High burdens of phosphorylated tau protein and distinct precuneus atrophy in sporadic early-onset Alzheimer's disease.

Early-onset Alzheimer's disease (EOAD) is a rare devastating subclassification of Alzheimer's disease (AD). EOAD affects individuals <65 years old, and accounts for 5%-10% of all AD cases. Previous studies on EOAD primarily focused on familial forms, whereas research on sporadic EOAD (sEOAD), which represents 85%-90% of EOAD cases, is limited. In this prospective cohort study, participants were recruited between 2018 and 2023 and included patients with sEOAD (n = 110), late-onset AD (LOAD, n = 89), young controls (YC, n = 50), and older controls (OC, n = 25). All AD patients fulfilled the diagnostic criteria based on biomarker evidence. Familial EOAD patients or non-AD dementia patients were excluded. Single molecule array technology was used to measure fluid biomarkers, including cerebrospinal fluid (CSF) and plasma amyloid beta (Aß) 40, Aß42, phosphorylated tau (P-tau) 181, total tau (T-tau), serum neurofilament light chain and glial fibrillary acidic protein (GFAP). Patients with sEOAD exhibited more severe executive function impairment and bilateral precuneus atrophy (P < 0.05, family-wise error corrected) than patients with LOAD. Patients with sEOAD showed elevated CSF and plasma P-tau181 levels (154.0 ± 81.2 pg/mL, P = 0.002; and 6.1 ± 2.3 pg/mL, P = 0.046). Moreover, precuneus atrophy was significantly correlated with serum GFAP levels in sEOAD (P < 0.001). Serum GFAP levels (area under the curve (AUC) = 96.0%, cutoff value = 154.3 pg/mL) displayed excellent diagnostic value in distinguishing sEOAD patients from the control group. These preliminary findings highlight the crucial role of tau protein phosphorylation in the pathogenesis and progression of sEOAD.

Blood-based biomarkers for Alzheimer's disease: a multicenter-based cross-sectional and longitudinal study in China.

Discrepancies in diagnostic biomarkers for Alzheimer's Disease (AD) may arise from racial disparities, risk factors, or lifestyle differences. Moreover, there has been a lack of systematic and multicenter studies to evaluate baselines of the AD biomarkers in Chinese populations. Thus, there is an urgent need for research to investigate the effectiveness of blood biomarkers for AD, specifically in the Chinese Han population, using a multicenter approach. In the present multicenter-based cross-sectional and longitudinal study, we evaluated 817 blood samples from 6 different clinical centers. We measured plasma amyloid beta (Aß)-40, Aß42, phosphorylated tau 181 (pTau), total tau (tTau), serum neurofilament light (NFL), and glial fibrillary acidic protein (GFAP). Additionally, 18F-florbetapir positron electron tomography and magnetic resonance imaging were also performed. A combination of the APOE genotype with plasma pTau and serum GFAP demonstrated exceptional performance in distinguishing Aß status. Furthermore, baseline GFAP levels exhibited a strong association with cognitive decline over time and brain atrophy, with higher GFAP levels predicting a faster rate of neurodegeneration. In summary, these results validate the practicality of blood biomarkers in the Chinese Han population, encompassing various regions within China. Additionally, they emphasize the potential of pTau and GFAP as non-invasive methods for detecting and screening AD at an early stage.

Molecules of senescent glial cells differentiate Alzheimer's disease from ageing.

BACKGROUND: Ageing is a major risk factor for Alzheimer's disease (AD), which is accompanied by cellular senescence and thousands of transcriptional changes in the brain. OBJECTIVES: To identify the biomarkers in the cerebrospinal fluid (CSF) that could help differentiate healthy ageing from neurodegenerative processes. METHODS: Cellular senescence and ageing-related biomarkers were assessed in primary astrocytes and postmortem brains by immunoblotting and immunohistochemistry. The biomarkers were measured in CSF samples from the China Ageing and Neurodegenerative Disorder Initiative cohort using Elisa and the multiplex Luminex platform. RESULTS: The cyclin-dependent kinase inhibitors p16/p21-positive senescent cells in human postmortem brains were predominantly astrocytes and oligodendrocyte lineage cells, which accumulated in AD brains. CCL2, YKL-40, HGF, MIF, S100B, TSP2, LCN2 and serpinA3 are biomarkers closely related to human glial senescence. Moreover, we discovered that most of these molecules, which were upregulated in senescent glial cells, were significantly elevated in the AD brain. Notably, CSF YKL-40 (ß=0.5412, p<0.0001) levels were markedly elevated with age in healthy older individuals, whereas HGF (ß=0.2732, p=0.0001), MIF (ß=0.33714, p=0.0017) and TSP2 (ß=0.1996, p=0.0297) levels were more susceptible to age in older individuals with AD pathology. We revealed that YKL-40, TSP2 and serpinA3 were useful biomarkers for discriminating patients with AD from CN individuals and non-AD patients. DISCUSSION: Our findings demonstrated the different patterns of CSF biomarkers related to senescent glial cells between normal ageing and AD, implicating these biomarkers could identify the road node in healthy path off to neurodegeneration and improve the accuracy of clinical AD diagnosis, which would help promote healthy ageing.

Correlation of blood-brain barrier leakage with cerebral small vessel disease including cerebral microbleeds in Alzheimer's disease.

Background: Blood-brain barrier (BBB) damage is considered an important part of Alzheimer's disease (AD) progression, and cerebral small-vessel disease (CSVD) is commonly associated with AD. However, the relationship between BBB damage, small cerebrovascular lesions, especially cerebral microbleeds (CMBs), and amyloid and tau biomarkers remains controversial. Therefore, our study aimed to further investigate their association in our cohort of patients with AD. Methods: A total of 139 individuals were divided into probable AD (18F-florbetapir PET positive, n = 101) and control group (cognitively normal, n = 38). The levels of cerebrospinal fluid (CSF) and plasma t-tau, p-tau181, Aß40, Aß42, and albumin were measured using corresponding commercial assay kits, and the CSF/plasma albumin ratio (Qalb), an indicator of BBB dysfunction, was calculated. CSVD burden and the number of CMBs were defined using magnetic resonance imaging. Results: Patients with AD had higher Qalb (p = 0.0024), higher numbers of CMBs (p = 0.03), and greater CSVD burden (p < 0.0001). In the AD group, CMBs and CSVD correlated with a higher Qalb (p = 0.03), and the numbers of CMBs negatively correlated with CSF Aß42 (p = 0.02). Conclusion: Blood-brain barrier damage was accompanied by a more severe burden of CSVD, including CMB, in patients with AD.

Plasma Core Alzheimer's Disease Biomarkers Predict Amyloid Deposition Burden by Positron Emission Tomography in Chinese Individuals with Cognitive Decline.

Blood-based biomarkers have been considered as a promising method for the diagnosis of Alzheimer's disease (AD). The reliability and accuracy of plasma core AD biomarkers, including phosphorylated tau (P-tau181), total tau (T-tau), Aß42, and Aß40, have also been confirmed in diagnosing AD and predicting cerebral ß-amyloid (Aß) deposition in Western populations, while fewer research studies have ever been conducted in China's Han population. In this study, we investigated the capability of plasma core AD biomarkers in predicting cerebral Aß deposition burden among the China Aging and Neurodegenerative Disorder Initiative (CANDI) cohort consisting of cognitively normal (CN), mild cognitive impairment (MCI), AD dementia, and non-Alzheimer's dementia disease (Non-ADD). Body fluid (plasma and CSF) AD core biomarkers were measured via single-molecule array (Simoa) immunoassay. The global standard uptake value ratio (SUVR) was then calculated by 18F-florbetapir PET, which was divided into positive (+) and negative (-). The most significant correlation between plasma and CSF was plasma P-tau181 (r = 0.526, P < 0.0001). Plasma P-tau181 and P-tau181/T-tau ratio were positively correlated with global SUVR (r = 0.257, P < 0.0001; r = 0.263, P < 0.0001, respectively), while Aß42 and Aß42/Aß40 ratio were negatively correlated with global SUVR (r = -0.346, P < 0.0001; r = -0.407, P < 0.0001, respectively). Interestingly, voxel-wise analysis showed that plasma P-tau181 and P-tau181/T-tau ratio were negatively related to 18F-florbetapir PET in the hippocampus and parahippocampal cortex. The optimal predictive capability in distinguishing all Aß+ participants from Aß- participants and MCI+ from MCI- subgroups was the plasma P-tau181/T-tau ratio (AUC = 0.825 and 0.834, respectively). Our study suggested that plasma P-tau181 and P-tau181/T-tau ratio possessed better diagnostic and predictive values than plasma Aß42 and Aß42/Aß40 in this cohort, a finding that may be useful in clinical practices and trials in China.

A combination model of AD biomarkers revealed by machine learning precisely predicts Alzheimer's dementia: China Aging and Neurodegenerative Initiative (CANDI) study.

INTRODUCTION: To test the utility of the "A/T/N" system in the Chinese population, we study core Alzheimer's disease (AD) biomarkers in a newly established Chinese cohort. METHODS: A total of 411 participants were selected, including 96 cognitively normal individuals, 94 patients with mild cognitive impairment (MCI) patients, 173 patients with AD, and 48 patients with non-AD dementia. Fluid biomarkers were measured with single molecule array. Amyloid beta (Aß) deposition was determined by 18 F-Flobetapir positron emission tomography (PET), and brain atrophy was quantified using magnetic resonance imaging (MRI). RESULTS: Aß42/Aß40 was decreased, whereas levels of phosphorylated tau (p-tau) were increased in cerebrospinal fluid (CSF) and plasma from patients with AD. CSF Aß42/Aß40, CSF p-tau, and plasma p-tau showed a high concordance in discriminating between AD and non-AD dementia or elderly controls. A combination of plasma p-tau, apolipoprotein E (APOE) genotype, and MRI measures accurately predicted amyloid PET status. DISCUSSION: These results revealed a universal applicability of the "A/T/N" framework in a Chinese population and established an optimal diagnostic model consisting of cost-effective and non-invasive approaches for diagnosing AD.

Correlation between Cerebrospinal Fluid Core Alzheimer's Disease Biomarkers and ß-Amyloid PET in Chinese Dementia Population.

The current diagnoses of Alzheimer's disease (AD) mainly rely on such measures as amyloid-ß (Aß) and tau neuropathology biomarkers in vivo via cerebrospinal fluid (CSF) and positron emission tomography (PET) imaging, which had been systematically studied in Caucasian individuals, whereas diagnostic performances of these approaches in Chinese dementia population still remain unclear. This study investigated the associations between the levels of CSF core AD biomarkers, including phosphorylated tau (p-Tau181), total tau (t-Tau), Aß42, and Aß40 measured by the single-molecule array (Simoa) and cerebral Aß deposition status assessed by 18F-Florbetapir PET (Aß PET), and evaluated the predictive values of CSF core AD biomarkers in discriminating Aß PET status in a clinical dementia cohort of the Chinese population, which consisted of patients with mild cognitive impairment (MCI), AD dementia, and non-Alzheimer's dementia disease (Non-ADD). Global standard uptake value ratios (SUVRs) were calculated by Aß PET, which was divided into positive (Aß+) and negative (Aß-) through visual analysis. CSF p-Tau181 and p-Tau181/t-Tau ratio were positively correlated with the global SUVR, while CSF Aß42 and Aß42/Aß40 ratio were negatively correlated with the global SUVR. CSF Aß40 has the highest predictive value in discriminating the MCI group from the AD group, while CSF p-Tau181 was applied to discriminate the AD group from the non-ADD group. CSF Aß42/Aß40 ratio, as the optimal predictive factor, was combined with APOE ε4 status rather than age and education, which could improve the predictive ability in differentiating the Aß+ group from the Aß- group. The results reveal the universal applicability of CSF core AD biomarkers and Aß PET imaging in Chinese dementia population, which is helpful in clinical practice and drug trials in China.

Insights into T-cell dysfunction in Alzheimer's disease.

T cells, the critical immune cells of the adaptive immune system, are often dysfunctional in Alzheimer's disease (AD) and are involved in AD pathology. Reports highlight neuroinflammation as a crucial modulator of AD pathogenesis, and aberrant T cells indirectly contribute to neuroinflammation by secreting proinflammatory mediators via direct crosstalk with glial cells infiltrating the brain. However, the mechanisms underlying T-cell abnormalities in AD appear multifactorial. Risk factors for AD and pathological hallmarks of AD have been tightly linked with immune responses, implying the potential regulatory effects of these factors on T cells. In this review, we discuss how the risk factors for AD, particularly Apolipoprotein E (ApoE), Aß, α-secretase, ß-secretase, γ-secretase, Tau, and neuroinflammation, modulate T-cell activation and the association between T cells and pathological AD hallmarks. Understanding these associations is critical to provide a comprehensive view of appropriate therapeutic strategies for AD.

Elevated ß-secretase 1 expression mediates CD4+ T cell dysfunction via PGE2 signalling in Alzheimer's disease.

Circulating CD4+ T cells are dysfunctional in Alzheimer's disease (AD), however, the underlying molecular mechanisms are not clear. In this study, we demonstrate that CD4+ T cells from AD patients and 5xFAD transgenic mice exhibit elevated levels of ß-secretase 1 (BACE1). Overexpression of BACE1 in CD4+ T cells potentiated CD4+ T-cell activation and T-cell-dependent immune responses. Mechanistically, BACE1 modulates prostaglandin E2 (PGE2) synthetase-microsomal prostaglandin E synthase 2 (mPGES2)-to promote mPGES2 maturation and PGE2 production, which increases T-cell receptor (TCR) signalling. Moreover, administration of peripheral PGE2 signalling antagonists partially ameliorates CD4+ T cell overactivation and AD pathology in 5xFAD mice. Overall, our results reveal a potential role for BACE1 in mediating CD4+ T-cell dysfunction in AD.

Progranulin Administration Attenuates ß-Amyloid Deposition in the Hippocampus of 5xFAD Mice Through Modulating BACE1 Expression and Microglial Phagocytosis.

Loss of function mutations in the progranulin (PGRN) gene is a risk factor for Alzheimer's disease (AD). Previous works reported that the deficiency of PGRN accelerates ß-amyloid (Aß) accumulation in AD transgenic mouse brains while overexpression of PGRN could restrain disease progression. However, mechanisms of PGRN in protecting against Aß deposition remains unclear. Here, using the 5xFAD AD mouse model, we show that intrahippocampal injection of PGRN protein leads to a reduction of Aß plaques, downregulation of beta-secretase 1 (BACE1), and enhanced microglia Aß phagocytosis in the mouse hippocampus. Furthermore, PGRN treatment inhibited BACE1 expression in N2a cells and primary culture neurons and improved the phagocytic capacity of microglia isolated from 5xFAD mouse brains. Collectively, our results provide further evidence that enhancing progranulin could be a promising option for AD therapy.