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

Glucagon is known to elevate the intracellular concentration of cyclic AMP in the hepatocyte. The increase in intracellular cyclic AMP is reflected by an increase in the plasma concentration of the nucleotide. Intravenous glucagon stimulation was performed on six obese non-diabetic human subjects before and after a three day fast. All patients responded to starvation by a lowering of plasma immunoreactive insulin and blood glucose. Whereas the plasma immunoreactive glucagon concentration increased over the three day period, the plasma and urinary cyclic AMP did not significantly change. Intravenous glucagon promoted qualitatively similar increases in the blood glucose and plasma concentrations of insulin and cyclic AMP before and after three days starvation.
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PMID:Urinary and plasma cyclic AMP levels during short term starvation in obese man: response to glucagon stimulation. 20 64

Fatty acid synthesis in the mammary gland of lactating rats in vivo was 5-fold higher than in the liver. Starvation decreased fatty acid synthesis in the gland 50-fold, whereas refeeding for 2h completely reversed this change. The plasma insulin concentration decreased 2-fold in starvation and was restored to the fed-rat value on refeeding. Glucagon and prolactin concentrations did not always change in parallel with lipogenesis, suggesting that insulin may be a regulator of this process in the gland.
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PMID:Evidence for a role of insulin in the regulation of lipogenesis in lactating rat mammary gland. Measurements of lipogenesis in vivo and plasma hormone concentrations in response to starvation and refeeding. 72 15

Glucagon binding by liver cell membranes was examined in rats with chronically elevated plasma levels of immunoreactive glucagon (IRG) resulting from insulin deficiency, starvation, or twice daily glucagon injections. The concentration of specific glucagon binding sites was significantly reduced in the three chronically hyperglucagonemic (IRG greater than 125 pg/ml) groups as compared with nondiabetic controls and insulin-treated diabetic control rats with only mild hyperglucagonemia. A reduction in glucagon binding sites did not occur with hyperglucagonemia of 12 h or less. Despite the reduced binding of glucagon in the three chronically hyperglucagonemic groups, the ability of glucagon to stimulate cAMP production was not reduced. It is concluded that while decreased glucagon binding occures in the forms of chronic hyperglucagonemia studied, it is not associated with a reduction in the ability of glucagon to stimulate cAMP production.
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PMID:Binding and biologic activity of glucagon in liver cell membranes of chronically hyperglucagonemic rats. 91 19

Glucagon treatment of fed rats (50 micrograms I.P. every 6 h for 3 days) induces significant increases in vitro of the basal short-circuit currents of the jejunum (52%) and proximal ileum (81%) and in their electrogenic secretory responses to stimulation by bethanechol, a muscarinic agonist. The results support a role for glucagon in the intestinal hypersecretion observed in starvation and nutrient deprivation.
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PMID:Enhanced electrogenic secretion in vitro by small intestine from glucagon-treated rats: implications for the diarrhoea of starvation. 135 76

Cultured rat hepatocytes were preincubated with glucagon or a cyclic AMP analogue for up to 24 h and lipid synthesis and secretion were determined during the next 2 h. Glucagon or cyclic AMP did not change the incorporation of choline or glycerol into phosphatidylcholine, or choline into sphingomyelin, in the cells after 0-12 h of preincubation. After 12 h these incorporations were increased. Incorporations into hepatic lysophosphatidylcholine were decreased after preincubation with glucagon or cyclic AMP for 0-12 h, but by 24 h they increased. There was no change in the lysophosphatidylcholine in the medium after preincubation with glucagon or cyclic AMP for up to 6 h, but increases occurred after preincubation from 12 to 24 h. The secretion of triacylglycerol was decreased after preincubation for 0-1 h, but it returned to control values after 4 h. After preincubation for 18-24 h the incorporation of glycerol into secreted triacylglycerol was increased. The results are discussed in relation to the control of lipid metabolism in starvation and diabetes.
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PMID:Biphasic effects of glucagon and cyclic AMP on the synthesis and secretion of lipids by rat hepatocytes. 165 86

Hepatic fatty acid synthase is regulated by nutritional state. Starvation decreases and refeeding increases the activity of avian fatty acid synthase, principally by regulating transcription of the gene (Back, B. W., Goldman, M. J., Fisch, J.E., Ochs, R.A., and Goodridge, A.G. (1986) J. Biol. Chem. 261, 4190-4197). In chick embryo hepatocytes in culture, the stimulatory effect of feeding on fatty acid synthase activity is mimicked by adding triiodothyronine and insulin; the inhibitory effect of starvation is mimicked by adding glucagon or cyclic AMP. We now show that triiodothyronine alone stimulates transcription of fatty acid synthase by 4- to 6-fold, about the same as the increase in fatty acid synthase mRNA. When added alone, insulin has little or no effect on transcription, mRNA level, or enzyme activity. In combination with triiodothyronine, however, insulin amplifies the response to triiodothyronine by about 2-fold, leading to an overall increase of about 10-fold. Insulin-like growth factor 1 (IGF-1) has the same effect as insulin, no effect by itself, and amplification of the stimulation by triiodothyronine. A maximally effective dose of insulin has no effect in the presence of a maximally effective dose of IGF-1, suggesting regulation by a common pathway. It takes much less IGF-1 than insulin to achieve a given effect, suggesting that both insulin and IGF-1 may act through IGF-1 receptors. Plasma levels of IGF-1 are decreased by starvation and increased by feeding (reviewed by Froesch, E.R., and Zapf, J. (1985) Diabetologia 28, 485-493). Thus, IGF-1 may play a physiological role in the regulation of hepatic fatty acid synthase during transitions between the starved and fed states, roles previously assigned primarily to insulin and glucagon. IGF-1 regulates transcription of the fatty acid synthase gene. Insulin and IGF-1 also have similar effects on activity, mRNA abundance, and transcription of the malic enzyme gene. Glucagon or dibutyryl cyclic AMP inhibit fatty acid synthase activity and mRNA level in hepatocytes in culture by 70-80% and 60%, respectively, but have no effect on transcription of the fatty acid synthase gene, suggesting a post-transcriptional mode of regulation for cyclic AMP.
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PMID:Triiodothyronine stimulates transcription of the fatty acid synthase gene in chick embryo hepatocytes in culture. Insulin and insulin-like growth factor amplify that effect. 217 Apr 11

Carnitine palmitoyltransferase (CPT total) activity and synthesis increase in states where the insulin/glucagon ratio is low, such as starvation and diabetes [Brady & Brady (1987) Biochem. J. 246, 641-646]. However, the effect of glucagon and insulin on CPT synthesis is unknown. The present experiments were designed to determine the effect of glucagon, cAMP [8-(chlorophenylthio) cyclic AMP], and insulin + cAMP on CPT transcription and mRNA amounts over time after injection. The CPT protein that was purified, used to generate antibody, and cloned in these studies was the 68 kDa mitochondrial protein described previously [Brady & Brady (1987) Biochem. J. 246, 641-646; Brady, Feng & Brady (1988) J. Nutr. 118, 1128-1136; Brady & Brady (1989) Diabetes 38, in the press]. Saline-injected control rats exhibited a 2-fold increase in hepatic CPT transcription rate and CPT mRNA over the 5 h experiment from 09:00 to 14:00 h. The effect was most probably due to the fasting state of the rats during the day. Glucagon injection caused an 8-fold increase in transcription rate by 90 min and a 4-fold increase in CPT mRNA by 90-120 min. The cAMP effect had reached a peak by the first time point taken (15 min). Transcription rate was increased 4-fold and CPT mRNA was increased 3-fold at this time. The combination of cAMP + insulin injection did not produce any significant increase in transcription rate or CPT mRNA over the saline-injected controls. CPT mRNA and transcription rate showed a clear dose-response to glucagon injection from 0 to 150 micrograms/100 g body wt. Total CPT activity and immunoreactive CPT were not increased during these experiments. The data indicate that glucagon and insulin interact in control of transcription rate and amount of CPT mRNA, but that increases in CPT immunoreactive protein and activity are temporally delayed. This lag probably relates to the half-life of the CPT protein in vivo, which has been estimated as 2-7 days.
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PMID:Regulation of carnitine palmitoyltransferase in vivo by glucagon and insulin. 254 60

The degradation of intracellular protein and other cytoplasmic macromolecules in liver is an ongoing process that regulates cytoplasmic mass and provides amino acids for energy and other metabolic uses early in starvation. Cellular proteins are conveniently divided into two general classes according to readily discernable differences in average rates of turnover. A short-lived class, having a half-life of approximately 10 min, comprises about 0.6% of total protein. Its degradation is not physiologically controlled, and the mechanism is probably nonlysosomal in nature. The second or long-lived group, with an average half-life 250 times greater, constitutes more than 99% of the cell's protein. By contrast, its breakdown is strongly regulated, and the site of catabolism is believed to be the vacuolar-lysosomal system. Cytoplasmic sequestration by lysosomes can be divided into two categories; macro- and microautophagy. The first is induced by amino acid and/or insulin deprivation. Amino acids are considered to be primary regulators, since they can control this process over the full range of induced proteolysis in the absence of hormones. Glucagon, cyclic AMP, and beta-agonists also stimulate macroautophagy in hepatocytes but have opposite effects in myocytes. Micrautophagy differs from the former in that the cytoplasmic "bite" is smaller and the uptake process is not acutely regulated. However, the latter does decrease during starvation in parallel with basal proteolysis, effects that might be linked to the loss of endoplasmic reticulum. The primary control of macroautophagy is accomplished through a small group of direct regulators (Leu, Tyr/Phe, Gln, Pro, Met, His, and Trp) and a specific coregulatory action of alanine. As a group, regulatory amino acids produce direct inhibitory responses in the perfused rat liver that are identical to those of the complete amino acid mixture at 0.5x and 4x (times) normal plasma concentrations. However, they lose effectiveness almost completely within a narrow zone centered at normal levels, a loss that can be abolished by the addition of alanine at its normal plasma concentration (0.5 mM). At this level, alanine does not inhibit directly. Interestingly, this zonal loss is also eliminated by insulin. Glucagon, though, specifically blocks the initial inhibition evoked by 0.5x amino acid mixtures and thus induces maximal rates of protein degradation at normal amino acid concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Mechanism and regulation of protein degradation in liver. 264 36

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

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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