Postprandial metabolic utilization of intact and hydrolyzed casein in humans

• Published in: The FASEB journal 2007-04, Vol.21 (5), p.A333-A333
• Main Authors: Amelie, Deglaire, Cecile, Bos, Gheorge, Airinei, Catherine, Luengo, Robert, Benamouzig, Jacques, Fauquant, Claire, Gaudichon, Paul, Moughan J, Daniel, Tome
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.21.5.A333-c

In a view to better understand the determinants of postprandial nitrogen (N) metabolism, we assessed the postprandial retention and oxidation of dietary N after ingestion of intact or hydrolyzed casein in humans. For this purpose, 10 healthy adult volunteers equipped with a naso‐intestinal tube ingested 15N‐labeled casein (30g) either intact (CA) or hydrolyzed (CH) in a mixed meal (700 kcal). Digesta, plasma and urine were sampled for 8 h after meal ingestion. Dietary N recovered at the terminal ileum was higher during the first 3h in CH than in CA. The real ileal digestibility was 93.9±1.5% (SD) for CA and 90.8±4.0% for CH. The appearance of 15N‐amino acids (AA) in the plasma of CH peaked at 3h, whereas for CA a plateau was reached only 5h postprandially. The incorporation of dietary N at 8h into serum protein was similar for CA and CH (8.9±2.6%). The deamination of casein‐derived AA, determined in the body and urinary urea pools, was faster but lower for CH than for CA. Endogenous urea production was 90% higher in CH than in CA. Finally, the net postprandial protein utilization ((N absorbed‐N deaminated)/N ingested) was similar for CA and CH (73.9±7.4%). In contrast to previous observations, the faster systemic appearance of dietary amino acids did not lead to a decrease in dietary N retention, however CA and CH were associated with different urea production rates and presumably urea recycling fluxes in the postprandial phase.