Wuxi Fisheries College, Nanjing Agricultural University, Wuxi, 214081, China.
Key Laboratory for Genetic Breeding of Aquatic Animals and Aquaculture Biology, Freshwater Fisheries Research Center (FFRC), Chinese Academy of Fishery Sciences (CAFS), Wuxi, 214081, China.
Fish Shellfish Immunol. 2019 Oct;93:474-483. doi: 10.1016/j.fsi.2019.08.006. Epub 2019 Aug 3.
Dietary administration of tryptophan has been proved improving growth performance of fish. An 8-week feeding trial was conducted to investigate the effects of dietary tryptophan level on antioxidant capacity and immune response through Nrf2 and TOR signaling pathway. The results showed that, 0.08% tryptophan level significantly increased plasma aspartate aminotransferase (AST), while immunoglobulin M (IgM) and alkaline phosphatase (ALP) were strikingly increased by 0.40% level. The level of plasma complement component 3 (C3), alanine aminotransferase (ALT) and albumin (ALB) were independent of tryptophan supplementation. Total superoxide dismutase (T-SOD), catalase (CAT), total antioxidant capacity (T-AOC) and glutathione (GSH) activity were increased with increasing dietary tryptophan level until 0.40% and then decreased, while the level of malondialdehyde (MDA) showed a reverse trend. 0.19% and 0.28% tryptophan level significantly improved the glutathione peroxidase 1 (GPx-1) activity. Compared with 0.08% dietary tryptophan level, 0.40% level significantly improved nuclear factor erythroid 2-related factor 2 (Nrf2), GPx, manganese superoxide dismutase (Mn-SOD), CAT and transforming growth factor-β (TGF-β) mRNA level, while Kelch-like ECH-associated protein 1 (Keap1) and interleukin 1β (IL-1β) mRNA level were significantly decreased. The relative expression of copper zinc superoxide dismutase (Cu/Zn-SOD), heme oxygenase-1 (HO-1), target of rapamycin (TOR), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), protein kinase B (Akt) and interleukin 10 (IL-10) were significantly improved by 0.28% diet, while the mRNA level of tumor necrosis factor-α (TNF-α) and nuclear factor-kappa B (NF-κB) were increased by 0.08% diet. Interleukin 8 (IL-8) mRNA level was not significantly affected by dietary tryptophan. Based on MDA and T-SOD value, the optimal dietary tryptophan level of juvenile blunt snout bream was determined to be 0.33% (1.03% of dietary protein) and 0.36% (1.13% of dietary protein), respectively, using quadratic regression analysis.
色氨酸的膳食管理已被证明能提高鱼类的生长性能。本试验进行了 8 周的喂养试验，通过 Nrf2 和 TOR 信号通路研究了不同色氨酸水平对鲤鱼抗氧化能力和免疫反应的影响。结果表明，0.08%的色氨酸水平显著提高了血浆天冬氨酸转氨酶（AST），而 0.40%的色氨酸水平则显著提高了免疫球蛋白 M（IgM）和碱性磷酸酶（ALP）的水平。血浆补体成分 3（C3）、丙氨酸转氨酶（ALT）和白蛋白（ALB）的水平与色氨酸补充无关。总超氧化物歧化酶（T-SOD）、过氧化氢酶（CAT）、总抗氧化能力（T-AOC）和谷胱甘肽（GSH）的活性随着膳食色氨酸水平的增加而增加，直到 0.40%后开始下降，而丙二醛（MDA）的水平则呈相反趋势。0.19%和 0.28%的色氨酸水平显著提高了谷胱甘肽过氧化物酶 1（GPx-1）的活性。与 0.08%的膳食色氨酸水平相比，0.40%的水平显著提高了核因子红细胞 2 相关因子 2（Nrf2）、GPx、锰超氧化物歧化酶（Mn-SOD）、CAT 和转化生长因子-β（TGF-β）的 mRNA 水平，而 Kelch 样 ECH 相关蛋白 1（Keap1）和白细胞介素 1β（IL-1β）的 mRNA 水平则显著降低。铜锌超氧化物歧化酶（Cu/Zn-SOD）、血红素加氧酶-1（HO-1）、雷帕霉素靶蛋白（TOR）、磷酸肌醇-4,5-二磷酸 3-激酶（PI3K）、蛋白激酶 B（Akt）和白细胞介素 10（IL-10）的相对表达水平均显著提高，而肿瘤坏死因子-α（TNF-α）和核因子-κB（NF-κB）的 mRNA 水平则提高了 0.08%的饮食。白细胞介素 8（IL-8）的 mRNA 水平不受膳食色氨酸的影响。基于 MDA 和 T-SOD 值，采用二次回归分析分别确定了幼鲳钝吻鲷的最佳膳食色氨酸水平为 0.33%（占膳食蛋白的 1.03%）和 0.36%（占膳食蛋白的 1.13%）。
