Colonic Gene expression of SPF mice fed either a Control Diet or a High Salt Diet

Compositional changes in the microbiota (dysbiosis) may be a basis for Irritable Bowel Syndrome (IBS) but biomarkers are currently unavailable to direct microbiota-directed therapy. We therefore examined whether changes in fecal β-defensin could be a marker of dysbiosis in a murine model. Experimental dysbiosis was induced using four interventions relevant to IBS: a mix of antimicrobials, westernized diets (high-fat/high-sugar and, high salt diets), or mild restraint stress. Fecal mouse β-defensin-3 and 16S rRNA-based microbiome profiles were assessed at baseline, during and following these interventions. Each intervention, except for mild restraint stress, altered compositional and diversity profiles of the microbiota. Exposure to antimicrobials or a high-fat/high-sugar diet, but not mild restraint stress, resulted in decreased fecal β-defensin-3 compared to baseline. In contrast, exposure to the high salt diet increased β-defensin-3 compared to baseline but this was not accompanied by discernible inflammatory changes in the host. We extracted total RNA from colonic tissues extracted from SPF mice that were fed either a control diet (n=5/sex, total=10) or a high salt diet (n=5/sex, total=10) for a period of one week. After RNA extraction, RNA samples were pooled to form 4 samples representing controls and another 4 samples representing mice on high salt diet intervention. We then ran a total of 8 samples through the NanoString nCounter® Gene Expression CodeSet for mouse immune, gut barrier and neurobiology related genes.