Effects of Brewer's Yeast Cell Wall on Fecal Steroid Excretion in Rats.

Abstract

To reveal the mechanism(s) of the cholesterol-lowering effect of brewer’s yeast cell wall (BYC), we examined the effect of BYC on fecal steroid excretion in rats fed a high-cholesterol and -fat (HCF) diet or a cholesterol-free standard (STD) diet. Male Sprague-Dawley rats were fed an HCF diet or an HCF diet supplemented with 5% or 10% BYC for 14 days. The addition of BYC to the HCF diet dose-dependently reduced the increment of serum total cholesterol concentration and increased the fecal bile acid and neutral steroid(cholesterol and coprostanol) excretion levels. In this experiment, a negative correlation between serum total cholesterol concentration and fecal bile acid excretion level was observed; however, a correlation between serum total cholesterol concentration and fecal neutral steroid excretion level was not observed. Next, male Sprague-Dawley rats were fed an STD diet or an STD diet supplemented with 5% or 10% BYC for 14 days, to investigate whether BYC could lower serum total cholesterol concentration in the rats with normal serum cholesterol concentrations. The addition of BYC to the STD diet also slightly increased the fecal bile acid excretion level; however, it did not affect the serum cholesterol concentration. Furthermore, we examined whether BYC can reduce the serum total cholesterol concentration in Sprague-Dawley rats fed an HCF diet prior to the administration of BYC, to increase the serum total cholesterol concentration. In this experimental model, BYC reduced serum total cholesterol concentration and increased fecal total steroid excretion level, and a negative correlation between serum total cholesterol concentration and fecal bile acid excretion level was observed. These results suggest that BYC reduces serum total cholesterol concentration by increasing fecal bile acid excretion level.