Metabolism of tricarboxylic acid cycle in rat kidney medulla in vitro

1. The metabolism of incubated slices of sponge-induced granulation tissue, harvested 4–90 days after the implantation, was studied with special reference to the capacity of collagen synthesis and to the energy metabolism. Data are also given on the nucleic acid contents during the observation period. Three metabolic phases were evident. 2. The viability of the slices for the synthesis of collagen was studied in various conditions. Freezing and homogenization destroyed the capacity of the tissue to incorporate proline into collagen. 3. Consumption of oxygen reached the maximum at 30–40 days. There was evidence that the pentose phosphate cycle was important, especially during the phases of the proliferation and the involution. The formation of lactic acid was maximal at about 20 days. 4. The capacity to incorporate proline into collagen hydroxyproline in vitro was limited to a relatively short period at 10–30 days. 5. The synthesis of collagen was dependent on the supply of oxygen and glucose, which latter could be replaced in the incubation medium by other monosaccharides but not by the metabolites of glucose or tricarboxylic acid-cycle intermediates.

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Tricarboxylic acid cycle dehydrogenases inhibition by naringenin: experimental and molecular modelling evidence

British Journal Of Nutrition ◽

10.1017/s0007114520000549 ◽

2020 ◽

Vol 123 (10) ◽

pp. 1117-1126

Author(s):

Pauline Maciel August ◽

Mateus Grings ◽

Marcelo Sartori Grunwald ◽

Geancarlo Zanatta ◽

Vinícius Stone ◽

...

Keyword(s):

Citrate Synthase ◽

Tricarboxylic Acid Cycle ◽

Cell Metabolism ◽

Tricarboxylic Acid ◽

Metabolic Effects ◽

Similar Reduction ◽

Acid Cycle ◽

Docking Simulations ◽

Female Wistar Rats

AbstractThe study of polyphenols’ effects on health has been gaining attention lately. In addition to reacting with important enzymes, altering the cell metabolism, these substances can present either positive or negative metabolic alterations depending on their consumption levels. Naringenin, a citrus flavonoid, already presents diverse metabolic effects. The objective of this work was to evaluate the effect of maternal naringenin supplementation during pregnancy on the tricarboxylic acid cycle activity in offspring’s cerebellum. Adult female Wistar rats were divided into two groups: (1) vehicle (1 ml/kg by oral administration (p.o.)) or (2) naringenin (50 mg/kg p.o.). The offspring were euthanised at 7th day of life, and the cerebellum was dissected to analyse citrate synthase, isocitrate dehydrogenase (IDH), α-ketoglutarate dehydrogenase (α-KGDH) and malate dehydrogenase (MDH) activities. Molecular docking used SwissDock web server and FORECASTER Suite, and the proposed binding pose image was created on UCSF Chimera. Data were analysed by Student’s t test. Naringenin supplementation during pregnancy significantly inhibited IDH, α-KGDH and MDH activities in offspring’s cerebellum. A similar reduction was observed in vitro, using purified α-KGDH and MDH, subjected to pre-incubation with naringenin. Docking simulations demonstrated that naringenin possibly interacts with dehydrogenases in the substrate and cofactor binding sites, inhibiting their function. Naringenin administration during pregnancy may affect cerebellar development and must be evaluated with caution by pregnant women and their physicians.

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Up-regulation of glucose metabolism in Kupffer cells following infusion of tumour necrosis factor

Biochemical Journal ◽

10.1042/bj2780515 ◽

1991 ◽

Vol 278 (2) ◽

pp. 515-519 ◽

Cited By ~ 19

Author(s):

Z Spolarics ◽

G J Bagby ◽

C H Lang ◽

J J Spitzer

Keyword(s):

Endothelial Cells ◽

Kupffer Cells ◽

Tumour Necrosis ◽

Glucose Oxidation ◽

Tricarboxylic Acid Cycle ◽

Tricarboxylic Acid ◽

Acid Cycle ◽

Necrosis Factor

Alterations of glucose metabolism and the oxidation of glutamine and palmitate were studied, by using specifically labelled substrates, in freshly isolated Kupffer cells and hepatic endothelial cells after infusion in vivo of human recombinant tumour necrosis factor-alpha (TNF; 7.5 x 10(5) IU/30 min per kg body wt., intravenously). Cells were incubated in a medium containing 5 mM-glucose, 0.4 mM-palmitate, 1 mM-lactate and 0.5 mM-glutamine. Administration of TNF in vivo increased glucose use in Kupffer cells by 70%. Glucose oxidation in the tricarboxylic acid cycle and flux in the Embden-Meyerhof (EM) pathway were elevated by 40 and 80% respectively. Treatment in vitro with 1 microM-phorbol 12-myristate 13-acetate (PMA) resulted in a similar percentage increase in glucose use by Kupffer cells prepared from either saline- or TNF-treated rats. However, PMA increased the activity of the hexose monophosphate shunt (HMS) by 3- and 10-fold in cells isolated from saline- or TNF-infused animals respectively. A phagocyte stimulus in vitro, opsonized zymosan, increased glucose use by 30% and doubled the flux through the HMS in Kupffer cells from saline-infused animals. The activity of the HMS in response to zymosan was increased by 400% after TNF treatment. In endothelial cells, basal glucose utilization was not altered by TNF treatment. PMA increased HMS activity in endothelial cells to a similar degree after saline or TNF infusion. Zymosan, however, increased HMS activity only in endothelial cells from TNF-treated rats. Oxidation of palmitate or glutamine was not affected by TNF treatment either under basal conditions or after challenge in vitro. Our data indicate that, after phagocytosis in vitro or protein kinase C activation, glucose use and flux through the HMS increase in Kupffer cells. This is accompanied by increased glycolytic flux, with no changes in glucose oxidation in the tricarboxylic acid cycle. After TNF exposure, followed by a secondary stimulus, the enhanced glucose use by Kupffer cells is primarily channelled through the HMS pathway. These data suggest that the increased glucose use in vivo by Kupffer cells found after immune-stimulated conditions may subserve primarily the increased need for NADPH and HMS intermediates.

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IN VITRO EFFECTS OF FLUORIDE ON TRICARBOXYLIC ACID CYCLE DEHYDROGENASES AND OXIDATIVE PHOSPHORYLATION: PART I

Journal of Histochemistry & Cytochemistry ◽

10.1177/15.4.195 ◽

1967 ◽

Vol 15 (4) ◽

pp. 195-201 ◽

Cited By ~ 14

Author(s):

C. JAMES LOVELACE ◽

GENE W. MILLER

Keyword(s):

Oxidative Phosphorylation ◽

Competitive Inhibition ◽

Tricarboxylic Acid Cycle ◽

Succinic Dehydrogenase ◽

Tricarboxylic Acid ◽

Initial Increase ◽

Acid Cycle ◽

Oxidase System ◽

Vitro Effect

Studies were conducted on the in vitro effect of fluoride on the succinic oxidase system utilizing mitochondria obtained from cauliflower. Preincubation of mitochondria with fluoride did not increase inhibition of succinic oxidase. Various other tricarboxylic acid cycle substrates were used to determine their sensitivity to fluoride; only succinate oxidation was affected. A series of succinate concentrations in the presence and in the absence of fluoride showed increased activity of succinic dehydrogenase, which indicated competitive inhibition. Various concentrations of phosphate in the absence of fluoride showed that phosphate had only slight effects on the succinic 2,6-dichlorophenolindophenol reductase component of the succinic oxidase system. In the absence of phosphate, various concentrations of fluoride showed an initial increase in activity followed by a decrease in activity of succinic 2,6-dichlorophenolindophenol reductase. In the presence of phosphate, fluoride caused marked inhibition of succinic 2,6-dichlorophenolindophenol reductase. It is believed that this inhibition results from an enzyme-fluorophosphate complex which has a lower dissociation constant than that of the enzyme-substrate complex. An oxidative phosphorylation study indicated that both respiration and phosphorylation were inhibited.

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Transamination of glutamate to tricarboxylic acid-cycle intermediates in cultured neurons correlates with the ability of oxo acids to support neuronal survival in vitro

Biochemical Journal ◽

10.1042/bj2340605 ◽

1986 ◽

Vol 234 (3) ◽

pp. 605-610 ◽

Cited By ~ 5

Author(s):

L Facci ◽

S D Skaper ◽

S Varon

Keyword(s):

Amino Acid ◽

Neuronal Survival ◽

Tricarboxylic Acid Cycle ◽

Tricarboxylic Acid ◽

Neuronal Cultures ◽

Acid Cycle ◽

Ciliary Ganglion Neurons ◽

Amino Acid Precursors ◽

Ganglion Neurons

Cultures of central-nervous-system neurons at low densities require for their survival exogenous pyruvate, alpha-oxoglutarate or oxaloacetate, even in the presence of high glucose concentrations. Most other alpha-oxo acids support cell survival only in the presence of alpha-amino acids which transaminate to alpha-oxoglutarate, oxaloacetate or pyruvate. The alpha-oxo acids therefore operate as acceptors of amino groups from appropriate donors to generate tricarboxylic acid-cycle-relevant substrates, and these alpha-oxo acids provide for neuronal support only insofar as they make it possible for exogenously supplied alpha-amino acid precursors to generate intracellularly one of the three critical metabolites. To examine more closely the relationship between transamination activity and neuronal survival, we measured 14CO2 production from [14C]glutamate in the presence of appropriate alpha-oxo acid partners by using 8-day-embryonic chick forebrain, dorsal-root-ganglion and ciliary-ganglion neurons. Neuronal survival was measured concurrently in monolayer neuronal cultures maintained with the corresponding amino acid/oxo acid pairs. Forebrain and ganglionic cell suspensions both produced 14CO2 from [14C]glutamate, which accurately correlated with 24 h neuronal survival. Concentrations of glutamate or alpha-oxo acid which provide for maximal neuronal survival also produced maximal amounts of 14CO2. The same ability to generate CO2 from glutamate (in the presence of the appropriate alpha-oxo acids) can ensure neuronal survival in 24 h cultures and therefore must meet energy or other metabolic needs of those neurons which glucose itself is unable to satisfy.

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Studies on the Metabolism of Locust Fat Body

Journal of Experimental Biology ◽

10.1242/jeb.36.4.665 ◽

1959 ◽

Vol 36 (4) ◽

pp. 665-675

Author(s):

A. N. CLEMENTS

Keyword(s):

Amino Acids ◽

Sodium Acetate ◽

Flight Muscle ◽

Fat Body ◽

Enzyme System ◽

Tricarboxylic Acid Cycle ◽

Succinic Dehydrogenase ◽

Tricarboxylic Acid ◽

Acid Cycle

1. The incorporation of glycine-14C (G), leucine-14C (G), sodium acetate-2-14C and glucose-14C (G) into Schistocerca fat body was studied under in vitro conditions, and the distribution of radioactivity in the various fat body fractions and the labelling of compounds within the fractions is described. 2. The overall picture was of high incorporation into fat and protein and of very low incorporation into glycogen. 3. Incubation with glycine-14C led to radioactivity appearing in the glycine and serine of the protein and of the amino acid pool. Incubation with sodium acetate-2-14C led to radioactivity appearing in glutamate, proline, aspartate and alanine, showing that the intermediates of the tricarboxylic acid cycle provide the carbon skeletons of certain amino acids. Glucose-14C was largely converted to trehalose. 4. Succinic dehydrogenase and the condensing enzyme system were shown to be present in fat body, contrary to previous reports. The succinic oxidase system was highly labile on homogenizing the tissue. 5. Fat body, unlike flight muscle, used glycine-14C and leucine-14C as respiratory substrates, and it is suggested that fat body acts like the vertebrate liver by transdeaminating amino acids and making them available for further metabolism by other tissues.

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C14-labeled glucose metabolism by bone from normal and parathyroid-treated rats

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1965.208.5.1036 ◽

1965 ◽

Vol 208 (5) ◽

pp. 1036-1041 ◽

Cited By ~ 6

Author(s):

Haripada Chattopadhyay ◽

Smith Freeman

Keyword(s):

Glucose Metabolism ◽

Tricarboxylic Acid Cycle ◽

Bone Matrix ◽

Tricarboxylic Acid ◽

Bicarbonate Buffer ◽

Acid Cycle ◽

Growing Rats ◽

Parathyroid Extract ◽

Tricarboxylic Acid Cycle Intermediates

Calvaria and the metaphyseal and epiphyseal sections of tibia and femora freed of bone marrow from young growing rats were incubated in vitro for 2 hr at 37 C in Krebs-Ringer bicarbonate buffer containing 2 mm glucose. The glucose was labeled either in the 1 position or in the 6 position or uniformly in all positions with C14. The incorporation of C14 into citrate, lactate, and various tricarboxylic acid cycle intermediates was studied. The release of C14O2 and the incorporation of C14 into bone matrix were also measured. Results obtained from bones of untreated control, parathyroid extract-treated, and parathyroidectomized animals were compared. It was found that treatment of animals with parathyroid extract increased the total accumulation of labeled citrate and malate as well as the incorporation of these acids into bone mineral. Bones from extract-treated animals also exhibited a significant decrease in the total accumulation of radioactive fumarate, succinate, and pyruvate. Lactate was the major end product of glucose metabolism, but its accumulation was only slightly influenced by parathyroid extract.

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Stimulation of [1-14C]oleate oxidation to 14CO2 in isolated rat hepatocytes by the catecholamines, vasopressin and angiotensin. A possible mechanism of action

Biochemical Journal ◽

10.1042/bj2120085 ◽

1983 ◽

Vol 212 (1) ◽

pp. 85-91 ◽

Cited By ~ 18

Author(s):

M C Sugden ◽

D I Watts

Keyword(s):

Phosphoenolpyruvate Carboxykinase ◽

Tricarboxylic Acid Cycle ◽

Rat Hepatocytes ◽

Tricarboxylic Acid ◽

Isolated Rat Hepatocytes ◽

Acid Cycle ◽

14Co2 Production ◽

Oxoglutarate Dehydrogenase ◽

Stimulation Of

Adrenaline, noradrenaline, vasopressin and angiotensin increased 14CO2 production from [1-14C]oleate by hepatocytes from fed rats but not by hepatocytes from starved rats. The hormones did not increase 14CO2 production when hepatocytes from fed rats were depleted of glycogen in vitro. Increased 14CO2 production from]1-14C]oleate in response to the hormones was observed when hepatocytes from starved rats were incubated with 3-mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase. 3-Mercaptopicolinate inhibited uptake and esterification of [1-14C]oleate, slightly increased 14CO2 production from [1-14C]oleate and greatly increased the [3-hydroxybutyrate]/[acetoacetate] ratio. In the presence of 3-mercaptopicolinate 14CO2 production in response to the catecholamines was blocked by the α-antagonist phentolamine and required extracellular Ca2+. The effects of vasopressin and angiotensin were also Ca2+-dependent. The actions of the hormones of 14CO2 production from [I-14C]oleate by hepatocytes from starved rats in the presence of 3-mercaptopicolinate thus have the characteristics of the response to the hormones found with hepatocytes from fed rats incubated without 3-mercaptopicolinate. The stimulatory effects of the hormones on 14CO2 production from [1-14C]oleate were not the result of decreased esterification (as the hormones increased esterification) or increased β-oxidation. It is suggested that the effect of the hormones to increase 14CO2 production from [1-14C]oleate are mediated by CA2+-activation of NAD+-linked isocitrate dehydrogenase, the 2-oxoglutarate dehydrogenase complex, and/or electron transport. The results also demonstrate that when the supply of oxaloacetate is limited it is utilized for gluconeogenesis rather than to maintain tricarboxylic acid-cycle flux.

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Metabolism of glucose, glutamine, long-chain fatty acids and ketone bodies by murine macrophages

Biochemical Journal ◽

10.1042/bj2390121 ◽

1986 ◽

Vol 239 (1) ◽

pp. 121-125 ◽

Cited By ~ 232

Author(s):

P Newsholme ◽

R Curi ◽

S Gordon ◽

E A Newsholme

Keyword(s):

Fatty Acids ◽

Citrate Synthase ◽

Ketone Bodies ◽

Tricarboxylic Acid Cycle ◽

Tricarboxylic Acid ◽

The Body ◽

Acid Cycle ◽

Coa Transferase ◽

Very High

Maximum activities of some key enzymes of metabolism were studied in elicited (inflammatory) macrophages of the mouse and lymph-node lymphocytes of the rat. The activity of hexokinase in the macrophage is very high, as high as that in any other major tissue of the body, and higher than that of phosphorylase or 6-phosphofructokinase, suggesting that glucose is a more important fuel than glycogen and that the pentose phosphate pathway is also important in these cells. The latter suggestion is supported by the high activities of both glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. However, the rate of glucose utilization by ‘resting’ macrophages incubated in vitro is less than the 10% of the activity of 6-phosphofructokinase: this suggests that the rate of glycolysis is increased dramatically during phagocytosis or increased secretory activity. The macrophages possess higher activities of citrate synthase and oxoglutarate dehydrogenase than do lymphocytes, suggesting that the tricarboxylic acid cycle may be important in energy generation in these cells. The activity of 3-oxoacid CoA-transferase is higher in the macrophage, but that of 3-hydroxybutyrate dehydrogenase is very much lower than those in the lymphocytes. The activity of carnitine palmitoyltransferase is higher in macrophages, suggesting that fatty acids as well as acetoacetate could provide acetyl-CoA as substrate for the tricarboxylic acid cycle. No detectable rate of acetoacetate or 3-hydroxybutyrate utilization was observed during incubation of resting macrophages, but that of oleate was 1.0 nmol/h per mg of protein or about 2.2% of the activity of palmitoyltransferase. The activity of glutaminase is about 4-fold higher in macrophages than in lymphocytes, which suggests that the rate of glutamine utilization could be very high. The rate of utilization of glutamine by resting incubated macrophages was similar to that reported for rat lymphocytes, but was considerably lower than the activity of glutaminase.

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