Effect of exercise on lipolytic sensitivity in endurance-trained
athletes.
Klein, Samuel, Edward F. Coyle, Robert R. Wolfe.
Department of Internal Medicine, Washington University School of
Medicine, St. Louis, Missouri; Department of Surgery, The University
of Texas Medical Branch and Shriners Burns Institute, Galveston,
Texas; Human Performance Laboratory, Department of Kinesiology and
Health, The University of Texas at Austin, Austin, Texas.
APStracts 2:0069A, 1995.
Studies performed in vitro suggest that an acute bout of exercise
increases the lipolytic response to [beta]-adrenergic stimulation. We
evaluated the effect of exercise on lipolytic sensitivity in vivo in
five endurance-trained athletes. The rate of appearance (Ra) of
glycerol in plasma, an index of whole-body lipolysis, was determined
during 60 min of epinephrine infusion (0.015 [mu]g.kg-1.min-1) on two
occasions: (1) at basal resting conditions and (2) 90 min after
completing 1 h of high-intensity (70% VO2) cycle ergometer exercise.
Total glycerol Ra during epinephrine infusion in the basal state
(352+/-35 [mu]mol.kg-1.60 min-1) was not significantly different from
the value obtained after high-intensity exercise (439+/-58
[mu]mol.kg-1.60 min-1). However, the increase in glycerol Ra above
baseline during epinephrine infusion was lower after (30+/-16
[mu]mol.kg-1.60 min-1) than before (148 +/- 28 [mu]mol.kg-1.60 min-1)
exercise because of the high post exercise baseline value (P < 0.05).
Mean plasma FFA concentration was lower during exercise than during
epinephrine infusion despite a greater rate of lipolysis during
exercise. The slope of change in plasma FFA with respect to glycerol
Ra was lower during exercise (0.0171+/-0.006) than during epinephrine
infusion (0.0835+/-0.018) (P < 0.05). We conclude that a single bout
of intense exercise does not increase in vivo lipolytic sensitivity
to [beta]-adrenergic stimulation in endurance-trained athletes. In
addition, plasma FFA concentration represents the balance between
plasma FFA inflow and tissue uptake and cannot be used as an index of
lipolytic activity during certain physiological conditions, such as
exercise.
Received 15 August 1994; accepted in final form 16 February 1995.
APS Manuscript Number A854-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 1 March 1995.