Explorando a conexão microbiota-cérebro no transtorno depressivo maior : alterações na composição microbiana - mecanismos e implicações

Abstract

A growing body of data establishes a connection between the gut microbiota and the development and functioning of the central nervous system, pointing to a bidirectional communication system associated not only with intestinal homeostasis but also with certain mental disorders, such as major depressive disorder (MDD). The objective of this study was to consolidate current literature on the composition of the gut microbiota in individuals with major depressive disorder compared to healthy controls, with a focus on identifying phyla, orders, families, and genera that are differentially abundant between these groups. Additionally, these groups were also compared in terms of their alpha and beta diversity measures. A systematic search of the PubMed, EMBASE, Web of Science, and PsycINFO databases was conducted following PRISMA guidelines, resulting in the inclusion of 29 studies, comprising 1352 MDD patients and 1284 control individuals. This investigation suggests that there are no consistent differences in alpha diversity (both in terms of richness and evenness) between the MDD and healthy populations. In contrast, beta diversity results appear to distinguish between these groups more reliably. Across the included literature, 80 genera, 56 families, 14 orders, and 12 phyla were identified as differentially abundant, varying between being more or less abundant in individuals with MDD. Among these, the genera Faecalibacterium, Clostridium, Ruminococcus, Dialister, Anaerostipes, and Roseburia; the families Oscillospiraceae, Prevotellaceae, and Bacteroidaceae; and the phylum Bacillota were found to be less abundant in MDD. Conversely, the genera Bifidobacterium, Oscillibacter, and Eggerthella; the families Bifidobacteriaceae and Enterobacteriaceae; and the phylum Actinomycetota were more abundant in the MDD group compared to the control group. Additionally, we found that certain microbial taxa were consistently less abundant in the MDD population. These taxa included groups that could synthesize short-chain fatty acids (SCFAs), taxa with anti-inflammatory potential, and taxa associated with reducing toxic kynurenine metabolites. Conversely, taxa associated with pro-inflammatory characteristics, IDO enzyme activation, and directing tryptophan metabolism towards the synthesis of neurotoxic kynurenine metabolites, were more abundant in the MDD group than in healthy controls. Thus, SCFAs are highlighted as molecules to be evaluated for their therapeutic potential, and the inflammatory and kynurenine pathways as possible targets. [resumo fornecido pelo autor]