Multifaceted effects of proline on intestinal injury, inflammation, and lipid metabolism in piglets induced by porcine epidemic diarrhea virus.

This study investigated the effects of proline on intestinal injury in piglets infected with porcine epidemic diarrhea virus (PEDV). Twenty-eight 7-day-old piglets were assigned to four groups: control (CON), proline (Pro), PEDV, and Pro + PEDV. Piglets in the Pro and Pro + PEDV groups received oral proline (500 mg/kg body weight) for 7 days. During the last 3 days, piglets in the PEDV and Pro + PEDV groups were inoculated with PEDV. Under PEDV infection, proline administration increased villus height and the villus height/crypt depth ratio in both the jejunum and ileum, and villus width and villus surface area in the ileum. Proline increased PEDV N protein abundance and interferon β (IFN-β) mRNA level in both intestinal segments, suppressed downstream antiviral genes in infected piglets, but upregulated these genes in the jejunum of uninfected piglets. Proline further increased interleukin 1β (IL-1β) concentrations and the expression of inflammation-related genes in the jejunum of infected piglets. Under PEDV infection, proline increased superoxide dismutase (SOD) activity in serum and jejunum, while reducing jejunal H2O2 concentration. Furthermore, proline downregulated genes related to lipid synthesis and ion transport in the jejunum of infected piglets. Transcriptomic and RT-qPCR analyses supported these findings, indicating that proline enhanced immune defense while suppressing lipid metabolism. In conclusion, proline alleviated PEDV-induced intestinal injury by improving villus morphology and enhancing antiviral and antioxidant defenses. However, it promoted viral replication and inflammation, while suppressing lipid metabolism. The multifaceted effects of proline on PEDV infection indicate its practical use warrants careful consideration.