Why does Human Milk Fortification (HMF) increase Urinary F2‐Isoprostanes in the Premature Infant?

Abstract

Human milk fortifiers (HMF) are routinely added to mother's milk (HM) for premature infant to make up for potential nutritional deficiencies. We reported data on 65 premature infants (birth weight < 1500 g) who were either fed HM with varying levels of HMF or formula (F) while they were in hospital receiving oral feeds. A significant increase (P<0.05) in urine_F2‐isoprostanes was found as HMF supplementation increased (Pediatr Res. 2011 Feb; 69(2): 160–4). Subsequently we used an in vitro model of Caco‐2 cells with HMF and lipopolysaccharide (LPS) known to induce inflammation in vivo. When paired with HMF, there was a significant increase in IL‐6 secretion above that of LPS alone. A sample of breast milk from our study supplemented with HMF (>; 50%) generated higher levels of intracellular oxidation in intestinal cells, as indicated by the redox‐sensitive dye Dichlorofluorescein (DCF). Furthermore we now have data from DNA Microarray experiments that, in intestinal cells, HMF significantly up regulates a battery of antioxidant response element (ARE)‐driven genes. Additionally, we have pilot data from fetal intestinal cells (FHS) exposed to either human milk (HM) or HM + HMF). Briefly, enterocyte cell cultures were exposed to digested HM +/− HMF. Following 24 hours recovery, RNA was collected, prepared for qRT‐PCR as per the SABiosciences RT2 ProfilerTM array, which screens for cytokines, chemokines, toll‐like receptors (TLRs) and linkers. Of note is the significant up‐regulation of several interleukins (IL1A, IL6, IL10, IL18) or IL18 receptor accessory protein (IL18RAP), and TLR4. Furthermore, an integrin gene (ITGB2) was significantly down‐regulated, which has implications for intestinal barrier function. This data suggests that some HMFs as constituted induce oxidative stress in vitro and in vivo.Supported by CIHR and MICH.