PSI-14 - Weaning stress increases bile cysteine and cysteinylglycine concentrations in pigs

Abstract: Weaning is a critical time for pigs that is associated with nutritional, social, and environmental stressors that lead to reduced feed intake and poor nutrient utilization. Cysteine is a sulfur amino acid and a key constituent of glutathione (GSH), a major intracellular antioxidant and potential regulator of intestinal redox status. Glutathione is present in biliary secretions and may be an important source of cysteine to intestine in newly weaned pigs. The objective of this study was to determine amino thiol and amino acid concentrations in bile. Piglets (initial BW = 7233 ± 683 g) were either weaned on day 21 of age (W; n = 9) and euthanized after 2 d or remained on the sow until day 23 of age (NW; n = 9) and were euthanized. Weaned pigs were fasted and allowed free access to water. After euthanasia, bile (directly from the gallbladder), jejunum, and ileum samples were collected. Bile amino acids and bile amino thiols were analyzed by reversed phase HPLC following precolumn derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and 4-fluoro-7-aminosulfonylbenzofurazan, respectively. Reverse transcription quantitative real-time PCR was performed to measure cysteine transporter expression in jejunum and ileum. Cysteine concentration was higher in W than NW pigs (1203 versus 324 ± 99 µmol/L; P < 0.0001). Both γ-glutamylcysteine (7.1 versus 2.2 ± 2.1 µmol/L), the direct precursor for GSH synthesis, and cysteinylglycine (203 versus 110 ± 30 µmol/L, the direct product of GSH degradation, were higher in W pigs than in NW pigs (P < 0.05). Bile GSH concentration tended to be higher in W than NW pigs (9.1 versus 5.3 ± 2.8 µmol/L; P = 0.07). Taurine, derived from cysteine oxidation, was higher in W than NW pigs (180 versus 91 ± 23 µmol/L; P < 0.05), whereas glutamate (11.4 versus 8.8 ± 1.9 µmol/L) and glycine (463 versus 403 ± 62 µmol/L), additional amino acid constituents of GSH, were not different between groups (P > 0.10). Expression of cysteine transporters SLC1A4, SLC1A5, SLC6A14, SLC6A19, SLC7A9, and SLC7A11 in jejunum and ileum were not different between groups (P > 0.10).Despite no feed intake after weaning, cysteine concentrations increase in bile. While this is likely due to bile accumulation in the gallbladder after weaning, high bile cysteine, cysteinylglycine, and glycine concentrations could potentially be a source of these amino acids for enterocytes during weaning stress.