The Microbiota-gut brain axis and its association with depression

Abstract

The gut microbiota is integrated by trillions of microorganisms that symbiotically interact with the host. During the last decade, researchers have focused on determining its role within the gut-brain axis and have suggested a link between their presence and mental disorders such as depression. The present bibliographic review gathers current knowledge on the microbiota-gut-brain axis, its relationship with depression and the use of microbiota as a potential therapeutic strategy. In this context, researchers have mainly used molecular tools to characterise the gut microbiota composition and animal models to understand the effects of a dysbiosis and establish its links with the development of human pathologies. Firmicutes and Bacteroidetes are the two main phyla present in our intestines. In addition, three enterotypes have been described in humans: Bacteroides, Prevotella and Ruminococcus. On another note, studies have proved the microbiota-gut-brain connection to be bidirectional, involving neural, endocrine and immunologic pathways. Current research on its contribution in depression is still at its infancy but it has recently been observed a correlation with the Bacteroides 2 enterotype in depressed patients and a decrease in Dialister and Coprococcus genera. Likewise, current knowledge on alternative therapies for depression based on microbiota interventions is limited but proposes some species from Bifidobacterium and Lactobacillus genera as well as Faecalibacterium prausnitzii as potential probiotic therapies. In conclusion, the microbiota-gut-brain axis is presented as a possible therapeutic target for depression but still requires further investigation.