Apolipoprotein E gene polymorphisms and serum cholesterol in healthy Irish adults: a proposed genetic marker for coronary artery disease risk

Influence of Apolipoprotein E on the Lipid Profile and Postprandial Triglyceride Levels in Brazilian Postmenopausal Women With Artery Disease

This study confirms the association of risk factors for coronary artery disease (CAD) and the apoE polymorphisms, specifically related to the APOE*4 allele, with coronary disease in postmenopausal women. Significantly altered values of the lipid profile were found in patients when compared with controls, independent of the presence of the APOE*4 allele. However, the controls showed higher high-density lipoprotein cholesterol (HDL-C) levels and reduced triglyceride (TG) levels, differing significantly from patients. In this case, the study of subgroups, considering the APOE*3/3 and APOE*3/4 genotypes, suggests that the APOE*4 allele is not implicated in the variations of the lipid profile of patients and determined an increase in the production levels of HDL-C and a reduction in TG highly benefiting the control group compared with APOE*3/3 genotype. The metabolic kinetics of TG, although with the same pattern between groups, and the presence of the APOE*4 allele are suggested to be associated with accelerated clearance compared with APOE*3 allele in non-CAD group.

Bosnian study of APOE distribution (BOSAD): a comparison with other European populations

BACKGROUND

The ε2, ε3 and ε4 alleles of APOE gene have been associated with several diseases in different populations. Data on the frequency of alleles are used in both a clinical and evolutionary context. Although the data on frequency of these alleles are numerous, there are no reports for the population of Bosnia and Herzegovina.

AIM

To estimate the frequency of APOE alleles in a healthy Bosnian population and compare it to data for other European populations.

SUBJECTS AND METHODS

Overall, 170 unrelated Bosnian subjects (108 female and 62 male), aged 53.0 (±5.0) years were included in this study. Genotypes were determined by real-time PCR.

RESULTS

In our group the prevalence of heterozygotes E2/E3, E2/E4 and E3/E4 was 20.6%, 3.5% and 12.9%, respectively, while the prevalence of homozygotes E2/E2, E3/E3, E4/E4 was 0.6%, 61.2% and 1.2%, respectively, with a mean frequency of ε2, ε3 and ε4 alleles of 12.6%, 78.0% and 9.4%, respectively.

CONCLUSIONS

In studied European populations we observed a linear, gradually increasing trend in the frequency of ε4 allele from South to North (Pearson's test 0,7656, p value <0.00001), and the Bosnian population fits into this pattern perfectly.

Apolipoprotein E, statins, and risk of intracerebral hemorrhage

BACKGROUND AND PURPOSE

Apolipoprotein E (ApoE) genotypes have been associated with lobar intracerebral hemorrhage (ICH). Although statins have been associated with an increased risk of ICH, meta-analyses have not consistently shown a statin-induced risk of ICH. Here, we test whether hypercholesterolemia (HC) and ApoE polymorphisms affect the risk of ICH by statin use.

METHODS

The Genetic and Environmental Risk Factors for Hemorrhagic Stroke (GERFHS) study is a prospective, demographically matched case-control study of ICH. A similar study of ICH, Genetic Risks for Medication-Related Hemorrhagic Stroke (GOCHA), was used as a replication cohort. Subjects were classified as normocholesterolemia, HC without statin use, and HC with statin use. Statistical comparisons were performed using Fisher exact test, χ2 tests, and the Breslow-Day test.

RESULTS

The discovery cohort consisted of 558 ICH cases and 1444 controls, and the replication cohort consisted of 1020 ICH cases and 382 controls. The association of lower risk for HC was not attenuated by statin use. Statin use was observed to confer a higher risk for lobar ICH in those carrying ApoE4/E4 and ApoE2/E4 genotypes in both discovery and replication cohorts, and a test for interaction showed a trend towards significance (P=0.11 for statin and ApoE4/E4).

CONCLUSIONS

Statin use does not seem to attenuate the association of HC with decreased risk for nonlobar ICH. Our data support a gene-by-drug effect for lobar ICH, but larger sample sizes are needed to confirm the association before any clinical change is warranted.

CLINICAL TRIAL REGISTRATION URL

http://clinicaltrials.gov. Unique identifier: NCT00930280.

APOE distribution in world populations with new data from India and the UK

BACKGROUND

The APOE gene and its protein product is associated with a number of plasma proteins like very-low density lipoprotein (VLDL), high density lipoprotein (HDL) chylomicrons, chylomicron remnants, and plays a crucial role in lipid metabolism. The APOE gene is polymorphic and common alleles (*E2, *E3 and *E4) have been associated with a number of common and complex diseases in different populations. Due to their crucial role in metabolism and clinical significance, it is imperative that allelic variation in different populations is analysed to evaluate the usage of APOE in an evolutionary and clinical context.

AIM

We report allelic variation at the APOE locus in three European and four Indian populations and evaluate global patterns of genetic variation at this locus. The large, intricate and unexpected heterogeneity of this locus in its global perspective may have insightful consequences, which we have explored in this paper.

SUBJECT AND METHODS

Apolipoprotein E genotypes were determined in four population groups (Punjabi Sikhs, Punjabi Hindus, Maria Gonds and Koch, total individuals = 497) of India and three regionally sub-divided British populations (Nottinghamshire, East Midlands and West Midlands, total individuals = 621). The extent and distribution of APOE allele frequencies were compared with 292 populations of the world using a variety of multivariate methods.

RESULTS

Three alleles, APOE*E2, APOE*E3 and APOE*E4, were observed with contrasting variation, although *E4 was absent in the tribal population of Koch. Higher heterozygosities (>43%) in British populations reflected their greater genetic diversity at this locus. The overall pattern of allelic diversity among these populations is comparable to many European and Indian populations. At a global level, higher frequencies of the *E2 allele were observed in Africa and Oceania (0.099 +/- 0.083 and 0.111 +/- 0.052, respectively). Similarly, *E4 allele averages were higher in Oceania (0.221 +/- 0.149) and Africa (0.209 +/- 0.090), while Indian and Asian populations showed the highest frequencies of *E3 allele. The coefficient of gene differentiation was found to be highest in South America (9.6%), although the highest genetic diversity was observed in Oceania (48.7%) and Africa (46.3%). APOE*E2 revealed a statistically significant decreasing cline towards the north in Asia (r = -0.407, d.f. = 70, p < 0.05), which is not compatible with the coronary heart disease statistics in this continent. APOE*E4 showed a significant increasing cline in North European populations. Spatial autocorrelation analysis shows that the variation at this locus is influenced by 'isolation by distance' with a strong positive correlation for lower distances up to 1313 km.

CONCLUSION

Overall APOE allelic variation in UK and Indian populations is comparable to previous studies but in tribal populations *E4 allele frequency was very low or absent. At a global level allelic variation shows that geography, isolation by distance, genetic drift and possibly pre-historical selection are responsible for shaping the spectrum of genetic variation at the APOE gene. Overall, APOE is a good anthropogenetic and clinical diagnostic marker.

ApoE genotype, cardiovascular risk and responsiveness to dietary fat manipulation

Cardiovascular risk is determined by the complex interactions between genetic and environmental factors. The apoE genotype represents the most-widely-studied single nucleotide polymorphism in relation to CVD risk, with >3600 publications cited in PubMed. Although originally described as a mediator of lipoprotein metabolism, the lipoprotein-independent functions of apoE are being increasingly recognised, with limited data available on the potential impact of genotype on these metabolic processes. Furthermore, although meta-analyses suggest that apoE4 carriers may have a 40-50% increased CVD risk, the associations reported in individual studies are highly heterogeneous and it is recognised that environmental factors such as smoking status and dietary fat composition influence genotype-phenotype associations. However, information is often derived from observational studies or small intervention trials in which retrospective genotyping of the cohort results in small group sizes in the rarer E2 and E4 subgroups. Either larger well-standardised intervention trials or smaller trials with prospective recruitment according to apoE genotype are needed to fully establish the impact of diet on genotype-CVD associations and to establish the potential of dietary strategies such as reduced total fat, saturated fat, or increased antioxidant intakes to counteract the increased CVD burden in apoE4 carriers.

The relationship between nutrient intake and cognitive performance in people at risk of dementia

BACKGROUND

There is evidence of a link between nutrient intake and cognitive impairment and decline in old age. There has been no study of nutrient intake in Irish subjects at risk of dementia.

AIM

To investigate the possible link between nutrient intake and cognitive performance in a group of Irish adults at risk of dementia, and to compare the nutrient intake in these adults stratified by the absence or presence of the apolipoprotein E (APOE) epsilon4 allele.

METHOD

Forty-four subjects, who were first-degree blood relatives of people with Alzheimer's disease, were recruited. Cognitive performance and nutritional intake were assessed and apolipoprotein E (APOE) genotype determined.

RESULTS

The intakes of cholesterol (P < 0.037) and Na (P < 0.037) were significantly higher in subjects with altered cognitive performance. There was no significant difference in nutrient intakes between APOE epsilon-4 allele positive and APOE epsilon-4 allele negative subjects.

CONCLUSION

The findings of this work suggest that dietary cholesterol and sodium intake may be linked to cognitive impairment.

Olfactory function in people with genetic risk of dementia

BACKGROUND

Screening for sensorial impairment is a secondary objective in the context of neurodegenerative diseases, including dementias. For example, olfactory dysfunction is among the first signs of Alzheimer's disease. There has been no study of olfactory function in Irish subjects at risk of dementia.

AIM

To investigate olfactory function in non-demented Irish persons, who carry genetic risk factors for dementia.

METHODS

Thirty-eight Irish adult subjects, who are at risk of dementia, were recruited. Cognitive performance and olfactory function were assessed and apolipoprotein E (APOE) genotype determined.

RESULTS

Three and six subjects had a Mini Mental State Examination (MMSE) and Brief Smell Identification Test (B-SIT) score, respectively, outside the normal range. While five out of the fifteen epsilon-4 allele positive subjects had B-SIT scores outside the normal range, only one out of the twenty-three epsilon-4 allele negative subjects had; the difference in this frequency was significant (P=0.025). There was no significant difference (P=0.266) in the frequency of abnormal MMSE scores between epsilon-4 allele groups.

CONCLUSION

Further investigation is required to explore the reasons for the higher prevalence of olfactory dysfunction in epsilon-4 allele positive subjects.

Population prevalence of APOE, APOC3 and PPAR-α mutations associated to hypertriglyceridemia in French Canadians

Hypertriglyceridemia (HTG) is known as a common metabolic disorder associated with increased production, decrease catabolism and/or decreased hepatic uptake of triglyceride (TG)-rich particles. We assessed, in the Quebec City population, the allele frequency and haplotype distributions of mutations in genes related to HTG, such as the apolipoprotein E (APOE) (C112R and C158R), the apolipoprotein CIII (APOC3) (C-482T and C3238G) and the peroxisome proliferator-activated receptor alpha (PPARalpha) (L162V) genes. A total of 938 anonymous unlinked newborns from the metropolitan Quebec City area have been genotyped. Allele frequencies observed in the Quebec City population differed from known frequencies determined in other Caucasian populations. The co-transmitted allele distribution between the two-marker genotypes APOE/APOC3(C3238G) and APOC3(C-482T)/PPARalpha(L162V) presented a weak deviation from the assumption of genetic independence. Also, we observed a non-independent distribution of the T-482/G3238 allele combinations within the APOC3 gene, suggesting strong linkage disequilibrium between the C-482T and C3238G polymorphisms. Moreover, comparisons of allele frequencies observed in the population of Québec City to those obtained in other Caucasian populations suggested that the population of Québec City may be at a lower risk of developing HTG due to APOE, APOC3 and PPARalpha genetic variants. However, the strong linkage disequilibrium and the two-marker genotype distributions observed in the APOC3 gene suggest that these two variants may functionally interact in the Québec City population.

Diet, genes and disease: implications for nutrition policy

There is extensive evidence to show that there is considerable variation in diet and disease patterns in Europe and that many of the dietary patterns are predictive of chronic disease. Increasingly, there is evidence that this dietary effect is mediated by genetic background. The present paper examines the role of polymorphisms within three genes, those responsible for the synthesis of apoE, 5,10-methylenetetrahydrofolate reductase (MTHFR) and PPARgamma. There is clear evidence to support the concept that the diet-disease link is moderated by genetic variation. The paper then considers whether this moderating effect will have implications for dietary recommendations. In the formulation of dietary reference values it has long been recognized that these values cannot cover the needs of all individuals. By setting the upper level at the mean value +2 sd, the needs of 97.5% of the population are covered. Setting a hypothetical scenario of a nutrient requirement of 200 mg/d and a polymorphism with an allelic frequency in the general population in the range of 0, 10, 20 and 30% that causes an increased nutrient requirement of 25%, there was no evidence that the traditional approach requires revision. Whilst it is recognized that genetic variability may not influence population goals, genetic variability will have to be taken into account in the clinical nutrition management of disease. To knowingly assign a patient to life-long treatment with a diet that for genetic reasons will have no success is both unethical and uneconomical. Once accepted in clinical nutrition, the diet-gene interaction will filter into the prevention of disease in public health nutrition.

Microsomal triglyceride transfer protein polymorphisms and lipoprotein levels in type 2 diabetes

BACKGROUND

Microsomal triglyceride transfer protein (MTP) regulates the assembly of chylomicrons in the intestine and very-low-density lipoprotein (VLDL) in the liver. Common polymorphisms have been described that do not affect lipoproteins in non-diabetic subjects. Their effect in diabetes has not been described in a Caucasian population.

AIM

To investigate the association of these three common polymorphisms with lipoproteins in type 2 diabetes.

METHODS

Eighty-two patients consumed a high-fat test meal. Chylomicron and VLDL apoB48, apoB100, cholesterol, triglycerides and phospholipids were measured fasting, and at 4 and 6 h postprandially. MTP genotyping was performed by PCR-RFLP.

RESULTS

Thirty-three subjects were heterozygous for the -493 G/T substitution. These patients had significantly lower LDL cholesterol (3.0 +/- 0.2 vs. 3.5 +/- 0.1 mmol/l, p < 0.02). In the postprandial period, they had higher levels of apoB48 in the VLDL fraction (4 h, 7.0 +/- 1.4 vs. 2.9 +/- 0.4 microg/ml plasma, p < 0.002; 6 h, 6.4 +/- 1.0 vs. 3.5 +/- 0.5 microg/ml plasma, p < 0.05). In the VLDL fraction there was significantly less cholesterol at 4 and 6 h (p < 0.05). The -400 A/T substitution gave very similar lipoprotein results, but there was significant linkage dysequilibrium between the two polymorphisms. No association was found between the -164 T/C polymorphism and either plasma lipids or the postprandial lipid profile. ApoE genotype was also examined, but did not influence the above results.

DISCUSSION

The common -493 G/T MTP polymorphism is associated with changes in VLDL and LDL in Type 2 diabetic patients. The importance of the changes in apoB48-containing small particles requires further investigation. The significantly lower LDL cholesterol suggests that this polymorphism may confer protection against atherosclerosis in type 2 diabetes.

Gene–gene interaction of PPARγ and ApoE affects coronary heart disease risk

BACKGROUND

Apolipoprotein epsilon4 has been proposed as a genetic predictor for CHD. Peroxisome proliferator-activated receptors (PPAR), a recent identified nuclear transcription factor, is involved in regulation of many target genes and plays an important role in lipid metabolism, insulin sensitivity, obesity and atherosclerosis. PPARgamma gene polymorphisms may affect the profile of CHD-related risk factors.

HYPOTHESIS

Interaction between PPARgamma gene polymorphism and apoE polymorphisms affect the presence of CHD.

METHOD

This is a case-control study, which enrolled 150 cases with CHD and 157 controls without CHD. Polymerase chain reaction-restricted fragments length polymorphism was used to determine the apoE genotype and PPARgamma C161-->T substitution.

RESULTS

ApoE epsilon4 allele was significantly more prevalent in CHD patients than in controls (13.05 vs. 7.35%, P<0.05). The apoE epsilon4 carries had significant higher LDL-C levels than other apoE carriers and this tendency could be modified by PPARgamma CT genotype. ApoE genotype epsilon4 was an independent risk factor for CHD (OR=4.29, 95%CI: 1.6-11.48, P=0.004). A significant interaction between apoE epsilon4 and PPARgamma CT genotype was detected with respect to the effect on CHD (P=0.045).

CONCLUSION

This is the first study to explore the effect of interaction between PPARgamma C161-->T variant and apoE epsilon4 genotype. The result exhibited an interaction effect of two genes on serum cholesterol level. The association of CHD to apoE genotype was subjected to the attenuation effect of PPARgamma CT genotype.