BACKGROUND—Dietary fibre influencesthe turnover and differentiation of the colonic epithelium, but itseffects on barrier function are unknown. AIMS—To determine whether alteringthe type and amount of fibre in the diet affects paracellularpermeability of intestinal epithelium, and to identify the mechanismsof action. METHODS—Rats were fed isoenergeticlow fibre diets with or without supplements of wheat bran (10%) ormethylcellulose (10%), for four weeks. Paracellular permeability wasdetermined by measurement of conductance and 51Cr-EDTA fluxacross tissue mounted in Ussing chambers. Faecal short chain fatty acid(SCFA) concentrations were assessed by gas chromatography, epithelialkinetics stathmokinetically, and mucosal brush border hydrolaseactivities spectrophotometrically. RESULTS—Body weight was similaracross the dietary groups. Conductance and 51Cr-EDTA fluxwere approximately 25% higher in animals fed no fibre, compared withthose fed wheat bran or methylcellulose in the distal colon, but not inthe caecum or jejunum. Histologically, there was no evidence ofepithelial injury or erosion associated with any diet. The fibresexerted different spectra of effects on luminal SCFA concentrations andpH, and on mucosal indexes, but both bulked the faeces, were trophic tothe epithelium, and stimulated expression of a marker of epithelial differentiation. CONCLUSIONS—Both a fermentable anda non-fermentable fibre reduce paracellular permeability specificallyin the distal colon, possibly by promoting epithelial celldifferentiation. The mechanisms by which the two fibres exert theireffects are likely to be different.
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