Weight loss in the healthy elderly might be a non-cognitive sign of preclinical Alzheimer's disease

Weight loss has been proposed as a sign of pre-clinical Alzheimer Disease (AD). To test this hypothesis, we have evaluated the association between longitudinal changes in weight trajectories, cognitive performance, AD biomarker profiles and brain structure in 363 healthy controls from the Alzheimer's Disease Neuroimaging Initiative (mean follow-up 50.5±30.5 months). Subjects were classified according to body weight trajectory into a weight loss group (WLG; relative weight loss ≥ 5%) and a non-weight loss group (non-WLG; relative weight loss < 5%). Linear mixed effects models were used to estimate the effect of body weight changes on ADAS-Cognitive score across time. Baseline CSF tau/AΔ ratio and AV45 PET uptake were compared between WLG and non-WLG by analysis of covariance. Atrophy maps were compared between groups at baseline and longitudinally at a 2-year follow-up using Freesurfer. WLG showed increased baseline levels of cerebrospinal fluid tau/AΔ ratio, increased PET amyloid uptake and diminished cortical thickness at baseline. WLG also showed faster cognitive decline and faster longitudinal atrophy. Our data support weight loss as a non-cognitive manifestation of pre-clinical AD

Cerebrospinal fluid profile of NPTX2 supports role of Alzheimer's disease-related inhibitory circuit dysfunction in adults with down syndrome

Alzheimer's disease (AD) is the major cause of death in adults with Down syndrome (DS). There is an urgent need for objective markers of AD in the DS population to improve early diagnosis and monitor disease progression. NPTX2 has recently emerged as a promising cerebrospinal fluid (CSF) biomarker of Alzheimer-related inhibitory circuit dysfunction in sporadic AD patients. The objective of this study was to evaluate NPTX2 in the CSF of adults with DS and to explore the relationship of NPTX2 to CSF levels of the PV interneuron receptor, GluA4, and existing AD biomarkers (CSF and neuroimaging). This is a cross-sectional, retrospective study of adults with DS with asymptomatic AD (aDS, n = 49), prodromal AD (pDS, n = 18) and AD dementia (dDS, n = 27). Non-trisomic controls (n = 34) and patients with sporadic AD dementia (sAD, n = 40) were included for comparison. We compared group differences in CSF NPTX2 according to clinical diagnosis and degree of intellectual disability. We determined the relationship of CSF NPTX2 levels to age, cognitive performance (CAMCOG, free and cued selective reminding, semantic verbal fluency), CSF levels of a PV-interneuron marker (GluA4) and core AD biomarkers; CSF Aβ1-42, CSF t-tau, cortical atrophy (magnetic resonance imaging) and glucose metabolism ([18F]-fluorodeoxyglucose positron emission tomography). Compared to controls, mean CSF NPTX2 levels were lower in DS at all AD stages; aDS (0.6-fold, adj.p 0.07). Low CSF NPTX2 levels were associated with low GluA4 in all clinical groups; controls (r 2 = 0.2, p = 0.003), adults with DS (r 2 = 0.4, p 0.3, p 0.3, p < 0.001), increased cortical atrophy (p < 0.05) and reduced glucose metabolism (p < 0.05). Low levels of CSF NPTX2, a protein implicated in inhibitory circuit function, is common to sporadic and genetic forms of AD. CSF NPTX2 represents a promising CSF surrogate marker of early AD-related changes in adults with DS

Neural correlates of episodic memory in adults with Down syndrome and Alzheimer’s disease

Background Adults with Down syndrome are at an ultra-high risk of developing early-onset Alzheimer's disease. Episodic memory deficits are one of the earliest signs of the disease, but their association with regional brain atrophy in the population with Down syndrome has not been explored. We aimed to investigate the neuroanatomical correlates of episodic memory in adults with Down syndrome and symptomatic Alzheimer's disease. Methods Single-center, cross-sectional study. A total of 139 adults with Down syndrome (85 asymptomatic and 54 with symptomatic Alzheimer's disease) were included in the study (mean age 43.6 +/- 10.9 years, 46% female). Episodic memory was assessed using the modified Cued Recall Test. Immediate (trial 1 free immediate recall, trial 3 free immediate recall, total free immediate recall score, and total immediate score) and delayed scores (free delayed recall score and total delayed score) were examined. Cortical thickness from magnetic resonance imaging was determined with surface-based morphometry using the FreeSurfer 6.0 software package. The clusters of reduced cortical thickness were compared between symptomatic and asymptomatic participants to create a cortical atrophy map. Then, the correlation between cortical thickness and the modified Cued Recall Test subscores were separately assessed in symptomatic and asymptomatic subjects, controlling for age, sex, and severity of intellectual disability. Results Compared with asymptomatic participants, those with symptomatic Alzheimer's disease showed a pattern of cortical atrophy in posterior parieto-temporo-occipital cortices. In symptomatic subjects, trial 1 immediate free recall significantly correlated with cortical atrophy in lateral prefrontal regions. Trial 3 free immediate recall and total free immediate recall were associated with the most widespread cortical atrophy. Total immediate score was related to posterior cortical atrophy, including lateral parietal and temporal cortex, posterior cingulate cortex, precuneus, and medial temporal lobe areas. Delayed memory scores were associated with cortical atrophy in temporoparietal and medial temporal lobe regions. No significant relationships were observed between episodic memory measures and cortical atrophy in asymptomatic subjects. Conclusions Different episodic memory measures were associated with cortical atrophy in specific brain regions in adults with Down syndrome and Alzheimer's disease. These results overlap with those described in sporadic Alzheimer's disease and further support the similarities between Down syndrome-associated Alzheimer's disease and that in the general population

Longitudinal Clinical and Cognitive Changes Along the Alzheimer Disease Continuum in Down Syndrome

IMPORTANCE Alzheimer disease (AD) is the main medical problem in adults with Down syndrome (DS). However, the associations of age, intellectual disability (ID), and clinical status with progression and longitudinal cognitive decline have not been established. OBJECTIVE To examine clinical progression along the AD continuum and its related cognitive decline and to explore the presence of practice effects and floor effects with repeated assessments. DESIGN, SETTING, AND PARTICIPANTS This is a single-center cohort study of adults (aged >18 years) with DS with different ID levels and at least 6 months of follow-up between November 2012 and December 2021. The data are from a population-based health plan designed to screen for AD in adults with DS in Catalonia. Spain. Individuals were classified as being asymptomatic, having prodromal AD, or having AD dementia. EXPOSURES Neurological and neuropsychological assessments. MAIN OUTCOMES AND MEASURES The main outcome was clinical change along the AD continuum. Cognitive decline was measured by the Cambridge Cognitive Examination for Older Adults With Down Syndrome and the modified Cued Recall Test. RESULTS A total of 632 adults with DS (mean [SD] age, 42.6 [11.4] years; 292 women [46.2%]) with 2847 evaluations (mean [SD] follow-up, 28.8 [18.7] months) were assessed. At baseline, there were 436 asymptomatic individuals, 69 patients with prodromal AD, and 127 with AD dementia. After 5 years of follow-up, 17.1% (95% CI, 12.5%-21.5%) of asymptomatic individuals progressed to symptomatic AD in an age-dependent manner (0.6% [95% CI, 0%-1.8%] for age = 50 years; P < .001), and 94.1% (95% CI. 84.6%-98.0%) of patients with prodromal AD progressed to dementia with no age dependency. Cognitive decline in the older individuals was most common among those who progressed to symptomatic AD and symptomatic individuals themselves. Importantly, individuals with mild and moderate ID had no differences in longitudinal cognitive decline despite having different performance at baseline. This study also found practice and floor effects, which obscured the assessment of longitudinal cognitive decline. CONCLUSIONS AND RELEVANCE This study found an association between the development of symptomatic AD and a high risk of progressive cognitive decline among patients with DS. These results support the need for population health plans to screen for AD-related cognitive decline from the fourth decade of life and provide important longitudinal data to inform clinical trials in adults with DS to prevent AD

Clinical and biomarker changes of Alzheimer's disease in adults with Down syndrome : a cross-sectional study

Altres ajuts: Instituto de Salud Carlos III, Fundació Bancaria La Caixa, Fundació La Marató de TV3, Medical Research Council, and National Institutes of Health.Alzheimer's disease and its complications are the leading cause of death in adults with Down syndrome. Studies have assessed Alzheimer's disease in individuals with Down syndrome, but the natural history of biomarker changes in Down syndrome has not been established. We characterised the order and timing of changes in biomarkers of Alzheimer's disease in a population of adults with Down syndrome. We did a dual-centre cross-sectional study of adults with Down syndrome recruited through a population-based health plan in Barcelona (Spain) and through services for people with intellectual disabilities in Cambridge (UK). Cognitive impairment in participants with Down syndrome was classified with the Cambridge Cognitive Examination for Older Adults with Down Syndrome (CAMCOG-DS). Only participants with mild or moderate disability were included who had at least one of the following Alzheimer's disease measures: apolipoprotein E allele carrier status; plasma concentrations of amyloid β peptides 1-42 and 1-40 and their ratio (Aβ), total tau protein, and neurofilament light chain (NFL); tau phosphorylated at threonine 181 (p-tau), and NFL in cerebrospinal fluid (CSF); and one or more of PET with 18 F-fluorodeoxyglucose, PET with amyloid tracers, and MRI. Cognitively healthy euploid controls aged up to 75 years who had no biomarker abnormalities were recruited from the Sant Pau Initiative on Neurodegeneration. We used a first-order locally estimated scatterplot smoothing curve to determine the order and age at onset of the biomarker changes, and the lowest ages at the divergence with 95% CIs are also reported where appropriate. Between Feb 1, 2013, and June 28, 2019 (Barcelona), and between June 1, 2009, and Dec 31, 2014 (Cambridge), we included 388 participants with Down syndrome (257 [66%] asymptomatic, 48 [12%] with prodromal Alzheimer's disease, and 83 [21%] with Alzheimer's disease dementia) and 242 euploid controls. CSF Aβ and plasma NFL values changed in individuals with Down syndrome as early as the third decade of life, and amyloid PET uptake changed in the fourth decade. 18 F-fluorodeoxyglucose PET and CSF p-tau changes occurred later in the fourth decade of life, followed by hippocampal atrophy and changes in cognition in the fifth decade of life. Prodromal Alzheimer's disease was diagnosed at a median age of 50·2 years (IQR 47·5-54·1), and Alzheimer's disease dementia at 53·7 years (49·5-57·2). Symptomatic Alzheimer's disease prevalence increased with age in individuals with Down syndrome, reaching 90-100% in the seventh decade of life. Alzheimer's disease in individuals with Down syndrome has a long preclinical phase in which biomarkers follow a predictable order of changes over more than two decades. The similarities with sporadic and autosomal dominant Alzheimer's disease and the prevalence of Down syndrome make this population a suitable target for Alzheimer's disease preventive treatments. Instituto de Salud Carlos III, Fundació Bancaria La Caixa, Fundació La Marató de TV3, Medical Research Council, and National Institutes of Health

Association of biological sex with clinical outcomes and biomarkers of Alzheimer's disease in adults with Down syndrome

The study of sex differences in Alzheimer's disease is increasingly recognized as a key priority in research and clinical development. People with Down syndrome represent the largest population with a genetic link to Alzheimer's disease (>90% in the 7th decade). Yet, sex differences in Alzheimer's disease manifestations have not been fully investigated in these individuals, who are key candidates for preventive clinical trials. In this double-centre, cross-sectional study of 628 adults with Down syndrome [46% female, 44.4 (34.6; 50.7) years], we compared Alzheimer's disease prevalence, as well as cognitive outcomes and AT(N) biomarkers across age and sex. Participants were recruited from a population-based health plan in Barcelona, Spain, and from a convenience sample recruited via services for people with intellectual disabilities in England and Scotland. They underwent assessment with the Cambridge Cognitive Examination for Older Adults with Down Syndrome, modified cued recall test and determinations of brain amyloidosis (CSF amyloid-β 42 / 40 and amyloid-PET), tau pathology (CSF and plasma phosphorylated-tau181) and neurodegeneration biomarkers (CSF and plasma neurofilament light, total-tau, fluorodeoxyglucose-PET and MRI). We used within-group locally estimated scatterplot smoothing models to compare the trajectory of biomarker changes with age in females versus males, as well as by apolipoprotein ɛ4 carriership. Our work revealed similar prevalence, age at diagnosis and Cambridge Cognitive Examination for Older Adults with Down Syndrome scores by sex, but males showed lower modified cued recall test scores from age 45 compared with females. AT(N) biomarkers were comparable in males and females. When considering apolipoprotein ɛ4, female ɛ4 carriers showed a 3-year earlier age at diagnosis compared with female non-carriers (50.5 versus 53.2 years, P = 0.01). This difference was not seen in males (52.2 versus 52.5 years, P = 0.76). Our exploratory analyses considering sex, apolipoprotein ɛ4 and biomarkers showed that female ɛ4 carriers tended to exhibit lower CSF amyloid-β 42/amyloid-β 40 ratios and lower hippocampal volume compared with females without this allele, in line with the clinical difference. This work showed that biological sex did not influence clinical and biomarker profiles of Alzheimer's disease in adults with Down syndrome. Consideration of apolipoprotein ɛ4 haplotype, particularly in females, may be important for clinical research and clinical trials that consider this population. Accounting for, reporting and publishing sex-stratified data, even when no sex differences are found, is central to helping advance precision medicine

APOE -by-sex interactions on brain structure and metabolism in healthy elderly controls

Altres ajuts: Marató TV3 (531/U/2014); NIH-NIA grants (AG022374, AG13616, AG12101)The APOE effect on Alzheimer Disease (AD) risk is stronger in women than in men but its mechanisms have not been established. We assessed the APOE -by-sex interaction on core CSF biomarkers, brain metabolism and structure in healthy elderly control individuals (HC). Cross-sectional study. HC from the Alzheimer's Disease Neuroimaging Initiative with available CSF (n = 274) and/or 3T-MRI (n = 168) and/or a FDG-PET analyses (n = 328) were selected. CSF amyloid-β (Aβ), total-tau (t-tau) and phospho-tau (p-tau) levels were measured by Luminex assays. We analyzed the APOE -by-sex interaction on the CSF biomarkers in an analysis of covariance (ANCOVA). FDG uptake was analyzed by SPM8 and cortical thickness (CTh) was measured by FreeSurfer. FDG and CTh difference maps were derived from interaction and group analyses. APOE4 carriers had lower CSF Aβ and higher CSF p-tau values than non-carriers, but there was no APOE -by-sex interaction on CSF biomarkers. The APOE -by-sex interaction on brain metabolism and brain structure was significant. Sex stratification showed that female APOE4 carriers presented widespread brain hypometabolism and cortical thinning compared to female non-carriers whereas male APOE4 carriers showed only a small cluster of hypometabolism and regions of cortical thickening compared to male non-carriers. The impact of APOE4 on brain metabolism and structure is modified by sex. Female APOE4 carriers show greater hypometabolism and atrophy than male carriers. This APOE -by-sex interaction should be considered in clinical trials in preclinical AD where APOE4 status is a selection criterion

APOE-by-sex interactions on brain structure and metabolism in healthy elderly controls

BACKGROUND: The APOE effect on Alzheimer Disease (AD) risk is stronger in women than in men but its mechanisms have not been established. We assessed the APOE-by-sex interaction on core CSF biomarkers, brain metabolism and structure in healthy elderly control individuals (HC). METHODS: Cross-sectional study. HC from the Alzheimer's Disease Neuroimaging Initiative with available CSF (n = 274) and/or 3T-MRI (n = 168) and/or a FDG-PET analyses (n = 328) were selected. CSF amyloid-β1-42 (Aβ1-42), total-tau (t-tau) and phospho-tau (p-tau181p) levels were measured by Luminex assays. We analyzed the APOE-by-sex interaction on the CSF biomarkers in an analysis of covariance (ANCOVA). FDG uptake was analyzed by SPM8 and cortical thickness (CTh) was measured by FreeSurfer. FDG and CTh difference maps were derived from interaction and group analyses. RESULTS: APOE4 carriers had lower CSF Aβ1-42 and higher CSF p-tau181p values than non-carriers, but there was no APOE-by-sex interaction on CSF biomarkers. The APOE-by-sex interaction on brain metabolism and brain structure was significant. Sex stratification showed that female APOE4 carriers presented widespread brain hypometabolism and cortical thinning compared to female non-carriers whereas male APOE4 carriers showed only a small cluster of hypometabolism and regions of cortical thickening compared to male non-carriers. CONCLUSIONS: The impact of APOE4 on brain metabolism and structure is modified by sex. Female APOE4 carriers show greater hypometabolism and atrophy than male carriers. This APOE-by-sex interaction should be considered in clinical trials in preclinical AD where APOE4 status is a selection criterion

Complex Neuroimaging Changes in Metabolite, Cortical Structures and Regional Vulnerabilities in the Alzheimer Disease Continuum

La enfermedad de Alzheimer es la principal causa de demencia. Patológicamente, está caracterizada por tau hiperfosforilada intracelular y el depósito de placas de amiloide extracelular. Estos procesos fisiopatológicos empiezan décadas antes de que aparezca el deterioro cognitivo, y conllevan atrofia cerebral y neurodegeneracion. La imagen por resonancia magnética (RM) nos permite caracterizar "invivo" los cambios corticales en las fases preclínicas de la enfermedad. Esta tesis incluye trabajos donde se estudian los cambios macroestructurales, microestrucutrales y de metabolitos corticales a lo largo del continuo de la EA. Este trabajo destaca la complejidad de estos cambios y su trayectoria no lineal, y analiza la vulnerabilidad regional que subyace a la propagación de tau en las fases tempranas de la enfermedad. En concreto, en el primer trabajo de esta tesis, se modeló matemáticamente la trayectoria de cambios de grosor cortical y difusividad cortical en la EA autosómica dominante. Demostramos que existe los cambios corticales siguen una trayectoria bifásica, donde en el inicio y relacionado con el acúmulo de amiloide, aparece un incremento del grosor cortical y un descenso de la difusividad cortical, que siguen a cambios hacia atrofia e incrementos de difusividad una vez tau adquiere valores patológicos (15 años antes de que empiecen los síntomas clínicos). En el segundo trabajo de esta tesis se caracterizó las alteraciones de metabolitos en el continuo de la EA en una muestra de adultos con Síndrome de Down usando resonancia magnética por espectroscopia (RMS). Este estudio demuestra el potencial de la RMS para detectar alteraciones relacionadas con la neurodegeneracion en la EA. En el tercer trabajo de esta tesis se investigó el potencial de la difusividad cortical como marcador de neurodegeneracion, y su relación con el acúmulo patológico de tau en las fases preclínicas de la EA. En el cuarto trabajo de esta tesis se estudió el perfil genético de la vulnerabilidad regional asociada al patrón de propagación de tau. Para este trabajo se desarrollaron herramientas basadas en teoría de grafos para caracterizar la propagación de tau, integrando información de alta resolución sobre expresión génica. Esta tesis supone potenciales implicaciones. En primer lugar, consolida la presencia de un modelo bifasico de cambios corticales que proporciona una explicacion a resultados aparentemente adversos en la literatura, y propone el potencial de la RM para capturar alteraciones estructurales en las etapas tempranas de la enfermedad. En segundo lugar, demuestra el potencial de la RMS como marcador no invasico para medir la neurodegeneracion e inflamacion en la poblacion con Sindrome de Down. En tercer lugar, propone que la difusividad cortical es un potencial marcador de neurodegeneracion mas sensible que el grosor cortical, con potencial para ser usado en ensayos clinicos. En ultimo lugar, propone un marco analitico para estudiar las vulnerabilidades regionales asociadas a la propagacion de tau, cuyos resultados pueden suponer una guia de investigacion a nuevas dianas farmacologicas. En conclusion, esta tesis destaca la complejidad de los cambios corticales en etapas preclinicas de la EA y su vulnerabilidad regional.Alzheimer disease (AD) is the most important cause of dementia. Its histopathological hallmarks are intracellular hyperphosphorylated tau and extracellular amyloid plaques, which start to accumulate decades before the onset of clinical symptoms and eventually lead to neurodegeneration and brain atrophy. Magnetic resonance imaging (MRI) provides a window to characterize in vivo the cortical changes in the preclinical and clinical phases of the disease. This thesis studied the cortical macrostructural, microstructural and metabolite changes along the AD continuum. It highlights the complex and non-linear alterations in the preclinical phase and analyzes the characteristic regional vulnerability underlying the spread of tau in early stages of the disease. Specifically, the first work of the thesis mathematically modeled the trajectory of cortical thickness and cortical mean diffusivity in autosomal dominant Alzheimer disease. This work demonstrated a biphasic trajectory of cortical alterations, in which the initial increases of amyloid were associated with increased cortical thickness and decreased cortical diffusivity, but were followed by cortical thinning and increased cortical diffusivity once tau becomes abnormal (15 years prior to symptom onset). The second work of this thesis characterized the alterations of metabolites along the AD continuum in a cohort of Down Syndrome using magnetic resonance spectroscopy (MRS). This work showed the potential of MRS to detect AD-related inflammation and neurodegeneration. The third work of this thesis investigated the potential of cortical diffusivity as a marker of neurodegeneration and its relationship with the accumulation of tau in preclinical AD. This work showed cortical diffusivity decreases were associated with the accumulation of tau in inferior temporal regions and predicted clinical deterioration. The fourth work of this thesis studied the genetic regional vulnerability associated to the stereotypical pattern of tau accumulation. This work developed a novel graph-theory-based framework to characterize the spread of tau integrating a high-resolution data of gene expression. This thesis has several important potential implications. First, it consolidates the biphasic trajectory of cortical alterations that reconciles previous conflicting results in the literature, greatly expand the potential of MRI to track changes in preclinical AD and provides a rationale to understand the (otherwise) paradoxical findings of increased atrophy in the active arm of anti-amyloid trials. Second, this thesis showed MRS could be a good noninvasive disease-stage biomarker in Down syndrome to track neurodegeneration and neuroinflammation. Third, it shows cortical mean diffusivity could be a more sensitive marker of neurodegeneration than cortical thickness that could be implemented in clinical trials. Finally, it provides a new framework to analyze the regional vulnerability underlying the spread of tau which could lead to the identification of new drug targets. In conclusion, this thesis highlights the complexity of the cortical changes preclinical AD and their regional vulnerability, but also demonstrates the potential of MRI to track these changes when using a multimodal approach, nonlinear models and new analytical frameworks