Bed Rest Decreases Whole-Body Protein Turnover in Post-Absorptive Man

1996 ◽  
Vol 90 (1) ◽  
pp. 73-75 ◽  
Author(s):  
G. E. A. Bettany ◽  
B. C. Ang ◽  
S. N. Georgiannos ◽  
D. Halliday ◽  
J. Powell-Tuck
Keyword(s):  
Protein Turnover ◽  
Bed Rest ◽  
Nitrogen Excretion ◽  
Daily Activities ◽  
Whole Body ◽  
Tracer Technique ◽  
Short Term ◽  
Body Protein ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

1. Whole-body protein turnover was measured using the [15N]glycine tracer technique in 10 post-absorptive healthy volunteers during normal daily activities and a period of bed rest. 2. Bed rest reduced whole-body protein turnover (25%), synthesis (26%) and breakdown (25%), but short-term urinary nitrogen excretion remained unchanged.

Whole body protein synthesis in healthy adult humans: 13CO2 technique vs. plasma precursor approach

1995 ◽  
Vol 268 (1) ◽  
pp. E174-E184 ◽  
Author(s):  
A. E. el-Khoury ◽  
M. Sanchez ◽  
N. K. Fukagawa ◽  
V. R. Young
Keyword(s):  
Protein Synthesis ◽  
Healthy Adult ◽  
Physiological State ◽  
Nitrogen Excretion ◽  
Whole Body ◽  
Body Protein ◽  
Adult Humans ◽  
Pool Model ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Different methods for the estimation of whole body protein synthesis (PS) in healthy adult humans were simultaneously compared in seven young adult subjects (6 males, 1 female) fed for 6 days a diet providing 1 g protein.kg-1.day-1 and approximately 188 kJ.kg-1.day-1. A 24-h intravenous tracer study with L-[1-13C]leucine was performed starting at 6 P.M. on day 6. During fasted (6 h) and fed (6 h) steady states, PS was estimated using an approach based on 13CO2 excretion (PSexcr) and on urinary nitrogen excretion data (corrected for changes in body urea pool). Simultaneously, we used the conventional two-pool model and plasma [13C]ketoisocaproate enrichment for estimating PS. The latter mean estimates of PS were significantly higher than PSexcr during fasting [861 +/- 58 (SD) vs. 663 +/- 160 mg protein.kg-1.6 h-1; P < 0.01] and feeding (985 +/- 63 vs. 779 +/- 127 mg protein.kg-1.6 h-1; P < 0.01) and were much less variable. In hourly small-meal feeding, urinary nitrogen excretion was not a reliable index of body protein oxidation when measured over short periods of 6 h, thereby introducing a lack of precision in PSexcr. We suggest that application of the 13CO2 technique to measure PS in humans is limited by the need for relatively prolonged experimental periods of urine collection and tracer infusion within a given physiological state.

Resistance training reduces whole-body protein turnover and improves net protein retention in untrained young males

2006 ◽  
Vol 31 (5) ◽  
pp. 557-564 ◽  
Author(s):  
Joseph W. Hartman ◽  
Daniel R. Moore ◽  
Stuart M. Phillips
Keyword(s):  
Resistance Training ◽  
Resistance Exercise ◽  
Nitrogen Balance ◽  
Protein Turnover ◽  
Whole Body ◽  
Body Protein ◽  
Protein Retention ◽  
The Impact ◽  
Net Protein ◽  
Urinary Nitrogen

It is thought that resistance exercise results in an increased need for dietary protein; however, data also exists to support the opposite conclusion. The purpose of this study was to determine the impact of resistance exercise training on protein metabolism in novices with the hypothesis that resistance training would reduce protein turnover and improve whole-body protein retention. Healthy males (n = 8, 22 ± 1 y, BMI = 25.3 ± 1.8 kg·m–2) participated in a progressive whole-body split routine resistance-training program 5d/week for 12 weeks. Before (PRE) and after (POST) the training, oral [15N]-glycine ingestion was used to assess nitrogen flux (Q), protein synthesis (PS), protein breakdown (PB), and net protein balance (NPB = PS – PB). Macronutrient intake was controlled over a 5d period PRE and POST, while estimates of protein turnover and urinary nitrogen balance (Nbal = Nin – urine Nout) were conducted. Bench press and leg press increased 40% and 50%, respectively (p < 0.01). Fat- and bone-free mass (i.e., lean muscle mass) increased from PRE to POST (2.5 ± 0.8 kg, p < 0.05). Significant PRE to POST decreases (p <0.05) occurred in Q (0.9 ± 0.1 vs. 0.6 ± 0.1 g N·kg–1·d–1), PS (4.6 ± 0.7 vs. 2.9 ± 0.3 g·kg–1·d–1), and PB (4.3 ± 0.7 vs. 2.4 ± 0.2 g·kg–1·d–1). Significant training-induced increases in both NPB (PRE = 0.22 ± 0.13 g·kg–1·d–1; POST = 0.54 ± 0.08 g·kg–1·d–1) and urinary nitrogen balance (PRE = 2.8 ± 1.7 g N·d–1; POST = 6.5 ± 0.9 g N·d–1) were observed. A program of resistance training that induced significant muscle hypertrophy resulted in reductions of both whole-body PS and PB, but an improved NPB, which favoured the accretion of skeletal muscle protein. Urinary nitrogen balance increased after training. The reduction in PS and PB and a higher NPB in combination with an increased nitrogen balance after training suggest that dietary requirements for protein in novice resistance-trained athletes are not higher, but lower, after resistance training.

Aspects of protein metabolism after elective surgery in patients receiving constant nutritional support

1990 ◽  
Vol 78 (6) ◽  
pp. 621-628 ◽  
Author(s):  
F. Carli ◽  
J. Webster ◽  
V. Ramachandra ◽  
M. Pearson ◽  
M. Read ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Metabolic Rate ◽  
Protein Metabolism ◽  
Protein Turnover ◽  
Resting Metabolic Rate ◽  
Plasma Concentrations ◽  
Whole Body ◽  
Body Protein ◽  
Urinary Nitrogen

1. The present study was designed in an attempt to resolve conflicting views currently in the literature relating to the effect of surgery on various aspects of protein metabolism. 2. Sequential post-operative (2, 4 and 6 days) changes in whole-body protein turnover, forearm arteriovenous difference of plasma amino acids, glucose, lactate and free fatty acids, muscle concentration of free amino acids, RNA and protein, urinary nitrogen and 3-methylhistidine, plasma concentrations of insulin, cortisol and growth hormone, and resting metabolic rate, were measured in six patients undergoing uncomplicated elective total abdominal hysterectomy. 3. All patients received a constant daily diet, either orally or intravenously, based on 0.1 g of nitrogen/kg and an energy content of 1.1 times the resting metabolic rate for 7 days before and 6 days after surgery. 4. Whole-body protein turnover, synthesis and breakdown increased significantly 2 days after surgery (P <0.05) and returned towards pre-operative levels thereafter. 5. Forearm release of branched-chain amino acids and alanine, and efflux of glucose and lactate, were enhanced 4 days after surgery (P <0.05). Muscle glutamine and alanine concentrations were decreased on the fourth and sixth days after surgery (P <0.05). The RNA/protein ratio (indicating the capacity for protein synthesis) was unaltered. 6. A significant increase in urinary nitrogen and 3-methylhistidine was observed on days 3 and 4 after surgery (P <0.05). Thereafter, these parameters remained elevated, although failing to reach statistical significance. 7. The resting metabolic rate was significantly increased (P <0.05) 2 days after surgery but the respiratory quotient (0.77) was unchanged. 8. These data support the contention that whole-body protein synthesis and breakdown increase after surgery. Differences observed pre- and post-operatively between leucine kinetic estimates and other methods of quantifying protein metabolism indicate that only like methodologies should be compared.

Protein kinetics in stable heart failure patients

2003 ◽  
Vol 94 (1) ◽  
pp. 295-300 ◽  
Author(s):  
Charles W. Cortes ◽  
Paul D. Thompson ◽  
Niall M. Moyna ◽  
Margaret D. Schluter ◽  
Maria J. Leskiw ◽  
...  
Keyword(s):  
Protein Metabolism ◽  
Protein Turnover ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Bed Rest ◽  
Whole Body ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Body Protein ◽  
Fractional Synthesis

Heart failure (HF) is a slow progressive syndrome characterized by low cardiac output and peripheral metabolic, biochemical, and histological alterations. Protein loss and reduced protein turnover occur with aging, but the consequences of congestive HF (CHF) superimposed on the normal aging response are unknown. This study has two objectives: 1) to determine whether there was a difference between older age-matched controls and those with stable HF (i.e., ischemic pathology) in whole body protein turnover and 2) to determine whether protein metabolism in liver and skeletal muscle protein turnover is impacted by CHF. We measured the whole body protein synthesis rate with a U-15N-labeled algal protein hydrolysate in 10 patients with CHF and in 10 age-matched controls. Muscle fractional synthesis rate of lateral vastus muscle was determined with [U-13C]alanine on muscle biopsies obtained by a standard percutaneous needle biopsy technique. Fractional synthesis rates of five plasma proteins of hepatic origin (fibrinogen, complement C-3, ceruloplasmin, transferrin, and very low-density lipoprotein apoliprotein B-100) were determined by using2H5-labeled l-phenylalanine as tracer. Results showed that whole body protein synthesis rate was reduced in CHF patients (3.09 ± 0.19 vs. 2.25 ± 0.71 g protein · kg−1 · day−1, P < 0.05) as was muscle fractional synthesis rate (3.02 ± 0.58 vs. 1.33 ± 0.71%/day, P < 0.05) and very low-density lipoprotein apoliprotein B-100 (265 ± 25 vs. 197 ± 16%/day, P < 0.05). CHF patients were hyperinsulinemic (9.6 ± 3.1 vs. 47.0 ± 7.8 μU/ml, P < 0.01). The results were compared with those found with bed rest patients. In conclusion, protein turnover is depressed in CHF patients, and both skeletal muscle and liver are impacted. These results are similar to those found with bed rest, which suggests that inactivity is a factor in depressed protein metabolism.

The Combined Effects of Infection and Malnutrition on Protein Metabolism in Children

1983 ◽  
Vol 65 (3) ◽  
pp. 313-324 ◽  
Author(s):  
A. M. Tomkins ◽  
P. J. Garlick ◽  
W. N. Schofield ◽  
J. C. Waterlow
Keyword(s):  
Protein Synthesis ◽  
Protein Metabolism ◽  
Group Iv ◽  
Nitrogen Excretion ◽  
Whole Body ◽  
Body Protein ◽  
Group Iii ◽  
Group I ◽  
Urinary Nitrogen Excretion ◽  
Weight For Age

1. Twenty-two children were studied as in-patients at a Nigerian Hospital. 2. They were divided into four groups on the basis of weight for age: I, adequately nourished, acutely infected; II, moderately under weight, acutely infected; III, malnourished, chronically infected; IV, malnourished, uninfected. 3. Urinary nitrogen excretion was highest in group I and lowest in groups III and IV. Urinary creatinine was highest in group I, but did not differ significantly in groups II, III and IV. The excretion of 3-methylhistidine closely paralleled that of creatinine. It is suggested that the high rates of creatinine and methylhistidine excretion in group I resulted in part from destruction of muscle. 4. Rates of whole body protein turnover were measured by administration of a single dose of [15N]glycine with measurement of the excretion of 15N in urinary NH3 for the next 9 h. 5. Rates of protein synthesis and breakdown were very high in infected children of groups I and II. Although rates were lower in the malnourished groups, in infected children of group III they were nearly twice as high as in the uninfected group IV. The net balance of protein (synthesis minus breakdown) was negative in group I, less negative in group II, zero in group III and positive in group IV. 6. Repeat measurements in group I during recovery from infection showed a decline in rates of excretion of nitrogen, creatinine and 3-methylhistidine. Rates of protein synthesis and breakdown declined and the protein balance became less negative, but these changes were not statistically significant. 7. Multiple regression analysis of the results of all groups taken together showed independent contributions to rates of protein metabolism from infection and nutritional state, especially plasma albumin. 8. It was concluded that infection caused a rise in protein breakdown which was larger than the concomitant rise in synthesis, leading to net loss of protein, and that these responses were reduced by malnutrition.

Effect of surgical injury and intraoperative hypothermia on whole body protein metabolism

1991 ◽  
Vol 260 (1) ◽  
pp. E118-E125 ◽  
Author(s):  
D. P. Taggart ◽  
D. C. McMillan ◽  
T. Preston ◽  
A. Shenkin ◽  
D. J. Wheatley ◽  
...  
Keyword(s):  
Protein Metabolism ◽  
Nitrogen Excretion ◽  
Whole Body ◽  
Isotopic Enrichment ◽  
Body Protein ◽  
Blood Temperature ◽  
15N Enrichment ◽  
Before And After ◽  
Male Patients ◽  
Urinary Nitrogen

Whole body protein turnover and urinary nitrogen and 3-methyl-L-histidine (3-MH) excretion were measured before and after cardiac surgery using cardiopulmonary bypass in 20 male patients randomized to an intraoperative blood temperature of 28 or 20 degrees C. Rates of whole body protein synthesis (WBPS) and breakdown (WBPB) were determined from the 15N isotopic enrichment of urinary urea, ammonium, and from a calculated end-product average (EPA) after a primed 24-h infusion of [15N]glycine. In the postoperative period, there was a 40% increase in median nitrogen excretion in the 28 degrees C group (P less than 0.03) and a 22% increase in the 20 degrees C group (P = 0.10). There was a 79% increase in the median postoperative 3-MH excretion in the 28 degrees C group (P = 0.01) and a 66% increase in the median postoperative 3-MH excretion in the 20 degrees C group (P less than 0.01). Postoperatively, there was a 23% fall in the median value of WBPS in the 28 degrees C group (P less than 0.01) and an 11% fall in the 20 degrees C group [not significant (NS)] measured by 15N enrichment of urinary urea. In contrast, when WBPS was measured from isotopic enrichment of urinary ammonium, there was an increase in the median value of the postoperative rates of WBPS in both groups, by 20% in the 28 degrees C group (P = NS) and 29% in the 20 degrees C group (P = 0.03). There was no significant change in the rate of WBPS and WBPB, judged by the postoperative EPA in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma leucine kinetics and urinary nitrogen excretion in intensively treated diabetes mellitus

1992 ◽  
Vol 263 (1) ◽  
pp. E173-E179 ◽  
Author(s):  
F. Lariviere ◽  
D. B. Kupranycz ◽  
J. L. Chiasson ◽  
L. J. Hoffer
Keyword(s):  
Diabetes Mellitus ◽  
Insulin Therapy ◽  
Protein Oxidation ◽  
Nitrogen Excretion ◽  
Protein Loss ◽  
Short Term ◽  
Body Protein ◽  
Leucine Oxidation ◽  
Protein Free Diet ◽  
Urinary Nitrogen

It is well known that inadequate insulin therapy stimulates body protein loss in insulin-dependent diabetes mellitus (IDDM). It is less well known, however, that accelerated body protein loss (as indicated by increased leucine oxidation) occurs in IDDM even during conventional glycemic control. It is not known whether intensified insulin therapy fully normalizes protein oxidation or, more importantly, whether such therapy is sufficient to allow the adaptive decrease of protein oxidation that normally occurs when protein intake is restricted below the customary surfeit level. We used two measures of protein oxidation [daily urinary nitrogen (N) excretion over several days of intensive insulin therapy and plasma [1-13C]leucine oxidation during short-term strict euglycemia] to assess the response of 7 men with IDDM and 12 normal men after adaptation first to a control diet providing maintenance energy and conventional (surfeit) protein then to an isoenergetic protein-free diet. After adaptation to the protein-free diet and during short-term strict euglycemia achieved using intravenous insulin, leucine turnover and oxidation decreased equivalently in normal and diabetic subjects. However, daily urinary obligatory N excretion, which indicated the effect of the low-protein diet and intensive subcutaneous insulin therapy over several days, was increased by 18% in the diabetic group (P less than 0.05). Even mildly elevated average blood glucose values well within the guidelines for intensive therapy were strongly correlated with high rates of urinary N excretion (r = 0.97, P = 0.0002). Thus insulin therapy of IDDM that imposes strict euglycemia is compatible with a normal ability to diminish body protein oxidation in response to protein restriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary protein on bed-rest-related changes in whole-body-protein synthesis

1990 ◽  
Vol 52 (3) ◽  
pp. 509-514 ◽  
Author(s):  
C A Stuart ◽  
R E Shangraw ◽  
E J Peters ◽  
R R Wolfe
Keyword(s):  
Protein Synthesis ◽  
Dietary Protein ◽  
Bed Rest ◽  
Whole Body ◽  
Body Protein
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