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Luczkowska K, Zhou Y, Ramos-Lobo AM, Brun T, Maechler P. Dietary protein load affects the energy and nitrogen balance requiring liver glutamate dehydrogenase to maintain physical activity. J Biol Chem 2024; 300:107473. [PMID: 38879007 PMCID: PMC11301064 DOI: 10.1016/j.jbc.2024.107473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 05/27/2024] [Accepted: 06/08/2024] [Indexed: 07/14/2024] Open
Abstract
Provision of amino acids to the liver is instrumental for gluconeogenesis while it requires safe disposal of the amino group. The mitochondrial enzyme glutamate dehydrogenase (GDH) is central for hepatic ammonia detoxification by deaminating excessive amino acids toward ureagenesis and preventing hyperammonemia. The present study investigated the early adaptive responses to changes in dietary protein intake in control mice and liver-specific GDH KO mice (Hep-Glud1-/-). Mice were fed chow diets with a wide coverage of protein contents; i.e., suboptimal 10%, standard 20%, over optimal 30%, and high 45% protein diets; switched every 4 days. Metabolic adaptations of the mice were assessed in calorimetric chambers before tissue collection and analyses. Hep-Glud1-/- mice exhibited impaired alanine induced gluconeogenesis and constitutive hyperammonemia. The expression and activity of GDH in liver lysates were not significantly changed by the different diets. However, applying an in situ redox-sensitive assay on cryopreserved tissue sections revealed higher hepatic GDH activity in mice fed the high-protein diets. On the same section series, immunohistochemistry provided corresponding mapping of the GDH expression. Cosinor analysis from calorimetric chambers showed that the circadian rhythm of food intake and energy expenditure was altered in Hep-Glud1-/- mice. In control mice, energy expenditure shifted from carbohydrate to amino acid oxidation when diet was switched to high protein content. This shift was impaired in Hep-Glud1-/- mice and consequently the spontaneous physical activity was markedly reduced in GDH KO mice. These data highlight the central role of liver GDH in the energy balance adaptation to dietary proteins.
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Affiliation(s)
- Karolina Luczkowska
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center, Geneva, Switzerland
| | - Yan Zhou
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center, Geneva, Switzerland
| | - Angela M Ramos-Lobo
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center, Geneva, Switzerland
| | - Thierry Brun
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center, Geneva, Switzerland
| | - Pierre Maechler
- Department of Cell Physiology and Metabolism, University of Geneva Medical Center, Geneva, Switzerland.
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2
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Identification of Single and Combined Serum Metabolites Associated with Food Intake. Metabolites 2022; 12:metabo12100908. [PMID: 36295810 PMCID: PMC9607433 DOI: 10.3390/metabo12100908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 09/16/2022] [Accepted: 09/23/2022] [Indexed: 11/17/2022] Open
Abstract
Assessment of dietary intake is challenging. Traditional methods suffer from both random and systematic errors; thus objective measures are important complements in monitoring dietary exposure. The study presented here aims to identify serum metabolites associated with reported food intake and to explore whether combinations of metabolites may improve predictive models. Fasting blood samples and a 4-day weighed food diary were collected from healthy Swedish subjects (n = 119) self-defined as having habitual vegan, vegetarian, vegetarian + fish, or omnivore diets. Serum was analyzed for metabolites by 1H-nuclear magnetic resonance spectroscopy. Associations between single and combined metabolites and 39 foods and food groups were explored. Area under the curve (AUC) was calculated for prediction models. In total, 24 foods or food groups associated with serum metabolites using the criteria of rho > 0.2, p < 0.01 and AUC ≥ 0.7 were identified. For the consumption of soybeans, citrus fruits and marmalade, nuts and almonds, green tea, red meat, poultry, total fish and shellfish, dairy, fermented dairy, cheese, eggs, and beer the final models included two or more metabolites. Our results indicate that a combination of metabolites improve the possibilities to use metabolites to identify several foods included in the current diet. Combined metabolite models should be confirmed in dose−response intervention studies.
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Yu X, He Q, Wang D. Dynamic Analysis of Major Components in the Different Developmental Stages of Tenebrio molitor. Front Nutr 2021; 8:689746. [PMID: 34616761 PMCID: PMC8488123 DOI: 10.3389/fnut.2021.689746] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 08/06/2021] [Indexed: 11/18/2022] Open
Abstract
The yellow mealworm, Tenebrio molitor, is an important resource insect with a high protein percentage that is widely farmed in many countries. In this study, the content dynamics for protein, fat, chitin, and other components in the whole development process of yellow mealworms were analyzed by sampling from different instars and combining with their growth conditions. The results of the component dynamic analyses in the different development stages showed that the percentages of protein, fat, and chitin were the highest in the larval stage, pupal stage, and adult stage, respectively. The results of amino acid composition dynamic analysis also indicated comparatively higher essential amino acids in the earlier instar (e.g., before the 9th instar) larvae. Therefore, we found that the earlier instar is better than the final instar as the insect farming harvest time. Furthermore, the larvae in the earlier instar consumed dramatically less feed and could effectively reduce the farming costs of insect farmers. This finding provides an alternative option to farm insects for different purposes and in an economic way.
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Affiliation(s)
- Xiao Yu
- Institute of Entomology, Northwest A&F University, Yangling, China
| | - Qiang He
- Institute of Entomology, Northwest A&F University, Yangling, China
| | - Dun Wang
- Institute of Entomology, Northwest A&F University, Yangling, China
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4
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Ogilvie AR, Watford M, Wu G, Sukumar D, Kwon J, Shapses SA. Decreased fasting serum glucogenic amino acids with a higher compared to normal protein diet during energy restriction in women: a randomized controlled trial. Amino Acids 2021; 53:1467-1472. [PMID: 34338883 DOI: 10.1007/s00726-021-03053-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 07/20/2021] [Indexed: 11/25/2022]
Abstract
Dietary protein alters circulating amino acid (AAs) levels and higher protein intake (HP) is one means of losing weight. We examined 34 overweight and obese women (57 ± 4 years) during 6 months of energy restriction (7.3 ± 3.8% weight loss) divided into groups consuming either normal protein (NP; 18.6 energy% protein) or HP (24.3 energy% protein). There was a reduction in fasting serum glucogenic AAs (p = 0.015) that also associated with greater weight loss (p < 0.05) in the HP group, but not in the NP group. These findings have implications for nutrient prioritization during energy restriction.
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Affiliation(s)
- A R Ogilvie
- Department of Nutritional Sciences, Rutgers University and NJ-Institute of Food Health and Nutrition, New Brunswick, NJ, USA
| | - M Watford
- Department of Nutritional Sciences, Rutgers University and NJ-Institute of Food Health and Nutrition, New Brunswick, NJ, USA
| | - G Wu
- Department of Animal Science, Texas A&M University, College Station, TX, USA
| | - D Sukumar
- Department of Nutrition Sciences, Drexel University, Philadelphia, PA, USA
| | - J Kwon
- Department of Nutritional Sciences, Rutgers University and NJ-Institute of Food Health and Nutrition, New Brunswick, NJ, USA
| | - S A Shapses
- Department of Nutritional Sciences, Rutgers University and NJ-Institute of Food Health and Nutrition, New Brunswick, NJ, USA.
- Department of Medicine, Rutgers-RWJ Medical School, New Brunswick, NJ, USA.
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5
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Cooper L, Ball RO, Pencharz PB, Sakai R, Elango R. Dispensable Amino Acids, except Glutamine and Proline, Are Ideal Nitrogen Sources for Protein Synthesis in the Presence of Adequate Indispensable Amino Acids in Adult Men. J Nutr 2020; 150:2398-2404. [PMID: 32879983 DOI: 10.1093/jn/nxaa180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 03/11/2020] [Accepted: 06/03/2020] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Nutritionally, there is a dietary requirement for indispensable amino acids (IAAs) but also a requirement for nitrogen (N) intake for the de novo synthesis of the dispensable amino acids (DAAs). It has been suggested that there might be a dietary requirement for specific DAAs. OBJECTIVES Experiment 1 tested whether 9 of the DAAs (Ala, Arg, Asn, Asp, Gln, Glu, Gly, Pro, Ser) are ideal N sources using the indicator amino acid oxidation (IAAO) technique. Experiment 2 examined whether there is a dietary requirement for Glu in adult men. METHODS Seven healthy men (aged 20-24 y) participated in 11 or 2 test diet intakes, in experiment 1 and 2, respectively, in a repeated measures design. In experiment 1, a base diet consisting of the IAA provided at the RDA was compared with test intakes with the base diet plus addition of individual DAAs to meet a 50:50 ratio of IAA:DAA on an N basis. In experiment 2, the diets corresponded to the amino acid pattern present in egg protein, in which all Glu and Gln was present as Glu, or removed, with Ser used to make the diets isonitrogenous. On each study day the IAAO protocol with l-[1-13C]phenylalanine was used to measure whole-body protein synthesis. RESULTS In experiment 1, repeated measures ANOVA with post hoc multiple comparisons showed that 7 of the 9 DAAs (Ala, Arg, Asn, Asp, Glu, Gly, Ser) decreased IAAO significantly (P < 0.05) compared with base IAA diet, the exceptions being Gln and Pro. In experiment 2, a paired t test did not find significant (P > 0.05) differences in the IAAO in response to removal and replacement of Glu intake. CONCLUSIONS The results suggest that in healthy men most DAAs are ideal N sources for protein synthesis, in the presence of adequate IAAs, and that endogenous synthesis of Glu is sufficient.Registered clinicaltrials.gov identifier: NCT02009917.
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Affiliation(s)
- Leah Cooper
- BC Children's Hospital Research Institute, BC Children's Hospital, Vancouver, British Columbia, Canada.,Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ronald O Ball
- Department of Agricultural, Food & Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Paul B Pencharz
- Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ryosei Sakai
- Research Institute for Bioscience Products & Fine Chemicals, Ajinomoto Co. Inc., Kawasaki-Shi, Japan
| | - Rajavel Elango
- BC Children's Hospital Research Institute, BC Children's Hospital, Vancouver, British Columbia, Canada.,Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada.,School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada
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6
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Ma W, Heianza Y, Huang T, Wang T, Sun D, Zheng Y, Hu FB, Rexrode KM, Manson JE, Qi L. Dietary glutamine, glutamate and mortality: two large prospective studies in US men and women. Int J Epidemiol 2019; 47:311-320. [PMID: 29140419 DOI: 10.1093/ije/dyx234] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2017] [Indexed: 12/18/2022] Open
Abstract
Background Emerging studies have related circulating glutamine metabolites to various chronic diseases such as cardiovascular disease and cancer; diet is the major source of nutrients involved in glutamine metabolism. However, it remains unknown whether dietary intakes of glutamine, glutamate,and their ratio are related to total and cause-specific mortality. Methods We followed 74 082 women from the Nurses' Health Study (1984-2012) and 42 303 men from the Health Professionals Follow-up Study (1986-2012), who were free of cardiovascular disease and cancer at baseline. Diet was updated every 2 to 4 years by using validated food frequency questionnaires. The content of glutamine and glutamate in foods was calculated based on protein fractions generated from gene sequencing methods and adjusted for total energy intake. Results We documented 30 424 deaths during 2 878 344 person-years of follow-up. After adjustment for potential confounders including lifestyle and dietary factors, higher intakes of glutamine and glutamine-to-glutamate ratio were associated with significantly lower risk of total and cause-specific mortality. Compared with people in the lowest quintile of dietary glutamine-to-glutamate ratio, the pooled hazard ratio (HR) in the highest quintile was 0.87 [95% confidence interval (CI): 0.84, 0.91; P for trend < 0.001) for total mortality, 0.81 (95% CI: 0.75, 0.88; P for trend < 0.001) for cardiovascular mortality, and 0.93 (95% CI: 0.87, 0.99; P for trend = 0.01) for cancer mortality. Conclusions We found dietary glutamine and glutamine-to-glutamate ratio were inversely related to risk of mortality, particularly cardiovascular mortality, independent of other dietary and lifestyle factors, in US men and women.
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Affiliation(s)
- Wenjie Ma
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Yoriko Heianza
- Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA
| | - Tao Huang
- Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA
| | - Tiange Wang
- Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA
| | - Dianjianyi Sun
- Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA
| | - Yan Zheng
- Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Frank B Hu
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Channing Division of Network Medicine
| | - Kathryn M Rexrode
- Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - JoAnn E Manson
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Channing Division of Network Medicine.,Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Lu Qi
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA.,Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA.,Channing Division of Network Medicine
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7
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Levitt DG, Levitt MD. A model of blood-ammonia homeostasis based on a quantitative analysis of nitrogen metabolism in the multiple organs involved in the production, catabolism, and excretion of ammonia in humans. Clin Exp Gastroenterol 2018; 11:193-215. [PMID: 29872332 PMCID: PMC5973424 DOI: 10.2147/ceg.s160921] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Increased blood ammonia (NH3) is an important causative factor in hepatic encephalopathy, and clinical treatment of hepatic encephalopathy is focused on lowering NH3. Ammonia is a central element in intraorgan nitrogen (N) transport, and modeling the factors that determine blood-NH3 concentration is complicated by the need to account for a variety of reactions carried out in multiple organs. This review presents a detailed quantitative analysis of the major factors determining blood-NH3 homeostasis – the N metabolism of urea, NH3, and amino acids by the liver, gastrointestinal system, muscle, kidney, and brain – with the ultimate goal of creating a model that allows for prediction of blood-NH3 concentration. Although enormous amounts of NH3 are produced during normal liver amino-acid metabolism, this NH3 is completely captured by the urea cycle and does not contribute to blood NH3. While some systemic NH3 derives from renal and muscle metabolism, the primary site of blood-NH3 production is the gastrointestinal tract, as evidenced by portal vein-NH3 concentrations that are about three times that of systemic blood. Three mechanisms, in order of quantitative importance, release NH3 in the gut: 1) hydrolysis of urea by bacterial urease, 2) bacterial protein deamination, and 3) intestinal mucosal glutamine metabolism. Although the colon is conventionally assumed to be the major site of gut-NH3 production, evidence is reviewed that indicates that the stomach (via Helicobacter pylori metabolism) and small intestine and may be of greater importance. In healthy subjects, most of this gut NH3 is removed by the liver before reaching the systemic circulation. Using a quantitative model, loss of this “first-pass metabolism” due to portal collateral circulation can account for the hyperammonemia observed in chronic liver disease, and there is usually no need to implicate hepatocyte malfunction. In contrast, in acute hepatic necrosis, hyperammonemia results from damaged hepatocytes. Although muscle-NH3 uptake is normally negligible, it can become important in severe hyperammonemia. The NH3-lowering actions of intestinal antibiotics (rifaximin) and lactulose are discussed in detail, with particular emphasis on the seeming lack of importance of the frequently emphasized acidifying action of lactulose in the colon.
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Affiliation(s)
- David G Levitt
- Department of Integrative Biology and Physiology, University of Minnesota
| | - Michael D Levitt
- Research Service, Veterans Affairs Medical Center, Minneapolis, MN, USA
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8
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Mori M, Smedberg M, Klaude M, Tjäder I, Norberg Å, Rooyackers O, Wernerman J. A tracer bolus method for investigating glutamine kinetics in humans. PLoS One 2014; 9:e96601. [PMID: 24810895 PMCID: PMC4014541 DOI: 10.1371/journal.pone.0096601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 04/10/2014] [Indexed: 11/18/2022] Open
Abstract
Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-13C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoRa) of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoRa of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p = 0.29 versus control), 6.1±0.4 µmol/kg/min with extra alanine only (p = 0.32 versus control), and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p = 0.049 versus control). In conclusion, a tracer bolus injection method to measure glutamine endoRa showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoRa in healthy volunteers, which was not attributable to the alanine part of the dipeptide.
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Affiliation(s)
- Maiko Mori
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Marie Smedberg
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Maria Klaude
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Inga Tjäder
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Åke Norberg
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Olav Rooyackers
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
| | - Jan Wernerman
- Department of Anesthesiology and Intensive Care Medicine, Karolinska University Hospital Huddinge, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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9
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Mori M, Rooyackers O, Smedberg M, Tjäder I, Norberg A, Wernerman J. Endogenous glutamine production in critically ill patients: the effect of exogenous glutamine supplementation. Crit Care 2014; 18:R72. [PMID: 24731231 PMCID: PMC4056090 DOI: 10.1186/cc13829] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 03/25/2014] [Indexed: 12/05/2022] Open
Abstract
Introduction Glutamine rate of appearance (Ra) may be used as an estimate of endogenous glutamine production. Recently a technique employing a bolus injection of isotopically labeled glutamine was introduced, with the potential to allow for multiple assessments of the glutamine Ra over time in critically ill patients, who may not be as metabolically stable as healthy individuals. Here the technique was used to evaluate the endogenous glutamine production in critically ill patients in the fed state with and without exogenous glutamine supplementation intravenously. Methods Mechanically ventilated patients (n = 11) in the intensive care unit (ICU) were studied on two consecutive days during continuous parenteral feeding. To allow the patients to be used as their own controls, they were randomized for the reference measurement during basal feeding without supplementation, before or after the supplementation period. Glutamine Ra was determined by a bolus injection of 13C-glutamine followed by a period of frequent sampling to establish the decay-curve for the glutamine tracer. Exogenous glutamine supplementation was given by intravenous infusion of a glutamine containing dipeptide, L-alanyl-L-glutamine, 0.28 g/kg during 20 hours. Results A 14% increase of endogenous glutamine Ra was seen at the end of the intravenous supplementation period as compared to the basal measurements (P = 0.009). Conclusions The bolus injection technique to measure glutamine Ra to estimate the endogenous production of glutamine in critically ill patients was demonstrated to be useful for repetitive measurements. The hypothesized attenuation of endogenous glutamine production during L-alanyl-L-glutamine infusion given as a part of full nutrition was not seen.
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10
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Soeters PB, Grecu I. Have we enough glutamine and how does it work? A clinician's view. ANNALS OF NUTRITION AND METABOLISM 2011; 60:17-26. [PMID: 22212454 DOI: 10.1159/000334880] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 11/03/2011] [Indexed: 11/19/2022]
Abstract
There is a gap between the scientific basis of the claim that in several disease states glutamine is lacking and the widespread belief that supplementation of glutamine to the nutritional regimen is beneficial in severely ill patients. Glutamine shortage exists when consuming tissues, playing a crucial role in the response to trauma and disease, receive insufficient amounts of glutamine. In these tissues (immune system, wound), glutamine is only partly oxidized but has more specific roles as nontoxic nitrogen carrier, precursor of several crucial metabolites required for cell proliferation and for maintenance of the redox potential, and as osmolyte. In inflammatory states, glutamine concentrations in plasma and tissues are decreased due to many disease-related factors, precluding its use as a reliable indicator of shortage. Isotope studies have yielded equivocal results, precluding their use as a reliable indicator of glutamine shortage or adequacy. The increase in the net release of glutamine from peripheral tissues to central tissues (immune system, liver, spleen, wound) in inflammatory states provides a better basis for the necessity to supplement the organism with extra glutamine in these conditions. Glutamine supplementation was beneficial in a few studies in burn or trauma patients. The clinical benefit of parenteral glutamine supplementation in patients with severe inflammation has been demonstrated more convincingly. The amounts of glutamine supplemented approximate the amounts released by peripheral tissues and utilized by central organs operative in host defense and are therefore in the physiological range.
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Affiliation(s)
- P B Soeters
- Department of Surgery, Maastricht, The Netherlands.
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11
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Julio-Pieper M, Flor PJ, Dinan TG, Cryan JF. Exciting times beyond the brain: metabotropic glutamate receptors in peripheral and non-neural tissues. Pharmacol Rev 2011; 63:35-58. [PMID: 21228260 DOI: 10.1124/pr.110.004036] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Metabotropic glutamate (mGlu) receptors are G-protein-coupled receptors expressed primarily on neurons and glial cells, where they are located in the proximity of the synaptic cleft. In the central nervous system (CNS), mGlu receptors modulate the effects of l-glutamate neurotransmission in addition to that of a variety of other neurotransmitters. However, mGlu receptors also have a widespread distribution outside the CNS that has been somewhat neglected to date. Based on this expression, diverse roles of mGlu receptors have been suggested in a variety of processes in health and disease including controlling hormone production in the adrenal gland and pancreas, regulating mineralization in the developing cartilage, modulating lymphocyte cytokine production, directing the state of differentiation in embryonic stem cells, and modulating gastrointestinal secretory function. Understanding the role of mGlu receptors in the periphery will also provide a better insight into potential side effects of drugs currently being developed for neurological and psychiatric conditions. This review summarizes the new potential roles of mGlu receptors and raises the possibility of novel pharmacological targets for various disorders.
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Affiliation(s)
- Marcela Julio-Pieper
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
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12
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Effects of glutamine supplementation on kidney of diabetic rat. Amino Acids 2009; 38:1021-30. [PMID: 19533301 DOI: 10.1007/s00726-009-0310-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Accepted: 05/25/2009] [Indexed: 01/08/2023]
Abstract
Glutamine is the most important donor of NH(3) in kidney playing an important role in acid-base buffering system. Besides this effect, glutamine presents many other relevant functions in the whole body, such as a precursor of arginine in adult and neonates. In addition to these effects, some studies have shown that glutamine can potentiate renal disease. In the present study, the effect of short-term treatment (15 days) with glutamine on control and diabetic rats was investigated. Using biochemical, histological and molecular biology analysis from control and diabetic rats we verified that glutamine supplementation increase in pro-inflammatory interleukins (IL)-1beta and IL-6 content in renal cortex and induce alteration in glomerular characteristics. This study showed that short-term treatment with glutamine in association with increased glucose levels could cause important alterations in glomerular morphology that may result in fast progression of kidney failure.
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Abstract
Glutamine is a non-essential amino acid that can be synthesized de novo from glutamate. This synthesis can be increased by intravenous infusion of carbon precursors (alpha-ketoglutarate or amino acids) in adults and in infants. The metabolism of glutamine is highly compartmentalized between the splanchnic tissues and the periphery, so that orally administered glutamine is completely metabolized in the splanchnic compartment. Data from studies in adults and children show that plasma levels of glutamine decline during acute stress and illness. Because of its importance in several physiological functions (the demonstrated benefits of supplemental glutamine in adult burns and trauma patients and the inhibitory effect on proteolysis in the skeletal muscle in vitro), it has been suggested that during 'acute stress' the demands of glutamine outweigh its de novo synthesis, resulting in a fall in plasma glutamine levels. As a consequence, glutamine has been considered a 'conditionally essential' amino acid. Because of its instability in solution, glutamine is not routinely added to the parenteral amino acid mixtures. A number of clinical trials of parenteral and enteral supplementation of glutamine have been performed. The outcome measures examined have varied between acute effects and long-term complex clinical events such as mortality and risk of infections. Although acute studies in LBW babies have shown some beneficial effects such as changes in protein metabolism and activation of immune system, these have not been translated into prolonged advantages such as reduction in mortality or in nosocomial infection. The reasons for these differences are discussed.
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Affiliation(s)
- Prabhu S Parimi
- Department of Pediatrics, Case Western Reserve University at MetroHealth Medical Center, 2500 MetroHealth Drive, Cleveland, OH 44109-1998, USA.
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14
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Jenssen T, Nurjhan N, Perriello G, Bucci A, Toft I, Gerich J. Determination of [14C] Glutamine Specific Activity in Plasma. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10826079408013767] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- T. Jenssen
- a University Hospital of Tromsoe, Department of Medicine , N-9038, Tromsoe , Norway
| | - N. Nurjhan
- b The Whittier Institute for Diabetes and Endocrinology , 9894 Genesee Avenue, La Jolla , California , 92037
| | - G. Perriello
- b The Whittier Institute for Diabetes and Endocrinology , 9894 Genesee Avenue, La Jolla , California , 92037
| | - A. Bucci
- c University of Pittsburgh, Department of Medicine , 230 Lothrop Street, Pittsburgh , Pennsylvania , 15261
| | - I. Toft
- a University Hospital of Tromsoe, Department of Medicine , N-9038, Tromsoe , Norway
| | - J. Gerich
- b The Whittier Institute for Diabetes and Endocrinology , 9894 Genesee Avenue, La Jolla , California , 92037
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15
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Rutten EPA, Engelen MPKJ, Castro CLN, Wouters EFM, Schols AMWJ, Deutz NEP. Decreased whole-body and splanchnic glutamate metabolism in healthy elderly men and patients with chronic obstructive pulmonary disease in the postabsorptive state and in response to feeding. J Nutr 2005; 135:2166-70. [PMID: 16140893 DOI: 10.1093/jn/135.9.2166] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Decreased plasma and muscle glutamate concentrations have been observed in patients with chronic obstructive pulmonary disease (COPD), suggesting disturbances in glutamate metabolism. The present study was conducted to further examine glutamate metabolism in 8 male COPD patients (68 +/- 4 y) by measurement of whole-body (WB) glutamate production and splanchnic glutamate extraction in the postabsorptive state as well as in response to feeding. Because COPD is particularly prevalent in the elderly and aging per se may also affect glutamate metabolism, 2 male control groups were included: 8 healthy elderly (63 +/- 3 y) and 8 young (22 +/- 1 y) subjects. On 2 test days, the stable isotope L-15N-glutamate was infused i.v. or enterally according to a primed constant and continuous infusion protocol. After 90 min of infusion, subjects ingested a carbohydrate-protein drink (28% milk protein, 72% maltodextrin) every 20 min for 2 h. Arterialized-venous blood samples were taken at the end of the postabsorptive and feeding periods. Postabsorptive WB glutamate production and splanchnic glutamate extraction were significantly lower in the elderly and COPD patients than in the young (P < 0.01). Feeding further decreased WB endogenous glutamate production in the elderly and COPD patients, with COPD patients tending (P = 0.07) to have a greater decrease. Splanchnic glutamate extraction increased during feeding in the elderly (P < 0.05) but did not change in COPD patients. In conclusion, aging reduces postabsorptive WB endogenous glutamate production and splanchnic glutamate extraction. COPD does not affect postabsorptive WB glutamate metabolism but may influence splanchnic glutamate metabolism during feeding.
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Affiliation(s)
- Erica P A Rutten
- Department of Respiratory Medicine, University Hospital, Maastricht, the Netherlands.
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16
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Costa Rosa LFBP. Exercise as a Time-conditioning Effector in Chronic Disease: a Complementary Treatment Strategy. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE : ECAM 2004; 1:63-70. [PMID: 15257327 PMCID: PMC442120 DOI: 10.1093/ecam/neh018] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2003] [Accepted: 02/29/2004] [Indexed: 01/26/2023]
Abstract
Exercise has been widely believed to be a preventive and therapeutic aid in the treatment of various pathophysiological conditions such as cardiovascular disease and cancer. A common problem associated with such pathologies is cachexia, characterized by progressive weight loss and depletion of lean and fat body mass, and is linked to poor prognosis. As this syndrome comprises changes in many physiological systems, it is tempting to assume that the modulation of the psychoneuroimmunoendocrine axis could attenuate or even prevent cachexia progression in cancer patients. Cancer cachexia is characterized by a disruption in the rhythmic secretion of melatonin, an important time-conditioning effector. This hormone, secreted by the pineal gland, transmits circadian and seasonal information to all organs and cells of the body, synchronizing the organism with the photoperiod. Considering that exercise modulates the immune response through at least two different mechanisms-metabolic and neuroendocrine-we propose that the adoption of a regular exercise program as a complementary strategy in the treatment of cancer patients, with the exercise bouts regularly performed at the same time of the day, will ameliorate cachexia symptoms and increase survival and quality of life.
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Affiliation(s)
- Luis F. B. P. Costa Rosa
- Laboratory of Metabolism, Department of Histology and Embryology, Institute of Biomedical Sciences, University of São Paulo, Brazil
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17
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Lacroix M, Gaudichon C, Martin A, Morens C, Mathé V, Tomé D, Huneau JF. A long-term high-protein diet markedly reduces adipose tissue without major side effects in Wistar male rats. Am J Physiol Regul Integr Comp Physiol 2004; 287:R934-42. [PMID: 15155276 DOI: 10.1152/ajpregu.00100.2004] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Although there is a considerable interest of high-protein, low-carbohydrate diets to manage weight control, their safety is still the subject of considerable debate. They are suspected to be detrimental to the renal and hepatic functions, calcium balance, and insulin sensitivity. However, the long-term effects of a high-protein diet on a broad range of parameters have not been investigated. We studied the effects of a high-protein diet in rats over a period of 6 mo. Forty-eight Wistar male rats received either a normal-protein (NP: 14% protein) or high-protein (HP: 50% protein) diet. Detailed body composition, plasma hormones and nutrients, liver and kidney histopathology, hepatic markers of oxidative stress and detoxification, and the calcium balance were investigated. No major alterations of the liver and kidneys were found in HP rats, whereas NP rats exhibited massive hepatic steatosis. The calcium balance was unchanged, and detoxification markers (GSH and GST) were enhanced moderately in the HP group. In contrast, HP rats showed a sharp reduction in white adipose tissue and lower basal concentrations of triglycerides, glucose, leptin, and insulin. Our study suggests that the long-term consumption of an HP diet in male rats has no deleterious effects and could prevent metabolic syndrome.
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Affiliation(s)
- Magali Lacroix
- Unité INRA 914 Physiologie de la Nutrition et Comportement Alimentaire, INA PG, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
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18
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Parimi PS, Devapatla S, Gruca LL, Amini SB, Hanson RW, Kalhan SC. Effect of enteral glutamine or glycine on whole-body nitrogen kinetics in very-low-birth-weight infants. Am J Clin Nutr 2004; 79:402-9. [PMID: 14985214 DOI: 10.1093/ajcn/79.3.402] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Glutamine is a critical amino acid for the metabolism of enterocytes, lymphocytes, and other proliferating cells. Although supplementation with glutamine has been suggested for growing infants, its effect on protein metabolism has not been examined. OBJECTIVE The objective was to examine the effect of enteral glutamine or glycine on whole-body kinetics of glutamine, phenylalanine, leucine, and urea in preterm infants. DESIGN Infants at <32 wk of gestation were given formula supplemented with either glutamine (0.6 g. kg(-1). d(-1); n = 9) or isonitrogenous amounts of glycine (n = 9) for 5 d. Eight infants fed unsupplemented formula served as control subjects. Glutamine, phenylalanine, leucine nitrogen flux, leucine carbon flux, and urea kinetics were quantified during a basal fasting period and in response to nutrient intake. RESULTS Growing preterm infants had a high weight-specific rate of appearance of glutamine, phenylalanine, and leucine nitrogen flux. When compared with the control treatment, enteral glutamine resulted in a high rate of urea synthesis, no change in the plasma glutamine concentration, and no change in the rate of appearance of glutamine. Glycine supplementation resulted in similar changes in nitrogen metabolism, but the magnitude of change was less than that in the glutamine group. In the nonsupplemented infants, the rate of appearance of leucine nitrogen flux was negatively correlated (rho = -0.72) with urea synthesis. In contrast, the correlation (rho = 0.75) was positive in the glutamine group. CONCLUSION Enterally administered glutamine in growing preterm infants is entirely metabolized in the gut and does not have a discernable effect on whole-body protein and nitrogen kinetics.
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Affiliation(s)
- Prabhu S Parimi
- Schwartz Center for Metabolism & Nutrition, MetroHealth Medical Center, Cleveland, OH 44109-1998, USA.
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19
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Abstract
In situations of stress, such as clinical trauma, starvation or prolonged, strenuous exercise, the concentration of glutamine in the blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Glutamine is used as a fuel by some cells of the immune system. Provision of glutamine or a glutamine precursor, such as branched chain amino acids, has been seen to have a beneficial effect on gut function, on morbidity and mortality, and on some aspects of immune cell function in clinical studies. It has also been seen to decrease the self-reported incidence of illness in endurance athletes. So far, there is no firm evidence as to precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated. Other aspects of glutamine and glutamine supplementation are also addressed.
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Affiliation(s)
- Linda Castell
- Nuffield Department of Anaesthetics, University of Oxford, England.
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20
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Morens C, Gaudichon C, Fromentin G, Marsset-Baglieri A, Bensaïd A, Larue-Achagiotis C, Luengo C, Tomé D. Daily delivery of dietary nitrogen to the periphery is stable in rats adapted to increased protein intake. Am J Physiol Endocrinol Metab 2001; 281:E826-36. [PMID: 11551861 DOI: 10.1152/ajpendo.2001.281.4.e826] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Dietary nitrogen was traced in rats adapted to a 50% protein diet and given a meal containing 1.50 g (15)N-labeled protein (HP-50 group). This group was compared with rats usually consuming a 14% protein diet and fed a meal containing either 0.42 g (AP-14 group) or 1.50 g (AP-50 group) of (15)N-labeled protein. In the HP group, the muscle nonprotein nitrogen pool was doubled when compared with the AP group. The main adaptation was the enhancement of dietary nitrogen transferred to urea (2.2 +/- 0.5 vs. 1.3 +/- 0.1 mmol N/100 g body wt in the HP-50 and AP-50 groups, respectively). All amino acids reaching the periphery except arginine and the branched-chain amino acids were depressed. Consequently, dietary nitrogen incorporation into muscle protein was paradoxically reduced in the HP-50 group, whereas more dietary nitrogen was accumulated in the free nitrogen pool. These results underline the important role played by splanchnic catabolism in adaptation to a high-protein diet, in contrast to muscle tissue. Digestive kinetics and splanchnic anabolism participate to a lesser extent in the regulation processes.
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Affiliation(s)
- C Morens
- Institut National de la Recherche Agronomique, Unité de Physiologie de la Nutrition et du Comportement Alimentaire, Institut National Agronomique de Paris-Grignon, F-75005 Paris, France
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21
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Abstract
In this introduction to the Proceedings of the Symposium on Glutamine, we consider various lines of evidence that might potentially lead to an answer to the question posed in the title. We begin with a short summary of the multiple functions of glutamine, which are extensive and, superficially at least, equally as impressive as those of glutamate. However, each of these amino acids may serve an equivalent role in some of these functions due to their ready metabolic interconversion. We raise the question whether glutamine is of primordial or rudimentary significance or whether it is a product of somebody else's existence. Thus, there is a short account of the prebiotic events of evolution that led to the appearance of glutamine and life on Earth. In doing this, it then appears that glutamine is a rather schizophrenic molecule, stable and thermodynamically reliable in biochemical environments, but labile in chemical ones. We then turn to the involvement of glutamine in mammalian N (nitrogen) commerce, with initial emphasis on the nitrogen cycle on Earth, then N transport and N excretion, before assessing its contribution to carbon/energy or C/E commerce. We hypothesize that, in addition to its utilization in immune cell function and in normal intestinal tissues, glutamine is a particularly key anapleurotic and energy-yielding substrate in conditions of hypoxia, anoxia and dysoxia. It also serves as a quantitatively important gluconeogenic metabolite under normal postabsorptive conditions. We postulate that in certain conditions, this carbon-energy econometric function might be by-passed with ornithine. In conclusion, the answer to the question above depends on the context, and this point will receive elaboration in many of the individual contributions that collaborate to form these Proceedings.
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Affiliation(s)
- V R Young
- Laboratory of Human Nutrition, School of Science and Clinical Research Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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22
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Humbert B, Nguyen P, Obled C, Bobin C, Vaslin A, Sweeten S, Darmaun D. Use of L-[(15)N] glutamic acid and homoglutathione to determine both glutathione synthesis and concentration by gas chromatography-mass spectrometry (GCMS). JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:726-735. [PMID: 11473395 DOI: 10.1002/jms.185] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A method for simultaneous measurement of both glutathione enrichment and concentration in a biological sample using gas chromatography mass spectrometry is described. The method is based on the preparation of N,S-ethoxycarbonylmethyl ester derivatives of glutathione, and the use of homoglutathione (glutamyl-cysteinyl--alanine) as an internal standard. A procedure for determination of glutamate concentration and enrichment is also reported. Both methods have within-day and day-to-day inter-assay coefficients of variation less than 5%, and recoveries of known added amounts of glutathione and glutamate are close to 100%. Taken together, these methods allowed determination of glutathione concentration and fractional synthesis rate in red blood cells using L-[(15)N] glutamic acid infusion. This approach was applied in vivo to investigate the effects of a 72 h fast, compared with a control overnight fast, on erythrocyte glutathione in a single dog. The 72 h fast was associated with a 39% decline in erythrocyte glutathione level, (2.9 +/- 0.4 versus 4.7 +/- 0.5 mmol l(-1), fasting versus control) with no change in glutathione fractional synthesis (67.4 versus 71.3% d(-1), fasting versus control).
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Affiliation(s)
- B Humbert
- INSERM U. 539, Centre de Recherche en Nutrition Humaine, Nantes, France
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23
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Abstract
We measured glutamine kinetics using L-[5-15N]glutamine and L-[ring-2H5]phenylalanine infusions in healthy subjects in the postabsorptive state and during ingestion of an amino acid mixture that included glutamine, alone or with additional glucose. Ingestion of the amino acid mixture increased arterial glutamine concentrations by approximately 20% (not by 30%; P < 0.05), irrespective of the presence or absence of glucose. Muscle free glutamine concentrations remained unchanged during ingestion of amino acids alone but decreased from 21.0 +/- 1.0 to 16.4 +/- 1.6 mmol/l (P < 0.05) during simultaneous ingestion of glucose due to a decrease in intramuscular release from protein breakdown and glutamine synthesis (0.82 +/- 0.10 vs. 0.59 +/- 0.06 micromol x 100 ml leg(-1) x min(-1); P < 0.05). In both protocols, muscle glutamine inward and outward transport and muscle glutamine utilization for protein synthesis increased during amino acid ingestion; leg glutamine net balance remained unchanged. In summary, ingestion of an amino acid mixture that includes glutamine increases glutamine availability and uptake by skeletal muscle in healthy subjects without causing an increase in the intramuscular free glutamine pool. Simultaneous ingestion of glucose diminishes the intramuscular glutamine concentration despite increased glutamine availability in the blood due to decreased glutamine production.
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Affiliation(s)
- B Mittendorfer
- Department of Surgery, University of Texas Medical Branch at Galveston, Galveston, TX 77550, USA
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24
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Abstract
Here, we compared the traditional nutritional definition of the dispensable and indispensable amino acids for humans with categorizations based on amino acid metabolism and function. The three views lead to somewhat different interpretations. From a nutritional perspective, it is quite clear that some amino acids are absolute dietary necessities if normal growth is to be maintained. Even so, growth responses to deficiencies of dispensable amino acids can be found in the literature. From a strictly metabolic perspective, there are only three indispensable amino acids (lysine, threonine and tryptophan) and two dispensable amino acids (glutamate and serine). In addition, a consideration of in vivo amino acid metabolism leads to the definition of a third class of amino acids, termed conditionally essential, whose synthesis can be carried out by mammals but can be limited by a variety of factors. These factors include the dietary supply of the appropriate precursors and the maturity and health of the individual. From a functional perspective, all amino acids are essential, and an argument in favor of the idea of the critical importance of nonessential and conditionally essential amino acids to physiological function is developed.
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Affiliation(s)
- P J Reeds
- U.S. Department of Agriculture/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
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25
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Forslund AH, Hambraeus L, van Beurden H, Holmbäck U, El-Khoury AE, Hjorth G, Olsson R, Stridsberg M, Wide L, Akerfeldt T, Regan M, Young VR. Inverse relationship between protein intake and plasma free amino acids in healthy men at physical exercise. Am J Physiol Endocrinol Metab 2000; 278:E857-67. [PMID: 10780942 DOI: 10.1152/ajpendo.2000.278.5.e857] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of a "normal" (n = 8) and "high" (n = 6) protein intake (1 and 2.5 g x kg(-1) x day(-1), respectively) and of exercise on plasma amino acid (AA) concentrations, insulin, and glucagon concentrations was followed throughout a continuous 24-h period in adult male subjects at energy balance after six days on a standardized diet and exercise program. Subjects were fasting from 2100 on day 6 to 1200 on day 7 and then fed 10 identical meals hourly until 2100. Physical exercise was performed (46% maximal oxygen uptake) between 0830 and 1000 (fasting) and in a fed state (1600-1730) on each day. The normal-protein group showed fasting plasma AA concentrations that were higher (P < 0.05) than those for the high-protein group, except for leucine, methionine, and tyrosine. Glutamine, glycine, alanine, taurine, and threonine concentrations were distinctly higher ( approximately 30% or greater) throughout the 24-h period in subjects consuming the normal- vs. the high-protein diets. Exercise appeared to increase, although not profoundly, the plasma concentrations of amino acids except for glutamate, histidine, ornithine, and tryptophan. The profound diet-related differences in plasma AA concentrations are only partially explained by differences in the renal clearance of the amino acids. We speculate on the possible metabolic basis for these findings.
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Affiliation(s)
- A H Forslund
- Department of Medical Sciences, Nutrition and Clinical Chemistry, Uppsala University, SE-75237 Uppsala, Sweden
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26
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Metges CC, Barth CA. Metabolic consequences of a high dietary-protein intake in adulthood: assessment of the available evidence. J Nutr 2000; 130:886-9. [PMID: 10736347 DOI: 10.1093/jn/130.4.886] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- C C Metges
- Department Biochemistry and Physiology of Nutrition, Deutsches Institut für Ernährungsforschung (German Institute of Human Nutrition) (DIfE), 14558 Bergholz-Rehbrücke, Germany
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27
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Abstract
In this introductory paper to the symposium, we consider why L-glutamate (GLU) is such an abundant biomolecule. We begin with a brief discussion of the prebiotic dawn of events and some evolutionary features of GLU in the biological and metabolic world. The properties of GLU are then examined with reference to its overall structural motif and to the reactivity of the molecule at the tautomeric 2 carbon and at the 4- and 5-C positions. This chemical viewpoint reveals that the GLU molecule offers a number of features/properties not shared by its homologs (amino adipic and aspartic acids). These properties make GLU a favorable choice for facilitating its involvement in multiple metabolic processes that play major roles in the nitrogen economy of the host, as well as serving as a nutrient, an energy-yielding substrate, a structural determinant and an excitatory molecule.
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Affiliation(s)
- V R Young
- Laboratory of Human Nutrition, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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28
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Abstract
Plasma glutamine turnover was determined using 1-14C-labeled glutamine in rats that consumed crystalline amino acid diets containing the equivalent of 16% protein with 25% of the amino acids as glutamine or a control diet containing no glutamine (or glutamate) for 10 days. Glutamine turnover in glutamine-fed animals was 66% of the rate in the control group. Glutamine feeding caused 20% higher levels of arterial plasma glutamine. Arterial-portal differences across the portal-drained viscera showed net glutamine uptake in control animals but no net uptake or release in the glutamine-fed group. Skeletal muscle glutamine synthetase activity was similar in both groups. The results indicate that long-term consumption of relatively large amounts of dietary glutamine decreases the turnover of plasma glutamine and thus reduces the need for endogenous glutamine synthesis.
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Affiliation(s)
- M Watford
- Department of Nutritional Sciences, Cook College, Rutgers University, New Brunswick, NJ 08901-8525, USA
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29
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Abstract
This review provides a critical evaluation of the metabolic rationale for the use of individual amino acids as nutritional ergogenic (work-generating) aids in athletes. The conclusion is that in contrast to the claims made on sport nutrition products, branched-chain amino acids do not improve endurance performance, that the evidence that glutamine supplements may improve immune function is rather weak, and that the available commercial supplements contain too little arginine to increase growth hormone levels. No studies have been performed to investigate the claim that tyrosine supplements can improve explosive exercise.
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Affiliation(s)
- A J Wagenmakers
- Department of Human Biology and Stable Isotope Research Centre, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, The Netherlands.
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30
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Bellisle F. Glutamate and the UMAMI taste: sensory, metabolic, nutritional and behavioural considerations. A review of the literature published in the last 10 years. Neurosci Biobehav Rev 1999; 23:423-38. [PMID: 9989429 DOI: 10.1016/s0149-7634(98)00043-8] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Monosodium glutamate (MSG) is used increasingly often in processed foods and in home cooking in the Western world. This substance is responsible for a pleasurable taste sensation, the Umami taste. This review covers recent developments in sensory studies of glutamate effects, and traces the Umami taste from sensory receptors on the tongue to the brain. The metabolism of glutamic acid, as revealed from recent literature, is described. A specific section is devoted to safety issues. In addition, effects of glutamic salts on nutrition and ingestive behaviours are shown to be potent. Animal and human works are treated separately, with special attention to the specific methods used in both cases. Future areas of research include further investigation of sensory physiology, role of glutamate as an excitatory substance in the brain, acquisition of food likes and impact on long-term food selection, food intake, and body weight control.
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Affiliation(s)
- F Bellisle
- INSERM U 341 and Service de Nutrition, Paris, France.
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31
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Messing B, Dutra SL, Thuillier F, Darmaun D, Desjeux JF. Whole-body protein metabolism assessed by leucine and glutamine kinetics in adult patients with active celiac disease. Metabolism 1998; 47:1429-33. [PMID: 9867069 DOI: 10.1016/s0026-0495(98)90065-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To assess the effect of increased renewal of intestinal epithelial cells on leucine and glutamine (Gln) turnover, 4-hour intravenous infusions of L-[1-(13)C]leucine and L-[2-(15)N]Gln were administered to five adult patients with active celiac disease in the postabsorptive state. There was a 35% increase in leucine flux (micromoles per kilogram per hour) in patients (117 +/- 17) compared with healthy controls (96 +/- 11, P < .03). Gln flux was increased by 13% in patients (377 +/- 35) versus controls (335 +/- 16, P < .04). These results suggest that active celiac disease, characterized by villous atrophy and crypt cell hyperplasia, is associated with a dramatic increase in whole-body protein breakdown as assessed by 13C-leucine, which may contribute per se to the protein malnutrition status of the patients. The increase in Gln utilization as assessed by L-[2-(15)N]Gln was moderate, but may have been offset due to the villose atrophy and ensuing reduced intestinal epithelial cell mass. The results are consistent with the concept that increased renewal of intestinal epithelial cells represents a sizable fraction of whole-body protein turnover and that Gln is an important fuel for epithelial intestinal cells in vivo.
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Affiliation(s)
- B Messing
- Saint-Lazare Hospital, INSERM U290, Paris, France
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32
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Yarasheski KE, Zachwieja JJ, Gischler J, Crowley J, Horgan MM, Powderly WG. Increased plasma gln and Leu Ra and inappropriately low muscle protein synthesis rate in AIDS wasting. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:E577-83. [PMID: 9755075 PMCID: PMC3177303 DOI: 10.1152/ajpendo.1998.275.4.e577] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Muscle protein wasting occurs in human immunodeficiency virus (HIV)-infected individuals and is often the initial indication of acquired immunodeficiency syndrome (AIDS). Little is known about the alterations in muscle protein metabolism that occur with HIV infection. Nine subjects with AIDS wasting (CD4 < 200/mm3), chronic stable opportunistic infections (OI), and >/=10% weight loss, fourteen HIV-infected men and one woman (CD4 > 200/mm3) without wasting or OI (asymptomatic), and six HIV-seronegative lean men (control) received a constant intravenous infusion of [1-13C]leucine (Leu) and [2-15N]glutamine (Gln). Plasma Leu and Gln rate of appearance (Ra), whole body Leu turnover, disposal and oxidation rates, and [13C]Leu incorporation rate into mixed muscle protein were assessed. Total body muscle mass/fat-free mass was greater in controls (53%) than in AIDS wasting (43%; P = 0.04). Fasting whole body proteolysis and synthesis rates were increased above control in the HIV+ asymptomatic group and in the AIDS-wasting group (P = 0. 009). Whole body Leu oxidation rate was greater in the HIV+ asymptomatic group than in the control and AIDS-wasting groups (P < 0.05). Fasting mixed muscle protein synthesis rate was increased in the asymptomatic subjects (0.048%/h; P = 0.01) but was similar in AIDS-wasting and control subjects (0.035 vs. 0.037%/h). Plasma Gln Ra was increased in AIDS-wasting subjects but was similar in control and HIV+ asymptomatic subjects (P < 0.001). These findings suggest that AIDS wasting results from 1) a preferential reduction in muscle protein, 2) a failure to sustain an elevated rate of mixed muscle protein synthesis while whole body protein synthesis is increased, and 3) a significant increase in Gln release into the circulation, probably from muscle. Several interesting explanations for the increased Gln Ra in AIDS wasting exist.
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Affiliation(s)
- K E Yarasheski
- Divisions of Metabolism, Endocrinology and Diabetes, and Infectious Disease, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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33
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Reeds PJ, Burrin DG, Davis TA, Stoll B. Amino acid metabolism and the energetics of growth. ARCHIV FUR TIERERNAHRUNG 1998; 51:187-97. [PMID: 9672716 DOI: 10.1080/17450399809381918] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The nonessential amino acids are involved in a large number of functions that are not directly associated with protein synthesis. Recent studies using a combination of transorgan balance and stable isotopic tracers have demonstrated that a substantial portion of the extra-splanchnic flux of glutamate, glutamine, glycine and cysteine derives from tissue synthesis. A key amino acid in this respect is glutamic acid. Little glutamic acid of dietary origin escapes metabolism in the small intestinal mucosa. Furthermore, because glutamic acid is the only amino acid that can be synthesized by mammals by reductive amination of a ketoacid, it is the ultimate nitrogen donor for the synthesis of other nonessential amino acids. Because the synthesis of glutamic acid and its product glutamine involve the expenditure of adenosine triphosphate (ATP), it seems possible that nonessential amino acid synthesis might have a significant bearing on the energetics of protein synthesis and, hence, of protein deposition. This paper discusses the topic of the energy cost of protein deposition, considers the metabolic physiology of amino acid oxidation and nonessential amino acid synthesis, and attempts to combine the information to speculate on the overall impact of amino acid metabolism on the energy exchanges of animals.
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Affiliation(s)
- P J Reeds
- USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, Tx. 77030-2600, USA
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Darmaun D, Welch S, Rini A, Sager BK, Altomare A, Haymond MW. Phenylbutyrate-induced glutamine depletion in humans: effect on leucine metabolism. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:E801-7. [PMID: 9612237 DOI: 10.1152/ajpendo.1998.274.5.e801] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The present study was designed to determine whether sodium phenylbutyrate (phi B) acutely induces a decrease in plasma glutamine in healthy humans, and, if so, will decrease estimates of whole body protein synthesis. In a first group of three healthy subjects, graded doses (0, 0.18, and 0.36 g.kg-1.day-1) of phi B were administered for 24 h before study: postabsorptive plasma glutamine concentration declined in a dose-dependent manner, achieving an approximately 25% decline for a dose of 0.36 g phi B.kg-1.day-1. A second group of six healthy adults received 5-h infusions of L-[1-14C]leucine and L-[1-13C]glutamine in the postabsorptive state on two separate days: 1) under baseline conditions and 2) after 24 h of oral treatment with phi B (0.36 g.kg-1.day-1) in a randomized order. The 24-h phenylbutyrate treatment was associated with 1) an approximately 26% decline in plasma glutamine concentration from 514 +/- 24 to 380 +/- 15 microM (means +/- SE; P < 0.01 with paired t-test) with no change in glutamine appearance rate or de novo synthesis; 2) no change in leucine appearance rate (Ra), an index of protein breakdown (123 +/- 7 vs. 117 +/- 5 mumol.kg-1.h-1; not significant); 3) an approximately 22% rise in leucine oxidation (Ox) from 23 +/- 2 to 28 +/- 2 mumol.kg-1.h-1 (P < 0.01), resulting in an approximately 11% decline in nonoxidative leucine disposal (NOLD = Ra-Ox), an index of protein synthesis, from 100 +/- 6 to 89 +/- 5 mumol.kg-1.h-1 (P < 0.05). The data suggest that, in healthy adults, 1) large doses of oral phenylbutyrate can be used as a "glutamine trap" to create a model of glutamine depletion; 2) a moderate decline in plasma glutamine does not enhance rates of endogenous glutamine production; and 3) a short-term depletion of plasma glutamine decrease estimates of whole body protein synthesis.
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Affiliation(s)
- D Darmaun
- Nemours Children's Clinic, Jacksonville, Florida 32207, USA
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Kreider ME, Stumvoll M, Meyer C, Overkamp D, Welle S, Gerich J. Steady-state and non-steady-state measurements of plasma glutamine turnover in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:E621-7. [PMID: 9142883 DOI: 10.1152/ajpendo.1997.272.4.e621] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
To compare steady-state glutamine turnover using nitrogen, carbon, and hydrogen tracers and to test the validity of monocompartmental equations to determine plasma glutamine turnover under non-steady-state conditions, we infused 10 normal postabsorptive volunteers simultaneously with [3,4-3H]glutamine, [2-15N]glutamine, and [U-14C]glutamine for 4 h to isotopic steady state. Eight of the ten subjects were subsequently infused in a stepwise fashion with exogenous glutamine. Plasma glutamine enrichment and specific activities fit a monoexponential model well (r = 0.89, 0.92, and 0.92 for [2-15N]-, [U-14C]-, and [3,4-3H]glutamine, respectively). Volumes of distribution for each tracer (362 +/- 58, 433 +/- 51, and 446 +/- 63 ml/kg) and the transfer rate constants (0.0224 +/- 0.0020, 0.0222 +/- 0.0020, and 0.0240 +/- 0.0023 min(-1)) for [2-15N]-, [U-14C]-, and [3,4-3H]glutamine, respectively, were not significantly different from one another. However, turnover of glutamine determined with [3,4-3H]glutamine (6.14 +/- 0.54 micromol x kg(-1) x min(-1)) exceeded that determined with [U-14C]glutamine (5.72 +/- 0.541 micromol x kg(-1) x min(-1); P < 0.03), which in turn exceeded that determined with [2-15N]glutamine (4.67 +/- 0.39 micromol x kg(-1) x min(-1), P < 0.01). The monocompartmental non-steady-state equations of both DeBodo et al. (DeBodo, R., R. Steele, A. Dunn, and J. Bishop. Rec. Prog. Horm. Res. 19: 445-448, 1963) and Finegood et al. (Finegood, D., R. Bergman, and M. Vranic. Diabetes 36: 914-924, 1987) yielded acceptable approximations of predicted rates of glutamine plasma appearance with deviations from predicted rates from 0.2 to 1.6% (Finegood et al.) and from 0.1 to 8.2% (DeBodo et al.). Use of a 0.75 pool fraction most closely approximated predicted rates.
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Affiliation(s)
- M E Kreider
- Department of Medicine, University of Rochester School of Medicine, New York 14642, USA
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Perriello G, Jorde R, Nurjhan N, Stumvoll M, Dailey G, Jenssen T, Bier DM, Gerich JE. Estimation of glucose-alanine-lactate-glutamine cycles in postabsorptive humans: role of skeletal muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:E443-50. [PMID: 7573421 DOI: 10.1152/ajpendo.1995.269.3.e443] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To evaluate transfer of carbon between plasma glucose and plasma alanine (glucose-alanine cycle) and lactate (Cori cycle), to assess the contribution of skeletal muscle to these cycles, and to determine whether a glucose-glutamine cycle exists in postabsorptive humans, we infused 11 normal overnight-fasted volunteers with [2-3H]glucose, [6-14C]glucose, and [3-13C]alanine to isotopic steady state and in 7 of these simultaneously measured forearm net balance, uptake, and release of labeled and unlabeled glucose, lactate, and alanine. We found that 40.9 +/- 3.3, 66.8 +/- 3.2, and 13.4 +/- 1.1%, respectively, of plasma alanine, lactate, and glutamine carbon came from plasma glucose. More plasma glucose was converted to plasma alanine than could be derived from plasma alanine (1.89 +/- 0.20 vs. 1.48 +/- 0.15 mumol.kg-1.min-1, P < 0.001). A similar direction of net carbon flux was found for lactate (8.5 vs. 4.2 mumol.kg-1.min-1), with only glutamine adding more carbon to plasma glucose than was received from it (1.0 vs. 0.75 mumol.kg-1.min-1). Skeletal muscle accounted for 50.2 +/- 3.9 and 45.5 +/- 5.7% of the overall appearance of alanine and lactate in plasma and 54.2 +/- 5.4 and 36.4 +/- 4.2% of their respective origins from plasma glucose. Skeletal muscle release of alanine and lactate that had been formed from plasma glucose accounted for 19.1 +/- 2.1 and 48.4 +/- 4.8%, respectively, of muscle glucose uptake and 42.4 +/- 5.5 and 49.9 +/- 5.8% of the overall release of alanine and lactate from muscle.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G Perriello
- Division of Endocrinology and Metabolism, Scripps Clinic, La Jolla, California 92037, USA
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Remer T, Manz F. Dietary protein as a modulator of the renal net acid excretion capacity: Evidence that an increased protein intake improves the capability of the kidney to excrete ammonium. J Nutr Biochem 1995. [DOI: 10.1016/0955-2863(95)00064-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Battezzati A, Brillon DJ, Matthews DE. Oxidation of glutamic acid by the splanchnic bed in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1995; 269:E269-76. [PMID: 7653544 DOI: 10.1152/ajpendo.1995.269.2.e269] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
[1,2-13C2]glutamate and [ring-2H5]phenylalanine were infused for 7 h into postabsorptive healthy subjects on two occasions. The tracer infusion was by the intravenous route for 3.5 h and by the nasogastric route for 3.5 h. The order of tracer infusion routes was switched between the two occasions. From the plasma tracer enrichment measurements at plateau during the intravenous and enteral infusion periods, we determined that 33 +/- 3% of the enterally delivered phenylalanine and 96 +/- 1% of the glutamate were removed on the first pass by the splanchnic bed; 78 +/- 3% of the enterally delivered [13C]glutamate tracer was recovered as exhaled CO2 compared with 79 +/- 2% of the intravenously infused tracer. The fraction of the enterally delivered tracer that was sequestered specifically on the first pass by the splanchnic bed was 75 +/- 2%. These results verify the previously reported large uptake of [15N]glutamate by the splanchnic bed [Matthews et al. Am. J. Physiol. 264 (Endocrinol. Metab. 27): E848-E854, 1993] and demonstrate that the uptake of tracer is not due to an artifactual loss of the 15N tracer by reversible transamination but to glutamate uptake for oxidation.
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Affiliation(s)
- A Battezzati
- Department of Medicine, Cornell University Medical College, New York, New York 10021, USA
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Manz F, Remer T, Decher-Spliethoff E, Höhler M, Kersting M, Kunz C, Lausen B. Effects of a high protein intake on renal acid excretion in bodybuilders. ZEITSCHRIFT FUR ERNAHRUNGSWISSENSCHAFT 1995; 34:10-5. [PMID: 7785291 DOI: 10.1007/bf01612779] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Bodybuilders often prefer a high protein diet to achieve maximum skeletal muscle hypertrophy. In this study the effect of a high protein diet on renal acid load and renal handling of proton excretion was studied comparing dietary intake and urinary ionograms in 37 male bodybuilders and 20 young male adults. Energy intake (+ 7%), protein intake (128 vs 88 g/d/1.73 m2), and renal net acid excretion (95 vs 64 mmol/d/1.73 m2) were higher in the bodybuilders than in the controls, however, urine-pH was only slightly lower (5.83 vs 6.12). In the bodybuilders renal ammonium excretion was higher at any given value of urine pH than in the controls. In a regression analysis protein intake proved to be an independent factor modulating the ratio between urine-pH and renal ammonium excretion. The concomitant increase of renal net acid excretion and maximum renal acid excretion capacity in periods of high protein intake appears to be a highly effective response of the kidney to a specific food intake leaving a large renal surplus capacity for an additional renal acid load.
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Affiliation(s)
- F Manz
- Forschungsinstitut für Kinderernährung, Dortmund
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Nurjhan N, Bucci A, Perriello G, Stumvoll M, Dailey G, Bier DM, Toft I, Jenssen TG, Gerich JE. Glutamine: a major gluconeogenic precursor and vehicle for interorgan carbon transport in man. J Clin Invest 1995; 95:272-7. [PMID: 7814625 PMCID: PMC295425 DOI: 10.1172/jci117651] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
To compare glutamine and alanine as gluconeogenic precursors, we simultaneously measured their systemic turnovers, clearances, and incorporation into plasma glucose, their skeletal muscle uptake and release, and the proportion of their appearance in plasma directly due to their release from protein in postabsorptive normal volunteers. We infused the volunteers with [U-14C] glutamine, [3-13C] alanine, [2H5] phenylalanine, and [6-3H] glucose to isotopic steady state and used the forearm balance technique. We found that glutamine appearance in plasma exceeded that of alanine (5.76 +/- 0.26 vs. 4.40 +/- 0.33 mumol.kg-1.min-1, P < 0.001), while alanine clearance exceeded glutamine clearance (14.7 +/- 1.3 vs. 9.3 +/- 0.8 ml.kg-1.min-1, P < 0.001). Glutamine appearance in plasma directly due to its release from protein was more than double that of alanine (2.45 +/- 0.25 vs. 1.16 +/- 0.12 mumol.kg-1.min-1, P < 0.001). Although overall carbon transfer to glucose from glutamine and alanine was comparable (3.53 +/- 0.24 vs 3.47 +/- 0.32 atoms.kg-1.min-1), nearly twice as much glucose carbon came from protein derived glutamine than alanine (1.48 +/- 0.15 vs 0.88 +/- 0.09 atoms.kg-1.min-1, P < 0.01). Finally, forearm muscle released more glutamine than alanine (0.88 +/- 0.05 vs 0.48 +/- 0.05 mumol.100 ml-1.min-1, P < 0.01). We conclude that in postabsorptive humans glutamine is quantitatively more important than alanine for transporting protein-derived carbon through plasma and adding these carbons to the glucose pool.
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Affiliation(s)
- N Nurjhan
- University of Rochester School of Medicine, New York 14642
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Castillo L, Ajami A, Branch S, Chapman TE, Yu YM, Burke JF, Young VR. Plasma arginine kinetics in adult man: response to an arginine-free diet. Metabolism 1994; 43:114-22. [PMID: 8289668 DOI: 10.1016/0026-0495(94)90166-x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
To explore the response of whole-body arginine metabolism to a change in arginine intake, plasma arginine kinetics were investigated in eight healthy adult men who received an L-amino acid diet supplying an Arg-rich or Arg-free intake for 6 days before undergoing a tracer study on day 7. The tracer protocol lasted for 8 hours. For the first 3 hours subjects remained in the postabsorptive (fasted) state, and during the following 5 hours they consumed small meals at 30-minute intervals. Primed continuous intravenous infusions of L-[guanidino-13C]arginine, L-[5,5,5-2H3]leucine, and [15N2]urea were administered to estimate plasma amino acid fluxes and the rate of urea production. For the fasted and fed states, plasma arginine fluxes (mumol.kg-1.h-1, mean +/- SD) were 69 +/- 8 and 87 +/- 12 (P < .01), respectively, for the Arg-rich diet and 63 +/- 14 and 51 +/- 7 (P < .01, from Arg-rich) for the Arg-free diet. Compared with the Arg-rich results, fed-state plasma arginine and ornithine concentrations were decreased (P < .01) and citrulline concentration was increased (P < .01) during the Arg-free diet period. Leucine fluxes and rates of urea production did not differ between the diet groups. The lower fed-state arginine flux in subjects receiving the Arg-free compared with the Arg-rich diet appears to be entirely due to the decreased rate of entry of arginine from the intestine in the former group.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- L Castillo
- Laboratory of Human Nutrition and the Clinical Research Center, Massachusetts Institute of Technology, Cambridge 02149
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