scholarly journals Glycogen synthesis in amphibian oocytes: evidence for an indirect pathway

1996 ◽  
Vol 315 (2) ◽  
pp. 455-460 ◽  
Author(s):  
Eduardo KESSI ◽  
Victoria GUIXÉ ◽  
Ana PRELLER ◽  
URETA URETA
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Dihydroxyacetone Phosphate ◽  
Indirect Pathway ◽  
Ic50 Value ◽  
Glucose Incorporation ◽  
Relationship Of ◽  
Hexose Phosphates

Glycogen is the main end product of glucose metabolism in amphibian oocytes. However, in the first few minutes after [U-14C]glucose microinjection most of the label is found in lactate. The burst of lactate production and the shape of the time curves for the labelling of glucose 6-phosphate, fructose 6-phosphate, glucose 1-phosphate and glycogen suggest a precursor–product relationship of lactate with respect to glycogen and its intermediates. Expansion (by microinjection) of the pool of glycolytic intermediates, such as dihydroxyacetone phosphate, glyceraldehyde 3-phosphate, 3-phosphoglycerate or phosphoenolpyruvate, results in a marked decrease in [U-14C]glucose incorporation into glycogen. After co-injection of doubly labelled glucoses, extensive detritiation (93%) of the glucosyl units of glycogen was observed with [2-3H,U-14C]glucose and partial detritiation with [3-3H,U-14C]glucose (34%) or [5-3H,U-14C]glucose (46%). After injection of [6-3H,U-14C]glucose, a small but significant and reproducible detritiation (13%) in glycogen was observed. Co-injection of [U-14C]glucose and 3-mercaptopicolinate resulted in marked inhibition of glycogen labelling. Half-maximal inhibition was observed at 0.58 mM 3-mercaptopicolinate, which agrees with the IC50 value (0.47 mM) for the inhibition in vitro of phosphoenolpyruvate carboxykinase activity. We conclude that in frog oocytes most of the glucosyl units are incorporated into glycogen by an indirect pathway involving breakdown of glucose to lactate, which is then converted into glycogen via gluconeogenesis. Both processes, glycolytic degradation of glucose to lactate and subsequent reconversion of the latter into hexose phosphates and glycogen, occur in the same cell.

ÉTUDE IN VITRO DU MÉTABOLISME DES HYDRATES DE CARBONE DANS LE LEUCOCYTE CIRCULANT DU COBAYE TRAITÉ À LA CORTISONE

1966 ◽  
Vol 51 (2) ◽  
pp. 193-202
Author(s):  
J. A. Antonioli ◽  
A. Vannotti
Keyword(s):  
Glucose Concentration ◽  
Intramuscular Injection ◽  
Acute Inflammation ◽  
Glycogen Content ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Glucose Consumption ◽  
List Type ◽  
Hydrates De Carbone

ABSTRACT 1. The metabolism of suspensions of circulating leucocytes has been studied after intramuscular injection of a dose of 50 mg/kg of a corticosteroid (cortisone acetate). The suspensions were incubated under aerobic conditions in the presence of a glucose concentration of 5.6 mm. Glucose consumption, lactate production, and variations in intracellular glycogen concentration were measured. After the administration of the corticosteroid, the anabolic processes of granulocyte metabolism were reversibly stimulated. Glucose consumption and lactate production increased 12 hours after the injection, but tended to normalize after 24 hours. The glycogen content of the granulocytes was enhanced, and glycogen synthesis during the course of the incubation was greatly stimulated. The action of the administered corticosteroid is more prolonged in females than in males. The injection of the corticosteroid caused metabolic modifications which resemble in their modulations and in their chronological development those found in circulating granulocytes of guinea-pigs suffering from sterile peritonitis. These results suggest, therefore, that, in the case of acute inflammation, the glucocorticosteroids may play an important role in the regulation of the metabolism of the blood leucocytes.

scholarly journals The effects of amylin on carbohydrate metabolism in skeletal muscle in vitro and in vivo

1990 ◽  
Vol 269 (1) ◽  
pp. 19-23 ◽  
Author(s):  
B Leighton ◽  
E Foot
Keyword(s):  
Glucose Utilization ◽  
Glycogen Synthesis ◽  
Intraperitoneal Administration ◽  
Muscle Preparation ◽  
Glucose Incorporation ◽  
Rat Soleus Muscle ◽  
Lactate Formation ◽  
Human Amylin

1. The effects of synthetic human amylin on basal and insulin-stimulated (100 and 1000 microunits/ml) rates of lactate formation, glucose oxidation and glycogen synthesis were measured in the isolated rat soleus muscle preparation incubated in the presence of various concentrations of glucose (5, 11 and 22 mM). 2. The rate of glucose utilization was increased by about 2-fold by increasing the glucose concentration from 5 to 22 mM. 3. Synthetic human amylin (10 nM) significantly inhibited (by 46-56%) glycogen synthesis, irrespective of the concentration of insulin or glucose present in the incubation medium. 4. Amylin (10 nM) did not affect insulin-stimulated rates of 2-deoxy[3H]glucose transport and phosphorylation. 5. Intraperitoneal administration of insulin (100 micrograms/kg) to rats in vivo stimulated the rate of [U-14C]glucose incorporation into glycogen in the diaphragm by about 80-fold. This rate was decreased (by 28%) by co-administration of amylin (66 micrograms/kg).

The Role of Insulin in the Regulation of PEPCK and Gluconeogenesis In Vivo

2009 ◽  
Vol 05 (01) ◽  
pp. 34 ◽  
Author(s):  
Christopher J Ramnanan ◽  
Dale S Edgerton ◽  
Alan D Cherrington ◽  
◽  
◽  
...  
Keyword(s):  
Messenger Rna ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Hepatic Glucose Production ◽  
Glycogen Synthesis ◽  
Glucose Production ◽  
Regulatory Control ◽  
Glycolytic Flux ◽  
Large Animals

The regulation of gluconeogenesis by insulin is complex and can involve insulin-mediated events in the liver, as well as in several non-hepatic tissues. Given the complexity of this regulation, it is no surprise that there is considerable debate regarding insulin’s ability to regulate the rate of gluconeogenic formation of glucose-6-phosphate (GNG flux to G6P)in vivo. Conventional ‘textbook’ teaching (based onin vitrostudies of rat liver) depicts that insulin can inhibit this pathway by suppressing the transcription of the enzyme phosphoenolpyruvate carboxykinase (PEPCK). PEPCK is widely considered to be a ‘rate-limiting’ enzyme with high control strength. Additionally, recent data in rodents have led to the conclusion that hyperinsulinemia in the brain can inhibit GNG flux to G6P, likely through transcriptional regulation of PEPCK. Recent data from the authors’ lab have confirmed that the molecular regulation of PEPCK messenger RNA (mRNA) and protein by insulin is conserved in large animals. Acute physiological hyperinsulinemia does not alter gluconeogenic formation of G6P, however, despite substantial reductions in PEPCK protein. This indicates that PEPCK has poor regulatory control over the pathwayin vivo. A physiological rise in insulin suppresses hepatic glucose production by inhibiting glycogenolysis and promoting glycogen synthesis, stimulating glycolytic flux, and redirecting gluconeogenically derived carbon to glycogen. This review documents the relevant ways in which insulin can regulate GNG flux to G6Pin vivo.

scholarly journals Cumulus expansion and glucose utilisation by bovine cumulus–oocyte complexes during in vitro maturation: the influence of glucosamine and follicle-stimulating hormone

Reproduction ◽  
2004 ◽  
Vol 128 (3) ◽  
pp. 313-319 ◽  
Author(s):  
Melanie L Sutton-McDowall ◽  
Robert B Gilchrist ◽  
Jeremy G Thompson
Keyword(s):  
Oocyte Maturation ◽  
In Vitro Maturation ◽  
Lactate Production ◽  
Glucose Consumption ◽  
Lactate Metabolism ◽  
Alternative Substrate ◽  
Glucose Incorporation ◽  
Developmental Capacity ◽  
Total Glucose

Glucose is an important metabolite and its presence during in vitro oocyte maturation (IVM) can have profound effects on the oocyte’s developmental capacity. We have demonstrated that glucose uptake increases over a 24 h IVM period, with most accounted for as l-lactate production. However, as maturation proceeds, l-lactate production remains constant, suggesting an alternative role for glucose metabolism. We hypothesised that in the latter stages of oocyte maturation, glucose not accounted for by l-lactate production is utilised for FSH-stimulated extracellular matrix (ECM) synthesis. To examine precursor utilisation for synthesis of ECM, bovine cumulus–oocyte complexes (COCs) were matured in ± FSH and/or glucosamine (an alternative substrate of matrix components). Measurements included COC diameters, glucose consumption and l-lactate production in spent media and [U-14C]glucose incorporation into ECM. FSH significantly stimulated both diameter and glucose consumption during 20–24 h maturation compared with unstimulated complexes, although co-incubation with glucosamine and FSH decreased total glucose consumption 1.7-fold compared with FSH alone (P < 0.05). Furthermore, there was a linear relationship between glucose and l-lactate metabolism in the presence of glucosamine, suggesting that the majority of glucose was being utilised for l-lactate production via glycolysis. In the presence of glucosamine, twofold less [U-14C]glucose was incorporated into matrix compared with COCs cultured without glucosamine. These results support the hypothesis that there is a link between glucose and glucosamine uptake in FSH-stimulated ECM synthesis. Furthermore, glucose has multiple fates within the COC during maturation and levels of utilisation are dependent on the composition of the maturation environment.

Effect of hepatic nerves on disposition of an intraduodenal glucose load

1993 ◽  
Vol 265 (3) ◽  
pp. E487-E496 ◽  
Author(s):  
M. C. Moore ◽  
G. I. Shulman ◽  
A. Giaccari ◽  
M. J. Pagliassotti ◽  
G. Cline ◽  
...  
Keyword(s):  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Glucose Infusion ◽  
Hepatic Glycogen ◽  
Indirect Pathway ◽  
Hepatic Glucose ◽  
Hepatic Glucose Uptake ◽  
Hepatic Nerves ◽  
Glycogen Synthase Activity

We examined the disposition of a continuous 4-h intraduodenal glucose infusion (8 mg.kg-1 x min-1, labeled with [1-13C]glucose and [3-3H]glucose) in nine conscious hepatic-denervated dogs. Cumulative net hepatic uptakes (in grams of glucose equivalents) were 13.7 +/- 2.5 glucose, 3.1 +/- 0.6 gluconeogenic amino acids, and 0.8 +/- 0.1 glycerol. Net hepatic glycogen synthesis totalled 11.0 +/- 0.9 g, 55-62% via the direct pathway. All values were similar to those in hepatic-innervated dogs. Glycogen synthase activity and rate of glycogen synthesis were positively correlated (r2 = 0.913, P < 0.05). Variability in net hepatic glycogen synthesis and the mass of glycogen synthesized via the indirect pathway was reduced in hepatic-denervated dogs (P < 0.05). In conclusion, the glycemic response and rate of net glycogen synthesis during an intraduodenal glucose infusion was no different in hepatic-denervated and -innervated dogs. Net hepatic glucose uptake was sufficient to account for all net hepatic glycogen synthesis and lactate production, consistent with an intrahepatic source of gluconeogenic precursors for glycogen synthesis via the indirect pathway. Hepatic nerves appear responsible for much of the variability in net hepatic glycogen synthesis and in the mass of glycogen synthesized via the indirect pathway in normal dogs.

scholarly journals Sensitivity of the soleus muscle to insulin in resting and exercising rats with experimental hypo- and hyper-thyroidism

1989 ◽  
Vol 263 (1) ◽  
pp. 243-247 ◽  
Author(s):  
A Dubaniewicz ◽  
H Kaciuba-Usciłko ◽  
K Nazar ◽  
L Budohoski
Keyword(s):  
Skeletal Muscle ◽  
Glucose Tolerance ◽  
Soleus Muscle ◽  
Interactive Effect ◽  
Glycogen Synthesis ◽  
Subcutaneous Administration ◽  
Lactate Production ◽  
Glucose Injection ◽  
Lactate Formation

1. The effects of hypothyroidism (caused by surgical thyroidectomy followed by treatment for 1 month with propylthiouracil) and of hyperthyroidism [induced by subcutaneous administration of L-tri-iodothyronine (T3)] on glucose tolerance and skeletal-muscle sensitivity to insulin were examined in rats. Glucose tolerance was estimated during 2 h after subcutaneous glucose injection (1 g/kg body wt.). The sensitivity of the soleus muscle to insulin was studied in vitro in sedentary and acutely exercised animals. 2. Glucose tolerance was impaired in both hypothyroid and hyperthyroid rats in comparison with euthyroid controls. 3. In the soleus muscle, responsiveness of the rate of lactate formation to insulin was abolished in hypothyroid rats, whereas the sensitivity of the rate of glycogen synthesis to insulin was unchanged. In hyperthyroid animals, opposite changes were found, i.e. responsiveness of the rate of glycogen synthesis was inhibited and the sensitivity of the rate of lactate production did not differ from that in control sedentary rats. 4. A single bout of exercise for 30 min potentiated the stimulatory effect of insulin on lactate formation in hyperthyroid rats and on glycogen synthesis in hypothyroid animals. 5. The data suggest that thyroid hormones exert an interactive effect with insulin in skeletal muscle. This is likely to be at the post-receptor level, inhibiting the effect of insulin on glycogen synthesis and stimulating oxidative glucose utilization.

scholarly journals Comparison of some metabolic parameters in the perfused and the incubated rat diaphragm muscle with diaphragm muscle in vivo

1971 ◽  
Vol 125 (1) ◽  
pp. 93-96 ◽  
Author(s):  
K. A. Rookledge
Keyword(s):  
Oxidative Phosphorylation ◽  
Water Content ◽  
Lactate Production ◽  
Metabolic Parameters ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Free Glucose ◽  
Hexose Phosphates

1. A method is described for perfusing the rat diaphragm muscle. 2. The following parameters were compared in both perfused and non-perfused incubated preparations: water content, sorbitol space, rate of lactate production, and the concentrations of tissue glucose, pyruvate, lactate, hexose phosphate intermediates, ATP and AMP. No significant differences were found. 3. Significant differences, however, were found on comparison of the tissue kept in vitro with the tissue in vivo. Immediately after removal of the tissue from the animal, the concentrations of the hexose phosphates and ATP were found to be much higher than after incubation or perfusion, and the concentrations of free glucose and of AMP were much lower, possibly indicating that the capacity for oxidative phosphorylation of glucose is impaired in vitro because of hypoxia.

Hypoglycemic effect of isoleucine involves increased muscle glucose uptake and whole body glucose oxidation and decreased hepatic gluconeogenesis

2007 ◽  
Vol 292 (6) ◽  
pp. E1683-E1693 ◽  
Author(s):  
Masako Doi ◽  
Ippei Yamaoka ◽  
Mitsuo Nakayama ◽  
Kunio Sugahara ◽  
Fumiaki Yoshizawa
Keyword(s):  
Glucose Uptake ◽  
Glucose Oxidation ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glycogen Synthesis ◽  
Isolated Hepatocytes ◽  
Hypoglycemic Effect ◽  
Whole Body ◽  
Hepatic Glycogen ◽  
Mrna Levels

Isoleucine, a branched chain amino acid, plays an important role in the improvement of glucose metabolism as evidenced by the increase of insulin-independent glucose uptake in vitro. This study evaluated the effect of isoleucine on glucose uptake and oxidation in fasted rats and on gluconeogenesis in vivo and in vitro. Oral administration of isoleucine decreased the plasma glucose level by 20% and significantly increased muscle glucose uptake by 71% without significant elevation of the plasma insulin level compared with controls at 60 min after administration. Furthermore, expiratory excretion of 14CO2 from [U-14C]glucose in isoleucine-administered rats was increased by 19% compared with controls. Meanwhile, isoleucine decreased AMP levels in the liver but did not affect hepatic glycogen synthesis. Under insulin-free conditions, isoleucine significantly inhibited glucose production when alanine was used as a glucogenic substrate in isolated hepatocytes. This inhibition by isoleucine was also associated with a decline in mRNA levels for phosphoenolpyruvate carboxykinase and glucose-6-phosphatase (G6Pase) and a decreased activity of G6Pase in isolated hepatocytes. These findings suggest that a reduction of gluconeogenesis in liver, along with an increase of glucose uptake in the muscle, is also involved in the hypoglycemic effect of isoleucine. In conclusion, isoleucine administration stimulates both glucose uptake in the muscle and whole body glucose oxidation, in addition to depressing gluconeogenesis in the liver, thereby leading to the hypoglycemic effect in rats.

scholarly journals Acute effects of phorbol esters on the protein-synthetic rate and carbohydrate metabolism of normal and mdx mouse muscles

1991 ◽  
Vol 275 (2) ◽  
pp. 477-483 ◽  
Author(s):  
P A MacLennan ◽  
A McArdle ◽  
R H Edwards
Keyword(s):  
Glucose Uptake ◽  
Carbohydrate Metabolism ◽  
Phorbol Esters ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Kinetic Studies ◽  
Mdx Mouse ◽  
Mdx Mice

1. mdx mice do not express dystrophin, the product of the gene which is defective in Duchenne and Becker muscular dystrophy. We have previously shown that protein-synthetic rates (ks) are increased in mdx mouse muscles [MacLennan & Edwards (1990) Biochem. J. 268, 795-797]. 2. The tumour-promoting stereoisomer of phorbol 12,13-didecanoate (4 beta-PDD) acutely increased the ks of muscles from mdx and wild-type (C57BL/10) mice incubated in vitro in the absence of insulin. The effects of 4 beta-PDD are presumably mediated by activation of protein kinase C (PKC). 3. The muscle glycogen concentrations of mdx mice were higher than those of C57BL/10 mice. Studies performed in vivo and in vitro suggested that the effect might be at least partially due to increased rate of glycogen synthesis in mdx muscle. 4. 4 beta-PDD increased the glycogen-synthetic rates rates of C57BL/10, but not mdx, muscles incubated in vitro in the absence of insulin. 5. In muscles from both species incubated in the absence of insulin, treatment with 4 beta-PDD also induced increased rates of glucose uptake and lactate production. Kinetic studies of C57BL/10 and mdx muscles suggested that 4 beta-PDD raised the Vmax. of glucose uptake, but did not alter the Km for the process. 6. The possible role of PKC in controlling the protein and carbohydrate metabolism of normal and mdx mouse muscles is discussed.

α-Glycerophosphate metabolism in muscle under aerobic and hypoxic conditions

1964 ◽  
Vol 206 (3) ◽  
pp. 599-602 ◽  
Author(s):  
Ruth D. Peterson ◽  
David Gaudin ◽  
Rose Mary Bocek ◽  
Clarissa H. Beatty
Keyword(s):  
Skeletal Muscle ◽  
Lactate Concentration ◽  
Lactate Production ◽  
Fold Increase ◽  
Diaphragm Muscle ◽  
Dihydroxyacetone Phosphate ◽  
Hypoxic Conditions ◽  
Measurable Amount

A significant amount of α-glycerophosphate (α-GP) was present in voluntary skeletal muscle of rats when the hind limb was frozen in situ. Ischemia of this muscle in situ caused a 7-fold increase in α-GP concentration and a 12-fold increase in lactate concentration. In vitro experiments with diaphragm muscle from rats and adductor fiber groups from rats and monkeys also demonstrated that hypoxic conditions caused a 2.5- to 4-fold rise in α-GP levels. The α-GP concentration in hypoxic red muscle was higher than that in hypoxic white muscle from rats. Lactate diffused into the medium from all types of muscle preparations. However, under aerobic conditions no measurable amount of α-GP appeared in the medium surrounding the fibers and only a small amount diffused out of the diaphragm muscle. Even when incubation was carried out under hypoxic conditions little α-GP was present in fiber medium. Although the diaphragm released ten times as much α-GP as the fiber groups, this amount was small in relation to lactate production. These data indicate that under anaerobic and hypoxic conditions dihydroxyacetone phosphate can compete with pyruvate for the cytoplasmic NADH in diaphragm and voluntary skeletal muscle.

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