Aberrant role of pyruvate kinase M2 in the regulation of gamma-secretase and memory deficits in Alzheimer's disease

Targeting hypoxia-related pathobiology in Alzheimer's disease: strategies for prevention and treatment

INTRODUCTION

Alzheimer's Disease (AD) is a neurodegenerative condition characterised by cognitive decline and memory impairment. Recent research highlights the important role of hypoxia, a state of insufficient oxygen availability, in exacerbating AD pathogenesis.

MATERIALS AND METHODS

Through the use of a number of different search engines like Scopus, PubMed, Bentham, and Elsevier databases, a literature review was carried out for investigating the role of hypoxia mediated pathobiology in AD. Only peerreviewed articles published in reputable journals in English language were included. Conversely, non-peer-reviewed articles, conference abstracts, and editorials were excluded, along with studies lacking experimental or clinical relevance or those unavailable in full text.

CONCLUSION

Hypoxia exacerbates core pathological features such as oxidative stress, neuroinflammation, mitochondrial dysfunction, amyloid-beta (Aβ) dysregulation, and hyperphosphorylation of tau protein. These interlinked mechanisms establish a self-perpetuating cycle of neuronal damage, accelerating disease progression. Addressing hypoxia as a modifiable risk factor offers potential for both prevention and treatment of AD. Exploring hypoxia and the HIF signalling pathway may help counteract the neuropathological and symptomatic effects of neurodegeneration.

PKM2-mediated metabolic reprogramming of microglia in neuroinflammation

Microglia, the resident immune cells of the central nervous system, undergo metabolic reprogramming during neuroinflammation, playing a crucial role in the pathogenesis of neurological disorders such as Parkinson's disease. This review focuses on Pyruvate Kinase M2 (PKM2), a key glycolytic enzyme, and its impact on microglial metabolic reprogramming and subsequent neuroinflammation. We explore the regulatory mechanisms governing PKM2 activity, its influence on microglial activation and immune responses, and its contribution to the progression of various neurological diseases. Finally, we highlight the therapeutic potential of targeting PKM2 as a novel strategy for treating neuroinflammation-driven neurological disorders. This review provides insights into the molecular mechanisms of PKM2 in neuroinflammation, aiming to inform the development of future therapeutic interventions.

Exploring the mechanism by which Zexie Tang regulates Alzheimer's disease: Insights from multi-omics analysis

BACKGROUND

Neurodegenerative disorders, such as Alzheimer's disease (AD), are characterized by a progressive decline in cognitive function. Modulating microglial metabolic reprogramming presents a promising therapeutic avenue for AD. Previous studies have shown that Zexie Tang (ZXT) possesses neuroprotective properties and can ameliorate cognitive impairment, but the underlying mechanisms remain unclear.

PURPOSE

This study aimed to investigate the efficacy of ZXT in improving cognitive function in AD mice using a multi-omics approach and to explore its potential role in modulating microglial metabolic reprogramming.

METHODS

Behavioral assessments were conducted to evaluate the effects of ZXT on cognitive function in APP/PS1 mice. H&E, Nissl, and Thioflavin S staining were performed to assess the impact of ZXT on brain pathology. A multi-omics approach, including transcriptomics, gut microbiota analysis, and metabolomics, was employed to elucidate the mechanisms of action of ZXT. RT-qPCR, immunoblotting, and immunofluorescence were used to validate the effects of ZXT on glycolipid metabolism, neuroinflammation, and the AMPK-mTOR-HIF1α pathway.

RESULTS

ZXT effectively protected against cognitive deficits, reduced hippocampal neuronal apoptosis, and decreased Aβ plaque deposition. Transcriptomics analysis revealed that ZXT was involved in immune system processes and metabolic processes and had a specific cellular response with microglia. Additionally, ZXT regulated the composition and functions of brain metabolites and gut microbiota. Our study demonstrated that ZXT positively influenced glucolipid metabolism and attenuated neuroinflammation, which were linked to the AMPK-mTOR-HIF1α pathway in the brain.

CONCLUSION

Our findings suggested that ZXT may mitigate cognitive deficits in APP/PS1 mice by modulating gut microbiota and enhancing brain energy metabolism. ZXT regulated glucolipid metabolism and neuroinflammation by modulating microglial metabolic reprogramming involving the AMPK-mTOR-HIF1α pathway.

EBP1 potentiates amyloid β pathology by regulating γ-secretase

The abnormal deposition of amyloid β (Aβ), produced by proteolytic cleavage events of amyloid precursor protein involving the protease γ-secretase and subsequent polymerization into amyloid plaques, plays a key role in the neuropathology of Alzheimer's disease (AD). Here we show that ErbB3 binding protein 1 (EBP1)/proliferation-associated 2G4 (PA2G4) interacts with presenilin, a catalytic subunit of γ-secretase, inhibiting Aβ production. Mice lacking forebrain Ebp1/Pa2g4 recapitulate the representative phenotypes of late-onset sporadic AD, displaying an age-dependent increase in Aβ deposition, amyloid plaques and cognitive dysfunction. In postmortem brains of patients with AD and 5x-FAD mice, we found that EBP1 is proteolytically cleaved by asparagine endopeptidase at N84 and N204 residues, compromising its inhibitory effect on γ-secretase, increasing Aβ aggregation and neurodegeneration. Accordingly, injection of AAV2-Ebp1 wild-type or an asparagine endopeptidase-uncleavable mutant into the brains of 5x-FAD mice decreased Aβ generation and alleviated the behavioral impairments. Thus, our study suggests that EBP1 acts as an inhibitor of γ-secretase on amyloid precursor protein cleavage and preservation of functional EBP1 could be a therapeutic strategy for AD.

Endothelial FOXM1 and Dab2 promote diabetic wound healing

Diabetes mellitus can cause impaired and delayed wound healing, leading to lower extremity amputations; however, the mechanisms underlying the regulation of vascular endothelial growth factor-dependent (VEGF-dependent) angiogenesis remain unclear. In our study, the molecular underpinnings of endothelial dysfunction in diabetes are investigated, focusing on the roles of disabled-2 (Dab2) and Forkhead box M1 (FOXM1) in VEGF receptor 2 (VEGFR2) signaling and endothelial cell function. Bulk RNA-sequencing analysis identified significant downregulation of Dab2 in high-glucose-treated primary mouse skin endothelial cells. In diabetic mice with endothelial deficiency of Dab2, in vivo and in vitro angiogenesis and wound healing were reduced when compared with wild-type diabetic mice. Restoration of Dab2 expression by injected mRNA-containing, LyP-1-conjugated lipid nanoparticles rescued impaired angiogenesis and wound healing in diabetic mice. Furthermore, FOXM1 was downregulated in skin endothelial cells under high-glucose conditions as determined by RNA-sequencing analysis. FOXM1 was found to bind to the Dab2 promoter, regulating its expression and influencing VEGFR2 signaling. The FOXM1 inhibitor FDI-6 reduced Dab2 expression and phosphorylation of VEGFR2. Our study provides evidence of the crucial roles of Dab2 and FOXM1 in diabetic endothelial dysfunction and establishes targeted delivery as a promising treatment for diabetic vascular complications.

SCRN: Single-Cell Gene Regulatory Network Identification in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, and it consumes considerable medical resources with increasing number of patients every year. Mounting evidence show that the regulatory disruptions altering the intrinsic activity of genes in brain cells contribute to AD pathogenesis. To gain insights into the underlying gene regulation in AD, we proposed a graph learning method, Single-Cell based Regulatory Network (SCRN), to identify the regulatory mechanisms based on single-cell data. SCRN implements the γ-decaying heuristic link prediction based on graph neural networks and can identify reliable gene regulatory networks using locally closed subgraphs. In this work, we first performed UMAP dimension reduction analysis on single-cell RNA sequencing (scRNA-seq) data of AD and normal samples. Then we used SCRN to construct the gene regulatory network based on three well-recognized AD genes (APOE, CX3CR1, and P2RY12). Enrichment analysis of the regulatory network revealed significant pathways including NGF signaling, ERBB2 signaling, and hemostasis. These findings demonstrate the feasibility of using SCRN to uncover potential biomarkers and therapeutic targets related to AD.

Novel Insights Into DLAT's Role in Alzheimer's Disease-Related Copper Toxicity Through Microglial Exosome Dynamics

BACKGROUND

Alzheimer's disease (AD) is a complex neurodegenerative disorder, with recent research emphasizing the roles of microglia and their secreted extracellular vesicles in AD pathology. However, the involvement of specific molecular pathways contributing to neuronal death in the context of copper toxicity remains largely unexplored.

OBJECTIVE

This study investigates the interaction between pyruvate kinase M2 (PKM2) and dihydrolipoamide S-acetyltransferase (DLAT), particularly focusing on copper-induced neuronal death in Alzheimer's disease.

METHODS

Gene expression datasets were analyzed to identify key factors involved in AD-related copper toxicity. The role of DLAT was validated using 5xFAD transgenic mice, while in vitro experiments were conducted to assess the impact of microglial exosomes on neuronal PKM2 transfer and DLAT expression. The effects of inhibiting the PKM2 transfer via microglial exosomes on DLAT expression and copper-induced neuronal death were also evaluated.

RESULTS

DLAT was identified as a critical factor in the pathology of AD, particularly in copper toxicity. In 5xFAD mice, increased DLAT expression was linked to hippocampal damage and cognitive decline. In vitro, microglial exosomes were shown to facilitate the transfer of PKM2 to neurons, leading to upregulation of DLAT expression and increased copper-induced neuronal death. Inhibition of PKM2 transfer via exosomes resulted in a significant reduction in DLAT expression, mitigating neuronal death and slowing AD progression.

CONCLUSION

This study uncovers a novel pathway involving microglial exosomes and the PKM2-DLAT interaction in copper-induced neuronal death, providing potential therapeutic targets for Alzheimer's disease. Blocking PKM2 transfer could offer new strategies for reducing neuronal damage and slowing disease progression in AD.

Interplay Between FoxM1 and Dab2 Promotes Endothelial Cell Responses in Diabetic Wound Healing

Diabetes mellitus can cause impaired and delayed wound healing, leading to lower extremity amputations; however, the mechanisms underlying the regulation of vascular endothelial growth factor (VEGF)-dependent angiogenesis remain uncertain and could reveal new therapeutic targets. In our study, the molecular underpinnings of endothelial dysfunction in diabetes were investigated, focusing on the roles of Disabled-2 (Dab2) and Forkhead Box M1 (FoxM1) in VEGF receptor 2 (VEGFR2) signaling and endothelial cell (EC) function. Bulk RNA-sequencing analysis identified significant downregulation of Dab2 in high concentrations glucose treated primary mouse skin ECs, simulating hyperglycemic conditions in diabetes mellitus. In diabetic mice with a genetic EC deficiency of Dab2 angiogenesis was reduced in vivo and in vitro when compared with wild-type mice. Restoration of Dab2 expression by injected mRNA-containing lipid nanoparticles rescued impaired angiogenesis and wound healing in diabetic mice. At the same time, FoxM1 was downregulated in skin ECs subjected to high glucose conditions as determined by RNA-sequencing analysis. FoxM1 was found to bind to the Dab2 promoter, regulating its expression and influencing VEGFR2 signaling. The FoxM1 inhibitor FDI-6 reduced Dab2 expression and phosphorylation of VEGFR2. These findings indicate that restoring Dab2 expression through targeted therapies can enhance angiogenesis and wound repair in diabetes. To explore this therapeutic potential, we tested LyP-1-conjugated lipid nanoparticles (LNPs) containing Dab2 or control mRNAs to target ECs and found the former significantly improved wound healing and angiogenesis in diabetic mice. This study provides evidence of the crucial roles of Dab2 and FoxM1 in diabetic endothelial dysfunction and establishes targeted delivery as a promising treatment for diabetic vascular complications.

The Role of PKM2 in Multiple Signaling Pathways Related to Neurological Diseases

Pyruvate kinase M2 (PKM2) is a key rate-limiting enzyme in glycolysis. It is well known that PKM2 plays a vital role in the proliferation of tumor cells. However, PKM2 can also exert its biological functions by mediating multiple signaling pathways in neurological diseases, such as Alzheimer's disease (AD), cognitive dysfunction, ischemic stroke, post-stroke depression, cerebral small-vessel disease, hypoxic-ischemic encephalopathy, traumatic brain injury, spinal cord injury, Parkinson's disease (PD), epilepsy, neuropathic pain, and autoimmune diseases. In these diseases, PKM2 can exert various biological functions, including regulation of glycolysis, inflammatory responses, apoptosis, proliferation of cells, oxidative stress, mitochondrial dysfunction, or pathological autoimmune responses. Moreover, the complexity of PKM2's biological characteristics determines the diversity of its biological functions. However, the role of PKM2 is not entirely the same in different diseases or cells, which is related to its oligomerization, subcellular localization, and post-translational modifications. This article will focus on the biological characteristics of PKM2, the regulation of PKM2 expression, and the biological role of PKM2 in neurological diseases. With this review, we hope to have a better understanding of the molecular mechanisms of PKM2, which may help researchers develop therapeutic strategies in clinic.

Systematic Analysis of Biological Processes Reveals Gene Co-expression Modules Driving Pathway Dysregulation in Alzheimer's Disease

Alzheimer's disease (AD) manifests as a complex systems pathology with intricate interplay among various genes and biological processes. Traditional differential gene expression (DEG) analysis, while commonly employed to characterize AD-driven perturbations, does not sufficiently capture the full spectrum of underlying biological processes. Utilizing single-nucleus RNA-sequencing data from postmortem brain samples across key regions-middle temporal gyrus, superior frontal gyrus, and entorhinal cortex-we provide a comprehensive systematic analysis of disrupted processes in AD. We go beyond the DEG-centric analysis by integrating pathway activity analysis with weighted gene co-expression patterns to comprehensively map gene interconnectivity, identifying region- and cell-type-specific drivers of biological processes associated with AD. Our analysis reveals profound modular heterogeneity in neurons and glia as well as extensive AD-related functional disruptions. Co-expression networks highlighted the extended involvement of astrocytes and microglia in biological processes beyond neuroinflammation, such as calcium homeostasis, glutamate regulation, lipid metabolism, vesicle-mediated transport, and TOR signaling. We find limited representation of DEGs within dysregulated pathways across neurons and glial cells, suggesting that differential gene expression alone may not adequately represent the disease complexity. Further dissection of inferred gene modules revealed distinct dynamics of hub DEGs in neurons versus glia, suggesting that DEGs exert more impact on neurons compared to glial cells in driving modular dysregulations underlying perturbed biological processes. Interestingly, we observe an overall downregulation of astrocyte and microglia modules across all brain regions in AD, indicating a prevailing trend of functional repression in glial cells across these regions. Notable genes from the CALM and HSP90 families emerged as hub genes across neuronal modules in all brain regions, suggesting conserved roles as drivers of synaptic dysfunction in AD. Our findings demonstrate the importance of an integrated, systems-oriented approach combining pathway and network analysis to comprehensively understand the cell-type-specific roles of genes in AD-related biological processes.

Pyruvate kinase M2 sustains cardiac mitochondrial quality surveillance in septic cardiomyopathy by regulating prohibitin 2 abundance via S91 phosphorylation

The endogenous mitochondrial quality control (MQC) system serves to protect mitochondria against cellular stressors. Although mitochondrial dysfunction contributes to cardiac damage during many pathological conditions, the regulatory signals influencing MQC disruption during septic cardiomyopathy (SC) remain unclear. This study aimed to investigate the involvement of pyruvate kinase M2 (PKM2) and prohibitin 2 (PHB2) interaction followed by MQC impairment in the pathogenesis of SC. We utilized LPS-induced SC models in PKM2 transgenic (PKM2TG) mice, PHB2S91D-knockin mice, and PKM2-overexpressing HL-1 cardiomyocytes. After LPS-induced SC, cardiac PKM2 expression was significantly downregulated in wild-type mice, whereas PKM2 overexpression in vivo sustained heart function, suppressed myocardial inflammation, and attenuated cardiomyocyte death. PKM2 overexpression relieved sepsis-related mitochondrial damage via MQC normalization, evidenced by balanced mitochondrial fission/fusion, activated mitophagy, restored mitochondrial biogenesis, and inhibited mitochondrial unfolded protein response. Docking simulations, co-IP, and domain deletion mutant protein transfection experiments showed that PKM2 phosphorylates PHB2 at Ser91, preventing LPS-mediated PHB2 degradation. Additionally, the A domain of PKM2 and the PHB domain of PHB2 are required for PKM2-PHB2 binding and PHB2 phosphorylation. After LPS exposure, expression of a phosphorylation-defective PHB2S91A mutant negated the protective effects of PKM2 overexpression. Moreover, knockin mice expressing a phosphorylation-mimetic PHB2S91D mutant showed improved heart function, reduced inflammation, and preserved mitochondrial function following sepsis induction. Abundant PKM2 expression is a prerequisite to sustain PKM2-PHB2 interaction which is a key element for preservation of PHB2 phosphorylation and MQC, presenting novel interventive targets for the treatment of septic cardiomyopathy.

Imbalance in Glucose Metabolism Regulates the Transition of Microglia from Homeostasis to Disease-Associated Microglia Stage 1

Microglia undergo two-stage activation in neurodegenerative diseases, known as disease-associated microglia (DAM). TREM2 mediates the DAM2 stage transition, but what regulates the first DAM1 stage transition is unknown. We report that glucose dyshomeostasis inhibits DAM1 activation and PKM2 plays a role. As in tumors, PKM2 was aberrantly elevated in both male and female human AD brains, but unlike in tumors, it is expressed as active tetramers, as well as among TREM2+ microglia surrounding plaques in 5XFAD male and female mice. snRNAseq analyses of microglia without Pkm2 in 5XFAD mice revealed significant increases in DAM1 markers in a distinct metabolic cluster, which is enriched in genes for glucose metabolism, DAM1, and AD risk. 5XFAD mice incidentally exhibited a significant reduction in amyloid pathology without microglial Pkm2 Surprisingly, microglia in 5XFAD without Pkm2 exhibited increases in glycolysis and spare respiratory capacity, which correlated with restoration of mitochondrial cristae alterations. In addition, in situ spatial metabolomics of plaque-bearing microglia revealed an increase in respiratory activity. These results together suggest that it is not only glycolytic but also respiratory inputs that are critical to the development of DAM signatures in 5XFAD mice.

Cardioprotective potential of compound 3K, a selective PKM2 inhibitor in isoproterenol-induced acute myocardial infarction: A mechanistic study

Myocardial infarction (MI) or heart attack arises from acute or chronic prolonged ischemic conditions in the myocardium. Although several risk factors are associated with MI pathophysiology, one of the risk factors is an imbalance in the oxygen supply. The current available MI therapies are still inadequate due to the complexity of MI pathophysiology. Pyruvate kinase M2 (PKM2) has been implicated in numerous CVDs pathologies. However, the effect of specific pharmacological intervention targeting PKM2 has not been studied in MI. Therefore, in this study, we explored the effect of compound 3K, a PKM2-specific inhibitor, in isoproterenol-induced acute MI model. In this study, in order to induce MI in rats, isoproterenol (ISO) was administered at a dose of 100 mg/kg over two days at an interval of 24 h. Specific PKM2 inhibitor, compound 3K (2 and 4 mg/kg), was administered in MI rats to investigate its cardioprotective potential. After the last administration of compound 3K, ECG and hemodynamic parameters were recorded using a PV-loop system. Cardiac histology, western blotting, and plasmatic cardiac damage markers were evaluated to elucidate the underlying mechanisms. Treatment of compound 3K significantly reduced ISO-induced alterations in ECG, ventricular functions, cardiac damage, infarct size, and cardiac fibrosis. Compound 3K treatment produced significant increase in PKM1 expression and decrease in PKM2 expression. In addition, HIF-1α, caspase-3, c-Myc, and PTBP1 expression were also reduced after compound 3K treatment. This study demonstrates the cardioprotective potential of compound 3K in MI, and its mechanisms of cardioprotective action.

Systematic Analysis of Biological Processes Reveals Gene Co-expression Modules Driving Pathway Dysregulation in Alzheimer's Disease

Alzheimer's disease (AD) manifests as a complex systems pathology with intricate interplay among various genes and biological processes. Traditional differential gene expression (DEG) analysis, while commonly employed to characterize AD-driven perturbations, does not sufficiently capture the full spectrum of underlying biological processes. Utilizing single-nucleus RNA-sequencing data from postmortem brain samples across key regions-middle temporal gyrus, superior frontal gyrus, and entorhinal cortex-we provide a comprehensive systematic analysis of disrupted processes in AD. We go beyond the DEG-centric analysis by integrating pathway activity analysis with weighted gene co-expression patterns to comprehensively map gene interconnectivity, identifying region- and cell-type-specific drivers of biological processes associated with AD. Our analysis reveals profound modular heterogeneity in neurons and glia as well as extensive AD-related functional disruptions. Co-expression networks highlighted the extended involvement of astrocytes and microglia in biological processes beyond neuroinflammation, such as calcium homeostasis, glutamate regulation, lipid metabolism, vesicle-mediated transport, and TOR signaling. We find limited representation of DEGs within dysregulated pathways across neurons and glial cells, indicating that differential gene expression alone may not adequately represent the disease complexity. Further dissection of inferred gene modules revealed distinct dynamics of hub DEGs in neurons versus glia, highlighting the differential impact of DEGs on neurons compared to glial cells in driving modular dysregulations underlying perturbed biological processes. Interestingly, we note an overall downregulation of both astrocyte and microglia modules in AD across all brain regions, suggesting a prevailing trend of functional repression in glial cells across these regions. Notable genes, including those of the CALM and HSP90 family genes emerged as hub genes across neuronal modules in all brain regions, indicating conserved roles as drivers of synaptic dysfunction in AD. Our findings demonstrate the importance of an integrated, systems-oriented approach combining pathway and network analysis for a comprehensive understanding of the cell-type-specific roles of genes in AD-related biological processes.

Inhibition of Pyruvate kinase M2 (PKM2) by shikonin attenuates isoproterenol-induced acute myocardial infarction via reduction in inflammation, hypoxia, apoptosis, and fibrosis

Myocardial infarction (MI) is a major cause of mortality and disability globally. MI results from acute or chronic myocardial ischemia characterized by an imbalance of oxygen demand and supply, leading to irreversible myocardial injury. Despite several significant efforts in the understanding of MI, the therapy of MI is not satisfactory due to its complicated pathophysiology. Recently, therapeutic potential of targeting pyruvate kinase M2 (PKM2) has been postulated in several cardiovascular diseases. PKM2 gene knockout and expression studies implicated the role of PKM2 in MI. However, the effects of pharmacological interventions targeting PKM2 have not been investigated in MI. Therefore, in the present study, effect of PKM2 inhibitor has been investigated in the MI along with elucidation of possible mechanism(s). MI in rats was induced by administrations of isoproterenol (ISO) at a dose of 100 mg/kg s.c. for two consecutives days at 24-h interval. At the same time, shikonin (PKM2 inhibitor) was administered at 2 and 4 mg/kg in ISO-induced MI rats. After the shikonin treatment, the ventricular functions were measured using a PV-loop system. Plasma MI injury markers, cardiac histology, and immunoblotting were performed to elucidate the molecular mechanism. Treatment of shikonin 2 and 4 mg/kg ameliorated cardiac injury, reduced infarct size, biochemical alterations, ventricular dysfunction, and cardiac fibrosis in ISO-induced MI. Expression of PKM2 in the ventricle was reduced while PKM1 expression increased in the shikonin treated group, indicating PKM2 inhibition restores PKM1 expression. In addition, PKM splicing protein (hnRNPA2B1 & PTBP1), HIF-1α, and caspase-3 expression were reduced after shikonin treatment. Our findings suggest that pharmacological inhibition of PKM2 with shikonin could be a potential therapeutic strategy to treat MI.

ROCK Inhibitor Fasudil Attenuates Neuroinflammation and Associated Metabolic Dysregulation in the Tau Transgenic Mouse Model of Alzheimer's Disease

BACKGROUND

The pathological manifestations of Alzheimer's disease (AD) include not only brain amyloid β protein (Aβ) containing neuritic plaques and hyperphosphorylated tau (p-- tau) containing neurofibrillary tangles but also microgliosis, astrocytosis, and neurodegeneration mediated by metabolic dysregulation and neuroinflammation.

METHODS

While antibody-based therapies targeting Aβ have shown clinical promise, effective therapies targeting metabolism, neuroinflammation, and p-tau are still an urgent need. Based on the observation that Ras homolog (Rho)-associated kinases (ROCK) activities are elevated in AD, ROCK inhibitors have been explored as therapies in AD models. This study determines the effects of fasudil, a ROCK inhibitor, on neuroinflammation and metabolic regulation in the P301S tau transgenic mouse line PS19 that models neurodegenerative tauopathy and AD. Using daily intraperitoneal (i.p.) delivery of fasudil in PS19 mice, we observed a significant hippocampal-specific decrease of the levels of phosphorylated tau (pTau Ser202/Thr205), a decrease of GFAP+ cells and glycolytic enzyme Pkm1 in broad regions of the brain, and a decrease in mitochondrial complex IV subunit I in the striatum and thalamic regions.

RESULTS

Although no overt detrimental phenotype was observed, mice dosed with 100 mg/kg/day for 2 weeks exhibited significantly decreased mitochondrial outer membrane and electron transport chain (ETC) protein abundance, as well as ETC activities.

CONCLUSION

Our results provide insights into dose-dependent neuroinflammatory and metabolic responses to fasudil and support further refinement of ROCK inhibitors for the treatment of AD.

Mass spectrometry in cerebrospinal fluid uncovers association of glycolysis biomarkers with Alzheimer's disease in a large clinical sample

Alzheimer's disease (AD) is a complex and heterogeneous neurodegenerative disorder with contributions from multiple pathophysiological pathways. One of the long-recognized and important features of AD is disrupted cerebral glucose metabolism, but the underlying molecular basis remains unclear. In this study, unbiased mass spectrometry was used to survey CSF from a large clinical cohort, comparing patients who are either cognitively unimpaired (CU; n = 68), suffering from mild-cognitive impairment or dementia from AD (MCI-AD, n = 95; DEM-AD, n = 72), or other causes (MCI-other, n = 77; DEM-other, n = 23), or Normal Pressure Hydrocephalus (NPH, n = 57). The results revealed changes related to altered glucose metabolism. In particular, two glycolytic enzymes, pyruvate kinase (PKM) and aldolase A (ALDOA), were found to be upregulated in CSF from patients with AD compared to those with other neurological conditions. Increases in full-length PKM and ALDOA levels in CSF were confirmed with immunoblotting. Levels of these enzymes furthermore correlated negatively with CSF glucose in matching CSF samples. PKM levels were also found to be increased in AD in publicly available brain-tissue data. These results indicate that ALDOA and PKM may act as technically-robust potential biomarkers of glucose metabolism dysregulation in AD.

Oxygen metabolism abnormality and Alzheimer's disease: An update

Oxygen metabolism abnormality plays a crucial role in the pathogenesis of Alzheimer's disease (AD) via several mechanisms, including hypoxia, oxidative stress, and mitochondrial dysfunction. Hypoxia condition usually results from living in a high-altitude habitat, cardiovascular and cerebrovascular diseases, and chronic obstructive sleep apnea. Chronic hypoxia has been identified as a significant risk factor for AD, showing an aggravation of various pathological components of AD, such as amyloid β-protein (Aβ) metabolism, tau phosphorylation, mitochondrial dysfunction, and neuroinflammation. It is known that hypoxia and excessive hyperoxia can both result in oxidative stress and mitochondrial dysfunction. Oxidative stress and mitochondrial dysfunction can increase Aβ and tau phosphorylation, and Aβ and tau proteins can lead to redox imbalance, thus forming a vicious cycle and exacerbating AD pathology. Hyperbaric oxygen therapy (HBOT) is a non-invasive intervention known for its capacity to significantly enhance cerebral oxygenation levels, which can significantly attenuate Aβ aggregation, tau phosphorylation, and neuroinflammation. However, further investigation is imperative to determine the optimal oxygen pressure, duration of exposure, and frequency of HBOT sessions. In this review, we explore the prospects of oxygen metabolism in AD, with the aim of enhancing our understanding of the underlying molecular mechanisms in AD. Current research aimed at attenuating abnormalities in oxygen metabolism holds promise for providing novel therapeutic approaches for AD.

Reinventing the Penumbra - the Emerging Clockwork of a Multi-modal Mechanistic Paradigm

The concept of the ischemic penumbra was originally defined as the area around a necrotic stroke core and seen as the tissue at imminent risk of further damage. Today, the penumbra is generally considered as time-sensitive hypoperfused brain tissue with decreased oxygen and glucose availability, salvageable tissue as treated by intervention, and the potential target for neuroprotection in focal stroke. The original concept entailed electrical failure and potassium release but one short of neuronal cell death and was based on experimental stroke models, later confirmed in clinical imaging studies. However, even though the basic mechanisms have translated well, conferring brain protection, and improving neurological outcome after stroke based on the pathophysiological mechanisms in the penumbra has yet to be achieved. Recent findings shape the modern understanding of the penumbra revealing a plethora of molecular and cellular pathophysiological mechanisms. We now propose a new model of the penumbra, one which we hope will lay the foundation for future translational success. We focus on the availability of glucose, the brain's central source of energy, and bioenergetic failure as core pathophysiological concepts. We discuss the relation of mitochondrial function in different cell types to bioenergetics and apoptotic cell death mechanisms, autophagy, and neuroinflammation, to glucose metabolism in what is a dynamic ischemic penumbra.

The Proteome Profile of Olfactory Ecto-Mesenchymal Stem Cells-Derived from Patients with Familial Alzheimer's Disease Reveals New Insights for AD Study

Alzheimer's disease (AD), the most common neurodegenerative disease and the first cause of dementia worldwide, has no effective treatment, and its pathological mechanisms are not yet fully understood. We conducted this study to explore the proteomic differences associated with Familial Alzheimer's Disease (FAD) in olfactory ecto-mesenchymal stem cells (MSCs) derived from PSEN1 (A431E) mutation carriers compared with healthy donors paired by age and gender through two label-free liquid chromatography-mass spectrometry approaches. The first analysis compared carrier 1 (patient with symptoms, P1) and its control (healthy donor, C1), and the second compared carrier 2 (patient with pre-symptoms, P2) with its respective control cells (C2) to evaluate whether the protein alterations presented in the symptomatic carrier were also present in the pre-symptom stages. Finally, we analyzed the differentially expressed proteins (DEPs) for biological and functional enrichment. These proteins showed impaired expression in a stage-dependent manner and are involved in energy metabolism, vesicle transport, actin cytoskeleton, cell proliferation, and proteostasis pathways, in line with previous AD reports. Our study is the first to conduct a proteomic analysis of MSCs from the Jalisco FAD patients in two stages of the disease (symptomatic and presymptomatic), showing these cells as a new and excellent in vitro model for future AD studies.

Identification of glycolytic proteins as binding partners of Bri2 BRICHOS domain

Human integral membrane protein 2B (ITM2B or Bri2) is a member of the BRICHOS family, that can attenuate Aβ pathology in the brain. As a result, the identification of novel Bri2 BRICHOS client proteins has been sought to help elucidate signaling pathways and the potential identification of novel therapeutic targets. To identify Bri2 BRICHOS interacting partners, we carried out a 'protein fishing' experiment using recombinant human (rh) Bri2 BRICHOS-coated magnetic particles, in combination with proteomic analysis on cytosolic and membrane fractions of cortical homogenates from C57BL/6 J WT mouse. We identified 4 proteins from the cytosolic fractions and 44 proteins from the membrane fractions that had significant interactions (p < 0.05) with Bri2 BRICHOS domain, of which 11 proteins were previously identified as proteins that interacted with Bri2 BRICHOS domain. Enrichment analysis of the retained proteins identified glycolysis/gluconeogenesis as the most enriched pathway, with several proteins identified playing roles in carbon metabolism, amino acid synthesis. The data suggested that Bri2 BRICHOS may have a role in cellular energy demands in the brain via glycolysis and mitochondrial oxidative phosphorylation and may play a role in mitochondrial homeostasis.

The Effects of Andrographis paniculata (Burm.F.) Wall. Ex Nees and Andrographolide on Neuroinflammation in the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases (NDs) affect millions of people worldwide, and to date, Alzheimer's and Parkinson's diseases are the most common NDs. Of the many risk factors for neurodegeneration, the aging process has the most significant impact, to the extent that it is tempting to consider neurodegenerative disease as a manifestation of accelerated aging. However, genetic and environmental factors determine the course of neurodegenerative disease progression. It has been proposed that environmental stimuli influence neuroplasticity. Some clinical studies have shown that healthy lifestyles and the administration of nutraceuticals containing bioactive molecules possessing antioxidant and anti-inflammatory properties have a preventive impact or mitigate symptoms in previously diagnosed patients. Despite ongoing research efforts, the therapies currently used for the treatment of NDs provide only marginal therapeutic benefits; therefore, the focus is now directly on the search for natural products that could be valuable tools in combating these diseases, including the natural compound Andrographis paniculata (Ap) and its main constituent, andrographolide (Andro). Preclinical studies have shown that the aqueous extract of Ap can modulate neuroinflammatory and neurodegenerative responses, reducing inflammatory markers and oxidative stress in various NDs. Therefore, in this review, we will focus on the molecular mechanisms by which Ap and Andro can modulate the processes of neurodegeneration and neuroinflammation, which are significant causes of neuronal death and cognitive decline.

Potential diagnostic value of CSF metabolism-related proteins across the Alzheimer's disease continuum

BACKGROUND

Alzheimer's disease (AD) cerebrospinal fluid (CSF) core biomarkers (Aβ42/40 ratio, p-tau, and t-tau) provide high diagnostic accuracy, even at the earliest stage of disease. However, these markers do not fully reflect the complex AD pathophysiology. Recent large scale CSF proteomic studies revealed several new AD candidate biomarkers related to metabolic pathways. In this study we measured the CSF levels of four metabolism-related proteins not directly linked to amyloid- and tau-pathways (i.e., pyruvate kinase, PKM; aldolase, ALDO; ubiquitin C-terminal hydrolase L1, UCHL1, and fatty acid-binding protein 3, FABP3) across the AD continuum. We aimed at validating the potential value of these proteins as new CSF biomarkers for AD and their possible involvement in AD pathogenesis, with specific interest on the preclinical phase of the disease.

METHODS

CSF PKM and ALDO activities were measured with specific enzyme assays while UCHL1 and FABP3 levels were measured with immunoassays in a cohort of patients composed as follows: preclinical AD (pre-AD, n = 19, cognitively unimpaired), mild cognitive impairment due to AD (MCI-AD, n = 50), dementia due to AD (ADdem, n = 45), and patients with frontotemporal dementia (FTD, n = 37). Individuals with MCI not due to AD (MCI, n = 30) and subjective cognitive decline (SCD, n = 52) with negative CSF AD-profile, were enrolled as control groups.

RESULTS

CSF UCHL1 and FABP3 levels, and PKM activity were significantly increased in AD patients, already at the pre-clinical stage. CSF PKM activity was also increased in FTD patients compared with control groups, being similar between AD and FTD patients. No difference was found in ALDO activity among the groups. UCHL1 showed good performance in discriminating early AD patients (pre-AD and MCI-AD) from controls (AUC ~ 0.83), as assessed by ROC analysis. Similar results were obtained for FABP3. Conversely, PKM provided the best performance when comparing FTD vs. MCI (AUC = 0.80). Combination of PKM, FABP3, and UCHL1 improved the diagnostic accuracy for the detection of patients within the AD continuum when compared with single biomarkers.

CONCLUSIONS

Our study confirmed the potential role of UCHL1 and FABP3 as neurodegenerative biomarkers for AD. Furthermore, our results validated the increase of PKM activity in CSF of AD patients, already at the preclinical phase of the disease. Increased PKM activity was observed also in FTD patients, possibly underlining similar alterations in energy metabolism in AD and FTD.

Mass Spectrometry in Cerebrospinal Fluid Uncovers Association of Glycolysis Biomarkers with Alzheimer's Disease in a Large Clinical Sample

Background

Alzheimer's disease (AD) is a complex heterogenous neurodegenerative disorder, characterized by multiple pathophysiologies, including disruptions in brain metabolism. Defining markers for patient stratification across these pathophysiologies is an important step towards personalized treatment of AD. Efficient brain glucose metabolism is essential to sustain neuronal activity, but hypometabolism is consistently observed in AD. The molecular changes underlying these observations remain unclear. Recent studies have indicated dysregulation of several glycolysis markers in AD cerebrospinal fluid and tissue.

Methods

In this study, unbiased mass spectrometry was used to perform a deep proteomic survey of cerebrospinal fluid (CSF) from a large-scale clinically complex cohort to uncover changes related to impaired glucose metabolism.

Results

Two glycolytic enzymes, Pyruvate kinase (PKM) and Aldolase A (ALDOA) were found to be specifically upregulated in AD CSF compared to other non-AD groups. Presence of full-length protein of these enzymes in CSF was confirmed through immunoblotting. Levels of tryptic peptides of these enzymes correlated significantly with CSF glucose and CSF lactate in matching CSF samples.

Conclusions

The results presented here indicate a general dysregulation of glucose metabolism in the brain in AD. We highlight two markers ALDOA and PKM that may act as potential functionally-relevant biomarkers of glucose metabolism dysregulation in AD.

Meta-analysis of published cerebrospinal fluid proteomics data identifies and validates metabolic enzyme panel as Alzheimer's disease biomarkers

To develop therapies for Alzheimer's disease, we need accurate in vivo diagnostics. Multiple proteomic studies mapping biomarker candidates in cerebrospinal fluid (CSF) resulted in little overlap. To overcome this shortcoming, we apply the rarely used concept of proteomics meta-analysis to identify an effective biomarker panel. We combine ten independent datasets for biomarker identification: seven datasets from 150 patients/controls for discovery, one dataset with 20 patients/controls for down-selection, and two datasets with 494 patients/controls for validation. The discovery results in 21 biomarker candidates and down-selection in three, to be validated in the two additional large-scale proteomics datasets with 228 diseased and 266 control samples. This resulting 3-protein biomarker panel differentiates Alzheimer's disease (AD) from controls in the two validation cohorts with areas under the receiver operating characteristic curve (AUROCs) of 0.83 and 0.87, respectively. This study highlights the value of systematically re-analyzing previously published proteomics data and the need for more stringent data deposition.

Effects of Pyruvate Kinase M2 (PKM2) Gene Deletion on Astrocyte-Specific Glycolysis and Global Cerebral Ischemia-Induced Neuronal Death

Ischemic stroke is caused by insufficient blood flow to the brain. Astrocytes have a role in bidirectionally converting pyruvate, generated via glycolysis, into lactate and then supplying it to neurons through astrocyte-neuron lactate shuttle (ANLS). Pyruvate kinase M2 (PKM2) is an enzyme that dephosphorylates phosphoenolpyruvate to pyruvate during glycolysis in astrocytes. We hypothesized that a reduction in lactate supply in astrocyte PKM2 gene deletion exacerbates neuronal death. Mice harboring a PKM2 gene deletion were established by administering tamoxifen to Aldh1l1-CreERT2; PKM2f/f mice. Upon development of global cerebral ischemia, mice were immediately injected with sodium l-lactate (250 mg/kg, i.p.). To verify our hypothesis, we compared oxidative damage, microtubule disruption, ANLS disruption, and neuronal death between the gene deletion and control subjects. We observed that PKM2 gene deletion increases the degree of neuronal damage and impairment of lactate metabolism in the hippocampal region after GCI. The lactate administration groups showed significantly reduced neuronal death and increases in neuron survival and cognitive function. We found that lactate supply via the ANLS in astrocytes plays a crucial role in maintaining energy metabolism in neurons. Lactate administration may have potential as a therapeutic tool to prevent neuronal damage following ischemic stroke.

Negative correlation between serum pyruvate kinase M2 and cognitive function in patients with cerebral small vessel disease

OBJECTIVE

Cerebral small vessel disease (CSVD) is one of the main contributing factors to vascular cognitive impairment (VCI), with an increasing incidence rate. However, the genesis of CSVD cognitive impairment remains unknown. Inflammation and metabolic disorders are considered important pathogenesis of CSVD. In addition to acting as the key regulator of aerobic glycolysis, pyruvate kinase muscle isozyme 2 (PKM2) is a proinflammatory mediator transcriptional activator that can promote an inflammatory response. This study explored whether serum PKM2 is associated with cognitive impairment in CSVD patients.

METHODS

The demographic data, history of risk factors, laboratory data, and cognitive function scale assessment of 219 CSVD patients were analyzed, and the correlation between the CSVD clinical data and neuroimaging parameters with serum PKM2 was further explored. The serum PKM2 level was determined by enzyme-linked immunosorbent assay using the collected serum samples. Insulin resistance (IR) was assessed with reference to the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). HOMA-IR was calculated using the formula HOMA-IR = fasting plasma glucose (FPG, mmol/L) × fasting insulin (FINS, μU/mL)/22.5. A binomial logistic regression model was referred to infer the risk factors for VCI, and the ability of serum PKM2 to diagnose VCI was assessed by using a ROC curve.

RESULTS

Serum PKM2 level was positively correlated with HOMA-IR (r = 0.206, P = 0.002), negatively correlated with MMSE and MOCA on the cognitive scale in CSVD patients, and higher in CSVD patients with white matter hyperintensities (WMH) (P < 0.001). When compared with patients without cognitive impairment, the serum PKM2 levels were elevated in cases with suspected dementia, mild dementia, mild to moderate dementia, and moderate to severe dementia, and the differences were statistically significant (P < 0.05). Serum PKM2 levels were correlated with cognitive screening test scores in CSVD.

CONCLUSION

The present findings indicated that the serum PKM2 level was positively correlated with HOMA-IR, WMH, and enlarged perivascular spaces and negatively correlated with cognitive function in CSVD patients.

Alternative Pharmacological Strategies for the Treatment of Alzheimer's Disease: Focus on Neuromodulator Function

Alzheimer's disease (AD) is a neurodegenerative disorder, comprising 70% of dementia diagnoses worldwide and affecting 1 in 9 people over the age of 65. However, the majority of its treatments, which predominantly target the cholinergic system, remain insufficient at reversing pathology and act simply to slow the inevitable progression of the disease. The most recent neurotransmitter-targeting drug for AD was approved in 2003, strongly suggesting that targeting neurotransmitter systems alone is unlikely to be sufficient, and that research into alternate treatment avenues is urgently required. Neuromodulators are substances released by neurons which influence neurotransmitter release and signal transmission across synapses. Neuromodulators including neuropeptides, hormones, neurotrophins, ATP and metal ions display altered function in AD, which underlies aberrant neuronal activity and pathology. However, research into how the manipulation of neuromodulators may be useful in the treatment of AD is relatively understudied. Combining neuromodulator targeting with more novel methods of drug delivery, such as the use of multi-targeted directed ligands, combinatorial drugs and encapsulated nanoparticle delivery systems, may help to overcome limitations of conventional treatments. These include difficulty crossing the blood-brain-barrier and the exertion of effects on a single target only. This review aims to highlight the ways in which neuromodulator functions are altered in AD and investigate how future therapies targeting such substances, which act upstream to classical neurotransmitter systems, may be of potential therapeutic benefit in the sustained search for more effective treatments.

Role of Pyruvate Kinase M2 (PKM2) in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the world's leading cause of death, accounting for 32% of all fatalities. Although therapeutic agents are available for CVDs, however, most of them have significant limitations such as the time-dependency effect, hypotension, and bradycardia. To overcome the limitations of current pharmacological therapies, new molecular targets and pathways need to be identified and investigated to provide better treatment options for CVDs. Recent evidence suggested the involvement of pyruvate kinase M2 (PKM2) and targeting PKM2 by its modulators (inhibitors and activators) has shown promising results in several CVDs. PKM2 regulates gene activation in the context of apoptosis, mitosis, hypoxia, inflammation, and metabolic reprogramming. PKM2 modulators might have a significant impact on the molecular pathways involved in CVD pathogenesis. Therefore, PKM2 modulators can be one of the therapeutic options for CVDs. This review provides an insight into PKM2 involvement in various CVDs along with their therapeutic potential.