Abstract L-glutamate and L-aspartate are functional amino acids essential for intestinal functions and physiological metabolism. This study aimed to investigate effects of L-glutamate, L-aspartate, and their combination on immunity and intestinal integrity of weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC). Sixty-five weaned pigs (7.59 ± 1.11 kg BW) were randomly assigned to five treatments (n = 13 per treatment): control (CON), CON + 1% glutamate (GLU), CON + 1% aspartate (ASP), CON + 1% glutamate + 1% aspartate (GAC), and CON + 50 mg/kg carbadox (ABX). All pigs were orally challenged with F18 ETEC (1010 CFU/dose/day) for three consecutive days. Serum was collected on d 0, 2, 4, 14, and 21 PI for inflammatory biomarker analysis using ELISA. Jejunal and ileal mucosa were collected on d 5 and 21 PI for assessing intestinal immunity and integrity via RT-qPCR. The study period lasted for four weeks, with a 7-day adaptation period and 21 days post-inoculation (PI). Data were analyzed using ANOVA in PROC MIXED of SAS with individual pig as the experimental unit. Compared with CON, GLU, ASP, or GAC groups decreased (P 0.05) serum C-reactive protein on d 0 and 4 PI. Compared with CON, ASP, GAC, or ABX groups decreased (P 0.05) serum IL-8 on d 2 PI, while GAC increased (P 0.05) serum TNF-α on d 4 PI. Additionally, GLU, ASP, GAC, or ABX groups decreased (P 0.05) serum haptoglobin compared with CON on d 14 and 21 PI. On d 5 PI, GAC-fed pigs showed highest (P 0.05) jejunal and ileal IL1β and ileal IL17A expression among all groups. Interestingly, GAC-fed pigs tended to have highest (P 0.10) jejunal TNFα but lowest (P 0.10) ileal TNFα expression among all groups. On d 21 PI, GLU or ASP groups increased (P 0.05) jejunal IL13 and tended to increase (P 0.10) jejunal IL4 expression compared with CON. GAC-fed pigs also tended to increase (P 0.10) jejunal IL4 and increased (P 0.05) ileal IL4 expression compared with CON. Moreover, GLU-fed pigs had highest (P 0.05) ileal TGFβ1 expression on d 21 PI among all groups. Compared with ABX, GAC-fed pigs tended to have lower (P 0.10) jejunal OCDN expression on d 5 PI while higher (P 0.10) jejunal MUC2 expression on d 21 PI. On d 5 PI, GLU, ASP, or ABX groups tended to decrease (P 0.10) ileal CLDN1 expression compared with CON. On d 21 PI, GLU, ASP, or GAC groups had lower (P 0.05) ileal ZO1 than ABX. In conclusion, glutamate and/or aspartate supplementation modulated immune responses and intestinal integrity, highlighting potential benefits to enhance disease resistance in ETEC-challenged weaned pigs.
Wongchanla et al. (Wed,) studied this question.