FACTORS AFFECTING PROTEIN BREAKDOWN IN SKELETAL MUSCLE

1978 ◽  
pp. 619-644 ◽  
Author(s):  
D.J. Millward ◽  
P.C. Bates ◽  
G.J. Laurent ◽  
C.C. Lo
Keyword(s):  
Skeletal Muscle ◽  
Protein Breakdown ◽  
Factors Affecting

scholarly journals Hypertrophy of Rat Skeletal Muscle Is Associated with Increased SIRT1/Akt/mTOR/S6 and Suppressed Sestrin2/SIRT3/FOXO1 Levels

2021 ◽  
Vol 22 (14) ◽  
pp. 7588
Author(s):  
Zoltan Gombos ◽  
Erika Koltai ◽  
Ferenc Torma ◽  
Peter Bakonyi ◽  
Attila Kolonics ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Hypertrophy ◽  
Male Rats ◽  
Cellular Interactions ◽  
Molecular Signaling ◽  
Protein Breakdown ◽  
Rat Skeletal Muscle ◽  
Plantaris Muscle ◽  
Skeletal Muscle Hypertrophy ◽  
Intensive Investigation

Despite the intensive investigation of the molecular mechanism of skeletal muscle hypertrophy, the underlying signaling processes are not completely understood. Therefore, we used an overload model, in which the main synergist muscles (gastrocnemius, soleus) of the plantaris muscle were surgically removed, to cause a significant overload in the remaining plantaris muscle of 8-month-old Wistar male rats. SIRT1-associated pro-anabolic, pro-catabolic molecular signaling pathways, NAD and H2S levels of this overload-induced hypertrophy were studied. Fourteen days of overload resulted in a significant 43% (p < 0.01) increase in the mass of plantaris muscle compared to sham operated animals. Cystathionine-β-synthase (CBS) activities and bioavailable H2S levels were not modified by overload. On the other hand, overload-induced hypertrophy of skeletal muscle was associated with increased SIRT1 (p < 0.01), Akt (p < 0.01), mTOR, S6 (p < 0.01) and suppressed sestrin 2 levels (p < 0.01), which are mostly responsible for anabolic signaling. Decreased FOXO1 and SIRT3 signaling (p < 0.01) suggest downregulation of protein breakdown and mitophagy. Decreased levels of NAD+, sestrin2, OGG1 (p < 0.01) indicate that the redox milieu of skeletal muscle after 14 days of overloading is reduced. The present investigation revealed novel cellular interactions that regulate anabolic and catabolic processes in the hypertrophy of skeletal muscle.

scholarly journals Phosphorescence quenching microrespirometry of skeletal muscle in situ

2011 ◽  
Vol 300 (1) ◽  
pp. H135-H143 ◽  
Author(s):  
Aleksander S. Golub ◽  
Michael A. Tevald ◽  
Roland N. Pittman
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Initial Slope ◽  
Phosphorescence Quenching ◽  
Factors Affecting ◽  
External Sources ◽  
Disappearance Curve ◽  
Residual Blood ◽  
532 Nm

We have developed an optical method for the evaluation of the oxygen consumption (V̇o2) in microscopic volumes of spinotrapezius muscle. Using phosphorescence quenching microscopy (PQM) for the measurement of interstitial Po2, together with rapid pneumatic compression of the organ, we recorded the oxygen disappearance curve (ODC) in the muscle of the anesthetized rats. A 0.6-mm diameter area in the tissue, preloaded with the phosphorescent oxygen probe, was excited once a second by a 532-nm Q-switched laser with pulse duration of 15 ns. Each of the evoked phosphorescence decays was analyzed to obtain a sequence of Po2 values that constituted the ODC. Following flow arrest and tissue compression, the interstitial Po2 decreased rapidly and the initial slope of the ODC was used to calculate the V̇o2. Special analysis of instrumental factors affecting the ODC was performed, and the resulting model was used for evaluation of V̇o2. The calculation was based on the observation of only a small amount of residual blood in the tissue after compression. The contribution of oxygen photoconsumption by PQM and oxygen inflow from external sources was evaluated in specially designed tests. The average oxygen consumption of the rat spinotrapezius muscle was V̇o2 = 123.4 ± 13.4 (SE) nl O2/cm3·s ( N = 38, within 6 muscles) at a baseline interstitial Po2 of 50.8 ± 2.9 mmHg. This technique has opened the opportunity for monitoring respiration rates in microscopic volumes of functioning skeletal muscle.

Insights into central and peripheral factors affecting the “oxidative performance” of skeletal muscle in aging

2006 ◽  
Vol 100 (5) ◽  
pp. 571-579 ◽  
Author(s):  
Alessandra Ferri ◽  
Saverio Adamo ◽  
Miriam Longaretti ◽  
Mauro Marzorati ◽  
Francesca Lanfranconi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Factors Affecting

scholarly journals Treatment of burned rats with insulin-like growth factor I inhibits the catabolic response in skeletal muscle

1998 ◽  
Vol 275 (4) ◽  
pp. R1091-R1098 ◽  
Author(s):  
Cheng-Hui Fang ◽  
Bing-Guo Li ◽  
Jing Jing Wang ◽  
Josef E. Fischer ◽  
Per-Olof Hasselgren
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Burn Injury ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Protein Breakdown ◽  
Turnover Rates ◽  
Breakdown Rates ◽  
Igf I ◽  
Catabolic Response

Thermal injury is associated with a pronounced catabolic response in skeletal muscle, reflecting inhibited protein synthesis and increased protein breakdown, in particular myofibrillar protein breakdown. Administration of insulin-like growth factor I (IGF-I) has a nitrogen-sparing effect after burn injury, but the influence of this treatment on protein turnover rates in skeletal muscle is not known. In the present study, we examined the effect of IGF-I on muscle protein synthesis and breakdown rates following burn injury in rats. After a 30% total body surface area burn injury or sham procedure, rats were treated with a continuous infusion of IGF-I (3.5 or 7 mg ⋅ kg−1 ⋅ 24 h−1) for 24 h. Protein synthesis and breakdown rates were determined in incubated extensor digitorum longus muscles. Burn injury resulted in increased total and myofibrillar protein breakdown rates and reduced protein synthesis in muscle. The increase in protein breakdown rates was blocked by both doses of IGF-I and the burn-induced inhibition of muscle protein synthesis was partially reversed by the higher dose of the hormone. IGF-I did not influence muscle protein turnover rates in nonburned rats. The results suggest that the catabolic response to burn injury in skeletal muscle can be inhibited by IGF-I.

Dietary protein deficiency reduces lysosomal and nonlysosomal ATP-dependent proteolysis in muscle

1992 ◽  
Vol 263 (2) ◽  
pp. E326-E334 ◽  
Author(s):  
N. E. Tawa ◽  
I. C. Kettelhut ◽  
A. L. Goldberg
Keyword(s):  
Skeletal Muscle ◽  
Dietary Protein ◽  
Cathepsin B ◽  
Normal Diet ◽  
Optimal Conditions ◽  
Protein Breakdown ◽  
Lysosomal Hydrolases ◽  
Lysosomal Protease ◽  
Lysosomal Proteases ◽  
Dependent Processes

When rats are fed a protein deficient (PD) diet for 7 days, rates of proteolysis in skeletal muscle decrease by 40-50% (N. E. Tawa, Jr., and A. L. Goldberg. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E317-325, 1992). To identify the underlying biochemical adaptations, we measured different proteolytic processes in incubated muscles. The capacity for intralysosomal proteolysis, as shown by sensitivity to methylamine or lysosomal protease inhibitors, fell 55-75% in muscles from PD rats. Furthermore, extracts of muscles of PD rats showed 30-70% lower activity of many lysosomal proteases, including cathepsins B, H, and C, and carboxypeptidases A and C, as well as other lysosomal hydrolases. The fall in cathepsin B and proteolysis was evident by 3 days on the PD diet, and both returned to control levels 3 days after refeeding of the normal diet. In muscles maintained under optimal conditions, 80-90% of protein breakdown occurs by nonlysosomal pathways. In muscles of PD rats, this ATP-dependent process was also 40-60% slower. Even though overall proteolysis decreased in muscles of PD rats, their capacity for Ca(2+)-dependent proteolysis increased (by 66%), as did the activity of the calpains (+150-250%). Thus the lysosomal and the ATP-dependent processes decrease coordinately and contribute to the fall in muscle proteolysis in PD animals.

ATP depletion stimulates calcium-dependent protein breakdown in chick skeletal muscle

1992 ◽  
Vol 262 (5) ◽  
pp. E637-E643 ◽  
Author(s):  
J. M. Fagan ◽  
E. F. Wajnberg ◽  
L. Culbert ◽  
L. Waxman
Keyword(s):  
Skeletal Muscle ◽  
Total Protein ◽  
Skeletal Muscles ◽  
Cysteine Proteases ◽  
Atp Depletion ◽  
Metabolic Energy ◽  
Myofibrillar Proteins ◽  
Protein Breakdown ◽  
Calcium Dependent ◽  
Intracellular Proteins

The contribution of metabolic energy to the degradation of intracellular proteins in skeletal muscle was investigated. Isolated chick skeletal muscles deprived of oxygen and muscles incubated in buffer under nonphysiological conditions containing inhibitors of glycolysis and mitochondrial respiration had lower concentrations or undetectable levels of ATP and faster rates of proteolysis. Both total protein breakdown and the breakdown of myofibrillar proteins were stimulated 35-124% in ATP-depleted tissues. However, ATP-depleted muscles incubated in buffer to which no Ca2+ was added showed slower rates of total protein breakdown and no significant change in myofibrillar proteolysis compared with control muscles. Trans-epoxysuccinyl-L-leucylamido(4-guanidino)butane (E-64), a compound that inhibits the calpains and the lysosomal cysteine proteases, completely blocked the Ca(2+)-stimulated breakdown of nonmyofibrillar and myofibrillar proteins in ATP-depleted muscles. However, Ca(2+)-stimulated proteolysis was not inhibited in ATP-depleted muscles incubated with weak bases to prevent lysosome function. These data suggest that intracellular proteins can be degraded in skeletal muscle in the absence of metabolic energy and that the calpains play a major role in the enhanced proteolysis in skeletal muscles depleted of ATP.

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