The Role of Bile Acids in the Overall Regulation of Steroid Metabolism

Bile acids, themselves end products of cholesterol catabolism, act to regulate virtually every step in cholesterol metabolism, including dietary absorption, endogenous synthesis, excretion, and bile acid formation. Although many aspects of the interaction between bile acids and cholesterol are poorly understood, in regard to bile acid synthesis the effect of bile acids is homeostatic. On the one hand, bile acid formation increases following bile acid deprivation in order to provide adequate bile acids to maintain fat absorption, whereas bile acid excess in the diet or circulation is compensated by diminished bile acid synthesis. Furthermore, the net effect of bile acid on cholesterol metabolism is to maintain a balance in which synthesis and absorption tend to equal excretion and degradation under diverse physiological conditions and, thus, to minimize either cholesterol accrual or cholesterol deficiency.