Submitted on April 9, 2007
Accepted on February 6, 2008
Insulin-like growth factor-I and glucagon-like peptide-2 responses to fasting followed by controlled or ad libitum refeeding in rats
David Warren Nelson1, Sangita G Murali2, Xiaowen Liu2, Matthew C Koopmann2, Jens Juul Holst3, and Denise M. Ney4*
1 nutritional sciences, university of wisconsin-madison, Madison, Wisconsin, United States
2 Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States
3 Department of Medical Physiology, The Panum Institute, University of Copenhagen, Copenhagen,, Denmark
4 Department of Nutritional Sciences, University of Wisconsin-Madison, Madison,, Wisconsin, United States
* To whom correspondence should be addressed. E-mail: ney{at}nutrisci.wisc.edu.
Luminal nutrients stimulate structural and functional regeneration in the intestine through mechanisms thought to involve insulin-like growth factor-I (IGF-I) and glucagon-like peptide-2 (GLP-2). We investigated the relationship between IGF-I and GLP-2 responses and mucosal growth in rats fasted for 48 h, then refed for 2 or 4 days by continuous intravenous (IV) or intragastric (IG) infusion or ad libitum feeding. Fasting induced significant decreases in body weight, plasma concentrations of IGF-I and bioactive GLP-2, jejunal mucosal cellularity (mass, protein, DNA and villus height), IGF-I mRNA, and ileal proglucagon mRNA. Plasma IGF-I concentration was restored to fed levels with 2 days of ad libitum, but not with 4 days of IV or IG refeeding. Administration of an inhibitor of endogenous GLP-2 (rat GLP-23-33) during ad libitum refeeding partially attenuated mucosal growth and prevented the increase in plasma IGF-I to fed levels; however, plasma GLP-2 and jejunal IGF-I mRNA were restored to fed levels. IG refeeding restored intestinal cellularity and functional capacity (sucrase activity and sodium-glucose transporter-1 expression) to fed levels whereas IV refeeding had no effect. Intestinal regeneration after 4 days of IG or 2 days of ad libitum refeeding was positively associated with increases in plasma concentrations of GLP-2 and jejunal IGF-I mRNA. These data suggest that luminal nutrients stimulate intestinal growth, in part, by increased expression of both GLP-2 and IGF-I.
