Specific adaptations in muscle and adipose tissue in response to
chronic systemic glucose oversupply in rats.
Laybutt, D. Ross, Donald J. Chisholm, and Edward W. Kraegen.
Garvan Institute of Medical Research, St Vincent's Hospital,
Sydney, NSW, 2010, AUSTRALIA
APStracts 4:0060E, 1997.
Rats minimise hyperglycaemia during chronic glucose infusion, but the
metabolic processes are unclear. We investigated the tissues involved
and the role of altered insulin sensitivity. Cannulated rats were
infused with glucose (40 mg/kg/min) for one (1d) or four (4d) days or
with saline (C). Hyperglycemia at 1d (15.3 1.0 mM) was absent at 4d
(7.5 0.3 mM), but hyperinsulinemia persisted. Whole body glucose
disposal was similarly elevated at 1d and 4d, implying increased
glucose clearance at 4d (2-fold, P<0.001). Muscle glucose
uptake and glycogen content declined in glucose-infused rats from 1d
to 4d whereas white adipose tissue (WAT) glucose uptake (6-fold,
P<0.001) and lipogenesis (3-fold, P<0.001) increased.
Muscle and liver triglyceride were doubled at both 1d and 4d
(P<0.05 vs C). Insulin sensitivity (assessed during euglycemic
clamps) decreased in muscle to 34% of C at 1d and 4d (P<0.001
vs C) and increased 5-fold in WAT from 1d to 4d (P<0.05).
Thus, chronic glucose infusion results in a slow increase in
efficiency of glucose clearance with enhanced WAT glucose uptake,
lipogenesis and insulin action. In contrast, the adaptation reduces
glucose oversupply to muscle. Muscle shows sustained insulin
resistance, with lipid accumulation a possible contributing factor.
Received 18 December 1996; accepted in final form 26 February
1997.
APS Manuscript Number E618-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 12 March 1997