EFFECTS OF THE WESTERN DIET AND PSYCHOLOGICAL STRESS ON GUT HEALTH

Long-Term Goals and Supporting Objectives: In a series of previous investigations, we demonstrated that mice fed a diet formulated to mimic average American macro and micronutrient intakes (Total Western Diet, TWD) have increased inflammatory gene expression, gut inflammation, colitis severity, aberrant crypt foci, tumorigenesis and changes to the gut microbiome relative to mice fed healthy control diets. Recently, others have shown that psychological stress (PS) has similar detrimental effects on gut health including increased expression of inflammatory genes, decreased mucin thickness, and changes to the gut microbiome. Considering that poor diet and PS are hallmarks of modern society and can occur simultaneously, we have a keen interest in determining interactions between diet, PS, and gut health. The work proposed in this seed grant would extend our well-established diet/colitis model to include another environmental stressor, PS. Moreover, we propose to use Raman spectroscopy (RS) coupled with machine learning to develop a novel gut inflammation measure that will be faster and less expensive than traditional histopathology measures. Based on our previous studies, we hypothesize that mice fed the TWD and subjected to PS will have increased inflammatory gene expression, gut inflammation, and colitis disease activity relative to mice fed the TWD without PS and or fed healthy control diets (with or without added PS). This novel data will increase our understanding of how diet and PS interact to modify gut health. Objectives. Determine interactions between diet and PS on gut health. To induce gut inflammation, we plan on using both our traditional dextran sodium sulfate (DSS) model, PS, and combinations of DSS and PS with mice fed either a healthy diet (AIN-93G) or the TWD. The following treatments are proposed: 1) Mice fed the AIN-93G control diet, 2) Mice fed the TWD, 3) Mice fed AIN-93G + DSS treatment, 4) Mice fed the TWD + DSS treatment, 5) Mice fed the AIN-93G diet + PS, 6) Mice fed the TWD + PS, 7) Mice fed the AIN-93G diet + DSS & PS, 8) Mice fed the TWD + DSS & PS. Planned gut inflammation endpoints will include colitis disease activity index (DAI), histopathology mucosal injury/inflammation score, and RS analysis of the colon. Microbiome taxonomy characterization will be performed by 16s sequencing. Colon mucosal immune gene expression will be analyzed using the nCounter Mouse PanCancer Immune panel which includes 770 immune-related genes. Untargeted metabolomics of fecal contents (>500 probed metabolites) will be performed by liquid chromatography tandem mass spectrometry (LC/MS-MS) to provide insight into metabolic pathways related to health and disease risk (e.g., malondialdehydes, glutathione metabolism, oxidative stress, and energy/glucose metabolism). Fecal short chain fatty acids (SCFA) will be analyzed by GC-FID using a targeted approach. The combination of these analyses will provide deep insight into interactions between diet, PS, the gut environment, and gut health.