scholarly journals Stimulation of glycogen synthesis and lipogenesis by glutamine in isolated rat hepatocytes

1987 ◽  
Vol 248 (2) ◽  
pp. 429-437 ◽  
Author(s):  
A Lavoinne ◽  
A Baquet ◽  
L Hue
Keyword(s):  
Glycogen Phosphorylase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Rat Hepatocytes ◽  
Diabetic Rats ◽  
Purine Analogues ◽  
Isolated Rat Hepatocytes ◽  
Body Production ◽  
Stimulation Of

Glutamine stimulated glycogen synthesis and lactate production in hepatocytes from overnight-fasted normal and diabetic rats. The effect, which was half-maximal with about 3 mM-glutamine, depended on glucose concentration and was maximal below 10 mM-glucose. beta-2-Aminobicyclo[2.2.1.]heptane-2-carboxylic acid, an analogue of leucine, stimulated glutaminase flux, but inhibited the stimulation of glycogen synthesis by glutamine. Various purine analogues and inhibitors of purine synthesis were found to inhibit glycogen synthesis from glucose, but they did not abolish the stimulatory effect of glutamine on glycogen synthesis. The correlation between the rate of glycogen synthesis and synthase activity suggested that the stimulation of glycogen synthesis by glutamine depended solely on the activation of glycogen synthase. This activation of synthase was not due to a change in total synthase, nor was it caused by a faster inactivation of glycogen phosphorylase, as was the case after glucose. It could, however, result from a stimulation of synthase phosphatase, since, after the addition of 1 nM-glucagon or 10 nM-vasopressin, glutamine did not interfere with the inactivation of synthase, but did promote its subsequent re-activation. Glutamine was also found to inhibit ketone-body production and to stimulate lipogenesis.

Fatty acid and amino acid modulation of glucose cycling in isolated rat hepatocytes

2001 ◽  
Vol 358 (3) ◽  
pp. 665-671 ◽  
Author(s):  
Lori A. GUSTAFSON ◽  
Mies NEEFT ◽  
Dirk-Jan REIJNGOUD ◽  
Folkert KUIPERS ◽  
Hans P. SAUERWEIN ◽  
...  
Keyword(s):  
Amino Acids ◽  
Glycogen Phosphorylase ◽  
Glycogen Synthase ◽  
Lactate Production ◽  
Rat Hepatocytes ◽  
Glycolytic Flux ◽  
Isolated Rat Hepatocytes ◽  
Glycogen Accumulation ◽  
Glycogen Deposition ◽  
Intracellular Glucose

We studied the influence of glucose/glucose 6-phosphate cycling on glycogen deposition from glucose in fasted-rat hepatocytes using S4048 and CP320626, specific inhibitors of glucose-6-phosphate translocase and glycogen phosphorylase respectively. The effect of amino acids and oleate was also examined. The following observations were made: (1) with glucose alone, net glycogen production was low. Inhibition of glucose-6-phosphate translocase increased intracellular glucose 6-phosphate (3-fold), glycogen accumulation (5-fold) without change in active (dephosphorylated) glycogen synthase (GSa) activity, and lactate production (4-fold). With both glucose 6-phosphate translocase and glycogen phosphorylase inhibited, glycogen deposition increased 8-fold and approached reported in vivo rates of glycogen deposition during the fasted → fed transition. Addition of a physiological mixture of amino acids in the presence of glucose increased glycogen accumulation (4-fold) through activation of GS and inhibition of glucose-6-phosphatase flux. Addition of oleate with glucose present decreased glycolytic flux and increased the flux through glucose 6-phosphatase with no change in glycogen deposition. With glucose 6-phosphate translocase inhibited by S4048, oleate increased intracellular glucose 6-phosphate (3-fold) and net glycogen production (1.5-fold), without a major change in GSa activity. It is concluded that glucose cycling in hepatocytes prevents the net accumulation of glycogen from glucose. Amino acids activate GS and inhibit flux through glucose-6-phosphatase, while oleate inhibits glycolysis and stimulates glucose-6-phosphatase flux. Variation in glucose 6-phosphate does not always result in activity changes of GSa. Activation of glucose 6-phosphatase flux by fatty acids may contribute to the increased hepatic glucose production as seen in Type 2 diabetes.

scholarly journals Difference in glucose sensitivity of liver glycolysis and glycogen synthesis. Relationship between lactate production and fructose 2,6-bisphosphate concentration

1984 ◽  
Vol 224 (3) ◽  
pp. 779-786 ◽  
Author(s):  
L Hue ◽  
F Sobrino ◽  
L Bosca
Keyword(s):  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Cytosolic Proteins ◽  
Glucose Injection ◽  
Opposite Situation ◽  
Glucose Sensitivity ◽  
Fructose 1,6 Bisphosphate

Incubation of isolated rat hepatocytes from fasted rats with 0-6 mM-glucose caused an increase in [fructose 2,6-bisphosphate] (0.2 to about 5 nmol/g) without net lactate production. A release of 3H2O from [3-3H]glucose was, however, detectable, indicating that phosphofructokinase was active and that cycling occurred between fructose 6-phosphate and fructose 1,6-bisphosphate. A relationship between [fructose 2,6-bisphosphate] and lactate production was observed when hepatocytes were incubated with [glucose] greater than 6 mM. Incubation with glucose caused a dose-dependent increase in [hexose 6-phosphates]. The maximal capacity of liver cytosolic proteins to bind fructose 2,6-bisphosphate was 15 nmol/g, with affinity constants of 5 × 10(6) and 0.5 × 10(6) M-1. One can calculate that, at 5 microM, more than 90% of fructose 2,6-bisphosphate is bound to cytosolic proteins. In livers of non-anaesthetized fasted mice, the activation of glycogen synthase was more sensitive to glucose injection than was the increase in [fructose 2,6-bisphosphate], whereas the opposite situation was observed in livers of fed mice. Glucose injection caused no change in the activity of liver phosphofructokinase-2 and decreased the [hexose 6-phosphates] in livers of fed mice.

scholarly journals The mechanism by which adenosine decreases gluconeogenesis from lactate in isolated rat hepatocytes

1987 ◽  
Vol 246 (2) ◽  
pp. 449-454 ◽  
Author(s):  
A Lavoinne ◽  
H A Buc ◽  
S Claeyssens ◽  
M Pinosa ◽  
F Matray
Keyword(s):  
Ketone Body ◽  
Adenine Nucleotides ◽  
Rat Hepatocytes ◽  
Adenosine Kinase ◽  
Isolated Rat Hepatocytes ◽  
Adenosine Deaminase 2 ◽  
Body Production ◽  
Gluconeogenic Substrates ◽  
Isolated Rat ◽  
Stimulation Of

Incubation of hepatocytes from 24 h-starved rats in the presence of 0.5 mM-adenosine decreased gluconeogenesis from lactate, but not from alanine. The inhibition of gluconeogenesis was associated with a stimulation of ketone-body production and an inhibition of pyruvate oxidation. These metabolic changes were suppressed in the presence of iodotubercidin (an inhibitor of adenosine kinase), but were reinforced in the presence of deoxycoformycin (an inhibitor of adenosine deaminase); 2-chloroadenosine induced no change in gluconeogenesis from lactate. These data indicate that the inhibition of gluconeogenesis by adenosine probably results from its conversion into adenine nucleotides. In the presence of lactate or pyruvate, but not with alanine or asparagine, this conversion resulted in a decrease in the [ATP]/[ADP] ratio in both mitochondrial and cytosolic compartments. Adenosine decreased the Pi concentration with all gluconeogenic substrates.

scholarly journals Phosphatidylinositol metabolism in rat hepatocytes stimulated by vasopressin

1981 ◽  
Vol 194 (1) ◽  
pp. 155-165 ◽  
Author(s):  
C J Kirk ◽  
R H Michell ◽  
D A Hems
Keyword(s):  
Glycogen Phosphorylase ◽  
Equilibrium Distribution ◽  
Rat Hepatocytes ◽  
Subcellular Fractionation ◽  
Isolated Rat Hepatocytes ◽  
Phosphatidylinositol Metabolism ◽  
Maximal Activation ◽  
Vasopressin Receptors ◽  
Stimulation Of

In isolated rat hepatocytes, vasopressin evoked a large increase in the incorporation of [32P]Pi into phosphatidylinositol, accompanied by smaller increases in the incorporation of [1-14C]oleate and [U-14C]glycerol. Incorporation of these precursors into the other major phospholipids was unchanged during vasopressin treatment. Vasopressin also promoted phosphatidylinositol breakdown in hepatocytes. Half-maximum effects on phosphatidylinositol breakdown and on phosphatidylinositol labelling occurred at about 5 nM-vasopressin, a concentration at which approximately half of the hepatic vasopressin receptors are occupied but which is much greater than is needed to produce half-maximal activation of glycogen phosphorylase. Insulin did not change the incorporation of [32P]Pi into the phospholipids of hepatocytes and it had no effect on the response to vasopressin. Although the incorporation of [32P]Pi into hepatocyte lipids was decreased when cells were incubated in a Ca2+-free medium, vasopressin still provoked a substantial stimulation of phosphatidylinositol labelling under these conditions. Studies with the antagonist [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid),8-arginine]vasopressin indicated that the hepatic vasopressin receptors that control phosphatidylinositol metabolism are similar to those that mediate the vasopressor response in vivo. When prelabelled hepatocytes were stimulated for 5 min and then subjected to subcellular fractionation. The decrease in [3H]phosphatidylinositol content in each cell fraction with approximately in proportion to its original phosphatidylinositol content. This may be a consequence of phosphatidylinositol breakdown at a single site, followed by rapid phosphatidylinositol exchange between membranes leading to re-establishment of an equilibrium distribution.

scholarly journals Stimulatory effect of the intestinal peptide PHI on glycogenolysis and gluconeogenesis in isolated rat hepatocytes

1983 ◽  
Vol 214 (3) ◽  
pp. 999-1002 ◽  
Author(s):  
J E Felíu ◽  
J Marco
Keyword(s):  
Cyclic Amp ◽  
Pyruvate Kinase ◽  
Glycogen Phosphorylase ◽  
Rat Hepatocytes ◽  
Fold Increase ◽  
Isolated Rat Hepatocytes ◽  
Mediated Effects ◽  
Dose Dependent ◽  
Isolated Rat ◽  
Stimulation Of

The newly isolated peptide PHI provoked a dose-dependent stimulation of glycogenolysis and gluconeogenesis in isolated rat hepatocytes; at 1 microM-PHI, both processes were increased 1.6-fold as compared with basal values. These PHI-mediated effects were accompanied by the activation of glycogen phosphorylase and the inactivation of pyruvate kinase. PHI (1 microM) also caused a 2-fold increase in hepatocyte cyclic AMP.

scholarly journals Comparison of the effects of various amino acids on glycogen synthesis, lipogenesis and ketogenesis in isolated rat hepatocytes

1991 ◽  
Vol 273 (1) ◽  
pp. 57-62 ◽  
Author(s):  
A Baquet ◽  
A Lavoinne ◽  
L Hue
Keyword(s):  
Amino Acids ◽  
Time Course ◽  
Glycogen Synthesis ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Aminoisobutyric Acid ◽  
Malonyl Coa ◽  
Lag Period ◽  
Isolated Rat ◽  
Stimulation Of

Several amino acids were found to stimulate glycogen synthesis and lipogenesis, and to inhibit ketogenesis in isolated rat hepatocytes. When hepatocytes were incubated in the presence of 20 mM-glucose, the amino acids could be classified in decreasing order of efficiency as follows: glutamine and proline, alanine, aminoisobutyric acid, asparagine and histidine for stimulation of glycogen synthesis; glutamine, proline and alanine for stimulation of lipogenesis; proline and glutamine for inhibition of ketogenesis. The study of the time course revealed that the rates were not linear and were preceded by a lag period. In all conditions studied, glutamine and proline were found to have similar quantitative effects on glycogen synthesis and lipid metabolism. However, their effects differ qualitatively. Indeed, the effects of proline on glycogen synthesis, lipogenesis and glutamate and aspartate content were faster. Moreover, proline increased the hydroxybutyrate/acetoacetate ratio, whereas glutamine did not change it. Incubation of hepatocytes with aminoisobutyric acid or under hypo-osmotic conditions, which increased cell volume and mimicked the amino acid-induced stimulation of glycogen synthesis, had little effect on lipogenesis. In hepatocytes incubated without glucose, ketogenesis was inhibited, in decreasing order of efficiency, by alanine, asparagine, glutamine and proline. Under these conditions, glutamine increased, alanine decreased and asparagine did not affect the concentration of malonyl-CoA. This indicates that the latter cannot be responsible for the inhibition of ketogenesis by alanine and asparagine.

scholarly journals Nitric oxide inhibits glycogen synthesis in isolated rat hepatocytes

1998 ◽  
Vol 330 (2) ◽  
pp. 1045-1049 ◽  
Author(s):  
Fleur SPRANGERS ◽  
P. Hans SAUERWEIN ◽  
A. Johannes ROMIJN ◽  
M. George van WOERKOM ◽  
J. Alfred MEIJER
Keyword(s):  
Nitric Oxide ◽  
Glucose Metabolism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
No Donor ◽  
Isolated Rat Hepatocytes ◽  
Intracellular Glucose

There is increasing evidence for the existence of intrahepatic regulation of glucose metabolism by Kupffer cell products. Nitric oxide (NO) is known to inhibit gluconeogenic flux through pyruvate carboxylase and phosphoenolpyruvate carboxykinase. However, NO may also influence glucose metabolism at other levels. Using hepatocytes from fasted rats incubated with the NO-donor S-nitroso-N-acetylpenicillamine, we have now found that the synthesis of glycogen from glucose is even more sensitive to inhibition by NO than gluconeogenesis. Inhibition of glycogen production by NO was accompanied by a rise in intracellular glucose 6-phosphate and UDPglucose. Activity of glycogen synthase, as measured in extracts of hepatocytes after the cells had been exposed to NO, was decreased. Experiments with gel-filtered liver extracts revealed that inhibition of glycogen synthase was caused by an inhibitory effect of NO on the conversion of glycogen synthase b into glycogen synthase a.

scholarly journals Fructose-induced increase in intracellular free Mg2+ ion concentration in rat hepatocytes: relation with the enzymes of glycogen metabolism

1997 ◽  
Vol 326 (3) ◽  
pp. 823-827 ◽  
Author(s):  
Vinciane GAUSSIN ◽  
Philippe GAILLY ◽  
Jean-Marie GILLIS ◽  
Louis HUE
Keyword(s):  
Glycogen Phosphorylase ◽  
Time Course ◽  
Buffer Capacity ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Rat Hepatocytes ◽  
Glycogen Metabolism ◽  
Dose Dependence ◽  
Ion Concentration ◽  
Extracellular Medium

In rat hepatocytes subjected to a fructose load, ATP content decreased from 3.8 to 2.6 μmol/g of cells. Under these conditions, the intracellular free Mg2+ ion concentration, as measured with mag-fura 2, increased from 0.25 to 0.43 μmol/g of cells and 0.35 μmol of Mg2+ ions were released per g of cells in the extracellular medium. Therefore the increase in the intracellular free Mg2+ ion concentration was less than expected from the decrease in ATP, indicating that approx. 80% of the Mg2+ ions released from MgATP2- were buffered inside the cells. When this buffer capacity was challenged with an extra Mg2+ ion load by blocking the fructose-induced Mg2+ efflux, again approx. 80% of the extra Mg2+ ion load was buffered. The remaining 20% appearing as free Mg2+ ions in fructose-treated hepatocytes could act as second messenger for enzymes having a Km for Mg2+ in the millimolar range. Fructose activated glycogen synthase and glycogen phosphorylase, although both the time course and the dose-dependence of activation were different. This was reflected in a stimulation of glycogen synthesis with concentrations of fructose below 5 mM. Indeed, activation of glycogen synthase reached a maximum at 30 min of incubation and was observed with small (5 mM or less) concentrations of fructose, whereas the activation of glycogen phosphorylase was almost immediate (within 5 min) and maximal with large doses of fructose. The fructose-induced activation of glycogen phosphorylase, but not that of glycogen synthase, could be related to an increase in free Mg2+ ion concentration.

scholarly journals Epidermal growth factor mimics insulin effects in rat hepatocytes

1986 ◽  
Vol 239 (3) ◽  
pp. 523-530 ◽  
Author(s):  
F Bosch ◽  
B Bouscarel ◽  
J Slaton ◽  
P F Blackmore ◽  
J H Exton
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Cyclic Amp ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Rat Hepatocytes ◽  
Maximum Effect ◽  
Similar Time ◽  
Isolated Rat Hepatocytes ◽  
Epidermal Growth

Epidermal growth factor (EGF) mimicked the effect of insulin to activate glycogen synthase and stimulate glycogen synthesis in isolated rat hepatocytes. Both agents required glucose (greater than 5 mM) and had similar time courses of action. The maximum effect of EGF was approx. 70% of that of insulin, and the half-maximally effective concentrations were 9 nM and 4 nM respectively. Combinations of the two agents produced additive responses. EGF also resembled insulin in its ability to inhibit the effects of 0.1-1.0 nM-glucagon on cyclic AMP and glycogen phosphorylase in hepatocytes. The maximum effect of EGF was approx. 70% of that of insulin, and the half-maximally effective concentrations were approx. 5 nM and 0.5 nM respectively. EGF and insulin inhibited phosphorylase activation by exogenous cyclic AMP, and inhibited cyclic AMP accumulation induced by forskolin. They also inhibited phosphorylase activation provoked by phenylephrine, but not by vasopressin. EGF added alone rapidly activated phosphorylase and increased cytosolic [Ca2+], but the effects were no longer apparent at 5 min and were smaller than those of vasopressin. Insulin did not induce these changes. In hepatocytes previously incubated with myo-[3H]inositol, EGF did not significantly increase myo-inositol 1,4,5-trisphosphate. However, its ability to increase cytosolic [Ca2+] was blocked by neomycin, an inhibitor of phosphatidylinositol bisphosphate hydrolysis. It is concluded that some, but not all, of the effects of EGF in liver are strikingly similar to those exerted by insulin, suggesting that these agents may have some similar mechanisms of action in this tissue.

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