Axonal damage and astrocytosis are biological correlates of grey matter network integrity loss: a cohort study in autosomal dominant Alzheimer disease

Brain development and maturation leads to grey matter networks that can be measured using magnetic resonance imaging. Network integrity is an indicator of information processing capacity which declines in neurodegenerative disorders such as Alzheimer disease (AD). The biological mechanisms causing this loss of network integrity remain unknown. Cerebrospinal fluid (CSF) protein biomarkers are available for studying diverse pathological mechanisms in humans and can provide insight into decline. We investigated the relationships between 10 CSF proteins and network integrity in mutation carriers (N=219) and noncarriers (N=136) of the Dominantly Inherited Alzheimer Network Observational study. Abnormalities in Aβ, Tau, synaptic (SNAP-25, neurogranin) and neuronal calcium-sensor protein (VILIP-1) preceded grey matter network disruptions by several years, while inflammation related (YKL-40) and axonal injury (NfL) abnormalities co-occurred and correlated with network integrity. This suggests that axonal loss and inflammation play a role in structural grey matter network changes.

Key points

Abnormal levels of fluid markers for neuronal damage and inflammatory processes in CSF are associated with grey matter network disruptions.The strongest association was with NfL, suggesting that axonal loss may contribute to disrupted network organization as observed in AD.Tracking biomarker trajectories over the disease course, changes in CSF biomarkers generally precede changes in brain networks by several years.

Preclinical trials in autosomal dominant AD: implementation of the DIAN-TU trial

The Dominantly Inherited Alzheimer's Network Trials Unit (DIAN-TU) was formed to direct the design and management of interventional therapeutic trials of international DIAN and autosomal dominant Alzheimer's disease (ADAD) participants. The goal of the DIAN-TU is to implement safe trials that have the highest likelihood of success while advancing scientific understanding of these diseases and clinical effects of proposed therapies. The DIAN-TU has launched a trial design that leverages the existing infrastructure of the ongoing DIAN observational study, takes advantage of a variety of drug targets, incorporates the latest results of biomarker and cognitive data collected during the observational study, and implements biomarkers measuring Alzheimer's disease (AD) biological processes to improve the efficiency of trial design. The DIAN-TU trial design is unique due to the sophisticated design of multiple drugs, multiple pharmaceutical partners, academics servings as sponsor, geographic distribution of a rare population and intensive safety and biomarker assessments. The implementation of the operational aspects such as home health research delivery, safety magnetic resonance imagings (MRIs) at remote locations, monitoring clinical and cognitive measures, and regulatory management involving multiple pharmaceutical sponsors of the complex DIAN-TU trial are described.

Pharmacokinetics of a novel transdermal rivastigmine patch for the treatment of Alzheimer's disease: a review

BACKGROUND

Cholinesterase inhibitors have all been available in oral formulations, but a rivastigmine transdermal patch has now been developed and is approved in many countries worldwide for the treatment of mild-to-moderate Alzheimer's disease (AD) (including the USA, Latin America, Europe and Asia).

OBJECTIVES

To review the available pharmacokinetic data that supported the rationale behind the development of the rivastigmine transdermal patch and its clinical effects in dementia therapy. This article will also discuss how the patch may alter the treatment paradigm for patients with AD.

RESULTS

The 9.5 mg/24 h rivastigmine patch was shown to provide comparable exposure to the highest recommended doses of capsules (12 mg/day) with significantly lower maximum plasma concentration (Cmax 8.7 vs. 21.6 ng/ml) and slower absorption rate (tmax 8.1 vs. 1.4 h). In a clinical trial of 1195 AD patients, this translated into similar efficacy with three times fewer reports of nausea and vomiting (7.2% vs. 23.1%, and 6.2% vs. 17.0% respectively). Consequently, more patients in the 9.5 mg/24 h patch group achieved their target therapeutic dose at the end of the study, compared with those in the 12 mg/day capsule group (95.9% vs. 64.4%).

CONCLUSION

The rivastigmine patch provides continuous drug delivery over 24 h and similar efficacy to the highest recommended dose of oral rivastigmine with improved tolerability. This may allow patients to achieve optimal therapeutic doses and to benefit from a longer duration of treatment.

IDEAL: a 6-month, double-blind, placebo-controlled study of the first skin patch for Alzheimer disease

The rivastigmine patch is the first transdermal treatment for Alzheimer disease (AD). By providing continuous delivery of drug into the bloodstream over 24 hours, transdermal delivery may offer benefits superior to those of oral administration. This study compared the efficacy, safety and tolerability of rivastigmine patches with capsules and placebo. IDEAL (Investigation of transDermal Exelon in ALzheimer's disease) was a 24-week, double-blind, double-dummy, placebo- and active-controlled study. Patients with AD were randomized to placebo or one of three active treatment target dose groups: 10-cm(2) rivastigmine patch (delivering 9.5 mg/24 hours); 20-cm(2) rivastigmine patch (17.4 mg/24 hours); or 6-mg BID rivastigmine capsules. Primary efficacy measures were the Alzheimer's Disease Assessment Scale-Cognitive subscale and Alzheimer's Disease Cooperative Study-Clinical Global Impression of Change. Secondary outcome measures assessed a range of domains, including behavior, cognitive performance, attention, executive functions, and activities of daily living. A total of 1,195 AD patients participated. All rivastigmine treatment groups showed significant improvement relative to placebo. The 10-cm(2) patch showed similar efficacy to capsules, with approximately two-thirds fewer reports of nausea (7.2% vs 23.1%) and vomiting (6.2% vs 17.0%), incidences statistically not significantly different from placebo (5.0% and 3.3% for nausea and vomiting, respectively). The 20-cm(2) patch showed earlier improvement and numerically superior cognitive scores vs the 10-cm(2) patch with similar tolerability to capsules. Local skin tolerability was good. The transdermal patch with rivastigmine may offer additional therapeutic benefits and may prove to be the best delivery system for this drug to treat AD.

A mutation in myotilin causes spheroid body myopathy

BACKGROUND

Spheroid body myopathy (SBM) is a rare, autosomal dominant, neuromuscular disorder, which has only been previously reported in a single large kindred. Identification of the mutated gene in this disorder may provide insight regarding abnormal neuromuscular function.

METHODS

The authors completed a detailed clinical evaluation on an extensive kindred diagnosed with SBM. Genome-wide linkage analysis was performed to localize the disease gene to a specific chromosomal region. Further marker genotyping and screening of a positional, functional candidate gene were completed to detect the disease-causing mutation. Pathologic analysis of muscle biopsy was performed on three individuals. Biochemical studies were performed on one muscle biopsy specimen from an affected individual.

RESULTS

Linkage to chromosome 5q23-5q31 was detected with a lod score of 2.9. Genotyping of additional markers in a larger sample of family members produced a maximum lod score of 6.1 and narrowed the critical interval to 12.2 cM. Screening of the candidate gene titin immunoglobulin domain protein (TTID, also known as MYOT) detected a cytosine-to-thymine mutation in exon 2 of all clinically affected family members. Similar pathologic changes were present in all muscle biopsy specimens. Immunohistologic and biochemical analysis revealed that the TTID protein, also known as myotilin, is a component of the insoluble protein aggregate.

CONCLUSIONS

A novel mutation in the TTID gene results in the clinical and pathologic phenotype termed "spheroid body myopathy." Mutations in this gene also cause limb-girdle muscular dystrophy 1A and are associated with myofibrillar myopathy.

Intravenous immunoglobulins containing antibodies against beta-amyloid for the treatment of Alzheimer's disease

OBJECTIVE

Active or passive immunisation can mitigate plaque pathology in murine models of Alzheimer's disease (AD). Recently, it has been shown that antibodies against beta-amyloid (Abeta) are present in human immunoglobulin preparations (IVIgG), which specifically recognise and inhibit the neurotoxic effects of Abeta. This study reports the results from a pilot study using IVIgG in patients with AD.

METHODS

Five patients with AD were enrolled and received monthly IVIgG over a 6 month period. Efficacy assessment included total Abeta/Abeta(1-42) measured in the CSF/serum as well as effects on cognition (ADAS-cog; CERAD) at baseline and at 6 months following IVIgG.

RESULTS

Following IVIgG, total Abeta levels in the CSF decreased by 30.1% (17.3-43.5%) compared to baseline (p<0.05). Total Abeta increased in the serum by 233% (p<0.05). No significant change was found in Abeta(1-42) levels in the CSF/serum. Using ADAS-cog, an improvement of 3.7+/-2.9 points was detected. Scores in the MMSE were essentially unchanged (improved in four patients, stable in one patient) following IVIgG compared to baseline.

CONCLUSION

Although the sample size of this pilot study is too small to draw a clear conclusion, the results of this pilot study provide evidence for a more detailed investigation of IVIgG for the treatment of AD.

Differential qualitative responses to rivastigmine in APOE ɛ4 carriers and noncarriers

This retrospective analysis of two double-blind, placebo-controlled studies in patients with mild to moderately severe AD investigated the efficacy of rivastigmine 6-12 mg/day on cognitive outcomes in patients with or without the apolipoprotein (APOE) epsilon4 allele. APOE data were collected from patients who consented to pharmacogenetic testing. Treatment differences within each subgroup were compared, using the Observed Case (OC) population. The APOE epsilon4 and non-APOE epsilon4 subgroups comprised 246 and 121 patients, respectively. Overall, APOE epsilon4 noncarriers showed greater decline than carriers (P<0.05). However, at 26 weeks, placebo-treated APOE epsilon4 patients declined 3.04 points below baseline on the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog), and rivastigmine-treated patients improved by 1.67 points. Non-APOE epsilon4 placebo-treated patients declined by 4.59 points and rivastigmine-treated patients declined by 0.48 points. Thus, non-APOE epsilon4 carriers showed a less favorable course under either placebo or rivastigmine, but both genotype-defined subgroups showed quantitatively similar responses to therapy (both P<0.05 vs placebo).

Value of CSF beta-amyloid1-42 and tau as predictors of Alzheimer's disease in patients with mild cognitive impairment

Subjects with mild cognitive impairment (MCI) are at a high risk of developing clinical Alzheimer's disease (AD). We asked to what extent the core biomarker candidates cerebro-spinal fluid (CSF) beta-amyloid(1-42) (Abeta(1-42)) and CSF tau protein concentrations predict conversion from MCI to AD. We studied 52 patients with MCI, 93 AD patients, and 10 healthy controls (HC). The MCI group was composed of 29 patients who had converted to AD during follow-up, and of 23 patients who showed no cognitive decline. CSF Abeta(1-42) and tau protein levels were assessed at baseline in all subjects, using enzyme-linked immunosorbent assays. For assessment of sensitivity and specificity, we used independently established reference values for CSF Abeta(1-42) and CSF tau. The levels of CSF tau were increased, whereas levels of Abeta(1-42) were decreased in MCI subjects. Abeta(1-42) predicted AD in converted MCI with a sensitivity of 59% and a specificity of 100% compared to HC. Tau yielded a greater sensitivity of 83% and a specificity of 90%. In a multiple Cox regression analysis within the MCI group, low baseline levels of Abeta(1-42), but not other predictor variables (tau protein, gender, age, apolipoprotein E epsilon4 carrier status, Mini Mental Status Examination score, observation time, antidementia therapy), correlated with conversion status (P<0.05). Our findings support the notion that CSF tau and Abeta(1-42) may be useful biomarkers in the early identification of AD in MCI subjects.

Does nitric oxide synthase contribute to the pathogenesis of Alzheimer's disease?: effects of beta-amyloid deposition on NOS in transgenic mouse brain with AD pathology

Oxidative stress is a risk factor for Alzheimer's disease (AD) whose major hallmark includes brain depositions of the amyloid beta peptide (Abeta) derived from the beta-amyloid precursor protein (APP). Our aim was to determine whether or not excessive Abeta deposition would alter nitric oxide synthase (NOS) activity, and thereby affect NOS-mediated superoxide formation. We compared NOS activity in brain extracts between Tg mice (expressing APP Swedish double mutation plus presenilin [PS-1] and nontransgenic [nTg] mice. Five brain regions, including cerebral cortex, hippocampus, cerebellum, and striatum from both nTg and Tg mice showed a detectable level of neuronal (n) NOS activity. Cerebellar extracts from both nTg and Tg mice displayed the highest level of nNOS activity, which was fourfold higher than cortical extracts. Although there was an increase in nNOS activity in Tg brain extracts, this did not attain statistical significance. A similar result was obtained for inducible NOS levels. Our results suggest that excess levels of Abeta failed to both trigger NOS activity and change NOS levels.

A multicenter, randomized, placebo controlled, multiple-dose, safety and pharmacokinetic study of AIT-082 (Neotrofin) in mild Alzheimer's disease patients

A phase 1, randomized, double-blind, placebo-controlled, dose escalation study of the purine derivative, AIT-082 (Neotrofin, NeoTherapeutics) was conducted in mild Alzheimer's disease (AD) patients to evaluate multiple-dose safety, tolerability, and pharmacokinetics. Possible short-term effects of AIT-082 on cognition and memory were preliminarily investigated. AIT-082 is currently being developed as a potential treatment for Alzheimer's disease and other neurological disorders. Pre-clinical studies indicate that AIT-082 has memory enhancing properties, stimulates neuritogenesis and the production of neurotrophic factors. Patients received an oral dose of AIT-082 or placebo daily for one week. Thirty-six AD patients were divided into three dose cohorts; each dose cohort consisted of twelve patients with 8 patients randomized to AIT-082 and 4 to placebo. The 3 doses of AIT-082 evaluated in this study were 100 mg/day, 500 mg/day, and 2,000 mg/day. There were no serious adverse events at any dose and the drug was well tolerated without significant side effects. AIT-082 was orally and rapidly absorbed, resulting in peak serum concentrations within 2 hours with an elimination half-life of approximately 20 hours. Higher doses resulted in corresponding increases in peak concentrations and areas under the curve (AUC). There was an approximate 2-fold accumulation in AIT-082 with daily dosing (as reflected by the AUC) at steady state. There were no significant differences by treatment arm on the clinical or neuropsychological evaluations. AIT-082 was rapidly absorbed by the oral route with a half-life suitable for dosing once or twice daily. No problems with tolerability or safety were found. AIT-082 appears suitable for testing in larger clinical trials for the treatment of AD and other neurologic disorders.

Galantamine provides broad benefits in patients with 'advanced moderate' Alzheimer's disease (MMSE < or = 12) for up to six months

We investigated whether galantamine (Reminyl), a cholinergic agent with a dual mode of action for the treatment of mild to moderate Alzheimer's disease (AD), would benefit patients with more advanced illness. We performed a post hoc analysis on pooled data from four pivotal studies in patients with 'advanced moderate' AD: baseline Mini-Mental State Evaluation (MMSE) scores < or = 12 (range 10-12; mean MMSE score 11) or Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) scores >30 (range 31-69; mean ADAS-cog score 39). Over 5-6 months, cognitive abilities were improved with galantamine versus placebo (p<0.001; mean treatment difference 6.5 points). At 6 months, galantamine benefited functional abilities (p<0.001 vs placebo). The first quartile of galantamine patients improved over baseline by 10.5 ADAS-cog points. Cognitive and functional abilities were maintained around baseline; behavioural symptoms were delayed. Over 6 months, galantamine provided a broad spectrum of benefits to patients with 'advanced moderate' AD.

Reduced levels of amyloid beta-peptide antibody in Alzheimer disease

OBJECTIVE

To investigate whether it was possible to detect the presence and different levels of naturally occurring anti-beta-amyloid (Abeta) antibodies in the CSF of patients with AD and age-matched controls by employing a sensitive ELISA.

BACKGROUND

Immunization with preaggregated amyloid beta-peptide (Abeta(1-42)) and administration of antibodies against Abeta into amyloid precursor protein APP(V717F)- transgenic mice (an animal model of AD) have recently been reported to dramatically reduce amyloid plaque deposition, neuritic dystrophy, and astrogliosis, most likely by enhancing Abeta clearance from brain.

METHODS

A sensitive ELISA was performed to detect levels of naturally occurring anti-Abeta antibodies in the CSF of patients with AD and age-matched controls. Additionally, an immunoprecipitation assay was performed to confirm that naturally occurring anti-Abeta antibodies also exist in the human blood.

RESULT

- Naturally occurring antibodies directed against Abeta were found in the CSF and plasma of patients with AD and healthy control subjects. Moreover, CSF anti-Abeta antibody titers are significantly lower in patients with AD compared with healthy control subjects.

CONCLUSION

Naturally occurring antibodies directed against Abeta exist in human CSF and plasma. The CSF anti-Abeta antibody titers may be helpful in better understanding the effects of future immunologic therapies for AD.

Chronic donepezil treatment is associated with slowed cognitive decline in Alzheimer's disease

OBJECTIVE

To compare rates of cognitive decline between probable Alzheimer's disease (AD) patients treated with long-duration cholinesterase inhibitors (ChE-Is) and those who remained untreated.

BACKGROUND

ChE-Is, including donepezil and tracrine, have shown beneficial effects on cognition and global functioning in patients with AD. The duration of these benefits is unknown because the longest double-blind placebo-controlled studies reported were only approximately 6 months long. Ethical concerns regarding randomization of patients to placebo for long periods make it difficult to undertake trials of longer duration.

METHODS

We identified patients in 4 AD centers who were or were not consistently treated with ChE-Is and who had demographic, psychometric and follow-up data. We compared 205 ChE-I-treated and 218 untreated AD patients on baseline variables hypothesized to differ between these groups, on baseline Mini Mental Status Examination (MMSE) scores and on rates of MMSE change at 1 year. The analysis was performed initially with all ChE-I-treated patients as a single group versus untreated subjects, and then with donepezil versus untreated subjects and tacrine versus untreated subjects.

RESULTS

As expected, treated and untreated patients differed with respect to age, education, ethnicity, percentage of community dwelling and exact days of follow-up (ANOVA and chi2) in several comparisons, but did not differ on baseline MMSE score. These baseline variables were highly intercorrelated. MMSE scores declined significantly more slowly after 1 year of ChE-I treatment compared to untreated patients (p = 0.05) after controlling for baseline differences in age, education, ethnicity and percentage of community dwelling. Slowing of decline was significant in the donepezil-treated patients (p = 0.007) but not in the tacrine-treated group (p = 0.33).

CONCLUSIONS

This study, utilizing concurrent, nonrandomized controls, suggests that donepezil continues to have efficacy over at least the first year of therapy. Other studies are needed to determine whether the benefits are maintained beyond 1 year.

A 52-week study of the efficacy of rivastigmine in patients with mild to moderately severe Alzheimer's disease

The efficacy of a centrally active cholinesterase inhibitor, rivastigmine tartrate (ENA 713; Exelon, in patients with mild to moderately severe Alzheimer's disease was evaluated in a 26-week open-label extension of a 26-week, double-blind, placebo-controlled study. By 52 weeks, patients originally treated with 6-12 mg/day rivastigmine had significantly better cognitive function than patients originally treated with placebo.

Epidemiology of dementia in Nigeria: results from the Indianapolis-Ibadan study

We determined the prevalence of dementia in a cohort of 2494 elderly Nigerians residents in Idikan Community, Ibadan, Nigeria. We utilized the Community Screening Instrument for Dementia to select subjects for clinical assessment in the second stage. The findings were compared with those of 2212 African Americans living in Indianapolis, studied simultaneously using similar methodology. The overall age-adjusted prevalence rates of dementia and Alzheimer's disease in Ibadan were 2.29% and 1.41%, respectively. These rates were much lower than the respective values of 8.24% and 6.24% obtained for African Americans. In Ibadan, Alzheimer's disease accounted for 64.3% of the cases, with old age and female gender being the significant risk factors, whilst 'living with others' appeared to be protective (P < 0.05). Amongst African Americans, on the other hand, old age, rural living below the age of 19 years, low educational attainment and family history of dementia were the risk factors. There was a lack of association between Alzheimer's disease and possession of the apolipoprotein E epsilon4 allele in the Nigerian sample, unlike the finding in African Americans, where significant association was shown. In addition, the frequencies of the vascular risk factors investigated were lower in Nigerians. Our results showed lower prevalence of dementia and Alzheimer's disease in Nigerians, compared with African Americans. There was no association between Alzheimer's disease and apolipoprotein E (epsilon4 allele) in the former. The differences in the frequencies of vascular risk factors between Nigerian subjects and African Americans would suggest involvement of environmental factors in disease process.

Cholinesterase inhibition for Alzheimer disease: a meta-analysis of the tacrine trials. Dementia Trialists' Collaboration

OBJECTIVES

To determine the effects of cholinesterase inhibition with tacrine hydrochloride for the symptoms of Alzheimer disease in terms of cognitive performance, clinical global impression, behavior, and functional autonomy.

DATA SOURCES

The Cochrane Dementia Group registry of trials.

STUDY SELECTION

Unconfounded, randomized, double-blind, placebo-controlled trials in which tacrine had been given for more than 1 day and that were completed before January 1, 1996.

DATA EXTRACTION

Two reviewers independently selected trials for inclusion and individual patient data were sought.

DATA SYNTHESIS

Data were analyzed from 12 trials that included 1984 patients with Alzheimer disease. At 12 weeks, cognitive performance, as measured by the Mini-Mental State Examination (score range, 0-30), was better in patients receiving tacrine than in patients receiving placebo by 0.62 points (95% confidence interval [CI], 0.23-1.00; P=.002). Compared with similar untreated patients who would be expected to deteriorate by 0.50 to 1.00 points on the Mini-Mental State Examination during 12 weeks, the progress of patients receiving tacrine would be expected to range between an improvement of 0.12 and a deterioration of 0.38 points. The odds ratio for improvement on the Clinical Global Impression of Change scale (range, 1-7) for patients receiving tacrine compared with those receiving placebo was 1.58 (95% CI, 1.18-2.11; P=.002). The behavioral noncognitive subscale of the Alzheimer's Disease Assessment Scale (range, 0-50) showed a difference in favor of tacrine of 0.58 points (95% CI, 0.17-1.00; P= .006). Improvement on the Progressive Deterioration Scale, largely an index of functional activities, was not significant (0.75; 95% CI, -0.43 to 1.93; P=.21). Age, severity of dementia, and exposure to tacrine prior to randomization had no clear influence on the treatment effect. There was a nonsignificant trend toward increasing effect with increasing dose for cognitive function and the Clinical Global Impression of Change. For patients without prior exposure to tacrine, the odds of patients' withdrawing during the study while they were receiving tacrine compared with placebo was 3.63 (95% CI, 2.80- 4.71; P<.001). Eleven (95% CI, 7-31) patients would need to be treated to achieve any improvement on the Clinical Global Impression scale, and 42 (95% CI, 23-125) to achieve a moderate or marked improvement. One patient would be expected to withdraw for every 4 (95% CI, 3-5) patients treated.

CONCLUSIONS

Cholinesterase inhibition with tacrine appears to reduce deterioration in cognitive performance during the first 3 months and increase the odds of global clinical improvement. Effects observed on measures of behavioral disturbance were of questionable clinical significance, and functional autonomy was not significantly affected. The clinical relevance of the benefits of cholinesterase inhibition remains controversial, and long-term trials with clinically relevant end points are required.

Combined tacrine and estrogen replacement therapy in patients with Alzheimer's disease

In light of evidence that estrogen replacement might affect cholinergic function, we examined possible effects of estrogen replacement therapy (ERT) on clinical response to the cholinesterase inhibitor tacrine in women with Alzheimer's disease (AD). In a previously reported 30-week, randomized, double-blind, placebo-controlled, multicenter clinical trial, 14.5% of 318 women with evaluable data had been receiving ERT before randomization. They were randomly assigned to receive placebo or tacrine. Women receiving ERT who were randomized to tacrine improved more than women not receiving ERT who were randomized either to tacrine or to placebo as assessed by cognitive (p < 0.01) and clinical global (p = 0.02) tests. These results provide evidence that prior and continuing ERT may enhance response to tacrine in women with AD. Furthermore, among women on ERT receiving tacrine, there tended to be greater improvement relative to placebo among those without an APOE-epsilon 4 allele. Randomized trials are needed.

Spheroid body myopathy revisited

Having reported spheroid body myopathy from Indiana (IN) inherited in an autosomal-dominant fashion several years ago, we now describe additional findings from the Oregon branch--briefly recorded earlier--and confirm earlier studies in another clinically affected IN member of this kinship demonstrating identical spheroid bodies within the myopathic muscle specimens. The spheroid bodies also contained increased amounts of desmin, alpha-B crystallin, and ubiquitin within muscle fibers. Our studies now have established that spheroid body myopathy is a member of the growing family of desminopathic neuromuscular conditions.

Molecular basis of phenotypic variability in sporadic Creutzfeldt-Jakob disease

We sequenced the prion protein gene and studied the biochemical characteristics and the intracerebral distribution of protease-resistant prion protein with Western blot and immunohistochemistry in 19 cases of sporadic Creutzfeldt-Jakob disease. We identified four groups of subjects defined by the genotype at codon 129 of the prion protein gene, the site of a common methionine/valine polymorphism, and two types of protease-resistant prion proteins that differed in size and glycosylation. The four Creutzfeldt-Jakob disease groups showed distinct clinicopathological features that corresponded to previously described variants. The typical Creutzfeldt-Jakob disease phenotype or myoclonic variant and the Heidenhain variant were linked to methionine homozygosity at codon 129 and to "type 1" protease-resistant prion protein. The atypical and rarer variants such as that with dementia of long duration, the ataxic variant, and the variant with kuru plaques were linked to different genotypes at codon 129 and shared the "type 2" protease-resistant prion protein. Our data indicate that the sporadic form of Creutzfeldt-Jakob disease comprises a limited number of variants. The methionine/valine polymorphism at codon 129 of the prion protein gene and two types of protease-resistant prion proteins are the major determinants of these variants. These findings suggest the existence of prion strains in humans and provide the molecular basis for a novel classification of sporadic Creutzfeldt-Jakob disease.

Familial and sporadic Alzheimer's disease: neuropathology cannot exclude a final common pathway

Whether all etiologic forms of Alzheimer's disease (AD) share a final common pathway is a major issue. We determined the severity and regional distribution of neuronal loss, amyloid plaques, neuritic plaques (NPs), and neurofibrillary tangles (NFTs), and calculated the ratio of neuronal loss to NPs and NFTs in brains of 19 familial AD (FAD) patients with linkage to chromosome 14, six AD patients with mutations of chromosome 21 (codon 717 of the beta-amyloid percursor protein gene), and 11 sporadic AD (SAD) patients. There was no difference in the pattern of distribution of the various pathologic features or in the ratio of neuronal loss to NPs or NFTs in any AD group. However, FAD groups could be distinguished from SAD by the greater severity and the lack of influence of apolipoprotein E genotype on pathology. These differences may reflect differences in age at onset rather than different etiopathologic mechanisms. The similarity of pathologic findings in the different AD groups provides evidence for a final common pathophysiologic pathway in AD.

Apolipoprotein E4 allele as a predictor of cholinergic deficits and treatment outcome in Alzheimer disease

Apolipoprotein E (apoE) is critical in the modulation of cholesterol and phospholipid transport between cells of different types. Human apoE is a polymorphic protein with three common alleles, APO epsilon 2, APO epsilon 3, and APO epsilon 4. ApoE4 is associated with sporadic and late-onset familial Alzheimer disease (AD). Gene dose was shown to have an effect on risk of developing AD, age of onset, accumulation of senile plaques in the brain, and reduction of choline acetyltransferase (ChAT) activity in the hippocampus of AD subjects. To characterize the possible impact of the apoE4 allele on cholinergic markers in AD, we examined the effect of apoE4 allele copy number on pre- and postsynaptic markers of cholinergic activity. ApoE4 allele copy number showed an inverse relationship with residual brain ChAT activity and nicotinic receptor binding sites in both the hippocampal formation and the temporal cortex of AD subjects. AD cases lacking the apoE4 allele showed ChAT activities close or within age-matched normal control values. The effect of the apoE4 allele on cholinomimetic drug responsiveness was assessed next in a group (n = 40) of AD patients who completed a double-blind, 30-week clinical trial of the cholinesterase inhibitor tacrine. Results showed that > 80% of apoE4-negative AD patients showed marked improvement after 30 weeks as measured by the AD assessment scale (ADAS), whereas 60% of apoE4 carriers had ADAS scores that were worse compared to baseline. These results strongly support the concept that apoE4 plays a crucial role in the cholinergic dysfunction associated with AD and may be a prognostic indicator of poor response to therapy with acetylcholinesterase inhibitors in AD patients.

Apolipoprotein E genotypes and Alzheimer's disease in a community study of elderly African Americans

As part of a community-based study of Alzheimer's disease (AD) in the African-American population age 65 and over, we have determined apolipoprotein E (Apo E) genotypes in 85 subjects (31 AD patients and 54 controls). The epsilon 4 allele of Apo E was strongly associated with AD in this population sample. The epsilon 4 allele frequency in AD patients was 40.3% compared with 13.9% in the control group, and 22.6% of the AD patients were homozygous for this allele compared with 3.7% of the control subjects (p = 0.01). This study extends the association of Apo E-epsilon 4 and AD to nonwhite populations and provides further evidence that the observed allelic association is biologically relevant.

Cerebrospinal fluid levels of amyloid beta-protein precursor are low in Gerstmann-Sträussler-Scheinker disease, Indiana kindred

We studied levels of amyloid beta-protein precursor (beta PP) in CSF from four patients affected with Gerstmann-Sträussler-Scheinker disease and one asymptomatic gene-carrier from an Indiana kindred. Levels of beta PP were decreased in all affected patients with the lowest levels occurring in the clinically most severely affected patients. Correlation of neuropathology with CSF data in three patients suggested that low beta PP in CSF may be associated with beta PP accumulation in neurites surrounding cortical and cerebellar amyloid deposits.

Clinical characteristics in a kindred with early-onset Alzheimer's disease and their linkage to a G-->T change at position 2149 of the amyloid precursor protein gene

Patients from five generations of a family developed presenile Alzheimer's disease (AD) early in the fifth decade. Recent memory, information-processing speed, sequential tracking, and conceptual reasoning were the earliest cognitive functions affected. Language and visuoperceptual skills were largely spared early in the course of the disease. Later, there were progressive cognitive deficits and inability to perform the activities of daily living. Death occurred, on average, 6 years after onset. Three autopsies in affected members revealed cerebral amyloid deposits and neurofibrillary tangles. Clinical and pathologic features were typical for familial AD. Direct DNA sequencing revealed a G-->T change at position 2149 of the amyloid precursor protein (APP) gene that resulted in the substitution of phenylalanine for valine in the transmembrane domain of the mature protein. This mutation was present in DNA from all four examined affected individuals and linked to the disease with a lod score of 3.25, and was the most probable cause of AD in this family.

Characterization of amyloid fibril beta-peptide in familial Alzheimer's disease with APP717 mutations

Amyloid fibrils were isolated from the brain tissue of two individuals who died with familial Alzheimer's disease, one with the phenylalanine 717 mutation in amyloid precursor protein (APP) and one with the isoleucine 717 APP mutation. After solubilization in guanidine hydrochloride and fractionation by sieve chromatography, low molecular weight fractions were treated with cyanogen bromide to generate the beta-peptide fragment starting after the methionine at position 35. Amino acid sequence analysis of all resultant peptides identified the peptide Val-Gly-Gly-Val-Val-Ile-Ala which represents residues 36-42 of the beta-amyloid peptide. No sequence beyond position 42 was found. These findings show that the amino acid substitution at position 717 is not incorporated into the amyloid deposits and suggests that the mutation may have metabolic affects which determine pathogenesis.

RFLP analysis for APP 717 mutations associated with Alzheimer's disease

Familial Alzheimer's disease (FAD) has been shown to be associated with three distinct point mutations within the same codon of the amyloid precursor protein (APP) gene. The mutation identified in the Indiana kindred is a G-->T transversion at the first position of the codon for amino acid 717, resulting in a substitution of phenylalanine for valine in the APP protein. Screening of persons at risk for the APP Phe-717 mutation using a variation of the polymerase chain reaction identified nine positives among 34 tested. In addition, DNA from 145 FAD subjects were tested for the three known APP 717 mutations.

A controlled trial of tacrine in Alzheimer's disease. The Tacrine Study Group

OBJECTIVE

To compare efficacy and safety of tacrine hydrochloride with placebo in patients with probable Alzheimer's disease.

DESIGN

A 12-week, double-blind, placebo-controlled, parallel-group study.

SETTING

Outpatients at 23 centers.

PATIENTS

Men and women with probable Alzheimer's disease, at least 50 years old, mildly to moderately impaired, without other significant medical conditions.

INTERVENTIONS

In the initial 6 weeks, patients received placebo, 20 mg/d of tacrine, or 40 mg/d of tacrine. In the second 6 weeks, half received the same treatment and half increased tacrine dose: those receiving placebo increased to 20 mg/d, those receiving 20 mg/d increased to 40 mg/d, and those receiving 40 mg/d increased to 80 mg/d.

PRIMARY OUTCOME MEASURES

Alzheimer's Disease Assessment Scale (ADAS) cognitive component and clinician-rated Clinical Global Impression of Change (CGIC).

RESULTS

Four hundred sixty-eight patients entered. After 12 weeks, dose-related improvement was significant on the ADAS cognitive (P = .014), clinician-rated CGIC (P = .014), and caregiver-rated CGIC (P = .006). Comparison of 80 mg/d with placebo showed significant improvement on the ADAS cognitive (P = .015), clinician-rated CGIC (P = .016), and caregiver-rated CGIC (P = .028). Significant effects appeared as early as 6 weeks on the ADAS cognitive and caregiver-rated CGIC. Among patients receiving 80 mg/d of tacrine, 51% achieved a four-point or greater improvement of the ADAS cognitive component after 12 weeks of treatment. Reversible asymptomatic transaminase elevations greater than three times normal occurred in 25% of patients. Other treatment-related events included nausea and/or vomiting (8%), diarrhea (5%), abdominal pain (4%), dyspepsia (3%), and rash (3%).

CONCLUSIONS

These results confirm the efficacy and safety of tacrine in some patients with Alzheimer's disease. After 12 weeks, the magnitude of the treatment effect is clinically important and recognized by the physician and caregiver. Liver toxicity is reversible and easily detected by weekly alanine aminotransferase determinations.

Low cerebrospinal-fluid concentrations of soluble amyloid beta-protein precursor in hereditary Alzheimer's disease

In Alzheimer's disease, deposits of amyloid beta-protein are apparently derived from intracellular processing of a large precursor protein. We have measured concentrations of this precursor in cerebrospinal fluid (CSF) from six members of a family affected by presenile Alzheimer's disease associated with a point mutation of the precursor gene. One gene carrier with clinical signs of the disorder had low CSF concentrations of the precursor, similar to those of three patients with sporadic Alzheimer's disease subsequently confirmed at necropsy. Two symptom-free gene carriers had CSF precursor concentrations similar to those of non-demented controls, though the value was lower in one, who had deficits revealed on neuropsychological testing, than in the other. These findings suggest that low concentrations of soluble amyloid precursor proteins in the CSF reflect the process that results in amyloid plaque formation and vascular deposition in Alzheimer's disease.

A mutation in the amyloid precursor protein associated with hereditary Alzheimer's disease

Alzheimer's disease is a form of localized amyloidosis characterized by cerebral cortical amyloid plaques, neurofibrillary tangles, and amyloid deposits within the walls of leptomeningeal vessels. Although most cases of Alzheimer's disease are sporadic, kindreds with autosomal-dominant inheritance of the syndrome suggest that a single mutation may be important in pathogenesis. Direct sequencing of DNA from a family with autopsy-proven Alzheimer's disease revealed a single amino acid substitution (Phe for Val) in the transmembrane domain of the amyloid precursor protein. This mutation correlates with the presence of Alzheimer's disease in all patients in this study, and may be the inherited factor causing both amyloid fibril formation and dementia.

The CAMDEX: a standardized instrument for the diagnosis of mental disorder in the elderly: a replication with a US sample

The Cambridge Mental Disorders of the Elderly Examination (CAMDEX) was developed by Roth, et al (1986) to assist in the early diagnosis and measurement of dementia in the elderly. In this study the CAMDEX was administered to a mixed group of independently diagnosed elderly psychiatric patients and control subjects in the United States. The CAMDEX was found to have a high interrater reliability with a mixed group of clinicians of varying backgrounds. The diagnostic scales and the cognitive section of the CAMDEX demonstrated considerable promise in distinguishing between independently diagnosed populations of depressed, demented, and normal subjects. The results suggest comparability between samples of subjects in England and the US, and that the CAMDEX is a promising instrument for use in both research and clinical settings.