The Release of Satiety-Inducing Immune Factors in Response to Fat, Carbohydrate, and Protein Diets

Abstract

Abstract Objectives To examine the release of satiety-inducing cytokines in response to diets rich in fat, carbohydrates or protein. Methods The feeding behavior of 40 male Sprague-Dawley rats was continuously monitored for 23 hours per day. Food was made available at 1200 each day and removed at 1800 each day. Rats were divided into 4 groups of 10 rats each and each group received a specific diet (60% fat, 60% carbohydrate, 60% protein, or normal rat chow) for 14 days. On the 15th day, rats were presented with their meal and allowed one hour to eat. Next, rats were removed from their chamber, administered an anesthetic dose of Chloral Hydrate, and had blood (hepatic portal vein) and tissue (small intestine) removed and saved for analysis before being euthanized. Samples were later tested for the presence of cytokines using standard ELIZAs. 2 rats from each group were not allowed to eat on the day of testing and their blood an tissue samples were used as a baseline. Results Results show a clear release of cytokines (IL-IB and TNF-a…but not IL-6) in both the blood and tissue samples collected. Tissue showed the highest release of IL-1B in response to the balanced diet (1050 pg/ml) with the other diets each releasing between 340–550 pg/ml. The baseline (no food) group of rats had IL-1B levels of 155 pg/ml. TNFa had a similar but lower release profile, while IL-6 was negligible. Conclusions The release of immune factors in response to diet is supported and may provide novel interventions with respect to satiety. It does not appear that the specific content of the diet is as critical as a balanced diet with respect to cytokine release. Fat, surprisingly, had a limited effect on the release of cytokines. It may be that fat requires more time to express its effects on the immune cells; or it may that fat based satiety uses mechanisms other than immune factors to enhance satiety. Overall, our findings point to a role for immune factors in the regulation of hunger and satiety that has only been minimally examined thus far. Continued work in this area is warranted to determine the effects of the immune system in normal eating behavior as well as disordered eating. Funding Sources This research was supported by the Millsaps College Faculty Development Grant and the Millsaps College Honors Project.