Barley β-glucan lowers serum cholesterol based on the up-regulation of cholesterol 7α-hydroxylase activity and mRNA abundance in cholesterol-fed rats

Barley, which is high in soluble dietary fiber (particularly beta-glucan), is thought to have hypocholesterolemic effects. The present study was performed to further elucidate the hypocholesterolemic actions of waxy barley, and the extent to which they can be attributed to beta-glucan. Male Sprague-Dawley rats (n=21) were fed control (fiber-free) diets, diets with the addition of 2.5% refined beta-glucan or 30% waxy barley that provides approximately 2.5% beta-glucan in the diet for 2 wk. Body weight gain and food efficiency of rats were unaffected by diet. P-glucan or waxy barley decreased serum levels of total cholesterol (p<0.05) by 13.5% or 18.9%, and also decreased LDL-cholesterol 19.4% or 24.3%, respectively. Addition of refined beta-glucan or waxy barley to the diet resulted in greater bile acid excretions (p<0.05) compared to the control group. The waxy barley diet up-regulated by 2.3 times and the beta-glucan diet by 1.5 times the activity of cholesterol 7alpha-hydroxylase (CYP7A1). Hepatic CYP7A1 mRNA level paralleled the increases in enzyme activity. The results of this study suggest that the hypocholesterolemic effects of both beta-glucan and a waxy barley diet may be due to the enhancement of CYP7A1 expression resulting from increased fecal excretion of bile acids.