Association of plasma and cortical amyloid beta is modulated by APOE ε4 status

BACKGROUND

Apolipoprotein E (APOE) ε4 allele's role as a modulator of the relationship between soluble plasma amyloid beta (Aβ) and fibrillar brain Aβ measured by Pittsburgh compound B positron emission tomography ([(11)C]PiB PET) has not been assessed.

METHODS

Ninety-six Alzheimer's Disease Neuroimaging Initiative participants with [(11)C]PiB scans and plasma Aβ1-40 and Aβ1-42 measurements at the time of PET scanning were included. Regional and voxelwise analyses of [(11)C]PiB data were used to determine the influence of APOE ε4 allele on association of plasma Aβ1-40, Aβ1-42, and Aβ1-40/Aβ1-42 with [(11)C]PiB uptake.

RESULTS

In APOE ε4- but not ε4+ participants, positive relationships between plasma Aβ1-40/Aβ1-42 and [(11)C]PiB uptake were observed. Modeling the interaction of APOE and plasma Aβ1-40/Aβ1-42 improved the explained variance in [(11)C]PiB binding compared with using APOE and plasma Aβ1-40/Aβ1-42 as separate terms.

CONCLUSIONS

The results suggest that plasma Aβ is a potential Alzheimer's disease biomarker and highlight the importance of genetic variation in interpretation of plasma Aβ levels.

Neocortical β-amyloid area is associated with dementia and APOE in the oldest-old

OBJECTIVE

Apolipoprotein E (APOE) ε2 carriers may be protected from dementia because of reduced levels of cortical β-amyloid. In the oldest-old, however, APOE ε2 carriers have high β-amyloid plaque scores and preserved cognition. We compared different measures of β-amyloid pathology across APOE genotypes in the oldest-old, and their relationship with dementia.

METHODS

The study included 96 participants from The 90+ Study. Using all information, dementia diagnoses were made. Neuropathological examination included staging for amyloid plaques and β-amyloid cortical percent area stained by NAB228 antibody.

RESULTS

Both APOE ε2 and APOE ε4 carriers had high Consortium to Establish a Registry for Alzheimer's Disease plaque scores. However, APOE ε2 carriers had low cortical β-amyloid percent areas. β-amyloid percent area was associated with dementia across APOE genotypes.

CONCLUSIONS

Lower levels of percent area in APOE ε2 carriers may reflect lower total β-amyloid and may contribute to APOE ε2 carriers' decreased risk of dementia, despite high β-amyloid plaque scores. The relationship between β-amyloid plaques and dementia in the oldest-old may vary by APOE genotype.

Assessment of Alzheimer's disease risk with functional magnetic resonance imaging: an arterial spin labeling study

Functional magnetic resonance imaging (fMRI) of older adults at risk for Alzheimer's disease (AD) by virtue of their cognitive (i.e., mild cognitive impairment [MCI]) and/or genetic (i.e., apolipoprotein E [APOE] ε4 allele) status demonstrate divergent brain response patterns during memory encoding across studies. Using arterial spin labeling MRI, we examined the influence of AD risk on resting cerebral blood flow (CBF) as well as the CBF and blood oxygenation level dependent (BOLD) signal response to memory encoding in the medial temporal lobes (MTL) in 45 older adults (29 cognitively normal [14 APOE ε4 carriers and 15 noncarriers]; 16 MCI [8 APOE ε4 carriers, 8 noncarriers]). Risk groups were comparable in terms of mean age, years of education, gender distribution, and vascular risk burden. Individuals at genetic risk for AD by virtue of the APOE ε4 allele demonstrated increased MTL resting state CBF relative to ε4 noncarriers, whereas individuals characterized as MCI showed decreased MTL resting state CBF relative to their cognitively normal peers. For percent change CBF, there was a trend toward a cognitive status by genotype interaction. In the cognitively normal group, there was no difference in percent change CBF based on APOE genotype. In contrast, in the MCI group, APOE ε4 carriers demonstrated significantly greater percent change in CBF relative to ε4 noncarriers. No group differences were found for BOLD response. Findings suggest that abnormal resting state CBF and CBF response to memory encoding may be early indicators of brain dysfunction in individuals at risk for developing AD.

Brain size and the compensation of Alzheimer's disease symptoms: a longitudinal cohort study

BACKGROUND

Greater intracranial volume (ICV) has been associated with less severe Alzheimer's disease (AD) symptoms at a given level of cerebral pathology. In this study we examine whether ICV modulates the association between clinical disease progression on the one hand and brain atrophy or the apolipoprotein E genotype on the other.

METHODS

Six hundred seventy-four subjects were studied from the AD Neuroimaging Initiative (ADNI). Subjects included 204 controls, 144 patients with AD dementia, and 326 with amnestic mild cognitive impairment (aMCI). Longitudinal analyses were conducted applying generalized estimating equations to examine the influence of ICV on clinical deterioration and atrophy progression. Follow-up data were available for up to 60 months after the baseline visit (mean 31.42 months, SD 13.12 months).

RESULTS

ICV was not directly associated with clinical worsening or atrophy progression. However, ICV attenuated the impact of atrophy and the apolipoprotein E ε4 allele on clinical disease progression in aMCI.

CONCLUSION

Greater ICV, that is, premorbid brain size, seems to protect against clinical deterioration in the face of AD-related brain atrophy in aMCI. The results support the theory of a compensatory role of brain reserve in contrast to a neuroprotective role. The protective effects of morphologic reserve seem to be limited to early clinical AD; once a certain threshold of neurodegenerative burden is passed, a larger premorbid brain no longer offers an advantage in this context.

Association between apolipoprotein E genotype, chronic liver disease, and hepatitis B virus

BACKGROUND/AIMS

Apolipoprotein E (ApoE) plays an important role in regulating lipid and lipoprotein metabolism, and ApoE genotypes are known to affect plasma lipoprotein concentrations. We investigated whether ApoE genotype determines the disease outcome in hepatitis B virus (HBV)-infected individuals, and verified the association between ApoE genotype and the occurrence of hepatocellular carcinoma (HCC) in patients with chronic liver diseases of various etiologies.

METHODS

This hospital-based, case-controlled study enrolled 156 subjects (47 healthy controls, 50 HBV-related liver cirrhosis patients, and 59 HCC patients). ApoE genotypes were determined using PCR-based ApoE genotyping kits. The biological significance of ApoE genotype was verified by measuring serum ApoE levels using an ELISA kits.

RESULTS

The ε3 allele was the most common allele, with allele frequencies among the entire cohort of 5.8%, 84.3%, and 9.9% for the ε2, ε3, and ε4 alleles, respectively. Significantly more of those patients carrying the ε3/3 genotype had developed liver cirrhosis compared to the control subjects. Being an ApoE4 carrier was associated with a lower probability of developing liver cirrhosis. The allele frequencies and genotype distribution of ApoE did not differ significantly between the liver cirrhosis and HCC patients. The serum level of ApoE was significantly higher in patients with liver cirrhosis than in the healthy controls, but did not differ significantly with the ApoE genotype.

CONCLUSIONS

The ApoE ε3/3 genotype frequency was higher in patients with HBV-associated liver cirrhosis than in the controls.

Role of APOE and Age at Enrollment in the Alzheimer's Disease Anti-Inflammatory Prevention Trial (ADAPT)

BACKGROUND

The Alzheimer's Disease Anti-inflammatory Prevention Trial (ADAPT) tested whether non-steroidal anti-inflammatory drugs (NSAIDs) can prevent Alzheimer's disease (AD). The results were null. We analyzed ADAPT data to examine if the effects of NSAIDs on AD risk differed depending upon APOE genotype or age as has been suggested by previous observational studies.

METHODS

ADAPT randomized 2,528 cognitively intact older adults to either celecoxib, naproxen sodium or placebo; 2,388 participants provided blood samples for APOE genotyping. Proportional hazards regression was used to estimate the effects of naproxen or celecoxib versus placebo on incident AD by age at enrollment and APOE genotype.

RESULTS

The proportion of subjects providing a biological sample did not differ between the treatment groups. In models of AD risk, none of the tests for 2-way interactions between either NSAID and age or APOE genotype were significant (p > 0.05).

CONCLUSIONS

The data did not support the hypothesis that the association between NSAIDs and AD risk differed by age or APOE genotype.

Lack of Association between Apolipoprotein E Polymorphism with Age at Onset of Subcortical Vascular Dementia

BACKGROUND AND PURPOSE

The relationship between apolipoprotein E (ApoE) and onset of vascular dementia remains controversial. The aim of this study was to evaluate the relationship between ApoE polymorphism and the onset of subcortical vascular dementia (SVaD) compared to Alzheimer's disease (AD) and normal controls.

METHODS

The study was comprised of 61 patients with SVaD (42 Binswanger type, 19 lacunar type) and 112 patients with AD (16 early-onset AD, 96 late-onset AD) as well as 284 age-, gender- and education-matched normal controls. The diagnosis of SVaD was based on modified NINDS-AIREN criteria, and the diagnosis of AD was based on NINCDS-ADRDA criteria. ApoE polymorphism was genotyped in all participants.

RESULTS

None of the three ApoE alleles was more prevalent in SVaD patients compared to normal controls, which was the case when both Binswanger and lacunar types were analyzed separately. ApoE ∊4 did not accelerate the onset of SVaD (OR 1.66, 95% CI: 0.8-3.4), in contrast to a significant relation with late-onset AD (OR 3.78, 95% CI: 2.2-6.5).

CONCLUSION

Our results suggest that ApoE polymorphism is not associated with the onset of SVaD and that the two subtypes of SVaD may share similar pathophysiologies.

Polymorphism of Apo lipoprotein E gene and the risk of multiple sclerosis

BACKGROUND

Apolipoprotein E (ApoE) gene encodes an important protein in reforming injuries of central nervous system (CNS). It is assumed that various ApoE alleles may be functionally different. The purpose of this study was to investigate the distribution of ApoE genotypes in multiple sclerosis (MS) patients in a small cohort of Iranians.

METHODS

In this case-control study, blood samples of patients and healthy volunteers were collected (n = 40) from Neurology Clinic of Alzahra Medical Complex. The ApoE genotypes were determined using DNA extracted from the samples by polymerase chain reaction (PCR) techniques followed by digestion with HhaI restriction enzyme. The results were adjusted for age of MS onset, sex, expanded disability status scale (EDSS), and type of MS (primary or secondary progressive). Results were statistically analyzed using chi-square test.

RESULTS

The ApoE3/E3 genotype was detected in the majority of MS patients and the control group. Frequency distribution of E4 allele did not differ significantly between the two groups. There was no difference between ApoE allele and age of disease onset, sex, expanded disability status, or type of multiple sclerosis.

CONCLUSIONS

We found no significant differences in genotype frequency between patients with multiple sclerosis and the control group. Despite the fact that small sample size was a limitation for our study, it seems that ApoE polymorphism may not be useful as a marker for screening patients with multiple sclerosis.

The Association between Sporadic Alzheimer's Disease and the Human ABCA1 and APOE Gene Polymorphisms in Iranian Population

BACKGROUND

Apolipoprotein E (APOE), which its ε4 allele has been reported as a risk factor in late onset Alzheimer's disease (AD), is the main cholesterol carrier in the brain. ATP-binding cassette transporter A1 (ABCA1) gene on chromosome 9, which has been known by genome-wide AD linkage study, has an important role in cellular cholesterol efflux. This study determines the association between sporadic AD and the human ABCA1 and APOE gene polymorphisms in Iranian population.

METHODS

154 AD cases and 162 control subjects from Iranian population were genotyped for APOE genotypes and ABCA1 polymorphism (R219K).

RESULTS

The frequency of ε2ε3 genotype was higher in control subjects comparing AD patients but was not significant (13% versus 5.8%) and ε3ε4 genotype frequency was significantly higher in AD cases comparing with control subjects. APOE-ε2 allele frequency in cases was lower than control subjects but this difference was not significant (4.5% versus 8%). Individuals carrying ε4 allele, developed AD 6.5 times more than non-carriers (OR=6.52, 95%CI=2.63-16.17). There was no significant association between ABCA1 polymorphism and AD.

CONCLUSION

Unlike other studies, R219K polymorphism was not dependent on gender and APOE-ε4 allele and there was no association between APOE and ABCA1 in AD patients compared to controls.

Association between Alzheimer's Disease and Apolipoprotein E Polymorphisms

BACKGROUND

Alzheimer's disease as a neurodegenerative disorder is the commonest type of dementia. A growing number of genes have been reported as the risk factors, which increase the susceptibility to Alzheimer's disease. Apolipoprotein E (APOE), which its ε4 allele has been reported as a risk factor in late onset Alzheimer's disease (AD), is the main cholesterol carrier in the brain. The main goal of this study was to assess the role of APOE genotypes and alleles in AD in Iranian population.

METHODS

This study was performed in Tehran, Iran from 2007 to 2008. Totally, 154 AD cases and 162 control subjects from Iranian population were genotyped for APOE using PCR method. Genotype and alleles frequencies for APOE were calculated and compared between AD case and control subjects by χ2 or Fisher's exact test. Type one error assumed less than 0.05.

RESULTS

The frequency of ε2ε3 genotype was significantly higher in control subjects than AD patients was (13.5% versus 5.2%, P< 0.05) and ε3ε4 genotype frequency was significantly higher in AD cases compared with control subjects. APOE -ε2 allele frequency in cases was lower than that of control subjects but this difference was not significant (4.2% versus 7.7%).

CONCLUSION

It seems that individuals carrying ε4 allele, develop AD 6.5 times more than non-carriers do (OR= 6.566, 95% CI= 2.89-14.92). It has been reported that ε4 allele acts in dose- age-dependent manner but we have shown that the risk of developing AD in male APOE -ε4 allele carriers is higher than that of female ε4 carriers.

Apolipoprotein e4 genotype and depressive symptoms as risk factors for dementia in an older korean population

OBJECTIVE

Growing evidence suggests the separate associations of apolipoprotein E e4 allele (apo E4) and depression with incident dementia. This study investigated the separate and combined effects of apo E4 and depression on the incidence of dementia in both men and women.

METHODS

Of 625 elderly without dementia at baseline, 518 (83%) were followed over a 2.4-year period and were assessed clinically for incident dementia. The apo E polymorphism was ascertained, and depression was identified using the Korean version of the Geriatric Depression Scale (KGDS). Covariates included age, gender, education, disability, alcohol history, physical activity, and vascular risk factors.

RESULTS

The incidence of dementia was significantly higher in elderly Koreans with both apo E4 and depression compared to those without both factors [adjusted odds ratio (95% CI)=5.85 (1.77-19.38)]. This interaction was significant in men (p=0.049), but not in women (p=0.354).

CONCLUSION

Depressed elderly people are at great risk for incident dementia in the presence of apo E4. Potential gender differences require further evaluation.