| Summary: | Arginine and methionine are indispensable amino acids (AA) for Atlantic salmon, meaning that salmon is unable to produce these AA endogenously and is fully dependent on dietary supply. In addition to be substrates for protein synthesis, these AA are involved in several metabolic pathways in the fish. Arginine is used for production of nitric oxide, creatine, urea and polyamines, while methionine is converted to the methyl donor S-adenosyl methionine (SAM), which is important for polyamine production by supplying the aminopropyl donor decarboxylated SAM. Thus, both arginine and methionine may influence polyamine production. Polyamines are essential for cell growth and differentiation and can modulate gene expression and energy metabolism, stabilize proteins and cell membranes. Polyamines can also induce apoptosis and formation of reactive oxygen species under too high concentrations. Dietary arginine supplementation have been demonstrated to reduce visceral mass while increasing lean mass in pigs and rodents, which has been linked to increased energy consumption caused by increased polyamine production. Hence we aimed to investigate whether arginine supplementation to Atlantic salmon could affect growth and deposition pattern, and to what extent any effects was linked to increased production and catabolism of polyamines. We also assessed if methionine affected polyamine production by modulating SAM availability. Two feeding trials were conducted, in juvenile and adult Atlantic salmon, with graded supplementation of arginine beyond the established requirement for growth. Tissue samples were taken to analyse gene expression, amino acids, polyamines and other metabolic parameters. Liver cells were isolated from the adult salmon fed graded inclusions of arginine and cultured in vitro together with activator/inhibitor of polyamine metabolism, in order to assess the importance of polyamine metabolism for cell survival and lipid metabolism. Metabolomic analysis applying HPLC-QTOF MS were performed on liver and plasma ...
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