TBA (24S108)

Microbial regulation of diurnal rhythms in the stressed gut: focus on tryptophan metabolism and barrier function

Author(s)

Cassandra E. Gheorghe 1,2,3, Sarah-Jane Leigh1,2,3, Gabriel S.S. Tofani1,3, Thomaz F. S. Bastiaanssen1,3, Joshua M. Lyte1,2,3, Elisa Gardellin1,2, Ashokkumar Govindan1,4, Conall Strain1,4, Sonia Martinez-Herrero1,2,3, Michael S. Goodson5, Nancy Kelley-Loughnane5, John F. Cryan1,,3, Gerard Clarke1,2

Department(s)/Institutions

1 APC Microbiome Ireland, University College Cork, Cork, T12 CY82, Ireland; 2 Department of Psychiatry and Neurobehavioural Science, University College Cork, Cork, T12 CY82, Ireland; 3 Department of Anatomy and Neuroscience, University College Cork, Cork, T12 CY82, Ireland; 4 Teagasc Moorepark Food Research Centre, Fermoy Co. Cork, P61 C996, Ireland; 5 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, 45324, OH, USA

Introduction

Tryptophan is a precursor of key molecules involved in stress-related disorders and circadian rhythmicity plays a crucial role in gut-brain axis signaling.

Aims/Background

Little is known about the effects of acute stress on the gut and subsequent implications for diurnal physiology at the host-microbe interface. Here, we assess whether tryptophan-metabolizing bacteria respond to acute stress.

Method

Adult male C57Bl/6 mice were exposed to 15-minute acute restraint stress, and ileum and colon were collected for ex vivo Ussing chamber experiments as well as gene expression assessment. Microbial depletion models were used to investigate how an intact gut microbiota shapes host tryptophan metabolism and gut barrier function over the day. The TrypNet database was used to predict tryptophan metabolite production potential over the day. Biological rhythmicity was assessed using custom-built R package Kronos.

Results

Acute restraint stress was sufficient to alter microbial tryptophan metabolism in mice with an intact microbiota. Furthermore, acute restraint stress transiently increased gastrointestinal paracellular permeability in vivo (p<0.01). We demonstrated that tryptophan-metabolizing bacteria and their predicted metabolites exhibit circadian rhythmicity, and that microbiota depletion affected gut tissue rhythmicity of barrier function and expression of genes involved in host tryptophan metabolism. Acute stress evoked functional changes in transepithelial resistance (p<0.01) and interacted with time-of-day to induce impairments to paracellular permeability specifically in the ileum (p<0.05).

Conclusions

These findings highlight a new role for the gut microbiota in region-specific responses to host-directed stressors and in regulating circadian rhythms of tryptophan metabolism and barrier function in the gut.