Growth hormone decreases muscle glutamine production and stimulates protein synthesis in hypercatabolic patients

2000 ◽  
Vol 279 (2) ◽  
pp. E323-E332 ◽  
Author(s):  
Gianni Biolo ◽  
Fulvio Iscra ◽  
Alessandra Bosutti ◽  
Gabriele Toigo ◽  
Beniamino Ciocchi ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Protein Synthesis ◽  
Amino Acid ◽  
De Novo ◽  
Muscle Protein ◽  
Recombinant Human Growth Hormone ◽  
Glutamine Metabolism ◽  
Trauma Patients ◽  
Mrna Levels ◽  
Glutamine Production

We determined the effects of 24-h recombinant human growth hormone (rhGH) infusion into a femoral artery on leg muscle protein kinetics, amino acid transport, and glutamine metabolism in eight adult hypercatabolic trauma patients. Metabolic pathways were assessed by leg arteriovenous catheterization and muscle biopsies with the use of stable amino acid isotopes. Muscle mRNA levels of selected enzymes were determined by competitive PCR. rhGH infusion significantly accelerated the inward transport rates of phenylalanine and leucine and protein synthesis, whereas the muscle protein degradation rate and cathepsin B and UbB polyubiquitin mRNA levels were not significantly modified by rhGH. rhGH infusion decreased the rate of glutamine de novo synthesis and glutamine precursor availability, total branched-chain amino acid catabolism, and nonprotein glutamate utilization. Thus net glutamine release from muscle into circulation significantly decreased after rhGH administration (∼50%), whereas glutamine synthetase mRNA levels increased after rhGH infusion, possibly to compensate for reduced glutamine precursor availability. We conclude that, after trauma, the anticatabolic action of rhGH is associated with a potentially harmful decrease in muscle glutamine production.

scholarly journals Action of growth hormone in vitro on the net uptake and incorporation into protein of amino acids in muscle from intact rabbits given protein-deficient diets

1976 ◽  
Vol 35 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. R. Turner ◽  
P. J. Reeds ◽  
K. A. Munday
Keyword(s):  
Amino Acids ◽  
Growth Hormone ◽  
Protein Synthesis ◽  
Amino Acid ◽  
De Novo ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Amino Acid Incorporation ◽  
Acid Incorporation

1. Net amino acid uptake, and incorporation into protein have been measured in vitro in the presence and absence of porcine growth hormone (GH) in muscle from intact rabbits fed for 5 d on low-protein (LP), protein-free (PF) or control diets.2. In muscle from control and LP animals GH had no effect on the net amino acid uptake but stimulated amino acid incorporation into protein, although this response was less in LP animals than in control animals.3. In muscle from PF animals, GH stimulated both amino acid incorporation into protein and the net amino acid uptake, a type of response which also occurs in hypophysectomized animals. The magnitude of the effect of GH on the incorporation of amino acids into protein was reduced in muscle from PF animals.4. The effect of GH on the net amino acid uptake in PF animals was completely blocked by cycloheximide; the uptake effect of GH in these animals was dependent therefore on de novo protein synthesis.5. It is proposed that in the adult the role of growth hormone in protein metabolism is to sustain cellular protein synthesis when there is a decrease in the level of substrate amino acids, similar to that which occurs during a short-term fast or when the dietary protein intake is inadequate.

Metabolic pathways implicated in the kinetic impairment of muscle glutamine homeostasis in adult and old glucocorticoid-treated rats

2004 ◽  
Vol 287 (4) ◽  
pp. E671-E676 ◽  
Author(s):  
R. Minet-Quinard ◽  
C. Moinard ◽  
F. Villie ◽  
M. P. Vasson ◽  
L. Cynober
Keyword(s):  
De Novo ◽  
Muscle Protein ◽  
Glutamine Metabolism ◽  
Control Group ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Protein Breakdown ◽  
Adult Rats ◽  
Old Rats ◽  
Glutamine Production

An impairment of muscle glutamine metabolism in response to dexamethasone (DEX) occurs with aging. To better characterize this alteration, we have investigated muscle glutamine release with regard to muscle glutamine production (net protein breakdown, de novo glutamine synthesis) in adult and old glucocorticoid-treated rats. Male Sprague-Dawley rats (3 or 24 mo old) were divided into seven groups: three groups received 1.5 mg/kg of DEX once a day by intraperitoneal injection for 3, 5, or 7 days; three groups were pair fed to the three treated groups, respectively; and one control group of healthy rats was fed ad libitum. Muscle glutamine synthetase activity increased earlier in old rats ( day 3) than in adult rats ( day 7), whereas an increase in muscle glutamine release occurred later in old rats ( day 5) than in adult DEX-treated rats ( day 3). Consequently, muscle glutamine concentration decreased later in old rats ( day 5) than in adults ( day 3). Finally, net muscle protein breakdown increased only in old DEX-treated rats ( day 7). In conclusion, the impairment of muscle glutamine metabolism is due to a combination of an increase in glutamine production and a delayed increase in glutamine release.

scholarly journals Dietary amylose/amylopectin ratio influences the expression of amino acid transporters and enzyme activities for amino acid metabolism in the gastrointestinal tract of goats

2021 ◽  
pp. 1-31
Author(s):  
Xiaokang Lv ◽  
Chuanshe Zhou ◽  
Tao Ran ◽  
Jinzhen Jiao ◽  
Yong Liu ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Amino Acid Transporters ◽  
Mrna Levels ◽  
Ileal Mucosa ◽  
Dietary Starch ◽  
High Amylose

Abstract This study was designed to investigate the effects of dietary starch structure on muscle protein synthesis and gastrointestinal amino acid (AA) transport and metabolism of goats. Twenty-seven Xiangdong black female goats (average body weight = 9.00 ± 1.12 kg) were randomly assigned to three treatments, i.e., fed a T1 (normal corn 100%, high amylose corn 0%), T2 (normal corn 50%, high amylose corn 50%) and T3 (normal corn 0%, high amylose corn 100%) diet for 35 days, respectively. All amino acids in the ileal mucosa were decreased linearly as amylose/amylopectin increased in diets (P<0.05). The plasma valine (linear, P=0.03), leucine (linear, P=0.04), and total amino acids content (linear, P=0.03) increased linearly with the increase in the ratio of amylose in the diet. The relative mRNA levels of SLC38A1 (linear, P=0.01), SLC3A2 (linear, P=0.02), and SLC38A9 (linear, P=0.02) in the ileum increased linearly with the increase in the ratio of amylose in the diet. With the increase in the ratio of amylose/amylopectin in the diet, the mRNA levels of ACADSB (linear, P=0.04), BCAT1 (linear, P=0.02), and BCKDHB (linear, P=0.01) in the ileum decreased linearly. Our results revealed that the protein abundances of p-mTOR (P<0.001), p-4EBP1 (P<0.001), and p-S6K1 (P<0.001) of T2 and T3 were significantly higher than that of T1. In general, a diet with a high amylose ratio could reduce the consumption of amino acids in the intestine, allowing more amino acids to enter the blood to maintain higher muscle protein synthesis through the mTOR pathway.

scholarly journals Insulin fails to enhance mTOR phosphorylation, mitochondrial protein synthesis, and ATP production in human skeletal muscle without amino acid replacement

2012 ◽  
Vol 303 (9) ◽  
pp. E1117-E1125 ◽  
Author(s):  
Rocco Barazzoni ◽  
Kevin R. Short ◽  
Yan Asmann ◽  
Jill M. Coenen-Schimke ◽  
Matthew M. Robinson ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Enzyme Activities ◽  
Muscle Protein ◽  
Mitochondrial Protein ◽  
Mitochondrial Genes ◽  
Mrna Levels ◽  
Mitochondrial Enzyme ◽  
Mitochondrial Protein Synthesis ◽  
Atp Production

Systemic insulin administration causes hypoaminoacidemia by inhibiting protein degradation, which may in turn inhibit muscle protein synthesis (PS). Insulin enhances muscle mitochondrial PS and ATP production when hypoaminoacidemia is prevented by exogenous amino acid (AA) replacement. We determined whether insulin would stimulate mitochondrial PS and ATP production in the absence of AA replacement. Using l-[1,2-13C]leucine as a tracer, we measured the fractional synthetic rate of mitochondrial as well as sarcoplasmic and mixed muscle proteins in 18 participants during sustained (7-h) insulin or saline infusion ( n = 9 each). We also measured muscle ATP production, mitochondrial enzyme activities, mRNA levels of mitochondrial genes, and phosphorylation of signaling proteins regulating protein synthesis. The concentration of circulating essential AA decreased during insulin infusion. Mitochondrial, sarcoplasmic, and mixed muscle PS rates were also lower during insulin (2–7 h) than during saline infusions despite increased mRNA levels of selected mitochondrial genes. Under these conditions, insulin did not alter mitochondrial enzyme activities and ATP production. These effects were associated with enhanced phosphorylation of Akt but not of protein synthesis activators mTOR, p70S6K, and 4EBP1. In conclusion, sustained physiological hyperinsulinemia without AA replacement did not stimulate PS of mixed muscle or protein subfractions and did not alter muscle mitochondrial ATP production in healthy humans. These results support that insulin and AA act in conjunction to stimulate muscle mitochondrial function and mitochondrial 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.

204 Awardee Talk: Recent Advances in Protein Nutrition in Horses

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 109-109
Author(s):  
Kristine Urschel
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Mass ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Protein Digestibility ◽  
Future Research ◽  
Amino Acid Supplementation ◽  
Protein Nutrition ◽  
Active Research

Abstract Protein has been recognized as an essential nutrient for animals for well over 100 years. Protein plays many important structural and metabolic roles, and some of its component amino acids have additional functions, including as regulatory molecules, as energy substrates and in the synthesis of other non-protein molecules. Skeletal muscle makes up approximately 50% of body weight in horses, with protein being the major non-water component. As an athletic species, the development and maintenance of muscle mass is of the utmost importance in horses. Because muscle mass is largely determined by the balance of rates of muscle protein synthesis and breakdown, understanding how these pathways are regulated and influenced by dietary protein and amino acid provision is essential. Historically, much research regarding protein nutrition in horses has focused on the protein digestibility of different feed ingredients, and the adequacy of different protein sources in supporting the growth and maintenance of horses. This presentation will focus on some of the current areas of active research relating to protein nutrition in horses: the activation of the signaling pathways that regulate muscle protein synthesis, amino acid supplementation in athletic horses, protein metabolism in aged and horses and those with insulin dysregulation, and amino acid and protein nutrition in predominantly forage-fed horses. There are many exciting opportunities for future research in the area of protein and amino acid nutrition in horses across the lifespan.

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