Serum lecithin:cholesterol acyltransferase activities of cynomolgus monkeys fed different carbohydrate diets

Although serum lecithin:cholesterol acyltransferase (LCAT) activity is known to be modulated by nutritional factors, little is known about the effects of dietary carbohydrate on this enzyme. Therefore, LCAT activities were assessed in cynomolgus monkeys fed diets for 6 weeks on 4 diets containing 77% of calories as sucrose or starch and cholesterol at 0 and 1 mg/kcal. Three different assay conditions were used in order to measure the overall LCAT activity and to differentiate enzyme activity from the effect of serum substrate and end-product lipoprotein alterations by diet on this enzyme. Molar rate of serum total LCAT activity was higher in sucrose than starch diets (P less than 0.01). Use of sera from sucrose-fed animals, either as substrate or enzyme source, increased the fractional rate of cholesterol esterification (P less than 0.01). Exogenous cholesterol lowered serum total LCAT activity only in sucrose diet (P less than 0.01). Use of sera from sucrose + cholesterol-fed animals as substrate significantly lowered the fractional rate of cholesterol esterification (P less than 0.01); whereas no such alterations were noted when this serum was used as enzyme source. The differential effect of starch and sucrose diets on LCAT activity suggests that the nature of dietary carbohydrates may affect LCAT activity in association with triglyceride metabolism by altering the amount of enzyme in terms of its activity and/or the nature of substrate and cholesterol ester acceptor lipoproteins.