RATE OF UTILIZATION OF GLUCOSE AND 'COMPARTMENTATION' OF ALPHA-OXOGLUTARATE AND GLUTAMATE IN RAT BRAIN.
Ontology highlight
ABSTRACT:
SUBMITTER: GAITONDE MK
PROVIDER: S-EPMC1206810 | biostudies-other | 1965 Jun
REPOSITORIES: biostudies-other
Similar Datasets
Project description:?-Ketoglutarate (?KG) is a metabolite of the tricarboxylic acid cycle, important for biomass synthesis and a precursor for biotechnological products like 1,4-butanediol. In the eukaryote Saccharomyces cerevisiae ?KG is present in different compartments. Compartmentation and (intra-)cellular transport could interfere with heterologous product pathways, generate futile cycles and reduce product yields. Batch and chemostat cultivations at low pH (??5) showed that ?KG can be transported, catabolized and used for biomass synthesis. The uptake mechanism of ?KG was further investigated under ?KG limited chemostat conditions at different pH (3, 4, 5, and 6). At very low pH (3, 4) there is a fraction of undissociated ?KG that could diffuse over the periplasmic membrane. At pH 5 this fraction is very low, and the observed growth and residual concentration requires a permease/facilitated uptake mechanism of the mono-dissociated form of ?KG. Consumption of ?KG under mixed substrate conditions was only observed for low glucose concentrations in chemostat cultivations, suggesting that the putative ?KG transporter is repressed by glucose. Fully 13C-labeled ?KG was introduced as a tracer during a glucose/?KG co-feeding chemostat to trace ?KG transport and utilization. The measured 13C enrichments suggest the major part of the consumed 13C ?KG was used for the synthesis of glutamate, and the remainder was transported into the mitochondria and fully oxidized. There was no enrichment observed in glycolytic intermediates, suggesting that there was no gluconeogenic activity under the co-feeding conditions. 13C based flux analysis suggests that the intracellular transport is bi-directional, i.e. there is a fast exchange between the cytosol and mitochondria. The model further estimates that most intracellular ?KG (88%) was present in the cytosol. Using literature reported volume fractions, the mitochondria/cytosol concentration ratio was 1.33. Such ratio will not require energy investment for transport towards the mitochondria (based on thermodynamic driving forces calculated with literature pH values). Growth on ?KG as sole carbon source was observed, suggesting that S. cerevisiae is not fully Krebs-negative. Using 13C tracing and modelling the intracellular use of ?KG under co-feeding conditions showed a link with biomass synthesis, transport into the mitochondria and catabolism. For the engineering of strains that use cytosolic ?KG as precursor, both observed sinks should be minimized to increase the putative yields.
| S-EPMC7393084 | biostudies-literature
Project description:The excitatory neurotransmitter glutamate has been reported to have a major impact on brain energy metabolism. Using primary cultures of rat hippocampal neurons, we observed that glutamate reduces glucose utilization in this cell type, suggesting alteration in mitochondrial oxidative metabolism. The aquaglyceroporin AQP9 and the monocarboxylate transporter MCT2, two transporters for oxidative energy substrates, appear to be present in mitochondria of these neurons. Moreover, they not only co-localize but they interact with each other as they were found to co-immunoprecipitate from hippocampal neuron homogenates. Exposure of cultured hippocampal neurons to glutamate 100 μM for 1 h led to enhanced expression of both AQP9 and MCT2 at the protein level without any significant change at the mRNA level. In parallel, a similar increase in the protein expression of LDHA was evidenced without an effect on the mRNA level. These data suggest that glutamate exerts an influence on neuronal energy metabolism likely through a regulation of the expression of some key mitochondrial proteins.
| S-EPMC4130107 | biostudies-literature
Project description:The development of key enzyme activities concerned with glucose metabolism was studied in six regions of the rat brain in animals from just before birth (-2 days) through the neonatal and suckling period until adulthood (60 days old). The brain regions studied were the cerebellum, medulla oblongata and pons, hypothalamus, striatum, mid-brain and cortex. The enzymes whose developmental patterns were investigated were hexokinase (EC 2.7.1.1), aldolase (EC 4.1.2.13), lactate dehydrogenase (EC 1.1.1.27) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). Hexokinase, aldolase and lactate dehydrogenase activities develop as a single cluster in all the regions studied, although the timing of this development varies from region to region. Glucose-6-phosphate dehydrogenase activity, however, declines relative to glycolytic enzyme activity as the brain matures. When the different brain regions are compared, it is clear that the medulla develops its glycolytic potential, as indicated by its potential enzyme activity, considerably earlier than the other regions (hypothalamus, striatum and mid-brain), with the cortex and cerebellar activities developing even later. This enzyme developmental sequence correlates well with the neurophylogenetic development of the brain and adds support to the hypothesis that the development of the potential for glycolysis in the brain is a necessary prerequisite for the development of neurological competence.
| S-EPMC1153316 | biostudies-other
Project description:The brain is dependent on glucose as a primary energy substrate, but is capable of utilizing ketones such as ?-hydroxybutyrate and acetoacetate, as occurs with fasting, starvation, or chronic feeding of a ketogenic diet. The relationship between changes in cerebral metabolic rates of glucose (CMRglc) and degree or duration of ketosis remains uncertain. To investigate if CMRglc decreases with chronic ketosis, 2-[(18)F]fluoro-2-deoxy-D-glucose in combination with positron emission tomography, was applied in anesthetized young adult rats fed 3 weeks of either standard or ketogenic diets. Cerebral metabolic rates of glucose (?mol/min per 100?g) was determined in the cerebral cortex and cerebellum using Gjedde-Patlak analysis. The average CMRglc significantly decreased in the cerebral cortex (23.0±4.9 versus 32.9±4.7) and cerebellum (29.3±8.6 versus 41.2±6.4) with increased plasma ketone bodies in the ketotic rats compared with standard diet group. The reduction of CMRglc in both brain regions correlates linearly by ?9% for each 1?mmol/L increase of total plasma ketone bodies (0.3 to 6.3?mmol/L). Together with our meta-analysis, these data revealed that the degree and duration of ketosis has a major role in determining the corresponding change in CMRglc with ketosis.
| S-EPMC3734783 | biostudies-literature
Project description:BACKGROUND: Cyclic guanosine monophosphate (cGMP) is the common second messenger for the cardiovascular effects of nitric oxide (NO) and natriuretic peptides, such as atrial or brain natriuretic peptide, which activate the soluble and particulate forms of guanylyl cyclase, respectively. However, natriuretic peptides and NO donors exert different effects on cardiac and vascular smooth muscle function. We therefore tested whether these differences are due to an intracellular compartmentation of cGMP and evaluated the role of phosphodiesterase (PDE) subtypes in this process. METHODS AND RESULTS: Subsarcolemmal cGMP signals were monitored in adult rat cardiomyocytes by expression of the rat olfactory cyclic nucleotide-gated (CNG) channel alpha-subunit and recording of the associated cGMP-gated current (ICNG). Atrial natriuretic peptide (10 nmol/L) or brain natriuretic peptide (10 nmol/L) induced a clear activation of ICNG, whereas NO donors (S-nitroso-N-acetyl-penicillamine, diethylamine NONOate, 3-morpholinosydnonimine, and spermine NO, all at 100 micromol/L) had little effect. The ICNG current was strongly potentiated by nonselective PDE inhibition with isobutyl methylxanthine (100 micromol/L) and by the PDE2 inhibitors erythro-9-(2-hydroxy-3-nonyl)adenine (10 micromol/L) and Bay 60-7550 (50 nmol/L). Surprisingly, sildenafil, a PDE5 inhibitor, produced a dose-dependent increase of I(CNG) activated by NO donors but had no effect (at 100 nmol/L) on the current elicited by atrial natriuretic peptide. CONCLUSIONS: These results indicate that in rat cardiomyocytes (1) the particulate cGMP pool is readily accessible at the plasma membrane, whereas the soluble pool is not; and (2) PDE5 controls the soluble but not the particulate pool, whereas the latter is under the exclusive control of PDE2. Differential spatiotemporal distributions of cGMP may therefore contribute to the specific effects of natriuretic peptides and NO donors on cardiac function.
| S-EPMC1877795 | biostudies-literature
Project description:The mitochondrial 2-oxoglutarate carrier (OGC), isolated and purified from rat brain mitochondria, was reconstituted into proteoliposomes to study the interaction with hemin, a porphyrin derivative, which may result from the breakdown of heme-containing proteins and plays a key role in several metabolic pathways. By kinetic approaches, on the basis of the single binding centre gated pore mechanism, we analyzed the effect of hemin on the transport rate of OGC in uptake and efflux experiments in proteoliposomes reconstituted in the presence of the substrate 2-oxoglutarate. Overall, our experimental data fit the hypothesis that hemin operates a competitive inhibition in the 0.5-10 µM concentration range. As a consequence of the OGC inhibition, the malate/aspartate shuttle might be impaired, causing an alteration of mitochondrial function. Hence, considering that the metabolism of porphyrins implies both cytoplasmic and mitochondrial processes, OGC may participate in the regulation of porphyrin derivatives availability and the related metabolic pathways that depend on them (such as oxidative phosphorylation and apoptosis). For the sake of clarity, a simplified model based on induced-fit molecular docking supported the in vitro transport assays findings that hemin was as good as 2-oxoglutarate to bind the carrier by engaging specific ionic hydrogen bond interactions with a number of key residues known for participating in the similarly located mitochondrial carrier substrate binding site.
| S-EPMC8393474 | biostudies-literature
Project description:D-Glutamate (D-Glu), an essential component of peptidoglycans, can be utilized as carbon and nitrogen source by Pseudomonas aeruginosa. DNA microarrays were employed to identify genes involved in D-Glu catabolism. Through gene knockout and growth phenotype analysis, the divergent dguR-dguABC (D-glutamate utilization) gene cluster was shown to participate in D-Glu catabolism and regulation. The dguA gene encodes a FAD-dependent D-amino acid dehydrogenase with D-Glu as its preferred substrate, and its promoter was specifically induced by exogenous D-Glu and D-Gln. The function of DguR as transcriptional activator of the dguABC operon was demonstrated by promoter activity measurements in vivo and by mobility shift assays with purified His-tagged DguR in vitro. Although the DNA-binding activity of DguR did not require D-Glu, the presence of D-Glu in the binding reaction was found to stabilize a preferred nucleoprotein complex. The dguB gene encodes a putative enamine/imine deaminase of the RidA family, but its role in D-Glu catabolism remained to be determined. While a lesion in dguC encoding a periplasmic solute binding protein did not affect growth on D-Glu, the AatJMQP transporter for acidic amino acid uptake was found essential for D-Glu and L-Glu utilization. Expression of this uptake system was subjected to induction by exogenous DL-Glu, most likely via the AauSR two-component system. In summary, DguA was identified in this study as a new member of the FAD-dependent amino acid dehydrogenase family for D-amino acid catabolism. DguR serves as a D-Glu sensor and transcriptional activator of the dguA promoter.
2013-05-03 | GSE46603 | GEO
Project description:Exercise, a proven method of boosting health and wellness, is thought to act as a protective factor against many neurological and psychological diseases. Recent studies on exercise and drug exposure have pinpointed some of the neurological mechanisms that may characterize this protective factor. Using positron emission tomography (PET) imaging techniques and the glucose analog [18F]-Fluorodeoxyglucose (18F-FDG), our team sought to identify how chronic aerobic exercise modulates brain glucose metabolism (BGluM) after drug-naïve rats were exposed to an acute dose of cocaine. Using sedentary rats as a control group, we observed significant differences in regional BGluM. Chronic treadmill exercise treatment coupled with acute cocaine exposure induced responses in BGluM activity in the following brain regions: postsubiculum (Post), parasubiculum (PaS), granular and dysgranular insular cortex (GI and DI, respectively), substantia nigra reticular (SNR) and compact part dorsal tier (SNCD), temporal association cortex (TeA), entopenduncular nucleus (EP), and crus 1 of the ansiform lobule (crus 1). Inhibition, characterized by decreased responses due to our exercise, was found in the ventral endopiriform nucleus (VEn). These areas are associated with memory and various motor functions. They also include and share connections with densely dopaminergic areas of the mesolimbic system. In conclusion, these findings suggest that treadmill exercise in rats mediates brain glucose response to an acute dose of cocaine differently as compared to sedentary rats. The modulated brain glucose utilization occurs in brain regions responsible for memory and association, spatial navigation, and motor control as well as corticomesolimbic regions related to reward, emotion, and movement.
| S-EPMC9788493 | biostudies-literature
Project description:D-Glutamate (D-Glu), an essential component of peptidoglycans, can be utilized as carbon and nitrogen source by Pseudomonas aeruginosa. DNA microarrays were employed to identify genes involved in D-Glu catabolism. Through gene knockout and growth phenotype analysis, the divergent dguR-dguABC (D-glutamate utilization) gene cluster was shown to participate in D-Glu catabolism and regulation. The dguA gene encodes a FAD-dependent D-amino acid dehydrogenase with D-Glu as its preferred substrate, and its promoter was specifically induced by exogenous D-Glu and D-Gln. The function of DguR as transcriptional activator of the dguABC operon was demonstrated by promoter activity measurements in vivo and by mobility shift assays with purified His-tagged DguR in vitro. Although the DNA-binding activity of DguR did not require D-Glu, the presence of D-Glu in the binding reaction was found to stabilize a preferred nucleoprotein complex. The dguB gene encodes a putative enamine/imine deaminase of the RidA family, but its role in D-Glu catabolism remained to be determined. While a lesion in dguC encoding a periplasmic solute binding protein did not affect growth on D-Glu, the AatJMQP transporter for acidic amino acid uptake was found essential for D-Glu and L-Glu utilization. Expression of this uptake system was subjected to induction by exogenous DL-Glu, most likely via the AauSR two-component system. In summary, DguA was identified in this study as a new member of the FAD-dependent amino acid dehydrogenase family for D-amino acid catabolism. DguR serves as a D-Glu sensor and transcriptional activator of the dguA promoter. Pseudomonas aeruginosa PAO1 was chosen as model to study gene response with different D-amino acids.
2013-05-03 | E-GEOD-46603 | biostudies-arrayexpress
Project description:High glucose (HG) increases the production of reactive oxygen species (ROS), leading to decreased glutamate uptake in Müller cells. The transient receptor potential cation channel 6 (TRPC6) channel, an oxidative stress-sensitive Ca2+-permeable cationic channel, is readily detected in Müller cells and highly expressed under HG conditions. Yet, the effect of high glucose-induced TRPC6 channel activation in Müller cells is poorly understood. We hypothesized that TRPC6 channel activation mediates high glucose-induced decreases in Müller cell glutamate uptake. We found RNA interference (RNAi) of the TRPC6 channel abolished HG-induced decreases in glutamate uptake and cell death. HG also decreased the expression of the glutamate-aspartate transporter (GLAST), which is the most important transporter involved in glutamate uptake. The mRNA level of ciliary neurotrophic factor (CNTF) in rMC-1 cells and the release of CNTF in the culture media was decreased, but the mRNA levels of IL-6 and vascular endothelial growth factor (VEGF) were increased under HG conditions. After RNAi silencing in rMC-1 cells, the mRNA levels of CNTF increased, but IL-6 and VEGF levels decreased. Furthermore, TRPC6 knockdown (KD) decreased expression of glial fibrillary acidic protein (GFAP) and increased expression of Kir4.1, pointing to inhibition of HG-induced gliosis in rMC-1 cells. ROS and intracellular Ca2+ levels decreased after TRPC6 knockdown. Exposure to Hyp9 (10 μM), a highly selective TRPC6 channel agonist, can aggravate HG-induced pathological changes. Collectively, our results suggest TRPC6 channel activation is involved in HG-induced decreases in glutamate uptake in rMC-1 cells. These findings provide novel insights into the role of TRPC6 in HG-induced retinal neurovasculopathy and suggest TRPC6 is a promising target for drug development for diabetic retinopathy (DR).
| S-EPMC7033573 | biostudies-literature