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

1. Measurements of the activities in rat liver of the four key enzymes involved in gluconeogenesis, i.e. pyruvate carboxylase (EC 6.4.1.1), phosphoenolpyruvate carboxykinase (EC 4.1.1.32), fructose 1,6-diphosphatase (EC 3.1.3.11) and glucose 6-phosphatase (EC 3.1.3.9), have been carried out, all four enzymes being measured in the same liver sample. Changes in activities resulting from starvation and diabetes have been studied. Changes in concentration (activity/unit wet weight of tissue) were compared with changes in the hepatic cellular content (activity/unit of DNA). 2. Each enzyme was found to increase in concentration during starvation for up to 3 days, but only glucose 6-phosphatase and phosphoenolpyruvate carboxykinase showed a significant rise in content. Fructose 1,6-diphosphatase appeared to decrease in content somewhat during the early stages of starvation. 3. There was a marked increase in the concentration of all four enzymes in non-starved rats made diabetic with alloxan or streptozotocin, for the most part similar responses being found for the two diabetogenic agents. On starvation, however, the enzyme contents in the diabetic animals tended to fall, often with streptozotocin-treated animals to values no greater than for the normal overnight-starved rat. Deprivation of food during the period after induction of diabetes with streptozotocin lessened the rise in enzyme activity. 4. The results are compared with other published values and factors such as substrate and activator concentrations likely to influence activity in vivo are considered. 5. Lack of correlation of change in fructose 1,6-diphosphatase with the other enzymes questions whether it should be included in any postulation of control of gluconeogenic enzymes by a single gene unit.
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PMID:A comparison of the effects of diabetes induced with either alloxan or streptozotocin and of starvation on the activities in rat liver of the key enzymes of gluconeogenesis. 432 34

Catecholamines induced an increase in the activity of rat adipose tissue and liver phosphopyruvate carboxylases that was maintained for 48h. The response of adipose tissue phosphopyruvate carboxylase was blocked by actinomycin D, corticosteroids and propranolol, whereas corticosteroids and propranolol did not affect the liver enzyme. Cortisol phosphate, like actinomycin D, interfered only with the initiation of the increase in enzyme activity caused by noradrenaline, but not with the process of enzyme accumulation. In contrast, cycloheximide was effective in blocking enzyme induction throughout the course of the catecholamine effect. Adrenocorticotrophic hormone caused a short-term induction of adipose tissue phosphopyruvate carboxylase, which could be blocked by propranolol. Hepatic phosphopyruvate carboxylase, but not the adipose tissue enzyme, was induced by dibutyryladenosine 3':5'-cyclic monophosphate and by glucagon. Both nicotinic acid and nicotinamide decreased the normal induction of adipose tissue phosphopyruvate carboxylase caused by starvation, but only nicotinamide increased the activity of the liver enzyme.
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PMID:The interaction of catecholamines and adrenal corticosteroids in the induction of phosphopyruvate carboxylase in rat liver and adipose tissue. 434 97

1. The purpose of this study was to determine the nature of the metabolic changes associated with carbohydrate and fat metabolism that occurred in the blood and liver of lactating dairy cows during starvation for 6 days. 2. During starvation, the blood concentrations of the free fatty acids and ketone bodies increased, whereas that of citrate decreased. After an initial increase, the blood concentration of glucose subsequently declined as starvation progressed. Starvation caused a significant decrease in the plasma concentration of serine and a significant increase in that of leucine. 3. After 6 days of starvation the hepatic concentrations of oxaloacetate, citrate, phosphoenolpyruvate, 2-phosphoglycerate, 3-phosphoglycerate, glucose, glycogen, ATP and NAD(+) had all decreased, as had the hepatic activities of phosphopyruvate carboxylase (EC 4.1.1.32) and pyruvate kinase (EC 2.7.1.40). 4. The above metabolic changes are similar to those previously found to occur in cows suffering from spontaneous ketosis (Baird et al., 1968; Baird & Heitzman, 1971). 5. Milk yield decreased progressively during starvation. 6. There were marked differences in the ability of individual animals to resist the onset of severe starvation ketosis.
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PMID:Effects of starvation on intermediary metabolism in the lactating cow. A comparison with metabolic changes occurring during bovine ketosis. 434 57

1. The intracellular location and maximal activities of enzymes involved in phosphoenolpyruvate synthesis have been investigated in pigeon liver. Enolase and pyruvate kinase were cytoplasmic, and the activities were 50-60 and 180-210mumoles/min./g. dry wt. at 25 degrees respectively. Phosphoenolpyruvate carboxykinase was present exclusively, and nucleoside diphosphokinase predominantly, in the mitochondria; the particles had to be disrupted to elicit maximal activities, which were 27-33 and 400-600mumoles/min./g. dry wt. at 25 degrees respectively. The activities of all four enzymes did not change significantly during 48hr. of starvation. 2. Conditions for incubation of washed isolated mitochondria were established, to give high rates of synthesis of phosphoenolpyruvate, linear with time and proportional to mitochondrial concentration. Inorganic phosphate and added adenine nucleotides were stimulatory, whereas added Mg(2+) inhibited, partly owing to activation of contaminant pyruvate kinase. Phosphoenolpyruvate formation occurred from oxaloacetate, malate, fumarate, succinate, alpha-oxoglutarate and citrate, in decreasing order of effectiveness. 3. The steady-state ATP/ADP ratio of mitochondrial suspensions was decreased in the presence of added 2.5mm-Mg(2+) (owing to stimulation of adenylate kinase and possibly of an adenosine triphosphatase), 0.5mm-Ca(2+) or 0.4mm-dinitrophenol. In each case the rate of substrate removal and oxygen uptake was increased, whereas phosphoenolpyruvate synthesis was inhibited. Citrate formation was enhanced, owing to de-inhibition of citrate synthase. These effects were not primarily related to changes in the oxaloacetate concentration. 4. Both phosphoenolpyruvate carboxykinase and nucleoside diphosphokinase were active within the atractylosidesensitive barrier to the mitochondrial metabolism of added adenine nucleotides. There was no correlation between the rate of substrate-level phosphorylation associated with the oxidation of alpha-oxoglutarate, and the synthesis of phosphoenolpyruvate. 5. The results suggest that phosphoenolpyruvate formation in pigeon-liver mitochondria is regulated partly by the phosphorylation state of the adenine and guanine nucleotides, and partly by variations in the oxaloacetate concentration, all in the mitochondrial matrix. 6. Phosphoenolpyruvate is assumed to be the metabolite transported from the mitochondria to the cytoplasm during gluconeogenesis from oxaloacetate in pigeon liver.
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PMID:The regulation of phosphoenolpyruvate synthesis in pigeon liver. 496 63

1. Metabolite contents were determined in freeze-clamped kidney from acidotic and starved rats in order to elucidate the rate-controlling steps which are responsible for the acceleration of gluconeogenesis in these situations. 2. In the kidney of rats which were made mildly acidotic by replacing drinking water with 1.5% ammonium chloride for 7 to 10 days (when the plasma bicarbonate concentration was 20mm) the content of phosphoenolpyruvate was increased from the control value of 35 to 63nmol/g and that of 3-phosphoglycerate from 85 to 154nmol/g. 3. Similar but smaller changes in these metabolites occurred in the kidney of starved rats but there were no such changes in the kidney of rats 12h after an infusion of 0.25m-hydrochloric acid, although plasma bicarbonate concentration fell to about 10mm on this treatment. 4. The renal concentration of glucose 6-phosphate was not raised in rats that received ammonium chloride, but was increased in starved and acutely acidotic rats. 5. The concentrations of alpha-oxoglutarate, malate and citrate were less than half the normal value in the kidney of both groups of acidotic rats. These changes can be accounted for on the basis of equilibrium relationships among reversible reactions, particularly as a result of the rise in intracellular ammonia content. A less marked decrease in alpha-oxoglutarate and malate was found in the kidney of starved rats. 6. The renal cortical cytoplasmic oxaloacetate concentration was calculated to be decreased in acidotic and starved rats. 7. These results are discussed in the light of the known enhancement by acidosis and starvation of renal gluconeogenesis. In particular they support the suggestion that the phosphoenolpyruvate carboxykinase reaction is a site of control of gluconeogenesis in kidney in these conditions.
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PMID:Effects of metabolic acidosis and starvation on the content of intermediary metabolites in rat kidney. 512 92

The activities of phosphoenolpyruvate carboxykinase, ;malic enzyme', citrate-cleavage enzyme and glucose 6-phosphate dehydrogenase were assayed in homogenates of rumen mucosa, liver and adipose tissue of cattle. Rumen mucosa cytoplasm contained activities of ;malic enzyme' approximately sevenfold those of phosphoenolpyruvate carboxykinase, suggesting that the conversion of propionate into lactate by rumen mucosa involves ;malic enzyme'. Neither starvation for 8 days nor feeding with a concentrate diet for at least 3 months before slaughter produced enzyme patterns in the tissues different from those in cattle given only hay, except that the all-concentrate diet caused increased activities of glucose 6-phosphate dehydrogenase and ;malic enzyme' in adipose tissues. Rumen mucosa, liver and adipose tissue contained phosphoenolpyruvate carboxykinase activity. ;Malic enzyme' was absent in liver. Citrate-cleavage enzyme activity was present in liver and adipose tissue but was quite low in rumen mucosa. Liver contained much less glucose 6-phosphate dehydrogenase activity than rumen mucosa or adipose tissue.
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PMID:Activity of selected gluconeogenic and lipogenic enzymes in bovine rumen mucosa, liver and adipose tissue. 581 73

Unusual guanosine nucleotides guanosine 5'-diphosphate 3'-diphosphate (ppGpp, also known as MSI) and guanosine 5'-diphosphate 3'-monophosphate (ppGp, also known as MSIII) accumulate to high concentrations in wild-type cells of Escherichia coli during amino acid starvation. We reported here that both nucleotides strongly inhibit the activity of enzymes IMP dehydrogenase and adenylosuccinate synthetase, the first enzymes of the guanylate and adenylate biosynthetic pathways. In both cases, ppGP (MSII) is a stronger inhibitor than ppGpp (MSI). On the other hand, these two nucleotides exhibited opposite effects on the activity of phosphoenolpyruvate carboxylase, the enzyme that utilizes phosphoenolpyruvate. At their respective physiological concentrations, the activity of phosphoenolpyruvate carboxylase is activated by ppGpp and inhibited by ppGp.
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PMID:Effect of unusual guanosine nucleotides on the activities of some Escherichia coli cellular enzymes. 611 28

Starvation and diabetes both caused a marked increase in the concentration of hepatic phosphoenolpyruvate caroboxykinase mRNA while the administration of insulin to diabetic rats or refeeding glucose to starved animals caused a marked reduction in the levels of enzyme mRNA as measured by hybridization using a cDNA probe.l The Administration of dibutyryl cAMP to a starved-refed cat caused an 8-fold induction of phosphoenolpyruvate carboxykinase mRNA in 1 h. Triamcinolone plus acidosis induced the levels of enzyme mRNA in kidney 3-fold within 6 h, however, starvation for 24h had only marginal effects. In all of the above conditions, the levels of phosphoenolpyruvate carboxykinase mRNA measured by hybridization assay agreed well with the relative levels of translatable mRNA for the enzyme. The half-time of phosphoenolpyruvate carboxykinase mRNA, determined after the administration of either alpha-amanitin or cordycepin to starved animals, was approximately 40 min. However, cycloheximide either alone or together with cordycepin, not only prevented the decrease in phosphoenolpyruvate carboxykinase mRNA sequence abundance, but induced it 2-fold. Cycloheximide itself, when injected into 21-day fetal rats in utero caused an induction of enzyme mRNA equal to that noted when dibutyryl cAMP was administered. The mRNA for phosphoenolpyruvate carboxykinase is approximately 2.8 kb in length, but nuclei from the livers of diabetic rats contain a number of putative precursor RNA species for the enzyme, up to 6.5 kb in size, all containing a poly(A) tail. Two hours after refeedng glucose to a starved rat, these nuclear RNA species could no longer be detected by hybridization to our cDNA probe.
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PMID:Rapid changes in the concentration of phosphoenolpyruvate carboxykinase mRNA in rat liver and kidney. Effects of insulin and cyclic AMP. 628 47

Renal gluconeogenic capacity was enhanced to 150% 24 h after partial hepatectomy, remained increased at 48 h (144%) and returned to normal values at 72 h. Glucose production by renal cortical slices from hepatectomized rats was also enhanced 48 h after surgery when pyruvate, alpha-ketoglutarate and fructose were used as gluconeogenic precursors. The stimulation of renal gluconeogenic capacity seems to be due to the increase of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase activities which behaved similarly to glucose production after hepatectomy. The renal metabolic response may be partially due to starvation in the first 24 h. Afterwards food intake became normalized and the acceleration of glucose production should be attributed to hepatectomy. Since there was no metabolic acidosis in our experimental conditions the involvement of glucocorticoids in the stimulation of renal phosphoenolpyruvate carboxykinase and glucose-6-phosphatase activities is suggested.
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PMID:[Stimulation of gluconeogenic capacity in partially hepatectomized rats (author's transl)]. 628 29

Recent studies have indicated that the starvation induced increase in hepatic phosphoenolpyruvate carboxykinase (PEPck; EC 4.1.1.32) is accelerated in hyperthyroid animals, whereas enzyme degradation is unaffected by the thyroid state. Therefore, the present study was undertaken to investigate the possible direct effect of T3 on the synthesis of this important gluconeogenic regulatory enzyme in vivo and in the isolated perfused liver. T3 injection in hypothyroid animals stimulated PEPck synthesis within 6-12 h. The effect, being dose dependent and significant for 0.1 microgram T3/100 g BW, could be demonstrated in animals fasted or fed a carbohydrate-rich diet. Although varying in the basal rate of synthesis, the T3-induced increase in PEPck synthesis was similar in intact, thyroidectomized, adrenalectomized, and hypophysectomized animals. No additive effect with glucocorticoids was observed, suggesting that endogenous glucocorticoids are not necessary for the hormone action. The T3-induced effect on PEPck synthesis was not mediated by alterations in the endogenous cAMP level, as was indicated (1) by the different time course of PEPck induction via (Bu)2cAMP or T3, and 2) by the finding that T3 was effective also in diabetic animals, despite maximally enhanced tissue cAMP levels. In these animals insulin antagonized the T3 action on the enzyme. T3-mediated PEPck synthesis was not prevented by propranolol. Conversely, an additive effect with isoproterenol on enzyme activity was observed. T3 (1 nM) added to the isolated liver of hypothyroid rats perfused with the synthetic fluorocarbon medium supplemented with 10% iodothyronine free serum, stimulated incorporation of labeled leucine into PEPck protein within a 6-h perfusion time. Taken together, our data demonstrate that T3 at a physiological dose stimulates hepatic PEPck synthesis.
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PMID:3,5,3'-Triiodothyronine-induced synthesis of rat liver phosphoenolpyruvate carboxykinase. 629 Jan 83


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