Plasma biosignature and brain pathology related to persistent cognitive impairment in late-life depression.

Cognitive impairment is highly prevalent among individuals with late-life depression (LLD) and tends to persist even after successful treatment. The biological mechanisms underlying cognitive impairment in LLD are complex and likely involve abnormalities in multiple pathways, or 'cascades,' reflected in specific biomarkers. Our aim was to evaluate peripheral (blood-based) evidence for biological pathways associated with cognitive impairment in older adults with LLD. To this end, we used a data-driven comprehensive proteomic analysis (multiplex immunoassay including 242 proteins), along with measures of structural brain abnormalities (gray matter atrophy and white matter hyperintensity volume via magnetic resonance imaging), and brain amyloid-ß (Aß) deposition (PiB-positron emission tomography). We analyzed data from 80 older adults with remitted major depression (36 with mild cognitive impairment (LLD+MCI) and 44 with normal cognitive (LLD+NC)) function. LLD+MCI was associated with differential expression of 24 proteins (P<0.05 and q-value <0.30) related mainly to the regulation of immune-inflammatory activity, intracellular signaling, cell survival and protein and lipid homeostasis. Individuals with LLD+MCI also showed greater white matter hyperintensity burden compared with LLD+NC (P=0.015). We observed no differences in gray matter volume or brain Aß deposition between groups. Machine learning analysis showed that a group of three proteins (Apo AI, IL-12 and stem cell factor) yielded accuracy of 81.3%, sensitivity of 75% and specificity of 86.4% in discriminating participants with MCI from those with NC function (with an averaged cross-validation accuracy of 76.3%, sensitivity of 69.4% and specificity of 81.8% with nested cross-validation considering the model selection bias). Cognitive impairment in LLD seems to be related to greater cerebrovascular disease along with abnormalities in immune-inflammatory control, cell survival, intracellular signaling, protein and lipid homeostasis, and clotting processes. These results suggest that individuals with LLD and cognitive impairment may be more vulnerable to accelerated brain aging and shed light on possible mediators of their elevated risk for progression to dementia.

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.

An improved algorithm of white matter hyperintensity detection in elderly adults.

Automated segmentation of the aging brain raises significant challenges because of the prevalence, extent, and heterogeneity of white matter hyperintensities. White matter hyperintensities can be frequently identified in magnetic resonance imaging (MRI) scans of older individuals and among those who have Alzheimer's disease. We propose OASIS-AD, a method for automatic segmentation of white matter hyperintensities in older adults using structural brain MRIs. OASIS-AD is an approach evolved from OASIS, which was developed for automatic lesion segmentation in multiple sclerosis. OASIS-AD is a major refinement of OASIS that takes into account the specific challenges raised by white matter hyperintensities in Alzheimer's disease. In particular, OASIS-AD combines three processing steps: 1) using an eroding procedure on the skull stripped mask; 2) adding a nearest neighbor feature construction approach; and 3) applying a Gaussian filter to refine segmentation results, creating a novel process for WMH detection in aging population. We show that OASIS-AD performs better than existing automatic white matter hyperintensity segmentation approaches.

Relationship of amyloid beta and neurofibrillary tau deposition in Neurodegeneration in Aging Down Syndrome (NiAD) study at baseline.

IMPORTANCE: Adults with Down syndrome (DS) are at high-risk of revealing Alzheimer's disease (AD) pathology, in part due to the triplication of chromosome 21 encoding the amyloid precursor protein. Adults with DS are uniformly affected by AD pathology by their 30's and have a 70% to 80% chance of clinical dementia by their 60's. Our previous studies have assessed longitudinal changes in amyloid beta (Aß) accumulation in DS. OBJECTIVE: The goal of the present study was to assess the presence of brain tau using [18F]AV-1451 positron emission tomography (PET) in DS and to assess the relationship of brain tau pathology to Aß using Pittsburgh Compound B (PiB)-PET. DESIGN: Cohort study. SETTING: Multi-center study. PARTICIPANTS: Participants consisted of a sample of individuals with DS and sibling controls recruited from the community; exclusion criteria included contraindications for magnetic resonance imaging (MRI) and/or a medical or psychiatric condition that impaired cognitive functioning. EXPOSURES: PET brain scans to assess Aß ([11C]PiB) and tau ([18F]AV-1451) burden. MAIN OUTCOMES AND MEASURES: Multiple linear regression models (adjusted for chronological age, sex and performance site) were used to examine associations between regional [18F]AV-1451 standard uptake value ratio (SUVR) (based on regions associated with Braak stages 1-6) and global [11C]PiB SUVR (as both a continuous and dichotomous variable). RESULTS: A cohort of 156 participants (mean age = 39.05, SD(8.4)) were examined. These results revealed a significant relationship between in vivo Aß and tau pathology in DS. As a dichotomous variable, [18F]AV-1451 retention was higher in each Braak region in PiB(+) participants. We also found, based on our statistical models, starting with the Braak 3 region of interest (ROI), an acceleration of [18F]AV-1451 SUVR deposition with [11C]PiB SUVR increases.

Long-term effects of the concomitant use of memantine with cholinesterase inhibition in Alzheimer disease.

BACKGROUND: Patients using cholinesterase inhibitors (ChEIs) have a delay in nursing home (NH) admission compared with those who were not using the medication. There are no long-term studies of the effects of memantine in combination with ChEIs use in Alzheimer disease (AD). This study was conducted to examine the effects of ChEIs and memantine on time to death and time to NH admission. METHODS: Time to NH admission and death was examined in 943 probable AD patients who had at least a 1-year follow-up evaluation. Of these patients, 140 (14.9%) used both ChEIs and memantine, 387 (41%) [corrected] used only ChEIs, and 416 (44.1%) [corrected] used neither. The mean (SD) follow-up time was 62.3 (35.8) months. The analysis was conducted with multivariable Cox proportional hazard models controlling for critical covariates (ie, age, education level, gender, severity of the dementia, hypertension, diabetes mellitus, heart disease, psychiatric symptoms and use of psychotropic medications). RESULTS: Compared with those who never used cognitive enhancers, patients who used ChEIs had a significant delay in NH admission (HR: 0.37, 95% CI 0.27 to 0.49); this effect was significantly augmented with the addition of memantine (HR: 0.29, 95% CI 0.11 to 0.72) (memantine+ChEI vs ChEI alone). ChEIs alone, or in combination with memantine had no significant association on time to death. CONCLUSIONS: This observational study revealed that the addition of the NMDA receptor antagonist memantine to the treatment of AD with ChEI significantly altered the treated history of AD by extending time to nursing home admission.

Alpha-substituted gamma-butyrolactones: new class of anticonvulsant drugs.

Alkyl-Substituted gamma-butyrolactones were synthesized and tested for their convulsant and anticonvulsant actions in mice and guinea pigs. The alpha-substituted compounds, alpha, alpha-dimethyl-, and alpha-ethyl-alpha-methyl-gamma-butyrolactone were anticonvulsant compounds with a spectrum of activity similar to that of ethosuximide. In contrast, beta-substituted compounds were convulsant agents similar to picrotoxinin. The alpha-substituted-gama-butyrolactones represent a new class of anticonvulsant drug with experimental and clinical potential.

Anti-Amyloid Effects of Small Molecule Aß-Binding Agents in PS1/APP Mice.

AIMS: One promising approach for treatment of Alzheimer's disease (AD) is use of anti-amyloid therapies, based on the hypothesis that increases in amyloid-beta (Aß) deposits in brain are a major cause of AD. Several groups have focused on Aß immunotherapy with some success. Small molecules derivatives of Congo red have been shown to inhibit Aß aggregation and protect against Aß neurotoxicity in vitro. The agents described here are all small molecule Aß-binding agents (SMAßBA's) derivatives of Congo red. MAIN METHODS: Here, we have explored the anti-amyloid properties of these SMAßBA's in mice doubly transgenic for human prensenilin-1 (PS1) and APP gene mutations that cause early-onset AD. Mice were treated with either methoxy-X04, X:EE:B34 and X:034-3-OMe1. After treatment, brains were examined for Aß-deposition, using histochemistry, and soluble and insoluble Aß levels were determined using ELISA. KEY FINDINGS: A range of anti-amyloid activity was observed with these three compounds. PS1/APP mice treated with methoxy-X04 and X:EE:B34 showed decrease in total Aß load, a decrease in Aß fibril load, and a decrease in average plaque size. Treatment with methoxy-X04 also resulted in a decrease in insoluble Aß levels. The structurally similar compound, X:034:3-OMe1, showed no significant effect on any of these measures. The effectiveness of the SMAßBA's may be related to a combination of binding affinity for Aß and entry into brain, but other factors appear to apply as well. SIGNIFICANCE: These data suggest that SMAßBA's may significantly decrease amyloid burden in brain during the pathogenesis of AD and could be useful therapeutics alone, or in combination with immunotherapy.

Reduced binding of Pittsburgh Compound-B in areas of white matter hyperintensities.

The amyloid imaging agent, Pittsburgh Compound-B, binds with high affinity to ß-amyloid (Aß) in the brain, and it is well established that PiB also shows non-specific retention in white matter (WM). However, little is known about retention of PiB in areas of white matter hyperintensities (WMH), abnormalities commonly seen in older adults. Further, it is hypothesized that WMH are related to both cognitive dysfunction and Aß deposition. The goal of the present study was to explore PiB retention in both normal-appearing WM (NAWM) and WMH in a group of elderly, cognitively normal individuals. In a group of cognitively normal elderly (n = 64; 86.5 ± 2.6 years) two analyses were applied: (1) ROIs were placed over periventricular areas in which WMH caps are commonly seen on all subjects, regardless of WMH burden or size. (2) Subject-specific maps of NAWM and WMH were co-registered with the PiB-PET images and mean SUVR values were calculated in these NAWM and WMH maps. PiB retention was significantly reduced in the ROIs of subjects with high WMH compared to subjects with low WMH. Additionally, in subjects with high WMH, there was significantly lower PiB retention in subject-specific maps of WMH compared to NAWM, which was not observed in subjects with low WMH, likely because of the small size of WMH maps in this group. These data suggest that WM in areas of WMH binds PiB less effectively than does normal WM. Further exploration of this phenomenon may lead to insights about the molecular basis of the non-specific retention of amyloid tracers in white matter.

Chrysamine-G binding to Alzheimer and control brain: autopsy study of a new amyloid probe.

Chrysamine-G (CG) is a carboxylic acid analogue of Congo red, a histologic dye which stains amyloid. CG binds to the beta-amyloid protein of Alzheimer's disease (AD) in vitro and partitions into the brain of normal mice. In this study, we demonstrate increased binding of [14C]CG to homogenates of several regions of AD brain as compared to control. The total binding of CG to AD brain was approximately two- to three-fold that of control brain. The cerebellum could be used as an internal standard for each brain as CG binding to cerebellum did not differ between AD and control. The binding of [14C]CG correlated with numbers of senile plaques and neurofibrillary tangles. In addition, CG could be used to stain cerebrovascular amyloid in tissue sections. These results suggest that CG may prove useful as an in vivo probe of amyloid deposition in AD.

Development of small molecule probes for the beta-amyloid protein of Alzheimer's disease.

This study describes the synthesis and in vitro testing of small molecule probes that may eventually prove useful as markers of amyloid deposition in living patients. The prototype agent, Chrysamine G (CG), is a derivative of Congo red. CG binds synthetic beta-amyloid well in vitro, as does a fluorinated derivative. The mechanism of binding appears to be the same as Congo red--through a bidentate attachment spanning several amyloid peptide chains. CG is much more lipophilic than Congo red and crosses the blood-brain barrier in normal mice, achieving a brain/blood ratio over 10/1. There was no acute toxicity in mice at doses 10 times those used in the distribution studies. CG appears to be a relatively high affinity probe for beta-amyloid that appears to have low toxicity and can cross the blood-brain barrier. These characteristics are promising for development of in vivo amyloid probes similar to CG.

Clinical and neurochemical effects of acetyl-L-carnitine in Alzheimer's disease.

In a double-blind, placebo study, acetyl-L-carnitine was administered to 7 probable Alzheimer's disease patients who were then compared by clinical and 31P magnetic resonance spectroscopic measures to 5 placebo-treated probable AD patients and 21 age-matched healthy controls over the course of 1 year. Compared to AD patients on placebo, acetyl-L-carnitine-treated patients showed significantly less deterioration in their Mini-Mental Status and Alzheimer's Disease Assessment Scale test scores. Furthermore, the decrease in phosphomonoester levels observed in both the acetyl-L-carnitine and placebo AD groups at entry was normalized in the acetyl-L-carnitine-treated but not in the placebo-treated patients. Similar normalization of high-energy phosphate levels was observed in the acetyl-L-carnitine-treated but not in the placebo-treated patients. This is the first direct in vivo demonstration of a beneficial effect of a drug on both clinical and CNS neurochemical parameters in AD.

Changes in brain membrane phospholipid and high-energy phosphate metabolism precede dementia.

A 52-year-old Caucasian male was followed with Mattis and 31P MRS examinations every 6 months for 33 months. At entry into the study, the subject had a normal clinical examination and normal Mattis scores but had alterations in MRS measures of membrane phospholipid and high-energy phosphate metabolism indistinguishable from those previously reported in mildly demented AD patients. After 33 months of follow-up, the subject had clinical and Mattis findings suggestive of possible incipient dementia and after 46 months of follow-up there was sufficient cognitive decline to make the diagnosis of dementia with a frontal lobe preponderance. The findings in this subject support the contention that alterations in brain membrane phospholipid and high-energy metabolism can be noninvasively detected by 31P MRS years before any clinical manifestations of the disease.

Alterations of cerebral metabolism in probable Alzheimer's disease: a preliminary study.

Previous in vitro and in vivo 31P MRS studies of Alzheimer's disease patients have revealed alterations in membrane phospholipid metabolism and PET studies have shown alterations in glucose and oxidative metabolism. This study of probable Alzheimer's disease patients demonstrates severity dependent alterations in measures of both high-energy phosphate and membrane phospholipid metabolism. Mildly demented Alzheimer's patients compared to the controls, have increases in the levels of phosphomonoesters, decreases in the levels of phosphocreatine and probably adenosine diphosphate, and an increased oxidative metabolic rate. As the dementia worsens, the levels of phosphocreatine and adenosine diphosphate increase, the levels of phosphomonoesters decrease, and the oxidative metabolic rate decreases. The phosphomonoester findings replicate previous findings and provide a new dimension to the molecular pathology of Alzheimer's disease, implicating basic defects in membrane metabolism. The changes in oxidative metabolic rate suggest the AD brain is under energetic stress. The changes in energy metabolites with increasing dementia could be a consequence of nerve terminal degeneration and are consistent with previous PET findings. 31P MRS provides new diagnostic and metabolic insights into this disease and would be a noninvasive method to follow the progression of the disease and the metabolic response to therapeutic interventions.

Analysis of magnetic resonance spectra by mole percent: comparison to absolute units.

A variety of metabolites present in perchloric acid extracts of brain tissue were measured by 1H and 31P magnetic resonance spectroscopy (MRS) and HPLC in the same tissue sample and the MRS results were expressed both in terms of mole % and mumole/g based on an internal standard. The levels of 16 metabolites were compared by linear regression analysis and the mole % results were found to correlate very well with the results expressed as mumole/g. To compare the two units under typical experimental conditions, the percent change in metabolites in a group of Alzheimer's disease brains was compared to a control group using both units. The results were essentially identical for the mole % and mumole/g methods. We conclude that the use of the mole % method of expressing MRS data yields results which are equivalent to those expressed in absolute units and suggest that, for in vivo MRS studies, use of the mole % method is preferable because fewer artifacts, such as partial volume effects, are introduced.

Quantitative 1H and 31P MRS of PCA extracts of postmortem Alzheimer's disease brain.

Several previous studies have shown metabolic abnormalities in perchloric acid extracts of postmortem Alzheimer's disease (AD) brain by both proton (1H) and phosphorus-31 (31P) magnetic resonance spectroscopy (MRS). In all of these studies the results were expressed in relative terms, in units of mol percent. The results of this study, expressed in the absolute units of mumol/g wet weight, verify the previous 1H and 31P MRS studies. Absolute increases were found for myo-inositol, aspartate, L-glutamate, alanine, phosphocholine, and the phosphodiesters,. Absolute decreases were found for phosphoethanolamine and N-acetyl-l-aspartate. Many of these changes also were observed in non-AD dementia brain extracts, but changes in myo-inositol, inositol-l-phosphate, aspartate, and L-glutamate appeared to be more specific for AD in extracts of many brain areas. These results suggest that compounds related to membrane degradation and excitatory neuro-transmission increase in Alzheimer's disease while compounds related to neuronal integrity and inhibitory neurotransmission are decreased.

Metabolic alterations in postmortem Alzheimer's disease brain are exaggerated by Apo-E4.

Alterations in phospholipid metabolites are a characteristic abnormality of Alzheimer's disease (AD). Many of these alterations have been demonstrated by magnetic resonance spectroscopy (MRS) studies of postmortem tissue. Phosphodiesters appear to be elevated late in the disease and phosphomonoesters appear to be elevated early in the disease and then decrease. Second to aging, the most robust risk factor for AD identified to date is the presence of the E4 allele of apolipoprotein-E (Apo-E). Because apolipoproteins are intimately involved in lipid metabolism, this study was performed to determine if the presence of the Apo-E4 allele affects the abnormalities in phospholipid metabolites in AD brain. Perchloric acid extracts from 12 Apo-E 3/3, 31 3/4, 6 4/4 AD brains and 5 Apo-E 3/3 control brains were studied by both proton magnetic resonance spectroscopy and phosphorus-31 magnetic resonance spectroscopy. When the E4-positive AD samples were compared with the 3/3 AD samples, an exaggeration in both phosphomonoester and phosphodiester abnormalities was observed. The decrease in N-acetyl-L-aspartate (NAA) was also exaggerated. These results suggest membrane phospholipid metabolite alterations observed in AD are more severe in the presence of the Apo-E4 allele.

Visualization of fibrillar amyloid deposits in living, transgenic Caenorhabditis elegans animals using the sensitive amyloid dye, X-34.

Transgenic Caenorhabditis elegans animals can be engineered to express high levels of the human beta amyloid peptide (Abeta). Histochemistry of fixed tissue from these animals reveals deposits reactive with the amyloid-specific dyes Congo Red and thioflavin S (Fay et al., J. Neurochem 71:1616, 1998). Here we show by immuno-electron microscopy that these animals contain intracellular immunoreactive deposits with classic amyloid fibrillar ultrastructure. These deposits can be visualized in living animals using the newly developed, intensively fluorescent, amyloid-specific dye X-34. This in vivo staining allows monitoring of amyloid deposition in individual animals over time. The specificity of this staining is demonstrated by examining transgenic animals expressing high levels of a non-fibrillar beta peptide variant, the beta single-chain dimer. These animals have deposits immunoreactive with anti-beta antibodies, but do not have X-34 deposits or deposits with a fibrillar ultrastructure. X-34 can also be used in vivo to visualize putative amyloid deposits resulting from accumulation of human transthyretin, another amyloidic protein. In vivo amyloid staining with X-34 may be a useful tool for monitoring anti-amyloidic treatments in real time or screening for genetic alterations that affect amyloid formation.

The 5-HTTPR*S/*L polymorphism and aggressive behavior in Alzheimer disease.

BACKGROUND: Aggressive behavior in Alzheimer disease (AD) has been linked to dysfunction of serotonin neurotransmission. Homozygosity for the long variant (*L) of an identified biallelic polymorphism of the serotonin transporter promoter region (5-HTTPR) is associated with increased expression of the transporter protein and increased speed of response to serotonin reuptake inhibitor treatment. OBJECTIVE: To determine whether the *L/*L genotype and the *L allele are associated with an increased risk of aggressive symptoms in patients with AD. DESIGN: Case-control study. SETTING: University hospital geriatric psychiatry inpatient program and Alzheimer disease research center. SUBJECTS: Fifty-eight patients with AD with a history of aggressive behavior and 79 never-aggressive patients with AD with comparable severity of cognitive impairment. MAIN OUTCOME MEASURES: The 5-HTTPR genotype and allele frequency. RESULTS: The *L/*L genotype was significantly associated with aggression in patients with AD (odds ratio, 2.8; 95% confidence interval, 1.2-6.5). Similar results were obtained for *L allele frequency. CONCLUSION: The 5-HTTPR*L allele and *L/*L genotype may predispose patients with AD to develop aggressive behavior.

N-acetyl-L-aspartate and other amino acid metabolites in Alzheimer's disease brain: a preliminary proton nuclear magnetic resonance study.

We used proton nuclear magnetic resonance spectroscopy in this preliminary study of perchloric acid extracts of 12 Alzheimer's disease (AD) and five control brain samples to measure the relative levels of taurine, aspartate, glutamine, glutamate, gamma-aminobutyric acid (GABA), and the putative neuronal marker, N-acetyl-L-aspartate (NAA). We found no significant changes in taurine, aspartate, or glutamine. NAA was lower in AD compared with control, and this decrease correlated with the number of senile plaques and neurofibrillary tangles in adjacent tissue sections. GABA levels also were lower in AD brain. Glutamate levels were greater in AD than control and showed a close, inverse correlation with NAA levels. These findings suggest that the decrease in NAA reflects neuronal loss and that remaining neurons could be exposed to a relative excess of glutamate and a relative lack of GABA. If present in the neurotransmitter pool, this imbalance could result in neurotoxic cell damage. This hypothesis is further supported by in vitro and in vivo phosphorus 31 nuclear magnetic resonance findings.

Reliability of NINDS-AIREN clinical criteria for the diagnosis of vascular dementia.

We evaluated the reliability of clinical diagnoses using the recently standardized criteria for the diagnosis of vascular dementia (VaD) developed by the National Institute of Neurological Disorders and Stroke (NINDS) and the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (AIREN). Two neurologists and two psychiatrists independently reviewed clinical data abstracted from those of 42 demented subjects participating in a longitudinal study of dementia at the University of Pittsburgh. For each patient we abstracted the clinical data on a standardized form. Each physician diagnosed each case according to the NINDS-AIREN criteria, using both clinical information and MRIs. We calculated the interrater agreement for all two-way combinations of clinicians with kappa statistics, which ranged from 0.46 (moderate agreement) to 0.72 (substantial agreement). The moderate reliability observed in this study may be attributable to patient-, clinician-, or criteria-centered sources of variance.