<i>Bifidobacterium animalis</i> subsp. <i>lactis</i> Bbm-19 ameliorates insomnia by remodeling the gut microbiota and restoring γ-aminobutyric acid and serotonin signaling

Insomnia is associated with dysregulation of the gut-brain axis, yet microbiome-targeted interventions remain underexplored. In this study, we investigated the effects of <i>Bifidobacterium animalis</i> subsp. <i>lactis</i> Bbm-19 (Bbm-19), a strain isolated from human breast milk, in a 4-chloro-DL-phenylalanine-induced mouse model of insomnia. Using integrated behavioral, neurochemical, immunological, and multi-omics approaches, this study demonstrates that insomnia is characterized by shortened sleep duration, prolonged sleep latency, anxiety-like behaviors, and reduced levels of serotonin and gamma-aminobutyric acid in the gut, serum, and brain. Administration of Bbm-19 significantly improved sleep parameters, reduced anxiety-like behaviors, and increased survival. Metagenomic and metabolomic analyses revealed that Bbm-19 restored gut microbiota balance, enriched beneficial taxa, including <i>Muribaculaceae</i> bacterium and <i>Stercoribacter</i> sp., and reprogrammed microbial metabolic modules, particularly those involved in amino acid metabolism (including alanine, aspartate, glutamate, arginine, proline, and tryptophan pathways). Targeted metabolomics confirmed increased levels of gamma-aminobutyric acid and serotonin in fecal and brain tissues, along with normalization of inflammatory cytokine profiles. Spearman correlation analysis linked Bbm-19-enriched taxa to improved neurotransmitter levels and sleep outcomes. Notably, Bbm-19 outperformed lorazepam in modulating gut-specific metabolic functions and synergistically enhanced its effects when co-administered. These findings demonstrate that Bbm-19 ameliorates insomnia through coordinated regulation of the gut microbiota, host metabolism, and neuroimmune signaling, highlighting its potential as a targeted psychobiotic intervention for sleep disorders.