scholarly journals Underestimation of the Pentose–Phosphate Pathway in Intact Primary Neurons as Revealed by Metabolic Flux Analysis

2013 ◽  
Vol 33 (12) ◽  
pp. 1843-1845 ◽  
Author(s):  
Patricia Rodriguez-Rodriguez ◽  
Emilio Fernandez ◽  
Juan P Bolaños
Keyword(s):  
Pentose Phosphate Pathway ◽  
Metabolic Flux ◽  
Pentose Phosphate ◽  
Flux Analysis ◽  
Primary Neurons ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Total Glucose ◽  
Rate Limiting ◽  
Glycolytic Rate

The rates of glucose oxidized at glycolysis and pentose–phosphate pathway (PPP) in neurons are controversial. Using [3-3H]-, [1-14C]-, and [6-14C]glucose to estimate fluxes through these pathways in resting, intact rat cortical primary neurons, we found that the rate of glucose oxidized through PPP was, apparently, ∼14% of total glucose metabolized. However, inhibition of PPP rate-limiting step, glucose-6-phosphate (G6P) dehydrogenase, increased approximately twofold the glycolytic rate; and, knockdown of phosphoglucose isomerase increased ∼1.8-fold the PPP rate. Thus, in neurons, a considerable fraction of fructose-6-phosphate returning from the PPP contributes to the G6P pool that re-enters PPP, largely underestimating its flux.

scholarly journals Wnt5a Increases the Glycolytic Rate and the Activity of the Pentose Phosphate Pathway in Cortical Neurons

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Pedro Cisternas ◽  
Paulina Salazar ◽  
Carmen Silva-Álvarez ◽  
L. Felipe Barros ◽  
Nibaldo C. Inestrosa
Keyword(s):  
Glucose Metabolism ◽  
Wnt Signaling ◽  
Pentose Phosphate Pathway ◽  
Neurodegenerative Disorders ◽  
Metabolic Flux ◽  
High Energy ◽  
Pentose Phosphate ◽  
The Brain ◽  
Glycolytic Rate

In the last few years, several reports have proposed that Wnt signaling is a general metabolic regulator, suggesting a role for this pathway in the control of metabolic flux. Wnt signaling is critical for several neuronal functions, but little is known about the correlation between this pathway and energy metabolism. The brain has a high demand for glucose, which is mainly used for energy production. Neurons use energy for highly specific processes that require a high energy level, such as maintaining the electrical potential and synthesizing neurotransmitters. Moreover, an important metabolic impairment has been described in all neurodegenerative disorders. Despite the key role of glucose metabolism in the brain, little is known about the cellular pathways involved in regulating this process. We report here that Wnt5a induces an increase in glucose uptake and glycolytic rate and an increase in the activity of the pentose phosphate pathway; the effects of Wnt5a require the intracellular generation of nitric oxide. Our data suggest that Wnt signaling stimulates neuronal glucose metabolism, an effect that could be important for the reported neuroprotective role of Wnt signaling in neurodegenerative disorders.

scholarly journals Combined Fluxomics and Transcriptomics Analysis of Glucose Catabolism via a Partially Cyclic Pentose Phosphate Pathway in Gluconobacter oxydans 621H

2013 ◽  
Vol 79 (7) ◽  
pp. 2336-2348 ◽  
Author(s):  
Tanja Hanke ◽  
Katharina Nöh ◽  
Stephan Noack ◽  
Tino Polen ◽  
Stephanie Bringer ◽  
...  
Keyword(s):  
Phase Ii ◽  
Growth Phase ◽  
Pentose Phosphate Pathway ◽  
Metabolic Flux ◽  
Glucose Dehydrogenase ◽  
Gluconobacter Oxydans ◽  
Pentose Phosphate ◽  
Flux Analysis ◽  
Content Type ◽  
Activity Measurements

ABSTRACTIn this study, the distribution and regulation of periplasmic and cytoplasmic carbon fluxes inGluconobacter oxydans621H with glucose were studied by13C-based metabolic flux analysis (13C-MFA) in combination with transcriptomics and enzyme assays. For13C-MFA, cells were cultivated with specifically13C-labeled glucose, and intracellular metabolites were analyzed for their labeling pattern by liquid chromatography-mass spectrometry (LC-MS). In growth phase I, 90% of the glucose was oxidized periplasmically to gluconate and partially further oxidized to 2-ketogluconate. Of the glucose taken up by the cells, 9% was phosphorylated to glucose 6-phosphate, whereas 91% was oxidized by cytoplasmic glucose dehydrogenase to gluconate. Additional gluconate was taken up into the cells by transport. Of the cytoplasmic gluconate, 70% was oxidized to 5-ketogluconate and 30% was phosphorylated to 6-phosphogluconate. In growth phase II, 87% of gluconate was oxidized to 2-ketogluconate in the periplasm and 13% was taken up by the cells and almost completely converted to 6-phosphogluconate. SinceG. oxydanslacks phosphofructokinase, glucose 6-phosphate can be metabolized only via the oxidative pentose phosphate pathway (PPP) or the Entner-Doudoroff pathway (EDP).13C-MFA showed that 6-phosphogluconate is catabolized primarily via the oxidative PPP in both phases I and II (62% and 93%) and demonstrated a cyclic carbon flux through the oxidative PPP. The transcriptome comparison revealed an increased expression of PPP genes in growth phase II, which was supported by enzyme activity measurements and correlated with the increased PPP flux in phase II. Moreover, genes possibly related to a general stress response displayed increased expression in growth phase II.

scholarly journals Amplified Expression of Fructose 1,6-Bisphosphatase in Corynebacterium glutamicum Increases In Vivo Flux through the Pentose Phosphate Pathway and Lysine Production on Different Carbon Sources

2005 ◽  
Vol 71 (12) ◽  
pp. 8587-8596 ◽  
Author(s):  
Judith Becker ◽  
Corinna Klopprogge ◽  
Oskar Zelder ◽  
Elmar Heinzle ◽  
Christoph Wittmann
Keyword(s):  
Corynebacterium Glutamicum ◽  
Pentose Phosphate Pathway ◽  
Metabolic Flux ◽  
Carbon Sources ◽  
Pentose Phosphate ◽  
Metabolic Effects ◽  
Flux Analysis ◽  
Lysine Production ◽  
Fructose 1,6 Bisphosphatase

ABSTRACT The overexpression of fructose 1,6-bisphosphatase (FBPase) in Corynebacterium glutamicum leads to significant improvement of lysine production on different sugars. Amplified expression of FBPase via the promoter of the gene encoding elongation factor TU (EFTU) increased the lysine yield in the feedback-deregulated lysine-producing strain C. glutamicum lysCfbr by 40% on glucose and 30% on fructose or sucrose. Additionally formation of the by-products glycerol and dihydroxyacetone was significantly reduced in the PEFTUfbp mutant. As revealed by 13C metabolic flux analysis on glucose the overexpression of FBPase causes a redirection of carbon flux from glycolysis toward the pentose phosphate pathway (PPP) and thus leads to increased NADPH supply. Normalized to an uptake flux of glucose of 100%, the relative flux into the PPP was 56% for C. glutamicum lysCfbr PEFTUfbp and 46% for C. glutamicum lysCfb r . The flux for NADPH supply was 180% in the PEFTUfbp strain and only 146% in the parent strain. Amplification of FBPase increases the production of lysine via an increased supply of NADPH. Comparative studies with another mutant containing the sod promoter upstream of the fbp gene indicate that the expression level of FBPase relates to the extent of the metabolic effects. The overexpression of FBPase seems useful for starch- and molasses-based industrial lysine production with C. glutamicum. The redirection of flux toward the PPP should also be interesting for the production of other NADPH-demanding compounds as well as for products directly stemming from the PPP.

scholarly journals The Entner-Doudoroff and Nonoxidative Pentose Phosphate Pathways Bypass Glycolysis and the Oxidative Pentose Phosphate Pathway in Ralstonia solanacearum

mSystems ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Poonam Jyoti ◽  
Manu Shree ◽  
Chandrakant Joshi ◽  
Tulika Prakash ◽  
Suvendra Kumar Ray ◽  
...  
Keyword(s):  
Network Analysis ◽  
Metabolic Network ◽  
Pentose Phosphate Pathway ◽  
Ralstonia Solanacearum ◽  
Metabolic Flux ◽  
Pentose Phosphate ◽  
Flux Analysis ◽  
Content Type ◽  
Metabolic Network Analysis ◽  
Balance Analysis

ABSTRACT In Ralstonia solanacearum, a devastating phytopathogen whose metabolism is poorly understood, we observed that the Entner-Doudoroff (ED) pathway and nonoxidative pentose phosphate pathway (non-OxPPP) bypass glycolysis and OxPPP under glucose oxidation. Evidence derived from 13C stable isotope feeding and genome annotation-based comparative metabolic network analysis supported the observations. Comparative metabolic network analysis derived from the currently available 53 annotated R. solanacearum strains, including a recently reported strain (F1C1), representing the four phylotypes, confirmed the lack of key genes coding for phosphofructokinase (pfk-1) and phosphogluconate dehydrogenase (gnd) enzymes that are relevant for glycolysis and OxPPP, respectively. R. solanacearum F1C1 cells fed with [13C]glucose (99% [1-13C]glucose or 99% [1,2-13C]glucose or 40% [13C6]glucose) followed by gas chromatography-mass spectrometry (GC-MS)-based labeling analysis of fragments from amino acids, glycerol, and ribose provided clear evidence that rather than glycolysis and the OxPPP, the ED pathway and non-OxPPP are the main routes sustaining metabolism in R. solanacearum. The 13C incorporation in the mass ions of alanine (m/z 260 and m/z 232), valine (m/z 288 and m/z 260), glycine (m/z 218), serine (m/z 390 and m/z 362), histidine (m/z 440 and m/z 412), tyrosine (m/z 466 and m/z 438), phenylalanine (m/z 336 and m/z 308), glycerol (m/z 377), and ribose (m/z 160) mapped the pathways supporting the observations. The outcomes help better define the central carbon metabolic network of R. solanacearum that can be integrated with 13C metabolic flux analysis as well as flux balance analysis studies for defining the metabolic phenotypes. IMPORTANCE Understanding the metabolic versatility of Ralstonia solanacearum is important, as it regulates the trade-off between virulence and metabolism (1, 2) in a wide range of plant hosts. Due to a lack of clear evidence until this work, several published research papers reported on the potential roles of glycolysis and the oxidative pentose phosphate pathway (OxPPP) in R. solanacearum (3, 4). This work provided evidence from 13C stable isotope feeding and genome annotation-based comparative metabolic network analysis that the Entner-Doudoroff pathway and non-OxPPP bypass glycolysis and OxPPP during the oxidation of glucose, a component of the host xylem pool that serves as a potential carbon source (5). The outcomes help better define the central carbon metabolic network of R. solanacearum that can be integrated with 13C metabolic flux analysis as well as flux balance analysis studies for defining the metabolic phenotypes. The study highlights the need to critically examine phytopathogens whose metabolism is poorly understood.

PROGESTERONE AND INSULIN-RESISTANCE: STUDIES OF PROGESTERONE ACTION ON GLUCOSE TRANSPORT, LIPOGENESIS AND LIPOLYSIS IN ISOLATED FAT CELLS OF THE FEMALE RAT

1981 ◽  
Vol 88 (3) ◽  
pp. 455-462 ◽  
Author(s):  
M.-TH. SUTTER-DUB ◽  
B. DAZEY ◽  
E. HAMDAN ◽  
M.-TH. VERGNAUD
Keyword(s):  
Glucose Metabolism ◽  
Pentose Phosphate ◽  
Fat Cells ◽  
Female Rat ◽  
Fat Cell ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Glucose Phosphorylation ◽  
Rate Limiting

The effects of progesterone on isolated rat adipocytes were studied in vitro during various steps of glucose metabolism, transport, lipogenesis and lipolysis. Progesterone decreased the phosphorylation of glucose into glucose-6-phosphate as assessed by measuring the uptake of 2-deoxyglucose but it had no effect on transmembrane transport of glucose as determined by measuring the entry of 3-0-methylglucose into the cell. As glucose phosphorylation is a rate-limiting step of the pentose-phosphate pathway, these data could explain the inhibition of lipogenesis and the enhancement of lipolysis observed when progesterone is present in incubation medium. Progesterone might thus modulate a regulatory step of glucose metabolism and antagonize insulin action in the fat cell.

scholarly journals 13C Metabolic Flux Analysis Indicates Endothelial Cells Attenuate Metabolic Perturbations by Modulating TCA Activity

Metabolites ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 226
Author(s):  
Bilal Moiz ◽  
Jonathan Garcia ◽  
Sarah Basehore ◽  
Angela Sun ◽  
Andrew Li ◽  
...  
Keyword(s):  
Pentose Phosphate Pathway ◽  
Metabolic Flux Analysis ◽  
Metabolic Flux ◽  
Isotope Labeling ◽  
Umbilical Vein ◽  
Pentose Phosphate ◽  
Metabolic Inhibitors ◽  
Flux Analysis ◽  
Therapeutic Effects ◽  
13C Metabolic Flux Analysis

Disrupted endothelial metabolism is linked to endothelial dysfunction and cardiovascular disease. Targeted metabolic inhibitors are potential therapeutics; however, their systemic impact on endothelial metabolism remains unknown. In this study, we combined stable isotope labeling with 13C metabolic flux analysis (13C MFA) to determine how targeted inhibition of the polyol (fidarestat), pentose phosphate (DHEA), and hexosamine biosynthetic (azaserine) pathways alters endothelial metabolism. Glucose, glutamine, and a four-carbon input to the malate shuttle were important carbon sources in the baseline human umbilical vein endothelial cell (HUVEC) 13C MFA model. We observed two to three times higher glutamine uptake in fidarestat and azaserine-treated cells. Fidarestat and DHEA-treated HUVEC showed decreased 13C enrichment of glycolytic and TCA metabolites and amino acids. Azaserine-treated HUVEC primarily showed 13C enrichment differences in UDP-GlcNAc. 13C MFA estimated decreased pentose phosphate pathway flux and increased TCA activity with reversed malate shuttle direction in fidarestat and DHEA-treated HUVEC. In contrast, 13C MFA estimated increases in both pentose phosphate pathway and TCA activity in azaserine-treated cells. These data show the potential importance of endothelial malate shuttle activity and suggest that inhibiting glycolytic side branch pathways can change the metabolic network, highlighting the need to study systemic metabolic therapeutic effects.

scholarly journals Responses of theCentral Metabolism in Escherichia coli to PhosphoglucoseIsomerase and Glucose-6-Phosphate DehydrogenaseKnockouts

2003 ◽  
Vol 185 (24) ◽  
pp. 7053-7067 ◽  
Author(s):  
Qiang Hua ◽  
Chen Yang ◽  
Tomoya Baba ◽  
Hirotada Mori ◽  
Kazuyuki Shimizu
Keyword(s):  
Escherichia Coli ◽  
Pentose Phosphate Pathway ◽  
Metabolic Flux ◽  
Tricarboxylic Acid Cycle ◽  
Flux Ratio ◽  
Pentose Phosphate ◽  
Phosphoglucose Isomerase ◽  
Overflow Metabolism ◽  
Flux Analysis ◽  
Glucose Catabolism

ABSTRACT The responses of Escherichia coli central carbon metabolism to knockout mutations in phosphoglucose isomerase and glucose-6-phosphate (G6P) dehydrogenase genes were investigated by using glucose- and ammonia-limited chemostats. The metabolic network structures and intracellular carbon fluxes in the wild type and in the knockout mutants were characterized by using the complementary methods of flux ratio analysis and metabolic flux analysis based on [U-13C]glucose labeling and two-dimensional nuclear magnetic resonance (NMR) spectroscopy of cellular amino acids, glycerol, and glucose. Disruption of phosphoglucose isomerase resulted in use of the pentose phosphate pathway as the primary route of glucose catabolism, while flux rerouting via the Embden-Meyerhof-Parnas pathway and the nonoxidative branch of the pentose phosphate pathway compensated for the G6P dehydrogenase deficiency. Furthermore, additional, unexpected flux responses to the knockout mutations were observed. Most prominently, the glyoxylate shunt was found to be active in phosphoglucose isomerase-deficient E. coli. The Entner-Doudoroff pathway also contributed to a minor fraction of the glucose catabolism in this mutant strain. Moreover, although knockout of G6P dehydrogenase had no significant influence on the central metabolism under glucose-limited conditions, this mutation resulted in extensive overflow metabolism and extremely low tricarboxylic acid cycle fluxes under ammonia limitation conditions.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

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