Apolipoprotein E: an important gene and protein to follow in laboratory medicine

Abstract

The human apolipoprotein (apo) E gene is polymorphic, with three common alleles (epsilon 2, epsilon 3, epsilon 4) coding for three isoforms (E2, E3, E4). The isoforms differ from each other by a single amino acid substitution, and also differ in their binding affinity for the four apo E receptors. Apo E polymorphism is an important determinant of risk for the development of cardiovascular and Alzheimer diseases, the prevalence of the epsilon 4 allele being increased in both kinds of patients compared with control subjects. Furthermore, the prevalence of the epsilon 4 allele differs among populations (range 5-40%, respectively, for Taiwanese and Papua New Guineans). Genotyping or phenotyping needs to be introduced in clinical laboratories. The choice of the method should be based on the types of patients who are examined. The apo E genotype is also a determinant of apo E plasma concentration. Standardization of apo E measurement is an important prerequisite before investigating the clinical interest of plasma apo E concentration. Determination of apo E genotype/phenotype and later the plasma concentration are expected to yield useful clinical laboratory information.

Influence of apolipoprotein E polymorphism on plasma vitamin A and vitamin E levels

“…The resulting allele frequencies were: ε2, 0·065; ε3, 0·868 and ε4, 0·067. This low prevalence of the ε4 allele as compared to that in other Caucasian populations [4,5] is in agreement with previous findings [36,42]. The distribution of the observed frequencies of the different apoE phenotypes was in Hardy-Weimberg equilibrium in the total population (χ 2 = 0·38, P = 0·83, 2 d.f.…”

Dissection and atherosclerosis of carotid arteries in the young: role of the apolipoprotein E polymorphism

“…Epidemiological evidence increasingly indicates that apolipoprotein E (APOE) genotype plays additional roles in the pathogenesis of cardiovascular disorders (Siest et al, 1995). APOE is a polymorphic member of a family of proteins that transports lipids in blood and cells and it is encoded by alleles residing on chromosome 19q13.2.…”

Serum zinc, copper, insulin and lipids in Alzheimer's disease epsilon 4 apolipoprotein E allele carriers*

“…On the other hand, apoE polymorphisms explain part of the variability of plasma cholesterol and apolipoprotein concentrations [19]. The epsilon 4 allele is associated with elevations in total cholesterol (TC) levels relative to the epsilon 3 allele, whereas the epsilon 2 allele has the opposite effect.…”