Whole Body Nitrogen Kinetics in Man: Determination from Plasma [Guanidino-15N]Arginine

1984 ◽  
Vol 66 (3) ◽  
pp. 337-342 ◽  
Author(s):  
Marc Yudkoff ◽  
Itzhak Nissim ◽  
Mark Glassman ◽  
Stanton Segal
Keyword(s):  
Protein Synthesis ◽  
Steady State ◽  
Molecular Medicine ◽  
Whole Body ◽  
Constant Infusion ◽  
Isotopic Enrichment ◽  
Healthy Young Adult ◽  
Metabolic Pool ◽  
15N Urea ◽  
Oral Doses

1. Whole body nitrogen turnover and protein synthesis were calculated by the method of D. Picou & T. Taylor-Roberts [Clinical Science and Molecular Medicine (1969) 36, 283–296] except that plateau plasma enrichment of [guanidino-15N]arginine was used in place of the [15N]urea enrichment after a constant infusion of [15N]-glycine. With this approach metabolic pool turnover and protein synthesis were 637.2 ± 73.0 mg of N day−1 kg−1 and 2964.0 ± 409.5 mg of protein day−1 kg−1 respectively. 2. Virtually identical isotopic enrichment in [guanidino-15N]arginine and [15N]urea were observed in a healthy young adult who took repeated oral doses of [15N]glycine for a period of 60 h: 0.47 (arginine) and 0.48 (urea) atom% excess. 3. The turnover of glycine nitrogen and of urea, determined from the constant infusion of [15N]glycine and [13C]urea, was 66.2 ± 3.3 mg of N day−1 kg−1 and 156.2 ± 4.3 mg of urea day−1 kg−1 respectively. The ratio of steady-state enrichment in arginine to that in glycine, reflecting the fraction of arginine derived from glycine, was 10.5%. By using the [guanidino-15N]arginine enrichment as representative of the expected enrichment in [15N]urea at plateau, it was calculated that approximately 25% of glycine N flux is directed toward the synthesis of urea, with the remainder directed to protein and quantitatively minor products like haem and creatinine. 4. Unlike steady-state [15N]urea labelling, which is achieved only after infusion of [15N]-glycine for several days, plateau isotopic abundance in [guanidino-15N]arginine was attained after only 1–2 h of [15N]glycine infusions, thereby allowing estimation of whole body nitrogen kinetics and the rate of transfer of glycine nitrogen to urea in a relatively brief experiment.

scholarly journals Comparison of different techniques for estimating rates of protein synthesis in vivo in healthy and bacteraemic rats

1985 ◽  
Vol 226 (1) ◽  
pp. 37-42 ◽  
Author(s):  
J J Pomposelli ◽  
J D Palombo ◽  
K J Hamawy ◽  
B R Bistrian ◽  
G L Blackburn ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Rectus Muscle ◽  
Stochastic Modelling ◽  
Whole Body ◽  
Constant Infusion ◽  
Second Phase ◽  
Sprague Dawley ◽  
Body Protein ◽  
To Receive

Previous studies have reported that use of a flooding dose of radiolabelled amino acid is a more precise technique than the constant infusion of tracer quantities for determining rates of protein synthesis in rapidly turning-over tissues in the rat. However, there has been little direct investigation comparing different methods under comparable conditions. Initially, 12 healthy male Sprague-Dawley rats, weighing approx. 100 g, were randomized to receive either a bolus intravenous injection of 100 mumol of L-leucine (containing 30 microCi of [1-14C]leucine)/100 g body wt., or a continuous 2 h tracer infusion of [14C]leucine. In the second phase of the experiment, 12 additional rats were intravenously injected with 1 × 10(8) colony-forming units of Pseudomonas aeruginosa and 16 h later randomized to receive one of two infusions described above. Total protein synthesis as well as fractional synthesis rates were determined in liver, rectus muscle and whole body. Synthesis rates measured in liver, muscle and whole body were significantly higher in bacteraemic rats than in healthy rats. The flooding-dose methodology gave significantly higher estimates of protein synthesis in the liver, skeletal muscle and whole body than did the continuous-infusion method using direct measurement of the acid-soluble fraction from the respective tissue. Indirect estimates of whole-body protein synthesis based on plasma enrichments and stochastic modelling gave the lowest values.

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.

Changes in leucine kinetics during meal absorption: effects of dietary leucine availability

1986 ◽  
Vol 250 (6) ◽  
pp. E695-E701 ◽  
Author(s):  
S. Nissen ◽  
M. W. Haymond
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Branched Chain Amino Acids ◽  
Whole Body ◽  
Constant Infusion ◽  
Leucine Oxidation ◽  
Amino Acid Availability ◽  
Dietary Amino Acid ◽  
Branched Chain

Whole-body leucine and alpha-ketoisocaproate (KIC) metabolism were estimated in mature dogs fed a complete meal, a meal devoid of branched-chain amino acids, and a meal devoid of all amino acids. Using a constant infusion of [4,5-3H]leucine and alpha-[1-14C]ketoisocaproate (KIC), combined with dietary [5,5,5-2H3]leucine, the rate of whole-body proteolysis, protein synthesis, leucine oxidation, and interconversion of leucine and KIC were estimated along with the rate of leucine absorption. Ingestion of the complete meal resulted in a decrease in the rate of endogenous proteolysis, a small increase in the estimated rate of leucine entering protein, and a twofold increase in the rate of leucine oxidation. Ingestion of either the meal devoid of branched-chain amino acids or devoid of all amino acids resulted in a decrease in estimates of whole-body rates of proteolysis and protein synthesis, decreased leucine oxidation, and a decrease in the interconversion of leucine and KIC. The decrease in whole-body proteolysis was closely associated with the rise in plasma insulin concentrations following meal ingestion. Together these data suggest that the transition from tissue catabolism to anabolism is the result, at least in part, of decreased whole-body proteolysis. This meal-related decrease in proteolysis is independent of the dietary amino acid composition or content. In contrast, the rate of protein synthesis was sustained only when the meal complete in all amino acids was provided, indicating an overriding control of protein synthesis by amino acid availability.

Evaluation of the isotopic equilibration between lactate and pyruvate

1988 ◽  
Vol 254 (4) ◽  
pp. E532-E535 ◽  
Author(s):  
R. R. Wolfe ◽  
F. Jahoor ◽  
H. Miyoshi
Keyword(s):  
Steady State ◽  
Metabolic Flux ◽  
Isotopic Exchange ◽  
Whole Body ◽  
Isotopic Enrichment ◽  
Isotopic Tracer ◽  
Anesthetized Dogs ◽  
Isotopic Equilibration ◽  
Lactate And Pyruvate ◽  
Kinetics Of

When an isotopic tracer is infused for the purpose of determining the rate of turnover or oxidation of a substrate, it is assumed that the resulting isotopic enrichment by the tracer will reflect the kinetics of only the pool of interest. However, this may not be the case when carbon-labeled lactate is infused, since rapid isotopic exchange with the intracellular pyruvate and alanine pools could potentially occur. Therefore we have determined the extent of isotopic exchange occurring during the infusion of [3-13C]lactate into six anesthetized dogs. In the steady state, pyruvate enrichment was 91 +/- 2.2% (means +/- SE) of the lactate enrichment, and alanine enrichment was 81 +/- 3.3% of the pyruvate enrichment and 72 +/- 2.6% of the lactate enrichment. In contrast, when [3-13C]alanine was infused (n = 2), pyruvate (and lactate) enrichment was 9.9% of the alanine enrichment. We therefore conclude that there is rapid isotopic equilibration between lactate and pyruvate but that interaction with alanine reflects the true metabolic flux rates, rather than isotopic exchange. Consequently, lactate kinetics, as traditionally determined, more accurately reflect whole body pyruvate kinetics.

scholarly journals Protein Intake to Maximize Whole-Body Anabolism during Postexercise Recovery in Resistance-Trained Men with High Habitual Intakes is Severalfold Greater than the Current Recommended Dietary Allowance

2019 ◽  
Author(s):  
Michael Mazzulla ◽  
Sidney Abou Sawan ◽  
Eric Williamson ◽  
Sarkis J Hannaian ◽  
Kimberly A Volterman ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Steady State ◽  
Amino Acid ◽  
Resistance Exercise ◽  
Protein Intake ◽  
Whole Body ◽  
Total Amino Acid ◽  
Acid Oxidation ◽  
Amino Acid Oxidation ◽  
Habitual Protein Intake

ABSTRACT Background Dietary protein supports resistance exercise–induced anabolism primarily via the stimulation of protein synthesis rates. The indicator amino acid oxidation (IAAO) technique provides a noninvasive estimate of the protein intake that maximizes whole-body protein synthesis rates and net protein balance. Objective We utilized IAAO to determine the maximal anabolic response to postexercise protein ingestion in resistance-trained men. Methods Seven resistance-trained men (mean ± SD age 24 ± 3 y; weight 80 ± 9 kg; 11 ± 5% body fat; habitual protein intake 2.3 ± 0.6 g·kg−1·d−1) performed a bout of whole-body resistance exercise prior to ingesting hourly mixed meals, which provided a variable amount of protein (0.20–3.00 g·kg−1·d−1) as crystalline amino acids modeled after egg protein. Steady-state protein kinetics were modeled with oral l-[1-13C]-phenylalanine. Breath and urine samples were taken at isotopic steady state to determine phenylalanine flux (PheRa), phenylalanine excretion (F13CO2; reciprocal of protein synthesis), and net balance (protein synthesis − PheRa). Total amino acid oxidation was estimated from the ratio of urinary urea and creatinine. Results Mixed model biphasic linear regression revealed a plateau in F13CO2 (mean: 2.00; 95% CI: 1.62, 2.38 g protein·kg−1·d−1) (r2 = 0.64; P ˂ 0.01) and in net balance (mean: 2.01; 95% CI: 1.44, 2.57 g protein·kg−1·d−1) (r2 = 0.63; P ˂ 0.01). Ratios of urinary urea and creatinine concentrations increased linearly (r = 0.84; P ˂ 0.01) across the range of protein intakes. Conclusions A breakpoint protein intake of ∼2.0 g·kg−1·d−1, which maximized whole-body anabolism in resistance-trained men after exercise, is greater than previous IAAO-derived estimates for nonexercising men and is at the upper range of current general protein recommendations for athletes. The capacity to enhance whole-body net balance may be greater than previously suggested to maximize muscle protein synthesis in resistance-trained athletes accustomed to a high habitual protein intake. This trial was registered at clinicaltrials.gov as NCT03696264.

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.

Use of the constant infusion technique for measuring rates of protein synthesis in the New Zealand White rabbit

1977 ◽  
Vol 38 (1) ◽  
pp. 1-17 ◽  
Author(s):  
G. A. Nicholas ◽  
G. E. Lobley ◽  
C. I. Harris
Keyword(s):  
Protein Synthesis ◽  
New Zealand ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Constant Infusion ◽  
Side Chain ◽  
List Type ◽  
Liver Protein ◽  
Body Protein ◽  
Infusion Technique

1.To study the potential of the constant-infusion technique for measuring rates of protein synthesis in New Zealand White rabbits, animals were infused for up to 6 h with radioactively-labelled tyrosine.2.Labelled tyrosine from plasma and tissues was isolated from labelled metabolites by ion-exchange chromatography.3.Analysis of serial blood and muscle biopsy samples removed under anaesthesia showed that the specific radioactivity (SR) of the free tyrosine pools reached an approximately constant value within 2 h.4.Certain commercial preparations of L-[side-chain 2,3-3H]tyrosine were contaminated with 300 mg radioactive D-tyrosine/g. The D-isomer appeared to enter the muscle intracellular pool.5.In constant-infusion experiments L-[3H]tyrosine could replace the uniformly-14C-labelled L-isomer for the determination of rates of protein synthesis in muscle. L-[side-chain 2,3-3H]tyrosine may not be suitable for use as a precursor for measuring rates of liver protein synthesis.6.Evidence is presented that the precursor of liver protein synthesis may not be well defined by the SR for free tyrosine of the homogenate.7.The technique was used to measure the rates of protein synthesis in adult rabbits. The rates of protein synthesis in liver and muscle were measured and from measurements of tyrosine flux the mean rate of whole-body protein synthesis was calculated as 13.8 g/kg per d.

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.

Measurement of urea kinetics in vivo by means of a constant tracer infusion of di-15N-urea

1981 ◽  
Vol 240 (4) ◽  
pp. E428-E434 ◽  
Author(s):  
R. R. Wolfe
Keyword(s):  
Steady State ◽  
Constant Infusion ◽  
Selected Ion Monitoring ◽  
Plasma Urea ◽  
Urea Production ◽  
Nonsteady State ◽  
Urea Metabolism ◽  
The Difference ◽  
15N Urea

We have assessed the feasibility of studying urea metabolism in vivo in both steady state and nonsteady state situations by means of the primed constant infusion of di-15N-urea and the analysis of the resulting enrichment in plasma urea. Both hepatectomized dogs with known rates of urea infusion and intact dogs were studied. The enrichment of the bistrimethylsilyl derivative of urea was determined on a gas chromatograph-mass spectrometer. Selected ion monitoring was set for m/e 189 (M - 15), m/e 190 (A + 1), and m/e 191 (A + 2), thus enabling the calculation of the rate of urea production from nonrecycled NH3 (from A + 2 data) (Ra N), the rate of recycling of NH3 into urea (Ra R) (from A + 1 data), and thus the total rate of urea production (Ra N + Ra R). When urine collections were made, the incorporation of urea-N into protein was estimated from the difference between Ra N and urea excretion. We found that, in the steady state in a hepatectomized dog, the rate of appearance of urea can be determined accurately. In the nonsteady state in both hepatectomized and intact dogs, urea appearance could be estimated within +/- 20% in most situations. The only situation in which this was not the case was when we attempted to measure rapid changes in Ra R. Thus, within limits, this can be a useful technique enabling the quantitation of various aspects of urea metabolism.

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