Supplementation with L-theanine promotes intestinal antioxidant ability via Nrf2 signaling pathway in weaning piglets and H2O2-induced IPEC-J2 cells

L-theanine enhances weaned piglets intestinal and IPEC-J2 cells antioxidant capacity by activating Nrf2 signaling pathway, thereby alleviating IPEC-J2 cells oxidative stress damage caused by H 2 O 2 . • L-theanine enhances intestinal antioxidant capacity in weaned piglets. • L-theanine alleviates H 2 O 2 -induced intestinal oxidative stress damage of IPEC-J2 cells. • This effect of L-theanine is achieved by activating Nrf2 signaling pathway. This study aimed to investigate the effect of L-theanine in regulating the intestinal antioxidant of weaned piglets and its underlying mechanism. We found that L-theanine increased the activities of antioxidant enzymes and the level of GSH, while decreased the MDA content of weaned piglet jejunum mucosa and H 2 O 2 -induced IPEC-J2 cells. In addition, the mRNA expression of SOD1 , SOD2 , GPx1 , CAT , HO-1 and NQO1 was also significantly increased in jejunum mucosa and H 2 O 2 -induced IPEC-J2 cells by L-theanine treatment. Furthermore, L-theanine promoted the nuclear Nrf2 expression and decreased the keap1 expression. However, blocking of Nrf2 signaling by ML385 (the Nrf2 inhibitor) repressed the promoting effects of L-theanine on the activities of antioxidative enzymes and the expression of antioxidant related genes, while increased the MDA content and keap1 expression in IPEC-J2 cells. These data provided the first evidence that L-theanine improved intestinal antioxidant ability of weaned piglets by activating Nrf2 signaling pathway.