Effects of semi-purified dietary fibers isolated from Lagenaria siceraria, Raphanus sativus and Lentinus edodes on fecal steroid excretions in rats

Abstract

Rats were fed diets, each of which contained 5% of the semi-purified dietary fiber (DF) preparations from three kinds of foods, continuously for a total of 7 weeks. The fat level was varied, and cholesterol (Chol) was added toward the end of the experimental period. After 7 weeks, decreases of serum and liver Chol concentrations were observed in the Shiitake (Lentinus edodes) group when compared to the cellulose (CP) group. In the absence of Chol, fecal excretions of several secondary bile acids and total bile acids were affected by the type of DF, showing an increase particularly in the Shiitake group. Total neutral steroid excretions were decreased in the test DF groups compared to the CP group at both fat levels, and were increased by Chol supplementation in all of the test DF groups. It was demonstrated that the effects of the three DF preparations on fecal steroid excretions somewhat differed depending on the dietary factors. In the absence of Chol, the lithocholic acid (LCA)/deoxycholic acid (DCA) ratio was significantly lowered in the test DF groups compared to the CP group by the fat level elevation, and was affected by the interaction of fiber with fat. This ratio responded more intensely to the dietary factors than the two other indices (composition ratios of fecal bile acids). However, this response was lost in the presence of Chol. These results suggest that further studies are warranted to examine if the intense response of the LCA/DCA ratio to the tested DF preparations and fat in the present study will also be shown to other DF and what significance it has in evaluating the function of DF.