Effect of FODMAPs on Mucosal Inflammation in IBS Patients
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.
Up to 15 % of adults in Western society suffer from irritable bowel syndrome (IBS), and it is
 the second leading cause, behind the common cold, of workplace absenteeism. This proposal
 addresses critical knowledge gaps in our understanding of IBS mechanisms. What environmental
 triggers cause pain symptoms to chronically wax and wane? A fundamental observation is that
 over 70% of IBS patients report that meals trigger abdominal pain and diarrhea. Therefore, we
 examined the effects of a diet low in fermentable oligo, di, monosaccharides and polyols
 (FODMAPs) because up to 50-70% IBS patients reported improved symptoms on this diet (McIntosh
 et al 2016; Halmos et al 2014). We found that symptoms, particularly pain, were markedly
 improved in IBS patients on a low compared to a high FODMAP diet. Moreover, we found in a
 subset of patients evidence that FODMAPs activate intestinal mast cells, a major source of
 proteases and histamine, and their expression appears to be associated with IBS symptoms,
 although this remains to be proven. Thus, this diet provides a useful clinical tool to
 stimulate protease activity and study their actions. Sensitization (modulation of
 intracellular mechanisms leading to exaggerated action potential discharge in response to a
 given stimulus) of nociceptive dorsal root ganglia (DRG) neurons by tissue mediators is a
 fundamental mechanism underlying abnormal pain signaling. We also have compelling evidence in
 human IBS patients that a family of proteases are key mediators underlying another critical
 knowledge gap that we identified, i.e. which tissue mediators can lead to sustained and
 amplified abdominal pain. We and others found these proteases are elevated in IBS tissues,
 and that they sensitize DRG neurons - the primary sensory neurons that innervate the colon.
 Based on these findings, our goal is to test the overarching hypothesis that diet can trigger
 recurrent symptoms in IBS through activation of tissue proteases that cause exaggerated pain
 by signaling to nociceptive DRG neurons. Recurrent exposure to such diet components and the
 resulting protease signaling is an important cause of the waxing and waning of symptoms over
 time. Thus, our objective is to characterize the relationship of a specific dietary
 intervention with protease activity in IBS patients.

 This will be a prospective study comparing the effect of low-FODMAP and high-FODMAP on
 symptoms and protease effects on the excitability of nociceptive DRG neurons. We will analyze
 the urinary metabolome as a secondary measure of mast cell mediators (i.e. histamine and
 proteases). We will also collect stool for possible future microbiome analysis as diet
 microbiome interactions (i.e. fermentation of the FODMAPs) may predict the magnitude of the
 response. The study will be conducted at Hotel Dieu Hospital's Gastroenterology clinics and
 endoscopy suite in Kingston, Ontario. This study will be comprised of the following four time
 periods: "baseline", "run-in", "high FODMAP diet", and "low FODMAP diet". Participants will
 undergo baseline assessment with questionnaires on demographics, IBS symptoms (IBS symptom
 severity scoring questionnaire), diet, as well as a questionnaire pertaining to psychological
 parameters. A detailed questionnaire pertaining to participants' diet will be administered at
 baseline. Baseline mucosal colonic biopsies will be obtained using limited flexible
 sigmoidoscopy. Baseline stool microbiota composition will be analysed by 16S rRNA gene
 profiling. Fecal calprotectin levels will be obtained from stool samples. Urine and blood
 metabolome will be analysed at baseline also using mass spectrometry. These will be repeated
 3 weeks later during a run-in period to assess if these measurements are stable in time or
 not. This run-in period will be 3 weeks long. After completion of the run-in period, patients
 will be asked to consume a high FODMAP diet for 3 weeks. All tests carried out at baseline
 and during the run-in period will be carried out for a third time. Participants will meet
 with investigators and be given dietary guidance, including a handout outlining foods to eat
 and avoid. A dietician will be involved extensively in this process to ensure the
 instructions are adequate and accurate. For the remainder of the study, patients will not be
 able to take antibiotics, and fibre supplements. After the 3-week-long high FODMAP diet
 period, participants will meet again with the dietician to obtain instructions on how to
 consume a low FODMAP diet. After 3 weeks on a low FODMAP diet, all baseline testing will be
 performed a fourth time. We aim to enroll 20 patients. Based on a 70% response rate to low
 FODMAP diet (Halmos et al. 2014), and our experience in previous studies, this number should
 be adequate.

 Please note that the biopsies taken at sigmoidoscopy will be processed at HDH for the
 supernatants, and then frozen for later electrophysiological studies at the Gastro-Intestinal
 Diseases Research Unit (GIDRU) at KGH.
Inclusion Criteria:

 -  Males and females 18 years of older

 -  Meet the Rome IV criteria for IBS (abdominal pain or discomfort at least 3 days per
 month in the last three months associated with two or more of the following:
 defecation, onset associated with change of frequency of stool or change associated
 with a change in form of stool. The symptoms must be going on for more than six months
 and be associated with an absence of routine clinical red flags)

 Exclusion Criteria:

 -  Patients with a history of gastric, small bowel or colonic surgery

 -  Patients with active Inflammatory Bowel Disease

 -  Patients with celiac disease

 -  Patients who are unable or unwilling to come off the following medications:
 antibiotics, stool bulking agents, narcotics, or lactulose.

 -  Patients who are already on a low-FODMAP diet or a diet that may be have substantially
 different FODMAP content from usual Canadian diet (paleolithic diet, specific
 carbohydrate diet, gluten-free diet, Atkins)

 -  Patients cannot have used antibiotics in the past 4 weeks.

 -  Pregnant patients will not be invited to participate. (Sexually active women of
 child-bearing age will be asked if it is possible that they are pregnant, and if there
 is a doubt, they will not be invited to participate.) Patients will confirm they are
 using birth control during the time they are participating in the study.