Glutamine Metabolism in Skeletal Muscle of Glucocorticoid-Treated Rats

1990 ◽  
Vol 79 (2) ◽  
pp. 139-147 ◽  
Author(s):  
M. Salleh M. Ardawi ◽  
Yasir S. Jamal
Keyword(s):  
Skeletal Muscle ◽  
Exchange Rates ◽  
Skeletal Muscles ◽  
Plasma Concentrations ◽  
Maximal Activity ◽  
Glutamine Metabolism ◽  
Dexamethasone Treatment ◽  
Concentration Difference

1. The effect of dexamethasone (30 μg day−-1 100 g−-1 body weight) on the regulation of glutamine metabolism was studied in skeletal muscles of rats after 9 days of treatment. 2. Dexamethasone resulted in negative nitrogen balance, and produced increases in the plasma concentrations of alanine (23.4%) and insulin (158%) but a decrease in the plasma concentration of glutamine (28.7%). 3. Dexamethasone treatment increased the rate of glutamine production in muscle, skin and adipose tissue preparations, with muscle production accounting for over 90% of total glutamine produced by the hindlimb. 4. Blood flow and arteriovenous concentration difference measurements across the hindlimb showed an increase in the net exchange rates of glutamine (25.3%) and alanine (90.5%) in dexamethasone-treated rats compared with corresponding controls. 5. Dexamethasone treatment produced significant decreases in the concentrations of skeletal muscle glutamine (51.8%) and 2-oxoglutarate (50.8%). The concentrations of alanine (16.2%), pyruvate (45.9%), ammonia (43.3%) and inosine 5′-phosphate (141.8%) were increased. 6. The maximal activity of glutamine synthetase was increased (21–34%), but there was no change in that of glutaminase, in muscles of dexamethasone-treated rats. 7. It is concluded that glucocorticoid administration enhances the rates of release of both glutamine and alanine from skeletal muscle of rats (both in vitro and in vivo). This may be due to changes in efflux and/or increased intracellular formation of glutamine and alanine.

Glutamine metabolism in the lungs of glucocorticoid-treated rats

1991 ◽  
Vol 81 (1) ◽  
pp. 37-42 ◽  
Author(s):  
M. Salleh ◽  
M. Ardawi
Keyword(s):  
Exchange Rates ◽  
Marked Change ◽  
Maximal Activity ◽  
Glutamine Metabolism ◽  
Dexamethasone Treatment ◽  
Concentration Difference ◽  
Blood Concentrations ◽  
Glucocorticoid Administration

1. The effect of dexamethasone (30 μg day−1 100 g−1 body weight) on the regulation of glutamine metabolism was studied in the lungs of rats after 9 days of treatment. 2. Dexamethasone resulted in a negative nitrogen balance, and produced decreases in the blood concentrations of glutamine (32.3%) and glutamate (25.3%) but an increase in the blood concentration of alanine (33.9%). 3. Dexamethasone treatment increases the rates of production of glutamine and alanine by lung slices incubated in vitro. 4. Blood flow and arteriovenous concentration difference measurement across the lungs exhibited an increase in the net exchange rates of glutamine (131.6%) and alanine (113.2%) in dexamethasone-treated rats compared with corresponding pair-fed controls. 5. Dexamethasone treatment produced significant decreases in the lung concentrations of glutamine (47.2%), glutamate (30.9%) and 2-oxoglutarate (57.3%). The concentrations of alanine (52.1%), ammonia (24.7%) and pyruvate (43.7%) were increased. 6. The maximal activity of glutamine synthetase was increased (21.5%), but there was no marked change in that of glutaminase, in the lungs of dexamethasone-treated rats. 7. It is concluded that glucocorticoid administration enhances the rates of production of glutamine and alanine from lungs of rats (both in vitro and in vivo). This may be due to changes in efflux and/or increased intracellular biosynthesis of glutamine and alanine.

Effect of glucocorticoid treatment on glucose and glutamine metabolism by the small intestine of the rat

1988 ◽  
Vol 75 (1) ◽  
pp. 93-100 ◽  
Author(s):  
M. Salleh M. Ardawi ◽  
May F. Majzoub ◽  
Eric A. Newsholme
Keyword(s):  
Small Intestine ◽  
Glucose Utilization ◽  
Citrate Synthase ◽  
Glutamine Metabolism ◽  
Dexamethasone Treatment ◽  
Glucocorticoid Treatment ◽  
Concentration Difference ◽  
Oxoglutarate Dehydrogenase

1. The effect of dexamethasone (30 μg day−1 100 g−1 body wt.) on the metabolism of glucose and glutamine was studied in the small intestine of rats after 9 days of treatment. 2. Dexamethasone treatment resulted in negative nitrogen balance (P < 0.001), and produced increases in the concentrations of plasma glucose (22%, P < 0.05), alanine (32%, P < 0.001) and insulin (127%, P < 0.001), but a decrease in the plasma concentration of glutamine (20%, P < 0.05). 3. Portal-drained visceral blood flow increased by approximately 22% (P < 0.001) in dexamethasone-treated rats, and was accompanied by a decrease in the arteriovenous concentration difference of glucose (43%, P < 0.001) and an increase in that of lactate (22%, P < 0.05), glutamine (35%, P < 0.01), glutamate (33%, P < 0.01) and alanine (21%, P < 0.05). 4. Enterocytes isolated from dexamethasone-treated rats showed decreased and increased rates of glucose and glutamine utilization, respectively. 5. The maximal activities of hexokinase, 6-phosphofructokinase, citrate synthase and oxoglutarate dehydrogenase were decreased (30–64%, P < 0.001) in intestinal mucosal scrapings of dexamethasone-treated rats, whereas the activity of glutaminase was increased (35%, P < 0.001). 6. It is concluded that glucocorticoid administration decreases the rate of glucose utilization but increases that of glutamine (both in vivo and in vitro) by the epithelial cells of the small intestine. This may be caused by changes in the maximal activities of key enzymes in the pathways of glucose and glutamine metabolism in these cells.

Expression of steroidogenic enzymes and synthesis of sex steroid hormones from DHEA in skeletal muscle of rats

2007 ◽  
Vol 292 (2) ◽  
pp. E577-E584 ◽  
Author(s):  
Katsuji Aizawa ◽  
Motoyuki Iemitsu ◽  
Seiji Maeda ◽  
Subrina Jesmin ◽  
Takeshi Otsuki ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Steroid Hormones ◽  
Skeletal Muscles ◽  
Muscle Cells ◽  
Sex Steroid Hormones ◽  
Sex Steroid ◽  
Dependent Manner ◽  
Steroidogenic Enzymes

The functional importance of sex steroid hormones (testosterone and estrogens), derived from extragonadal tissues, has recently gained significant appreciation. Circulating dehydroepiandrosterone (DHEA) is peripherally taken up and converted to testosterone by 3β-hydroxysteroid dehydrogenase (HSD) and 17β-HSD, and testosterone in turn is irreversibly converted to estrogens by aromatase cytochrome P-450 (P450arom). Although sex steroid hormones have been implicated in skeletal muscle regulation and adaptation, it is unclear whether skeletal muscles have a local steroidogenic enzymatic machinery capable of metabolizing circulating DHEA. Thus, here, we investigate whether the three key steroidogenic enzymes (3β-HSD, 17β-HSD, and P450arom) are present in the skeletal muscle and are capable of generating sex steroid hormones. Consistent with our hypothesis, the present study demonstrates mRNA and protein expression of these enzymes in the skeletal muscle cells of rats both in vivo and in culture (in vitro). Importantly, we also show an intracellular formation of testosterone and estradiol from DHEA or testosterone in cultured muscle cells in a dose-dependent manner. These findings are novel and important in that they provide the first evidence showing that skeletal muscles are capable of locally synthesizing sex steroid hormones from circulating DHEA or testosterone.

scholarly journals In Vivo Activation of STAT3 Signaling in Satellite Cells and Myofibers in Regenerating Rat Skeletal Muscles

2002 ◽  
Vol 50 (12) ◽  
pp. 1579-1589 ◽  
Author(s):  
Katsuya Kami ◽  
Emiko Senba
Keyword(s):  
Skeletal Muscle ◽  
Satellite Cells ◽  
Muscle Regeneration ◽  
Intracellular Signaling ◽  
Skeletal Muscles ◽  
Early Stage ◽  
Skeletal Muscle Regeneration ◽  
Stat3 Signaling

Although growth factors and cytokines play critical roles in skeletal muscle regeneration, intracellular signaling molecules that are activated by these factors in regenerating muscles have been not elucidated. Several lines of evidence suggest that leukemia inhibitory factor (LIF) is an important cytokine for the proliferation and survival of myoblasts in vitro and acceleration of skeletal muscle regeneration. To elucidate the role of LIF signaling in regenerative responses of skeletal muscles, we examined the spatial and temporal activation patterns of an LIF-associated signaling molecule, the signal transducer and activator transcription 3 (STAT3) proteins in regenerating rat skeletal muscles induced by crush injury. At the early stage of regeneration, activated STAT3 proteins were first detected in the nuclei of activated satellite cells and then continued to be activated in proliferating myoblasts expressing both PCNA and MyoD proteins. When muscle regeneration progressed, STAT3 signaling was no longer activated in differentiated myoblasts and myotubes. In addition, activation of STAT3 was also detected in myonuclei within intact sarcolemmas of surviving myofibers that did not show signs of necrosis. These findings suggest that activation of STAT3 signaling is an important molecular event that induces the successful regeneration of injured skeletal muscles.

The in vitro effect of corticosterone on insulin binding and glucose metabolism in mouse skeletal muscles

1985 ◽  
Vol 63 (9) ◽  
pp. 1133-1138 ◽  
Author(s):  
M. H. Tan ◽  
A. Bonen
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Extensor Digitorum Longus ◽  
Insulin Binding ◽  
In Vivo Model ◽  
In Vitro System ◽  
Vitro Effect ◽  
Contralateral Muscle

We studied the in vitro effect of corticosterone on insulin binding, uptake of 2-deoxy-D-glucose, glycolysis, and glycogenesis in the soleus and extensor digitorum longus (EDL) of Swiss–Webster mice. In each experiment, one muscle (soleus/EDL) was incubated with corticosterone (0.1, 1, 50, and 100 μg/mL) and the respective contralateral muscle was incubated without corticosterone, but at the same insulin and pH levels. Corticosterone did not affect insulin binding in both muscles. However, corticosterone decreased the uptake of 2-deoxy-D-glucose and the rate of glycolysis and glycogenesis in both muscles when the dose was pharmacologic (50 and 100 μg/mL), but not when it was physiologic (0.1 and 1 μg/mL). For glycolysis and glycogenesis, the suppression was greater in the EDL when compared with the soleus. This suppression was seen in both basal and insulin-stimulated conditions. In this in vitro system, where the experimental muscle is not exposed to prior hyperinsulinemia as in the in vivo model, corticosterone, at pharmacologic doses, affects postreceptor events without altering the insulin binding in the skeletal muscle.

Fish muscle glycogen phosphorylase

1968 ◽  
Vol 46 (5) ◽  
pp. 423-432 ◽  
Author(s):  
M. Yamamoto
Keyword(s):  
Skeletal Muscle ◽  
Glycogen Phosphorylase ◽  
Active Form ◽  
Maximal Activity ◽  
Fish Muscle ◽  
Salmo Gairdneri ◽  
Rabbit Muscle ◽  
Muscle Phosphorylase

Glycogen phosphorylase b was purified 70- to 90-fold from skeletal muscle of rainbow trout (Salmo gairdneri). The purified enzyme exhibited maximal activity near pH 6.8 at 37°. Of several 5′-nucleotides tested, only 5′-AMP caused stimulation of phosphorylase b. The Km value for glucose-1-phosphate was 10–15 mM, and for 5′-AMP, 0.2–0.4 mM. Glucose (25 mM) and ATP (5 mM) were both inhibitory, but glucose-6-phosphate (5 mM) had no effect. Inactive trout muscle phosphorylase was converted to the active form in vivo by subjecting a fish to physical exercise. The conversion of fish muscle phosphorylase b to a was also catalyzed in vitro with purified rabbit muscle phosphorylase b kinase in the presence of ATP and Mg++. Evidence is presented to indicate the presence of phosphorylase b kinase and phosphorylase phosphatase in trout skeletal muscle.

scholarly journals Glutamine metabolism in skeletal muscles from the broiler chick (Gallus domesticus) and the laboratory rat (Rattus norvegicus)

1991 ◽  
Vol 274 (3) ◽  
pp. 769-774 ◽  
Author(s):  
G Wu ◽  
J R Thompson ◽  
V E Baracos
Keyword(s):  
Skeletal Muscle ◽  
Rattus Norvegicus ◽  
Skeletal Muscles ◽  
Species Difference ◽  
Plasma Concentrations ◽  
Subcellular Location ◽  
Glutamine Metabolism ◽  
Oxidative Decarboxylation ◽  
Rat Skeletal Muscle ◽  
Glutaminase Activity

Oxidative decarboxylation of L-[1-14C]glutamine was studied in isolated chick and rat skeletal muscles incubated in the presence of glucose, insulin and plasma concentrations of amino acids. (1) The rate of oxidative decarboxylation of L-[1-14C]glutamine was high, and exceeded that of L-[1-14C]leucine in all muscles. (2) The rate of oxidative decarboxylation of L-[1-14C]glutamine increased with increasing intracellular concentrations of glutamine. (3) The activities of glutamine aminotransferases K and L were more than 10-fold greater in rat than in chick skeletal muscles. (4) Mitochondrial phosphate-activated glutaminase activity was approx. 10-fold greater in chick than in rat skeletal muscles and increased with increasing glutamine concentrations. (5) An inhibitor of glutaminase, 6-diazo-5-oxo-L-norleucine, inhibited the rate of glutamine decarboxylation in chick, but not in rat, skeletal muscle. These findings suggest that glutamine degradation in skeletal muscle may be substantial and may make an important contribution to the regulation of intramuscular glutamine concentrations. A species difference in the pathways and the subcellular location for the conversion of glutamine into 2-oxoglutarate in rat and chick skeletal muscles is implied by the relative activities of glutamine-degrading enzymes.

scholarly journals Physiological glucocorticoid levels regulate glutamine and insulin-mediated glucose metabolism in skeletal muscle of the rat. Studies with RU 486 (mifepristone)

1991 ◽  
Vol 274 (1) ◽  
pp. 187-192 ◽  
Author(s):  
B Leighton ◽  
M Parry-Billings ◽  
G Dimitriadis ◽  
J Bond ◽  
E A Newsholme ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Plasma Glucose ◽  
Dark Period ◽  
Feeding Activity ◽  
Glycogen Synthesis ◽  
Glutamine Metabolism ◽  
Ru 486

This study examined the effects of antagonism of the peak level of glucocorticoids in vivo, which occurs as rats enter the feeding/activity (dark) period on glucose and glutamine metabolism in incubated isolated rat soleus muscle preparations. Thus the rats were treated with the potent glucocorticoid antagonist RU 486 2 h before and 1 and 2 h into the dark period. Both the content of glutamine in skeletal muscle in vivo and plasma glucose and glutamine concentrations were elevated midway through the dark period, compared with the beginning of the period. RU 486 prevented the increases in plasma glucose and glutamine and caused a significant decrease in both the rate of release of glutamine in soleus muscle in vitro and the content of glutamine in gastrocnemius muscle. The sensitivity of soleus muscle to insulin in vitro is markedly decreased when isolated midway through the dark period (i.e. at 03:00 h) [Leighton, Kowalchuk, Challiss & Newsholme (1988) Am. J. Physiol. 255, E41-E45]. We now show that the concentrations of insulin required to stimulate lactate formation and glycogen synthesis half-maximally were 95 and 250 muunits/ml respectively, and treatment of rats with RU 486 decreased these values to 55 and 90 muunits of insulin/ml respectively. Thus antagonism of the action of the normal circadian rise in the level of glucocorticoids in rats reverses insulin insensitivity in soleus muscles in vitro.

scholarly journals Intra-arterial AICA-riboside administration induces NO-dependent vasodilation in vivo in human skeletal muscle

2009 ◽  
Vol 297 (3) ◽  
pp. E759-E766 ◽  
Author(s):  
Marlies Bosselaar ◽  
Hanneke Boon ◽  
Luc J. C. van Loon ◽  
Petra H. H. van den Broek ◽  
Paul Smits ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Plasma Concentrations ◽  
Metabolic Effects ◽  
Nucleoside Transporter ◽  
In Vitro Experiments

In animal models, administration of the adenosine analog AICA-riboside has shown beneficial effects on ischemia-reperfusion injury and glucose homeostasis. The vascular and/or metabolic effects of AICA-riboside administration in humans remain to be established. AICA-riboside was infused intra-arterially in four different dosages up to 8 mg·min−1·dl−1 in 24 healthy subjects. Forearm blood flow (FBF) and glucose uptake and plasma glucose, free fatty acid, and AICA-riboside concentrations were assessed. We also combined AICA-riboside infusion (2 mg·min−1·dl−1) with the intra-arterial administration of the adenosine receptor antagonist caffeine (90 μg·min−1·dl−1; n = 6) and with the endothelial NO synthase inhibitor l-NMMA (0.4 mg·min−1·dl−1; n = 6). Additional in vitro experiments were performed to explain our in vivo effects of AICA-riboside in humans. AICA-riboside increased FBF dose dependently from 2.0 ± 0.2 to 13.2 ± 1.9 ml·min−1·dl−1 maximally ( P < 0.05 for all dosages). The latter was not reduced by caffeine administration but was significantly attenuated by l-NMMA infusion. Despite high plasma AICA-riboside concentrations, forearm glucose uptake did not change. In vitro experiments showed rapid uptake of AICA-riboside by the equilibrative nucleoside transporter in erythrocytes and subsequent phosphorylation to AICA-ribotide. We conclude that AICA-riboside induces a potent vasodilator response in humans that is mediated by NO. Despite high local plasma concentrations, AICA-riboside does not increase skeletal muscle glucose uptake.

Factors Controlling Movement of Skeletal Muscles

Leonardo ◽  
2015 ◽  
Vol 48 (3) ◽  
pp. 270-271
Author(s):  
Miranda D. Grounds
Keyword(s):  
Skeletal Muscle ◽  
Extracellular Matrix ◽  
Cell Membrane ◽  
Skeletal Muscles ◽  
Muscle Cells ◽  
The Body ◽  
Skeletal Muscle Cells ◽  
3 Dimensional

The contraction of specialized skeletal muscle cells results in classic movements of bones and other parts of the body that are vital for life. There is exquisite control over the movement of diverse types of muscles. This paper indicates the way in which skeletal muscles (myofibres) are formed; then factors that contribute to generating the movement are outlined: these include the nerve, sarcomeres, cytoskeleton, cell membrane and the extracellular matrix. The factors controlling the movement of mature myofibres in 3-dimensional tissues in vivo are vastly more complex than for tissue cultured immature muscle cells in an artificial in vitro environment.

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