Introduction
The continuous growth of the aquaculture sector requires an understanding on how to improve fish robustness throughout the production cycle. Nutrition and concomitantly gut health are core components to promote performance and juvenile quality. Methods and biomarkers for assessing dietary effects on fish growth and health will contribute to increase biological efficiency.
An inflammatory process will automatically affect cellular metabolism, and consequently the methylation balance that is pivotal to animal homeostasis. Nowadays, changes in the concentrations of specific metabolites involved in the methylation cycle are utilized as biomarkers for Humans diseases. In some cases, the methylation potential, measured as plasma levels of S-adenosyl methionine (SAM) and S-adenosyl homocysteine (SAH), may highlight homeostatic disruptions in the gut. In addition, SAM is a known precursor of glutathione and its modulation associated to apoptosis and polyamine synthesis in intestinal inflammatory conditions.
Soy saponin (SAP) have been shown to provoke mild to severe intestinal inflammatory processes in fish. In this study Nile tilapia (Oreochromis niloticus) and gilthead seabream (Sparus aurata) juveniles were fed with a commercial-like diet supplemented with SAP with the purpose of assessing if the metabolites of methylation cycle could shed some light on possible biomarkers for gut disruption in fish.
Tilapia were fed one of the two diets for three days. Seabream juveniles were fed diet pellets by the “assisted-feeding” technique. Fish were fed one of the two diets according to the experimental treatment: CTRL – fish fed diet without SAP; SAP– fish fed diet containing SAP (98% chemical purity). All fish were fed at 3% of body weight. Two groups of 15 per species and treatment were transferred to 100 L cylindric-conical tanks and kept at optimal conditions.
At 3 days of feeding for tilapia, 24h after assisted-feeding for seabream, intestine was sampled in 12 tilapia and 9 seabream juveniles per treatment (n=2) for SAM and SAH analyses. Data analysis was performed using t-test. Also, data was subjected to principal component analysis (PCA) using the ggbiplot and factoextra packages for the open-source software R version 4.2.1 (R Core team).
Preliminary results suggest that methylation capacity could be species-specific since the ratio SAM:SAH was 3-fold higher in tilapia than in gilthead seabream. A lower capacity could be expected since tilapia were fed a higher amount of SAP during the feeding period. These results are a novel approach in fish to assess the intestine response to a nutritional insult.
This work was funded through Project FICA, co-financed by COMPETE 2020, CRESC Algarve 2020, Portugal 2020 and the European Union through ERDF under reference ALG-01-0247-FEDER-047175. This study received Portuguese national funds from FCT – Foundation for Science and Technology through projects UIDB/04326/2020, UIDP/04326/2020 and LA/P/0101/2020 to CCMAR.