Developmental differences in the IGF-I system response to severe and chronic calorie malnutrition.
Recent studies in children suggest that there are age-related differences in the insulin-like growth factor I (IGF-I) response to malnutrition. To extend this observation, immature 4-wk-old male rats were fasted for 3 days, fed ad libitum (control), or fed 60 or 40% of control calories (restricted) and compared with 8-wk-old young adults. Over the 3-wk study period, serum total IGF-I levels of the older rats were stable despite reduced insulin levels, whereas IGF-I increased 2.2-fold in the younger controls. With the 40% diet, younger and older rats changed body weight +1 and -1 body wt/day, respectively (P < 0.0001). The restricted younger animals reduced serum IGF-I IGF binding protein-3, acid-labile subunit, and growth hormone binding protein levels significantly more than the restricted older animals. Fasting decreased most of these parameters by 40%, serum insulin by approximately 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.
Oster
M H
MH
Endocrine Research, Department of Genentech, South San Francisco, California 94080, USA. oster@gene.com
Levin
N
N
Fielder
P J
PJ
Robinson
I C
IC
Baxter
R C
RC
Cronin
M J
MJ
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D002352:Carrier Proteins / Q000097:blood; D002908:Chronic Disease; D004435:Eating; D002149:Energy Intake; D005215:Fasting; D006023:Glycoproteins / Q000097:blood; D006304:Health Status; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D009748:Nutrition Disorders / Q000378:metabolism* / Q000473:pathology; D009929:Organ Size; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins
D002352:Carrier Proteins; D006023:Glycoproteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D012333:RNA, Messenger; D011994:Recombinant Proteins; C075944:insulin-like growth factor binding protein, acid labile subunit; D007334:Insulin-Like Growth Factor I; C051815:somatotropin-binding protein