[A study of low density lipoprotein in a patient with hyper-high density lipoprotein cholesterolemia with normal...

We examined a patient with hyper-cholesterolemia with a high level of HDL2 and LDL-cholesterol in serum. The metabolism of lipoproteins in this case was different from that in well-known hyper-high density lipoproteinemia or hyper-low density lipoproteinemia, because the patient had normal levels of cholesterolester transfer protein, lipoprotein lipase and hepatic triglyceride lipase activity. This study describes the characterization of LDL obtained from the patient's serum. LDL from the patient was separated by ultracentrifuge, and analyzed by gradient PAGE. The molecular weight of two LDL from the patient have been estimated to be approximately 1250 and 1450kDa by polyacrylamide gel electrophoresis, and were larger than those of normal individuals and patients with typical hypercholesterolemia (approximately 1150kDa in molecular weight). The LDL from the patient was separated into three fractions by HPLC, and their lipid composition was not significantly different from that of normal LDL. The high level and large size of LDL from the patient may be caused by a reduction in the transfer of cholesterol from LDL to HDL2, or an equilibrium of cholesterol with the increased HDL2.