Oxidation of [(13)C]glycerol ingested along with glucose during prolonged exercise.
The respective oxidation of glycerol and glucose (0.36 g/kg each) ingested simultaneously immediately before exercise (120 min at 68 +/- 2% maximal oxygen uptake) was measured in six subjects using (13)C labeling. Indirect respiratory calorimetry corrected for protein and glycerol oxidation was used to evaluate the effect of glucose + glycerol ingestion on the oxidation of glucose and fat. Over the last 80 min of exercise, 10.0 +/- 0.8 g of exogenous glycerol were oxidized (43% of the load), while exogenous glucose oxidation was 21% higher (12.1 +/- 0.7 g or 52% of the load). However, because the energy potential of glycerol is 18% higher than that of glucose (4.57 vs. 3.87 kcal/g), the contribution of both exogenous substrates to the energy yield was similar (4.0-4.1%). Total glucose and fat oxidation were similar in the placebo (144.4 +/- 13.0 and 60.5 +/- 4.2 g, respectively) and the glucose + glycerol (135.2 +/- 12.0 and 59.4 +/- 6.5 g, respectively) trials, whereas endogenous glucose oxidation was significantly lower than in the placebo trial (123.7 +/- 11.7 vs. 144.4 +/- 13.0 g). These results indicate that exogenous glycerol can be oxidized during prolonged exercise, presumably following conversion into glucose in the liver, although direct oxidation in peripheral tissues cannot be ruled out.
Burelle
Y
Y
Département de Kinésiologie, Université de Montréal, CP 6128 Centre Ville, Montréal H3C 3J7, Canada G9A 5H7.
Massicotte
D
D
Lussier
M
M
Lavoie
C
C
Hillaire-Marcel
C
C
Péronnet
F
F
D000284:Administration, Oral; D000328:Adult; D001944:Breath Tests; D002153:Calorimetry, Indirect / Q000379:methods; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism*; D005990:Glycerol / Q000008:administration & dosage / Q000378:metabolism*; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*
D002247:Carbon Isotopes; D002245:Carbon Dioxide; D005947:Glucose; D005990:Glycerol