Understanding How Metabolites Link Diet, Host, and Microbiota in a Dysfunctional Gut Model Is Important to Establishing a System-wide Understanding of Gut Function (P20-035-19)

OBJECTIVES: Nutrition modulates the interactions between the host and the gut microbiota. Changes in metabolites resulting from this interaction in a healthy compared to a perturbed gut is a critical approach to identify putative biomarkers that can be used to assess how diet effects gut function. Bile acids (BAs) are metabolites produced from cholesterol and the microbial-conversion of BAs play an important role in digestion and metabolism. Modification of BA metabolism has been reported in participants with Irritable Bowel Syndrome (IBS), which is characterised by abdominal bloating, pain, dysfunction, and a perturbed gut microbiota. One aim of the clinical nutrition study was to characterise BA profiles of healthy control and IBS participants. This work is part of a wider study investigating gut health and how food can be used to alleviate symptoms. METHODS: Healthy control and IBS participants were recruited and IBS subtypes determined (n = 337) (Rome Criteria IV). Biological samples and dietary questionnaire information were collected. 97 plasma samples (n = 42 healthy control, n = 25 IBS-diarrhoea, n = 17 IBS-constipation, n = 13 IBS-mixed) were quantitatively analysed for 13 BAs using a SCIEX 6500 + QTrap liquid chromatography-mass spectrometer in multiple reaction monitoring mode. Partial least squares discriminant analysis (SIMCA 14.1) and analysis of variance (Metaboanalyst 4.0) were used to perform multivariate and univariate analyses respectively. Ethical approval was obtained from the University of Otago Human Ethics Committee (Health) (Reference H16/094). RESULTS: Univariate analysis of the 13 BAs showed no significant difference within or between IBS subtypes or healthy controls (P > 0.05). However, multivariate analysis of 13 BAs showed separation of the data between IBS subtypes and healthy controls indicating that while individual BA concentrations did not vary significantly, differences in profiles existed in IBS participants. CONCLUSIONS: Data from a subset of an IBS cohort shows BA metabolism is likely perturbed in IBS. Further analysis of faecal samples will provide additional information that could confirm the relationships to IBS subtypes, and provide putative biomarkers for food interventions targeting improvement of gut comfort and function. FUNDING SOURCES: High-Value Nutrition National Science Challenge, New Zealand.