Glutamine Synthesis Research Articles

GCs-beta and B-arrestins Regulate Nrf2 via NR4As Productive Pathway Mediated by B-adrenergic for Anti-inflammation and Adopting Myocardial and Immune Functions

The nuclear receptors “NR4As” productive pathway is the so important pathways for activating classic estrogen receptors and are important for regulating the adopted cellular anti-inflammatory growth (mediated by glucocorticoids, Nrf2, Ang2-AT2, and VEGF-A synthesis)which considered as the basic for B-arrestins synthesis which adopt B Adrenergic, and Nrf2 synthesis, that Nrf2 is strong activator to ACE functions for promoting Ang2-AT2 and VEGF-A synthesis for running the adopted anti-inflammatory growth and heme oxygenase. The modulation of oxidative stress will be done by serotonin synthesis (regulated by tryptophan “TGG”) which will promote melatonin synthesis which necessary to activate glucocorticoids productions via NR4A2 pathway followed by B-arrestins and Nrf2 productions for activating Ang2-AT2 and VEGF-A productions. That melatonin synthesis will be associated with GTPase production which promote and activate OPA1 repairs and functions, and responsible for activating glutamine synthesis which stabilize Leu functions through Nrf2 functions. This study concluded that NR4As productive pathway are the important pathway for improving anti-oxidation through improving IL6 productivity to IL17 productions, and is important for glucocorticoids-beta synthesis followed by B-arrestins productions which activate B Adrenergic synthesis that are necessary for activating Nrf2 production that followed by activating ACE for Ang2-AT2 and VEGF-A synthesis for running anti-inflammatory growth, modulating antioxidative stress, activate heme oxygenase, modulating brain function and memories growth , and activating T-cells and B-cell functions. That NR4As exert multilevel regulations of brain function and cardiac functions that protect immune survival from vascular cardiac diseases, and are the primary modulator to pro-inflammation and stimulator for variety of active genes and subunits started by estrogen and GCs-beta productions which followed by activating B-arrestins which activate B Adrenergic synthesis which has the roles of activating Nrf2 productions for adopting antioxidative functions, heme oxygenase, vasoconstriction functions, and anti-inflammatory growth mediated by Ang2-AT2 and VEGF-A synthesis.

Transcriptome profiling of genes regulated by phosphate-solubilizing bacteria Bacillus megaterium P68 in potato (Solanum tuberosum L.).

The insoluble phosphorus in the soil is extremely difficult to be absorbed and used directly through the potato root system. Although many studies have reported that phosphorus-solubilizing bacteria (PSB) can promote plant growth and uptake of phosphorus, the molecular mechanism of phosphorus uptake and growth by PSB has not been investigated yet. In the present study, PSB were isolated from rhizosphere soil in soybean. The data of potato yield and quality revealed that the strain P68 was the most effective In the present study, PSB identification, potato field experiment, pot experiment and transcriptome profiling to explored the role of PSB on potato growth and related molecular mechanisms. The results showed that the P68 strain (P68) was identified as Bacillus megaterium by sequencing, with a P-solubilizing ability of 461.86 mg·L-1 after 7-day incubation in National Botanical Research Institute's Phosphate (NBRIP) medium. Compared with the control group (CK), P68 significantly increased the yield of potato commercial tubers by 17.02% and P accumulation by 27.31% in the field. Similarly, pot trials showed that the application of P68 significantly increased the biomass, total phosphorus content of the potato plants, and available phosphorus of the soil up by 32.33, 37.50, and 29.15%, respectively. Furthermore, the transcriptome profiling results of the pot potato roots revealed that the total number of bases was about 6G, and Q30 (%) was 92.35-94.8%. Compared with the CK, there were a total of 784 differential genes (DEGs) regulated when treated with P68, which 439 genes were upregulated and 345 genes were downregulated. Interestingly, most of the DEGs were mainly related to cellular carbohydrate metabolic process, photosynthesis, and cellular carbohydrate biosynthesis process. According to the KEGG pathway analysis, a total of 46 categorical metabolic pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were annotated to 101 DEGs found in potato roots. Compared with the CK, most of the DEGs were mainly enriched in glyoxylate and dicarboxylate metabolism (sot00630), nitrogen metabolism (sot00910), tryptophan metabolism (sot00380), and plant hormone signal transduction (sot04075), and these DEGs might be involved in the interactions between Bacillus megaterium P68 and potato growth. The qRT-PCR analysis of differentially expressed genes showed that inoculated treatments P68 significantly upregulated expression of the phosphate transport, nitrate transport, glutamine synthesis, and abscisic acid regulatory pathways, respectively, and the data from qRT-PCR were consistent with that obtained from RNA-seq. In summary, PSB may be involved in the regulation of nitrogen and phosphorus nutrition, glutaminase synthesis, and abscisic acid-related metabolic pathways. This research would provide a new perspective for studying the molecular mechanism of potato growth promotion by PSB in the level of gene expression and related metabolic pathways in potato roots under the application of Bacillus megaterium P68.

Astrocytes regulate inhibitory neurotransmission through GABA uptake, metabolism, and recycling.

Synaptic regulation of the primary inhibitory neurotransmitter γ-aminobutyric acid (GABA) is essential for brain function. Cerebral GABA homeostasis is tightly regulated through multiple mechanisms and is directly coupled to the metabolic collaboration between neurons and astrocytes. In this essay, we outline and discuss the fundamental roles of astrocytes in regulating synaptic GABA signaling. A major fraction of synaptic GABA is removed from the synapse by astrocytic uptake. Astrocytes utilize GABA as a metabolic substrate to support glutamine synthesis. The astrocyte-derived glutamine is subsequently transferred to neurons where it serves as the primary precursor of neuronal GABA synthesis. The flow of GABA and glutamine between neurons and astrocytes is collectively termed the GABA-glutamine cycle and is essential to sustain GABA synthesis and inhibitory signaling. In certain brain areas, astrocytes are even capable of synthesizing and releasing GABA to modulate inhibitory transmission. The majority of oxidative GABA metabolism in the brain takes place in astrocytes, which also leads to synthesis of the GABA-related metabolite γ-hydroxybutyric acid (GHB). The physiological roles of endogenous GHB remain unclear, but may be related to regulation of tonic inhibition and synaptic plasticity. Disrupted inhibitory signaling and dysfunctional astrocyte GABA handling are implicated in several diseases including epilepsy and Alzheimer's disease. Synaptic GABA homeostasis is under astrocytic control and astrocyte GABA uptake, metabolism, and recycling may therefore serve as relevant targets to ameliorate pathological inhibitory signaling.

Liver Injury and Metabolic Dysregulation in Largemouth Bass (Micropterus salmoides) after Ammonia Exposure.

Elevated environmental ammonia leads to respiratory disorders and metabolic dysfunction in most fish species, and the majority of research has concentrated on fish behavior and gill function. Prior studies have rarely shown the molecular mechanism of the largemouth bass hepatic response to ammonia loading. In this experiment, 120 largemouth bass were exposed to total ammonia nitrogen of 0 mg/L or 13 mg/L for 3 and 7 days, respectively. Histological study indicated that ammonia exposure severely damaged fish liver structure, accompanied by increased serum alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activity. RT-qPCR results showed that ammonia exposure down-regulated the expression of genes involved in glycogen metabolism, tricarboxylic acid cycle, lipid metabolism, and urea cycle pathways, whereas it up-regulated the expression of genes involved in gluconeogenesis and glutamine synthesis pathways. Thus, ammonia was mainly converted to glutamine in the largemouth bass liver during ammonia stress, which was rarely further used for urea synthesis. Additionally, transcriptome results showed that ammonia exposure also led to the up-regulation of the oxidative phosphorylation pathway and down-regulation of the mitogen-activated protein kinase signaling pathway in the liver of largemouth bass. It is possible that the energy supply of oxidative phosphorylation in the largemouth bass liver was increased during ammonia exposure, which was mediated by the MAPK signaling pathway.

MYC/Glutamine Dependency Is a Therapeutic Vulnerability in Pancreatic Cancer with Deoxycytidine Kinase Inactivation-Induced Gemcitabine Resistance.

Our study revealed the key pathways involved in gemcitabine resistance in PDAC, thus providing potential therapeutic strategies.

In organello real-time NMR metabolomics of mitochondria: An S. cerevisiae model of Barth syndrome displays perturbed metabolism.

Mitochondria are central to cellular metabolism, generating more than 90% of the ATP energy currency of the cell. Dysfunction of mitochondria occurs in a number of diseases including cancer, cardiopathy, and neurodegeneration, as well as heritable mitochondrial diseases such as Barth syndrome (BTHS). BTHS is caused by faulty cardiolipin (CL) remodeling, wherein mutations of the transacylase Tafazzin result in a defective enzyme and a build-up of the precursor, monolysocardiolipin. The aim of this study is to investigate how defects in CL remodeling affect the tricarboxylic acid (TCA) cycle. The rationale, is that CL – the hallmark lipid of mitochondria, is crucial for proper cristae morphology and mitochondrial bioenergetic function. Since enzymes in the TCA cycle are membrane-bound, altered lipid content could perturb mitochondrial membranes, and hence the activities of enzymes involved in metabolism. We used real-time 1H-13C HSQC NMR to characterize the fate of 13C-pyruvate in mitochondria isolated from S. cerevisiae. We compared wild-type (WT) mitochondria with ∆taz1 - a knockout that models BTHS, and ∆crd1 – a CL remodeling mutant that lacks CL completely. Following uptake of 13C-pyruvate, fifteen new 13C-labeld metabolites could be identified in the mitochondria over the course of ∼2 h. While many metabolites showed similar kinetics between the three strains, levels of mevalonate - a precursor in cholesterol synthesis, appears to be elevated in ∆taz1. Synthesis of glutamine showed large differences between all three strains. Overall, the turnover of pyruvate, appeared more sluggish in the CL remodeling mutants compared to WT. The studies demonstrate that proper CL remodeling is required for optimal TCA cycle activity, and may shed light on the etiology of BTHS, as well as point the way to therapeutic interventions.

Glutamine synthetase limits β-catenin-mutated liver cancer growth by maintaining nitrogen homeostasis and suppressing mTORC1.

Glutamine synthetase (GS) catalyzes de novo synthesis of glutamine that facilitates cancer cell growth. In the liver, GS functions next to the urea cycle to remove ammonia waste. As a dysregulated urea cycle is implicated in cancer development, the impact of GS's ammonia clearance function has not been explored in cancer. Here, we show that oncogenic activation of β-catenin (encoded by CTNNB1) led to a decreased urea cycle and elevated ammonia waste burden. While β-catenin induced the expression of GS, which is thought to be cancer promoting, surprisingly, genetic ablation of hepatic GS accelerated the onset of liver tumors in several mouse models that involved β-catenin activation. Mechanistically, GS ablation exacerbated hyperammonemia and facilitated the production of glutamate-derived nonessential amino acids, which subsequently stimulated mechanistic target of rapamycin complex 1 (mTORC1). Pharmacological and genetic inhibition of mTORC1 and glutamic transaminases suppressed tumorigenesis facilitated by GS ablation. While patients with hepatocellular carcinoma, especially those with CTNNB1 mutations, have an overall defective urea cycle and increased expression of GS, there exists a subset of patients with low GS expression that is associated with mTORC1 hyperactivation. Therefore, GS-mediated ammonia clearance serves as a tumor-suppressing mechanism in livers that harbor β-catenin activation mutations and a compromised urea cycle.

Potential inhibitors of FemC to combat Staphylococcus aureus: virtual screening, molecular docking, dynamics simulation, and MM-PBSA analysis

FemC is a methicillin resistance factor involved in the alterations of peptidoglycan and glutamine synthesis in Staphylococcus aureus. To identify the potent antibacterial agents, antibacterial molecules were screened against the predicted and validated FemC model. Based on docking scores, presence of essential interactions with active site residues of FemC, pharmacokinetic, and ADMET properties, six candidates were shortlisted and subjected to molecular dynamics to evaluate the stability of FemC-ligand complexes. Further, per residue decomposition analysis and Molecular Mechanics/Poisson-Boltzmann Surface Area (MMPBSA) analysis confirmed that S15, M16, S17, R31, R43, Q47, K48 and R49 of FemC played a vital role in the formation of lower energy stable FemC-inhibitor(s) complexes. Therefore, in the present study, the reported six molecules (Z317461228, Z92241701, Z30923155, Z30202349, Z2609517102 and Z92470167) may pave the path to design the scaffold of novel potent antimicrobials against S. aureus. Communicated by Ramaswamy H. Sarma

New progress of glutamine metabolism in the occurrence, development, and treatment of ovarian cancer from mechanism to clinic.

Glutamine is a non-essential amino acid that can be synthesized by cells. It plays a vital role in the growth and proliferation of mammalian cells cultured in vitro. In the process of tumor cell proliferation, glutamine not only contributes to protein synthesis but also serves as the primary nitrogen donor for purine and pyrimidine synthesis. Studies have shown that glutamine-addicted tumor cells depend on glutamine for survival and reprogram glutamine utilization through the Krebs cycle. Potential therapeutic approaches for ovarian cancer including blocking the entry of glutamine into the tricarboxylic acid cycle in highly aggressive ovarian cancer cells or inhibiting glutamine synthesis in less aggressive ovarian cancer cells. Glutamine metabolism is associated with poor prognosis of ovarian cancer. Combining platinum-based chemotherapy with inhibition of glutamine metabolic pathways may be a new strategy for treating ovarian cancer, especially drug-resistant ovarian cancer. This article reviews the role of glutamine metabolism in the biological behaviors of ovarian cancer cells, such as proliferation, invasion, and drug resistance. Its potential use as a new target or biomarker for ovarian cancer diagnosis, treatment, and the prognosis is investigated.

Progress in the Preclinical and Clinical Study of Resveratrol for Vascular Metabolic Disease.

Vascular metabolic dysfunction presents in various diseases, such as atherosclerosis, hypertension, and diabetes mellitus. Due to the high prevalence of these diseases, it is important to explore treatment strategies to protect vascular function. Resveratrol (RSV), a natural polyphenolic phytochemical, is regarded as an agent to regulate metabolic pathways. Many studies have proven that RSV has beneficial effects on improving metabolism in endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), which provide new directions to treat vascular metabolic diseases. Herein, we overviewed that RSV could regulate cell metabolism activity by inhibiting glucose uptake, suppressing glycolysis, preventing cells from fatty acid-related damages, reducing lipogenesis, increasing fatty acid oxidation, enhancing lipolysis, elevating uptake and synthesis of glutamine, and increasing NO release. Furthermore, in clinical trials, although the results from different studies remain controversial, we proposed that RSV had better therapeutic effects at high concentrations and for patients with metabolic disorders.

Glial Glutamine Homeostasis in Health and Disease.

Glutamine is an essential cerebral metabolite. Several critical brain processes are directly linked to glutamine, including ammonia homeostasis, energy metabolism and neurotransmitter recycling. Astrocytes synthesize and release large quantities of glutamine, which is taken up by neurons to replenish the glutamate and GABA neurotransmitter pools. Astrocyte glutamine hereby sustains the glutamate/GABA-glutamine cycle, synaptic transmission and general brain function. Cerebral glutamine homeostasis is linked to the metabolic coupling of neurons and astrocytes, and relies on multiple cellular processes, including TCA cycle function, synaptic transmission and neurotransmitter uptake. Dysregulations of processes related to glutamine homeostasis are associated with several neurological diseases and may mediate excitotoxicity and neurodegeneration. In particular, diminished astrocyte glutamine synthesis is a common neuropathological component, depriving neurons of an essential metabolic substrate and precursor for neurotransmitter synthesis, hereby leading to synaptic dysfunction. While astrocyte glutamine synthesis is quantitatively dominant in the brain, oligodendrocyte-derived glutamine may serve important functions in white matter structures. In this review, the crucial roles of glial glutamine homeostasis in the healthy and diseased brain are discussed. First, we provide an overview of cellular recycling, transport, synthesis and metabolism of glutamine in the brain. These cellular aspects are subsequently discussed in relation to pathological glutamine homeostasis of hepatic encephalopathy, epilepsy, Alzheimer's disease, Huntington's disease and amyotrophic lateral sclerosis. Further studies on the multifaceted roles of cerebral glutamine will not only increase our understanding of the metabolic collaboration between brain cells, but may also aid to reveal much needed therapeutic targets of several neurological pathologies.

Thioredoxins regulate the metabolic fluxes throughout the tricarboxylic acid cycle and associated pathways in a light-independent manner

The metabolic fluxes throughout the tricarboxylic acid cycle (TCAC) are inhibited in the light by the mitochondrial thioredoxin (TRX) system. However, it is unclear how this system orchestrates the fluxes throughout the TCAC and associated pathways in the dark. Here we carried out a13C–HCO3 labelling experiment in Arabidopsis leaves from wild type (WT) and mutants lacking TRX o1 (trxo1), TRX h2 (trxh2), or both NADPH-dependent TRX reductase A and B (ntra ntrb) exposed to 0, 30 and 60 min of dark or light conditions. No 13C-enrichment in TCAC metabolites in illuminated WT leaves was observed. However, increased succinate content was found in parallel to reductions in Ala in the light, suggesting the latter operates as an alternative carbon source for succinate synthesis. By contrast to WT, all mutants showed substantial changes in the content and 13C-enrichment in TCAC metabolites under both dark and light conditions. Increased 13C-enrichment in glutamine in illuminated trxo1 leaves was also observed, strengthening the idea that TRX o1 restricts in vivo carbon fluxes from glycolysis and the TCAC to glutamine. We further demonstrated that both photosynthetic and gluconeogenic fluxes toward glucose are increased in trxo1 and that the phosphoenolpyruvate carboxylase (PEPc)-mediated 13C-incorporation into malate is higher in trxh2 mutants, as compared to WT. Our results collectively provide evidence that TRX h2 and the mitochondrial NTR/TRX system regulate the metabolic fluxes throughout the TCAC and associated pathways, including glycolysis, gluconeogenesis and the synthesis of glutamine in a light-independent manner.

Astrocyte energy and neurotransmitter metabolism in Alzheimer's disease: Integration of the glutamate/GABA-glutamine cycle.

Astrocytes contribute to the complex cellular pathology of Alzheimer's disease (AD). Neurons and astrocytes function in close collaboration through neurotransmitter recycling, collectively known as the glutamate/GABA-glutamine cycle, which is essential to sustain neurotransmission. Neurotransmitter recycling is intimately linked to astrocyte energy metabolism. In the course of AD, astrocytes undergo extensive metabolic remodeling, which may profoundly affect the glutamate/GABA-glutamine cycle. The consequences of altered astrocyte function and metabolism in relation to neurotransmitter recycling are yet to be comprehended. Metabolic alterations of astrocytes in AD deprive neurons of metabolic support, thereby contributing to synaptic dysfunction and neurodegeneration. In addition, several astrocyte-specific components of the glutamate/GABA-glutamine cycle, including glutamine synthesis and synaptic neurotransmitter uptake, are perturbed in AD. Integration of the complex astrocyte biology within the context of AD is essential for understanding the fundamental mechanisms of the disease, while restoring astrocyte metabolism may serve as an approach to arrest or even revert clinical progression of AD.

FMRP-related retinal phenotypes: Evidence of glutamate-glutamine metabolic cycle impairment

FMRP, the fragile X mental retardation protein coded by the FMR1 gene, is an RNA-binding protein that assists transport, stabilization and translational regulation of specific synaptic mRNAs. Its expression has been found in multiple cell types of central nervous system (CNS) including glial cells where its involvement in glutamate neurotransmitter homeostasis have been shown. Indeed, glutamate homeostasis deficit has been observed in absence of FMRP in-vivo in cortex and hippocampus structures as well as in vitro on astroglial cell culture. Interestingly, the retina which is an extension of the CNS is presenting electrophysiological alterations in absence of FMRP in both human and murine models suggesting neurotransmitter impairments. Therefore, we investigate the consequences of Fmrp absence on Glutamate-Glutamine cycle in whole retinas and primary retinal Müller cells culture which are the main glial cells of the retina. Using the Fmr1-/y mice, we have shown in vivo and in vitro that the absence of Fmrp in Müller cells is characterized by loss of Glutamate-Glutamine cycle homeostasis due to a lower Glutamine Synthetase protein expression and activity. The lack of Fmrp in the retina induces a reduced flow of glutamine synthesis. Our data established for the first time in literature a direct link between the lack of Fmrp and neurotransmitter homeostasis in the retina.

Intestinal Klebsiella pneumoniae Contributes to Pneumonia by Synthesizing Glutamine in Multiple Myeloma.

Simple SummaryMultiple myeloma (MM) is characterized by the presence of systemic clinical manifestations. Among them, pneumonia accounts for a significant cause of morbidity and mortality, highlighting an urgent need to explore possible susceptibility and potential mechanisms of pneumonia in MM. Recently, the gut–lung axis has emphasized the relevance of gut microbiota and pneumonia, indicating that the compromised function of gut microbiota may be susceptible to pneumonia. It has been previously shown that intestinal Klebsiella pneumonia enriches in MM patients and promotes MM progression in our previous work. In addition, host metabolism has been identified as a key regulator of MM. However, what role the altered gut microbiota plays in MM with pneumonia remains unknown. In this study, we explored the association between gut microbiota and MM with pneumonia. This is the first study to identify and elucidate the function of gut microbiota involved in MM with pneumonia.Pneumonia accounts for a significant cause of morbidity and mortality in multiple myeloma (MM) patients. It has been previously shown that intestinal Klebsiella pneumonia (K. pneumonia) enriches in MM and promotes MM progression. However, what role the altered gut microbiota plays in MM with pneumonia remains unknown. Here, we show that intestinal K. pneumonia is significantly enriched in MM with pneumonia. This enriched intestinal K. pneumonia links to the incidence of pneumonia in MM, and intestinal colonization of K. pneumonia contributes to pneumonia in a 5TGM1 MM mice model. Further targeted metabolomic assays reveal the elevated level of glutamine, which is consistently increased with the enrichment of K. pneumonia in MM mice and patients, is synthesized by K. pneumonia, and leads to the elevated secretion of TNF-α in the lung normal fibroblast cells for the higher incidence of pneumonia. Inhibiting glutamine synthesis by establishing glnA-mutated K. pneumonia alleviates the incidence of pneumonia in the 5TGM1 MM mice model. Overall, our work proposes that intestinal K. pneumonia indirectly contributes to pneumonia in MM by synthesizing glutamine. Altogether, we unveil a gut–lung axis in MM with pneumonia and establish a novel mechanism and a possible intervention strategy for MM with pneumonia.

Hypoxia-triggered O-GlcNAcylation in the brain drives the glutamate–glutamine cycle and reduces sensitivity to sevoflurane in mice

BackgroundHypersensitivity to general anaesthetics predicts adverse postoperative outcomes in patients. Hypoxia exerts extensive pathophysiological effects on the brain; however, whether hypoxia influences sevoflurane sensitivity and its underlying mechanisms remain poorly understood. MethodsMice were acclimated to hypoxia (oxygen 10% for 8 h day−1) for 28 days and anaesthetised with sevoflurane; the effective concentrations for 50% of the animals (EC50) showing loss of righting reflex (LORR) and loss of tail-pinch withdrawal response (LTWR) were determined. Positron emission tomography–computed tomography, O-glycoproteomics, seahorse analysis, carbon-13 tracing, site-specific mutagenesis, and electrophysiological techniques were performed to explore the underlying mechanisms. ResultsCompared with the control group, the hypoxia-acclimated mice required higher concentrations of sevoflurane to present LORR and LTWR (EC50LORR: 1.61 [0.03]% vs 1.46 [0.04]%, P<0.01; EC50LTWR: 2.46 [0.14]% vs 2.22 [0.06]%, P<0.01). Hypoxia-induced reduction in sevoflurane sensitivity was correlated with elevation of protein O-linked N-acetylglucosamine (O-GlcNAc) modification in brain, especially in the thalamus, and could be abolished by 6-diazo-5-oxo-l-norleucine, a glutamine fructose-6-phosphate amidotransferase inhibitor, and mimicked by thiamet-G, a selective O-GlcNAcase inhibitor. Mechanistically, O-GlcNAcylation drives de novo synthesis of glutamine from glucose in astrocytes and promotes the glutamate–glutamine cycle, partially via glycolytic flux and activation of glutamine synthetase. ConclusionsIntermittent hypoxia exposure decreased mouse sensitivity to sevoflurane anaesthesia through enhanced O-GlcNAc-dependent modulation of the glutamate–glutamine cycle in the brain.

Intravenous branched-chain amino-acid-free solution for the treatment of metabolic decompensation episodes in Spanish pediatric patients with maple syrup urine disease.

BackgroundMetabolic decompensation episodes (DEs) in Maple Syrup urine disease (MSUD) result in brain accumulation of toxic branched-chain amino acids (BCAAs) and their respective branched-chain α-keto acids that could induce neuroinflammation, disturb brain bioenergetics, and alter glutamate and glutamine synthesis. These episodes require immediate intervention to prevent irreversible neurological damage. Intravenous (IV) administration of BCAA-free solution could represent a powerful alternative for emergency treatment of decompensations.MethodsThis pediatric series discusses the management of DEs in MSUD patients with IV BCAA-free solution, as an emergency treatment for DEs or as a prophylactic in cases requiring surgery. Clinical evolution, amino acid profile and adverse effects were evaluated.ResultsWe evaluated the use of BCAA-free solution in 5 DEs in 5 MSUD pediatric patients, all with significantly elevated plasma leucine levels at admission (699–3296 μmol/L) and in 1 episode of risk of DE due to surgery. Leucine normalization was achieved in all cases with resolution or improvement of clinical symptoms following IV BCAA-free solution. The duration of administration ranged from 3–20 days. Administration of IV BCAA-free solution at the beginning of a DE could reverse depletion of the amino acids that compete with BCAAs for the LAT1 transporter, and the observed depletion of alanine, despite IV alanine supplementation. No related adverse events were observed.ConclusionsAdministration of standardized IV BCAA-free solution in emergency settings constitutes an important and safe alternative for the treatment of DEs in MSUD, especially in pediatric patients for whom oral or enteral treatment is not viable.

Investigating the role of GLUL as a survival factor in cellular adaptation to glutamine depletion via targeted stable isotope resolved metabolomics.

Cellular glutamine synthesis is thought to be an important resistance factor in protecting cells from nutrient deprivation and may also contribute to drug resistance. The application of ‟targeted stable isotope resolved metabolomics” allowed to directly measure the activity of glutamine synthetase in the cell. With the help of this method, the fate of glutamine derived nitrogen within the biochemical network of the cells was traced. The application of stable isotope labelled substrates and analyses of isotope enrichment in metabolic intermediates allows the determination of metabolic activity and flux in biological systems. In our study we used stable isotope labelled substrates of glutamine synthetase to demonstrate its role in the starvation response of cancer cells. We applied 13C labelled glutamate and 15N labelled ammonium and determined the enrichment of both isotopes in glutamine and nucleotide species. Our results show that the metabolic compensatory pathways to overcome glutamine depletion depend on the ability to synthesise glutamine via glutamine synthetase. We demonstrate that the application of dual-isotope tracing can be used to address specific reactions within the biochemical network directly. Our study highlights the potential of concurrent isotope tracing methods in medical research.

Molecular Characterization and Nutrition Regulation of the Glutamine Synthetase Gene in Triploid Crucian Carp

Glutamine synthetase (GS) is a key enzyme that catalyzes the synthesis of glutamine from glutamate, which plays a role in the promotion of muscle cell growth and in improving the flavor of meats. In this study, a GS gene encoding 371 amino acids was cloned from triploid crucian carp and showed the highest level of similarity with the GS gene found in Cyprinus carpio. Meanwhile, GS was differentially expressed in different tissues, and its day–night expression changes showed obvious oscillation. Additionally, the effects of glutamate and glutamine on GS expression in muscle cells were investigated in vitro and in vivo. We found that its expression was obviously increased due to high levels of glutamate (2 mg/mL) but decreased by glutamine in vitro. However, it was significantly promoted by glutamate and glutamine in vivo, with an optimal concentration of 2%. Furthermore, the use of lysine–glutamate dipeptides as feed additives also had a positive influence on GS expression (the optimal concentration is 0.8%). Finally, we explored the effects of different protein levels and sources on the expression of GS, and the results demonstrated that GS had the highest expression at the 35% protein level, but no significant differences were observed in the different protein sources between the fish meal diet (FM) and the mixed diet comprising soybean meal and rapeseed meal (SM). This study sheds new light on the regulation of GS in teleost fish and provides new perceptions and strategies for the formulation of high-quality feed for triploid crucian carp.

First description of a clinical glutamine-dependent Escherichia coli with a missense mutation in the glnA

IntroductionSmall-colony variants (SCVs) of bacteria are subpopulations with a small colony size, low growth rate, and atypical colony morphology. The purpose of this study was to comprehensively elucidate the characteristics and underlying mechanism of the development of a glutamine-dependent SCV of E. coli, GU-92SCV, isolated from the blood of a patient with pyelonephritis. MethodsThe GU-92SCV strain was tested for auxotrophy testing for glutamine. DNA mutations in genes related to glutamine synthesis were analysed by sequencing. The isolate's proliferation and antimicrobial susceptibility in Mueller-Hinton II medium supplemented with glutamine were examined. ResultsThe colony of the GU-92SCV strain did not grow on Mueller-Hinton II agar, but growth around the filter paper containing l-glutamine was enhanced on Mueller-Hinton II agar. The GU-92SCV strain had a single nucleotide substitution in glnA, c.193G>A, corresponding to p.Asp65Asn. Changing c.193G>A to the wild-type sequence in glnA restored these phenotypes. Because GU-92SCV did not grow in Mueller-Hinton II broth, antimicrobial susceptibility test results were not obtained; however, in the presence of 10 mg mL−1l-glutamine, the results were consistent with those of the revertant strain GU-92REV. ConclusionTo the best of our knowledge, this is the first clinical isolation of a glutamine-dependent E. coli SCV from a patient blood culture. Our data showed that glnA was important for the growth of E. coli in Mueller-Hinton II medium, which also required the presence of glutamine when performing antimicrobial susceptibility testing for glutamine-dependent SCV strains.