UBC Theses and Dissertations
Impact of early environmental exposures on the mouse gut microbiota and immune responses Tasnim, Nishat
Gut microbiota assembly begins at birth, and the two key factors that influence the successful transmission of beneficial gut microbes to the infant are the mother and the external environment. The role of the environment in the assembly of the gut microbiota has yet to be elucidated. Global comparisons have revealed a decrease in gut microbiota diversity attributed to Western diets and lifestyle, and sanitation of the living environment. The goal of the study was to determine the importance of early environmental exposures on gut microbiota development and immunoregulation. In order to determine whether early environmental exposures altered the gut microbiome, we simulated three different environments by adding forest soil and urban soil respectively to the cage bedding of two groups of mouse cages and adding no soil to the bedding material of the third group of mouse cages, from birth until weaning and measured the effect of these early-life environmental exposures on gut microbiota, short-chain fatty acid (SCFA) production, and immune responses in neonatal and young adult mice. We hypothesized that early environmental exposures to soils would increase the diversity of the gut microbiota compared to pathogen-free no soil environment and alter colonic immune cell populations associated with changes in local and systemic cytokine production and SCFA profiles. Our findings indicated that the early-life soil exposure transiently altered the richness of the neonatal gut microbiota and contributed 5-9% variation in the bacterial community structure between individuals during early-life and adulthood. These microbiota alterations were associated with altered bacterial metabolite production, increased inflammatory cytokine and chemokine responses, and increased neonatal macrophage stimulation. Early exposure to urban soil specifically increased the of bacterial taxonomic family Clostridiaceae in the infant and mature gut microbiota, and significantly increased production of propionic acid in young adult mice. Taken together, these results supported the hypothesis that early environmental exposures play a role in gut microbiota richness and community composition, SCFA production, and immune responses. The results of this study provide preliminary insights to move forward through future studies on factors that implicate environmental biodiversity and inflammatory disorders through changes in the gut microbiota.
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