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)

PRENATAL NUTRITION OF LAMBS, BEARS—AND BABIES?

PEDIATRICS ◽  
1972 ◽  
Vol 50 (3) ◽  
pp. 357-358
Author(s):  
George F. Cahill
Keyword(s):  
Oxygen Consumption ◽  
Amino Acid ◽  
Calculated Data ◽  
High Rate ◽  
Co2 Production ◽  
Acid Oxidation ◽  
Prenatal Nutrition ◽  
Amino Acid Oxidation ◽  
Urea Production

The two superbly documented papers from the Battaglia group by James et al. and Gresham et al. are most provocative, since they challenge current dogma that glucose is the primary fetal fuel. As evidence, they present several indisputable observations: measured transplacental glucose difference accounts for only 40% of measured fetal oxygen consumption or CO2 production, and a surprisingly high rate of fetal urea production attests to a high rate of amino acid oxidation. The following Table summarizes both their directly determined and their calculated data with several further extrapolations by this reviewer, must have been transferred from mother to fetus.

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.

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 Amino acid homeostasis and signalling in mammalian cells and organisms

2017 ◽  
Vol 474 (12) ◽  
pp. 1935-1963 ◽  
Author(s):  
Stefan Bröer ◽  
Angelika Bröer
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Food Intake ◽  
Essential Amino Acids ◽  
Acid Oxidation ◽  
Plasma Amino Acids ◽  
Amino Acid Oxidation ◽  
Amino Acid Levels ◽  
Amino Acid Depletion

Cells have a constant turnover of proteins that recycle most amino acids over time. Net loss is mainly due to amino acid oxidation. Homeostasis is achieved through exchange of essential amino acids with non-essential amino acids and the transfer of amino groups from oxidised amino acids to amino acid biosynthesis. This homeostatic condition is maintained through an active mTORC1 complex. Under amino acid depletion, mTORC1 is inactivated. This increases the breakdown of cellular proteins through autophagy and reduces protein biosynthesis. The general control non-derepressable 2/ATF4 pathway may be activated in addition, resulting in transcription of genes involved in amino acid transport and biosynthesis of non-essential amino acids. Metabolism is autoregulated to minimise oxidation of amino acids. Systemic amino acid levels are also tightly regulated. Food intake briefly increases plasma amino acid levels, which stimulates insulin release and mTOR-dependent protein synthesis in muscle. Excess amino acids are oxidised, resulting in increased urea production. Short-term fasting does not result in depletion of plasma amino acids due to reduced protein synthesis and the onset of autophagy. Owing to the fact that half of all amino acids are essential, reduction in protein synthesis and amino acid oxidation are the only two measures to reduce amino acid demand. Long-term malnutrition causes depletion of plasma amino acids. The CNS appears to generate a protein-specific response upon amino acid depletion, resulting in avoidance of an inadequate diet. High protein levels, in contrast, contribute together with other nutrients to a reduction in food intake.

A New Technique for Measuring Protein Turnover in the Gut, Liver and Kidneys of Lean and Obese Mice with [3H]Glutamic Acid

1978 ◽  
Vol 54 (4) ◽  
pp. 425-430
Author(s):  
B. G. Miller ◽  
R. F. Grimble ◽  
T. G. Taylor
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
Total Radioactivity ◽  
Obese Mouse ◽  
Obese Mice ◽  
Tissue Protein ◽  
Liver And Kidney ◽  
A New Technique ◽  
Kidney Liver

1. We have measured the incorporation of an intraperitoneal injection of [3H]glutamate into the protein of the gut, liver and kidney of lean and obese siblings of the genetically obese mouse. 2. Recycling of the 3H was minimized by using glutamate labelled at the C-2 position. Loss of label from the amino acid pool by transamination and deamination was rapid, with a half-life of 4 h. 3. In tissue protein the amino acid showing the highest 3H radioactivity was glutamate. 4. The half-lives for protein synthesis and catabolism were calculated from the decay curves of both specific and total radioactivity of [3H]glutamate in tissue protein. No significant differences were found between kidney, liver and gut in lean and obese mice.

scholarly journals PSXI-31 Program Chair Poster Pick: Determination of the threonine requirement in adult and senior Labrador Retrievers using the indicator amino acid oxidation technique

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 321-322
Author(s):  
Jordan T Weil ◽  
Jessica L Varney ◽  
Jason W Fowler ◽  
Craig N Coon
Keyword(s):  
Amino Acid ◽  
Control Diet ◽  
Genetic Selection ◽  
Isotope Ratio Mass Spectrometry ◽  
Acid Oxidation ◽  
Amino Acid Oxidation ◽  
Amino Acid Requirements ◽  
Indispensable Amino Acids ◽  
Nutrient Profiles ◽  
Labrador Retrievers

Abstract Although nutrient profiles for canines have been developed in the past, the need to update amino acid (AA) requirements has gained importance as genetic selection changes the recommended nutrients. Correctly feeding AA to canines can have enormous effects, considering a deficiency or excess of such nutrient can lead to weight loss, disease, or in some cases, death. Amino acid requirements can be determined through the nitrogen balance or indicator amino acid oxidation (IAAO) methods. In this experiment, the IAAO technique was used to determine the threonine (Thr) requirement in Labrador retrievers. A total of six dogs (6 adult and 6 senior) were subjected to six diets with varying levels of Thr, ranging from deficient to excess. Diets were formulated to 1.6x NRC values for all indispensable amino acids. The control diet was fed for two days, followed by a day in which the test diet was fed, a tracer AA was supplied, and breath samples were collected. On test day, a priming dose of L-[1-13C]phenylalanine (Cambridge Isotope Laboratories, Inc.) based on the subject’s body weight was first supplied, followed by [1-13C]Phe doses every thirty minutes, spanning a four hour period. A respiration mask was placed on each subject every thirty minutes (Oxymax, Columbus Instruments), 13CO2 was collected, and enrichment was determined by isotope ratio mass spectrometry (IRMS). Results for IRMS were converted to atom percent excess (APE) and analyzed using a piecewise model of best fit (JMP® Pro 15). The segmented line regression showed that the Thr mean and population requirements were determined to be 1.21 ± 0.24 and 0.92 ± 0.17 g/1000kcal (mean ± 2SD) for adult and senior dogs, respectively. As the pet food industry becomes more specialized in diets relating to aging, and diseased canines, updating the amino acid requirements related to such animals is increasingly important.

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