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Results for “LIVER GLYCOGEN”

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At least 19 recordsLinked to original sources
PubMed1973

Effects of endotoxin on gluconeogenesis, glycogen synthesis, and liver glycogen synthase in mice.

This study was undertaken to characterize the nature of carbohydrate loss due to endotoxin poisoning in mice and to elucidate mechanisms responsible for the changes. Female ICR mice, fasted overnight, were injected intraperitoneally with a mean lethal dose of endotoxin extracted from Salmonella typhimurium strain SR-11. Liver glycogen levels, alanine-U-(14)C and pyruvate-2-(14)C incorporation into blood glucose and liver glycogen, glucose-U-(14)C incorporation into liver glycogen, and liver glycogen synthase activities were measured at intervals after treatment. Liver glycogen in fasted mice given endotoxin was diminished significantly as early as 1 h after treatment. Liver glycogen synthase was significantly decreased in poisoned mice at 17 h. The use of actinomycin D showed that the induction of this enzyme due to fasting or hydrocortisone, or both, was inhibited by endotoxin. The incorporation of the (14)C-label from alanine-U-(14)C, pyruvate-2-(14)C, or glucose-U-(14)C into blood glucose and liver glycogen was substantially impaired in endotoxemic animals at 12 h. Decreases in incorporation occurred as early as 4 h after treatment. The progressive increase in glycogen synthase activity observed in fasted controls was not seen in endotoxin-poisoned mice. The administration of a glucose or pyruvate load to endotoxin-treated mice did not restore gluconeogenesis, glycogen synthesis, or liver glycogen synthase activity to normal levels. The in vivo activation of glycogen synthase by glucose was significantly reduced in endotoxemic animals. These changes indicate reduced carbohydrate synthesis as a probable cause for rapid sugar loss during endotoxemia in mice.

Alanine↗
PubMed2000

Effects of supranormal liver glycogen content on hyperglucagonemia-induced liver glycogen breakdown.

The purpose of the present study was to test the hypothesis that a higher hepatic glycogen level is associated with higher glucagon-induced hepatic glycogen depletion. Four groups of anesthetized rats received three injections (at times 0, 30, and 60 min) of glucagon (intravenously, 20 [microg/kg). Among these groups, hepatic glycogen levels had previously been manipulated either by an overloading diet (Fast-refed), a reduction in food intake (1/2-fast), or exercise (75 min of running, 26 m/ min, 0% grade). A fourth group had normal hepatic glycogen levels. A fifth group of rats was injected only with saline (0.9% NaCl). Liver glycogen concentrations were measured every 30 min during the course of the 90-min experiment, using liver samples obtained from the open liver biopsy technique. Plasma glucagon concentrations were significantly higher (P < 0.05) in the glucagon-injected groups than in the saline-injected group. As expected, liver glycogen levels were significantly higher (P < 0.01; 1.6-fold) in the Fast-refed group than in all other groups. Glucagon-induced decreases in liver glycogen concentrations were similar in Fast-refed than in normally fed and exercised rats when the overall 90-min period was considered. However, during the course of the last 30-min period, liver glycogen was significantly (P < 0.01) decreased only in the Fast-refed group. The Fast-refed, normally fed, and exercised groups had a similar glucagon-induced hyperglycemia that was significantly more elevated (P < 0.01) than glucose levels measured in the saline-injected group. Glucagon-induced reactive hyperinsulinemia was observed only in the Fast-refed and normally fed rats, and not in the exercised and 1/2-fast rats. It is concluded that supranormal levels of liver glycogen may be associated with a larger hyperglucagonemia-induced liver glycogen breakdown.

Animal Nutritional Physiological Phenomena↗
PubMed1988

Circadian studies of plasma cortisol, thyroid hormone, protein, glucose and ion concentration, liver glycogen concentration and liver and spleen weight in rainbow trout, Salmo gairdneri Richardson.

1. Although there are many reports in the literature of circadian rhythms in plasma hormone and metabolite levels, the data are highly variable between research groups. The present study attempts to re-examine whether circadian rhythm in plasma cortisol, thyroid hormone, ions, glucose and protein levels and liver glycogen levels are evident in rainbow trout, Salmo gairdneri, and determine whether there is a significant correlation between any of the measured variables. 2. Significant fluctuations throughout the day were found in all measured variables; although these fluctuations appear to be a normal component in the homeostatic function of rainbow trout, their timing was neither consistent nor predictable. 3. "Circadian-like" patterns were observed in levels of plasma cortisol, glucose, Mg2+ and K+ concentrations and liver glycogen concentration. 4. Seasonal variations in these circadian-like rhythms were found in liver glycogen and plasma cortisol, Mg2+ and K+ concentrations. 5. Plasma cortisol and glucose concentrations were affected by time of feeding. 6. There were significant correlations between plasma thyroid hormone and plasma protein levels, but no other significant correlation between any of the measured variables was found.

Animals↗
PubMed1996

Liver glycogen in fasted rat livers does not improve outcome of liver transplantation.

Controversy exists over how the nutritional condition of the donor liver affects transplant outcome. Some studies suggest that livers from fasted animals (liver glycogen-depleted) are more readily injured than livers from fed animals. Our previous study suggested the opposite, i.e., livers from donors fasted for 4 days were significantly more viable on orthotopic liver transplantation. Fasting may decrease the sensitivity of the liver to an inflammatory response or block Kupffer cell activation following transplantation. Thus, long-term fasting may be beneficial for reasons unrelated to liver glycogen content. In this study we attempted to separate out the roles of fasting and liver glycogen in liver transplant outcome by fasting donors for 2 days and then feeding them only glucose to elevate liver glycogen. Rats (Brown Norway) were fed (standard diet), fasted (4 days), or fasted 2 days and then fed glucose (in water) for 2 days. Livers were preserved for either 30 or 44 h in UW solution and transplanted. Four-day fasting of the donor improved the survival rate in liver transplantation (50%-100% in 30-h cold storage, 29%-83% in 44-h cold storage). However, feeding glucose for 2 days to fasted animals caused a decrease in survival in this series of transplants (40% in 30-h cold storage, 0% in 44-h cold storage). In the glucose-fed group, liver glycogen was 240% of that in the control group. This suggests that the presence of a high concentration of liver glycogen is not beneficial to the preserved and transplanted rat liver.

Animals↗
PubMed1984

Phosphorylation and inactivation of liver glycogen synthase by liver protein kinases.

A rapid method for purifying glycogen synthase a from rat liver was developed and the enzyme was tested as a substrate for nine different protein kinases, six of which were isolated from rat liver. The enzyme was phosphorylated on a 17-kDa CNBr fragment to approximately 1 phosphate/87-kDa subunit by phosphorylase b kinase from muscle or liver with a decrease in the activity ratio (-Glc-6-P/+Glc-6-P) from 0.95 to 0.6. Calmodulin-dependent glycogen synthase kinase from rabbit liver produced a similar phosphorylation pattern, but a smaller activity change. The catalytic subunit of beef heart cAMP-dependent protein kinase incorporated greater than 1 phosphate/subunit initially into a 17-kDa CNBr peptide and then into a 27-30-kDa CNBr peptide, with an activity ratio decrease to 0.5. Glycogen synthase kinases 3, 4, and 5 and casein kinase 1 were purified from rat liver. Glycogen synthase kinase 3 rapidly phosphorylated liver glycogen synthase to 1.5 phosphate/subunit with incorporation of phosphate into 3 CNBr peptides and a decrease in the activity ratio to 0.3. Glycogen synthase kinase 4 produced a pattern of phosphorylation and inactivation of liver synthase which was very similar to that caused by phosphorylase b kinase. Glycogen synthase kinase 5 incorporated 1 phosphate/subunit into a 24-kDa CNBr peptide, but did not alter the activity of the synthase. Casein kinase 1 phosphorylated and inactivated liver synthase with incorporation of phosphate into a 24-kDa CNBr peptide. This kinase and glycogen synthase kinase 4 were more active against muscle glycogen synthase. Calcium-phospholipid-dependent protein kinase from brain phosphorylated liver and muscle glycogen synthase on 17- and 27-kDa CNBr peptides, respectively. However, there was no change in the activity ratio of either enzyme. The following conclusions are drawn. 1) Liver glycogen synthase a is subject to multiple site phosphorylation. 2) Phosphorylation of some sites does not per se control activity of the enzyme under the assay conditions used. 3) Liver contains most, if not all, of the protein kinases active on glycogen synthase previously identified in skeletal muscle.

Animals↗
PubMed1987

The polymorphic locus for glycogen storage disease VI (liver glycogen phosphorylase) maps to chromosome 14.

Human liver glycogen phosphorylase deficiency, also known as glycogen storage disease type VI (GSD VI) or Hers disease, is characterized by hepatomegaly and reduced or absent glycogenolytic response to the injection of glucagon. The recently isolated cDNA encoding the liver isozyme of glycogen phosphorylase was used to map the gene and identify restriction-fragment polymorphisms in normal Caucasians as a prerequisite for detecting linked GSD VI abnormalities. Results of restriction-enzyme analysis using a downstream fragment of the liver glycogen phosphorylase cDNA indicated the existence of a single gene copy per haploid genome. Hybridization of this downstream liver phosphorylase probe to dual laser-excited, sorted human chromosomes localized the gene to human chromosome 14. When the downstream probe was tested on genomic DNA cut with seven different restriction enzymes, a single MspI restriction-fragment-length polymorphism (RFLP) was observed in a single individual. In contrast, similar Southern blots performed with an upstream portion of the cDNA encoding liver phosphorylase revealed common RFLPs for four of eight enzymes tested, with minor polymorphic allele frequencies ranging from 33% to 44%. One of the four enzymes (TaqI) revealed two independent polymorphisms. If random distribution of these haplotypes among normal and disease loci, is assumed, approximately 92% of fetuses at risk for Hers disease will be informative when tested with the upstream liver phosphorylase probe.

Chromosome Mapping↗
PubMed1990

Intermolecular chemical heterogeneity of liver glycogen.

Rabbit liver glycogen is shown to contain small amounts of covalently bound phosphate and glucosamine, and to display intermolecular heterogeneity with respect to the proportions of these two trace components. The difference in phosphate content over five fractions, separated on DEAE-cellulose, ranged from 2 to 155 molecular proportions relative to glycogen of Mr 10(7), while the glucosamine content varied from 0.6 to 2.3 molecular proportions. In parallel, the average molecular size and the turbidity of the glycogen fractions increased with increasing phosphate and glucosamine contents, the molecular weight profile taking the form of a change in the ratio of two glycogen components of distinctly different sizes. The varying presence of the phosphate and glucosamine, apart from their own significance, may help in gaining an insight into the overall properties of glycogen itself, such as the relative ages of individual molecules and the existence of different metabolic pools.

Animals↗
PubMed1982

Effects of alloxan diabetes on the turnover of rat liver glycogen synthase. Comparison with liver phosphorylase.

Rat liver glycogen synthase shows almost a 2-fold increase in activity 8 days after onset of alloxan diabetes. Immunological and catalytic criteria indicate that the change in activity is associated with an increase in the amount of enzyme in the diabetic. Apparent rates of degradation were determined for isolated glycogen synthase and phosphorylase from the livers of 2-, 5-, and 8-day diabetic, insulin-treated diabetic and normal rats using the double isotope ([3H]leucine and [14C]leucine) labeling method (Arias, I. M., Doyle, D., and Schimke, R. T. (1969) J. Biol. Chem. 244, 3303-3315). Relative rates of enzyme synthesis and degradation were determined by comparing the 3H incorporation and 3H/14C ratios of the isolated enzymes to the isotope labeling of a liver fraction representing the average of liver proteins. Glycogen synthase showed a gradual increase in the rate of degradation through the course of diabetes with an average relative rate of degradation in the 8-day diabetic 1.8 times greater than the normal. The relative rate of synthesis for glycogen synthase in the diabetic was 2.2- to 2.5-fold greater than the normal. Phosphorylase from 5- and 8-day diabetic rats had relative rates of degradation 4.0-5.3 times greater than enzyme from the normal. In the diabetic, the rate of degradation of phosphorylase was greater than for synthase while the opposite was observed in the normal rat. The relative rate of synthesis for phosphorylase from diabetic rats was approximately 4.5-fold greater than normal. The increased concentration of glycogen synthase in the diabetic liver is because of an increased rate of synthesis and not a decreased rate of enzyme degradation.

Animals↗
PubMed1984

Phosphorylation of rat liver glycogen synthase bound to the glycogen particle.

Rat liver glycogen synthase bound to the glycogen particle was partially purified by repeated high-speed centrifugation. This synthase preparation was labeled with 32P by incubations with cAMP-dependent protein kinase and cAMP-independent synthase (casein) kinase-1 in the presence of [gamma-32P]ATP. The phosphorylated synthase was separated from other proteins in the glycogen pellet by immunoprecipitation with rabbit anti-rat liver glycogen synthase serum. Analysis of the immunoprecipitates by sodium dodecyl sulfate-gel electrophoresis showed that synthase subunits of Mr 85,000 and 80,000 were present in varying proportions. The 32P-labeled synthase in the immunoprecipitate was digested with trypsin, and the resulting peptides were analyzed by isoelectric focusing. Synthase bound to the glycogen particle was phosphorylated by cAMP-dependent protein kinase at more sites and by cAMP-independent synthase (casein) kinase-1 at less sites than when the homogeneous synthase was incubated with these kinases. Phosphorylation of synthase in the glycogen pellet by either cAMP-dependent protein kinase or cAMP-independent synthase (casein) kinase-1 did not cause a significant inactivation as has been observed when the synthase was incubated with these kinases. Inactivation of synthase in the glycogen pellet, however, can be achieved by the combination of both kinases. This inactivation appears to result from the phosphorylation of a new site by cAMP-independent synthase (casein) kinase-1 neighboring a site previously phosphorylated by cAMP-dependent protein kinase.

Animals↗
PubMed1980

Variations of meal-to-meal liver glycogen in rats.

Liver glycogen content was determined in free feeding rats sacrificed at the beginning of nocturnal meals or 60 min later. It was found that the glycogen content at the beginning of meals and 60 min later was highly correlated with the cumulative food intake since the beginning of the dark cycle, and therefore, increased from meal to meal. The comparison of these correlations between the cumulative food intake and the liver glycogen at the beginning of the meal and 60 min after ruled out the possibility that a constant decrement of glycogen might be involved in both meal onset and prandial periodicity of feeding. Rather the results are consistent with the view that the glycogen load during the night is a minute carbohydrate store which, like the fat store, is involved in the diurnal 12/12 hr feeding periodicity.

Animals↗