Effects of exercise and feeding on the hexosamine biosynthetic
pathway in rat skeletal muscle.
Nelson, Bryce A., Katherine A. Robinson, Jeffrey S. Koning, and Maria
G. Buse .
Department of Medicine (Division of Endocrinology, Diabetes and
Medical Genetics) and of Biochemistry/Molecular Biology, Medical
University of South Carolina, 171 Ashley Avenue, Charleston, South
Carolina, 29425
APStracts 4:0004E, 1997.
Products of the hexosamine biosynthesis pathway (HSNP) have been
implicated in glucose induced insulin resistance. We measured the
major products of HSNP, UDP-N-acetyl hexosamines (UDP-HexNAc), and
the activity of glutamine:fructose-6-phosphate amido- transferase
(GFAT, rate-limiting enzyme) in rat hindlimb muscles immediately and
1, 3, and 16 hrs. post-exercise (swimming) in fed and fasted rats and
sedentary controls. Muscle glycogen decreased by 50-75% post
-exercise. In sedentary rats muscle GFAT activity decreased by _30%
(p<0.002) after an 18 hr. fast. GFAT activity was not affected
by exercise under any condition. Muscle UDP-HexNAc increased _30%
post-exercise (p<0.01) in ad lib fed but not in fasted rats.
UDP-HexNAc remained elevated (_30%, p < 0.002) for 16 hrs if
animals were fed post-exercise. Concentrations of UDP-hexoses, GDP
-mannose, and UDP were unchanged post-exercise. Conclusions: Muscle
GFAT activity is regulated by the nutritional state but not by acute
exercise. Glucose flux via HNSP may be increased post-exercise in
muscles of ad lib fed rats. Increased HSNP products may serve as
negative feedback regulators to limit excessive muscle glycogen
deposition post-exercise.
Received 4 September 1996; accepted in final form 13 December
1996.
APS Manuscript Number E432-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 21 January 1997