scholarly journals The effect of age and unilateral leg immobilization for 2 weeks on substrate utilization during moderate-intensity exercise in human skeletal muscle

2016 ◽  
Vol 594 (8) ◽  
pp. 2339-2358 ◽  
Author(s):  
A. Vigelsø ◽  
M. Gram ◽  
R. Dybboe ◽  
A. B. Kuhlman ◽  
C. Prats ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Substrate Utilization ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Effect Of Age

Progressive increase in human skeletal muscle AMPKα2 activity and ACC phosphorylation during exercise

2002 ◽  
Vol 282 (3) ◽  
pp. E688-E694 ◽  
Author(s):  
T. J. Stephens ◽  
Z.-P. Chen ◽  
B. J. Canny ◽  
B. J. Michell ◽  
B. E. Kemp ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Human Skeletal Muscle ◽  
Glycogen Content ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Western Blots ◽  
Muscle Glycogen Content ◽  
Muscle Creatine

The effect of prolonged moderate-intensity exercise on human skeletal muscle AMP-activated protein kinase (AMPK)α1 and -α2 activity and acetyl-CoA carboxylase (ACCβ) and neuronal nitric oxide synthase (nNOSμ) phosphorylation was investigated. Seven active healthy individuals cycled for 30 min at a workload requiring 62.8 ± 1.3% of peak O2consumption (V˙o 2 peak) with muscle biopsies obtained from the vastus lateralis at rest and at 5 and 30 min of exercise. AMPKα1 activity was not altered by exercise; however, AMPKα2 activity was significantly ( P < 0.05) elevated after 5 min (∼2-fold), and further elevated ( P < 0.05) after 30 min (∼3-fold) of exercise. ACCβ phosphorylation was increased ( P < 0.05) after 5 min (∼18-fold compared with rest) and increased ( P< 0.05) further after 30 min of exercise (∼36-fold compared with rest). Increases in AMPKα2 activity were significantly correlated with both increases in ACCβ phosphorylation and reductions in muscle glycogen content. Fat oxidation tended ( P = 0.058) to increase progressively during exercise. Muscle creatine phosphate was lower ( P < 0.05), and muscle creatine, calculated free AMP, and free AMP-to-ATP ratio were higher ( P < 0.05) at both 5 and 30 min of exercise compared with those at rest. At 30 min of exercise, the values of these metabolites were not significantly different from those at 5 min of exercise. Phosphorylation of nNOSμ was variable, and despite the mean doubling with exercise, statistically significance was not achieved ( P = 0.304). Western blots indicated that AMPKα2 was associated with both nNOSμ and ACCβ consistent with them both being substrates of AMPKα2 in vivo. In conclusion, AMPKα2 activity and ACCβ phosphorylation increase progressively during moderate exercise at ∼60% of V˙o 2 peak in humans, with these responses more closely coupled to muscle glycogen content than muscle AMP/ATP ratio.

Glutamine supplementation promotes anaplerosis but not oxidative energy delivery in human skeletal muscle

2001 ◽  
Vol 280 (4) ◽  
pp. E669-E675 ◽  
Author(s):  
Mark Bruce ◽  
Dumitru Constantin-Teodosiu ◽  
Paul L. Greenhaff ◽  
Leslie H. Boobis ◽  
Clyde Williams ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Vastus Lateralis ◽  
Tca Cycle ◽  
Glutamine Supplementation ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Energy Status ◽  
Moderate Intensity Exercise ◽  
Significant Difference

The aims of the present study were twofold: first to investigate whether TCA cycle intermediate (TCAI) pool expansion at the onset of moderate-intensity exercise in human skeletal muscle could be enhanced independently of pyruvate availability by ingestion of glutamine or ornithine α-ketoglutarate, and second, if it was, whether this modification of TCAI pool expansion had any effect on oxidative energy status during subsequent exercise. Seven males cycled for 10 min at ∼70% maximal O2 uptake 1 h after consuming either an artificially sweetened placebo (5 ml/kg body wt solution, CON), 0.125 g/kg body wtl-(+)-ornithine α-ketoglutarate dissolved in 5 ml/kg body wt solution (OKG), or 0.125 g/kg body wt l-glutamine dissolved in 5 ml/kg body wt solution (GLN). Vastus lateralis muscle was biopsied 1 h postsupplement and after 10 min of exercise. The sum of four measured TCAI (ΣTCAI; citrate, malate, fumarate, and succinate, ∼85% of total TCAI pool) was not different between conditions 1 h postsupplement. However, after 10 min of exercise, ΣTCAI (mmol/kg dry muscle) was greater in the GLN condition (4.90 ± 0.61) than in the CON condition (3.74 ± 0.38, P < 0.05) and the OKG condition (3.85 ± 0.28). After 10 min of exercise, muscle phosphocreatine (PCr) content was significantly reduced ( P < 0.05) in all conditions, but there was no significant difference between conditions. We conclude that the ingestion of glutamine increased TCAI pool size after 10 min of exercise most probably because of the entry of glutamine carbon at the level of α-ketoglutarate. However, this increased expansion in the TCAI pool did not appear to increase oxidative energy production, because there was no sparing of PCr during exercise.

Intramuscular triacylglycerol utilization in human skeletal muscle during exercise: is there a controversy?

2002 ◽  
Vol 93 (4) ◽  
pp. 1185-1195 ◽  
Author(s):  
Matthew J. Watt ◽  
George J. F. Heigenhauser ◽  
Lawrence L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Muscle Biopsy ◽  
Human Skeletal Muscle ◽  
Moderate Intensity ◽  
Resonance Spectroscopy ◽  
Moderate Exercise ◽  
Moderate Intensity Exercise ◽  
Trained Subjects ◽  
Skeletal Muscle Biopsy ◽  
Isotope Tracer

Intramuscular triacylglyerols (IMTGs) represent a potentially important energy source for contracting human skeletal muscle. Although the majority of evidence from isotope tracer and 1H-magnetic resonance spectroscopy (MRS) studies demonstrate IMTG utilization during exercise, controversy regarding the importance of IMTG as a metabolic substrate persists. The controversy stems from studies that measure IMTG in skeletal muscle biopsy samples and report no significant net IMTG degradation during prolonged moderate-intensity (55–70% maximal O2 consumption) exercise lasting 90–120 min. Although postexercise decrements in IMTG levels are often reported from direct muscle measurements, the marked between-biopsy variability (∼23%) that has been reported with this technique in untrained subjects is larger than the expected decrease in IMTG content, effectively precluding significant findings. In contrast, recent data obtained in endurance-trained subjects demonstrated reduced variability between duplicate biopsies (∼12%), and significant changes in IMTG were detected after 120 min of moderate-intensity exercise. Therefore, it is our contention that the muscle biopsy, isotope tracer, and 1H-MRS techniques report significant and energetically important oxidation of free fatty acids derived from IMTGs during prolonged moderate exercise.

scholarly journals Exercise and insulin cause GLUT-4 translocation in human skeletal muscle

1999 ◽  
Vol 277 (4) ◽  
pp. E733-E741 ◽  
Author(s):  
Anders Thorell ◽  
Michael F. Hirshman ◽  
Jonas Nygren ◽  
Lennart Jorfeldt ◽  
Jørgen F. P. Wojtaszewski ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Vastus Lateralis Muscle ◽  
Moderate Intensity Exercise ◽  
Euglycemic Hyperinsulinemic Clamp ◽  
Glut 4 ◽  
Increase Glucose Uptake ◽  
Glut 4 Translocation

Studies in rodents have established that GLUT-4 translocation is the major mechanism by which insulin and exercise increase glucose uptake in skeletal muscle. In contrast, much less is known about the translocation phenomenon in human skeletal muscle. In the current study, nine healthy volunteers were studied on two different days. On one day, biopsies of vastus lateralis muscle were taken before and after a 2-h euglycemic-hyperinsulinemic clamp (0.8 mU ⋅ kg−1 ⋅ min−1). On another day, subjects exercised for 60 min at 70% of maximal oxygen consumption (V˙o 2 max), a biopsy was obtained, and the same clamp and biopsy procedure was performed as that during the previous experiment. Compared with insulin treatment alone, glucose infusion rates were significantly increased during the postexercise clamp for the periods 0–30 min, 30–60 min, and 60–90 min, but not during the last 30 min of the clamp. Plasma membrane GLUT-4 content was significantly increased in response to physiological hyperinsulinemia (32% above rest), exercise (35%), and the combination of exercise plus insulin (44%). Phosphorylation of Akt, a putative signaling intermediary for GLUT-4 translocation, was increased in response to insulin (640% above rest), exercise (280%), and exercise plus insulin (1,000%). These data demonstrate that two normal physiological conditions, moderate intensity exercise and physiological hyperinsulinemia ∼56 μU/ml, cause GLUT-4 translocation and Akt phosphorylation in human skeletal muscle.

scholarly journals Regulation and role of hormone-sensitive lipase activity in human skeletal muscle

2004 ◽  
Vol 63 (2) ◽  
pp. 315-322 ◽  
Author(s):  
Matthew J. Watt ◽  
Lawrence L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Aerobic Exercise ◽  
Human Skeletal Muscle ◽  
Fatty Acyl ◽  
Hormone Sensitive Lipase ◽  
Moderate Intensity ◽  
Control Points ◽  
Moderate Intensity Exercise ◽  
Hormone Sensitive

Hormone-sensitive lipase (HSL) is believed to play a regulatory role in initiating the degradation of intramuscular triacylglycerol (IMTG) in skeletal muscle. A series of studies designed to characterise the response of HSL to three stimuli: exercise of varying intensities and durations; adrenaline infusions; altered fuel supply have recently been conducted in human skeletal muscle. In an attempt to understand the regulation of HSL activity the changes in the putative intramuscular and hormonal regulators of the enzyme have also been measured. In human skeletal muscle at rest there is a high constitutive level of HSL activity, which is not a function of biopsy freezing. The combination of low adrenaline and Ca2+levels and resting levels of insulin appear to dictate the level of HSL activity at rest. During the initial minute of low and moderate aerobic exercise HSL is activated by contractions in the apparent absence of increases in circulating adrenaline. During intense aerobic exercise, adrenaline may contribute to the early activation of HSL. The contraction-induced activation may be related to increased Ca2+and/or other unknown intramuscular activators. As low- and moderate-intensity exercise continues beyond a few minutes, activation by adrenaline through the cAMP cascade may also occur. With prolonged moderate-intensity exercise beyond 1–2 h and sustained high-intensity exercise, HSL activity decreases despite continuing increases in adrenaline, possibly as a result of increasing accumulations of free AMP, activation of AMP kinase and phosphorylation of inhibitory sites on HSL. The existing work in human skeletal muscle also suggests that there are numerous levels of control involved in the regulation of IMTG degradation, with control points downstream from HSL also being important. For example, it must be remembered that the actual flux (IMTG degradation) through HSL may be allosterically inhibited during prolonged exercise as a result of the accumulation of long-chain fatty acyl-CoA.

scholarly journals Increasing skeletal muscle carnitine content in older individuals increases whole‐body fat oxidation during moderate‐intensity exercise

Aging Cell ◽  
2021 ◽  
Vol 20 (2) ◽  
Author(s):  
Carolyn Chee ◽  
Chris E. Shannon ◽  
Aisling Burns ◽  
Anna L. Selby ◽  
Daniel Wilkinson ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Body Fat ◽  
Fat Oxidation ◽  
Whole Body ◽  
Moderate Intensity ◽  
Older Individuals ◽  
Moderate Intensity Exercise

Exercise training increases branched-chain oxoacid dehydrogenase kinase content in human skeletal muscle

2007 ◽  
Vol 293 (3) ◽  
pp. R1335-R1341 ◽  
Author(s):  
Krista R. Howarth ◽  
Kirsten A. Burgomaster ◽  
Stuart M. Phillips ◽  
Martin J. Gibala
Keyword(s):  
Skeletal Muscle ◽  
Exercise Training ◽  
Protein Content ◽  
Human Skeletal Muscle ◽  
Acute Exercise ◽  
Citrate Synthase ◽  
Muscle Protein ◽  
Moderate Intensity ◽  
Main Effect ◽  
Branched Chain

The branched-chain oxoacid dehydrogenase complex (BCOAD) is rate determining for the oxidation of branched-chain amino acids (BCAAs) in skeletal muscle. Exercise training blunts the acute exercise-induced activation of BCOAD (BCOADa) in human skeletal muscle (McKenzie S, Phillips SM, Carter SL, Lowther S, Gibala MJ, Tarnopolsky MA. Am J Physiol Endocrinol Metab 278: E580–E587, 2000); however, the mechanism is unknown. We hypothesized that training would increase the muscle protein content of BCOAD kinase, the enzyme responsible for inactivation of BCOAD by phosphorylation. Twenty subjects [23 ± 1 yr; peak oxygen uptake (V̇o2peak) = 41 ± 2 ml·kg−1·min−1] performed 6 wk of either high-intensity interval or continuous moderate-intensity training on a cycle ergometer ( n = 10/group). Before and after training, subjects performed 60 min of cycling at 65% of pretraining V̇o2peak, and needle biopsy samples (vastus lateralis) were obtained before and immediately after exercise. The effect of training was demonstrated by an increased V̇o2peak, increased citrate synthase maximal activity, and reduced muscle glycogenolysis during exercise, with no difference between groups (main effects, P < 0.05). BCOADa was lower after training (main effect, P < 0.05), and this was associated with a ∼30% increase in BCOAD kinase protein content (main effect, P < 0.05). We conclude that the increased protein content of BCOAD kinase may be involved in the mechanism for reduced BCOADa after exercise training in human skeletal muscle. These data also highlight differences in models used to study the regulation of skeletal muscle BCAA metabolism, since exercise training was previously reported to increase BCOADa during exercise and decrease BCOAD kinase content in rats (Fujii H, Shimomura Y, Murakami T, Nakai N, Sato T, Suzuki M, Harris RA. Biochem Mol Biol Int 44: 1211–1216, 1998).

Regulation of CPT I activity in intermyofibrillar and subsarcolemmal mitochondria from human and rat skeletal muscle

2004 ◽  
Vol 286 (1) ◽  
pp. E85-E91 ◽  
Author(s):  
Veronic Bezaire ◽  
George J. F. Heigenhauser ◽  
Lawrence L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Vastus Lateralis ◽  
Moderate Intensity ◽  
Rat Skeletal Muscle ◽  
Moderate Intensity Exercise ◽  
Mitochondrial Fractions ◽  
Decreasing Ph ◽  
Subsarcolemmal Mitochondria ◽  
Cpt I

Carnitine palmitoyltransferase I (CPT I) is considered the rate-limiting enzyme in the transfer of long-chain fatty acids (LCFA) into the mitochondria and is reversibly inhibited by malonyl-CoA (M-CoA) in vitro. In rat skeletal muscle, M-CoA levels decrease during exercise, releasing the inhibition of CPT I and increasing LCFA oxidation. However, in human skeletal muscle, M-CoA levels do not change during moderate-intensity exercise despite large increases in fat oxidation, suggesting that M-CoA is not the sole regulator of increased CPT I activity during exercise. In the present study, we measured CPT I activity in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondria isolated from human vastus lateralis (VL), rat soleus (Sol), and red gastrocnemius (RG) muscles. We tested whether exercise-related levels (∼65% maximal O2 uptake) of calcium and adenylate charge metabolites (free AMP, ADP, and Pi) could override the M-CoA-induced inhibition of CPT I activity and explain the increased CPT I flux during exercise. Protein content was ∼25-40% higher in IMF than in SS mitochondria in all muscles. Maximal CPT I activity was similar in IMF and SS mitochondria in all muscles (VL: 282 ± 46 vs. 280 ± 51; Sol: 390 ± 81 vs. 368 ± 82; RG: 252 ± 71 vs. 278 ± 44 nmol·min-1·mg protein-1). Sensitivity to M-CoA did not differ between IMF and SS mitochondria in all muscles (25-31% inhibition in VL, 52-70% in Sol and RG). Calcium and adenylate charge metabolites did not override the M-CoA-induced inhibition of CPT I activity in mitochondria isolated from VL, Sol, and RG muscles. Decreasing pH from 7.1 to 6.8 reduced CPT I activity by ∼34-40% in both VL mitochondrial fractions. In summary, this study reports no differences in CPT I activity or sensitivity to M-CoA between IMF and SS mitochondria isolated from human and rat skeletal muscles. Exercise-induced increases in calcium and adenylate charge metabolites do not appear responsible for upregulating CPT I activity in human or rat skeletal muscle during moderate aerobic exercise.

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