epiglucan and 7-alpha-hydroxy-4-cholesten-3-one

Underlying mechanisms responsible for the cholesterol-lowering effect of β-glucan have been proposed, yet have not been fully demonstrated. The primary aim of this study was to determine whether the consumption of barley β-glucan lowers cholesterol by affecting the cholesterol absorption, cholesterol synthesis or bile acid synthesis. In addition, this study was aimed to assess whether the underlying mechanisms are related to cholesterol 7α hydroxylase (CYP7A1) SNP rs3808607 as proposed by us earlier. In a controlled, randomised, cross-over study, participants with mild hypercholesterolaemia (n 30) were randomly assigned to receive breakfast containing 3 g high-molecular weight (HMW), 5 g low-molecular weight (LMW), 3 g LMW barley β-glucan or a control diet, each for 5 weeks. Cholesterol absorption was determined by assessing the enrichment of circulating 13C-cholesterol over 96 h following oral administration; fractional rate of synthesis for cholesterol was assessed by measuring the incorporation rate of 2H derived from deuterium oxide within the body water pool into the erythrocyte cholesterol pool over 24 h; bile acid synthesis was determined by measuring serum 7α-hydroxy-4-cholesten-3-one concentrations. Consumption of 3 g HMW β-glucan decreased total cholesterol (TC) levels (P=0·029), but did not affect cholesterol absorption (P=0·25) or cholesterol synthesis (P=0·14). Increased bile acid synthesis after consumption of 3 g HMW β-glucan was observed in all participants (P=0·049), and more pronounced in individuals carrying homozygous G of rs3808607 (P=0·033). In addition, a linear relationship between log (viscosity) of β-glucan and serum 7α-HC concentration was observed in homozygous G allele carriers. Results indicate that increased bile acid synthesis rather than inhibition of cholesterol absorption or synthesis may be responsible for the cholesterol-lowering effect of barley β-glucan. The pronounced TC reduction in G allele carriers of rs3808607 observed in the previous study may be due to enhanced bile acid synthesis in response to high-viscosity β-glucan consumption in those individuals.

Topics: Alleles; beta-Glucans; Bile Acids and Salts; Carbon Isotopes; Cholestenones; Cholesterol; Cholesterol 7-alpha-Hydroxylase; Cholesterol, Dietary; Cholesterol, LDL; Cross-Over Studies; Dietary Fiber; Female; Genotype; Hordeum; Humans; Hypercholesterolemia; Intestinal Absorption; Male; Middle Aged; Molecular Weight; Plant Extracts; Polymorphism, Single Nucleotide

To study whether oat bran with native beta-glucans increases bile acid excretion and bile acid synthesis as measured by serum concentrations of 7alpha-hydroxy-4-cholesten-3-one (7alpha-HC).. Short-term interventional crossover study evaluating cholesterol absorption, ileal excretion of cholesterol and bile acids, and serum levels of cholesterol and bile acid metabolites. Differences between diets evaluated with Wilcoxon's signed rank-sum test.. Outpatients at a metabolic-ward kitchen.. Nine volunteers with conventional ileostomies.. Two 3-day-diet periods, with controlled, blinded basal diet including 75 g extruded oat bran breakfast cereal daily, with either 11.6 g native or hydrolysed beta-glucans.. Native oat bran increased median excretion of bile acids by 144% (P=0.008). Cholesterol excretion remained unchanged, cholesterol absorption decreased by 19% (P=0.013), whereas the sum of bile acid and cholesterol excretion increased by 40% (P=0.008) compared with hydrolysed oat bran. 7alpha-HC reflecting bile acid synthesis increased by 57% (P=0.008) within 24 h of consumption, whereas serum lathosterol concentration reflecting cholesterol synthesis increased by 12% (P=0.015).. Oat bran with native beta-glucans increases bile acid excretion within 24 h of consumption and this increase can also be detected by rising serum concentrations of 7alpha-HC. Thus, 7alpha-HC could be used for rapid detection of dietary effects on bile acid metabolism. These effects could possibly be explained by entrapment of whole micelles in the gut owing to higher viscosity.

Topics: Adult; Aged; Aged, 80 and over; Avena; beta-Glucans; Bile Acids and Salts; Biomarkers; Cholestenones; Cholesterol; Cross-Over Studies; Dietary Fiber; Female; Humans; Ileostomy; Intestinal Absorption; Kinetics; Male; Middle Aged