A reappraisal of protein turnover values in neonates fed human milk or formula

1989 ◽  
Vol 67 (4) ◽  
pp. 282-286 ◽  
Author(s):  
P. B. Pencharz ◽  
R. Clarke ◽  
A. Papageorgiou ◽  
L. Farri
Keyword(s):  
Birth Weight ◽  
Human Milk ◽  
Nitrogen Metabolism ◽  
Protein Turnover ◽  
Nitrogen Isotopes ◽  
Nitrogen Excretion ◽  
Constant Infusion ◽  
Turnover Rates ◽  
Protein Nitrogen ◽  
Urea Nitrogen

We investigated the effect of human milk feeding on the nitrogen metabolism of appropriate-for-gestational age infants of birth weight 1.5–2.0 kg. Eight infants received pooled mature human milk. The remaining 20 were divided into two equal groups, who received one of two low-protein, milk-based formulae. The formulae were identical in composition except for the protein source, which was either casein- or whey-predominant. The three diet groups received similar total nitrogen (390 mg N∙kg−1∙d−1) and energy (500 kJ∙kg−1∙d−1) intakes. The human-milk-fed group, however, received a significantly higher intake of nonprotein and urea nitrogen and a significantly lower true protein nitrogen. Nitrogen metabolism was studied using a modified constant infusion of [15N]glycine, mixed with the feeding every 2–3 h. Urine was collected in approximately 3-h aliquots and analysed for total ammonia and urea nitrogen. Excretion of the 15N label was measured in urinary urea and ammonia. No differences were seen between the three diet groups in total [15N]urea or [15N]ammonia urinary excretion. However, the concentration of 15N in urinary urea in the human-milk-fed group was lower than in the two formula-fed groups. This reduction in concentration appeared due to a higher dietary intake of urea among the human-milk-fed group, and the consequent dilution of the label in the urine. As a result, protein turnover rates calculated from the [15N]urea end product were artificially raised in the milk-fed group, and were significantly higher than those in the formula groups. No differences were noted between the three diet groups in nitrogen turnover rates derived from the ammonia label. These rates averaged 61% of those derived from the urea end product. The two nitrogenous end products (ammonia and urea) appear to reflect different aspects of the neonates' nitrogen metabolism, in the form of pools or compartments that may be interchanging but are not always equilibrated.Key words: human milk, premature infant, low birth weight, nitrogen isotopes, protein metabolism.

PROTEIN TURNOVER IN WHEAT AND SNAPDRAGON LEAVES: PRELIMINARY INVESTIGATIONS

1963 ◽  
Vol 41 (7) ◽  
pp. 969-983 ◽  
Author(s):  
J. A. Hellebust ◽  
R. G. S. Bidwell
Keyword(s):  
Amino Acids ◽  
Protein Turnover ◽  
Soluble Sugars ◽  
Turnover Rates ◽  
Time Intervals ◽  
Protein Nitrogen ◽  
Protein Amino Acids ◽  
Specific Activities ◽  
Wheat Leaves ◽  
Biochemical Differentiation

Detached primary wheat leaves and attached cotyledons and primary leaves of snapdragons were allowed to photoassimilate C14O2 for short periods of time. They were subsequently kept in air and samples were taken at various time intervals and analyzed for protein nitrogen, and amounts and total radioactivities of soluble sugars and amino acids and protein amino acids. A method of estimating protein turnover from these data is discussed. Amounts and specific activities of respired carbon were also determined for wheat leaves.Minimum protein turnover rates of about 0.5 to 1.5% per hour were found in rapidly growing snapdragon leaves and in snapdragon cotyledons. Lower rates were found in detached, non-growing wheat leaves and slowly growing snapdragon leaves. Little contribution could have been made by proteins as substrates for respiration in detached wheat leaves. It is suggested that protein turnover in leaves is mainly associated with growth and biochemical differentiation.

PROTEIN METABOLISM AND RESPIRATION IN ATTACHED AND DETACHED PRIMARY WHEAT LEAVES

1964 ◽  
Vol 42 (4) ◽  
pp. 357-366 ◽  
Author(s):  
J. A. Hellebust ◽  
R. G. S. Bidwell
Keyword(s):  
Protein Metabolism ◽  
Protein Turnover ◽  
Soluble Sugars ◽  
Turnover Rates ◽  
Protein Amino Acid ◽  
Protein Nitrogen ◽  
Short Period ◽  
Detached Leaves ◽  
Amino Acid Turnover ◽  
Wheat Leaves

Attached and detached wheat leaves were supplied with C14O2 for a short period in light. They were then kept for 20 hours in the dark followed by 20 hours in light in air. Samples were taken at the beginning and end of each period and analyzed for protein nitrogen; and for amounts and total activities of respired carbon, soluble sugars, and amino acids and of protein amino acids.Similar patterns of protein metabolism were found in the two sets of leaves. The estimated protein amino acid turnover rates were somewhat higher in the detached than in the attached leaves but this may have been due to greater participation of soluble compounds which could not be translocated in detached leaves. There was a rapid synthesis of amides in the detached leaves during the light period, but this occurred at the expense of soluble sugars and supplied nitrogen salts rather than from protein breakdown products.Some contribution was made to respired CO2 by proteins during a period when protein turnover as well as a net decrease in proteins took place. During senescence, protein degradation contributed a considerable amount of carbon to respiration, but no protein turnover took place.

A comparison of the estimates of whole-body protein turnover in parenterally fed neonates obtained using three different end products

1989 ◽  
Vol 67 (6) ◽  
pp. 624-628 ◽  
Author(s):  
P. Pencharz ◽  
J. Beesley ◽  
P. Sauer ◽  
J. Van Aerde ◽  
U. Canagarayar ◽  
...  
Keyword(s):  
Nitrogen Metabolism ◽  
Protein Metabolism ◽  
Protein Turnover ◽  
The Other ◽  
Whole Body ◽  
Turnover Rates ◽  
Body Protein ◽  
Future Studies ◽  
Simultaneous Measurements ◽  
End Products

Protein turnover rates in neonates have been calculated largely by measuring urinary [15N]urea enrichment following administration of [15N]glycine. Although ammonia has been increasingly recognized as an end product of nitrogen metabolism, in neonates it yields a different estimate of protein turnover than does urea. Comparisons of ammonia and urea end products in parenterally fed neonates have not previously been reported. A third and independent way of estimating protein turnover, developed for adults, is to use breath 13CO2 as an end product following administration of [1-3C]leucine. We therefore carried out simultaneous measurements of protein turnover in 10 parenterally fed neonates, using the three end products. The infants were clinically stable, weighed 2.6 ± 0.2 kg, and received 3.1 ± 0.2 g∙kg−1∙d−1 of amino acid, 2.2 ± 0.1 g∙kg−1∙d−1 of lipids, and an energy intake of 90 ± 4 kcal∙kg−1∙d−1 (1 kcal = 4.186 kJ). The turnover estimates derived from the 13CO2 and [15N]urea end products were very similar. The [15N]ammonia end product produced values approximately 66% (p < 0.01) of the other two. We conclude that the ammonia and urea end products probably originate in different precursor pools. The similarity of the urea and breath carbon dioxide results helps validate the use of the urea end product in studying the nitrogen metabolism of parenterally fed neonates. Ideally in future studies two or more end products should be used, since they provide information about different aspects of the nenonates' protein metabolism.Key words: neonates, protein metabolism, nitrogen-15, [1-13C]leucine.

Comparison of 15N-Labelled Glycine, Aspartate, Valine and Leucine for Measurement of Whole-Body Protein Turnover

1979 ◽  
Vol 57 (3) ◽  
pp. 281-283 ◽  
Author(s):  
M. Taruvinga ◽  
A. A. Jackson ◽  
M. H. N. Golden
Keyword(s):  
Amino Acids ◽  
Protein Turnover ◽  
Ammonia Nitrogen ◽  
Whole Body ◽  
Constant Infusion ◽  
Turnover Rates ◽  
Body Protein ◽  
End Products ◽  
Lower Protein ◽  
Branched Chain

1. Whole-body protein turnover was measured in rats by constant infusion of 15N-labelled glycine, aspartate, valine and leucine and measuring the enrichment of hepatic and renal urea and ammonia nitrogen. 2. The values obtained with [15N]glycine were comparable with values reported with methods based on different assumptions. 3. [15N]Aspartate gave rise to an increased enrichment of urea and ammonia and hence to lower protein-turnover rates. 4. [15N]Valine and [15N]leucine gave low enrichments of nitrogenous end products and hence to high protein-turnover rates. 5. All 15N-labelled amino acids are not equally suitable for measuring whole-body protein turnover by the end-product method. The relative amounts of 15N going to the end products can be predicted from the known individual metabolism of aspartate and the branched-chain amino acids.

Nutrition Indices in Obese Continuous Peritoneal Dialysis Patients with Inadequate and Adequate Urea Clearance

2002 ◽  
Vol 22 (4) ◽  
pp. 506-512 ◽  
Author(s):  
Antonios H. Tzamaloukas ◽  
Karen S. Servilla ◽  
Glen H. Murata ◽  
Richard M. Hoffman
Keyword(s):  
Nitrogen Excretion ◽  
Obese Patients ◽  
Urea Clearance ◽  
Cross Sectional ◽  
Protein Nitrogen ◽  
Urea Nitrogen ◽  
Creatinine Excretion ◽  
Continuous Peritoneal Dialysis ◽  
Clearance Study ◽  
Small Solute

♦ Objective To test whether better nutrition is associated more with adequate urea clearance than with inadequate urea clearance in obese patients on continuous peritoneal dialysis (CPD). ♦ Design Retrospective analysis of clearance and nutrition indices in obese CPD patients. Only obese patients were analyzed. Obesity was defined as a ratio of actual weight to desired weight (W/DW) ≥ 1.2. The dose of dialysis was considered adequate at weekly Kt/V urea ≥ 2.0. Small solute clearances and nutrition indices were compared between patients with weekly Kt/V urea < 2.0 and patients with weekly Kt/V urea ≥ 2.0 at the first clearance study. ♦ Setting Four university-affiliated and two private dialysis units in Canada and the United States. ♦ Patients A total of 270 CPD patients with W/DW ≥ 1.2 at the first clearance study. ♦ Results Among the 270 obese CPD patients, 157 (58.1%) were underdialyzed (weekly Kt/V urea 1.66 ± 0.22) and 113 (41.9%) had adequate dialysis (weekly Kt/V urea 2.51 ± 0.47) at the first clearance study. Creatinine clearance values also differed between the underdialyzed and adequately dialyzed obese groups (55.6 ± 15.2 vs 87.6 ± 29.8 L/1.73 m2 weekly, respectively, p < 0.001). The underdialyzed group contained fewer women (39.5% vs 60.2%, p < 0.001) and more patients with anuria (35.0% vs 8.8%, p < 0.001), and had higher serum urea (20.7 ± 6.9 vs 18.2 ± 5.3 mmol/L, p = 0.001) and serum creatinine (974 ± 283 vs 734 ± 275 μmol/L, p < 0.001), marginally lower serum albumin (35.8 ± 5.2 vs 37.2 ± 6.4 g/L, p = 0.082), lower urea nitrogen excretion (5778 ± 2290 vs 7085 ± 2238 mg/24 hr, p < 0.001) and indices derived from urea nitrogen excretion (protein nitrogen appearance and normalized protein nitrogen appearance), and lower creatinine excretion (1034 ± 349 vs 1217 ± 432 mg/24 hr, p < 0.001) and indices derived from creatinine excretion (lean body mass normalized to actual or desired weight) than the adequately dialyzed group. ♦ Conclusion Nutrition indices derived from urea nitrogen and creatinine excretion are worse in underdialyzed than in adequately dialyzed obese CPD patients. This finding may have clinical importance, despite the mathematical coupling between small solute clearances and excretion rates in cross-sectional studies, because of evidence from other studies that small solute excretion rate in cross-sectional studies is a robust independent predictor of outcome in CPD.

Some effects of water restriction on nitrogen metabolism of cattle

1969 ◽  
Vol 20 (1) ◽  
pp. 185 ◽  
Author(s):  
RF Thornton ◽  
NG Yates
Keyword(s):  
Nitrogen Metabolism ◽  
Energy Intake ◽  
Water Intake ◽  
Nitrogen Concentration ◽  
Nitrogen Retention ◽  
Nitrogen Excretion ◽  
Water Restriction ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Faecal Nitrogen

Water restriction was found to decrease nitrogen retention in cattle when compared with periods of similar digestible energy intake but unrestricted water intake. The decreased nitrogen retention was associated with increases in both faecal nitrogen output and urinary urea excretion. The rise in urinary urea nitrogen excretion appeared to be mediated through increased plasma urea nitrogen concentration.

The effect of a reduction in food intake during late pregnancy on nitrogen metabolism in ewes

1976 ◽  
Vol 86 (1) ◽  
pp. 111-116 ◽  
Author(s):  
J. A. Guada ◽  
J. J. Robinson ◽  
C. Fraser
Keyword(s):  
Birth Weight ◽  
Food Intake ◽  
Food Restriction ◽  
Late Pregnancy ◽  
Plasma Free Fatty Acid ◽  
Metabolizable Energy ◽  
Nitrogen Excretion ◽  
Urea Nitrogen ◽  
Pregnant Sheep ◽  
The Relationship

SUMMARYTwelve Finnish Landrace × Dorset Horn ewes with a mean litter size of 1·92 and a mean body weight of 75±3 kg were individually penned from 80 days of gestation to parturition and offered a diet with a metabolizable energy (ME) and crude protein content in the dry matter of 9·7 MJ/kg and 11·4% respectively. At 120 days of gestation daily ME intake was abruptly reduced from a mean of 0·48 to 0·25 MJ/kg W0·75for a period of 10 days.The observed increase in the plasma concentration of urea due to the reduction in food intake was better correlated with lamb birth weight (r= 0·87) than was the increase in plasma free fatty acid concentration (r= 0·53) or the decrease in plasma glucose concentration (r= 0·76). Mean daily nitrogen balance decreased from a mean of 5·6 g before food restriction to – 1·8 g after food restriction. Although the effect was not significant, single bearing ewes excreted more total and urea nitrogen in the urine than multiple bearing ewes before food restriction. During food restriction the trend was reversed. The change in urea nitrogen excretion (Y, g/day) that resulted from the reduction in food intake was correlated (r= 0·73,P< 0·01) with lamb birth weight (X, kg); the relationship wasY= 0·54(±0·16)X – 3·48. It was estimated that the daily loss of nitrogen from the maternal body during the period of food restriction was approximately 80% of published values for the urinary nitrogen excretion of fasting non-pregnant sheep.

PROTEIN TURNOVER IN ATTACHED WHEAT AND TOBACCO LEAVES

1964 ◽  
Vol 42 (1) ◽  
pp. 1-12 ◽  
Author(s):  
J. A. Hellebust ◽  
R. G. S. Bidwell
Keyword(s):  
Amino Acids ◽  
Protein Turnover ◽  
Specific Activity ◽  
Soluble Sugars ◽  
Turnover Rates ◽  
Protein Nitrogen ◽  
Tobacco Leaves ◽  
Long Time ◽  
Protein Amino Acids ◽  
Wheat Leaves

Attached primary and secondary wheat leaves were supplied continuously with C14O2 during daily periods of photosynthesis for 3 days. Samples were analyzed for amounts and total activities of respired carbon, soluble sugars and amino acids, protein amino acids, and protein nitrogen. By labelling all possible protein precursors to the same extent it was possible to eliminate doubts about the specific activity of carbon entering protein. Hence turnover rates could be accurately established. Because tobacco leaves last for a long time, it was possible to label their proteins, wait until soluble compounds were at a low specific activity, and then measure turnover of proteins as radioactivity in them decreased.Protein amino acid turnover rates of 0.4–0.5% per hour were obtained in rapidly growing secondary wheat leaves and 0.2–0.3% per hour in non-growing primary wheat leaves. Turnover rates of 0.15–0.2% per hour were found in expanding tobacco leaves, but little or no turnover was found in fully expanded tobacco leaves.It is suggested that protein turnover is a facet of the biochemical differentiation that accompanies development, enlargement, or change in function of an organ without concomitant net protein synthesis.

A Retrospective Analysis of the Effects of an Exclusively Human Milk Protein Diet on Neonatal Feeding Tolerance

2020 ◽  
Author(s):  
Jessica Wickland ◽  
Christine Wade ◽  
Becky Micetic ◽  
Keith Meredith ◽  
Gregory Martin
Keyword(s):  
Birth Weight ◽  
Human Milk ◽  
Milk Protein ◽  
Very Low Birth Weight ◽  
Bovine Milk ◽  
Milk Diet ◽  
Vlbw Infants ◽  
Key Points ◽  
Human Milk Protein ◽  
Feeding Tolerance

Objective This study was aimed to evaluate the effect of human milk protein fortifier (HMPF) versus bovine milk protein fortifier (BMPF) on feeding tolerance defined as the time to reach full feeds and necrotizing enterocolitis (NEC) in premature very low birth weight (VLBW) infants. Study Design A retrospective review using the BabySteps Database included 493 infants born ≤33 weeks of gestational age and ≤1,250 g (g) birth weight. A total of 218 infants fed a human milk diet (HMD) with BMPF were compared with 275 infants fed an HMD with HMPF. Results Full feeds were reached significantly sooner in the HMPF group (median: 14 vs. 16 days, p = 0.04). Weight at full feeds was significantly lower in the HMPF group (1,060 vs. 1110 g, p = 0.03). Conclusion Using HMPF to provide an exclusively HMD allowed VLBW infants to achieve full feeds sooner, but did not affect rate of NEC compared with using a BMPF with an HMD. Key Points

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