Protein markers for the differential diagnosis of vascular dementia and Alzheimer's disease

Plasma Proteomic Biomarkers in Alzheimer's Disease and Cardiovascular Disease: A Longitudinal Study

The co-occurrence of Alzheimer's disease (AD) and cardiovascular diseases (CVDs) in older adults highlights the necessity for the exploration of potential shared risk factors. A total of 566 adults were selected from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, including 111 individuals with AD, 383 with mild cognitive impairment (MCI), and 410 with CVD. The multivariable linear mixed model (LMM) was used to investigate the associations of AD and CVD with longitudinal changes in 146 plasma proteomic biomarkers (measured at baseline and the 12-month follow-up). The LMM showed that 48 biomarkers were linked to AD and 46 to CVD (p < 0.05). Both AD and CVD were associated with longitudinal changes in 14 biomarkers (α1Micro, ApoH, β2M, BNP, complement C3, cystatin C, KIM1, NGAL, PPP, TIM1, THP, TFF3, TM, and VEGF), and both MCI and CVD were associated with 12 biomarkers (ApoD, AXL, BNP, Calcitonin, CD40, C-peptide, pM, PPP, THP, TNFR2, TTR, and VEGF), suggesting intricate connections between cognitive decline and cardiovascular health. Among these, the Tamm Horsfall Protein (THP) was associated with AD, MCI, CVD, and APOE-ε4. This study provides valuable insights into shared and distinct biological markers and mechanisms underlying AD and CVD.

Protein profile pattern analysis: A multifarious, in vitro diagnosis technique for universal screening

Universal health care is attracting increased attention nowadays, because of the large increase in population all over the world, and a similar increase in life expectancy, leading to an increase in the incidence of non-communicable (various cancers, coronary diseases, neurological and old-age-related diseases) and communicable diseases/pandemics like SARS-COVID 19. This has led to an immediate need for a healthcare technology that should be cost-effective and accessible to all. A technology being considered as a possible one at present is liquid biopsy, which looks for markers in readily available samples like body fluids which can be accessed non- or minimally- invasive manner. Two approaches are being tried now towards this objective. The first involves the identification of suitable, specific markers for each condition, using established methods like various Mass Spectroscopy techniques (Surface-Enhanced Laser Desorption/Ionization Mass Spectroscopy (SELDI-MS), Matrix-Assisted Laser Desorption/Ionization (MALDI-MS), etc., immunoassays (Enzyme-Linked Immunoassay (ELISA), Proximity Extension Assays, etc.) and separation methods like 2-Dimensional Polyacrylamide Gel Electrophoresis (2-D PAGE), Sodium Dodecyl-Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), Capillary Electrophoresis (CE), etc. In the second approach, no attempt is made the identification of specific markers; rather an efficient separation method like High-Performance Liquid Chromatography/ Ultra-High-Performance Liquid Chromatography (HPLC/UPLC) is used to separate the protein markers, and a profile of the protein pattern is recorded, which is analysed by Artificial Intelligence (AI)/Machine Learning (MI) methods to derive characteristic patterns and use them for identifying the disease condition. The present report gives a summary of the current status of these two approaches and compares the two in the use of their suitability for universal healthcare.

Cystatins: unravelling the biological implications for neuroprotection

Cystatins, a family of proteins known for their inhibitory role against cysteine proteases, have garnered significant attention in the field of neurodegeneration. Numerous genetic, experimental, and clinical studies concerning cystatin C suggest it plays an important role in the course of neurodegenerative diseases. Its beneficial effects are associated with cysteine protease inhibition, impact on β-amyloid aggregation, as well as regulation of cell proliferation, autophagy, and apoptosis. Cystatin isolated from chicken egg white, called ovocystatin, has been widely used in medical and pharmaceutical research due to its structural and biological similarities to human cystatin C. This article focuses on the potential use of cystatins, with special emphasis on easily obtained ovocystatin, in the treatment of neurodegenerative diseases, such as dementia. The current evidence on cystatin use has shed light on its mechanisms of action and therapeutic implications for neuroprotection and maintenance of cognitive functions.

A machine learning approach to unmask novel gene signatures and prediction of Alzheimer's disease within different brain regions

Alzheimer's disease (AD) is a progressive neurodegenerative disorder whose aetiology is currently unknown. Although numerous studies have attempted to identify the genetic risk factor(s) of AD, the interpretability and/or the prediction accuracies achieved by these studies remained unsatisfactory, reducing their clinical significance. Here, we employ the ensemble of random-forest and regularized regression model (LASSO) to the AD-associated microarray datasets from four brain regions - Prefrontal cortex, Middle temporal gyrus, Hippocampus, and Entorhinal cortex- to discover novel genetic biomarkers through a machine learning-based feature-selection classification scheme. The proposed scheme unraveled the most optimum and biologically significant classifiers within each brain region, which achieved by far the highest prediction accuracy of AD in 5-fold cross-validation (99% average). Interestingly, along with the novel and prominent biomarkers including CORO1C, SLC25A46, RAE1, ANKIB1, CRLF3, PDYN, numerous non-coding RNA genes were also observed as discriminator, of which AK057435 and BC037880 are uncharacterized long non-coding RNA genes.

Genome-wide scan in Hispanics highlights candidate loci for brain white matter hyperintensities

Objective:

To investigate genetic variants influencing white matter hyperintensities (WMHs) in the understudied Hispanic population.

Methods:

Using 6.8 million single nucleotide polymorphisms (SNPs), we conducted a genome-wide association study (GWAS) to identify SNPs associated with WMH volume (WMHV) in 922 Hispanics who underwent brain MRI as a cross-section of 2 community-based cohorts in the Northern Manhattan Study and the Washington Heights–Inwood Columbia Aging Project. Multiple linear modeling with PLINK was performed to examine the additive genetic effects on ln(WMHV) after controlling for age, sex, total intracranial volume, and principal components of ancestry. Gene-based tests of association were performed using VEGAS. Replication was performed in independent samples of Europeans, African Americans, and Asians.

Results:

From the SNP analysis, a total of 17 independent SNPs in 7 genes had suggestive evidence of association with WMHV in Hispanics (p < 1 × 10⁻⁵) and 5 genes from the gene-based analysis with p < 1 × 10⁻³. One SNP (rs9957475 in GATA6) and 1 gene (UBE2C) demonstrated evidence of association (p < 0.05) in the African American sample. Four SNPs with p < 1 × 10⁻⁵ were shown to affect binding of SPI1 using RegulomeDB.

Conclusions:

This GWAS of 2 community-based Hispanic cohorts revealed several novel WMH-associated genetic variants. Further replication is needed in independent Hispanic samples to validate these suggestive associations, and fine mapping is needed to pinpoint causal variants.

Plasma protein profiling for potential biomarkers in the early diagnosis of Alzheimer's disease

OBJECTIVES

Alzheimer's disease (AD) is the most common cause of dementia in elderly persons. Since the pathology of AD develops slowly from a preclinical or early phase into a fully expressed clinical syndrome, at the time of diagnosis the disease has been progressing for many years. To facilitate the early diagnosis of AD, we performed protein profiling of blood in patients with mild AD as defined by the Functional Assessment Staging (FAST) scale.

METHODS

Plasma samples from mild AD patients and healthy controls were analyzed using two-dimensional differential gel electrophoresis (2D-DIGE) combined with matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF/MS) followed by peptide mass fingerprinting.

RESULTS

Three downregulated proteins were identified: apolipoprotein A-1, alpha-2-HS-glycoprotein, and afamin. Two proteins, including apolipoprotein A-4 and fibrinogen gamma chain, were upregulated in mild AD patients.

DISCUSSION

Our results suggest that altered expression levels of these proteins in plasma may yield candidate biomarkers for the early diagnosis of AD.

ABBREVIATIONS

AD, Alzheimer's disease; FAST, Functional Assessment Staging; 2D-DIGE, two-dimensional differential gel electrophoresis; MALDI-TOF/TOF/MS, matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry; CSF, cerebrospinal fluid; Aβ, amyloid beta; MMSE, Mini Mental State Examination; MRI, magnetic resonance imaging; NINCDS-ADRDA, National Institute for Neurological Diseases and Stroke/Alzheimer's Disease and Related Disorders Association; CHAPS, 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate; DTT, dithiothreitol; SDS-PAGE, SDS-polyacrylamide gel electrophoresis; DIA, differential in-gel analysis; BVA, biological variation analysis; CBB, Coomassie brilliant blue; 2DE, two-dimensional gel electrophoresis; TFA, trifluoroacetic acid; ACTH, adrenocorticotropic hormone; Apo A-1, apolipoprotein A-1; AHSG, alpha-2-HS-glycoprotein; Apo A-4, apolipoprotein A-4; MCI, mild cognitive impairment.

Analysis of the Cerebrospinal Fluid Proteome in Alzheimer's Disease

Alzheimer’s disease is a neurodegenerative disorder accounting for more than 50% of cases of dementia. Diagnosis of Alzheimer’s disease relies on cognitive tests and analysis of amyloid beta, protein tau, and hyperphosphorylated tau in cerebrospinal fluid. Although these markers provide relatively high sensitivity and specificity for early disease detection, they are not suitable for monitor of disease progression. In the present study, we used label-free shotgun mass spectrometry to analyse the cerebrospinal fluid proteome of Alzheimer’s disease patients and non-demented controls to identify potential biomarkers for Alzheimer’s disease. We processed the data using five programs (DecyderMS, Maxquant, OpenMS, PEAKS, and Sieve) and compared their results by means of reproducibility and peptide identification, including three different normalization methods. After depletion of high abundant proteins we found that Alzheimer’s disease patients had lower fraction of low-abundance proteins in cerebrospinal fluid compared to healthy controls (p<0.05). Consequently, global normalization was found to be less accurate compared to using spiked-in chicken ovalbumin for normalization. In addition, we determined that Sieve and OpenMS resulted in the highest reproducibility and PEAKS was the programs with the highest identification performance. Finally, we successfully verified significantly lower levels (p<0.05) of eight proteins (A2GL, APOM, C1QB, C1QC, C1S, FBLN3, PTPRZ, and SEZ6) in Alzheimer’s disease compared to controls using an antibody-based detection method. These proteins are involved in different biological roles spanning from cell adhesion and migration, to regulation of the synapse and the immune system.

Common Aging Signature in the Peripheral Blood of Vascular Dementia and Alzheimer's Disease

Alzheimer's disease (AD) and vascular dementia (VaD) are the two most dominant forms of dementia in elderly people. Due to the large overlap between AD and VaD in clinical observations, great controversies exist regarding the distinction and connection between these two types of senile dementia. Here for the first time, we resort to the gene expression pattern of the peripheral blood to compare AD and VaD objectively. In our previous work, we have demonstrated that the dysregulation of gene expression in AD is unique among the examined diseases including neurological diseases, cancer, and metabolic diseases. In this study, we found that the dysregulation of gene expression in AD and VaD is quite similar to each other at both functional and gene levels. Interestingly, the dysregulation started at the early stages of the diseases, namely mild cognitive impairment (MCI) and vascular cognitive impairment (VCI). We have also shown that this signature is distinctive from that of peripheral vascular diseases. Comparison with aging studies revealed that the most profound change in AD and VaD, namely ribosome, is consistent with the accelerated aging scenario. This study may have implications to the common mechanism between AD and VaD.

Brain lipidomes of subcortical ischemic vascular dementia and mixed dementia

Despite its importance as the leading cause of vascular dementia, the primary pathogenic mechanisms in subcortical ischemic vascular dementia (SIVD) have remained elusive. Because of the lack of approved therapeutic agents for SIVD, there is a pressing need to identify novel therapeutic targets. Comparative lipidomic analyses of SIVD and mixed dementia (i.e., SIVD and Alzheimer's disease, MixD) may also confer new insights pertaining to the possible interaction between neurodegenerative and vascular mechanisms in the pathogenesis of dementia. Liquid chromatography coupled to mass spectrometry was used to comprehensively analyze the lipidomes of white and gray matter from the temporal cortex of nondemented controls, SIVD, and MixD subjects. Detailed molecular profiles highlighted the pathologic relevance of gray matter sphingolipid fatty acyl chain heterogeneity in dementia. In addition, the levels of sulfatides and lysobisphosphatidic acids were progressively increased in the temporal cortex gray matter from control to SIVD to MixD. White matter phospholipid profiles indicated possible adaptive mechanisms (i.e., increased unsaturation) to chronic ischemia in SIVD and elevated membrane degradation in MixD.

Peripheral blood mononuclear cells as a laboratory to study dementia in the elderly

The steady and dramatic increase in the incidence of Alzheimer's disease (AD) and the lack of effective treatments have stimulated the search for strategies to prevent or delay its onset and/or progression. Since the diagnosis of dementia requires a number of established features that are present when the disease is fully developed, but not always in the early stages, the need for a biological marker has proven to be urgent, in terms of both diagnosis and monitoring of AD. AD has been shown to affect peripheral blood mononuclear cells (PBMCs) that are a critical component of the immune system which provide defence against infection. Although studies are continuously supplying additional data that emphasize the central role of inflammation in AD, PBMCs have not been sufficiently investigated in this context. Delineating biochemical alterations in AD blood constituents may prove valuable in identifying accessible footprints that reflect degenerative processes within the Central Nervous System (CNS). In this review, we address the role of biomarkers in AD with a focus on the notion that PBMCs may serve as a peripheral laboratory to find molecular signatures that could aid in differential diagnosis with other forms of dementia and in monitoring of disease progression.

Lipid raft disarrangement as a result of neuropathological progresses: a novel strategy for early diagnosis?

Lipid rafts are the preferential site of numerous membrane signaling proteins which are involved in neuronal functioning and survival. These proteins are organized in multiprotein complexes, or signalosomes, in close contact with lipid classes particularly represented in lipid rafts (i.e. cholesterol, sphingolipids and saturated fatty acids), which may contribute to physiological responses leading to neuroprotection. Increasing evidence indicates that alteration of lipid composition in raft structures as a consequence of neuropathologies, such as Alzheimer's disease (AD) and Parkinson's disease (PD), causes a dramatic increase in lipid raft order. These phenomena may correlate with perturbation of signalosome activities, likely contributing to neurodegenerative progression. Interestingly, significant disruption of stable raft microenvironments has been already observed in the first stages of either AD or PD, suggesting that these alterations may represent early events in the neuropathological development. In this regard, the search for biochemical markers, such as specific metabolic products altered in the brain at the first steps of the disease, presently represents an important challenge for early diagnostic strategies. Alterations of these biomarkers may be reflected in either plasma or cerebrospinal fluid, thus representing a potential strategy to predict an accurate diagnosis. We propose that pathologically-linked lipid raft markers may be interesting candidates to be explored at this level, although it has not been studied so far to what extent alteration of different signalosome components may be reflected in peripheral fluids. In this mini-review, we will discuss on relevant aspects of lipid rafts that contribute to the modulation of neuropathological events related to AD and PD. An interesting hypothesis is that anomalies on raft biomarkers measured at peripheral fluids might mirror the lipid raft pathology observed in early stages of AD and PD.