title: Dietary tryptophan and methionine as modulators of European seabass (Dicentrarchus labrax) immune status and inflammatory response.
abstract: Amino acids regulate key metabolic pathways important to immune responses and their nutritional supply may increase synthesis of immune-related proteins. The present study aimed to evaluate the effects of dietary supplementation of tryptophan and methionine on European seabass (Dicentrarchus labrax) cellular and humoral status. The immunomodulatory effects of tryptophan and methionine during an inflammatory insult was also evaluated after intraperitoneal injection with inactivated Photobacterium damselae subsp. piscicida (Phdp). A practical isonitrogenous (45% crude protein) and isolipidic (16% crude fat) diets was formulated to include fish meal and a blend of plant feedstuffs as protein sources and fish oil as the main lipid source (CRL diet). Two other diets were formulated similar to the control but including L-tryptophan or L-methionine at ×2 the requirement level (diets TRP and MET, respectively). European seabass weighing 275 g were fed the experimental diets for a period of 15 days before being sampled (trial 1). Then, fish were subjected to a peritoneal inflammation by intraperitoneally injecting UV killed Phdp (10(6) colony forming units ml(-1)) and sampled following 4 and 24 h post-injection (trial 2). Fish injected with a saline solution served as control. The haematological profile, peripheral cell dynamics and several plasma immune parameters were determined in trials 1 and 2, whereas cell migration to the inflammatory focus was also determined in trial 2. MET positively affected European seabass immune status by improving the peripheral leucocyte response, complement activity and bactericidal capacity, a stronger cellular recruitment to the inflammatory focus, and higher plasma peroxidase and bactericidal activities. TRP also seemed to improve immunostimulation, as there was a trend to augment both cell-mediated immunity and humoral capacity. However, TRP failed to improve an inflammatory response, verified by a decrease in blood phagocyte numbers and lack of immune cells recruitment. In summary, it is confirmed that MET has a pronounced influence on the innate immune response to inflammation, which is more evident than TRP, and raises its potential to incorporate in functional feeds to be used in prophylactic strategies against predictable unfavourable events.
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal; Instituto de Ciências Biomédicas Abel Salazar (ICBAS-UP), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal. Electronic address: mcasimiro@ciimar.up.pt.
authors.forename: Marina
authors.initials: M
authors.lastname: Machado
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal; Departamento de Biologia, Faculdade de Ciências da Universidade do Porto (FCUP), 4169-007 Porto, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Azeredo
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal.
authors.forename: Patricia
authors.initials: P
authors.lastname: Díaz-Rosales
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal; Instituto de Ciências Biomédicas Abel Salazar (ICBAS-UP), Universidade do Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Afonso
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal.
authors.forename: Helena
authors.initials: H
authors.lastname: Peres
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal; Departamento de Biologia, Faculdade de Ciências da Universidade do Porto (FCUP), 4169-007 Porto, Portugal.
authors.forename: Aires
authors.initials: A
authors.lastname: Oliva-Teles
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR/CIMAR), Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal. Electronic address: bcostas@ciimar.up.pt.
authors.forename: Benjamín
authors.initials: B
authors.lastname: Costas
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001492:Bass / Q000276:immunology* / Q000378:metabolism; D004032:Diet / Q000662:veterinary*; D019587:Dietary Supplements; D007111:Immunity, Cellular; D056724:Immunity, Humoral; D056747:Immunomodulation; D007274:Injections, Intraperitoneal / Q000662:veterinary; D008715:Methionine / Q000276:immunology*; D010776:Photobacterium / Q000502:physiology; D014364:Tryptophan / Q000276:immunology*
chemical_list: D014364:Tryptophan; D008715:Methionine
keywords: Amino acids; Immune response; Immunomodulation; Inflammation; Photobacterium damselae subsp. piscicida