Impact of the probiotic Bacillus coagulans on loperamide-induced delayed bowel movement in Sprague–Dawley rats†

This study investigated the effects of Bacillus coagulans on alleviating loperamide-induced constipation. To evaluate the efficacy of B. coagulans in Sprague–Dawley (SD) rats, fecal parameters, the intestinal transit rate, and changes in intestinal mucosal cells were measured through histological analysis. Additionally, serotonin levels, water absorption, tight junction-related gene expression, and the cecal short-chain fatty acid (SCFA) content were analyzed. The administration of B. coagulans significantly altered the fecal weight and moisture content and improved gastrointestinal transit in rats with loperamide-induced constipation. Furthermore, B. coagulans supplementation restored the thickness of both muscular and mucosal layers that had been reduced by loperamide and significantly increased the area of intestinal cells, including Cajal and crypt cells. B. coagulans administration upregulated the expression levels of tryptophan hydroxylase and aquaporin genes, which were downregulated by loperamide. As the dose of B. coagulans increased, there was a corresponding upregulation in the expression of tight junction-related genes, including occludin (OCLN), zonula occludens 1 (ZO-1), and claudin 1 (CLDN1). Additionally, the levels of c-kit, AQP 3, and OCLN proteins, which were elevated by loperamide treatment, were reduced with higher concentrations of B. coagulans. Loperamide decreased the acetic acid content; however, high doses of B. coagulans increased it, leading to a significant increase in the total cecal SCFA content. Thus, B. coagulans shows potential as a probiotic for improving constipation.