Amyloid-β Levels Research Articles

Levels of Retinal Amyloid-β Correlate with Levels of Retinal IAPP and Hippocampal Amyloid-β in Neuropathologically Evaluated Individuals.

Background:Previous studies have used immunohistology to demonstrate Alzheimer’s disease (AD) characteristic accumulation of amyloid-β (Aβ) in the retina of AD patients, a finding indicating retina examination as a potential diagnostic tool for AD pathology.Objective:To further explore this idea by investigating whether levels of Aβ42 and Aβ40 in retina are associated with corresponding levels in hippocampus, neuropathological assessments, apolipoprotein E (APOE) genotype, and levels of islet amyloid polypeptide (IAPP).Methods:Levels of high molecular weight (HMW) Aβ42, Aβ40, and IAPP in ultra-centrifuged homogenates of retina and hippocampus from patients with AD, multiple sclerosis, AD with Lewy bodies, and non-demented controls were analyzed using Mesoscale Discovery electrochemiluminescence technology employing immunoassay and enzyme-linked immunosorbent assay.Results:Higher levels of retinal and hippocampal Aβ42-HMW, Aβ40-HMW, and IAPP-HMW were found in individuals with high neuropathological scores of Aβ plaques and in individuals carrying the APOE ɛ4 allele. The retinal levels of Aβ42-HMW and Aβ40-HMW correlated with corresponding levels in hippocampus as well as with neurofibrillary tangles (NFT) and Aβ scores. Retinal IAPP-HMW correlated with retinal levels of Aβ42-HMW and with NFT and Aβ scores.Conclusion:These results show that different isoforms of Aβ can be detected in the human retina and moreover support the growing number of studies indicating that AD-related pathological changes occurring in the brain could be reflected in the retina.

LDL Receptor Deficiency Does not Alter Brain Amyloid-β Levels but Causes an Exacerbation of Apoptosis.

Familial hypercholesterolemia (FH) is a genetic disorder caused by dysfunction of low density lipoprotein receptors (LDLr), resulting in elevated plasma cholesterol levels. FH patients frequently exhibit cognitive impairment, a finding recapitulated in LDLr deficient mice (LDLr-/-), an animal model of FH. In addition, LDLr-/- mice are more vulnerable to the deleterious memory impact of amyloid-β (Aβ), a peptide linked to Alzheimer's disease. Here, we investigated whether the expression of proteins involved in Aβ metabolism are altered in the brains of adult or middle-aged LDLr-/- mice. After spatial memory assessment, Aβ levels and gene expression of LDLr related-protein 1, proteins involved in Aβ synthesis, and apoptosis-related proteins were evaluated in prefrontal cortex and hippocampus. Moreover, the location and cell-specificity of apoptosis signals were evaluated. LDLr-/- mice presented memory impairment, which was more severe in middle-aged animals. Memory deficit in LDLr-/- mice was not associated with altered expression of proteins involved in Aβ processing or changes in Aβ levels in either hippocampus or prefrontal cortex. We further found that the expression of Bcl-2 was reduced while the expression of Bax was increased in both prefrontal cortex and hippocampus in 3- and 14-month-old LDLr-/-mice Finally, LDLr-/- mice presented increased immunoreactivity for activated caspase-3 in the prefrontal cortex and hippocampus. The activation of caspase 3 was predominantly associated with neurons in LDLr-/- mice. Cognitive impairment in LDLr-/- mice is thus accompanied by an exacerbation of neuronal apoptosis in brain regions related to memory formation, but not by changes in Aβ processing or levels.

Vortioxetine administration attenuates cognitive and synaptic deficits in 5×FAD mice.

Vortioxetine has been reported to exhibit a variety of neurobiological functions and neuroprotective effects. In the present study, we aimed to investigate the effects of vortioxetine on cognitive performance in a transgenic mouse model of Alzheimer's disease (AD). We administered vortioxetine (10mg/kg, i.p., every day, for approximately 6weeks), which acts on multiple 5-serotonin (5-HT) receptors, to 3.5-month-old 5×FAD mice. Subsequently, we used the open field (OF) test to detect anxiety-like behavior in the mice. The novel object recognition (NOR) test and Morris water maze (MWM) were used to assess the cognitive states of the 5×FAD mice. We also measured the levels of insoluble amyloid plaques and soluble β-amyloid (Aβ) plaques. Finally, we explored the expression levels of postsynaptic density protein 95 (PSD95), synaptophysin (SYP), and synaptotagmin-1 (SYT1) in the hippocampus of the mice. The administration of vortioxetine effectively reversed the reduction in anxiety-type behaviors in 5×FAD mice and improved the impairment in recognition memory and spatial reference memory. However, we did not find that vortioxetine decreased or delayed the formation of amyloid plaques or Aβ. Interestingly, we found a significant increase in the expression levels of PSD95, SYP, and SYT1 in the 5×FAD mice after vortioxetine treatment compared with the control group. These results demonstrate that vortioxetine may improve cognitive impairment in 5×FAD mice. The role in cognitive improvement may be related to the beneficial effects of vortioxetine on synaptic function.

Effects of acute sleep loss on diurnal plasma dynamics of CNS health biomarkers in young men.

ObjectiveDisrupted sleep increases CSF levels of tau and β-amyloid (Aβ) and is associated with an increased risk of Alzheimer disease (AD). Our aim was to determine whether acute sleep loss alters diurnal profiles of plasma-based AD-associated biomarkers.MethodsIn a 2-condition crossover study, 15 healthy young men participated in 2 standardized sedentary in-laboratory conditions in randomized order: normal sleep vs overnight sleep loss. Plasma levels of total tau (t-tau), Aβ40, Aβ42, neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP) were assessed using ultrasensitive single molecule array assays or ELISAs, in the fasted state in the evening prior to, and in the morning after, each intervention.ResultsIn response to sleep loss (+17.2%), compared with normal sleep (+1.8%), the evening to morning ratio was increased for t-tau (p = 0.035). No changes between the sleep conditions were seen for levels of Aβ40, Aβ42, NfL, or GFAP (all p > 0.10). The AD risk genotype rs4420638 did not significantly interact with sleep loss–related diurnal changes in plasma levels of Aβ40 or Aβ42 (p > 0.10). Plasma levels of Aβ42 (−17.1%) and GFAP (−12.1%) exhibited an evening to morning decrease across conditions (p < 0.05).ConclusionsOur exploratory study suggests that acute sleep loss results in increased blood levels of t-tau. These changes provide further evidence that sleep loss may have detrimental effects on brain health even in younger individuals. Larger cohorts are warranted to delineate sleep vs circadian mechanisms, implications for long-term recurrent conditions (e.g., in shift workers), as well as interactions with other lifestyle and genetic factors.

Long-term UVA exposure to the eye compromises memory and learning ability in mice via corticotropin-releasing hormone type 2 receptor.

Long-term eye exposure to ultraviolet (UV)A can effect memory and learning ability. However, the underlying mechanism behind these effects remain unknown. In this study, we used HR-1 mice to study effects of long-term UVA eye irradiation. The eyes or dorsal skin of the mice were exposed to UVA at the dose of 110kj/m2 using an FL20SBLB-A lamp three times a week over 12 months. We measured the levels of reactive oxygen species, corticotropin-releasing hormone (CRH), urocortin 2, and CRH type 2 receptor (CRHR-2) in the brain of treated and control animals. Their memory and learning ability following exposure to UVA was analyzed by the standard water maze test. Our results showed that the levels of reactive oxygen species, CRH, urocortin 2, and CRHR-2 increased significantly following long-term UVA irradiation, and the effects were more pronounced in animals subjected to eye irradiation than those subjected to dorsal skin irradiation. Furthermore, the UVA exposure led to an increase in the levels of β-amyloid and microglia in the brain. These results indicated that UVA eye irradiation potentially mediated a decline in memory and learning ability via enhancing levels of urocortin 2, microglia, and β-amyloid in the brain.

In the blood: biomarkers for amyloid pathology and neurodegeneration in Alzheimer's disease.

This scientific commentary refers to 'Plasma total-tau, neurofilament light chain and amyloid-β levels and risk of dementia: a population-based study' by de Wolf et al. (https://doi.org/10.1093/brain/awaa054), and 'Relationship of amyloid-b1-42 in blood and brain amyloid: Ginkgo Evaluation of Memory Study' by Lopez et al. (https://doi.org/10.1093/braincomms/fcz038), two papers that illustrate these latest developments.

Sequential butylphthalide therapy combined with dual antiplatelet therapy in the treatment of acute cerebral infarction.

Objective:To observe the clinical efficacy of sequential butylphthalide therapy combined with dual antiplatelet therapy in the treatment of elderly patients with acute cerebral infarction (ACI).Methods:One hundred and twenty-two elderly patients with ACI who were admitted to the department of neurology of our hospital at May 2016-August 2018 were selected grouped into a control group and an observation group by random number table method, 61 in each group. On the basis of conventional treatment, the patients in the control group were given dual antiplatelet therapy (aspirin enteric-coated tablets + clopidogrel bisulfate tablets), while the patients in the observation group were given sequential butylphthalide therapy on the basis of the control group. The clinical effects of the two groups were compared after four weeks of treatment, and the changes of National Institutes of Health Stroke Scale (NIHSS), ADL score, plasma 3-mercaptopyruvate sulphurtransferase (3-MST) and Amyloid β42 (Aβ42) levels and the occurrence of adverse reactions during treatment were recorded.Results:The clinical efficacy of the observation group was better than that of the control group (P<0.05). There was no significant difference in NIHSS and ADL scores between the two groups before treatment (P>0.05). After treatment, the NIHSS and ADL scores of the observation group were better than those of the control group (P<0.05). There was no significant difference in plasma levels of 3-MST and AB42 between the two groups before treatment (P>0.05). The level of plasma 3-MST in the observation group was higher than that in the control group, and the level of plasma Aβ42 was lower than that in the control group (P<0.05). No serious adverse reactions occurred during the treatment period in both groups.Conclusion:Butylphthalide sequential therapy combined with dual antiplatelet therapy is effective in the treatment of elderly ACI. It can effectively improve the plasma level of 3-MST and decrease the plasma level of Aβ42, which is conducive to improving the living ability and neurological function of patients and has high safety.

Use of ocular biomarkers as a potential tool for early diagnosis of Alzheimer's disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide which unfortunately has no known effective cure to date. Despite many clinical trials indicating the effectiveness of preclinical treatment, a sensitive tool for screening of AD is yet to be developed. Due to multiple similarities between ocular and the brain tissue, the eye is being explored by researchers for this purpose, with utmost attention focused on the retinal tissue. Besides visual functional impairment, neuronal degeneration and apoptosis, retinal nerve fiber degeneration, increase in the cup-to-disc ratio, and retinal vascular thinning and tortuosity are the changes observed in the retinal tissue which are related to AD. Studies have shown that targeting these changes in the retina is an effective way of reducing the degeneration of retinal neuronal tissue. Similar mechanisms of neurodegeneration have been demonstrated in the brain and the eyes of AD patients. Multiple studies are underway to investigate the potential of diagnosing AD and detection of amyloid-β (Aβ) levels in the retinal tissue. Since the tissues in the anterior segment of the eye are more accessible for in vivo imaging and examination, they have more potential as screening biomarkers. This article provides a concise review of available literature on the ocular biomarkers in anterior and posterior segments of the eye including the cornea, aqueous humour (AH), crystalline lens, and retina in AD. This review will also highlight the newer technological tools available for the detection of potential biomarkers in the eye for early diagnosis of AD.

Major Surgery Affects Memory in Individuals with Cerebral Amyloid-β Pathology.

Major surgery has been associated with perioperative neurocognitive disorders (PND), but the contributing factors and long-term prognosis are uncertain. We hypothesize that preclinical Alzheimer's disease (AD) might predispose to cognitive deterioration after surgery. To analyze the effect of amyloid-β on the cognitive trajectory after orthopedic surgery in a sample of non-demented subjects. Non-demented individuals older than 65 years that were on the waiting list for orthopedic surgery with spinal anesthesia underwent a neuropsychological assessment before and after surgery. During surgery, cerebrospinal fluid samples were obtained to determine AD biomarkers. Cumulative incidence of PND was 55.2%during a mean follow-up of nine months. The most affected cognitive domains were executive function and constructional praxis. The presence of abnormal levels of amyloid-β was associated to a postoperative impairment in verbal and visual memory tests. According to their AD biomarker profile, participants were categorized as either Amyloid Positive (A+) or Amyloid Negative (A-). The incidence of PND did not differ between both groups. The A- group showed a tendency similar to the global sample, worsening in executive function tests and improving on memory scales due to practice effects. In contrast, the A + group showed a notable worsening on memory performance. Our findings support the hypothesis that surgery may promote or accelerate memory decline in cognitively asymptomatic subjects with brain amyloid-β deposits.

Biomarker potential of brain-secreted extracellular vesicles in blood in Alzheimer's disease.

Brain cells secrete extracellular microvesicles (EVs) that cross the blood-brain barrier. Involved in cell-to-cell communication, EVs contain surface markers and a biologically active cargo of molecules specific to their tissue (and cell) of origin, reflecting the tissue or cell's physiological state. Isolation of brain-secreted EVs (BEVs) from blood provides a minimally invasive way to sample components of brain tissue in Alzheimer's disease (AD), and is considered a form of "liquid biopsy." We performed a comprehensive review of the PubMed literature to assess the biomarker and therapeutic potential of blood-isolated BEVs in AD. We summarize methods used for BEV isolation, validation, and novel biomarker discovery, as well as provide insights from 26 studies in humans on the biomarker potential in AD of four cell-specific BEVs isolated from blood: neuron-, neural precursor-, astrocyte-, and brain vasculature-derived BEVs. Of these, neuron-derived BEVs has been investigated on several fronts, and these include levels of amyloid-β and tau proteins, as well as synaptic proteins. In addition, we provide a synopsis of the current landscape of BEV-based evaluation/monitoring of AD therapeutics based on two published trials and a review of registered clinical trials. Blood-isolated BEVs have emerged as a novel player in the study of AD, with enormous potential as a diagnostic, evaluation of therapeutics, and treatment tool. The literature has largely concentrated on neuron-derived BEVs in the blood in AD. Given the multifactorial pathophysiology of AD, additional studies, in neuron-derived and other brain cell-specific BEVs are warranted to establish BEVs as a robust blood-based biomarker of AD.

Fasudil reduces β-amyloid levels and neuronal apoptosis in APP/PS1 transgenic mice via inhibition of the Nogo-A/NgR/RhoA signaling axis.

Recent studies have shown that Nogo-A and the Nogo-A receptor affect β-amyloid metabolism and the downstream Rho GTP enzyme signaling pathway, which may affect the levels of β-amyloid and tau. Nogo-A may play a key role in the pathogenesis of Alzheimer's disease. However, the underlying molecular mechanisms of Fasudil treatment in Alzheimer's disease are not yet clear. Our results have found that Fasudil treatment for two months substantially ameliorated behavioral deficits, diminished β-amyloid plaque and tau protein pathology, and alleviated neuronal apoptosis in APP/PS1 transgenic mice. More importantly, two well-established markers for synaptic function, growth-associated protein 43 and synaptophysin, were upregulated after Fasudil treatment. Finally, the levels of Nogo-A, Nogo-A receptor complex NgR/p75NTR/LINGO-1 and the downstream Rho/Rho kinase signaling pathway were significantly reduced. These findings suggest that Fasudil exerts its neuroprotective function in Alzheimer's disease by inhibiting the Nogo-A/NgR1/RhoA signaling pathway.

The Protective effect of Pomegranate and Red Beetroot Juices against Aluminum Toxicity in Brains of Male Rats

The purpose of this work is to investigate the protective effect of pomegranate, red beetroot juices or their mixture on the brain toxicity induced by AlCl3 in rats. Five groups (7 rats each) were used in the experiment; one of them continued feeding on basal diet only during the period of experiment (normal control). Another group was injected daily by AlCl3 beginning from the 14th day and served as positive control while the remaining three groups were treated by pomegranate, red beetroot and their mixture juices from the first day till the end of the experiment and from the 14th day, they were injected by AlCl3 until the end of the experiment. Phenolic compounds, flavonoids, vitamin C and DPPH scavenging activity of pomegranate and red beetroot juices were estimated. The results revealed that the positive group exhibited low levels of growth parameters, hemoglobin, iron and high level of aluminum as compared to normal control, while the treated groups revealed significant improvements in these parameters. Concerning antioxidant parameters, the three treated groups showed significant increases in superoxide dismutase, glutathione and total protein and significant decreases in malondialdehyde and acetylcholine esterase in their serum and brains as compared to positive control. However, the β-amyloid level decreased while RNA and DNA contents increased significantly in brains of the treated rats in comparing with the positive control. The mixture juice exhibited the best protective effect among the three juices against aluminum toxicity, so it is important for those who suffering from aluminum toxicity.

A New Discovery of MicroRNA-455-3p in Alzheimer's Disease.

MicroRNA-455-3p (miR-455-3p) is identify as a member of broadly conserved miRNA family expressed in most of the phylum and species. In humans, miR-455 is present on the human chromosome 9 at locus 9q32 and encoded by the human COL27A1 gene (collagen type XXVII alpha 1 chain). The role of miR-455 has been implicated in various human diseases such as cartilage development, adipogenesis, preeclampsia, and cancers, e.g., colon cancer, prostate cancer, hepatocellular carcinoma, renal cancer, oral squamous cancer, skin cancer, and non-small cell lung cancer. Recently, our laboratory discovered the biomarker and therapeutic relevance of miR-455-3p in Alzheimer's disease (AD). Our global microarray analysis of serum samples from AD patients, mild cognitive individuals (MCI), and healthy subjects unveiled the high level of miR-455-3p in AD patients relative to MCI and healthy controls. Further, validation analysis using different kinds of AD samples such as serum, postmortem brains, AD fibroblasts, AD B-lymphocytes, AD cell lines, AD mouse models, and AD cerebrospinal fluid confirmed the biomarker potential of miR-455-3p. The mechanistic link of miR-455-3p in AD was determined via modulation of amyloid-β protein precursor (AβPP) and amyloid-β (Aβ) levels. Luciferase reporter assay confirmed AβPP as validated target of miR-455-3p. Our study on mouse neuroblastoma cells revealed the protective role of miR-455-3p against Aβ-induced toxicities. We also noticed that miR-455-3p enhances cell survival and lifespan extension. High level of miR-455-3p reduces Aβ toxicity, enhances mitochondrial biogenesis and synaptic activity, and maintains healthy mitochondrial dynamics. Based on these evidences, we cautiously conclude that miR-455-3p is a promising peripheral biomarker and therapeutic candidate for AD.

Cerebrospinal fluid and blood Aβ levels in Down syndrome patients with and without dementia: a meta-analysis study.

Abnormal β-amyloid (Aβ) levels were found in patients with Down syndrome (DS). However, Aβ levels in patients with DS and DS with dementia (DSD) vary considerably across studies. Therefore, we performed a systematic literature review and quantitatively summarized the clinical Aβ data on the cerebrospinal fluid (CSF) and blood of patients with DS and those with DSD using a meta-analytical technique. We performed a systematic search of the PubMed and Web of Science and identified 27 studies for inclusion in the meta-analysis. Random-effects meta-analysis indicated that the levels of blood Aβ1-40 and Aβ1-42 were significantly elevated in patients with DS compared with those in healthy control (HC) subjects. In contrast, there were no significant differences between patients with DS and those with DSD in the blood Aβ1-40 and Aβ1-42 levels. The CSF Aβ1-42 levels were significantly decreased in patients with DS compared to those in HC subjects. Further, CSF Aβ1-42 levels were significantly decreased in patients with DSD compared to those with DS, with a large effect size. Taken together, our results demonstrated that blood Aβ1-40 and Aβ1-42 levels were significantly increased in patients with DS while CSF Aβ1-42, but not Aβ1-40 levels were significantly decreased in patients with DS.

Low CSF β-amyloid levels predict early regional grey matter atrophy in multiple sclerosis

Background and purposeGrey matter (GM) atrophy is present from the earliest stages of multiple sclerosis (MS) and occurs largely in a nonrandom manner. However, the biological mechanisms underlying the progression of regional atrophy are still unclear. Aim of this study is to investigate whether amyloid pathology might be involved in determining the pattern of GM atrophy over time. MethodsForty-six subjects were recruited: 31 newly diagnosed relapsing-remitting (RR-) MS patients and 15 age- and sex-matched healthy controls (HC). Aβ levels were determined in CSF samples from all subjects. All participants underwent brain magnetic resonance imaging (MRI) at baseline, and 23 out of 31 patients at one year follow-up. T1-weighted scans were segmented using the Geodesic Information Flows software. Non-parametric statistical tests were used for between-group comparisons and multiple regression analyses. ResultsCSF Aβ concentration was the best predictor of global GM loss over time after age (β = 0.403; p = 0.024), in particular in the left precuneus (p = 0.045), in the left middle cingulate gyrus (p = 0.009), in the left precentral gyrus (p = 0.021) and in the right angular gyrus (p = 0.029). ConclusionsCSF Aβ levels seem to be crucial in MS early brain volume loss as GM atrophy manifests in regions particularly vulnerable to early Aβ deposition.

Proteinopathy and longitudinal changes in functional connectivity networks in Parkinson disease.

To evaluate resting-state functional connectivity as a potential prognostic biomarker of Parkinson disease (PD) progression. The study examined longitudinal changes in cortical resting-state functional connectivity networks in participants with PD compared to controls as well as in relation to baseline protein measures and longitudinal clinical progression. Individuals with PD without dementia (n = 64) and control participants (n = 27) completed longitudinal resting-state MRI scans and clinical assessments including full neuropsychological testing after overnight withdrawal of PD medications ("off"). A total of 55 participants with PD and 20 control participants also completed baseline β-amyloid PET scans and lumbar punctures for CSF protein levels of α-synuclein, β-amyloid, and tau. Longitudinal analyses were conducted with multilevel growth curve modeling, a type of mixed-effects model. Functional connectivity within the sensorimotor network and the interaction between the dorsal attention network with the frontoparietal control network decreased significantly over time in participants with PD compared to controls. Baseline CSF α-synuclein protein levels predicted decline in the sensorimotor network. The longitudinal decline in the dorsal attention-frontoparietal internetwork strength correlated with the decline in cognitive function. These results indicate that α-synuclein levels may influence longitudinal declines in motor-related functional connectivity networks. Further, the interaction between cortical association networks declines over time in PD prior to dementia onset and may serve as a prognostic marker for the development of dementia.

Pupillometry evaluation of melanopsin retinal ganglion cell function and sleep-wake activity in pre-symptomatic Alzheimer's disease.

Melanopsin-expressing retinal ganglion cells (mRGCs), intrinsically photosensitive RGCs, mediate the light-based pupil response and the light entrainment of the body's circadian rhythms through their connection to the pretectal nucleus and hypothalamus, respectively. Increased awareness of circadian rhythm dysfunction in neurological conditions including Alzheimer's disease (AD), has led to a wave of research focusing on the role of mRGCs in these diseases. Postmortem retinal analyses in AD patients demonstrated a significant loss of mRGCs, and in vivo measurements of mRGC function with chromatic pupillometry may be a potential biomarker for early diagnosis and progression of AD. We performed a prospective case-control study in 20 cognitively healthy study participants: 10 individuals with pre-symptomatic AD pathology (pre-AD), identified by the presence of abnormal levels of amyloid β42 and total Tau proteins in the cerebrospinal fluid, and 10 age-matched controls with normal CSF amyloid β42 and Tau levels. To evaluate mRGC function, we used a standardized protocol of chromatic pupillometry on a Ganzfeld system using red (640 nm) and blue (450 nm) light stimuli and measured the pupillary light response (PLR). Non-invasive wrist actigraphy and standardized sleep questionnaires were also completed to evaluate rest-activity circadian rhythm. Our results did not demonstrate a significant difference of the PLR between pre-AD and controls but showed a variability of the PLR in the pre-AD group compared with controls on chromatic pupillometry. Wrist actigraphy showed variable sleep-wake patterns and irregular circadian rhythms in the pre-AD group compared with controls. The variability seen in measurements of mRGC function and sleep-wake cycle in the pre-AD group suggests that mRGC dysfunction occurs in the pre-symptomatic AD stages, preceding cognitive decline. Future longitudinal studies following progression of these participants can help in elucidating the relationship between mRGCs and circadian rhythm dysfunction in AD.

Ablation of reactive astrocytes exacerbates disease pathology in a model of Alzheimer's disease.

The role of astrocytes in the progression of Alzheimer's disease (AD) remains poorly understood. We assessed the consequences of ablating astrocytic proliferation in 9 months old double transgenic APP23/GFAP‐TK mice. Treatment of these mice with the antiviral agent ganciclovir conditionally ablates proliferating reactive astrocytes. The loss of proliferating astrocytes resulted in significantly increased levels of monomeric amyloid‐β (Aβ) in brain homogenates, associated with reduced enzymatic degradation and clearance mechanisms. In addition, our data revealed exacerbated memory deficits in mice lacking proliferating astrocytes concomitant with decreased levels of synaptic markers and higher expression of pro‐inflammatory cytokines. Our data suggest that loss of reactive astrocytes in AD aggravates amyloid pathology and memory loss, possibly via disruption of amyloid clearance and enhanced neuroinflammation.

Composite Scores of Plasma Tau and β-Amyloids Correlate with Dementia in Down Syndrome.

Dementia frequently occurs in Down syndrome (DS) patients, and early intervention is important in its management. We have previously demonstrated a positive correlation of plasma β-amyloid Aβ42 levels and negative correlations of Aβ40 and tau levels with dementia in DS. In this study, we examined more cases and constructed composite scores with both tau and amyloids to correlate with dementia in DS. Plasma Aβ42, Aβ40, and tau proteins were measured by an immunomagnetic reduction assay in DS patients. Data were randomly and repeatedly split into training and validating sets, and logistic regression was applied to calculate the area under the curve (AUC) for each biomarker. A total of 73 DS patients (among them, 23 had neurodegeneration) and 77 controls were recruited. In DS patients without dementia, plasma Aβ40 and tau levels were highly elevated, but Aβ42 levels were lower than those of the healthy controls. DS patients with dementia, compared with DS patients with no dementia, had a large decline in Aβ40 and tau but a rise in Aβ42. For biomarker scores correlating with dementia, Aβ40 revealed an AUC of 0.912; the composite score of Aβ40 × tau revealed an AUC of 0.953; and a combined composite score of 0.1 for Aβ40 × Tau +0.9 Tau × Aβ40/Aβ42 achieved the highest AUC of 0.965. Therefore, composite biomarker scores including both plasma tau and β-amyloid levels correlate with dementia in DS better than using individual biomarker scores. The pattern of tau decline and Aβ42 rise in DS patients with dementia are also different from previous findings in Alzheimer's disease.

Association of Longitudinal β-Amyloid Accumulation Determined by Positron Emission Tomography With Clinical and Cognitive Decline in Adults With Probable Lewy Body Dementia

In patients with probable dementia with Lewy bodies (DLB), overlapping Alzheimer disease pathology is frequent and is associated with faster decline and shorter survival. More than half of patients with DLB have elevated β-amyloid levels on carbon-11 labeled Pittsburgh compound B (PiB) positron emission tomography, but the trajectory of longitudinal β-amyloid accumulation and its associations with clinical and cognitive decline in DLB are not known. To determine the trajectory of β-amyloid accumulation in patients with probable DLB and to investigate the associations of β-amyloid accumulation with measures of clinical and cognitive decline over time in DLB. This cohort study included 35 consecutive patients with probable DLB from the Mayo Clinic Alzheimer Disease Research Center and matched them by age, sex, and apolipoprotein e4 status with 140 cognitively unimpaired participants from the population-based Mayo Clinic Study of Aging. Participants were observed from April 2010 to September 2017. Data analysis was conducted from January 2018 to January 2019. Baseline and follow-up PiB positron emission tomography and comprehensive clinical evaluations. Rate of change in PiB standardized uptake value ratios (SUVRs) by PiB SUVR and time in years; the associations between baseline PiB SUVR, change in PiB SUVR, and change in several measures of clinical and cognitive decline. A total of 175 participants were evaluated (35 [20.0%] with probable DLB; mean [SD] age, 69.6 [7.3] years; 16 [45.7%] apolipoprotein e4 carriers; 31 [88.6%] men; and 140 [80.0%] cognitively unimpaired adults; mean [SD] age, 69.7 [7.2] years; 64 [45.7%] apolipoprotein e4 carriers; 124 [88.6%] men). In both groups, the rates of change in PiB SUVR showed an initial acceleration at lower baseline PiB SUVR followed by a deceleration at higher baseline PiB SUVR, thus forming an inverted-U shape. The trajectories of the rates of change in PiB SUVR did not differ between participants with probable DLB and cognitively unimpaired participants in terms of shape (P = .59) or vertical shift (coefficient [SE] 0.007 [0.006]; P = .22). The integral association of cumulative PiB SUVR with time in years showed a sigmoid-shaped functional form in both groups. In participants with probable DLB, higher baseline PiB SUVR and change in PiB SUVR were associated with more rapid clinical decline, as measured by the Clinical Dementia Rating, sum of boxes (baseline PiB SUVR: regression coefficient [SE], 1.90 [0.63]; P = .005; R2 = 0.215; change in PiB SUVR, regression coefficient [SE], 16.17 [7.47]; P = .04; R2 = 0.124) and the Auditory Verbal Learning Test, delayed recall (baseline PiB SUVR, regression coefficient [SE], -2.09 [0.95]; P = .04; R2 = 0.182; change in PiB SUVR, regression coefficient [SE], -25.05 [10.04]; P = .02; R2 = 0.221). In this study, the rate of change in PiB SUVR among participants with probable DLB increased, peaked, and then decreased, which was similar to the trajectory in cognitively unimpaired participants and the Alzheimer disease dementia continuum. Higher baseline PiB SUVR and change in PiB SUVR were associated with more rapid clinical and cognitive decline over time. Measuring the change in PiB SUVR has implications for designing anti-β-amyloid randomized clinical trials for individuals with probable DLB.