In recent years, high-fat diet (HFD) has been widely applied in aquaculture, which reduces the intestinal health of cultured fish. The current study evaluated the protective effects of nano-selenium (nano-Se) on intestinal health of juvenile grass carp (Ctenopharyngodon idella) fed with HFD. A total of 135 experimental fish were fed with a regular diet (Con), a HFD (HFD) and a HFD containing nano-Se at 0.6 mg/kg (HSe) for 10 weeks. The results showed that dietary nano-Se significantly improved the survival rate and feed efficiency which were reduced by HFD in juvenile grass carp (P < 0.05). Also, nano-Se (0.6 mg/kg) supplement alleviated intestinal damage caused by the HFD, thus maintaining the integrity of the intestine. Moreover, it significantly up-regulated the expression of genes related to tight junction (ZO-1, claudin-3 and occludin), anti-oxidization (GPx4a andGPx4b), and the protein of ZO-1 in the intestine of juvenile grass carp, which were depressed by the HFD (P < 0.05). Furthermore, nano-Se supplementation significantly suppressed the expressions of genes related to the inflammation, including inflammatory cytokines (IL-8, IL-1β, IFN-γ, TNF-α and IL-6), signaling molecules (TLR4, p38 MAPK and NF-κB p65), and protein expression of NF-κB p65 and TNF-α in the intestine of juvenile grass carp which were induced by the HFD (P < 0.05). Besides, dietary nano-Se normalized the intestinal microbiota imbalance of juvenile grass carp caused by the HFD through increasing the abundance of the beneficial bacteria, e.g., Fusobacteria. Finally, dietary nano-Se increased the production of short chain fatty acids (SCFA) in the intestine, especially for butyric acid and caproic acid, which were negatively related to the increase of intestinal permeability and inflammation. In summary, supply of nano-Se (0.6 mg/kg) in HFD could effectively alleviate intestinal injury of juvenile grass carp by improving intestinal barrier function and reducing intestinal inflammation and oxidative stress. These positive effects may be due to the regulation of nano-Se on intestinal microbiota and the subsequently increased beneficial SCFA levels.

近年来，高脂饲料（HFD）在水产养殖中得到广泛应用，降低了养殖鱼类的肠道健康。目前的研究评估了纳米硒 (nano-Se) 对喂食 HFD的幼鱼 ( Ctenopharyngodon idella )肠道健康的保护作用。共有 135 条实验鱼以常规饲料 (Con)、HFD (HFD) 和含有 0.6 mg/kg (HSe) 的纳米硒的 HFD 喂养 10 周。结果表明，日粮纳米硒显着提高了幼草鱼因HFD而降低的成活率和饲料利用率（P < 0.05)。此外，纳米硒（0.6 mg/kg）补充剂可减轻 HFD 引起的肠道损伤，从而保持肠道的完整性。此外，它显著上调有关紧密连接的基因的表达（ZO-1 ，Ç laudin-3和ö ccludin），抗氧化（GPx4a和GPx4b）和ZO-1的少年的肠中蛋白HFD 抑制的草鱼 ( P  < 0.05)。此外，纳米硒补充剂显着抑制炎症相关基因的表达，包括炎症细胞因子（IL-8、IL-1β、IFN-γ、HFD诱导的幼草鱼肠道中TNF-α和IL-6）、信号分子（TLR4、p38 MAPK和NF-κB p65）及NF-κB p65和TNF-α的蛋白表达（P < 0.05)。此外，膳食纳米硒通过增加有益细菌（例如梭杆菌）的丰度，使由HFD引起的幼草鱼肠道微生物群失衡正常化。最后，膳食纳米硒增加了肠道中短链脂肪酸（SCFA）的产生，尤其是丁酸和己酸，它们与肠道通透性和炎症的增加呈负相关。综上所述，在HFD中添加纳米硒（0.6 mg/kg）可通过改善肠道屏障功能、减轻肠道炎症和氧化应激来有效缓解幼草鱼肠道损伤。这些积极作用可能是由于纳米硒对肠道微生物群的调节以及随后增加的有益 SCFA 水平。