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.

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.

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.

Influence of protein intake on whole body and splanchnic leucine kinetics in humans

1997 ◽  
Vol 272 (4) ◽  
pp. E584-E591 ◽  
Author(s):  
M. Cayol ◽  
Y. Boirie ◽  
F. Rambourdin ◽  
J. Prugnaud ◽  
P. Gachon ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Intake ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
The Body ◽  
Whole Body ◽  
Body Protein ◽  
Leucine Kinetics ◽  
Protein X ◽  
Pool Model

The influence of the protein content of the meal on protein turnover was investigated in the splanchnic bed and in the remaining parts of the body in humans. Two groups of five subjects consumed every 20 min a liquid formula providing either 1.5 g protein x kg(-1) x day(-1) (P) or no protein (PF). L-[1-(13)C]leucine and L-[5,5,5-(2)H3]leucine were administered by vein and gut, respectively. An open two-pool model was developed to calculate leucine kinetics in both compartments, with the assumption that the enrichment of the tracers incorporated into very low density lipoprotein apolipoprotein B100 at isotopic steady state could reflect the leucine labeling in the splanchnic region. Nonsplanchnic uptake and release of leucine were not significantly different in the two groups. Within the splanchnic area, leucine uptake was 2.1 times higher in the P than in the PF group (P < 0.01), whereas leucine release was reduced but not significantly (-19%) in the P group compared with the PF group. Moreover, data derived from this model showed that protein intake induced an increase in whole body protein synthesis and no change in whole body protein breakdown. Albumin synthesis, as well as its contribution to whole body protein synthesis, was significantly enhanced by protein intake.

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.

Apparent compartmentation of body nitrogen in one human subject: its consequences in measuring the rate of whole-body protein synthesis with 15N

1985 ◽  
Vol 68 (3) ◽  
pp. 271-282 ◽  
Author(s):  
Edward B. Fern ◽  
Peter J. Garlick ◽  
John C. Waterlow
Keyword(s):  
Protein Synthesis ◽  
Experimental Period ◽  
Oral Route ◽  
The Body ◽  
Whole Body ◽  
Body Protein ◽  
Pool Model ◽  
Harmonic Average ◽  
Empirical Context ◽  
Oral Doses

1. The rate of protein synthesis in the whole body was measured in one fed subject with seven 15N-labelled amino acids (intravenous and oral doses) and two 15N protein mixtures (oral doses only). The rates were determined individually from the urinary excretion of ammonia and total urea over a 12 h experimental period. 2. Except with oral glycine and alanine, the synthesis rates given by ammonia and urea were appreciably different within each study when calculated on the assumption of a single pool of metabolic nitrogen in the body. In general, intravenous administration of the tracers gave higher rates with urea and the oral route gave higher rates with ammonia. 3. The differences between intravenous and oral doses of 15N could be reduced significantly by calculating synthesis rates from either the arithmetic or harmonic average of flux rates given by ammonia and urea. The averages correspond to estimates of the total flux in a two-pool model of metabolic nitrogen when it is assumed either that both pools receive an equal amount of tracer (arithmetic) or that both have the same rate of nitrogen turnover (harmonic). 4. By so reducing the effect of physical separation of nitrogen in the body, the metabolic aspects of compartmentation of the tracer could be examined. The results show that the absolute value obtained for protein synthesis depends on the source of labelled nitrogen. The data are discussed in this empirical context.

Whole-body protein metabolism due to trauma in man as estimated by L-[15N]alanine

1981 ◽  
Vol 241 (1) ◽  
pp. E64-E71 ◽  
Author(s):  
R. H. Birkhahn ◽  
C. L. Long ◽  
D. Fitkin ◽  
M. Jeevanandam ◽  
W. S. Blakemore
Keyword(s):  
Protein Synthesis ◽  
Protein Metabolism ◽  
Single Pulse ◽  
Whole Body ◽  
Trauma Patients ◽  
Body Protein ◽  
Protein Pool ◽  
Pool Model ◽  
Infusion Method ◽  
Protein Free Diet

Changes in whole-body protein metabolism due to several skeletal trauma were estimated in five male volunteers and four male trauma patients using a single pulse of [15N]alanine and [13C]urea. The isotopic decay data were computer curve-fitted to obtain the best estimates for eight parameters of a four-pool model. The trauma patients excreted almost 5 times as much urinary nitrogen and utilized 33% more energy than did the volunteers on the same hypocaloric, protein-free diet. Trauma was found to expand the "active metabolic nitrogen" pool and the transfer rates of nitrogen into and out of a "slow turnover protein" pool. Whole-body protein synthesis increased 37% above normal and protein breakdown increased 79% above normal due to trauma. These values were in agreement with those determined at the same time using a [14C]leucine continuous infusion method. The data show that trauma accelerates the nitrogen flow and both protein synthesis and breakdown. This mechanism for negative nitrogen balance is consistent with that found for other severe stresses but is different from milder stresses.

Utilization of amino acids by preruminant lambs. I. The effect of alterations in total essential amino acid intake at constant nitrogen intake

1977 ◽  
Vol 28 (5) ◽  
pp. 917 ◽  
Author(s):  
H Dove ◽  
GR Pearce ◽  
DE Tribe
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Nitrogen Balance ◽  
Control Diet ◽  
Essential Amino Acids ◽  
Conclusive Evidence ◽  
Metabolizable Energy ◽  
Nitrogen Excretion ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Male crossbred lambs weighing 12.5 kg (period 1), 20 kg (period 2) and 30 kg (period 3) were infused per abomasum with milk-based diets in which crude protein (CP) and energy contents were constant at a given Iiveweight, but in which the proportion of CP supplied as essential amino acids (EAA) varied from 120 to 876 g EAA/kg CP. Responses in liveweight gain, nitrogen balance and metabolizable energy (ME) intake (period 1 only) were measured. A number of lambs died while receiving diets containing very high or very low proportions of EAA. Possible reasons for these deaths are discussed. In all periods liveweight gains were greatest in lambs given the control diet (513 g EAA/kg CP). In period 1 this liveweight gain was close to that expected on the basis of energy intake, but in periods 2 and 3, liveweight gains on the control diets were less than anticipated. Reductions in liveweight gain were greater for diets containing low proportions of EAA than those containing high proportions. The infusion of diets containing low proportions of EAA markedly increased urinary nitrogen excretion. The effect of diets containing high proportions was less pronounced. As a result of these effects, lambs given the control diet had the highest daily nitrogen balance in all periods. Nitrogen balance was less severely affected by the dietary changes than liveweight gain, particularly with 30 kg lambs. It is suggested that the reduced retention of apparently digested nitrogen in diets other than the control diets reflected the unsuitability of the pattern of absorbed amino acids for protein synthesis. The effect of diet on the components of energy balance in period 1 was less pronounced than its effect on nitrogen balance. The metabolizability of apparently digested energy was lower in diets other than the control diet, especially those containing low proportions of EAA. This is attributed to the energy cost of increased urinary nitrogen excretion on such diets. Alternative interpretations of the results are discussed, and it is suggested that dietary amino acids will be utilized most efficiently for protein synthesis by the tissues of the lamb when essential and non-essential amino acids are provided in approximately equal proportions. There was no conclusive evidence that this optimum proportion was different for older lambs.

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)

Metabolism of Carbon 14 Methyl-Labeled Sodium Acetate Following Thermal Trauma in the Rat

1956 ◽  
Vol 185 (2) ◽  
pp. 265-268 ◽  
Author(s):  
John W. Braasch ◽  
Stanley M. Levenson ◽  
Leo V. Crowley ◽  
H. Mortye Vinecour ◽  
Julia A. Vinecour
Keyword(s):  
Protein Synthesis ◽  
Sodium Acetate ◽  
Nitrogen Excretion ◽  
Ether Anesthesia ◽  
Tissue Protein ◽  
Thermal Trauma ◽  
Carbon 14 ◽  
Tissue Protein Synthesis ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Observations on the metabolism of C14 methyl-labeled sodium acetate have been obtained in 14 control and 11 burned rats. The C14 acetate was given intraperitoneally 3 days after ether anesthesia (control) or after anesthesia and thermal trauma. The losses of C14 in expired air and urine were measured in both groups. The data suggest that tissue protein synthesis from acetate is proceeding in the burned rats and at rates which are almost certainly not slower than in normal rats. This would suggest that generalized antianabolism is not the basis for the increased urinary nitrogen excretion after burns.

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