Dietary fatty acids have been shown to exert a clear effect on the stress response,
modulating the release of cortisol. The role of fatty acids on the expression of
steroidogenic genes has been described in mammals, but little is known in fish. The effect
of different fatty acids on the release of cortisol and expression of stress-related genes
of European sea bass (Dicentrarchus labrax) head kidney, induced by a
pulse of adenocorticotrophin hormone (ACTH), was studied. Tissue was maintained in
superfusion with 60 min of incubation with EPA, DHA, arachidonic acid (ARA), linoleic acid
or α-linolenic acid (ALA) during 490 min. Cortisol was measured by RIA. The quantification
of stress-related genes transcripts was conducted by One-Step TaqMan real-time RT-PCR.
There was an effect of the type of fatty acid on the ACTH-induced release of cortisol,
values from ALA treatment being elevated within all of the experimental period. The
expression of some steroidogenic genes, such as the steroidogenic acute regulatory protein
(StAR) and c-fos, were affected by fatty acids, ALA
increasing the expression of StAR after 1 h of ACTH stimulation whereas DHA, ARA and ALA
increased the expression of c-fos after 20 min. ARA
increased expression of the 11β-hydroxylase gene. Expression of heat shock protein 70
(HSP70) was increased in all the experimental treatments except for ARA. Results
corroborate previous studies of the effect of different fatty acids on the release of
cortisol in marine fish and demonstrate that those effects are mediated by alteration of
the expression of steroidogenic genes.