Sequential release of milk protein―derived bioactive peptides in the jejunum in healthy humans

• Published in: The American journal of clinical nutrition 2013-06, Vol.97 (6), p.1314-1323
• Main Authors: BOUTROU, Rachel, GAUDICHON, Claire, DUPONT, Didier, JARDIN, Julien, AIRINEI, Gheorghe, MARSSET-BAGLIERI, Agnes, BENAMOUZIG, Robert, TOME, Daniel, LEONIL, Joëlle
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Biological and medical sciences; Caseins - analysis; Caseins - metabolism; Chromatography, Liquid; Diet; Dietary Proteins - administration & dosage; Digestion; Digestive system; Endorphins - analysis; Endorphins - metabolism; Feeding. Feeding behavior; Female; Food and Nutrition; Fundamental and applied biological sciences. Psychology; Humans; Hydrolysis; Intestinal Mucosa - metabolism; Jejunum - metabolism; Kinetics; Life Sciences; Male; Mass spectrometry; Meals; Milk Proteins - analysis; Milk Proteins - metabolism; Nitrogen - analysis; Nitrogen - metabolism; Nutrition; Peptides; Peptides - metabolism; Proteins; Single-Blind Method; Tandem Mass Spectrometry; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Whey Proteins; Young Adult
• ISSN: 0002-9165; 1938-3207
• DOI: 10.3945/ajcn.112.055202

The digestive hydrolysis of dietary proteins leads to the release of peptides in the intestinal tract, where they may exert a variety of functions, but their characterization and quantification are difficult. We aimed to characterize and determine kinetics of the formation of peptides present in the jejunum of humans who ingested casein or whey proteins by using mass spectrometry and to look for and quantify bioactive peptides. Subjects were equipped with a double-lumen nasogastric tube that migrated to the proximal jejunum. A sample collection was performed for 6 h after the ingestion of 30 g (15)N-labeled casein (n = 7) or whey proteins (WPs; n = 6). Nitrogen flow rates were measured, and peptides were identified by using mass spectrometry. After casein ingestion, medium-size peptides (750-1050 kDa) were released during 6 h, whereas larger peptides (1050-1800 kDa) were released from WPs in the first 3 h. A total of 356 and 146 peptides were detected and sequenced in the jejunum after casein and WP ingestion, respectively. β-casein was the most important precursor of peptides, including bioactive peptides with various activities. The amounts of β-casomorphins (β-casein 57-, 58-, 59-, and 60-66) and β-casein 108-113 released on the postprandial window were sufficient to elicit the biological action of these peptides (ie, opioid and antihypertensive, respectively). Clear evidence is shown of the presence of bioactive peptides in the jejunum of healthy humans who ingested casein. Our findings raise the question about the physiologic conditions under which these peptides can express their bioactivity in humans. This trial was registered at clinicaltrials.gov as NCT00862329.