Age‐Related Changes in Rat and Primate Plasma Cholesterol Metabolism

ABSTRACT: Plasma lipids, lipoproteins and the enzyme, lecithin:cholesterol acyltransferase (LCAT), were studied in three age groups of Sprague‐Dawley rats and non‐human primates (Macaca nemestrina). In the rats, serum cholesterol levels did not change significantly from 2 months (82 ± 6 mg/dl) to 12 months of age (88 ± 9 mg/dl) but increased sharply by 24 months (173 ± 85 mg/ dl). LCAT activity (cholesterol esterified per ml per hr) decreased slightly, but a more significant decrease with age was noted in the fractional rate of cholesterol esterification (percent cholesterol esterified per hr). Fasting resulted in a progressive decrease in the serum cholesterol level, usually accompanied by an increase in the fractional rate of cholesterol esterification. In the primate study, three age groups were used. On each serum sample, the following determinations were made: free and total cholesterol, triglycerides, high‐density lipoprotein (HDL) cholesterol, and LCAT. In the serum from 4‐year, 10‐year and 20‐year‐old animals, only a few significant changes were observed. There was a slight tendency for the levels of serum cholesterol and triglycerides to increase with age, but larger changes were noted in high‐density and low‐density lipoprotein (LDL) compartments. HDL cholesterol increased while LDL cholesterol decreased with age. The significance of these findings in relation to human cholesterol metabolism, atherosclerosis, and aging is discussed. 1979 The American Geriatrics Society