Genetic effect of apolipoprotein(a) and apolipoprotein E polymorphisms on plasma quantitative risk factors for coronary heart disease in American black women

The prevalence of Alzheimer neuropathologic lesions is similar in blacks and whites

Alzheimer disease is the most common dementia in older Americans, but its impact on blacks is not clearly understood. We examined prospectively 200 autopsy brains at the Office of the Chief Medical Examiner in Maryland and compared the frequency and severity of Alzheimer lesions in blacks and whites. Histologic sections of the hippocampus and entorhinal and neocortices were immunostained for Abeta and tau proteins. Subjects were genotyped for ApoE. Abeta deposits were rated as none, sparse, moderate, or frequent; tau lesions were rated into 4 groups corresponding to Braak scores; and Abeta angiopathy was classified as present or absent. Outcome scores were treated as ordinal variables and analyzed by proportional odds logistic regression. Abeta plaques were present in 60% of black males, 58% of white males, 74% of black females, and 74% of white females. Tau lesions were present in 96% of black males, 88% of white males, 96% of black females, and 96% of white females. Neither race nor gender was a significant factor in the frequency or severity of Alzheimer lesions, and ApoE4 increased the risk for Alzheimer lesions similarly in blacks and whites.

Cholesterol ester transfer protein, apolipoprotein E and lipoprotein lipase genotypes in patients with coronary artery disease in the Turkish population

The aim of this study was to compare patients with coronary artery disease (CAD) to healthy objects, in order to explore a possible association between CAD and the variants in the gene encoding cholesterol ester transfer protein (CETP), apolipoprotein E (Apo E) and lipoprotein lipase (LPL). The relationship between CETP MspI, apo E and LPL PvuII gene polymorphisms and serum lipids were investigated in 173 patients with CAD and 111 healthy controls. The frequency of Apo epsilon4 (p < 0.05) and CETP M1 (p < 0.01) alleles were higher in the CAD group than in the control group. In the CAD group, those with the Msp M1 allele had higher levels of total cholesterol (TC) (p = 0026) and low-density lipoprotein cholesterol (LDL-C) than those with the Msp M2 allele. Subjects with an epsilon2 allele had the lowest levels of TC and LDL-C, while subjects with the epsilon4 allele had the highest. In the control group, CETP, the Msp M2 allele was associated with a higher level of high-density lipoprotein cholesterol (HDL-C) (p = 0.012) than the Msp M1 allele. The distributions of LPL genotype and allele did not differ between the CAD and control groups. The present study demonstrates that the CETP Msp1 and Apo E gene polymorphisms are associated with variations in lipids in patients with CAD and healthy controls in Turkish population.

Definition of the phenotype

Definition of the phenotype is a key issue in designing any genetic study whose goal is to detect disease genes. This chapter describes strategies to increase the power to detect susceptibility loci for complex diseases. A narrowly defined disease phenotype can offer advantages over broad definitions. Studies of clinical disease can also benefit from judicious selection of endophenotypes and related quantitative traits for analysis. The effect of diagnostic and measurement error is also discussed; power is maximized when strategies to reduce error are incorporated into a study design.

Effects of the ApoE polymorphism on plasma lipoproteins in Mexican Americans

PURPOSE

To evaluate the impact of apolipoprotein E (apoE) genotypes on lipoprotein measurements relative to that of other known cardiovascular risk factors in participants of a large population-based family study.

METHODS

We measured concentrations of apoE, the major constituents of HDL (cholesterol, apoAI), LDL-C (cholesterol and apoB), and fraction of apoE in lipoprotein size classes in 859 participants of the San Antonio Family Heart Study, and then tested the association between the three common apoE genotypes (epsilon2epsilon3, epsilon3epsilon3, and epsilon3epsilon4) and lipoprotein traits using the measured genotype approach to account for residual familial correlations.

RESULTS

Allele frequencies in this population for epsilon2, epsilon3, and epsilon4 were 3.5%, 89.6%, and 6.9%, respectively. As expected, adjusted apoE concentrations were highest in those with epsilon2epsilon3, intermediate in those with epsilon3epsilon3, and lowest in those with epsilon3epsilon4. The concentrations of total cholesterol, LDL-C and apoB were lowest in those with epsilon2epsilon3, intermediate in those with epsilon3epsilon3, and highest in those with epsilon3epsilon4. There was no significant effect of apoE genotypes on triglycerides, HDL-C, or apoAI levels. Compared to subjects with epsilon3epsilon4, subjects with epsilon2epsilon3 had relatively less apoE in LDL and HDL(1), and relatively more in HDL(2) and HDL(3) size fractions. The effect of apoE genotypes was significantly greater on apoB in women than in men. ApoE genotypes accounted for 4.5%, 12.3%, and 4.7% of the total genetic variation in apoB, apoE, and LDL-C, respectively.

CONCLUSION

ApoE genotypes account for a modest, albeit significant, proportion of phenotypic variation in concentrations of LDL-C, apoB, and apoE, and distributions of apoE among lipoproteins in this population; these genotypes have a greater effect on apoB levels in women than in men.

[Apolipoprotein E gene polymorphism and risk of hypercholesterolemia: a case control study in a working population of Valencia]

BACKGROUND

The apolipoprotein E (apoE) gene is polymorphic with three common alleles (epsilon 2, epsilon 3, epsilon 4) whose allelic frequency and association with lipid levels varies from population to population. The aim of this study was to estimate the association between these genetic variants and the risk of hypercholesterolemia in a Mediterranean Spanish population.

PATIENTS AND METHODS

A case-control study in a working population from Valencia was carried out. A total of 330 cases (148 men and 182 women) with moderate hypercholesterolemia (total cholesterol > 200 mg/dl or with lipid lowering treatment) and age range 20 to 60 years, were identified. 330 normocholesterolemic controls matched by age and sex were selected. From all of them data of apoE genotype, body mass index, lipid and lipoprotein levels, socioeconomic and life-style variables were obtained.

RESULTS

The epsilon 2 allele frequency was statistically lower in cases (0.033) than in controls (0.086). The epsilon 4 allele frequency was higher in cases (0.115) than in controls (0.039). In the crude logistic regression analysis, the apoE polymorphism was related (p < 0.001) to the risk of hypercholesterolemia. After adjustment by age, body mass index, educational level, tobacco smoking, alcohol consumption and physical activity the epsilon 2 allele was associated with a lower risk of hypercholesterolemia (odds ratio [OR] = 0.36; 95% confidence interval (CI): 0.20-0.64), and the epsilon 4 allele was associated with a higher risk (OR = 3.04; 95% CI: 1.82-5.06).

CONCLUSIONS

The apoE genotype was significantly related to the risk of moderate hypercholesterolemia in the Mediterranean Spanish population.

A unifying hypothesis of Alzheimer's disease. III. Risk factors

Normal ageing and Alzheimer's disease (AD) have many features in common and, in many respects, both conditions only differ by quantitative criteria. A variety of genetic, medical and environmental factors modulate the ageing-related processes leading the brain into the devastation of AD. In accordance with the concept that AD is a metabolic disease, these risk factors deteriorate the homeostasis of the Ca(2+)-energy-redox triangle and disrupt the cerebral reserve capacity under metabolic stress. The major genetic risk factors (APP and presenilin mutations, Down's syndrome, apolipoprotein E4) are associated with a compromise of the homeostatic triangle. The pathophysiological processes leading to this vulnerability remain elusive at present, while mitochondrial mutations can be plausibly integrated into the metabolic scenario. The metabolic leitmotif is particularly evident with medical risk factors which are associated with an impaired cerebral perfusion, such as cerebrovascular diseases including stroke, cardiovascular diseases, hypo- and hypertension. Traumatic brain injury represents another example due to the persistent metabolic stress following the acute event. Thyroid diseases have detrimental sequela for cerebral metabolism as well. Furthermore, major depression and presumably chronic stress endanger susceptible brain areas mediated by a host of hormonal imbalances, particularly the HPA-axis dysregulation. Sociocultural and lifestyle factors like education, physical activity, diet and smoking may also modulate the individual risk affecting both reserve capacity and vulnerability. The pathophysiological relevance of trace metals, including aluminum and iron, is highly controversial; at any rate, they may adversely affect cellular defences, antioxidant competence in particular. The relative contribution of these factors, however, is as individual as the pattern of the factors. In familial AD, the genetic factors clearly drive the sequence of events. A strong interaction of fat metabolism and apoE polymorphism is suggested by intercultural epidemiological findings. In cultures, less plagued by the 'blessings' of the 'cafeteria diet-sedentary' Western lifestyle, apoE4 appears to be not a risk factor for AD. This intriguing evidence suggests that, analogous to cardiovascular diseases, apoE4 requires a hyperlipidaemic lifestyle to manifest as AD risk factor. Overall, the etiology of AD is a key paradigm for a gene-environment interaction. Copyright 2000 John Wiley & Sons, Ltd.

Independent effects of Apo E phenotype and plasma triglyceride on lipoprotein particle sizes in the fasting and postprandial states

LDL particle sizes and Apo E phenotypes were determined in 212 subjects of whom 51 had angina. LDL diameter was significantly less in subjects with an epsilon2 allele (24.76+/-0.08 vs 24.94+/-0.02 nm, P=0.02), and this was evident for both E2/E3 (24.77+/-0.09 nm) and E2/E4 (24.69+/-0.08 nm) phenotypes. Although there was a negative relation between LDL diameter and plasma triglyceride, the effect of apo E2 was still evident with adjustment for triglyceride. In multiple regression analysis, the significant determinants of LDL diameter were gender (with females having larger particles than males), body mass index, and the presence (or absence) of E2. HDL particle sizes and compositions were determined on fasting samples and, additionally, 5 and 8 hours after a fat-rich meal for 48 coronary heart disease cases and 49 control subjects. Fasting HDL particle sizes were not related to the presence of E2 but were significantly smaller for subjects possessing an epsilon4 allele (8. 09+/-0.08 vs 8.39+/-0.05 nm, P=0.003) and were negatively related to plasma triglyceride. However, the effect of E4 persisted after adjustment for triglyceride. In a multiple regression analysis, the only significant determinant of fasting HDL diameter was the presence (or absence) of E4 with fasting plasma triglyceride just failing to reach significance (P=0.06). There was a postprandial increase in HDL diameter that was less marked in subjects with coronary heart disease. The postprandial increase in HDL diameter was of sufficient magnitude to result in size reclassification of HDL particles. The influence of E4 was also evident at both postprandial time points. Compositional analysis demonstrated that the increase in HDL diameters postprandially could be attributed to triglyceride enrichment, with an accompanying fall in cholesterol ester content. Phospholipid changes postprandially were biphasic with an initial fall followed by a rise in concentration. The increase in triglyceride content was significantly less in those subjects with angina despite an equivalent rise in plasma triglyceride. The present study demonstrates significant, but different, effects of variation in apo E phenotype on the particle sizes of both HDL and LDL. Such effects were still evident with adjustment for differences in plasma triglyceride and suggests that variation in apo E phenotype exerts effects on lipoprotein particle sizes by mechanisms additional to those dependent on change in plasma triglyceride.

Therapeutic efficiency of lipoprotein(a) reduction by low-density lipoprotein immunoapheresis

This study was performed to investigate the effect of low-density lipoprotein (LDL) immunoapheresis on lipoprotein(a) [Lp(a)] reduction in patients with heterozygous and homozygous familial hyperlipidemia (N=16) and insufficient response to lipid-lowering agents. By desorption of approximately 5,700+/-500 mL of plasma, a mean reduction in total cholesterol of 62% (P < .001) and in LDL-cholesterol of 70% (P < .001) was achieved. Lp(a), which was elevated at study entry in seven of these patients (82.1+/-34.3 mg/dL; range, 48 to 148 mg/dL), was reduced during the initial LDL-apheresis procedure by 74.8%+/-14.1% (P < .001). Long-term apheresis treatment performed at weekly intervals resulted in an mean reduction in Lp(a) pretreatment values to 39.1+/-28.5 mg/dL (-54%; P < .001). Desorbed Lp(a) was measured at the waste of the columns for 31 apheresis treatments. Lp(a) concentration of the column waste was higher in patients with elevated serum Lp(a) pretreatment values as compared with those with Lp(a) serum values within the normal range (elevated Lp(a), 1,420+/-380 mg; without elevated Lp(a), 235+/-190 mg; P < .001). The rate of return of Lp(a) following apheresis treatment scheduled at weekly intervals was comparable to that of LDL-cholesterol.

Lipoprotein(a) and the significance of the association between platelet glycoprotein IIIa polymorphisms and the risk of premature myocardial infarction

Platelet glycoprotein IIb/IIIa may be involved in the pathogenesis of myocardial infarction as the key element in platelet aggregation and as the binding site of lipoprotein(a) to platelets, inhibiting plasminogen binding and activation. Recently, a strong association between the P1A2 polymorphism of the glycoprotein IIIa gene and acute coronary thrombosis has been reported. although this has not been confirmed. In an associated study, we determined plasma lipoprotein levels, the apo E genotype and the P1A genotype in 250 males under 55 years with myocardial infarction and they were compared with 250 age- and sex-matched controls. Patients showed an over-representation of the epsilon3/4 genotype with respect to the control group. We found that there were no differences in the allelic frequency of P1A2 between case patients and age-matched controls (chi2 = 0.05, P = 0.92) and that subjects bearing the P1A2 allele showed higher plasma lipoprotein(a) concentration than p1A1/P1A1 individuals. Therefore, in this population there is no association between carriage of p1A2 allele and increased risk of myocardial infarction but the carriage of P1A2 is associated with higher plasma Lp(a) concentration.

Association of apolipoprotein genetic polymorphisms with plasma cholesterol in a Japanese rural population. The Shibata Study

The association between apolipoprotein (apo) genetic polymorphisms and lipid phenotypes remains to be determined because such studies have reported contradictory results. We have measured plasma total cholesterol (TC) and HDL cholesterol (HDL-C) in a cross-sectional sample of 1328 (462 men and 866 women) Japanese (aged 40 to 80 years) and analyzed their DNA for the following genotypes: apoA1-C3 Msp I and Sst I sites; apoB signal peptide insertion/deletion, Xba I site and 3' variable number of tandem repeats (VNTR); and apoE. Using multivariate analyses (ANOVA) we found that (1) the polymorphisms of apoA1-C3 and apoB genes are not significantly associated with TC or HDL-C and (2) the polymorphism of the apoE gene is significantly related with TC and the TC:HDL-C ratio. The epsilon 2 carriers have lower levels of TC and a lower TC:HDL-C ratio, epsilon 3 carriers have intermediate levels, and epsilon 4 carriers have higher levels. These findings held whether sexes were analyzed separately or together. Although an opposite trend in HDL-C levels was observed, it did not reach the level of statistical significance. Multiple regression analyses have shown that apoE polymorphism accounts for about 2.3% of the variation in TC and TC:HDL-C ratio irrespective of sex. When the subjects are divided into two groups according to their age (< or = 59 and > or = 60 years old), the effect of apoE alleles on serum cholesterols appears to be diluted in the younger age group whereas it appears to be accentuated in the older group for both sexes. Our findings suggest that among the apo genetic polymorphisms examined, the apoE gene may be considered as a possible candidate for the "high-risk" strategy of atherosclerosis prevention in the Japanese population.

Genetic variation in factor VII associated with variation in plasma lipoprotein(a) concentration

Cross-sectional and prospective studies have shown that individuals with high plasma lipoprotein(a) [Lp(a)] concentrations are at increased risk for coronary heart disease. Size polymorphism of the apolipoprotein(a) [apo(a)] glycoprotein accounts for approximately 35% of the variation in plasma Lp(a) concentrations. However, there is no convincing evidence for associations between plasma Lp(a) and common genetic variation outside APO(a), the gene that encodes apo(a). We tested for association of common genetic variation of candidate genes in lipid metabolism and also of F7 with variation of plasma Lp(a) concentrations in Alberta Hutterites. Variation at codon 353 of F7 has been associated with variation in the plasma factor VII activity (FVIIc), with the 353Q allele associated with lower FVIIc and the 353R allele associated with higher FVIIc. We found significant associations between variation in plasma concentrations of Lp(a) and both apo(a) isoform size and F7 codon 353 genotype (both P < .0001). The effects on plasma Lp(a) concentration of the alleles at codon 353 were additive. The average effects of the F7 353Q and 353R alleles were, respectively, to decrease by 1.71 micrograms/mL and to increase by 0.301 microgram/mL plasma Lp(a) concentration from the sample mean. This suggests that common genomic variation in F7 is associated with variation in plasma Lp(a) concentration.

Apolipoprotein E polymorphism has no independent effect on plasma levels of lipoprotein(a)

Previous studies show conflicting results concerning an influence of apolipoprotein E (apo E) phenotype on lipoprotein(a) (Lp(a)) plasma levels. We speculated that it is not the apo E phenotype itself but rather its effect on plasma lipid concentrations that might influence Lp(a) levels. In 1562 subjects concentrations of triglycerides, LDL-cholesterol and Lp(a) were measured by standard laboratory methods. Apo(a) and apo E isoforms were determined by sodium dodecyl sulfate gel electrophoresis and isoelectric focusing, respectively, followed by immunoblotting. An univariate analysis revealed a significant influence of apo(a) isoforms, apo E phenotype, triglycerides and LDL-cholesterol on Lp(a) plasma levels (ANOVA: P < 0.001, P < 0.02, P < 0.001 and P < 0.001, respectively). In a multivariate analysis, however, the influence of the apo E phenotype was no longer significant (P>0.10), whereas apo(a) isoforms, LDL-cholesterol quintiles and triglyceride quintiles explained 29.2, 2.8 and 1.0% of the variation of the Lp(a) levels (for all three variables: P < 0.001). We conclude that apo E polymorphism does not exert an independent effect on Lp(a) concentrations. Any influence is mediated through the effect of apo E polymorphism on plasma lipids.

Influence of apo E phenotype on postprandial triglyceride and glucose responses in subjects with and without coronary heart disease

Apolipoprotein E phenotypes and fasting lipid and other biochemical parameters were determined in 51 patients with recently diagnosed coronary heart disease (CHD) and 164 control subjects. The age of the participants was 62.5 +/- 6.6 (S.D.) and 63% were male. Forty-eight CHD cases and 51 control subjects were also studied for 8 h after a fat-rich meal. Apo E phenotypes did not differ significantly between CHD cases and control subjects although there was a tendency for under-representation of E2/E3 in the cases (6% versus 16%). Fifteen CHD cases and 37 (of 164) control subjects had at least one epsilon 4 allele. Fasting plasma triglyceride concentrations were not different between CHD cases and controls but were significantly elevated in subjects with an epsilon 4 allele. CHD cases did, however, have a significantly elevated fasting insulin compared with controls. Postprandial triglyceride responses were not different between CHD cases and controls. However, postprandial triglyceride responses were elevated in subjects (CHD cases and controls) who had an epsilon 4 allele. In multivariate analysis, both epsilon 4 allele status and body mass index (BMI) were significant determinants of postprandial triglyceride responses. Postprandial glucose responses were also elevated in subjects with an epsilon 4 allele. When comparison of CHD cases and controls was restricted to those without an epsilon 4 allele, CHD cases showed a borderline significant (P = 0.05) difference in time course from controls, with a slower decline in plasma triglyceride from the peak response. Fasting and postprandial triglyceride and postprandial glucose responses are strongly dependent on the presence of an epsilon 4 allele. The elevation in postprandial triglyceride responses associated with an epsilon 4 allele can obscure differences associated with the presence of CHD and suggests that although elevated postprandial triglyceride response may be a risk factor for CHD, it is not the major reason for the association between the possession of an epsilon 4 allele and coronary disease.

Small genetic effects in complex diseases: a review of regulatory sequence variants in dyslipoproteinemia and atherosclerosis

OBJECTIVE

Most reported mutations that affect lipoprotein metabolism are found within the coding sequences of genes. Recently, a few mutations that occur within promoter sequences have been detected. These promoter sequence variants are the topic of the present review.

METHODS

Some of these variants are fairly common genomic variants in the promoter regions for candidate genes in lipoprotein metabolism, such as APOA1, APOC3, LPA, and LPL. It is possible that such regulatory sequence variants can result in chronic, modestly altered levels of expression of qualitatively normal gene products. This might have a cumulative effect on quantitative phenotypes, such as plasma lipoprotein concentrations, over the long term. Such an effect might not be detected by existing clinical, biochemical, and/or physiological assays.

RESULTS

At present, the most consistent evidence from several lines of experiments indicates that genomic variation in the APOC3 promoter creates slightly elevated plasma triglyceride concentrations within the physiologic range. This altered expression appears to predispose to hypertriglyceridemia in the presence of secondary factors. Genetic variants that produce small effects on promoter function might thus be one component of the predisposition to complex diseases.

CONCLUSION

The aggregate of many small effects may create or contribute to a background of susceptibility that, under appropriate conditions, leads to development of frank dyslipidemia and atherosclerosis.