Role of inflammatory and hemostatic biomarkers in Alzheimer's and vascular dementia - A pilot study from a tertiary center in Northern India

Integrated bioinformatics analysis and biological experiments to identify key immune genes in vascular dementia

Objectives

This study aimed to identify key immune genes to provide new perspectives on the mechanisms and diagnosis of vascular dementia (VaD) based on bioinformatic methods combined with biological experiments in mice.

Methods

We obtained gene expression profiles from a Gene Expression Omnibus database (GSE186798). The gene expression data were analysed using integrated bioinformatics and machine learning techniques to pinpoint potential key immune-related genes for diagnosing VaD. Moreover, the diagnostic accuracy was evaluated through receiver operating characteristic curve analysis. The microRNA, transcription factor (TF), and drug-regulating hub genes were predicted using the database. Immune cell infiltration has been studied to investigate the dysregulation of immune cells in patients with VaD. To evaluate cognitive impairment, mice with bilateral common carotid artery stenosis (BCAS) were subjected to behavioural tests 30 d after chronic cerebral hypoperfusion. The expression of hub genes in the BCAS mice was determined using a quantitative polymerase chain reaction(qPCR).

Results

The results of gene set enrichment and gene set variation analyses indicated that immune-related pathways were upregulated in patients with VaD. A total of 1620 immune genes were included in the combined immune dataset, and 323 differentially expressed genes were examined using the GSE186798 dataset. Thirteen potential genes were identified using differential gene analysis. Protein-protein interaction network design and functional enrichment analysis were performed using the immune system as the main subject. To evaluate the diagnostic value, two potential core genes were selected using machine learning. Two putative hub genes, Rac family small GTPase 1(RAC1) and CKLF-like MARVEL transmembrane domain containing 5 (CMTM5) exhibit good diagnostic value. Their high confidence levels were confirmed by validating each biomarker using a different dataset. According to GeneMANIA, VaD pathophysiology is strongly associated with immune and inflammatory responses. The data were used to construct miRNA hub gene, TFs-hub gene, and drug-hub gene networks. Varying levels of immune cell dysregulation were also observed. In the animal experiments, a BCAS mouse model was employed to mimic VaD in humans, further confirmed using the Morris water maze test. The mRNA expression of RAC1 and CMTM5 was significantly reduced in the BCAS group, which was consistent with the results of the integrated bioinformatics analysis.

Conclusions

RAC1 and CMTM5 are differentially expressed in the frontal lobes of BCAS mice, suggesting their potential as biomarkers for diagnosing and prognosis of VaD. These findings pave the way for exploring novel molecular mechanisms aimed at preventing or treating VaD.

D-dimer - a multifaceted molecule

D-dimer, a universally unique marker for fibrin degradation, is generated through the enzymatic interplay of thrombin, factor XIIIa, and plasmin. The emergence of D-dimer-containing fibrin molecules occurs in both intravascular and extravascular spaces during pivotal physiological processes like haemostasis, thrombosis, and tissue repair. Given the inherently physiological nature of fibrin formation and fibrinolysis, basal levels of D-dimer fragments are present in plasma. Beyond its role as a marker of routine physiological processes, aberrations in D-dimer levels are indicative of a spectrum of conditions, both non-pathological and pathological. The clinical utility of D-dimer has been firmly established, particularly in scenarios like venous thromboembolism (VTE), pulmonary embolism (PE), deep vein thrombosis (DVT), and disseminated intravascular coagulation (DIC). Additionally, recent applications have extended to assess the prognosis of COVID-19. While D-dimer is commonly associated with thrombotic conditions, its elevation is not confined to these conditions alone. Elevated D-dimer levels are observed across various diseases, where its significance extends beyond diagnostic indicators to prognostic implications.

Circulating cytokines and vascular dementia: A bi-directional Mendelian randomization study

Inflammatory responses are associated with the development of vascular dementia (VaD). Circulating cytokines modulate the inflammatory response and are important for the immune system. To further elucidate the role of the immune system in VaD, we used Mendelian randomization (MR) to comprehensively and bi-directionally assess the role of circulating cytokines in VaD. Using state-of-the-art genome-wide association studies, we primarily assessed whether different genetic levels of 41 circulating cytokines affect the risk of developing VaD and, in turn, whether the genetic risk of VaD affects these circulating cytokines. We used inverse variance weighting (IVW) and several other MR methods to assess the bidirectional causality between circulating cytokines and VaD, and performed sensitivity analyses. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was inversely associated with VaD risk [odds ratio (OR): 0.74, 95 % confidence interval (CI): 0.60-0.92, P = 0.007, 0.007]. VaD was associated with seven circulating cytokines: macrophage inflammatory protein 1b (MIP-1 beta) [OR: 1.05, 95 % CI: 1.01-1.08, P = 0.009], Interleukin-12p70 (IL-12) [OR: 1.04, 95 % CI: 1.00-1.08, P = 0.047], Interleukin-17 (IL-17) [OR: 1.04, 95 % CI: 1.00-1.07, P = 0.038], Interleukin-7 (IL-7) [OR: 1.07, 95 % CI: 1.02-1.12, P = 0.009], Interferon gamma (IFN-γ) [OR: 1.03, 95 % CI: 1.00-1.07, P = 0.046], Granulocyte-colony stimulating factor (GCSF) [OR: 1.06, 95 % CI: 1.02-1.09, P = 0.001], Fibroblast growth factor (FGF) [P = 0.001], and Fibroblast growth factor (FGF) [P = 0.001]. Fibroblast growth factor basic (FGF-Basic) [OR: 1.04, 95 % CI: 1.01-1.08, P = 0.02] were positively correlated. Circulating cytokines are associated with VaD, and further studies are needed to determine whether they are effective targets for intervention to prevent or treat VaD.

Hepatopancreatic metabolic disorders and their implications in the development of Alzheimer's disease and vascular dementia

Dementia has been faced with significant public health challenges and economic burdens that urges the need to develop safe and effective interventions. In recent years, an increasing number of studies have focused on the relationship between dementia and liver and pancreatic metabolic disorders that result in diseases such as diabetes, obesity, hypertension and dyslipidemia. Previous reports have shown that there is a plausible correlation between pathologies caused by hepatopancreatic dysfunctions and dementia. Glucose, insulin and IGF-1 metabolized in the liver and pancreas probably have an important influence on the pathophysiology of the most common dementias: Alzheimer's and vascular dementia. This current review highlights recent studies aimed at identifying convergent mechanisms, such as insulin resistance and other diseases, linked to altered hepatic and pancreatic metabolism, which are capable of causing brain changes that ultimately lead to dementia.

Molecular biomarkers for vascular cognitive impairment and dementia

As disease-specific interventions for dementia are being developed, the ability to identify the underlying pathology and dementia subtypes is increasingly important. Vascular cognitive impairment and dementia (VCID) is the second most common cause of dementia after Alzheimer disease, but progress in identifying molecular biomarkers for accurate diagnosis of VCID has been relatively limited. In this Review, we examine the roles of large and small vessel disease in VCID, considering the underlying pathophysiological processes that lead to vascular brain injury, including atherosclerosis, arteriolosclerosis, ischaemic injury, haemorrhage, hypoperfusion, endothelial dysfunction, blood-brain barrier breakdown, inflammation, oxidative stress, hypoxia, and neuronal and glial degeneration. We consider the key molecules in these processes, including proteins and peptides, metabolites, lipids and circulating RNA, and consider their potential as molecular biomarkers alone and in combination. We also discuss the challenges in translating the promise of these biomarkers into clinical application.

Deep learning based diagnosis of Alzheimer's disease using FDG-PET images

PURPOSE

The aim of this study is to develop a deep neural network to diagnosis Alzheimer's disease and categorize the stages of the disease using FDG-PET scans. Fluorodeoxyglucose positron emission tomography (FDG-PET) is a highly effective diagnostic tool that accurately detects glucose metabolism in the brain of AD patients.

MATERIAL AND METHODS

In this work, we have developed a deep neural network using FDG-PET to discriminate Alzheimer's disease subjects from stable mild cognitive impairment (sMCI), progressive mild cognitive impairment (pMCI), and cognitively normal (CN) cohorts. A total of 83 FDG-PET scans are collected from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, including 21 subjects with CN, 21 subjects with sMCI, 21 subjects with pMCI, and 20 subjects with AD.

RESULTS

The method has achieved remarkable accuracy rates of 99.31% for CN vs. AD, 99.88% for CN vs. MCI, 99.54% for AD vs. MCI, and 96.81% for pMCI vs. sMCI. Based on the experimental results.

CONCLUSION

The results show that the proposed method has a significant generalisation ability as well as good performance in predicting the conversion of MCI to AD even in the absence of direct information. FDG-PET is a well-known biomarker for the identification of Alzheimer's disease using transfer learning.

Cellular mechanisms of fibrin (ogen): insight from neurodegenerative diseases

Neurodegenerative diseases are prevalent and currently incurable conditions that progressively impair cognitive, behavioral, and psychiatric functions of the central or peripheral nervous system. Fibrinogen, a macromolecular glycoprotein, plays a crucial role in the inflammatory response and tissue repair in the human body and interacts with various nervous system cells due to its unique molecular structure. Accumulating evidence suggests that fibrinogen deposits in the brains of patients with neurodegenerative diseases. By regulating pathophysiological mechanisms and signaling pathways, fibrinogen can exacerbate the neuro-pathological features of neurodegenerative diseases, while depletion of fibrinogen contributes to the amelioration of cognitive function impairment in patients. This review comprehensively summarizes the molecular mechanisms and biological functions of fibrinogen in central nervous system cells and neurodegenerative diseases, including Alzheimer's disease, Multiple Sclerosis, Parkinson's disease, Vascular dementia, Huntington's disease, and Amyotrophic Lateral Sclerosis. Additionally, we discuss the potential of fibrinogen-related treatments in the management of neurodegenerative disorders.

Role of inflammatory markers in the diagnosis of vascular contributions to cognitive impairment and dementia: a systematic review and meta-analysis

Vascular contribution to cognitive impairment and dementia (VCID) is a clinical label encompassing a wide range of cognitive disorders progressing from mild to major vascular cognitive impairment (VCI), which is also defined as vascular dementia (VaD). VaD diagnosis is mainly based on clinical and imaging findings. Earlier biomarkers are needed to identify subjects at risk to develop mild VCI and VaD. In the present meta-analysis, we comprehensively evaluated the role of inflammatory biomarkers in differential diagnosis between VaD and Alzheimer’s disease (AD), and assessed their prognostic value on predicting VaD incidence. We collected literature until January 31, 2021, assessing three inflammatory markers [interleukin(IL)-6, C-reactive protein (CRP), tumor necrosis factor (TNF)-α] from blood or cerebrospinal fluid (CSF) samples. Thirteen cross-sectional and seven prospective studies were included. Blood IL-6 levels were cross-sectionally significantly higher in people with VaD compared to AD patients (SMD: 0.40, 95% CI: 0.18 to 0.62) with low heterogeneity (I²: 41%, p = 0.13). Higher IL-6 levels were also associated to higher risk of incident VaD (relative risk: 1.28, 95% CI: 1.03 to 1.59, I²: 0%). IL-6 in CSF was significantly higher in people with VaD compared to healthy subjects (SMD: 0.77, 95% CI: 0.17 to 1.37, I²: 70%), and not compared to AD patients, but due to limited evidence and high inconsistency across studies, we could not draw definite conclusion. Higher blood IL-6 levels might represent a useful biomarker able to differentiate people with VaD from those with AD and might be correlated with higher risk of future VaD.

Evaluation of plasma amyloid peptides Aβ1-40 and Aβ1-42 as diagnostic biomarker of alzheimer's disease, its association with different grades of clinical severity and 18f-fluorodeoxyglucose positron emission tomography Z score in the Indian population: A case-control study

Background:

We estimated plasma amyloid-peptides levels (Aβ_1-42 and Aβ_1-40) as diagnostic biomarker of Alzheimer's disease (AD) and evaluated its association with clinical severity and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) Z score of the different brain regions in the Indian population.

Patients and Methods:

A case-control study was conducted. Diagnostic and statistical manual-IV, Dubois, and NIA-AA criteria were used for the diagnosis of AD. The plasma Aβ_1-42 and Aβ_1-40 concentration and 18F-FDG PET Z score were estimated for different brain regions.

Results:

Forty-seven cognitive impairment patients (AD = 29, mild cognitive impairment = 18) and 33 age-matched controls were enrolled. Plasma Aβ_1-42 level was significantly higher in the AD group compared to controls (P = 0.046) and a cut-off >5.7 ng/mL has a specificity of 96.9%, sensitivity of 27.6%, positive predictive value 88.9%, and negative predictive value 60.4% for differentiating AD patients from controls. Significant correlation was seen between Aβ_1-40/Aβ_1-42 ratio and 18F-FDG PET Z score in the bilateral-parietal, temporal, frontal-association area, and posterior-cingulate areas.

Conclusion:

As a diagnostic biomarker of AD, plasma Aβ_1-42 level showed good specificity but low sensitivity in the Indian population.

Elevated Plasma Level of D-dimer Predicts the High Risk of Early Cognitive Impairment in Type 2 Diabetic Patients as Carotid Artery Plaques become Vulnerable or Get Aggravated

BACKGROUND AND OBJECTIVE

D-dimer prompts fibrinolysis system, which is involved in Alzheimer's disease and the complications of type 2 diabetic patients, especially among those with carotid artery plaques. Hence, this study aims to investigate the role of D-dimer in early cognitive impairment among type 2 diabetic patients with carotid artery plaques.

METHODS

A total of 175 Chinese patients with type 2 diabetes were recruited and divided into two groups according to the Montreal Cognitive Assessment score. Demographic data were collected, plasma D-dimer was tested through VIDAS D-dimer New, neuropsychological tests were examined, and carotid artery plaques were detected by ultrasound and further stratified by vulnerability and level.

RESULTS

A total of 67 types 2 diabetic patients with Mild Cognitive Impairment (MCI) displayed significantly increased plasma D-dimer levels compared with their health-cognition controls (p = 0.011). Plasma D-dimer concentration was negatively related with Digit Span Test scores in diabetic patients with vulnerable plaques (r=-0.471, p=0.023) and Stroop Color Word Test C (number) in diabetic patients with stable plaques (r=-0.482, p<0.001). Multivariable regression analysis further showed that D-dimer concentration was an independent factor of diabetic MCI with carotid artery plaque (p=0.005), and D-dimer concentration especially contributed to the high risk of MCI with vulnerable plaques (p=0.028) or high levels of carotid plaque (p=0.023).

CONCLUSION

Elevated D-dimer level predicts the high risk of early cognitive impairment in type 2 diabetic patients with carotid artery plaques, especially vulnerable plaques or high levels of carotid plaques.

Relationship between fibrinogen level and its regulatory gene with Alzheimer's disease and vascular dementia

Objective

Methods

Results

Conclusions

Emerging Biomarkers in Vascular Cognitive Impairment and Dementia: From Pathophysiological Pathways to Clinical Application

Vascular pathology is the second most common neuropathology of dementia after Alzheimer’s disease (AD), with small vessels disease (SVD) being considered the major cause of vascular cognitive impairment and dementia (VCID). This review aims to evaluate pathophysiological pathways underlying a diagnosis of VCID. Firstly, we will discuss the role of endothelial dysfunction, blood-brain barrier disruption and neuroinflammation in its pathogenesis. Then, we will analyse different biomarkers including the ones of inflammatory responses to central nervous system tissue injuries, of coagulation and thrombosis and of circulating microRNA. Evidences on peripheral biomarkers for VCID are still poor and large-scale, prospectively designed studies are needed to translate these findings into clinical practice, in order to set different combinations of biomarkers to use for differential diagnosis among types of dementia.

Serum Exosomal miR-223 Serves as a Potential Diagnostic and Prognostic Biomarker for Dementia

The aims of this study were to examine the levels of serum and exosomal miR-137, miR-155 and miR-223, three neuroinflammation-related miRNAs, in dementia patients and to explore the value of these miRNAs for the diagnosis and prognostic evaluation of dementia. Thirty-two patients with dementia were enrolled, and sixteen volunteers without dementia served as controls. Serum exosomes were isolated by precipitation with ExoQuick and characterized by western blotting, nanoparticle-tracking analysis and immunofluorescence microscopy. The levels of both total serum miRNAs and serum exosomal miRNAs were determined by real-time quantitative PCR. Total serum miRNAs and serum exosomal miRNAs were both detected to be down-regulated. The median level of serum exosomal miR-223 was significantly decreased in dementia patients (p < 0.01). The level of miR-223 was significantly correlated with Mini-Mental State Examination (MMSE) scores, Clinical Dementia Rating (CDR) scores, magnetic resonance spectroscopy (MRS) spectral ratios and serum concentrations of IL-1β, IL-6, TNF-α, and CRP. The diagnostic utility of exosomal miR-233 was evaluated by the area under the receiver operating characteristic (ROC) curve, and the area under the curve (AUC) was 0.875. This study suggests that serum exosomal miR-223 is a promising biomarker for diagnosing dementia and evaluating the progression of disease.