Rachael H. Buck

BACKGROUND: It 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. METHODS: Using 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). RESULTS: Multiple 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. CONCLUSION: At 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.

OBJECTIVES: The aim of the present study was to examine the growth and tolerance of infants fed infant formulas with a caloric density closer to human milk (HM) supplemented with human milk oligosaccharides (HMOs) and to study uptake of the HMOs. METHODS: A prospective, randomized, controlled, growth and tolerance study was conducted in healthy, singleton infants (birth weight ≥2490 g), who were enrolled by day of life (DOL) 5. Formula-fed infants were randomized to 1 of 3 formulas with a caloric density of 64.3 kcal/dL. Each formula contained galactooligosaccharides, and the 2 experimental formulas contained varying levels (0.2 and 1.0 g/L) of the HMO 2'-fucosyllactose (2'FL). The 3 formula groups were compared with an HM-fed reference group. Infants were exclusively fed either formula (n = 189) or HM (n = 65) from enrollment to 119 DOL. 2'FL was measured in the blood and urine collected from a subset of infants at DOL 42 and 119, and in HM collected from breast-feeding mothers at DOL 42. RESULTS: There were no significant differences among any groups for weight, length, or head circumference growth during the 4-month study period. All of the formulas were well tolerated and comparable for average stool consistency, number of stools per day, and percent of feedings associated with spitting up or vomit. 2'FL was present in the plasma and urine of infants fed 2'FL, and there were no significant differences in 2'FL uptake relative to the concentration fed. CONCLUSIONS: This is the first report of infants fed 2'FL-fortified formulas with a caloric density similar to HM. Growth and 2'FL uptake were similar to those of HM-fed infants.

BACKGROUND: The prebiotic nature of human milk oligosaccharides (HMOs) and increasing evidence of direct immunomodulatory effects of these sugars suggest that they may have some therapeutic potential in allergy. Here, we assess the effect of two HMOs, 2'-fucosyllactose and 6'-sialyllactose, on symptomatology and immune responses in an ovalbumin-sensitized mouse model of food allergy. METHODS: The effects of oral treatment with 2'-fucosyllactose and 6'-sialyllactose on anaphylactic symptoms induced by oral ovalbumin (OVA) challenge in sensitized mice were investigated. Mast cell functions in response to oral HMO treatment were also measured in the passive cutaneous anaphylaxis model, and direct effects on IgE-mediated degranulation of mast cells were assessed. RESULTS: Daily oral treatment with 2'-fucosyllactose or 6'-sialyllactose attenuated food allergy symptoms including diarrhea and hypothermia. Treatment with HMOs also suppressed antigen-induced increases in mouse mast cell protease-1 in serum and mast cell numbers in the intestine. These effects were associated with increases in the CD4(+) CD25(+) IL-10(+) cell populations in the Peyer's patches and mesenteric lymph nodes, while 6'-sialyllactose also induced increased IL-10 and decreased TNF production in antigen-stimulated splenocytes. Both 2'-fucosyllactose and 6'-sialyllactose reduced the passive cutaneous anaphylaxis response, but only 6'-sialyllactose directly inhibited mast cell degranulation in vitro, at high concentrations. CONCLUSIONS: Our results suggest that 2'-fucosyllactose and 6'-sialyllactose reduce the symptoms of food allergy through induction of IL-10(+) T regulatory cells and indirect stabilization of mast cells. Thus, human milk oligosaccharides may have therapeutic potential in allergic disease.