Identifying_gut_microbial_metabolites_and_the_bacteria_responsible_for_their_formation

The gut microbiota plays a vital role in inflammation and in the development of many diseases including diabetes, cardiovascular disease and cancer. Links between host diet and the gut microbiota are known to influence disease risk. However, relatively little is known about the functionality and role of even the most dominant commensal organisms within the human host. Many of the products of microbial metabolism of dietary compounds remain uncharacterised and consequently, their mechanisms of action unknown. There is a large amount of literature suggesting that plant phytochemicals have anti-cancer properties. Data regarding the metabolism and bioavailability of phytochemicals is lacking, particularly with reference to their release and transformation by the activities of the gut microbiota, and absorption from the colon. Additionally, the relationship between the main macronutrients (carbohydrate and protein) and non-nutrient phytochemicals is poorly understood. It is likely that it is a combination of these dietary factors that modulates both the gut bacteria and the overall metabolite profile, both in the gut and in the systemic circulation. To assess this, we carried out acute human dietary intervention studies designed to address the combined effects of the macro- and non-nutrient components of the diet, along with the gut microbial composition on the production of microbial metabolites. Volunteers were fed products rich in phenylpropanoid metabolites, carbohydrate and/or protein (sources: oat, strawberry, kale, spinach, soya and pea), and faecal, blood and urine samples were collected before volunteers commenced the trial and then at 0, 3 and 5 days during intervention. Bacterial communities in the faecal samples were profiled using 16S rRNA gene sequencing, with the aim of identifying important relationships between the bio-available metabolites, gut bacteria, macronutrient sources and inflammatory activity.