Hypocholesterolemic effect of capsaicinoids in rats fed diets with or without cholesterol.

The potential mechanism of the hypocholesterolemic effect of capsaicinoids in rats fed with cholesterol-enriched and cholesterol-free diets was determined. Capsaicinoids favorably modified the lipoprotein profile of rats. Capsaicinoids consumption down-regulated the mRNA levels of hepatic 3-hydroxyl-3-methylglutaryl CoA (HMG-CoA) reductase by 0.55-fold and hepatic cholesterol-7α-hydroxylase (CYP7A1) by 0.53-fold in the cholesterol-free diet group (P < 0.05) but up-regulated the CYP7A1 level by 1.38-fold in the cholesterol-enriched diet group (P < 0.05). It also increased the expression levels of ileal bile acid binding protein and apical sodium-dependent bile acid transporter in the ileum, as well as transient receptor potential vanilloid type-1 in the liver and ileum in the different groups. Capsaicinoids reduced the amount of bile acids in feces by -15.97% and contents of the small intestine by -9.64% in the cholesterol-free diet group (P < 0.05) but increased both by 13.06% and 10.20%, respectively, in the cholesterol-enriched diet group. The cholesterol-lowering action of capsaicinoids in the cholesterol-free diet group was attributed to the inhibition of hepatic cholesterol synthesis, whereas that in the cholesterol-enriched diet group was attributed to the stimulation of the conversion of cholesterol to bile acids and the increasing excretions of bile acids in feces.