Influence of muscle glycogen content on metabolic regulation.
Weltan, Sandra M., Andrew N. Bosch, Steven C. Dennis, and Timothy D.
Noakes.
Department of Physiology, University of Cape Town Medical School,
Observatory 7925, South Africa. Phone: (27) - (21) - 686-7330, Fax:
(27) - (21) - 686-7530, E-mail: abosch@sports.uct.ac.za
APStracts 4:0215E, 1997.
Euglycaemia (E) was maintained in 13 subjects with low muscle glycogen
(LG) (LGE, n=8; LGEI, n=5) and 6 subjects with normal muscle glycogen
(NGE), while hyperglycaemia (H) was maintained in 8 LG subjects
(LGH). All subjects cycled for 145 minutes at 70% of VO2 max during
the infusions. Insulin (I) was infused in LGEI, at 0.2 mU/kg/min.
During exercise, RER was lower and norepinephrine higher in LGE than
in NGE. In LGEI and LGH, RER at the start of exercise was the same as
in LGE, but did not decrease as in LGE. Free fatty acids (FFA) were
higher and plasma insulin concentrations lower in LGE than NGE, LGEI
or LGH over the first 45 minutes of exercise. Rate of glucose
infusion (Ri) and rate of glucose oxidation (Rox) were higher in LGH
and LGEI than in NGE or LGE, and Ri matched Rox in all groups except
LGH where Ri was greater than Rox. Muscle glycogen disappearance was
greater in NGE than LGE, LGEI or LGH, but the latter 3 groups did not
differ. In conclusion, this study showed that low muscle glycogen
content results in a decrease in RER and an increase in FFA, fat
oxidation and norepinephrine both at rest and during exercise, does
not affect Rox when euglycaemia is maintained by infusion of glucose
alone. Rox was increased only during I and H.
Received 11 Novemner 1996; accepted in final form 22 September
1997.
APS Manuscript Number E566-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 October 1997