The Effect of Processed Grain Consumption on the Dentogingival Microbiome and Host Response in Periodontal Disease

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PROJECT SUMMARY/ABSTRACT Periodontal disease (PD) affects approximately 50% of the world population. Microbial dysbiosis and gingival inflammation are well-recognized in PD. However, the role of diet on these parameters is minimally explored. Increased PD incidence coincides with the adoption of the western diet that is characterized by consumption of highly processed, refined grains. Grain processing alters both nutritional and structural properties of grains via removal of the outer bran layer to isolate inner starch-rich components. This disrupts the integrity of the grain structure, resulting in increased starch bioavailability and finer grain texture. Refined grain consumption is associated with increased incidence of PD. However, the mechanisms by which refined grains increase PD incidence are unexplored. Digestion commences in the oral phase via starch hydrolysis by salivary amylase and mechanical digestion by mastication. Saccharides are made available to bacteria in the oral cavity via starch hydrolysis by salivary amylase. Increased saccharide availability alters microbial carbohydrate metabolism, driving microbial dysbiosis within dentogingival biofilm communities. Dentogingival surfaces provide an opportunity for mature microbial biofilm formation. Excess biofilm formation drives dysbiosis as successional colonization increases the representation of periodontal pathogens within the community. As such, mechanical debridement is required to disrupt biofilm formation. Increased diet texture has been shown to decrease biofilm accumulation. Moreover, increased masticatory forces by hard diets induce a protective inflammatory response in gingival tissues, consistent with the role of the gingiva as a physiological barrier. As grain processing increases starch bioavailability and its susceptibility to salivary amylase, this may increase saccharide availability to bacteria in the oral cavity and encourage dysbiosis. Moreover, as grain processing disrupts the integrity of the grain structure, such changes may reduce masticatory forces and thereby encourage excess microbial colonization and reduce gingival barrier function. Therefore, I hypothesize that processed grains induce PD progression by promoting microbial dysbiosis and/or by conferring reduced gingival barrier function via local influences within the oral cavity. This proposal will address my hypothesis via two specific aims: 1) Determine the impact of processed grains on development of multispecies dentogingival biofilms in vitro, and 2) Determine the impact of processed grains on the dentogingival microbiome, periodontal immune response, and gingival barrier function in vivo. These aims will be achieved utilizing a combination of in vitro and in vivo models to recapitulate changes in the dentogingival microbiome and periodontal immunity in response to processed grain consumption. Outcomes from this investigation will improve the understanding of the role of diet in PD progression and will create avenues for the development of novel therapeutic applications that leverage the oral microbiome for prevention of PD onset and progression.