The Essential Role of Insulin-Like Growth Factor-1 in the Intestinal Tropic Effects of Glucagon-Like Peptide-2 in Mice
2006; Elsevier BV; Volume: 131; Issue: 2 Linguagem: Inglês
10.1053/j.gastro.2006.05.055
ISSN1528-0012
AutoresPhilip E. Dubé, Catherine L. Forse, Jasmine Bahrami, Patricia L. Brubaker,
Tópico(s)Genetic Syndromes and Imprinting
ResumoBackground & Aims: Glucagon-like peptide-2 (GLP-2) is an intestinal hormone that acts through unknown pathways to induce intestinal growth. We investigated the role of the insulin-like growth factors (IGF-1 and IGF-2) as mediators of GLP-2–enhanced growth in the murine intestine. Methods: IGF-1 expression and secretion were determined in GLP-2–responsive primary intestinal cultures treated with GLP-2. Parameters of intestinal growth were assessed in wild-type (CD1, Igf1+/+ and Igf2+), heterozygous (Igf1+/−), and null (Igf1−/− and Igf2−P) mice treated chronically with saline, GLP-2, IGF-1, or R-Spondin1. Results: GLP-2 increased IGF-1 messenger RNA expression and IGF-1 secretion in intestinal cultures and increased expression of IGF-1 messenger RNA in mouse small intestine in vivo. Igf1+/+ and Igf2+ mice responded to .1 μg/g−1 per day−1 GLP-2 with increased intestinal weights, morphometric parameters, and proliferative indices. In contrast, Igf1−/− mice were unresponsive to the same dose of GLP-2, failing to demonstrate changes in intestinal weight, morphometry, or proliferation. However, a significant effect of 1 μg/g−1 per day−1 GLP-2 was observed in Igf1−/− mice, but only in terms of small intestinal weight when normalized for body weight. Furthermore, Igf2−P mice demonstrated a partially impaired response in terms of small intestinal growth. Both Igf1−/− and Igf2−P mice exhibited normal-enhanced intestinal growth in response to IGF-1 and/or R-Spondin1. Conclusions: GLP-2 enhances intestinal IGF-1 expression and secretion, and IGF-1 is required for small and large intestinal growth in response to GLP-2. These findings identify IGF-1 as an essential mediator of the intestinotropic actions of GLP-2. Background & Aims: Glucagon-like peptide-2 (GLP-2) is an intestinal hormone that acts through unknown pathways to induce intestinal growth. We investigated the role of the insulin-like growth factors (IGF-1 and IGF-2) as mediators of GLP-2–enhanced growth in the murine intestine. Methods: IGF-1 expression and secretion were determined in GLP-2–responsive primary intestinal cultures treated with GLP-2. Parameters of intestinal growth were assessed in wild-type (CD1, Igf1+/+ and Igf2+), heterozygous (Igf1+/−), and null (Igf1−/− and Igf2−P) mice treated chronically with saline, GLP-2, IGF-1, or R-Spondin1. Results: GLP-2 increased IGF-1 messenger RNA expression and IGF-1 secretion in intestinal cultures and increased expression of IGF-1 messenger RNA in mouse small intestine in vivo. Igf1+/+ and Igf2+ mice responded to .1 μg/g−1 per day−1 GLP-2 with increased intestinal weights, morphometric parameters, and proliferative indices. In contrast, Igf1−/− mice were unresponsive to the same dose of GLP-2, failing to demonstrate changes in intestinal weight, morphometry, or proliferation. However, a significant effect of 1 μg/g−1 per day−1 GLP-2 was observed in Igf1−/− mice, but only in terms of small intestinal weight when normalized for body weight. Furthermore, Igf2−P mice demonstrated a partially impaired response in terms of small intestinal growth. Both Igf1−/− and Igf2−P mice exhibited normal-enhanced intestinal growth in response to IGF-1 and/or R-Spondin1. Conclusions: GLP-2 enhances intestinal IGF-1 expression and secretion, and IGF-1 is required for small and large intestinal growth in response to GLP-2. These findings identify IGF-1 as an essential mediator of the intestinotropic actions of GLP-2. Glucagon-like peptide-2 (GLP-2) is an intestinal meal-stimulated peptide hormone produced by proteolytic processing of proglucagon in enteroendocrine L cells.1Dube P.E. Brubaker P.L. 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Recombinant human R-Spondin1 was a kind gift of Nuvelo, Inc (San Carlos, CA). Because no intestinal cell line has been reported to date that expresses both a functional GLP-2R and IGF-1, we analyzed a heterogeneous whole intestinal primary culture model for these parameters. Fetal rat intestinal cell (FRIC) cultures were therefore prepared as previously described.50Anini Y. Brubaker P.L. Role of leptin in the regulation of glucagon-like peptide-1 secretion.Diabetes. 2003; 52: 252-259Crossref PubMed Scopus (225) Google Scholar Briefly, whole intestines of fetal Wistar rats, gestational age 19–20 days, were enzymatically digested and cultured for 24 hours in Dulbecco’s modified Eagle medium containing 4.5 g/L glucose, 5% (vol/vol) fetal bovine serum, 50 IU/mL penicillin, and 50 μg/mL streptomycin. Experimental replicates were performed on cultures derived from independent litters, wherein multiple replicates were performed to make n = 1. RNA was extracted using the RNeasy kit, following the manufacturer’s instructions, including deoxyribonuclease I digestion (Qiagen Inc, Mississauga, Ontario, Canada). Qualitative reverse-transcription polymerase chain reaction (RT-PCR) was performed with the primers in Table 1, using the One-Step RT-PCR kit (Qiagen Inc), as described in the following text. Quantification of IGF-1 messenger RNA (mRNA) expression was performed using real-time RT-PCR, as described in the following text, with the rat IGF-1 primer/probe set indicated in Table 1 (Applied Biosystems, Foster City, CA).Table 1Primers and TaqMan Gene Expression Assays Used in RT-PCRTargetPrimer sequence/TaqMan catalog no.ReferenceMouse GLP-2RTaqMan: Mm01329473_mlRat GLP-2R5′-ATCCGTCTCCTGTCGCTCCG-3′5′-CGTTGATTTCGCCAATCTGTATTT-3′Mouse proglucagonTaqMan: Mm00801712_mlMouse IGF-15′-GCTGAGCTGGTGGATGCTCTTCAGTTC-3′80Kocamis H. Gahr S.A. Batelli L. Hubbs A.F. Killefer J. 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The media and cells were extract
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