N-Glycans are an important source of milk oligosaccharides. In addition to free oligosaccharides found in milk, N-glycans can also be utilized by gut microbes. A potential for milk N-glycans to act as gut microbe regulators in suckling animals has attracted considerable attention; however, sow milk N-glycans and their potential effects upon the piglet's gut microbes in vivo remain unknown. In the present study, we profiled the milk N-glycans of Meishan and Yorkshire sows during lactation using UPLC and a mass spectrometry-based glycome method, and we explored the correlations between milk N-glycans and offspring gut microbiota. Twenty-two N-glycan structures were identified in sow milk, among which 36% (8 out of 22) were fucosylated, 41% (9 out of 22) were sialylated, and 14% (3 out of 22) were high mannosylated. An N-glycan with a NeuGc structure (namely PNO20, GlcNAc4-Man3-Gal2-Fuc-Neu5Gc) was identified in sow milk for the first time. No compositional differences between the two breeds or between different lactation times were found in porcine milk N-linked oligosaccharides (PNOs); however, the abundances of different structures within this class did vary. The relative abundances of fucosylated PNO3 (GlcNAc4-Man3-Fuc) and sialylated PNO18 (GlcNAc4-Man3-Gal2-NeuAc) increased during lactation, and Meishan sows demonstrated a higher ( P < 0.05) abundance of mannosylated PNO10 (GlcNAc2-Man6) and sialylated PNO17 (GlcNAc5-Man3-Gal-NeuAc) than Yorkshire sows. Apparent correlations between milk N-glycans and offspring gut microbial populations were found; for example, mannosylated PNO21 (GlcNAc2-Man9) was positively correlated with OTU706 ( Lactobacillus amylovorus) and OTU1380 ( Bacteroides uniformis). Overall, our results indicate that the milk N-glycome of Meishan and Yorkshire sows differs in N-glycome characteristics and that this is correlated to abundances of certain piglet gut microbes. These findings provide a reference for future elucidation of the involvement of gut microbes in milk N-glycan metabolism, which is important to the health both of large domestic animals and humans.

中文翻译：

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猪牛奶N-糖原及其与后代肠道微生物组的潜在关系的新见解。

N-聚糖是牛奶低聚糖的重要来源。除了牛奶中发现的游离寡糖外，肠道微生物还可以利用N-聚糖。牛奶中的N-聚糖在哺乳动物中充当肠道微生物调节剂的潜力已经引起了广泛关注。然而，母乳中的N-聚糖及其在体内对仔猪肠道微生物的潜在影响仍然未知。在本研究中，我们使用UPLC和基于质谱的糖组学方法对梅山和约克郡母猪泌乳期的牛奶N-聚糖进行了分析，并探讨了牛奶N-聚糖与后代肠道菌群之间的相关性。在母乳中鉴定出22种N-聚糖结构，其中36％（22个中的8个）被岩藻糖基化，41％（22个中的9个）被唾液酸化，而14％（22个中的3个）被高甘露糖基化。首次在母乳中鉴定出具有NeuGc结构的N-聚糖（即PNO20，GlcNAc4-Man3-Gal2-Fuc-Neu5Gc）。在猪乳N-连接寡糖（PNOs）中，没有发现两个品种之间或不同泌乳时间之间的成分差异。但是，此类中不同结构的丰度确实有所不同。泌乳期间，岩藻糖基化的PNO3（GlcNAc4-Man3-Fuc）和唾液酸化的PNO18（GlcNAc4-Man3-Gal2-NeuAc）的相对丰度增加，梅山母猪的甘露糖基化的PNO10（GlcNAc2-Man6）的丰度更高（P <0.05）。唾液酸化的PNO17（GlcNAc5-Man3-Gal-NeuAc）比约克郡母猪多。发现牛奶中的N-聚糖与后代肠道微生物数量之间存在明显的相关性。例如，甘露糖基化的PNO21（GlcNAc2-Man9）与OTU706（木糖乳杆菌）和OTU1380（统一细菌）呈正相关。总体而言，我们的结果表明，梅山和约克郡母猪的牛奶N糖基团在N糖基团特征方面存在差异，这与某些仔猪肠道微生物的丰度相关。这些发现为今后阐明肠道微生物参与牛奶N-聚糖代谢提供了参考，这对大型家畜和人类的健康都很重要。