Brain-Region Specific Metabolic Abnormalities in Parkinson's Disease and Levodopa-Induced Dyskinesia

Friend or foe: Lactate in neurodegenerative diseases

Lactate, a byproduct of glycolysis, was considered as a metabolic waste until identified by studies on the Warburg effect. Increasing evidence elucidates that lactate functions as energy fuel, signaling molecule, and donor for protein lactylation. Altered lactate utilization is a common metabolic feature of the onset and progression of neurodegenerative diseases, such as Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, Parkinson's disease and Huntington's disease. This review offers an overview of lactate metabolism from the perspective of production, transportation and clearance, and the role of lactate in neurodegenerative progression, as well as a summary of protein lactylation and the signaling function of lactate in neurodegenerative diseases. Besides, this review delves into the dual roles of changed lactate metabolism during neurodegeneration and explores prospective therapeutic methods targeting lactate. We propose that elucidating the correlation between lactate and neurodegeneration is pivotal for exploring innovative therapeutic interventions for neurodegenerative diseases.

Possible role of lncRNAs in amelioration of Parkinson's disease symptoms by transplantation of dopaminergic cells

Long non-coding RNAs (lncRNAs) are biomarkers for diagnosis and treatment of Parkinson's disease (PD). Since dopaminergic cell transplantation is a clinical method to treat PD, this study investigated the effects of dopaminergic cell therapy on the expression of some lncRNAs and genes related to PD. In this study, Twenty-eight rats were randomly assigned to four experimental groups. The control group (Sal group) received saline injections. The Par group was a PD rat model with 6-hydroxydopamine (6-OHDA) injection in right striatum (ST). PD animals were transplanted by undifferentiated P19 stem cells (Par-E group), and P19-derived dopaminergic cells (Par-N group). Cell transplant effects were evaluated using behavioral tests (cylinder, open field, and rotarod tests), and histological methods (H&E and Nissl staining, and immunohistochemistry). Moreover, the expression of lncRNAs MALAT1, MEG3, and SNHG1, alongside specific neuronal (synaptophysin) and dopaminergic (tyrosine hydroxylase) markers was evaluated by qRT-PCR. Behavioral and histopathological examinations revealed that cell transplantation partially compensated dopaminergic cell degeneration in ST and substantia nigra (SN) of PD rats. The expression of MALAT1, SNHG1, and MEG3 was decreased in the ST of the Par group, while MEG3 and SNHG1 gene expression was increased in PBMC relative to the Sal group. In PBMC of the Par-N group, all three lncRNAs showed a reduction in their expression. Conversely, MALAT1 and SNHG1 expression was increased in ST tissue, while MEG3 gene expression was decreased compared to the Sal group. In conclusion, dopaminergic cell transplantation could change the lncRNAs expression. Furthermore, it partially improves symptoms in PD rats.

Fibroblast growth factor 21 ameliorates behavior deficits in Parkinson's disease mouse model via modulating gut microbiota and metabolic homeostasis

AIMS

The effects of FGF21 on Parkinson's disease (PD) and its relationship with gut microbiota have not been elucidated. This study aimed to investigate whether FGF21 would attenuate behavioral impairment through microbiota-gut-brain metabolic axis in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced PD mice model.

METHODS

Male C57BL/6 mice were rendomized into 3 groups: vehicle (CON); MPTP 30 mg/kg/day i.p. injection (MPTP); FGF21 1.5 mg/kg/d i.p. injection plus MPTP 30 mg/kg/day i.p. injection (FGF21 + MPTP). The behavioral features, metabolimics profiling, and 16 s rRNA sequencing were performed after FGF21 treatment for 7 days.

RESULTS

MPTP-induced PD mice showed motor and cognitive deficits accompanied by gut microbiota dysbiosis and brain-region-specific metabolic abnormalities. FGF21 treatment dramatically attenuated motor and cognitive dysfunction in PD mice. FGF21 produced a region-specific alteration in the metabolic profile in the brain in ways indicative of greater ability in neurotransmitter metabolism and choline production. In addition, FGF21 also re-structured the gut microbiota profile and increased the relative abundance of Clostridiales, Ruminococcaceae, and Lachnospiraceae, thereby rescuing the PD-induced metabolic disorders in the colon.

CONCLUSION

These findings indicate that FGF21 could affect behavior and brain metabolic homeostasis in ways that promote a favorable colonic microbiota composition and through effects on the microbiota-gut-brain metabolic axis.

Gut microbiome-derived ammonia modulates stress vulnerability in the host

Ammonia has been long recognized as a metabolic waste product with well-known neurotoxic effects. However, little is known about the beneficial function of endogenous ammonia. Here, we show that gut ammonia links microbe nitrogen metabolism to host stress vulnerability by maintaining brain glutamine availability in male mice. Chronic stress decreases blood ammonia levels by altering gut urease-positive microbiota. A representative urease-producing strain, Streptococcus thermophilus, can reverse depression-like behaviours induced by gut microbiota that was altered by stress, whereas pharmacological inhibition of gut ammonia production increases stress vulnerability. Notably, abnormally low blood ammonia levels limit the brain's availability of glutamine, a key metabolite produced by astrocytes that is required for presynaptic γ-aminobutyric acid (GABA) replenishment and confers stress vulnerability through cortical GABAergic dysfunction. Of therapeutic interest, ammonium chloride (NH4Cl), a commonly used expectorant in the clinic, can rescue behavioural abnormalities and GABAergic deficits in mouse models of depression. In sum, ammonia produced by the gut microbiome can help buffer stress in the host, providing a gut-brain signalling basis for emotional behaviour.

Metabolic Disturbances in the Gut-brain Axis of a Mouse Model of MPTP-induced Parkinsonism Evaluated by Nuclear Magnetic Resonance

Parkinson's Disease is a synucleinopathy that primarily affects the dopaminergic cells of the central nervous system, leading to motor and gastrointestinal disturbances. However, intestinal peripheral neurons undergo a similar neurodegeneration process, marked by α-synuclein (αSyn) accumulation and loss of mitochondrial homeostasis. We investigated the metabolic alterations in different biometrics that compose the gut-brain axis (blood, brain, large intestine, and feces) in an MPTP-induced mouse model of sporadic Parkinson's Disease. Animals received escalating administration of MPTP. Tissues and fecal pellets were collected, and the metabolites were identified through the untargeted Nuclear Magnetic Resonance spectroscopic (1H NMR) technique. We found differences in many metabolites from all the tissues evaluated. The differential expression of metabolites in these samples mainly reflects inflammatory aspects, cytotoxicity, and mitochondrial impairment (oxidative stress and energy metabolism) in the animal model used. The direct evaluation of fecal metabolites revealed changes in several classes of metabolites. This data reinforces previous studies showing that Parkinson's disease is associated with metabolic perturbation not only in brain-related tissues, but also in periphery structures such as the gut. In addition, the evaluation of the microbiome and metabolites from gut and feces emerge as promising sources of information for understanding the evolution and progression of sporadic Parkinson's Disease.

Brain-wide transcriptome-based metabolic alterations in Parkinson's disease: human inter-region and human-experimental model correlations

Alterations in brain metabolism are closely associated with the molecular hallmarks of Parkinson's disease (PD). A clear understanding of the main metabolic perturbations in PD is therefore important. Here, we retrospectively analysed the expression of metabolic genes from 34 PD-control post-mortem human brain transcriptome data comparisons from literature, spanning multiple brain regions. We found high metabolic correlations between the Substantia nigra (SN)- and cerebral cortex-derived tissues. Moreover, three clusters of PD patient cohorts were identified based on perturbed metabolic processes in the SN - each characterised by perturbations in (a) bile acid metabolism (b) omega-3 fatty acid metabolism, and (c) lipoic acid and androgen metabolism - metabolic themes not comprehensively addressed in PD. These perturbations were supported by concurrence between transcriptome and proteome changes in the expression patterns for CBR1, ECI2, BDH2, CYP27A1, ALDH1B1, ALDH9A1, ADH5, ALDH7A1, L1CAM, and PLXNB3 genes, providing a valuable resource for drug targeting and diagnosis. Also, we analysed 58 PD-control transcriptome data comparisons from in vivo/in vitro disease models and identified experimental PD models with significant correlations to matched human brain regions. Collectively, our findings suggest metabolic alterations in several brain regions, heterogeneity in metabolic alterations between study cohorts for the SN tissues and the need to optimize current experimental models to advance research on metabolic aspects of PD.

Evaluation of the therapeutic potential of cerebrolysin and/or lithium in the male Wistar rat model of Parkinson's disease induced by reserpine

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease worldwide and represents a challenge for clinicians. The present study aims to investigate the effects of cerebrolysin and/or lithium on the behavioral, neurochemical and histopathological alterations induced by reserpine as a model of PD. The rats were divided into control and reserpine-induced PD model groups. The model animals were further divided into four subgroups: rat PD model, rat PD model treated with cerebrolysin, rat PD model treated with lithium and rat PD model treated with a combination of cerebrolysin and lithium. Treatment with cerebrolysin and/or lithium ameliorated most of the alterations in oxidative stress parameters, acetylcholinesterase and monoamines in the striatum and midbrain of reserpine-induced PD model. It also ameliorated the changes in nuclear factor-kappa and improved the histopathological picture induced by reserpine. It could be suggested that cerebrolysin and/or lithium showed promising therapeutic potential against the variations induced in the reserpine model of PD. However, the ameliorating effects of lithium on the neurochemical, histopathological and behavioral alterations induced by reserpine were more prominent than those of cerebrolysin alone or combined with lithium. It can be concluded that the antioxidant and anti-inflammatory effects of both drugs played a significant role in their therapeutic potency.

Neuroprotective potential of cinnamoyl derivatives against Parkinson's disease indicators in Drosophila melanogaster and in silico models

Parkinson's disease (PD) is a movement disorder resulting from the loss of dopaminergic neurons over time. While there is no cure for PD, available conventional therapies aid to manage the motor symptoms. Natural products (NPs) derived from plants are among the most potent alternative therapies for PD. This study explored the neuroprotective potential of selected cinnamoyl derivatives namely toussaintine A (1), E-toussaintine E (2), asperphenamate (3) and julocrotine (4) against PD indicators using rotenone-challenged Drosophila melanogaster and in silico models. The compounds were first assessed for their toxicity preceding treatment experiments. Adult flies (aged 1-4 days) were exposed to varying concentrations of the compounds for 7 days. During the experiment, the mortality of flies was observed, and the lethal concentration (LC₅₀) of each tested compound was determined. The LC₅₀ values were found to be 50.1, 55.6, 513.5, and 101.0 µM for compounds 1, 2, 3, and 4, respectively. For seven days, we exposed flies to 500 µM of rotenone and co-fed with a chosen dose of 40 µM of each test compound in the diet. Using a negative geotaxis test, rotenone-challenged flies exhibited compromised climbing ability in comparison to control flies, the condition that was reversed by the action of studied compounds. Rotenone exposure also elevated malondialdehyde levels in the brain tissues, as measured by lipid peroxidation, when compared to control flies. In flies exposed to rotenone and co-fed with the compounds, this effect was lessened. In flies exposed to rotenone, mRNA levels of antioxidant enzymes such as superoxide dismutase and catalase were raised but were normalized in flies treated with the investigated compounds. Moreover, in-silico studies examined the inhibitory ability of compounds 1-4 against selected PD molecular targets, revealing the strong power of toussaintine A (1) against Adenosine receptor 2 (A2AR) and monoamine oxidase B. Thus, our findings suggest that cinnamoyl derivatives have neuroprotective potential via reducing the oxidative burden and improving locomotor ability after toxin invectives. In particular, compound 1 at lower doses can simultaneously be a potential inhibitor of A2AR and an anti-oxidative mediator in the development of anti-PD agents.

Metabolomics as a Crucial Tool to Develop New Therapeutic Strategies for Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Alzheimer’s (AD), Parkinson’s (PD), and amyotrophic lateral sclerosis (ALS), share common pathological mechanisms, including metabolism alterations. However, their specific neuronal cell types affected and molecular biomarkers suggest that there are both common and specific alterations regarding metabolite levels. In this review, we were interested in identifying metabolite alterations that have been reported in preclinical models of NDs and that have also been documented as altered in NDs patients. Such alterations could represent interesting targets for the development of targeted therapy. Importantly, the translation of such findings from preclinical to clinical studies is primordial for the study of possible therapeutic agents. We found that N-acetyl-aspartate (NAA), myo-inositol, and glutamate are commonly altered in the three NDs investigated here. We also found other metabolites commonly altered in both AD and PD. In this review, we discuss the studies reporting such alterations and the possible pathological mechanism underlying them. Finally, we discuss clinical trials that have attempted to develop treatments targeting such alterations. We conclude that the treatment combination of both common and differential alterations would increase the chances of patients having access to efficient treatments for each ND.

Current Knowledge on the Background, Pathophysiology and Treatment of Levodopa-Induced Dyskinesia-Literature Review

Levodopa remains the primary drug for controlling motor symptoms in Parkinson’s disease through the whole course, but over time, complications develop in the form of dyskinesias, which gradually become more frequent and severe. These abnormal, involuntary, hyperkinetic movements are mainly characteristic of the ON phase and are triggered by excess exogenous levodopa. They may also occur during the OFF phase, or in both phases. Over the past 10 years, the issue of levodopa-induced dyskinesia has been the subject of research into both the substrate of this pathology and potential remedial strategies. The purpose of the present study was to review the results of recent research on the background and treatment of dyskinesia. To this end, databases were reviewed using a search strategy that included both relevant keywords related to the topic and appropriate filters to limit results to English language literature published since 2010. Based on the selected papers, the current state of knowledge on the morphological, functional, genetic and clinical features of levodopa-induced dyskinesia, as well as pharmacological, genetic treatment and other therapies such as deep brain stimulation, are described.

l-Lactate: Food for Thoughts, Memory and Behavior

More and more evidence shows how brain energy metabolism is the linkage between physiological and morphological synaptic plasticity and memory consolidation. Different types of memory are associated with differential inputs, each with specific inputs that are upstream diverse molecular cascades depending on the receptor activity. No matter how heterogeneous the response is, energy availability represents the lowest common denominator since all these mechanisms are energy consuming and the brain networks adapt their performance accordingly. Astrocytes exert a primary role in this sense by acting as an energy buffer; glycogen granules, a mechanism to store glucose, are redistributed at glance and conveyed to neurons via the Astrocyte–Neuron Lactate Shuttle (ANLS). Here, we review how different types of memory relate to the mechanisms of energy delivery in the brain.

Age-Related Neurometabolomic Signature of Mouse Brain

Neurometabolites are the ultimate gene products in the brain and the most precise biomolecular indicators of brain endophenotypes. Metabolomics is the only "omics" that provides a moment-to-moment "snapshot" of brain circuits' biochemical activities in response to external stimuli within the context of specific genetic variations. Although the expression levels of neurometabolites are highly dynamic, the underlying metabolic processes are tightly regulated during brain development, maturation, and aging. Therefore, this study aimed to identify mouse brain metabolic profiles in neonatal and adult stages and reconstruct both the active metabolic network and the metabolic pathway functioning. Using high-throughput metabolomics and bioinformatics analyses, we show that the neonatal mouse brain has its distinct metabolomic signature, which differs from the adult brain. Furthermore, lipid metabolites showed the most profound changes between the neonatal and adult brain, with some lipid species reaching 1000-fold changes. There were trends of age-dependent increases and decreases among lipids and non-lipid metabolites, respectively. A few lipid metabolites such as HexCers and SHexCers were almost absent in neonatal brains, whereas other non-lipid metabolites such as homoarginine were absent in the adult brains. Several molecules that act as neurotransmitters/neuromodulators showed age-dependent levels, with adenosine and GABA exhibiting around 100- and 10-fold increases in the adult compared with the neonatal brain. Of particular interest is the observation that purine and pyrimidines nucleobases exhibited opposite age-dependent changes. Bioinformatics analysis revealed an enrichment of lipid biosynthesis pathways in metabolites, whose levels increased in adult brains. In contrast, pathways involved in the metabolism of amino acids, nucleobases, glucose (glycolysis), tricarboxylic acid cycle (TCA) were enriched in metabolites whose levels were higher in the neonatal brains. Many of these pathways are associated with pathological conditions, which can be predicted as early as the neonatal stage. Our study provides an initial age-related biochemical directory of the mouse brain and warrants further studies to identify temporal brain metabolome across the lifespan, particularly during adolescence and aging. Such neurometabolomic data may provide important insight about the onset and progression of neurological/psychiatric disorders and may ultimately lead to the development of precise diagnostic biomarkers and more effective preventive/therapeutic strategies.

Cell competition from development to neurodegeneration

Cell competition is a process by which suboptimal cells are eliminated to the benefit of cells with higher fitness. It is a surveillance mechanism that senses differences in the fitness status by several modes, such as expression of fitness fingerprints, survival factor uptake rate and resistance to mechanical stress. Fitness fingerprints-mediated cell competition recognizes isoforms of the transmembrane protein Flower, and translates the relative fitness of cells into distinct fates through the Flower code. Impairments in cell competition potentiate the development of diseases like cancer and ageing-related pathologies. In cancer, malignant cells acquire a supercompetitor behaviour, killing the neighbouring cells and overtaking the tissue, thus avoiding elimination. Neurodegenerative disorders affect millions of people and are characterized by cognitive decline and locomotor deficits. Alzheimer's disease is the most common form of dementia, and one of the largely studied diseases. However, the cellular processes taking place remain unclear. Drosophila melanogaster is an emerging neurodegeneration model due to its versatility as a tool for genetic studies. Research in a Drosophila Alzheimer's disease model detected fitness markers in the suboptimal and hyperactive neurons, thus establishing a link between cell competition and Alzheimer's disease. In this Review, we overview cell competition and the new insights related to neurodegenerative disorders, and discuss how research in the field might contribute to the development of new therapeutic targets for these diseases.

Ordinal classification of the affectation level of 3D-images in Parkinson diseases

Parkinson’s disease is characterised by a decrease in the density of presynaptic dopamine transporters in the striatum. Frequently, the corresponding diagnosis is performed using a qualitative analysis of the 3D-images obtained after the administration of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}$$\end{document}123I-ioflupane, considering a binary classification problem (absence or existence of Parkinson’s disease). In this work, we propose a new methodology for classifying this kind of images in three classes depending on the level of severity of the disease in the image. To tackle this problem, we use an ordinal classifier given the natural order of the class labels. A novel strategy to perform feature selection is developed because of the large number of voxels in the image, and a method for generating synthetic images is proposed to improve the quality of the classifier. The methodology is tested on 434 studies conducted between September 2015 and January 2019, divided into three groups: 271 without alteration of the presynaptic nigrostriatal pathway, 73 with a slight alteration and 90 with severe alteration. Results confirm that the methodology improves the state-of-the-art algorithms, and that it is able to find informative voxels outside the standard regions of interest used for this problem. The differences are assessed by statistical tests which show that the proposed image ordinal classification could be considered as a decision support system in medicine.

Ameliorative effects of flavonoids and polyketides on the rotenone induced Drosophila model of Parkinson's disease

Parkinson's disease (PD) is a movement disorder associated with the progressive loss of dopaminergic neurons (DA). PD treatment remains unsatisfactory as the current synthetic drugs in clinical use relies on managing only motor symptoms. This study investigated antioxidant potentials of selected compounds namely, 5,6,7,4'-tetramethoxyflavone (1), 6-hydroxy-2,3,4,4'-tetramethoxychalcone (2), 6-methoxyhamiltone A (3), diosquinone (4) and toussantine D (5) against rotenone (6) induced PD in Drosophila melanogaster. Toxicity of these compounds was conducted by monitoring flies' survival for seven days and determining the lethal concentrations (LC₅₀). Whereas compound 1 had LC₅₀ value of 91.3 μM within three days, compounds 2, 3, 4, and 5 had LC₅₀ values of 87.2, 58.0, 64.0 and > 1000 μM, respectively on the seventh day of the experiment. We exposed flies (1-4 days old) to 500 μM rotenone and co-treated with different doses of the test compounds in the diet for seven days at final concentrations of 11.0, 43.6 and 87.2 μM for compounds 2 and 3. The concentrations used for compound 4 were 8.0, 32.0 and 64.0 μM, while 250, 500 and 1000 μM were used for compound 5. Rotenone fed flies showed impaired climbing ability compared to control flies, the phenotype that was rescued by the treatment of tested phytochemicals. Rotenone toxicity also increased malondialdehyde levels assayed by lipid peroxidation in the brain tissues relative to control flies. This effect was reduced in flies exposed to rotenone and co-treated with the phytochemicals. Moreover, expression levels of mRNA of antioxidant enzymes; superoxide dismutase and catalase were elevated in flies exposed to rotenone and normalized in flies that were co-treated with tested compounds. Besides compound 1, this study provides overall evidence that the tested flavonoids and polyketides ameliorated the rotenone provoked neurotoxicity in D. melanogaster by battling the induced oxidative stress in brain cells including DA neurons and hence rescue the locomotor behaviour deficits.