Search

Therapeutic modulation of TREM2-dependent microglial function might provide an additional strategy to slow the progression of Alzheimer's disease. Although studies in animal models suggest that TREM2 is protective against Alzheimer's pathology, its effect on tau pathology and its potential beneficial role in people with Alzheimer's disease is still unclear. Our aim was to study associations between the dynamics of soluble TREM2, as a biomarker of TREM2 signalling, and amyloid β (Aβ) deposition, tau-related pathology, neuroimaging markers, and cognitive decline, during the progression of autosomal dominant Alzheimer's disease.We did a longitudinal analysis of data from the Dominantly Inherited Alzheimer Network (DIAN) observational study, which includes families with a history of autosomal dominant Alzheimer's disease. Participants aged over 18 years who were enrolled in DIAN between Jan 1, 2009, and July 31, 2019, were categorised as either carriers of pathogenic variants in PSEN1, PSEN2, and APP genes (n=155) or non-carriers (n=93). We measured amounts of cleaved soluble TREM2 using a novel immunoassay in CSF samples obtained every 2 years from participants who were asymptomatic (Clinical Dementia Rating [CDR]=0) and annually for those who were symptomatic (CDR>0). CSF concentrations of Aβ40, Aβ42, total tau (t-tau), and tau phosphorylated on threonine 181 (p-tau) were measured by validated immunoassays. Predefined neuroimaging measurements were total cortical uptake of Pittsburgh compound B PET (PiB-PET), cortical thickness in the precuneus ascertained by MRI, and hippocampal volume determined by MRI. Cognition was measured using a validated cognitive composite (including DIAN word list test, logical memory delayed recall, digit symbol coding test [total score], and minimental status examination). We based our statistical analysis on univariate and bivariate linear mixed effects models.In carriers of pathogenic variants, a high amyloid burden at baseline, represented by low CSF Aβ42 (β=-4·28 × 10-2 [SE 0·013], p=0·0012), but not high cortical uptake in PiB-PET (β=-5·51 × 10-3 [0·011], p=0·63), was the only predictor of an augmented annual rate of subsequent increase in soluble TREM2. Augmented annual rates of increase in soluble TREM2 were associated with a diminished rate of decrease in amyloid deposition, as measured by Aβ42 in CSF (r=0·56 [0·22], p=0·011), in presymptomatic carriers of pathogenic variants, and with diminished annual rate of increase in PiB-PET (r=-0·67 [0·25], p=0·0060) in symptomatic carriers of pathogenic variants. Presymptomatic carriers of pathogenic variants with annual rates of increase in soluble TREM2 lower than the median showed a correlation between enhanced annual rates of increase in p-tau in CSF and augmented annual rates of increase in PiB-PET signal (r=0·45 [0·21], p=0·035), that was not observed in those with rates of increase in soluble TREM2 higher than the median. Furthermore, presymptomatic carriers of pathogenic variants with rates of increase in soluble TREM2 above or below the median had opposite associations between Aβ42 in CSF and PiB-PET uptake when assessed longitudinally. Augmented annual rates of increase in soluble TREM2 in presymptomatic carriers of pathogenic variants correlated with decreased cortical shrinkage in the precuneus (r=0·46 [0·22]), p=0·040) and diminished cognitive decline (r=0·67 [0·22], p=0·0020).Our findings in autosomal dominant Alzheimer's disease position the TREM2 response within the amyloid cascade immediately after the first pathological changes in Aβ aggregation and further support the role of TREM2 on Aβ plaque deposition and compaction. Furthermore, these findings underpin a beneficial effect of TREM2 on Aβ deposition, Aβ-dependent tau pathology, cortical shrinkage, and cognitive decline. Soluble TREM2 could, therefore, be a key marker for clinical trial design and interpretation. Efforts to develop TREM2-boosting therapies are ongoing.German Research Foundation, US National Institutes of Health.

"Brain-predicted age" quantifies apparent brain age compared to normative neuroimaging trajectories. Advanced brain-predicted age has been well established in symptomatic Alzheimer disease (AD), but is underexplored in preclinical AD. Prior brain-predicted age studies have typically used structural MRI, but resting-state functional connectivity (FC) remains underexplored. Our model predicted age from FC in 391 cognitively normal, amyloid-negative controls (ages 18-89). We applied the trained model to 145 amyloid-negative, 151 preclinical AD, and 156 symptomatic AD participants to test group differences. The model accurately predicted age in the training set. FC-predicted brain age gaps (FC-BAG) were significantly older in symptomatic AD and significantly younger in preclinical AD compared to controls. There was minimal correspondence between networks predictive of age and AD. Elevated FC-BAG may reflect network disruption during symptomatic AD. Reduced FC-BAG in preclinical AD was opposite to the expected direction, and may reflect a biphasic response to preclinical AD pathology or may be driven by inconsistency between age-related vs. AD-related networks. Overall, FC-predicted brain age may be a sensitive AD biomarker.

Orientador: José Eduardo Tanus dos Santos Tese (doutorado) - Universidade Estadual de Campinas. Faculdade de Ciências Médicas Resumo: A exposição ao mercúrio (Hg) causa efeitos deletérios à saúde, incluindo doenças cardiovasculares. Embora os mecanismos não estejam precisamente definidos, metaloproteinases (MMPs) -2 e -9 podem estar envolvidas. Expressão e atividades aumentadas destas MMPs são demonstradas em diversas condições patológicas, e estudos demonstraram que os níveis circulantes de MMPs poderiam ser usados como marcadores de risco cardiovascular. O gene que codifica a MMP-9 apresenta polimorfismos que afetam a expressão e o nível de atividade desta enzima, sendo que dois deles, presentes na região promotora [C- 1562T e (CA)n], são funcionalmente importantes, tendo sido associados a diversas doenças. Investigamos se existe associação entre os níveis circulantes de MMP-2, MMP-9 e seus inibidores endógenos (TIMPs) -2 e -1 com os níveis circulantes de Hg, em indivíduos expostos ao metal por consumo de peixes, na Amazônia Brasileira. Em seguida, examinamos se os polimorfismos da MMP-9 afetam os níveis circulantes de MMP-9, nestes indivíduos. Para isso, analisamos as concentrações de Hg no sangue e plasma desses indivíduos por espectrometria de massas com plasma indutivamente acoplado (ICP-MS). As concentrações de MMPs e TIMPs foram medidas nas amostras de plasma por zimografia e ELISA, respectivamente. Espécies reativas ao ácido tiobarbitúrico (TBARS) foram medidas no plasma, para dosar estresse oxidativo. Os níveis de selênio (Se) foram determinados por ICP-MS, por este ser um antioxidante. O DNA genômico foi extraído das amostras de sangue e os genótipos dos polimorfismos C- 1562T e (CA)n foram determinados. A relação entre os bioindicadores de Hg e os níveis de MMPs, assim como a relação entre os genótipos da MMP-9 e os níveis de MMP-9 foram examinados usando modelos de regressão múltipla. Não foi encontrada relação entre Hg no sangue ou plasma e MMPs. Contudo, Hg no plasma foi negativamente associado com os níveis de TIMPs, resultando em aumento nas razões MMP-9/TIMP-1 e MMP-2/TIMP-2, o que indica uma associação positiva entre Hg no plasma e o grau de atividade de MMP-9 e MMP-2. Os polimorfismos da MMP-9 não se relacionaram aos níveis de MMP-9 quando todos os indivíduos foram analisados juntos. No entanto, quando dividimos a população estudada em terços, com base nas concentrações plasmáticas de Hg, o polimorfismo (CA)n afetou o grau de atividade da MMP-9 no grupo com níveis mais baixos de Hg no plasma. Os níveis de MMP-9 foram mais altos em pessoas com genótipos que incluíam o alelo com mais de 21 repetições CA (alelos H), e menos naqueles cujo genótipo incluía alelos com menos de 21 repetições CA (alelos L). Nos grupos com níveis intermediários ou altos de Hg no plasma, este polimorfismo não teve efeito. Nenhuma associação foi encontrada entre o polimorfismo C- 1562T e os níveis de MMP-9, nos três grupos. Esses achados mostram o efeito do Hg sobre o grau de atividade de MMPs,e que o efeito do Hg sobre a MMP-9 é modulado pelo polimorfismo (CA)n da MMP- 9. O aumento do grau de atividade poderia aumentar o risco de desenvolvimento de doenças cardiovasculares em pessoas expostas ao Hg, principalmente nas que apresentam o genótipo HH. Abstract: Mercury (Hg) exposure causes health problems, including cardiovascular diseases. Although the mechanisms are not precisely defined, metalloproteinases (MMP) -2 and -9 may be involved. Increased expression and activities of these MMPs are demonstrated in several pathological conditions, and recent studies have demonstrated that circulating levels of MMPs could be used as a blood-borne biomarker for cardiovascular risk, even in healthy individuals. The gene encoding MMP-9 presents genetic polymorphisms which affects the expression and activity level of this enzyme, two of them, present in the promoter region [C- 1562T and (CA)n] are functionally relevant, having been involved in several diseases. We investigated if the association between circulating levels of MMP-2, MMP- 9 and their endogenous inhibitors (TIMPs) -2 and -1 with circulating levels of Hg in individuals exposed to metal through consumption of fish in the Brazilian Amazon. Then, we examined whether these MMP-9 polymorphisms affect circulating MMP-9 net levels in persons exposed to mercury. For this purpose, we analyzed the concentrations of blood and plasma Hg by inductively coupled plasma-mass spectrometry (ICP-MS). MMPs and TIMPs concentrations were measured in plasma samples by zymography and ELISA, respectively. Thiobarbituric acid-reactive species (TBARS) were measured in plasma to assess oxidative stress. Selenium (Se) levels were determined by ICPMS, because it is an antioxidant. Genomic DNA was extracted from whole blood, and genotypes for the C- 1562T and the microsatellite (CA)n polymorphisms were determined. The relationships between biomarkers of Hg and MMPs levels, as well as the relationship between MMP-9 genotypes and MMP-9 levels, were examined using multivariate regression models. No relationship was found between Hg in blood or plasma and MMPs. However, plasma Hg levels were negatively associated with TIMPs levels, and thereby with increasing MMP-9/ TIMP-1 and MMP-2/TIMP-2 ratios, thus indicating a positive association between plasma Hg and circulating net MMP-9 and MMP-2 activities. The polymorphisms of MMP-9 were not related to MMP-9 net levels when all subjects were analyzed together. However, when we divided the population into tertiles of plasma Hg concentrations, the polymorphism (CA)n affected MMP-9 concentrations and MMP-9/TIMP-1 ratios in people with lower levels of Hg. MMP-9 levels were higher in persons with genotypes including alleles with more than 21 CA repeats (H alleles) and lower in those whose genotype including alleles with less than 21 CA repeats (L alleles). Conversely, this polymorphism had no effects in persons with intermediate or high plasma Hg level. No association was found between the C-1562T polymorphism and MMP-9 levels in the three groups. These findings show the effect of Hg on MMP-9 net, and that this effect is modulated by the (CA)n polymorphism of MMP-9. The increase in MMPs levels could increase the risk of developing cardiovascular diseases in persons exposed to Hg, especially those with HH genotype. Doutorado Doutor em Farmacologia

Allelic variation in the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism moderates increases in cerebrospinal fluid (CSF) levels of tau and phosphorylated tau 181 (p-tau181), measured using immunoassay, and cognitive decline in presymptomatic dominantly inherited Alzheimer disease (DIAD). Advances in mass spectrometry show that CSF tau phosphorylation occupancy at threonine 181 and 217 (p-tau181/tau181, p-tau217/tau217) increases with initial β-amyloid (Aβ) aggregation, while phosphorylation occupancy at threonine 205 (p-tau205/tau205) and level of total tau increase when brain atrophy and clinical symptoms become evident.To determine whether site-specific tau phosphorylation occupancy (ratio of phosphorylated to unphosphorylated tau) is associated with BDNF Val66Met in presymptomatic and symptomatic DIAD.This cross-sectional cohort study included participants from the Dominantly Inherited Alzheimer Network (DIAN) and Aβ-positive cognitively normal older adults in the Alzheimer's Disease Neuroimaging Initiative (ADNI). Data were collected from 2009 through 2018 at multicenter clinical sites in the United States, United Kingdom, and Australia, with no follow-up. DIAN participants provided a CSF sample and completed clinical and cognitive assessments. Data analysis was conducted between March 2020 and March 2021.Mass spectrometry analysis was used to determine site-specific tau phosphorylation level; tau levels were also measured using immunoassay. Episodic memory and global cognitive composites were computed.Of 374 study participants, 144 were mutation noncarriers, 156 were presymptomatic mutation carriers, and 74 were symptomatic carriers. Of the 527 participants in the network, 153 were excluded because their CSF sample, BDNF status, or both were unavailable. Also included were 125 Aβ-positive cognitively normal older adults in the ADNI. The mean (SD) age of DIAD participants was 38.7 (10.9) years; 43% were women. The mean (SD) age of participants with preclinical sporadic AD was 74.8 (5.6) years; 52% were women. In presymptomatic mutation carriers, compared with Val66 homozygotes, Met66 carriers showed significantly poorer episodic memory (d = 0.62; 95% CI, 0.28-0.95), lower hippocampal volume (d = 0.40; 95% CI, 0.09-0.71), and higher p-tau217/tau217 (d = 0.64; 95% CI, 0.30-0.97), p-tau181/tau181 (d = 0.65; 95% CI, 0.32-0.99), and mass spectrometry total tau (d = 0.43; 95% CI, 0.10-0.76). In symptomatic mutation carriers, Met66 carriers showed significantly poorer global cognition (d = 1.17; 95% CI, 0.65-1.66) and higher p-tau217/tau217 (d = 0.53; 95% CI, 0.05-1.01), mass spectrometry total tau (d = 0.78; 95% CI, 0.28-1.25), and p-tau205/tau205 (d = 0.97; 95% CI, 0.46-1.45), when compared with Val66 homozygotes. In preclinical sporadic AD, Met66 carriers showed poorer episodic memory (d = 0.39; 95% CI, 0.00-0.77) and higher total tau (d = 0.45; 95% CI, 0.07-0.84) and p-tau181 (d = 0.46; 95% CI, 0.07-0.85).In DIAD, clinical disease stage and BDNF Met66 were associated with cognitive impairment and levels of site-specific tau phosphorylation. This suggests that pharmacological strategies designed to increase neurotrophic support in the presymptomatic stages of AD may be beneficial.

International audience; Development of tau-based therapies for Alzheimer's disease requires an understanding of the timing of disease-related changes in tau. We quantified the phosphorylation state at multiple sites of the tau protein in cerebrospinal fluid markers across four decades of disease progression in dominantly inherited Alzheimer's disease. We identified a pattern of tau staging where site-specific phosphorylation changes occur at different periods of disease progression and follow distinct trajectories over time. These tau phosphorylation state changes are uniquely associated with structural, metabolic, neurodegenerative and clinical markers of disease, and some (p-tau217 and p-tau181) begin with the initial increases in aggregate amyloid-β as early as two decades before the development of aggregated tau pathology. Others (p-tau205 and t-tau) increase with atrophy and hypometabolism closer to symptom onset. These findings provide insights into the pathways linking tau, amyloid-β and neurodegeneration, and may facilitate clinical trials of tau-based treatments.

Lead (Pb) is a toxic metal that is widely used by metallurgical industries such as car battery recycling. Exposure to the metal may modify the redox status of the cells and consequently result in changes in activities of important enzymes such as delta-aminolevulinic acid dehydratase (ALAD) and glutathione peroxidase (GPx). Similarly, genetic polymorphisms may modulate the activities of enzymes related to detoxification processes of the metal and may modify Pb body burden. Therefore, the aims of the present study were (i) to evaluate the correlation between blood lead levels (BLL) and activities of the enzymes ALAD and GPx, and (ii) to determine whether activities of these enzymes may be influenced by polymorphisms in ALAD and GPx genes in Brazilian automotive battery workers chronically exposed to Pb, as well as the effects of these polymorphisms on BLL. Our study included 257 participants; BLL were determined by inductively couple plasma-mass spectrometry (ICP-MS), and the activities of the enzymes ALAD and GPx were quantified spectrophotometrically; and genotyping of ALAD (rs1800435) and GPx-1 (rs1800668) polymorphisms was performed by TaqMan assays (real-time polymerase chain reaction, RT-PCR). Significant negative correlations were found between BLL and ALAD activity. Subjects who carried at least one polymorphic allele for ALAD gene displayed markedly lower ALAD activities, while no significant effect was observed regarding GPx-1 polymorphism and activity of the same enzyme. Further, ALAD and GPx-1 polymorphisms exerted no marked influence on BLL. Taken together, our results showed that BLL affected ALAD but not GPx activities, and these were not modulated by polymorphisms in ALAD and GPx gene. Further, the rs1800435 SNP showed a tendency to modulate ALAD activity, while the rs1800668 SNP did not modulate GPx activity in Brazilian automotive battery workers exposed to Pb.

Orientador: João Batista de Miranda Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas Resumo: Introdução: A osteotomia valgizante no terço proximal da tíbia é considerada um método confiável para o tratamento de pacientes jovens com osteoartrite medial do joelho, associado a alinhamento em varo. Entretanto, procedimentos realizados para a correção de desalinhamentos no plano frontal podem alterar o alinhamento do plano sagital. Vários fatores estão relacionados ao aumento da inclinação posterior do planalto tibial pós-osteotomia valgizante no terço proximal da tíbia. Hipótese: O posicionamento posterior da placa-calço está relacionado com menor alteração da inclinação posterior do planalto tibial. Modelo do estudo: Estudo clínico retrospectivo. Métodos: Foram realizadas 42 osteotomias entre abril de 2007 e agosto de 2008. Imagens radiográficas em perfil do joelho foram obtidas no pré-operatório e no pós-operatório recente. Determinou-se o ângulo formado entre a tangente do planalto tibial medial e uma linha perpendicular ao eixo da cortical posterior da tíbia por medidas goniométricas manuais, antes e após cirurgia. Determinou-se também a posição relativa da placa-calço em relação à cortical posterior da tíbia. Resultados: Houve aumento de aproximadamente 34% no valor da inclinação posterior do planalto tibial após a cirurgia, com a média subindo de 7,6° para 10,2° (p = 0,0006). Existe correlação entre o ângulo de inclinação do planalto tibial pré-operatório e o seu valor pós-cirúrgico (r = 0,4131 e p = 0,0065). A posição relativa e o tamanho do implante não influenciaram as alterações do alinhamento sagital. Conclusão: Nesta população amostral houve aumento estatisticamente significativo da angulação da superfície articular tibial proximal, no plano sagital, após osteotomia valgizante no terço proximal da tíbia. O posicionamento posterior da placa-calço não foi relacionado a um menor aumento desta angulação Abstract: Background: The high tibial osteotomy is considered a reliable method for the treatment of young patients with medial knee osteoarthritis associated with varus alignment. However, procedures performed to correct misalignments in the frontal plane can change the alignment of the sagittal plane. Several factors are related to the increase in the posterior inclination of the tibial plateau after high tibial osteotomy. Hypothesis: The posterior positioning of the Puddu plate causes less alteration of the posterior inclination of the tibial plateau. Study design: Retrospective clinical trial. Methods: Forty-two opening-wedge high tibial osteotomies were carried out. Lateral radiographic images of the knee were obtained preoperatively and right after surgery. The angle between the tangent of the medial tibial plateau and a line perpendicular to the axis of the posterior tibial cortex was determined by manual goniometric measurements before and after surgery. We also determined the relative position of the Puddu plate in relation to the posterior tibial cortex. Results: There was an increase of approximately 34% in the tibial slope after surgery, with the mean value rising from 7.6° to 10.2°. This difference was statistically significant (p = 0.0006). There is a correlation between the preoperative and postoperative inclination angles of the tibial plateau (r = 0.4131, p = 0.0065). The relative position and the size of the implant did not influence the changes in sagittal alignment. Conclusion: There was a statistically significant increase in the angulation of the proximal tibial articular surface in the sagittal plane after high tibial osteotomy. The posterior positioning of the Puddu plate was not related to a smaller increase of this angle Mestrado Fisiopatologia Cirúrgica Mestre em Ciências

A ossificação heterotópica é uma complicação freqüente após a lesão medular. Os avanços graduais no campo da fisiopatologia, reabilitação e novos métodos de tratamento são uma esperança para a reversão do quadro clínico do lesado medular num futuro próximo. O objetivo desse estudo é avaliar a resposta da ossificação heterotópica das articulações coxo femorais à estimulação elétrica neuromuscular em pacientes tetraplégicos após trauma raquimedular. Seis pacientes foram submetidos à estimulação elétrica neuromuscular por um período médio de 16,6 meses, sendo avaliados radiologicamente. Foi identificada a melhora radiológica em dois pacientes e a não progressão do quadro nos demais. A estimulação elétrica neuromuscular em lesados medulares pode ser um método válido no tratamento da ossificação heterotópica e prevenção de sua progressão. Heterotropic ossification is a common complication after spinal cord injury. Gradual advancements in the physiopathology and rehabilitation fields, and new treatment methods are a hope for the recovery of the clinical picture of injured individuals in the near future. The objective of this study was to evaluate the heterotropic ossification response of the thigh-femoral joints to neuromuscular electric stimulation in tetraplegic patients after rachial-medullar trauma. Six patients were submitted to neuromuscular electric stimulation for an average period of 16.6 months, being evaluated for X-ray imaging. Improvements on X-ray images were identified in two patients and the non-progression of the picture was observed in the remaining patients. Neuromuscular electric stimulation in spinal cord-injured individuals could be a useful method for treating heterotropic ossification and related progression prevention.

Neurofilament light chain, a putative measure of neuronal damage, is measurable in blood and CSF and is predictive of cognitive function in individuals with Alzheimer’s disease. There has been limited prior work linking neurofilament light and functional connectivity, and no prior work has investigated neurofilament light associations with functional connectivity in autosomal dominant Alzheimer’s disease. Here, we assessed relationships between blood neurofilament light, cognition, and functional connectivity in a cross-sectional sample of 106 autosomal dominant Alzheimer’s disease mutation carriers and 76 non-carriers. We employed an innovative network-level enrichment analysis approach to assess connectome-wide associations with neurofilament light. Neurofilament light was positively correlated with deterioration of functional connectivity within the default mode network and negatively correlated with connectivity between default mode network and executive control networks, including the cingulo-opercular, salience, and dorsal attention networks. Further, reduced connectivity within the default mode network and between the default mode network and executive control networks was associated with reduced cognitive function. Hierarchical regression analysis revealed that neurofilament levels and functional connectivity within the default mode network and between the default mode network and the dorsal attention network explained significant variance in cognitive composite scores when controlling for age, sex, and education. A mediation analysis demonstrated that functional connectivity within the default mode network and between the default mode network and dorsal attention network partially mediated the relationship between blood neurofilament light levels and cognitive function. Our novel results indicate that blood estimates of neurofilament levels correspond to direct measurements of brain dysfunction, shedding new light on the underlying biological processes of Alzheimer’s disease. Further, we demonstrate how variation within key brain systems can partially mediate the negative effects of heightened total serum neurofilament levels, suggesting potential regions for targeted interventions. Finally, our results lend further evidence that low-cost and minimally invasive blood measurements of neurofilament may be a useful marker of brain functional connectivity and cognitive decline in Alzheimer’s disease.