Glucagon-like Peptide (GLP)-2 Action in the Murine Central Nervous System Is Enhanced by Elimination of GLP-1 Receptor Signaling

Julie Lovshin,Jennifer Estall,Bernardo Yusta,Theodore J Brown,Daniel J Drucker

doi:10.1074/jbc.m009382200

Abstract

Glucagon-like peptide-2 (GLP-2) regulates energy homeostasis via effects on nutrient absorption and maintenance of gut mucosal epithelial integrity. The biological actions of GLP-2 in the central nervous system (CNS) remain poorly understood. We studied the sites of endogenous GLP-2 receptor (GLP-2R) expression, the localization of transgenic LacZ expression under the control of the mouse GLP-2R promoter, and the actions of GLP-2 in the murine CNS. GLP-2R expression was detected in multiple extrahypothalamic regions of the mouse and rat CNS, including cell groups in the cerebellum, medulla, amygdala, hippocampus, dentate gyrus, pons, cerebral cortex, and pituitary. A 1.5-kilobase fragment of the mouse GLP-2R promoter directed LacZ expression to the gastrointestinal tract and CNS regions in the mouse that exhibited endogenous GLP-2R expression, including the cerebellum, amygdala, hippocampus, and dentate gyrus. Intracerebroventricular injection of GLP-2 significantly inhibited food intake during dark-phase feeding in wild-type mice. Disruption of glucagon-like peptide-1 receptor (GLP-1R) signaling with the antagonist exendin-(9-39) in wild-type mice or genetically in GLP-1R(-)/- mice significantly potentiated the anorectic actions of GLP-2. These findings illustrate that CNS GLP-2R expression is not restricted to hypothalamic nuclei and demonstrate that the anorectic effects of GLP-2 are transient and modulated by the presence or absence of GLP-1R signaling in vivo.

Highlights

Glucagon-like peptide-2 (GLP-2) regulates energy homeostasis via effects on nutrient absorption and maintenance of gut mucosal epithelial integrity
We studied the sites of endogenous GLP-2 receptor (GLP-2R) expression, the localization of transgenic LacZ expression under the control of the mouse GLP-2R promoter, and the actions of GLP-2 in the murine central nervous system (CNS)
We reexamined the localization of rodent CNS GLP-2R expression using a combination of reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry analyses

Summary

EXPERIMENTAL PROCEDURES

All animal experiments were approved and carried out strictly in accordance with the Canadian Council on Animal Care guidelines and the Animal Care Committee at the Toronto General Hospital, University Health Network (Toronto, Ontario, Canada). PCR products were separated by gel electrophoresis; transferred onto a nylon membrane (GeneScreen, Life Technologies, Inc.); and hybridized with 1) a 32P-labeled internal cDNA probe for the rat GLP-2R [33, 34], 2) a 32P-labeled internal lacZ oligonucleotide (5Ј-TCAGGAAGATCGCACTCCAGC-3Ј), or 3) a 32P-labeled internal cDNA probe for rat glyceraldehyde-3-phosphate dehydrogenase [39]. Analysis of GLP-2R Signaling in GLP-2R-transfected Baby Hamster Kidney (BHK) Cells—BHK fibroblast cells stably transfected with either the rat GLP-1R or GLP-2R were propagated as previously described [42], and the levels of intracellular cAMP were assayed following exposure to individual peptides in Dulbecco’s modified Eagle’s medium containing 100 ␮M 3-isobutyl-1-methylxanthine as reported [41, 42]. Animals were injected with peptide either at 7 p.m. (for dark-phase feeding studies) or at 10 a.m. following an overnight fast of 15 h (for fasting studies)

RESULTS

Peripheral tissues

DISCUSSION