Apolipoprotein E Genotype and Cardiovascular Diseases in the Elderly

Meta-Analysis of White Matter Hyperintensity Volume Differences Between APOE ε4 Carriers and Noncarriers

Several studies have suggested that white matter hyperintensity volume (WMHV) is increased among apolipoprotein E (APOE) ε4 carriers while others have reported contradictory findings. Although APOE ε4 carriage is associated with greater AD pathology, it remains unclear whether cerebrovascular damage is also associated with APOE ε4 carriage. The aim of this meta-analysis was to determine whether WMHV is associated with APOE ε4 carrier status. 12 studies that were included yielded a total sample size of 16,738 adult subjects (ε4 carrier n = 4,721; ε4 noncarrier n = 12,017). There were no significant differences in WMHV between ε4 carriers and noncarriers (Hedge's g = 0.07; 95% CI (-0.01 to 0.15), P = 0.09). Subgroup analysis of community-based studies (n = 8) indicated a small effect size where ε4 carriers had greater WMHV relative to noncarriers (Hedge's g = 0.09 95% CI (0.02 to 0.16), P = 0.008). Among clinic-based studies (n = 3) there was no significant difference in WMHV by APOE ε4 carrier status (Hedge's g = -0.09, 95% CI (-0.60 to 0.41), P = 0.70). Observed APOE ε4-associated WMHV differences may be context-dependent and may also be confounded by a lack of standardization for WMHV segmentation.

Systolic Blood Pressure Is Associated with Increased Brain Amyloid Load in Mild Cognitively Impaired Participants: Alzheimer's Disease Neuroimaging Initiatives Study

BACKGROUND

Cardiovascular disease (CVD), including elevated blood pressure (BP), is known to promote Alzheimer's disease (AD) risk. Although brain amyloid load is a recognized hallmark of pre-symptomatic AD, its relationship to increased BP is less known. The objective of this study was to examine the relationship of BP to brain estimates of amyloid-β (Aβ) and standard uptake ratio (SUVr). We hypothesized that increased BP is associated with increased SUVr.

METHODS

Using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), we stratified BP according to the Seventh Joint National Committee (JNC) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure Classification (JNC VII). Florbetapir (AV-45) SUVr was derived from the averaged frontal, anterior cingulate, precuneus, and parietal cortex relative to the cerebellum. A linear mixed-effects model enabled the elucidation of amyloid SUVr relationships to BP. The model discounted the effects of demographics, biologics, and diagnosis at baseline within APOE genotype groups. The least squares means procedure was used to estimate the fixed-effect means. All analyses were performed using the Statistical Analysis System (SAS).

RESULTS

In non-ɛ4 carrier MCI subjects, escalating JNC categories of BP was associated with increasing mean SUVr using JNC-4 as a reference point (low-normal (JNC1) p = 0.018; normal (JNC-1) p = 0.039; JNC-2 p = 0.018 and JNC-3 p = 0.04). A significantly higher brain SUVr was associated with increasing BP despite adjustment for demographics and biological variables in non-ɛ4 carriers but not in ɛ4-carriers. This observation supports the view that CVD risk may promote increased brain amyloid load, and potentially, amyloid-mediated cognitive decline.

CONCLUSION

Increasing levels of JNC classification of BP is dynamically associated with significant changes in brain amyloid burden in non-ɛ4 carriers but not in ɛ4-carrier MCI subjects. Though not statistically significant, amyloid burden tended to decrease with increasing BP in ɛ4 homozygote, perhaps motivated by increased vascular resistance and the need for higher brain perfusion pressure.

APOE Effects on Late Life Cognitive Trajectories in Diverse Racial/Ethnic Groups

OBJECTIVE

This study evaluated: (1) apolipoprotein E (APOE) ϵ4 prevalence among Black, Latino, and White older adults, (2) associations of APOE ϵ4 status with baseline level and change over time of cognitive outcomes across groups, and (3) combined impact of APOE ϵ4 prevalence and magnitude of effect on cognitive decline within each racial/ethnic group.

METHOD

Participants included 297 White, 138 Latino, and 149 Black individuals from the longitudinal UC Davis Diversity Cohort who had APOE genotyping and ≥2 cognitive assessments. Magnitude of associations of ϵ4 with cognitive baseline and change across racial/ethnic groups was tested with multilevel parallel process longitudinal analyses and multiple group models.

RESULTS

ϵ4 prevalence in Black (46%) and White participants (46%) was almost double that of Latino participants (24%). ϵ4 was associated with poorer baseline episodic memory only in White participants (p = .001), but had a moderately strong association with episodic memory change across all racial/ethnic groups (Blacks= -.061 SD/year, Latinos = -.055,Whites= -.055). ϵ4 association with semantic memory change was strongest in White participants (-.071), intermediate in Latino participants (-.041), and weakest in Black participants (-.022).

CONCLUSION

Calculated cognitive trajectories across racial/ethnic groups were influenced in an additive manner by ϵ4 prevalence and strength of association with cognitive decline within the group. Group differences in ϵ4 prevalences and associations of ϵ4 with cognition may suggest different pathways from APOE to cognitive decline, and, AD possibly having less salient impact on cognitive decline in non-White participants. Differential effects of APOE on episodic memory and non-memory cognition have important implications for understanding how APOE influences late life cognitive decline.

APOE genotype, hippocampus, and cognitive markers of Alzheimer's disease in American Indians: Data from the Strong Heart Study

BACKGROUND

The apolipoprotein E (APOE) ε4 allele confers higher risk of neurodegeneration and Alzheimer's disease (AD), but differs by race/ethnicity. We examined this association in American Indians.

METHODS

The Strong Heart Study is a population-based cohort of American Indians who were 64 to 95 years of age in 2010 to 2013. APOE ε4 status, brain imaging, and neuropsychological testing was collected in N = 811 individuals. Summary statistics, graphics, and generalized linear regressions-adjusted for sociodemographics, clinical features, and intracranial volume with bootstrap variance estimator-compared APOE ε4 carriers with non-carriers.

RESULTS

APOE ε4 carriers comprised 22% of the population (0.7% homozygotes). Participants were mean 73 years, 67% female, and 54% had some college education. The majority were obese (>50%), hypertensive (>80%), and diabetic (>50%). Neither imaging findings nor multidomain cognitive testing showed any substantive differences between APOE ε4 carriers and non-carriers.

CONCLUSION

We found no evidence of neurodegenerative risk from APOE ε4 in American Indians. Additional studies are needed to examine potential protective features.

Associations between race, APOE genotype, cognition, and mortality among urban middle-aged white and African American adults

We examined associations between cognition and mortality and how these relationships vary by race and Apolipoprotein E (APOE) genotype, in a longitudinal study of 2346 middle-aged White and African American adults (30–64 years at baseline) from the Healthy Aging in Neighborhoods of Diversity across the Life Span cohort study. Baseline cognition spanned global mental status, and several domains obtained using principal components analysis (PCA; PCA1: verbal memory/fluency; PCA2: attention/working memory; PCA3: executive function/visuo-spatial abilities). Cox regression models evaluated associations between cognition and all-cause and cardiovascular disease (CVD)-mortality. Interactions between cognition and APOE2 as well as APOE4 allelic dose were tested, and race was a key effect modifier. Higher APOE4 dose was associated with increased CVD-mortality (hazard ratio [HR] per allele = 1.37; 95% CI 1.01–1.86, p = 0.041); APOE2 dosage’s association with CVD-mortality was non-significant (HR = 0.60; 95% CI 0.35–1.03, p = 0.065). Higher PCA3 was associated with lower all-cause (HR = 0.93; 95% CI 0.87–0.99, p = 0.030) and CVD (HR = 0.85; 95% CI 0.77–0.95, p = 0.001) mortality risks, the latter association being more pronounced among Whites. PCA2 interacted synergistically with APOE2 dosage, reducing risks for all-cause mortality (PCA2 × APOE2: − 0.33 ± 0.13, p = 0.010) and CVD mortality (PCA2 × APOE2: − 0.73 ± 0.31, p = 0.019). In conclusion, greater executive function/visuo-spatial abilities were associated with reduced CVD-specific mortality, particularly among Whites. Greater “attention/working memory” coupled with higher APOE2 dosage was linked with reduced all-cause and CVD mortality risks.

Race, APOE genotypes, and cognitive decline among middle-aged urban adults

Background

Associations of Apolipoprotein (APOE) ε2 or ε4 (APOE2 or APOE4) dosages with cognitive change may differ across racial groups.

Methods

Longitudinal data on 1770 middle-aged White and African American adults was compiled from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS 2004-2013) study. APOE2 and APOE4 dosages were the two main exposures, while v₁ and annual rate of change in cognitive performance (between v₁ and v₂) on 11 test scores were the main outcomes of interest (v1: 2004–2009 and v2: 2009–2013). Mixed-effects linear regression models were conducted adjusting for socio-demographic, lifestyle, and health-related potential confounders. Race (African American vs. White) and sex within racial groups were main effect modifiers.

Results

Upon adjustment for multiple testing and potential confounders, APOE4 allelic dosage was associated with faster decline on a test of verbal memory among Whites only (CVLT-List A: γ₁₂ = − 0.363 ± 0.137, p = 0.008), but not among African Americans. In contrast, among African American women, APOE4 dosage was linked to slower decline on a test of attention (BTA: γ₁₂ = + 0.106 ± 0.035, p = 0.002), while no association was detected among African American men. APOE2 and APOE4 dosages showed inconsistent results in other domains of cognition overall and across racial groups that did not survive correction for multiple testing.

Conclusions

In conclusion, APOE4 dosage was associated with faster decline on a test of verbal memory among Whites only, while exhibiting a potential protective effect among African American women in the domain of attention. Further longitudinal studies are needed to replicate our race and sex-specific findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00855-y.

Associations of APOE e2 genotype with cerebrovascular pathology: a postmortem study of 1275 brains

OBJECTIVE

We assessed the association of apolipoprotein E (APOE) genotype with cerebrovascular disease (CVD) in a large neuropathological database maintained by the National Alzheimer's Coordinating Center (NACC). Such a comprehensive investigation of APOE and CVD pathology has not heretofore been conducted. We focused on APOE e2, an established neuroprotective genetic variant against Alzheimer's disease.

METHODS

To implement these objectives APOE associations in the NACC database of 1275 brains with 11 CVD pathologies, including old and recent infarcts, haemorrhages, cerebral amyloid angiopathy (CAA) and arteriosclerosis, were examined. These pathologies were uniformly and semiquantitatively measured across 39 Alzheimer's Disease Center sites. We used χ2 statistics and ordinal regression to assess the significance of associations and Bonferroni corrected for multiple comparisons.

RESULTS

Of the cases, 98 were e2/e3 or e2/e2 genotypes ('e2' carriers), 621 were e3 homozygotes ('e3' group), and 556 were e4/e3 (442) or e4/e4 (114) genotypes ('e4' group). Results indicated that the APOE e4 allele significantly increased risk for CAA. After stratification by CAA presence/absence, we found that in those cases in which CAA was present, APOE e2 significantly increased risk for gross haemorrhage. All other associations were negative.

CONCLUSIONS

In this, the largest study of APOE e2 effects on pathologically verified CVD, e2 was not protective against any CVD pathology compared with e3 homozygotes, including CAA. Regarding the latter pathology, e4 was associated with increases in its severity. Furthermore, and perhaps unexpectedly, e2 significantly increased risk of acute/subacute gross haemorrhage in the presence of CAA. Thus, there were limits to e2 neuroprotection against amyloidosis, despite its known and large protective effects against diffuse and neuritic amyloid plaques compared with e3/e3 and e4 carriers in this very collection.

Identification of Dysregulated Genes for Late-Onset Alzheimer's Disease Using Gene Expression Data in Brain

BACKGROUND

Alzheimer's Disease (AD) is a neurodegenerative complex brain disease that represents a public health concern. AD is considered the fifth leading cause of death in Americans who are older than 65 years which prioritizes the importance of understanding the etiology of AD in its early stages before the onset of symptoms. This study attempted to further understand Alzheimer's disease (AD) etiology by investigating the dysregulated genes using gene expression data from multiple brain regions.

METHODS

A linear mixed-effects model for differential gene expression analysis was used in a sample of 15 AD and 30 control subjects, each with data from four different brain regions, in order to deal with the hierarchical multilevel data. Post-hoc Gene Ontology and pathway enrichment analyses provided insights on the biological implications in AD progression. Supervised machine learning algorithms were used to assess the discriminative power of the top 10 candidate genes in distinguishing between the two groups.

RESULTS

Enrichment analyses revealed biological processes and pathways that are related to structural constituents and organization of the axons and synapses. These biological processes and pathways imply dysfunctional axon and synaptic transmission between neuronal cells in AD. Random Forest classification algorithm gave the best accuracy on the test data with F1-score of 0.88.

CONCLUSION

The differentially expressed genes were associated with axon and synaptic transmissions which affect the neuronal connectivity in cognitive systems involved in AD pathophysiology. These genes may open ways to explore new effective treatments and early diagnosis before the onset of clinical symptoms.

Use of an Exposome Approach to Understand the Effects of Exposures From the Natural, Built, and Social Environments on Cardio-Vascular Disease Onset, Progression, and Outcomes

Obesity, diabetes, and hypertension have increased by epidemic proportions in recent years among African Americans in comparison to Whites resulting in significant adverse cardiovascular disease (CVD) disparities. Today, African Americans are 30% more likely to die of heart disease than Whites and twice as likely to have a stroke. The causes of these disparities are not yet well-understood. Improved methods for identifying underlying risk factors is a critical first step toward reducing Black:White CVD disparities. This article will focus on environmental exposures in the external environment and how they can lead to changes at the cellular, molecular, and organ level to increase the personal risk for CVD and lead to population level CVD racial disparities. The external environment is defined in three broad domains: natural (air, water, land), built (places you live, work, and play) and social (social, demographic, economic, and political). We will describe how environmental exposures in the natural, built, and social environments "get under the skin" to affect gene expression though epigenetic, pan-omics, and related mechanisms that lead to increased risk for adverse CVD health outcomes and population level disparities. We also will examine the important role of metabolomics, proteomics, transcriptomics, genomics, and epigenomics in understanding how exposures in the natural, built, and social environments lead to CVD disparities with implications for clinical, public health, and policy interventions. In this review, we apply an exposome approach to Black:White CVD racial disparities. The exposome is a measure of all the exposures of an individual across the life course and the relationship of those exposures to health effects. The exposome represents the totality of exogenous (external) and endogenous (internal) exposures from conception onwards, simultaneously distinguishing, characterizing, and quantifying etiologic, mediating, moderating, and co-occurring risk and protective factors and their relationship to disease. Specifically, it assesses the biological mechanisms and underlying pathways through which chemical and non-chemical environmental exposures are associated with CVD onset, progression and outcomes. The exposome is a promising approach for understanding the complex relationships among environment, behavior, biology, genetics, and disease phenotypes that underlie population level, Black: White CVD disparities.

Lipoprotein(a) and Its Potential Association with Thrombosis and Inflammation in COVID-19: a Testable Hypothesis

PURPOSE OF REVIEW

The COVID-19 pandemic has infected over > 11 million as of today people worldwide and is associated with significant cardiovascular manifestations, particularly in subjects with preexisting comorbidities and cardiovascular risk factors. Recently, a predisposition for arterial and venous thromboses has been reported in COVID-19 infection. We hypothesize that besides conventional risk factors, subjects with elevated lipoprotein(a) (Lp(a)) may have a particularly high risk of developing cardiovascular complications.

RECENT FINDINGS

The Lp(a) molecule has the propensity for inhibiting endogenous fibrinolysis through its apolipoprotein(a) component and for enhancing proinflammatory effects such as through its content of oxidized phospholipids. The LPA gene contains an interleukin-6 (IL-6) response element that may induce an acute phase-type increase in Lp(a) levels following a cytokine storm from COVID-19. Thus, subjects with either baseline elevated Lp(a) or those who have an increase following COVID-19 infection, or both, may be at very high risk of developing thromboses. Elevated Lp(a) may also lead to acute destabilization of preexisting but quiescent atherosclerotic plaques, which might induce acute myocardial infarction and stroke. Ongoing studies with IL-6 antagonists may be informative in understanding this relationship, and registries are being initiated to measure Lp(a) in subjects infected with COVID-19. If indeed an association is suggestive of being causal, consideration can be given to systematic testing of Lp(a) and prophylactic systemic anticoagulation in infected inpatients. Therapeutic lipid apheresis and pharmacotherapy for the reduction of Lp(a) levels may minimize thrombogenic potential and proinflammatory effects. We propose studies to test the hypothesis that Lp(a) may contribute to cardiovascular complications of COVID-19.

Inhibition of Lung Tumor Development in ApoE Knockout Mice via Enhancement of TREM-1 Dependent NK Cell Cytotoxicity

Apolipoprotein E (ApoE) is known to regulate lipid homeostasis and associated with atherosclerogenesis. Eventhough atherosclerogenesis is associated with tumor development, the role of ApoE in lung tumorigenesis and metastasis is not clear. Thus, the tumor growth and metastasis were compared in WT and ApoE knockout (KO) mice. Urethane-induced lung tumor incidence and B16F10 lung metastasis in ApoE knockout (KO) mice were significantly reduced in comparison to that in WT mice. Knockdown of ApoE expression in lung cancer cells and B16F10 cells also decreased cancer cell growth and metastasis. The inhibitory effect of ApoE KO on tumor development and metastasis was associated with increase of infiltration of NK cells. NK cells derived from ApoE KO mice showed much greater cytotoxicity than those from WT mice. These cytotoxic effect of NK cells derived from ApoE KO mice was associated with higher expression of Granzyme B, Fas Ligand, IFN-γ, TNF-α, NKG2D, NKp46, and DNAM-1 expression. Triggering receptor expressed on myeloid cell (TREM)-1 is a proinflammatory mediator expressed on NK cells, and is known to be associated with NK cell cytotoxicity. Thus, we investigated the role of TREM-1 on ApoE KO mice originated NK cell mediated cytotoxicity for cancer cells. Blockade of TREM-1 expression with a TREM-1 antagonist prevented NK cell-mediated cytotoxicity. TREM-1 antibody recovered cytotoxic effect of NK cells derived from KO mice of T-bet, which upregulating gene for TREM-1. These data indicate that ApoE KO suppressed lung tumor development and metastasis via increase of TREM-1-dependent anti-tumor activity of NK cells.

Diabetes Is Associated with Cognitive Decline in Middle-Aged Patients

BACKGROUND

Diabetes is a major contributor to dementia in the elderly. Identifying mild cognitive decline in younger individuals with diabetes could aid in preventing the progression of the disease. The aim of our study is to compare whether patients with diabetes experience greater cognitive decline than those without diabetes.

METHODS

We conducted a cross-sectional study using population-based recruitment to identify a cohort of individuals with diabetes and corresponding control group without diabetes of 55-65 years of age. We defined diabetes according to the American Diabetes Association and conducted a battery of standardized neuropsychological tests consisting of nine verbal and nonverbal tasks assessing three cognitive domains. We defined cognitive decline as an abnormal test in one or more of the domains. We used hierarchical regression to predict abnormal cognitive function by diabetes status, adjusting for gender, education, hypertension, and depression.

RESULTS

We included 142 patients with diabetes and 167 control group patients. Those with diabetes had a mean age of 59 ± 4 years, 54% were women, the mean education level was 11 ± 4.5 years of schooling, and their hemoglobin A1c was 8.6 ± 2.5. They had an overall lower mean of all five executive function measures, all seven attention measures, and all five memory measures (P < 0.05). In multivariate analyses, all executive function beta coefficients for diabetes were significant, whereas attention had four out of seven and memory had four out of five.

CONCLUSIONS

Diabetes is associated with cognitive decline in younger patients with diabetes. Preventive strategies should be developed for the prevention of dementia in younger populations.

APOE ε4 Modulation of Training Outcomes in Several Cognitive Domains in a Sample of Cognitively Intact Older Adults

BACKGROUND

Most research points to the ɛ4 allele of the apolipoprotein E (APOE) gene as the most recognizable genetic risk factor associated with Alzheimer's disease pathogenesis. It has been also suggested that the APOEɛ4 allele has a negative influence on cognitive functioning, which begins long before cognitive impairment becomes manifest. However, still, little is known about the APOEɛ4 interaction with cognitive intervention programs.

OBJECTIVE

The main goal of this study was to explore whether there was a differential APOE genotype modulation effect after cognitive training in different domains, such as language comprehension, executive functions, and memory. Contrary to other studies, hippocampal volume was controlled for.

METHODS

Fifty older adults (65+ years; 30 women and 20 men) participated in a multi-domain cognitive training that involved 30 sessions taking place over 12 weeks. Half of the participants were APOEɛ4 carriers. The control group was matched in age, gender, normalized hippocampal volume, cognitive reserve, Mini-Mental State Examination score, and Geriatric Depression Scale-Short Version.

RESULTS

The study revealed that there were consistent treatment benefits in complex sentence comprehension (noncanonical sentences and sentences with two propositions), a domain that was not directly trained, but only in the A POEɛ4 noncarrier group.

CONCLUSION

Genetic profile modulates training outcomes in sentence comprehension.

Update on the laboratory investigation of dyslipidemias

The role of the clinical laboratory is evolving to provide more information to clinicians to assess cardiovascular disease (CVD) risk and target therapy more effectively. Current routine methods to measure LDL-cholesterol (LDL-C), the Friedewald calculation, ultracentrifugation, electrophoresis and homogeneous direct methods have established limitations. Studies suggest that LDL and HDL size or particle concentration are alternative methods to predict future CVD risk. At this time there is no consensus role for lipoprotein particle or subclasses in CVD risk assessment. LDL and HDL particle concentration are measured by several methods, namely gradient gel electrophoresis, ultracentrifugation-vertical auto profile, nuclear magnetic resonance and ion mobility. It has been suggested that HDL functional assays may be better predictors of CVD risk. To assess the issue of lipoprotein subclasses/particles and HDL function as potential CVD risk markers robust, simple, validated analytical methods are required. In patients with small dense LDL particles, even a perfect measure of LDL-C will not reflect LDL particle concentration. Non-HDL-C is an alternative measurement and includes VLDL and CM remnant cholesterol and LDL-C. However, apolipoprotein B measurement may more accurately reflect LDL particle numbers. Non-fasting lipid measurements have many practical advantages. Defining thresholds for treatment with new measurements of CVD risk remain a challenge. In families with genetic variants, ApoCIII and lipoprotein (a) may be additional risk factors. Recognition of familial causes of dyslipidemias and diagnosis in childhood will result in early treatment. This review discusses the limitations in current laboratory technologies to predict CVD risk and reviews the evidence for emergent approaches using newer biomarkers in clinical practice.

Cognitive and motor functioning in elderly glucocerebrosidase mutation carriers

Mutations in the glucocerebrosidase (GBA) gene are a strong genetic risk factor for the development of Parkinson's disease and dementia with Lewy Bodies. However the penetrance of GBA mutations is low for these diseases in heterozygous carriers. The aim of this study was to examine the relationship between mutation status and cognitive and motor functioning in a sample of community-dwelling older adults. Using linear mixed effects models, we examined the effect of heterozygous mutation status on 736 community-dwelling older adults (≥70 years) without dementia or Parkinson's disease assessed over an average of 6 years, 28 of whom had a single GBA mutation (primarily N370S). Verbal memory was measured using the picture version of the Free and Cued Selective Reminding Test, and carriers showed significantly (p < 0.05) greater decline in verbal memory over time. There was no difference in motor function or any other cognitive domain. Taken together, these results suggest an effect, but an overall limited burden, of harboring a single GBA mutation in aging mutation carriers.

Etiologic Framework for the Study of Neurodegenerative Disorders as Well as Vascular and Metabolic Comorbidities on the Grounds of Shared Epidemiologic and Biologic Features

Background: During the last two decades, protein aggregation at all organismal levels, from viruses to humans, has emerged from a neglected area of protein science to become a central issue in biology and biomedicine. This article constitutes a risk-based review aimed at supporting an etiologic scenario of selected, sporadic, protein-associated, i.e., conformational, neurodegenerative disorders (NDDs), and their vascular- and metabolic-associated ailments.

Methods: A rationale is adopted, to incorporate selected clinical data and results from animal-model research, complementing epidemiologic evidences reported in two prior articles.

Findings: Theory is formulated assuming an underlying conformational transmission mechanism, mediated either by horizontal transfer of mammalian genes coding for specific aggregation-prone proteins, or by xeno-templating between bacterial and host proteins. We build a few population-based and experimentally-testable hypotheses focusing on: (1) non-disposable surgical instruments for sporadic Creutzfeldt-Jakob disease (sCJD) and other rapid progressive neurodegenerative dementia (sRPNDd), multiple system atrophy (MSA), and motor neuron disease (MND); and (2) specific bacterial infections such as B. pertussis and E. coli for all forms, but particularly for late-life sporadic conformational, NDDs, type 2 diabetes mellitus (T2DM), and atherosclerosis where natural protein fibrils present in such organisms as a result of adaptation to the human host induce prion-like mechanisms.

Conclusion: Implications for cohort alignment and experimental animal research are discussed and research lines proposed.

Can APOE and MTHFR polymorphisms have an influence on the severity of cardiovascular manifestations in Italian Pseudoxanthoma elasticum affected patients?

Background

The clinical phenotype of Pseudoxanthoma elasticum (PXE) affected patients, although progressive with age, is very heterogeneous, even in the presence of identical ABCC6 mutations, thus suggesting the occurrence of modifier genes. Beside typical skin manifestations, the cardiovascular (CV) system, and especially the peripheral vasculature, is frequently and prematurely compromised.

Methods and results

A cohort of 119 Italian PXE patients has been characterized for apolipoprotein E (APOE) and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms by PCR. The severity of the clinical phenotype has been quantified according to the Phenodex PXE International score system. Statistical analysis (chi² test, odd ratio, regression analysis, analysis of variance) were done by GraphPad. Data demonstrate that the frequency of APOE alleles is similar in PXE patients and in healthy subjects and that the allelic variant E2 confers a protection against the age-related increase of CV manifestations. By contrast, PXE patients are characterized by high frequency of the MTHFR-T677T polymorphism. With age, CV manifestations in T677T, but also in C677T, patients are more severe than those associated with the C677C genotype. Interestingly, compound heterozygosity for C677T and A1298C polymorphisms is present in 70% of PXE patients.

Conclusions

PXE patients may be screened for these polymorphisms in order to support clinicians for a better management of disease-associated CV complications.

Fatty acid metabolism in carriers of apolipoprotein E epsilon 4 allele: is it contributing to higher risk of cognitive decline and coronary heart disease?

Apolipoprotein E (ApoE) is a protein playing a pivotal role in lipid homeostasis since it regulates cholesterol, triglyceride and phospholipid metabolism in the blood and the brain. APOE gene regulates the expression of this protein and has three different alleles: ε2, ε3 and ε4. Carrying an APOE4 allele is recognised as a genetic risk factor of late-onset Alzheimer’s disease (LOAD) and coronary heart disease (CHD). Consuming fatty fish, rich in long chain omega-3 fatty acids (LC omega-3), seems to be associated with risk reduction of developing LOAD and CHD but this link seems not to hold in APOE4 carriers, at least in LOAD. In CHD trials, APOE4 carriers supplemented with LC omega-3 were categorized as differential responders to the treatment with regards to CHD risk markers. This is potentially because fatty acid metabolism is disturbed in APOE4 carriers compared to the non-carriers. More specifically, homeostasis of LC omega-3 is disrupted in carriers of APOE4 allele and this is potentially because they β-oxidize more LC omega-3 than the non-carriers. Therefore, there is a potential shift in fatty acid selection for β-oxidation towards LC omega-3 which are usually highly preserved for incorporation into cell membranes.

Role of APOE genotype in gait decline and disability in aging

OBJECTIVES

Although apolipoprotein E (APOE) genetic variation may influence risk of gait decline and disability in aging through multiple mechanisms, a systematic examination of this relationship has been lacking. Our objective was to quantify the risk of gait decline and disability associated with the APOE ε4 allele in aging.

METHODS

We evaluated 627 community-dwelling adults aged 70 and older (white 67.8%) with APOE genotype and quantitative gait measurements participating in the Einstein Aging Study over a median follow-up of 3.0 years. Main outcomes were gait speed decline (cm/s/year) and incident disability.

RESULTS

APOE ε4 allele frequency was 24.1%. Presence of APOE ε4 was not significantly associated with gait speed decline overall (p = .37) but was associated with faster gait speed decline in older men (estimate: -1.16, 95% CI: -2.31 to -0.01, p = .04). The interaction between the ε4 allele and male sex predicted gait speed decline (estimate: -1.70, 95% CI: -3.33 to -0.07, p = .04). Presence of the APOE ε4 allele was associated with increased risk of disability in older men (HR 3.72, 95% CI: 1.44-9.59, p = .007). Associations of the ε4 allele with study outcomes remained significant even after accounting for several potential confounders including vascular and cognitive status. The strength of the associations was stronger in the white subgroup.

CONCLUSION

This preliminary report suggests that the APOE ε4 allele is associated with increased risk of gait speed decline and disability in older men.

Risk factors for β-amyloid deposition in healthy aging: vascular and genetic effects

IMPORTANCE

Identifying risk factors for increased β-amyloid (Aβ) deposition is important for targeting individuals most at risk for developing Alzheimer disease and informing clinical practice concerning prevention and early detection.

OBJECTIVE

To investigate risk factors for Aβ deposition in cognitively healthy middle-aged and older adults. Specifically, we hypothesized that individuals with a vascular risk factor such as hypertension, in combination with a genetic risk factor for Alzheimer disease (apolipoprotein E ε4 allele), would show greater amyloid burden than those without such risk.

DESIGN

Cross-sectional study.

SETTING

General community.

PARTICIPANTS

One hundred eighteen well-screened and cognitively normal adults, aged 47 to 89 years. Participants were classified in the hypertension group if they reported a medical diagnosis of hypertension or if blood pressure exceeded 140 mm Hg systolic/90 mm Hg diastolic, as measured across 7 occasions at the time of study.

INTERVENTION

Participants underwent Aβ positron emission tomography imaging with radiotracer fluorine 18-labeled florbetapir. Participants were genotyped for apolipoprotein E and were classified as ε4(+) or ε4(-).

MAIN OUTCOME MEASURE

Amyloid burden.

RESULTS

Participants in the hypertension group with at least 1 ε4 allele showed significantly greater amyloid burden than those with only 1 risk factor or no risk factors. Furthermore, increased pulse pressure was strongly associated with increased mean cortical amyloid level for subjects with at least 1 ε4 allele.

CONCLUSIONS AND RELEVANCE

Vascular disease is a prevalent age-related condition that is highly responsive to both behavioral modification and medical treatment. Proper control and prevention of risk factors such as hypertension earlier in the life span may be one potential mechanism to ameliorate or delay neuropathological brain changes with aging.

KIF6 719Arg allele is associated with statin effects on cholesterol levels in amnestic mild cognitive impairment and Alzheimer's disease patients

KIF6 719Arg allele carriers are thought to have a greater lipid lowering response from statin therapy than non-carriers. Given the continued interest in the relationship between cholesterol, statin use, amnestic mild cognitive impairment (aMCI), and Alzheimer's disease (AD), investigating the role of KIF6 719Arg carrier status in these relationships may be of importance. Data from 86 patients (36 aMCI, 50 AD) with an average age of 76.87 ± 8.22 years were used for this study. Total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL), and triglycerides were the outcome variables. 719Arg carriers taking statins had significantly lower TC (p < 0.001) and LDL (p < 0.001) levels than 719Arg carriers not taking statins. In addition, 719Arg carriers not taking statins had significantly higher TC (p = 0.004) and LDL (p < 0.001) than 719Arg non-carriers taking statins. Additional analyses indicated that ApoE ε4 carrier status and statin use interaction is also associated with lower TC (p = 0.04), but not LDL (p = 0.06). The interaction between 719Arg and ApoE ε4 carrier status on TC and LDL was not significant. This study is the first to demonstrate an association between lower cholesterol levels and statin use among KIF6 719Arg allele carriers with aMCI and AD. Accounting for 719Arg carrier status may be important in future studies investigating the link between cholesterol and AD and also for AD and aMCI clinical trials using statins as a treatment.

Age-related trends of blood pressure levels by apolipoprotein E genotype: the Bambuì Cohort Study of Ageing (1997-2008)

The role of apolipoprotein E (apoE) polymorphisms in regulating blood pressure (BP) is still not clear. The aim of this study was to examine longitudinal changes in BP levels by apoE genotypes in a population-based prospective cohort of elderly subjects, and explore interactions with plasma lipids and uric acid. Subjects whose apoE genes had been genotyped at baseline (1408, representing 80.8% of all the elderly residents in Bambuì city, south-eastern Brazil; age range 60-95 years) were included in the analysis. Repeated BP measurements were obtained in four waves. Multi-level random-effects pattern-mixture models were used to evaluate the age-related BP trajectories, accounting for non-ignorable dropouts/deaths and handling heterogeneities as random parameter variations. Subjects with the ɛ4/4 genotype and high levels of low-density lipoprotein cholesterol had higher systolic BP levels at 60 years of age than those with the other genotypes (154.5 vs. 133.2 mm Hg, P=0.020), but this was not the case among the older subjects. Systolic BP increased more rapidly with age in the ɛ2 carriers, leading to significantly higher levels among the oldest. This relationship seemed to be modulated by uric acid levels, as it was present in the subjects with the ɛ2/3 genotype and high uric acid levels, and in those with the ɛ2/4 genotype and low or normal uric acid levels. The differences in systolic BP between the genotypes were age dependent, and the shift between the ɛ4 and ɛ2 alleles suggest that these alleles are involved in the different mechanisms leading to increased BP in middle-aged and elderly subjects.

Age-related differences in memory and executive functions in healthy APOE ɛ4 carriers: the contribution of individual differences in prefrontal volumes and systolic blood pressure

Advanced age and vascular risk are associated with declines in the volumes of multiple brain regions, especially the prefrontal cortex, and the hippocampus. Older adults, even unencumbered by declining health, perform less well than their younger counterparts in multiple cognitive domains, such as episodic memory, executive functions, and speed of perceptual processing. Presence of a known genetic risk factor for cognitive decline and vascular disease, the ɛ4 allele of the apolipoprotein E (APOE) gene, accounts for some share of those declines; however, the extent of the joint contribution of genetic and physiological vascular risk factors on the aging brain and cognition is unclear. In a sample of healthy adults (age 19-77), we examined the effects of a vascular risk indicator (systolic blood pressure, SBP) and volumes of hippocampus (HC), lateral prefrontal cortex (lPFC), and prefrontal white matter (pFWM) on processing speed, working memory (WM), and recognition memory. Using path analyses, we modeled indirect effects of age, SBP, and brain volumes on processing speed, WM, and memory and compared the patterns of structural relations among those variables in APOE ɛ4 carriers and ɛ3 homozygotes. Among ɛ4 carriers, age differences in WM were explained by increase in SBP, reduced FWM volume, and slower processing. In contrast, lPFC and FWM volumes, but not BP, explained a share of age differences in WM among ɛ3 homozygotes. Thus, even in healthy older carriers of the APOE ɛ4 allele, clinically unremarkable increase in vascular risk may be associated with reduced frontal volumes and impaired cognitive functions.

Should mild cognitive impairment be subtyped?

PURPOSE OF REVIEW

To review evidence on the validity and utility of recent approaches to subtyping late-life mild cognitive impairment.

RECENT FINDINGS

There is growing evidence that amnestic mild cognitive impairment is associated with biomarkers for Alzheimer's disease, while nonamnestic mild cognitive impairment maps more closely to cerebrovascular disease. The former is more likely to progress to dementia than the latter. Mild impairment in multiple cognitive domains appears to represent a more advanced disease state than single-domain impairment, and is more likely to progress to dementia. The cognitive subtypes have imprecise boundaries and have limited ecological validity. Approaches to subtyping that also incorporate biomarkers increase diagnostic specificity and have greater predictive value. However, these approaches have yet to be validated outside specialized memory clinic populations.

SUMMARY

Mild cognitive impairment as currently defined is still etiologically and prognostically heterogeneous, particularly outside specialty clinical settings. The objective of further subtyping is to delineate subgroups that are more clinically homogeneous. The current cognitive subtypes have some validity and utility but additional approaches should be explored so as to enhance these properties.