Keynote - Gut Microbiome: Myths and Metabolites

8th Munich Metabolomics Symposium
Applications of clinical metabolomics in oncology and cardiovascular diseases
Virtual event November 12th, 2021
Part 1 - Oncology & Immunology
Organized by Helmholtz Zentrum Munich, Technical University Munich, and biocrates
Prof. Dr. Hannelore Daniel
Technical University Munich, Germany
Abstract
There are around 60.000 scientific papers on “human gut microbiome” found in PubMed but science is still not able to define what constitutes a “healthy microbiome” And, it is as difficult to give meaning to associated changes in metabolite profiles either obtained in stool or plasma samples. I shall be addressing the microbiome from a historical perspective and present the myth´s about its quantitative and qualitative dimensions. Moreover, I shall demonstrate with examples the role of the biochemistry provided by gut microorganisms in synthesis of essential nutrients and what they can contribute to the demands of the human body. I also will demonstrate the major contribution of the microbiome to nitrogen handling that couple´s dietary protein intake and interorgan nitrogen fluxes to capabilities of microorganisms to control their ecological niche. In view of the species-diversity of the microbiome it is not surprising that the biochemical repertoire is as variable and that consequently the responses to the same dietary constituents can vary considerably across individuals and cohorts and that may well contribute also to the limited efficacy of dietary interventions in study cohorts. What caused some excitement was the observation that microbiome signatures could obviously predict for example also postprandial glucose responses. That has generated a certain hype and has been the fundament of a variety of commercial offers that combine stool analysis with glucose monitors as part of health-management. However, most recent studies assessing differences in gastrointestinal transit time (GTT) in cohorts demonstrate convincingly that GTT is a key determinant of microbiome diversity and of postprandial glucose kinetics as well and that this is best explained by the overarching control of gut motility. But, this is not a new finding since studies employing prokinetic agents or drugs that inhibit GTT inversely change the number of bacteria excreted in stool, affect stool water content and microbiome diversity. In this respect it is good to see that microbiome research that was largely ignoring key features of gut physiology now collects information on stool frequency, volume, appearance time of collection ect. - all shown to affect microbiome composition - and all known to be affected by diseases, diet or medication. That leaves microbiome science currently behind with the “chicken or egg” problem.