UBC Theses and Dissertations
The complexity of understanding human milk components and infant brain development Moukarzel, Sara
Understanding which and how human milk components contribute to infant brain development is complicated in part by their large diversity, complex arrangement in the milk matrix and potential interaction in metabolism. This research addressed the importance of studying the composition of minor milk lipids and of exploring their relationship with non-lipid milk components in infant brain development. More specifically, the milk fat globule membrane (MFGM), a complex tri-layer of cholesterol, glycoproteins, and polar lipids including ethanolamine plasmalogens (Pls-PE), naturally emulsifies milk triacylglycerols but is not currently added to infant milk substitutes. Clinical evidence suggests MFGM plays a role in cognitive function. Whether MFGM directly affects the developing brain is unclear. Due to analytical challenges, little is known about the fatty acid composition of human MFGM lipids, particularly Pls-PE. Pls-PE may be enriched in long-chain polyunsaturated fatty acids (LC-PUFA) such as docosahexaenoic acid (DHA), an important neural lipid during development. Additionally, milk contains different forms of water-soluble choline (WSC) compounds (free choline, glycerophosphocholine, phosphocholine) for which distinct biological roles are unknown, although choline as a molecule per se is an important structural component of the brain and a precursor of the neurotransmitter acetylcholine. After developing an analytical method for separation and recovery of milk Pls-PE, the first study demonstrated both human and cow milk Pls-PE are enriched in LC-PUFA including DHA compared to other phospholipids. Milk Pls-PE DHA does not seem to vary with maternal DHA intake. Using artificially-reared infant rats, the second study showed that developmental brain phospholipids and metabolites differ between rats fed formula with or without MFGM, with a closer phospholipid composition to mother-reared rats in rats fed MFGM. By analyzing human preterm and term milk samples for WSC composition using mass spectrometry in the third study, we confirmed previous findings of the wide variability in WSC total content and composition in human milk and reported no significant association between individual WSC compounds. These studies provide new knowledge that milk contains novel components potentially relevant to the brain, and, while the mechanisms for improved cognition remain unclear, MFGM affects neonatal brain phospholipid composition.
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