Oral [(13)C]glucose and endogenous energy substrate oxidation during prolonged treadmill running.
Six male subjects were studied during running exercise (120 min, 69% maximal oxygen consumption) with ingestion of a placebo or 3.5 g/kg of [(13)C]glucose (approximately 2 g/min). Indirect respiratory calorimetry corrected for urea excretion in urine and sweat, production of (13)CO(2) at the mouth, and changes in plasma glucose (13)C/(12)C were used to compute energy substrate oxidation. The oxidation rate of exogenous glucose increased from 1.02 at minute 60 to 1.22 g/min at minute 120 providing approximately 24 and 33% of the energy yield (%En). Glucose ingestion did not modify protein oxidation, which provided approximately 4-5%En, but significantly increased glucose oxidation by approximately 7%, reduced lipid oxidation by approximately 16%, and markedly reduced endogenous glucose oxidation (1.25 vs. 2.21 g/min between minutes 80 and 120, respectively). The oxidation rate of glucose released from the liver (0.38 and 0.47 g/min, or 10-13%En at minutes 60 and 120, respectively), and of plasma glucose (1.30-1.69 g/min, or 34 and 45%En and 50 and 75% of glucose oxidation) significantly increased from minutes 60 to 120, whereas the oxidation of muscle glycogen significantly decreased (1.28 to 0.58 g of glucose/min, or 34 and 16%En and 50 and 25% of glucose oxidation). These results indicate that, during moderate prolonged running exercise, ingestion of a very large amount of glucose significantly reduces endogenous glucose oxidation, thus sparing muscle and/or liver glycogen stores.
Couture
Stéphane
S
Département de Kinésiologie, Université de Montréal, Montréal, Québec, Canada H3C 3J7.
Massicotte
Denis
D
Lavoie
Carole
C
Hillaire-Marcel
Claude
C
Péronnet
François
F
D000284:Administration, Oral; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002247:Carbon Isotopes; D004734:Energy Metabolism / Q000187:drug effects*; D005947:Glucose / Q000008:administration & dosage* / Q000378:metabolism* / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D012420:Running / Q000502:physiology*; D013997:Time Factors
D001786:Blood Glucose; D002247:Carbon Isotopes; D006003:Glycogen; D005947:Glucose