La malaltia d’Alzheimer: dels orígens històrics a la prevenció. Actualitat de la recerca

[cat] La malaltia d’Alzheimer, descrita ara ja fa més d’un segle, continua sent un dels principals focus de recerca en l’àmbit de les malalties neurodegeneratives. S’ha avançat en el coneixement de molts aspectes neurobiològics i clínics del que succeeix quan el cervell d’una persona resulta afectat per aquesta malaltia. Ara bé, el desconeixement de les causes i el fet de no disposar encara de cap tractament capaç de curar la malaltia ni d’aturar-ne el progrés continuen sent els principals motors de la recerca. Cal apressarse, ja que les previsions epidemiològiques, lligades a l’envelliment poblacional mundial, apunten a un increment considerable de casos, amb els consegüents costos personals, econòmics i sociosanitaris. Només la recerca científica pot tenir la clau per modificar aquests auguris. Per arribar al punt en què ens trobem a dia d’avui, farem una breu repassada de l’origen històric de la malaltia i veurem com, tot i els avenços realitzats i les fites aconseguides, les qüestions fonamentals de fa més d’un segle encara són plenament vigents en les hipòtesis i els objectius de recerca actuals. Tanmateix, parlarem de les possibilitats de prevenció de l’Alzheimer i es farà una breu exposició de l’estat actual de la recerca en aquest tema, fent especial èmfasi en la investigació que es duu a terme des del BarcelonaBeta Brain Research Center i la Fundació Pasqual Maragall.[spa] La enfermedad de Alzheimer, descrita hace ya más de un siglo, continúa siendo uno de los principales focos de investigación en el ámbito de las enfermedades neurodegenerativas. Se ha avanzado en el conocimiento de muchos aspectos neurobiológicos y clínicos de lo que sucede cuando el cerebro de una persona resulta afectado por esta enfermedad. Ahora bien, el desconocimiento de sus causas y el hecho de no disponer aún de ningún tratamiento o intervención capaz de curar la enfermedad ni de frenar su progreso continúan siendo los principales motores de la investigación. Hay que apresurarse, ya que las previsiones epidemiológicas, ligadas al envejecimiento poblacional mundial, apuntan a un incremento considerable de casos, con los consiguientes costes personales, económicos y sociosanitarios. Solo la investigación científica puede tener la clave para modificar tales augurios. Para llegar al punto en el que nos encontramos a día de hoy, haremos un breve repaso del origen histórico de la enfermedad y veremos cómo, a pesar de los avances realizados y las metas alcanzadas, las cuestiones fundamentales de hace más de un siglo aún son plenamente vigentes en las hipótesis y los objetivos de investigación actuales. Asimismo, hablaremos de las posibilidades de prevención del Alzheimer y se hará una breve exposición del estado actual de la investigación en este tema, haciendo especial énfasis en los estudios que se llevan a cabo desde el BarcelonaBeta Brain Research Center y la Fundación Pasqual Maragall

Traditional plant functional groups explain variation in economic but not size-related traits across the tundra biome

Aim Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups represent variation in six ecologically important plant traits. Location Tundra biome. Time period Data collected between 1964 and 2016. Major taxa studied 295 tundra vascular plant species. Methods We compiled a database of six plant traits (plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, seed mass) for tundra species. We examined the variation in species‐level trait expression explained by four traditional functional groups (evergreen shrubs, deciduous shrubs, graminoids, forbs), and whether variation explained was dependent upon the traits included in analysis. We further compared the explanatory power and species composition of functional groups to alternative classifications generated using post hoc clustering of species‐level traits. Results Traditional functional groups explained significant differences in trait expression, particularly amongst traits associated with resource economics, which were consistent across sites and at the biome scale. However, functional groups explained 19% of overall trait variation and poorly represented differences in traits associated with plant size. Post hoc classification of species did not correspond well with traditional functional groups, and explained twice as much variation in species‐level trait expression. Main conclusions Traditional functional groups only coarsely represent variation in well‐measured traits within tundra plant communities, and better explain resource economic traits than size‐related traits. We recommend caution when using functional group approaches to predict tundra vegetation change, or ecosystem functions relating to plant size, such as albedo or carbon storage. We argue that alternative classifications or direct use of specific plant traits could provide new insights for ecological prediction and modelling

CSF glial biomarkers YKL40 and sTREM2 are associated with longitudinal volume and diffusivity changes in cognitively unimpaired individuals

Cerebrospinal fluid (CSF) YKL40 and sTREM2 are astroglial and microglial activity biomarkers, respectively. We assessed whether CSF YKL40 and sTREM2 baseline levels are associated with longitudinal brain volume and diffusivity changes in cognitively unimpaired adults. Two brain MRI scans of 36 participants (57 to 78-years old, 12 male) were acquired in a 2-year interval. A beta(42), p-tau, YKL40 and sTREM2 concentrations in CSF were determined at baseline. We calculated gray and white matter volume changes per year maps (Delta GM and Delta WM, respectively) by means of longitudinal pairwise registration, and mean diffusivity variation per year (Delta MD) by subtraction. We checked voxel-wise for associations between Delta GM, Delta WM and Delta MD and baseline CSF level of YKL40 and sTREM2 and verified to what extent these associations were modulated by age (YKL40xAGE and sTREM2xAGE interactions). We found a positive association between Delta GM and YKL40 in the left inferior parietal region and no association between sTREM2 and Delta GM. Negative associations were also observed between Delta GM and YKL40xAGE (bilateral frontal areas, left precuneus and left postcentral and supramarginal gyri) and sTREM2xAGE (bilateral temporal and frontal cortex, putamen and left middle cingulate gyrus). We found negative associations between Delta WM and YKL40xAGE (bilateral superior longitudinal fasciculus) and sTREM2xAGE (bilateral superior longitudinal fasciculus, left superior corona radiata, retrolenticular external capsule and forceps minor, among other regions) but none between Delta WM and neither YKL40 nor sTREM2. Delta MD was positively correlated with YKL40 in right orbital region and negatively with sTREM2 in left lingual gyrus and precuneus. In addition, significant associations were found between Delta MD and YKL40xAGE (tail of left hippocampus and surrounding areas and right anterior cingulate gyrus) and sTREM2xAGE (right superior temporal gyrus). Areas showing statistically significant differences were disjoint in analyses involving YKL40 and sTREM2. These results suggest that glial biomarkers exert a relevant and distinct influence in longitudinal brain macro- and microstructural changes in cognitively unimpaired adults, which appears to be modulated by age. In younger subjects increased glial markers (both YKL40 and sTREM2) predict a better outcome, as indicated by a decrease in Delta GM and Delta WM and an increase in Delta MD, whereas in older subjects this association is inverted and higher levels of glial markers are associated with a poorer neuroimaging outcome

Interactive effect of age and APOE-ε4 allele load on white matter myelin content in cognitively normal middle-aged subjects

The apolipoprotein E gene (APOE) ε4 allele has a strong and manifold impact on cognition and neuroimaging phenotypes in cognitively normal subjects, including alterations in the white matter (WM) microstructure. Such alterations have often been regarded as a reflection of potential thinning of the myelin sheath along axons, rather than pure axonal degeneration. Considering the main role of APOE in brain lipid transport, characterizing the impact of APOE on the myelin coating is therefore of crucial interest, especially in healthy APOE-ε4 homozygous individuals, who are exposed to a twelve-fold higher risk of developing Alzheimer's disease (AD), compared to the rest of the population. We examined T1w/T2w ratio maps in 515 cognitively healthy middle-aged participants from the ALFA study (ALzheimer and FAmilies) cohort, a single-site population-based study enriched for AD risk (68 APOE-ε4 homozygotes, 197 heterozygotes, and 250 non-carriers). Using tract-based spatial statistics, we assessed the impact of age and APOE genotype on this ratio taken as an indirect descriptor of myelin content. Healthy APOE-ε4 carriers display decreased T1w/T2w ratios in extensive regions in a dose-dependent manner. These differences were found to interact with age, suggesting faster changes in individuals with more ε4 alleles. These results obtained with T1w/T2w ratios, confirm the increased vulnerability of WM tracts in APOE-ε4 healthy carriers. Early alterations of myelin content could be the result of the impaired function of the ε4 isoform of the APOE protein in cholesterol transport. These findings help to clarify the possible interactions between the APOE-dependent non-pathological burden and age-related changes potentially at the source of the AD pathological cascade

Altered mechanisms of protein synthesis in frontal cortex in Alzheimer disease and a mouse model

Expression of the nucleolar chaperones nucleolin (NCL) and nucleophosmin (NPM1), upstream binding transcription factor (UBTF), rRNA18S, rRNA28S, and several genes encoding ribosomal proteins (RPs) is decreased in frontal cortex area 8 at advanced stages of Alzheimer's disease (AD). This is accompanied by reduced protein levels of elongation factors eEF1A and eEF2. Changes are more marked in AD cases with rapid course (rpAD), as initiation factor eIF3η is significantly down-regulated and several RP genes up-regulated in rpAD when compared with typical AD. These changes contrast with those seen in APP/PS1 transgenic mice used as a model of AD-like β-amyloidopathy; Ncl mRNA, rRNA18S, rRNA28S and seven out of fifteen assessed RP genes are up-regulated in APP/PS1 mice aged 20 months; only eEF2 protein levels are reduced in transgenic mice. Our findings show marked altered expression of molecules linked to the protein synthesis machinery from the nucleolus to the ribosome in frontal cortex at terminal stages of AD which differs from that seen in APP/PS1 transgenic mice, thus further suggesting that molecular signals in mouse models do not apply to real human disease counterparts

Variably protease-sensitive prionopathy presenting within ALS/FTD spectrum

We report clinico‐pathological features of a 65‐year‐old woman and a 56‐year‐old man with a 5‐year clinical history who had clinical and neuropathological characteristics of upper and lower motor neuron disease consistent with amyotrophic lateral sclerosis, and a frontotemporal atrophy pattern in case 2 without TDP‐43 pathology. Instead, spongiform change and pathological prion protein deposits were observed in several brain regions. No prion protein gene mutations were found. Western blot analysis showed a five‐band profile compatible with variably protease‐sensitive prionopathy. We conclude that this disease can display prolonged disease duration and clinico‐pathological features within the ALS/FTLD spectrum.This work was funded by Department of Public Health Generalitat de Catalunya grant ; Spanish “Ministerio de Economía y Competitividad, Subprograma Técnicos de Apoyo 2014” grant ; Spanish Fondo de Investigaciones Sanitarias grant FIS PI16‐01673‐FEDER; Spanish Ministry of Health ‐ Instituto Carlos III grant Miguel Servet ‐ CP16/00041; Fundació La Marató de TV3 grant 20141610

Determination of neuronal antibodies in suspected and definite Creutzfeldt-Jakob disease

IMPORTANCE Creutzfeldt-Jakob disease (CJD) and autoimmune encephalitis with antibodies against neuronal surface antigens (NSA-abs) may present with similar clinical features. Establishing the correct diagnosis has practical implications in the management of care for these patients. OBJECTIVE To determine the frequency of NSA-abs in the cerebrospinal fluid of patients with suspected CJD and in patients with pathologically confirmed (ie, definite) CJD. DESIGN, SETTING, AND PARTICIPANTS A mixed prospective (suspected) and retrospective (definite) CJD cohort study was conducted in a reference center for detection of NSA-abs. The population included 346 patients with suspected CJD and 49 patients with definite CJD. MAIN OUTCOMES AND MEASURES Analysis of NSA-abs in cerebrospinal fluid with brain immunohistochemistry optimized for cell-surface antigens was performed. Positive cases in the suspected CJD group were further studied for antigen specificity using cell-based assays. All definite CJD cases were comprehensively tested for NSA-abs, with cell-based assays used for leucine-rich glioma-inactivated 1 (LGI1), contactin-associated protein-like 2 (CASPR2), N-methyl-D-aspartate (NMDA), and glycine (GlY) receptors. RESULTS Neuronal surface antigens were detected in 6 of 346 patients (1.7%) with rapid neurologic deterioration suggestive of CJD. None of these 6 patients fulfilled the diagnostic criteria for probable or possible CJD. The target antigens included CASPR2, LGI1, NMDAR, aquaporin 4, Tr (DNER [δ/notch-like epidermal growth factor-related receptor]), and an unknown protein. Four of the patients developed rapidly progressive dementia, and the other 2 patients had cerebellar ataxia or seizures that were initially considered to be myoclonus without cognitive decline. The patient with Tr-abs had a positive 14-3-3 test result. Small cell lung carcinoma was diagnosed in the patient with antibodies against an unknown antigen. All patients improved or stabilized after appropriate treatment. None of the 49 patients with definite CJD had NSA-abs. CONCLUSIONS AND RELEVANCE A low, but clinically relevant, number of patients with suspected CJD had potentially treatable disorders associated with NSA-abs. In contrast, none of 49 patients with definite CJD had NSA-abs, including NMDAR-abs, GlyR-abs, LGI1-abs, or CASPR2-abs. These findings suggest that cerebrospinal fluid NSA-abs analysis should be included in the diagnostic workup of patients with rapidly progressive central nervous system syndromes, particularly when they do not fulfill the diagnostic criteria of probable or possible CJD

Dementia with lewy bodies: molecular pathology in the frontal cortex in typical and rapidly progressive forms

Objectives: the goal of this study was to assess mitochondrial function, energy, and purine metabolism, protein synthesis machinery from the nucleolus to the ribosome, inflammation, and expression of newly identified ectopic olfactory receptors (ORs) and taste receptors (TASRs) in the frontal cortex of typical cases of dementia with Lewy bodies (DLB) and cases with rapid clinical course (rpDLB: 2 years or less) compared with middle-aged non-affected individuals, in order to learn about the biochemical abnormalities underlying Lewy body pathology. Methods: real-time quantitative PCR, mitochondrial enzymatic assays, and analysis of β-amyloid, tau, and synuclein species were used. Results: the main alterations in DLB and rpDLB, which are more marked in the rapidly progressive forms, include (i) deregulated expression of several mRNAs and proteins of mitochondrial subunits, and reduced activity of complexes I, II, III, and IV of the mitochondrial respiratory chain; (ii) reduced expression of selected molecules involved in energy metabolism and increased expression of enzymes involved in purine metabolism; (iii) abnormal expression of nucleolar proteins, rRNA18S, genes encoding ribosomal proteins, and initiation factors of the transcription at the ribosome; (iv) discrete inflammation; and (v) marked deregulation of brain ORs and TASRs, respectively. Severe mitochondrial dysfunction involving activity of four complexes, minimal inflammatory responses, and dramatic altered expression of ORs and TASRs discriminate DLB from Alzheimer's disease. Altered solubility and aggregation of α-synuclein, increased β-amyloid bound to membranes, and absence of soluble tau oligomers are common in DLB and rpDLB. Low levels of soluble β-amyloid are found in DLB. However, increased soluble β-amyloid 1-40 and β-amyloid 1-42, and increased TNFα mRNA and protein expression, distinguish rpDLB. Conclusion: molecular alterations in frontal cortex in DLB involve key biochemical pathways such as mitochondria and energy metabolism, protein synthesis, purine metabolism, among others and are accompanied by discrete innate inflammatory response

Cross-sectional and longitudinal association of sleep and Alzheimer biomarkers in cognitively unimpaired adults

Sleep abnormalities are prevalent in Alzheimer's disease, with sleep quality already impaired at its preclinical stage. Epidemiological and experimental data point to sleep abnormalities contributing to the risk of Alzheimer's disease. However, previous studies are limited by either a lack of Alzheimer's disease biomarkers, reduced sample size or cross-sectional design. Understanding if, when, and how poor sleep contributes to Alzheimer's disease progression is important so that therapies can be targeted to the right phase of the disease. Using the largest cohort to date, the European Prevention of Alzheimer's Dementia Longitudinal Cohort Study, we test the hypotheses that poor sleep is associated with core Alzheimer's disease CSF biomarkers cross-sectionally and predicts future increments of Alzheimer's disease pathology in people without identifiable symptoms of Alzheimer's disease at baseline. This study included 1168 adults aged over 50 years with CSF core Alzheimer's disease biomarkers (total tau, phosphorylated tau and amyloid-beta), cognitive performance, and sleep quality (Pittsburgh sleep quality index questionnaire) data. We used multivariate linear regressions to analyse associations between core Alzheimer's disease biomarkers and the following Pittsburgh sleep quality index measures: total score of sleep quality, binarized score (poor sleep categorized as Pittsburgh sleep quality index > 5), sleep latency, duration, efficiency and disturbance. On a subsample of 332 participants with CSF taken at baseline and after an average period of 1.5 years, we assessed the effect of baseline sleep quality on change in Alzheimer's disease biomarkers over time. Cross-sectional analyses revealed that poor sleep quality (Pittsburgh sleep quality index total > 5) was significantly associated with higher CSF t-tau; shorter sleep duration (9 versus 0) was associated with lower CSF amyloid-beta. Longitudinal analyses showed that greater sleep disturbances (1-9 versus 0 and >9 versus 0) were associated with a decrease in CSF Aβ42 over time. This study demonstrates that self-reported poor sleep quality is associated with greater Alzheimer's disease-related pathology in cognitively unimpaired individuals, with longitudinal results further strengthening the hypothesis that disrupted sleep may represent a risk factor for Alzheimer's disease. This highlights the need for future work to test the efficacy of preventive practices, designed to improve sleep at pre-symptomatic stages of disease, on reducing Alzheimer's disease pathology

Quantitative informant- and self-reports of subjective cognitive decline predict amyloid beta PET outcomes in cognitively unimpaired individuals independently of age and APOE ε4

Introduction: Amyloid beta (Aβ) pathology is an Alzheimer's disease early hallmark. Here we assess the value of longitudinal self- and informant reports of cognitive decline to predict Aβ positron emission tomography (PET) outcome in cognitively unimpaired middle-aged individuals. Methods: A total of 261 participants from the ALFA+ study underwent [18F]flutemetamol PET and Subjective Cognitive Decline Questionnaire (SCD-Q) concurrently, and 3 years before scan. We used logistic regressions to evaluate the ability of SCD-Q scores (self and informant) to predict Aβ PET visual read, and repeated analysis of variance to assess whether changes in SCD-Q scores relate to Aβ status. Results: Self-perception of decline in memory (odds ratio [OR] = 1.2), and informant perception of executive decline (OR = 1.6), increased the probability of a positive scan. Informant reports 3 years before scanning predicted Aβ PET outcome. Longitudinal increase of self-reported executive decline was predictive of Aβ in women (P = .003). Discussion: Subjective reports of cognitive decline are useful to predict Aβ and may improve recruitment strategies