Transcriptional regulation of decreased protein synthesis during skeletal muscle unloading

1989 ◽  
Vol 66 (3) ◽  
pp. 1093-1098 ◽  
Author(s):  
G. Howard ◽  
J. M. Steffen ◽  
T. E. Geoghegan
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Blot Hybridization ◽  
Qualitative Assessment ◽  
Whole Body ◽  
Dot Blot ◽  
Total Rna ◽  
Actin Mrna ◽  
Alpha Actin ◽  
Muscle Unloading

Muscle atrophy resulting from disuse is associated with marked decrements in protein synthesis. The objective of the present investigation was to determine levels of total muscle RNA and the content and composition of the mRNA fraction as a qualitative assessment of the potential regulatory role of transcriptional alterations in unloaded skeletal muscles. Hindlimb muscle unloading was produced by whole-body suspension of rats for up to 7 days. The soleus, gastrocnemius, and extensor digitorum longus (EDL) were excised from 1-, 3-, and 7-day suspended and pair-fed controls, and RNA was extracted by homogenization in 5 M guanidinium thiocyanate. Total RNA and mRNA contents were lower in soleus and gastrocnemius after 7 days of suspension compared with pair-fed controls, but total RNA and mRNA concentrations (per g muscle and per microgram total RNA, respectively) were unaltered. alpha-Actin mRNA, assessed by dot blot hybridization, was significantly reduced in soleus after 1 (37%), 3 (28%), and 7 (59%) days of suspension and in gastrocnemius after 3 (44%) and 7 (41%) days. However, alpha-actin mRNA was unchanged in the EDL after suspension. Protein synthesis directed by RNA extracted from soleus and EDL indicated marked (30–400%) alterations in mRNAs coding for several small (15- to 25-kDa) proteins. The results of this study suggest that altered transcription and availability of specific mRNAs could contribute significantly to the regulation of protein synthesis during unloading of skeletal muscle.

Reduction of glutamine synthetase mRNA in hypertrophied skeletal muscle

1992 ◽  
Vol 262 (6) ◽  
pp. R1131-R1136 ◽  
Author(s):  
M. T. Falduto ◽  
A. P. Young ◽  
G. Smyrniotis ◽  
R. C. Hickson
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Activity ◽  
Glutamine Synthetase ◽  
Contractile Activity ◽  
Blot Hybridization ◽  
Posttranslational Regulation ◽  
Mrna Levels ◽  
Dot Blot ◽  
Total Rna ◽  
Rna Concentration

Skeletal muscle glutamine synthetase (GS) expression is reduced by endurance exercise and is increased when normal innervation is interrupted. This investigation was undertaken to determine whether GS expression is downregulated by the increased contractile activity associated with functional overload. Plantaris muscles overloaded for 30 days by synergist ablation were 70% heavier than those in sham-operated and unoperated control muscles. GS mRNA levels from hypertrophied muscles, measured by Northern and dot-blot hybridization, were reduced to 30% of controls. Changes in total RNA concentration and the proportion of poly(A)+ RNA in the total RNA pool did not account for the decline in GS mRNA. Despite reduced levels of GS mRNA, GS enzyme activity (nmol.h-1.mg protein-1) was unchanged in the hypertrophied muscles (overload, 79 +/- 5; control, 82 +/- 4). To further examine the lack of relationship between GS mRNA and enzyme activity, the concentration of glutamine, a known posttranslational modifier of GS activity, was measured. Consistent with the observed enzyme activities, muscle glutamine was unchanged in hypertrophied muscle (overload, 6.2 +/- 0.3; control, 5.8 +/- 0.4 mumol/g tissue). These results suggest that translational or posttranslational regulation, other than through alterations in glutamine concentration. may play a role in maintaining GS enzyme levels in hypertrophied muscle. Moreover, the regulation of GS activity in muscle hypertrophy may differ from the regulation with endurance training, in which changes in enzyme activity parallel changes in mRNA.

Changes in actin synthesis and alpha-actin-mRNA content in rat muscle during immobilization

1984 ◽  
Vol 247 (1) ◽  
pp. C39-C44 ◽  
Author(s):  
P. A. Watson ◽  
J. P. Stein ◽  
F. W. Booth
Keyword(s):  
Gastrocnemius Muscle ◽  
Blot Hybridization ◽  
Rapid Onset ◽  
Constant Infusion ◽  
Synthesis Rate ◽  
Dot Blot ◽  
Adult Rat ◽  
Actin Mrna ◽  
Alpha Actin ◽  
Specific Mrna

The fractional rates of actin synthesis in adult rat gastrocnemius muscle from control and 6-h hindlimb-immobilized animals were determined by the constant-infusion technique. The rate of actin synthesis in gastrocnemius muscle was significantly decreased from control values during the 6th h of hindlimb immobilization. The content of alpha-actin-specific mRNA was then estimated in adult rat gastrocnemius muscle from control, 6-h, 72-h, and 7-day immobilized animals by “dot blot” hybridization. RNA extracted from control and immobilized animals was secured on nitrocellulose filters and hybridized to 32P-labeled plasmid p749 (containing a cDNA sequence produced from rat alpha-actin mRNA). The relative content of alpha-actin-specific mRNA in gastrocnemius muscle was significantly decreased at 7 days of immobilization but not at 6 or 72 h of immobilization. It is concluded that a change in the content of alpha-actin mRNA does not contribute significantly to the rapid onset of the decrease in actin synthesis rate observed after 6 h of immobilization. An alteration in the translation of alpha-actin-specific mRNA must occur to account for the early decline in actin synthesis during immobilization.

Stimulation of myofibrillar synthesis by exercise is mediated by more efficient translation of mRNA

1999 ◽  
Vol 86 (4) ◽  
pp. 1220-1225 ◽  
Author(s):  
Stephen Welle ◽  
Kirti Bhatt ◽  
Charles A. Thornton
Keyword(s):  
Protein Synthesis ◽  
Resistance Exercise ◽  
Vastus Lateralis ◽  
Mrna Translation ◽  
Human Muscle ◽  
Total Rna ◽  
Resistance Exercises ◽  
Actin Mrna ◽  
Membrane Hybridization ◽  
Stimulation Of

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.

Effects of advanced age on whole-body protein synthesis and skeletal muscle mechanistic target of rapamycin signaling in horses

2013 ◽  
Vol 74 (11) ◽  
pp. 1433-1442 ◽  
Author(s):  
Ashley L. Wagner ◽  
Kristine L. Urschel ◽  
Alejandra Betancourt ◽  
Amanda A. Adams ◽  
David W. Horohov
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Advanced Age ◽  
Target Of Rapamycin ◽  
Whole Body ◽  
Body Protein ◽  
Mechanistic Target Of Rapamycin

scholarly journals Exercise-related changes in protein turnover in mammalian striated muscle

1991 ◽  
Vol 160 (1) ◽  
pp. 127-148 ◽  
Author(s):  
D. F. Goldspink
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Protein Turnover ◽  
Striated Muscle ◽  
Contractile Activity ◽  
Whole Body ◽  
Phenotypic Properties ◽  
Type Of Exercise ◽  
Passive Stretch

Contractile activity is an important determinant of the size, rate of protein turnover and phenotypic properties of muscle. Animal models that decrease muscle activity invariably accelerate the rate of protein degradation, usually complementing decreases in the rate of protein synthesis. The net effect is muscle atrophy. By contrast, increased activity and/or passive stretch enhance the synthesis of new proteins, whilst protein catabolism may be either decreased or increased. Muscle hypertrophy results. Endurance activities in man and animals usually induce cardiac hypertrophy, and increased fatigue resistance in skeletal muscle. During exercise the whole body and its skeletal musculature exhibit a negative nitrogen balance, and there is general agreement that rates of protein synthesis are decreased. Changes in protein degradation are, however, much less clearly defined. Resistance exercises induce the opposite changes, with the size of the heart remaining unchanged whilst the bulk and strength of skeletal muscle increase. No real consensus currently exists about the nature of the changes in protein turnover with this type of exercise. More carefully designed and executed experiments are required.

Polyadenylated RNA, actin mRNA, and myosin heavy chain mRNA in young and old human skeletal muscle

1996 ◽  
Vol 270 (2) ◽  
pp. E224-E229 ◽  
Author(s):  
S. Welle ◽  
K. Bhatt ◽  
C. Thornton
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Human Skeletal Muscle ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Type I ◽  
Polyadenylated Rna ◽  
Actin Mrna

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.

Prolonged bed rest decreases skeletal muscle and whole body protein synthesis

1996 ◽  
Vol 270 (4) ◽  
pp. E627-E633 ◽  
Author(s):  
A. A. Ferrando ◽  
H. W. Lane ◽  
C. A. Stuart ◽  
J. Davis-Street ◽  
R. R. Wolfe
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Bed Rest ◽  
Whole Body ◽  
Protein Breakdown ◽  
Skeletal Muscle Protein ◽  
Model Calculations ◽  
Body Protein

We sought to determine the extent to which the loss of lean body mass and nitrogen during inactivity was due to alterations in skeletal muscle protein metabolism. Six male subjects were studied during 7 days of diet stabilization and after 14 days of stimulated microgravity (-6 degrees bed rest). Nitrogen balance became more negative (P < 0.03) during the 2nd wk of bed rest. Leg and whole body lean mass decreased after bed rest (P < 0.05). Serum cortisol, insulin, insulin-like growth factor I, and testosterone values did not change. Arteriovenous model calculations based on the infusion of L-[ring-13C6]-phenylalanine in five subjects revealed a 50% decrease in muscle protein synthesis (PS; P < 0.03). Fractional PS by tracer incorporation into muscle protein also decreased by 46% (P < 0.05). The decrease in PS was related to a corresponding decrease in the sum of intracellular amino acid appearance from protein breakdown and inward transport. Whole body protein synthesis determined by [15N]alanine ingestion on six subjects also revealed a 14% decrease (P < 0.01). Neither model-derived nor whole body values for protein breakdown change significantly. These results indicate that the loss of body protein with inactivity is predominantly due to a decrease in muscle PS and that this decrease is reflected in both whole body and skeletal muscle measures.

Adult Trichostrongylus colubriformis infection did not affect protein synthesis rate in whole-body, intestinal, hepatic and skeletal muscle tissues of lambs fed fresh Lucerne (Medicago sativa)

2007 ◽  
Vol 87 (3) ◽  
pp. 315-325 ◽  
Author(s):  
E. N. Bermingham ◽  
W. C. McNabb ◽  
I. A. Sutherland ◽  
B. R. Sinclair ◽  
B. P. Treloar ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Medicago Sativa ◽  
Parasitic Infection ◽  
Whole Body ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Lymphoid Tissues ◽  
Trichostrongylus Colubriformis ◽  
Body Protein

The effects of an established Trichostrongylus colubriformis infection on the whole-body and fractional protein synthesis rates in the small intestine, liver, lymphoid tissues, skeletal muscle and skin were determined in lambs fed fresh Lucerne (Medicago sativa; 800 g DM d-1) on day 48 post-infection. Lambs were dosed with 6000 L3 T. colubriformis larvae for 6 d (n = 5) or kept as parasite-free controls (n = 6). On day 45, the lambs received a bolus injection of deuterated water to measure the size of the whole-body water pool. On day 48, the lambs were continuously infused with [3, 4-3H]-valine into the jugular vein and [1-13C]-valine in the abomasum for 8 h. During the infusion, mesenteric artery blood and terminal tissue samples were collected for measuring the isotopic activity of plasma water, plasma valine, intra cellular valine and protein-bound valine. Intestinal worm numbers on day 48 were higher (P < 0.001) in the infected lambs, however, there was no effect (P > 0.10) of parasitic infection on feed intake, liveweight gain, whole-body protein synthesis and fractional protein synthesis of most tissues. Key words: Parasite infection, protein synthesis, lambs

Aminoacylation of initiator methionyl-tRNA(i) under conditions inhibitory to initiation of protein synthesis

1993 ◽  
Vol 264 (2) ◽  
pp. E257-E263 ◽  
Author(s):  
K. M. Ojamaa ◽  
S. R. Kimball ◽  
L. S. Jefferson
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Rat Liver ◽  
Diabetic Rats ◽  
Peptide Chain ◽  
Perfused Rat Liver ◽  
Chain Initiation ◽  
Total Rna ◽  
Tissue Content ◽  
Total Tissue

Inhibition of protein synthesis in perfused rat liver deprived of either methionine or tryptophan results from a defect in peptide-chain initiation. Similarly, the decreased rate of protein synthesis in liver from rats deprived of food for 24 h and in skeletal muscle after 2 days of diabetes results from a defect in initiation. In the present study, the tissue content of tRNA(iMet) and its level of aminoacylation were measured in these conditions to determine whether methionyl-tRNA(iMet) formation is a mechanism involved in the regulation of initiation. The extent of aminoacylation of tRNA(iMet) in livers perfused with supplemented medium or medium deficient in either methionine or tryptophan was 64 +/- 2, 61 +/- 3, and 66 +/- 2% of the total accepting activity, respectively. The total tissue content of tRNA(iMet), expressed as a percentage of total RNA, was 1.7 +/- 0.1, 1.6 +/- 0.1, and 1.6 +/- 0.1 for the three conditions, respectively. In livers from starved rats, the extent of aminoacylation of tRNA(iMet) was 80 +/- 7% and the total tissue content of tRNA(iMet) was 1.9 +/- 0.1% compared with control values of 82 +/- 6 and 2.0 +/- 0.1%, respectively. In skeletal muscle from diabetic rats, the extent of aminoacylation of tRNA(iMet) was 79 +/- 4% and the total tissue content of tRNA(iMet) was 2.0 +/- 0.3% compared with values of 79 +/- 5 and 2.0 +/- 0.2% for control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

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