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1
Fiorotto, Marta L., Teresa A. Davis, and Peter J. Reeds. "Regulation of myofibrillar protein turnover during maturation in normal and undernourished rat pups." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 278, no. 4 (April 1, 2000): R845—R854. http://dx.doi.org/10.1152/ajpregu.2000.278.4.r845.
Повний текст джерелаАнотація:
The study tested the hypothesis that a higher rate of myofibrillar than sarcoplasmic protein synthesis is responsible for the rapid postdifferentiation accumulation of myofibrils and that an inadequate nutrient intake will compromise primarily myofibrillar protein synthesis. Myofibrillar (total and individual) and sarcoplasmic protein synthesis, accretion, and degradation rates were measured in vivo in well-nourished (C) rat pups at 6, 15, and 28 days of age and compared at 6 and 15 days of age with pups undernourished (UN) from birth. In 6-day-old C pups, a higher myofibrillar than sarcoplasmic protein synthesis rate accounted for the greater deposition of myofibrillar than sarcoplasmic proteins. The fractional synthesis rates of both protein compartments decreased with age, but to a greater degree for myofibrillar proteins (−54 vs. −42%). These decreases in synthesis rates were partially offset by reductions in degradation rates, and from 15 days, myofibrillar and sarcoplasmic proteins were deposited in constant proportion to one another. Undernutrition reduced both myofibrillar and sarcoplasmic protein synthesis rates, and the effect was greater at 6 (−25%) than 15 days (−15%). Decreases in their respective degradation rates minimized the effect of undernutrition on sarcoplasmic protein accretion from 4 to 8 days and on myofibrillar proteins from 13 to 17 days. Although these adaptations in protein turnover reduced overall growth of muscle mass, they mitigated the effects of undernutrition on the normal maturational changes in myofibrillar protein concentration.
2
Welle, S., C. Thornton, R. Jozefowicz, and M. Statt. "Myofibrillar protein synthesis in young and old men." American Journal of Physiology-Endocrinology and Metabolism 264, no. 5 (May 1, 1993): E693—E698. http://dx.doi.org/10.1152/ajpendo.1993.264.5.e693.
Повний текст джерелаАнотація:
We tested the hypothesis that healthy older men (> 60 yr old) have a slower rate of myofibrillar protein synthesis than young men (< 35 yr old). Myofibrillar protein synthesis was determined by the in vivo incorporation of L-[1-13C]leucine into myofibrillar proteins obtained by muscle biopsy. Subjects were eight young (21-31 yr) and eight older (62-81 yr) men, all healthy and moderately active. There was no significant difference in the mean height and weight of the two age groups, but the older group had 12% less lean body mass (determined by 40K counting) and 21% less muscle mass (estimated by urinary creatinine excretion). Upper leg strength was approximately one-third lower in the older subjects according to isokinetic dynamometry. The fractional rate of myofibrillar protein synthesis was 28% slower in the older group (0.039 +/- 0.009 vs. 0.054 +/- 0.010 %/h, mean +/- SD, P < 0.01). Total myofibrillar protein synthesis, estimated as total myofibrillar mass (from creatinine excretion) times the fractional synthesis rate, was 44% slower in the older group (1.4 vs. 2.5 g/h, P < 0.001). Whole body protein synthesis, assessed as the difference between leucine disappearance rate and leucine oxidation, was marginally slower (8%, P = 0.10) in the older group, but not when the data were adjusted for lean body mass. Myofibrillar protein synthesis was a smaller fraction of whole body protein synthesis in the older group (12 vs. 19%). Reduced myofibrillar protein synthesis may be an important mechanism of the muscle atrophy associated with aging.
3
Welle, Stephen, Kerri Burgess, and Sangeeta Mehta. "Stimulation of skeletal muscle myofibrillar protein synthesis, p70 S6 kinase phosphorylation, and ribosomal protein S6 phosphorylation by inhibition of myostatin in mature mice." American Journal of Physiology-Endocrinology and Metabolism 296, no. 3 (March 2009): E567—E572. http://dx.doi.org/10.1152/ajpendo.90862.2008.
Повний текст джерелаАнотація:
Knocking out myostatin activity during development increases the rate of muscle protein synthesis. The present study was done to determine whether postdevelopmental loss of myostatin activity stimulates myofibrillar protein synthesis and the phosphorylation of some of the proteins involved in regulation of protein synthesis rate. Myostatin activity was inhibited for 4 days, in 4- to 5-mo-old male mice, with injections of an anti-myostatin antibody (JA16). The mean myofibrillar synthesis rate increased 19% ( P < 0.01) relative to the mean rate in saline-treated mice, as determined by incorporation of deuterium-labeled phenylalanine. JA16 increased phosphorylation of p70 S6 kinase (S6K) and ribosomal protein S6 (rpS6) 1.9-fold ( P < 0.05). It did not affect phosphorylation of eukaryotic initiation factor 4E-binding protein-1 or Akt. Microarrays and real-time PCR analyses indicated that JA16 administration did not selectively enrich levels of mRNAs encoding myofibrillar proteins, ribosomal proteins, or translation initiation and elongation factors. Rapamycin treatment did not affect the rate of myofibrillar protein synthesis whether or not the mice received JA16 injections, although it eliminated the phosphorylation of S6K and rpS6. We conclude that the normal level of myostatin activity in mature muscle is sufficient to inhibit myofibrillar synthesis rate and phosphorylation of S6K and rpS6. Reversal of the inhibition of myofibrillar synthesis with an anti-myostatin antibody is not dependent on mTOR activation.
4
Welle, S., C. Thornton, M. Statt, and B. McHenry. "Postprandial myofibrillar and whole body protein synthesis in young and old human subjects." American Journal of Physiology-Endocrinology and Metabolism 267, no. 4 (October 1, 1994): E599—E604. http://dx.doi.org/10.1152/ajpendo.1994.267.4.e599.
Повний текст джерелаАнотація:
Rates of incorporation of leucine (using L-[1-13C]leucine as a tracer) into myofibrillar and whole body proteins were determined in healthy old (> 60 yr old, n = 7) and young (< 30 yr old, n = 9) men and women who were fed small meals (4% of daily energy) every 30 min. There was no difference in whole body incorporation of leucine into proteins in the young (148 +/- 5 mumol.h-1.kg lean body mass-1, means +/- SE) and old groups (150 +/- 3 mumol.h-1.kg lean body mass-1). However, the fractional myofibrillar protein synthesis in the vastus lateralis muscle was 28% slower in the older group (0.063 +/- 0.004 vs. 0.088 +/- 0.003 %/h, P < 0.001). Extrapolation of these results to whole body myofibrillar synthesis (fractional rate x myofibrillar mass estimated by creatinine excretion) indicated that, in the older group, total myofibrillar synthesis was 43% slower (1.8 +/- 0.2 vs. 3.1 +/- 0.2 g/h, P < 0.01) and that their myofibrillar synthesis was a smaller portion of whole body protein synthesis (15 +/- 1 vs. 23 +/- 1%, P < 0.001). Compared with age-matched postabsorptive subjects, whole body protein synthesis was approximately 25% faster, and fractional myofibrillar synthesis was approximately 50% faster in these fed subjects, both young and old. We conclude that myofibrillar synthesis is slower in older subjects during both postabsorptive and postprandial conditions but that aging does not impair the stimulatory effect of feeding on protein synthesis.
5
Welle, Stephen, Sangeeta Mehta, and Kerri Burgess. "Effect of postdevelopmental myostatin depletion on myofibrillar protein metabolism." American Journal of Physiology-Endocrinology and Metabolism 300, no. 6 (June 2011): E993—E1001. http://dx.doi.org/10.1152/ajpendo.00509.2010.
Повний текст джерелаАнотація:
It is unclear whether the muscle hypertrophy induced by loss of myostatin signaling in mature muscles is maintained only by increased protein synthesis or whether reduced proteolysis contributes. To address this issue, we depleted myostatin by activating Cre recombinase for 2 wk in mature mice in which Mstn exon 3 was flanked by loxP sequences. The rate of phenylalanine tracer incorporation into myofibrillar proteins was determined 2, 5, and 24 wk after Cre activation ended. At all of these time points, myostatin-deficient mice had increased gastrocnemius and quadriceps muscle mass (≥27%) and increased myofibrillar synthesis rate per gastrocnemius muscle (≥19%) but normal myofibrillar synthesis rates per myofibrillar mass or RNA mass. Mean fractional myofibrillar degradation rates (estimated from the difference between rate of synthesis and rate of change in myofibrillar mass) and muscle concentrations of free 3-methylhistidine (from actin and myosin degradation) were unaffected by myostatin knockout. Overnight food deprivation reduced myofibrillar synthesis and ribosomal protein S6 phosphorylation and increased concentrations of 3-methylhistidine, muscle RING finger-1 mRNA, and atrogin-1 mRNA. Myostatin depletion did not affect these responses to food deprivation. These data indicate that maintenance of the muscle hypertrophy caused by loss of myostatin is mediated by increased protein synthesis per muscle fiber rather than suppression of proteolysis.
6
Welle, Stephen, and Charles A. Thornton. "High-protein meals do not enhance myofibrillar synthesis after resistance exercise in 62- to 75-yr-old men and women." American Journal of Physiology-Endocrinology and Metabolism 274, no. 4 (April 1, 1998): E677—E683. http://dx.doi.org/10.1152/ajpendo.1998.274.4.e677.
Повний текст джерелаАнотація:
This study tested the hypothesis that increasing the protein content of isocaloric meals increases the rate of myofibrillar synthesis in muscle of healthy subjects over 60 yr old and enhances the stimulation of myofibrillar synthesis induced by resistance exercise. Myofibrillar synthesis of sedentary and exercised quadriceps muscle was determined by incorporation ofl-[1-13C]leucine. During the tracer infusion, subjects consumed meals with a low (7% of energy, n = 6)-, normal (14%, n = 6)-, or high (28%, n = 6)-protein content. In sedentary muscle, the mean (± SE) myofibrillar synthesis was 1.56 ± 0.13%/day in the low-protein group, 1.73 ± 0.11 %/day in the normal-protein group, and 1.76 ± 0.10%/day in the high-protein group ( P = 0.42). Myofibrillar synthesis was faster in exercised muscle (mean 27%, P < 10−6) in all groups (2.10 ± 0.14 %/day in low protein; 2.18 ± 0.10 %/day in normal protein; 2.11 ± 0.09 %/day in high protein; P = 0.84). The stimulation of myofibrillar synthesis by exercise was not significantly different among low-protein [0.54 ± 0.12 %/day (37 ± 9%)], normal-protein [0.46 ± 0.08 %/day (28 ± 5%)], and high-protein groups [0.34 ± 0.04 %/day (20 ± 3%); P = 0.31]. We conclude that high-protein meals do not enhance the stimulation of myofibrillar protein synthesis induced by resistance exercise.
7
Welle, S., C. Thornton, and M. Statt. "Myofibrillar protein synthesis in young and old human subjects after three months of resistance training." American Journal of Physiology-Endocrinology and Metabolism 268, no. 3 (March 1, 1995): E422—E427. http://dx.doi.org/10.1152/ajpendo.1995.268.3.e422.
Повний текст джерелаАнотація:
Muscle protein synthesis is slower in healthy older men and women than in young adults, but whether this results from relative disuse rather than aging is unclear. The present study was done to examine rates of myofibrillar protein synthesis before and after a 3-mo progressive resistance exercise program in young and old men and women. Protein synthesis was determined by incorporation of the tracer L-[1-13C]leucine into myofibrillar proteins obtained from the vastus lateralis muscle by needle biopsy. Before exercise, mean fractional myofibrillar synthesis was 33% slower (P < 0.01) in nine older subjects (62-72 yr old, 5 men and 4 women) than in 9 young subjects (22-31 yr old, 5 men and 4 women). Initial strength, as determined by three-repetition-maximum tests, was significantly less in the older group. Strength and training weights increased similarly in young and old groups, when expressed in relation to baseline values. Posttraining myofibrillar synthesis was determined on the day after the final training session. There was not a significant change in fractional myofibrillar synthesis in either the young or the old group after training, and the rate in the older group remained 27% slower (P < 0.05). Whole body protein turnover increased approximately 10% only in the younger group, and 24-h urinary 3-methylhistidine excretion (an index of myofibrillar proteolysis) was not significantly affected by training. These data suggest that the slower myofibrillar synthesis rate in older subjects cannot be explained by disuse.
8
Wall, Benjamin T., Nicholas A. Burd, Rinske Franssen, Stefan H. M. Gorissen, Tim Snijders, Joan M. Senden, Annemie P. Gijsen, and Luc J. C. van Loon. "Presleep protein ingestion does not compromise the muscle protein synthetic response to protein ingested the following morning." American Journal of Physiology-Endocrinology and Metabolism 311, no. 6 (December 1, 2016): E964—E973. http://dx.doi.org/10.1152/ajpendo.00325.2016.
Повний текст джерелаАнотація:
Protein ingestion before sleep augments postexercise muscle protein synthesis during overnight recovery. It is unknown whether postexercise and presleep protein consumption modulates postprandial protein handling and myofibrillar protein synthetic responses the following morning. Sixteen healthy young (24 ± 1 yr) men performed unilateral resistance-type exercise (contralateral leg acting as a resting control) at 2000. Participants ingested 20 g of protein immediately after exercise plus 60 g of protein presleep (PRO group; n = 8) or equivalent boluses of carbohydrate (CON; n = 8). The subsequent morning participants received primed, continuous infusions of l-[ ring-2H5]phenylalanine and l-[1-13C]leucine combined with ingestion of 20 g intrinsically l-[1-13C]phenylalanine- and l-[1-13C]leucine-labeled protein to assess postprandial protein handling and myofibrillar protein synthesis in the rested and exercised leg in CON and PRO. Exercise increased postabsorptive myofibrillar protein synthesis rates the subsequent day ( P < 0.001), with no differences between CON and PRO. Protein ingested in the morning increased myofibrillar protein synthesis in both the exercised and rested leg ( P < 0.01), with no differences between treatments. Myofibrillar protein bound l-[1-13C]phenylalanine enrichments were greater in the exercised (0.016 ± 0.002 and 0.015 ± 0.002 MPE in CON and PRO, respectively) vs. rested (0.010 ± 0.002 and 0.009 ± 0.002 MPE in CON and PRO, respectively) leg ( P < 0.05), with no differences between treatments ( P > 0.05). The additive effects of resistance-type exercise and protein ingestion on myofibrillar protein synthesis persist for more than 12 h after exercise and are not modulated by protein consumption during acute postexercise recovery. This work provides evidence of an extended window of opportunity where presleep protein supplementation can be an effective nutrient timing strategy to optimize skeletal muscle reconditioning.
9
Preedy, V. R., and P. J. Garlick. "Inhibition of protein synthesis by glucagon in different rat muscles and protein fractions in vivo and in the perfused rat hemicorpus." Biochemical Journal 251, no. 3 (May 1, 1988): 727–32. http://dx.doi.org/10.1042/bj2510727.
Повний текст джерелаАнотація:
The effect of glucagon on the rate of muscle protein synthesis was examined in vivo and in the isolated perfused rat hemicorpus. An inhibition of protein synthesis in skeletal muscles from overnight-fasted rats at various plasma concentrations of glucagon was demonstrated in vivo. The plantaris muscle (Type II, fibre-rich) was more sensitive than the soleus (Type I, fibre-rich). Myofibrillar and sarcoplasmic proteins were equally sensitive in vivo. However, protein synthesis in mixed protein and in sarcoplasmic and myofibrillar fractions of the heart was unresponsive to glucagon in vivo. In isolated perfused muscle preparations from fed animals, the addition of glucagon also decreased the synthesis of mixed muscle proteins in gastrocnemius (Type I and II fibres) and plantaris, but not in the soleus. The sarcoplasmic and myofibrillar fractions of the plantaris were also equally affected in vitro. Similar results were observed in vitro with 1-day-starved rats, but the changes were less marked.
10
Welle, Stephen, Kirti Bhatt, and Carl A. Pinkert. "Myofibrillar protein synthesis in myostatin-deficient mice." American Journal of Physiology-Endocrinology and Metabolism 290, no. 3 (March 2006): E409—E415. http://dx.doi.org/10.1152/ajpendo.00433.2005.
Повний текст джерелаАнотація:
Either increased protein synthesis or prolonged protein half-life is necessary to support the excessive muscle growth and maintenance of enlarged muscles in myostatin-deficient mice. This issue was addressed by determining in vivo rates of myofibrillar protein synthesis in mice with constitutive myostatin deficiency (MstnΔE3/ΔE3) or normal myostatin expression (Mstn+/+) by measuring tracer incorporation after a systemic flooding dose of l-[ ring-2H5]phenylalanine. At 5–6 wk of age, MstnΔE3/ΔE3 mice had increased muscle mass (40%), fractional rates of myofibrillar synthesis (14%), and protein synthesis per whole muscle (60%) relative to Mstn+/+ mice. With maturation, fractional rates of synthesis declined >50% in parallel with decreased DNA and RNA [total, 28S rRNA, and poly(A) RNA] concentrations in muscle. At 6 mo of age, MstnΔE3/ΔE3 mice had even greater increases in muscle mass (90%) and myofibrillar synthesis per muscle (85%) relative to Mstn+/+ mice, but the fractional rate of synthesis was normal. Estimated myofibrillar protein half-life was not affected by myostatin deficiency. Muscle DNA concentrations were reduced in both young and mature MstnΔE3/ΔE3 mice, whereas RNA concentrations were normal, so the ratio of RNA to DNA was ∼30% greater than normal in MstnΔE3/ΔE3 mice. Thus the increased protein synthesis and RNA content per muscle in myostatin-deficient mice cannot be explained entirely by an increased number of myonuclei.
11
Meidell, R. S., A. Sen, S. A. Henderson, M. F. Slahetka, and K. R. Chien. "Alpha 1-adrenergic stimulation of rat myocardial cells increases protein synthesis." American Journal of Physiology-Heart and Circulatory Physiology 251, no. 5 (November 1, 1986): H1076—H1084. http://dx.doi.org/10.1152/ajpheart.1986.251.5.h1076.
Повний текст джерелаАнотація:
The effects of adrenergic stimulation on the rates of protein synthesis, degradation, and accumulation were examined in primary cultures of neonatal rat heart cells. Treatment of myocardial cells with norepinephrine increased total cellular protein content and the rate of incorporation of radiolabeled tyrosine into trichloroacetic acid insoluble protein. alpha 1-Adrenergic, but not alpha 2- or beta-adrenergic blockade, inhibited these norepinephrine induced increases. The rate of protein synthesis estimated from the kinetics of equilibrium labeling and from combined equilibrium and pulse labeling was increased by norepinephrine stimulation, whereas protein degradation estimated by release of previously incorporated radiolabeled tyrosine or in pulse-chase experiments was unaffected. To determine whether alpha 1-adrenergic stimulation produced similar effects on the turnover of myofibrillar proteins, rates of synthesis and degradation were estimated for a myofibrillar-enriched protein fraction and for myosin heavy chain and actin. Norepinephrine treatment produced increases in the synthesis of myofibrillar protein without significantly altering degradation rates. These experiments suggest that alpha 1-adrenergic stimulation increases myocardial cell protein content by accelerating protein synthesis.
12
Wall, Benjamin T., Marlou L. Dirks, Tim Snijders, Jan-Willem van Dijk, Mario Fritsch, Lex B. Verdijk, and Luc J. C. van Loon. "Short-term muscle disuse lowers myofibrillar protein synthesis rates and induces anabolic resistance to protein ingestion." American Journal of Physiology-Endocrinology and Metabolism 310, no. 2 (January 15, 2016): E137—E147. http://dx.doi.org/10.1152/ajpendo.00227.2015.
Повний текст джерелаАнотація:
Disuse leads to rapid loss of skeletal muscle mass and function. It has been hypothesized that short successive periods of muscle disuse throughout the lifespan play an important role in the development of sarcopenia. The physiological mechanisms underlying short-term muscle disuse atrophy remain to be elucidated. We assessed the impact of 5 days of muscle disuse on postabsorptive and postprandial myofibrillar protein synthesis rates in humans. Twelve healthy young (22 ± 1 yr) men underwent a 5-day period of one-legged knee immobilization (full leg cast). Quadriceps cross-sectional area (CSA) of both legs was assessed before and after immobilization. Continuous infusions of l-[ ring-2H5]phenylalanine and l-[1-13C]leucine were combined with the ingestion of a 25-g bolus of intrinsically l-[1-13C]phenylalanine- and l-[1-13C]leucine-labeled dietary protein to assess myofibrillar muscle protein fractional synthetic rates in the immobilized and nonimmobilized control leg. Immobilization led to a 3.9 ± 0.6% decrease in quadriceps muscle CSA of the immobilized leg. Based on the l-[ ring-2H5]phenylalanine tracer, immobilization reduced postabsorptive myofibrillar protein synthesis rates by 41 ± 13% (0.015 ± 0.002 vs. 0.032 ± 0.005%/h, P < 0.01) and postprandial myofibrillar protein synthesis rates by 53 ± 4% (0.020 ± 0.002 vs. 0.044 ± 0.003%/h, P < 0.01). Comparable results were found using the l-[1-13C]leucine tracer. Following protein ingestion, myofibrillar protein bound l-[1-13C]phenylalanine enrichments were 53 ± 18% lower in the immobilized compared with the control leg (0.007 ± 0.002 and 0.015 ± 0.002 mole% excess, respectively, P < 0.05). We conclude that 5 days of muscle disuse substantially lowers postabsorptive myofibrillar protein synthesis rates and induces anabolic resistance to protein ingestion.
13
Preedy, V. R., and P. H. Sugden. "The effects of fasting or hypoxia on rates of protein synthesis in vivo in subcellular fractions of rat heart and gastrocnemius muscle." Biochemical Journal 257, no. 2 (January 15, 1989): 519–27. http://dx.doi.org/10.1042/bj2570519.
Повний текст джерелаАнотація:
We measured rates of protein synthesis in vivo in subcellular fractions (soluble, myofibrillar and stromal fractions) of the heart and the gastrocnemius from rats after fasting or under hypoxic conditions (i.e. atmospheres containing 5% or 10% O2). Such interventions are known to inhibit protein synthesis under some circumstances. The recovery of tissue protein after fractionation was 80-100%. The proportions of protein present in the soluble and stromal fractions were different in the two muscles. The rates of protein synthesis in the myofibrillar and stromal fractions were less than those for total mixed tissue protein, whereas the rate for soluble protein was greater. Both fasting and moderate hypoxia (10% O2 for 24 h) inhibited protein synthesis in the gastrocnemius. In this tissue, the synthesis of the myofibrillar fraction was apparently the most sensitive to inhibition, and this resulted in some significant increases in the soluble-fraction/myofibrillar-fraction protein-synthesis rate ratios. In the heart, fasting inhibited protein synthesis, but moderate hypoxia (10% O2 for 24 h) did not. The rate of protein synthesis in the cardiac myofibrillar fraction was again more sensitive to fasting than were the rates in the other fractions, but it was not as sensitive as that in the gastrocnemius. Under severely hypoxic conditions (5% O2 for 1 or 2 h), protein synthesis was decreased in all fractions in both tissues. These results suggest that the rates of protein synthesis in these relatively crude subcellular fractions vary.
14
Trommelen, Jorn, Imre W. K. Kouw, Andrew M. Holwerda, Tim Snijders, Shona L. Halson, Ian Rollo, Lex B. Verdijk, and Luc J. C. van Loon. "Presleep dietary protein-derived amino acids are incorporated in myofibrillar protein during postexercise overnight recovery." American Journal of Physiology-Endocrinology and Metabolism 314, no. 5 (May 1, 2018): E457—E467. http://dx.doi.org/10.1152/ajpendo.00273.2016.
Повний текст джерелаАнотація:
The purpose of this study was to determine the impact of ingesting 30 g casein protein with and without 2 g free leucine before sleep on myofibrillar protein synthesis rates during postexercise overnight recovery. Thirty-six healthy young men performed a single bout of resistance-type exercise in the evening (1945) after a full day of dietary standardization. Thirty minutes before sleep (2330), subjects ingested 30 g intrinsically l-[1-13C]phenylalanine-labeled protein with (PRO+leu, n = 12) or without (PRO, n = 12) 2 g free leucine, or a noncaloric placebo (PLA, n = 12). Continuous intravenous l-[ ring-2H5]phenylalanine, l-[1-13C]leucine, and l-[ ring-2H2]tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole body protein net balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into myofibrillar protein. Protein ingestion before sleep improved overnight whole body protein net balance ( P < 0.001). Myofibrillar protein synthesis rates did not differ significantly between treatments as assessed by l-[ ring-2H5]phenylalanine (0.057 ± 0.002, 0.055 ± 0.002, and 0.055 ± 0.004%/h for PLA, PRO, and PRO+leu, respectively; means ± SE; P = 0.850) or l-[1-13C]leucine (0.080 ± 0.004, 0.073 ± 0.004, and 0.083 ± 0.006%/h, respectively; P = 0.328). Myofibrillar l-[1-13C]phenylalanine enrichments increased following protein ingestion but did not differ between the PRO and PRO+leu treatments. In conclusion, protein ingestion before sleep improves whole body protein net balance and provides amino acids that are incorporated into myofibrillar protein during sleep. However, the ingestion of 30 g casein protein with or without additional free leucine before sleep does not increase muscle protein synthesis rates during postexercise overnight recovery.
15
Shad, Brandon J., Janice L. Thompson, James Mckendry, Andrew M. Holwerda, Yasir S. Elhassan, Leigh Breen, Luc J. C. van Loon, and Gareth A. Wallis. "Daily Myofibrillar Protein Synthesis Rates in Response to Low- and High-Frequency Resistance Exercise Training in Healthy, Young Men." International Journal of Sport Nutrition and Exercise Metabolism 31, no. 3 (May 1, 2021): 209–16. http://dx.doi.org/10.1123/ijsnem.2020-0274.
Повний текст джерелаАнотація:
The impact of resistance exercise frequency on muscle protein synthesis rates remains unknown. The aim of this study was to compare daily myofibrillar protein synthesis rates over a 7-day period of low-frequency (LF) versus high-frequency (HF) resistance exercise training. Nine young men (21 ± 2 years) completed a 7-day period of habitual physical activity (BASAL). This was followed by a 7-day exercise period of volume-matched, LF (10 × 10 repetitions at 70% one-repetition maximum, once per week) or HF (2 × 10 repetitions at ∼70% one-repetition maximum, five times per week) resistance exercise training. The participants had one leg randomly allocated to LF and the other to HF. Skeletal muscle biopsies and daily saliva samples were collected to determine myofibrillar protein synthesis rates using 2H2O, with intracellular signaling determined using Western blotting. The myofibrillar protein synthesis rates did not differ between the LF (1.46 ± 0.26%/day) and HF (1.48 ± 0.33%/day) conditions over the 7-day exercise training period (p > .05). There were no significant differences between the LF and HF conditions over the first 2 days (1.45 ± 0.41%/day vs. 1.25 ± 0.46%/day) or last 5 days (1.47 ± 0.30%/day vs. 1.50 ± 0.41%/day) of the exercise training period (p > .05). Daily myofibrillar protein synthesis rates were not different from BASAL at any time point during LF or HF (p > .05). The phosphorylation status and total protein content of selected proteins implicated in skeletal muscle ribosomal biogenesis were not different between conditions (p > .05). Under the conditions of the present study, resistance exercise training frequency did not modulate daily myofibrillar protein synthesis rates in young men.
16
Murphy, Caoileann H., Tyler A. Churchward-Venne, Cameron J. Mitchell, Nathan M. Kolar, Amira Kassis, Leonidas G. Karagounis, Louise M. Burke, John A. Hawley, and Stuart M. Phillips. "Hypoenergetic diet-induced reductions in myofibrillar protein synthesis are restored with resistance training and balanced daily protein ingestion in older men." American Journal of Physiology-Endocrinology and Metabolism 308, no. 9 (May 1, 2015): E734—E743. http://dx.doi.org/10.1152/ajpendo.00550.2014.
Повний текст джерелаАнотація:
Strategies to enhance weight loss with a high fat-to-lean ratio in overweight/obese older adults are important since lean loss could exacerbate sarcopenia. We examined how dietary protein distribution affected muscle protein synthesis during energy balance (EB), energy restriction (ER), and energy restriction plus resistance training (ER + RT). A 4-wk ER diet was provided to overweight/obese older men (66 ± 4 yr, 31 ± 5 kg/m2) who were randomized to either a balanced (BAL: 25% daily protein/meal × 4) or skewed (SKEW: 7:17:72:4% daily protein/meal; n = 10/group) pattern. Myofibrillar and sarcoplasmic protein fractional synthetic rates (FSR) were measured during a 13-h primed continuous infusion of l-[ ring-13C6]phenylalanine with BAL and SKEW pattern of protein intake in EB, after 2 wk ER, and after 2 wk ER + RT. Fed-state myofibrillar FSR was lower in ER than EB in both groups ( P < 0.001), but was greater in BAL than SKEW ( P = 0.014). In ER + RT, fed-state myofibrillar FSR increased above ER in both groups and in BAL was not different from EB ( P = 0.903). In SKEW myofibrillar FSR remained lower than EB ( P = 0.002) and lower than BAL ( P = 0.006). Fed-state sarcoplasmic protein FSR was reduced similarly in ER and ER + RT compared with EB ( P < 0.01) in both groups. During ER in overweight/obese older men a BAL consumption of protein stimulated the synthesis of muscle contractile proteins more effectively than traditional, SKEW distribution. Combining RT with a BAL protein distribution “rescued” the lower rates of myofibrillar protein synthesis during moderate ER.
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Preedy, V. R., and T. J. Peters. "The effect of chronic ethanol ingestion on synthesis and degradation of soluble, contractile and stromal protein fractions of skeletal muscles from immature and mature rats." Biochemical Journal 259, no. 1 (April 1, 1989): 261–66. http://dx.doi.org/10.1042/bj2590261.
Повний текст джерелаАнотація:
1. An investigation was carried out into the response of soluble, myofibrillar and stromal protein fractions of skeletal muscle to chronic ethanol feeding. Groups of male Wistar rats, of approx. 85 or 280 g body wt., were pair-fed on a nutritionally complete liquid diet containing glucose or a diet in which 36% of the total energy was provided by ethanol. After 6 weeks, rates of protein synthesis were measured with a flooding dose of L-[4-3H]phenylalanine. 2. The protein contents of soluble, myofibrillar and stromal fractions in gastrocnemius muscle from small and large rats were decreased by ethanol feeding. Greater changes were observed in small than in large rats. 3. Fractional synthesis rates of soluble, myofibrillar and stromal proteins of gastrocnemius were all decreased by ethanol treatment. All fractions responded similarly, though percentage decreases in large rats were greater than in small rats. Absolute synthesis rates in gastrocnemius muscles were also decreased after ethanol treatment. All protein fractions responded similarly, and the magnitudes of the responses in large and small rats were also similar. 4. Fractional rates of breakdown, measured by the difference between fractional growth and synthesis rates, were apparently decreased, in both sets of rats, in all protein fractions. 5. It was concluded that chronic ethanol exposure causes perturbations in soluble, myofibrillar and stromal protein accretion by a mechanism involving unidirectional changes in protein synthesis and possibly breakdown.
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Miller, Benjamin F., Mette Hansen, Jens L. Olesen, Allan Flyvbjerg, Peter Schwarz, John A. Babraj, Kenneth Smith, Michael J. Rennie, and Michael Kjaer. "No effect of menstrual cycle on myofibrillar and connective tissue protein synthesis in contracting skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 290, no. 1 (January 2006): E163—E168. http://dx.doi.org/10.1152/ajpendo.00300.2005.
Повний текст джерелаАнотація:
We tested the hypothesis that acute exercise would stimulate synthesis of myofibrillar protein and intramuscular collagen in women and that the phase of the menstrual cycle at which the exercise took place would influence the extent of the change. Fifteen young, healthy female subjects were studied in the follicular (FP, n = 8) or the luteal phase (LP, n = 7, n = 1 out of phase) 24 h after an acute bout of one-legged exercise (60 min of kicking at 67% Wmax), samples being taken from the vastus lateralis in both the exercised and resting legs. Rates of synthesis of myofibrillar and muscle collagen proteins were measured by incorporation of [13C]leucine. Myofibrillar protein synthesis (means ± SD; rest FP: 0.053 ± 0.009%/h, LP: 0.055 ± 0.013%/h) was increased at 24-h postexercise (FP: 0.131 ± 0.018%/h, P < 0.05, LP: 0.134 ± 0.018%/h, P < 0.05) with no differences between phases. Similarly, muscle collagen synthesis (rest FP: 0.024 ± 0.017%/h, LP: 0.021 ± 0.006%/h) was elevated at 24-h postexercise (FP: 0.073 ± 0.016%/h, P < 0.05, LP: 0.072 ± 0.015%/h, P < 0.05), but the responses did not differ between menstrual phases. Therefore, there is no effect of menstrual cycle phase, at rest or in response to an acute bout of exercise, on myofibrillar protein synthesis and muscle collagen synthesis in women.
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Holwerda, Andrew M., Freek G. Bouwman, Miranda Nabben, Ping Wang, Janneau van Kranenburg, Annemie P. Gijsen, Jatin G. Burniston, Edwin C. M. Mariman, and Luc J. C. van Loon. "Endurance-Type Exercise Increases Bulk and Individual Mitochondrial Protein Synthesis Rates in Rats." International Journal of Sport Nutrition and Exercise Metabolism 30, no. 2 (March 1, 2020): 153–64. http://dx.doi.org/10.1123/ijsnem.2019-0281.
Повний текст джерелаАнотація:
Physical activity increases muscle protein synthesis rates. However, the impact of exercise on the coordinated up- and/or downregulation of individual protein synthesis rates in skeletal muscle tissue remains unclear. The authors assessed the impact of exercise on mixed muscle, myofibrillar, and mitochondrial protein synthesis rates as well as individual protein synthesis rates in vivo in rats. Adult Lewis rats either remained sedentary (n = 3) or had access to a running wheel (n = 3) for the last 2 weeks of a 3-week experimental period. Deuterated water was injected and subsequently administered in drinking water over the experimental period. Blood and soleus muscle were collected and used to assess bulk mixed muscle, myofibrillar, and mitochondrial protein synthesis rates using gas chromatography–mass spectrometry and individual muscle protein synthesis rates using liquid chromatography–mass spectrometry (i.e., dynamic proteomic profiling). Wheel running resulted in greater myofibrillar (3.94 ± 0.26 vs. 3.03 ± 0.15%/day; p < .01) and mitochondrial (4.64 ± 0.24 vs. 3.97 ± 0.26%/day; p < .05), but not mixed muscle (2.64 ± 0.96 vs. 2.38 ± 0.62%/day; p = .71) protein synthesis rates, when compared with the sedentary condition. Exercise impacted the synthesis rates of 80 proteins, with the difference from the sedentary condition ranging between −64% and +420%. Significantly greater synthesis rates were detected for F1-ATP synthase, ATP synthase subunit alpha, hemoglobin, myosin light chain-6, and synaptopodin-2 (p < .05). The skeletal muscle protein adaptive response to endurance-type exercise involves upregulation of mitochondrial protein synthesis rates, but it is highly coordinated as reflected by the up- and downregulation of various individual proteins across different bulk subcellular protein fractions.
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Kilroe, Sean P., Jonathan Fulford, Andrew M. Holwerda, Sarah R. Jackman, Benjamin P. Lee, Annemie P. Gijsen, Luc J. C. van Loon, and Benjamin T. Wall. "Short-term muscle disuse induces a rapid and sustained decline in daily myofibrillar protein synthesis rates." American Journal of Physiology-Endocrinology and Metabolism 318, no. 2 (February 1, 2020): E117—E130. http://dx.doi.org/10.1152/ajpendo.00360.2019.
Повний текст джерелаАнотація:
Short-term muscle disuse has been reported to lower both postabsorptive and postprandial myofibrillar protein synthesis rates. This study assessed the impact of disuse on daily myofibrillar protein synthesis rates following short-term (2 and 7 days) muscle disuse under free living conditions. Thirteen healthy young men (age: 20 ± 1 yr; BMI: 23 ± 1 kg/m−2) underwent 7 days of unilateral leg immobilization via a knee brace, with the nonimmobilized leg acting as a control. Four days before immobilization participants ingested 400 mL of 70% deuterated water, with 50-mL doses consumed daily thereafter. Upper leg bilateral MRI scans and muscle biopsies were collected before and after 2 and 7 days of immobilization to determine quadriceps volume and daily myofibrillar protein synthesis rates. Immobilization reduced quadriceps volume in the immobilized leg by 1.7 ± 0.3 and 6.7 ± 0.6% after 2 and 7 days, respectively, with no changes in the control leg. Over the 1-wk immobilization period, myofibrillar protein synthesis rates were 36 ± 4% lower in the immobilized (0.81 ± 0.04%/day) compared with the control (1.26 ± 0.04%/day) leg ( P < 0.001). Myofibrillar protein synthesis rates in the control leg did not change over time ( P = 0.775), but in the immobilized leg they were numerically lower during the 0- to 2-day period (16 ± 6%, 1.11 ± 0.09%/day, P = 0.153) and were significantly lower during the 2- to 7-day period (44 ± 5%, 0.70 ± 0.06%/day, P < 0.001) when compared with the control leg. We conclude that 1 wk of muscle disuse induces a rapid and sustained decline in daily myofibrillar protein synthesis rates in healthy young men.
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Simpson, D. G., W. W. Sharp, T. K. Borg, R. L. Price, L. Terracio, and A. M. Samarel. "Mechanical regulation of cardiac myocyte protein turnover and myofibrillar structure." American Journal of Physiology-Cell Physiology 270, no. 4 (April 1, 1996): C1075—C1087. http://dx.doi.org/10.1152/ajpcell.1996.270.4.c1075.
Повний текст джерелаАнотація:
Mechanical forces play an essential role in regulating the synthesis and assembly of contractile proteins into the sarcomeres of cardiac myocytes. To examine if physical forces might also regulate the turnover of contractile proteins at a posttranslational site of control, beating and nonbeating neonatal cardiac myocytes (NCM) were subjected to a 5% static stretch. The L-type calcium channel blocker nifedipine (12 microM) was used to inhibit contraction. Pulse-chase biosynthetic labeling experiments demonstrated that contractile arrest accelerated the loss of isotopic tracer from the total myofibrillar protein fraction, myosin heavy chain (MHC), and actin, but not desmin. Myofibrillar abnormalities developed in parallel with these metabolic changes. A 5% static load appeared to partially stabilize myofibrillar structure in nonbeating NCM and suppressed the loss of isotopic tracer from the total myofibrillar protein fraction, MHC, and actin in beating and nonbeating NCM. Contractile activity and/or a static stretch promoted the accumulation of MHC, actin, and desmin. Applying a static load to myocytes that lacked preexisting myofibrils did not promote the assembly of sarcomeres or alter protein turnover. These data indicate that the turnover of MHC and actin is correlated with the organizational state of the myofibrillar apparatus.
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van Vliet, Stephan, Alan Fappi, Dominic N. Reeds, and Bettina Mittendorfer. "No independent or combined effects of vitamin D and conjugated linoleic acids on muscle protein synthesis in older adults: a randomized, double-blind, placebo-controlled clinical trial." American Journal of Clinical Nutrition 112, no. 5 (August 29, 2020): 1382–89. http://dx.doi.org/10.1093/ajcn/nqaa240.
Повний текст джерелаАнотація:
ABSTRACT Background Aging is associated with skeletal muscle anabolic resistance (i.e., reduced muscle protein synthesis during anabolic conditions such as hyperaminoacidemia). The results from studies conducted in cell culture systems and animals suggest that both vitamin D and conjugated linoleic acids (CLAs) stimulate muscle protein synthesis. Objectives To conduct a randomized, double-blind, placebo-controlled clinical trial to determine the independent and combined effects of dietary vitamin D and CLA supplementation on myofibrillar protein synthesis rates in sedentary older adults. Methods Thirty-two sedentary, older adults were randomized to receive either: 1) 2000 IU vitamin D-3 (Vit D) per day; 2) 4000 mg CLA per day; 3) both Vit D (2000 IU/d) and CLA (4000 mg/d); or 4) placebo for 8 wk. Myofibrillar protein synthesis rates were evaluated by using intravenous [ring-2H5]phenylalanine infusion in conjunction with muscle biopsies during basal, postabsorptive conditions and during combined amino acid and insulin infusion before and after the supplementation period. Results Before the intervention, basal myofibrillar protein synthesis rates were not different among groups (Placebo: 0.033 ± 0.003; Vit D: 0.034 ± 0.002; CLA: 0.029 ± 0.005; Vit D + CLA: 0.038 ± 0.005 %·h-1), and hyperinsulinemia–hyperaminoacidemia increased myofibrillar protein synthesis rates by ∼35%. Compared with placebo, neither Vit D nor CLA nor combined Vit D + CLA supplementation affected the basal myofibrillar protein synthesis rates (placebo: 0.040 ± 0.004%/h; Vit D: 0.044 ± 0.006%/h; CLA: 0.039 ± 0.006%/h; Vit D + CLA: 0.040 ± 0.007%/h) or the hyperinsulinemia–hyperaminoacidemia–induced increase in myofibrillar protein synthesis (percentage increase from basal before and after the interventions: placebo, 30 ± 11 and 36 ± 11; Vit D, 38 ± 8 and 34 ± 10; CLA, 50 ± 14 and 51 ± 16; Vit D + CLA, 29 ± 15 and 35 ± 8). Conclusions Vitamin D and/or CLA supplementation, at the doses provided in our study, does not have muscle anabolic effects in sedentary older adults. The study was registered at clinicaltrials.gov (NCT03115775).
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CAMERA, DONNY M., DANIEL W. D. WEST, STUART M. PHILLIPS, TRACY RERECICH, TRENT STELLINGWERFF, JOHN A. HAWLEY, and VERNON G. COFFEY. "Protein Ingestion Increases Myofibrillar Protein Synthesis after Concurrent Exercise." Medicine & Science in Sports & Exercise 47, no. 1 (January 2015): 82–91. http://dx.doi.org/10.1249/mss.0000000000000390.
Повний текст джерела
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Welle, S., K. Bhatt, and C. Thornton. "Polyadenylated RNA, actin mRNA, and myosin heavy chain mRNA in young and old human skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 270, no. 2 (February 1, 1996): E224—E229. http://dx.doi.org/10.1152/ajpendo.1996.270.2.e224.
Повний текст джерелаАнотація:
The myofibrillar protein synthesis rate in old human skeletal muscle is slower than that in young adult muscle. To examine whether this difference in protein synthesis rate is explained by reduced availability of the mRNAs that encode the most abundant myofibrillar proteins, we determined relative hybridization signals from probes for actin mRNA, myosin heavy chain mRNA, and total polyadenylated RNA in vastus lateralis muscle biopsies taken from young (22- to 31-yr-old) and old (61- to 74-yr-old) human subjects. The mean fractional rate of myofibrillar synthesis was 38% slower in the older muscles, as determined by incorporation of a stable isotope tracer. Total actin and myosin heavy chain mRNAs, and polyadenylated RNA, were determined using slot-blot assays. Isoform-specific determinations of alpha-actin mRNA, type I myosin heavy chain mRNA, and type IIa myosin heavy chain mRNA were done with ribonuclease protection assays. Hybridization signals were expressed relative to tissue DNA content. There was no difference between age groups in total polyadenylated RNA or in any of the specific mRNAs. We conclude that the slower myofibrillar synthesis rate in older muscle is not caused by reduced mRNA availability.
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Fuchs, Cas J., Joey S. J. Smeets, Joan M. Senden, Antoine H. Zorenc, Joy P. B. Goessens, Wouter D. van Marken Lichtenbelt, Lex B. Verdijk, and Luc J. C. van Loon. "Hot-water immersion does not increase postprandial muscle protein synthesis rates during recovery from resistance-type exercise in healthy, young males." Journal of Applied Physiology 128, no. 4 (April 1, 2020): 1012–22. http://dx.doi.org/10.1152/japplphysiol.00836.2019.
Повний текст джерелаАнотація:
The purpose of this study was to assess the impact of postexercise hot-water immersion on postprandial myofibrillar protein synthesis rates during recovery from a single bout of resistance-type exercise in healthy, young men. Twelve healthy, adult men (age: 23 ± 1 y) performed a single bout of resistance-type exercise followed by 20 min of water immersion of both legs. One leg was immersed in hot water [46°C: hot-water immersion (HWI)], while the other leg was immersed in thermoneutral water (30°C: CON). After water immersion, a beverage was ingested containing 20 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine labeled milk protein with 45 g of carbohydrates. In addition, primed continuous L-[ ring-2H5]-phenylalanine and L-[1-13C]-leucine infusions were applied, with frequent collection of blood and muscle samples to assess myofibrillar protein synthesis rates in vivo over a 5-h recovery period. Muscle temperature immediately after water immersion was higher in the HWI compared with the CON leg (37.5 ± 0.1 vs. 35.2 ± 0.2°C; P < 0.001). Incorporation of dietary protein-derived L-[1-13C]-phenylalanine into myofibrillar protein did not differ between the HWI and CON leg during the 5-h recovery period (0.025 ± 0.003 vs. 0.024 ± 0.002 MPE; P = 0.953). Postexercise myofibrillar protein synthesis rates did not differ between the HWI and CON leg based upon L-[1-13C]-leucine (0.050 ± 0.005 vs. 0.049 ± 0.002%/h; P = 0.815) and L-[ ring-2H5]-phenylalanine (0.048 ± 0.002 vs. 0.047 ± 0.003%/h; P = 0.877), respectively. Hot-water immersion during recovery from resistance-type exercise does not increase the postprandial rise in myofibrillar protein synthesis rates. In addition, postexercise hot-water immersion does not increase the capacity of the muscle to incorporate dietary protein-derived amino acids in muscle tissue protein during subsequent recovery. NEW & NOTEWORTHY This is the first study to assess the effect of postexercise hot-water immersion on postprandial myofibrillar protein synthesis rates and the incorporation of dietary protein-derived amino acids into muscle protein. We observed that hot-water immersion during recovery from a single bout of resistance-type exercise does not further increase myofibrillar protein synthesis rates or augment the postprandial incorporation of dietary protein-derived amino acids in muscle throughout 5 h of postexercise recovery.
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Fuchs, Cas J., Wesley J. H. Hermans, Andrew M. Holwerda, Joey S. J. Smeets, Joan M. Senden, Janneau van Kranenburg, Annemie P. Gijsen, et al. "Branched-chain amino acid and branched-chain ketoacid ingestion increases muscle protein synthesis rates in vivo in older adults: a double-blind, randomized trial." American Journal of Clinical Nutrition 110, no. 4 (June 28, 2019): 862–72. http://dx.doi.org/10.1093/ajcn/nqz120.
Повний текст джерелаАнотація:
ABSTRACTBackgroundProtein ingestion increases muscle protein synthesis rates. However, limited data are currently available on the effects of branched-chain amino acid (BCAA) and branched-chain ketoacid (BCKA) ingestion on postprandial muscle protein synthesis rates.ObjectiveThe aim of this study was to compare the impact of ingesting 6 g BCAA, 6 g BCKA, and 30 g milk protein (MILK) on the postprandial rise in circulating amino acid concentrations and subsequent myofibrillar protein synthesis rates in older males.MethodsIn a parallel design, 45 older males (age: 71 ± 1 y; BMI: 25.4 ± 0.8 kg/m2) were randomly assigned to ingest a drink containing 6 g BCAA, 6 g BCKA, or 30 g MILK. Basal and postprandial myofibrillar protein synthesis rates were assessed by primed continuous l-[ring-13C6]phenylalanine infusions with the collection of blood samples and muscle biopsies.ResultsPlasma BCAA concentrations increased following test drink ingestion in all groups, with greater increases in the BCAA and MILK groups compared with the BCKA group (P < 0.05). Plasma BCKA concentrations increased following test drink ingestion in all groups, with greater increases in the BCKA group compared with the BCAA and MILK groups (P < 0.05). Ingestion of MILK, BCAA, and BCKA significantly increased early myofibrillar protein synthesis rates (0–2 h) above basal rates (from 0.020 ± 0.002%/h to 0.042 ± 0.004%/h, 0.022 ± 0.002%/h to 0.044 ± 0.004%/h, and 0.023 ± 0.003%/h to 0.044 ± 0.004%/h, respectively; P < 0.001), with no differences between groups (P > 0.05). Myofibrillar protein synthesis rates during the late postprandial phase (2–5 h) remained elevated in the MILK group (0.039 ± 0.004%/h; P < 0.001), but returned to baseline values following BCAA and BCKA ingestion (0.024 ± 0.005%/h and 0.024 ± 0.005%/h, respectively; P > 0.05).ConclusionsIngestion of 6 g BCAA, 6 g BCKA, and 30 g MILK increases myofibrillar protein synthesis rates during the early postprandial phase (0–2 h) in vivo in healthy older males. The postprandial increase following the ingestion of 6 g BCAA and BCKA is short-lived, with higher myofibrillar protein synthesis rates only being maintained following the ingestion of an equivalent amount of intact milk protein. This trial was registered at Nederlands Trial Register (www.trialregister.nl) as NTR6047.
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Davis, Teresa A., Marta L. Fiorotto, Philip R. Beckett, Douglas G. Burrin, Peter J. Reeds, Diane Wray-Cahen, and Hanh V. Nguyen. "Differential effects of insulin on peripheral and visceral tissue protein synthesis in neonatal pigs." American Journal of Physiology-Endocrinology and Metabolism 280, no. 5 (May 1, 2001): E770—E779. http://dx.doi.org/10.1152/ajpendo.2001.280.5.e770.
Повний текст джерелаАнотація:
We recently demonstrated in neonatal pigs that, with amino acids and glucose maintained at fasting levels, the stimulation of protein synthesis in longissimus dorsi muscle with feeding can be reproduced by a physiological rise in insulin alone. In the current report, we determine whether the response of protein synthesis to insulin in the neonatal pig is 1) present in muscles of different fiber types, 2) proportional in myofibrillar and sarcoplasmic proteins, 3) associated with increased translational efficiency and ribosome number, and 4) present in other peripheral tissues and in viscera. Hyperinsulinemic-euglycemic-amino acid clamps were performed in 7- and 26-day-old pigs infused with 0, 30, 100, or 1,000 ng · kg−0.66 · min−1 of insulin to reproduce insulin levels present in fasted, fed, refed, and supraphysiological conditions, respectively. Tissue protein synthesis was measured using a flooding dose ofl-[4-3H]phenylalanine. Insulin increased protein synthesis in gastrocnemius muscle and, to a lesser degree, masseter muscle. The degree of stimulation of protein synthesis by insulin was similar in myofibrillar and sarcoplasmic proteins. Insulin increased translational efficiency but had no effect on ribosome number in muscle. All of these insulin-induced changes in muscle protein synthesis decreased with age. Insulin also stimulated protein synthesis in cardiac muscle and skin but not in liver, intestine, spleen, pancreas, or kidney. The results support the hypothesis that insulin mediates the feeding-induced stimulation of myofibrillar and sarcoplasmic protein synthesis in muscles of different fiber types in the neonate by increasing the efficiency of translation. However, insulin does not appear to be involved in the feeding-induced stimulation of protein synthesis in visceral tissues. Thus different mechanisms regulate the growth of peripheral and visceral tissues in the neonate.
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Holwerda, Andrew M., Kevin J. M. Paulussen, Maarten Overkamp, Joy P. B. Goessens, Irene Fleur Kramer, Will K. W. H. Wodzig, Lex B. Verdijk, and Luc J. C. van Loon. "Dose-Dependent Increases in Whole-Body Net Protein Balance and Dietary Protein-Derived Amino Acid Incorporation into Myofibrillar Protein During Recovery from Resistance Exercise in Older Men." Journal of Nutrition 149, no. 2 (February 1, 2019): 221–30. http://dx.doi.org/10.1093/jn/nxy263.
Повний текст джерелаАнотація:
ABSTRACT Background Age-related decline in skeletal muscle mass is at least partly attributed to anabolic resistance to food intake. Resistance exercise sensitizes skeletal muscle tissue to the anabolic properties of amino acids. Objective The present study assessed protein digestion and amino acid absorption kinetics, whole-body protein balance, and the myofibrillar protein synthetic response to ingestion of different amounts of protein during recovery from resistance exercise in older men. Methods Forty-eight healthy older men [mean ± SEM age: 66 ± 1 y; body mass index (kg/m2): 25.4 ± 0.3] were randomly assigned to ingest 0, 15, 30, or 45 g milk protein concentrate after a single bout of resistance exercise consisting of 4 sets of 10 repetitions of leg press and leg extension and 2 sets of 10 repetitions of lateral pulldown and chest press performed at 75–80% 1-repetition maximum. Postprandial protein digestion and amino acid absorption kinetics, whole-body protein metabolism, and myofibrillar protein synthesis rates were assessed using primed, continuous infusions of l-[ring-2H5]-phenylalanine, l-[ring-2H2]-tyrosine, and l-[1-13C]-leucine combined with ingestion of intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled protein. Results Whole-body net protein balance showed a dose-dependent increase after ingestion of 0, 15, 30, or 45 g of protein (0.015 ± 0.002, 0.108 ± 0.004, 0.162 ± 0.008, and 0.215 ± 0.009 μmol Phe · kg−1 · min−1, respectively; P < 0.001). Myofibrillar protein synthesis rates were higher after ingesting 30 (0.0951% ± 0.0062%/h, P = 0.07) or 45 g of protein (0.0970% ± 0.0062%/h, P < 0.05) than after 0 g (0.0746% ± 0.0051%/h). Incorporation of dietary protein–derived amino acids (l-[1-13C]-phenylalanine) into de novo myofibrillar protein showed a dose-dependent increase after ingestion of 15, 30, or 45 g protein (0.0171 ± 0.0017, 0.0296 ± 0.0030, and 0.0397 ± 0.0026 mole percentage excess, respectively; P < 0.05). Conclusions Dietary protein ingested during recovery from resistance exercise is rapidly digested and absorbed. Whole-body net protein balance and dietary protein-derived amino acid incorporation into myofibrillar protein show dose-dependent increases. Ingestion of ≥30 g protein increases postexercise myofibrillar protein synthesis rates in older men. This trial was registered at Nederlands Trial Register as NTR4492.
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Pinckaers, Philippe J. M., Michelle E. G. Weijzen, Lisanne H. P. Houben, Antoine H. Zorenc, Imre W. K. Kouw, Lisette CPGM de Groot, Lex B. Verdijk, Tim Snijders, and Luc JC van Loon. "The Muscle Protein Synthetic Response Following Ingestion of Corn Protein, Milk Protein and Their Protein Blend in Young Males." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 651. http://dx.doi.org/10.1093/cdn/nzaa049_044.
Повний текст джерелаАнотація:
Abstract Objectives The muscle protein synthetic response to the ingestion of animal based proteins has been reported to be superior to the ingestion of plant based proteins. The lesser anabolic properties of plant based compared with animal based proteins has been attributed to differences in essential amino acid (EAA) contents and amino acid composition. This study compares post-prandial muscle protein synthesis rates following the ingestion of 30 g milk protein with the ingestion of 30 g corn protein or a blend of 30 g corn and milk protein in vivo, in young males. Methods In a randomized, double blind, parallel-group design, 36 healthy young males (26 ± 4 y) received a primed continuous infusion of L-[ring-13C6]-phenylalanine and ingested 30 g milk protein (MILK), 30 g corn protein (CORN), or a blend of 15 g corn protein plus 15 g milk protein (CORN + MILK) (n = 12 per group). Blood and muscle biopsies were collected for 5 h following protein ingestion to assess post-prandial plasma amino acid profiles and myofibrillar protein synthesis rates. Data were analyzed with 2-way repeated measures ANOVA and independent samples t-test. Data are expressed as mean ± SD. Results MILK increased plasma EAA concentrations more when compared to CORN (incremental area under curve (iAUC): 151 ± 31 vs 77 ± 19 mmol/L/300 min, respectively; P < 0.001). Both milk and corn protein ingestion increased myofibrillar protein synthesis rates (P < 0.001), with no differences between MILK and CORN (from 0.014 ± 0.014 to 0.053 ± 0.013 and from 0.017 ± 0.011 to 0.052 ± 0.013%/h, respectively; time*treatment P = 0.661). When MILK was compared to CORN + MILK, the iAUC for plasma EAA concentrations increased more in MILK when compared to CORN + MILK (151 ± 31 vs 126 ± 24 mmol/L/300 min, respectively; P = 0.036). Corn plus milk protein ingestion also increased myofibrillar protein synthesis rates (from 0.015 ± 0.015 to 0.052 ± 0.024%/h; P < 0.001), with no differences between MILK and CORN + MILK (time*treatment P = 0.823). Conclusions Ingestion of 30 g milk protein, 30 g corn protein, or a blend of 15 g corn plus 15 g milk protein increases muscle protein synthesis rates in vivo in young males. Post-prandial muscle protein synthesis rates following the ingestion of 30 g milk protein do not differ from rates observed after ingesting 30 g corn protein or a blend providing 15 g milk plus 15 g corn protein in vivo, in young males. Funding Sources TiFN.
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Mitchell, Cameron J., Randall F. D’Souza, Sarah M. Mitchell, Vandre C. Figueiredo, Benjamin F. Miller, Karyn L. Hamilton, Fredrick F. Peelor, et al. "Impact of dairy protein during limb immobilization and recovery on muscle size and protein synthesis; a randomized controlled trial." Journal of Applied Physiology 124, no. 3 (March 1, 2018): 717–28. http://dx.doi.org/10.1152/japplphysiol.00803.2017.
Повний текст джерелаАнотація:
Muscle disuse results in the loss of muscular strength and size, due to an imbalance between protein synthesis (MPS) and breakdown (MPB). Protein ingestion stimulates MPS, although it is not established if protein is able to attenuate muscle loss with immobilization (IM) or influence the recovery consisting of ambulatory movement followed by resistance training (RT). Thirty men (49.9 ± 0.6 yr) underwent 14 days of unilateral leg IM, 14 days of ambulatory recovery (AR), and a further six RT sessions over 14 days. Participants were randomized to consume an additional 20 g of dairy protein or placebo with a meal during the intervention. Isometric knee extension strength was reduced following IM (−24.7 ± 2.7%), partially recovered with AR (−8.6 ± 2.6%), and fully recovered after RT (−0.6 ± 3.4%), with no effect of supplementation. Thigh muscle cross-sectional area decreased with IM (−4.1 ± 0.5%), partially recovered with AR (−2.1 ± 0.5%), and increased above baseline with RT (+2.2 ± 0.5%), with no treatment effect. Myofibrillar MPS, measured using deuterated water, was unaltered by IM, with no effect of protein. During AR, MPS was increased only with protein supplementation. Protein supplementation did not attenuate the loss of muscle size and function with disuse or potentiate recovery but enhanced myofibrillar MPS during AR. NEW & NOTEWORTHY Twenty grams of daily protein supplementation does not attenuate the loss of muscle size and function induced by 2 wk of muscle disuse or potentiate recovery in middle-age men. Average mitochondrial but not myofibrillar muscle protein synthesis was attenuated during immobilization with no effect of supplementation. Protein supplementation increased myofibrillar protein synthesis during a 2-wk period of ambulatory recovery following disuse but without group differences in phenotype recovery.
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Gasier, Heath G., James D. Fluckey, Stephen F. Previs, Michael P. Wiggs, and Steven E. Riechman. "Acute resistance exercise augments integrative myofibrillar protein synthesis." Metabolism 61, no. 2 (February 2012): 153–56. http://dx.doi.org/10.1016/j.metabol.2011.07.001.
Повний текст джерела
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Silver, G., and J. D. Etlinger. "Regulation of myofibrillar accumulation in chick muscle cultures: evidence for the involvement of calcium and lysosomes in non-uniform turnover of contractile proteins." Journal of Cell Biology 101, no. 6 (December 1, 1985): 2383–91. http://dx.doi.org/10.1083/jcb.101.6.2383.
Повний текст джерелаАнотація:
The effect of calcium on myofibrillar turnover in primary chick leg skeletal muscle cultures was examined. Addition of the calcium ionophore A23187 at subcontraction threshold levels (0.38 microM) increased significantly rates of efflux of preloaded 45Ca+2 but had no effect on total protein accumulation. However, A23187 as well as ionomycin caused decreased accumulation of the myofibrillar proteins, myosin heavy chain (MHC), myosin light chain 1f (LC1f), 2f (LC2f), alpha-actin (Ac), and tropomyosin (TM). A23187 increased the degradation rate of LC1f, LC2f, and TM after 24 h. In contrast, the calcium ionophore caused decreased degradation of Ac and troponin-C and had no effect on the degradation of MHC, troponin-T, troponin-I, or alpha, beta-desmin (Dm). In addition, A23187 did not alter degradation of total myotube protein. The ionophore had little or no effect on the synthesis of total myotube proteins, but caused a marked decrease in the synthesis of MHC, LC1f, LC2f, Ac, TM, and Dm after 48 h. The mechanisms involved in calcium-stimulated degradation of the myofibrillar proteins were also investigated. Increased proteolysis appeared to involve a lysosomal pathway, since the effect of the Ca++ ionophore could be blocked by the protease inhibitor leupeptin and the lysosomotropic agents methylamine and chloroquine. The effects of A23187 occur in the presence of serum, a condition in which no lysosomal component of overall protein degradation is detected. The differential effect of A23187 on the degradative rates of the myofibrillar proteins suggests a dynamic structure for the contractile apparatus.
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Robinson, Matthew M., Christopher Bell, Frederick F. Peelor та Benjamin F. Miller. "β-Adrenergic receptor blockade blunts postexercise skeletal muscle mitochondrial protein synthesis rates in humans". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 301, № 2 (серпень 2011): R327—R334. http://dx.doi.org/10.1152/ajpregu.00160.2011.
Повний текст джерелаАнотація:
β-Adrenergic receptor (AR) signaling is a regulator of skeletal muscle protein synthesis and mitochondrial biogenesis in mice. We hypothesized that β-AR blockade blunts postexercise skeletal muscle mitochondrial protein synthesis rates in adult humans. Six healthy men (mean ± SD: 26 ± 6 yr old, 39.9 ± 4.9 ml·kg−1·min−1 peak O2 uptake, 26.7 ± 2.0 kg/m2 body mass index) performed 1 h of stationary cycle ergometer exercise (60% peak O2 uptake) during 1) β-AR blockade (intravenous propranolol) and 2) administration of saline (control). Skeletal muscle mitochondrial, myofibrillar, and sarcoplasmic protein synthesis rates were assessed using [2H5]phenylalanine incorporation into skeletal muscle proteins after exercise. The mRNA content of signals for mitochondrial biogenesis was determined using real-time PCR. β-AR blockade decreased mitochondrial (from 0.217 ± 0.076 to 0.135 ± 0.031%/h, P < 0.05), but not myofibrillar or sarcoplasmic, protein synthesis rates. Peroxisome proliferator-activated receptor-γ coactivator-1α mRNA was increased ∼2.5-fold ( P < 0.05) at 5 h compared with 1 h postexercise but was not influenced by β-AR blockade. We conclude that decreased β-AR signaling during cycling can blunt the postexercise increase in mitochondrial protein synthesis rates without affecting mRNA content.
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Young, R. B., D. M. Moriarity, C. E. McGee, W. R. Farrar, and H. E. Richter. "Protein metabolism in chicken muscle cell cultures treated with cimaterol." Journal of Animal Science 68, no. 4 (April 1, 1990): 1158–69. http://dx.doi.org/10.2527/1990.6841158x.
Повний текст джерелаАнотація:
Abstract Primary muscle cell cultures were prepared from the leg muscle of 12-d broiler chicken embryos. The partitioning agent cimaterol (10−6 to 10−10M) was added on d 1 and each day thereafter, and cells were studied after 7 d in culture. Cimaterol had no effect at any level either on the percentage of nuclei within multinucleated myotubes or on the total number of nuclei within myotubes. At 10−7M cimaterol, the quantity of the myofibrillar protein fraction was increased by 25.1 ± 8.0% (P <.05) and the quantity of myosin heavy chain was increased by 30.9 ± 4.5% (P < .05). To understand the basis for the increase in myofibrillar protein, the incorporation rate of [3H]Leu was measured in pulse labeling experiments. The apparent synthesis rate of the soluble protein fraction and the crude myofibrillar fraction was not significantly increased by cimaterol; however, cimaterol levels greater than 10−8M caused a 10 to 12% increase (P < .05) in the incorporation rate of [3H]Leu into myosin heavy chain. The effect of cimaterol on release of [3H]Leu from prelabeled protein also was assessed in pulse-chase experiments; the apparent rate of protein degradation was inhibited by 10 to 15% (P < .05) at the higher levels of cimaterol. Dot blot analysis indicated that the quantity of myosin heavy chain mRNA was elevated in cimaterol-treated cultures. Thus, the increased quantity of myofibrillar proteins in embryonic broiler muscle cell cultures is the combined result of a stimulation in the rate of protein synthesis and an inhibition in the rate of protein degradation.
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Robinson, Meghann J., Nicholas A. Burd, Leigh Breen, Tracy Rerecich, Yifan Yang, Amy J. Hector, Steven K. Baker, and Stuart M. Phillips. "Dose-dependent responses of myofibrillar protein synthesis with beef ingestion are enhanced with resistance exercise in middle-aged men." Applied Physiology, Nutrition, and Metabolism 38, no. 2 (February 2013): 120–25. http://dx.doi.org/10.1139/apnm-2012-0092.
Повний текст джерелаАнотація:
Aging impairs the sensitivity of skeletal muscle to anabolic stimuli, such as amino acids and resistance exercise. Beef is a nutrient-rich source of dietary protein capable of stimulating muscle protein synthesis (MPS) rates in older men at rest. To date, the dose–response of myofibrillar protein synthesis to graded ingestion of protein-rich foods, such as beef, has not been determined. We aimed to determine the dose–response of MPS with and without resistance exercise to graded doses of beef ingestion. Thirty-five middle-aged men (59 ± 2 years) ingested 0 g, 57 g (2 oz; 12 g protein), 113 g (4 oz; 24 g protein), or 170 g (6 oz; 36 g protein) of (15% fat) ground beef (n = 7 per group). Subjects performed a bout of unilateral resistance exercise to allow measurement of the fed state and the fed plus resistance exercise state within each dose. A primed constant infusion of l-[1-13C]leucine was initiated to measure leucine oxidation and of l-[ring-13C6]phenylalanine was initiated to measure myofibrillar MPS. Myofibrillar MPS was increased with ingestion of 170 g of beef to a greater extent than all other doses at rest and after resistance exercise. There was more leucine oxidation with ingestion of 113 g of beef than with 0 g and 57 g, and it increased further after ingestion of 170 g of beef (all p < 0.05). Ingestion of 170 g of beef protein is required to stimulate a rise in myofibrillar MPS over and above that seen with lower doses. An isolated bout of resistance exercise was potent in stimulating myofibrillar MPS, and acted additively with feeding.
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Simpson, D. G., M. L. Decker, W. A. Clark, and R. S. Decker. "Contractile activity and cell-cell contact regulate myofibrillar organization in cultured cardiac myocytes." Journal of Cell Biology 123, no. 2 (October 15, 1993): 323–36. http://dx.doi.org/10.1083/jcb.123.2.323.
Повний текст джерелаАнотація:
Adult feline ventricular myocytes cultured on a laminin-coated substratum reestablish intercellular junctions, yet disassemble their myofibrils. Immunofluorescence microscopy reveals that these non-beating heart cells lack vinculin-positive focal adhesions; moreover, intercellular junctions are also devoid of vinculin. When these quiescent myocytes are stimulated to contract with the beta-adrenergic agonist, isoproterenol, extensive vinculin-positive focal adhesions and intercellular junctions emerge. If solitary myocytes are stimulated to beat, an elaborate series of vinculin-positive focal adhesions develop which appear to parallel the reassembly of myofibrils. In cultures where neighboring myocytes reestablish cell-cell contact, myofibrils appear to reassemble from the fascia adherens rather than focal contacts. Activation of beating is accompanied by a significant reduction in the rate of total and cytoskeletal protein synthesis; in fact, myofibrillar reassembly, redevelopment of focal adhesions and fascia adherens junctions require no protein synthesis for at least 24 h, implying the existence of an assembly competent pool of cytoskeletal proteins. Maturation of the fasciae adherens and the appearance of vinculin within Z-line/costameres, does require de novo synthesis of new cytoskeletal proteins. Changes in cytoskeletal protein turnover appear dependent on beta agonist-induced cAMP production, but myofibrillar reassembly is a cAMP-independent event. Such observations suggest that mechanical forces, in the guise of contractile activity, regulate vinculin distribution and myofibrillar order in cultured adult feline heart cells.
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Sundaram, Priyanka, Zhiyu Pang, Miao Miao, Lu Yu, and Simon S. Wing. "USP19-deubiquitinating enzyme regulates levels of major myofibrillar proteins in L6 muscle cells." American Journal of Physiology-Endocrinology and Metabolism 297, no. 6 (December 2009): E1283—E1290. http://dx.doi.org/10.1152/ajpendo.00409.2009.
Повний текст джерелаАнотація:
The ubiquitin-proteasome system plays an important role in the degradation of myofibrillar proteins that occurs in muscle wasting. Many studies have demonstrated the importance of enzymes mediating conjugation of ubiquitin. However, little is known about the role of deubiquitinating enzymes. We previously showed that the USP19-deubiquitinating enzyme is induced in atrophying skeletal muscle (Combaret L, Adegoke OA, Bedard N, Baracos V, Attaix D, Wing SS. Am J Physiol Endocrinol Metab 288: E693–E700, 2005). To further explore the role of USP19, we used small interfering RNA (siRNA) in L6 muscle cells. Lowering USP19 by 70–90% in myotubes resulted in a 20% decrease in the rate of proteolysis and an 18% decrease in the rate of protein synthesis, with no net change in protein content. Despite the decrease in overall synthesis, there were ∼1.5-fold increases in protein levels of myosin heavy chain (MHC), actin, and troponin T and a ∼2.5-fold increase in tropomyosin. USP19 depletion also increased MHC and tropomyosin mRNA levels, suggesting that this effect is due to increased transcription. Consistent with this, USP19 depletion increased myogenin protein and mRNA levels approximately twofold. Lowering myogenin using siRNA prevented the increase in MHC and tropomyosin upon USP19 depletion, indicating that myogenin mediated the increase in myofibrillar proteins. Dexamethasone treatment lowered MHC and increased USP19. Depletion of USP19 reversed the dexamethasone suppression of MHC. These studies demonstrate that USP19 modulates transcription of major myofibrillar proteins and indicate that the ubiquitin system not only mediates the increased protein breakdown but is also involved in the decreased protein synthesis in atrophying skeletal muscle.
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Phillips, Stuart M. "Short-Term Training: When Do Repeated Bouts of Resistance Exercise Become Training?" Canadian Journal of Applied Physiology 25, no. 3 (June 1, 2000): 185–93. http://dx.doi.org/10.1139/h00-014.
Повний текст джерелаАнотація:
Chronic resistance training induces increases in muscle fibre cross-sectional area (CSA), otherwise known as hypertrophy. This is due to an increased volume percentage of myofibrillar proteins within a given fibre. The exact time-course for muscle fibre hypertrophy is not well-documented but appears to require at least 6-7 weeks of regular resistive training at reasonably high intensity before increases in fibre CSA are deemed significant. Proposed training-induced changes in neural drive are hypothesized to increase strength due to increased synchrony of motor unit firing, reduced antagonist muscle activity and/or a reduction in any bilateral strength deficit. Nonetheless, increases in muscle protein synthesis were observed following an isolated bout of resistance exercise. In addition, muscle balance was positive, following resistance exercise when amino acids were infused/ingested. This showed that protein accretion occurred during the postexercise period. The implications of this hypothesis for training-induced increases in strength are discussed. Key words: hypertrophy, muscle protein synthesis, muscle protein breakdown, myofibrillar protein, strength.
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Hobler, Scott C., Arthur B. Williams, Josef E. Fischer, and Per-Olof Hasselgren. "IGF-I stimulates protein synthesis but does not inhibit protein breakdown in muscle from septic rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 274, no. 2 (February 1, 1998): R571—R576. http://dx.doi.org/10.1152/ajpregu.1998.274.2.r571.
Повний текст джерелаАнотація:
Sepsis is associated with reduced protein synthesis and increased protein degradation in skeletal muscle. We examined the effects of insulin-like growth factor I (IGF-I) on protein synthesis and breakdown in muscles from nonseptic and septic rats. Sepsis was induced by cecal ligation and puncture; control rats were sham operated. Extensor digitorum longus muscles were incubated in the absence or presence of IGF-I at concentrations ranging from 100 ng/ml to 10 μg/ml. Total and myofibrillar protein breakdown rates were measured as net release of tyrosine and 3-methylhistidine, respectively. Protein synthesis was determined by measuring incorporation of [U-14C]phenylalanine into protein. IGF-I stimulated protein synthesis in a dose-dependent fashion in muscles from both sham-operated and septic rats, with a maximal effect seen at a hormone concentration between 500 and 1,000 ng/ml. IGF-I inhibited total and myofibrillar protein breakdown in muscles from sham-operated rats, whereas in muscles from septic rats, IGF-I had no effect on protein breakdown, even at high concentrations. The results suggest that protein breakdown in skeletal muscle becomes resistant to IGF-I during sepsis and that this resistance reflects a postreceptor defect.
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Hall-Angeras, M., U. Angeras, P. O. Hasselgren, and J. E. Fischer. "Effects of elevated temperature on protein breakdown in muscles from septic rats." American Journal of Physiology-Cell Physiology 258, no. 4 (April 1, 1990): C589—C592. http://dx.doi.org/10.1152/ajpcell.1990.258.4.c589.
Повний текст джерелаАнотація:
Elevated temperature has been proposed to contribute to accelerated muscle protein degradation during fever and sepsis. The present study examined the effect of increased temperature in vitro on protein turnover in skeletal muscles from septic and control rats. Sepsis was induced by cecal ligation and puncture (CLP); control rats were sham operated. After 16 h, the extensor digitorum longus (EDL) and soleus (SOL) muscles were incubated at 37 or 40 degrees C. Protein synthesis was determined by measuring incorporation of [14C]phenylalanine into protein. Total and myofibrillar protein breakdown was assessed from release of tyrosine and 3-methylhistidine (3-MH), respectively. Total protein breakdown was increased at 40 degrees C by 15% in EDL and by 29% in SOL from control rats, whereas 3-MH release was not affected. In muscles from septic rats, total and myofibrillar protein breakdown was increased by 22 and 30%, respectively, at 40 degrees C in EDL but was not altered in SOL. Protein synthesis was unaffected by high temperature both in septic and nonseptic muscles. The present results suggest that high temperature is not the primary mechanism of increased muscle protein breakdown in sepsis because the typical response to sepsis, i.e., a predominant increase in myofibrillar protein breakdown, was not induced by elevated temperature in normal muscle. It is possible, however, that increased temperature may potentiate protein breakdown that is already stimulated by sepsis because elevated temperature increased both total and myofibrillar protein breakdown in EDL from septic rats.
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Welle, Stephen, Kirti Bhatt, and Charles A. Thornton. "Stimulation of myofibrillar synthesis by exercise is mediated by more efficient translation of mRNA." Journal of Applied Physiology 86, no. 4 (April 1, 1999): 1220–25. http://dx.doi.org/10.1152/jappl.1999.86.4.1220.
Повний текст джерелаАнотація:
Resistance exercises stimulate protein synthesis in human muscle, but the roles of changes in mRNA concentrations and changes in the efficiency of mRNA translation have not been defined. The present study was done to determine whether resistance exercise affects concentrations of total RNA, total mRNA, actin mRNA, or myosin heavy-chain mRNA (total and isoform specific). Eight subjects, 62–75 yr old, performed unilateral knee extensions at 80% of their one-repetition-maximum capacity on days 1, 3, and 6 of the study. On day 7, biopsies of exercised and nonexercised vastus lateralis muscles were obtained. Myofibrillar synthesis was determined by stable- isotope incorporation, and mRNA concentrations were determined by membrane hybridization and PCR-based methods. The exercise stimulated myofibrillar synthesis [30 ± 6 (SE)%] without affecting RNA or mRNA concentrations. The effect of exercise on protein synthesis in individual subjects did not correlate with the effect on total RNA and mRNA concentrations. These data suggest that the stimulation of myofibrillar synthesis by resistance exercise is mediated by more efficient translation of mRNA.
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Davis, Teresa A., Marta L. Fiorotto, Douglas G. Burrin, Peter J. Reeds, Hanh V. Nguyen, Philip R. Beckett, Rhonda C. Vann, and Pamela M. J. O'Connor. "Stimulation of protein synthesis by both insulin and amino acids is unique to skeletal muscle in neonatal pigs." American Journal of Physiology-Endocrinology and Metabolism 282, no. 4 (April 1, 2002): E880—E890. http://dx.doi.org/10.1152/ajpendo.00517.2001.
Повний текст джерелаАнотація:
In neonatal pigs, the feeding-induced stimulation of protein synthesis in skeletal muscle, but not liver, can be reproduced by insulin infusion when essential amino acids and glucose are maintained at fasting levels. In the present study, 7- and 26-day-old pigs were studied during 1) fasting, 2) hyperinsulinemic-euglycemic-euaminoacidemic clamps, 3) euinsulinemic-euglycemic-hyperaminoacidemic clamps, and 4) hyperinsulinemic-euglycemic-hyperaminoacidemic clamps. Amino acids were clamped using a new amino acid mixture enriched in nonessential amino acids. Tissue protein synthesis was measured using a flooding dose ofl-[4-3H]phenylalanine. In 7-day-old pigs, insulin infusion alone increased protein synthesis in various skeletal muscles (from +35 to +64%), with equivalent contribution of myofibrillar and sarcoplasmic proteins, as well as cardiac muscle (+50%), skin (+34%), and spleen (+26%). Amino acid infusion alone increased protein synthesis in skeletal muscles (from +28 to +50%), also with equivalent contribution of myofibrillar and sarcoplasmic proteins, as well as liver (+27%), pancreas (+28%), and kidney (+10%). An elevation of both insulin and amino acids did not have an additive effect. Similar qualitative results were obtained in 26-day-old pigs, but the magnitude of the stimulation of protein synthesis by insulin and/or amino acids was lower. The results suggest that, in the neonate, the stimulation of protein synthesis by feeding is mediated by either amino acids or insulin in most tissues; however, the feeding-induced stimulation of protein synthesis in skeletal muscle is uniquely regulated by both insulin and amino acids.
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Svanberg, E., H. Zachrisson, C. Ohlsson, B. M. Iresjo, and K. G. Lundholm. "Role of insulin and IGF-I in activation of muscle protein synthesis after oral feeding." American Journal of Physiology-Endocrinology and Metabolism 270, no. 4 (April 1, 1996): E614—E620. http://dx.doi.org/10.1152/ajpendo.1996.270.4.e614.
Повний текст джерелаАнотація:
The aim was to evaluate the role of insulin and insulin-like growth factor I (IGF-I) in activation of muscle protein synthesis after oral feeding. Synthesis rate of globular and myofibrillar proteins in muscle tissue was quantified by a flooding dose of radioactive phenylalanine. Muscle tissue expression of IGF-I mRNA was measured. Normal (C57 Bl) and diabetic mice (type I and type II) were subjected to an overnight fast (18 h) with subsequent refeeding procedures for 3 h with either oral chow intake or provision of insulin, IGF-I, glucose, and amino acids. Anti-insulin and anti-IGF-I were provided intraperitoneally before oral refeeding in some experiments. An overnight fast reduced synthesis of both globular (38 +/- 3%) and myofibrillar proteins (54 +/- 3%) in skeletal muscles, which was reversed by oral refeeding. Muscle protein synthesis, after starvation/ refeeding, was proportional and similar to changes in skeletal muscle IGF-I mRNA expression. Diabetic mice responded quantitatively similarly to starvation/refeeding in muscle protein synthesis compared with normal mice (C57 Bl). Both anti-insulin and anti-IGF-I attenuated significantly the stimulation of muscle protein synthesis in response to oral feeding, whereas exogenous provision of either insulin or IGF-I to overnight-starved and freely fed mice did not clearly stimulate protein synthesis in skeletal muscles. Our results support the suggestion that insulin and IGF-I either induce or facilitate the protein synthesis machinery in skeletal muscles rather than exerting a true stimulation of the biosynthetic process during feeding.
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Varanoske, Alyssa, Stephen Hennigar, Lee Margolis, Claire Berryman, Mahalakshmi Shankaran, Tyler Field, Hector Palacios, et al. "Effects of Prolonged Energy Restriction and Dietary Protein on Muscle Protein Synthesis and Proteome Dynamics in Obese Zucker Rats." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 670. http://dx.doi.org/10.1093/cdn/nzaa049_063.
Повний текст джерелаАнотація:
Abstract Objectives High protein (HP) diets during short-term energy restriction (ER) attenuate energy-mediated reductions in muscle protein synthesis (MPS). MPS-adaptive responses to HP diets during prolonged ER are not well described. This study examined the effects of prolonged ER and HP on MPS and the synthesis rates of numerous individual muscle proteins. Methods Female 6-wk-old obese Zucker (leprfa+/fa+, n = 48) rats were randomized to one of four diet groups for 10 weeks: ad libitum-standard protein (AL-SP; 14% protein), AL-HP (35% protein), ER-SP, and ER-HP (both fed 60% of intake of AL-SP). At the start of week 10, D2O was administered by intraperitoneal injection and isotopic equilibrium was maintained daily by providing D2O in drinking water. Rats were euthanized after 1 week of labeling, and mixed-MPS (gastrocnemius), absolute mixed-MPS (mixed-MPS x muscle protein content), proteome dynamics, and protein half-lives [rate/d (k) = –ln(1-f)/d, where f is mixed-MPS and t is time in days; t1/2 (days) = ln(2)/k] were quantified. Results Mixed-MPS was not altered by energy status and protein intake. Gastrocnemius mass was lower (P < 0.001) in ER-fed rats than AL-fed rats and higher (P = 0.034) for AL-HP than AL-SP. As a result, absolute mixed-MPS was lower (P < 0.005) in ER than AL, regardless of dietary protein. Absolute synthesis in 24 of 26 myofibrillar, 32 of 61 mitochondrial, and 55 of 60 cytoplasmic measured proteins were lower in ER than AL (P < 0.05), regardless of dietary protein. The difference in absolute synthesis of myofibrillar, mitochondrial, and cytoplasmic proteins due to ER compared to AL was 28%, 16%, and 27%, respectively. Comparison of HP and SP within each energy state revealed lower turnover rates and prolonged half-lives for a majority of measured muscle proteins in HP than in SP in both ER and AL conditions (P < 0.001). Conclusions Prolonged ER in obese Zucker rats exerted a strong suppressive effect on myofibrillar, mitochondrial, and cytoplasmic MPS, suggesting reduced protein accretion contributed to lower gastrocnemius mass in ER-fed rats. Lower turnover rates of most muscle proteins in HP-fed rats without reductions in protein pool size (i.e., tissue mass) suggests prolonged HP intake, independent of energy, may prolong muscle protein lifespan of in obese Zucker rats. Funding Sources Supported by USAMRDC; authors’ views not official U.S. Army or DoD policy.
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Kouw, Imre W. K., Naomi M. Cermak, Nicholas A. Burd, Tyler A. Churchward-Venne, Joan M. Senden, Annemarie P. Gijsen, and Luc J. C. van Loon. "Sodium nitrate co-ingestion with protein does not augment postprandial muscle protein synthesis rates in older, type 2 diabetes patients." American Journal of Physiology-Endocrinology and Metabolism 311, no. 2 (August 1, 2016): E325—E334. http://dx.doi.org/10.1152/ajpendo.00122.2016.
Повний текст джерелаАнотація:
The age-related anabolic resistance to protein ingestion is suggested to be associated with impairments in insulin-mediated capillary recruitment and postprandial muscle tissue perfusion. The present study investigated whether dietary nitrate co-ingestion with protein improves muscle protein synthesis in older, type 2 diabetes patients. Twenty-four men with type 2 diabetes (72 ± 1 yr, 26.7 ± 1.4 m/kg2 body mass index, 7.3 ± 0.4% HbA1C) received a primed continuous infusion of l-[ring-2H5]phenylalanine and l-[1-13C]leucine and ingested 20 g of intrinsically l-[1-13C]phenylalanine- and l-[1-13C]leucine-labeled protein with (PRONO3) or without (PRO) sodium nitrate (0.15 mmol/kg). Blood and muscle samples were collected to assess protein digestion and absorption kinetics and postprandial muscle protein synthesis rates. Upon protein ingestion, exogenous phenylalanine appearance rates increased in both groups ( P < 0.001), resulting in 55 ± 2% and 53 ± 2% of dietary protein-derived amino acids becoming available in the circulation over the 5h postprandial period in the PRO and PRONO3 groups, respectively. Postprandial myofibrillar protein synthesis rates based on l-[ring-2H5]phenylalanine did not differ between groups (0.025 ± 0.004 and 0.021 ± 0.007%/h over 0–2 h and 0.032 ± 0.004 and 0.030 ± 0.003%/h over 2–5 h in PRO and PRONO3, respectively, P = 0.7). No differences in incorporation of dietary protein-derived l-[1-13C]phenylalanine into de novo myofibrillar protein were observed at 5 h (0.016 ± 0.002 and 0.014 ± 0.002 mole percent excess in PRO and PRONO3, respectively, P = 0.8). Dietary nitrate co-ingestion with protein does not modulate protein digestion and absorption kinetics, nor does it further increase postprandial muscle protein synthesis rates or the incorporation of dietary protein-derived amino acids into de novo myofibrillar protein in older, type 2 diabetes patients.
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Hasselgren, P. O., O. Zamir, J. H. James, and J. E. Fischer. "Prostaglandin E2 does not regulate total or myofibrillar protein breakdown in incubated skeletal muscle from normal or septic rats." Biochemical Journal 270, no. 1 (August 15, 1990): 45–50. http://dx.doi.org/10.1042/bj2700045.
Повний текст джерелаАнотація:
The role of prostaglandins in the regulation of muscle protein breakdown is controversial. We examined the influence of arachidonic acid (5 microM), prostaglandin E2 (PGE2) (2.8 microM) and the prostaglandin-synthesis inhibitor indomethacin (3 microM) on total and myofibrillar protein breakdown in rat extensor digitorum longus and soleus muscles incubated under different conditions in vitro. In other experiments, the effects of indomethacin, administered in vivo to septic rats (3 mg/kg, injected subcutaneously twice after induction of sepsis by caecal ligation and puncture) on plasma levels and muscle release of PGE2 and on total and myofibrillar protein breakdown rates were determined. Total and myofibrillar proteolysis was assessed by measuring production by incubated muscles of tyrosine and 3-methylhistidine respectively. Arachidonic acid or PGE2 added during incubation of muscles from normal rats did not affect total or myofibrillar protein degradation under a variety of different conditions in vitro. Indomethacin inhibited muscle PGE2 production by incubated muscles from septic rats, but did not lower proteolytic rates. Administration in vivo of indomethacin did not affect total or myofibrillar muscle protein breakdown, despite effective plasma levels of indomethacin with decreased plasma PGE2 levels and inhibition of muscle PGE2 release. The present results suggest that protein breakdown in skeletal muscle of normal or septic rats is not regulated by PGE2 or other prostaglandins.
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Davies, Robert W., Joseph J. Bass, Brian P. Carson, Catherine Norton, Marta Kozior, Daniel J. Wilkinson, Matthew S. Brook, Philip J. Atherton, Ken Smith, and Philip M. Jakeman. "The Effect of Whey Protein Supplementation on Myofibrillar Protein Synthesis and Performance Recovery in Resistance-Trained Men." Nutrients 12, no. 3 (March 21, 2020): 845. http://dx.doi.org/10.3390/nu12030845.
Повний текст джерелаАнотація:
Background: The aim of this study was to investigate the effect of whey protein supplementation on myofibrillar protein synthesis (myoPS) and muscle recovery over a 7-d period of intensified resistance training (RT). Methods: In a double-blind randomised parallel group design, 16 resistance-trained men aged 18 to 35 years completed a 7-d RT protocol, consisting of three lower-body RT sessions on non-consecutive days. Participants consumed a controlled diet (146 kJ·kg−1·d−1, 1.7 g·kg−1·d−1 protein) with either a whey protein supplement or an isonitrogenous control (0.33 g·kg−1·d−1 protein). To measure myoPS, 400 ml of deuterium oxide (D2O) (70 atom %) was ingested the day prior to starting the study and m. vastus lateralis biopsies were taken before and after RT-intervention. Myofibrillar fractional synthetic rate (myoFSR) was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Pyr-IRMS). Muscle recovery parameters (i.e., countermovement jump height, isometric-squat force, muscle soreness and serum creatine kinase) were assessed daily. Results: MyoFSR PRE was 1.6 (0.2) %∙d−1 (mean (SD)). Whey protein supplementation had no effect on myoFSR (p = 0.771) or any recovery parameter (p = 0.390–0.989). Conclusions: Over an intense 7-d RT protocol, 0.33 g·kg−1·d−1 of supplemental whey protein does not enhance day-to-day measures of myoPS or postexercise recovery in resistance-trained men.
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Kim, Yeongmin, Sanghee Park, Jinseok Lee, Jiwoong Jang, Jiyeon Jung, Jin-Ho Koh, Cheol Soo Choi, Robert R. Wolfe, and Il-Young Kim. "Essential Amino Acid-Enriched Diet Alleviates Dexamethasone-Induced Loss of Muscle Mass and Function through Stimulation of Myofibrillar Protein Synthesis and Improves Glucose Metabolism in Mice." Metabolites 12, no. 1 (January 16, 2022): 84. http://dx.doi.org/10.3390/metabo12010084.
Повний текст джерелаАнотація:
Dexamethasone (DEX) induces dysregulation of protein turnover, leading to muscle atrophy and impairment of glucose metabolism. Positive protein balance, i.e., rate of protein synthesis exceeding rate of protein degradation, can be induced by dietary essential amino acids (EAAs). In this study, we investigated the roles of an EAA-enriched diet in the regulation of muscle proteostasis and its impact on glucose metabolism in the DEX-induced muscle atrophy model. Mice were fed normal chow or EAA-enriched chow and were given daily injections of DEX over 10 days. We determined muscle mass and functions using treadmill running and ladder climbing exercises, protein kinetics using the D2O labeling method, molecular signaling using immunoblot analysis, and glucose metabolism using a U-13C6 glucose tracer during oral glucose tolerance test (OGTT). The EAA-enriched diet increased muscle mass, strength, and myofibrillar protein synthesis rate, concurrent with improved glucose metabolism (i.e., reduced plasma insulin concentrations and increased insulin sensitivity) during the OGTT. The U-13C6 glucose tracing revealed that the EAA-enriched diet increased glucose uptake and subsequent glycolytic flux. In sum, our results demonstrate a vital role for the EAA-enriched diet in alleviating the DEX-induced muscle atrophy through stimulation of myofibrillar proteins synthesis, which was associated with improved glucose metabolism.
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Kumar, Vinod, Philip Atherton, Kenneth Smith, and Michael J. Rennie. "Human muscle protein synthesis and breakdown during and after exercise." Journal of Applied Physiology 106, no. 6 (June 2009): 2026–39. http://dx.doi.org/10.1152/japplphysiol.91481.2008.
Повний текст джерелаАнотація:
Skeletal muscle demonstrates extraordinary mutability in its responses to exercise of different modes, intensity, and duration, which must involve alterations of muscle protein turnover, both acutely and chronically. Here, we bring together information on the alterations in the rates of synthesis and degradation of human muscle protein by different types of exercise and the influences of nutrition, age, and sexual dimorphism. Where possible, we summarize the likely changes in activity of signaling proteins associated with control of protein turnover. Exercise of both the resistance and nonresistance types appears to depress muscle protein synthesis (MPS), whereas muscle protein breakdown (MPB) probably remains unchanged during exercise. However, both MPS and MPB are elevated after exercise in the fasted state, when net muscle protein balance remains negative. Positive net balance is achieved only when amino acid availability is increased, thereby raising MPS markedly. However, postexercise-increased amino acid availability is less important for inhibiting MPB than insulin, the secretion of which is stimulated most by glucose availability, without itself stimulating MPS. Exercise training appears to increase basal muscle protein turnover, with differential responses of the myofibrillar and mitochondrial protein fractions to acute exercise in the trained state. Aging reduces the responses of myofibrillar protein and anabolic signaling to resistance exercise. There appear to be few, if any, differences in the response of young women and young men to acute exercise, although there are indications that, in older women, the responses may be blunted more than in older men.
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Özerman Edis, Bilge, Muhammet Bektaş, and Rüstem Nurten. "Myofibrillar degeneration with diphtheria toxin." Turkish Journal of Biochemistry 45, no. 4 (July 28, 2020): 351–57. http://dx.doi.org/10.1515/tjb-2019-0109.
Повний текст джерелаАнотація:
AbstractObjectivesCardiac damage in patient with diphtheritic myocarditis is reported as the leading cause of mortality. Diphtheria toxin (DTx) is a well-known bacterial toxin inducing various cytotoxic effects. Mainly, catalytic fragment inhibits protein synthesis, induces cytotoxicity, and depolymerizes actin filaments. In this study, we aimed to demonstrate the extent of myofibrillar damage under DTx treatment to porcine cardiac tissue samples.MethodsTissue samples were incubated with DTx for 1–3 h in culture conditions. To analyze whole toxin (both fragments) distribution, conjugation of DTx with FITC was performed. Measurements were carried out with fluorescence spectrophotometer before and after dialysis. Immunofluorescence microscopy was used to show localization of DTx-FITC (15 nM) on cardiac tissue incubated for 2 h. Ultrastructural characterization of cardiac tissue samples treated with DTx (15 or 150 nM) was performed with transmission electron microscopy.ResultsDTx exerts myofibrillar disorganization. Myofilament degeneration, mitochondrial damage, vacuolization, and abundant lipid droplets were determined with 150 nM of DTx treatment.ConclusionsThis finding is an addition to depolymerization of actin filaments as a result of the DTx-actin interactions in in vitro conditions, indicating that myofilament damage can occur with DTx directly besides protein synthesis inhibition. Ultrastructural results support the importance of filamentous actin degeneration at diphtheritic myocarditis.