Absence of the apolipoprotein E ε4 allele is associated with working memory impairment in Parkinson's disease

Association of PICALM with Cognitive Impairment in Parkinson's Disease

BACKGROUND

Cognitive impairment is one of the most disabling nonmotor symptoms in Parkinson's disease (PD). Recently, a genome-wide association study in Alzheimer's disease has identified the PICALM rs3851179 polymorphism as one of the most significant susceptibility genes for Alzheimer's disease after APOE. The aim of this study was to determine the potential role of PICALM and its genetic interaction with APOE in the development of cognitive decline in PD.

METHODS

A discovery cohort of 712 patients with PD were genotyped for PICALM (rs3851179) and APOE (rs429358 and rs7412) polymorphisms. The association of PICALM and APOE-PICALM genetic interaction with cognitive dysfunction in PD was studied using logistic regression models, and the relationship of PICALM with cognitive decline onset was assessed with Cox regression analysis. PICALM effect was then replicated in an international, independent cohort (Parkinson's Progression Markers Initiative, N = 231).

RESULTS

PICALM rs3851179 TT genotype was significantly associated with a decreased risk of cognitive impairment in PD (TT vs. CC + CT, P = 0.041, odds ratio = 0.309). Replication studies further demonstrated its protective effect on cognitive impairment in PD. In addition, the protective effect of the PICALM rs3851179 TT genotype was more pronounced in the APOE ε4 (-) carriers from the discovery cohort (P = 0.037, odds ratio = 0.241), although these results were not replicated in the Parkinson's Progression Markers Initiative cohort.

CONCLUSIONS

Our results support the fact that PICALM is associated with cognitive impairment in PD. The understanding of its contribution to cognitive decline in PD could provide new targets for the development of novel therapies. © 2020 International Parkinson and Movement Disorder Society.

Quantification of total apolipoprotein E and its isoforms in cerebrospinal fluid from patients with neurodegenerative diseases

BACKGROUND

The human APOE gene, which codes for apolipoprotein E (apoE), has three major polymorphic alleles: ε2, ε3, and ε4 that give rise to amino acid substitutions. APOE-ε4 is a strong risk factor of sporadic Alzheimer's disease (AD) but the reason why is still unknown despite intense research for more than 20 years. The aim of the study was to investigate if the concentrations of total apoE and the specific apoE isoforms in cerebrospinal fluid (CSF) differ between various neurodegenerative diseases and control individuals, as well as among the APOE genotypes.

METHODS

Quantification of total apoE and specific apoE isoforms (E2, E3, and E4) in CSF was performed using high-resolution parallel reaction monitoring mass spectrometry. In total, 1820 individuals were involved in the study including clinically diagnosed AD patients (n = 228), cognitively unimpaired (CU) patients (n = 896), and patients with other neurodegenerative disorders (n = 696). Follow-up data was available for 100 individuals, assessed at two time points. Subjects were dichotomized based on an Aβ42/40 CSF concentration ratio cut-off into Aβ positive (Aβ+, < 0.091) and Aβ negative (Aβ-, > 0.091) groups.

RESULTS

Even though there was a significant increase of total apoE in the amyloid β-positive (Aβ+) group compared with amyloid β-negative (Aβ-) individuals (p < 0.001), the magnitude of the effect was very small (AUC = 0.55). Moreover, CSF total apoE concentrations did not differ between Aβ- CU controls and clinically diagnosed AD patients. There was a difference in concentration between isoforms in heterozygous individuals in an isoform-dependent manner (E2 < E3 < E4) (p < 0.001, AUC = 0.64-0.69), and these associations remained when dichotomizing the samples into Aβ+ and Aβ- groups (p < 0.01, AUC = 0.63-0.74). In the cohort with follow-up samples, neither total apoE nor isoform-specific apoE concentrations differed between the two time points (p > 0.05).

CONCLUSIONS

The results indicate that neither the concentrations of total apoE nor the different apoE isoforms in CSF are associated with APOE-ε4 carrier status, Aβ status, or clinical dementia diagnoses.

Systematic review of genetic variants associated with cognitive impairment and depressive symptoms in Parkinson's disease

OBJECTIVE

Cognitive impairment and depression are among the most prevalent and most disabling non-motor symptoms in Parkinson's disease (PD). The genetic factors that are associated with these symptoms remain uncertain. This systematic review aims to summarise the prevailing evidence from all genetic association studies investigating the genetic variants associated with cognitive impairment and depressive symptoms in people with PD.

METHOD

A systematic review using five online databases: PubMed, PsycINFO, CINAHL, EMBASE and OpenGrey (PROSPERO protocol: CRD42017067431). We completed the quality assessment using the Q-Genie tool.

RESULTS

2353 articles were screened, and 43 articles were found to be eligible to be included. A meta-analysis of studies investigating LRRK2 rs34637584 confirmed that the minor allele carriers had significantly less cognitive impairment (p = 0.015). Further meta-analyses showed that GBA variants rs76763715 (p < 0.001) and rs421016 (p = 0.001) were significantly associated with more cognitive impairment in people with PD. Minor alleles of GBA variants rs76763715, rs421016, rs387906315 and rs80356773 were associated with more depressive symptoms in PD. Moreover, APOE ε4 allele has been associated with more cognitive impairment in PD. BDNF (rs6265) and CRY1 (rs2287161) variants have been associated with more depressive symptoms in people with PD.

CONCLUSIONS

PD carriers of GBA variants are at high risk for cognitive decline and depression. Screening for these variants may facilitate early identification and effective management of these non-motor symptoms. The molecular mechanisms underlying favourable cognitive functioning in LRRK2 rs34637584 variant carriers warrant further investigation.

Apolipoprotein E Polymorphisms and Parkinson Disease With or Without Dementia: A Meta-Analysis Including 6453 Participants

A large number of case-control studies have investigated the association of apolipoprotein E ( APOE) polymorphisms with Parkinson disease (PD) and Parkinson disease dementia (PDD), with inconsistent results. This meta-analysis aimed to evaluate the relationship between APOE polymorphisms and PD/PDD risk. We searched for published studies in PubMed, Web of Science, WanFang Data (in Chinese), and CNKI (in Chinese) from inception to June 2017. Case-control studies reporting part or complete APOE genotype and allele frequency data were included. Pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated using RevMan 5.3 software. A total of 39 studies involving 6453 cases with PD, with 461 cases with PDD, and 6855 controls were included in this meta-analysis. The results showed that the APOE ε3 allele was a protective factor for PD (OR = 0.90, 95% CI: 0.81-0.99; P = .04), whereas no significant differences in PD risk among all cases compared to controls were found for APOE ε2 and ε4. In Asian subgroups, the APOE ε4 allele was shown to be a risk factor for PD (OR = 1.22, 95% CI: 1.01-1.46; P = .04). Additionally, APOE polymorphisms were significantly associated with PDD risk in the entire case group (ε3: OR = 0.72, 95% CI: 0.58-0.89, P = .003; ε4: OR = 1.46, 95% CI: 1.12-1.88, P = .004) and in Asian subgroups.

Meta-Analysis of the Relationship between the APOE Gene and the Onset of Parkinson's Disease Dementia

Purpose

To clarify the relationship between certain genotypes or alleles of the APOE gene and the onset risk of Parkinson's disease dementia (PDD).

Methods

The PubMed, Cochrane, Embase, CBM, CNKI, and Wanfang databases were searched to identify all case-control studies and cohort studies published before October 30, 2017, that investigated the association between the APOE gene and the onset of PDD. Manual information retrieval was also performed. All studies that met the quality requirements were included in a meta-analysis performed using RevMan 5.3 software.

Results

The meta-analysis included 17 studies, with a total of 820 patients in the PDD group and 1,922 in the non-PDD group. The influence of the APOE gene on PDD onset was analyzed from three aspects: five genotypes vs. ε3/3, ε2+/ε4+ vs. ε3/3, and ε4+ vs. ε4-. The risk factors for PDD may include the genotypes ε3/4 (OR 1.47, 95% CI 1.14-1.89) and ε4/4 (OR 2.93, 95% CI 1.20-7.14). In patients with PDD, there was no significant difference in the distribution of ε2+ vs. ε3/3 (OR 1.35, 95% CI 0.97-1.87, P=0.07). The risk of PDD was 1.61 times greater in ε4+ compared with ε3/3 (OR 1.61, 95% CI 1.24-2.08, P=0.0003). As the results indicated that ε2+ did not play a role as a risk factor or a protective factor, we divided the population into ε4+ and ε4- for the meta-analysis and found that, among patients with Parkinson's disease, the dementia risk of those with ε4+ was 1.72 times greater than that of those with ε4- (OR 1.72, 95% CI 1.41-2.10, P < 0.00001). Subgroup analysis in accordance with different geographical regions revealed that ε4+ was a risk factor for PDD in people from all regions.

Conclusions

Among the APOE genotypes, ε2+ is neither a risk factor nor a protective factor for PDD, while ε4+ is a risk factor for PDD. The present results are applicable to Asian, European, and American patients with Parkinson's disease. Regarding the single APOE genotypes, ε3/4 and ε4/4 may be risk factors for PDD; however, further studies with large sample sizes are needed to verify this.

The genetic association between apolipoprotein E gene polymorphism and Parkinson disease: A meta-Analysis of 47 studies

OBJECTIVE

Although the relationship between apolipoprotein E (ApoE) gene polymorphisms and the risk of Parkinson disease (PD) has been established, the results were inconsistent and inconclusive.

METHODS

A comprehensive search examining the association between APOE polymorphisms and PD through PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI), and Cochrane Library databases was performed without published year limited.

RESULTS

A total of 47 studies with 7533 cases and 14442 controls were included in present study. The results showed statistically significant association between risk factor ApoE ε4 allele and PD in Asian population (P = .003, odds ratio, OR [95% confidence interval, CI] = 1.43 [1.13,1.80]). Genotype ε2ε4 have significantly associated with PD in Asian population (P = .004, OR [95% CI] = 4.43 [1.62,12.10]). Genotype ε3ε4 was significantly associated with PD in Latin-American population (P = .01, OR [95% CI] = 1.44 [1.08,1.91]). In addition, the frequency of the genotype ε3ε4 is lower in PD group than that in the control group in Caucasian population, and the difference of genotype ε3ε4 is also statistically significant (P = .006, OR [95% CI] = 0.86 [0.77,0.96]). Although significant heterogeneity was observed among all studies, the results were shown to be stabilized by sensitive analysis. No publish bias was observed.

CONCLUSIONS

This meta-analysis suggests that the APOE ε4, but no ε2, might be a risk factor for PD in Asian population. Furthermore, the genotype ε2ε4 may be a susceptible factor for PD in Asian population, and the genotype ε3ε4 may be a susceptible factor for PD in both Caucasian and Latin-American populations.

Biomarkers for dementia and mild cognitive impairment in Parkinson's disease

Cognitive decline is one of the most frequent and disabling nonmotor features of Parkinson's disease. Around 30% of patients with Parkinson's disease experience mild cognitive impairment, a well-established risk factor for the development of dementia. However, mild cognitive impairment in patients with Parkinson's disease is a heterogeneous entity that involves different types and extents of cognitive deficits. Because it is not currently known which type of mild cognitive impairment confers a higher risk of progression to dementia, it would be useful to define biomarkers that could identify these patients to better study disease progression and possible interventions. In this sense, the identification among patients with Parkinson's disease and mild cognitive impairment of biomarkers associated with dementia would allow the early detection of this process. This review summarizes studies from the past 25 years that have assessed the potential biomarkers of dementia and mild cognitive impairment in Parkinson's disease patients. Despite the potential importance, no biomarker has as yet been validated. However, features such as low levels of epidermal and insulin-like growth factors or uric acid in plasma/serum and of Aß in CSF, reduction of cerebral cholinergic innervation and metabolism measured by PET mainly in posterior areas, and hippocampal atrophy in MRI might be indicative of distinct deficits with a distinct risk of dementia in subgroups of patients. Longitudinal studies combining the existing techniques and new approaches are needed to identify patients at higher risk of dementia. © 2016 International Parkinson and Movement Disorder Society.

Biomarkers of cognitive decline in Parkinson's disease

Cognitive impairment is a frequent and devastating non-motor symptom of Parkinson's disease (PD). Impaired cognition has a major impact on either quality of life or mortality in patients with PD. Notably, the rate of cognitive decline and pattern of early cognitive deficits in PD are highly variable between individuals. Given that the underlying mechanisms of cognitive decline or dementia associated with PD remain unclear, there is currently no mechanism-based treatment available. Identification of biological markers, including neuroimaging, biofluids and common genetic variants, that account for the heterogeneity of PD related cognitive decline could provide important insights into the pathological processes that underlie cognitive impairment in PD. These combined biomarker approaches will enable early diagnosis and provide indicators of cognitive progression in PD patients. This review summarizes recent advances in the development of biomarkers for cognitive impairments in PD.

Cognitive, neuropsychiatric, and motor features associated with apolipoprotein E ε4 allele in a sample of Bulgarian patients with late-onset Parkinson's disease

OBJECTIVE

To evaluate the role of apolipoprotein E (APOE) ε4 allele on cognitive, neuropsychiatric, and motor features in a sample of Bulgarian patients with late-onset Parkinson's disease (LOPD, age at onset > 55 years).

METHODS

A total of 16 patients with LOPD having APOE ε3/ε4 genotype were compared to 30 patients with LOPD having APOE ε3/ε3 genotype and 20 healthy control individuals. Detailed cognitive assessment and evaluation of neuropsychiatric and motor symptoms were performed.

RESULTS

The patients with LOPD had significantly lower scores in all cognitive domains compared to controls. The patients with LOPD carrying an ε4 allele showed some significant differences in their cognitive, motor, and neuropsychiatric features.

CONCLUSIONS

The data suggest a role of the APOE genotype as a disease-modifying factor.

Molecular neuropathogenesis of Alzheimer's disease: an interaction model stressing the central role of oxidative stress

Alzheimer's disease (AD) exhibits a complex etiology that simultaneously manifests as a complex cellular, neurobiological, molecular, anatomic-physiological and clinical entity. Other significant psychiatric conditions, such as depression and schizophrenia, may also present with complex and concurrent clinical and/or molecular phenotypes. These neuropsychiatric pathologies also originate from both environmental and genetic factors. We analyzed the molecular phenotypes of AD and discuss them with respect to the classical theories, which we integrated into mechanisms that share molecular and/or anatomical connections. Based on these mechanisms, we propose an interaction model and discuss the model in light of studies that refute or support it. Given the spectrum of AD phenotypes, we limit the scope of our discussion to a few, which facilitates concrete analysis. In addition, the study of specific, individual pathogenic phenotypes may be critical to defining the complex mechanisms leading to AD, thereby improving strategies for developing novel therapies.

Function and comorbidities of apolipoprotein e in Alzheimer's disease

Alzheimer's disease (AD)—the most common type of dementia among the elderly—represents one of the most challenging and urgent medical mysteries affecting our aging population. Although dominant inherited mutation in genes involved in the amyloid metabolism can elicit familial AD, the overwhelming majority of AD cases, dubbed sporadic AD, do not display this Mendelian inheritance pattern. Apolipoprotein E (APOE), the main lipid carrier protein in the central nervous system, is the only gene that has been robustly and consistently associated with AD risk. The purpose of the current paper is thus to highlight the pleiotropic roles and the structure-function relationship of APOE to stimulate both the functional characterization and the identification of novel lipid homeostasis-related molecular targets involved in AD.

Profile of cognitive impairment in Parkinson's disease

Cognitive impairment (CI) is a common nonmotor complication of Parkinson's disease (PD), and is associated with significant disability for patients and burden for caregivers. Similar to motor symptoms, the characteristics of CI in PD can be quite variable, both in terms of what cognitive domains are impaired, and the timing of onset and rate of progression. This review will examine the profile of cognitive domain impairments observed in PD, with a focus on early CI (without dementia). We will also discuss possible relationships between specific cognitive domain impairments in PD and pathological processes such as Lewy-related pathology and Alzheimer's disease. It is our hypothesis that the specific characteristics of CI observed in individual PD patients provide clues to the underlying pathological processes, and that understanding the biological basis of this clinical phenomenon will assist in directing disease-specific treatments. Given the high lifetime risk for CI in PD, it is imperative that we improve our understanding and treatments for this common and disabling problem in PD.

Anxiety affects working memory only in left hemibody onset Parkinson disease patients

OBJECTIVE

This investigation sought to examine the potential moderating influence of heightened anxiety on working memory in Parkinson disease (PD) patients. Further, we wanted to determine whether this moderating influence of anxiety differentially affects PD patients with left hemibody (LBH) versus right hemibody (RHB) onset of motor symptoms.

BACKGROUND

Research has examined the neurocognitive effects of depression in PD. However, a paucity of research has examined the effects of heightened anxiety in PD. We predicted that LHB PD patients with heightened anxiety would perform worse on a measure of working memory than RHB PD patients.

METHOD

A total of 59 PD patients completed the state-trait anxiety inventory and were also administered the digit span subtest of the Wechsler Memory Scale-III.

RESULTS

The results supported the hypotheses, indicating that the LHB PD patients with heightened anxiety performed significantly worse than the RHB PD patients with heightened anxiety and the LHB PD patients with low anxiety.

CONCLUSIONS

These findings suggest that left hemibody onset PD patients may experience more disability in their activities of daily living. Future research should explore whether differences also exist between PD patients with and without the diagnosed anxiety disorders.