VHIR Seminar led by Joel Doré. Research Director. Institut National de la Recherche Agronomique (INRA). Jouy-en-Josas, France.
Abstract: The human intestinal tract harbours a complex microbial ecosystem which plays a key role in nutrition and health. Interactions between food constituents, microbes and the host organism derive from a long co-evolution that resulted in a mutualistic association.
Current investigations into the human faecal metagenome are delivering an extensive gene repertoire representative of functional potentials of the human intestinal microbiota. The most redundant genomic traits of the human intestinal microbiota are identified and thereby its functional balance. These observation point towards the existence of enterotypes, i.e. microbiota sharing specific traits but yet independent of geographic origin, age, sex etc.. It also shows a unique segregation of the human population into individuals with low versus high gene-counts. In the end, it not only gives an unprecedented view of the intestinal microbiota, but it also significantly expands our ability to look for specificities of the microbiota associated with human diseases and to ultimately validate microbial signatures of prognostic and diagnostic value in immune mediated diseases.
Metagenomics of the human intestinal tract was applied to specifically compare obese versus lean individuals as well as to explore the dynamic changes associated with a severe calory-restricted diet. Microbiota structure differs with body-mass index and a limited set of marker species may be used as diagnostic model with a >85% predictive value. Among obese subjects; the overall phenotypic characteristics are worse in individuals with low gene counts microbiota, including a worse evolution of morphometric parameters over a period of 10 years, a low grade inflammatory context also associated with insulin-resistance, and the worst response to dietary constraints in terms of weight loss or improvement of biological and inflammatory characteristics. Low gene count microbiota is also associated with less favourable conditions in inflammatory bowel disease, such as higher relapse rate in ulcerative colitis patients.
Finally, microbiota transplantation has seen a regain of interest with applications expanding from Clostridium difficile infections to immune mediated and metabolic diseases.
The human intestinal microbiota should hence be regarded as a true organ, amenable to rationally designed modulation for human health.