Konjac glucomannan with probiotics acts as a combination laxative to relieve constipation in mice by increasing short-chain fatty acid metabolism and 5-hydroxytryptamine hormone release

Various probiotics and natural products can help to relieve constipation. This study aimed to explore the constipation-relieving effects and potential mechanism of a combination laxative of konjac glucomannan and probiotics. This study evaluated the gastrointestinal-tract viability of probiotics in vitro. A constipation model was constructed in BALB/c mice, and the efficacies of the combinations verified in terms of their bowel movement–promoting effects, including the first black-stool defecation time and gastrointestinal transit rates of mice. Colonization by the probiotics was determined by quantitative real-time polymerase chain reaction. Hematoxylin-eosin staining, gas chromatography, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, and Western blot were also used for analysis. Lactobacillus paracasei X11 (X11) and L. casei YRL577 (YRL577) had outstanding gastrointestinal-tract viability. Konjac glucomannan (KGM) + X11, Prunus persica + X11, and Prunus persica + YRL577 significantly relieved constipation. In addition, KGM promoted the colonization of X11. Meanwhile, KGM + X11 effectively promoted the metabolism of short-chain fatty acids in mice better than other combinations, and the 5-hydroxytryptamine (5-HT) content in the KGM + X11 group was the highest among all the groups. Therefore, KGM + X11 was selected for further research. The combination laxative promoted the secretion of 5-HT, up-regulated mRNA and protein levels of 5-HT receptor 4 and serotonin transporter via the 5-HT pathway, and effectively relieved constipation. The combination laxative konjac glucomannan–probiotic (KGM + X11) promoted defecation in constipated mice, possibly by increasing short-chain fatty acid metabolism and 5-HT hormone release.