Hydrolyzed dietary casein as compared with the intact protein reduces postprandial peripheral, but not whole-body, uptake of nitrogen in humans.
BACKGROUND
Compared with slow proteins, fast proteins are more completely extracted in the splanchnic bed but contribute less to peripheral protein accretion; however, the independent influence of absorption kinetics and the amino acid (AA) pattern of dietary protein on AA anabolism in individual tissues remains unknown.


OBJECTIVE
We aimed to compare the postprandial regional utilization of proteins with similar AA profiles but different absorption kinetics by coupling clinical experiments with compartmental modeling.


METHODS
Experimental data pertaining to the intestine, blood, and urine for dietary nitrogen kinetics after a 15N-labeled intact (IC) or hydrolyzed (HC) casein meal were obtained in parallel groups of healthy adults (n = 21) and were analyzed by using a 13-compartment model to predict the cascade of dietary nitrogen absorption and regional metabolism.


RESULTS
IC and HC elicited a similar whole-body postprandial retention of dietary nitrogen, but HC was associated with a faster rate of absorption than was IC, resulting in earlier and stronger hyperaminoacidemia and hyperinsulinemia. An enhancement of both catabolic (26%) and anabolic (37%) utilization of dietary nitrogen occurred in the splanchnic bed at the expense of its further peripheral availability, which reached 18% and 11% of ingested nitrogen 8 h after the IC and HC meals, respectively.


CONCLUSIONS
The form of delivery of dietary AAs constituted an independent factor of modulation of their postprandial regional metabolism, with a fast supply favoring the splanchnic dietary nitrogen uptake over its peripheral anabolic use. These results question a possible effect of ingestion of protein hydrolysates on tissue nitrogen metabolism and accretion. This trial was registered at clinicaltrials.gov as NCT00873951.
Deglaire
Amélie
A
INRA, CRNH-IdF, UMR914 Nutrition Physiology and Ingestive Behavior, Paris, France.
Fromentin
Claire
C
Fouillet
Hélène
H
Airinei
Gheorghe
G
Gaudichon
Claire
C
Boutry
Claire
C
Benamouzig
Robert
R
Moughan
Paul J
PJ
Tomé
Daniel
D
Bos
Cécile
C
D000328:Adult; D000596:Amino Acids / Q000493:pharmacokinetics*; D001775:Blood Circulation / Q000502:physiology; D002364:Caseins / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D006868:Hydrolysis; D006946:Hyperinsulinism / Q000209:etiology; D007408:Intestinal Absorption / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009584:Nitrogen / Q000493:pharmacokinetics*; D019518:Postprandial Period; D013152:Splanchnic Circulation / Q000502:physiology
D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D009584:Nitrogen