Yaoqian Pan, Erin Terpstra, Yanqing Wang, Fangfang Qiao, Jin Wang, Yigang Tong, Bo Pan
Dysregulation and Diagnostic Potential of microRNA in Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is one of the most common neurodegenerative diseases and is considered to be the main cause of cognitive impairment in elderly people. The major symptom of AD is progressive dementia that eventually results in dysfunction of daily life. Due to the fact that AD has a long period of incubation before clinical symptoms emerge, the available therapeutic treatments can only improve the symptoms but not delay the progression of AD. Therefore, there is an urgent need to explore effective diagnostic approaches to catch and better treat the disease before clinical symptoms appear. Recent research revealed that abnormal expression of certain miRNA could have a crucial role in the pathological process of neurodegenerative disease including AD. Furthermore, given that AD patients show increased level of miRNAs in the blood and cerebrospinal fluid, miRNAs are considered promising non-invasive candidates for AD diagnosis and prognosis. Here, we reviewed the current research related to implications of miRNAs during the development of AD, summarized of actively used approaches to identifying potential miRNA biomarkers in body fluids, and discussed the diagnostic potential of microRNAs as biomarkers for AD.
Saak V. Ovsepian, Valerie B. O’Leary (Handling Associate Editor: Vasily Vorobyov)
Neuronal Activity and Amyloid Plaque Pathology: An Update
Abstract: A breakthrough in Alzheimer’s disease (AD) research came with the discovery of the link between activity-dependent release of amyloid-β (Aβ) from neurons and formation of amyloid plaques. Along with elucidating the cellular basis of behavioral-dependent fluctuations in Aβ levels in the brain, insights have been gained toward understanding the mechanisms that warrant selective vulnerability of various forebrain circuits to amyloid pathology. The notion of elevated activity as a source of excessive Aβ production and plaque formation is, however, in conflict with ample electrophysiological data, which demonstrate exceedingly intense activity (both intrinsic and synaptic) of neurons in several brain regions that are spared or marginally affected by amyloid plaques of AD. Thus, the link between the functional load of brain circuits and their vulnerability to amyloidosis, while evident, is also complex and remains poorly understood. Here, we discuss emerging data suggestive of a major role for super-intense synchronous activity of cortical and limbic networks in excessive Aβ production and plaque formation. It is proposed that dense recurrent wiring of associative areas prone to epileptic seizures might be of critical relevance to their higher susceptibility to plaque pathology and related functional impairments.
Peter J. Whitehouse, Daniel R. George
A Tale of Two Reports: What Recent Publications from the Alzheimer’s Association and Institute of Medicine say about the State of the Field
Gemma Tumminelli, Ilaria Di Donato, Valentina Guida, Alessandra Rufa, Alessandro De Luca, Antonio Federico
Oculodentodigital Dysplasia with Massive Brain Calcification and a New Mutation of GJA1 Gene
Abstract: Oculodentodigital dysplasia (ODDD) [MIM 164200] is a rare disorder caused by mutations in the gap junction alpha 1 (GJA1) gene encoding for connexin 43 (Cx43). Typical signs include type III syndactyly, microphtalmia, microdontia, and neurological disturbances. We report a 59-year-old man having clinical symptoms and signs suggestive of ODDD, with some rarely reported features, that is the presence of gross calcifications of basal ganglia and cerebellar nuclei. Mutation analysis of GJA1 gene identified an unreported heterozygous missense mutation [NM_000165.3:c.124G>C;p.(Glu42Gln)], which may be thought to alter the brain microvessels leading to massive calcifications, as in primary familial brain calcification.
Glynda J Kinsella, David Ames, Elsdon Storey, Ben Ong, Kerryn E. Pike, Michael M. Saling, Linda Clare, Elizabeth Mullaly, Elizabeth Rand
Strategies for Improving Memory: A Randomized Trial of Memory Groups for Older People, including those with Mild Cognitive Impairment
Abstract: Background. Governments are promoting the importance of maintaining cognitive health into older age to minimize risk of cognitive decline and dementia. Older people with amnestic mild cognitive impairment (aMCI) are particularly vulnerable to memory challenges in daily activities and are seeking ways to maintain independent living. Objective. To evaluate the effectiveness of memory groups for improving memory strategies and memory ability of older people, especially those with aMCI. Methods. 113 healthy older adults (HOA) and 106 adults with aMCI were randomized to a six-week memory group or a waitlist control condition. Outcome was evaluated through knowledge and use of memory strategies, memory ability (self-report and neuropsychological tests), and wellbeing. Assessments included a six-month follow-up. Results. Using intention to treat analyses, there were intervention effects for HOA and aMCI groups in strategy knowledge (HOA: η2 = 0.20; aMCI: η2 = 0.06), strategy use (HOA: η2 = 0.18; aMCI: η2 = 0.08), and wellbeing (HOA: η2 = 0.11; aMCI: η2 = 0.05). There were also intervention effects in the HOA group, but not the aMCI group, in self-reported memory ability (η2 = 0.06) and prospective memory tests (η2 = 0.02). By six-month follow-up, gains were found on most HOA outcomes. In the aMCI group gains were found in strategy use, and by this stage, gains in prospective memory were also found. Conclusion. Memory groups can engage older people in techniques for maintaining cognitive health and improve memory performance, but more modest benefits are seen for older adults with aMCI.
Judy C. Triplett, Aaron M. Swomley, Jian Cai, Jon B. Klein, D. Allan Butterfield (Handling Associate Editor: Patrizia Mecocci)
Quantitative Phosphoproteomic Analyses of the Inferior Parietal Lobule from Three Different Pathological Stages of Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD), the most common age-related neurodegenerative disorder, is clinically characterized by progressive neuronal loss resulting in loss of memory and dementia. AD is histopathologically characterized by the extensive distribution of senile plaques and neurofibrillary tangles, and synapse loss. Amnestic mild cognitive impairment (MCI) is generally accepted to be an early stage of AD. MCI subjects have pathology and symptoms that fall on the scale intermediately between ‘normal’ cognition with little or no pathology and AD. A rare number of individuals, who exhibit normal cognition on psychometric tests but whose brains show widespread postmortem AD pathology, are classified as ‘asymptomatic’ or ‘preclinical’ AD (PCAD). In this study, we evaluated changes in protein phosphorylation states in the inferior parietal lobule of subjects with AD, MCI, PCAD, and control brain using a 2-D PAGE proteomics approach in conjunction with Pro-Q Diamond phosphoprotein staining. Statistically significant changes in phosphorylation levels were found in 19 proteins involved in energy metabolism, neuronal plasticity, signal transduction, and oxidative stress response. Changes in the disease state phosphoproteome may provide insights into underlying mechanisms for the preservation of memory with expansive AD pathology in PCAD and the progressive memory loss in amnestic MCI that escalates to the dementia and the characteristic pathology of AD brain.
Xuying Sun*, Ronghong Ma*, Xiuqing Yao*, Xiaoling Shang*, Qun Wang, Jianzhi Wang, Gongping Liu *These authors have contributed equally to this work.
Concanavalin Agglutinin Levels are Decreased in Peripheral Blood of Alzheimer’s Disease Patients
Abstract: Alzheimer’s disease (AD) seriously threatens patients’ lives and causes severe burden to the families. Early prevention and treatment can alleviate the development of the disease; therefore it is important to find new effective and non-traumatic biomarkers for early diagnosis. In this study, peripheral blood samples were collected from 24 AD patients and the same number of age- and gender-matched control subjects. Lectin reactive glycosylation levels including beta-D-galactosyl ricinus communis agglutinin 120 (RCA), peanut agglutinin (PNA), concanavalin agglutinin (Con A), alpha-L-fucosyl ulex europeus agglutinin (UEA), dolichos biflorus agglutinin, and galanthus nivalis (GNL), in the red blood cells of peripheral blood were examined by western blotting. We found that lectin levels were altered with aging and gender; some lectin levels were different between AD patients and the control subjects. Only Con A levels were significantly decreased in AD patients compared to age-matched control subjects. These results suggest that Con A levels in peripheral blood may be a potent diagnostic marker for AD.
Sergio Salmerón, Isabel Huedo, Melisa López-Utiel, Isabel Soler-Moratalla, Teresa Flores-Ruano, Miguel Fernández-Sánchez, Alicia Noguerón, Rachelle S. Doody, Pedro Abizanda
Validation of the Spanish Version of the Baylor Profound Mental Status Examination
Abstract: Background: There are no short valid instruments to evaluate cognitive status in severe Alzheimer's disease (AD) patients in the Spanish language. Objective: To validate the Spanish version of the Baylor Profound Mental Status Examination (BPMSE-Sp). Methods: The Baylor Profound Mental Status Examination (BPMSE) was translated to Spanish and back translated. Validation was conducted in 100 patients with severe probable AD with a Mini-Mental State Examination (MMSE)<12. We assessed internal consistency (Cronbach’s alpha), concurrent validity (Pearson’s correlations) with the MMSE, Severe Impairment Battery (SIB), Neuropsychiatric Inventory Short Form (NPI-Q) and the Functional Assessment Staging and reliability. Results: The mean age of patients was 84.9; 74% were female; 64% were institutionalized. The mean MMSE was 5.6; the mean BMPSE-Sp was 13.6; the mean BPMSE-Sp behavior was 1.2; the mean SIB was 42.2; and the mean NPI-Q was 4.7. BMPSE-Sp presented good internal consistency (Cronbach α=0.84). There were significant correlations between the BPMSE-Sp and MMSE (r=0.86, p<0.001), and between the BPMSE-Sp and SIB (r=0.92, p<0.001). Inter-rater and test-retest reliability were in both cases excellent, ranging between 0.96 and 0.99 (p<0.001). BMPSE-Sp had fewer floor and ceiling effects than the MMSE. Conclusions: The BPMSE-Sp is a valid tool for use in daily practice and research in the evaluation of cognitive function of patients with severe AD.
Anna Bryndis Einarsdottir, Sveinn Hakon Hardarson, Jona Valgerdur Kristjansdottir, David Thor Bragason, Jon Snaedal, Einar Stefánsson
Retinal Oximetry Imaging in Alzheimer’s Disease
Abstract: Background: Structural and physiological abnormalities have been reported in the retina in Alzheimer’s disease (AD). Retinal oximetry detects changes in retinal oxygen metabolism in many eye diseases, where structural changes are seen. Objective: To compare oxygen saturation in retinal blood vessels in patients with AD and a healthy cohort. Methods: Oxygen saturation of hemoglobin was measured in retinal blood vessels, using imaging with spectrophotometric noninvasive retinal oximeter. 18 individuals with mild to moderate dementia of the Alzheimer-type (stage 3-5 according to the Global Deterioration Scale) and 18 healthy subjects underwent retinal oximetry in a case control study. Results: Retinal oxygen saturation in arterioles and venules in patients with moderate AD was significantly elevated compared to healthy individuals. Retinal arterioles have 94.2±5.4% oxygen saturation in moderate AD compared with 90.5±3.1% in healthy subjects (mean±SD, n=10, p=0.028). Retinal venules were 51.9±6.0% saturated in moderate AD compared with 49.7±7.0% in healthy subjects (mean± SD, n=10, p=0.02). Conclusion: This is the first study of retinal oxygen metabolism in any central nervous system disease. It discovers abnormalities in retinal oxygen metabolism in AD. The findings are similar to those seen in age-related macular degeneration and diabetic retinopathy. Noninvasive retinal oximetry may offer new insights into pathophysiology of AD. Further studies are needed to confirm and expand these findings.
Bora Yoon, Yong S. Shim, Hee-Kyung Park, SunA Park, Seong Hye Choi, Dong Won Yang (Handling Associate Editor: Sang Won Seo)
Predictive Factors for Disease Progression in Patients With Early-Onset Alzheimer’s Disease
Abstract: Background: Only a few studies have investigated disease progression in patients with early-onset Alzheimer’s disease (EOAD). Therefore, the aim of this study was to investigate disease progression in patients with EOAD and the influence of various factors, such as gender, education, and apolipoprotein E (APOE) genotype on disease progression. Methods: A total of 288 EOAD patients were enrolled in the study. Linear mixed models were used to investigate the rate of cognitive and functional decline in terms of age at onset, gender, education, follow-up period, and APOE genotype. Results: EOAD patients showed an annual decline of -1.54 points/years in the Korean version mini-mental examination score, an annual increase of 3.46 points/year in the Seoul instrumental activities of daily living (SIADL) score, and an annual increase of 1.15 points/year in the clinical dementia rating scale-sum of boxes score. After stratification, higher educated patients showed faster disease progression in all three parameters, and female patients demonstrated faster disease progression as assessed by the SIADL score. Age at onset and APOE genotype had no influence on disease progression. Conclusion: We confirmed the rate of disease progression in Korean patients with EOAD in real-life hospital-based clinical practice. The results of this study suggest that education and female gender, not APOE genotype, may be important as independent strong predictive factors for disease progression in patients with EOAD.
Jonathan Spiegel, Elizabeth Pirraglia, Yi Li, Wai Tsui, Lidia Glodzik, Ricardo S. Osorio, Leslie A. Saint Louis, Catherine Randall, Tracy Butler, Jinfeng Xu, Raymond P. Zinkowski, Henrik Zetterberg, Juan Fortea, Silvia Fossati, Thomas Wisniewski, Peter Davies, Kaj Blennow, Mony J. de Leon
Greater Specificity for Cerebrospinal Fluid P-tau231 over P-tau181 in the Differentiation of Healthy Controls from Alzheimer’s Disease
Abstract: Cerebrospinal fluid (CSF) measures of phosphorylated-tau (P-tau) 231 and P-tau181 are two biomarkers for the identification of tau pathology as related to Alzheimer’s disease (AD). While both are pathologically validated, their relative diagnostic performances are not well known. This cross-sectional diagnostic study of 87 normal (NL) subjects and 28 AD subjects compared CSF P-tau231 with CSF P-tau181. Logistic regression modeling demonstrated that the P-tau231 was superior to the P-tau181 in the diagnostic classifications. At a fixed 85% sensitivity cutoff, the ROC analysis shows that P-tau231 has greater overall specificity than P-tau181. While both P-tau analytes demonstrated equivalent negative predictive accuracies, P-tau231 yielded significantly fewer false positives. Moreover, P-tau231, but not P-tau181, demonstrated sensitivity to the E4 genotype. A postmortem validation with 9 AD subjects confirmed the superiority of the CSF P-tau231 specificity. This study suggests that P-tau231 has the potential to improve the CSF tau biomarker diagnosis of AD.
Adriana Savastano, Hans Klafki, Ute Haußmann, Timo Jan Oberstein, Petr Muller, Oliver Wirths, Jens Wiltfang, Thomas A. Bayer
N-Truncated Aβ2-X Starting with Position Two in Sporadic Alzheimer’s Disease Cases and Two Alzheimer Mouse Models>
Abstract: According to the modified amyloid hypothesis, the key event in the pathogenesis of Alzheimer’s disease (AD) is the deposition of neurotoxic amyloid β-peptides (Aβs) in plaques and cerebral blood vessels. Additionally to full-length peptides, a great diversity of N-truncated Aβ variants is derived from the larger amyloid-β protein precursor (AβPP). Vast evidence suggests that Aβx-42 isoforms play an important role in triggering neurodegeneration due to their high abundance, amyloidogenic propensity and toxicity. Although N-truncated Aβ peptides and Aβx-42 species appear to be the crucial players in AD etiology, the Aβ2-x isoforms did not receive much attention yet. The present study is the first to show immunohistochemical evidence of Aβ2-x in cases of AD and its distribution in AβPP/PS1KI and 5XFAD transgenic mouse models using a novel antibody pAB77 that has been developed using Aβ2-14 as antigen. Positive plaques and congophilic amyloid angiopathy (CAA) were observed in AD cases and in both mouse models. While in AD cases, abundant CAA and less pronounced plaque pathology was evident, the two mouse models showed predominantly extracellular Aβ deposits and minor CAA staining. Western blotting and a capillary isoelectric focusing immunoassay demonstrated the high specificity of the antibody pAb77 against Aβ-variants starting with the N-terminal Alanine-2.
Camilla N. Clark, Jennifer M. Nicholas, Elizabeth Gordon, Hannah L. Golden, Miriam H. Cohen, Felix J. Woodward, Kirsty Macpherson, Catherine F. Slattery, Catherine J. Mummery, Jonathan M. Schott, Jonathan D. Rohrer, Jason D. Warren
Altered Sense of Humor in Dementia
Abstract: Sense of humor is potentially relevant to social functioning in dementias but has been little studied in these diseases. We designed a semi-structured informant questionnaire to assess humor behavior and preferences in patients with behavioral variant frontotemporal dementia (bvFTD; n=15), semantic dementia (SD; n=7), progressive nonfluent aphasia (PNFA; n=10), and Alzheimer’s disease (AD; n=16) versus healthy age-matched individuals (n=21). Altered (including frankly inappropriate) humor responses were significantly more frequent in bvFTD and SD than PNFA or AD. All patient groups liked satirical and absurdist comedy significantly less than did healthy controls; this pattern was reported premorbidly for satirical comedy in bvFTD, PNFA, and AD. Liking for slapstick comedy did not differ between groups. Altered sense of humor is particularly salient in bvFTD and SD but also frequent in AD and PNFA. Humor may be a sensitive probe of social cognitive impairment in dementia, with diagnostic, biomarker and social implications.
Qun Lin Chan, Xin Xu, Muhammad Amin Shaik, Steven Shih Tsze Chong, Richard Jor Yeong Hui, Christopher Li-Hsian Chen, YanHong Dong
Clinical Utility of the Informant AD8 as a Dementia Case Finding Instrument in Primary Healthcare
Abstract: The informant AD8 has excellent discriminant ability for dementia case finding in tertiary healthcare settings. However, its clinical utility for dementia case finding at the forefront of dementia management, primary healthcare, is unknown. Therefore, we recruited participants from two primary healthcare centers in Singapore and measured their performance on the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Clinical Dementia Rating (CDR), and a local formal neuropsychological battery, in addition to the AD8. Logistic regression was conducted to examine the associations between demographic factors and dementia. Area under the receiver operating characteristics (ROC) curve analysis was used to establish the optimal cut-off points for dementia case finding. Of the 309 participants recruited, 243 (78.7%) had CDR=0, 22 (7.1%) CDR=0.5, and 44 (14.2%) CDR≥1. Age was strongly associated with dementia, and the optimal age for dementia case finding in primary healthcare settings was ≥75 years. In this age group, the AD8 has excellent dementia case finding capability and was superior to the MMSE and equivalent to the MoCA [AD8 AUC (95% CI): 0.95 (0.91-0.99), cut-off: ≥3, sensitivity: 0.90, specificity: 0.88, PPV: 0.79 and NPV: 0.94; MMSE AUC (95% CI): 0.87 (0.79-0.94), p=0.04; MoCA AUC (95% CI): 0.88 (0.82-0.95), p=0.06]. In conclusion, the AD8 is well suited for dementia case finding in primary healthcare settings.
Huajie Li, Haihao Zhu, Max Wallack, Mkaya Mwamburi, Samer O. Abdul-Hay, Malcolm A. Leissring, Wei Qiao Qiu
Age and Its Association with Low Insulin and High Amyloid-β Peptides in Blood
Abstract: Age is the major risk factor for developing Alzheimer’s disease (AD), and modifying age-related factors may help to delay the onset of the disease. The goal of this study was to investigate the relationship between age and the metabolic factors related to the risk of developing AD. The concentrations of insulin, amylin, and amyloid-β peptide (Aβ) in plasma were measured. We further measured the activity of serum Aβ degradation by using fluorescein- and biotin-labeled Aβ40. Apolipoprotein E4 allele (ApoE4) and cognitive impairment were characterized. Subjects were divided into three age groups: 60-70, 70-80, and ≥ 80 years old. We found that the older the subjects, the lower the concentration of insulin (p = 0.001) and the higher the concentration of Aβ1-40 (p = 0.004) in plasma. However, age was not associated with the concentration of another pancreatic peptide, amylin, and only marginally with Aβ1-42. These relationships remained in the absence of diabetes, cardiovascular disease, and stroke, and regardless of the presence of ApoE4 and cognitive impairment. Both age and ApoE4 were inversely associated with, while insulin was positively associated with, the activities of Aβ degradation in serum. Our study suggested that low concentration of insulin and high concentration of Aβ40 are aging factors related to the risk of AD.
Fu-Dong Li*, Fan He*, Ting-Rui Chen, Yuan-Yuan Xiao, Shang-Tong Lin, Wei Shen, Xin-Yi Wang, Yu-Jia Zhai, Xiao-Peng Shang, Jun-Fen Lin *These authors contributed equally to this work.
Reproductive History and Risk of Cognitive Impairment in Elderly Women: A Cross-Sectional Study in Eastern China
Abstract: Background: Epidemiological studies suggest that proxies of higher lifetime estrogen exposure are associated with better cognitive function in postmenopausal women, but this has not been found consistently. Objective: To determine whether reproductive history, an important modifier of estrogen exposure across the lifetime, is associated with risk of cognitive impairment in postmenopausal women. Methods: We analyzed the baseline data from Zhejiang Major Public Health Surveillance Program (ZPHS) including 4,796 postmenopausal women. Cognitive impairment was assessed through the application of Mini-Mental State Examination questionnaire. Logistic regression models, controlled for an extensive range of potential confounders, were generated to examine the associations between women’s reproductive history and risk of cognitive impairment in their later life. Results: The length of reproductive period was inversely associated with risk of cognitive impairment (p=0.001). Odds ratio (OR) of cognitive impairment were 1.316 (95% CI 1.095~1.582) for women with 5 or more times of full-term pregnancies, compared with those with 1~4 times of full-term pregnancies. Women without incomplete pregnancy had a significant higher risk of cognitive impairment (OR=1.194, 95% CI 1.000~1.429), compared with the reference (1~2 times of incomplete pregnancies). Oral contraceptive use (OR=0.489, 95% CI 0.263~0.910) and intrauterine device (IUD) use (OR=0.684, 95% CI 0.575~0.815) were associated with significantly reduced risk of cognitive impairment. Conclusion: Our results indicated that shorter reproductive period, higher number of full-term pregnancies and no incomplete pregnancy history were associated with an increased risk of cognitive impairment. In contrast, oral contraceptive and IUD use corresponded to reduced risk of cognitive impairment.
Mira Mäkelä, Anders Paetau, Tuomo Polvikoski, Liisa Myllykangas, Maarit Tanskanen (Handling Associate Editor: Irina Alafuzoff)
Capillary Amyloid-β Protein Deposition in a Population-Based Study (Vantaa 85+)
Abstract: Background: Capillary amyloid-β (capAβ) deposition in the cerebral cortex is the neuropathological feature providing the basis for categorizing cerebral amyloid angiopathy (CAA) into two distinct types, CAA-Type1 with capAβ and CAA-Type2 without capAβ. Objective: We investigated the neuropathological and clinical characteristics of capAβ deposition in a prospective population-based study. Methods: Vantaa 85+ includes 601 individuals aged ≥85 years, of which 300 were studied clinically and neuropathologically. 278 subjects were analyzed for the apolipoprotein E (APOE) genotype. The diagnosis of capAβ was determined using immunohistochemistry against Aβ, and of CAA using Congo red confirmed by Aβ immunohistochemistry, both analyzed in six brain areas. The severity of capAβ was graded semi-quantitatively, and the severity of CAA was based on the percentage of affected vessels. Alzheimer’s disease (AD)-type neuropathology (CERAD score and Braak stage) was analyzed using standard methods. Results: CAA-Type1 was present in 86/300, CAA-Type2 in 135/300, and 79/300 had no CAA. CapAβ was most frequent in the occipital lobe (79/86). CAA-Type1 was associated with the severity of CAA (p<0.001), dementia (p<0.001), severe AD-type neuropathology (p-value 0.09 for CERAD C and 0.017 for Braak stages V-VI), and APOE ε4 allele carrier status (p<0.001). Conclusions: This population-based study confirmed the presence of distinct CAA-Type1 and its association with the severity of CAA, severe AD-type neuropathology, and the APOE ε4 carrier status. Both the severity and localization of the deposition seemed to determine the clinical significance of capAβ.
Roberta Lizio*, Claudio Del Percio*, Nicola Marzano, Andrea Soricelli, Görsev G. Yener, Erol Başar, Ciro Mundi, Salvatore De Rosa, Antonio Ivano Triggiani, Raffaele Ferri, Dario Arnaldi, Flavio Mariano Nobili, Susanna Cordone, Susanna Lopez, Filippo Carducci, Giulia Santi, Loreto Gesualdo, Paolo M. Rossini, Enrica Cavedo Margherita Mauri, Giovanni B. Frisoni, Claudio Babiloni *These authors contributed equally to this work.
Neurophysiological Assessment of Alzheimer’s Disease Individuals by a Single Electroencephalographic Marker
Abstract: Here we presented a single electroencephalographic (EEG) marker for a neurophysiological assessment of Alzheimer’s disease (AD) patients already diagnosed by current guidelines. The ability of the EEG marker to classify 127 AD individuals and 121 matched cognitively intact normal elderly (Nold) individuals was tested. Furthermore, its relationship to AD patients’ cognitive status and structural brain integrity was examined. Low-resolution brain electromagnetic tomography (LORETA) freeware estimated cortical sources of resting state eyes-closed EEG rhythms. The EEG marker was defined as the ratio between the activity of parieto-occipital cortical sources of delta (2-4 Hz) and low-frequency alpha (8-10.5 Hz) rhythms. Results showed 77.2% of sensitivity in the recognition of the AD individuals; 65% of specificity in the recognition of the Nold individuals; and 0.75 of area under the receiver-operating characteristic curve. Compared to the AD subgroup with the EEG maker within one standard deviation of the Nold mean (EEG-), the AD subgroup with EEG+ showed lower global cognitive status, as revealed by Mini-Mental State Evaluation score, and more abnormal values of white-matter and cerebrospinal fluid normalized volumes, as revealed by structural magnetic resonance imaging. We posit that cognitive and functional status being equal, AD patients with EEG+ should receive special clinical attention due to a neurophysiological “frailty”. EEG+ label can be also used in clinical trials (i) to form homogeneous groups of AD patients diagnosed by current guidelines and (ii) as end-point to evaluate intervention effects.
Benjamin Lebwohl, José A. Luchsinger, Daniel E. Freedberg, Peter H.R. Green, Jonas F. Ludvigsson (Handling Associate Editor: Sandrine Andrieu)
Risk of Dementia in Patients with Celiac Disease: A Population-Based Cohort Study
Abstract: Background: Patients with celiac disease (CD) frequently report cognitive symptoms when they are exposed to gluten, and cognitive deficits have been quantified in patients with newly diagnosed CD. Objective: To determine whether patients with CD have an increased risk of dementia. Methods: Using a population-based database of older adults (age ≥50 years) with histologically proven CD (duodenal/jejunal villous atrophy) from all 28 pathology departments in Sweden, we compared the incidence of a subsequent dementia diagnosis to those of age- and gender-matched controls. Results: Among patients with CD (n=8,846) and controls (n=43,474), the median age was 63 years and 56% were female. During a median follow-up time of 8.4 years, dementia was diagnosed in 4.3% of CD patients and 4.4% of controls (HR 1.07; 95% CI 0.95-1.20). Although there was an increased risk of dementia in the first year following a diagnosis of CD (HR 1.73; 95%CI 1.15-2.61), this risk was not present in the whole observation period. Among those subjects with a dementia subtype specified, the increased risk was restricted to vascular dementia (HR 1.28; 95% CI 1.00-1.64) and was not present for Alzheimer’s dementia (HR 1.12; 95% CI 0.91-1.37). Conclusions: Patients with CD are not at increased risk for dementia overall, though subgroup analysis suggests that they may be at increased risk for vascular dementia.
Leandro García Barrado, Els Coart, Hugo M.J. Vanderstichele, Tomasz Burzykowski
Transferring Cut-Off Values Between Assays for Cerebrospinal Fluid Alzheimer’s Disease Biomarkers
Abstract: Current technologies quantifying cerebrospinal fluid biomarkers to identify subjects with Alzheimer’s disease pathology report different concentrations in function of technology and suffer from between-laboratory variability. Hence, lab- and technology-specific cut-off values are required. It is common practice to establish cut-off values on small datasets and, in the absence of well-characterized samples, to transfer the cut-offs to another assay format using ‘side-by-side’ testing of samples with both assays. We evaluated the uncertainty in cut-off estimation and the performance of two methods of cut-off transfer by using two clinical datasets and simulated data. The cut-off for the new assay was transferred by applying the commonly-used linear regression approach and a new Bayesian method, which consists of using prior information about the current assay for estimation of the biomarker’s distributions for the new assay. Simulations show that cut-offs established with current sample sizes are insufficiently precise and also show the effect of increasing sample sizes on the cut-offs’ precision. The Bayesian method results in unbiased and less variable cut-offs with substantially narrower 95% confidence intervals compared to the linear regression transfer. For the BIODEM datasets, the transferred cut-offs for Aβ1-42 are 167.5 pg/mL (95% credible interval [156.1, 178.0] and 172.8 pg/mL (95%CI [147.6, 179.6]) with Bayesian and linear regression methods, respectively. For the EUROIMMUN assay, the estimated cut-offs are 402.8 pg/mL (95% credible interval [348.0, 473.9]) and 364.4 pg/mL (95%CI [269.7, 426.8]). Sample sizes and statistical methods used to establish and transfer cut-off values have to be carefully considered to guarantee optimal diagnostic performance of biomarkers.
Bernard G. Schreurs, D. Larry Sparks (Handling Associate Editor: Othman Ghribi)
Dietary High Cholesterol and Trace Metals in the Drinking Water Increase Levels of ABCA1 in the Rabbit Hippocampus and Temporal Cortex
Abstract: Background: Cholesterol-fed rabbits have been documented to show increased amyloid-β (Aβ) deposits in the brain that can be exacerbated by the quality of drinking water especially if rabbits drink tap water or distilled water containing copper. One mechanism of cholesterol and Aβ clearance may be through the ATP-binding cassette transporter A1 (ABCA1). Objective and Methods: Using an ABCA1 antibody, we determined the number of ABCA1-immunopositive neurons in three areas of rabbit brain as a function of feeding 2% cholesterol and providing tap water, distilled water, or distilled water to which aluminum, copper, or zinc was added. Results: The number of neurons with ABCA1 immunoreactivity was increased significantly as a result of dietary cholesterol in the rabbit hippocampus and inferior and superior temporal cortex. The number of neurons with ABCA1 immunoreactivity was further increased in all three areas as a result of cholesterol-fed rabbits drinking tap water or distilled water with copper. Finally, cholesterol-fed rabbits that drank distilled water with aluminum also showed an increased number of ABCA1-immunopositive neurons in inferior and superior temporal cortex. Conclusions: These data suggest that ABCA1 levels increase in parallel with previously documented increases in Aβ levels as a result of high dietary cholesterol and copper in the drinking water. Addition of aluminum to distilled water may have a similar effect in the temporal cortex. ABCA1 has been proposed as a means of clearing Aβ from the brain and manipulations that increase Aβ also result in an increase of clearance machinery.
Ane Nørgaard, Christina Jensen-Dahm, Christiane Gasse, Hanne Vibe Hansen, Gunhild Waldemar (Handling Associate Editor: Peter Nestor)
Time Trends in Antipsychotic Drug Use in Patients with Dementia: A Nationwide Study
Abstract: Background: Antipsychotics are often used to treat neuropsychiatric symptoms in dementia, but the evidence for effect is limited. Antipsychotics have been associated with increased risk of adverse events and mortality in patients with dementia, leading to safety regulations worldwide. Objective: To investigate time trends in use of antipsychotics and other psychotropic drugs in dementia care. Methods: The study included longitudinal data on all Danish residents ≥65 years. The study population was defined on January 1 of each year from 2000-2012. Data included prescriptions, discharge diagnoses, and somatic and psychiatric comorbidities. Multivariate time trend analyses of psychotropic drug use in patients with dementia within 4-year age bands were performed. Results: Overall, among patients with dementia the prevalence of antipsychotic drug use decreased from 31.3% in 2000 to 20.4% in 2012. The decreasing use of antipsychotics was accompanied by decreasing use of anxiolytics and hypnotics/sedatives, but an increase in the use of antidepressants from 43.3% in 2000 to 53.8% in 2012. These changes were significant across almost all age groups. Treatment intensity among patients using antipsychotics increased as the annual median number of defined daily doses (DDD) increased from 33.3 to 42.0 DDD. Conclusions: The changing patterns of psychotropic drug use may be caused by warnings against use of antipsychotics. Further research is needed to explore the implications for patient safety.
Melissa Edwards, James Hall, Benjamin Williams, Leigh Johnson, Sid O’Bryan (Handling Associate Editor: Robert Rissman)
Molecular Markers of Amnestic Mild Cognitive Impairment among Mexican Americans
Abstract: Background: Mexican Americans face a significant health disparity when it comes to Alzheimer’s disease (AD) as they present with higher rates of the disease and develop AD at an earlier age compared to other ethnic groups. Recent work identified a proteomic profile of AD among this population; however, no work to date has sought to examine the biological profile of pre-AD among Mexican Americans. Objective: This study aims to identify an amnestic mild cognitive impairment (aMCI) proteomic profile among Mexican Americans. Methods: Data were analyzed from 284 Mexican American participants (aMCI, n=73; normal controls, n=211) from the Health & Aging Brain among Latino Elders study. Fasting serum samples were analyzed using a multi-plex biomarker assay platform. A biomarker profile was generated using random forest analyses. Results: Among aMCI cases, the biomarker profile was found to be largely inflammatory with the top three markers shown to include TNFα, IL10, and TARC. The overall diagnostic accuracy of the biomarkers in detecting aMCI was 96% (sensitivity=0.82; specificity=0.97). Inclusion of clinical variables with the selected biomarkers did not impact the overall detection accuracy (area under the curve=0.96) with a slight improvement in specificity (specificity=0.99) and associated decrease in sensitivity (sensitivity=0.74). Conclusion: The biomarker profile of aMCI was shown to be different from our previously generated AD profile among Mexican Americans, which was largely metabolic in nature. The findings implicate a possible interplay between inflammatory and metabolic processes and additional work is needed to further examine this.
Simone Agostini, Roberta Mancuso, Francesca Baglio, Monia Cabinio, Ambra Hernis, Franca Rosa Guerini, Elena Calabrese, Raffaello Nemni, Mario Clerici (Handling Associate Editor: Marco Bozzali)
Lack of Evidence for a Role of HHV-6 in the Pathogenesis of Alzheimer’s Disease
Abstract: Background: Alzheimer’s disease (AD), the most common form of dementia worldwide, is associated with impairment in the mechanisms associated with the clearing of amyloid-β within a scenario of neuroinflammation. The etiopathogenesis of the AD is unclear, but a role for viral infection is suspected to play a role in initiating the disease. We recently described a positive correlation between high titers of HSV-1-specific antibodies (Ab) and the volumes of brain regions typically affected in disease. Objective: The exploration of a possible role for Herpesviridae in AD was extended by analyzing HHV-6-specific humoral immunity in individuals with AD or a diagnosis of amnestic mild cognitive impairment (aMCI), a condition that is often prodromic of the development of AD. Methods: 59 AD, 60 aMCI, and 61 age-matched healthy controls were enrolled in the study. Serum HHV-6 IgG antibody titers and avidity index were tested by ELISA. Two randomly selected subgroups of AD and aMCI in whom HHV-6 serum antibodies were detected underwent brain magnetic resonance imaging (MRI) by 1.5 T scanner. Results: HHV-6 seroprevalence, antibody titers, and avidity were similar in the three groups. No correlation was found between Ab titers or avidity and brain volumes, either overall or in the regions typically affected by disease. Conclusions: The lack of any relation between humoral immune response against HHV-6 and AD and aMCI seems to rule out a role for this virus in the pathogenesis of AD.
Sandra E. Leh, Andrea M. Kälin, Clemens Schroeder, Min T.M. Park, Mallar M. Chakravarty, Patrick Freund, Anton F. Gietl, Florian Riese, Spyros Kollias, Christoph Hock, Lars Michels (Handling Associate Editor: Ralph Buchert)
Volumetric and Shape Analysis of the Thalamus and Striatum in Amnestic Mild Cognitive Impairment
Abstract: Alterations in brain structures, including progressive neurodegeneration, are a hallmark in patients with Alzheimer’s disease (AD). However, pathological mechanisms, such as the accumulation of amyloid and the proliferation of tau, are thought to begin years, even decades, before the initial clinical manifestations of AD. In this study, we compare the brain anatomy of amnestic mild cognitive impairment patients (aMCI, n = 16) to healthy subjects (CS, n = 22) using cortical thickness, subcortical volume, and shape analysis, which we believe to be complimentary to volumetric measures. We were able to replicate “classical” cortical thickness alterations in aMCI in the hippocampus, amygdala, putamen, insula, and inferior temporal regions. Additionally, aMCI showed significant thalamic and striatal shape differences. We observed higher global amyloid deposition in aMCI, a significant correlation between striatal displacement and global amyloid, and an inverse correlation between executive function and left-hemispheric striatal displacement. In contrast, no volumetry differences were detected in thalamic, striatal, and hippocampal regions. Our results provide new evidence for early subcortical neuroanatomical changes in patients with aMCI, which are linked to cognitive abilities and amyloid deposition. Hence, shape analysis may aid in the identification of structural biomarkers for identifying individuals at highest risk of conversion to AD.
Firoozeh Nafar, J. Bradley Williams, Karen M. Mearow (Handling Associate Editor: Jose Abisambra)
Astrocytes Release HspB1 in Response to Amyloid-β Exposure in vitro
Abstract:Although heat shock proteins are thought to function primarily as intracellular chaperones, the release and potential extracellular functions of heat shock proteins have been the focus of an increasing number of studies. Our particular interest is HspB1 (Hsp25/27) and as astrocytes are an in vivo source of HspB1 it is a reasonable possibility they could release HspB1 in response to local stresses. Using primary cultures of rat cortical astrocytes, we investigated the extracellular release of HspB1 with exposure to amyloid-β (Aβ). In order to assess potential mechanisms of release, we cotreated the cells with compounds that can modulate protein secretion including Brefeldin A, Methyl β-cyclodextrin, and MAP kinase inhibitors. Exposure to Aβ (0.1, 1.0, 2.0 µM) for 24-48 h resulted in a selective release of HspB1 that was insensitive to BFA treatment; none of the other inhibitors had any detectable influence. Protease protection assays indicated that some of the released HspB1 was associated with a membrane bound fraction, and analysis of exosomal preparations indicated the presence of HspB1 in exosomes. Finally, immunoprecipitation experiments demonstrated that the extracellular HspB1 was able to interact with extracellular Aβ. In summary, Aβ can stimulate release of HspB1 from astrocytes, this release is insensitive to Golgi or lipid raft disruption, and HspB1 can be found either free in the medium or associated with exosomes. This release suggests that there is a potential for extracellular HspB1 to be able to bind and sequester extracellular Aβ.