fumarates and Hypoxia

In this study the authors examine the effects of acute hypoxia due to extracorporeal circulation (ECC) and the role played by L-carnitine treatment on some plasmatic metabolites linked to glycolytic cellular metabolism. To obtain biochemical data, 120 patients in extracorporeal circulation during aortopulmonary bypass surgery were evaluated. The patients received either sodium bicarbonate (40 patients), or L-carnitine during ECC (40 patients) or before and during ECC (40 patients), and plasma samples were collected before ECC, during ECC and after ECC. The levels of lactate and pyruvate showed significant alterations in sodium bicarbonate-treated patients, and there was also a considerable imbalance in the succinate/fumarate ratio. This means that tissue hypoxia due to ECC leads to cellular oxidative damage and to a considerable decrease in the intracellular energy pools. The use of L-carnitine antagonizes the oxidative stress, as is well documented by the levels of plasmatic metabolites which remain confined to normal amounts.

Topics: Bicarbonates; Carnitine; Double-Blind Method; Extracorporeal Circulation; Female; Fumarates; Humans; Hypoxia; Lactates; Lactic Acid; Male; Middle Aged; Pyruvates; Random Allocation; Sodium; Sodium Bicarbonate; Succinates; Succinic Acid

Topics: Amides; Aminopyrine; Analgesics; Clinical Trials as Topic; Drug Evaluation; Fumarates; Humans; Hypoxia; Piperidines; Placebos; Propionates; Pyridines

Komagataeibacter xylinus is an aerobic strain that produces bacterial cellulose (BC). Oxygen levels play a critical role in regulating BC synthesis in K. xylinus, and an increase in oxygen tension generally means a decrease in BC production. Fumarate nitrate reduction protein (FNR) and aerobic respiration control protein A (ArcA) are hypoxia-inducible factors, which can signal whether oxygen is present in the environment. In this study, FNR and ArcA were used to enhance the efficiency of oxygen signaling in K. xylinus, and globally regulate the transcription of the genome to cope with hypoxic conditions, with the goal of improving growth and BC production. FNR and ArcA were individually overexpressed in K. xylinus, and the engineered strains were cultivated under different oxygen tensions to explore how their overexpression affects cellular metabolism and regulation. Although FNR overexpression did not improve BC production, ArcA overexpression increased BC production by 24.0% and 37.5% as compared to the control under oxygen tensions of 15% and 40%, respectively. Transcriptome analysis showed that FNR and ArcA overexpression changed the way K. xylinus coped with oxygen tension changes, and that both FNR and ArcA overexpression enhanced the BC synthesis pathway. The results of this study provide a new perspective on the effect of oxygen signaling on growth and BC production in K. xylinus and suggest a promising strategy for enhancing BC production through metabolic engineering. KEY POINTS: • K. xylinus BC production increased after overexpression of ArcA • The young's modulus is enhanced by the ArcA overexpression • ArcA and FNR overexpression changed how cells coped with changes in oxygen tension.

Topics: Cellulose; Fumarates; Gluconacetobacter xylinus; Humans; Hypoxia; Nitrates; Oxygen

Succinate dehydrogenase (SDH) plays an important role in reverse electron transfer during hypoxia/anoxia, in particular, in ischemia, when blood supply to an organ is disrupted, and oxygen is not available. It was detected in the voltammetry studies about three decades ago that the SDHA/SDHB subcomplex of SDH can have such a strong nonlinear property as a "tunnel-diode" behavior in reverse quinol-fumarate reductase direction. The molecular and kinetic mechanisms of this phenomenon, that is, a strong drop in the rate of fumarate reduction as the driving force is increased, are still unclear. In order to account for this property of SDH, we developed and analyzed a mechanistic computational model of reverse electron transfer in the SDHA/SDHB subcomplex of SDH. It was shown that a decrease in the rate of succinate release from the active center during fumarate reduction quantitatively explains the experimentally observed tunnel-diode behavior in SDH and threshold values of the electrode potential of about -80 mV. Computational analysis of ROS production in the SDHA/SDHB subcomplex of SDH during reverse electron transfer predicts that the rate of ROS production decreases when the tunnel-diode behavior appears. These results predict a low rate of ROS production by the SDHA/SDHB subcomplex of SDH during ischemia.

Topics: Electron Transport Complex II; Fumarates; Humans; Hydroquinones; Hypoxia; Reactive Oxygen Species; Succinate Dehydrogenase; Succinates

Oxidative stress is a hallmark of ischemic stroke pathogenesis causing neuronal malfunction and cell death. Up-regulation of anti-oxidative genes through activation of the NF-E2-related transcription factor 2 (Nrf2) is one of the key mechanisms in cellular defense against oxidative stress. Fumaric acid esters (FAEs) represent a class of anti-oxidative and anti-inflammatory molecules that are already in clinical use for multiple sclerosis therapy. Purpose of this study was to investigate whether FAEs promote neuronal survival upon ischemia, and analyze putative underlying molecular mechanisms in neurons. Murine organotypic hippocampal slice cultures, and two neuronal cell lines were treated with dimethyl fumarate (DMF) and monomethyl fumarate (MMF). Ischemic conditions were generated by exposing cells and slice cultures to oxygen-glucose deprivation (OGD), and cell death was determined through propidium iodide staining. Treatment with both DMF and MMF immediately after OGD during reoxygenation strongly reduced cell death in hippocampal cultures ex vivo. Both DMF and MMF promoted neuronal survival in HT-22 and SH-SY5Y cell lines exposed to ischemic stress. DMF but not MMF activated the anti-oxidative Nrf2 pathway in neurons. Accordingly, Nrf2 knockdown in murine neurons abrogated the protective effect of DMF but not MMF. Moreover, FAEs did not activate the hypoxia-inducible factor (HIF) pathway suggesting that this pathway may not significantly contribute to FAE mediated neuroprotection. Our results may provide the basis for a new therapeutic approach to treat ischemic pathologies such as stroke with a drug that already has a broad safety record in humans.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Antioxidants; Brain Ischemia; Cell Line; Cell Survival; Esters; Fumarates; Glucose; Hippocampus; Humans; Hypoxia; Hypoxia-Inducible Factor 1; Mice; Mice, Inbred C57BL; Neurons; NF-E2-Related Factor 2; Signal Transduction

2SC [S-(2-succino)-cysteine] is a chemical modification formed by a Michael addition reaction of fumarate with cysteine residues in proteins. Formation of 2SC, termed 'succination' of proteins, increases in adipocytes grown in high-glucose medium and in adipose tissues of Type 2 diabetic mice. However, the metabolic mechanisms leading to increased fumarate and succination of protein in the adipocyte are unknown. Treatment of 3T3 cells with high glucose (30 mM compared with 5 mM) caused a significant increase in cellular ATP/ADP, NADH/NAD+ and Δψm (mitochondrial membrane potential). There was also a significant increase in the cellular fumarate concentration and succination of proteins, which may be attributed to the increase in NADH/NAD+ and subsequent inhibition of tricarboxylic acid cycle NAD+-dependent dehydrogenases. Chemical uncouplers, which dissipated Δψm and reduced the NADH/NAD+ ratio, also decreased the fumarate concentration and protein succination. High glucose plus metformin, an inhibitor of complex I in the electron transport chain, caused an increase in fumarate and succination of protein. Thus excess fuel supply (glucotoxicity) appears to create a pseudohypoxic environment (high NADH/NAD+ without hypoxia), which drives the increase in succination of protein. We propose that increased succination of proteins is an early marker of glucotoxicity and mitochondrial stress in adipose tissue in diabetes.

Topics: 3T3 Cells; Adipocytes; Animals; Blotting, Western; Cell Survival; Citric Acid Cycle; Electrophoresis, Gel, Two-Dimensional; Fumarates; Glucose; Hypoxia; Malates; Membrane Potential, Mitochondrial; Mice; Mitochondria; Oxidative Phosphorylation; Oxidative Phosphorylation Coupling Factors; Oxidative Stress; Succinic Acid; Sweetening Agents

Two main entry points for electrons into the mitochondrial respiratory chain are NADH:ubiquinone oxidoreductase (complex I) and succinate:ubiquinone oxidoreductase (complex II). Metabolic regulation of these two respiratory complexes is not understood in detail. It has been suggested that the Krebs cycle metabolic intermediate oxaloacetate (OAA) inhibits complex II in vivo, whereas complex I undergoes a reversible active/de-active transition. In normoxic and anoxic hearts it has been shown that the proportion of complex I in the active and de-active states is different suggesting a possible mode of regulation of the enzyme by oxygen concentration. In the current studies rapid isolation of mitochondrial membranes in a state that preserves the activity of both complex I and complex II has been achieved using Langendorff perfused rat hearts. The findings indicate that the state of activation of complex I is controlled by the oxygen saturation in the perfusate. In addition, these studies show that complex II is fully active in the mitochondrion and not inhibited by OAA regardless of the oxygen concentration.

Topics: Animals; Electron Transport Complex I; Electron Transport Complex II; Fumarates; Heart; Hypoxia; In Vitro Techniques; Intracellular Membranes; Male; Malonates; Mitochondria, Heart; Multienzyme Complexes; Myocardium; NADH, NADPH Oxidoreductases; Oxaloacetic Acid; Oxygen; Perfusion; Potassium Cyanide; Rats; Rats, Sprague-Dawley; Succinate Dehydrogenase

The keto (linear) form of exogenous fructose 1,6-bisphosphate, a highly charged glycolytic intermediate, may utilize a dicarboxylate transporter to cross the cell membrane, support glycolysis, and produce ATP anaerobically. We tested the hypothesis that fumarate, a dicarboxylate, and 3-phosphoglycerate (3-PG), an intermediate structurally similar to a dicarboxylate, can support contraction in vascular smooth muscle during hypoxia. To assess ATP production during hypoxia we measured isometric force maintenance in hog carotid arteries during hypoxia in the presence or absence of 20 mM fumarate or 3-PG. 3-PG improved maintenance of force (p < 0.05) during the 30-80 min period of hypoxia. Fumarate decreased peak isometric force development by 9.5% (p = 0.008) but modestly improved maintenance of force (p < 0.05) throughout the first 80 min of hypoxia. 13C-NMR on tissue extracts and superfusates revealed 1,2,3,4-(13)C-fumarate (5 mM) metabolism to 1,2,3,4-(13)C-malate under oxygenated and hypoxic conditions suggesting uptake and metabolism of fumarate. In conclusion, exogenous fumarate and 3-PG readily enter vascular smooth muscle cells, presumably by a dicarboxylate transporter, and support energetically important pathways.

Topics: Animals; Biological Transport; Carbon Isotopes; Carotid Arteries; Cell Membrane; Fumarates; Glyceric Acids; Hypoxia; Muscle, Smooth, Vascular; Nuclear Magnetic Resonance, Biomolecular; Swine; Time Factors

It has been demonstrated that perfusion of myocardium with glutamic acid or tricarboxylic acid cycle intermediates during hypoxia or ischemia, improves cardiac function, increases ATP levels, and stimulates succinate production. In this study isolated adult rat heart cells were used to investigate the mechanism of anaerobic succinate formation and examine beneficial effects attributed to ATP generated by this pathway. Myocytes incubated for 60 min under hypoxic conditions showed a slight loss of ATP from an initial value of 21 +/- 1 nmol/mg protein, a decline of CP from 42 to 17 nmol/mg protein and a fourfold increase in lactic acid production to 1.8 +/- 0.2 mumol/mg protein/h. These metabolite contents were not altered by the addition of malate and 2-oxoglutarate to the incubation medium nor were differences in cell viability observed; however, succinate release was substantially accelerated to 241 +/- 53 nmol/mg protein. Incubation of cells with [U-14C]malate or [2-U-14C]oxoglutarate indicates that succinate is formed directly from malate but not from 2-oxoglutarate. Moreover, anaerobic succinate formation was rotenone sensitive. We conclude that malate reduction to succinate occurs via the reverse action of succinate dehydrogenase in a coupled reaction where NADH is oxidized (and FAD reduced) and ADP is phosphorylated. Furthermore, by transaminating with aspartate to produce oxaloacetate, 2-oxoglutarate stimulates cytosolic malic dehydrogenase activity, whereby malate is formed and NADH is oxidized. In the form of malate, reducing equivalents and substrate are transported into the mitochondria where they are utilized for succinate synthesis.

Topics: Adenosine Triphosphate; Animals; Cell Survival; Chromatography, High Pressure Liquid; Deoxyglucose; Fumarates; Hypoxia; Ketoglutaric Acids; Malates; Myocardium; Phosphocreatine; Rats; Succinates; Succinic Acid

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Alanine; Animals; Aspartic Acid; Citrates; Fumarates; Glutamates; Hypoxia; In Vitro Techniques; Malates; Male; Mitochondria, Heart; Myocardium; Phosphocreatine; Rats; Succinates

Topics: Animals; Aspartic Acid; Carbon Dioxide; Fumarates; Glutamates; Hypoxia; Kinetics; Myocardium; Rabbits; Succinates

Topics: Alanine; Aminooxyacetic Acid; Animals; Cardiomyopathies; Fumarates; Glutamates; Hypoxia; Ketoglutaric Acids; Lactates; Malates; Mitochondria, Heart; Myocardium; Papillary Muscles; Rabbits; Succinates

The objective of this investigation was to determine if the succinate that accumulates in anoxic or hypoxic tissues of mammals is (a) increased in concentration in the blood, (b) excreted in the urine or (c) recycled in some manner. Rats were subjected to 0.4 atm and the plasma analyzed for succinate and fumarate at 2 hours, 24 hours and 28 days. Significant increases of succinate or succinate plus fumarate were obtained at 2 hours and 28 days at 0.4 atm. Analysis of 24-hour samples of urine obtained from controls and animals at 0.4 atm for 28 days demonstrated that no substantial increase in succinate excretion occurred with acclimation. Lung slices were incubated in Krebs-Ringer bicarbonate and succinate and gassed with O2:CO2 (95:5). Such oxygenated lung slices not only utilized succinate but produced a comparable quantity of fumerate plus malate. It is concluded that succinate produced from fumarate and alpha-ketoglutarate in peripheral hypotic tissue is transported by the blood to the oxygenated lungs. There it is oxidized to fumarate and recycled as fumarate and malate to the periphery. In this way metabolites can act as electron shuttles between peripheral cells and lung.

Topics: Animals; Fumarates; Hypoxia; Lung; Malates; Male; Rats; Succinates

Topics: Animals; Benzyl Compounds; Biological Transport; Blood-Brain Barrier; Brain; Brain Chemistry; Carbon Isotopes; Cerebrovascular Circulation; Cycloheptanes; Dogs; Female; Fumarates; Glucose; Hypoxia; Male; Mice; Quaternary Ammonium Compounds; Quinidine; Rats

Topics: Animals; Blood Pressure; Carbon Dioxide; Carbon Isotopes; Cell Membrane Permeability; Dogs; Fumarates; Humans; Hydrogen-Ion Concentration; Hydroxybutyrates; Hypoxia; Lactates; Liver; Oxaloacetates; Oxidation-Reduction; Oxygen; Perfusion; Pyruvates; Succinates

Topics: Adult; Appetite Depressants; Cardiac Output; Female; Fumarates; Humans; Hypertension, Pulmonary; Hypoxia; Male; Middle Aged; Oxazoles; Oxygen; Respiration

1. The ability of tricarboxylic acid-cycle metabolites to influence the physiological performance of the perfused anaerobic rat heart was investigated. Energy expenditure/h [(beats/min)x60xsystolic pressure/g of protein] for various anoxic conditions compared with oxygenated control hearts were: 5mm-glucose, 4.5%; 20mm- or 40mm-glucose, 10%; 20mm-glucose plus fumerate+malate+glutamate, 29%; 20mm-glucose plus oxaloacetate and alpha-oxoglutarate, 31%. 2. The energy expenditure/lactate production ratio was increased by the tricarboxylic acid-cycle metabolites, indicating that alterations in anaerobic physiological performance did not result from changes in glycolysis. 3. Analysis of tissue constituents provided further indication of an enhanced energy status for fumarate+malate+glutamate- and oxaloacetate+alpha-oxoglutarate-perfused hearts; tissue concentrations of both glycogen and ATP were higher than in the 20mm-glucose-perfused groups. 4. A marked increase in the accumulation of succinate in tissues perfused with oxaloacetate+alpha-oxoglutarate or fumarate+malate+glutamate provided further evidence that these metabolites were stimulating mitochondrial energy production under anoxia. 5. These studies indicate that mitochondrial ATP production can be stimulated in an isolated mammalian tissue perfused under anaerobiosis with a resulting enhancement of cell function.

Topics: Adenosine Triphosphate; Animals; Citric Acid Cycle; Fumarates; Glucose; Glutamates; Glycogen; Glycolysis; Heart; Heart Rate; Hypoxia; In Vitro Techniques; Ketoglutaric Acids; Lactates; Malates; Male; Metabolism; Myocardium; Oxaloacetates; Oxygen; Perfusion; Phosphocreatine; Rats; Succinates

Topics: Adenosine Triphosphate; Amino Acids; Animals; Azides; Brain; Carbon Isotopes; Cyanides; Dicarboxylic Acids; Dinitrophenols; Fumarates; Glucose; Hypoxia; Ketoglutaric Acids; Lactates; Oxaloacetates; Phosphocreatine; Pyruvates; Rats; Succinates

Topics: Acetylcholine; Aniline Compounds; Animals; Dinitrophenols; Fumarates; Glucose; Glutamates; Hormones; Hypoxia; In Vitro Techniques; Insulin; Islets of Langerhans; Malonates; Mannose; Phenazines; Rabbits; Salicylates; Secretory Rate; Tolbutamide