Increasing habitual protein intake results in reduced postprandial efficiency of peripheral, anabolic wheat protein nitrogen use in humans.
BACKGROUND
The postprandial retention of dietary protein decreases when the prevailing protein intake increases.


OBJECTIVE
We investigated the influence of the prevailing protein intake on the regional utilization and anabolic use of wheat protein during the postprandial non-steady state in humans.


METHODS
Healthy adults (n = 8) were adapted for 7 d, first to a normal-protein diet (NP: 1 g x kg(-1) x d(-1)) and then to a high-protein diet (HP: 2 g x kg(-1) x d(-1)). After each adaptation period, the subjects received the same single, solid mixed meal containing [15N]-labeled wheat protein. The postprandial kinetics of dietary nitrogen were then measured for 8 h in blood and urine. These data were further analyzed by using a multicompartmental model to predict the postprandial kinetics of dietary nitrogen in unsampled pools.


RESULTS
The postprandial whole-body retention of wheat protein nitrogen, measured 8 h after meal ingestion, decreased by 10% when the subjects switched from the NP diet to the HP diet. According to modeling results, this resulted from an increased splanchnic utilization of dietary nitrogen for urea production, whereas its incorporation into splanchnic proteins was unchanged, leading to a 20-30% decrease in peripheral availability and anabolic use in HP-adapted compared with NP-adapted subjects having ingested the same protein load.


CONCLUSIONS
By combining clinical experimentation with compartmental modeling, we provide a global overview of postprandial dietary protein metabolism. Increasing prior protein intake was shown to reduce the postprandial retention of wheat protein nitrogen, mainly by diminishing the efficiency of its peripheral availability and anabolic use.
Juillet
Barbara
B
INRA, AgroParisTech, UMR914 Nutrition Physiology and Ingestive Behavior, CRNH-IdF, Paris, France.
Fouillet
Hélène
H
Bos
Cécile
C
Mariotti
François
F
Gausserès
Nicolas
N
Benamouzig
Robert
R
Tomé
Daniel
D
Gaudichon
Claire
C
D000222:Adaptation, Physiological; D000328:Adult; D019540:Area Under Curve; D001806:Blood Urea Nitrogen; D018592:Cross-Over Studies; D004044:Dietary Proteins / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes; D009751:Nutritional Requirements; D019518:Postprandial Period; D014908:Triticum
D004044:Dietary Proteins; D009587:Nitrogen Isotopes; D009584:Nitrogen