scholarly journals Protein turnover is elevated in muscle of mdx mice in vivo

1990 ◽  
Vol 268 (3) ◽  
pp. 795-797 ◽  
Author(s):  
P A MacLennan ◽  
R H T Edwards
Keyword(s):  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Mdx Mice ◽  
Turnover Rates ◽  
Wild Type ◽  
Dystrophin Deficiency ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

mdx mice lack the protein dystrophin, the absence of which causes Duchenne muscular dystrophy in humans. To examine how mdx mice maintain muscle mass despite dystrophin deficiency, we measured protein turnover rates in muscles of mdx and wild-type (C57BL/10) mice in vivo. At all ages studied, rates of muscle protein synthesis and degradation were higher in mdx than in C57BL/10 mice.

scholarly journals The effect of glutamine on protein turnover in chick skeletal muscle in vitro

1990 ◽  
Vol 265 (2) ◽  
pp. 593-598 ◽  
Author(s):  
G Wu ◽  
J R Thompson
Keyword(s):  
Protein Synthesis ◽  
Skeletal Muscles ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Plasma Concentrations ◽  
Glutamine Concentration ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

The effect of glutamine on the rates of protein synthesis and degradation was studied in isolated chick extensor digitorum communis muscles incubated in the presence of plasma concentrations of amino acids. Addition of 0.5-15 mM-glutamine increases (P less than 0.01) intracellular glutamine concentrations by 31-670%. There is a positive relationship (r = 0.975, P less than 0.01) between intracellular glutamine concentration and the rate of muscle protein synthesis measured by the incorporation of [3H]phenylalanine. The stimulating effect of 15 mM-glutamine on protein synthesis was decreased from 58 to 19% in muscles incubated in the absence of tyrosine. The rates of protein degradation, estimated from [3H]phenylalanine release from muscle proteins prelabelled in vivo, decreased (P less than 0.05) by 15-30% in the presence of 4-15 mM-glutamine when compared with muscles incubated in the presence of physiological concentrations of glutamine (0.5-1 mM). Glutamine concentrations ranging from 2 to 15 mM appear to have an overall anabolic effect on chick skeletal muscles incubated in vitro.

P0915PROTEIN ENERGY WASTING IS ASSOCIATED WITH A DECLINE IN MUSCLE PROTEIN SYNTHESIS IN CKD PATIENTS

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Michela Saio ◽  
Antonella Sofia ◽  
Rodolfo Russo ◽  
Leda Cipriani ◽  
Giacomo Garibotto ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Metabolism ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Stage Iv ◽  
Kinetic Studies ◽  
Ckd Stage ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Abstract Background and Aims Skeletal muscle is a highly adaptive tissue, however even small imbalances between protein synthesis and degradation can lead to substantial protein loss. Althought proteolysis plays a major role in the development of cachexia in CKD (chronic kidney disease), the responses of muscle protein metabolism to malnutrition had not been completely elucidated. We evaluated retrospectively the results of kinetic studies of protein turnover estimated by the forearm perfusion method associated with H2phenylalanine kinetic, obtained in CKD patients and controls in the last 25 years. Method We analyzed 59 forearm H2phenylalanine kinetic studies obtained in 14 controls (C) (M 11, F 3) and 45 patients with CKD, of whom 15 (M 10, F 5) were on conservative treatment (CKD stage IV-V), 16 (M 14, F 2) under maintenance hemodialysis (HD), 14 (M 12, F 2) in peritoneal dialysis (DP); all subjects were on non-restricted protein/calorie (0.8-1.1 g/kg and 28-32 kcal/kg, respectively) diets. Ten (M 9, F 1) HD patients had Protein Energy Wasting. Acidosis was corrected in all patients (HCO3 24.2±1.9 mmol/L) and studies were performed in the post-absorptive overnight fasted state at rest. Results Overall, Muscle protein synthesis and degradation were similar (p=NS) in patients and controls. Protein net balance was reduced in patients with PD and those with CKD Stage IV-V (p <0.003 - p <0.014) indicating a reduced catabolic state and nitrogen conservation. However PEW HD patients showed reduced rates of protein synthesis and degradation (p <0.048 and p <0.04 respectively). In addition the efficiency of muscle protein turnover, a parameter expressing muscle's ability to reuse amino acids derived from degradation into protein synthesis, was significantly reduced in HD PEW patients vs. controls (55.5 vs. 61.2 %, p <0.018, respectively) and vs. not malnourished patients in conservative treatment (70.1 % p <0.0025) or in PD (74.6 % p <0.005). Conclusion In CKD patients, in absence of acidosis, muscle is able to increase the efficiency of protein metabolism for the maintenance of nitrogen balance. However, in PEW patients, combined alterations of protein synthesis and degradation proceed together to a reduced efficiency of amino acids recycled into protein synthesis and contribute to maintaining wasting. These data also suggest that calorie/protein requirements of CKD patients with PEW may be higher than currently theorized.

Effects of food deprivation on protein synthesis and degradation in rat skeletal muscles

1976 ◽  
Vol 231 (2) ◽  
pp. 441-448 ◽  
Author(s):  
JB Li ◽  
AL Goldberg
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Food Deprivation ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Rna Content ◽  
Fasted Rats ◽  
Synthesis And Degradation

The effects of food deprivation on protein turnover in rat soleus and extensor digitorum longus (EDL) were investigated. Muscles were removed from fed or fasted growing rats, and protein synthesis and breakdown were measured during incubation in vitro. Rates of synthesis and degradation were higher in the dark soleus than in the pale EDL. One day after food removal protein synthesis and RNA content in the EDL decreased. On the 2nd day of fasting, rates of protein catabolism in this muscle increased. Little or no change in synthesis and degradation occurred in the soleus. Consequently, during fasting the soleus lost much less weight than the EDL and other rat muscles. In unsupplemented buffer or in medium containing amino acids, glucose, and insulin, the muscles of fasted rats showed a lower rate of protein synthesis expressed per milligram of tissue but not per microgram of RNA. Thus the decrease in muscle RNA on fasting was responsible for the reduced synthesis observed under controlled in vitro conditions. In vivo the reduction in muscle protein synthesis on fasting results both from a lower RNA content and lower rate of synthesis per microgram of RNA. Reduced supply of glucose, insulin, and amino acids may account for the lower rate of synthesis per microgram of RNA demonstrable in vivo.

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 Effect of a protein-free diet on muscle protein turnover and nitrogen conservation in euthyroid and hyperthyroid rats

1984 ◽  
Vol 217 (2) ◽  
pp. 471-476 ◽  
Author(s):  
W J Carter ◽  
W S van der Weijden Benjamin ◽  
F H Faas
Keyword(s):  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Nitrogen Excretion ◽  
Muscle Protein Turnover ◽  
Protein Depletion ◽  
Serum T3 ◽  
Nitrogen Conservation ◽  
Protein Free Diet ◽  
Synthesis And Degradation

Although protein turnover in skeletal muscle is increased in hyperthyroidism and decreased in hypothyroidism, a deficient protein intake tends to increase serum T3 (tri-iodothyronine) while decreasing muscle protein turnover. To determine whether this diet-induced decrease in protein turnover can occur independent of thyroid status, we have examined muscle protein turnover and nitrogen conservation in hyperthyroid rats fed on a protein-free diet. After inducing hyperthyroidism by giving 20 micrograms of T3/100g body wt. daily for 7 days, groups of euthyroid and hyperthyroid animals were divided into subgroups fed on basal and protein-free diets. Muscle protein turnover was measured by N tau-methylhistidine excretion and [14C]tyrosine infusion. Urinary nitrogen output of euthyroid and hyperthyroid animals fed on the protein-free diet was also measured. Although hyperthyroidism increased the baseline rates of muscle protein synthesis and degradation, it did not prevent a decrease in these values in response to protein depletion. Furthermore, hyperthyroid rats showed greatly decreased nitrogen excretion in response to the protein-free diet, although not to values for euthyroid rats. These findings suggest that protein depletion made the experimental animals less responsive to the protein-catabolic effects of T3.

scholarly journals Interrogation of Dystrophin and Dystroglycan Complex Protein Turnover After Exon Skipping Therapy

2021 ◽  
pp. 1-20
Author(s):  
James S. Novak ◽  
Rita Spathis ◽  
Utkarsh J. Dang ◽  
Alyson A. Fiorillo ◽  
Ravi Hindupur ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Protein Expression ◽  
Protein Turnover ◽  
Isotope Labeling ◽  
Exon Skipping ◽  
Mdx Mice ◽  
Wild Type ◽  
Gene Correction ◽  
Dystrophin Protein

Recently, the Food and Drug Administration granted accelerated approvals for four exon skipping therapies –Eteplirsen, Golodirsen, Viltolarsen, and Casimersen –for Duchenne Muscular Dystrophy (DMD). However, these treatments have only demonstrated variable and largely sub-therapeutic levels of restored dystrophin protein in DMD patients, limiting their clinical impact. To better understand variable protein expression and the behavior of truncated dystrophin protein in vivo, we assessed turnover dynamics of restored dystrophin and dystroglycan complex (DGC) proteins in mdx mice after exon skipping therapy, compared to those dynamics in wild type mice, using a targeted, highly-reproducible and sensitive, in vivo stable isotope labeling mass spectrometry approach in multiple muscle tissues. Through statistical modeling, we found that restored dystrophin protein exhibited altered stability and slower turnover in treated mdx muscle compared with that in wild type muscle (∼44 d vs. ∼24 d, respectively). Assessment of mRNA transcript stability (quantitative real-time PCR, droplet digital PCR) and dystrophin protein expression (capillary gel electrophoresis, immunofluorescence) support our dystrophin protein turnover measurements and modeling. Further, we assessed pathology-induced muscle fiber turnover through bromodeoxyuridine (BrdU) labeling to model dystrophin and DGC protein turnover in the context persistent fiber degeneration. Our findings reveal sequestration of restored dystrophin protein after exon skipping therapy in mdx muscle leading to a significant extension of its half-life compared to the dynamics of full-length dystrophin in normal muscle. In contrast, DGC proteins show constant turnover attributable to myofiber degeneration and dysregulation of the extracellular matrix (ECM) in dystrophic muscle. Based on our results, we demonstrate the use of targeted mass spectrometry to evaluate the suitability and functionality of restored dystrophin isoforms in the context of disease and propose its use to optimize alternative gene correction strategies in development for DMD.

scholarly journals Proteome dynamics during homeostatic scaling in cultured neurons

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Aline Ricarda Dörrbaum ◽  
Beatriz Alvarez-Castelao ◽  
Belquis Nassim-Assir ◽  
Julian D Langer ◽  
Erin M Schuman
Keyword(s):  
Protein Synthesis ◽  
Protein Function ◽  
Protein Turnover ◽  
Experimental Approach ◽  
Large Fraction ◽  
Synaptic Proteins ◽  
Turnover Rates ◽  
Cellular Environment ◽  
Protein Synthesis And Degradation ◽  
Synthesis And Degradation

Protein turnover, the net result of protein synthesis and degradation, enables cells to remodel their proteomes in response to internal and external cues. Previously, we analyzed protein turnover rates in cultured brain cells under basal neuronal activity and found that protein turnover is influenced by subcellular localization, protein function, complex association, cell type of origin, and by the cellular environment (Dörrbaum et al., 2018). Here, we advanced our experimental approach to quantify changes in protein synthesis and degradation, as well as the resulting changes in protein turnover or abundance in rat primary hippocampal cultures during homeostatic scaling. Our data demonstrate that a large fraction of the neuronal proteome shows changes in protein synthesis and/or degradation during homeostatic up- and down-scaling. More than half of the quantified synaptic proteins were regulated, including pre- as well as postsynaptic proteins with diverse molecular functions.

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