Carbohydrate metabolism in human skeletal muscle during exercise is not regulated by G-1,6-P2

1988 ◽  
Vol 65 (1) ◽  
pp. 487-489 ◽  
Author(s):  
A. Katz ◽  
K. Sahlin ◽  
J. Henriksson
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Work Load ◽  
Short Term ◽  
Catalytic Function ◽  
Muscle Ph ◽  
Induced Changes ◽  
Femoris Muscle

Glucose 1,6-bisphosphate (G-1,6-P2) is a potent activator of phosphofructokinase (PFK) and an inhibitor of hexokinase in vitro. It has been suggested that increases in G-1,6-P2 are a main means by which PFK can achieve significant catalytic function in vivo despite falling pH and that increases in G-1,6-P2 will inhibit hexokinase in vivo. The purpose of the present study was to determine whether contraction-induced changes in flux through PFK and hexokinase are associated with changes in G-1,6-P2 in skeletal muscle. Ten men performed bicycle exercise for 10 min at 40 and 75% of maximal O2 uptake (VO2max) and to fatigue [4.8 +/- 0.6 (SE) min] at 100% VO2max. Biopsies were obtained from the quadriceps femoris muscle at rest and after each work load and analyzed for G-1,6-P2. G-1,6-P2 averaged 111 +/- 13 mumol/kg dry wt at rest and 121 +/- 16, 123 +/- 15, and 123 +/- 11 mumol/kg dry wt after the low-, moderate-, and high-intensity exercise bouts, respectively (P less than 0.05 for all means vs. rest). Flux through PFK was estimated to increase exponentially as the exercise intensity increased and muscle pH decreased at the higher work loads, whereas flux through hexokinase was estimated to increase during exercise at 40 and 75% VO2max but decrease sharply at 100% VO2max. These data demonstrate that flux through neither PFK nor hexokinase is mediated by changes in G-1,6-P2 in human skeletal muscle during short-term dynamic exercise.

scholarly journals FGF-2–dependent signaling activated in aged human skeletal muscle promotes intramuscular adipogenesis

2021 ◽  
Vol 118 (37) ◽  
pp. e2021013118 ◽  
Author(s):  
Sebastian Mathes ◽  
Alexandra Fahrner ◽  
Umesh Ghoshdastider ◽  
Hannes A. Rüdiger ◽  
Michael Leunig ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transcriptional Activation ◽  
Human Skeletal Muscle ◽  
Muscle Growth ◽  
Muscle Cells ◽  
Adeno Associated Virus ◽  
Adult Skeletal Muscle

Aged skeletal muscle is markedly affected by fatty muscle infiltration, and strategies to reduce the occurrence of intramuscular adipocytes are urgently needed. Here, we show that fibroblast growth factor-2 (FGF-2) not only stimulates muscle growth but also promotes intramuscular adipogenesis. Using multiple screening assays upstream and downstream of microRNA (miR)-29a signaling, we located the secreted protein and adipogenic inhibitor SPARC to an FGF-2 signaling pathway that is conserved between skeletal muscle cells from mice and humans and that is activated in skeletal muscle of aged mice and humans. FGF-2 induces the miR-29a/SPARC axis through transcriptional activation of FRA-1, which binds and activates an evolutionary conserved AP-1 site element proximal in the miR-29a promoter. Genetic deletions in muscle cells and adeno-associated virus–mediated overexpression of FGF-2 or SPARC in mouse skeletal muscle revealed that this axis regulates differentiation of fibro/adipogenic progenitors in vitro and intramuscular adipose tissue (IMAT) formation in vivo. Skeletal muscle from human donors aged >75 y versus <55 y showed activation of FGF-2–dependent signaling and increased IMAT. Thus, our data highlights a disparate role of FGF-2 in adult skeletal muscle and reveals a pathway to combat fat accumulation in aged human skeletal muscle.

scholarly journals Microdialysis of skeletal muscle at rest

1999 ◽  
Vol 58 (4) ◽  
pp. 919-923 ◽  
Author(s):  
Jan Henriksson
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Human Skeletal Muscle ◽  
Human Metabolism ◽  
High Expectations ◽  
Perfusate Flow ◽  
Muscle Research ◽  
Interstitial Glucose

Techniques in human skeletal muscle research are by necessity predominantly 'descriptive'.Microdialysis has raised high expectations that it could meet the demand for a method that allows 'mechanistic' investigations to be performed in human skeletal muscle. In the present review, some views are given on how well the initial expectations on the use of the microdialysis technique in skeletal muscle have been fulfilled, and the areas in which additional work is needed in order to validate microdialysis as an important metabolic technique in this tissue. The microdialysis catheter has been equated to an artificial blood vessel, which is introduced into the tissue. By means of this 'vessel' the concentrations of compounds in the interstitial space can be monitored. The concentration of substances in the collected samples is dependent on the rate of perfusate flow. When perfusate flow is slow enough to allow complete equilibration between interstitial and perfusate fluids, the concentration in the perfusate is maximal and identical to the interstitial concentration. Microdialysis data may be influenced by changes in blood flow, especially in instances where the tissue diffusivity limits the recovery in vivo, i.e. when recovery in vitro is 100 %, whereas the recovery in vivo is less than 100 %. Microdialysis data indicate that a significant arterial-interstitial glucose concentration gradient exists in skeletal muscle but not in adipose tissue at rest. While the concentrations of glucose and lactate in the dialysate from skeletal muscle are close to the expected values, the glycerol values obtained for muscle are still puzzling. Ethanol added to the perfusate will be cleared by the tissue at a rate that is determined by the nutritive blood flow (the microdialysis ethanol technique). It is concluded that microdialysis of skeletal muscle has become an important technique for mechanistic studies in human metabolism and nutrition.

scholarly journals In Vivo Fatigue Reduces In Vitro Performance In Human Skeletal Muscle Fibers

2021 ◽  
Vol 53 (8S) ◽  
pp. 110-111
Author(s):  
Austin W. Ricci ◽  
Scott J. Mongold ◽  
Grace E. Privett ◽  
Karen W. Needham ◽  
Damien M. Callahan
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Muscle Fibers ◽  
Skeletal Muscle Fibers ◽  
In Vitro Performance

scholarly journals Age and prior exercise in vivo determine the subsequent in vitro molecular profile of myoblasts and nonmyogenic cells derived from human skeletal muscle

2019 ◽  
Vol 316 (6) ◽  
pp. C898-C912 ◽  
Author(s):  
Cecilie J. L. Bechshøft ◽  
Simon M. Jensen ◽  
Peter Schjerling ◽  
Jesper L. Andersen ◽  
Rene B. Svensson ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Stem Cell ◽  
Human Skeletal Muscle ◽  
Cell Function ◽  
Myogenic Differentiation ◽  
Molecular Profile ◽  
Muscle Stem Cell ◽  
Myogenic Cells

The decline in skeletal muscle regenerative capacity with age is partly attributed to muscle stem cell (satellite cell) dysfunction. Recent evidence has pointed to a strong interaction between myoblasts and fibroblasts, but the influence of age on this interaction is unknown. Additionally, while the native tissue environment is known to determine the properties of myogenic cells in vitro, how the aging process alters this cell memory has not been established at the molecular level. We recruited 12 young and 12 elderly women, who performed a single bout of heavy resistance exercise with the knee extensor muscles of one leg. Five days later, muscle biopsies were collected from both legs, and myogenic cells and nonmyogenic cells were isolated for in vitro experiments with mixed or separated cells and analyzed by immunostaining and RT-PCR. A lower myogenic fusion index was detected in the cells from the old versus young women, in association with differences in gene expression levels of key myogenic regulatory factors and senescence, which were further altered by performing exercise before tissue sampling. Coculture with nonmyogenic cells from the elderly led to a higher myogenic differentiation index compared with nonmyogenic cells from the young. These findings show that the in vitro phenotype and molecular profile of human skeletal muscle myoblasts and fibroblasts is determined by the age and exercise state of the original in vivo environment and help explain how exercise can enhance muscle stem cell function in old age.

Static stretch increases c-Jun NH2-terminal kinase activity and p38 phosphorylation in rat skeletal muscle

2001 ◽  
Vol 280 (2) ◽  
pp. C352-C358 ◽  
Author(s):  
Marni D. Boppart ◽  
Michael F. Hirshman ◽  
Kei Sakamoto ◽  
Roger A. Fielding ◽  
Laurie J. Goodyear
Keyword(s):  
Skeletal Muscle ◽  
Muscle Contraction ◽  
Protein Kinases ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Eccentric Contractions ◽  
Sprague Dawley ◽  
Static Stretch

Physical exercise and contraction increase c-Jun NH2-terminal kinase (JNK) activity in rat and human skeletal muscle, and eccentric contractions activate JNK to a greater extent than concentric contractions in human skeletal muscle. Because eccentric contractions include a lengthening or stretch component, we compared the effects of isometric contraction and static stretch on JNK and p38, the stress-activated protein kinases. Soleus and extensor digitorum longus (EDL) muscles dissected from 50- to 90-g male Sprague-Dawley rats were subjected to 10 min of electrical stimulation that produced contractions and/or to 10 min of stretch (0.24 N tension, 20–25% increase in length) in vitro. In the soleus muscle, contraction resulted in a small, but significant, increase in JNK activity (1.8-fold above basal) and p38 phosphorylation (4-fold). Static stretch had a much more profound effect on the stress-activated protein kinases, increasing JNK activity 19-fold and p38 phosphorylation 21-fold. Increases in JNK activation and p38 phosphorylation in response to static stretch were fiber-type dependent, with greater increases occurring in the soleus than in the EDL. Immunohistochemistry performed with a phosphospecific antibody revealed that activation of JNK occurred within the muscle fibers. These studies suggest that the stretch component of a muscle contraction may be a major contributor to the increases in JNK activity and p38 phosphorylation observed after exercise in vivo.

Anaerobic metabolism in human skeletal muscle during short-term, intense activity

1992 ◽  
Vol 70 (1) ◽  
pp. 157-165 ◽  
Author(s):  
Lawrence L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Anaerobic Capacity ◽  
Muscular Activity ◽  
Maximal Activity ◽  
Considerable Effort ◽  
Short Term ◽  
Direct Measurements ◽  
Intense Activity

The ability of human skeletal muscle to provide anaerobically derived ATP during short-term, intense activity is examined. The paper emphasizes the information obtained from direct measurements of substrates, intermediates, and products of the pathways in muscle that provide anaerobically derived ATP. The capacity of muscle to provide ATP via anaerobic pathways is ~370 mmol/kg dry muscle (dm) during dynamic exercise lasting ~3 min. Anaerobic glycolysis provided ~80%, phosphocreatine (PCr) degradation ~16%, and depletion of the ATP store ~4% of the total ATP provided. When the blood flow to the working muscles is reduced or occluded, the anaerobic capacity decreases to ~300 mmol/kg dm. This reduction is due to a lower glycolytic capacity associated with an inability to remove lactate from the muscles. Directly measured maximal rates of anaerobically derived ATP provision from PCr degradation and glycolysis during intense muscular activity are each ~9–10 mmol∙kg−1 dm∙s−1. Evidence suggests that both of these pathways are activated instantaneously at the onset of maximal activity. Spring training does little to the capacity or rates of the pathways, although a 10–20% increase in glycolytic ATP provision has been reported. The only study comparing direct and indirect estimates of the anaerobic capacity in humans suggests that O2 deficit measured at the mouth accurately predicts the anaerobic capacity of a single muscle group and that O2 debt does not. There are many unresolved issues regarding the capacity of the PCr and glycogenolytic–glycolytic systems to provide ATP during short-term intense muscular activity in humans. Considerable effort is now being directed to understanding the in vivo regulation of the regulatory and flux-generating glycogenolytic enzyme, phosphorylase.Key words: glycogenosis, glycolysis, phosphocreatine, ATP, sprinting.

Localization and function of ATP-sensitive potassium channels in human skeletal muscle

2003 ◽  
Vol 284 (2) ◽  
pp. R558-R563 ◽  
Author(s):  
Jens Jung Nielsen ◽  
Michael Kristensen ◽  
Ylva Hellsten ◽  
Jens Bangsbo ◽  
Carsten Juel
Keyword(s):  
Skeletal Muscle ◽  
Muscle Activity ◽  
Human Skeletal Muscle ◽  
Knee Extensor ◽  
Human Muscle ◽  
Functional Importance ◽  
Gradient Technique ◽  
And Function

The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique or the sucrose-gradient technique in combination with Western blotting demonstrated that the KATP channels are mainly located in the sarcolemma. This localization was confirmed by immunohistochemical measurements. With the microdialysis technique, it was demonstrated that local application of the KATP channel inhibitor glibenclamide reduced ( P < 0.05) interstitial K+ at rest from ∼4.5 to 4.0 mM, whereas the concentration in the control leg remained constant. Glibenclamide had no effect on the interstitial K+ accumulation during knee-extensor exercise at a power output of 60 W. In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the KATP channels are active at rest and contribute to the accumulation of interstitial K+.

scholarly journals Endothelin-1 Reduces Glucose Uptake in Human Skeletal Muscle In Vivo and In Vitro

Diabetes ◽  
2011 ◽  
Vol 60 (8) ◽  
pp. 2061-2067 ◽  
Author(s):  
A. Shemyakin ◽  
F. Salehzadeh ◽  
D. Esteves Duque-Guimaraes ◽  
F. Bohm ◽  
E. Rullman ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Human Skeletal Muscle ◽  
Endothelin 1
Sign in / Sign up

Export Citation Format

Share Document