Acute postprandial changes in leucine metabolism as assessed with an intrinsically labeled milk protein

Boirie‌, Yves; Gachon, Pierre; Corny, S.; Fauquant, Jacques; Maubois, J.L.; Beaufrère, B.

doi:10.1152/ajpendo.1996.271.6.e1083

Cited by 112 publications

(164 citation statements)

References 11 publications

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“…When the non-steady-state equations of Shipley & Clarke (1972) were applied to the fasting± feeding data of el Khoury et al (1995b), taking account of changes in the plasma leucine concentration as a measure of changes in the free leucine pool, the increase in synthesis in response to a meal was substantially greater than that obtained by the usual method of calculation (Waterlow, 1995). This conclusion is supported by a study of Boirie et al (1996), who fed a single meal containing labelled protein. Applying the non-steady-state equations, they showed that the response to the meal was an increase in synthesis with little change in breakdown.…”

Section: Fasting and Feedingmentioning

confidence: 72%

The mysteries of nitrogen balance

Waterlow¹

1999

Nutr. Res. Rev.

113

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The ®rst part of this review is concerned with the balance between N input and output as urinary urea. I start with some observations on classical biochemical studies of the operation of the urea cycle. According to Krebs, the cycle is instantaneous and automatic, as a result of the irreversibility of the ®rst enzyme, carbamoyl-phosphate synthetase 1 (EC 6.3.5.5; CPS-I), and it should be able to handle many times the normal input to the cycle. It is now generally agreed that acetyl glutamate is a necessary co-factor for CPS-1, but not a regulator. There is abundant evidence that changes in dietary protein supply induce coordinated changes in the amounts of all ®ve urea-cycle enzymes. How this coordination is achieved, and why it should be necessary in view of the properties of the cycle mentioned above, is unknown. At the physiological level it is not clear how a change in protein intake is translated into a change of urea cycle activity. It is very unlikely that the signal is an alteration in the plasma concentration either of total amino-N or of any single amino acid. The immediate substrates of the urea cycle are NH 3 and aspartate, but there have been no measurements of their concentration in the liver in relation to urea production. Measurements of urea kinetics have shown that in many cases urea production exceeds N intake, and it is only through transfer of some of the urea produced to the colon, where it is hydrolysed to NH 3 , that it is possible to achieve N balance. It is beginning to look as if this process is regulated, possibly through the operation of recently discovered urea transporters in the kidney and colon. The second part of the review deals with the synthesis and breakdown of protein. The evidence on whole-body protein turnover under a variety of conditions strongly suggests that the components of turnover, including amino acid oxidation, are in¯uenced and perhaps regulated by amino acid supply or amino acid concentration, with insulin playing an important but secondary role. Molecular biology has provided a great deal of information about the complex processes of protein synthesis and breakdown, but so far has nothing to say about how they are coordinated so that in the steady state they are equal. A simple hypothesis is proposed to ®ll this gap, based on the self-evident fact that for two processes to be coordinated they must have some factor in common. This common factor is the amino acid pool, which provides the substrates for synthesis and represents the products of breakdown. The review concludes that although the achievement and maintenance of N balance is a fact of life that we tend to take for granted, there are many features of it that are not understood, principally the control of urea production and excretion to match the intake, and the coordination of protein synthesis and breakdown to maintain a relatively constant lean body mass.

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Section: Fasting and Feedingmentioning

confidence: 72%

The mysteries of nitrogen balance

Waterlow¹

1999

Nutr. Res. Rev.

113

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“…Additionally in humans, the ingestion of rapidly absorbed whey proteins results in an enhanced postprandial whole body protein synthesis and oxidation rate than those measured following the ingestion of the slowly absorbed casein. Since the oxidation rate is increased to a greater extent than the synthesis rate, this leads to a reduced net 13 C-leucine balance during the 7 h following the meal [2,32]. This suggests that the postprandial protein deposition would be reduced with non clotting diets as compared to clotting ones.…”

Section: Discussionmentioning

confidence: 99%

The incorporation of solubilized wheat proteins in milk replacers for veal calves: effects on growth performance and muscle oxidative capacity

et al. 2003

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-Replacement of skim milk proteins by solubilized wheat protein (SWP) in milk replacers for veal calves would contribute to the reduction in feeding costs. The occurrence of metabolic disorders has, however, been reported. Forty-two male calves received one of three treatments over 140 days: a control diet, a diet containing SWP without or with branched-chain amino acid supplementation. Liveweight gain, carcass yield, color and conformation did not show any significant differences. No metabolic disorders were noted. Supplementation with branched-chain amino acids reduced the marginal Val deficiency but did not modify the growth performances. With the SWP containing diets, the plasma metabolite profile was characteristic of those observed with non-clotting diets. It was statistically correlated to the changes in the orientation of the Semitendinosus muscle energy metabolism towards a more oxidative type and to indications of a lower efficiency of amino acid utilisation for protein deposition. At the present levels of inclusion, SWP proved to be an interesting alternative to the sole use of whey as the protein source in milk replacers for veal calves.veal / preruminant calf / wheat proteins / milk replacer / growth / blood parameters Reprod. Nutr. Dev. 43 (2003) 57-76 57

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“…Total, exogenous, and endogenous phenylalanine rate of appearance (R a) and plasma availability of dietary phenylalanine (i.e., fraction of dietary phenylalanine that appeared in the systemic circulation, Pheplasma) were calculated using modified Steele's equations (6,9). These parameters were calculated as follows:…”

Section: H5]phenylalanine and L-[ring-mentioning

confidence: 99%

“…So far, no study has assessed the impact of ingesting different amounts of whey protein on protein digestion and absorption kinetics, whole body protein balance, and postprandial muscle protein synthesis rates in older adults. Because the metabolic fate of amino acids ingested as dietary protein cannot be assessed by oral or intravenous administration of labeled free amino acids (6,8), we specifically produced intrinsically labeled whey protein by infusing cows with large quantities of L- [1-13 C]phenylalanine, collecting milk, and purifying the whey protein fraction (21). The use of intrinsically labeled whey protein allowed us to assess the impact of ingesting different amounts of whey protein on in vivo protein digestion and absorption kinetics and subsequent muscle protein accretion without the need for extensive assumptions and extrapolations.…”

mentioning

confidence: 99%

Amino acid absorption and subsequent muscle protein accretion following graded intakes of whey protein in elderly men

Pennings

Groen

Lange³

et al. 2012

American Journal of Physiology-Endocrinology and Metabolism

284

228

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Whey protein ingestion has been shown to effectively stimulate postprandial muscle protein accretion in older adults. However, the impact of the amount of whey protein ingested on protein digestion and absorption kinetics, whole body protein balance, and postprandial muscle protein accretion remains to be established. We aimed to fill this gap by including 33 healthy, older men (73 ± 2 yr) who were randomly assigned to ingest 10, 20, or 35 g of intrinsically l-[1-13C]phenylalanine-labeled whey protein ( n = 11/treatment). Ingestion of labeled whey protein was combined with continuous intravenous l-[ ring-2H5]phenylalanine and l-[ ring-2H2]tyrosine infusion to assess the metabolic fate of whey protein-derived amino acids. Dietary protein digestion and absorption rapidly increased following ingestion of 10, 20, and 35 g whey protein, with the lowest and highest (peak) values observed following 10 and 35 g, respectively ( P < 0.05). Whole body net protein balance was positive in all groups (19 ± 1, 37 ± 2, and 58 ± 2 μmol/kg), with the lowest and highest values observed following ingestion of 10 and 35 g, respectively ( P < 0.05). Postprandial muscle protein accretion, assessed by l-[1-13C]phenylalanine incorporation in muscle protein, was higher following ingestion of 35 g when compared with 10 ( P < 0.01) or 20 ( P < 0.05) g. We conclude that ingestion of 35 g whey protein results in greater amino acid absorption and subsequent stimulation of de novo muscle protein synthesis compared with the ingestion of 10 or 20 g whey protein in healthy, older men.

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Acute postprandial changes in leucine metabolism as assessed with an intrinsically labeled milk protein

Cited by 112 publications

References 11 publications

The mysteries of nitrogen balance

The mysteries of nitrogen balance

The incorporation of solubilized wheat proteins in milk replacers for veal calves: effects on growth performance and muscle oxidative capacity

Amino acid absorption and subsequent muscle protein accretion following graded intakes of whey protein in elderly men

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