Cholesterol synthesis and degradation in normal rats fed a cholesterol-free diet with excess cystine

Feeding a diet with excess cystine to rats resulted in hypercholesterolemia . To understand the mechanism of the hypercholesterolemia, cholesterol synt hesis and degradation, bile acid content of bile, and fecal steroids were d etermined. The in vivo incorporation of tritiated water into hepatic choles terol, and activity of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase in rats fed a high-cystine diet were significantly higher than those in rats f ed a control diet. The activity of hepatic cholesterol 7 alpha-hydroxylase was similar between two groups. Little effect of cystine supplementation wa s found an fecal sterol excretion although there were some changes in bilia ry excretion of cholic acid derivatives. These results indicate that hyperc holesterolemia caused by feeding of a high-cystine diet may be due to the s timulation of hepatic cholesterol synthesis.