Differences in direct pharmacological effects and antioxidative properties of mature breast milk and an infant formula

S Spasic1, N Lugonja1, O Laugier1, A Nikolic-Kokic2, Z Orescanin-Dusic2, I Spasojevic3, M.M. Vrvic4. 1Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Department of Chemistry, Serbia, 2Institute for Biological Research, University of Belgrade, Department of Physiology, Serbia, 3Institute for Multidisciplinary Research, University of Belgrade, Redox science, Serbia, 4Faculty of Chemistry, University of Belgrade,, Biochemistry, Serbia

Early onset and exclusive breastfeeding provides a significant health benefit to infants in comparison to infant formulas. There is growing evidence that presence of some specific protein components in mother’s milk are responsible for observed significant health benefit in infants feed with mother’s milk. The aim of this paper was to compare mature breast milk and a standard infant formula by examining their effects on smooth muscle contraction and their antioxidative properties. Electron paramagnetic resonance (EPR) spin-trapping spectroscopy was used to compare the antioxidative capacities of breast milk (obtained on the 9th week of lactation) with a commercial infant formula against hydroxyl radical production in the Fenton reaction. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and sulphydril group (–SH) content were determined in the milks. Pharmacological research was performed on the isolated rat uterus obtained from virgin female Wistar rats (200-250g; 3 months of age). All protocols for handling experimental animals were approved by the local ethics committee for animal experimentation which strictly follows international regulations. The rats were kept at 22oC, housed three per cage and fed ad libitum. Rat uteri were isolated during the oestrous phase of the oestrous cycle. The oestrous phase was determined by daily vaginal ravage. All rats were killed by cervical dislocation. The uterine horns were rapidly excised and carefully cleaned of surrounding connective tissue and mounted vertically in a 10 ml volume organ bath containing De Jalon’s solution (NaCl 154 mM, KCl 5.6 mM, CaCl2 x 2H2O 0.41 mM, NaHCO3 5.9 mM and glucose 2.8 mM), under 1 g tension . The bath was maintained at 37○C and aerated with 95% oxygen and 5% carbon dioxide. After an equilibration period (about 30 min) when the uteri established stable calcium ion-induced contractions, single doses of either breast milk or the infant formula (500µl) were applied. Myometrial tension was recorded isometrically with a TSZ-04-E isolated organ bath transducer (Experimetria, Budapest; Hungary).

Results were tested by one-way ANOVA and post hoc compared by Tukey’s HSD t-test. Statistically significant increased total SOD was observed in the breast milk in comparison to infant formula. The content of -SH groups was statistically significant decreased in infant formula in comparison to the breast milk. In contrast to the infant formula, breast milk exerted a relaxing effect on isolated non-vascular smooth muscle. Using EPR and the Fenton reaction as a radical-generating system, we showed that breast milk possesses a three-fold higher antioxidative activity against the hydroxyl radical compared to the infant formula. In both samples, generation of the hydroxyl radical (·OH) led to the production of carbon-centered radicals. The ascorbyl radical was detected in breast milk but not in the infant formula.

Human milk has direct pharmacological effects and provides better antioxidant protection than the infant formula due to the presence of specific protein components such as human SOD.