Dementia of the Alzheimer type

Key neuropsychiatric symptoms in common dementias: prevalence and implications for caregivers, clinicians, and health systems

The purpose of this study was to compare neuropsychiatric symptoms (NPS) among people with common dementias and equip interdisciplinary clinicians and health services planners with large-sample data necessary to plan care for patients and families. We analyzed selected variables from baseline assessments of older adults with dementia of one or more etiologies (N = 3,768) from the National Alzheimer's Coordinating Center data repository. Dementias included Alzheimer's disease (AD), Lewy body dementia (DLB), behavioral variant frontotemporal dementia (bvFTD), and vascular dementia (VaD). We compared the prevalence of four NPS clusters (agitation/aggression, depression/dysphoria, anxiety, irritability/lability) across dementia etiologies and stages using logistic regression and AD as the reference group. NPS profiles differed significantly across dementia types and stages. Compared with primary AD, DLB was associated with greater odds of depression/dysphoria (OR = 1.68, 95% confidence interval [CI] 1.28, 2.20) and anxiety (OR = 1.80, 95% CI 1.37, 2.36), with similar findings when DLB was diagnosed in combination with AD (depression/dysphoria: OR = 1.79, 95% CI 1.11, 2.89; anxiety: OR = 1.88, 95% CI 1.17, 3.02). Primary bvFTD was associated with greater odds of agitation/aggression (OR = 1.59, 95% CI 1.17, 2.18). The prevalence of anxiety and irritability/lability was highest in moderate stages of dementia, and agitation/aggression was most prevalent in severe dementia. Differential diagnosis and staging of dementias and inclusion of single and overlapping etiologies is important for planning and implementing appropriate strategies to anticipate, report, and intervene with key NPS that complicate home and health care.

Confirmatory factor analysis of the ADNI Neuropsychological Battery

The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a large multi-center study designed to develop optimized methods for acquiring longitudinal neuroimaging, cognitive, and biomarker measures of AD progression in a large cohort of patients with Alzheimer's disease (AD), patients with Mild Cognitive Impairment, and healthy controls. Detailed neuropsychological testing was conducted on all participants. We examined the factor structure of the ADNI Neuropsychological Battery across older adults with differing levels of clinical AD severity based on the Clinical Dementia Rating Scale (CDR). Confirmatory factor analysis (CFA) of 23 variables from 10 neuropsychological tests resulted in five factors (memory, language, visuospatial functioning, attention, and executive function/processing speed) that were invariant across levels of cognitive impairment. Thus, these five factors can be used as indicators of cognitive function in older adults who are participants in ADNI.

Education, leisure activities and cognitive and functional ability of Alzheimer's disease patients: A follow-up study

Education and participation in leisure activities appear to be highly relevant variables in Alzheimer's disease (AD) and usually form the basis of the Cognitive Reserve construct.

Facilitators and barriers to safe emergency department transitions for community dwelling older people with dementia and their caregivers: a social ecological study

BACKGROUND

Internationally, older adults visit the ED at a rate higher than other age groups. Little attention has been given to ED care for older people with dementia, although concern for such care is growing with the increasing number of individuals worldwide affected by this significant disabling problem. It is critical to understand ED transitional processes and consequences because the complexity of dementia care poses multiple challenges to optimizing safety, effectiveness and quality of care during admission, assessment, and treatment in this setting.

METHOD

Using an interpretive, descriptive exploratory design with three iterative, interrelated phases, we conducted interviews, created a photographic narrative journal (PNJ), and finally held photo elicitation focus groups to identify factors that facilitate or impede safe transitional care for community dwelling older adults with dementia in two Canadian emergency departments, and to identify practice solutions for nurses. We purposively sampled to recruit ten older adult-family caregiver dyads, ten ED RNs, and four Nurse Practitioners. Data were analyzed using constant comparative analysis.

RESULTS

Four interconnected reinforcing consequences emerged from our analysis: being under-triaged; waiting and worrying about what was wrong; time pressure with lack of attention to basic needs; and, relationships and interactions leading to feeling ignored, forgotten and unimportant. Together these consequences stem from a triage system that does not recognize atypical presentation of disease and illness. This potentiated a cascade of vulnerability in older people with dementia and their caregivers. Nurses experienced time pressure challenges that impeded their ability to be responsive to basic care needs.

CONCLUSIONS

In an aging population where dementia is becoming more prevalent, the unit of care in the ED must include both the older person and their family caregiver. Negative reinforcing consequences can be interrupted when nurses communicate and engage more regularly with the older adult-caregiver dyad to build trust. System changes are also needed to support the ability of nurses to carry out best practices.

Sexual dimorphism in healthy aging and mild cognitive impairment: a DTI study

Previous PET and MRI studies have indicated that the degree to which pathology translates into clinical symptoms is strongly dependent on sex with women more likely to express pathology as a diagnosis of AD, whereas men are more resistant to clinical symptoms in the face of the same degree of pathology. Here we use DTI to investigate the difference between male and female white matter tracts in healthy older participants (24 women, 16 men) and participants with mild cognitive impairment (21 women, 12 men). Differences between control and MCI participants were found in fractional anisotropy (FA), radial diffusion (DR), axial diffusion (DA) and mean diffusion (MD). A significant main effect of sex was also reported for FA, MD and DR indices, with male control and male MCI participants having significantly more microstructural damage than their female counterparts. There was no sex by diagnosis interaction. Male MCIs also had significantly less normalised grey matter (GM) volume than female MCIs. However, in terms of absolute brain volume, male controls had significantly more brain volume than female controls. Normalised GM and WM volumes were found to decrease significantly with age with no age by sex interaction. Overall, these data suggest that the same degree of cognitive impairment is associated with greater structural damage in men compared with women.

Development of a magnetic immunosorbent for on-chip preconcentration of amyloid β isoforms: Representatives of Alzheimer's disease biomarkers

Determination of amyloid β (Aβ) isoforms and in particular the proportion of the Aβ 1-42 isoform in cerebrospinal fluid (CSF) of patients suspected of Alzheimer's disease might help in early diagnosis and treatment of that illness. Due to the low concentration of Aβ peptides in biological fluids, a preconcentration step prior to the detection step is often necessary. This study utilized on-chip immunoprecipitation, known as micro-immunoprecipitation (μIP). The technique uses an immunosorbent (IS) consisting of magnetic beads coated with specific anti-Aβ antibodies organized into an affinity microcolumn by a magnetic field. Our goal was to thoroughly describe the critical steps in developing the IS, such as selecting the proper beads and anti-Aβ antibodies, as well as optimizing the immobilization technique and μIP protocol. The latter includes selecting optimal elution conditions. Furthermore, we demonstrate the efficiency of anti-Aβ IS for μIP and specific capture of 5 Aβ peptides under optimized conditions using various subsequent analytical methods, including matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), capillary electrophoresis, microchip electrophoresis, and immunoblotting. Synthetic Aβ peptides samples prepared in buffer and spiked in human CSF were analyzed. Finally, on-chip immunoprecipitation of Aβ peptides in human CSF sample was performed.

Microglial scavenger receptors and their roles in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is increasing in prevalence with the aging population. Deposition of amyloid-β (Aβ) in the brain of AD patients is a hallmark of the disease and is associated with increased microglial numbers and activation state. The interaction of microglia with Aβ appears to play a dichotomous role in AD pathogenesis. On one hand, microglia can phagocytose and clear Aβ, but binding of microglia to Aβ also increases their ability to produce inflammatory cytokines, chemokines, and neurotoxic reactive oxygen species (ROS). Scavenger receptors, a group of evolutionally conserved proteins expressed on the surface of microglia act as receptors for Aβ. Of particular interest are SCARA-1 (scavenger receptor A-1), CD36, and RAGE (receptor for advanced glycation end products). SCARA-1 appears to be involved in the clearance of Aβ, while CD36 and RAGE are involved in activation of microglia by Aβ. In this review, we discuss the roles of various scavenger receptors in the interaction of microglia with Aβ and propose that these receptors play complementary, nonredundant functions in the development of AD pathology. We also discuss potential therapeutic applications for these receptors in AD.

Analysis of spontaneous MEG activity in mild cognitive impairment and Alzheimer's disease using spectral entropies and statistical complexity measures

Alzheimer's disease (AD) is the most common cause of dementia. Over the last few years, a considerable effort has been devoted to exploring new biomarkers. Nevertheless, a better understanding of brain dynamics is still required to optimize therapeutic strategies. In this regard, the characterization of mild cognitive impairment (MCI) is crucial, due to the high conversion rate from MCI to AD. However, only a few studies have focused on the analysis of magnetoencephalographic (MEG) rhythms to characterize AD and MCI. In this study, we assess the ability of several parameters derived from information theory to describe spontaneous MEG activity from 36 AD patients, 18 MCI subjects and 26 controls. Three entropies (Shannon, Tsallis and Rényi entropies), one disequilibrium measure (based on Euclidean distance ED) and three statistical complexities (based on Lopez Ruiz-Mancini-Calbet complexity LMC) were used to estimate the irregularity and statistical complexity of MEG activity. Statistically significant differences between AD patients and controls were obtained with all parameters (p < 0.01). In addition, statistically significant differences between MCI subjects and controls were achieved by ED and LMC (p < 0.05). In order to assess the diagnostic ability of the parameters, a linear discriminant analysis with a leave-one-out cross-validation procedure was applied. The accuracies reached 83.9% and 65.9% to discriminate AD and MCI subjects from controls, respectively. Our findings suggest that MCI subjects exhibit an intermediate pattern of abnormalities between normal aging and AD. Furthermore, the proposed parameters provide a new description of brain dynamics in AD and MCI.

Towards the prevention of potential aluminum toxic effects and an effective treatment for Alzheimer's disease

In 1991, treatment with low dose intramuscular desferrioxamine (DFO), a trivalent chelator that can remove excessive iron and/or aluminum from the body, was reported to slow the progression of Alzheimer's disease (AD) by a factor of two. Twenty years later this promising trial has not been followed up and why this treatment worked still is not clear. In this critical interdisciplinary review, we provide an overview of the complexities of AD and involvement of metal ions, and revisit the neglected DFO trial. We discuss research done by us and others that is helping to explain involvement of metal ion catalyzed production of reactive oxygen species in the pathogenesis of AD, and emerging strategies for inhibition of metal-ion toxicity. Highlighted are insights to be considered in the quests to prevent potentially toxic effects of aluminum toxicity and prevention and intervention in AD.

Cognitive impairment in humanized APP×PS1 mice is linked to Aβ(1-42) and NOX activation

Cognitive impairment in Alzheimer's disease (AD) is strongly associated with both extensive deposition of amyloid β peptides and oxidative stress, but the exact role of these indices in the development of dementia is not clear. This study was designed to determine the relationship between cognitive impairment, activation of the free radical producing enzyme NADPH oxidase (NOX), and progressive changes in Aβ deposition and solubility in humanized APP×PS1 knock-in mice of increasing age. Data show that cognitive performance and expression of key synaptic proteins were progressively decreased in aging APP×PS1 mice. Likewise, NOX activity and expression of the specific NOX subunit NOX4 were significantly increased in APP×PS1 mice in an age-dependent manner, and NOX activity and cognitive impairment shared a significant linear relationship. Data further show that age-dependent increases in Aβ(1-42) had a significant linear relationship with both NOX activity and cognitive performance in APP×PS1 knock-in mice. Collectively, these data show that NOX expression and activity are significantly upregulated with age in this humanized model of Aβ pathogenesis, and suggest that NOX-associated redox pathways are intimately linked to both the loss of cognitive function and the deposition of Aβ(1-42).

Deposition of hyperphosphorylated tau in cerebellum of PS1 E280A Alzheimer's disease

Early-onset familial Alzheimer's disease (AD) caused by presenilin-1 mutation E280A (PS1-E280A) presents wide clinical and neuropathological variabilities. We characterized clinically and neuropathologically PS1-E280A focusing in cerebellar involvement and compared it with early-onset sporadic Alzheimer's disease (EOSAD). Twelve E280A brains and 12 matched EOSAD brains were analyzed for beta-amyloid and hyperphosphorylated tau (pTau) morphology, beta-amyloid subspecies 1-40, 1-42 levels, pTau levels, and expression of stress kinases in frontal cortex and cerebellum. The data were correlated to clinical and genetic findings. We observed higher beta-amyloid load, beta-amyloid 1-42 and pTau concentrations in frontal cortex of PS1-E280A compared with EOSAD. High beta-amyloid load was found in the cerebellum of PS1-E280A and EOSAD patients. In PS1-E280A, beta-amyloid localized to the molecular and Purkinje cell layers, whereas EOSAD showed them in Purkinje and granular cell layers. Surprisingly, 11 out of 12 PS1-E280A patients showed deposition of pTau in the cerebellum. Also, seven out of 12 PS1-E280A patients presented cerebellar ataxia. We conclude that deposition of beta-amyloid in the cerebellum is prominent in early-onset AD irrespective of genetic or sporadic origin. The presence of pTau in cerebellum in PS1-E280A underscores the relevance of cerebellar involvement in AD and might be correlated to clinical phenotype.

Caregiving, residence, race, and depressive symptoms

The objective of this study is to evaluate the psychological responses to caregiving between black and white dementia caregivers measured by self-reports of depressive symptoms evaluating the impact of sub-components of the Center for Epidemiologic Studies Depression Scale (CES-D) and residential arrangements of the caregiving dyad. The method included 87 intergenerational family caregivers enrolled in the Duke Caregiver Study (50 white and 37 black). Total CES-D and the four sub-components were modeled as dependent measures in separate linear regressions. Three models were examined. The first model tested race, living arrangements, and their interaction. The second model adjusted for age, gender, education, income, health status, cultural justification for caregiving, crime concerns, systolic blood pressure, diastolic blood pressure, and glycosylated hemoglobin. A third model added adjustment for caregiver burden. The results showed that there was a significant race by residence interaction for CES-D, somatic symptoms and depressive affect such that when the dyads are living apart-with the care recipient in their own home or in an institutional setting-whites reported more depressive symptoms than blacks. When the dyads lived together, this was reversed, and blacks reported higher depressive symptoms than whites. To conclude, all the parameters such as race, living arrangements, and the components of depression need to be taken into account to understand the impact of caregiving on the emotional health of caregivers.

Conceptual evolution in Alzheimer's disease: implications for understanding the clinical phenotype of progressive neurodegenerative disease

Over the past several decades, our understanding of Alzheimer's disease (AD) has seen an evolution from the dichotomous concept of normal versus AD in the dementia state to a more accurate and complete appreciation of AD as a progressive disorder with clinical, biological, and pathological features occurring along a continuum from normal to end-stage disease. Integrating our understanding of the relationships and interplay between the clinical, biological, and pathological features of AD may allow the identification of AD at even preclinical, completely asymptomatic stages of the disease. This review attempts to summarize the clinical stages of AD in terms of epidemiology, historical evolution of disease stage diagnoses, cognitive/neuropsychologic features, psychiatric/behavioral manifestations, and functional decline in the context of our developing understanding of the biological processes responsible for the pathogenesis of AD described in detail in the accompanying articles.

Neurodegenerative diseases: exercising toward neurogenesis and neuroregeneration

Currently, there is still no effective therapy for neurodegenerative diseases (NDD) such as Alzheimer's disease (AD) and Parkinson's disease (PD) despite intensive research and on-going clinical trials. Collectively, these diseases account for the bulk of health care burden associated with age-related neurodegenerative disorders. There is therefore an urgent need to further research into the molecular pathogenesis, histological differentiation, and clinical management of NDD. Importantly, there is also an urgency to understand the similarities and differences between these two diseases so as to identify the common or different upstream and downstream signaling pathways. In this review, the role iron play in NDD will be highlighted, as iron is key to a common underlying pathway in the production of oxidative stress. There is increasing evidence to suggest that oxidative stress predisposed cells to undergo damage to DNA, protein and lipid, and as such a common factor involved in the pathogenesis of AD and PD. The challenge then is to minimize elevated and uncontrolled oxidative stress levels while not affecting basal iron metabolism, as iron plays vital roles in sustaining cellular function. However, overload of iron results in increased oxidative stress due to the Fenton reaction. We discuss evidence to suggest that sustained exercise and diet restriction may be ways to slow the rate of neurodegeneration, by perhaps promoting neurogenesis or antioxidant-related pathways. It is also our intention to cover NDD in a broad sense, in the context of basic and clinical sciences to cater for both clinician's and the scientist's needs, and to highlight current research investigating exercise as a therapeutic or preventive measure.

NOX activity is increased in mild cognitive impairment

This study was undertaken to investigate the profile of NADPH oxidase (NOX) in the clinical progression of Alzheimer's disease (AD). Specifically, NOX activity and expression of the regulatory subunit p47phox and the catalytic subunit gp91phox was evaluated in affected (superior and middle temporal gyri) and unaffected (cerebellum) brain regions from a longitudinally followed group of patients. This group included both control and late-stage AD subjects, and also subjects with preclinical AD and with amnestic mild cognitive impairment (MCI) to evaluate the profile of NOX in the earliest stages of dementia. Data show significant elevations in NOX activity and expression in the temporal gyri of MCI patients as compared with controls, but not in preclinical or late-stage AD samples, and not in the cerebellum. Immunohistochemical evaluations of NOX expression indicate that whereas microglia express high levels of gp91phox, moderate levels of gp91phox also are expressed in neurons. Finally, in vitro experiments showed that NOX inhibition blunted the ability of oligomeric amyloid beta peptides to injure cultured neurons. Collectively, these data show that NOX expression and activity are upregulated specifically in a vulnerable brain region of MCI patients, and suggest that increases in NOX-associated redox pathways in neurons might participate in the early pathogenesis of AD.

Cost-of-illness studies of dementia: a systematic review focusing on stage dependency of costs

OBJECTIVE

To review cost-of-illness (COI) studies of dementia from Europe and North America which report costs per patient by disease stage.

METHOD

A systematic literature search was performed in electronic databases. Studies were classified according to important determinants of costs. Results were converted into year 2006 USD-PPP, and summarized as costs for formal and informal care in mild, moderate and severe dementia.

RESULTS

28 studies were evaluated. They used a wide range of methods. Costs more than doubled from mild to severe dementia. Patterns and size of estimated costs depended primarily on study objectives (estimation of total costs-net costs), living arrangements of patients (community-dwelling-institutionalized) and inclusion of informal care.

CONCLUSION

This review is the first to have focused on costs in different stages of dementia. The stage is an important determinant of costs. However, characteristics of individual studies need to be considered, when making use of their results.

Antipsychotic use and the risk of hip fracture among older adults afflicted with dementia

OBJECTIVE

To quantify the association between use of antipsychotic (AP) medications and the risk of hip fracture among older adults residing in a nursing home (NH) and afflicted with dementia.

DESIGN

Nested case-control study.

SETTING

NHs in California, Florida, Illinois, New York, and Ohio in 2001-2002 (N=586).

PARTICIPANTS

The source population consisted of long-stay Medicaid-eligible residents living in NHs with at least 20 beds, who were 65 years of age or older and had a diagnosis of dementia but were not receiving hospice care, were not comatose, bedfast, paralyzed, or in a wheelchair, and had no record of a previous hip fracture (N=69,027). There were 764 cases of hip fracture identified; up to 5 controls, matched to cases on NH and quarter of Minimum Data Set (MDS) assessment, were randomly selected from the source population (N=3582).

MEASUREMENTS

Cases of hip fracture were identified and medication use was ascertained from Medicaid claims data. Resident-level characteristics, including dementia severity, were obtained from resident MDS assessments.

RESULTS

Current use of APs conveyed a small increased risk of hip fracture (adjusted odds ratio=1.26; 95% confidence interval: 1.05 -1.52). When analyzed separately, users of conventional antipsychotics had a slightly higher risk of hip fracture than residents on atypical agents. Long-term use of APs conferred a greater risk of hip fracture than short-term use.

CONCLUSION

APs appear to increase the risk of hip fracture among older adults with dementia residing in an NH. Hip fractures may be a contributory mechanism to the increased risk mortality observed among AP users.

Neurobehavioral differences between Alzheimer's disease and frontotemporal dementia: a meta-analysis

The differential diagnosis of Alzheimer's disease (AD) and frontotemporal dementia (FTD) remains a difficult clinical issue. A recent meta-analysis by Hutchinson and Mathias (2007) found that many cognitive tests do not adequately differentiate between these types of dementia. However, their study did not examine the ability of neurobehavioral scales to distinguish between AD and FTD. The data from 33 studies, published between January 1994 and December 2008, examining the neurobehavioral symptoms of persons with AD (N = 2,305) and FTD (N = 971) were therefore analyzed. Weighted Cohen's d effect sizes, percentage overlap statistics, confidence intervals, and fail-safe Ns were calculated for each scale. The most discriminating measures were the Schedules for Clinical Assessment in Neuropsychiatry and the Scale for Emotional Blunting. The Middelheim Frontality Score and the Frontal Behavior Inventory also had excellent discriminative ability, surpassing the cognitive tests examined previously. Numerous other scales additionally showed large and significant differences between the AD and FTD groups, highlighting the importance of assessing neurobehavioral symptoms in this context. While these latter measures may be useful in providing a clinical profile of patients with dementia, greater overlap in the scores of patients with AD and FTD limits their usefulness in the context of differential diagnosis.

Private costs almost equal health care costs when intervening in mild Alzheimer's: a cohort study alongside the DAISY trial

Background

Alzheimer's disease is the leading cause of dementia and affects about 25 million people worldwide. Recent studies have evaluated the effect of early interventions for dementia, but few studies have considered private time and transportation costs associated with the intervention. This study assessed the total economic costs associated with a multifaceted intervention for mild Alzheimer's disease, including an estimate of the ratio of public to private costs.

Methods

The study sample comprised 163 dyads of patients and caregivers who received a multifaceted intervention of counselling sessions, courses and informational packages. The typical duration of the intervention was 7 months. A micro-costing approach was applied using prospectively collected data on resource utilisation that included estimates of participant time and transportation. Precision estimates were calculated using a bootstrapping technique and structural uncertainty was assessed with sensitivity analysis.

Results

The direct intervention cost was estimated at EUR 1,070 (95% CI 1,029;1,109). The total cost (including private costs) was estimated at EUR 2,020 (95% CI 1,929;2,106) i.e. the ratio of private to public costs was almost 1:1.

Conclusion

Intervention for mild Alzheimer's disease can be undertaken at a relatively low cost to public funds. However, policy planners should pay attention to the significant private costs associated with an intervention, which may ultimately pose a threat to equity in access to health care.

Trial registration

Current Controlled Trials ISRCTN74848736.

Up-regulation of the type 3 ryanodine receptor is neuroprotective in the TgCRND8 mouse model of Alzheimer's disease

The cellular pathology of Alzheimer's disease is progressive and protracted leading eventually to considerable neuronal death. The underlying mechanisms of the pathology are complex but changes in the control of intracellular Ca2+ are believed to contribute to the demise of neurons. In this study, we investigated the functional consequences of an increase in the expression of the type 3 isoform of the ryanodine receptor (RyR3). We found that although cortical neurons from TgCRND8 mice secreted significantly more amyloid beta protein and showed significantly increased RyR3 expression, they were no more sensitive to cell stress than non-transgenic neurons. Furthermore, despite increased intracellular Ca2+ release in response to ryanodine, we found that basal Ca2+, K+-evoked Ca2+ responses, and capacitative Ca2+ entry were no different in TgCRND8 neurons compared with non-transgenic neurons. Therefore, as RyR3 up-regulation did not affect neuronal health or global Ca2+ homeostasis, we investigated the effect of reducing RyR3 expression using small interfering RNA. Surprisingly, a reduction of RyR3 expression in TgCRND8, but not in non-transgenic, neurons increased neuronal death. These data reveal a new role for RyR3 and indicate a novel potential therapeutic target to delay or prevent the progression of Alzheimer's disease.

Gender- and age-dependent gamma-secretase activity in mouse brain and its implication in sporadic Alzheimer disease

Alzheimer disease (AD) is an age-related disorder. Aging and female gender are two important risk factors associated with sporadic AD. However, the mechanism by which aging and gender contribute to the pathogenesis of sporadic AD is unclear. It is well known that genetic mutations in γ-secretase result in rare forms of early onset AD due to the aberrant production of Aβ42 peptides, which are the major constituents of senile plaques. However, the effect of age and gender on γ-secretase has not been fully investigated. Here, using normal wild-type mice, we show mouse brain γ-secretase exhibits gender- and age-dependent activity. Both male and female mice exhibit increased Aβ42∶Aβ40 ratios in aged brain, which mimics the effect of familial mutations of Presenilin-1, Presenlin-2, and the amyloid precursor protein on Aβ production. Additionally, female mice exhibit much higher γ-secretase activity in aged brain compared to male mice. Furthermore, both male and female mice exhibit a steady decline in Notch1 γ-secretase activity with aging. Using a small molecule affinity probe we demonstrate that male mice have less active γ-secretase complexes than female mice, which may account for the gender-associated differences in activity in aged brain. These findings demonstrate that aging can affect γ-secretase activity and specificity, suggesting a role for γ-secretase in sporadic AD. Furthermore, the increased APP γ-secretase activity seen in aged females may contribute to the increased incidence of sporadic AD in women and the aggressive Aβ plaque pathology seen in female mouse models of AD. In addition, deceased Notch γ-secretase activity may also contribute to neurodegeneration. Therefore, this study implicates altered γ-secretase activity and specificity as a possible mechanism of sporadic AD during aging.

Alzheimer's disease is type 3 diabetes-evidence reviewed

Alzheimer's disease (AD) has characteristic histopathological, molecular, and biochemical abnormalities, including cell loss; abundant neurofibrillary tangles; dystrophic neurites; amyloid precursor protein, amyloid-beta (APP-Abeta) deposits; increased activation of prodeath genes and signaling pathways; impaired energy metabolism; mitochondrial dysfunction; chronic oxidative stress; and DNA damage. Gaining a better understanding of AD pathogenesis will require a framework that mechanistically interlinks all these phenomena. Currently, there is a rapid growth in the literature pointing toward insulin deficiency and insulin resistance as mediators of AD-type neurodegeneration, but this surge of new information is riddled with conflicting and unresolved concepts regarding the potential contributions of type 2 diabetes mellitus (T2DM), metabolic syndrome, and obesity to AD pathogenesis. Herein, we review the evidence that (1) T2DM causes brain insulin resistance, oxidative stress, and cognitive impairment, but its aggregate effects fall far short of mimicking AD; (2) extensive disturbances in brain insulin and insulin-like growth factor (IGF) signaling mechanisms represent early and progressive abnormalities and could account for the majority of molecular, biochemical, and histopathological lesions in AD; (3) experimental brain diabetes produced by intracerebral administration of streptozotocin shares many features with AD, including cognitive impairment and disturbances in acetylcholine homeostasis; and (4) experimental brain diabetes is treatable with insulin sensitizer agents, i.e., drugs currently used to treat T2DM. We conclude that the term "type 3 diabetes" accurately reflects the fact that AD represents a form of diabetes that selectively involves the brain and has molecular and biochemical features that overlap with both type 1 diabetes mellitus and T2DM.

Mechanisms of microglia accumulation in Alzheimer's disease: therapeutic implications

In Alzheimer's disease (AD), and other conditions affecting integrity of the blood-brain barrier, microglia can originate in the bone marrow, migrate into the blood and enter the brain in a chemokine-dependent manner. CCR2, a chemokine receptor that controls mononuclear phagocyte infiltration into the brain in multiple sclerosis, bacterial meningitis and neuropathic pain, also regulates microglia accumulation in mouse models of AD. CCR2 deficiency leads to lower microglia accumulation and higher brain beta-amyloid (Abeta) levels, indicating that early microglial accumulation promotes Abeta clearance. In support of this protective role, enhancing microglia accumulation delays progression of AD. AD mice that constitutively express interleukin-1 in the brain, or that are deficient in peripheral mononuclear phagocyte transforming growth factor-beta signaling, have increased microglia accumulation around beta-amyloid plaques and reduced AD-like pathology. Regulating microglia recruitment into the brain is a novel therapeutic strategy to delay or stop progression of AD. Here, we review the role of microglia in AD and the mechanisms of their accumulation and discuss implications for AD therapy.