- Institute of Physiology, Zurich Center of Integrative Human Physiology and NCCR Kidney.CH, University of Zurich, Zurich, Switzerland
| | - François Verrey
- Institute of Physiology, Zurich Center of Integrative Human Physiology and NCCR Kidney.CH, University of Zurich, Zurich, Switzerland
- * E-mail:
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Holeček M. Branched-chain amino acid supplementation in treatment of liver cirrhosis: Updated views on how to attenuate their harmful effects on cataplerosis and ammonia formation. Nutrition 2017; 41:80-85. [PMID: 28760433 DOI: 10.1016/j.nut.2017.04.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/15/2017] [Accepted: 04/05/2017] [Indexed: 12/13/2022]
Abstract
Branched-chain amino acid (BCAA; valine, leucine, and isoleucine) supplementation is common for patients with liver cirrhosis due to decreased levels of BCAA in the blood plasma of these patients, which plays a role in pathogenesis of hepatic encephalopathy and cachexia. The unique pharmacologic properties of BCAA also are a factor for use as supplementation in this population. In the present article, BCAA is shown to provide nitrogen to alpha-ketoglutarate (α-KG) for synthesis of glutamate, which is a substrate for ammonia detoxification to glutamine (GLN) in the brain and muscles. The article also demonstrates that the favorable effects of BCAA supplementation might be associated with three adverse effects: draining of α-KG from tricarboxylic acid cycle (cataplerosis), increased GLN content and altered glutamatergic neurotransmission in the brain, and activated GLN catabolism to ammonia in the gut and kidneys. Cataplerosis of α-KG can be attenuated by dimethyl-α-ketoglutarate, l-ornithine-l-aspartate, and ornithine salt of α-KG. The pros and cons of GLN elimination from the body using phenylbutyrate (phenylacetate), which may impair liver regeneration and decrease BCAA levels, should be examined. The therapeutic potential of BCAA might be enhanced also by optimizing its supplementation protocol. It is concluded that the search for strategies attenuating adverse and increasing positive effects of the BCAA is needed to include the BCAA among standard medications for patients with cirrhosis of the liver.
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Affiliation(s)
- Milan Holeček
- Department of Physiology, Charles University, Faculty of Medicine in Hradec Kralove, Czech Republic.
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Chen XM, Guo GL, Sun L, Yang QS, Wang GQ, Qin GX, Zhang DM. Effects of Ala-Gln feeding strategies on growth, metabolism, and crowding stress resistance of juvenile Cyprinus carpio var. Jian. FISH & SHELLFISH IMMUNOLOGY 2016; 51:365-372. [PMID: 26945938 DOI: 10.1016/j.fsi.2016.02.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 02/21/2016] [Accepted: 02/29/2016] [Indexed: 06/05/2023]
Abstract
The present study was conducted to evaluate the effects of different L-alanyl-l-glutamine (Ala-Gln) feeding strategies on the growth performance, metabolism and crowding stress resistance related parameters in juvenile Jian carp (Cyprinus carpio var. Jian) under crowded condition (80 g/L). Juvenile Jian carp (initial weight 26.1 ± 0.6 g) were distributed into five groups which fed with graded concentrations (0% or 1.0%) of Ala-Gln for eight weeks. Control group (I, 0/0) fed with control diet (0% Ala-Gln) throughout the feeding trial. The other four groups employed different control and experimental diet feeding strategies ranging from two weeks control diet fed and two weeks experimental diet (1% Ala-Gln) fed (II, 0/2) to eight weeks experimental diet fed (V, 4/4). Results revealed that Mean weight gain (MEG) under all different feeding strategies of Ala-Gln were significantly higher than that of the control group (p < 0.05), and MEG of group II (201.90%) was even higher than that of group IV (184.70%). Liver glycogen and blood total protein of groups II, III and V were significantly higher than that in groups I and IV (p < 0.05). The highest level of serum thyroxine (10.07 ng/ml), insulin-like growth factor-I (52.40 ng/ml) and insulin (9.73 μ IU/mL) were observed in group V. However, diet supplemented with Ala-Gln did not affect the levels of serum glucose, cortisol and catecholamine in fish. The mRNA expression of GR1a, GR1b and GR2 were also significantly changed in Ala-Gln supplementation groups compared with control group (p < 0.05). After fish intraperitoneally injected with virulent Aeromonas hydrophila, the fish survival rates were significantly increased in all Ala-Gln supplementation groups compared with control group (p < 0.05). Results from the present experiment showed the importance of dietary supplementation of Ala-Gln in benefaction of the growth performance, metabolism and crowding stress resistance in Jian carp breeding. The optimal feeding strategy was alternatively fed with control diet and then experimental diet at an interval of two weeks for juvenile Jian carp under crowded condition.
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Affiliation(s)
- Xiu-Mei Chen
- College of Animal Science and Technology, Jilin Agricultural University, Changchun 130118, China
| | - Gui-Liang Guo
- Testing Center of Quality and Safety in Aquatic Product, 777 CaiYu Road, Changchun, Jilin, China
| | - Li Sun
- Testing Center of Quality and Safety in Aquatic Product, 777 CaiYu Road, Changchun, Jilin, China
| | - Qiu-Shi Yang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun 130118, China
| | - Gui-Qin Wang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun 130118, China.
| | - Gui-Xin Qin
- College of Animal Science and Technology, Jilin Agricultural University, Changchun 130118, China
| | - Dong-Ming Zhang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun 130118, China
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Dietary glutamine supplementation effects on amino acid metabolism, intestinal nutrient absorption capacity and antioxidant response of gilthead sea bream (Sparus aurata) juveniles. Comp Biochem Physiol A Mol Integr Physiol 2015; 191:9-17. [PMID: 26424608 DOI: 10.1016/j.cbpa.2015.09.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 09/17/2015] [Accepted: 09/18/2015] [Indexed: 01/04/2023]
Abstract
A study was undertaken to evaluate dietary glutamine supplementation effects on gilthead sea bream performance, intestinal nutrient absorption capacity, hepatic and intestinal glutamine metabolism and oxidative status. For that purpose gilthead sea bream juveniles (mean weight 13.0g) were fed four isolipidic (18% lipid) and isonitrogenous (43% protein) diets supplemented with 0, 0.5, 1 and 2% glutamine for 6weeks. Fish performance, body composition and intestinal nutrient absorption capacity were not affected by dietary glutamine levels. Hepatic and intestinal glutaminase (GlNase), glutamine synthetase (GSase), alanine aminotransferase, aspartate aminotransferase and glutamate dehydrogenase activities were also unaffected by dietary glutamine supplementation. In the intestine GlNase activity was higher and GSase/GlNase ratio was two-fold lower than in the liver, suggesting a higher use of glutamine for energy production by the intestine than by the liver. The liver showed higher catalase and glucose-6-phosphate dehydrogenase activities, while the intestine presented higher glutathione peroxidase and glutathione reductase activities and oxidised glutathione content, which seems to reveal a higher glutathione dependency of the intestinal antioxidant response. Total and reduced glutathione contents in liver and intestine and superoxide dismutase activity in the intestine were enhanced by dietary glutamine, though lipid peroxidation values were not affected. Overall, differences between liver and intestine glutamine metabolism and antioxidant response were identified and the potential of dietary glutamine supplementation to gilthead sea bream's antioxidant response was elucidated.
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Holecek M. Ammonia and amino acid profiles in liver cirrhosis: Effects of variables leading to hepatic encephalopathy. Nutrition 2015; 31:14-20. [DOI: 10.1016/j.nut.2014.03.016] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 03/20/2014] [Accepted: 03/23/2014] [Indexed: 02/07/2023]
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Holecek M. Evidence of a vicious cycle in glutamine synthesis and breakdown in pathogenesis of hepatic encephalopathy-therapeutic perspectives. Metab Brain Dis 2014; 29:9-17. [PMID: 23996300 PMCID: PMC3930847 DOI: 10.1007/s11011-013-9428-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 08/13/2013] [Indexed: 12/21/2022]
Abstract
There is substantial clinical and experimental evidence that ammonia is a major factor in the pathogenesis of hepatic encephalopathy. In the article is demonstrated that in hepatocellular dysfunction, ammonia detoxification to glutamine (GLN) in skeletal muscle, brain, and likely the lungs, is activated. In addition to ammonia detoxification, enhanced GLN production may exert beneficial effects on the immune system and gut barrier function. However, enhanced GLN synthesis may exert adverse effects in the brain (swelling of astrocytes or altered neurotransmission) and stimulate catabolism of branched-chain amino acids (BCAA; valine, leucine, and isoleucine) in skeletal muscle. Furthermore, the majority of GLN produced is released to the blood and catabolized in enterocytes and the kidneys to ammonia, which due to liver injury escapes detoxification to urea and appears in peripheral blood. As only one molecule of ammonia is detoxified in GLN synthesis whereas two molecules may appear in GLN breakdown, these events can be seen as a vicious cycle in which enhanced ammonia concentration activates synthesis of GLN leading to its subsequent catabolism and increase in ammonia levels in the blood. These alterations may explain why therapies targeted to intestinal bacteria have only a limited effect on ammonia levels in patients with liver failure and indicate the needs of new therapeutic strategies focused on GLN metabolism. It is demonstrated that each of the various treatment options targeting only one the of the ammonia-lowering mechanisms that affect GLN metabolism, such as enhancing GLN synthesis (BCAA), suppressing ammonia production from GLN breakdown (glutaminase inhibitors and alpha-ketoglutarate), and promoting GLN elimination (phenylbutyrate) exerts substantial adverse effects that can be avoided if their combination is tailored to the specific needs of each patient.
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Affiliation(s)
- Milan Holecek
- Department of Physiology, Faculty of Medicine in Hradec Kralove, Charles University in Prague, Simkova 870, 500 38, Hradec Kralove, Czech Republic,
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Arthur S, Saha P, Sundaram S, Kekuda R, Sundaram U. Regulation of sodium-glutamine cotransport in villus and crypt cells by glucocorticoids during chronic enteritis. Inflamm Bowel Dis 2012; 18:2149-57. [PMID: 22508450 DOI: 10.1002/ibd.22924] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 01/30/2012] [Indexed: 12/09/2022]
Abstract
BACKGROUND Assimilation of the preferred nutrient of enterocytes is mediated primarily by sodium (Na)-dependent cotransport (NGct) in the intestine. The predominant NGcT in villus cells, B0AT1, is inhibited secondary to a decrease in cotransporter numbers during chronic intestinal inflammation. In contrast, NGcT mediated by SN2 in crypt cells is stimulated secondary to increased affinity of the cotransporter for glutamine during chronic ileitis. Glucocorticoid is a mainstay of treatment for inflammatory bowel disease. However, its effect on NGcT is not known. METHODS The inhibition of B0AT1 in villus cells during chronic intestinal inflammation was reversed back to normal by methylprednisolone (MP). This was secondary to the restoration of the cotransporter numbers in the brush border membrane rather than an alteration in the affinity. The stimulation of NGcT in crypt cells during chronic ileitis was also restored back to its normal levels by MP treatment. This reversal was secondary to the restoration of the altered affinity of the cotransporter SN2 for glutamine. RESULTS Kinetic studies and western blot analysis were consistent with functional studies for both cotransporters. Thus, glucocorticoids restore two uniquely altered Na-glutamine cotransporters, B0AT1 in villus and SN2 in crypt cells during chronic enteritis. CONCLUSIONS These data indicate that glucocorticoids function as an upstream broad spectrum immune modulator in the chronically inflamed intestine.
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Affiliation(s)
- Subha Arthur
- Section of Digestive Diseases and Clinical and Translational Science Institute West Virginia University Health Sciences Center, Morgantown, West Virginia 26506, USA
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Affiliation(s)
- Milan Holecek
- Charles University in Prague, Hradec Kralove, Czech Republic
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12
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13
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Maintenance of villous height and crypt depth in piglets by providing continuous nutrition after weaning. ACTA ACUST UNITED AC 2010. [DOI: 10.1017/s1357729800014417] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractThirty-two piglets weaned at 28 days of age were used to test the hypothesis that maintenance of nutrition after weaning would prevent the normal decline in villous height and increase in crypt depth and hence preserve the structure and function of the small intestine. Piglets were allocated to one of four treatments at weaning: (1) control group killed at weaning; (2) piglets offered a dry starter diet ad libitum; (3) piglets offered ewes' fresh milk; and (4) piglets offered ewes' fresh milk plus 20 g t-glutamine per I. Piglets in treatments (3) and (4) were offered ewes' fresh milk every 2 h in a feeding schedule that increased from 1·2 I per piglet on the 1st day after weaning to 2·4 I on days 4 and 5. On the 5th day all piglets were killed and samples of small intestine were taken for histological and biochemical examination. Feeding ewes' milk or ewes' milk plus 20 g L-glutamine per I maintained (P > 0·05) villous height and crypt depth compared with piglets killed at weaning. In contrast, piglets given a dry starter diet had shorter villi (P < 0·001), deeper crypts (P < 0·001), and proportionately 0·21 to 0·28 less protein (P > 0·05) in their intestinal mucosa. Piglets given the starter diet proportionately grew from 0·49 to 0·62 more slowly (P < 0·01), ate the same amount of dry matter (DM; P > 0·05), but consumed proportionately 0·30 less energy (P < 0·001) than their counterparts given the milk diets. No treatment differences in the specific activity of lactase and sucrase were observed (P > 0·05). Significant correlations existed between voluntary food intake and villous height at the proximal jejunum for piglets given the starter diet and ewes' milk (P < 0·05 and P = 0·073, respectively). In turn, villous height was significantly correlated (r = 0·78 to 0·87, P < 0·05) with the rate of body-weight gain after weaning in these two groups. For piglets offered ewes' milk plus glutamine, an increase in DM intake was associated only with increases in crypt depth (P < 0·01). These data show that the structure and function of the small intestine can be preserved when a milk diet is given after weaning, and suggest an association between food intake and villous height in determining post-weaning weight gain.
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Sheridan RL, Prelack K, Yu YM, Lydon M, Petras L, Young VR, Tompkins RG. Short-term enteral glutamine does not enhance protein accretion in burned children: a stable isotope study. Surgery 2004; 135:671-8. [PMID: 15179374 DOI: 10.1016/j.surg.2003.11.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
OBJECTIVE Glutamine is a nonessential amino acid that, in recent years, has been found to play important roles in several metabolic and immunologic processes. It has been theorized that, in a stressed state, it may become "conditionally essential" because the patient's ability to manufacture glutamine may not be adequate to meet their needs under this condition. We chose to evaluate the ability of 48 hours of enteral glutamine to enhance immediate nitrogen accretion in stressed pediatric burn patients. METHODS Nine children with serious burns who were tolerating tube feedings were enrolled in a human studies committee-approved protocol in which they received 48 hours of enteral feedings with glutamine replacing 20% of essential and nonessential amino acids and 48 hours of isonitrogenous, isocaloric standard enteral feedings. This interval was chosen to help ensure that the study periods were comparable from a metabolic perspective. At the end of each period, protein kinetics were determined by a primed constant infusion of L-[1-(13)C] leucine tracer. The order of the studies was randomized. Seven children completed both phases of the study. Results were compared by paired t test and are presented as mean +/- standard error of the mean. RESULTS During the glutamine feeding period, the leucine flux and leucine oxidation rate were significantly lower than those in the conventional feeding period. This reflects a reduction in total leucine intake from 80 +/- 11 to 62 +/- 10 micromol/kg per hour. However, there was no significant difference in the net balance of leucine accretion into proteins between these 2 dietary periods, which indicated that enriched glutamine feeding for 48 hours did not result in an immediate whole body protein gain in this group of pediatric patients. In addition, plasma glutamine concentration showed a moderate increase after 48 hours of supplementation but did not reach significance. CONCLUSION Rapid protein accretion does not occur with short-term enteral glutamine supplementation. Several days of glutamine supplementation may be required to restore plasma glutamine levels and stimulate protein synthesis.
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Affiliation(s)
- Robert L Sheridan
- Department of Surgery, Shriners Burns Hospital, Boston, MA 02114, USA
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15
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Abstract
The objective of this research is to explore the amino acid carrier-mediated pathway for nasal uptake of tyrosine-linked model compounds. These molecules were synthesized by ether linkage between the aromatic hydroxyl group of L-tyrosine and the terminal hydroxyl group of model compounds. An enzymatically stable linkage was utilized to link the model compounds to L-tyrosine so that the loss of the compound from perfusate signals absorption only without complication from metabolism. The rat in situ nasal perfusion technique was utilized in this investigation. The analyte concentrations remaining in the nasal perfusates were quantitated by a reversed-phase high-performance liquid chromatography. All L-tyrosine-linked model compounds were absorbed across the nasal mucosa (15-50% absorbed), and the extent of nasal absorption was concentration dependent. The apparent first-order rate constants of intact conjugate loss from the nasal perfusate were calculated. The Michaelis-Menten kinetic model was applied to fit the perfusion data. The Michaelis constant, K(m), and maximum or saturation rate of compound loss from the perfusate, V(max), were calculated from Lineweaver-Burk plots [e.g., K(m) and V(max) are 0.57 mM and 0.00515 micromol/min, respectively, for one of the model compounds, O-(4-carboxyphenylmethyl)-L-tyrosine]. The absorption characteristics of all these model compounds exhibited saturable kinetics, whereas their parent compounds, possessing different octanol-water partition coefficients, showed either no absorption or transport by passive diffusion. Nasal uptake of L-tyrosine conjugates was inhibited by L-tyrosine. The results from this study indicate that nasal absorption of L-tyrosine-linked compounds is probably through an amino acid transport system. Exploitation of the amino acid transport pathway may be utilized to improve nasal absorption of poorly permeable drugs.
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Affiliation(s)
- C Yang
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri, 5005 Rockhill Road, Kansas City, Missouri 64110, USA
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16
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Chambon-Savanovitch C, Farges MC, Raul F, Blachier F, Davot P, Cynober L, Vasson MP. Can a glutamate-enriched diet counteract glutamine depletion in endotoxemic rats? J Nutr Biochem 1999; 10:331-7. [PMID: 15539307 DOI: 10.1016/s0955-2863(99)00005-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/1998] [Accepted: 01/26/1999] [Indexed: 11/29/2022]
Abstract
The study evaluated whether a glutamate-enriched diet would restore glutamine tissue pools and maintain tissue trophicity in endotoxemic rats. For this purpose, young male Sprague-Dawley rats received an intraperitoneal injection of lipopolysaccharide (LPS) from Escherichia coli at 3 mg/kg body weight. After 24 hours of food deprivation, the rats were enterally refed for 48 hours using Osmolite enriched with glutamate at 4 g/kg/d (LPS-Glu group, n = 7) or glycine isonitrogenous to glutamate (LPS-Gly group, n = 7). A control group (healthy group, n = 7) had free access to a standard rodent diet. Tissue weights and protein contents were significantly lower in both LPS-treated groups than in the healthy group. No plasma or tissue accumulation of glutamate was observed except in the liver. Glutamine concentrations were increased in the jejunum, liver, and plasma in the LPS-Glu group versus the other two groups (P < 0.05). Conversely, they were depleted in muscles of the endotoxemic groups versus the healthy group (P < 0.05). Villus height was significantly greater in the LPS-Glu group than in the LPS-Gly group in the jejunum (P < 0.05), but not in the ileum. In conclusion, a glutamate-enriched diet administered enterally to endotoxemic rats can counteract glutamine depletion in the splanchnic area but not in muscles. In addition, glutamate displayed a trophic effect restricted to the jejunum.
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Affiliation(s)
- C Chambon-Savanovitch
- Biochemistry, Molecular Biology and Nutrition Laboratory, EA 1742, Pharmacy School and Research Center for Human Nutrition, Clermont-Ferrand, France
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Pluske JR, Hampson DJ, Williams IH. Factors influencing the structure and function of the small intestine in the weaned pig: a review. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0301-6226(97)00057-2] [Citation(s) in RCA: 421] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Horvath K, Jami M, Hill ID, Papadimitriou JC, Magder LS, Chanasongcram S. Isocaloric glutamine-free diet and the morphology and function of rat small intestine. JPEN J Parenter Enteral Nutr 1996; 20:128-34. [PMID: 8676531 DOI: 10.1177/0148607196020002128] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND The importance of L-glutamine as metabolic fuel for enterocytes and its role in prevention of mucosal atrophy during total parenteral nutrition is well documented. No data are available to date that document whether a glutamine-free complete enteral diet, requiring full energy expenditure for hydrolysis and absorption, is associated with changes in the morphology and function of the small intestine. Our aim was to examine the effect of such a diet during a 4-week period on the morphology and function of the small intestine of rats. METHODS Three isocaloric solid rat food, containing 0%, 4%, and 8% of glutamate, respectively, were fed to three groups of rats. On the 7th and 28th days the morphology of the jejunum, the subcellular structure of enterocytes on transmission electron microscopy, enzyme activities, blood, and muscle glutamine were examined and compared in the three groups. RESULTS The rats on the glutamine-free diet had significantly lower mucosal wet weight, protein and DNA content, and number of intraepithelial lymphocytes on the 7th day, whereas the number of mitoses in the Lieberkuhn's crypts was significantly less on the 28th day. The height of the enterocytes and villi was 20% higher on average in the glutamine-free group. Electron microscopy revealed either early (swelling of cristae) or terminal (swelling of matrix) mitochondrial degenerative changes, homogenization of apical cytoplasm, and degeneration and fragmentation of microvilli with loss of their rootlets. The Na+, K(+)-ATPase activity was markedly decreased in the glutamine-free group compared with that of the other groups, most likely because of a diminished energy supply. Among brush border membrane enzymes, lactase activity decreased markedly (p < .05) in the first week. The glutamine-free diet resulted in an increase of the lung glutamine synthetase activity and decrease in muscle glutamine content by the 28th day of the diet. CONCLUSIONS Our study shows for the first time that a complete enteral diet, deficient only in glutamine, is associated with significant early morphologic and functional changes in the small intestine. The precise effect on intracellular events and the time of onset of these changes needs to be clarified in the future.
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Affiliation(s)
- K Horvath
- Department of Pediatrics, University of Maryland, Baltimore 21201-1595, USA
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19
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Pan M, Stevens BR. Protein kinase C-dependent regulation of L-arginine transport activity in Caco-2 intestinal cells. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1239:27-32. [PMID: 7548140 DOI: 10.1016/0005-2736(95)00136-q] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The regulation of plasma membrane L-arginine transport activity was investigated in differentiated and undifferentiated states of the human intestinal cell line, Caco-2. The sodium-independent, leucine-insensitive uptake of L-arginine measured in this study has been assigned by us previously to system y+ in Caco-2 cells. Treatment of cells with serum-free media containing epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha), or the protein kinase C (PKC) activator 12-O-tetradecanoylphorbol 13-acetate (TPA), stimulated system y+ arginine transport activity in Caco-2 cells. Transport upregulation by these growth factors or by TPA was blocked by cycloheximide or the PKC inhibitor chelerythrine. Arginine uptake was diminished during the course of differentiation, attributable to a reduction in the transport system y+ capacity (Vmax) with no change in apparent affinity (Km). TPA stimulated arginine uptake required at least 3 h of continual exposure, and increased the membrane's transport capacity (Vmax) in both undifferentiated and differentiated cells. TPA elevated the diminished transport Vmax of differentiated cells TPA to the elevated Vmax value associated with undifferentiated cells. We conclude that upregulation of arginine transport is part of a pleiotropic response to EGF/TGF alpha, and that this involves PKC and de novo synthesis of polypeptides associated with system y+ transport activity.
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Affiliation(s)
- M Pan
- Department of Physiology, College of Medicine, University of Florida, Gainesville 32610-0274, USA
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Mailliard ME, Stevens BR, Mann GE. Amino acid transport by small intestinal, hepatic, and pancreatic epithelia. Gastroenterology 1995; 108:888-910. [PMID: 7875494 DOI: 10.1016/0016-5085(95)90466-2] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- M E Mailliard
- Department of Medicine, College of Medicine, University of Florida, Gainesville
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21
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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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22
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Sanchís D, Alemany M, Remesar X. L-alanine transport in small intestine brush-border membrane vesicles of obese rats. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1192:159-66. [PMID: 8018696 DOI: 10.1016/0005-2736(94)90114-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Membrane vesicles from the small intestine brush border were obtained and used to determine the possible effects of genetic or nutritional obesity on L-alanine uptake. Membrane vesicles from Zucker fa/fa obese rats and cafeteria diet-fed Zucker Fa/? rats showed the same characteristics as those of standard diet-fed lean animals. All preparations showed sodium-dependent transport as the main pathway for L-alanine uptake within the substrate concentration range tested. The apparent substrate affinity constant (Km) values and the pattern of inhibition of Na(+)-dependent L-alanine uptake by other amino acids (L-leucine and L-glutamine), suggests that system B involved in the transport of dipolar amino acids (formerly named Neutral Brush Border System) participates in the Na(+)-dependent transport of L-alanine. The affinity constant (Km) for L-alanine was essentially the same for all the groups studied (in the range of 10 mM). However, there was a higher (P < 0.05) maximal capacity (Vmax) in preparations from diet-induced obese animals (cafeteria diet) than that of genetically obese rats. These results indicate that either nutritional or genetic obesity may modify the capacity but not the affinity of transport systems for L-alanine uptake in the brush border of rat small intestine.
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Affiliation(s)
- D Sanchís
- Departament de Bioquímica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Spain
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23
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Inoue Y, Copeland EM, Souba WW. Growth hormone enhances amino acid uptake by the human small intestine. Ann Surg 1994; 219:715-22; discussion 722-4. [PMID: 8203982 PMCID: PMC1243230 DOI: 10.1097/00000658-199406000-00016] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
OBJECTIVE The effects of growth hormone (GH) on the luminal transport of amino acids and glucose by the human small intestine were investigated. SUMMARY BACKGROUND DATA The anabolic effect of growth hormone administration is associated with nitrogen retention and an increase muscle strength, but the impact of growth hormone on nutrient uptake from the gut lumen has not been examined. METHODS Twelve healthy patients received a daily subcutaneous dose of low-dose GH (0.1 mg/kg), high-dose GH (0.2 mg/kg), or no treatment (controls) for 3 days before surgery. At operation, ileum (8 patients) or jejunum (4 patients) was resected, and brush border membrane vesicles (BBMVs) were prepared by differential centrifugation. Vesicle purity was confirmed by a 16-fold enrichment of marker enzymes. The carrier-mediated transport of glutamine (System B), leucine (System L), alanine (System B), arginine (System y+), MeAIB (methyl alpha-aminoisobutyric acid [System A]), and glucose (Na(+)-dependent glucose transporter) by BBMVs was measured by a rapid mixing/filtration technique. RESULTS Treatment with low-dose GH resulted in a statistically insignificant increase in amino acid transport rates in jejunal and ileal BBMVs. High-dose GH resulted in a generalized 20%-to 70%-stimulation of amino acid transport, whereas glucose transport was not affected. The effects of GH were similar in ileum and jejunum. Kinetic analysis of the transport of glutamine (the most abundant amino acid in the body and the principal gut fuel) and the essential amino acid leucine revealed that the increase in transport was caused by a 50% increase in carrier Vmax, consistent with an increase in the number of functional carriers in the brush border membrane. Pooled analysis of transport velocities demonstrated that total rates of amino acid uptake from the gut lumen were increased significantly by 35% in GH-treated patients. CONCLUSIONS The ability of GH to enhance amino acid uptake from the gut lumen provides energy and precursors for protein synthesis in the gut mucosa, as well as additional substrate for anabolism in other organs.
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Affiliation(s)
- Y Inoue
- Department of Surgery, University of Florida College of Medicine, Gainesville
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24
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Welbourne TC, Joshi S. Enteral glutamine spares endogenous glutamine in chronic acidosis. JPEN J Parenter Enteral Nutr 1994; 18:243-7. [PMID: 7914940 DOI: 10.1177/0148607194018003243] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Metabolic acidosis associated with the catabolic state mobilizes muscle nitrogen and releases it into blood as glutamine (GLN) targeted for renal consumption and base generation. Because GLN removed by the kidneys during acidosis is a major drain on the GLN available to other sites, subsequent deprivation may lead to impaired organ function. Conversely, GLN supplementation may spare endogenous supplies and restore organ function. To test this, Sprague-Dawley rats weighing between 250 and 350 g were pair-fed elemental diets supplemented with GLN 4.9 g/L (GLN-ED) or an equivalent mixture of neutral amino acids substituted for GLN (ED). Acid loading was effected by adding hydrochloric acid to the liquid diet (110 mmol/L). Animals were studied in metabolic cages for five consecutive 24-hour urine collection periods and then anesthetized for short-term studies of interorgan fluxes and tissue GLN content. Acidosis effected an increase in ammonium nitrogen excretion (fivefold) and a reciprocal decrease (24%) in urea nitrogen excretion. Enteral GLN had no effect on the acidosis-effected ammonium (2170 +/- 71 vs 2059 +/- 361 mumol/100 g, ED vs GLN-ED, respectively) or urea excretion (5522 +/- 95 vs 5915 +/- 984 mumol/100 g, ED vs GLN-ED, respectively). Although arterial blood GLN was not increased in the GLN-ED group (531 +/- 58 vs 438 +/- 51 nmol/mL, p = .10), both liver and muscle GLN were elevated (11,650 +/- 1137 nmol/g vs 7063 +/- 578 and 5503 +/- 489 and 4742 +/- 333 nmol/g, respectively, each p < .05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Souba WW, Pacitti AJ. How amino acids get into cells: mechanisms, models, menus, and mediators. JPEN J Parenter Enteral Nutr 1992; 16:569-78. [PMID: 1494216 DOI: 10.1177/0148607192016006569] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The bloodstream provides a readily available pool of amino acids, which can be taken up by all cells of the body to support the myriad of biochemical reactions that are essential for life. The transport of amino acids into the cytoplasm occurs via functionally and biochemically distinct amino acid transport systems that have been defined on the basis of their amino acid selectivities and physico-chemical properties. Each system presumably relates to a discrete putative membrane-bound transporter protein that resides within the cell membrane and functions to translocate the amino acid from the extracellular environment into the cytoplasm. Many of these transporters require sodium for maximal activity. The sodium-dependent model presented is consistent with "preferred random" kinetics, with sodium binding preferentially before the amino acid. The transporter acts as an enzyme that catalyzes the movement of its bound amino acid (and sodium) into the cell. In this review, the authors provide a conceptual view of the mechanism of carrier-mediated amino acid transport as well as an overview of the various models that can be used in the laboratory to study this process. In addition, the known agencies that accomplish transport and their regulation by nutrition, hormones, and other mediators of critical illness are discussed.
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Affiliation(s)
- W W Souba
- Department of Surgery, University of Florida College of Medicine, Gainesville
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27
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Souba WW, Pan M, Stevens BR. Kinetics of the sodium-dependent glutamine transporter in human intestinal cell confluent monolayers. Biochem Biophys Res Commun 1992; 188:746-53. [PMID: 1445319 DOI: 10.1016/0006-291x(92)91119-b] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The intestinal epithelium metabolism of glutamine plays a critical role in inter-organ nitrogen flow. Although it is known that glutamine is the primary oxidative energy source and nucleotide precursor in intestinal cells, the luminal uptake of glutamine by the apical surface of enterocytes is poorly understood. In this study we have uncovered the sodium-dependent transporter system responsible for L-glutamine uptake by the apical membrane of a human intestinal epithelial cell line. The sodium-dependent Michaelis constant (Km) = 247 +/- 45 microM glutamine, and Jmax = 4.44 +/- 0.65 x 10(-9) mole min-1(mg protein)-1 (37 degrees C). Glutamine shares the transporter with alanine, as demonstrated by unlabeled glutamine inhibition of [3H]alanine uptake kinetics with a purely competitive-type inhibition pattern, and glutamine inhibition Ki = 205 +/- 18 microM by Dixon analysis. The inhibition pattern for a series of amino acid analogs indicated that this intestinal apical membrane sodium-dependent transporter for glutamine is distinct from any other transport system found in membranes of non-intestinal cells.
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Affiliation(s)
- W W Souba
- Department of Surgery, College of Medicine, University of Florida, Gainesville 32610-0274
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28
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Rodríguez-Martín A, Bel N, Remesar X. Membrane vesicles from brown adipose tissue: a tool for the study of amino acid transport. The case of L-alanine. Biosci Rep 1992; 12:115-22. [PMID: 1330053 DOI: 10.1007/bf02351216] [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: 12/26/2022] Open
Abstract
A density gradient method is used to isolate membrane vesicles from brown adipose tissue. These respond to changes in osmolarity and show the classical overshoot pattern when L-alanine uptake is assayed. Transport is shown to be effected by two components: a linear (Kd = 0.498 min-1) and Na(+)-dependent saturable component (Km = 2.3 mM) and a Vmax = 19.9 pmol/micrograms protein.min). This pattern is similar to that shown by cells isolated from brown adipose tissue.
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Dudrick PS, Salloum RM, Copeland EM, Souba WW. The early response of the jejunal brush border glutamine transporter to endotoxemia. J Surg Res 1992; 52:372-7. [PMID: 1593875 DOI: 10.1016/0022-4804(92)90118-j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The early effects of endotoxin (4 hr after a single dose of Escherichia coli LPS, 7.5 mg/kg) on L-glutamine (GLN) transport across the jejunal brush border of rats were studied. Jejunal brush border membrane vesicles (BBMVs) were prepared by a Mg2+ aggregation/differential centrifugation technique. Vesicle purity and integrity were confirmed by a 15-fold enrichment of brush border marker enzymes, osmotic activity, transport overshoots in the presence of sodium, and similar 1- and 2-hr equilibrium values. L-[3H]GLN transport in jejunal BBMVs was measured by a millipore filtration technique. Na(+)-dependent glutamine transport, which accounted for greater than 80% of total transport, was increased twofold in BBMVs from endotoxin-treated rats (67 +/- 5 pmole/mg protein/15 sec vs 38 +/- 3, P less than 0.01). Endotoxin treatment did not alter the activity of the Na(+)-independent carrier. Simultaneously, intestinal extraction of glutamine from the bloodstream fell by 56% (15.1 +/- 2.3% in controls vs 6.6 +/- 1.3% in endotoxin-treated rats, P less than 0.01). This reduction in the uptake of circulating glutamine could not be accounted for by a fall in the arterial concentration. Thus, soon after endotoxemia brush border glutamine uptake is increased while consumption of glutamine across the basolateral membrane is decreased. This increased uptake may support protein synthesis and may provide a biochemical rationale for the use of early enteral nutrition after the onset of critical illness.
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Affiliation(s)
- P S Dudrick
- Department of Surgery, University of Florida College of Medicine, Gainesville
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30
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Salloum RM, Copeland EM, Souba WW. Brush border transport of glutamine and other substrates during sepsis and endotoxemia. Ann Surg 1991; 213:401-9; discussion 409-10. [PMID: 2025060 PMCID: PMC1358459 DOI: 10.1097/00000658-199105000-00004] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effects of severe infection on luminal transport of amino acids and glucose by the small intestine were investigated. Studies were done in endotoxin-treated rats and in septic patients who underwent resection of otherwise normal small bowel. In rats the kinetics of the brush border glutamine transporter and the glutaminase enzyme were examined. In patients the effects of severe infection on the transport of glutamine, alanine, leucine, and glucose were studied. Transport was measured using small intestinal brush border membrane vesicles that were prepared by Mg++ aggregation/differential centrifugation. Uptake of radiolabeled substrate was measured using a rapid mixing/filtration technique. Vesicles demonstrated 15-fold enrichments of enzyme markers, classic overshoots, transport into an osmotically active space, and similar 2-hour equilibrium values. The sodium-dependent pathway accounted for nearly 90% of total carrier-mediated transport. Kinetic studies on rat jejunal glutaminase indicated a decrease in activity as early as 2 hours after endotoxin secondary to a decrease in enzyme affinity for glutamine (Km = 2.23 +/- 0.20 mmol/L [millimolar] in controls versus 4.55 +/- 0.67 in endotoxin, p less than 0.03), rather than a change in Vmax. By 12 hours the decrease in glutaminase activity was due to a decrease in Vmax (222 +/- 36 nmol/mg protein/min in controls versus 96 +/- 16 in endotoxin, p less than 0.03) rather than a significant change in Km. Transport data indicated a decrease in sodium-dependent jejunal glutamine uptake 12 hours after endotoxin secondary to a 35% reduction in maximal transport velocity (Vmax = 325 +/- 12 pmol/mg protein/10 sec in controls versus 214 +/- 8 in endotoxin, p less than 0.0001) with no change in Km (carrier affinity). Sodium-dependent glutamine transport was also decreased in septic patients, both in the jejunum (Vmax for control jejunum = 786 +/- 96 pmol/mg protein/10 sec versus 417 +/- 43 for septic jejunum, p less than 0.01) and in the ileum (Vmax of control ileum = 1126 +/- 66 pmol/mg protein/10 sec versus 415 +/- 24 in septic ileum, p less than 0.001) The rate of jejunal transport of alanine, leucine, and glucose was also decreased in septic patients by 30% to 50% (p less than 0.01). These data suggest that there is a generalized down-regulation of sodium-dependent carrier-mediated substrate transport across the brush border during severe infection, which probably occurs secondary to a decrease in transporter synthesis or an increase in the rate of carrier degradation.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- R M Salloum
- Department of Surgery, University of Florida College of Medicine, Gainesville 32610
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31
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Salloum RM, Copeland EM, Bland KI, Souba WW. Selective stimulation of brush border glutamine transport in the tumor-bearing rat. J Surg Res 1991; 50:391-7. [PMID: 2020190 DOI: 10.1016/0022-4804(91)90208-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Intestinal extraction of circulating glutamine across the basolateral membrane is diminished in the tumor-bearing rat (TBR). This study was designed to investigate the effects of progressive malignant growth on brush border glutamine transport in order to gain further insight into the adaptive/regulatory changes in intestinal glutamine metabolism that occur in the tumor-bearing rat. Fischer 344 rats (225 +/- 5 g) were implanted with fibrosarcoma cells and were studied at various time points after implantation when the tumors comprised 7%, 20%, and 29% of total body weight. Control and tumor-bearing rats were pair-fed throughout the study. Jejunal brush border membrane vesicles (BBMVs) were prepared by magnesium aggregation/differential centrifugation and transport of radioactively labeled L-glutamine, L-leucine, L-alanine, and D-glucose by BBMVs was measured using a Millipore filtration technique. BBMVs were enriched 15-fold in alkaline phosphatase, indicating brush border vesicle purity. Uptake of all substrates occurred into an osmotically active space, exhibited overshoots, and had similar 1-hr equilibrium values. The rate of glutamine uptake by BBMVs from all tumor-bearing rats was significantly greater than controls, regardless of tumor size. The increase in transport activity was not due to a change in carrier affinity but rather to an increase in maximal transport velocity. In rats with small tumors (7% of body weight), the Vmax was 431 +/- 40 pmole/mg protein/10 sec compared to 259 +/- 30 in control animals (P less than 0.01). In marked contrast, the mean transport of alanine was diminished in BBMVs from TBR (31 +/- 3 pmole/mg protein/10 sec in TBR vs 23 +/- 2 in controls, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R M Salloum
- Department of Surgery, University of Florida College of Medicine, Gainesville 32610
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Herskowitz K, Bode BP, Block ER, Souba WW. The effects of endotoxin on glutamine transport by pulmonary artery endothelial cells. J Surg Res 1991; 50:356-61. [PMID: 2020187 DOI: 10.1016/0022-4804(91)90203-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effects of endotoxin on glutamine transport by cultured pulmonary artery endothelial cells (PAECs) were studied in order to gain further insight into the regulation of the altered lung glutamine metabolism that characterizes severe infection. Incubation of PAECs with endotoxin (1 micrograms/ml) resulted in a significant increase in System ASC-mediated glutamine transport which did not occur for 8 hr and was maximal after 12 hr of exposure. Kinetic studies indicated that the increase in carrier-mediated activity was not due to a change in Km (101 +/- 6 microM in controls vs 97 +/- 4 microM in endotoxin-treated cells, P = NS), but rather to a 73% increase in Vmax (840 +/- 60 pmole/mg protein/30 sec in controls vs 1450 +/- 80 in endotoxin-treated cells, P less than 0.001). The increase in glutamine uptake by PAECs was completely blocked by actinomycin D and cycloheximide, indicating that the accelerated glutamine transport was most probably due to an increase in transporter synthesis. Endotoxin stimulates glutamine uptake by PAECs, either directly or indirectly, an adaptive response which may be necessary to support cellular metabolism, structure, and function.
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Affiliation(s)
- K Herskowitz
- Department of Surgery, University of Florida College of Medicine, Gainesville 32610
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