<i>Bifidobacterium longum</i> subsp. <i>infantis</i> NKU FB3-14 attenuates loperamide-induced constipation through regulation of gut microbiota

Abstract Objectives Constipation is a prevalent gastrointestinal issue, and the efficacy of probiotics in alleviating constipation has been well demonstrated. This study aimed to investigate the impact of Bifidobacterium longum subsp. infantis NKU FB3-14 on loperamide-induced constipation by focusing on improving intestinal barrier function and modulating gut microbiota composition. Materials and Methods The constipated model mice induced by loperamide were treated with NKU FB3-14, and the laxative effect was assessed based on fecal water content, first black stool time and gastrointestinal transit rate. Gastrointestinal regulatory peptides in serum and intestinal neurotransmitter and inflammatory cytokines in colon tissues were measured using enzyme-linked immunosorbent assay kits. Changes in the composition of gut microbiota were analyzed through 16S ribosomal DNA (rDNA) sequencing. Additionally, high-performance liquid chromatography (HPLC) was performed to quantify levels of short-chain fatty acids (SCFAs) in feces. Results Treatment with NKU FB3-14 increased fecal water content, shortened the first black stool time, and improved the small intestine transit rate. Motilin and substance-P significantly decreased in the model group, and only motilin increased in the FB3-14 group; somatostatin and vasoactive intestinal peptide were decreased in the model mice and both increased in the FB3-14 group; 5-hydroxytryptamine (5-HT) levels in the colon tissue were upregulated following NKU FB3-14 treatment. Histological examination revealed thinner colonic mucosa in the model group along with significant increases in tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interleukin 17 (IL-17) levels in the colon tissues, which were alleviated by NKU FB 3-14 treatment. Furthermore, NKU FB3-14 intervention resulted in reduced abundance of Desulfobacterota and Desulfovibrio while increasing the abundance of Ruminococcaceae and Eubacterium; a higher level of butyric acid was observed in feces. Conclusions In summary, our findings demonstrated that NKU FB3-14 treatment significantly enhanced intestinal motility, regulated the expression levels of gastrointestinal regulatory peptides, prevented damage to colonic barriers, and ameliorated gut microbiota imbalance associated with loperamide-induced constipation.