Abstract
BackgroundIt has been hypothesized that human milk oligosaccharides (HMOs) confer systemic health benefits to breastfed infants; however, plausible mechanisms for some effects, such as systemic immunomodulation, require HMOs to access the bloodstream of the developing infant. While small concentrations of HMOs have been detected in the urine of breastfed infants there are no published studies of these oligosaccharides accessing the plasma compartment of breastfed infants. Here we determined the relative fractions of several ingested HMOs in infant urine and plasma. Plasma from formula-fed infants was used as a control.MethodsUsing gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry/tandem mass spectrometry (LC/MS/MS), and high performance liquid chromatography (HPLC), we analyzed the urine and plasma from 17 healthy formula-fed infants and 16 healthy breast-fed infants (and the milk from their mothers).ResultsMultiple HMOs were detected in the urine and plasma of breastfed infants, but not in formula-fed infants. Levels of 2′-fucosyllactose (2′FL), 3FL and lacto-N-neotetraose (LNnT) in both plasma (r = 0.98, p<0.001; r = 0.75, p = 0.002; r = 0.71, p = 0.004) and urine (r = 0.81, p<0.001; r = 0.56, p = 0.026; NS) correlated significantly with concentrations in the corresponding breast milk. The relative fractions of HMOs were low, 0.1% of milk levels for plasma and 4% of milk levels for urine. Within the breastfed cohort, there were significant differences between secretor and nonsecretor groups in levels of several fucosylated HMOs.ConclusionAt least some ingested HMOs are absorbed intact into the circulation and excreted in the urine and their concentrations in these fluids correlate with levels of the corresponding mother's milk. While relative fractions of absorbed HMOs were low, these levels have been shown to have biological effects in vitro, and could explain some of the postulated benefits of human milk.
Highlights
Human milk contains large amounts of soluble milk oligosaccharides, 5–23 g/L, representing the third largest solid component following lactose and lipids [1]
The purpose of this study was to explore the fate of milk glycans once they are consumed by the infant, and to investigate the influence of breast milk with its high content of human milk oligosaccharides (HMOs) compared to that of cow’s-milk based infant formula, containing low levels of only a few small oligosaccharides
Global untargeted profiling revealed the presence of seven milk oligosaccharides (29FL, 3FL, LNnT, LNFP I, LNFP II,III, 69SL and 69SLN) in the infant urine samples (Figure 2), and all except 69SLN were present in breast milk
Summary
Human milk contains large amounts of soluble milk oligosaccharides, 5–23 g/L, representing the third largest solid component following lactose and lipids [1]. In a recent study profiling the HMO content of breast milk, Totten et al proposed a method for determining secretor status based exclusively on the relative quantitation of milk oligosaccharides. They determined a 29FL/3FL abundance ratio of .6.5 to be a specific marker for describing an individual as a secretor, and were able to correctly identify 42 out of 44 secretors. Erney et al [10] analyzed hundreds of milk samples for HMO content, making special effort in detecting and quantifying 29FL They determined that western blots of proteins from milk samples that contained even minute quantities of 29FL were detected by Ulex Europeaus agglutinin I, providing a different criterion to assign secretor status to milk samples in the absence of serological determinations. Plasma from formula-fed infants was used as a control
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