German J Bruce, Lebrilla Carlito, Mills David A
University of California, Davis, Davis, CA, United States.
Department of Food Science and Technology, Davis, CA, United States.
Front Nutr. 2022 Jun 10;9:922907. doi: 10.3389/fnut.2022.922907. eCollection 2022.
The origin of lactation and the composition, structures and functions of milk's biopolymers highlight the Darwinian pressure on lactation as a complete, nourishing and protective diet. Lactation, under the driving pressure to be a sustainable bioreactor, was under selection pressure of its biopolymers with diverse functions acting from the mammary gland through the digestive system of the infant. For example, milk is extensively glycosylated and the glycan structures and their functions are now emerging. Milk contains free oligosaccharides; complex polymers of sugars whose stereospecific linkages are not matched by glycosidic enzymes within the mammalian infant gut. These glycan polymers reach the lower intestine undigested. In this microbe-rich environment, bacteria compete to release and ferment the sugars different hydrolytic strategies. One specific type of bacteria, subsp. , () is uniquely equipped with a repertoire of genes encoding enzymes capable of taking up, hydrolyzing and metabolizing the complex glycans of human milk. This combination of a distinct food supply and unique genetic capability shapes the composition and metabolic products of the entire microbial community within the lower intestine of breast fed infants. The intestinal microbiome dominated by , shields the infant from the growth of gram negative enteropathogens and their endotoxins as a clear health benefit. The world is facing unprecedented challenges to produce a food supply that is both nourishing, safe and sustainable. Scientists need to guide the future of agriculture and food in response to these 21st century challenges. Lactation provides an inspiring model of what that future research strategy could be.
泌乳的起源以及乳汁生物聚合物的组成、结构和功能凸显了泌乳作为一种完整、营养且具保护作用的饮食所面临的达尔文式压力。在成为可持续生物反应器的驱动压力下，泌乳受到其生物聚合物的选择压力影响，这些生物聚合物具有多种功能，从乳腺作用于婴儿的消化系统。例如，乳汁被广泛糖基化，其聚糖结构及其功能正在逐渐显现。乳汁含有游离寡糖；这些糖的复杂聚合物的立体特异性连接无法被哺乳动物婴儿肠道内的糖苷酶所匹配。这些聚糖聚合物未被消化就到达下肠道。在这个微生物丰富的环境中，细菌通过不同的水解策略竞争释放和发酵这些糖。一种特定类型的细菌，即亚种（），独特地配备了一系列编码能够摄取、水解和代谢人乳复杂聚糖的酶的基因。这种独特的食物供应和独特的遗传能力的组合塑造了母乳喂养婴儿下肠道内整个微生物群落的组成和代谢产物。以该细菌为主导的肠道微生物群保护婴儿免受革兰氏阴性肠道病原体及其内毒素的生长影响，这显然对健康有益。世界在生产既营养、安全又可持续的食物供应方面正面临前所未有的挑战。科学家需要应对这些21世纪的挑战，引领农业和食品的未来发展。泌乳为未来的研究策略提供了一个鼓舞人心的模式。
