Novel oligosaccharides with the sialyl-Lea structure in human milk

Human Milk Oligosaccharides (HMOS): Structure, Function, and Enzyme-Catalyzed Synthesis

The important roles played by human milk oligosaccharides (HMOS), the third major component of human milk, in the health of breast-fed infants have been increasingly recognized, as the structures of more than 100 different HMOS have now been elucidated. Despite the recognition of the various functions of HMOS as prebiotics, antiadhesive antimicrobials, and immunomodulators, the roles and the applications of individual HMOS species are less clear. This is mainly due to the limited accessibility to large amounts of individual HMOS in their pure forms. Current advances in the development of enzymatic, chemoenzymatic, whole-cell, and living-cell systems allow for the production of a growing number of HMOS in increasing amounts. This effort will greatly facilitate the elucidation of the important roles of HMOS and allow exploration into the applications of HMOS both as individual compounds and as mixtures of defined structures with desired functions. The structures, functions, and enzyme-catalyzed synthesis of HMOS are briefly surveyed to provide a general picture about the current progress on these aspects. Future efforts should be devoted to elucidating the structures of more complex HMOS, synthesizing more complex HMOS including those with branched structures, and developing HMOS-based or HMOS-inspired prebiotics, additives, and therapeutics.

N-linked glycan profiling of mature human milk by high-performance microfluidic chip liquid chromatography time-of-flight tandem mass spectrometry

N-Linked glycans of skim human milk proteins were determined for three mothers. N-Linked glycans are linked to immune defense, cell growth, and cell-cell adhesion, but their functions in human milk are undetermined. Protein-bound N-linked glycans were released with peptidyl N-glycosidase F (PNGase F), enriched by graphitized carbon chromatography, and analyzed with Chip-TOF MS. To be defined as N-glycans, compounds were required, in all three procedural replicates, to match, within 6 ppm, against a theoretical human N-glycan library and be at least 2-fold higher in abundance in PNGase F-treated than in control samples. Fifty-two N-linked glycan compositions were identified, and 24 were confirmed via tandem mass spectra analysis. Twenty-seven compositions have been found previously in human milk, and 25 are novel compositions. By abundance, 84% of N-glycans were fucosylated and 47% were sialylated. The majority (70%) of total N-glycan abundance was composed of N-glycans found in all three milk samples.

Structures and application of oligosaccharides in human milk

Comparative study of the oligosaccharide profiles of individual human milk revealed the presence of three different patterns. Four oligosaccharides containing the Fucalpha1-2Gal group were missing in the milk of non-secretor, and three oligosaccharides containing the Fucalpha1-4GlcNAc group were missing in the milk of Lewis negative individuals. Disappearance of some major oligosaccharides in these samples led to the finding of five novel minor oligosaccharides, which were hidden under the missing oligosaccharides. Following these studies, structures of many novel milk oligosaccharides were elucidated. At least 13 core oligosaccharides were found in these oligosaccharides. By adding alpha-fucosyl residues and sialic acid residues to these core oligosaccharides, more than one hundred oligosaccharides were formed. All these oligosaccharides contain lactose at their reducing termini. This evidence, together with the deletion phenomena found in the milk oligosaccharides of non-secretor and Lewis negative individuals, suggested that the oligosaccharides are formed from lactose by the concerted action of glycosyltransferases, which are responsible for elongation and branching of the Galbeta1-4GlcNAc group in the sugar chains of glycoconjugates on the surface of epithelial cells. Therefore, oligosaccharides in human milk could include many structures, starting from the Galbeta1-4GlcNAc group in the sugar chains of various glycoconjugates. Many lines of evidence recently indicated that virulent enteric bacteria and viruses start their infection by binding to particular sugar chains of glycoconjugates on the target cell surfaces. Therefore, milk oligosaccharides could be useful for developing drugs, which inhibit the infection of bacteria and viruses.

The trail of my studies on glycoproteins from enterokinase to tumor markers

This review describes the results of the author's studies on glycoproteins which have been carried out for more than 50 years. Starting from the elucidation of basic structures of glycoproteins, i.e. the structure of the linkage between an amino acid and a sugar and the occurrence of the beta-mannosidic linkage as the common structure of glycoproteins, the author became interested in the cell membrane glycoproteins focused on the comparison of cancer cells versus normal cells. These studies were then extended to the establishment of sugar-directed and cancer-associated monoclonal antibodies. Some of the monoclonal antibodies are useful for cancer diagnosis.

Structural determination of novel lacto-N-decaose and its monofucosylated analogue from human milk by electrospray tandem mass spectrometry and 1H NMR spectroscopy

We have isolated and characterised two neutral oligosaccharides, one nonfucosylated and the other monofucosylated, from human milk that are based on the doubly branched lacto-N-decaose core. Their structures have been determined by a combined use of electrospray tandem mass spectrometry (ES-MS/MS) and NMR spectroscopy. The sequences of the three branches resulted from the double-branching, including the identity and location of the blood-group-related Lewis determinant and partial linkages, were elucidated by the unique method of high sensitivity negative-ion ES-MS/MS analysis. Their full structure assignment was completed by methylation analysis and 1H NMR. The monofucosylated lacto-N-decaose, Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(Galbeta1-3GlcNAcbeta1-3)Galbeta1-4GlcNAcbeta1-6(Galbeta1-3GlcNAcbeta1-3)Galbeta1-4Glc is a novel sequence, whereas the nonfucosylated lacto-N-decaose, Galbeta1-4GlcNAcbeta1-6(Galbeta1-3GlcNAcbeta1-3)Galbeta1-4GlcNAcbeta1-6(Galbeta1-3GlcNAcbeta1-3)Galbeta1-4Glc, has not been isolated and identified as an individual oligosaccharide.

Determination by electrospray mass spectrometry and 1H-NMR spectroscopy of primary structures of variously fucosylated neutral oligosaccharides based on the iso-lacto-N-octaose core

We have isolated a nonfucosylated and three variously fucosylated neutral oligosaccharides from human milk that are based on the iso-lacto-N-octaose core. Their structures were characterized by the combined use of electrospray mass spectrometry (ES-MS) and NMR spectroscopy. The branching pattern and blood group-related Lewis determinants, together with partial sequences and linkages of these oligosaccharides, were initially elucidated by high-sensitivity ES-MS/MS analysis, and then their full structure assignment was completed by methylation analysis and 1H-NMR. Three new structures were identified. The nonfucosylated iso-lacto-N-octaose, Galbeta1-3GlcNAcbeta1-3Galbeta1-4GlcNAcbeta1-6[Galbeta1-3GlcNAcbeta1-3]Galbeta1-4Glc, has not previously been reported as an individual oligosaccharide. The monofucosylated and trifucosylated iso-lacto-N-octaose, Galbeta1-3GlcNAcbeta1-3Galbeta1-4(Fucalpha1-3) GlcNAcbeta1-6[Galbeta1-3GlcNAcbeta1-3]Galbeta1-4Glc and Galbeta1-3(Fucalpha1-4)GlcNAcbeta1-3Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6[Galbeta1-3(Fucalpha1-4)GlcNAcbeta1-3]Galbeta1-4Glc, both containing an internal Lex epitope, are also novel structures.

Offline coupling of low-pressure anion-exchange chromatography with MALDI-MS to determine the elution order of human milk oligosaccharides

Pooled human milk oligosaccharides were separated into neutral and several acidic oligosaccharide fractions by preparative anion-exchange chromatography (AEC) using AG 1-X2. The oligosaccharides were eluted stepwise using deionized water and three different concentrations of ammonium acetate buffer, pH 6.8. The elution order of the compounds was determined directly by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of the AEC effluent without any cleanup or concentration steps. Up to a concentration of 500 mM ammonium acetate, the masses of acidic oligosaccharides could be detected by screening the fractions in an automated mode. The combination of the improved chromatographic procedure, the applied MALDI matrices, and operating parameters is suitable for the detection of neutral oligosaccharides as well as acidic oligosaccharides. The method provides high sensitivity and mass accuracy, including for the high-molecular-weight monosialylated oligosaccharides up to 2751.5 Da. The applied ionic strength of the anion-exchange eluents enables a rapid and an unambiguous composition assignment by MALDI-MS for neutral, monosialylated, and disialylated oligosaccharides from human milk. The acidic fractions have to be desalted by electrodialysis and were finally analyzed by HPAEC-PAD to get a high-resolution "fingerprint" of structures present in each fraction. From these analyses, it can be concluded that the isomeric variety of monosialylated oligosaccharides occurring in human milk is higher than estimated before.

A detailed analysis of neutral and acidic carbohydrates in human milk

Reverse- and normal-phase chromatography have been used to separate a number of standard human milk oligosaccharides derivatized via a reductive amination reaction with 2-aminoacridone (2-AMAC). Analytes were detected by spectrofluorimetry and injected simultaneously with a hydrolyzed dextran ladder derivatized with methyl-4-aminobenzoate. The latter probe does not fluoresce at the wavelength of emission by the 2-AMAC derivatives, and the derivatized, hydrolyzed dextran components were visualized by their ultraviolet absorbance. This procedure gave precise measurements of the "size" of 2-AMAC oligosaccharides in terms of their glucose equivalent values. Analytical amounts of 2-AMAC oligosaccharide standards were also isolated for further characterization by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospray ionization (ESI) mass spectrometry. MS-MS was also used to provide information on oligosaccharide sequences. This methodology was used successfully to characterize mixtures of neutral and acidic oligosaccharides from samples of human milk. This approach could be usefully applied to the study of glycoforms from a variety of samples such as those released from glycoproteins/glycolipids; these have been reported to be altered in a number of diseases, for example, cancer, cystic fibrosis, and autoimmune disease such as rheumatoid arthritis.

Analysis of high-molecular-weight oligosaccharides from human milk by liquid chromatography and MALDI-MS

Pooled human milk oligosaccharides were fractionated by anion-exchange chromatography on AG 1-X2 and by an improved gel filtration procedure that allowed the separation of large oligosaccharides on Toyopearl HW 40 (S) and Bio-Gel P-6 columns, respectively. The analysis of the resulting nonderivatizated fractions by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) revealed several neutral and acidic high-molecular-weight oligosaccharides. So far unknown acidic oligosaccharides containing up to 20 monomers were detected in a molecular mass range of 2094-3626 Da. Furthermore, neutral structures containing up to 35 monosaccharides were identified after fractionation on Toyopearl HW 40 (S) and subsequent P-6 fractionation, demonstrating the suitability of the applied method for the preparation of oligosaccharides in this high-molecular-mass range. The composition of the detected oligosaccharides was found to be the same as those previously identified in oligosaccharides of lower masses. However, an enormous structural heterogeneity was observed when acidic and neutral fractions were characterized by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). From our analysis we may conclude that each molecular mass identified by MALDI-MS corresponds to a variety of isomeric structures. The total number of oligosaccharides occurring in human milk may consequently be much higher than estimated before.

A novel pentasaccharide from immunostimulant oligosaccharide fraction of buffalo milk

A processed oligosaccharide mixture of buffalo milk induced significant stimulation of antibody, delayed-type hypersensitivity response to sheep red blood cells in BALB/c mice. This also stimulated non-specific immune response of the animals measured in terms of macrophage migration index. A novel pentasaccharide has been isolated from the oligosaccharide containing fraction having immunostimulant activity of buffalo milk. This compound was isolated by a combination of gel filtration chromatography, silica gel column chromatography of derivatised oligosaccharides while the homogeneity was confirmed by high performance liquid chromatography. The results of structural analyses, i.e. proton nuclear magnetic resonance, fast atom bombardment mass spectrometry, chemical transformations and degradations are consistent with the following structure: GlcNAcbeta(1-->3)Galbeta(1-->4)GlcNAcbeta(1-->3)Gal beta(1-->4)Glc

Growth, development and differentiation: a functional food science approach

Few other aspects of food supply and metabolism are of greater biological importance than the feeding of mothers during pregnancy and lactation, and of their infants and young children. Nutritional factors during early development not only have short-term effects on growth, body composition and body functions but also exert long-term effects on health, disease and mortality risks in adulthood, as well as development of neural functions and behaviour, a phenomenon called 'metabolic programming'. The interaction of nutrients and gene expression may form the basis of many of these programming effects and needs to be investigated in more detail. The relation between availability of food ingredients and cell and tissue differentiation and its possible uses for promoting health and development requires further exploration. The course of pregnancy, childbirth and lactation as well as human milk composition and the short- and long-term outcome of the child are influenced by the intake of foods and particularly micronutrients, e.g. polyunsaturated fatty acids, Fe, Zn and I. Folic acid supplementation from before conception through the first weeks of pregnancy can markedly reduce the occurrence of severe embryonic malformations; other potential benefits of modulating nutrient supply on maternal and child health should be further evaluated. The evaluation of dietary effects on child growth requires epidemiological and field studies as well as evaluation of specific cell and tissue growth. Novel substrates, growth factors and conditionally essential nutrients (e.g. growth factors, amino acids, polyunsaturated fatty acids) may be potentially useful as ingredients in functional foods and need to be assessed carefully. Intestinal growth, maturation, and adaptation as well as long-term function may be influenced by food ingredients such as oligosaccharides, gangliosides, high-molecular-mass glycoproteins, bile salt-activated lipase, pre- and probiotics. There are indications for some beneficial effects of functional foods on the developing immune response, for example induced by antioxidant vitamins, trace elements, fatty acids, arginine, nucleotides, and altered antigen contents in infant foods. Peak bone mass at the end of adolescence can be increased by dietary means, which is expected to be of long-term importance for the prevention of osteoporosis at older ages. Future studies should be directed to the combined effects of Ca and other constituents of growing bone, such as P, Mg and Zn, as well as vitamins D and K, and the trace elements F and B. Pregnancy and the first postnatal months are critical time periods for the growth and development of the human nervous system, processes for which adequate substrate supplies are essential. Early diet seems to have long-term effects on sensory and cognitive abilities as well as behaviour. The potential beneficial effects of a balanced supply of nutrients such as I, Fe, Zn and polyunsaturated fatty acids should be further evaluated. Possible long-term effects of early exposure to tastes and flavours on later food choice preferences may have a major impact on public health and need to be further elucidated. The use of biotechnology and recombinant techniques may offer the opportunity to include various bioactive substances in special dietary products, such as human milk proteins, peptides, growth factors, which may have beneficial physiological effects, particularly in infancy and early childhood.

1H NMR analysis of novel sialylated and fucosylated lactose-based oligosaccharides having linear GlcNAc(beta 1-6) Gal and Neu5Ac(alpha 2-6) GlcNAc sequences

Three novel oligosaccharides of human infant faeces have been fully characterised by methylation analysis and 500/600 MHz 1H NMR spectroscopy including DQF-COSY, TQF-COSY, TOCSY and ROESY experiments. The oligosaccharides were shown to be lactose-based structures two of which were substituted at C-6 of Gal with either the Le(x) trisaccharide, Gal(beta 1-4)[Fuc(alpha 1-3)]GlcNAc(beta 1-, or Neu5Ac(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-. They differ from other free oligosaccharides previously isolated from the human by having the (1-->6) linkage to Gal in the absence of a (1-->3) branch. The third oligosaccharide has Neu5Ac(alpha 2-6) linked to GlcNAc of the trisaccharide GlcNAc(beta 1-3)Gal(beta 1-4)Glc. This is a linear fragment of the disialylated tetrasaccharide sequence Neu5Ac(alpha 2-3)Gal(beta 1-3)[Neu5Ac(alpha 2-6)]GlcNAc(beta 1-found in the milk oligosaccharide disialyl LNT (the GlcNAc residue of the tetrasaccharide linked to lactose) and also of N-linked chains (GlcNAc linked to Man).

Primary structure of human milk octa-, dodeca- and tridecasaccharides determined by a combination of 1H-NMR spectroscopy and fast-atom-bombardment mass spectrometry. Evidence for a new core structure, the para-lacto-N-octaose

Two octasaccharides, two dodecasaccharides and a tridecasaccharide have been isolated from human milk by a combination of paper chromatography, high-performance liquid chromatography and high-performance anion-exchange chromatography. Their structural analysis investigated by 400-MHz 1H- and 13C-NMR spectroscopy and by mass spectrometry led to the following structures. [formula: see text] The two octasaccharides have been previously characterized in human milk; the complete assignment of the 1H and 13C spectra is reported here. One of the dodecasaccharides is a tetrafucosyl derivative with a new core: typeI-(beta 1-3)-typeII-(beta 1-3)-typeII-(beta 1-3)-Gal((beta 1-4)Glc, where typeI = Gal(beta 1-3)GlcNAc and typeII = Gal(beta 1-4)GlcNAc. These oligosaccharides display simultaneously Lewis(b) and Lewis(x) determinants or Lewis(a), Lewis(b) and Lewis(x) determinants.

Characterization of mucin-type oligosaccharides with the sialyl-Le(a) structure from human colorectal adenocarcinoma cells

Oligosaccharides with the sialyl-Le(a) structure have been isolated on an affinity column of a monoclonal antibody, MSW 113, from mucin-type glycoproteins derived from the surfaces of SW 1116 and LS 180 cells, and their secretions. The oligosaccharides were polydisperse with respect to molecular size, the oligosaccharides derived from glycoproteins in culture media being larger than those in cell lysates, as assessed by gel filtration. Some of the oligosaccharides were susceptible to degradation by endo-beta-galactosidase (E. freundii), as judged from the change in the gel filtration pattern. These results indicate that oligosaccharides with the sialyl-Le(a) structure derived from mucin-type glycoproteins produced by human colonic cancer cells are extremely large in size and complex in structure, and that some of them contain the poly-N-acetyllactosamine structure.