Apolipoprotein E4 and coronary heart disease in middle-aged men who smoke: a prospective study

Current Data and New Insights into the Genetic Factors of Atherogenic Dyslipidemia Associated with Metabolic Syndrome

Atherogenic dyslipidemia plays a critical role in the development of metabolic syndrome (MetS), being one of its major components, along with central obesity, insulin resistance, and hypertension. In recent years, the development of molecular genetics techniques and extended analysis at the genome or exome level has led to important progress in the identification of genetic factors (heritability) involved in lipid metabolism disorders associated with MetS. In this review, we have proposed to present the current knowledge related to the genetic etiology of atherogenic dyslipidemia, but also possible challenges for future studies. Data from the literature provided by candidate gene-based association studies or extended studies, such as genome-wide association studies (GWAS) and whole exome sequencing (WES,) have revealed that atherogenic dyslipidemia presents a marked genetic heterogeneity (monogenic or complex, multifactorial). Despite sustained efforts, many of the genetic factors still remain unidentified (missing heritability). In the future, the identification of new genes and the molecular mechanisms by which they intervene in lipid disorders will allow the development of innovative therapies that act on specific targets. In addition, the use of polygenic risk scores (PRS) or specific biomarkers to identify individuals at increased risk of atherogenic dyslipidemia and/or other components of MetS will allow effective preventive measures and personalized therapy.

Human ApoE2 Endows Stronger Contractility in Rat Cardiomyocytes Enhancing Heart Function

(1) Background: Apolipoprotein E (ApoE) is a critical plasma apolipoprotein for lipid transport and nonlipid-related functions. Humans possess three isoforms of ApoE (2, 3, and 4). ApoE2, which exhibits beneficial effects on cardiac health, has not been adequately studied. (2) Methods: We investigated the cardiac phenotypes of the humanized ApoE knock-in (hApoE KI) rats and compared to wild-type (WT) and ApoE knock-out (ApoE KO) rats using echocardiography, ultrasound, blood pressure measurements, histology strategies, cell culture, Seahorse XF, cardiomyocyte contractility and intracellular Ca²⁺ tests, and Western blotting; (3) Results: hApoE2 rats exhibited enhanced heart contractile function without signs of detrimental remodeling. Isolated adult hApoE2 cardiomyocytes had faster and stronger sarcomere contractility because of more mitochondrial energy generation and stimulation-induced fast and elevated intracellular Ca²⁺ transient. The abundant energy is a result of elevated mitochondrial function via fatty acid β-oxidation. The fast and elevated Ca²⁺ transient is associated with decreased sarcoplasmic reticulum (SR) Ca²⁺ ATPase (SERCA2) and increased expression of cardiac ryanodine receptor 2 (RyR2) conducting a potent Ca²⁺ release from SR.; (4) Conclusions: Our studies validated the association of polymorphic ApoEs with cardiac health in the rat model, and revealed the possible mechanisms of the protective effect of ApoE2 against heart diseases.

Etiologic Puzzle of Coronary Artery Disease: How Important Is Genetic Component?

In the modern era, coronary artery disease (CAD) has become the most common form of heart disease and, due to the severity of its clinical manifestations and its acute complications, is a major cause of morbidity and mortality worldwide. The phenotypic variability of CAD is correlated with the complex etiology, multifactorial (caused by the interaction of genetic and environmental factors) but also monogenic. The purpose of this review is to present the genetic factors involved in the etiology of CAD and their relationship to the pathogenic mechanisms of the disease. Method: we analyzed data from the literature, starting with candidate gene-based association studies, then continuing with extensive association studies such as Genome-Wide Association Studies (GWAS) and Whole Exome Sequencing (WES). The results of these studies revealed that the number of genetic factors involved in CAD etiology is impressive. The identification of new genetic factors through GWASs offers new perspectives on understanding the complex pathophysiological mechanisms that determine CAD. In conclusion, deciphering the genetic architecture of CAD by extended genomic analysis (GWAS/WES) will establish new therapeutic targets and lead to the development of new treatments. The identification of individuals at high risk for CAD using polygenic risk scores (PRS) will allow early prophylactic measures and personalized therapy to improve their prognosis.

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.

Contributions of Interactions Between Lifestyle and Genetics on Coronary Artery Disease Risk

PURPOSE OF THE REVIEW

To summarize current knowledge on interactions between genetic variants and lifestyle factors (G×L) associated with the development of coronary artery disease (CAD) and prioritize future research.

RECENT FINDINGS

Genetic risk and combined lifestyle factors and behaviors have a log-additive effect on the risk of developing CAD. First, we describe genetic and lifestyle factors associated with CAD and then focus on G×L interactions. The majority of G×L interaction studies are small-scale candidate gene studies that lack replication and therefore provide spurious results. Only a few studies, of which most use genetic risk scores or genome-wide approaches to test interactions, are robust in number and analysis strategy. These studies provide evidence for the existence of G×L interactions in the development of CAD. Further G×L interactions studies are important as they contribute to our understanding of disease pathophysiology and possibly provide insights for improving interventions or personalized recommendations.

Effects of atorvastatin and/or probucol on recovery of atherosclerosis in high-fat-diet-fed apolipoprotein E-deficient mice

INTRODUCTION

We have investigated the possible effects and mechanism of atorvastatin, a statin, and/or probucol, a powerful antioxidant used to lower cholesterol before 1995, on the atherosclerosis development.

METHODS

Apolipoprotein-E-deficient (ApoE^-/-) mice fed with the high fat diet were randomly divided into 3 groups (n = 10/each group): Placebo, Atorvastatin (10 mg/ kg/d), and atorvastatin (10 mg/kg/d) plus probucol (10 mg/kg/d) groups. C57BL/6 J mice were fed with normal diet as the control group (n = 10). Animals were sacrificed 10 weeks after the intervention. To evaluate the experimental atherosclerosis, blood tests were used for measuring serum lipoprotein profile, Western blots for endoplasmic reticulum (ER) stress protein expression, H&E staining for plaque lesions, immunohistology for macrophages, inflammatory cytokines, innate immune receptor TLR-4, transcription factor NF-κB, and atherosclerosis plaques.

RESULTS

Compared with the control group, ApoE^-/- mice in the placebo group showed with the significantly (p < 0.05) higher levels of serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL) and oxidized low density lipoprotein (ox-LDL), PERK, GRP78, CHOP, IL-1β, TNF-α and NF-κB, but with the lower levels of high-density lipoprotein cholesterol (HDL) and TLR-4, and also the increase in macrophages and the aortic media collagen, and the decrease in the elastic fibers (p < 0.01). Treatment with atorvastatin recovered all these features (p < 0.05 or p < 0.01) near to the levels in the control group. In addition, the combination of atorvastatin and probucol has shown the slightly stronger effect than the use of atorvastatin alone without statistical significances when comparing most bio-markers of atherosclerosis, but with significant differences in the reduction of the plaque lesion areas and macrophages (p < 0.05).

CONCLUSIONS

Atorvastatin and/or probucol suppresses ER stress and increase the level of TLR-4, which lowers NF-κB, resulting in the recovery of atherosclerosis in the ApoE^-/- mouse model.

Tissue-specific Network Analysis of Genetic Variants Associated with Coronary Artery Disease

Coronary artery disease (CAD) is a leading cause of death worldwide. Recent genome-wide association studies have identified more than one hundred susceptibility loci associated with CAD. However, the underlying mechanism of these genetic loci to CAD susceptibility is still largely unknown. We performed a tissue-specific network analysis of CAD using the summary statistics from one of the largest genome-wide association studies. Variant-level associations were summarized into gene-level associations, and a CAD-related interaction network was built using experimentally validated gene interactions and gene coexpression in coronary artery. The network contained 102 genes, of which 53 were significantly associated with CAD. Pathway enrichment analysis revealed that many genes in the network were involved in the regulation of peripheral arteries. In summary, we performed a tissue-specific network analysis and found abnormalities in the peripheral arteries might be an important pathway underlying the pathogenesis of CAD. Future functional characterization might further validate our findings and identify potential therapeutic targets for CAD.

An Overview of Novel Dietary Supplements and Food Ingredients in Patients with Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease

Metabolic syndrome (MetS) is characterized by interconnected factors related to metabolic disturbances, and is directly related to the occurrence of some diseases such as cardiovascular diseases and type 2 diabetes. MetS is described as one or both of insulin resistance and visceral adiposity, considered the initial causes of abnormalities that include hyperglycemia, elevated blood pressure, dyslipidemia, elevated inflammatory markers, and prothrombotic state, as well as polycystic ovarian syndrome in women. Other than in MetS, visceral adiposity and the pro-inflammatory state are also key in the development of non-alcoholic fatty liver disease (NAFLD), which is the most prevalent chronic liver disease in modern society. Both MetS and NAFLD are related to diet and lifestyle, and their treatment may be influenced by dietary pattern changes and the use of certain dietary supplements. This study aimed to review the role of food ingredients and supplements in the management of MetS and NAFLD specifically in human clinical trials. Moreover, bioactive compounds and polyunsaturated fatty acids (PUFAs) may be used as strategies for preventing the onset of and treatment of metabolic disorders, such as MetS and NAFLD, improving the inflammatory state and other comorbidities, such as obesity, dyslipidemias, and cardiovascular diseases (CVD).

Loss of Cardioprotective Effects at the ADAMTS7 Locus as a Result of Gene-Smoking Interactions

BACKGROUND

Common diseases such as coronary heart disease (CHD) are complex in etiology. The interaction of genetic susceptibility with lifestyle factors may play a prominent role. However, gene-lifestyle interactions for CHD have been difficult to identify. Here, we investigate interaction of smoking behavior, a potent lifestyle factor, with genotypes that have been shown to associate with CHD risk.

METHODS

We analyzed data on 60 919 CHD cases and 80 243 controls from 29 studies for gene-smoking interactions for genetic variants at 45 loci previously reported to be associated with CHD risk. We also studied 5 loci associated with smoking behavior. Study-specific gene-smoking interaction effects were calculated and pooled using fixed-effects meta-analyses. Interaction analyses were declared to be significant at a P value of <1.0×10-3 (Bonferroni correction for 50 tests).

RESULTS

We identified novel gene-smoking interaction for a variant upstream of the ADAMTS7 gene. Every T allele of rs7178051 was associated with lower CHD risk by 12% in never-smokers (P=1.3×10-16) in comparison with 5% in ever-smokers (P=2.5×10-4), translating to a 60% loss of CHD protection conferred by this allelic variation in people who smoked tobacco (interaction P value=8.7×10-5). The protective T allele at rs7178051 was also associated with reduced ADAMTS7 expression in human aortic endothelial cells and lymphoblastoid cell lines. Exposure of human coronary artery smooth muscle cells to cigarette smoke extract led to induction of ADAMTS7. CONCLUSIONS: Allelic variation at rs7178051 that associates with reduced ADAMTS7 expression confers stronger CHD protection in never-smokers than in ever-smokers. Increased vascular ADAMTS7 expression may contribute to the loss of CHD protection in smokers.

The influence of ApoE genotype on the lipid profile and lipoproteins during normal pregnancy in a Southern African population

BACKGROUND

Pregnancy is associated with increases in fasting triglycerides and total cholesterol.1 ApoE isoforms are known to influence the concentration of cholesterol, with apoE2 homozygosity lowering and apoE4 homozygosity raising the cholesterol concentration compared with E3 homozygosity.2 The lipid profiles ApoE status and prevalence of small dense LDL species were evaluated for subjects attending an antenatal clinic.

RESULTS

Samples from 690 women aged between 16 and 42 years of age were analyzed during and after pregnancy. The fasting plasma triglyceride concentration (in mmol/L) was significantly higher in pregnancy (median = 1.5, IQR 1.0-2.0 vs median = 0.6, IQR 0.5-0.8 respectively, p < 0.0001). Similarly, the total cholesterol (in mmol/L) was increased during pregnancy (median=4.1, IQR 3.6-4.7 vs median 3.5, IQR 3.1-3.5, respectively p=0.0167). The median LDL cholesterol and HDL cholesterol did not change. Higher proportions of small density LDL species were seen during pregnancy compared to after pregnancy. The distribution of the LDL species during pregnancy and 6 weeks post-partum were significantly different p<0.0001 with the smaller species being much higher during pregnancy.

CONCLUSION

ApoE4 genotype was associated with increased total cholesterol and LDL cholesterol concentrations during pregnancy. Pregnancy results in a reversible remodeling of LDL to smaller species, the significance of which is unknown but may indicate a predisposition to atherosclerosis.

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.

Impact of Genotype on EPA and DHA Status and Responsiveness to Increased Intakes

At a population level, cardioprotective and cognitive actions of the fish oil (FO) derived long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been extensively demonstrated. In addition to dietary intake, which is limited for many individuals, EPA and DHA status is dependent on the efficiency of their biosynthesis from α-linolenic acid. Gender and common gene variants have been identified as influencing the rate-limiting desaturase and elongase enzymes. Response to a particular intake or status is also highly heterogeneous and likely influenced by genetic variants which impact on EPA and DHA metabolism and tissue partitioning, transcription factor activity, or physiological end-point regulation. Here, available literature relating genotype to tissue LC n-3 PUFA status and response to FO intervention is considered. It is concluded that the available evidence is relatively limited, with much of the variability unexplained, though APOE and FADS genotypes are emerging as being important. Although genotype × LC n-3 PUFA interactions have been described for a number of phenotypes, few have been confirmed in independent studies. A more comprehensive understanding of the genetic, physiological and behavioural modulators of EPA and DHA status and response to intervention is needed to allow refinement of current dietary LC n-3 PUFA recommendations and stratification of advice to “vulnerable” and responsive subgroups.

Behavioural Risk Factors in Mid-Life Associated with Successful Ageing, Disability, Dementia and Frailty in Later Life: A Rapid Systematic Review

Background

Smoking, alcohol consumption, poor diet and low levels of physical activity significantly contribute to the burden of illness in developed countries. Whilst the links between specific and multiple risk behaviours and individual chronic conditions are well documented, the impact of these behaviours in mid-life across a range of later life outcomes has yet to be comprehensively assessed. This review aimed to provide an overview of behavioural risk factors in mid-life that are associated with successful ageing and the primary prevention or delay of disability, dementia, frailty and non-communicable chronic conditions.

Methods

A literature search was conducted to identify cohort studies published in English since 2000 up to Dec 2014. Multivariate analyses and a minimum follow-up of five years were required for inclusion. Two reviewers screened titles, abstracts and papers independently. Studies were assessed for quality. Evidence was synthesised by mid-life behavioural risk for a range of late life outcomes.

Findings

This search located 10,338 individual references, of which 164 are included in this review. Follow-up data ranged from five years to 36 years. Outcomes include dementia, frailty, disability and cardiovascular disease. There is consistent evidence of beneficial associations between mid-life physical activity, healthy ageing and disease outcomes. Across all populations studied there is consistent evidence that mid-life smoking has a detrimental effect on health. Evidence specific to alcohol consumption was mixed. Limited, but supportive, evidence was available relating specifically to mid-life diet, leisure and social activities or health inequalities.

Conclusions

There is consistent evidence of associations between mid-life behaviours and a range of late life outcomes. The promotion of physical activity, healthy diet and smoking cessation in all mid-life populations should be encouraged for successful ageing and the prevention of disability and chronic disease.

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).

A systematic review and meta-analysis of 130,000 individuals shows smoking does not modify the association of APOE genotype on risk of coronary heart disease

Background

Conflicting evidence exists on whether smoking acts as an effect modifier of the association between APOE genotype and risk of coronary heart disease (CHD).

Methods and results

We searched PubMed and EMBASE to June 11, 2013 for published studies reporting APOE genotype, smoking status and CHD events and added unpublished data from population cohorts. We tested for presence of effect modification by smoking status in the relationship between APOE genotype and risk of CHD using likelihood ratio test.

In total 13 studies (including unpublished data from eight cohorts) with 10,134 CHD events in 130,004 individuals of European descent were identified. The odds ratio (OR) for CHD risk from APOE genotype (ε4 carriers versus non-carriers) was 1.06 (95% confidence interval (CI): 1.01, 1.12) and for smoking (present vs. past/never smokers) was OR 2.05 (95%CI: 1.95, 2.14). When the association between APOE genotype and CHD was stratified by smoking status, compared to non-ε4 carriers, ε4 carriers had an OR of 1.11 (95%CI: 1.02, 1.21) in 28,789 present smokers and an OR of 1.04 (95%CI 0.98, 1.10) in 101,215 previous/never smokers, with no evidence of effect modification (P-value for heterogeneity = 0.19). Analysis of pack years in individual participant data of >60,000 with adjustment for cardiovascular traits also failed to identify evidence of effect modification.

Conclusions

In the largest analysis to date, we identified no evidence for effect modification by smoking status in the association between APOE genotype and risk of CHD.

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We examined evidence for an interaction between APOE genotype, smoking and risk of coronary heart disease.

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This was conducted in the largest meta-analysis of published and unpublished data sets to date (>130,000 individuals).

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Our analysis did not identify evidence of interaction.

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These findings bring into question presence of a clinically meaningful interaction between APOE genotype and smoking.

Genetic factors may play a prominent role in the development of coronary heart disease dependent on important environmental factors

OBJECTIVE

The aim of the study was to examine whether various lifestyle factors modify genetic influences on coronary heart disease (CHD).

DESIGN

The effect of lifestyle factors [including smoking, sedentary lifestyle, alcohol intake and body mass index (BMI)] on risk of CHD was evaluated via Cox regression models in a twin study of gene-environment interaction. Using structure equation modelling, we estimated genetic variance of CHD dependent on lifestyle factors.

SUBJECTS

In total, 51 065 same-sex twins from 25 715 twin pairs born before 1958 and registered in the Swedish Twin Registry were eligible for this study. During the 40-year follow-up, 7264 incident CHD events were recorded.

RESULTS

Smoking, sedentary lifestyle and above average BMI were significantly associated with increased CHD incidence. The heritability of CHD decreased with increasing age, as well as with increasing levels of BMI, in both men and women.

CONCLUSIONS

The difference in the genetic component of CHD as a function of BMI suggests that genetic factors may play a more prominent role for disease development in the absence of important environmental factors. Increased knowledge of gene-environment interactions will be important for a full understanding of the aetiology of CHD.

Mitochondrial genetic background modulates bioenergetics and susceptibility to acute cardiac volume overload

Dysfunctional bioenergetics has emerged as a key feature in many chronic pathologies such as diabetes and cardiovascular disease. This has led to the mitochondrial paradigm in which it has been proposed that mtDNA sequence variation contributes to disease susceptibility. In the present study we show a novel animal model of mtDNA polymorphisms, the MNX (mitochondrial-nuclear exchange) mouse, in which the mtDNA from the C3H/HeN mouse has been inserted on to the C57/BL6 nuclear background and vice versa to test this concept. Our data show a major contribution of the C57/BL6 mtDNA to the susceptibility to the pathological stress of cardiac volume overload which is independent of the nuclear background. Mitochondria harbouring the C57/BL6J mtDNA generate more ROS (reactive oxygen species) and have a higher mitochondrial membrane potential relative to those with C3H/HeN mtDNA, independent of nuclear background. We propose this is the primary mechanism associated with increased bioenergetic dysfunction in response to volume overload. In summary, these studies support the 'mitochondrial paradigm' for the development of disease susceptibility, and show that the mtDNA modulates cellular bioenergetics, mitochondrial ROS generation and susceptibility to cardiac stress.

Human apolipoprotein E isoforms differentially affect bone mass and turnover in vivo

The primary role of apolipoprotein E (apoE) is to mediate the cellular uptake of lipoproteins. However, a new role for apoE as a regulator of bone metabolism in mice has recently been established. In contrast to mice, the human APOE gene is characterized by three common isoforms APOE ε2, ε3, and ε4 that result in different metabolic properties of the apoE isoforms, but it remains controversial whether the APOE polymorphism influences bone traits in humans. To clarify this, we investigated bone phenotypes of apoE knock-in (k.i.) mice, which express one human isoform each (apoE2 k.i., apoE3 k.i., apoE4 k.i.) in place of the mouse apoE. Analysis of 12-week-old female k.i. mice revealed increased levels of biochemical bone formation and resorption markers in apoE2 k.i. animals as compared to apoE3 k.i. and apoE4 k.i., with a reduced osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) ratio in apoE2 k.i., indicating increased turnover with prevailing resorption in apoE2 k.i. Accordingly, histomorphometric and micro-computed tomography (µCT) analyses demonstrated significantly lower trabecular bone mass in apoE2 than in apoE3 and apoE4 k.i. animals, which was reflected by a significant reduction of lumbar vertebrae maximum force resistance. Unlike trabecular bone, femoral cortical thickness, and stability was not differentially affected by the apoE isoforms. To extend these observations to the human situation, plasma from middle-aged healthy men homozygous for ε2/ε2, ε3/ε3, and ε4/ε4 (n = 21, n = 80, n = 55, respectively) was analyzed with regard to bone turnover markers. In analogy to apoE2 k.i. mice, a lower OPG/RANKL ratio was observed in the serum of ε2/ε2 carriers as compared to ε3/ε3 and ε4/ε4 individuals (p = 0.02 for ε2/ε2 versus ε4/ε4). In conclusion, the current data strongly underline the general importance of apoE as a regulator of bone metabolism and identifies the APOE ε2 allele as a potential genetic risk factor for low trabecular bone mass and vertebral fractures in humans.

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.

The pharmacogenetics of antiretroviral therapy

PURPOSE OF REVIEW

Although the past 20 years have seen many advances in HIV pharmacotherapy, host variability has only been more recently recognized as an important driver of both treatment response and toxicity. This review will focus on the importance of variability in drug metabolizing enzymes and the potential research and clinical applications of these findings in HIV care.

RECENT FINDINGS

The treatment of HIV is complex and involves chronic treatment with multiple drugs and drug classes. Recent research has been important in uncovering genetic differences in drug metabolizing and drug transporter genes, which underpin dose-dependent toxicity and efficacy, but also in genes defining differences in immune response and human leukocyte antigen genes, which restrict processes that are less dependent on the drug dose.

SUMMARY

The advancement of pharmacogenetics will continue to further our knowledge of disease-drug interactions and pathogenesis. Ultimately, the goals of pharmacogenetics and pharmacogenomics in HIV medicine will be the development of the right drugs for the right patient or population. The strong association between HLA-B5701 and abacavir hypersensitivity reaction shows promise for a genetic screening test to be feasibly incorporated into clinical practice. The clinical applicability of many findings demonstrating associations between single nucleotide polymorphisms, particularly in drug metabolism and transporter genes and drug efficacy and toxicity, are currently uncertain.

Pathology supported genetic testing and treatment of cardiovascular disease in middle age for prevention of Alzheimer's disease

Chronic, multi-factorial conditions caused by a complex interaction between genetic and environmental risk factors frequently share common disease mechanisms, as evidenced by an overlap between genetic risk factors for cardiovascular disease (CVD) and Alzheimer's disease (AD). Single nucleotide polymorphisms (SNPs) in several genes including ApoE, MTHFR, HFE and FTO are known to increase the risk of both conditions. The E4 allele of the ApoE polymorphism is the most extensively studied risk factor for AD and increases the risk of coronary heart disease by approximately 40%. It furthermore displays differential therapeutic responses with use of cholesterol-lowering statins and acetylcholinesterase inhibitors, which may also be due to variation in the CYP2D6 gene in some patients. Disease expression may be triggered by gene-environment interaction causing conversion of minor metabolic abnormalities into major brain disease due to cumulative risk. A growing body of evidence supports the assessment and treatment of CVD risk factors in midlife as a preventable cause of cognitive decline, morbidity and mortality in old age. In this review, the concept of pathology supported genetic testing (PSGT) for CVD is described in this context. PSGT combines DNA testing with biochemical measurements to determine gene expression and to monitor response to treatment. The aim is to diagnose treatable disease subtypes of complex disorders, facilitate prevention of cumulative risk and formulate intervention strategies guided from the genetic background. CVD provides a model to address the lifestyle link in most chronic diseases with a genetic component. Similar preventative measures would apply for optimisation of heart and brain health.

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.

The apolipoprotein E polymorphism and cardiovascular diseases--an autopsy study

BACKGROUND

Numerous studies have addressed the association between the apolipoprotein E polymorphism and cardiovascular disease, but only a few reports are based on findings at autopsy. In the present retrospective study, we have used autopsy findings from a general hospital population to further investigate this issue.

METHODS AND RESULTS

We collected information from 1522 consecutive autopsy reports (886 men, mean age 65.7 years; 636 women, mean age 69.7 years) conducted at Oslo University Hospital, Norway, in the period from 1996 to 2000. Cause of death and signs related to cardiovascular disease including the degree of atherosclerosis in the aorta and the coronary arteries, signs of myocardial infarction, heart weight, and signs of cerebrovascular disease were recorded. The patients were genotyped, and the apolipoprotein E allele frequencies (ɛ2, 8.0%; ɛ3, 72.6%; and ɛ4, 19.4%) were not statistically different from a group of healthy controls. Approximately 35% of the patients died from a cardiovascular disease. Genotypes differed significantly (P<.05), with more ɛ4-carriers (34.3% vs. 29.6%) and fewer ɛ2-carriers (11.8% vs. 13.9%) among patients who died from cardiovascular disease compared to those who died from other causes. A similar distribution of genotypes was seen in patients recorded with myocardial infarction or cerebrovascular disease. There was an association between the presence of ɛ4 and atherosclerosis in the aorta and coronary arteries, but this did not reach statistical significance. Among patients with signs of coronary heart disease, standardized heart weights were significantly higher in ɛ2-carriers compared to ɛ4-carriers.

CONCLUSION

The present autopsy study suggests that the risk of developing and dying from cardiovascular disease, including coronary heart disease and cerebrovascular disease, is influenced by the apolipoprotein E polymorphism.

Apolipoprotein E genotype affects tissue metallothionein levels: studies in targeted gene replacement mice

The apolipoprotein E (APOE) genotype is an important risk factor for ageing and age-related diseases. The APOE4 genotype (in contrast to APOE3) has been shown to be associated with oxidative stress and chronic inflammation. Metallothioneins (MT) exhibit antioxidant and anti-inflammatory activity, and MT overexpression has been shown to increase lifespan in mice. Interactions between APOE and MT, however, are largely unknown. Hence, we determined the effect of the APOE4 versus APOE3 genotype on MT levels in targeted gene replacement mice. APOE4 versus APOE3 mice exhibited significantly lower hepatic MT1 and MT2 mRNA as well as lower MT protein levels. The decrease in hepatic MT protein levels in APOE4 as compared to APOE3 mice was accompanied by lower nuclear Nrf1, a protein partly controlling MT gene expression. Cell culture experiments using hepatocytes identified allyl-isothiocyanate (AITC) as a potent MT inductor in vitro. Therefore, we supplemented APOE3 and APOE4 mice with AITC. However, AITC (15 mg/kg b.w.) could only partly correct for decreased MT1 and MT2 gene expression in APOE4 mice in vivo. Furthermore, cholesterol significantly decreased both Nrf1 and MT mRNA levels in Huh7 cells indicating that differences in MT gene expression between the two genotypes could be related to differences in hepatic cholesterol concentrations. Overall, present data suggest that the APOE genotype is an important determinant of tissue MT levels in mice and that MT gene expression may be impaired by the APOE4 genotype.

Apolipoprotein E genotype and the cardiovascular disease risk phenotype: impact of sex and adiposity (the FINGEN study)

Here the impact of APOE genotype on CHD risk in UK adults is reported, along with an analysis of APOE genotype × BMI/age/sex interactions. APOE genotype had a significant impact on fasting total:LDL-cholesterol (TC:LDL-C) ratio, triglycerides, % HDL3, and the Framingham 10-year CVD risk score (P<0.05), with an overall trend towards lower and higher risk in E2- and E4-carriers, respectively, relative to the wild-type E3/E3 genotype. A greater impact of genotype on TC:HDL-C was observed in females, which explained 16% of the variability in this outcome versus 6% in males. APOE genotype was also associated with plasma C-reactive protein and adhesion molecule concentrations (P<0.05), with significant genotype × BMI interactions observed. Our observations indicate that the association between the APOE genotype and CHD risk is unlikely to be homogenous and highlights the risk of inaccurate estimations of genotype-phenotype associations in population subgroups without appropriate stratification for sex and adiposity.

Apolipoprotein isoform E4 does not increase coronary heart disease risk in carriers of low-density lipoprotein receptor mutations

BACKGROUND

In humans, the E4 allele of the apolipoprotein E gene is associated with increased coronary heart disease risk. Surprisingly, in rodents, apolipoprotein E4 only accelerates the atherosclerotic process when transgenic for the human low-density lipoprotein receptor (LDLR) protein. We therefore investigated whether the LDLR locus interacted with the apolipoprotein E gene genotype on coronary heart disease risk in patients clinically diagnosed with familial hypercholesterolemia with and without LDLR mutation. We investigated whether the presence of an LDLR mutation diminishing LDLR function was protective in E4/E4 carriers.

METHODS AND RESULTS

In a cohort of 2400 patients clinically diagnosed with familial hypercholesterolemia, we found an LDLR gene mutation in 1383 patients, whereas in 1013 patients, such mutation was not present. In 92 patients homozygous for the apolipoprotein E4, the presence of an LDLR mutation conferred lower coronary heart disease risk (hazard ratio, 0.16; 95% CI, 0.05-0.58; P=0.005). Mirroring these results, the apolipoprotein E4/E4 genotype was also associated with lower coronary heart disease risk in patients with familial hypercholesterolemia with an LDLR mutation (hazard ratio, 0.26; hazard ratio, 0.08-0.80; P=0.02).

CONCLUSIONS

LDLR function is key to the detrimental effects of apolipoprotein E4 in humans. Kinetic studies in humans are now required to study the consequences of our observation for prevention of both coronary heart disease and Alzheimer disease.

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.

The mitochondrial paradigm for cardiovascular disease susceptibility and cellular function: a complementary concept to Mendelian genetics

While there is general agreement that cardiovascular disease (CVD) development is influenced by a combination of genetic, environmental, and behavioral contributors, the actual mechanistic basis of how these factors initiate or promote CVD development in some individuals while others with identical risk profiles do not, is not clearly understood. This review considers the potential role for mitochondrial genetics and function in determining CVD susceptibility from the standpoint that the original features that molded cellular function were based upon mitochondrial-nuclear relationships established millions of years ago and were likely refined during prehistoric environmental selection events that today, are largely absent. Consequently, contemporary risk factors that influence our susceptibility to a variety of age-related diseases, including CVD were probably not part of the dynamics that defined the processes of mitochondrial-nuclear interaction, and thus, cell function. In this regard, the selective conditions that contributed to cellular functionality and evolution should be given more consideration when interpreting and designing experimental data and strategies. Finally, future studies that probe beyond epidemiologic associations are required. These studies will serve as the initial steps for addressing the provocative concept that contemporary human disease susceptibility is the result of selection events for mitochondrial function that increased chances for prehistoric human survival and reproductive success.

Association between genetic variants in the Coenzyme Q10 metabolism and Coenzyme Q10 status in humans

BACKGROUND

Coenzyme Q10 (CoQ10) is essential for mitochondrial energy production and serves as an antioxidants in extra mitochondrial membranes. The genetics of primary CoQ10 deficiency has been described in several studies, whereas the influence of common genetic variants on CoQ10 status is largely unknown. Here we tested for non-synonymous single-nucleotidepolymorphisms (SNP) in genes involved in the biosynthesis (CoQ3G272S , CoQ6M406V, CoQ7M103T), reduction (NQO1P187S, NQO2L47F) and metabolism (apoE3/4) of CoQ10 and their association with CoQ10 status. For this purpose, CoQ10 serum levels of 54 healthy male volunteers were determined before (T0) and after a 14 days supplementation (T14) with 150 mg/d of the reduced form of CoQ10.

FINDINGS

At T0, the CoQ10 level of heterozygous NQO1P187S carriers were significantly lower than homozygous S/S carriers (0.93 ± 0.25 μM versus 1.34 ± 0.42 μM, p = 0.044). For this polymorphism a structure homology-based method (PolyPhen) revealed a possibly damaging effect on NQO1 protein activity. Furthermore, CoQ10 plasma levels were significantly increased in apoE4/E4 genotype after supplementation in comparison to apoE2/E3 genotype (5.93 ± 0.151 μM versus 4.38 ± 0.792 μM, p = 0.034). Likewise heterozygous CoQ3G272S carriers had higher CoQ10 plasma levels at T14 compared to G/G carriers but this difference did not reach significance (5.30 ± 0.96 μM versus 4.42 ± 1.67 μM, p = 0.082).

CONCLUSIONS

In conclusion, our pilot study provides evidence that NQO1P187S and apoE polymorphisms influence CoQ10 status in humans.

Nrf2-dependent gene expression is affected by the proatherogenic apoE4 genotype-studies in targeted gene replacement mice

An apoE4 genotype is an important risk factor for cardiovascular and other chronic diseases. The higher cardiovascular disease risk of apoE4 carriers as compared to the apoE3 genotype has been mainly attributed to the differences in blood lipids between the two genotype subgroups. Recently, a potential protective role of the transcription factor Nrf2 in cardiovascular disease prevention has been suggested. In this study, we show that Nrf2-dependent gene expression is affected by the apoE genotype. ApoE4 vs. apoE3 mice exhibited lower hepatic Nrf2 nuclear protein levels. Furthermore, mRNA and protein levels of Nrf2 target genes including glutathione-S-transferase, heme oxygenase-1 and NAD(P)H dehydrogenase, quinone 1 were significantly lower in apoE4 as compared to apoE3 mice. Lower hepatic mRNA levels of phase II enzymes, as observed in apoE4 vs. apoE3 mice, were accompanied by higher mRNA levels of phase I enzymes including Cyp26a1 and Cyp3a16. Furthermore, miRNA-144, miRNA-125b, and miRNA-29a involved in Nrf2 signaling, inflammation, and regulation of phase I enzyme gene expression were affected by the apoE genotype. We provide first evidence that Nrf2 is differentially regulated in response to the apoE genotype.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

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.

Use of genotype frequencies in medicated groups to investigate prescribing practice: APOE and statins as a proof of principle

BACKGROUND

If treatments are used to modify a trait, then patients with high-risk genotypes for the trait should be found at higher frequency in treatment groups than in the general population. The frequency ratio of high- to low-risk genotypes treated should reflect the mean threshold above which the treatment is given in the population. As an example, we hypothesized that because APOE (apolipoprotein E) alleles affect the LDL cholesterol (LDLc) concentration, APOE genotype frequencies in statin takers should act as a proxy for the prevailing treatment threshold of LDLc.

METHODS

We used LDLc, statin usage, and APOE genotype data from the British Women's Heart and Health Study (n=2289; age, 60-79 years) and calculated the genotype ratio treatment index (GRTI) by dividing the proportion of ε3/ε2 or ε3/ε4 participants prescribed a statin by the proportion of ε3/ε3 participants prescribed a statin, both overall and according to socioeconomic class, geographic region, and coronary heart disease (CHD) status. Genotype-specific LDLc distributions were used to calculate the mean LDLc treatment threshold.

RESULTS

For genotype ε3/ε2, the GRTI was 0.52 (95% CI, 0.30-0.87) for statin takers overall, 0.22 (95% CI, 0.00-0.56) for those without CHD, and 0.69 (95% CI, 0.31-1.18) for those with CHD. The GRTIs for those without and with CHD backcalculate to LDLc thresholds of 5.65 mmol/L (95% CI, 5.50-5.82 mmol/L) and 4.39 mmol/L (95% CI, 4.21-4.59 mmol/L), respectively. Scotland and North England showed dissimilar GRTIs, which backcalculated to LDLc thresholds of 5.06 mmol/L (95% CI, 4.83-5.28 mmol/L) and 5.44 mmol/L (95% CI, 5.19-5.69 mmol/L), respectively, for all women.

CONCLUSIONS

The findings illustrate how genotype frequencies can be a proxy for treatment thresholds used in clinical practice. Genome-wide studies have identified>500 disease-relevant polymorphisms. GRTIs from cost-efficient genotyping, in combination with phenotypic data, may have wide potential in health services research.

Early institutionalization: neurobiological consequences and genetic modifiers

Children raised in the profound deprivation associated with institutionalization are at elevated risk for negative outcomes across a host of social and cognitive domains. This risk appears to be mitigated by early foster care or adoption into a family setting. Although pervasive developmental problems have been noted in a substantial proportion of previously institutionalized children, marked variation exists in the nature and severity of these deficits. Increasing evidence suggests that institutional deprivation impacts the developing brain, potentially underlying the wide range of outcomes with which it is associated. In the current review we examine the neural consequences of institutionalization and genetic factors associated with differences in outcome in an effort to characterize the consequences of early deprivation at a neurobiological level. Although the effects of institutional deprivation have been studied for more than 50 years much remains unanswered regarding the pathways through which institutionalization impacts child development. Through a more complete and nuanced assessment of the neural correlates of exposure and recovery as well as a better understanding of the individual factors involved we will be better able to delineate the impact of early adversity in the setting of severe social deprivation.

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.

Apolipoprotein E polymorphism and the characteristics of diseased vessels in male Chinese patients with angiographic coronary artery disease: a case-case study

BACKGROUND

Variations in the apolipoprotein E (apo E) gene may predict the incidence of coronary artery disease (CAD). However, the correlation between apo E polymorphism and the severity of CAD is still unclear.

HYPOTHESIS

Apolipoprotein E polymorphism can predict CAD.

METHODS

Used a case-case study of 213 Chinese angiographically-defined CAD patients who were screened for apo E genotypes. The characteristics of their diseased vessels were recorded.

RESULTS

Apolipoprotein E4 carriers had > 75% stenosis, more wide-ranging and longer vessel disease, a greater number of diseased vessels, and a higher Gensini score than apo E2 carriers or individuals with the apo E3/3 genotype. Apolipoprotein E2 carriers had < or =75% stenosis and a shorter length of vessel disease than individuals with the apo E3/3 genotype or apo E4 carriers. The severity of stenosis, length of vessel disease, and number of diseased vessels were affected by the interaction between genotype and body mass index, family history of CAD, total plasma cholesterol level, smoking history, and hypertension history.

CONCLUSION

The apo E4 allele may serve as an independent genetic marker predicting severity of CAD. Other CAD risk factors may accelerate the process of pathogenesis. The apo E2 allele may play a protective role.

Selection on alleles affecting human longevity and late-life disease: the example of apolipoprotein E

It is often claimed that genes affecting health in old age, such as cardiovascular and Alzheimer diseases, are beyond the reach of natural selection. We show in a simulation study based on known genetic (apolipoprotein E) and non-genetic risk factors (gender, diet, smoking, alcohol, exercise) that, because there is a statistical distribution of ages at which these genes exert their influence on morbidity and mortality, the effects of selection are in fact non-negligible. A gradual increase with each generation of the ε2 and ε3 alleles of the gene at the expense of the ε4 allele was predicted from the model. The ε2 allele frequency was found to increase slightly more rapidly than that for ε3, although there was no statistically significant difference between the two. Our result may explain the recent evolutionary history of the epsilon 2, 3 and 4 alleles of the apolipoprotein E gene and has wider relevance for genes affecting human longevity.

Smoking and atherosclerotic cardiovascular disease: Part IV: Genetic markers associated with smoking

Genes influence smoking behavior, affect the metabolism of nicotine and specific chemicals produced during combustion, and enhance (or diminish) pathomechanistic pathways associated with the atherogenic potential of smoking, including oxidative stress, its inflammatory burden or procoagulant potential. Genome-wide association studies have revolutionized the search for new functional genetic markers with ever increasing marker density and the precision in identifying new genetic loci without the need for prior knowledge of functional pathways. Nevertheless, the statistical challenge remains to identify the few true positives, the need for replication of findings and the tedious work of identifying functional genetic variants and their mode of action. Genetic variation within a gene or in areas of the genetic code that control the expression of such a gene is far from being understood. Major advances include the detection of large-scale copy-number variants in the human genome and the demonstration of the decisive role of ‘miRNA’ in controlling gene expression. The role of the genomic methylation pattern in controlling the transcription of the underlying genetic sequence and its role in interacting with environmental influences have yet to be explored in depth. Although candidate genes and their genetic variants have been associated with atherosclerosis and cigarette smoking, a major breakthrough has still to be made.

Serum lipid and blood pressure responses to quercetin vary in overweight patients by apolipoprotein E genotype

Our objective was to examine the effect of a quercetin supplementation on blood pressure, lipid metabolism, markers of oxidative stress, inflammation, and body composition in an at-risk population of 93 overweight-obese volunteers aged 25-65 y with metabolic syndrome traits in relation to apolipoprotein (apo) E genotype. Participants were randomized to receive 150 mg/d quercetin in a double-blinded, placebo-controlled, crossover trial with 6-wk treatment periods separated by a 5-wk washout period. Retrospectively, 5 apoE genotype variants were found (epsilon2/epsilon3, n = 3; epsilon3/epsilon3, n = 60; epsilon3/epsilon4, n = 23; epsilon2/epsilon4, n = 4; and epsilon4/epsilon4, n = 3). Participants were classified into the following 3 apoE phenotypes: apoE2 (n = 3), apoE3 (n = 60), and apoE4 (n = 26). Data were analyzed for apoE3 and apoE4 subgroups. Quercetin decreased systolic blood pressure by 3.4 mm Hg (P < 0.01) in the apoE3 group, whereas no significant effect was observed in the apoE4 group. Quercetin decreased serum HDL cholesterol (P < 0.01) and apoA1 (P < 0.01) and increased the LDL:HDL cholesterol ratio (P < 0.05) in the apoE4 subgroup, whereas the apoE3 subgroup had no significant changes in these variables. Quercetin significantly decreased plasma oxidized LDL and tumor necrosis factor-alpha in the apoE3 and apoE4 groups, whereas no significant inter-group differences were found. Serum C-reactive protein and nutritional status (body weight, waist circumference, fat mass, fat-free mass) were unaffected compared with placebo. In conclusion, quercetin exhibited blood pressure-lowering effects in overweight-obese carriers of the apo epsilon3/epsilon3 genotype but not in carriers of the epsilon4 allele. Furthermore, quercetin supplementation resulted in a reduction in HDL cholesterol and apoA1 in apo epsilon4 carriers.

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.