A Sex-Specific Molecular and Behavioural Analysis of the Impacts of Obesogenic Diet Exposure and Probiotic Treatment: Insights Into Specific Nutritional Determinants of Health and Disease

Abstract

Nutrition-related environmental exposures (e.g., diet ingredients, vitamins, probiotic strains) have been reported to impact the composition of the gut microbiota, the microbiota-associated metabolites produced, and host health. This microbiota-gut-brain axis is related to a variety of behavioural and physiological outcomes, including anxiety or anxiety-related behaviours, feeding and obesity development, along with metabolic and immune-related hormonal responses. As well, the relationship between anxiety and obesity, with respect to how each affects the development and severity of the other, remains to be fully explained. Thus, the work in this dissertation focused on behavioural and physiological responses of male and female Long–Evans rats exposed to different types of purified and non-purified rodent diets, in isolation or in combination with the administration of the commercially available probiotic formulation, CEREBIOME®. The first study examined differences in the health-related effects of a commonly used Western diet and two of its control diet formulations (i.e., a high-carbohydrate protein-matched purified control compared to a commonly administered standard laboratory rodent chow). Next, these diet-specific alterations were expanded by including the additional factor of probiotic treatment to study the potential mitigative effects of a combination of two bacterial strains on poor diet exposure. The results of both studies highlight the differential health-related outcomes that result from the administration of specific experimental or control diets, along with specific strains of probiotic bacteria. Indeed, the work herein and emerging studies in this area are consistently highlighting diet-specific and probiotic strain-specific health outcomes. As emphasized more in the thesis, male and female rodents do not respond to these experimental manipulations in the same ways. Thus, characterizing sex differences in response to environmental factors that impact disease risk or severity is one vital component of studying the development and prevention of health and disease. Studies such as the ones presented in this dissertation advance our understanding of how nutritional factors contribute to psychological and physiological health outcomes in the hopes that we can work to improve prevention and treatment options for these accompanying disease states.