Title: IDDF2019-ABS-0298 Lactobacillus rhamnosus ggsupernatant improves bowel function via Upregulating 5HT4R and MUC2 expression and modulating microbe environment in mice
Abstract: <h3>Background</h3> <i>Lactobacillus rhamnosus GG</i> (<i>LGG</i>) has been reported to improve bowel function in constipation patients. However, the effects and mechanism of <i>LGG</i> on bowel function remains unclear. 5-Hydroxytryptamine4 Receptor is a critical receptor relating to the intestine motility and secretion function. In this study, we aimed to investigate whether <i>LGG</i> could improve the defecation function <i>via</i> upregulating 5-HT4R and modulating gut microbiota in mice. <h3>Methods</h3> Male C57BL/6 mice 6–8 weeks in age were randomly divided into 3 groups: MRS group (n=10), Tegaserod group (positive control, n=15) and<i> LGG</i> group (n=15), and MRS broth, tegasromide maleate and<i>LGG</i> supernatant were gavaged respectively for 7 days. YAMC cells and Caco2 cells were used for experiment<i> in vitro</i>. Defecation parameter including the number of pellets in 2 hours, fecal weight, fecal dry weight, fecal water content, and the gastrointestinal transit time (GITT) were detected. PAS and AB-PAS staining were used to evaluate goblet cells number in mice colon, and 5-HT4R and MUC2 expression were determined Real-time PCR and Western blotting <i>in vivo</i> and<i> in vitro</i>. Gut microbiota and short-chain fatty acid were analyzed by 16 sRNA pyrosequencing analysis and gas chromatography method. <h3>Results</h3> The number of defecation pellets in 2 h, fecal weight, fecal dry weight and fecal water content in the Tegasromide group and <i>LGG</i> group were significantly increased compared with those in the MRS group, PAS staining showed that the average number of goblet cells in Tegasromide group and <i>LGG</i> group were significantly increased in mice colon sections compared with MRS group. AB-PAS showed increased cavitated goblet cells in the <i>LGG</i> group, and the mRNA and protein levels of 5-HT4R and MUC2 were upregulated both <i>In vitro</i> and<i> in vivo.</i> In this study, increased levels of<i> Alistipes</i>, <i>Allobaculum,</i> and <i>Desulfovibrioin</i> were found in the <i>LGG</i> group which have been reported to be involved in intestine motility, intestinal barrier. <h3>Conclusions</h3> <i>LGG</i> supernatant could improve defecation function in mice accompanied by upregulating 5-HT4R and MUC2 production, and modulating gut microbiota. Thus, this study will provide a better understanding of probiotics for the prevention and treatment of constipation.