Apolipoprotein E epsilon4 allele frequency in vascular dementia

APOE4 is a Risk Factor and Potential Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease, the main pathological hallmark of which is the loss of neurons, resulting in cognitive and memory impairments. Sporadic late-onset AD is a prevalent form of the disease and the apolipoprotein E4 (APOE4) genotype is the strongest predictor of the disease development. The structural variations of APOE isoforms affect their roles in synaptic maintenance, lipid trafficking, energy metabolism, inflammatory response, and BBB integrity. In the context of AD, APOE isoforms variously control the key pathological elements of the disease, including Aβ plaque formation, tau aggregation, and neuroinflammation. Taking into consideration the limited number of therapy choices that can alleviate symptoms and have little impact on the AD etiology and progression to date, the precise research strategies guided by apolipoprotein E (APOE) polymorphisms are required to assess the potential risk of age-related cognitive decline in people carrying APOE4 genotype. In this review, we summarize the evidence implicating the significance of APOE isoforms on brain functions in health and pathology with the aim to identify the possible targets that should be addressed to prevent AD manifestation in individuals with the APOE4 genotype and to explore proper treatment strategies.

The Value of Brain Structural Magnetic Resonance Imaging Combined with APOE--ε4 Genotype in Early Diagnosis and Disease Progression of Senile Vascular Cognitive Impairment No Dementia

Objective

To explore the value of brain structure magnetic resonance imaging combined with APOE-ε4 genotype in the early diagnosis and disease progression of elderly patients with vascular cognitive impairment no dementia (VCIND).

Methods

The first stroke patients admitted to our hospital from March 2017 to December 2018 were collected, including 130 cases of vascular cognitive impairment no dementia (VCIND group) and 50 cases of the control group (NC group). The basic information of all subjects was recorded, and APOE-ε4 alleles of all subjects were detected. The neuropsychological test scale evaluated the cognitive psychology of the subjects, and they were scanned by multi-parameter MRI. After follow-up, VCIND patients were divided into the dementia group and the nondementia group. MRI scans were again performed, and the risk factors of VCIND patients developing dementia were analyzed.

Results

Compared with the NC group, patients in the VCIND group had shorter years of education, more patients with hypertension, higher levels of homocysteine (Hcy), and lower cognitive ability. Patients with White Matter Volume (WMV), White Matter Hyperintensity (WMH), Lacunar Infarction (LI), elevated Fazekas scores, and APOE-ε4 gene carriers are more likely to develop VCIND. After 12 months of follow-up, compared with the nondementia group, the number of WMV, WMH, Fazekas scores, and APOE-ε4 gene carriers in the dementia group was significantly increased. In addition, the progression-free survival rate of APOE-ε4 gene carriers was significantly lower than that of nonAPOE-ε4 gene carriers.

Conclusion

Years of education, hypertension, high levels of Hcy, elevated WMV, WMH, LI, and Fazekas scores, and carrying the APOE-ε4 gene are risk factors for VCIND in stroke patients. Craniocerebral structural MRI combined with APOE-ε4 genotype has a diagnostic role in the early diagnosis and disease progression of elderly patients with VCIND.

ApoE Cascade Hypothesis in the pathogenesis of Alzheimer's disease and related dementias

The ε4 allele of the apolipoprotein E gene (APOE4) is a strong genetic risk factor for Alzheimer's disease (AD) and several other neurodegenerative conditions, including Lewy body dementia (LBD). The three APOE alleles encode protein isoforms that differ from one another only at amino acid positions 112 and 158: apoE2 (C112, C158), apoE3 (C112, R158), and apoE4 (R112, R158). Despite progress, it remains unclear how these small amino acid differences in apoE sequence among the three isoforms lead to profound effects on aging and disease-related pathways. Here, we propose a novel "ApoE Cascade Hypothesis" in AD and age-related cognitive decline, which states that the biochemical and biophysical properties of apoE impact a cascade of events at the cellular and systems levels, ultimately impacting aging-related pathogenic conditions including AD. As such, apoE-targeted therapeutic interventions are predicted to be more effective by addressing the biochemical phase of the cascade.

Vascular Dementia and Underlying Sex Differences

Vascular dementia (VaD) is the second most common form of dementia after Alzheimer's disease (AD); where Alzheimer's accounts for 60-70% of cases of dementia and VaD accounts for 20% of all dementia cases. VaD is defined as a reduced or lack of blood flow to the brain that causes dementia. VaD is also known occasionally as vascular contributions to cognitive impairment and dementia (VCID) or multi-infarct dementia (MID). VCID is the condition arising from stroke and other vascular brain injuries that cause significant changes to memory, thinking, and behavior, and VaD is the most severe stage while MID is produced by the synergistic effects caused by multiple mini strokes in the brain irrespective of specific location or volume. There are also subtle differences in the presentation of VaD in males and females, but they are often overlooked. Since 1672 when the first case of VaD was reported until now, sex and gender differences have had little to no research done when it comes to the umbrella term of dementia in general. This review summarizes the fundamentals of VaD followed by a focus on the differences between sex and gender when an individual is diagnosed. In addition, we provide critical evidence concerning sex and gender differences with a few of the main risk factors of VaD including pre-existing health conditions and family history, gene variants, aging, hormone fluctuations, and environmental risk factors. Additionally, the pharmaceutical treatments and possible mitigation of risk factors is explored.

Atherosclerosis: The Culprit and Co-victim of Vascular Dementia

Vascular dementia (VD), a cerebrovascular disease which causes cognitive impairment, is one of the significant factors that affects the quality of senectitude. Atherosclerosis (AS) is a chronic inflammatory syndrome and closely associated with VD. Analyzing the role of AS in VD contribute greatly to its early detection and prevention, but their relationship has not been integrated into a complete network. This review summarizes AS biomarkers as VD predictors for the first time and describes the direct mechanisms of AS causing VD from five aspects: vascular morphogenesis, hemodynamic change, neurovascular unit damage (NVU), oxidative stress, and microRNA (miRNA). Finally, it discriminates the relationship between AS and VD in common risk factors which can be disease or some molecules. In particular, these data imply that the role of AS in VD is not only a pathogenic factor but also a comorbidity in VD. This review aims to bring new ideas for the prediction and treatment of VD.

Apolipoprotein E ε4 allele is associated with vascular cognitive impairment no dementia in Chinese population

BACKGROUND

The association between apolipoprotein E (APOE) ε4 allele and vascular cognitive impairment no dementia (VCIND) is still controversial.

OBJECTIVE

To examine the relationship between the APOE ε4 allele and patients with VCIND after cerebral infarction.

METHODS

This study included first-ever cerebral infarction patients 3-12 months after the attack at the Xuanwu Hospital between June 2012 and December 2014. Patients were divided into VCIND group and normal cognition group (NC group).The APOE ε4 carriers (including ε2/ε4, ε3/ε4 and ε4/ε4 genotypes) and ε4 allele frequency were analyzed in relation to cognition grouping after cerebral infarction. MRI features of infarctions and some known risk factors for VCIND，as confounding factors, were also analyzed for correlation with VCIND at the same time.

RESULTS

Participants (n = 707) were divided into the VCIND (n = 361) and NC (n = 346) groups. The percentage of APOE ε4 carriers was higher in the VCIND group (23.6%) than in the NC group (12.7%, P < .001).The APOE ε4 allele frequency was higher in the VCIND group (12.5%) than in the NC group (6.7%, P = .001). Regardless of other confounding factors, such as male gender (OR = 1.963, 95%CI: 1.394-2.763, P < .001), age (OR = 1.034, 95%CI: 1.017-1.052, P < .001), education (OR = 0.834, 95%CI: 0.795-0.875, P < .001), hypertension (OR = 2.044, 95%CI: 1.460-2.861, P < .001), hyperlipidemia (OR = 0.682, 95%CI: 0.482-0.965, P = .031), infarction lesion diameter (OR = 1.044, 95%CI: 1.017-1.072, P = .001) and white matter lesions (OR = 1.330, 95%CI: 1.126-1.571, P = .001), the APOE ε4 allele was independently associated with VCIND (OR = 2.244, 95%CI: 1.454-3.463, P < .001).

CONCLUSION

These results confirms the hypothesis that the APOE ε4 allele is a risk factor associated with VCIND after cerebral infarction.

Small Vessel Disease-Related Dementia: An Invalid Neurovascular Coupling?

The arteriosclerosis-dependent alteration of brain perfusion is one of the major determinants in small vessel disease, since small vessels have a pivotal role in the brain's autoregulation. Nevertheless, as far as we know, endothelium distress can potentiate the flow dysregulation and lead to subcortical vascular dementia that is related to small vessel disease (SVD), also being defined as subcortical vascular dementia (sVAD), as well as microglia activation, chronic hypoxia and hypoperfusion, vessel-tone dysregulation, altered astrocytes, and pericytes functioning blood-brain barrier disruption. The molecular basis of this pathology remains controversial. The apparent consequence (or a first event, too) is the macroscopic alteration of the neurovascular coupling. Here, we examined the possible mechanisms that lead a healthy aging process towards subcortical dementia. We remarked that SVD and white matter abnormalities related to age could be accelerated and potentiated by different vascular risk factors. Vascular function changes can be heavily influenced by genetic and epigenetic factors, which are, to the best of our knowledge, mostly unknown. Metabolic demands, active neurovascular coupling, correct glymphatic process, and adequate oxidative and inflammatory responses could be bulwarks in defense of the correct aging process; their impairments lead to a potentially catastrophic and non-reversible condition.

Therapeutic approaches targeting Apolipoprotein E function in Alzheimer's disease

One of the primary genetic risk factors for Alzheimer’s disease (AD) is the presence of the Ɛ4 allele of apolipoprotein E (APOE). APOE is a polymorphic lipoprotein that is a major cholesterol carrier in the brain. It is also involved in various cellular functions such as neuronal signaling, neuroinflammation and glucose metabolism. Humans predominantly possess three different allelic variants of APOE, termed E2, E3, and E4, with the E3 allele being the most common. The presence of the E4 allele is associated with increased risk of AD whereas E2 reduces the risk. To understand the molecular mechanisms that underlie APOE-related genetic risk, considerable effort has been devoted towards developing cellular and animal models. Data from these models indicate that APOE4 exacerbates amyloid β plaque burden in a dose-dependent manner. and may also enhance tau pathogenesis in an isoform-dependent manner. Other studies have suggested APOE4 increases the risk of AD by mechanisms that are distinct from modulation of Aβ or tau pathology. Further, whether plasma APOE, by influencing systemic metabolic pathways, can also possibly alter CNS function indirectly is not complete;y understood. Collectively, the available studies suggest that APOE may impact multiple signaling pathways and thus investigators have sought therapeutics that would disrupt pathological functions of APOE while preserving or enhancing beneficial functions. This review will highlight some of the therapeutic strategies that are currently being pursued to target APOE4 towards preventing or treating AD and we will discuss additional strategies that holds promise for the future.

Genetic Variation in the Ontario Neurodegenerative Disease Research Initiative

Background/Objective:

Apolipoprotein E (APOE) E4 is the main genetic risk factor for Alzheimer’s disease (AD). Due to the consistent association, there is interest as to whether E4 influences the risk of other neurodegenerative diseases. Further, there is a constant search for other genetic biomarkers contributing to these phenotypes, such as microtubule-associated protein tau (MAPT) haplotypes. Here, participants from the Ontario Neurodegenerative Disease Research Initiative were genotyped to investigate whether the APOE E4 allele or MAPT H1 haplotype are associated with five neurodegenerative diseases: (1) AD and mild cognitive impairment (MCI), (2) amyotrophic lateral sclerosis, (3) frontotemporal dementia (FTD), (4) Parkinson’s disease, and (5) vascular cognitive impairment.

Methods:

Genotypes were defined for their respective APOE allele and MAPT haplotype calls for each participant, and logistic regression analyses were performed to identify the associations with the presentations of neurodegenerative diseases.

Results:

Our work confirmed the association of the E4 allele with a dose-dependent increased presentation of AD, and an association between the E4 allele alone and MCI; however, the other four diseases were not associated with E4. Further, the APOE E2 allele was associated with decreased presentation of both AD and MCI. No associations were identified between MAPT haplotype and the neurodegenerative disease cohorts; but following subtyping of the FTD cohort, the H1 haplotype was significantly associated with progressive supranuclear palsy.

Conclusion:

This is the first study to concurrently analyze the association of APOE isoforms and MAPT haplotypes with five neurodegenerative diseases using consistent enrollment criteria and broad phenotypic analysis.

Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies

Polymorphism in the apolipoprotein E (APOE) gene is a major genetic risk determinant of late-onset Alzheimer disease (AD), with the APOE*ε4 allele conferring an increased risk and the APOE*ε2 allele conferring a decreased risk relative to the common APOE*ε3 allele. Strong evidence from clinical and basic research suggests that a major pathway by which APOE4 increases the risk of AD is by driving earlier and more abundant amyloid pathology in the brains of APOE*ε4 carriers. The number of amyloid-β (Aβ)-dependent and Aβ-independent pathways that are known to be differentially modulated by APOE isoforms is increasing. For example, evidence is accumulating that APOE influences tau pathology, tau-mediated neurodegeneration and microglial responses to AD-related pathologies. In addition, APOE4 is either pathogenic or shows reduced efficiency in multiple brain homeostatic pathways, including lipid transport, synaptic integrity and plasticity, glucose metabolism and cerebrovascular function. Here, we review the recent progress in clinical and basic research into the role of APOE in AD pathogenesis. We also discuss how APOE can be targeted for AD therapy using a precision medicine approach.

Raman Spectroscopy to Diagnose Alzheimer's Disease and Dementia with Lewy Bodies in Blood

Accurate identification of Alzheimer's disease (AD) is still of major clinical importance considering the current lack of noninvasive and low-cost diagnostic approaches. Detection of early stage AD is particularly desirable as it would allow early intervention or recruitment of patients into clinical trials. There is also an unmet need for discrimination of AD from dementia with Lewy bodies (DLB), as many cases of the latter are misdiagnosed as AD. Biomarkers based on a simple blood test would be useful in research and clinical practice. Raman spectroscopy has been implemented to analyze blood plasma of a cohort that consisted of early stage AD, late-stage AD, DLB, and healthy controls. Classification algorithms achieved high accuracy for the different groups: early stage AD vs healthy with 84% sensitivity, 86% specificity; late-stage AD vs healthy with 84% sensitivity, 77% specificity; DLB vs healthy with 83% sensitivity, 87% specificity; early-stage AD vs DLB with 81% sensitivity, 88% specificity; late-stage AD vs DLB with 90% sensitivity, 93% specificity; and lastly, early-stage AD vs late-stage AD 66% sensitivity and 83% specificity. G-score values were also estimated between 74% and 91%, demonstrating that the overall performance of the classification model was satisfactory. The wavenumbers responsible for differentiation were assigned to important biomolecules, which can serve as a panel of biomarkers. These results suggest a cost-effective, blood-based test for neurodegeneration in dementias.

Apoε4 disrupts neurovascular regulation and undermines white matter integrity and cognitive function

The ApoE4 allele is associated with increased risk of small vessel disease, which is a cause of vascular cognitive impairment. Here, we report that mice with targeted replacement (TR) of the ApoE gene with human ApoE4 have reduced neocortical cerebral blood flow compared to ApoE3-TR mice, an effect due to reduced vascular density rather than slowing of microvascular red blood cell flow. Furthermore, homeostatic mechanisms matching local delivery of blood flow to brain activity are impaired in ApoE4-TR mice. In a model of cerebral hypoperfusion, these cerebrovascular alterations exacerbate damage to the white matter of the corpus callosum and worsen cognitive dysfunction. Using 3-photon microscopy we found that the increased white matter damage is linked to an enhanced reduction of microvascular flow resulting in local hypoxia. Such alterations may be responsible for the increased susceptibility to hypoxic-ischemic lesions in the subcortical white matter of individuals carrying the ApoE4 allele.

ApoE4 is a risk factor for small vessel disease, which can lead to cognitive impairment. Here the authors assess the microvasculature of the corpus callosum using 3-photon microscopy and find that mice expressing the ApoE4 allele are more susceptible than wild-type to white matter injury and cognitive impairment in a model of hypoperfusion-induced hypoxia.

Differential diagnosis of Alzheimer's disease using spectrochemical analysis of blood

The progressive aging of the world's population makes a higher prevalence of neurodegenerative diseases inevitable. The necessity for an accurate, but at the same time, inexpensive and minimally invasive, diagnostic test is urgently required, not only to confirm the presence of the disease but also to discriminate between different types of dementia to provide the appropriate management and treatment. In this study, attenuated total reflection FTIR (ATR-FTIR) spectroscopy combined with chemometric techniques were used to analyze blood plasma samples from our cohort. Blood samples are easily collected by conventional venepuncture, permitting repeated measurements from the same individuals to monitor their progression throughout the years or evaluate any tested drugs. We included 549 individuals: 347 with various neurodegenerative diseases and 202 age-matched healthy individuals. Alzheimer's disease (AD; n = 164) was identified with 70% sensitivity and specificity, which after the incorporation of apolipoprotein ε4 genotype (APOE ε4) information, increased to 86% when individuals carried one or two alleles of ε4, and to 72% sensitivity and 77% specificity when individuals did not carry ε4 alleles. Early AD cases (n = 14) were identified with 80% sensitivity and 74% specificity. Segregation of AD from dementia with Lewy bodies (DLB; n = 34) was achieved with 90% sensitivity and specificity. Other neurodegenerative diseases, such as frontotemporal dementia (FTD; n = 30), Parkinson's disease (PD; n = 32), and progressive supranuclear palsy (PSP; n = 31), were included in our cohort for diagnostic purposes. Our method allows for both rapid and robust diagnosis of neurodegeneration and segregation between different dementias.

Protective effects of APOE e2 against disease progression in subcortical vascular mild cognitive impairment patients: A three-year longitudinal study

Although the association between apolipoprotein E (APOE) genotype and disease progression is well characterized in patients with Alzheimer's disease, such a relationship is unknown in patients with subcortical vascular cognitive impairment. We evaluated whether APOE genotype is associated with disease progression in subcortical vascular mild cognitive impairment (svMCI) patients. We prospectively recruited 72 svMCI patients (19 APOE4 carriers, 42 APOE3 homozygotes, and 11 APOE2 carriers). Patients were annually followed-up with brain MRI and neuropsychological tests for three years and underwent a second Pittsburgh compound B (PiB)-PET at a mean interval of 32.3 months. Amyloid-ß burden was quantified by PiB standardized uptake value ratio (SUVR), and the amount of small vessel disease was quantified by number of lacune and small vessel disease score on MRI. We also measured cortical thickness. During the three years of follow-up, compared to the APOE3 homozygotes, there was less increase in PiB SUVR among APOE2 carriers (p = 0.023), while the APOE genotype did not show significant effects on small vessel disease progression. APOE2 carriers also showed less cortical thinning (p = 0.023) and a slower rate of cognitive decline (p = 0.009) compared to those with APOE3 homozygotes. Our findings suggest that, in svMCI patients, APOE2 has protective effects against amyloid-ß accumulation, cortical thinning, and cognitive decline.

Genetics of Vascular Dementia: Systematic Review and Meta-Analysis

BACKGROUND

Vascular dementia (VaD) is the second most common type of dementia. So far, little is known about the contribution of genetic polymorphisms to the risk of VaD. Many candidate genetic polymorphisms have been examined in a large number of studies. However, due to the conflicting results, the genetics of VaD is still behind the shadow.

OBJECTIVE

We conducted a comprehensive meta-analysis on associations between genetic polymorphisms of any gene and VaD to investigate the genetics of VaD.

METHOD

We sought the published studies of associations between any genetic polymorphism and VaD and critically appraised them. We assessed the effects of genetic models by calculating pooled odds ratios (ORs), investigating the origin of heterogeneity by subgroup analysis, and testing the robustness by random effect model and sensitivity analysis.

RESULTS

69 studies with 4,462 cases and 11,583 controls were included. We identified APOE ɛ2/ɛ3/ɛ4 and additional four genetic polymorphisms including MTHFR C677T, PON1 L55M, TGF-β1 +29C/T, and TNF-α -850C/T associated with VaD. Tested by random effect model and sensitivity analysis, the pooled results show nice robustness.

CONCLUSIONS

Our comprehensive meta-analysis highlighted the genetic contribution to sporadic VaD. Because of the small amount of data on associations between genetic polymorphisms, except for APOE, and VaD, more studies are needed to test the existing genetic polymorphisms and detect other related genetic variants.

Post-stroke cognitive decline: an update and perspectives for clinical research

The close relationship between stroke and dementia is an important health issue. Ischaemic stroke can facilitate the onset of vascular dementia as well as aggravate pre-existing cognitive decline. The onset of cognitive decline may become manifest immediately following the onset of ischaemic stroke, but often there is a delay in the development of cognitive decline after a stroke. This delay can be seen as a therapeutic time window allowing interventions to be applied to preserve cognition following stroke. Both neurodegenerative and vascular mechanisms are activated and probably result in overlapping processes within the neurovascular unit. This review focuses on the incidence and prevalence of cognitive decline following stroke, predisposing stroke aetiologies, pre-stroke decline, imaging factors and biomarkers. Outcomes are discussed in relation to timing of assessment and neuropsychological tests used for evaluation of cognitive decline in ischaemic stroke patients. Including such tests in routine evaluations of stroke patients after some weeks or months is recommended. Finally, an outlook on ongoing and planned intervention trials is added and some recommendations for future research are proposed.

Influence of socio-demographic features and apolipoprotein E epsilon 4 expression on the prevalence of dementia and cognitive impairment in a population of 70-74-year olds: the InveCe.Ab study

The age-specific prevalence rates of dementia vary widely. Studies focusing on specific age groups are needed to provide reliable estimates for healthcare providers and policy makers. We estimated the prevalence of dementia, dementia subtypes and cognitive impairment in "InveCe.Ab" (ClinicalTrials.gov, NCT01345110), a single-step multidimensional population-based study of 70-74-year olds living in Abbiategrasso (Milan, Italy). We also looked for associations with socio-demographic factors and the presence of the apolipoprotein E-ɛ4 allele. The overall dementia prevalence was 3% (95%CI: 2.1-4.1%) [Alzheimer's disease (AD): 1.2% (95%CI 0.6-1.9%); vascular dementia (VD): 1.4% (95%CI: 0.8-2.2%)]. Being single was found to be a risk factor for vascular dementia; subjects born in southern Italy were shown to be at greater risk both of overall dementia and of vascular dementia. The prevalence of cognitive impairment, with or without subjective cognitive complaints (cognitive impairment, no dementia, CIND) was 7.8% (95%CI: 6.4-9.4%). As regards the CIND subgroups, the prevalence of subjects with subjective cognitive complaints (mild cognitive impairment, MCI) was 5.0% (95%CI 3.9-6.3%), while the prevalence of those without MCI (CIND-other) was 2.8% (95%CI: 1.9-3.8). The males had a higher risk of MCI and CIND-other; the older subjects were more likely to have MCI, and those born in north-eastern Italy to have CIND-other. The prevalence of AD was higher among the apolipoprotein E-ɛ4 carriers. Our data highlight the importance of dementia and cognitive impairment in the transitional period from adulthood to old age, and reveal the presence of different associations with socio-demographic and genetic factors.

Effects of APOE ε4 on brain amyloid, lacunar infarcts, and white matter lesions: a study among patients with subcortical vascular cognitive impairment

The relationship between the apolipoprotein E ε4 allele (APOE4) and factors associated with vascular cognitive impairment (VCI) is unclear. We aimed to examine the effects of APOE4 on brain amyloid beta using Pittsburg compound B (PiB) and subcortical cerebrovascular disease, as assessed by lacunes and white matter hyperintensities (WMH) in subcortical VCI (SVCI) patients. We recruited 230 subjects with normal cognition, 111 subjects with cognitive impairment due to clinically defined Alzheimer's disease (ADCI), and 134 subjects with clinically defined SVCI. A PiB retention ratio greater than 1.5 was considered to be PiB positive. Logistic regression analysis was performed to investigate whether APOE4 increased the risk for each cognitive impairment group. Multiple linear regression analysis was performed to investigate whether APOE4 was associated with brain amyloid beta, lacunes, and WMH. APOE4 did not increase the risk of PiB(-) SVCI (odds ratio [OR], 1.50; 95% confidence interval [CI], 0.79-2.84), whereas APOE4 increased the risk of PiB(+) SVCI (OR, 4.52; 95% CI, 1.70-11.97) and PiB(+) ADCI (odds ratio, 4.84; 95% CI, 2.54-7.91). In SVCI patients, APOE4 was positively associated with PiB retention ratio, whereas APOE4 was not associated with the number of lacunes or with WMH volume. Our results suggest that amyloid beta burden can occur in patients with and without subcortical cerebrovascular disease, and that it is associated with APOE4. However APOE4 might be independent of subcortical cerebrovascular disease.

Apolipoprotein E gene polymorphism in a Chinese population with vascular dementia: a meta-analysis

BACKGROUND

Apolipoprotein E (ApoE) gene has been reported to be associated with the development of vascular dementia (VD); however, results from observational studies are conflicting.

METHODS

We surveyed all case-control studies on ApoE gene and VD patients with comprehensive search and review of the references. A meta-analysis was performed to demonstrate the association of ApoE gene with VD by random effects models. The association was assessed by odds ratio (OR) with 95% confidence intervals (CI).

RESULTS

A total of 18 studies including 935 patients and 1,686 controls were eligible and abstracted. ApoE ε3/4 and ε4/4 genotype, as well as ε4 allele (OR = 1.95, 95% CI: 1.52-2.49; OR = 3.47, 95% CI: 1.85-6.51 and OR = 2.12, 95% CI: 1.64-2.74, respectively) were associated with an increased risk of VD, while ApoE ε3/3 genotype and ε3 allele (OR = 0.65, 95% CI: 0.53-0.79 and OR = 0.65, 95% CI: 0.53-0.80, respectively) trended to protect against VD. There was no significant difference in ApoE ε2 allele frequency, ε2/2, ε2/3 or ε2/4 genotype between VD and controls (OR = 0.85, 95% CI: 0.61-1.17; OR = 0.89, 95% CI: 0.39-2.01; OR = 0.82, 95% CI: 0.61-1.09 and OR = 1.03, 95% CI: 0.57-1.84, respectively).

CONCLUSIONS

Our results support a genetic association between ApoE polymorphism and VD in the Chinese population.

Early biomarkers for post-stroke cognitive impairment

The aim of this study was to investigate whether some biomarkers could predict cognitive impairment after stroke. One hundred fifty-two first-ever stroke patients were recruited within 6-72 h after the onset of symptoms. Blood was drawn within 1 h after admission for determining biomarkers. Cognitive function was assayed 2 weeks after stroke. The patients were divided into four groups: stroke, vascular cognitive impairment with no dementia (VCIND), vascular dementia (VaD), and mixed dementia (MD). Forty healthy subjects were used as controls. The results indicated that lower soluble receptor levels for advanced glycation end products (sRAGE) and higher β-secretase enzyme (BACE1) and neprilysin (NEP) levels were found in the VCIND, VaD, and MD groups. In addition, the percentages of ε3/ε4 genotypes and ε4 alleles in the VCIND, VaD, and MD groups were higher than in the stroke group. Correlation analysis determined that sRAGE, BACE1, and NEP were significantly related to the results of neuropsychological assessments. Logistic regression analysis, however, suggested that only sRAGE and BACE1 changed ahead of cognitive impairment after stroke. In conclusion, only BACE1 and sRAGE, not NEP or APOE genotypes, may be biomarkers diagnosing post-stroke cognitive impairment.

ApoE gene polymorphism and vascular dementia in Chinese population: a meta-analysis

Vascular dementia is the second common cause of dementia, only second to Alzheimer's disease in later life. The Apolipoprotein E (ApoE) gene polymorphism as a risk factor in vascular dementia has been suggested, but direct evidence from genetic association studies remains inconclusive even in Chinese population. Therefore, we performed this meta-analysis in order to evaluate the relationship between ApoE gene polymorphism and susceptibility to vascular dementia in Chinese population by pooling data from all relevant case-control studies published domestically and abroad from January 1990 to May 2011. 18 case-control studies were selected. Meta-analysis results showed that the pooled OR value of vascular dementia subjects in Chinese population with ε4 allele carriers was 2.07 [95% CI (1.69, 2.53)], and the pooled OR value of vascular dementia subjects with E4/E4 genotype was 3.34 [95% CI (1.89, 5.88)]. These results suggest that ApoE polymorphism is significantly associated with susceptibility to vascular dementia in Chinese population. The subject with at least one ε4 allele or E4/E4 genotype has higher risk suffering from vascular dementia than others.

Apolipoprotein E in Alzheimer's disease and other neurological disorders

Apolipoprotein E (APOE) is a 299-aminoacid protein encoded by the APOE gene. Three common polymorphisms in the APOE gene, ɛ2, ɛ3, and ɛ4, result in a single aminoacid change in the APOE protein. APOE ɛ2, ɛ3, and ɛ4 alleles strongly alter, in a dose-dependent manner, the likelihood of developing Alzheimer's disease and cerebral amyloid angiopathy. In particular, APOE ɛ4 is associated with increased risk for Alzheimer's disease whereas APOE ɛ2 is associated with decreased risk. The effects of APOE genotype on risk of these diseases are likely to be mediated by differential effects of APOE on amyloid-β accumulation in the brain and its vasculature. Response to treatment for Alzheimer's disease might differ according to APOE genotype. Because convincing evidence ties the APOE genotype to risk of Alzheimer's disease and cerebral amyloid angiopathy, APOE has been studied in other neurological diseases. APOE ɛ4 is associated with poor outcome after traumatic brain injury and brain haemorrhage, although the mechanisms underlying these associations are unclear. The possibility that APOE has a role in these and other neurological diseases has been of great interest, but convincing associations have not yet emerged.

Telomere length and ApoE polymorphism in mild cognitive impairment, degenerative and vascular dementia

BACKGROUND

Clarifying the aetiology of dementia is of crucial importance in the management of patients as well as for research purposes but it is not always possible clinically. Therefore the identification of biological markers should complement clinical approaches. Telomere shortening is emerging as an important mechanism in vascular aging and the pathogenesis of hypertension and atherosclerosis. Thus, telomere length could be a potential candidate to accurately separate vascular from degenerative cognitive impairment.

OBJECTIVES

To evaluate the usefulness of telomere length alone or combined with ApoE polymorphism in diagnosing mild cognitive impairment (MCI) and in differentiating Alzheimer's disease (AD) from vascular (VaD) and mixed dementia (MD).

METHODS

Telomere length in peripheral blood lymphocytes was performed by flow cytometry in 439 patients (mean age, 85.1 years): 204 cognitively normal, 187 demented patients: 80 AD, 86 MD, and 21 with VaD; and 48 patients with MCI. Simple and multiple ordered logistic regressions were used to predict the risk of dementia from telomere length, ApoE polymorphism and age.

RESULTS

ApoEε4 was statistically associated with patients with dementia (p<0.001) compared to cognitively normal or MCI patients; but not with the aetiologies of dementia (AD, VaD and MD) (p=0.385). No significant differences in telomere length were found among patients with different aetiologies or severities of dementia. In the global model, the combination of telomere length and ApoE polymorphism did not confer a significantly higher dementia risk (OR=0.95, 95% CI=0.69-1.32; p=0.784) than APOEε4 alone (OR=2.12, 95% CI=1.15-3.9; p=0.016).

CONCLUSION

This longitudinal study in very old patients provided no evidence suggesting that telomere length alone could be used to distinguish between the different types of dementia or MCI, nor combined with the ApoE polymorphism.

Association between APOE epsilon4 allele and vascular dementia: The Cache County study

BACKGROUND

The APOE epsilon4 allele is an established risk factor for Alzheimer's disease, but reports of its association with vascular dementia (VaD) have been inconsistent. We examined the relationship between APOE epsilon4 allele and the risk of incident VaD in a large, population-based cohort of elderly adults with up to 10 years of follow-up between 1995 and 2005.

METHODS

A total of 3,424 elderly men and women free of dementia were genotyped at the baseline assessment. Incident VaD was identified through standardized procedures administered at 3 follow-up assessments. Cox proportional hazards models were used to evaluate the risk of VaD associated with APOE epsilon4.

RESULTS

The adjusted hazard ratio was 1.6 for the participants with 1 APOE epsilon4 allele (95% CI: 0.9-2.7; p = 0.083) and 4.4 for those with 2 APOE epsilon4 alleles (95% CI: 1.6-12.5; p = 0.005). The increased risk did not appear to be mediated by vascular risk factors.

CONCLUSIONS

The APOE epsilon4 allele is associated with an increased risk of VaD in a dose-dependent fashion and accounts for almost 20% of VaD in the population.

Increased frequency of positive family history of dementia in sporadic CJD

OBJECTIVE

To analyze whether a positive family history of dementia (PFHD) is more common in sporadic CJD (sCJD) than in healthy/population controls and to study associated risk factors.

PATIENTS/METHODS

Six hundred and eighty-five sCJD patients and 659 sex-/age-matched controls were included. A PFHD in parents/grandparents/siblings was evaluated. The PRNP M129V polymorphism and ApoE genotype in sCJD with/without PFHD were determined by PCR.

RESULTS

PFHD was found in 12.1% of sCJD patients and 5.6% of controls (p<0.001). No significant difference in M129V polymorphism was found between sCJD with and without PFHD. Thirty-six percent of sCJD patients with PFHD, 26% without PFHD and 19% of healthy controls had at least one ApoE4 allele. Compared to controls, ApoE4 allele frequency (p=0.005) and proportion of ApoE4 allele carriers (p=0.019) were significantly higher in sCJD with PFHD.

INTERPRETATION

A higher frequency of the ApoE4 allele in sCJD with a PFHD could be indicative of an additional risk factor in CJD.

Association of CETP polymorphisms with the risk of vascular dementia and white matter lesions

Cholesteryl ester transfer protein (CETP), a component of the high density lipoprotein (HDL), plays a central role in reverse cholesterol transport. We investigated the association of two putative functional CETP polymorphisms (C-629A and I405V) with the risk of vascular dementia (VD) and tested if this association is influenced by the presence of APOE4 allele. Our study included 163 VD patients (mean age: 74.25 +/- 7.9 years) and 452 cognitively healthy probands (mean age: 70.81 +/- 7.9 years). As a biological correlate, the association of CETP gene variants with white matter lesion (WML) load was investigated. Neither the C-629A (P = 0.169) nor the I405V (P = 0.840) polymorphism was associated with VD risk in the whole sample. However, in non-carriers of the APOE4 allele, homozygote carriers of the CETP C-629A A allele presented with an increased risk of VD (P = 0.01). Whereas in APOE4 carriers, no association of CETP polymorphisms with VD risk was detected. In addition, carriers of the CETP C-629A AA genotype presented with decreased WML load in the frontal brain (P = 0.009). Our results suggest that CETP gene polymorphisms might influence WML load and the risk of VD, the latter in non-carriers of the APOE4 allele.

C-reactive protein mediates the effect of apolipoprotein E on cytomegalovirus infection

BACKGROUND

Although the apolipoprotein (APOE)-epsilon4 allele has been shown to determine the outcome of several infections, its relationship with cytomegalovirus (CMV) has not been explored. We examine whether APOE determines CMV and herpes simplex virus type 1 (HSV-1) antibody levels and assess whether C-reactive protein (CRP) mediates any observed relationships.

METHODS

We conducted a cross-sectional analysis of a randomly selected subset (n = 1561/1789) of participants aged 60-101 in the Sacramento Area Latino Study on Aging. Blood samples were tested for APOE genotype, CRP, and immunoglobulin G antibodies to CMV and HSV-1. Multivariate logistic regression was used to examine the association between epsilon4 and CMV and HSV antibody levels. We also assessed whether CRP mediates the effects of any observed associations between epsilon4 and viral antibody levels.

RESULTS

CMV antibody and CRP levels varied significantly by APOE genotype. The association between CRP and CMV antibody was strengthened in the presence of epsilon4. In contrast, this effect was not observed in HSV-1. We found that APOE-epsilon4 carriers had significantly lower levels of CRP yet significantly higher levels of CMV antibodies, suggesting a mediating pathway.

CONCLUSIONS

APOE-epsilon4 carriers may experience immunological aberrations that lead to lower levels of CRP and correspondingly higher CMV antibody levels.

ApoE distribution and family history in genetic prion diseases in Germany

We analyzed the ApoE genotype in patients with genetic prion diseases (gPD) with respect to family history (FH) of dementia/prion disease (PD) compared to non-demented controls. Fifty-nine gPD patients and 51 sex-/age-matched controls were included. A positive FH of dementia and PD (PFH) were evaluated. The prion protein gene (PRNP) codon 129 and ApoE genotype were determined by polymerase chain reaction (PCR). The frequency of FH of neurodegenerative disorder/prion disease/dementia varied in different PRNP mutations. PFH was found in 87% of D178N patients, but was rarer in others. Although the ApoE genotype distribution was not significantly different between gPD patients and controls, the protective E2 alleles were more frequent in controls than in patients without a PFH and even less frequent in those with a PFH (18, 16, and 11%). E4 alleles as a risk factor of Alzheimer's disease were more common in controls and patients with a PFH than in those without PFH (25, 21, and 13%). No effect of the codon 129 genotype was detected. Only about two-thirds of gPD patients had PFH of PD, while in one-third, PFH of slowly progressive dementia was reported. Underreporting of PFH of gPD may play a role; however, the varying PFH frequency across various mutations is not explained by this factor only.

Cognitive performance in elderly women: significance of the 19bp insertion/deletion polymorphism in the 5' flank of the dopamine beta-hydroxylase gene, educational level, body fat measures, serum triglyceride, alcohol consumption and age

BACKGROUND

Genetic and environmental factors influence cognitive aging. The gene encoding dopamine beta-hydroxylase (DBH) could be one such factor since this hydroxylase converts dopamine to norepinephrine both of which are involved in cognition regulation.

OBJECTIVE

To assess the effect of the 19bp insertion/deletion polymorphism in the 5' flank of the DBH gene on cognitive performance in elderly women relative to other factors of cognitive aging.

METHODS

We examined a cross-sectional sample of 1371 postmenopausal women. Cognitive abilities were assessed by the 6-item orientation-memory-concentration test. The 19bp insertion/deletion polymorphism of the DBH gene was genotyped and apolipoprotein E (APOE) epsilon4 allele status was determined. In addition blood pressure, body fat mass and blood lipids were measured. Information was also obtained by personal interviews. Data were analyzed by regression analysis.

RESULTS

Cognition was univariately associated with DBH genotype (p = 0.04). A univariate association of borderline significance was observed for APOE epsilon4 allele status (p = 0.07). Exclusion of women with severe cognition impairment did not alter the strength of the association with the DBH gene polymorphism markedly (p = 0.06) but obliterated the weak association between APOE epsilon4 allele status and cognition. The association of the DBH gene polymorphism with cognition persisted after adjustment for other variables (p = 0.03).

CONCLUSIONS

The 19bp insertion/deletion polymorphism of the DBH gene influences cognition in elderly women and might have a stronger effect than APOE epsilon4 allele status on mild cognitive impairment. Both genetic polymorphisms had a significantly smaller impact on cognition than age, education, alcohol consumption and body fat measures.

Apolipoprotein E genotypes in hospitalized elderly patients with vascular dementia

BACKGROUND

Polymorphism in the apolipoprotein E (APOE) gene is the major genetic risk factor associated with late-onset Alzheimer's Disease (AD). However, it is still unclear if a relationship exists between the APOE epsilon4 allele and vascular dementia (VaD) in elderly subjects.

OBJECTIVES

To evaluate the prevalence of APOE alleles in elderly patients with VaD compared to AD patients and to control subjects with no cognitive impairment (NoCI).

PATIENTS AND METHODS

We evaluated 396 consecutive patients aged > or =65 years with definite or suspected cognitive impairment with a clinical (Mini-Mental State Examination, Clinical Dementia Rating, Geriatric Depression Scale), functional (Activities of Daily Living, Instrumental Activities of Daily Living), comorbidity (Cumulative Illness Rating Scale) and instrumental (CT scan, NMR) assessment. Diagnosis of dementia was made according to NINCDS-ADRDA and NINDS-AIREN Work Group and the DSM-IV. APOE genotypes were analyzed by a recently described method resulting in positive/negative chain reaction products for each APOE genotype. Statistical analysis was carried out using the Pearson chi(2), the Kruskal-Wallis test and the ANOVA post hoc comparisons.

RESULTS

A total of 287 elderly patients (males = 138, females = 149, mean age = 77.8 +/- 6.9 years, range = 65-98) with diagnoses of VaD (n = 97), AD (n = 82) or NoCI (n = 108) were included in the study. A significantly higher APOE epsilon4 allele frequency was observed in AD patients compared to VaD and/or NoCI subjects, while no differences were found between VaD patients and subjects with NoCI (AD = 24.3%, VaD = 10.3, NoCI = 8.7, p < 0.05). Furthermore, a significantly lower APOE epsilon3 allele frequency was observed in AD patients compared to VaD and/or NoCI subjects but not between VaD and NoCI patients (AD = 71.3%, VaD = 80.9, NoCI = 83.4, p < 0.05). No significant differences were observed in the APOE epsilon2 allele (VaD = 8.8%, AD = 4.4, NoCI = 7.9, p = n.s.) among the 3 groups.

CONCLUSIONS

In this population, the frequency of the APOE epsilon4 allele is lower in VaD than in AD.