Chronic restraint stress affects the diurnal rhythms of gut microbial composition and metabolism in a mouse model of depression

Background: Depression is a common mental disorder accompanied by gut microbiota dysbiosis, which disturbs the metabolism of the host. While diurnal oscillation of the intestinal microbiota is involved in regulating host metabolism, the characteristics of the intestinal microbial circadian rhythm in depression remain unknown. Our aim was to investigate the microbial circadian oscillation signature and related metabolic pathways in a mouse model with depression-like behaviours.

Methods: Chronic restraint stress (CRS) was used to induce depressive-like behaviours in C57BL/6J mice. The open field test (OFT) and forced swimming test (FST) were used to evaluate anxiety- and depressive-like behaviours in the control and CRS groups. Afterwards, faecal samples from the two groups were collected every four hours from ZT2 (9:00 am) to ZT22 (5:00 am). Faecal 16 S rRNA gene sequencing and metabolomics analysis were performed, and the microbial circadian rhythm was analysed via the MetaCycle package in R/RStudio.

Results: CRS mice exhibited depressive-like behaviours after 4 weeks of restriction. Alpha- and beta-diversity analyses revealed that the microbial composition in control and CRS mice oscillated throughout the day. The circadian rhythm analyses revealed that at the phylum level, Bacteroidota, Firmicutes, Cyanobacteria and Patescibacteria showed circadian rhythmicity in the CRS group. At the genus level, Dubosiella and Romboutsia showed circadian rhythmicity in the control group, and Dubosiella abundance was correlated with tryptophan and galactose metabolism. In the CRS group, Bacteroides, Parabacteroides, and Rikenellaceae_RC9_gut_group showed circadian rhythmicity; among these genera, Parabacteroides was related to tryptophan metabolism, axon regeneration, phenylalanine metabolism and tyrosine metabolism.

Conclusion: Our data highlight the importance of observing the diurnal oscillation of the microbiome in host with depressive-like states. Rhythmicity in the microbiome may affect the host by regulating distinct metabolic pathways during the light and dark phases. A better combination of microbiota composition and oscillation would help to offer novel insight into key genera and their potential effects on depression.