Effects of oleoylethanolamide (OEA) on food intake and locomotor activity in goldfish (Carassius auratus)

Abstract

Energy homeostasis in vertebrates is regulated by neuroendocrine systems by adjusting caloric intake to energy expenditure. Oleoylethanolamide (OEA), an endogenous lipid synthesized in the intestine, plays a significant role in the regulation of energy balance in mammals, modulating feeding, locomotor activity and lipid metabolism. To date, the role of OEA in non-mammalian vertebrates and particularly in fish remains to be explored. The aim of the present study was to elucidate the possible role of OEA on food intake and locomotor activity in the cyprinid Carassius auratus. Goldfish were intraperitoneally (IP) injected with 10 µl vehicle/g body weight (bw) or containing OEA (5 µg/g bw). Food intake was individually quantified at different time intervals post-injection (0-2, 2-8 and 0-8 h). Swimming activity was registered in tanks with 6 fish at the same time periods. Blood samples were collected at 2 h post-injection to quantify plasma glucose and triglyceride levels. The IP administration of OEA significantly reduced food intake and swimming activity at 2 h post-injection, but not during the next discrete interval (2-8 h), suggesting that OEA acts at short time in goldfish, in agreement with previous findings in mammals. A significant reduction in circulating triglycerides induced by OEA was observed at 2 h post-injection, as reported in mammals. In summary, present results show for the first time in a non-mammalian vertebrate that OEA, a bioactive lipid amide, may be involved in the regulation of feeding, locomotor activity and lipid metabolism.