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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of starvation, glucose refeeding, dibutyryl cAMP, and dexamethasone on expression of the gene for phosphoenolpyruvate carboxykinase (GTP) [GTP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.32] from rat liver cytosol was studied by using a cloned cDNA probe. The rate of transcription of the gene for phosphoenolpyruvate carboxykinase in hepatic nuclei isolated from starved rats decreased rapidly after refeeding with glucose. Administration of dibutyryl cAMP to glucose-refed animals increased the rate of phosphoenolpyruvate carboxykinase gene transcription seven-fold within 20 min. Phosphoenolpyruvate carboxykinase mRNA in the cytosol is 2.8 kilobases long whereas liver nuclei contain four precursor RNA species that are up to 6.5 kilobases long. Feeding glucose to starved rats rapidly decreased the sequence abundance of enzyme mRNA in both nuclei and cytosol. However, the decrease in cytosolic phosphoenolpyruvate carboxykinase mRNA was preceded by a transient increase in enzyme mRNA over the first 20 min after glucose refeeding. Administration of dibutyryl cAMP to glucose-refed starved animals increased the concentration of the nuclear RNA precursors of phosphoenolpyruvate carboxykinase five- to eight-fold within 30 min and induced the mRNA for the cytosolic enzyme over a period of 60 min. We conclude that cAMP induces phosphoenolpyruvate carboxykinase mRNA by increasing the rate of gene transcription.
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PMID:cAMP stimulates transcription of the gene for cytosolic phosphoenolpyruvate carboxykinase in rat liver nuclei. 629 Oct 25

The presence of high phosphoenolpyruvate carboxykinase (EC 4.1.1.32) activity in mouse islet cytosol has been demonstrated. The enzyme was activated by Mn2+ with a Ka of 100 X 10(-6) mol/l. The mean total activity of the Mn2+-stimulated phosphoenolpyruvate carboxykinase in islet cytosol estimated at 22 degrees C with saturating concentrations of the substrates oxaloacetate and ITP was 146 pmol/min per micrograms DNA. Km was calculated to be 6 X 10(-6) mol/l for oxaloacetate and 140 X 10(-6) mol/l for ITP. The islet phosphoenolpyruvate carboxykinase activity was not increased after starvation of the animals for 48 h. Preincubation of the cytosol at 4 degrees C with Fe2+, quinolinate, ATP, Pi, glucose 6-phosphate, fructose 1,6-bisphosphate, NAD+, NADH, oxaloacetate, ITP, cyclic AMP and Ca2+ had no effect on the enzyme activity. However, preincubation of the cytosol at 37 degrees C with ATP-Mg inhibited the Mn2+-stimulated phosphoenolpyruvate carboxykinase activity progressively with time and in a concentration-dependent manner. A similar but weaker inhibitory effect was observed with p[NH]ppA, whereas p[CH2]ppA, ADP, AMP, adenosine and Pi had no effect. It is tentatively suggested that ATP and p[NH]ppA either by adenylation or otherwise affect the interaction between islet phosphoenolpyruvate carboxykinase and the recently discovered Mr = 29000 protein modulator of the enzyme in such a way - perhaps by causing a dissociation between them - that phosphoenolpyruvate carboxykinase loses its sensitivity to Mn2+ activation.
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PMID:Phosphoenolpyruvate carboxykinase in mouse pancreatic islets. ATP-induced changes in sensitivity to Mn2+ activation. 638 41

Phosphoenolpyruvate carboxykinase was purified from mitochondria of guinea-pig liver by affinity chromatography on GMP-Sepharose. The enzyme was purified 100-fold to a high degree of electrophoretic homogeneity as judged by detection of a single protein band on sodium dodecyl sulphate/polyacrylamide gels. The yield was about 16%. The Mr of the purified enzyme was estimated to be 68500 +/- 680 by analysis on sodium dodecyl sulphate/polyacrylamide gels. Antibodies raised in rabbits against the purified enzyme were highly specific for mitochondrial phosphoenolpyruvate carboxykinase and did not precipitate the cytosolic form of this enzyme from either rat or guinea-pig liver cytosol. The use of this antibody showed that starvation does not increase the amount of the enzyme. However, neonatal-development-dependent increase in its activity is shown to be mediated by accumulation of phosphoenol pyruvate carboxykinase-specific protein.
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PMID:Phosphoenolpyruvate carboxykinase from guinea-pig liver mitochondria. Immunological evidence for increase in enzyme amount during neonatal development. 643 67

Metabolic rates and adenine nucleotide content of liver and kidney from hibernating ground squirrels were measured and compared to rats to study the biochemical adaptation to hibernation. High rates of renal and hepatic gluconeogenesis were observed in squirrels, particularly from propionate and glycerol compared to rat. During hibernation and starvation soluble phosphoenolpyruvate carboxykinase activity was increased in both liver and kidney. Although metabolic rates are decreased during hibernation the results suggest that the enzymic complement is maintained at high activity even during torpor.
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PMID:Effect of hibernation on liver and kidney metabolism in 13-lined ground squirrels. 650 11

The coordinated expression of two genes specifically induced by glucose starvation is demonstrated in a hamster fibroblast cell line, K12. Using two cDNA plasmids, p4A3 and p3C5, as hybridization probes, we examine the kinetics of induction of these genes when the cells are grown in medium deprived of glucose. The results show that (i) after a lag period of about 8 hr, there is a rapid and simultaneous increase of the p4A3 and p3C5 mRNA levels and (ii) the elevation of the mRNA levels for p4A3 and p3C5 is largely due to new transcription. In addition, we compare the mRNA transcripts encoded by these glucose-regulated genes in culture cells and phosphoenolpyruvate carboxykinase, the enzyme that catalyzes the rate-limiting step in gluconeogenesis in fasted rats. Our results indicate that the expression of phosphoenolpyruvate carboxykinase is not inducible by glucose starvation in our culture cells.
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PMID:Induction of two genes by glucose starvation in hamster fibroblasts. 658 7

3-Mercaptopicolinate (3-MPA) is a specific inhibitor of phosphoenolpyruvate carboxykinase (PEP CK). In vivo the hypoglycaemic action of 3-MPA in 24 h-starved rats was abolished on intragastric glucose refeeding. Nonetheless, 3-MPA decreased hepatic glycogen content and rate of synthesis in starved animals re-fed glucose. The inference is that on re-feeding after starvation hepatic glycogen is synthesised mainly de novo via glyconeogenesis involving PEP CK. 3-MPA increased hepatic lipogenesis in water- and glucose-fed normal and diabetic rats. This increase is presumed to result from inhibition of PEP CK and consequent diversion of pyruvate from gluconeogenesis to lipogenesis. In contrast, 3-MPA inhibited brown-fat lipogenesis in water- and glucose-fed rats.
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PMID:Direction of carbon flux in starvation and after refeeding: in vitro and in vivo effects of 3-mercaptopicolinate. 667 46

In rat, hamster, guinea-pig, pig, kid, and calf liver, starvation or carbohydrate starvation increased cytosolic phosphoenolpyruvate carboxykinase activity without changing the mitochondrial activity whereas in chick liver, starvation did not alter the activity in both fractions. Liver glycogen content changed in a reciprocal way to the cytosolic phosphoenolpyruvate carboxykinase activity. In prenatal kid and chick liver, phosphoenolpyruvate carboxykinase activity appeared in both cytosolic and mitochondrial fractions, and in chick liver, considerable increase of the cytosolic activity was observed from a few days before hatching to 4 days after hatching.
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PMID:Effects of nutrition and ontogeny on liver cytosolic and mitochondrial phosphoenolpyruvate carboxykinase activity of the rat, hamster, guinea-pig, pig, kid, calf and chick. 671 28

This study examined the effects of starvation and of feeding to rats diets that contain varying protein, carbohydrate and fat levels on serine metabolism in isolated hepatocytes. The conversion of [14C]serine and [14C]lactate to 14CO2 and [14C]glucose was measured in the presence and absence of 5 mM quinolinic acid (QA) or 1 mM 3-mercaptopicolinic acid (MPA), inhibitors of phosphoenolpyruvate carboxykinase. Inclusion of MPA eliminated the contribution of the serine dehydratase-mediated pathway of serine metabolism to glucose production, allowing estimation of serine aminotransferase-mediated metabolism. Addition of MPA reduced [14C]glucose formation from [14C]serine to between 3 and 47% of control values in all dietary treatments. Addition of 10 mM threonine or 10 mM pyruvate depressed [14C]glucose production in hepatocytes from the groups fed 80% protein. Differences in serine metabolism were observed within each protein group, depending on the carbohydrate and fat ratio of the diet. These results suggest the following: 1) MPA is a more potent gluconeogenic inhibitor than QA, permitting estimation of relative flux through two pathways of serine metabolism; 2) serine metabolism occurs primarily via serine dehydratase, although the contribution of serine aminotransferase varies depending upon the nutritional state of the rat, and 3) changing a single dietary component at the expense of another may mask the intricacies of metabolic homeostasis.
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PMID:Effect of starvation and diet composition on two pathways of L-serine metabolism in isolated rat hepatocytes. 680 39

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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PMID:Glutamine metabolism in lymphocytes of the rat. 688 97

The plasma levels of corticosterone, insulin and glucagon, and the concomitant changes in the levels of several liver enzymes and metabolites were measured in intact rats in the basal state during 24 hours and under conditions of food deprivation and hypoxia. The levels of the following enzymes and metabolites were examined: phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, pyruvate kinase, phosphofructokinase, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, glucose, glucose-6-phosphate, glycogen, fructose-6-phosphate, hexokinase, tyrosine amino-transferase and tryptophan oxygenase. During food deprivation, the increased gluconeogenesis is possibly a result of glucagon activity. In contrast, however, during hypoxia the increase in gluconeogenesis seems to be a result of the higher plasma level of corticosterone. During starvation, the insulin concentration dropped steadily and came close to zero.
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PMID:Plasma concentrations of glucose, corticosterone, glucagon and insulin and liver content of metabolic substrates and enzymes during starvation and additional hypoxia in the rat. 703 Aug 99


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