Sepsis-induced attenuation of glucagon and 8-bromo-cyclic amp
modulation of phosphoenolpyruvate carboxykinase gene expression.
Deutschman, Clifford S., Antonio De Maio, Mark G. Clemens.
Department of Anesthesia, University of Pennsylvania School of
Medicine, Philadelphia PA, 19104-4283 and #the Division of Pediatric
Surgery, Department of Surgery, Johns Hopkins University School of
Medicine, Baltimore MD, 21205
APStracts 2:0089R, 1995.
Sepsis is associated with alterations in hepatic gluconeogenesis. We
have previously demonstrated that this change is associated with
reduced expression of the Phosphoenolpyruvate Carboxykinase (PEPCK)
gene, despite an endogenous hormonal milieu which should favor
increased expression of the gene. To further elucidate the mechanisms
involved, we induced sepsis in fasted Sprague-Dawley rats via cecal
ligation and single puncture with sham operated animals serving as
controls, and performed two sets of experiments. First, liver tissue
was obtained from septic and sham-operated animals at 2, 6, 16 and 24
hours following the induction of sepsis. Northern blot hybridization
analysis revealed a progressive, sepsis-induced decrease in
expression of PEPCK and an increase in the expression beta
fibrinogen, an acute phase reactant. In the second set of
experiments, we tested whether this reduced expression resulted from
an attenuated response to 1) glucagon and 2) 8-Bromo-cyclic adenosine
monophosphate (8-Br-cAMP). Twenty-four hours fter the induction of
sepsis, the liver was isolated and perfused with either Krebs buffer
with substrate only (unstimulated controls), Krebs buffer + substrate
+ 10-8M glucagon or Krebs buffer + substrate + 10-5M 8-bromo-cAMP. In
sham operated animals, perfusion with glucagon increased PEPCK mRNA
levels and activity while perfusion with buffer alone did not change
mRNA levels and decreased activity. Glucagon perfusion of septic
livers did not change either PEPCK mRNA levels or activity. Perfusion
of sham operated animals with 8-Br-cAMP increased PEPCK mRNA levels
and activity while perfusion with buffer alone resulted in decrease
in mRNA levels and activity. Perfusion of septic livers with 8-Br
-cAMP did not change PEPCK mRNA levels or activity. We conclude that
sepsis induced by cecal ligation and puncture results in a time
-dependent decrease in PEPCK mRNA levels which is not the result of a
global depression in hepatic gene expression and that sepsis renders
the PEPCK gene unresponsive to glucagon and 8-Br-cAMP. These findings
imply that the mechanism underlying the sepsis-induced defect in
PEPCK gene expression involves factors distal to glucagon-stimulated
cAMP production.
Received 10 January 1995; accepted in final form 23 March 1995.
APS Manuscript Number R23-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 April 1995.