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Journal of Diabetes Research
Volume 2018 (2018), Article ID 6482958, 6 pages
https://doi.org/10.1155/2018/6482958
Research Article

Liraglutide, a GLP-1 Receptor Agonist, Which Decreases Hypothalamic 5-HT2A Receptor Expression, Reduces Appetite and Body Weight Independently of Serotonin Synthesis in Mice

Department of Diabetes Technology, Tohoku University Graduate School of Biomedical Engineering, Sendai, Japan

Correspondence should be addressed to Katsunori Nonogaki; pj.ca.ukohot.dem.crt@ustak

Received 23 September 2017; Revised 17 November 2017; Accepted 14 December 2017; Published 1 February 2018

Academic Editor: Toshiyasu Sasaoka

Copyright © 2018 Katsunori Nonogaki and Takao Kaji. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A recent report suggested that brain-derived serotonin (5-HT) is critical for maintaining weight loss induced by glucagon-like peptide-1 (GLP-1) receptor activation in rats and that 5-HT2A receptors mediate the feeding suppression and weight loss induced by GLP-1 receptor activation. Here, we show that changes in daily food intake and body weight induced by intraperitoneal administration of liraglutide, a GLP-1 receptor agonist, over 4 days did not differ between mice treated with the tryptophan hydroxylase (Tph) inhibitor p-chlorophenylalanine (PCPA) for 3 days and mice without PCPA treatment. Treatment with PCPA did not affect hypothalamic 5-HT2A receptor expression. Despite the anorexic effect of liraglutide disappearing after the first day of treatment, the body weight loss induced by liraglutide persisted for 4 days in mice treated with or without PCPA. Intraperitoneal administration of liraglutide significantly decreased the gene expression of hypothalamic 5-HT2A receptors 1 h after injection. Moreover, the acute anorexic effects of liraglutide were blunted in mice treated with the high-affinity 5-HT2A agonist (4-bromo-3,6-dimethoxybenzocyclobuten-1-yl) methylamine hydrobromide 14 h or 24 h before liraglutide injection. These findings suggest that liraglutide reduces appetite and body weight independently of 5-HT synthesis in mice, whereas GLP-1 receptor activation downregulates the gene expression of hypothalamic 5-HT2A receptors.