Interleukin-1beta-converting enzyme-deficient mice resist central but not systemic endotoxin-induced anorexia.

Interleukin-1beta (IL-1beta) mediates many of the behavioral responses to infection and inflammation, and IL-1beta-converting enzyme (ICE) processes intracellular IL-1beta, leading to its maturation and secretion. Here we demonstrate that intracerebroventricular injections of lipopolysaccharide (LPS) produced a greater reduction in both food intake and food-motivated behavior in wild-type compared with ICE-deficient (ICE -/-) mice. This defect occurred although ICE -/- mice were able to fully respond to intracerebroventricular injections of IL-1beta. In contrast, ICE -/- mice remained fully responsive to intraperitoneal injections of LPS. These results indicate that brain, but not peripheral, IL-1beta plays a critical role in the depression in food intake that occurs during inflammation.