Glucagon-Like Peptide-1 Receptor Agonist, Exendin-4, Regulates Feeding-Associated Neuropeptides in Hypothalamic Neurons in Vivo and in Vitro

Feb 16, 2012Endocrinology

The appetite hormone exendin-4 controls feeding-related brain signals in hypothalamus neurons inside and outside the body

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Abstract

Exendin-4 induces anorexia by activating specific neuropeptidergic neurons in the hypothalamus.

Activation of α-melanocyte-stimulating hormone/proopiomelanocortin and neuropeptide Y neurons occurs in the arcuate nucleus during exendin-4-induced anorexia.
Neuropeptide Y and neurotensin-expressing neurons are activated in the paraventricular nucleus with exendin-4 administration.
Ghrelin-expressing neurons in multiple hypothalamic regions (arcuate, paraventricular, and periventricular) are also activated by exendin-4.
Exendin-4 increases levels of cAMP and activates signaling pathways that regulate neuropeptide mRNA expression.
Neuropeptides neurotensin and ghrelin may mediate the anorexic effects of exendin-4 through a protein kinase A-dependent mechanism.

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Exendin-4, a long-acting glucagon-like peptide-1 receptor (GLP-1R) agonist, is a potential regulator of feeding behavior through its ability to inhibit gastric emptying, reduce food intake, and induce satiety. GLP-1R activation by exendin-4 induces anorexia; however, the specific populations of neuropeptidergic neurons activated by exendin-4 within the hypothalamus, the central regulator of energy homeostasis, remain unclear. This study determines whether exendin-4 regulates hypothalamic neuropeptide expression and explores the signaling mechanisms involved. The distribution and quantity of exendin-4-induced c-Fos immunoreactivity were evaluated to determine activation of α-melanocyte-stimulating hormone/proopiomelanocortin, neuropeptide Y, neurotensin (NT), and ghrelin neurons in hypothalamic nuclei during exendin-4-induced anorexia in mice. Additionally, exendin-4 action on NT and ghrelin transcript regulation was examined in immortalized hypothalamic neurons. With anorexia induced by intracerebroventricular exendin-4, α-melanocyte-stimulating hormone/proopiomelanocortin and neuropeptide Y neurons were activated in the arcuate nucleus, with simultaneous activation of NT-expressing neurons in the paraventricular nucleus, and ghrelin-expressing neurons in the arcuate nucleus, paraventricular nucleus, and periventricular hypothalamus, suggesting that neurons in one or more of these areas mediate the anorexic action of exendin-4. In the hypothalamic neuronal cell models, exendin-4 increased cAMP, cAMP response element-binding protein/activating transcription factor-1 and c-Fos activation, and via a protein kinase A-dependent mechanism regulated NT and ghrelin mRNA expression, indicating that these neuropeptides may serve as downstream mediators of exendin-4 action. These findings provide a previously unrecognized link between central GLP-1R activation by exendin-4 and the regulation of hypothalamic NT and ghrelin. Further understanding of this central GLP-1R activation may lead to safe and effective therapeutics for the treatment of metabolic disorders.

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Glucagon-Like Peptide-1 Receptor Agonist, Exendin-4, Regulates Feeding-Associated Neuropeptides in Hypothalamic Neurons in Vivo and in Vitro

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