Grant: Discovery Grants Program - Individual

Interactions between gut microbes and their hosts are now known to be important in many aspects of host defence, playing roles in choreographing immune activity and in immune system development. Nevertheless, many questions remain related to the mechanisms of gut microbes' interactions with host cells that are important for host defence and immune homeostasis at the intestinal barrier. Host cells at the intestinal interface encounter not only gut microbes, but also products of microbial metabolism, and varied food components. Lactic acid bacteria (LAB) are gut microbes that are often consumed in fermented foods and as probiotics. Understanding the mechanisms through which LAB influence the immune system provides valuable insight into specific mechanisms of probiotic action as well as the actions of gut microbes on a broader scale. LAB in fermented foods are both influenced by, and cause changes in, food components; this in turn can alter their impact on the immune system when these foods are consumed. One objective of this work is to examine how LAB in fermented milk interact with host cells, and how these interactions are influenced by microbial products made during milk fermentation. Dietary fibres and prebiotics are often consumed in foods for their potential health benefits, mediated in part through their impact on gut microbial activity. Fermentation of fibres and prebiotics leads to microbial metabolite production, including short chain fatty acids with downstream effects on the immune system. Another objective of this research is to determine how these products modulate actions of gut microbes such as LAB and alter their impact on the immune system. Since components of several dietary fibres and prebiotics can also directly activate cells of the immune system, information about direct and indirect effects is useful for understanding their impact on host defence. In addition, current evidence indicating that effects of fibres and prebiotics on the immune system differ between sexes points to an important role for host factors such as estrogen in diet-microbe interactions. Thus, it is important to test differences in the impact of dietary components and supplements on females and males. A third objective of this research is to analyze direct and indirect effects of dietary fibres and prebiotics on the immune system, taking sex-based differences into account. Anticipated outcomes of this research will be new insight into how the immune system is affected by food components, LAB, microbial products, the interactions between them, and a clearer understanding of differences in impact between sexes. Students involved in this research will gain experience and knowledge that can contribute to better understanding of applications for food components, probiotics and the outcomes of gut microbial activity on host defence, elements important for dietary strategies in the daily lives of Canadians.