Associations of Apolipoprotein ε4 Genotypes with Motor and Nonmotor Symptoms in Parkinson's Disease: A Cross-Sectional Study

Background

The apolipoprotein E (APOE) ε4 allele has been associated with cognitive decline in Parkinson's disease (PD), but little is known about its relationship with motor and other nonmotor symptoms and whether APOE ε4 retains an influence on cognition when other factors are considered.

Objective

To investigate the impact of APOE ε4 on motor/nonmotor symptoms and its relationship with other factors affecting cognition in individuals with PD.

Methods

We analyzed data from 7616 individuals, comparing motor/nonmotor symptoms in different APOE genotypes using binary logistic regression. Multivariate logistic regression examined factors associated with cognitive impairments, including APOE ε4, Geriatric Depression Scale (GDS) score, Non-motor Symptom Questionnaire (NMS) score, Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part II score, and physical activity level.

Results

APOE ε4 heterozygosity was modestly associated with lower cognitive scores (odds ratio [OR], 0.92; 95% confidence interval [CI], 0.87-0.99), whereas no significant association was found for any other nonmotor and motor symptoms. However, in multivariate analysis, cognitive impairment was associated with higher GDS (OR, 1.28; 95% CI, 1.23-1.34), NMS (OR, 1.22; 95% CI, 1.19-1.25), and MDS-UPDRS Part II (OR, 1.07; 95% CI, 1.06-1.09) scores, whereas physical activity was negatively associated (OR, 0.99; 95% CI, 0.98-0.99). APOE ε4 was no longer significant after adjusting for these factors.

Conclusions

There is a link between cognition and APOE ε4 in patients with PD; however, when considering multiple factors, APOE ε4 plays a subordinate role. Other factors, such as depression, physical activity, and other nonmotor symptoms, demonstrate a stronger influence on cognitive impairment.

Modulation of associations between education years and cortical volume in Alzheimer's disease vulnerable brain regions by Aβ deposition and APOE ε4 carrier status in cognitively normal older adults

Background

Education years, as a measure of cognitive reserve, have been shown to affect the progression of Alzheimer's disease (AD), both pathologically and clinically. However, inconsistent results have been reported regarding the association between years of education and intermediate structural changes in AD-vulnerable brain regions, particularly when AD risk factors were not considered during the preclinical phase.

Objective

This study aimed to examine how Aβ deposition and APOE ε4 carrier status moderate the relationship between years of education and cortical volume in AD-vulnerable regions among cognitively normal older adults.

Methods

A total of 121 participants underwent structural MRI, [18F] flutemetamol PET-CT imaging, and neuropsychological battery assessment. Multiple regression analysis was conducted to examine the interaction between years of education and the effects of potential modifiers on cortical volume. The associations between cortical volume and neuropsychological performance were further explored in subgroups categorized based on AD risk factors.

Results

The cortical volume of the left lateral occipital cortex and bilateral fusiform gyrus demonstrated a significant differential association with years of education, depending on the presence of Aβ deposition and APOE ε4 carrier status. Furthermore, a significant relationship between the cortical volume of the bilateral fusiform gyrus and AD-nonspecific cognitive function was predominantly observed in individuals without AD risk factors.

Conclusion

AD risk factors exerted varying influences on the association between years of education and cortical volume during the preclinical phase. Further investigations into the long-term implications of these findings would enhance our understanding of cognitive reserves in the preclinical stages of AD.

Impact of transcranial direct current stimulation on white matter microstructure integrity in mild cognitive impairment patients according to effect modifiers as risk factors for Alzheimer's disease

Background

Little research exists on how individual risk factors for Alzheimer's disease (AD) affect the intermediate phenotype after transcranial direct current stimulation (tDCS), despite the importance of precision medicine-based therapeutic approaches.

Objective

To determine how an application of sequential tDCS (2 mA/day, left dorsolateral prefrontal cortex, 10 sessions) affects changes in white matter (WM) microstructure integrity in 63 mild cognitive impairment (MCI) patients with effect modifiers such as Aβ deposition, APOE ε4 carrier status, BDNF Val66Met polymorphism status, and sex.

Methods

We examined individual effect modifier-by-tDCS interactions and multiple effect modifiers-by-tDCS interactions for diffusion metrics. We also evaluated the association between baseline Aβ deposition and changes in WM microstructure integrity following tDCS.

Results

We found that APOE ε4 carrier status and sex had a significant interaction with tDCS, resulting in increased fractional anisotropy (FA) in the right uncinate fasciculus (UF) after stimulation. Additionally, we observed multiple effect modifiers-by-tDCS interactions on WM integrity of the right UF, leading to a more pronounced increase in FA values in APOE ε4 carriers and females with Val66 homozygotes. Finally, baseline Aβ deposition was positively associated with a difference in FA of the left cingulum in the hippocampal area, which showed a positive association with the changes in the score for delayed memory.

Conclusion

Our study shows the differential impact of individual AD risk factors on changes in the early intermediate phenotype after sequential tDCS in MCI patients. This research emphasizes the importance of precision medicine approaches in tDCS for the prodromal stages of AD.

Association of Circulating Caprylic Acid with Risk of Mild Cognitive Impairment and Alzheimer's Disease in the Alzheimer's Disease Neuroimaging Initiative (ADNI) Cohort

OBJECTIVE

Medium-chain fatty acids (MCFAs) can rapidly cross the blood-brain barrier and provide an alternative energy source for the brain. This study aims to determine 1) whether plasma caprylic acid (C8:0) is associated with risk of incident mild cognitive impairment (MCI) among baseline cognitively normal (CN) participants, and incident Alzheimer's Disease (AD) among baseline MCI participants; and 2) whether these associations differ by sex, comorbidity of cardiometabolic diseases, apolipoprotein E (APOE) ε4 alleles, and ADAS-Cog 13.

METHODS

Within the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort, plasma C8:0 was measured at baseline in 618 AD-free participants aged 55 to 91. Logistic regression models were used to estimate odds ratios (ORs) and 95% CIs with incident MCI and AD as dependent variables, separately.

RESULTS

The inverse association between circulating C8:0 and risk of incident MCI was of borderline significance. The inverse association between circulating levels of C8:0 and risk of incident MCI was significant among CN participants with ≥1 cardiometabolic diseases [OR (95% CI): 0.75 (0.58-0.98) (P=0.03)], those with one copy of APOE ε4 alleles [OR (95% CI): 0.43 (0.21-0.89) (P=0.02)], female [OR (95% CI): 0.60 (0.38-0.94) (P=0.02)], and ADAS-Cog 13 above the median [OR (95%CI): 0.69 (0.50-0.97)(P=0.03)] after adjusting for all covariates.

CONCLUSION

The inverse associations were present only among subgroups of CN participants, including female individuals, those with one or more cardiometabolic diseases, or one APOE ε4 allele, or higher ADAS-Cog 13 scores. If confirmed, this finding will facilitate precision prevention of MCI, in turn, AD among CN older adults.

APOE alleles modulate associations of plasma metabolites with variants from multiple genes on chromosome 19q13.3

The APOE ε2, ε3, and ε4 alleles differentially impact various complex diseases and traits. We examined whether these alleles modulated associations of 94 single-nucleotide polymorphisms (SNPs) harbored by 26 genes in 19q13.3 region with 217 plasma metabolites using Framingham Heart Study data. The analyses were performed in the E2 (ε2ε2 or ε2ε3 genotype), E3 (ε3ε3 genotype), and E4 (ε3ε4 or ε4ε4 genotype) groups separately. We identified 31, 17, and 22 polymorphism-metabolite associations in the E2, E3, and E4 groups, respectively, at a false discovery rate P _FDR < 0.05. These entailed 51 and 19 associations with 20 lipid and 12 polar analytes. Contrasting the effect sizes between the analyzed groups showed 20 associations with group-specific effects at Bonferroni-adjusted P < 7.14E-04. Three associations with glutamic acid or dimethylglycine had significantly larger effects in the E2 than E3 group and 12 associations with triacylglycerol 56:5, lysophosphatidylethanolamines 16:0, 18:0, 20:4, or phosphatidylcholine 38:6 had significantly larger effects in the E2 than E4 group. Two associations with isocitrate or propionate and three associations with phosphatidylcholines 32:0, 32:1, or 34:0 had significantly larger effects in the E4 than E3 group. Nine of 70 SNP-metabolite associations identified in either E2, E3, or E4 groups attained P _FDR < 0.05 in the pooled sample of these groups. However, none of them were among the 20 group-specific associations. Consistent with the evolutionary history of the APOE alleles, plasma metabolites showed higher APOE-cluster-related variations in the E4 than E2 and E3 groups. Pathway enrichment mainly highlighted lipids and amino acids metabolism and citrate cycle, which can be differentially impacted by the APOE alleles. These novel findings expand insights into the genetic heterogeneity of plasma metabolites and highlight the importance of the APOE-allele-stratified genetic analyses of the APOE-related diseases and traits.

Reassessing Diabetes and APOE Genotype as Potential Interacting Risk Factors for Alzheimer's Disease

Objective: To assess whether diabetes alone or in association with Apolipoprotein E (APOE) ε4 genotype increases the risk of Alzheimer's Disease (AD) diagnosis. Methods: A retrospective cohort study of 33,456 participants from the National Alzheimer's Coordinating Center database. Results: Participants with one or two APOE ε4 alleles had 2.71 (CI:2.55-2.88) and 9.37 (CI:8.14-10.78) times higher odds of AD diagnosis, respectively, relative to those with zero ε4 alleles. In contrast, diabetic participants showed 1.07 (CI:0.96-1.18) times higher odds of AD relative to nondiabetics. Diabetes did not exacerbate the odds of AD in APOE ε4 carriers. APOE ε4 carriage was correlated with declines in long-term memory and verbal fluency, which were strongly correlated with conversion to AD. However, diabetes was correlated with working memory decline, which had a relatively weak correlation with AD. Conclusions: Unlike APOE ε4, there was little evidence that diabetes was a risk factor for AD.

Case Report: Coexistence of Alzheimer-Type Neuropathology in Fragile X-Associated Tremor Ataxia Syndrome

This case documents the co-occurrence of the fragile X-associated tremor ataxia syndrome (FXTAS) and Alzheimer-type neuropathology in a 71-year-old premutation carrier with 85 CGG repeats in the fragile X mental retardation 1 (FMR1) gene, in addition to an apolipoprotein E (APOE) ε4 allele. FXTAS and Alzheimer's Disease (AD) are late-onset neurodegenerative diseases that share overlapping cognitive deficits including processing speed, working memory and executive function. The prevalence of coexistent FXTAS-AD pathology remains unknown. The clinical picture in this case was marked with rapid cognitive decline between age 67 and 71 years in addition to remarkable MRI changes. Over the 16 months between the two clinical evaluations, the brain atrophied 4.12% while the lateral ventricles increased 26.4% and white matter hyperintensities (WMH) volume increased 15.6%. Other regions atrophied substantially faster than the whole brain included the thalamus (-6.28%), globus pallidus (-10.95%), hippocampus (-6.95%), and amygdala (-7.58%). A detailed postmortem assessment included an MRI with confluent WMH and evidence of cerebral microbleeds (CMB). The histopathological study demonstrated FXTAS inclusions in neurons and astrocytes, a widespread presence of phosphorylated tau protein and, amyloid β plaques in cortical areas and the hippocampus. CMBs were noticed in the precentral gyrus, middle temporal gyrus, visual cortex, and brainstem. There were high amounts of iron deposits in the globus pallidus and the putamen consistent with MRI findings. We hypothesize that coexistent FXTAS-AD neuropathology contributed to the steep decline in cognitive abilities.

Differential Effects of the Interaction Between the Education and APOE ε4 Allele on Amyloid-beta Retention and Memory Performances in Cognitively Normal Older Adults and Alzheimer's Disease Patients

BACKGROUND

Despite the effect of education and APOE ε4 allele on amyloid-beta (Aβ) retention and memory, previous studies have not dealt with an interaction between two factors on Aβ deposition and memory function in the course of Alzheimer's disease (AD).

OBJECTIVE

To evaluate education by APOE ε4 allele interactions for Aβ retention and neuropsychological test scores in cognitively normal older adults without Aβ deposition [CN(Aβ-), n=45] and Alzheimer's disease patients with Aβ retention [AD(Aβ+), n=33].

METHODS

Multiple regression analyses (adjusted for age, gender) were conducted to examine the effects of education, APOE ε4 allele, and the interaction between the two factors on global, regional Aβ load quantified using [18F]flutemetamol standardized uptake value ratio with the pons as a reference region, and on neuropsychological test scores in each group.

RESULTS

The interaction between education and APOE ε4 allele had an effect on amyloid load in parietal lobes (uncorrected p<0.05) and striatum (Bonferroni corrected p<0.05) in each CN(Aβ-) and AD(Aβ+). There was also an interaction effect of education and APOE ε4 allele on the memory performance in each CN(Aβ-) and AD(Aβ+) (uncorrected p<0.05). APOE ε4 carriers of both groups showed opposing slopes with each other in the correlation between the education years and Aβ load, memory performance.

CONCLUSION

The current results suggest a possible explanation of the differential effects of education and APOE ε4 allele interactions on AD pathology and memory function at the beginning and end of AD progress. However, further study with a validating cohort is needed for confirming this explanation.

Sex-Specific Effects of Apolipoprotein ε4 Allele on Mortality in Very Old and Centenarian Japanese Men

The apolipoprotein E4 (APOE ε4) allele has attracted attention as an age-related genetic factor, both in neurology and gerontology. To understand the effects of the APOE ε4 allele on mortality in elderly individuals, we combined Japanese prospective cohort studies comprising 535 very old individuals (85-99 years of age) and 930 centenarians (over 100 years of age) and analyzed the association between mortality rates and candidate factors, including the APOE ε4 allele. APOE genotyping revealed an inverse correlation between the APOE ε4 allele carrier rate and age. Additionally, APOE ε4 allele carrier rate in centenarian men was significantly lower than that in centenarian women. The association analysis between APOE ε4 allele carriers and all-cause mortality indicated that APOE ε4 carriers showed significantly higher mortality rates than the APOE ε4 noncarriers among men in the very old group. Further analysis using Cox proportional hazard models indicated that cause-specific mortalities, including pneumonia and severe dementia, were associated with APOE ε4 carriers. These findings indicate that the APOE ε4 allele shows phenotypic male-specific adverse effects in the very old, which would explain the high mortality rate observed in this group, resulting in a low APOE ε4 allele carrier rate in centenarian men.

APOE genotypes as a risk factor for age-dependent accumulation of cerebrovascular disease in older adults

INTRODUCTION

Apolipoprotein E (APOE) is a susceptibility gene for late-onset Alzheimer's disease neuropathology; less is known about the relationship between APOE and cerebrovascular disease (CVD) neuropathology.

METHODS

We investigated associations of APOE status with arteriolosclerosis, macroinfarcts and microinfarcts, and atherosclerosis in 1383 adults (65.9-108.2 years at death) with and without dementia. Excluding ε2/ε4 carriers, multivariable regressions for each CVD-related neuropathology compared ε4 and ε2 carriers to ε3/ε3 carriers adjusting for confounders including age and Alzheimer's neuropathology.

RESULTS

Three hundred forty-two individuals (24.7%; ∼87.7 years at death; 39.9% nondemented) were ε3/ε4 or ε4/ε4, and 180 (13.0%; ∼89.9 years at death; 66.6% nondemented) were ε2/ε3 or ε2/ε2. ε4 carriers had higher odds of macroinfarcts (odds ratio = 1.41, 95% confidence interval: 1.02-1.94, P = .03), whereas ε2 carriers had higher odds of moderate-to-severe arteriolosclerosis (odds ratio = 1.68, 95% confidence interval: 1.15-2.45, P = .006) compared to ε3/ε3 carriers. Age-stratified analyses suggested that these relationships were driven by ε4 carriers <90 years at death and ε2 carriers ≥90 years at death, respectively.

DISCUSSION

APOE differentially affects type and timing of CVD-related neuropathology.

Impact of apolipoprotein E genotypes on vitamin E and memantine treatment outcomes in Alzheimer's disease

Introduction

Because apolipoprotein E (APOE) genotypes are known risk factors for Alzheimer's disease (AD), they have been measured in clinical trial participants to determine their effect on treatment outcome.

Methods

We determined APOE genotypes in a subset of subjects (N = 415) who participated in a randomized controlled trial of vitamin E and memantine in 613 veterans with mild-to-moderate AD.

Results

Similar to the primary study, substudy participants receiving vitamin E also had slower functional decline than those receiving placebo. Overall, there was no difference in the rate of functional decline between APOE ε4 allele carriers and noncarriers. A significant interaction was observed between treatment and the APOE genotype on AD progression: ε4 carriers declined faster than noncarriers in the vitamin E plus memantine treatment arm.

Discussion

APOE genotypes may modulate AD treatment response and should be included in the design of future randomized controlled trials.

ABCA7 gene and the risk of Alzheimer's disease in Han Chinese in Taiwan

The ATP-binding cassette, subfamily A, member 7 gene (ABCA7) was recently identified as a susceptible gene of Alzheimer's disease (AD) in the Caucasian population and African Americans. To test its genetic effect in the Han-Chinese population, 536 AD cases and 307 cognitive-intact, elder controls were genotyped for ABCA7 rs3764650 and apolipoprotein E (APOE) ε2/ε3/ε4 alleles. Global cognitive performance was assessed by the Mini-Mental State Examination in both AD patients and controls. For AD patients, comprehensive evaluation of each cognitive domain was further conducted as the following: (1) attention (forward and backward digit span); (2) memory (12-item word recall test); (3) executive function (category verbal fluency); (4) processing speed (Trail making test, part A); and (5) naming task (Boston naming test). ABCA7 rs3764650 was significantly associated with AD and the GG genotype carried a reduced risk for AD (odds ratio = 0.52, p = 0.0026). The association was further confirmed in 1802 population-based, healthy controls from Taiwan Biobank as a replicate (odds ratio = 0.70, p = 0.032). After adjustment of age, sex, and APOE ε4 allele, rs3764650 remained to be an independent predictor of AD (p = 0.001). The influence of ABCA7 was only evident in individuals without APOE ε4 alleles (p = 0.0004) but absent in ε4 carriers (p = 0.91). None of the cognitive tests was related to ABCA7 rs3764650 genotypes. The minor allele frequency and effect size of rs3764650 disclosed in the Han-Chinese population differed from those reported in the Caucasians and African Americans. Further studies were warranted to elucidate ABCA7's effect among different ethnic groups.