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Xing X, Sun Q, Wang R, Wang Y, Wang R. Impacts of glutamate, an exercise-responsive metabolite on insulin signaling. Life Sci 2024; 341:122471. [PMID: 38301875 DOI: 10.1016/j.lfs.2024.122471] [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: 11/28/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/03/2024]
Abstract
AIMS Disruption of the insulin signaling pathway leads to insulin resistance (IR). IR is characterized by impaired glucose and lipid metabolism. Elevated levels of circulating glutamate are correlated with metabolic indicators and may potentially predict the onset of metabolic diseases. Glutamate receptor antagonists have significantly enhanced insulin sensitivity, and improved glucose and lipid metabolism. Exercise is a well-known strategy to combat IR. The aims of our narrative review are to summarize preclinical and clinical findings to show the correlations between circulating glutamate levels, IR and metabolic diseases, discuss the causal role of excessive glutamate in IR and metabolic disturbance, and present an overview of the exercise-induced alteration in circulating glutamate levels. MATERIALS AND METHODS A literature search was conducted to identify studies on glutamate, insulin signaling, and exercise in the PubMed database. The search covered articles published from December 1955 to January 2024, using the search terms of "glutamate", "glutamic acid", "insulin signaling", "insulin resistance", "insulin sensitivity", "exercise", and "physical activity". KEY FINDINGS Elevated levels of circulating glutamate are correlated with IR. Excessive glutamate can potentially hinder the insulin signaling pathway through various mechanisms, including the activation of ectopic lipid accumulation, inflammation, and endoplasmic reticulum stress. Glutamate can also modify mitochondrial function through Ca2+ and induce purine degradation mediated by AMP deaminase 2. Exercise has the potential to decrease circulating levels of glutamate, which can be attributed to accelerated glutamate catabolism and enhanced glutamate uptake. SIGNIFICANCE Glutamate may act as a mediator in the exercise-induced improvement of insulin sensitivity.
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Affiliation(s)
- Xiaorui Xing
- School of Exercise and Health, Shanghai University of Sport, Shanghai 200438, China
| | - Qin Sun
- School of Exercise and Health, Shanghai University of Sport, Shanghai 200438, China
| | - Ruwen Wang
- School of Exercise and Health, Shanghai University of Sport, Shanghai 200438, China
| | - Yibing Wang
- School of Exercise and Health, Shanghai University of Sport, Shanghai 200438, China.
| | - Ru Wang
- School of Exercise and Health, Shanghai University of Sport, Shanghai 200438, China.
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Parstorfer M, Poschet G, Kronsteiner D, Brüning K, Friedmann-Bette B. Targeted Metabolomics in High Performance Sports: Differences between the Resting Metabolic Profile of Endurance- and Strength-Trained Athletes in Comparison with Sedentary Subjects over the Course of a Training Year. Metabolites 2023; 13:833. [PMID: 37512540 PMCID: PMC10383823 DOI: 10.3390/metabo13070833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/03/2023] [Accepted: 07/07/2023] [Indexed: 07/30/2023] Open
Abstract
Little is known about the metabolic differences between endurance and strength athletes in comparison with sedentary subjects under controlled conditions and about variation of the metabolome throughout one year. We hypothesized that (1) the resting metabolic profile differs between sedentary subjects and athletes and between perennially endurance- and strength-trained athletes and (2) varies throughout one year of training. We performed quantitative, targeted metabolomics (Biocrates MxP® Quant 500, Biocrates Life Sciences AG, Innsbruck, Austria) in plasma samples at rest in three groups of male adults, 12 strength-trained (weightlifters, 20 ± 3 years), 10 endurance-trained athletes (runners, 24 ± 3 years), and 12 sedentary subjects (25 ± 4 years) at the end of three training phases (regeneration, preparation, and competition) within one training year. Performance and anthropometric data showed significant (p < 0.05) differences between the groups. Metabolomic analysis revealed different resting metabolic profiles between the groups with acetylcarnitines, di- and triacylglycerols, and glycerophospho- and sphingolipids, as well as several amino acids as the most robust metabolites. Furthermore, we observed changes in free carnitine and 3-methylhistidine in strength-trained athletes throughout the training year. Regular endurance or strength training induces changes in the concentration of several metabolites associated with adaptations of the mitochondrial energy and glycolytic metabolism with concomitant changes in amino acid metabolism and cell signaling.
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Affiliation(s)
- Mario Parstorfer
- Department of Sports Medicine, University Hospital Heidelberg, 69120 Heidelberg, Germany
- Olympic Training Centre Rhine-Neckar, 69120 Heidelberg, Germany
| | - Gernot Poschet
- Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Dorothea Kronsteiner
- Institute of Medical Biometry and Informatics, University of Heidelberg, 69120 Heidelberg, Germany
| | - Kirsten Brüning
- Olympic Training Centre Rhine-Neckar, 69120 Heidelberg, Germany
| | - Birgit Friedmann-Bette
- Department of Sports Medicine, University Hospital Heidelberg, 69120 Heidelberg, Germany
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3
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Parthimos TP, Schulpis KH, Karousi AD, Loukas YL, Dotsikas Y. The relationship between neurotransmission-related amino acid blood concentrations and neuropsychological performance following acute exercise. APPLIED NEUROPSYCHOLOGY. ADULT 2022:1-15. [PMID: 35227132 DOI: 10.1080/23279095.2022.2043327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Amino acid neurotransmitters, including glutamate, phenylalanine, tyrosine, alanine, and glycine, underlie the majority of the excitatory and inhibitory neurotransmission in the nervous system, and acute exercise has been shown to modulate their concentrations. We aimed to determine whether any correlation exists between the above-mentioned amino acid blood concentrations and the neuropsychological performance after an acute exercise intervention. Sixty basketball players were randomly assigned to one of two experimental conditions: exercise or inactive resting. All participants underwent a comprehensive neuropsychological assessment and blood samples were taken on a Guthrie card before and after the end of the experimental conditions. Amino acid blood concentrations were significantly elevated and cognitive performance significantly improved post-exercise on specific neuropsychological assessments. Significant intervention × group interaction effects were apparent for Trail Making Test part-B [F(1,58) = 20.46, p < .0001, η2 = .26] and Digit Span Backwards [F(1,58) = 15.47, p < .0001, η2 = .21] neuropsychological assessments. Additionally, regression analysis indicated that tyrosine accounted for 38.0% of the variance in the Trail Making Test part-A test. These results suggest that elevated blood concentrations of neurotransmission-related amino acids are associated with improved neuropsychological performance after a single bout of high-intensity exercise.
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Affiliation(s)
- Theodore P Parthimos
- Division of Psychology, Faculty of Life and Health Sciences, De Montfort University, Leicester, UK
| | - Kleopatra H Schulpis
- Institute of Child Health, Research Center, "Aghia Sophia" Children's Hospital, Athens, Greece
| | - Alexandra D Karousi
- Department of Psychology, Human Sciences Research Centre, College of Life and Natural Sciences, University of Derby, Derby, UK
| | - Yannis L Loukas
- Laboratory of Pharm. Analysis, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Yannis Dotsikas
- Laboratory of Pharm. Analysis, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
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4
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Low-Dose Ammonium Preconditioning Enhances Endurance in Submaximal Physical Exercises. Sports (Basel) 2021; 9:sports9020029. [PMID: 33669436 PMCID: PMC7920466 DOI: 10.3390/sports9020029] [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: 12/30/2020] [Revised: 02/07/2021] [Accepted: 02/10/2021] [Indexed: 11/17/2022] Open
Abstract
Preconditioning is often used in medicine to protect organs from ischemic damage and in athletes to enhance the performances. We tested whether low-dose ammonium preconditioning (AMP) could have a beneficial effect on physical exercises (PE). We used Cardiopulmonary Exercise Testing (CPET) on a treadmill to investigate the effects of low-dose AMP on the physical exercise capacity of professional track and field athletes and tested twenty-five athletes. Because of the individual differences between athletes, we performed a preliminary treadmill test (Pre-test) and, according to the results, the athletes were randomly allocated into the AMP and control (placebo, PL) group based on the similarity of the total distance covered on a treadmill. In the AMP group, the covered distance increased (11.3 ± 3.6%, p < 0.02) compared to Pre-test. Similarly, AMP significantly increased O2 uptake volume—VO2 (4.6 ± 2.3%, p < 0.03) and pulmonary CO2 output—VCO2 (8.7 ± 2.8%, p < 0.01). Further, the basic blood parameters (pH, pO2, and lactate) shift was lower despite the greater physical exercise progress in the AMP group compared to Pre-test, whereas in the placebo group there were no differences between Pre-test and Load-test. Importantly, the AMP significantly increased red blood cell count (6.8 ± 2.0%, p < 0.01) and hemoglobin concentration (5.3 ± 1.9%, p < 0.01), which might explain the beneficial effects in physical exercise progress. For the first time, we showed that low-dose AMP had clear beneficial effects on submaximal PE.
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5
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Khan TA, Sievenpiper JL, Fernstrom JD. Commentary: Dietary Glutamic Acid, Obesity, and Depressive Symptoms in Patients With Schizophrenia. Front Psychiatry 2021; 12:725786. [PMID: 34721103 PMCID: PMC8551475 DOI: 10.3389/fpsyt.2021.725786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 08/27/2021] [Indexed: 11/29/2022] Open
Affiliation(s)
- Tauseef A Khan
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.,Toronto 3D Knowledge Synthesis and Clinical Trials Unit, St. Michael's Hospital, Toronto, ON, Canada.,Clinical Nutrition and Risk Factor Modification Centre, St. Michael's Hospital, Toronto, ON, Canada
| | - John L Sievenpiper
- Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.,Toronto 3D Knowledge Synthesis and Clinical Trials Unit, St. Michael's Hospital, Toronto, ON, Canada.,Clinical Nutrition and Risk Factor Modification Centre, St. Michael's Hospital, Toronto, ON, Canada.,Division of Endocrinology & Metabolism, Department of Medicine, St. Michael's Hospital, Toronto, ON, Canada.,Scientist, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada
| | - John D Fernstrom
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States.,Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
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6
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Türküner MS, Özcan F. Monosodium glutamate restricts the adipogenic potential of 3T3‐L1 preadipocytes through mitotic clonal expansion. Cell Biol Int 2019; 44:744-754. [DOI: 10.1002/cbin.11269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Accepted: 11/23/2019] [Indexed: 01/10/2023]
Affiliation(s)
- Mehmet Soner Türküner
- Department of Molecular Biology and Genetics, Graduate School of Natural and Applied Sciences Gebze Technical University (GTU) Gebze Kocaeli 41400 Turkey
| | - Ferruh Özcan
- Department of Molecular Biology and Genetics, Graduate School of Natural and Applied Sciences Gebze Technical University (GTU) Gebze Kocaeli 41400 Turkey
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7
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Barnes T, Di Sebastiano KM, Vlavcheski F, Quadrilatero J, Tsiani EL, Mourtzakis M. Glutamate increases glucose uptake in L6 myotubes in a concentration- and time-dependent manner that is mediated by AMPK. Appl Physiol Nutr Metab 2018; 43:1307-1313. [PMID: 29847739 DOI: 10.1139/apnm-2018-0174] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Various in vivo studies have investigated the insulin response that is elicited when glutamate is elevated in circulation or in a given tissue; fewer studies have investigated the effects of glutamate on glucose uptake and handling. Glutamate ingestion in humans can attenuate rises in blood glucose following a carbohydrate load in the absence of increases in serum insulin concentrations. However, the underlying mechanisms have yet to be investigated. To elucidate the effects of glutamate on glucose handling in skeletal muscle tissue, differentiated rat L6 myocytes were treated with glutamate, and glucose uptake was assessed with the use of 2-[3H]-deoxy-d-glucose ([3H]-2-DG). Cells treated with 2 mmol/L glutamate experienced the greatest increase in [3H]-2-DG uptake relative to the control condition (177% ± 2% of control, P < 0.001) and the uptake was similar to that of metformin (184% ± 4%, P < 0.001). In line with these findings, differentiated glucose transporter 4 (GLUT4)-overexpressing myotubes treated with 2 mmol/L glutamate displayed significantly increased GLUT4 translocation when compared with the control condition (159% ± 8% of control, P < 0.001) and to an extent similar to that of insulin and metformin (181% ± 7% and 159% ± 12%, respectively). An AMP-activated protein kinase (AMPK) inhibitor (Compound C) abolished the glutamate-stimulated glucose uptake (98% ± 12% of control), and Western blotting revealed significantly elevated AMPK phosphorylation (278% ± 17% of control, P < 0.001) by glutamate. Our findings suggest that when muscle cells are exposed to increased glutamate concentrations, glucose uptake into these cells is augmented through AMPK activation, through mechanisms distinct from those of insulin and leucine.
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Affiliation(s)
- Tyler Barnes
- a Department of Kinesiology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada
| | - Katie M Di Sebastiano
- a Department of Kinesiology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada
| | - Filip Vlavcheski
- b Department of Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Joe Quadrilatero
- a Department of Kinesiology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada
| | | | - Marina Mourtzakis
- a Department of Kinesiology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada
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8
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Acute effects of monosodium glutamate addition to whey protein on appetite, food intake, blood glucose, insulin and gut hormones in healthy young men. Appetite 2018; 120:92-99. [DOI: 10.1016/j.appet.2017.08.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 06/07/2017] [Accepted: 08/19/2017] [Indexed: 12/16/2022]
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9
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Matthews JC, Huang J, Rentfrow G. High-affinity glutamate transporter and glutamine synthetase content in longissimus dorsi and adipose tissues of growing Angus steers differs among suckling, weanling, backgrounding, and finishing production stages1. J Anim Sci 2016; 94:1267-75. [DOI: 10.2527/jas.2015-9901] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- J. C. Matthews
- Department of Animal and Food Sciences, University of Kentucky, Lexington 40546
| | - J. Huang
- Department of Animal and Food Sciences, University of Kentucky, Lexington 40546
| | - G. Rentfrow
- Department of Animal and Food Sciences, University of Kentucky, Lexington 40546
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10
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Camerino SRAES, Lima RCP, França TCL, Herculano EDA, Rodrigues DSA, Gouveia MGDS, Cameron LC, Prado ES. Keto analogue and amino acid supplementation and its effects on ammonemia and performance under thermoneutral conditions. Food Funct 2016; 7:872-80. [DOI: 10.1039/c5fo01054c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Keto analogue and amino acid supplementation decreases ammonemia during exercise without affecting performance.
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Affiliation(s)
| | | | | | | | | | | | - L. C. Cameron
- Laboratory of Protein Biochemistry
- Federal University of State of Rio de Janeiro
- Rio de Janeiro
- Rio de Janeiro
- Brazil
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11
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Glutamate supplementation is associated with improved glucose metabolism following carbohydrate ingestion in healthy males. Br J Nutr 2013; 110:2165-72. [DOI: 10.1017/s0007114513001633] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Glutamate is linked to the glycolytic process, particularly when co-ingested with carbohydrate, but its effects on glucose metabolism are poorly characterised. The present study aimed to (1) specifically examine the effects of carbohydrate administration on circulating glutamate concentrations and (2) investigate the effect of increased glutamate availability, independent of carbohydrate ingestion, on glucose metabolism. A total of nine participants underwent four trials: (1) glutamate supplement+carbohydrate drink (GLU+CHO); (2) glutamate supplement+placebo drink (GLU); (3) placebo supplement+carbohydrate drink (CHO); (4) placebo supplement+placebo drink (CON). Following a fasting blood sample, participants ingested monosodium l-glutamate (MSG; 150 mg/kg body weight) or placebo capsules at each trial followed by a 75 g carbohydrate or a non-energy placebo drink 30 min later. Blood samples were taken at 0, 10, 20, 30, 40, 50, 60, 75, 90, 105 and 120 min. Plasma glutamate concentrations were significantly elevated relative to baseline during the GLU (approximately 10-fold) and GLU+CHO trials (approximately 6-fold). The glucose response to a carbohydrate load was blunted when glutamate was increased in the circulation (peak serum glucose: 5·50 (se 0·54) mmol/l during the GLU+CHO trial v. 7·69 (se 0·53) mmol/l during the CHO trial, P< 0·05). On average, c-peptide results revealed that insulin secretion did not differ between the GLU+CHO and CHO trials; however, four participants demonstrated increased insulin secretion during the GLU+CHO trial and five participants demonstrated decreased insulin secretion under the same conditions. In conclusion, when administration is staggered, MSG and carbohydrate supplementation can be used to manipulate plasma glutamate; however, future studies should control for this dichotomous insulin response.
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12
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Lee A, Anderson AR, Stevens M, Beasley S, Barnett NL, Pow DV. Excitatory amino acid transporter 5 is widely expressed in peripheral tissues. Eur J Histochem 2013; 57:e11. [PMID: 23549460 PMCID: PMC3683608 DOI: 10.4081/ejh.2013.e11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/15/2013] [Accepted: 01/15/2013] [Indexed: 11/24/2022] Open
Abstract
It is routinely stated in the literature that Excitatory Amino Acid Transporter 5 (EAAT5) is a retina-specific glutamate transporter. EAAT5 is expressed by retinal photoreceptors and bipolar cells, where it serves as a slow transporter and as an inhibitory glutamate receptor, the latter role is due to the gating of a large chloride conductance. The dogma of an exclusively retinal distribution has arisen because Northern blot analyses have previously shown only modest hybridisation in non-retinal tissues. Others have re-interpreted this as indicating that EAAT5 was only present in retinal tissues. However, this view appears to be erroneous; recent evidence demonstrating abundant expression of EAAT5 in rat testis prompted us to re-examine this dogma. A new antibody was developed to an intracellular loop region of rat EAAT5. This new tool, in concert with RT-PCR and sequencing, demonstrated that EAAT5 is widely distributed at the mRNA and protein levels in many non-nervous tissues including liver, kidney, intestine, heart, lung, and skeletal muscle. We conclude that EAAT5 is a widely distributed protein. Whether it functions in all locations as a glutamate transporter, or mainly as a glutamate-gated chloride conductance, remains to be determined.
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Affiliation(s)
- A Lee
- UQ Centre for Clinical Research, The University of Queensland, Brisbane, QLD, Australia, Queensland, Australia.
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13
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Liu Y, Lange R, Langanky J, Hamma T, Yang B, Steinacker JM. Improved training tolerance by supplementation with α-Keto acids in untrained young adults: a randomized, double blind, placebo-controlled trial. J Int Soc Sports Nutr 2012; 9:37. [PMID: 22857787 PMCID: PMC3467174 DOI: 10.1186/1550-2783-9-37] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 07/24/2012] [Indexed: 11/10/2022] Open
Abstract
Background Exercise causes a variety of physiological and metabolic changes that can in turn reduce exercise tolerance. One of the potential mechanisms responsible for fatigue is “exercise-induced hyperammonemia”. Previous studies have shown that supplementation with amino acids can increase training tolerance. The α-keto acids are biochemical analogs of amino acids and can be converted to amino acids through transamination, thus reducing the cellular ammonia level. This double blind, placebo-controlled study was designed to investigate the effects of α-keto acid supplementation (KAS) on training tolerance, training effect, and stress-recovery state. Methods Thirty-three untrained young male adults underwent four weeks of training (5 sessions/week; 30 minutes running at the individual anaerobic threshold followed by 3 x 3 minute sprints/each session). Throughout the 4 weeks of training and one week of recovery, subjects took α-ketoglutarate (AKG group, 0.2 g/kg/d, n = 9), branched-chain keto acids (BCKA group, 0.2 g/kg/d, n = 12) or isocaloric placebo (control group, n = 12) daily. Results The 4th week training volume, maximum power output and muscle torque were higher in the AKG group (175 ± 42 min, 412 ± 49 Watts and 293 ± 58 Newton meters, respectively, P<0.05) and the BCKA group (158 ± 35, 390 ± 29 and 273 ± 47, P<0.05) than in the control group (92 ± 70, 381 ± 67 and 233 ± 43). The general stress and emotional exhaustion as assessed by the rest-stress-questionnaire-sport after the 3rd week of training increased significantly in the control group (P<0.05), but not in the KAS groups. Conclusions Under KAS, subjects could bear a higher training volume and reach a higher power output and peak muscle torque, accompanied by a better stress-recovery-state. Thus, KAS improves exercise tolerance and training effects along with a better stress-recovery state. Whether the improved training tolerance by KAS is associated with effects on ammonia homeostasis requires further observation.
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Affiliation(s)
- Yuefei Liu
- Section of Sports and Rehabilitation Medicine, Department of Internal Medicine II, University of Ulm, Ulm, D-89070, Germany.
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14
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Davalli AM, Perego C, Folli FB. The potential role of glutamate in the current diabetes epidemic. Acta Diabetol 2012; 49:167-83. [PMID: 22218826 DOI: 10.1007/s00592-011-0364-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 12/19/2011] [Indexed: 12/27/2022]
Abstract
In the present article, we propose the perspective that abnormal glutamate homeostasis might contribute to diabetes pathogenesis. Previous reports and our recent data indicate that chronically high extracellular glutamate levels exert direct and indirect effects that might participate in the progressive loss of β-cells occurring in both T1D and T2D. In addition, abnormal glutamate homeostasis may impact all the three accelerators of the "accelerator hypothesis" and could partially explain the rising frequency of T1D and T2D.
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Affiliation(s)
- Alberto M Davalli
- Diabetes and Endocrinology Unit, Department of Internal Medicine, San Raffaele Scientific Institute, 20132, Milan, Italy.
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15
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Cheng S, Rhee EP, Larson MG, Lewis GD, McCabe EL, Shen D, Palma MJ, Roberts LD, Dejam A, Souza AL, Deik AA, Magnusson M, Fox CS, O'Donnell CJ, Vasan RS, Melander O, Clish CB, Gerszten RE, Wang TJ. Metabolite profiling identifies pathways associated with metabolic risk in humans. Circulation 2012; 125:2222-31. [PMID: 22496159 DOI: 10.1161/circulationaha.111.067827] [Citation(s) in RCA: 459] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Although metabolic risk factors are known to cluster in individuals who are prone to developing diabetes mellitus and cardiovascular disease, the underlying biological mechanisms remain poorly understood. METHODS AND RESULTS To identify pathways associated with cardiometabolic risk, we used liquid chromatography/mass spectrometry to determine the plasma concentrations of 45 distinct metabolites and to examine their relation to cardiometabolic risk in the Framingham Heart Study (FHS; n=1015) and the Malmö Diet and Cancer Study (MDC; n=746). We then interrogated significant findings in experimental models of cardiovascular and metabolic disease. We observed that metabolic risk factors (obesity, insulin resistance, high blood pressure, and dyslipidemia) were associated with multiple metabolites, including branched-chain amino acids, other hydrophobic amino acids, tryptophan breakdown products, and nucleotide metabolites. We observed strong associations of insulin resistance traits with glutamine (standardized regression coefficients, -0.04 to -0.22 per 1-SD change in log-glutamine; P<0.001), glutamate (0.05 to 0.14; P<0.001), and the glutamine-to-glutamate ratio (-0.05 to -0.20; P<0.001) in the discovery sample (FHS); similar associations were observed in the replication sample (MDC). High glutamine-to-glutamate ratio was associated with lower risk of incident diabetes mellitus in FHS (odds ratio, 0.79; adjusted P=0.03) but not in MDC. In experimental models, administration of glutamine in mice led to both increased glucose tolerance (P=0.01) and decreased blood pressure (P<0.05). CONCLUSIONS Biochemical profiling identified circulating metabolites not previously associated with metabolic traits. Experimentally interrogating one of these pathways demonstrated that excess glutamine relative to glutamate, resulting from exogenous administration, is associated with reduced metabolic risk in mice.
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Affiliation(s)
- Susan Cheng
- Cardiology Division, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114, USA
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16
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Baad-Hansen L, Cairns B, Ernberg M, Svensson P. Effect of systemic monosodium glutamate (MSG) on headache and pericranial muscle sensitivity. Cephalalgia 2010; 30:68-76. [PMID: 19438927 DOI: 10.1111/j.1468-2982.2009.01881.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
We conducted a double-blinded, placebo-controlled, crossover study to investigate the occurrence of adverse effects such as headache as well as pain and mechanical sensitivity in pericranial muscles after oral administration of monosodium glutamate (MSG). In three sessions, 14 healthy men drank sugar-free soda that contained either MSG (75 or 150 mg/kg) or NaCl (24 mg/kg, placebo). Plasma glutamate level, pain, pressure pain thresholds and tolerance levels, blood pressure (BP), heart rate and reported adverse effects were assessed for 2 h. No muscle pain or robust changes in mechanical sensitivity were detected, but there was a significant increase in reports of headache and subjectively reported pericranial muscle tenderness after MSG. Systolic BP was elevated in the high MSG session compared with low MSG and placebo. These findings add new information to the concept of MSG headache and craniofacial pain sensitivity.
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Affiliation(s)
- L Baad-Hansen
- Department of Clinical Oral Physiology, School of Dentistry, University of Aarhus, Aarhus, Denmark.
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17
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Acute supplementation with keto analogues and amino acids in rats during resistance exercise. Br J Nutr 2010; 104:1438-42. [DOI: 10.1017/s0007114510002321] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
During exercise, ammonia levels are related to the appearance of both central and peripheral fatigue. Therefore, controlling the increase in ammonia levels is an important strategy in ameliorating the metabolic response to exercise and in improving athletic performance. Free amino acids can be used as substrates for ATP synthesis that produces ammonia as a side product. Keto analogues act in an opposite way, being used to synthesise amino acids whilst decreasing free ammonia in the blood. Adult male rats were divided into four groups based on receiving either keto analogues associated with amino acids (KAAA) or a placebo and resistance exercise or no exercise. There was an approximately 40 % increase in ammonaemia due to KAAA supplementation in resting animals. Exercise increased ammonia levels twofold with respect to the control, with a smaller increase (about 20 %) in ammonia levels due to exercise. Exercise itself causes a significant increase in blood urea levels (17 %). However, KAAA reduced blood urea levels to 75 % of the pre-exercise values. Blood urate levels increased 28 % in the KAAA group, independent of exercise. Supplementation increased glucose levels by 10 % compared with control animals. Exercise did not change glucose levels in either the control or supplemented groups. Exercise promoted a 57 % increase in lactate levels in the control group. Supplementation promoted a twofold exercise-induced increase in blood lactate levels. The present results suggest that an acute supplementation of KAAA can decrease hyperammonaemia induced by exercise.
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Wilkinson DJ, Smeeton NJ, Watt PW. Ammonia metabolism, the brain and fatigue; revisiting the link. Prog Neurobiol 2010; 91:200-19. [PMID: 20138956 DOI: 10.1016/j.pneurobio.2010.01.012] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 01/27/2010] [Accepted: 01/29/2010] [Indexed: 12/15/2022]
Abstract
This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.
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Affiliation(s)
- Daniel J Wilkinson
- Department of Sport and Exercise Science, Chelsea School, University of Brighton, 30 Carlisle Road, Eastbourne, UK.
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Hackl S, van den Hoven R, Zickl M, Spona J, Zentek J. The effects of short intensive exercise on plasma free amino acids in standardbred trotters. J Anim Physiol Anim Nutr (Berl) 2009; 93:165-73. [DOI: 10.1111/j.1439-0396.2007.00801.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Bougnères P, Valleron AJ. Causes of early-onset type 1 diabetes: toward data-driven environmental approaches. ACTA ACUST UNITED AC 2009; 205:2953-7. [PMID: 19075294 PMCID: PMC2605242 DOI: 10.1084/jem.20082622] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A new study reveals distinctive metabolic changes that precede the development of type 1 diabetes (T1D), tossing a stone into the quiet waters of T1D immunology and genetics. The causes of these metabolic changes and their relationship to autoimmunity and beta cell destruction are not yet known, but the identification of a metabolic phenotype linked to susceptibility to type I diabetes may help pave the way to a new era of investigation of T1D causality.
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Affiliation(s)
- Pierre Bougnères
- Department of Pediatric Endocrinology and U561 INSERM, Saint Vincent de Paul Hospital, Paris V René Descartes University, Paris, France.
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21
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Mourtzakis M, Graham TE, González-Alonso J, Saltin B. Glutamate availability is important in intramuscular amino acid metabolism and TCA cycle intermediates but does not affect peak oxidative metabolism. J Appl Physiol (1985) 2008; 105:547-54. [DOI: 10.1152/japplphysiol.90394.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle glutamate is central to reactions producing 2-oxoglutarate, a tricarboxylic acid (TCA) cycle intermediate that essentially expands the TCA cycle intermediate pool during exercise. Paradoxically, muscle glutamate drops ∼40–80% with the onset of exercise and 2-oxoglutarate declines in early exercise. To investigate the physiological relationship between glutamate, oxidative metabolism, and TCA cycle intermediates (i.e., fumarate, malate, 2-oxoglutarate), healthy subjects trained (T) the quadriceps of one thigh on the single-legged knee extensor ergometer (1 h/day at 70% maximum workload for 5 days/wk), while their contralateral quadriceps remained untrained (UT). After 5 wk of training, peak oxygen consumption (V̇o2peak) in the T thigh was greater than that in the UT thigh ( P < 0.05); V̇o2peak was not different between the T and UT thighs with glutamate infusion. Peak exercise under control conditions revealed a greater glutamate uptake in the T thigh compared with rest (7.3 ± 3.7 vs. 1.0 ± 0.1 μmol·min−1·kg wet wt−1, P < 0.05) without increase in TCA cycle intermediates. In the UT thigh, peak exercise (vs. rest) induced an increase in fumarate (0.33 ± 0.07 vs. 0.02 ± 0.01 mmol/kg dry wt (dw), P < 0.05) and malate (2.2 ± 0.4 vs. 0.5 ± 0.03 mmol/kg dw, P < 0.05) and a decrease in 2-oxoglutarate (12.2 ± 1.6 vs. 32.4 ± 6.8 μmol/kg dw, P < 0.05). Overall, glutamate infusion increased arterial glutamate ( P < 0.05) and maintained this increase. Glutamate infusion coincided with elevated fumarate and malate ( P < 0.05) and decreased 2-oxoglutarate ( P < 0.05) at peak exercise relative to rest in the T thigh; there were no further changes in the UT thigh. Although glutamate may have a role in the expansion of the TCA cycle, glutamate and TCA cycle intermediates do not directly affect V̇o2peak in either trained or untrained muscle.
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Rutten EPA, Engelen MPKJ, Gosker H, Bast A, Cosemans K, Vissers YLJ, Wouters EFM, Deutz NEP, Schols AMWJ. Metabolic and functional effects of glutamate intake in patients with chronic obstructive pulmonary disease (COPD). Clin Nutr 2008; 27:408-15. [PMID: 18433945 DOI: 10.1016/j.clnu.2008.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Revised: 02/21/2008] [Accepted: 03/04/2008] [Indexed: 11/28/2022]
Abstract
BACKGROUND & AIMS Patients with chronic obstructive pulmonary disease (COPD) often suffer from skeletal muscle weakness due to muscle wasting and altered muscle metabolism. Decreased muscle glutamate concentration in COPD is consistently reported and is associated with decreased muscle glutathione concentration and early lactic acidosis. We hypothesized that an increased availability of glutamate via glutamate ingestion increases muscle glutamate concentration leading to acute improvements in skeletal muscle energy metabolism and function. METHODS Two experiments were conducted. In experiment 1, in two groups of 6 male COPD patients (FEV(1): 44.8+/-3.4%pred) and 6 healthy controls, blood samples and muscle biopsies were taken at 0 and 80 min after repeated glutamate (30 mg/kg BW) or control ingestion (1.25 ml/kg BW), and after 20 min cycling at 50% peak workload. In experiment 2, in 10 COPD patients (FEV(1): 36.1+/-2.5%pred), the effect of the two drinks was tested on cycle endurance time and contractile quadriceps fatigue measured by magnetic stimulation before and after cycling at 75% peak workload. RESULTS Glutamate ingestion increased plasma (p<0.01) but not muscle glutamate concentration. Muscle total and reduced glutathione and plasma lactate concentration were not affected by glutamate ingestion. Glutamate ingestion did not influence contractile muscle fatigue and endurance time. CONCLUSION Continuous oral glutamate ingestion for 80 min did not lead to an acute effect on skeletal muscle substrate metabolism and muscle performance in COPD patients and in age-matched healthy controls.
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Affiliation(s)
- Erica P A Rutten
- Department of Respiratory Medicine, University of Maastricht, Maastricht, the Netherlands.
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Bassini-Cameron A, Monteiro A, Gomes A, Werneck-de-Castro JPS, Cameron L. Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way. Br J Sports Med 2008; 42:260-6. [DOI: 10.1136/bjsm.2007.040378] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Carvalho-Peixoto J, Alves R, Cameron LC. Glutamine and carbohydrate supplements reduce ammonemia increase during endurance field exercise. Appl Physiol Nutr Metab 2007; 32:1186-90. [DOI: 10.1139/h07-091] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Blood ammonia concentration increases during endurance exercise and has been proposed as a cause for both peripheral and central fatigue. We examined the impact of glutamine and (or) carbohydrate supplementation on ammonemia in high-level runners. Fifteen men in pre-competitive training ran 120 min (~34 km) outdoors on 4 occasions. On the first day, the 15 athletes ran without the use of supplements and blood samples were taken every 30 min. After that, each day for 4 d before the next 3 exercise trials, we supplemented the athletes’ normal diets in bolus with carbohydrate (1 g·kg–1·d–1), glutamine (70 mg·kg–1·d–1), or a combination of both in a double-blind study. Blood ammonia level was determined before the run and every 30 min during the run. During the control trial ammonia increased progressively to approximately 70% above rest concentration. Following supplementation, independent of treatment, ammonia was not different (p > 0.05) for the first 60 min, but for the second hour it was lower than in the control (p < 0.05). Supplementation in high-level, endurance athletes reduced the accumulation of blood ammonia during prolonged, strenuous exercise in a field situation.
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Affiliation(s)
- Jacqueline Carvalho-Peixoto
- Laboratório de Bioquímica de Proteínas, Universidade Federal do Estado do Rio de Janeiro, Brazil
- Programa de Pós-Graduação em Ciência da Motricidade Humana, Universidade Castelo Branco – Rio de Janeiro, Brazil
- Instituto de Genética e Bioquímica, Universidade Federal de Uberlândia, Brazil
| | - Robson Cardilo Alves
- Laboratório de Bioquímica de Proteínas, Universidade Federal do Estado do Rio de Janeiro, Brazil
- Programa de Pós-Graduação em Ciência da Motricidade Humana, Universidade Castelo Branco – Rio de Janeiro, Brazil
- Instituto de Genética e Bioquímica, Universidade Federal de Uberlândia, Brazil
| | - Luiz-Claudio Cameron
- Laboratório de Bioquímica de Proteínas, Universidade Federal do Estado do Rio de Janeiro, Brazil
- Programa de Pós-Graduação em Ciência da Motricidade Humana, Universidade Castelo Branco – Rio de Janeiro, Brazil
- Instituto de Genética e Bioquímica, Universidade Federal de Uberlândia, Brazil
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Böning D, Klarholz C, Himmelsbach B, Hütler M, Maassen N. Causes of differences in exercise-induced changes of base excess and blood lactate. Eur J Appl Physiol 2006; 99:163-71. [PMID: 17115177 DOI: 10.1007/s00421-006-0328-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/05/2006] [Indexed: 11/25/2022]
Abstract
It has been concluded from comparisons of base excess (BE) and lactic acid (La) concentration changes in blood during exercise-induced acidosis that more H+ than La- leave the muscle and enter interstitial fluid and blood. To examine this, we performed incremental cycle tests in 13 untrained males and measured acid-base status and [La] in arterialized blood, plasma, and red cells until 21 min after exhaustion. The decrease of actual BE (-deltaABE) was 2.2 +/- 0.5 (SEM) mmol l(-1) larger than the increase of [La]blood at exhaustion, and the difference rose to 4.8 +/- 0.5 mmol l(-1) during the first minutes of recovery. The decrease of standard BE (SBE), a measure of mean BE of interstitial fluid (if) and blood, however, was smaller than the increase of [La] in the corresponding volume (delta[La](if+blood)) during exercise and only slightly larger during recovery. The discrepancy between -deltaABE and delta[La]blood mainly results from the Donnan effect hindering the rise of [La]erythrocyte to equal values like [La]plasma. The changing Donnan effect during acidosis causes that Cl- from the interstitial fluid enter plasma and erythrocytes in exchange for HCO3(-). A corresponding amount of La- remains outside the blood. SBE is not influenced by ion shifts among these compartments and therefore is a rather exact measure of acid movements across tissue cell membranes, but changes have been compared previously to delta[La]blood instead to delta[La](if+blood). When performing correct comparisons and considering Cl-/HCO3(-) exchange between erythrocytes and extracellular fluid, neither the use of deltaABE nor of deltaSBE provides evidence for differences in H+ and La- transport across the tissue cell membranes.
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Affiliation(s)
- Dieter Böning
- Institute of Sports Medicine, Charité, University Medicine Berlin, Arnimallee 22, 14195, Berlin, Germany.
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Beyreuther K, Biesalski HK, Fernstrom JD, Grimm P, Hammes WP, Heinemann U, Kempski O, Stehle P, Steinhart H, Walker R. Consensus meeting: monosodium glutamate - an update. Eur J Clin Nutr 2006; 61:304-13. [PMID: 16957679 DOI: 10.1038/sj.ejcn.1602526] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Update of the Hohenheim consensus on monosodium glutamate from 1997: Summary and evaluation of recent knowledge with respect to physiology and safety of monosodium glutamate. DESIGN Experts from a range of relevant disciplines received and considered a series of questions related to aspects of the topic. SETTING University of Hohenheim, Stuttgart, Germany. METHOD The experts met and discussed the questions and arrived at a consensus. CONCLUSION Total intake of glutamate from food in European countries is generally stable and ranged from 5 to 12 g/day (free: ca. 1 g, protein-bound: ca. 10 g, added as flavor: ca. 0.4 g). L-Glutamate (GLU) from all sources is mainly used as energy fuel in enterocytes. A maximum intake of 6.000 [corrected] mg/kg body weight is regarded as safe. The general use of glutamate salts (monosodium-L-glutamate and others) as food additive can, thus, be regarded as harmless for the whole population. Even in unphysiologically high doses GLU will not trespass into fetal circulation. Further research work should, however, be done concerning the effects of high doses of a bolus supply at presence of an impaired blood brain barrier function. In situations with decreased appetite (e.g., elderly persons) palatability can be improved by low dose use of monosodium-L-glutamate.
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MacInnes A, Timmons JA. Metabolic adaptations to repeated periods of contraction with reduced blood flow in canine skeletal muscle. BMC PHYSIOLOGY 2005; 5:11. [PMID: 16018808 PMCID: PMC1187899 DOI: 10.1186/1472-6793-5-11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2005] [Accepted: 07/14/2005] [Indexed: 11/16/2022]
Abstract
Background Patients suffering from Intermittent Claudication (IC) experience repeated periods of muscle contraction with low blood flow, throughout the day and this may contribute to the hypothesised skeletal muscle abnormalities. However, no study has evaluated the consequences of intermittent contraction with low blood flow on skeletal muscle tissue. Our aim was to generate this basic physiological data, determining the 'normal' response of healthy skeletal muscle tissue. We specifically proposed that the metabolic responses to contraction would be modified under such circumstances, revealing endogenous strategies engaged to protect the muscle adenine nucleotide pool. Utilizing a canine gracilis model (n = 9), the muscle was stimulated to contract (5 Hz) for three 10 min periods (separated by 10 min rest) under low blood flow conditions (80% reduced), followed by 1 hr recovery and then a fourth period of 10 min stimulation. Muscle biopsies were obtained prior to and following the first and fourth contraction periods. Direct arterio-venous sampling allowed for the calculation of muscle metabolite efflux and oxygen consumption. Results During the first period of contraction, [ATP] was reduced by ~30%. During this period there was also a 10 fold increase in muscle lactate concentration and a substantial increase in muscle lactate and ammonia efflux. Subsequently, lactate efflux was similar during the first three periods, while ammonia efflux was reduced by the third period. Following 1 hr recovery, muscle lactate and phosphocreatine concentrations had returned to resting values, while muscle [ATP] remained 20% lower. During the fourth contraction period no ammonia efflux or change in muscle ATP content occured. Despite such contrasting metabolic responses, muscle tension and oxygen consumption were identical during all contraction periods from 3 to 10 min. Conclusion repeated periods of muscle contraction, with low blood flow, results in cessation of muscle ammonia production which is suggestive of a dramatic reduction in flux through AMP deaminase.
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Affiliation(s)
- Alan MacInnes
- Cardiovascular Research Department, Pfizer Global R&D, St. Louis, MO63017, USA
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - James A Timmons
- Cardiovascular Research Department, Pfizer Global R&D, St. Louis, MO63017, USA
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
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Rutten EPA, Engelen MPKJ, Schols AMWJ, Deutz NEP. Skeletal muscle glutamate metabolism in health and disease: state of the art. Curr Opin Clin Nutr Metab Care 2005; 8:41-51. [PMID: 15585999 DOI: 10.1097/00075197-200501000-00007] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
PURPOSE OF REVIEW Glutamate is an amino acid of interest because it participates in many metabolic pathways. However, there is evidence that skeletal muscle glutamate metabolism is disturbed in disease. This review presents current knowledge regarding the metabolic function and regulation of glutamate in skeletal muscle under physiological and pathophysiological circumstances. Furthermore, several options for modulating muscle glutamate concentration in order to improve glutamate metabolism are discussed. RECENT FINDINGS The high correlation between muscle glutamate concentration and muscle glutathione concentration suggests that glutamate plays a determining role in the glutathione synthesis pathway. During exercise, glutamate plays a central role in energy provision because it participates in the tricarboxylic acid and the purine nucleotide cycles. However, a consistent finding in several diseases is reduced skeletal muscle glutamate. Remarkably, only few studies focused on modulation of muscle glutamate status either by exercise or by nutritional supplementation. There are several options for modulating glutamate metabolism, but the specific effects of the individual options require further elucidation. Nutritional supplementation of glutamate or its precursors glutamine, (ornithine) alpha-ketoglutarate, or the branched chain amino acids can influence muscle glutamate status. SUMMARY Specific intervention studies must be conducted to investigate the effect of supplementation on skeletal muscle glutamate turnover and its related metabolic and functional consequences in healthy individuals and in patients with acute or chronic disease.
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Affiliation(s)
- Erica P A Rutten
- Department of Respiratory Medicine, Maastricht University, Maastricht, The Netherlands.
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Abstract
PURPOSE OF REVIEW Despite much current debate regarding central and peripheral neural mechanisms which may be responsible for the onset of fatigue during prolonged exercise, maintenance of nutritional and hydration status remains critical for successful participation in ultra-endurance exercise. This review focuses on substrate and fluid homeostasis during ultra-endurance exercise and the use of nutritional supplementation both as ergogenic aid and to attenuate exercise-induced immunosuppression. RECENT FINDINGS Current evidence continues to support mandatory high carbohydrate intakes (1). before the event to maximize muscle glycogen stores, (2). during the event to prevent hypoglycaemia and (3). after the event to optimize post-event repletion of endogenous carbohydrate stores. No consistent performance benefit has yet been shown following a high-fat diet. Greater utilization of intrafascicular triglyceride stores appears to account for additional fat utilization in females. Recent trends towards excessive fluid intake have resulted in frequent reports of hyponatraemic hyperhydration in ultra-distance athletes, with greater incidence in women than in men. Carbohydrate supplementation during the event attenuates immunosuppressive hormonal and cytokine responses to ultra-endurance exercise, but may impair vitamin C absorption, while the ergogenic value of caffeine supplementation in ultra-endurance performance is currently being questioned. SUMMARY Meeting macronutrient and fluid intake demands remains an important priority for ultra-endurance athletes. Yet these athletes are reported to present with a high incidence of disordered eating patterns during periods of training, and excessive fluid replacement strategies have resulted in an increased incidence of water intoxication with resultant central nervous system dysfunction.
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Affiliation(s)
- Edith M Peters
- Department of Physiology, Nelson Mandela Faculty of Health Sciences, University of Natal, Durban, South Africa.
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