Lönnerdal Bo
Nestle Nutr Inst Workshop Ser. 2019;90:83-92. doi: 10.1159/000490297. Epub 2019 Mar 13.
Human milk contains a wide variety of bioactive components, including long-chain fatty acids, complex oligosaccharides, and bioactive proteins. More recently, it was discovered that breast milk also contains exosomes, i.e., microvesicles containing microRNAs (miRNAs) with sizes of ∼22 nucleotides. Several of these miRNAs have been shown to originate from the mammary gland, and many of them are involved in cellular development and immune function. Exosome-mediated transfer of miRNAs is a novel mechanism of genetic exchange between cells. It is therefore possible that exosomes in milk may survive digestion and deliver miRNAs to intestinal cells, or, if transferred into the blood stream, to cells in other tissues. In vitro work has shown that exosomes and their miRNA cargo can survive proteolytic digestion and that intestinal epithelial cells take up the exosomes and deliver them to the nucleus. Research on human adults consuming cow milk has shown that major bovine milk miRNAs are found in the circulation postprandially, further suggesting that exosomes can resist conditions in the gastrointestinal tract and be delivered to the systemic circulation. Thus, it is possible that milk miRNAs may transfer genetic material to the infant and thereby affect gene transcription and regulation of cellular events in several tissues.
人乳含有多种生物活性成分，包括长链脂肪酸、复合寡糖和生物活性蛋白。最近发现，母乳中还含有外泌体，即含有大小约为22个核苷酸的微小RNA（miRNA）的微囊泡。其中一些miRNA已被证明起源于乳腺，并且它们中的许多都参与细胞发育和免疫功能。外泌体介导的miRNA转移是细胞间基因交换的一种新机制。因此，乳汁中的外泌体有可能在消化过程中存活下来，并将miRNA传递给肠道细胞，或者，如果进入血流，则传递给其他组织中的细胞。体外研究表明，外泌体及其携带的miRNA能够在蛋白水解消化中存活，并且肠道上皮细胞会摄取外泌体并将其输送到细胞核。对饮用牛奶的成年人的研究表明，餐后循环中会发现主要的牛乳miRNA，这进一步表明外泌体能够抵抗胃肠道环境并被输送到体循环。因此，乳汁中的miRNA有可能将遗传物质传递给婴儿，从而影响多个组织中的基因转录和细胞事件的调控。
