Effects of Dietary Emulsifiers on Vasopressin and Oxytocin in Mice

Microbiota are micro-organisms that colonize the internal and external surfaces of the body and contribute to developmental processes and the microbiota-gut-brain axis, thereby to the high comorbidity between mental and gastrointestinal diseases. Recent evidence suggests that the gut microbiota influence the expression of vasopressin (AVP), a neuropeptide that mediates anxiety, stress and sickness behaviors and oxytocin (OXT), a neuropeptide that modulates social behavior and energy homeostasis. One way that the gut microbiota can be altered is through diet. Dietary emulsifiers, ambiphillic molecules used to stabilize emulsions of oil and water, alter the gut microbiome and increase intestinal inflammation. Recently, we have demonstrated that the emulsifiers carboxymethylcellulose (CMC) and polysorbate 80 (P80) increase anxiety-like behavior and reduce social behavior. Here, we investigate the roles of AVP and OXT as potential neural mechanisms by which emulsifiers alter anxiety and social behaviors. To test, male and female mice were weaned at 3 weeks of age, started in water (control), CMC or P80 treatment, and remained on treatment throughout the duration of the experiment. A standard battery of anxiety and social behavior tests was conducted starting at 10 weeks of age. A week following the completion of the last behavioral task, mice were euthanized, and brains were harvested and processed immunoreactivity (IR) of AVP and OXT in brain areas associated with stress and metabolism, such as the paraventricular nucleus of the hypothalamus (PVN) and paraventricular nucleus of the thalamus (PVT). There was no main effect of treatment in AVP-IR in the PVN or PVT or OXT-IR in the PVN. There was a main effect of sex in AVP-IR in the PVN. Therefore, the results do not support the hypothesis regarding vasopressin and oxytocin expression in the PVN and PVT of mice with emulsifier-induced intestinal inflammation. Altered expression of AVP and OXT may not be a mechanism by which dietary emulsifiers cause changes in anxietylike and social behavior. INDEX WORDS: Microbiota-gut-brain axis, emulsifiers, vasopressin, oxytocin, paraventricular nucleus of the hypothalamus, paraventricular nucleus of the thalamus EFFECTS OF DIETARY EMULSIFIERS ON VASOPRESSIN AND OXYTOCIN IN MICE by KRISHNA DINESH MEHTA An Honors Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Bachelors of Neuroscience in the College of Arts and Sciences Georgia State University