Effect of starvation on glutamine ammoniagenesis and gluconeogenesis in isolated mouse kidney tubules

It has been shown recently that glutamine is taken up by the mouse kidney in vivo. However, knowledge about the fate of this amino acid and the regulation of its metabolism in the mouse kidney remains poor. Given the physiological and pathophysiological importance of renal glutamine metabolism and the increasing use of genetically modified mice in biological research, we have conducted a study to characterize glutamine metabolism in the mouse kidney. Proximal tubules isolated from fed and 48h-starved mice and then incubated with a physiological concentration of glutamine, removed this amino acid and produced ammonium ions at similar rates. In agreement with this observation, activities of the ammoniagenic enzymes, glutaminase and glutamate dehydrogenase, were not different in the renal cortex of fed and starved mice, but the glutamate dehydrogenase mRNA level was elevated 4.5-fold in the renal cortex from starved mice. In contrast, glucose production from glutamine was greatly stimulated whereas the glutamine carbon removed, that was presumably completely oxidized in tubules from fed mice, was virtually suppressed in tubules from starved animals. In accordance with the starvation-induced stimulation of glutamine gluconeogenesis, the activities and mRNA levels of glucose-6-phosphatase, and especially of phosphoenolpyruvate carboxykinase, but not of fructose-1,6-bisphosphatase, were increased in the renal cortex of starved mice. On the basis of our in vitro results, the elevated urinary excretion of ammonium ions observed in starved mice probably reflected an increased transport of these ions into the urine at the expense of those released into the renal veins rather than a stimulation of renal ammoniagenesis.

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Growth hormone decreases muscle glutamine production and stimulates protein synthesis in hypercatabolic patients

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.279.2.e323 ◽

2000 ◽

Vol 279 (2) ◽

pp. E323-E332 ◽

Cited By ~ 34

Author(s):

Gianni Biolo ◽

Fulvio Iscra ◽

Alessandra Bosutti ◽

Gabriele Toigo ◽

Beniamino Ciocchi ◽

...

Keyword(s):

Growth Hormone ◽

Protein Synthesis ◽

Amino Acid ◽

De Novo ◽

Muscle Protein ◽

Recombinant Human Growth Hormone ◽

Glutamine Metabolism ◽

Trauma Patients ◽

Mrna Levels ◽

Glutamine Production

We determined the effects of 24-h recombinant human growth hormone (rhGH) infusion into a femoral artery on leg muscle protein kinetics, amino acid transport, and glutamine metabolism in eight adult hypercatabolic trauma patients. Metabolic pathways were assessed by leg arteriovenous catheterization and muscle biopsies with the use of stable amino acid isotopes. Muscle mRNA levels of selected enzymes were determined by competitive PCR. rhGH infusion significantly accelerated the inward transport rates of phenylalanine and leucine and protein synthesis, whereas the muscle protein degradation rate and cathepsin B and UbB polyubiquitin mRNA levels were not significantly modified by rhGH. rhGH infusion decreased the rate of glutamine de novo synthesis and glutamine precursor availability, total branched-chain amino acid catabolism, and nonprotein glutamate utilization. Thus net glutamine release from muscle into circulation significantly decreased after rhGH administration (∼50%), whereas glutamine synthetase mRNA levels increased after rhGH infusion, possibly to compensate for reduced glutamine precursor availability. We conclude that, after trauma, the anticatabolic action of rhGH is associated with a potentially harmful decrease in muscle glutamine production.

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Changes in mRNAs for enzymes of glutamine metabolism in kidney and liver during ammonium chloride acidosis

AJP Renal Physiology ◽

10.1152/ajprenal.1994.267.3.f400 ◽

1994 ◽

Vol 267 (3) ◽

pp. F400-F406 ◽

Cited By ~ 9

Author(s):

A. C. Schoolwerth ◽

P. A. deBoer ◽

A. F. Moorman ◽

W. H. Lamers

Keyword(s):

Phosphoenolpyruvate Carboxykinase ◽

Rat Kidney ◽

Glutamine Metabolism ◽

Kidney Cortex ◽

Mrna Levels ◽

Rat Kidney Cortex ◽

Physiological Conditions ◽

Glutamine Synthase ◽

Sustained Increase

Changes in protein and mRNAs for enzymes of glutamine metabolism were determined in rat kidney cortex at different times after induction of NH4Cl acidosis. After NH4Cl, phosphoenolpyruvate carboxykinase (PEPCK) mRNA increased 16-fold by 10 h (P < 0.05) and then returned to control levels by 30 h. In situ hybridization (ISH) showed that PEPCK mRNA was confined to medullary rays; after NH4Cl, expression of PEPCK expanded throughout the cortex, reaching a maximal intensity at 10 h. Phosphate-dependent glutaminase (PDG) and glutamate dehydrogenase (GDH) mRNAs increased 8- and 2.6-fold, respectively (both P < 0.05), by 10 h before decreasing; the increased expression was confirmed by ISH. Immunohistochemistry showed that increased PEPCK, PDG, and GDH protein occurred at variable times after the rise in mRNAs. The increase was confined to proximal tubules and was sustained, a finding noted also by Western blot analysis. In contrast, glutamine synthase protein and mRNA, confined to deep cortex and outer medullar, did not change after NH4Cl. These studies reveal striking changes in PEPCK and PDG mRNAs in rat renal cortex during acidosis. The ISH pattern suggested that increased amounts of PEPCK were synthesized in recruited cells which contained little enzyme under physiological conditions. mRNA levels for PEPCK, PDG, and GDH peaked at 10 h before returning to control levels. Despite the decrease in mRNAs, a sustained increase in proteins was noted.

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Glutamine metabolism in lymphocytes of the rat

Biochemical Journal ◽

10.1042/bj2120835 ◽

1983 ◽

Vol 212 (3) ◽

pp. 835-842 ◽

Cited By ~ 292

Author(s):

M S M Ardawi ◽

E A Newsholme

Keyword(s):

Amino Acids ◽

Concanavalin A ◽

Phosphoenolpyruvate Carboxykinase ◽

Thymidine Incorporation ◽

Adenine Nucleotides ◽

Glutamine Metabolism ◽

Mesenteric Lymph Nodes ◽

Mesenteric Lymph ◽

End Products ◽

Stimulation Of

The metabolism of glutamine in resting and concanavalin-A-stimulated lymphocytes was investigated. In incubated lymphocytes isolated from rat mesenteric lymph nodes, the rates of oxygen and glutamine utilization and that of aspartate production were approximately linear with respect to time for 60 min, and the concentrations of adenine nucleotides plus the ATP/ADP or ATP/AMP concentration ratios remained approximately constant for 90 min. The major end products of glutamine metabolism were glutamate, aspartate and ammonia: the carbon from glutamine may contribute about 30% to respiration. When both glucose and glutamine were presented to the cells, the rates of utilization of both substances increased. Evidence was obtained that the stimulation of glycolysis by glutamine could be due, in part, to an activation of 6-phosphofructokinase. Starvation of the donor animal increased the rate of glutamine utilization. The phosphoenolpyruvate carboxykinase inhibitor mercaptopicolinate decreased the rate of glutamine utilization by 28%; the rates of accumulation of glutamate and ammonia were decreased, whereas those of lactate, aspartate and malate were increased. The mitogen concanavalin A increased the rate of glutamine utilization (by about 51%). The rate of [3H]thymidine incorporation into DNA caused by concanavalin A in cultured lymphocytes was very low in the absence of glutamine; it was increased about 4-fold at 1 microM-glutamine and was maximal at 0.3 mM-glutamine; neither other amino acids nor ammonia could replace glutamine.

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Importance of glutamate dehydrogenase stimulation for glucose and glutamine synthesis in rabbit renal tubules incubated with various amino acids.

Acta Biochimica Polonica ◽

10.18388/abp.1998_4278 ◽

1998 ◽

Vol 45 (3) ◽

pp. 825-831

Author(s):

K Winiarska ◽

P Bozko ◽

T Lietz ◽

J Bryła

Keyword(s):

Glutamate Dehydrogenase ◽

Phosphoenolpyruvate Carboxykinase ◽

Lactate Production ◽

Renal Tubules ◽

Glycerol Utilization ◽

Key Enzyme ◽

Glutamine Synthesis ◽

Glutamate Synthesis ◽

Glucose Formation ◽

Stimulation Of

The effect of 2-aminobicyclo[2.2.1]heptan-2-carboxylic acid (BCH), an L-leucine nonmetabolizable analogue and an allosteric activator of glutamate dehydrogenase, on glucose and glutamine synthesis was studied in rabbit renal tubules incubated with alanine, aspartate or proline in the presence of glycerol and octanoate, i.e. under conditions of efficient glucose formation. With alanine+glycerol+octanoate the addition of BCH resulted in a stimulation of alanine and glycerol consumption, accompanied by an increased glucose, lactate and glutamine synthesis. In contrast, when alanine was substituted by either aspartate or proline, BCH altered neither glucose formation nor glutamine and glutamate synthesis, while an accelerated glycerol utilization was accompanied by a small increase in lactate production. In view of the BCH-induced changes in intracellular metabolite levels the acceleration of gluconeogenesis by BCH in the presence of alanine+glycerol+octanoate is probably due to (i) increased uptake of alanine via alanine aminotransferase, (ii) stimulation of phosphoenolpyruvate carboxykinase, a key-enzyme of gluconeogenesis, (iii) rise of glucose-6-phosphatase activity, as well as (iv) activation of the malate-aspartate shuttle resulting in an augmented glycerol utilization for lactate and glucose synthesis.

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Time course of renal glutamate dehydrogenase induction during NH4Cl loading in rats

AJP Renal Physiology ◽

10.1152/ajprenal.1992.262.6.f999 ◽

1992 ◽

Vol 262 (6) ◽

pp. F999-F1006 ◽

Cited By ~ 4

Author(s):

P. A. Wright ◽

R. K. Packer ◽

A. Garcia-Perez ◽

M. A. Knepper

Keyword(s):

Glutamate Dehydrogenase ◽

Time Course ◽

Renal Cortex ◽

Ammonium Excretion ◽

Mrna Levels ◽

Outer Medulla ◽

Acid Intake ◽

Blood Ph ◽

Outer Stripe ◽

Acid Loading

To study mechanisms involved in renal glutamate dehydrogenase (GDH) regulation in response to systemic acid loading, we have measured blood pH, ammonium excretion, renal GDH mRNA levels, and GDH activity in rats. Acid intake (0.28 M NH4Cl in drinking water for 3 days) increased GDH mRNA levels in the renal cortex, but had no effect in the outer stripe of the outer medulla, inner stripe of the outer medulla, or the inner medulla. Rats were subjected to a step change in acid intake by alkali loading for 3 days (7.2 meq NaHCO3 per day in food slurry) and shifting to acid loading for up to 7 days (7.2 meq NH4Cl in food slurry). Ammonium excretion rose rapidly, increasing by 14-fold in the first 24-h period and 38-fold in the second 24-h period. Cortical GDH mRNA levels were increased relative to alkali-loaded values by 3.7-fold in 24 h, 4.3-fold in 4 days, but only 2.2-fold in 7 days. GDH activity was unchanged after 24 h of acid intake, but was significantly increased after 48 h. We concluded the following: 1) GDH mRNA is present in all regions of the kidney, but levels increase in response to acid loading only in the renal cortex; 2) GDH mRNA levels increase within 1 day after the initiation of acid loading, but the associated increase in functional enzyme activity takes 2 or more days; and 3) the large increases in ammonium excretion that occur in the first day after initiation of acid loading are not dependent on increased GDH activity.

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Effect of phenylephrine on glutamate and glutamine metabolism in isolated perfused rat liver

Biochemical Journal ◽

10.1042/bj2210651 ◽

1984 ◽

Vol 221 (3) ◽

pp. 651-658 ◽

Cited By ~ 33

Author(s):

D Häussinger ◽

H Sies

Keyword(s):

Glutamate Dehydrogenase ◽

Rat Liver ◽

Glutamine Metabolism ◽

Isolated Perfused Rat Liver ◽

Perfused Rat Liver ◽

Alpha Adrenergic Receptors ◽

14Co2 Production ◽

Oxoglutarate Dehydrogenase ◽

Glutamine Uptake ◽

Stimulation Of

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.

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Effect of hyperbaric oxygenation on metabolism of glutamine in the liver

Biomeditsinskaya Khimiya ◽

10.18097/pbmc20146003364 ◽

2014 ◽

Vol 60 (3) ◽

pp. 364-371 ◽

Cited By ~ 4

Author(s):

P.N. Savilov

Keyword(s):

Glutamine Synthetase ◽

Glutamate Dehydrogenase ◽

Hyperbaric Oxygenation ◽

Inhibitory Effect ◽

Glutamine Metabolism ◽

Albino Rats ◽

Functional Heterogeneity ◽

Glutamine Concentration ◽

Hyperoxic Exposure ◽

Stimulation Of

The effect of three-day course of hyperbaric oxygenation (HBO; 3 atm, 50 min, 1 session per day) on glutamine metabolism in the liver has been investigated in 72 adult albino rats. The content of ammonia, glutamate, glutamine, activity of glutamine synthetase (GS), phosphate-dependent glutaminase (PDG), and glutamate dehydrogenase (GDH) were studied in left (LLL) and median (MLL) lobes of the liver. The course of HBO had an inhibitory effect on all the enzymes studied. Inhibitory effect of hyperoxia on GDH activity persisted up to day 11 after the course of HBO in both lobes of the liver, while decreased glutamate normalized in both lobes. Reduced glutamine concentration normalized to day 4, and the concentration of ammonia and remained elevated for 11 days after the end of hyperoxic exposure. Inhibitory effect of hyperoxia on GS activity in LLL and MLL disappeared on day 4 and day 11 day after the end of the HBO course. PDG activity reduced by HBO in both lobes normalized to the day 4 day after oxygenation; however, on day 11 it selectively decreased in LLL, where simultaneous stimulation of GS activity was also observed. The results demonstrate different sensitivity of liver GS, PDG and GDH of normal rats to the inhibitory effect of HBO. Different dynamics of GS and PDG activity in LLL and MLL of oxygenated rats suggests functional heterogeneity of the glutamine cycle in hepatocytes of liver lobes after HBO

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Stimulation of glutamine metabolism by 3-aminopicolinate in isolated dog kidney-cortex tubules

Biochemical Journal ◽

10.1042/bj2100483 ◽

1983 ◽

Vol 210 (2) ◽

pp. 483-487 ◽

Cited By ~ 2

Author(s):

D Durozard ◽

G Baverel

Keyword(s):

Phosphoenolpyruvate Carboxykinase ◽

Glutamine Metabolism ◽

Kidney Cortex ◽

Kidney Tubules ◽

Direct Stimulation ◽

Dog Kidney ◽

Glucose Synthesis ◽

Isolated Dog Kidney ◽

Gluconeogenic Substrates ◽

Stimulation Of

1. The effects of 3-aminopicolinate, a known hyperglycaemic agent in the rat, on glutamine metabolism were studied in isolated dog kidney tubules. 2. 3-Aminopicolinate greatly stimulated glutamine (but not glutamate) removal and glutamate accumulation from glutamine as well as formation of ammonia, aspartate, lactate, alanine and glucose. 3. The increased accumulation of aspartate from glutamine and glutamate, and the inhibition of glucose synthesis from various non-nitrogenous gluconeogenic substrates, as well as the increased accumulation of malate from succinate, support the proposal that 3-aminopicolinate is an inhibitor rather than a stimulator of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in dog kidney tubules. 4. With glutamine as substrate, the increase in flux through glutamate dehydrogenase (EC 1.4.1.3) could not explain the large increase in glutamine removal caused by 3-aminopicolinate. 5. Inhibition by amino-oxyacetate of accumulation of aspartate and alanine from glutamine caused by 3-aminopicolinate did not prevent the acceleration of glutamine utilization. 6. These data are consistent with a direct stimulation of glutaminase (EC 3.5.1.2) by 3-aminopicolinate in dog kidney tubules.

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