Delta-frequency stimulation of cerebellar projections can compensate for schizophrenia-related medial frontal dysfunction.

Schizophrenia involves abnormalities in the medial frontal cortex that lead to cognitive deficits. Here we investigate a novel strategy to normalize medial frontal brain activity by stimulating cerebellar projections. We used an interval timing task to study elementary cognitive processing that requires both frontal and cerebellar networks that are disrupted in patients with schizophrenia. We report three novel findings. First, patients with schizophrenia had dysfunctional delta rhythms between 1-4 Hz in the medial frontal cortex. We explored cerebellar-frontal interactions in animal models and found that both frontal and cerebellar neurons were modulated during interval timing and had delta-frequency interactions. Finally, delta-frequency optogenetic stimulation of thalamic synaptic terminals of lateral cerebellar projection neurons rescued timing performance as well as medial frontal activity in a rodent model of schizophrenia-related frontal dysfunction. These data provide insight into how the cerebellum influences medial frontal networks and the role of the cerebellum in cognitive processing.

Pathways to Alzheimer's disease.

Recent trials of anti-amyloid agents have not produced convincing improvements in clinical outcome in Alzheimer's disease; however, the reason for these poor or inconclusive results remains unclear. Recent genetic data continue to support the amyloid hypothesis of Alzheimer's disease with protective variants being found in the amyloid gene and both common low-risk and rare high-risk variants for disease being discovered in genes that are part of the amyloid response pathways. These data support the view that genetic variability in how the brain responds to amyloid deposition is a potential therapeutic target for the disease, and are consistent with the notion that anti-amyloid therapies should be initiated early in the disease process.

The association between biomarkers in cerebrospinal fluid and structural changes in the brain in patients with Alzheimer's disease.

BACKGROUND: Biochemical changes in the cerebrospinal fluid (CSF) could reflect pathophysiological processes in Alzheimer's disease (AD). However, it is still not clear how these processes correlate with grey matter (GM) volume and microstructural changes in the brain. OBJECTIVE: To assess the relationship between CSF biomarkers and structural brain changes in AD. DESIGN AND SETTING: Cross-sectional study in a memory clinic-based sample. SUBJECTS: A total of 78 subjects were included in the study: 22 with subjective cognitive impairment (SCI), 35 with mild cognitive impairment (MCI) and 21 with AD. MAIN OUTCOME MEASURES: Voxel-wise correlations between CSF biomarkers, including ß-amyloid42 (Aß42), tau phosphorylated at position threonine 181 and total tau protein, and GM volume, self-diffusion fractional anisotropy (FA) and mean diffusivity (MD) maps using voxel-based morphometry and tract-based spatial statistical analyses. FA and MD maps were obtained using diffusion tensor imaging. RESULTS: In the whole sample (patients with SCI, MCI and AD), there was positive correlation between GM volume and Aß42 concentration, and negative correlation with total tau protein. Higher FA was only related to higher concentration of Aß42. MD showed significant negative correlation with Aß42 and positive correlation with T-tau levels. The majority of brain regions with significant correlation with CSF biomarkers overlapped with the default mode network and extended to the adjacent white matter. CONCLUSIONS: Early AD pathological changes can be detected with voxel-based morphometric analysis and diffusion tensor imaging measurements. Furthermore, there was an association between CSF AD biomarkers and structural brain changes in areas related to the default mode network.

Clinical trials and late-stage drug development for Alzheimer's disease: an appraisal from 1984 to 2014.

The modern era of drug development for Alzheimer's disease began with the proposal of the cholinergic hypothesis of memory impairment and the 1984 research criteria for Alzheimer's disease. Since then, despite the evaluation of numerous potential treatments in clinical trials, only four cholinesterase inhibitors and memantine have shown sufficient safety and efficacy to allow marketing approval at an international level. Although this is probably because the other drugs tested were ineffective, inadequate clinical development methods have also been blamed for the failures. Here, we review the development of treatments for Alzheimer's disease during the past 30 years, considering the drugs, potential targets, late-stage clinical trials, development methods, emerging use of biomarkers and evolution of regulatory considerations in order to summarize advances and anticipate future developments. We have considered late-stage Alzheimer's disease drug development from 1984 to 2013, including individual clinical trials, systematic and qualitative reviews, meta-analyses, methods, commentaries, position papers and guidelines. We then review the evolution of drugs in late clinical development, methods, biomarkers and regulatory issues. Although a range of small molecules and biological products against many targets have been investigated in clinical trials, the predominant drug targets have been the cholinergic system and the amyloid cascade. Trial methods have evolved incrementally: inclusion criteria have largely remained focused on mild-to-moderate Alzheimer's disease criteria, recently extending to early or prodromal Alzheimer disease or 'mild cognitive impairment due to Alzheimer's disease', for drugs considered to be disease modifying. The duration of trials has remained at 6-12 months for drugs intended to improve symptoms; 18- to 24-month trials have been established for drugs expected to attenuate clinical course. Cognitive performance, activities of daily living, global change and severity ratings have persisted as the primary clinically relevant outcomes. Regulatory guidance and oversight have evolved to allow for enrichment of early-stage Alzheimer's disease trial samples using biomarkers and phase-specific outcomes. In conclusion, validated drug targets for Alzheimer's disease remain to be developed. Only drugs that affect an aspect of cholinergic function have shown consistent, but modest, clinical effects in late-phase trials. There is opportunity for substantial improvements in drug discovery and clinical development methods.

Phase 1/2a Intravenous and Subcutaneous Oligomer-Specific Antibody KHK6640 in Mild to Moderate Alzheimer's Disease.

BACKGROUND: KHK6640 is a novel humanized anti-amyloid beta oligomer-specific antibody. Both KHK6640 and the mouse parent antibody E64 have demonstrated high potency and efficacy for cognitive improvement in several rodent Alzheimer's disease models, including an anti-amyloid beta injection mouse model and in age-matched double transgenic littermates. The favorable safety and pharmacokinetic profiles of KHK6640 reported in preclinical studies warrant clinical trials in Alzheimer's disease patients. OBJECTIVES: We evaluated the safety, pharmacokinetics, and efficacy of intravenous and subcutaneous oligomer-specific antibody KHK6640 in treating patients with prodromal Alzheimer's disease or mild to moderate Alzheimer's disease. DESIGN: Phase I/2a, multicenter, randomized, double-blind, placebo-controlled trial. SETTING: Nine sites in Europe participated in this clinical trial. PARTICIPANTS: 97 patients with prodromal Alzheimer's disease or mild to moderate Alzheimer's disease. INTERVENTION: Single and multiple ascending intravenous and subcutaneous doses of KHK6640 in doses ranging from 0.1 mg/kg to 20 mg/kg or placebo was administered to patients monthly for six months. MEASUREMENTS: Primary outcomes were safety including amyloid-related imaging abnormalities for edema and hemorrhage, assessed with magnetic resonance imaging. Plasma and cerebrospinal fluid samples were analyzed to investigate pharmacokinetics and KHK6640 effects on biomarkers. Cognition, brain glucose metabolism and amyloid load were exploratory outcomes. RESULTS: No amyloid-related imaging abnormalities for edema were observed. Amyloid-related imaging abnormalities for hemorrhage were comparable to that of placebo and population background. KHK6640 exposure was approximately dose-equivalent, with a serum terminal elimination half-life of approximately 19 days. KHK6640 pharmacokinetics in serum and cerebrospinal fluid, including cerebrospinal fluid oligomers trapped by the antibody were dose related. Positive trends seen in the positron emission tomography brain glucose metabolism and amyloid load, cerebrospinal tau but cognition assessments were inconclusive, due to low numbers. CONCLUSIONS: KHK6640 was well-tolerated across all doses, without any amyloid-related imaging abnormalities for edema, and amyloid-related imaging abnormalities for hemorrhage was as population background. The demonstrated dose-response of specific target biomarkers provides dosing guidance on dose and administration method selection for further clinical development.

MAPK14 and CNR1 gene variant interactions: effects on brain volume deficits in schizophrenia patients with marijuana misuse.

BACKGROUND: Adolescent marijuana use is associated with increased risk for schizophrenia. We previously reported that marijuana misuse in conjunction with specific cannabinoid receptor 1 (CNR1) genetic variants (rs12720071-G-allele carriers) contributed to white-matter (WM) brain volume deficits in schizophrenia patients. In this study, we assessed the influence of another cannabinoid-related gene, mitogen-activated protein kinase 14 (MAPK14), and potential MAPK14-CNR1 gene-gene interactions in conferring brain volume abnormalities among schizophrenia patients with marijuana abuse/dependence. MAPK14 encodes a member of the MAPK family involved in diverse cellular processes, including CNR1-induced apoptosis. METHOD: We genotyped 235 schizophrenia patients on nine MAPK14 tag single nucleotide polymorphisms (tSNPs). Approximately one quarter of the sample had marijuana abuse or dependence. Differential effects of MAPK14 tSNPs on brain volumes across patients with versus without marijuana abuse/dependence were examined using ANCOVA. RESULTS: Of the MAPK14 tSNPs, only rs12199654 had significant genotype effects and genotype × marijuana misuse interaction effects on WM volumes. rs12199654-A homozygotes with marijuana abuse/dependence had significantly smaller total cerebral and lobar WM volumes. The effects of MAPK14 rs12199654 on WM volume deficits remained significant even after controlling for the CNR1 rs12720071 genotype. There were significant main effects of the MAPK14 CNR1 diplotype and diplotype × marijuana interaction on WM brain volumes, with both genetic variants having additive contributions to WM volume deficits only in patients with marijuana misuse. CONCLUSIONS: Given that CNR1-induced apoptosis is preceded by increased MAPK phosphorylation, our study suggests that potential MAPK14-CNR1 gene-gene interactions may mediate brain morphometric features in schizophrenia patients with heavy marijuana use.

Statistical epistasis and progressive brain change in schizophrenia: an approach for examining the relationships between multiple genes.

Although schizophrenia is generally considered to occur as a consequence of multiple genes that interact with one another, very few methods have been developed to model epistasis. Phenotype definition has also been a major challenge for research on the genetics of schizophrenia. In this report, we use novel statistical techniques to address the high dimensionality of genomic data, and we apply a refinement in phenotype definition by basing it on the occurrence of brain changes during the early course of the illness, as measured by repeated magnetic resonance scans (i.e., an 'intermediate phenotype.') The method combines a machine-learning algorithm, the ensemble method using stochastic gradient boosting, with traditional general linear model statistics. We began with 14 genes that are relevant to schizophrenia, based on association studies or their role in neurodevelopment, and then used statistical techniques to reduce them to five genes and 17 single nucleotide polymorphisms (SNPs) that had a significant statistical interaction: five for PDE4B, four for RELN, four for ERBB4, three for DISC1 and one for NRG1. Five of the SNPs involved in these interactions replicate previous research in that, these five SNPs have previously been identified as schizophrenia vulnerability markers or implicate cognitive processes relevant to schizophrenia. This ability to replicate previous work suggests that our method has potential for detecting a meaningful epistatic relationship among the genes that influence brain abnormalities in schizophrenia.

Cerebrospinal Flt3 ligand correlates to tau protein levels in primary Sjögren's syndrome.

OBJECTIVES: Primary Sjögren's syndrome (pSS) is an autoimmune disease affecting the exocrine glands and internal organs including the central nervous system (CNS). The fms-related tyrosine kinase 3 ligand (Flt3L) is a maturation factor essential for brain homeostasis. Blood levels of Flt3L are increased in inflammatory diseases including the inflamed salivary glands in pSS. The present study evaluated the role of Flt3L in the CNS of patients with pSS and in two non-autoimmune conditions, fibromyalgia (FM) and Alzheimer's disease (AD). METHOD: Levels of Flt3L were measured in cerebrospinal fluid (CSF) and serum of patients with pSS (n = 15), FM (n = 29), and AD (n = 39) and related to CNS symptoms and to markers of inflammation and degeneration. RESULTS: Levels of CSF Flt3L in pSS and AD were significantly lower than in FM (p = 0.005 and p = 0.0003, respectively). Flt3L in pSS correlated to tau proteins [total tau (T-tau), r = 0.679; phosphorylated tau (P-tau), r = 0.646] and to a marker for microglia activation, monocyte chemoattractant protein 1 (MCP-1). Similar correlations were present in FM and AD patients. One-third of pSS patients had low levels of CSF Flt3L. This group had decreased levels of amyloid precursor protein metabolites (Aß40 and Aß42) in CSF, which was not seen in FM patients. CONCLUSIONS: This study shows a strong correlation between CSF Flt3L and tau proteins in pSS patients suggesting ongoing degradation/remodelling in the CNS. In pSS patients, low levels of Flt3L were linked to changes in amyloid turnover and may represent processes similar to those in AD.

Two galantamine titration regimens in patients switched from donepezil.

OBJECTIVES: In addition to inhibiting acetylcholinesterase, galantamine has allosteric-modulating activity at nicotinic receptors. This may make galantamine an attractive option for patients starting treatment for Alzheimer's disease (AD), but also for those who have not benefited from their current therapy. This study explored outcomes in subjects with AD transitioning from donepezil because of insufficient tolerability or efficacy. MATERIALS AND METHODS: Subjects previously receiving donepezil for mild-to-moderate AD were enrolled in a 12-week randomized, open-label study. After screening and a 7-day washout, subjects were randomly allocated to galantamine fast (8 mg/week increments) or slow (8 mg/4 week) titration to 16-24 mg. Efficacy outcomes included the Alzheimer's Disease Assessment Scale - cognitive subscale (ADAS-cog/11), Mini-Mental State Examination (MMSE), Clinician's Interview-Based Impression of Change - Plus Caregiver's Input (CIBIC-plus) and Alzheimer's Disease Cooperative Study - Activities of Daily Living Inventory (ADCS-ADL). RESULTS: Eighty-six of 89 patients (fast titration, n = 44; slow titration, n = 45) completed the study. At week 12, ADAS-cog/11 score improved from screening by 2.6 and 0.6 in the fast- and slow-titration arms, respectively (overall, -1.6; P = 0.002). MMSE scores improved slightly in both arms (overall, +0.9; P = 0.002). Two-thirds of patients had improvement or no change on the CIBIC-plus at week 12. ADCS-ADL scores did not change significantly from screening in either treatment arm. Galantamine was generally well tolerated; nausea (5.6%) and bradycardia (4.5%) were the most commonly reported adverse events. CONCLUSIONS: Patients in whom donepezil is ineffective or poorly tolerated may benefit from a switch to galantamine.

Global and regional cortical thinning in first-episode psychosis patients: relationships with clinical and cognitive features.

BACKGROUND: The thickness of the cortical mantle is a sensitive measure for identifying alterations in cortical structure. We aimed to explore whether first episode schizophrenia patients already show a significant cortical thinning and whether cortical thickness anomalies may significantly influence clinical and cognitive features. METHOD: We investigated regional changes in cortical thickness in a large and heterogeneous sample of schizophrenia spectrum patients (n=142) at their first break of the illness and healthy controls (n=83). Magnetic resonance imaging brain scans (1.5 T) were obtained and images were analyzed by using brains2. The contribution of sociodemographic, cognitive and clinical characterictics was investigated. RESULTS: Patients showed a significant total cortical thinning (F=17.55, d=-0.62, p<0.001) and there was a diffuse pattern of reduced thickness (encompassing frontal, temporal and parietal cortices) (all p's<0.001, d's>0.53). No significant group×gender interactions were observed (all p's>0.15). There were no significant associations between the clinical and pre-morbid variables and cortical thickness measurements (all r's<0.12). A weak significant negative correlation between attention and total (r=-0.24, p=0.021) and parietal cortical thickness (r=-0.27, p=0.009) was found in patients (thicker cortex was associated with lower attention). Our data revealed a similar pattern of cortical thickness changes related to age in patients and controls. CONCLUSIONS: Cortical thinning is independent of gender, age, age of onset and duration of the illness and does not seem to significantly influence clinical and functional symptomatology. These findings support a primary neurodevelopment disorder affecting the normal cerebral cortex development in schizophrenia.

No neurochemical evidence of brain injury after blast overpressure by repeated explosions or firing heavy weapons.

BACKGROUND: Psychiatric and neurological symptoms are common among soldiers exposed to blast without suffering a direct head injury. It is not known whether such symptoms are direct consequences of blast overpressure. OBJECTIVE: To examine if repeated detonating explosions or firing if of heavy weapons is associated with neurochemical evidence of brain damage. MATERIALS AND METHODS: Three controlled experimental studies. In the first, army officers were exposed to repeated firing of a FH77B howitzer or a bazooka. Cerebrospinal fluid (CSF) was taken post-exposure to measure biomarkers for brain damage. In the second, officers were exposed for up to 150 blasts by firing a bazooka, and in the third to 100 charges of detonating explosives of 180 dB. Serial serum samples were taken after exposure. Results were compared with a control group consisting of 19 unexposed age-matched healthy volunteers. RESULTS: The CSF biomarkers for neuronal/axonal damage (tau and neurofilament protein), glial cell injury (GFAP and S-100b), blood-brain barrier damage (CSF/serum albumin ratio) and hemorrhages (hemoglobin and bilirubin) and the serum GFAP and S-100b showed normal and stable levels in all exposed officers. DISCUSSION: Repeated exposure to high-impact blast does not result in any neurochemical evidence of brain damage. These findings are of importance for soldiers regularly exposed to high-impact blast when firing artillery shells or other types of heavy weapons.

Changes in CSF acetyl- and butyrylcholinesterase activity after long-term treatment with AChE inhibitors in Alzheimer's disease.

OBJECTIVES: To measure cerebrospinal fluid (CSF) activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in patients with Alzheimer's disease (AD) participating in randomized clinical trials from three European centers, before and after long-term treatment with different AChE inhibitors (AChEIs). MATERIALS AND METHODS: Of the 144 patients included in the study, 104 were treated with donepezil, 15 with galantamine, 16 with rivastigmine, and nine with placebo. CSF AChE and BChE activities were measured at baseline and after 1- year treatment. RESULTS: Donepezil and galantamine groups showed a significant increase in CSF AChE activity at follow-up, while no changes for BChE activity were observed; in donepezil group, a positive correlation between plasma concentration and AChE activity was documented. Conversely, in rivastigmine group, a decrease in CSF activity of both enzymes was observed. CSF AChE and BChE activities were not correlated with the clinical outcome in any group considered. CSF biomarkers did not show any change after treatment. CONCLUSIONS: AChEIs differently influence the activity of target enzymes in CSF independent of their pharmacodynamic effects.

Computerized cognition assessment during acetylcholinesterase inhibitor treatment in Alzheimer's disease.

OBJECTIVES: Alzheimer's disease assessment scale-cognitive subscale (ADAS-Cog) has become a standard clinical trials outcome for cognition, but has been recognized as deficient in areas including coverage of cognitive domains, sensitivity and standardization. Computerized test batteries may address some of these issues. The cognitive drug research computerized assessment (CDR) system is validated in Alzheimer's disease (AD). This study was designed to further evaluate validity in relation to ADAS-Cog, mini mental state examination (MMSE) and cerebrospinal fluid (CSF) biomarkers and psychometric properties, in a population of Alzheimer's patients on stable anticholinesterase treatment. MATERIALS AND METHODS: Patients completed cognition assessments, CSF and blood sampling at baseline and 6 months later. Data for 65 patients were evaluated. RESULTS: The CDR system demonstrated good psychometric properties in this population. Measures of psychomotor speed showed possible sensitivity to decline over 6 months. CONCLUSIONS: There are a number of methodological problems with current cognition assessment methodology for clinical trials. Computerized measures and in particular millisecond reaction time measures, may address many of these issues.

The stability of AQT processing speed, ADAS-Cog and MMSE during acetylcholinesterase inhibitor treatment in Alzheimer's disease.

OBJECTIVES: To explore the longitudinal stability of measures of cognition during treatment with acetylcholinesterase inhibitors (AchEI) in patients with Alzheimer's disease (AD). MATERIALS AND METHODS: Cognitive status was measured in a cohort of 60 patients at 6 months after initiation of treatment with AchEI (baseline) and after an additional 6 months of treatment (endpoint). A Quick Test of Cognitive Speed (AQT), Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), and MMSE were administered concurrently. RESULTS: Correlations (rho) between age and AQT processing speed were non-significant, but were significant for ADAS-Cog and Mini Mental State Examination (MMSE). AQT and ADAS-Cog means did not differ significantly between baseline and endpoint. There was a small, significant reduction in MMSE point scores. Measures of stability (Spearman's rho) were moderate-to-high for all tests. Means for subgroups did not differ as a function of medication type. CONCLUSIONS: AQT processing speed, ADAS-Cog, and MMSE measures proved stable during the second 6 months of treatment with AChEI.

Brain imaging: applications in psychiatry.

Various brain imaging techniques have become available in the past decade. These include techniques to evaluate brain structure, such as computed tomography and magnetic resonance imaging, and techniques to assess functional activity, such as measurement of regional cerebral blood flow, single photon emission computed tomography, and positron emission tomography. These techniques can be used to map brain structure and function in normal human beings, and they have enlarged our knowledge of the pathophysiology of mental illnesses by demonstrating structural, metabolic, and neurochemical abnormalities in a wide range of mental disorders.

Linking mind and brain in the study of mental illnesses: a project for a scientific psychopathology.

Brain research on mental illnesses has made substantial advances in recent years, supported by conceptual and technological developments in cognitive neuroscience. Brain-based cognitive models of illnesses such as schizophrenia and depression have been tested with a variety of techniques, including the lesion method, tract tracing, neuroimaging, animal modeling, single-cell recording, electrophysiology, neuropsychology, and experimental cognitive psychology. A relatively sophisticated picture is emerging that conceptualizes mental illnesses as disorders of mind arising in the brain. Convergent data using multiple neuroscience techniques indicate that the neural mechanisms of mental illnesses can be understood as dysfunctions in specific neural circuits and that their functions and dysfunctions can be influenced or altered by a variety of cognitive and pharmacological factors.

Thalamic abnormalities in schizophrenia visualized through magnetic resonance image averaging.

Schizophrenia is a complex illness characterized by multiple types of symptoms involving many aspects of cognition and emotion. Most efforts to identify its underlying neural substrates have focused on a strategy that relates a single symptom to a single brain region. An alternative hypothesis, that the variety of symptoms could be explained by a lesion in midline neural circuits mediating attention and information processing, is explored. Magnetic resonance images from patients and controls were transformed with a "bounding box" to produce an "average schizophrenic brain" and an "average normal brain." After image subtraction of the two averages, the areas of difference were displayed as an effect size map. Specific regional abnormalities were observed in the thalamus and adjacent white matter. An abnormality in the thalamus and related circuitry explains the diverse symptoms of schizophrenia parsimoniously because they could all result from a defect in filtering or gating sensory input, which is one of the primary functions of the thalamus in the human brain.

Long-term rivastigmine treatment in a routine clinical setting.

OBJECTIVE: The aim of the study was to observe the effects of long-term rivastigmine treatment in patients with mild to moderate Alzheimer's disease (AD) in a routine clinical setting. METHODS: This was a prospective, open-label, observational, multicentre, non-randomized study. Outcome measures included the Mini Mental State Examination (MMSE), the Clinician's Interview-Based Impression of Change (CIBIC) and the Alzheimer's Disease Assessment Scale - cognitive subscale (ADAS-cog). RESULTS: Of 217 patients initiated into rivastigmine treatment, 62% (n = 135) remained on treatment for 24 months. Most patients droped out due to nursing home placement or side effects. Eighty per cent and 67% of completers exhibited a symptomatic attenuation of cognitive decline (< or = 4-point deterioration) as assessed by using the MMSE and ADAS-cog respectively. Forty-four per cent showed an unchanged/improved CIBIC rating. CONCLUSIONS: Over 60% of patients remained on treatment for 2 years in this routine clinical setting. In patients who remained on treatment, rivastigmine appeared to stabilize their condition and prevented or delayed symptomatic decline.

The mechanisms of schizophrenia.

Current investigations of the mechanisms of schizophrenia usually employ one of three possible explanatory models: a single disease entity model, a multiple disease entity model, and a dimensions of psychopathology model. None of these is at present preeminent. These models are used to explore four different types of mechanisms that may produce the symptoms of schizophrenia: neurodevelopmental, neural circuitry, genetic/molecular mechanisms, and chemical anatomy.

Cerebrospinal fluid-induced retardation of amyloid ß aggregation correlates with Alzheimer's disease and the APOE ε4 allele.

Misfolding and aggregation of amyloid ß (Aß) are key features of Alzheimer's disease (AD) pathogenesis, but the molecular events controlling this process are not known in detail. In vivo, Aß aggregation and plaque formation occur in the interstitial fluid of the brain extracellular matrix. This fluid communicates freely with cerebrospinal fluid (CSF). Here, we examined the effect of human CSF on Aß aggregation kinetics in relation to AD diagnosis and carrier status of the apolipoprotein E (APOE) ε4 allele, the main genetic risk factor for sporadic AD. The aggregation of Aß was inhibited in the presence of CSF and, surprisingly, the effect was more pronounced in APOE ε4 carriers. However, by fractionation of CSF using size exclusion chromatography, it became evident that it was not the ApoE protein itself that conveyed the inhibition, since the retarding species eluted at lower volume, corresponding to a much higher molecular weight, than ApoE monomers. Cholesterol quantification and immunoblotting identified high-density lipoprotein particles in the retarding fractions, indicating that such particles may be responsible for the inhibition. These results add information to the yet unresolved puzzle on how the risk factor of APOE ε4 functions in AD pathogenesis.