Effects of acute exercise on hepatic lipogenic enzymes in fasted
and refed rats.
Griffiths, Margaret A., David H. Baker, Xing-Xian Yu, Jan Novakofski,
Lawrence Oscai, and Li Li Ji.
Department of Kinesiology and Division of Nutritional Sciences,
University of Illinois at Urbana-Champaign, Department of
Kinesiology, University of Illinois at Chicago, Department of
Kinesiology, University of Wisconsin-Madison
APStracts 2:0185A, 1995.
The effects of an acute bout of prolonged exhaustive exercise on the
activities of hepatic lipogenic enzymes have been investigated. Male
Sprague-Dawley rats were randomly divided into three groups: fasted
for 48 hours without refeeding (FA), and fasted for 48 hours and
refed a diet high in fructose (RF) or cornstarch (RC). Half of each
group of rats exercised on a treadmill at 20 m/min, 5% grade until
exhaustion and the other half group rested for the same amount of
time without food. Dietary intakes during refeeding were kept equal
between the exercised and rested control animals. Activities of all
hepatic lipogenic enzymes measured, i.e., fatty acid synthase (FAS),
L-type pyruvate kinase (L-PK), ATP citrate lyase, malic enzyme, and
glucose 6-phosphate dehydrogenase, were induced dramatically by
fasting-refeeding and were significantly higher (P<0.05) in the RF
vs. RC rats. FAS actively was increased 19 and 39 fold, respectively,
in the RC and RF rats compared to FA rats. Exercise decreased FAS
activity to 1/3 of the resting control values in both RC and RF
(P<0.05), but not in FA. L-PK activity was elevated by 55% and 100%
respectively, comparing RC and RF with FA (P<0.05). FA and RF rats
also showed a reduction of L-PK activity with exercise. No
significant alteration of other lipogenic enzymes was observed after
exercise. Enzymatic down regulation of FAS and L-PK with exercise was
associated with significantly elevated plasma levels of glucagon and
depressed levels of insulin in the fasted-refed rats, regardless of
diet. Exercised rats also demonstrated lower levels of hepatic
pyruvate content and decreased blood glucose concentration compared
with the rested rats. It is concluded that dietary induction of key
hepatic lipogenic enzymes can be inhibited by an acute bout of
exhaustive exercise and that this enzymatic down regulation is most
dramatic in rats receiving a high-fructose diet.
Received 26 October 1994; accepted in final form 12 April 1995.
APS Manuscript Number A1105-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.