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

Sialylation in the gut: From mucosal protection to disease pathogenesis

Sialylation, a crucial post-translational modification of glycoconjugates, entails the attachment of sialic acid (SA) to the terminal glycans of glycoproteins and glycolipids through a tightly regulated enzymatic process involving various enzymes. This review offers a comprehensive exploration of sialylation within the gut, encompassing its involvement in mucosal protection and its impact on disease progression. The sialylation of mucins and epithelial glycoproteins contributes to the integrity of the intestinal mucosal barrier. Furthermore, sialylation regulates immune responses in the gut, shaping interactions among immune cells, as well as their activation and tolerance. Additionally, the gut microbiota and gut-brain axis communication are involved in the role of sialylation in intestinal health. Altered sialylation patterns have been implicated in various intestinal diseases, including inflammatory bowel disease (IBD), colorectal cancer (CRC), and other intestinal disorders. Emerging research underscores sialylation as a promising avenue for diagnostic, prognostic, and therapeutic interventions in intestinal diseases. Potential strategies such as sialic acid supplementation, inhibition of sialidases, immunotherapy targeting sialylated antigens, and modulation of sialyltransferases have been utilized in the treatment of intestinal diseases. Future research directions will focus on elucidating the molecular mechanisms underlying sialylation alterations, identifying sialylation-based biomarkers, and developing targeted interventions for precision medicine approaches.

Combining 2'-fucosyllactose and galactooligosaccharides exerts anti-inflammatory effects and promotes gut health

This study investigated the potential of 2'-Fucosyllactose (2'-FL) and galactooligosaccharides (GOS) combinations as a novel and cost-effective substitute for human milk oligosaccharides (HMOs) in promoting gut health and reducing inflammation. In vitro studies using Caco-2 cells showed that 2'-FL and GOS combinations (H1: GOS:2'-FL ratio of 1.8:1; H2: ratio of 3.6:1) reduced lipopolysaccharide-induced inflammation by decreasing pro-inflammatory markers, while individual treatments had no significant effects. In a mouse model of dextran sulfate sodium (DSS)-induced colitis, combined 2'-FL and GOS supplementation alleviated symptoms, improved gut permeability, and enhanced intestinal structure, with the GH1 group (H1 combo with DSS) being the most effective. 2'-FL and GOS combinations also enhanced short-chain fatty acid production in infant fecal batch fermentation and mouse fecal analysis, with GH1 showing the most promising results. GH1 supplementation altered gut microbiota in mice with DSS-induced colitis, promoting microbial diversity and a more balanced Firmicutes to Bacteroidota ratio. Infant formula products (IFPs) containing 2'-FL and GOS combinations (IFP2: 174 mg GOS and 95 mg 2'-FL per 14 g serving, 1.8:1 ratio; IFP3: 174 mg GOS and 48 mg 2'-FL per 14 g serving, 3.6:1 ratio) demonstrated gastrointestinal protective and anti-inflammatory properties in a coculture model of Caco-2 and THP-1 cells. These findings suggest that 2'-FL and GOS combinations have potential applications in advanced infant formulas and supplements to promote gut health and reduce inflammation.

Infant Microbiota Communities and Human Milk Oligosaccharide Supplementation Independently and Synergistically Shape Metabolite Production and Immune Responses in Healthy Mice

BACKGROUND

Multiple studies have demonstrated associations between the early-life gut microbiome and incidence of inflammatory and autoimmune disease in childhood. Although microbial colonization is necessary for proper immune education, it is not well understood at a mechanistic level how specific communities of bacteria promote immune maturation or drive immune dysfunction in infancy.

OBJECTIVES

In this study, we aimed to assess whether infant microbial communities with different overall structures differentially influence immune and gastrointestinal development in healthy mice.

METHODS

Germ-free mice were inoculated with fecal slurries from Bifidobacterium longum subspecies infantis positive (BIP) or B. longum subspecies infantis negative (BIN) breastfed infants; half of the mice in each group were also supplemented with a pool of human milk oligosaccharides (HMOs) for 14 d. Cecal microbiome composition and metabolite production, systemic and mucosal immune outcomes, and intestinal morphology were assessed at the end of the study.

RESULTS

The results showed that inoculation with a BIP microbiome results in a remarkably distinct microbial community characterized by higher relative abundances of cecal Clostridium senu stricto, Ruminococcus gnavus, Cellulosilyticum sp., and Erysipelatoclostridium sp. The BIP microbiome produced 2-fold higher concentrations of cecal butyrate, promoted branched short-chain fatty acid (SCFA) production, and further modulated serotonin, kynurenine, and indole metabolism relative to BIN mice. Further, the BIP microbiome increased the proportions of innate and adaptive immune cells in spleen, while HMO supplementation increased proliferation of mesenteric lymph node cells to phorbol myristate acetate and lipopolysaccharide and increased serum IgA and IgG concentrations.

CONCLUSIONS

Different microbiome compositions and HMO supplementation can modulate SCFA and tryptophan metabolism and innate and adaptive immunity in young, healthy mice, with potentially important implications for early childhood health.

Gastrointestinal barrier function, immunity, and neurocognition: The role of human milk oligosaccharide (hMO) supplementation in infant formula

Breastmilk is seen as the gold standard for infant nutrition as it provides nutrients and compounds that stimulate gut barrier, immune, and brain development to the infant. However, there are many instances where it is not possible for an infant to be fed with breastmilk, especially for the full 6 months recommended by the World Health Organization. In such instances, infant formula is seen as the next best approach. However, infant formulas do not contain human milk oligosaccharides (hMOs), which are uniquely present in human milk as the third most abundant solid component. hMOs have been linked to many health benefits, such as the development of the gut microbiome, the immune system, the intestinal barrier, and a healthy brain. This paper reviews the effects of specific hMOs applied in infant formula on the intestinal barrier, including the not-often-recognized intestinal alkaline phosphatase system that prevents inflammation. Additionally, impact on immunity and the current proof for effects in neurocognitive function and the corresponding mechanisms are discussed. Recent studies suggest that hMOs can alter gut microbiota, modulate intestinal immune barrier function, and promote neurocognitive function. The hMOs 2'-fucosyllactose and lacto-N-neotetraose have been found to have positive effects on the development of infants and have been deemed safe for use in formula. However, their use has been limited due to their cost and complexity of synthesis. Thus, although many benefits have been described, complex hMOs and combinations of hMOs with other oligosaccharides are the best approach to stimulate gut barrier, immune, and brain development and for the prevention of disease.

2'-Fucosyllactose alleviates OVA-induced food allergy in mice by ameliorating intestinal microecology and regulating the imbalance of Th2/Th1 proportion

Food allergy (FA) has become a prominent problem in public health. 2'-Fucosyllactose (2'-FL) was reported to alleviate FA symptoms; however, the regulatory mechanism is still unclear. This study evaluated the 2'-FL antiallergic potential in an ovalbumin (OVA)-sensitized mouse model and explored the systemic effects of 2'-FL on gut microecology and the intestinal immune barrier. The results showed that 2'-FL alleviated allergy symptoms, decreased serum allergic indicator levels, enhanced the intestinal barrier, and attenuated low-grade inflammation. The up-regulation of G protein-coupled receptors (GPRs) was associated with higher levels of short-chain fatty acids (SCFAs) in 2'-FL intervention mice. 2'-FL also improved the intestinal microbiota diversity and increased the abundance of Akkermansia, Lachnospiraceae UCG-006, and Ruminococcaceae while suppressing Muribaculaceae, Desulfovibrionaceae, and Erysipelotrichaceae. Additionally, 2'-FL ameliorated the imbalance of Th2/Th1, mainly by decreasing Th2-type immune response and enhanced CD4 + Foxp3 + Treg immunoreaction. These results suggest that 2'-FL restores intestinal barrier defects, gut microbiota disorder, and immune impairment while alleviating ovalbumin-induced allergic symptoms in FA mice.

High-Level Production of Lacto-N-neotetraose in Escherichia coli by Stepwise Optimization of the Biosynthetic Pathway

Lacto-N-neotetraose (LNnT), an abundant human milk oligosaccharide (HMO), has been approved as a novel functional additive for infant formulas. Therefore, LNnT biosynthesis has attracted extensive attention. Here, a high LNnT-producing, low lacto-N-triose II (LNT II)-residue Escherichia coli strain was constructed. First, an initial LNnT-producing chassis strain was constructed by blocking lactose, UDP-N-acetylglucosamine, and UDP-galactose competitive consumption pathways and introducing β-1,3-N-acetylglucosaminyltransferase LgtA and β-1,4-galactosyltransferase LgtB. Subsequently, the supply of LNnT precursors was increased by enhancing UDP-N-acetylglucosamine and UDP-galactose synthesis, inactivating LNT II extracellular transporter SetA, and improving UTP synthesis. Then, modular engineering strategy was used to optimize LNnT biosynthetic pathway fluxes. Moreover, pathway fluxes were fine-tuned by modulating translation initiation strength of essential genes lgtB, prs, and lacY. Finally, LNnT production reached 6.70 g/L in a shake flask and 19.40 g/L in a 3 L bioreactor with 0.47 g/(L h) productivity, with 1.79 g/L LNT II residue, highest productivity level, and lowest LNT II residue thus far.

[Human milk oligosaccharides play major roles in child development and future health]

Human milk oligosaccharides (HMO) represent the third largest component of human breast milk (BM). The BM level is comprised between 5 to 20 g per liter and they have a great structural complexity with more than 150 HMO characterized to date. In this review, we present a summary of the main experimental and clinical data that have demonstrated their multiple biological roles in infants such as for gut development, microbiota, immune protection and neurodevelopment. Some HMO-enriched infant formulas are available yet, even if their benefits on the infant health remain to be confirmed. Further researches could allow therapeutic use in preterm newborns or in infants with intestinal diseases. Experimental data suggest that they could also be used in the prevention of some chronic diseases with immunometabolic or neurodevelopmental components.

Structure-function relationship and impact on the gut-immune barrier function of non-digestible carbohydrates and human milk oligosaccharides applicable for infant formula

Human milk oligosaccharides (hMOs) in mothers' milk play a crucial role in guiding the colonization of microbiota and gut-immune barrier development in infants. Non-digestible carbohydrates (NDCs) such as synthetic single hMOs, galacto-oligosaccharides (GOS), inulin-type fructans and pectin oligomers have been added to infant formula to substitute some hMOs' functions. HMOs and NDCs can modulate the gut-immune barrier, which is a multiple-layered functional unit consisting of microbiota, a mucus layer, gut epithelium, and the immune system. There is increasing evidence that the structures of the complex polysaccharides may influence their efficacy in modulating the gut-immune barrier. This review focuses on the role of different structures of individual hMOs and commonly applied NDCs in infant formulas in (i) direct regulation of the gut-immune barrier in a microbiota-independent manner and in (ii) modulation of microbiota composition and microbial metabolites of these polysaccharides in a microbiota-dependent manner. Both have been shown to be essential for guiding the development of an adequate immune barrier, but the effects are very dependent on the structural features of hMO or NDC. This knowledge might lead to tailored infant formulas for specific target groups.

De novo biosynthesis of 2'-fucosyllactose in engineered Pichia pastoris

PURPOSE

Pichia pastoris is well known for its ability to produce short and low-immunogenic humanized glycosyl chains onto recombinant glycoproteins, it was thus speculated to be applicable to synthesize oligosaccharides. In this study, generally recognized as safe (GRAS) microorganism Pichia pastoris GS115 was tested for its potential to be used as a new synthetic chassis to produce the most abundant human milk oligosaccharide 2'-fucosyllactose (2'-FL).

METHODS

To enable the de novo synthesis of 2'-FL, lactose transporter lac12, two enzymes of gmd, gmer, and fucosyltransferases futC were integrated into the genome of P. pastoris, under the control of constitutive P_GAP promoter.

RESULTS

The resulting recombinant yeasts yielded up to 0.276 g/L through culture optimization in a 5 L bioreactor.

CONCLUSION

To our knowledge, this is the first report of 2'-FL production in engineered Pichia pastoris. This work is a good starting point to produce 2'-FL using Pichia pastoris as a viable chassis.

Role of human milk oligosaccharide metabolizing bacteria in the development of atopic dermatitis/eczema

Despite affecting up to 20% of infants in the United States, there is no cure for atopic dermatitis (AD), also known as eczema. Atopy usually manifests during the first six months of an infant's life and is one predictor of later allergic health problems. A diet of human milk may offer protection against developing atopic dermatitis. One milk component, human milk oligosaccharides (HMOs), plays an important role as a prebiotic in establishing the infant gut microbiome and has immunomodulatory effects on the infant immune system. The purpose of this review is to summarize the available information about bacterial members of the intestinal microbiota capable of metabolizing HMOs, the bacterial genes or metabolic products present in the intestinal tract during early life, and the relationship of these genes and metabolic products to the development of AD/eczema in infants. We find that specific HMO metabolism gene sets and the metabolites produced by HMO metabolizing bacteria may enable the protective role of human milk against the development of atopy because of interactions with the immune system. We also identify areas for additional research to further elucidate the relationship between the human milk metabolizing bacteria and atopy. Detailed metagenomic studies of the infant gut microbiota and its associated metabolomes are essential for characterizing the potential impact of human milk-feeding on the development of atopic dermatitis.

Butyrate Differentiates Permissiveness to Clostridioides difficile Infection and Influences Growth of Diverse C. difficile Isolates

A disrupted "dysbiotic" gut microbiome engenders susceptibility to the diarrheal pathogen Clostridioides difficile by impacting the metabolic milieu of the gut. Diet, in particular the microbiota-accessible carbohydrates (MACs) found in dietary fiber, is one of the most powerful ways to affect the composition and metabolic output of the gut microbiome. As such, diet is a powerful tool for understanding the biology of C. difficile and for developing alternative approaches for coping with this pathogen. One prominent class of metabolites produced by the gut microbiome is short-chain fatty acids (SCFAs), the major metabolic end products of MAC metabolism. SCFAs are known to decrease the fitness of C. difficile in vitro, and high intestinal SCFA concentrations are associated with reduced fitness of C. difficile in animal models of C. difficile infection (CDI). Here, we use controlled dietary conditions (8 diets that differ only by MAC composition) to show that C. difficile fitness is most consistently impacted by butyrate, rather than the other two prominent SCFAs (acetate and propionate), during murine model CDI. We similarly show that butyrate concentrations are lower in fecal samples from humans with CDI than in those from healthy controls. Finally, we demonstrate that butyrate impacts growth in diverse C. difficile isolates. These findings provide a foundation for future work which will dissect how butyrate directly impacts C. difficile fitness and will lead to the development of diverse approaches distinct from antibiotics or fecal transplant, such as dietary interventions, for mitigating CDI in at-risk human populations. IMPORTANCE Clostridioides difficile is a leading cause of infectious diarrhea in humans, and it imposes a tremendous burden on the health care system. Current treatments for C. difficile infection (CDI) include antibiotics and fecal microbiota transplant, which contribute to recurrent CDIs and face major regulatory hurdles, respectively. Therefore, there is an ongoing need to develop new ways to cope with CDI. Notably, a disrupted "dysbiotic" gut microbiota is the primary risk factor for CDI, but we incompletely understand how a healthy microbiota resists CDI. Here, we show that a specific molecule produced by the gut microbiota, butyrate, is negatively associated with C. difficile burdens in humans and in a mouse model of CDI and that butyrate impedes the growth of diverse C. difficile strains in pure culture. These findings help to build a foundation for designing alternative, possibly diet-based, strategies for mitigating CDI in humans.

Recent progress in health effects and biosynthesis of lacto-N-tetraose, the most dominant core structure of human milk oligosaccharide

Human milk oligosaccharides (HMOs), which are a group of complex carbohydrates highly abundant in human milk, have been recognized as critical functional biomolecules for infant health. Lacto-N-tetraose (LNT) is one of the most abundant HMO members and the most dominant core structure of HMO. The promising physiological effects of LNT have been well documented, including prebiotic property, antiadhesive antimicrobial activity, and antiviral effect. Its safety has been evaluated and it has been commercially added to infant formula as a functional ingredient. Because of great commercial importance of LNT, increasing attention has been paid to its highly efficient biological production. In particular, microbial synthesis based on metabolic engineering displays obvious advantages in large-scale production of LNT. This review contains important information about the recent progress in physiological effects, safety evaluation, and biosynthesis of LNT.

Specific Human Milk Oligosaccharides Differentially Promote Th1 and Regulatory Responses in a CpG-Activated Epithelial/Immune Cell Coculture

Proper early life immune development creates a basis for a healthy and resilient immune system, which balances immune tolerance and activation. Deviations in neonatal immune maturation can have life-long effects, such as development of allergic diseases. Evidence suggests that human milk oligosaccharides (HMOS) possess immunomodulatory properties essential for neonatal immune maturation. To understand the immunomodulatory properties of enzymatic or bacterial produced HMOS, the effects of five HMOS (2'FL, 3FL, 3'SL, 6'SL and LNnT), present in human milk have been studied. A PBMC immune model, the IEC barrier model and IEC/PBMC transwell coculture models were used, representing critical steps in mucosal immune development. HMOS were applied to IEC cocultured with activated PBMC. In the presence of CpG, 2'FL and 3FL enhanced IFNγ (p < 0.01), IL10 (p < 0.0001) and galectin-9 (p < 0.001) secretion when added to IEC; 2'FL and 3FL decreased Th2 cell development while 3FL enhanced Treg polarization (p < 0.05). IEC were required for this 3FL mediated Treg polarization, which was not explained by epithelial-derived galectin-9, TGFβ nor retinoic acid secretion. The most pronounced immunomodulatory effects, linking to enhanced type 1 and regulatory mediator secretion, were observed for 2'FL and 3FL. Future studies are needed to further understand the complex interplay between HMO and early life mucosal immune development.

Necrotizing enterocolitis, gut microbes, and sepsis

Necrotizing enterocolitis (NEC) is a devastating disease in premature infants and the leading cause of death and disability from gastrointestinal disease in this vulnerable population. Although the pathophysiology of NEC remains incompletely understood, current thinking indicates that the disease develops in response to dietary and bacterial factors in the setting of a vulnerable host. As NEC progresses, intestinal perforation can result in serious infection with the development of overwhelming sepsis. In seeking to understand the mechanisms by which bacterial signaling on the intestinal epithelium can lead to NEC, we have shown that the gram-negative bacterial receptor toll-like receptor 4 is a critical regulator of NEC development, a finding that has been confirmed by many other groups. This review article provides recent findings on the interaction of microbial signaling, the immature immune system, intestinal ischemia, and systemic inflammation in the pathogenesis of NEC and the development of sepsis. We will also review promising therapeutic approaches that show efficacy in pre-clinical studies.

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.

Human Milk Oligosaccharide 2'-Fucosyllactose Inhibits Ligand Binding to C-Type Lectin DC-SIGN but Not to Langerin

Human milk oligosaccharides (HMOs) and their most abundant component, 2'-Fucosyllactose (2'-FL), are known to be immunomodulatory. Previously, it was shown that HMOs and 2'-FL bind to the C-type lectin receptor DC-SIGN. Here we show, using a ligand-receptor competition assay, that a whole mixture of HMOs from pooled human milk (HMOS) and 2'-FL inhibit the binding of the carbohydrate-binding receptor DC-SIGN to its prototypical ligands, fucose and the oligosaccharide Lewis-B, (Le^b) in a dose-dependent way. Interestingly, such inhibition by HMOS and 2'-FL was not detected for another C-type lectin, langerin, which is evolutionarily similar to DC-SIGN. The cell-ligand competition assay using DC-SIGN expressing cells confirmed that 2'-FL inhibits the binding of DC-SIGN to Le^b. Molecular dynamic (MD) simulations show that 2'-FL exists in a preorganized bioactive conformation before binding to DC-SIGN and this conformation is retained after binding to DC-SIGN. Le^b has more flexible conformations and utilizes two binding modes, which operate one at a time via its two fucoses to bind to DC-SIGN. Our hypothesis is that 2'-FL may have a reduced entropic penalty due to its preorganized state, compared to Le^b, and it has a lower binding enthalpy, suggesting a better binding to DC-SIGN. Thus, due to the better binding to DC-SIGN, 2'-FL may replace Le^b from its binding pocket in DC-SIGN. The MD simulations also showed that 2'-FL does not bind to langerin. Our studies confirm 2'-FL as a specific ligand for DC-SIGN and suggest that 2'-FL can replace other DC-SIGN ligands from its binding pocket during the ligand-receptor interactions in possible immunomodulatory processes.

Microbiota independent effects of oligosaccharides on Caco-2 cells -A semi-targeted metabolomics approach using DI-FT-ICR-MS coupled with pathway enrichment analysis

Milk oligosaccharides (MOS) and galactooligosaccharides (GOS) are associated with many benefits, including anti-microbial effects and immune-modulating properties. However, the cellular mechanisms of these are largely unknown. In this study, the effects of enriched GOS and MOS mixtures from caprine and bovine milk consisting mainly 6'-galactosyllactose, 3'-sialyllactose, and 6'-sialyllactose on Caco-2 cells were investigated, and the treatment-specific metabolomes were described. In the control, the cells were treated with a sugar mix consisting of one-third each of glucose, galactose and lactose. A local metabolomics workflow with pathway enrichment was established, which specifically addresses DI-FT-ICR-MS analyses and includes adaptations in terms of measurement technology and sample matrices. By including quality parameters, especially the isotope pattern, we increased the precision of annotation. The independence from online tools, the fast adaptability to changes in databases, and the specific adjustment to the measurement technology and biomaterial used, proved to be a great advantage. For the first time it was possible to find 71 active pathways in a Caco-2 cell experiment. These pathways were assigned to 12 main categories, with amino acid metabolism and carbohydrate metabolism being the most dominant categories in terms of the number of metabolites and metabolic pathways. Treatment of Caco-2 cells with high GOS and glucose contents resulted in significant effects on several metabolic pathways, whereas the MOS containing treatments resulted only for individual metabolites in significant changes. An effect based on bovine or caprine origin alone could not be observed. Thus, it was shown that MOS and GOS containing treatments can exert microbiome-independent effects on the metabolome of Caco-2 cells.

2'-Fucosyllactose Remits Colitis-Induced Liver Oxygen Stress through the Gut-Liver-Metabolites Axis

Liver oxygen stress is one of the main extraintestinal manifestations of colitis and 5% of cases develop into a further liver injury and metabolic disease. 2′-fucosyllactose (2′-FL), a main member of human milk oligosaccharides (HMOs), has been found to exert efficient impacts on remitting colitis. However, whether 2′-FL exerts the function to alleviate colitis-induced liver injury and how 2′-FL influences the metabolism via regulating gut microbiota remain unknown. Herein, in our study, liver oxygen stress was measured by measuring liver weight and oxygen-stress-related indicators. Then, 16S full-length sequencing analysis and non-target metabolome in feces were performed to evaluate the overall responses of metabolites and intestinal bacteria after being treated with 2′-FL (400 mg/kg b.w.) in colitis mice. The results showed that, compared with the control group, the liver weight of colitis mice was significantly decreased by 18.30% (p < 0.05). After 2′-FL treatment, the liver weight was significantly increased by 12.65% compared with colitis mice (p < 0.05). Meanwhile, they exhibited higher levels of oxidation in liver tissue with decreasing total antioxidant capacity (T-AOC) (decreased by 17.15%) and glutathione (GSH) levels (dropped by 22.68%) and an increasing malondialdehyde (MDA) level (increased by 36.24%), and 2′-FL treatment could reverse those tendencies. Full-length 16S rRNA sequencing revealed that there were 39 species/genera differentially enriched in the control, dextran sulphate sodium (DSS), and DSS + 2′-FL groups. After treatment with 2′-FL, the intestinal metabolic patterns, especially glycometabolism and the lipid-metabolism-related process, in DSS mice were strikingly altered with 33 metabolites significantly down-regulated and 26 metabolites up-regulated. Further analysis found DSS induced a 40.01%, 41.12%, 43.81%, and 39.86% decline in acetic acid, propionic acid, butyric acid, and total short chain fatty acids (SCFAs) in colitis mice (all p < 0.05), respectively, while these were up-regulated to different degrees in the DSS + 2′-FL group. By co-analyzing the data of gut microbiota and metabolites, glycometabolism and lipid-metabolism-associated metabolites exhibited strong positive/negative relationships with Akkermansia_muciniphila (all p < 0.01) and Paraprevotella spp. (all p < 0.01), suggesting that the two species might play crucial roles in the process of 2′-FL alleviating colitis-induced liver oxygen stress. In conclusion, in the gut−liver−microbiotas axis, 2′-FL mediated in glucose and lipid-related metabolism and alleviated liver oxygen stress via regulating gut microbiota in the DSS-induced colitis model. The above results provide a new perspective to understand the probiotic function of 2′-FL.

Human Milk Oligosaccharides Impact Cellular and Inflammatory Gene Expression and Immune Response

Human milk harbors complex carbohydrates, including human milk oligosaccharides (HMOs), the third most abundant component after lactose and lipids. HMOs have been shown to impact intestinal microbiota, modulate the intestinal immune response, and prevent pathogenic bacterial binding by serving as decoy receptors. However, the direct effect of HMOs on intestinal function and immunity remains to be elucidated. To address this knowledge gap, 21-day-old germ-free mice (C57BI/6) were orally gavaged with 15 mg/day of pooled HMOs for 7 or 14 days and euthanized at day 28 or 35. A set of mice was maintained until day 50 to determine the persistent effects of HMOs. Control groups were maintained in the isolators for 28, 35, or 50 days of age. At the respective endpoints, intestinal tissues were subjected to histomorphometric and transcriptomic analyses, while the spleen and mesenteric lymph nodes (MLNs) were subjected to flow cytometric analysis. The small intestine (SI) crypt was reduced after HMO treatment relative to control at days 28 and 35, while the SI villus height and large intestine (LI) gland depth were decreased in the HMO-treated mice relative to the control at day 35. We report significant HMO-induced and location-specific gene expression changes in host intestinal tissues. HMO treatment significantly upregulated genes involved in extracellular matrix, protein ubiquitination, nuclear transport, and mononuclear cell differentiation. CD4+ T cells were increased in both MLNs and the spleen, while CD8+ T cells were increased in the spleen at day 50 in the HMO group in comparison to controls. In MLNs, plasma cells were increased in HMO group at days 28 and 35, while in the spleen, only at day 28 relative to controls. Macrophages/monocytes and neutrophils were lower in the spleen of the HMO group at days 28, 35, and 50, while in MLNs, only neutrophils were lower at day 50 in the 14-day HMO group. In addition, diphtheria toxoid and tetanus toxoid antibody-secreting cells were higher in HMO-supplemented group compared to controls. Our data suggest that HMOs have a direct effect on gastrointestinal tract metabolism and the immune system even in the absence of host microbiota.

Babies, Bugs, and Barriers: Dietary Modulation of Intestinal Barrier Function in Early Life

The intestinal barrier is essential in early life to prevent infection, inflammation, and food allergies. It consists of microbiota, a mucus layer, an epithelial layer, and the immune system. Microbial metabolites, the mucus, antimicrobial peptides, and secretory immunoglobulin A (sIgA) protect the intestinal mucosa against infection. The complex interplay between these functionalities of the intestinal barrier is crucial in early life by supporting homeostasis, development of the intestinal immune system, and long-term gut health. Exclusive breastfeeding is highly recommended during the first 6 months. When breastfeeding is not possible, milk-based infant formulas are the only safe alternative. Breast milk contains many bioactive components that help to establish the intestinal microbiota and influence the development of the intestinal epithelium and the immune system. Importantly, breastfeeding lowers the risk for intestinal and respiratory tract infections. Here we review all aspects of intestinal barrier function and the nutritional components that impact its functionality in early life, such as micronutrients, bioactive milk proteins, milk lipids, and human milk oligosaccharides. These components are present in breast milk and can be added to milk-based infant formulas to support gut health and immunity. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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.

Recent Advances on Lacto-N-neotetraose, a Commercially Added Human Milk Oligosaccharide in Infant Formula

Human milk oligosaccharides (HMOs) act as the important prebiotics and display many unique health effects for infants. Lacto-N-neotetraose (LNnT), an abundant HMO, attracts increasing attention because of its unique beneficial effects to infants and great commercial importance. It occurs in all groups of human milk, but the concentration generally decreases gradually with the lactation period. It has superior prebiotic property for infants, and its other health effects have also been verified, including being immunomodulatory, anti-inflammatory, preventing necrotizing enterocolitis, antiadhesive antimicrobials, antiviral activity, and promoting maturation of intestinal epithelial cells. Safety evaluation and clinical trial studies suggest that LNnT is safe and well-tolerant for infants. It has been commercially added as a functional ingredient in infant formula. LNnT can be synthesized via chemical, enzymatic, or cell factory approachs, among which the metabolic engineering-based cell factory synthesis is considered to be the most practical and effective. In this article, the occurrence and physiological effects of LNnT were reviewed in detail, the safety evaluation and regulation status of LNnT were described, various approaches to LNnT synthesis were comprehensively summarized and compared, and the future perspectives of LNnT-related studies were provided.

Effects of Different Feeding Methods on the Structure, Metabolism, and Gas Production of Infant and Toddler Intestinal Flora and Their Mechanisms

In this study, we evaluated the effects of different feeding methods on the characteristics of intestinal flora and gas production in infants and toddlers by using an in vitro simulated intestinal microecology fermentation and organoid model. We found that the feeding method influences intestinal gas and fecal ammonia production in infants and toddlers. Supplementation with milk powder for infants in the late lactation period could promote the proliferation of beneficial bacteria, including Bifidobacteria. Intestinal flora gas production in a culture medium supplemented with fucosyllactose (2′-FL) was significantly lower than that in media containing other carbon sources. In conclusion, 2′-FL may reduce gas production in infant and toddler guts through two mechanisms: first, it cannot be used by harmful intestinal bacteria to produce gas; second, it can inhibit intestinal mucosa colonization by harmful bacteria by regulating the expression of intestinal epithelial pathogenic genes/signaling pathways, thus reducing the proliferation of gas-producing harmful bacteria in the gut.

Testing the effects of processing on donor human Milk: Analytical methods

Holder pasteurization is the current recommended method for donor human milk treatment. This method effectively eliminates most life-threatening contaminants in donor milk, but it also greatly reduces some of its biological properties. Consequently, there is a growing interest for developing novel processing methods that can ensure both microbial inactivation and a higher retention of the functional components of donor milk. Our aim was to offer a comprehensive overview of the analytical techniques available for the evaluation of such methods. To suggest an efficient workflow for the analysis of processed donor milk, a safety analytical panel as well as a nutritional value and functionality analytical panel are discussed, together with the principles, benefits, and drawbacks of the available techniques. Concluding on the suitability of a novel method requires a multifactorial approach which can be achieved by a combination of analytical targets and by using complementary assays to cross-validate the obtained results.

Variations in the Composition of Human Milk Oligosaccharides Correlates with Effects on Both the Intestinal Epithelial Barrier and Host Inflammation: A Pilot Study

Background: Human milk oligosaccharides are complex, non-digestible carbohydrates that directly interact with intestinal epithelial cells to alter barrier function and host inflammation. Oligosaccharide composition varies widely between individual mothers, but it is unclear if this inter-individual variation has any impact on intestinal epithelial barrier function and gut inflammation. Methods: Human milk oligosaccharides were extracted from the mature human milk of four individual donors. Using an in vitro model of intestinal injury, the effects of the oligosaccharides on the intestinal epithelial barrier and select innate and adaptive immune functions were assessed. Results: Individual oligosaccharide compositions shared comparable effects on increasing transepithelial electrical resistance and reducing the macromolecular permeability of polarized (Caco-2Bbe1) monolayers but exerted distinct effects on the localization of the intercellular tight junction protein zona occludins-1 in response to injury induced by a human enteric bacterial pathogen Escherichia coli, serotype O157:H7. Immunoblots showed the differential effects of oligosaccharide compositions in reducing host chemokine interleukin 8 expression and inhibiting of p38 MAP kinase activation. Conclusions: These results provide evidence of both shared and distinct effects on the host intestinal epithelial function that are attributable to inter-individual differences in the composition of human milk oligosaccharides.

Human milk oligosaccharides and infant gut microbiota: Molecular structures, utilization strategies and immune function

Human milk oligosaccharides (HMOs) are a unique class of non-digestible carbohydrates present in the mother milk, which play a key role in the development of infant gut microbiota, epithelial barrier and immune function. The deficiency of HMOs in the bovine milk-based infant formula has been widely recognized as a major culprit for the much higher incidence of immune disorders of formula-fed infants. This report was to give an up-to-date review on the structure characteristics of HMOs and the possible mechanisms, and strategies for their cellular uptake, and metabolism by the gut bacteria and the associated effects on the infant gut microbiome, and immune function. Most previous studies have been carried out in animals or in vitro model systems on the utilization strategies for HMOs in infant bacteria and their roles in infant microbiome, and gut immune function. A few HMO molecules have been synthesized artificially and applied in infant formulas.

Role of milk carbohydrates in intestinal health of nursery pigs: a review

Intestinal health is essential for the resistance to enteric diseases and for nutrient digestion and absorption to support growth. The intestine of nursery pigs are immature and vulnerable to external challenges, which cause negative impacts on the structure and function of the intestine. Among nutritional interventions, the benefits of milk are significant for the intestinal health of pigs. Milk coproducts have traditionally been used in starter feeds to improve the growth of nursery pigs, but their use is somewhat limited due to the high costs and potential risks of excessive lactose on the intestine. Thus, understanding a proper feeding level of milk carbohydrates is an important start of the feeding strategy. For nursery pigs, lactose is considered a highly digestible energy source compared with plant-based starch, whereas milk oligosaccharides are considered bioactive compounds modulating intestinal immunity and microbiota. Therefore, milk carbohydrates, mainly composed of lactose and oligosaccharides, have essential roles in the intestinal development and functions of nursery pigs. The proper feeding levels of lactose in starter feeds could be variable by weaning age, body weight, or genetic lines. Effects of lactose and milk oligosaccharides have been broadly studied in human health and animal production. Therefore, this review focuses on the mechanisms of lactose and milk oligosaccharides affecting intestinal maturation and functions through modulation of enterocyte proliferation, intestinal immunity, and intestinal microbiota of nursery pigs.

Use of a Liquid Supplement Containing 2 Human Milk Oligosaccharides: The First Double-Blind, Randomized, Controlled Trial in Pre-term Infants

There is growing evidence supporting the benefit of human milk oligosaccharides (HMOs) on reducing risk of illnesses and improving immune function in newborn infants, but evidence in pre-term infants is lacking. This randomized, double-blind, placebo-controlled trial (NCT03607942) of pre-term infants evaluated the effects of HMO supplementation on feeding tolerance, growth, and safety in 7 neonatal units in France. Pre-term infants (27-33 weeks' gestation, birth weight <1,700 g) were randomized early after birth to receive HMO supplement (n = 43) [2'-fucosyllactose (2'FL) and lacto-N-neotetraose (LNnT) in a 10:1 ratio (0.374 g/kg body weight/day)] or an isocaloric placebo (n = 43) consisting of only glucose (0.140 g/kg/day) until discharge from the neonatal unit. Anthropometric z-scores were calculated using Fenton growth standards. Primary outcome was feeding tolerance, measured by non-inferiority (NI) in days to reach full enteral feeding (FEF) from birth in HMO vs. placebo group (NI margin = 4+ days). Mean number of days on intervention prior to FEF was 8.9 and 10.3 days in HMO and placebo, respectively. Non-inferiority in time to reach FEF in HMO (vs. placebo) was achieved [LS mean difference (95% CI) = -2.16 (-5.33, 1.00); upper bound of 95% CI < NI margin] in full analysis set and similar for per protocol. Adjusted mean time to reach FEF from birth was 2 days shorter in HMO (12.2) vs. placebo (14.3), although not statistically significant (p = 0.177). There was no difference in weight-for-age z-scores between groups throughout the FEF period until discharge. Length-for-age z-scores were higher in HMO at FEF day 14 [0.29 (0.02, 0.56), p = 0.037] and 21 [0.31 (0.02, 0.61), p = 0.037]. Head circumference-for-age z-score was higher in HMO vs. placebo at discharge [0.42 (0.12, 0.71), p = 0.007]. Occurrence of adverse events (AEs) was similar in both groups and relatively common in this population, whereas 2.3 and 14.3%, respectively, experienced investigator-confirmed, related AEs. HMO supplementation is safe and well-tolerated in pre-term infants. After 9 days of supplementation, the HMO group reached FEF 2 days earlier vs. placebo, although the difference was not statistically significant. In addition, HMO supplementation supports early postnatal growth, which may have a positive impact on long-term growth and developmental outcomes.

Evaluation of 2'-Fucosyllactose and Bifidobacterium longum Subspecies infantis on Growth, Organ Weights, and Intestinal Development of Piglets

Human milk is rich in oligosaccharides that influence intestinal development and serve as prebiotics for the infant gut microbiota. Probiotics and 2’-fucosyllactose (2’-FL) added individually to infant formula have been shown to influence infant development, but less is known about the effects of their synbiotic administration. Herein, the impact of formula supplementation with 2’-fucosyllactose (2’-FL) and Bifidobacterium longum subsp. infantis Bi-26 (Bi-26), or 2’-FL + Bi-26 on weight gain, organ weights, and intestinal development in piglets was investigated. Two-day-old piglets (n = 53) were randomized in a 2 × 2 design to be fed a commercial milk replacer ad libitum without (CON) or with 1.0 g/L 2’-FL. Piglets in each diet were further randomized to receive either glycerol stock alone or Bi-26 (10⁹ CFU) orally once daily. Body weights and food intake were monitored from postnatal day (PND) 2 to 33/34. On PND 34/35, animals were euthanized and intestine, liver and brain weights were assessed. Intestinal samples were collected for morphological analyses and measurement of disaccharidase activity. Dry matter of cecum and colon contents and Bifidobacterium longum subsp. infantis abundance by RT-PCR were also measured. All diets were well tolerated, and formula intake did not differ among the treatment groups. Daily body weights were affected by 2’-FL, Bi-26, and day, but no interaction was observed. There was a trend (p = 0.075) for greater total body weight gain in CON versus all other groups. Jejunal and ascending colon histomorphology were unaffected by treatment; however, there were main effects of 2’-FL to increase (p = 0.040) and Bi-26 to decrease (p = 0.001) ileal crypt depth. The addition of 2’-FL and/or Bi-26 to milk replacer supported piglet growth with no detrimental effects on body and organ weights, or intestinal structure and function.

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.

Six Oligosaccharides' Variation in Breast Milk: A Study in South China from 0 to 400 Days Postpartum

This study investigated the variation in oligosaccharide levels in the breast milk of south Chinese mothers in a prolonged breastfeeding period of up to 400 days postpartum. A total of 488 breast milk samples were collected from 335 healthy mothers at five different time points: 0–5 days, 10–15 days, 40–45 days, 200–240 days, and 300–400 days postpartum. A high-performance anion-exchange chromatography-pulsed amperometric detector (HPAEC-PAD) was used to quantify 2′-fucosyllactose (2′-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), 3′-sialyllactose (3′-SL) and 6′-sialyllactose (6′-SL). In this study, we found six oligosaccharides that were present in breast milk from 0 to 400 days postpartum. The median value ranges of individual oligosaccharide components in this study were 1013–2891 mg/L 2′-FL, 193–1421 mg/L 3-FL, 314–1478 mg/L LNT, 44–255 mg/L LNnT, 111–241 mg/L 3′-SL, and 23–602 mg/L6′-SL. HMO levels decreased over the lactation periods, except for 3-FL, which increased throughout lactation. The predominant fucosylated and sialylated HMOs were 2′-FL and 6′-SL at 40–45 days postpartum and changed to 3-FL and 3′-SL at 200–240 days postpartum. Results from this study showed that lactating women continue to provide their offspring with a high level of 2′-FL one year after delivery, suggesting that 2′-FL may play an important role for infants in early life. Our findings also provide further evidence in support of breastfeeding after one-year postpartum.

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.

Human milk oligosaccharides alleviate stress-induced visceral hypersensitivity and associated microbiota dysbiosis

Pain-related functional gastrointestinal disorders (FGIDs) are characterized by visceral hypersensitivity (VHS) associated with alterations in the microbiota-gut-brain axis. Since human milk oligosaccharides (HMOs) modulate microbiota, gut and brain, we investigated whether HMOs impact VHS, and explored the role of gut microbiota. To induce VHS, C57BL/6JRj mice received hourly water avoidance stress (WAS) sessions for 10 d, or antibiotics (ATB) for 12 d. Challenged and unchallenged (Sham) animals were fed AIN93M diet (Cont) or AIN93M containing 1% of a 6-HMO mix (HMO6). VHS was assessed by monitoring the visceromotor response to colorectal distension. Fecal microbiome was analyzed by shotgun metagenomics. The effect of HMO6 sub-blends on VHS and nociceptive pathways was further tested using the WAS model. In mice fed Cont, WAS and ATB increased the visceromotor response to distension. HMO6 decreased WAS-mediated electromyographic rise at most distension volumes and overall Area Under Curve (AUC=6.12±0.50 in WAS/HMO6 vs. 9.46±0.50 in WAS/Cont; P<.0001). In contrast, VHS in ATB animals was not improved by HMO6. In WAS, HMO6 promoted most microbiota taxa and several functional pathways associated with low VHS and decreased those associated with high VHS. Among the sub-blends, 2'FL+DFL and LNT+6'SL reduced visceromotor response close to Sham/Cont values and modulated serotoninergic and CGRPα-related pathways. This research further substantiates the capacity of HMOs to modulate the microbiota-gut-brain communication and identifies mitigation of abdominal pain as a new HMO benefit. Ultimately, our findings suggest the value of specific HMO blends to alleviate pain associated FGIDs such as infantile colic or Irritable Bowel Syndrome.

Multifunctional Benefits of Prevalent HMOs: Implications for Infant Health

Breastfeeding is the best source of nutrition during infancy and is associated with a broad range of health benefits. However, there remains a significant and persistent need for innovations in infant formula that will allow infants to access a wider spectrum of benefits available to breastfed infants. The addition of human milk oligosaccharides (HMOs) to infant formulas represents the most significant innovation in infant nutrition in recent years. Although not a direct source of calories in milk, HMOs serve as potent prebiotics, versatile anti-infective agents, and key support for neurocognitive development. Continuing improvements in food science will facilitate production of a wide range of HMO structures in the years to come. In this review, we evaluate the relationship between HMO structure and functional benefits. We propose that infant formula fortification strategies should aim to recapitulate a broad range of benefits to support digestive health, immunity, and cognitive development associated with HMOs in breastmilk. We conclude that acetylated, fucosylated, and sialylated HMOs likely confer important health benefits through multiple complementary mechanisms of action.

Human Milk Oligosaccharides: A Comprehensive Review towards Metabolomics

Human milk oligosaccharides (HMOs) are the third most represented component in breast milk. They serve not only as prebiotics but they exert a protective role against some significant neonatal pathologies such as necrotizing enterocolitis. Furthermore, they can program the immune system and consequently reduce allergies and autoimmune diseases’ incidence. HMOs also play a crucial role in brain development and in the gut barrier’s maturation. Moreover, the maternal genetic factors influencing different HMO patterns and their modulation by the interaction and the competition between active enzymes have been widely investigated in the literature, but there are few studies concerning the role of other factors such as maternal health, nutrition, and environmental influence. In this context, metabolomics, one of the newest “omics” sciences that provides a snapshot of the metabolites present in bio-fluids, such as breast milk, could be useful to investigate the HMO content in human milk. The authors performed a review, from 2012 to the beginning of 2021, concerning the application of metabolomics to investigate the HMOs, by using Pubmed, Researchgate and Scopus as source databases. Through this technology, it is possible to know in real-time whether a mother produces a specific oligosaccharide, keeping into consideration that there are other modifiable and unmodifiable factors that influence HMO production from a qualitative and a quantitative point of view. Although further studies are needed to provide clinical substantiation, in the future, thanks to metabolomics, this could be possible by using a dipstick and adding the eventual missing oligosaccharide to the breast milk or formula in order to give the best and the most personalized nutritional regimen for each newborn, adjusting to different necessities.

Efficient biosynthesis of lacto-N-neotetraose by a novel β-1,4-galactosyltransferase from Aggregatibacter actinomycetemcomitans NUM4039

Lacto-N-neotetraose (LNnT) is a unique tetrasaccharide naturally occurring in human milk, as an important member of human milk oligosaccharides. Because of promising beneficial effects, it has been commercially added as a functional fortifier in infant formula. β-1,4-Galactosyltransferase (β-1,4-GalT) catalyzes LNnT biosynthesis from uridine 5'-diphospho-galactose (UDP-Gal) to lacto-N-triose II (LNT II). There have been only two LNnT-producing bacterial β-1,4-GalTs, including the ones from Neisseria meningitidis and Histophilus somni. In this study, a novel LNnT-producing β-1,4-GalT was identified from Aggregatibacter actinomycetemcomitans. The enzyme was easily overexpressed in E. coli in soluble form. It displayed much higher transglycosylation versus hydrolysis activity, indicating its great potential in LNnT biosynthesis. The enzyme produced 13 mM LNnT from 20 mM LNT II and 60 mM UDP-Gal, with the yield of 65 % on LNT II and very low level of UDP-Gal hydrolysis. Therefore, it could be considered as a good candidate for the practical LNnT production.

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.

Structure-Specific Fermentation of Galacto-Oligosaccharides, Isomalto-Oligosaccharides and Isomalto/Malto-Polysaccharides by Infant Fecal Microbiota and Impact on Dendritic Cell Cytokine Responses

SCOPE

Next to galacto-oligosaccharides (GOS), starch-derived isomalto-oligosaccharide preparation (IMO) and isomalto/malto-polysaccharides (IMMP) could potentially be used as prebiotics in infant formulas. However, it remains largely unknown how the specific molecular structures of these non-digestible carbohydrates (NDCs) impact fermentability and immune responses in infants.

METHODS AND RESULTS

In vitro fermentation of GOS, IMO and IMMP using infant fecal inoculum of 2- and 8-week-old infants shows that only GOS and IMO are fermented by infant fecal microbiota. The degradation of GOS and IMO coincides with an increase in Bifidobacterium and production of acetate and lactate, which is more pronounced with GOS. Individual isomers with an (1↔1)-linkage or di-substituted reducing terminal glucose residue are more resistant to fermentation. GOS, IMO, and IMMP fermentation digesta attenuates cytokine profiles in immature dendritic cells (DCs), but the extent is dependent on the infants age and NDC structure.

CONCLUSION

The IMO preparation, containing reducing and non-reducing isomers, shows similar fermentation patterns as GOS in fecal microbiota of 2-week-old infants. Knowledge obtained on the substrate specificities of infant fecal microbiota and the subsequent regulatory effects of GOS, IMO and IMMP on DC responses might contribute to the design of tailored NDC mixtures for infants of different age groups.

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.

Immunomodulatory Effects of Human Colostrum and Milk

The immune system is not fully developed in human neonates and infants; breastfeeding is important in this stage as the bioactive components of human breast milk are known to have anti-microbial, anti-inflammatory, and immunomodulatory effects, and can therefore contribute to an infant's immunity against allergies, asthma, autoimmune diseases, and inflammatory bowel disease. Herein, the positive effect on the immune system by human colostrum and milk are reviewed.

Gold standard for nutrition: a review of human milk oligosaccharide and its effects on infant gut microbiota

Human milk is the gold standard for nutrition of infant growth, whose nutritional value is mainly attributed to human milk oligosaccharides (HMOs). HMOs, the third most abundant component of human milk after lactose and lipids, are complex sugars with unique structural diversity which are indigestible by the infant. Acting as prebiotics, multiple beneficial functions of HMO are believed to be exerted through interactions with the gut microbiota either directly or indirectly, such as supporting beneficial bacteria growth, anti-pathogenic effects, and modulation of intestinal epithelial cell response. Recent studies have highlighted that HMOs can boost infants health and reduce disease risk, revealing potential of HMOs in food additive and therapeutics. The present paper discusses recent research in respect to the impact of HMO on the infant gut microbiome, with emphasis on the molecular basis of mechanism underlying beneficial effects of HMOs.

A Novel β-1,4-Galactosyltransferase from Histophilus somni Enables Efficient Biosynthesis of Lacto-N-Neotetraose via Both Enzymatic and Cell Factory Approaches

Human milk oligosaccharides (HMOs) attract particular attention because of their health benefits for infants. Lacto-N-neotetraose (LNnT) is one of the most abundant neutral core structures of HMOs. Bacterial β-1,4-galactosyltransferase (β-1,4-GalT) displays an irreplaceable role in the practical application of LNnT biosynthesis. In this study, a novel β-1,4-GalT from Histophilus somni was identified to efficiently synthesize LNnT from UDP-Gal and lacto-N-triose II (LNT II). The optimum pH and temperature were determined to be pH 6.0 and 30 °C, respectively. The enzyme showed both transgalactosylation and hydrolysis activity, with a specific activity of 3.7 and 6.6 U/mg, respectively. LNnT was synthesized using H. somni β-1,4-GalT via both enzymatic and cell factory approaches, and both approaches provided an LNnT ratio with the remaining LNT II at approximately 1:2 when reactions attained a balance. These findings indicated that H. somni β-1,4-GalT has a potential in biosynthesis of LNnT and derivatives in future.

Human Milk Oligosaccharides: Their Effects on the Host and Their Potential as Therapeutic Agents

Breastmilk is known to be very important for infants because it provides nutrients and immunological compounds. Among these compounds, human milk oligosaccharides (HMOs) represent the third most important component of breastmilk after lipids and lactose. Several experiments demonstrated the beneficial effects of these components on the microbiota, the immune system and epithelial barriers, which are three major biological systems. Indeed, HMOs induce bacterial colonization in the intestinal tract, which is beneficial for health. The gut bacteria can act directly and indirectly on the immune system by stimulating innate immunity and controlling inflammatory reactions and by inducing an adaptive immune response and a tolerogenic environment. In parallel, HMOs directly strengthen the intestinal epithelial barrier, protecting the host against pathogens. Here, we review the molecular mechanisms of HMOs in these different compartments and highlight their potential use as new therapeutic agents, especially in allergy prevention.

Engineered Microbial Routes for Human Milk Oligosaccharides Synthesis

Human milk oligosaccharides (HMOs) are one of the important ingredients in human milk, which have attracted great interest due to their beneficial effect on the health of newborns. The large-scale production of HMOs has been researched using engineered microbial routes due to the availability, safety, and low cost of host strains. In addition, the development of molecular biology technology and metabolic engineering has promoted the effectiveness of HMOs production. According to current reports, 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), 3'-sialyllactose (3'-SL), 6'-sialyllactose (6'-SL), and some fucosylated HMOs with complex structures have been produced via the engineered microbial route, with 2'-FL having been produced the most. However, due to the uncertainty of metabolic patterns, the selection of host strains has certain limitations. Aside from that, the expression of appropriate glycosyltransferase in microbes is key to the synthesis of different HMOs. Therefore, finding a safe and efficient glycosyltransferase has to be addressed when using engineered microbial pathways. In this review, the latest research on the production of HMOs using engineered microbial routes is reported. The selection of host strains and adapting different metabolic pathways helped researchers designing engineered microbial routes that are more conducive to HMOs production.

LIN28B induces a differentiation program through CDX2 in colon cancer

Most colorectal cancers (CRCs) are moderately differentiated or well differentiated, a status that is preserved even in metastatic tumors. However, the molecular mechanisms underlying CRC differentiation remain to be elucidated. Herein, we unravel a potentially novel posttranscriptional regulatory mechanism via a LIN28B/CDX2 signaling axis that plays a critical role in mediating CRC differentiation. Owing to a large number of mRNA targets, the mRNA-binding protein LIN28B has diverse functions in development, metabolism, tissue regeneration, and tumorigenesis. Our RNA-binding protein IP (RIP) assay revealed that LIN28B directly binds CDX2 mRNA, which is a pivotal homeobox transcription factor in normal intestinal epithelial cell identity and differentiation. Furthermore, LIN28B overexpression resulted in enhanced CDX2 expression to promote differentiation in subcutaneous xenograft tumors generated from CRC cells and metastatic tumor colonization through mesenchymal-epithelial transition in CRC liver metastasis mouse models. A ChIP sequence for CDX2 identified α-methylacyl-CoA racemase (AMACR) as a potentially novel transcriptional target of CDX2 in the context of LIN28B overexpression. We also found that AMACR enhanced intestinal alkaline phosphatase activity, which is known as a key component of intestinal differentiation, through the upregulation of butyric acid. Overall, we demonstrated that LIN28B promotes CRC differentiation through the CDX2/AMACR axis.

Non-Digestible Oligosaccharides and Short Chain Fatty Acids as Therapeutic Targets against Enterotoxin-Producing Bacteria and Their Toxins

Enterotoxin-producing bacteria (EPB) have developed multiple mechanisms to disrupt gut homeostasis, and provoke various pathologies. A major part of bacterial cytotoxicity is attributed to the secretion of virulence factors, including enterotoxins. Depending on their structure and mode of action, enterotoxins intrude the intestinal epithelium causing long-term consequences such as hemorrhagic colitis. Multiple non-digestible oligosaccharides (NDOs), and short chain fatty acids (SCFA), as their metabolites produced by the gut microbiota, interact with enteropathogens and their toxins, which may result in the inhibition of the bacterial pathogenicity. NDOs characterized by diverse structural characteristics, block the pathogenicity of EPB either directly, by inhibiting bacterial adherence and growth, or biofilm formation or indirectly, by promoting gut microbiota. Apart from these abilities, NDOs and SCFA can interact with enterotoxins and reduce their cytotoxicity. These anti-virulent effects mostly rely on their ability to mimic the structure of toxin receptors and thus inhibiting toxin adherence to host cells. This review focuses on the strategies of EPB and related enterotoxins to impair host cell immunity, discusses the anti-pathogenic properties of NDOs and SCFA on EPB functions and provides insight into the potential use of NDOs and SCFA as effective agents to fight against enterotoxins.

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.

Blends of Human Milk Oligosaccharides Confer Intestinal Epithelial Barrier Protection in Vitro

Breastfeeding is integral in the proper maturation of the intestinal barrier and protection against inflammatory diseases. When human milk (HM) is not available, supplementation with HM bioactives like Human Milk Oligosaccharides (HMOs) may help in providing breastfeeding barrier-protective benefits. An increasing HMO variety is becoming industrially available, enabling approaching the HMO complexity in HM. We aimed at assessing the impact of blends of available HMOs on epithelial barrier function in vitro. The capacity of individual [2'-Fucosyllactose (2'FL), Difucosyllactose, Lacto-N-tetraose, Lacto-N-neotetraose, 3'-Siallylactose and 6'-Siallylactose] or varying combinations of 3, 5 and 6 HMOs to modulate fluorescein-isothiocyanate (FITC)-labelled Dextran 4 KDa (FD4) translocation and/or transepithelial resistance (TEER) was characterized in Caco-2: HT29- methotrexate (MTX) cell line monolayers before and after an inflammatory challenge with TNF-α and IFN-γ. The six HMO blend (HMO6) dose-dependently limited the cytokine-induced FD4 translocation and TEER decrease and increased TEER values before challenge. Similarly, 3 and 5 HMO blends conferred a significant protection against the challenge, with 2'FL, one of the most abundant but most variable oligosaccharides in HM, being a key contributor. Overall, our results suggest differential ability of specific HMOs in modulating the intestinal barrier and support the potential of supplementation with combinations of available HMOs to promote gut health and protect against intestinal inflammatory disorders.