Alistipes: The influence of a commensal on anxiety and depression

The interaction between the gut microbiome and the brain is increasingly recognized as a potential cause for pathophysiology. With a variety of mechanisms for altering host central nervous system (CNS) function, including tryptophan metabolism and releasing modulatory metabolites, the human microbiome is emerging as a target for the development of therapies against disorders such as anxiety and depression. In this review, the gut microbiota and the microbiome-gut-brain axis will be discussed. Then, the mechanisms by which gut microbiota interacts with the CNS with a focus on anxiety and depression will be outlined. Following this, potential mechanisms whereby Alistipes may modulate behaviour including the inflammatory, serotonin and secondary metabolites hypotheses are highlighted. Throughout the review controversies involving these pathways are mentioned. Elucidating a mechanism for a clear link between Alistipes and anxiety/depression may lead to novel approaches to treating these disorders.