A New Technique for Measuring Protein Turnover in the Gut, Liver and Kidneys of Lean and Obese Mice with [3H]Glutamic Acid

1978 ◽  
Vol 54 (4) ◽  
pp. 425-430
Author(s):  
B. G. Miller ◽  
R. F. Grimble ◽  
T. G. Taylor
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
Total Radioactivity ◽  
Obese Mouse ◽  
Obese Mice ◽  
Tissue Protein ◽  
Liver And Kidney ◽  
A New Technique ◽  
Kidney Liver

1. We have measured the incorporation of an intraperitoneal injection of [3H]glutamate into the protein of the gut, liver and kidney of lean and obese siblings of the genetically obese mouse. 2. Recycling of the 3H was minimized by using glutamate labelled at the C-2 position. Loss of label from the amino acid pool by transamination and deamination was rapid, with a half-life of 4 h. 3. In tissue protein the amino acid showing the highest 3H radioactivity was glutamate. 4. The half-lives for protein synthesis and catabolism were calculated from the decay curves of both specific and total radioactivity of [3H]glutamate in tissue protein. No significant differences were found between kidney, liver and gut in lean and obese mice.

AMINO ACID UTILIZATION AND PROTEIN SYNTHESIS IN THE OVINE FETUS IN UTERO

1984 ◽  
Vol 64 (5) ◽  
pp. 287-288 ◽  
Author(s):  
D. D. KITTS ◽  
A. L. SCHAEFER ◽  
C. R. KRISHNAMURTI
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Key Words ◽  
Protein Turnover ◽  
In Utero ◽  
Intermediary Metabolites ◽  
Tissue Protein ◽  
Amino Acid Utilization ◽  
Ovine Fetus

The utilization of amino acids in chronically catheterized ovine fetuses was measured by isotopic and nonisotopic procedures. Extensive incorporation of amino acid carbon into tissue protein was accompanied by high protein turnover and recycling rates of amino acid carbon. Alternative utilization of amino acids included oxidation and conversion into intermediary metabolites. Key words: Amino acids, utilization, fetus

scholarly journals Relation of protein synthesis and amino acid oxidation: effects of protein deprivation.

1985 ◽  
Vol 33 (3) ◽  
pp. 328-331
Author(s):  
V.V.A.M. Schreurs ◽  
G. Mensink ◽  
H.A. Boekholt ◽  
R.E. Koopmanschap
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
High Rate ◽  
Male Rats ◽  
Synthesis Rate ◽  
Acid Oxidation ◽  
Protein Deprivation ◽  
Amino Acid Oxidation ◽  
Liver And Kidney

For up to 3 weeks 10 male rats weighing about 300 g were given diets which had 20% protein or were free from protein but supplied similar amounts of energy. The rats were killed at intervals; the last 2 were given L-[U-14C]tyrosine by infusion 4 h before they were killed. The deprived rats showed restricted amino acid oxidation and a decreased rate of protein synthesis. Amino acid oxidation continued by an uneven loss of proteins from the tissues. In muscle the composition and relative synthesis rate of the constituent proteins were not affected. Liver and kidney, compared with other tissues tended to maintain a relatively high rate of protein turnover. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals The relationship between protein turnover and energy balance in lean and genetically obese (ob/ob)mice

1979 ◽  
Vol 42 (2) ◽  
pp. 185-199 ◽  
Author(s):  
B. G. Miller ◽  
W. R. Otto ◽  
R. F. Grimble ◽  
D. A. York ◽  
T. G. Taylor
Keyword(s):  
Protein Synthesis ◽  
Energy Balance ◽  
Dietary Intake ◽  
Protein Content ◽  
Energy Intake ◽  
Total Protein ◽  
Protein Turnover ◽  
Obese Mice ◽  
Tissue Protein ◽  
The Relationship

1. Groups of lean and genetically obese (ob/ob) mice were adapted to varying energy intakes and the rates of total protein turnover in liver, gut and kidney were measured.2. Lean mice gained less weight when fed above maintenance and lost less weight when fed below maintenance than obese mice.3. Hepatic protein turnover (mg/d) was sigmoidally related to digestible energy intake in lean mice but showed no significant changes with dietary intake in obese mice.4. The changes in protein turnover resulted from changes in both the half-lives of protein synthesis and catabolism and in tissue protein content.5. In the lean mice, protein turnover in kidney and gut was not significantly changed with increasing energy intake until the highest level was reached.6. The findings suggest that protein turnover may be an important cycle for the regulation of energy balance in mice and that this cycle is impaired in the genetically obese (ob/ob) mice.

Human muscle protein synthesis and breakdown during and after exercise

2009 ◽  
Vol 106 (6) ◽  
pp. 2026-2039 ◽  
Author(s):  
Vinod Kumar ◽  
Philip Atherton ◽  
Kenneth Smith ◽  
Michael J. Rennie
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
Acute Exercise ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Mitochondrial Protein ◽  
Human Muscle ◽  
Muscle Protein Turnover ◽  
Amino Acid Availability

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.

Leucine and mTORC1: a complex relationship

2012 ◽  
Vol 302 (11) ◽  
pp. E1329-E1342 ◽  
Author(s):  
Kayleigh M. Dodd ◽  
Andrew R. Tee
Keyword(s):  
Signal Transduction ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
Muscle Growth ◽  
Protein Translation ◽  
Amino Acid Availability ◽  
Intracellular Amino Acid ◽  
System L ◽  
Mtorc1 Signaling

Amino acid availability is a rate-limiting factor in the regulation of protein synthesis. When amino acid supplies become restricted, mammalian cells employ homeostatic mechanisms to rapidly inhibit processes such as protein synthesis, which demands high levels of amino acids. Muscle cells in particular are subject to high protein turnover rates to maintain amino acid homeostasis. Mammalian target of rapamycin complex 1 (mTORC1) is an evolutionary conserved multiprotein complex that coordinates a network of signaling cascades and functions as a key mediator of protein translation, gene transcription, and autophagy. Signal transduction through mTORC1, which is centrally involved in muscle growth through enhanced protein translation, is governed by intracellular amino acid supply. The branched-chain amino acid leucine is critical for muscle growth and acts in part through activation of mTORC1. Recent research has revealed that mTORC1 signaling is coordinated primarily at the lysosomal membranes. This discovery has sparked a wealth of research in this field, revealing several different signaling molecules involved in transducing the amino acid signal to mTORC1, including the Rag GTPases, MAP4K3, and Vps34/ULK1. This review evaluates the current knowledge regarding cellular mechanisms that control and sense the intracellular amino acid pool. We discuss the role of leucine and mTORC1 in the regulation of amino acid transport via the system L and system A transporters such as LAT1 and SNAT2, as well as protein degradation via autophagic and proteasomal pathways. We also describe the complexities of energy homeostasis via AMPK and cell receptor-mediated growth signals that also converge on mTORC1. Leucine is a particularly potent regulator of protein turnover, to the extent where leucine stimulation alone is sufficient to stimulate mTORC1 signal transduction. The significance of leucine in this context is not yet known; however, recent advancements in this area will also be covered within this review.

scholarly journals Comparative metabolism of L-methionine, DL-methionine and DL-2-hydroxy 4-methylthiobutanoic acid by broiler chicks

1985 ◽  
Vol 54 (3) ◽  
pp. 621-633 ◽  
Author(s):  
C. Linda Saunderson
Keyword(s):  
Protein Synthesis ◽  
Tissue Distribution ◽  
Broiler Chicks ◽  
Tissue Protein ◽  
Body Tissues ◽  
Comparative Metabolism ◽  
Liver And Kidney

1. Metabolism, in broiler chicks, of DL-2-hydroxy 4-methylthiobutanoic acid (DL-HMB), DL-methionine and L-methionine was compared in vivo using 14C-labelled tracers.2. The distribution of L-[1-14C]methionine and DL-[1-14C]HMB in the major body tissues was examined for a period of 120 min after administration.3. The relative oxidation (14CO2, exhaled), excretion and incorporation into tissue protein of L-[l-14C]methionine, DL-[l-14C]methionine and DL-[1-14C]HMB were measured in fed birds.4. Tissue distribution of L-[1-14C]methionine and DL-[1-14C]HMB differed during 60–90 min following administration.5. The production of 14CO2, from each of the tracers was similar but excretion of 14C-labelled material was very different with the greatest excretion from DL-[1-14C]HMB and the least from L[1-14C]methionine.6. The incorporation of 14C into tissue proteins varied with the tracer given and the tissue examined. Liver and kidney had equivalent incorporation from each of the tracers while other tissues examined showed lower incorporation from DL-[1-14C]methionine and DL-[1-14C]HMB.7. The results show that DL-HMB, D-methionine and L-methionine are metabolized differently in vivo and that they are excreted in differing proportions. There is also a difference in the ability of each to act as a precursor for protein synthesis in tissues other than liver.

scholarly journals PROTEIN METABOLISM IN TUMOR CELLS AT VARIOUS STAGES OF GROWTH IN VIVO

1974 ◽  
Vol 62 (3) ◽  
pp. 585-593 ◽  
Author(s):  
Massimo Olivotto ◽  
Francesco Paoletti
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Tumor Cells ◽  
Protein Metabolism ◽  
Protein Turnover ◽  
Specific Activity ◽  
Cell Mass ◽  
Ascites Hepatoma ◽  
Two Phases

Protein metabolism of Yoshida ascites hepatoma cells was studied in the early phase of logarithmic proliferation and in the following stage in which cell mass remains constant (resting phase). The rate of protein synthesis was measured by a short-time incorporation of [8H]lysine, while degradation was concurrently assessed by following the decrease of specific activity of [14C]lysine-labeled proteins. Most of the labeled amino acid injected intraperitoneally into the animal was immediately available for the tumor cells, with only a minor loss towards the extra-ascitic compartment. It was thus possible to calculate the dilution of the isotope in the ascitic pool of the lysine, which increased concurrently with the ascitic plasma volume. Amino acid transport capacity did not change in the log vs. the resting cells. This fact permitted the correction of the specific activity of the proteins synthesized by tumors in the two phases, taking into account the dilution effect. Protein synthesis was found to proceed at a constant rate throughout each of the two phases, although it was 30% lower during the resting as compared to the log phase. When cell mass attained the steady-state, protein degradation occurred at such a level as to balance the synthesis. Throughout the resting phase the amount of lysine taken up by the cells and renewed from the blood remained unchanged. Protein turnover, as studied in subcellular fractions, exhibited a similar rate in nuclei and microsomes, where it proceeded at a higher level than in mitochondria. On the whole, the results encourage the use of the Yoshida ascites hepatoma as a suitable model for studying protein turnover in relation to cell growth in vivo.

Protein turnover, amino acid profile and amino acid flux in juvenile shrimp Litopenaeus vannamei: effects of dietary protein source

2002 ◽  
Vol 205 (20) ◽  
pp. 3107-3122 ◽  
Author(s):  
Eleni Mente ◽  
Peter Coutteau ◽  
Dominic Houlihan ◽  
Ian Davidson ◽  
Patrick Sorgeloos
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Litopenaeus Vannamei ◽  
Dietary Protein ◽  
Protein Turnover ◽  
High Growth ◽  
Amino Acid Profile ◽  
Casein Diet ◽  
Single Meal ◽  
Amino Acid Flux

SUMMARY The effect of dietary protein on protein synthesis and growth of juvenile shrimps Litopenaeus vannamei was investigated using three different diets with equivalent protein content. Protein synthesis was investigated by a flooding dose of tritiated phenylalanine. Survival, specific growth and protein synthesis rates were higher, and protein degradation was lower, in shrimps fed a fish/squid/shrimp meal diet, or a 50% laboratory diet/50%soybean meal variant diet, than in those fed a casein-based diet. The efficiency of retention of synthesized protein as growth was 94% for shrimps fed the fish meal diet, suggesting a very low protein turnover rate; by contrast, the retention of synthesized protein was only 80% for shrimps fed the casein diet. The amino acid profile of the casein diet was poorly correlated with that of the shrimps. 4 h after a single meal the protein synthesis rates increased following an increase in RNA activity. A model was developed for amino acid flux, suggesting that high growth rates involve a reduction in the turnover of proteins, while amino acid loss appears to be high.

scholarly journals Dietary lysine deficiency greatly affects muscle and liver protein turnover in growing chickens

1996 ◽  
Vol 75 (6) ◽  
pp. 853-865 ◽  
Author(s):  
S. Tesseraud ◽  
R. Peresson ◽  
J. Lopes ◽  
A.M. Chagneau
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Pectoralis Major Muscle ◽  
Pectoralis Major ◽  
Translational Efficiency ◽  
Liver Protein ◽  
Deficient Diet ◽  
Principal Mechanism ◽  
Tissue Protein

We analysed the respective influences of age and lysine deficiency on skeletal muscle and liver protein turnover. Growing male broilers were fed ad libirum on isoenergetic diets containing 2OO g crude protein/kg which varied in their lysine content (7·7 or 10·1 g/kg). Fractional rates of protein synthesis (FSR) were measured in vivo in the liver and the pectoralis major muscle of 2-, 3- and 4-week-old chickens (flooding dose of l-[143H]phenylalanine). Fractional rates of proteolysis (FBR) were estimated for the same tissues as the difference between synthesis and growth. Over the 2-week period liver FSR and FBR were unchanged, whereas muscle FSR decreased with age. This developmental decline was related to the lower capacity for protein synthesis (Cs) without any modifications of the translational efficiency. Whatever the age, lysine deficiency resulted in significant decreases in body weight, tissue protein content and tissue protein deposition, apparently because of reduced amounts of proteins synthesized. We recorded a difference in the response of the two tissues to lysine deficiency, the pectoralis major being more sensitive than the liver. When comparing birds of the same age, liver FSR and FBR were not modified by the diet, where as muscle FSR, Cs and FBR were higher in chicks fed on a lysinc-deficient diet than in the controls. Conversely, when chicks of similar weights were compared, the main effect of the dietary deficiency was an increase in muscle FBR. The results suggest that lysine deficiency not only delayed chick development so that protein turnover was affected, but also induced greater changes in metabolism. Thus, the principal mechanism whereby muscle mass decreased appeared to be a change in FBR.

Whole body protein synthesis: studies with different amino acids in the rat

1989 ◽  
Vol 257 (5) ◽  
pp. E639-E646 ◽  
Author(s):  
C. Obled ◽  
F. Barre ◽  
D. J. Millward ◽  
M. Arnal
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Body Protein ◽  
Tissue Specific ◽  
Dose Method ◽  
Infusion Method

These studies were undertaken to determine to what extent constant infusion measurements and plasma sampling could provide sensible answers for rates of whole body protein turnover and also which amino acid would be the most representative probe of whole body protein turnover. Whole body protein synthesis rates were estimated in 70-g rats with L-[U-14C]threonine, L-[U-14C]lysine, L-[U-14C]tyrosine, L-[U-14C]phenylalanine, and L-[1-14C]leucine by either simultaneous tracer infusion of four amino acids or by injections of large quantities of 14C-labeled amino acids. In the infusion experiment, indirect estimates of whole body protein turnover based on free amino acid specific radioactivity and stochastic modeling were compared with direct measurement of the incorporation of the tracer into proteins. These two methods of analysis provided similar results for each amino acid, although in each case fractional synthesis rates were lower (by between 26 and 63%) when calculations were based on plasma rather than tissue specific radioactivity. With the flooding-dose method, whole body fractional protein synthesis rates were 41.4, 25.6, 31.1, and 31.4% with threonine, lysine, phenylalanine, and leucine, respectively. These values were similar to those obtained by the continuous infusion method using tissue specific radioactivity for threonine and lysine. For leucine, however, the flooding-dose method provided an intermediate value between the two estimates derived either from the plasma or the tissue specific radioactivity in the infusion method.(ABSTRACT TRUNCATED AT 250 WORDS)

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