URBANA, Ill.—Researchers at the University of Illinois, Urbana, found a diet rich in soluble fiber, such as pectin from apples and other fruits and vegetables, protects against endotoxin-induced sickness behavior by polarizing mice Th2 and promotes alternative activation of macrophages when compared to a diet containing only insoluble fiber (Brain Behav Immun. 2010 Feb 6).
Mice fed soluble fiber became less sick and recovered faster from endotoxin-induced sickness behaviors than mice fed insoluble fiber. In response to intraperitoneal endotoxin, mice fed soluble fiber had up-regulated IL-1RA and reduced IL-1beta and TNF-alpha in the brain as compared to mice fed insoluble fiber. Mice fed soluble fiber had a basal increase in IL-4 in the ileum and spleen which was absent in MyD88 knockout mice. Con-A stimulated splenocytes from mice fed soluble fiber showed increased IL-4 and IL-5 and decreased IL-2, IL-12 and IFN-gamma when compared to mice fed insoluble fiber. Likewise, endotoxin-stimulated macrophages from mice fed soluble fiber demonstrated decreased IL-1beta, TNF-alpha, IFN-gamma, IL-12 and nitrate, and increased IL-1RA, arginase 1 and Ym1 when compared to mice fed insoluble fiber. The behavioral protection afforded by feeding mice soluble fiber was reduced in IL-4 knockout mice, as was the impact of soluble fiber on Con-A stimulated splenocytes and endotoxin activated macrophages.