UMLS:C0038187 - FACTA Search

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

The fraction of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase in the dephosphorylated (active) form in rat liver in vivo was measured after various experimental treatments of animals. Intraperitoneal injection of glucose (to raise serum insulin concentrations) into rats 4 h into the light phase (L-4) resulted in a transient (30 min) increase in the expressed (E)/total (T) activity ratio of HMG-CoA reductase without any change in total activity (obtained after complete dephosphorylation of the enzyme). Conversely, intravenous injection of guinea-pig anti-insulin serum into rats 4 h into the dark phase (D-4) significantly depressed the E/T ratio within 20 min. Intravenous injection of glucagon into normal rats at this time point did not affect the degree of phosphorylation of the enzyme, in spite of a 10-fold increase in hepatic cyclic AMP concentration induced by the hormone treatment. A 3-fold increase in the concentration of the cyclic nucleotide induced by adrenaline infusion was similarly ineffective in inducing any change in expressed or total activities of hepatic HMG-CoA reductase. However, when insulin secretion was inhibited, either by the induction of streptozotocin-diabetes or by simultaneous infusion of somatostatin, glucagon treatment was able to depress the expressed activity of HMG-CoA reductase (i.e. it increased the phosphorylation of the enzyme). Therefore insulin appears to have a dominant role in the regulation of the phosphorylation state of hepatic HMG-CoA reductase. In apparent corroboration of this suggestion, short-term 4 h food deprivation of animals before D-4 resulted in a marked decrease in the E/T activity ratio of reductase, which was not affected further by an additional 8 h starvation. By contrast, the total activity of the enzyme was not significantly affected by 4 h starvation, but was markedly diminished after 12 or 24 h starvation. Longer-term starvation also produced a chronic increase in the degree of phosphorylation of the enzyme. These results are discussed in relation to the role of reversible phosphorylation in the control of hepatic HMG-CoA reductase activity in vivo.
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PMID:Acute effects of starvation and treatment of rats with anti-insulin serum, glucagon and catecholamines on the state of phosphorylation of hepatic 3-hydroxy-3-methylglutaryl-CoA reductase in vivo. 288 48

Previous studies from our laboratory established that in Escherichia coli, glycogen synthesis is regulated by both the relA gene, which mediates the stringent response, and by cyclic AMP. However, those studies raised the question of whether this dual regulatory system functions in an independent or a dependent manner. We show here that this regulation is independent, i.e., each regulatory process can express its action in the absence of the other. Triggering the stringent response by amino acid starvation increased glycogen synthesis even in mutants lacking the ability to synthesize cyclic AMP or lacking cyclic AMP receptor protein; and cyclic AMP addition stimulated glycogen synthesis in relA mutant strains. We also show that physiological concentrations of GTP inhibit ADP-glucose synthetase (glucose-1-phosphate adenylyltransferase, EC 2.7.7.27), the rate-limiting enzyme of bacterial glycogen synthesis, in vitro. Because the stringent response is known to cause an abrupt decrease in the cellular level of GTP, modulation of ADP-glucose synthetase activity by this nucleotide could account for a substantial portion of the step-up in the cellular rate of glycogen synthesis observed when the stringent response is triggered.
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PMID:Independence of cyclic AMP and relA gene stimulation of glycogen synthesis in intact Escherichia coli cells. 298 98

Four clones derived from a carbohydrate-induced rat liver cDNA library were found to hybridize with a 5.4-kilobase mRNA species encoding a 36 kDa protein. This mRNA was abundant in the liver, barely detectable in adipocytes and kidney, and absent from the other tissues tested. In the liver, the mRNA was fully induced by a carbohydrate-rich diet, but was undetectable during both starvation and feeding with a protein-rich or lipid-rich diet. Adrenalectomized, thyroidectomized and diabetic animals did not express the mRNA in their liver when re-fed with the carbohydrate-rich diet. When these animals were given the missing hormone, the amount of hybridizable RNA returned to normal values, but administration of the hormone alone failed to induce mRNA synthesis in starved animals. Both glucagon and its second messenger, cyclic AMP, abolished the induction of the mRNA in re-fed animals. Exogenous insulin, whatever the dose, did not reverse the inhibitory action of glucagon. In an isolated nuclei transcription system, no detectable RNA transcripts were found in starved animals, whereas feeding the animals with the carbohydrate-rich diet led to a maximum rate of gene transcription. Although unidentified, this mRNA proves to be a remarkable marker of dietary and hormonal control of gene expression in vivo. It will provide a useful model for further analysis of the role of cyclic AMP in regulating the transcription of eukaryotic genes.
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PMID:Characterization and metabolic regulation of a liver-specific 5.4-kilobase mRNA whose synthesis is transcriptionally induced by carbohydrates and repressed by glucagon and cyclic AMP. 298 43

In chickens, the liver functions in gluconeogenesis to recycle lactate carbon (Cori cycle) and the kidney is the major organ for net gluconeogenesis from substrates such as pyruvate and amino acids. This is markedly different from mammalian systems where the liver is the primary gluconeogenic organ. The limited ability of chicken hepatocytes to synthesize glucose is explained, at least in part, by the observation that phosphoenolpyruvate carboxykinase (GTP) (EC 4.1.1.32) in these cells is located exclusively in the mitochondria. The kidney possesses a cytosolic form of this enzyme that adapts to dietary and acid-base stimuli. The relative abundance of mRNA coding for the cytosolic enzyme has been detected by using a specific cDNA probe. Starvation increases the level of this mRNA in chicken kidney and also results in the appearance of the message in chicken liver. Isolated hepatocytes have been used to determine which hormones regulate expression of the hepatic gene. Incubations with glucagon, epinephrine, norepinephrine, dexamethasone, or dibutyryl cyclic AMP increase the relative abundance of the message in liver cells isolated from fed chickens. Despite considerable levels of this mRNA in the liver of starved chickens, functional cytosolic enzyme activity is not detected. This indicates some form of posttranscriptional regulation. The studies summarized illustrate the usefulness of isolated hepatocytes and recombinant DNA probes in the study of hormonal regulation of hepatic gene expression.
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PMID:Gluconeogenesis in the chicken: regulation of phosphoenolpyruvate carboxykinase gene expression. 298 55

We are studying cell differentiation in Dictyostelium discoideum by examining the regulation of genes that are preferentially expressed in different cell types. A system has been established in which prestalk- and prespore-cell-specific genes are expressed in single cells in response to culture conditions. We confirm our previous results showing that cyclic AMP induces prestalk genes and now show that it is also required for prespore gene induction. The expression of both classes of genes is additionally dependent on the presence of a factor(s) secreted by developing cells which we call conditioned medium factor(s). An assay for conditioned medium factor(s) shows that it is detectable within 2.5 h after the onset of development. Conditioned medium factor(s) also promotes the expression of genes induced early in development, but has no detectable effect on the expression of actin genes and a gene expressed maximally in vegetative cells. In the presence of conditioned medium factor(s), exogenous cyclic AMP at the onset of starvation fails to induce the prespore and prestalk genes. The addition of cyclic AMP between 2 and 12 h of starvation results in rapid prestalk gene expression, whereas prespore genes are induced at an invarient time (approximately 18 h after the onset of starvation). These data suggest that cyclic AMP and conditioned medium factor(s) are sufficient for prestalk gene induction, whereas an additional parameter(s) is involved in the control of prespore gene induction. In contrast to several previous studies, we show that multicellularity is not essential for the expression of either prespore or prestalk genes. These data indicate that prespore and prestalk genes have cell-type-specific as well as shared regulatory factors.
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PMID:A secreted factor and cyclic AMP jointly regulate cell-type-specific gene expression in Dictyostelium discoideum. 298 66

We undertook a study to define the role of cyclic AMP [cAMP] in modulating the secretion of transcobalamin II (TC-II) in the mouse macrophage like cell line J774. J774 was observed to secrete large amounts of TC-II, particularly in the presence of 8-bromo cAMP or cholera toxin or when grown in medium supplemented with low concentrations of horse serum (1% or 5%) or in serum-free medium. Variant cell lines derived from J774 and deficient either in adenylate cyclase (ac -) or cAMP-dependent protein kinase (pk -) activity showed very low and intermediate levels of basal secretory activity of TC-II, respectively, compared to J774. Maximum secretory activity of TC-II was observed in J774 under conditions in which growth was poorest (in the presence of 8-bromo-cAMP or 1% or 5% horse serum-supplemented medium or in serum-free medium). Cells grown in serum-free medium were found to have elevated basal adenylate cyclase activity and cAMP levels compared to those grown in medium supplemented with 20% horse serum. The data from this study demonstrate a negative correlation between growth activity and TC-II secretion in the J774 cell line. The stimulatory effect of exogenous cAMP on TC-II secretion by J774, the reduced secretory activity of the variant lines ac- and pk- and the observed increase in cell cAMP levels under conditions of serum starvation in which TC-II secretion is considerably enhanced, suggest that cell cAMP is an important modulator of TC-II secretion and growth behavior in the J774 cell line.
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PMID:The modulation of transcobalamin II (TC-II) production by cyclic adenosine 3',5'-monophosphate in the murine macrophage cell line J774: relationship to growth behavior. 300 44

Pertinent hepatic metabolites and enzymes were examined in rats fed a high carbohydrate (HC) diet and during the first 24 h of either starvation or feeding a high protein (HP) diet. Consumption of the HC diet induced slight but definite 24-h oscillations in hepatic concentrations of cyclic AMP, glycogen, glucose 6-phosphate, fructose 2,6-bisphosphate, fructose 1,6-bisphosphate and phosphoenolpyruvate, as well as the activities of 6-phosphofructo-2-kinase/fructose 2,6-bisphosphatase and phosphoenolpyruvate carboxykinase. The transition to starvation or the HP diet induced, within 12 h, concurrent increases in cyclic AMP and phosphoenolpyruvate and decreases in glycogen, glucose 6-phosphate, fructose 6-phosphate, fructose 2,6-bisphosphate and fructose 1,6-bisphosphate. These changes were associated with a decrease in the ratio of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and an increase in phosphoenolpyruvate carboxykinase. These results suggest that the activity of the fructose 6-phosphate/fructose 1,6-bisphosphate cycle is similar during the first 24 h of starvation or HP consumption.
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PMID:Studies on the early changes in rat hepatic fructose 2,6-bisphosphate and enzymes in response to a high protein diet. 300 33

Plasma insulin, glucagon, glucose, free fatty acids and glycerol, hepatic cyclic AMP and glycogen, and liver phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-bisphosphatase (FBPase), glucose 6-phosphatase (G6Pase) and alanine amino transferase (AAT) activities were examined in adult rats during the first 24 h of either starvation or consumption of a high protein, carbohydrate-free (HP) diet. Under both nutritional conditions, plasma insulin fell within 12 h and remained constant thereafter. Glucagon increased 12 h after the start of the experiment and peaked between 18-24 h. The insulin: glucagon ratio was lower during the last 12 h of the experiment. In both experimental groups, liver cyclic AMP increased progressively and peaked between 15-24 h, but it increase was higher on HP diet than on starvation. Whereas plasma glucose remained low on starvation for 24 h, it returned to normal on consumption of the HP diet. In both groups, liver glycogen fell within 12 h and remained low until the end of experiment. FBPase, G6Pase and AAT did not change on starvation, while they increased toward the end of 1 d HP consumption. During starvation or consumption of the HP diet, PEPCK increased progressively and peaked between 15-24 h, but the increase was greater with the HP diet than with starvation. These findings suggest that in the first 24 hours, the adaptative response of hepatic gluconeogenesis is higher with a HP diet than upon starvation.
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PMID:Comparison between starvation and consumption of a high protein diet: plasma insulin and glucagon and hepatic activities of gluconeogenic enzymes during the first 24 hours. 300 46

Mucosa isolated from the proximal third of the small intestine of infant rats had much lower cyclic nucleotide concentrations (expressed both per unit wet weight and per unit DNA content) than those determined in the intestinal wall. The steady-state concentrations of both cyclic AMP and cyclic GMP in jejunum showed dramatic increases during the first 5 d post partum. Another increase in cyclic nucleotide concentrations was observed in the isolated mucosa between d 15 and 21. Starvation for 24 h always resulted in lower intestinal cyclic nucleotide concentrations than those of the fed littermates. This effect was more pronounced in younger animals and more evident for cyclic AMP values. Three-week-old rats fed a high carbohydrate diet for 24-48 h exhibited more pronounced elevations in the concentrations of cyclic nucleotides from the jejunal mucosa than did rats fed a high fat diet.
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PMID:Effect of age and diet on cyclic nucleotide concentrations in the intestinal mucosa of developing rats. 300 53

The effects of starvation, refeeding a diet high in carbohydrate, administration of glucagon and cyclic AMP, thyroidectomy, and adrenalectomy on transcription of the gene for liver L-type pyruvate kinase and on the accumulation of cytoplasmic mRNA for L-type pyruvate kinase were investigated in rat. Transcription of the gene was undetectable in either fasted or protein-fed rats. Refeeding fasted rats a carbohydrate-rich diet stimulated an increase in L-type pyruvate kinase mRNA, preceded by an increase in the gene transcription. Transcription was maximal at 12 h of refeeding, decreasing to 10% of maximum at 72 h. The level of L-type pyruvate kinase mRNA remained constant at 50% of maximum for at least 120 h. Neither thyroidectomy nor adrenalectomy affected gene transcription in fasted rats refed the carbohydrate-rich diet, despite a decrease in mRNA abundance to 40 and 20%, respectively, of controls fed a normal diet. Glucagon or cyclic AMP totally blocked the increase in transcription of the L-type pyruvate kinase gene caused by feeding a carbohydrate-rich diet to previously fasted rats. Nevertheless, the level of L-type pyruvate kinase mRNA remained high for 3 h after glucagon administration. After 3 h, the mRNA decreased rapidly with a half-life less than 1 h. Thus, expression of the gene for L-type pyruvate kinase is regulated at both transcriptional and post-transcriptional levels. The transcription is regulated by two major effectors, one positive, namely carbohydrates, and one negative, namely glucagon (via cyclic AMP). Both agents probably act at the level of the mRNA stability as well. Glucocorticoids and thyroid hormones do not regulate transcription of the gene for L-type pyruvate kinase but do appear to be required for a normal accumulation of the transcripts in the cytoplasm.
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PMID:Transcriptional and post-transcriptional regulation of L-type pyruvate kinase gene expression in rat liver. 301 91

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