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Digested formula but not digested fresh human milk causes death of intestinal cells in vitro: implications for
Alexander H Penn1, Angelina E Altshuler, James W Small
1Department of Bioengineering, University of California, San Diego, La Jolla, California, USA. apenn@bioeng.ucsd.edu
Insights
Formula digestion releases cytotoxic free fatty acids (FFAs) that harm infant intestines, unlike breast milk. This finding may explain why premature infants fed formula have higher rates of necrotizing enterocolitis (NEC).
Area of Science:
- Neonatal nutrition
- Gastrointestinal physiology
- Cellular toxicology
Background:
- Premature infants fed formula face higher necrotizing enterocolitis (NEC) risk compared to breastfed infants.
- The mechanisms behind intestinal necrosis in NEC and breast milk's protective effects remain unclear.
- A hypothesis suggests formula, post-lipase digestion, contains cytotoxic free fatty acids (FFAs) absent in fresh breast milk.
Purpose of the Study:
- To investigate the role of free fatty acids (FFAs) in the pathogenesis of necrotizing enterocolitis (NEC).
- To compare the cytotoxic effects of digested formula versus breast milk on intestinal cells and neutrophils.
Main Methods:
- Infant formulas and human milk were digested using pancreatic lipase, proteases, or rat intestinal luminal fluid.
- In vitro assays assessed FFA levels and cytotoxicity on intestinal epithelial cells, endothelial cells, and neutrophils.
- Lipase inhibitors and FFA-binding treatments were used to evaluate their protective effects.
Main Results:
- Lipase digestion of formula, but not milk, induced significant cell death in neutrophils, endothelial cells, and epithelial cells.
- Digested formula exhibited significantly higher FFA levels compared to digested milk.
- Pretreatment with lipase inhibitors or FFA-binding agents reduced formula-induced cytotoxicity.
Conclusions:
- Free fatty acid-induced cytotoxicity is a potential contributor to necrotizing enterocolitis (NEC) development.
- These findings highlight a key difference in the intestinal response to formula versus breast milk in premature infants.
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.
Conclusion:
FFA-induced cytotoxicity may contribute to the pathogenesis of NEC.
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