| Glutamate availability is important in intramuscular amino acid metabolism and TCA cycle intermediates but does not affect peak oxidative metabolism. | |
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MedLine Citation:
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PMID: 18511521 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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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 approximately 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 (VO2peak) in the T thigh was greater than that in the UT thigh (P<0.05); VO2peak 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 micromol.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 micromol/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 VO2peak in either trained or untrained muscle. |
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Authors:
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M Mourtzakis; T E Graham; J González-Alonso; B Saltin |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2008-05-29 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 105 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2008 Aug |
Date Detail:
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Created Date: 2008-08-05 Completed Date: 2008-10-10 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 547-54 Citation Subset: IM |
Affiliation:
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Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada. mmourtza@healthy.uwaterloo.ca |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Adult Alanine Transaminase / metabolism Amino Acids / metabolism* Anaerobic Threshold / physiology Blood Glucose / metabolism Carbon Dioxide / blood Citric Acid Cycle / physiology* Glucagon / blood Glutamic Acid / metabolism* Humans Insulin / blood Leg / physiology Male Muscle, Skeletal / metabolism* Nitrogen / metabolism Organ Size / physiology Oxidation-Reduction Oxygen / blood Oxygen Consumption / physiology Physical Fitness / physiology |
| Chemical | |
Reg. No./Substance:
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0/Amino Acids; 0/Blood Glucose; 11061-68-0/Insulin; 124-38-9/Carbon Dioxide; 56-86-0/Glutamic Acid; 7727-37-9/Nitrogen; 7782-44-7/Oxygen; 9007-92-5/Glucagon; EC 2.6.1.2/Alanine Transaminase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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