Utilization for protein synthesis of 2-ketoisocaproate relative to utilization of leucine, as estimated from exhalation of labelled CO2

1988 ◽  
Vol 75 (3) ◽  
pp. 301-307 ◽  
Author(s):  
Kenji Imura ◽  
Tetsuya Shiota ◽  
Louis M. Swain ◽  
MacKenzie Walser
Keyword(s):  
Protein Synthesis ◽  
Oral Administration ◽  
Whole Body ◽  
Body Protein ◽  
First Pass ◽  
The Mean ◽  
Co2 Excretion

1. We have previously shown that the ratio (RWBP) of incorporation of label from 2-ketoisocaproate (KIC) into the leucine of whole-body protein to the simultaneous incorporation of label from leucine itself into protein is a measure of the nutritional efficiency of KIC as a substitute for leucine. 2. In order to determine whether RWBP can be estimated indirectly from measurement of labelled CO2 excretion, rats were injected orally or intravenously with [4,5-3H]leucine and either [1-14C]leucine or [1-14C]KIC. Expired CO2 was collected for 6 h. 3. The results show that 9–14% of KIC underwent first-pass oxidation after oral administration. When isotopes were given intravenously, the mean rate of excretion of 14CO2 from KIC, after 20 min, remained 1.8 times the mean rate of excretion of 14CO2 from leucine. 4. Mean RWBP, measured in whole-body protein in rats given isotopes orally or intravenously along with small or large doses of carriers, was the same as mean RWBP estimated from mean cumulative CO2 excretion. 5. We conclude (1) that nutritional efficiency of KIC relative to leucine can be estimated from measurement of labelled CO2 excretion, and (2) that the relative inefficiency of KIC as a substitute for leucine in the rat is attributable to first-pass oxidation of 9–14% (when given orally) and 80% greater susceptibility to systemic oxidation than leucine.

Protein Metabolism in Human Neonates: Nitrogen-Balance Studies, Estimated Obligatory Losses of Nitrogen and Whole-Body Turnover of Nitrogen

1977 ◽  
Vol 52 (5) ◽  
pp. 485-498 ◽  
Author(s):  
P. B. Pencharz ◽  
W. P. Steffee ◽  
W. Cochran ◽  
N. S. Scrimshaw ◽  
W. M. Rand ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Nitrogen Balance ◽  
Growth And Development ◽  
Term Infant ◽  
Nitrogen Losses ◽  
Whole Body ◽  
Nitrogen Flux ◽  
Body Protein ◽  
Mean Values ◽  
The Mean

1. Aspects of nitrogen metabolism in the human neonate were assessed in one full-term infant and six premature infants by means of nitrogen-balance measurements, estimates of obligatory nitrogen losses and determinations of whole-body nitrogen turnover. 2. Our data indicate that the mean protein requirement for maintenance is 1·1 g of protein day−1 kg−1 and that 3·8 g of protein day−1 kg−1 should be sufficient for adequate growth in healthy premature babies. 3. The mean obligatory urinary, faecal and total nitrogen losses were estimated to be 24, 106 and 145 mg day−1 kg−1 respectively. These figures are compared with published values for older infants, and the possible metabolic basis for changes in nitrogen losses during growth and development is discussed. 4. Mean values for whole-body protein synthesis and breakdown were 26·3 ± 7·0 and 23·8 ± 7·4 g of protein day−1 kg−1 respectively. Dietary nitrogen intake accounted for 6–18% of the nitrogen flux through the metabolic pool; urea excretion accounted for 2% of the nitrogen flux. 5. The net protein gain, estimated from nitrogen-balance data, accounted for 9·6% of total daily protein synthesis. 6. These results are discussed in relation to published estimates of whole-body protein synthesis and breakdown at various ages. Their possible significance in the assessment of a ‘maintenance’ requirement for protein and amino acids during the period of rapid growth and development is also considered.

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

scholarly journals Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects

2021 ◽  
pp. 1-9
Author(s):  
Jorn Trommelen ◽  
Andrew M. Holwerda ◽  
Philippe J. M. Pinckaers ◽  
Luc J. C. van Loon
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Stable Isotope ◽  
Dietary Protein ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Human Subjects ◽  
Whole Body ◽  
Body Protein

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.

Contribution of Skin to Whole-Body Protein Synthesis in Rats at Different Stages of Maturity

1992 ◽  
Vol 122 (11) ◽  
pp. 2167-2173 ◽  
Author(s):  
Christiane Obled ◽  
Maurice Arnal
Keyword(s):  
Protein Synthesis ◽  
Whole Body ◽  
Body Protein

Measurement of protein turnover in the small intestine of lambs. 2. Effects of feed intake

1997 ◽  
Vol 128 (2) ◽  
pp. 233-246 ◽  
Author(s):  
S. A. NEUTZE ◽  
J. M. GOODEN ◽  
V. H. ODDY
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Small Intestine ◽  
Experimental Model ◽  
Feed Intake ◽  
Protein Turnover ◽  
Jugular Vein ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Body Protein

This study used an experimental model, described in a companion paper, to examine the effects of feed intake on protein turnover in the small intestine of lambs. Ten male castrate lambs (∼ 10 months old) were offered, via continuous feeders, either 400 (n = 5) or 1200 (n = 5) g/day lucerne chaff, and mean experimental liveweights were 28 and 33 kg respectively. All lambs were prepared with catheters in the cranial mesenteric vein (CMV), femoral artery (FA), jugular vein and abomasum, and a blood flow probe around the CMV. Cr-EDTA (0·139 mg Cr/ml, ∼ 0·2 ml/min) was infused abomasally for 24 h and L-[2,6-3H]phenylalanine (Phe) (420±9·35 μCi into the abomasum) and L-[U-14C]phenylalanine (49·6±3·59 μCi into the jugular vein) were also infused during the last 8 h. Blood from the CMV and FA was sampled during the isotope infusions. At the end of infusions, lambs were killed and tissue (n = 4) and digesta (n = 2) samples removed from the small intestine (SI) of each animal. Transfers of labelled and unlabelled Phe were measured between SI tissue, its lumen and blood, enabling both fractional and absolute rates of protein synthesis and gain to be estimated.Total SI mass increased significantly with feed intake (P < 0·05), although not on a liveweight basis. Fractional rates of protein gain in the SI tended to increase (P = 0·12) with feed intake; these rates were −16·2 (±13·7) and 23·3 (±15·2) % per day in lambs offered 400 and 1200 g/day respectively. Mean protein synthesis and fractional synthesis rates (FSR), calculated from the mean retention of 14C and 3H in SI tissue, were both positively affected by feed intake (0·01 < P < 0·05). The choice of free Phe pool for estimating precursor specific radioactivity (SRA) for protein synthesis had a major effect on FSR. Assuming that tissue free Phe SRA represented precursor SRA, mean FSR were 81 (±15) and 145 (±24) % per day in lambs offered 400 and 1200 g/day respectively. Corresponding estimates for free Phe SRA in the FA and CMV were 28 (±2·9) and 42 (±3·5) % per day on 400 g/day, and 61 (±2·9) and 94 (±6·0) on 1200 g/day. The correct value for protein synthesis was therefore in doubt, although indirect evidence suggested that blood SRA (either FA or CMV) may be closest to true precursor SRA. This evidence included (i) comparison with flooding dose estimates of FSR, (ii) comparison of 3H[ratio ]14C Phe SRA in free Phe pools with this ratio in SI protein, and (iii) the proportion of SI energy use associated with protein synthesis.Using the experimental model, the proportion of small intestinal protein synthesis exported was estimated as 0·13–0·27 (depending on the choice of precursor) and was unaffected by feed intake. The contribution of the small intestine to whole body protein synthesis tended to be higher in lambs offered 1200 g/day (0·21) than in those offered 400 g/day (0·13). The data obtained in this study suggested a role for the small intestine in modulating amino acid supply with changes in feed intake. At high intake (1200 g/day), the small intestine increases in mass and CMV uptake of amino acids is less than absorption from the lumen, while at low intake (400 g/day), this organ loses mass and CMV uptake of amino acids exceeds that absorbed. The implications of these findings are discussed.

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.

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