Barley β-Glucan Lowers Serum Cholesterol Based on the Up-Regulation of Cholesterol 7 α-Hydroxylase Activity and mRNA Abundance in Cholesterol-Fed Rats

Abstract

Barley, which is high in soluble dietary fiber (particularly β-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 β-glucan. Male Sprague-Dawley rats (n=21) were fed control (fiber-free) diets, diets with the addition of 2.5% refined β-glucan or 30% waxy barley that provides approximately 2.5% β-glucan in the diet for 2 wk. Body weight gain and food efficiency of rats were unaffected by diet. β-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 β-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 β-glucan diet by 1.5 times the activity of cholesterol 7 α-hydroxylase (CYP7A1). Hepatic CYP7A1 mRNA level paralleled the increases in enzyme activity. The results of this study suggest that the hypocholesterolemic effects of both β-glucan and a waxy barley diet may be due to the enhancement of CYP7A1 expression resulting from increased fecal excretion of bile acids.