First evidence on the role of palmitoylethanolamide in energy homeostasis in fish

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The objective of this study was to investigate the role of palmitoylethanolamide (PEA) in the regulation of energy homeostasis in goldfish (Carassius auratus). We examined the effects of acute or chronic intraperitoneal treatment with PEA (20 μg·g−1 body weight) on parameters related to food intake and its regulatory mechanisms, locomotor activity, glucose and lipid metabolism, and the possible involvement of transcription factors and clock genes on metabolic changes in the liver. Acute PEA treatment induced a decrease in food intake at 6 and 8 h postinjection, comparable to that observed in mammals. This PEA anorectic effect in goldfish could be mediated through interactions with leptin and NPY, as PEA increased hepatic expression of leptin aI and reduced hypothalamic expression of npy. The PEA chronic treatment reduced weight gain, growth rate, and locomotor activity. The rise in glycolytic potential together with the increased potential of glucose to be transported into liver suggests an enhanced use of glucose in the liver after PEA treatment. In addition, part of glucose may be exported to be used in other tissues. The activity of fatty acid synthase (FAS) increased after chronic PEA treatment, suggesting an increase in the hepatic lipogenic capacity, in contrast with the mammalian model. Such lipogenic increment could be linked with the PEA-induction of REV-ERBα and BMAL1 found after the chronic treatment. As a whole, the present study shows the actions of PEA in several compartments related to energy homeostasis and feeding behavior, supporting a regulatory role for this N-acylethanolamine in fish.