The relationship between changes in body composition and insulin
responsiveness in models of the aging rat.
Barzilai, Nir, and Luciano Rossetti.
Department of Medicine, Division of Endocrinology, and the Diabetes
Research and Training Center Albert Einstein College of Medicine,
Bronx, NY 10461
APStracts 2:0129E, 1995.
Increased body weight (BW) is one of several confounding factors which
may contribute to the development of insulin resistance in human
aging. Therefore, aging-associated increase in body weight was
determined (by 3H2O) in Sprague-Dawley (S-D, n=40) rats, and was
highly correlated with increased lean body mass (LBM), fat mass (FM),
plasma insulin and FFA levels (r2>0.850, P<0.01 for all).
Insulin responsiveness (18mU/kg/min) (Rd =270+/-10 [mu]mol/kg
LBM/min, P<0.01) decreased by 17 % between 2 month (mo) and 4
mo, but did not decline further at 14 mo. This decrease was inversely
correlated to the increase in FM between 2 mo and 4 mo (r2=0.522,
P<0.05). The decline in Rd was accompanied by an approximately
20% decrease in glycolytic rate by 4 mo (P<0.01) and in glycogen
synthesis rate at 14 mo (P<0.01), when compared with 2 mo rats .
Thus, early impairment in intra-cellular glucose metabolism occurred
concomitantly with an initial, rapid, and disproportionate increase
in FM when compared with LBM. Further increases in FM after 4 mo of
age was not associated with a further decrease in insulin
responsiveness in both S-D and Fischer 344 aging rats.
Received 23 February 1995; accepted in final form 19 April 1995.
APS Manuscript Number E90-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.