Sex-specific modulation of amyloid-ß on tau phosphorylation underlies faster tangle accumulation in females.

Females are disproportionately affected by dementia due to Alzheimer's disease. Despite a similar amyloid-ß (Aß) load, a higher load of neurofibrillary tangles (NFTs) is seen in females than males. Previous literature has proposed that Aß and phosphorylated-tau (p-tau) synergism accelerates tau tangle formation, yet the effect of biological sex in this process has been overlooked. In this observational study, we examined longitudinal neuroimaging data from the TRIAD and ADNI cohorts from Canada and USA, respectively. We assessed 457 participants across the clinical spectrum of Alzheimer's disease. All participants underwent baseline multimodal imaging assessment, including MRI and PET, with radioligands targeting Aß plaques and tau tangles, respectively. CSF data were also collected. Follow-up imaging assessments were conducted at 1- and 2-year intervals for the TRIAD cohort and 1-, 2- and 4-year intervals for the ADNI cohort. The upstream pathological events contributing to faster tau progression in females were investigated-specifically, whether the contribution of Aß and p-tau synergism to accelerated tau tangle formation is modulated by biological sex. We hypothesized that cortical Aß predisposes tau phosphorylation and tangle accumulation in a sex-specific manner. Findings revealed that Aß-positive females presented higher CSF p-tau181 concentrations compared with Aß-positive males in both the TRIAD (P = 0.04, Cohen's d = 0.51) and ADNI (P = 0.027, Cohen's d = 0.41) cohorts. In addition, Aß-positive females presented faster NFT accumulation compared with their male counterparts (TRIAD: P = 0.026, Cohen's d = 0.52; ADNI: P = 0.049, Cohen's d = 1.14). Finally, the triple interaction between female sex, Aß and CSF p-tau181 was revealed as a significant predictor of accelerated tau accumulation at the 2-year follow-up visit (Braak I: P = 0.0067, t = 2.81; Braak III: P = 0.017, t = 2.45; Braak IV: P = 0.002, t = 3.17; Braak V: P = 0.006, t = 2.88; Braak VI: P = 0.0049, t = 2.93). Overall, we report sex-specific modulation of cortical Aß in tau phosphorylation, consequently facilitating faster NFT progression in female individuals over time. This presents important clinical implications and suggests that early intervention that targets Aß plaques and tau phosphorylation may be a promising therapeutic strategy in females to prevent the further accumulation and spread of tau aggregates.

Sutimlimab in Cold Agglutinin Disease.

BACKGROUND: Cold agglutinin disease is a rare autoimmune hemolytic anemia characterized by hemolysis that is caused by activation of the classic complement pathway. Sutimlimab, a humanized monoclonal antibody, selectively targets the C1s protein, a C1 complex serine protease responsible for activating this pathway. METHODS: We conducted a 26-week multicenter, open-label, single-group study to assess the efficacy and safety of intravenous sutimlimab in patients with cold agglutinin disease and a recent history of transfusion. The composite primary end point was a normalization of the hemoglobin level to 12 g or more per deciliter or an increase in the hemoglobin level of 2 g or more per deciliter from baseline, without red-cell transfusion or medications prohibited by the protocol. RESULTS: A total of 24 patients were enrolled and received at least one dose of sutimlimab; 13 patients (54%) met the criteria for the composite primary end point. The least-squares mean increase in hemoglobin level was 2.6 g per deciliter at the time of treatment assessment (weeks 23, 25, and 26). A mean hemoglobin level of more than 11 g per deciliter was maintained in patients from week 3 through the end of the study period. The mean bilirubin levels normalized by week 3. A total of 17 patients (71%) did not receive a transfusion from week 5 through week 26. Clinically meaningful reductions in fatigue were observed by week 1 and were maintained throughout the study. Activity in the classic complement pathway was rapidly inhibited, as assessed by a functional assay. Increased hemoglobin levels, reduced bilirubin levels, and reduced fatigue coincided with inhibition of the classic complement pathway. At least one adverse event occurred during the treatment period in 22 patients (92%). Seven patients (29%) had at least one serious adverse event, none of which were determined by the investigators to be related to sutimlimab. No meningococcal infections occurred. CONCLUSIONS: In patients with cold agglutinin disease who received sutimlimab, selective upstream inhibition of activity in the classic complement pathway rapidly halted hemolysis, increased hemoglobin levels, and reduced fatigue. (Funded by Sanofi; CARDINAL ClinicalTrials.gov number, NCT03347396.).

Plasma phosphorylated tau181 outperforms [18F] fluorodeoxyglucose positron emission tomography in the identification of early Alzheimer disease.

BACKGROUND AND PURPOSE: This study was undertaken to compare the performance of plasma p-tau181 with that of [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the identification of early biological Alzheimer disease (AD). METHODS: We included 533 cognitively impaired participants from the Alzheimer's Disease Neuroimaging Initiative. Participants underwent PET scans, biofluid collection, and cognitive tests. Receiver operating characteristic analyses were used to determine the diagnostic accuracy of plasma p-tau181 and [18F]FDG-PET using clinical diagnosis and core AD biomarkers ([18F]florbetapir-PET and cerebrospinal fluid [CSF] p-tau181) as reference standards. Differences in the diagnostic accuracy between plasma p-tau181 and [18F]FDG-PET were determined by bootstrap-based tests. Correlations of [18F]FDG-PET and plasma p-tau181 with CSF p-tau181, amyloid ß (Aß) PET, and cognitive performance were evaluated to compare associations between measurements. RESULTS: We observed that both plasma p-tau181 and [18F]FDG-PET identified individuals with positive AD biomarkers in CSF or on Aß-PET. In the MCI group, plasma p-tau181 outperformed [18F]FDG-PET in identifying AD measured by CSF (p = 0.0007) and by Aß-PET (p = 0.001). We also observed that both plasma p-tau181 and [18F]FDG-PET metabolism were associated with core AD biomarkers. However, [18F]FDG-PET uptake was more closely associated with cognitive outcomes (Montreal Cognitive Assessment, Mini-Mental State Examination, Clinical Dementia Rating Sum of Boxes, and logical memory delayed recall, p < 0.001) than plasma p-tau181. CONCLUSIONS: Overall, although both plasma p-tau181 and [18F]FDG-PET were associated with core AD biomarkers, plasma p-tau181 outperformed [18F]FDG-PET in identifying individuals with early AD pathophysiology. Taken together, our study suggests that plasma p-tau181 may aid in detecting individuals with underlying early AD.

Plasma pTau-217 and N-terminal tau (NTA) enhance sensitivity to identify tau PET positivity in amyloid-ß positive individuals.

INTRODUCTION: We set out to identify tau PET-positive (A+T+) individuals among amyloid-beta (Aß) positive participants using plasma biomarkers. METHODS: In this cross-sectional study we assessed 234 participants across the AD continuum who were evaluated by amyloid PET with [18 F]AZD4694 and tau-PET with [18 F]MK6240 and measured plasma levels of total tau, pTau-181, pTau-217, pTau-231, and N-terminal tau (NTA-tau). We evaluated the performances of plasma biomarkers to predict tau positivity in Aß+ individuals. RESULTS: Highest associations with tau positivity in Aß+ individuals were found for plasma pTau-217 (AUC [CI95% ] = 0.89 [0.82, 0.96]) and NTA-tau (AUC [CI95% ] = 0.88 [0.91, 0.95]). Combining pTau-217 and NTA-tau resulted in the strongest agreement (Cohen's Kappa = 0.74, CI95%  = 0.57/0.90, sensitivity = 92%, specificity = 81%) with PET for classifying tau positivity. DISCUSSION: The potential for identifying tau accumulation in later Braak stages will be useful for patient stratification and prognostication in treatment trials and in clinical practice. HIGHLIGHTS: We found that in a cohort without pre-selection pTau-181, pTau-217, and NTA-tau showed the highest association with tau PET positivity. We found that in Aß+ individuals pTau-217 and NTA-tau showed the highest association with tau PET positivity. Combining pTau-217 and NTA-tau resulted in the strongest agreement with the tau PET-based classification.

14-3-3 [Formula: see text]-reported early synaptic injury in Alzheimer's disease is independently mediated by sTREM2.

INTRODUCTION: Synaptic loss is closely associated with tau aggregation and microglia activation in later stages of Alzheimer's disease (AD). However, synaptic damage happens early in AD at the very early stages of tau accumulation. It remains unclear whether microglia activation independently causes synaptic cleavage before tau aggregation appears. METHODS: We investigated 104 participants across the AD continuum by measuring 14-3-3 zeta/delta ([Formula: see text]) as a cerebrospinal fluid biomarker for synaptic degradation, and fluid and imaging biomarkers of tau, amyloidosis, astrogliosis, neurodegeneration, and inflammation. We performed correlation analyses in cognitively unimpaired and impaired participants and used structural equation models to estimate the impact of microglia activation on synaptic injury in different disease stages. RESULTS: 14-3-3 [Formula: see text] was increased in participants with amyloid pathology at the early stages of tau aggregation before hippocampal volume loss was detectable. 14-3-3 [Formula: see text] correlated with amyloidosis and tau load in all participants but only with biomarkers of neurodegeneration and memory deficits in cognitively unimpaired participants. This early synaptic damage was independently mediated by sTREM2. At later disease stages, tau and astrogliosis additionally mediated synaptic loss. CONCLUSIONS: Our results advertise that sTREM2 is mediating synaptic injury at the early stages of tau accumulation, underlining the importance of microglia activation for AD disease propagation.

Equivalence of plasma p-tau217 with cerebrospinal fluid in the diagnosis of Alzheimer's disease.

INTRODUCTION: Plasma biomarkers are promising tools for Alzheimer's disease (AD) diagnosis, but comparisons with more established biomarkers are needed. METHODS: We assessed the diagnostic performance of p-tau181 , p-tau217 , and p-tau231 in plasma and CSF in 174 individuals evaluated by dementia specialists and assessed with amyloid-PET and tau-PET. Receiver operating characteristic (ROC) analyses assessed the performance of plasma and CSF biomarkers to identify amyloid-PET and tau-PET positivity. RESULTS: Plasma p-tau biomarkers had lower dynamic ranges and effect sizes compared to CSF p-tau. Plasma p-tau181 (AUC = 76%) and p-tau231 (AUC = 82%) assessments performed inferior to CSF p-tau181 (AUC = 87%) and p-tau231 (AUC = 95%) for amyloid-PET positivity. However, plasma p-tau217 (AUC = 91%) had diagnostic performance indistinguishable from CSF (AUC = 94%) for amyloid-PET positivity. DISCUSSION: Plasma and CSF p-tau217 had equivalent diagnostic performance for biomarker-defined AD. Our results suggest that plasma p-tau217 may help reduce the need for invasive lumbar punctures without compromising accuracy in the identification of AD. HIGHLIGHTS: p-tau217 in plasma performed equivalent to p-tau217 in CSF for the diagnosis of AD, suggesting the increased accessibility of plasma p-tau217 is not offset by lower accuracy. p-tau biomarkers in plasma had lower mean fold-changes between amyloid-PET negative and positive groups than p-tau biomarkers in CSF. CSF p-tau biomarkers had greater effect sizes than plasma p-tau biomarkers when differentiating between amyloid-PET positive and negative groups. Plasma p-tau181 and plasma p-tau231 performed worse than p-tau181 and p-tau231 in CSF for AD diagnosis.

Complement-mediated hemolysis persists year round in patients with cold agglutinin disease.

BACKGROUND: Cold agglutinin disease (CAD) is a rare autoimmune hemolytic anemia mediated by immunoglobulin M autoantibodies that bind to the "I" antigen on erythrocytes. IgM binding results in either agglutination at ≤37°C, activation of the classical complement pathway, or both. Patients with CAD can have transient agglutination-mediated circulatory symptoms triggered by exposure to cold conditions. Separately, patients with CAD can experience complement-mediated symptoms such as anemia, hemolysis, and fatigue, but the effect of the season on these complement-mediated manifestations of CAD and clinical outcomes is not well understood. METHODS: Using data from the Optum® de-identified Electronic Health Record dataset, we compared hemoglobin, markers of hemolysis (bilirubin and lactate dehydrogenase [LDH]), and healthcare resource utilization (HRU) between seasons for 594 patients (62% female; 66% aged ≥65 years) with CAD (defined as having CAD-related terms in their clinical notes on ≥3 separate occasions between December 2008 and May 2016). Laboratory parameters and HRU were compared between seasons using multivariate regression models. RESULTS: Estimated median hemoglobin (9.87 g/dL in summer and 9.86 g/dL in winter; P = 0.944) and bilirubin (1.04 mg/dL in summer and 1.09 mg/dL in winter; P = 0.257) were similar in winter versus summer. While LDH was statistically significantly higher in winter compared with summer (P < 0.001), the estimated median value was above normal for both seasons (309 U/L in summer and 367 U/L in winter). HRU measures and transfusion and thromboembolism rates were similar across seasons. CONCLUSIONS: Patients with CAD had evidence of persistent chronic hemolysis, HRU, and thromboembolism risk year round.

Sutimlimab improves quality of life in patients with cold agglutinin disease: results of patient-reported outcomes from the CARDINAL study.

Patients with cold agglutinin disease (CAD) experience fatigue and poor quality of life. However, previous CAD-related studies have not explored patient-reported outcomes such as the Functional Assessment of Chronic Illness Therapy (FACIT)-Fatigue. Sutimlimab, a C1s complement inhibitor, has been shown to halt haemolysis in CAD. Here, we present 26-weeks' patient-reported data from CARDINAL Part A (ClinicalTrials.gov, NCT03347396), which assessed efficacy and safety of sutimlimab in patients with CAD and recent history of transfusion. Aside from measuring changes in haemolytic markers, FACIT-Fatigue was measured at the treatment assessment timepoint (TAT; average of weeks 23, 25, and 26). Exploratory endpoints included the change in EuroQol 5-dimension 5-level questionnaire (EQ-5D-5L) and the 12-Item Short Form Health Survey (SF-12) at TAT, and Patient Global Impression of Change (PGIC), and Patient Global Impression of (fatigue) Severity (PGIS) at week 26. Mean (range) FACIT-Fatigue scores increased from 32.5 (14.0-47.0) at baseline (a score indicative of severe fatigue) to 44.3 (28.0-51.0) at TAT. Considerable improvements were reported for EQ-5D-5L at TAT, SF-12 scores at TAT, and PGIC and PGIS scores at week 26. Sutimlimab treatment resulted in sustained improvements in symptoms of fatigue and overall quality of life in patients with CAD. NCT03347396. Registered 20 November, 2017.

Mitochondrial complex I abnormalities underlie neurodegeneration and cognitive decline in Alzheimer's disease.

BACKGROUND AND PURPOSE: Abnormal mitochondrial metabolism has been described in the Alzheimer's disease (AD) brain. However, the relationship between AD pathophysiology and key mitochondrial processes remains elusive. The purpose of this study was to investigate whether mitochondrial complex I dysfunction is associated with amyloid aggregation or glucose metabolism and brain atrophy in patients with mild AD using positron emission tomography (PET). METHODS: Amyloid- and tau-positive symptomatic AD patients with clinical dementia rating 0.5 or 1 (N = 30; mean age ± standard deviation: 71.8 ± 7.6 years) underwent magnetic resonance imaging and PET scans with [18 F]2-tert-butyl-4-chloro-5-2H-pyridazin-3-one (BCPP-EF), [11 C]Pittsburgh Compound-B (PiB) and [18 F]fluorodeoxyglucose (FDG) to assess brain atrophy, mitochondrial complex I dysfunction, amyloid deposition, and glucose metabolism, respectively. Local cortical associations among these biomarkers and gray matter volume were evaluated with voxel-based regressions models. RESULTS: [18 F]BCPP-EF standardized uptake value ratio (SUVR) was positively correlated with [18 F]FDG SUVR in the widespread brain area, while its associations with gray matter volume were restricted to the parahippocampal gyrus. Reductions in [18 F]BCPP-EF SUVR were associated with domain-specific cognitive performance. We did not observe regional associations between mitochondrial dysfunction and amyloid burden. CONCLUSIONS: In symptomatic cases, although mitochondrial complex I reduction is linked to a wide range of downstream neurodegenerative processes such as hypometabolism, atrophy, and cognitive decline, a link to amyloid was not observable. The data presented here support [18 F]BCPP-EF as an excellent imaging tool to investigate mitochondrial dysfunction in AD.

Carcinogenesis: the cancer cell-mast cell connection.

BACKGROUND: In mammals, inflammation is required for wound repair and tumorigenesis. However, the events that lead to inflammation, particularly in non-healing wounds and cancer, are only partly understood. FINDINGS: Mast cells, due to their great plasticity, could orchestrate the inflammatory responses inducing the expression of extraembryonic programs of normal and pathological tissue formation. This heterogeneity of mast cells could allow a microenvironment to be recreated similar to the extraembryonic structures, i.e., amnion and yolk sac, which are needed for embryonic development. Mast cells could provide a framework for understanding the connection between inflammation and tumor growth, invasion and metastasis. In this way, the mast cells could express inflammatory phenotypes, which would enable the cancer stem cells to develop. Thus, the cancer cell uses mast cells to express the extraembryonic functions that are needed to allow the cancer stem cell to proliferate and invade. If so, then by using this appropriate inflammatory interstitial microenvironment, a cancer stem cell can reach maximum levels of growth and invasion inside the host. CONCLUSION: Therefore, the comparison of tumors with wounds that do not heal would be supported since both pathological processes use extraembryonic mechanisms by mast cells. The adoption of these mechanisms warrants tumor survival in an embryonic-like state.

Hepatic encephalopathy: Sometimes more portal than hepatic.

Hepatic encephalopathy is a severe complication of both chronic and acute liver diseases. The term hepatic encephalopathy stems from the belief that hepatic insufficiency is its fundamental etiopathogenic factor. However, most clinical cases show liver failure along with mesenteric venous portal hypertension. This portal hypertension would explain the abnormal mechanical forces suffered by the digestive tract in the early stages of the disorder. These forces could regulate some gut biochemical pathological pathways in a process known as mechanotransduction. Thus, portal hypertension would begin with the establishment of a mechanotransduced afferent or sensory inflammatory gut-brain pathway, resulting in functional and structural changes in the central nervous system. In this review, we will revisit the term "hepatic encephalopathy" in light of new results where portal hypertension occurs before liver failure and is accompanied by brain changes. Moreover, we will point out cellular links that can explain the microbiota, immune, gut, and brain axis disturbances found in this disorder.

The gestational power of mast cells in the injured tissue.

The inflammatory response expressed after wound healing would be the recapitulation of systemic extra-embryonic functions, which would focus on the interstitium of the injured tissue. In the injured tissue, mast cells, provided for a great functional heterogeneity, could play the leading role in the re-expression of extra-embryonic functions, i.e., coelomic-amniotic and trophoblastic-vitelline. Moreover, mast cells would favor the production of a gastrulation-like process, which in certain tissues and organs would induce the regeneration of the injured tissue. Therefore, the engraftment of mesenchymal stem cells and mast cells, both with an extra-embryonic regenerative phenotype, would achieve a blastema, from the repaired and regenerated injured tissue, rather than by fibrosis, which is commonly made through wound-healing.

Successful treatment of acquired hemophilia a with rituximab and steroids in a 5-year-old girl.

Acquired hemophilia A is a very rare, serious bleeding disorder. We describe a 5-year-old female who developed an acquired factor VIII inhibitor, and while under treatment with steroids, had an intestinal perforation with peritonitis and septic shock, making her a poor candidate for further immunosuppression. She was treated with rituximab with rapid, complete eradication of the inhibitor. She represents the first published case of a pediatric patient with acquired hemophilia A successfully treated with rituximab.

Ultrasound-Guided Transversus Abdominis Plane Block as an Effective Path to Reduce Opioid Consumption After Laparoscopic Bariatric Surgery: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

Effective postoperative pain management is essential to the patient's recovery. The use of opioids as the primary line of pain treatment has been known to increase rates of length of stay, pulmonary complications, paralytic ileus, and nausea and vomiting. Therefore, guidelines strongly recommend alternative paths to reduce opioid consumption through multimodal analgesia, and the transversus abdominis plane block(USG-TAP) has been considered to be one of these optimistic alternatives. A comprehensive systematic search was conducted in four databases until April 2024. We only considered for this analysis randomized controlled trials that assessed the USG-TAP as part of multimodal anesthesia in patients undergoing laparoscopic bariatric surgery. Eleven studies comprising 789 patients were included in the meta-analysis. Our results showed a significant decrease in opioid consumption after the first 24 h of surgery (MD - 32.02 mg; 95% IC - 51.33, - 12.71; p < 0.01) and fewer patients required extra-dose of opioid (OR 0.20; 95% IC 0.07, 0.62; p < 0.01). The pain score showed to be also improved with the TAP block (MD - 0.69; 95% IC - 1.32, - 0.07; p = 0.03). No difference concerning time to deambulate, nausea and vomiting, and time of surgery was observed among the studies. This study reinforces the benefits of the use of USG-TAP block as part of multimodal analgesia in patients undergoing laparoscopic bariatric surgery.

Tau follows principal axes of functional and structural brain organization in Alzheimer's disease.

Alzheimer's disease (AD) is a brain network disorder where pathological proteins accumulate through networks and drive cognitive decline. Yet, the role of network connectivity in facilitating this accumulation remains unclear. Using in-vivo multimodal imaging, we show that the distribution of tau and reactive microglia in humans follows spatial patterns of connectivity variation, the so-called gradients of brain organization. Notably, less distinct connectivity patterns ("gradient contraction") are associated with cognitive decline in regions with greater tau, suggesting an interaction between reduced network differentiation and tau on cognition. Furthermore, by modeling tau in subject-specific gradient space, we demonstrate that tau accumulation in the frontoparietal and temporo-occipital cortices is associated with greater baseline tau within their functionally and structurally connected hubs, respectively. Our work unveils a role for both functional and structural brain organization in pathology accumulation in AD, and supports subject-specific gradient space as a promising tool to map disease progression.

In-vivo neuronal dysfunction by Aß and tau overlaps with brain-wide inflammatory mechanisms in Alzheimer's disease.

The molecular mechanisms underlying neuronal dysfunction in Alzheimer's disease (AD) remain uncharacterized. Here, we identify genes, molecular pathways and cellular components associated with whole-brain dysregulation caused by amyloid-beta (Aß) and tau deposits in the living human brain. We obtained in-vivo resting-state functional MRI (rs-fMRI), Aß- and tau-PET for 47 cognitively unimpaired and 16 AD participants from the Translational Biomarkers in Aging and Dementia cohort. Adverse neuronal activity impacts by Aß and tau were quantified with personalized dynamical models by fitting pathology-mediated computational signals to the participant's real rs-fMRIs. Then, we detected robust brain-wide associations between the spatial profiles of Aß-tau impacts and gene expression in the neurotypical transcriptome (Allen Human Brain Atlas). Within the obtained distinctive signature of in-vivo neuronal dysfunction, several genes have prominent roles in microglial activation and in interactions with Aß and tau. Moreover, cellular vulnerability estimations revealed strong association of microglial expression patterns with Aß and tau's synergistic impact on neuronal activity (q < 0.001). These results further support the central role of the immune system and neuroinflammatory pathways in AD pathogenesis. Neuronal dysregulation by AD pathologies also associated with neurotypical synaptic and developmental processes. In addition, we identified drug candidates from the vast LINCS library to halt or reduce the observed Aß-tau effects on neuronal activity. Top-ranked pharmacological interventions target inflammatory, cancer and cardiovascular pathways, including specific medications undergoing clinical evaluation in AD. Our findings, based on the examination of molecular-pathological-functional interactions in humans, may accelerate the process of bringing effective therapies into clinical practice.

Hormone therapy is associated with lower Alzheimer's disease tau biomarkers in post-menopausal females -evidence from two independent cohorts.

BACKGROUND: Females represent approximately 70% of the Alzheimer's disease (AD) cases and the literature has proposed a connection between the decreased estrogen levels during menopause and an increased AD risk. Previous investigations have predominantly focused on assessing how hormone therapy (HT) affects the likelihood of AD development and cognitive deterioration. However, as the research framework has shifted toward a biomarker-defined AD and alterations in specific biomarkers could take place years before cognitive decline becomes discernible, it is crucial to examine how HT influences AD biomarkers. The main goal of this study was to evaluate the impact of HT on AD biomarker-informed pathophysiology in both cognitively unimpaired (CU) and cognitively impaired (CI) post-menopausal females across the aging and AD spectrum. METHODS: This cross-sectional study included post-menopausal females without HT history (HT-) and with HT (HT+) at the time of PET imaging assessment from two cohorts: the Translational Biomarkers in Aging and Dementia (TRIAD) cohort, and the Alzheimer's Disease Neuroimaging Initiative (ADNI). Participants underwent magnetic resonance imaging (MRI), positron emission tomography (PET) and biofluid collection. Voxel-based t-tests were performed to assess the differences in amyloid-ß (Aß) and tau neurofibrillary tangles (NFTs) loads between HT- and HT + females. Linear regression models with interaction terms were also conducted to examine the interactive effects of HT and Aß-PET on regional tau-PET. RESULTS: HT + females demonstrated significantly lower tau-PET standardized uptake value ratio (SUVR) in Braak I-II ROIs (P < 0.05, Hedges' g = 0.73), Braak III-IV ROIs (P < 0.0001, Hedges' g = 0.74) and Braak V-VI ROIs (P < 0.0001, Hedges' g = 0.69) compared to HT- females. HT + females also showed significantly lower CSF p-tau181 (P < 0.001) and plasma p-tau181 (P < 0.0001) concentrations. Additionally, results from multivariate linear regression models indicated that HT interacts with cortical Aß and is associated with lower regional NFT load. CONCLUSIONS: Overall, findings from this observational study suggest that HT is associated with lower tau neuroimaging and fluid biomarkers in postmenopausal females. Due to the close link between tau and cognition, this study highlights the need for large randomized controlled trials designed to systemically study the influences of HT on AD biomarkers and disease progression.

Personalized whole-brain neural mass models reveal combined Aß and tau hyperexcitable influences in Alzheimer's disease.

Neuronal dysfunction and cognitive deterioration in Alzheimer's disease (AD) are likely caused by multiple pathophysiological factors. However, mechanistic evidence in humans remains scarce, requiring improved non-invasive techniques and integrative models. We introduce personalized AD computational models built on whole-brain Wilson-Cowan oscillators and incorporating resting-state functional MRI, amyloid-ß (Aß) and tau-PET from 132 individuals in the AD spectrum to evaluate the direct impact of toxic protein deposition on neuronal activity. This subject-specific approach uncovers key patho-mechanistic interactions, including synergistic Aß and tau effects on cognitive impairment and neuronal excitability increases with disease progression. The data-derived neuronal excitability values strongly predict clinically relevant AD plasma biomarker concentrations (p-tau217, p-tau231, p-tau181, GFAP) and grey matter atrophy obtained through voxel-based morphometry. Furthermore, reconstructed EEG proxy quantities show the hallmark AD electrophysiological alterations (theta band activity enhancement and alpha reductions) which occur with Aß-positivity and after limbic tau involvement. Microglial activation influences on neuronal activity are less definitive, potentially due to neuroimaging limitations in mapping neuroprotective vs detrimental activation phenotypes. Mechanistic brain activity models can further clarify intricate neurodegenerative processes and accelerate preventive/treatment interventions.