title: Intraileal casein infusion increases plasma concentrations of amino acids in humans: A randomized cross over trial.
abstract: Activation of the ileal brake by casein induces satiety signals and reduces energy intake. However, adverse effects of intraileal casein administration have not been studied before. These adverse effects may include impaired amino acid digestion, absorption and immune activation.
  
  
  
  To investigate the effects of intraileal infusion of native casein on plasma amino acid appearance, immune activation and gastrointestinal (GI) symptoms.
  
  
  
  A randomized single-blind cross over study was performed in 13 healthy subjects (6 male; mean age 26 ± 2.9 years; mean body mass index 22.8 ± 0.4 kg/m-2), who were intubated with a naso-ileal feeding catheter. Thirty minutes after intake of a standardized breakfast, participants received an ileal infusion, containing either control (C) consisting of saline, a low-dose (17.2 kcal) casein (LP) or a high-dose (51.7 kcal) of casein (HP) over a period of 90 min. Blood samples were collected for analysis of amino acids (AAs), C-reactive protein (CRP), pro-inflammatory cytokines and oxylipins at regular intervals. Furthermore, GI symptom questionnaires were collected before, during and after ileal infusion.
  
  
  
  None of the subjects reported any GI symptoms before, during or after ileal infusion of C, LP and HP. Plasma concentrations of all AAs analyzed were significantly increased after infusion of HP as compared to C (p < 0.001), and most AAs were increased after infusion of LP (p < 0.001). In total, 12.49 ± 1.73 and 3.18 ± 0.87 g AAs were found in plasma after intraileal infusion of HP and LP, corresponding to 93 ± 13% (HP) and 72 ± 20% (LP) of AAs infused as casein, respectively. Ileal casein infusion did not affect plasma concentrations of CRP, IL-6, IL-8, IL-1β and TNF-α. Infusion of HP resulted in a decreased concentration of 11,12-dihydroxyeicosatrienoic acid whereas none of the other oxylipins analyzed were affected.
  
  
  
  A single intraileal infusion of native casein results in a concentration and time dependent increase of AAs in plasma, suggesting an effective digestion and absorption of AAs present in casein. Also, ileal infusion did not result in immune activation nor in GI symptoms. CLINICALTRIALS.GOV: NCT01509469.
authors.affiliation: Top Institute Food and Nutrition, Wageningen, The Netherlands; The Netherlands Organization for Applied Scientific Research, TNO, Zeist, The Netherlands; Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands. Electronic address: dina.ripken@tno.nl.
authors.forename: Dina
authors.initials: D
authors.lastname: Ripken
authors.affiliation: Top Institute Food and Nutrition, Wageningen, The Netherlands; Division of Gastroenterology-Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Mark
authors.initials: M
authors.lastname: van Avesaat
authors.affiliation: Division of Gastroenterology-Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Freddy J
authors.initials: FJ
authors.lastname: Troost
authors.affiliation: Division of Gastroenterology-Hepatology, Department of Internal Medicine, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Ad A
authors.initials: AA
authors.lastname: Masclee
authors.affiliation: Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: Renger F
authors.initials: RF
authors.lastname: Witkamp
authors.affiliation: Top Institute Food and Nutrition, Wageningen, The Netherlands.
authors.forename: Henk F
authors.initials: HF
authors.lastname: Hendriks
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000097:blood; D000328:Adult; D000596:Amino Acids / Q000097:blood*; D062408:Breakfast; D002097:C-Reactive Protein / Q000378:metabolism; D002364:Caseins / Q000008:administration & dosage*; D018592:Cross-Over Studies; D016207:Cytokines / Q000097:blood; D004063:Digestion; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007082:Ileum / Q000378:metabolism; D007441:Intubation, Gastrointestinal; D008297:Male; D012527:Satiation; D016037:Single-Blind Method; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: C410128:11,12-dihydroxyeicosatrienoic acid; D000596:Amino Acids; D002364:Caseins; D016207:Cytokines; D002097:C-Reactive Protein; D015126:8,11,14-Eicosatrienoic Acid
keywords: Amino acid absorption; Ileal brake; Protein