Leucine Mitigates Porcine Epidemic Diarrhea Virus-Induced Colonic Damage in Piglets via Suppression of Viral Replication and Restoration of Intestinal Homeostasis

The preventive effect of leucine (Leu) against colonic damage in piglets infected with porcine epidemic diarrhea virus (PEDV) was examined in this study. Three groups (n = 6) were randomly assigned to eighteen 7-day-old Du-roc × Landrace × Large piglets (body weight [BW] = 2.58 ± 0.05 kg): Control, PEDV-infected (PEDV), and Leu-supplemented + PEDV-infected (Leu + PEDV). Following a three-day period of acclimatization, the Leu + PEDV group was given Leu (400 mg/kg BW) orally every day. On day eight, the PEDV and Leu + PEDV groups were challenged with PEDV, while the Control group was given Dulbecco’s Modified Eagle’s Medium. Colonic tissues were collected on day 11. PEDV infection induced severe colonic damage by an increase in crypt, disrupting intestinal homeostasis, including impaired barrier integrity (matrix metalloproteinase-7 and matrix metalloproteinase-13 upregulation), mucus disorganization (mucin 5AC elevation), oxidative stress (reduced catalase activity and increased malondialdehyde levels), inflammation, electrolyte imbalance and enhanced viral replication. Leu supplementation reversed these injuries by alleviating oxidative stress, suppressing inflammation, inhibiting viral replication and stabilizing ion homeostasis. This study provides a scientific basis for Leu as a nutritional intervention to alleviate PEDV-induced colonic damage in piglets.