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.

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.

Whole-Body Protein Turnover before and after Resection of Colorectal Tumours

1983 ◽  
Vol 64 (1) ◽  
pp. 101-108 ◽  
Author(s):  
R. E. Glass ◽  
E. B. Fern ◽  
P. J. Garlick
Keyword(s):  
Protein Synthesis ◽  
Primary Tumour ◽  
Experimental Period ◽  
Whole Body ◽  
Tumour Resection ◽  
Surgical Removal ◽  
Protein Breakdown ◽  
Nitrogen Flux ◽  
Body Protein ◽  
Before And After

1. The rate of whole-body nitrogen flux; protein synthesis and protein breakdown were measured in patients with colorectal cancer (Dukes A—C) just before and 12 weeks after surgical removal of the tumour. The rates were determined from the urinary excretion of 15N in ammonia and in urea over a 9 h period after an oral dose of [15N]glycine. 2. The food intake during the 2 study days was identical for individual patients. The amount each received was determined from measurement of their intake of food ad libitum on the day preceding the pre-operative study and was consumed in six equal portions every 2 h during the experimental period. 3. No significant differences in the rates of nitrogen flux, protein synthesis and protein breakdown were found before and after tumour resection, whether calculated from the excretion of 15N in ammonia or in urea. Some changes in flux, both increases and decreases, were observed in individual patients after tumour removal but these could not be related to classification of the tumour, or to the presence of pre-operative anorexia or weight loss. 4. The results suggest that the primary tumour itself does not alter the overall rate of protein metabolism in the whole body.

Influence of low-energy diets on whole-body protein turnover in obese subjects

1980 ◽  
Vol 238 (3) ◽  
pp. E235-E244 ◽  
Author(s):  
P. J. Garlick ◽  
G. A. Clugston ◽  
J. C. Waterlow
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Normal Diet ◽  
Low Energy ◽  
Whole Body ◽  
Dietary Energy ◽  
Body Protein ◽  
Obese Subjects ◽  
Oral Doses ◽  
Low Energy Diet

Rates of whole-body protein synthesis and breakdown in obese subjects have been measured by three methods: constant intravenous infusion of [1-14C]leucine, repeated oral doses of [15N]glycine, and a single oral dose of [15N]glycine. The three techniques gave similar rates of synthesis and breakdown when the subjects received a normal diet containing 8.0 MJ and 70 g protein. After 3 wk on a low-energy diet (2.1 MJ), repeat measurements were made. When the low-energy diet contained protein (50 g), rates of protein synthesis and breakdown were little different from those with the normal diet. When the low-energy diet contained no protein, there was a 40% fall in whole-body protein synthesis and a smaller fall in breakdown. Excretion of 3-methylhistidine in the urine did not change with either low-energy diet. We conclude that the decrease in dietary energy from 8.0 to 2.1 MJ did not influence protein turnover, but that dietary protein was necessary if rates of whole-body protein synthesis and breakdown were to be maintained.

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.

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.

Diet and nitrogen metabolism during spaceflight on the shuttle

1996 ◽  
Vol 81 (1) ◽  
pp. 82-97 ◽  
Author(s):  
T. P. Stein ◽  
M. J. Leskiw ◽  
M. D. Schluter
Keyword(s):  
Protein Synthesis ◽  
Dietary Intake ◽  
Energy Intake ◽  
Nitrogen Balance ◽  
Nitrogen Retention ◽  
The Body ◽  
Whole Body ◽  
Flight Period ◽  
Flight Duration ◽  
Body Protein

Human spaceflight is associated with a loss of body protein. To investigate this problem, dietary intake, nitrogen balance, the whole body protein, and fibrinogen protein synthesis rates were measured on the crews of two Spacelab Life Sciences (SLS) shuttle missions before, during, and after spaceflight. The first mission, SLS-1, lasted 9.5 days, and the second, SLS-2, lasted 15 days. The 15N-glycine method was used for the protein synthesis measurements. The following results were obtained. 1) There was a rapid decline in weight for the first 5 days and then the body weight appeared to stabilize. 2) The mean energy intake preflight was 39.0 +/- 2.5 kcal x kg-1 x day-1 (n = 10). There was a sharp drop in dietary intake on flight day 1, with recovery by the second day, and then energy intake was constant at 30.4 +/- 1.5 kcal x kg-1 x day-1 (n = 12) for the remainder of the flight period (P < 0.05). 3) Nitrogen retention was decreased during flight, with the magnitude of the decrease lessening toward the end of the mission. The daily mean nitrogen balance changed from 58 +/- 9 mg x kg-1 x day-1 (n = 9) preflight to 16 +/- 3 mg N x kg-1 x day-1; P < 0.05; n = 11) in flight, corresponding to a loss of approximately 1 kg of lean body mass over 14 days. 4) Whole body protein synthesis was increased early in flight and on recovery, as was fibrinogen synthesis. We conclude that 1) the rapid readjustment and stabilization of energy intake and the improved nitrogen retention with increasing flight duration are consistent with a rapid metabolic accommodation to the novel environment; and that 2) the increased protein turnover indicates that a metabolic stress response is an important factor in this adjustment process.

scholarly journals Tissue and whole-body protein synthesis in immature Zucker rats and their relationship to protein deposition

1982 ◽  
Vol 204 (2) ◽  
pp. 393-398 ◽  
Author(s):  
P J Reeds ◽  
P Haggarty ◽  
K W J Wahle ◽  
J M Fletcher
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Post Partum ◽  
The Body ◽  
Whole Body ◽  
Zucker Rats ◽  
Body Protein ◽  
Protein Deposition ◽  
Fractional Rate ◽  
Obese Rats

The rates of protein synthesis in skeletal muscle, intestine, liver and in the whole body of immature (18 and 25 days old) lean and obese male Zucker rats were measured. In addition, the rate of deposition of whole-body and skeletal-muscle protein over the period 16-27 days post partum was measured by comparative slaughter and analysis of the composition of the body. At 16 days post partum, lean and obese rats had similar body protein contents, but thereafter the rate of protein deposition in the body and skeletal-muscle mass was decreased in the obese rats. The decrease was particularly marked before 21 days of age, and between 23 and 27 days post partum the fractional rate of protein deposition was the same in lean and obese rats. Of the tissues that were studied, only skeletal muscle had a lower fractional rate of protein synthesis in the obese rats. At 18 days post partum, the decrease in the absolute rate of protein synthesis in skeletal muscle accounted for at least 80% of the decline in protein synthesis in the whole body. After weaning, phenotypic differences in protein synthesis was less marked than at 18 days of age, and skeletal muscle accounted for only 50% of the difference in body protein synthesis between phenotypes. The possibility that a change in the function of the adrenal cortex contributes to differences in protein metabolism between lean and obese Zucker rats is discussed.

scholarly journals ESTIMATION OF TOTAL PROTEIN SYNTHESIS, ACCRETION AND DEGRADATION IN RATS

1978 ◽  
Vol 58 (3) ◽  
pp. 355-368 ◽  
Author(s):  
W. T. BUCKLEY ◽  
L. P. MILLIGAN
Keyword(s):  
Amino Acids ◽  
Body Weight ◽  
Protein Synthesis ◽  
Continuous Infusion ◽  
Total Protein ◽  
Whole Body ◽  
Body Protein ◽  
Pool Model ◽  
Continuous Feeding ◽  
The Mean

A method of estimating the rates of total protein synthesis, accretion and degradation in rats was investigated. Rats maintained on a continuous feeding regimen were given L-(U-14C) tyrosine and L-(U-14C) phenylalanine either with the diet or by continuous infusion while N consumption and excretion were measured. The percent of administered 14C expired as 14CO2 was used to calculate the rate of phenylalanine hydroxylation as well as the rate of phenylalanine incorporation into body protein according to a two-pool model of phenylalanine and protein metabolism. Finally, the whole body rates of protein synthesis, accretion and degradation in growing rats were calculated. All rats received 12 g of feed per day. Those that were given (14C) amino acids with the diet were growing at a mean rate of 3.0 g/day and had a mean body weight of 160 g. The mean rates of protein synthesis, accretion and degradation for these rats were 1.76, 0.74 and 1.02 g of protein/day, respectively. Rats that were given (14C) amino acids by continuous infusion were growing at a mean rate of 2.9 g/day and had a mean body weight of 123 g. The mean rates of protein synthesis, accretion and degradation in these rats were 1.39, 0.80 and 0.59 g protein/day, respectively.

scholarly journals Effect of dietary protein on energy metabolism including protein synthesis in the spiny lobster Sagmariasus verreauxi

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shuangyao Wang ◽  
Chris G. Carter ◽  
Quinn P. Fitzgibbon ◽  
Basseer M. Codabaccus ◽  
Gregory G. Smith
Keyword(s):  
Protein Synthesis ◽  
Energy Metabolism ◽  
Dietary Protein ◽  
Spiny Lobster ◽  
Ammonia Excretion ◽  
Metabolic Energy ◽  
Whole Body ◽  
Body Protein ◽  
Energy Substrate ◽  
Sagmariasus Verreauxi

AbstractThis is the first study in an aquatic ectotherm to combine a stoichiometric bioenergetic approach with an endpoint stochastic model to explore dietary macronutrient content. The combination of measuring respiratory gas (O2 and CO2) exchange, nitrogenous (ammonia and urea) excretion, specific dynamic action (SDA), metabolic energy substrate use, and whole-body protein synthesis in spiny lobster, Sagmariasus verreauxi, was examined in relation to dietary protein. Three isoenergetic feeds were formulated with varying crude protein: 40%, 50% and 60%, corresponding to CP40, CP50 and CP60 treatments, respectively. Total CO2 and ammonia excretion, SDA magnitude and coefficient, and protein synthesis in the CP60 treatment were higher compared to the CP40 treatment. These differences demonstrate dietary protein influences post-prandial energy metabolism. Metabolic use of each major energy substrate varied at different post-prandial times, indicating suitable amounts of high-quality protein with major non-protein energy-yielding nutrients, lipid and carbohydrate, are critical for lobsters. The average contribution of protein oxidation was lowest in the CP50 treatment, suggesting mechanisms underlying the most efficient retention of dietary protein and suitable dietary inclusion. This study advances understanding of how deficient and surplus dietary protein affects energy metabolism and provides approaches for fine-scale feed evaluation to support sustainable aquaculture.

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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