This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dubé, P. E. Articles by Brubaker, P. L. Search for Related Content PubMed PubMed Citation Articles by Dubé, P. E. Articles by Brubaker, P. L.

Glucagon-Like Peptide-2 Activates β-Catenin Signaling in the Mouse Intestinal Crypt: Role of Insulin-Like Growth Factor-I

Departments of Physiology (P.E.D., K.J.R., P.L.B.) and Medicine (P.L.B.), University of Toronto, Toronto, Ontario, Canada M5S 1A8

Address all correspondence and requests for reprints to: Dr. P. L. Brubaker, University of Toronto, Medical Sciences Building, Room 3366, 1 King’s College Circle, Toronto, Ontario, Canada M5S 1A8. E-mail: p.brubaker{at}utoronto.ca.

Chronic administration of glucagon-like peptide-2 (GLP-2) induces intestinal growth and crypt cell proliferation through an indirect mechanism requiring IGF-I. However, the intracellular pathways through which IGF-I mediates GLP-2-induced epithelial tropic signaling remain undefined. Because β-catenin and Akt are important regulators of crypt cell proliferation, we hypothesized that GLP-2 activates these signaling pathways through an IGF-I-dependent mechanism. In this study, fasted mice were administered Gly²-GLP-2 or LR³-IGF-I (positive control) for 0.5–4 h. Nuclear translocation of β-catenin in non-Paneth crypt cells was assessed by immunohistochemistry and expression of its downstream proliferative markers, c-myc and Sox9, by quantitative RT-PCR. Akt phosphorylation and activation of its targets, glycogen synthase kinase-3β and caspase-3, were determined by Western blot. IGF-I receptor (IGF-IR) and IGF-I signaling were blocked by preadministration of NVP-AEW541 and through the use of IGF-I knockout mice, respectively. We found that GLP-2 increased β-catenin nuclear translocation in non-Paneth crypt cells by 72 ± 17% (P < 0.05) and increased mucosal c-myc and Sox9 mRNA expression by 90 ± 20 and 376 ± 170%, respectively (P < 0.05–0.01), with similar results observed with IGF-I. This effect of GLP-2 was prevented by blocking the IGF-IR as well as ablation of IGF-I signaling. GLP-2 also produced a time- and dose-dependent activation of Akt in the intestinal mucosa (P < 0.01), most notably in the epithelium. This action was reduced by IGF-IR inhibition but not IGF-I knockout. We concluded that acute administration of GLP-2 activates β-catenin and proliferative signaling in non-Paneth murine intestinal crypt cells as well as Akt signaling in the mucosa. However, IGF-I is required only for the GLP-2-induced alterations in β-catenin.