PSII-25 Cysteine utilization for liver taurine and intestinal glutathione production is affected by weaning in pigs

Abstract Cysteine is a sulfur amino acid with key roles in pig production but how cysteine metabolism and requirements are affected by acute nutritional stress at weaning is unclear. The objective of this study was to determine weaning-induced changes in the abundance and activity of enzymes involved in cysteine utilization in the liver and small intestine. Pigs [initial body weight (BW) = 7.23 ± 0.68 kg] were either weaned at 21 d age and euthanized at 23 d age (W; n = 9) or remained with the sow and euthanized at 23 d age (NW; n = 9). Weaned pigs were fasted to replicate an acute nutritional stress but had free access to water. At euthanasia, liver, jejunum, and ileum tissues were collected. Liver abundance of cysteine dioxygenase 1 (CDO1) and cysteine sulfinic acid decarboxylase (CSAD), enzymes needed for cysteine oxidation to taurine, were determined by immunoblot. Reaction products of GCL and GSS, enzymes needed for glutathione (GSH) production, and CDO1 (liver only) were determined by HPLC. Tissue taurine and GSH concentrations were determined by HPLC. Liver CDO1 activity (0.31 versus 0.52 ± 0.10 nmol cysteine sulfinic acid/mgּ proteinּ min-1); P = 0.14), CDO1 abundance (3.98 versus 7.47 ± 1.96 AU; P = 0.22), and CSAD abundance (1.50 versus 1.54 ± 0.16 AU; P = 0.88) were not different between W and NW pigs. Liver GCL activity (2.49 versus 4.15 ± 0.25 nmol γ-glutamylcysteine/(mgּ proteinּ min-1); P < 0.001) and GSS activity (1.54 versus 1.92 nmol GSH/(mgּ proteinּ min-1); P < 0.001) were less in W compared with NW pigs. Liver taurine concentration increased in W compared with NW pigs (2,250 versus 4,726 ± 471 nmol/g; P < 0.01), whereas liver GSH concentration was not different between W and NW pigs (2,825 versus 2,921 ± 245 nmol/g; P > 0.10). Jejunum GCL activity was not different between W and NW pigs (0.56 versus 0.39 ± 0.07 nmol γ-glutamylcysteine/(mg proteinּ min-1); P = 0.10), whereas GSS activity tended to be lower in W compared with NW pigs (1.11 versus 1.38 ± 0.10 nmol GSH/(mg proteinּ min-1); P = 0.07). Ileum GCL (0.36 versus 0.32 ± 0.07 nmol γ-glutamylcysteine/(mg proteinּ min-1) and GSS activities (1.04 versus 1.02 ± 0.07 nmol GSH/(mg proteinּ min-1) were not different between W and NW pigs (P > 0.10). However, both jejunum (1,379 versus 1,720 ± 70 nmol/g) and ileum (1,497 versus 1,740 ± 74 nmol/g) GSH concentrations were less in W compared with NW pigs (P < 0.05). Despite limited feed intake, liver oxidation of cysteine to taurine was maintained in pigs after weaning. These findings imply that excess endogenous cysteine is oxidized to taurine rather than utilized for gut GSH production.