title: Endogenous human milk peptide release is greater after preterm birth than term birth.
abstract: BACKGROUND
  Hundreds of naturally occurring milk peptides are present in term human milk. Preterm milk is produced before complete maturation of the mammary gland, which could change milk synthesis and secretion processes within the mammary gland, leading to differences in protein expression and enzymatic activity, thereby resulting in an altered peptide profile.
  
  
  OBJECTIVE
  This study examined differences in peptides present between milk from women delivering at term and women delivering prematurely.
  
  
  METHODS
  Nano-LC tandem mass spectrometry was employed to identify naturally occurring peptides and compare their abundances between term and preterm human milk samples at multiple time points over lactation. Term milk samples were collected from 8 mothers and preterm milk was collected from 14 mothers. The 28 preterm and 32 term human milk samples were divided into 4 groups based on day of collection (<14, 14-28, 29-41, and 42-58 d).
  
  
  RESULTS
  Preterm milk peptide counts, ion abundance, and concentration were significantly higher in preterm milk than term milk. Bioinformatic analysis of the cleavage sites for peptides identified suggested that plasmin was more active in preterm milk than term milk and that cytosol aminopeptidase and carboxypeptidase B2 likely contribute to extensive milk protein breakdown. Many identified milk peptides in both term and preterm milk overlapped with known functional peptides, including antihypertensive, antimicrobial, and immunomodulatory peptides.
  
  
  CONCLUSIONS
  The high protein degradation by endogenous proteases in preterm milk might attenuate problems because of the preterm infant's immature digestive system. This trial was registered at clinicaltrials.gov as NCT01817127.
authors.affiliation: Department of Food Science and Technology Foods for Health Institute dcdallas@ucdavis.edu.
authors.forename: David C
authors.initials: DC
authors.lastname: Dallas
authors.affiliation: Dairy Science and Technology Group, Wageningen University and Research Centre, Wageningen, The Netherlands.
authors.forename: Christina J
authors.initials: CJ
authors.lastname: Smink
authors.affiliation: Department of Food Science and Technology.
authors.forename: Randall C
authors.initials: RC
authors.lastname: Robinson
authors.affiliation: Department of Food Science and Technology.
authors.forename: Tian
authors.initials: T
authors.lastname: Tian
authors.affiliation: Department of Chemistry, and.
authors.forename: Andres
authors.initials: A
authors.lastname: Guerrero
authors.affiliation: Department of Chemistry, and.
authors.forename: Evan A
authors.initials: EA
authors.lastname: Parker
authors.affiliation: Department of Food Science and Technology Foods for Health Institute.
authors.forename: Jennifer T
authors.initials: JT
authors.lastname: Smilowitz
authors.affiliation: Dairy Science and Technology Group, Wageningen University and Research Centre, Wageningen, The Netherlands.
authors.forename: Kasper A
authors.initials: KA
authors.lastname: Hettinga
authors.affiliation: Department of Pediatrics, University of California, Davis, Davis, CA; and.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Underwood
authors.affiliation: Foods for Health Institute Department of Chemistry, and.
authors.forename: Carlito B
authors.initials: CB
authors.lastname: Lebrilla
authors.affiliation: Department of Food Science and Technology Foods for Health Institute.
authors.forename: J Bruce
authors.initials: JB
authors.lastname: German
authors.affiliation: Department of Food Science and Technology Foods for Health Institute.
authors.forename: Daniela
authors.initials: D
authors.lastname: Barile
mesh_terms: D002853:Chromatography, Liquid; D005069:Evaluation Studies as Topic; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007774:Lactation; D008894:Milk Proteins / Q000378:metabolism; D008895:Milk, Human / Q000737:chemistry*; D010455:Peptides / Q000378:metabolism*; D047928:Premature Birth; D011446:Prospective Studies; D053719:Tandem Mass Spectrometry; D047929:Term Birth
chemical_list: D008894:Milk Proteins; D010455:Peptides
keywords: carboxypeptidase B2; cytosol aminopeptidase; functional peptide; human milk; mass spectrometry; peptidomics; plasmin; premature; term