scholarly journals Muscle-Specific Deletion of the Glut4 Glucose Transporter Alters Multiple Regulatory Steps in Glycogen Metabolism

2005 ◽  
Vol 25 (21) ◽  
pp. 9713-9723 ◽  
Author(s):  
Young-Bum Kim ◽  
Odile D. Peroni ◽  
William G. Aschenbach ◽  
Yasuhiko Minokoshi ◽  
Ko Kotani ◽  
...  
Keyword(s):  
Glucose Transport ◽  
Glycogen Phosphorylase ◽  
Glucose Transporter ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Hexokinase Ii ◽  
Phosphorylase Activity ◽  
Fasted State ◽  
Glycogen Phosphorylase Activity ◽  
Glycogen Synthase Activity

ABSTRACT Mice with muscle-specific knockout of the Glut4 glucose transporter (muscle-G4KO) are insulin resistant and mildly diabetic. Here we show that despite markedly reduced glucose transport in muscle, muscle glycogen content in the fasted state is increased. We sought to determine the mechanism(s). Basal glycogen synthase activity is increased by 34% and glycogen phosphorylase activity is decreased by 17% (P < 0.05) in muscle of muscle-G4KO mice. Contraction-induced glycogen breakdown is normal. The increased glycogen synthase activity occurs in spite of decreased signaling through the insulin receptor substrate 1 (IRS-1)-phosphoinositide (PI) 3-kinase-Akt pathway and increased glycogen synthase kinase 3β (GSK3β) activity in the basal state. Hexokinase II is increased, leading to an approximately twofold increase in glucose-6-phosphate levels. In addition, the levels of two scaffolding proteins that are glycogen-targeting subunits of protein phosphatase 1 (PP1), the muscle-specific regulatory subunit (RGL) and the protein targeting to glycogen (PTG), are strikingly increased by 3.2- to 4.2-fold in muscle of muscle-G4KO mice compared to wild-type mice. The catalytic activity of PP1, which dephosphorylates and activates glycogen synthase, is also increased. This dominates over the GSK3 effects, since glycogen synthase phosphorylation on the GSK3-regulated site is decreased. Thus, the markedly reduced glucose transport in muscle results in increased glycogen synthase activity due to increased hexokinase II, glucose-6-phosphate, and RGL and PTG levels and enhanced PP1 activity. This, combined with decreased glycogen phosphorylase activity, results in increased glycogen content in muscle in the fasted state when glucose transport is reduced.

Response of mouse liver glycogen cycle enzymes to endotoxin treatment

1976 ◽  
Vol 231 (4) ◽  
pp. 1285-1289 ◽  
Author(s):  
O Giger ◽  
RE McCallum
Keyword(s):  
Mouse Liver ◽  
Glycogen Phosphorylase ◽  
Glycogen Synthase ◽  
Lethal Dose ◽  
Active Form ◽  
Liver Glycogen ◽  
Phosphorylase Activity ◽  
Induced Changes ◽  
Glycogen Phosphorylase Activity ◽  
Glycogen Synthase Activity

The present study was undertaken to characterize endotoxin-induced changes in carbohydrate metabolism and more specifically, to determine the contribution of glycogenolysis to the loss of liver glycogen. Female ICR mice, fasted overnight, were injected with a median lethal dose (LD50, 9 mg/kg) of endotoxin extracted from Salmonella typhimurium strain SR-11. Glycogen synthase and glycogen phosphorylase activities were measured at 0.5 and 6 h after treatment. Endotoxin treatment did not alter total glycogen synthase activity, but the amount of enzyme present in the active form was significantly lower in endotoxic mice. There was no significant increase in glycogen phosphorylase activity in endotoxin-treated mice. Glycogen phosphorylase was activated to the same extent in control and endotoxic mice by decapitation or intravenous epinephrine (25 or 1 mug/kg). The results of this study indicate no significant increase in glycogen phosphorylase activity in endotoxic mice, contraindicating enhanced glycogenolysis as a mechanism for depletion of carbohydrate following endotoxin injection. Altered activation of glycogen synthase, however, may contribute to the loss of glycogen during endotoxemia.

scholarly journals Wine Yeast Strains Engineered for Glycogen Overproduction Display Enhanced Viability under Glucose Deprivation Conditions

2002 ◽  
Vol 68 (7) ◽  
pp. 3339-3344 ◽  
Author(s):  
R. Pérez-Torrado ◽  
J. V. Gimeno-Alcañiz ◽  
E. Matallana
Keyword(s):  
Glycogen Phosphorylase ◽  
Glycogen Synthase ◽  
Glucose Deprivation ◽  
Wine Yeast ◽  
Glycogen Metabolism ◽  
Growth Conditions ◽  
Phosphorylase Activity ◽  
Industrial Use ◽  
Glycogen Phosphorylase Activity ◽  
Glycogen Synthase Activity

ABSTRACT We used metabolic engineering to produce wine yeasts with enhanced resistance to glucose deprivation conditions. Glycogen metabolism was genetically modified to overproduce glycogen by increasing the glycogen synthase activity and eliminating glycogen phosphorylase activity. All of the modified strains had a higher glycogen content at the stationary phase, but accumulation was still regulated during growth. Strains lacking GPH1, which encodes glycogen phosphorylase, are unable to mobilize glycogen. Enhanced viability under glucose deprivation conditions occurs when glycogen accumulates in the strain that overexpresses GSY2, which encodes glycogen synthase and maintains normal glycogen phosphorylase activity. This enhanced viability is observed under laboratory growth conditions and under vinification conditions in synthetic and natural musts. Wines obtained from this modified strain and from the parental wild-type strain don't differ significantly in the analyzed enological parameters. The engineered strain might better resist some stages of nutrient depletion during industrial use.

Cell specific events occurring during development

Development ◽  
1976 ◽  
Vol 35 (2) ◽  
pp. 335-343
Author(s):  
Charles L. Rutherford
Keyword(s):  
Inorganic Phosphate ◽  
Glycogen Phosphorylase ◽  
Glycogen Content ◽  
Cell Types ◽  
Specific Cell ◽  
Phosphorylase Activity ◽  
A Cell ◽  
Specific Degradation ◽  
Glycogen Phosphorylase Activity ◽  
Spore Cell

Ultra-microfluorometric techniques were adapted to follow the time sequence of glycogen degradation during the differentiation of two cell types in Dictyostelium discoideum. Glycogen content, glycogen phosphorylase activity, and inorganic phosphate accumulation were localized in specific cell types during stalk and spore development. Glycogen levels in pre-stalk cells remained constant during the pseudoplasmodium and early culmination stages of development. However, as pre-stalk cells migrated into the position of stalk formation, a cell specific degradation of glycogen was observed. The loss of glycogen from pre-stalk cells was accompanied by an increase in the activity of glycogen phosphorylase. This increase in activity from 0·04 to 0·14 moles/h/kg dry wt. occurred as pre-stalk cells entered the position of stalk formation. An inverse relationship was found between glycogen levels and inorganic phosphate (Pi) levels in the developing stalk. During the process of stalk construction, a gradient of Pi levels occurred from the apex to the base of the developing stalk. Glycogen degradation from pre-spore cells lagged behind that of pre-stalk cells. No change in pre-spore cell glycogen levels was observed until stalk construction was nearly completed. The results emphasize the importance of the physical position of a cell with respect to its composition and fate during development.

scholarly journals Glycogen Phosphorylase, the Product of the glgP Gene, Catalyzes Glycogen Breakdown by Removing Glucose Units from the Nonreducing Ends in Escherichia coli

2006 ◽  
Vol 188 (14) ◽  
pp. 5266-5272 ◽  
Author(s):  
Nora Alonso-Casajús ◽  
David Dauvillée ◽  
Alejandro Miguel Viale ◽  
Francisco José Muñoz ◽  
Edurne Baroja-Fernández ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Glycogen Phosphorylase ◽  
Glycogen Content ◽  
Biological Function ◽  
Wild Type ◽  
Phosphorylase Activity ◽  
Glycogen Accumulation ◽  
E Coli ◽  
Glycogen Phosphorylase Activity ◽  
Glycogen Breakdown

ABSTRACT To understand the biological function of bacterial glycogen phosphorylase (GlgP), we have produced and characterized Escherichia coli cells with null or altered glgP expression. glgP deletion mutants (ΔglgP) totally lacked glycogen phosphorylase activity, indicating that all the enzymatic activity is dependent upon the glgP product. Moderate increases of glycogen phosphorylase activity were accompanied by marked reductions of the intracellular glycogen levels in cells cultured in the presence of glucose. In turn, both glycogen content and rates of glycogen accumulation in ΔglgP cells were severalfold higher than those of wild-type cells. These defects correlated with the presence of longer external chains in the polysaccharide accumulated by ΔglgP cells. The overall results thus show that GlgP catalyzes glycogen breakdown and affects glycogen structure by removing glucose units from the polysaccharide outer chains in E. coli.

scholarly journals Overexpression of Glutamine:Fructose-6-Phosphate Amidotransferase in Rat-1 Fibroblasts Enhances Glucose-Mediated Glycogen Accumulation via Suppression of Glycogen Phosphorylase Activity*

Endocrinology ◽  
2000 ◽  
Vol 141 (6) ◽  
pp. 1962-1970 ◽  
Author(s):  
Errol D. Crook ◽  
Gregory Crenshaw ◽  
Geddati Veerababu ◽  
Lalit P. Singh
Keyword(s):  
Glycogen Phosphorylase ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Dependent Manner ◽  
Down Regulation ◽  
Glycogen Accumulation ◽  
Hexosamine Biosynthesis ◽  
Important Regulator ◽  
Glycogen Phosphorylase Activity ◽  
Dose Dependent

Abstract The hexosamine biosynthesis pathway (HBP) mediates many of the adverse effects of excess glucose. We have shown previously that glucose down-regulates basal and insulin-stimulated glycogen synthase (GS) activity. Overexpression of the rate-limiting enzyme in the HBP, glutamine:fructose-6-phosphate amidotransferase (GFA), mimics these effects of high glucose and renders the cells more sensitive to glucose. Here we examine the role of the HBP in regulating cellular glycogen content. Glycogen content and glycogen phosphorylase (GP) activity were determined in Rat-1 fibroblasts that overexpress GFA. In both GFA and controls there was a dose-dependent increase in glycogen content (∼8-fold) in cells cultured in increasing glucose concentrations (1–20 mm). There was a shift to the left in the glucose dose-response curve for glycogen content in GFA cells (ED50 for glycogen content = 5.80 ± 1.05 vs. 8.84 ± 0.87 mm glucose, GFA vs. control). Inhibition of GFA reduced glycogen content by 28.4% in controls cultured in 20 mm glucose. In a dose-dependent manner, glucose resulted in a more than 35% decrease in GP activity in controls. GP activity in GFA cells was suppressed compared with that in controls, and there was no glucose-induced down-regulation of GP activity. Glucosamine and uridine mimicked the effects of glucose on glycogen content and GP activity. However, chronic overexpression of GFA is a unique model of hexosamine excess, as culturing control cells in low dose glucosamine (0.1–0.25 mm) did not suppress GP activity and did not eliminate the glucose-mediated down-regulation of GP activity. We conclude that increased flux through the HBP results in enhanced glycogen accumulation due to suppression of GP activity. These results demonstrate that the HBP is an important regulator of cellular glucose metabolism and supports its role as a cellular glucose/satiety sensor.

Decreased insulin action on muscle glucose transport after eccentric contractions in rats

1996 ◽  
Vol 81 (5) ◽  
pp. 1924-1928 ◽  
Author(s):  
Sven Asp ◽  
Erik A. Richter
Keyword(s):  
Glucose Transport ◽  
Insulin Action ◽  
Glucose Transporter ◽  
Glycogen Synthase ◽  
Eccentric Contractions ◽  
Gastrocnemius Muscles ◽  
Muscle Glucose Transport ◽  
And Control ◽  
Glycogen Synthase Activity ◽  
Calf Muscles

Asp, Sven, and Erik A. Richter. Decreased insulin action on muscle glucose transport after eccentric contractions in rats. J. Appl. Physiol. 81(5): 1924–1928, 1996.—We have recently shown that eccentric contractions (Ecc) of rat calf muscles cause muscle damage and decreased glycogen and glucose transporter GLUT-4 protein content in the white (WG) and red gastrocnemius (RG) but not in the soleus (S) (S. Asp, S. Kristiansen, and E. A. Richter. J. Appl. Physiol. 79: 1338–1345, 1995). To study whether these changes affect insulin action, hindlimbs were perfused at three different insulin concentrations (0, 200, and 20,000 μU/ml) 2 days after one-legged eccentric contractions of the calf muscles. Compared with control, basal glucose transport was slightly higher ( P < 0.05) in Ecc-WG and -RG, whereas it was lower ( P < 0.05) at both submaximal and maximal insulin concentrations in the Ecc-WG and at maximal concentrations in the Ecc-RG. In the Ecc-S, the glucose transport was unchanged in hindquarters perfused in the absence or presence of a submaximal stimulating concentration of insulin, whereas it was slightly ( P < 0.05) higher during maximal insulin stimulation compared with control S. At the end of perfusion the glycogen concentrations were lower in both Ecc-gastrocnemius muscles compared with control muscles at all insulin concentrations. Fractional velocity of glycogen synthase increased similarly with increasing insulin concentrations in Ecc- and control WG and RG. We conclude that insulin action on glucose transport but not glycogen synthase activity is impaired in perfused muscle exposed to prior eccentric contractions.

Glycogen content has no effect on skeletal muscle glycogenolysis during short-term tetanic stimulation

1990 ◽  
Vol 68 (5) ◽  
pp. 1883-1888 ◽  
Author(s):  
L. L. Spriet ◽  
L. Berardinucci ◽  
D. R. Marsh ◽  
C. B. Campbell ◽  
T. E. Graham
Keyword(s):  
Skeletal Muscle ◽  
Glycogen Phosphorylase ◽  
Glycogen Content ◽  
Tetanic Stimulation ◽  
Phosphorylase Activity ◽  
Short Term ◽  
Glycogen Phosphorylase Activity ◽  
Anaerobic Environment

The effect of skeletal muscle glycogen content on in situ glycogenolysis during short-term tetanic electrical stimulation was examined. Rats were randomly assigned to one of three conditions: normal (N, stimulated only), supercompensated (S, stimulated 21 h after a 3-h swim), and fasted (F, stimulated after a 20-h fast). Before stimulation, glycogen contents in the white (WG) and red gastrocnemius (RG) and soleus (SOL) muscles were increased by 13-25% in S and decreased by 15-27% in F compared with N. Hindlimb blood flow was occluded 60 s before stimulation to produce a predominantly anaerobic environment. Muscles were stimulated with trains of supramaximal impulses (100 ms at 80 Hz) at a rate of 1 Hz for 60 s. Muscle glycogenolysis was measured from the decrease in glycogen content and estimated from the accumulation of glycolytic intermediates in the closed system. The resting glycogen content had no effect on measured or estimated glycogenolysis in all muscles studied. Average glycogenolysis in the WG, RG, and SOL muscles was 98.4 +/- 4.3, 60.9 +/- 4.0, and 11.2 +/- 3.6 mumol glucosyl U/g dry muscle, respectively. Hindlimb tension production was similar across conditions. The results suggest that in vivo glycogen phosphorylase activity in skeletal muscle is not regulated by the content of its substrate glycogen (range 80-165 mumol/g) during short-term tetanic stimulation in an anaerobic environment.

Regulation of muscle glycogen phosphorylase activity following short-term endurance training

1996 ◽  
Vol 270 (2) ◽  
pp. E328-E335 ◽  
Author(s):  
A. Chesley ◽  
G. J. Heigenhauser ◽  
L. L. Spriet
Keyword(s):  
Endurance Training ◽  
Muscle Glycogen ◽  
Glycogen Phosphorylase ◽  
Citrate Synthase ◽  
Phosphorylase Activity ◽  
Short Term ◽  
Mitochondrial Potential ◽  
Before And After ◽  
Glycogen Phosphorylase Activity ◽  
Muscle Biopsies

The purpose of this study was to examine the regulation (hormonal, substrate, and allosteric) of muscle glycogen phosphorylase (Phos) activity and glycogenolysis after short-term endurance training. Eight untrained males completed 6 days of cycle exercise (2 h/day) at 65% of maximal O2 uptake (Vo2max). Before and after training subjects cycled for 15 min at 80% of Vo2max, and muscle biopsies and blood samples were obtained at 0 and 30 s, 7.5 and 15 min, and 0, 5, 10, and 15 min of exercise. Vo2max was unchanged with training but citrate synthase (CS) activity increased by 20%. Muscle glycogenolysis was reduced by 42% during the 15-min exercise challenge following training (198.8 +/- 36.9 vs. 115.4 +/- 25.1 mmol/kg dry muscle), and plasma epinephrine was blunted at 15 min of exercise. The Phos a mole fraction was unaffected by training. Muscle phosphocreatine utilization and free Pi and AMP accumulations were reduced with training at 7.5 and 15 min of exercise. It is concluded that posttransformational control of Phos, exerted by reductions in substrate (free Pi) and allosteric modulator (free AMP) contents, is responsible for a blunted muscle glycogenolysis after 6 days of endurance training. The increase in CS activity suggests that the reduction of muscle glycogenolysis was due in part to an enhanced mitochondrial potential.

Regulation of glycolytic enzymes during anoxia in the turtle Pseudemys scripta

1989 ◽  
Vol 257 (2) ◽  
pp. R278-R283 ◽  
Author(s):  
S. P. Brooks ◽  
K. B. Storey
Keyword(s):  
Heart Muscle ◽  
Glycogen Phosphorylase ◽  
White Muscle ◽  
Fold Increase ◽  
Glycolytic Enzymes ◽  
Phosphorylase Activity ◽  
Enzyme Form ◽  
Red Muscle ◽  
Km Value ◽  
Glycogen Phosphorylase Activity

The glycolytic enzymes glycogen phosphorylase, phosphofructokinase (PFK), and pyruvate kinase (PK) were assessed in liver, heart, red muscle, and white muscle of aerobic and 5-h anoxic turtles (Pseudemys scripta) for changes in total activity and kinetic parameters. Anoxia induced statistically significant changes in these glycolytic enzymes in each of the four organs assayed. Compared with normoxic controls, anoxic liver showed a 3.3-fold increase in glycogen phosphorylase activity, a 1.5-fold increase in the PFK I50 value for citrate (concentration that inhibits initial activity by 50%), a 1.5-fold increase in the PFK Michaelis constant (Km) value for fructose 6-phosphate (P), and an increased maximal activity of PK. Anoxic heart muscle showed a 2.6-fold decrease in glycogen phosphorylase activity and, for PFK, a 1.7-fold decrease in the Km value for ATP and a twofold increase in the I50 value for citrate. In anoxic white muscle, PFK showed a fivefold lower Km value for fructose-6-P and a threefold lower activator concentration producing half-maximal activation (A50) for potassium phosphate than the aerobic enzyme form. Changes in anoxic white muscle PK included a twofold increase in the Km value for ADP and a 1.7-fold decrease in the I50 value for alanine. In red muscle, anoxia affected only the Km value for ATP, which was 50% higher than the value for the aerobic enzyme form. Fructose 2,6-diphosphate (P2) levels also decreased in heart muscle and increased in red and white muscle during anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

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