Lipid Compositions of Plasma Major Lipoproteins and Lipoprotein Lipase Activity in Hypolipidemic and Hyperlipidemic Siblings with Familial LCAT Deficiency

There were marked differences in terms of serum cholesterol concentration among three Japanese siblings (one female, two males) with familial IX AT deficiency, who have been living in the same circumstances. Percentage distribution of cholesterol among three major lipoprotein fractions, namely VLDL. LDL and HDL. suggested that the observed differences in cholesterol concentration might be merely a reflection of VLDL concentration. While the lipid compositions of the major lipoprotein fractions of the patients differed greatly from those of the normal controls, the compositions were very similar among all three patients. Total cholesterol decreased and triglyceride increased in each lipoprotein fraction of the patients, leading to the definite increase in triglyceride-cholesterol (TG/TC) ratio in all lipoprotein fractions. Esterified cholesterol concentration and hence cholesterol ester (CE) ratio decreased significantly in LDL and HDL. but not in VLDL except one patient. The enzyme replacement therapy by fresh frozen plasma transfusion increased total cholesterol and decreased the TG/TC ratio, together with a concurrent increase in LCAT activity and CE ratio. Lipoprotein lipase (LPL) activity decreased definitely in all patients. This decrease was not due to either a decrease in HDL concentration in the patients, or an existence of any inhibitors of LPL activity in the circulation. Although serum lecithin concentration increased and lysolecithin concentration decreased in all patients, both lecithin and lysolecithin tended to increase in VLDL and decrease in HDL. The ratio of lysolecithin to lecithin is higher in VLDL than in HDL, and markedly increased VHDL fraction in the patients. These results suggested some important role of LCAT on triglyceride catabolism and some contributions of LPL deficiency as a part of the syndrome of familial LCAT deficiency.