Current Alzheimer Research - Volume 9, Issue 8, 2012

Different authors described that transthyretin (TTR) is decreased in the cerebrospinal fluid (CSF) of Alzheimer's disease (AD) patients and thus TTR is a potential CSF biomarker in AD. However, descriptions of what happens to TTR in plasma of these patients are lacking in the literature. We investigated TTR levels in plasma samples from 55 patients with mild-cognitive impairment (MCI), 56 patients with AD and 41 non-demented controls, and found that TTR is decreased in both MCI and AD groups, suggesting that TTR might be used for staging early AD. In MCI and AD groups, women showed significantly lower plasma TTR levels when compared to MCI and AD men, respectively, and to women control group. In the AD women group, TTR levels correlated with disease stage, reflecting disease severity. Although MCI and AD men groups presented TTR levels lower than men in the control group, the difference was not statistically significant. Genetic analysis for ApoE revealed no relationship between TTR levels and the presence of the ε4 allele, for both men and women, in both patient groups. Importantly, we assessed thyroxine binding to TTR in plasma and found, in both MCI and AD groups, that TTR had reduced capacity to carry the hormone. Finally, we measured plasma estradiol levels in women and showed a reduction in both groups. Thus, this study prompts TTR as an early plasma biomarker in AD indicating that disease modulation by TTR is gender dependent; this study provides hypotheses into the mechanisms involved.

The role of microglia in β-amyloid (Aβ) deposition or clearance in the Alzheimer's disease (AD) brain remains unclear. Previous in vivo studies have focused primarily on the association of microglia with Aβ-positive parenchymal plaques, but have given little consideration to the possible interaction between Aβ and non-plaque associated microglia. Further, it is not known if microglia play a direct role in mediating Aβ uptake following anti-aggregant treatment. We report here the identification of Aβ-positive processes throughout the cortex and hippocampus of TgCRND8 mice expressing the human Swedish (KM670/671NL) and Indiana (V717F) amyloid precursor protein mutations, which localized to ionized calcium binding protein-1-positive resident microglia that were not associated with extracellular plaques. Oral administration of 1-deoxy-1-fluoro-scyllo-inositol, a scyllo-inositol analogue, to TgCRND8 mice improved spatial memory impairments and suppressed amyloid pathology in a dose-dependent manner. Further, treatment with 1-deoxy-1- fluoro-scyllo-inositol significantly increased hippocampal intra-microglial Aβ levels without stimulating microglial proliferation or peripheral macrophage recruitment. These results reveal a novel, beneficial role for non-plaque associated microglia in the regulation of cerebral Aβ levels in a mouse model of AD.

The clinical progression of Alzheimer disease (AD) was studied in European subjects under treatment with AChE inhibitors (AChE-I) in relation to geographical location over a 2-years period. One thousand three hundred and six subjects from 11 European countries were clustered into 3 regions (North, South, West) and investigated with biannual follow-up over 2 years. Primary outcomes were cognitive, functional and behavioral measures. Caregiver burden, hospital admission and admission to nursing home were also recorded. Participant cognitive function declined non-linearly over time (MMSE: -1.5 pts/first year, -2.5 pts/second year; ADAScog: + 3.5 pts/first year, + 4.8 pts/second year), while the progression of behavioral disturbances (NPI scale) was linear. Neither scale showed regional differences, and progression of the disease was similar across Europe despite different health care systems. Functional decline (ADL, IADL) tended to progress more rapidly in Southern Europe (p=0.09), while progression of caregiver burden (Zarit Burden Interview) was most rapid in Northern Europe (5.6 pts/y, p=0.04). Incidences of hospital admission (10.44, 95%CI: 8.13-12.75, p<0.001) and admission to nursing home (2.97, 95%CI: 1.83-4.11, p<0.001) were lowest in Southern Europe. In general cognitive and functional decline was slower than in former cohorts. European geographical location reflecting differences in culture and in health care system does not impact on the progression of AD but does influence the management of AD subjects and caregiver burden.

It has been hypothesized that pro-inflammatory cytokines may play a pathogenic role in Alzheimer's disease (AD), and that n-3 polyunsaturated fatty acids may be protective against the development and progression of this disease. A reduced release of inflammatory cytokines by lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs) from AD patients dietary supplemented with a mixture of eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) was recently reported. On this basis, we investigated the possible differential effects of the two purified fatty acids on inflammatory cytokine release, a subject still not explored, even though of great pharmacological interest. We treated in vitro phytohaemagglutinin (PHA)- or LPS-stimulated PBMCs from AD patients and age-matched healthy controls (HCs) with purified EPA or DHA. Higher pro- to anti-inflammatory cytokine ratios, indicative of a pro-inflammatory profile, were observed in PHA-stimulated PBMCs from AD patients in basal conditions. The addition of both EPA and DHA markedly reduced the cytokine release, with DHA showing always a more prominent effect than EPA. However, whereas DHA reduced only the high IL-1β/IL-10 ratio, EPA was able to reduce also the IL-6/IL-10 ratio. In stimulated PMBCs from HCs the reducing effect on cytokine release was not always observed, or observed at a lower degree. In conclusion, whereas DHA appeared more powerful in inhibiting each single inflammatory cytokine, the proinflammatory profile of the AD patients' cells was better reverted by EPA to a profile more similar to that found in HCs. A combination of both the fatty acids, seems to be still the best solution.

According to the amyloid hypothesis, abnormal processing of the β-amyloid precursor protein in Alzheimer's disease patients increases the production of β-amyloid toxic peptides, which, after forming highly aggregated fibrillar structures, lead to extracellular plaques formation, neuronal loss and dementia. However, a great deal of evidence has point to intracellular small oligomers of amyloid peptides, probably transient intermediates in the process of fibrillar structures formation, as the most toxic species. In order to study the amyloid-DNA interaction, we have selected here three different forms of the amyloid peptide: Aβ1-40, Aβ25-35 and a scrambled form of Aβ25-35. Surface Plasmon Resonance was used together with UV-visible spectroscopy, Electrophoresis and Electronic Microscopy to carry out this study. Our results prove that, similarly to the full length Aβ1-42, all conformations of toxic amyloid peptides, Aβ1-40 and Aβ25-35, may bind DNA. In contrast, the scrambled form of Aβ25-35, a non-aggregating and nontoxic form of this peptide, could not bind DNA. We conclude that although the amyloid-DNA interaction is closely related to the amyloid aggregation proneness, this cannot be the only factor which determines the interaction, since small oligomers of amyloid peptides may also bind DNA if their predominant negatively charged amino acid residues are previously neutralized.

Alzheimer's disease is the most common cause of dementia in elderly persons. Quick diagnosis of Alzheimer's disease will allow treatments that may help slow its progression. The correlation between cerebrospinal fluid (CSF) parameters and progression of Alzheimer's disease is higher than and independent of other risk factors. We have compared sixteen CSF samples of clinically diagnosed Alzheimer's disease patients with non demented subjects using proteomics approach. Apolipoprotein E, apolipoprotein J, complement C4b, hemopexin and complement factor B were identified as differentially expressed proteins. Pathway analyses show that these proteins have interacting partners in Alzheimer's and apoptotic pathways. The possible roles of these proteins in relation to the disease are discussed.

Brain task-negative networks (default mode network, DMN) and task-positive networks appear to operate largely in opposition, such that task-negative networks show activation during resting states, whilst task-positive networks are deactivated with the reverse being true during goal-oriented behavior. Altered DMN and task-positive network activity has been observed in amnestic mild cognitive impairment (aMCI) subjects. However, no study has directly linked the patterns of between-state differences in the same aMCI cohort regarding these two types of functional networks. The spatial and temporal characteristics of intrinsic, low frequency BOLD signal fluctuations both during resting state and episodic memory fMRI task were assessed in 28 aMCI subjects and 23 matched healthy controls, using a posterior cingulate cortex- based temporal correlation analysis. aMCI subjects showed impaired attenuation in the DMN between rest and task state, and greater cognitive impairment was associated with decreased ability to attenuate DMN during task engagement. Moreover, more redistributed resource from DMN appeared to be required in aMCI to maintain the similar task performance possibly to offset their inability to engage task-positive networks. In order to complete a given task, mobilized and redistributed resources of DMN appeared to replace task-positive network function to some degrees in aMCI subjects. This may represent an inability to control the switching of functional modes between these types of network.

A chronic inflammatory response possibly mediated by Amyloid β (Aβ) is believed to be a major factor in the pathology of Alzheimer's disease (AD). Studies suggest that the mediators of the inflammatory response, which might contribute to brain damage, involve cytokines, such as IL-1β. IL-1β could play an important part in the development of pathologic conditions. There is also an endogenous interleukin-1 receptor antagonist (IL-1RA) in IL-1 family, which could prevent the actions of IL-1β by competing for receptor binding without inducing any signal transduction. Therefore, the balance of IL-1β vs IL-1RA is a critical parameter in determining not only whether excessive host inflammation will occur, but also the degree of subsequent host cell damage and associated toxicity. In our previous study, it has been determined that the anti-inflammatory action of Gossypium herbaceam L. extracts (GHE) was involved in its neuroprotection. However, the effects of GHE on IL-1β and IL-1RA have not been clearly defined in the experimental rat model of AD induced by Aβ. Therefore, the current study is performed to evaluate whether GHE could affect the disequilibrium of IL-1RA/IL-1β ratio in the hippocampus of rats after Aβ treatment. Subsequently, we further identify that GHE could efficaciously promote Akt and GSK3β phosphorylation, and thereby contribute to IL-1β release decrease as well as a concurrent increase in the level of IL-1RA through NF-κB and MAPK pathways. As a consequence, GHE is potentially beneficial to maintain the endogenous IL-1RA/ IL-1β balance in the hippocampus of rats and it might be a potential agent to ameliorate inflammatory process in AD.

Granular non-fibrillar aggregates (GNAs) are identified as possible toxic species in Alzheimer's disease. GNAs form on the surface of negatively charged biological membranes and as a consequence of an acidic environment, off the polymerization pathway at neutral pH. Aβ (1-40) GNAs disturb the bilayer structure of model membranes and seem to be more toxic to cells with negatively charged membranes (consequence of chronic pre-apoptosis). GNAs may be relevant in physiological situations associated to Alzheimer's disease: a local acidic pH at the cell surface (consequence of lipid oxidation or other cell insults) and acidification as a consequence of vascular events causing hypoxia. Together with previous descriptions of granular aggregates with poly-glutamine peptides related to Huntington's disease and the SH3 domain of PI3, GNAs related to Alzheimer's disease are a further example of a possible common aggregation and toxicity mechanism in conformational diseases. GNAs may represent a new pharmacological target in Alzheimer's disease.

In this article, we use longitudinal morphometry (shape and size) measures of hippocampus in subjects with mild dementia of Alzheimer type (DAT) and nondemented controls in logistic discrimination. The morphometric measures we use are volume and metric distance measures at baseline and follow-up (two years apart from baseline). Morphometric differences with respect to a template hippocampus were measured by the metric distance obtained from the large deformation diffeomorphic metric mapping (LDDMM) algorithm. LDDMM assigns metric distances on the space of anatomical images, thereby allowing for the direct comparison and quantization of morphometric changes. We also apply principal component analysis (PCA) on volume and metric distance measures to obtain principal components that capture some salient aspect of morphometry. We construct classifiers based on logistic regression to distinguish diseased and healthy hippocampi (hence potentially diagnose the mild form of DAT). We consider logistic classifiers based on volume and metric distance change over time (from baseline to follow-up), on the raw volumes and metric distances, and on principal components from various types of PCA analysis. We provide a detailed comparison of the performance of these classifiers and guidelines for their practical use. Moreover, combining the information conveyed by volume and metric distance measures by PCA can provide a better biomarker for detection of dementia compared to volume, metric distance, or both.

Alzheimer's disease (AD) is the most prevalent type of dementia. Despite considerable advances in diagnostic accuracy, diagnostic procedures that are easily accessible are still sorely needed. Blood biomarkers are therefore in the focus of research. Platelets contain a high concentration of the amyloid precursor protein (APP), which has been mentioned as a potentially useful diagnostic marker. The aim of the present study was to analyze various cell adhesion molecules (CAMs), cytokines, growth factors, and matrix metalloproteinases (MMPs) in platelets of AD and mild cognitively impaired (MCI) patients as compared to healthy controls. Our data show a significant decrease in the levels of epidermal growth factor (EGF) and of MMP-2 in platelets of AD patients and decreased levels of MMP-2 in MCI. The APP ratio was slightly but not significantly decreased in AD patients, whereas CD40L and serotonin were unchanged. Our findings demonstrate specific changes in AD platelets. Whether these biomarkers can be established as potential early diagnostic biomarkers for AD remains to be established in longitudinal studies.

Background/Aims: Hypercholesterolemia in midlife increases risk for Alzheimer's disease (AD) and contributes to cerebrovascular dysregulation - an early finding in preclinical AD pathology. Statins improve vascular reactivity, but it is unknown if they increase regional cerebral blood flow (CBF) in individuals at risk for AD. Methods: In a randomized, controlled, double-blind pilot study, 16 asymptomatic middle-aged adults with parental history of AD were randomized to atorvastatin or placebo daily for 4 months. At baseline and month 4, regional CBF was measured using arterial spin-labeling magnetic resonance imaging and endothelial function was measured using brachial artery ultrasound. Results: At baseline, participants with low HDL-cholesterol, higher global vascular risk, and greater endothelial dysfunction had reduced regional CBF in areas of the brain related to memory and learning (all p<0.03). Using voxel-based analysis, 4 months of atorvastatin increased CBF in bilateral hippocampi, fusiform gyrus, putamen and insular cortices compared to placebo. Conclusion: In this pilot study, atorvastatin increased regional CBF in persons at risk for AD. Further research is warranted to confirm whether statins increase CBF in areas of the brain related to memory and learning and whether such perfusion changes are associated with a delay in the onset of AD. Clinical Trial Registration: http://clinicaltrials.gov Identifier: NCT00751907.