Multi-omics elucidate octapeptin mechanisms in alleviating intestinal injury in mice challenged with ETEC K88 via...

The mechanisms whereby antimicrobial peptides (AMPs) confer intestinal protection during enteric bacterial infection remain unclear. Here, we examined the protective effects and underlying mechanisms of the AMP, octapeptin, against intestinal infection induced by enterotoxigenic Escherichia coli K88 (ETEC K88) in mice. Octapeptin ameliorated intestinal injury by modulating gut microbiome-host interactions. When compared with ETEC K88 mice, octapeptin significantly attenuated growth retardation, systemic oxidative stress, pro-inflammatory cytokine elevation, and ileal morphological damage. Integrated cecal microbiome, metabolome, and ileal transcriptome analyses revealed that octapeptin reversed ETEC K88-induced dysbiosis, notably increasing beneficial genera abundance. Concomitantly, octapeptin altered microbial metabolite profiles and significantly influenced ileal gene expression in circadian rhythm regulation. Correlation analysis and variance partitioning further identified a coherent "microbiota-metabolite-transcriptome" axis underlying these phenotypic improvements. Thus, octapeptin alleviates ETEC K88-induced intestinal injury via multi-level interactions that restore microbial ecology and regulate host circadian and immune pathways, thereby highlighting host-directed AMP mechanisms.IMPORTANCEAntimicrobial peptides are promising alternatives to antibiotics, but how they work inside the body remains poorly understood. Using a multi-omics approach, this study shows that octapeptin, a natural cyclic lipopeptide, protects mice against intestinal infection by reshaping the gut microbiota, reprogramming gut metabolites, and stabilizing host circadian clock genes that are disrupted by infection. These findings reveal a previously unrecognized link between gut microbes and the intestinal circadian clock. This mechanistic framework could guide the development of peptide-based strategies to prevent enteric infections in animals.