scholarly journals Exogenous amino acids stimulate net muscle protein synthesis in the elderly.

1998 ◽  
Vol 101 (9) ◽  
pp. 2000-2007 ◽  
Author(s):  
E Volpi ◽  
A A Ferrando ◽  
C W Yeckel ◽  
K D Tipton ◽  
R R Wolfe
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
The Elderly

Oral amino acids stimulate muscle protein anabolism in the elderly despite higher first-pass splanchnic extraction

1999 ◽  
Vol 277 (3) ◽  
pp. E513-E520 ◽  
Author(s):  
Elena Volpi ◽  
Bettina Mittendorfer ◽  
Steven E. Wolf ◽  
Robert R. Wolfe
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
The Elderly ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Healthy Elderly ◽  
First Pass

Muscle protein synthesis and breakdown and amino acid transport were measured in 7 healthy young (30 ± 2 yr) and 8 healthy elderly (71 ± 2 yr) volunteers in the postabsorptive state and during the oral administration of an amino acid mixture withl-[ ring-2H5]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Phenylalanine first-pass splanchnic extraction was measured by addingl-[ ring-13C6]phenylalanine to the mixture. In the postabsorptive state, no differences in muscle amino acid kinetics were detected between young and elderly volunteers. Phenylalanine first-pass splanchnic extraction was significantly higher in the elderly ( P < 0.003) during ingestion of amino acids, but the delivery to the leg increased to the same extent in both groups. Phenylalanine transport into the muscle, muscle protein synthesis, and net balance increased significantly ( P < 0.01) and similarly in both the young and the elderly. We conclude that, despite an increased splanchnic first-pass extraction, muscle protein anabolism can be stimulated by oral amino acids in the elderly as well as in the young.

scholarly journals Exercise, Amino Acids, and Aging in the Control of Human Muscle Protein Synthesis

2011 ◽  
Vol 43 (12) ◽  
pp. 2249-2258 ◽  
Author(s):  
DILLON K. WALKER ◽  
JARED M. DICKINSON ◽  
KYLE L. TIMMERMAN ◽  
MICAH J. DRUMMOND ◽  
PAUL T. REIDY ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Human Muscle

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.

Effects of glucose, pyruvate, lactate, and amino acids on muscle protein synthesis

1982 ◽  
Vol 242 (3) ◽  
pp. E184-E192 ◽  
Author(s):  
M. P. Hedden ◽  
M. G. Buse
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Creatine Phosphate ◽  
Serum Amino Acids ◽  
14Co2 Production ◽  
Beta Hydroxybutyrate ◽  
Free Media ◽  
Effect Of Glucose

Protein synthesis was measured in rat diaphragms incubated with serum amino acids + 0.35 mM L-[2,6-3H]tyrosine and different energy-yielding substrates. Muscles incubated with 5.5 mM glucose (with or without actinomycin D) synthesized more protein than those incubated with 11 mM pyruvate or 11 mM lactate. Tissue ATP decreased during incubation with lactate, but pyruvate maintained ATP, ADP, and creatine phosphate as well as glucose. Glucose 6-phosphate decreased in muscles incubated in glucose-free media. 14CO2 production from substrates was [1-14C]pyruvate greater than [1-14C]lactate greater than [3,4-14C]glucose. Intracellular lactate/pyruvate was measured to assess cytoplasmic free NADH/NAD+; the effect of different media on these ratios was lactate greater than glucose = lactate + pyruvate greater than pyruvate + glucose greater than pyruvate. Lactate + pyruvate (8.8 + 2.2 mM) supported protein synthesis better than pyruvate and as well as glucose. Adding glucose to pyruvate accelerated protein synthesis and increased NADH/NAD+. Iodoacetate (0.1 mM) inhibited glycolytic NAD reduction and abolished the stimulatory effect of glucose on protein synthesis in the presence of pyruvate. Supplementation of pyruvate media with 1 mM leucine or isoleucine stimulated protein synthesis, but beta-hydroxybutyrate, malate, alpha-ketoisocaproate, and all other amino acids were ineffective. The cytoplasmic redox potential may act as a translational modulator of protein synthesis in skeletal muscle.

An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein

1997 ◽  
Vol 273 (1) ◽  
pp. E122-E129 ◽  
Author(s):  
G. Biolo ◽  
K. D. Tipton ◽  
S. Klein ◽  
R. R. Wolfe
Keyword(s):  
Amino Acids ◽  
Blood Flow ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Protein Kinetics ◽  
Amino Acid Infusion

Six normal untrained men were studied during the intravenous infusion of a balanced amino acid mixture (approximately 0.15 g.kg-1.h-1 for 3 h) at rest and after a leg resistance exercise routine to test the influence of exercise on the regulation of muscle protein kinetics by hyperaminoacidemia. Leg muscle protein kinetics and transport of selected amino acids (alanine, phenylalanine, leucine, and lysine) were isotopically determined using a model based on arteriovenous blood samples and muscle biopsy. The intravenous amino acid infusion resulted in comparable increases in arterial amino acid concentrations at rest and after exercise, whereas leg blood flow was 64 +/- 5% greater after exercise than at rest. During hyperaminoacidemia, the increases in amino acid transport above basal were 30-100% greater after exercise than at rest. Increases in muscle protein synthesis were also greater after exercise than at rest (291 +/- 42% vs. 141 +/- 45%). Muscle protein breakdown was not significantly affected by hyperminoacidemia either at rest or after exercise. We conclude that the stimulatory effect of exogenous amino acids on muscle protein synthesis is enhanced by prior exercise, perhaps in part because of enhanced blood flow. Our results imply that protein intake immediately after exercise may be more anabolic than when ingested at some later time.

Coordinated increase in albumin, fibrinogen, and muscle protein synthesis during hemodialysis: role of cytokines

2004 ◽  
Vol 286 (4) ◽  
pp. E658-E664 ◽  
Author(s):  
Dominic S. C. Raj ◽  
Elizabeth A. Dominic ◽  
Robert Wolfe ◽  
Vallabh O. Shah ◽  
Arthur Bankhurst ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Whole Body ◽  
Constant Infusion ◽  
Fractional Synthesis ◽  
Stage Renal Disease ◽  
End Stage ◽  
Esrd Patients

Serum albumin, fibrinogen levels, and lean body mass are important predictors of outcome in end-stage renal disease (ESRD). We estimated the fractional synthesis rates of albumin (FSR-A), fibrinogen (FSR-F), and muscle protein (FSR-M) in nine ESRD patients and eight controls, using primed constant infusion of l-[ ring-13C6]phenylalanine. Cytokine profile and arteriovenous balance of amino acids were also measured. ESRD patients were studied before (Pre-HD) and during hemodialysis (HD). Plasma IL-6, IL-10, and C-reactive protein increased significantly during HD. Despite a decrease in the delivery of amino acids to the leg, the outflow of the amino acids increased during HD. The net balance of amino acids became more negative during HD, indicating release from the muscle. HD increased leg muscle protein synthesis (45%) and catabolism (108%) but decreased whole body proteolysis (15%). FSR-A during HD (9.7 ± 0.9%/day) was higher than pre-HD (6.5 ± 0.9%/day) and controls (5.8 ± 0.5%/day, P < 0.01). FSR-F increased during HD (19.7 ± 2.6%/day vs. 11.8 ± 0.6%/day, P < 0.01), but it was not significantly different from that of controls (14.4 ± 1.4%/day). FSR-M intradialysis (1.77 ± 0.19%/day) was higher than pre-HD (1.21 ± 0.25%/day) and controls (1.30 ± 0.32%/day, P < 0.001). Pre-HD FSR-A, FSR-F, and FSR-M values were comparable to those of controls. There was a significant and positive correlation between plasma IL-6 and the FSRs. Thus, in ESRD patients without metabolic acidosis, the fractional synthesis rates of albumin, fibrinogen, and muscle protein are not decreased pre-HD. However, HD increases the synthesis of albumin, fibrinogen, and muscle protein. The coordinated increase in the FSRs is facilitated by constant delivery of amino acids derived from the muscle catabolism and intradialytic increase in IL-6.

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