Impact of the probiotic <i>Bacillus coagulans</i> on loperamide-induced delayed bowel movement in Sprague–Dawley rats

This study investigated the effects of <i>Bacillus coagulans</i> on alleviating loperamide-induced constipation. To evaluate the efficacy of <i>B. coagulans</i> 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 <i>B. coagulans</i> significantly altered the fecal weight and moisture content and improved gastrointestinal transit in rats with loperamide-induced constipation. Furthermore, <i>B. coagulans</i> 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. <i>B. coagulans</i> administration upregulated the expression levels of tryptophan hydroxylase and aquaporin genes, which were downregulated by loperamide. As the dose of <i>B. coagulans</i> increased, there was a corresponding upregulation in the expression of tight junction-related genes, including occludin (<i>OCLN</i>), zonula occludens 1 (<i>ZO-1</i>), and claudin 1 (<i>CLDN1</i>). Additionally, the levels of c-kit, AQP 3, and OCLN proteins, which were elevated by loperamide treatment, were reduced with higher concentrations of <i>B. coagulans</i>. Loperamide decreased the acetic acid content; however, high doses of <i>B. coagulans</i> increased it, leading to a significant increase in the total cecal SCFA content. Thus, <i>B. coagulans</i> shows potential as a probiotic for improving constipation.