Lacticaseibacillus casei IDCC 3451 alleviates cognitive and behavioral functions by reshaping the gut microbiome and regulating intestinal barrier integrity in chronic stress animal models

Lacticaseibacillus casei IDCC 3451 (3451) was evaluated for its effects on the gut-brain axis using Caenorhabditis elegans ( C. elegans ) and mouse models of stress and inflammation. In C. elegans , 3451 extended lifespans by 25 %, improved motility, and chemotaxis, enhanced survival under pathogen challenge, and reduced amyloid beta accumulation by 42 %. Transcriptomic profiling revealed upregulation of genes involved in neurotransmitter signaling and serine/threonine pathways. In the unpredictable chronic mild stress (UCMS) mouse model, 3451 administration increased the time spent in the center of the open field by 65 % and reduced immobility in the forced swim test by 32 %, indicating anxiolytic and antidepressant effects. Serum levels of aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) were decreased by 18 % and 24 %, respectively. Additionally, 3451 restored the expressions of 5HT1AR, GABAR, and tight junction proteins, including ZO-1 and Claudin1 . Metabolomic analysis showed increased glycine and decreased palmitic acid levels, associated with an increased abundance of Ruminococcus and Akkermansia . In the dextran sulfate sodium (DSS)-induced colitis model, 3451 reduced the disease activity index by 36 %, improved colon histology, increased goblet cell preservation, and upregulated ZO-1 and IL-10 expression. Threonine levels were also increased and correlated with a higher abundance of Coprococcus . These findings demonstrate that 3451 improved behavioral and intestinal outcomes through coordinated modulation of host signaling, metabolite production, and gut microbial composition, highlighting its therapeutic potential for managing IBD and neurobehavioral disorders. This graphical abstract illustrates the therapeutic potential of Lacticaseibacillus casei IDCC 3451 on gut and neurological health through a multiomics approach. Administration of dextran sulfate sodium (DSS) induces colon damage in mice, leading to colitis and microbiota dysbiosis. Treatment with 3451 targets the host gut-brain axis, modulating gut microbiota composition and microbial-derived metabolite production. The Caenorhabditis elegans model treated with 3451 extended lifespan, heightened immunity, and reduced amyloid beta accumulation, with upregulated serine/threonine activation-related and neurotransmitter receptor-related genes. In vivo mouse studies revealed that 3451 alleviates depression, anxiety, and cognitive impairments in the unpredictable chronic mild stress (UCMS) model by mitigating inflammatory markers, restoring neurotransmitter receptor gene expression. In the DSS-induced colitis model, 3451 alleviated intestinal inflammation, restored intestinal health by modulating inflammatory cytokines, mitigating colon structural disruption, and enhancing tight junction protein gene expression. These benefits were linked to increased threonine production and changes in gut microbial composition, highlighting the potential of 3451 for treating inflammatory bowel disease (IBD) and neurological disorders. • L. casei IDCC 3451 improved stress-induced behavioral and cognitive deficits. • IDCC 3451 restored gut microbiota and host metabolites in colitis and UCMS models. • Multi-omics analysis revealed systemic effects of IDCC 3451 on the gut–brain axis. • IDCC 3451 enhanced barrier integrity and neuroimmune balance in mice and worms. • Findings support IDCC 3451 as a psychobiotic candidate for gut–brain disorders.