scholarly journals Beetroot juice supplementation reduces whole body oxygen consumption but does not improve indices of mitochondrial efficiency in human skeletal muscle

2015 ◽  
Vol 594 (2) ◽  
pp. 421-435 ◽  
Author(s):  
J. Whitfield ◽  
A. Ludzki ◽  
G. J. F. Heigenhauser ◽  
J. M. G. Senden ◽  
L. B. Verdijk ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Human Skeletal Muscle ◽  
Whole Body ◽  
Beetroot Juice ◽  
Mitochondrial Efficiency

Estimation of capillary density in human skeletal muscle based on maximal oxygen consumption rates

2003 ◽  
Vol 285 (6) ◽  
pp. H2382-H2391 ◽  
Author(s):  
B. J. McGuire ◽  
T. W. Secomb
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Oxygen Transport ◽  
Human Skeletal Muscle ◽  
Maximal Exercise ◽  
Maximal Oxygen Consumption ◽  
Capillary Density ◽  
Transport Processes ◽  
Whole Body ◽  
Density Values

A previously developed Krogh-type theoretical model was used to estimate capillary density in human skeletal muscle based on published measurements of oxygen consumption, arterial partial pressure of oxygen, and blood flow during maximal exercise. The model assumes that oxygen consumption in maximal exercise is limited by the ability of capillaries to deliver oxygen to tissue and is therefore strongly dependent on capillary density, defined as the number of capillaries per unit cross-sectional area of muscle. Based on an analysis of oxygen transport processes occurring at the microvascular level, the model allows estimation of the minimum number of straight, evenly spaced capillaries required to achieve a given oxygen consumption rate. Estimated capillary density values were determined from measurements of maximal oxygen consumption during knee extensor exercise and during whole body cycling, and they range from 459 to 1,468 capillaries/mm2. Measured capillary densities, obtained with either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects, are generally lower, ranging from 123 to 515 capillaries/mm2. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction and muscle biopsy samples typically are strongly contracted. The results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle.

RPS6 phosphorylation occurs to a greater extent in the periphery of human skeletal muscle fibers, near focal adhesions, after anabolic stimuli

2021 ◽  
Author(s):  
Nathan Hodson ◽  
Michael Mazzulla ◽  
Maksym N. H. Holowaty ◽  
Dinesh Kumbhare ◽  
Daniel R. Moore
Keyword(s):  
Skeletal Muscle ◽  
Focal Adhesion ◽  
Human Skeletal Muscle ◽  
Muscle Fibers ◽  
Focal Adhesions ◽  
Immunofluorescent Staining ◽  
Whole Body ◽  
Vastus Lateralis Muscle ◽  
Cell Periphery ◽  
Rps6 Phosphorylation

Following anabolic stimuli (mechanical loading and/or amino acid provision) the mechanistic target of rapamycin complex 1 (mTORC1), a master regulator of protein synthesis, translocates toward the cell periphery. However, it is unknown if mTORC1-mediated phosphorylation events occur in these peripheral regions or prior to translocation (i.e. in central regions). We therefore aimed to determine the cellular location of a mTORC1-mediated phosphorylation event, RPS6Ser240/244, in human skeletal muscle following anabolic stimuli. Fourteen young, healthy males either ingested a protein-carbohydrate beverage (0.25g/kg protein, 0.75g/kg carbohydrate) alone (n=7;23±5yrs;76.8±3.6kg;13.6±3.8%BF, FED) or following a whole-body resistance exercise bout (n=7;22±2yrs;78.1±3.6kg;12.2±4.9%BF, EXFED). Vastus lateralis muscle biopsies were obtained at rest (PRE) and 120 and 300min following anabolic stimuli. RPS6Ser240/244 phosphorylation measured by immunofluorescent staining or immunoblot was positively correlated (r=0.76, p<0.001). Peripheral staining intensity of p-RPS6Ser240/244 increased above PRE in both FED and EXFED at 120min (~54% and ~138% respectively, p<0.05) but was greater in EXFED at both post-stimuli time points (p<0.05). The peripheral-central ratio of p-RPS6240/244 staining displayed a similar pattern, even when corrected for total RPS6 distribution, suggesting RPS6 phosphorylation occurs to a greater extent in the periphery of fibers. Moreover, p-RPS6Ser240/244 intensity within paxillin-positive regions, a marker of focal adhesion complexes, was elevated at 120min irrespective of stimulus (p=0.006) before returning to PRE at 300min. These data confirm that RPS6Ser240/244 phosphorylation occurs in the region of human muscle fibers to which mTOR translocates following anabolic stimuli and identifies focal adhesion complexes as a potential site of mTORC1 regulation in vivo.

Relationship between whole body oxygen consumption and skeletal muscle glucose metabolism during walking in older adults: FDG PET study

2011 ◽  
Vol 23 (3) ◽  
pp. 175-182 ◽  
Author(s):  
Hiroyuki Shimada ◽  
Daina Sturnieks ◽  
Yosuke Endo ◽  
Yuichi Kimura ◽  
Takao Suzuki ◽  
...  
Keyword(s):  
Older Adults ◽  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Glucose Metabolism ◽  
Fdg Pet ◽  
Whole Body

scholarly journals β-Hydroxybutyrate is reduced in humans with obesity-related NAFLD and displays a dose-dependent effect on skeletal muscle mitochondrial respiration in vitro

2020 ◽  
Vol 319 (1) ◽  
pp. E187-E195 ◽  
Author(s):  
Jacob T. Mey ◽  
Melissa L. Erickson ◽  
Christopher L. Axelrod ◽  
William T. King ◽  
Chris A. Flask ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Insulin Sensitivity ◽  
Mitochondrial Respiration ◽  
Liver Fat ◽  
Whole Body ◽  
Fat Accumulation ◽  
Impaired Insulin ◽  
Hepatic Fat

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic fat accumulation and impaired insulin sensitivity. Reduced hepatic ketogenesis may promote these pathologies, but data are inconclusive in humans and the link between NAFLD and reduced insulin sensitivity remains obscure. We investigated individuals with obesity-related NAFLD and hypothesized that β-hydroxybutyrate (βOHB; the predominant ketone species) would be reduced and related to hepatic fat accumulation and insulin sensitivity. Furthermore, we hypothesized that ketones would impact skeletal muscle mitochondrial respiration in vitro. Hepatic fat was assessed by 1H-MRS in 22 participants in a parallel design, case control study [Control: n = 7, age 50 ± 6 yr, body mass index (BMI) 30 ± 1 kg/m2; NAFLD: n = 15, age 57 ± 3 yr, BMI 35 ± 1 kg/m2]. Plasma assessments were conducted in the fasted state. Whole body insulin sensitivity was determined by the gold-standard hyperinsulinemic-euglycemic clamp. The effect of ketone dose (0.5–5.0 mM) on mitochondrial respiration was conducted in human skeletal muscle cell culture. Fasting βOHB, a surrogate measure of hepatic ketogenesis, was reduced in NAFLD (−15.6%, P < 0.01) and correlated negatively with liver fat ( r2 = 0.21, P = 0.03) and positively with insulin sensitivity ( r2 = 0.30, P = 0.01). Skeletal muscle mitochondrial oxygen consumption increased with low-dose ketones, attributable to increases in basal respiration (135%, P < 0.05) and ATP-linked oxygen consumption (136%, P < 0.05). NAFLD pathophysiology includes impaired hepatic ketogenesis, which is associated with hepatic fat accumulation and impaired insulin sensitivity. This reduced capacity to produce ketones may be a potential link between NAFLD and NAFLD-associated reductions in whole body insulin sensitivity, whereby ketone concentrations impact skeletal muscle mitochondrial respiration.

Fasting inhibits insulin-mediated glycolysis and anaplerosis in human skeletal muscle

1991 ◽  
Vol 261 (5) ◽  
pp. E598-E605 ◽  
Author(s):  
C. E. Castillo ◽  
A. Katz ◽  
M. K. Spencer ◽  
Z. Yan ◽  
B. L. Nyomba
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Glycogen Synthase ◽  
Fat Free Mass ◽  
Whole Body ◽  
Glucose Disposal ◽  
Glycolytic Flux ◽  
Quadriceps Femoris Muscle ◽  
Before And After ◽  
Femoris Muscle

uglycemic (approximately 5.5 mM) hyperinsulinemic (60 mU.m-2.min-1) clamps were performed for 2 h after a 10-h fast and after a prolonged (72-h) fast. Biopsies were obtained from the quadriceps femoris muscle before and after each clamp. The rate of whole body glucose disposal was approximately 50% lower during the clamp after the 72-h fast (P less than or equal to 0.001). The increase in carbohydrate (CHO) oxidation (which is proportional to glycolysis) during the clamp after the 10-h fast (to 13.8 +/- 1.5 mumol.kg fat free mass-1.min-1) was completely abolished during the clamp after the 72-h fast (1.7 +/- 0.6; P less than or equal to 0.001). During the clamp after the 10-h fast, postphosphofructokinase (PFK) intermediates and malate in muscle increased, whereas glutamate decreased (P less than or equal to 0.05-0.001 vs. basal) and citrate did not change. During the clamp after the 72-h fast, there were no significant changes in post-PFK intermediates or glutamate (P greater than 0.05 vs. basal), but there was a decrease in citrate (P less than or equal to 0.01 vs. basal). Euglycemic hyperinsulinemia increased glycogen synthase fractional activity in muscle under both conditions but to a greater extent after the 72-h fast (P less than or equal to 0.01). It is concluded that insulin (after 10-h fast) increases glycolytic flux and the content of malate in muscle, which is probably due to increased anaplerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged moderate-intensity aerobic exercise does not alter apoptotic signaling and DNA fragmentation in human skeletal muscle

2010 ◽  
Vol 298 (3) ◽  
pp. E534-E547 ◽  
Author(s):  
Joe Quadrilatero ◽  
Eric Bombardier ◽  
Sarah M. Norris ◽  
Jason L. Talanian ◽  
Matthew S. Palmer ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Aerobic Exercise ◽  
Dna Fragmentation ◽  
Human Skeletal Muscle ◽  
Proteolytic Enzymes ◽  
Whole Body ◽  
Moderate Intensity ◽  
Type I ◽  
Apoptotic Signaling ◽  
Protein Levels

Apoptosis in skeletal muscle plays an important role in age- and disease-related tissue dysfunction. Physical activity can influence apoptotic signaling; however, this process has not been well studied in human skeletal muscle. The purpose of this study was to perform a comprehensive analysis of apoptosis-related proteins/enzymes, DNA fragmentation, and oxidative stress in skeletal muscle of humans during an acute bout of prolonged moderate-intensity exercise. Eight healthy, recreationally active individuals (age 20.8 ± 0.5 yr, V̇o2peak 51.2 ± 0.9 ml · kg−1 · min−1, BMI 21.5 ± 0.8 kg/m2) exercised on a cycle ergometer at ∼60% V̇o2peak for 2 h. Muscle biopsies were obtained at rest as well as at 60 and 120 min of exercise. Although exercise was associated with a significant whole body and muscle metabolic response, there were no significant changes in the content of antiapoptotic (ARC, Bcl-2, Hsp70, XIAP) and proapoptotic (AIF, Bax, Smac) proteins, activity of proteolytic enzymes (caspase-3, caspase-8, caspase-9), DNA fragmentation, or TUNEL-positive nuclei in skeletal muscle. Furthermore, the protein levels of several antioxidant enzymes (catalase, CuZnSOD, MnSOD), concentrations of GSH and GSSG, and degree of ROS generation in skeletal muscle were not altered by exercise. Fiber type-specific analysis also revealed that ARC ( P < 0.001) and Hsp70 ( P < 0.05) protein were significantly higher in type I compared with type IIA and type IIAX/X fibers; however, protein levels were not affected by exercise. These findings suggest that a single bout of prolonged moderate-intensity aerobic exercise is not sufficient to alter apoptotic signaling in skeletal muscle of healthy humans.

Changes in Whole-Body Oxygen Consumption and Skeletal Muscle Mitochondria During Linezolid-Induced Lactic Acidosis

2016 ◽  
Vol 44 (7) ◽  
pp. e579-e582 ◽  
Author(s):  
Alessandro Protti ◽  
Dario Ronchi ◽  
Gabriele Bassi ◽  
Francesco Fortunato ◽  
Andreina Bordoni ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Lactic Acidosis ◽  
Whole Body ◽  
Muscle Mitochondria ◽  
Skeletal Muscle Mitochondria

Contribution of BAT and skeletal muscle to thermogenesis induced by ephedrine in man

1985 ◽  
Vol 248 (5) ◽  
pp. E507-E515 ◽  
Author(s):  
A. Astrup ◽  
J. Bulow ◽  
J. Madsen ◽  
N. J. Christensen
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Adipose Tissue ◽  
Oxygen Consumption ◽  
Local Temperature ◽  
Whole Body ◽  
Tissue Blood Flow ◽  
Muscle Oxygen ◽  
Brown Adipose ◽  
Muscle Oxygen Consumption

This investigation was performed to examine the role of brown adipose tissue (BAT) in thermogenesis induced by ephedrine in man. Light microscopy of biopsies from necropsy cases showed BAT to occur most frequently in the perirenal fat. Perirenal BAT thermogenesis was investigated in five lean men before and during stimulation with 1 mg ephedrine orally X kg body wt-1. Perirenal BAT thermogenesis was assessed by continuous measurements of local temperature and blood flow with the 133xenon clearance method. In the same study the effect of ephedrine on skeletal muscle oxygen consumption was estimated by measurements of leg blood flow and arteriovenous oxygen difference. The perirenal adipose tissue blood flow increased approximately twofold, whereas the local temperature increased approximately 0.1 degrees C on an average. Assuming that man possesses 700 g of BAT with a similar thermogenic capacity, this tissue contributed only 10 ml X min-1 to the 40 ml X min-1 increase in oxygen consumption in the subject whose perirenal BAT showed the most pronounced response to ephedrine. The leg oxygen consumption increased on an average 60% after ephedrine. By extrapolation of this value to whole body skeletal muscle, approximately 50% of the increase in oxygen consumption induced by ephedrine may take place in skeletal muscle. It is concluded that skeletal muscle is a tissue of importance with respect to the thermogenic effect of sympathomimetics in man, whereas the results do not support a major role for perirenal BAT.

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