scholarly journals Soluble RANKL exaggerates hindlimb suspension‐induced osteopenia but not muscle protein balance

2020 ◽  
Author(s):  
Toni L. Speacht ◽  
Charles H. Lang ◽  
Henry J. Donahue
Keyword(s):  
Muscle Protein ◽  
Hindlimb Suspension ◽  
Protein Balance

scholarly journals Skeletal muscle protein balance in mTOR heterozygous mice in response to endotoxin and leucine

2010 ◽  
Vol 24 (S1) ◽  
Author(s):  
Charles H. Lang ◽  
Robert A. Frost ◽  
Sarah K. Bronson ◽  
Christopher J. Lynch ◽  
Thomas C. Vary
Keyword(s):  
Skeletal Muscle ◽  
Muscle Protein ◽  
Skeletal Muscle Protein ◽  
Protein Balance

A Clinically Relevant Decrease in Contractile Force Differentially Regulates Control of Glucocorticoid Receptor Translocation in Mouse Skeletal Muscle

2021 ◽  
Author(s):  
Kirsten R. Dunlap ◽  
Jennifer L. Steiner ◽  
Michael L. Rossetti ◽  
Scot R. Kimball ◽  
Bradley S. Gordon
Keyword(s):  
Protein Synthesis ◽  
Glucocorticoid Receptor ◽  
Resistance Exercise ◽  
Muscle Atrophy ◽  
Nuclear Translocation ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Contractile Force ◽  
Force Generation ◽  
Protein Balance

Muscle atrophy decreases physical function and overall health. Increased glucocorticoid production and/or use of prescription glucocorticoids can significantly induce muscle atrophy by activating the glucocorticoid receptor thereby transcribing genes that shift protein balance in favor of net protein degradation. While mechanical overload can blunt glucocorticoid-induced atrophy in young muscle, those affected by glucocorticoids generally have impaired force generation. It is unknown whether contractile force alters the ability of resistance exercise to mitigate glucocorticoid receptor translocation and induce a desirable shift in protein balance when glucocorticoids are elevated. In the present study, mice were subjected to a single bout of unilateral, electrically induced muscle contractions by stimulating the sciatic nerve at 100 Hz or 50 Hz frequencies to elicit high force or moderate force contractions of the tibialis anterior, respectively. Dexamethasone was used to activate the glucocorticoid receptor. Dexamethasone increased glucocorticoid signaling, including nuclear translocation of the receptor, but this was mitigated only by high force contractions. The ability of high force contractions to mitigate glucocorticoid receptor translocation coincided with a contraction-mediated increase in muscle protein synthesis, which did not occur in the dexamethasone treated mice subjected to moderate force contractions. Though moderate force contractions failed to increase protein synthesis following dexamethasone treatment, both high and moderate force contractions blunted the glucocorticoid-mediated increase in LC3 II:I marker of autophagy. Thus, these data show that force generation is important for the ability of resistance exercise to mitigate glucocorticoid receptor translocation and promote a desirable shift in protein balance when glucocorticoids are elevated.

scholarly journals Optimization of an in vitro bioassay to monitor growth and formation of myotubes in real time

2016 ◽  
Vol 36 (3) ◽  
Author(s):  
Sylvia M. Murphy ◽  
Maeve Kiely ◽  
Philip M. Jakeman ◽  
Patrick A. Kiely ◽  
Brian P. Carson
Keyword(s):  
Skeletal Muscle ◽  
Real Time ◽  
Muscle Protein ◽  
In Vitro Bioassay ◽  
Protein Balance ◽  
Proliferation And Differentiation

In the present paper we have developed, described and validated an in vitro bioassay to monitor skeletal muscle proliferation and differentiation. We have also demonstrated the use of this assay to evaluate factors which may affect muscle protein balance.

Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects

2005 ◽  
Vol 288 (4) ◽  
pp. E645-E653 ◽  
Author(s):  
René Koopman ◽  
Anton J. M. Wagenmakers ◽  
Ralph J. F. Manders ◽  
Antoine H. G. Zorenc ◽  
Joan M. G. Senden ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Whole Body ◽  
Vastus Lateralis Muscle ◽  
Protein Balance ◽  
Body Protein ◽  
Breakdown Rates ◽  
Postexercise Recovery ◽  
Male Subjects

The present study was designed to determine postexercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or free leucine. Eight male subjects were randomly assigned to three trials in which they consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 min of resistance exercise. A primed, continuous infusion of l-[ ring-13C6]phenylalanine was applied, with blood samples and muscle biopsies collected to assess fractional synthetic rate (FSR) in the vastus lateralis muscle as well as whole body protein turnover during 6 h of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu compared with the CHO and CHO+PRO trials (+240 ± 19% and +77 ± 11%, respectively, P < 0.05). Whole body protein breakdown rates were lower, and whole body protein synthesis rates were higher, in the CHO+PRO and CHO+PRO+Leu trials compared with the CHO trial ( P < 0.05). Addition of leucine in the CHO+PRO+Leu trial resulted in a lower protein oxidation rate compared with the CHO+PRO trial. Protein balance was negative during recovery in the CHO trial but positive in the CHO+PRO and CHO+PRO+Leu trials. In the CHO+PRO+Leu trial, whole body net protein balance was significantly greater compared with values observed in the CHO+PRO and CHO trials ( P < 0.05). Mixed muscle FSR, measured over a 6-h period of postexercise recovery, was significantly greater in the CHO+PRO+Leu trial compared with the CHO trial (0.095 ± 0.006 vs. 0.061 ± 0.008%/h, respectively, P < 0.05), with intermediate values observed in the CHO+PRO trial (0.0820 ± 0.0104%/h). We conclude that coingestion of protein and leucine stimulates muscle protein synthesis and optimizes whole body protein balance compared with the intake of carbohydrate only.

scholarly journals Reduced skeletal muscle protein balance in paediatric Crohn's disease

2020 ◽  
Vol 39 (4) ◽  
pp. 1250-1257 ◽  
Author(s):  
Amanda Davies ◽  
Aline Nixon ◽  
Rafeeq Muhammed ◽  
Kostas Tsintzas ◽  
Sian Kirkham ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Muscle Protein ◽  
Skeletal Muscle Protein ◽  
Protein Balance ◽  
Paediatric Crohn’S Disease

scholarly journals Increased net muscle protein balance in response to simultaneous and separate ingestion of carbohydrate and essential amino acids following resistance exercise

2014 ◽  
Vol 39 (3) ◽  
pp. 329-339 ◽  
Author(s):  
Oliver C. Witard ◽  
Tara L. Cocke ◽  
Arny A. Ferrando ◽  
Robert R. Wolfe ◽  
Kevin D. Tipton
Keyword(s):  
Amino Acids ◽  
Resistance Exercise ◽  
Acute Exercise ◽  
Muscle Protein ◽  
Exercise Bout ◽  
Essential Amino Acids ◽  
Delayed Response ◽  
Protein Balance ◽  
Post Exercise ◽  
Exercise Muscle

Relative to essential amino acids (EAAs), carbohydrate (CHO) ingestion stimulates a delayed response of net muscle protein balance (NBAL). We investigated if staggered ingestion of CHO and EAA would superimpose the response of NBAL following resistance exercise, thus resulting in maximal anabolic stimulation. Eight recreationally trained subjects completed 2 trials: combined (COMB — drink 1, CHO+EAA; drink 2, placebo) and separated (SEP — drink 1, CHO; drink 2, EAA) post-exercise ingestion of CHO and EAA. Drink 1 was administered 1 h following an acute exercise bout and was followed 1 h later by drink 2. A primed, continuous infusion of l-[ring-13C6]-phenylalanine was combined with femoral arteriovenous sampling and muscle biopsies for the determination of muscle protein kinetics. Arterial amino acid concentrations increased following ingestion of EAA in both conditions. No difference between conditions was observed for phenylalanine delivery to the leg (COMB: 167 ± 23 μmol·min−1·(100 mL leg vol)−1 × 6 h; SEP: 167 ± 21 μmol·min−1·(100 mL leg vol)−1 × 6 h, P > 0.05). In the first hour following ingestion of the drink containing EAA, phenylalanine uptake was 50% greater for the SEP trial than the COMB trial. However, phenylalanine uptake was similar for COMB (110 ± 19 mg) and SEP (117 ± 24 mg) over the 6 h period. These data suggest that whereas separation of CHO and EAA ingestion following exercise may have a transient physiological impact on NBAL, this response is not reflected over a longer period. Thus, separation of CHO and EAA ingestion is unnecessary to optimize post-exercise muscle protein metabolism.

Free Amino Acid Pool and Muscle Protein Balance after Resistance Exercise

2003 ◽  
Vol 35 (5) ◽  
pp. 784-792 ◽  
Author(s):  
HANNU T. PITK??NEN ◽  
TARJA NYK??NEN ◽  
JUHA KNUUTINEN ◽  
KAISA LAHTI ◽  
OLAVI KEIN??NEN ◽  
...  
Keyword(s):  
Amino Acid ◽  
Resistance Exercise ◽  
Free Amino Acid ◽  
Free Amino ◽  
Muscle Protein ◽  
Amino Acid Pool ◽  
Protein Balance ◽  
Free Amino Acid Pool ◽  
Acid Pool

scholarly journals Soluble RANKL exaggerates hindlimb suspension-induced osteopenia but not muscle protein balance

2020 ◽  
Author(s):  
Toni L. Speacht ◽  
Charles H. Lang ◽  
Henry J. Donahue
Keyword(s):  
Bone Loss ◽  
Muscle Protein ◽  
Plasma Concentrations ◽  
Bone Volume ◽  
Hindlimb Suspension ◽  
Muscle Loss ◽  
Trabecular Thickness ◽  
Global Protein Synthesis ◽  
Receptor Activator ◽  
Muscle Protein Metabolism

ABSTRACTWe examined the hypothesis that exaggerating unloading-induced bone loss using a combination of hindlimb suspension (HLS) and exogenous injections of receptor activator of nuclear factor kappa-B ligand (RANKL) also exaggerates muscle loss. Forty, male C57Bl/6J mice (16 weeks) were subjected to HLS or normal ambulation (ground control, GC) for 14 days. Mice received 3 intraperitoneal injections of either human recombinant soluble RANKL or PBS as control (n=10/group) at 24 hour intervals starting on Day 1 of HLS. GC + RANKL and HLS mice exhibited similar decreases in trabecular bone volume and density in both proximal tibias and distal femurs. However, RANKL affected trabecular number, separation, and connectivity density, while HLS decreased trabecular thickness. The combination of RANKL and HLS exacerbated these changes. Similarly, GC + RANKL and HLS mice saw comparable decreases in cortical bone volume, thickness, and strength in femur midshafts, and combination treatment exacerbated these changes. Plasma concentrations of P1NP were increased in both groups receiving RANKL, while CTX concentrations were unchanged. HLS decreased gastrocnemius weight and was associated with a reduction in global protein synthesis, and no change in proteasome activity. This change was correlated with a decrease in S6K1 and S6 phosphorylation, but no change in 4E-BP1 phosphorylation. Injection of RANKL did not alter muscle protein metabolism in GC or HLS mice. Our results suggest that injection of soluble RANKL exacerbates unloading-induced bone loss, but not unloading-induced muscle loss. This implies a temporal disconnect between muscle and bone loss in response to unloading.

Muscle glutamine and the regulation of muscle protein balance in endotoxemia

1990 ◽  
Vol 9 (1) ◽  
pp. 34 ◽  
Author(s):  
D.J. Millward
Keyword(s):  
Muscle Protein ◽  
Protein Balance

Method for the determination of the arteriovenous muscle protein balance during non-steady-state blood and muscle amino acid concentrations

2005 ◽  
Vol 289 (6) ◽  
pp. E1064-E1070 ◽  
Author(s):  
Christos S. Katsanos ◽  
David L. Chinkes ◽  
Melinda Sheffield-Moore ◽  
Asle Aarsland ◽  
Hisamine Kobayashi ◽  
...  
Keyword(s):  
Steady State ◽  
Amino Acid ◽  
Muscle Protein ◽  
Volume Of Distribution ◽  
Protein Balance ◽  
Nonsteady State ◽  
Balance Technique ◽  
Amino Acid Concentrations ◽  
Rate Of Accumulation

We describe a method based on the traditional arteriovenous balance technique in conjunction with muscle biopsies for the determination of leg muscle protein balance during the nonsteady state in blood amino acid concentrations. Six young, healthy individuals were studied in the postabsorptive state (pre-Phe) and after a bolus ingestion of ∼0.5 g phenylalanine (post-Phe). Post-Phe free phenylalanine concentrations in blood and muscle increased ( P < 0.05), but the respective concentrations of the amino acid threonine did not change. The average post-Phe leg net balance (NB) for threonine decreased from basal ( P < 0.05), but that for phenylalanine did not change. A volume of distribution for free phenylalanine in the leg was calculated based on the leg lean mass and the relative muscle water content and used to estimate the rate of accumulation of free phenylalanine in the leg. When the post-Phe NB for phenylalanine was corrected for the rate of accumulation of free phenylalanine in the leg, the post-Phe NB for phenylalanine decreased from basal ( P < 0.05). This corrected value was not different ( P > 0.05) from the value predicted for the phenylalanine NB based on the pre- and post-Phe NB responses for threonine. We conclude that the protein NB in non-steady-state blood phenylalanine concentrations can be determined from the arteriovenous phenylalanine NB by accounting for changes in free phenylalanine within its volume of distribution.

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