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

The purpose of the study was to determine the response of liver and brown (BAT) and white (WAT) adipose tissue lipogenesis and total body weight in rats subjected to multiple cycles of 3 days of fasting and 3 days of refeeding. Rats fasted for 3 days showed significant reduction in body weight. These changes were reversed on 3 days' refeeding. Body weight was much higher in rats fed ad libitum than in animals experiencing more than one cycle of 3 days of fasting followed by 3 days of refeeding. Despite the significant body weight reduction, an unusual increase of lipogenesis in WAT was found after multiple cycles of starvation-refeeding of rats on standard laboratory diet. The rate of lipogenesis in the liver and BAT was also elevated but to a much smaller extent. A parallel increase in enzymatic activities related to fatty acid synthesis, ie, fatty acid synthase, acetyl-coenzyme A carboxylase, adenosine triphosphate (ATP)-citrate lyase, NADP-linked malic enzyme, and hexose monophosphate shunt dehydrogenases, suggests that the increased rate of lipogenesis in WAT is a consequence of increased lipogenic enzyme activities. These data suggest that upregulation of WAT lipogenesis occurs after the multiple cycles of the starvation-refeeding protocol. An unusual increase of lipogenesis in rat WAT may have a survival advantage, because starved-refed rats must develop the ability to ingest large amounts of food during a refeeding period to store it in a convenient form than can be used as an oxidizable substrate during a period of starvation. Moreover, these results suggest that it is possible to develop appropriate starvation-refeeding conditions that may inhibit body weight gain.
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PMID:Unususal increase of lipogenesis in rat white adipose tissue after multiple cycles of starvation-refeeding. 900 62

Nitrogen starvation enhances up to 8-fold the cellular level of the NADP+-dependent isocitrate dehydrogenase activity (isocitrate:NADP+ oxidoreductase (decarboxylating), IDH, EC 1.1.1.42) in the thermophilic filamentous non-N2-fixing cyanobacterium Phormidium laminosum. The enzyme was purified 650-fold to electrophoretic homogeneity from nitrogen-starved cells with an activity yield of 25% and a specific activity of 500 U (mg protein)-1. The native enzyme showed a pI of 5.9 and it was a dimer of 107 kDa consisting of two identical subunits of 53 kDa. The activity required the presence of a divalent metal cation as an essential activator, Mn2+ or Mg2+ being the most effective. The optimum temperature for activity was 55 degrees C and the Ea for catalysis was 39.7 kJ mol-1. An optimum pH for activity of 8.5 was found and the calculated pKE1, pKE2 and pKES1 of enzyme ionisation groups were 6.0, 8.9 and 6.3, respectively. Km values of 22, 50 and 24 microM were calculated for d,l-isocitrate, NADP and Mn2+, respectively, in the Mn2+-dependent reaction and 70, 32 and 159 microM for d,l-isocitrate, NADP and Mg2+, respectively, in the Mg2+-dependent reaction. The decarboxylating activity was inhibited by ATP, ADP and by its reaction products 2-oxoglutarate and NADPH2. Polyclonal antibodies raised against the pure IDH were used to assess the presence of the enzyme in cells subjected to nitrogen starvation.
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PMID:Purification, properties and enhanced expression under nitrogen starvation of the NADP+-isocitrate dehydrogenase from the cyanobacterium Phormidium laminosum. 1020 82

Mitochondrial NAD-dependent (IDH) and cytosolic NADP-dependent isocitrate dehydrogenases have been considered as candidates for the production of 2-oxoglutarate required by the glutamine synthetase/glutamate synthase cycle. The increase in IDH transcripts in leaf and root tissues, induced by nitrate or NH4+ resupply to short-term N-starved tobacco (Nicotiana tabacum) plants, suggested that this enzyme could play such a role. The leaf and root steady-state mRNA levels of citrate synthase, acotinase, IDH, and glutamine synthetase were found to respond similarly to nitrate, whereas those for cytosolic NADP-dependent isocitrate dehydrogenase and fumarase responded differently. This apparent coordination occurred only at the mRNA level, since activity and protein levels of certain corresponding enzymes were not altered. Roots and leaves were not affected to the same extent either by N starvation or nitrate addition, the roots showing smaller changes in N metabolite levels. After nitrate resupply, these organs showed different response kinetics with respect to mRNA and N metabolite levels, suggesting that under such conditions nitrate assimilation was preferentially carried out in the roots. The differential effects appeared to reflect the C/N status after N starvation, the response kinetics being associated with the nitrate assimilatory capacity of each organ, signaled either by nitrate status or by metabolite(s) associated with its metabolism.
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PMID:Simultaneous expression of NAD-dependent isocitrate dehydrogenase and other krebs cycle genes after nitrate resupply to short-term nitrogen-starved tobacco 1039 6

In the C(4) plant maize (Zea mays L.), two ferredoxin isoproteins, Fd I and Fd II, are expressed specifically in mesophyll and bundle-sheath cells, respectively. cDNAs for these ferredoxins were introduced separately into the cyanobacterium Plectonema boryanum with a disrupted endogenous ferredoxin gene, yielding TM202 and KM2-9 strains expressing Fd I and Fd II. The growth of TM202 was retarded under high light (130 micromol/m(2)/s), whereas KM2-9 grew at a normal rate but exhibited a nitrogen-deficient phenotype. Measurement of photosynthetic O(2) evolution revealed that the reducing power was not efficiently partitioned into nitrogen assimilation in KM2-9. After starvation of the cells in darkness, the P700 oxidation level under far-red illumination increased significantly in TM202. However, it remained low in KM2-9, indicating an active cyclic electron flow. In accordance with this, the cellular ratio of ATP/ADP increased and that of NADPH/NADP(+) decreased in KM2-9 as compared with TM202. These results demonstrated that the two cell type-specific ferredoxins differentially modulate electron flow around photosystem I.
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PMID:Differential electron flow around photosystem I by two C(4)-photosynthetic-cell-specific ferredoxins. 1101 7

Recently, we have found that despite the significant reduction of body weight after multiple starvation-refeeding cycles, white adipose tissue (WAT) exhibits surprisingly high rates of lipogenesis and lipogenic enzyme activities. The purpose of this study was to determine the response of WAT lipogenic enzyme mRNAs of rats subjected to multiple cycles of 3 days fasting and 3 days of refeeding. Despite the body weight reduction, significant increase of lipogenic enzymes (ie, fatty acid synthase [FAS], acetyl-coenzyme A [CoA] carboxylase [ACC], adenosine triphosphate (ATP)-citrate lyase [ACL], NADP-linked malic enzyme [ME], and glucose 6-phosphate dehydrogenase [G6PDH]) mRNAs in WAT was found after multiple cycles of starvation-refeeding of rats on standard laboratory diet. These findings, together with the results published recently, indicate that multiple cycles of starvation-refeeding cause the increased lipogenesis in WAT by upregulation of the lipogenic enzymes gene expression.
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PMID:Increase of lipogenic enzyme mRNA levels in rat white adipose tissue after multiple cycles of starvation-refeeding. 1139 54

Pyridine nucleotide pools were measured in intact plastids from roots of barley (Hordeum vulgare L.) during the onset of NO2- assimilation and compared with the in vitro effect of the NADPH/NADP ratio on the activity of plastidic glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) from N-sufficient or N-starved roots. The NADPH/NADP ratio increased from 0.9 to 2.0 when 10 mM glucose-6-phosphate was supplied to intact plastids. The subsequent addition of 1 mM NaNO2 caused a rapid decline in this ratio to 1.5. In vitro, a ratio of 1.5 inactivated barley root plastid G6PDH by approximately 50%, suggesting that G6PDH could remain active during NO2- assimilation even at the high NADPH/NADP ratios that would favor a reduction of ferredoxin, the electron donor of NO2- reductase. Root plastid G6PDH was sensitive to reductive inhibition by dithiothreitol (DTT), but even at 50 mM DTT the enzyme remained more than 35% active. In root plastids from barley starved of N for 3 d, G6PDH had a substantially reduced specific activity, had a lower Km for NADP, and was less inhibited by DTT than the enzyme from N-sufficient root plastids, indicating that there was some effect of N starvation on the G6PDH activity in barley root plastids.
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PMID:In Vivo and in Vitro Studies of Glucose-6-Phosphate Dehydrogenase from Barley Root Plastids in Relation to Reductant Supply for NO2- Assimilation. 1222 80

Two members of the aldo-keto reductase family 11 from Bacillus subtilis have been crystallized and their oxidoreductase activity confirmed. AKR11A is a protein induced by inositol and repressed by glucose. AKR11B is induced when the cell is stressed by heat, acid, ethanol, starvation or osmotic shock and is therefore classified as a general stress protein. The expected NADPH-dependent sugar reductase activities for both proteins have been confirmed kinetically with several substrates. AKR11B exhibited typical aldo-keto reductase kinetics. However, only trace activity was found in AKR11A. To examine the effects of differences in sequence on the structures and functions of these enzymes, a crystallographic study has been initiated. AKR11A has been crystallized in its apo form and AKR11B crystals were obtained in complex with NADP(+).
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PMID:Expression, crystallization and activities of the two family 11 aldo-keto reductases from Bacillus subtilis. 1255 58

Specimens of the fruit beetle Pachnoda sinuata were starved for up to 30 days. The weight of the beetles declined consistently throughout the starvation period. Concentrations of carbohydrates and alanine in flight muscles, fat body and haemolymph decreased rapidly after onset of starvation, while the concentration of proline remained high. Whereas the lipid concentrations in the haemolymph did not change significantly upon starvation, the lipid content in flight muscles and fat body decreased significantly.Beetles that had been starved for 14 days responded to injection of Mem-CC, the endogenous neuropeptide from its corpora cardiaca, with hyperprolinaemia and a decrease in the alanine level, but no such effect was monitored after prolonged starvation of 28 days. Regardless of the period of starvation, Mem-CC injection could not cause hypertrehalosaemia or hyperlipaemia, although carbohydrates were increased in fed beetles after injection.Flight ability of beetles that had been starved for 15 or 30 days was apparently not impaired. During such periods, beetles used proline exclusively as fuel for flight as evidenced by the increase in the level of alanine in the haemolymph and decrease of the level of proline; the concentrations of carbohydrates and lipids remained unchanged.Activities of malic enzyme and alanine aminotransferase (enzymes involved in transamination in proline metabolism), glyceraldehyde-3-phosphate dehydrogenase (enzyme of glycolysis), 3-hydroxyacyl-CoA dehydrogenase (enzyme of beta-oxidation of fatty acids) and of malate dehydrogenase (enzyme of Krebs cycle) were measured in fat body and flight muscles. In flight muscle tissue the maximum activity of NAD(+)-dependent malic enzyme increased, while that of glyceraldehyde-3-phosphate dehydrogenase decreased during starvation, and malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and alanine aminotransferase were unchanged. In fat body tissue, activities of NADP(+)-dependent malic enzyme and 3-hydroxyacyl-CoA dehydrogenase increased during food deprivation and activities of glyceraldehyde-3-phosphate dehydrogenase, malate dehydrogenase and alanine aminotransferase remained unchanged.
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PMID:Metabolic changes in the African fruit beetle, Pachnoda sinuata, during starvation. 1277 Feb 39

1. The synthesis of ascorbic acid in rat-liver extracts is impaired during starvation, and more from glucuronolactone and glucuronate than from gulonate and gulonolactone. 2. The formation of xylulose from gulonate and from gulonolactone is greatly enhanced during starvation, whereas it is decreased from glucuronolactone and from glucuronate. 3. The activity of the enzymes of the glucuronic acid pathway during starvation has been determined in rat-liver preparations. Gulonolactone oxidase is decreased, NAD-linked gulonate dehydrogenase is enhanced, and uronolactonase, aldonolactonase and NADP-linked hexonate dehydrogenase are unchanged. 4. The impairment of ascorbic acid synthesis from gulonate observed during starvation can be accounted for by the depressed activity of gulonolactone oxidase. 5. The cause of the enhanced formation of xylulose has been located in the sedimentable fraction of liver homogenate. 6. The hypothesis is formulated of an increased utilization of the glucuronic acid pathway during starvation.
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PMID:REGULATION OF ASCORBIC ACID AND OF XYLULOSE SYNTHESIS IN RAT-LIVER EXTRACTS. THE EFFECT OF STARVATION ON THE ENZYMES OF THE GLUCURONIC ACID PATHWAY. 1434 84

When Brassica nigra leaf petiole suspension cells were subjected to 7 days of inorganic phosphate (Pi) starvation the extractable activity of: (a) pyrophosphate:fructose 6-phosphate 1-phosphotransferase, nonphosphorylating NADP-glyceraldehyde 3-phosphate dehydrogenase, phosphoenolpyruvate phosphatase, and phosphoenolpyruvate carboxylase increased at least fivefold, (b) phosphorylating NAD-glyceraldehyde 3-phosphate dehydrogenase decreased about sixfold, and (c) ATP:fructose 6-phosphate 1-phosphotransferase, 3-phosphoglycerate kinase, pyruvate kinase, or NAD malic enzyme was not altered. Pi deprivation also resulted in significant reductions in extractable levels of Pi, ATP, ADP, fructose 2,6-bisphosphate, and soluble protein, but caused a sixfold elevation in free amino acid concentrations. No change in inorganic pyrophosphate concentration was observed following Pi starvation. It is hypothesized that pyrophosphate:fructose 6-phosphate 1-phosphotransferase, nonphosphorylating NADP-glyceraldehyde 3-phosphate dehydrogenase, and phosphoenolpyruvate phosphatase bypass nucleotide phosphate or Pi-dependent glycolytic reactions during sustained periods of Pi depletion.
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PMID:Phosphate Starvation Inducible ;Bypasses' of Adenylate and Phosphate Dependent Glycolytic Enzymes in Brassica nigra Suspension Cells. 1666 22


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