A comparison of rat small intestinal insulin and insulin-like growth factor I receptors during fasting and refeeding.
Insulin-like growth factor I (IGF-I) and insulin may be important regulators of intestinal growth. To investigate small intestinal IGF-I receptors (IGF-IR) and insulin receptors (IR) during intestinal cell atrophy and regeneration, we compared indexes of IGF-IR and IR expression in rat jejunum after 72 h of fasting and 24-72 h of enteral refeeding. Fasting induced intestinal atrophy, reduced plasma insulin and IGF-I concentrations, and markedly decreased jejunal IGF-I messenger RNA (mRNA) levels; these changes were reversed by refeeding. Fasting significantly increased jejunal specific insulin binding, IR content (to 230% of the fed control value), and the 9.6- and 7.4-kilobase IR mRNA transcript levels (to 202% and 218% of control values, respectively). These IR indexes rapidly decreased to control levels with refeeding. Levels of IGF-IR (by Scatchard analysis) and IGF-I-R mRNA were not significantly altered with fasting. The 11-kilobase IGF-IR mRNA transcript increased significantly during the first 24 h of refeeding (to 166% of the control value), and IGF-IR number rose 3-fold. We conclude that rat jejunal IR and IGF-IR are differentially regulated by nutrient availability. Up-regulation of jejunal IGF-I and IGF-IR expression during refeeding suggests a role for the IGF action pathway in gut trophic responses to enteral nutrients.
Ziegler
T R
TR
Joslin Research Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA.
Almahfouz
A
A
Pedrini
M T
MT
Smith
R J
RJ
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005215:Fasting; D005502:Food; D015870:Gene Expression; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*
D001786:Blood Glucose; D007328:Insulin; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin