Oligosaccharides from human milk induce growth arrest via G2/M by influencing growth-related cell cycle genes in intestinal epithelial cells

Anticancer and anti-angiogenic activities of mannooligosaccharides extracted from coconut meal on colorectal carcinoma cells in vitro

Colorectal carcinoma (CRC) is one of the most common malignancies, though there are no effective therapeutic regimens at present. This study aimed to investigate the inhibitory effects of mannooligosaccharides extracted from coconut meal (CMOSs) on the proliferation and migration of human colorectal cancer HCT116 cells in vitro. The results showed that CMOSs exhibited significant inhibitory activity against HCT116 cell proliferation in a concentration-dependent manner with less cytotoxic effects on the Vero normal cells. CMOSs displayed the ability to increase the activation of caspase-8, -9, and -3/7, as well as the generation of reactive oxygen species (ROS). Moreover, CMOSs suppressed HCT116 cell migration in vitro. Interestingly, treatment of human microvascular endothelial cells (HMVECs) with CMOSs resulted in the inhibition of cell proliferation, cell migration, and capillary-like tube formation, suggesting its anti-vascular angiogenesis. In summary, the results of this study indicate that CMOSs could be a valuable therapeutic candidate for CRC treatment.

Recent progress on health effects and biosynthesis of two key sialylated human milk oligosaccharides, 3'-sialyllactose and 6'-sialyllactose

Human milk oligosaccharides (HMOs), the third major solid component in breast milk, are recognized as the first prebiotics for health benefits in infants. Sialylated HMOs are an important type of HMOs, accounting for approximately 13% of total HMOs. 3'-Sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL) are two simplest sialylated HMOs. Both SLs display promising prebiotic effects, especially in promoting the proliferation of bifidobacteria and shaping the gut microbiota. SLs exhibit several health effects, including antiadhesive antimicrobial ability, antiviral activity, prevention of necrotizing enterocolitis, immunomodulatory activity, regulation of intestinal epithelial cell response, promotion of brain development, and cognition improvement. Both SLs have been approved as "Generally Recognized as Safe" by the American Food and Drug Administration and are commercially added to infant formula. The biosynthesis of SLs using enzymatic or microbial approaches has been widely studied. The enzymatic synthesis of SLs can be realized by two types of enzymes, sialidases with trans-sialidase activity and sialyltransferases. Microbial synthesis can be achieved by the multiple recombinant bacteria in one-pot reaction, which express the enzymes involved in SL synthesis pathways separately or in combination, or by metabolically engineered strains in a fermentation process. In this article, the physiological properties of 3'-SL and 6'-SL are summarized in detail and the biosynthesis of these SLs via enzymatic and microbial synthesis is comprehensively reviewed.

Current Advances in Structure-Function Relationships and Dose-Dependent Effects of Human Milk Oligosaccharides

HMOs (human milk oligosaccharides) are the third most important nutrient in breast milk. As complex glycans, HMOs play an important role in regulating neonatal intestinal immunity, resisting viral and bacterial infections, displaying anti-inflammatory characteristics, and promoting brain development. Although there have been some previous reports of HMOs, a detailed literature review summarizing the structure-activity relationships and dose-dependent effects of HMOs is lacking. Hence, after introducing the structures and synthetic pathways of HMOs, this review summarizes and categorizes identified structure-function relationships of HMOs. Differential mechanisms of different structural HMOs utilization by microorganisms are summarized. This review also emphasizes the recent advances in the interactions between different health benefits and the variance of dosage effect based on in vitro cell tests, animal experiments, and human intervention studies. The potential relationships between the chemical structure, the dosage selection, and the physiological properties of HMOs as functional foods are vital for further understanding of HMOs and their future applications.

Human Milk Oligosaccharides Are Present in Amniotic Fluid and Show Specific Patterns Dependent on Gestational Age

(1) Background: Human milk oligosaccharides (HMOs) are already found in maternal circulation in early pregnancy, changing with gestational age. HMOs are also present in cord blood and amniotic fluid (AF). We aimed to assess HMO profiles in AF over the course of gestation. (2) Methods: AF was collected during diagnostic amniocentesis, fetal surgery, or C-section from 77 women with a gestational age of ranging from 14.3 to 40.9 weeks. Samples were analysed using high performance liquid chromatography with fluorescence detection. (3) Results: We found lactose and up to 16 HMO structures in all AF samples investigated, starting at 14 weeks of gestation. Overall, 3′-sialyllactose (3′SL) and 2′-fucosyllactose (2′FL) were the most abundant HMOs. Individual and total HMO concentrations were significantly positively correlated with gestational age. HMO composition also changed between early, mid- and late pregnancy, with relative concentrations of 3′SL significantly decreasing (44%, 25%, 24%) and 2′FL increasing (7%, 13%, 21%), respectively. (4) Conclusion: Our study shows that HMOs are already present in AF early in pregnancy. This demonstrates extensive contact of the fetus with a broad variety of HMOs, suggesting roles for HMOs in fetal tissue development during the time course of pregnancy.

Structure-Function Relationships of Human Milk Oligosaccharides on the Intestinal Epithelial Transcriptome in Caco-2 Cells and a Murine Model of Necrotizing Enterocolitis

SCOPE

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal emergency affecting preterm infants. Breastmilk protects against NEC, partly due to human milk oligosaccharides (HMOs). HMO compositions are highly diverse, and it is unclear if anti-NEC properties are specific to carbohydrate motifs. Here, this study compares intestinal epithelial transcriptomes of five synthetic HMOs (sHMOs) and examines structure-function relationships of HMOs on intestinal signaling.

METHODS AND RESULTS

This study interrogates the transcriptome of Caco-2Bbe1 cells in response to five synthetic HMOs (sHMOs) using RNA sequencing: 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3FL), 6'-siallyllactose (6'-SL), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT). Protection against intestinal barrier dysfunction and inflammation occurred in an HMO-dependent manner. Each sHMO exerts a unique set of host transcriptome changes and modulated unique signaling pathways. There is clustering between HMOs bearing similar side chains, with little overlap in gene regulation which is shared by all sHMOs. Interestingly, most sHMOs protect pups against NEC, exerting divergent mechanisms on intestinal cell morphology and inflammation.

CONCLUSIONS

These results demonstrate that while structurally distinct HMOs impact intestinal physiology, their mechanisms of action differ. This finding establishes the first structure-function relationship of HMOs in the context of intestinal cell signaling responses and offers a functional framework by which to screen and design HMO-like compounds.

Human Milk Oligosaccharides in Cord Blood Are Altered in Gestational Diabetes and Stimulate Feto-Placental Angiogenesis In Vitro

(1) Background: Human milk oligosaccharides (HMOs) are present in maternal serum during pregnancy and their composition is altered in gestational diabetes (GDM). HMOs are also in fetal cord blood and in contact with the feto-placental endothelium, potentially affecting its functions, such as angiogenesis. We hypothesized that cord blood HMOs are changed in GDM and contribute to increased feto-placental angiogenesis, hallmark of GDM. (2) Methods: Using HPLC, we quantified HMOs in cord blood of women with normal glucose tolerance (NGT, n = 25) or GDM (n = 26). We investigated in vitro angiogenesis using primary feto-placental endothelial cells (fpECs) from term placentas after healthy pregnancy (n = 10), in presence or absence of HMOs (100 µg/mL) isolated from human milk, 3′-sialyllactose (3′SL, 30 µg/mL) and lactose (glycan control) and determined network formation (Matrigel assay), proliferation (MTT assays), actin organization (F-actin staining), tube formation (fibrin tube formation assay) and sprouting (spheroid sprouting assay). (3) Results: 3′SL was higher in GDM cord blood. HMOs increased network formation, HMOs and 3’SL increased proliferation and F-actin staining. In fibrin assays, HMOs and 3’SL increased total tube length by 24% and 25% (p < 0.05), in spheroid assays, by 32% (p < 0.05) and 21% (p = 0.056), respectively. Lactose had no effect. (4) Conclusions: Our study suggests a novel role of HMOs in feto-placental angiogenesis and indicates a contribution of HMO composition to altered feto-placental vascularization in GDM.

Artificial Intelligence in Functional Food Ingredient Discovery and Characterisation: A Focus on Bioactive Plant and Food Peptides

Scientific research consistently demonstrates that diseases may be delayed, treated, or even prevented and, thereby, health may be maintained with health-promoting functional food ingredients (FFIs). Consumers are increasingly demanding sound information about food, nutrition, nutrients, and their associated health benefits. Consequently, a nutrition industry is being formed around natural foods and FFIs, the economic growth of which is increasingly driven by consumer decisions. Information technology, in particular artificial intelligence (AI), is primed to vastly expand the pool of characterised and annotated FFIs available to consumers, by systematically discovering and characterising natural, efficacious, and safe bioactive ingredients (bioactives) that address specific health needs. However, FFI-producing companies are lagging in adopting AI technology for their ingredient development pipelines for several reasons, resulting in a lack of efficient means for large-scale and high-throughput molecular and functional ingredient characterisation. The arrival of the AI-led technological revolution allows for the comprehensive characterisation and understanding of the universe of FFI molecules, enabling the mining of the food and natural product space in an unprecedented manner. In turn, this expansion of bioactives dramatically increases the repertoire of FFIs available to the consumer, ultimately resulting in bioactives being specifically developed to target unmet health needs.

Concentrations of oligosaccharides in human milk and child growth

BACKGROUND

The relationship between human milk oligosaccharides (HMO) and child growth has been investigated only insufficiently with ambiguous results. Therefore, this study examines potential influencing factors of HMO concentrations and how HMO are associated with child growth parameters.

METHODS

Milk samples from the German LIFE Child cohort of healthy children were analyzed for 9 HMO. Putative associations with maternal and child cofactors and child height, head circumference and BMI between 3 months and 7 years of age were examined. Secretor status, defined as the presence of 2'-fucosyllactose, was investigated for associations with infant outcomes.

RESULTS

Our population consisted of 21 (14.7%) non-secretor and 122 (85.3%) secretor mothers. Maternal age was significantly associated with higher 3'SL concentrations; gestational age was associated with LNT, 6'SL and LNFP-I. Pre-pregnancy BMI was negatively associated with LNnT only in non-secretors. The growth velocity of non-secretors' children was inversely associated with LNnT at 3 months to 1 year (R = 0.95 [0.90, 0.99], p = 0.014), 1 to 2 years (R = 0.80 [0.72, 0.88], p < 0.001) and 5 to 6 years (R = 0.71 [0.57, 0.87], p = 0.002). 2'FL was negatively associated with BMI consistently, reaching statistical significance at 3 months and 4 and 5 years. Children of non-secretors showed higher BMI at 3 months, 6 months, and 3, 6, and 7 years of age.

CONCLUSION

We found that some associations between HMO and infant growth may extend beyond the infancy and breastfeeding periods. They highlight the importance of both maternal and infant parameters in the understanding of the underlying associations.

TRIAL REGISTRATION

The study is registered with ClinicalTrial.gov: NCT02550236 .

Building Robust Assemblages of Bacteria in the Human Gut in Early Life

The neonatal body provides a range of potential habitats, such as the gut, for microbes. These sites eventually harbor microbial communities (microbiotas). A "complete" (adult) gut microbiota is not acquired by the neonate immediately after birth. Rather, the exclusive, milk-based nutrition of the infant encourages the assemblage of a gut microbiota of low diversity, usually dominated by bifidobacterial species. The maternal fecal microbiota is an important source of bacterial species that colonize the gut of infants, at least in the short-term. However, development of the microbiota is influenced by the use of human milk (breast feeding), infant formula, preterm delivery of infants, caesarean delivery, antibiotic administration, family details and other environmental factors. Following the introduction of weaning (complementary) foods, the gut microbiota develops in complexity due to the availability of a diversity of plant glycans in fruits and vegetables. These glycans provide growth substrates for the bacterial families (such as members of the Ruminococcaceae and Lachnospiraceae) that, in due course, will dominate the gut microbiota of the adult. Although current data are often fragmentary and observational, it can be concluded that the nutrition that a child receives in early life is likely to impinge not only on the development of the microbiota at that time but also on the subsequent lifelong, functional relationships between the microbiota and the human host. The purpose of this review, therefore, is to discuss the importance of promoting the assemblage of functionally robust gut microbiotas at appropriate times in early life.

Utilization efficiency of human milk oligosaccharides by human-associated Akkermansia is strain-dependent

Akkermansia muciniphila are mucin degrading bacteria found in the human gut and are often associated with positive human health. However, despite being detected as early as one month of age, little is known about the role of Akkermansia in the infant gut. Human milk oligosaccharides (HMOs) are abundant components of human milk and are structurally similar to the oligosaccharides that comprise mucin, the preferred growth substrate of human-associated Akkermansia. A limited subset of intestinal bacteria has been shown to grow well on HMOs and mucin. We therefore examined the ability of genomically diverse strains of Akkermansia to grow on HMOs. First, we screened 85 genomes representing the four known Akkermansia phylogroups to examine their metabolic potential to degrade HMOs. Furthermore, we examined the ability of representative isolates to grow on individual HMOs in a mucin background and analyzed the resulting metabolites. All Akkermansia genomes were equipped with an array of glycoside hydrolases associated with HMO-deconstruction. Representative strains were all able to grow on HMOs with varying efficiency and growth yield. Strain CSUN-19 belonging to the AmIV phylogroup, grew to the highest level in the presence of fucosylated and sialylated HMOs. This activity may be partially related to the increased copy numbers and/or the enzyme activities of the α-fucosidases, α-sialidases, and β-galactosidases. This examines the utilization of individual purified HMOs by Akkermansia strains representing all known phylogroups. Further studies are required to examine how HMO ingestion influences gut microbial ecology in infants harboring different Akkermansia phylogroups. Importance Human milk oligosaccharides (HMOs) are the third most abundant component of breast milk and provide several benefits to developing infants including recruitment of beneficial bacteria to the human gut. Akkermansia are largely considered beneficial bacteria and have been detected in colostrum, breast milk, and young infants. A. muciniphila Muc^T belonging to the AmI phylogroup contribute to the HMO deconstruction capacity of the infant. Here, using phylogenomics, we examined the genomic capacity of four Akkermansia phylogroups to deconstruct HMOs. Indeed, each phylogroup contained differences in the genomic capacity to deconstruct HMOs and representative strains of each phylogroup were able to grow using HMOs. These Akkermansia-HMO interactions potentially influence gut microbial ecology in early life - a critical time for the development of the gut microbiome and infant health.

An Expert Panel Statement on the Beneficial Effects of Human Milk Oligosaccharides (HMOs) in Early Life and Potential Utility of HMO-Supplemented Infant Formula in Cow's Milk Protein Allergy

This review by pediatric gastroenterology and allergy-immunology experts aimed to address the biological roles of human milk oligosaccharides (HMOs) and the potential utility of HMOs in prevention of allergy with particular emphasis on cow^’s milk protein allergy (CMPA). The participating experts consider HMOs amongst the most critical bioactive components of human milk, which act as antimicrobials and antivirals by preventing pathogen adhesion to epithelial cells, as intestinal epithelial cell modulators by enhancing maturation of intestinal mucosa and intestinal epithelial barrier function, as prebiotics by promoting healthy microbiota composition and as immunomodulators by modulating immune cells indirectly and directly. Accordingly, the participating experts consider the proposed link between HMOs and prevention of allergy to be primarily based on the impact of HMO on gut microbiota, intestinal mucosal barrier, immunomodulation and immune maturation. Along with the lower risk of respiratory and gastrointestinal infections, HMO-supplemented formulas seem to be promising alternatives in the management of CMPA. Nonetheless, the effects of individual as well as complex mixtures of HMO in terms of clear clinical and immunological effects and tolerance development need to be further explored to fully realize the immunomodulatory mechanisms and the potential for HMOs in prevention of allergic diseases and CMPA.

Physiological effects, biosynthesis, and derivatization of key human milk tetrasaccharides, lacto-N-tetraose, and lacto-N-neotetraose

Human milk oligosaccharides (HMOs) have recently attracted ever-increasing interest because of their versatile physiological functions. In HMOs, two tetrasaccharides, lacto-N-tetraose (LNT) and lacto-N-neotetraose (LNnT), constitute the essential components, each accounting 6% (w/w) of total HMOs. Also, they serve as core structures for fucosylation and sialylation, generating functional derivatives and elongation generating longer chains of core structures. LNT, LNnT, and their fucosylated and/or sialylated derivatives account for more than 30% (w/w) of total HMOs. For derivatization, LNT and LNnT can be modified into a series of complex fucosylated and/or sialylated HMOs by transferring fucose residues at α1,2-, α1,3-, and α1,3/4-linkage and/or sialic acid residues at α2,3- and α2,6-linkage. Such structural diversity allows these HMOs to possess great commercial value and an application potential in the food and pharmaceutical industries. In this review, we first elaborate the physiological functions of these tetrasaccharides and derivatives. Next, we extensively review recent developments in the biosynthesis of LNT, LNnT, and their derivatives in vitro and in vivo by employing advanced enzymatic reaction systems and metabolic engineering strategies. Finally, future perspectives in the synthesis of these HMOs using enzymatic and metabolic engineering approaches are presented.

Recent advance in infant nutrition: Human milk oligosaccharides

Breast feeding and human milk are the standards for infant feeding and nutrition. Human milk oligosaccharides (HMOs) are the third most abundant solid component in human milk. To date, more than 200 structural different HMOs have been identified and some can be synthesized by the food industry. HMOs are one of the major differences between human milk and formula milk, and current evidence demonstrates their various beneficial effects toward infants' health: acting as anti-adhesive antimicrobials, immune modulators, and intestinal cell response modulators, as well as providing prebiotics effect and neurodevelopment and cognition effects. HMOs compositions vary among mothers, influenced by the stage of lactation, duration of pregnancy and maternal genetic factors. However, there are still some unknown factors affecting the compositions of HMOs and requiring further research for clarification. A combination of preclinical and clinical cohort studies may help to identify whether an individual HMO contributes to disease protection. In recent years, 2'-fucosyllactose (2'-FL) and lacto-N-neotetraose (LNnT) have been approved as food ingredients by official authorities. Infant formulae supplemented with these HMOs are well-tolerated. However, more prospective clinical studies are warranted to elucidate HMOs' significance in infant nutrition. Breast milk feeding remains the best option for infants nutrition and development. Whenever breast milk is not adequate or unavailable, infant formula supplemented with HMOs might be considered as an alternative.

In Love with Shaping You-Influential Factors on the Breast Milk Content of Human Milk Oligosaccharides and Their Decisive Roles for Neonatal Development

Human milk oligosaccharides (HMOs) are structurally versatile sugar molecules constituting the third major group of soluble components in human breast milk. Based on the disaccharide lactose, the mammary glands of future and lactating mothers produce a few hundreds of different HMOs implicating that their overall anabolism utilizes rather high amounts of energy. At first sight, it therefore seems contradictory that these sugars are indigestible for infants raising the question of why such an energy-intensive molecular class evolved. However, in-depth analysis of their molecular modes of action reveals that Mother Nature created HMOs for neonatal development, protection and promotion of health. This is not solely facilitated by HMOs in their indigestible form but also by catabolites that are generated by microbial metabolism in the neonatal gut additionally qualifying HMOs as natural prebiotics. This narrative review elucidates factors influencing the HMO composition as well as physiological roles of HMOs on their way through the infant body and within the gut, where a major portion of HMOs faces microbial catabolism. Concurrently, this work summarizes in vitro, preclinical and observational as well as interventional clinical studies that analyzed potential health effects that have been demonstrated by or were related to either human milk-derived or synthetic HMOs or HMO fractions.

Human Milk Oligosaccharides Protect against Necrotizing Enterocolitis by Activating Intestinal Cell Differentiation

SCOPE

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal emergency and currently the leading cause of mortality in preterm infants. Recent studies show that human milk oligosaccharides (HMOs) reduce the frequency and incidence of NEC; however, the molecular mechanisms for their protection are largely unexplored.

METHODS AND RESULTS

To address this gap, a genome-wide profiling of the intestinal epithelial transcriptome in response to HMOs using RNA-sequencing is performed. It is found that HMOs alter the host transcriptome in 225 unique target genes pertaining to cell proliferation and differentiation, including upregulation of stem cell differentiation marker HMGCS2. To validate these results, differentiation in Caco-2Bbe1 (Caco-2) intestinal cells is verified by Alcian Blue staining and transepithelial electrical resistance (TER) recordings. Furthermore, an in vivo model of NEC is also employed whereby neonatal pups are gavage fed HMOs. Interestingly, HMOs-fed pups show enhanced cell MUC2 differentiation and HMGCS2 expression.

CONCLUSIONS

These findings demonstrate HMOs protect against NEC in part by altering the differentiation of the crypt-villus axis. In addition, this study suggests that pooled HMOs directly induce a series of biological processes, which provide mechanistic insights to how HMOs protect the host intestine.

Human Milk Oligosaccharides Activate Epidermal Growth Factor Receptor and Protect Against Hypoxia-Induced Injuries in the Mouse Intestinal Epithelium and Caco2 Cells

BACKGROUND

Hypoxia-induced intestinal barrier injuries lead to necrotizing enterocolitis (NEC). Although NEC in preterm neonates is preventable by human milk oligosaccharides (HMOs), the underlying mechanism remains unknown.

OBJECTIVE

To reveal the role and mechanism of HMOs in protecting against hypoxia-induced injuries in intestinal epithelium of neonatal mice and cultured Caco2 cells.

METHODS

NEC was induced by hypoxia and cold stress. Seventy C57BL/C pups (7-d-old) were divided into 5 groups and fed maternal breast milk (BM), formula alone (FF), or the formula added with HMOs at 5 (LHMO), 10 (MHMO), or 20 mg/mL (HHMO) for 3 d. Ileal hypoxia inducible factor 1α (HIF1α) and cleaved Caspase 3 were determined, along with staining for Ki-67 protein to labeled proliferative cells. In vitro, adherent Caco2 cells (undifferentiated, passage 14) were treated with HMOs, galacto-oligosaccharides, fructo-oligosaccharides, or mixed oligosaccharides at 10 mg/mL for 1 d exposed to 1% O2. Cell proliferation and apoptosis, along with phosphorylated epidermal growth factor receptor (P-EGFR) and 38KD MAPK (P-P38), were assayed in differentiated or undifferentiated Caco2 cells.

RESULTS

Compared with the FF-fed mice, those fed MHMO and HHMO had 52% lower (P < 0.05) NEC scores, 60-80% greater (P < 0.05) KI67-positive cell numbers, and 56-71% decreases (P < 0.05) in ileal HIF1α and cleaved Caspase 3 (56-71%). Compared with those untreated, the HMO-treated Caco2 cells displayed 60% greater (P < 0.05) proliferative activity and 19% lower (P < 0.05) apoptotic cells after the hypoxia exposure. The HMO treatment led to 58% or 10-fold increases (P < 0.05) of P-EGFR and 48-89% decreases (P < 0.05) of P-P38 in either differentiated or undifferentiated Caco2 cells compared with the controls.

CONCLUSION

Supplementing HMOs at 10-20 mg/mL into the formula for neonatal mice or media for Caco2 cells conferred protection against the hypoxia-induced injuries. The protection in the Caco2 cells was associated with an activation of EGFR.

Microbiota-dependent and -independent effects of dietary fibre on human health

Dietary fibre, such as indigestible oligosaccharides and polysaccharides, occurs in many foods and has gained considerable importance related to its beneficial effects on host health and specific diseases. Dietary fibre is neither digested nor absorbed in the small intestine and modulates the composition of the gut microbiota. New evidence indicates that dietary fibre also interacts directly with the epithelium and immune cells throughout the gastrointestinal tract by microbiota-independent effects. This review focuses on how dietary fibre improves human health and the reported health benefits that are connected to molecular pathways, in (a) a microbiota-independent manner, via interaction with specific surface receptors on epithelial and immune cells regulating intestinal barrier and immune function, and (b) a microbiota-dependent manner via maintaining intestinal homeostasis by promoting beneficial microbes, including Bifidobacteria and Lactobacilli, limiting the growth, adhesion, and cytotoxicity of pathogenic microbes, as well as stimulating fibre-derived microbial short-chain fatty acid production. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

A Bacterial β1-3-Galactosyltransferase Enables Multigram-Scale Synthesis of Human Milk Lacto-N-tetraose (LNT) and Its Fucosides

β1-3-Linked galactosides such as Galβ1‒3GlcNAcβOR are common carbohydrate motifs found in human milk oligosaccharides (HMOSs), glycolipids, and glycoproteins. Efficient and scalable enzymatic syntheses of these structures have proven challenging due to the lack of access to a highly active β1‒3-galactosyltransferase (β3GalT) in large amounts. Previously reported E. coli β3GalT (EcWbgO) has been identified as a limiting factor for producing a β1-3-galactose-terminated human milk oligosaccharide lacto-N-tetraose (LNT) by fermentation. Here we report the identification of an EcWbgO homolog from C. violaceum (Cvβ3GalT) which showed a high efficiency in catalyzing the formation of LNT from lacto-N-triose (LNT II). With the highly active Cvβ3GalT, multigram-scale (>10 gram) synthesis of LNT from lactose was achieved using a sequential one-pot multienzyme (OPME) glycosylation process. The access to Cvβ3GalT enabled enzymatic synthesis of several fucosylated HMOSs with or without further sialylation including LNFP II, S-LNF II, LNDFH I, LNFP V, and DiFuc-LNT. Among these, LNFP V and DiFuc-LNT would not be accessible by enzymatic synthesis if an active β3GalT were not available.

Milk Glycans and Their Interaction with the Infant-Gut Microbiota

Human milk is a unique and complex fluid that provides infant nutrition and delivers an array of bioactive molecules that serve various functions. Glycans, abundant in milk, can be found as free oligosaccharides or as glycoconjugates. Milk glycans are increasingly linked to beneficial outcomes in neonates through protection from pathogens and modulation of the immune system. Indeed, these glycans influence the development of the infant and the infant-gut microbiota. Bifidobacterium species commonly are enriched in breastfed infants and are among a limited group of bacteria that readily consume human milk oligosaccharides (HMOs) and milk glycoconjugates. Given the importance of bifidobacteria in infant health, numerous studies have examined the molecular mechanisms they employ to consume HMOs and milk glycans, thus providing insight into this unique enrichment and shedding light on a range of translational opportunities to benefit at-risk infants.

Human Milk Oligosaccharides: The Journey Ahead

Breast milk is a complex biological fluid that is rich in nutrients and bioactive agents that support the healthy growth and development of the newborns. Human milk oligosaccharides (HMOs) are unconjugated glycans that constitute an important component of the protection conferred by breast milk on the neonate. HMOs may act locally on the neonatal intestine by acting as signalling molecules and directly interacting with the host cells. Although fucosylated and sialylated HMOs have little nutritional value, they exert important prebiotic as well as immunomodulatory effects on the infant gut. However, there is heterogeneity in the quantity and quality of HMOs in breast milk produced by mothers under influence of the genetic and environmental factors. This review encompasses the salient aspects of HMOs such as composition, function, structural diversity, and functional impact on the growth and survival of newborns. In this review, the current knowledge on HMOs is contextualised to discuss the gaps in scientific understanding and the avenues for future research.

Donkey milk oligosaccharides influence the growth-related characteristics of intestinal cells and induce G2/M growth arrest via the p38 pathway in HT-29 cells

Donkey milk is considered to be a valuable nutritional source. Deeper knowledge of the constituents of donkey milk is necessary. As multifunctional components of milk, oligosaccharides have been reported to have the potential to support intestine development. We studied the composition and content of donkey milk oligosaccharides (DMOs). Sialylated oligosaccharides were found to be the primary oligosaccharides in DMOs, consisting of 3'-sialyllactose (SL) and 6'-SL. The amount of 3'-SL and 6'-SL in donkey milk was 18.3 ± 0.7 mg L^-1 and 33.1 ± 0.7 mg L^-1, respectively. Moreover, we found that DMOs induced differentiation, promoted apoptosis and inhibited proliferation in HT-29, Caco-2 and HIEC cells in a concentration-dependent manner, suggesting that DMOs promote maturation of intestinal epithelial cells. The mechanism of the DMOs' effects on HT-29 cells was associated with activation of the p38 pathway and cell cycle arrest at the G2/M phase. Our research will help understand the biological functions of DMOs and assess their potential roles in infant nutrition.

The Role of Two Human Milk Oligosaccharides, 2'-Fucosyllactose and Lacto-N-Neotetraose, in Infant Nutrition

Human breast milk contains numerous biomolecules. Human milk oligosaccharides (HMOs) are the third most abundant component of breast milk, after lactose and lipids. Amongst the synthetized HMOs, 2'-fucosyllactose (2'-FL) and lacto-N-neotetraose (LNnT) are widely studied and are considered safe for infant nutrition. Several studies have reported the health benefits of HMOs, which include modulation of the intestinal microbiota, anti-adhesive effect against pathogens, modulation of the intestinal epithelial cell response, and development of the immune system. The amount and diversity of HMOs are determined by the genetic background of the mothers (HMO secretors or non-secretors). The non-secretor mothers secrete lower HMOs than secretor mothers. The breastfed infants of secretor mothers gain more health benefit than those of non-secretor mothers. In conclusion, supplementation of infant formula with 2'-FL and LNnT is a promising innovation for infant nutrition.

Human Milk Oligosaccharides Protect against Necrotizing Enterocolitis by Inhibiting Intestinal Damage via Increasing the Proliferation of Crypt Cells

SCOPE

Necrotizing enterocolitis (NEC) is a devastating disease that is highly lethal in premature infants. Human milk oligosaccharides (HMOs) efficiently reduce the incidence of NEC. However, the protective mechanism of HMO treatment is unknown. It is hypothesized that HMOs protect against NEC by inhibiting the damage to intestinal epithelial cells.

METHODS AND RESULTS

C57BL/6 pups are challenged with hypoxia and cold stress to induce NEC. All pups are sacrificed after 72 h. It is found that HMO administration reduces the concentrations of IL-8 in the serum and ileum of all NEC mice. Ileum toll-like receptor 4 (TLR4) protein expression and nuclear factor kappa-B (NFκB) pathway activation are inhibited. The proliferative ability of enterocytes in the ileum is restored as determined by labeling with proliferation markers (Ki67, SOX9). In a 3D culture intestinal crypt organoids study, HMO treatment improves the maturation of organoid cells and increases the ratio of proliferative cells under lipopolysaccharides (LPS) treatment. HMO treatment downregulates TLR4 expression in the organoid cells, thus reducing the effect of LPS.

CONCLUSION

HMOs protect intestinal epithelial cells from injury by accelerating the turnover of crypt cells by reducing the expression of TLR4 on intestinal epithelial cells.

Alleviation of Intestinal Inflammation by Oral Supplementation With 2-Fucosyllactose in Mice

Milk oligosaccharides exert a prebiotic action that contributes to the development of the infant gut microbiota during lactation. Given that milk oligosaccharides remain intact after passage through stomach and small intestine, they can potentially influence the composition of the gut microbiota when ingested as dietary supplements after weaning. To address the regulatory effects of specific oligosaccharides in colitis linked to the microbiota composition, we have supplemented interleukin-10 null (Il10 ^-/-) mice with four fucosylated and sialylated oligosaccharides. We found that oral supplementation with 2-fucosyllactose significantly decreased the severity of colitis as displayed by reduced inflammatory marker expression, histological and diarrhea scores, an increased epithelial integrity and less pronounced colon shortening. Oral supplementation with 2-fucosyllactose led to a marked expansion of the commensal Ruminococcus gnavus, which was accompanied by an enhanced cecal concentration of propionate. Decreased activation of immune cells by R. gnavus was confirmed by reconstitution of antibiotic-treated Il10 ^-/- mice and by stimulation of dendritic cells in vitro. This study demonstrates that post-weaning administration of specific oligosaccharides can shift the composition of the gut microbiota to lessen chronic inflammation as observed in Il10 ^-/- mice. The expansion of R. gnavus sets a positive microbial environment at the cost of pro-inflammatory Gram-negative bacteria, thereby lowering intestinal inflammation.

Milk Oligosaccharides From Different Cattle Breeds Influence Growth-Related Characteristics of Intestinal Cells

Oligosaccharides are present in human milk (HMO) in large amounts and in a high variety: Among other functions they are considered to influence the gut microbiota and gut maturation in infants. Due to the large volume of milk available bovine milk oligosaccharides (BMO) may be an alternative source of functional ingredients to potentially mimic HMO functions. Thus, we investigated direct effects of bovine milk oligosaccharides (BMO) from different cattle breeds on proliferation, differentiation and apoptosis in transformed (HT-29 and Caco-2) and non-transformed human intestinal cells (HIE cells). We observed a profound growth-inhibition effect induced by all BMO isolates in HT-29, Caco-2, and HIE cells in a dose-dependent manner. The effects varied not only between cell lines, i.e., HT-29 and Caco-2 cells were more sensitive than HIE cells, but also between the cattle breeds. Regarding the induction of differentiation, BMO induced differentiation only in HIE cells without affecting apoptosis. Cell cycle analysis via flow cytometry showed that growth inhibition was associated with a G2/M arrest in all cell lines. Expression levels detected by quantitative real-time RT-PCR revealed that this G2/M arrest was associated with changes in mRNA expression levels of cyclin A and B. Cyclin-dependent kinase inhibitors p21^cip1 and p27^kip1 and the tumor suppressor p53 were only enhanced in HIE cells necessary for arresting cells in the G2/M phase and induction of differentiation. In HT-29 and Caco-2 cells, a loss of p53 expression failed to induce G2/M associated induction of differentiation. The HIE cell specific differentiation induced by BMO was a result of influencing the phosphorylation states of EGFR (epidermal growth factor receptor) and MAP kinase, i.e., ERK1/2 (extracellular signal-regulated kinase 1/2), p38-α, and Akt2 phosphorylation. These results suggest that BMO inhibited intestinal cell proliferation and altered cell cycle dynamics by affecting corresponding regulator genes and mitogen-activated protein kinase signaling. As the development and maturation of digestive and absorptive processes depends on gut differentiation processes, our in vitro experiments show that breed-specific BMO are natural substances influencing various parameter which may be important in vivo in gastrointestinal development. This, however, needs to be proven in future studies.

Sialyllactose and Galactooligosaccharides Promote Epithelial Barrier Functioning and Distinctly Modulate Microbiota Composition and Short Chain Fatty Acid Production In Vitro

Human milk oligosaccharides (HMO) and prebiotic oligosaccharides are proposed to confer several health benefits to the infant. They shape the microbiota, have anti-inflammatory properties, and support epithelial barrier functioning. However, in order to select the best oligosaccharides for inclusion in infant formulas, there is a need to increase our understanding of the specific effects of HMO and prebiotics on the host immune system. Therefore, we investigated the effects of the HMO sialyllactose (SL), and galactooligosaccharides (GOS) on epithelial barrier functioning, microbiota composition, and SCFA production. The effect of GOS and SL on epithelial barrier functioning and microbiota composition was investigated using in vitro models. Epithelial barrier function was investigated by transcriptome analysis of fully polarized Caco-2 cells exposed for 6 h to SL or GOS. In addition, epithelial cell growth, alkaline phosphatase production, and re-epithelization was studied. Further, we investigated the effect of SL and GOS on microbiota composition and SCFA production using in vitro fecal batch cultures. Transcriptome analysis showed that SL and GOS both induced pathways that regulate cell cycle control. This gene-expression profile translated to a phenotype of halted proliferation and included the induction of alkaline phosphatase activity, a marker of epithelial cell differentiation. SL and GOS also promoted re-epithelialization in an in vitro epithelial wound repair assay. SL and GOS did show distinct modulation of microbiota composition, promoting the outgrowth of Bacteroides and bifidobacteria, respectively, which resulted in distinct changes in SCFA production profiles. Our results show that SL and GOS can both modulate epithelial barrier function by inducing differentiation and epithelial wound repair, but differentially promote the growth of specific genera in the microbiota, which is associated with differential changes in SCFA profiles.

Evaluation of Sialyllactose Supplementation of a Prebiotic-Containing Formula on Growth, Intestinal Development, and Bacterial Colonization in the Neonatal Piglet

BACKGROUND

Sialyllactose (SL) is a highly abundant oligosaccharide in human milk that has been shown to influence intestinal maturation and cognitive development and exert bifidogenic effects on the gut microbiota. The SL content of infant formula is significantly less than that of human milk, therefore there is interest in determining the effect of supplementing SL to infant formula at the levels in human milk on neonatal outcomes.

OBJECTIVE

The aim of this study was to investigate the effect of varying doses of dietary SL compared with a milk replacer formula on weight gain, gastrointestinal development, and microbiota composition in piglets.

METHODS

Thirty-eight intact male piglets were randomly assigned to 1 of 4 experimental diets from 2 to 32-33 d of age. Diets were formulated to contain SL at 0 mg/L (CON), 130 mg/L (LOW), 380 mg/L (MOD), or 760 mg/L (HIGH). At 32-33 d of age, blood was collected for serum chemistry and blood cellular analyses, and coagulation time. Immediately after humane killing, the small intestine was excised and intestinal segments fixed for quantification of mucin-producing goblet cells and morphologic analysis. In addition, mucosal disaccharide activity was assessed. Colonic luminal contents and feces were collected for measurement of pH, dry matter, volatile fatty acids, and the microbiota.

RESULTS

SL at ≤760 mg/L supported normal growth, intestinal development, and enzyme activity as well as serum chemistries and hematology (P > 0.05). In addition, SL supplementation did not affect overall microbiota structure and diversity in ascending colon contents and feces, but had minor effects on the relative abundances of specific microbes.

CONCLUSIONS

The findings in this study demonstrate that SL addition to a prebiotic-containing formula was well-tolerated by neonatal piglets, supported normal growth, and did not result in any adverse effects on serum chemistries or intestinal development.

Human Milk Oligosaccharides: 2'-Fucosyllactose (2'-FL) and Lacto-N-Neotetraose (LNnT) in Infant Formula

The authors reviewed the published evidence on the presence of oligosaccharides in human milk (HMO) and their benefits in in vitro and in vivo studies. The still limited data of trials evaluating the effect of mainly 2′-fucosyllactose (2′-FL) on the addition of some of HMOs to infant formula were also reviewed. PubMed was searched from January 1990 to April 2018. The amount of HMOs in mother’s milk is a dynamic process as it changes over time. Many factors, such as duration of lactation, environmental, and genetic factors, influence the amount of HMOs. HMOs may support immune function development and provide protection against infectious diseases directly through the interaction of the gut epithelial cells or indirectly through the modulation of the gut microbiota, including the stimulation of the bifidobacteria. The limited clinical data suggest that the addition of HMOs to infant formula seems to be safe and well tolerated, inducing a normal growth and suggesting a trend towards health benefits. HMOs are one of the major differences between cow’s milk and human milk, and available evidence indicates that these components do have a health promoting benefit. The addition of one or two of these components to infant formula is safe, and brings infant formula closer to human milk. More prospective, randomized trials in infants are need to evaluate the clinical benefit of supplementing infant formula with HMOs.

Immunologically Active Components in Human Milk and Development of Atopic Disease, With Emphasis on Food Allergy, in the Pediatric Population

Breast-feeding is currently recommended to prevent the development of allergic diseases; however, data are conflicting and mechanisms are unclear. The immunomodulatory composition of human milk is poorly characterized and varies between mothers. We and others have shown that high levels of human milk IgA and certain cytokines and human milk oligosaccharides are associated with protection against food allergy in the infant, but it is unclear whether they are responsible for or simply biomarkers of the vertical transfer of protection. Because human milk has pre- and probiotic properties, the anti-allergy protection afforded by human milk may be due to its control on the developing gut microbiome. In mice, murine milk IgA supports gut homeostasis and shapes the microbiota, which in turn diversifies the intestinal IgA repertoire that reciprocally promotes the diversity of gut microbiome; these mechanisms are poorly understood in humans. In addition, several human milk bioactives are immunostimulatory, which may in part provide protection against allergic diseases. The regulation of immunologically active components in human milk is incompletely understood, although accumulating evidence suggests that IgA and cytokines in human milk reflect maternal exposures. This review summarizes the current literature on human milk components that have been associated with protection against food allergy and related allergic disorders in early childhood and discusses the work relating to regulation of these levels in human milk and possible mechanisms of action.

Metabolism of Caprine Milk Carbohydrates by Probiotic Bacteria and Caco-2:HT29⁻MTX Epithelial Co-Cultures and Their Impact on Intestinal Barrier Integrity

The development and maturation of the neonatal intestine is generally influenced by diet and commensal bacteria, the composition of which, in turn, can be influenced by the diet. Colonisation of the neonatal intestine by probiotic Lactobacillus strains can strengthen, preserve, and improve barrier integrity, and adherence of probiotics to the intestinal epithelium can be influenced by the available carbon sources. The goal of the present study was to examine the role of probiotic lactobacilli strains alone or together with a carbohydrate fraction (CF) from caprine milk on barrier integrity of a co-culture model of the small intestinal epithelium. Barrier integrity (as measured by trans epithelial electrical resistance (TEER)), was enhanced by three bacteria/CF combinations (Lactobacillus rhamnosus HN001, L. plantarum 299v, and L. casei Shirota) to a greater extent than CF or bacteria alone. Levels of occludin mRNA were increased for all treatments compared to untreated co-cultures, and L. plantarum 299v in combination with CF had increased mRNA levels of MUC4, MUC2 and MUC5AC mucins and MUC4 protein abundance. These results indicate that three out of the four probiotic bacteria tested, in combination with CF, were able to elicit a greater increase in barrier integrity of a co-culture model of the small intestinal epithelium compared to that for either component alone. This study provides additional insight into the individual or combined roles of microbe–diet interactions in the small intestine and their beneficial contribution to the intestinal barrier.

Mother's Milk: A Purposeful Contribution to the Development of the Infant Microbiota and Immunity

Breast milk is the perfect nutrition for infants, a result of millions of years of evolution. In addition to providing a source of nutrition, breast milk contains a diverse array of microbiota and myriad biologically active components that are thought to guide the infant’s developing mucosal immune system. It is believed that bacteria from the mother’s intestine may translocate to breast milk and dynamically transfer to the infant. Such interplay between mother and her infant is a key to establishing a healthy infant intestinal microbiome. These intestinal bacteria protect against many respiratory and diarrheal illnesses, but are subject to environmental stresses such as antibiotic use. Orchestrating the development of the microbiota are the human milk oligosaccharides (HMOs), the synthesis of which are partially determined by the maternal genotype. HMOs are thought to play a role in preventing pathogenic bacterial adhesion though multiple mechanisms, while also providing nutrition for the microbiome. Extracellular vesicles (EVs), including exosomes, carry a diverse cargo, including mRNA, miRNA, and cytosolic and membrane-bound proteins, and are readily detectable in human breast milk. Strongly implicated in cell–cell signaling, EVs could therefore may play a further role in the development of the infant microbiome. This review considers the emerging role of breast milk microbiota, bioactive HMOs, and EVs in the establishment of the neonatal microbiome and the consequent potential for modulation of neonatal immune system development.

Human Milk Oligosaccharides Attenuate Antigen-Antibody Complex Induced Chemokine Release from Human Intestinal Epithelial Cell Lines

There has been increased interest in the use of dietary ingredients, including prebiotics such as human-milk oligosaccharides (HMOs), as therapeutic strategies for food allergy. Understanding the mechanisms underlying the beneficial effects of HMOs is important to realizing their therapeutic potential. Here we demonstrate that the HMO, 6'-sialyllactose (6'SL) inhibited chemokine (IL-8 and CCL20) release from T-84 and HT-29 cells stimulated with antigen-antibody complex, TNFα or PGE₂ ; an effect that was PPARγ dependent and associated with decreased activity of the transcription factors AP-1 and NFκB. In contrast, 2'-fucosyllactose (2'FL) selectively inhibited CCL20 release in response to antigen antibody complex in a PPARγ independent manner. This study reinforces the concept that structurally different oligosaccharides have distinct biological activities and identifies, for the first time, that the HMOs, 6'SL, and 2'FL, modulate human epithelial cell responses related to allergic disease. These findings encourage further investigation of the therapeutic potential of specific HMOs in food allergy.

PRACTICAL APPLICATION

This study provides evidence for direct effects of HMOs in addition to their prebiotic role and demonstrates, for the first time, modulation of Ag-IgE complex activation of human epithelial cells that may have important implications for food-allergy. The study also reinforces the concept that structurally different oligosaccharides have distinct biological activities. In determining the composition of infant formula, addition of oligosaccharides with specific structures may provide direct modulation of immune responses and potentially attenuate symptoms or development of food allergy.

Diversity of Human Milk Oligosaccharides and Effects on Early Life Immune Development

One of the well-known features of human milk, is the capacity to protect against the risk and impact of neonatal infections, as well as to influence the onset of allergic and metabolic disease manifestations. The major objective of this review is to provide a detailed overview regarding the role of human milk, more specifically the diversity in human milk oligosaccharides (HMOS), on early life immune development. Novel insights in immune modulatory effects of HMOS obtained by in vitro as well as in vivo studies, adds to the understanding on how early life nutrition may impact immune development. Extensive description and analysis of single HMOS contributing to the diversity within the composition provided during breastfeeding will be discussed with specific emphasis on immune development and the susceptibility to neonatal and childhood infections.

Milk Oligosaccharides Inhibit Human Rotavirus Infectivity in MA104 Cells

Background: Oligosaccharides in milk act as soluble decoy receptors and prevent pathogen adhesion to the infant gut. Milk oligosaccharides reduce infectivity of a porcine rotavirus strain; however, the effects on human rotaviruses are less well understood.Objective: In this study, we determined the effect of specific and abundant milk oligosaccharides on the infectivity of 2 globally dominant human rotavirus strains.Methods: Four milk oligosaccharides-2'-fucosyllactose (2'FL), 3'-sialyllactose (3'SL), 6'-sialyllactose (6'SL), and galacto-oligosaccharides-were tested for their effects on the infectivity of human rotaviruses G1P[8] and G2P[4] through fluorescent focus assays on African green monkey kidney epithelial cells (MA104 cells). Oligosaccharides were added at different time points in the infectivity assays. Infections in the absence of oligosaccharides served as controls.Results: When compared with infections in the absence of glycans, all oligosaccharides substantially reduced the infectivity of both human rotavirus strains in vitro; however, virus strain-specific differences in effects were observed. Compared with control infections, the maximum reduction in G1P[8] infectivity was seen with 2'FL when added after the onset of infection (62% reduction, P < 0.01), whereas the maximum reduction in G2P[4] infectivity was seen with the mixture of 3'SL + 6'SL when added during infection (73% reduction, P < 0.01). The mixture of 3'SL + 6'SL at the same ratio as is present in breast milk was more potent in reducing G2P[4] infectivity (73% reduction, P < 0.01) than when compared with 3'SL (47% reduction) or 6'SL (40% reduction) individually. For all oligosaccharides the reduction in infectivity was mediated by an effect on the virus and not on the cells.Conclusions: Milk oligosaccharides reduce the infectivity of human rotaviruses in MA104 cells, primarily through an effect on the virus. Although breastfed infants are directly protected, the addition of specific oligosaccharides to infant formula may confer these benefits to formula-fed infants.

Major human milk oligosaccharides are absorbed into the systemic circulation after oral administration in rats

Human milk oligosaccharides (HMO) are involved in many biological functions influencing infant health. Although HMO act locally at the intestine, recent evidence has demonstrated that HMO are partially incorporated into the systemic circulation of breast-fed infants. In the last few years, a large amount of research has been conducted using preclinical models to uncover new biological functions of HMO. The aim of this study was to evaluate the absorption and urine excretion of HMO in rats. We administered a single oral dose of the following HMO: 2'-fucosyllactose (2'-FL), 6'-sialyllactose and lacto-N-neotetraose at different concentrations to adult rats. The time course of absorption of HMO into the bloodstream and their appearance in urine was studied. Our results showed that rats, similar to human infants, are able to effectively absorb a portion of HMO from the intestine into plasma and to excrete them in urine. On the basis of this, we also conducted a specific kinetic absorption study with 2'-FL, the most predominant HMO in human milk, in 9–11-d-old rat pups. Our results confirmed that a significant amount of 2'-FL was absorbed into the systemic circulation and subsequently excreted in urine during lactation in rats in a dose-depended manner. We also found basal levels of these HMO in plasma and urine of adult rats as well as rat pups as a natural result of nursing. Our data suggest that the rat may be a useful preclinical model that provides new insights into the metabolism and functions of HMO.

Sialylated galacto-oligosaccharides and 2′-fucosyllactose reduce necrotising enterocolitis in neonatal rats

Necrotising enterocolitis (NEC) is one of the most frequent and fatal intestinal disorders in preterm infants and has very limited treatment options. Breast-fed infants are at a 6–10-fold lower NEC risk than formula-fed infants, and we have previously shown that human milk oligosaccharides (HMO) improved survival and reduced pathology in a rat NEC model. The HMO disialyllacto-N-tetraose (DSLNT) was most effective, and sialylation was shown to be essential for its protective effect. Galacto-oligosaccharides (GOS), currently added to some infant formula, but not containing sialic acid, had no effect. In addition to DSLNT, our previous work also showed that the neutral HMO fraction, which contains high concentrations of 2′-fucosyllactose (2′FL), slightly improved pathology scores. Here, we assessed the in vivo efficacy of 2′FL, as well as of GOS that we enzymatically sialylated (Sia-GOS). Neonatal rats were randomised into the following study groups – dam-fed (DF), formula-fed (FF), FF containing pooled HMO (10 mg/ml), GOS (8 mg/ml), Sia-GOS (500 µm) or 2′FL (2 mg/ml) – and subjected to the established NEC protocol. The DF and HMO groups had the lowest pathology scores with mean values of 0·67 (sd 0·34) and 0·90 (sd 0·47), respectively. The FF group had significantly elevated pathology scores of 2·02 (sd 0·63). Although the addition of GOS to the formula had no protective effect and generated scores of 2·00 (sd 0·63), the addition of Sia-GOS or 2′FL significantly lowered pathology scores to 1·32 (sd 0·56) (P<0·0034) and 1·43 (sd 0·51) (P<0·0040), respectively. The results warrant further studies to investigate the underlying mechanisms and to assess safety and efficacy in human neonates.

Effect of a Semi-Purified Oligosaccharide-Enriched Fraction from Caprine Milk on Barrier Integrity and Mucin Production of Co-Culture Models of the Small and Large Intestinal Epithelium

Caprine milk contains the highest amount of oligosaccharides among domestic animals, which are structurally similar to human milk oligosaccharides (HMOs). This suggests caprine milk oligosaccharides may offer similar protective and developmental effects to that of HMOs. However, to date, studies using oligosaccharides from caprine milk have been limited. Thus, this study aimed to examine the impact of a caprine milk oligosaccharide-enriched fraction (CMOF) on barrier function of epithelial cell co-cultures of absorptive enterocytes (Caco-2 cells) and mucus-secreting goblet cells (HT29-MTX cells), that more closely simulate the cell proportions found in the small (90:10) and large intestine (75:25). Treatment of epithelial co-cultures with 0.4, 1.0, 2.0 and 4.0 mg/mL of CMOF was shown to have no effect on metabolic activity but did enhance cell epithelial barrier integrity as measured by trans-epithelial electrical resistance (TEER), in a dose-dependent manner. The CMOF at the maximum concentration tested (4.0 mg/mL) enhanced TEER, mucin gene expression and mucin protein abundance of epithelial co-cultures, all of which are essential components of intestinal barrier function.

Recent advances on separation and characterization of human milk oligosaccharides

Free human milk oligosaccharides (HMOs) are unique due to their highly complex nature and important emerging biological and protective functions during early life such as prebiotic activity, pathogen deflection, and epithelial and immune cell modulation. Moreover, four genetically determined heterogeneous HMO secretory groups are known to be based on their structure and composition. Over the years, several analytical techniques have been applied to characterize and quantitate HMOs, including nuclear magnetic resonance spectroscopy, high-performance liquid chromatography (HPLC), high pH anion-exchange chromatography, off-line and on-line mass spectrometry (MS), and capillary electrophoresis (CE). Even if these techniques have proven to be efficient and simple, most glycans have no significant UV absorption and derivatization with fluorophore groups prior to separation usually results in higher sensitivity and an improved chromatographic/electrophoretic profile. Consequently, the analysis by HPLC/CE of derivatized milk oligosaccharides with different chromophoric active tags has been developed. However, UV or fluorescence detection does not provide specific structural information and this is a key point in particular related to the highly complex nature of the milk glycan mixtures. As a consequence, for a specific determination of complex mixtures of oligomers, analytical separation is usually required with evaluation by means of MS, which has been successfully applied to HMOs, resulting in efficient compositional analysis and profiling in various milk samples. This review aims to give an overview of the current state-of-the-art techniques used in HMO analysis.

Dietary Isomers of Sialyllactose Increase Ganglioside Sialic Acid Concentrations in the Corpus Callosum and Cerebellum and Modulate the Colonic Microbiota of Formula-Fed Piglets

BACKGROUND

Sialyllactose is a key human milk oligosaccharide and consists of sialic acid (SA) bound to a lactose molecule. Breastfed infants have increased accumulation of ganglioside-bound SA compared with formula-fed infants.

OBJECTIVE

This study aimed to determine whether different isomers of sialyllactose enrich brain SA and modulate the microbiome of developing neonatal piglets.

METHODS

Day-old pigs were randomly allocated to 6 diets (control, 2 or 4 g 3'-sialyllactose/L, 2 or 4 g 6'-sialyllactose/L, or 2 g polydextrose/L + 2 g galacto-oligosaccharides/L; n = 9) and fed 3 times/d for 21 d. Pigs were killed, and the left hemisphere of the brain was dissected into cerebrum, cerebellum, corpus callosum, and hippocampus regions. SA was determined by using a modified periodic acid-resorcinol reaction. Microbial composition of the intestinal digesta was analyzed with the use of 16S ribosomal DNA Illumina sequencing.

RESULTS

Dietary sialyllactose did not affect feed intake, growth, or fecal consistency. Ganglioside-bound SA in the corpus callosum of pigs fed 2 g 3'-sialyllactose or 6'-sialyllactose/L increased by 15% in comparison with control pigs. Similarly, ganglioside-bound SA in the cerebellum of pigs fed 4 g 3'-sialyllactose/L increased by 10% in comparison with control pigs. Significant (P < 0.05, Adonis Test) microbiome differences were observed in the proximal and distal colons of piglets fed control compared with 4-g 6'-sialyllactose/L formulas. Differences were attributed to an increase in bacterial taxa belonging to species Collinsella aerofaciens (phylum Actinobacteria), genera Ruminococcus and Faecalibacterium (phylum Firmicutes), and genus Prevotella (phylum Bacteroidetes) (Wald test, P < 0.05, DeSeq2) compared with piglets fed the control diet. Taxa belonging to families Enterobacteriaceae and Enterococcaceae (phylum Proteobacteria), as well as taxa belonging to family Lachnospiraceae and order Lactobacillales (phylum Firmicutes), were 2.3- and 4-fold lower, respectively, in 6'-sialyllactose-fed piglets than in controls.

CONCLUSIONS

Supplementation of formula with 3'- or 6'-sialyllactose can enrich ganglioside SA in the brain and modulate gut-associated microbiota in neonatal pigs. We propose 2 potential routes by which sialyllactose may positively affect the neonate: serving as a source of SA for neurologic development and promoting beneficial microbiota.

Human breast milk: A review on its composition and bioactivity

Breast milk is the perfect nutrition for infants, a result of millions of years of evolution, finely attuning it to the requirements of the infant. Breast milk contains many complex proteins, lipids and carbohydrates, the concentrations of which alter dramatically over a single feed, as well as over lactation, to reflect the infant's needs. In addition to providing a source of nutrition for infants, breast milk contains a myriad of biologically active components. These molecules possess diverse roles, both guiding the development of the infants immune system and intestinal microbiota. Orchestrating the development of the microbiota are the human milk oligosaccharides, the synthesis of which are determined by the maternal genotype. In this review, we discuss the composition of breast milk and the factors that affect it during the course of breast feeding. Understanding the components of breast milk and their functions will allow for the improvement of clinical practices, infant feeding and our understanding of immune responses to infection and vaccination in infants.

Human Milk Oligosaccharides Inhibit Candida albicans Invasion of Human Premature Intestinal Epithelial Cells

BACKGROUND

Human milk oligosaccharides (HMOs) are a highly abundant, diverse group of unique glycans that are postulated to promote the development of a protective bacterial microbiota in the intestine and prevent adhesive and invasive interactions of pathogenic bacteria with mucosal epithelia. Candida albicans, a prevalent fungal colonizer of the neonatal gut, causes the majority of fungal disease in premature infants and is highly associated with life-threatening intestinal disorders.

OBJECTIVE

The objective of the current study was to test the hypothesis that HMOs protect human premature intestinal epithelial cells (pIECs) from invasion by C. albicans.

METHODS

To study fungal invasion, a quantitative immunocytochemical assay was used to distinguish invading from noninvading C. albicans cells in the presence and absence of HMOs. To understand how HMOs affect C. albicans invasion of pIECs, the expression of C. albicans virulence traits that are important for invasiveness (hyphal morphogenesis and ability to associate with host cells) were quantified.

RESULTS

Treatment with HMOs reduced invasion of pIECs by C. albicans in a dose-dependent manner by 14-67%, with a physiologic concentration (15mg/mL) of HMOs causing a 52% reduction in invasion (P < 0.05). The decreased invasive ability of C. albicans was associated with hyphal lengths that were ∼30% shorter (P < 0.05), likely because of a delay in the induction of hyphal morphogenesis after inoculation of yeast onto pIECs, which correlated with a 23% reduction in the combined expression level of hyphal-specific genes (P < 0.05). In addition, HMOs caused a 40% decrease in the number of C. albicans cells able to associate with pIECs at the time of hyphal induction (P < 0.05).

CONCLUSIONS

These results, obtained with the use of a primary pIEC model, indicate that HMOs reduce virulence characteristics of C. albicans and suggest a role for HMOs in protecting the premature infant intestine from invasion and damage by C. albicans hyphae.

Attenuation of food allergy symptoms following treatment with human milk oligosaccharides in a mouse model

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.

Beneficial effects of human milk oligosaccharides on gut microbiota

Human milk is the gold standard for nourishment of early infants because it contains a number of bioactive components, such as human milk oligosaccharides (HMOs). The high concentration and structural diversity of HMOs are unique to humans. HMOs are a group of complex and diverse glycans that are resistant to gastrointestinal digestion and reach the infant colon as the first prebiotics. N-acetyl-glucosamine containing oligosaccharides were first identified 50 years ago as the 'bifidus factor', a selective growth substrate for intestinal bifidobacteria, thus providing a conceptual basis for HMO-specific bifidogenic activity. Bifidobacterial species are the main utilisers of HMOs in the gastrointestinal tract and represent the dominant microbiota of breast-fed infants, and they may play an important role in maintaining the general health of newborn children. Oligosaccharides are also known to directly interact with the surface of pathogenic bacteria, and various oligosaccharides in milk are believed to inhibit the binding of pathogens and toxins to host cell receptors. Furthermore, HMOs are thought to contribute to the development of infant intestine and brain. Oligosaccharides currently added to infant formula are structurally different from the oligosaccharides naturally occurring in human milk and, therefore, they are unlikely to mimic some of the structure-specific effects. In this review, we describe how HMOs can modulate gut microbiota. This article summarises information up to date about the relationship between the intestinal microbiota and HMOs, and other possible indirect effects of HMOs on intestinal environment.

Galacto-oligosaccharides and Colorectal Cancer: Feeding our Intestinal Probiome

Prebiotics are ingredients selectively fermented by the intestinal microbiota that promote changes in the microbial community structure and/or their metabolism, conferring health benefits to the host. Studies show that β (1-4) galacto-oligosaccharides [β (1-4) GOS], lactulose and fructo-oligosaccharides increase intestinal concentration of lactate and short chain fatty acids, and stool frequency and weight, and they decrease fecal concentration of secondary bile acids, fecal pH, and nitroreductase and β-glucuronidase activities suggesting a clear role in colorectal cancer (CRC) prevention. This review summarizes research on prebiotics bioassimilation, specifically β (1-4) GOS, and their potential role in CRC. We also evaluate research that show that the impact of prebiotics on host physiology can be direct or through modulation of the gut intestinal microbiome, specifically the probiome (autochtonous beneficial bacteria), we present studies on a potential role in CRC progression to finally describe the current state of β (1-4) GOS generation for industrial production.

Human milk oligosaccharides influence maturation of human intestinal Caco-2Bbe and HT-29 cell lines

Stimulation of gastrointestinal tract maturation is 1 of the many benefits of human milk. Human milk oligosaccharides (HMOs) are abundant in human milk and are reported to promote enterocyte differentiation in vitro. The objective of this study was to assess the impact of 3 predominant HMOs on multiple aspects of enterocyte maturation in vitro. Ranging from crypt-like to differentiated enterocytes, we used the well-characterized intestinal cell lines HT-29 and Caco-2Bbe to model early and late stages of differentiation, respectively. With this model of the crypt-villus axis made up of preconfluent HT-29, preconfluent Caco-2Bbe, and postconfluent Caco-2Bbe cultures, we characterized the impact of lacto-N-neotetraose (LNnT), 2'-fucosyllactose (2'FL), and 6'-sialyllactose on epithelial cell kinetics and function. All 3 HMOs dose-dependently inhibited cell proliferation in undifferentiated HT-29 and Caco-2Bbe cultures (P < 0.05). In contrast to previous reports, only treatment with 2'FL at concentrations similar to human milk increased alkaline phosphatase activity by 31% (P = 0.044) in HT-29 cultures and increased sucrase activity by 54% (P = 0.005) in well-differentiated Caco-2Bbe cultures. LNnT at concentrations similar to that reported for human milk increased transepithelial resistance by 21% (P = 0.002) in well-differentiated Caco-2Bbe cells. In summary, all 3 HMOs reduced cell proliferation in an epithelial cell model of the crypt-villus axis. However, effects on differentiation, digestive function, and epithelial barrier function differed between the HMOs tested. These results suggest differential roles for specific HMOs in maturation of the gastrointestinal tract.