Serum
lipoproteins and
apolipoproteins were analyzed in 199 patients with acute
myocardial infarction (CCU group), and in 211 normal healthy individuals (control group). It was shown that serum
lipoprotein abnormalities, especially elevated
low density lipoprotein (
LDL) levels, are closely related to
atherogenesis in relatively young patients and in subjects with severe coronary lesions. The frequency of
apo E4 was higher and that of E2 was lower in the CCU group than in the control group.
Apo E mutants, E7 and E5, were also frequent in the CCU group. Subjects with an E3/2 phenotype had reduced
LDL and increased VLDL levels, and those with an E4/3 phenotype had increased
LDL levels in serum. These results suggest that
apo E4 is a positive risk factor and
apo E2 a negative risk factor for
atherosclerosis. The action of
apo E isoproteins to increase or decrease serum
LDL levels may be one of the mechanisms of
atherosclerosis. Furthermore, the effect of
apo E isoforms on serum
lipoproteins was evident even in childhood. The mutant
apo E binding to
LDL receptors were investigated to clarify the metabolism of
apo E5 and apo E7. The affinity of
apo E5 was twice that of the wild form of
apo E3. Apo E7, however, had a lower receptor affinity than
apo E3. Therefore, the authors postulate that individuals with
apo E5 have increased risk of developing
hypercholesterolemia and subsequent
atherosclerosis. From the binding data of apo E7, the action of apo E7 is considered similar to that of
apo E2.