Lipid digestion is critical for infant development, and yet, the interconnection between lipid digestion and the microbiota is largely understudied. This review focuses on digestion of the human milk fat globule and summarizes the current understanding of the mechanisms underlying this process in infants. We first discuss the partial hydrolysis of milk fat in the stomach, which leads to rearrangement of lipid droplets, creating a lipid-water interface necessary for duodenal lipolysis. In the first few months of life, secretion of pancreatic triglyceride lipase, phospholipase A2, and bile salts is immature. The dominant lipases aiding fat digestion in the newborn small intestine are therefore pancreatic lipase-related protein 2 and bile salt-stimulated lipase from both the exocrine pancreas and milk. We summarize the interaction between ionic fatty acids and cations to form insoluble fatty acid soaps and how it is influenced by various factors, including cation availability, pH, and bile salt concentration, as well as saturation and chain length of fatty acids. We further argue that the formation of the soap complex does not contribute to lipid bioavailability. Next, the possible roles that the gut microbiota plays in lipid digestion and absorption are discussed. Finally, we provide a perspective on how the manufacturing process of infant formula and dairy products may alter the physical properties and structure of lipid droplets, thereby altering the rate of lipolysis.

中文翻译：

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健康婴儿对人乳脂肪的消化

脂质消化对婴儿发育至关重要，然而，脂质消化与微生物群之间的相互联系在很大程度上尚未得到充分研究。本综述侧重于人乳脂肪球的消化，并总结了目前对婴儿这一过程的潜在机制的理解。我们首先讨论胃中乳脂肪的部分水解，这导致脂滴的重排，产生十二指肠脂解所需的脂水界面。在生命的最初几个月，胰腺甘油三酯脂肪酶、磷脂酶 A2 和胆汁盐的分泌尚不成熟。因此，帮助新生儿小肠脂肪消化的主要脂肪酶是胰脂肪酶相关蛋白 2 和来自外分泌胰腺和乳汁的胆盐刺激脂肪酶。我们总结了离子脂肪酸和阳离子之间形成不溶性脂肪酸皂的相互作用，以及它如何受到各种因素的影响，包括阳离子可用性、pH 值和胆汁盐浓度，以及脂肪酸的饱和度和链长。我们进一步认为，肥皂复合物的形成对脂质生物利用度没有贡献。接下来，讨论肠道微生物群在脂质消化和吸收中可能发挥的作用。最后，我们提供了婴儿配方奶粉和乳制品的制造过程如何改变脂滴的物理特性和结构，从而改变脂解速率的观点。以及脂肪酸的饱和度和链长。我们进一步认为，肥皂复合物的形成对脂质生物利用度没有贡献。接下来，讨论肠道微生物群在脂质消化和吸收中可能发挥的作用。最后，我们提供了婴儿配方奶粉和乳制品的制造过程如何改变脂滴的物理特性和结构，从而改变脂解速率的观点。以及脂肪酸的饱和度和链长。我们进一步认为，肥皂复合物的形成对脂质生物利用度没有贡献。接下来，讨论肠道微生物群在脂质消化和吸收中可能发挥的作用。最后，我们提供了婴儿配方奶粉和乳制品的制造过程如何改变脂滴的物理特性和结构，从而改变脂解速率的观点。