Joana Oliveira, Márcio Costa, Maria Soares Cachide de Almeida, Odete A. B. da Cruz e Silva, Ana Gabriela Henriques
Protein Phosphorylation is a Key Mechanism in Alzheimer’s Disease
Abstract: Altered protein phosphorylation states of several proteins are closely associated with Alzheimer’s disease (AD). Among these are the amyloid-β precursor protein (AβPP) and the tau protein. In fact, altered protein phosphorylation states already provide strong biomarkers for AD diagnosis, as is the case with hyperphosphorylated tau. It follows that modulating signaling cascades provides an attractive avenue for exploring novel therapeutic strategies. This review focuses on some of the major protein kinases and protein phosphatases relevant to AD. Of particular relevance, posttranslational modifications dynamically regulate protein activity, subcellular localization, and stability. Protein phosphorylation states can mediate complex formation as well as regulate protein function, and this is important for cellular physiology but can likewise contribute to the development of neuropathological conditions. Furthermore, applying a system approach provides a more comprehensive understanding of the signaling events associated with AD and highlights possible convergence points that may contribute to the different AD pathological hallmarks.
Irving E. Vega, Laura Y. Cabrera, Cassandra M. Wygant, Daniel Velez-Ortiz, Scott E. Counts (Handling Associate Editor: Jose Abisambra)
Alzheimer’s Disease in the Latino Community: Intersection of Genetics and Social Determinants of Health
Abstract: Alzheimer’s disease (AD) is the most common type of dementia among individuals 65 or older. There are more than 5 million diagnosed cases in the US alone and this number is expected to triple by 2050. Therefore, AD has reached epidemic proportions with significant socioeconomic implications. While aging in general is the greatest risk factor for AD, several additional demographic factors that have contributed to the rise in AD in the US are under study. One such factor is associated with the relatively fast growth of the Latino population. Several reports indicate that AD is more prevalent among blacks and Latinos. However, the reason for AD disparity among different ethnic groups is still poorly understood and highly controversial. The Latino population is composed of different groups based on nationality, namely South and Central America, Mexico, and Caribbean Hispanics. This diversity among the Latino population represents an additional challenge since there are distinct characteristics associated with AD and comorbidities. In this review, we aim to bring attention to the intersection between social determinants of health and genetic factors associated with AD within the Latino community. We argue that understanding the interplay between identified social determinants of health, co-morbidities, and genetic factors could lead to community empowerment and inclusiveness in research and healthcare services, contributing to improved diagnosis and treatment of AD patients. Lastly, we propose that inserting a neuroethics perspective could help understand key challenges that influence healthcare disparities and contribute to increased risk of AD among Latinos.
Arthur Cassa Macedo, Sara Balouch, Naji Tabet
Is Sleep Disruption a Risk Factor for Alzheimer’s Disease?
Abstract: Sleep disturbances are routinely encountered in Alzheimer’s disease (AD) and affect about 25-40% of patients in the mild-to-moderate stages of the disease. In many, sleep pathology may represent a symptom of the underlying neurodegeneration. However, a history of sleep disruption occurring years prior to onset of cognitive symptoms could represent a potential risk factor for AD. The aim of the present narrative review was to evaluate current evidence linking sleep disturbances with AD development and to understand the mechanisms that may contribute to this. Although the mechanisms by which poor sleep may contribute to AD genesis is not fully understood, emerging evidence linking disturbances in the sleep wake cycle with Aβ deposition is shedding light on the relationship between sleep pathology and the subsequent development of AD. Aβ burden appears to be enhanced by sleep-wake cycle disruptions and is suspected as being an important mechanism by which sleep disruptions contribute in AD development. Other mechanisms triggered by sleep disruption may also be involved in AD development, such as brain hypoxia, oxidative stress, circadian activity rhythms disturbances, overexpression of orexins, and blood-brain barrier impairment. Further understanding of the link between sleep disturbances and future development of AD is still needed before sleep disturbances are clearly marked as a preventable risk factor for AD. In these circumstances, early lifestyle interventions to help increase the quantity and quality of sleep may have a favorable outcome on decreasing the incidence of AD and this needs to be investigated further.
Mengxi Tang, Changiz Taghibiglou (Handling Associate Editor: Jia Liu)
The Mechanisms of Action of Curcumin in Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is a neurodegenerative disorder of the elderly. As the prevalence of AD rises in the 21st century, there is an urgent need for the development of effective pharmacotherapies. Currently, drug treatments target the symptoms of the disease and do not modify or halt the disease progress. Thus, natural compounds have been investigated for their ability to treat AD. This review examines the efficacy of curcumin, a polyphenol derived from turmeric herb, to treat AD. We summarize the in vivo and in vitro research describing the mechanisms of action in which curcumin modifies AD pathology: curcumin inhibits the formation and promotes the disaggregation of amyloid-β plaques, attenuates the hyperphosphorylation of tau and enhances its clearance, binds copper, lowers cholesterol, modifies microglial activity, inhibits acetylcholinesterase, mediates the insulin signaling pathway, and is an antioxidant. In conclusion, curcumin has the potential to be more efficacious than current treatments. However, its usefulness as a therapeutic agent may be hindered by its low bioavailability. If the challenge of low bioavailability is overcome, curcumin-based medications for AD may be in the horizon.
Rostislav Skrabana, Branislav Kovacech, Peter Filipcik, Norbert Zilka, Santosh Jadhav, Tomas Smolek, Eva Kontsekova, Michal Novak (Handling Associate Editor: Maria Deli)
Neuronal Expression of Truncated Tau Efficiently Promotes Neurodegeneration in Animal Models: Pitfalls of Toxic Oligomer Analysis
Abstract: Animal models of neurodegeneration induced by neuronal expression of truncated tau protein emerge as an important tool for understanding the pathogenesis of human tauopathies and for therapy development. Here we highlight common features of truncated tau models and make a critical assessment of possible pitfalls in their analysis. Particularly, the amount of soluble tau oligomers, which are suspected to be neurotoxic agents participating on the spreading of pathology inside the brain, may be overestimated due to a post-lysis oxidative tau oligomerization. Using a mouse brain lysate spiked with recombinant truncated and full length tau forms, we show that tau oligomers might inadvertently be produced during the isolation procedure. This finding is further corroborated by the analysis of brain lysates originated from a mouse model expressing truncated tau variant. Our results underline the necessity of thiol-protecting conditions during the analysis of tau oligomers involved in the etiopathogenesis of various tauopathies including Alzheimer’s disease.
Sandra L. Siedlak, Yingfei Jiang, Mikayla L. Huntley, Luwen Wang, Ju Gao, Fei Xie, Jingyi Liu, Bo Su, George Perry, Xinglong Wang
TMEM230 Accumulation in Granulovacuolar Degeneration Bodies and Dystrophic Neurites of Alzheimer’s Disease
Abstract: Transmembrane Protein 230 (TMEM230) is a newly identified protein associated with Parkinson's disease (PD) found in Lewy bodies and Lewy neurites of patients with PD or dementia with Lewy body disease. However, TMEM230 has not yet been investigated in the most common neurodegenerative disorder, Alzheimer's disease (AD). Here, we demonstrate that the expression of TMEM230 is specifically increased in neurons in AD patients. Importantly, both granulovacuolar degeneration (GVD) and dystrophic neurites (DNs), two prominent characteristic pathological structures associated with AD, contain TMEM230 aggregates. TMEM230 immunoreactivity can be detected in neurofibrillary tangles-containing neurons and hyperphosphorylated tau positive DNs. TMEM230 accumulation is also noted around senile plaques. These findings identifying TMEM230 as a component of GVD and DNs suggest TMEM230 dysregulation as a likely mechanism playing an important role in the pathogenesis of AD.
Collin Y. Liu, Yu Ohki, Taisuke Tomita, Satoko Osawa, Bruce R. Reed, William Jagust, Victoria Van Berlo, Lee-Way Jin, Helena C. Chui, Giovanni Coppola, John M. Ringman
Two Novel Mutations in the First Transmembrane Domain of Presenilin1 Cause Young-Onset Alzheimer’s Disease
Abstract: Background: The presenilin-1 protein (PS1) is the catalytic unit of γ-secretase implicated in the production of abnormally long forms of amyloid-β (Aβ), including Aβ42, proteins thought critical in the pathogenesis of Alzheimer’s disease (AD). In AD of autosomal dominant inheritance, the majority of pathogenic mutations have been found in the PSEN1 gene within which the location of the mutation can provide clues as to the mechanism of pathogenesis. Objective: To describe clinical features of two novel mutations in the transmembrane portion 1 (TMD-1) of PSEN1 as well as biochemical features in one and neuropathological findings in the other. Methods: Two index patients with young onset AD with an autosomal dominant pattern of inheritance underwent clinical and imaging assessments, as well as PSEN1 sequencing. Postmortem examination was completed in one patient. An artificial construct in which the P88L mutation was introduced was created to examine its effects on γ-secretase cleavage. Results: Two novel variants in TMD-1 (P88L and V89L) were identified in affected probands. The neuropathological findings of AD were confirmed in the V89L mutation. Both patients presented around age 40 with early short-term memory deficits followed by seizures and corticospinal tract signs. The P88L mutation additionally featured early myoclonus followed by Parkinsonism. The causal role of the P88L mutation is supported by demonstration that this mutation dramatically increased Aβ42 and decreased APP and Notch intracellular domain production in vitro. Conclusion: Changes in a single amino acid in codon 88 and 89 of TMD-1 can result in young-onset AD. The TMD-1 of PS1 is a region important for the γ-secretase cleavage of Aβ.
Alexandre V. Ivachtchenko, Ilya Okun, Vladimir Aladinskiy, Yan Ivanenkov, Angela Koryakova, Ruben Karapetyan, Oleg Mitkin, Ramiz Salimov, Andrey Ivashchenko (Handling Associate Editor: Ilya Bezprozvanny)
AVN-492, A Novel Highly Selective 5-HT6R Antagonist: Preclinical Evaluation
Abstract: Discovery of 5-HT6 receptor subtype and its exclusive localization within the central nervous system led to extensive investigations of its role in Alzheimer’s disease, schizophrenia, and obesity. In the present study, we present preclinical evaluation of a novel highly-potent and highly-selective 5-HT6R antagonist, AVN-492. The affinity of AVN-492 to bind to 5-HT6R (Ki = 91 pM) was more than three orders of magnitude higher than that to bind to the only other target, 5-HT2BR, (Ki = 170 nM). Thus, the compound displayed great 5-HT6R selectivity against all other serotonin receptor subtypes, and is extremely specific against any other receptors such as adrenergic, GABAergic, dopaminergic, histaminergic, etc. AVN-492 demonstrates good in vitro and in vivo ADME profile with high oral bioavailability and good brain permeability in rodents. In behavioral tests, AVN-492 shows anxiolytic effect in elevated plus-maze model, prevents an apomorphine-induced disruption of startle pre-pulse inhibition (the PPI model) and reverses a scopolamine- and MK-801-induced memory deficit in passive avoidance model. No anti-obesity effect of AVN-492 was found in a murine model. The data presented here strongly indicate that due to its high oral bioavailability, extremely high selectivity, and potency to block the 5-HT6 receptor, AVN-492 is a very promising tool for evaluating the role the 5-HT6 receptor might play in cognitive and neurodegenerative impairments. AVN-492 is an excellent drug candidate to be tested for treatment of such diseases, and is currently being tested in Phase I trials.
Christian S. Musaeus*, Mouhsin M. Shafi*, Emiliano Santarnecchi, Susan T. Herman, Daniel Z. Press *These authors contributed equally to this work.
Levetiracetam Alters Oscillatory Connectivity in Alzheimer’s Disease
Abstract: Seizures occur at a higher frequency in people with Alzheimer’s disease (AD) but overt, clinically obvious events are infrequent. Evidence from animal models and studies in mild cognitive impairment suggest that subclinical epileptic discharges may play a role in the clinical and pathophysiological manifestations of AD. In this feasibility study, the neurophysiological and cognitive effects of acute administration of levetiracetam (LEV) are measured in patients with mild AD to test whether it could have a therapeutic benefit. AD participants were administered low dose LEV (2.5 mg/kg), higher dose LEV (7.5 mg/kg), or placebo in a double-blind, within-subject repeated measures study with EEG recorded at rest before and after administration. After administration of higher dose of LEV, we found significant decreases in coherence in the delta band (1-3.99 Hz) and increases in the low beta (13-17.99 Hz) and the high beta band (24-29.99 Hz). Furthermore, we found trends toward increased power in the frontal and central regions in the high beta band (24-29.99 Hz). However, there were no significant changes in cognitive performance after this single dose administration. The pattern of decreased coherence in the lower frequency bands and increased coherence in the higher frequency bands suggests a beneficial effect of LEV for patients with AD. Larger longitudinal studies and studies with healthy age-matched controls are needed to determine whether this represents a relative normalization of EEG patterns, whether it is unique to AD as compared to normal aging, and whether longer term administration is associated with a beneficial clinical effect.
Marie-Theres Pertl, Thomas Benke, Laura Zamarian, Margarete Delazer
Effects of Healthy Aging and Mild Cognitive Impairment on a Real-Life Decision-Making Task
Abstract: In this study, we investigated the effects of age and of mild cognitive impairment (MCI) on decision making under risk by adopting a task representing real-life health-related situations and involving complex numerical information. Moreover, we assessed the relationship of real-life decision making to other cognitive functions such as number processing, executive functions, language, memory, and attention. For this reason, we compared the performance of 19 healthy, relatively younger adults with that of 18 healthy older adults and the performance of the 18 healthy older adults with that of 17 patients with MCI. Results indicated difficulties in real-life decision making for the healthy older adults compared with the healthy, relatively younger adults. Difficulties of patients with MCI relative to the healthy older adults arose in particular in difficult items requiring processing of frequencies and fractions. Significant effects of age and of MCI in processing of frequencies were also evident in a ratio number comparison task. Decision-making performance of healthy participants and the patient group correlated significantly with number processing. There was a further significant correlation with executive functions for the healthy participants and with reading comprehension for the patients. Our results suggest that healthy older individuals and patients with MCI make less advantageous decisions when the information is complex and high demands are put on executive functions and numerical abilities. Moreover, we show that executive functions and numerical abilities are not only essential in laboratory gambling tasks but also in more realistic and ecological decision situations within the health context.
Ryan J. Dougherty, Stephanie A. Schultz , Taylor K. Kirby, Elizabeth A. Boots, Jennifer M. Oh, Dorothy Edwards, Catherine L. Gallagher, Cynthia M. Carlsson, Barbara B. Bendlin, Sanjay Asthana, Mark A. Sager, Bruce P. Hermann, Bradley T. Christian, Sterling C. Johnson, Dane B. Cook, Ozioma C. Okonkwo
Moderate Physical Activity is associated with Cerebral Glucose Metabolism in Adults at Risk for Alzheimer’s Disease
Abstract: The objective of this study was to investigate the relationship between accelerometer-measured physical activity (PA) and glucose metabolism in asymptomatic late-middle-aged adults. Ninety-three cognitively healthy late-middle-aged adults from the Wisconsin Registry for Alzheimer’s Prevention participated in this cross-sectional study. They underwent 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging and wore an accelerometer (ActiGraph GT3X+) to measure free-living PA. Accelerometer data yielded measures of light (LPA), moderate (MPA), and vigorous (VPA) intensity PA. FDG-PET images were scaled to the cerebellum and pons, and cerebral glucose metabolic rate was extracted from specific regions of interest (ROIs) known to be hypometabolic in AD, i.e., hippocampus, posterior cingulate, inferior temporal cortex, and angular gyrus. Regression analyses were utilized to examine the association between PA and glucose metabolism, while adjusting for potential confounds. There were associations between MPA and glucose metabolism in all ROIs examined. In contrast, LPA was not associated with glucose uptake in any ROI and VPA was only associated with hippocampal FDG uptake. Secondary analyses did not reveal associations between sedentary time and glucose metabolism in any of the ROIs. Exploratory voxel-wise analysis identified additional regions where MPA was significantly associated with glucose metabolism including the precuneus, supramarginal gyrus, amygdala, and middle frontal gyrus. These findings suggest that the intensity of PA is an important contributor to neuronal function in a late-middle-aged cohort, with MPA being the most salient. Prospective studies are necessary for fully elucidating the link between midlife engagement in PA and later life development of AD.
Pilar Cañabate, Gabriel Martínez, Maitée Rosende-Roca, Mariola Moreno, Silvia Preckler, Sergi Valero, Oscar Sotolongo, Isabel Hernández, Montserrat Alegret, Gemma Ortega, Ana Espinosa, Ana Mauleón, Liliana Vargas, Octavio Rodríguez, Carla Abdelnour, Domingo Sánchez, Elvira Martín, Agustín Ruiz, Lluís Tárraga, Mercè Boada
Social Representation of Dementia: An Analysis of 5,792 Consecutive Cases Evaluated in a Memory Clinic
Abstract: Background: Different interpretations of cognitive impairment and dementia due to differences in health structures, such as cultural differences could affect the diagnosis and treatment of the condition. it is reasonable to expect that the social and family impact of the disease and coping strategies will differ among societies. Objective: The general aim of this study is to understand the social representations of dementia, its associated practices, and the effects they imply. Methods: People diagnosed with clinical dementia and their families were assessed from 2005 to 2015 in the memory clinic of the Fundació ACE, Institut Català de Neurociències Aplicades in Barcelona, Spain. Results: 9,898 people were examined and 5,792 were diagnosed with dementia. For those with a caregiver (71%), the decision-making fell on the person with dementia in 16.2% of the cases; and for those without a caregiver, in 26.4% of the cases the family did not perceive the deficits as a disease, which led to multiple risk situations (74.6%). Conclusions: The recognition of dementia as part of aging is common among families. Consequently, risk situations may arise and diagnosis and access to treatment may be delayed. The incorporation of a social appraisal to the diagnostic process is a necessity to evaluate these situations.
Ajai K Tripathi, Shilpita Karmakar, Abhishek Asthana, Ajay Ashok, Vilok Desai, Shounak Baksi, Neena Singh
Transport of Non-Transferrin Bound Iron to the Brain: Implications for Alzheimer’s Disease
Abstract: A direct correlation between brain iron and Alzheimer’s disease (AD) raises questions regarding the transport of non-transferrin-bound iron (NTBI), a toxic but less researched pool of circulating iron that is likely to increase due to pathological and/or iatrogenic systemic iron overload. Here, we compared the distribution of radiolabeled-NTBI (59Fe-NTBI) and transferrin-bound iron (59Fe-Tf) in mouse models of iron overload in the absence or presence of inflammation. Following a short pulse, most of the 59Fe-NTBI was taken up by the liver, followed by the kidney, pancreas, and heart. Notably, a strong signal of 59Fe-NTBI was detected in the brain ventricular system after 2 h, and the brain parenchyma after 24 h. 59Fe-Tf accumulated mainly in the femur and spleen, and was transported to the brain at a much slower rate than 59Fe-NTBI. In the kidney, 59Fe-NTBI was detected in the cortex after 2 h, and outer medulla after 24 hours. Most of the 59Fe-NTBI and 59Fe-Tf from the kidney was reabsorbed; negligible amount was excreted in the urine. Acute inflammation increased the uptake of 59Fe-NTBI by the kidney and brain from 2-24 hours. Chronic inflammation, on the other hand, resulted in sequestration of iron in the liver and kidney, reducing its transport to the brain. These observations provide direct evidence for the transport of NTBI to the brain, and reveal a complex interplay between inflammation and brain iron homeostasis. Further studies are necessary to determine whether transient increase in NTBI due to systemic iron overload is a risk factor for AD.
Guiyou Liu, Jing-yi Sun, Meiling Xu, Xiao-yi Yang, Bao-liang Sun (Handling Associate Editor: Jin-Tai Yu)
SORL1 Variants Show Different Association with Early‑Onset and Late-Onset Alzheimer’s Disease Risk
Abstract: A recent study sequenced the full coding region of SORL1 in 1,255 early-onset Alzheimer’s disease (EOAD) cases and 1,938 control individuals, and investigated the contribution of genetic variability in SORL1 to EOAD risk in a European cohort. This study identified six common variants and five low frequency variants in the SORL1 coding sequence. However, none of these 11 variants was significantly associated with EOAD risk after adjusting for multiple testing. We consider whether these 11 SORL1 variants identified in European EOAD contribute to late-onset Alzheimer’s disease (LOAD) risk in individuals of European ancestry. Here, we investigated these 11 SORL1 variants identified in European EOAD and LOAD risk in individuals of European ancestry using a large-scale LOAD GWAS. Our results indicate that three genetic variants rs2070045, rs2276412, and rs17125548 as well as their tagged genetic variants contribute to LOAD risk in European population. We further investigate whether these variants could affect SORL1 expression using multiple expression quantitative trait loci (eQTLs) datasets. Our findings suggest that three genetic variants rs2070045, rs1699102, and rs3824968 could significantly regulate SORL1 expression in human brain tissues. We believe that our findings further provide important supplementary information about the involvement of the SORL1 variants in LOAD risk.
Jill K. Morris, Roxanne Adeline Z. Uy, Eric D. Vidoni, Heather M. Wilkins, Ashley E. Archer, John P. Thyfault, John M. Miles, Jeffrey M. Burns
Effect of APOE ε4 Genotype on Metabolic Biomarkers in Aging and Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) may have heterogeneous pathophysiological underpinnings, with risk factors including apolipoprotein ε4 (APOE4) genotype and insulin resistance. We hypothesized that distinct phenotypes exist within AD. We examined APOE4 and metabolic biomarkers in 338 subjects (n=213 nondemented (ND), n=125 AD). We further characterized steady state free fatty acid (FFA) levels in a subset of 45 participants who had also participated in a hyperinsulinemic-euglycemic clamp. Insulin resistance (HOMA-IR) was elevated in AD versus ND (p=0.04) and in APOE4 noncarriers versus carriers (p<0.01). This was driven by increased fasting insulin in AD versus ND (p<0.01) and in APOE4 non-carriers versus carriers (p=0.01). Fasting glucose was not different. In subjects who underwent a clamp, there was a group x genotype interaction on FFA levels during hyperinsulinemia (p=0.03). APOE4 non-carriers with AD had higher FFA levels, while APOE4 carriers with AD exhibited lower FFA levels. Metabolic dysfunction is overrepresented in individuals with AD dementia who do not carry the APOE4 allele. This suggests that important subsets of AD phenotypes may exist that diverge metabolically.
Elhanan Pinner, Yaron Gruper, Micha Ben Zimra, Don Kristt, Moshe Laudon, David Naor, Nava Zisapel
CD44 Splice Variants as Potential Players in Alzheimer’s Disease Pathology
Abstract: Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive deficits, deposition of amyloid-β (Aβ) plaques, intracellular neurofibrillary tangles, and neuronal cell death. Neuroinflammation is commonly believed to participate in AD pathogenesis. CD44 is an inflammation-related gene encoding a widely-distributed family of alternatively spliced cell surface glycoproteins that have been implicated in inflammation, metastases, and inflammation-linked neuronal injuries. Here we investigated the expression patterns of CD44S (which does not contain any alternative exon) and CD44 splice variants in postmortem hippocampal samples from AD patients and matched non-AD controls. The expression of CD44S and CD44 splice variants CD44V3, CD44V6, and CD44V10 was significantly higher in AD patients compared to non-AD controls. Immunohistochemistry of human hippocampal sections revealed that CD44S differentially localized to neuritic plaques and astrocytes, whereas CD44V3, CD44V6, and CD44V10 expression was mostly neuronal. Consistent with these findings, we found that the expression of CD44V6 and CD44V10 was induced by Aβ peptide in neuroblastoma cells and primary neurons. Furthermore, in loss of function studies we found that both CD44V10-specific siRNA and CD44V10 antibody protected neuronal cells from Aβ-induced toxicity, suggesting a causal relationship between CD44V10 and neuronal cell death. These data indicate that certain CD44 splice variants contribute to AD pathology and that CD44V10 inhibition may serve as a new neuroprotective treatment strategy for this disease.
Norimichi Nakamura, Yasumasa Ohyagi, Tomohiro Imamuraa, Yuki T. Yanagihara, Kyoko M. Iinuma, Naoko Soejima, Hiroyuki Murai, Ryo Yamasaki, Jun-ichi Kira
Apomorphine Therapy for Neuronal Insulin Resistance in a Mouse Model of Alzheimer’s Disease
Abstract: Apomorphine (APO) promotes intraneuronal amyloid-β (Aβ) degradation and improves memory function in an Alzheimer’s disease (AD) model, 3xTg-AD mice. Since insulin resistance is increased in AD neurons, we investigated the effects of APO on brain insulin resistance in 3xTg-AD mice at early and late stages. After 1-month subcutaneous injection of Apokyn® to 3xTg-AD mice at 6 or 12 months of age, memory function was significantly improved in both age groups. Protein levels of insulin-degrading enzyme (IDE), which is linked to insulin signaling and degrades Aβ, significantly increased in the 3xTg-AD mice brain compared with non-transgenic mice, and were further increased by APO. Protein levels of two types of serine-phosphorylated insulin receptor substrate-1 (IRS-1), pS616 and pS636/639, significantly decreased following APO treatment in the 13-month-old 3xTg-AD mice brain, suggesting improved brain insulin resistance. Immunostaining of the IDE, pS616 and pS636/639 IRS-1 demonstrated similar changes due to APO treatment. Thus, brain insulin resistance is considered an important therapeutic target in AD, and APO may provide improved neuronal insulin resistance.
Sai Tian, Jing Han, Rong Huang, Jie Sun, Rongrong Cai, Yanjue Shen, Shaohua Wang
Increased Plasma Homocysteine Level is associated with Executive Dysfunction in Type 2 Diabetic Patients with Mild Cognitive Impairment
Abstract: Background: Homocysteine (Hcy) is involved in the pathogenesis of type 2 diabetes mellitus (T2DM) and Alzheimer’s disease. Objective: We aimed to investigate the role of Hcy in T2DM patients with mild cognitive impairment (MCI), and to determine whether methylene tetrahydrofolate reductase (MTHFR) C677T or cystathionine beta-synthase (CBS) 844ins68 polymorphism is related to T2DM-associated MCI. Methods: We recruited 285 T2DM patients and divided them into two groups, 140 patients with MCI, and 145 healthy-cognition controls, on the basis of Montreal Cognitive Assessment (MoCA) scores. Demographic characteristics, clinical parameters, and neuropsychological tests were assessed. MTHFR C677T and CBS 844ins68 polymorphisms were analyzed. Results: The MCI group exhibited significantly higher plasma total Hcy (tHcy) levels than control group (p < 0.001). Plasma tHcy level was negatively correlated with MoCA scores (p = 0.002), but positively associated with Trail Making Test A and B scores (p = 0.044; p = 0.005, respectively). Multivariable logistic regression model showed that high tHcy level was an independent factor for MCI in T2DM patients. No significant difference was observed in the genotype or allele distributions of MTHFR and CBS between MCI and control groups. We did not find significant MCI risks in MTHFR T allele compared with C allele, and in CBS I allele compared with D allele (OR = 1.361, p = 0.067; OR = 1.048, p = 0.909, respectively). Conclusion: Increased plasma tHcy level was significantly related to T2DM-associated MCI, especially executive dysfunction. Further investigation with a large population size should be conducted to confirm these findings.
Yuxia Li*, Bin Jing*, Han Liu, Yifan Li, Xuan Gao, Yongqiu Li, Bin Mu, Haikuo Yu, Jinbo Cheng, Peter B. Barker, Hongxing Wang, Ying Han *These authors contributed equally to this work.
Frequency-Dependent Changes in the Amplitude of Low-Frequency Fluctuations in Mild Cognitive Impairment with Mild Depression
Abstract: Background: Depression is a potential marker of preclinical Alzheimer’s disease (AD). However, little is known about the abnormal characteristics revealed by resting-state functional magnetic resonance imaging (rs-fMRI) in mild cognitive impairment (MCI) subjects with depressive symptoms (MCI-d). Objective: The study was to examine whether abnormalities in amplitudes of low-frequency oscillation occurred in MCI-d and tried to find the possible spectrum showed higher recognition ability to the diagnosis by utilizing functional MRI (fMRI). Methods: The amplitude of low-frequency fluctuation (ALFF) and fractional ALFF (fALFF) within full frequency (0.01-0.1Hz), slow-5 (0.01–0.027 Hz), and slow-4 (0.027–0.073 Hz) were computed using resting-state fMRI data of 27 MCI without depressive symptoms, 19 MCI-d, and 32 well-matched healthy controls (HC). Analysis of covariance was performed on ALFF and fALFF among MCI, MCI-d, and HC groups. Results: Several brain regions showed significant differences in ALFF and fALFF within full frequency, slow-5, and slow-4 bands among three groups. Importantly, receiver operating characteristic analysis revealed that the ALFF values in the full frequency band in the left parahippocampal gyrus and the left precuneus, Slow 5 value in ALFF in the left inferior frontal gyrus, and Slow 4 value in ALFF in the left precuneus could effectively differentiate MCI-d from MCI patients. Conclusion: In this study, we found that several changes in special brain regions are associated with MCI and MCI-d patients. And the differences depend on the studied frequency bands of rs-fMRI data. The affective network and the default-mode network might be damaged simultaneously in MCI-d patients.
Daniel G. Amen, William S. Harris, Parris M. Kidd, Somayeh Meysami, Cyrus A. Raji
Quantitative Erythrocyte Omega-3 EPA Plus DHA Levels are Related to Higher Regional Cerebral Blood Flow on Brain SPECT
Abstract: Background: The interrelationships between omega-3 fatty acids status, brain perfusion, and cognition are not well understood. Objective: To evaluate if SPECT brain imaging of cerebral perfusion and cognition varies as a function of omega-3 fatty acid levels. Methods: A random sample of 166 study participants was drawn from a psychiatric referral clinical for which erythrocyte quantification of omega-3 eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) (the Omega-3 Index) was available. Quantitative brain SPECT was done on 128 regions based on a standard anatomical Atlas Persons with erythrocyte EPA+DHA concentrations were dichotomized based on membership in top 50th percentile versus bottom 50th percentile categories. Two-sample t-tests were done to identify statistically significant differences in perfusion between the percentile groups. Partial correlations were modeled between EPA+DHA concentration and SPECT regions. Neurocognitive status was assessed using computerized testing (WebNeuro) and was separately correlated to cerebral perfusion on brain SPECT imaging and omega-3 EPA+DHA levels. Results: Partial correlation analyses showed statistically significant relationships between higher omega-3 levels and cerebral perfusion were in the right parahippocampal gyrus (r = 0.20, p = 0.03), right precuneus (r = 0.20, p = 0.03), and vermis subregion 6 (p = 0.21, p = 0.03). Omega-3 Index levels separately correlated to the feeling subsection of the WebNeuro (r = 0.25, p = 0.01). Conclusion: Quantitative omega-3 EPA+DHA erythrocyte concentrations are independently correlated with brain perfusion on SPECT imaging and neurocognitive tests. These results have implications for the role of omega-3 fatty acids toward contributing to cognitive reserve.
Ramón López-Higes*, Inmaculada C. Rodríguez-Rojo*, José M. Prados, Pedro Montejo, David Del-Río, María Luisa Delgado-Losada, Mercedes Montenegro, David López-Sanz, Ana Barabash *These authors contributed equally to this work.
APOE ε4 Modulation of Training Outcomes in Several Cognitive Domains in a Sample of Cognitively Intact Older Adults
Abstract: Background: Most research points to the ε4 allele of the apolipoprotein E (APOE) gene as the most recognizable genetic risk factor associated with Alzheimer’s disease pathogenesis. It has been also suggested that the APOE ε4 allele has a negative influence on cognitive functioning, which begins long before cognitive impairment becomes manifest. However, still, little is known about the APOE ε4 interaction with cognitive intervention programs. Objective: The main goal of this study was to explore whether there was a differential APOE genotype modulation effect after cognitive training in different domains, such as language comprehension, executive functions, and memory. Contrary to other studies, hippocampal volume was controlled for. Methods: Fifty older adults (65+ years; 30 women and 20 men) participated in a multi-domain cognitive training that involved 30 sessions taking place over 12 weeks. Half of the participants were APOE ε4 carriers. The control group was matched in age, gender, normalized hippocampal volume, cognitive reserve, Mini-Mental State Examination score, and Geriatric Depression Scale-Short Version. Results: The study revealed that there were consistent treatment benefits in complex sentence comprehension (noncanonical sentences and sentences with two propositions), a domain that was not directly trained, but only in the APOE ε4 noncarrier group. Conclusion: Genetic profile modulates training outcomes in sentence comprehension.
Stephane Nave, Rachelle S. Doody, Mercè Boada, Timo Grimmer, Juha-Matti Savola, Paul Delmar, Meike Pauly-Evers, Tania Nikolcheva, Christian Czech, Edilio Borroni, Benedicte Ricci, Juergen Dukart, Marie Mannino, Tracie Carey, Emma Moran, Inma Gilaberte, Nicoletta Milani Muelhardt, Irene Gerlach, Luca Santarelli, Susanne Ostrowitzki, Paulo Fontoura (Handling Associate Editor: Krista Lanctôt)
Sembragiline in Moderate Alzheimer’s Disease: Results of a Randomized, Double-Blind, Placebo-Controlled Phase II Trial (MAyflOwer RoAD)
Abstract: Background: Sembragiline is a potent, selective, long-acting, and reversible MAO-B inhibitor developed as a potential treatment for Alzheimer’s disease (AD). Objective: To evaluate the safety, tolerability, and efficacy of sembragiline in patients with moderate AD. Methods: In this Phase II study (NCT01677754), 542 patients with moderate dementia (MMSE 13–20) on background acetylcholinesterase inhibitors with/without memantine were randomized (1:1:1) to sembragiline 1 mg, 5 mg, or placebo once daily orally for 52 weeks. Results: No differences between treated groups and placebo in adverse events or in study completion. The primary endpoint, change from baseline in ADAS-Cog11, was not met. At Week 52, the difference between sembragiline and placebo in ADAS-Cog11 change from baseline was -0.15 (p=0.865) and 0.90 (p=0.312) for 1 and 5 mg groups, respectively. Relative to placebo at Week 52 (but not at prior assessment times), the 1 mg and 5 mg sembragiline groups showed differences in ADCS-ADL of 2.64 (p=0.051) and 1.89 (p=0.160), respectively. A treatment effect in neuropsychiatric symptoms (as assessed by the difference between sembragiline and placebo on BEHAVE-AD-FW) was also seen at Week 52 only: -2.80 (p=0.014; 1 mg) and -2.64 (p=0.019; 5 mg), respectively. A post hoc subgroup analysis revealed greater treatment effects on behavior and functioning in patients with more severe baseline behavioral symptoms (above the median). Conclusions: This study showed that sembragiline was well-tolerated in patients with moderate AD. The study missed its primary and secondary endpoints. Post hoc analyses suggested potential effect on neuropsychiatric symptoms and functioning in more behaviorally impaired study population at baseline.
John Fredy Ochoa, Joan Francesc Alonso, Jon Edinson Duque, Carlos Andrés Tobón, Ana Baena, Francisco Lopera, Miguel Angel Mañanas, Alher Mauricio Hernández
Precuneus Failures in Subjects of the PSEN1 E280A Family at Risk of Developing Alzheimer’s Disease Detected Using Quantitative Electroencephalography
Abstract: Background: Presenilin-1 (PSEN1) mutations are the most common cause of familial early onset Alzheimer’s disease (AD). The PSEN1 E280A (E280A) mutation has an autosomal dominant inheritance and is involved in the production of amyloid-β. The largest family group of carriers with E280A mutation is found in Antioquia, Colombia. The study of mutation carriers provides a unique opportunity to identify brain changes in stages previous to AD. Electroencephalography (EEG) is a low cost and minimally invasiveness technique that enables the following of brain changes in AD. Objective: To examine how previous reported differences in EEG for Theta and Alpha-2 rhythms in E280A subjects are related to specific regions in cortex and could be tracked across different ages. Methods: EEG signals were acquired during resting state from non-carriers and carriers, asymptomatic and symptomatic subjects from E280A kindred from Antioquia, Colombia. Independent component analysis (ICA) and inverse solution methods were used to locate brain regions related to differences in Theta and Alpha-2 bands. Results: ICA identified two components, mainly related to the Precuneus, where the differences in Theta and Alpha-2 exist simultaneously at asymptomatic and symptomatic stages. When the ratio between Theta and Alpha-2 is used, significant correlations exist with age and a composite cognitive scale. Conclusion: Theta and Alpha-2 rhythms are altered in E280A subjects. The alterations are possible to track at Precuneus regions using EEG, ICA, and inverse solution methods.
Kacie D. Deters, Shannon L. Risacher, Sungeun Kim, Kwangsik Nho, John D. West, Kaj Blennow, Henrik Zetterberg, Leslie M. Shaw, John Q. Trojanowski, Michael W. Weiner, Andrew J. Saykin for the Alzheimer Disease Neuroimaging Initiative
Plasma Tau Association with Brain Atrophy in Mild Cognitive Impairment and Alzheimer’s Disease
Abstract: Background: Peripheral (plasma) and central (cerebrospinal fluid, CSF) measures of tau are higher in Alzheimer’s disease (AD) relative to prodromal stages and controls. While elevated CSF tau concentrations have been shown to be associated with lower grey matter density (GMD) in AD-specific regions, this correlation has yet to be examined for plasma in a large study. Objective: Determine the neuroanatomical correlates of plasma tau using voxel-based analysis. Methods: Cross-sectional data for 508 ADNI participants were collected for clinical, plasma total-tau (t-tau), CSF amyloid (Aβ42) and tau, and MRI variables. The relationship between plasma tau and GMD and between CSF t-tau and GMD were assessed on a voxel-by-voxel basis using regression models. Age, sex, APOE ε4 status, diagnosis, and intracranial volume were used as covariates where appropriate. Participants were defined as amyloid positive (Aβ+) if CSF Aβ42 was
Byungseung Moon, Seongheon Kim, MD, Young Ho Park, Jae-Sung Lim, Young Chul Youn, SangYun Kim, Jae-Won Jang, for the Alzheimer’s Disease Neuroimaging Initiative
Depressive Symptoms are Associated with Progression to Dementia in Patients with Amyloid-Positive Mild Cognitive Impairment
Abstract: Background: Depressive symptoms are prevalent in patients with mild cognitive impairment (MCI) and are considered to be a risk factor for progression to dementia. Objective: The purpose of this study was to evaluate whether depressive symptoms in MCI promote disease progression in a manner related to amyloid status, and to determine the relationship between depressive symptoms and longitudinal cerebral structural changes. Methods: Baseline data for 336 patients with MCI (75 with depression and 261 without) from the Alzheimer’s Disease Neuroimaging Initiative study were analyzed. All participants underwent comprehensive cognitive testing, volumetric magnetic resonance imaging (MRI), and [18F]AV45 positron emission tomography amyloid imaging. Depressive symptoms were measured using the Neuropsychiatric Inventory Questionnaire. A voxel-based morphometric analysis using volumetric brain MRI data was used to compare longitudinal structural changes related to depressive symptoms. Results: The conversion rate to dementia was different between patients with and without depression in amyloid-positive MCI (40.8% versus 19.7%, respectively; p=0.006). Patients who were amyloid-positive at baseline also exhibited a greater degree of 2-year cognitive decline. Depression in amyloid-positive MCI was associated with longitudinal cortical atrophy in the left cingulate gyrus. Conclusion: Our study indicates that the presence of depressive symptoms in patients with amyloid-positive MCI is associated with higher progression to dementia and longitudinal cortical atrophy.
Pavla Cermakova, Maja Nelson, Juraj Secnik, Sara Garcia-Ptacek, Kristina Johnell, Johan Fastbom, Lena Kilander, Bengt Winblad, Maria Eriksdotter, Dorota Religa
Living Alone with Alzheimer’s Disease: Data from SveDem, the Swedish Dementia Registry
Abstract: Background: Many people with Alzheimer’s disease (AD) live alone in their own homes. There is a lack of knowledge about whether these individuals receive the same quality of diagnostics and treatment for AD as patients who are cohabiting. Objectives: To investigate the diagnostic work-up and treatment of community-dwelling AD patients who live alone. Methods: We performed a cross-sectional cohort study based on data from the Swedish Dementia Registry (SveDem). We studied patients diagnosed with AD between 2007 and 2015 (n=26,163). Information about drugs and comorbidities was acquired from the Swedish Prescribed Drug Register and the Swedish Patient Register. Results: 11,878 (46%) patients lived alone, primarily older women. After adjusting for confounders, living alone was inversely associated with receiving computed tomography (OR 0.90; 95% CI 0.82-0.99), magnetic resonance imaging (OR 0.91; 95% CI 0.83-0.99), and lumbar puncture (OR 0.86; 95% CI 0.80-0.92). Living alone was also negatively associated with the use of cholinesterase inhibitors (OR 0.81; 95% CI 0.76; 0.87), memantine (OR 0.77; 95% CI 0.72; 0.83), and cardiovascular medication (OR 0.92; 0.86; 0.99). On the other hand, living alone was positively associated with the use of antidepressants (OR 1.15; 95% CI 1.08; 1.22), antipsychotics (OR 1.41; 95% CI 1.25; 1.58), and hypnotics and sedatives (OR 1.09; 95% CI 1.02; 1.17). Conclusions: Solitary living AD patients do not receive the same extent of care as those who are cohabiting.
Anna Pink, Scott A. Przybelski, Janina Krell-Roesch, Gorazd B. Stokin, Rosebud O. Roberts, Michelle M. Mielke, David S. Knopman, Clifford R. Jack Jr., Ronald C. Petersen, Yonas E. Geda
Cortical Thickness and Depressive Symptoms in Cognitively Normal Individuals: The Mayo Clinic Study of Aging
Abstract: Altered cortical thickness has been observed in aging and various neurodegenerative disorders. Furthermore, reduced hippocampal volume has been reported in late-life depression. Even mild depressive symptoms are common in the elderly. However, little is known about the structural MRI measures of depressive symptoms in normal cognitive aging. Thus we sought to examine the association between depressive symptoms with cortical thickness and hippocampal volume as measured by brain MRI among community-dwelling participants. We conducted a cross-sectional study derived from the ongoing population-based Mayo Clinic Study of Aging, involving cognitively normal participants (N=1,507) aged ≥ 70 years. We observed that depressive symptoms were associated with lower global cortical thickness and lower thickness in specific prefrontal and temporal cortical regions, labeled by FreeSurfer software, version 5.3. As expected, the strength of correlation was very small, given that participants were community-dwelling with only mild depressive symptoms. We did not observe associations between hippocampal volume and depressive symptoms. These findings may provide insight into the structural correlates of mild depressive symptoms in elderly participants.
Lihua Gu, Zhijun Zhang
Exploring Potential Electrophysiological Biomarkers in Mild Cognitive Impairment: A Systematic Review and Meta-Analysis of Event-Related Potential Studies
Abstract: Background: Early diagnosis and effective management are pivotal steps in preventing the transition from mild cognitive impairment (MCI) to Alzheimer's disease. Previous investigations indicated that some event-related potential (ERP) components in MCI are sensitive to cognitive decline. However, several comparative analyses of these components in MCI and healthy controls (HC) yielded inconsistent results. Objective: The aim was to perform a systematic review and meta-analysis of ERP studies on MCI patients. Methods: We systematically searched on PubMed and Web of Science for MCI-related ERP studies published from April 1986 to August 2016. Standard mean difference estimates of all components were compared between MCI and HC. Results: Our study showed increased P50 amplitude at the Cz site; reduced N2pc amplitude and delayed P200 latency at the Cz site; N200 latency at the Cz and Pz sites, and P300 latency at the Cz and Pz sites in MCI patients compared to HC. Conclusions: In summary, our study indicated that some ERP components, such as P50 and N2pc amplitude, P200, N200, and P300 latency might be potential electrophysiological biomarkers for MCI diagnosis.
Yen Ying Lim, Robert Williamson, Simon M. Laws, Victor L. Villemagne, Pierrick Bourgeat, Christopher Fowler, Stephanie Rainey-Smith, Olivier Salvado, Ralph N. Martins, Christopher C. Rowe, Colin L. Masters, Paul Maruff, for the AIBL Research Group
Effect of APOE Genotype on Amyloid Deposition, Brain Volume, and Memory in Cognitively Normal Older Individuals
Abstract: Background: The association between the apolipoprotein E (APOE) ε4 allele and high risk of developing Alzheimer’s disease (AD) dementia before the age of 80 has been recognized for over 30 years. However, the timing and mode of action of APOE is not understood, nor has there been a detailed analysis of the effect of APOE genotype on memory, hippocampal volume, and amyloid-β (Aβ) levels in cognitively normal adults. Objective: Examine the effect of APOE allelic genotype on the relationship between Aβ levels, hippocampal volume, and memory in cognitively normal adults. Methods: This is a cross-sectional study of 989 cognitively normal older adults enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study, all of whom underwent APOE genotyping and memory assessment. A subset of this group underwent PET neuroimaging for Aβ (n=585) and MRI for hippocampal volume (n=303). Results: APOE ε4 homozygotes (ε4/ε4) showed significantly worse episodic memory and higher Aβ levels than ε4 heterozygotes. The relationship between increasing Aβ levels and worse episodic memory was significant for ε3 homozygotes (ε3/ε3), ε4 heterozygotes, and strongest for ε4 homozygotes. There were no differences in hippocampal volume between APOE groups; the relationship between smaller hippocampal volume and worse episodic memory was significant only for ε4 homozygotes. Conclusion: APOE acts in a co-dominant fashion on Aβ levels, episodic memory, and hippocampal volume in cognitively normal older adults. APOE ε4 is central to the events that lead to AD in cognitively normal older adults, likely through a quantitative role in the disruption of Aβ clearance.
Mandy Busse, Enrico Michler, Franz von Hoff, Henrik Dobrowolny, Roland Hartig, Thomas Frodl, Stefan Busse
Alterations in the Peripheral Immune System in Dementia
Abstract: Alterations in the immune response that result in inflammation might play a role in the pathology of dementias. In order to analyze changes of the peripheral immune system associated with different types of dementias, we determined several innate and adaptive cell populations in whole blood using flow cytometry. We included patients with Alzheimer’s disease (AD; n=60), vascular dementia (VaD; n=20), and frontotemporal dementia (FTD; n=12) at the time point of diagnosis and 24 age-matched neuropsychiatric healthy persons. Monocytes and NK cells were diminished in VaD, but not in AD and FTD. B cell and T cell numbers were decreased in all investigated forms of dementia. Changes in the contribution of naïve/memory T cells were only present in AD. Correlation and regression analyses revealed associations between altered immune cell populations and Q Albumin as marker for the integrity of the blood-cerebrospinal fluid-barrier, Mini-Mental State Examination values, and age. The peripheral immune system is altered in AD, VaD, and FTD. However, each disorder presents unique changes in the investigated cell types indicating different mechanisms underlying the pathology.