Cafeteria feeding induces interleukin-1β mRNA expression in rat liver and brain

Abstract

Food intake affects gut-immune function and can provide a strong intestinal antigen challenge resulting in activation of host defense mechanisms in the digestive system. Previously, we showed that feeding rats a cafeteria diet increases non-rapid eye movement sleep by a subdiaphragmatic mechanism. Food intake and sleep regulation and the immune system share the regulatory molecule interleukin-1β (IL-1β). Thus this study examined the effects of a cafeteria diet on IL-1β mRNA and IL-1 receptor accessory protein (IL-1RAP) mRNA expression in rat liver and brain. Rats were fed normal rat chow or a palatable diet consisting of bread, chocolate, and shortbread cookies (cafeteria diet). After 3 days, midway between the light period of the lightdark cycle, rats were killed by decapitation. Feeding rats a cafeteria diet resulted in increased IL-1β mRNA expression in the liver and hypothalamus compared with rats fed only the normal rat chow. In addition, cafeteria feeding decreased IL-1RAP mRNA levels in the liver and brain stem. These results indicate that feeding has direct effects on cytokine production and together with other data suggest that the increased sleep that accompanies increased feeding may be the result of increased brain IL-1β. These results further suggest that cytokine-to-brain communication may be important in normal physiological conditions, such as feeding, as well as being important during inflammatory responses.