scholarly journals Leucine Is More Readily Oxidized When Ingested as an Isolated Nutrient versus Incorporated in Its Whole-Food Matrix

2021 ◽  
Vol 5 (Supplement_2) ◽  
pp. 516-516
Author(s):  
Kevin J.M. Paulussen ◽  
Andrew Askow ◽  
Amadeo Salvador ◽  
Colleen McKenna ◽  
Susannah Scaroni ◽  
...  
Keyword(s):  
Amino Acids ◽  
Free Amino ◽  
Food Source ◽  
Whole Body ◽  
Leucine Oxidation ◽  
Time To Peak ◽  
Oxidation Rates ◽  
Dietary Amino Acids ◽  
Plasma Leucine ◽  
Stimulation Of

Abstract Objectives The ingestion of free amino acids, or isolated sources of protein, results in faster postprandial release of dietary amino acids into circulation, which stimulates muscle protein synthesis rates. However, indirect evidence suggests that this rapid release of dietary amino acids after the ingestion of free amino acids is coupled with higher amino acid oxidation rates when compared to a whole-food source. Whole food protein results in a reduced peak amplitude and prolonged postprandial aminoacidemia. This study aimed to assess the effects of eating a whole food source of protein on the stimulation of whole-body leucine oxidation rates versus eating these same nutrients in isolated form in healthy young adults. Methods In a crossover design, 10 recreationally active adults (24 ± 4 y; 5 M, 5 F) performed an acute bout of resistance exercise followed by the ingestion of salmon (SAL) (20.5 g protein and 7.5 g fat) or its matched constituents as crystalline amino acids and fish oil (ISO). Participants received priming doses of NaH13CO2 and L-[1–13C]leucine before initiating a constant L-[1–13C]leucine infusion. Blood and breath samples were collected at rest and after resistance exercise at regular intervals for the measurement of whole-body leucine oxidation rates and plasma leucine profiles. Data were tested using linear fixed effects models with time and group as fixed factors with Bonferroni's post hoc test. Results Postprandial plasma leucine concentrations did not differ between the SAL and ISO conditions (P > 0.05). Time to peak plasma leucine concentrations was faster in ISO (50 ± 27 min) vs. SAL (114 ± 64 min,  P = 0.022) condition. Postprandial leucine oxidation rates were elevated from baseline at t = 30 min to t = 120 min in ISO and t = 60 min to t = 180 min in SAL (P < 0.001), with no total differences between group (P = 0.129). Time to peak leucine oxidation occurred sooner in ISO (66 ± 22 min;  1.358 ± 0.699 nmol · kg−1 · min−1) when compared to the SAL condition (105 ± 20 min;  1.067 ± 0.3076 nmol · kg−1 · min−1; P = 0.002). Conclusions We show that the ingestion of a whole-food source of protein resulted in a delayed stimulation of leucine oxidation when compared to free amino acid ingestion, but a similar net increase in oxidation during the 5 h postprandial period in healthy young adults. Funding Sources USDA National Institute of Food and Agriculture Hatch project 1017928

Nitrogen Homoeostasis in Man: Diurnal Changes in Nitrogen Excretion, Leucine Oxidation and Whole Body Leucine Kinetics during a Reduction from a High to a Moderate Protein Intake

1994 ◽  
Vol 86 (2) ◽  
pp. 185-193 ◽  
Author(s):  
Marcelo R. Quevedo ◽  
Gill M. Price ◽  
David Halliday ◽  
Paul J. Pacy ◽  
D. Joe Millward
Keyword(s):  
Protein Intake ◽  
Protein Diet ◽  
Nitrogen Excretion ◽  
Whole Body ◽  
Diurnal Changes ◽  
N Losses ◽  
Leucine Oxidation ◽  
Leucine Kinetics ◽  
Synthesis And Degradation ◽  
Stimulation Of

1. The adaptation of the diurnal cycle of nitrogen (N) homoeostasis during a change in protein intake was investigated with diurnal measurements of N and leucine balance and turnover during a reduction from a high to a moderate protein intake in normal adults. 2. In experiment 1, during a 9 day period after a reduction from 1.82 to 0.77 g of protein day−1 kg−1, N excretion fell slowly at a similar rate in fed and fasted states so that the lowered intake was unable to replete any of the postabsorptive losses for 3 days. There was a marked negative N balance, which persisted throughout the study, although with a significant reduction in N losses in both fed and fasted states on day 4, balances during days 4–9 (−32.8 ± 28.3 mg of N day−1 kg−1) were less negative than during days 1–3 (−79.1 ± 60.4 mg of N day−1 kg−1). 3. In experiment 2, during a 14 day period after a reduction from 1.89 to 0.77 g of protein day−1kg−1, [1-13C]leucine oxidation and turnover were measured by primed intravenous infusion, during fasting and feeding in subjects before and on days 3, 7 and 14 after the dietary change. Leucine oxidation fell by 32% (P < 0.05) on day 3 in the fed state and by 12% (P < 0.05) during fasting, falling further in each case by day 7 with improved balance. N losses predicted from the leucine oxidation fell with the same time course as the measured N excretion in experiment 1, but the predicted losses were lower, so that the overall negative leucine balance on day 3 (−22 ± 17 mg of N day−1 kg−1) became positive by day 7 (+ 15 ± 21 mg of N day−1 kg−1). 4. Rates of protein synthesis and degradation calculated from leucine kinetics indicated that feeding the high protein diet resulted in a 60% inhibition of degradation and a 15% (P < 0.05) stimulation of synthesis. With the moderate protein diet the improving fasting balance between days 3 and 7 was the result of a non-significant fall in degradation. Feeding the moderate protein diet abolished the stimulation of synthesis and significantly lowered the inhibition of degradation (31 ± 9%). The improving fed balance between days 3 and 7 was the result of changes in the rates of synthesis and degradation which were below the detection limits of the methods. The daily sum of fasted and fed rates of synthesis (4.33 g day−1 kg−1) did not change with the lowered intake, whereas the rate of degradation increased significantly from 3.61 to 4.26 g day−1 kg−1). 5. Thus, in response to a lower protein intake, adaptation of amino acid oxidation and N excretion occurs, with a similar pattern of gradual reductions in fed and fasted periods during the first week. Thus protein requirements are influenced by the habitual protein intake, which influences the nutritional demand for protein for repletion of fasting losses, the efficiency of such repletion and the consequent dietary need.

scholarly journals Oxidation of an indicator amino acid by young pigs receiving diets with varying levels of lysine or threonine, and an assessment of amino acid requirements

1983 ◽  
Vol 50 (2) ◽  
pp. 391-399 ◽  
Author(s):  
Kyu-Il Kim ◽  
James I. Elliott ◽  
Henry S. Bayley
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Free Amino ◽  
Skim Milk ◽  
Linear Increase ◽  
Single Amino Acid ◽  
Dietary Level ◽  
Dietary Amino Acids ◽  
Young Pigs ◽  
Amino Acid Requirements

1. The catabolism of [14C]phenylalanine was used to indicate the effects of varying the dietary level of lysine and threonine on the retention of dietary amino acids by 2-week-old pigs receiving diets containing skim milk and a mixture of free amino acids.2. Reducing the dietary level of lysine from 16 to 12 g/kg had no influence on phenylalanine oxidation, reducing the lysine level from 12 to 11 then to 10 g/kg caused an almost linear increase in phenylalanine oxidation whereas further reduction to 9 or 8 g/kg resulted in a less-marked increase in phenylalanine oxidation. This showed that 12 g lysine/kg was required to maximize amino acid retention and indicated that lysine was conserved more effectively at low dietary concentrations than at dietary concentrations approaching the requirement.3. Reducing the dietary level of threonine from 8 to 6 g/kg had no influence on phenylalanine oxidation, whereas further reduction to 4 g/kg caused a linear increase in phenylalanine catabolism showing that 6 g threonine/kg was required to maximize amino acid retention.4. Reduction of the levels of lysine, threonine and methionine from the generous levels characteristic of a diet containing 240 g protein from skim milk/kg, to the requirement levels determined separately in the presence of the generous levels of all the other amino acids, resulted in a twofold increase in phenylalanine catabolism. This shows that the pig seems able to conserve limiting intakes of a single amino acid, but not if the intakes of two or three amino acids are limiting.

STUDIES ON THE LEGUME ROOT NODULE BACTERIA: III. GROWTH FACTOR REQUIREMENTS FOR EFFECTIVE, INEFFECTIVE, AND PARASITIC STRAINS

1952 ◽  
Vol 30 (6) ◽  
pp. 693-700 ◽  
Author(s):  
D. C. Jordan
Keyword(s):  
Amino Acids ◽  
Free Amino ◽  
Root Nodule ◽  
Amino Acid Content ◽  
Sweet Clover ◽  
Nodule Bacteria ◽  
Experimental Conditions ◽  
Before And After ◽  
Growth Initiation ◽  
Stimulation Of

Under the experimental conditions used, amino acids played a very important part in the growth initiation of washed cells of alfalfa – sweet clover rhizobia. There were, however, distinct differences in utilization, both among genetically related mutants, and among other cultures when compared before and after plant passage. None of 15 vitamins, purines, and pyrimidines was able to initiate growth and hence these rhizobia are able to synthesize these compounds when a readily utilizable nitrogen source is present. Because of this fact, the stimulation of these bacteria by yeast extract is probably due, primarily, to the amino acid content. No strain was found able to concentrate free amino acids intracellularly or, when grown in lysine or tyrosine media, to excrete additional amino acids. No differences were found among effective, ineffective, or parasitic rhizobia in biochemical requirements.

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 Macronutrients and essential amino acids on digestive process of the freshwater teleost Matrinxã

2021 ◽  
Vol 15 (4) ◽  
pp. 413-421
Author(s):  
Rodrigo Yamakami Camilo ◽  
Claucia Aparecida Honorato ◽  
Rudã Fernandes Brandão Santos ◽  
Ive Marchioni Avilez ◽  
Luciana Cristina De Almeida ◽  
...  
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Lipolytic Activity ◽  
Essential Amino Acids ◽  
Freshwater Teleost ◽  
Activity Increase ◽  
Digestive Process ◽  
Pyloric Cecum ◽  
Dietary Amino Acids

The objective of this work was to evaluate the effect of macronutrients and essential amino acids on digestive process of the freshwater teleost Matrinxã (Brycon amazonicus). Juveniles were fed with diets containing starch plus free amino acids or oil plus free amino acids for 15 days. These fish were compared with others fed with diets containing starch or oil without addition of free amino acids. After the experimental span, 12 fish from each treatment were randomly sampled to collect stomach, pyloric cecum, anterior and posterior intestine for assaying digestive enzymes activity. Increase of gastric proteolysis due to dietary amino acids were observed. Amylolytic, proteolytic and lipolytic activities in intestine sections were also positive related to dietary amino acids. However, proteolytic and lipolytic activities in pyloric cecum were not responsive to dietary changes. Moreover, the absence of starch in the diets resulted in decrease of amylolysis, and very low levels of oil did not change the lipolytic activity. In conclusion, activities of amylase, protease and lipase of Matrinxãare selectively responsive to addition of free essential amino acids concerning the gut section.

Meal stimulation of albumin synthesis: a significant contributor to whole body protein synthesis in humans

1992 ◽  
Vol 263 (4) ◽  
pp. E794-E799 ◽  
Author(s):  
P. De Feo ◽  
F. F. Horber ◽  
M. W. Haymond
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Combined Treatment ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Albumin Synthesis ◽  
Body Protein ◽  
Peripheral Tissues ◽  
Stimulation Of

The present studies were performed to test the hypothesis that the liver, by increasing the synthesis of specific plasma proteins during the absorption of an amino acid meal, may play an important role in the temporary "storage" of ingested essential amino acids and to explore the effects of glucocorticosteroids and recombinant human growth hormone (rhGH) on these processes. The fractional synthetic rates of albumin and fibrinogen were determined using simultaneous infusions of intravenous [1-14C]leucine and intraduodenal [4,5-3H]leucine after 22 h fasting and during absorption of glucose and amino acids in four groups of normal subjects treated for 1 wk with placebo, prednisone (0.8 mg.kg-1.day-1), rhGH (0.1 mg.kg-1.day-1), or combined treatment. When compared with the fasted state and independent of the route of tracer delivery and hormonal treatment, albumin, but not fibrinogen, synthesis increased (P < 0.0001) during absorption of a mixed glucose amino acid meal in all groups. This increase in albumin synthesis accounted for 28% of the increase in whole body protein synthesis associated with feeding and for 24, 22, and 14% in the prednisone, rhGH, and combined treatment groups, respectively. These data suggest that the stimulation of albumin synthesis observed during feeding prevents irreversible oxidative losses of a significant fraction of ingested essential amino acids and may serve as a vehicle to capture excess dietary amino acids and transport them to peripheral tissues to sustain local protein synthesis.

Relation between plasma and tissue parameters of leucine metabolism in fed and starved rats

1986 ◽  
Vol 250 (6) ◽  
pp. E615-E621 ◽  
Author(s):  
J. A. Vazquez ◽  
H. S. Paul ◽  
S. A. Adibi
Keyword(s):  
Continuous Infusion ◽  
Total Protein ◽  
Specific Activity ◽  
Whole Body ◽  
Leucine Incorporation ◽  
Body Protein ◽  
Leucine Metabolism ◽  
Leucine Oxidation ◽  
The Difference ◽  
Plasma Leucine

By use of a primed continuous infusion of [1-14C]leucine, we investigated parameters of leucine metabolism in plasma, expired air, and tissues of fed and 48-h starved rats. The ratios of muscle to plasma specific activity of alpha-ketoisocaproate (KIC) in fed and starved rats were not significantly different from 1. The ratio of muscle to plasma specific activity of leucine was also not significantly different from 1 in fed rats, but was significantly lower than 1 in starved rats. The rate of leucine oxidation was 28-34% higher when calculation was based on plasma KIC rather than leucine specific activity. However, starvation significantly increased the rate of leucine oxidation with either specific activity. The rates of leucine incorporation into whole-body protein, calculated as the difference between plasma leucine turnover and oxidation, were unaffected by starvation, but the incorporations into total protein measured directly were significantly decreased in liver and muscle. We conclude that leucine or KIC specific activity in muscle is better predicted by plasma KIC than leucine specific activity, and the difference between rates of plasma leucine turnover and oxidation does not appear to be a valid measurement of leucine incorporation into whole-body protein.

Changes in leucine kinetics during meal absorption: effects of dietary leucine availability

1986 ◽  
Vol 250 (6) ◽  
pp. E695-E701 ◽  
Author(s):  
S. Nissen ◽  
M. W. Haymond
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Branched Chain Amino Acids ◽  
Whole Body ◽  
Constant Infusion ◽  
Leucine Oxidation ◽  
Amino Acid Availability ◽  
Dietary Amino Acid ◽  
Branched Chain

Whole-body leucine and alpha-ketoisocaproate (KIC) metabolism were estimated in mature dogs fed a complete meal, a meal devoid of branched-chain amino acids, and a meal devoid of all amino acids. Using a constant infusion of [4,5-3H]leucine and alpha-[1-14C]ketoisocaproate (KIC), combined with dietary [5,5,5-2H3]leucine, the rate of whole-body proteolysis, protein synthesis, leucine oxidation, and interconversion of leucine and KIC were estimated along with the rate of leucine absorption. Ingestion of the complete meal resulted in a decrease in the rate of endogenous proteolysis, a small increase in the estimated rate of leucine entering protein, and a twofold increase in the rate of leucine oxidation. Ingestion of either the meal devoid of branched-chain amino acids or devoid of all amino acids resulted in a decrease in estimates of whole-body rates of proteolysis and protein synthesis, decreased leucine oxidation, and a decrease in the interconversion of leucine and KIC. The decrease in whole-body proteolysis was closely associated with the rise in plasma insulin concentrations following meal ingestion. Together these data suggest that the transition from tissue catabolism to anabolism is the result, at least in part, of decreased whole-body proteolysis. This meal-related decrease in proteolysis is independent of the dietary amino acid composition or content. In contrast, the rate of protein synthesis was sustained only when the meal complete in all amino acids was provided, indicating an overriding control of protein synthesis by amino acid availability.

Metabolic responses to nephrosis: effect of a low-protein diet

1994 ◽  
Vol 266 (3) ◽  
pp. F432-F438 ◽  
Author(s):  
E. J. Choi ◽  
J. Bailey ◽  
R. C. May ◽  
T. Masud ◽  
B. J. Maroni
Keyword(s):  
Weight Loss ◽  
Dietary Protein ◽  
Protein Diet ◽  
Nitrogen Excretion ◽  
Whole Body ◽  
Protein Catabolism ◽  
Body Protein ◽  
Leucine Oxidation ◽  
Oxidation Rates ◽  
And Control

To determine whether dietary protein restriction (LPD) causes protein catabolism in adriamycin nephrosis, nephrotic and control rats were paired by weight and gavage fed an 8.5% protein diet for 3 days (protocol 1) or 12 days (protocol 2). Fasting whole body protein turnover was then measured using a constant infusion of L-[1-14C]leucine. After 3 days of LPD, proteinuria decreased slightly and body weight did not change in either group. In contrast, leucine oxidation and urinary urea nitrogen excretion in nephrotic rats decreased by 18% and 37%, respectively (P < or = 0.05). After 12 days of LPD, weight loss did not differ between groups. In contrast to protocol 1, proteinuria decreased by 45% in nephrotic rats fed LPD for 12 days, and leucine oxidation rats increased to the level of control rats. Rates of whole body protein synthesis (PS) and degradation (PD) did not differ between nephrotic and control rats receiving LPD for 3 or 12 days, but were significantly lower than rates measured in rats fed 22% protein. We conclude that 1) proteinuria stimulates protein conservation even when dietary protein intake is restricted; 2) the decrease in amino acid oxidation was dependent on moderate proteinuria, since prolonged LPD ameliorated nephrosis and leucine oxidation rates increased to control levels; and 3) since weight loss and rates of whole body PS and PD in nephrotic and control animals were indistinguishable, moderate proteinuria did not increase protein catabolism.

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