Glucagon-like peptide containing pathways in the regulation of feeding behaviour.
The pre-proglucagon derived peptides, glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) are both involved in a wide variety of peripheral functions, such as glucose homeostasis, gastric emptying, intestinal growth, insulin secretion as well as the regulation of food intake. Pre-proglucagon is also found in the brainstem in a small population of nerve cells in the nucleus of the solitary tract (NTS) that process the pre-propeptide as in the gut to yield GLP-1 and GLP-2. GLP-1 containing nerve fibres and the GLP-1 receptor are found predominantly in hypothalamic midline nuclei. GLP-1 given centrally to naive rats results in a marked induction of c-Fos protein in the supraoptic nucleus, paraventricular nucleus of the hypothalamus (PVN) and central nucleus of the amygdala, but only a moderate increase in the arcuate nucleus. The pattern of c-Fos activation is compatible with the appetite suppressing effects of GLP-1. This anorectic effect of GLP-1 appears to be mediated by the PVN, as direct injections of GLP-1 into this nucleus cause anorexia without concomitant taste aversion, suggesting a specific action upon neuronal circuits involved in the regulation of feeding. Recent experiments have also shown that GLP-1 is implicated in mediating signals from the gastrointestinal tract pertaining to discomfort and malaise. The distribution of the co-localised peptide, GLP-2, displays a perfect overlap with GLP-1 in the CNS with the highest concentration in the diffuse ventral part of the dorsomedial nucleus (DMHv). In contrast to the widely distributed GLP-1 receptor mRNA, GLP-2 receptor mRNA is exclusively expressed in the compact part of the DMH (DMHc). Interestingly, the DMHc is also the only nucleus responding to central administration of GLP-2 with a significant increase in the number of c-Fos positive cells. When injected into the lateral ventricle, GLP-2 has a marked inhibitory effect on feeding. The effect of GLP-2 on feeding is both behaviourally and pharmacologically specific. Future experiments will elucidate whether or not GLP-1 and GLP-2 are involved in the long-term or short-term regulation of feeding behaviour and hence have an impact on bodyweight.
Tang-Christensen
M
M
Department of Medical Anatomy Sect B, University of Copenhagen, Copenhagen, Denmark. mtc@ccbr.dk
Vrang
N
N
Larsen
P J
PJ
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D004435:Eating / Q000502:physiology*; D005215:Fasting / Q000502:physiology; D005934:Glucagon / Q000502:physiology*; D052216:Glucagon-Like Peptide 1; D006706:Homeostasis; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology; D010446:Peptide Fragments / Q000502:physiology*; D011498:Protein Precursors / Q000502:physiology*; D051381:Rats
D009478:Neuropeptide Y; D010446:Peptide Fragments; D011498:Protein Precursors; D000804:Angiotensin II; D052216:Glucagon-Like Peptide 1; D005934:Glucagon