scholarly journals The fate of absorbed and exogenous ammonia as influenced by forage or forage–concentrate diets in growing sheep

1996 ◽  
Vol 76 (2) ◽  
pp. 231-248 ◽  
Author(s):  
G. E. Lobley ◽  
P. J. M. Weijs ◽  
A. Connell ◽  
A. G. Calder ◽  
D. S. Brown ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ammonium Salt ◽  
Free Amino ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Minor Role ◽  
N Removal ◽  
A Minor ◽  
Branched Chains

Changes in splanchnic energy and N metabolism were studied in sheep, prepared with vascular catheters across the portal-drained viscera (PDV) and the Liver, and maintained on supramaintenance intakes of either grass or grass + barley pellets. The animals were challenged, on both diets, with 4 d intra- mesenteric vein infusions of NH4CI (25 µmol/min) plus NH4HCO3(at either 0 or 125 µmol/min). On the final day of each treatment the natural abundance NH4Cl was replaced with15NH4Cl over a 10 h infusion while over the same period [l-13C]leucine was infused via a jugular vein. Measurements were made of blood flow plus mass transfers of NH3, urea, free amino acids and O2, across the PDV and liver. Enrichments of [14N15N]urea and [15N15N]urea plus [15N]glutamine, aspartate and glutamate were also monitored. Whole-body urea flux was determined by infusion of [14C]urea. At the end of the study the animals were infused for 3 h with15NH4CI, killed and liver samples assayed for intracellular free amino acid enrichments and concentrations. Blood flows across the splanchnic region were unaffected by either diet or level of ammonium salt infusion. At the lower ammonium salt infusion there was a trend for greater absorption of NH3across the PDV (P<0·10) with grass + barley than with the grass diet, while removal of urea was unaltered. At the higher ammonium salt infusions there was a significantly greater appearance of NH, across the PDV and this exceeded the extra infused. Urea-N removal, however, was also elevated and by more than that required to account for the additional NH3. The PDV contributed 19–28% to whole-body O2consumption and the liver 23–32%. Hepatic extraction of absorbed NH3was complete on all treatments and systemic pH remained constant. The fractions of urea-N apparently derived from NH3, were similar on the grass (0·59–0·64) and grass + barley (0·64–0·67) diets. Hepatic production of urea agreed well with urea flux measurements. Between the two levels of ammonium salt infusion and within diets the additional NH3removed across the PDV was accounted for by the increased urea-N production. The [14N15N]: [15N15N] ratio of the urea produced was 97:3, while the enrichment of hepatic intracellular free aspartate was lower than that of [14N15N]urea. Glutamine enrichments were 0·23–0·37 those of [14N15N]urea, indicating a minor role for those hepatocytes (probably perivenous) which contain glutamine synthetase (EC6.3.1.2). Leucine kinetics, either for the whole body or splanchnic tissues, were not different between diets or level of ammonium salt infusion, except for oxidation which was less on the grassfbarley ration. Amino acid concentrations were lower on the grass + barley diet but net PDV absorptions were similar. The pattern of essential amino acids absorbed into the PDV showed good agreement with the published composition of mixed rumen microbial protein. Fractional disappearances of absorbed free essential amino acids across the liver varied from 0·4 (branched chains) to near unity (histidine, phenylalanine)

scholarly journals Splanchnic-bed transfers of amino acids in sheep blood and plasma, as monitored through use of a multiple U-13C-labelled amino acid mixture

1996 ◽  
Vol 75 (2) ◽  
pp. 217-235 ◽  
Author(s):  
G. E. Lobley ◽  
A. Connell ◽  
D. K. Revell ◽  
B. J. Bequette ◽  
D. S. Brown ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Free Amino Acids ◽  
Free Amino ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Gas Chromatography Mass Spectrometry ◽  
Acid Mixture ◽  
Body Protein ◽  
Hydrolysis Of

AbstractThe response in whole-body and splanchnic tissue mass and isotope amino acid transfers in both plasma and blood has been studied in sheep offered 800 g lucerne (Medicago sutiva) pellets/d. Amino acid mass transfers were quantified over a 4 h period,by arterio-venous procedures, across the portal-drained viscera (PDV) and liver on day 5 of an intravenous infusion of either vehicle or the methylated products, choline (0.5 g/d) plus creatine (10 g/d). Isotopic movements were monitored over the same period during a 10 h infusion of a mixture of U-13C-labelled amino acids obtained from hydrolysis of labelled algal cells. Sixteen amino acids were monitored by gas chromatography-mass spectrometry, with thirteen of these analysed within a single chromatographic analysis. Except for methionine, which is discussed in a previous paper, no significant effects of choline plus creatine infusion were observed on any of the variables reported. Whole-body protein irreversible-loss rates ranged from 158 to 245 g/d for the essential amino acids, based on the relative enrichments (dilution of the U-13C molecules by those unlabelled) of free amino acids in arterial plasma, and 206-519 g/d, when blood free amino acid relative enrichments were used for the calculations. Closer agreement was obtained between lysine, threonine, phenylalanine and the branched-chain amino acids. Plasma relative enrichments always exceeded those in blood (P < 0.001), possibly due to hydrolysis of peptides or degradation of protein within the erythrocyte or slow equilibration between plasma and the erythrocyte. Net absorbed amino acids across the PDV were carried predominantly in the plasma. Little evidence was obtained of any major and general involvement of the erythrocytes in the transport of free amino acids from the liver. Net isotope movements also supported these findings. Estimates of protein synthesis rates across the PDV tissues from [U-13C] leucine kinetics showed good agreement with previous values obtained with single-labelled leucine. Variable rates were obtained between the essential amino acids, probably due to different intracellular dilutions. Isotope dilution across the liver was small and could be attributed predominantly to uni-directional transfer from extracellular sources into the hepatocytes and this probably dominates the turnover of the intracellular hepatic amino acid pools.

scholarly journals The relative effects of a low-protein-high-carbohydrate diet on the free amino acid composition of liver and muscle

1976 ◽  
Vol 36 (2) ◽  
pp. 219-230
Author(s):  
P. G. Lunn ◽  
R. G. Whitehead ◽  
B. A. Baker
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Free Amino Acid ◽  
Acid Concentration ◽  
Free Amino ◽  
Essential Amino Acids ◽  
Protein Diet ◽  
Low Protein Diet ◽  
Total Amino Acid ◽  
Low Protein

1. Free amino acid concentrations in the plasma have been compared with those in liver and quadriceps muscle, in rats fed on diets containing 209 (control) and 31 (low-protein) g protein/kg. The effects of the low-protein diet on diurnal variations in these values were also measured.2. In the plasma, the total amino acid concentration was significantly lower in animals given the low-protein diet, at all times of day except 12.00 hours. In the liver, and to a lesser extent the muscle, total amino acid concentration was maintained.3. In the control animals, diurnal variation in the concentrations of both essential and non-essential amino acids was very similar in plasma, liver and muscle. In animals given the low-protein diet, although the same diurnal pattern was maintained for non-essential amino acids, that occurring among the essential amino acids had virtually disappeared.4. In plasma, the mean 24 h concentration of essential amino acids decreased from 24· mmol/l in control animals to only 1·29 mmol/l in the low-protein-fed animals. Concentrations in muscle and liver were reduced by a similar proportion (from 8·6 to 5·56 μmol/g and from 8·67 to 5·05 μmol/g respectively). Conversely the concentrations of non-essential amino acids in animals given the low-protein diet were increased in plasma (from 1·53 to 2·00 mmol/l), muscle (from 12·5 to 14·3 μmol/g), and liver (from 16·8 to 20·5 μmol/g), muscle showing the lowest increase.5. With the exceptions of lysine, threonine, cystine and tyrosine, the concentrations of all other essential amino acids were reduced more in liver than in muscle. The relationship between this and the failure to maintain plasma albumin concentrations is discussed.

scholarly journals Nonessential amino acid usage for protein replenishment in humans: a method of estimation

2019 ◽  
Vol 110 (2) ◽  
pp. 255-264 ◽  
Author(s):  
Paolo Tessari
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Quality ◽  
Essential Amino Acids ◽  
World Health ◽  
Whole Body ◽  
Published Data ◽  
Total Proteins ◽  
Body Protein ◽  
Amino Acid Turnover

ABSTRACT Background Essential amino acids (EAAs) are key factors in determining dietary protein quality. Their RDAs have been estimated. However, although nonessential amino acids (NEAAs) are utilized for protein synthesis too, no estimates of their usage for body protein replenishment have been proposed so far. Objective The aim of this study was to provide minimum, approximate estimates of NEAA usage for body protein replenishment/conservation in humans. Methods A correlation between the pattern of both EAAs and NEAAs in body proteins, and their usage, was assumed. In order to reconstruct an “average” amino acid pattern/composition of total body proteins (as grams of amino acid per gram of protein), published data of relevant human organs/tissues (skeletal muscle, liver, kidney, gut, and collagen, making up ∼74% of total proteins) were retrieved. The (unknown) amino acid composition of residual proteins (∼26% of total proteins) was assumed to be the same as for the sum of the aforementioned organs excluding collagen. Using international EAA RDA values, an average ratio of EAA RDA to the calculated whole-body EAA composition was derived. This ratio was then used to back-calculate NEAA usage for protein replenishment. The data were calculated also using estimated organ/tissue amino acid turnover. Results The individual ratios of World Health Organization/Food and Agriculture Organization/United Nations University RDA to EAA content ranged between 1.35 (phenylalanine + tyrosine) and 3.68 (leucine), with a mean ± SD value of 2.72 ± 0.81. In a reference 70-kg subject, calculated NEAA usage for body protein replenishment ranged from 0.73 g/d for asparagine to 3.61 g/d for proline. Use of amino acid turnover data yielded similar results. Total NEAA usage for body protein replenishment was ∼19 g/d (45% of total NEAA intake), whereas ∼24 g/d was used for other routes. Conclusion This method may provide indirect minimum estimates of the usage of NEAAs for body protein replacement in humans.

AMINO ACIDS IN THE BLOOD AND URINE OF NORMAL AND ARTHRITIC SUBJECTS BEFORE AND AFTER A GLYCINE LOAD GIVEN WITH AND WITHOUT ADRENOCORTICOTROPIN

1957 ◽  
Vol 35 (1) ◽  
pp. 1005-1016 ◽  
Author(s):  
J. B. Derrick ◽  
Audrey P. Hanley
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Chromatographic Analysis ◽  
Free Amino ◽  
Serum Levels ◽  
Essential Amino Acids ◽  
Single Amino Acid ◽  
Normal Individuals ◽  
Before And After ◽  
Serum And Urine

Observations have been made on the specific free amino acids (chromatographic analysis) and other nitrogenous constituents in the serum and urine of normal and arthritic men under controlled dietary conditions, before and after a glycine load and adrenocorticotropin administered separately and together.Differences in the metabolism of amino acids between normal individuals and arthritics, particularly of alanine, proline, glutamic acid, taurine, and possibly tyrosine (and/or tryptophan) and cystine, were apparent. The differences were largely confined to the non-essential amino acids. Concomitant increases seen in the serum levels and in the excretion of several amino acids, in response to a load of a single amino acid, indicate that the increases in excretion are more than a matter of competition for reabsorption in the kidney. A prerenal phenomenon appears to be involved, possibly interconversion of amino acids. This concept is supported by the evidence that the increases in the serum levels were restricted to the non-essential amino acids.

AMINO ACIDS IN THE BLOOD AND URINE OF NORMAL AND ARTHRITIC SUBJECTS BEFORE AND AFTER A GLYCINE LOAD GIVEN WITH AND WITHOUT ADRENOCORTICOTROPIN

1957 ◽  
Vol 35 (11) ◽  
pp. 1005-1016 ◽  
Author(s):  
J. B. Derrick ◽  
Audrey P. Hanley
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Chromatographic Analysis ◽  
Free Amino ◽  
Serum Levels ◽  
Essential Amino Acids ◽  
Single Amino Acid ◽  
Normal Individuals ◽  
Before And After ◽  
Serum And Urine

Observations have been made on the specific free amino acids (chromatographic analysis) and other nitrogenous constituents in the serum and urine of normal and arthritic men under controlled dietary conditions, before and after a glycine load and adrenocorticotropin administered separately and together.Differences in the metabolism of amino acids between normal individuals and arthritics, particularly of alanine, proline, glutamic acid, taurine, and possibly tyrosine (and/or tryptophan) and cystine, were apparent. The differences were largely confined to the non-essential amino acids. Concomitant increases seen in the serum levels and in the excretion of several amino acids, in response to a load of a single amino acid, indicate that the increases in excretion are more than a matter of competition for reabsorption in the kidney. A prerenal phenomenon appears to be involved, possibly interconversion of amino acids. This concept is supported by the evidence that the increases in the serum levels were restricted to the non-essential amino acids.

Amino acids suppress proteolysis independent of insulin throughout the neonatal period

1997 ◽  
Vol 272 (4) ◽  
pp. E592-E599 ◽  
Author(s):  
B. B. Poindexter ◽  
C. A. Karn ◽  
J. A. Ahlrichs ◽  
J. Wang ◽  
C. A. Leitch ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Neonatal Period ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Amino Acid Availability ◽  
Dose Dependent Fashion ◽  
Term Newborns ◽  
Dose Dependent ◽  
Acid Administration

To determine how increased amino acid availability alters rates of whole body proteolysis and the irreversible catabolism of the essential amino acids leucine and phenylalanine throughout the neonatal period, leucine and phenylalanine kinetics were measured under basal conditions and in response to intravenous amino acids in two separate groups of healthy, full-term newborns (at 3 days and 3 wk of age). The endogenous rates of appearance of leucine and phenylalanine (reflecting proteolysis) were suppressed equally in both groups and in a dose-dependent fashion (by approximately 10% with 1.2 g x kg(-1) x day(-1) and by approximately 20% with 2.4 g x kg(-1) x day(-1)) in response to intravenous amino acid delivery. Insulin concentrations remained unchanged from basal values during amino acid administration. The irreversible catabolism of leucine and phenylalanine increased in a stepwise fashion in response to intravenous amino acids; again, no differences were observed between the two groups. This study clearly demonstrates that the capacity to acutely increase rates of leucine oxidation and phenylalanine hydroxylation is fully present early in the neonatal period in normal newborns. Furthermore, these data suggest that amino acid availability is a primary regulator of proteolysis in normal newborns throughout the neonatal period.

scholarly journals Use of plasma-free amino acids as biomarkers for detecting and predicting disease risk

2020 ◽  
Vol 78 (Supplement_3) ◽  
pp. 79-85
Author(s):  
Kenji Nagao ◽  
Takeshi Kimura
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Free Amino ◽  
Disease Risk ◽  
The Elderly ◽  
Essential Amino Acids ◽  
Clinical Findings ◽  
Amino Acid Supplementation ◽  
Diabetes Prediction ◽  
Plasma Free Amino Acids

Abstract This paper reviews developments regarding the use of plasma-free amino acid (PFAA) profiles as biomarkers for detecting and predicting disease risk. This work was initiated and first published in 2006 and was subsequently developed by Ajinomoto Co., Inc. After commercialization in 2011, PFAA-based tests were adopted in over 1500 clinics and hospitals in Japan, and numerous clinician-led studies have been performed to validate these tests. Evidence is accumulating that PFAA profiles can be used for diabetes prediction and evaluation of frailty; in particular, decreased plasma essential amino acids could contribute to the pathophysiology of severe frailty. Integration of PFAA evaluation as a biomarker and effective essential amino acid supplementation, which improves physical and mental functions in the elderly, could facilitate the development of precision nutrition, including personalized solutions. This present review provides the background for the technology as well as more recent clinical findings, and offers future possibilities regarding the implementation of precision nutrition.

Effect of diet and infusion of volatile fatty acids into the rumen on the concentration of plasma free amino acids in sheep

1982 ◽  
Vol 48 (3) ◽  
pp. 519-526 ◽  
Author(s):  
J. R. Mercer ◽  
E. L. Miller
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Free Amino ◽  
Volatile Fatty Acids ◽  
Plasma Concentrations ◽  
Essential Amino Acids ◽  
Protein Nitrogen ◽  
Post Infusion ◽  
Limiting Amino Acid ◽  
The Mean

1. The effect of supplementing barley diets with urea (U), extracted decorticated groundnut meal (GNM) or Peruvian fish meal (PFM) on plasma free amino acid concentrations in sheep have been examined and the first limiting amino acid has been indicated by measuring the changes in the concentration of the plasma essential amino acids (PEAA) during a rumen infusion of a volatile fatty acid (VFA) mixture.2. Three wethers fitted with rumen and re-entrant duodenal cannulas were given isonitrogenous, isoenergetic diets containing (g/kg dry matter (DM)) U 20, GNM 106 or PFM 78, the crude protein (nitrogen × 6.25) contents being 139, 145 and 148 respectively. The sheep were fed hourly, the mean daily dm intake being 0.634 kg.3. Plasma concentrations of valine, threonine, lysine, isoleucine and leucine were linearly related to their concentrations in duodenal digesta.4. A VFA mixture was infused into the rumen for 6 h to supply (mmol/min) acetate 1.47, propionate 0.22 and n-butyrate 0.27. Blood samples were taken 6 h before, during and 12 h after the end of the infusion.5. The concentration of all PEAA decreased relative to the pre-infusion and post-infusion controls but there were no significant differences between diets.6. The mean decreases in concentration averaged over all three diets showed that the decrease in concentration of methionine (41.5%) was far greater than for any other essential amino acid suggesting that under these conditions methionine was the first limiting amino acid.

Intracellular Free Amino Acids in Muscle Tissue of Patients with Chronic Uraemia: Effect of Peritoneal Dialysis and Infusion of Essential Amino Acids

1978 ◽  
Vol 54 (1) ◽  
pp. 51-60 ◽  
Author(s):  
J. Bergström ◽  
P. Fürst ◽  
L.-O. Norée ◽  
E. Vinnars
Keyword(s):  
Amino Acids ◽  
Peritoneal Dialysis ◽  
Amino Acid ◽  
Muscle Tissue ◽  
Free Amino Acids ◽  
Free Amino ◽  
Essential Amino Acids ◽  
Chronic Uraemia ◽  
Muscle Water ◽  
Intracellular Concentrations

1. Free amino acids were determined in the plasma and in the muscle tissue of 14 patients with chronic uraemia; eight were not on dialysis and six were having regular peritoneal dialysis. The concentration of each amino acid in muscle water was calculated with the chloride method. 2. In both groups of patients there were low intracellular concentrations of threonine, valine, tyrosine and carnosine, and high glycine/valine and phenylalanine/tyrosine ratios. Both groups of patients had increased amounts of 1- and 3-methylhistidine in plasma and in muscle water. 3. The non-dialysed patients had low intracellular concentrations of lysine, and the dialysed patients had high intracellular concentrations of lysine, isoleucine, leucine and of some of the non-essential amino acids. 4. After peritoneal dialysis for 22 h, the plasma concentration of several amino acids decreased but the intracellular concentrations of most amino acids did not change significantly. 5. Intravenous administration of essential amino acids and histidine during the last 4 h of dialysis increased in muscle the total free amino acids, the ratio of essential to non-essential amino acids and the valine and phenylalanine concentrations. 6. The results demonstrated that the plasma and muscle concentrations of several amino acids are grossly abnormal in chronic uraemia. Non-dialysed and dialysed patients exhibit important differences, especially in the intracellular amino acid patterns. Infusion of essential amino acids may result in enhancement of protein synthesis.

scholarly journals Consumption of a Specially-Formulated Mixture of Essential Amino Acids Promotes Gain in Whole-Body Protein to a Greater Extent than a Complete Meal Replacement in Older Women with Heart Failure

Nutrients ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1360 ◽  
Author(s):  
Il-Young Kim ◽  
Sanghee Park ◽  
Ellen T. H. C. Smeets ◽  
Scott Schutzler ◽  
Gohar Azhar ◽  
...  
Keyword(s):  
Heart Failure ◽  
Amino Acids ◽  
Amino Acid ◽  
Body Mass ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Meal Replacement ◽  
Anabolic Response ◽  
Body Protein ◽  
Net Protein

Heart failure in older individuals is normally associated with a high body mass index and relatively low lean body mass due to, in part, a resistance to the normal anabolic effect of dietary protein. In this study we have investigated the hypothesis that consumption of a specially-formulated composition of essential amino acids (HiEAAs) can overcome anabolic resistance in individuals with heart failure and stimulate the net gain of body protein to a greater extent than a commercially popular protein-based meal replacement beverage with greater caloric but lower essential amino acid (EAA) content (LoEAA). A randomized cross-over design was used. Protein kinetics were determined using primed continuous infusions of L-(2H5)phenylalanine and L-(2H2)tyrosine in the basal state and for four hours following consumption of either beverage. Both beverages induced positive net protein balance (i.e., anabolic response). However, the anabolic response was more than two times greater with the HiEAA than the LoEAA (p < 0.001), largely through a greater suppression of protein breakdown (p < 0.001). Net protein accretion (g) was also greater in the HiEAA when data were normalized for either amino acid or caloric content (p < 0.001). We conclude that a properly formulated EAA mixture can elicit a greater anabolic response in individuals with heart failure than a protein-based meal replacement. Since heart failure is often associated with obesity, the minimal caloric value of the HiEAA formulation is advantageous.

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