•Glucose homeostasis is rearranged by dexamethasone (DEX) treatment with long-term deleterious effects.•DEX significantly reduced circulating levels of endogenous cortisol as well as hematocrit.•DEX ...significantly upregulates gene expression of brain trh along with hypophyseal pomcb and gh.•In contrast to control or cortisol groups, DEX does not promote anion-absorptive currents in the distal intestine.•Only DEX treatment promoted significant differences between proximal and distal intestinal regions’ transepithelial electric resistance.
This study approached the long-term oral administration of cortisol (F) and dexamethasone (DEX), two synthetic glucocorticoids, compared to a control group (CT) in the juveniles of a marine teleost, the gilthead seabream (Sparus aurata). Physiologically, DEX treatment impaired growth, which appears to be linked to carbohydrate allocation in muscle and liver, hepatic triglycerides depletion, and reduced hematocrit. Hypophyseal gh mRNA expression was 2-fold higher in DEX than in CT or F groups. Similarly, hypothalamic trh and hypophyseal pomcb followed this pattern. Plasma cortisol levels were significantly lower in DEX than in CT, while F presented intermediate levels. In the posterior intestine, measured short circuit-current (Isc) was more anion absorptive in CT and F compared to the DEX group, whereas Isc remained unaffected in the anterior intestine. The derived transepithelial electric resistance (TEER) significantly differed between intestinal regions in the DEX group. These results provide new insights to understand better potential targeted biomarkers indicative of the differential glucocorticoid or mineralocorticoid-receptors activation in fish.
Aquaculture procedures usually induce stress that affects the physiological status of fish. For this reason, the inclusion of additives in fish feeds to palliate stress might be a good alternative. ...This study aimed to assess the antimicrobial activity of citronella (Cymbopogon nardus) essential oil (CEO) against bacterial pathogens and to determine its dietary impact on the growth performance of Sparus aurata. In vitro tests confirmed that CEO possesses antimicrobial activity against several fish-specific pathogens. For the in vivo tests, three experimental groups were fed for 60 days with different concentrations of CEO: CTRL (0 mL kg−1 fish feed); CEO1 (1 mL kg−1 fish feed); and CEO2 (2 mL kg−1 fish feed). At the end of the experiment, the physiological status was characterized. Subsequently, the specimens of the CTRL and CEO2 groups were subjected to a challenge with an injection of Poly I:C for immune stimulation. Although S. aurata individuals tolerated CEO inclusion without compromising growth performance, it significantly reduced glycogen in the CEO2 group, concomitant to an increment of total peripheral leucocytes. Moreover, different hematological profiles’ responsive patterns against an inflammatory stimulus were observed. In conclusion, our results suggest that the use of CEO as a fish feed additive can prevent bacterial outbreaks and improve potential in vivo disease resistance in S. aurata without negatively affecting growth.
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