#3454 IMPACT OF SYMBIOTICS ON UREMIC TOXINS PRODUCTION, RENAL FUNCTION AND PEW SYNDROME IN SHIME AND CKD MICE MODELS
Authors: Beau Alice , Benoit Bérengère , Jammes Marie , Pinteur Claudie , Fouque Denis , Glorieux Griet , Vidal Hubert , Natividad Jane , Koppe Laetitia 
Published: June 2023

Abstract

Background and Aims
Alterations in gut microbiota in CKD patients have been linked to CKD progression, cachexia, and mortality. Gut dysbiosis is associated by modification of gut-microbiota-derived metabolites, including a decrease of short-chain fatty acids (SCFAs), an increase in gut-derived uremic toxins. Therefore, modulation of gut microbiota seems to be an attractive therapeutic approach. In silico studies led to the selection of bacterial species able to increase SCFAs production, improve gut function without having the enzymatic machinery for producing uremic toxins. The propose of this study is to indentify the impact of two different symbiotics containing the selected bacteria: 1) on both uremic toxins and SCFAs production using a Simulator of the Human Intestinal Microbial Ecosystem (SHIME) colonized with fresh feces from CKD or healthy controls (HC) and subsequently 2) on renal function, metabolic parameters, intestinal microbiota and gut-microbiota-derived metabolites in a mouse model of CKD (5/6 nephrectomy).

Method
1) The SHIME® system manufactured by ProDigest (Ghent, Belgium) consists of systems comprising five double-wall biovessels simulating the stomach (ST), small intestine (SI), ascending colon (AC), transverse colon (TC), and descending colon (DC). The supernatant of the homogenized fecal slurry was inoculated into the AC (25 mL), TC (40 mL), and DC (30 mL), respectively. After fecal inoculation, SHIME system were fed in ST twice day with two different symbiotics (P1 or P2) for 10 days. After 7 days, we applied a diet amino acid (AA) challenge to all the groups. SCFAs and uremic toxins were quantified every day. 2) CKD mice received either P1 or P2 admix for 6 weeks. We measured food intake, body composition and renal function including renal fibrosis quantification. Plasma metabolomic and feces metagenomic analyses were performed.

Results
In vitro, the concentration of precursor of uremic toxins (indols and p-cresol) tended to be higher in DC colonized by feces from CKD patients and AA challenge increased uremic toxins production more significantly in CKD compared to HC. CKD microbiome showed a lower butyrate concentration at baseline and higher propionate and acetate production. Both P1 and P2 significantly limited uremic toxins production during AA challenge and increase SCFA production. In vivo, both symbiotics increased body weight (+14%) and food intake (+31%) compared to CKD mice on chow diet. Treatment did not impact lipid or glucose metabolism but fat accretion in epididymal was restored with P1. Both diets, but particularly P1, significantly reduced plasmatic urea, proteinuria, and kidney fibrosis. Symbiotics improved intestinal barrier with a greater expression of Occludin in the ileum. Metagenomic analyses of the gut microbiota indicated that the alfa-diversity was not different across groups while the beta-diversity was similar to the sham group if CKD mice were treated with symbiotics. Both symbiotics reduced significantly plasma levels of deleterious uremic toxins such as p-cresyl sulfate and indoxyl sulfate and symbiotics reduce fecal module of trypotophan degradation and other modules related to AA metabolism. Both diets increased fecal bacteria modules related to SCFAs production.

Conclusion
We have shown both in vitro and in vivo that a symbiotic association can reduce uremic toxins production and increase SCFA production by inducing a significant change in gut microbiota composition and function. These metabolic changes are associated with improved appetite, decreased uremic cachexia, and preserved renal function. This data needs be confirmed in a human clinical trial.