Insulin Resistance in Rats Exposed to a High Fat Diet

Type II diabetes is a serious, chronic metabolic disease that has serious impacts on both the health and quality of life in patients diagnosed with the disease. Type II diabetes is also a very prevalent disease both in the United States and around the world. There is still a lot that is unknown about Type II diabetes, and this study will aim to answer some of these questions. The question posed in this study is whether insulin resistance changes as a function of time after the start of a high fat diet. We hypothesized that peripheral insulin resistance would be observed in animals placed on a high fat diet; and peripheral insulin resistance would have a positive correlation with time. In order to test the hypotheses, four Sprague-Dawley male rats were placed on a high fat diet for 8 weeks, during which time they were subjected to three intraperitonal insulin tolerance tests ((NovoLogTM 1 U/kg). These three tests were conducted at baseline (week 1), week 4, and week 8 of the high fat diet. The test consisted of serially determining plasma glucose levels via a pin prick methodology, and exposing a droplet of blood to the test strip of a glucometer (ACCUCHEKTM, Roche Diagnostics). Two plasma glucose baselines were taken, and then every 15 minutes following insulin injection for one hour. Glucose disposal rates were then calculated by simply dividing the glucose levels at each time point by the baseline value, and multiplying by 100. Area under the curve data was calculated via definite integral. The area under the curve data was then subjected to a single analysis of variance (ANOVA), with a statistical significance threshold of p<0.05. The results of the study did not indicate the development of peripheral insulin resistance in the animals placed on a high fat diet. Insulin-mediated glucose disposal was about 50% at 30 minutes in all four animals, during all three testing periods. Furthermore, the ANOVA resulted in p=0.92, meaning that the data was not statistically significant. In conclusion, peripheral insulin resistance was not observed in the animals, meaning no determination could be made on the relation between time and insulin resistance.