Accumulation Of Glutamate Research Articles

Aquaporins and Neuropathic Pain.

Neuropathic pain is a chronic secondary pain condition resulting from lesions or diseases of the peripheral or central nervous system (CNS). Neuropathic pain is closely related to edema, inflammation, increased neuronal excitability, and central sensitization caused by glutamate accumulation. Aquaporins (AQPs), mainly responsible for the transport and clearance of water and solute, play important roles in developing CNS diseases, especially neuropathic pain. This review focuses on the interaction of AQPs with neuropathic pain, and the potential of AQPs, especially aquaporins 4, as therapeutic targets.

Metabotropic glutamate receptor 1 alpha: a unique receptor variant with variable implications for Alzheimer's disease pathogenesis.

Metabotropic glutamate receptor 1 alpha: a unique receptor variant with variable implications for Alzheimer's disease pathogenesis.

Astrocyte-neuron communication mediated by the Notch signaling pathway: focusing on glutamate transport and synaptic plasticity.

Maintaining glutamate homeostasis after hypoxic ischemia is important for synaptic function and neural cell activity, and regulation of glutamate transport between astrocyte and neuron is one of the important modalities for reducing glutamate accumulation. However, further research is needed to investigate the dynamic changes in and molecular mechanisms of glutamate transport and the effects of glutamate transport on synapses. The aim of this study was to investigate the regulatory mechanisms underlying Notch pathway mediation of glutamate transport and synaptic plasticity. In this study, Yorkshire neonatal pigs (male, age 3 days, weight 1.0-1.5 kg, n = 48) were randomly divided into control (sham surgery group) and five hypoxic ischemia subgroups, according to different recovery time, which were then further subdivided into subgroups treated with dimethyl sulfoxide or a Notch pathway inhibitor (N-[N-(3, 5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester). Once the model was established, immunohistochemistry, immunofluorescence staining, and western blot analyses of Notch pathway-related proteins, synaptophysin, and glutamate transporter were performed. Moreover, synapse microstructure was observed by transmission electron microscopy. At the early stage (6-12 hours after hypoxic ischemia) of hypoxic ischemic injury, expression of glutamate transporter excitatory amino acid transporter-2 and synaptophysin was downregulated, the number of synaptic vesicles was reduced, and synaptic swelling was observed; at 12-24 hours after hypoxic ischemia, the Notch pathway was activated, excitatory amino acid transporter-2 and synaptophysin expression was increased, and the number of synaptic vesicles was slightly increased. Excitatory amino acid transporter-2 and synaptophysin expression decreased after treatment with the Notch pathway inhibitor. This suggests that glutamate transport in astrocytes-neurons after hypoxic ischemic injury is regulated by the Notch pathway and affects vesicle release and synaptic plasticity through the expression of synaptophysin.

Amino Acids Metabolism in Retinopathy: From Clinical and Basic Research Perspective.

Retinopathy, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and retinopathy of prematurity (ROP), are the leading cause of blindness among seniors, working-age populations, and children. However, the pathophysiology of retinopathy remains unclear. Accumulating studies demonstrate that amino acid metabolism is associated with retinopathy. This study discusses the characterization of amino acids in DR, AMD, and ROP by metabolomics from clinical and basic research perspectives. The features of amino acids in retinopathy were summarized using a comparative approach based on existing high-throughput metabolomics studies from PubMed. Besides taking up a large proportion, amino acids appear in both human and animal, intraocular and peripheral samples. Among them, some metabolites differ significantly in all three types of retinopathy, including glutamine, glutamate, alanine, and others. Studies on the mechanisms behind retinal cell death caused by glutamate accumulation are on the verge of making some progress. To develop potential therapeutics, it is imperative to understand amino acid-induced retinal functional alterations and the underlying mechanisms. This review delineates the significance of amino acid metabolism in retinopathy and provides possible direction to discover therapeutic targets for retinopathy.

Etomidate-Induced Myoclonus in Sprague-Dawley Rats Involves Neocortical Glutamate Accumulation and N -Methyl- d -Aspartate Receptor Activity.

Etomidate-induced myoclonus, a seizure-like movement, is of interest to anesthetists. However, its origin in the brain and its underlying mechanism remain unclear. Adult male Sprague-Dawley rats were anesthetized with etomidate, propofol, or lidocaine plus etomidate. We assessed the incidence of myoclonus, behavioral scores, and levels of glutamate and γ-aminobutyric acid (GABA) in the neocortex and hippocampus. To determine the origin and how N -methyl- d -aspartate receptors (NMDARs) modulate etomidate-induced neuroexcitability, the local field potential and muscular tension were monitored. Calcium imaging in vitro and immunoblotting in vivo were conducted to investigate the mechanisms underlying myoclonus. The incidence of etomidate (1.5 mg/kg in vivo)-induced myoclonus was higher than that of propofol (90% vs 10%, P = .0010) and lidocaine plus etomidate (90% vs 20%, P = .0050). Etomidate at doses of 3.75 and 6 mg/kg decreased the mean behavioral score at 1 (mean difference [MD]: 1.80, 95% confidence interval [CI], 0.58-3.02; P = .0058 for both), 2 (MD: 1.60, 95% CI, 0.43-2.77; P = .0084 and MD: 1.70, 95% CI, 0.54-2.86; P = .0060), 3 (MD: 1.60, 95% CI, 0.35-2.85; P = .0127 and MD: 1.70, 95% CI, 0.46-2.94; P = .0091) minutes after administration compared to etomidate at a dose of 1.5 mg/kg. In addition, 0.5 and 1 µM etomidate in vitro increased neocortical intracellular calcium signaling; this signaling decreased when the concentration increased to 5 and 10 μM. Etomidate increased the glutamate level compared to propofol (mean rank difference: 18.20; P = .003), and lidocaine plus etomidate (mean rank difference: 21.70; P = .0002). Etomidate in vivo activated neocortical ripple waves and was positively correlated with muscular tension amplitude (Spearman's r = 0.785, P < .0001). Etomidate at 1.5 mg/kg decreased the K-Cl cotransporter isoform 2 (KCC2) level compared with propofol (MD: -1.15, 95% CI, -1.47 to -0.83; P < .0001) and lidocaine plus etomidate (MD: -0.64, 95% CI, -0.96 to -0.32; P = .0002), DL-2-amino-5-phosphopentanoic acid (AP5) suppressed these effects, while NMDA enhanced them. Etomidate-induced myoclonus or neuroexcitability is concentration dependent. Etomidate-induced myoclonus originates in the neocortex. The underlying mechanism involves neocortical glutamate accumulation and NMDAR modulation and myoclonus correlates with NMDAR-induced downregulation of KCC2 protein expression.

PNO1 inhibits autophagy-mediated ferroptosis by GSH metabolic reprogramming in hepatocellular carcinoma

Effective strategies for hepatocellular carcinoma, which is the second leading cause of death worldwide, remain limited. A growing body of emerging evidence suggests that ferroptosis activation is a novel promising approach for the treatment of this malignancy. Nevertheless, the potential therapeutic targets and molecular mechanisms of ferroptosis remain elusive. In this study, we found that PNO1 is a bona fide inhibitor of ferroptosis and that autophagy induced by PNO1 promotes cystine/glutamate antiporter SLC7A11 while increasing the synthesis and accumulation of intracellular glutamate. This increase is followed by an equally proportional addition in cystine uptake, which consequently enhances system Xc- activity that leads to the inhibition of ferroptosis. In the maintenance of redox homeostasis, system Xc- activated via PNO1-autophagy metabolism is responsible for maintaining cysteine for glutathione (GSH) synthesis, and the final GSH metabolic reprogramming protects HCC cells from ferroptosis. The combination of PNO1 inhibition with drugs causing ferroptosis induction, particularly sorafenib, the first-line drug associated with ferroptosis in liver cancer shows therapeutic promise in vitro and in vivo. Together, our findings indicated that PNO1 protects HCC cells from ferroptotic death through autophagy-mediated GSH metabolic remodeling, and we identified a candidate therapeutic target that may potentiate the effect of ferroptosis-based antitumor therapy.

Changes in sugar, organic acid and free amino acid levels and the expression of genes involved in the primary metabolism of oleocellosis in citrus peels

Oleocellosis is a physiological disorder in citrus fruit and causes extensive economic damage due to the surface blemishes it creates. It was reported that oleocellosis always occurs during preharvest maturation and postharvest storage. In the present study, the oleocellosis incidence of Jincheng orange, Navel orange and Ponkan were found to be different during preharvest maturation, however, no differences were found during postharvest storage. Additionally, it was interesting that the outbreak period of oleocellosis incidence was 0–12 d during postharvest storage. Climate change has been reported as a factor promoting oleocellosis development. However, little information is available regarding how primary metabolites and the expression of genes involved in sugar, organic acid and free amino acid metabolism in citrus change to adjust to new environments. Metabolic profiling obtained by gas chromatography-mass spectrometry (GC‒MS) and amino acid analysis showed that the accumulations of fructose, glucose, sucrose, maltose, mannose, citric acid, α-ketoglutarate, 2-keto-d-gluconic acid, glutamate, valine, glycine and threonine might play major roles in adaptation to changes in oleocellosis peels for three types of citrus fruit. However, decreased contents of malic acid, gluconic acid and proline were observed, possibly due to consumption in energy metabolism or reflecting a unique characteristic in this disorder. Regarding gene expression in primary metabolism pathways obtained by high-throughput mRNA sequencing (RNA-Seq) technology, upregulated genes encoding alpha-glucosidase, beta-glucosidase, beta-fructofuranosidase, alpha-amylase, beta-amylase, malate dehydrogenase, CTP synthase (glutamine hydrolysing), serine-glyoxylate transaminase, serine/glycine hydroxymethyltransferase and proline dehydrogenase were the main changes in this disorder.

Lutein Decreases Inflammation and Oxidative Stress and Prevents Iron Accumulation and Lipid Peroxidation at Glutamate-Induced Neurotoxicity.

The xanthophyll carotenoid lutein has been widely used as supplementation due to its protective effects in light-induced oxidative stress. Its antioxidant and anti-inflammatory features suggest that it has a neuroprotective role as well. Glutamate is a major excitatory neurotransmitter in the central nervous system (CNS), which plays a key role in regulating brain function. Excess accumulation of intracellular glutamate accelerates an increase in the concentration of reactive oxygen species (ROS) in neurons leading to glutamate neurotoxicity. In this study, we focused on the effects of glutamate on SH-SY5Y neuroblastoma cells to identify the possible alterations in oxidative stress, inflammation, and iron metabolism that affect the neurological function itself and in the presence of antioxidant lutein. First, ROS measurements were performed, and then catalase (CAT) and Superoxide Dismutase (SOD) enzyme activity were determined by enzyme activity assay kits. The ELISA technique was used to detect proinflammatory TNFα, IL-6, and IL-8 cytokine secretions. Alterations in iron uptake, storage, and release were followed by gene expression measurements and Western blotting. Total iron level detections were performed by a ferrozine-based iron detection method, and a heme assay kit was used for heme measurements. The gene expression toward lipid-peroxidation was determined by RT-PCR. Our results show glutamate changes ROS, inflammation, and antioxidant enzyme activity, modulate iron accumulation, and may initiate lipid peroxidation in SH-SY5Y cells. Meanwhile, lutein attenuates the glutamate-induced effects on ROS, inflammation, iron metabolism, and lipid peroxidation. According to our findings, lutein could be a beneficial, supportive treatment in neurodegenerative disorders.

CsGDH2.1 negatively regulates theanine accumulation in late-spring tea plants (Camellia sinensis var. sinensis).

Theanine, a unique and the most abundant non-proteinogenic amino acid in tea plants, endows tea infusion with the umami taste and anti-stress effects. Its content in tea correlates highly with green tea quality. Theanine content in new shoots of tea plants is high in mid-spring and greatly decreases in late spring. However, how the decrease is regulated is largely unknown. In a genetic screening, we observed that a yeast mutant, glutamate dehydrolase 2 (gdh2), was hypersensitive to 40mM theanine and accumulated more theanine. This result implied a role of CsGDH2s in theanine accumulation in tea plants. Therefore, we identified the two homologs of GDH2, CsGDH2.1 and CsGDH2.2, in tea plants. Yeast complementation assay showed that the expression of CsGDH2.1 in yeast gdh2 mutant rescued the theanine hypersensitivity and hyperaccumulation of this mutant. Subcellular localization and tissue-specific expression showed CsGDH2.1 localized in the mitochondria and highly expressed in young tissues. Importantly, CsGDH2.1 expression was low in early spring, and increased significantly in late spring, in the new shoots of tea plants. These results all support the idea that CsGDH2.1 regulates theanine accumulation in the new shoots. Moreover, the in vitro enzyme assay showed that CsGDH2.1 had glutamate catabolic activity, and knockdown of CsGDH2.1 expression increased glutamate and theanine accumulation in the new shoots of tea plants. These findings suggested that CsGDH2.1-mediated glutamate catabolism negatively regulates theanine accumulation in the new shoots in late spring, and provides a functional gene for improving late-spring green tea quality.

Etomidate-induced myoclonus correlates with the dysfunction of astrocytes and glutamate transporters in the neocortex of Sprague-Dawley rats.

Etomidate-induced myoclonus is common in clinical anesthesia. Propofol and lidocaine, as other sedative hypnotic and anticonvulsant drugs, rarely induce myoclonus. The mechanism of the myoclonus remains unclear. Eighty-four adult male Sprague-Dawley (SD) rats anesthetized intravenously with etomidate, propofol, or lidocaine plus etomidate were observed of the behavioral changes at 0, 1, 2, 3, 4 and 5 min after anesthesia. Five minutes later, glutamate levels were measured in the cerebrospinal fluid (CSF), neocortex and hippocampus. The mRNAs and proteins expression of EAAT1, EAAT2, and GFAP in the neocortex and hippocampus were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot and immunofluorescence staining. Etomidate increased the mean behavioral scores at different time points and the neocortical glutamate level compared with the propofol (p=0.0283) and the lidocaine plus etomidate group (p=0.0035); The correlation analysis revealed a strong correlation between the mean behavioral score and the neocortical glutamate content (Spearman's r=0.6638, p=0.0027). No significant difference was found in the EAAT1, EAAT2, or GFAP mRNAs in the neocortex and hippocampus among three groups; etomidate decreased EAAT1 (p=0.0416 and p=0.0127) and EAAT2 (p=0.0363 and p=0.0109) proteins but increased the GFAP (p=0.0145 and p=0.0149) protein in the neocortex compared to the propofol and lidocaine plus etomidate group. Furthermore, etomidate activated GFAP-positive cells in the neocortex, but conversely inhibited proteins of EAATs in motor cortex. Etomidate-induced myoclonus is associated with neocortical glutamate accumulation. Suppression of the astrogliosis in neocortex and promoting extracellular glutamate uptake by regulating glutamate transporters (EAATs) in the motor cortex may be the therapeutic target for prevention of etomidate-induced myoclonus.

Potential effects of Alpha lipoic acid on behavioral alteration and glutamate accumulation during d-gal-induced brain aging in male rats

Background: Alpha lipoic acid has both hydrophilic and hydrophobic characteristics and is abundantly distributed in cellular membranes and the cytoplasm. It is among the top cell- protective antioxidants. Material and methods : The present work investigated the possible therapeutic effects of alpha lipoic acid in a male rat model of brain aging induced by D-galactose. Four equal-sized groups of 40 male rats were randomly assigned: G1, the control group, G2, and G3, which each received daily doses of 200 mg/kg of D-gal for 30 days. Alpha lipoic acid was given orally for 30 days to the G4 D-gal + alpha lipoic acid group at 200 mg/kg bw, IP. daily with 100 mg/kg. thirty days of IP. Glutamate is deposited in the brain, according to research on behavioral alterations and brain glutamate. Indicators of oxidative stress are increased Our Results show that whereas brain glutamate deposition declines in the D-gal model of aging, the Forced Swimming Test (FST) and Morris Water Maze Test considerably rise (MWM).

Role of Aβ in Alzheimer's-related synaptic dysfunction.

Synaptic dysfunction is closely related to Alzheimer’s disease (AD) which is also recognized as synaptic disorder. β-amyloid (Aβ) is one of the main pathogenic factors in AD, which disrupts synaptic plasticity and mediates the synaptic toxicity through different mechanisms. Aβ disrupts glutamate receptors, such as NMDA and AMPA receptors, which mediates calcium dyshomeostasis and damages synapse plasticity characterized by long-term potentiation (LTP) suppression and long-term depression (LTD) enhancement. As Aβ stimulates and Ca2+ influx, microglial cells and astrocyte can be activated and release cytokines, which reduces glutamate uptake and further impair synapse function. Besides, extracellular glutamate accumulation induced by Aβ mediates synapse toxicity resulting from reduced glutamate receptors and glutamate spillovers. Aβ also mediates synaptic dysfunction by acting on various signaling pathways and molecular targets, disrupting mitochondria and energy metabolism. In addition, Aβ overdeposition aggravates the toxic damage of hyperphosphorylated tau to synapses. Synaptic dysfunction plays a critical role in cognitive impairment of AD. The review addresses the possible mechanisms by which Aβ mediates AD-related synaptic impairment from distant perspectives.

Time and Brain Region-Dependent Excitatory Neurochemical Alterations in Bilateral Common Carotid Artery Occlusion Global Ischemia Model.

Strict metabolic regulation in discrete brain regions leads to neurochemical changes in cerebral ischemia. Accumulation of extracellular glutamate is one of the early neurochemical changes that take place during cerebral ischemia. Understanding the sequential neurochemical processes involved in cerebral ischemia-mediated excitotoxicity before the clinical intervention of revascularization and reperfusion may greatly influence future therapeutic strategies for clinical stroke recovery. This study investigated the influence of time and brain regions on excitatory neurochemical indices in the bilateral common carotid artery occlusion (BCCAO) model of global ischemia. Male Wistar rats were subjected to BCCAO for 15 and 60min to evaluate the effect of ischemia duration on excitatory neurochemical indices (dopamine level, glutamine synthetase, glutaminase, glutamate dehydrogenase, aspartate aminotransferase, monoamine oxidase, acetylcholinesterase, and Na+ K+ ATPase activities) in the discrete brain regions (cortex, striatum, cerebellum, and hippocampus). BCCAO without reperfusion caused marked time and brain region-dependent alterations in glutamatergic, glutaminergic, dopaminergic, monoaminergic, cholinergic, and electrogenic homeostasis. Prolonged BCCAO decreased cortical, striatal, and cerebellar glutamatergic, glutaminergic, dopaminergic, cholinergic, and electrogenic activities; increased hippocampal glutamatergic, glutaminergic, dopaminergic, and cholinergic activities, increased cortical and striatal monoaminergic activity; decreased cerebellar and hippocampal monoaminergic activity; and decreased hippocampal electrogenic activity. This suggests that excitatory neurotransmitters play a major role in the tissue-specific metabolic plasticity and reprogramming that takes place between the onset of cardiac arrest-mediated global ischemia and clinical intervention of recanalization. These tissue-specific neurochemical indices may serve as diagnostic and therapeutic strategies for mitigating the progression of ischemic damage before revascularization.

Amitriptyline improves cognitive and neuronal function in a rat model that mimics dementia with lewy bodies

Dementia with Lewy bodies (DLB), a highly prevalent neurodegenerative disorder, causes motor and cognitive deficits. The main pathophysiologies of DLB are glutamate excitotoxicity and accumulation of Lewy bodies comprising α-synuclein (α-syn) and β-amyloid (Aβ). Amitriptyline (AMI) promotes expression of glutamate transporter-1 and glutamate reuptake. In this study, we measured the effects of AMI on behavioral and neuronal function in a DLB rat model. We used rivastigmine (RIVA) as a positive control. To establish the DLB rat model, male Wistar rats were stereotaxically injected with recombinant adenoassociated viral vector with the SNCA gene (10 μg/10 μL) and Aβ (5 μg/2.5 μL) into the left ventricle and prefrontal cortex, respectively. AMI (10 mg/kg/day, i.p.), RIVA (2 mg/kg/day, i.p.), or saline was injected intraperitoneally after surgery. From the 29th day, behavioral tests were performed to evaluate the motor and cognitive functions of the rats. Immunohistochemical staining was used to assess neuronal changes. We measured the α-syn level, number of newborn cells, and neuronal density in the hippocampus and in the nigrostriatal dopaminergic system. The DLB group exhibited deficit in object recognition. Both the AMI and RIVA treatments reversed these deficits. Histologically, the DLB rats exhibited cell loss in the substantia nigra pars compacta and in the hippocampal CA1 area. AMI reduced this cell loss, but RIVA did not. In addition, the DLB rats exhibited a lower number of newborn cells and higher α-syn levels in the dentate gyrus (DG). AMI did not affect α-syn accumulation but recovered neurogenesis in the DG of the rats, whereas RIVA reversed the α-syn accumulation but did not affect neurogenesis in the rats. We suggest that AMI may have potential for use in the treatment of DLB.

A neuro-metabolic account of why daylong cognitive work alters the control of economic decisions

Behavioral activities that require control over automatic routines typically feel effortful and result in cognitive fatigue. Beyond subjective report, cognitive fatigue has been conceived as an inflated cost of cognitive control, objectified by more impulsive decisions. However, the origins of such control cost inflation with cognitive work are heavily debated. Here, we suggest a neuro-metabolic account: the cost would relate to the necessity of recycling potentially toxic substances accumulated during cognitive control exertion. We validated this account using magnetic resonance spectroscopy (MRS) to monitor brain metabolites throughout an approximate workday, during which two groups of participants performed either high-demand or low-demand cognitive control tasks, interleaved with economic decisions. Choice-related fatigue markers were only present in the high-demand group, with a reduction of pupil dilation during decision-making and a preference shift toward short-delay and little-effort options (a low-cost bias captured using computational modeling). At the end of the day, high-demand cognitive work resulted in higher glutamate concentration and glutamate/glutamine diffusion in a cognitive control brain region (lateral prefrontal cortex [lPFC]), relative to low-demand cognitive work and to a reference brain region (primary visual cortex [V1]). Taken together with previous fMRI data, these results support a neuro-metabolic model in which glutamate accumulation triggers a regulation mechanism that makes lPFC activation more costly, explaining why cognitive control is harder to mobilize after a strenuous workday.

Glutamate drives ‘local Ca2+ release’ in cardiac pacemaker cells

The sinoatrial node (SAN) is the origin of the electrical signals for rhythmic heartbeats in mammals. The spontaneous firing of SAN pacemaker cells (SANPCs) triggers cardiac contraction. ‘Local Ca2+ release’ (LCR), a unique cellular activity, acts as the ‘engine’ of the spontaneous firing of SANPCs. However, the mechanism of LCR initiation remains unclear. Here, we report that endogenous glutamate drives LCRs in SANPCs. Using a glutamate sensor, we unraveled a tight correlation between glutamate accumulation and LCR occurrence, indicating a potential relationship between glutamate and LCRs. Intracellular application of glutamate significantly enhanced the LCRs in both intact and permeabilized SANPCs. Mechanistically, we revealed that mitochondrial excitatory amino acid transporter 1 (EAAT1)-dependent mitochondrial glutamate import promoted ROS generation, which in turn led to the oxidation of Ca2+-handling proteins, ultimately resulting in enhanced LCRs. Importantly, EAAT1 depletion reduced both the spontaneous firing rates of isolated SANPCs and the heart rate in vitro and in vivo, suggesting the central role of EAAT1 as a glutamate transporter in the regulation of cardiac autonomic rhythm. In conclusion, our results indicate that glutamate serves as an LCR igniter in SANPCs, adding a potentially important element to the coupled-clock theory that explains the origin of spontaneous firing. These findings shed new light on the future prevention and treatment of cardiac pacemaker cell-related arrhythmias.

(Digital Presentation) Simultaneous and Real-Time Electrochemical Detection of Multiple Biomarkers in a Microfluidic Chip

Dysregulations in metabolic and physiological cellular processes are generally accompanied by changes in concentration profiles of multiple biomarkers. Measuring dynamic changes in concentrations of several affected biomarkers can enhance our comprehension of the underlying disease pathophysiology and/or mechanisms of cytotoxicity. Most analytical detection techniques require samples to be obtained at pre-defined times for offline analysis. However, the inadequate temporal resolution of these methods can lead to key biological events that occur at shorter timescales, being overlooked. Electrochemical biosensors are relatively simple, cost-effective detection techniques that have been used extensively for continuous analyte monitoring, and more recently, for sensing multiple analytes. We describe the design and functionality of a novel electrochemical detection platform, comprising a screen-printed Pt electrode array, a microfluidic chip, and an automated pump and valve system, capable of quantitatively detecting up to eight analytes. As a proof of concept, we show the simultaneous, sensitive, and selective amperometric detection of four essential biomarkers- glucose, lactate, glutamate, and acetylcholine, in real time. We also demonstrate the biological application of this platform by continuously monitoring exocytotic glutamate release from human induced pluripotent stem cell-derived neuronal cultures over time. Excessive accumulation of glutamate in the synaptic cleft leads to prolonged stimulation of glutamate receptors on neurons, triggering a cascade of neurotoxic events that ultimately results in loss of neuronal function and cell death. The results suggest that our multianalyte electrochemical sensor platform can be coupled with more complex biological systems such as in vitro organotypic models, for the accurate monitoring of biomarker changes during adverse events like acute neurotoxicity and microbial infection.

Mechanism of reduced muscle atrophy via ketone body (D)-3-hydroxybutyrate

BackgroundMuscle atrophy is an increasingly global health problem affecting millions, there is a lack of clinical drugs or effective therapy. Excessive loss of muscle mass is the typical characteristic of muscle atrophy, manifesting as muscle weakness accompanied by impaired metabolism of protein and nucleotide. (D)-3-hydroxybutyrate (3HB), one of the main components of the ketone body, has been reported to be effective for the obvious hemodynamic effects in atrophic cardiomyocytes and exerts beneficial metabolic reprogramming effects in healthy muscle. This study aims to exploit how the 3HB exerts therapeutic effects for treating muscle atrophy induced by hindlimb unloaded mice.ResultsAnabolism/catabolism balance of muscle protein was maintained with 3HB via the Akt/FoxO3a and the mTOR/4E-BP1 pathways; protein homeostasis of 3HB regulation includes pathways of ubiquitin–proteasomal, autophagic-lysosomal, responses of unfolded-proteins, heat shock and anti-oxidation. Metabolomic analysis revealed the effect of 3HB decreased purine degradation and reduced the uric acid in atrophied muscles; enhanced utilization from glutamine to glutamate also provides evidence for the promotion of 3HB during the synthesis of proteins and nucleotides.Conclusions3HB significantly inhibits the loss of muscle weights, myofiber sizes and myofiber diameters in hindlimb unloaded mouse model; it facilitates positive balance of proteins and nucleotides with enhanced accumulation of glutamate and decreased uric acid in wasting muscles, revealing effectiveness for treating muscle atrophy.Graphical

Metabolic Engineering of Bacillus amyloliquefaciens to Efficiently Synthesize L-Ornithine From Inulin.

Bacillus amyloliquefaciens is the dominant strain used to produce γ-polyglutamic acid from inulin, a non-grain raw material. B. amyloliquefaciens has a highly efficient tricarboxylic acid cycle metabolic flux and glutamate synthesis ability. These features confer great potential for the synthesis of glutamate derivatives. However, it is challenging to efficiently convert high levels of glutamate to a particular glutamate derivative. Here, we conducted a systematic study on the biosynthesis of L-ornithine by B. amyloliquefaciens using inulin. First, the polyglutamate synthase gene pgsBCA of B. amyloliquefaciens NB was knocked out to hinder polyglutamate synthesis, resulting in the accumulation of intracellular glutamate and ATP. Second, a modular engineering strategy was applied to coordinate the degradation pathway, precursor competition pathway, and L-ornithine synthesis pathway to prompt high levels of intracellular precursor glutamate for l-ornithine synthesis. In addition, the high-efficiency L-ornithine transporter was further screened and overexpressed to reduce the feedback inhibition of L-ornithine on the synthesis pathway. Combining these strategies with further fermentation optimizations, we achieved a final L-ornithine titer of 31.3 g/L from inulin. Overall, these strategies hold great potential for strengthening microbial synthesis of high value-added products derived from glutamate.

Ablation of Liver X receptor β in mice leads to overactive macrophages and death of spiral ganglion neurons

Age-related hearing loss is the most common type of hearing impairment, and is typically characterized by the loss of spiral ganglion neurons (SGNs). The two Liver X receptors (LXRs) are oxysterol-activated nuclear receptors which in adults, regulate genes involved in cholesterol homeostasis and modulation of macrophage activity. LXRβ plays a key role in maintenance of health of dopaminergic neurons in the substantia nigra, large motor neurons in the spinal cord, and retinal ganglion cells in adult mice. We now report that LXRβ is expressed in the SGNs of the cochlea and that loss of LXRβ leads to age-related cochlea degeneration. We found that in the cochlea of LXRβ–/– mice, there is loss of SGNs, activation of macrophages, demyelination in the spiral ganglion, decrease in glutamine synthetase (GS) expression and increase in glutamate accumulation in the cochlea. Part of the cause of damage to the SGNs might be glutamate toxicity which is known to be very toxic to these cells. Our study provides a so far unreported role of LXRβ in maintenance of SGNs whose loss is a very common cause of hearing impairment.