title: Hydrolysis of casein accelerates gastrointestinal transit via reduction of opioid receptor agonists released from casein in rats.
abstract: BACKGROUND
  Protein hydrolysate accelerates gastrointestinal transit (GIT) and feeding advancement in preterm infants compared to native protein. In rat pups, opioid receptor agonists released from casein during digestion such as beta-casomorphins slow down GIT. We hypothesized that hydrolysis of casein reduces the opioid activity released during digestion thereby accelerating GIT compared to native casein.
  
  
  OBJECTIVE
  The aim of the present study was to investigate whether casein hydrolysate accelerates GIT compared to native casein and whether pretreatment with naloxone, an opioid receptor blocker, abolishes this difference in rat pups.
  
  
  METHODS
  In a randomized controlled trial following a 2 x 2 factorial design, 216 female Wistar rat pups were fed with pellets based on hydrolyzed or native casein. After pretreatment with naloxone or normal saline, carmine red was administered by oro-gastric gavage as a tracer for GIT velocity measurement. Four hours later the animals were sacrificed, their intestine was removed and the length of the colon from the cecocolonic junction to the anus was measured. GIT was recorded as percentage of the total colonic length (percentage of colonic transit) passed by carmine red. Data were given as mean +/- SD.
  
  
  RESULTS
  GIT was significantly higher with hydrolyzed casein compared to native casein formula (77.4 +/- 17 and 51.2 +/- 20%), but there was no difference after naloxone pretreatment (77.1 +/- 16 and 76.5 +/- 17%).
  
  
  CONCLUSIONS
  The present data suggest that hydrolysis of casein accelerates GIT via reduction of opioid activity released during digestion. Further studies are required to investigate to which extent these rat pub data apply to preterm infants.
authors.affiliation: Department of Pediatrics, Ulm University, Ulm, Germany. walter.mihatsch@medizin.uni-ulm.de
authors.forename: W A
authors.initials: WA
authors.lastname: Mihatsch
authors.forename: A R
authors.initials: AR
authors.lastname: Franz
authors.forename: B
authors.initials: B
authors.lastname: Kuhnt
authors.forename: J
authors.initials: J
authors.lastname: Högel
authors.forename: F
authors.initials: F
authors.lastname: Pohlandt
mesh_terms: D000818:Animals; D002364:Caseins / Q000378:metabolism* / Q000494:pharmacology*; D005260:Female; D005772:Gastrointestinal Transit / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000819:agonists*
chemical_list: D002364:Caseins; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D009270:Naloxone; C475729:casein hydrolysate