Regulation of plasma fatty acid oxidation during low and high
intensity exercise.
Sidossis, Labros S., Amalia Gastaldelli, Samuel Klein, and Robert R.
Wolfe.
Metabolism Unit, Shriners Burns Institute, 815 Market Str.,
Galveston, TX, and the Departments of Anesthesiology, Internal
Medicine, Surgery, and Biochemistry, University of Texas Medical
Branch, Galveston, TX 77550.
APStracts 4:0036E, 1997.
In the present study we have 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% VO2 peak
for 60 min and at 80% VO2 peak 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% VO2 peak to
prevent the expected decrease in plasma FFA concentration. Plasma
oleate and total FFA availability were similar in the two
experiments. Oleate oxidation decreased from 2.8+/-0.6 (40% VO2 peak)
to 1.8+/-0.2 [mu]mol.kg-1.min-1 (80% VO2 peak, P<0.05),
whereas octanoate oxidation increased from 1.0E-05+/-1.0E-06 (40% VO2
peak) to 1.3E-05+/-5.1E-06 [mu]mol.kg-1.min-1 (80% VO2 peak,
P<0.05). Furthermore, the percent of oleate uptake oxidized
decreased from 67.7+/-2.8% (40% VO2 peak) to 51.8+/-4.6% (80% VO2
peak, P<0.05), whereas the percent of octanoate oxidized was
similar during exercise at 40% and 80% VO2 peak (84.8+/-2.7% vs
89.3+/-2.7%, respectively). Our data suggest that, in addition to
sub-optimal FFA availability, fatty acid oxidation is likely limited
during high intensity exercise because of direct inhibition of long
-chain fatty acid entry into mitochondria.
Received 9 August 1996; accepted in final form 29 January 1997.
APS Manuscript Number E387-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 20 February 1997