scholarly journals PROTEIN METABOLISM AND PROTEIN RESERVES DURING ACUTE STERILE INFLAMMATION

1945 ◽  
Vol 82 (1) ◽  
pp. 65-76 ◽  
Author(s):  
S. C. Madden ◽  
W. A. Clay
Keyword(s):  
Amino Acids ◽  
Nitrogen Balance ◽  
Protein Intake ◽  
Oral Feeding ◽  
Nitrogen Excretion ◽  
Protein Nitrogen ◽  
Body Protein ◽  
Low Protein ◽  
Positive Balance ◽  
Urinary Nitrogen

Adult dogs were given a proteinless diet plus casein, 80 calories/kilo, 0.4 gm. nitrogen/kilo/day. Sterile controlled inflammation was produced by subcutaneous injection of turpentine. The reaction is characterized by local swelling, induration, and abscess formation, terminated by rupture or incision after 3 to 5 days and by general reactions of malaise, fever, leucocytosis, and increased urinary nitrogen. For 3 to 6 days after turpentine the nitrogen intake was provided in seven experiments by amino acids given parenterally (a solution of the ten essential amino acids (Rose) plus glycine). A normal dog with a normal protein intake showed a negative nitrogen balance after turpentine—urinary nitrogen doubled even as in inflammation during fasting. A protein-depleted dog (low protein reserves produced by very low protein intake) given a normal protein intake after turpentine maintained nitrogen balance—urinary nitrogen rose only slightly. With a high (doubled) protein intake the depleted dog showed strongly positive balance. Normal dogs with high (doubled) protein intakes react to turpentine with doubled urinary nitrogen outputs on individual days and therefore are maintained in approximate nitrogen balance and weight balance. This end may be achieved equally well or better by oral feeding, when such is possible and absorption unimpaired. The increased nitrogen excretion after injury is again shown directly related to the state of body protein reserves. Increased catabolism not inhibition of anabolism best explains the excess urinary nitrogen. Protection during injury of valuable protein reserves appears possible through an adequate intake of protein nitrogen.

Enteral hyperalimentation in head injury

1985 ◽  
Vol 62 (2) ◽  
pp. 186-193 ◽  
Author(s):  
Guy L. Clifton ◽  
Claudia S. Robertson ◽  
Charles F. Contant
Keyword(s):  
Head Injury ◽  
Nitrogen Balance ◽  
Severe Head Injury ◽  
Nitrogen Excretion ◽  
Metabolic Complications ◽  
Protein Nitrogen ◽  
Enteral Hyperalimentation ◽  
Lower Protein ◽  
Protein Group ◽  
Urinary Nitrogen

✓ The objectives of this study were to determine the ability of enteral hyperalimentation to meet the caloric and protein requirements in acute severe head injury, and to study the effect of increasing protein intake on nitrogen balance. This consecutive series of 20 patients suffered acute severe head injury and remained comatose for at least 24 hours. They were all without other major injuries, and were treated with steroids. These patients were randomly placed in two comparable treatment groups: one group was fed with an enteral formula containing 14% of its calories as protein and the other group received a formula containing 22% protein calories. Feedings were advanced to replace 140% of caloric expenditure measured by indirect calorimetry, averaging 3500 kcal/24 hr. Balance periods of the targeted intake were 7 days in duration, and were begun during the 1st week after injury for 65% of patients and in the 2nd week after injury for 35% of patients. The lower protein group received an average of 26.8 gm/24 hr of nitrogen, equivalent to 188 gm of protein, and the higher protein group 34.3 gm/24 hr, equivalent to 231 gm of protein. Nitrogen balance was −9.2 ± 6.7 gm/24 hr in the lower protein group and −5.3 ± 5.0 gm/24 hr in the higher protein group, but the difference did not reach statistical significance because of sample size and variability in extent of catabolism among patients. Despite the hyperalimentation, there was a mean negative cumulative nitrogen balance of 200 gm by the 2nd week after injury, and only three patients achieved net nitrogen equilibrium for the 7-day balance period. Despite enteral hyperalimentation, the patients' weight fell by 15% in the 2nd week, serum albumin was often decreased, and creatinine-height index decreased over time but remained in a normal range. Monitoring urinary urea nitrogen, which has been advocated as a generally available technique for measuring urinary nitrogen concentration, was found to be a poor measure of urinary nitrogen excretion. This work has demonstrated: 1) that high caloric and protein feedings may be delivered for prolonged periods enterally for most patients in the acute phase of head injury with few metabolic complications, and 2) that increasing the nitrogen content of feedings from 14% to 22% may somewhat improve nitrogen retention, although nitrogen equilibrium is seldom achieved.

Studies on marsupial nutrition. VI. The utilization of dietry urea by the Euro or Hill Kangaroo, Macropus robustus (Gould)

1969 ◽  
Vol 17 (2) ◽  
pp. 187 ◽  
Author(s):  
GD Brown
Keyword(s):  
Nitrogen Balance ◽  
Dietary Protein ◽  
Nitrogen Retention ◽  
Nitrogen Excretion ◽  
Microbial Protein ◽  
Digestive Physiology ◽  
Protein Nitrogen ◽  
Feeding Trials ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Macropod marsupials, the kangaroos and wallabies, are characterized by a ruminant-like digestive physiology. One feature of digestion in eutherian species of ruminants is the ability of these animals to utilize non-protein nitrogen through the conversion of such nitrogen to microbial protein by the microorganisms in the rumen. In the present experiments with the euro or hill kangaroo (M. robustus), the utilization of dietary protein (casein) and non-protein nitrogen (urea) has been compared by means of nitrogen balance feeding trials. No consistent differences between the levels of nitrogen retention and urinary nitrogen excretion were observed for euros fed rations supplemented with either casein or urea. It is suggested that the digestion of nitrogen by the ruminant-like macropod marsupials is similar to that of eutherian species of ruminant herbivores.

scholarly journals Leucine turnover in patients with nephrotic syndrome: evidence suggesting body protein conservation.

1998 ◽  
Vol 9 (6) ◽  
pp. 1067-1073 ◽  
Author(s):  
V S Lim ◽  
M Wolfson ◽  
K E Yarasheski ◽  
M J Flanigan ◽  
J D Kopple
Keyword(s):  
Mass Spectrometry ◽  
Nephrotic Syndrome ◽  
Protein Degradation ◽  
Nitrogen Balance ◽  
Protein Intake ◽  
Whole Body ◽  
Turnover Rates ◽  
Body Protein ◽  
Control Subjects ◽  
Positive Balance

Whole-body leucine flux was measured in eight patients with nephrotic syndrome and in five healthy subjects by primed-constant infusion of L-[1-13C leucine]. Plasma enrichment of 13C leucine and 13C alpha-keto-isocaproate (13C KIC) was measured by gas chromatography/mass spectrometry, and expired 13CO2 was measured by isotope ration mass spectrometry. Leucine kinetics, calculated from the primary pool enrichment [13C leucine], showed no difference between the nephrotic patients and the control subjects. Kinetics derived from the reciprocal pool [1-13C KIC] enrichment, however, showed that leucine turnover rates were reduced in the nephrotic patients. The values (mumol/kg per h, means +/- SD) comparing the patients and the control subjects are as follows: rate of leucine release from protein degradation, 99 +/- 6 and 117 +/- 12 (P = 0.007); leucine oxidation rate, 15 +/- 7 and 22 +/- 3 (P = 0.04); rate of leucine incorporation into body protein [S], 84 +/- 10 and 95 +/- 6 (P = 0.04); protein turnover rate, 3.99 +/- 0.49 and 4.72 +/- 0.25 g/kg per d (P = 0.007). Nitrogen balance, measured only in the nephrotic patients, showed a mean positive balance of 0.5 g/d. In the nephrotic and control subjects, protein intake levels were 0.84 +/- 0.16 and 1.17 +/- 0.18 g/kg per d (P = 0.002), respectively, and energy intake levels were 33.3 +/- 8.5 and 33.9 +/- 2.4 kcal/kg per d, respectively. Linear correlations between leucine turnover rates and protein intake were highly significant. This study found that nephrotic patients given a modestly protein-restricted diet were able to maintain positive nitrogen balance. Moreover, leucine flux measurements showed downregulation of protein degradation and amino acid oxidation, reflecting appropriate adaptation to a lower protein intake.

Utilization of amino acids by preruminant lambs. I. The effect of alterations in total essential amino acid intake at constant nitrogen intake

1977 ◽  
Vol 28 (5) ◽  
pp. 917 ◽  
Author(s):  
H Dove ◽  
GR Pearce ◽  
DE Tribe
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Nitrogen Balance ◽  
Control Diet ◽  
Essential Amino Acids ◽  
Conclusive Evidence ◽  
Metabolizable Energy ◽  
Nitrogen Excretion ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Male crossbred lambs weighing 12.5 kg (period 1), 20 kg (period 2) and 30 kg (period 3) were infused per abomasum with milk-based diets in which crude protein (CP) and energy contents were constant at a given Iiveweight, but in which the proportion of CP supplied as essential amino acids (EAA) varied from 120 to 876 g EAA/kg CP. Responses in liveweight gain, nitrogen balance and metabolizable energy (ME) intake (period 1 only) were measured. A number of lambs died while receiving diets containing very high or very low proportions of EAA. Possible reasons for these deaths are discussed. In all periods liveweight gains were greatest in lambs given the control diet (513 g EAA/kg CP). In period 1 this liveweight gain was close to that expected on the basis of energy intake, but in periods 2 and 3, liveweight gains on the control diets were less than anticipated. Reductions in liveweight gain were greater for diets containing low proportions of EAA than those containing high proportions. The infusion of diets containing low proportions of EAA markedly increased urinary nitrogen excretion. The effect of diets containing high proportions was less pronounced. As a result of these effects, lambs given the control diet had the highest daily nitrogen balance in all periods. Nitrogen balance was less severely affected by the dietary changes than liveweight gain, particularly with 30 kg lambs. It is suggested that the reduced retention of apparently digested nitrogen in diets other than the control diets reflected the unsuitability of the pattern of absorbed amino acids for protein synthesis. The effect of diet on the components of energy balance in period 1 was less pronounced than its effect on nitrogen balance. The metabolizability of apparently digested energy was lower in diets other than the control diet, especially those containing low proportions of EAA. This is attributed to the energy cost of increased urinary nitrogen excretion on such diets. Alternative interpretations of the results are discussed, and it is suggested that dietary amino acids will be utilized most efficiently for protein synthesis by the tissues of the lamb when essential and non-essential amino acids are provided in approximately equal proportions. There was no conclusive evidence that this optimum proportion was different for older lambs.

scholarly journals Adaptation of urinary nitrogen excretion in infants to changes in protein intake

1968 ◽  
Vol 22 (2) ◽  
pp. 315-323 ◽  
Author(s):  
H. Chan
Keyword(s):  
G Protein ◽  
Protein Intake ◽  
High Protein Diet ◽  
Protein Diet ◽  
Nitrogen Excretion ◽  
Low Protein Diet ◽  
Body Protein ◽  
Low Protein ◽  
Protein Pool ◽  
Total Body

1. Thirty-six nitrogen-balance measurements were made on children recovering from malnutrition. Two types of diet were used: a high-protein diet providing from 1·25 to 6·0 g protein/kg per day which supported normal growth, and a low-protein diet providing 0·75 g protein/kg per day on which the children were approximately in N balance. Both diets provided 120 kcal/kg per day.2. The size of the labile protein pool was estimated from the N lost on changing from a high- to a low-protein diet. After the change of diet a new equilibrium was reached in about 3 days.3. Labile protein, as defined above, represented about 1·2% of the total body protein on changing from 6·0 to 0·75 g protein/kg per day, and about 0·2% of total body protein on changing from 1·5 to 0·75 g protein/kg per day. The magnitude of the labile protein pool did not appear to be related to the nutritional state of the child.4. It is concluded that the labile protein pool is not a reservoir which can be filled, but that losses of N which occur on reducing the protein intake of an infant reflect a lag in metabolic adjustment.

scholarly journals Feasibility of achieving different protein targets using a hypocaloric high-protein enteral formula in critically ill patients

Critical Care ◽  
2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Pierre Singer ◽  
Itai Bendavid ◽  
Ilana BenArie ◽  
Liran Stadlander ◽  
Ilya Kagan
Keyword(s):  
Critically Ill ◽  
Nitrogen Balance ◽  
High Protein ◽  
Nitrogen Excretion ◽  
Protein Targets ◽  
Protein Target ◽  
Group A ◽  
Group B ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Abstract Background and aims Combining energy and protein targets during the acute phase of critical illness is challenging. Energy should be provided progressively to reach targets while avoiding overfeeding and ensuring sufficient protein provision. This prospective observational study evaluated the feasibility of achieving protein targets guided by 24-h urinary nitrogen excretion while avoiding overfeeding when administering a high protein-to-energy ratio enteral nutrition (EN) formula. Methods Critically ill adult mechanically ventilated patients with an APACHE II score > 15, SOFA > 4 and without gastrointestinal dysfunction received EN with hypocaloric content for 7 days. Protein need was determined by 24-h urinary nitrogen excretion, up to 1.2 g/kg (Group A, N = 10) or up to 1.5 g/kg (Group B, N = 22). Variables assessed included nitrogen intake, excretion, balance; resting energy expenditure (REE); phase angle (PhA); gastrointestinal tolerance of EN. Results Demographic characteristics of groups were similar. Protein target was achieved using urinary nitrogen excretion measurements. Nitrogen balance worsened in Group A but improved in Group B. Daily protein and calorie intake and balance were significantly increased in Group B compared to Group A. REE was correlated to PhA measurements. Gastric tolerance of EN was good. Conclusions Achieving the protein target using urinary nitrogen loss up to 1.5 g/kg/day was feasible in this hypercatabolic population. Reaching a higher protein and calorie target did not induce higher nitrogen excretion and was associated with improved nitrogen balance and a better energy intake without overfeeding. PhA appears to be related to REE and may reflect metabolism level, suggestive of a new phenotype for nutritional status. Trial registration 0795-18-RMC.

Branched-Chain Amino Acids, Nitrogen Excretion and Injury in Man

1976 ◽  
Vol 50 (5) ◽  
pp. 393-399 ◽  
Author(s):  
J. H. Wedge ◽  
R. De Campos ◽  
A. Kerr ◽  
R. Smith ◽  
Rose Farrell ◽  
...  
Keyword(s):  
Amino Acids ◽  
Venous Blood ◽  
Branched Chain Amino Acids ◽  
Nitrogen Excretion ◽  
Adult Males ◽  
Blood Concentrations ◽  
Branched Chain ◽  
Injured Patients ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

1. Venous blood concentrations of the branched-chain amino acids, valine, leucine and isoleucine, and urinary nitrogen excretion have been measured in sixteen adult males, from 2 h to 7 days after injury, and in four adults after elective skin grafts. 2. In the injured group the concentrations of these amino acids rose significantly 24 h after injury and had doubled at 4 days and remained high; in contrast the skin-graft patients showed no significant change. 3. In those injured patients with initial hyperketonaemia, defined as more than 0·2 mmol/l, the increase in concentrations of branched-chain amino acids at the fourth and seventh days after injury was significantly less than in those with normoketonaemia, and was accompanied by lower urinary nitrogen excretion throughout the whole period. 4. It is suggested that the changes in the concentration of branched-chain amino acids after injury indicate decreased uptake by muscle or excessive release due to an imbalance between protein synthesis and protein catabolism in this tissue.

scholarly journals Association of protein intake with the outcomes of critically ill patients: a post hoc analysis of the PermiT trial

2018 ◽  
Vol 108 (5) ◽  
pp. 988-996 ◽  
Author(s):  
Y M Arabi ◽  
H M Al-Dorzi ◽  
S Mehta ◽  
H M Tamim ◽  
S H Haddad ◽  
...  
Keyword(s):  
Propensity Score ◽  
Critically Ill ◽  
Nitrogen Balance ◽  
Critically Ill Patients ◽  
Protein Intake ◽  
Nitrogen Excretion ◽  
Post Hoc Analysis ◽  
Lower Protein ◽  
Protein Group ◽  
Post Hoc

ABSTRACT Background The optimal amount of protein intake in critically ill patients is uncertain. Objective In this post hoc analysis of the PermiT (Permissive Underfeeding vs. Target Enteral Feeding in Adult Critically Ill Patients) trial, we tested the hypothesis that higher total protein intake was associated with lower 90-d mortality and improved protein biomarkers in critically ill patients. Design In this post hoc analysis of the PermiT trial, we included patients who received enteral feeding for ≥3 consecutive days. Using the median protein intake of the cohort as a cutoff, patients were categorized into 2 groups: a higher-protein group (>0.80 g · kg–1 · d–1) and a lower-protein group (≤0.80 g · kg–1 · d–1). We developed a propensity score for receiving higher protein. Primary outcome was 90-d mortality. We also compared serial values of prealbumin, transferrin, 24-h urinary nitrogen, and 24-h nitrogen balance on days 1, 7, and 14. Results Among the 729 patients included in this analysis, the average protein intake was 0.8 ± 0.3 g · kg–1 · d–1 [1.0 ± 0.2 g · kg–1 · d–1 in the higher-protein group (n = 365) and 0.6 ± 0.2 g · kg–1 · d–1 in the lower-protein group (n = 364); P < 0.0001]. There was no difference in 90-d mortality between the 2 groups [88/364 (24.2%) compared with 94/363 (25.9%), propensity score–adjusted OR: 0.80; 95% CI: 0.56, 1.16; P = 0.24]. Higher protein intake was associated with an increase in 24-h urea nitrogen excretion compared with lower protein intake, but without a significant change in prealbumin, transferrin, or 24-h nitrogen balance. Conclusions In the PermiT trial, a moderate difference in protein intake was not associated with lower mortality. Higher protein intake was associated with increased nitrogen excretion in the urine without a corresponding change in prealbumin, transferrin, or nitrogen balance. Protein intake needs to be tested in adequately powered randomized controlled trials targeting larger differences in protein intake in high-risk populations.

EFFECTS OF GRADED DIETARY PROTEIN LEVELS ON UREA RECYCLING IN THE PIG

1982 ◽  
Vol 62 (4) ◽  
pp. 1193-1197 ◽  
Author(s):  
P. A. THACKER ◽  
J. P. BOWLAND ◽  
L. P. MILLIGAN ◽  
E. WELTZIEN
Keyword(s):  
Dietary Protein ◽  
Protein Diet ◽  
Nitrogen Excretion ◽  
Entry Rate ◽  
Protein Nitrogen ◽  
Protein Levels ◽  
Low Protein ◽  
Key Words Pig ◽  
Urea Recycling ◽  
Protein Diets

The kinetics of urea recycling were determined in six female crossbred pigs utilizing a radioisotope dilution technique. The experimental animals were fed three times daily 500 g of a corn-soybean meal diet formulated to contain 8.4, 15.8 or 24.7% crude protein. Nitrogen digestibility, urinary nitrogen excretion, total nitrogen excretion and retained nitrogen were highest on the 24.7% protein diet and decreased with decreasing dietary protein. Urea pool size, entry rate and excretion rate were also highest on the 24.7% protein diet and decreased with decreasing protein intake. Expressed as a percentage of the total entry rate, a significantly higher percentage of urea was recycled in pigs fed the low protein diets compared with those fed a higher protein diet. Key words: Pig, urea, recycling, kinetics, protein

Resistance training reduces whole-body protein turnover and improves net protein retention in untrained young males

2006 ◽  
Vol 31 (5) ◽  
pp. 557-564 ◽  
Author(s):  
Joseph W. Hartman ◽  
Daniel R. Moore ◽  
Stuart M. Phillips
Keyword(s):  
Resistance Training ◽  
Resistance Exercise ◽  
Nitrogen Balance ◽  
Protein Turnover ◽  
Whole Body ◽  
Body Protein ◽  
Protein Retention ◽  
The Impact ◽  
Net Protein ◽  
Urinary Nitrogen

It is thought that resistance exercise results in an increased need for dietary protein; however, data also exists to support the opposite conclusion. The purpose of this study was to determine the impact of resistance exercise training on protein metabolism in novices with the hypothesis that resistance training would reduce protein turnover and improve whole-body protein retention. Healthy males (n = 8, 22 ± 1 y, BMI = 25.3 ± 1.8 kg·m–2) participated in a progressive whole-body split routine resistance-training program 5d/week for 12 weeks. Before (PRE) and after (POST) the training, oral [15N]-glycine ingestion was used to assess nitrogen flux (Q), protein synthesis (PS), protein breakdown (PB), and net protein balance (NPB = PS – PB). Macronutrient intake was controlled over a 5d period PRE and POST, while estimates of protein turnover and urinary nitrogen balance (Nbal = Nin – urine Nout) were conducted. Bench press and leg press increased 40% and 50%, respectively (p < 0.01). Fat- and bone-free mass (i.e., lean muscle mass) increased from PRE to POST (2.5 ± 0.8 kg, p < 0.05). Significant PRE to POST decreases (p <0.05) occurred in Q (0.9 ± 0.1 vs. 0.6 ± 0.1 g N·kg–1·d–1), PS (4.6 ± 0.7 vs. 2.9 ± 0.3 g·kg–1·d–1), and PB (4.3 ± 0.7 vs. 2.4 ± 0.2 g·kg–1·d–1). Significant training-induced increases in both NPB (PRE = 0.22 ± 0.13 g·kg–1·d–1; POST = 0.54 ± 0.08 g·kg–1·d–1) and urinary nitrogen balance (PRE = 2.8 ± 1.7 g N·d–1; POST = 6.5 ± 0.9 g N·d–1) were observed. A program of resistance training that induced significant muscle hypertrophy resulted in reductions of both whole-body PS and PB, but an improved NPB, which favoured the accretion of skeletal muscle protein. Urinary nitrogen balance increased after training. The reduction in PS and PB and a higher NPB in combination with an increased nitrogen balance after training suggest that dietary requirements for protein in novice resistance-trained athletes are not higher, but lower, after resistance training.

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