Alterations in Tyrosine and Protein Kinetics Produced by Injury and Branched Chain Amino Acid Administration in Rats

1983 ◽  
Vol 64 (3) ◽  
pp. 321-331 ◽  
Author(s):  
Akio Sakamoto ◽  
Lyle L. Moldawer ◽  
John D. Palombo ◽  
Sukumar P. Desai ◽  
Bruce R. Bistrian ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Secretory Protein ◽  
Plasma Amino Acid ◽  
Whole Body ◽  
Protein Kinetics ◽  
Body Protein ◽  
Branched Chain Amino Acid ◽  
Branched Chain ◽  
Acid Administration

1. To determine whether the alterations in amino acid metabolism after injury were a result of changes in protein synthesis, whole body tyrosine and individual tissue protein kinetics were estimated 24 h after three different forms of stress in rats. 2. in addition, injured rats were either starved or infused with 180 mg of nitrogen/day (as branched chain amino acids or l-alanine) to ascertain whether the mechanism and degree of nitrogen sparing were unique to branched chain amino acid administration or whether they could be attributed to the infusion of α-amino nitrogen. 3. in the more catabolic types of injury, increased nitrogen loss during starvation appeared to be due to both an increased plasma amino acid appearance and a greater percentage being oxidized. Rates of tyrosine incorporation into whole body protein were also enhanced and could be explained in part by increases in the fractional synthesis rate of hepatic non-secretory protein. 4. Both branched chain amino acid and l-alanine administration reduced endogenous tyrosine oxidation and improved nitrogen balance. However, branched chain amino acid administration significantly increased amino acid incorporation into whole body protein and fractional synthetic rates of skeletal muscle, kidney and hepatic non-secretory protein. 5. It is concluded that the catabolic response to severe injury is consistent with increased rates of plasma amino acid appearance and branched chain amino acid administration spares body protein by improving amino acid utilization for whole body protein synthesis.

scholarly journals Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects

2021 ◽  
pp. 1-9
Author(s):  
Jorn Trommelen ◽  
Andrew M. Holwerda ◽  
Philippe J. M. Pinckaers ◽  
Luc J. C. van Loon
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Stable Isotope ◽  
Dietary Protein ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Human Subjects ◽  
Whole Body ◽  
Body Protein

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.

Leucine metabolism in lactating and dry goats: effect of insulin and substrate availability

1993 ◽  
Vol 265 (3) ◽  
pp. E402-E413 ◽  
Author(s):  
S. Tesseraud ◽  
J. Grizard ◽  
E. Debras ◽  
I. Papet ◽  
Y. Bonnet ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Degradation ◽  
Whole Body ◽  
Initial Slope ◽  
Sensitivity Index ◽  
Early Lactation ◽  
Dry Period ◽  
Body Protein ◽  
Lactating Goats

Early lactating goats show insulin resistance with respect to extramammary glucose utilization. However, much less is known about the two major factors, insulin and plasma amino acid concentration, that regulate protein metabolism in lactating goats. To examine this question, the in vivo effect of acute insulin was studied in goats during early lactation (12-31 days postpartum), midlactation (98-143 days postpartum), and the dry period (approximately 1 yr postpartum). Insulin was infused (at 0.36 or 1.79 nmol/min) under euglycemic and eukaliemic clamps. In addition, appropriate amino acid infusion was used to blunt insulin-induced hypoaminoacidemia or to create hyperaminoacidemia and maintain this condition under insulin treatment. Leucine kinetics were assessed using a primed continuous infusion of L-[1-14C]-leucine, which started 2.5 h before insulin. In all animals the insulin treatments failed to stimulate the nonoxidative leucine disposal (an estimate of whole body protein synthesis) under both euaminoacidemic and hyperaminoacidemic conditions. Thus, in goat as well as humans, infusion of insulin fails to stimulate protein synthesis even when combined with a substantially increased provision of amino acids. In contrast, insulin treatments caused a dose-dependent inhibition of the endogenous leucine appearance (an estimate of whole body protein degradation). Under euaminoacidemia the initial slope from the plot of the endogenous leucine appearance as a function of plasma insulin (an insulin sensitivity index) was steeper during early lactation than when compared with the dry period. A similar trend occurred during midlactation but not to any significant degree. These differences were abolished under hyperaminoacidemia. It was concluded that the ability of physiological insulin to inhibit protein degradation was improved during lactation, demonstrating a clear-cut dissociation between the effects of insulin on protein and glucose metabolism. This adaptation no doubt may provide a mechanism to save body protein.

Branched chain amino acid enriched elemental diets support hepatic protein synthesis in injured rats

1985 ◽  
Vol 5 (7) ◽  
pp. 737-748 ◽  
Author(s):  
Javier Sobrado ◽  
James J. Pomposelli ◽  
Kazuma Yamazaki ◽  
Alberto Maiz ◽  
Lyle L. Moldawer ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Branched Chain Amino Acid ◽  
Elemental Diets ◽  
Branched Chain ◽  
Hepatic Protein Synthesis

scholarly journals The effect of a high dose of 3-hydroxy-3-methylbutyrate on protein metabolism in growing lambs

1997 ◽  
Vol 77 (6) ◽  
pp. 885-896 ◽  
Author(s):  
Isabelle Papet ◽  
Piotr Ostaszewski ◽  
Francoise Glomot ◽  
Christiane Obled ◽  
Magali Faure ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Free Amino Acid ◽  
Protein Metabolism ◽  
Free Amino ◽  
Skeletal Muscles ◽  
Whole Body ◽  
Control Group ◽  
High Dose ◽  
Body Protein

AbstractThe effect of a high dose of 3-hydroxy-3-methylbutyrate (HMB, a leucine catabolite) on protein metabolism was investigated in growing male lambs fed on hay and concentrate. Concentrate was supplemented with either Ca(HMB)2 (4g/kg) or Ca(C03)2 in experimental (HMB) and control groups respectively. Both groups consisted of six 2-month old lambs. Three complementary methods to study protein metabolism were carried out consecutively 2·5 months after beginning the dietary treatment: whole body phenylalanine fluxes, postprandial plasma free amino acid time course and fractional rates of protein synthesis in skeletal muscles. Feeding a high dose of HMB led to a significant increase in some plasma free amino acids compared with controls. Total, oxidative and non-oxidative phenylalanine fluxes were not modified by dietary HMB supplementation. Similarly, an acute infusion of HMB, in the control group, did not change these fluxes. In skeletal muscles, fractional rates of protein synthesis were not affected by long-term dietary supplementation with HMB. Taken together our results showed that administration of a high dose of HMB to lambs was able to modify plasma free amino acid pattern without any effect on whole-body protein turnover and skeletal muscle protein synthesis

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