Animal Nutrition Institute, Sichuan Agricultural University, Cheng Du, Sichuan, 611130, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Cheng Du, Sichuan, 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Cheng Du, Sichuan, 611130, China.
Animal Nutrition Institute, Sichuan Agricultural University, Cheng Du, Sichuan, 611130, China.
Fish Shellfish Immunol. 2017 Nov;70:609-620. doi: 10.1016/j.fsi.2017.09.049. Epub 2017 Sep 20.
The current study explored the protective effect of leucine on antioxidant status, apoptosis and tight junction damage in the gill of grass carp (Ctenopharyngodon idella Val.). The trial was conducted by feeding grass carp with six graded level of leucine (7.1, 8.9, 11.0, 13.3, 15.2 and 17.1 g kg diet) for 8 weeks. The fish were fed to apparent satiation 4 times per day. The results indicated that compared with the leucine deficiency group, 8.9-11.3 g leucine kg diet supplementations decreased protein carbonyl (PC), malondialdehyde (MDA) and ROS contents, which may be partially attributed to the improvement of antioxidant status in the gill by increasing hydroxyl radical capacity and anti-superoxide radicals, glutathione contents and the activities and mRNA levels of Cu/Zn superoxide dismutase (SOD1), glutathione peroxidase (GPx), catalase (CAT), glutathione-S-transferase (GST) and glutathione reductase (GR), that referring to the up-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA expression. Moreover, leucine deficiency induced DNA fragmentation via the up-regulation of caspase-3, caspase-8 and caspase-9 expressions and down-regulation of target of rapamycin and ribosomal S6 protein kinase 1 expressions. Furthermore, leucine deficiency increased interleukin-1β (IL-1β), interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) mRNA expression and decreased IL-10 and transforming growth factor β (TGF-β), which was partly related to nuclear factor κB (NF-κB) and its inhibitor (IκB). In contrast, the relative mRNA expression of IL-1, IL-8 and TNF-α was down-regulated with 8.9-11.3 g leucine kg diet supplementations. Finally, the relative mRNA expression of tight junction protein, including occludin, zonula occludens-1, claudin b, claudin 3 and claudin 12 was up-regulated with leucine diet supplementations. Our results indicate that leucine protected the fish gill structural integrity partially because of the inhibition of apoptosis, the improvement of antioxidant status, the regulation of tight junction protein and related signalling molecules mRNA expressions in the fish gill.
本研究探讨了亮氨酸对草鱼（Ctenopharyngodon idella Val.）鳃抗氧化状态、细胞凋亡和紧密连接损伤的保护作用。试验通过给草鱼投喂 6 个不同水平的亮氨酸（7.1、8.9、11.0、13.3、15.2 和 17.1 g/kg 饲料），为期 8 周。每天投喂 4 次，直至鱼吃饱为止。结果表明，与亮氨酸缺乏组相比，8.9-11.3 g/kg 亮氨酸饲料补充可降低蛋白质羰基（PC）、丙二醛（MDA）和 ROS 含量，这可能部分归因于通过增加羟自由基能力和抗超氧自由基、谷胱甘肽含量以及铜/锌超氧化物歧化酶（SOD1）、谷胱甘肽过氧化物酶（GPx）、过氧化氢酶（CAT）、谷胱甘肽-S-转移酶（GST）和谷胱甘肽还原酶（GR）的活性和 mRNA 水平，改善了鳃的抗氧化状态，核因子红细胞 2 相关因子 2（Nrf2）mRNA 表达上调。此外，亮氨酸缺乏通过上调半胱天冬酶-3、半胱天冬酶-8 和半胱天冬酶-9 的表达以及下调雷帕霉素靶蛋白和核糖体 S6 蛋白激酶 1 的表达诱导 DNA 片段化。此外，亮氨酸缺乏增加白细胞介素-1β（IL-1β）、白细胞介素-8（IL-8）和肿瘤坏死因子-α（TNF-α）mRNA 表达，降低白细胞介素-10 和转化生长因子-β（TGF-β），这与核因子 κB（NF-κB）及其抑制剂（IκB）部分相关。相反，随着 8.9-11.3 g/kg 亮氨酸饲料补充，IL-1、IL-8 和 TNF-α 的相对 mRNA 表达下调。最后，紧密连接蛋白（包括闭合蛋白、闭锁小带蛋白-1、Claudin b、Claudin 3 和 Claudin 12）的相对 mRNA 表达随着亮氨酸饮食的补充而上调。我们的研究结果表明，亮氨酸通过抑制细胞凋亡、改善抗氧化状态、调节鱼鳃紧密连接蛋白和相关信号分子 mRNA 表达来部分保护鱼鳃的结构完整性。
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