Current Alzheimer Research - Volume 14, Issue 7, 2017

Objectives: Long-term safety and tolerability of ACC-001 (vanutide cridificar), an antiamyloid- beta therapeutic vaccine, was evaluated in subjects with mild to moderate Alzheimer's disease. Design: Phase 2a extension studies of randomized parent trials were conducted in the United States, European Union, and Japan. Methods: Four immunizations of ACC-001 were administered at the same 3 dose levels (3, 10, and 30 μg) to subjects randomized in the parent studies; ACC-001 was administered with QS-21 adjuvant. Safety, tolerability, and immunogenicity were assessed during active treatment and 6-month follow-up. Results: ACC-001 + QS-21 was well tolerated in the United States (N=110) and European Union (N=50), and Japan (N=53) extension studies; safety profile was similar to that observed in the parent studies, and no new safety signals were identified. Overall, injection site reactions were the most common adverse event in these studies. Anti-amyloid antibody titers were elicited in all groups, with the highest titers observed in subjects who received ACC-001 + QS-21 in both the parent and extension studies. Conclusions: Long-term exposure to ACC-001 + QS-21 was well tolerated in subjects with Alzheimer's disease, suggesting that side effects do not pose a principal limitation for anti-amyloid active immunotherapy. The highest anti-amyloid-beta IgG titers are elicited during long-term therapy with ACC-001 + QS-21 compared with other regimens.

Background: The USA National Task Group (NTG) guidelines advocate the use of an adapted version of Dementia Screening Questionnaire for Individuals with Intellectual Disabilities (DSQIID) for dementia screening of individuals with Down syndrome (DS) and with other forms of ID (non-DS). Objective: In order to meet these guidelines, this study verifies the psychometric properties of an Italian version of the original DSQIID in a population composed of adults aged 40 years and over with DS and non-DS ID. Methods: Internal consistency, inter-rater and intra-rater reliabilities, structural validity, convergent validity and known group differences of DSQIID-I were assessed with 200 individuals with ID (mean of 55.2 years; range: 40-80 years) recruited from 15 different centers in Italy. Diagnosis of dementia was done according to IASSID diagnostic criteria and its degree of clinical certainty was defined according to Silverman et al.'s classification (2004). Results: Cronbach's alpha for the DSQIID-I was 0.94. The ICCs for inter-rater and test-retest reliability were both 0.89. A Principal Component analysis revealed three domains, namely memory and confusion- related items, motor and functional disabilities, depression and apathy, which explained almost 40% of the overall variance. The total DSQIID-I score correlated significantly with DMR and differed significantly among those individuals (n = 34) with cognitive decline from those without (n = 166). Age, gender and severity of ID were unrelated to the DSQIID-I. Conclusion: The present study confirms the cross-cultural value of DSQIID which was proved to be a psychometrically valid and user-friendly observer-rated scale for dementia screening in adults with both DS and non-DS ID.

Background: Brain derived neurotrophic factor (BDNF) may play a central role in the pathogenesis of Alzheimer's disease (AD) through neurotrophic effects on basal cholinergic neurons. Reduced serum levels of BDND are observed among AD patients and may predict AD risk. Nevertheless, knowledge about factors associated with its levels in blood is lacking. Objective: To identify clinical and demographic correlates of serum BDNF levels. Methods: BDNF was measured from serum collected between 1992-1996 and 1998-2001 in participants from the Original and Offspring cohorts of the Framingham Study, respectively. A cross-sectional analysis was done to evaluate the relationship between clinical measures and BDNF levels using standard linear regression and stepwise models. Analyses were conducted in the total sample and separately in each cohort, and were adjusted for age and sex. Results: BDNF was measured in 3,689 participants (mean age 65 years, 56% women; 82% Offspring). Cigarette smoking and high total cholesterol were associated with elevated BDNF levels, and history of atrial fibrillation was associated with decreased levels. Elevated BDNF levels were related to greater physical activity and lower Tumor Necrosis Factor-α levels in Offspring. Stepwise models also revealed associations with statin use, alcohol consumption and Apolipoprotein E4 genotype. Conclusion: Serum BDNF correlates with various metabolic, inflammatory and life-style measures which in turn have been linked with risk of AD. Future studies of serum BDNF should adjust for these correlates and are needed to further explore the underlying interplay between BDNF and other factors in the pathophysiology of cognitive impairment and AD.

Background: Chronic neuroinflammation caused by activation of microglia and astrocytes in the brain contributes to neuronal loss and disease progression in Alzheimer's disease (AD). Recent research has identified type 2 diabetes mellitus (T2DM) as a risk factor for AD. High blood glucose (hyperglycemia) and the phenomenon of insulin resistance are being considered as the major factors contributing to an increased risk of AD. However, the mechanisms involved in this interaction remain unclear. Objective: High glucose has been shown to increase release of pro-inflammatory mediators from various immune cells, including microglia. Since astrocytes are the most abundant glial cell type in the brain, we investigated the effects of elevated glucose concentrations (5.5-30.5 mM) on selected functions of cultured human astrocytes in the presence of inflammatory stimuli. Method: Experiments were conducted using primary human astrocytes and U-118 MG astrocytoma cells. Results: High glucose (30.5 mM) increased mRNA expression of interleukin (IL)-6 and secretion of both IL-6 and IL-8 by astrocytes. This astrocytic inflammatory response to high glucose did not appear to be mediated by augmented p38 or p44/42 mitogen activated protein kinase (MAPK) signaling pathways. In addition, high glucose increased the susceptibility of undifferentiated human SH-SY5Y neuronal cells and retinoic-acid differentiated SH-SY5Y cells to injury by hydrogen peroxide (H2O2) and fibrillar amyloid beta-42 protein (Aβ42), respectively. Conclusion: Our data indicate that hyperglycemia in T2DM may be one of the factors contributing to the observed increased risk of AD by exacerbating astrocyte-mediated neuroinflammation and neuronal injury caused by disease-associated agents.

Background: Anti-aggregation drugs play an important role in therapeutic approaches for Alzheimer's disease. We have previously developed a number of compounds that are able to inhibit the pathological aggregation of Tau protein. One common obstacle to application is the limited penetration across the plasma membranes into cells, where Tau aggregation occurs in the cytosol. We used an inducible N2a cell line which expresses the repeat domain of tau and develops tau aggregates. Objective: Several peptide-polymer conjugates were synthesized to enhance the uptake of compounds into cells and thus to improve their biomedical application. The aim of this study was to test whether the peptide-inhibitor complexes still retain their inhibitory activity on Tau aggregation. Method: We screened peptide sequences with high binding capacity to a subset of aggregation inhibitors and identified them by fluorescence microscopy and MALDI MS/MS with regard to drug solubility and effective complexion. To explore whether the synthesized complexes can influence the aggregation propensity of Tau we performed in vitro and cellular assays. The effect on toxicity was investigated by measuring apoptosis markers. Results/Conclusion: The tested peptide-compound complexes show no decrease in the total Tau levels but decreased ratios of soluble to pelletable Tau species. This indicates a conversion of insoluble Tau oligomers into soluble forms which appear to be less toxic than the insoluble ones, as seen by a decrease of apoptotic cells. Thus the peptide-compound complexes have a higher potency than the compounds alone due to improved bioavailability of the drug.

Background: The GSK3β has been associated to pathological functions in neurodegenerative diseases. This kinase is involved in hyperphosphorylation of microtubule-associated tau protein, leading to aggregation andformation of NFTs. It has clearly been shown that GSK3β is regulated at posttranslational level: phosphorylation at Tyr216 activates kinase, while phosphorylation at Ser9 is essential to inhibit its activity. Objectives: At present, there are contradictory findings about the possibility that GSK3β may be regulated at gene level. Previous data showed overexpression of GSK3β mRNA in hypomethylating conditions, pointing out to the existence of epigenetic mechanisms responsible for GSK3β gene regulation. Analysis of human GSK3β promoter through bisulphite modification, both in neuroblastoma cells and in postmortem frontal cortex from AD patients (AD patients both at Braak stages I-II and at stages V-VI) , allowed us to characterize the methylation pattern of a putative CpG islands in human GSK3β 5'- flanking region. Results: The analysis evidenced overall hypomethylation of CpG and non-CpG cytosine residues both in cells and in human brain (AD patients and control subjects). We found that GSK3β mRNA was overexpressed only in patients with initial AD, with no effect on the levels of the protein. On the other hand, we unexpectedly observed the decrease of the inactive GSK3β in cortex from AD patients at Braak stages I-II, whereas considerable increase was observed in AD patients at stages V-VI compared to the control subjects. Conclusions: These results point out that GSK3β hyperactivity, and then NFTs formation, could come into function at an early stage of the disease and then turn off at the last stages.

Background: Alzheimer's disease (AD) is defined as a progressive and irreversible neurodegenerative disorder, the onset of which is mainly characterized by decreased cognition, memory loss, and mental confusion. Objective: This study sought to quantify mRNA expression of the APBA2, INSR and IDE genes in brain samples from patients with AD and controls. Methods: We investigated the mRNA expression of the APBA2, INSR and IDE genes in 150 RNA samples from entorhinal cortex, auditory cortex, and the hippocampus of individuals with AD and elderly controls using real time PCR. APOE genotypes were determined by PCR-RFLP. Results: When the total brain samples were analyzed collectively, a decrease in IDE gene expression was found in AD patients relative to healthy elderly controls. However, when the samples were analyzed separately according to the region of the brain, there was a significant upregulation of INSR expression in the hippocampus and the entorhinal cortex in the AD patient group. We did not observe any statistical differences when gene expression was compared in the different regions of the brain of AD patients. When the E4 allele of apolipoprotein-E was considered in AD patients, the presence of this allele was found to be associated with decreased APBA2 gene expression. The same analysis using the INSR and IDE genes showed no significant statistical differences. Conclusion: These results support the hypothesis that APBA2, IDE, and particularly INSR gene expression in different areas of Alzheimer’s patient’s brains could represent new markers for use in clinical diagnoses in the near future.

Background: Whether the presence of the Apolipoprotein E 4 allele modulates hippocampal connectivity networks in abnormal ageing has yet to be fully clarified. Objective: Allele-dependent differences in this pattern of functional connectivity were investigated in patients with very mild neurodegeneration of the Alzheimer's type, carriers and non-carriers of the 4 allele. Method: A seed-based connectivity approach was used. The two groups were similar in demographics, volumetric measures of brain structure, and cognitive profiles. Results:4-carriers had increased connectivity between the seed area in the left hippocampus and 1) a left insular/lateral prefrontal region and 2) the contralateral right parietal cortex. Moreover, hippocampus- to-parietal connectivity in the group of 4 carriers was positively associated with memory performance, indicating that the between-group difference reflects compensatory processes. Retrospective analyses of functional connectivity based on patients from the ADNI initiative confirmed this pattern. Conclusion: We suggest that increased connectivity with areas external to the Default Mode Network (DMN) reflects both compensatory recruitment of additional areas, and pathological interwining between the DMN and the salience network as part of a global 4-dependent circuital disruption. These differences indicate that the 4 allele is associated with a more profound degree of DMN network breakdown even in the prodromal stage of neurodegeneration.

Background: Astrocytes contribute to neuroinflammation that accompanies neurodegenerative disorders such as Alzheimer's disease (AD). In this sense, the toxicity of these diseases might be attenuated through the modulation of astrocytic inflammatory responses. Recently, the CD300f immunoreceptor was described as a new member of the CD300 immunoreceptor family, showing promising modulatory properties. Objective: Here, we investigated whether overexpression of hCD300f (the human isoform of CD300f) in astrocytes protects hippocampal neurons against the degeneration induced by amyloid-beta (Aβ) oligomer. Method: Astrocyte monolayers were transfected with hCD300f before seeding the hippocampal neurons, and then the co-culture was exposed to Aβ1-42 oligomers (5 μM, 48h). Results: hCD300f expression significantly abrogated the neuronal loss elicited by Aβ. This effect was dependent on neuron-astrocyte cell-cell interactions since no protection was observed using conditioned media from transfected astrocytes. Astrocyte modulation was dependent on the cytoplasmic signaling tail of hCD300f. Furthermore hCD300f expression did not affect the ability of astrocytes to uptake Aβ1-42 oligomers by endocytosis, which discards the possibility that increased Aβ1-42 clearance could mediate neuroprotection by hCD300f. Conclusion: These results suggest that the astrocyte-directed expression of the hCD300f immune receptor can be a neuroprotective strategy in AD disease.

Background: Vision-based speed of processing (VSOP) training can result in broad cognitive improvements in older adults with amnestic mild cognitive impairment (aMCI). What remains unknown, however, is what neurophysiological mechanisms account for the observed training effect. Much of the work in this area has focused on the central nervous system, neglecting the fact that the peripheral system can contributes to changes of the central nervous system and vice versa. Objective: We examined the prospective relationship between an adaptive parasympathetic nervous system response to cognitive stimuli and VSOP training-induced plasticity. Method: Twenty-one participants with aMCI (10 for VSOP training, and 11 for mental leisure activities (MLA) control) were enrolled. We assessed high-frequency heart rate variability (HF-HRV) during training sessions, and striatum-related neural networks and cognition at baseline and post-training. Results: Compared to MLA, the VSOP group showed a significant U-shaped pattern of HF-HRV response during training, as well as decreases in connectivity strength between bilateral striatal and prefrontal regions. These two effects were associated with training-induced improvements in both the trained (attention and processing speed) and transferred (working memory) cognitive domains. Conclusion: This work provides novel support for interactions between the central and the peripheral nervous systems in relation to cognitive training, and motivates further studies to elucidate the causality of the observed link.

In the past, the blood-brain barrier (BBB) has been characterized mainly as a layer of endothelial cells forming the vessel/capillary wall of the brain. More recently, the BBB is considered to be a part of a highly dynamic and interactive system called the neurovascular unit (NVU), consisting of vascular cells, glial cells, and neurons. The list of central nervous system (CNS) pathologies involving BBB dysfunction is rapidly growing. The opening of the BBB and subsequent infiltration of serum components to the brain can lead to a host of processes resulting in progressive synaptic and neuronal dysfunction and loss. Such processes have been implicated in different diseases, including vascular dementias, stroke, Alzheimer´s disease (AD), Parkinson´s disease, multiple sclerosis, amyotrophic lateral sclerosis, hypoxia, ischemia, and diabetes mellitus. Tauopathies represent a heterogeneous group of around 20 different neurodegenerative diseases characterized by abnormal deposition of microtubule-associated protein tau in cells of the nervous system. Increased microvascular permeability has been more typically related to cerebrovascular deposition of amyloid-β (Aβ), but in contrast very little is known about the connection between functional impairment of the BBB and the misfolded tau proteins. Here, we review what is known about tauopathies, the BBB, and the NVU.

Objective: To systematically review the relationship between the cerebral microinfarcts and dementia. Methods: We conducted a systematic review and meta-analyses using the MEDLINE, EMBASE#140;the Cochrane library, and BIOSIS preview for studies published in the period from January 1st, 1997 to April 1st, 2014. We also searched the reference lists of relevant studies and review articles. Studies had to be controlled, with participants divided into a dementia group and a control group. Experimental participants included must be demented individuals with dementia syndromes (dementia overall, AD, and vascular dementia (VaD)). Outcome measures should include the presence of microinfarcts lesions. The effect size was estimated as odds ratio (OR) with 95% confidence intervals (CIs). Heterogeneity was assessed using Cochran's Q-test and I2-statistic. Results: We pooled data from 12 studies, including 2181 people. Cerebral microinfarcts were significantly associated with dementia in random effects model [the odds ratios (OR) 2.15, 95% confidence interval (95% CI) 1.46-3.15, P=0.0008]. There was no evidence of an association between the microinfarcts and Alzheimer's disease (AD) in random effects model (OR 2.81, 95% CI 0.94-8.42, P=0.06). Conclusion: These results suggest that cerebral microinfarcts are significantly associated with dementia. Whether cerebral microinfarcts are associated with AD needs to be further investigated.