Role of Leucine in Protein Metabolism During Exercise and Recovery

2002 ◽  
Vol 27 (6) ◽  
pp. 646-662 ◽  
Author(s):  
Donald K. Layman
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Branched Chain Amino Acids ◽  
New Findings ◽  
Branched Chain

Exercise produces changes in protein and amino acid metabolism. These changes include degradation of the branched-chain amino acids, production of alanine and glutamine, and changes in protein turnover. One of the amino acid most affected by exercise is the branched-chain amino acid leucine. Recently, there has been an increased understanding of the role of leucine in metabolic regulations and remarkable new findings about the role of leucine in intracellular signaling. Leucine appears to exert a synergistic role with insulin as a regulatory factor in the insulin/phosphatidylinositol-3 kinase (PI3-K) signal cascade. Insulin serves to activate the signal pathway, while leucine is essential to enhance or amplify the signal for protein synthesis at the level of peptide initiation. Studies feeding amino acids or leucine soon after exercise suggest that post-exercise consumption of amino acids stimulates recovery of muscle protein synthesis via translation regulations. This review focuses on the unique roles of leucine in amino acid metabolism in skeletal muscle during and after exercise. Key words: branched-chain amino acids, insulin, protein synthesis, skeletal muscle

Amino acid metabolism in the Zucker diabetic fatty rat: effects of insulin resistance and of type 2 diabetes

2004 ◽  
Vol 82 (7) ◽  
pp. 506-514 ◽  
Author(s):  
Enoka P Wijekoon ◽  
Craig Skinner ◽  
Margaret E Brosnan ◽  
John T Brosnan
Keyword(s):  
Insulin Resistance ◽  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Plasma Concentrations ◽  
Branched Chain Amino Acids ◽  
Insulin Resistant ◽  
Branched Chain

We investigated amino acid metabolism in the Zucker diabetic fatty (ZDF Gmi fa/fa) rat during the prediabetic insulin-resistant stage and the frank type 2 diabetic stage. Amino acids were measured in plasma, liver, and skeletal muscle, and the ratios of plasma/liver and plasma/skeletal muscle were calculated. At the insulin-resistant stage, the plasma concentrations of the gluconeogenic amino acids aspartate, serine, glutamine, glycine, and histidine were decreased in the ZDF Gmi fa/fa rats, whereas taurine, α-aminoadipic acid, methionine, phenylalanine, tryptophan, and the 3 branched-chain amino acids were significantly increased. At the diabetic stage, a larger number of gluconeogenic amino acids had decreased plasma concentrations. The 3 branched-chain amino acids had elevated plasma concentrations. In the liver and the skeletal muscles, concentrations of many of the gluconeogenic amino acids were lower at both stages, whereas the levels of 1 or all of the branched-chain amino acids were elevated. These changes in amino acid concentrations are similar to changes seen in type 1 diabetes. It is evident that insulin resistance alone is capable of bringing about many of the changes in amino acid metabolism observed in type 2 diabetes.Key words: plasma amino acids, liver amino acids, muscle amino acids, gluconeogenesis.

Regulation of amino acid metabolism by epinephrine

1990 ◽  
Vol 258 (5) ◽  
pp. E878-E887
Author(s):  
S. Del Prato ◽  
R. A. DeFronzo ◽  
P. Castellino ◽  
J. Wahren ◽  
A. Alvestrand
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Insulin Infusion ◽  
Acid Metabolism ◽  
Quadriceps Muscle ◽  
Branched Chain Amino Acids ◽  
Venous Catheterization ◽  
Branched Chain ◽  
Insulin Replacement

The effect of epinephrine on amino acid (AA) metabolism was examined in 33 healthy volunteers who participated in four studies. Nine subjects participated in study I, which consisted of four parts: euglycemic insulin clamp, insulin plus epinephrine, insulin plus epinephrine plus propranolol, and insulin plus propranolol. In study II six subjects received epinephrine with hepatic-femoral venous catheterization. In study III five individuals received epinephrine with somatostatin plus basal insulin replacement. In study IV quadriceps muscle biopsy was performed in six subjects after epinephrine or insulin infusion. Both epinephrine and insulin caused a generalized decline in all plasma AA except alanine. With combined epinephrine-insulin infusion, the decrease in plasma AA was additive. Propranolol blocked the hypoaminoacidemic effect of epinephrine but failed to alter the AA lowering action of insulin. Epinephrine, while maintaining basal insulinemia, reduced the catechol's hypoaminoacidemic effect by 39%. After epinephrine, splanchnic alanine uptake increased, but plasma alanine remained constant because of a parallel rise in muscle alanine production. Plasma/intracellular concentrations of branched-chain amino acids (BCAA) and all gluconeogenic amino acids, except alanine, decreased after both epinephrine and insulin. In summary, the effect of epinephrine on plasma/intracellular total, gluconeogenic, and BCAA concentrations is similar to insulin.

Removal of infused amino acids by splanchnic and leg tissues in humans

1986 ◽  
Vol 250 (4) ◽  
pp. E407-E413 ◽  
Author(s):  
R. A. Gelfand ◽  
M. G. Glickman ◽  
R. Jacob ◽  
R. S. Sherwin ◽  
R. A. DeFronzo
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Branched Chain Amino Acids ◽  
Acid Uptake ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Significant Uptake ◽  
Branched Chain

To compare the contributions of splanchnic and skeletal muscle tissues to the disposal of intravenously administered amino acids, regional amino acid exchange was measured across the splanchnic bed and leg in 11 normal volunteers. Postabsorptively, net release of amino acids by leg (largely alanine and glutamine) was complemented by the net splanchnic uptake of amino acids. Amino acid infusion via peripheral vein (0.2 g X kg-1 X h-1) caused a doubling of plasma insulin and glucagon levels and a threefold rise in blood amino acid concentrations. Both splanchnic and leg tissues showed significant uptake of infused amino acids. Splanchnic tissues accounted for approximately 70% of the total body amino acid nitrogen disposal; splanchnic uptake was greatest for the glucogenic amino acids but also included significant quantities of branched-chain amino acids. In contrast, leg amino acid uptake was dominated by the branched-chain amino acids. Based on the measured leg balance, body skeletal muscle was estimated to remove approximately 25-30% of the total infused amino acid load and approximately 65-70% of the infused branched-chain amino acids. Amino acid infusion significantly stimulated both the leg efflux and the splanchnic uptake of glutamine (not contained in the infusate). We conclude that when amino acids are infused peripherally in normal humans, splanchnic viscera (liver and gut) are the major sites of amino acid disposal.

Interorgan metabolism of amino acids in streptozotocin-diabetic ketoacidotic rat

1983 ◽  
Vol 244 (2) ◽  
pp. E151-E158 ◽  
Author(s):  
J. T. Brosnan ◽  
K. C. Man ◽  
D. E. Hall ◽  
S. A. Colbourne ◽  
M. E. Brosnan
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Amino Acid ◽  
Branched Chain Amino Acids ◽  
Diabetic Rats ◽  
Normal Rat ◽  
Diabetic Brain ◽  
Streptozotocin Diabetic Rats ◽  
Branched Chain ◽  
Amino Acid Concentrations

Amino acid concentrations in whole blood, liver, kidney, skeletal muscle, and brain were measured and arteriovenous differences calculated for head, hindlimb, kidney, gut, and liver in control and streptozotocin-diabetic rats. In the control rats, glutamine was released by muscle and utilized by intestine, intestine released citrulline and alanine, liver removed alanine, and the kidneys removed glycine and produced serine. In diabetic rats, the major changes from the pattern of fluxes seen in the normal rat were the release of many amino acids from muscle, with glutamine and alanine predominating, and the uptake of these amino acids by the liver. Glutamine removal by the intestine was suppressed in diabetes, but a large renal uptake of glutamine was evident. Branched-chain amino acids were removed by the diabetic brain, and consequently, brain levels of a number of large neutral amino acids were decreased in diabetes.

Sign in / Sign up

Export Citation Format

Share Document