The present study was conducted to test the hypothesis that dietary supplementation with a nano chitosan–zinc complex (CP–Zn, 100 mg/kg Zn) could alleviate weaning stress in piglets challenged with enterotoxigenic Escherichia coli K88 by improving growth performance and intestinal antioxidant capacity. The in vivo effects of CP–Zn on growth performance variables (including gastrointestinal digestion and absorption functions and the levels of key proteins related to muscle growth) and the antioxidant capacity of the small intestine (SI) were evaluated in seventy-two weaned piglets. The porcine jejunal epithelial cell line IPEC-J2 was used to further investigate the antioxidant mechanism of CP–Zn in vitro. The results showed that CP–Zn supplementation increased the jejunal villus height and decreased the diarrhoea rate in weaned piglets. CP–Zn supplementation also improved growth performance (average daily gain and average daily feed intake), increased the activity of carbohydrate digestion-related enzymes (amylase, maltase, sucrase and lactase) and the mRNA expression levels of nutrient transporters (Na+-dependent glucose transporter 1, glucose transporter type 2, peptide transporter 1 and excitatory amino acid carrier 1) in the jejunum and up-regulated the expression levels of mammalian target of rapamycin (mTOR) pathway-related proteins (insulin receptor substrate 1, phospho-mTOR and phospho-p70S6K) in muscle. In addition, CP–Zn supplementation increased glutathione content, enhanced total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-px) activity, and reduced malondialdehyde (MDA) content in the jejunum. Furthermore, CP–Zn decreased the content of MDA and reactive oxygen species, enhanced the activity of T-SOD and GSH-px and up-regulated the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway-related proteins (Nrf2, NAD(P)H:quinone oxidoreductase 1 and haeme oxygenase 1) in lipopolysaccharide-stimulated IPEC-J2 cells. Collectively, these findings indicate that CP–Zn supplementation can improve growth performance and the antioxidant capacity of the SI in piglets, thus alleviating weaning stress.

中文翻译：

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纳米壳聚糖-锌复合物提高断奶仔猪小肠的生长性能和抗氧化能力

本研究旨在验证以下假设，即日粮中添加纳米壳聚糖-锌复合物（CP-Zn，100 mg/kg Zn）可以减轻受到产肠毒素攻击的仔猪的断奶应激。大肠杆菌K88 通过提高生长性能和肠道抗氧化能力。这体内在 72 头断奶仔猪中评估了 CP-Zn 对生长性能变量（包括胃肠消化和吸收功能以及与肌肉生长相关的关键蛋白水平）和小肠抗氧化能力（SI）的影响。猪空肠上皮细胞系IPEC-J2用于进一步研究CP-Zn的抗氧化机制体外. 结果表明，CP-Zn补充剂增加了断奶仔猪的空肠绒毛高度并降低了腹泻率。CP-Zn 补充剂还改善了生长性能（平均日增重和平均日采食量），增加了碳水化合物消化相关酶（淀粉酶、麦芽糖酶、蔗糖酶和乳糖酶）的活性和营养转运蛋白的 mRNA 表达水平（Na+依赖葡萄糖转运蛋白 1、葡萄糖转运蛋白 2 型、肽转运蛋白 1 和兴奋性氨基酸载体 1) 在空肠中并上调哺乳动物雷帕霉素靶蛋白 (mTOR) 通路相关蛋白（胰岛素受体底物 1、磷酸-mTOR 和磷酸化-p70S6K）在肌肉中。此外，CP-Zn 补充剂增加了谷胱甘肽含量，增强了总超氧化物歧化酶 (T-SOD) 和谷胱甘肽过氧化物酶 (GSH-px) 的活性，并降低了空肠中丙二醛 (MDA) 的含量。此外，CP-Zn降低了MDA和活性氧的含量，增强了T-SOD和GSH-px的活性，上调了核因子红细胞2相关因子2（Nrf2）通路相关蛋白的表达水平。 Nrf2，NAD(P)H：脂多糖刺激的 IPEC-J2 细胞中的醌氧化还原酶 1 和血红素加氧酶 1)。总的来说，这些研究结果表明，补充 CP-Zn 可以提高仔猪的生长性能和 SI 的抗氧化能力，从而减轻断奶应激。