Distribution of apolipoprotein E between apo B- and non apo B-containing lipoproteins according to apo E phenotype.
Apolipoprotein E (apo E) is a component of all the classes of lipoproteins and can be distributed among apo B- (LpB) and non apo B-containing lipoproteins (Lp-non-B). Using a new electroimmunoassay kit, plasma apo E, apo E in Lp-non-B (apo E-Lp-non-B) and apo E in LpB (apo E-LpB) levels were measured in healthy control subjects (n=481) from 3 centers participating in the ECTIM study (Etude Cas-Témoins sur l'Infarctus du Myocarde), a population-based study on myocardial infarction. The distribution of apo E among lipoproteins was analyzed according to the apo E phenotype after adjustment for center, body mass index, tobacco use, alcohol consumption and triglycerides. Apo E was higher (average excess: + 0.32; P < 0.0001) and lower (average excess: -0.12; P < 0.0001) in subjects carrying the allele epsilon2 and the allele epsilon4 respectively, than in apo E3/3 subjects. These differences are the consequence of variations in apo E-Lp-non-B which clearly differed between the groups classified according to their apo E phenotype (P < 0.0001). The average excess of apo E Lp non-B compared to apo E3/3 subjects was + 0.43 (P < 0.0001) and -0.22 (P < 0.0001) for the epsilon2 and epsilon4 alleles respectively. Apo E-LpB was lower in subjects carrying the epsilon2 allele (P < 0.02) while the presence of the epsilon4 allele did not modify this parameter. The proportion of apo E within HDL was clearly higher and lower in subjects carrying apo E2 and apo E4 respectively than in apo E3/3 subjects. Although triglyceride levels were dependent on the apo E phenotype, the adjustment of the proportion of apo E in HDL for triglycerides hardly modified the results. For the first time, these results, using direct measurements on a large number of subjects, confirm the greater preference of apo E4 over apo E2 for LpB and vice versa for Lp-non-B. They also show a greater affinity of apo E2 for HDL compared to apo E3. This high affinity of apo E2 for HDL could be due to the formation of the apo E-A-II complex. These results indicate that apo E phenotype modulates the distribution of apo E among lipoproteins and suggest differences in lipoprotein metabolism between apo E2, apo E3 and apo E4.
Luc
G
G
Department of Atherosclerosis, SERLIA and INSERM U325, Institut Pasteur de Lille, France.
Ducimetiere
P
P
Bard
J M
JM
Arveiler
D
D
Evans
A
A
Cambien
F
F
Fruchart
J C
JC
Fievet
C
C
D000328:Adult; D000368:Aged; D000483:Alleles; D001055:Apolipoproteins B / Q000097:blood*; D001057:Apolipoproteins E / Q000097:blood* / Q000235:genetics*; D016022:Case-Control Studies; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D015243:Cholesterol, VLDL / Q000097:blood; D006801:Humans; D008074:Lipoproteins / Q000097:blood; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000235:genetics*; D010641:Phenotype; D012307:Risk Factors; D014280:Triglycerides / Q000097:blood
D001055:Apolipoproteins B; D001057:Apolipoproteins E; D008076:Cholesterol, HDL; D015243:Cholesterol, VLDL; D008074:Lipoproteins; D014280:Triglycerides; C030104:lipoprotein cholesterol; D002784:Cholesterol