Post-Absorptive Whole Body Leucine Kinetics and Quadriceps Muscle Protein Synthetic Rate (MPSR) in the Post-Viral Syndrome

1988 ◽  
Vol 75 (s19) ◽  
pp. 36P-37P ◽  
Author(s):  
P.J. Pacy ◽  
M. Read ◽  
T.J. Peters ◽  
D. Halliday
Keyword(s):  
Muscle Protein ◽  
Quadriceps Muscle ◽  
Whole Body ◽  
Synthetic Rate ◽  
Leucine Kinetics

Whole Body Leucine Kinetics and Fractional Quadriceps Muscle Synthetic Rate (MPSR) in Alcoholic Patients

1988 ◽  
Vol 75 (s19) ◽  
pp. 36P-36P
Author(s):  
P.J. Pacy ◽  
M Read ◽  
V. Preedy ◽  
T.J. Peters ◽  
D Halliday
Keyword(s):  
Quadriceps Muscle ◽  
Whole Body ◽  
Synthetic Rate ◽  
Leucine Kinetics

Effects of acute creatine monohydrate supplementation on leucine kinetics and mixed-muscle protein synthesis

2001 ◽  
Vol 91 (3) ◽  
pp. 1041-1047 ◽  
Author(s):  
G. Parise ◽  
S. Mihic ◽  
D. MacLennan ◽  
K. E. Yarasheski ◽  
M. A. Tarnopolsky
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Fat Free Mass ◽  
Whole Body ◽  
Synthetic Rate ◽  
Fractional Synthetic Rate ◽  
Before And After ◽  
Total Creatine ◽  
Plasma Leucine

Creatine monohydrate (CrM) supplementation during resistance exercise training results in a greater increase in strength and fat-free mass than placebo. Whether this is solely due to an increase in intracellular water or whether there may be alterations in protein turnover is not clear at this point. We examined the effects of CrM supplementation on indexes of protein metabolism in young healthy men ( n = 13) and women ( n = 14). Subjects were randomly allocated to CrM (20 g/day for 5 days followed by 5 g/day for 3–4 days) or placebo (glucose polymers) and tested before and after the supplementation period under rigorous dietary and exercise controls. Muscle phosphocreatine, creatine, and total creatine were measured before and after supplementation. A primed-continuous intravenous infusion of l-[1-13C]leucine and mass spectrometry were used to measure mixed-muscle protein fractional synthetic rate and indexes of whole body leucine metabolism (nonoxidative leucine disposal), leucine oxidation, and plasma leucine rate of appearance. CrM supplementation increased muscle total creatine (+13.1%, P < 0.05) with a trend toward an increase in phosphocreatine (+8.8%, P = 0.09). CrM supplementation did not increase muscle fractional synthetic rate but reduced leucine oxidation (−19.6%) and plasma leucine rate of appearance (−7.5%, P < 0.05) in men, but not in women. CrM did not increase total body mass or fat-free mass. We conclude that short-term CrM supplementation may have anticatabolic actions in some proteins (in men), but CrM does not increase whole body or mixed-muscle protein synthesis.

Skeletal muscle myosin heavy-chain synthesis rate in healthy humans

1997 ◽  
Vol 272 (1) ◽  
pp. E45-E50 ◽  
Author(s):  
P. Balagopal ◽  
O. Ljungqvist ◽  
K. S. Nair
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Muscle Protein ◽  
Mechanical Energy ◽  
Whole Body ◽  
Synthesis Rate ◽  
Tissue Fluid ◽  
Skeletal Muscle Myosin ◽  
Body Protein ◽  
Synthetic Rate

Mixed muscle protein synthetic rate has been measured in humans. These measurements represent the average of synthetic rates of all muscle proteins with variable rates. We determined to what extent the synthesis rate of mixed muscle protein in humans reflects that of myosin heavy chain (MHC), the main contractile protein responsible for the conversion of ATP to mechanical energy as muscle contraction. Fractional synthetic rates of MHC and mixed muscle protein were measured from the increment of [13C]leucine in these proteins in vastus lateralis biopsy samples taken at 5 and 10 h during a primed continuous infusion of L-[1-13C]leucine in 10 young healthy subjects. Calculations were done by use of plasma [13C]ketoisocaproate (KIC) and muscle tissue fluid [13C]leucine as surrogate measures of leucyl-tRNA. Fractional synthetic rate of MHC with plasma KIC (0.0299 +/- 0.0043%/h) and tissue fluid leucine (0.0443 +/- 0.0056%/h) were only 72 +/- 3% of that of mixed muscle protein (0.0408 +/- 0.0032 and 0.0603 +/- 0.0059%/h, respectively, with KIC and tissue fluid leucine). Contribution of MHC (7 +/- 1 mg.kg-1.h-1) to synthetic rates of whole body mixed muscle protein (36 +/- 5 mg.kg-1.h-1) and whole body protein (127 +/- 4 mg.kg-1.h-1) is only 18 +/- 1 and 5 +/- 1%, respectively. This relatively low contribution of MHC to whole body and mixed muscle protein synthesis warrants direct measurement of synthesis rate of MHC in conditions involving abnormalities of muscle contractile function.

Rate of protein synthesis in skeletal muscle of normal man and patients with muscular dystrophy: A reassessment

1988 ◽  
Vol 74 (3) ◽  
pp. 237-240 ◽  
Author(s):  
D. Halliday ◽  
P. J. Pacy ◽  
K. N. Cheng ◽  
F. Dworzak ◽  
J. N. A. Gibson ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Muscle Protein ◽  
Normal Subjects ◽  
Quadriceps Muscle ◽  
Fed State ◽  
Synthetic Rate ◽  
New Finding ◽  
Normal Man ◽  
Relative Differences ◽  
Muscle Biopsies

1. Quadriceps muscle protein synthetic rate has been determined in healthy subjects in the post-absorptive (n = 18) and fed (n = 10) states and in patients with a variety of myopathies, by analysis of the enrichment of serial muscle biopsies taken during primed continuous infusion of l[1-13C]leucine. 2. Quadriceps protein synthetic rates in normal subjects were (mean ± sd) 0.046 ± 0.012 and 0.075 ± 0.014%/h in the post-absorptive and fed states respectively. These results are significantly lower than we previously reported (M. J. Rennie et al., Clinical Science, 1982, 63, 519–523 [1]) but show the same relative differences of direction and magnitude, confirming the effects of feeding previously reported. In patients with muscular dystrophy, muscle protein synthetic rate was, as previously reported [1], much lower in the fed state than in normal subjects. A new finding is that for patients with myotonic dystrophy the rate is also depressed in the postabortive state. 3. We suggest that the present estimates in post-absorptive and fed normal subjects be used as reference values for quadriceps mixed muscle protein synthetic rate.

Whole-body leucine and muscle protein kinetics in rats fed varying protein intakes

1984 ◽  
Vol 246 (5) ◽  
pp. E444-E451 ◽  
Author(s):  
B. C. Laurent ◽  
L. L. Moldawer ◽  
V. R. Young ◽  
B. R. Bistrian ◽  
G. L. Blackburn
Keyword(s):  
Dietary Protein ◽  
Protein Intake ◽  
Muscle Protein ◽  
Specific Radioactivity ◽  
Rectus Muscle ◽  
Whole Body ◽  
Dietary Protein Intake ◽  
Body Protein ◽  
Leucine Kinetics ◽  
Ad Libitum

Whole-body leucine kinetics and rectus muscle synthetic rates were evaluated in postabsorptive rats fed semipurified diets that varied in the casein content. Rats were allowed to consume ad libitum a 2% casein diet or were pair-fed or ad libitum-fed 6, 20, or 40% casein diets for 14 days. After overnight starvation, rates of whole-body leucine kinetics and rectus muscle synthetic rates were determined with a 2-h constant intravenous infusion of L-[1-14C]leucine. The postabsorptive response to inadequate protein intakes included a significant reduction in the release of leucine from whole-body protein degradation as well as subsequent reutilization for protein synthesis. In contrast, dietary protein intake at levels greater than required for maximal growth were not associated with any increases in leucine incorporation into whole-body protein or muscle fractional synthetic rates. Rates of whole-body leucine oxidation based on plasma leucine specific radioactivities underestimated total oxidation by 22-27%, and this was relatively constant as the protein component of the diet was varied. In addition, the muscle acid-soluble leucine specific radioactivity was similar to the plasma alpha-ketoisocaproate enrichment, regardless of dietary protein intake.

Decrease in human quadriceps muscle protein turnover consequent upon leg immobilization

1987 ◽  
Vol 72 (4) ◽  
pp. 503-509 ◽  
Author(s):  
J. N. A. Gibson ◽  
D. Halliday ◽  
W. L. Morrison ◽  
P. J. Stoward ◽  
G. A. Hornsby ◽  
...  
Keyword(s):  
Protein Turnover ◽  
Muscle Protein ◽  
Fibre Diameter ◽  
Quadriceps Muscle ◽  
Fibre Volume ◽  
Type I ◽  
Protein Breakdown ◽  
Muscle Protein Turnover ◽  
Muscle Protein Breakdown ◽  
Synthetic Rate

1. Quadriceps muscle protein turnover was assessed in the post-absorptive state in six men immediately after the end of unilateral leg immobilization (37 ± 4 days) in a plaster cast after tibial fracture. A primed-constant intravenous infusion of l-[1-13C]leucine was administered over 7 h. Quadriceps needle biopsies, taken bilaterally at the end of the infusion, were analysed for muscle protein leucine enrichment with 13C. 2. Quadriceps muscle protein synthetic rate, calculated from the fractional incorporation of [13C]leucine into protein compared with the average enrichment of blood α-ketoisocaproate, was 0.046 ±0.012%/h in the uninjured leg, but was only 0.034 ±0.007%/h in the quadriceps of the previously fractured leg (P > 0.05, means ± sd). 3. Muscle RNA activity (i.e. protein synthetic rate per RNA) fell from 0.27 ±0.08 μg of protein synthesized h−1 μg−1 of RNA in the control leg to 0.14 ±0.03 μg of protein synthesized h−1 μg−1 of RNA in the immobilized leg (P > 0.02). 4. Immobilization was associated with a significant atrophy of type I muscle fibres (mean diameter 69.5 ±21 μm immobilized, 81.1 ±18 μm control, P > 0.05), but no significant change occurred in type II fibre diameter. Mean quadriceps fibre volume calculated from the values for fibre diameter and percentage of each fibre type, was smaller in the injured leg by 10.6%; this value was near to the calculated difference in muscle thigh volume (calculated from thigh circumference and skin-fold thickness) which was less by 8.3%. 5. From estimated mean daily values for quadriceps protein synthetic rate (1.65 ±0.44%/day in the control legs and 1.22±0.28%/day in the injured legs) and change in fibre volume, mean daily muscle protein breakdown rates were calculated as 1.65%/ day and 1.53%/day respectively, suggesting that muscle protein breakdown was not enhanced and may have fallen. 6. The results suggest a decrease in muscle protein turnover during limb immobilization in man, with the decrement in muscle mass being due mainly to a substantial (25%) depression of muscle protein synthesis.

scholarly journals Co-ingestion of leucine with protein does not further augment post-exercise muscle protein synthesis rates in elderly men

2008 ◽  
Vol 99 (3) ◽  
pp. 571-580 ◽  
Author(s):  
René Koopman ◽  
Lex B. Verdijk ◽  
Milou Beelen ◽  
Marchel Gorselink ◽  
Arie Nieuwenhuijzen Kruseman ◽  
...  
Keyword(s):  
Physical Activity ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Protein Hydrolysate ◽  
Muscle Protein Synthesis ◽  
Whole Body ◽  
Elderly Men ◽  
Body Protein ◽  
Synthetic Rate ◽  
Fractional Synthetic Rate

Leucine has been suggested to have the potential to modulate muscle protein metabolism by increasing muscle protein synthesis. The objective of this study was to investigate the surplus value of the co-ingestion of free leucine with protein hydrolysate and carbohydrate following physical activity in elderly men. Eight elderly men (mean age 73 ± 1 years) were randomly assigned to two cross-over treatments consuming either carbohydrate and protein hydrolysate (CHO+PRO) or carbohydrate, protein hydrolysate with additional leucine (CHO+PRO+leu) after performing 30 min of standardized physical activity. Primed, continuous infusions with l-[ring-13C6]phenylalanine and l-[ring-2H2]tyrosine were applied, and blood and muscle samples were collected to assess whole-body protein turnover as well as protein fractional synthetic rate in the vastus lateralis muscle over a 6 h period. Whole-body protein breakdown and synthesis rates were not different between treatments. Phenylalanine oxidation rates were significantly lower in the CHO+PRO+leu v. CHO+PRO treatment. As a result, whole-body protein balance was significantly greater in the CHO+PRO+leu compared to the CHO+PRO treatment (23·8 (sem 0·3) v. 23·2 (sem 0·3) μmol/kg per h, respectively; P < 0·05). Mixed muscle fractional synthetic rate averaged 0·081 (sem 0·003) and 0·082 (sem 0·006) %/h in the CHO+PRO+leu and CHO+PRO treatment, respectively (NS). Co-ingestion of leucine with carbohydrate and protein following physical activity does not further elevate muscle protein fractional synthetic rate in elderly men when ample protein is ingested.

Effect of fetal growth on maternal protein metabolism in postabsorptive rat

1987 ◽  
Vol 252 (3) ◽  
pp. E380-E390 ◽  
Author(s):  
P. R. Ling ◽  
B. R. Bistrian ◽  
G. L. Blackburn ◽  
N. Istfan
Keyword(s):  
Protein Synthesis ◽  
Late Pregnancy ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Efficient Utilization ◽  
Synthetic Rate ◽  
Leucine Kinetics ◽  
Degradation Rates ◽  
Fractional Synthetic Rate ◽  
Plasma Leucine

Rates of protein synthesis were measured in whole fetuses and maternal tissues at 17 and 20 days of gestation in postabsorptive rats using continuous infusion of L-[1–14C]leucine. Fetal protein degradation rates were derived from the fractional rates of synthesis and growth. Whole-body (plasma) leucine kinetics in the mother showed a significant reduction of the fraction of plasma leucine oxidized in the mothers bearing older fetuses, a slight increase in the plasma flux, with total leucine oxidation and incorporation into protein remaining similar at the two gestational ages. Estimates of fractional protein synthesis in maternal tissues revealed an increase in placental and hepatic rates at 20 days of gestation, whereas the fractional synthetic rate in muscle remained unchanged. A model for estimation of the redistribution of leucine between plasma and tissues is described in detail. This model revealed a more efficient utilization of leucine in fetal protein synthesis in comparison with other maternal tissues, a greater dependency of the fetus on plasma supply of leucine, and a significant increase (2-fold) in the release of leucine from maternal muscle as the fetal requirements increased proportionately with its size. The latter conclusion, supported by nitrogen analysis and the ratio of bound-to-free leucine in maternal tissues, confirms the importance of maternal stores in maintaining the homeostasis of essential amino acids during late pregnancy.

Muscle and bone in paraplegic patients, and the effect of functional electrical stimulation

1988 ◽  
Vol 75 (5) ◽  
pp. 481-487 ◽  
Author(s):  
P. J. Pacy ◽  
R. Hesp ◽  
D. A. Halliday ◽  
D. Katz ◽  
Gillian Cameron ◽  
...  
Keyword(s):  
Bone Density ◽  
Bone Mineral Content ◽  
Bone Mineral ◽  
Mineral Content ◽  
Muscle Protein ◽  
Distal Tibia ◽  
Lumbar Vertebrae ◽  
Quadriceps Muscle ◽  
Whole Body ◽  
Body Protein

1. Four paraplegic men volunteered for an exercise programme in which their paralysed quadriceps muscles were stimulated by means of computer-regulated electrical impulses applied through external electrodes. The first exercise regimen consisted of leg raising against a graded load, and during the second regimen exercise took the form of cycling on a modified bicycle ergometer. Each subject exercised five times weekly for 10 weeks during the first regimen and 32 weeks during the second regimen. 2. Whole-body protein turnover determined by l-[1-13C]leucine during feeding remained constant during both exercise regimens, when expressed either in terms of body weight or fat-free mass derived from measurements of total body potassium. 3. Quadriceps muscle protein synthetic rate increased during the study, from 0.0712 to 0.0985%/h (P < 0.05), as did quadriceps muscle area assessed by computed tomography. 4. Bone mineral content for lumbar vertebrae was normal in all four patients, but for the femoral mid-shaft bone mineral content averaged only 66% of normal for three of the patients. Trabecular bone density in the distal tibia ranged from normal to 2% of normal for the men with the shortest and longest periods of disability, respectively. No changes in bone mineral content or bone density occurred during the exercise period.

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