Current Alzheimer Research - Volume 9, Issue 10, 2012

Alzheimer's disease is associated with sleep disorders. Recently, animal studies demonstrated a link between hypocretin, a sleep-regulation neurotransmitter, and AD pathology. In this study, we investigated the circadian rhythm of hypocretin-1 in Alzheimer's Disease (AD) patients and controls. Moreover, we assessed the relation between CSF hypocretin-1 and amyloid-β. A continuous CSF sampling study via indwelling intrathecal catheter was performed to collect hourly CSF samples of six patients with AD (59-85 yrs, MMSE 16-26) and six healthy volunteers (64-77 yrs). CSF hypocretin-1 and Aβ42 concentrations were determined at 8 individual time points over 24 hours. A circadian pattern was assessed by fitting a 24 hour sine curve to the hypocretin-1 data using mixed model analysis. Clinical diagnosis and Aβ42 were entered into the model as time invariant covariates to determine differences between AD and controls, and correlate Aβ42 to hypocretin-1 levels. A hypocretin-1 circadian rhythm with an amplitude of 11.5 pg/ml was found in clinical AD patients, which did not differ from the control group (7.15 pg/ml). Lower mean CSF Aβ42 levels were related to lower hypocretin-1 levels; 1.6 pg/ml hypocretin-1 per 10 pg/ml Aβ42 (p=0.03), and a higher amplitude of the hypocretin-1 circadian rhythm (0.4 pg/ml, p=0.03). CSF hypocretin-1 has a circadian rhythm for which we could show no difference between AD and controls. However, the association between mean Aβ42 levels and mean hypocretin-1 levels and amplitude may suggest a relationship between AD pathology and hypocretin disturbance, which could hold possibilities for treatment of AD related sleep disorders.

Objectives: Amyloid immunotherapy trials are central in Alzheimer disease (AD) drug development, with the potential to influence all future disease-modifying randomized controlled trials (RCTs). This study investigates practical experiences of staff and participants in immunotherapy RCTs. Setting and methods: The Clinical Trial Research Unit of the Memory Clinic at Karolinska University Hospital, Sweden is an experienced centre specialized in Alzheimer RCTs, where four active and passive phase I/II immunotherapy trials are currently ongoing. Meetings were held with staff members, who were asked to describe their experiences and suggest necessary improvements. In addition, a pilot study was conducted to investigate motivations and expectations of participants in immunotherapy RCTs. A questionnaire was sent to 20 patients, and another similar questionnaire to their caregivers. Results: The main issues emphasized by staff members concerned the critical window of opportunity for recruiting RCTs participants, the much higher level of effort required of patients and caregivers in immunotherapy RCTs compared to classical cholinesterase inhibitor RCTs, problematic informed consent procedures, and confidentiality limitations in trials with different sponsors. For patients and caregivers, the main reason for participating in RCTs was the wish to help research and other people, followed by the need for information, continuity of care, safety and support. Compared to patients, caregivers' expectations of trial results were more realistic. Conclusions: More open debates of practical experiences from different trial centres and sponsors are essential for optimizing trial designs and improving conditions for participants.

Background: The Alzheimer's Disease Neuroimaging Initiative (ADNI) was created to develop standards for brain imaging and biomarkers for diagnosis and treatment trials. Using the ADNI dataset, experts have found that low cerebrospinal fluid amyloid-β1-42 (CSF Aβ1-42) concentration and high total-tau/Aβ1-42 ratio are highly predictive of progression in amnestic mild cognitive impairment (aMCI), and recommended these biomarkers to support the diagnosis of prodromal Alzheimer's disease and select patients for clinical trials. However, biomarker selection criteria may introduce systematic bias that undermines their utility. Methods: We tested for systematic biases among individuals undergoing lumbar puncture in the ADNI dataset who fulfilled the following entry criteria: (1) aMCI with CSF Aβ1-42 ≤ 192 pG/mL, compared to aMCI with Aβ1-42 > 192 pG/mL, and (2) aMCI with total-tau/Aβ1-42 > 0.39, compared to aMCI with total-tau/Aβ1-42 ≤ 0.39, as well as comparisons between participants with aMCI with and without lumbar puncture. Findings: Individuals with low CSF Aβ1-42 scored significantly poorer than individuals with high Aβ1-42 on several baseline measures of disease severity, including Logical Memory II (3.24 vs 4.73; p<0.001), Functional Activities Questionnaire (4.30 vs 2.37; p<0.001), and Alzheimer's Disease Assessment Scale-cognitive (12.23 vs 10.09; p=0.002). Similar results were found using high total-tau/Aβ1-42. No differences were found for individuals with and without lumbar puncture except for marital status. Interpretations: Individuals with aMCI with low Aβ1-42 in the ADNI dataset appear to have more advanced disease than those with high Aβ1-42. Selection criteria based on ADNI, as well as design of future studies, must account for potential confounds between biomarker status and disease severity to ensure that the former, and not the latter, is the true determinant of predictive accuracy.

Although there is a consensus on the reduced levels of Aβ1-42 in the CSF of patients with AD, studies of plasma Aβ levels were inconsistent and have limited clinical value. We developed an immunomagnetic reduction assay (IMR) to determine the plasma levels of Aβ. We surveyed patients with varying AD severity (CDR = 0.5, n=16; CDR ≥ 1, n=18) and controls (n=26). Significant group differences were apparent in the levels of Aβ1-42 (F = 5.54, p = 0.002) and the Aβ1-42/Aβ1-40 ratio (F = 24.198, p < 0.001). Post-hoc analyses showed significant differences in the Aβ1-42 levels of controls and AD patients (p = 0.001) and in the Aβ1-42/Aβ1-40 ratio of control, MCI and AD subjects (all p ≤ 0.001). Regression analysis of Aβ1-42/Aβ1-40 ratios on dementia severity showed an adjusted R2 of 0.553 (p = 0.001). We identified a cut-off of 16.1 pg/ml for Aβ1-42 to differentiate control subjects from patients (both AD and MCI) with 85.3% sensitivity and 88.5% specificity. We also obtained a cut-off value of 0.303 for Aβ1-42/Aβ1-40 ratios with 85.3% sensitivity and 96.2% specificity. APOE ε4 carriers had significantly higher Aβ1-42/Aβ1-40 ratios than the non-carriers (F = 4.839, p = 0.015). An independent group of case-control subjects validated both cut-off values for Aβ1-42/Aβ1-40 (100% sensitivity and 83.3% specificity) and for Aβ1-42 (100% sensitivity and 75.3% specificity). In a subgroup of longitudinal follow- up study, we found that the plasma Aβ was relatively stable with an interval of approximately 3 months. In conclusion, we found that the plasma Aβ1-42 is a useful biomarker for AD. The Aβ1-42/Aβ1-40 ratio improves the diagnostic power of the plasma Aβ biomarkers. The iron nanoparticles and IMR provides a novel method to measure plasma Aβ and could serve as an important clinical tool for the diagnosis of neurodegenerative diseases.

Background: Inasmuch as Alzheimer's disease (AD) is difficult to diagnose, patients with suspected dementias are often given FDA approved medications, including donepezil, rivastigmine, memantine HCl, or a combination, prior to diagnosis, and some respond with improved cognition. The present study demonstrates how concentrations of a select group of serum protein biomarkers can provide the basis for sensitive and specific differential diagnosis of AD in drug treated patients. Optimization is addressed by taking into account whether the patients and controls have or do not have increased risk of AD die to the presence or absence of Apolipoprotein E4. Methods: For differential diagnosis of AD, prospectively collected newly drawn blood serum samples were obtained from drug treated Alzheimer's disease and Parkinson's disease patients from a first (39 drug treated DTAD, and 31 age matched normal controls) and second medical center (56 drug treated DTPD, 47 age-matched normal controls). Analytically validated quantitative 2D gel electrophoresis (%CV≤20%; LOD ≥0.5ng/spot, 300μg/ml of blood serum) was employed with patient and control sera for differential diagnosis of AD. Protein quantitation was subjected to statistical analysis by single variable Dot, Box and Whiskers and Receiver Operator Characteristics (ROC) plots for individual biomarker performance, and multivariate linear discriminant analysis for joint performance of groups of biomarkers. Protein spots were identified and characterized by LC MS/MS of in-gel trypsin digests, amino acid sequence spans of the identified peptides, and the protein spot molecular weights and isoelectric points. Results: The single variable statistical profiles of 58 individual protein biomarker concentrations of the DTAD patient group differed from those of the normal and/or the disease control groups. Multivariate linear discriminant analysis of blood serum concentrations of the 58 proteins distinguished drug treated Alzheimer's disease (DTAD) patients from drug treated Parkinson's disease (DTPD) patients and age matched normal controls (collectively not-DTAD, DTAD Sensitivity 87.2%, Not-DTAD Specificity 87.2). Moreover, when the patients and controls were stratified into carriers or non-carriers of Alzheimer's high risk Apolipoprotein E ε4 allele and/or the Apolipoprotein E4 protein, the DTAD, DTPD and control Apo E4 (+) profiles were more divergent from one another than the corresponding Apo E4 (-) profiles. Multivariate stepwise linear discriminant analysis selected 17 of the 58 biomarkers as optimal and complimentary for distinguishing Apo E4 (+) DTAD patients from Apo E4 (+) DTPD and Apo E4 (+) controls (collectively Apo E4 (+) not-DTAD, DTAD Sensitivity 100%, not-DTAD Specificity 100%) and 22 of the 58 biomarkers for distinguishing Apo E4 (-) DTAD patients from Apo E4 (-) DTPD and Apo E4 (-) controls (collectively Apo E4 (-) not-DTAD, DTAD Sensitivity 94.4%, not- DTAD Specificity 94.4%). Only 6 of the selected proteins were common to both the Apo E4 (+) and the Apo E4 (-) discriminant functions. Recombining of the results of Apo E4 (+) and Apo E4 (-) discriminations provided overall sensitivity for total DTAD of 97.4% and specificity for total not-DTAD of 95.7%. Conclusions: These results can form the basis of a blood test for differential diagnosis of Alzheimer's disease patients already under treatment (DTAD) by anti dementia drugs, including donepezil, rivastigmine, memantine HCl, or a combination thereof. Also, the profile differences and the rise in specificity and sensitivity obtained by handling the Apo E4 (+) and Apo E4 (-) groups separately supports the concept that they are different patient and control populations in terms of the “normal” physiology, the pathophysiology of disease, and the response to drug treatment. Taking that into account enables increased sensitivity and specificity of differential diagnosis of Alzheimer's disease.

Recent studies have shown that the translocase of outer mitochondrial membrane 40 homolog (TOMM40) contains a polymorphic poly-T variant, the long variant of which is associated with an increase in AD incidence among APOE ε3 carriers. Current methods to isotype the poly-T region rely on long PCR, subcloning and sequencing to distinguish among the allelic variants. While such methods are extremely accurate as well as quantitative in determining the number of T residues in the poly-T region, the process can be cumbersome, time consuming and expensive to employ in routine laboratories. To this end, we have developed a quick and simple method to isotype the human TOMM40 variablelength polymorphism using a PCR- and restriction digest-based approach, enabling rapid genotyping of TOMM40 variants.

Over 200 Alzheimer's disease (AD) drug candidates have failed in development, and other neuropsychiatric trials have had their validity compromised. Studies suggest that methodological errors can be a source for these compromises and failures. We gained access to documentation for phenserine, an experimental AD drug that reached phase III clinical trials. The 06 Phase III trial was cited by the developers as grounds for their abandonment of the development. We compared evidence for interventions to control methodological errors and grounds for moving through phases of drug development to 40 other randomly selected AD developments we had studied. We analyzed methods and conditions of the 06 phenserine clinical trial, for biases able to account for its abandonment during development. The phenserine development failed to control error sources able to affect the outcomes. There are statistically significant relationships in the 06 clinical trial between outcomes at research sites and levels of variance, placebo group improvements and other factors. We conclude that phenserine was abandoned, at least in part, due to a clinical trial invalidated by relationships among its methods and outcomes.

Cerebral okadaic acid (OA) administration induces Alzheimer's disease (AD)-like phenotype in rats. Alterations in glutamate levels associated with hyperactivation of cyclin dependent kinase 5 (Cdk5) signaling pathway downstream Tau phosphorylation may participate in the genesis of this pathological phenotype. Here, we examined the efficacy of memantine (MN) pretreatment on reducing OA-induced AD-like phenotypes in rats. Wistar rats were given daily intraperitoneal injections of MN for 3 days and then given an intrahippocampal infusion of OA. Animals were divided into four groups: control (CO), MN, OA and MN/OA. Spontaneous locomotion and spatial memory performance were assessed by open field and Morris water maze respectively. Additionally, we measured glutamate levels in the cerebrospinal fluid (CSF) and the immunocontent of Cdk5, p35, p25 and phosphorylated Tau (pTauSer199/202) in the hippocampus. Spontaneous locomotion did not differ between groups. The OA group showed a significant decrease in spatial memory performance compared to all groups. The OA infusion also increased CSF glutamate levels and the immunocontents of Cdk5, p25 and pTauSer199/202 in the hippocampus. Conversely, pretreatment with MN prevented OA-induced spatial memory deficits and the increment of CSF glutamate level; which paralleled with normal immunocontents of Cdk5, p25 and pTau- Ser199/202 proteins. There were positive correlations between spatial memory performance and the neurochemical parameters. In summary, pretreatment with MN prevents spatial memory deficits induced by intrahippocampal OA administration in rats. The prevention of increase CSF glutamate levels, along with the reduced hippocampal phosphorylation of TauSer199/202 by Cdk5/p25 signaling pathway, are the mechanisms proposed to participate in the prophylactic effects of MN in this AD-like model.

The identification and validation of biomarkers for preclinical patients with mild cognitive impairment (MCI) at-risk for Alzheimer's disease (AD) development is increasingly important. We used the cytofluorimetric analysis of unfolded p53 to determine the prognostic ability of the protein as predictive signature from MCI to AD in a longitudinal study of a population of presymptomatic patients with the clinical diagnosis of MCI. Venous blood samples from 24 healthy subjects, 28 MCI and 15 AD were analyzed with the cytofluorimetric method for unfolded p53 protein detection. Twenty-four MCI patients had clinical follow-up subsequent to the analysis for unfolded p53. Elevated levels of the conformationally altered protein were able to discriminate both MCI and AD patients comparing with healthy subjects. Longitudinal follow-up revealed that 7/24 MCI patients progressed to AD. All converters (100%) were predicted by elevated levels of unfolded p53, with a positive predictive value of 87.5%. These data support and extend our previous observation that the cytofluorimetric approach for unfolded p53 protein was able to discriminate AD patients from healthy subjects and to predict the progression from MCI to AD in presymptomatic patients before clinical diagnosis for AD was evident.

Quantitative outcome variables in Alzheimer's disease (AD) are of interest because of their low longitudinal variability compared with that of repeated clinical and cognitive measurements. Conventional MR-based volumetry of structures within and beyond the medial temporal lobe has proven to be useful in the diagnostic work up of early AD patients, and measures of atrophy have the potential to monitor the efficacy of disease-modifying agents. The extensive application of new non-conventional MR-based techniques to the study of AD, such as proton magnetic resonance spectroscopy, diffusion tensor MRI, and functional MRI, has undoubtedly improved our understanding of the pathophysiology of the disease, and might lead to the identification of additional useful markers of disease progression. This review summarizes the main results obtained from the application of conventional and non-conventional MRI in AD patients, and supports their more extensive use in studies of disease evolution and clinical trials.

It is already known that progressive degeneration of cholinergic neurons in brain areas such as the hippocampus and the cortex leads to memory deficits, as observed in Alzheimer's disease. This work verified the effects of the infusion of amyloid-β (Aβ) peptide associated to an attentional rehearsal on the density of α7 nicotinic cholinergic receptor (nAChR) in the brain of male Wistar rats. Animals received intracerebroventricular infusion of Aβ or vehicle (control - C) and their attention was stimulated weekly (Stimulated Aβ group: S-Aβ and Stimulated Control group: SC) or not (Non- Stimulated Aβ group: N-SAβ and Non-Stimulated Control group: N-SC), using an active avoidance apparatus. Conditioned avoidance responses (CAR) were registered. Chronic infusion of Aβ caused a 37% reduction in CAR for N-SAβ. In S-Aβ, this reduction was not observed. At the end, brains were extracted and autoradiography for α7 nAChR was conducted using [125I]-α-bungarotoxin. There was an increase in α7 density in hippocampus, cortex and amygdala of SAβ animals, together with the memory preservation. In recent findings from our lab using mice infused with Aβ and the α7 antagonist methyllycaconitine, and stimulated weekly in the same apparatus, it was observed that memory maintenance was abolished. So, the increase in α7 density in brain areas related to memory might be related to a participation of this receptor in the long-lasting change in synaptic plasticity, which is important to improve and maintain memory consolidation.

The tight coupling between neuronal activity and the local increase of blood flow termed neurovascular coupling is essential for normal brain function. This mechanism of regulation is compromised in Alzheimer's Disease (AD). In order to determine whether a purely vascular dysfunction or a neuronal alteration of blood vessels diameter control could be responsible for the impaired neurovascular coupling observed in AD, blood vessels reactivity in response to different pharmacological stimulations was examined in double transgenic APPxPS1 mice model of AD. Blood vessels movements were monitored using infrared videomicroscopy ex vivo, in cortical slices of 8 month-old APPxPS1 and wild type (WT) mice. We quantified vasomotor responses induced either by direct blood vessel stimulation with a thromboxane A2 analogue, the U46619 (9,11-dideoxy-11a,9a-epoxymethanoprostaglandin F2α) or via the stimulation of interneurons with the nicotinic acetylcholine receptor (nAChRs) agonist DMPP (1,1-Dimethyl-4- phenylpiperazinium iodide). Using both types of stimulation, no significant differences were detected for the amplitude of blood vessel diameter changes between the transgenic APPxPS1 mice model of AD and WT mice, although the kinetics of recovery were slower in APPxPS1 mice. We find that activation of neocortical interneurons with DMPP induced both vasodilation via Nitric Oxide (NO) release and constriction via Neuropeptide Y (NPY) release. However, we observed a smaller proportion of reactive blood vessels following a neuronal activation in transgenic mice compared with WT mice. Altogether, these results suggest that in this mouse model of AD, deficiency in the cortical neurovascular coupling essentially results from a neuronal rather than a vascular dysfunction.