scholarly journals The estimation of rates of utilization of glucose and ketone bodies in the brain of the suckling rat using compartmental analysis of isotopic data

1974 ◽  
Vol 142 (3) ◽  
pp. 527-544 ◽  
Author(s):  
Jill E. Cremer ◽  
Dennis F. Heath
Keyword(s):  
Ketone Bodies ◽  
Lipid Synthesis ◽  
Compartmental Analysis ◽  
British Library ◽  
Acetyl Coa ◽  
Intermediary Metabolites ◽  
Lending Library ◽  
Old Rats ◽  
The Brain

The brains of 18-day-old rats utilize glucose and ketone bodies. The rates of acetyl-CoA formation from these substrates and of glycolysis were determined in vivo from the labelling of intermediary metabolites after intraperitoneal injection of d-[2-14C]glucose, l(+)-[3-14C]- and l(+)-[U-14C]-lactate and d(−)-3-hydroxy[14C]butyrate. Compartmental analysis was used in calculating rates to allow for the rapid exchange of blood and brain lactate, the presence in brain of at least two pools each of glucose and lactate, and the incomplete equilibration of oxaloacetate with aspartate and of 2-oxoglutarate with glutamate. Results were as follows. 1. Glucose and ketone bodies labelled identical pools of tricarboxylate-cycle metabolites, and were in every way alternative substrates. 2. The combined rate of oxidation of acetyl-CoA derived from pyruvate (and hence glucose) and ketone bodies was 1.05μmol/min per g. 3. Ketone bodies contributed 0.11–0.53μmol/min per g in proportion to their concentration in blood, with a mean rate of 0.30μmol/min per g at 1.24mm. 4. Pyruvate and ketone bodies were converted into lipid at 0.018 and 0.008μmol/min per g respectively. 5. Glycolysis, at 0.48μmol/min per g, was more rapid in most rats than pyruvate utilization by oxidation and lipid synthesis, resulting in a net output of lactate from brain to blood. 6. Rates of formation of brain glutamate, glutamine and aspartate were also measured. Further information on the derivation of the models has been deposited as Supplementary Publication SUP 50034 (18 pages) at the British Library, Lending Division (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7QB, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1973) 131, 5.

scholarly journals Effect of hyperphenylalaninaemia on lipid synthesis from ketone bodies by rat brain

1976 ◽  
Vol 154 (2) ◽  
pp. 319-325 ◽  
Author(s):  
M S. Patel ◽  
O E. Owen
Keyword(s):  
Rat Brain ◽  
Ketone Bodies ◽  
Brain Slices ◽  
Lipid Synthesis ◽  
Coa Transferase ◽  
Old Rats ◽  
And Function ◽  
Developing Rat

The effect of hyperphenylalaninaemia on the metabolism of ketone bodies in vivo and in vitro by developing rat brain was investigated. The incorporation in vivo of [14C]acetoacetate into cerebral lipids was decreased by both chronic (for 3 days) and acute (for 6h) hyperphenylalaninaemia induced by injecting phenylalanine into 1-week-old rats. In studies in vitro it was observed that the incorporation of the radioactivity from [14C]acetoacetate and 3-hydroxy[14C]butyrate into cerebral lipids was inhibited by phenyl-pyruvate, but not by phenylalanine. Phenylpyruvate also inhibited the incorporation of 3H from 3H2O into lipids by brain slices metabolizing either 3-hydroxybutyrate or acetoacetate in the presence of glucose. These findings suggest that the decrease in the incorporation in vivo of [14C]acetoacetate into cerebral lipids in hyperphenylalaninaemic rats is most likely caused by phenylpyruvate and not by phenylalanine. Phenylpyruvate as well as phenylalanine had no inhibitory effects on ketone-body-catabolizing enzymes, namely 3-hydroxybutyrate dehydrogenase, 3-oxo acid CoA-transferase and acetoacetyl-CoA thiolase, in rat brain. Phenylpyruvate but not phenylalanine inhibited the activity of the 2-oxoglutarate dehydrogenase complex from rat and human brain. These findings suggest that the metabolism of ketone bodies is impaired in brains of untreated phenylketonuric patients, and in turn may contribute to the diminution of mental development and function associated with phenylketonuria.

The transport of ketone bodies into the brain of the rat (in vivo)

1977 ◽  
Vol 34 (1) ◽  
pp. 1-13 ◽  
Author(s):  
P.M. Daniel ◽  
E.R. Love ◽  
S.R. Moorhouse ◽  
O.E. Pratt
Keyword(s):  
Ketone Bodies ◽  
The Brain

scholarly journals Effect of phenylpyruvate on enzymes involved in fatty acid synthesis in rat brain

1973 ◽  
Vol 134 (2) ◽  
pp. 545-555 ◽  
Author(s):  
John M. Land ◽  
John B. Clark
Keyword(s):  
Fatty Acid ◽  
Citrate Synthase ◽  
Mitochondrial Protein ◽  
Fatty Acid Synthetase ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Adult Rats ◽  
Malonyl Coa ◽  
Old Rats ◽  
The Brain

1. The activities of, and the effects of phenylpyruvate on, citrate synthase (EC 4.1.3.7), acetyl-CoA carboxylase (EC 6.4.1.2) and fatty acid synthetase derived from the brains of 14-day-old and adult rats were investigated. 2. The brain citrate synthase from 14-day-old rats had a Km for oxaloacetate of 2.38μm and for acetyl-CoA of 16.9μm, and a Vmax. of 838nmol of acetyl-CoA incorporation/min per mg of mitochondrial protein. From adult rat brain this enzyme had a Km for oxaloacetate of 2.5μm and for acetyl-CoA of 16.6μm and a Vmax. of 1070nmol of acetyl-CoA incorporated/min per mg of mitochondrial protein. Phenylpyruvate inhibited the enzyme from adult and young rat brains in a competitive fashion with respect to acetyl-CoA, with a Ki of 700μm. 3. The brain acetyl-CoA carboxylase from 14-day-old rats had a Km for acetyl-CoA of 21μm and a Vmax. of 0.248nmol/min per mg of protein, and from adult rats a Km for acetyl-CoA of 21μm and a Vmax. of 0.173nmol/min per mg of protein. The enzyme from young and adult rats required citrate (Ka=3mm) for activation and were inhibited non-competitively by phenylpyruvate, with a Ki of 10mm. 4. The brain fatty acid synthetase from 14-day-old rats had a Km for acetyl-CoA of 7.58μm and a Vmax. of 1.1 nmol of malonyl-CoA incorporated/min per mg of protein, and from adult rats a Km for acetyl-CoA of 4.9μm and a Vmax. of 0.48nmol of malonyl-CoA incorporated/min per mg of protein. Phenylpyruvate acted as a competitive inhibitor with respect to acetyl-CoA with a Ki of 250μm for the enzyme from 14-day-old rats. 5. These results are discussed with respect to phenylketonuria, and it is suggested that the inhibition of the brain fatty acid synthetase and possibly the citrate synthetase by phenylpyruvate could explain the defective myelination characteristic of this condition.

scholarly journals Regulation of glucose and ketone-body metabolism in brain of anaesthetized rats

1974 ◽  
Vol 138 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Neil B. Ruderman ◽  
Peter S. Ross ◽  
Michael Berger ◽  
Michael N. Goodman
Keyword(s):  
Glucose Uptake ◽  
Ketone Body ◽  
Ketone Bodies ◽  
Acetyl Coa ◽  
Total Blood ◽  
Diabetic Ketosis ◽  
Pyruvate Oxidation ◽  
Ketone Body Metabolism ◽  
Arteriovenous Difference ◽  
The Brain

1. The effects of starvation and diabetes on brain fuel metabolism were examined by measuring arteriovenous differences for glucose, lactate, acetoacetate and 3-hydroxybutyrate across the brains of anaesthetized fed, starved and diabetic rats. 2. In fed animals glucose represented the sole oxidative fuel of the brain. 3. After 48h of starvation, ketone-body concentrations were about 2mm and ketone-body uptake accounted for 25% of the calculated O2 consumption: the arteriovenous difference for glucose was not diminished, but lactate release was increased, suggesting inhibition of pyruvate oxidation. 4. In severe diabetic ketosis, induced by either streptozotocin or phlorrhizin (total blood ketone bodies >7mm), the uptake of ketone bodies was further increased and accounted for 45% of the brain 's oxidative metabolism, and the arteriovenous difference for glucose was decreased by one-third. The arteriovenous difference for lactate was increased significantly in the phlorrhizin-treated rats. 5. Infusion of 3-hydroxybutyrate into starved rats caused marked increases in the arteriovenous differences for lactate and both ketone bodies. 6. To study the mechanisms of these changes, steady-state concentrations of intermediates and co-factors of the glycolytic pathway were determined in freeze-blown brain. 7. Starved rats had increased concentrations of acetyl-CoA. 8. Rats with diabetic ketosis had increased concentrations of fructose 6-phosphate and decreased concentrations of fructose 1,6-diphosphate, indicating an inhibition of phosphofructokinase. 9. The concentrations of acetyl-CoA, glycogen and citrate, a potent inhibitor of phosphofructokinase, were increased in the streptozotocin-treated rats. 10. The data suggest that cerebral glucose uptake is decreased in diabetic ketoacidosis owing to inhibition of phosphofructokinase as a result of the increase in brain citrate. 11. The inhibition of brain pyruvate oxidation in starvation and diabetes can be related to the accelerated rate of ketone-body metabolism; however, we found no correlation between the decrease in glucose uptake in the diabetic state and the arteriovenous difference for ketone bodies. 12. The data also suggest that the rates of acetoacetate and 3-hydroxybutyrate utilization by brain are governed by their concentrations in plasma. 13. The finding of very low concentrations of acetoacetate and 3-hydroxybutyrate in brain compared with plasma suggests that diffusion across the blood –brain barrier may be the rate-limiting step in their metabolism.

Kanamycin Inhibits Cochlear-Renal ODC in Neonatal Rats

1992 ◽  
Vol 107 (4) ◽  
pp. 501-510 ◽  
Author(s):  
Andrew T. Lyos ◽  
William E. Winter ◽  
Charles M. Henley
Keyword(s):  
Organ Of Corti ◽  
Lateral Wall ◽  
Inhibitory Effect ◽  
Polyamine Biosynthesis ◽  
Key Enzyme ◽  
Old Rats ◽  
In Vivo Effects ◽  
The Brain

Ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, is important in development and regeneration. We hypothesize that aminoglycoside inhibition of ODC mediates developmental hypersensitivity to aminoglycoside ototoxicity. Kanamycin effects on ODC activity (decarboxylation of ornithine) in vitro were determined in the postmitochondriai fraction of cochlear and renal homogenates from 11-day-old rats. Kanamycin inhibited cochlear and renal ODC by an uncompetitive mechanism. For the cochlear enzyme, the inhibitor constant (Ki) for kanamycin was 99 ± 25 (μmol/L; for the renal enzyme, the Ki = 1.5 ± 0.1 mmol/L. In vivo effects of kanamycin on cochlear, renal, brain ODC activity were determined in rats treated with kanamycin (400 mg/kg/day, intramuscularly) or saline during postnatal days 11 through 20, the hypersensitive period for ototoxicity. Rats were killed on postnatal days 12,14,16, and 20 and ODC was assayed. Kanamycin significantly inhibited ODC in the lateral wall-organ of Corti and kidney (ANOVA α = 0.05), but had no effect on cochlear nerve and no consistent inhibitory effect in the brain. These results suggest that ODC is a potential target of kanamycin in susceptible tissues and may be a contributing factor in developmental sensitivity to the drug by inhibiting repair and developmental processes mediated by ODC.

scholarly journals Quantitative analysis of intermediary metabolism in rat hepatocytes incubated in the presence and absence of ethanol with a substrate mixture including ketoleucine

1989 ◽  
Vol 258 (1) ◽  
pp. 121-140 ◽  
Author(s):  
J M Baranyai ◽  
J J Blum
Keyword(s):  
Ketone Bodies ◽  
Rat Hepatocytes ◽  
Metabolic Model ◽  
Oxygen Utilization ◽  
Acetyl Coa ◽  
Atp Production ◽  
Considerable Excess ◽  
Metabolic Conditions ◽  
Label Incorporation

Hepatocytes isolated from livers of fed rats were incubated with a mixture of glucose (10 mM), ribose (1.0 mM), acetate (1.25 mM), alanine (3.5 mM), glutamate (2.0 mM), aspartate (2.0 mM), 4-methyl-2-oxovaleric acid (ketoleucine) (3.0 mM), and, in paired flasks, 10 mM-ethanol. One substrate was 14C-radiolabelled in any given incubation. Incorporation of 14C into glucose, glycogen, CO2, lactate, alanine, aspartate, glutamate, acetate, urea, lipid glycerol, fatty acids and the 1- and 2,3,4-positions of ketone bodies was measured after 20 and 40 min of incubation under quasi-steady-state conditions. Data were analysed with the aid of a realistic structural metabolic model. In each of the four conditions examined, there were approx. 77 label incorporation measurements and several measurements of changes in metabolite concentrations. The considerable excess of measurements over the 37 independent flux parameters allowed for a stringent test of the model. A satisfactory fit to these data was obtained for each condition. There were large bidirectional fluxes along the gluconeogenic/glycolytic pathways, with net gluconeogenesis. Rates of ureagenesis, oxygen consumption and ketogenesis were high under all four conditions studied. Oxygen utilization was accurately predicted by three of the four models. There was complete equilibration between mitochondrial and cytosolic pools of acetate and of CO2, but for several of the metabolic conditions, two incompletely equilibrated pools of mitochondrial acetyl-CoA and oxaloacetate were required. Ketoleucine was utilized at a rate comparable to that reported by others in perfused liver and entered the mitochondrial pool of acetyl-CoA directly associated with ketone body formation. Ethanol, which was metabolized at rates comparable to those in vivo, caused relatively few changes in overall flux patterns. Several effects related to the increased NADH/NAD+ ratio were observed. Pyruvate dehydrogenase was completely inhibited and the ratio of acetoacetate to 3-hydroxybutyrate was decreased; flux through glutamate dehydrogenase, the citric acid cycle, and ketoleucine dehydrogenase were, however, only slightly inhibited. Net production of ATP occurred in all conditions studied and was increased by ethanol. Futile cycling was quantified at the glucose/glucose 6-phosphate, glycogen/glucose 6-phosphate, fructose 6-phosphate/fructose 1,6-bis-phosphate, and phosphoenolpyruvate/pyruvate/oxaloacetate substrate cycles. Cycling at these four loci consumed about 22% of cellular ATP production in control hepatocytes and 14% in ethanol-treated cells.

scholarly journals Down-regulation of the mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase gene by insulin: the role of the forkhead transcription factor FKHRL1

2002 ◽  
Vol 366 (1) ◽  
pp. 289-297 ◽  
Author(s):  
Alícia NADAL ◽  
Pedro F. MARRERO ◽  
Diego HARO
Keyword(s):  
Ketone Bodies ◽  
Control Site ◽  
Luciferase Reporter ◽  
Acid Oxidation ◽  
Transcription Start ◽  
Forkhead Transcription Factor ◽  
The Brain

Normal physiological responses to carbohydrate shortages cause the liver to increase the production of ketone bodies from the acetyl-CoA generated from fatty acid oxidation. This allows the use of ketone bodies for energy, thereby preserving the limited glucose for use by the brain. This adaptative response is switched off by insulin rapidly inhibiting the expression of the mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (HMGCS2) gene, which is a key control site of ketogenesis. We decided to investigate the molecular mechanism of this inhibition. In the present study, we show that FKHRL1, a member of the forkhead in rhabdosarcoma (FKHR) subclass of the Fox family of transcription factors, stimulates transcription from transfected 3-hydroxy-3-methylglutaryl-CoA synthase promoter-luciferase reporter constructs, and that this stimulation is repressed by insulin. An FKHRL1-responsive sequence AAAAATA, located 211bp upstream of the HMGCS2 gene transcription start site, was identified by deletion analysis. It binds FKHRL1 in vivo and in vitro and confers FKHRL1 responsiveness on homologous and heterologous promoters. If it is mutated, it partially blocks the effect of insulin in HepG2 cells, both in the absence and presence of overexpressed FKHRL1. These results suggest that FKHRL1 contributes to the regulation of HMGCS2 gene expression by insulin.

scholarly journals Lipid biosynthesis in liver slices of the foetal guinea pig

1976 ◽  
Vol 154 (1) ◽  
pp. 149-158 ◽  
Author(s):  
C T Jones ◽  
I K Ashton
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Fatty Acid Synthetase ◽  
Lipid Synthesis ◽  
Short Chain Fatty Acids ◽  
Acetate Incorporation ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Citrate Lyase ◽  
Effect Of Glucose

Lipid synthesis as measured by the incorporation of acetate or 3H2O into slices of foetal liver, is much higher than in slices of adult liver and shows a peak at about two-thirds of gestation. At this time the synthesis from glucose was low and reached a peak 10 days later. The changes in the activity of ATP citrate lyase, which mirrored acetate incorporation, and the effect of glucose and pyruvate on acetate corporation into lipid suggests that some of the lipid synthesis occurs via intramitochondrial acetyl-CoA production from acetate. Despite this, lipid synthesis was not inhibited by (-)-hydroxycitrate. The low rate of synthesis from glucose at two-thirds of gestation is ascribed to the low activity of pyruvate carboxylase at this time and a role for a phosphoenolpyruvate carboxykinase in providing oxaloacetate for lipogenesis is proposed. The activity of fatty acid synthetase broadly agreed with the changes in lipid synthesis, whereas the activity of acetyl-CoA carboxylase was barely sufficient to account for the rates of lipid synthesis in vivo. Acetate and short-chain fatty acids are likely to be the major precursors for lipid synthesis in vivo.

Sign in / Sign up

Export Citation Format

Share Document