THE EFFECTS OF DIETARY TRYPTOPHAN IN THE LIVER PROTEOME OF GILTHEAD SEABREAM

Tryptophan is a neutral, aromatic amino acid that is essential for animals , but  is the least abundant amino acid in teleosts and therefore, dietary uptake is the main  source of tryptophan for these animals. Providing adequate levels of this amino acid is critically important for fish growth but also for fish welfare, as tryptophan has been shown to modulate fish behaviour, stress responses, and antioxidant and immune systems.  Biotechnological tools like proteomics are in the spotlight to understand the impact of nutritional factors supplementation on the organism key metabolic pathways, essential for suitable growth. The current study aimed to evaluate the effects of tryptophan , a s a dietary supplement on Gilthead seabream ( Sparus aurata ) growth performance  and  nutritional proteome condition.   

Triplicate groups of 150 seabream (initial body weight: 13.3 ± 0.3g) were randomly distributed in 1000-L tanks under standard rearing conditions . Fish were hand-fed ad libitum during 92 days, with two agglomerated diets  formulated  at 2 different  concentrations - high tryptophan concentration (HTRP) and low tryptophan concentration (LTRP) - regarding the putative requirements for this species.  Fish were then sampled for i ) growth performance evaluation in a time-scale, ii) nutritional status by body composition analysis and iii)  liver collection for biochemical and proteomic characterization.

After 12 weeks of trial, growth performance was similar between diets. Hepatic visceral indicators, body proximate composition and metabolites fingerprinting were not affected by the tryptophan dietary levels. Nevertheless,  differences were found between liver proteome  of fish fed with these different diets.  Our findings suggest that the dietary supplementation of tryptophan constitute a valuable nutritional approach  to potentiate the immune system of captive fish, the allostatic and stress responses towards environmental disturbances. The optimization of the nitrogenous fraction of diets towards proteomics , therefore, demonstrates to be valuable for the dietary  EEA standardization limits, with consequences on aquaculture en vironmental  fingerprint and for the aquafeeds industry.