The pre-symptomatic stage of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD) occurs several decades before the clinical onset. Changes in the lysosomal network, i.e. the autophagosomal, endosomal and lysosomal vesicular system, are among the first alterations observed. There are currently no treatments to slow or cure neurodegenerative diseases, and there is a great need for discovery of treatment targets in cellular pathways where pathology pre-dates the neuronal death. It is also crucial to be able to diagnose neurodegenerative diseases earlier, both to enable early intervention treatment and aid in selecting clinical trial populations before the patient has widespread pathology. This thesis aims at investigating the potential of lysosomal network proteins as biomarkers and therapeutic targets in neurodegenerative disease. A targeted search for lysosomal network proteins was performed in cerebrospinal fluid (CSF) from AD patients, and seven proteins: early endosomal antigen 1 (EEA1), lysosomal-associated membrane proteins 1 and 2 (LAMP-1, LAMP-2), lysozyme, microtubule-associated protein 1 light chain 3 (LC3), Rab3 and Rab7, were elevated. The levels of EEA1, LAMP-1, LAMP-2, LC3, lysozyme and Rab3 were also measured in CSF from parkinsonian syndrome patients: PD, clinically diagnosed 4-repeat tauopathy, pathologically confirmed corticobasal degeneration (CBD) and pathologically confirmed progressive supranuclear palsy (PSP) patients. LAMP-1 and LAMP-2 were decreased in PD. LC3 and lysozyme levels were increased in 4-repeat tauopathy patients. EEA1 was decreased and lysozyme increased in PSP, and LAMP-1, LAMP-2, LC3 and lysozyme were increased in CBD. The lysosomal network proteins had different CSF protein profiles in all the parkinsonian syndromes, as well as in AD. It should be emphasized that only a select few of the lysosomal network proteins were observed to be changed, rather than a general change in lysosomal network proteins, which implicates the involvement of these seven proteins in specific pathological processes. The most interesting candidates, LAMP-2 and lysozyme, were selected for further study for their involvement in the pathology of AD. Lysozyme was found to co-localise with Aβ plaques in AD patients and overexpression prolonged survival and improved the activity in a Drosophila model of AD. Lysozyme was found to alter the aggregation pathway of Aβ1-42, to counteract the formation of toxic Aβ species and to protect from Aβ1-42 induced cell toxicity. Aβ1-42 in turn was found to increase the expression of lysozyme in both neuronal and glial cells. These data suggest that lysozyme levels rise in AD as a compensatory response which is protective against Aβ associated toxicity. LAMP-2 mRNA and protein were found increased in brain areas relevant for AD pathology and various cellular models showed complex involvement of LAMP-2 in Aβ related pathology, with extensive crosstalk between LAMP-2 and Aβ. Exposure to oligomeric Aβ1-42 caused an upregulation of LAMP-2 and in turn, overexpression of LAMP-2 caused a reduction in secreted levels of Aβ1-42, as well as changing the generation pattern of Aβ and affecting clearance and secretion of Aβ1-42. These data indicate that the increased levels of LAMP-2 in AD could be an attempt to regulate Aβ generation and secretion. In summary, this thesis reports that utilising lysosomal network proteins as biomarkers and novel therapeutic targets for neurodegenerative diseases holds great promise.

Introduction: La démence peut être causée par la maladie d’Alzheimer (MA), la maladie cérébrovasculaire (MCEREV), ou une combinaison des deux. Lorsque la maladie cérébrovasculaire est associée à la démence, les chances de survie sont considérées réduites. Il reste à démontrer si le traitement avec des inhibiteurs de la cholinestérase (ChEIs), qui améliore les symptômes cognitifs et la fonction globale chez les patients atteints de la MA, agit aussi sur les formes vasculaires de démence. Objectifs: La présente étude a été conçue pour déterminer si la coexistence d’une MCEREV était associée avec les chances de survie ou la durée de la période jusqu’au placement en hebergement chez les patients atteints de la MA et traités avec des ChEIs. Des études montrant de moins bons résultats chez les patients souffrant de MCEREV que chez ceux n’en souffrant pas pourrait militer contre l’utilisation des ChEIs chez les patients atteints à la fois de la MA et la MCEREV. L'objectif d'une seconde analyse était d'évaluer pour la première fois chez les patients atteints de la MA l'impact potentiel du biais de « temps-immortel » (et de suivi) sur ces résultats (mort ou placement en hebergement). Méthodes: Une étude de cohorte rétrospective a été conduite en utilisant les bases de données de la Régie de l’Assurance Maladie du Québec (RAMQ) pour examiner la durée de la période jusqu’au placement en hebergement ou jusqu’au v décès des patients atteints de la MA, âgés de 66 ans et plus, avec ou sans MCEREV, et traités avec des ChEIs entre le 1er Juillet 2000 et le 30 Juin 2003. Puisque les ChEIs sont uniquement indiquées pour la MA au Canada, chaque prescription de ChEIs a été considérée comme un diagnostic de la MA. La MCEREV concomitante a été identifié sur la base d'un diagnostic à vie d’un accident vasculaire cérébral (AVC) ou d’une endartériectomie, ou d’un diagnostic d'un accident ischémique transitoire au cours des six mois précédant la date d’entrée. Des analyses séparées ont été conduites pour les patients utilisant les ChEIs de façon persistante et pour ceux ayant interrompu la thérapie. Sept modèles de régression à risque proportionnel de Cox qui ont varié par rapport à la définition de la date d’entrée (début du suivi) et à la durée du suivi ont été utilisés pour évaluer l'impact du biais de temps-immortel. Résultats: 4,428 patients ont répondu aux critères d’inclusion pour la MA avec MCEREV; le groupe de patients souffrant seulement de la MA comptait 13,512 individus. Pour le critère d’évaluation composite considérant la durée de la période jusqu’au placement en hebergement ou jusqu’au décès, les taux de survie à 1,000 jours étaient plus faibles parmi les patients atteints de la MA avec MCEREV que parmi ceux atteints seulement de la MA (p<0.01), mais les différences absolues étaient très faibles (84% vs. 86% pour l’utilisation continue de ChEIs ; 77% vs. 78% pour la thérapie avec ChEIs interrompue). Pour les critères d’évaluation secondaires, la période jusqu’au décès était plus courte chez les patients avec la MCEREV que sans la MCEREV, mais la période jusqu’au vi placement en hebergement n’était pas différente entre les deux groupes. Dans l'analyse primaire (non-biaisée), aucune association a été trouvée entre le type de ChEI et la mort ou le placement en maison d'hébergement. Cependant, après l'introduction du biais de temps-immortel, on a observé un fort effet différentiel. Limitations: Les résultats peuvent avoir été affectés par le biais de sélection (classification impropre), par les différences entre les groupes en termes de consommation de tabac et d’indice de masse corporelle (ces informations n’étaient pas disponibles dans les bases de données de la RAMQ) et de durée de la thérapie avec les ChEIs. Conclusions: Les associations entre la coexistence d’une MCEREV et la durée de la période jusqu’au placement en hebergement ou au décès apparaissent peu pertinentes cliniquement parmi les patients atteints de la MA traités avec des ChEIs. L’absence de différence entre les patients atteints de la MA souffrant ou non de la MCEREV suggère que la coexistence d’une MCEREV ne devrait pas être une raison de refuser aux patients atteints de la MA l’accès au traitement avec des ChEIs. Le calcul des « personne-temps » non exposés dans l'analyse élimine les estimations biaisées de l'efficacité des médicaments. / Introduction: Dementia may be caused by Alzheimer’s disease (AD), cerebrovascular disease (CVD), or a combination of both. When CVD is associated with dementia, survival is thought to be reduced. It is unclear whether treatment with cholinesterase inhibitors (ChEIs), which has been found to improve cognitive symptoms and global function in AD patients, has similar benefits in vascular forms of dementia. Objectives: The present study was designed to determine whether co-existing CVD is associated with survival or time to nursing home placement (NHP) among AD patients treated with ChEIs. Findings of poorer outcomes in patients with versus without CVD might argue against the use of ChEIs for AD patients in whom CVD co-exists. The objective of a second analysis was to assess for the first time in patients with AD the potential impact of immortal time (and followup) bias on risk for these outcomes. Methods: A retrospective cohort study was undertaken using the Régie de l’Assurance Maladie du Québec (RAMQ) databases to examine the time to NHP or death for AD patients aged 66+, with or without CVD, treated with ChEIs between July 1, 2000, and June 30, 2003. Because ChEIs are approved only for AD in Canada, a ChEI prescription was used as a surrogate for an AD diagnosis. Concomitant CVD was identified on the basis of a lifetime diagnosis of stroke or ii endarterectomy, or a diagnosis of transient ischemic attack within the six months prior to the index date. Separate analyses were performed for patients with persistent ChEI use and those who discontinued ChEI therapy. Seven Cox proportional hazard regression models which varied in the definition of the index date (start of follow-up) and the duration of follow-up were used to evaluate the impact of immortal time bias. Results: 4,428 patients met inclusion criteria for AD with CVD; 13,512 were classified as having AD alone. For the composite endpoint of NHP or death, 1,000-day survival rates were lower among AD patients with versus without CVD (p<0.01), but absolute differences were very small (84% vs. 86% with continuous ChEI use; 77% vs. 78% with discontinuous ChEI therapy). Of the secondary endpoints, time to death was shorter for patients with versus without CVD, but time to NHP did not differ between groups. In the primary, unbiased analysis, no association was found between ChEI treatment type and death or NHP. However, after introduction of immortal time bias, a strong differential effect was observed. Limitations: Results may have been affected by selection (misclassification) bias, between-group differences in smoking and body mass index (information on which was not available in the RAMQ databases), and duration of ChEI therapy. Conclusions: Associations between co-existing CVD and time to NHP or death appeared to be of little clinical relevance among AD patients treated with ChEIs. iii The lack of difference between AD patients with and without CVD suggests that CVD should not be used as a reason to deny AD patients access to ChEI treatment. Properly accounting for unexposed person-time in the analysis eliminates biased estimates of drug efficacy.

In this thesis study we examined glycogen synthase kinase-3β (GSK-3β) and its effects over Nrf2 and Pin 1 as it relates to Alzheimer’s disease (AD). AD is a neurodegenerative disease characterized by a prolonged high oxidative environment. Transcription factor Nrf2 is vital in the brain’s defense against oxidative insults through its up-regulation of over 100 antioxidants. Depletion of the brain’s antioxidant defense system results in intolerance to an oxidative environment, contributing to the progression of AD. The regulatory Pin 1 protein promotes cellular homeostasis, and when down-regulated results in increased deposits of neurofibrillary tangles (NFTs) and amyloid-β (Aβ) plaques, the two pathological hallmarks of AD. Using aged SAMP8 mice treated with antisense oligonucleotide (AO) directed at GSK-3β and random AO, the data presented here demonstrate decreased oxidative stress and increased Nrf2 transcriptional activity and Pin 1 levels as a result of the down-regulation of GSK-3β. Collectively, these results implicate GSK-3β activity in the increased oxidative stress of AD and support its inhibition as a possible therapeutic treatment for the disease. Further, we elucidate a possible mechanism connecting GSK-3β to the loss of tolerance to an oxidative environment and increased deposits of NFTs and Aβ plaques observed in AD.

Today, as we live longer, dementia diseases are becoming more prevalent around the world. Thus, further knowledge of how to maintain levels of cognitive functioning in old age and how to identify factors that postpone the onset of dementia are of acute interest. Lifestyle patterns and social life are important aspects to consider in this regard. This thesis includes three studies. Study I investigated the association between participation in various leisure activities in old age (≥65 years) and risk of incident all-cause dementia. Analyses of the total follow-up time period (15 years) showed that higher levels of “Social” and “Total” leisure activity were associated with decreased risk of dementia. In Study II, the aim was to investigate the association between various aspects of social relationships in old age (≥65 years) and risk of incidents of all-cause dementia and Alzheimer's disease. Results showed that over the total follow-up period (16 years) higher values on the relationship index were associated with reduced risk of both dementia and Alzheimer's disease. Visiting/visits of friends and acquaintances more than once a week was related to decreased risk for all-cause dementia, but not for Alzheimer's disease. However, in neither Study I nor II did any of these factors alter the risk of all-cause dementia or Alzheimer's disease when near-onset dementias were removed from the analyses (Study I, up to five years; Study II, up to three years). In Study III the aim was to investigate the association between social network size and cognitive ability in a middle-aged (40–60 years) sample. The idea was that if social network size can moderate negative age-related influence on memory functions, it might also put an individual on a cognitive trajectory that is beneficial in old age. Results from longitudinal analyses showed that baseline network size was positively related to five-year changes in semantic memory and with changes in both semantic and episodic memory at the ten-year follow-up. Social network size was unrelated to changes in visuospatial performance. Taken together, enrichment factors measured in old age (≥ 65 years) did not alter the risk of all-cause dementia or Alzheimer's disease when near-onset dementias were removed from the analyses. These results might reflect protective short-term effects or reverse causality, meaning that in the prodromal phase of dementia individuals tend to withdraw from activity. Social network size in middle age (40-60 years), however, appears to have beneficial long-term effects on cognitive functioning. The results highlight the importance of long follow-up periods and the need to adjust for the influences of reverse causality when investigating the impact of a socially and mentally active life on cognitive functioning.

Proteins are fundamental structural, enzymatic and regulatory components of cells. Analysis of proteins, such as by measuring their concentrations, characterizing their modifications, and detecting their interactions, provides insights in how biological systems work physiologically or pathologically at the molecular level. To perform such analysis, molecular tools with good sensitivity, specificity, high multiplexing and throughput capacity are needed. In this thesis, four different assays were developed and applied to detect and profile proteins and protein complexes in human body fluids, and in cells or tissues. These assays are based on targeting proteins or protein complexes by oligonucleotide-conjugated antibodies, and subsequent proximity dependent enzymatic reactions involving the attached DNA reporter sequences. In paper I, a solid-phase proximity ligation assay (SP-PLA) was applied to detect synthetic and endogenous amyloid beta protofibrils. The SP-PLA provided better sensitivity and increased dynamic range than a traditional enzyme-linked immunosorbent assay (ELISA). In paper II, in situ PLA was applied to investigate the correlation between MARK2-dependent phosphorylation of tau and Alzheimer’s disease. Greater numbers of MARK2-tau interactions and of phosphorylated tau proteins were observed in brain tissues from Alzheimer’s patients than in healthy controls. In paper III, a multiplex SP-PLA was applied to identify protein biomarker candidates in amyotrophic lateral sclerosis (ALS) disease and in the analgesic mechanism of spinal cord stimulation (SCS). Among 47 proteins in human cerebrospinal fluid (CSF) samples, four were found at significantly lower concentrations (p-values &lt; 0.001) in the samples from ALS patients compared to those from healthy controls (follistatin, IL-1α, IL-1β, and KLK5). No significant changes of the analyzed proteins were found in the CSF samples of neuropathic pain patients in   the stimulated vs. non-stimulated condition using SCS. In paper IV, a new technology termed the proximity barcoding assay (PBA) was developed to profile individual protein complexes. The performance of PBA was demonstrated on artificially assembled streptavidin-biotin oligonucleotide complexes. PBA was also proven to be capable of profiling transcriptional pre-initiation complexes from nuclear extract of a hepatic cell line.

Objective: To study awareness of cognitive dysfunction in patients with very mild Alzheimer’s disease (AD) and subjects with mild cognitive impairment (MCI). Methods: A complaint interview covering 13 cognitive domains was administered to 82 AD and 79 MCI patients and their caregivers. The patient groups were comparable according to age and education, and Mini Mental State Examination (MMSE) scores were ≥24 in all cases. The discrepancy between the patients’ and caregivers’ estimations of impairments was taken as a measure of anosognosia. Results: Self-reports of cognitive difficulties were comparable for AD and MCI patients. However, while in comparison to caregivers MCI patients reported significantly more cognitive impairment (p < 0.05), AD patients complained significantly less cognitive dysfunctions (p < 0.001). Conclusions: While most MCI patients tend to overestimate cognitive deficits when compared to their caregiver’s assessment, AD patients in early stages of disease underestimate cognitive dysfunctions. Anosognosia can thus be regarded as a characteristic symptom at a stage of very mild AD (MMSE ≥24) but not MCI. Accordingly, medical history even in mildly affected patients should always include information from both patient and caregiver. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

L’originalité de cette recherche est de s’intéresser aux caractéristiques de l’environnement physique et à leur impact sur les capacités de navigation et de mémoire spatiale. Ce domaine jusqu’alors peu investigué, représente pourtant un enjeu sociétal pour l’autonomie et le bien-être de la personne. Des difficultés de navigation ont notamment été décrites dans le vieillissement normal et la maladie d’Alzheimer (MA) dès le stade débutant. Or, l’environnement physique peut soutenir les capacités/compétences spatiales des individus, ou au contraire les perturber. L’objectif de cette recherche est d’évaluer l’effet structurant des éléments d’un environnement réel riche en repères, le jardin thérapeutique « art, mémoire et vie » du CHRU de Nancy, sur l’apprentissage d’un trajet et l’acquisition des connaissances spatiales, chez une population de sujets atteints de MA. En effet l'organisation spatiale de ce jardin a été conçue pour contribuer entre autres, à atténuer les difficultés de ces personnes en termes de cognition spatiale.L’ensemble des éléments du jardin a été répertorié et intégré dans une classification inspirée des travaux de Lynch (1960) et Zeisel et Tyson (1999). Trente sujets à un stade léger à modéré de la MA et 30 sujets âgés sains appariés ont réalisé le protocole suivant : (1) un apprentissage de trajet (aller et retour), durant lequel leur description verbale du parcours était enregistrée ; (2) une série de tâches évaluant l’acquisition des connaissances spatiales ; (3) des tests cognitifs standards. Le discours a été retranscrit verbatim et soumis à une analyse de contenu. Les résultats montrent une capacité d’apprentissage de trajet résiduelle significative chez les sujets du groupe MA, tant à l’aller qu’au retour. La répétition du trajet et la richesse de l’environnement en termes de repère semblent avoir contribué à ce résultat. Les performances aux tâches expérimentales ont été croisées avec l’analyse du discours et avec les tests cognitifs standards. Les résultats mettent en évidence un rôle prépondérant de certaines caractéristiques des éléments de l’environnement, telles que la saillance et l’affordance, sur les performances d’apprentissage de trajet et de mémoire spatiale et ceci de manière encore plus marquée chez les sujets du groupe MA. L’effet structurant des éléments de l’environnement est discuté d'une part chez les sujets âgés sains au regard des processus cognitifs impliqués dans la navigation et l’acquisition des connaissances spatiales et d'autre part des processus préservés et dysfonctionnels au cours de la MA / The originality of this research is to focus on the characteristics of the physical environment and their impact on navigation and spatial memory capabilities. This field, until then little investigated, represents a societal stake for the autonomy and the well-being of the person. In particular, navigation difficulties have been described in normal aging and Alzheimer's disease (AD) in the early stage. However, the physical environment can support individuals' spatial abilities/skills, or, on the contrary, disrupt them.The aim of the present study is to assess the structuring effect of the elements of a real environment rich in landmarks, the “art, memory and life” healing garden of the CHRU of Nancy, on route learning, and on the acquisition of the spatial knowledge, in a population of subjects with AD. Indeed, the spatial organization of this garden has been designed to contribute, among other things, to alleviate the difficulties of these people in terms of spatial cognition.All the elements of the garden have been listed and integrated into a classification inspired by the works of Lynch (1960) and Zeisel and Tyson (1999). Thirty subjects with mild to moderate AD and 30 matched healthy subjects underwent the following protocol: (1) route learning (forward and return trips), during which the verbal description of the route was recorded; (2) a series of tasks assessing the acquisition of spatial knowledge of the garden as well as (3) standard cognitive tests. The speech was transcribed verbatim and subjected to a content analysis.The results show a significant residual route learning ability in the MA group, both on the forward and return trips. The repetition of the route and the richness of the environmental landmarks seem to have contributed to this result. Experimental task performances were cross-checked with discourse analysis and standard cognitive tests. The results highlight a preponderant role of certain characteristics of environmental elements, such as saliency and affordance, on the learning performances of route and spatial memory, and this even more markedly in the subjects of the MA group.The structuring effect of the elements of the environment is discussed on the one hand in healthy older subjects with regard to cognitive processes involved in the navigation and acquisition of spatial knowledge and on the other hand preserved and dysfunctional processes in the course of Alzheimer’s disease

No description available.

Introdução: Com o envelhecimento da população mundial projeta-se o crescimento das taxas de doenças potencialmente relacionadas à idade como as demências, especialmente a doença de Alzheimer (DA). Os sujeitos com Comprometimento Cognitivo Leve (CCL) são considerados uma população de risco para desenvolver demência, no entanto, as taxas de incidência de CCL e conversão para demência apresentam considerável variabilidade em parte atribuída a características da amostra e aos diferentes critérios utilizados. Objetivos: Determinar a incidência de demência e Comprometimento Cognitivo Leve em uma coorte de idosos saudáveis de base comunitária; determinar as variáveis demográficas, clínicas e sociais associadas ao desenvolvimento de prejuízo cognitivo, e avaliar o risco de progressão dos indivíduos com Comprometimento Cognitivo Leve para demência comparada com sujeitos cognitivamente normais. Métodos: Os dados foram derivados de uma coorte de idosos residentes na comunidade (N = 345), inicialmente saudáveis e independentes (Estudo PALA - Porto Alegre Longitudinal Aging - study). O seguimento inicial com duração máxima de oito anos teve o objetivo de avaliar a incidência de DA e CCL. Para avaliar a progressão de CCL para DA partimos de 10 anos de seguimento, incluindo os oito anos da primeira análise e consideramos um máximo de 70 meses (média de 45 meses) para avaliar a ocorrência dos novos desfechos. Os participantes que preencheram os critérios de inclusão do estudo e consentiram em participar foram avaliados com uma detalhada entrevista clínica composta de variáveis demográficas, clínicas e sociais. Os sintomas psiquiátricos foram avaliados pela escala SRQ - Self Report Questionnaire, escala MADRS - Montgomery-Asberg Depression Rating Scale e aplicados os critérios para depressão maior do Manual de Diagnóstico e Estatístico de Transtornos Mentais (4ª Edição; DSM-IV). O Mini Exame do Estado Mental (MEEM) e a Escala Clínica de Demência (CDR – Clinical Dementia Rating) foram aplicados para avaliação cognitiva. Adicionalmente a independência para as atividades da vida diária foram acessadas pela escala ADL - Activities of Daily Living. Para diagnóstico dos casos incidentes de doença de Alzheimer foi utilizado os critérios diagnósticos do DSM-IV e do NINCDS/ADRDA, associado à descrição dos critérios de Kawas para DA consistente. Para diagnóstico de Comprometimento Cognitivo Leve, o critério da Clínica Mayo foi aplicado para a primeira análise, e o critério para CCL do tipo Alzheimer (ou DA prodrômica) foi utilizado para a segunda análise tendo em vista a incorporação de dados disponíveis e a evolução dos critérios. As trajetórias possíveis do CCL foram classificadas em três categorias: conversão, estabilização e reconversão. Os sujeitos considerados para a primeira análise - casos incidentes de CCL e DA foram os participantes que apresentavam pelo menos uma visita de seguimento no período de oito anos a partir da linha de base (N = 245) e as análises estatísticas foram baseadas no diagnóstico estabelecido na última visita de seguimento. Para os falecidos durante o período, dados retrospectivos foram obtidos através de uma entrevista telefônica com um informante confiável. Os dados clínicos e demográficos de linha de base foram utilizados para cálculo dos fatores preditivos dos desfechos do estudo. Para a segunda análise – risco de conversão de CCL para DA – trajetórias do CCL, a amostra foi composta dos 21 indivíduos que desenvolveram CCL e 220 indivíduos cognitivamente normais (N = 241). Resultados: Os resultados da primeira análise mostraram taxa de incidência de CCL de 13,2 por 1.000 pessoas-ano e incidência de DA de 14,8 por 1.000 pessoas-ano. O desenvolvimento de prejuízo cognitivo foi associado com educação (razão de chance [RC] = 0,86) e o escore do MEEM de base (RC = 0,81). Os resultados da segunda análise mostraram que dos 21 sujeitos com CCL, 38% desenvolveram demência, 24% permaneceram estáveis e 38% melhoraram. A taxa de conversão anual para DA foi de 8,5%, CCL foi associado significativamente a maior risco de conversão para DA (HR = 49,83; p = 0,004), mesmo ajustado para idade, escolaridade, sexo e escore no MEEM. Conclusão: A incidência de DA nessa amostra foi maior do que a descrita em estudo prévio realizado no Brasil, mas está dentro da variabilidade observada internacionalmente. Escores mais baixos no Mini Exame do Estado Mental na linha de base, mesmo que dentro da normalidade, e níveis mais baixos de educação foram preditores da ocorrência de prejuízo cognitivo. Quanto à trajetória do CCL, independentemente da heterogeneidade observada, os participantes com CCL do tipo Alzheimer apresentaram risco significativamente maior de desenvolver demência na DA, demonstrando o impacto do uso destes critérios que enfatizam o comprometimento da memória episódica de longo prazo e buscam identificar sujeitos com maior probabilidade de ser portadores de patologia Alzheimer. / Background: The increase of the rates of age-related diseases as dementia, especially Alzheimer's disease (AD), is projected with the aging of the world population. Subjects with Mild Cognitive Impairment (MCI) are considered a population at risk for developing dementia. However, MCI incidence rates and rates of conversion to dementia have shown considerable variability that could be partially attributed to characteristics of the sample and to different criteria. Objective: To determine the incidence of dementia and mild cognitive impairment in a cohort of community-based healthy elderly individuals; to determine the demographic, clinical and social variables associated with the development of cognitive impairment; and to assess the risk of progression of individuals with mild cognitive impairment to dementia compared with cognitively normal subjects. Methods: Data were derived from a cohort of elderly community residents (N = 345), who were initially healthy and independent (PALA – Porto Alegre Longitudinal Aging – study). The follow-up of a maximum of eight years was used to evaluate the incidence of AD and MCI. To evaluate the progression of MCI to dementia due to AD we set off the 10-year follow-up, including the previous 8-year of the first analysis, and consider the maximum of 70 months (mean 45 months) for these new outcomes. Participants who met the inclusion criteria of the study and consented to participate were evaluated with a detailed clinical interview consisted of demographic, clinical and social variables. Psychiatric symptoms were assessed with the SRQ scale (Self Report Questionnaire), the MADRS (Montgomery-Asberg Depression Rating Scale), and the Diagnostic and Statistical Manual of Mental Disorders (4th edition, DSM-IV) criteria for Major Depression. Cognitive assessment was checked with the Mini Mental State Examination (MMSE) and the Clinical Dementia Rating Scale (CDR). Independence for the activities of daily living was assessed with the ADL scale (Activities of Daily Living). Incident cases of probable Alzheimer's disease were assigned through the DSM-IV and the NINCDS-ADRDA diagnostic criteria, with the additional designation from Kawas and colleagues of consistent AD. Detection of Mild Cognitive Impairment for the first analysis was carried out with the MCI Mayo Clinic criteria. The MCI of the Alzheimer type criteria (or Prodromal AD) were used for the second analysis, incorporating available data of the sample and the ongoing evolution of the criteria. The possible MCI trajectories were classified into three categories: conversion, stabilization, and reconversion. The subjects for the first analysis – MCI and AD incidence – were the participants who had at least one follow-up visit in the 8-year period from the baseline (N = 245), and the statistical analyzes were based on the diagnosis established in last follow-up interview. For the deceased during the period, retrospective data were obtained through a telephone interview with a knowledgeable collateral source focusing on dementia. The baseline clinical and demographic data were analyzed as predictors of the study outcomes. For the second analysis – risk of MCI progression to AD, and MCI trajectories – the sample was composed of 21 individuals who developed MCI and 220 cognitively normal subjects (N = 241). Results: The results of the first analysis showed the MCI incidence rate of 13.2 per 1,000 person-years and the AD incidence of 14.8 per 1,000 person-years. The development of cognitive impairment was associated with education (odds ratio [OR] = 0.86) and baseline MMSE scores (OR = 0.81). The results of second analysis showed that of the 21 MCI subjects, 38% developed dementia, 24% remained stable, and 38% improved. The annual AD conversion rate was 8.5%, and MCI was significantly associated with increased risk of progression to AD (HR = 49.83; p = 0.004), even adjusted for age, education, gender and MMSE scores. Conclusion: The AD incidence in this sample was higher than that described in a previous study carried out in Brazil, but was within the international estimates. Lower baseline scores on the Mini Mental State Examination, although within the normal range, and lower levels of education were predictors of cognitive impairment. Regardless the observed heterogeneity of the MCI trajectories, participants with MCI of the Alzheimer type showed significantly higher risk of developing dementia due to AD, demonstrating the impact of the emphasis on the episodic long-term memory impairment of the criteria, which finally searches to identify those individuals more likely to have Alzheimer's pathology.

A doença de Alzheimer (DA) é uma patologia neurodegenerativa progressiva e a forma de demência mais prevalente no mundo. As alterações fisiopatológicas da DA têm sido associadas a dois marcadores neuropatológicos clássicos: a deposição de placas de β- amilóide e a formação de emaranhados neurofibrilares da proteína tau hiperfosforilada. Porém, devido a complexidade da DA, outros mecanismos têm sido propostos como coadjuvantes no processo neurodegenerativo, entre eles eventos neuroinflamatórios, a quebra da homeostasia de sistemas de neurotransmissão e disfunção sináptica. Esta pletora de eventos patológicos parece preceder a fase de demência por um longo período onde a doença age de forma silenciosa, ou seja, onde não existem evidências sintomatológicas. Na presente tese, avançamos no entendimento de vias de sinalização associadas com a hipersforforilação da proteína tau envolvendo a disfunção da proteína fosfatase 2A e neurotoxicidade do sistema glutamatérgico. Além disso, avaliamos os radiofármacos de tomografia de emissão de pósitrons (PET) disponíveis para visualização in vivo e não invasiva da fisiopatologia da DA. Finalmente, avaliamos um novo biomarcador de PET, o [11C]ABP688, para visualizar flutuações no sistema glutamatérgico e avançamos no entendimento do impacto das células gliais no sinal do PET [18F]FDG, o radiofármaco mais utilizado na clínica atualmente para visualizar metabolismo de glicose cerebral. O [11C]ABP688 pode ser diretamente incluído em estudos clínicos e a reconceptualização do [18F]FDG proposta nesta tese pode alterar a maneira atual como vemos o metabolismo de glicose na DA e em outras doenças neurodegenerativas. Finalmente, nesta tese, avançamos em termos de mecanismos, e no contexto da busca por um diagnóstico precoce e acurado da DA. / Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most prevalent cause of dementia worldwide. The AD pathophysiological features have been associated to two main classic neuropathological markers: depositon of β-amyloid plaques and formation of neurofibrillary tangles of hyperphosphorylated tau. Due to AD complexity, however, additional mechanisms have been proposed as contributors to the neurodegenerative process, such as neuroinflammatory changes, altered neurotransmission, and synaptic dysfunction. These pathological events seem to precede the dementia phase by many years, resulting in a long silent period, i.e., a preclinical phase. In this thesis, we advanced in the understanding of signaling pathways associated with tau hyperphosphorylation, which includes dysfunction of protein phosphatase 2A (PP2A) and glutamatergic neurotoxicity. Furthermore, we underscored radiopharmaceuticals currently available for imaging AD pathophysiology in vivo and non-invasively with positron emission tomography (PET). Finally, we evaluated a new PET biomarker, [11C]ABP688, for visualizing glutamatergic fluctuations and advanced in the understating of how glial cells contribute to the [18F]FDG signal, the widely used radiopharmaceutical in clinical settings for visualizing cerebral glucose metabolism. Our findings have high translational value and direct impact in clinical settings, which can potentially alter the way we interpret glucose metabolism in AD and other neurodegenerative disorders. In summary, in this thesis, we have advanced in terms of molecular mechanisms, and in the use of PET biomarkers toward an early and accurate diagnosis of AD.