scholarly journals Specificity of the effects of leucine and its metabolites on protein degradation in skeletal muscle

1984 ◽  
Vol 222 (3) ◽  
pp. 579-586 ◽  
Author(s):  
W E Mitch ◽  
A S Clark
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Muscle Protein ◽  
Adult Rats ◽  
Limb Muscles ◽  
Leucine Catabolism ◽  
Muscle Protein Degradation ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

The effects of leucine, its metabolites, and the 2-oxo acids of valine and isoleucine on protein synthesis and degradation in incubated limb muscles of immature and adult rats were tested. Leucine stimulated protein synthesis but did not reduce proteolysis when leucine transamination was inhibited. 4-Methyl-2-oxopentanoate at concentrations as low as 0.25 mM inhibited protein degradation but did not change protein synthesis. The 2-oxo acids of valine and isoleucine did not change protein synthesis or degradation even at concentrations as high as 5 mM. 3-Methylvalerate, the irreversibly decarboxylated product of 4-methyl-2-oxopentanoate, decreased protein degradation at concentrations greater than or equal to 1 mM. This was not due to inhibition of 4-methyl-2-oxopentanoate catabolism, because 0.5 mM-3-methylvalerate did not suppress proteolysis, even though it inhibited leucine decarboxylation by 30%; higher concentrations of 3-methylvalerate decreased proteolysis progressively without inhibiting leucine decarboxylation further. During incubation with [1-14C]- and [U-14C]-leucine, it was found that products of leucine catabolism formed subsequent to the decarboxylation of 4-methyl-2-oxopentanoate accumulated intracellularly. This pattern was not seen during incubation with radiolabelled valine. Thus, the effect of leucine on muscle proteolysis requires transamination to 4-methyl-2-oxopentanoate. The inhibition of muscle protein degradation by leucine is most sensitive to, but not specific for, its 2-oxo acid, 4-methyl-2-oxopentanoate.

scholarly journals Comparison of protein synthesis and degradation in incubated and perfused muscle

1983 ◽  
Vol 212 (3) ◽  
pp. 649-653 ◽  
Author(s):  
A S Clark ◽  
W E Mitch
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Insulin Treatment ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Muscle Protein Degradation ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Rates of muscle protein synthesis and degradation measured in the perfused hindquarter were compared with those in incubated epitrochlearis muscles. With fed or starved mature rats, results without insulin treatment were identical. With insulin treatment, protein synthesis in perfused hindquarters was greater, though protein degradation was the same. Thus rates of muscle protein degradation estimated by these two methods in vitro correspond closely.

scholarly journals Pentoxifylline improves insulin action limiting skeletal muscle catabolism after infection

1999 ◽  
Vol 163 (1) ◽  
pp. 15-24 ◽  
Author(s):  
T Vary ◽  
D Dardevet ◽  
J Grizard ◽  
L Voisin ◽  
C Buffiere ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Protein Degradation ◽  
Muscle Protein ◽  
Plasma Concentrations ◽  
Skeletal Muscle Protein ◽  
Muscle Protein Metabolism ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

We investigated the ability of pentoxifylline (PTX) to modulate protein synthesis and degradation in the presence and absence of insulin during incubation of epitrochlearis muscle, 2 or 6 days after injection of Escherichia coli. On days 2 and 6 after infection, protein synthesis was inhibited by 25%, whereas proteolysis was enhanced by 75%. Insulin (2 nM) in vitro stimulated protein synthesis in muscles from infected rats to the same extent as in controls. The ability of insulin to limit protein degradation was severely blunted 48 h after infection. On day 6 after infection, insulin inhibited proteolysis to a greater extent than on day 2. PTX suppressed the increase in plasma concentrations of tumor necrosis factor more than 600-fold after injection of bacteria, and partially prevented the inhibition of protein synthesis and stimulation of protein degradation during sepsis. Moreover, PTX administration maintained the responsiveness of protein degradation to insulin during sepsis. Thus cytokines may influence skeletal muscle protein metabolism during sepsis, both indirectly through inhibition of the effects of insulin on proteolysis, and directly on the protein synthesis and degradation machinery.

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

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

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

scholarly journals Skeletal muscle protein synthesis and degradation in patients with chronic renal failure

1994 ◽  
Vol 45 (5) ◽  
pp. 1432-1439 ◽  
Author(s):  
Giacomo Garibotto ◽  
Rodolfo Russo ◽  
Antonella Sofia ◽  
Maria Rita Sala ◽  
Cristina Robaudo ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Renal Failure ◽  
Protein Synthesis ◽  
Chronic Renal Failure ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Skeletal Muscle Protein ◽  
Skeletal Muscle Protein Synthesis ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Protein synthesis and degradation in skeletal muscle of normal and dystrophic hamsters

1980 ◽  
Vol 239 (6) ◽  
pp. E401-E406
Author(s):  
J. B. Li
Keyword(s):  
Protein Synthesis ◽  
Protein Degradation ◽  
Muscle Protein ◽  
Normal Muscle ◽  
Dystrophic Muscle ◽  
Body Weights ◽  
Insulin Dependent ◽  
Muscle Protein Degradation ◽  
Lysosomal Proteases ◽  
Synthesis And Degradation

Dystrophic hamsters (BIO 53.58) had lower body weights and gastrocnemius muscle weights than normal hamsters (BIO RB). Dystrophic muscle contained less protein than normal muscle. The proportion of collagenous to noncollagenous protein remained unchanged. Loss of protein in the dystrophic muscle was the result of an increase in the rate of protein degradation. This was accompanied by higher activities of two lysosomal proteases, cathepsins B and D. The net effect of the increase in protein degradation was blunted by an increase in the rate of synthesis of total protein and myosin. The faster rate of synthesis in dystrophic muscle was partially due to an increase in the concentration of cellular RNA. Rates of peptide-chain initiation and protein synthesis decreased in muscles of normal hamsters perfused in the absence of insulin. In the presence of insulin, these processes were maintained at higher rates. However, the rate of protein synthesis in dystrophic muscle appeared less insulin-dependent than normal muscle. Protein degradation was inhibited by insulin in both types of muscle.

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