Gastroenterology

Gastroenterology

Volume 130, Issue 1, January 2006, Pages 150-164
Gastroenterology

Basic–alimentary tract
GLP-2 Receptor Localizes to Enteric Neurons and Endocrine Cells Expressing Vasoactive Peptides and Mediates Increased Blood Flow

https://doi.org/10.1053/j.gastro.2005.11.005Get rights and content

Background & Aims: Glucagon-like peptide-2 (GLP-2) is a nutrient-responsive hormone that exerts diverse actions in the gastrointestinal tract, including enhancing epithelial cell survival and proliferation, mucosal blood flow, and nutrient uptake and suppressing gastric motility and secretion. These actions are mediated by the G-protein-coupled receptor, GLP-2R. Cellular localization of the GLP-2R and the nature of its signaling network in the gut, however, are poorly defined. Thus, our aim was to establish cellular localization of GLP-2R and functional connection to vascular action of GLP-2 in the gut.

Methods: Intestinal cellular GLP-2R localization was determined with real-time, quantitative reverse-transcription polymerase chain reaction (qRT-PCR) of laser capture microdissected subtissue and fluorescence in situ hybridization and also with double and/or triple immunostaining of human and pig tissue using a validated GLP-2R polyclonal antibody. Superior mesenteric arterial blood flow and intestinal eNOS expression and phosphorylation were measured in TPN-fed pigs acutely (4 h) infused with GLP-2.

Results: We show that the porcine GLP-2R mRNA was expressed in the villus epithelium and myenteric plexus. GLP-2R protein was co-localized by confocal immunohistochemistry with serotonin in enteroendocrine cells and also with endothelial nitric oxide synthase (eNOS)-expressing and vasoactive intestinal polypeptide-positive enteric neurons. In neonatal pigs, GLP-2 infusion dose-dependently stimulated intestinal blood flow and coordinately upregulated the expression of intestinal eNOS mRNA, protein, and phosphorylation (eNOS-Ser1117).

Conclusions: We conclude that the GLP-2-induced stimulation of blood flow is mediated by vasoactive neurotransmitters that are colocalized with GLP-2R in 2 functionally distinct cell types within the gastrointestinal tract.

Section snippets

Endogenous GLP-2-Deficient Pig Model

The protocol of this study was approved by the Animal Care and Use Committee of Baylor College of Medicine. Thirty-two, 12-day-old female pigs (3.3 ± 0.2 kg, Large White × Hampshire × Duroc) were surgically implanted with catheters in a carotid artery and an external jugular vein and with an ultrasonic flow probe on the SMA under general anesthesia.21 The pigs were maintained with total parenteral nutrition (TPN) for 1 week to suppress secretion of endogenous GLP-2. Then, the first group of

Expression of Porcine GLP-2 Receptor mRNA

The expression of porcine GLP-2 receptor (pGLP-2R) mRNA was determined by real-time qRT-PCR of morphologically defined villus epithelium and myenteric plexus procured by laser capture microdissection (Figure 1). First, a partial pGLP-2R DNA (456 bp) was cloned and sequenced, having an 86% of identity to that of human GLP-2R (hGLP-2R) DNA (accession No: AF105367). Based on the sequence of this partial pGLP-2R, primers and probe were designed for real-time qRT-PCR. A high-sensitivity, 1-step

Discussion

We have demonstrated that the GLP-2R is localized to enteroendocrine cells and enteric neurons in both the human and porcine intestine. Moreover, we show that the GLP-2R is colocalized with 5-HT-containing enteroendocrine cells and with eNOS-expressing and VIP-positive enteric neurons. The evidence of dual GLP-2R expression in both enteroendocrine cells and enteric neurons resolves previous contradictory observations.12, 14 More importantly, however, these findings establish a spatial framework

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    Supported by federal funds from the US Department of Agriculture, Agricultural Research Service under Cooperative Agreement NO 58-6250-6-001, the National Institutes of Health grant HD33920 (to D.G.B.), and the Texas Gulf Coast Digestive Diseases Center supported by National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Disease grant P30 DK56338.

    This work is a publication of the USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine and Texas Children’s Hospital, Houston, Texas. The contents of this publication do not necessarily reflect the views or policies of the US Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the US government.

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