Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nicotinamide is metabolized primarily into NAD and N1-methylnicotinamide in cultured cells of normal rat kidney. The metabolic pathways for the nicotinamide metabolites are independently regulated and are influenced by the growth stage of the cells. N1-Methylnicotinamide levels are 1.5--2-fold elevated in cells growth-arrested by treatment with histidinol, thymidine, or picolinic acid, or by serum starvation. This increase is due to a more rapid rate of synthesis rather than decrease in excretion. The rates of both synthesis and degradation of NAD are increased in serum-starved cells so that the NAD concentration is the same as it is in growing cells. NAD and N1- methylnicotinamide levels are not significantly increased when the intracellular nicotinamide concentration is increased 20-fold by addition of excess nicotinamide to the culture medium, demonstrating that the size of the nicotinamide pool does not limit synthesis of these compounds. In medium containing normal amounts of nicotinamide, the apparent first-order rate constant for the decay of NAD, radioactively labeled in the nicotinamide moiety, is about 4 h-1. Labeled N1-methylnicotinamide is not metabolized, but rather is excreted into the medium with a first-order rate constant of 3.9 h-1. The rate of loss of label from NAD, but not from N1-methylnicotinamide, is increased about twofold by addition of excess nicotinamide to the culture medium. This could be explained by a dilution of a labeled nicotinamide pool which is formed during NAD degradation and which is recycled into NAD but not into N1-methylnicotinamide. The results demonstrate a rapid turnover of NAD at the bond joining nicotinamide and ADP-ribose, in agreement with previous studies. In addition, the results show that nicotinamide is metabolized into N1-methylnicotinamide with what appears to be a carefully regulated synthetic mechanism. The existence of significant amounts of N1-methylnicotinamide in cultured cells raises the question of the physiological importance of this compound.
 ...
PMID:Metabolism of NAD and N1-methylnicotinamide in growing and growth-arrested cells. 645 Jun 82

The activity of some NAD- and NADP-dependent dehydrogenases involved in generation of the reducing equivalents for lipogenesis and the activity and some kinetic parameters of ATP-citrate (pro-3S)-lyase from rat liver, i. e. the enzyme involved in the formation of CoASAc, the primary substrate of fatty acid biosynthesis, were studied. The changes in the activity of NADP-dependent dehydrogenase and ATP-citrate(pro-3S)-lyase, as well as the affinity of the latter for sitrate and CoA and the rate of lipogenesis in starved rats and in rats kept on a carbohydrate-rich diet after starvation appeared to be parallel. Nicotinamide decreased the activity of all NADP-dependent dehydrogenases under study, which was especially well-pronounced after nicotinamide addition against increased lipogenesis. The affinity of ATP-citrate(pro-3S)-lyase for citrate and CoA decreased simultaneously with the decrease in the concentration of the latter. These changes can possibly induce the decrease of lipogenesis rate in rat liver after addition of nicotinamide.
 ...
PMID:[Possible mechanisms of the inhibiting effect of nicotinamide on lipogenesis in rat liver]. 645 46

ADP-ribosylation of proteins was analyzed by in vivo labeling of cells with [3H]adenosine, followed by separation of their protein components by two-dimensional isoelectric focusing/NaDodSO4 polyacrylamide gel electrophoresis. We show here that in several cell types of avian and mammalian origin the major [34H]adenosine acceptor in vivo is a polypeptide with a Mr of 83,000 and isoelectric point of approximately equal to 5.3. This polypeptide is identical to one of the stress-inducible and glucose-regulated proteins (here called SP83) previously described in avian and mammalian cells. Snake venom phosphodiesterase digestion of purified 3H-labeled SP83 releases 5'-AMP and a minor fraction of 2'-(5"-phosphoribosyl)-5-AMP. In vitro labeling with [32P]NAD+ of total cell lysates made in the presence of non-ionic detergents also results in incorporation of radioactivity into SP83. Both of these results strongly suggest that the modification is an ADP-ribosylation. Heat shock and glucose starvation of cells induce a rapid and extensive decrease in the incorporation of ADP-ribose into SP83, suggesting that ADP-ribosylation may be important for the regulation of the function of this protein.
 ...
PMID:ADP-ribosylation of the Mr 83,000 stress-inducible and glucose-regulated protein in avian and mammalian cells: modulation by heat shock and glucose starvation. 657 54

Higher eukaryotes contain tRNA transglycosylases that incorporate the guanine derivative queuine from the nutritional environment into specific tRNAs by exchange with guanine at position 34. Alterations in the queuosine content of specific tRNAs are suggested to be involved in regulatory mechanisms of major routes of metabolism during differentiation. Dictyostelium discoideum has been applied as a model to investigate the function of queuine or queuine-containing tRNAs. Axenic strains are supplied with queuine by peptone, but they grow equally well in a defined queuine-free medium. Queuine-lacking amoebae, starved in suspension culture for 24 h, lose their ability to differentiate into stalk cells and spores, whereas amoebae sufficiently supplied with queuine will overcome this metabolic stress and undergo further development when plated on agar. The results presented here show that D(-)-lactate occurs in the slime mould in millimolar amounts and that its level is remarkably decreased in queuine-lacking cells after 24 h of starvation in suspension culture. On isoelectric-focusing polyacrylamide gels, nine different forms of NAD-dependent D(-)-lactate dehydrogenase can be separated from extracts of vegetative cells, and six forms from extracts of the starved cells. Under queuine limitation, one form is missing in the starved cells. Low amounts of L(+)-lactate are usually found in vegetative amoebae but significantly less in queuine-lacking cells. Five forms of NAD-dependent L(+)-lactate dehydrogenase are detectable in extracts from vegetative, queuine-treated cells, and slight alterations occur in queuine-deficient amoebae. In the starved cells only one form of L(+)-lactate dehydrogenase is found, irrespective of the supply of queuine to the cells. A cytochrome of type b with an absorption maximum at 559 nm accumulates during starvation only in queuine-lacking cells; it might be a component of an NAD-independent lactic acid oxidoreductase as is cytochrome b 557 in yeast and be responsible for the reduced level of lactate in cells lacking queuine in tRNA.
 ...
PMID:Specific changes in lactate levels, lactate dehydrogenase patterns and cytochrome b559 in Dictyostelium discoideum caused by queuine. 669 26

Incubation of Ehrlich ascites tumor cells in their own ascites fluid induced a reversible metabolic adaptation to these "starvation" conditions which was associated with a fragmentation of DNA. Endogenous poly(ADP-ribose) residues also increased, reaching within 1-3 h values 6-10 times higher than in cells taken directly from the mouse peritoneum. The NAD content changed only slightly while dimethyl sulfate-induced accumulation of poly(ADP-ribose) (10-fold within 30 min) was associated with a rapid depletion of NAD (85% lost at 30 min). Nevertheless, turnover of poly(ADP-ribose) as measured by the decay rate of the polymer upon addition of benzamide was dramatically stimulated in both situations, reaching apparently identical half-lives (t 1/2 approximately equal to 1 min) in "starved" and in alkylated cells. However, since penetration of benzamide into the nucleus may be the rate-limiting factor in these studies, turnover of poly(ADP-ribose) in dimethyl sulfate-treated cells may still be much higher than that in "starved" cells. In cells treated with dimethyl sulfate, suppression of poly(ADP-ribose) synthesis by benzamide did not interfere with DNA fragmentation or with DNA resealing as determined by the nucleoid procedure. By contrast, starvation induced a type of DNA incision that was prevented by benzamide. It is proposed that starvation-induced scission of DNA occurs at specific ("regulatory?") sites requiring poly(ADP-ribose) formation to take place, while fragmentation of DNA at random as seen with alkylating agents is associated with, but not dependent on, increased poly(ADP-ribosyl)ation.
 ...
PMID:Stimulation of poly(ADP-ribosyl)ation during Ehrlich ascites tumor cell "starvation" and suppression of concomitant DNA fragmentation by benzamide. 683 44

1. The evolution with age of the metabolic response of adipose tissue to fasting has been investigated in two groups of rats, at different ages, fed and fasted. 2. The protein tissue content increases in response to fasting in young rats but not in adult-old ones. This indicates a lower lipomobilizing response to starvation with increasing age. 3. In contrast to young rats, the adult rat lactate is not increased by fasting while pyruvate is increased. 4. As a result of lactate and pyruvate variations, NAD/NADH is also changed: after fasting it decreases in young rats, while it increases in older rats. 5. Absolute NAD level is decreased by fasting both in young and older rats. 6. These data provide experimental support for the decreased sensitivity of fat pads from older animals to stimuli affecting lipolysis.
 ...
PMID:Age-related changes in rat adipose tissue in response to fasting: protein, lactate and pyruvate levels. 685 66

We examined the relationship between glucose-induced insulin release and the intermediary metabolism of islets from fed and fasted rats. Isolated islets were perifused and insulin release measured in the effluent. At various times after switching islets from 2.4 to 8.6 or 14.5 mM glucose or from 2.4 to 14.5 and back to 2.4 mM glucose, islets were quickly frozen, freeze dried, and subsequently analyzed for tissue content of glucose-6-P, fructose-1,6-P2 plus triose-P, Pi, ATP, ADP, 5'-AMP, NADH, NADPH, total NAD, and total NADP using enzymatic fluorometric procedures. When islets from fed rats were exposed to high glucose, there were concomitant increases of insulin release and islet content of glucose-6-P, fructose-1,6-P2 plus triose-P, NADH, and NADPH. During stimulation Pi and 5'-AMP content fell markedly. The total adenine nucleotide content remained constant. Similar secretory and metabolic changes occurred when 1.5 mM Pi was added to the perifusion fluid. When glucose-stimulated islets were switched back to low glucose for 10 min, all substances but fructose-1,6-P2 plus triose-P, 5'-AMP, NADPH, and possibly ATP returned to the prestimulatory level. Starvation of rats for 3 days blocked the secretory response to 8.6 mM glucose. Fructose-1,6-P2 plus triose-P rose but it did not attain the level existing in islets from fed rats. The ratios (ATP)/(5'-AMP) and (ATP)/(Pi)(adp) increased to the values observed in glucose-stimulated islets of fed rats. The metabolic changes in islets from fed rats exposed to high glucose are consistent with an activation of glycolysis occurring concomitantly with stimulated rates of insulin release. This occurs despite the decrease of important activators of glycolysis--Pi and 5'-AMP. The enhanced glycolysis possibly results from P-fructokinase activation by increased fructose-6-P levels. Activation of glycolysis with 8.6 mM glucose was not as pronounced in islets from starved rats. Despite the different secretory response of islets from fet and fasted rats, the changes of phosphorylation state in the islets, in particular, Pi and 5'-AMP levels, were similar.
 ...
PMID:Effects of glucose on insulin release and on intermediary metabolism of isolated perifused pancreatic islets from fed and fasted rats. 699 11

Pregnant dogs were starved for 72 hr before a term delivery. Maternal (1.68 +/- 0.39 versus 0.74 +/- 0.20 mM) and fetal (0.39 +/- 0.03 versus 0.22 +/- 0.07) circulating free fatty acids and maternal (2.99 +/- 0.79 versus 1.04 +/- 0.84) and fetal (2.53 +/- 0.35 versus 1.01 +/- 0.32) ketones were elevated whereas blood glucose values remained unchanged at the time of delivery. After birth, pups born to starved mothers had significantly lower blood glucose values during 3, 6, 9, and 24 hours of neonatal fasting. Intracerebral glucose concentrations paralleled those in the blood as they were depressed at 3, 6, and 9 hours of age. Cerebral glycogen content was lower in pups born to starved mothers at 6 (2.72 +/- 0.43 versus 4.32 +/- 0.56 mumoles/g) and 24 (2.31 +/- 0.17 versus 3.48 +/- 0.39 mumoles/g) hr, whereas UDP-glucose concentrations were significantly elevated in these pups during fetal, 3, 9, and 24 hr of age. Phosphoenolpyruvate was higher after maternal starvation in the fetus and at 6 and 9 hr, whereas cerebral pyruvate concentrations were elevated at 3, 6, and 9 hr of age. The elevation of pyruvate with no alteration of lactate concentration resulted in an elevated cytoplasmic NAD/NADH ratio at 3 hr of age (1381 +/- 194 versus 792 +/- 198). Cerebral alpha-ketoglutarate and calculated oxaloacetate concentrations were elevated throughout the day after maternal starvation whereas malate concentrations were depressed at 3 and 9 hr of age. Cerebral energy charge was unaffected, whereas the calculated energy reserve was lower at 3, 6, and 24 hours. Cerebral amino acids demonstrated elevated aspartate concentrations at 3 and 6 hr. Cerebral glutamine concentrations were lower during fetal stage (7.86 +/- 0.52 versus 10.01 +/- 0.41 mumoles/g) and 3, 6, and 9 hr of life.
 ...
PMID:Fetal and neonatal cerebral metabolism following maternal canine starvation. 724 89

The steady state concentration of carbohydrate and adenosine phosphate metabolites in rat and rabbit liver and in rabbit skeletal muscle and oxidative phosphorylation parameters of rat and rabbit liver mitochondria were compared. The effects of 24 hr starvation on the energy metabolism of liver and skeletal muscle of the animals were investigated. The steady state concentrations of glycogen and phosphoenolpyruvate in normal rabbit liver were found to be much lower than in the rat and other mammalian livers (45.7 mumoles of glucose equivalents and 38 nmoles of PEP per 1 g of liver wet mass, respectively). On the contrast, the concentrations of glucose 6-phosphate, pyruvate and Pi in rabbit skeletal muscle were unusually high (up to 3, 1 and 15 mumoles per 1 g, respectively). In terms of glucose, pyruvate, lactate, Pi, adenine nucleotide contents and cytosolic NAD+/NADH ratio in the liver, and glycogen, glucose, lactate, creatine and adenosine phosphates in skeletal muscle and oxidative and phosphorylated properties of isolated liver mitochondria, no significant differences between rat and rabbit were found. During 24 hr starvation gluconeogenesis in rabbit liver occurred earlier and was more intensive than in rat liver. This is indicative of the existence of interspecies differences in the control mechanisms of carbohydrate and phosphorus metabolism.
 ...
PMID:[Comparative study of energy metabolism in the liver and skeletal muscles of rat and rabbit. Effect of starvation]. 727 60

1. Deoxycorticosterone, which does not enhance tryptophan pyrrolase activity, also fails to alter the concentrations of the NAD(P) couples in livers of fed rats, whereas corticosterone increases both pyrrolase activity and dinucleotide concentrations. 2. Starvation of rats increases serum corticosterone concentration, lipolysis, tryptophan availability to the liver, tryptophan pyrrolase activity and liver [NADP(H)]. Glucose prevents all these changes. 3. The beta-adrenoceptor-blocking agent propranolol prevents the starvation-induced lipolysis and the consequent increase in tryptophan availability to the liver, but does not influence the increase in serum corticosterone concentration, liver pyrrolase activity and [NADP(H)]. 4. Actinomycin D, which prevents the starvation-induced increases in liver pyrrolase activity and [NADP(H)], does not affect those in serum corticosterone concentration and tryptophan availability to the liver. 5. Allopurinol, which blocks the starvation-induced enhancement of pyrrolase activity, also abolishes the increases in liver [NADP(H)], but not those in serum corticosterone concentration or tryptophan availability to the liver. 6. It is suggested that liver tryptophan pyrrolase activity plays an important role in NAD+ synthesis from tryptophan in the rat.
 ...
PMID:Possible involvement of the enhanced tryptophan pyrrolase activity in the corticosterone- and starvation-induced increases in concentrations of nicotinamide-adenine dinucleotides (phosphates) in rat liver. 730 70


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>