scholarly journals Myostatin Inhibition-Induced Increase in Muscle Mass and Strength Was Amplified by Resistance Exercise Training, and Dietary Essential Amino Acids Improved Muscle Quality in Mice

Nutrients ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 1508
Author(s):  
Jiwoong Jang ◽  
Sanghee Park ◽  
Yeongmin Kim ◽  
Jiyeon Jung ◽  
Jinseok Lee ◽  
...  
Keyword(s):  
Amino Acids ◽  
Muscle Mass ◽  
Mitochondrial Biogenesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Essential Amino Acids ◽  
Muscle Quality ◽  
Resistance Exercise Training ◽  
Muscle Protein Turnover ◽  
Myostatin Inhibition

It has been frequently reported that myostatin inhibition increases muscle mass, but decreases muscle quality (i.e., strength/muscle mass). Resistance exercise training (RT) and essential amino acids (EAAs) are potent anabolic stimuli that synergistically increase muscle mass through changes in muscle protein turnover. In addition, EAAs are known to stimulate mitochondrial biogenesis. We have investigated if RT amplifies the anabolic potential of myostatin inhibition while EAAs enhance muscle quality through stimulations of mitochondrial biogenesis and/or muscle protein turnover. Mice were assigned into ACV (myostatin inhibitor), ACV+EAA, ACV+RT, ACV+EAA +RT, or control (CON) over 4 weeks. RT, but not EAA, increased muscle mass above ACV. Despite differences in muscle mass gain, myofibrillar protein synthesis was stimulated similarly in all vs. CON, suggesting a role for changes in protein breakdown in muscle mass gains. There were increases in MyoD expression but decreases in Atrogin-1/MAFbx expression in ACV+EAA, ACV+RT, and ACV+EAA+RT vs. CON. EAA increased muscle quality (e.g., grip strength and maximal carrying load) without corresponding changes in markers of mitochondrial biogenesis and neuromuscular junction stability. In conclusion, RT amplifies muscle mass and strength through changes in muscle protein turnover in conjunction with changes in implicated signaling, while EAAs enhance muscle quality through unknown mechanisms.

scholarly journals Unaffected Arm Muscle Hypercatabolism in Dysphagic Subacute Stroke Patients: The Effects of Essential Amino Acid Supplementation

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Roberto Aquilani ◽  
Mirella Boselli ◽  
Giuseppe D’Antona ◽  
Paola Baiardi ◽  
Federica Boschi ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Essential Amino Acids ◽  
Amino Acid Supplementation ◽  
Stroke Patients ◽  
Unaffected Side ◽  
Stroke Population ◽  
Subacute Stroke

Alterations in muscle protein turnover of the unaffected side of stroke patients could contribute to physical disability. We investigated whether hypercatabolic activity occurred in unaffected arm muscle and whether supplemented essential amino acids (EAAs) could limit muscle hypercatabolism (MH). Thirty-eight dysphagic subacute stroke subjects (<3 months after acute event) (29 males + 9 females; 69.7 ± 11.4 yrs) were enrolled and randomized to receive 8 g/day EAAs (n= 19; EAA group) or isocaloric placebo (maltodextrin;n= 19, Plac group). Before randomization, all patients had their arterial (A) and venous (V) amino acids measured and muscle (A − V) differences calculated in the unaffected arm. Eight matched and healthy subjects served as controls. When compared to healthy controls, the entire stroke population showed significant muscle release (= negative value A − V) of the amino acid phenylalanine (phenyl-) indicating a prevalence of MH. Moreover, randomized EAA and Plac groups had similar rates of MH. After 38 days from the start of the protocol, the EAA group but not the Plac group had MH converted to balanced protein turnover or anabolic activity. We concluded that muscle protein metabolism of the unaffected arm of dysphagic subacute stroke individuals could be characterized by MH which can be corrected by supplemented EAAs.

scholarly journals Acute Effects of Peritoneal Dialysis with Dialysates Containing Dextrose or Dextrose and Amino Acids on Muscle Protein Turnover in Patients with Chronic Renal Failure

2001 ◽  
Vol 12 (3) ◽  
pp. 557-567
Author(s):  
GIACOMO GARIBOTTO ◽  
ANTONELLA SOFIA ◽  
ALBERTO CANEPA ◽  
STEFANO SAFFIOTI ◽  
PAOLO SACCO ◽  
...  
Keyword(s):  
Amino Acids ◽  
Peritoneal Dialysis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Cumulative Effect ◽  
Insulin Levels ◽  
Muscle Protein Turnover ◽  
Combined Use ◽  
High Insulin

Abstract. Whether changes in substrate and insulin levels that occur during peritoneal dialysis (PD) have effects on muscle protein dynamics was evaluated by studying muscle protein synthesis (PS), breakdown (PB), and net protein balance (NB) by the forearm perfusion method associated with the kinetics of 3H-phenylalanine in acute, crossover studies in which PD patients served as their own controls. Studies were performed (1) in the basal state and during PD with dialysates that contained dextrose alone in different concentrations (protocol 1: eight patients), (2) during PD with dialysates that contained dextrose alone or dextrose and amino acids (AA) (protocol 2: five patients), and (3) in time controls (five patients). PD with dextrose alone induced (1) a two- to threefold increase in insulin, as well as a 20 to 25% decrease in AA, mainly BCAA, levels; (2) an insulin-related decline (-18%) in forearm PB (P<0.002); (3) a 20% decrease in muscle PS (P<0.04), which was related to arterial BCAA and K+ (P<0.02 to 0.05); (4) a persistent negative NB; and (5) a decrease in the efficiency of muscle protein turnover, expressed as the ratio NB/PB. PD with dextrose+AA versus PD with dextrose induced (1) similarly high insulin levels but with a significant increase in total arterial AA (+30 to 110%), mainly valine; (2) a reduced release of AA from muscle (P<0.05); and (3) a decrease in the negative NB observed during PD with dextrose, owing to an increase (approximately 20%) in muscle PS, without any further effect on muscle PB. This study indicates that in PD patients in the fasting state, the moderate hyperinsulinemia that occurs during PD with dextrose alone causes an antiproteolytic action that is obscured by a parallel decrease in AA availability for PS. Conversely, the combined use of dextrose and AA results in a cumulative effect, because of the suppression of endogenous muscle PB (induced by insulin) and the stimulation of muscle PS (induced by AA availability). The hypothesis, therefore, is that in patients who are treated with PD, when fasting or when nutrient intake is reduced, muscle mass could be maintained better by the combined use of dextrose and AA.

Model to assess muscle protein turnover: domain of validity using amino acyl-tRNA vs. surrogate measures of precursor pool

2003 ◽  
Vol 285 (5) ◽  
pp. E1142-E1149 ◽  
Author(s):  
Gianna Toffolo ◽  
Robert Albright ◽  
Michael Joyner ◽  
Niki Dietz ◽  
Claudio Cobelli ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Compartment Model ◽  
Tissue Fluid ◽  
Protein Breakdown ◽  
Muscle Protein Turnover ◽  
Three Compartment Model ◽  
Surrogate Measures ◽  
Domain Of Validity

Current models to measure protein turnover across muscle bed are based on many surrogate measures of amino acyl-tRNA. We measured muscle protein turnover based on tracer-to-tracee ratios of the stable isotopes of leucine, phenylalanine, and ketoisocaproate (KIC) in artery and vein and muscle amino acyl-tRNA and muscle tissue fluid (TF) in 26 healthy subjects. A three-compartment model calculation based on arteriovenous and tRNA measurements was first performed and its domain of validity assessed. The results were then compared with those using simpler approaches based on surrogate measures of tRNA such as those of TF and KIC and a one-compartment model based on arteriovenous amino acids. In 96% of cases, the model using tRNA was applicable, but only in a lower percentage of cases were the results using surrogate measures applicable. Protein breakdown, protein synthesis, and shunting of amino acids from artery to vein were consistently underestimated, and fluxes of amino acid from artery to intracellular compartment and from intracellular compartment to vein were overestimated, when surrogate measures were used. The one-compartment model also underestimated protein breakdown and synthesis. Measurements using tissue fluid gave results closer to those based on tRNA. In conclusion, a three-compartment model using arteriovenous samples and amino acyl-tRNA provides measurements of muscle protein turnover of acceptable precision in 96% of cases. The precision was unacceptable in a substantial percentage of cases, and the accuracy of the estimation of protein fluxes was significantly affected when surrogate measures were used.

scholarly journals A Muscle-Centric Perspective on Intermittent Fasting: A Suboptimal Dietary Strategy for Supporting Muscle Protein Remodeling and Muscle Mass?

2021 ◽  
Vol 8 ◽  
Author(s):  
Eric Williamson ◽  
Daniel R. Moore
Keyword(s):  
Skeletal Muscle ◽  
Muscle Mass ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Insulin Response ◽  
Intermittent Fasting ◽  
Muscle Protein Turnover ◽  
Healthy Humans ◽  
Dietary Strategy

Muscle protein is constantly “turning over” through the breakdown of old/damaged proteins and the resynthesis of new functional proteins, the algebraic difference determining net muscle gain, maintenance, or loss. This turnover, which is sensitive to the nutritional environment, ultimately determines the mass, quality, and health of skeletal muscle over time. Intermittent fasting has become a topic of interest in the health community as an avenue to improve health and body composition primarily via caloric deficiency as well as enhanced lipolysis and fat oxidation secondary to attenuated daily insulin response. However, this approach belies the established anti-catabolic effect of insulin on skeletal muscle. More importantly, muscle protein synthesis, which is the primary regulated turnover variable in healthy humans, is stimulated by the consumption of dietary amino acids, a process that is saturated at a moderate protein intake. While limited research has explored the effect of intermittent fasting on muscle-related outcomes, we propose that infrequent meal feeding and periods of prolonged fasting characteristic of models of intermittent fasting may be counter-productive to optimizing muscle protein turnover and net muscle protein balance. The present commentary will discuss the regulation of muscle protein turnover across fasted and fed cycles and contrast it with studies exploring how dietary manipulation alters the partitioning of fat and lean body mass. It is our position that intermittent fasting likely represents a suboptimal dietary approach to remodel skeletal muscle, which could impact the ability to maintain or enhance muscle mass and quality, especially during periods of reduced energy availability.

Muscle Protein Turnover and the Molecular Regulation of Muscle Mass during Hypoxia

2017 ◽  
Vol 49 (7) ◽  
pp. 1340-1350 ◽  
Author(s):  
STEFAN M. PASIAKOS ◽  
CLAIRE E. BERRYMAN ◽  
CHRISTOPHER T. CARRIGAN ◽  
ANDREW J. YOUNG ◽  
JOHN W. CARBONE
Keyword(s):  
Muscle Mass ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Molecular Regulation ◽  
Muscle Protein Turnover

Skeletal and cardiac muscle protein turnover during cold acclimation in young rats

2000 ◽  
Vol 278 (3) ◽  
pp. R705-R711 ◽  
Author(s):  
T. A. McAllister ◽  
J. R. Thompson ◽  
S. E. Samuels
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Cold Acclimation ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Turnover ◽  
Protein Mass ◽  
The Absolute

The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5°C (cold) or 25°C (control). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. Protein mass by day 20 was ∼28% lower in skeletal muscle (gastrocnemius and soleus) and ∼24% higher in heart in cold compared with control rats ( P < 0.05). In skeletal muscle, the fractional rates of protein synthesis ( k syn) and degradation ( k deg) were not significantly different between cold and control rats, although k syn was lower (approximately −26%) in cold rats on day 5; consequent to the lower protein mass, the absolute rates of protein synthesis (approximately −21%; P < 0.05) and degradation (approximately −13%; P < 0.1) were lower in cold compared with control rats. In heart, overall, k syn(approximately +12%; P < 0.1) and k deg(approximately +22%; P < 0.05) were higher in cold compared with control rats; consequently, the absolute rates of synthesis (approximately +44%) and degradation (approximately +54%) were higher in cold compared with control rats ( P < 0.05). Plasma triiodothyronine concentration was higher ( P < 0.05) in cold compared with control rats. These data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover. In heart, unlike skeletal muscle, rates of protein turnover did not appear to immediately return to normal as increased rates of protein turnover were observed beyond day 5. These data also indicate that increased rates of protein turnover in skeletal muscle are unlikely to contribute to increased metabolic heat production during cold acclimation.

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