According to Utermann et al, Apo E is usually separated into three major isoforms, ie E1, E2, E3, and he reported three phenotypes of Apo E, Apo E-N, Apo E-ND, Apo E-D, according to the Apo E2/E3 ratios.
In this study we examined Apo E polymorphism by isoelectric focusing and ultracentrifugal lipoprotein analysis in 124 Japanese subjects including 5 patients with primary type III hyperlipoproteinemia.
Following results were obtained.
1) The Apo E protein focused into four main bands, Apo E1′, E1, E2, E3 (normal pattern) and fifth band (Apo E4), (variant pattern).
2) In primary type III hyperlipoproteinemia, Apo E3 was deficient, wherease Apo E2 and Apo E1 increased.
3) We examined distribution of Apo E patterns according to Apo E3/E2 ratios in 124 subjects. The distribution of the Apo E3/E2 ratios showed a trimodality. All the patients with primary type III hyperlipoproteinemia were in the lowest mode (E3/E2 below 0.3) which represents Apo E-D. In the remainders, 34 subjects were in the middle mode (E3/E2, between 0.6-1.4) which represents Apo E-ND. and 85 subjects were in the highest mode (E3/E2 above 1.5) which represents Apo E-N.
These cutoff points correspond to those which Utermann had reported in the German populations. Thus, there were no differences in Apo E phenotypes between Japanese and German populations.
4) In 3 patients out of 5 patients with primary type III hyperlipoproteinemia, we measured postheparin lipolytic activity. Two cases (H. N., M. K.) showed a decreased hepatic lipase activity (H-TGL) and a normal lipoprotein lipase activity (LPL).
But one case (S. I.) showed a normal H-TGL and LPL.
5) VLDL-TC/VLDL-TG and VLDL-TC/whole serum TG ratios were higher in Apo E-ND than in Apo E-N, and higher in Apo E-D than in Apo E-ND.
These results suggests that Apo E3 deficiency had a effect which increases lipoprotein remnants.
