scholarly journals Ketone bodies activate gluconeogenesis in isolated rabbit renal cortical tubules incubated in the presence of amino acids and glycerol.

1997 ◽  
Vol 44 (2) ◽  
pp. 323-331 ◽  
Author(s):  
T Lietz ◽  
K Winiarska ◽  
J Bryła
Keyword(s):  
Amino Acids ◽  
Ketone Bodies ◽  
Glucose Production ◽  
Kidney Cortex ◽  
Renal Tubules ◽  
Carboxylase Activity ◽  
Glutamate Dehydrogenase Activity ◽  
Glutamine Synthesis ◽  
Glucose Formation ◽  
Stimulation Of

In isolated rabbit renal kidney-cortex tubules 2 mM glycerol, which is a poor gluconeogenic substrate, does not induce glucose formation in the presence of alanine, while it activates gluconeogenesis on substitution of alanine by aspartate, glutamate or proline. The addition of either 5 mM 3-hydroxybutyrate or 5 mM acetoacetate to renal tubules incubated with alanine + glycerol causes a marked induction of glucose production associated with inhibition of glutamine synthesis. In contrast, the rate of the latter process is not altered by ketones in the presence of glycerol and either aspartate, glutamine or proline despite the stimulation of glucose formation. Acceleration of gluconeogenesis by ketone bodies in the presence of amino acids and glycerol is probably due to (i) stimulation of pyruvate carboxylase activity, (ii) activation of malate-aspartate shuttle as concluded from elevated intracellular levels of malate, aspartate and glutamate, as well as (iii) diminished supply of ammonium for glutamine synthesis from alanine resulting from a decrease in glutamate dehydrogenase activity.

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

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.

Renal tissue metabolism in the rat during chronic metabolic alkalosis: importance of glycolysis

1986 ◽  
Vol 64 (11) ◽  
pp. 1419-1426 ◽  
Author(s):  
Guy Lemieux ◽  
James Berkofsky ◽  
Christiane Lemieux
Keyword(s):  
Metabolic Alkalosis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Production ◽  
Renal Tissue ◽  
Renal Tubules ◽  
Potassium Supplement ◽  
Glutamate Dehydrogenase Activity ◽  
Lactate And Pyruvate ◽  
Leg Muscle

Chronic metabolic alkalosis was induced in rats drinking 0.3 M NaHCO3 and receiving 1 mg furosemide/100 g body weight per day intraperitoneally. Another group of animals received a potassium supplement in the form of 0.3 M KHCO3. In this group, hypokalemia did not develop and muscle potassium fell by only 18% versus 50% in those not receiving potassium. In vitro renal production of ammonia and uptake of glutamine fell by 40% with a decrease in the activity of glutaminase I and glutamate dehydrogenase. Activity of phosphofructokinase, a major enzyme of glycolysis, rose only in the kidney of animals receiving a potassium supplement. Fructose-1,6-diphosphatase fell as well as phosphoenolpyruvate carboxykinase. Malate dehydrogenase also fell. The activity of phosphofructokinase also rose in the liver, heart, and leg muscle. The major biochemical changes in the renal cortex were the following: glutamate, α-ketoglutarate, malate, lactate, pyruvate, alanine, aspartate, and citrate rose as well as calculated oxaloacetate. The concentration of intermediates like 2-phosphoglycerate, 3-phosphoglycerate, and glucose-6-phosphate fell. The cytosolic redox potential (NAD+/NADH) decreased. In addition to the fall in ammoniagenesis, it could be demonstrated in vitro that the renal tubules incubated with glutamine showed decreased glucose production and increased production of lactate and pyruvate. The concentration of lactate was elevated in all tissues examined including liver, heart, and leg muscle. This study confirms in the rat that decreased renal ammoniagenesis takes place following decreased uptake of glutamine in metabolic alkalosis. All other changes are accounted for by the process of increased glycolysis, which appears to take place in all tissues in metabolic alkalosis. All reported changes were more significant in animals receiving supplement of potassium, indicating that associated potassium deficiency plays a role in counteracting the observed changes now expected in metabolic alkalosis.

scholarly journals Stimulation by glucose of gluconeogenesis in hepatocytes isolated from starved rats

1987 ◽  
Vol 245 (3) ◽  
pp. 661-668 ◽  
Author(s):  
M Rigoulet ◽  
X M Leverve ◽  
P J A M Plomp ◽  
A J Meijer
Keyword(s):  
Steady State ◽  
Production Rate ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Production ◽  
Carboxylase Activity ◽  
Maximal Stimulation ◽  
Intracellular Concentrations ◽  
Effect Of Glucose ◽  
Stimulation Of

Control properties of the gluconeogenic pathway in hepatocytes isolated from starved rats were studied in the presence of glucose. The following observations were made. (1) Glucose stimulated the rate of glucose production from 20 mM-glycerol, from a mixture of 20 mM-lactate and 2 mM-pyruvate, or from pyruvate alone; no stimulation was observed with 20 mM-alanine or 20 mM-dihydroxyacetone. Maximal stimulation was obtained between 2 and 5 mM-glucose, depending on the conditions. At concentrations above 6 mM, gluconeogenesis declined again, so that at 10 mM-glucose the glucose production rate became equal to that in its absence. (2) With glycerol, stimulation of gluconeogenesis by glucose was accompanied by oxidation of cytosolic NADH and reduction of mitochondrial NAD+ and was insensitive to the transaminase inhibitor amino-oxyacetate; this indicated that glucose accelerated the rate of transport of cytosolic reducing equivalents to the mitochondria via the glycerol 1-phosphate shuttle. (3) With lactate plus pyruvate (10:1) as substrates, stimulation of gluconeogenesis by glucose was almost additive to that obtained with glucagon. From an analysis of the effect of glucose on the curves relating gluconeogenic flux and the steady-state intracellular concentrations of gluconeogenic intermediates under various conditions, in the absence and presence of glucagon, it was concluded that addition of glucose stimulated both phosphoenolpyruvate carboxykinase and pyruvate carboxylase activity.

scholarly journals Glutamine synthesis from glucose and ammonium chloride by guinea-pig kidney tubules

1994 ◽  
Vol 297 (1) ◽  
pp. 69-74 ◽  
Author(s):  
C Michoudet ◽  
M F Chauvin ◽  
G Baverel
Keyword(s):  
Glucose Metabolism ◽  
Guinea Pig ◽  
Carbon Skeleton ◽  
Kidney Cortex ◽  
Physiological Concentration ◽  
Pig Kidney ◽  
Glucose Carbon ◽  
Glutamine Synthesis ◽  
Stimulation Of

1. At a physiological concentration (5 mM), glucose was found to be metabolized by isolated kidney cortex tubules prepared from fed guinea pigs. 2. The release of 14CO2 from [U-14C]glucose indicated that oxidation of the glucose carbon skeleton represented about 50% of the glucose removed; significant amounts of lactate and glutamine also accumulated. 3. Addition of 0.1-10 mM NH4Cl led to a dose-dependent stimulation of glucose metabolism which was accompanied by a large increase in lactate and glutamine accumulation and, to a lesser extent, in glucose oxidation. 4. Comparison of the release of 14CO2 from [1-14C]- and [6-14C]glucose indicates that, in both the absence and the presence of NH4Cl, the pentose phosphate shunt was only a minor pathway of glucose metabolism. 5. The central role of pyruvate carboxylase in the conversion of glucose carbon into glutamine carbon was demonstrated by using a bicarbonate-free medium and measuring the fixation of 14CO2 from [14C]bicarbonate, which was recovered mostly at C-1 of glutamine plus glutamate. 6. The NH4Cl-induced stimulation of glucose removal was secondary not only to increased glutamine synthesis, as shown by the effect of methionine sulphoximine, an inhibitor of glutamine synthetase, but also to the stimulation of phosphofructokinase activity by NH4Cl. 7. Renal arterio-venous difference measurements revealed that, in vivo, the guinea-pig kidney removed glucose from the circulating blood, which suggests that glucose carbon may contribute to the carbon skeleton of the glutamine released by this organ.

scholarly journals Regulation of renal gluconeogenesis by calcium ions, hormones and adenosine 3′:5′-cyclic monophosphate

1973 ◽  
Vol 134 (1) ◽  
pp. 157-165 ◽  
Author(s):  
Anne Roobol ◽  
George A. O. Alleyne
Keyword(s):  
Rat Kidney ◽  
Glucose Production ◽  
Kidney Cortex ◽  
Carboxylase Activity ◽  
Hormonal Stimulation ◽  
Rat Kidney Cortex ◽  
Cyclic Monophosphate ◽  
Rate Limiting Step ◽  
Cortex Slices ◽  
Rate Limiting

1. The effect of Ca2+, glucagon, adrenaline and adenosine 3′:5′-cyclic monophosphate on gluconeogenesis by rat kidney-cortex slices was studied. 2. Glucose formation from a range of substrates, with the exception of glycerol, was increased by an increase in extracellular Ca2+ concentration. 3. Hormones and adenosine 3′:5′-cyclic monophosphate, at low Ca2+ concentrations, stimulated glucose production from several substrates, but not from glycerol, fructose, malate or fumarate. 4. Hormonal stimulation was not detected in the absence of Ca2+ or at 2.5mm-Ca2+. 5. Ca2+, hormones and adenosine 3′:5′-cyclic monophosphate had no effect on phosphoenolpyruvate carboxylase activity. 6. It is proposed that Ca2+ and adenosine 3′:5′-cyclic monophosphate-mediated hormone action activate the same rate-limiting step in gluconeogenesis: this step is tentatively identified as the rate of transfer of substrates across the mitochondrial membrane.

scholarly journals Combined Effect of Arginine, Valine, and Serine on Exercise-Induced Fatigue in Healthy Volunteers: A Randomized, Double-Blinded, Placebo-Controlled Crossover Study

Nutrients ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 862 ◽  
Author(s):  
Yuichi Tsuda ◽  
Makoto Yamaguchi ◽  
Teruyuki Noma ◽  
Eiji Okaya ◽  
Hiroyuki Itoh
Keyword(s):  
Amino Acids ◽  
Healthy Volunteers ◽  
Perceived Exertion ◽  
Ketone Bodies ◽  
Blood Analysis ◽  
Rating Of Perceived Exertion ◽  
Physical Parameters ◽  
Positive Effects ◽  
Exercise Induced ◽  
Double Blinded

Although several kinds of amino acids (AAs) are known to affect physiological actions during exercise, little is known about the combined effects of a mixture of several AAs on fatigue during exercise. The aim of the present study was to investigate the effect of an AA mixture supplement containing arginine, valine, and serine on exercise-induced fatigue in healthy volunteers. These AAs were selected because they were expected to reduce fatigue during exercise by acting the positive effects synergistically. A randomized, double-blinded, placebo-controlled crossover trial was conducted. Thirty-nine males ingested an AA mixture containing 3600 mg of arginine, 2200 mg of valine, and 200 mg of serine or a placebo each day for 14 days. On the 14th day, the participants completed an exercise trial on a cycle ergometer at 50% of VO2max for 120 min. After the two-week washout period, the participants repeated the same trial with the other test sample. The participant’s feeling of fatigue based on a visual analog scale (VAS) and a rating of perceived exertion (RPE), as well as blood and physical parameters were evaluated. The feeling of fatigue based on VAS and RPE were significantly improved in AA compared to those in placebo. In the blood analysis, the increase in serum total ketone bodies during exercise and plasma tryptophan/branched-chain amino acids were significantly lower in AA than those in placebo. The present study demonstrated that supplementation with an AA mixture containing arginine, valine, and serine reduced the feeling of fatigue during exercise. The AA mixture also changed several blood parameters, which may contribute to the anti-fatigue effect.

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