When Rhythms Meet the Blues: Circadian Interactions with the Microbiota-Gut-Brain Axis.

The microbiota-gut-brain axis encompasses a bidirectional mode of communication between the microorganisms residing in our gut, and our brain function and behavior. The composition of the gut microbiota is subject to diurnal variation and is entrained by host circadian rhythms. In turn, a diverse microbiota is essential for optimal regulation of host circadian pathways. Disruption of the cyclical nature of this microbe-host interaction profoundly influences disease pathology and severity. This review aims to summarize current knowledge on this bidirectional relationship. Indeed, the past few years have revealed promising data regarding the relationship between the microbiota-gut-brain axis and circadian rhythms and how they act in concert to influence disease, but further research needs to be done to examine how they coalesce to modulate severity of, and risk for, certain diseases. Moreover, there is a need for a greater understanding of the molecular mechanisms underlying the close relationship between circadian-microbiome-brain interactions.
Competing Interests: Declaration of Interests The authors are not aware of any affiliations, memberships, funding, or financial holdings that might be perceived as affecting the objectivity of this review. However, T.G.D. and J.F.C. have been invited speakers at meetings organized by Yakult, Alkermes, Ordesa, Servier, Lundbeck, Janssen, and AstraZeneca, and have received research funding from Mead Johnson, Cremo, Nutricia, Dupont, Pharmavite, and 4D Pharma. All other authors declare no competing interests.
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