Suppression of cholesterol biosynthesis by constituents of Barley Kernel

Abstract

Hepatic β-hydroxy-β-methylglutaryl CoA (HMG-CoA) reductase, cholesterol 7α-hydroxylase (7α-hyd), and fatty acid synthetase (FAS) activities and cholesterol levels were determined in chicks fed isonitrogenous corn- and high-protein barley flour (HPBF) based diets. HMG-CoA reductase (−27%), 7α-hyd (−30%), and serum cholesterol (−13%) were reduced, whereas FAS increased (28%) in comparison to a corn-based (control) diet. Fractions obtained by serial extractions of HPBF with solvents of increasing polarity were fed at levels equivalent to 20% HPBF in a corn-based diet to female White Leghorn (WHL) chickens for 3 weeks. A petroleum ether-soluble fraction of HPBF produced 3 effects: an increase in body weight (18%), a strong suppression of HMG-CoA reductase (−36%) and FAS (−40%) accompanied by decreases in serum triglyceride (−9%) and cholesterol levels (−23%). The methanol-soluble fraction produced a significant suppression of HMG-CoA reductase (−49%) and serum cholesterol level (−29%), and an increase in FAS activity (95%). These effects were duplicated in 7-week-old broiler chickens which also showed a significant decrease in chol-LDL (low density lipoprotein) levels by these fractions. The factor(s) lowering serum cholesterol concentration was about equally divided between the polar and non-polar fractions, and each was significantly more effective than the 20% HPBF in the corn-based diet. The observed effects on lipogenesis and cholesterogenesis might be attibuted to a number of chemical constituents of HPBF, but cannot be attributed to the water-insoluble plant fibers.