AUTHOR=Gómez-Boronat Miguel , Isorna Esther , Armirotti Andrea , Delgado María J. , Piomelli Daniele , de Pedro Nuria 

TITLE=Diurnal Profiles of N-Acylethanolamines in Goldfish Brain and Gastrointestinal Tract: Possible Role of Feeding

JOURNAL=Frontiers in Neuroscience

VOLUME=13

YEAR=2019

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2019.00450

DOI=10.3389/fnins.2019.00450

ISSN=1662-453X

ABSTRACT=<p><italic>N</italic>-acylethanolamines (NAEs) are a family of endogenous lipid signaling molecules that are involved in regulation of energy homeostasis in vertebrates with a putative role on circadian system. The aim of this work was to study the existence of daily fluctuations in components of NAEs system and their possible dependence on food intake. Specifically, we analyzed the content of oleoylethanolamide (OEA), palmitoylethanolamide (PEA), stearoylethanolamide (SEA), their precursors (NAPEs), as well as the expression of <italic>nape-pld</italic> (NAEs synthesis enzyme), <italic>faah</italic> (NAEs degradation enzyme), and <italic>pparα</italic> (NAEs receptor) in gastrointestinal and brain tissues of goldfish (<italic>Carassius auratus</italic>) throughout a 24-h cycle. Daily profiles of <italic>bmal1a</italic> and <italic>rev</italic>-erbα expression in gastrointestinal tissues were also quantified because these clock genes are also involved in lipid metabolism, are PPAR-targets in mammals, and could be a link between NAEs and circadian system in fish. Gastrointestinal levels of NAEs exhibited daily fluctuations, with a pronounced and rapid postprandial increase, the increment being likely caused by food intake as it is not present in fasted animals. Such periprandial differences were not found in brain, supporting that NAEs mobilization occurs in a tissue-specific manner and suggesting that these three NAEs could be acting as peripheral satiety signals. The abundance of <italic>pparα</italic> mRNA displayed a daily rhythm in the intestine and the liver, suggesting a possible rhythmicity in the NAEs functionality. The increment of <italic>pparα</italic> expression during the rest phase can be related with its role stimulating lipid catabolism to obtain energy during the fasting state of the animals. In addition, the clock genes <italic>bmal1a</italic> and <italic>rev</italic>-erbα also showed daily rhythms, with a <italic>bmal1a</italic> increment after feeding, supporting its role as a lipogenic factor. In summary, our data show the existence of all components of NAEs system in fish (OEA, PEA, SEA, precursors, synthesis and degradation enzymes, and the receptor PPARα), supporting the involvement of NAEs as peripheral satiety signals.</p>