Source and Quality of Enteral Nutrition Influences Oxidative Stress in Preterm Infants: A Prospective Cohort Study

Abstract

Background: Preterm infants are at risk of oxidative stress from neonatal intensive care interventions. 8-Oxo-2'-deoxyguanosine (8-oxodG), generated by oxygen radical attack on DNA, is a potential marker of oxidative stress. The aim of the present study was to investigate the impact of quality and source of enteral nutrition (EN) on renal excretion of 8-oxodG in preterm infants.

Methods: Spontaneous urine samples were collected on postnatal days 26-31 in 33 preterm infants. Infants were fed either breast milk (BM), formula (FM), or BM/FM mixtures. Daily iron (Fe) supplementation was started day 28 ± 1 postnatally. 8-oxodG was determined by highperformance liquid chromatography-electrochemical detection (HPLC-EC).

Results: The 8-oxodG/creatinine ratio was significantly higher in infants fed FM vs FM/BM (38.7 ± 28.7 vs 16.7 ± 12.2 nmol 8-oxodG/mmol creatinine, P < 0.0001) or BM (11.6 ± 10.4 nmol 8-oxodG/mmol creatinine, P < 0.0001). There was no significant effect of Fe supplementation (P = 0.547). 8-OxodG excretion showed significant interindividual variation but was similar within pairs of twins.

Conclusion: Quality and source of EN seem to influence oxidative stress in preterm infants. The underlying pathophysiological mechanism is unclear and needs further investigation. It may be speculated that other mechanisms than Fe supplementation contribute to oxidative stress, such as cow's milk protein-mediated up-regulation of the intestinal inflammatory cascade.

Keywords: 8-oxo-2′-deoxyguanosine; biomarker; breast milk; high-performance liquid chromatography; human milk fortification; preterm formula.