Glucose infusion partially attenuates the endogenous glucose production response and increases total glucose uptake during intense exercise. Manzon, Anthony, Simon J. Fisher, Jos[acute]e A. Morais, Lorraine Lipscombe, Marie-Claude Guimond, Sharon J. Nessim, Ronald J. Sigal, Jeffrey B. Halter, Mladen Vranic, and Errol B. Marliss. McGill Nutrition and Food Science Centre, Royal Victoria Hospital, 687 Pine Avenue, West, Montreal, Quebec, Canada, H3A 1A1, Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario, 5S 1A8, Department of Internal Medicine and Institute of Gerontology, University of Michigan, 300 North Ingalls Street - Room NI3A00, VA Medical Center, Ann Arbor, Ann Arbor, Michigan 48109
APStracts 5:0170A, 1998.
Glucose infusion can prevent the increase in glucose production (Ra) and increase glucose uptake (Rd) during exercise of moderate intensity. We postulated that 1) because in postabsorptive intense exercise (>80% VO2 max) the 8 fold increase in Ra may be mediated by catecholamines rather than glucagon and insulin, exogenous glucose infusion would not prevent the Ra increment, and 2) such infusion would cause greater glucose uptake (Rd). Fit young male subjects were exercised at >85% VO2 max for 14 min in the postabsorptive state (controls, C, n=12), or at minute 210 of a 285 min glucose infusion. In n=7 the infusion was constant at (CI) 4 mg/kg/min, and in n=7 it was varied (VI) to mimic the exercise Ra response in C. Although glucose suppressed Ra to zero, (with glycemia [cedilla]C 6 mM and insulin [cedilla]C 150 pmol/L), an endogenous Ra response to exercise occurred, to peak increments 2/3 those in C, in both CI and VI. Glucagon was unchanged, and very small increases in glucagon/insulin ratio occurred in all 3 groups. Catecholamine responses were similar in all 3 groups, and correlation coefficients of Ra with plasma norepinephrine and epinephrine were significant in all. In all CI and VI Rd at rest was 2X C, increased earlier in exercise and was higher for the 1h of recovery with glucose infusion. Thus, the Ra response was only partly attenuated, and the catecholamines are likely to be the regulators. This suggests that an acute endogenous Ra rise is possible even in the postprandial state. Furthermore, that more circulating glucose is used by muscle during exercise and early recovery suggests that muscle glycogen is spared.

Received 18 November 1997; accepted in final form 9 April 19980
APS Manuscript Number A1066-7.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 24 April 1998