Serum lipids, lipoproteins and apolipoprotein E phenotypes in relatives of patients with type III hyperlipoproteinaemia.

Eighty-six relatives of nineteen probands with type III hyperlipoproteinaemia were studied to determine the occurrence of hyperlipidaemia and to investigate the relation between apo E phenotypes, the occurrence of hyperlipidaemia, and the composition of the very low density lipoprotein (VLDL) fraction. Thirty-nine relatives were hyperlipidaemic: four type IIa or IIb, nine type III and twenty-six type IV. The predisposition for hyperlipidaemia was independent of the apo E phenotype. Hyperlipidaemic relatives with apo E phenotype E2/2 had a significantly (P less than 0.01) higher VLDL-cholesterol/VLDL-triglycerides ratio (1.26 +/- 0.35, n = 9) than those heterozygous for apo E allele epsilon 2 (0.66 +/- 0.12, n = 23) or without apo E allele epsilon 2 (0.69 +/- 0.11, n = 7). Normolipidaemic homozygous apo E-2 relatives had also a significantly (P less than 0.05) higher ratio (0.97 +/- 0.19, n = 6) than those heterozygous for (0.77 +/- 0.19, n = 31) or without the apo E allele epsilon 2 (0.74 +/- 0.13, n = 10). Thus, both hyper- and normolipidaemic apo E2 homozygotes have higher concentrations of VLDL remnants than the subjects heterozygous or without allele epsilon 2.