<i>Weissella confusa</i> WIKIM51 (Wilac D001) improves constipation and gut health in a loperamide-induced mouse model

<i>Weissella confusa</i> WIKIM51 (Wilac D001) has been reported to reduce body fat, but its potential effects on constipation remain unclear. This study is the first to demonstrate that Wilac D001 alleviates loperamide-induced constipation <i>in vivo</i> by enhancing gut barrier function, and modulating gut microbiota. Mice were orally administered vehicle, bisacodyl, low-dose (1 × 10⁹ CFU g^-1), or high-dose (1 × 10¹⁰ CFU g^-1) Wilac D001 for 4 weeks, and constipation was induced with loperamide (10 mg kg^-1) during the final 11 days. Wilac D001 significantly increased fecal water content by approximately 27% compared with the loperamide group, and also improved fecal pellet weight, intestinal transit, and defecation time. It restored the expression of tight junction proteins (ZO1, Claudin1, Occludin) and reduced aquaporins, suggesting improved barrier integrity. Key regulators of gut motility, including c-Kit, SCF, VPAC1, 5-HT₄R, somatostatin, and vasoactive intestinal peptide, were also significantly modulated. Gut microbiota analysis revealed increased abundance of beneficial bacteria such as <i>Akkermansia muciniphila</i>, <i>Bacteroides acidifaciens</i>, <i>Weissella</i>, and S24-7. These findings suggest that Wilac D001 effectively alleviates constipation and supports gut health through coordinated actions on intestinal structure, hormonal signaling, and microbiota composition, highlighting its potential as a functional probiotic for gut health management.