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

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

Mild forms of glucose-6-phosphatase deficiency (glycogenosis type I) may remain undetected till indirect consequences of the metabolic bloc clarify the diagnosis in early adulthood. Since humoral regulation could play a decisive role in the metabolic adaption to hypoglycemia, caused by the enzyme deficiency, we studied insulin-, glucocorticoid-, catecholamine- and somatotropin-secretion in a 27 year old man with a mild glycogenosis type I. Basal and simulated insulin release was decreased, the glucocorticoid secretion lay in the lowest part of the normal range, whereas catecholamine and somatotropin secretion showed no significant change. Thus, the humoral adaption in glucose-6-phosphate deficiency corresponds to the hormonal regulation in prolonged starvation.
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PMID:[Late manifestation of glycogenosis I in early adulthood]. 704 Sep 26

Liver glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) and malic enzyme (ME, EC 1.1.1.40) activities were measured in rats that were starved for 2 days and then fed a high-glucose, adequate-protein diet for 3 days. During refeeding the rats were injected with thyroxine to block glycogen accumulations preceeding the enzyme "overshoot". The G6PD and ME "overshoot" at the end of refeeding was still evident in spite of a 90% reduction in the glycogen peak. The results showed that the glycogen accumulation prior to the enzyme "overshoot" was not obligatory to the subsequent rise in enzyme activity. The sequential accumulation/breakdown of liver glycogen (day 1 refeeding) followed by the accumulation of liver fat (day 2 of refeeding) are probably the result of the changes in enzymatic pathways available to deal with the inflow of excess glucose. Such dissociation of glycogen accumulation and G6PD and ME "overshoot" during starvation-refeeding makes it highly unlikely that either glucose or glucose-6-phosphate derived from glycogen would be the direct, primary inducer of G6PD or ME in rat liver.
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PMID:Induction of rat liver glucose-6-phosphate dehydrogenase and malic enzyme during blockage of glycogen accumulation. 744 69

We have reported previously that levels of insulin-like growth factor I (IGF-I) and IGF-II in fetal sheep plasma decrease with maternal starvation and increase following an infusion of glucose to the starved fetus, while a fetal infusion of insulin elevates UGF-I alone. We now report the changes in the circulating IGF-II/M6P receptor and plasma IGF binding proteins (IGFBPs), as measured by western blotting and ligand blotting, respectively, in fetus and mother during this study. In fetal plasma, the circulating IGF-II/mannose-6-phosphate (M6P) receptor, IGFBP-3 and IGFBP-4 were reduced during starvation. While circulating IGF-II/M6P receptor and IGFBP-4 levels were increased following the fetal insulin or glucose infusion, IGFBP-3 was unchanged and increased only after 48 h of maternal refeeding. Both IGFBP-1 and IGFBP-2 increased with starvation but while IGFBP-1 levels returned to control values following both insulin and glucose infusion, levels of IGFBP-2 were not reduced significantly by either infusion or by refeeding. In maternal plasma, levels of IGFBP-3 and IGFBP-4 decreased while IGFBP-1 and IGFBP-2 increased after 48 h of starvation. Levels of each IGFBP were unaltered following the fetal infusions but returned to values obtained during the control period after refeeding. These data show that each of the IGF carrier proteins is sensitive of changes in nutrition, either acutely, such as IGFBP-1, or chronically, as for IGFBP-3. This suggests that the circulating IGF-II/M6P receptor and the IGFBP's may modulate IGF activity in the fetus during different nutritional states.
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PMID:Circulating insulin-like growth factor II/mannose-6-phosphate receptor and insulin-like growth factor binding proteins in fetal sheep plasma are regulated by glucose and insulin. 752 43

Under a limited set of hitherto incompletely defined conditions, inhibition of respiration has been shown to cause transient oscillations in NAD(P)H fluorescence of yeast cells. In this paper, we apply a new method [1992, Anal. Biochem. 204, 118-132] for extraction of intracellular metabolites. This method involves spraying the cells into -40 degrees C methanol; the neutral pH allows extraction of nearly all intracellular metabolites, including NADH. Close to the shift from glucose to ethanol as a growth substrate, the cells acquire a make-up amenable to sustained oscillations in intracellular concentrations of NADH and glycolytic intermediates such as glucose-6-phosphate. NADH was found to oscillate between 200 microM and 400 microM intracellular concentration. The cellular make-up determining the tendency to oscillate is 'remembered' by the cells after three hours of starvation.
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PMID:Around the growth phase transition S. cerevisiae's make-up favours sustained oscillations of intracellular metabolites. 843 31

To analyze the role of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31) during seed development, two cDNA clones encoding two isoforms of PEPCase were isolated from a seed-specific library of Vicia faba. The two sequences (VfPEPCase1 and VfPEPCase2) have a sequence identity of 82 and 89% on the nucleotide and amino acid levels. The VfPEPCase1 mRNA was found to be predominantly expressed in roots and developing cotyledons whereas the VfPEPCase2 mRNA was more abundant in green and maternal tissues. In the cotyledons, PEPCase mRNAs accumulated from early to mid cotyledon stage and decreased thereafter. The PEPCase activity increased continuously during cotyledon development. The enzyme was strongly activated by glucose-6-phosphate, but not by glucose, fructose or sucrose. Asparagine was weakly activating whereas malate, aspartate and glutamate were inhibitory. The inhibitors became less effective with increasing pH. Aspartate was a much stronger inhibitor of cotyledonary PEPCase than glutamate at both pH 7.0 and 7.5. The sensitivity of PEPCase to malate inhibition decreased from early to mid cotyledon stage at a time when storage proteins are synthesized. This indicates activation on the protein level, possibly by protein phosphorylation. Nitrogen starvation in the presence of hexoses but not sucrose decreased mRNA levels of VfPEPCase1 and enzyme activity, indicating control on the mRNA level by both carbon and nitrogen. It is concluded that in developing cotyledons PEPCase is probably important for the synthesis of organic acids to provide carbon skeletons for amino acid synthesis.
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PMID:Phosphoenolpyruvate carboxylase in developing seeds of Vicia faba L.: gene expression and metabolic regulation. 1021 2

The metabolic responses occurring in cucumber (Cucumis sativus L.) roots (a strategy-I plant) grown under iron-deficiency conditions were studied in-vivo using 31P-nuclear magnetic resonance spectroscopy. Iron starvation induced activation of metabolism leading to the consumption of stored carbohydrates to produce the NAD(P)H, ATP and phosphoenolpyruvate necessary to sustain the increased activity of the NAD(P)H:Fe(3+)-reductase, the H(+)-ATPase (EC 3.6.1.35) and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Activation of catabolic pathways was supported by the enhancement of glycolytic enzymes and concentrations of the metabolites glucose-6-phosphate and fructose-6-phosphate, and by enhancement of the respiration rate. Moreover, Fe-deficiency induced a slight increase in the cytoplasmic (pHc) and vacuolar (pHv) pHs as well as a dramatic decrease in the vacuolar phosphate (Pi) concentration. A comparison was done using fusicoccin (FC), a fungal toxin which stimulates proton extrusion. Changes in pHc and pHv were measured after addition of FC. Under these conditions, a dramatic alkalinization of the pHv of -Fe roots was observed, as well as a concomitant Pi movement from the vacuole to the cytoplasm. These results showed that Fe starvation was indeed accompanied by the activation of metabolic processes useful for sustaining the typical responses occurring at the plasma-membrane level (i.e. increases in the NAD(P)H:Fe(3+)-reductase and H(+)-ATPase activities) as well as those involved in the homeostasis of pHc. The decrease in vacuolar Pi levels induced by Fe-deficiency and FC and movement of Pi from the vacuole to the cytoplasm suggest a possible involvement of this compound in the cellular pH-stat system.
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PMID:Metabolic responses in cucumber (Cucumis sativus L.) roots under Fe-deficiency: a 31P-nuclear magnetic resonance in-vivo study. 1087 32

Phosphoenolpyruvate carboxylase (PEPCase) activity was investigated in cucumber roots grown under iron starvation. The enzyme extracted from plants grown in the presence and in the absence of Fe was characterized both kinetically and biochemically. Extractable PEPCase activity was increased by 4-fold in the absence of Fe. This increase began about 5 d after Fe starvation. Western blot analysis revealed the presence of two polypeptides with apparent molecular masses of 103 and 108 kDa. At the beginning both the polypeptides were equally present in the control and in the Fe-deficient roots. After 10 d of Fe starvation the increase was clearly evident and concerned, in particular, the polypeptide of 103 kDa whose enhancement was around 3-fold with respect to the control. Re-supply of iron to Fe-starved roots decreased both the activity and the concentration of the enzyme to the control values. Determination of kinetic parameters revealed that the K:(m) values for the substrates were the same, while the V:(max) was increased by four times for the enzyme extracted from Fe-deficient roots. Also the responses to pH changes and to the allosteric modulators malate and glucose-6-phosphate were different. The kinetic data, the increase in PEPCase specific activity and in the PEPCase polypeptides concentration seem to indicate that under Fe deficiency the enzyme regulation might be, in part, exerted at the transcriptional level.
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PMID:Phosphoenolpyruvate carboxylase in cucumber (Cucumis sativus L.) roots under iron deficiency: activity and kinetic characterization. 1111 68

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

To examine the role of glucose-6-phosphatase (G6Pase) in glucose homeostasis in the diabetes-like experimental model of carnivorous fish, we analysed postprandial variations and the effect of starvation, ration size and diet composition on the regulation of G6Pase expression at the enzyme activity and mRNA level in the liver of gilthead sea bream (Sparus aurata). G6Pase expression increased in long-term starved or energy-restricted fish. In contrast to data reported for other fish species, short-term regulation of G6Pase expression was found in regularly fed S. aurata. G6Pase mRNA levels were lowest between 4 and 15 h after food intake, whereas minimal enzyme activity was observed 10-15 h postprandially. Alterations of plasma glucose levels affect G6Pase in mammals. However, the carbohydrate content of the diet did not affect hepatic expression of G6Pase in S. aurata, suggesting that a different molecular mechanism is involved in the control of G6Pase expression in fish. Although G6Pase was unaffected, high-carbohydrate low-protein diets increased glucokinase (GK) expression and thus allowed a metabolic adaptation favouring glycolysis over gluconeogenesis. Interestingly, only the nutritional conditions that promoted variations in the blood glucose levels resulted in changes in the hepatic expression of G6Pase. These findings indicate a concerted regulation of G6Pase and GK expression and suggest that the direction and rate of the glucose-glucose-6-phosphate substrate cycle flux is finely regulated in the liver of S. aurata, challenging the role attributed to deficient regulation of G6Pase or GK expression in the low ability of carnivorous fish to metabolize glucose.
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PMID:Nutritional regulation of glucose-6-phosphatase gene expression in liver of the gilthead sea bream (Sparus aurata). 1249 82


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