Biliary cholesterol and bile acid excretion do not increase in hamsters fed cereal-based diets containing cholesterol

The major compensatory responses to increased cholesterol consumption are d ecreased cholesterol synthesis and increased cholesterol excretion through the bile either as free cholesterol or bile acids. The objective of this st udy was to test the hypothesis that biliary cholesterol excretion is increa sed in hamsters fed low levels of cholesterol reflecting normal human intak e. The hypothesis was based on observations that hamsters generally resist changes in bile acid synthesis when fed large amounts of cholesterol: there fore, increased biliary cholesterol excretion represents a potentially sign ificant pathway for elimination of excess cholesterol in this species, Hams ters were fed modified NIH-07 cereal-based diets containing 0.02%, 0.03%, a nd 0.05% cholesterol (0.04, 0.06, and 0.10 mp cholesterol/kcal, respectivel y). The primary response to increasing amounts of dietary cholesterol was d ownregulation of whole-body cholesterol synthesis, reduced from 3.93 +/- 0. 14 mu mol . d(-1) . 100 g(-1) body weight in hamsters fed 0.02% cholesterol to 0.52 +/- 0.14 mu mol . d(-1) . 100 g(-1) in the 0.05% cholesterol group . Biliary cholesterol excretion was also slightly reduced in hamsters fed 0 .05% cholesterol, whereas bile acid excretion was not altered by dietary ch olesterol, Despite a pronounced downregulation of whole-body cholesterol sy nthesis, liver and plasma cholesterol concentrations increased in hamsters fed 0.05% cholesterol, The data indicate that increased biliary cholesterol excretion is not: a major compensatory route of cholesterol excretion in h amsters consuming cholesterol, Furthermore, cholesterol added to the diet a t: 0.05% appears to be the approximate threshold at which compensatory mech anisms can prevent increases in liver and plasma cholesterol in male Syrian hamsters, Consequently, this species may be an appropriate animal model fo r "hyperresponding" individuals in the human population. Copyright (C) 1999 by W.B. Saunders Company.