Developmental differences in the insulin-like growth factor-i
system response to severe and chronic calorie malnutrition.
Oster, Michelle H., Nancy Levin, Paul J. Fielder, Iain C. A. F.
Robinson, Robert C. Baxter, and Michael J. Cronin.
Endocrine Research Department (M.H.O, N.L., M.J.C),
Pharmacokinetics and Metabolism Department (P.J.F.), Genentech, Inc.,
460 Point San Bruno Boulevard, South San Francisco, California 94080
and National Institute for Medical Research (I.C.A.F.R), The
Ridgeway, Mill Hill, London NW7 1AA England and Kolling Institute of
Medical Research (R.C.B.) Royal North Shore Hospital
APStracts 2:0250E, 1995.
Recent studies in children suggest there are age-related differences
in the IGF-I response to malnutrition. To extend this observation,
immature 4-week old male rats were fasted for 3 days, fed ad libitum
(control), 60% or 40% of control calories (restricted) and compared
to 8-week old young adults. Over the 3 week study period, serum total
IGF-I levels of the older rats were stable despite reduced insulin
levels, while IGF-I increased 2.2 - fold in the younger controls.
With the 40% diet, younger and older rats changed body weight +1 and
-1 g body weight per day, respectively (P < 0.0001). The
restricted younger animals reduced serum IGF-I, IGFBP-3, acid-labile
subunit (ALS) and growth hormone binding protein (GHBP) levels
significantly more than the restricted older animals. Fasting
decreased most of these parameters by 40%, serum insulin by 80% and
body weight by 9%, regardless of age. We conclude that the
suppression of the IGF-I system in response to chronic
undernutrition, but not acute fasting, is greater in maturing than
young adult rats.
Received 14 August 1995; accepted in final form 28 November 1995.
APS Manuscript Number E389-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 12 December 95