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.

scholarly journals An Evaluation of Protein Intake for Metabolic Demands and the Quality of Dietary Protein in Rats Using an Indicator Amino Acid Oxidation Method

2011 ◽  
Vol 57 (6) ◽  
pp. 418-425 ◽  
Author(s):  
Aki OGAWA ◽  
Yuka NARUSE ◽  
Yasutaka SHIGEMURA ◽  
Yukiko KOBAYASHI ◽  
Isao SUZUKI ◽  
...  
Keyword(s):  
Amino Acid ◽  
Dietary Protein ◽  
Protein Intake ◽  
Acid Oxidation ◽  
Oxidation Method ◽  
Amino Acid Oxidation

scholarly journals Tryptophan Requirement in School-Age Children Determined by the Indicator Amino Acid Oxidation Method is Similar to Current Recommendations

2019 ◽  
Vol 149 (2) ◽  
pp. 280-285 ◽  
Author(s):  
Abeer Al-mokbel ◽  
Glenda Courtney-Martin ◽  
Rajavel Elango ◽  
Ronald O Ball ◽  
Paul B Pencharz ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein Intake ◽  
School Age Children ◽  
Acid Mixture ◽  
Acid Oxidation ◽  
School Age ◽  
Mixed Effect ◽  
Effect Change ◽  
Amino Acid Oxidation ◽  
The Mean

ABSTRACT Background The requirement for dietary tryptophan in school-age children has never been empirically derived. Objective The objective of our study was to determine the tryptophan requirement of school-age children using the indicator amino acid oxidation technique. Methods Volunteer healthy school-age children, between 8 and 12 y, were enrolled and the oxidation of l-[13C]-phenylalanine to 13CO2 measured in response to graded intakes of dietary tryptophan. Seven children (3 boys, 4 girls) participated in the study and received randomly assigned tryptophan intakes ranging from 0.5 to 9.75 mg.kg-1.d-1 for a total of 36 studies. The diets provided energy at 1.5 times each subject's resting energy expenditure and were isocaloric. Protein was provided as an amino acid mixture on the basis of the egg protein pattern, and phenylalanine and tyrosine were maintained constant across the protein intake concentrations at 25 and 40 mg.kg−1.d−1. All subjects were adapted for 2 d before the study day to a protein intake of 1.5 g.kg−1.d−1. The mean tryptophan requirement was determined by applying a mixed-effect change-point regression analysis to F13CO2 (label tracer oxidation in 13CO2 breath) which identified a breakpoint in the F13CO2 in response to graded amounts of tryptophan. Results The mean [estimated average requirement (EAR)] and upper 95% CI, (approximating the RDA) of tryptophan requirements were estimated to be 4.7 and 6.1 mg.kg−1.d−1, respectively. Conclusion Our results are similar to the current recommended EAR and RDA of 5 and 6 mg.kg−1.d−1 for healthy growing children based on the factorial calculation. Clinical Trials Registration No. NCT02018588.

scholarly journals Hepatic detoxification of ammonia in the ovine liver: possible consequences for amino acid catabolism

1995 ◽  
Vol 73 (5) ◽  
pp. 667-685 ◽  
Author(s):  
G. E. Lobley ◽  
A. Connell ◽  
M. A. Lomax ◽  
D. S. Brown ◽  
E. Milne ◽  
...  
Keyword(s):  
Amino Acid ◽  
Kinetic Data ◽  
Free Amino ◽  
Liver Blood Flow ◽  
Whole Body ◽  
Acid Oxidation ◽  
Urea Synthesis ◽  
Amino Acid Oxidation ◽  
N Metabolism ◽  
Glutamate Synthesis

The effects of either low (25 μmol/min) or high (235 μmol/min) infusion of NH4Cl into the mesenteric vein for 5 d were determined on O2consumption plus urea and amino acid transfers across the portal-drained viscera (PDV) and liver of young sheep. Kinetic transfers were followed by use of15NH4Cl for 10 h on the fifth day with simultaneous infusion of [1-13C]lleucine to monitor amino acid oxidation. Neither PDV nor liver blood flow were affected by the additional NH3loading, although at the higher rate there was a trend for increased liver O2consumption. NH3-N extraction by the liver accounted for 64–70% of urea-N synthesis and at the lower infusion rate the additional N required could be more than accounted for by hepatic removal of free amino acids. At the higher rate of NH3administration additional sources of N were apparently required to account fully for urea synthesis. Protein synthesis rates in the PDV and liver were unaffected by NH3infusion but both whole-body (P< 0·05) and splanchnic tissue leucine oxidation were elevated at the higher rate of administration. Substantial synthesis of [15N]glutamine occurred across the liver, particularly with the greater NH3supply, and enrichments exceeded considerably those of glutamate. The [15N]urea synthesized was predominantly as the single labelled, i.e. [14N15N], species. These various kinetic data are compatible with the action of ovine hepatic glutamate dehydrogenase (EC1.4.1.2) in periportal hepatocytes in the direction favouring glutamate deamination. Glutamate synthesis and uptake is probably confined to the perivenous cells which do not synthesize urea. The implications of NH3detoxification to the energy and N metabolism of the ruminant are discussed.

scholarly journals The mysteries of nitrogen balance

1999 ◽  
Vol 12 (1) ◽  
pp. 25-54 ◽  
Author(s):  
J. C Waterlow
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Urea Cycle ◽  
N Balance ◽  
Single Amino Acid ◽  
Whole Body ◽  
Acid Oxidation ◽  
Physiological Level ◽  
Body Protein ◽  
Urea Production

AbstractThe first part of this review is concerned with the balance between N input and output as urinary urea. I start with some observations on classical biochemical studies of the operation of the urea cycle. According to Krebs, the cycle is instantaneous and automatic, as a result of the irreversibility of the first enzyme, carbamoyl-phosphate synthetase 1 (EC 6.3.5.5; CPS-I), and it should be able to handle many times the normal input to the cycle. It is now generally agreed that acetyl glutamate is a necessary co-factor for CPS-1, but not a regulator. There is abundant evidence that changes in dietary protein supply induce coordinated changes in the amounts of all five urea-cycle enzymes. How this coordination is achieved, and why it should be necessary in view of the properties of the cycle mentioned above, is unknown. At the physiological level it is not clear how a change in protein intake is translated into a change of urea cycle activity. It is very unlikely that the signal is an alteration in the plasma concentration either of total amino-N or of any single amino acid. The immediate substrates of the urea cycle are NH3 and aspartate, but there have been no measurements of their concentration in the liver in relation to urea production. Measurements of urea kinetics have shown that in many cases urea production exceeds N intake, and it is only through transfer of some of the urea produced to the colon, where it is hydrolysed to NH3, that it is possible to achieve N balance. It is beginning to look as if this process is regulated, possibly through the operation of recently discovered urea transporters in the kidney and colon. The second part of the review deals with the synthesis and breakdown of protein. The evidence on whole-body protein turnover under a variety of conditions strongly suggests that the components of turnover, including amino acid oxidation, are influenced and perhaps regulated by amino acid supply or amino acid concentration, with insulin playing an important but secondary role. Molecular biology has provided a great deal of information about the complex processes of protein synthesis and breakdown, but so far has nothing to say about how they are coordinated so that in the steady state they are equal. A simple hypothesis is proposed to fill this gap, based on the self-evident fact that for two processes to be coordinated they must have some factor in common. This common factor is the amino acid pool, which provides the substrates for synthesis and represents the products of breakdown. The review concludes that although the achievement and maintenance of N balance is a fact of life that we tend to take for granted, there are many features of it that are not understood, principally the control of urea production and excretion to match the intake, and the coordination of protein synthesis and breakdown to maintain a relatively constant lean body mass.

scholarly journals Assessing the whole-body protein synthetic response to feeding in vivo in human subjects

2021 ◽  
pp. 1-9
Author(s):  
Jorn Trommelen ◽  
Luc J. C. van Loon
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Intake ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Human Subjects ◽  
Whole Body ◽  
Body Protein ◽  
Breakdown Rates

All tissues are in a constant state of turnover, with a tightly controlled regulation of protein synthesis and breakdown rates. Due to the relative ease of sampling skeletal muscle tissue, basal muscle protein synthesis rates and the protein synthetic responses to various anabolic stimuli have been well defined in human subjects. In contrast, only limited data are available on tissue protein synthesis rates in other organs. Several organs such as the brain, liver and pancreas, show substantially higher (basal) protein synthesis rates when compared to skeletal muscle tissue. Such data suggest that these tissues may also possess a high level of plasticity. It remains to be determined whether protein synthesis rates in these tissues can be modulated by external stimuli. Whole-body protein synthesis rates are highly responsive to protein intake. As the contribution of muscle protein synthesis rates to whole-body protein synthesis rates is relatively small considering the large amount of muscle mass, this suggests that other organ tissues may also be responsive to (protein) feeding. Whole-body protein synthesis rates in the fasted or fed state can be quantified by measuring plasma amino acid kinetics, although this requires the production of intrinsically labelled protein. Protein intake requirements to maximise whole-body protein synthesis may also be determined by the indicator amino acid oxidation technique, but the technique does not allow the assessment of actual protein synthesis and breakdown rates. Both approaches have several other methodological and inferential limitations that will be discussed in detail in this paper.

Leucine and protein metabolism in the lactating dairy cow mammary gland: responses to supplemental dietary crude protein intake

1996 ◽  
Vol 63 (2) ◽  
pp. 209-222 ◽  
Author(s):  
Brian J. Bequette ◽  
John A. Metcalf ◽  
Diane Wray-Cahen ◽  
F. R. Colette Backwell ◽  
John D. Sutton ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Mammary Gland ◽  
Amino Acid ◽  
Protein Metabolism ◽  
Protein Intake ◽  
Crude Protein ◽  
Milk Protein ◽  
Protein Supplementation ◽  
Whole Body ◽  
Body Protein

SummaryMammary gland protein metabolism, determined by an arteriovenous difference technique, was monitored in four Holstein-Friesian dairy cows in response to supplemental dietary protein (provided as rumen-protected soyabean meal) during late lactation (weeks 24–30). Each cow was offered two isoenergetic diets composed of grass silage (170 g crude protein/kg dry matter) plus either a low (108 g/kg) or medium (151 g/kg) crude protein concentrate in a single crossover design involving two 21 d periods. On day 21, arteriovenous measurements across the mammary gland were made during a 13 h continuous i.v. infusion of [1-13C]leucine and with frequent (2 hourly) milk sampling during the final 6 h. Although total milk yield was slightly increased (+1 kg/d) by protein supplementation, milk protein yield was not significantly affected. Whole body protein flux (protein synthesis plus oxidation) was not significantly affected by supplementation. Total mammary gland protein synthesis (milk plus non-milk protein) was also not affected by supplementation but on both diets gland synthesis was always greater (by 20–59%) than milk protein output. The fractional oxidation rate of leucine by the mammary gland was significantly increased by protein supplementation (0·047 v. 0·136). Although the enrichment of leucine in secreted milk protein continued to increase, the final value (at 13 h) was 0·94 of the arterial plasma free leucine plateau value (not significantly different), suggesting almost exclusive use of plasma free leucine for milk protein synthesis. Based on current feeding schemes for dairy cattle, a fixed proportion (0·65–0·75) of the additional protein intake (+490 g/d) should have been partitioned into milk protein. Instead, leucine oxidation by the mammary gland was increased. Whether oxidation of other amino acids was also enhanced is unknown but if amino acid oxidation and the ‘additional’ non-milk protein synthesis occurring in the gland are not crucial to milk synthesis, then by reducing such activities improvements in the efficiency of converting absorbed amino acid into milk protein can be achieved.

scholarly journals Intraoperative protein sparing with glucose

2005 ◽  
Vol 99 (3) ◽  
pp. 898-901 ◽  
Author(s):  
Thomas Schricker ◽  
Ralph Lattermann ◽  
Franco Carli
Keyword(s):  
Amino Acid ◽  
Colorectal Surgery ◽  
Normal Saline ◽  
Whole Body ◽  
Control Group ◽  
Acid Oxidation ◽  
Intravenous Glucose ◽  
Amino Acid Oxidation ◽  
Leucine Oxidation ◽  
Glucose Group

We examined the hypothesis that glucose infusion inhibits amino acid oxidation during colorectal surgery. We randomly allocated 14 patients to receive intravenous glucose at 2 mg·kg−1·min−1 (glucose group) starting with the surgical incision or an equivalent amount of normal saline 0.9% (control group). The primary endpoint was whole body leucine oxidation; secondary endpoints were leucine rate of appearance and nonoxidative leucine disposal as determined by a stable isotope tracer technique (l-[1-13C]leucine). Circulating concentrations of glucose, lactate, insulin, glucagon, and cortisol were measured before and after 2 h of surgery. Leucine rate of appearance, an estimate of protein breakdown, and nonoxidative leucine disposal, an estimate of protein synthesis, decreased in both groups during surgery ( P < 0.05). Leucine oxidation intraoperatively decreased from 13 ± 3 to 4 ± 3 μmol·kg−1·h−1 in the glucose group ( P < 0.05 vs. control group) whereas it remained unchanged in the control group. Hyperglycemia during surgery was more pronounced in patients receiving glucose (9.7 ± 0.5 mmol/l, P < 0.05 vs. control group) than in patients receiving normal saline (7.1 ± 1.0 mmol/l). The administration of glucose caused an increase in the circulating concentration of insulin ( P < 0.05) resulting in a lower glucagon/insulin quotient than in the control group ( P < 0.05). Intraoperative plasma cortisol concentrations increased in both groups ( P < 0.05), whereas plasma concentrations of lactate and glucagon did not change. The provision of small amounts of glucose was associated with a decrease in amino acid oxidation during colorectal surgery.

Ammonium chloride-induced acidosis increases protein breakdown and amino acid oxidation in humans

1992 ◽  
Vol 263 (4) ◽  
pp. E735-E739 ◽  
Author(s):  
D. Reaich ◽  
S. M. Channon ◽  
C. M. Scrimgeour ◽  
T. H. Goodship
Keyword(s):  
Amino Acid ◽  
Ammonium Chloride ◽  
Protein Turnover ◽  
Healthy Subjects ◽  
Whole Body ◽  
Acid Oxidation ◽  
Protein Breakdown ◽  
Body Protein ◽  
Amino Acid Oxidation ◽  
Kinetics Of

The effect of acidosis on whole body protein turnover was determined from the kinetics of infused L-[1-13C]leucine. Seven healthy subjects were studied before (basal) and after (acid) the induction of acidosis with 5 days oral ammonium chloride (basal pH 7.42 +/- 0.01, acid pH 7.35 +/- 0.03). Bicarbonate recovery, measured from the kinetics of infused NaH13CO3, was increased in the acidotic state (basal 72.9 +/- 1.2 vs. acid 77.6 +/- 1.6%; P = 0.06). Leucine appearance from body protein (PD), leucine disappearance into body protein (PS), and leucine oxidation (O) increased significantly (PD: basal 120.5 +/- 5.6 vs. acid 153.9 +/- 6.2, P < 0.01; PS: basal 98.8 +/- 5.6 vs. acid 127.0 +/- 4.7, P < 0.01; O: basal 21.6 +/- 1.1 vs. acid 26.9 +/- 2.3 mumol.kg-1.h-1, P < 0.01). Plasma levels of the amino acids threonine, serine, asparagine, citrulline, valine, leucine, ornithine, lysine, histidine, arginine, and hydroxyproline increased significantly with the induction of acidosis. These results confirm that acidosis in humans is a catabolic factor stimulating protein degradation and amino acid oxidation.

scholarly journals Relation of protein synthesis and amino acid oxidation: effects of protein deprivation.

1985 ◽  
Vol 33 (3) ◽  
pp. 328-331
Author(s):  
V.V.A.M. Schreurs ◽  
G. Mensink ◽  
H.A. Boekholt ◽  
R.E. Koopmanschap
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
High Rate ◽  
Male Rats ◽  
Synthesis Rate ◽  
Acid Oxidation ◽  
Protein Deprivation ◽  
Amino Acid Oxidation ◽  
Liver And Kidney

For up to 3 weeks 10 male rats weighing about 300 g were given diets which had 20% protein or were free from protein but supplied similar amounts of energy. The rats were killed at intervals; the last 2 were given L-[U-14C]tyrosine by infusion 4 h before they were killed. The deprived rats showed restricted amino acid oxidation and a decreased rate of protein synthesis. Amino acid oxidation continued by an uneven loss of proteins from the tissues. In muscle the composition and relative synthesis rate of the constituent proteins were not affected. Liver and kidney, compared with other tissues tended to maintain a relatively high rate of protein turnover. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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