Neutral oligosaccharide content of preterm human milk

Daily variations in oligosaccharides of human milk determined by microfluidic chips and mass spectrometry

Human milk is a complex biological fluid that provides not only primary nourishment for infants but also protection against pathogens and influences their metabolic, immunologic, and even cognitive development. The presence of oligosaccharides in remarkable abundance in human milk has been associated to provide diverse biological functions including directing the development of an infant's intestinal microflora and immune system. Recent advances in analytical tools offer invaluable insights in understanding the specific functions and health benefits these biomolecules impart to infants. Oligosaccharides in human milk samples obtained from five different individual donors over the course of a 3 month lactation period were isolated and analyzed using HPLC-Chip/TOF-MS technology. The levels and compositions of oligosaccharides in human milk were investigated from five individual donors. Comparison of HPLC-Chip/TOF-MS oligosaccharides profiles revealed heterogeneity among multiple individuals with no significant variations at different stages of lactation within individual donors.

Intestinal microflora of human infants and current trends for its nutritional modulation

Diet, among other environmental and genetic factors, is currently recognised to have an important role in health and disease. There is increasing evidence that the human colonic microbiota can contribute positively towards host nutrition and health. As such, dietary modulation has been proposed as important for improved gut health, especially during the highly sensitive stage of infancy. Differences in gut microflora composition and incidence of infection occur between breast- and formula-fed infants. Human milk components that cannot be duplicated in infant formulae could possibly account for these differences. However, various functional food ingredients such as oligosaccharides, prebiotics, proteins and probiotics could effect a beneficial modification in the composition and activities of gut microflora of infants. The aim of the present review is to describe existing knowledge on the composition and metabolic activities of the gastrointestinal microflora of human infants and discuss various possibilities and opportunities for its nutritional modulation.

Oligosaccharides in infant formula

Breast-feeding is the golden standard for infant feeding. However, the majority of a few week old infants are fed with a second choice infant feeding, cow's milk based formula. Amongst the multiple differences between human and cow's milk regards the development of the gastro-intestinal flora: the flora of the breast-fed infant being richer in bifidobacteria and lactobacilli. Both species are known to be potentially beneficial for the health of the host. The absence of oligosaccharides, the third largest component in human milk, in cow's milk is likely to account for the differences in colonic flora. The oligosaccharide content and concentration in breast milk is — just as for the other macronutrients — a dynamic process, making it impossible for industry to mimic nature. However, if the composition cannot be mimicked, the effect and function can be imitated. The addition of two oligosaccharides, galacto-oligosaccharides and inulin, to cow's milk based infant formula has been shown to have a bifidogenic effect, and to stimulate the growth of bifidi and lactobacilli. In conclusion, the addition of oligosaccharides to cow's milk based infant formula brings this alternative, second choice infant feeding one step closer to the golden standard of human milk. But, prolonged breast-feeding should still be promoted with maximum effort.

A strategy for annotating the human milk glycome

Oligosaccharides in human milk represent a group of bioactive molecules that have evolved to be an abundant and diverse component of human milk, even though they have no direct nutritive value to the infant. A recent hypothesis proposes that they could be substrates for the development of the intestinal microflora and the mucosal immune system. The inability to determine the exact composition of these oligosaccharides limits research and the ability to understand their biological functions. Oligosaccharides isolated from the lipids and proteins of individual human milk samples were analyzed by a combination of techniques including microchip liquid chromatography mass spectrometry (HPLC-Chip/MS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT ICR MS). Accurate mass measurements obtained using an orthogonal time-of-flight (o-TOF) mass spectrometry provided oligosaccharide composition for approximately 200 individual molecular species. Comparison of HPLC-Chip/MS profiles from five different women revealed variations in milk oligosaccharide compositions. HPLC-Chip/MS profiling provides a method for routinely identifying milk oligosaccharides. Tandem MS in combination with exoglycosidase digestion provides unambiguous differentiation of structural isomers.

Determination of each neutral oligosaccharide in the milk of Japanese women during the course of lactation

Using reverse-phase HPLC after pyridylamination, we quantified the concentrations of major neutral oligosaccharides in the milk of sixteen Japanese women collected at 4, 10, 30 and 100 d postpartum. In colostrum and mature milk (30 d lactation), lacto-N-fucopentaose (LNFP) I was the most abundant oligosaccharide, followed by 2'-fucosyllactose (2'-FL) + lacto-N-difucotetraose (LNDFT), LNFP II + lacto-N-difucohexaose II (LNDFH II), and 3-fucosyllactose (3-FL). Together these accounted for 73 % of the total weight of neutral oligosaccharides in colostrum and mature milk. Changes in concentration occurred during the course of lactation. LNFP I and 2'-FL + LNDFT increased from 4 to 10 d postpartum, and then declined by 100 d. LNFP II + LNDFH II steadily increased during the first 30 d and then declined. In contrast, 3-FL increased steadily throughout the entire 100 d of study. Large differences were observed between our data and previously published data in Italian women, in terms of both the concentration and temporal changes of each oligosaccharide. These differences may be caused by different assay methodology, although racial differences cannot be ruled out.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Oligosaccharides in human milk: structural, functional, and metabolic aspects

Research on human milk oligosaccharides (HMOs) has received much attention in recent years. However, it started about a century ago with the observation that oligosaccharides might be growth factors for a so-called bifidus flora in breast-fed infants and extends to the recent finding of cell adhesion molecules in human milk. The latter are involved in inflammatory events recognizing carbohydrate sequences that also can be found in human milk. The similarities between epithelial cell surface carbohydrates and oligosaccharides in human milk strengthen the idea that specific interactions of those oligosaccharides with pathogenic microorganisms do occur preventing the attachment of microbes to epithelial cells. HMOs may act as soluble receptors for different pathogens, thus increasing the resistance of breast-fed infants. However, we need to know more about the metabolism of oligosaccharides in the gastrointestinal tract. How far are oligosaccharides degraded by intestinal enzymes and does oligosaccharide processing (e.g. degradation, synthesis, and elongation of core structures) occur in intestinal epithelial cells? Further research on HMOs is certainly needed to increase our knowledge of infant nutrition as it is affected by complex oligosaccharides.