Microlipid-induced oxidative stress in human breastmilk: in vitro effects on intestinal epithelial cells.

OBJECTIVES: To (1) determine whether medium chain fatty acids (Microlipid) added to human breastmilk generates reactive oxygen species (ROS), and (2) measure the physiological effect(s) of Microlipid) (ML)-supplemented human breastmilk in an enterocyte cell culture bioassay. METHODS: ML was added to milk according to manufacturer's recommendations and total hydroperoxides measured at intervals with the FOX 2 and TBARS assays. Physiological effects of supplementation were measured using a human enterocyte cell line (Caco-2BBE) and/or a primary human fetal intestinal cell culture (FHS-74 Int). Endpoints included: intracellular oxidative stress, transepithelial electrical resistance (TEER), apoptosis, and interleukin (IL)-6 production. RESULTS: Immediately postsupplementation, ML did not significantly increase ROS, as determined by both the FOX 2 and TBARS assays. Further, storage of milk + ML at 4 degrees C prevented significant increases in total hydroperoxides. However, by 4 hours postsupplementation at room temperature, both assays revealed significantly higher hydroperoxide and lipid peroxide levels. ML-supplemented milk stored at room temperature for 4 hours had the following effects in cell culture bioassays: elevated oxidative stress, increased rates of apoptosis, decreased transmembrane electrical resistance (TEER) values and, in both cell culture assays, significantly increased secretion of IL-6. CONCLUSIONS: Based on our measurements of extracellular and intracellular ROS, milk supplemented with fresh ML does not induce significant oxidative stress. However, when stored for 4 hours at room temperature, ML induces significant levels of oxidative stress. Decreases in TEER and increases in apoptosis and IL-6 secretion are consistent with ML-induced oxidative stress. It therefore is likely that in clinical situations, if ML-supplemented milk is not administered quickly, the newborn may be placed at greater risk of oxidative stress.

Nutritional modulation of neonatal outcomes.

In humans, growth and development continues until early adulthood when bone, muscle, and nervous tissue reaches final stages of maturity. Adequate levels of nutritional intake and utilization are critical to optimize ongoing growth. The goal of nutritional therapy for premature or ill neonates has been to provide sufficient nutrients to allow growth to continue at rates seen in utero. Functional immaturity of the gut in the premature infant makes absorption and utilization of nutritional substrates difficult. Premature infants are at risk for developing necrotizing enterocolitis, a potentially lethal bowel disorder. The etiology of necrotizing enterocolitis is not well understood, and a number of theories of causation have been proposed. Breast milk, the optimal source of nutrition for the neonate, is believed to confer some protection against necrotizing enterocolitis. A number of breast milk components have been credited with antiinflammatory properties. Breast milk is recognized for its benefits, yet for preterm infants breast milk alone does not promote adequate growth. A number of breast milk supplements have been investigated to facilitate growth and development and to prevent necrotizing enterocolitis. This article addresses development of the fetal gastrointestinal system, focusing on the biological mediators for normal function and the role of human breast milk and its additives in optimizing neonatal growth. The possible etiologies of necrotizing enterocolitis are discussed in terms of the relationship between this disease and enteral feeding practices.