Plasma biomarkers of Alzheimer's disease in the continuum of dementia with Lewy bodies

Cerebrospinal fluid and blood neurofilament light chain in Parkinson's disease and atypical parkinsonian syndromes: a systematic review and Bayesian network meta-analysis

BACKGROUND AND OBJECTIVE

The value of neurofilament light chain (NfL) levels as a biomarker for the diagnosis and differential diagnosis in patients with Parkinson's disease (PD) and atypical parkinsonian syndromes (APS) remains controversial. Furthermore, few studies have directly compared NfL levels among specific APS categories. This study aimed to compare cerebrospinal fluid (CSF) and blood NfL levels among PD, APS, other PD-related disorders, and controls, as well as rank NfL levels across these groups.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were searched from the inception up to November 1st, 2024, to identify eligible studies reporting CSF or blood NfL concentrations in PD, PD dementia (PDD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), corticobasal syndrome (CBS), vascular parkinsonism (VP), essential tremor (ET), idiopathic rapid eye movement sleep behavior disorder (iRBD), and controls. The Bayesian approach was utilized to estimate the standardized mean difference (SMD) and the associated 95% credible intervals (CrIs) of NfL levels. The surface under the cumulative ranking curve (SUCRA) was employed to evaluate the ranking probabilities of NfL levels. Subgroup analysis and meta-regression were conducted to explore the sources of heterogeneity.

RESULTS

The present network meta-analysis (NMA) included 78 studies with 13,120 participants (4050 controls, 5021 PD, 191 PDD, 1173 MSA, 887 PSP, 1254 DLB, 319 CBS, 160 ET, 65 iRBD, and 0 VP). Of these, the NMA of CSF NfL included 34 studies with 6,013 participants, while the NMA of blood NfL included 49 studies with 7,787 participants. Both CSF and blood NfL levels were significantly elevated in patients with PD and APS compared to controls. Compared to PD patients, CSF NfL levels were significantly elevated in MSA (SMD 1.85; 95% CrI 1.55-2.15), CBS (1.42; 1.08-1.75), PSP (1.35; 1.06-1.64), and DLB 0.52; 0.20-0.85) patients. Similarly, blood NfL levels were significantly higher in patients with MSA (1.36; 1.02-1.71), PDD (1.19; 0.65-1.72), PSP (1.15; 0.77-1.54), CBS (0.92; 0.11-1.72), and DLB (0.63; 0.14-1.12) compared to PD. Among APS, CSF NfL levels in MSA patients were significantly higher than those in PSP, DLB, and CBS patients, while blood NfL levels in MSA patients were significantly higher only compared to DLB. In both CSF and blood NfL, MSA patients exhibited the highest probability of ranking first for NfL level elevations (CSF: SUCRA = 0.998; blood: SUCRA = 0.925). Age significantly influenced the SMD of the comparison between MSA and PD in CSF NfL (β = -0.15; p = 0.016).

CONCLUSIONS

CSF and blood NfL levels in PD and APS are higher than those in controls, and all APS categories show higher levels than PD, suggesting that NfL levels may serve as a potential biomarker for the differential diagnosis between PD and APS. However, caution is warranted when using NfL as a diagnostic biomarker for PD. Significant differences in NfL levels are also observed between certain APS categories. Patients with MSA exhibit the highest NfL levels among PD and related disorders.

Plasma Biomarkers and Disease Prognosis in Mild Cognitive Impairment with Lewy Bodies

BACKGROUND

Little is known about the prognostic value of plasma biomarkers in mild cognitive impairment with Lewy bodies (MCI-LB).

OBJECTIVES

To investigate the association of four plasma biomarkers with disease progression in MCI.

METHODS

Plasma amyloid-beta (Aβ)42/40, glial fibrillary acidic protein (GFAP), neurofilament light (NfL), and phosphorylated tau 181 (pTau181) were measured at baseline in a longitudinal MCI cohort (n = 131).

RESULTS

Baseline plasma NfL was associated with increased risk of dementia/death in the entire cohort. In MCI-LB, baseline plasma NfL, GFAP, and pTau181 were associated with increased risk of dementia/death and increased cognitive decline measured by the Addenbrooke's Cognitive Examination-Revised.

CONCLUSIONS

pTau181, GFAP, and NfL are associated with more rapid disease progression in MCI-LB and, with further validation, could be useful to support prognosis and stratification for clinical practice and treatment trials. Further work, including clinicopathological studies, is needed to understand the biological correlates of these markers in MCI-LB. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Polygenic risk discriminates Lewy body dementia from Alzheimer's disease

INTRODUCTION

Lewy body dementia (LBD) shares genetic risk factors with Alzheimer's disease (AD), including apolipoprotein E (APOE), but is distinguishable at the genome-wide level. Polygenic risk scores (PRS) may therefore improve diagnostic classification.

METHODS

We assessed diagnostic classification using AD-PRS excluding APOE (AD-PRSno APOE), APOE risk score (APOE-RS), and plasma phosphorylated tau 181 (p-tau181), in 83 participants with LBD, 27 with positron emission tomography amyloid beta (Aβ)positive mild cognitive impairment or AD (MCI+/AD), and 57 controls.

RESULTS

Together AD-PRSno APOE and APOE-RS performed similarly to p-tau181 in discriminating MCI+/AD from controls (area under the curve 76% vs. 79%) and LBD (71% vs. 72%). In LBD, Aβ positivity was significantly associated with APOE-RS, but not with AD-PRSno APOE, or p-tau181. Combining AD-PRSno APOE, APOE-RS, and p-tau181 improved the discrimination of MCI+/AD from controls (81%) and LBD (75%), and the detection of Aβ in LBD (82%).

DISCUSSION

Aβ deposition in LBD was associated with APOE, while MCI+/AD was also associated with AD-PRS beyond APOE. AD-PRS explains phenotypic variance not captured by APOE or p-tau181.

HIGHLIGHTS

We investigated Alzheimer's disease (AD) polygenic risk score (PRS), apolipoprotein E (APOE), and plasma phosphorylated tau 181 (p-tau181) to classify AD and Lewy body dementia (LBD). AD-PRS with APOE achieved similar classification accuracy to p-tau181. AD-PRS without APOE significantly contributed to discriminating AD from LBD. Amyloid beta positivity in LBD was associated with APOE but not AD-PRS without APOE or p-tau181. Combining AD-PRS, APOE, and p-tau181 improved diagnostic classification accuracy.

Comparison of Plasma p-tau217 and [18F]FDG-PET for Identifying Alzheimer Disease in People With Early-Onset or Atypical Dementia

BACKGROUND AND OBJECTIVES

To compare the diagnostic performance of an immunoassay for plasma concentrations of phosphorylated tau (p-tau) 217 with visual assessments of fluorine-18 fluorodeoxyglucose [18F]FDG-PET in individuals who meet appropriate use criteria for Alzheimer dementia (AD) biomarker assessments.

METHODS

We performed a retrospective analysis of individuals with early-onset (age <65 years at onset) and/or atypical dementia (features other than memory at onset), who were evaluated at a tertiary care memory clinic. All participants underwent measurements of CSF biomarkers (Aβ42, p-tau181, and total tau levels), as well as [18F]FDG-PET scans, amyloid-PET scans, and plasma p-tau217 quantifications. To determine whether the [18F]FDG-PET images were compatible with AD, images were visually rated by 2 nuclear medicine experts. Using a contingency analysis, we evaluated the accuracy of [18F]FDG-PET scan interpretation and plasma p-tau217 for an AD biomarker profile in CSF and for amyloid-PET positivity.

RESULTS

A total of 81 individuals with early onset and/or atypical dementia were included in this study (mean age = 65 years; 48/81 female (59%). Both [18F]FDG-PET and plasma p-tau217 showed high levels of agreement with reference standard AD biomarkers ([18F]FDG-PET area under the curve [AUC]: 71%; plasma p-tau217 AUC: 81%). Although both biomarkers had similar specificity for AD [18F]FDG-PET: 70%, CI: 0.56-0.81; plasma p-tau217: 70%, CI: 0.56-0.81), plasma p-tau217 had higher sensitivity for AD (plasma p-tau217: 97%, CI: 0.85-0.99 vs [18F]FDG-PET: 73%, CI: 0.57-0.85) (p = 0.01). Overall accuracy was also higher for plasma p-tau217 (AUC = 84%, CI: 0.75-0.93 vs 72%, CI: 0.60-0.83 of [18F]FDG-PET) (p = 0.02). The same pattern of results was observed when using amyloid-PET as the reference standard.

DISCUSSION

Our study provides evidence that plasma p-tau217 has strong discriminative accuracy for AD among patients with early-onset and/or atypical dementia assessed in specialized settings. Future work should replicate these findings in secondary care settings.

Sleep disorders and risk of alzheimer's disease: A two-way road

Substantial sleep impairment in patients with Alzheimer's disease (AD) is one of the emerging points for continued efforts to better understand the disease. Individuals without cognitive decline, an important marker of the clinical phase of AD, may show early alterations in the sleep-wake cycle. The objective of this critical narrative review is to explore the bidirectional pathophysiological correlation between sleep disturbances and Alzheimer's Disease. Specifically, it examines how the disruption of sleep homeostasis in individuals without dementia could contribute to the pathogenesis of AD, and conversely, how neurodegeneration in individuals with Alzheimer's Disease might lead to dysregulation of the sleep-wake cycle. Recent scientific results indicate that sleep disturbances, particularly those related to impaired glymphatic clearance, may act as an important mechanism associated with the genesis of Alzheimer's Disease. Additionally, amyloid deposition and tau protein hyperphosphorylation, along with astrocytic hyperactivation, appear to trigger changes in neurotransmission dynamics in areas related to sleep, which may explain the onset of sleep disturbances in individuals with AD. Disruption of sleep homeostasis appears to be a modifiable risk factor in Alzheimer's disease. Whenever possible, the use of non-pharmacological strategies becomes important in this context. From a different perspective, additional research is needed to understand and treat the dysfunction of the sleep-wake cycle in individuals already affected by AD. Early recognition and correction of sleep disturbances in this population could potentially mitigate the progression of dementia and improve the quality of life for those with AD.

Clinical and diagnostic implications of Alzheimer's disease copathology in Lewy body disease

Concomitant Alzheimer's disease (AD) pathology is a frequent event in the context of Lewy body disease (LBD), occurring in approximately half of all cases. Evidence shows that LBD patients with AD copathology show an accelerated disease course, a greater risk of cognitive decline and an overall poorer prognosis. However, LBD-AD cases may show heterogeneous motor and non-motor phenotypes with a higher risk of dementia and, consequently, be not rarely misdiagnosed. In this review, we summarize the current understanding of LBD-AD by discussing the synergistic effects of AD neuropathological changes and Lewy pathology and their clinical relevance. Furthermore, we provide an extensive overview of neuroimaging and fluid biomarkers under assessment for use in LBD-AD and their possible diagnostic and prognostic values. AD pathology can be predicted in vivo by means of CSF, MRI and PET markers, whereas the most promising technique to date for identifying Lewy pathology in different biological tissues is the α-synuclein seed amplification assay. Pathological imaging and CSF AD biomarkers are associated with a higher likelihood of cognitive decline in LBD but do not always mirror the neuropathological severity as in pure AD. Implementing the use of blood-based AD biomarkers might allow faster screening of LBD patients for AD copathology, thus improving the overall diagnostic sensitivity for LBD-AD. Finally, we discuss the literature on novel candidate biomarkers being exploited in LBD-AD to investigate other aspects of neurodegeneration, such as neuroaxonal injury, glial activation and synaptic dysfunction. The thorough characterization of AD copathology in LBD should be taken into account when considering differential diagnoses of dementia syndromes, to allow prognostic evaluation on an individual level, and to guide symptomatic and disease-modifying therapies.

Network Pharmacology and Molecular Docking Identify the Potential Mechanism and Therapeutic Role of Scutellaria baicalensis in Alzheimer's Disease

Aim

Scutellaria baicalensis, a traditional Chinese medicinal herb renowned for its anti-inflammatory, antioxidant, and anti-tumor properties, has shown promise in alleviating cognitive impairment associated with Alzheimer's disease. Nonetheless, the exact neuroprotective mechanism of Scutellaria baicalensis against Alzheimer's disease remains unclear. In this study, network pharmacology was employed to explore the possible mechanisms by which Scutellaria baicalensis protects against Alzheimer's disease.

Methods

The active compounds of Scutellaria baicalensis were retrieved from the TCMSP database, and their corresponding targets were identified. Alzheimer's disease-related targets were obtained through searches in the GeneCards and OMIM databases. Cytoscape 3.6.0 software was utilized to construct a regulatory network illustrating the "active ingredient-target" relationships. Subsequently, the target genes affected by Scutellaria baicalensis in the context of Alzheimer's disease were input into the String database to establish a PPI network. GO analysis and KEGG analysis were conducted using the DAVID database to predict the potential pathways associated with these key targets. Following this, the capacity of these active ingredients to bind to core targets was confirmed through molecular docking. In vitro experiments were then carried out for further validation.

Results

A total of 36 active ingredients from Scutellaria baicalensis were screened out, which corresponded to 365 targets. Molecular docking results demonstrated the robust binding abilities of Baicalein, Wogonin, and 5,2'-Dihydroxy-6,7,8-trimethoxyflavone to key target proteins (SRC, PIK3R1, and STAT3). In vitro experiments showed that the active components of Scutellaria baicalensis can inhibit STAT3 expression by downregulating the PIK3R1/SRC pathway in Neuro 2A cells.

Conclusion

In summary, these findings collectively suggest that Scutellaria baicalensis holds promise as a viable treatment option for Alzheimer's disease.

A critical appraisal of blood-based biomarkers for Alzheimer's disease

Biomarkers that predict the clinical onset of Alzheimer's disease (AD) enable the identification of individuals in the early, preclinical stages of the disease. Detecting AD at this point may allow for more effective therapeutic interventions and optimized enrollment for clinical trials of novel drugs. The current biological diagnosis of AD is based on the AT(N) classification system with the measurement of brain deposition of amyloid-β (Aβ) ("A"), tau pathology ("T"), and neurodegeneration ("N"). Diagnostic cut-offs for Aβ1-42, the Aβ1-42/Aβ1-40 ratio, tau and hyperphosphorylated-tau concentrations in cerebrospinal fluid have been defined and may support AD clinical diagnosis. Blood-based biomarkers of the AT(N) categories have been described in the AD continuum. Cross-sectional and longitudinal studies have shown that the combination of blood biomarkers tracking neuroaxonal injury (neurofilament light chain) and neuroinflammatory pathways (glial fibrillary acidic protein) enhance sensitivity and specificity of AD clinical diagnosis and improve the prediction of AD onset. However, no international accepted cut-offs have been identified for these blood biomarkers. A kit for blood Aβ1-42/Aβ1-40 is commercially available in the U.S.; however, it does not provide a diagnosis, but simply estimates the risk of developing AD. Although blood-based AD biomarkers have a great potential in the diagnostic work-up of AD, they are not ready for the routine clinical use.