Research Project
10478316
PROJECT SUMMARY Crohn's disease (CD) affects more than 1.5 million individuals in the US alone and several million worldwide. Despite significant advances in our understanding of the mechanism(s) of chronic intestinal inflammation, the precise cause of disease is still unknown; therefore, available treatment modalities are not curative and possess significant side effects. Increasing evidence suggest that the interactions between dietary components, including food additives and artificial sweeteners (AS), the gut microbiome and the host mucosal immune system, may play a critical role in either promoting or alleviating intestinal inflammation. However, little is known regarding the specific role of AS that are used in large amounts by the general population, including IBD patients, to control body weight and blood glucose, and their impact on the pathogenesis of small intestinal inflammation, characteristic of CD. This renewal application will focus on the effects of different AS on the gut microbiome and the intestinal mucosal immune system in the pathogenesis of SAMP CD-like ileitis. The central hypothesis is that AS may have detrimental effects in regulating chronic intestinal inflammation by promoting proinflammatory host-microbial interactions. The specific aims are: 1) Characterize the effects of different AS on the development of ileitis in SAMP mice. We will test the hypothesis that AS have pro-inflammatory effects in the development of CD-like ileitis. A series of in vivo experiments using 4 different commonly used AS (Equal, Sweet'N Low, Splenda and Stevia) and their matched vehicle controls (Dextrose and Maltodextrin) or water and table sugar (sucrose), will be tested in preclinical studies. 2) Determine the effects of AS on the composition and function of the gut microbiome. The working hypothesis of this aim is that AS induce primary proinflammatory changes on gut microbiome composition that are sufficient to promote intestinal inflammation in CD-like ileitis. We will first feed AS to germ-free (GF) SAMP mice and control mice to determine the effects of AS on the severity of GF-SAMP intestinal inflammation. We will then perform a series of in vitro experiments using stool samples from mice and humans to characterize the effects of AS products and ingredients on gut microbiome composition. Finally, we will conduct `humanized' FMT experiments into GF-SAMP mice (with feces from CD patients or healthy donors) to determine if the AS-altered fecal microbiota increases the severity of intestinal inflammation in transplanted GF-SAMP mice in vivo. 3) Determine the effects of artificial sweeteners on the gut mucosal immune system. Using bone marrow chimera experiments and lymphocyte-depleted SAMP (i.e., SAMPxRag2-/-) mice, we will first determine the role of T and B cells in response to AS. We will then study the role of Teff and Treg cells by utilizing newly generated (SAMP×Foxp3gfp mice). Finally, using state-of-the-art scRNAseq techniques, we will identify specific cell clusters mediating the mucosal immune response to AS. The overall objective of this proposal is to understand how different AS alter host-microbial interactions in IBD with the ultimately goal of understanding which AS is safe in these patients and their mechanism(s) of action.
