title: Digested formula but not digested fresh human milk causes death of intestinal cells in vitro: implications for necrotizing enterocolitis.
abstract: BACKGROUND
  Premature infants fed formula are more likely to develop necrotizing enterocolitis (NEC) than those who are breastfed, but the mechanisms of intestinal necrosis in NEC and protection by breast milk are unknown. We hypothesized that after lipase digestion, formula, but not fresh breast milk, contains levels of unbound free fatty acids (FFAs) that are cytotoxic to intestinal cells.
  
  
  METHODS
  We digested multiple term and preterm infant formulas or human milk with pancreatic lipase, proteases (trypsin and chymotrypsin), lipase + proteases, or luminal fluid from a rat small intestine and tested FFA levels and cytotoxicity in vitro on intestinal epithelial cells, endothelial cells, and neutrophils.
  
  
  RESULTS
  Lipase digestion of formula, but not milk, caused significant death of neutrophils (ranging from 47 to 99% with formulas vs. 6% with milk) with similar results in endothelial and epithelial cells. FFAs were significantly elevated in digested formula vs. milk and death from formula was significantly decreased with lipase inhibitor pretreatment, or treatments to bind FFAs. Protease digestion significantly increased FFA binding capacity of formula and milk but only enough to decrease cytotoxicity from milk.
  
  
  CONCLUSIONS
  FFA-induced cytotoxicity may contribute to the pathogenesis of NEC.
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California, USA. apenn@bioeng.ucsd.edu
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Penn
authors.forename: Angelina E
authors.initials: AE
authors.lastname: Altshuler
authors.forename: James W
authors.initials: JW
authors.lastname: Small
authors.forename: Sharon F
authors.initials: SF
authors.lastname: Taylor
authors.forename: Karen R
authors.initials: KR
authors.lastname: Dobkins
authors.forename: Geert W
authors.initials: GW
authors.lastname: Schmid-Schönbein
mesh_terms: D000818:Animals; D002417:Cattle; D016923:Cell Death; D020345:Enterocolitis, Necrotizing / Q000209:etiology* / Q000473:pathology; D006801:Humans; D066298:In Vitro Techniques; D007225:Infant Food; D007231:Infant, Newborn; D007234:Infant, Premature; D008895:Milk, Human