Effect of FODMAPs on Mucosal Inflammation in IBS Patients

OBJECTIVE: To gain mechanistic insights, we will compare effects of low fermentable oligosaccharides, disaccharides and monosaccharides and polyols (FODMAP) and high FODMAP diets on symptoms and colonic protease expression in patients with diarrhea predominant irritable bowel syndrome (IBS-D). We will measure how protease changes affect excitability of pain sensing neurons and correlate this with measurements of the metabolome and the microbiome. DESIGN: We aim to perform a single blind prospective study of patients with diarrhea predominant IBS (Rome IV criteria) who will sequentially consume a high and low FODMAP diets, each for 3 weeks. Symptoms will be assessed using the IBS symptom severity scoring (IBS-SSS). Electrophysiological studies of changes in mouse dorsal root ganglia neurons in response to colonic mucosal/lamina propria supernatants will be carried out. Protease antagonist will be used to specifically assess protease expression. The metabolome will be evaluated using metabolic profiling in urine using mass spectrometry. Stool microbiota composition will be analysed by 16S rRNA gene profiling. All the above testing will be performed at 4 time points: at baseline, 3 weeks following a run-in period, after a 3-week-long high FODMAP diet, and after a 3-week-long low FODMAP diet period. HYPOTHESIS: We anticipate that colonic tissue protease effects on the excitability of dorsal root ganglia (DRG) neurons will increase with a high FODMAP diet and decrease with a low FODMAP diet, but that this may not be found in all patients. The magnitude of the effect may vary and this variation could be due to differences in the individual patients microbiome.