Skeletal and heart muscle protein turnover during long-term exposure to high environmental temperatures in young rats

2000 ◽  
Vol 78 (7) ◽  
pp. 557-564 ◽  
Author(s):  
S E Samuels ◽  
T A McAllister ◽  
J R Thompson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Mass ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Control Group ◽  
Skeletal Muscle Protein ◽  
Protein Mass ◽  
Fractional Rate

A study was undertaken to determine the long-term effects of a hot environment on protein turnover in skeletal and cardiac muscles of young homeothermic animals. Three groups of 36 male 28 day old rats were housed at 35°C (hot group), 25°C (control group), or 25°C but pair-fed to the intake of the hot group (pair-fed group). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. By day 20, soleus and gastrocnemius (skeletal muscle) protein masses were 7 and 14% lower in the hot group and 31 and 21% lower in the pair-fed group compared with the control group (P < 0.05). The fractional rate of protein synthesis (ksyn) was on average 11% lower (P < 0.05) in the hot group compared with control rats and was not different from pair-fed rats. The fractional rate of skeletal muscle protein degradation (kdeg) in hot rats was slightly lower than in control rats; kdegwas on average 18% higher (P < 0.05) in the pair-fed group compared with the hot group and this difference appeared to be most prominent on day 5. In heart, by day 20, protein mass was 30% lower in the hot group and 40% lower in the pair-fed group compared with control rats (P < 0.05). ksynwas on average 19% lower (P < 0.05) in the hot group compared with the control group, but not different from pair-fed rats. In the heart there were no differences in kdegamong treatments. Plasma triiodothyronine (T3) concentration was lower in the hot group, but not in the pair-fed group, compared with controls. In conclusion, chronic exposure to hot environments was associated with lower skeletal and cardiac muscle mass and protein turnover; lower protein mass in this tissue was due to decreased ksyn; this is consistent with lower plasma T3concentrations. In pair-fed rats, ksynwas also reduced, but interestingly kdegwas not, resulting in a greater loss of skeletal muscle mass. These results suggest that heat exposure invokes physiological adaptations to preserve skeletal muscle mass despite decreased food intake. In the heart, loss of protein was a result of decreased ksyn, which can be primarily ascribed to lower food intake.Key words: protein synthesis, protein metabolism, acclimation, heat stress.

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.

scholarly journals The effect of protein depletion and repletion on muscle-protein turnover in the chick

1981 ◽  
Vol 194 (3) ◽  
pp. 811-819 ◽  
Author(s):  
M L MacDonald ◽  
R W Swick
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Control Diet ◽  
Breast Muscle ◽  
Synthesis Rate ◽  
Protein Depletion ◽  
Protein Mass ◽  
Fractional Rate

Rates of growth and protein turnover in the breast muscle of young chicks were measured in order to assess the roles of protein synthesis and degradation in the regulation of muscle mass. Rates of protein synthesis were measured in vivo by injecting a massive dose of L-[1-14C]valine, and rates of protein degradation were estimated as the difference between the synthesis rate and the growth rate of muscle protein. In chicks fed on a control diet for up to 7 weeks of age, the fractional rate of synthesis decreased from 1 to 2 weeks of age and then changed insignificantly from 2 to 7 weeks of age, whereas DNA activity was constant for 1 to 7 weeks. When 4-week-old chicks were fed on a protein-free diet for 17 days, the total amount of breast-muscle protein synthesized and degraded per day and the amount of protein synthesized per unit of DNA decreased. Protein was lost owing to a greater decrease in the rate of protein synthesis, as a result of the loss of RNA and a lowered RNA activity. When depleted chicks were re-fed the control diet, rapid growth was achieved by a doubling of the fractional synthesis rate by 2 days. Initially, this was a result of increased RNA activity; by 5 days, the RNA/DNA ratio also increased. There was no evidence of a decrease in the fractional degradation rate during re-feeding. These results indicate that dietary-protein depletion and repletion cause changes in breast-muscle protein mass primarily through changes in the rate of protein synthesis.

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 Anabolic Properties of Mixed Wheat-Legume Pasta Products in Old Rats: Impact on Whole-Body Protein Retention and Skeletal Muscle Protein Synthesis

Nutrients ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1596 ◽  
Author(s):  
Insaf Berrazaga ◽  
Jérôme Salles ◽  
Karima Laleg ◽  
Christelle Guillet ◽  
Véronique Patrac ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Mass ◽  
Protein Quality ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Milk Proteins ◽  
Skeletal Muscle Protein ◽  
Skeletal Muscle Protein Synthesis ◽  
Old Rats

The mechanisms that are responsible for sarcopenia are numerous, but the altered muscle protein anabolic response to food intake that appears with advancing age plays an important role. Dietary protein quality needs to be optimized to counter this phenomenon. Blending different plant proteins is expected to compensate for the lower anabolic capacity of plant-based when compared to animal-based protein sources. The objective of this work was to evaluate the nutritional value of pasta products that were made from a mix of wheat semolina and faba bean, lentil, or split pea flour, and to assess their effect on protein metabolism as compared to dietary milk proteins in old rats. Forty-three old rats have consumed for six weeks isoproteic and isocaloric diets containing wheat pasta enriched with 62% to 79% legume protein (depending on the type) or milk proteins, i.e., casein or soluble milk proteins (SMP). The protein digestibility of casein and SMP was 5% to 14% higher than legume-enriched pasta. The net protein utilization and skeletal muscle protein synthesis rate were equivalent either in rats fed legume-enriched pasta diets or those fed casein diet, but lower than in rats fed SMP diet. After legume-enriched pasta intake, muscle mass, and protein accretion were in the same range as in the casein and SMP groups. Mixed wheat-legume pasta could be a nutritional strategy for enhancing the protein content and improving the protein quality, i.e., amino acid profile, of this staple food that is more adequate for maintaining muscle mass, especially for older individuals.

scholarly journals Serum extracellular vesicle miR-203a-3p content is associated with skeletal muscle mass and protein turnover during disuse atrophy and regrowth

2020 ◽  
Vol 319 (2) ◽  
pp. C419-C431
Author(s):  
Douglas W. Van Pelt ◽  
Ivan J. Vechetti ◽  
Marcus M. Lawrence ◽  
Kathryn L. Van Pelt ◽  
Parth Patel ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Mass ◽  
Muscle Atrophy ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Weight Bearing ◽  
Mirna Content ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Small noncoding microRNAs (miRNAs) are important regulators of skeletal muscle size, and circulating miRNAs within extracellular vesicles (EVs) may contribute to atrophy and its associated systemic effects. The purpose of this study was to understand how muscle atrophy and regrowth alter in vivo serum EV miRNA content. We also associated changes in serum EV miRNA with protein synthesis, protein degradation, and miRNA within muscle, kidney, and liver. We subjected adult (10 mo) F344/BN rats to three conditions: weight bearing (WB), hindlimb suspension (HS) for 7 days to induce muscle atrophy, and HS for 7 days followed by 7 days of reloading (HSR). Microarray analysis of EV miRNA content showed that the overall changes in serum EV miRNA were predicted to target major anabolic, catabolic, and mechanosensitive pathways. MiR-203a-3p was the only miRNA demonstrating substantial differences in HS EVs compared with WB. There was a limited association of EV miRNA content to the corresponding miRNA content within the muscle, kidney, or liver. Stepwise linear regression demonstrated that EV miR-203a-3p was correlated with muscle mass and muscle protein synthesis and degradation across all conditions. Finally, EV miR-203a-3p expression was significantly decreased in human subjects who underwent unilateral lower limb suspension (ULLS) to induce muscle atrophy. Altogether, we show that serum EV miR-203a-3p expression is related to skeletal muscle protein turnover and atrophy. We suggest that serum EV miR-203a-3p content may be a useful biomarker and future work should investigate whether serum EV miR-203a-3p content is mechanistically linked 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 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.

Effect of glycogen availability on human skeletal muscle protein turnover during exercise and recovery

2010 ◽  
Vol 109 (2) ◽  
pp. 431-438 ◽  
Author(s):  
Krista R. Howarth ◽  
Stuart M. Phillips ◽  
Maureen J. MacDonald ◽  
Douglas Richards ◽  
Natalie A. Moreau ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Whole Body ◽  
Skeletal Muscle Protein ◽  
Protein Balance ◽  
Body Protein ◽  
Muscle Protein Turnover ◽  
Net Protein

We examined the effect of carbohydrate (CHO) availability on whole body and skeletal muscle protein utilization at rest, during exercise, and during recovery in humans. Six men cycled at ∼75% peak O2 uptake (V̇o2peak) to exhaustion to reduce body CHO stores and then consumed either a high-CHO (H-CHO; 71 ± 3% CHO) or low-CHO (L-CHO; 11 ± 1% CHO) diet for 2 days before the trial in random order. After each dietary intervention, subjects received a primed constant infusion of [1-13C]leucine and l-[ring-2H5]phenylalanine for measurements of the whole body net protein balance and skeletal muscle protein turnover. Muscle, breath, and arterial and venous blood samples were obtained at rest, during 2 h of two-legged kicking exercise at ∼45% of kicking V̇o2peak, and during 1 h of recovery. Biopsy samples confirmed that the muscle glycogen concentration was lower in the L-CHO group versus the H-CHO group at rest, after exercise, and after recovery. The net leg protein balance was decreased in the L-CHO group compared with at rest and compared with the H-CHO condition, which was primarily due to an increase in protein degradation (area under the curve of the phenylalanine rate of appearance: 1,331 ± 162 μmol in the L-CHO group vs. 786 ± 51 μmol in the H-CHO group, P < 0.05) but also due to a decrease in protein synthesis late in exercise. There were no changes during exercise in the rate of appearance compared with rest in the H-CHO group. Whole body leucine oxidation increased above rest in the L-CHO group only and was higher than in the H-CHO group. The whole body net protein balance was reduced in the L-CHO group, largely due to a decrease in whole body protein synthesis. These data extend previous findings by others and demonstrate, using contemporary stable isotope methodology, that CHO availability influences the rates of skeletal muscle and whole body protein synthesis, degradation, and net balance during prolonged exercise in humans.

Effects of thyroxine on protein turnover in rat skeletal muscle.

1978 ◽  
Vol 235 (2) ◽  
pp. E231
Author(s):  
K E Flaim ◽  
J B Li ◽  
L S Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Skeletal Muscle Protein ◽  
Lysosomal Protease ◽  
Skeletal Muscle Protein Synthesis ◽  
Synthetic Capacity ◽  
Dose Levels

The effects of thyroxine (T4) on protein turnover in skeletal muscle were studied using normal, thyroidectomized (thyrex), and hypophysectomized (hypox) rats. Thyrex rats had a depressed growth rate that was accompanied by 50% reductions in the level of RNA and the rate of protein synthesis in gastrocnemius muscle, as determined in the perfused hemicorpus. Protein synthetic efficiency (protein synthesis per unit RNA) was decreased by 18%. Daily treatment of thyrex rats with T4 at different dose levels for up to 16 days led to improved growth rates, elevated RNA concentrations, and increased protein synthesis rates. The primary effect of T4 was to increase the protein synthetic capacity of muscle. Protein degradation, determined in the perfused hemicorpus, and activity of a lysosomal protease, determined in unperfused muscle, were reduced in the thyrex condition. Treatment of thyrex rats with T4 increased protein degradative rates, but not protease activity. Hypox rats, which also exhibited depressed skeletal muscle protein synthesis, responded to T4 and combined T4 and growth hormone with marked improvements in protein synthesis.

scholarly journals Effects of experimental hyperthyroidism on protein turnover in skeletal and cardiac muscle as measured by [14C]tyrosine infusion

1982 ◽  
Vol 204 (1) ◽  
pp. 69-74 ◽  
Author(s):  
W J Carter ◽  
W S V W Benjamin ◽  
F H Faas
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Heart Muscle ◽  
Protein Turnover ◽  
Cardiac Myocyte ◽  
Muscle Protein ◽  
Muscle Growth ◽  
Protein Breakdown ◽  
Fractional Rate

The effect of T3 (3,3′,5-tri-iodothyronine) on protein turnover in skeletal and cardiac muscle was measured in intact rats by means of a 6 h [14C]tyrosine-infusion technique. Treatment with 25-30 micrograms of T3/100 g body wt. daily for 4-7 days increased the fractional rate of protein synthesis in skeletal muscle. Since the fractional growth rate of the muscle was decreased or unchanged, T3 treatment increased the rate of muscle protein breakdown. These findings suggest that increased protein degradation is an important factor in decreasing skeletal-muscle mass in hyperthyroidism. In contrast with skeletal muscle, T3 treatment for 7 days caused an equivalent increase in the rate of cardiac muscle growth and protein synthesis. This suggests that hyperthyroidism does not increase protein breakdown in heart muscle as it does in skeletal muscle. The failure of T3 to increase proteolysis in heart muscle may be due to a different action on the cardiac myocyte or to systemic effects of T3 which increase cardiac work.

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