Effects of dietary NEXT ENHANCE®150 on growth performance and expression of immune and intestinal integrity related genes in gilthead sea bream (Sparus aurata L.)

Gilthead sea bream juveniles were fed different doses (0, 50, 100, 200, 300ppm) of NEXT ENHANCE®150 (NE) for 9 weeks. Feed gain ratio (FGR) was improved by a 10% with all the doses, but feed intake decreased in a dose dependent manner. The optimum inclusion level to achieve maximum growth was set at 100ppm. The hepatosomatic index did not vary and only at the highest dose, viscerosomatic and splenosomatic indexes were significantly decreased. No significant changes were found in haematological parameters, plasma biochemistry, total antioxidant capacity and respiratory burst. In a second trial, NE was given at 100ppm alone (D1) or in combination with the prebiotic PREVIDA® (0.5%) (PRE) (D2) for 17 weeks. There were no differences in the growth rates, and FGR was equally improved for D1 and D2. No significant changes in haematology and plasma antioxidant capacity were detected. The histological examination of the liver and the intestine showed no outstanding differences in the liver, but the number of mucosal foldings appeared to be higher in D1 and D2 vs CTRL diet and the density of enterocytes and goblet cells also appeared higher, particularly in the anterior intestine. A 87-gene PCR-array was constructed based on our transcriptomic database (www.nutrigroup-iats.org/seabreamdb) and applied to samples of anterior (AI) and posterior (PI) intestine. It included 54 new gene sequences and other sequences as markers of cell differentiation and proliferation, intestinal architecture and permeability, enterocyte mass and epithelial damage, interleukins and cytokines, pattern recognition receptors (PRR), and mitochondrial function and biogenesis. More than half of the studied genes had significantly different expression between AI and PI segments. The functional significance of this differential tissue expression is discussed. The experimental diets induced significant changes in the expression of 26 genes. The intensity of these changes and the number of genes that were significantly regulated were higher at PI than at AI. At PI, both diets invoked a clear down-regulation of genes involved in cell differentiation and proliferation, some involved in cell to cell communication, cytokines and several PRR. By contrast, up-regulation was mostly found for genes related to enterocyte mass, cell epithelial damage and mitochondrial activity at AI. The changes were of the same order for D1 and D2, except for fatty acid-binding proteins 2 and 6 and the PRR fucolectin, which were higher in D2 and D1 fed fish, respectively. Thus, NE alone or in combination with PRE seems to induce an anti-inflammatory and anti-proliferative transcriptomic profile with probable improvement in the absorptive capacity of the intestine that would explain the improved FGR. © 2015 Elsevier Ltd.
This work has been carried out with financial support from the Commission of the European Communities, specific RTD programme of Framework Programme 7, (FP7/2007-2013) under grant projects ARRAINA (KBBE-2011-288925) and AQUAEXCEL (262336) under TNA project 0019/02/04/14 to ANDROMEDA. It does not necessarily reflect the EU views and in no way anticipates the Commission's future policy in this area. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Additional funding has been received by Spanish MINECO project no. AGL2013-48560 and Generalitat Valenciana (PROMETEOII/2014/085 and ISIC/2012/003).