Total Protein Synthesis in Elderly People: A Comparison of Results with [15N]glycine and [14C]leucine

1977 ◽  
Vol 53 (3) ◽  
pp. 277-288 ◽  
Author(s):  
M. H. N. Golden ◽  
J. C. Waterlow
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Specific Radioactivity ◽  
The Elderly ◽  
Synthesis Rate ◽  
Total N ◽  
Body Protein ◽  
Total Body ◽  
Plasma Leucine ◽  
The Individual

1. Total body protein turnover was studied in six elderly patients. 2. During the study they were fed by continuous infusion of a liquid formula through a nasogastric tube. l-[1-14C]Leucine and [15N]glycine were infused at a constant rate for 30 h. The labelled glycine was infused into the intragastric line; the labelled leucine was given either by this route or intravenously. 3. The specific radioactivity of free leucine in plasma and the rate of output of 14CO2 in expired air both reached a plateau at 10 h, and remained constant until the end of the infusion at 30 h. 4. The 15N abundance in urinary urea and total N was very similar. In neither was a plateau reached by 30 h but in four out of the six patients the abundance in urinary NH4+ had attained a plateau by the end of the infusion. 5. Flux rates and rates of protein synthesis were calculated in four ways: (A) from the specific radioactivity of plasma leucine at plateau; (B) from the proportion of dose excreted as 14CO2 at plateau; (C) from the final rates of 15N excretion in urea or total urinary N; (D) from the final or plateau rates of 15N excretion in urinary NH4+. 6. On average, the estimates of synthesis rate obtained by methods B and C agreed closely; those given by methods A and D were lower. Methods A, B and D ranked the individual patients in almost identical order. 7. The comparison of methods makes it possible to examine the validity of the assumptions on which the different methods depend. Method B is probably theoretically the most satisfactory and, of the methods used in this work, probably gives the best estimate of the absolute turnover rate. The other methods can be used for comparative purposes. 8. The results suggest that the rate of protein turnover is reduced in the elderly, compared with younger subjects.

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 Protein synthesis in tissues of growing lambs

1981 ◽  
Vol 46 (3) ◽  
pp. 409-419 ◽  
Author(s):  
S. R. Davis ◽  
T. N. Barry ◽  
G. A. Hughson
Keyword(s):  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Specific Radioactivity ◽  
Biceps Femoris ◽  
Whole Body ◽  
Tissue Homogenate ◽  
Body Protein ◽  
Tissue Protein ◽  
Biceps Femoris Muscle ◽  
Plasma Leucine

1. The fractional rate of protein synthesis (FSR) in tissues of nine growing lambs (4–5 months of age) was estimated following continuous infusion of L-[4,5–3H]leucine for a period of 7 h. Minimum and upper estimates of FSR were obtained assuming that the specific radioactivity (SRA) of leucine in blood plasma and tissue homogenate respectively defined that of leucyl tRNA.2. Mean upper estimates of tissue protein FSR (/d) were skin 0·35, longissimus dorsi muscle 0·05, biceps femoris muscle 0·04, liver 0·54, rumen 0·79, cardiac muscle 0·09. Minimum estimates of tissue protein FSR ranged from 0·03 (muscle) to 0·15 (liver).3. Plasma leucine flux was closely related to body protein content and dietary leucine absorption (r 0·94).4. The rate of whole-body protein synthesis (WBS) derived from plasma leucine flux corrected for oxidation and localized recycling of leucine into protein was similar to that calculated from the sum of daily protein synthesis in individual tissues using the upper estimate of FSR, i.e. 610 g/d v. 581 g/d.5. The estimate of WBS derived from plasma leucine flux directly (241 g/d) was similar to that calculated from the sum of minimum estimates of daily protein synthesis in individual tissues (214 g/d).6. The ratio, intracellular leucine SRA:plasma leucine SRA tended to increase with increasing dietary leucine absorption in all tissues although these factors were only significantly correlated (P < 0·05) in cardiac muscle, skin and rumen. Such relationships suggest an increased exchange of plasma leucine with intracellular leucine with increased food intake.7. It was estimated that the energy cost of protein synthesis accounted for approximately 42% of daily heat production.

Whole body protein synthesis: studies with different amino acids in the rat

1989 ◽  
Vol 257 (5) ◽  
pp. E639-E646 ◽  
Author(s):  
C. Obled ◽  
F. Barre ◽  
D. J. Millward ◽  
M. Arnal
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Turnover ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Body Protein ◽  
Tissue Specific ◽  
Dose Method ◽  
Infusion Method

These studies were undertaken to determine to what extent constant infusion measurements and plasma sampling could provide sensible answers for rates of whole body protein turnover and also which amino acid would be the most representative probe of whole body protein turnover. Whole body protein synthesis rates were estimated in 70-g rats with L-[U-14C]threonine, L-[U-14C]lysine, L-[U-14C]tyrosine, L-[U-14C]phenylalanine, and L-[1-14C]leucine by either simultaneous tracer infusion of four amino acids or by injections of large quantities of 14C-labeled amino acids. In the infusion experiment, indirect estimates of whole body protein turnover based on free amino acid specific radioactivity and stochastic modeling were compared with direct measurement of the incorporation of the tracer into proteins. These two methods of analysis provided similar results for each amino acid, although in each case fractional synthesis rates were lower (by between 26 and 63%) when calculations were based on plasma rather than tissue specific radioactivity. With the flooding-dose method, whole body fractional protein synthesis rates were 41.4, 25.6, 31.1, and 31.4% with threonine, lysine, phenylalanine, and leucine, respectively. These values were similar to those obtained by the continuous infusion method using tissue specific radioactivity for threonine and lysine. For leucine, however, the flooding-dose method provided an intermediate value between the two estimates derived either from the plasma or the tissue specific radioactivity in the infusion method.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Contribution of liver, skin and skeletal muscle to whole-body protein synthesis in the young lamb

1988 ◽  
Vol 60 (1) ◽  
pp. 77-84 ◽  
Author(s):  
D. Attaix ◽  
E. Aurousseau ◽  
A. Manghebati ◽  
M. Arnal
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Tissue Homogenate ◽  
Synthesis Rate ◽  
Body Protein ◽  
Tissue Protein ◽  
Large Injection ◽  
Tensor Fasciae Latae

1. Protein fractional synthesis rate (FSR) was measured in some major tissues and in the whole body of six 1-week-old sucking lambs by a large injection of L-[3H]valine.2. Upper estimates of tissue protein FSR (%/d), assuming that the tissue-homogenate free-valine specific radioactivity defined that of valyl tRNA, were 115.0 in liver, 24.1 in skin, 22.9 in the white M. tensor fasciae latae, 21.6 in the red M. diaphragma and 19–6 in the remainder (exsanguinated whole body without liver and gastrointestinal tract) of lambs.3. Absolute synthesis rates (ASR) of tissue protein were 17, 19 and 42 g/d in the liver, skin and skeletal muscle respectively, and 112 g/d in the remainder. The ASR of whole-body protein, derived from the tissue values, was 146 g/d, i.e. 33 g/d per kg body-weight. The calculated whole-body protein FSR was 23.9 %/d.4. The relative percentage contribution of liver, skin and skeletal muscle to whole-body protein synthesis was 11.7, 13.1, and 29.0.5. We concluded that tissue protein FSR in lambs were in exactly the same decreasing order, from visceral tissues to skeletal muscles, as observed in rats. The ovine FSR estimates and the partitioning of protein synthesis between tissues were in the same range as values recently obtained by flooding-dose experiments in immature rats, piglets, and even in chicks. These findings suggest that inter-species differences are rather limited.

Studies of Amino Acid and Protein Metabolism in Normal Man with l-[U-14C]Tyrosine

1976 ◽  
Vol 50 (6) ◽  
pp. 525-532 ◽  
Author(s):  
W. P. T. James ◽  
P. J. Garlick ◽  
P. M. Sender ◽  
J. C. Waterlow
Keyword(s):  
Amino Acid ◽  
Protein Turnover ◽  
Excretion Rate ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Individual Values ◽  
Body Protein ◽  
Normal Man ◽  
Tracer Amount ◽  
The Individual

1. Six men were infused intravenously for 10 h with a tracer amount of l-[U-14C]tyrosine while on a standardized food intake. 2. Measurements of plasma l-[14C]-tyrosine specific radioactivity and the excretion rate of 14CO2 were made at frequent intervals and showed plateau labelling of plasma and expired carbon dioxide within 6–8 h. The tyrosine flux was calculated from the specific radioactivity in plasma at plateau value. 3. The excretion rate of 14CO2, corrected for retention of label within the bicarbonate pool, showed that oxidation accounted for 20% of the tyrosine flux. Urinary excretion of label was negligible. 4. Rates of protein synthesis were calculated from the flux of tyrosine after subtracting the proportion oxidized. Although the mean rate of synthesis was consistent with other measurements of protein turnover, the individual values ranged from 284 to 387 g/day. The variation was not reduced by relating turnover to body weight, lean body mass or energy expenditure. 5. Estimating the rates of protein breakdown from the tyrosine flux involved some assumptions about pathways of phenylalanine metabolism. The use of a labelled essential amino acid would therefore give more accurate values for short-term measurements of whole body protein turnover.

Effect of testosterone on muscle mass and muscle protein synthesis

1989 ◽  
Vol 66 (1) ◽  
pp. 498-503 ◽  
Author(s):  
R. C. Griggs ◽  
W. Kingston ◽  
R. F. Jozefowicz ◽  
B. E. Herr ◽  
G. Forbes ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Mass ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Whole Body ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Total Body Potassium ◽  
Body Protein ◽  
Total Body

We have studied the effect of a pharmacological dose of testosterone enanthate (3 mg.kg-1.wk-1 for 12 wk) on muscle mass and total-body potassium and on whole-body and muscle protein synthesis in normal male subjects. Muscle mass estimated by creatinine excretion increased in all nine subjects (20% mean increase, P less than 0.02); total body potassium mass estimated by 40K counting increased in all subjects (12% mean increase, P less than 0.0001). In four subjects, a primed continuous infusion protocol with L-[1–13C]leucine was used to determine whole-body leucine flux and oxidation. Whole-body protein synthesis was estimated from nonoxidative flux. Muscle protein synthesis rate was determined by measuring [13C]leucine incorporation into muscle samples obtained by needle biopsy. Testosterone increased muscle protein synthesis in all subjects (27% mean increase, P less than 0.05). Leucine oxidation decreased slightly (17% mean decrease, P less than 0.01), but whole-body protein synthesis did not change significantly. Muscle morphometry showed no significant increase in muscle fiber diameter. These studies suggest that testosterone increases muscle mass by increasing muscle protein synthesis.

scholarly journals The effect of acute and chronic administration of the β-agonist, cimaterol, on protein synthesis in ovine skin and muscle

1994 ◽  
Vol 71 (4) ◽  
pp. 501-513 ◽  
Author(s):  
J. E. Nash ◽  
H. J. G. Rocha ◽  
V. Buchanz ◽  
G. A. Calder ◽  
E. Milne ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Chronic Administration ◽  
Whole Body ◽  
Synthesis Rate ◽  
Total N ◽  
Body Protein ◽  
Peripheral Tissues ◽  
N Retention ◽  
Wool Growth

The action of intravenous infusion of the βagonist cimaterol(2.5 mg/d) on whole-body N retention and protein synthesis in peripheral tissues was examined in growing sheep. Wool growth was determined from skin patch clippings and adjusted to total fibre production. Protein synthesis was measured, using sequential large dose injections of [ l-I3C]valine, leucine and phenylalanine and then [ring-d,]-phenylalanine, on biopsy samples from skin and m. longissirnus dovsi taken before β-agonist administration, at day 3 and day 15 of cimaterol infusion, and 15 d after withdrawal of the drug. Cimaterol increased total N retention by 1.9–2.3 g N/d (P < 0.01) over three successive 5 d periods. In contrast, wool growth was significantly reduced by 0.7 g N/d (P < 0.001) and the proportion of total N retained in wool declined from 0.71 to 0.25 (P < 0.01). The reduction in woo1 growth was accompanied by a decrease in protein fractional synthesis rate (FSR) in skin (11.6 v. 6.3%/d, P < 0.01). Muscle protein FSR, on the other hand, was markedly stimulated during cimaterol infusion (1.45 v. 3.01 %/d, P < 0.001) as was RNA concentration (P < 0.001), RNA:protein (P < 0.001) and protein:DNA (P < 0.05). The estimated increase in total protein synthesis in muscle (+ 24 to 30 g/d) due to cimaterol administration was counterbalanced by reductions for skin (-25 to 27 g/d); this may account for the lack of changes in whole-body protein synthesis following β-agonist administration reported in other studies. Although N retention rapidly returned to control values following withdrawal of the drug, both wool growth and skin protein synthesis remained depressed, while muscle protein FSR declined, but not to pre-treatment values. These results suggest a persistent action of cimaterol, but whether this is a function of residue concentrations or long-term metabolic responses is not known

scholarly journals Whole body and tissue protein synthesis in cattle

1980 ◽  
Vol 43 (3) ◽  
pp. 491-502 ◽  
Author(s):  
G. E. Lobley ◽  
Vivien Milne ◽  
Joan M. Lovie ◽  
P. J. Reeds ◽  
K. Pennie
Keyword(s):  
Protein Synthesis ◽  
Total Synthesis ◽  
Total Protein ◽  
Specific Radioactivity ◽  
Live Weight ◽  
Whole Body ◽  
Tissue Homogenate ◽  
Body Protein ◽  
Tissue Protein ◽  
The Individual

The daily rates of synthesis of protein by the whole body and by the individual tissues were determined in two Hereford × Friesian heifers (236 kg and 263 kg live weight), and a dry Friesian cow (628 kg live weight).The rate of whole-body protein synthesis (g protein/d) was estimated from the total flux through the blood of [3H]leucine and [3H]tyrosine following infusion at a constant rate for 8 h.The fractional rates of protein synthesis (ks) in the tissues (g synthesized/d per g tissue protein) were obtained after slaughter of the animals at the end of the infusion period. The fractional rate of protein synthesis was calculated assuming that the specific radioactivity of free tyrosine in either the blood (to giveks, b) or the tissue homogenate (to giveks, h) defined closely the specific radioactivity of the amino acid precursor for protein synthesis. Total protein synthesis (As, borAs, h; g/d) in an individual tissue was calculated as the product ofks, b) (orks, h) × protein content.Based on the total leucine flux, i.e. without correction for oxidation, 1.6 kg protein were synthesized daily in the heifers; for the cow this value was 2.0 kg/d.The sum of the daily total synthesis in the major tissues (muscle+bone+brain, gastrointestinal tract (GIT), liver, hide) gave values of 1.4–1.9 kg/d based onAs, b, and 2.2–3.0 kg/d based onAs, h.The percentage contributions of the individual tissues to the total protein synthesis were similar in all three animals, for example based onAs, hmuscle was 12–16; carcass (muscle+bone+brain) 32–33; GIT 38–46; liver 7–8; skin 14–21%.The contribution of muscle to total synthesis estimated from the leucine flux was 19–22%; this value is in agreement with those calculated on the same basis for other species.The energy cost of protein synthesis was estimated to account for a maximum of 30% of heat production.

Resting metabolic rate and protein turnover in apparently healthy elderly Gambian men

1995 ◽  
Vol 268 (6) ◽  
pp. E1083-E1088 ◽  
Author(s):  
C. Benedek ◽  
P. Y. Berclaz ◽  
E. Jequier ◽  
Y. Schutz
Keyword(s):  
Body Composition ◽  
Body Weight ◽  
Protein Synthesis ◽  
G Protein ◽  
Protein Turnover ◽  
The Elderly ◽  
Young Group ◽  
Whole Body ◽  
Protein Breakdown ◽  
Body Protein

Body composition, resting energy expenditure (REE), and whole body protein metabolism were studied in 26 young and 28 elderly Gambian men matched for body mass index during the dry season in a rural village in The Gambia. REE was measured by indirect calorimetry (hood system) in the fasting state and after five successive meals. Rates of whole body nitrogen flux, protein synthesis, and protein breakdown were determined in the fed state from the level of isotopic enrichment of urinary ammonia over a period of 12 h after a single oral dose of [15N]glycine. Expressed in absolute value, REE was significantly lower in the elderly compared with the young group (3.21 +/- 0.07 vs. 4.04 +/- 0.07 kJ/min, P < 0.001) and when adjusted to body weight (3.29 +/- 0.05 vs. 3.96 +/- 0.05 kJ/min, P < 0.0001) and fat-free mass (FFM; 3.38 +/- 0.01 vs. 3.87 +/- 0.01 kJ/min, P < 0.0001). The rate of protein synthesis averaged 207 +/- 13 g protein/day in the elderly and 230 +/- 13 g protein/day in the young group, whereas protein breakdown averaged 184 +/- 13 g protein/day in the elderly and 203 +/- 13 g protein/day in the young group (nonsignificant). When values were adjusted for body weight or FFM, they did not reveal any difference between the two groups. It is concluded that the reduced REE adjusted for body composition observed in elderly Gambian men is not explained by a decrease in protein turnover.

scholarly journals Tissue protein synthesis and nucleic acid concentrations in steers treated with somatotropin

1989 ◽  
Vol 62 (3) ◽  
pp. 657-671 ◽  
Author(s):  
J. H. Eisemann ◽  
A. C. Hammond ◽  
T. S. Rumsey
Keyword(s):  
Protein Synthesis ◽  
Small Intestine ◽  
Nucleic Acid ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Tissue Homogenate ◽  
Synthesis Rate ◽  
Body Protein ◽  
Tissue Protein ◽  
Tissue Protein Synthesis

The effect of injection with bovine somatotropin (bST) on the fractional rate of protein synthesis (FSR) in tissues of beef steers was studied using a continuous infusion of [1-14C]leucine. Minimum and maximum FSR were calculated from free leucine specific radioactivity (SRA) in plasma or tissue homogenate respectively. Tissue nucleic acid concentrations were also quantified. Tissue samples were obtained from several muscles, sections of the small intestine and liver. In response to bST, both minimum and maximum FSR increased in muscle but not liver or intestinal tissues. Absolute synthesis rate increased in several muscles and small intestine tissues. Treatment with bST increased the relative SRA of protein-bound leucine in muscles compared with liver; increased the amount of protein synthesis per unit empty body-weight (EBW) in most muscles; and increased weight of small intestine relative to EBW, suggesting a differential response between liver and the other tissues measured. Compositional changes in response to bST occurred only in muscles. DNA concentration increased while protein:DNA decreased in the gastrocnemius muscle and RNA:DNA increased in the longissimus dorsi. The maximum percentage contribution of tissue protein synthesis to whole-body protein synthesis was 12·6, 25·7 and 20·5, and 13·0, 29·4 and 25·8 for liver, muscle, and small intestine in placebo-treated and bST-injected steers respectively.

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