Barley Leaves Improves Loperamide-Induced Constipation via Gut Barrier and Microbiota Modulation in Mice

Constipation is a common gastrointestinal disorder that seriously affects quality of life and is associated with multiple secondary complications. Barley leaves (BLs) have been suggested as potential functional foods for constipation prevention. Here, we investigated the preventive effects of common barley leaves (CBLs) and hulless barley leaves (HBLs) in a loperamide-induced constipation model in C57BL/6 mice. Both BLs improved stool parameters and gastrointestinal transit. Notably, high-dose HBLs increased stool weight to 263.84 ± 66.70 mg and stool amount to 250.20 ± 66.88 pellets, which were 12.7 and 11.1 times higher than those in the model group, respectively. BLs also modulated gut motility-related hormones (MTL, SP, Gas, SS, and VIP) and normalized colonic AQP3, AQP4, and 5-HT₄R expression levels. Furthermore, BLs enhanced SCFAs production and modulated gut microbiota by increasing Bacteroides abundance and decreasing Akkermansia abundance. CBLs and HBLs also exhibited distinct mechanisms. High-dose CBLs affected SERT expression, whereas HBLs uniquely decreased Alistipes abundance and increased SCFA production. These findings suggest that BLs may help prevent loperamide-induced constipation in mice by modulating the gut barrier and microbiota. Future studies should identify key active components and validate efficacy in longer-term and clinical studies.