Plasma lipoprotein abnormalities in heterozygotes for familial lecithin:cholesterol acyltransferase deficiency

Measurement of plasma lecithin:cholesterol acyltransferase (LCAT) activity was used to segregate unaffected family members (n = 8) from heterozygotes (n = 8) and homozygotes (n = 2) in a large LCAT-deficient kindred. The activity was absent in the homozygotes and was decreased to 50% of normal in the heterozygotes. Endogenous cholesterol esterification rate measurements did not differentiate the heterozygotes from the unaffected family members or normal subjects. The heterozygotes had significantly higher fasting plasma triglycerides, apo B, and lower HDL-cholesterol and apo AI than the unaffected family members. The HDL of the heterozygotes had the same mass of free cholesterol and triglyceride, but the mass of cholesteryl ester was reduced by 47%. The differences were not related to abnormal postheparin lipolytic activities. However, cholesteryl ester transfer activity in the lipoprotein-free (d greater than 1.21 bottom) fraction of plasma was significantly (P less than .05) decreased in the heterozygotes when compared to unaffected members. We conclude that the low LCAT activity is the likely cause of the qualitative and quantitative differences in the plasma lipoproteins of the heterozygotes in this family with LCAT deficiency. However, the low HDL and apo A-I levels are not associated with either a family or personal history of premature atherosclerosis.