Functions Of Human Milk Oligosaccharides Research Articles

Gut microbiota: A key role for human milk oligosaccharides in regulating host health early in life.

Human milk oligosaccharides (HMOs) are an evolutionarily significant advantage bestowed by mothers for facilitating the development of the infant's gut microbiota. They can avoid absorption in the stomach and small intestine, reaching the colon successfully, where they engage in close interactions with gut microbes. This process also enables HMOs to exert additional prebiotic effects, including regulating the mucus layer, promoting physical growth and brain development, as well as preventing and mitigating conditions such as NEC, allergies, and diarrhea. Here, we comprehensively review the primary ways by which gut microbiota, including Bifidobacteria and other genera, utilize HMOs, and we classify them into five central pathways. Furthermore, we emphasize the metabolic benefits of bacteria consuming HMOs, particularly the recently identified intrinsic link between HMOs and the metabolic conversion of tryptophan to indole and its derivatives. We also examine the extensive probiotic roles of HMOs and their recent research advancements, specifically concentrating on the unsummarized role of HMOs in regulating the mucus layer, where their interaction with the gut microbiota becomes crucial. Additionally, we delve into the principal tools used for functional mining of new HMOs. In conclusion, our study presents a thorough analysis of the interaction mechanism between HMOs and gut microbiota, emphasizing the cooperative utilization of HMOs by gut microbiota, and provides an overview of the subsequent probiotic effects of this interaction. This review provides new insights into the interaction of HMOs with the gut microbiota, which will inform the mechanisms by which HMOs function.

Human milk oligosaccharides as prebiotics.

Based on its richness in immune-related components such as human milk, human milk oligosaccharides (HMOs), milk proteins, and lipids, breast milk can be considered the first functional food that humans encounter in their lifetime. According to WHO recommendations breast milk has to be the only food in an infant's diet in the first six months of age which is then continued up to two years of age with the suitable complementary foods. Regarding breast milk balanced composition, it is considered as the best food of infants thus many studies have been carried out to determine the benefits of breast milk. Based on numerous studies breast milk have a tendency to reduce the risk of type 2 diabetes, obesity, allergies, celiac disease, necrotizing enterocolitis (NEC), gastrointestinal tract infections and some type of cancers. The benefits of breast milk can be explained by its special combination which includes; macronutrients, micronutrients and bioactive components such as immunoglobulins, hormones, growth factors and oligosaccharides. One of the essential bioactive compounds of breast milk is known as human milk oligosaccharides (HMOs). HMOs are unique, bioactive carbohydrates which are identified as the most significant components of breast milk. Since they have structural complexity and multifunctional properties, they are one of the most wondered components of breast milk. HMOs promote the development of the neonatal intestinal immune, and nervous systems. This article briefly describes the history, complex structure and different functions of HMOs and highlight the importance of maternal diet for HMO biosynthesis.

Effects of Human Milk Oligosaccharides in Infant Health Based on Gut Microbiota Alteration

The primary active components of breast milk are human milk oligosaccharides (HMOs). HMOs provide many benefits to infants, including regulating their metabolism, immune system, and brain development. Recent studies have emphasized that HMOs act as prebiotics by the metabolism of intestinal microorganisms to produce short-chain fatty acids, which are crucial for infant development. In addition, HMOs with different structural characteristics can form different microbial compositions. HMOs-induced predominant microbes, including Bifidobacterium infantis, B. bifidum, B. breve, and B. longum, and their metabolites demonstrated pertinent health-promoting properties. Meanwhile, HMOs could also directly reduce the occurrence of diseases through the effects of preventing pathogen infection. In this review, we address the probable function of HMOs inside the HMOs-gut microbiota-infant network, by describing the physiological functions of HMOs and the implications of diet on the HMOs-gut microbiota-infant network.

How far is it from infant formula to human milk? A look at the human milk oligosaccharides

Human milk is the gold standard for the nutrition of infants. Human milk oligosaccharides (HMOs) are structurally diverse sugars highly abundant in human milk but not present in infant formula. The interest in HMOs has gradually increased in recent years due to their beneficial functions on infants. Here we summarize the structures and composition of HMOs, and compare the differences of oligosaccharides in human and other mammals. The absorption and metabolism of HMOs are discussed. Then we discuss existing studies on the functional biology of HMOs. Additionally, the structure-function relationships of HMOs are presented. Finally, this review summarizes the oligosaccharides in recent infant formula as well as limitations and future perspectives of HMOs research. The structures and composition of HMOs are affected by many factors. Large amounts of HMOs are metabolized by gut microbiota, and few are absorbed into circulation to perform physiological functions. Evidences from in vitro and in vivo studies, as well as clinical trials suggest that HMOs modulate gut microbiota, reduce pathogen adhesion, modulate epithelial cell and immune responses, reduce the risk of necrotizing enterocolitis and promote brain development and cognition. The specific structure determines different functions. Currently two HMOs, 2′-fucosyllactose and Lacto- N -Neotetraose, have been demonstrated safe and well-tolerated to be added into infant formula. However, the application in HMOs has been limited due to their insufficient availability. Thus, basic and clinical studies of HMOs need to be further elucidated. • The structures and composition of human milk oligosaccharides are summarized. • The absorption and metabolism of human milk oligosaccharides are discussed. • The biological functions of human milk oligosaccharides are reviewed. • The structure-function relationships of human milk oligosaccharides are presented. • The limitations and future perspectives of HMOs research are outlined.

Metabolic fate of dietary sialic acid and its influence on gut and oral bacteria

In recent years, the biological functions of human milk oligosaccharides and the potential toxic effects of red meat on human health have attracted considerable attention. Sialic acid is an important carbohydrate in milk and red meat, corresponding to sialylated oligosaccharides and N-glycolylneuraminic acid (NeuGc, one type of sialic acid). Herein, we reviewed the metabolic fate of dietary sialic acid in the body and their effects on gut and oral microbes. In summary, dietary NeuAc monomer is directly excreted through urine after being assimilated through the intestines and is not utilized by the human body; in contrast, dietary NeuGc from red meat is easily utilized by the human body and can be incorporated into the brain and other organs. Sialoglycans can be partially utilized by the human body, but they do not affect the cognitive development and growth of children. Dietary sialic acid may mainly regulate the growth and metabolism of gastrointestinal microbiota and human health and development through the gut–brain axis.

Cohousing-mediated microbiota transfer from milk bioactive components-dosed mice ameliorate colitis by remodeling colonic mucus barrier and lamina propria macrophages

ABSTRACT Human milk oligosaccharides (HMOs) and milk fat globule membrane (MFGM) are highly abundant in breast milk, and have been shown to exhibit potent immunomodulatory effects. Yet, their role in the gut microbiota modulation in relation to colitis remains understudied. Since the mixtures of fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS) perfectly mimic the properties and functions of HMOs, the combination of MFGM, FOS, and GOS (CMFG) has therefore been developed and used in this study. Here, CMFG were pre-fed to mice for three weeks to investigate its preventive effect on dextran sodium sulfate (DSS) induced colitis. Moreover, CMFG-treated and vehicle-treated mice were cohoused to further elucidate the preventive role of the gut microbiota transfer in colitis. At the end of the study, 16S rDNA gene amplicon sequencing, short-chain fatty acids (SCFAs) profiling, transcriptome sequencing, histological analysis, immunofluorescence staining and flow cytometry analysis were conducted. Our results showed that CMFG pre-supplementation alleviated DSS-induced colitis as evidenced by decreased disease activity index (DAI) score, reduced body weight loss, increased colon length and mucin secretion, and ameliorated intestinal damage. Moreover, CMFG reduced macrophages in the colon, resulting in decreased levels of IL-1β, IL-6, IL-8, TNF-α, and MPO in the colon and circulation. Furthermore, CMFG altered the gut microbiota composition and promoted SCFAs production in DSS-induced colitis. Markedly, the cohousing study revealed that transfer of gut microbiota from CMFG-treated mice largely improved the DSS-induced colitis as evidenced by reduced intestinal damage and decreased macrophages infiltration in the colon. Moreover, transfer of the gut microbiota from CMFG-treated mice protected against DSS-induced gut microbiota dysbiosis and promotes SCFAs production, which showed to be associated with colitis amelioration. Collectively, these findings demonstrate the beneficial role of CMFG in the gastrointestinal diseases, and further provide evidence for the rational design of effective prophylactic functional diets in both animals and humans.

Recent advances and challenges in microbial production of human milk oligosaccharides

Human milk oligosaccharides (HMOs) are one of the major differences between livestock milk and human milk, and the prebiotic functions of HMOs have been verified through in vitro and clinical trials. The most abundant HMOs include 2′-fucysollactose (2′-FL), 3-fucosyllactose (3-FL), lacto-N-neotetraose (LNnT) and lacto-N-tetraose (LNT); their application and synthesis have attracted wide attentions. In recent years, the biotechnological production of 2′-FL, 3-FL, LNnT and LNT have emerged based on techniques such as whole-cell catalysis and fermentation. In particular, the development of metabolic engineering and synthetic biology methods and strategies have facilitated efficient biosynthesis of these HMOs. However, these advantages have not been systematically reviewed yet. In this review, we first discuss the structures and applications of HMOs; secondly, strategies of microbial synthesis of the most abundant 2′-FL, 3-FL, LNnT and LNT are summarized and compared. Finally, challenges and perspectives of efficient microbial production of HMOs as well as strategies for overcoming the challenges are discussed. This review reveals the whole picture of recent development in HMOs microbial synthesis and can further facilitate the understanding of limiting factors, and further propose a few directions to promote the development of efficient production hosts.

Perspective: Human Milk Oligosaccharides: Fuel for Childhood Obesity Prevention?

Obesity begins early but has lifelong consequences for health and well-being. Breastfeeding is thought to be preventive against obesity, but the extent and cause of this association are not well understood. Human milk oligosaccharides (HMOs) are abundant in human milk and not present in commercially available infant formula. These complex sugars are thought to contribute to the development of the infant gut microbiome and immune system. Recently, they have been investigated as a potential link between breastfeeding and lower obesity risk. So far, only a few human studies have examined HMO composition of human milk in association with the infant's concurrent anthropometry or subsequent growth in infancy, with conflicting results. However, HMOs have been shown to modulate the gut microbiome profile by selectively promoting the growth of specific bacteria, such as bifidobacteria. Moreover, there are differences in the gut microbiome of lean and obese humans, and there is some evidence that the early composition of the gut microbiome can predict later obesity. Although it seems that HMOs might have a role in infant growth and adiposity, there is not enough consistent evidence to understand their potential role in obesity prevention. More data, particularly from large or longitudinal studies, are needed to clarify the functions of HMOs and other breast-milk components in determining long-term health.

Correlating Infant Fecal Microbiota Composition and Human Milk Oligosaccharide Consumption by Microbiota of 1-Month-Old Breastfed Infants.

ScopeUnderstanding the biological functions of human milk oligosaccharides (HMOs) in shaping gastrointestinal (GI) tract microbiota during infancy is of great interest. A link between HMOs in maternal milk and infant fecal microbiota composition is examined and the role of microbiota in degrading HMOs within the GI tract of healthy, breastfed, 1‐month‐old infants is investigated.Methods and resultsMaternal breast milk and infant feces are from the KOALA Birth Cohort. HMOs are quantified in milk and infant fecal samples using liquid chromatography‐mass spectrometry. Fecal microbiota composition is characterized using Illumina HiSeq 16S rRNA gene amplicon sequencing. The composition is associated with gender, delivery mode, and milk HMOs: Lacto‐N‐fucopentaose I and 2′‐fucosyllactose. Overall, Bifidobacterium, Bacteroides, Escherichia–Shigella, and Parabacteroides are predominating genera. Three different patterns in infant fecal microbiota structure are detected. GI degradation of HMOs is strongly associated with fecal microbiota composition, and there is a link between utilization of specific HMOs and relative abundance of various phylotypes (operational taxonomic units).ConclusionsHMOs in maternal milk are among the important factors shaping GI tract microbiota in 1‐month‐old breastfed infants. An infant's ability to metabolize different HMOs strongly correlates with fecal microbiota composition and specifically with phylotypes within genera Bifidobacterium, Bacteroides, and Lactobacillus.

Shaping the Infant Microbiome With Non-digestible Carbohydrates.

Natural polysaccharides with health benefits are characterized by a large structural diversity and differ in building blocks, linkages, and lengths. They contribute to human health by functioning as anti-adhesives preventing pathogen adhesion, stimulate immune maturation and gut barrier function, and serve as fermentable substrates for gut bacteria. Examples of such beneficial carbohydrates include the human milk oligosaccharides (HMOs). Also, specific non-digestible carbohydrates (NDCs), such as galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS) are being produced with this purpose in mind, and are currently added to infant formula to stimulate the healthy development of the newborn. They mimic some functions of HMO, but not all. Therefore, many research efforts focus on identification and production of novel types of NDCs. In this review, we give an overview of the few NDCs currently available [GOS, FOS, polydextrose (PDX)], and outline the potential of alternative oligosaccharides, such as pectins, (arabino)xylo-oligosaccharides, and microbial exopolysaccharides (EPS). Moreover, state-of-the-art techniques to generate novel types of dietary glycans, including sialylated GOS (Sia-GOS) and galactosylated chitin, are presented as a way to obtain novel prebiotic NDCs that help shaping the infant microbiome.

Mother Knows Best: Deciphering the Antibacterial Properties of Human Milk Oligosaccharides.

This Account describes the risky proposition of organizing a multidisciplinary team to interrogate a challenging problem in chemical biology: characterizing how human milk, at the molecular level, protects infants from infectious diseases. At the outset, our initial hypothesis was that human milk oligosaccharides (HMOs) possess antimicrobial and antivirulence activities. Early on, we discovered that HMOs do indeed modulate bacterial growth and biofilm production for numerous bacterial pathogens. In light of this discovery, three priorities emerged for our program moving forward. The first was to decode the mode of action behind this activity. The second was to decipher the functional effects of HMO structural diversity as there are ca. 200 unique HMOs present in human milk. Finally, we set our sights on discovering novel uses for HMOs as we believed this would uniquely position our team to achieve a major breakthrough in human health and wellness. Through a combination of fractionation techniques, chemical synthesis, and industrial partnerships, we have determined the identities of several HMOs with potent antimicrobial activity against the important neonate pathogen Group B Streptococcus (Group B Strep; GBS). In addition to a structure-activity relationship (SAR) study, we observed that HMOs are effective adjuvants for intracellular-targeting antibiotics against GBS. This included two antibiotics that GBS has evolved resistance to. At their half maximal inhibitory concentration (IC50), heterogeneous HMOs reduced the minimum inhibitory concentration (MIC) of select antibiotics by up to 32-fold. Similarly, we observed that HMOs potentiate the activity of polymyxin B (Gram-negative-selective antibiotic) against GBS (Gram-positive species). Based on these collective discoveries, we hypothesized that HMOs function by increasing bacterial cell permeability, which would be a novel mode of action for these molecules. This hypothesis was validated as HMOs were found to increase membrane permeability by around 30% compared to an untreated control. The question that remains is how exactly HMOs interact with bacterial membranes to induce permeability changes (i.e., through promiscuous insertion into the bilayer, engagement of proteins involved in membrane synthesis, or HMO-capsular polysaccharide interactions). Our immediate efforts in this regard are to apply chemoproteomics to identify the molecular target(s) of HMOs. These investigations are enabled through manipulation of HMOs produced via total synthesis or enzymatic and whole-cell microbial biotransformation.

Bovine Milk Oligosaccharide Contents Show Remarkable Seasonal Variation and Intercow Variation.

Human milk oligosaccharides (OS) play an important role in protecting the neonate. In addition to fructo-oligosaccharides and galacto-oligosaccharides, bovine milk OS have great potential to be used in pediatric food products to mimic the functions of human milk OS. Currently, little is known about the accumulation of OS in bovine milk in relation to genetic and environmental factors. A systematic survey on seasonal variation of 14 major OS was thus conducted with 19 cows over the entire milking season using a liquid chromatography-mass spectrometry technique. This study revealed a number of significant correlations between structurally related and structurally nonrelated OS and a substantial individual animal difference for all 14 OS. Most of the 14 OS displayed a remarkable seasonal variation in abundance (up to 10-fold change), with the highest abundance observed in April and May (i.e., autumn) for the majority of the 19 cows.

Reaction kinetics and galactooligosaccharide product profiles of the β-galactosidases from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae.

β-Galactosidase enzymes are used in the dairy industry to convert lactose into galactooligosaccharides (GOS) that are added to infant formula to mimic the molecular sizes and prebiotic functions of human milk oligosaccharides. Here we report a detailed analysis of the clearly different GOS profiles of the commercial β-galactosidases from Bacillus circulans, Kluyveromyces lactis and Aspergillus oryzae. Also the GOS yields of these enzymes differed, varying from 48.3% (B. circulans) to 34.9% (K. lactis), and 19.5% (A. oryzae). Their incubation with lactose plus the monosaccharides Gal or Glc resulted in altered GOS profiles. Experiments with 13C6 labelled Gal and Glc showed that both monosaccharides act as acceptor substrates in the transgalactosylation reactions. The data shows that the lactose isomers β-d-Galp-(1→2)-d-Glcp, β-d-Galp-(1→3)-d-Glcp and β-d-Galp-(1→6)-d-Glcp are formed from acceptor reactions with free Glc and not by rearrangement of Glc in the active site.

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.

Human Milk Oligosaccharides Important for Infant Defense

Human milk is the “gold standard” nutrition for infants. Human milk contains all necessary nutrients needed for infant growth and developments. Human milk oligosaccharides (HMOs) are important functional ingredients found in human milk, in addition to standard nutrients. They have complex structure and represent third predominant components in human milk. Functions of HMOs are not fully understood but it is thought that they play an important role in the development of immune system, the prevention of pathogenic infection and, in the modulation of infant gut microbiota. HMOs are indigestible to human digestive enzymes and act as prebiotics. Study shows that HMOs favors promoting the colonisation of Bifidobacteria, which is found to be beneficial and major microbiome in the gut of breast-fed infants. HMOs show anti pathogenic effects and may protect infants from different pathogenic microorganisms such as, Campylobacter jejuni, Campylobacter pylori, Escherichia coli, Vibrio cholera and Rotavirus. HMOs may provide specific and/or non-specific immune defense to infants via various mechanisms. They may shape the growth of intestinal microflora, may prevent the attachment of pathogenic microorganisms to intestinal cells and may influence inflammatory processes by reducing leukocyte binding to endothelial cells. In vivo defense functions of HMOs in the human milk-fed infants have not been established yet. Future research may focus on to elucidate and verify the beneficial effects of HMOs for the breast-fed infant, as well as impact of HMOs to the health of the breast-feeding mother and the composition of other milk components.

Introduction to the Symposium

On May 16–17th, 2011, the First International Symposium on the Glycobiology of Human Milk Oligosaccharides was held at the Tivoli Hotel in Copenhagen, Denmark. The symposium was supported by Glycom A/S, Kongens Lyngby, Denmark. Human milk oligosaccharides (HMO)7 represent the third most predominant component in human milk but are absent from infant formula (1–3). Thus, oligosaccharide content represents the largest compositional gap between human milk and infant formula. Our understanding of HMO structure and natural variation in human milk has markedly expanded in the past decade, primarily due to advances in analytical methods (4, 5). HMO exert a number of important physiological functions, particularly in the early postpartum period, including facilitating the establishment of a healthy microbiota enriched bifidobacteria (6, 7), blocking the attachment of pathogens (8), and educating the neonatal immune system (9). Until now, direct study of dietary HMO function has been limited and commercialization has been blocked by lack of available material and high costs. Virtually no HMO were available from extractive sources and only a few synthesized in extremely low quantities and prohibitively high costs. However, due to the enormous biotechnological progress in HMO synthesis, the field is entering a new era focusing on specific biological effects of HMO in animals and humans.

Human milk oligosaccharides: prebiotics and beyond

Human milk oligosaccharides (HMO) are complex glycans that are present at very high concentrations in human milk but not in infant formula. The significant energy expended by mothers to make these complex glycans suggests they must be important. How do maternal HMOs benefit the breast-fed infant? How are HMOs synthesized in the human mammary gland? How can we provide formula-fed infants with HMOs or HMO-like glycans? This article reviews current knowledge and open questions on the biosynthesis and functions of HMOs.

Incorporation of orally applied 13C-galactose into milk lactose and oligosaccharides

Biosynthesis and functions of human milk oligosaccharides (HMO) are not well known. A typical housekeeping enzyme, beta1,4-galactosyltransferase, links galactose to glucose to form lactose which is then used as backbone for the assembly of HMO. We investigated whether milk lactose and HMO may be labeled in vivo by an orally given (13)C-galactose bolus. Eleven exclusively breastfeeding mothers were given a (13)C-galactose bolus at the end of their breakfast. Milk and urine samples from each nursing up to 36 h were analyzed for carbohydrate composition by high-performance thin-layer chromatography, high-pH anion-exchange chromatography, and fast atom bombardment mass spectrometry. (13)C enrichment of milk fractions, urinary carbohydrates, lactose, and oligosaccharides as well as of breath CO(2) was determined by isotope ratio mass spectrometry. Up to 10% of the orally given galactose bolus was directly transported to the mammary gland and incorporated into milk components. Characteristic for most milk samples was the appearance of two (13)C-peaks, the first immediately after the (13)C-bolus was taken and the second on the next morning. The highest (13)C enrichment was found in lactose followed by neutral and acidic oligosaccharides. In breath samples, the (13)C-excretion followed the same pattern as in milk. (13)C nuclear magnetic resonance of isolated lactose revealed (13)C only at C(1)-atom of galactose and C(1)-atom of glucose. This label was without any exception at the same position as the (13)C-label of the orally applied galactose. Neutral and acidic HMO can easily be (13)C-labeled in vivo which facilitates investigations of their metabolic fate in infants.

Human milk oligosaccharides are resistant to enzymatic hydrolysis in the upper gastrointestinal tract

Human milk oligosaccharides (HMOs) show a complexity and variety not found in milk of any other species. Although progress has been made in the past 3 decades with regard to identification and structural characterization of HMOs, not much is known about the physiologic functions of HMOs. As a prerequisite for biological activity in infant metabolism, HMOs have to resist enzymatic hydrolysis in the gastrointestinal tract. To assess the extent to which selected HMOs are hydrolyzed, we carried out in vitro digestion studies using enzyme preparations of human and porcine pancreas and intestinal brush border membranes (BBMs). Fractions of HMOs, including structurally defined isolated oligosaccharides, were digested for up to 20 h with human pancreatic juice and BBMs prepared from human or porcine intestinal tissue samples. HMOs were incubated by using a porcine pancreatic homogenate and BBMs as enzyme sources. HMOs and digestion products were identified by mass spectrometry and anion-exchange chromatography. Additionally, free D-glucose, L-fucose, and N-acetylneuraminic acid were determined enzymatically. Whereas maltodextrin (control) was rapidly and completely hydrolyzed, neutral and acidic HMOs showed a profound resistance against pancreatic juice and BBM hydrolases. However, cleavage of most of the HMOs was achieved by using a pancreatic homogenate containing intracellular, including lysosomal, enzymes in addition to secreted enzymes. The results of this study strongly suggest that HMOs are not hydrolyzed by enzymes in the upper small intestine. Although intact HMOs may be absorbed, we postulate that a majority of HMOs reach the large intestine, where they serve as substrates for bacterial metabolism. Therefore, HMOs might be considered the soluble fiber fraction of human milk.