fumaric-acid 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

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