title: Regulation of plasma fatty acid oxidation during low- and high-intensity exercise.
abstract: In the present study we examined the hypothesis that fatty acid oxidation is less during high-intensity exercise than during moderate-intensity exercise because of inhibition of long-chain fatty acid entry into the mitochondria. Six volunteers exercised at 40% peak oxygen consumption (VO2peak) for 60 min and at 80% VO2peak for 30 min on two different occasions. [1-13C]oleate, a long-chain fatty acid, and [1-14C]octanoate, a medium-chain fatty acid, were infused for the duration of the studies. Lipids and heparin were infused during exercise at 80% VO2peak to prevent the expected decrease in plasma free fatty acid (FFA) concentration. Plasma oleate and total FFA availability were similar in the two experiments. Oleate oxidation decreased from 2.8 +/- 0.6 (40% VO2peak) to 1.8 +/- 0.2 mumol.kg-1.min-1 (80% VO2peak, P < 0.05), whereas octanoate oxidation increased from 1.0e-05 +/- 1.0e-06 (40% VO2peak) to 1.3e-05 +/- 5.1e-06 mumol.kg-1.min-1 (80% VO2peak, P < 0.05). Furthermore, the percentage of oleate uptake oxidized decreased from 67.7 +/- 2.8% (40% VO2peak) to 51.8 +/- 4.6% (80% VO2peak, P < 0.05), whereas the percentage of octanoate oxidized was similar during exercise at 40 and 80% VO2peak (84.8 +/- 2.7 vs. 89.3 +/- 2.7%, respectively). Our data suggest that, in addition to suboptimal FFA availability, fatty acid oxidation is likely limited during high-intensity exercise because of direct inhibition of long-chain fatty acid entry into mitochondria.
authors.affiliation: Metabolism Unit, Shriners Burns Institute, Galveston, Texas 77550, USA.
authors.forename: L S
authors.initials: LS
authors.lastname: Sidossis
authors.forename: A
authors.initials: A
authors.lastname: Gastaldelli
authors.forename: S
authors.initials: S
authors.lastname: Klein
authors.forename: R R
authors.initials: RR
authors.lastname: Wolfe
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000097:blood; D007773:Lactates / Q000097:blood; D008297:Male; D019301:Oleic Acid / Q000097:blood; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D005082:Physical Exertion; D014280:Triglycerides / Q000097:blood*
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007773:Lactates; D014280:Triglycerides; D019301:Oleic Acid