Increased plasma apolipoprotein E-rich high-density lipoprotein and its effect on serum high-density lipoprotein cholesterol determination in patients with familial hyperalphalipoproteinemia due to cholesteryl ester transfer activity deficiency

Abstract

Plasma apo E-rich HDL was studied in regard to its quantity and chemical composition in the members of a family with cholesteryl ester transfer activity deficiency, exhibiting familial hyperalphalipoproteinemia. The approach involved a simple precipitation method established in our laboratory. Serum apo E-rich HDL concentrations for two homozygous members were elevated up to 66 and 60 mg/dl in terms of cholesterol (normal, 6.7 +/- 2.3 mg/dl, n = 38), and to 9.4 and 10.8 mg/dl in terms of apo E (normal, 2.6 +/- 1.5 mg/dl, n = 38). The cholesterol/apo E ratio (mole/mole) of apo E-rich HDL was higher in two homozygotes (669 and 531) than in two cholestatic patients with elevated apo E-rich HDL (268 and 149) and in normal subjects (242 +/- 115, n = 38). Chromatographic studies of the serum from a homozygote showed enlargement of all HDL subclasses and apo E in the larger HDL subclass. These facts indicate that the increase of apo E-rich HDL in this disease occurs secondarily to the enlargement of HDL particles, which require substances to cover their cores, having expanded due to the accumulation of cholesteryl ester. The sera from the homozygotes gave HDL cholesterol concentrations which were remarkably discrepant among commercial precipitating reagents, because of the difference in recovery of apo E-rich HDL with these reagents.