IDH2 and GLUD1 depletion arrests embryonic development through an H4K20me3 epigenetic barrier in porcine parthenogenetic embryos.

Isocitrate dehydrogenase 2 (IDH2) and glutamate dehydrogenase 1 (GLUD1) are key enzymes involved in the production of α-ketoglutarate (α-KG), a metabolite central to the tricarboxylic acid cycle and glutamine metabolism. In this study, we investigated the impact of IDH2 and GLUD1 on early porcine embryonic development following IDH2 and GLUD1 knockdown (KD) via double-stranded RNA (dsRNA) microinjection. Results showed that KD reduced α-KG levels, leading to delayed embryonic development, decreased blastocyst formation, increased apoptosis, reduced blastomere proliferation, and pluripotency. Additionally, IDH2 and GLUD1 KD induced abnormally high levels of trimethylation of lysine 20 of histone H4 (H4K20me3) at the 4-cell stage, likely resulting in transcriptional repression of embryonic genome activation (EGA)-related genes. Notably, KD of lysine methyltransferase 5C ( KMT5C) and supplementation with exogenous α-KG reduced H4K20me3 expression and partially rescued these defects, suggesting a critical role of IDH2 and GLUD1 in the epigenetic regulation and proper development of porcine embryos. Overall, this study highlights the significance of IDH2 and GLUD1 in maintaining normal embryonic development through their influence on α-KG production and subsequent epigenetic modifications.

Energy metabolism-related GLUD1 contributes to favorable clinical outcomes of IDH-mutant glioma.

BACKGROUND: Glioma is the most common brain tumor. IDH mutations occur frequently in glioma, indicating a more favorable prognosis. We aimed to explore energy metabolism-related genes in glioma to promote the research and treatment. METHODS: Datasets were obtained from TCGA and GEO databases. Candidate genes were screened by differential gene expression analysis, then functional enrichment analysis was conducted on the candidate genes. PPI was also carried out to help determine the target gene. GSEA and DO analysis were conducted in the different expression level groups of the target gene. Survival analysis and immune cell infiltrating analysis were performed as well. RESULTS: We screened 34 candidate genes and selected GLUD1 as the target gene. All candidate genes were significantly enriched in 10 KEGG pathways and 330 GO terms. GLUD1 expression was higher in IDH-mutant samples than IDH-wildtype samples, and higher in normal samples than tumor samples. Low GLUD1 expression was related to poor prognosis according to survival analysis. Most types of immune cells were negatively related to GLUD1 expression, but monocytes and activated mast cells exhibited significantly positive correlation with GLUD1 expression. GLUD1 expression was significantly related to 119 drugs and 6 immune checkpoint genes. GLUD1 was able to serve as an independent prognostic indicator of IDH-mutant glioma. CONCLUSION: In this study, we identified an energy metabolism-related gene GLUD1 potentially contributing to favorable clinical outcomes of IDH-mutant glioma. In glioma, GLUD1 related clinical outcomes and immune landscape were clearer, and more valuable information was provided for immunotherapy.

GLUD1 determines murine muscle stem cell fate by controlling mitochondrial glutamate levels.

Muscle stem cells (MuSCs) enable muscle growth and regeneration after exercise or injury, but how metabolism controls their regenerative potential is poorly understood. We describe that primary metabolic changes can determine murine MuSC fate decisions. We found that glutamine anaplerosis into the tricarboxylic acid (TCA) cycle decreases during MuSC differentiation and coincides with decreased expression of the mitochondrial glutamate deaminase GLUD1. Deletion of Glud1 in proliferating MuSCs resulted in precocious differentiation and fusion, combined with loss of self-renewal in vitro and in vivo. Mechanistically, deleting Glud1 caused mitochondrial glutamate accumulation and inhibited the malate-aspartate shuttle (MAS). The resulting defect in transporting NADH-reducing equivalents into the mitochondria induced compartment-specific NAD+/NADH ratio shifts. MAS activity restoration or directly altering NAD+/NADH ratios normalized myogenesis. In conclusion, GLUD1 prevents deleterious mitochondrial glutamate accumulation and inactivation of the MAS in proliferating MuSCs. It thereby acts as a compartment-specific metabolic brake on MuSC differentiation.

Evolution of Glutamate Metabolism via GLUD2 Enhances Lactate-Dependent Synaptic Plasticity and Complex Cognition.

Human evolution is characterized by rapid brain enlargement and the emergence of unique cognitive abilities. Besides its distinctive cytoarchitectural organization and extensive inter-neuronal connectivity, the human brain is also defined by high rates of synaptic, mainly glutamatergic, transmission, and energy utilization. While these adaptations' origins remain elusive, evolutionary changes occurred in synaptic glutamate metabolism in the common ancestor of humans and apes via the emergence of GLUD2, a gene encoding the human glutamate dehydrogenase 2 (hGDH2) isoenzyme. Driven by positive selection, hGDH2 became adapted to function upon intense excitatory firing, a process central to the long-term strengthening of synaptic connections. It also gained expression in brain astrocytes and cortical pyramidal neurons, including the CA1-CA3 hippocampal cells, neurons crucial to cognition. In mice transgenic for GLUD2, theta-burst-evoked long-term potentiation (LTP) is markedly enhanced in hippocampal CA3-CA1 synapses, with patch-clamp recordings from CA1 pyramidal neurons revealing increased sNMDA receptor currents. D-lactate blocked LTP enhancement, implying that glutamate metabolism via hGDH2 potentiates L-lactate-dependent glia-neuron interaction, a process essential to memory consolidation. The transgenic (Tg) mice exhibited increased dendritic spine density/synaptogenesis in the hippocampus and improved complex cognitive functions. Hence, enhancement of neuron-glia communication, via GLUD2 evolution, likely contributed to human cognitive advancement by potentiating synaptic plasticity and inter-neuronal connectivity.

Inhibition of GLUD1 mediated by LASP1 and SYVN1 contributes to hepatitis B virus X protein-induced hepatocarcinogenesis.

Glutamate dehydrogenase 1 (GLUD1) is implicated in oncogenesis. However, little is known about the relationship between GLUD1 and hepatocellular carcinoma (HCC). In the present study, we demonstrated that the expression levels of GLUD1 significantly decreased in tumors, which was relevant to the poor prognosis of HCC. Functionally, GLUD1 silencing enhanced the growth and migration of HCC cells. Mechanistically, the upregulation of interleukin-32 through AKT activation contributes to GLUD1 silencing-facilitated hepatocarcinogenesis. The interaction between GLUD1 and AKT, as well as α-ketoglutarate regulated by GLUD1, can suppress AKT activation. In addition, LIM and SH3 protein 1 (LASP1) interacts with GLUD1 and induces GLUD1 degradation via the ubiquitin-proteasome pathway, which relies on the E3 ubiquitin ligase synoviolin (SYVN1), whose interaction with GLUD1 is enhanced by LASP1. In hepatitis B virus (HBV)-related HCC, the HBV X protein (HBX) can suppress GLUD1 with the participation of LASP1 and SYVN1. Collectively, our data suggest that GLUD1 silencing is significantly associated with HCC development, and LASP1 and SYVN1 mediate the inhibition of GLUD1 in HCC, especially in HBV-related tumors.

Evolutionary Changes in Primate Glutamate Dehydrogenases 1 and 2 Influence the Protein Regulation by Ligands, Targeting and Posttranslational Modifications.

There are two paralogs of glutamate dehydrogenase (GDH) in humans encoded by the GLUD1 and GLUD2 genes as a result of a recent retroposition during the evolution of primates. The two human GDHs possess significantly different regulation by allosteric ligands, which is not fully characterized at the structural level. Recent advances in identification of the GDH ligand binding sites provide a deeper perspective on the significance of the accumulated substitutions within the two GDH paralogs. In this review, we describe the evolution of GLUD1 and GLUD2 after the duplication event in primates using the accumulated sequencing and structural data. A new gibbon GLUD2 sequence questions the indispensability of ancestral R496S and G509A mutations for GLUD2 irresponsiveness to GTP, providing an alternative with potentially similar regulatory features. The data of both GLUD1 and GLUD2 evolution not only confirm substitutions enhancing GLUD2 mitochondrial targeting, but also reveal a conserved mutation in ape GLUD1 mitochondrial targeting sequence that likely reduces its transport to mitochondria. Moreover, the information of GDH interactors, posttranslational modification and subcellular localization are provided for better understanding of the GDH mutations. Medically significant point mutations causing deregulation of GDH are considered from the structural and regulatory point of view.

Bioinformatics analysis identifies GLUD1 as a prognostic indicator for clear cell renal cell carcinoma.

BACKGROUND: Renal cell carcinoma (RCC) is a common primary tumor of the kidney and is divided into three major subtypes, of which clear cell renal cell carcinoma (ccRCC) has the highest incidence. Glutamate dehydrogenase 1 (GLUD1) encodes glutamate dehydrogenase 1, which catalyzes the oxidative deamination of glutamate. METHODS: We analyzed TCGA data using R language software and used multiple online databases to explore the relationship of GLUD1 with signaling pathways and drug sensitivity as well as GLUD1 protein expression and methylation. RESULTS: The results showed that GLUD1 mRNA expression was reduced in tumor tissues and correlated with the progression of ccRCC. Univariate and multivariate Cox analysis showed that GLUD1 could be used as a prognostic marker for ccRCC. GLUD1 expression in ccRCC was associated with immune cells infiltration and multiple classical signaling pathways. In addition, GLUD1 mRNA expression was related to drug sensitivity. CONCLUSIONS: These findings provide new ideas for finding new prognostic molecular markers and therapeutic targets for ccRCC.

GLUD1 inhibits hepatocellular carcinoma progression via ROS-mediated p38/JNK MAPK pathway activation and mitochondrial apoptosis.

Glutamate dehydrogenase 1 (GLUD1) is an important enzyme in glutamine metabolism. Previously, we found GLUD1 was down-regulated in tumor tissues of hepatocellular carcinoma (HCC) patients by proteomics study. To explore its role in the progression of HCC, the expressional level of GLUD1 was firstly examined and presented as that both the protein and mRNA levels were down-regulated in tumor tissues compared to the normal liver tissues. GLUD1 overexpression significantly inhibited HCC cells proliferation, migration, invasion and tumor growth both in vitro and in vivo, while GLUD1 knocking-down promoted HCC progression. Metabolomics study of GLUD1 overexpressing and control HCC cells showed that 129 differentially expressed metabolites were identified, which mainly included amino acids, bases, and phospholipids. Moreover, metabolites in mitochondrial oxidative phosphorylation system (OXPHOS) were differentially expressed in GLUD1 overexpressing cells. Mechanistic studies showed that GLUD1 overexpression enhanced mitochondrial respiration activity and reactive oxygen species (ROS) production. Excessive ROS lead to mitochondrial apoptosis that was characterized by increased expression levels of p53, Cytochrome C, Bax, Caspase 3 and decreased expression level of Bcl-2. Furthermore, we found that the p38/JNK MAPK pathway was activated in GLUD1 overexpressing cells. N-acetylcysteine (NAC) treatment eliminated cellular ROS and blocked p38/JNK MAPK pathway activation, as well as cell apoptosis induced by GLUD1 overexpression. Taken together, our findings suggest that GLUD1 inhibits HCC progression through regulating cellular metabolism and oxidative stress state, and provide that ROS generation and p38/JNK MAPK pathway activation as promising methods for HCC treatment.

Circular RNA Dipeptidyl Peptidase 4 (circDPP4) Stimulates the Expression of Glutamate Dehydrogenase 1 to Contribute to the Malignant Phenotypes of Prostate Cancer by Sponging miR-497-5p.

Circular RNA dipeptidyl peptidase 4 (circDPP4) has been confirmed as a novel oncogene in prostate cancer (PCa). In this study, we aimed to explore the underlying mechanism of circDPP4 in PCa progression. Levels of circDPP4, microRNA (miR)-497-5p, glutamate dehydrogenase 1 (GLUD1), proliferating cell nuclear antigen (PCNA), BCL2 associated X, apoptosis regulator (Bax), E-cadherin and Ki67 were gauged by a quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, or immunohistochemical method. We assessed the roles of variables in PCa cell phenotypes by measuring cell growth, apoptosis, motility and invasiveness. We performed RNA immunoprecipitation (RIP) and dual-luciferase reporter assays to confirm the interactions of circDPP4/miR-497-5p and miR-497-5p/GLUD1. A xenograft model was established to gauge the effect of circDPP4 in the tumorigenicity of PCa cells. PCa tumor tissues and cell lines revealed higher levels of circDPP4 and GLUD1 and a lower expression of miR-497-5p than controls. CircDPP4 silencing hindered the growth, motility and invasiveness of PCa cells. Conversely, silencing circDPP4 enhanced PCa cell apoptosis. Mechanistic analysis showed that circDPP4 functioned as a miR-497-5p sponge to reduce the suppressive action of miR-497-5p on GLUD1, which was validated as a direct miR-497-5p target. Furthermore, circDPP4 knockdown weakened the tumorigenicity of PCa cells. CircDPP4 facilitated PCa process by mediating the miR-497-5p/GLUD1 axis, providing a possible therapy target for PCa.

Intravenous recombinant cerebellin 1 treatment restores signalling by spinal glutamate delta 1 receptors and mitigates chronic pain.

BACKGROUND AND PURPOSE: Chronic pain remains a major clinical problem that needs effective therapeutic agents. Glutamate delta 1 (GluD1) receptors and the protein cerebellin 1 (Cbln1) are down-regulated in the central amygdala (CeA) in models of inflammatory and neuropathic pain. One treatment with Cbln1, intracerebroventricularly (ICV) or in CeA, normalized GluD1 and reduced AMPA receptor expression, resulting in lasting (7-10 days) pain relief. Unlike many CNS-targeting biological agents, the structure of Cbln1 suggests potential blood-brain barrier penetration. Here, we have tested whether systemic administration of Cbln1 provides analgesic effects via action in the CNS. EXPERIMENTAL APPROACH: Analgesic effects of intravenous recombinant Cbln1 was assessed in complete Freund's adjuvant inflammatory pain model in mice. GluD1 knockout and a mutant form of Cbln1 were used. KEY RESULTS: A single intravenous injection of Cbln1 mitigated nocifensive and averse behaviour in both inflammatory and neuropathic pain models. This effect of Cbln1 was dependent on GluD1 receptors and required binding to the amino terminal domain of GluD1. Time course of analgesic effect was similar to previously reported ICV and intra-CeA injection. GluD1 in both spinal cord and CeA was down -regulated in the inflammatory pain model, whereas GluD1 expression in spinal cord but not in CeA, was partly normalized by intravenous Cbln1. Importantly, recombinant Cbln1 was detected in the synaptoneurosomes in spinal cord but not in the CeA. CONCLUSIONS AND IMPLICATIONS: Our results describe a novel mechanism by which systemic Cbln1 induces analgesia potentially by central actions involving normalization of signalling by spinal cord GluD1 receptors.

Clinical features, functional consequences, and rescue pharmacology of missense GRID1 and GRID2 human variants.

GRID1 and GRID2 encode the enigmatic GluD1 and GluD2 proteins, which form tetrameric receptors that play important roles in synapse organization and development of the central nervous system. Variation in these genes has been implicated in neurodevelopmental phenotypes. We evaluated GRID1 and GRID2 human variants from the literature, ClinVar, and clinical laboratories and found that many of these variants reside in intolerant domains, including the amino terminal domain of both GRID1 and GRID2. Other conserved regions, such as the M3 transmembrane domain, show different intolerance between GRID1 and GRID2. We introduced these variants into GluD1 and GluD2 cDNA and performed electrophysiological and biochemical assays to investigate the mechanisms of dysfunction of GRID1/2 variants. One variant in the GRID1 distal amino terminal domain resides at a position predicted to interact with Cbln2/Cbln4, and the variant disrupts complex formation between GluD1 and Cbln2, which could perturb its role in synapse organization. We also discovered that, like the lurcher mutation (GluD2-A654T), other rare variants in the GRID2 M3 domain create constitutively active receptors that share similar pathogenic phenotypes. We also found that the SCHEMA schizophrenia M3 variant GluD1-A650T produced constitutively active receptors. We tested a variety of compounds for their ability to inhibit constitutive currents of GluD receptor variants and found that pentamidine potently inhibited GluD2-T649A constitutive channels (IC50 50 nM). These results identify regions of intolerance to variation in the GRID genes, illustrate the functional consequences of GRID1 and GRID2 variants, and suggest how these receptors function normally and in disease.

A comparative analysis of fruit fly and human glutamate dehydrogenases in Drosophila melanogaster sperm development.

Glutamate dehydrogenases are enzymes that take part in both amino acid and energy metabolism. Their role is clear in many biological processes, from neuronal function to cancer development. The putative testis-specific Drosophila glutamate dehydrogenase, Bb8, is required for male fertility and the development of mitochondrial derivatives in spermatids. Testis-specific genes are less conserved and could gain new functions, thus raising a question whether Bb8 has retained its original enzymatic activity. We show that while Bb8 displays glutamate dehydrogenase activity, there are significant functional differences between the housekeeping Gdh and the testis-specific Bb8. Both human GLUD1 and GLUD2 can rescue the bb8 ms mutant phenotype, with superior performance by GLUD2. We also tested the role of three conserved amino acids observed in both Bb8 and GLUD2 in Gdh mutants, which showed their importance in the glutamate dehydrogenase function. The findings of our study indicate that Drosophila Bb8 and human GLUD2 could be novel examples of convergent molecular evolution. Furthermore, we investigated the importance of glutamate levels in mitochondrial homeostasis during spermatogenesis by ectopic expression of the mitochondrial glutamate transporter Aralar1, which caused mitochondrial abnormalities in fly spermatids. The data presented in our study offer evidence supporting the significant involvement of glutamate metabolism in sperm development.

A Very Rare Case of Diabetes Mellitus Occurring in a Patient With Hyperinsulinism Hyperammonemia Syndrome.

Background/Objective: To illustrate an unusual case of type 2 diabetes mellitus (T2DM) developing many years after the diagnosis of hyperinsulinism hyperammonemia (HI/HA) syndrome. Case Report: This article reports about a 36-year-old female with a history of congenital hyperinsulinism due to HI/HA syndrome, which was diagnosed in infancy. The patient presented with hypoglycemia and seizures as an infant and was treated with diazoxide and a low-protein diet for many years with reduction in her hypoglycemic events. She subsequently developed T2DM >30 years later. Genetic analysis was positive for a glutamate dehydrogenase 1 gene (GLUD1) alteration. She was treated with metformin and a glucagon-like peptide 1 agonist, with significant improvement in her blood glucose control and weight loss. Discussion: HI/HA syndrome is a rare genetic syndrome that manifests in childhood with signs and symptoms of hypoglycemia and neurologic symptoms. This is the first case reported in the literature of a patient with HI/HA syndrome due to a GLUD1 alteration who developed T2DM much later in life. Patients with this disorder usually have recurrent hypoglycemia and require long-term medical therapy or very occasionally may have a resolution. She had class 3 obesity and evidence of insulin resistance, which likely contributed to her risk of diabetes. Conclusion: This is a rare case of T2DM presenting in a patient with HI/HA syndrome. This should be considered a possible outcome in patients with this disorder, especially in the presence of obesity.

Structural insights into the ligand binding domain of GluD1 and GluD2 receptors.

GluD1 and GluD2 subunits (also known as delta 1 and 2) are the members of the delta family of ionotropic glutamate receptors. They are particularly puzzling, since they are unable to bind glutamate, but rather bind glycine and d-serine via their classical ligand binding domain (LBD). While GluD2 has been the subject of intensive research over the past decades, it is only recently that GluD1 received similar interest and very few studies compare the properties of these two membrane proteins. In their research article included in this issue, Masternak et al. resolved the 3D structure of the GluD1 LBD, compared its d-serine sensitivity with that of GluD2 and identified critical residues involved in the dynamics of the LBD.

Potentiation of neuronal activity by tonic GluD1 current in brain slices.

Ion channel function of native delta glutamate receptors (GluDR ) is incompletely understood. Previously, we and others have shown that activation of Gαq protein-coupled receptors (GqPCR) produces a slow inward current carried by GluD1R . GluD1R also carries a tonic cation current of unknown cause. Here, using voltage-clamp electrophysiological recordings from adult mouse brain slices containing the dorsal raphe nucleus, we find no role of ongoing G-protein-coupled receptor activity in generating or sustaining tonic GluD1R currents. Neither augmentation nor disruption of G protein activity affects tonic GluD1R currents, suggesting that ongoing G-protein-coupled receptor activity does not give rise to tonic GluD1R currents. Further, the tonic GluD1R current is unaffected by the addition of external glycine or D-serine, which influences GluD2R current at millimolar concentrations. Instead, GqPCR-stimulated and tonic GluD1R currents are regulated by physiological levels of external calcium. In current-clamp recordings, block of GluD1R channels hyperpolarizes the membrane by ~7 mV at subthreshold potentials, reducing excitability. Thus, GluD1R carries a G-protein-independent tonic current that contributes to subthreshold neuronal excitation in the dorsal raphe nucleus.

Glutamate dehydrogenase hyperinsulinism: mechanisms, diagnosis, and treatment.

Congenital hyperinsulinism (CHI) is a genetically heterogeneous disease, in which intractable, persistent hypoglycemia is induced by excessive insulin secretion and increased serum insulin concentration. To date,15 genes have been found to be associated with the pathogenesis of CHI. Glutamate dehydrogenase hyperinsulinism (GDH-HI) is the second most common type of CHI and is caused by mutations in the glutamate dehydrogenase 1 gene. The objective of this review is to summarize the genetic mechanisms, diagnosis and treatment progress of GDH-HI. Early diagnosis and treatment are extremely important to prevent long-term neurological complications in children with GDH-HI.

Spectrum of neuro-developmental disorders in children with congenital hyperinsulinism due to activating mutations in GLUD1.

Background: Hyperinsulinism/hyperammonemia (HI/HA) syndrome is the second most common type of congenital hyperinsulinism caused by an activating GLUD1 mutation. Objective: The aim of this study was to determine the clinical profile and long-term neurological outcomes in children with HI/HA syndrome. Method: This study is a retrospective review of patients with GLUD1 mutation, treated at two centers in the UK and Russia, over a 15-year period. Different risk factors for neuro-developmental disorders were analysed by Mann-Whitney U test and Fisher's exact P test. Results: We identified 25 cases with GLUD1 mutations (12 males). Median age of presentation was 7 months (12 h-18 months). Hypoglycaemic seizures were the presenting feature in 24 (96%) cases. Twenty four cases responded to diazoxide and protein restriction whilst one patient underwent partial pancreatectomy. In total, 13 cases (52%) developed neurodevelopmental manifestations. Epilepsy (n = 9/25, 36%), learning difficulties (n = 8/25, 32%) and speech delay (n = 8/25, 32%) were the most common neurological manifestation. Median age of presentation for epilepsy was 12 months with generalised tonic-clonic seizures being the most common (n = 4/9, 44.4%) followed by absence seizures (n = 3/9, 33.3%). Early age of presentation (P = 0.02), diazoxide dose (P = 0.04) and a mutation in exon 11 or 12 (P = 0.01) were associated with neurological disorder. Conclusion: HI/HA syndrome is associated with wide spectrum of neurological disorders. These neurological manifestations were more frequent in cases with mutations affecting the GTP-binding site of GLUD1 in our cohort.

GLUD1 suppresses renal tumorigenesis and development via inhibiting PI3K/Akt/mTOR pathway.

Growing cancer cells are addicted to glutamine. Glutamate dehydrogenase 1 (GLUD1) is one of key enzymes in glutamine metabolism and plays a critical role in the malignancy of diverse tumors. However, its role and molecular mechanism in clear cell renal cell carcinoma (ccRCC) development and progression remain unknown. In this study, analysis results of the GEO/TCGA/UALCAN database showed that GLUD1 level was downregulated in ccRCC tissues. Immunohistochemistry and western blotting results further validated the downregulation of GLUD1 level in ccRCC tissues. GLUD1 level was gradually decreased as ccRCC stage and grade progressed. Low GLUD1 level was associated with a shorter survival and higher IC50 value for tyrosine kinase inhibitors (TKIs) in ccRCC, reminding that GLUD1 level could predict the prognosis and TKIs sensitivity of ccRCC patients. High level of methylation in GLUD1 promoter was positively correlated with the downregulation of GLUD1 level and was negatively correlated with survival of ccRCC patients. GLUD1 overexpression suppressed RCC cell proliferation, colony formation and migration by inhibiting PI3K/Akt/mTOR pathway activation. Low GLUD1 level correlated with suppressive immune microenvironment (TIME) in ccRCC. Together, we found a novel tumor-suppressing role of GLUD1 in ccRCC which was different from that in other tumors and a new mechanism for inhibiting PI3K/Akt/mTOR activation and TIME in ccRCC. These results provide a theoretical basis for GLUD1 as a therapeutic target and prognostic marker in ccRCC.

Characterizing the neurological phenotype of the hyperinsulinism hyperammonemia syndrome.

BACKGROUND: Hyperinsulinism hyperammonemia (HI/HA) syndrome is caused by activating mutations in GLUD1, encoding glutamate dehydrogenase (GDH). Atypical absence seizures and neuropsychological disorders occur at high rates in this form of hyperinsulinism. Dysregulated central nervous system (CNS) glutamate balance, due to GDH overactivity in the brain, has been hypothesized to play a role. This study aimed to describe the neurologic phenotype in HI/HA syndrome and investigate CNS glutamate levels using glutamate weighted chemical exchange saturation transfer magnetic resonance imaging (GluCEST MRI). In this cross-sectional study, 12 subjects with HI/HA syndrome had plasma ammonia measurement, self- or parent-completed neurocognitive assessments, electroencephalogram (EEG), and GluCEST MRI at 7 T performed. GluCEST MRI measures were compared to a historic reference population of 10 healthy adults. RESULTS: Subjects were five males and seven females with median age of 25.5 years. Seventy-five percent of subjects reported a history of neurodevelopmental problems and 42% had neurocognitive assessment scores outside the normal range. Fifty percent had interictal EEG findings of generalized, irregular spike and wave discharges. Higher variability in hippocampal GluCEST asymmetry (p = 0.002), and in peak hippocampal GluCEST values (p = 0.008), was observed in HI/HA subjects (n = 9 with interpretable MRI) compared to the healthy reference population (n = 10). CONCLUSIONS: The high prevalence of abnormal neurocognitive assessment scores and interictal EEG findings observed highlights the importance of longitudinal neuropsychological assessment for individuals with HI/HA syndrome. Our findings demonstrate the potential application of GluCEST to investigate persistent knowledge gaps in the mechanisms underlying the unique neurophenotype of this disorder.

Glutamate regulates gliosis of BMSCs to promote ENS regeneration through α-KG and H3K9/H3K27 demethylation.

BACKGROUND: There is a lack of effective therapies for enteric nervous system (ENS) injury. Our previous study showed that transplanted bone marrow-derived mesenchymal stem cells (BMSCs) play a "glia-like cells" role in initiating ENS regeneration in denervated mice. Cellular energy metabolism is an important factor in maintaining the biological characteristics of stem cells. However, how cellular energy metabolism regulates the fate of BMSCs in the ENS-injured microenvironment is unclear. METHODS: The biological characteristics, energy metabolism, and histone methylation levels of BMSCs following ENS injury were determined. Then, glutamate dehydrogenase 1 (Glud1) which catalyzes the oxidative deamination of glutamate to α-KG was overexpressed (OE) in BMSCs. Further, OE-Glud1 BMSCs were targeted-transplanted into the ENS injury site of denervated mice to determine their effects on ENS regeneration. RESULTS: In vitro, in the ENS-injured high-glutamate microenvironment, the ratio of α-ketoglutarate (α-KG) to succinate (P < 0.05), the histone demethylation level (P < 0.05), the protein expression of glial cell markers (P < 0.05), and the gene expression of Glud1 (P < 0.05) were significantly increased. And the binding of H3K9me3 to the GFAP, S100B, and GDNF promoter was enhanced (P < 0.05). Moreover, α-KG treatment increased the monomethylation and decreased the trimethylation on H3K9 (P < 0.01) and H3K27 (P < 0.05) in BMSCs and significantly upregulated the protein expression of glial cell markers (P < 0.01), which was reversed by the α-KG competitive inhibitor D-2-hydroxyglutarate (P < 0.05). Besides, overexpression of Glud1 in BMSCs exhibited increases in monomethylation and decreases in trimethylation on H3K9 (P < 0.05) and H3K27 (P < 0.05), and upregulated protein expression of glial cell markers (P < 0.01). In vivo, BMSCs overexpressing Glud1 had a strong promotion effect on ENS regeneration in denervated mice through H3K9/H3K27 demethylation (P < 0.05), and upregulating the expression of glial cell protein (P < 0.05). CONCLUSIONS: BMSCs overexpressing Glud1 promote the expression of glial cell markers and ENS remodeling in denervated mice through regulating intracellular α-KG and H3K9/H3K27 demethylation.