Impact of Enteral Supplementation in Human Milk on Lipid Oxidation and Redox Balance

Abstract

Oxidative stress due to reactive oxygen species may be linked to the etiology of neonatal diseases, such as necrotizing enterocolitis and respiratory distress syndrome. Iron and vitamin C enteral supplements for premature infants (PT) added to human milk (HM) may induce lipid oxidation due to free radical formation. We hypothesized that these supplements added to HM causes oxidation of milk fats in vitro, and affects intracellular redox balance. We further hypothesized that these supplements induce oxidative DNA damage and apoptosis. Lipid peroxidation in HM was measured by Fox-2 and TBARS assays; fatty acid composition of supplemented HM was measured by gas chromatography. Two cell culture bioassays were used to determine the effects of iron and vitamin C supplementation; FHs-74 Int cells, a primary fetal intestinal culture, and Caco-2BBe intestinal cells, a secondary differentiated cell. Lipid oxidation products increased after the addition of iron in HM. This was accompanied by reduced content of mono and polyunsaturated fatty acids in HM. Vitamin C and iron admixtures in HM led to lower peroxides than iron alone in HM, contrary to expectations. The vitamins A and D (examined to study components of TRIVISOL, Mead Johnson, Evansville, USA) exhibited antioxidant activity in this study. Iron induced significant intracellular oxidative stress in FHs-74 Int cells and also increased DNA damage and apoptosis. We conclude that iron supplementation has the potential to cause formation of reactive oxygen species (ROS) both in HM and in cells exposed to iron supplemented milk. These effects in turn may increase oxidative stress in PT infants. Supported by Manitoba Institute of Child Health and Canadian Institutes of Health Research