The intestinal epithelium plays an essential role in digestion and nutrient absorption and functions as a physical barrier against the entry of luminal inflammatory molecules, such as dietary antigens and microbial toxins. Therefore, an impaired intestinal barrier can result in intestinal inflammation and damage. Our previous studies demonstrated that supplemental dietary fibers reduced intestinal inflammation via different mechanisms. Supplemental fermentable fibers such as guar gum （GG） and its partial hydrolysate （PHGG） reduced intestinal inflammation in a murine model of colitis. Specifically, GG and PHGG reduced the impairment of the tight junction barrier and expression of inflammatory cytokines in the colon. These effects of GG and PHGG were associated with increased levels of fecal short-chain fatty acids （SCFAs）, major metabolites of the intestinal microbiota. In human intestinal Caco-2 cells, SCFAs not only increased tight junction barrier integrity but also suppressed the inflammatory response induced by tumor necrosis factor-α （TNF-α）. Supplemental psyllium fiber also ameliorated disease symptoms in colitic mice. However, the ameliorative effect seemed to be independent of microbial SCFA production and was involved in the up-regulation of extracellular matrix molecules in the colon. Caco-2 cells grown on collagen and fibronectin coating showed lower dextran permeability, indicating the strengthening of intestinal barrier integrity. In addition, GG fiber directly stimulated dectin-1 and Toll-like receptor 2 and reduced the inflammatory response induced by TNF-α in Caco-2 cells. GG-mediated inflammatory response reduction was associated with the expression of suppressor of cytokine signaling-1.
Key Words:dietary fiber，short-chain fatty acid，intestinal barrier，tight junction，suppressor of cytokine signaling |
