Glucagon-like peptide-2 activates beta-catenin signaling in the mouse intestinal crypt: role of insulin-like growth factor-I.
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 beta-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 Gly(2)-GLP-2 or LR(3)-IGF-I (positive control) for 0.5-4 h. Nuclear translocation of beta-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-3beta 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 beta-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 beta-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 beta-catenin.
Dubé
Philip E
PE
Department of Physiology, University of Toronto, Ontario, Canada M5S 1A8.
Rowland
Katherine J
KJ
Brubaker
Patricia L
PL
D000818:Animals; D005215:Fasting / Q000378:metabolism; D005260:Female; D053767:Glucagon-Like Peptide 2 / Q000494:pharmacology*; D006609:High Mobility Group Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008871:Microvilli; D008954:Models, Biological; D051058:Oncogene Protein v-akt / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors; D055758:SOX9 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism*
D053767:Glucagon-Like Peptide 2; D006609:High Mobility Group Proteins; D019394:Ki-67 Antigen; C084339:LR(3)IGF-I; C498355:Mki67 protein, mouse; C501177:NVP-AEW541; D011743:Pyrimidines; D011758:Pyrroles; D055758:SOX9 Transcription Factor; C527933:Sox9 protein, mouse; D014157:Transcription Factors; D051176:beta Catenin; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D051058:Oncogene Protein v-akt