Institute of Nutritional Sciences, University of Giessen, Wilhelmstrasse 20, 35392 Giessen, Germany.
Glycobiology. 2014 Feb;24(2):185-94. doi: 10.1093/glycob/cwt099. Epub 2013 Nov 18.
Human milk oligosaccharides (HMOs) have been paid much attention due to their beneficial effects observed in vitro, e.g., prebiotic, anti-infective and anti-inflammatory properties. However, in vivo investigations with regard to HMO metabolism and functions are rare. The few data available indicate that HMOs are absorbed to a low extent and excreted via urine without noteworthy modifications, whereas the major proportion reaches infant's colon undigested. Via intrinsic (13)C-labeling of HMOs during their biosynthesis in the mammary gland of 10 lactating women, we were able to follow the fate of (13)C-labeled oligosaccharides (OSs) from their secretion in milk to the excretion in the urine of their breastfed infants. To a certain extent, we could therefore discriminate between original HMOs and non-labeled OSs derived from degradation of HMOs or endogenous glycoconjugates. By means of our novel, rapid, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based approach, we found a homogeneous time pattern of isotopomer enrichment in milk among all subjects and between single OS species. In contrast, the time curves from infants' urine varied strongly between individuals and OS species, though the overall MALDI-TOF MS profile resembled those of the mothers' milk. Our data suggest that neutral HMOs might be processed and/or utilized differentially after or upon absorption from the gut, as deduced from their structure-dependent variation in the extent of tracer enrichment and in the retention times in infant's organism. This sheds new light on the role of HMOs within infant's body, beyond the intestine and its microbiota alone.
人乳寡糖（HMOs）因其在体外观察到的有益作用而备受关注，例如，益生元、抗感染和抗炎特性。然而，关于 HMO 代谢和功能的体内研究很少。现有的少量数据表明，HMOs 的吸收程度很低，主要通过尿液排泄，没有明显的修饰，而大部分则未被消化到达婴儿的结肠。通过对 10 位哺乳期妇女乳腺中 HMO 生物合成过程中的（13）C 标记，我们能够追踪（13）C 标记寡糖（OSs）从分泌到母乳中婴儿尿液排泄的命运。在一定程度上，我们因此可以区分原始 HMOs 和非标记的 OSs，这些 OSs 源自 HMOs 的降解或内源性糖缀合物。通过我们新颖、快速的基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）方法，我们发现所有受试者和单个 OS 物种的乳汁中同位素丰度富集的同质时间模式。相比之下，婴儿尿液中的时间曲线在个体和 OS 物种之间差异很大，尽管整体 MALDI-TOF MS 谱与母亲乳汁的谱相似。我们的数据表明，中性 HMOs 可能在肠道吸收后或吸收后被不同地加工和/或利用，这可以从其结构依赖性示踪剂富集程度和在婴儿体内保留时间的变化中推断出来。这为 HMOs 在婴儿体内的作用提供了新的认识，超越了肠道及其微生物群的单独作用。
