Risk Factor For Sporadic Alzheimer's Disease Research Articles

Sleep and APOE-ε4 have a synergistic effect on plasma biomarkers and longitudinal cognitive decline in older adults.

Sleep disorders are prevalent among patients with Alzheimer's disease (AD), and the APOE ε4 genotype is a key genetic risk factor for sporadic AD. However, the combined effect of the genotype and sleep disorders on cognitive decline remains uncertain. A total of 972 participants were drawn from the SILCODE cohort, comprising 655 without the ε4 allele (APOE-) and 317 with ε4 allele (APOE+). Data were collected, including neuropsychological assessments, sleep measurements, plasma biomarkers, and PET imaging. A Sleep Composite Index (SCI) was created, categorizing participants into high risk (Sleep+) and low risk (Sleep-). Significant predictions of dementia risk associated with plasma p-tau181, neurofilament light chain (NfL), and SCI. Individuals with both Sleep+ and APOE+ had a higher risk of dementia compared to those with Sleep-. The Sleep+/APOE+ group had higher plasma NfL levels than the Sleep-/APOE- group. Similar trends emerged in plasma NfL levels among the Aβ PET-positive subgroup. Plasma NfL levels explained 23% of the relationship between SCI and cognitive impairment. Our study highlights sleep disorder was associated with cognitive decline, with plasma NfL playing a partial mediating role. These findings explain how sleep disorders affect cognitive function and emphasize the importance of healthy sleep for older adults.

Towards A Cell Biology of Alzheimer’s Disease

In many neurodegenerative disorders, including Alzheimer's Disease (AD), the dysfunction of multiple cell types causes neuronal cell death, but the precise cellular processes involved remain incompletely understood for any neurodegenerative disease. Strikingly, synapses are often affected early during pathogenesis, probably because presynaptic terminals are distant outstations of neurons that are the most vulnerable part of a neuron. In AD, multiple mutations in APP and presenilin genes cause rare familial cases, while the ApoE4 variant of the ApoE gene represents the strongest genetic risk factor for sporadic AD in the general population. APP and presenilin gene mutations are thought to induce AD pathogenesis by overproducing pathogenic Abeta variants, and ApoE4 is thought to influence Abeta clearance, but how Abeta might incite AD pathogenesis and how ApoE4 might predispose to AD pathogenesis remains incompletely understood. Moreover, compelling evidence implicates microglial and possibly astrocytic dysfunction in AD pathogenesis. In my lab, we have taken a cell-biological approach to these questions with a focus on synapses because of their prominent role in AD, recognizing that synapse impairments in AD may also be secondary to microglial dysfunction. We have examined how pathogenic APP mutations, chronic impairments of presenilin function, or ApoE4 may act on synapses, using human neurons trans-differentiated from ES and iPS cells as a model. In my presentation, I will discuss the current status of this project which is far from providing a definitive account of AD pathogenesis but may offer a basis for understanding the most basic processes underlying such pathogenesis.

APOE Christchurch-mimetic therapeutic antibody reduces APOE-mediated toxicity and tau phosphorylation.

We discovered that the APOE3 Christchurch (APOE3Ch) variant may provide resistance to Alzheimer's disease (AD). This resistance may be due to reduced pathological interactions between ApoE3Ch and heparan sulfate proteoglycans (HSPGs). We developed and characterized the binding, structure, and preclinical efficacy of novel antibodies targeting human ApoE-HSPG interactions. We found that one of these antibodies, called 7C11, preferentially bound ApoE4, a major risk factor for sporadic AD, and disrupts heparin-ApoE4 interactions. We also determined the crystal structure of a Fab fragment of 7C11 and used computer modeling to predict how it would bind to ApoE. When we tested 7C11 in mouse models, we found that it reduced recombinant ApoE-induced tau pathology in the retina of MAPT*P301S mice and curbed pTau S396 phosphorylation in brains of systemically treated APOE4 knock-in mice. Targeting ApoE-HSPG interactions using 7C11 antibody may be a promising approach to developing new therapies for AD.

Whole-exome sequencing detected a novel APP variant in a Han-Chinese family with Alzheimer's disease.

Alzheimer's disease (AD) is an incurable and debilitating neurodegenerative disease that results in the progressive degeneration and death of nerve cells. Mutations in the APP gene, which encodes an amyloid precursor protein, is the strongest genetic risk factor for sporadic AD. We studied the APP gene (NM_000484.3: c.2045A > T; p.E682V) variants carried by members of a family suffering from AD using whole-exome sequencing and Sanger sequencing. In this study, we identified a new variant of the APP gene (NM_000484.3: c.2045A > T; p.E682V) in members of a family with AD. This provides potential targets for subsequent studies and information that can be used in genetic counselling.

Cholesterol twists the transmembrane Di-Gly region of amyloid-precursor protein.

Nearly 95% of Alzheimer's disease (AD) occurs sporadically without genetic linkage. Aging, hypertension, high cholesterol content, and diabetes are known nongenomic risk factors of AD. Aggregation of Aβ peptides is an initial event of AD pathogenesis. Aβ peptides are catabolic products of a type I membrane protein called amyloid precursor protein (APP). Aβ40 is the major product, whereas the 2-residue-longer version, Aβ42, induces amyloid plaque formation in the AD brain. Since cholesterol content is one risk factor for sporadic AD, we aimed to explore whether cholesterol in the membrane affects the structure of the APP transmembrane region, thereby modulating the γ-secretase cutting behavior. Here, we synthesized several peptides containing the APP transmembrane region (sequence 693-726, corresponding to the Aβ22-55 sequence) with one or two Cys mutations for spin labeling. We performed three electron spin resonance experiments to examine the structural changes of the peptides in liposomes composed of dioleoyl phosphatidylcholine and different cholesterol content. Our results show that cholesterol increases membrane thickness by 10% and peptide length accordingly. We identified that the di-glycine region of Aβ36-40 (sequence VGGVV) exhibits the most profound change in response to cholesterol compared with other segments, explaining how the presence of cholesterol affects the γ-secretase cutting site. This study provides spectroscopic evidence showing how cholesterol modulates the structure of the APP transmembrane region in a lipid bilayer.

Repurposing drugs against Alzheimer's disease: can the anti-multiple sclerosis drug fingolimod (FTY720) effectively tackle inflammation processes in AD?

Therapeutic approaches providing effective medication for Alzheimer's disease (AD) patients after disease onset are urgently needed. Previous studies in AD mouse models and in humans suggested that physical exercise or changed lifestyle can delay AD-related synaptic and memory dysfunctions when treatment started in juvenile animals or in elderly humans before onset of disease symptoms. However, a pharmacological treatment that can reverse memory deficits in AD patients was thus far not identified. Importantly, AD disease-related dysfunctions have increasingly been associated with neuro-inflammatory mechanisms and searching for anti-inflammatory medication to treat AD seems promising. Like for other diseases, repurposing of FDA-approved drugs for treatment of AD is an ideally suited strategy to reduce the time to bring such medication into clinical practice. Of note, the sphingosine-1-phosphate analogue fingolimod (FTY720) was FDA-approved in 2010 for treatment of multiple sclerosis patients. It binds to the five different isoforms of Sphingosine-1-phosphate receptors (S1PRs) that are widely distributed across human organs. Interestingly, recent studies in five different mouse models of AD suggest that FTY720 treatment, even when starting after onset of AD symptoms, can reverse synaptic deficits and memory dysfunction in these AD mouse models. Furthermore, a very recent multi-omics study identified mutations in the sphingosine/ceramide pathway as a risk factor for sporadic AD, suggesting S1PRs as promising drug target in AD patients. Therefore, progressing with FDA-approved S1PR modulators into human clinical trials might pave the way for these potential disease modifying anti-AD drugs.

Of dolphins, humans, other long-lived animals and Alzheimer's disease (Commentary on Vacher et al.).

Of dolphins, humans, other long-lived animals and Alzheimer's disease (Commentary on Vacher et al.).

BIN1 rs744373 SNP and APOE alleles specifically associate to common diseases

APOE ε4 and BIN1 are the two main genetic risk factors for sporadic Alzheimer's Disease (AD). Among several BIN1 variants, the rs744373 is frequently associated with AD risk by contributing to tau pathology and poor cognitive performance. This study addressed the association of APOE and BIN1 rs744373 to specific characteristics in a Portuguese primary care-based study group, denoted pcb-Cohort. The study included 590 participants from five primary care health centers in the Aveiro district of Portugal. Individuals were evaluated and scored for cognitive and clinical characteristics, and blood samples were collected from the volunteers meeting the inclusion and exclusion criteria (N = 505). APOE and BIN1 genotypes were determined, and their association with cognitive characteristics and other diseases that might contribute to cognitive deficits, namely depression, hypertension, type 2 diabetes, dyslipidemia, osteoarticular diseases, gastrointestinal diseases, cardiovascular and respiratory diseases, was assessed. The diseases attributed to the study group were those previously diagnosed and confirmed by specialists. The results generated through multivariate analysis show that APOE ε4 carriers significantly associated with poorer cognitive performance (OR = 2.527; p = 0.031). Additionally, there was a significant risk of dyslipidemia for APOE ε4 carriers (OR = 1.804; p = 0.036), whereas BIN1 rs744373 risk-allele carriers were at a significantly lower risk of having dyslipidemia (OR = 0.558; p = 0.006). Correlations were evident for respiratory diseases in which APOE ε4 showed a protective tendency (OR = 0.515; p = 0.088), and BIN1 had a significative protective profile (OR = 0.556; p = 0.026). Not of statistical significance, APOE ε2 showed a trend to protect against type 2 diabetes (OR = 0.342; p = 0.093), in contrast BIN1 rs744373 risk-allele carriers were more likely to exhibit the disease (OR = 1.491; p = 0.099). The data here presented clearly show, for the first time, that the two top genetic risk factors for sporadic AD impact a similar group of common diseases, namely dyslipidemia, respiratory diseases, and type 2 diabetes.

Presenilin Is Essential for ApoE Secretion, a Novel Role of Presenilin Involved in Alzheimer's Disease Pathogenesis.

Alzheimer's disease (AD) is a debilitating dementia characterized by progressive memory loss and aggregation of amyloid-β (Aβ) protein into amyloid plaques in patient brains. Mutations in presenilin (PS) lead to abnormal generation of Aβ, which is the major cause of familial AD (FAD), and apolipoprotein E4 (ApoE4) is the major genetic risk factor for sporadic AD (SAD) onset. However, whether dysfunction of PS is involved in the pathogenesis of SAD is largely unknown. We found that ApoE secretion was completely abolished in PS-deficient cells and markedly decreased by inhibition of γ-secretase activity. Blockade of γ-secretase activity by a γ-secretase inhibitor, DAPT, decreased ApoE secretion, suggesting an important role of γ-secretase activity in ApoE secretion. Reduced ApoE secretion is also observed in nicastrin-deficient cells with reduced γ-secretase activity. PS deficiency enhanced nuclear translocation of ApoE and binding of ApoE to importin α4, a nuclear transport receptor. Moreover, the expression of PS mutants in PS-deficient cells suppressed the restoration effects on ApoE secretion compared with the expression of wild-type PS. Plasma ApoE levels were lower in FAD patients carrying PS1 mutations compared with normal control subjects. Our findings suggest a novel role of PS contributing to the pathogenesis of SAD by regulating ApoE secretion.SIGNIFICANCE STATEMENT Familial AD (FAD) typically results from mutations in the genes encoding amyloid precursor protein, presenilin 1 (PS1), or PS2. Many PS mutants have been found to exert impaired γ-secretase activity and increased amyloid-β 42 (Aβ42)/Aβ40 ratio, which induce early amyloid deposition and FAD. On the other hand, apolipoprotein E4 (ApoE4) is the major genetic risk factor for sporadic AD (SAD) and contributes to AD pathogenesis because it has reduced Aβ clearance capability compared with ApoE3 and ApoE2. FAD and SAD have long been considered to be caused by these two independent mechanisms; however, for the first time, we demonstrated that PS is essential for ApoE secretion and PS mutants affected ApoE secretion in vitro and in human samples, suggesting a novel mechanism by which PS is also involved in SAD pathogenesis.

A Scoping Review of Dietary Factors Conferring Risk or Protection for Cognitive Decline in APOE ε4 Carriers.

Alzheimer's disease (AD) is a progressive and fatal neurodegenerative disease. The strongest genetic risk factor for sporadic AD is carriage of the ε4 allele of the Apolipoprotein E (APOE) gene. Strategies to slow the progression of AD, including dietary interventions, may be modified by the pathogenic effect of this polymorphism. Our objective in this review was to determine the extent and quality of the literature investigating how dietary factors and interventions interact with the APOE ε4 genotype to impact cognitive decline in AD. To that end, we performed a systematic scoping review of published English-language articles involving human subjects. We found evidence suggesting that adherence to a Mediterranean diet may reduce cognitive decline among APOE ε4 carriers, whereas ketogenic agents appear to be ineffective. Diets high in saturated fats may be particularly harmful for APOE ε4 carriers. We identified several topics, including the use of ω-3 fatty acid and antioxidant supplements, for which additional high level evidence is needed.

Regulation of beta-amyloid production in neurons by astrocyte-derived cholesterol

Alzheimer's disease (AD) is characterized by the presence of amyloid β (Aβ) plaques, tau tangles, inflammation, and loss of cognitive function. Genetic variation in a cholesterol transport protein, apolipoprotein E (apoE), is the most common genetic risk factor for sporadic AD. In vitro evidence suggests that apoE links to Aβ production through nanoscale lipid compartments (lipid clusters), but its regulation in vivo is unclear. Here, we use superresolution imaging in the mouse brain to show that apoE utilizes astrocyte-derived cholesterol to specifically traffic neuronal amyloid precursor protein (APP) in and out of lipid clusters, where it interacts with β- and γ-secretases to generate Aβ-peptide. We find that the targeted deletion of astrocyte cholesterol synthesis robustly reduces amyloid and tau burden in a mouse model of AD. Treatment with cholesterol-free apoE or knockdown of cholesterol synthesis in astrocytes decreases cholesterol levels in cultured neurons and causes APP to traffic out of lipid clusters, where it interacts with α-secretase and gives rise to soluble APP-α (sAPP-α), a neuronal protective product of APP. Changes in cellular cholesterol have no effect on α-, β-, and γ-secretase trafficking, suggesting that the ratio of Aβ to sAPP-α is regulated by the trafficking of the substrate, not the enzymes. We conclude that cholesterol is kept low in neurons, which inhibits Aβ accumulation and enables the astrocyte regulation of Aβ accumulation by cholesterol signaling.

Association of the MAOB rs1799836 Single Nucleotide Polymorphism and APOE ε4 Allele in Alzheimer’s Disease

The dopaminergic system is functionally compromised in Alzheimer's Disease (AD). The activity of Monoamine Oxidase B (MAOB), the enzyme involved in the degradation of dopamine, is increased during AD. Also, increased expression of MAOB occurs in the postmortem hippocampus and neocortex of patients with AD. The MAOB rs1799836 polymorphism modulates MAOB transcription, consequently influencing protein translation and MAOB activity. We recently showed that cerebrospinal fluid levels of amyloid β1-42 are decreased in patients carrying the A allele in MAOB rs1799836 polymorphism. The present study compares MAOB rs1799836 polymorphism and APOE, the only confirmed genetic risk factor for sporadic AD. We included 253 participants, 127 of whom had AD, 57 had mild cognitive impairment, 11 were healthy controls, and 58 suffered from other primary causes of dementia. MAOB and APOE polymorphisms were determined using TaqMan SNP Genotyping Assays. We observed that the frequency of APOE ε4/ε4 homozygotes and APOE ε4 carriers is significantly increased among patients carrying the AA MAOB rs1799836 genotype. These results indicate that the MAOB rs1799836 polymorphism is a potential genetic biomarker of AD and a potential target for the treatment of decreased dopaminergic transmission and cognitive deterioration in AD.

Data‐driven approach reveals heterogeneity and region‐specific association of white matter hyperintensities with the APOE genotype

AbstractBackgroundWe used a transparent machine learning algorithm to identify subtypes of white matter damage in aging and to characterize their clinical representations. White matter hyperintensities (WMH), a common finding on brain magnetic resonance imaging (MRI), are known to be associated with cognitive impairment and dementia. Previous studies have shown spatial heterogeneity of WMH appearance, but the contribution of Alzheimer disease (AD) dementia and related genetic risk factors to this heterogeneity remains unclear. We sought to investigate the heterogeneity of WMH, in the general population, leveraging state of the art pattern analysis methods and exploring whether the APOE genotype is contributing to this heterogeneity.MethodA sample of N=1836 people was obtained from the Study of Health in Pomerania (SHIP), Germany, covering a wide age range (22–84 years, median age 52.2±13.16). WMH were automatically segmented on multi‐modal MRI scans and decomposed into four spatially distinctive components using Non‐Negative Matrix Factorization (NNMF), a machine‐learning based structural covariance method. Associations of these components with the APOE genotype (available for n=303) was investigated in subjects older than 60 years of age, using a multivariable linear regression model for each component, with WMH component loadings as the outcome variable and APOE genotype (encoded as shown in Table 1) as the independent variable. Age, sex and ship sub‐cohort were included as covariates. All reported P‐values were Bonferroni corrected for multiple comparisons.ResultData‐driven approach identified four WMH components, consistent with clinical categorization in deep and periventricular lesions, while further dividing periventricular WMH into posterior, frontal and dorsal components (Figure 1). APOE genotype was significantly associated with the dorsal periventricular WMH component (P=0.035, Bonferroni corrected), but not with the other three WMH components (Table 1).ConclusionWe obtained a high consistency of data‐driven WMH components and established clinical categorizations. Our data demonstrated that the appearance of WMH follows heterogeneous regional distribution patterns. Additionally, the APOE genotype, the strongest genetic risk factor for sporadic AD, is specifically associated with one of the components indicating spatial specificity and a potential link to early MRI changes in the predementia phase.

The Mechanistic Role of Bridging Integrator 1 (BIN1) in Alzheimer's Disease.

Alzheimer's disease (AD) is the leading cause of dementia. The majority of AD cases are late-onset, multifactorial cases. Genome-wide association studies have identified more than 30 loci associated with sporadic AD (SAD), one of which is Bridging integrator 1 (BIN1). For the past few years, there has been a consensus that BIN1 is second only to APOE as the strongest genetic risk factor for SAD. Therefore, many researchers have put great effort into studying the mechanism by which BIN1 might be involved in the pathogenetic process of AD. To date, plenty of evidence has shown that BIN1 may participate in several pathways in AD, including tau and amyloid pathology. In addition, BIN1 has been indicated to take part in other relevant pathways such as inflammation, apoptosis, and calcium homeostasis. In this review, we systemically summarize the research progress on how BIN1 participates in the development of AD, with the expectation of providing promising perspectives for future research.

Exposure of ultrafine particulate matter causes glutathione redox imbalance in the hippocampus: A neurometabolic susceptibility to Alzheimer's pathology

Particulate matter (PM) exposure is related to an increased risk of sporadic Alzheimer's disease (AD), the pathogenesis of which is explained by chronic neurometabolic disturbance. Therefore, PM-induced alterations in neurometabolism might herald AD. We aimed to identify brain region-specific changes in metabolic pathways associated with ultrafine particle (UFP) exposure and to determine whether such metabolic alterations are linked to susceptibility to AD. We constructed UFP exposure chambers and generated UFP by the pyrolysis method, which produces no toxic oxidized by-products of combustion, such as NOx and CO. Twenty male C57BL6 mice (11–12 months old) were exposed either to UFP or room air in the chambers for 3 weeks. One week following completion of UFP exposure, regional brain tissues, including the olfactory bulb, cortex, hippocampus, and cerebellum, were obtained and analyzed by metabolomics based on GC–MS and LC-MS, western blot analysis, and immunohistochemistry. Our results demonstrated that the metabolomic phenotype was distinct within the 4 different anatomical regions following UFP exposure. The highest level of metabolic change was identified in the hippocampus, a vulnerable region involved in AD pathogenesis. In this region, one of the key changes was perturbed redox homeostasis via alterations in the methionine-glutathione pathway. UFP exposure also induced oxidative stress and neuroinflammation, and importantly, increased Alzheimer's beta-amyloid levels in the hippocampus. These results suggest that inhaled UFP-induced perturbation in hippocampal redox homeostasis has a role in the pathogenesis of AD. Therefore, chronic exposure to UFP should be regarded as a cumulative environmental risk factor for sporadic AD.

Analysis of Salivary Microbiome in Patients with Alzheimer's Disease.

Recent studies found that poor oral hygiene was associated with increased risk of dementia, and the number of oral bacteria significantly increased in the brain tissues of patients with Alzheimer's disease (AD), suggesting that the oral microbiota may play an important role in the pathogenesis of AD. However, the actual composition of oral bacteria communities in patients with AD and whether these oral bacteria are associated with disease severity remain largely unknown. Also, the APOEɛ4 polymorphism is a strong risk factor for sporadic AD, and it would be pertinent to see if the bacterial flora was different in those patients who were APOEɛ4 positive. A total of 78 subjects were recruited in this study, including 39 patients with AD and 39 healthy controls. Saliva was collected from each subject. 16S ribosomal RNA (16S rRNA) sequencing was conducted to analyze the salivary microbiota, and Sanger sequencing was performed to analyze the APOE genotype. There was a significantly lower richness and diversity of saliva microbiota detected in AD patients than healthy controls. The relative abundance of Moraxella, Leptotrichia, and Sphaerochaeta in the saliva of AD patients greatly increased, whereas that of Rothia was significantly reduced. Compared with APOEɛ4 (-) patients, the level of Abiotrophia and Desulfomicrobium was comparatively abundant, while Actinobacillus and Actinomyces decreased significantly in patients carrying the APOEɛ4. No bacteria were found to be associated with the severity of AD. This is the first study to analyze the salivary microorganisms in patients with AD, and we discovered that the composition of salivary microbiome was altered in AD, providing further support for the role of the oral microbiome in AD development.

Alzheimer's Amyloidopathy: An Alternative Aspect.

The ‘amyloid hypothesis’ dominates Alzheimer’s disease (AD) research but has failed to deliver effective therapies. Amyloid precursor protein (APP) and presenilin-1 (PSEN1) genetic mutations are undoubtedly pathogenic, albeit by unclear mechanisms. Conversely, high dose B-vitamins convincingly slow brain atrophy in a pre-stage state of sporadic AD. Here we suggest a link between sporadic and genetic AD: 1) Increased serum homocysteine, a marker of B-vitamin deficiencies, is a significant risk factor for sporadic AD. It also correlates with elevated levels of antichymotrypsin, a serine protease inhibitor. 2) Family members with codon 717 APP mutations and dementia have low serum vitamin B12 values. Overexpression of the APP domain coding for a Kunitz type serine protease inhibitor might explain this. 3) PSEN1 mutations disrupt lysosomal function due to reduced proteolytic activity. They also trap cobalamin (B12) within lysosomes, leading to intracellular deficiency of the vitamin. In summary, APP and PSEN1 mutations both confer a risk for reduced protease activity and B12 bio-availability. Comparably, sporadic AD features a constellation of increased protease inhibition and B-vitamin deficiencies, the central part of which is believed to be B12. These concordant observations in three disparate AD etiologies suggest a common neuropathogenic pathway. This hypothesis is evaluable in laboratory and clinical trials.

Dr. Jekyll and Mr. Hyde: ApoE explains opposing effects of neuronal LRP1.

Alzheimer's disease (AD) is the leading cause of dementia, and its pathogenesis is initiated by the accumulation of amyloid-β (Aβ) into extracellular plaques. Apolipoprotein E4 (ApoE4) is the largest genetic risk factor for sporadic AD and contributes to AD pathogenesis by influencing clearance and seeding of the initial aggregation of Aβ. In this issue of the JCI, Tachibana et al. investigated the relationship between neuronal LRP1 expression and ApoE4-mediated seeding of Aβ and showed that knockout of neuronal LRP1 prevents the increase in Aβ pathology caused by ApoE4 expression. These findings give insight into potential therapeutic targets for the preclinical phase of AD and the pathogenesis of Aβ pathology.

Generation of a set of isogenic, gene-edited iPSC lines homozygous for all main APOE variants and an APOE knock-out line

Alzheimer's disease (AD) is the most frequent neurodegenerative disease amongst the elderly. The SNPs rs429358 and rs7412 in the APOE gene are the most common risk factor for sporadic AD, and there are three different alleles commonly referred to as APOE-ε2, APOE-ε3 and APOE-ε4. Induced pluripotent stem cells (iPSCs) hold great promise to model AD as such cells can be differentiated in vitro to the required cell type. Here we report the use of CRISPR/Cas9 technology employed on iPSCs from a healthy individual with an APOE-ε3/ε4 genotype to obtain isogenic APOE-ε2/ε2, APOE-ε3/ε3, APOE-ε4/ε4 lines as well as an APOE-knock-out line.

Role of phosphatidylcholine-DHA in preventing APOE4-associated Alzheimer's disease.

Dietary and supplemental intake of the ω-3 fatty acid docosahexaenoic acid (DHA) reduces risk of Alzheimer’s disease (AD) and ameliorates symptoms. The apolipoprotein E (APOE)4 allele is the strongest risk factor for sporadic AD, exclusive of age. APOE4 carriers respond well to the DHA present in fish but do not respond as well to dietary supplements. The mechanisms behind this varied response remain unknown. I posit that the difference is that fish contain DHA in phospholipid form, whereas fish oil supplements do not. This influences whether DHA is metabolized to nonesterified DHA (free DHA) or a phospholipid form called lysophosphatidylcholine DHA (DHA-lysoPC). Free DHA is transported across the outer membrane leaflet of the blood–brain barrier (BBB) via passive diffusion, and DHA-lysoPC is transported across the inner membrane leaflet of the BBB via the major facilitator superfamily domain-containing protein 2A. I propose that APOE4 carriers have impaired brain transport of free DHA but not of DHA-lysoPC, as a consequence of a breakdown in the outer membrane leaflet of the BBB, putting them at increased risk for AD. Dietary sources of DHA in phospholipid form may provide a means to increase plasma levels of DHA-lysoPC, thereby decreasing the risk of AD.—Patrick, R. P. Role of phosphatidylcholine-DHA in preventing APOE4-associated Alzheimer’s disease.