Effect of haematocrit value and pO2 on the redox state and metabolism of the perfused liver.
Ontology highlight
ABSTRACT:
SUBMITTER: Mayes PA
PROVIDER: S-EPMC1163804 | biostudies-other | 1976 Jun
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Nitrogen balances were measured in isolated perfused rat livers in the presence and absence of nitrogen donors. In all instances the balance apparently was incomplete. The expression [alanine][alpha-oxoglutarate]/[pyruvate][glutamate] remained fairly constant under the metabolic conditions studied, indicating that it may be at near-equilibrium. The source of the extra nitrogen seems to be derived from increased hepatic proteolysis. The addition of a nitrogen donor to the perfusate arrested proteolysis, as did the addition of pyruvate. The free mitochondrial [NAD(+)]/[NADH] ratio, calculated from the glutamate dehydrogenase and beta-hydroxybutyrate dehydrogenase reactants, showed similar values and exhibited parallel changes under most metabolic situations studied. These results suggest that, under the reported experimental conditions, both dehydrogenases share a common mitochondrial NAD pool. Glutamate dehydrogenase plays an important role in hepatic nitrogen metabolism in vivo.
| S-EPMC1166219 | biostudies-other
Project description:The tumor protein P53 (TP53, or p53) has complex and at times seemingly contradictory roles in the regulation of metabolism and ferroptosis sensitivity. We find that the actions of p53 influence the redox state, which can trigger changes in redox-sensitive proteins, thereby modifying metabolic processes and response to ferroptosis.
| S-EPMC8018455 | biostudies-literature
Project description:PURPOSE:Acute myeloid leukemia (AML) is a hematologic malignancy characterized by the accumulation of immature myeloid precursor cells. AML is poorly responsive to conventional chemotherapy and a diagnosis of AML is usually fatal. More effective and less toxic forms of therapy are desperately needed. AML cells are known to be highly dependent on the amino acid glutamine for their survival. These studies were directed at determining the effects of glutaminase inhibition on metabolism in AML and identifying general weaknesses that can be exploited therapeutically. EXPERIMENTAL DESIGN:AML cancer cell lines, primary AML cells, and mouse models of AML and acute lymphoblastic leukemia (ALL) were utilized. RESULTS:We show that blocking glutamine metabolism through the use of a glutaminase inhibitor (CB-839) significantly impairs antioxidant glutathione production in multiple types of AML, resulting in accretion of mitochondrial reactive oxygen species (mitoROS) and apoptotic cell death. Moreover, glutaminase inhibition makes AML cells susceptible to adjuvant drugs that further perturb mitochondrial redox state, such as arsenic trioxide (ATO) and homoharringtonine (HHT). Indeed, the combination of ATO or HHT with CB-839 exacerbates mitoROS and apoptosis, and leads to more complete cell death in AML cell lines, primary AML patient samples, and in vivo using mouse models of AML. In addition, these redox-targeted combination therapies are effective in eradicating ALL cells in vitro and in vivo. CONCLUSIONS:Targeting glutamine metabolism in combination with drugs that perturb mitochondrial redox state represents an effective and potentially widely applicable therapeutic strategy for treating multiple types of leukemia.
| S-EPMC6642698 | biostudies-literature
Project description:Overflow metabolism in the form of aerobic acetate excretion by Escherichia coli is an important physiological characteristic of this common industrial microorganism. Although acetate formation occurs under conditions of high glucose consumption, the genetic mechanisms that trigger this phenomenon are not clearly understood. We report on the role of the NADH/NAD ratio (redox ratio) in overflow metabolism. We modulated the redox ratio in E. coli through the expression of Streptococcus pneumoniae (water-forming) NADH oxidase. Using steady-state chemostat cultures, we demonstrated a strong correlation between acetate formation and this redox ratio. We furthermore completed genome-wide transcription analyses of a control E. coli strain and an E. coli strain overexpressing NADH oxidase. The transcription results showed that in the control strain, several genes involved in the tricarboxylic acid (TCA) cycle and respiration were repressed as the glucose consumption rate increased. Moreover, the relative repression of these genes was alleviated by expression of NADH oxidase and the resulting reduced redox ratio. Analysis of a promoter binding site upstream of the genes which correlated with redox ratio revealed a degenerate sequence with strong homology with the binding site for ArcA. Deletion of arcA resulted in acetate reduction and increased the biomass yield due to the increased capacities of the TCA cycle and respiration. Acetate formation was completely eliminated by reducing the redox ratio through expression of NADH oxidase in the arcA mutant, even at a very high glucose consumption rate. The results provide a basis for studying new regulatory mechanisms prevalent at reduced NADH/NAD ratios, as well as for designing more efficient bioprocesses.
| S-EPMC1472329 | biostudies-literature
Project description:Addition of phenylephrine to isolated perfused rat liver is followed by an increased 14CO2 production from [1-14C]glutamate, [1-14C]glutamine, [U-14C]proline and [3-14C]pyruvate, but by a decreased 14CO2 production from [1-14C]pyruvate. Simultaneously, there is a considerable decrease in tissue content of 2-oxoglutarate, glutamate and citrate. Stimulation of 14CO2 production from [1-14C]glutamate is also observed in the presence of amino-oxyacetate, suggesting a stimulation of glutamate dehydrogenase and 2-oxoglutarate dehydrogenase fluxes by phenylephrine. Inhibition of pyruvate dehydrogenase flux by phenylephrine is due to an increased 2-oxoglutarate dehydroxygenase flux. Phenylephrine stimulates glutaminase flux and inhibits glutamine synthetase flux to a similar extent, resulting in an increased hepatic glutamine uptake. Whereas the effects of NH4+ ions and phenylephrine on glutaminase flux were additive, activation of glutaminase by glucagon was considerably diminished in the presence of phenylephrine. The reported effects are largely overcome by prazosin, indicating the involvement of alpha-adrenergic receptors in the action of phenylephrine. It is concluded that stimulation of gluconeogenesis from various amino acids by phenylephrine is due to an increased flux through glutamate dehydrogenase and the citric acid cycle.
| S-EPMC1144094 | biostudies-other
Project description:Mitochondria sense changes resulting from the ischemia and subsequent reperfusion of an organ and mitochondrial reactive oxygen species (ROS) production initiates a series of events, which over time result in the development of full-fledged ischemia-reperfusion injury (IRI), severely affecting graft function and survival after transplantation. ROS activate the innate immune system, regulate cell death, impair mitochondrial and cellular performance and hence organ function. Arresting the development of IRI before the onset of ROS production is currently not feasible and clinicians are faced with limiting the consequences. Ex vivo machine perfusion has opened the possibility to ameliorate or antagonize the development of IRI and may be particularly beneficial for extended criteria donor organs. The molecular events occurring during machine perfusion remain incompletely understood. Accumulation of succinate and depletion of adenosine triphosphate (ATP) have been considered key mechanisms in the initiation; however, a plethora of molecular events contribute to the final tissue damage. Here we discuss how understanding mitochondrial dysfunction linked to IRI may help to develop novel strategies for the prevention of ROS-initiated damage in the evolving era of machine perfusion.
| S-EPMC7246795 | biostudies-literature
Project description:1. The rates of gluconeogenesis from most substrates tested in the perfused livers of well-fed rats were about half of those obtained in the livers of starved rats. There was no difference for glycerol. 2. A diet low in carbohydrate increased the rates of gluconeogenesis from some substrates but not from all. In general the effects of a low-carbohydrate diet on rat liver are less marked than those on rat kidney cortex. 3. Glycogen was deposited in the livers of starved rats when the perfusion medium contained about 10mm-glucose. The shedding of glucose from the glycogen stores by the well-fed liver was greatly diminished by 10mm-glucose and stopped by 13.3mm-glucose. Livers of well-fed rats that were depleted of their glycogen stores by treatment with phlorrhizin and glucagon synthesized glycogen from glucose. 4. When two gluconeogenic substrates were added to the perfusion medium additive effects occurred only when glycerol was one of the substrates. Lactate and glycerol gave more than additive effects owing to an increased rate of glucose formation from glycerol. 5. Pyruvate also accelerated the conversion of glycerol into glucose, and the accelerating effect of lactate can be attributed to a rapid formation of pyruvate from lactate. 6. Butyrate and oleate at 2mm, which alone are not gluconeogenic, increased the rate of gluconeogenesis from lactate. 7. The acceleration of gluconeogenesis from lactate by glucagon was also found when gluconeogenesis from lactate was stimulated by butyrate and oleate. This finding is not compatible with the view that the primary action of glucagon in promoting gluconeogenesis is an acceleration of lipolysis. 8. The rate of gluconeogenesis from pyruvate at 10mm was only 70% of that at 5mm. This ;inhibition' was abolished by oleate or glucagon.
| S-EPMC1198388 | biostudies-other
Project description:Over the past three decades, L-proline has become recognized as an important metabolite for trypanosomatids. It is involved in a number of key processes, including energy metabolism, resistance to oxidative and nutritional stress and osmoregulation. In addition, this amino acid supports critical parasite life cycle processes by acting as an energy source, thus enabling host-cell invasion by the parasite and subsequent parasite differentiation. In this paper, we demonstrate that L-proline is oxidized to ?(1)-pyrroline-5-carboxylate (P5C) by the enzyme proline dehydrogenase (TcPRODH, E.C. 1.5.99.8) localized in Trypanosoma cruzi mitochondria. When expressed in its active form in Escherichia coli, TcPRODH exhibits a Km of 16.58±1.69 µM and a Vmax of 66±2 nmol/min mg. Furthermore, we demonstrate that TcPRODH is a FAD-dependent dimeric state protein. TcPRODH mRNA and protein expression are strongly upregulated in the intracellular epimastigote, a stage which requires an external supply of proline. In addition, when Saccharomyces cerevisiae null mutants for this gene (PUT1) were complemented with the TcPRODH gene, diminished free intracellular proline levels and an enhanced sensitivity to oxidative stress in comparison to the null mutant were observed, supporting the hypothesis that free proline accumulation constitutes a defense against oxidative imbalance. Finally, we show that proline oxidation increases cytochrome c oxidase activity in mitochondrial vesicles. Overall, these results demonstrate that TcPRODH is involved in proline-dependant cytoprotection during periods of oxidative imbalance and also shed light on the participation of proline in energy metabolism, which drives critical processes of the T. cruzi life cycle.
| S-EPMC3718742 | biostudies-literature
Project description:1. Liver from hyper- and hypo-thyroid male fed rats were perfused with whole blood and their metabolism was compared with euthyroid controls. 2. Hyperthyroid livers produced more bile than controls and hypothyroid livers produced less. 3. Glucose output by all livers was similar; glycogen declined only during perfusion of hyperthyroid livers. Lactate uptake increased in hyperthyroid but decreased in hypothyroid livers. These results may be explained by changes in oxidation of carbohydrate rather than in gluconeogenesis. 4. Secretion of triacylglycerol was decreased in hyperthyroid and not changed significantly in hypothyroid livers. 5. Fractional extraction of infused [1-14C]oleate was unaltered. Hyperthyroid livers oxidized more oleate to CO2 and ketone bodies, esterified less and incorporated less into lipoproteins of d less than 1.006. Hypothyroid livers oxidized and esterified oleate to the same extent as controls; their decreased O2 consumption was due to diminished oxidation of other (non-lipid) substrates; 14C-labelled ketone-body formation was increased, but at the expense of 14CO2 production. 6. Lipogenesis (measured with 3H2O) was unaltered in hyperthyroid but was decreased in hypothyroid livers. Incorporation of 3H and 14C into triacylglycerol relative to phospholipid decreased in hyperthyroid and increased in hypothyroid livers. Cholesterol synthesis was similar in all perfusions. 7. During oleate infusion, the cytosolic redox state, as indicated by the perfusate [lactate]/[pyruvate] ratio, was decreased in hyperthyroid and increased in hypothyroid livers. No change in [3-hydroxybutyrate]/[acetoacetate] was detected. 8. The importance of relating the concentration of plasma non-esterified fatty acids to the interpretation of metabolic data obtained under differing thyroid status is emphasized.
| S-EPMC1162988 | biostudies-other
Project description:1. Loading the isolated perfused liver from well-fed rats with xylitol (20mm) caused a depletion of adenine nucleotides and P(i) and an accumulation of alpha-glycerophosphate. The ATP content fell to 66% of the control value after 10min and to 32% after 80min. The ADP and AMP contents also fell. After 80min 63% of the total adenine nucleotides and 59% of the P(i) had been lost. 2. The alpha-glycerophosphate content rose from 0.13 to 4.74mumol/g at 10min and reached 8.02mumol/g at 40min. 3. Xylitol was rapidly metabolized, the main products being glucose, lactate and pyruvate. 4. The [lactate]/[pyruvate] ratio in the presence of xylitol rose to 30-40. 5. On perfusion of livers from starved animals the main product of xylitol metabolism was glucose and the mean ratio xylitol removed/glucose formed was 1.29 (corrected for endogenous glucose and lactate production). This is close to the predicted value of 1.2. 6. Evidence is presented indicating that the loss of adenine nucleotides caused by xylitol is not due to the increased ATP consumption but to the accumulation of alpha-glycerophosphate and depletion of P(i). 7. The loss of adenine nucleotides accounts for the hyperuricaemia which can occur after xylitol infusion in man. 8. The relevance of the findings to the clinical use of xylitol as an energy source is discussed.
| S-EPMC1177829 | biostudies-other