Frequencies of Apolipoprotein E Isoforms in Patients with Different Typesof Hyperlipoproteinaemia

Overview

Background.
Apolipoprotein E is a polymorphic protein playing a crucial role in the metabolism of plasmalipoproteins. Three alleles referred to as e2, e3 and e4 code for three common isoforms of apoE. The most frequentallele in the population at large is e3 allele. e2 and e4 alleles are connected with lipoprotein disorders as well as withother diseases. The aim of our study was to establish frequencies of apoE coding alleles in patients with differenttypes of hyperlipidaemia (HLP) and to reveal differences in their distribution in comparison with the generalpopulation.Methods and Results. Therefore apoE genotype was assayed in 752 patients with primary HLP and 291 subjectsrandomly selected from the general Czech population. Allele frequencies were determined separately in a group ofpatients with familial hypercholesterolaemia (FH), polygenic hypercholesterolaemia (PHC), familial combinedhyperlipidaemia (FCH) and in patients with type III. hyperlipidaemia (III).In patients with HLP a significantly higher frequency of e4 allele than in control subjects was found. In the groupof FH patients frequency of the e2 allele was higher than in control subjects. In patients with PHC a significantlyhigher frequency of the e4 allele and lower frequency of the e2 allele were observed. In the group of FCH patientsdistribution of e alleles did not differ from the control group. Frequency of the e2 allele in patients with type III.hyperlipidaemia was significantly higher than in controls.Conclusions. We conclude that there exist significant differences in frequencies of apoE coding alleles betweenpatients with primary hyperlipidaemia and a randomly selected population sample. The revealed differences in allelicdistribution suggest that the impact of apoE polymorphism is not uniform in all types of hyperlipidaemia.

Key words:
hyperlipoproteinaemia, apolipoprotein E, polymorphism, frequency of allele.