Artificial sweeteners (AS) are ubiquitous in food and beverage products, yet little is known about their effects on the gastrointestinal (GI) tract, and whether they play a role in the development of GI symptoms, especially in patients with irritable bowel syndrome. Utilizing the PubMed and Embase databases, we conducted a search for articles on individual AS and each of these terms: fermentation, absorption, and GI tract. Standard protocols for a systematic review were followed. At the end of our search, we found a total of 617 eligible papers, 26 of which were included. Overall, there is limited medical literature available on this topic. The 2 main areas on which there is data to suggest that AS affect the GI tract include motility and the gut microbiome, though human data is lacking, and most of the currently available data is derived from in vivo studies. The effect on motility is mainly indirect via increased incretin secretion, though the clinical relevance of this finding is unknown as the downstream effect on motility was not studied. The specific effects of AS on the microbiome have been conflicting and the available studies have been heterogeneous in terms of the population studied and both the AS and doses evaluated. Further research is needed to assess whether AS could be a potential cause of GI symptoms. This is especially pertinent in patients with irritable bowel syndrome, a population in whom dietary interventions are routinely utilized as a management strategy.

OBJECTIVES/SPECIFIC AIMS: Objectives and goals of this study are to (i) determine whether IBS-D patients randomized to either rifaximin or low FODMAP diet show improvement in IBS-related symptoms; and (2) identify using longitudinal analyses how SIBO status and fecal microbiota features associate with response to either rifaximin or low FODMAP dietary intervention. METHODS/STUDY POPULATION: 42 patients ≥ 18 years of age who meet Rome IV criteria for IBS-D will be randomized to receive either rifaximin or low FODMAP diet intervention. The primary outcome will be the proportion of responders to intervention which is defined as ≥ 30% reduction in mean daily abdominal pain or bloating by visual analog scale compared with baseline. Exclusion criteria will include: (a) history of microscopic colitis, inflammatory bowel disease, celiac disease, or other organic disease that could explain symptoms, (b) prior gastrointestinal surgery, other than appendectomy or cholecystectomy > 6 months prior to study initiation, (c) prior use of rifaximin or formal dietary interventions for IBS-D, (d) use of antibiotics within the past 3 months, or (e) use of probiotics within 1 month of study entry. Glucose hydrogen breath tests will be performed at the beginning and end of the trial to evaluate for SIBO. Fecal samples will be collected at 0, 2, and 6 weeks to determine changes in fecal microbial composition and structure. RESULTS/ANTICIPATED RESULTS: This study seeks to examine whether longitudinal analyses of small intestinal and colonic microbiota can subtype IBS-D subjects into clinically relevant phenotypes. A total of 18 subjects have been enrolled into the study. Clinical variables, hydrogen breath test results, and fecal microbiota data are being collected for ongoing analysis. DISCUSSION/SIGNIFICANCE OF IMPACT: Results from this study may help move treatment of IBS from a purely symptom based approach to a more individualized approach by stratifying IBS-D patients into distinct clinical phenotypes which are amenable to targeted therapeutic approaches.

INTRODUCTION: Diarrhea-predominant irritable bowel syndrome (IBS-D) is a chronic, disabling condition. Treatments for IBS-D, including rifaximin, a nonabsorbable antibiotic, and a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP), improve symptoms in ≤50% of patients. We hypothesized that changes in the gut microbiota predict response to treatment for IBS-D. METHODS: We randomized 17 patients meeting Rome IV criteria for IBS-D to receive either rifaximin 550 mg three times daily x 14 days or a low FODMAP diet x 4 wks. The primary outcome was proportion of responders to intervention defined by ≥30% improvement in mean daily abdominal pain or bloating scores. The secondary outcome was ≥50-point decrease in IBS-Severity Symptom Scoring (IBS-SSS) compared with baseline. Fecal samples were collected at baseline and 2, 4 and 5 wks. The microbial community in these specimens was characterized by 16S rRNA encoding-gene sequence analysis. RESULTS: There were 6 subjects (60.0%) in the rifaximin group and 4 subjects (57.1%) in the low FODMAP group that met the primary endpoint (P > .99) (Table 1). Patients in the rifaximin group had significant improvements in abdominal pain (P = .01), bloating (P = .02), and IBS-SSS (P = .009) compared with baseline. Patients in the low FODMAP group showed improvement in IBS-SSS only (P = .06) at the end of treatment. Responders to treatment had unique inter- and intra-individual temporal characteristics compared with non-responders. Responders to rifaximin and low FODMAP diet showed a distinct microbial community structure at baseline compared with non-responders (P = .001 for both, Figure 1A). Responders to rifaximin (P = .08) and low FODMAP diet (P = .01) also exhibited lower degrees of microbial community change during therapy compared with non-responders (Figure 1B). Responders to rifaximin (Figure 2A) and low FODMAP diet (Figure 2B) showed changes in several taxa at baseline and longitudinally compared with non-responders. CONCLUSION: Responders to therapy with rifaximin and low FODMAP diet show a distinct fecal microbial community structure at baseline. Many microbiome features at baseline predict response to treatment. Longitudinal analyses show responders have a more resilient community structure to either rifaximin or dietary modification compared with non-responders. The functional significance of these microbial changes in responders vs. non-responders is unclear, but may be the focus of future studies.