Health-protective and adverse effects of the apolipoprotein E epsilon2 allele in older men

Protective role of the apolipoprotein E2 allele in age-related disease traits and survival: evidence from the Long Life Family Study

The apolipoprotein E (apoE) is a classic example of a gene exhibiting pleiotropism. We examine potential pleiotropic associations of the apoE2 allele in three biodemographic cohorts of long-living individuals, offspring, and spouses from the Long Life Family Study, and intermediate mechanisms, which can link this allele with age-related phenotypes. We focused on age-related macular degeneration, bronchitis, asthma, pneumonia, stroke, creatinine, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, diseases of heart (HD), cancer, and survival. Our analysis detected favorable associations of the ε2 allele with lower LDL-C levels, lower risks of HD, and better survival. The ε2 allele was associated with LDL-C in each gender and biodemographic cohort, including long-living individuals, offspring, and spouses, resulting in highly significant association in the entire sample (β = -7.1, p = 6.6 × 10^-44). This allele was significantly associated with HD in long-living individuals and offspring (relative risk [RR] = 0.60, p = 3.1 × 10^-6) but this association was not mediated by LDL-C. The protective effect on survival was specific for long-living women but it was not explained by LDL-C and HD in the adjusted model (RR = 0.70, p = 2.1 × 10^-2). These results show that ε2 allele may favorably influence LDL-C, HD, and survival through three mechanisms. Two of them (HD- and survival-related) are pronounced in the long-living parents and their offspring; the survival-related mechanism is also sensitive to gender. The LDL-C-related mechanism appears to be independent of these factors. Insights into mechanisms linking ε2 allele with age-related phenotypes given biodemographic structure of the population studied may benefit translation of genetic discoveries to health care and personalized medicine.

Apolipoprotein E polymorphism and functional disability in Brazilian elders: the Bambuí Health and Aging Study

Numerous studies have associated the apolipoprotein E (apoE) ε4 allele with worse health status, but few have assessed the existence of genotype-dependent variations in functional performance. Among participants in the Bambuí Health and Aging Study, Minas Gerais State, Brazil, 1,408 elderly underwent apoE genotyping. Functionality was assessed with a questionnaire, and individuals were classified as dependent in basic activities of daily living (BADLs), instrumental activities of daily living (IADLs), and mobility. The association between apoE genotype and functional status was assessed by logistic regression, taking confounding factors into account. Presence of ε4 allele was associated with lower odds of mobility deficit (OR = 0.65; 95%CI: 0.47-0.92) in the adjusted analysis. There were no significant differences in relation to presence of dependency in BADLs and IADLs. The reasons are not entirely understood, but they may involve the role of ε4 allele as a "thrifty gene" in a sample exposed to high risk of infectious and nutritional diseases in the past.

Trade-offs in the effects of the apolipoprotein E polymorphism on risks of diseases of the heart, cancer, and neurodegenerative disorders: insights on mechanisms from the Long Life Family Study

The lack of evolutionary established mechanisms linking genes to age-related traits makes the problem of genetic susceptibility to health span inherently complex. One complicating factor is genetic trade-off. Here we focused on long-living participants of the Long Life Family Study (LLFS), their offspring, and spouses to: (1) Elucidate whether trade-offs in the effect of the apolipoprotein E e4 allele documented in the Framingham Heart Study (FHS) are a more general phenomenon, and (2) explore potential mechanisms generating age- and gender-specific trade-offs in the effect of the e4 allele on cancer, diseases of the heart, and neurodegenerative disorders assessed retrospectively in the LLFS populations. The e4 allele can diminish risks of cancer and diseases of the heart and confer risks of diseases of the heart in a sex-, age-, and LLFS-population-specific manner. A protective effect against cancer is seen in older long-living men and, potentially, their sons (>75 years, relative risk [RR]>75=0.48, p=0.086), which resembles our findings in the FHS. The protective effect against diseases of the heart is limited to long-living older men (RR>76=0.50, p=0.016), as well. A detrimental effect against diseases of the heart is characteristic for a normal LLFS population of male spouses and is specific for myocardial infarction (RR=3.07, p=2.1×10(-3)). These trade-offs are likely associated with two inherently different mechanisms, including disease-specific (detrimental; characteristic for a normal male population) and systemic, aging-related (protective; characteristic for older long-living men) mechanisms. The e4 allele confers risks of neurological disorders in men and women (RR=1.98, p=0.046). The results highlight the complex role of the e4 allele in genetic susceptibility to health span.

Causal relevance of circulating high-density lipoprotein cholesterol with cancer: a Mendelian randomization meta-analysis

We summarized published data on the associations of apolipoprotein E (APOE) gene ε2/ε3/ε4 polymorphism with both cancer risk and circulating lipid profiles, aiming to examine the causal relevance between lipids and cancer risk. Article identification and data abstraction were conducted in duplicate and independently by two authors. Data were analyzed by STATA software. Twenty-five articles that examined the associations of APOE gene ε2/ε3/ε4 polymorphism with either cancer risk (n = 22) or circulating lipid changes (n = 4) were eligible. The presence of ε2 and ε4 alleles showed no overall associations with overall cancer risk when compared with ε3 allele. The ε4 allele was significantly associated with 1.40-fold (odds ratio or OR = 1.40; 95% confidence interval or CI: 1.00–1.94; P = 0.047) increased risk of developing cancer in Asian populations, and the presence of heterogeneity was low (I² = 37.6%). Carriers of ε3/ε4 genotype had a significant reduction in circulating HDL-C (WMD = −2.62; 95% CI: −4.19 to −1.04; P = 0.001) without heterogeneity (I² = 16.6%). The predicted odds of having cancer for 1 mg/dL reduction in circulating HDL-C was 1.14 (95% CI: 1.00 to 1.89). The findings of this Mendelian randomization meta-analysis demonstrate that reduced circulating HDL-C might be a potentially causal risk factor for the development of overall cancer in Asians.

Unraveling genetic origin of aging-related traits: evolving concepts

Discovering the genetic origin of aging-related traits could greatly advance strategies aiming to extend health span. The results of genome-wide association studies (GWAS) addressing this problem are controversial, and new genetic concepts have been fostered to advance the progress in the field. A limitation of GWAS and new genetic concepts is that they do not thoroughly address specifics of aging-related traits. Integration of theoretical concepts in genetics and aging research with empirical evidence from different disciplines highlights the conceptual problems in studies of genetic origin of aging-related traits. To address these problems, novel approaches of systemic nature are required. These approaches should adopt the non-deterministic nature of linkage of genes with aging-related traits and, consequently, reinforce research strategies for improving our understanding of mechanisms shaping genetic effects on these traits. Investigation of mechanisms will help determine conditions that activate specific genetic variants or profiles and explore to what extent these conditions that shape genetic effects are conserved across human lives and generations.

Association between apolipoprotein E genotype and cancer susceptibility: a meta-analysis

BACKGROUND

Apolipoprotein E (ApoE), a protein primarily involved in lipoprotein metabolism, occurs in three isoforms (E2, E3 and E4). Studies evaluating the association between APOE genotype and incidence of malignancies have given inconclusive results.

OBJECTIVE

The objective of the present study was to analyze the association between APOE genotype and incidence of cancer by a meta-analysis.

METHODS

We conducted a literature search in the electronic databases for studies with information on APOE genotype in malignancies. Sixteen studies (14 case-control and 2 cohort; 77,970 controls and 12,010 cases) were included for the present meta-analysis. Pooled odds ratios (OR) with 95 % confidence intervals (CI) were calculated assuming a random-effect model for all the genotypes and alleles. Subgroup analyses based on study design, ethnicity of populations, site of cancer and source of controls were performed as a post hoc measure. Appropriate tests to detect heterogeneity, publication bias and sensitivity were done at all stages. The review protocol is registered with the PROSPERO database vide registration number CRD42013006496.

RESULTS

The pooled effect measure for the comparisons did not reveal an association in primary analyses. In the subgroup analyses, we observed a negative association between APOE4+ genotypes and overall risk of cancer in the cohort study subgroup (pooled OR 0.86; 95 % CI 0.82-0.91; p < 0.00001; I (2) = 0 %). Sensitivity analyses did not alter the overall pooled effect measure, and there were no evidences to suggest a publication bias.

CONCLUSION

Overall, the present meta-analysis did not show any association between APOE alleles and genotypes with incidence of cancer in general.

Trade-off in the effect of the APOE gene on the ages at onset of cardiocascular disease and cancer across ages, gender, and human generations

Decades of studies of candidate genes show their complex role in aging-related traits. We focus on apolipoprotein E e2/3/4 polymorphism and ages at onset of cardiovascular diseases (CVD) and cancer in the parental and offspring generations of the Framingham Heart Study participants to gain insights on the role of age and gender across generations in genetic trade-offs. The analyses show that the apolipoprotein E e4 allele carriers live longer lives without cancer than the non-e4 allele carriers in each generation. The role of the e4 allele in onset of CVD is age- and generation-specific, constituting two modes of sexually dimorphic genetic trade-offs. In offspring, the e4 allele confers risk of CVD primarily in women and can protect against cancer primarily in men of the same age. In the parental generation, genetic trade-off is seen in different age groups, with a protective role of the e4 allele against cancer in older men and its detrimental role in CVD in younger women. The puzzling complexity of genetic mechanisms working in different genders, ages, and environments calls for more detail and systemic analyses beyond those adapted in current large-scale genetic association studies.

Connections between apolipoprotein E genotypes and the development of cardiovascular diseases

Elevated plasma lipid level is one of the main risk factors for cardiovascular diseases, which are considered to be pimary causes of death. Apolipoprotein E plays a part in the lipid transport in the blood, thus polimophisms of that affect the lipid composition of the plasma. The three most common alleles of apolipoprotein E are e2, e3, e4. Out of the two non-wild type alleles, the e2 and e4, the latter was shown to play a role in the development of cardiovascular diseases and Alzheimer’s disease. Some studies mention the e2/e2 homozygote genotype as one of the causes of hyperlipoproteinemia type III. Besides lipid metabolism, apolipoprotein E also influences the manifestation of cardiovascular diseases through other biochemical pathways, therefore it is essential to explore the molecular background of these metabolic pathways. Orv. Hetil., 2012, 153, 2070–2076.

ApoE and quality of life in nonagenarians

OBJECTIVES

ApoE ε4 is associated with adverse health conditions that negatively impact the quality of life (QOL). The relationship between ApoE ε4 and QOL has not been explored in the oldest old. Our study aimed to examine ApoE in the oldest old and explore its association with QOL.

DESIGN

Cross-sectional cohort study.

SETTING

A medium sized community in Olmsted County, Minnesota.

PARTICIPANTS

Individuals aged 90 to 99 years, living independently or in long term care environments.

MEASUREMENTS

We collected demographic information and measured cognitive function (Short Test of Mental Status, Mini-Mental State Examination, Mattis Dementia Rating Scale), QOL (Linear Analogue Self Assessment), and ApoE distribution. Subjects were classified as cognitively normal, mild cognitive impairment, dementia, or dementia with stroke and/or parkinsonism (DEMSP). Regression model was used to assess the predictors of QOL.

RESULTS

A total of 121 subjects (45 cognitively normal, 13 with mild cognitive impairment, 34 with dementia, 29 DEMSP) aged 90-99 years, 106 (87.6 %) females, were included. Frequency of ApoE ε3 allele was highest (194 [80.2%]: ε2/3 18, ε3/3 77, ε3/4 22) followed by ApoE ε4 (25 [10.3%]: ε2/4 3, ε3/4 22) and ApoE ε2 (23 [9.5%; ε2/2 1, ε2/3 18, ε2/4 3). None of the subjects carried ApoE ε4/4 genotype. QOL was similar between ApoE ε4 carrier and noncarriers. Physical well-being, emotional well-being, intellectual well-being, social connectedness, and coping ability were positively associated with QOL, whereas male sex, DEMSP, pain frequency, and pain severity were negatively associated.

CONCLUSIONS

The most common ApoE in the oldest old was ε3/3 genotype and ε3 allele. No association was found between ApoE ε4 and QOL. However, those with high physical, emotional and intellectual well being, social connectedness, and coping ability had the highest overall QOL.

Acute exercise stress activates Nrf2/ARE signaling and promotes antioxidant mechanisms in the myocardium

Oxidative stress has been implicated in the pathogenesis of cardiovascular diseases, including myocardial hypertrophy and infarction. Although impairment of antioxidant defense mechanisms has been thought to provoke oxidative stress-induced myocardial dysfunction, it has been difficult to clearly demonstrate. Nuclear erythroid 2 p45-related factor 2 (Nrf2) is a redox-sensitive, basic leucine zipper protein that regulates the transcription of several antioxidant genes. We previously reported that sustained activation of Nrf2 upregulates transcription of a number of endogenous antioxidants in the heart. Here, we show that acute exercise stress (AES) results in activation of Nrf2/ARE (antioxidant response element) signaling and subsequent enhancement of antioxidant defense pathways in wild-type (WT) mouse hearts, while oxidative stress, along with blunted defense mechanisms, was observed in Nrf2-/- mice. We also find that AES is associated with increased trans-activation of ARE-containing genes in exercised animals when compared to age-matched sedentary WT mice. However, enhanced oxidative stress in response to AES was observed in Nrf2-/- mice due to lower basal expression and marked attenuation of the transcriptional induction of several antioxidant genes. Thus, AES induces ROS and promotes Nrf2 function, but disruption of Nrf2 increases susceptibility of the myocardium to oxidative stress. Our findings suggest the basis for a nonpharmacological approach to activate Nrf2/ARE signaling, which might be a potential therapeutic target to protect the heart from oxidative stress-induced cardiovascular complications.

Potential peripheral biomarkers for the diagnosis of Alzheimer's disease

Advances in the discovery of a peripheral biomarker for the diagnosis of Alzheimer's would provide a way to better detect the onset of this debilitating disease in a manner that is both noninvasive and universally available. This paper examines the current approaches that are being used to discover potential biomarker candidates available in the periphery. The search for a peripheral biomarker that could be utilized diagnostically has resulted in an extensive amount of studies that employ several biological approaches, including the assessment of tissues, genomics, proteomics, epigenetics, and metabolomics. Although a definitive biomarker has yet to be confirmed, advances in the understanding of the mechanisms of the disease and major susceptibility factors have been uncovered and reveal promising possibilities for the future discovery of a useful biomarker.

Angiotensin-converting enzyme (ACE) genotypes and disability in hospitalized older patients

The association between angiotensin-converting enzyme (ACE) genotypes and functional decline in older adults remains controversial. To assess if ACE gene variations influences functional abilities at older age, the present study explored the association between the common ACE insertion/deletion (I/D) polymorphism and disability measured with activities of daily living (ADL) in hospitalized older patients. We analyzed the frequency of the ACE genotypes (I/I, I/D, and D/D) in a population of 2,128 hospitalized older patients divided according to presence or absence of ADL disability. Logistic regression analysis adjusted for possible confounding factors, identified an association between the I/I genotype with ADL disability (OR=1.54, 95% CI 1.04-2.29). This association was significant in men (OR=2.01, 95% CI 1.07-3.78), but not in women (OR=1.36, 95% CI 0.82-2.25). These results suggested a possible role of the ACE polymorphism as a genetic marker for ADL disability in hospitalized older patients.

Apolipoprotein E-related all-cause mortality in hospitalized elderly patients

The most common apolipoprotein E (APOE) allelic variation is implicated in many age-related diseases and human longevity with controversial findings. We investigated the effect of APOE gene polymorphism on all-cause mortality in elderly patients taking into consideration the functional disability, cognitive impairment, malnutrition, and the occurrence of common age-related diseases. APOE genotypes were determined in 2,124 geriatric hospitalized patients (46.5% men and 53.5% women; mean age, 78.2 +/- 7.1 years; range, 65-100 years). At hospital admission, all patients underwent a comprehensive geriatric assessment to evaluate functional disability, cognitive status, nutritional status, and comorbidity. The main and secondary diagnoses at hospital discharge were also recorded. Mortality status was evaluated in all patients after a maximum follow-up of 5 years (range, from 1.26 to 5.23 years; median, 2.86 years). During the study period, 671 patients died (32.0%). At hospital admission, these patients showed a significant higher prevalence of cardiovascular diseases (56.3% vs 53.4%; p = 0.007), neoplasias (32.3% vs 13.7%; p < 0.001), and lower prevalence of neurodegenerative diseases (17.7% vs 20.7%; p < 0.001) than survived patients. Moreover, they also showed an higher prevalence of disability (52.0% vs 25.6%; p < 0.001), cognitive impairment (31.0% vs 18.8%; p < 0.001), and malnutrition (74.0% vs 46.1%; p < 0.001) than survived patients. In the overall study population, the APOE epsilon2 allele was significantly associated to neurodegenerative diseases (odds ratio = 0.59; 95% confidence interval (CI), 0.37-0.94). No significant association between the APOE polymorphism and disability, malnutrition, co-morbidity status, and with all-cause mortality was observed. In patients with cardiovascular diseases, however, a decreased risk of all-cause mortality was found in the epsilon2 allele carriers (hazard ratio = 0.56; 95% CI, 0.36-0.88). In this population, APOE allele variants might play a role on cardiovascular disease-related mortality.

Leukocyte telomere length is associated with disability in older u.s. Population

OBJECTIVES

To determine whether mean leukocyte telomere length (LTL) serves as a biomarker of disability assessed according to activities of daily living (ADLs) and what factors may modify this relationship.

DESIGN

Retrospective cross-sectional study.

SETTING

A subset of the National Long Term Care Survey (NTLCS), a Medicare-based U.S. population longitudinal study focused on trends of overall health and functional status in older adults.

PARTICIPANTS

Six hundred and twenty-four individuals from the 1999 wave of the NTLCS cohort.

MEASUREMENTS

Relative LTL determined according to quantitative polymerase chain reaction. LTL has previously been shown to correlate with common age-related disorders and mortality, as well as with socioeconomic status.

RESULTS

A sex difference in LTL was observed but not age-dependent shortening or association with socioeconomic status. LTL was associated with disability and functional status assessed according to ADLs. The association between ADLs and LTL was stronger in subjects without diabetes mellitus, whereas associations were not seen when only subjects with diabetes mellitus were analyzed. Associations between LTL and cardiovascular disease (CVD) and cancer were also present in the group without diabetes mellitus but not in the group with diabetes mellitus.

CONCLUSION

These findings support the concept that LTL is a biomarker of overall well-being that is predictive of disability of older individuals in the U.S. population. Diabetes mellitus plays an important role as a modifier of the association between LTL and disability, CVD, and cancer. These associations have clinical implications because of the potential predictive value of LTL and deserve further investigation.

Comparative study of apolipoprotein-E polymorphism and plasma lipid levels in dyslipidemic and asymptomatic subjects, and their implication in cardio/cerebro-vascular disorders

Polymorphisms in the apolipoprotein-E (apoE) gene may modulate lipoprotein metabolism at different steps and influence total and low density lipoprotein (LDL) cholesterol (LDLc) levels, as well as other lipid features. Population studies have documented significant differences in the frequency of apoE alleles which are related to the prevalence of various cardio-vascular and neuro-psychiatric diseases. In this study, the apoE genotypes and allele frequencies were analyzed in 216 individuals (109 dyslipidemic and 107 normo-lipidic subjects), and the relative contribution of apoE polymorphism on plasma lipid and lipoprotein levels, as well as risk factors was evaluated. In normo-lipidic volunteers, the frequencies of epsilon2, epsilon3 and epsilon4 alleles were 0.042, 0.832 and 0.126, while in dyslipidemic subjects 0.046, 0.835 and 0.119, respectively. No significant difference was observed among epsilon2, epsilon3 or epsilon4 and plasma lipid-lipoprotein levels in the dyslipidemic group. In normo-lipidemics, however, total cholesterol, LDLc and non-HDLc plasma levels were significantly lower in epsilon2 subjects when compared to epsilon3 and epsilon4 individuals. The allelic frequencies of apoE epsilon2, epsilon3 and epsilon4 were similar in dyslipidemic and normo-lipemic subjects, suggesting that apoE polymorphisms have no effect on plasma lipid-lipoprotein levels in dyslipidemic subjects. In contrast, in normo-lipemic subjects the epsilon2 allele showed to be associated with lower total cholesterol and LDLc levels, the mark of a better lipid profile. Depending on other co-existing factors, the epsilon2 allele, therefore, may play either a protective or pathogenic role. This elementary knowledge is a fundamental prerequisite for a possible diagnostic application of these lipoproteins as biomarkers to predict adverse cardio-vascular and/or neuro-psychiatric maladies.

Plasma biomarkers for mild cognitive impairment and Alzheimer's disease

PURPOSE OF REVIEW

With the move toward development of disease modifying treatments, there is a need for more specific diagnosis of early Alzheimer's disease (AD) and mild cognitive impairment (MCI), plasma biomarkers are likely to play an important role in this. We review the current state of knowledge on plasma biomarkers for MCI and AD, including unbiased proteomics and very recent longitudinal studies.

RECENT FINDINGS

With the use of proteomics methodologies, some proteins have been identified as potential biomarkers in plasma and serum of AD patients, including alpha-1-antitrypsin, complement factor H, alpha-2-macroglobulin, apolipoprotein J, apolipoprotein A-I. The findings of cross-sectional studies of plasma amyloid beta (A beta) levels are conflicting, but some recent longitudinal studies have shown that low plasma A beta 1-42 or A beta 1-40 levels, or A beta 1-42/A beta 1-40 ratio may be markers of cognitive decline. Other potential biomarkers for MCI and AD reflecting a variety of pathophysiological processes have been assessed, including isoprostanes and homocysteine (oxidative stress), total cholesterol and ApoE4 allele (lipoprotein metabolism), and cytokines and acute phase proteins (inflammation). A panel of 18 signal proteins was reported as markers of MCI and AD.

SUMMARY

A variety of potential plasma biomarkers for AD and MCI have been identified, however the findings need replication in longitudinal studies. This area of research promises to yield interesting results in the near future.