Effect of Fat-Free Diets and Lipid Unsaturation on Rat Tissue Cholesterol Levels.

Abstract

Lipids with different degrees of unsaturation, as measured by iodine number were obtained by use of un-hydrogenated oil, completely hydrogenated oil, and a 1:1 mixture of the two. By this method iodine numbers of 130, 1.5, and 61 for corn oil and 137, 1.5, and 57 for safflower oil were obtained. These lipids were incorporated at 1 5% level by weight into fat-free purified diets. Diets with (2%) or without cholesterol were fed ad libitum to groups of 8 male weanling rats each for a period of 8 weeks. In the absence of dietary cholesterol, neither total plasma nor hepatic cholesterol concentration was affected by the absence or degree of unsaturation of dietary lipid. Plasma cholesterol concentration was increased with dietary cholesterol but was not influenced by the degree of unsaturation of the dietary lipid. Hepatic cholesterol concentrations were directly related to degree of unsaturation of dietary lipid when cholesterol was fed. The increase in hepatic cholesterol was confined to esterified cholesterol. Inasmuch as an increase in hepatic cholesterol was obtained with a fat-free diet containing cholesterol, dietary lipid was not obligatory for cholesterol absorption.