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

Exopolysaccharides from Bifidobacterium longum subsp. infantis and Bifidobacterium adolescentis modulate Toll-like receptor signaling

BACKGROUND

Exopolysaccharides (EPS) from probiotic bacteria like bifidobacteria, have gained considerable attention for the beneficial effects they exert in the gastrointestinal environment. Here, we investigated whether EPS isolated from Bifidobacterium longum subsp. infantis and Bifidobacterium adolescentis can interact with Toll-like receptors (TLRs) in a structure-dependent way and subsequently we investigated whether they influence cytokine-production in dendritic cells (DCs).

RESULTS

EPS from both B. infantis and B. adolescentis were found to be structurally different and were able to inhibit signaling of TLR2 and TLR4 in an EPS-type dependent fashion. EPS from B. infantis was shown to have stronger inhibitory effects on TLR2/1, whereas EPS from B. adolescentis showed stronger effects for TLR2/6 and TLR4. Incubation of DCs with EPS alone had no effect, however stimulation of DCs with spend-medium of epithelial cells incubated with EPS reduced production of the cytokines MCP-1/CCL2 and TNFα.

CONCLUSION

Here we show that EPS from B. infantis and B. adolescentis have structure-dependent immunomodulatory effects, indicating that EPS might be important effector molecules responsible for the health benefits of bifidobacteria.

Division mechanism of labor in Diqing Tibetan Pigs gut microbiota for dietary fiber efficiently utilization

The Diqing Tibetan (TP) pig is an roughage tolerance breed that inhabits an area with the highest altitude distribution in the world and can be maintained on a diet containing 90 % forage material in confined production systems. Our results showed that TP pigs had a strong capability for high-efficiency utilization of arabinose and xylose. Metagenomic analysis revealed that the secretion of carbohydrate esterases was mainly undertaken by fecal strains of Microbacterium, Alistipes, Acinetobacter, and Faecalibacterium, while Microbacterium, Prevotella, Turicibacter, Lactobacillus, Clostridium, and Streptococcus were responsible for most of the secretion of glycoside hydrolases. Then, a brand new species, which was named Microbacterium sp. Qiao 01 was captured and appeared to have the highest fiber utilization ability in vitro, degrading 36.54 % of the neutral detergent fiber in corn stover. Our results provide strong evidence that efficient utilization of dietary fiber by TP pigs is due to the emergence of highly specialized microbial strategies in the gut. Microorganisms showed preferences and a clear division of labor in the degradation process of dietary fiber. This study has great practical significance for improving the utilization efficiency of livestock feed and alleviating the tension of food insecurity.

Impact of GOS and 2'-FL on the production and structural composition of membrane-associated exopolysaccharides by B. adolescentis and B. infantis

Bifidobacteria, which are increasingly linked to health benefits to the host, produce structurally complex exopolysaccharides which are considered to be effector molecules responsible for health effects. It is currently not clear how the bacterial growth conditions, and especially the carbon source, affect the structural composition of the EPS. Here we present our investigations into the impact of the addition of 2'-fucosyllactose (2'-FL) and galactooligosaccharides (GOS), which are non-digestible carbohydrates added to infant formula, as the sole carbon source during the growth of B. adolescentis and B. infantis. Intriguingly, B. adolescentis produced EPS with larger molecular weights in the presence of GOS or a mixture of GOS/2'-FL. B. infantis showed increased growth levels in the presence of 2'-FL, and also produced an α-1,4-glucan polymer, whose amount was increased when grown on GOS. These findings highlight the species-specific effects of growth conditions on EPS structures.

Recent Progress in Physiological Significance and Biosynthesis of Lacto-N-triose II: Insights into a Crucial Biomolecule

Lacto-N-triose II (LNTri II), an important precursor for human milk oligosaccharide (HMOs) synthesis, has garnered significant attention due to its structural features and physiological properties. Composed of galactose (Gal), N-acetylglucosamine (GlcNAc), and glucose (Glc), with the chemical structure GlcNAcβ1,3Galβ1,4Glc, the distinctive structure of LNTri II confers various physiological functions such as promoting the growth of beneficial bacteria, regulating the infant immune system, and preventing certain gastrointestinal diseases. Extensive research efforts have been dedicated to elucidating efficient enzymatic synthesis pathways for LNTri II production, with particular emphasis on the transglycosylation activity of β-N-acetylhexosaminidases and the action of β-1,3-N-acetylglucosaminyltransferases. Additionally, metabolic engineering and cell factory approaches have been explored, harnessing the potential of engineered microbial hosts for the large-scale biosynthesis of LNTri II. This review summarizes the structure, derivatives, physiological effects, and biosynthesis of LNTri II.

Dietary fibre optimisation in support of global health

The human gut microbiota influences its host via multiple molecular pathways, including immune system interactions, the provision of nutrients and regulation of host physiology. Dietary fibre plays a crucial role in maintaining a healthy microbiota as its primary nutrient and energy source. Industrialisation has led to a massive decrease of habitual fibre intake in recent times, and fibre intakes across the world are below the national recommendations. This goes hand in hand with other factors in industrialised societies that may negatively affect the gut microbiota, such as medication and increased hygiene. Non-communicable diseases are on the rise in urbanised societies and the optimisation of dietary fibre intake can help to improve global health and prevent disease. Early life interventions shape the developing microbiota to counteract malnutrition, both in the context of industrialised nations with an overabundance of cheap, highly processed foods, as well as in Low- and Middle-Income Countries (LMICs). Adequate fibre intake should, however, be maintained across the life course to promote health. Here we will discuss the current state of dietary fibre research in the global context and consider different intervention approaches.

Revealing the therapeutic properties of gut microbiota: transforming cancer immunotherapy from basic to clinical approaches

The immune system plays a pivotal role in the battle against cancer, serving as a formidable guardian in the ongoing fight against malignant cells. To combat these malignant cells, immunotherapy has emerged as a prevalent approach leveraging antibodies and peptides such as anti-PD-1, anti-PD-L1, and anti-CTLA-4 to inhibit immune checkpoints and activate T lymphocytes. The optimization of gut microbiota plays a significant role in modulating the defense system in the body. This study explores the potential of certain gut-resident bacteria to amplify the impact of immunotherapy. Contemporary antibiotic treatments, which can impair gut flora, may diminish the efficacy of immune checkpoint blockers. Conversely, probiotics or fecal microbiota transplantation can help re-establish intestinal microflora equilibrium. Additionally, the gut microbiome has been implicated in various strategies to counteract immune resistance, thereby enhancing the success of cancer immunotherapy. This paper also acknowledges cutting-edge technologies such as nanotechnology, CAR-T therapy, ACT therapy, and oncolytic viruses in modulating gut microbiota. Thus, an exhaustive review of literature was performed to uncover the elusive link that could potentiate the gut microbiome's role in augmenting the success of cancer immunotherapy.

Dietary Intake of Fructooligosaccharides Protects against Metabolic Derangements Evoked by Chronic Exposure to Fructose or Galactose in Rats

SCOPE

Diets rich in fat and sugars evoke chronic low-grade inflammation, leading to metabolic derangements. This study investigates the impact of fructose and galactose, two commonly consumed simple sugars, on exacerbation of the harmful effects caused by high fat intake. Additionally, the potential efficacy of fructooligosaccharides (FOS), a fermentable dietary fiber, in counteracting these effects is examined.

METHODS AND RESULTS

Male Sprague-Dawley rats (six/group) are fed 8 weeks as follows: control 5% fat diet (CNT), 20% fat diet (FAT), FAT+10% FOS diet (FAT+FOS), FAT+25% galactose diet (FAT+GAL), FAT+GAL+10% FOS diet (FAT+GAL+FOS), FAT+25% fructose diet (FAT+FRU), FAT+FRU+10% FOS diet (FAT+FRU+FOS). The dietary manipulations tested do not affect body weight gain, blood glucose, or markers of systemic inflammation whereas significant increases in plasma concentrations of triacylglycerols, cholesterol, aspartate aminotransferase, and alanine aminotrasferase are detected in both FAT+FRU and FAT+GAL compared to CNT. In the liver and skeletal muscle, both sugars induce significant accumulation of lipids and advanced glycation end-products (AGEs). FOS supplementation prevents these impairments.

CONCLUSION

This study extends the understanding of the deleterious effects of a chronic intake of simple sugars and demonstrates the beneficial role of the prebiotic FOS in dampening the sugar-induced metabolic impairments by prevention of lipid and AGEs accumulation.

Effects of 2'-fucosyllactose on the composition and metabolic activity of intestinal microbiota from piglets after in vitro fermentation

BACKGROUND

As indigestible carbohydrates, milk oligosaccharides possess various benefits for newborns, mainly through intestinal microbiota, among which 2'-fucosyllactose (2'-FL) is the most predominant milk oligosaccharide. However, knowledge about the fermentative characteristics of 2'-FL in the gut remains limited, especially in the small intestine. The aim of this study is to explore the differential fermentability of 2'-FL by the small and large intestinal microbiota of piglets using fructo-oligosaccharide (FOS) and lactose as controls in an in vitro batch fermentation experiment. During fermentation, microbial composition was characterized along with gas production and short-chain fatty acid production.

RESULTS

2'-Fucosyllactose showed differential fermentability in jejunal and colonic fermentation. Compared with the colon, 2'-FL produced less gas in the jejunum than in the FOS and lactose groups (P < 0.05). Meanwhile, 2'-FL exhibited a different influence on the microbial composition and metabolism in the jejunum and colon compared with FOS and lactose. In the jejunum, compared with the FOS and lactose groups, the 2'-FL group showed a higher abundance of Bacteroides, Prevotella, and Blautia, but a lower abundance of Streptococcus and Lactobacillus (P < 0.05), with a higher level of propionate and a lower level of lactate during fermentation (P < 0.05). In the colon, compared with the FOS and lactose groups, 2'-FL increased the abundance of Blautia, Faecalibacterium, and Lachnospiraceae FCS020, but decreased the abundance of Prevotella_9, Succinivibrio, and Megasphaera (P < 0.05) with an increase in acetate production (P < 0.05).

CONCLUSION

Overall, the results suggested that the small intestinal microbiota had the potential to ferment milk oligosaccharides. Meanwhile, in comparison with FOS and lactose, 2'-FL selectively stimulated the growth of propionate-producing bacteria in the jejunum and acetate-producing bacteria in the colon. These results demonstrated the differences in fermentation properties of 2'-FL by small and large intestinal microbiota and provided new evidence for the application of 2'-FL in optimizing gut microbiota. © 2023 Society of Chemical Industry.

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.

Prebiotics in New-Born and Children's Health

At present, prebiotics, like probiotics, are receiving more attention as a promising tool for health maintenance. Many studies have recognized the role of prebiotics in preventing and treating various illnesses including metabolic disorders, gastrointestinal disorders, and allergies. Naturally, prebiotics are introduced to the human body in the first few hours of life as the mother breastfeeds the newborn. Prebiotic human milk oligosaccharides (HMOs) are the third largest constituent of human breastmilk. Studies have proven that HMOs modulate an infant's microbial composition and assist in the development of the immune system. Due to some health conditions of the mother or beyond the recommended age for breastfeeding, infants are fed with formula. Few types of prebiotics have been incorporated into formula to yield similar beneficial impacts similar to breastfeeding. Synthetic HMOs have successfully mimicked the bifidogenic effects of breastmilk. However, studies on the effectiveness and safety of consumption of these synthetic HMOs are highly needed before massive commercial production. With the introduction of solid foods after breastfeeding or formula feeding, children are exposed to a range of prebiotics that contribute to further shaping and maturing their gut microbiomes and gastrointestinal function. Therefore, this review evaluates the functional role of prebiotic interventions in improving microbial compositions, allergies, and functional gastrointestinal disorders in children.

Prebiotics Progress Shifts in the Intestinal Microbiome That Benefits Patients with Type 2 Diabetes Mellitus

Hypoglycemic medications that could be co-administered with prebiotics and functional foods can potentially reduce the burden of metabolic diseases such as Type 2 Diabetes Mellitus (T2DM). The efficacy of drugs such as metformin and sulfonylureas can be enhanced by the activity of the intestinal microbiome elaborated metabolites. Functional foods such as prebiotics (e.g., oligofructose) and dietary fibers can treat a dysbiotic gut microbiome by enhancing the diversity of microbial niches in the gut. These beneficial shifts in intestinal microbiome profiles include an increased abundance of bacteria such as Faecalibacterium prauznitzii, Akkermancia muciniphila, Roseburia species, and Bifidobacterium species. An important net effect is an increase in the levels of luminal SCFAs (e.g., butyrate) that provide energy carbon sources for the intestinal microbiome in cross-feeding activities, with concomitant improvement in intestinal dysbiosis with attenuation of inflammatory sequalae and improved intestinal gut barrier integrity, which alleviates the morbidity of T2DM. Oligosaccharides administered adjunctively with pharmacotherapy to ameliorate T2DM represent current plausible treatment modalities.

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.

Pre-, pro-, syn-, and Postbiotics in Infant Formulas: What Are the Immune Benefits for Infants?

The first objective of infant formulas is to ensure the healthy growth of neonates and infants, as the sole complete food source during the first months of life when a child cannot be breastfed. Beyond this nutritional aspect, infant nutrition companies also try to mimic breast milk in its unique immuno-modulating properties. Numerous studies have demonstrated that the intestinal microbiota under the influence of diet shapes the maturation of the immune system and influences the risk of atopic diseases in infants. A new challenge for dairy industries is, therefore, to develop infant formulas inducing the maturation of immunity and the microbiota that can be observed in breastfed delivered vaginally, representing reference infants. Streptococcus thermophilus, Lactobacillus reuteri DSM 17938, Bifidobacterium breve (BC50), Bifidobacterium lactis Bb12, Lactobacillus fermentum (CECT5716), and Lactobacillus rhamnosus GG (LGG) are some of the probiotics added to infant formula, according to a literature review of the past 10 years. The most frequently used prebiotics in published clinical trials are fructo-oligosaccharides (FOSs), galacto-oligosaccharides (GOSs), and human milk oligosaccharides (HMOs). This review sums up the expected benefits and effects for infants of pre-, pro-, syn-, and postbiotics added to infant formula regarding the microbiota, immunity, and allergies.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

2'-Fucosyllactose Promotes the Production of Short-Chain Fatty Acids and Improves Immune Function in Human-Microbiota-Associated Mice by Regulating Gut Microbiota

As a natural prebiotic in human milk, 2'-fucosyllactose (2'-FL) is actively used in infant formula (IF). However, the 2'-FL influence on the improvement of gut microbiota and the regulation of the immune function remains unknown. In this study, human microbiota-associated (HMA) mice were used to demonstrate that feeding 2'-FL-containing IF was comparable to human milk at levels of immune cytokines (IL-2, IL-9, IL-10, and sIgA) and short-chain fatty acids (SCFAs, i.e., acetate and propionate). In addition, 2'-FL increased the abundance of Blautia and Olsenella and improved the anti-inflammatory cytokine IL-10 levels. The abundance of Blautia and Olsenella positively correlated with the IL-10 levels. 2'-FL also decreased the abundance of Enterorhabdus and Lachnospiraceae_UCG-006 and elevated SCFA levels, showing a negative correlation between these genera and SCFAs. Our findings revealed that feeding 2'-FL-containing IF drives the levels of cytokines and SCFAs toward human milk levels by shaping the beneficial gut microbiota profile.

Combining galacto-oligosaccharides and 2'-fucosyllactose alters their fermentation kinetics by infant fecal microbiota and influences AhR-receptor dependent cytokine responses in immature dendritic cells

Galacto-oligosaccharides (GOS) and 2′-fucosyllactose (2′-FL) are non-digestible carbohydrates (NDCs) that are often added to infant formula to replace the functionalities of human milk oligosaccharides (HMOs). It is not known if combining GOS and 2′-FL will affect their fermentation kinetics and subsequent immune-modulatory effects such as AhR-receptor stimulation. Here, we used an in vitro set-up for the fermentation of 2′-FL and GOS, either individually or combined, by fecal microbiota of 8-week-old infants. We found that GOS was fermented two times faster by the infant fecal microbiota when combined with 2′-FL, while the combination of GOS and 2′-FL did not result in a complete degradation of 2′-FL. Fermentation of both GOS and 2′-FL increased the relative abundance of Bifidobacterium, which coincided with the production of acetate and lactate. Digesta of the fermentations influenced dendritic cell cytokine secretion differently under normal conditions and in the presence of the AhR-receptor blocker CH223191. We show that, combining GOS and 2′-FL accelerates GOS fermentation by the infant fecal microbiota of 8-week-old infants. In addition, we show that the fermentation digesta of GOS and 2′-FL, either fermented individually or combined, can attenuate DC cytokine responses in a similar and in an AhR-receptor dependent way.

Galacto-oligosaccharides (GOS) and 2′-fucosyllactose (2′-FL) are non-digestible carbohydrates (NDCs) that are often added to infant formula to replace the functionalities of human milk oligosaccharides (HMOs).

Resveratrol in Intestinal Health and Disease: Focusing on Intestinal Barrier

The integrity of intestinal barrier determines intestinal homeostasis, which could be affected by various factors, like physical, chemical, and biological stimuli. Therefore, it is of considerable interest and importance to maintain intestinal barrier function. Fortunately, many plant polyphenols, including resveratrol, could affect the health of intestinal barrier. Resveratrol has many biological functions, such as antioxidant, anti-inflammation, anti-tumor, and anti-cardiovascular diseases. Accumulating studies have shown that resveratrol affects intestinal tight junction, microbial composition, and inflammation. In this review, we summarize the effects of resveratrol on intestinal barriers as well as the potential mechanisms (e.g., inhibiting the growth of pathogenic bacteria and fungi, regulating the expression of tight junction proteins, and increasing anti-inflammatory T cells while reducing pro-inflammatory T cells), and highlight the applications of resveratrol in ameliorating various intestinal diseases.

Human milk oligosaccharides and non-digestible carbohydrates reduce pathogen adhesion to intestinal epithelial cells by decoy effects or by attenuating bacterial virulence

This work investigated the effects of different chemical structures of human milk oligosaccharides (hMOs) and non-digestible carbohydrates (NDCs) on pathogen adhesion by serving as decoy receptors. Pre-exposure of pathogens to inulins and low degree of methylation (DM) pectin prevented binding to gut epithelial Caco2-cells, but effects were dependent on the molecules' chemistry, pathogen strain and growth phase. Pre-exposure to 3-fucosyllactose increased E. coli WA321 adhesion (28%, p < 0.05), and DM69 pectin increased E. coli ET8 (15 fold, p < 0.05) and E. coli WA321 (50%, p < 0.05) adhesion. Transcriptomics analysis revealed that DM69 pectin upregulated flagella and cell membrane associated genes. However, the top 10 downregulated genes were associated with lowering of bacteria virulence. DM69 pectin increased pathogen adhesion but bacterial virulence was attenuated illustrating different mechanisms may lower pathogen adhesion. Our study illustrates that both hMOs and NDCs can reduce adhesion or attenuate virulence of pathogens but that these effects are chemistry dependent.

The Impact of Intestinal Microorganisms and Their Metabolites on Type 1 Diabetes Mellitus

BACKGROUND

Type 1 diabetes mellitus (T1DM) is an autoimmune disease with a complex etiology comprising numerous genetic and environmental factors; however, many of the mechanisms underlying disease development remain unclear. Nevertheless, a critical role has recently been assigned to intestinal microorganisms in T1DM disease pathogenesis. In particular, a decrease in intestinal microbial diversity, increase in intestinal permeability, and the translocation of intestinal bacteria to the pancreas have been reported in patients and animal models with T1DM. Moreover, intestinal microbial metabolites differ between healthy individuals and patients with T1DM. Specifically, short-chain fatty acid (SCFA) production, which contributes to intestinal barrier integrity and immune response regulation, is significantly reduced in patients with T1DM. Considering this correlation between intestinal microorganisms and T1DM, many studies have investigated the potential of intestinal microbiota in preventive and therapeutic strategies for T1DM.

OBJECTIVE

The aim of this review is to provide further support for the notion that intestinal microbiota contributes to the regulation of T1DM occurrence and development. In particular, this article reviews the involvement of the intestinal microbiota and the associated metabolites in T1DM pathogenesis, as well as recent studies on the involvement of the intestinal microbiota in T1DM prevention and treatment.

CONCLUSION

Intestinal microbes and their metabolites contribute to T1DM occurrence and development and may become a potential target for novel therapeutics.

Distinct fermentation of human milk oligosaccharides 3-FL and LNT2 and GOS/inulin by infant gut microbiota and impact on adhesion of Lactobacillus plantarum WCFS1 to gut epithelial cells

Human milk oligosaccharides (hMOs) are unique bioactive components in human milk. 3-Fucosyllactose (3-FL) is an abundantly present hMO that can be produced in sufficient amounts to allow application in infant formula. Lacto-N-triaose II (LNT2) can be obtained by acid hydrolysis of lacto-N-neotetraose (LNnT). Both 3-FL and LNT2 have been shown to have health benefits, but their impact on infant microbiota composition and microbial metabolic products such as short-chain fatty acids (SCFAs) is unknown. To gain more insight in fermentability, we performed in vitro fermentation studies of 3-FL and LNT2 using pooled fecal microbiota from 12-week-old infants. The commonly investigated galacto-oligosaccharides (GOS)/inulin (9 : 1) served as control. Compared to GOS/inulin, we observed a delayed utilization of 3-FL, which was utilized at 60.3% after 36 h of fermentation, and induced the gradual production of acetic acid and lactic acid. 3-FL specifically enriched bacteria of Bacteroides and Enterococcus genus. LNT2 was fermented much faster. After 14 h of fermentation, 90.1% was already utilized, and production of acetic acid, succinic acid, lactic acid and butyric acid was observed. LNT2 specifically increased the abundance of Collinsella, as well as Bifidobacterium. The GOS present in the GOS/inulin mixture was completely fermented after 14 h, while for inulin, only low DP was rapidly utilized after 14 h. To determine whether the fermentation might lead to enhanced colonization of commensal bacteria to gut epithelial cells, we investigated adhesion of the commensal Lactobacillus plantarum WCFS1 to Caco-2 cells. The fermentation digesta of LNT2 collected after 14 h, 24 h, and 36 h, and GOS/inulin after 24 h of fermentation significantly increased the adhesion of L. plantarum WCFS1 to Caco-2 cells, while 3-FL had no such effect. Our findings illustrate that fermentation of hMOs is very structure-dependent and different from the commonly applied GOS/inulin, which might lead to differential potencies to stimulate adhesion of commensal cells to gut epithelium and consequent microbial colonization. This knowledge might contribute to the design of tailored infant formulas containing specific hMO molecules to meet the need of infants during the transition from breastfeeding to formula.

Chicory inulin enhances fermentation of 2'-fucosyllactose by infant fecal microbiota and differentially influences immature dendritic cell and T-cell cytokine responses under normal and Th2-polarizing conditions

Scope: Non-digestible carbohydrates (NDCs) such as native chicory inulin and 2'-fucosyllactose (2'-FL) are added to infant formula to mimic some of the human milk oligosaccharide (HMO) functions. It is unknown whether combining inulin and 2'-FL influences their fermentation kinetics and whether the immune-modulatory effects of these NDCs are different under normal and inflammatory-prone Th2-polarizing conditions. Methods and results: We investigated the in vitro fermentation of 2'-FL and native chicory inulin, fermented individually and combined, using fecal inocula of 8-week-old infants. Native inulin was fermented in a size-dependent fashion and expedited the fermentation of 2'-FL. Fermentation of both native inulin and 2'FL increased the relative abundance of Bifidobacterium, which coincided with the production of acetate and lactate. The fermentation digesta of all fermentations differentially influenced both dendritic cell and T-cell cytokine responses under normal culture conditions or in presence of the Th2-polarizing cytokines IL-33 and TSLP, with the most pronounced effect for IL-1β in the presence of TSLP. Conclusions: Our findings show that native inulin can expedite the fermentation of 2'-FL by infant fecal microbiota and that these NDC fermentation digesta have different effects under normal and Th2-polarizing conditions, indicating that infants with different immune backgrounds might benefit from tailored NDC formulations.

Human milk oligosaccharide 2'-fucosyllactose supplementation improves gut barrier function and signaling in the vagal afferent pathway in mice

2′-Fucosyllactose (2′-FL) is one of the predominant oligosaccharides found in human milk and has several well-established beneficial effects in the host. It has previously been shown that 2′-FL can improve the metabolic phenotype in high-fat (HF)-fed mice. Here we investigated whether dietary supplementation with 2′-FL was associated with improved intestinal barrier integrity, signaling in the vagal afferent pathway and cognitive function. Mice were fed either a low-fat (LF, 10% fat per kcal) or HF (45% fat per kcal) diet with or without supplementation of 2′-FL (10% w/w) in the diet for 8 weeks. Body weight, energy intake, fat and lean mass, intestinal permeability (ex vivo in Ussing chambers), lipid profiles, gut microbiome and microbial metabolites, and cognitive functions were measured. Vagal afferent activity was measured via immunohistochemical detection of c-Fos protein in the brainstem in response to peripheral administration of cholecystokinin (CCK). 2′-FL significantly attenuated the HF-induced increase in fat mass and energy intake. 2′-FL significantly reduced intestinal permeability and significantly increased expression of interleukin (IL)-22, a cytokine known for its protective role in the intestine. Additionally, 2′-FL led to changes in the gut microbiota composition and in the associated microbial metabolites. Signaling in the vagal afferent pathway was improved but there was no effect on cognitive function. In conclusion, 2′-FL supplementation improved the metabolic profiles, gut barrier integrity, lipid metabolism and signaling in the vagal afferent pathway. These findings support the utility of 2′-FL in the control of gut barrier function and metabolic homeostasis under a metabolic challenge.

2’-Fucosyllactose (2’-FL), a predominant human milk oligosaccharide, attenuates HF diet-induced metabolic and intestinal barrier impairment, improves gut hormone resistance, and alters the intestinal microbiota and microbiota-derived metabolites.

Human milk oligosaccharides and non-digestible carbohydrates prevent adhesion of specific pathogens via modulating glycosylation or inflammatory genes in intestinal epithelial cells

Human milk oligosaccharides (hMOs) and non-digestible carbohydrates (NDCs) are known to inhibit the adhesion of pathogens to the gut epithelium, but the mechanisms involved are not well understood. Here, the effects of 2'-FL, 3-FL, DP3-DP10, DP10-DP60 and DP30-DP60 inulins and DM7, DM55 and DM69 pectins were studied on pathogen adhesion to Caco-2 cells. As the growth phase influences virulence, E. coli ET8, E. coli LMG5862, E. coli O119, E. coli WA321, and S. enterica subsp. enterica LMG07233 from both log and stationary phases were tested. Specificity for enteric pathogens was tested by including the lung pathogen K. pneumoniae LMG20218. Expression of the cell membrane glycosylation genes of galectin and glycocalyx and inflammatory genes was studied in the presence and absence of 2'-FL or NDCs. Inhibition of pathogen adhesion was observed for 2'-FL, inulins, and pectins. Pre-incubation with 2'-FL downregulated ICAM1, and pectins modified the glycosylation genes. In contrast, K. pneumoniae LMG20218 downregulated the inflammatory genes, but these were restored by pre-incubation with pectins, which reduced the adhesion of K. pneumoniae LMG20218. In addition, DM69 pectin significantly upregulated the inflammatory genes. 2'-FL and pectins but not inulins inhibited pathogen adhesion to the gut epithelial Caco-2 cells through changing the cell membrane glycosylation and inflammatory genes, but the effects were molecule-, pathogen-, and growth phase-dependent.

Nutritional strategies for mucosal health: the interplay between microbes and mucin glycans

Many aspects of the mechanisms underlying the symbiosis between humans and gut microbes remain unknown and encompass some of the most intriguing questions in microbiome research. An important factor in this symbiosis is the interplay between microbes and human-produced glycans in mucin and breast milk. In this Opinion paper, I propose a synergy between the structural diversity of human mucin glycans and the enzymatic repertoire of the gut microbiome. The contribution of microbes to mucosal health is discussed, and the role of breast milk glycans in mucosal colonization by microbes is explained. The use of prebiotic mucin glycans in general, and specialized infant and medical nutrition in particular, should be considered as the field of interest to modulate the microbiota and improve mucosal health.

Galactooligosaccharide pretreatment alleviates damage of the intestinal barrier and inflammatory responses in LPS-challenged mice

Galactooligosaccharides (GOS) have been identified as beneficial prebiotics for animals and human beings. Most studies have focused on the effect of GOS on the hindgut populated with abundant microbes. However, few research studies have been conducted on the small intestine, and many results are inconsistent due to the purity of GOS, commonly mixed with monosaccharides or lactose. Therefore, pure GOS with definite structures were prepared and used in the present study to evaluate their effects on intestinal barrier function, inflammatory responses and short-chain fatty acids (SCFAs) produced in the colon of mice challenged with lipopolysaccharide (LPS). The results of 1H and 13C nuclear magnetic resonance spectral analyses indicated that the main structures of GOS with a degree of polymerization of 3 (trisaccharide) and 4 (tetrasaccharide) are [β-Gal-(1 → 6)-β-Gal(1 → 4)-β-Glc] and [β-Gal-(1 → 6)-β-Gal-(1 → 6)-β-Gal-(1 → 4)-β-Glc], respectively. The results of an in vivo study in mice showed that intragastric administration of 0.5 g per kg BW GOS attenuated intestinal barrier damage and inflammatory responses induced by LPS in the jejunum and ileum, as indicated by increasing villus height and villus-to-crypt ratio, up-regulated intestinal tight junction (ZO-1, occludin, and claudin-1) gene expression, and down-regulated pro-inflammatory cytokines such as IL-1β, IL-6, IFN-γ, and TNF-α gene expression. Nevertheless, the protective effects of GOS on the intestinal barrier are independent of glucagon-like peptide 2. In addition, 0.5 g per kg BW GOS administration promoted the recovery of colonic acetate, propionate, butyrate, and total SCFA production reduced by LPS challenge. The obtained results provide practical evidence that pure GOS can act as protective agents for intestinal health.

Digestion, fermentation, and pathogen anti-adhesive properties of the hMO-mimic di-fucosyl-β-cyclodextrin

Human milk is widely acknowledged as the best food for infants, and that is not just because of nutritional features. Human milk also contains a plethora of bioactive molecules, including a large set of human milk oligosaccharides (hMOs). Especially fucosylated hMOs have received attention for their anti-adhesive effects on pathogens, preventing attachment to the intestine and infection. Because hMOs are generally challenging to produce in sufficient quantities to study and ultimately apply in (medical) infant formula, novel compounds that are inspired by hMO structures (so-called "mimics") are interesting compounds to produce and evaluate for their biological effects. Here we present our thorough study into the digestion, fermentation and anti-adhesive capacity of the novel compound di-fucosyl-β-cyclodextrin (DFβCD), which was inspired by the molecular structures of hMOs. We establish that DFβCD is not digested by α-amylase and also resistant to fermentation by microbial enzymes from a 9 month-old infant inoculum. In addition, we reveal that DFβCD blocks adhesion of enterotoxigenic E. coli (ETEC) to Caco-2 cells, especially when DFβCD is pre-incubated with ETEC prior to addition to the Caco-2 cells. This suggests that DFβCD functions through a decoy effect. We expect that our results inspire the generation and biological evaluation of other fucosylated hMOs and mimics, to obtain a comprehensive overview of the anti-adhesive power of fucosylated glycans.