scholarly journals Comparisons of urinary creatinine, skeletal muscle mass, and indices of muscle protein catabolism in rats fed ad libitum, with restricted food intake, and deprived of food.

1989 ◽  
Vol 35 (3) ◽  
pp. 199-209 ◽  
Author(s):  
Toru RIKIMARU ◽  
Tomoko OOZEKI ◽  
Mineko ICHIKAWA ◽  
Hidemichi EBISAWA ◽  
Yoshiaki FUJITA
Keyword(s):  
Skeletal Muscle ◽  
Food Intake ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Muscle Protein ◽  
Protein Catabolism ◽  
Urinary Creatinine ◽  
Ad Libitum ◽  
Restricted Food Intake

Aging, exercise, and muscle protein metabolism

2009 ◽  
Vol 106 (6) ◽  
pp. 2040-2048 ◽  
Author(s):  
René Koopman ◽  
Luc J. C. van Loon
Keyword(s):  
Physical Activity ◽  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Food Intake ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
The Elderly ◽  
Age Related

Aging is accompanied by a progressive loss of skeletal muscle mass and strength, leading to the loss of functional capacity and an increased risk of developing chronic metabolic disease. The age-related loss of skeletal muscle mass is attributed to a disruption in the regulation of skeletal muscle protein turnover, resulting in an imbalance between muscle protein synthesis and degradation. As basal (fasting) muscle protein synthesis rates do not seem to differ substantially between the young and elderly, many research groups have started to focus on the muscle protein synthetic response to the main anabolic stimuli, i.e., food intake and physical activity. Recent studies suggest that the muscle protein synthetic response to food intake is blunted in the elderly. The latter is now believed to represent a key factor responsible for the age-related decline in skeletal muscle mass. Physical activity and/or exercise stimulate postexercise muscle protein accretion in both the young and elderly. However, the latter largely depends on the timed administration of amino acids and/or protein before, during, and/or after exercise. Prolonged resistance type exercise training represents an effective therapeutic strategy to augment skeletal muscle mass and improve functional performance in the elderly. The latter shows that the ability of the muscle protein synthetic machinery to respond to anabolic stimuli is preserved up to very old age. Research is warranted to elucidate the interaction between nutrition, exercise, and the skeletal muscle adaptive response. The latter is needed to define more effective strategies that will maximize the therapeutic benefits of lifestyle intervention in the elderly.

scholarly journals Higher skeletal muscle protein synthesis and lower breakdown after chemotherapy in cachectic mice

2001 ◽  
Vol 281 (1) ◽  
pp. R133-R139 ◽  
Author(s):  
S. E. Samuels ◽  
A. L. Knowles ◽  
T. Tilignac ◽  
E. Debiton ◽  
J. C. Madelmont ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Cancer Cachexia ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Human Condition ◽  
Skeletal Muscle Protein ◽  
Tumor Bearing

The influence of cancer cachexia and chemotherapy and subsequent recovery of skeletal muscle protein mass and turnover was investigated in mice. Cancer cachexia was induced using colon 26 adenocarcinoma, which is characteristic of the human condition, and can be cured with 100% efficacy using an experimental nitrosourea, cystemustine (C6H12CIN3O4S). Reduced food intake was not a factor in these studies. Three days after cachexia began, healthy and tumor-bearing mice were given a single intraperitoneal injection of cystemustine (20 mg/kg). Skeletal muscle mass in tumor-bearing mice was 41% lower ( P < 0.05) than in healthy mice 2 wk after cachexia began. Skeletal muscle wasting was mediated initially by decreased protein synthesis (−38%; P < 0.05) and increased degradation (+131%; P < 0.05); later wasting resulted solely from decreased synthesis (∼−54 to −69%; P < 0.05). Acute cytotoxicity of chemotherapy did not appear to have an important effect on skeletal muscle protein metabolism in either healthy or tumor-bearing mice. Recovery began 2 days after treatment; skeletal muscle mass was only 11% lower than in healthy mice 11 days after chemotherapy. Recovery of skeletal muscle mass was affected initially by decreased protein degradation (−80%; P < 0.05) and later by increased protein synthesis (+46 to +73%; P < 0.05) in cured compared with healthy mice. This study showed that skeletal muscle wasted from cancer cachexia and after chemotherapeutic treatment is able to generate a strong anabolic response by making powerful changes to protein synthesis and degradation.

scholarly journals Skeletal Muscle Recovery from Disuse Atrophy: Protein Turnover Signaling and Strategies for Accelerating Muscle Regrowth

2020 ◽  
Vol 21 (21) ◽  
pp. 7940
Author(s):  
Timur M. Mirzoev
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Mass ◽  
Mechanical Loading ◽  
Protein Turnover ◽  
Skeletal Muscle Mass ◽  
Molecular Mechanisms ◽  
Muscle Protein ◽  
Muscle Recovery ◽  
Mechanical Unloading

Skeletal muscle fibers have a unique capacity to adjust their metabolism and phenotype in response to alternations in mechanical loading. Indeed, chronic mechanical loading leads to an increase in skeletal muscle mass, while prolonged mechanical unloading results in a significant decrease in muscle mass (muscle atrophy). The maintenance of skeletal muscle mass is dependent on the balance between rates of muscle protein synthesis and breakdown. While molecular mechanisms regulating protein synthesis during mechanical unloading have been relatively well studied, signaling events implicated in protein turnover during skeletal muscle recovery from unloading are poorly defined. A better understanding of the molecular events that underpin muscle mass recovery following disuse-induced atrophy is of significant importance for both clinical and space medicine. This review focuses on the molecular mechanisms that may be involved in the activation of protein synthesis and subsequent restoration of muscle mass after a period of mechanical unloading. In addition, the efficiency of strategies proposed to improve muscle protein gain during recovery is also discussed.

scholarly journals Dietary protein and exercise training in ageing

2010 ◽  
Vol 70 (1) ◽  
pp. 104-113 ◽  
Author(s):  
René Koopman
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Exercise Training ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Human Subjects ◽  
The Elderly ◽  
Age Related

Ageing is accompanied by a progressive loss of skeletal muscle mass and strength, leading to the loss of functional capacity and an increased risk for developing chronic metabolic diseases such as diabetes. The age-related loss of skeletal muscle mass results from a chronic disruption in the balance between muscle protein synthesis and degradation. As basal muscle protein synthesis rates are likely not different between healthy young and elderly human subjects, it was proposed that muscles from older adults lack the ability to regulate the protein synthetic response to anabolic stimuli, such as food intake and physical activity. Indeed, the dose–response relationship between myofibrillar protein synthesis and the availability of essential amino acids and/or resistance exercise intensity is shifted down and to the right in elderly human subjects. This so-called ‘anabolic resistance’ represents a key factor responsible for the age-related decline in skeletal muscle mass. Interestingly, long-term resistance exercise training is effective as a therapeutic intervention to augment skeletal muscle mass, and improves functional performance in the elderly. The consumption of different types of proteins, i.e. protein hydrolysates, can have different stimulatory effects on muscle protein synthesis in the elderly, which may be due to their higher rate of digestion and absorption. Current research aims to elucidate the interactions between nutrition, exercise and the skeletal muscle adaptive response that will define more effective strategies to maximise the therapeutic benefits of lifestyle interventions in the elderly.

The mechanistic and ergogenic effects of phosphatidic acid in skeletal muscle

2015 ◽  
Vol 40 (12) ◽  
pp. 1233-1241 ◽  
Author(s):  
Brandon James Shad ◽  
Benoit Smeuninx ◽  
Philip James Atherton ◽  
Leigh Breen
Keyword(s):  
Skeletal Muscle ◽  
Phosphatidic Acid ◽  
Resistance Exercise ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Food Sources ◽  
Whole Body ◽  
Skeletal Muscle Protein

Skeletal muscle mass plays a vital role in locomotion, whole-body metabolic health, and is a positive predictor of longevity. It is well established the mammalian target of rapamycin (mTOR) is a central regulator of skeletal muscle protein turnover. The pursuit to find novel nutrient compounds or functional food sources that possess the ability to activate mTOR and promote skeletal muscle protein accretion has been on going. Over the last decade, a key role has been proposed for the phospholipid phosphatidic acid (PA) in mTOR activation. Mechanical load-induced (i.e., resistance exercise) intramuscular PA can directly bind to and activate mTOR. In addition, PA provided exogenously in cell culture heightens mTOR activity, albeit indirectly. Thus, endogenously generated PA and exogenous provision of PA appear to act through distinct mechanisms that converge on mTOR and, potentially, may amplify muscle protein synthesis. In support of this notion, limited evidence from humans suggests that resistance exercise training combined with oral supplemental PA enhances strength gains and muscle hypertrophy. However, the precise mechanisms underpinning the augmented muscle remodelling response with supplemental PA remain elusive. In this review, we will critically examine available evidence from cell cultures and animal and human experimental models to provide an overview of the mechanisms through which endogenous and exogenous PA may act to promote muscle anabolism, and discuss the potential for PA as a therapeutic tool to maintain or restore skeletal muscle mass in the context of ageing and disease.

scholarly journals Combined in vivo muscle mass, muscle protein synthesis and muscle protein breakdown measurement: a ‘Combined Oral Stable Isotope Assessment of Muscle (COSIAM)’ approach

GeroScience ◽  
2021 ◽  
Author(s):  
Jessica Cegielski ◽  
Daniel J. Wilkinson ◽  
Matthew S. Brook ◽  
Catherine Boereboom ◽  
Bethan E. Phillips ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Stable Isotope ◽  
Muscle Mass ◽  
Protein Turnover ◽  
Skeletal Muscle Mass ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Protein Breakdown ◽  
Muscle Protein Breakdown

AbstractOptimising approaches for measuring skeletal muscle mass and turnover that are widely applicable, minimally invasive and cost effective is crucial in furthering research into sarcopenia and cachexia. Traditional approaches for measurement of muscle protein turnover require infusion of expensive, sterile, isotopically labelled tracers which limits the applicability of these approaches in certain populations (e.g. clinical, frail elderly). To concurrently quantify skeletal muscle mass and muscle protein turnover i.e. muscle protein synthesis (MPS) and muscle protein breakdown (MPB), in elderly human volunteers using stable-isotope labelled tracers i.e. Methyl-[D3]-creatine (D3-Cr), deuterium oxide (D2O), and Methyl-[D3]-3-methylhistidine (D3-3MH), to measure muscle mass, MPS and MPB, respectively. We recruited 10 older males (71 ± 4 y, BMI: 25 ± 4 kg.m2, mean ± SD) into a 4-day study, with DXA and consumption of D2O and D3-Cr tracers on day 1. D3-3MH was consumed on day 3, 24 h prior to returning to the lab. From urine, saliva and blood samples, and a single muscle biopsy (vastus lateralis), we determined muscle mass, MPS and MPB. D3-Cr derived muscle mass was positively correlated to appendicular fat-free mass (AFFM) estimated by DXA (r = 0.69, P = 0.027). Rates of cumulative myofibrillar MPS over 3 days were 0.072%/h (95% CI, 0.064 to 0.081%/h). Whole-body MPB over 6 h was 0.052 (95% CI, 0.038 to 0.067). These rates were similar to previous literature. We demonstrate the potential for D3-Cr to be used alongside D2O and D3-3MH for concurrent measurement of muscle mass, MPS, and MPB using a minimally invasive design, applicable for clinical and frail populations.

scholarly journals In utero glucocorticoid exposure reduces fetal skeletal muscle mass in rats independent of effects on maternal nutrition

2012 ◽  
Vol 302 (10) ◽  
pp. R1143-R1152 ◽  
Author(s):  
Ganga Gokulakrishnan ◽  
Irma J. Estrada ◽  
Horacio A. Sosa ◽  
Marta L. Fiorotto
Keyword(s):  
Skeletal Muscle ◽  
Food Intake ◽  
Maternal Nutrition ◽  
Muscle Protein ◽  
Fetal Liver ◽  
Muscle Growth ◽  
Tyrosine Aminotransferase ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Ad Libitum

Maternal stress and undernutrition can occur together and expose the fetus to high glucocorticoid (GLC) levels during this vulnerable period. To determine the consequences of GLC exposure on fetal skeletal muscle independently of maternal food intake, groups of timed-pregnant Sprague-Dawley rats ( n = 7/group) were studied: ad libitum food intake (control, CON); ad libitum food intake with 1 mg dexamethasone/l drinking water from embryonic day (ED)13 to ED21 (DEX); pair-fed (PF) to DEX from ED13 to ED21. On ED22, dams were injected with [3H]phenylalanine for measurements of fetal leg muscle and diaphragm fractional protein synthesis rates (FSR). Fetal muscles were analyzed for protein and RNA contents, [3H]phenylalanine incorporation, and MuRF1 and atrogin-1 (MAFbx) mRNA expression. Fetal liver tyrosine aminotransferase (TAT) expression was quantified to assess fetal exposure to GLCs. DEX treatment reduced maternal food intake by 13% ( P < 0.001) and significantly reduced placental mass relative to CON and PF dams. Liver TAT expression was elevated only in DEX fetuses ( P < 0.01). DEX muscle protein masses were 56% and 70% than those of CON ( P < 0.01) and PF ( P < 0.05) fetuses, respectively; PF muscles were 80% of CON ( P < 0.01). Muscle FSR decreased by 35% in DEX fetuses ( P < 0.001) but were not different between PF and CON. Only atrogin-1 expression was increased in DEX fetus muscles. We conclude that high maternal GLC levels and inadequate maternal food intake impair fetal skeletal muscle growth, most likely through different mechanisms. When combined, the effects of decreased maternal intake and maternal GLC intake on fetal muscle growth are additive.

Physiologic and molecular bases of muscle hypertrophy and atrophy: impact of resistance exercise on human skeletal muscle (protein and exercise dose effects)This paper is one of a selection of papers published in this Special Issue, entitled 14th International Biochemistry of Exercise Conference – Muscles as Molecular and Metabolic Machines, and has undergone the Journal’s usual peer review process.

2009 ◽  
Vol 34 (3) ◽  
pp. 403-410 ◽  
Author(s):  
Stuart M. Phillips
Keyword(s):  
Skeletal Muscle ◽  
Resistance Exercise ◽  
Muscle Mass ◽  
Skeletal Muscle Mass ◽  
Muscle Protein ◽  
Peer Review Process ◽  
Muscle Protein Synthesis ◽  
Common Finding ◽  
Disuse Atrophy ◽  
Age Related

Normally, skeletal muscle mass is unchanged, beyond periods of growth, but it begins to decline in the fourth or fifth decade of life. The mass of skeletal muscle is maintained by ingestion of protein-containing meals. With feeding, muscle protein synthesis (MPS) is stimulated and a small suppression of muscle protein breakdown (MPB) occurs, such that protein balance becomes positive (MPS > MPB). As the postprandial period subsides and a transition toward fasting occurs, the balance of muscle protein turnover becomes negative again (MPB > MPS). Thus, during maintenance of skeletal muscle mass, the long-term net result is that MPS is balanced by MPB. Acutely, however, it is of interest to determine what regulates feeding-induced increases in MPS, since it appears that, in a number of scenarios (for example aging, disuse, and wasting diseases), a suppression of MPS in response to feeding is a common finding. In fact, recent findings point to the fact that loss of skeletal muscle mass with disuse and aging is due not chronic changes in MPS or MPB, but to a blunted feeding-induced rise in MPS. Resistance exercise is a potent stimulator of MPS and appears to synergistically enhance the gains stimulated by feeding. As such, resistance exercise is an important countermeasure to disuse atrophy and to age-related declines in skeletal muscle mass. What is less well understood is how the intensity and volume of the resistance exercise stimulus is sufficient to result in rises in MPS. Recent advances in this area are discussed here, with a focus on human in vivo data.

Translational Control of Protein Synthesis: Implications for Understanding Changes in Skeletal Muscle Mass

2001 ◽  
Vol 11 (s1) ◽  
pp. S143-S149 ◽  
Author(s):  
Leonard S. Jefferson ◽  
Scot R. Kimball
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Mass ◽  
Translation Initiation ◽  
Translational Control ◽  
Skeletal Muscle Mass ◽  
Molecular Mechanisms ◽  
Muscle Protein ◽  
Ribosomal Subunit ◽  
Mrna Binding

Gain or loss of skeletal muscle mass is due largely to the establishment of an imbalance between rates of protein synthesis and degradation. A key determinant of the rate of protein synthesis is translation initiation, a process regulated in part through binding of initiator methionyl-tRNA (met-tRNAi) and messenger RNA (mRNA) to a 40S ribosomal subunit. Either the met-tRNAi or mRNA binding step can become limiting for protein synthesis. Furthermore, the mRNA binding step can modulate translation of specific mRNAs with or without changes in the overall rate of protein synthesis. This report highlights molecular mechanisms involved in mediating control of the mRNA binding step in translation initiation. Particular attention is given to the effect of exercise on this step and to how the branched-chain amino acid leucine stimulates muscle protein synthesis after exercise. Potential mechanisms for exercise induced increase in muscle mass are discussed.

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