Apolipoprotein E and change in episodic memory in blacks and whites

Neuropathology-based APOE genetic risk score better quantifies Alzheimer's risk

INTRODUCTION

Apolipoprotein E (APOE) ε4-carrier status or ε4 allele count are included in analyses to account for the APOE genetic effect on Alzheimer's disease (AD); however, this does not account for protective effects of APOE ε2 or heterogeneous effect of ε2, ε3, and ε4 haplotypes.

METHODS

We leveraged results from an autopsy-confirmed AD study to generate a weighted risk score for APOE (APOE-npscore). We regressed cerebrospinal fluid (CSF) amyloid and tau biomarkers on APOE variables from the Wisconsin Registry for Alzheimer's Prevention (WRAP), Wisconsin Alzheimer's Disease Research Center (WADRC), and Alzheimer's Disease Neuroimaging Initiative (ADNI).

RESULTS

The APOE-npscore explained more variance and provided a better model fit for all three CSF measures than APOE ε4-carrier status and ε4 allele count. These findings were replicated in ADNI and observed in subsets of cognitively unimpaired (CU) participants.

DISCUSSION

The APOE-npscore reflects the genetic effect on neuropathology and provides an improved method to account for APOE in AD-related analyses.

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.

Apolipoprotein E (APOE) genotype, dementia, and memory performance among Caribbean Hispanic versus US populations

INTRODUCTION

Apolipoprotein E (APOE) is considered the major susceptibility gene for developing Alzheimer's disease. However, the strength of this risk factor is not well established across diverse Hispanic populations.

METHODS

We investigated the associations among APOE genotype, dementia prevalence, and memory performance (immediate and delayed recall scores) in Caribbean Hispanics (CH), African Americans (AA), Hispanic Americans (HA) and non-Hispanic White Americans (NHW). Multivariable logistic regressions and negative binomial regressions were used to examine these associations by subsample.

RESULTS

Our final dataset included 13,516 participants (5198 men, 8318 women) across all subsamples, with a mean age of 74.8 years. Prevalence of APOE ε4 allele was similar in CHs, HAs, and NHWs (21.8%-25.4%), but was substantially higher in AAs (33.6%; P < 0.001). APOE ε4 carriers had higher dementia prevalence across all groups.

DISCUSSION

APOE ε4 was similarly associated with increased relative risk of dementia and lower memory performance in all subsamples.

Reduced brain activity during a working memory task in middle-aged apolipoprotein E ε4 carriers with overweight/obesity

Objective

The apolipoprotein E ε4 (APOE ε4) allele and midlife obesity are independent risk factors for Alzheimer's disease (AD). Both of these risk factors are also associated with differences in brain activation, as measured by blood oxygenation level-dependent (BOLD) responses, in the absence of detectable cognitive deficits. Although the presence of these risk factors may influence brain activity during working memory tasks, no study to date has examined whether the presence of the ε4 allele explains variation in working memory brain activity while matching for levels of overweight/obesity. The primary aim of this study was to determine whether the presence of the ε4 allele is associated with differences in task-functional magnetic resonance imaging (fMRI) brain activation in adults with overweight/obesity. We predicted that ε4 carriers would have greater brain activation in regions that support working memory.

Methods

This ancillary study included 48 (n = 24 APOE ε4 carriers; n = 24 APOE ε4 non-carriers), sedentary middle-aged adults (Mean age = 44.63 ± 8.36 years) with overweight/obesity (Mean BMI = 32.43 ± 4.12 kg/m²) who were matched on demographic characteristics. Participants were a subsample enrolled in 12-month randomized clinical trial examining the impact of energy-restricted diet and exercise on cardiovascular health outcomes. Participants completed a n-back working memory task with fMRI, which were completed within one month of the start of the intervention. Participants also underwent pseudo-continuous arterial spin labeling scans, a MRI measure of cerebral blood flow (CBF).

Results

Compared to non-ε4 carriers with overweight/obesity, ε4 carriers with overweight/obesity had lower fMRI brain activity in the middle frontal gyrus, pre and post central gyrus, supramarginal gyrus, superior temporal gyrus, lateral occipital cortex, and angular gyrus (z range = 2.52-3.56) during the n-back working memory task. Differences persisted even when controlling for CBF in these brain regions.

Conclusion

These results indicate that presence of the APOE ε4 allele in middle-aged adults with overweight/obesity is related to altered brain activity during a working memory paradigm, which may confer risk for accelerated neurocognitive decline in late adulthood. Future research is needed to clarify the clinical implications of these findings in the context of risk for AD.

Amyloid, cerebrovascular disease, and neurodegeneration biomarkers are associated with cognitive trajectories in a racially and ethnically diverse, community-based sample

We characterized the additive contribution of cerebrovascular biomarkers to amyloid and neurodegeneration biomarkers (AV(N)) when modeling prospective, longitudinal cognitive trajectories within 3 major racial/ethnic groups. Participants (n = 172; age = 69-96 years; 62% women; 31%/49%/20% Non-Hispanic White/Non-Hispanic Black/Hispanic) from the Washington Heights-Inwood Columbia Aging Project were assessed for amyloid (Florbetaben PET), neurodegeneration (cortical thickness, hippocampal volume), and cerebrovascular disease (white matter hyperintensity (WMH), infarcts). Neuropsychological assessments occurred every 2.3 ± 0.6 years for up to 6 visits (follow-up time: 4.2 ± 3.2 years). Linear mixed-effects models were stratified by race/ethnicity groups. Higher amyloid was associated with faster memory decline in all 3 racial/ethnic groups, but was related to faster cognitive decline beyond memory in minoritized racial/ethnic groups. Higher WMH was associated with faster language, processing speed/executive function, and visuospatial ability decline in Non-Hispanic Black participants, while infarcts were associated with faster processing speed/executive function decline in Non-Hispanic White participants. Complementary information from AD, neurodegenerative, and cerebrovascular biomarkers explain decline in multiple cognitive domains, which may differ within each racial/ethnic group. Importantly, treatment strategies exist to minimize vascular contributions to cognitive decline.

Diagnostic accuracy and differential associations between ratings of functioning and neuropsychological performance in non-Hispanic Black and White older adults

ObjectiveWe recently demonstrated that relative to consensus-based methods, actuarial methods may improve diagnostic accuracy across the continuum of cognitively normal (CN), mild cognitive impairment (MCI), and dementia in the overall National Alzheimer's Coordinating Center (NACC) cohort. However, the generalizability and comparative utility of current methods of diagnosing MCI and dementia due to Alzheimer's disease and related disorders (ADRD) are significantly understudied in non-Hispanic Black (NHB) older adults. Thus, we extended our previous investigation to more specifically explore the utility of consensus-based and actuarial diagnostic methods in NHB older adults.Method: We compared baseline consensus and actuarial diagnostic rates, and associations of ratings of functioning with neuropsychological performance and diagnostic outcomes, in NHB (n = 963) and non-Hispanic White (NHW; n = 4577) older adults in the NACC cohort.Results: 60.0% of the NHB subsample, versus 29.2% of the NHW subsample, included participants who met actuarial criteria for MCI despite being classified as CN or impaired-not-MCI per consensus. Additionally, associations between ratings of functioning and neuropsychological performance were less consistent in NHB participants than in NHW participants.Conclusions: Our results provide evidence of differential degrees of association between reported functioning and neuropsychological performance in NHB and NHW older adults, which may contribute to racial group differences in diagnostic rates, and prompt consideration of the strengths and weaknesses of consensus-based and actuarial diagnostic approaches in assessing neurocognitive functioning in NHB older adults.

Examination of race and gender differences in predictors of neuropsychological decline and development of Alzheimer's disease

ObjectiveBlack adults are diagnosed with Alzheimer's disease (AD) at higher rates than White adults. Biopsychosocial risk factors that differentially affect individuals by race, including health, education, and APOE e4, may explain these findings. Some research suggests that the risk for AD associated with the APOE e4 allele may differ by race. Gender differences in AD have also been identified but remain understudied. We examined race, APOE status, vascular risk factors, education, and the interaction of APOE e4 status and race as predictors of cognitive decline and the development of Alzheimer's disease between genders in a large longitudinal sample of older adults. Methods: Participants (N = 4336) were selected from the National Alzheimer's Coordinating Center's Uniform Data Set who completed measures of verbal fluency, naming, and immediate/delayed story memory across 5 years. Analyses were stratified by gender. Follow up interactions examined statistical significance of differences. Results: APOE e4 by race interactions were largely non-significant and dropped from most models. When controlling for health, education, referral source, and Uniform Data Set form (when applicable), few racial differences in cognitive performance over time emerged. Black participants obtained lower scores than White participants on a majority of baseline measures. Race findings did not differ by gender. Hypertension was more strongly predictive of decline in delayed memory among women. Conclusions: Analyses did not support that APOE e4 differentially affects Black individuals. Hypertension may be a more relevant risk factor among women. Results raise questions regarding the accuracy of baseline scores in predicting decline for Black individuals.

Association of Lewy Bodies With Age-Related Clinical Characteristics in Black and White Decedents

OBJECTIVE

The associations of Lewy bodies (LBs) with olfactory dysfunction, parkinsonism, and higher odds of dementia were assessed in Black and White community-dwelling elders and racial differences in these associations were tested.

METHODS

Black decedents (n = 81) were matched 2-to-1 by age, sex, years of education, and follow-up time in the study with White decedents (n = 154) from 4 longitudinal studies of dementia and aging. Participants underwent uniform clinical examination and cognitive, motor, and olfactory testing. LBs were detected in 7 brain regions by α-synuclein immunohistochemistry and racial differences in their association with olfaction, parkinsonism, and odds of dementia were determined using regression analyses.

RESULTS

The mean scores of the odor test, global parkinsonism signs, and global cognition were lower in Black than White decedents; the frequency of dementia was similar in both groups. The frequency of LBs was similar in Black and White decedents (∼25%), as was the frequency of LBs in individual brain regions, while the mean LB counts/mm2 were similar in all regions except the cingulate cortex, which showed higher mean LB counts in Black decedents. In regression analyses, LBs were associated with impaired olfaction (-2.23, 95% confidence interval [CI] -3.45 to -1.01) and higher odds of dementia (odds ratio 3.0, 95% CI 1.10-8.17) in both racial groups; an association with parkinsonism was stronger in Black than White decedents.

CONCLUSIONS

The frequency, distribution, and clinical manifestations of LBs are similar in Black and White elders.

Trajectories of Multiple Behavioral Risk Factors and Their Associations With Cognitive Function Trajectories Among Older African Americans and White Americans

Objectives: This study examined the joint trajectories of behavioral risk factors (smoking, alcohol drinking, and body mass index) and their associations with cognitive function trajectories among older African Americans and white Americans. Methods: Data from the Health and Retirement Study (1998-2014) were used. Group-based mixture modeling and multinomial logistic regression analysis were performed. Results: Three joint trajectories of behavioral risk factors (overweight, smoking and drinking, and drinking and overweight) and three cognitive function trajectories (low, moderate, and high) were identified. A significantly higher percentage of African Americans were in the "overweight," "smoking and drinking," and "low" cognitive functioning groups as measured by the total cognition composite score compared to white Americans. After accounting for covariates, the "drinking and overweight" group was associated with the "moderate" or "high" cognitive functioning group. Discussion: Future interventions targeting the combinations of behavioral risk factors are needed to promote healthy aging among high-risk populations.

Apolipoprotein ɛ4 Allele and Subjective Cognitive Functioning in Parents of Adults With Disabilities

OBJECTIVES

Parents of individuals with disabilities face ongoing responsibilities of providing care and support for their children, even during the child's adulthood. Past research has shown that this caregiving role is linked to chronic stress and subsequent adverse health outcomes for parents, including impaired cognition. This study examines the impacts of genetic risk for cognitive impairment (apolipoprotein [APOE] ɛ4 allele) among parents of adults with disabilities and comparison parents whose adult children do not have disabilities.

METHOD

We performed rank order regression analysis of data from the Wisconsin Longitudinal Study (2004-2006 and 2010-2012 surveys and DNA samples). Participants included parents of adults with disabilities (247 mothers and 159 fathers) and comparison parents whose adult children were not disabled (1,482 mothers and 954 fathers).

RESULTS

Mothers who had adult children with disabilities and who were APOE ɛ4 carriers reported significantly declining levels of subjective cognitive functioning over time, but mothers of adults with disabilities who did not have the APOE ɛ4 allele did not manifest this change. Among comparison group mothers, cognitive change over time was not a function of their APOE ɛ4 carrier status. Fathers' cognitive function did not differ significantly by either parental status or APOE ɛ4 carrier status.

DISCUSSION

The results show that older mothers of adults with disabilities are more susceptible to cognitive impairment than their age peers if they have the genetic risk factor of APOE ɛ4 allele.

TOMM40-APOE haplotypes are associated with cognitive decline in non-demented Blacks

INTRODUCTION

The goal was to investigate effects of APOE-TOMM40-'523 haplotypes on cognitive decline in non-demented non-Hispanic Blacks (NHB), and determine whether effects differ from non-Hispanic Whites (NHW).

METHODS

The impact of zero to two copies of the '523-Short variant (S; poly-T alleles < 20) within apolipoprotein E (APOE) genotype on a composite measure of global cognition and five domains was examined.

RESULTS

In NHB with ε3/ε3 (N = 294), '523-S/S was associated with faster decline in global cognition (β = -0.048, P = 0.017), episodic memory (β = -0.05, P = 0.031), and visuospatial ability (β = -0.037, P = 0.034) relative to those without '523-S. For NHB ε4+ (N = 182), '523-S/S had slower decline in global cognition (β = 0.047, P = 0.042) and visuospatial ability (β = 0.07, P = 0.0005) relative to '523-S non-carriers. NHB ε4+ with '523-S also had a slower rate of decline than NHWs ε4+ with '523-S.

DISCUSSION

'523-S/S has a different effect on cognitive decline among NHB dependent on APOE allele. Differences in the effect of ε4-'523-S in NHB may explain prior mixed findings on ε4 and decline in this population.

Amyloid PET Imaging in Self-Identified Non-Hispanic Black Participants of the Anti-Amyloid in Asymptomatic Alzheimer's Disease (A4) Study

OBJECTIVE

To examine whether amyloid PET in cognitively normal (CN) individuals screened for the Anti-Amyloid in Asymptomatic Alzheimer's Disease (A4) study differed across self-identified non-Hispanic White and Black (NHW and NHB) groups.

METHODS

We examined 3,689 NHW and 144 NHB participants who passed initial screening for the A4 study and underwent amyloid PET. The effect of race on amyloid PET was examined using logistic (dichotomous groups) and linear (continuous values) regression controlling for age, sex, and number of APOE ε4 and APOE ε2 alleles. Associations between amyloid and genetically determined ancestry (reflecting African, South Asian, East Asian, American, and European populations) were tested within the NHB group. Potential interactions with APOE were assessed.

RESULTS

NHB participants had lower rates of amyloid positivity and lower continuous amyloid levels compared to NHW participants. This race effect on amyloid was strongest in the APOE ε4 group. Within NHB participants, those with a lower percentage of African ancestry had higher amyloid. A greater proportion of NHB participants did not pass initial screening compared to NHW participants, suggesting potential sources of bias related to race in the A4 PET data.

CONCLUSION

Reduced amyloid was observed in self-identified NHB participants who passed initial eligibility criteria for the A4 study. This work stresses the importance of investigating AD biomarkers in ancestrally diverse samples as well as the need for careful consideration regarding study eligibility criteria in AD prevention trials.

Longitudinal associations between dietary quality and Alzheimer's disease genetic risk on cognitive performance among African American adults

Poor diet quality (DQ) is associated with poor cognition and increased neurodegeneration, including Alzheimer's disease (AD). We are interested in the role of DQ on cognitive functioning (by sex and increasing genetic risk for AD), in a sample of African American (AA) middle-aged adults. We analysed a sub-group of participants (about 55 % women; mean follow-up time of about 4·7 years) from the Healthy Aging in Neighborhoods of Diversity across the Life Span study with a genetic risk score for AD (hAlzScore). The Healthy Eating Index-2010, Dietary Approaches to Stop Hypertension and the mean adequacy ratio computed at baseline (2004-2009) and follow-up visits (2009-2013) were used to assess initial DQ and change over time. Linear mixed-effects regression models were utilised, adjusting for select covariates, selection bias and multiple testing. DQ change (ΔDQ) was associated with California Verbal Learning Test-List A - overall (0·15 (se 0·06), P = 0·008) and in women (0·21 (se 0·08), P = 0·006), at highest AD risk, indicating protective effects over time. Greater AD risk was longitudinally associated with poorer Clock Command Test scores in men. Poor DQ was positively and cross-sectionally associated with Trails B scores, but in women only. Better-quality diet was associated with a slower decline in verbal memory among AA women, with greater AD risk. Insufficient clinical evidence and/or mixed findings dictate that more studies are needed to investigate brain morphology and volume changes in relation to DQ in an at-risk population for AD, over time.

Peripheral Blood Biomarkers Coupled with the Apolipoprotein E4 Genotype Are Strongly Associated with Semantic and Episodic Memory Impairments in Elderly Subjects with Amnestic Mild Cognitive Impairment and Alzheimer's Disease

BACKGROUND

The Apolipoprotein E4 (ApoE4) genotype is strongly associated with Alzheimer's disease (AD), although the presence of the ApoE4 allele alone is not sufficient to explain AD. The pathophysiology of amnestic mild cognitive impairment (aMCI) remains unclear.

OBJECTIVE

This study aims to examine associations between peripheral blood biomarkers coupled with ApoE4 and episodic and semantic memory.

METHODS

The CERAD battery was completed and various biomarkers were assayed in 60 subjects with aMCI, 60 with AD, and 62 healthy controls.

RESULTS

Deficits in semantic and episodic memory were significantly predicted by anion gap and bicarbonate, albumin, and glucose coupled with ApoE4. Furthermore, these peripheral biomarkers interacted with ApoE to predict greater memory impairments.

CONCLUSIONS

Peripheral blood biomarkers may interact with pathways related to ApoE4 to predict greater semantic and episodic memory impairments, thus contributing to the pathophysiology of aMCI and AD. Our data suggest that the transition from aMCI to AD could at least in some cases be associated with significant interactions between ApoE4 and those peripheral blood biomarkers.

Predictors of Heterogeneity in Cognitive Function: APOE-e4, Sex, Education, Depression, and Vascular Risk

OBJECTIVE

Mild cognitive impairment and dementia are clinically heterogeneous disorders influenced by diverse risk factors. Improved characterization of the effect of multiple risk factors influence on specific cognitive functions may improve understanding of mechanisms in early cognitive change and lead to more effective interventions.

METHODS

Structural equation modeling (SEM) simultaneously examined the effects of modifiable (education, depression, and metabolic/vascular risk) and nonmodifiable risk factors (age, sex, and apolipoprotein E-ɛ4 allele [APOE-e4] status) on specific cognitive domains in 461 cognitively normal older adults.

RESULTS

The hypothesized model(s) provided an adequate fit for the data. Sex differences in cognition, depression, and vascular risk were found. On average, men were higher in vascular risk with generally lower cognitive performance than women; women were more likely to have depression. APOE-e4 associated with depression but not age, sex, or metabolic/vascular risk. Depression associated with lower executive attention, memory, and language performance, whereas metabolic/vascular risk associated with lower executive attention, memory, and working memory. Older age and lower education are associated with worse performance across the cognitive domains. The combined risk factors accounted for 16%-47% of the variance in the cognitive domains.

CONCLUSIONS

Results highlight the combined effect of risk factors on cognitive function. Future research is needed to determine whether the multifactorial risk effects on cognition vary by sex. Precision medicine approaches that integrate neuropsychological services may improve diagnostic accuracy and earlier identification of those at risk of cognitive decline.

Cognitive changes in patient living with HIV-AIDS and apolipoprotein-E polymorphism: is there an association?

Patients with HIV-AIDS treated with antiretroviral drugs still have high prevalence of cognitive disorders and many factors are likely to contribute for ongoing neurologic decline such as chronic low-level infection, coinfections with hepatitis B and C and genetic influences, both the virus and the host. Some evidences suggest that the genetic APOE polymorphism may be an associated risk factor. This study aimed to evaluate the association between APOE polymorphisms and cognitive disorders in patients with HIV-AIDS. This was a cross-sectional study comprising 133 patients aged 19-59 years old, with HIV-AIDS and were assisted at the infectious disease outpatient clinics at Hospital Universitário Oswaldo Cruz, in Recife, Brazil. For cognitive evaluation, Mini-Mental State Examination test (MMSE) and Montreal Cognitive Assessment test (MoCA) were used. The determination of APOE gene polymorphism was performed by using the PCR-RFLP technique. Sociodemographic and clinical characteristics were not significantly associated to APOE ε4 polymorphism, except for the high results of CD4 rate (p < 0.015). There was an absence associated between APOE ε4 polymorphism and neurocognitive tests. This study found no association between cognitive alterations and APOE polymorphism in patients with HIV-AIDS in the Northeast of Brazil. The imbalance of APOE allelic frequency distribution, according to Hardy-Weinberg law, there could be an adjustment phase of its equilibrium suffered by the HIV virus, however, the mechanism is still unknown.

Limbic-predominant age-related TDP-43 encephalopathy in Black and White decedents

OBJECTIVE

The association of limbic-predominant age-related transactive response DNA-binding protein 43 encephalopathy neuropathologic change (LATE-NC) with cognition and dementia was assessed in community-dwelling Black elders, and racial differences in these associations were tested.

METHODS

Black (n = 76) and White (n = 152) decedents from 4 longitudinal clinical pathologic studies of aging were matched 2 to 1 by age at death, sex, years of education, dementia status, and follow-up time. LATE-NC detected by immunohistochemistry was dichotomized into none/mild and moderate/severe groups. Distribution and clinical and pathologic characteristics of LATE-NC and its association with cognitive profiles and odds of dementia were determined in Black decedents, and racial differences in these associations were assessed.

RESULTS

The overall frequency of LATE-NC in Black and White decedents was similar (40.8% vs 45.4%). Black decedents with moderate/severe LATE-NC were older, had significantly lower global cognition scores, particularly in memory domains, and had higher frequency of Alzheimer disease, hippocampal sclerosis, and cerebral amyloid angiopathy than the LATE-NC none/mild group. LATE-NC in Black decents was independently associated with impaired global cognition, episodic and semantic memory, and visuospatial abilities. There were no racial differences in clinical features or pathologic distribution of LATE-NC except for a significant increase in the mean cytoplasmic inclusions in the entorhinal and mid temporal cortices in White compared to Black decedents. In addition, no racial differences in the cognitive profiles or the odds of dementia were observed in Black vs White decedents.

CONCLUSIONS

Consistent with findings in White decedents, LATE-NC in Black decedents is associated with impaired cognition, including memory domains.

Apolipoprotein E ε4 allele effects on longitudinal cognitive trajectories are sex and age dependent

INTRODUCTION

Questions remain about whether apolipoprotein E (APOE)-ε4 effects on cognitive decline are similar in men and women and how APOE-ε4 and age interact to influence decline in different cognitive domains.

METHODS

In sex-stratified analyses, baseline age-dependent associations between APOE-ε4 status and longitudinal cognitive trajectories were examined in cognitively normal Caucasian older adults (631 men, 561 women, baseline age range: 50-93, 6733 assessments).

RESULTS

In men, older baseline age was associated with greater effects of APOE-ε4 on longitudinal decline in memory and executive function, detectible from baseline age of 64 and 68, respectively. In women, older baseline age was associated with greater APOE-ε4 effects on longitudinal decline in attention, detectible at baseline age of 66. No significant APOE-ε4 effects were found for language, visual-spatial ability, or processing speed.

DISCUSSION

Results highlight the importance of considering sex and age when assessing APOE-ε4-associated vulnerability to cognitive decline.

Childhood trauma interacts with ApoE to influence neurocognitive function in women living with HIV

HIV-associated neurocognitive disorder (HAND) describes a spectrum of behavioural, motor and cognitive disturbances that can occur secondary to HIV infection. Less severe forms of the disorder persist despite advances in antiretroviral medication efficacy and availability. Childhood trauma (CT) may predispose individuals to developing HAND. As genetic variation in human apolipoprotein E (ApoE) has been implicated in cognitive decline and may mediate the development of long-term health outcomes following CT, we investigated the influence of ApoE and CT on cognitive function in the context of HIV. One hundred twenty-eight HIV-positive Xhosa women completed the Childhood Trauma Questionnaire-Short Form (CTQ-SF) as well as the HIV Neurobehavioural Research Center neurocognitive test battery. rs7412 and rs429358 were genotyped using KASP assays, and this data was used to determine the ApoE isoform. Baseline differences in demographic and clinical variables according to CT exposure were calculated. Analysis of covariance was used to assess the contributions of CT and ApoE variants, as well as their interaction, to cognitive function. Eighty-eight participants reported experiencing CT. The rs7412 C allele protected against the harmful effect of CT on motor scores using an additive model. The interaction of ApoE ε4 and CT was associated with worse attention/working memory scores. ApoE ε4, alone and in combination with CT, is associated with poorer cognitive function. Further research into this gene-environment interaction may assist in identifying at-risk individuals for targeted interventions.

The Contribution of Genetic Factors to Cognitive Impairment and Dementia: Apolipoprotein E Gene, Gene Interactions, and Polygenic Risk

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Although it has been studied for years, the pathogenesis of AD is still controversial. Genetic factors may play an important role in pathogenesis, with the apolipoprotein E (APOE) gene among the greatest risk factors for AD. In this review, we focus on the influence of genetic factors, including the APOE gene, the interaction between APOE and other genes, and the polygenic risk factors for cognitive function and dementia. The presence of the APOE ε4 allele is associated with increased AD risk and reduced age of AD onset. Accelerated cognitive decline and abnormal internal environment, structure, and function of the brain were also found in ε4 carriers. The effect of the APOE promoter on cognition and the brain was confirmed by some studies, but further investigation is still needed. We also describe the effects of the associations between APOE and other genetic risk factors on cognition and the brain that exhibit a complex gene⁻gene interaction, and we consider the importance of using a polygenic risk score to investigate the association between genetic variance and phenotype.

Apolipoprotein E Genotypes, Age, Race, and Cognitive Decline in a Population Sample

OBJECTIVES

To examine the effects of age and race on the association of apolipoprotein E (APOE) genotypes with cognitive decline in a population sample.

DESIGN

Longitudinal study of 18 years' duration.

SETTING

Biracial urban US population sample.

PARTICIPANTS

There were a total of 5807 participants, 60% African American (AA) and 40% European American (EA).

MEASUREMENTS

A composite cognitive function based on individual tests of episodic memory, perceptual speed, and the Mini-Mental State Examination.

RESULTS

The frequencies of APOE ε2/ε3 (14% vs 12%), ε2/ε4 (4% vs 2%), ε3/ε4 (29% vs 22%), and ε4/ε4 (4% vs 2%) genotypes were higher among AAs than EAs. After adjusting for demographic factors, the rate of decline in global cognition was twice as high among participants with the APOE ε4/ε4 genotype compared to participants with the APOE ε3/ε3 genotype (0.097 vs 0.048 SD units [SDUs] per year; P < .0001). This doubling was not different between AAs (0.091 vs 0.045 SDUs per year) and EAs (0.118 vs 0.059 SDUs per year) (P_interaction = .63). The APOE ε3/ε4 genotype was associated with a higher rate of decline with age (P_interaction = .021), while the APOE ε2/ε4 genotype (P_interaction = .016) and the APOE ε2/ε3 genotype (P_interaction = .043) were associated with a lower rate of decline with higher age. The APOE ε2/ε2 genotype was associated with a lower rate of decline in episodic memory, while the APOE ε2/ε4 was associated with a higher rate of decline in episodic memory and perceptual speed.

CONCLUSIONS

The association of the APOE genotypes with cognitive decline was not different between AAs and EAs. However, individuals with different APOE genotypes showed a lower or a higher rate of decline with age. J Am Geriatr Soc 67:734-740, 2019.

Cognitive Aging in Black and White Americans: Cognition, Cognitive Decline, and Incidence of Alzheimer Disease Dementia

BACKGROUND

US-based studies have reported that older blacks perform worse than older whites on cognitive tests and have higher risk of Alzheimer disease dementia (AD). It is unclear whether these findings reflect differences in cognitive decline.

METHODS

The Chicago Health and Aging Project followed individuals, 65+ years old (64% black, 36% white), for up to 18 years. Participants underwent triennial cognitive assessments; stratified randomized samples underwent assessments for AD. We compared black and white participants' cognitive performance, cognitive decline rate (N = 7,735), and AD incidence (N = 2,144), adjusting for age and sex.

RESULTS

Black participants performed worse than white participants on the cognitive tests; 441 participants developed AD. Black participants' incident AD risk was twice that of whites (RR = 1.9; 95% CI, 1.4, 2.7), with 58 excess cases/1,000 occurring among blacks (95% CI, 28, 88). Among noncarriers of APOE ε4, blacks had 2.3 times the AD risk (95% CI, 1.5, 3.6), but among carriers, race was not associated with risk (RR = 1.1; 95% CI, 0.6, 2.0; Pinteraction = 0.05). However, cognitive decline was not faster among blacks: the black-white difference in 5-year change in global cognitive score was 0.007 standard unit (95% CI, -0.034, 0.047). Years of education accounted for a sizable portion of racial disparities in cognitive level and AD risk, in analyses using a counterfactual approach.

CONCLUSIONS

The higher risk of AD among blacks may stem from lower level of cognitive test performance persisting throughout the observation period rather than faster rate of late-life cognitive decline. Disparities in educational attainment may contribute to these performance disparities. See video abstract at, http://links.lww.com/EDE/B299.

Sex differences in the association between apolipoprotein E ε4 allele and Alzheimer's disease markers

Introduction

We determined whether the effect of apolipoprotein E (APOE)-ε4 genotype on Alzheimer's disease (AD) markers differs in men and women across AD stages.

Methods

Among normal control (NC) participants (N = 702) and participants with mild cognitive impairment (N = 576) and AD (N = 305), we examined the associations of sex and APOE-ε4 carrier status with cortical amyloid-β (Aβ) burden, hippocampal volume ratio (HpVR; hippocampal volume/intracranial volume × 10³), brain glucose metabolism, and verbal memory.

Results

In NC, APOE-ε4 related to greater Aβ burden and poorer verbal memory across sex but to smaller HpVR and hypometabolism in men only. In mild cognitive impairment, APOE-ε4 related to smaller HpVR, hypometabolism, greater Aβ burden, and poorer verbal memory across sex. In AD, APOE-ε4 related to greater Aβ burden in men only and smaller HpVR across sex and showed no association with hypometabolism or verbal memory.

Discussion

Sex differences in the association between APOE-ε4 and AD markers vary by disease stage.

In Thai Nationals, the ApoE4 Allele Affects Multiple Domains of Neuropsychological, Biobehavioral, and Social Functioning Thereby Contributing to Alzheimer's Disorder, while the ApoE3 Allele Protects Against Neuropsychiatric Symptoms and Psychosocial Deficits

The apolipoprotein E epsilon 4 (ApoE4) allele is the strongest genetic risk factor for Alzheimer's disorder (AD) and is associated with semantic and episodic memory deficits. The aim of this study was to examine the associations between ApoE alleles (E2, E3, E4) and genotypes and neuropsychological tests, behavioral functions, and dementia symptoms as assessed using Consortium to Establish a Registry for Alzheimer's Disease (CERAD). This study included 60 patients with Alzheimer's disorder (AD), 60 with mild cognitive disorder (MCI), and 62 normal volunteers. ApoE4 carriers and individuals with E3/E4 and E4/E4 genotypes show an increased incidence of AD, but not MCI. ApoE4 carriers and especially E4/E4 homozygotes show a worse outcome on the CERAD total score, Blessed Dementia Scale, and Short Blessed Test and lower scores on the Verbal Fluency Test, Boston Naming Test, Constructional Praxis Recall, and Word List Memory, Recall, and Recognition. ApoE4 carriers and E4/E3 heterozygotes show higher scores on the Clock Drawing Test. ApoE4 carriers show a worse outcome on the CERAD clinical history scores of memory, language, personality, ADL, orientation, and social skills, while allele AopE3 carriers show better scores on activities of daily living (ADL) and social skills. ApoE3 carriers show lower total weighted, irritability/aggression, and behavioral dysregulation scores on the Behavior Rating Scale for Dementia. The results show that in Thai individuals, the presence of ApoE4 allele is accompanied by a multifarious decline in neurocognitive functions and behavioral features and that ApoE3 may convey protection against neuropsychiatric symptoms and a decline in social skills. ApoE4 and especially the E4/E4 genotype may affect multiple domains of cognitive, biobehavioral, and social functioning thereby contributing to AD phenomenology.

Religious Orders Study and Rush Memory and Aging Project

BACKGROUND

The Religious Orders Study and Rush Memory and Aging Project are both ongoing longitudinal clinical-pathologic cohort studies of aging and Alzheimer's disease (AD).

OBJECTIVES

To summarize progress over the past five years and its implications for understanding neurodegenerative diseases.

METHODS

Participants in both studies are older adults who enroll without dementia and agree to detailed longitudinal clinical evaluations and organ donation. The last review summarized findings through the end of 2011. Here we summarize progress and study findings over the past five years and discuss new directions for how these studies can inform on aging and AD in the future.

RESULTS

We summarize 1) findings on the relation of neurobiology to clinical AD; 2) neurobiologic pathways linking risk factors to clinical AD; 3) non-cognitive AD phenotypes including motor function and decision making; 4) the development of a novel drug discovery platform.

CONCLUSION

Complexity at multiple levels needs to be understood and overcome to develop effective treatments and preventions for cognitive decline and AD dementia.

HIV-associated neurocognitive disorder

Human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) affects roughly half the HIV-positive population. The symptoms of cognitive slowing, poor concentration, and memory problems can impact on everyday life. Its diagnosis is validated where possible by identifying deficits in two cognitive domains on neuropsychologic testing in patients either with or without symptoms. Corroborating evidence may be found on imaging, blood tests, and cerebrospinal fluid analysis, though sensitive and specific biomarkers are currently lacking. The introduction of combined antiretroviral therapy in the 1990s has generated a therapeutic paradox whereby the number of severe cases of HAND has fallen, yet milder forms continue to rise in prevalence. New emphasis has been placed on identifying the cause of apparent ongoing HIV infection and inflammation of the central nervous system (CNS) in the face of durable systemic viral suppression, and how this equates to the neuronal dysfunction underlying HAND. The interaction with aging and comorbidities is becoming increasingly common as the HIV-positive population enters older adulthood, with neurodegenerative, metabolic, and vascular causes of cognitive impairment combining and probably accelerating in the context of chronic HIV infection. Therapies targeted to the CNS, but without neurotoxic side-effects, are being investigated to attempt to reduce the likelihood of developing, and improving, HAND.

Using an Alzheimer Disease Polygenic Risk Score to Predict Memory Decline in Black and White Americans Over 14 Years of Follow-up

Evidence on whether genetic predictors of Alzheimer disease (AD) also predict memory decline is inconsistent, and limited data are available for African ancestry populations. For 8253 non-Hispanic white (NHW) and non-Hispanic black (NHB) Health and Retirement Study participants with memory scores measured 1 to 8 times between 1998 and 2012 (average baseline age=62), we calculated weighted polygenic risk scores [AD Genetic Risk Score (AD-GRS)] using the top 22 AD-associated loci, and an alternative score excluding apolipoprotein E (APOE) (AD-GRSexAPOE). We used generalized linear models with AD-GRS-by-age and AD-GRS-by-age interactions (age centered at 70) to predict memory decline. Average NHB decline was 26% faster than NHW decline (P<0.001). Among NHW, 10% higher AD-GRS predicted faster memory decline (linear β=-0.058 unit decrease over 10 y; 95% confidence interval,-0.074 to -0.043). AD-GRSexAPOE also predicted faster decline for NHW, although less strongly. Among NHB, AD-GRS predicted faster memory decline (linear β=-0.050; 95% confidence interval, -0.106 to 0.006), but AD-GRSexAPOE did not. Our nonsignificant estimate among NHB may reflect insufficient statistical power or a misspecified AD-GRS among NHB as an overwhelming majority of genome-wide association studies are conducted in NHW. A polygenic score based on previously identified AD loci predicts memory loss in US blacks and whites.

APOE ε4-TOMM40 '523 haplotypes and the risk of Alzheimer's disease in older Caucasian and African Americans

Patterns of linkage between the ε4 allele of Apolipoprotein E (APOE) and '523 poly-T alleles in the adjacent gene, TOMM40, differ between Caucasian and African Americans. The extent to which this difference affects the risk of Alzheimer's disease (AD) is unclear. We compared the APOE ε4-TOMM40 '523 haplotypes between older Caucasian and African Americans, and examined their relationship with AD dementia. Data came from three community based cohort studies of diverse participants. APOE genotypes were determined by polymorphisms of rs429358 and rs7412. TOMM40 '523 genotypes were defined by the poly-T repeat length of rs10524523 (short ['523-S]: poly-T ≤ 19, long ['523-L]: 20 ≤ poly-T ≤ 29, and very long ['523-VL]: poly-T ≥ 30). Cox proportional hazards models examined the effect of haplotype variation on the risk of incident AD dementia. A total of 1,848 Caucasian and 540 African American individuals were included in the study. In Caucasians, nearly none (0.8%) of the non-ε4 carriers and almost all (94.2%) of the ε4 carriers had '523-L. The classification was highly concordant. Each ε4 allele doubled the risk for AD dementia and the dose effect was evident. Almost identical effect size and effect pattern were observed for TOMM40 '523-L. In African Americans, nearly none (1.1%) of the non-ε4 carriers had '523-L, but only 47.8% of the ε4 carriers had '523-L. The concordance was weaker compared with Caucasians. The effect patterns on incident AD dementia differed distinctively between ε4 and '523-L carriers. Further, both genotypic and allelic data support that among African Americans the ε4-'523-L haplotype had stronger effect on risk of AD dementia than other ε4-'523 haplotypes.

Precuneus degeneration in nondemented elderly individuals with APOE ɛ4: Evidence from structural and functional MRI analyses

Neurodegenerative diseases such as Alzheimer's disease (AD) have been recognized to exhibit disease-specific brain vulnerability patterns. Apolipoprotein E (APOE) ɛ4 allele imparts a high genetic risk of developing AD. Whether the APOE ɛ4 allele damages the brain when cognitive functions are still intact is important to understand, especially for possible early detection and intervention. This study aimed to examine the selective degeneration pattern associated with the APOE ɛ4 allele in the brains of cognitively normal elderly subjects. We enrolled 35 cognitively healthy ɛ4 carriers and 40 non-carriers (53 to 81 years old) to evaluate group differences in cortical thickness and brain activation during a memory-encoding task. We also assessed the functional connectivity of the brain regions with both structural and functional damages. The results from the neuropsychological tests showed that the performances of ɛ4 carriers and non-carriers were comparable. Primarily, we found that the precuneus exhibited thinner cortical thickness and decreased deactivation during memory encoding. Furthermore, the connectivity analyses show that carriers exhibited damaged connectivity of the precuneus to several regions in the default mode network and the attention/executive control network. Our study reveals the degeneration pattern of the ɛ4 allele, which could be used as a potential biomarker for early detection for possible interventions and treatments. Hum Brain Mapp 38:271-282, 2017. © 2016 Wiley Periodicals, Inc.

Potential contribution of the Alzheimer's disease risk locus BIN1 to episodic memory performance in cognitively normal Type 2 diabetes elderly

In recent years, several promising susceptibility loci for late-onset Alzheimer's disease (AD) were discovered, by implementing genome-wide association studies (GWAS) approach. Recent GWAS meta-analysis has demonstrated the association of 19 loci (in addition to the APOE locus) with AD in the European ancestry population at genome-wide significance level. Since Type 2 Diabetes (T2D) is a substantial risk factor for cognitive decline and dementia, the 19 single nucleotide polymorphisms (SNPs) that represent the 19 AD loci were studied for association with performance in episodic memory, a primary cognitive domain affected by AD, in a sample of 848 cognitively normal elderly Israeli Jewish T2D patients. We found a suggestive association of SNP rs6733839, located near the bridging integrator 1 (BIN1) gene, with this phenotype. Controlling for demographic (age, sex, education, disease duration and ancestry) covariates, carriers of two copies of the AD risk allele T (TT genotype) performed significantly worse (p=0.00576; p=0.00127 among Ashkenazi origin sub-sample) in episodic memory compared to carriers of the C allele (CT+CC genotypes). When including additional potential covariates (clinical and APOE genotype), results remained significant (p=0.00769; p=0.00148 among Ashkenazi). Interestingly, as validated in multiple large studies, BIN1 is one of the most established AD risk loci, with a high odds ratio. Although preliminary and require further replications, our findings support a contribution of BIN1 to individual differences in episodic memory performance among T2D patients.

Cholesterol and cognitive performance among community volunteers from the Czech Republic

BACKGROUND

Research shows that lipid levels may be associated with cognitive function, particularly among women. We aimed to examine total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), high-density lipoprotein (HDL), and HDL/LDL ratio in relation to cognitive performance, measured with six well-established cognitive domains and a composite cognitive score (CCS).

METHODS

In this cross-sectional study, biomarkers and neuropsychological assessment were available for 141 adults with MMSE scores ≥ 24 (mean age = 69 years, 47% female, mean education = 14.4 years) attending a neuropsychological evaluation. Ordinary least squares regressions were adjusted for age, gender, education, and depressive symptoms in Model 1 and also for apolipoprotein E4 (APOE4) status in Model 2.

RESULTS

High-density lipoprotein cholesterol (HDL-C) was associated with better CCS (β = 0.24; p = 0.014). This association was significant among women (β = 0.30; p = 0.026) and not among men (β = 0.20; p = 0.124). HDL-C was also related to attention/working memory (β = 0.24; p = 0.021), again only among women (β = 0.37; p = 0.012) and not men (β = 0.15; p = 0.271). Adjusting for APOE4 yielded significance for high HDL-C and CCS (β = 0.24; p = 0.022).

CONCLUSIONS

HDL-C was the main lipoprotein affecting cognitive function, with results somewhat more pronounced among women. Research should investigate the possibility of finding ways to boost HDL-C levels to potentially promote cognitive function.

APOE ε4 allele is associated with worse performance in memory dimensions of the mini-mental state examination: the Bambuí Cohort Study of Aging

OBJECTIVE

This study aimed to investigate the correlation between apolipoprotein E (APOE) ε4 and the mini-mental state examination (MMSE) dimension in an elderly population, using baseline data from the Bambui (Brazil) Cohort Study of Aging.

DESIGN

We conducted a community-based cross-sectional study.

SETTING

The study took place at Bambui city, Minas Gerais State, Southeast Brazil.

PARTICIPANTS

A total of 1408 (87.7%) cohort participants had complete information on the MMSE and health measures.

MEASUREMENTS

The association between each of five dimensions (concentration, language/praxis, orientation, attention, and memory) underlying the MMSE and APOE ε4 allele was assessed using multivariate linear regression models. Potential confounding variables included sociodemographic factors and selected biomarkers.

RESULTS

The main finding is a strong negative association between the presence of APOE ε4 allele and memory dimension in the MMSE (fully adjusted β coefficient = -0.14; 95% confidence interval: -0.27 to -0.04; p = 0.016). No other cognitive dimensions showed significant associations with the APOE ε4 allele.

CONCLUSION

This study is the first to investigate the association between dimensions of the MMSE, obtained from principal component analysis and APOE ε4 carrier status in community-dwelling older adults taking into account a range of potential confounding factors. We found a strong negative association between the presence of APOE ε4 allele and scores on memory dimension of the MMSE, but no effect on other dimensions. Our results reinforce previous data on the literature that APOE ε4 allele has a significant effect on cognitive performance that can be detected even in screening tests, such as the MMSE.

Cytomegalovirus infection and risk of Alzheimer disease in older black and white individuals

BACKGROUND

Human cytomegalovirus (CMV) is prevalent in older adults and has been implicated in many chronic diseases of aging. This study investigated the relation between CMV and the risk of Alzheimer disease (AD).

METHODS

Data come from 3 cohort studies that included 849 participants (mean age [±SD], 78.6 ± 7.2 years; mean education duration [±SD], 15.4 ± 3.3 years; 25% black).

RESULTS

A solid-phase enzyme-linked immunosorbent assay was used for detecting type-specific immunoglobulin G antibody responses to CMV and herpes simplex virus type 1 (HSV-1) measured in archived serum samples. Of 849 participants, 73.4% had serologic evidence of exposure to CMV (89.0% black and 68.2% white; P < .001). During an average of 5.0 years of follow-up, 93 persons developed AD. CMV seropositivity was associated with an increased risk of AD (relative risk, 2.15; 95% confidence interval, 1.42-3.27) and a faster rate of decline in global cognition (estimate [±standard error], -0.02 ± 0.01; P = .03) in models that controlled for age, sex, education duration, race, vascular risk factors, vascular diseases, and apolipoprotein ε4 level. Results were similar in black and white individuals for both incident AD and change in cognitive function and were independent of HSV-1 status.

CONCLUSIONS

These results suggest that CMV infection is associated with an increased risk of AD and a faster rate of cognitive decline in older diverse populations.

Validation of a polygenic risk score for dementia in black and white individuals

OBJECTIVE

To determine whether a polygenic risk score for Alzheimer's disease (AD) predicts dementia probability and memory functioning in non-Hispanic black (NHB) and non-Hispanic white (NHW) participants from a sample not used in previous genome-wide association studies.

METHODS

Non-Hispanic white and NHB Health and Retirement Study (HRS) participants provided genetic information and either a composite memory score (n = 10,401) or a dementia probability score (n = 7690). Dementia probability score was estimated for participants' age 65+ from 2006 to 2010, while memory score was available for participants age 50+. We calculated AD genetic risk scores (AD-GRS) based on 10 polymorphisms confirmed to predict AD, weighting alleles by beta coefficients reported in AlzGene meta-analyses. We used pooled logistic regression to estimate the association of the AD-GRS with dementia probability and generalized linear models to estimate its effect on memory score.

RESULTS

Each 0.10 unit change in the AD-GRS was associated with larger relative effects on dementia among NHW aged 65+ (OR = 2.22; 95% CI: 1.79, 2.74; P < 0.001) than NHB (OR=1.33; 95% CI: 1.00, 1.77; P = 0.047), although additive effect estimates were similar. Each 0.10 unit change in the AD-GRS was associated with a -0.07 (95% CI: -0.09, -0.05; P < 0.001) SD difference in memory score among NHW aged 50+, but no significant differences among NHB (β = -0.01; 95% CI: -0.04, 0.01; P = 0.546). [Correction added on 29 July 2014, after first online publication: confidence intervalshave been amended.] The estimated effect of the GRS was significantly smaller among NHB than NHW (P < 0.05) for both outcomes.

CONCLUSION

This analysis provides evidence for differential relative effects of the GRS on dementia probability and memory score among NHW and NHB in a new, national data set.

The ApoE4 genotype modifies the relationship of long-term glycemic control with cognitive functioning in elderly with type 2 diabetes

AIM

To assess whether the APOE4 genotype affects the relationship of long-term glycemic control with cognitive function in elderly with type 2 diabetes (T2D).

METHODS

Participants were cognitively normal and pertained to a Diabetes Registry which provided access to HbA1c levels and other T2D related factors since 1998. Glycemic control was defined as the mean of all HbA1c measurements available (averaging 18 measurements) per subject. Four cognitive domains (episodic memory, semantic categorization, attention/working memory and executive function), based on factor analysis and an overall cognitive score (the sum of the 4 cognitive domains) were the outcome measures.

RESULTS

The analysis included 808 subjects; 107 (11.9%) subjects had ≥1ApoE4 allele. In ApoE4 carriers, higher mean HbA1c level was significantly associated with lower scores on all cognitive measures except attention/working memory (p-values ranging from 0.047 to 0.003). In ApoE4 non-carriers, higher mean HbA1c level was significantly associated with lower scores on executive function, but not with other cognitive measures-despite the larger sample size. Compared to non-carriers, there were significantly stronger associations in ApoE4 carriers for overall cognition (p=0.02), semantic categorization (p=0.03) and episodic memory (p=0.02), and the difference for executive function approached statistical significance (p=0.06).

CONCLUSION

In this cross-sectional study of cognitively normal T2D subjects, higher mean HbA1c levels were generally associated with lower cognitive performance in ApoE4 carriers, but not in non-carriers, suggesting that ApoE4 affects the relationship between long-term glycemic control and cognition, so APOE4 carriers may be more vulnerable to the insults of poor glycemic control.

Effects of APOE ε4, age, and HIV on glial metabolites and cognitive deficits

OBJECTIVE

We aimed to evaluate the combined effects of HIV and APOE ε4 allele(s) on glial metabolite levels, and on known cognitive deficits associated with either condition, across the ages.

METHODS

One hundred seventy-seven participants, primarily of white and mixed race (97 seronegative subjects: aged 44.7 ± 1.3 years, 85 [87.6%] men, 28 [28.9%] APOE ε4+; 80 HIV+ subjects: aged 47.3 ± 1.1 years, 73 [91.3%] men, 23 [28.8%] APOE ε4+), were assessed cross-sectionally for metabolite concentrations using proton magnetic resonance spectroscopy in 4 brain regions and for neuropsychological performance.

RESULTS

Frontal white matter myo-inositol was elevated in subjects with HIV across the age span but showed age-dependent increase in seronegative subjects, especially in APOE ε4+ carriers. In contrast, only seronegative APOE ε4+ subjects showed elevated myo-inositol in parietal cortex. All APOE ε4+ subjects had lower total creatine in basal ganglia. While all HIV subjects showed greater cognitive deficits, HIV+ APOE ε4+ subjects had the poorest executive function, fluency memory, and attention/working memory. Higher myo-inositol levels were associated with poorer fine motor function across all subjects, slower speed of information processing in APOE ε4+ subjects, and worse fluency in HIV+ APOE ε4+ subjects.

CONCLUSIONS

In frontal white matter of subjects with HIV, the persistent elevation and lack of normal age-dependent increase in myo-inositol suggest that persistent glial activation attenuated the typical antagonistic pleiotropic effects of APOE ε4 on neuroinflammation. APOE ε4 negatively affects energy metabolism in brain regions rich in dopaminergic synapses. The combined effects of HIV infection and APOE ε4 may lead to greater cognitive deficits, especially in those with greater neuroinflammation. APOE ε4 allele(s) may be a useful genetic marker to identify white and mixed-race HIV subjects at risk for cognitive decline.

Building a pipeline to discover and validate novel therapeutic targets and lead compounds for Alzheimer's disease

Cognitive decline, Alzheimer's disease (AD) and other causes are major public health problems worldwide. With changing demographics, the number of persons with dementia will increase rapidly. The treatment and prevention of AD and other dementias, therefore, is an urgent unmet need. There have been considerable advances in understanding the biology of many age-related disorders that cause dementia. Gains in understanding AD have led to the development of ante-mortem biomarkers of traditional neuropathology and the conduct of several phase III interventions in the amyloid-β cascade early in the disease process. Many other intervention strategies are in various stages of development. However, efforts to date have met with limited success. A recent National Institute on Aging Research Summit led to a number of requests for applications. One was to establish multi-disciplinary teams of investigators who use systems biology approaches and stem cell technology to identify a new generation of AD targets. We were recently awarded one of three such grants to build a pipeline that integrates epidemiology, systems biology, and stem cell technology to discover and validate novel therapeutic targets and lead compounds for AD treatment and prevention. Here we describe the two cohorts that provide the data and biospecimens being exploited for our pipeline and describe the available unique datasets. Second, we present evidence in support of a chronic disease model of AD that informs our choice of phenotypes as the target outcome. Third, we provide an overview of our approach. Finally, we present the details of our planned drug discovery pipeline.

Capacity building and collaborative research on cross-national studies in the Asian region

To build capacity and collaborative research for future cross-national studies in the Asian and Pacific Islander (API) region, priority research topics were identified and discussed at the April 2013 Conference to Promote Global Health in Taipei. These topics included (1) Neuroscience on HIV/HCV and amphetamine-type stimulants (ATS), led by Drs. Linda Chang, Gene-Jack Wang, and Betty Tai; (2) ATS and mental health disorders, led by Drs. Richard Rawson and Wilson Compton; and (3) HIV/HCV transmission and social networks, led by Drs. Steven Shoptaw and Jacques Normand. Potential genetic studies spanning these topical areas as well as the importance of smoking cessation were further discussed, led by Dr. Ming Li. Additional priority research topics were also identified: (4) Drug use prevention, and (5) Family involvement to improve treatment adherence and recovery. Workgroups on these topics will be formed to prioritize research questions within the respective topical area and to determine the next steps. The ultimate goal of these workgroups is to stimulate collaboration that will eventually lead to research studies addressing critical issues related to the rising substance abuse and HIV infection rates in many Asian countries and, at the same time, to advance the scientific knowledge of substance abuse and HIV infection.