Glu Concentrations Research Articles

Glutamate concentration of medial prefrontal cortex is inversely associated with addictive behaviors: a translational study

In both preclinical and clinical settings, dysregulated frontostriatal circuits have been identified as the underlying neural substrates of compulsive seeking/taking behaviors manifested in substance use disorders and behavioral addictions including internet gaming disorder (IGD). However, the neurochemical substrates for these disorders remain elusive. The lack of comprehensive cognitive assessments in animal models has hampered our understanding of neural plasticity in addiction from these models. In this study, combining data from a rat model of compulsive taking/seeking and human participants with various levels of IGD severity, we investigated the relationship between regional glutamate (Glu) concentration and addictive behaviors. We found that Glu levels were significantly lower in the prelimbic cortex (PrL) of rats after 20-days of methamphetamine self-administration (SA), compared to controls. Glu concentration after a punishment phase negatively correlated with acute drug-seeking behavior. In addition, changes in Glu levels from a drug naïve state to compulsive drug taking patterns negatively correlated with drug-seeking during both acute and prolonged abstinence. The human data revealed a significant negative correlation between Glu concentration in the dorsal anterior cingulate cortex (dACC), the human PrL counterpart, and symptoms of IGD. Interestingly, there was a positive correlation between Glu levels in the dACC and self-control, as well as mindful awareness. Further analysis revealed that the dACC Glu concentration mediated the relationship between self-control/mindful awareness and IGD symptoms. These results provide convergent evidence for a protective role of dACC/PrL in addiction, suggesting interventions to enhance dACC glutamatergic functions as a potential strategy for addiction prevention and treatment.

Elevated peripheral glutamate and upregulated expression of NMDA receptor NR1 subunit in insomnia disorder.

The present study explored the serum glutamate (Glu), glutamine (Gln), glutamic acid dehydrogenase (GAD) concentrations and the mRNA expression levels of the N-methyl-D-aspartate receptor (NMDAR) NR1 subunit in the peripheral blood of patients with insomnia disorder (ID). To our knowledge, this is the first study showing an increase in the mRNA expression levels of the NMDAR NR1 subunit in patients with ID. This study included 30 ID patients and 30 matched healthy controls. We investigated the demographic and illness information and assessed subjective sleep quality using the Pittsburgh Sleep Quality Index. The Hamilton Depression Scale-17 and Hamilton Anxiety Scale were used to evaluate the patients' symptoms of depression and anxiety, respectively. The quantifications of Glu, Gln and GAD concentrations were performed by Enzyme-linked immunosorbent assay (ELISA). Real-time PCR was used to detect the mRNA expression levels of the NMDAR NR1 subunit in peripheral blood. Compared with the healthy control group, the serum Glu concentrations and the mRNA expression levels of the NMDAR NR1 subunit in the ID group were significantly higher. However, there was no significant difference in Gln and GAD between the two groups. The receiver operating characteristic (ROC) analysis showed that the mRNA expression levels of the NMDAR NR1 subunit could distinguish ID patients from healthy individuals (area under the curve: 0.758; sensitivity: 73.3%; specificity: 76.7%). A negative correlation was found between the mRNA expression levels of the NMDAR NR1 subunit for age, total duration of illness, and age of first onset in the ID group, whereas a positive correlation was detected for daytime dysfunction. Glutamatergic neurotransmission was abnormal in ID patients. Additionally, the mRNA expression levels of the NMDAR NR1 subunit appeared to have potential as a clinical biomarker for ID. However, the sample size of our study was limited, and future studies with larger sample sizes are needed to further validate and explore the mechanisms involved and to assess the reliability of the biomarker.

Chiral sensing of glucose by surface-enhanced Raman spectroscopy

BackgroundChiral-selective molecular interactions are considered crucial in numerous physiological processes. Chiral-selective analytical methods of biomolecules with sufficient sensitivity are of great interest in numerous applications. Several surface-enhanced Raman scattering (SERS)-based methods have recently been reported for chiral sensing of biomolecules. However, the lack of molecular-level understanding of SERS spectral changes of reporter and analyte molecules may mislead the development of chiral detection methods. ResultsWe report the chiral sensing of glucose (Glu) by SERS of L- and D-phenylalanine (Phe) with colloidal gold nanoparticles (AuNPs) synthesized by borohydride ions. The Phe SERS showed drastic spectral changes only when Glu of the same chirality as Phe was added, which also showed strong dependence on Glu concentration. The increase of δ(COO−) and decrease of νs(COO−) modes in Phe SERS, exclusively observed with the chiral-selective bimolecular interactions of chirally matching Glu, are understood as modified surface adsorption geometry of the carboxylate group. Quantitative spectral analysis for the Glu concentration of a specific chirality showed the detection limit down to 2 × 10−9 - 2 × 10−7 M levels depending on the existence of the opposite enantiomer of Glu. SignificanceIn this study, we demonstrated that the Phe SERS on AuNPs can be utilized in the chiral sensing of Glu molecules with quantitative concentration analysis. The bimolecular interactions of surface-adsorbed Phe and chirally matching Glu are suggested for the chiral recognition of Phe SERS. These results imply that a molecule-level understanding is indispensable for developing SERS-based chiral sensing methods.

Valine biased glycogen consumption to promote energy metabolism of Portunus trituberculatus and increased protein and essential amino acid deposition in muscle

The present research assessed the impact of dietary valine on nutritional and energy metabolism, as well as muscle development in swimming crabs (Portunus trituberculatus) over a period of six weeks. Swimming crabs, initially weighing around 23.34 ± 0.03 g, were given six diets identical in nitrogen and lipid levels (45 % and 8 % respectively). These diets contained valine contents of 0.99 %, 1.24 %, 1.56 %, 1.69 %, 1.90 %, and 2.20 % respectively. One hundred and eighty crabs were randomized into six treatments, each treatment including three replicates. The results suggested that significant increases were discovered in FW, PWG, as well as SGR of crabs when dietary valine increasing from 0.99 % to 1.69 %, but these measurements decreased when dietary valine increased to 2.20 %. Compare to the control treatment, crabs that were given diets with 1.90 % and 2.20 % valine showed increased level of muscle protein. Crabs that were given the diets containing 1.56 % and 1.69 % valine showed significantly increased concentration of GLU in hemolymph compared to the control group. Additionally, crabs that were given the diets containing 1.69 % valine and 1.90 % valine respectively showed significantly increased concentrations of T-CHO and TG in hepatopancreas. Hepatic glycogen concentration significantly decreased as the level of valine in diets increased from 0.99 % to 1.56 %, but significantly increased as valine level further increased to 2.20 %. Compared with the control group, crabs that were given diets with 1.90 % valine showed increased expression levels of genes associated to amino acid metabolism (pi3k, akt, alt, ast, 4ebp1 and eif4e3) and energy metabolism (pk, cs1, idh, nd1, cytb and cox2). Crabs given diets containing 2.20 % valine showed significantly increased expression level of pepck in hepatopancreas, while crabs given diets containing 1.24 %, 1.56 %, and 1.69 % valine exhibited significantly increased expression level of cpt1 in hepatopancreas. Crabs given the diet with 1.69 % valine had the highest expression levels of tor and pax7 in muscle. Increased dietary valine significantly reduced myofiber density but promoted higher frequency of myofibers in larger diameters. In conclusion, the optimal valine requirement for P. trituberculatus was 1.56 % of diet based on PWG by a quadratic modeling. 1.69–1.90 % valine promoted amino acid metabolism and muscle growth, moreover, enhanced energy metabolism by driving the consumption of glycogen rather than lipids.

Comparative effects of ammonium nitrogen on perchlorate degradation performance under heterotrophic condition with different carbon sources

Perchlorate (ClO4-) mainly exists in the form of ammonium perchlorate in industrial production. However, the degradation mechanisms of different concentrations of ammonium nitrogen (NH4+-N) and ClO4- mixed pollutants in the environment are not well understood. This study aims to explore the potential of different types of carbon sources for ClO4- and NH4+-N biodegradation. Experimental results showed that the concentration and type of carbon sources are decisive to simultaneous removal of NH4+-N and ClO4-. Under condition of C(COD)/C(ClO4-) ratio of 21.15 ± 4.40, the simultaneously removal efficiency of ClO4- and NH4+-N in acetate (Ace) was relatively higher than that in methanol (Met). C(NH4+-N)/C(ClO4-) ratio of 9.66 ± 0.51 and C(COD)/C(ClO4-) ratio of 2.51 ± 0.87 promoted ClO4- reduction in glucose-C (Glu-C). However, high concentration of Glu could cause pH decrease (from 7.57 to 4.59), thereby inhibiting ClO4- reduction. High-throughput sequencing results indicated that Proteobacteria and Bacteroidetes have made a major contribution to the simultaneous removal of NH4+-N and ClO4-. They are two representative bacterial phyla for participating in both ClO4- reduction and denitrification. Notably, the abundance of main ClO4- degrading bacteria (such as Proteobacteria, Chloroflexi, and Firmicutes) significantly increased by 528.57 % in Glu-C. It can be inferred that the concentration of carbon source and NH4+-N were the most important factors determining the removal efficiency of ClO4- by influencing changes in the core microbial community. This study will provide new techniques and mechanistic insights for the simultaneous removal of mixed ClO4- and nitrogen pollutants, which can also provide theoretical support for innovation in future biological treatment processes.

Smartphone-assisted portable swabs for blood glucose management: A point-of-use assay for dual-mode visual detection based on bifunctional carbon dots

Controlling glucose (Glu) intake is a “required course” for diabetics, thus quickly and precisely measuring the amount of Glu in food is crucial. For this purpose, a novel smartphone-assisted portable swab for the dual-mode visual detection of Glu was constructed combined the selectivity of natural enzymes with the controllable catalytic activity of nanozymes. Glu was specifically decomposed by glucose oxidase (natural enzyme) to produce H2O2, which was catalyzed by carbon dots (FeMn/N-CDs, nanozyme) to accelerate the reaction of o-phenylenediamine (OPD, colorless) to produce 2,3-diaminophenazine (DAP, yellow). As a result, the absorbance at 450 nm gradually increased with the increasing concentration of Glu, leading to a color change in the system from colorless to yellow. Meanwhile, the fluorescence of FeMn/N-CDs gradually decreased at 450 nm, while the fluorescence of DAP gradually increased at 550 nm, allowing for both ratiometric fluorescence and colorimetric dual-mode detection. Furthermore, natural enzyme and nanozyme together with OPD were co-loaded on the swabs to achieve cascade catalysis of Glu. The assembled portable swabs have detection ranges of 1–600 μM (LOD = 0.37 μM) and 4–1200 μM (LOD = 1.19 μM) for the colorimetric and fluorometric detection, respectively. The field test results on real samples demonstrated that the portable swabs have great promise for use in efficiently and accurately guiding the dietary intake of diabetics.

Correlation of striatal dopamine D2/3 receptor availability with GABA level in the anterior cingulate cortex in healthy controls but not in alcohol-dependent subjects and individuals at high risk: A multimodal magnetic resonance spectroscopy and positron emission tomography study.

The association of impaired dopaminergic neurotransmission with the development and maintenance of alcohol use disorder is well known. More specifically, reduced dopamine D2/3 receptors in the striatum of subjects with alcohol dependence (AD) compared to healthy controls have been found in previous studies. Furthermore, alterations of gamma-aminobutyric acid (GABA) and glutamate (Glu) levels in the anterior cingulate cortex (ACC) of AD subjects have been documented in several studies. However, the interaction between cortical Glu levels and striatal dopamine D2/3 receptors has not been investigated in AD thus far. This study investigated dopamine D2/3 receptor availability via 18F-fallypride positron emission tomography (PET) and GABA as well as Glu levels via magnetic resonance spectroscopy (MRS) in 19 detoxified AD subjects, 18 healthy controls (low risk, LR) controls and 19 individuals at high risk (HR) for developing AD, carefully matched for sex, age and smoking status. We found a significant negative correlation between GABA levels in the ACC and dopamine D2/3 receptor availability in the associative striatum of LR but not in AD or HR individuals. Contrary to our expectations, we did not observe a correlation between Glu concentrations in the ACC and striatal D2/3 receptor availability. The results may reflect potential regulatory cortical mechanisms on mesolimbic dopamine receptors and their disruption in AD and individuals at high risk, mirroring complex neurotransmitter interactions associated with the pathogenesis of addiction. This is the first study combining 18F-fallypride PET and MRS in AD subjects and individuals at high risk.

Electrochemical detection of glutamate and histamine using redox-labeled stimuli-responsive polymer as a synthetic target receptor.

Glutamate (Glu) and histamine (His) are two major neurotransmitters that play many critical roles in brain physiological functions and neurological disorders. Therefore, specific and sensitive monitoring of Glu and His is essential in the diagnosis and treatment of various mental health and neurodegenerative disorders. Both being non-electroactive species, direct electrochemical detection of Glu and His has been challenging. Herein, we report a stimuli-responsive polymer-based biosensor for the electrochemical detection of Glu and His. The polymer-based target receptors consist of a linear chain stimuli-responsive templated polymer hybrid that is labeled with an osmium-based redox-active reporter molecules to elicit conformation-dependent electrochemical responses. The polymers are then attached to a gold electrode to implement an electrochemical sensor. The cyclic voltammetry (CV) and square-wave voltammetry (SWV) results confirmed the polymers' conformational changes due to the specific target (i.e., Glu and His) recognition and the corresponding electrochemical detection capabilities. The voltammetry results indicate that this biosensor can be used as a 'signal-on' and 'signal-off' sensors for the detection of Glu and His concentrations, respectively. The developed biosensor also showed excellent regeneration capability by fully recovering the initial current signal after rinsing with deionized water. To further validate the polymer's utility as a target bioreceptor, the surface plasmon resonance (SPR) technique was used to characterize the binding affinity between the designed polymers and the target chemical. The SPR results exhibited the equilibrium dissociation constants (KD) of 2.40 μM and 1.54 μM for the polymer-Glu and polymer-His interactions, respectively. The results obtained this work strongly suggest that the proposed sensing technology could potentially be used as a platform for monitoring non-electroactive neurochemicals from animal models.

Measuring fecal neurotransmitter concentrations using Dried Fecal Spot (DFS)-based LC-MS/MS bioanalysis

Background: Guthrie implemented dried blood spot (DBS)-based bioanalytical techniques in the 1960s in order to screen for phenylketonuria (PKU) disease in neonates. Historically, the dominant matrix analyzed using the “Guthrie card” platform has been whole blood, but recent advances in device technology now allow for whole blood-to-plasma sample processing prior to drying and subsequent bioanalysis. This project aimed to use this dried matrix technologies in an entirely new direction by performing dried fecal spot (DFS)-based bioanalysis for analytical microbiology and microbiome applications. Homogenized fecal sample extracts were loaded onto quantitative DBS (qDBS) devices and were allowed to dry overnight, then were shipped at ambient shipping temperature. The DBS spots were processed and subjected to LC-MS/MS-based targeted metabolomics using our Glutamate Cycle method (Glu, Gln, and GABA). Methods & Results: Fecal samples were collected from each of the five human subjects enlisted in the following cohorts: 1) healthy controls; 2) patients with diarrhea; and, 3) Clostridioides diffcile-infected (CDI) patients. A volume of ice-cold methanol:water (1:1, v:v) equivalent to a fecal density of 50 mg/mL was added into individual homogenization tubes that each contained 100 mg of 1.4 mm silica beads. Fecal samples were homogenized using 5 bead-beating cycles (4 m/s for each 20 s pulse). After centrifugation (@500 g), a 20-μL sample supernatant volume was loaded onto qDBS devices that yielded an exact 10-μL DFS spot volume on the embedded cards. Dried DFS spots were removed from the device and homogenized in a 200-μL volume of an IS solution. The Glu, Gln, and GABA concentration of each sample was compared against the concentrations measured in the matched frozen fecal extracts. We were able to successfully detect GABA in both the standard extraction method and in our processed DFS samples. Interestingly, we observed large variability between patient samples and there were no statistically significant differences between the cohorts. Conclusion: Collectively, these data demonstrate the utility of our method for measuring the concentrations of Glu, Gln and GABA contained in our processed DFS-based sample sets. This study was supported by the NIH K01K123195-01 (MAE). The Texas Children’s Hospital Department of Pathology provides salary support to Texas Children’s Microbiome Center-Metabolomics Lab staff, and purchased all of the reagents, the consumables and durable supplies, and the liquid chromatography-tandem mass spectrometry (LC-MS/MS) equipment described. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The impact of spectral basis set composition on estimated levels of cingulate glutamate and its associations with different personality traits

Background1H-MRS is increasingly used in basic and clinical research to explain brain function and alterations respectively. In psychosis research it is now one of the main tools to investigate imbalances in the glutamatergic system. Interestingly, however, the findings are extremely variable even within patients of similar disease states. One reason may be the variability in analysis strategies, despite suggestions for standardization. Therefore, our study aimed to investigate the extent to which the basis set configuration– which metabolites are included in the basis set used for analysis– would affect the spectral fit and estimated glutamate (Glu) concentrations in the anterior cingulate cortex (ACC), and whether any changes in levels of glutamate would be associated with psychotic-like experiences and autistic traits.MethodsTo ensure comparability, we utilized five different exemplar basis sets, used in research, and two different analysis tools, r-based spant applying the ABfit method and Osprey using the LCModel.ResultsOur findings revealed that the types of metabolites included in the basis set significantly affected the glutamate concentration. We observed that three basis sets led to more consistent results across different concentration types (i.e., absolute Glu in mol/kg, Glx (glutamate + glutamine), Glu/tCr), spectral fit and quality measurements. Interestingly, all three basis sets included phosphocreatine. Importantly, our findings also revealed that glutamate levels were differently associated with both schizotypal and autistic traits depending on basis set configuration and analysis tool, with the same three basis sets showing more consistent results.ConclusionsOur study highlights that scientific results may be significantly altered depending on the choices of metabolites included in the basis set, and with that emphasizes the importance of carefully selecting the configuration of the basis set to ensure accurate and consistent results, when using MR spectroscopy. Overall, our study points out the need for standardized analysis pipelines and reporting.

Metabolic profiling identifies Qrich2 as a novel glutamine sensor that regulates microtubule glutamylation and mitochondrial function in mouse sperm

In our prior investigation, we discerned loss-of-function variants within the gene encoding glutamine-rich protein 2 (QRICH2) in two consanguineous families, leading to various morphological abnormalities in sperm flagella and male infertility. The Qrich2 knockout (KO) in mice also exhibits multiple morphological abnormalities of the flagella (MMAF) phenotype with a significantly decreased sperm motility. However, how ORICH2 regulates the formation of sperm flagella remains unclear. Abnormal glutamylation levels of tubulin cause dysplastic microtubules and flagella, eventually resulting in the decline of sperm motility and male infertility. In the current study, by further analyzing the Qrich2 KO mouse sperm, we found a reduced glutamylation level and instability of tubulin in Qrich2 KO mouse sperm flagella. In addition, we found that the amino acid metabolism was dysregulated in both testes and sperm, leading to the accumulated glutamine (Gln) and reduced glutamate (Glu) concentrations, and disorderly expressed genes responsible for Gln/Glu metabolism. Interestingly, mice fed with diets devoid of Gln/Glu phenocopied the Qrich2 KO mice. Furthermore, we identified several mitochondrial marker proteins that could not be correctly localized in sperm flagella, which might be responsible for the reduced mitochondrial function contributing to the reduced sperm motility in Qrich2 KO mice. Our study reveals a crucial role of a normal Gln/Glu metabolism in maintaining the structural stability of the microtubules in sperm flagella by regulating the glutamylation levels of the tubulin and identifies Qrich2 as a possible novel Gln sensor that regulates microtubule glutamylation and mitochondrial function in mouse sperm.

A GOX/RGO-CS-Fc/AuNPs nanosensing membrane in a light-addressable potentiometric biosensor for glucose specific detection

Glucose (Glu) is an important source of energy and metabolic intermediate for animal and plant cells. In this study, a high-performance biosensor for specific detection of Glu was constructed by combining a light-addressable potentiometric biosensor (LAPS) and a specific sensitive unit. The specific sensitive unit was adopted a silicon-based capacitive structure, and the glucose oxidase/reduced graphene oxide -chitosan-ferrooxidase/gold nanoparticles (GOX/RGO-CS-Fc/AuNPs) was modified onto the silicon-based working electrode to construct an nanosensing membrane. The interaction between the specific sensitive unit and Glu resulted in the formation of a bilayer potential, and the field effect generated by the bilayer potential caused a change in the capacitance of the silicon structure, which resulted in a change in the photocurrent-voltage characteristics of the LAPS. Through the potential shift in the photocurrent-voltage characteristics, the LAPS was capable of detection the concentration of Glu. Under optimal conditions, the potential shift was linearly correlated with the Glu concentration from 0.01 mg/mL to 4.00 mg/mL with R2 of 0.9821, and the limited detection was 0.001 mg/mL. In addition, the LAPS showed good recovery (97.92 %–105.72 %), admirable specificity and stability in detection Glu in human serum samples.

Enhanced NMDA receptor pathway and glutamate transmission in the hippocampal dentate gyrus mediate the spatial learning and memory impairment of obese rats.

Obesity has been linked with the impairment of spatial memory and synaptic plasticity but the molecular mechanisms remained unidentified. Since glutamatergic transmission and NMDA receptor neural pathways in hippocampal dentate gyrus (DG) are essential in the learning and memory, we aimed to investigate glutamate (Glu) and NMDA receptor signaling of DG in spatial learning and memory in diet-induced obesity (DIO) rats. Spatial learning and memory were assessed via Morris water maze (MWM) test on control (Ctr) and DIO rats. Extracellular concentration of Glu in the DG was determined using in vivo microdialysis and HPLC. The protein expressions of NMDA receptor subunit 2B (NR2B), brain-derived neurotrophic factor (BDNF), the activation of calcium/calmodulin-dependent kinase II (CaMKII) and cAMP-response-element-binding protein (CREB) in the DG were observed by western blot. Spatial learning and memory were impaired in DIO rats compared to those of Ctr. NR2B expression was increased, while BDNF expression and CaMKII and CREB activation were decreased in DG of DIO rats. Extracellular concentration of Glu was increased in Ctr on the 3rd and 4th days of the MWM test, but significant further increment was observed in DIO rats. Microinjection of an NMDA antagonist (MK-801) into the DG reversed spatial learning and memory impairment. Such effects were accompanied by greater BDNF expression and CaMKII/CREB activation in the DG of DIO rats. In conclusion, the enhancement of Glu-NMDA receptor transmission in the hippocampal DG contributes to the impairment of spatial learning and memory in DIO rats, maybe via the modulation of CaMKII-CREB-BDNF signaling pathway.

Excess dietary Lys reduces feed intake, stimulates jejunal CCK secretion and alters essential and non-essential blood AA profile in pigs

BackgroundCommercial diets are frequently formulated to meet or exceed nutrient levels including those of limiting essential amino acids (AA) covering potential individual variations within the herd. However, the provision of dietary excess of AA, such as Lys, may lead to reduced appetite and growth in pigs. The mechanisms modulating these responses have not been extensively investigated. This study evaluated the effect of Lys dietary excesses on performance and satiety biomarkers in post weaning pigs.MethodsTwenty-four pigs aged 21 d and weighing 6.81 ± 0.12 kg (mean ± SEM) were individually housed and offered 1 of 4 dietary treatments for 3 weeks: a diet containing a standardized ileal digestible Lys reaching 100% (T0), 120% (T1), 150% (T2) or 200% (T3) of the NRC (2012) requirements. At the end of the experiment, blood samples from the cephalic vein of the T0 and T3 groups were obtained for AA analysis. In addition, primary intestinal cultures from T0 pigs were used, following their humane killing, to evaluate the effect of Lys on gut hormone secretion and AA sensors gene expression under ex vivo conditions.ResultsFeed intake was linearly reduced (P < 0.001) and the weight gain to feed ratio reduced (P < 0.10) with increased dietary levels of Lys during the third- and first-week post weaning, respectively. Cholecystokinin concentration (P < 0.05) and the metabotropic glutamate receptor 1 and the solute carrier family 7 member 2 (P < 0.10) gene expression was enhanced in proximal jejunum tissues incubated with Lys at 20 mmol/L when compared to the control (Lys 0 mmol/L). Plasma Lys and Glu (P < 0.05) concentration increased in the T3 compared to T0 pigs. In contrast, plasma levels of His, Val, Thr, Leu (P < 0.05) and Gln (P < 0.10) were lower in T3 than T0 pigs.ConclusionThe present results confirm that excess dietary Lys inhibits hunger in pigs. Moreover, the results provide evidence of pre- and post-absorptive mechanisms modulating these responses. Lys dietary excesses should be narrowed, when possible, to avoid negative effects of the AA on appetite in pigs.

Mapping Changes in Glutamate with Glutamate-Weighted MRI in Forced Swim Test Model of Depression in Rats.

Chemical exchange saturation transfer with glutamate (GluCEST) imaging is a novel technique for the non-invasive detection and quantification of cerebral Glu levels in neuromolecular processes. Here we used GluCEST imaging and 1H magnetic resonance spectroscopy (1H MRS) to assess in vivo changes in Glu signals within the hippocampus in a rat model of depression induced by a forced swim test. The forced swimming test (FST) group exhibited markedly reduced GluCEST-weighted levels and Glu concentrations when examined using 1H MRS in the hippocampal region compared to the control group (GluCEST-weighted levels: 3.67 ± 0.81% vs. 5.02 ± 0.44%, p < 0.001; and Glu concentrations: 6.560 ± 0.292 μmol/g vs. 7.133 ± 0.397 μmol/g, p = 0.001). Our results indicate that GluCEST imaging is a distinctive approach to detecting and monitoring Glu levels in a rat model of depression. Furthermore, the application of GluCEST imaging may provide a deeper insight into the neurochemical involvement of glutamate in various psychiatric disorders.

Neuroprotective Effects of Noncanonical PAR1 Agonists on Cultured Neurons in Excitotoxicity.

Serine proteases regulate cell functions through G protein-coupled protease-activated receptors (PARs). Cleavage of one peptide bond of the receptor amino terminus results in the formation of a new N-terminus ("tethered ligand") that can specifically interact with the second extracellular loop of the PAR receptor and activate it. Activation of PAR1 by thrombin (canonical agonist) and activated protein C (APC, noncanonical agonist) was described as a biased agonism. Here, we have supposed that synthetic peptide analogs to the PAR1 tethered ligand liberated by APC could have neuroprotective effects like APC. To verify this hypothesis, a model of the ischemic brain impairment based on glutamate (Glu) excitotoxicity in primary neuronal cultures of neonatal rats has been used. It was shown that the nanopeptide NPNDKYEPF-NH2 (AP9) effectively reduced the neuronal death induced by Glu. The influence of AP9 on cell survival was comparable to that of APC. Both APC and AP9 reduced the dysregulation of intracellular calcium homeostasis in cultured neurons induced by excitotoxic Glu (100 µM) or NMDA (200 µM) concentrations. PAR1 agonist synthetic peptides might be noncanonical PAR1 agonists and a basis for novel neuroprotective drugs for disorders related to Glu excitotoxicity such as brain ischemia, trauma and some neurodegenerative diseases.

Exfoliation of an extruded Mg-4Li-1Ca alloy in presence of glucose and bovine serum albumin

Exfoliation corrosion (EFC) on extruded Mg-4Li-1Ca alloys as bone implant materials has not been reported. This study aimed to elucidate the degradation mechanism of a corrosion type-exfoliation occurred on an extruded Mg-4Li-1Ca alloy under the interaction of glucose (Glu) and bovine serum albumin (BSA) in Hank’s solution. The alloy microstructure, chemical composition, texture, stress distribution and Volta potential maps were characterized using metallographic microscopy, scanning electron microscopy and electron backscattered diffraction, and scanning Kelvin Probe. The alloy corrosion behavior was investigated via electrochemical testing and hydrogen evolution rate methods. X-ray diffraction, Fourier transform infrared spectrometry, X-ray photoelectron spectrometer, and fluorescence microscopy were used to analyze the corrosion products and the adsorption of the organic molecules. The experimental results indicated that the anodic second phase (Mg2Ca) were distributed in lamellar and rod-like patterns along the extrusion direction of the alloy, a lower Volta potential for Mg2Ca, texture and residual stresses also promote EFC. An increase in Glu concentration exacerbated the EFC, whereas BSA inhibited the EFC of the alloy. Higher Glu concentrations in BSA in turn inhibited EFC since Glu can complex with amino acids in proteins to form Glu-amino acid amides, which promoted protein adsorption and thereby forming a dense protective film on the alloy surface. The preferential dissolution of the Mg2Ca phase particles led to the complexation and adsorption of Glu and protein. This study enriches the understanding of the corrosion types in biomedical Mg-4Li-1Ca alloy and paving the way for enhancing the EFC resistance of the alloy.

Participation of glutamic acid in the catecholamines release from the amygdala of rabbits

Glutamic acid (Glu), as the most stimulating neurotransmitter, occurs in almost all structures of the central nervous system (CNS). Especially high concentrations are found in the structures of the motivational system (hypothalamus, hippocampus, amygdala, prefrontal cortex – mPFC) and the motor system (striatum, caudate nucleus, pallidum). Glu is also found in the autonomic nervous system (ANS), as well as in peripheral tissues and organs (in the adrenal glands, especially important in stress; the hypothalamic-pituitary-adrenal axis – HPA axis). Catecholamines (CA), including dopamine (DA), norepinephrine (NE), and/or epinephrine (E), are major neurotransmitters that mediate various CNS functions, such as motor control, cognition, emotion, memory processing, pain, stress, and endocrine modulation. The aim of the study was to investigate the in vitro effect of different concentrations of Glu (5, 50, and 200 μM in a volume of 1 ml of Krebs medium) on CA release from rabbit amygdala sections collected after decapitation of 12-week-old female rabbits. The same piece of tissue was transferred every 30 minutes to successive incubation wells containing Glu in an appropriate dose. The medium collected from the wells after 30, 60, and 90 minutes of incubation was frozen until DA, NE, and E analyses were performed by the RIA method. The results showed that Glu differently affected CA release from the amygdala. Generally, an inhibitory effect of Glu on CA release from the amygdala was observed. It was surprising to find the highest concentration of E in the amygdala compared to NA and even DA.

Silicon-based field-effect glucose biosensor based on reduced graphene oxide-carboxymethyl chitosan-platinum nanocomposite material modified LAPS

In this study, a label-free glucose (Glu) biosensor was designed by modifying reduced graphene oxide-carboxymethyl chitosan-platinum nanoparticles (RGO-CMCS-Pt NPs) on a silicon-based light-addressable potentiometric sensor (LAPS) based on the field effect tube principle. Under the bias voltage, a modulated light source is directed onto the semiconductor layer of the sensor, generating a weak photocurrent. Simultaneously, Glu is catalyzed by glucose oxidase (GOD) to produce gluconic acid and H2O2. The H2O2 further decomposes to facilitate electron transfer, disrupting the potential balance on the biosensor surface and causing changes in the photocurrent-bias voltage (I-V) curve. The voltage offset demonstrated a linear relationship with the Glu concentration ranging from 0.01 mg/mL to 4.0 mg/mL. The linear equation was △V= 19.17331 C+ 75.46574 (R2 =0.98831) with a high sensitivity of 19.17 mV*mL/mg and a low detection limit (LOD) of 0.01 mg/mL (S/N = 3). Furthermore, the Glu biosensor exhibited good specificity, reproducibility, and stability, the biosensor also realized the detection of glucose in human serum samples with a relative standard deviation ranging from 0.63% to 3.47%, and the results were consistent with the hospital's biochemical indicators, which demonstrated the potential application of the prepared biosensor in the clinical detection of Glu.

Amino acid metabolism response to post-anthesis drought stress during critical periods of elite wheat (Triticum aestivum L.) endosperm development

Drought is an important environmental factor leading to wheat yield loss in arid areas. The accumulation of amino acids during the filling stage is closely related to wheat drought resistance and yield, but the mechanism is still unclear. In this study, winter wheat plants (cultivars Xindong 18 (XD18) and Xindong 22 (XD22)) were subjected to post-anthesis drought treatment (DT) and sufficient water treatment (WT), and the measurement of free amino acid and carbohydrates content and the proteomic and transcriptomic analysis of wheat grains were conducted 7 and 14 days after anthesis (DAA). Finally, the improvement effect of application of exogenous glutamate (Glu) on the drought resistance of wheat was validated by hydroponic and field experiments. The results showed that sucrose and soluble sugar contents of XD22 grains were higher than those of XD18 grains under DT. The grain weight and filling rate of both wheat cultivars increased in the early stage of DT but reduced in the late stage. The content of most free amino acids in grains reduced under DT, but the Glu content increased. Regression analysis of grain weight and free amino acid content found that Glu was involved in the responses of wheat to DT and WT. The transcriptomic analysis results showed that XD18-DT7/WT7 and XD22-DT7/WT7 had 161 and 350 differentially expressed genes (DEGs) related to amino acid metabolism, respectively, and XD18-DT14/WT14 and XD22-DT14/WT14 had 380 and 326 DEGs related to amino acid metabolism, respectively. Proteomic analysis results showed that XD18-DT7/WT7 and XD22-DT7/WT7 had 163 and 117 differentially expressed proteins (DEPs） related to amino acid metabolism, respectively, and XD18-DT14/WT14 and XD22-DT14/WT14 had 29 and 109 DEPs related to amino acid metabolism, respectively. Besides, the expression level of most DEPs involved in Glu metabolism (> 95 %) was significantly up-regulated at the early stage of DT. It should be noted that the application of different concentrations of exogenous Glu at seedling stage, heading stage, and flowering stage significantly reduced wheat root/shoot ratio and relative conductivity (RC) under DT, and increased the SPAD value, grain weight, and filling rate. The free amino acids and carbohydrates in wheat grains changed significantly under DT, and a large number of DEPs involved in the Glu metabolism pathway were up-regulated to cope with drought stress. Finally, exogenous Glu application can improve the drought resistance of drought-stressed wheat at seedling and filling stages and increase grain weight.