Date of Award

Spring 4-26-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Neuroscience Institute

First Advisor

Dr. Marise Parent

Abstract

Over the past five decades, per capita caloric intake has increased by approximately 28% in the United States. A hallmark of the current standard American diet is an excess of energy sources from saturated fat and refined carbohydrates. High energy diets such as the “Western” diet cause numerous pathologies, including non-alcoholic fatty liver disease (NAFLD), high blood pressure, dyslipidemia, and peripheral insulin resistance. High energy diets also negatively impact the hippocampus, a brain area important for learning and memory. It is not surprising, then, that high energy diets impair hippocampal-dependent memory. The experiments in this dissertation investigate possible diet-induced consequences that may contribute to the impairing effects of high energy diets on hippocampal-dependent memory. Our initial experiments found that diet-induced NAFLD impairs hippocampal-dependent memory, but these cognitive deficits were not due to decreases in insulin-like growth factor-1 (IGF-1) or hippocampal insulin signaling. Next, we found that a high energy diet increased the ability of epinephrine to increase blood glucose concentrations, indicating a novel way in which high energy diets impair liver function. The final set of experiments found that high energy diets do not necessarily impair memory but instead may prevent the memory-enhancing effects of acute stress. Taken together, these results indicate that high energy diets interact with acute stress to negatively impact hippocampal-dependent memory, and that hippocampal insulin resistance and IGF-1are not likely involved.

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