Current Alzheimer Research - Volume 14, Issue 3, 2017

Neurodegenerative diseases may directly affect memory performance, thus leading to functional impairments. An increasing body of evidence suggests an association between dietary intake of omega-3 fatty acids and memory functioning in animal models as well as in human studies. Recent evidence supports a potential beneficial role of omega-3 fatty acid supplementation on psychopathological and cognitive symptoms, beside their established positive effects on cardiovascular health. Objective: We summarize relevant and recent evidence from epidemiological, interventional and experimental studies investigating dietary consumption of omega-3 fatty acids and emphazing mechanisms of memory disorders, with a focus on mild cognitive impairment (MCI) and dementia. Omega-3 fatty acid could represent an affordable and accessible adjunctive treatment option to improve cognitive and non-cognitive function with a focus on MCI or dementia. However, apart from its translational promise, which is based on mechanistic models and evidence from animal studies, evidence for clinical benefits in humans is lacking. Method: To follow this research question, a search through electronic databases for the following search terms to identify relevant studies was conducted: ‘omega 3 fatty acids’, ‘cognition’, ‘memory’, ´Alzheimer´s Disease ´, ´dementia´, ´MCI`. Studies were included if they presented original data and were published in English between 1990 and 2015. Results: To our the best of our knowledge, there are only 8 interventional studies that investigated the effects of n3-PUFAs in dementia patients, while 6 studies were conducted in healthy individuals, which in combination show equivocal results. Conclusion: This verifies the need for larger and (more) well designed clinical trials.

Objectives: To compare the 4-year survival, institutionalization, cognitive and functional decline of Alzheimer’s patients with specific follow-up in memory centers versus usual care. Design: Four year longitudinal follow-up. Settings: The French Network of memory centers in Alzheimer’s disease (REAL-FR study) and The French population-based study (3C study). Participants: 728 patients aged ≥ 65, living at home, meeting criteria for probable Alzheimer’s disease and having Mini Mental State Examination (MMSE) scores between 10 and 26 at baseline were included. Measurements: Cox proportional hazards models were performed to test the effectiveness of a specific follow-up in memory centers (REAL-FR study) versus usual care (3C study) on the 4-year survival and institutionalization. Linear mixed models were used to assess cognitive and functional decline in both groups. Results: After adjustment for confounding factors, the 4-year survival did not differ significantly between patients followed-up in memory centers and those who had recourse to usual care (usual care: Hazard Ratio adjusted (HRa) = 0.87, 95% confidence interval (CI) 0.53-1.43, p=0.59). Patients with a specific follow-up in memory centers had a higher risk of being institutionalized (usual care: HRa = 0.24, 95% CI 0.12-0.48, p<0.001). They also exhibited a significant greater cognitive and functional decline over time. Conclusion: Our findings failed to demonstrate any potential benefits of a specific follow-up in memory centers on clinically meaningful outcomes in the natural history of Alzheimer’s disease. Recourse to care in memory centers may have been the consequence of a faster dementia progression and a greater burden of Alzheimer’s disease, all leading to detrimental consequences on various prognostic outcomes.

Background: In recent years, 5-hydroxytryptamine subtype 6 receptor (5-HT6 receptor, 5- HT6R) has emerged as a promising therapeutic target for the treatment of neuropathological disorders, including Alzheimer’s disease (AD) and schizophrenia. 5-HT6 receptors were hypothesized to be implicated in the processes of learning, memory, and cognition with 5-HT6R antagonists being effective in animal models of cognition and memory impairment. Several selective 5-HT6R ligands are currently undergoing clinical trials for treatment of AD. Methods: We describe results of preclinical development of a novel and highly selective and potent 5- HT6R antagonist, AVN-322, as a clinical candidate for the treatment of AD to improve concurrent debilitation of memory and cognition in the AD patients, and schizophrenia as a substance with antipsychotic effect. In the manuscript, we present its in vitro and vivo efficacy, ADME, pharmacokinetics in animals and in humans, and toxicity. Results: While having high binding affinity in medium picomolar range, the lead compound demonstrates substantially better selectivity index then the reference drug candidates currently being tested in clinical studies. AVN-322 showed high oral bioavailability and favorable blood-brain barrier (BBB) penetration. In vivo testing revealed its clear cognition enhancing effect. AVN-322 significantly restored both scopolamine- and MK-801-induced cognitive dysfunction and demonstrated antipsychotic potential. Conclusion: Taking into account its good safety profile and favorable pharmacokinetics, AVN-322 can be reasonably considered as a novel drug candidate for the treatment of neurological disorders such as AD and/or schizophrenia.

Background: The ever-increasing number of people living with Alzheimer’s disease urges to develop more effective therapies. Despite considerable success, anti-Alzheimer immunotherapy still faces the challenge of intracerebral and intracellular delivery. This work introduces in situ production of anti-amyloid beta (Aβ) antibody after intracerebral injection of PEG-PAsp(DET)/mRNA polyplexes as a novel immunotherapy approach and a safer alternative compared to high systemic antibodies doses or administration of adenovirus encoding anti- Aβ antibodies. Methods: We used mRNA encoding three different Aβ-specific scFV with a secretion signal for passive immunotherapy. scFv contained a 6xHis-tag for immuno-detection. The secretion signal from IL2 (IL2ss) was added to allow extracellular engagement of senile plaques. Aβ affinity of scFv was measured by surface plasmon resonance. To allow intracellular delivery, scFv were administered as polyplexes formed with our smart copolymer polyethylene glycol-poly[N’-[N-(2-aminoethyl)-2-aminoethyl] aspartamide] [PEG-PAsp (DET)]. We evaluated scFv expression in cellulo by Western blot and ELISA, their ability to disaggregate amyloid aggregates by thioflavine T assay. Moreover, in vivo expression and therapeutic activity were evaluated in a murine amyloidosis model, by anti-6xHis-tag ELISA and anti- Aβ ELISA, respectively. Results: The selected anti-amyloid beta scFv showed affinity towards Aβ and disaggregated Aβ fibers in vitro. Whereas both DNA and mRNA transfection led to scFV expression in cancer cells, only mRNA led to detectable scFv expression in primary neurons. In addition, the use of IL2ss increased by 3.4-fold scFv secretion by primary neurons over mRNA polyplexes devoid of secretion signal. In vivo, a 3 to 11- fold of intracranial scFv levels was measured for mRNA compared to DNA polyplexes and higher in vivo scFv levels were obtained with mRNA containing IL2ss over non-secreted mRNA. Intracranial injection of anti-Aβ mRNA polyplexes with IL2ss resulted in 40 % Aβ decrease in an acute amyloidosis model; with no decrease detected with control scFv mRNA nor DNA polyplexes. However, no Aβ decrease was detected in a more challenging transgenic model of Alzheimer’s disease. Conclusion: Our results introduce a concerted approach not only for Alzheimer’s disease treatment but also for immunotherapy against neurological diseases. The effectivity of our platform required the intracranial delivery of anti-Aβ scFv as mRNA not DNA, as mRNA with an IL2ss secretion sequence to favor engagement of Aβ in the amyloidosis model, complexation with a smart copolymer for efficient transfection of primary neurons and to achieve detectable mRNA expression in the brain during 48h. Amyloid burden decrease in an acute amyloidosis model was only achieved when these three factors (mRNA coding scFv, smart copolymer, IL2ss) were integrated into a single formulation.

Background/Objectives: Increasing evidence suggests the importance of neuroinflammation in the pathogenesis of Alzheimer’s disease (AD), which is a complex neurodegenerative disorder. Complement activation occurs in the brain of patients with AD and seems to contribute to an important local inflammatory state. Increased expression of the fourth serum complement component 4 (C4) has been observed in AD patients in many studies. This protein has two isoforms, encoded by two genes: C4A and C4B localized to the HLA class III region. These genes exhibit copy number variations (CNVs) and this different gene copy number can influence C4 protein levels. We focalized our attention on these two genes, determining the distribution of CNVs in AD patients, compared with healthy controls, in order to analyse their possible involvement in AD pathogenesis. Methods: We investigated 191 AD patients and 300 healthy controls. The C4A and C4B copy numbers were assessed by quantitative PCR (qPCR). Results: The results obtained showed a statistically significant increase in the number of copies for both C4A and C4B in AD patients, compared with healthy controls (p<0,001). Conclusion: The presence of high C4A and C4B copy numbers in AD patients could explain the increased C4 protein expression observed in AD patients, thus highlighting a possible role for C4A and C4B CNVs in the risk of developing AD.

Background: Sleep disorders other than sleep apnea (non-apnea sleep disorder, NSD), esp. insomnia and excessive daytime sleepiness, has been reported to induce higher risk of cognitive decline and dementia in previous longitudinal follow-up studies. However, large-scale nationwide populationbased study may further confirm the association between NSD and dementia. Methods: It was a nationwide population-based retrospective study. We used data from Taiwan’s National Health Insurance Research Database (NHIRD) between January 2000 and December 2011. The NSD cohort comprised 92,079 patients aged over 20 years with no preexisting dementia. The comparison cohort was propensity-score matched 1:1 with 92079 controls. Incident dementia cases were identified to the end of 2011. The NSD cohort to non-NSD cohort adjusted hazard ratios (aHRs) of dementia were assessed using multivariable Cox proportional hazards regression analysis. Results: Incidence of dementia was 4.19 and 2.95 per 1,000 person-years in the NSD and non-NSD cohorts, respectively, with an aHR of 1.46 (95% CI=1.38–1.54; p<0.0001). Risk of dementia was higher in both gender and whole age subgroup, with slightly higher in men (aHR: 1.48, 95% CI=1.35–1.62, p<0.0001) and in the younger population (aHR: 2.79, 95% CI=1.63–4.78, p<0.0001). Dementia was most likely to occur in the first year of follow-up (aHR: 1.73, 95% CI=1.49–2.02; p<0.0001), but dementia risk remained high 5 years after NSD diagnosis compared to controls (aHR: 1.44, 95% CI=1.32–1.57; p<0.0001). Conclusion: NSD may be an early indicator of decline in cognitive functioning and onset of dementia in the short-term period. It also carries a higher risk for dementia in the long run. Patients with NSD should require close monitoring for cognitive decline.

Background: Alzheimer´s disease, a progressive and degenerative disorder of the brain, is the most common cause of dementia among the elderly. To face its multifactorial nature, the use of single compounds that can simultaneously modulate different targets involved in the neurodegenerative cascade has emerged as an interesting therapeutic approach. Objective: This work investigated the ability of uleine, the major indole alkaloid purified from stem barks of the Brazilian medicinal plant Himatanthus lancifolius, to interact with crucial Alzheimer´s disease disruptive targets associated with two of its major neurodegenerative pathways: acetylcholinesterase and butyrylcholinesterase (cholinergic pathway) and β-secretase and β-amyloid peptide (amyloidogenic pathway). Methods: Uleine’s capacity to inhibit human acetylcholinesterase and butyrylcholinesterase enzymes was determined measuring the difference between reaction rates with and without uleine monitored at 412 nm using 5,5’- dithiobis-(2- nitrobenzoic acid) as colorimetric agent. FRET based assay was used to evaluate β-secretase inhibition using DABCYL- Ser-Glu-Val-Asn-Leu-Asp-Ala-Glu-Phe-EDANS as substrate and β-amyloid peptide spontaneous aggregation assay was performed using the thioflavin T spectroscopy assay. Cell viability and toxicity experiments with PC12 and SH-SY5Y cell lines were performed using the MTT colorimetric assay. Results: Uleine demonstrated strong inhibitory activities for both cholinesterases (IC50 279.0±4.5 and 24.0±1.5 μM, respectively) and β-secretase (IC50 180±22 nM). Above all, uleine significantly inhibited the self-aggregation of amyloid- β peptide and was not toxic for PC12 or SH-SY5Y neuronal cells. Conclusion: These data show for the first time that the natural compound uleine has a novel, multieffective ability to decelerate or even inhibit the development of Alzheimer´s disease.

Background: Alzheimer’s disease (AD) pathogenesis is primarily hallmarked by the production and accumulation of amyloid beta (Aβ) peptide. Along with the understanding of the neurodegenerative disease progression and its pathophysiological mechanisms, development of anti-Aβ targeted effective therapeutics is essential for AD management. Numerous therapeutic approaches targeting the production, toxicity and removal of Aβ are being attempted worldwide. Prime need is to design inhibitors which can slow down the Aβ aggregation process in a physiological environment. Bexarotene (targretin) is the first of the U.S. Food and Drug Administration approved oral retinoid X receptors (RXR)-selective retinoids, or rexinoids. It is effectively used for the treatment of advanced, refractory cutaneous T cell lymphoma, and also reportedly reduces Aβ levels in AD mouse models. Administration of bexarotene facilitates intracellular Aβ clearance via RXR regulated apolipoprotein E (ApoE) production. Objective: To the best of our knowledge, this is the first structural attempt to find binding interactions of the drug bexarotene with monomeric Aβ peptide. Method: We checked binding possibilities of bexarotene by using structural bioinformatics method. Results: We found in our study the basic amino acids His13 and Lys 16 of Aβ peptide to be crucial for the interaction with bexarotene. Conclusion: We speculate that direct binding of bexarotene to free Aβ peptide may lessen the concentration of free Aβ peptides in the brain and hamper the propensity of the peptide’s clumping and aggregating behavior. Further experimental validation of the results of this study would be required for its therapeutic success.

Background: Two large-scale genome-wide association studies have identified rs610932 and rs670139 polymorphisms within the MS4A gene cluster as being significantly associated with susceptibility to Alzheimer’s disease (AD) in those with European ancestry. A number of studies have focused on the association between MS4A gene variants and AD in Caucasian and East Asian populations. However, the results remain inconsistent owing to the small sample size in each study. Objective: We performed a meta-analysis to explore whether rs610932 and rs670139 polymorphisms are associated with susceptibility to AD. Method: 19 studies with 34,119 cases and 56,956 controls concerning rs610932 and 18 studies with 33,622 cases and 55,322 controls concerning rs670139 were included in this meta-analysis by searching the PubMed, MEDLINE, and AlzGene databases. Results: Our results showed significant associations between rs610932 and rs670139 polymorphisms and AD in the pooled population using an additive model. In subgroup analysis, we also identified a significant association of rs610932 in the Asian population under additive [odds ratio=0.82, 95% confidence interval 0.69-0.99, p=0.03] and dominant models (odds ratio=0.82, 95% confidence interval 0.72-0.95, p=0.006), but not under a recessive model. However, no association was found between rs670139 and AD patients using all three of these models in the Asian population. Conclusion: Our results suggest that the rs610932 polymorphism contributes to AD susceptibility in Caucasian and Asian populations. To our knowledge, this is the largest meta-analysis to investigate the association between MS4A gene polymorphisms and AD in Asian and European populations.

Background: Alzheimer’s disease (AD) is the most common form of dementia. The process of AD can begin 20 years before any symptom of cognitive loss. Thus, the development of systems for early diagnosis and prevention is very important. The mechanism of AD is still under debate. Nevertheless, higher levels of glycated albumin in cerebrospinal fluid and plasma are observed in AD patients. Therefore, glycated albumin could be a biomarker of AD development. Methods: Electrochemical biosensor for direct determination of glycated albumin was based on thiol derivative of pentetic acid (DTPA) complex with Cu(II) created on gold electrode surface. His-tagged domains of Receptors for Advanced Glycation End Products (RAGE) were applied as analytical active element for glycated albumin recognition. The binding of glycated albumin by His6- RAGE domains was monitored using Osteryoung square - wave voltammetry. Results: Electrodes modified with His6 - RAGE VC1 natural domain generated decrease of Cu(II) redox currents in the presence of glycated albumin. Human albumin, Aβ 1-40 and S100B protein caused negligible influence on biosensors responses towards glycated albumin. The detection limits were: 2.3 pM, 1.1 pM, 2.9 pM and 3.1 pM in the presence of: buffer, buffer + albumin, buffer + S100B, buffer + Aβ1-40 , respectively. Conclusion: The presented electrochemical biosensor was successfully applied for the determination of glycated albumin. Considering analytical parameters such as good selectivity and sensitivity in pM range, biosensor could be recommended as an analytical tool for medical samples analysis.