title: 13C-labeled oligosaccharides in breastfed infants' urine: individual-, structure- and time-dependent differences in the excretion.
abstract: 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.
authors.affiliation: Institute of Nutritional Sciences, University of Giessen, Wilhelmstrasse 20, 35392 Giessen, Germany.
authors.forename: Viktoria
authors.initials: V
authors.lastname: Dotz
authors.forename: Silvia
authors.initials: S
authors.lastname: Rudloff
authors.forename: Dennis
authors.initials: D
authors.lastname: Blank
authors.forename: Günter
authors.initials: G
authors.lastname: Lochnit
authors.forename: Rudolf
authors.initials: R
authors.lastname: Geyer
authors.forename: Clemens
authors.initials: C
authors.lastname: Kunz
mesh_terms: D001942:Breast Feeding; D002240:Carbohydrate Sequence; D002247:Carbon Isotopes / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D007206:Individuality; D007231:Infant, Newborn; D007422:Intestines / Q000737:chemistry; D007774:Lactation / Q000378:metabolism*; D008895:Milk, Human / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism* / Q000652:urine; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013997:Time Factors; D016482:Urinalysis
chemical_list: D002247:Carbon Isotopes; D009844:Oligosaccharides
keywords: MALDI-TOF MS; human milk oligosaccharides; in vivo; metabolic fate; stable isotope