Effect of simulated gastrointestinal digestion on sialic acid and gangliosides present in human milk and infant formulas

Novel hypothesis for infant methemoglobinemia: Survival and metabolism of nitrite-producers from vegetables under gastrointestinal stress and intestinal adhesion

Infants have digestive environments that are more favorable for microbial proliferation and subsequent endogenous nitrite production than those of adults, but direct evidence of this has been lacking. In this study, we propose a novel epidemiology of infant methemoglobinemia by demonstrating the risk posed by nitrite-producers in the gastrointestinal tract. Nitrite-producers from vegetables (n = 323) were exposed to stress factors of the gastrointestinal environment (gastric pH, intestinal bile salts, anaerobic atmosphere) reflecting 4 different postnatal age periods (Neonate, ≤1 month; Infant A, 1-3 months; Infant B, 3-6 months; Infant C, 6-12 months). "High-risk" strains with a nitrate-to-nitrite conversion rate of ≥1.3 %, the minimum rate corresponding to nitrite overproduction, under the Neonate stress condition were analyzed for intestinal adhesion. Among all the phyla, Pseudomonadota achieved the highest survival (P < 0.05; survival rate of 51.3-71.8 %). Possible cross-protection against bile resistance due to acid shock was observed for all the phyla. All the high-risk strains exhibited moderate autoaggregation (14.0-36.4 %), whereas only a few exhibited satisfactory surface hydrophobicity (>40 %). The Pantoea agglomerans strain strongly adhered to Caco-2 cells (7.4 ± 1.1 %). This study showed the ability of the Pantoea, Enterobacter, and Klebsiella strains to survive under gastrointestinal stress for ≤12 months, to excessively produce nitrite under neonatal stress conditions, and to settle in the human intestine. To our knowledge, this is the first study to reveal the role of the natural flora of vegetables in the epidemiology of infant methemoglobinemia through a multilateral approach.

Efficient in vitro digestion of lipids and proteins in bovine milk fat globule membrane ingredient (MFGMi) and whey-casein infant formula with added MFGMi

The relative immaturity of the infant digestive system has the potential to affect the bioavailability of dietary lipids, proteins, and their digested products. We performed a lipidomic analysis of a commercial bovine milk fat globule membrane ingredient (MFGMi) and determined the profile of lipids and proteins in the bioaccessible fraction after in vitro digestion of both the ingredient and whey-casein-based infant formula without and with MFGMi. Test materials were digested using a static 2-phase in vitro model, with conditions simulating those in the infant gut. The extent of digestion and the bioaccessibility of various classes of neutral and polar lipids were monitored by measuring a wide targeted lipid profile using direct infusion-mass spectrometry. Digestion of abundant proteins in the ingredient and whey-casein infant formula containing the ingredient was determined by denaturing PAGE with imaging of Coomassie Brilliant Blue stained bands. Cholesterol esters, diacylglycerides, triacylglycerides, phosphatidylcholines, and phosphatidylethanolamines in MFGMi were hydrolyzed readily during in vitro digestion, which resulted in marked increases in the amounts of free fatty acids and lyso-phospholipids in the bioaccessible fraction. In contrast, sphingomyelins, ceramides, and gangliosides were largely resistant to simulated digestion. Proteins in MFGMi and the infant formulas also were hydrolyzed efficiently. The results suggest that neutral lipids, cholesterol esters, phospholipids, and proteins in MFGMi are digested efficiently during conditions that simulate the prandial lumen of the stomach and small intestine of infants. Also, supplementation of whey-casein-based infant formula with MFGMi did not appear to alter the profiles of lipids and proteins in the bioaccessible fraction after digestion.

Stable isotope ratio analysis of carbon to distinguish sialic acid from freshly stewed bird's nest products

Freshly stewed bird's nest products are easily adulterated with exogenous synthetic sialic acid to enhance the grade of the products and sell at high prices. This paper identifies the carbon stable isotope characteristics of sialic acid from natural and commercially synthetic sources using stable isotope ratio mass spectrometry (IRMS). Specifically, an off-line pretreatment technique combined with on-line LC-IRMS was developed to accurately determine δ¹³C values of sialic acid in a freshly stewed bird's nest. This method has no obvious isotope fractionation and good reproducibility. EA-IRMS was used to determine the δ¹³C values of commercial sialic acid. The results showed that the δ¹³C values of sialic acid from natural and synthetic sources were -29.90% ± 0.42% and -16.26% ± 3.91%, respectively, with distinct carbon stable isotope distribution characteristics. By defining a δ¹³C threshold value of -28.54% for natural SA, additional commercial SA from a minimum of 10% can be identified. Therefore, δ¹³C was proposed as a suitable tool for verifying the authenticity of fresh stewed bird's nests on the market.

Milk polar lipids composition and functionality: a systematic review

Polar lipids including glycerophospholipids and sphingophospholipids are important nutrients and milk is a major source, particularly for infants. This systematic review describes the human and bovine milk polar lipid composition, structural organization, sources for formulation, and physiological functionality. A total of 2840 records were retrieved through Scopus, 378 were included. Bovine milk is a good source of polar lipids, where yield and composition are highly dependent on the choice of dairy streams and processing. In milk, polar lipids are organized in the milk fat globule membrane as a tri-layer encapsulating triglyceride. The overall polar lipid concentration in human milk is dependent on many factors including lactational stage and maternal diet. Here, reasonable ranges were determined where possible. Similar for bovine milk, where differences in milk lipid concentration proved the largest factor determining variation. The role of milk polar lipids in human health has been demonstrated in several areas and critical review indicated that brain, immune and effects on lipid metabolism are best substantiated areas. Moreover, insights related to the milk fat globule membrane structure-function relation as well as superior activity of milk derived polar lipid compared to plant-derived sources are emerging areas of interest regarding future research and food innovations.

Bioavailability of Peptides Derived from the In Vitro Digestion of Human Milk Assessed by Caco-2 Cell Monolayers

Human milk-protein-derived peptides exhibit an array of bioactivities. Certain bioactivities cannot be exerted unless the peptides are absorbed across the gastrointestinal lumen into the bloodstream. The purpose of study was to determine which peptides derived from in vitro digestion of human milk could cross human intestinal Caco-2 cell monolayers. Our results showed that the numbers of peptides absorbed by the Caco-2 cell monolayer were different at different concentrations (44 peptides out of 169 peptides detected at 10 μg/mL, 124 peptides out of 204 peptides detected at 100 μg/mL, and 175 peptides out of 236 peptides detected at 1000 μg/mL). Four peptides (NLHLPLP (β-casein [138-144]), PLAPVHNPI (β-casein [216-224]), PLMQQVPQPIPQ (β-casein [148-159]), and FDPQIPK (β-casein [126-132])) crossed to the basolateral chamber of the Caco-2 monolayer incubated with peptides at all three concentrations. Among the peptides identified in the basolateral chambers, three peptides (NLHLPLP (β-casein [138-144]), LENLHLPLP (β-casein [136-144]), and QVVPYPQ (β-casein [182-188])) are known ACE-inhibitors; one peptide (LLNQELLLNPTHQIYPV (β-casein [197-213])) is antimicrobial, and another peptide (QVVPYPQ (β-casein [182-188])) has antioxidant activity. These findings indicate that specific milk peptides may be able to reach the bloodstream and exert bioactivity.

Peptides Derived from In Vitro and In Vivo Digestion of Human Milk Are Immunomodulatory in THP-1 Human Macrophages

BACKGROUND

Milk proteins contain many encrypted bioactive peptides. Whether these bioactive peptides are released in the infant intestine and exert immunomodulatory activity remains unknown.

OBJECTIVE

This study examined in vitro immunomodulatory activities of peptides from in vitro- and in vivo-digested human milk.

METHODS

Peptides were extracted from in vitro-digested human milk and pooled intestinal samples from 8 infants fed human milk. Peptides extracted from in vitro-digested samples were fractionated. The in vitro effects of these peptides and fractions on the secretion of TNF-α and IL-8 in LPS-treated human immune THP-1 macrophages were evaluated. The significance of differences between in vitro peptide fraction treatment and control on cytokine production was analyzed by t test. LC-MS/MS-based peptidomics was conducted to identify the peptides. The peptides were screened for potential bioactivity using a sequence homology search using the Milk Bioactive Peptide Database (MBPDB).

RESULTS

Six fractions of the peptide mixture extracted from the in vitro-digested human milk significantly inhibited TNF-α production by LPS-challenged THP-1 macrophages. Fractions F4, F8, F11, F14, and F17 attenuated IL-8 secretion, and F6/7 and F18 increased IL-8 secretion. Peptides extracted from the pooled in vivo intestinal samples attenuated both TNF-α and IL-8 secretion. There were 266 and 418 peptides identified in the in vitro and in vivo samples, respectively. Among the peptides, 34 and 50 in the in vitro and in vivo samples, respectively, had >80% sequence similarity to bioactive peptides in the MBPDB.

CONCLUSIONS

Peptides released by in vitro and in vivo infant digestion of human milk were immunomodulatory in human immune cells; fractions F4, F8, and F11 were anti-inflammatory; and F6/7 and F18 were proinflammatory. Thirteen peptides were present in all fractions with anti-inflammatory activity, and 38 peptides were present in all fractions with proinflammatory activity. These peptides potentially contributed to the observed immunomodulatory activity of the peptide mixtures.

Advances in static in vitro digestion models after the COST action Infogest consensus protocol

In vitro digestion models are essential to predictively evaluate the bioaccessibility and bioactivity of food molecules or natural products. Dynamic models better simulate the gastrointestinal conditions as they reproduce similar physiological environments. Despite this, static methods, also known as biochemical methods, represent a simple and useful approach for the study of different types of molecules, with a broad applicability in the nutritional, pharmaceutical, and toxicological fields. In addition, static models can be validated, avoiding the disadvantage of a difficult reproducibility of dynamic in vitro systems and inter-individual variations of in vivo experiments. A crucial point in the standardization of static models was the COST Action Infogest in 2014, which elaborated an international consensus static digestion method to harmonize experimental conditions and has general guidelines, thus allowing the comparison of studies and data. The aim of our review is to underline the impact of the Infogest consensus method and the development and evolution of in vitro static methods in the following years, with a focus on food applications.

Maternal diet with sea urchin gangliosides promotes neurodevelopment of young offspring via enhancing NGF and BDNF expression

Neurodevelopment of fetal and infant brains is an essential process not just during infancy but throughout the whole life. Previous studies have verified the neurotrophic effects of GM1 and milk gangliosides (GLSs) on brain development. However, it remains unclear whether the maternal GLS diet during the perinatal period can program the brain development of young offspring. Sea urchin, as a popular sea food, is a good resource of marine-derived GLSs. This study evaluated the effects of maternal diet with sea urchin gangliosides (SU-GLSs) on the utero and neonatal neurodevelopment and compared their efficacy with common GM1 and sialic acid (SA). Herein, SU-GLSs, as well as GM1 and SA, were orally administered to pregnant mice from pregnancy to lactation. The morphological and functional development of the brain was evaluated in postnatal 15-day (P15) mice. SU-GLSs were superior to GM1 and SA in enhancing neuritogenesis, spinous dendrite growth and synapse function in the hippocampus and cortex of P15 mice. Mechanistic studies found that SU-GLSs upregulated the expressions of NGF and BDNF more effectively than GM1 and SA. Furthermore, different glycosylated SU-GLSs promoted the neural differentiation of Neuro2a cells in a structure-selective manner. Sulfate-type and disialo-type GLSs were more effective than GM1. These findings suggested that maternal SU-GLS diet could promote the neurodevelopment of young offspring and would be a potential nutrition enriching substance for the early developing brain.

An overview and future prospects of sialic acids

Sialic acids (Sias) are negatively charged functional monosaccharides present in a wide variety of natural sources (plants, animals and microorganisms). Sias play an important role in many life processes, which are widely applied in the medical and food industries as intestinal antibacterials, antivirals, anti-oxidative agents, food ingredients, and detoxification agents. Most Sias are composed of N-acetylneuraminic acid (Neu5Ac, >99%), and Sia is its most commonly used name. In this article, we review Sias in terms of their structures, applications, determination methods, metabolism, and production strategies. In particular, we summarise and compare different production strategies, including extraction from natural sources, chemical synthesis, polymer decomposition, enzymatic synthesis, whole-cell catalysis, and de novo biosynthesis via microorganism fermentation. We also discuss research on their physiological functions and applications, barriers to efficient production, and strategies for overcoming these challenges. We focus on efficient de novo biosynthesis strategies for Neu5Ac via microbial fermentation using novel synthetic biology tools and methods that may be applied in future. This work provides a comprehensive overview of recent advances on Sias, and addresses future challenges regarding their functions, applications, and production.

Potentiometric analysis of sialic acid with a flexible carbon cloth based on boronate affinity and molecularly imprinted polymers

A potentiometric sensor for sialic acid detection was designed based on a boronic acid-containing MIP modified carbon cloth electrode.

Effects of Refrigerated and Frozen Storage on Holder-Pasteurized Donor Human Milk: A Systematic Review

BACKGROUND

Pasteurized donor human milk (PDHM) is the recommended feeding alternative for preterm infants when mother's own milk is not available. Use of PDHM in United States neonatal hospitals is increasing, although guidelines for the refrigerated and frozen storage are limited.

OBJECTIVE

We aimed to review the current evidence for the storage of Holder PDHM (HPDHM) under refrigerated and frozen storage conditions.

METHODS

A systematic review of the literature was conducted for studies published between 1985 and May 2018. Studies were included if they studied the storage of Holder-pasteurized human milk under refrigerated or frozen storage conditions.

RESULTS

Fourteen studies met the inclusion criteria. Five studies addressed refrigerated storage and nine studies addressed frozen storage. There was little overlap in the outcomes measured or the analytical methods employed. There was concordance in three studies reporting no microbial growth over 4-9 days of refrigerated storage, and in five studies reporting a reduction in fat during 1-8 months of frozen storage. Only one study assessed the storage of HPDHM that had been fortified.

CONCLUSIONS

Long-term refrigerated and frozen storage of HPDHM affects some components in milk more than others. While there is evidence of microbial purity during four or more days of refrigerated storage in clinical conditions, there is limited research on the impact of macro and micronutrients, or the impact of fortifiers. More research is needed in these areas.

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.

Evaluation of Sialic Acid in Infant Feeding: Contents and Bioavailability

Sialic acid (Sia) contents and bioaccessibility (BA) in human milk (HM) and infant formulas (IFs) were determined, and Sia intakes by infants between 0 and 6 months of age were evaluated. Total Sia contents in HM decreased during lactation from 136.14 to 24.47 mg/100 mL. The total Sia contents in IFs (13.15-25.78 mg/100 mL) were lower than in HM and were not related to the addition of ingredients acting as sources of Sia in their formulation. The Sia intakes derived from IF consumption were lower than in HM, and only one IF reached the intakes provided by HM from the age of 2 months. Despite the lower total Sia content in IFs, the BA of Sia in IFs (88.08-92.96%) was significantly greater than in mature HM (72.51%) and similar to that found in colostrum (96.43%). However, the Sia contents in the available soluble fraction of IFs did not reach those provided by HM.

Comparative analysis of human milk and infant formula derived peptides following in vitro digestion

It has long been recognised that there are differences between human milk and infant formulas which lead to differences in health and nutrition for the neonate. In this study we examine and compare the peptide profile of human milk and an exemplar infant formula. The study identifies both similarities and differences in the endogenous and postdigestion peptide profiles of human milk and infant formula. This includes differences in the protein source of these peptides but also with the region within the protein producing the dominant proteins. Clustering of similar peptides around regions of high sequence identity and known bioactivity was also observed. Together the data may explain some of the functional differences between human milk and infant formula, while identifying some aspects of conserved function between bovine and human milks which contribute to the effectiveness of modern infant formula as a substitute for human milk.

Membrane Glycolipids Content Variety in Gastrointestinal Tumors and Transplantable Hepatomas in Mice

Background

The aim of this study was to investigate the variety of plasma contents of membrane glycolipids in 65 gastrointestinal tumors and 31 transplant hepatomas in mice.

Material/Methods

The experimental model was a transplantable murine hepatoma. Experimental mice were divided into 3 groups.

Results

The LSA and TSA content in the 2 groups were significantly difference (p<0.01), and were significantly lower in the therapeutic group than in the control group (p<0.01).

Conclusions

These results indicate that membrane glycolipids index LSA and TSA are sensitive markers in gastrointestinal tumors. In the transplanted hepatomas in mice, they may be considered as ancillary indicators for judging the therapeutic effect of hepatoma.

Diagnosis value of membrane glycolipids biochemistry index in intracranial and gastrointestinal tumors

The diagnostic value of membrane glycolipid biochemistry index, the lipid-bound sialic acid (LSA) and total sialic acid (TSA) in cerebrospinal fluid (CSF) was evaluated in 30 intracranial and 65 gastrointestinal tumors. The plasma LSA, TSA and red cell membrane sialic acid (R-SA) in were determined according to the method of Sevenmerhulm. Our results showed that the levels of LSA and TSA in CSF of intracranial tumor patients was higher than that of normal group(p<0.01). The concentration of TSA and LSA in patients with malignant glioma was higher than that of benign meningioma patients(P<0.01). No significance was found between intracranial halmatoma patients and normal control group for levels of membrane glycolipids (p>0.05). Results also found that the plasma LSA, TSA and R-SA of gastric carcinoma were significantly higher than those of control group (p<0.05); while no significant difference was found in the plasma LSA, TSA and R-SA levels between chronic gastritis, gastrohelcoma and normal control group (p>0.05). Plasma LSA, TSA and R-SA levels of gastric carcinoma patient were significantly higher than those of chronic gastritis patients and gastrohelcoma patients(p<0.05). It was also found that plasma LSA, TSA and R-SA contents were significantly higher in large intestine carcinoma patients than in benign in stestine tumor patients (p<0.05) while no significant difference was found between intestine benign tumor and normal control group (p>0.05). The levels of LSA, TSA and R-SA were obviously higher in the patients with metastasis than in the ones without (p<0.05.) The membrane glycolipid biochemistry index LSA and TSA in CSF are sensive markers for diagnosing intracranial tumors. For gastrointestinal malignant tumors the plasma LSA TSA and red blood cell membrane SA may be considered as auxiliary indicators for diagnosis. They can be used for distinguishing benign from malignant tumors.

Hydrolysis of milk gangliosides by infant-gut associated bifidobacteria determined by microfluidic chips and high-resolution mass spectrometry

Gangliosides are receiving considerable attention because they participate in diverse biological processes. Milk gangliosides appear to block pathogen adhesion and modify the intestinal ecology of newborns. However, the interaction of milk gangliosides with gut bifidobacteria has been little investigated. The digestion products of a mixture of gangliosides isolated from milk following incubation with six strains of bifidobacteria were studied using nanoHPLC Chip Q-TOF MS. To understand ganglioside catabolism in vitro, the two major milk gangliosides--GM3 and GD3--remaining in the media after incubation with bifidobacteria were quantified. Individual gangliosides were identified through postprocessing precursor ion scans, and quantitated with the "find by molecular feature" algorithm of MassHunter Qualitative Analysis software. Bifidobacterium infantis and B. bifidum substantially degraded the GM3 and GD3, whereas B. longum subsp. longum and B. animalis subsp. lactis only showed moderate degradation. MALDI FTICR MS analysis enabled a deeper investigation of the degradation and identified ganglioside degradation specifically at the outer portions of the glycan molecules. These results indicate that certain infant gut-associated bifidobacteria have the ability to degrade milk gangliosides releasing sialic acid, and that these glycolipids could play a prebiotic role in the infant gut.

Quantitative analysis of gangliosides in bovine milk and colostrum-based dairy products by ultrahigh performance liquid chromatography-tandem mass spectrometry

Milk gangliosides have gained considerable attention because they participate in diverse biological processes, including neural development, pathogen binding, and activation of the immune system. Herein, we present a quantitative measurement of the gangliosides present in bovine milk and other dairy products and byproducts. Ultrahigh performance liquid chromatography separation was used for high-throughput analysis and achieved a short running time without sacrificing chromatographic resolution. Dynamic multiple reaction monitoring was conducted for 12 transitions for GM3 and 12 transitions for GD3. Transitions to sialic acid fragments (m/z 290.1) were chosen for the quantitation. There was a considerable amount of gangliosides in day 2 milk (GM3, 0.98 mg/L; GD3, 15.2 mg/L) which dramatically decreased at day 15 and day 90. GM3 and GD3 were also analyzed in pooled colostrum, colostrum cream, colostrum butter, and colostrum buttermilk. The separation and analytical approaches here proposed could be integrated into the dairy industry processing adding value to side-streams.

Gangliosides and sialic acid effects upon newborn pathogenic bacteria adhesion: an in vitro study

The effect of the main gangliosides (GM(1), GM(3), GD(3)) and free sialic acid (Neu5Ac) upon the adhesion of pathogenic bacteria implicated in infant diarrhoea is assessed in vitro using the Caco-2 cell line. Concentrations of the bioactive compounds found in the bioaccessible (soluble) fraction of infant formula and human milk are employed. Bacterial adhesion behaviour included enterotoxigenic Escherichia coli (ETEC), enteropathogenic E.coli (EPEC), Listeria monocytogenes, Salmonella entericaserovartyphi, Shigella sonnei, Campylobacter jejuni and Helicobacter pylori. Three different approaches were assayed: pre-incubation of bacteria and compounds before addition to cells (competition); pre-incubation of the cells with compounds (exclusion); and pre-incubation of cells with bacteria (displacement). Furthermore, the spatial localization of the most abundant gangliosides, GM(3) and GD(3), in Caco-2 cells has been determined using confocal microscopy. Results show that GM(3), GD(3), GM(1) and Neu5Ac at the assayed concentrations are able to interfere with the adhesion of several pathogenic bacteria involved in neonatal diseases-the greatest effect corresponding to Neu5Ac, followed by GD(3), GM(1) and GM(3). Gangliosides GM(3) and GD(3) are located in the apical and basolateral membranes of the Caco-2 cells.