Vascular risk factors and Alzheimer's disease

Coronary artery disease is associated with cognitive decline independent of changes on magnetic resonance imaging in cognitively normal elderly adults

OBJECTIVES

To examine in cognitively normal elderly adults whether vascular factors predict cognitive decline and whether these associations are mediated by magnetic resonance imaging (MRI) measures of subclinical vascular brain injury.

DESIGN

Prospective multisite longitudinal study of subcortical ischemic vascular diseases.

SETTING

Memory and aging centers in California.

PARTICIPANTS

Seventy-four participants who were cognitively normal at entry and underwent at least two neuropsychological evaluations and two MRI examinations over an average follow-up of 6.9 years.

MEASUREMENTS

Item response theory was used to create composite scores of global, verbal memory, and executive functioning. Volumetric MRI measures included white matter hyperintensities (WMHs), silent brain infarcts (SBIs), hippocampus, and cortical gray matter (CGM). Linear mixed-effects models were used to examine the associations between vascular factors, MRI measures, and cognitive scores.

RESULTS

History of coronary artery disease (CAD) was associated with greater declines in global cognition, verbal memory, and executive function. The CAD associations remained after controlling for changes in WMHs, SBIs, and hippocampal and CGM volumes.

CONCLUSION

History of CAD may be a surrogate marker for clinically significant atherosclerosis, which also affects the brain. Structural MRI measures of WMHs and SBIs do not fully capture the potential adverse effects of atherosclerosis on the brain. Future longitudinal studies of cognition should incorporate direct measures of atherosclerosis in cerebral arteries, as well as more sensitive neuroimaging measures.

Arterial hypertension, cerebrovascular diseases and dementia

Arterial hypertension (AH) is the most relevant risk factor for acute cerebrovascular disease in general. However, the prevalence of AH is not the same for the different stroke subtypes and is particularly high in lacunar infarcts and atherothrombotic stroke, low in infarcts of unusual cause and undetermined origin, and intermediate in cardioembolic stroke. This risk factor has also been related to vascular dementia and Alzheimer’s disease and their pathological manifestations (senile plaques, neurofibrillary tangles, hippocampal atrophy). The mechanisms linking AH to Alzheimer’s disease remain to be elucidated but some recent studies showed that white matter lesions seen on cerebral magnetic resonance imaging appear to be a good marker of this association. Hypertension-associated pathological changes in the brain and its vasculature include vascular remodelling and impaired cerebral autoregulation like hypoperfusion, ischemia and hypoxia, which may initiate the pathological process of Alzheimer’s disease and the expression of dementia. Therefore, prompt diagnosis and adequate control of hypertension and different vascular risk factors are the rational basis for a more effective strategy in the secondary prevention of cerebrovascular disease and dementia.

Comorbidity and the rate of cognitive decline in patients with Alzheimer dementia

OBJECTIVE

This study aimed to investigate the impact of comorbidity on cognitive and functional decline in patients with Alzheimer dementia (AD).

METHODS

One hundred and two AD outpatients examined at the Psychiatry Department of the CF2 Polyclinic in Bucharest, Romania and re-evaluated after 2 years. Comorbidity was rated using the Cumulative Illness Rating Scale for Geriatrics (CIRS-G).

RESULTS

Baseline mean age (SD) was 75.4 (8.2) years, median CDR (range) was 2 (1-3), and mean MMSE (SD) 14.2 (4.9). MMSE declined to 11.2 (4.8) during follow-up. Baseline mean total CIRS-G score (SD) was 13.8 (5.4), median number of endorsed categories (range) was 8 (1-14), and mean severity index (SD) 1.9 (0.4). Main comorbidity areas were cardiovascular, ear, nose and throat, genitourinary, musculoskeletal/integument, and neurological. Severity of comorbidity increased with dementia severity (p <0.001). Baseline comorbidity was related to increased rate of cognitive decline; truncated regression coefficients (p-values) were 0.01 (0.02) for CIRS-G total score, and 0.15 (0.006) for severity index (controlled for age, sex, education, and AD treatment). Faster cognitive decline was associated with faster functional decline: OR (95% CI) was 5.2 (1.9-13.6) for increased rate of ADL change and 3.8 (1.0-14.1) for increased rate of IADL change (controlled for age, sex, education, AD medication, and comorbidity). Comorbidity tended to increase functional decline; however, the associations were not statistically significant.

CONCLUSIONS

In this group of patients with AD, comorbidity increased the rate of cognitive decline. Considering comorbidity instead of focusing on separate conditions may be more helpful in managing AD.

The association of genetic variants in interleukin-1 genes with cognition: findings from the cardiovascular health study

The inflammatory cytokine interleukin-1 (IL1) potentially plays a role in cognitive deterioration through pathology due to a dementing disorder or due to an aging process. Study of genetic variants in the IL1 genes has been mostly limited to diseases such as Alzheimer's, however, there may be benefit to studying a continuous measure of cognition. Using data from the Cardiovascular Health Study, we evaluate genetic variation in the genes encoding inflammatory agonists IL1A and IL1B, and the antagonist IL1RN, with repeated measures of global cognition (3MS) and processing speed (DSST), using mixed effects models. We found statistically significant minor allele SNP associations with baseline performance on the 3MS in the IL1RN gene for Caucasians (rs17042917: beta=0.47, 95%CI=0.09, 0.85, p=0.016; rs4251961: beta=-0.36, 95%CI=-0.13,-0.60, p=0.0027; rs931471: beta=0.39, 95%CI=0.13, 0.65, p=0.0032), and the IL1B gene for African Americans (rs1143627: beta=1.6, 95%CI=0.48, 2.8; p=0.006 and rs1143634: beta=2.09, 95%CI=0.39, 3.8; p=0.016). Associations appear to be weaker in a subgroup with higher education level. Upon removing those diagnosed with dementia, effect sizes and statistical significance attenuated. These results provide supporting evidence that genetic variants in IL1 genes may be involved in inflammatory-related lowered cognition, that higher education may modify genetic predisposition, and that these associations may be driven by a dementia process.

Atrial fibrillation (AF) and cognitive impairment in the elderly: a case-control study

AF is able not only to increase the risk of cognitive decline due to acute cerebrovascular events, but also to reduce cardiac output, with the consequence of impaired cerebral perfusion. The aim of this study was to evaluate the association between AF, dementia and depression in patients with negative anamnesis for past strokes. Our sample included 26 patients with a diagnosis of AF (paroxystic, persistent, permanent) and 31 patients with sinus rhythm, enrolled as controls. All selected patients underwent a Multidimensional Geriatric Assessment in order to investigate cognitive and behavioral functions. Statistical analysis of results showed a greater frequency of latent cognitive impairment in patients with AF, even in the absence of memory disorders. As a matter of facts, AF patients showed Mini Mental State Examination (MMSE) scores significantly lower than those with sinus rhythm (p<0.05) and Geriatric Depression Scale (GDS) scores higher than those without AF, evidencing a greater risk of depression too (p<0.02). Results showed a statistically significant association between AF, depression and cognitive impairment in early stage. In conclusion, AF is not only associated with the risk of developing cognitive impairment, but it can also be considered as a risk factor for dementia and depression, even in the absence of medical history of past stroke.

Assessment of the Virchow-Robin Spaces in Alzheimer disease, mild cognitive impairment, and normal aging, using high-field MR imaging

BACKGROUND AND PURPOSE

VRSs are the perivascular spaces surrounding the deep perforating arteries in the brain. Although VRS variations with age and disease pathologies have been reported previously, the radiologic characteristics of the VRS in relation to AD are poorly understood. This study investigated the prevalence, spatial distribution, and severity of the VRS in AD, MCI, and older adults who were CN. It also investigated the relationship of the VRS to white matter changes.

MATERIALS AND METHODS

Structural MR imaging data were acquired from 158 participants (AD = 37, MCI = 71, CN = 50, mean age = 74.97 ± 7.20 years) who had undergone T1WI at 3T. The severity of VRS in the white matter, basal ganglia, hippocampus, and brain stem structures was evaluated by using a semiquantitative scale, adapted from existing rating scales. A VRS total score summarizing the subscales was calculated to assess the whole-brain VRSs.

RESULTS

VRSs were observed in multiple brain regions of all participants, typically presented as <2-mm well-margined symmetric round-, oval- and linear-shaped hypointensities on T1WI. The VRS total score increased with leukoaraiosis, atrophy, and advanced age (P < .001). Individuals with AD and MCI showed greater levels of VRS than control subjects. The VRS total score discriminated individuals with AD and those who were CN with an accuracy of 0.79 (95% CI, 0.69-0.89).

CONCLUSIONS

VRSs are common in older adults and are more severe in AD and MCI than in CN. Whether increased VRSs can be reliably used to aid in AD diagnosis warrants further investigation.

Differential regulation of BACE1 expression by oxidative and nitrosative signals

Background

It is well established that both cerebral hypoperfusion/stroke and type 2 diabetes are risk factors for Alzheimer's disease (AD). Recently, the molecular link between ischemia/hypoxia and amyloid precursor protein (APP) processing has begun to be established. However, the role of the key common denominator, namely nitric oxide (NO), in AD is largely unknown. In this study, we investigated redox regulation of BACE1, the rate-limiting enzyme responsible for the β-cleavage of APP to Aβ peptides.

Results

Herein, we studied events such as S-nitrosylation, a covalent modification of cysteine residues by NO, and H₂O₂-mediated oxidation. We found that NO and H₂O₂ differentially modulate BACE1 expression and enzymatic activity: NO at low concentrations (<100 nM) suppresses BACE1 transcription as well as its enzymatic activity while at higher levels (0.1-100 μM) NO induces S-nitrosylation of BACE1 which inactivates the enzyme without altering its expression. Moreover, the suppressive effect on BACE1 transcription is mediated by the NO/cGMP-PKG signaling, likely through activated PGC-1α. H₂O₂ (1-10 μM) induces BACE1 expression via transcriptional activation, resulting in increased enzymatic activity. The differential effects of NO and H₂O₂ on BACE1 expression and activity are also reflected in their opposing effects on Aβ generation in cultured neurons in a dose-dependent manner. Furthermore, we found that BACE1 is highly S-nitrosylated in normal aging brains while S-nitrosylation is markedly reduced in AD brains.

Conclusion

This study demonstrates for the first time that BACE1 is highly modified by NO via multiple mechanisms: low and high levels of NO suppress BACE1 via transcriptional and post translational regulation, in contrast with the upregulation of BACE1 by H₂O₂-mediated oxidation. These novel NO-mediated regulatory mechanisms likely protect BACE1 from being further oxidized by excessive oxidative stress, as from H₂O₂ and peroxynitrite which are known to upregulate BACE1 and activate the enzyme, resulting in excessive cleavage of APP and Aβ generation; they likely represent the crucial house-keeping mechanism for BACE1 expression/activation under physiological conditions.

AVR/NAVR deficiency lowers blood pressure and differentially affects urinary concentrating ability, cognition, and anxiety-like behavior in male and female mice

Arginine vasopressin (AVP) and angiotensin II (ANG II) are distinct peptide hormones involved in multiple organs modulating renal, cardiovascular, and brain functions. They achieve these functions via specific G protein-coupled receptors, respectively. The AVR/NAVR locus encodes two overlapping V2-type vasopressin isoreceptors: angiotensin-vasopressin receptor (AVR) responding to ANG II and AVP equivalently, and nonangiotensin vasopressin receptor (NAVR), which binds vasopressin exclusively. AVR and NAVR are expressed from a single gene by alternative promoter usage that is synergistically upregulated by testosterone and estrogen. This study tested the hypothesis that AVR/NAVR modulates urinary concentrating ability, blood pressure, and cognitive performance in vivo in a sex-specific manner. We developed a C57BL/6 inbred AVR/NAVR(-/-) knockout mouse that showed lower blood pressure in both male and female subjects and a urinary-concentrating defect restricted to male mice. We also detected sex-specific effects on cognitive and anxiety-like behaviors. AVR/NAVR(-/-) male mice exhibited impaired visuospatial and associative learning, while female mice showed improved performance in both type of cognition. AVR/NAVR deficiency produced an anxiolytic-like effect in female mice, while males were unaffected. Analysis of AVR- and NAVR-mediated phosphorylation/dephosphorylation of signaling proteins revealed activation/deactivation of known modulators of cognitive function. Our studies identify AVR/NAVR as key receptors involved in blood pressure regulation and sex-specific modulation of renal water homeostasis, cognitive function, and anxiety-like behavior. As such, the AVR/NAVR receptor system provides a molecular mechanism for sexually diergic traits and a putative common pathway for the emerging association of hypertension and cognitive decline and dementia.

Linking cardiometabolic disorders to sporadic Alzheimer's disease: a perspective on potential mechanisms and mediators

There is increasing evidence that the incidence of Alzheimer's disease (AD) is significantly influenced by cardiovascular risk factors in association with a cluster of metabolic diseases including diabetes and atherosclerosis. The shared risk is also reflected in the dietary and lifestyle links to both metabolic disorders and AD-type cognitive dysfunction. Recent studies with genetic and diet-induced animal models have begun to illuminate convergent mechanisms and mediators between these two categories of disease conditions with distinct tissue-specific pathologies. Although it is clear that peripheral inflammation and insulin resistance are central to the pathogenesis of the disorders of metabolic syndrome, it seems that the same mechanisms are also in play across the blood-brain barrier that lead to AD-like molecular and cognitive changes. This review highlights these convergent mechanisms and discusses the role of cerebrovascular dysfunction as a conduit to brain emergence of these pathogenic processes that might also represent future therapeutic targets in AD in common with metabolic disorders.

Contribution of systemic inflammation to chronic neurodegeneration

Systemic infection or inflammation gives rise to signals that communicate with the brain and leads to changes in metabolism and behaviour collectively known as sickness behaviour. In healthy young individuals, these changes are normally transient with no long-term consequences. The microglia are involved in the immune to brain signalling pathways. In the aged or diseased brain, the microglia have a primed phenotype as a consequence of changes in their local microenvironment. Systemic inflammation impacts on these primed microglia and switches them from a relatively benign to an aggressive phenotype with the enhanced synthesis of pro-inflammatory mediators. Recent evidence suggests that systemic inflammation contributes to the exacerbation of acute symptoms of chronic neurodegenerative disease and may accelerate disease progression. The normal homeostatic role that microglia play in signalling about systemic infections and inflammation becomes maladaptive in the aged and diseased brain and this offers a route to therapeutic intervention. Prompt treatment of systemic inflammation or blockade of signalling pathways from the periphery to the brain may help to slow neurodegeneration and improve the quality of life for individuals suffering from chronic neurodegenerative disease.

Promoting successful cognitive aging: a comprehensive review

Promoting successful cognitive aging is a topic of major importance to individuals and the field of public health. This review presents a coherent framework not only for evaluating factors, protective activities, and enhancing agents that have already been proposed, but also ones that will be put forward in the future. The promotion of successful cognitive aging involves the dual goals of preventing loss of information processing capacity and cognitive reserve, and enhancing brain capacity and cognitive reserve. Four major lines of evidence are available for evaluating whether a proposed factor promotes successful cognitive aging: 1) epidemiologic/cohort studies; 2) animal/basic science studies; 3) human "proof-of-concept" studies; and 4) human intervention studies. Each line of evidence has advantages and limitations that will be discussed. Through illustrative examples, we trace the ways in which each method informs us about the potential value of several proposed factors. Currently, lines of converging evidence allow the strongest case to be made for physical and cognitively stimulating activities. Although epidemiological data seem to favor the use of statins to lower the risk of dementia, more definitive recommendations await further randomized controlled studies. There is presently no clear evidence that antioxidants or Ginkgo biloba promote successful cognitive aging. The impact of resveratrol, fish oil, and a long list of other proposed agents needs to be determined. Clinicians remain well-positioned to identify and aggressively treat vascular risk factors, diabetes, sleep disorders, and other conditions that may reduce brain capacity, and to encourage activities that can build cognitive reserve.

Linkage to 20p13 including the ANGPT4 gene in families with mixed Alzheimer's disease and vascular dementia

This study aimed at identifying novel susceptibility genes for a mixed phenotype of Alzheimer's disease and vascular dementia. Results from a genome scan showed strongest linkage to 20p13 in 18 families, and subsequent fine mapping was performed with both microsatellites and single-nucleotide polymorphisms in 18 selected candidate transcripts in an extended sample set of 30 families. The multipoint linkage peak was located at marker rs2144151 in the ANGPT4 gene, which is a strong candidate gene for vascular disease because of its involvement in angiogenesis. Although the significance of the linkage decreased, we find this result intriguing, considering that we included additional families, and thus the reduced linkage signal may be caused by genetic heterogeneity.

Vascular risk factor detection and control may prevent Alzheimer's disease

The vascular hypothesis of Alzheimer disease (AD), first proposed by us in 1993, provides substantial evidence that suggests vascular risk factors (VRF) play a critical role in the development of cognitive decline and AD during aging. Cardiovascular and carotid artery disease, two major risk factors to AD, can conspire or independently induce chronic brain hypoperfusion (CBH) decades before any symptoms of cognitive impairment are expressed. The pathologic construct linking CBH to cognitive impairment and AD remains unclear but evidence shows that it may provide an opportunity to intervene in the prevention or delay of dementia onset. A preliminary randomized clinical study in cognitively healthy middle age individuals to undergo screening using carotid Doppler ultrasound, echocardiography and ankle-brachial index is proposed. These office tools are non-invasive, cost-effective, easily applied in one session and relatively accurate procedures with no inherent harmful effects. More importantly, ultrasound can help identify asymptomatic patients most likely to develop progressive cognitive decline due to persistent CBH secondary to progressive cardiovascular or carotid artery pathology. When these VRF are detected within the heart or carotid arteries, optimal medical treatment or management may be indicated to prevent or slow down further disease progression that fosters cognitive deterioration generated from such conditions. Secondary screening tools such as neuroimaging, neurocognitive testing and CSF markers may be used to confirm ultrasound findings. Prevention-by-detection of VRF and target treatment, if found effective, could significantly promote healthier mental and physical aging and lessen the socio-economic calamity anticipated from the growing prevalence of dementia.

Meta-analysis of the methylenetetrahydrofolate reductase C677T polymorphism and susceptibility to Alzheimer's disease

No clear consensus has been reached at the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and Alzheimer's disease (AD) risk. Thus in this meta-analysis, a total of 19 case-control studies was assessed to evaluate the possible association. The data demonstrated that the frequency of T677 allele (T vs. C) was significantly associated with susceptibility to AD in all subjects (OR=1.15, 95% CI=1.06-1.26) and in East Asians (OR=1.22, 95% CI=1.08-1.39). There was statistical difference between AD patients and the controls under recessive genetic mode (CT+TT vs. CC) and homozygote comparison (TT vs. CC) in all subjects and in East Asians as well. Despite a small effect of the polymorphism on late-onset AD (LOAD) risk, MTHFR C677T polymorphism was not a major risk factor for LOAD in East Asians and Caucasians. A subgroup analysis in the subjects without APOE epsilon4 alleles showed T677 allele significantly increased risk of AD in all subjects (OR=1.21, 95% CI: 1.04-1.42) and in East Asians (OR=1.28, 95% CI: 1.06-1.55). However, no association was found in Caucasians. In conclusion, this meta-analysis supports that MTHFR C677T polymorphism is capable of causing AD susceptibility in East Asians, not in Caucasians.

Effect of a purpose in life on risk of incident Alzheimer disease and mild cognitive impairment in community-dwelling older persons

CONTEXT

Emerging data suggest that psychological and experiential factors are associated with risk of Alzheimer disease (AD), but the association of purpose in life with incident AD is unknown.

OBJECTIVE

To test the hypothesis that greater purpose in life is associated with a reduced risk of AD.

DESIGN

Prospective, longitudinal epidemiologic study of aging.

SETTING

Senior housing facilities and residences across the greater Chicago metropolitan area.

PARTICIPANTS

More than 900 community-dwelling older persons without dementia from the Rush Memory and Aging Project.

MAIN OUTCOME MEASURES

Participants underwent baseline evaluations of purpose in life and up to 7 years of detailed annual follow-up clinical evaluations to document incident AD. In subsequent analyses, we examined the association of purpose in life with the precursor to AD, mild cognitive impairment (MCI), and the rate of change in cognitive function.

RESULTS

During up to 7 years of follow-up (mean, 4.0 years), 155 of 951 persons (16.3%) developed AD. In a proportional hazards model adjusted for age, sex, and education, greater purpose in life was associated with a substantially reduced risk of AD (hazard ratio, 0.48; 95% confidence interval, 0.33-0.69; P < .001). Thus, a person with a high score on the purpose in life measure (score = 4.2, 90th percentile) was approximately 2.4 times more likely to remain free of AD than was a person with a low score (score = 3.0, 10th percentile). This association did not vary along demographic lines and persisted after the addition of terms for depressive symptoms, neuroticism, social network size, and number of chronic medical conditions. In subsequent models, purpose in life also was associated with a reduced risk of MCI (hazard ratio, 0.71; 95% confidence interval, 0.53-0.95; P = .02) and a slower rate of cognitive decline (mean [SE] global cognition estimate, 0.03 [0.01], P < .01).

CONCLUSION

Greater purpose in life is associated with a reduced risk of AD and MCI in community-dwelling older persons.

Microglia in neurodegenerative disease

Microglia, the resident macrophages of the CNS, are exquisitely sensitive to brain injury and disease, altering their morphology and phenotype to adopt a so-called activated state in response to pathophysiological brain insults. Morphologically activated microglia, like other tissue macrophages, exist as many different phenotypes, depending on the nature of the tissue injury. Microglial responsiveness to injury suggests that these cells have the potential to act as diagnostic markers of disease onset or progression, and could contribute to the outcome of neurodegenerative diseases. The persistence of activated microglia long after acute injury and in chronic disease suggests that these cells have an innate immune memory of tissue injury and degeneration. Microglial phenotype is also modified by systemic infection or inflammation. Evidence from some preclinical models shows that systemic manipulations can ameliorate disease progression, although data from other models indicates that systemic inflammation exacerbates disease progression. Systemic inflammation is associated with a decline in function in patients with chronic neurodegenerative disease, both acutely and in the long term. The fact that diseases with a chronic systemic inflammatory component are risk factors for Alzheimer disease implies that crosstalk occurs between systemic inflammation and microglia in the CNS.

Cholesterol in Alzheimer's disease and other amyloidogenic disorders

The complex association of cholesterol metabolism and Alzheimer's disease is presented in depth, including the possible benefits to be gained from cholesterol-lowering statin therapy. Then follows a survey of the role of neuronal membrane cholesterol in Abeta pore formation and Abeta fibrillogenesis, together with the link with membrane raft domains and gangliosides. The contribution of structural studies to Abeta fibrillogenesis, using TEM and AFM, is given some emphasis. The role of apolipoprotein E and its isoforms, in particular ApoE4, in cholesterol and Abeta binding is presented, in relation to genetic risk factors for Alzheimer's disease. Increasing evidence suggests that cholesterol oxidation products are of importance in generation of Alzheimer's disease, possibly induced by Abeta-produced hydrogen peroxide. The body of evidence for a link between cholesterol in atherosclerosis and Alzheimer's disease is increasing, along with an associated inflammatory response. The possible role of cholesterol in tau fibrillization, tauopathies and in some other non-Abeta amyloidogenic disorders is surveyed.

Severity of CIND and MCI predict incidence of dementia in an ischemic stroke cohort

BACKGROUND

The utility of poststroke cognitive status, namely dementia, cognitive impairment no dementia (CIND), mild cognitive impairment (MCI), and no cognitive impairment (NCI), in predicting dementia has been previously examined. However, no studies to date have compared the ability of subtypes of MCI and CIND to predict dementia in a poststroke population.

METHODS

A cohort of ischemic stroke patients underwent neuropsychological assessment annually for up to 5 years. Dementia was defined using the DSM-IV criteria. Univariate and multivariable Cox proportional regression was performed to determine the ability of MCI subtypes, CIND severity, and individual domains of impairment to predict dementia.

RESULTS

A total of 362 patients without dementia were followed up for a mean of 3.4 years (17% drop out), with 24 developing incident dementia. Older age, previous and recurrent stroke, and CIND and MCI subtypes were significant predictors of dementia. In multivariable analysis controlling for treatment allocation, patients who were older, had previous or recurrent stroke, and had either CIND moderate or multiple domain MCI with amnestic component were at elevated risk for dementia. In multivariable domain analysis, recurrent strokes, age, and previous strokes, verbal memory, and visual memory were significant predictors of dementia. Receiver operating characteristic curve analysis showed that CIND moderate (area under the curve: 0.893) and multiple domain MCI with amnestic component (area under the curve: 0.832) were significant predictors of conversion to dementia. All other classifications of cognitive impairment had areas under the curve less than 0.7.

CONCLUSION

Stroke patients with cognitive impairment no dementia (CIND) moderate are at higher risk of developing dementia, while CIND mild patients are not at increased risk of developing dementia.

Profile of hippocampal volumes and stroke risk varies by neuropsychological definition of mild cognitive impairment

Wide-ranging conceptual and diagnostic approaches to defining mild cognitive impairment (MCI) have led to highly variable prevalence and progression rates. We sought to examine whether bilateral hippocampal volumes and cerebrovascular risk factors in individuals characterized by two different neuropsychological definitions of MCI subtypes would also differ. Participants were 65 nondemented, community-dwelling, older adults, ages 62-91 years, drawn from a larger group of individuals enrolled in a longitudinal study of normal aging. A comprehensive neuropsychological definition of MCI that required the presence of more than one impaired score in a cognitive domain resulted in expected anatomical results; hippocampal volumes were significantly smaller in the aMCI group as compared to cognitively normal or nonamnestic MCI participants. However, a typical definitional scheme for classifying MCI based only on the presence of one impaired score within a cognitive domain did not result in hippocampal differences between groups. Global stroke risk factors did not differ between the two definitional schemes, although the relationship between stroke risk variables and neuropsychological performance did vary by diagnostic approach. The comprehensive approach demonstrated associations between stroke risk and cognition, whereas the typical approach did not. Use of more sophisticated clinical decision-making and diagnostic approaches that incorporate comprehensive neuropsychological assessment techniques is supported by this convergence of neuropsychological, neuropathological, and stroke risk findings.

Epidemiological pathology of dementia: attributable-risks at death in the Medical Research Council Cognitive Function and Ageing Study

BACKGROUND

Dementia drug development aims to modulate pathological processes that cause clinical syndromes. Population data (epidemiological neuropathology) will help to model and predict the potential impact of such therapies on dementia burden in older people. Presently this can only be explored through post mortem findings. We report the attributable risks (ARs) for dementia at death for common age-related degenerative and vascular pathologies, and other factors, in the MRC Cognitive Function and Ageing Study (MRC CFAS).

METHODS AND FINDINGS

A multicentre, prospective, longitudinal study of older people in the UK was linked to a brain donation programme. Neuropathology of 456 consecutive brain donations assessed degenerative and vascular pathologies. Logistic regression modelling, with bootstrapping and sensitivity analyses, was used to estimate AR at death for dementia for specific pathologies and other factors. The main contributors to AR at death for dementia in MRC CFAS were age (18%), small brain (12%), neocortical neuritic plaques (8%) and neurofibrillary tangles (11%), small vessel disease (12%), multiple vascular pathologies (9%), and hippocampal atrophy (10%). Other significant factors include cerebral amyloid angiopathy (7%) and Lewy bodies (3%).

CONCLUSIONS

Such AR estimates cannot be derived from the living population; rather they estimate the relative contribution of specific pathologies to dementia at death. We found that multiple pathologies determine the overall burden of dementia. The impact of therapy targeted to a specific pathology may be profound when the dementia is relatively "pure," but may be less impressive for the majority with mixed disease, and in terms of the population. These data justify a range of strategies, and combination therapies, to combat the degenerative and vascular determinants of cognitive decline and dementia. Please see later in the article for the Editors' Summary.

Carotid artery ultrasound and echocardiography testing to lower the prevalence of Alzheimer's disease

The use of two clinic office techniques, carotid artery ultrasound and echocardiography (CAUSE), to detect deficient brain blood flow delivery in the healthy, cognitively normal, older individual is proposed. Evidence indicates that persistent heart-to-brain blood flow deficit involving low cardiac output or low ejection fraction and carotid artery narrowing can promote cognitive impairment and that such impairment may lead to Alzheimer's disease (AD) or vascular dementia (VaD). A number of independent epidemiologic studies reported cardiovascular and cerebrovascular disease to be risk factors to AD and VaD. The clinical rationale for CAUSE is to detect and prevent progression of cognitive dysfunction in elderly persons and is based on the general understanding that mild cognitive impairment is a preclinical threshold to AD or VaD with high conversion rates to either dementia. The use of CAUSE is anticipated to prevent or attenuate, by appropriate clinical management, mild cognitive impairment arising from persistent brain hypoperfusion, a condition implicated in the promotion of cognitive impairment in the elderly and a common preclinical feature seen in AD and VaD. As detection of lowered cerebral perfusion from cardiac and carotid artery pathology is achieved using these cost-effective, noninvasive, and relatively accurate ultrasound procedures, a significant reduction in the number of new AD and VaD cases would be anticipated after appropriate patient treatment. In this context, a brief summary is presented outlining recent medical and surgical treatments that may improve cerebral blood flow insufficiency. The merit of CAUSE in screening and treating mentally healthy elderly persons who are identified as being at risk of cognitive decline is that it could blunt the soaring socioeconomic impact that will hammer the health care system of many nations by the mounting dementia prevalence rate expected in the next 25 years. A 5- year delay in the onset of AD could reduce the prevalence of AD by 50%. We are making preparations to test the merit of CAUSE in a clinical study of a cognitively healthy elderly population.

Systemic inflammation and disease progression in Alzheimer disease

BACKGROUND

Acute and chronic systemic inflammation are characterized by the systemic production of the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) that plays a role in immune to brain communication. Previous preclinical research shows that acute systemic inflammation contributes to an exacerbation of neurodegeneration by activation of primed microglial cells.

OBJECTIVE

To determine whether acute episodes of systemic inflammation associated with increased TNF-alpha would be associated with long-term cognitive decline in a prospective cohort study of subjects with Alzheimer disease.

METHODS

Three hundred community-dwelling subjects with mild to severe Alzheimer disease were cognitively assessed, and a blood sample was taken for systemic inflammatory markers. Each subject's main caregiver was interviewed to assess the presence of incident systemic inflammatory events. Assessments of both patient and caregiver were repeated at 2, 4, and 6 months.

RESULTS

Acute systemic inflammatory events, found in around half of all subjects, were associated with an increase in the serum levels of proinflammatory cytokine TNF-alpha and a 2-fold increase in the rate of cognitive decline over a 6-month period. High baseline levels of TNF-alpha were associated with a 4-fold increase in the rate of cognitive decline. Subjects who had low levels of serum TNF-alpha throughout the study showed no cognitive decline over the 6-month period.

CONCLUSIONS

Both acute and chronic systemic inflammation, associated with increases in serum tumor necrosis factor alpha, is associated with an increase in cognitive decline in Alzheimer disease.

Brain glucose transporters, O-GlcNAcylation and phosphorylation of tau in diabetes and Alzheimer's disease

Type 2 diabetes mellitus (T2DM) increases the risk for Alzheimer's disease (AD), but the underlying mechanism is unknown. In this study, we determined the levels of major brain glucose transporters, O-GlcNAcylation and phosphorylation of tau in the postmortem brain tissue from frontal cortices of 7 controls, 11 T2DM subjects, 10 AD subjects and 8 additional subjects who had both T2DM and AD. We found that the neuronal glucose transporter 3 was decreased to a bigger extent in T2DM brain than in AD brain. The O-GlcNAcylation levels of global proteins and of tau were also decreased in T2DM brain as seen in AD brain. Phosphorylation of tau at some of the AD abnormal hyperphosphorylation sites was increased in T2DM brain. These results suggest that T2DM may contribute to the increased risk for AD by impairing brain glucose uptake/metabolism and, consequently, down-regulation of O-GlcNAcylation, which facilitates abnormal hyperphosphorylation of tau.

Therapy for Alzheimer's Disease: How Effective are Current Treatments?

Available symptomatic therapies for the treatment of Alzheimer's disease (AD) have been based on known neurotransmitter dysfunctions associated with the illness. The second-generation cholinesterase inhibitors and the N-methyl D-aspartate receptor antagonist memantine have been widely prescribed and studied. Meta-analyses of these therapies were reviewed, focusing on effectiveness and tolerability. Although many of the meta-analyses demonstrate statistically significant improvements, some question if these benefits are sufficient to justify their current widespread and protracted use. This has spurred the development of new disease-modifying therapies that aim to have a greater impact on this debilitating illness.

The amyloid-beta peptide of Alzheimer's disease binds Cu(I) in a linear bis-his coordination environment: insight into a possible neuroprotective mechanism for the amyloid-beta peptide

Oxidative stress has been suggested to contribute to neuronal apoptosis associated with Alzheimer's disease (AD). Copper may participate in oxidative stress through redox-cycling between its +2 and +1 oxidation states to generate reactive oxygen species (ROS). In vitro, copper binds to the amyloid-beta peptide of AD, and in vivo, copper is associated with amyloid plaques characteristic of AD. As a result, the AbetaCu(I) complex may be a critical reactant involved in ROS associated with AD etiology. To characterize the AbetaCu(I) complex, we have pursued X-ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopy of AbetaCu(II) and AbetaCu(I) (produced by ascorbate reduction of AbetaCu(II)). The AbetaCu(II) complex Cu K-edge XAS spectrum is indicative of a square-planar Cu(II) center with mixed N/O ligation. Multiple scattering analysis of the extended X-ray absorption fine structure (EXAFS) data for AbetaCu(II) indicates that two of the ligands are imidazole groups of histidine ligands, indicating a (N(Im))(2)(N/O)(2) Cu(II) ligation sphere for AbetaCu(II). After reduction of the AbetaCu(II) complex with ascorbate, the edge region decreases in energy by approximately 4 eV. The X-ray absorption near-edge spectrum region of AbetaCu(I) displays an intense pre-edge feature at 8984.1(2) eV. EXAFS data fitting yielded a two-coordinate geometry, with two imidazole ligands coordinated to Cu(I) at 1.877(2) A in a linear geometry. Ascorbate reduction of AbetaCu(II) under inert atmosphere and subsequent air oxidation of AbetaCu(I) to regenerate AbetaCu(II) was monitored by low-temperature EPR spectroscopy. Slow reappearance of the AbetaCu(II) EPR signal indicates that O(2) oxidation of the AbetaCu(I) complex is kinetically sluggish and Abeta damage is occurring following reoxidation of AbetaCu(I) by O(2). Together, these results lead us to hypothesize that Cu(I) is ligated by His13 and His14 in a linear coordination environment in Alphabeta, that Abeta may be playing a neuroprotective role, and that metal-mediated oxidative damage of Abeta occurs over multiple redox cycles.