Regulation of glucose production during intense submaximal exercise
in untrained humans.
Coggan, Andrew R., Comasio A. Raguso, Amalia Gastaldelli, Bradley D.
Williams, and Robert R. Wolfe.
Metabolism Unit, Shriners Burns Institute, and Departments of
Anesthesiology and Surgery, University of Texas Medical Branch,
Galveston, TX 77550
APStracts 4:0083E, 1997.
To determine whether alterations in insulin and/or glucagon secretion
play an important role in stimulating glucose production (Ra) during
intense but submaximal exercise, we studied six untrained subjects
during 30 min of cycling at 80% of peak oxygen uptake on two
occasions: once under control conditions and once when alterations in
insulin and glucagon secretion were prevented using the pancreatic
islet clamp technique. In the latter experiments, glucose was infused
during exercise to match glycemia with control levels. Glucose
kinetics were measured in both trials using a primed, continuous
infusion of [6,6-2H]glucose. In the control trial, glucose Ra rose
from 11.9+/-0.8 [mu]mol.min-1.kg-1 at rest to 42.5+/-4.3 [mu]mol.min
-1.kg-1 by the end of exercise. A similar increment was observed in
the islet clamp experiments, with endogenous Ra peaking at 37.2+/-7.9
[mu]mol.min-1.kg-1. This was true even though glucagon concentration
did not change from basal and insulin concentration actually rose
(the latter apparently due to a decrease in insulin clearance during
intense exercise). Thus, neither decrements in insulin or increments
in glucagon are apparently required to stimulate glucose Ra during
high intensity exercise. Since epinephrine levels rose only slightly,
it appears that either neurally-released norepinephrine or some
other, as-yet-unidentified factor is responsible for stimulating
glucose Ra under the present conditions.
Received 25 November 1996; accepted in final form 3 April 1997.
APS Manuscript Number E586-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 15 April 1997