American Journal of Clinical Nutrition, Vol 8, 411-423, Copyright © 1960 by The American Society for Clinical Nutrition, Inc.

Regulation of Cholesterol Biosynthesis and Catabolism

¹ From the Wistar Institute of Anatomy and Biology, and the Department of Biochemistry, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

The formation of cholesterol by the liver, regulated by a type of homeostatic control, is influenced by the hepatic level of free cholesterol or glycogen, or both, and by the availability of the proper enzymes. Here the factors affecting the hepatic biosynthesis of cholesterol are detailed, including the influence of dietary composition and fasting. The specific effects on cholesterol synthesis of feeding cholesterol, various steroids, saturated and unsaturated fats and thyroid hormone are reviewed. Also considered are the effects of radiation, glycolysis and various pharmacologic agents.

In the degradation of cholesterol, the chief metabolic end products are bile acids, although cholesterol may also be converted into sex hormones and adrenocortical hormones. The steps involved in the degradation of cholesterol to bile acids are reviewed, along with the various factors which increase or decrease cholesterol catabolism. Since degradation of cholesterol depends on the levels of bile salts in the liver, any factor which will increase the turnover of bile acids will also accelerate cholesterol catabolism and may in turn lower serum cholesterol.