Dietary ganglioside reduces proinflammatory signaling in the intestine. J Nutr Metab. 2012;2012:280286. [PMID: 22506104 PMCID: PMC3306953 DOI: 10.1155/2012/280286]

Characterization of GM3 Gangliosides in Human Milk throughout Lactation: Insights from the Analysis with the Use of Reversed-Phase Liquid Chromatography Coupled to Quadrupole Time-Of-Flight Mass Spectrometry

Gangliosides are complex lipids found in human milk that play important structural and biological functions. In this study, we utilized reversed-phase liquid chromatography coupled to quadrupole time-of-flight mass spectrometry to evaluate the molecular distribution of GM3 in human milk samples collected at distinct lactation stages, ranging from colostrum to advanced lactation samples. Throughout lactation, GM3 d40:1 emerged as the most abundant GM3 species, except in colostrum, where GM3 d42:2 prevailed. The relative content of GM3 species containing very long N-fatty acyl (N-FA) substituents with >22 carbon atoms decreased, while the content of GM3 species containing 14:0, 18:0, 18:1, and 20:0 N-FA substituents increased in the later months of lactation. These findings highlight the divergence of GM3 profiles across the lactation period. Moreover, considerable interindividual variance was observed among the analyzed samples. The assessment of the GM3 profiles contributes to our understanding of the dynamic composition of human milk.

Sphingolipids: From structural components to signaling hubs

In late November 2019, Prof. Lina M. Obeid passed away from cancer, a disease she spent her life researching and studying its intricate molecular underpinnings. Along with her husband, Prof. Yusuf A. Hannun, Obeid laid down the foundations of sphingolipid biochemistry and oversaw its remarkable evolution over the years. Lipids are a class of macromolecules that are primarily associated with cellular architecture. In fact, lipids constitute the perimeter of the cell in such a way that without them, there cannot be cells. Hence, much of the early research on lipids identified the function of this class of biological molecules as merely structural. Nevertheless, unlike proteins, carbohydrates, and nucleic acids, lipids are elaborately diverse as they are not made up of monomers in polymeric forms. This diversity in structure is clearly mirrored by functional pleiotropy. In this chapter, we focus on a major subset of lipids, sphingolipids, and explore their historic rise from merely inert structural components of plasma membranes to lively and necessary signaling molecules that transmit various signals and control many cellular processes. We will emphasize the works of Lina Obeid since she was an integral pillar of the sphingolipid research world.

Gene family expansion and functional diversification of chitinase and chitin synthase genes in Atlantic salmon (Salmo salar)

Chitin is one of the most abundant polysaccharides in nature, forming important structures in insects, crustaceans, and fungal cell walls. Vertebrates on the other hand are generally considered "nonchitinous" organisms, despite having highly conserved chitin metabolism-associated genes. Recent work has revealed that the largest group of vertebrates, the teleosts, have the potential to both synthesize and degrade endogenous chitin. Yet, little is known about the genes and proteins responsible for these dynamic processes. Here, we used comparative genomics, transcriptomics, and chromatin accessibility data to characterize the repertoire, evolution, and regulation of genes involved in chitin metabolism in teleosts, with a particular focus on Atlantic salmon. Reconstruction of gene family phylogenies provides evidence for an expansion of teleost and salmonid chitinase and chitin synthase genes after multiple whole-genome duplications. Analyses of multi-tissue gene expression data demonstrated a strong bias of gastrointestinal tract expression for chitin metabolism genes, but with different spatial and temporal tissue specificities. Finally, we integrated transcriptomes from a developmental time series of the gastrointestinal tract with chromatin accessibility data to identify putative transcription factors responsible for regulating chitin metabolism gene expression (CDX1 and CDX2) as well as tissue-specific divergence in the regulation of gene duplicates (FOXJ2). The findings presented here support the hypothesis that chitin metabolism genes in teleosts play a role in developing and maintaining a chitin-based barrier in the teleost gut and provide a basis for further investigations into the molecular basis of this barrier.

Interorgan Metabolism of Ganglioside Is Altered in Type 2 Diabetes

GM3 is implicated in cell signaling, inflammation and insulin resistance. The intestinal mucosa metabolizes ganglioside and provides gangliosides for uptake by peripheral tissues. Gangliosides downregulate acute and chronic inflammatory signals. It is likely that transport of intestinal derived gangliosides to other tissues impact the same signals characteristic of inflammatory change in other chronic conditions such as Type 2 Diabetes (T2DM). The postprandial ceramide composition of GM3 and other gangliosides in plasma and chylomicrons has not been examined in T2DM. The present study assessed if diet or T2DM alters ganglioside components in plasma and chylomicrons secreted from the intestinal mucosa after a meal. GD1, GD3, and GM3 content of chylomicrons and plasma was determined by LC/triple quad MS in non-diabetic (control) and T2DM individuals in the fasting and postprandial state after 2 days of consuming a low or high fat diet in a randomized blinded crossover design. Diet fat level did not alter baseline plasma or chylomicron ganglioside levels. Four hours after the test meal, plasma monounsaturated GD3 was 75% higher, plasma saturated GD3 was 140% higher and plasma polyunsaturated GM3 30% lower in diabetic subjects compared to control subjects. At 4 h, chylomicron GD1 was 50% lower in T2DM compared to controls. The proportion of d34:1 in GD3 was more abundant and d36:1 in GD1 less abundant in T2DM compared to control subjects at 4 h. The present study indicates that T2DM alters ceramide composition of ganglioside available for uptake by peripheral tissues.

Safety and tolerance assessment of milk fat globule membrane-enriched infant formulas in healthy term Chinese infants: a randomised multicenter controlled trial

Background

Milk fat globule membrane (MFGM), natural to breast milk, is essential for neonatal development, but lacking from standard infant formulas.

Objectives

To evaluate the safety and tolerability of MFGM supplementation in formula for infants 0 to 12 months.

Methods

In a prospective, multicentre, double-blind, randomized trial, healthy term infants were randomized to a standard formula (SF, n = 104) or an MFGM-enriched formula (MF, n = 108) for 6 months and a corresponding follow-on formula until 12 months. Exclusively breast-fed infants (n = 206) were recruited as the reference group (BFR). Tolerance and safety events were recorded continuously. Anthropometric measurements were assessed at enrolment, 42 days and 4, 6, 8 and 12 months.

Results

Infants (n = 375) completed the study with average dropout of < 20%. Stool frequency, color, and consistency between SF and MF were not significantly different throughout, except the incidence of loose stools in MF at 6 months being lower than for SF (odds ratio 0.216, P < 0.05) and the frequency of green-colored stools at 12 months being higher in MF (CI 95%, odds ratio 8.92, P < 0.05). The BFR had a higher frequency of golden stools and lower rate of green stools (4–6 months) than the two formula-fed groups (P < 0.05). SF displayed more diarrhoea (4.8%) than MF (1%) and BFR (1%) at the 8-month visit (P < 0.05). BFR (0–1%) had significantly less (P < 0.05) lower respiratory infections than MF (4.6–6.5%) and SF (2.9–5.8%) at 6- and 8-months, respectively. Formula intake, frequency of spit-up/vomiting or poor sleep were similar between SF and MF. Growth rate (g/day) was similar at 4, 6, 8 and 12 months between the 3 groups, but growth rate for BFR was significantly higher than for SF and MF at 42 days (95% CI, P = 0.001).

Conclusions

MFGM-enriched formula was safe and well-tolerated in healthy term infants between 0 and 12 months, and total incidences of adverse events were similar to that for the SF group. A few differences in formula tolerance were observed, however these differences were not in any way related to poor growth.

Comparative Lipidomics Analysis of Human and Ruminant Milk Reveals Variation in Composition and Structural Characteristics

In the present study, the different lipidomes between human milk and ruminant milk were compared. The 471, 376, 467, and 87 differential lipids were identified in human versus cow, goat, sheep, and camel groups, respectively. According to multivariate statistical analysis, lipids in human and camel milk were closer but differed from other milk. The distributions of long-chain and polyunsaturated fatty acids of triglycerides (TGs), the proportions of functional TGs (OPO, OPL, and PPO), and many kinds of phospholipids (PLs) (PS, PI, GD, GM3, and Cer) in human milk were similar to those in camel milk. The similar structure of TGs and proportion of PLs in human milk to camel milk might contribute to their similar digestion and bioactivity properties. Camel milk could be considered as a new resource of lipid base for infant formula. Minor PLs should also be considered for designing formula. Our results provide a new sight for humanized lipids in infant formula.

Roles of Milk Fat Globule Membrane on Fat Digestion and Infant Nutrition

Milk fats are present as globules emulsified in the aqueous phase of milk and stabilized by a delicate membrane architecture called milk fat globule membrane (MFGM). The unique structure and composition of the MFGM play an important role in fat digestion and the metabolic programming of neonates. The objective of this review is to compare the structure, composition, and physicochemical characteristics of fat globules in human milk, bovine milk, and infant formula. It provides an overview of the fat digestion process and enzymes in healthy infants, and describes the possible roles of the MFGM in association with factors affecting fat digestion. Lastly, the health benefits of the MFGM on infant nutrition and future perspectives are discussed with a focus on brain development, metabolic response, and gut health.

Ganglioside Alters Phospholipase Trafficking, Inhibits NF-κB Assembly, and Protects Tight Junction Integrity

Background and Aims: Dietary gangliosides are present in human milk and consumed in low amounts from organ meats. Clinical and animal studies indicate that dietary gangliosides attenuate signaling processes that are a hallmark of inflammatory bowel disease (IBD). Gangliosides decrease pro-inflammatory markers, improve intestinal permeability, and reduce symptoms characteristic in patients with IBD. The objective of this study was to examine mechanisms by which dietary gangliosides exert beneficial effects on intestinal health. Methods: Studies were conducted in vitro using CaCo-2 intestinal epithelial cells. Gangliosides were extracted from milk powder and incubated with differentiated CaCo-2 cells after exposure to pro-inflammatory stimuli. Gut barrier integrity was assessed by electron microscopy, epithelial barrier function was examined by measuring transepithelial electric resistance, and content of HBD-2, IL-23, NF-κB, and sPLA₂ was assessed by ELISA. Results: Ganglioside attenuated the decrease in integrity of tight junctions induced by pro-inflammatory stimuli and improved epithelial barrier function (P < 0.05). Ganglioside decreased the basolateral secretion of sPLA₂ (P ≤ 0.05), lowered HBD-2 and IL-23 levels (P ≤ 0.05), and inhibited NF-κB activation (P ≤ 0.05). Conclusions: In summary, the present study indicates that ganglioside GD3 improves intestinal integrity by altering sPLA₂ trafficking, and the production of pro-inflammatory mediators is mitigated by decreasing assembly of the NF-κB complex. Dietary gangliosides may have promising potential beneficial effects in IBD as decreased inflammatory signaling, improved intestinal integrity, and maintenance of epithelial barrier function have been demonstrated in vitro.

CircHECTD1 up-regulates mucin 1 expression to accelerate hepatocellular carcinoma development by targeting microRNA-485-5p via a competing endogenous RNA mechanism

Background:

Non-coding RNAs have attracted considerable attention for their vital role in cancer. The purpose of this study was to determine the effects of non-coding RNAs on hepatocellular carcinoma (HCC) and reveal their regulatory mechanism in the pathophysiological process.

Methods:

We measured the expression of mucin 1 (MUC1) and miR-485-5p in tissues from 15 HCC patients and in liver cancer cell lines by quantitative real-time polymerase chain reaction and Western blot, screened for aberrantly expressed microRNAs (miRNAs) by miRNA microarrays. Bioinformatics tools were used to find the miRNA and circular RNA that regulated MUC1, which were validated by RNA immunoprecipitation assay and luciferase reporter assay. Cell counting kit-8, Transwell assays, and flow cytometry were used to conduct functional experiments. Proteins were examined by western blot and immunohistochemical staining assays. Significant differences between groups were estimated using the one-way analysis of variance. A P < 0.05 was considered statistically significant.

Results:

MUC1 was overexpressed in HCC tissues compared with that in paratumor tissues (normal vs. tumor, 1.007 ± 0.215 vs. 75.213 ± 18.403, t = 18.401, P < 0.001) while miR-485-5p was down-regulated (normal vs. tumor, 4.894 ± 0.684 vs. 1.586 ± 0.398, t = 16.191, P < 0.001). Inhibition of miR-485-5p promoted cell proliferation (73.33% ± 5.13% vs. 41.33% ± 3.51%, t = 8.913, P < 0.001), migration (102 ± 8 cells vs. 46 ± 8 cells, t = 8.681, P < 0.001), invasion (59 ± 7 cells vs. 28 ± 2 cells, t = 8.034, P < 0.01), and suppressed apoptosis (22.64% ± 6.97% vs. 36.33% ± 3.96%, t = 2.958, P < 0.05) of HepG2 cells with which MUC1 is knocked down. Mechanically, miR-485-5p binds to MUC1, while circHECTD1 binds to miR-485-5p, resulting in the indirect up-regulation of the MUC1 level.

Conclusions:

Our findings reveal that circHECTD1 facilitates HCC progression by sponging miR-485-5p to up-regulate MUC1.

Lipid Composition, Digestion, and Absorption Differences among Neonatal Feeding Strategies: Potential Implications for Intestinal Inflammation in Preterm Infants

Necrotizing enterocolitis (NEC) is a significant cause of morbidity and mortality in the neonatal population. Formula feeding is among the many risk factors for developing the condition, a practice often required in the cohort most often afflicted with NEC, preterm infants. While the virtues of many bioactive components of breast milk have been extolled, the ability to digest and assimilate the nutritional components of breast milk is often overlooked. The structure of formula differs from that of breast milk, both in lipid composition and chemical configuration. In addition, formula lacks a critical digestive enzyme produced by the mammary gland, bile salt-stimulated lipase (BSSL). The gastrointestinal system of premature infants is often incapable of secreting sufficient pancreatic enzymes for fat digestion, and pasteurization of donor milk (DM) has been shown to inactivate BSSL, among other important compounds. Incompletely digested lipids may oxidize and accumulate in the distal gut. These lipid fragments are thought to induce intestinal inflammation in the neonate, potentially hastening the development of diseases such as NEC. In this review, differences in breast milk, pasteurized DM, and formula lipids are highlighted, with a focus on the ability of those lipids to be digested and subsequently absorbed by neonates, especially those born prematurely and at risk for NEC.

Investigating host-microbiome interactions by droplet based microfluidics

BACKGROUND

Despite the importance of the mucosal interface between microbiota and the host in gut homeostasis, little is known about the mechanisms of bacterial gut colonization, involving foraging for glycans produced by epithelial cells. The slow pace of progress toward understanding the underlying molecular mechanisms is largely due to the lack of efficient discovery tools, especially those targeting the uncultured fraction of the microbiota.

RESULTS

Here, we introduce an ultra-high-throughput metagenomic approach based on droplet microfluidics, to screen fosmid libraries. Thousands of bacterial genomes can be covered in 1 h of work, with less than ten micrograms of substrate. Applied to the screening of the mucosal microbiota for β-N-acetylgalactosaminidase activity, this approach allowed the identification of pathways involved in the degradation of human gangliosides and milk oligosaccharides, the structural homologs of intestinal mucin glycans. These pathways, whose prevalence is associated with inflammatory bowel diseases, could be the result of horizontal gene transfers with Bacteroides species. Such pathways represent novel targets to study the microbiota-host interactions in the context of inflammatory bowel diseases, in which the integrity of the mucosal barrier is impaired.

CONCLUSION

By compartmentalizing experiments inside microfluidic droplets, this method speeds up and miniaturizes by several orders of magnitude the screening process compared to conventional approaches, to capture entire metabolic pathways from metagenomic libraries. The method is compatible with all types of (meta)genomic libraries, and employs a commercially available flow cytometer instead of a custom-made sorting system to detect intracellular or extracellular enzyme activities. This versatile and generic workflow will accelerate experimental exploration campaigns in functional metagenomics and holobiomics studies, to further decipher host-microbiota relationships. Video Abstract.

Breast Milk Lipids and Fatty Acids in Regulating Neonatal Intestinal Development and Protecting against Intestinal Injury

Human breast milk is the optimal source of nutrition for infant growth and development. Breast milk fats and their downstream derivatives of fatty acids and fatty acid-derived terminal mediators not only provide an energy source but also are important regulators of development, immune function, and metabolism. The composition of the lipids and fatty acids determines the nutritional and physicochemical properties of human milk fat. Essential fatty acids, including long-chain polyunsaturated fatty acids (LCPUFAs) and specialized pro-resolving mediators, are critical for growth, organogenesis, and regulation of inflammation. Combined data including in vitro, in vivo, and human cohort studies support the beneficial effects of human breast milk in intestinal development and in reducing the risk of intestinal injury. Human milk has been shown to reduce the occurrence of necrotizing enterocolitis (NEC), a common gastrointestinal disease in preterm infants. Preterm infants fed human breast milk are less likely to develop NEC compared to preterm infants receiving infant formula. Intestinal development and its physiological functions are highly adaptive to changes in nutritional status influencing the susceptibility towards intestinal injury in response to pathological challenges. In this review, we focus on lipids and fatty acids present in breast milk and their impact on neonatal gut development and the risk of disease.

Dietary Polar Lipids and Cognitive Development: A Narrative Review

Polar lipids are amphiphilic lipids with a hydrophilic head and a hydrophobic tail. Polar lipids mainly include phospholipids and sphingolipids. They are structural components of neural tissues, with the peak rate of accretion overlapping with neurodevelopmental milestones. The critical role of polar lipids in cognitive development is thought to be mediated through the regulation of signal transduction, myelination, and synaptic plasticity. Animal products (egg, meat, and dairy) are the major dietary sources of polar lipids for children and adults, whereas human milk and infant formula provide polar lipids to infants. Due to the differences observed in both concentration and proportion of polar lipids in human milk, the estimated daily intake in infants encompasses a wide range. In addition, health authorities define neither intake recommendations nor guidelines for polar lipid intake. However, adequate intake is defined for 2 nutrients that are elements of these polar lipids, namely choline and DHA. To date, limited studies exist on the brain bioavailability of dietary polar lipids via either placental transfer or the blood-brain barrier. Nevertheless, due to their role in pre- and postnatal development of the brain, there is a growing interest for the use of gangliosides, which are sphingolipids, as a dietary supplement for pregnant/lactating mothers or infants. In line with this, supplementing gangliosides and phospholipids in wild-type animals and healthy infants does suggest some positive effects on cognitive performance. Whether there is indeed added benefit of supplementing polar lipids in pregnant/lactating mothers or infants requires more clinical research. In this article, we report findings of a review of the state-of-the-art evidence on polar lipid supplementation and cognitive development. Dietary sources, recommended intake, and brain bioavailability of polar lipids are also discussed.

Analysis of a lectin microarray identifies altered sialylation of mouse serum glycoproteins induced by whole-body radiation exposure

Microarrays containing 45 different lectins were analyzed to identify global changes in the glycosylation of serum glycoproteins from mice exposed to whole-body γ-radiation. The results showed that radiation exposure increased and decreased the relative amounts of α-2,3- and α-2,6-sialic acids, respectively. The expression of α-2,3- and α-2,6-sialyltransferase genes in the liver was analyzed to determine whether changes in their expression were responsible for the sialic acid changes. The increase in α-2,3-sialic acid correlated with St3gal5 upregulation after radiation exposure; however, a decrease in St6gal1 expression was not observed. Analysis of a PCR array of genes expressed in irradiated mouse livers revealed that irradiation did not alter the expression of most of the included genes. These results suggest that glycomic screening of serum glycoproteins using lectin microarrays can be a powerful tool for identifying radiation-induced changes in the post-translational addition of sugar moieties to proteins. In addition, the results indicate that altered sialylation of glycoproteins may be an initial response to acute radiation exposure.

Chemistry of Human Breast Milk-A Comprehensive Review of the Composition and Role of Milk Metabolites in Child Development

Early nutrition has an enormous influence on a child's physiological function, immune system maturation, and cognitive development. Human breast milk (HBM) is recognized as the gold standard for human infant nutrition. According to a WHO report, breastfeeding is considered as an unequaled way of providing ideal food to the infant, which is required for his healthy growth and development. HBM contains various macronutrients (carbohydrates, proteins, lipids, and vitamins) as well as numerous bioactive compounds and interactive elements (growth factors, hormones, cytokines, chemokines, and antimicrobial compounds. The aim of this review is to summarize and discuss the current knowledge about metabolites, which are the least understood components of HBM, and their potential role in infant development. We focus on small metabolites (<1500 Da) and characterize the chemical structure and biological function of polar metabolites such as human milk oligosaccharides, nonprotein molecules containing nitrogen (creatine, amino acids, nucleotides, polyamines), and nonpolar lipids. We believe that this manuscript will provide a comprehensive insight into a HBM metabolite composition, chemical structure, and their role in a child's early life nutrition.

Application of industrial treatments to donor human milk: influence of pasteurization treatments, storage temperature, and time on human milk gangliosides

Donor milk is the best option when mother’s own milk is unavailable. Heat treatments are applied to ensure donor milk safety. The effects of heat treatments on milk gangliosides—bioactive compounds with beneficial antibacterial, anti-inflammatory, and prebiotic roles—have not been studied. The most abundant gangliosides in non-homogenized human milk were characterized and quantified by liquid chromatography–mass spectrometry (LC–MS)/MS before and after pasteurization treatments mimicking industrial conditions (63 °C/30 min, 72 °C/15 s, 127 °C/5 s, and 140 °C/6 s). Ganglioside stability over a 3-month period was assessed following the storage at 4 and 23 °C. Independent of the heat treatment applied, gangliosides were stable after 3 months of storage at 4 or 23 °C, with only minor variations in individual ganglioside structures. These findings will help to define the ideal processing and storage conditions for donor milk to maximize the preservation of the structure of bioactive compounds to enhance the health of fragile newborns. Moreover, these results highlight the need for, and provide a basis for, a standardized language enabling biological and food companies, regulatory agencies, and other food stakeholders to both annotate and compute the ways in which production, processing, and storage conditions alter or maintain the nutritive, bioactive, and organoleptic properties of ingredients and foods, as well as the qualitative effects these foods and ingredients may have on conferring phenotype in the consuming organism.

Donor human milk, the best alternative to mother’s own milk, usually needs to be pasteurized before use out of safety concerns. Daniela Barile at University of California Davis, USA, and colleagues studied the effects of heat treatment and storage temperature and time on milk gangliosides, a class of sugar-derived compounds important for neural and brain development of newborns, among other bioactivities. They found that, while there were minor structural changes during mimicked industrial pasteurization processes, gangliosides remain stable for at least three months either in the refrigerator or at room temperature. These results may help standardize the processing protocols and storage conditions for donor milk, and the methods can be extended to other bioactive components.

Modification of Ganglioside Content of Human Gastric Epithelial Cell Membrane Decreases Helicobacter pylori Adhesion

BACKGROUND

In polarized cells, ganglioside location determines ganglioside function. Diet alters ganglioside content and composition in cell membranes. Ganglioside acts as a receptor for Helicobacter pylori. H pylori infects the stomach epithelium and may cause peptic ulcer disease and gastric cancer. The present study used purified gangliosides to modify the ganglioside composition of human gastric epithelial cells in vitro to reduce H pylori adhesion.

METHODS

A human gastric epithelial cell line (NCI-N87) was cultured with a ganglioside mix or with pure ganglioside (GM3 or GD3) at different concentrations (0-30 μg/mL) and ganglioside membrane content of gastric cells was determined after 48 hours. LC/triple quadrupole MS was used to analyse ganglioside concentration. H pylori was inoculated into the culture media of gastric cells previously treated with gangliosides GM3 or GD3 or a combination of GM3 and GD3.

RESULTS

GD3 and GM3 content increased in the plasma membrane in a dose-dependent manner. Gastric cells treated with GD3 showed more GM3 content than GD3 (P < 0.01). Ganglioside content was modified in the apical membrane, but GM3 and GD3 were also found in the basolateral membrane after treatments. Gastric cells treated with GM3, GD3 or the combination of GM3:GD3 decreased H pylori adhesion to gastric cells at all ganglioside concentrations tested by 80% compared with untreated gastric cells (P < 0.05).

CONCLUSIONS

These observations suggest that GD3 and GM3 present in the stomach lumen may be taken up into the apical gastric membrane and decrease H pylori adhesion to the epithelium.

The Role of Sphingolipids on Innate Immunity to Intestinal Salmonella Infection

Salmonella spp. remains a major public health problem for the whole world. To reduce the use of antimicrobial agents and drug-resistant Salmonella, a better strategy is to explore alternative therapy rather than to discover another antibiotic. Sphingolipid- and cholesterol-enriched lipid microdomains attract signaling proteins and orchestrate them toward cell signaling and membrane trafficking pathways. Recent studies have highlighted the crucial role of sphingolipids in the innate immunity against infecting pathogens. It is therefore mandatory to exploit the role of the membrane sphingolipids in the innate immunity of intestinal epithelia infected by this pathogen. In the present review, we focus on the role of sphingolipids in the innate immunity of intestinal epithelia against Salmonella infection, including adhesion, autophagy, bactericidal effect, barrier function, membrane trafficking, cytokine and antimicrobial peptide expression. The intervention of sphingolipid-enhanced foods to make our life healthy or pharmacological agents regulating sphingolipids is provided at the end.

Cardiolipins Act as a Selective Barrier to Toll-Like Receptor 4 Activation in the Intestine

Intestinal homeostasis mechanisms must protect the host intestinal tissue from endogenous lipopolysaccharides (LPSs) produced by the intestinal microbiota. In this report, we demonstrate that murine intestinal fecal lipids effectively block Toll-like receptor 4 (TLR4) responses to naturally occurring Bacteroidetes sp. LPS. Cardiolipin (CL) represents a significant proportion of the total intestinal and fecal lipids and, furthermore, potently antagonizes TLR4 activation by reducing LPS binding at the lipopolysaccharide binding protein (LBP), CD14, and MD-2 steps of the TLR4 signaling pathway. It is further demonstrated that intestinal lipids and CL are less effective at neutralizing more potent Enterobacteriaceae-type LPS, which is enriched in feces obtained from mice with dextran sodium sulfate (DSS)-treated inflammatory bowel disease. The selective inhibition of naturally occurring LPS structures by intestinal lipids may represent a novel homeostasis mechanism that blocks LPS activation in response to symbiotic but not dysbiotic microbial communities.

IMPORTANCE

The guts of animals harbor a variety of Gram-negative bacteria associated with both states of intestinal health and states of disease. Environmental factors, such as dietary habits, can drive the microbial composition of the host animal's intestinal bacterial community toward a more pathogenic state. Both beneficial and harmful Gram-negative bacteria are capable of eliciting potentially damaging inflammatory responses from the host intestinal tissues via a lipopolysaccharide (LPS)-dependent pathway. Physical mucosal barriers and antibodies produced by the intestinal immune system protect against the undesired inflammatory effects of LPS, although it is unknown why some bacteria are more effective at overcoming the protective barriers than others. This report describes the discovery of a lipid-type protective barrier in the intestine that reduces the deleterious effects of LPSs from beneficial bacteria but is less effective in dampening the inflammatory effects of LPSs from harmful bacteria, providing a novel mechanistic insight into inflammatory intestinal disorders.

Role of Sphingolipids in Infant Gut Health and Immunity

Sphingomyelin (SM), glycosphingolipids, and gangliosides are important polar lipids in the milk fat globule membrane but are not found in standard milk replacement formulas. Because digestion and absorption of SM and glycosphingolipids generate the bioactive metabolites ceramide, sphingosine, and sphingosine-1-phosphate (S1P), and because intact gangliosides may have beneficial effects in the gut, this may be important for gut integrity and immune maturation in the neonate. The brush border enzymes that hydrolyze milk SM, alkaline sphingomyelinase (nucleotide phosphodiesterase pyrophosphatase 7), and neutral ceramidase are expressed at birth in both term and preterm infants. Released sphingosine is absorbed, phosphorylated to S1P, and converted to palmitic acid via S1P-lyase in the gut mucosa. Hypothetically, S1P also may be released from absorptive cells and exert important paracrine actions favoring epithelial integrity and renewal, as well as immune function, including secretory IgA production and migration of T lymphocyte subpopulations. Gluco-, galacto-, and lactosylceramide are hydrolyzed to ceramide by lactase-phlorizin hydrolase, which also hydrolyzes lactose. Gangliosides may adhere to the brush border and is internalized, modified, and possibly transported into blood, and may exert protective functions by their interactions with bacteria, bacterial toxins, and the brush border.

Fostering Inflammatory Bowel Disease: Sphingolipid Strategies to Join Forces

Complex sphingolipids are essential structural components of intestinal membranes, providing protection and integrity to the intestinal mucosa and regulating intestinal absorption processes. The role of sphingolipid signaling has been established in numerous cellular events, including intestinal cell survival, growth, differentiation, and apoptosis. A significant body of knowledge demonstrates that intestinal sphingolipids play a crucial role, as such and through their signaling pathways, in immunity and inflammatory disorders. In this review, we report on and discuss the current knowledge on the metabolism, signaling, and functional implications of sphingolipids in inflammatory bowel disease (IBD), focusing on the different aspects of sphingolipid actions on inflammatory responses and on the potential of sphingolipid-targeted molecules as anti-IBD therapeutic agents.

Increased catabolism and decreased unsaturation of ganglioside in patients with inflammatory bowel disease

AIM: To investigate whether accelerated catabolism of ganglioside and decreased ganglioside content contribute to the etiology of pro-inflammatory intestinal disease.

METHODS: Intestinal mucosa from terminal ileum or colon was obtained from patients with ulcerative colitis or inflammatory Crohn’s disease (n = 11) undergoing bowel resection and compared to control samples of normal intestine from patients with benign colon polyps (n = 6) and colorectal cancer (n = 12) in this observational case-control study. Gangliosides and phospholipids of intestinal mucosa were characterized by class and ceramide or fatty acid composition using liquid chromatography triple-quad mass spectrometry. Content and composition of ganglioside classes GM1, GM3, GD3, GD1a, GT1 and GT3 were compared among subject groups. Content and composition of phospholipid classes phosphatidylcholine (PC) and phosphatidylethanolamine were compared among subject groups. Unsaturation index of individual ganglioside and phospholipid classes was computed and compared among subject groups. Ganglioside catabolism enzymes beta-hexosaminidase A (HEXA) and sialidase-3 (NEU3) were measured in intestinal mucosa using western blot and compared among subject groups.

RESULTS: Relative GM3 ganglioside content was 2-fold higher (P < 0.05) in intestine from patients with inflammatory bowel disease (IBD) compared to control intestine. The quantity of GM3 and ratio of GM3/GD3 was also higher in IBD intestine than control tissue (P < 0.05). Control intestine exhibited 3-fold higher (P < 0.01) relative GD1a ganglioside content than IBD intestine. GD3 and GD1a species of ganglioside containing three unsaturated bonds were present in control intestine, but were not detected in IBD intestine. The relative content of PC containing more than two unsaturated bonds was 30% lower in IBD intestine than control intestine (P < 0.05). The relative content of HEXA in IBD intestine was increased 1.7-fold (P < 0.05) and NEU3 was increased 8.3-fold (P < 0.01) compared to normal intestine. Intestinal mucosa in IBD is characterized by increased GM3 content, decreased GD1a, and a reduction in polyunsaturated fatty acid constituents in GD3, GD1a and PC.

CONCLUSION: This study suggests a new paradigm by proposing that IBD occurs as a consequence of increased metabolism of specific gangliosides.

Lipid Quality in Infant Nutrition: Current Knowledge and Future Opportunities

Dietary lipids are key for infants to not only meet their high energy needs but also fulfill numerous metabolic and physiological functions critical to their growth, development, and health. The lipid composition of breast milk varies during lactation and according to the mother's diet, whereas the lipid composition of infant formulae varies according to the blend of different fat sources. This report compares the compositions of lipids in breast milk and infant formulae, and highlights the roles of dietary lipids in term and preterm infants and their potential biological and health effects. The major differences between breast milk and formulae lie in a variety of saturated fatty acids (such as palmitic acid, including its structural position) and unsaturated fatty acids (including arachidonic acid and docosahexaenoic acid), cholesterol, and complex lipids. The functional outcomes of these differences during infancy and for later child and adult life are still largely unknown, and some of them are discussed, but there is consensus that opportunities exist for improvements in the qualitative lipid supply to infants through the mother's diet or infant formulae. Furthermore, research is required in several areas, including the needs of term and preterm infants for long-chain polyunsaturated fatty acids, the sites of action and clinical effects of lipid mediators on immunity and inflammation, the role of lipids on metabolic, neurological, and immunological outcomes, and the mechanisms by which lipids act on short- and long-term health.

Ganglioside GD1a suppresses LPS-induced pro-inflammatory cytokines in RAW264.7 macrophages by reducing MAPKs and NF-κB signaling pathways through TLR4

Gangliosides, sialic acid-containing glycosphingolipids, have been considered to be involved in the development, differentiation, and function of nervous systems in vertebrates. However, the mechanisms for anti-inflammation caused by gangliosides are not clear. In this paper, we investigated the anti-inflammation effects of ganglioside GD1a by using RAW264.7 macrophages. Our data demonstrated that treatment of macrophages with lipopolysaccharide significantly increased the production of NO and pro-inflammatory cytokines. GD1a suppressed the induction of iNOS and COX-2 mRNA and protein expression and secretory pro-inflammatory cytokines in culture medium, such as TNFα, IL-1α and IL-1β. In addition, LPS-induced phosphorylation of mitogen-activating protein kinases and IκBα degradation followed by translocation of the NF-κB from the cytoplasm to the nucleus were attenuated after GD1a treatment. Furthermore, GD1a probably inhibited LPS binding to macrophages and LPS-induced accumulation between TLR4 and MyD88. Taken together, the results demonstrated that ganglioside GD1a inhibited LPS-induced inflammation in RAW 264.7 macrophages by suppressing phosphorylation of mitogen-activating protein kinases and activation of NF-κB through repressing the Toll-like receptor 4 signaling pathway.

Dietary GD3 ganglioside reduces the incidence and severity of necrotizing enterocolitis by sustaining regulatory immune responses

OBJECTIVES

Gangliosides are glycosphingolipids, rich in colostrum and in membrane microdomains, which promote enterocyte growth and differentiation, and modulate TH1/TH2 responses. In an in vitro intestinal explant model of necrotizing enterocolitis (NEC), gangliosides have been shown to ameliorate intestinal injury; however, possible immunomodulatory mechanisms associated with this observation, as well as potential in vivo protective effects of gangliosides, remain unknown. The present study evaluates the effects of dietary GD3, the predominant ganglioside in neonatal rat intestine, both on the clinicopathologic expression of disease and on ileal Foxp3+ T regulatory cell immune responses in an experimental NEC model.

METHODS

Newborn rat pups were fed gavage formula (NEC) or formula supplemented with 15 μg/mL GD3 (GD3-NEC). Dam-fed (DF) littermates served as controls. NEC was induced by asphyxia and cold stress. At 96 hours, ileal gross and histologic changes were evaluated, and ileal cytokine profiles, Foxp3 expression, and Foxp3+ cell numbers were determined.

RESULTS

GD3 decreased the incidence and gross and histopathologic severity of NEC. Ileal Foxp3 expression and Foxp3+ cell numbers were significantly decreased in the NEC group compared with DF. GD3 increased ileal Foxp3 expression and Foxp3+ cell numbers, in association with upregulation of anti-inflammatory cytokine interleukin (IL)-10 and chemokines, tissue inhibitor of metalloproteinases 1, IL-1 receptor antagonist (IL-1ra), and suppressed proinflammatory mediators.

CONCLUSIONS

These data suggest that dietary GD3 protects newborn rats from NEC, in part, by augmenting mucosal Foxp3+ T regulatory immune responses.

Coupling Mass Spectrometry-Based "Omic" Sciences with Bioguided Processing to Unravel Milk's Hidden Bioactivities

Many of milk's functional molecules could not be discovered until the right concordance of novel separation and analytical technologies were developed and applied. Many health-promoting components still await discovery due to technical challenges in their identification, isolation and testing. As new analytical technologies are assembled, new functional milk molecules will be discovered. Bovine milk is a source of a wide array of known bioactive compounds from a variety of molecular classes, including free glycans, lipids, glycolipids, peptides, proteins, glycoproteins, stem cells and microRNA. Because milk is such a complex mixture, when analyzed without fractionation or purification, many components mask the analytical signal of others, so some components cannot be detected. Modern analytics allow for the discovery and characterization of hundreds of novel milk compounds with high-resolution and high-accuracy. Liquid chromatography paired with electrospray ionization allows the separation of peptides, glycans and glycolipids for improved mass spectrometric detection. Target proteins and glycoproteins can now be purified from intact milk or other dairy streams by chromatography in order to better characterize these proteins for new bioactivities. The combination of advanced analytics with the new engineering capabilities will allow for high molecular resolution and separation techniques that can be scaled-up to semi-industrial and industrial scale for translation of lab-based discoveries. Bioguided analysis and design of dairy processing side streams will result in the transformation of waste into isolated functional ingredients to add value to dietary products.