Failure of leptin to affect basal and insulin-stimulated glucose metabolism of rat skeletal muscle in vitro

In contrast to adipose tissue and heart, the in vitro sensitivity of skeletal muscle to insulin is enhanced by starvation. To determine the basis for this, insulin binding and its ability to stimulate glucose metabolism were examined in the incubated rat soleus. In solei from 50-g rats, starvation for 48 h enhanced insulin binding by 50-100% at concentrations of 100 ng/ml or less. Starvation also resulted in higher basal and insulin-stimulated rates of glycogen synthesis, glycolysis, and glucose uptake. The enhanced effect of insulin only occurred at concentrations less than 50-75 ng/ml, in keeping with the increased binding of insulin in this concentration range. On the other hand, under conditions in which binding at equilibrium was the same, glucose uptake was still higher in the starved group, suggesting that some postreceptor event may have been more sensitive to insulin. These studies confirm that the in vitro sensitivity of rat skeletal muscle to insulin is enhanced by 48 h of starvation. They suggest that this is due at least partially to an increase in insulin binding at physiological concentrations.

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In vitro studies on the effect of glucocorticoids on the metabolism of perfused rat skeletal muscle

Acta Endocrinologica ◽

10.1530/acta.0.107s110-a ◽

1984 ◽

Vol 104 (4_Supplb) ◽

pp. S110-S111

Author(s):

P. SCHADEWALDT ◽

H. MEYER

Keyword(s):

Skeletal Muscle ◽

In Vitro Studies ◽

Rat Skeletal Muscle

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Proton leak induced by reactive oxygen species produced during in vitro anoxia/reoxygenation in rat skeletal muscle mitochondria

Journal of Bioenergetics and Biomembranes ◽

10.1007/s10863-006-9002-9 ◽

2006 ◽

Vol 38 (1) ◽

pp. 23-32 ◽

Cited By ~ 20

Author(s):

Rachel Navet ◽

Ange Mouithys-Mickalad ◽

Pierre Douette ◽

Claudine M. Sluse-Goffart ◽

Wieslawa Jarmuszkiewicz ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Skeletal Muscle ◽

Reactive Oxygen ◽

Proton Leak ◽

Oxygen Species ◽

Rat Skeletal Muscle ◽

Muscle Mitochondria ◽

Skeletal Muscle Mitochondria

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Reversible ATP-induced inactivation of branched-chain 2-oxo acid dehydrogenase

Biochemical Journal ◽

10.1042/bj1920155 ◽

1980 ◽

Vol 192 (1) ◽

pp. 155-163 ◽

Cited By ~ 45

Author(s):

R Odessey

Keyword(s):

Skeletal Muscle ◽

Liver Mitochondria ◽

Initial Activity ◽

Rat Skeletal Muscle ◽

Kidney Mitochondria ◽

Physiological Conditions ◽

Acid Dehydrogenase ◽

Skeletal Muscle Mitochondria ◽

Branched Chain

The branched chain 2-oxo acid dehydrogenase from rat skeletal muscle, heart, kidney and liver mitochondria can undergo a reversible activation-inactivation cycle in vitro. Similar results were obtained with the enzyme from kidney mitochondria of pig and cow. The dehydrogenase is markedly inhibited by ATP and the inhibition is not reversed by removing the nucleotide. The non-metabolizable ATP analogue adenosine 5′-[beta gamma-imido] triphosphate can block the effect of ATP when added with the nucleotide, but has no effect by itself, nor can it reverse the inhibition in mitochondria preincubated with ATP. These findings suggest that the branched chain 2-oxo acid dehydrogenase undergoes a stable modification that requires the splitting of the ATP gamma-phosphate group. In skeletal muscle mitochondria the rate of inhibition by ATP is decreased by oxo acid substrates and enhanced by NADH. The dehydrogenase can be reactivated 10-20 fold by incubation at pH 7.8 in a buffer containing Mg2+ and cofactors. Reactivation is blocked by NaF (25 mM). The initial activity of dehydrogenase extracted from various tissues of fed rats varies considerably. Activity is near maximal in kidney and liver whereas the dehydrogenase in heart and skeletal muscle is almost completely inactivated. These studies emphasize that comparisons of branched chain 2-oxo acid dehydrogenase activity under various physiological conditions or in different tissues must take into account its state of activation. Thus the possibility exists that the branched chain 2-oxo acid dehydrogenase may be physiologically regulated via a covalent mechanism.

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Properties of 5′-deiodinase of 3,3′,5′-triiodothyronine in rat skeletal muscle

Acta Endocrinologica ◽

10.1530/acta.0.1200069 ◽

1989 ◽

Vol 120 (1) ◽

pp. 69-74 ◽

Cited By ~ 4

Author(s):

Fujiko Tsukahara ◽

Teruko Nomoto ◽

Michiko Maeda

Keyword(s):

Skeletal Muscle ◽

Drinking Water ◽

Incubation Medium ◽

Marked Reduction ◽

Daily Administration ◽

Type I ◽

Rat Skeletal Muscle ◽

Thyroid Status ◽

Altered Thyroid

Abstract. To characterize rT3 5′-deiodinase (5′D) in rat skeletal muscle, the effects of altered thyroid status and PTU on rT3 5′D were studied. rT3 5′D activity was measured by incubating homogenates of rat skeletal muscle with [125]rT3, iodine labelled in the outer ring, in the presence of 20 mmol/l DL-dithiothreitol. This activity was observed to increase significantly 24 h after a single sc injection of T3 (75 μg/kg). The increase following the daily administration of this drug (15 or 75 μg/kg) for 3 and 14 days was dependent on the dose and number of previous days of injection. A significant decrease in activity was observed 2 weeks after thyroidectomy. The addition of 0.1 mmol/l 6-n-propyl-2-thiouracil (PTU) to the incubation medium in vitro caused a marked reduction in the activity in homogenates of skeletal muscle from hypothyroid, euthyroid and hyperthyroid rats. PTU, present at 0.05% in the drinking water for 2 weeks virtually abolished it. The properties of rT3 5′D in rat skeletal muscle thus appear to be essentially the same as those of type I enzyme with respect to response toward altered thyroid status and PTU.

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Characterization of β-adrenoceptors on rat skeletal muscle cells grown in vitro

Biochemical Pharmacology ◽

10.1016/0006-2952(90)90491-3 ◽

1990 ◽

Vol 40 (5) ◽

pp. 1043-1048 ◽

Cited By ~ 11

Author(s):

Marie-Helene Disatnik ◽

Sanford R. Sampson ◽

Asher Shainberg

Keyword(s):

Skeletal Muscle ◽

Muscle Cells ◽

Skeletal Muscle Cells ◽

Rat Skeletal Muscle

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AMP-activated protein kinase activity and glucose uptake in rat skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2001.280.5.e677 ◽

2001 ◽

Vol 280 (5) ◽

pp. E677-E684 ◽

Cited By ~ 152

Author(s):

Nicolas Musi ◽

Tatsuya Hayashi ◽

Nobuharu Fujii ◽

Michael F. Hirshman ◽

Lee A. Witters ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Kinase ◽

Glucose Uptake ◽

Muscle Contractions ◽

Treadmill Running ◽

Dependent Manner ◽

Rat Skeletal Muscle ◽

Amp Activated Protein Kinase ◽

Dose Dependent

The AMP-activated protein kinase (AMPK) has been hypothesized to mediate contraction and 5-aminoimidazole-4-carboxamide 1-β-d-ribonucleoside (AICAR)-induced increases in glucose uptake in skeletal muscle. The purpose of the current study was to determine whether treadmill exercise and isolated muscle contractions in rat skeletal muscle increase the activity of the AMPKα1 and AMPKα2 catalytic subunits in a dose-dependent manner and to evaluate the effects of the putative AMPK inhibitors adenine 9-β-d-arabinofuranoside (ara-A), 8-bromo-AMP, and iodotubercidin on AMPK activity and 3- O-methyl-d-glucose (3-MG) uptake. There were dose-dependent increases in AMPKα2 activity and 3-MG uptake in rat epitrochlearis muscles with treadmill running exercise but no effect of exercise on AMPKα1 activity. Tetanic contractions of isolated epitrochlearis muscles in vitro significantly increased the activity of both AMPK isoforms in a dose-dependent manner and at a similar rate compared with increases in 3-MG uptake. In isolated muscles, the putative AMPK inhibitors ara-A, 8-bromo-AMP, and iodotubercidin fully inhibited AICAR-stimulated AMPKα2 activity and 3-MG uptake but had little effect on AMPKα1 activity. In contrast, these compounds had absent or minimal effects on contraction-stimulated AMPKα1 and -α2 activity and 3-MG uptake. Although the AMPKα1 and -α2 isoforms are activated during tetanic muscle contractions in vitro, in fast-glycolytic fibers, the activation of AMPKα2-containing complexes may be more important in regulating exercise-mediated skeletal muscle metabolism in vivo. Development of new compounds will be required to study contraction regulation of AMPK by pharmacological inhibition.

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