11 - The impact of obesity on ingestion-induced hippocampal Arc expression in male rats

Abstract

Obesity is a chronic disease that affects more than 33% of American adults and roughly 13% of adults worldwide. Obesity has many peripheral impacts, such as cardiovascular diseases, type II diabetes, and arthritis. Obesity also influences the functioning of the brain. In particular, obesity and overeating impair the function of the hippocampus, which is vital for memory. In humans, impairing the memory of a meal increases subsequent intake. In rats, our lab has shown that sucrose ingestion activates molecules necessary for hippocampal memory formation, such as activity regulated cytoskeleton associated protein (Arc). We hypothesize that obesity disrupts hippocampal-dependent memory formation of a meal, which could further contribute to obesity. We predict that high-fat diet-induced obesity impairs sucrose ingestion-induced Arc mRNA expression. To test this, rats were placed on a high-fat diet or a control diet for 8 weeks. On the experimental day, rats were given access to sucrose meal for 10 minutes; euthanized, and the hippocampus, fat pads, and liver were extracted. The hippocampus will be tested for the concentration of Arc mRNA by quantitative real-time polymerase chain reaction (qRT-PCR). It is predicted that the number of calories consumed, body, liver and fat pad mass, and the amount of sucrose consumed by the experimental rats will be greater than that of the control rats. More importantly, sucrose-induced Arc mRNA expression is expected to be reduced in the experimental rats compared to the control rats. This would be consistent with the hypothesis that obesity disrupts the hippocampal formation of a memory of a meal.