Apoprotein E polymorphism and coronary artery disease. Increased prevalence of apolipoprotein E-4 in angiographically verified coronary patients

Effect of serum lipids, lipoproteins, and apolipoproteins on vascular and nonvascular mortality in the elderly

The purpose of this study was to determine the effect of serum lipids, lipoprotein fractions, and apolipoprotein (apo) A-1, B and E on mortality from vascular and nonvascular causes in an unselected elderly population. The random sample of 347 community-living individuals aged 65 years or older was obtained in 1982. Serum total cholesterol, LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), triglyceride, and apo A-1, B and E were determined at baseline. After the 11-year follow-up, 199 of the participants had died, and 148 were still alive. Mortality data from vascular and nonvascular causes by the end of 1993 were obtained from official registers. In the univariate analysis, a low total cholesterol level was associated with death due to both vascular and nonvascular causes (P value for trend, .021 and .0027, respectively). After the adjustment for other risk factors, the inverse association between total cholesterol and vascular mortality disappeared, but low total cholesterol was still a significant predictor of death due to nonvascular causes. Adjusted relative risks (RRs) of death due to nonvascular causes for those with elevated total cholesterol (5.1 to 6.5, 6.6 to 8.0, and > 8.0 mmol/L) compared with the reference group (< or = 5.0 mmol/L) were 0.5 (95% confidence interval [CI], 0.2 to 1.2), 0.6 (0.2 to 1.0), and 0.2 (0 to 0.8), respectively. Neither concentrations of HDL-C, LDL-C, triglyceride, nor apo B were associated with vascular or nonvascular mortality. On the other hand, low concentration of apo A-1 predicted vascular death. The RR for the lowest tertile was 1.6 (1.1 to 2.5) compared with the highest tertile. Furthermore, the occurrence of the apo E e4 allele was associated with increased risk of vascular mortality (RR, 1.5; 95% CI, 1.0 to 2.2), but the risk was not related to the levels of lipids, lipoproteins, or other apolipoproteins at baseline. Nonvascular mortality also tended to be predicted by the presence of the e4 allele (RR, 1.5; 95% CI, 0.9 to 2.5). In an unselected elderly population, the allelic variation of apo E, i.e., the presence of the e4 allele, and a low concentration of apo A-1 were more accurate indicators of vascular mortality than total cholesterol or lipoprotein fractions. The risk associated with the apo E polymorphism is unrelated to dyslipidemia.

Evidence that the apolipoprotein E-genotype effects on lipid levels can change with age in males: a longitudinal analysis

We previously reported that change, with age, in plasma levels of total cholesterol (TC) and LDL cholesterol (LDL-C) differed between apolipoprotein E (APOE) genotypes epsilon 3 epsilon 3 and epsilon 3 epsilon 4, in a sample of 77 older, unrelated males. By use of a larger sample from that cohort, followed longitudinally during 1969-87, the change in TC and in LDL-C, between the epsilon 3 epsilon 3 and epsilon 3 epsilon 4 APOE genotypes, over three exams, was reanalyzed. Additionally, the change in triglycerides (TG) and in HDL-cholesterol (HDL-C), between the epsilon 3 epsilon 3 and epsilon 3 epsilon 4 APOE genotypes-as well as the differences between the epsilon 3 epsilon 3 and epsilon 3 epsilon 2 genotypes, for TC, LDL-C, TG, and HDL-C-were contrasted over the three exams. At exam 1 TG was higher in the epsilon 3 epsilon 4 group than in the epsilon 3 epsilon 3 group (mean age 48 years), and at exams 2 and exam 3 (mean ages 58 and 63 years, respectively) it was similar (P = .009 for the exam-by-genotype-interaction effect in the repeated-measures analysis). A similar trend was seen for TC (P = .03), yet previously detected LDL-C effects were not apparent (P = .46). Those with the epsilon 3 epsilon 2 genotype had higher TG and lower LDL-C and TC at each exam than were seen in those with the epsilon 3 epsilon 3 genotype, although the differences in the values were not always statistically significant. Differences in TC, LDL-C, and TG, between the epsilon 3 epsilon 2-genotype and epsilon 3 epsilon 3-genotype groups, did not significantly change over the three exams. HDL-C levels were relatively stable over the exams; however, the exam-by-genotype interaction was significant for the epsilon 3 epsilon 2 genotype versus the epsilon 3 epsilon 3 genotype (P = .02). The epsilon 4 allele effects on TG and TC changed between longitudinal exams and may be age dependent. Changes, with age, in the effect of the epsilon 3 epsilon 4 genotype on lipids may impact the risk of developing atherosclerotic disease.

Polymorphism of the apolipoprotein E gene and early carotid atherosclerosis defined by ultrasonography in asymptomatic adults

Clinical and autoptical studies have suggested a predisposing role of the allele E4 of apolipoprotein E (apoE) in the development of atherosclerosis and cardiovascular disease. To investigate the possible contribution of apoE allele polymorphism to the carotid intima-media thickness (IMT) as assessed by ultrasound, we studied 260 asymptomatic nondiabetic subjects (121 men, 139 women; mean +/- SD age, 53 +/- 7 years), randomly selected from the population register of the inhabitants of Trieste, Italy. B-mode ultrasound was used to quantify the maximum IMT at 12 sites on the near and far wall of the common, bifurcation, and internal carotid arteries. ApoE genotypes were determined from amplified apoE sequences by restriction isotyping. The frequencies of E2, E3, and E4 alleles were 0.073, 0.827, and 0.100, respectively. As expected, subjects with E4 allele had the highest levels of total serum cholesterol and LDL cholesterol, subjects with E2 allele had the lowest levels, and those with E3 genotype had intermediate levels. The echographic measurements of carotid IMT showed increasing values from E2 to E4 carriers. After adjustment for total and LDL cholesterol serum levels, triglycerides, ratio of LDL to HDL cholesterol, age, sex, and body mass index, ANCOVA showed that the common carotid IMT was significantly greater (P = .029) in subjects with E4 allele compared with E3 carriers. Our data confirm the influence of apoE4 on cholesterol levels and clearly show that apoE genotype affects carotid atherosclerosis in its early stages in middle-aged asymptomatic subjects.

Association of lipoprotein cholesterol and triglycerides with the severity of coronary artery disease in men and women

The differences between the lipid profiles of male and female patients and the effect of plasma lipids on the extent of coronary artery disease were evaluated in 122 angiographically assessed coronary artery disease patients (95 males and 27 females) and 60 controls. Both male and female patients had lower HDL-cholesterol and higher total cholesterol, LDL-cholesterol, triglyceride, VLDL-cholesterol and VLDL-triglyceride concentrations than the controls. The VLDL lipid values did not differ significantly between the male patients with different extent of CAD, whereas the VLDL lipid values of female patients tended to increase with an increasing severity of CAD. High Lp(a) (> or = 35 mg/dl) values were more prevalent in patients with > 50% coronary stenosis compared to patients with < 50% stenosis and the controls (29%, 17% and 12%, respectively). The apolipoprotein E phenotypes and epsilon allele frequencies were similar in the patients and the controls. Low HDL-cholesterol and high LDL-cholesterol are CAD risk factors for both sexes. For women, elevated VLDL-triglycerides seem to be an additional risk factor for CAD.

Cerebrovascular disease, the apolipoprotein e4 allele, and cognitive decline in a community-based study of elderly men

BACKGROUND AND PURPOSE

Cerebrovascular disease and the apolipoprotein e4 (APOE*4) allele are both important risk factors for cognitive decline. We investigated the combined effect of APOE*4 and cerebrovascular disease on cognitive decline.

METHODS

Data are from a cohort of 353 men, aged 69 to 89 years at baseline, living in Zutphen, Netherlands. The 30-point Mini-Mental State Examination (MMSE) was used to measure cognitive decline (drop of > 2 points) from 1990 to 1993 (14% of the sample). Odds ratios (OR [95% confidence interval]) for cognitive decline were adjusted for age, education, and baseline MMSE score.

RESULTS

Compared with those without APOE*4 and without a history of cerebrovascular disease, the adjusted OR was 4.7 (1.7 to 12.7) for subjects without APOE*4 but with cerebrovascular disease, 3.3 (1.6 to 6.8) for those with APOE*4 and no cerebrovascular disease, and 17.2 (2.7 to 110.0) for those with both risk factors. The risk for cerebrovascular disease and APOE*4 combined was more than expected from the separate effects. The combined risk of coronary heart disease and APOE*4 was 6.1 (1.7 to 22.3). The analysis of cardiovascular risk factors showed that the risk of cognitive decline was highest in subjects with both APOE*4 and a high cholesterol level, high fibrinogen level, normal blood pressure, or diabetes mellitus.

CONCLUSIONS

Cerebrovascular disease and APOE*4 may have a synergistic effect on cognitive decline.

Apolipoprotein E genotype epsilon 4/epsilon 2 in the STANISLAS Cohort Study--dominance of the epsilon 2 allele?

Apolipoprotein (apo) E has been discussed as a marker for cardiovascular risk, but information about lipid traits in healthy individuals having one of the rare apoE genotypes (epsilon 4/epsilon 2, epsilon 2/epsilon 2 or epsilon 4/epsilon 4) is scarce. Our work was designed to answer the following questions: 1. Are the allelic effects of epsilon 2 and epsilon 4 on lipid traits additive or dominant? 2. If there is additivity, do the allelic effects of epsilon 2 and epsilon 4 have the same magnitude? 3. Are the allelic effects neutralised in epsilon 4/ epsilon 2 individuals who are under the influence of both rare alleles? Allelic effects on apoB and apoE serum levels were codominant. Allelic models are thus not adequate to study the influence of apoE polymorphism on these traits. Allelic effects were additive for total cholesterol, LDL-C, HDL-C and apoAI, with epsilon 2 having a greater impact than epsilon 4. Serum levels differed significantly between epsilon 4/epsilon 2 and epsilon 3/epsilon 3 individuals only for apoE (p < 0.001) and for apoB (p < 0.05).

Frequencies of five genetic polymorphisms in coronarographed patients and effects on lipid levels in a supposedly healthy population

Allele frequencies of genetic polymorphisms were compared between supposedly healthy subjects and angiographically proven coronary artery disease patients. The polymorphic candidate loci investigated were the apolipoprotein (apo) B signal peptide and XbaI polymorphism, the apo E polymorphism and two polymorphism of lipoprotein lipase (LPL) gene: Hind/III and PvuII. Apo B signal peptide and HindIII/LPL polymorphisms showed significant differences in allele partition between cases and controls; the rare alleles of both polymorphisms were less frequent (p < 0.05) in cases. We looked for associations between the polymorphisms and lipid concentration variability in a supposedly healthy population (145 men and 144 women). Apo B signal peptide, apo E and PvuII/LPL polymorphisms seem to influence some lipid metabolism parameters significantly. Apo AI and LpCIII levels were significantly different among apo B signal peptide genotypes: Del homozygotes had the highest concentrations of both variables. The epsilon 4 allele of apo E polymorphism was associated with increased concentrations of total cholesterol, LDL cholesterol and apo B. Increased LpAI:AII levels observed in E3 homozygotes (p < 0.01) have not previously been reported. LpAI:AII concentration was also influenced by PvuII/LPL polymorphisms.

Apolipoprotein E alleles and risk of coronary disease. A meta-analysis

A meta-analysis was undertaken to assess the impact of apolipoprotein E (apo E) alleles (epsilon 2, epsilon 3, and epsilon 4) on coronary disease in 14 published observational studies (9 clinical coronary disease and 5 coronary angiography). In comparison with epsilon 3, the epsilon 4 allele was associated with greater odds for coronary heart disease, and summary estimates of the odds ratios (ORs) and (95% confidence intervals) for both sexes combined were OR = 0.98 (0.85-1.14) for epsilon 2 and OR = 1.26 (1.13-1.41) for epsilon 4. Separate analyses for men and women showed similar associations. In angiographic studies the relative odds for significant coronary artery disease among both sexes combined was OR = 0.76 (0.55-1.05) for epsilon 2 and OR = 1.11 (0.88-1.40) for epsilon 4. The overall impression is that epsilon 4 is associated with clinical and coronary disease and that results are similar in men and women.

Apolipoprotein E polymorphism is associated with segment-specific extracranial carotid artery intima-media thickening

BACKGROUND AND PURPOSE

Apolipoprotein E (apoE) polymorphism affects plasma cholesterol and may influence risk of atherosclerosis. We investigated the association of apoE with carotid artery wall thickening (an index of atherosclerosis) in individuals with and without coronary artery disease (CAD).

METHODS

ApoE phenotypes were resolved in 260 individuals equally represented by angiographically determined CAD case subjects and disease-free control subjects. Carotid artery intima-media thickening (IMT) was evaluated by B-mode ultrasound. Associations of apoE (E2, E3, or E4) with risk factors and IMT were evaluated in general linear models adjusted for age, sex, and CAD status with and without other traditional risk factors.

RESULTS

Total cholesterol (TC) and LDL cholesterol were associated with apoE isoforms. Mean TC and LDL cholesterol were lower in E2 (n = 33) carriers than E3 (n = 155) and E4 (n = 66) carriers (each P < .001). IMT also varied by apoE. E2 carriers had less common carotid IMT than E3 and E4 carriers (P < .01), while internal carotid IMT was less in E2 and E3 carriers than in E4 carriers (P < .02). Bifurcation IMT was not associated with apoE (P = .24). ApoE polymorphism remained associated with common (P < .01) and internal (P < .04) IMT, and the association of apoE with mean IMT of all sites reached significance (P < .04) after adjustment for age, sex, CAD status, TC, LDL cholesterol, HDL cholesterol, triglycerides, diabetes, hypertension, and smoking.

CONCLUSIONS

ApoE polymorphism is associated with segment specific carotid IMT. The association of apoE with carotid IMT was statistically independent of apoE-associated variation in LDL cholesterol levels.

Apolipoprotein E polymorphism and stroke in a population sample aged 75 years or more

BACKGROUND AND PURPOSE

We investigated apolipoprotein E polymorphism stroke risk in a population sample of 1810 persons aged 75 years or more in Stockholm (the Kungsholmen Project). Information on cognition at cohort inception (from 1987 to 1989) and on stroke occurrence (from 1969 to 1994) is available for the cohort. In the cohort, cognitive impairment is associated with the epsilon 4 allele, and longer survival in subjects aged > or = 85 years with good cognition is associated with the epsilon 2 allele and the absence of epsilon 4.

METHODS

We compared stroke incidence in the 1077 of 1124 genotyped subjects who carried epsilon 2/3, epsilon 3/3, or epsilon 3/4 and estimated the proportion of cognitive impairment attributable to stroke.

RESULTS

Risk of stroke did not vary with apolipoprotein E polymorphism (P = .82): 24% of 87 incident stroke patients during follow-up compared with 25% of 827 subjects with normal cognition and no stroke diagnosis at baseline carried the epsilon 3/4 genotype. An estimated 9% of cognitive impairment was attributable to stroke. Notably, a reduced epsilon 3/4 frequency of 20% was found in subjects who survived a prior stroke and were included in the cohort, and risk of hemorrhagic stroke tended to be associated with the presence of the epsilon 3/4 genotype and the absence of epsilon 2/3.

CONCLUSIONS

This population-based study indicates that apolipoprotein E polymorphism is not a risk factor for ischemic stroke in subjects aged > or = 75 years (although it might possibly influence survival after stroke occurrence and be a risk factor for infrequent hemorrhagic stroke) and that approximately 10% of cognitive impairment in this age group is attributable to stroke.

The effect of physical activity on serum total and low-density lipoprotein cholesterol concentrations varies with apolipoprotein E phenotype in male children and young adults: The Cardiovascular Risk in Young Finns Study

Apolipoprotein E (apo E) determines serum total (TC) and low-density lipoprotein (LDL-C) cholesterol concentrations and is thus associated with coronary heart disease (CHD) risk. We studied if the effect of physical activity (PA) on serum TC and LDL-C concentrations varies with apo E phenotype in a population-based sample of children and young adults with regular PA. The study cohort consisted of subjects aged 9, 12, 15, 18, 21, and 24 years in 1986 (N = 1,498) participating in a large multicenter study of cardiovascular risk factors in children and young adults. Serum lipid concentrations were determined enzymatically, and apo E phenotypes by isoelectric focusing and immunoblotting. The composition of the diet was determined by a 48-hour recall method, and a PA index was calculated on the basis of frequency, intensity, and duration of activity assessed by a questionnaire. LDL-C (P = .0082), TC (P = .014), and the high-density lipoprotein cholesterol (HDL-C)/TC ratio (P = .0004) responses to exercise varied with apo E phenotype. The effect of PA on LDL-C, TC, or HDL/TC was not found in apo E phenotype E4/4. A moderate inverse effect of PA on TC and LDL-C and a positive effect on HDL/TC was found in subjects with E4/3 and E3/3 phenotypes. Similar but stronger associations were found between these variables within the group of E3/2 males. The effect of PA on serum lipid levels was strongest within the phenotype E3/2. These associations were not explained by dietary habits. Apo E phenotype partly determines the effect of PA on serum TC and LDL-C in Finnish male children and young adults with regular PA.

The relation of apolipoprotein E polymorphism to multiple cardiovascular risk in children: the Bogalusa Heart Study

Apolipoprotein (apo) E is an important genetic determinant of serum lipoprotein concentrations and coronary artery disease risk. Multiple cardiovascular risk factors in addition to lipoproteins were examined by apoE phenotype in a random subsample (n = 746) of 8-17-year old children from a total community. The apoE2 group (n = 58) carrying E2/2 and E3/2 phenotypes showed lower age-, race- and sex-adjusted mean values of body mass index (BMI: weight/height2), percent body fat, fasting plasma insulin and LDL cholesterol, and a higher value of HDL cholesterol than the apoE3 group (n = 476) carrying the E3/3 phenotype (P < 0.01). In contrast, the apoE4 group (n = 212) carrying E4/4 and E3/4 phenotypes displayed higher values of total cholesterol and LDL cholesterol (P < 0.01). Both insulin and BMI, which correlated with each other, showed an association to triglycerides and systolic blood pressure in all three phenotype groups; whereas only BMI associated with LDL cholesterol, total cholesterol to HDL cholesterol ratio and diastolic blood pressure in all three phenotype groups (P < 0.05 to P < 0.0001). A marked increase in the prevalence of clustering of adverse (top tertile) total cholesterol to HDL cholesterol ratio with increased levels (top tertile) of one or two risk factors (BMI, insulin, and systolic blood pressure) occurred in the apoE3 and apoE4 groups, especially in the latter (P < 0.01 to P < 0.0001), but not in the apoE2 group. The prevalence of parental history of heart attack and diabetes mellitus among the three phenotype groups paralleled this trend. Thus, the risk status of apoE polymorphism may be associated with a constellation of cardiovascular risk factors in early life.

Genotypes with the apolipoprotein epsilon4 allele are predictors of coronary heart disease mortality in a longitudinal study of elderly Finnish men

Earlier we reported that allelic variation in the gene coding for apolipoprotein (apoE is a significant predictor of variation in the risk of coronary heart disease (CHD) death in a longitudinal study of elderly Finnish men. Here we address the question: which of the apoE genotypes confers the risk information in these men, and whether such information persists after other CHD risk factors are considered? We followed two cohorts of elderly Finnish men aged 65 to 84 years, one in Eastern (n = 281) and the other in the Southwestern (n = 344) Finland for 5 years during which 26 (9.3%) of the men from the Eastern cohort and 40 (11.6%) of the men in the Southwestern cohort died from CHD. Baseline high density lipoprotein (HDL) cholesterol and (HDL cholesterol)2 in the Eastern cohort and age, and total and HDL cholesterol and smoking status in the Southwestern cohort were significant predictors of CHD death (P < 0.05). The apoE genotypes were significant predictors in the Southwestern cohort at P = 0.02 and in the Eastern cohort at P = 0.18. In multivariable models, information about apoE genotypes improved the prediction at P = 0.1O level of statistical significance in both cohorts. When genotypes were considered separately, the episilon2/4 combined with the epsilon4/4 in the Eastern cohort (odds ratio = 7.69, 95% CI = 1.67-35.52) and the epsilon 3/4 in the Southwestern cohort (odds ratio = 2.44, 95% CI = 1.165.10) had sigificantly greater odds of CHD death compared to the common F3/3 genotype. We conclude that apoE genotypes confer risk information about CHD death in two cohorts of elderly Finnish men in a longitudinal study, and this information persists after adjustment for other CHD risk factors. Because different genotypes were predictors in these two cohorts, we further conclude that the utility of a particular genotype as a predictor of CHD death in other populations may depend on the distribution of risk factor profiles at baseline, geographically defined environmental exposures, the CHD mortality history, and the evolutionary history of background genotypes in the population considered.

Incomplete dominance of type III hyperlipoproteinemia is associated with the rare apolipoprotein E2 (Arg136-->Ser) variant in multigenerational pedigree studies

In the process of screening apolipoprotein (apo) E genotypes in a population of subjects with lipid abnormalities, we have identified five subjects (one homozygote and four heterozygotes) with an abnormal 109 base pairs band following apo E restriction isotyping of amplified DNA with the restriction endonuclease CfoI. The polymerase chain reaction (PCR) products were cloned and their sequencing revealed a C-->A substitution at the first nucleotide of codon 136. This mutation resulted in an amino acid substitution Arg to Ser, previously described as apo E2 Christchurch. Family studies were carried out for four of the probands. In these kindreds, stepwise multiple regression analyses indicated that 78% of the cholesterol variability in men was predicted by body mass index, age and the rare apo E2 (Arg136-->Ser) variant. In women, age and the apo E2 (Arg136-->Ser variant predicted 54.9% of the variability in cholesterol levels. Linkage analysis suggested that the presence of the apo E2 (Arg136-->Ser) variant was linked with the occurrence of cholesterol enriched triglyceride rich lipoproteins and with an incomplete dominance of type III hyperlipoproteinemia. Our data indicates that this mutation may be a relatively common cause of dyslipidemia in the Spanish population.

Clinical chemistry of common apolipoprotein E isoforms

Apolipoprotein E plays a central role in clearance of lipoprotein remnants by serving as a ligand for low-density lipoprotein and apolipoprotein E receptors. Three common alleles (apolipoprotein E(2), E(3) and E(4)) give rise to six phenotypes. Apolipoprotein E(3) is the ancestral form. Common apolipoprotein E isoforms derive from nucleotide substitutions in codons 112 and 158. Resulting cysteine-arginine substitutions cause differences in: affinities for low-density lipoprotein and apolipoprotein E receptors, low-density lipoprotein receptor activities, distribution of apolipoprotein E among lipoproteins, low-density lipoprotein formation rate, and cholesterol absorption. Accompanying changes in triglycerides, cholesterol and low-density lipoprotein may promote atherosclerosis development. Over 90% of patients with familial dysbetalipoproteinaemia have apolipoprotein E(2)/E(2). Apolipoprotein E(4) may promote atherosclerosis by its low-density lipoprotein raising effect. Establishment of apolipoprotein E isoforms may be important for patients with diabetes mellitus and several non-atherosclerotic diseases. Apolipoprotein E phenotyping exploits differences in isoelectric points. Isoelectric focusing uses gels that contain pH 4-7 ampholytes and urea. Serum is directly applied, or prepurified by delipidation, lipoprotein precipitation or dialysation. Isoelectric focusing is followed by immunofixation/protein staining. Another approach is electro- or diffusion blotting, followed by protein staining or immunological detection with anti-apolipoprotein E antibodies and an enzyme-conjugated second antibody. Apolipoprotein E genotyping demonstrates underlying point mutations. Analyses of polymerase chain reaction products are done by allele-specific oligonucleotide probes, restriction fragment length polymorphism, single-stranded conformational polymorphism, the primer-guided nucleotide incorporation assay, or denaturating gradient gel electrophoresis. Detection with primers that either or not initiate amplification is performed with the amplification refractory mutation system. Disparities between phenotyping and genotyping may derive from isoelectric focusing methods that do not adequately separate apolipoprotein E posttranslational variants, storage artifacts or faint isoelectric focusing bands.

Apolipoprotein E polymorphism influence on lipids, apolipoproteins and Lp(a) in a Spanish population underexpressing apo E4

The apolipoprotein E (apo E) polymorphism in a Spanish working population of Tenerife (Canary Islands, Spain) was analyzed. The distribution of apo E alleles (epsilon 3, 0.850; epsilon 2, 0.075; epsilon 4, 0.075) and phenotypes (E3/3, 72.6%; E3/4, 13%; E3/2, 11.5%; E4/4, 0.8%; E2/2, 1.5%; E4/2, 0.5%) was significantly different from those of a combined Caucasian population owing to a lower frequency of apo E4. We have also investigated the effect of apo E polymorphism on serum levels of cholesterol, LDL-cholesterol, HDL-cholesterol, Lp(a) and apolipoproteins A-I, B and E. The average effect of E4 (in whole sample and men only, respectively) was to raise serum levels of total cholesterol (by 4.1 mg/dl and 8.3 mg/dl), LDL-cholesterol (by 6.5 mg/dl and 9 mg/dl), and apo B (5.3 mg/dl and 4.5 mg/dl). The average effect of E2 was to lower serum levels of total cholesterol (by 14.8 mg/dl mg/dl and 8.3 mg/dl), LDL-cholesterol (by 20.2 mg/dl and 15.5 mg/dl) and apo B (11.5 mg/dl and 6.5 mg/dl), and to raise apo E (1.14 mg/dl and 3.4 mg/dl and 3.4 mg/dl). We found significantly higher serum triglyceride levels in individuals carrying E4, but no differences were found in serum HDL-cholesterol, apo A-I or Lp(a) by alleles. Data confirm previous reports about an underexpression of apo E4 in societies living in Southern Europe, and its repercussion in a more beneficial lipid profile and relatively low cardiovascular mortality rate in the Mediterranean region.

Impact of apolipoprotein E genotype variation on means, variances, and correlations of plasma lipid, lipoprotein, and apolipoprotein traits in octogenarians

The impact of apolipoprotein (apo) E genotype variation on means, variances and correlations between plasma lipid traits was studied in male and female octogenarians. Females had significantly higher mean levels of all 10 of the measured plasma lipid traits than males. The subset of concomitants (i.e., age, height, weight, body mass index, glucose and uric acid) that made a statistically significant contribution to interindividual variability was different in males and females for every trait considered. Gender-specific associations between variation in apo E genotype and variation in particular measures of lipid metabolism, adjusted for concomitant variation, were observed: in females there were no statistically significant associations while in males the means of the three common apo E genotypes were significantly different for adjusted measures of total cholesterol, low density lipoprotein cholesterol and low density lipoprotein-apo B. The common apo E genotypes were heterogeneous with respect to intragenotypic variance for adjusted log-transformed triglyceride levels in females only. Finally, the three common apo E genotypes were heterogeneous with respect to the correlation between traits, adjusted for concomitant variation, and gender influenced the manner in which the genotypes differed for specific correlations. This study documents that variation in the apo E gene has a significant impact on means, variances and correlations of plasma lipid traits in octogenarians, but the effects are context-, that is gender- and age-, dependent.

Apolipoprotein E4 phenotype is not an important risk factor for coronary heart disease or stroke in elderly subjects

The allele e4 (apo e4) of apolipoprotein E (apo E) has been associated with an increased risk for coronary heart disease (CHD) in cross-sectional studies in middle-aged subjects. We investigated the risk of CHD and stroke with respect to the number of apo e4 alleles in a prospective study of a Finnish nondiabetic cohort including 1067 subjects 65 to 74 years old at baseline. During the 3.5-year follow-up, CHD mortality was 2.8%, total CHD incidence 6.9%, and the cumulative occurrence of CHD (prevalence at baseline and the 3.5-year incidence combined) 17.0%. The incidence of stroke was 3.4%, and the cumulative occurrence of stroke was 6.0%. The CHD mortality was 3.4% in subjects with no apo e4 allele (n = 734), 1.7% in those with one apo e4 allele (n = 296), and 0% in subjects with two apo e4 alleles (n = 37) (P = NS between the three groups). The incidence of CHD according to the number of apo e4 alleles was 6.9% (no apo e4 alleles), 7.4% (one apo e4 allele), and 2.7% (two apo e4 alleles), and the cumulative occurrence of CHD was 16.5%, 18.6%, and 13.5%, respectively (P = NS). The incidence of stroke was 3.8% in subjects with no apo e4 allele, 2.7% in those with one apo e4 allele, and 0% in those with two apo e4 alleles (P = NS). The cumulative occurrence of stroke was 6.0%, 6.4%, and 2.7%, respectively (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein E polymorphism, serum lipids, myocardial infarction and severity of angiographically verified coronary artery disease in men and women

In several populations, the apolipoprotein E (apo E) allele epsilon 4 is associated with high concentration of plasma total and low density lipoprotein (LDL)-cholesterol and coronary artery disease (CAD). We determined the apo E phenotypes of 309 patients with angiographically verified CAD and 38 patients without CAD by isoelectric focusing and Western blotting. In men with CAD, the plasma total and LDL-cholesterol increased according to apo E phenotype in the following order: E3/2 < E3/3 < E4/3 < E4/4 (P = 0.03 for total cholesterol, P = 0.007 for LDL-cholesterol). In women, there was a similar trend (P = 0.22 for total cholesterol, P = 0.15 for LDL-cholesterol). The relative frequency of men with three vessel CAD increased (P = 0.43) together with LDL-cholesterol levels (P = 0.05) according to apo E phenotype E3/2, E3/3, E4/3, E4/4. Total and LDL-cholesterol levels were higher in patients with three vessel CAD than in patients with less serious types of CAD (P = 0.02 for total cholesterol, P = 0.007 for LDL-cholesterol). The relative frequency of patients with myocardial infarction increased according to apo E phenotype (P = 0.51). Both in men and women, there were no differences between apo E phenotypes in age at occurrence of the first myocardial infarction. The apo E allele frequencies of patients with CAD vs. without CAD were 2.3% vs. 1.3% for epsilon 2, 79.0% vs. 76.3% for epsilon 3 and 18.7% vs. 22.4% for epsilon 4. There were no statistically significant differences in apo E allele or phenotype frequencies between patients with CAD and without CAD or between patients with CAD and the general Finnish population. Our results support previous studies in suggesting that the apo E allele epsilon 4 is a risk factor for atherosclerosis, which affects plasma total and LDL-cholesterol. In addition, our results suggest that the apo E allele determines the severity of CAD.

Apolipoprotein E polymorphism predicts death from coronary heart disease in a longitudinal study of elderly Finnish men

BACKGROUND

There is ample evidence from cross-sectional studies of an association between allelic variation of the gene coding for apolipoprotein E (apoE) and interindividual variation in plasma lipids, and the presence of coronary heart disease (CHD). There have been no prospective studies, however, to evaluate the usefulness of allelic variation of the apoE gene for predicting CHD.

METHODS AND RESULTS

Two samples of elderly Finnish men were followed for 5 years, one in the east (n = 297) and the other in the southwest of Finland (n = 369). At baseline, when the apoE genotypes were assessed, the men were 65 to 84 years old. At the end of the follow-up, the vital status of each man was determined, and cause of death was coded. At baseline, relative frequencies of the three alleles-epsilon 2, epsilon 3, and epsilon 4--were 0.037, 0.827, and 0.136 in the eastern and 0.062, 0.763, and 0.175 in the southwestern samples, respectively (chi 2 = 8.89, df = 2, P < .012 for difference between the samples). During the 5-year follow-up, a total of 28 deaths from CHD were recorded in the eastern and 42 in the southwestern sample. Relative CHD mortality was not heterogeneous between the samples. Among those who died from CHD, there was a doubling of the relative epsilon 4 allele frequency in both samples (chi 2 = 4.70, df = 1, P < .03 for the eastern sample; chi 2 = 7.11, df = 1, P < .01 for the southwestern sample).

CONCLUSIONS

Allelic variation in the apoE gene is a statistically significant predictor of CHD death in these samples of elderly Finnish men.

ApoE polymorphism and predisposition to coronary heart disease in youths of different European populations. The EARS Study. European Atherosclerosis Research Study

The European Atherosclerosis Research Study was based on the comparison of offspring having a paternal history of premature myocardial infarction with age- and sex-matched control subjects. Case (n = 635) and control (n = 1259) subjects aged 18 through 26 years were recruited from 14 universities of 11 European countries. The allele distributions of apolipoprotein (apo) E polymorphism differed between populations, with a clear-cut gradient for allele epsilon 4 frequency decreasing from 0.18 in Finland to 0.11 in the south of Europe, following the gradient of coronary heart disease mortality rates. The association of apoE polymorphism with plasma total cholesterol, low-density lipoprotein cholesterol, apoB, and apoE levels was consistent with the now well-identified effects of epsilon 2 and epsilon 4 alleles on these traits. Both epsilon 2 and epsilon 4 alleles equally increased the level of triglycerides, and epsilon 2 had a lowering effect on lipoprotein(a) concentration. There were also weak effects of epsilon 2 and epsilon 4 on high-density lipoprotein cholesterol, apoA-I, and apoA-I-containing lipoprotein levels that paralleled those on apoE levels. The main finding of this study was the significant association of the apoE polymorphism with a paternal history of myocardial infarction. The association was consistent across regions, except in the south. When excluding this region, the population-adjusted odds ratios by reference to phenotype E3/3 were estimated as 0.23, 0.61, 0.78, 1.16, and 1.33 for E2/2, E3/2, E4/2, E4/3, and E4/4, respectively. The apoE locus largely explained the case/control difference of apoB level.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of apolipoprotein E polymorphism on lipoproteins and risk of myocardial infarction. The ECTIM Study

Human apolipoprotein (apo) E, a polymorphic protein with three common alleles, epsilon 2, epsilon 3, and epsilon 4, plays an important role in lipoprotein metabolism. This article describes the association of this polymorphism with lipids, apolipoproteins, and lipoproteins with a particular regard to lipoprotein particles, as defined by their apolipoprotein content, as well as the risk of myocardial infarction in a multicenter population-based case-control study (ECTIM study). In the ECTIM study, 574 male patients aged 25 to 64 were examined 3 to 9 months after myocardial infarction in four regions participating in the World Health Organization MONICA project: Belfast (Northern Ireland) and Lille, Strasbourg, and Toulouse (France). Control subjects (n = 722) were randomly selected from the regional populations. The distribution of apoE phenotypes was significantly different across the four control samples (P = .04), with a higher frequency of the epsilon 4 allele in Belfast (14.3%) than in Toulouse (8.2%). The association of apoE polymorphism with biological measurements was studied in the control groups (n = 640) after men with coronary heart disease or those taking hypolipidemic drugs were omitted, with the apoE3/3 phenotype as a reference after adjustment for concomitant factors. Individuals carrying the epsilon 2 allele had lower levels of plasma cholesterol, low-density lipoprotein cholesterol (LDL-C), and apoB and higher levels of triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), apoC-III, apoE, lipoprotein (Lp) C-III:B, and Lp E:B. However, the effect of the epsilon 2 allele on triglyceride, VLDL-C, apoE, and Lp E:B parameters was heterogeneous across the populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging and genetic variation of plasma apolipoproteins. Relative loss of the apolipoprotein E4 phenotype in centenarians

We determined the common polymorphism of apolipoprotein E (E2, E3, and E4), apolipoprotein B Xba I polymorphism, and apolipoprotein C-III Sst I polymorphism in almost all Finnish centenarians alive in 1991 (n = 179/185). Plasma lipid and lipoprotein levels in different apolipoprotein genotypes were also measured. In comparison with younger Finnish populations studied previously, the frequency of the apolipoprotein E epsilon 2 allele was almost twice as high (7.0% versus 4.1%; P < .05) and that of the epsilon 4 allele only approximately one third as high (8.4% versus 22.7%; P < .001) in the centenarians. Plasma cholesterol and high-density lipoprotein cholesterol levels tended to be lowest in the group with the epsilon 2 allele (4.33 mmol/L and 1.41 mmol/L, respectively), intermediate in those with the epsilon 3 allele (4.57 mmol/L and 1.48 mmol/L, respectively), and highest in those with the epsilon 4 allele (4.82 mmol/L and 1.60 mmol/L, respectively). The frequencies of the apolipoprotein B X1 and X2 alleles (Xba I restriction site absent or present, respectively) among the centenarians and among the young Finns were not significantly different, whereas the apolipoprotein C-III S2 allele (Sst I restriction site present) occurred more often in the centenarians (frequency, 12.9%) than in the youngest reference population (frequency, 8.8%; P < .05). Centenarians with the apolipoprotein B X2X2 genotype and apolipoprotein E4 phenotype had a higher mean plasma cholesterol level than those with the X1X1 genotype and E2 phenotype (5.24 versus 3.43 mmol/L; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Health-based reference values of the Mini-Finland Health Survey: 2. Cholesterol in total serum and in different lipoprotein fractions

The reference values for cholesterol concentrations in the whole serum and in its VLDL, LDL and HDL fractions have been produced based on the data obtained in the Mini-Finland Health Survey. The lipoprotein fractions were separated with ultracentrifugation. The aim was to obtain reference values for the apparently healthy, ambulatory population. Two health-derived criteria were used to select subjects for reference populations: those based on the literature available and those based on the recommendations published by the Committee on Reference Values of the Scandinavian Society for Clinical Chemistry and Clinical Physiology, with slight modifications. The 95% inner reference intervals of total serum cholesterol in all the subjects and in the two selection groups were 4.2-9.0, 4.2-8.4, and 4.2-8.5 mmol l-1 for men, and 4.2-9.4, 4.1-8.6, and 4.2-9.0 mmol l-1 for women, respectively. The corresponding medians were 6.3, 6.2 and 6.2 mmol l-1 in men, and 6.4, 6.0 and 6.1 mmol l-1 in women, respectively. Frequency distribution curves showed clear skewness to the right in VLDL cholesterol and slight skewness in LDL and HDL cholesterol. In women there was a clear rise in total, VLDL and LDL cholesterol after the early middle age, whereas HDL cholesterol was lower in the older age groups. In men the age dependency was not as prominent; total cholesterol levels showed lower levels in older men. Of the background lifestyle factors alcohol consumption, smoking, obesity and physical exercise had negligible associations with total, VLDL, LDL and HDL cholesterol reference intervals.

A microtiter plate assay for determining apolipoprotein E genotype and discovery of a rare allele

Genotype determination using the solid-phase minisequencing method of Syvänen et al. (1990, 1993) has been adapted for use with fluorescein-labeled dideoxynucleotides (F-ddNTPs). PCR is performed using one biotinylated primer and one unbiotinylated primer. The biotinylated products are captured in streptavidin-coated microtiter wells. Following removal of nonbiotinylated strands with NaOH, the bound strands are hybridized with a primer adjacent to the polymorphic site being tested. Using T7 DNA polymerase, the primer is extended using one F-ddNTP in the presence of the other three unlabeled ddNTPs. Incorporation of the F-ddNTP is detected by binding antifluorescein antibody conjugated with alkaline phosphatase followed by incubation with a chromogenic substrate. This assay was used to determine APOE genotypes for 75 subjects. The APOE genotypes were also determined using a method involving the incorporation of mobility-shifting nucleotide analogs (Livak et al., 1992). Investigation of the one discrepancy between the two methods revealed that one subject carries a rare APOE allele that has a 3 bp deletion.

Genetic influences on age-related change in total cholesterol, low density lipoprotein-cholesterol, and triglyceride levels: longitudinal apolipoprotein E genotype effects

This study addressed the possible influence of apolipoprotein E (apo E) genotype on age-related changes in total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), and triglyceride (TG) levels in older males. Apo E is a component of LDL, is a ligand for the LDL receptor, and apo E genotype has been consistently associated with variation in mean levels of TC and LDL-C, and also appears to influence TG levels. Using male twins followed longitudinally between mean ages of 48 and 63 years, the change in TC, LDL-C, and TG over time for individuals with the epsilon 3 epsilon 3 and the epsilon 3 epsilon 4 genotypes was contrasted. At exam 1 mean TC and LDL-C levels were lower in the epsilon 3 epsilon 3 group than in the epsilon 3 epsilon 4 group, but at exam 3 mean TC and LDL-C levels were significantly higher in the epsilon 3 epsilon 3 group than in the epsilon 3 epsilon 4 group. The rate of change in TC and LDL-C with age differed significantly between epsilon 3 epsilon 3 and epsilon 3 epsilon 4 groups. Results for TG were not statistically significantly. These findings suggest that the apo E genotype effects on risk of coronary artery disease may be age-dependent. This study demonstrates the value of longitudinal studies in refining models for genetic risk factors for disease.

Apolipoprotein E and B polymorphisms--longevity factors assessed in nonagenarians

To test if the prevalence of genetic risk factors for coronary heart disease (CHD) is low in individuals who have reached an extremely old age, the allele frequencies of apolipoprotein E (apo E) and B (apo B) polymorphisms and plasma lipoprotein(a) levels were investigated in nonagenarians and in younger control groups. The frequency of the epsilon 4 allele of apo E was significantly lower in the nonagenarians than in the middle-aged and young adults (P < 0.05). Also, the frequency of EcoRI allele R- of apo B was low in the nonagenarians, whereas the allele frequency for the XbaI polymorphism of apo B and plasma lipoprotein(a) concentrations did not differ between the nonagenarians and the younger groups. These findings strongly suggest that the presence of these potential genetic risk factors for CHD, namely the epsilon 4 allele of apo E and the R- allele of apo B, decreases the probability of an individual reaching an extremely old age.

ApoE4 polymorphism increases the risk for exercise-induced silent myocardial ischemia in older men

The apolipoprotein (apo) E4 polymorphism is associated with increased risk for symptomatic coronary artery disease (CAD). This study examines whether the apo epsilon allele is associated with an increased risk for exercise-induced silent myocardial ischemia (SI) in healthy, older (62 +/- 7 years; mean +/- SD), normocholesterolemic, nonsmoking male volunteers. The apo epsilon 4 allele was present in 20 of 45 (44%) men with SI on graded exercise treadmill testing compared with 22 of 127 (17%) men of comparable age with normal exercise tests (P < .001), resulting in a crude relative risk of 2.57 (95% confidence limits, 1.57 to 4.23) for SI in men with the apo epsilon 4 allele compared with those without the epsilon 4 allele. Although the lipoprotein lipid levels did not differ between men with normal exercise tests and those with SI, the men with the apoE 4/3 phenotype had higher total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels than those with the apoE 2/3 and 3/3 phenotypes (P < .05). Men with SI and the apoE 4/3 phenotype were older (64 +/- 5 versus 57 +/- 8 years, P < .01) and leaner (P < .01) than the normal non-SI men with the apoE 4/3 phenotype. The older age of the men with SI and the apoE 4/3 phenotype is consistent with a progression of atherosclerosis over time. Men with SI and the apoE 3/3 phenotype were of comparable age and body composition to apoE 3/3 phenotype men with normal exercise tests. Thus, even in the presence of normal LDL-C levels, the apo epsilon 4 allele may predispose older men to SI.

Underexpression of the apolipoprotein E4 isoform in an Italian population

Apolipoprotein (apo) E polymorphism was examined in a population of Italian blood donors. A significantly reduced frequency of the epsilon 4 allele was observed in comparison to a combined Caucasian population. Apo E polymorphism was also associated with significant differences in plasma lipid and lipoprotein levels. Notably, total and low-density lipoprotein cholesterol as well as triglycerides were increased, whereas high-density lipoprotein cholesterol was decreased in carriers of the E4 isoform. This is the first report of a significantly lower frequency of the apo E4 isoform in a European population. The reduced occurrence of an apo E isoform, which is associated with a more atherogenic lipid/lipoprotein profile, may be a contributory factor to the relatively lower incidence of cardiovascular disease in the Italian population.

Response of cholesterol synthesis to cholesterol feeding in men with different apolipoprotein E genotypes

To investigate the influence of dietary cholesterol level and apolipoprotein (apo) E polymorphism on cholesterol synthesis, seven apo E2/- and six apo E4/- normolipidemic subjects consumed self-selected diets containing low cholesterol ([LC] 250 mg/d) and high cholesterol ([HC] 800 mg/d) levels for approximately 20 days. On day 20, subjects were given 0.7 g deuterium oxide (D2O)/kg body water followed by maintenance doses. Cholesterol synthesis was measured as the uptake rate of D into plasma free cholesterol over 24 hours. Serum total cholesterol levels were higher (P < .05) in the apo E4/- versus apo E2/- group over both dietary periods. No influence of dietary cholesterol content on serum levels was observed, nor was there an effect of apo E genotype or dietary cholesterol level on cholesterogenesis. However, a genotype-independent association was observed between both cholesterogenesis (P < .001) and the increase in cholesterogenesis (P = .05) with the change in serum total cholesterol level subsequent to high-cholesterol feeding. These findings suggest that (1) apo E genotype is not associated with cholesterol synthesis rate in subjects on self-selected diets, and (2) hyporesponders to a dietary cholesterol challenge display higher synthetic rates than hyperresponders. The observation of lower cholesterol synthesis in individuals with the largest increases in serum cholesterol level after a dietary cholesterol challenge suggests a passive rather than dominant role of cholesterol synthesis in regulating serum levels.

Gallstone cholesterol content is related to apolipoprotein E polymorphism

BACKGROUND

The genetically determined phenotypes of apolipoprotein E are related to variations in lipoprotein levels and in the enterohepatic metabolism of cholesterol and bile acids. The present study was designed to elucidate the role of apolipoprotein E polymorphism in gallstone formation.

METHODS

Apolipoprotein E phenotype was determined in 169 consecutive cholecystectomy patients and in 200 controls. The cholesterol content of the gallstones (n = 169), the presence of cholesterol monohydrate crystals of fresh gallbladder bile (n = 142), and the nucleation time (n = 35) were also analyzed.

RESULTS

The median cholesterol content of the gallstones was higher in the apolipoprotein E4 category (phenotypes E4/4 and E4/3, 97%) than in the E3 (E3/3, 78%) and E2 patients (E2/2 and E2/3, 76%, P = 0.0003). In E4 patients, cholesterol crystals were found immediately after surgery in 27 of 40 (68%), whereas in E3 and E2 groups in 36 of 88 (41%), and 4 of 14 (29%) of the patients (P = 0.0001). The median nucleation time in E4 patients (2.5 days) was shorter than in patients with E3 (5.5 days) or E2 (6.0 days) (P = 0.0016).

CONCLUSIONS

These data indicate that apolipoprotein E polymorphism affects cholesterol content of cholelithiasis. We suggest that this phenomenon is mediated by the altered formation of cholesterol monohydrate crystals in different apolipoprotein E phenotypes.

Apolipoprotein E phenotype is related to macro- and microangiopathy in patients with non-insulin-dependent diabetes mellitus

The role of apoliprotein E (apo E) in modulating the susceptibility of individuals with non-insulin-dependent diabetes mellitus (NIDDM) to atherosclerotic vascular disease was studied in 143 male and 128 female patients with NIDDM. The data show that the apolipoprotein phenotype E2 somehow protects from macrovascular complications in NIDDM both in men and women. E2 also tends to protect from microvascular complications. In contrast, apo E phenotypes E4/4 and E4/3 tend to increase the risk for macroangiopathy in NIDDM patients. The lower prevalence of macroangiopathy in the subjects with E2 was associated with lower plasma total and LDL cholesterol concentrations and low plasma lipoprotein(a) levels. Overall, this study demonstrates the role of the apo E phenotype to modulate the risk for diabetic complications in patients with NIDDM. The confirmation of the association of apo E polymorphism with diabetic complications warrants, however, long-term follow-up studies.

The apolipoprotein E gene and the serum low-density lipoprotein cholesterol response to dietary fiber

Our goal was to determine whether differences in apolipoprotein E (apo E) influenced the response to dietary changes aimed at reducing serum cholesterol levels, especially increases in fiber. Apo E phenotype and genotype were determined in 43 men and 24 women who had previously taken part in parallel 2-week metabolic dietary studies involving either wheat bran or oat bran supplementation at a level of 6.8 g fiber/1,000 kcal. Fasting blood lipid measurements had been made at the beginning and end of the 2-week metabolic period. Reductions in low-density lipoprotein (LDL) cholesterol levels across both oat and wheat bran diets were significantly different depending on the E allele (P = .048). The LDL cholesterol level reduction for E2 carriers (0.60 +/- 0.14 mmol/L, n = 13) was greater than that for E3 homozygotes (0.21 +/- 0.07 mmol/L, n = 38; P = .014) and E4 carriers (0.28 +/- 0.12 mmol/L, n = 16; P = .09). Only the change in dietary fiber on the oat bran diet was related significantly to the decrease in LDL cholesterol levels (r = -.47, P = .007; n = 32). No such relationship was seen on the wheat bran diet (r = -.010, P = .59; n = 33). Carriers of the E2 allele appear to be more responsive than noncarriers to a dietary change involving increased fiber intake. The data also support a lipid-lowering advantage of oat bran over wheat bran. Current dietary recommendations to reduce serum lipid levels may vary in effectiveness depending on distribution of apo E alleles in the different populations studied.

Relation of apolipoprotein E phenotype to myocardial infarction and mortality from coronary artery disease

The apolipoprotein E polymorphism is a genetic determinant of low-density lipoprotein (LDL) cholesterol. Its status as a risk factor for coronary artery disease (CAD), either through a causal relation with LDL cholesterol level or independently, is less clearly established. Data from the Multiple Risk Factor Intervention Trial were used to examine the influence of apolipoprotein E phenotype on risk of coronary events. Of the 12,866 randomized participants, 619 were studied in a nested case-control design. CAD deaths (93) and nonfatal myocardial infarctions (113) were matched to 412 controls. The allele frequencies of apolipoprotein E in the white subset (epsilon 2 = 0.06, epsilon 3 = 0.79, and epsilon 4 = 0.15) were very similar to other nonselected white American populations, and the relation of apolipoprotein E on total and LDL cholesterol was generally similar to that seen in other studies, with the epsilon 2 allele being associated with lower and the epsilon 4 allele with higher total and LDL cholesterol. Allele frequencies were not the same for patients and control subjects. The presence of epsilon 4 was associated with an increased risk of CAD that was most evident for fatal cases. There was no relation between changes in LDL cholesterol over time during the trial and apolipoprotein E phenotypes.

Lipoprotein profile of a Greenland Inuit population. Influence of anthropometric variables, Apo E and A4 polymorphism, and lifestyle

Previously it has been reported that Greenland Inuit (Eskimos) from the Uummannaq district display low levels of plasma cholesterol and triglycerides and relatively high levels of high density lipoprotein (HDL) when compared with healthy Danish control subjects (Lancet 1971;1:1143-1146). Here we present data obtained in 1989 that show the following. In a group of 133 healthy adult Greenland Inuit from Nanortalik, the levels of plasma cholesterol and low density lipoprotein (LDL) cholesterol (6.39 and 4.39 mmol/l, respectively) were slightly higher than "normal" values found in western societies, whereas the HDL cholesterol level was markedly higher (1.64 mmol/l). Compared with most Caucasian populations, the Inuit population we studied exhibits a high apolipoprotein (APO)E*4 allele frequency (0.229), whereas the APOE*2 allele frequency was extremely low (0.015). In contrast to Caucasian populations, in the Inuit population the apoE polymorphism showed only a minor influence on the plasma lipid and (apo)lipoprotein levels, as evaluated by multiple regression analysis, with the exception of apoE levels. This absence of an effect could be explained by the low very low density lipoprotein (VLDL) plus intermediate density lipoprotein (IDL) cholesterol levels. The contributions of eicosapentaenoic acid and linoleic acid to the total amount of fatty acids in plasma cholesterol esters differed markedly from those reported in 1971 for another Greenland Inuit population (3.2% versus 15.8% and 49.5% versus 20.4%, respectively), thereby resembling values now found in the average western population. Even in those Inuit who reported exclusive consumption of the traditional Inuit diet (13% of the population), the fatty acid composition of the plasma cholesterol esters closely resembled the values measured in western populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein epsilon 4 homozygosity in young men with coronary heart disease

We have compared apolipoprotein E gene polymorphism in 91 Australian men aged 30-50 who had been referred for coronary angioplasty and in 172 healthy younger men. 5 of the 19 patients who were less than 40 years of age were homozygous for the epsilon 4 allele, representing a 16-fold increase in prevalence compared with controls. In patients aged 40-50 the epsilon 4 allele frequency was 60% higher than it was in controls. Inheritance of epsilon 4 seems to confer risk of premature ischaemic heart disease in males, homozygotes being especially at risk at a younger age.

Lipoproteins and their genetic variation in subjects with and without angiographically verified coronary artery disease

To examine the concentration of serum lipoproteins and the association of their genetic variation with the occurrence of coronary artery disease (CAD), composite serum lipoprotein profiles including lipoprotein(a) (Lp[a]), apolipoprotein (apo) E phenotypes, and apo B Xba I genotypes were determined in patients with angiographically verified CAD (CAD+ group, n = 111) and in subjects with no angiographic evidence of CAD (CAD- group, n = 46). In addition, we determined the concentrations of serum lipids, lipoproteins, and apolipoproteins in 96 healthy controls. Both CAD- and CAD+ groups had lower concentrations of apos A-I and A-II but higher concentrations of serum total and very low density lipoprotein triglyceride and very low density lipoprotein cholesterol than did healthy controls. The mean concentrations of serum total and low density lipoprotein cholesterol and the median values of Lp(a) were similar in the CAD+ and CAD- groups, both having higher concentrations of low density lipoprotein cholesterol and apo B than the healthy controls. Irrespective of gender, patients with CAD had significantly lower serum high density lipoprotein cholesterol than did those without CAD (1.48 +/- 0.40 versus 1.16 +/- 0.29 mmol/l, p less than 0.001). In women, the mean serum total and very low density lipoprotein triglyceride concentration was also higher in the CAD+ than in the CAD- group. The frequency of the apo E4 allele (epsilon 4) was significantly higher in the CAD+ group (0.293) than in the CAD- group (0.174; p less than 0.001). The frequencies of the two apo B alleles, X1 (Xba I restriction site absent) and X2 (Xba I restriction site present), were similar in the two groups. Stepwise discriminant analysis revealed that in men, serum high density lipoprotein cholesterol had the highest power to discriminate for CAD. In addition, the concentration of plasma apo B levels and the occurrence of apo E phenotypes were independently associated with CAD in men. In women, the only independent factor associated with CAD after adjustment for beta-blocker and diuretics usage was the concentration of serum triglycerides.

Determination of apolipoprotein E phenotypes from stored or postmortem serum samples

In order to assess the validity of Apo E phenotyping from stored specimens, phenotypes determined from fresh serum samples were compared with those from stored (8 years at -20 degrees C) samples from the same individuals (n = 42). The effect of early postmortem period on Apo E phenotype determinability was studied by taking four duplicate blood samples from eight cadavers 2, 6, 12, and 24 h after death. Apo E phenotyping was performed directly from serum by isoelectric focusing and immunoblotting. From the cadavers, the same Apo E phenotypes were obtained 2, 6, 12, and 24 h after death. After eight years' storage five out of ten Apo E4/4 phenotypes were falsely recorded as Apo E4/3 and one out of six Apo E4/3, one out of 12 Apo E4/2 were falsely interpreted as Apo E3/3. Phenotypes Apo E2/2 (n = 2), Apo E3/2 (n = 10), and Apo E3/3 (n = 2) were correctly assessed after 8 years of storage. In the total material, 17% (7/42) of Apo E phenotypes were incorrectly assessed after the storage.

Association of apolipoprotein E and B polymorphisms with serum lipids

Genetic polymorphism of apolipoprotein E (apoE) and the Xbal restriction-fragment-length polymorphisms (RFLP) of the gene for apolipoprotein B (apoB) have both been shown to be associated with plasma lipid concentration. We studied the combined effect of these gene polymorphisms on serum cholesterol concentrations in 300 subjects aged nine to 18 years. In three way ANOVA, there was a statistically significant interaction between the effects of apoE phenotype and gender on serum cholesterol (P = 0.009). Therefore, males and females were analysed separately by two way ANOVA: there was no interaction between the effects of apoE phenotype and apoB Xbal polymorphism in either gender. In females, there were independent effects of both the apoE phenotype (P = 0.020) and the apoB Xbal genotype (P = 0.037) on serum cholesterol, but in males these effects were not statistically significant. These data suggest that variations at the apolipoprotein B and E gene locus play a role in the determination of serum cholesterol concentration in young female Finns.

Relation of coronary heart disease and apolipoprotein E phenotype in patients with non-insulin dependent diabetes

OBJECTIVES

To examine the relation between coronary heart disease and the apolipoprotein E phenotypes in patients with non-insulin dependent diabetes mellitus.

DESIGN

Cross sectional study.

SETTING

District around Kuopio University Central Hospital, East Finland.

SUBJECTS

138 men with non-insulin dependent diabetes and 64 men without diabetes as controls.

MAIN OUTCOME MEASURE

Apolipoprotein E phenotype, electrocardiographic abnormalities, other signs of coronary heart disease.

RESULTS

The prevalences of definite myocardial infarction and ischaemic electrocardiographic changes were highest in the diabetic men with the phenotypes E4/4 or E4/3 (25% (95% confidence interval 18% to 32%) and 50% (42% to 58%) respectively), although the difference between the phenotype groups was not significant. The prevalence of angina pectoris was 69% (61% to 77%) in men with the phenotypes E4/4 or E4/3 (p = 0.005 compared with other phenotypes), 41% (33% to 49%) in men with phenotype E3/3, and 47% (39% to 55%) in those with phenotypes E2/2 or E2/3. Similarly, the simultaneous presence of angina pectoris and ischaemic electrocardiographic changes was highest in the diabetic men with the phenotypes E4/4 or E4/3 (42% v 22% in those with E3/3 and 29% in those with E2/2, E2/3; p = 0.038). Overall, the prevalence of any evidence of coronary heart disease among the diabetic subjects with the phenotypes E4/4 or E4/3 was 81% (p = 0.011 compared with other phenotypes), 58% in those with phenotype E3/3, and 53% in those with phenotypes E2/2 or E3/3.

CONCLUSION

Apolipoprotein E phenotypes E4/4 and E4/3 modulate the risk of coronary heart disease in men with non-insulin dependent diabetes.

Apolipoprotein E phenotypes, serum lipoproteins and apolipoproteins in angiographically assessed coronary heart disease

To determine the influence of the apolipoprotein E polymorphism on the occurrence of coronary artery disease (CAD) and on serum lipids, lipoproteins and apolipoproteins we studied 145 patients with angiographically defined CAD and compared them with 153 control subjects without history or complaints of vascular disease and with 35 subjects without significant stenosis on coronary arteriography. Subjects with hypertension, diabetes mellitus and endocrine or metabolic disorders were excluded. Covariance analysis and logistic regression analysis were performed with adjustment for age, sex, smoking habits and relative body weight. There were no significant differences for the apoE phenotypes on risk of cardiovascular disease. The CAD group had significantly higher mean values of serum cholesterol and triglycerides, very-low-density lipoprotein (VLDL)-cholesterol and VLDL-triglycerides, low-density lipoprotein (LDL)-cholesterol and apoprotein B; they had lower high-density lipoprotein (HDL)-cholesterol and apo A-I. The combination of LDL-cholesterol, apoA-I and VLDL-cholesterol was the best model in predicting cardiovascular disease. ApoE phenotype group E3/E2 had significantly lower values for serum cholesterol, LDL-cholesterol, and apoB and higher levels of apoE in comparison with the phenotype groups E3/E3 and E4/E3. The combination of LDL-cholesterol, cholesterol, apoE and VLDL-triglycerides was the best model in predicting the apoE phenotype. Thus, taking other risk factors into account, the apoE phenotype is not an independent risk factor for CAD; the apoE polymorphism influences lipoprotein levels and possibly, in that way, indirectly also the risk for CAD.

Apolipoprotein E polymorphisms affect atherosclerosis in young males. Pathobiological Determinants of Atherosclerosis in Youth (PDAY) Research Group

Investigators in eight communities collected aortas, right coronary arteries, blood and liver samples, and associated information from 720 young males, aged 15-34 years, who died of external causes. Genotypes for apolipoprotein (apo) E isoforms (E2, E3, and E4) were determined from hepatic DNA by restriction isotyping (restriction enzyme isoform genotyping) of amplified apo E sequences. Pathologists graded the arteries for atherosclerotic lesions, and a central laboratory measured lipoprotein cholesterol concentrations. Allele frequencies were different between blacks and whites (p less than 0.0001). E2 and E4 frequencies were higher and E3 frequency was lower in blacks than in whites. Among the common genotypes in both whites and blacks, E2E3 heterozygotes had the lowest levels of total serum cholesterol and low density lipoproteins, E3E4 had the highest levels, and E3E3 had intermediate levels. Apo E genotypes differed in mean percent surface area involvement with lesions in the thoracic aorta and the abdominal aorta of both whites and blacks (p less than or equal to 0.0002). Among the common genotypes, E2E3 heterozygotes had the least involvement of both thoracic and abdominal aortas with lesions, E3E4 had the greatest involvement (with the exception of the thoracic aorta in whites), and E3E3 had intermediate involvement. Apo E genotype accounted for 5.7% in whites and 5.9% in blacks of the observed variation in lesions for the thoracic aorta, and for 5.9% in whites and 7.0% in blacks for the abdominal aorta. Adjusting for cholesterol levels did not change apo E genotypic effects appreciably, an observation suggesting that genotypic effects on arterial lesions may not be mediated entirely by changes in serum cholesterol concentrations.

A phenocopy of type III dysbetalipoproteinemia occurring in a candidate family for a putative apo E receptor defect

On theoretical grounds, an apo E receptor defect should be manifested by the accumulation of lipoprotein remnants that are normally cleared by this receptor and cannot be processed by the normal apo B, E receptor (LDL-receptor). Furthermore, the defect should not be selective for a specific apo E phenotype since none of the isoforms would be cleared preferentially. Our search for such an occurrence led us to the discovery, in five members of a family of ten, of a unique dyslipoproteinemia mimicking type III. As in type III, plasma levels of cholesterol, triglycerides, VLDL-cholesterol, VLDL-triglycerides and apo E, as well as the VLDL-C/TG ratio, were high. LDL-cholesterol and HDL-cholesterol tended to be low. The clearance of plasma triglycerides after a fat load was impaired. Tubero-eruptive xanthomas, arcus corneae and manifestations of atherosclerosis were present in some individuals. In contrast to type III, the dyslipoproteinemia occurred in subjects bearing three different apo E phenotypes: E4/2, E4/3 and E3/2. VLDL-apo B levels were markedly increased, the VLDL-C/VLDL-B ratio was low and a double pre-beta band was present on lipoprotein electrophoresis. In spite of high apo E and borderline high apo CIII plasma levels, levels of the lipoprotein particles LpCIII:B and LpE:B, which characterize type III, were not raised. Rapid weight loss or treatment with a fibrate was observed to normalize the lipoprotein profile. It is surmised that the apo E-rich lipoprotein particles accumulating in this type III phenocopy with "hyperapoprebetalipoproteinemia" could be those that are normally cleared by an apo E receptor.

Apolipoprotein E polymorphism association with lipoprotein profile in endogenous hypertriglyceridemia and familial hypercholesterolemia

Apolipoprotein (apo) E polymorphism was among the first-reported genetic polymorphisms that explained part of the normal variation in plasma cholesterol concentrations in humans. The aim of this study was to assess the influence of allelic variation at the apo E gene locus on the plasma lipoprotein profile in hyperlipidemia. The lipoprotein levels of hyperlipidemic subjects of the major apo E phenotypes (E3/2, E3/3, and E4/3) were compared. One hundred eighty-two subjects with endogenous hypertriglyceridemia and 98 subjects with familial hypercholesterolemia due to a 10-kb deletion in their low density lipoprotein (LDL) receptor genes were compared with 424 normolipidemic controls from the same environmental background. LDL concentrations were lower in the E3/2 subset than in the E3/3 or E4/3 subset in the control, hypertriglyceridemic, and familial hypercholesterolemic groups. In absolute values, the magnitude of the effect was greatest in the familial hypercholesterolemic group. However, the direction and percentage change were identical in the presence or absence of the LDL receptor defect, indicating that the apo E phenotype effect is independent of LDL receptor status. Triglyceride and very low density lipoprotein (VLDL) cholesterol concentrations were higher in E3/2 than in E3/3 or E4/3 hypertriglyceridemic subjects, but this difference was not found in the familial hypercholesterolemic or control group. Thus, there seems to be a specific interaction between apo E isoforms and VLDL metabolism in hypertriglyceridemia; allelic variation at the apo E gene locus seems to be associated with specific alterations in the plasma lipoprotein profile of subjects with well-defined types of hyperlipidemia.