Cysteine exerts an essential role in maintaining intestinal integrity and function independent of glutathione.

SCOPE Enteral feeding is a primary source of cysteine for intestinal mucosa given negligible transsulfuration activity in enterocytes and furthermore very few cysteine uptake from arterial blood. This study aims to explore the role of cysteine in maintaining intestinal integrity and function. METHODS AND RESULTS The intestinal porcine enterocytes (IPEC-J2) were cultured in a cysteine-deprived medium with or without glutathione supplementation upon the inhibitions of glutathione synthesis or degradation. As a result, cysteine deprivation impaired mitochondrial function, suppressed mechanistic target of rapamycin (mTOR) signaling and activated general control nonderepressible 2 (GCN2) signaling, and might lead to resultant ferroptosis. Glutathione supplementation could restore the impairment through degradating into cysteine, while glutathione synthesis inhibition did not disturb the role of cysteine in keeping the intestinal epithelial cells. Furthermore, piglets were fed with cysteine-deficient, -adequate and -surplus diet for 28 d as a porcine model. We evidenced that intestinal integrity and individual growth benefit from adequate dietary cysteine. CONCLUSION Adequate dietary cysteine supply is essential for intestinal mucosal integrity, epithelial cell turnover and amino acid sensing as well as optimal individual growth. Cysteine exerts its role independent of glutathione and glutathione restores the impairment of cysteine-deprivation on intestinal mucosal through degrading into cysteine. This article is protected by copyright. All rights reserved.