Alterations of Gut Microbiota due to External Stress and the Associated Health Outcomes – A Systematic Review

Abstract

Background. Alterations of gut microbiota have been investigated for their association with many pathologies. Studies have reported significant changes to the composition and diversity of gut microbiota due to external stress using 16S ribosomal RNA sequencing. However, the threat of those alterations to the host's health is poorly studied. This systematic review was performed to explore the associated health outcomes with alterations of gut microbiota in mice exposed to external stresses. Methods. The database PubMed was searched for primary research papers published between 2013 and 2023, for case–control studies detecting gut microbiota in mice exposed to psychosocial, dietary, chemical, and environmental stress. The risk of bias in the studies was assessed using SYRCLE. The α-diversity and the abundance of gut microbiota in mice in stress groups compared to control groups were analysed qualitatively. Results. Eleven studies involving male or female mice were included. The risk of bias in the studies ranged from low to moderate risk. Faecal, caecal, and colonic samples showed no significant difference in the α-diversity of gut bacteria in approximately half of the studies and a lower diversity in the other half. Many variations in the abundance of gut bacteria from the same samples at the taxonomic levels of phylum, genus, family, and species. Conclusions. Alterations of gut microbiota were observed in mice after stress exposure and were thought to be associated with increased inflammation and other health outcomes. Further studies are needed to provide more evidence and explanation for the pathologies associated with changes to gut microbiota.