Current Alzheimer Research - Volume 10, Issue 9, 2013

Delayed neurological health consequences of environmental exposures during military service have been generally underappreciated. The rapidly expanding understanding of Alzheimer’s disease (AD) pathogenesis now makes it possible to quantitate some of the likely long-term health risks associated with military service. Military risk factors for AD include both factors elevated in military personnel such as tobacco use, traumatic brain injury (TBI), depression, and post-traumatic stress disorder (PTSD) and other nonspecific risk factors for AD including, vascular risk factors such as obesity and obesity-related diseases (e.g., metabolic syndrome), education and physical fitness. The degree of combat exposure, Vietnam era Agent Orange exposure and Gulf War Illness may also influence risk for AD. Using available data on the association of AD and specific exposures and risk factors, the authors have conservatively estimated 423,000 new cases of AD in veterans by 2020, including 140,000 excess cases associated with specific military exposures. The cost associated with these excess cases is approximately $5.8 billion to $7.8 billion. Mitigation of the potential impact of military exposures on the cognitive function of veterans and management of modifiable risk factors through specifically designed programs will be instrumental in minimizing the impact of AD in veterans in the future decades.

Introduction A screening process that could provide early and accurate diagnosis or prognosis for Alzheimer’s disease (AD) would enable earlier intervention, and enable current and future treatments to be more effective. Ocular pathology and changes to vision and ocular function are being investigated for early detection and monitoring of AD. Objective To explore the relationship between pupil flash response (PFR) parameters, AD and brain amyloid plaque burden. Methods NineteenADandseventyhealthy control (HC) participants were recruited from the Australian Imaging, Biomarkers and Lifestyle (AIBL) Flagship Study of Ageing. Thepotential correlations betweenPFRparameters and1) AD and 2) brain amyloid plaque burden in the HC group (as a pre-clinical feature of AD), were investigated in this study. Results Our results demonstratestatistically significant relationships between PFR parameters, neocortical plaque burden and AD. A logistical model combining PFR parameters provided AD-classification performance with sensitivity 84.1%, specificity 78.3% and area under the curve 89.6%. Furthermore, some of the AD specific PFR parameters were also associated withneocortical plaque burden in pre-clinical AD. Conclusions These PFR changes show potential as an adjunct for noninvasive, cost-effective screening for pre-clinical AD.

The present study compares four different structural magnetic resonance imaging techniques used to measure gray matter (GM) atrophy in Alzheimer’s disease (AD): manual and automated volumetry, cortical thickness (CT) and voxel-based morphometry (VBM). These techniques are used interchangeably in AD research and thus far it is unclear which technique is superior in detecting abnormalities early in the disease process. 18 healthy participants without any memory impairment, 18 patients with MCI, and 17 patients with mild AD were included and between-group differences were investigated in AD signature regions (areas in the prefrontal cortex (PFC), medial temporal lobe (MTL) and posterior parietal cortex (PPC)). Both manual volumetric measurements and VBM were able to detect GM atrophy in the early stages (differentiation controls and MCI), mainly in the MTL. In the early phase, automated volumetric measurements showed GM differences in the PPC but not in the MTL. In our sample, CT measurements were not sensitive for group differences in the early stages. PFC regions showed abnormalities in the later stages (controls vs AD) when manual volumetric measurements or VBM are employed. Manual volumetric measurements together with VBM are preferred techniques for assessing GM differences showing abnormalities in most of the investigated regions, with a predominance of the MTL in the early phase. Automated FreeSurfer volumetric measurements show similar performances in the early phase, displaying group differences in the PPC but not in MTL regions. Measurements of CT are less sensitive in the MCI stage and its sensitivity is restricted to the MTL and PPC regions in later stages of the disease (AD).

Background: Considering the scarcity of longitudinal assessments of reliability, there is need for a more precise understanding of cognitive decline in Alzheimer’s Disease (AD). The primary goal was to assess longitudinal changes in inter-rater reliability, test retest reliability and internal consistency of scores of the ADAS-Cog. Methods: 2,618 AD subjects were enrolled in seven randomized, double-blind, placebo-controlled, multicenter-trials from 1986 to 2009. Reliability, internal-consistency and cross-sectional analysis of ADAS-Cog and MMSE across seven visits were examined. Results: Intra-class correlation (ICC) for ADAS-Cog was moderate to high supporting their reliability. Absolute Agreement ICCs 0.392 (Visit-7) to 0.806 (Visit-2) showed a progressive decrease in correlations across time. Item analysis revealed a decrease in item correlations, with the lowest correlations for Visit 7 for Commands (ICC=0.148), Comprehension (ICC=0.092), Spoken Language (ICC=0.044). Discussion: Suitable assessment of AD treatments is maintained through accurate measurement of clinically significant outcomes. Targeted rater education ADAS-Cog items over-time can improve ability to administer and score the scale.

Due to the increasing incidence of Alzheimer’s disease (AD), many studies have aimed to improve its diagnosis. Particular attention has been focused on measuring volumes of brain structures. Only few studies have investigatedwhether the cerebellar volume changes with the stage of dementia. It is controversial whether the serum apolipoprotein E (ApoE) level is an appropriate AD marker. This study was designed to clarify the significance of both cerebellar volume measurements and ApoE level measurements as markers of neurodegenerative changes. This study included 55 subjects with AD, 30 subjects with mild cognitive impairments (MCI), and a control group with 30 subjects. We measured the brain, cerebellum, and brain stem volumes with magnetic resonance imaging (MRI). We determined serum ApoE levels, APOE genotypes, and neuropsychological test scores. In the control group, we found that ApoE levels were significantly higher for subjects with the APOE 2/3 genotype than those with the 4/4 genotype. This finding may indicate that ApoE plays a protective role against AD development in subjects with the APOE 2/3 genotype. ApoE levels were not significantly different in patients with AD and MCI. No correlations were found between serum ApoE levels and Mini-Mental State Examination (MMSE) scores or the volumes of brain structures. This study could not confirm the appropriateness of the cerebellum volume as an early AD marker. Correlations were found between cerebellar volume, brain volume, and the MMSE scores.

Aim: Substantial evidence links atherosclerosis and Alzheimer’s disease (AD). Apolipoproteins, such as apolipoprotein E, have a causal relationship with both diseases. The rs11136000 SNP within the CLU gene, which encodes clusterin (apolipoprotein J), is also associated with increased AD risk. The aim of this study was to investigate the relationship between plasma clusterin and the rs11136000 genotype in mild cognitive impairment (MCI) and AD. Methods: Plasma and DNA samples were collected from control, MCI and AD subjects (n=142, 111, 154, respectively). Plasma clusterin was determined by ELISA and DNA samples were genotyped for rs11136000 by TaqMan assay. Results: Plasma clusterin levels were higher in MCI and AD subjects vs. controls (222.3±61.3 and 193.6±58.2 vs. 178.6±52.3 µg/ml, respectively; p<0.001 for both comparisons), and in MCI vs. AD (p<0.05). Plasma clusterin was not influenced by genotype in the MCI and AD subjects, although in control subjects plasma clusterin was lower in the TT vs. TC genotypes (157.6±53.4 vs. 188.6±30.5 µg/ml; p<0.05). Conclusion: This study examined control, MCI and AD subjects, identifying for the first time that plasma clusterin levels were influenced, not only by the presence of AD, but also the transitional stage of MCI, while rs11136000 genotype only influenced plasma clusterin levels in the control group. The increase in plasma clusterin in MCI and AD subjects may occur in response to the disease process and would be predicted to increase binding capacity for amyloid-beta peptides in plasma, enhancing their removal from the brain.

Serum levels of β-amyloid (Aβ) peptides may represent an early biomarker in the diagnosis of Alzheimer’s disease (AD). In the present study, we investigated the temporal kinetic changes in the levels of serum Aβ 1-42 and 40 in an amyloid precursor protein (APP)/presenilin (PS)1 double transgenic mouse model of AD. Serum Aβ peptide levels in 2-, 3-, 6-, 9- and 18-month old, and liver Aβ 1-40 level in 6-month old mice were measured using enzyme-linked immunosorbent assay (ELISA) kits. Results revealed that serum Aβ levels peaked in 3-month old transgenic mice, and the Aβ level in non-transgenic and transgenic mice is comparable in liver. Compared to the 6-month old transgenic mice, Congo red staining showed that the 3-month old transgenic mice had minimum brain Aβ plaques, corresponding to the early stage of Alzheimer-like plaque pathology, and confocal microscope images showed that the deposition of Aβ in their cerebral vessels was minimal. Furthermore, results of the water maze test, showed that memory was normal for the 3- month old transgenic mice when compared to age-matched non-transgenic mice. These results suggest that serum Aβ peptide levels may be peaked during the early stage of AD. Monitoring serum Aβ peptide levels in the potential AD population may provide an early diagnosis of AD prior to the appearance of clinical symptoms.

Neurodegeneration is induced by tryptamine, a human diet constituent, which easily crosses the blood/brain barrier. Tryptamine neurotoxicity, caused by tryptophanyl-tRNA synthetase (TrpRS) inhibition and downregulation leads to tryptophanyl-tRNA deficiency and synthesis of aberrant proteins. We identified axonal defects in hippocampus of tryptamine- treated mice similar to those observed in human brain of patients with Alzheimer's disease, multiple sclerosis and epilepsy using anti-TrpRS site-directed antibodies. The axonal defects are characterized by swellings that accumulate abnormal amounts of helical filaments and amyloid. Tryptamine produced a decreased density of somatic mitochondria concomitant with neuronal loss in mouse hippocampus. In addition, tryptamine evoked accumulation and clustering of small mitochondria in mouse hippocampus causing axonal swellings. Similarly, mitochondrial fission, fusion and clustering were revealed in human neuronal cells after tryptamine administration. Moreover the tryptamine-induced mitochondrial neuropathology includes electron-dense deposits comprising helical fibrils, cristae disruption, cristolysis, mitochondrial swelling and mitochondria-derived vesicles. TrpRS+ helical filamentous tangles formed in both neuronal and kidney cells following tryptamine treatment suggest a tryptamine broad cytotoxic repertoire in damaging vital organs. Tryptamine elicited vesicularization of inner and outer mitochondrial membranes, axonal and cell membranes. Ultrastructurally, fragmentation of swollen degenerated mitochondria, small mitochondria clustering and neurofibrillary tangles are associated with axonal membrane protrusions attributed as neuritic swellings at a lower magnification. TrpRS+ axonal swellings associated with neuropathology of patients and tryptamine-treated human cells suggest that under toxic concentrations, tryptamine is implicated as a causative agent in neurodegeneration resembling that defining a number of human diseases.

Alzheimer's disease (AD) is a neurodegenerative disease that is a great public health problem worldwide. The cause and mechanism of AD are not well understood. Inhalational anesthetics have been suggested to induce neurotoxicity, leading to memory deficits and the progression of AD. However, recent data have shown that inhalational anesthetics may protect against neurotoxicity and are not associated with an increased risk of AD. We used a Drosophila model to directly investigate the neurologic effects of the inhalational anesthetic sevoflurane on AD. Five- to six-day-old control and AD-transgenic flies were exposed to 2.1% or 3% sevoflurane 4 and 16 times for 1 hour each time. Electroretinograms (ERG), retinal immunohistochemistry, climbing ability, and survival were analyzed after sevoflurane treatment. The data were evaluated using Student’s t-test or a one-way ANOVA with a supplementary Fisher’s LSD (Least Significant Difference) test. Statistical significance was set at p<0.05. The ΔERG, climbing ability, and survival were lower in ADtransgenic flies. Exposure to 2.1% sevoflurane 4 and 16 times and to 3% sevoflurane 16 times rescued the ΔERG in ADtransgenic flies. Sevoflurane exposure did not attenuate the climbing ability or survival of control and AD-transgenic flies. The inhalational anesthetic sevoflurane might not have exerted neurotoxic effects on control and AD-transgenic flies; in fact, sevoflurane might confer selective neuroprotection on the retinal function of AD-transgenic flies. These results suggest the need for future studies to determine the potential effects of anesthetics on AD-associated neuroprotection or neurotoxicity.