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Cited by 431Muscle metabolism and nutritionCardiovascular and exercise physiologyAmino Acid Enzymes and Metabolism

Amino acid metabolism in exercising man

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Felig, Philip, Wahren, John·1971·Journal of Clinical Investigation
DOI 10.1172/jci106771PMC PMC292220
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Abstract

Arterial concentration and net exchange across the leg and splanchnic bed of 19 amino acids were determined in healthy, postabsorptive subjects in the resting state and after 10 and 40 min of exercise on a bicycle ergometer at work intensities of 400, 800, and 1200 kg-m/min. Arterio-portal venous differences were measured in five subjects undergoing elective cholecystectomy. In the resting state significant net release from the leg was noted for 13 amino acids, and significant splanchnic uptake was observed for 10 amino acids. Peripheral release and splanchnic uptake of alanine exceeded that of all other amino acids, accounting for 35-40% of total net amino acid exchange. Alanine and other amino acids were released in small amounts (relative to net splanchnic uptake) by the extrahepatic splanchnic tissues drained by the portal vein. During exercise arterial ananine rose 20-25% with mild exertion and 60-96% at the heavier work loads. Both at rest and during exercise a direct correlation was observed between arterial alanine and arterial pyruvate levels. Net amino acid release across the exercising leg was consistently observed at all levels of work intensity only for alanine. Estimated leg alanine output increased above resting levels in proportion to the work load. Splanchnic alanine uptake during exercise exceeded that of all other amino acids and increased by 15-20% during mild and moderate exercise, primarily as a consequence of augmented fractional extraction of alanine. For all other amino acids, there was no change in arterial concentration during mild exercise. At heavier work loads, increases of 8-35% were noted for isoleucine, leucine, methionine, tyrosine, and phenylalanine, which were attributable to altered splanchnic exchange rather than augmented peripheral release. The data suggest that (a) synthesis of alanine in muscle, presumably by transamination of glucose-derived pyruvate, is increased in exercise probably as a consequence of increased availability of pyruvate and amino groups; (b) circulating alanine serves an important carrier function in the transport of amino groups from peripheral muscle to the liver, particularly during exercise; (c) a glucose-alanine cycle exists whereby alanine, synthesized in muscle, is taken up by the liver and its glucose-derived carbon skeleton is reconverted to glucose.

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  • Alanine is a dispensable amino acid that can be synthesized endogenously by the liver, acting as an subsidiary source of energy during extreme circumstances such as starvation and prolonged endurance exercise.

    “Alanine is a dispensable amino acid that can be synthesized endogenously by the liver, acting as an subsidiary source of energy during extreme circumstances such as starvation and prolonged endurance exercise [186].”

    From Regulation of Energy Substrate Metabolism in Endurance Exercise (2021) · cites this paper as [186]

    The glucose–alanine cycle discussion and Figure 9 (p. 2712) describe endogenous alanine synthesis during exercise and its conversion to glucose by the liver. They place alanine synthesis in muscle, not the liver. The paper does not establish alanine as a subsidiary energy source during starvation or prolonged endurance exercise; its reported exercise observations extend to 40 minutes. (LLM, conf=0.88)

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Research works printed but not linked: 2

  1. Bradley, S. E. 1946. Liver function as studied by hepatic vein catheterization. In Transactions of the Fifth Con- ference on Liver Injury. Josiah Macy Jr. Foundation, New York. 38.
  2. Miller, L. L. 1962. The role of the liver and the non- hepatic tissues in the regulation of free amino acid Amino Acid Metabolism in Exercising Man 2713 levels in the blood. In Amino Acid Pools, Proceedings of the Symposium on Free Amino Acids, City of Hope Medical Center, 1961.

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Authors
Felig, P., & Wahren, J.
Affiliations
Karolinska Institutet (SE)
Venue
Journal of Clinical Investigation
Publisher
American Society for Clinical Investigation
Published
1971-12-01
Volume
50
Issue
12
Pages
2703-2714
ISSN
0021-9738 (ISSN-L)
DOI
10.1172/jci106771
PMC
PMC292220
OpenAlex
W2042316825
Cited by
431
References
37
Citations by year
2026: 3 · 2025: 2 · 2024: 10 · 2023: 5 · 2022: 9 · 2021: 10 · 2020: 13 · 2019: 3 · 2018: 3 · 2017: 4 · 2016: 3 · 2015: 3 · 2014: 4 · 2013: 6 · 2012: 2
FWCI
9.04
Type
journal article
Language
en
Open access
Locations
  • Journal of Clinical Investigation (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
Medical Research Council
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
  • Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Amino Acid Enzymes and Metabolism
Keywords
amino acid metabolism, physical activity, alanine, pyruvate, glucose-alanine cycle, transamination, work intensity, cholecystectomy
MeSH terms
Abdomen, Adult, Alanine, Amino Acids, Physical Exertion, Forearm, Glucose, Humans, Lactates, Leg, Liver, Male, Methods, Muscles, Oxygen Consumption, Pyruvates, Regional Blood Flow, Rest, Time Factors

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