According to Utermann et al, Apo
E
is usually separated into three major isoforms, ie
E
1,
E
2,
E
3
, and he reported three phenotypes of Apo
E
, Apo
E
-N, Apo
E
-ND, Apo
E
-D, according to the Apo
E
2/
E
3
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
E
1′,
E
1,
E
2,
E
3
(normal pattern) and fifth band (Apo
E
4
), (variant pattern).
2) In primary type III hyperlipoproteinemia, Apo
E
3
was deficient, wherease Apo
E
2 and Apo
E
1 increased.
3
) We examined distribution of Apo
E
patterns according to Apo
E
3
/
E
2 ratios in 124 subjects. The distribution of the Apo
E
3
/
E
2 ratios showed a trimodality. All the patients with primary type III hyperlipoproteinemia were in the lowest mode (
E
3
/
E
2 below 0.
3
) which represents Apo
E
-D. In the remainders, 34 subjects were in the middle mode (
E
3
/
E
2, between 0.6-1.
4
) which represents Apo
E
-ND. and 85 subjects were in the highest mode (
E
3
/
E
2 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
E
3
deficiency had a effect which increases lipoprotein remnants.
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