Parkinson's disease and Alzheimer's disease: a Mendelian randomization study

A current review on P2X7 receptor antagonist patents in the treatment of neuroinflammatory disorders: a patent review on antagonists

Chronic inflammation is defined by an activated microglial state linked to all neurological disorders, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (a motor neuron disease that affects the brain and spinal cord). P2X7 receptors (P2X7R) are ATP-activated ion-gated channels present on microglial surfaces. Prolonged ATP release under pathological settings results in sustained P2X7R activation, which leads to inflammasome development and cytokine release. P2X7R and its enabling roles have recently been linked to neurodegenerative diseases, making it a potential research subject. This research provides an overview of current patents for chemicals, biologics, and medicinal applications. The World Intellectual Property Organization (WIPO), European Patent Office (EPO, Espacenet), and the United States Patent and Trademark Office (USPTO) databases were searched for patents using the keywords "P2X7R and Neuroinflammation." During the study period from 2015 to 2021, 103 patents were examined. The countries that protected these innovations were the United States, PCT (Patent Cooperation Treaty states), Europe, Canada, Australia, and India. Janssen Pharmaceutica NV had the most applications, followed by Acetelion Pharmaceuticals LTD., Renovis Inc., Kelly Michael G, Kincaid Jhon, Merck Patent GMBH, H Lundbeck A/S, and many more. The P2X7R is a possible diagnostic and therapeutic target for cancer, pain disorders, and inflammation. For P2X7 R, several compounds have been discovered and are presently the subject of clinical trial investigations. This study featured patents for P2X7R antagonists, which help treat conditions including neuroinflammation.

Food for thought: Making the case for food produced via regenerative agriculture in the battle against non-communicable chronic diseases (NCDs)

Non-communicable diseases (NCDs) pose a global health challenge, leading to substantial morbidity, mortality, and economic strain. Our review underscores the escalating incidence of NCDs worldwide and highlights the potential of regenerative agriculture (RA) products in mitigating these diseases. We also explore the efficacy of dietary interventions in NCD management and prevention, emphasizing the superiority of plant-based diets over those high in processed foods and red meat. Examining the role of the gut microbiome in various diseases, including liver disorders, allergies, metabolic syndrome, inflammatory bowel disease, and colon cancer, we find compelling evidence implicating its influence on disease development. Notably, dietary modifications can positively affect the gut microbiome, fostering a symbiotic relationship with the host and making this a critical strategy in disease prevention and treatment. Investigating agricultural practices, we identify parallels between soil/plant and human microbiome studies, suggesting a crucial link between soil health, plant- and animal-derived food quality, and human well-being. Conventional/Industrial agriculture (IA) practices, characterized in part by use of chemical inputs, have adverse effects on soil microbiome diversity, food quality, and ecosystems. In contrast, RA prioritizes soil health through natural processes, and includes avoiding synthetic inputs, crop rotation, and integrating livestock. Emerging evidence suggests that food from RA systems surpasses IA-produced food in quality and nutritional value. Recognizing the interconnection between human, plant, and soil microbiomes, promoting RA-produced foods emerges as a strategy to improve human health and environmental sustainability. By mitigating climate change impacts through carbon sequestration and water cycling, RA offers dual benefits for human and planetary health and well-being. Emphasizing the pivotal role of diet and agricultural practices in combating NCDs and addressing environmental concerns, the adoption of regional RA systems becomes imperative. Increasing RA integration into local food systems can enhance food quality, availability, and affordability while safeguarding human health and the planet's future.

Vitamin K2 in Health and Disease: A Clinical Perspective

Vitamins are essential organic compounds that vary widely in chemical structure and are vital in small quantities for numerous biochemical and biological functions. They are critical for metabolism, growth, development and maintaining overall health. Vitamins are categorised into two groups: hydrophilic and lipophilic. Vitamin K (VK), a lipophilic vitamin, occurs naturally in two primary forms: phylloquinone (VK1), found in green leafy vegetables and algae, and Menaquinones (VK2), present in certain fermented and animal foods and widely formulated in VK supplements. This review explores the possible factors contributing to VK deficiency, including dietary influences, and discusses the pharmacological and therapeutic potential of supplementary VK2, examining recent global clinical studies on its role in treating diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, cardiovascular disease, chronic kidney disease, diabetes, neurodegenerative disorders and cancers. The analysis includes a review of published articles from multiple databases, including Scopus, PubMed, Google Scholar, ISI Web of Science and CNKI, focusing on human studies. The findings indicate that VK2 is a versatile vitamin essential for human health and that a broadly positive correlation exists between VK2 supplementation and improved health outcomes. However, clinical data are somewhat inconsistent, highlighting the need for further detailed research into VK2's metabolic processes, biomarker validation, dose-response relationships, bioavailability and safety. Establishing a Recommended Daily Intake for VK2 could significantly enhance global health.

Integrating multi-omics data to reveal the effect of genetic variant rs6430538 on Alzheimer's disease risk

Introduction

Growing evidence highlights a potential genetic overlap between Alzheimer's disease (AD) and Parkinson's disease (PD); however, the role of the PD risk variant rs6430538 in AD remains unclear.

Methods

In Stage 1, we investigated the risk associated with the rs6430538 C allele in seven large-scale AD genome-wide association study (GWAS) cohorts. In Stage 2, we performed expression quantitative trait loci (eQTL) analysis to calculate the cis-regulated effect of rs6430538 on TMEM163 in both AD and neuropathologically normal samples. Stage 3 involved evaluating the differential expression of TMEM163 in 4 brain tissues from AD cases and controls. Finally, in Stage 4, we conducted a transcriptome-wide association study (TWAS) to identify any association between TMEM163 expression and AD.

Results

The results showed that genetic variant rs6430538 C allele might increase the risk of AD. eQTL analysis revealed that rs6430538 up-regulated TMEM163 expression in AD brain tissue, but down-regulated its expression in normal samples. Interestingly, TMEM163 showed differential expression in entorhinal cortex (EC) and temporal cortex (TCX). Furthermore, the TWAS analysis indicated strong associations between TMEM163 and AD in various tissues.

Discussion

In summary, our findings suggest that rs6430538 may influence AD by regulating TMEM163 expression. These discoveries may open up new opportunities for therapeutic strategies targeting AD.

A bacterial cellulose-based LiSrVO4:Eu3+ nanosensor platform for smartphone sensing of levodopa and dopamine: point-of-care diagnosis of Parkinson's disease

Among the catecholamines, dopamine (DA) is essential in regulating multiple aspects of the central nervous system. The level of dopamine in the brain correlates with neurological diseases such as Parkinson's disease (PD). However, dopamine is unable to cross the blood-brain barrier (BBB). Therefore, levodopa (LD) is used to restore normal dopamine levels in the brain by crossing the BBB. Thus, the control of LD and DA levels is critical for PD diagnosis. For this purpose, LiSr0.0985VO4:0.015Eu3+ (LSV:0.015Eu3+) nanoplates were synthesized by the microwave-assisted co-precipitation method, and have been employed as an optical sensor for the sensitive and selective detection of catecholamines. The synthesized LSV:0.015Eu3+ nanoplates emitted red fluorescence with a high quantum yield (QY) of 48%. By increasing the LD and DA concentrations, the fluorescence intensity of LSV:0.015Eu3+ nanoplates gradually decreased. Under optimal conditions, the linear dynamic ranges were 1-40 μM (R2 = 0.9972) and 2-50 μM (R2 = 0.9976), and the detection limits (LOD) were 279 nM, and 390 nM for LD and DA, respectively. Herein, an instrument-free, rapid quantification visual assay was developed using a paper-based analytical device (PAD) with LSV:0.015Eu3+ fixed on the bacterial cellulose nanopaper (LEBN) to determine LD and DA concentrations with ease of operation and low cost. A smartphone was coupled with the PAD device to quantitatively analyze the fluorescence intensity changes of LSV:0.015Eu3+ using the color recognizer application (APP). In addition, the LSV:0.015Eu3+ nanosensor showed acceptable repeatability and was used to analyze real human urine, blood serum, and tap water samples with a recovery of 96-107%.

Exploring the Potential of Antidiabetic Agents as Therapeutic Approaches for Alzheimer's and Parkinson's Diseases: A Comprehensive Review

Alzheimer's and Parkinson's are two prevalent neurodegenerative disorders with significant societal and healthcare burdens. The search for effective therapeutic approaches to combat these diseases has led to growing interest in exploring the potential of antidiabetic agents. This comprehensive review aims to provide a detailed overview of the current literature on using antidiabetic agents as therapeutic interventions for Alzheimer's and Parkinson's diseases. We discuss the underlying pathological mechanisms of these neurodegenerative diseases, including protein misfolding, inflammation, oxidative stress, and mitochondrial dysfunction. We then delve into the potential mechanisms by which antidiabetic agents may exert neuroprotective effects, including regulation of glucose metabolism and insulin signaling, anti-inflammatory effects, modulation of oxidative stress, and improvement of mitochondrial function and bioenergetics. We highlight in vitro, animal, and clinical studies that support the potential benefits of antidiabetic agents in reducing disease pathology and improving clinical outcomes. However, we also acknowledge these agents' limitations, variability in treatment response, and potential side effects. Furthermore, we explore emerging therapeutic targets and novel approaches, such as glucagon-like peptide-1 receptor (GLP-1R) agonists, insulin sensitizer drugs, neuroinflammation-targeted therapies, and precision medicine approaches. The review concludes by emphasizing the need for further research, including large-scale clinical trials, to validate the efficacy and safety of antidiabetic agents in treating Alzheimer's and Parkinson's disease. The collaboration between researchers, clinicians, and pharmaceutical companies is essential in advancing the field and effectively treating patients affected by these debilitating neurodegenerative disorders.

Design and Characterization of Pressure Monitoring and Insertion system for Intraparenchymal Convection Enhanced Delivery

Neurological disorders are a significant societal and economic burden. Common pharmacological therapies often can only manage symptoms and have limited efficacy. Intraparenchymal convection enhanced delivery (IP CED) is a neurosurgical technique for direct brain delivery of therapeutics. Currently, the main applications of IP CED are targeted chemotherapy for glioblastoma and gene therapy. While IP CED has advantages over systemic approaches, its benefits can be drastically reduced by inadequate coverage as low as 21% of target anatomy, excessive infusion durations greater than 2 hours, and off-target effects. Addressing the limitations of IP CED requires thorough investigation and optimization of the relevant fluid dynamic and operational parameters. In this work, we present the design, fabrication, and characterization of low-cost, open-source, and fully automated CED cannula insertion control and pressure-monitoring systems. Using these automated CED control systems, we investigate the effects of pressure, insertion velocity, and flow rates on several outcome variables, including reflux, volume distribution, and infusion cloud morphology during CED infusions in brain phantoms.Clinical Relevance- CED pressure properties may be able to implicate reflux incidents and could provide clinicians with valuable, real-time information regarding ongoing infusions without the need for costly medical imaging modalities.

DOPA pheomelanin is increased in nigral neuromelanin of Parkinson's disease

Neuromelanin (NM) in dopaminergic neurons of human substantia nigra (SN) has a melanic component that consists of pheomelanin and eumelanin moieties and has been proposed as a key factor contributing to dopaminergic neuron vulnerability in Parkinson's disease (PD). While eumelanin is considered as an antioxidant, pheomelanin and related oxidative stress are associated with compromised drug and metal ion binding and melanoma risk. Using postmortem SN from patients with PD or Alzheimer's disease (AD) and unaffected controls, we identified increased L-3,4-dihydroxyphenylalanine (DOPA) pheomelanin and increased ratios of dopamine (DA) pheomelanin markers to DA in PD SN compared to controls. Eumelanins derived from both DOPA and DA were reduced in PD group. In addition, we report an increase in DOPA pheomelanin relative to DA pheomelanin in PD SN. In AD SN, we observed unaltered melanin markers despite reduced DOPA compared to controls. Furthermore, synthetic DOPA pheomelanin induced neuronal cell death in vitro while synthetic DOPA eumelanin showed no significant effect on cell viability. Our findings provide insights into the different roles of pheomelanin and eumelanin in PD pathophysiology. We anticipate our study will lead to further investigations on pheomelanin and eumelanin individually as biomarkers and possibly therapeutic targets for PD.

Disease-modifying vs symptomatic treatments: Splitting over lumping

Clinical trials of putative disease-modifying therapies in neurodegeneration have obeyed the century-old principle of convergence, or lumping, whereby any feature of a clinicopathologic disease entity is considered relevant to most of those affected. While this convergent approach has resulted in important successes in trials of symptomatic therapies, largely aimed at correcting common neurotransmitter deficiencies (e.g., cholinergic deficiency in Alzheimer's disease or dopaminergic deficiency in Parkinson's disease), it has been consistently futile in trials of neuroprotective or disease-modifying interventions. As individuals affected by the same neurodegenerative disorder do not share the same biological drivers, splitting such disease into small molecular/biological subtypes, to match people to therapies most likely to benefit them, is vital in the pursuit of disease modification. We here discuss three paths toward the splitting needed for future successes in precision medicine: (1) encourage the development of aging cohorts agnostic to phenotype in order to enact a biology-to-phenotype direction of biomarker development and validate divergence biomarkers (present in some, absent in most); (2) demand bioassay-based recruitment of subjects into disease-modifying trials of putative neuroprotective interventions in order to match the right therapies to the right recipients; and (3) evaluate promising epidemiologic leads of presumed pathogenetic potential using Mendelian randomization studies before designing the corresponding clinical trials. The reconfiguration of disease-modifying efforts for patients with neurodegenerative disorders will require a paradigm shift from lumping to splitting and from proteinopathy to proteinopenia.

White blood cell count and chronic obstructive pulmonary disease: A Mendelian Randomization study

Blood leukocyte counts (e.g., eosinophil count) are important biomarkers for the onset, classification, and exacerbation of chronic obstructive pulmonary disease (COPD). The causal relationships between them are necessary for the development of COPD treatment strategy, but remain unclear. Here, we implement two-sample bi-directional univariable Mendelian Randomization (MR) and multivariable MR to investigate the causal relationships. Univariable MR find that elevated blood eosinophil count significantly increases the risk of COPD (odds ratio (OR) = 1.22, 95% confidence interval (CI): 1.14-1.30, P = 1.54 × 10^-09) and COPD-related hospitalization (OR = 1.44, 95% CI: 1.15-1.80, P = 1.36 × 10^-03). Besides, it also significantly decreases the ratio of forced expiratory volume in the first second over forced vital capacity (FEV₁/FVC ratio) (OR = 0.942, 95% CI: 0.914-0.971, P = 1.02 × 10^-04). These findings are fully supported by multivariate MR results. Interestingly, univariable MR reveals a weak causal relationship between elevated blood eosinophil count and COPD risk in younger people (<65 years) (OR = 1.39, 95% CI: 1.10-1.75, P = 5.52 × 10^-03), but not older individuals (OR = 1.20, 95% CI: 0.926-1.55, P = 0.17). Finally, reverse univariable MR reveals the onset of COPD and the decreased FEV₁/FVC ratio both lead to increased blood neutrophil count (OR = 1.03, 95% CI: 1.01-1.05, P = 3.40 × 10^-03 and OR = 0.947, 95% CI: 0.91-0.986, P = 8.75 × 10^-03 respectively). In summary, this MR study demonstrates that high blood eosinophil count is an independent causal mediator of COPD risk, FEV₁/FVC decline, and COPD-related hospitalization. The increase in neutrophil count is induced by COPD onset or FEV₁/FVC decline. This suggests eosinophil, but not neutrophil, may be used as a therapeutic target for preventing the onset and exacerbation of COPD and FEV₁/FVC decline. Therefore, a non-neutrophil-targeted therapeutic strategy for neutrophilic COPD is required in the future.

Genetic predisposition to neurodegenerative diseases and risk of stroke: A Mendelian randomization study

Background

Traditional epidemiological studies suggested that Neurodegenerative diseases (ND) might correlate with stroke. We intend to explore whether the two most common neurodegenerative diseases [Alzheimer’s disease (AD) and Parkinson’s disease (PD)] are causally associated with stroke and its subtypes.

Methods

Two-sample Mendelian Randomization (MR) method was used to explore the causal relationships. Candidate genetic instrumental variables (IVs) for AD and PD were collected from the genome-wide association studies (GWAS) in European populations. The inverse-variance weighted (IVW) method was the primary method of MR analysis, and the weighted median method was supplementary. In addition, the MR-Egger method and the MR-PRESSO test were used as well.

Results

We found no causal effects of AD on stroke, Ischemic stroke (IS), or Intracerebral hemorrhage (ICH). As for PD and stroke, our preliminary results showed PD could causally influence the risk of stroke [odds ratio (OR): 1.04; 95% confidence interval (CI): 1.02–1.07; P = 0.001 by the IVW method], although the alternative method did not support this result. We identified the positive causal relationship between PD and the risk of IS (OR = 1.04; 95% CI: 1.02–1.07; P = 0.001 by the IVW method), and the alternative MR methods produced similar results. The present study found there was no causal relationship between PD and ICH.

Conclusion

This study found a causal relationship between genetic susceptibility to PD and the incidence of stroke (especially IS) in the European population; however, there was no causal relation between AD and stroke risk.

Animal models in the study of Alzheimer's disease and Parkinson's disease: A historical perspective

Alzheimer's disease and Parkinson's disease are two of the most prevalent and disabling neurodegenerative diseases globally. Both are proteinopathic conditions and while occasionally inherited, are largely sporadic in nature. Although the advances in our understanding of the two have been significant, they are far from complete and neither diagnosis nor the current practices in treatment and rehabilitation is adequately helpful. Animal models have historically found application as testing beds for novel therapeutics and continue to be valuable aids in pharmacological research. This review chronicles the development of those models in the context of Alzheimer's and Parkinson's disease, and highlights the shifting paradigms in studying two human-specific conditions in non-human organisms.

Marine Algae-Derived Bioactive Compounds: A New Wave of Nanodrugs?

Marine algae are rich in bioactive nutraceuticals (e.g., carbohydrates, proteins, minerals, fatty acids, antioxidants, and pigments). Biotic (e.g., plants, microorganisms) and abiotic factors (e.g., temperature, pH, salinity, light intensity) contribute to the production of primary and secondary metabolites by algae. Easy, profitable, and sustainable recovery methods include novel solid-liquid and liquid-liquid extraction techniques (e.g., supercritical, high pressure, microwave, ultrasound, enzymatic). The spectacular findings of algal-mediated synthesis of nanotheranostics has attracted further interest because of the availability of microalgae-based natural bioactive therapeutic compounds and the cost-effective commercialization of stable microalgal drugs. Algal extracts can serve as stabilizing/capping and reducing agents for the synthesis of thermodynamically stable nanoparticles (NPs). Different types of nanotherapeutics have been synthesized using physical, chemical, and biological methods. Marine algae are a fascinating source of lead theranostics compounds, and the development of nanotheranostics has been linked to enhanced drug efficacy and safety. Indeed, algae are remarkable nanobiofactories, and their pragmatic properties reside in their (i) ease of handling; (ii) capacity to absorb/accumulate inorganic metallic ions; (iii) cost-effectiveness; and (iv) capacity of eco-friendly, rapid, and healthier synthesis of NPs. Preclinical and clinical trials shall enable to really define effective algal-based nanotherapies. This review aims to provide an overview of the main algal compounds that are nutraceuticals and that can be extracted and purified for nanotheranostic purposes.

TOMM40 '523' poly-T repeat length is a determinant of longitudinal cognitive decline in Parkinson's disease

The translocase of outer mitochondrial membrane 40 (TOMM40) ‘523’ polymorphism has previously been associated with age of Alzheimer’s disease onset and cognitive functioning in non-pathological ageing, but has not been explored as a candidate risk marker for cognitive decline in Parkinson’s disease (PD). Therefore, this longitudinal study investigated the role of the ‘523’ variant in cognitive decline in a patient cohort from the Parkinson’s Progression Markers Initiative. As such, a group of 368 people with PD were assessed annually for cognitive performance using multiple neuropsychological protocols, and were genotyped for the TOMM40 ‘523’ variant using whole-genome sequencing data. Covariate-adjusted generalised linear mixed models were utilised to examine the relationship between TOMM40 ‘523’ allele lengths and cognitive scores, while taking into account the APOE ε genotype. Cognitive scores declined over the 5-year study period and were lower in males than in females. When accounting for APOE ε4, the TOMM40 ‘523’ variant was not robustly associated with overall cognitive performance. However, in APOE ε3/ε3 carriers, who accounted for ~60% of the whole cohort, carriage of shorter ‘523’ alleles was associated with more severe cognitive decline in both sexes, while carriage of the longer alleles in females were associated with better preservation of global cognition and a number of cognitive sub-domains, and with a delay in progression to dementia. The findings indicate that when taken in conjunction with the APOE genotype, TOMM40 ‘523’ allele length is a significant independent determinant and marker for the trajectory of cognitive decline and risk of dementia in PD.

Glutathione-decorated fluorescent carbon quantum dots for sensitive and selective detection of levodopa

Levodopa has been a standard drug for treating Parkinson's disease since the 1960s, but it has caused many side effects such as wearing-off, motor fluctuation, and dystonia. In this work, we developed glutathione-conjugated carbon quantum dots (GSH-CQDs) as a novel fluorescent sensor for sensitive and selective detection of levodopa. The GSH-CQDs were prepared by EDC/NHS coupling reaction of glutathione (GSH) with amine-functionalized CQDs (N-CQDs) synthesized using meta-phenylenediamine and ethylenediamine. The synthesized GSH-CQDs emitted bright green fluorescence with a high quantum yield (QY) of 22.42 ± 6.88%. However, upon the addition of levodopa to GSH-CQDs under alkaline conditions, the fluorescence of GSH-CQDs was quenched. Since levodopa is converted to dopaquinone in an alkaline environment, it is presumed that thiol groups of GHS-CQDs form covalent bonds with dopaquinone, causing fluorescence quenching through photoinduced electron transfer. Therefore, as the concentration of levodopa increased, the fluorescence intensity of GSH-CQDs was gradually decreased. Under optimal conditions, a linear response was observed in the range of 0.05-1 μM, and limit of detection (LOD) was determined to be 0.057 μM. The GSH-CQDs exhibited high specificity to levodopa over other non-target biological substances, quinone derivatives, and Parkinson's medications. Furthermore, the capability of this GSH-CQDs sensor for monitoring levodopa in human serum were validated with excellent precision and recovery rates of 100.20-103.33%.

Data-driven biomarker analysis using computational omics approaches to assess neurodegenerative disease progression

The complexity of biological systems suggests that current definitions of molecular dysfunctions are essential distinctions of a complex phenotype. This is well seen in neurodegenerative diseases (ND), such as Alzheimer's disease (AD) and Parkinson's disease (PD), multi-factorial pathologies characterized by high heterogeneity. These challenges make it necessary to understand the effectiveness of candidate biomarkers for early diagnosis, as well as to obtain a comprehensive mapping of how selective treatment alters the progression of the disorder. A large number of computational methods have been developed to explain network-based approaches by integrating individual components for modeling a complex system. In this review, high-throughput omics methodologies are presented for the identification of potent biomarkers associated with AD and PD pathogenesis as well as for monitoring the response of dysfunctional molecular pathways incorporating multilevel clinical information. In addition, principles for efficient data analysis pipelines are being discussed that can help address current limitations during the experimental process by increasing the reproducibility of benchmarking studies.

COVID-19 in age-related neurodegenerative diseases: is there a role for vitamin D3 as a possible therapeutic strategy?

The coronavirus disease (COVID-19), identified in Wuhan, China, on December 2019, was declared a pandemic by the World Health Organization, on March, 2020. Since then, efforts have been gathered to describe its clinical course and to determine preventive measures and treatment strategies. Adults older than 65 years of age are more susceptible to serious clinical symptoms and present higher mortality rates. Angiotensin-converting enzyme 2 (ACE2) is a major receptor for some coronavirus infection, including SARS-COV-2, but is also a crucial determinant in anti-inflammation processes during the renin-angiotensin system (RAS) functioning - converting angiotensin II to angiotensin 1-7. The decline in ACE2 expression that occurs with aging has been associated to the higher morbidity and mortality rates in older adults. These observations highlight the importance of investigating the association between COVID-19 and age-related neurodegenerative disorders, i.e., Parkinson's and Alzheimer's diseases. A possible option to reduce the risk of COVID-19 is vitamin D supplementation, due to its anti-inflammatory and immune-system-modulating effects. It has also been suggested that vitamin D supplementation plays a role in slowing progression of Parkinson and Alzheimer. The present study is a literature review of articles published on the theme COVID-19, Parkinson and Alzheimer's diseases, and the role played by vitamin D. PUBMED, MEDLINE, and EMBASE databases were consulted. Results confirm neurodegenerative and neuroinflammatory effects of COVID-19, aggravated in Parkinson's and Alzheimer's patients, and the important role of vitamin D as a possible therapeutic strategy. Nevertheless, randomized controlled trials and large population studies are still warranted.

Using Mendelian randomization to understand and develop treatments for neurodegenerative disease

Common neurodegenerative diseases are thought to arise from a combination of environmental and genetic exposures. Mendelian randomization is a powerful way to leverage existing genetic data to investigate causal relationships between risk factors and disease. In recent years, Mendelian randomization has gathered considerable traction in neurodegenerative disease research, providing valuable insights into the aetiology of these conditions. This review aims to evaluate the impact of Mendelian randomization studies on translational medicine for neurodegenerative diseases, highlighting the advances made and challenges faced. We will first describe the fundamental principles and limitations of Mendelian randomization and then discuss the lessons from Mendelian randomization studies of environmental risk factors for neurodegeneration. We will illustrate how Mendelian randomization projects have used novel resources to study molecular pathways of neurodegenerative disease and discuss the emerging role of Mendelian randomization in drug development. Finally, we will conclude with our view of the future of Mendelian randomization in these conditions, underscoring unanswered questions in this field.

Shared cerebral metabolic pathology in non-transgenic animal models of Alzheimer's and Parkinson's disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common chronic neurodegenerative disorders, characterized by motoric dysfunction or cognitive decline in the early stage, respectively, but often by both symptoms in the advanced stage. Among underlying molecular pathologies that PD and AD patients have in common, more attention is recently paid to the central metabolic dysfunction presented as insulin resistant brain state (IRBS) and altered cerebral glucose metabolism, both also explored in animal models of these diseases. This review aims to compare IRBS and alterations in cerebral glucose metabolism in representative non-transgenic animal PD and AD models. The comparison is based on the selectivity of the neurotoxins which cause experimental PD and AD, towards the cellular membrane and intracellular molecular targets as well as towards the selective neurons/non-neuronal cells, and the particular brain regions. Mitochondrial damage and co-expression of insulin receptors, glucose transporter-2 and dopamine transporter on the membrane of particular neurons as well as astrocytes seem to be the key points which are further discussed in a context of alterations in insulin signalling in the brain and its interaction with dopaminergic transmission, particularly regarding the time frame of the experimental AD/PD pathology appearance and the correlation with cognitive and motor symptoms. Such a perspective provides evidence on IRBS being a common underlying metabolic pathology and a contributor to neurodegenerative processes in representative non-transgenic animal PD and AD models, instead of being a direct cause of a particular neurodegenerative disorder.