In vitro serum cholesterol esterification in coronary artery disease

The mean serum in vitro cholesterol esterification as determined by the decrease in the concentration of free cholesterol after incubation of serum for 3, 6, 24, and 48 hours has been compared in four groups: subjects with acute myocardial infarction, subjects with chronic coronary artery disease, age-matched healthy controls, and young healthy controls. The original data revealed a significantly decreased esterification in subjects with chronic coronary artery disease compared to the group of age-matched controls (p < 0.05), and a significantly increased free cholesterol in subjects with acute myocardial infarction compared to the age-matched healthy subjects (p < 0.05). Comparisons of these four groups were then made by removal of those subjects with total cholesterol > 300 mg. per 100 ml. and < 195 mg. per 100 ml. because it was felt that a meaningful comparison could be made only if the mean total cholesterol concentration could be held constant for each group. This was also done to avoid the possibility that, since cholesterol esterification tends to be higher in subjects with hypercholesterolemia, those groups with coronary artery disease might show mean esterifications that were overly weighted by the presence of more subjects with total cholesterol > 300 mg. per 100 ml. When the statistical analysis was performed, the mean in vitro cholesterol esterification was significantly decreased at 6 hours (p < 0.02), 24 hours, and 48 hours (p < 0.01 in) subjects with chronic coronary artery disease compared to age-matched controls and was significantly decreased at 6 hours (p < 0.05) and 48 hours (p < 0.01) in subjects with acute myocardial infarction compared to the age-matched controls. The average slope describing cholesterol esterification over time was significantly decreased in acute myocardial infarction and chronic coronary artery disease (p < 0.01). On the other hand, there were no significant differences between the young healthy group and the older age-matched healthy subjects. Although these findings suggest the possibility that subjects with coronary artery disease have a deficiency of lecithin: cholesterol acyltransferase, the limitations of this study are stressed. It is unlikely that a firm conclusion will be available until an accurate method of determining the initial rate of plasma cholesterol esterification is available and until the enzyme is purified.