Dietary novel oils modulate neural function and preserve locomotor response in gilthead sea bream (Sparus aurata) juveniles by regulating synthesis and contents of fatty acids in brain

Abstract

N-3 long-chain polyunsaturated fatty acids (LC-PUFA), particularly docosahexaenoic acid (22:6n-3, DHA), are the most important fatty acids with physiological significance in brain function of all vertebrates. Recently, novel lipid sources are available for the industry, including products obtained from microorganisms. Dietary fatty acid profiles may affect tissue composition and cell functioning. To determine the effect of novel lipid sources on behaviour and neural function in gilthead sea bream (Sparus aurata), juveniles were fed three isoproteic and isoenergetic diets containing either (FO), a microalgae oil combined with poultry oil (DD) or only poultry oil (PO). Behaviour response, brain fatty acid composition and relative expression of neurogenesis and neural activity related-genes in telencephalon were evaluated during 5 months of feeding with the experimental diets. Brain of sea bream fed diet PO showed the highest DHA content as well as increased desaturation and elongation products, contrary to the dietary pattern. This, together with an increased telencephalic fads2 expression denoted the effective activation of LC-PUFA synthesis and retention as a compensatory mechanism for a dietary deficiency. Furthermore, neurod6, bdnf and nos1 were proportionally upregulated in relation to the neural DHA content. Locomotor performance during cruising and escape responses was not affected by the experimental diets. However, there was a tendency for escape latency to be longest in fish fed PO and DD diets, and a relationship between escape latency and brain n-6 docosapentaenoic acid (DPA) contents was suggested. Indeed, the relation of n-6 DPA with behavioural deficits was shown previously in mammals and might deserve further attention and corroboration in fish as well in the future