GLP-2 receptor localizes to enteric neurons and endocrine cells expressing vasoactive peptides and mediates increased blood flow.
OBJECTIVE
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.
Guan
Xinfu
X
USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA.
Karpen
Heidi E
HE
Stephens
John
J
Bukowski
John T
JT
Niu
Sanyong
S
Zhang
Guangcheng
G
Stoll
Barbara
B
Finegold
Milton J
MJ
Holst
Jens J
JJ
Hadsell
Darryl
D
Hadsell
Darry L
DL
Nichols
Buford L
BL
Burrin
Douglas G
DG
D000818:Animals; D019858:Enteroendocrine Cells / Q000502:physiology; D005260:Female; D000067758:Glucagon-Like Peptide-2 Receptor; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007421:Intestine, Small / Q000098:blood supply* / Q000294:innervation* / Q000502:physiology; D008638:Mesenteric Arteries / Q000502:physiology; D009474:Neurons / Q000502:physiology; D052250:Nitric Oxide Synthase Type III / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D018027:Receptors, Glucagon / Q000032:analysis* / Q000502:physiology*; D012039:Regional Blood Flow; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013552:Swine; D014660:Vasoactive Intestinal Peptide / Q000096:biosynthesis
D000067758:Glucagon-Like Peptide-2 Receptor; D012333:RNA, Messenger; D018027:Receptors, Glucagon; D014660:Vasoactive Intestinal Peptide; D052250:Nitric Oxide Synthase Type III