THE ROLE OF SIALIC ACID IN INFANT NUTRITION AND BRAIN DEVELOPMENT

在大脑发育的关键时期，不理想的营养对人类大脑有持续的影响。早产儿尤其容易受到伤害，因为大脑发育在妊娠26周达到顶峰，并在生命的第一年保持较高水平。那些在出生后第一个月用母乳喂养的婴儿与用标准配方奶粉喂养的婴儿相比，具有显著的智力优势。虽然像DHA这样的n-3脂肪酸被认为是重要的，但母乳中的其他成分可能对大脑发育更重要。我们感兴趣的是一种叫做唾液酸的糖化合物。它在人乳中大量存在（高达1g-L），但在婴儿配方奶粉中仅少量存在。唾液酸是脑细胞的重要结构和功能成分。它直接参与神经细胞的传递、记忆的形成和细胞间的交流。在大脑发育高峰期，年幼的婴儿，尤其是早产儿，不太可能合成足够的唾液酸来满足他们的需要。在这些时候，他们依靠母乳和婴儿配方奶粉来提供必要的组成部分。然而，如果他们的饮食中唾液酸的来源不足，可能会对智力发展产生持久的影响。这个研究项目解决了几个问题。1. 在出生后的最初几周内补充口服唾液酸是否能提高大脑唾液酸水平和学习行为？2. 是否有剂量-反应关系，越好越好？3. 补充剂是否会影响大脑中编码关键酶的基因表达？4. 膳食补充是否会影响参与唾液酸合成的肝酶的活性？如果我们的发现可以外推到人类婴儿身上，它们将对儿童所有类型的认知和行为缺陷的病因学产生影响，包括学习困难和注意力缺陷障碍。

Sub-optimal nutrition during critical periods of brain growth has persistent effects on the human brain. Premature infants are especially vulnerable because brain growth reaches its peak at 26 weeks gestation and remains high throughout the first year of life. Those fed human milk in the first month after birth have been shown to have a significant intellectual advantage compared with infants fed standard infant formulas. While the n-3 fatty acids such as DHA are thought to be important, other components of human milk may be of greater significance for brain growth. Our interest is in a sugar compound called sialic acid. It occurs in remarkably large amounts in human milk (up to 1g-L) but is present in only small quantities in infant formulas. Sialic acid is an important structural and functional component of brain cells. It is directly involved in nerve cell transmission, memory formation and cell-to-cell communication. During peak brain growth, young infants, especially pre-term ones, are unlikely to be able to synthesise sufficient sialic acid to meet their needs. At these times, they rely on human milk and infant formulas to supply the necessary building blocks. If their diet is a poor source of sialic acid, however, there may be lasting consequences for intellectual development. This research project addresses several questions. 1. Does oral sialic acid supplementation over the first few weeks of life increase both brain sialic acid levels as well as learning behaviour? 2. Is there any dose-response relationship - is more better? 3. Does supplementation influence the expression of genes encoding key enzymes in the brain? 4. Does dietary supplementation affect the activity of the liver enzyme involved in synthesis of sialic acid? If our findings can be extrapolated to human infants, they will have implications for the etiology of all types of cognitive and behavioural defects in children, including learning difficulties and attention deficit disorder.