COMPARATIVE-EVALUATION OF THE EFFECTS OF 2 DIFFERENT FORMS OF DIETARYFIBER (RICE BRAN VS WHEAT BRAN) ON RAT COLONIC MUCOSA AND FECAL MICROFLORA

The aim of the study was to compare the physiological consequences of two dietary fibre sources on the faecal microflora and colonic mucosal growth in rats. The studied sources, a moderately well-soluble fibre (rice bran, RB) and a less well-soluble fibre (wheat bran, WB), were i ncluded in diets of rats at a level of 10% for 3 weeks and compared wi th a totally fibre-deprived diet. RB significantly increased faecal wa ter compared to the control diet (p < 0.05). Faecal nitrogen content a nd bacterial mass, as estimated from the 2,6-diaminopimelic acid (DAPA ) output, were greatly and significantly increased by RB, and to a les ser extent by WB, compared to the control diet. Total bile acid excret ion was significantly higher by rats fed RB than by those fed WB. Faec al bacterial enzyme activities tested (beta-glucuronidase, mucinase an d nitroreductase) were significantly reduced by the two different fibr e sources, but RB was more effective than WB, except for nitroreductas e activity which was reduced at the same level for each fibre source. Although measurements of mucosal colonic weight and RNA content were s ignificantly different between groups fed RB and WB (p < 0.05), DNA co ntent and the ratio RNA/DNA did not significantly differ between these groups. Our results indicate that the differential changes observed i n beta-glucuronidase and mucinase activities and DAPA and bile acid ex cretion may depend on the nature of the fibre consumed. They also sugg est that RB, which had similar effects, sometimes more marked than WB, on the studied parameters, may be a new valuable fibre source.