Long term steroid metabolism balance studies in subjects on cholesterol-free and cholesterol-rich diets: comparison between normal and hypercholesterolemic individuals.

Regulation of cholesterol metabolism was investi- gated in eight hypercholesterolemic and five normal individ- uals by combined intravenous pulse-labeling with radioactive cholesterol and fecal steroids balance techniques. Mean serum cholesterol concentrations ranged from 168 to 7 17 mg/dl. Experiments were scheduled in the following sequence: a cho- lesterol-free diet period lasting 4-6 weeks (PI); cholesterol intake of 1350 mg/day lasting 9-10 weeks (PII); and a cho- lesterol-free diet for 2 weeks (PIII). It was observed that body cholesterol synthesis in PI and absorption of dietary choles- terol in PI1 were completely independent of the serum cho- lesterol levels and varied widely among the subjects. During the cholesterol intake period, seven individuals maintained a negative fecal steroid balance, whereas six others accumulated cholesterol in the body (positive balance) irrespective of cho- lesterol concentration. A strong positive correlation was found between dietary cholesterol absorption and cholesterol bal- ance in PI1 and reflected two events: I) decreased synthesis as the major mechanism to prevent body storage of choles- terol, whereas the increase of fecal bile acids and endogenous neutral steroids excretion played a secondary role; 2) increas- ing amounts of cholesterol accumulated in the body propor- tionally to the amount absorbed, whenever the latter surpassed the ability of the compensatory mechanisms. These compen- satory mechanisms seem to have been equally efficient in both normal and hypercholesterolemic subjects. Changes in serum cholesterol subsequent to cholesterol feeding were also un- related to the amount absorbed and to the steroid balance in PIL-MaranhGo, R. C., and E. C. R. Quintgo. Long-term steroid metabolism balance studies in subjects on cholesterol- free and cholesterol-rich diets: comparison between normal and hypercholesterolemic individuals. J. Lipid Res. 1983. 24 167-173.