Weaning stress in pigs is associated with low feed intake and poor nutrient utilization. Cysteine is a sulfur amino acid with key roles in pig production, but how cysteine metabolism and requirements are affected by weaning stress should be better defined. The objective of this study was to determine the collective impact of weaning and feed restriction on tissue cysteine metabolism. Pigs were weaned at 21-d age without access to feed (W; 6.90 ± 0.81 kg; n = 9; reflecting acute nutritional stress) or were not weaned and remained with the sow (nonweaned [NW]; 6.81 ± 0.65 kg; n = 8). At euthanasia (23-d age), blood, bile, liver, jejunum, and ileum tissues were collected. Plasma, bile, and tissue amino acid and amino thiol concentrations were analyzed by HPLC. The activity of glutamate cysteine ligase (GCL) and glutathione synthetase (GSS), enzymes needed for glutathione (GSH) production, and cysteine dioxygenase 1 (CDO1) were determined with activity assays followed by HPLC analysis of reaction products. Plasma (271 vs. 192 ± 19 µmol/L; P < 0.001) and liver (417 vs. 298 ± 33 nmol/g; P < 0.05) Cys concentrations were increased in W compared to NW pigs. Despite greater plasma Cys, jejunum and ileum Cys content were not affected by weaning (P > 0.10), whereas γ-glutamylcysteine (γ-GlyCys), the immediate precursor of GSH, declined in both jejunum (14.3 vs. 9.7 ± 1.4 nmol/g; P < 0.01) and ileum (11.2 vs. 6.4 ± 0.8 nmol/g; P < 0.001) in W pigs. Glutathione content was lower in the jejunum (1,379 vs. 1,720 ± 70 nmol/g; P < 0.05) and ileum (1,497 vs. 1,740 ± 74 nmol/g; P < 0.05) in W pigs. In the jejunum, GCL activity tended to be greater (0.56 vs. 0.39 ± 0.07 nmol γ-GluCys • mg−1 • min−1; P < 0.10), whereas GSS activity tended to be lower (1.11 vs. 1.38 ± 0.10 nmol GSH • mg−1 • min−1; P < 0.10) in W compared to NW pigs. In the ileum, the activities of GCL and GSS were not affected by weaning (P > 0.10). Although liver CDO1 activity was not different between groups (P < 0.10), liver taurine was greater in W compared to NW pigs (5,115 vs. 2,336 ± 912 nmol/g; P = 0.001). Bile concentrations of Cys (1,203 vs. 279 ± 103 µmol/L; P < 0.001) and cysteinylglycine (203 vs. 117 ± 33 µmol/L; P < 0.10), the direct product of GSH degradation, were greater in W compared to NW pigs. Collectively, these results suggest that systemic Cys is not effectively utilized for gut GSH production in newly weaned pigs; instead, it is oxidized to taurine and eliminated in bile.

中文翻译：

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断奶时采食量低会降低猪肠道谷胱甘肽水平，并促进半胱氨酸氧化为牛磺酸


猪的断奶应激与采食量低和营养利用率差有关。半胱氨酸是一种硫氨基酸，在生猪生产中起关键作用，但断奶应激如何影响半胱氨酸代谢和需求应更好地定义。本研究的目的是确定断奶和饲喂限制对组织半胱氨酸代谢的集体影响。猪在 21 日龄断奶，无需饲料（W;6.90 ± 0.81 kg;n = 9;反映急性营养应激）或未断奶并留在母猪身边（未断奶 [NW];6.81 ± 0.65 kg;n = 8）。在安乐死 （23 d 龄） 时，收集血液、胆汁、肝脏、空肠和回肠组织。通过 HPLC 分析血浆、胆汁和组织氨基酸和氨基硫醇浓度。通过活性测定测定谷氨酸半胱氨酸连接酶 （GCL） 和谷胱甘肽合成酶 （GSS）、生产谷胱甘肽 （GSH） 所需的酶和半胱氨酸双加氧酶 1 （CDO1） 的活性，然后对反应产物进行 HPLC 分析。血浆（271 vs. 192 ± 19 μmol/L;P < 0.001） 和肝脏 （417 vs. 298 ± 33 nmol/g;P < 0.05） 与 NW 猪相比，W 的 Cys 浓度增加。尽管血浆 Cys 较高，但空肠和回肠 Cys 含量不受断奶影响 （P > 0.10），而 GSH 的直接前体 γ-谷氨酰半胱氨酸 （γ-GlyCys） 在空肠中均下降 （14.3 vs. 9.7 ± 1.4 nmol/g;P < 0.01） 和回肠 （11.2 vs. 6.4 ± 0.8 nmol/g;P < 0.001） 在 W 猪中。空肠中的谷胱甘肽含量较低（1,379 vs. 1,720 ± 70 nmol/g;P < 0.05）和回肠 （1,497 vs. 1,740 ± 74 nmol/g;P < 0.05） 在 W 猪中。在空肠中，GCL 活性往往更大 （0.56 vs. 0.39 ± 0.07 nmol γ-GluCys • mg-1 • min-1;P < 0.10），而 GSS 活性往往较低 （1.11 vs. 1.38 ± 0.10 nmol GSH • 毫克-1 • 最小-1;P < 0.10） 与 NW 猪相比。在回肠中，GCL 和 GSS 的活性不受脱机的影响 （P > 0.10）。尽管各组之间肝脏 CDO1 活性没有差异 （P < 0.10），但与 NW 猪相比，W 中的肝脏牛磺酸更高 （5,115 vs. 2,336 ± 912 nmol/g;P = 0.001）。Cys 的胆汁浓度 （1,203 vs. 279 ± 103 μmol/L;P < 0.001） 和半胱氨酰甘氨酸 （203 vs. 117 ± 33 μmol/L;P < 0.10） 是 GSH 降解的直接产物，与 NW 猪相比，W 中的产量更高。总的来说，这些结果表明，系统性 Cys 没有被有效地用于新断奶仔猪的肠道 GSH 生产;相反，它被氧化成牛磺酸并在胆汁中消除。