scholarly journals Carbohydrate ingestion does not alter skeletal muscle AMPK signaling during exercise in humans

2006 ◽  
Vol 291 (3) ◽  
pp. E566-E573 ◽  
Author(s):  
Robert S. Lee-Young ◽  
Matthew J. Palmer ◽  
Kelly C. Linden ◽  
Kieran LePlastrier ◽  
Benedict J. Canny ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasma Glucose ◽  
Plasma Epinephrine ◽  
Muscle Lactate ◽  
Carbohydrate Ingestion ◽  
Ampk Signaling ◽  
Glucose Levels ◽  
Exercise Induced ◽  
Exercise In Humans

There is evidence that increasing carbohydrate (CHO) availability during exercise by raising preexercise muscle glycogen levels attenuates the activation of AMPKα2 during exercise in humans. Similarly, increasing glucose levels decreases AMPKα2 activity in rat skeletal muscle in vitro. We examined the effect of CHO ingestion on skeletal muscle AMPK signaling during exercise in nine active male subjects who completed two 120-min bouts of cycling exercise at 65 ± 1% V̇o2 peak. In a randomized, counterbalanced order, subjects ingested either an 8% CHO solution or a placebo solution during exercise. Compared with the placebo trial, CHO ingestion significantly ( P < 0.05) increased plasma glucose levels and tracer-determined glucose disappearance. Exercise-induced increases in muscle-calculated free AMP (17.7- vs. 11.8-fold), muscle lactate (3.3- vs. 1.8-fold), and plasma epinephrine were reduced by CHO ingestion. However, the exercise-induced increases in skeletal muscle AMPKα2 activity, AMPKα2 Thr172 phosphorylation and acetyl-CoA Ser222 phosphorylation, were essentially identical in the two trials. These findings indicate that AMPK activation in skeletal muscle during exercise in humans is not sensitive to changes in plasma glucose levels in the normal range. Furthermore, the rise in plasma epinephrine levels in response to exercise was greatly suppressed by CHO ingestion without altering AMPK signaling, raising the possibility that epinephrine does not directly control AMPK activity during muscle contraction under these conditions in vivo.

Skeletal muscle pyruvate dehydrogenase activity during maximal exercise in humans

1995 ◽  
Vol 269 (3) ◽  
pp. E458-E468 ◽  
Author(s):  
C. T. Putman ◽  
N. L. Jones ◽  
L. C. Lands ◽  
T. M. Bragg ◽  
M. G. Hollidge-Horvat ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Pyruvate Dehydrogenase ◽  
Maximal Exercise ◽  
Vastus Lateralis ◽  
Active Form ◽  
Lactate Production ◽  
Glycolytic Flux ◽  
Muscle Lactate ◽  
Mitochondrial Oxidation ◽  
Exercise In Humans

The regulation of the active form of pyruvate dehydrogenase (PDHa) and related metabolic events were examined in human skeletal muscle during repeated bouts of maximum exercise. Seven subjects completed three consecutive 30-s bouts of maximum isokinetic cycling, separated by 4 min of recovery. Biopsies of the vastus lateralis were taken before and immediately after each bout. PDHa increased from 0.45 +/- 0.15 to 2.96 +/- 0.38, 1.10 +/- 0.11 to 2.91 +/- 0.11, and 1.28 +/- 0.18 to 2.82 +/- 0.32 mmol.min-1.kg wet wt-1 during bouts 1, 2, and 3, respectively. Glycolytic flux was 13-fold greater than PDHa in bouts 1 and 2 and 4-fold greater during bout 3. This discrepancy between the rate of pyruvate production and oxidation resulted in substantial lactate accumulation to 89.5 +/- 11.6 in bout 1, 130.8 +/- 13.8 in bout 2, and 106.6 +/- 10.1 mmol/kg dry wt in bout 3. These events coincided with an increase in the mitochondrial oxidation state, as reflected by a fall in mitochondrial NADH/NAD, indicating that muscle lactate production during exercise was not an O2-dependent process in our subjects. During exercise the primary factor regulating PDHa transformation was probably intracellular Ca2+. In contrast, the primary regulatory factors causing greater PDHa during recovery were lower ATP/ADP and NADH/NAD and increased concentrations of pyruvate and H+. Greater PDHa during recovery facilitated continued oxidation of the lactate load between exercise bouts.

Reversal of enhanced muscle glucose transport after exercise: roles of insulin and glucose

1990 ◽  
Vol 259 (5) ◽  
pp. E685-E691 ◽  
Author(s):  
E. A. Gulve ◽  
G. D. Cartee ◽  
J. R. Zierath ◽  
V. M. Corpus ◽  
J. O. Holloszy
Keyword(s):  
Skeletal Muscle ◽  
Insulin Sensitivity ◽  
Glucose Transport ◽  
Transport Process ◽  
Sugar Transport ◽  
Transport Activity ◽  
High Concentration ◽  
Exercise Induced ◽  
Muscle Glucose Transport

Exercise stimulates insulin-independent glucose transport in skeletal muscle and also increases the sensitivity of the glucose transport process in muscle to insulin. A previous study [D. A. Young, H. Wallberg-Henriksson, M. D. Sleeper, and J. O. Holloszy. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E331–E335, 1987] showed that the exercise-induced increase in glucose transport activity disappears rapidly when rat epitrochlearis muscles are incubated for 3 h in vitro in the absence of insulin and that 7.5 microU/ml insulin in the incubation medium apparently slowed the loss of enhanced sugar transport. We examined whether addition of insulin several hours after exercise increases glucose transport to the same extent as continuous insulin exposure. Addition of 7.5 microU/ml insulin 2.5 h after exercise (when glucose transport has returned to basal levels) increased sugar transport to the same level as that which resulted from continuous insulin exposure. This finding provides evidence for an increase in insulin sensitivity rather than a slowing of reversal of the exercise-induced increase in insulin-independent glucose transport activity. Glucose transport was enhanced only at submaximal, not at maximal, insulin concentrations. Exposure to a high concentration of glucose and a low insulin concentration reduced the exercise-induced increase in insulin-sensitive glucose transport. Incubation with a high concentration of 2-deoxy-D-glucose (2-DG) did not alter the increase in insulin sensitivity, even though a large amount of 2-DG entered the muscle and was phosphorylated.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Shikonin Increases Glucose Uptake in Skeletal Muscle Cells and Improves Plasma Glucose Levels in Diabetic Goto-Kakizaki Rats

PLoS ONE ◽  
2011 ◽  
Vol 6 (7) ◽  
pp. e22510 ◽  
Author(s):  
Anette I. Öberg ◽  
Kamal Yassin ◽  
Robert I. Csikasz ◽  
Nodi Dehvari ◽  
Irina G. Shabalina ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Plasma Glucose ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Glucose Levels

Effects of prolonged low frequency stimulation on skeletal muscle sarcoplasmic reticulum

1995 ◽  
Vol 73 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
E. R. Chin ◽  
H. J Green ◽  
F. Grange ◽  
J. Dossett-Mercer ◽  
P. J. O'Brien
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Atpase Activity ◽  
Metabolic Response ◽  
Contractile Activity ◽  
Creatine Phosphate ◽  
Energy Status ◽  
Muscle Lactate ◽  
Muscle Energy

The role of prolonged electrical stimulation on sarcoplasmic reticulum (SR) Ca2+sequestration measured in vitro and muscle energy status in fast white and red skeletal muscle was investigated. Fatigue was induced by 90 min intermittent 10-Hz stimulation of rat gastrocnemius muscle, which led to reductions (p < 0.05) in ATP, creatine phosphate, and glycogen of 16, 55, and 49%, respectively, compared with non-stimulated muscle. Stimulation also resulted in increases (p < 0.05) in muscle lactate, creatine, Pi, total ADP, total AMP, IMP, and inosine. Calculated free ADP (ADPf) and free AMP (AMPf) were elevated 3- and 15-fold, respectively. No differences were found in the metabolic response between tissues obtained from the white (WG) and red (RG) regions of the gastrocnemius. No significant reductions in SR Ca2+ATPase activity were observed in homogenate (HOM) or a crude SR fraction (CM) from WG or RG muscle following exercise. Maximum Ca2+uptake in HOM and CM preparations was similar in control (C) and stimulated (St) muscles. However, Ca2+uptake at 400 nM free Ca2+was significantly reduced in CM from RG (0.108 ± 0.04 to 0.076 ± 0.02 μmol∙mg−1protein∙min−1in RG–C and RG–St, respectively). Collectively, these data suggest that reductions in muscle energy status are dissociated from changes in SR Ca2+ATPase activity in vitro but are related to Ca2+uptake at physiological free [Ca2+] in fractionated SR from highly oxidative muscle. Dissociation of SR Ca2+ATPase activity from Ca2+uptake may reflect differences in the mechanisms evaluated by these techniques.Key words: sarcoplasmic reticulum, contractile activity, Ca2+sequestration, energy status, red and white gastrocnemius.

CARBOHYDRATE INGESTION ATTENUATES THE INCREASE IN PLASMA IL-6, BUT NOT SKELETAL MUSCLE IL-6 MRNA, DURING EXERCISE IN HUMANS

2001 ◽  
Vol 33 (5) ◽  
pp. S51
Author(s):  
R L. Starkie ◽  
M J. Arkinstall ◽  
I Koukoulas ◽  
J A. Hawley ◽  
M A. Febbraio
Keyword(s):  
Skeletal Muscle ◽  
Carbohydrate Ingestion ◽  
Exercise In Humans

In vivo effect of Trigonella foenum graecum on the expression of pyruvate kinase, phosphoenolpyruvate carboxykinase, and distribution of glucose transporter (GLUT4) in alloxan-diabetic rats

2006 ◽  
Vol 84 (6) ◽  
pp. 647-654 ◽  
Author(s):  
Sameer Mohammad ◽  
Asia Taha ◽  
Kamal Akhtar ◽  
R.N.K. Bamezai ◽  
Najma Zaheer Baquer
Keyword(s):  
Skeletal Muscle ◽  
Pyruvate Kinase ◽  
Plasma Glucose ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Transporter ◽  
Diabetic Rats ◽  
Altered Expression ◽  
Glucose Levels ◽  
Glucose Transporter Glut4

Plasma glucose levels are maintained by a precise balance between glucose production and its use. Liver pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK), 2 key enzymes of glycolysis and gluconeogenesis, respectively, play a crucial role in this glucose homeostasis along with skeletal muscle glucose transporter (GLUT4). In the diabetic state, this balance is disturbed owing to the absence of insulin, the principal factor controlling this regulation. In the present study, alloxan-diabetic animals having high glucose levels of more than 300 mmol/L have been taken and the administration of Trigonella seed powder (TSP) to the diabetic animals was assessed for its effect on the expression of PK and PEPCK in liver and GLUT4 distribution in skeletal muscle of alloxan-diabetic rats. TSP treatment to the diabetic animals resulted in a marked decrease in the plasma glucose levels. Trigonella treatment partially restored the altered expression of PK and PEPCK. TSP treatment also corrected the alterations in the distribution of GLUT4 in the skeletal muscle.

scholarly journals Catecholamines inhibit Ca2+-dependent proteolysis in rat skeletal muscle through β2-adrenoceptors and cAMP

2001 ◽  
Vol 281 (3) ◽  
pp. E449-E454 ◽  
Author(s):  
Luiz Carlos C. Navegantes ◽  
Neusa M. Z. Resano ◽  
Renato H. Migliorini ◽  
Ísis C. Kettelhut
Keyword(s):  
Skeletal Muscle ◽  
Extensor Digitorum Longus ◽  
Plasma Epinephrine ◽  
Dibutyryl Camp ◽  
Rat Skeletal Muscle ◽  
Adrenergic Agonist ◽  
Norepinephrine Content ◽  
Increased Activity ◽  
Dependent Pathway

Overall proteolysis and the activity of skeletal muscle proteolytic systems were investigated in rats 1, 2, or 4 days after adrenodemedullation. Adrenodemedullation reduced plasma epinephrine by 95% and norepinephrine by 35% but did not affect muscle norepinephrine content. In soleus and extensor digitorum longus (EDL) muscles, rates of overall proteolysis increased by 15–20% by 2 days after surgery but returned to normal levels after 4 days. The rise in rates of protein degradation was accompanied by an increased activity of Ca2+-dependent proteolysis in both muscles, with no significant change in the activity of lysosomal and ATP-dependent proteolytic systems. In vitro rates of Ca2+-dependent proteolysis in soleus and EDL from normal rats decreased by ∼35% in the presence of either 10−5 M clenbuterol, a β2-adrenergic agonist, or epinephrine or norepinephrine. In the presence of dibutyryl cAMP, proteolysis was reduced by 62% in soleus and 34% in EDL. The data suggest that catecholamines secreted by the adrenal medulla exert an inhibitory control of Ca2+-dependent proteolysis in rat skeletal muscle, mediated by β2-adrenoceptors, with the participation of a cAMP-dependent pathway.

Effects of Caffeine, Halothane, and 4-Chloro-m -cresol on Skeletal Muscle Lactate and Pyruvate in Malignant Hyperthermia–susceptible and Normal Swine as Assessed by Microdialysis

2006 ◽  
Vol 104 (1) ◽  
pp. 90-100 ◽  
Author(s):  
Saiid Bina ◽  
George Cowan ◽  
John Karaian ◽  
Sheila Muldoon ◽  
Paul Mongan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Malignant Hyperthermia ◽  
Lipid Emulsion ◽  
Dose Effect ◽  
P System ◽  
Muscle Rigidity ◽  
Dependent Manner ◽  
Muscle Lactate ◽  
Diagnostic Potential

Background Skeletal muscle fibers from malignant hyperthermia (MH)-susceptible humans and swine are markedly more sensitive to ryanodine receptor (RyR1) agonists than those from normal individuals. Reproducible shifts in the dose-response of skeletal muscle to caffeine and halothane are the basis of the current in vitro diagnostic caffeine-halothane contracture test. In an attempt to develop a less invasive MH diagnostic test, the authors determined the effects of RyR1 agonists (caffeine, 4-chloro-m-cresol [4CmC], and halothane) on the adductor muscle with respect to the lactate-pyruvate (L/P) system that was percutaneously dialyzed using a microdialysis technique in homozygous MH-susceptible compared with normal swine. Methods Animals were anesthetized (ketamine-propofol) and artificially ventilated. Sets of six CMA/20 microdialysis catheters were implanted; each catheter was perfused with different RyR1 agonist concentrations. After a 30-min equilibration after implantation, one of the catheters was perfused (2 microl/min) with vehicle (0.9% saline or lipid emulsion), and the other five were perfused with caffeine (1-64 mM), 4CmC (0.1-8 mM), or halothane (prepared in lipid emulsion; 10-500 mM). Outflow dialysate fractions collected at 10-min intervals and L/P parameters were measured enzymatically. Results Only in the MH-susceptible group did all RyR1 agonists increase dialysate L/P in a dose-dependent manner. The dose-effect relations were most prominent with 4CmC. With the halothane lipid emulsion, data scatter was high compared with that of the caffeine group and especially the 4CmC group. There were no signs of global muscle rigidity, systemic hypermetabolism, or a clinical MH episode during microdialysis RyR1 perfusion. Conclusions The authors data demonstrate that the in vivo muscle microdialysis of the porcine L/P system reveals distinct differences between MH-susceptible and MH-normal muscle, especially in response to highly specific RyR1 agonists such as 4CmC. The microdialysis L/P technique seems to have an MH diagnostic potential in the clinical setting.

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