Growth hormone acutely stimulates forearm muscle protein synthesis in normal humans

1991 ◽  
Vol 260 (3) ◽  
pp. E499-E504 ◽  
Author(s):  
D. A. Fryburg ◽  
R. A. Gelfand ◽  
E. J. Barrett
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Growth Hormone ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Skeletal Muscle Protein ◽  
Skeletal Muscle Protein Synthesis ◽  
Igf I ◽  
Normal Humans

The short-term effects of growth hormone (GH) on skeletal muscle protein synthesis and degradation in normal humans are unknown. We studied seven postabsorptive healthy men (age 18-23 yr) who received GH (0.014 micrograms.kg-1.min-1) via intrabrachial artery infusion for 6 h. The effects of GH on forearm amino acid and glucose balances and on forearm amino acid kinetics [( 3H]Phe and [14C]Leu) were determined after 3 and 6 h of the GH infusion. Forearm deep vein GH rose to 35 +/- 6 ng/ml in response to GH, whereas systemic levels of GH, insulin, and insulin-like growth factor I (IGF-I) were unchanged. Forearm glucose uptake did not change during the study. After 6 h, GH suppressed forearm net release (3 vs. 6 h) of Phe (P less than 0.05), Leu (P less than 0.01), total branched-chain amino acids (P less than 0.025), and essential neutral amino acids (0.05 less than P less than 0.1). The effect on the net balance of Phe and Leu was due to an increase in the tissue uptake for Phe (71%, P less than 0.05) and Leu (37%, P less than 0.005) in the absence of any significant change in release of Phe or Leu from tissue. In the absence of any change in systemic GH, IGF-I, or insulin, these findings suggest that locally infused GH stimulates skeletal muscle protein synthesis. These findings have important physiological implications for both the role of daily GH pulses and the mechanisms through which GH can promote protein anabolism.

Age-related differences in skeletal muscle protein synthesis: relation to markers of immune activation

2005 ◽  
Vol 288 (5) ◽  
pp. E883-E891 ◽  
Author(s):  
Michael J. Toth ◽  
Dwight E. Matthews ◽  
Russell P. Tracy ◽  
Michael J. Previs
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Skeletal Muscle Protein ◽  
Skeletal Muscle Protein Synthesis ◽  
Igf I ◽  
Factor Α ◽  
Actin Protein ◽  
Necrosis Factor

Aging is associated with decreased skeletal muscle mass and function. These changes are thought to derive, in part, from a reduction in skeletal muscle protein synthesis. Although some studies have shown reduced postabsorptive muscle protein synthesis with age in humans, recent studies have failed to find an age effect. In addition to this disparity, few studies have attempted to characterize the hormonal factors that may contribute to changes in protein synthesis. Thus we examined the effect of age on skeletal muscle protein metabolism, with a specific emphasis on myosin heavy chain (MHC) protein, and the relationship of protein synthesis rates to plasma hormone levels. We measured body composition, muscle function, muscle protein synthesis, MHC and actin protein content, MHC isoform distribution, and plasma concentrations of cytokines and insulin-like growth factor-I (IGF-I) in 7 young [29 ± 2 (SE) yr] and 15 old (72 ± 1 yr; P < 0.01) volunteers. Mixed-muscle (−19%; P = 0.11), MHC (−22%; P = 0.08), and nonmyofibrillar (−17%; P = 0.10) protein synthesis all tended to be lower in old volunteers. Old volunteers were characterized by increased circulating tumor necrosis factor-α receptor II ( P < 0.05) and reduced IGF-I ( P < 0.01). In addition, plasma C-reactive protein, interleukin-6, and tumor necrosis factor-α receptor II concentrations were negatively related to mixed-muscle and MHC protein synthesis rates (range of r values: −0.422 to −0.606; P < 0.05 to <0.01). No differences in MHC or actin protein content were found. Old volunteers showed reduced ( P < 0.05) MHC IIx content compared with young volunteers but no differences in MHC I or IIa. Our data show strong trends toward reduced postabsorptive muscle protein synthesis with age. Moreover, reduced muscle protein synthesis rates were related to increased circulating concentrations of several markers of immune activation.

Insulin and amino acids independently stimulate skeletal muscle protein synthesis in neonatal pigs

2003 ◽  
Vol 284 (1) ◽  
pp. E110-E119 ◽  
Author(s):  
Pamela M. J. O'Connor ◽  
Jill A. Bush ◽  
Agus Suryawan ◽  
Hanh V. Nguyen ◽  
Teresa A. Davis
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Insulin Dose ◽  
Skeletal Muscle Protein ◽  
Neonatal Pigs ◽  
Skeletal Muscle Protein Synthesis ◽  
Dose Response Effect

Infusion of physiological levels of insulin and/or amino acids reproduces the feeding-induced stimulation of muscle protein synthesis in neonates. To determine whether insulin and amino acids independently stimulate skeletal muscle protein synthesis in neonates, insulin secretion was blocked with somatostatin in fasted 7-day-old pigs ( n = 8–12/group) while glucose and glucagon were maintained at fasting levels and insulin was infused to simulate either less than fasting, fasting, intermediate, or fed insulin levels. At each dose of insulin, amino acids were clamped at either the fasting or fed level; at the highest insulin dose, amino acids were also reduced to less than fasting levels. Skeletal muscle protein synthesis was measured using a flooding dose ofl-[4-3H]phenylalanine. Hyperinsulinemia increased protein synthesis in skeletal muscle during hypoaminoacidemia and euaminoacidemia. Hyperaminoacidemia increased muscle protein synthesis during hypoinsulinemia and euinsulinemia. There was a dose-response effect of both insulin and amino acids on muscle protein synthesis. At each insulin dose, hyperaminoacidemia increased muscle protein synthesis. The effects of insulin and amino acids on muscle protein synthesis were largely additive until maximal rates of protein synthesis were achieved. Amino acids enhanced basal protein synthesis rates but did not enhance the sensitivity or responsiveness of muscle protein synthesis to insulin. The results suggest that insulin and amino acids independently stimulate protein synthesis in skeletal muscle of the neonate.

Sign in / Sign up

Export Citation Format

Share Document