Relationship Between Oligosaccharides and Glycoconjugates Content in Human Milk and the Development of the Gut Barrier

A novel "microbiota-host interaction model" to study the real-time effects of fermentation of non-digestible carbohydrate (NDCs) on gut barrier function

In this study, an in vitro co-culture model using an electric cell-substrate impedance sensing system (ECIS) for testing the impact of real-time fermentation of non-digestible carbohydrates (NDCs) by the intestinal microbiota on gut barrier function was established. We applied Lactobacillus plantarum WCFS1 as a model intestinal bacterium and alginate-pectin as immobilization polymers as well as a source of NDCs to determine the impact of pectin fermentation on the barrier function of T84 gut epithelial cells. In the first design, L. plantarum WCFS1 was encapsulated in an alginate capsule followed by embedding in an agar layer to mimic a firm mucus layer that might be present in the colon. In this experimental design, the presence of the agar layer interfered with the transepithelial electrical resistance (TEER) measurement of T84 cells. Subsequently, we removed the agar layer and used encapsulated bacteria in an alginate gel and found that the TEER measurement was adequate. The encapsulation of the L. plantarum WCFS1 does avoid direct contact with cells. Also, the encapsulation system allows higher amounts of packing densities of L. plantarum WCFS1 in a limited space which can limit the oxygen concentration within the capsule and therefore create anaerobic conditions. To test this design, T84 cells were co-incubated with L. plantarum alginate-capsules supplemented with graded loads of fermentable pectin (0, 4, and 8 mg/ml per capsule) to investigate the effect of pectin fermentation on gut barrier function. We observed that as the pectin content in the L. plantarum capsules increased, pectin showed a gradually stronger protective effect on the TEER of the gut epithelium. This could partly be explained by enhanced SCFA production as both lactate and acetate were enhanced in L. plantarum containing alginate capsules with 8 mg/ml pectin. Overall, this newly designed in vitro co-culture model allows for studying the impact of bacteria-derived fermentation products but also for studying the direct effects of NDCs on gut barrier function in a relatively high-throughput way.

Human Milk Oligosaccharides: A Critical Review on Structure, Preparation, Their Potential as a Food Bioactive Component, and Future Perspectives

Human milk is the gold standard for infant feeding. Human milk oligosaccharides (HMOs) are a unique group of oligosaccharides in human milk. Great interest in HMOs has grown in recent years due to their positive effects on various aspects of infant health. HMOs provide various physiologic functions, including establishing a balanced infant's gut microbiota, strengthening the gastrointestinal barrier, preventing infections, and potential support to the immune system. However, the clinical application of HMOs is challenging due to their specificity to human milk and the difficulties and high costs associated with their isolation and synthesis. Here, the differences in oligosaccharides in human and other mammalian milk are compared, and the synthetic strategies to access HMOs are summarized. Additionally, the potential use and molecular mechanisms of HMOs as a new food bioactive component in different diseases, such as infection, necrotizing enterocolitis, diabetes, and allergy, are critically reviewed. Finally, the current challenges and prospects of HMOs in basic research and application are discussed.

Specific Milk Composition of miR-30b Transgenic Mice Associated with Early Duodenum Maturation in Offspring with Lasting Consequences for Growth

BACKGROUND

Milk composition is complex and includes numerous components essential for offspring growth and development. In addition to the high abundance of miR-30b microRNA, milk produced by the transgenic mouse model of miR-30b-mammary deregulation displays a significantly altered fatty acid profile. Moreover, wild-type adopted pups fed miR-30b milk present an early growth defect.

OBJECTIVE

This study aimed to investigate the consequences of miR-30b milk feeding on the duodenal development of wild-type neonates, a prime target of suckled milk, along with comprehensive milk phenotyping.

METHODS

The duodenums of wild-type pups fed miR-30b milk were extensively characterized at postnatal day (PND)-5, PND-6, and PND-15 using histological, transcriptomic, proteomic, and duodenal permeability analyses and compared with those of pups fed wild-type milk. Milk of miR-30b foster dams collected at mid-lactation was extensively analyzed using proteomic, metabolomic, and lipidomic approaches and hormonal immunoassays.

RESULTS

At PND-5, wild-type pups fed miR-30b milk showed maturation of their duodenum with 1.5-fold (P < 0.05) and 1.3-fold (P < 0.10) increased expression of Claudin-3 and Claudin-4, respectively, and changes in 8 duodenal proteins (P < 0.10), with an earlier reduction in paracellular and transcellular permeability (183 ng/mL fluorescein sulfonic acid [FSA] and 12 ng/mL horseradish peroxidase [HRP], respectively, compared with 5700 ng/mL FSA and 90 ng/mL HRP in wild-type; P < 0.001). Compared with wild-type milk, miR-30b milk displayed an increase in total lipid (219 g/L compared with 151 g/L; P < 0.05), ceramide (17.6 μM compared with 6.9 μM; P < 0.05), and sphingomyelin concentrations (163.7 μM compared with 76.3 μM; P < 0.05); overexpression of 9 proteins involved in the gut barrier (P < 0.1); and higher insulin and leptin concentrations (1.88 ng/mL and 2.04 ng/mL, respectively, compared with 0.79 ng/mL and 1.06 ng/mL; P < 0.01).

CONCLUSIONS

miR-30b milk displays significant changes in bioactive components associated with neonatal duodenal integrity and maturation, which could be involved in the earlier intestinal closure phenotype of the wild-type pups associated with a lower growth rate.

Online PGC-LC-ESI-MS/MS comparative analysis of variations in human milk O-glycopatterns from different secretor status

O-glycome is one of the important components of glycoconjugates in human milk which is speculated to provide protective features similar to those observed in free oligosaccharides. The effects of maternal secretor status on free oligosaccharides and N-glycome in milk have been well researched and documented. Currently, milk O-glycome of secretors (Se+) and nonsecretors (Se-) was investigated through reductive β-elimination combined with porous graphitized carbon-liquid chromatography-electrospray ionization-tandem mass spectrometry. A total of 70 presumptive O-glycan structures were identified, of which 25 O-glycans (including 14 sulfated O-glycans) were reported for the first time. Notably, 23 O-glycans exhibited significant differences between Se+ and Se- samples (p < 0.05). Compared to Se- group, the O-glycans of the Se+ group was two times more abundant in the total glycosylation, sialylation, fucosylation, and sulfation (p < 0.01). In conclusion, approximately one-third of the milk O-glycosylation was influenced by maternal FUT2-related secretor status. Our data will lay a foundation for the study of O-glycans structure-function relationship.

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.

Human Milk Oligosaccharides Are Associated with Lactation Stage and Lewis Phenotype in a Chinese Population

Background: Human milk oligosaccharides (HMOs) are the third most abundant component of human milk. Various factors may affect the concentration of HMOs, such as the lactation period, Lewis blood type, and the maternal secretor gene status. Objectives: The purpose of this study is to investigate factors associated with HMO concentrations in Chinese populations. Methods: A sub-sample of 481 was randomly selected from a large cross-sectional study in China (n = 6481) conducted in eight provinces (Beijing, Heilongjiang, Shanghai, Yunnan, Gansu, Guangdong, Zhejiang, and Shandong) between 2011 and 2013. HMO concentrations were determined by a high-throughput UPLC-MRM method. Various factors were collected through face-to-face interviews. Anthropometric measurement was conducted by trained staff. Results: Median total HMO concentration was 13.6 g/L, 10.7 g/L, and 6.0 g/L for colostrum, transitional milk, and mature milk, respectively. HMO concentration decreased significantly as the lactation period increased (p < 0.0001). There were significant differences of average total HMO concentration between secretor mothers and non-secretor mothers (secretor 11.3 g/L vs. non-secretor 5.8 g/L, p < 0.0001). There were significant differences of average total HMO concentrations among three Lewis blood types (p = 0.003). Comparing with the concentration of total oligosaccharides of Le+ (a−b+), average of total oligosaccharides concentrations increased by 3.9 (Le+ (a+b−), p = 0.004) and 1.1 g/L (Le− (a−b−), p = 0.049). The volume of breast milk expressed and the province the mother came from affected the concentration of total oligosaccharides (all p < 0.0001). Maternal BMI (p = 0.151), age (p = 0.630), prematurity (p = 0.850), mode of delivery (p = 0.486), infants’ gender (p = 0.685), maternal education level (p = 0.989), maternal occupation (p = 0.568), maternal allergic history (p = 0.370), maternal anemia (p = 0.625), pregnancy-induced hypertension (p = 0.739), gestational diabetes (p = 0.514), and parity (p = 0.098) were not significantly correlated with the concentration of milk oligosaccharides. The concentrations of 2′-fucosyllactose (2′-FL), lacto-N-neotetraose (LNnT), sialyllacto-N-tetraose c (LSTc), lacto-N-fucopentaose I (LNFP-I), disialylated lacto-N-tetraose (DSLNT), difucosyl-para-lacto-N-neohexaose (DFpLNnH), difucosyl-lacto-N-hexaose (DFLNH[a]), and 3-sialyllactose (3′-SL) showed a gradual downward trend, while the concentration of 3-fucosyllactose (3-FL) showed a gradual upward trend among three lactation stages (p < 0.05). Conclusions: The concentration of HMOs changes throughout lactation, and it varies between different HMOs. HMO concentrations differed between lactation stage, maternal secretor gene status, Lewis blood type, volume of breast milk expressed, and the province the mother came from. Prematurity, mode of delivery, parity, infants’ gender, and maternal characteristics did not affect the HMO concentration. Geographical region may be not associated with HMOs concentration in human milk. There may be a mechanism for co-regulation of the secretion of some of the oligosaccharides such as 2′FL vs. 3FL, 2′FL vs. LNnT, and lacto-N-tetraose (LNT).

Impact of dietary fibers in infant formulas on gut microbiota and the intestinal immune barrier

Human milk (HM) is the gold standard for the nutrition of infants. An important component of HM is human milk oligosaccharides (hMOs), which play an important role in gut microbiota colonization and gut immune barrier establishment, and thereby contribute to the maturation of the immune system in early life. Guiding these processes is important as disturbances have life-long health effects and can lead to the development of allergic diseases. Unfortunately, not all infants can be exclusively fed with HM. These infants are routinely fed with infant formulas that contain hMO analogs and other non-digestible carbohydrates (NDCs) to mimic the effects of hMOs. Currently, the hMO analogs 2'-fucosyllactose (2'-FL), galacto-oligosaccharides (GOS), fructo-oligosaccharides (FOS), and pectins are added to infant formulas; however, these NDCs cannot mimic all hMO functions and therefore new NDCs and NDC mixtures need to become available for specific groups of neonates like preterm and disease-prone neonates. In this review, we discuss human data on the beneficial effects of infant formula supplements such as the specific hMO analog 2'-FL and NDCs as well as their mechanism of effects like stimulation of microbiota development, maturation of different parts of the gut immune barrier and anti-pathogenic effects. Insights into the structure-specific mechanisms by which hMOs and NDCs exert their beneficial functions might contribute to the development of new tailored NDCs and NDC mixtures. We also describe the needs for new in vitro systems that can be used for research on hMOs and NDCs. The current data suggest that "tailored infant formulas" for infants of different ages and healthy statuses are needed to ensure a healthy development of the microbiota and the gut immune system of infants.

The Human Milk Oligosaccharides 3-FL, Lacto-N-Neotetraose, and LDFT Attenuate Tumor Necrosis Factor-α Induced Inflammation in Fetal Intestinal Epithelial Cells In Vitro through Shedding or Interacting with Tumor Necrosis Factor Receptor 1

SCOPE

Human milk oligosaccharides (hMOs) can attenuate inflammation by modulating intestinal epithelial cells, but the mechanisms of action are not well-understood. Here, the effects of hMOs on tumor necrosis factor-α (TNF-α) induced inflammatory events in gut epithelial cells are studied.

METHODS AND RESULTS

The modulatory effects of 2'-fucosyllactose, 3-fucosyllactose (3-FL), 6'-sialyllactose, lacto-N-tetraose, lacto-N-neotetraose (LNnT), lactodifucotetraose (LDFT), and lacto-N-triaose (LNT2) on immature (FHs 74 Int) and adult (T84) intestinal epithelial cells with or without TNF-α are determined. Interleukin-8 (IL-8) secretion in FHs 74 Int and T84 are quantified to determine hMO induced attenuation of inflammatory events by ELISA. 3-FL, LNnT, and LDFT significantly attenuate TNF-α induced inflammation in FHs 74 Int, while LNT2 induces IL-8 secretion in T84. In addition, microscale thermophoresis assays and ELISA are used to study the possible mechanisms of interaction between effective hMOs and tumor necrosis factor receptor 1 (TNFR1). 3-FL, LNnT, and LDFT exert TNFR1 ectodomain shedding while LNnT also shows binding affinity to TNFR1 with a Kd of 900 ± 660 nM.

CONCLUSION

The findings indicate that specific hMO types attenuate TNF-α induced inflammation in fetal gut epithelial cells through TNFR1 in a hMO structure-dependent fashion suggest possibilities to apply hMOs in management of TNF-α dependent diseases.

Characterization of a non-glycosylated fraction from honey proteins of Melipona beecheii with antimicrobial activity against Escherichia coli O157:H7

AIMS

To analyse the non-glycosylated protein fraction from Melipona beecheii honey for antimicrobial activity against Escherichia coli O157:H7.

METHODS AND RESULTS

The proteins from M. beecheii honey were separated according to their degree of glycosylation using Concanavalin A-affinity chromatography. The total protein extract and its fractions were analysed by 1D and 2D electrophoresis. We also determined the antimicrobial and antihaemolytic activities of the total protein extract and the non-glycosylated fraction. Furthermore, we evaluated the effect of this non-glycosylated fraction for the expression of the Stx1, Stx2, EAE and HlyA pathogen genes. Melipona beecheii honey contained at least 24 proteins with molecular weights ranging between 7·6 and 95 kDa and isoelectric points between 3 and 10, three proteins from the 24 are non-glycosylated. The non-glycosylated fraction had an MIC₉₀ of 1·128 µg ml^-1 , and this fraction inhibited the haemolytic activity of the pathogen, as well as reduced the expression of Stx1, Stx2 and HlyA. The MbF1-2 protein from the non-glycosylated fraction was sequenced and identified as a homologue of the royal jelly-like protein of Melipona quadrifasciata.

CONCLUSIONS

The non-glycosylated protein fraction from M. beecheii honey greatly contributes to antibacterial activity and it is composed of at least three proteins, of which MbF1-2 provided over 50% of the antimicrobial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study showed significant antimicrobial activity from several proteins present in the honey of M. beecheii. Interestingly, the non-glycosylated protein fraction demonstrated antihaemolytic activity and adversely affected the expression of virulence genes in Escherichia coli O157:H7; these proteins have the potential to be used in developing therapeutic agents against this bacterium.

Effects of Human Milk Oligosaccharides on the Adult Gut Microbiota and Barrier Function

Human milk oligosaccharides (HMOs) shape the gut microbiota in infants by selectively stimulating the growth of bifidobacteria. Here, we investigated the impact of HMOs on adult gut microbiota and gut barrier function using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), Caco2 cell lines, and human intestinal gut organoid-on-chips. We showed that fermentation of 2'-O-fucosyllactose (2'FL), lacto-N-neotetraose (LNnT), and combinations thereof (MIX) led to an increase of bifidobacteria, accompanied by an increase of short chain fatty acid (SCFA), in particular butyrate with 2'FL. A significant reduction in paracellular permeability of FITC-dextran probe was observed using Caco2 cell monolayers with fermented 2'FL and MIX, which was accompanied by an increase in claudin-8 gene expression as shown by qPCR, and a reduction in IL-6 as determined by multiplex ELISA. Using gut-on-chips generated from human organoids derived from proximal, transverse, and distal colon biopsies (Colon Intestine Chips), we showed that claudin-5 was significantly upregulated across all three gut-on-chips following treatment with fermented 2'FL under microfluidic conditions. Taken together, these data show that, in addition to their bifidogenic activity, HMOs have the capacity to modulate immune function and the gut barrier, supporting the potential of HMOs to provide health benefits in adults.

More than sugar in the milk: human milk oligosaccharides as essential bioactive molecules in breast milk and current insight in beneficial effects

Human milk is the gold standard for newborn infants. Breast milk not only provides nutrients, it also contains bioactive components that guide the development of the infant's intestinal immune system, which can have a lifelong effect. The bioactive molecules in breast milk regulate microbiota development, immune maturation and gut barrier function. Human milk oligosaccharides (hMOs) are the most abundant bioactive molecules in human milk and have multiple beneficial functions such as support of growth of beneficial bacteria, anti-pathogenic effects, immune modulating effects, and stimulation of intestine barrier functions. Here we critically review the current insight into the benefits of bioactive molecules in mother milk that contribute to neonatal development and focus on current knowledge of hMO-functions on microbiota and the gastrointestinal immune barrier. hMOs produced via genetically engineered microorganisms are now applied in infant formulas to mimic the nutritional composition of breast milk as closely as possible, and their prospects and scientific challenges are discussed in depth.

Human Milk Oligosaccharides Differently Modulate Goblet Cells Under Homeostatic, Proinflammatory Conditions and ER Stress

SCOPE

Human milk oligosaccharides (hMOs) have beneficial effects on intestinal barrier function, but the mechanisms of action are not well understood. Here, the effects of hMOs on goblet cells, which indicate that some hMOs may enhance mucus barrier function through direct modulation of goblet cell function, are studied.

METHODS AND RESULTS

The modulatory effects of 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), lacto-N-triaose II (LNT2), and galacto-oligosaccharides (GOS) on the expression of goblet cell secretory related genes MUC2, TFF3, and RETNLB, and the Golgi-sulfotransferase genes CHST5 and GAL3ST2 of LS174T are determined by real-time quantitative RT-PCR. 3-FL, LNT2, and GOS-modulated LS174T gene expression profiles in a dose- and time-dependent manner. In addition, the upregulation of MUC2 is confirmed by immunofluorescence staining. Effects of 2'-FL, 3-FL, LNT2, and GOS on gene transcription of LS174T are also assessed during exposure to TNF-α, IL-13, or tunicamycin. During TNF-α challenge, 3-FL and LNT2 enhance MUC2 and TFF3 gene expression. After IL-13 exposure, 2'-FL, 3-FL, and LNT2 all show upregulating effects on MUC2; 3-FL and LNT2 also enhance TFF3 expression. LNT2 significantly reverses Tm-induced downregulation of TFF3, RETNLB, and CHST5.

CONCLUSION

The findings indicate that hMOs may enhance mucus barrier function through direct modulation of intestinal goblet cells. Effects are structure- and stressor-dependent.

Symposium review: Dairy-derived oligosaccharides-Their influence on host-microbe interactions in the gastrointestinal tract of infants

Oligosaccharides are the third most abundant component in human milk. It is widely accepted that they play several important protective, physiological, and biological roles, including selective growth stimulation of beneficial gut microbiota, inhibition of pathogen adhesion, and immune modulation. However, until recently, very few commercial products on the market have capitalized on these functions. This is mainly because the quantities of human milk oligosaccharides required for clinical trials have been unavailable. Recently, clinical studies have tested the potential beneficial effects of feeding infants formula containing 2'-fucosyllactose, which is the most abundant oligosaccharide in human milk. These studies have opened this field for further well-designed studies, which are required to fully understand the role of human milk oligosaccharides. However, one of the most striking features of human milk is its diversity of oligosaccharides, with over 200 identified to date. It may be that a mixture of oligosaccharides is even more beneficial to infants than a single structure. For this reason, the milk of domestic animals has become a focal point in recent years as an alternative source of complex oligosaccharides with associated biological activity. This review will focus specifically on free oligosaccharides found in bovine and caprine milk and the biological roles associated with such structures. These dairy streams are ideal sources of oligosaccharides, given their wide availability and use in so many regularly consumed dairy products. The aim of this review was to provide an overview of research into the functional role of bovine and caprine milk oligosaccharides in host-microbial interactions in the gut and provide current knowledge related to the isolation of oligosaccharides as ingredients for incorporation in functional or medical foods.