Dietary fat saturation and cholesterol turnover in aging rats

Abstract

Aging has been shown to result in changes in cholesterol metabolism resulting in Increased concentration in the serum. The turnover of cholesterol is regulated, in part, by its retention in peripheral tissues. Conversion of cholesterol to acidic form in peripheral tissues has been reported. This report examines the retention of 4-14C-cholesterol in the livers and carcasses of male and female rats fed diets containing fats of polyunsaturated to saturated ratio 0.2 (BT diet) or 1 (M diet)until they were 9, 12, 15, 18, or 21 months of age. The tracer cholesterol was given 28 days prior to necropsy and tissues were analyzed for neutral and acidic 14C, cholesterol and cholanoic acids. Age beyond 1 year resulted in an increase of retention of 14C-cholesterol in the carcass while concentration remained constant, indicating slower turnover of cholesterol. There was no consistent diet effect, but males had greater retention than females. Retention of 14C which had been transformed to an acidic form followed an age pattern similar to that of cholesterol, except M diet caused greater retention of acidic 14C after 15 months than did BT diet. Carcasses contained about 1 mg cholesterol per gm and 30–100 μg/gm of cholanoic acids regardless of weight, age, sex or diet. Changes in sterol turnover and peripheral tissue catabolism of cholesterol are concluded to be affected by age and to contribute to the mechanism of increase in serum cholesterol with advancing age.