Measurement of the synthesis of liver-produced plasma proteins with special reference to their regulation by dietary protein and amino acid supply

Prior studies have reported that dietary protein dilution (DPD) or amino acid dilution promotes heightened water intake (i.e., hyperdipsia) however, the exact dietary requirements and the mechanism responsible for this effect are still unknown. Here, we show that dietary amino acid (AA) restriction is sufficient and required to drive hyperdipsia during DPD. Our studies demonstrate that particularly dietary essential AA (EAA) restriction, but not non-EAA, is responsible for the hyperdipsic effect of total dietary AA restriction (DAR). Additionally, by using diets with varying amounts of individual EAA under constant total AA supply, we demonstrate that restriction of threonine (Thr) or tryptophan (Trp) is mandatory and sufficient for the effects of DAR on hyperdipsia and that liver-derived fibroblast growth factor 21 (FGF21) is required for this hyperdipsic effect. Strikingly, artificially introducing Thr de novo biosynthesis in hepatocytes reversed hyperdipsia during DAR. In summary, our results show that the DPD effects on hyperdipsia are induced by the deprivation of Thr and Trp, and in turn, via liver/hepatocyte-derived FGF21.

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Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects

Proceedings of The Nutrition Society ◽

10.1017/s0029665120008034 ◽

2021 ◽

pp. 1-9

Author(s):

Jorn Trommelen ◽

Andrew M. Holwerda ◽

Philippe J. M. Pinckaers ◽

Luc J. C. van Loon

Keyword(s):

Protein Synthesis ◽

Amino Acid ◽

Stable Isotope ◽

Dietary Protein ◽

Protein Metabolism ◽

Muscle Protein ◽

Human Subjects ◽

Whole Body ◽

Body Protein

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.

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Ileal amino acid digestibility of some novel dietary protein sources for growing chickens

Journal of the Science of Food and Agriculture ◽

10.1002/jsfa.2657 ◽

2006 ◽

Vol 86 (15) ◽

pp. 2603-2608 ◽

Cited By ~ 5

Author(s):

Velmurugu Ravindran ◽

Patrick CH Morel

Keyword(s):

Amino Acid ◽

Dietary Protein ◽

Protein Sources

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Dietary protein paradox: decrease of amino acid availability induced by high-protein diets

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1993.264.6.g1057 ◽

1993 ◽

Vol 264 (6) ◽

pp. G1057-G1065 ◽

Cited By ~ 11

Author(s):

C. Moundras ◽

C. Remesy ◽

C. Demigne

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Dietary Protein ◽

High Protein ◽

Glutamine Metabolism ◽

Metabolic Adaptation ◽

Casein Diet ◽

Serine Dehydratase ◽

High Protein Diets ◽

Protein Diets

The aim of the present study was to evaluate the effect of changes in dietary protein level on overall availability of amino acids for tissues. For this purpose, rats were adapted to diets containing various concentrations of casein (7.5, 15, 30, and 60%) and were sampled either during the postprandial or postabsorptive period. In rats fed the protein-deficient diet, glucogenic amino acids (except threonine) tended to accumulate in plasma, liver, and muscles. In rats fed high-protein diets, the hepatic balance of glucogenic amino acids was markedly enhanced and their liver concentrations were consistently depressed. This response was the result of a marked induction of amino acid catabolism (a 45-fold increase of liver threonine-serine dehydratase activity was observed with the 60% casein diet). The muscle concentrations of threonine, serine, and glycine underwent changes parallel to plasma and liver concentrations, and a significant reduction of glutamine was observed. During the postabsorptive period, adaptation to high-protein diets resulted in a sustained catabolism of most glucogenic amino acids, which accentuated the drop in their concentrations (especially threonine) in all the compartments studied. The time course of metabolic adaptation from a 60 to a 15% casein diet has also been investigated. Adaptation of alanine and glutamine metabolism was rapid, whereas that of threonine, serine, and glycine was delayed and required 7-11 days. This was paralleled by a relatively slow decay of liver threonine-serine dehydratase (T-SDH) activity in contrast to the rapid adaptation of pyruvate kinase activity after refeeding a high-carbohydrate diet.(ABSTRACT TRUNCATED AT 250 WORDS)

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Dietary efficiency of natural, semi-synthetic and synthetic diets with special reference to qualitative amino acid requirements of the Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae)

Journal of Stored Products Research ◽

10.1016/0022-474x(68)90016-7 ◽

1968 ◽

Vol 4 (3) ◽

pp. 249-257 ◽

Cited By ~ 8

Author(s):

A.K. Bhattacharya ◽

N.C. Pant

Keyword(s):

Amino Acid ◽

Special Reference ◽

Trogoderma Granarium ◽

Khapra Beetle ◽

Amino Acid Requirements

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The effect of feeding high levels of low-quality proteins to growing chickens

British Journal Of Nutrition ◽

10.1017/s0007114575000426 ◽

1975 ◽

Vol 34 (3) ◽

pp. 363-373 ◽

Cited By ~ 20

Author(s):

E. Wetnli ◽

T. R. Morris ◽

T. P. Shresta

Keyword(s):

Growth Rate ◽

Amino Acid ◽

Dietary Protein ◽

Soya Bean ◽

Maximum Efficiency ◽

Food Utilization ◽

The Third ◽

Bean Meal ◽

Groundnut Meal ◽

Soya Bean Meal

1. Three growth trials were done using male broiler chicks. In the first two trials, groundnut meal was used, with and without supplementary methionine and lysine. In the third trial, soya-bean meal was used with and without supplementary methionine. Protein levels ranged in the first trial from 120 to 420 g/kg diet and in the third trial from 120 to 300 g/kg diet. Thus the assumed minimal amino acid requirements of the chick were supplied by high levels of low-quality dietary protein.2. Diets based on cereals and groundnut meal did not support maximum live-weight gain or maximum efficiency of food utilization at any level of dietary protein. When the principal deficiencies of lysine and methionine were corrected, this protein mixture was capable of supporting the same growth rate as a control diet of cereals and herring meal.3. Diets based on maize and soya-bean meal did not support quite the same growth rate as similar diets supplemented with methionine, even though the protein level in the unsupplemented diets was sufficient to meet the assumed methionine requirements.4. These results are interpreted as examples of amino acid imbalance in diets composed of familiar feeding-stuffs. It is concluded that one cannot assume that the poor quality of a protein source can always be offset by increasing the concentration of dietary protein.

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