Direct Phenotyping of Human Apolipoprotein E in Plasma: Application to Population Frequency Distribution in Paris (France)

Apolipoprotein E (Apo E) is a component of VLDL and HDL and plays a significant role in the regulation of cholesterol concentration. An improvement in isoelectric focusing for Apo E phenotyping is presented: the plasma Apo E was dissociated from lipoproteins by the use of Tween 20; the optimal concentration of type V neuraminidase was determined (1 U/ml); up to 48 samples were analyzed per plate and revealed by immunoblotting. Using this method, we have determined Apo E phenotypes and estimated their association with total cholesterol and Apo B levels in 498 healthy blood donors in Paris (France). The relative frequencies of Apo E alleles E2, E3 and E4 in this population were 0.079, 0.801 and 0.120, respectively. The association between Apo E phenotypes and concentration of Apo B-containing lipoproteins was confirmed (Apo B (g/l): E4/E3 subjects, 1.10 ± 0.29; E3/E2 subjects, 0.93 ± 0.22; both significantly different from E3/E3 subjects, 0.99 ± 0.28). Total cholesterol (mmol/l): E4/E3 subjects, 5.43 ± 1.15; E3/E2 subjects, 4.79 ± 0.83; both significantly different from E3/E3 subjects, 5.03 ± 1.11.