title: Oxidation of [13C]glucose ingested before and/or during prolonged exercise.
abstract: Ingestion of glucose before exercise results in a transient increase in plasma insulin concentrations. We hypothesized that if glucose was also ingested during the exercise period the elevated plasma insulin concentration could increase exogenous glucose oxidation. The oxidation rate of glucose ingested 30 min before (50 g) and/or during (110 or 160 g in fractionated doses) exercise [120 min; 67.3 (1.2)% maximal O(2) uptake] was studied on six young male subjects, using (13)C-labelling. Ingestion of glucose before exercise significantly increased plasma insulin concentration [from 196 (45) to 415 (57) pmol l(-1)] but the value returned to pre-exercise level within the first 30 min of exercise in spite of a continuous increase in plasma glucose concentration. Ingestion of glucose 30 min before exercise did not increase the oxidation of exogenous glucose between minutes 30 and 60 during the exercise period [0.36 (0.03) vs 0.30 (0.02) g min(-1), when placebo or unlabelled glucose was ingested respectively]. Over the last 90 min of exercise, when glucose was ingested only during exercise, 49.2 (3.1) g [0.55 (0.04) g min(-1)) was oxidized, while when it was ingested both before and during exercise, 65.7 (4.6) g [0.73 (0.05) g min(-1)] was oxidized [26.7 (2.1) g of the 50 g ingested before exercise but only 39.0 (2.4) g of the 110 g ingested during the exercise period]. Thus, ingestion of glucose 30 min before the beginning of exercise did not enhance the oxidation rate of exogenous glucose ingested during the exercise period, although the total amount of exogenous glucose oxidized was larger than when ingested only during the exercise period.
authors.affiliation: Département des sciences de l'activité physique, Université du Québec à Trois Rivières, CP 500, G9A 5H7, Trois Rivières, Quebec, Canada.
authors.forename: Anny
authors.initials: A
authors.lastname: Caron
authors.forename: Carole
authors.initials: C
authors.lastname: Lavoie
authors.forename: François
authors.initials: F
authors.lastname: Péronnet
authors.forename: Claude
authors.initials: C
authors.lastname: Hillaire-Marcel
authors.forename: Denis
authors.initials: D
authors.lastname: Massicotte
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D002247:Carbon Isotopes / Q000008:administration & dosage / Q000493:pharmacokinetics; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D006801:Humans; D007328:Insulin / Q000097:blood*; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D007328:Insulin; D005947:Glucose