Role of carbohydrate in control of the adenine nucleotide pool in human skeletal muscle during exercise
Spencer, Mark Kendall
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Permalink
https://hdl.handle.net/2142/20108
Description
Title
Role of carbohydrate in control of the adenine nucleotide pool in human skeletal muscle during exercise
Author(s)
Spencer, Mark Kendall
Issue Date
1994
Doctoral Committee Chair(s)
Ji, Li Li
Department of Study
Kinesiology and Community Health
Discipline
Kinesiology and Community Health
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Chemistry, Biochemistry
Language
eng
Abstract
The relationship between carbohydrate (CHO) availability and the adenine nucleotide pool in human skeletal muscle during exercise has been investigated during short-term high intensity cycling exercise (Study I), or sustainable heavy cycling exercise (Study II), with and without prior muscle glycogen lowering. In study III, subjects performed sustainable heavy cycling exercise with and without carbohydrate ingestion.
In Study I, during low glycogen, glycogen utilization and the glycolytic rate were maintained although fructose 6-phosphate (activates phosphofructokinase) was lower, and inosine monophosphate was greater. This supports the hypothesis that increased AMP can compensate for decreased fructose 6-phosphate to maintain phosphofructokinase activation as well as stimulate AMP deaminase and increase inosine monophosphate accumulation.
In Study II during low glycogen exercise, the rate of glycogen utilization, sum of hexose monophosphates and lactate were decreased, while IMP was increased compared exercise with high glycogen. Increases in tricarboxylic acid cycle intermediates and acetylcarnitine were greater during high glycogen. It is possible that larger increases in ADP and AMP during low glycogen (reflected by higher inosine monophosphate) activate phosphofructokinase, and isocitrate dehydrogenase, as well as stimulate oxidative phosphorylation when insufficient substrate for acetyl CoA and tricarboxylic acid cycle intermediate formation is provided by glycolysis.
In Study III, the sum of hexose monophosphates, lactate and alanine were higher after carbohydrate ingestion exercise than after placebo exercise. Tricarboxylic acid cycle intermediates increased more and inosine monophosphate increased less after exercise with carbohydrate ingestion than placebo. Exogenous carbohydrate can attenuate decreases in tricarboxylic acid cycle intermediates and glycolytic intermediates during prolonged exercise. This may be achieved by increasing the availability of hexose monophosphates for glycolysis.
These studies demonstrate that decreased carbohydrate availability affects glycolytic flux when muscle glycogen is very low. Additionally, the intermediates of glycolysis and the tricarboxylic acid cycle are reduced and inosine monophosphate formation is increased during exercise with limited carbohydrate availability.
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