German J Bruce, Argov-Argaman Nurit, Boyd Ben J
Nestle Nutr Inst Workshop Ser. 2019;90:217-225. doi: 10.1159/000490320. Epub 2019 Mar 13.
The evolution of lactation and the composition, structures, and functions of milk's biopolymers illustrates that the Darwinian pressure on lactation selected for gene products with considerable structural complexity and diverse functions within the digestive system. For example, complex sugar polymers - oligosaccharides - possess unique properties in guiding the growth of intestinal bacteria that are not possible by feeding their simple sugars. The proteins of milk are diverse with some exhibiting enzymatic activities towards other milk components rendering those components both more digestible but also releasing biologically active products. Thus, research into milk's biopolymers has been most enlightening when milk was investigated for the formation and disassembly of its structures and for the functions within the infant. To date however, the most complex structure in mammalian milk, the fat globule, has not been effectively examined beyond its simple composition. The globules of milk are heterogeneous in size, composition, and function. With new research tools, scientists are beginning to understand the mechanisms that control the assembly of globules in the mammary gland and the disassembly within the infant.
泌乳的进化以及乳汁生物聚合物的组成、结构和功能表明，对泌乳的达尔文式选择倾向于选择在消化系统中具有相当结构复杂性和多样功能的基因产物。例如，复杂的糖聚合物——低聚糖——在引导肠道细菌生长方面具有独特的特性，而仅喂食简单糖类则无法做到这一点。乳汁中的蛋白质种类繁多，有些对其他乳汁成分具有酶活性，这使得这些成分更易消化，同时还能释放生物活性产物。因此，当研究乳汁生物聚合物在其结构的形成和分解以及在婴儿体内的功能时，对乳汁生物聚合物的研究最具启发性。然而，迄今为止，哺乳动物乳汁中最复杂的结构——脂肪球，除了其简单的组成之外，尚未得到有效研究。乳汁中的脂肪球在大小、组成和功能上是异质的。借助新的研究工具，科学家们开始了解控制乳腺中脂肪球组装以及婴儿体内脂肪球分解的机制。
