BRAIN
SIALIC ACID CONTENT: COMPARISON BREAST-FED VS FORMULA-FED INFANTS
Wang B, Brand Miller J, Petocz
P, McVeagh P
Human Nutrition Unit, Department of Biochemistry,
University of Sydney, NSW, Australia
Objective:
Nervous tissues contain large amounts of sialic acid (SA) bound to
gangliosides and glycoproteins. Gangliosides play an important role in cell
differentiation, transmembrane signaling and memory formation.
SA–containing proteins appear to act as receptors for neurotransmitters and
play a role in information storage. In animal models, levels of SA in brain
gangliosides and glycoproteins are influenced by nutritional intake and
correlate with learning ability. The aim of our study was to compare the SA
concentration in brain frontal cortex of breast-fed and formula-fed infants
who died of sudden infant death syndrome.
Methods: Twenty-five frontal
cortex samples were collected as part of a previous study on long chain
fatty acids in brain cortex. Twelve infants were
breast-fed, 9 formula-fed and the rest unknown. The mean age at death of
breast-fed and formula-fed infants was 11 and 13 wks respectively.
Gangliosides were extracted, isolated and purified according to published
methods. Ganglioside-bound, protein-bound and free SA were
determined using HPLC. Fatty acids, including docosahexaenoic acid (DHA)
were re-analysed to validate the integrity of the samples after long
storage at -80°C.
Results: There was a significant positive correlation between protein-bound
SA and age at death (P = 0.02), but not for ganglioside-bound SA (P =
0.24). Ganglioside-bound SA was 8% higher in males while protein-bound SA
was 5% higher in females, although neither reached statistical
significance. On average, breast-fed infants were about 2 wks younger than
formula-fed infants and all of the latter were male. We therefore used a multivariate general linear model for the components of SA
adjusting for type of feed and sex, with age at death as a covariate. The
overall differences of feeding methods were significant (P = 0.024).
Ganglioside-bound, protein-bound and total SA were significantly higher in
breast-fed infants (P = 0.013, 0.01 and 0.005 respectively).
Conclusions: These findings are
unique and provide objective evidence of differences in brain development
in breast-fed vs formula-fed infants. The higher concentration of
ganglioside-bound, protein-bound & total SA in frontal cortex in the
breast-fed group may explain the known neurological and intellectual
advantages of breast-feeding.