Effects of aging and caloric restriction on IGF-I, IGF-I receptor, IGFBP-3 and IGFBP-4 gene expression in the rat stomach and colon.
The purpose of this study was to determine the effects of aging and caloric restriction (CR) on insulin-like growth factor-I (IGF-I), IGF-I receptor (IGF-IR), IGF-binding protein-3 (IGFBP-3) and IGFBP-4 expression in the stomach and colon of male Fischer 344 rats. Stomach and colonic RNA were prepared from ad libitum (AL) fed or long-term CR rats. Stomach IGF-I, IGFBP-3 and IGFBP-4 mRNA levels increased significantly (P</=0.05), while colonic IGF-I mRNA levels were unchanged in aged AL rats. In aged CR rats, stomach IGFBP-3 mRNA levels decreased. Stomach and colonic IGF-IR mRNA levels declined with aging in AL and CR rats (P</=0.05). Colonic IGFBP-3 mRNA levels decreased significantly with aging in AL rats. There were no changes in colonic IGFBP-4 mRNA levels in aged AL or CR rats. Increased expression of stomach IGF-I, IGFBP-3 and IGFBP-4 in aged AL rats suggests that the stomach attempts to preserve IGF activity by increasing local expression of IGF-I and IGFBPs. Because the aging colon has a propensity to develop cancer, it may adapt to increased colonic IGF-I expression by reducing IGF-IR and IGFBP-3 expression. Additionally, CR lowers colonic IGF-I expression in aged rats (24 months) which may also be a protective adaptive mechanism.
Hallberg
L M
LM
Department of Surgery, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0725, USA.
Ikeno
Y
Y
Englander
E
E
Greeley
G H
GH
D000375:Aging / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D003106:Colon / Q000378:metabolism*; D002149:Energy Intake; D005753:Gastric Mucosa / Q000378:metabolism*; D015870:Gene Expression; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics*; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008297:Male; D012333:RNA, Messenger; D051381:Rats; D011916:Rats, Inbred F344; D017526:Receptor, IGF Type 1 / Q000235:genetics*
D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1