The Significant Increase in Cardiovascular Disease Risk inAPOEɛ4 Carriers is Evident Only in Men Who Smoke: Potential Relationship Between Reduced Antioxidant Status and ApoE4

The Association between Apolipoprotein E Genotypes and Serum Malondialdehyde Level with End-Stage Renal Disease

Background

The Apolipoprotein E (ApoE) polymorphism plays an important role in the pathophysiology of end-stage renal disease (ESRD). Additionally, ApoE may contribute to the progression of oxidative stress. Thus, this study aimed to determine the ApoE gene polymorphism and evaluate the malondialdehyde (MDA) level in ESRD patients and healthy individuals.

Methods

The present cross-sectional study was conducted at 2010 at Kermanshah University of Medical Sciences (Kermanshah, Iran). The study population comprised ESRD patients (n=136) and healthy individuals (n=137). The MDA level was assessed using high-performance liquid chromatography (HPLC), and the frequencies of ApoE gene alleles were analyzed using restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). The data were analyzed using Statistical Package for Social Sciences (SPSS), version 13. The significant differences of ApoE genotypes in case and control groups were assessed using Pearson's Chi square tests, and two-tailed Student's tests. A logistic regression model was used to calculate the odd ratio. P<0.05 was considered statistically significant.

Results

According to the results, ESRD patients had a higher frequency of the E2/E3 genotype than the healthy group (P<0.001). The results indicated that E3/E4 genotype frequency in the patients' group was higher than that of the control group (P=0.026). Furthermore, the E3/E2 (OR=5.7, 95% CI=2.68-12.14) (P<0.001) and E3/E4 (OR=1.57, 95% CI=1.05-2.34) (P=0.029) genotypes were found to increase the risk of ESRD. Moreover, the MDA level in ESRD patients was higher than the healthy individuals (P<0.001). The patients with E3/E2 (P<0.001) and E3/E4 (P<0.001) genotypes had a higher level of MDA than the control group.

Conclusion

According to the findings, patients with ESRD had higher genotypes of E3/E2 and E3/E4, which suggests a higher risk of developing ESRD.

Association of Vitamin E and Cognitive Decline in Older Adults with and without the APOEɛ4 Allele: A Biracial Population-Based Community Study

BACKGROUND

The association of different types of tocopherols (vitamin E) with cognition might vary by the APOEɛ4 allele status.

OBJECTIVE

We examined the association of dietary tocopherols with cognitive decline among participants with and without the APOEɛ4 allele over a median of 12 years.

METHODS

2,193 participants from the Chicago Health and Aging Project were included in the analyses. Global cognition was assessed in three-year cycles. We used a 144-item FFQ to assess dietary intakes of tocopherols and hME Sequenom mass-array platform to assess APOE genotype. We used linear mixed effects models to examine the relationship between tocopherol from food sources and global cognitive decline.

RESULTS

The mean baseline age was 74.1 (SD = 5.9) years. Among APOEɛ4 carriers, participants in the highest quintile of intakes of dietary vitamin E had a slower cognitive decline of 0.022 SDU (95% CI: 0.000, 0.043) compared to those in the lowest quintile. A higher intake of dietary α-tocopherol from food sources only was associated with slower cognitive decline in APOEɛ4 carriers (p for trend 0.002) but not among the non-carriers (p for trend 0.937). Among APOEɛ4 carriers, those in the highest quintile of intake of α-tocopherol had a 16.4% slower rate of decline of global cognition compared to those in the lowest quintile (β= 0.034, 95% CI: 0.013, 0.054).

CONCLUSIONS

Individuals consuming high α-tocopherol from food sources had slower cognitive decline among APOEɛ4 carriers. In older adults, different forms of vitamin E might moderate the relationship of APOEɛ4 with global cognition.

COVID-19 enters the expanding network of apolipoprotein E4-related pathologies

COVID-19 incidence and case fatality rates (CFR) differ among ethnicities, stimulating efforts to pinpoint genetic factors that could explain these phenomena. In this regard, the multiallelic apolipoprotein E (APOE) gene has recently been interrogated in the UK biobank cohort, demonstrating associations of the APOE ε4/ε4 genotype with COVID-19 severity and mortality. The frequency of the ε4 allele and thus the distribution of APOE ε4/ε4 genotype may differ among populations. We have assessed APOE genotypes in 1638 Greek individuals, based on haplotypes derived from SNP rs7412 and rs429358 and found reduced frequency of ε4/ε4 compared to the British cohort. Herein we discuss this finding in relation to CFR and hypothesize on the potential mechanisms linking APOE ε4/ε4 to severe COVID-19. We postulate that the metabolic deregulation ensued by APOE4, manifested by elevated cholesterol and oxidized lipoprotein levels, may be central to heightened pneumocyte susceptibility to infection and to exaggerated lung inflammation associated with the ε4/ε4 genotype. We also discuss putative dietary and pharmacological approaches for the prevention and management of COVID-19 in APOE ε4/ε4 individuals.

Epigenome-450K-wide methylation signatures of active cigarette smoking: The Young Finns Study

Smoking as a major risk factor for morbidity affects numerous regulatory systems of the human body including DNA methylation. Most of the previous studies with genome-wide methylation data are based on conventional association analysis and earliest threshold-based gene set analysis that lacks sensitivity to be able to reveal all the relevant effects of smoking. The aim of the present study was to investigate the impact of active smoking on DNA methylation at three biological levels: 5'-C-phosphate-G-3' (CpG) sites, genes and functionally related genes (gene sets). Gene set analysis was done with mGSZ, a modern threshold-free method previously developed by us that utilizes all the genes in the experiment and their differential methylation scores. Application of such method in DNA methylation study is novel. Epigenome-wide methylation levels were profiled from Young Finns Study (YFS) participants' whole blood from 2011 follow-up using Illumina Infinium HumanMethylation450 BeadChips. We identified three novel smoking related CpG sites and replicated 57 of the previously identified ones. We found that smoking is associated with hypomethylation in shore (genomic regions 0-2 kilobases from CpG island). We identified smoking related methylation changes in 13 gene sets with false discovery rate (FDR) ≤ 0.05, among which is olfactory receptor activity, the flagship novel finding of the present study. Overall, we extended the current knowledge by identifying: (i) three novel smoking related CpG sites, (ii) similar effects as aging on average methylation in shore, and (iii) a novel finding that olfactory receptor activity pathway responds to tobacco smoke and toxin exposure through epigenetic mechanisms.

APOE and metabolic dysfunction in Alzheimer's disease

The strongest genetic risk factor for sporadic Alzheimer's disease (AD) is carriage of the E4 allele of APOE. Metabolic dysfunction also increases risk of dementia and AD. Facing a need for effective therapies and an aging global population, studies aimed at uncovering new therapeutic targets for AD have become critical. Insight into the biology underlying the effects of E4 and metabolic impairment on the brain may lead to novel therapies to reduce AD risk. An understudied hallmark of both AD patients and E4 individuals is a common metabolic impairment-cerebral glucose hypometabolism. This is a robust and replicated finding in humans, and begins decades prior to cognitive decline. Possession of E4 also appears to alter several other aspects of cerebral glucose metabolism, fatty acid metabolism, and management of oxidative stress through the pentose phosphate pathway. A critical knowledge gap in AD is the mechanism by which APOE alters cerebral metabolism and clarification as to its relevance to AD risk. Facing a need for effective therapies, studies aimed at uncovering new therapeutic targets have become critical. One such approach is to gain a better understanding of the metabolic mechanisms that may underlie E4-associated cognitive dysfunction and AD risk.

THE EXPOSOME IN HUMAN EVOLUTION: FROM DUST TO DIESEL

Global exposures to air pollution and cigarette smoke are novel in human evolutionary history and are associated with about 16 million premature deaths per year. We investigate the history of the human exposome for relationships between novel environmental toxins and genetic changes during human evolution in six phases. Phase I: With increased walking on savannas, early human ancestors inhaled crustal dust, fecal aerosols, and spores; carrion scavenging introduced new infectious pathogens. Phase II: Domestic fire exposed early Homo to novel toxins from smoke and cooking. Phases III and IV: Neolithic to preindustrial Homo sapiens incurred infectious pathogens from domestic animals and dense communities with limited sanitation. Phase V: Industrialization introduced novel toxins from fossil fuels, industrial chemicals, and tobacco at the same time infectious pathogens were diminishing. Thereby, pathogen-driven causes of mortality were replaced by chronic diseases driven by sterile inflammogens, exogenous and endogenous. Phase VI: Considers future health during global warming with increased air pollution and infections. We hypothesize that adaptation to some ancient toxins persists in genetic variations associated with inflammation and longevity.

Analysis of SLCO1B1 and APOE genetic polymorphisms in a large ethnic Hakka population in southern China

OBJECTIVE

Statins are the most widely used lipid-lowering drugs, which have a significant effect on the inhibition of cardiovascular disease. The efficacy and side effects of statins are associated with the polymorphisms of SLCO1B1 and APOE genes. The purpose of this study was to analyze the SLCO1B1 and APOE gene polymorphisms in the Hakka population of southern China.

METHODS

A total of 3249 subjects including 2019 males and 1230 females participated in this study. Polymerase chain reaction (PCR)-fluorescence probe technique for polymorphisms analysis and analyzed the genotypes frequencies of SLCO1B1 and APOE genes.

RESULTS

The frequencies of SLCO1B1 521T>C between men and women were statistically significant (SLCO1B1 521TT, χ2  = 8.431, P = .004; SLCO1B1 521TC, χ2  = 7.436, P = .007). The frequencies of haplotypes *1b/*1b (40.07%) and *1a/*1b (32.56%) of SLCO1B1 gene accounted for 72.63%, followed by *1b/*15(14.40%), *1a/*1a (5.82%), *1a/*15 (5.57%), *15/*15 (1.45%), and *1a/*5 (0.12%). The frequencies of haplotypes *1a/*15 and *1b/*1b of SLCO1B1 gene between men and women were statistically significant (*1a/*15, χ2  = 6.789, P = .009; *1b/*1b, χ2  = 3.998, P = .004). In this study, genotype ɛ3/ɛ3 accounted for 69.04%, followed by ɛ3/ɛ4 (16.19%), ɛ2/ɛ3 (11.60%), ɛ2/ɛ4 (1.35%), ɛ4/ɛ4 (1.08%), and ɛ2/ɛ2 (0.74%) in all subjects, in which ɛ3 had the greatest allele frequency (82.93%), followed by ɛ4 (9.85%) and ɛ2 (7.22%). We found that 47 subjects carrying the SLCO1B1 521 (CC) polymorphism who had not any myopathy caused by statins.

CONCLUSIONS

We analyzed the SLCO1B1 and APOE gene polymorphisms in the Hakka population of southern China. This study provides a reference for the individualized meditation for Hakka population in this area.

Functional, Cellular, and Molecular Remodeling of the Heart under Influence of Oxidative Cigarette Tobacco Smoke

Passive and active chronic cigarette smoking (CS) remains an international epidemic and a key risk factor for cardiovascular disease (CVD) development. CS-induced cardiac damage is divided into two major and interchangeable mechanisms: (1) direct adverse effects on the myocardium causing smoking cardiomyopathy and (2) indirect effects on the myocardium by fueling comorbidities such as atherosclerotic syndromes and hypertension that eventually damage and remodel the heart. To date, our understanding of cardiac remodeling following acute and chronic smoking exposure is not well elucidated. This manuscript presents for the first time the RIMD (oxidative stress (R), inflammation (I), metabolic impairment (M), and cell death (D)) detrimental cycle concept as a major player in CS-induced CVD risks and direct cardiac injury. Breakthroughs and latest findings in the field with respect to structural, functional, cellular, and molecular cardiac remodeling following chronic smoking exposure are summarized. This review also touches the genetics/epigenetics of smoking as well as the smoker's paradox and highlights the most currently prominent pharmacological venues to mitigate CS-induced adverse cardiac remodeling.

Association of APOE gene polymorphism with lipid profile and coronary artery disease in Afro-Caribbeans

OBJECTIVES

Apolipoprotein E gene (APOE) polymorphism is associated with the lipid profile and cardio-vascular disease. However, these relationships vary between ethnic groups. We evaluated, for the first time in an Afro-Caribbean population, the distribution of APOE polymorphisms and their associations with coronary artery disease (CAD), the lipid profile and other cardio-metabolic risk factors.

METHODS

We studied 712 Afro-Caribbean subjects including 220 with documented CAD and 492 healthy subjects. TaqMan assays were performed to genotype rs7412 and rs429358, the two variants that determine the APOE alleles ε2, ε3 and ε4. The association between APOE genotype and the lipid profile was analysed by comparing ε2 carriers, ε3 homozygotes and ε4 carriers.

RESULTS

The frequencies of ε2, ε3 and ε4 in the overall sample were 8%, 70% and 22%, respectively. CAD was not associated with APOE polymorphism. The total cholesterol level was higher in ε4 carriers compared with ε2 carriers: 5.07 vs 4.59 mmol/L (P = 0.016). The LDL-cholesterol level was lower in APOE ε2 carriers compared with ε3 homozygotes and ε4 carriers: 2.65 vs 3.03 and 3.17 mmol/L, respectively (p = 0.002). The total cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios were similar in the three allelic groups. APOE polymorphism was not associated with diabetes, hypertension, waist circumference or body mass index.

CONCLUSIONS

Our results indicate that APOE gene polymorphism is associated with the lipid profile but not with CAD in Afro-Caribbean people. This lack of association with CAD may be explained by the low atherogenic profile observed in ε4 carriers, which may warrant further investigation.

APOE genotype and stress response - a mini review

The APOE gene is one of currently only two genes that have consistently been associated with longevity. Apolipoprotein E (APOE) is a plasma protein which plays an important role in lipid and lipoprotein metabolism. In humans, there are three major APOE isoforms, designated APOE2, APOE3, and APOE4. Of these three isoforms, APOE3 is most common while APOE4 was shown to be associated with age-related diseases, including cardiovascular and Alzheimer’s disease, and therefore an increased mortality risk with advanced age. Evidence accumulates, showing that oxidative stress and, correspondingly, mitochondrial function is affected in an APOE isoform-dependent manner. Accordingly, several stress response pathways implicated in the aging process, including the endoplasmic reticulum stress response and immune function, appear to be influenced by the APOE genotype. The investigation and development of treatment strategies targeting APOE4 have not resolved any therapeutic yet that could be entirely recommended. This mini-review provides an overview on the state of research concerning the impact of the APOE genotype on stress response-related processes, emphasizing the strong interconnection between mitochondrial function, endoplasmic reticulum stress and the immune response. Furthermore, this review addresses potential treatment strategies and associated pitfalls as well as lifestyle interventions that could benefit people with an at risk APOE4 genotype.

The Apoe(-/-) mouse model: a suitable model to study cardiovascular and respiratory diseases in the context of cigarette smoke exposure and harm reduction

Atherosclerosis-prone apolipoprotein E-deficient (Apoe(-/-)) mice display poor lipoprotein clearance with subsequent accumulation of cholesterol ester-enriched particles in the blood, which promote the development of atherosclerotic plaques. Therefore, the Apoe(-/-) mouse model is well established for the study of human atherosclerosis. The systemic proinflammatory status of Apoe(-/-) mice also makes them good candidates for studying chronic obstructive pulmonary disease, characterized by pulmonary inflammation, airway obstruction, and emphysema, and which shares several risk factors with cardiovascular diseases, including smoking. Herein, we review the results from published studies using Apoe(-/-) mice, with a particular focus on work conducted in the context of cigarette smoke inhalation studies. The findings from these studies highlight the suitability of this animal model for researching the effects of cigarette smoking on atherosclerosis and emphysema.

[Recent Knowledge of Smoking and Peripheral Arterial Disease in Lower Extremities]

Peripheral arterial disease (PAD) is an atherosclerotic obstructive disease of the arteries in lower extremities. Patients with PAD show high rates of mortality from coronary artery disease (CAD) and stroke. Smoking as well as diabetes is an important risk factor for PAD. A lesion of PAD in the lower extremities tends to be more proximal in smokers than in nonsmokers and to be more distal in patients with diabetes than in nondiabetics. By a systematic review, the odds ratio for PAD of smokers vs nonsmokers has been reported to be in the range of 1.7-7.4. Previous epidemiological studies suggest a stronger association of smoking with PAD than that with CAD. Nitric oxide (NO) is an important molecule suppressing the progression of atherosclerosis, but this function is compromised by smoking. Smoking decreases the bioactivity of NO and the expression level of NO synthase. In addition, smoking results in deteriorations of risk factors for atherosclerosis such as decreases in blood HDL (high-density lipoprotein) cholesterol and tissue plasminogen activator levels and increases in the levels of blood triglycerides, LDL (low-density lipoprotein) cholesterol, fibrinogen and the von Willebrand factor. Thus, smoking increases blood coagulability and deteriorates the blood lipid profile, resulting in thrombogenetic proneness and dyslipidemia. Smoking also increases the generation of atherogenic oxidized LDL in blood and decreases antiatherogenic prostacyclin production in the vascular endothelium. Smoking cessation is important for the prevention and therapy of PAD, and to this end, counseling by physicians and nicotine replacement therapy are useful and strongly recommended for patients with PAD.

Effects of APOE rs429358, rs7412 and GSTM1/GSTT1 Polymorphism on Plasma and Erythrocyte Antioxidant Parameters and Cognition in Old Chinese Adults

Apolipoprotein E (APOE) and oxidative damage were correlated with the risk of Alzheimer’s disease (AD). Glutathione S-transferase (GST) polymorphism was proved to be associated with body antioxidant capacity and involved in the oxidative damage related chronic diseases. To explore the combined effects of APOE rs429358, rs7412 and GSTM1/T1 polymorphism on antioxidant parameters and cognition in old Chinese adults, a community-based cross-sectional study was carried out in 477 Chinese adults aged from 55 to 75. Information on demography and lifestyle of the participants was collected with a questionnaire. Cognitive function was measured by using a Montreal Cognitive Assessment (MoCA) test. Fasting venous blood samples were collected for APOE rs429358, rs7412 and GSTM1/T1 genotyping, and parameter measurement. No association of APOE rs7412, rs429358 and GSTM1/T1 polymorphisms with cognition was detected in the old Chinese adults. APOE rs429358, rs7412 polymorphism was mainly associated with plasma α-tocopherol, low density lipoprotein cholesterol (LDL-C) and plasma total antioxidant capacity (T-AOC) levels (p < 0.05). Interaction of APOE rs429358 and GSTT1 genotype on the plasma triglyceride (TG) level and erythrocyte catalase (CAT) and GST enzyme activities were detected (p < 0.05). The subjects with APOE rs429358 T/C + C/C and GSTT1− genotype were found to have the highest plasma TG level, erythrocyte CAT enzyme activity, and the lowest GST enzyme activity compared to subjects with other genotypes (p < 0.05). Lowest erythrocyte CAT enzyme activity and highest glutathione peroxidase (GSH-Px) enzyme activity were detected in the subjects with APOE rs7412 T/C + T/T and GSTM1+ genotype as compared with subjects with other genotypes. The levels of plasma and erythrocyte antioxidant parameters were APOE genotype associated. GSTM1 or GSTT1 genotype modified the influence of APOE rs7412, rs429358 polymorphism on antioxidant parameters.

Mechanotransduction Mechanisms for Intraventricular Diastolic Vortex Forces and Myocardial Deformations: Part 2

Epigenetic mechanisms are fundamental in cardiac adaptations, remodeling, reverse remodeling, and disease. A primary goal of translational cardiovascular research is recognizing whether disease-related changes in phenotype can be averted by eliminating or reducing the effects of environmental epigenetic risks. There may be significant medical benefits in using gene-by-environment interaction knowledge to prevent or reverse organ abnormalities and disease. This survey proposes that "environmental" forces associated with diastolic RV/LV rotatory flows exert important, albeit still unappreciated, epigenetic actions influencing functional and morphological cardiac adaptations. Mechanisms analogous to Murray's law of hydrodynamic shear-induced endothelial cell modulation of vascular geometry are likely to link diastolic vortex-associated shear, torque and "squeeze" forces to RV/LV adaptations. The time has come to explore a new paradigm in which such forces play a fundamental epigenetic role, and to work out how heart cells react to them. Findings from various imaging modalities, computational fluid dynamics, molecular cell biology and cytomechanics are considered. The following are examined, among others: structural dynamics of myocardial cells (endocardium, cardiomyocytes, and fibroblasts), cytoskeleton, nucleoskeleton, and extracellular matrix; mechanotransduction and signaling; and mechanical epigenetic influences on genetic expression. To help integrate and focus relevant pluridisciplinary research, rotatory RV/LV filling flow is placed within a working context that has a cytomechanics perspective. This new frontier in cardiac research should uncover versatile mechanistic insights linking filling vortex patterns and attendant forces to variable expressions of gene regulation in RV/LV myocardium. In due course, it should reveal intrinsic homeostatic arrangements that support ventricular myocardial function and adaptability.

Paraoxonase (PON1) polymorphisms Q192R and L55M are not associated with human longevity: A meta-analysis

BACKGROUND

Genetic mutations in the paraoxonase 1 (PON1) encoding gene have been considered to affect mortality and of these the functional promoter region polymorphisms Q192R and L55M are among the most widely studied.

OBJECTIVE

The aim of this study was to determine whether the Q192R and L55M polymorphisms of PON1 can increase susceptibility to longevity. A meta-analysis was performed to obtain a comprehensive estimation of the association between Q192R and L55M and longevity in long-lived individuals (LLIs) aged 80 years or more.

MATERIAL AND METHODS

A search was carried out in the PubMed database (from January 2001 to May 2014) to obtain data on the role of PON1 polymorphisms in longevity and a pooled odds ratio (OR) with a 95% confidence interval (CI) was used to assess the associations.

RESULTS

The meta-analysis was based on 9 studies of PON1 Q192R and 5 studies of PON1 L55M that covered a total of 5086 LLIs and 4494 controls. Overall, significantly increased risks were not observed for either Q192R or L55M. The results of the statistical calculations were as follows: R vs. Q (additive model): OR = 1.080, 95% CI = 0.989-1.179, p = 0.088 and RR + RQ vs. QQ (dominant model): OR = 1.099, 95% CI = 0.975-1.240, p = 0.124; M vs. L (additive model): OR = 0.946, 95% CI = 0.862-1.039, p = 0.245 and MM + ML vs. LL (dominant model): OR = 0.951, 95% CI = 0.836-1.081, p = 0.442 for Q192R and L55M, respectively. The results did not change with an age cut-off among the LLIs of ≥ 93 years.

CONCLUSION

No evidence that the Q192R and L55M polymorphisms of PON1 impacted on the probability of reaching extreme ages was found although this cannot be completely ruled out; however, the possibility of population-specific effects due to the influence of and interaction between different genes or environmental factors could not be ruled out.

Aging and cardiovascular diseases: the role of gene-diet interactions

In the study of longevity, increasing importance is being placed on the concept of healthy aging rather than considering the total number of years lived. Although the concept of healthy lifespan needs to be defined better, we know that cardiovascular diseases (CVDs) are the main age-related diseases. Thus, controlling risk factors will contribute to reducing their incidence, leading to healthy lifespan. CVDs are complex diseases influenced by numerous genetic and environmental factors. Numerous gene variants that are associated with a greater or lesser risk of the different types of CVD and of intermediate phenotypes (i.e., hypercholesterolemia, hypertension, diabetes) have been successfully identified. However, despite the close link between aging and CVD, studies analyzing the genes related to human longevity have not obtained consistent results and there has been little coincidence in the genes identified in both fields. The APOE gene stands out as an exception, given that it has been identified as being relevant in CVD and longevity. This review analyzes the genomic and epigenomic factors that may contribute to this, ranging from identifying longevity genes in model organisms to the importance of gene-diet interactions (outstanding among which is the case of the TCF7L2 gene).

Nutrigenetics and personalized nutrition: are we ready for DNA-based dietary advice?

Common genetic variation affects individual nutrient requirements and the use of DNA-based dietary advice, derived from nutrigenetics, has been growing. The growth is about to accelerate as the cost of genotyping continues to fall and research results from major nutrigenetics projects are published. There is still some skepticism; some barriers remain including some commercial tests, which make exaggerated, incorrect claims. There is a need for more public resources dedicated to unbiased, objective review and dissemination of nutrigenetics information; however, nutrigenetics evidence should be assessed in the context of standard nutritional evidence and should not require higher standards. This article argues that we are ready for some DNA-based dietary advice in general nutrition and it can be beneficial. Examples of the scientific validity and health utility of gene-diet interactions will be given and the development of guidelines for assessment and validation of benefits will be discussed.

Current Genetics and Epigenetics of Smoking/Tobacco-Related Cardiovascular Disease

Genetic and epigenetic factors are of great importance in cardiovascular biology and disease. Tobacco-smoking, one of the most important cardiovascular risk factors, is itself partially determined by genetic background and is associated with altered epigenetic patterns. This could render the genetics and epigenetics of smoking-related cardiovascular disease a textbook example of environmental epigenetics and modern approaches to multimodal data analysis. A pronounced association of smoking-related methylation patterns in the F2RL3 gene with prognosis in patients with stable coronary heart disease has recently been described. Nonetheless, surprisingly little concrete knowledge on the role of specific genetic variants and epigenetic modifications in the development of cardiovascular diseases in people who smoke has been accumulated. Beyond the current knowledge, the present review briefly outlines some chief challenges and priorities for moving forward in this field.

Effects of apolipoprotein E genotypes on metabolic profile and oxidative stress in southwest Chinese women with polycystic ovary syndrome

OBJECTIVE

Apolipoprotein (APO) E genetic polymorphism plays an important role in lipid and lipoprotein metabolism, and has been shown to be associated with the risk of metabolic and cardio-cerebrovascular diseases and late-onset Alzheimer's disease. It is not clear, however, whether there are any relationships between the APOE genotypes and PCOS in Chinese women. The aim of this study was to investigate the relationship between APOE genotypes and the risk of polycystic ovary syndrome (PCOS) and to evaluate the effects of the genotypes on metabolic profile and oxidative stress in south-west Chinese women.

STUDY DESIGN

A total of 625 patients with PCOS based on the Rotterdam consensus criteria and 514 control women from a population of Chinese Han nationality in the Chengdu area were studied during 2006-2012. APOE genotypes were determined by PCR and restriction fragment length polymorphism analysis. Clinical and metabolic parameters, serum malondialdehyde concentration, and total antioxidant capacity were analyzed.

RESULTS

No significant differences were found in the frequencies of APOE genotypes (E2/2, E2/3, E2/4, E3/3, E3/4, E4/4) and alleles (ε2, ε3, ε4) between PCOS and control groups. Compared with ε3 homozygotes (APOE3/3), however, ε2 carriers (APOE2/2+APOE2/3+APOE2/4) had significantly higher body mass index, waist circumference and waist-to-hip ratio, a more adverse glucose and insulin metabolic profile, lower high density lipoprotein (HDL)-cholesterol (C) and APOA1 levels, higher triglyceride (TG)/HDL-C ratio and prevalence of metabolic syndrome (MS), whereas ε4 carriers (APOE3/4+APOE4/4) had higher total cholesterol (TC) and low density lipoprotein (LDL)-C levels in patients with PCOS.

CONCLUSIONS

In a cohort of south-west Chinese women, there were no significant associations between any APOE genotype and PCOS. The APOE ε2 allele seems to be related to abdominal obesity, insulin resistance and MS in PCOS women.

Interactive effects of ApoE polymorphism, alcohol and smoking on age-related trends of blood pressure levels in elderly men: the Bambuì Cohort Study of Ageing (1997-2008)

Data from a population-based prospective study were used to examine longitudinal changes in blood pressure (BP) and seek interactions between apolipoprotein E (ApoE) genotypes, smoking and alcohol in a cohort of 557 elderly Brazilian men. Repeated BP measurements were obtained in four waves, and multi-level random-effects pattern-mixture models were used to evaluate age-related BP trajectories while accounting for non-ignorable dropouts/deaths and handling heterogeneities as random parameter variations. Alcohol was associated with high systolic BP in ε2 carriers and those with the ε3/3 genotype, but not in ε4 carriers. This was dependent on age and smoking habits: at the age of 60, expected systolic BP in alcohol drinking ε2 carriers was 16.5 mm Hg higher than in the reference group of non-smokers/non-drinkers if they were not smokers (P=0.049), and 28.6 mm Hg higher if they were also smokers (P=0.004). The youngest smoking/non-drinking ε2 carriers had lower systolic BP, but it increased rapidly and led to higher expected levels among older carriers. Alcohol consumption, alone or together with smoking, interacts with the effects of ApoE genotype on systolic BP, probably nullifying the more favourable lipid profile of ε2 carriers. The interactions of gene-modifiable risk factors have major public health implications.

The genetic contribution to disease risk and variability in response to diet: where is the hidden heritability?

Ten years ago, it was assumed that disease risk prediction and personalised nutrition based on genetic information would now be in widespread use. However, this has not (yet) transpired. The interaction of genetic make-up, diet and health is far more complex and subtle than originally thought. With a few notable exceptions, the impact of identified common genetic variants on phenotype is relatively small and variable in their penetrance. Furthermore, the known variants account for only a fraction of what we believe to be the total genetic contribution to disease risk and heterogeneity in response to environmental change. Here, the question ‘how far have we progressed and are we likely to get there’ (Rimbach and Minihane, 2009) is revisited with regard to the translation of genetic knowledge into public health benefit. It is concluded that progress to date has been modest. It is hoped that recent technological developments allowing the detection of rarer variants and future use of more hypothesis-driven targeted data analysis will reveal most of the currently ‘hidden’ significant genetic variability.

A case-control study on the effect of Apolipoprotein E genotypes on gastric cancer risk and progression

Background

Apolipoprotein E (ApoE) is a multifunctional protein playing both a key role in the metabolism of cholesterol and triglycerides, and in tissue repair and inflammation. The ApoE gene (19q13.2) has three major isoforms encoded by ε2, ε3 and ε4 alleles with the ε4 allele associated with hypercholesterolemia and the ε2 allele with the opposite effect. An inverse relationship between cholesterol levels and gastric cancer (GC) has been previously reported, although the relationship between apoE genotypes and GC has not been explored so far.

Methods

One hundred and fifty-six gastric cancer cases and 444 hospital controls were genotyped for apoE polymorphism (ε2, ε3, ε4 alleles). The relationship between GC and putative risk factors was measured using the adjusted odds ratios (ORs) and their 95% confidence intervals (CIs) from logistic regression analysis. A gene-environment interaction analysis was performed. The effect of the apoE genotypes on survival from GC was explored by a Kaplan–Meier analysis and Cox proportional hazard regression model.

Results

Subjects carrying at least one apoE ε2 allele have a significant 60% decrease of GC risk (OR=0.40, 95% CI: 0.19 – 0.84) compared with ε3 homozygotes. No significant interaction emerged between the ε4 or ε2 allele and environmental exposures, nor ε2 or ε4 alleles affected the median survival times, even after correcting for age, gender and stadium.

Conclusions

Our study reports for the first time a protective effect of the ε2 allele against GC, that might be partly attributed to the higher antioxidant properties of ε2 compared with the ε3 or ε4 alleles. Given the study’s sample size, further studies are required to confirm our findings.

ApoE genotype: from geographic distribution to function and responsiveness to dietary factors

ApoE is a key protein in lipid metabolism with three major isoforms.ApoEallele frequencies show non-random global distribution especially in Europe with highapoEε3frequency in the Mediterranean area, whereas theapoEε4genotype is enriched in Northern Europe. TheapoEε4genotype is one of the most important genetic risk factors for age-dependent chronic diseases, including CVD and Alzheimer's disease (AD). The apoE polymorphism has been shown to impact on blood lipids, biomarkers of oxidative stress and chronic inflammation, which all may contribute to the isoform-dependent disease risk. Studies in mice and human subjects indicate that theapoEε3but not theapoEε4genotype may significantly benefit from dietary flavonoids (e.g. quercetin) andn-3 fatty acids. Metabolism of lipid soluble vitamins E and D is likewise differentially affected by theapoEgenotype. Epidemiological and experimental evidence suggest a better vitamin D status inapoEε4than ε3subjects indicating a certain advantage of ε4over ε3. The present review aims at evaluation of current data available on interactions between apoE polymorphism and dietary responsiveness to flavonoids, fat soluble vitamins andn-3 fatty acids. Likewise, distinct geographic distribution and chronic disease risk of the different apoE isoforms are addressed.

Interaction of apolipoprotein E genotype with smoking and physical inactivity on coronary heart disease risk in men and women

OBJECTIVE

Apolipoprotein E genotype (APOE) polymorphism affects lipid levels and coronary heart disease (CHD) risk. However, these associations may be modified by lifestyle factors. Therefore, we studied whether smoking, physical inactivity or overweight interact with APOE on cholesterol levels and CHD risk.

METHODS

Combining two Swedish case-control studies yielded 1735 CHD cases and 4654 population controls (3747 men, 2642 women). Self-reported questionnaire lifestyle data included smoking (ever [current or former regular] or never) and physical inactivity (mainly sitting leisure time). We obtained LDL cholesterol levels and APOE genotypes. CHD risk was modelled using logistic regression to obtain odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for relevant covariates.

RESULTS

Smoking interacted with APOE on CHD risk; adjusted ORs for ever versus never smoking were 1.45 (95% CI 1.00-2.10) in ɛ2 carriers, 2.25 (95% CI 1.90-2.68) in ɛ3 homozygotes and 2.37 (95% CI 1.85-3.04) in ɛ4 carriers. Female ɛ4 carriers had OR 3.62 (95% CI 2.32-5.63). The adjusted ORs for physical inactivity were 1.09 (95% CI 0.73-1.61), 1.34 (95% CI 1.12-1.61), and 1.79 (95% CI 1.38-2.30) in ɛ2, ɛ3ɛ3 and ɛ4 groups, respectively. No interaction was seen between overweight and APOE for CHD risk, or between any lifestyle factor and APOE for LDL cholesterol levels.

CONCLUSION

The APOE ɛ2 allele counteracted CHD risk from smoking in both genders, while the ɛ4 allele was seen to potentiate this risk mainly in women. Similar ɛ2 protection and ɛ4 potentiation was suggested for CHD risk from physical inactivity.

Determinants of paraoxonase activity in healthy adults

SCOPE

Paraoxonase-1 (PON-1), associated with HDL, is regarded as anti-atherogenic, attributed to its ability to hydrolyze oxidized lipids. Here, the impact of PON and apolipoprotein E genotypes, age, alcohol and HDL-cholesterol (HDL-C) on PON activity is examined.

METHODS AND RESULTS

In total, 104 healthy UK adults participated in the study, with basal (PONA) and stimulated (PONB) PON-1 activities and arylesterase activity determined in these individuals. In univariate and correlation analysis age, HDL-C, alcohol intake and both PON genotypes were significantly associated with PONA and PONB activities (p<0.05). However, in the standard linear regression model, which explained 69% of the variability in both PONA (p<0.001) and PONB activities (p<0.001) only PON Q192R genotype emerged as a significant independent determinant, with four to fivefold higher levels in the RR versus wild-type QQ genotype groups. For PON arylesterase, HDL-C (p=0.030), apolipoprotein E (p=0.023) and PON Q192R (p=0.002) and PON L55M (p=0.002) genotypes collectively explained 14% of the total variability in the regression model.

CONCLUSION

Our results indicate that PON genotypes are stronger determinants of PON activity relative to the other potential modulators assessed. The relative impact of dietary components on PON activities remains to be established.

Structural equation modeling of gene-environment interactions in coronary heart disease

Coronary heart disease (CHD) is a complex disease, which is influenced not only by genetic and environmental factors but also by gene-environment (GE) interactions in interconnected biological pathways or networks. The classical methods are inadequate for identifying GE interactions due to the complex relationships among risk factors, mediating risk factors (e.g., hypertension, blood lipids, and glucose), and CHD. Our aim was to develop a two-level structural equation model (SEM) to identify genes and GE interactions in the progress of CHD to take into account the causal structure among mediating risk factors and CHD (Level 1), and hierarchical family structure (Level 2). The method was applied to the Framingham Heart Study (FHS) Offspring Cohort data. Our approach has several advantages over classical methods: (1) it provides important insight into how genes and contributing factors affect CHD by investigating the direct, indirect, and total effects; and (2) it aids the development of biological models that more realistically reflect the complex biological pathways or networks. Using our method, we are able to detect GE interaction of SERPINE1 and body mass index (BMI) on CHD, which has not been reported. We conclude that SEM modeling of GE interaction can be applied in the analysis of complex epidemiological data sets.

Case-control study of apoE gene polymorphism in young CHD patients and controls in the Serbian population

Apolipoprotein E displays polymorphism with three common alleles, e2, e3, and e4. The aim of this research was to determine apoE gene polymorphism in a group of healthy patients and a group of patients with CHD, and to reveal the relation between anthropometric and biochemical parameters and the apoE genotype. In CHD group significantly higher values of blood pressure, waist circumference, BMI and fat %, triglycerides, insulin (HOMA IR) and CRP were found. A statistically significant higher presence of the e3e4 genotype and e4 allele was detected in the CHD group. Statistically significant differences between waist circumference, BMI, insulin and HOMA IR were found between subjects with e3e3 and e3e4 genotypes.

A case-control study on the effect of apoliprotein E genotype on head and neck cancer risk

BACKGROUND

The apolipoprotein E gene (apoE) has three major isoforms encoded by the ε2, ε3, and ε4 alleles, with the ε4 allele associated with hypercholesterolemia and the ε2 allele with the opposite effect. An inverse relationship between cholesterolemia and head and neck cancer (HNC) has been previously reported, although the relationship between apoE genotypes and HNC has not been explored to date.

METHODS

Four hundred and seventeen HNC cases and 436 hospital controls were genotyped for apoE polymorphisms. Adjusted odds ratios (ORs) and 95% confidence intervals (CI) from logistic regression were used to explore the relationship between HNC and putative risk factors. A gene-environment interaction analysis was done.

RESULTS

A borderline significant 40% decreased HNC risk (OR, 0.58; 95% CI, 0.31-1.05) was observed for individuals carrying at least one ε2 allele. Females carrying at least one ε2 allele showed a 60% risk reduction (OR, 0.43; 95% CI, 0.21-0.90) for HNC compared with ε3 homozygotes. A statistically significant interaction was found between alcohol use and the ε4 allele (P for interaction = 0.04), with a 2-fold increased risk (OR, 2.06; 95% CI, 0.95-4.48) among ever drinkers with an ε4 allele, with respect to ε3 homozygote nondrinkers.

CONCLUSIONS

Our study provides novel evidence of a possible protective effect of the ε2 allele against HNC, probably due to its increased antioxidant properties.

IMPACT

According to our results, apolipoprotein E may play a different role in carcinogenesis other than its well-known role in regulating blood serum cholesterol levels.

Implications of apolipoprotein E genotype on inflammation and vitamin E status

In Western societies the apolipoprotein E4 (apoE4) genotype is associated with increased morbidity and mortality and represents a significant risk factor for cardiovascular and Alzheimer's disease. In a recent study we observed significantly lower tissue alpha-tocopherol (alpha-TOH) concentrations in apoE4 compared with apoE3 mice. Furthermore, genes encoding for proteins involved in peripheral alpha-TOH transport and degradation were affected by the apoE genotype. Thus, the apoE4 genotype may be associated with lower vitamin E retention in peripheral tissues. This is possibly related to an altered lipoprotein metabolism including increased alpha-TOH retention in LDL, a decreased expression of lipoprotein receptors and impaired cellular vitamin E delivery system, and a greater intracellular degradation of tocopherols in the apoE4 genotype. An increasing number of studies in cultured cells, transgenic mice and human volunteers indicate a more pro-inflammatory state associated with the apoE4 allele. In apoE4 macrophages there is an enhanced transactivation of the key redox sensitive transcription factor NF-kappaB accompanied by a higher production of pro-inflammatory molecules (tumor necrosis factor alpha, interleukin 1beta, macrophage inflammatory protein 1-alpha) and a lower production of anti-inflammatory interleukin 10, as compared with apoE3 macrophages. Both tissue vitamin E retention and biomarkers of chronic inflammation may be affected by the apoE genotype.

Circulating oxidized low-density lipoproteins and arterial elasticity: comparison between men with metabolic syndrome and physically active counterparts

Background

Accumulation of oxidized low-density lipoproteins in the intimae of arteries and endothelial dysfunction are key events in the development of atherosclerosis. Patients with metabolic syndrome are at high risk for cardiovascular diseases but the linkage between metabolic syndrome and atherosclerosis is incompletely understood. We studied whether the levels of oxidized LDL and arterial elasticity differ between metabolic syndrome patients and physically active controls.

Methods

40 men with metabolic syndrome and 40 physically active controls participated in this cross-sectional study. None of the study subjects had been diagnosed with cardiovascular disease. Levels of oxidized LDL were assessed by a two-site ELISA immunoassay. Arterial elasticity was assessed non-invasively by the HDI/PulseWave™ CR-2000 arterial tonometer.

Results

Levels of oxidized LDL were 89.6 ± 33.1 U/L for metabolic syndrome subjects and 68.5 ± 23.6 U/L for controls (p = 0.007). The difference remained significant after adjustment for LDL cholesterol. Large artery elasticity index (C1) was 16.2 ± 4.1 mL/mmHgx10 for metabolic syndrome subjects and 19.4 ± 3.7 mL/mmHgx10 for controls (p = 0.001), small artery indices (C2) were 7.0 ± 3.2 mL/mmHgx100 and 6.5 ± 2.9 mL/mmHgx100 (NS), respectively.

Conclusions

Subjects with metabolic syndrome had elevated levels of oxidized LDL and reduced large arterial elasticity compared to controls. This finding may partly explain the increased risk for cardiovascular diseases among metabolic syndrome patients.

Trial registration

ClinicalTrials.gov NCT01114763

No or only population-specific effect of PON1 on human longevity: a comprehensive meta-analysis

Paraoxonase 1 (PON1) has been suggested as a plausible candidate gene for human longevity due to its modulation of cardiovascular disease risk, by preventing oxidation of atherogenic low-density lipoprotein. The role of the PON1 192 Q/R polymorphism has been analyzed for association with survival at old age in several populations, albeit with controversial results. To reconcile the conflicting evidence, we performed a large association study with two samples of 2357 Germans and 1025 French, respectively. We combined our results with those from seven previous studies in the largest and most comprehensive meta-analysis on PON1 192 Q/R and longevity to-date, to include a total of 9580 individuals. No significant association of PON1 192 Q/R with longevity was observed, for either R allele or carriership. This finding relied on very large sample sizes, is supported by different analysis methods and is therefore considered very robust. Moreover, we have investigated a potential interaction of PON1 192 Q/R with APOE epsilon4 using data from four populations. Whereas a significant result was found in the German sample, this could not be confirmed in the other examined groups. Our large-scale meta-analysis provided no evidence that the PON1 192 Q/R polymorphism is associated with longevity, but this does not exclude the possibility of population-specific effects due to the influence of, and interaction between, different genetic and/or environmental factors (e.g. diet).

Detecting gene-by-smoking interactions in a genome-wide association study of early-onset coronary heart disease using random forests

Background

Genome-wide association studies are often limited in their ability to attain their full potential due to the sheer volume of information created. We sought to use the random forest algorithm to identify single-nucleotide polymorphisms (SNPs) that may be involved in gene-by-smoking interactions related to the early-onset of coronary heart disease.

Methods

Using data from the Framingham Heart Study, our analysis used a case-only design in which the outcome of interest was age of onset of early coronary heart disease.

Results

Smoking status was dichotomized as ever versus never. The single SNP with the highest importance score assigned by random forests was rs2011345. This SNP was not associated with age alone in the control subjects. Using generalized estimating equations to adjust for sex and account for familial correlation, there was evidence of an interaction between rs2011345 and smoking status.

Conclusion

The results of this analysis suggest that random forests may be a useful tool for identifying SNPs taking part in gene-by-environment interactions in genome-wide association studies.

Validation study of genetic associations with coronary artery disease on chromosome 3q13-21 and potential effect modification by smoking

The CATHGEN study reported associations of chromosome 3q13-21 genes (KALRN, MYLK, CDGAP, and GATA2) with early-onset coronary artery disease (CAD). This study attempted to independently validate those associations. Eleven single nucleotide polymorphisms (SNPs) were examined (rs10934490, rs16834817, rs6810298, rs9289231, rs12637456, rs1444768, rs1444754, rs4234218, rs2335052, rs3803, rs2713604) in patients (N = 1618) from the Intermountain Heart Collaborative Study (IHCS). Given the higher smoking prevalence in CATHGEN than IHCS (41% vs. 11% in controls, 74% vs. 29% in cases), smoking stratification and genotype-smoking interactions were evaluated. Suggestive association was found for GATA2 (rs2713604, p = 0.057, OR = 1.2). Among smokers, associations were found in CDGAP (rs10934490, p = 0.019, OR = 1.6) and KALRN (rs12637456, p = 0.011, OR = 2.0) and suggestive association was found in MYLK (rs16834871, p = 0.051, OR = 1.8, adjusting for gender). No SNP association was found among non-smokers, but smoking/SNP interactions were detected for CDGAP (rs10934491, p = 0.017) and KALRN (rs12637456, p = 0.010). Similar differences in SNP effects by smoking status were observed on re-analysis of CATHGEN. CAD associations were suggestive for GATA2 and among smokers significant post hoc associations were found in KALRN, MYLK, and CDGAP. Genetic risk conferred by some of these genes may be modified by smoking. Future CAD association studies of these and other genes should evaluate effect modification by smoking.

Apolipoprotein E polymorphism interacts with cigarette smoking in progression of multiple sclerosis

BACKGROUND AND PURPOSE

The influence of apolipoprotein E (ApoE) polymorphism on clinical severity of multiple sclerosis (MS) is still controversial. Cigarette smoking has been suggested to influence the progression of disability in these patients. In this study, we aimed to investigate whether an interaction of smoking with the ApoE polymorphism influences the progression of disability in MS patients.

METHODS

Smoking history from 205 female patients with MS was obtained. Clinical data collected include age at onset, disease duration, annual relapse rate, the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Severity Score (MSSS). ApoE polymorphism was examined in all patients and stratified according to smoking status and associations with the clinical data investigated.

RESULTS

There were no significant associations between cigarette smoking and any of the clinical characteristics in the whole group of patients. In women carrying the ApoE E4 isoform, smokers had a lower EDSS (P = 0.033) and MSSS (P = 0.023) in comparison with non-smokers.

CONCLUSION

Our data suggest that in women with MS carrying the ApoE E4 isoform, cigarette smoking may have a protective influence on disease progression and accumulation of disability. These findings need to be confirmed by future large longitudinal studies.

Selenium level is associated with apoE epsilon4 in rural elderly Chinese

OBJECTIVE

Se is an essential trace element in human nutrition associated with antioxidant activity. Previous studies on predictors of toenail Se or serum Se have mostly concentrated on demographic factors such as age and gender. The present paper examines the association between apoE genotype and Se levels in nail samples in a rural elderly Chinese cohort.

DESIGN

Two thousand Chinese aged 65 years and over from four counties in China were enrolled in a cohort to study the association of Se with cognitive decline. Nail samples were collected from each participant and analysed for Se levels. Dietary Se intake was estimated from an FFQ using Se contents measured in food items collected from each village. Blood samples on filter cards were collected and analysed for apoE genotype. Mixed-effect models were constructed with nail Se level as the dependent variable and each village as the random effect, which controlled for the potential confounding effect from correlation in Se measures obtained from participants residing in the same village.

RESULTS

In this elderly Chinese cohort, carriers of the apoE epsilon4 allele had significantly lower Se levels measured in nail samples than non-carriers after adjusting for other significant covariates and controlling for estimated dietary Se intake. There was no significant difference between the two genotypes on estimated Se dietary intake (P = 0.6451).

CONCLUSIONS

Future studies are needed to examine the mechanism underlying the association between the apoE epsilon4 allele and Se levels, including the role of oxidative stress and that of reduced lipid metabolism in the apoE epsilon4 carriers.

Gene-gene and gene-environment interactions: new insights into the prevention, detection and management of coronary artery disease

Despite the recent success of genome-wide association studies (GWASs) in identifying loci consistently associated with coronary artery disease (CAD), a large proportion of the genetic components of CAD and its metabolic risk factors, including plasma lipids, type 2 diabetes and body mass index, remain unattributed. Gene-gene and gene-environment interactions might produce a meaningful improvement in quantification of the genetic determinants of CAD. Testing for gene-gene and gene-environment interactions is thus a new frontier for large-scale GWASs of CAD. There are several anecdotal examples of monogenic susceptibility to CAD in which the phenotype was worsened by an adverse environment. In addition, small-scale candidate gene association studies with functional hypotheses have identified gene-environment interactions. For future evaluation of gene-gene and gene-environment interactions to achieve the same success as the single gene associations reported in recent GWASs, it will be important to pre-specify agreed standards of study design and statistical power, environmental exposure measurement, phenomic characterization and analytical strategies. Here we discuss these issues, particularly in relation to the investigation and potential clinical utility of gene-gene and gene-environment interactions in CAD.

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.

Interactions of functional apolipoprotein E gene promoter polymorphisms with smoking on aortic atherosclerosis

BACKGROUND

Apolipoprotein E gene (APOE) interacts with environmental factors in defining risk for atherosclerosis. We studied whether the APOE epsilon2/epsilon3/epsilon4 genotype or APOE promoter polymorphisms -219G/T and +113G/C might interact with smoking on the development of fatty streaks. We also studied the previously unknown effects of +113G/C on transcriptional activity.

METHODS AND RESULTS

The fatty streak areas of aorta were measured morphometrically in subjects of the Helsinki Sudden Death Study. Within APOE epsilon3/epsilon3 subjects, there was a strong interaction between smoking and both -219G/T (P=0.009) and +113G/C (P=0.003) promoter polymorphisms on abdominal aorta fatty streak area: the -219T- and +113C-allele carriers had larger lesion areas compared with G/G (12.7% versus 5.9%, P=0.007; 12.9% versus 6.3%, P=0.010, respectively) within nonsmokers. Within smokers, the associations were inverse. Moreover, smoking increased the fatty streak area within -219G/G or +113G/G genotypes and -219G/+113G/epsilon3 haplotype carriers. Functional studies in reporter assay showed that in comparison with the +113G allele, the +113C allele had higher transcriptional activity and bound transcription factors from liver cell nuclear extract with significantly lower affinity.

CONCLUSIONS

In middle-aged Finnish men with APOE epsilon3/epsilon3 genotype, the APOE promoter polymorphisms -219G/T and +113G/C interact with smoking in modulating aortic atherosclerosis. The +113G/C polymorphism has an effect on transcriptional activity.

Influence of apolipoprotein E genotype and dietary α-tocopherol on redox status and C-reactive protein levels in apolipoprotein E3 and E4 targeted replacement mice

The molecular basis of the positive association between apoE4 genotype and CVD remains unclear. There is directin vitroevidence indicating that apoE4 is a poorer antioxidant relative to the apoE3 isoform, with some indirectin vivoevidence also available. Therefore it was hypothesised that apoE4 carriers may benefit from α-tocopherol (α-Toc) supplementation. Targeted replacement mice expressing the human apoE3 and apoE4 were fed with a diet poor (0 mg/kg diet) or rich (200 mg/kg diet) in α-Toc for 12 weeks. Neither apoE genotype nor dietary α-Toc exerted any effects on the antioxidant defence system, including glutathione, catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase activities. In addition, no differences were observed in mitogen-induced lymphocyte proliferation. α-Toc concentrations were modestly higher in plasma and lower in tissues of apoE4 compared with apoE3 mice, with the greatest differences evident in the lung, suggesting that an apoE4 genotype may reduce α-Toc delivery to tissues. A tendency towards increased plasma F2-isoprostanes in apoE4 mice was observed, while liver thiobarbituric acid-reactive substances did not differ between apoE3 and apoE4 mice. In addition, C-reactive protein (CRP) concentrations were reduced in apoE4 mice indicating that this positive effect on CRP may in part negate the increased CVD risk associated with an apoE4 genotype.

Cardiovascular disease risk prediction using genetic information (gene scores): is it really informative?

PURPOSE OF REVIEW

DNA-based tests for assessment of genetic predisposition to coronary heart disease need to provide information over and above that of conventional risk factors. The efficacy of selected 'candidate' gene loci in risk algorithms, to improve the predictive accuracy for coronary heart disease, remains to be demonstrated.

RECENT FINDINGS

Although many candidate genes for coronary heart disease have been tested, the optimal set of risk genotypes has yet to be identified. There is only a relatively modest risk to be expected in association with any single genotype, published estimates are in the range of 1.12-1.73. Thus the risk associated with any one genotype is modest, but, in combination, selected genotypes may be associated with a clinically significant risk. Since the allele frequency for many of these variants is high, many individuals will carry several 'risk alleles'. A small number of selected single nucleotide polymorphisms should complement the conventional risk factors to identify high-risk individuals in whom correction of 'modifiable risk factors' through lifestyle interventions or medication would be most beneficial.

SUMMARY

As our understanding of how genetic variation impacts on common diseases advances, the novel loci identified by genome-wide association scans associated with disease risk will rapidly improve these risk algorithms.

Impact of apoE genotype on oxidative stress, inflammation and disease risk

Although in developing countries an apolipoprotein E4 (apoE4) genotype may offer an evolutionary advantage, as it has been shown to offer protection against certain infectious disease, in Westernised societies it is associated with increased morbidity and mortality, and represents a significant risk factor for cardiovascular disease, late-onset Alzheimer's disease and other chronic disorders. ApoE is an important modulator of many stages of lipoprotein metabolism and traditionally the increased risk was attributed to higher lipid levels in E4 carriers. However, more recent evidence demonstrates the multifunctional nature of the apoE protein and the fact that the impact of genotype on disease risk may be in large part due to an impact on oxidative status or the immunomodulatory/anti-inflammatory properties of apoE. An increasing number of studies in cell lines, targeted replacement rodents and human volunteers indicate higher oxidative stress and a more pro-inflammatory state associated with the epsilon4 allele. The impact of genotype on the antioxidant and immunomodulatory/anti-inflammatory properties of apoE is the focus of the current review. Furthermore, current information on the impact of environment (diet, exercise, smoking status, alcohol) on apoE genotype-phenotype associations are discussed with a view to identifying particular lifestyle strategies that could be adapted to counteract the 'at-risk' E4 genotype.

Gender, a significant factor in the cross talk between genes, environment, and health

BACKGROUND

Although men and women share most genetic information, they have significantly different disease susceptibilities that go well beyond the expected gender-specific diseases. Sex influences the risk of nearly all common diseases that affect both men and women, including atherosclerosis and diabetes and their preceding risk factors (eg, hyperlipidemia, insulin resistance, and obesity).

OBJECTIVE

The goal of this article was to examine the interplay between genes, gender, and disease susceptibility, and assess it in the context of the added complexity of environmental factors (ie, dietary habits, smoking, alcohol consumption) in the modulation of the balance between health and disease.

METHODS

Original and review articles published by the author were reexamined for evidence of gene-gender interactions.

RESULTS

Evidence from some key factors in lipid metabolism (apolipoprotein E [APOE])and obesity (perilipin [PLIN]) indicates that the interplay between genes, gender, and environmental factors modulates disease susceptibility. In the Framingham Heart Study, complex interactions have been shown between a promoter polymorphism at the apolipoprotein A1 gene, gender, and dietary poly-unsaturated fatty acid intake that modulate plasma concentrations of high-density lipoprotein cholesterol. Likewise, highly and clinically relevant interactions have been observed between the APOE gene common alleles APOE2 , APOE3, and APOE4 , gender, and smoking that determine cardiovascular disease risk. Most interesting is the gender-dependent association between common polymorphisms at the PLIN locus and obesity risk that has been replicated in several populations around the world.

CONCLUSIONS

These data support the idea that gender-specific differences in morbidity and mortality may be mediated in part by genetic factors and by their differential response to the environment. The new knowledge generated by a more careful and complete elucidation of the complex interactions predisposing to common diseases will result in an increased ability to provide successful personalized behavioral recommendations to prevent chronic disorders.

Estimating interaction between genetic and environmental risk factors: efficiency of sampling designs within a cohort

Large prospective cohorts originally assembled to study environmental risk factors are increasingly exploited to study gene-environment interactions. Given the cost of genetic studies in large samples, being able to select a subsample for genotyping that contains most of the information from the cohort would lead to substantial savings. We consider nested case-control and case-cohort sampling designs with and without stratification and compare their efficiency relative to the entire cohort for estimating the effects of genetic and environmental risk factors and their interactions. Asymptotic calculations show that the relative efficiency of the case-cohort and nested case-control designs implementing the same sampling stratification are similar over a range of scenarios for the relationships among genes, environmental exposures, and disease status. Sampling equal numbers of exposed and unexposed subjects improves efficiency when the exposure is rare. The case-cohort designs had a slight advantage in simulations of sampling designs within the Framingham Offspring Study, using the interaction between apolipoprotein E and smoking on the risk of coronary heart disease as an example. It was possible to estimate the interaction effect with precision close to that of the full cohort when using case-cohort or nested case-control samples containing fewer than half the subjects of the cohort.

Differential effects of apolipoprotein E3 and E4 on markers of oxidative status in macrophages

ApoE is secreted by macrophages at the lesion site of the atherosclerotic plaque, where it is thought to play a protective role against atherosclerosis independently of its effects on lipid metabolism. Of the three common isoforms for apoE, apoE4 is associated with higher risk of cardiovascular disease (CVD). In vitro studies have shown that recombinant apoE may act as an antioxidant in an isoform-dependent manner (E2 > E3 > E4). The oxidative status of the macrophages plays a key role in the process of atherosclerosis. In the present study the possible differential actions of apoE3 and apoE4 on several parameters of oxidative status were determined in stably transfected murine macrophages (RAW 264-7-apoE3 and - apoE4). No differences between genotypes were observed after peroxide challenge in either protection against cytotoxicity or in cell membrane oxidation, and modest differences were observed in the non-enzymatic antioxidants (glutathione and alpha-tocopherol) in apoE3 v. apoE4 macrophages. Importantly, cells secreting apoE4 showed increased membrane oxidation under basal conditions, and produced more NO and superoxide anion radicals than the apoE3 macrophages after stimulation. The present data suggest that apoE genotype influences the oxidative status of macrophages, and this could partly contribute to the higher CVD risk observed in apoE4 carriers.

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.