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Microbiome associations with the gut-brain axis : gut-microbiota changes in major depressive disorder and infant neurodevelopment Hunter Moreno, Sebastian


The colonization of the microbiome occurs early in life, before the full development of many systems, and its alteration into a dysbiosis state has been associated with several diseases. This has led to the concept of bidirectional communication between the host and the microbiota that promotes the host’s well-being. Because of its importance, new investigations and therapeutic interventions are being developed around the gut-brain axis to understand several conditions such as mood disorders and promoting brain development. This research aimed to further our understanding of the role the gut microbiome has in two different case studies relating to the gut-brain axis: an in-depth microbiome analysis in patients with major depressive disorder and how antidepressants alter the microbiota, and the association of the early microbiome with measurements of early cognitive development in infants. Research on depression was performed on samples from the American Gut Project, a self-selected cohort and open platform database. We compared both a 16S and metagenomic dataset to assess their strength in identifying microbial and metabolic pathway differences between a healthy and depressed population and identifying microbial signatures associated with the disorder, while correcting for important confounding variables such as bowel quality and alcohol consumption. Overall, both datasets identified similar trends, although the metagenomic samples had better performance in all the assays. An antidepressant assay was done in an in-vitro community derived from fecal samples, and treatment with fluoxetine and venlafaxine caused significant changes to the microbiota, reducing its diversity, and shifting the microbial composition and underlying microbial networks. The study on infant neurodevelopment was performed in 56 infants under six months of age, measuring social attention, language discrimination and neural rhythm tracking as measurements of brain development, and associated them to their microbiome. Although the tests were underpowered, associations between social attention and neural rhythm tracking and the microbiome were observed, such as increased Bifidobacterium and Eggerthella and reduced Hungatella and Streptococcus in infants with a successful Point and Gaze test. Overall, we observed potential associations between the microbiome and the gut-brain axis through changes in the microbiota composition and metabolic pathways in depression and infant neurodevelopment.

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