Stability of milk fat globule membrane proteins toward human enzymatic gastrointestinal digestion

Comparative lipidomics analysis of in vitro lipid digestion of sheep milk: Influence of homogenization and heat treatment

This study investigated the changes in sheep milk lipids during in vitro gastrointestinal digestion in response to heat treatment (75°C/15 s and 95°C/5 min) and homogenization (200/50 bar) using lipidomics. Homogenized and pasteurized sheep milk had higher levels of polar lipids in gastric digesta emptied at 20 min than raw sheep milk. Intense heat treatment of homogenized sheep milk resulted in a reduced level of polar lipids compared with homogenized-pasteurized sheep milk. The release rate of free fatty acids during small intestinal digestion for gastric digesta emptied at 20 min followed the order: raw ≤ pasteurized < homogenized-pasteurized ≤ homogenized-heated sheep milk; the rate for gastric digesta emptied at 180 min showed a reverse order. No differences in the lipolysis degree were observed among differently processed sheep milks. These results indicated that processing treatments affect the lipid composition of digesta and the lipolysis rate but not the lipolysis degree during small intestinal digestion.

Enzymatic prodrug degradation in the fasted and fed small intestine: In vitro studies and interindividual variability in human aspirates

The aim of the current study was (1) to develop an automation-based protocol for in vitro assessment of enzymatic drug stability at fasted- and fed-state intestinal conditions, (2) to characterize the inter-individual variability of drug degradation in fasted- and fed-state human intestinal fluids, and (3) to compare the obtained in vitro results to drug degradation in human intestinal fluids by taking variability into account. In human intestinal fluids, drug degradation displayed large inter-individual variability, with coefficients of variance generally ranging between 30 and 70 %. The effect of food on the inter-individual variability was highly dependent on the type of drug. The increase of pH in the range between 5.0 and 7.0 significantly accelerated the degradation rate of the studied drugs both in the in vitro and ex vivo experiments. In contrast, the increase of bile salt and phospholipid concentrations in the in vitro screen decreased strongly the degradation rate of the hydrophobic drugs. The developed automated in vitro screen mimicked relatively well the ex vivo degradation of all drugs in the fasted state, whereas in the fed state the degradation of only one of the drugs was adequately reproduced.

Differences in fat digestion from milk of different Species: In vitro gastrointestinal digestion model for infants

The differences in the milk fat digestion from goat milk (GM), camel milk (CM), bovine milk (BM), sheep milk (SM), mare milk (MM) and human milk (HM) using an in vitro gastrointestinal digestion model for simulated infants were investigated. The particle size distributions in goat and mare milk were similar to that of HM after digestion in the small intestine. During in vitro digestion, the zeta-potential change of MM was more consistent with that of HM. After 60 min of gastric digestion, the lipolysis degree (LD) of different milks were<2%, of which the highest LD was MM (1.84%), followed by HM (1.45%). At the end of intestinal digestion, the LD of HM was the highest, reaching 88.47%, and the LD of SM was similar to that of HM, reaching 83.92%, followed by GM (57.00%), BM (40.98%) and MM (39.37%), respectively, the LD of CM was only 29.99%, which was much lower than HM. The results of the glyceride composition hierarchical clustering analysis revealed that MM and HM were clustered into one category at the end of gastric and intestinal digestion. This study provides a scientific basis for the development of lipid ingredients in infant formula.

Effects of Cow's Milk Processing on MicroRNA Levels

MicroRNAs (miRNAs) regulate gene expression and might resist adverse physicochemical conditions, which makes them potential biomarkers. They are being investigated as biomarkers of dairy production systems, based on the variations in their levels in raw milk depending on animal diet and management. Whether miRNA levels can serve as biomarkers for dairy products remains unclear, since technological or culinary treatments, such as fermentation, may alter their levels. Here, 10 cow dairy farms were sampled in Asturias (north-west Spain) and milk samples were subjected to microwave heating or used to produce yogurt or cheese. Total RNA was isolated from raw milk and three derived products, and levels of seven miRNAs, selected based on previous studies as possible milk production system biomarkers, were assessed by RT-qPCR. The treatments decreased levels of all miRNAs to some extent. These results also imply that cheesemaking increases the concentration of miRNAs in this product; raw milk and cheese supposedly may provide similar concentrations of miRNAs, higher than those of yogurt and microwaved milk. They also indicate that the content of certain miRNAs in raw milk cannot necessarily be extrapolated to other dairy products.

Digestion of human milk processed by high pressure processing and Holder pasteurization using a dynamic in vitro model of the preterm infant

Holder pasteurization (HoP) (62.5 °C, 30 min) of donor human milk is widely used to inactivate potential pathogens but may lead to denaturation and aggregation of bioactive proteins, reducing their functionality. In contrast, high pressure processing (HPP) is a non-thermal technique that minimally affects assessed bioactive components; however, it is unclear how HPP affects protein digestion, and retention of functional bioactive proteins. Raw or processed (HoP; HPP[500 MPa,10 min]) pools of milk (N = 3, from 9 donors) were subjected in triplicate to in vitro digestion simulating the preterm infant gastrointestinal tract. Compared to raw or HPP, HoP increased intestinal proteolysis of lactoferrin and bioactive milk fat globule membrane proteins. Lysozyme activity was impacted by digestion following HoP (72 % to 7 %)-significantly more than HPP (75 % to 34 %) or raw (100 % to 39 %), which did not differ. Proteins in HPP-treated donor milk are digested no different than raw milk, while preserved bioactivity remains functional upon digestion.

The role of human milk fats in shaping neonatal development and the early life gut microbiota

Human breast milk (HBM) is the main source of nutrition for neonates across the critical early-life developmental period. The highest demand for energy is due to rapid neurophysiological expansion post-delivery, which is largely met by human milk lipids (HMLs). These HMLs also play a prebiotic role and potentially promote the growth of certain commensal bacteria, which, via HML digestion, supports the additional transfer of energy to the infant. In tandem, HMLs can also exert bactericidal effects against a variety of opportunistic pathogens, which contributes to overall colonisation resistance. Such interactions are pivotal for sustaining homeostatic relationships between microorganisms and their hosts. However, the underlying molecular mechanisms governing these interactions remain poorly understood. This review will explore the current research landscape with respect to HMLs, including compositional considerations and impact on the early life gut microbiota. Recent papers in this field will also be discussed, including a final perspective on current knowledge gaps and potential next research steps for these important but understudied breast milk components.

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.

Interfacial composition in infant formulas powder modulate lipid digestion in simulated in-vitro infant gastrointestinal digestion

The interface structure and composition of fat globules are very important for the digestion and metabolism of fat and growth in infants. Interface composition of fat globules in infant formula (IF) supplemented with milk fat globule membranes (MFGM) and lecithin in different ways were analyzed and their effects on fat digestion properties were evaluated. The results showed that the distribution of phospholipids at the interface and structural of Concept IF1 and Concept IF2 that were more similar to those of human milk (HM) than that of conventionally processed IF3. Concept IF2 and IF3 supplemented with lecithin had larger initial particle size and more sphingomyelin (SM) (23.12 ± 0.26 %, 26.94 ± 0.34 %) than Concept IF1, and Concept IF2 had the smallest proportion of casein in the interfacial. Due to its interface composition, Concept IF2 had the highest degree of lipolysis (85.07 ± 0.76 %), the phospholipid ring structure can always be observed during gastric digestion, and a final fatty acid composition released that was more similar to HM. Concept IF1 and IF3 were different from HM and Concept IF2 in terms of structure and lipolysis rate, although superior to commercial IF4. These indicate that changes in the interfacial composition and structure of fat globules improve the digestive properties of fats in IF. Overall, the results reported herein are useful in designing new milk formulas that better simulate HM.

Milk exosomes: an oral drug delivery system with great application potential

Exosomes are extracellular vesicles with the smallest diameter, usually divided into cellular sources and body fluid sources. Due to their special properties different from cell-derived exosomes, the application of milk exosomes as an oral drug delivery system has increased greatly. This article introduces the physical and chemical properties of exosomes, separation technology, dyeing and labeling technology, targeted modification technology, and the application of milk exosomes in drug loading and disease therapies.

The Immunological Role of Milk Fat Globule Membrane

Human milk is the ideal food for newborns until the age of six months. Human milk can be defined as a dynamic living tissue, containing immunological molecules, such as immunoglobulins, supra-molecular structures, such as the milk fat globule membrane (MFGM), and even entire cells, such as the milk microbiota. The milk composition changes throughout lactation to fulfill the infant’s requirements and reflect the healthy/disease status of the lactating mother. Many bioactive milk components are either soluble or bound to the MFGM. In this work, we focus on the peculiar role of the MFGM components, from their structural organization in fat globules to their route into the gastrointestinal tract. Immunometabolic differences between human and bovine MFGM components are reported and the advantages of supplementing infant formula with the MFGM are highlighted.

The role of orally ingested milk fat globule membrane on intestinal barrier functions evaluated with a suckling rat pup supplementation model and a human enterocyte model

Milk fat globule membrane (MFGM), the membrane surrounding secreted fat droplets in milk, contains components involved in a wide range of bioprocesses including cell proliferation and differentiation. The intestine is relatively immature and permeable at birth. Since MFGM is partly resistant to digestion in infancy, we hypothesized that orally ingested MFGM promotes intestinal development by enhancing intestinal barrier functions in early life. An established suckling rat model was used; Sprague-Dawley rats were bred, and litters were culled to 10 pups/dam. Pups were supplemented orally with MFGM (0, 100, or 300 mg/kg/day) from postnatal day 1 to 20. Intestine samples were collected for histology, qRT-PCR, immunoblotting, and immunohistochemistry analysis. Additionally, differentiated Caco-2 cells were used to assess effects of MFGM on the human intestinal barrier. Control and MFGM-supplemented rat pups showed similar growth. Intestinal differentiation and expression of tight junction proteins in jejunum and colon were significantly increased by orally ingested MFGM, and MFGM supplementation significantly activated PI3K/Akt/mTOR, MAPK, and MLCK signaling pathways, suggesting that MFGM promotes intestinal development by triggering various signaling pathways. In human enterocytes (polarized Caco-2 cells), MFGM (400 µg/mL for 72 h) decreased permeability, as revealed by increased transepithelial electrical resistance. In Caco-2 cells, MFGM also enhanced expression of tight junction proteins, including claudin-4 and ZO-2. In conclusion, orally ingested MFGM may exert beneficial roles in intestinal development by activating various cell signaling pathways to upregulate tight junction proteins and thereby increasing intestinal barrier functions.

Brain – immune – gut benefits with early life supplementation of milk fat globule membrane

The milk fat globule membrane (MFGM) has been recognized as a milk component for more than 60 years, but its exact benefits remain unknown. Research on human MFGM has revealed that the membrane holds a host of bioactive components with potential benefits for the brain–immune–gut (BiG) axis in early life. Gangliosides and sphingomyelin, components within the MFGM, have been included in infant formulas for many years. Recent advancements in dairy milk processing have allowed the successful separation of MFGM from bovine milk, enabling it to be used for supplementing infant formulas. Evidence indicates the potential benefits of MFGM in early life supplementation, including better cognitive development, reduction of infection risks, and modulation of the gut microbiome. However, larger and more robust randomized trials are needed, in addition to long‐term outcome data beyond the infancy period.

Variation in milk fat globule size and composition: A source of bioactives for human health

Milk fat globules (MFGs) are secreted from the mammalian gland and are composed of a triacylglycerol core surrounded by a triple membrane structure, the milk fat globule membrane (MFGM). The MFGM contains complex lipids and proteins reported to have nutritional, immunological, neurological and digestive functions. Human and ruminant milk are shown to share a similar MFG structure but with different size, profile and abundance of protein and polar lipids. This review summarizes the reported data on human, bovine, caprine and ovine MFG composition and concentration of bioactive components in different MFG-size fractions. A comprehensive understanding of compositional variations between milk from different species and MFG size fractions may help promote various milk sources as targeted supplements to improve human development and health. MFG size and MFGM composition are species-specific and affected by lactation, diet and breed (or maternal origin). Purification and enrichment methods for some bioactive proteins and lipids present in the MFGM have yet to be established or are not scaled sufficiently to be used to supplement human diets. To overcome this problem, MFG size selection through fractionation or herd selection may provide a convenient way to pre-enrich the MFG fraction with specific protein and lipid components to fulfill human dietary and health requirements.

Impact of gastric coagulation on the kinetics of release of fat globules from milk of different species

The behavior of fat globules during the gastric digestion of raw and pasteurized cow, goat, and sheep whole milks was studied using a human gastric simulator. Microstructural and physicochemical analysis revealed that, initially, the coagulation of the milks in the human gastric simulator resulted in the majority of the milk fat globules being entrapped within the curd. As the digestion progressed, the proportion of fat globules entrapped within the aggregated protein matrix (curd) decreased; there was also some flocculation as well as coalescence of the fat globules within the curd. The liberation of the entrapped fat globules from the curd to the liquid phase of the chyme was strongly dependent on the disintegration and hydrolysis of the structured casein network. Surprisingly, the fat globules released (or already present) into the liquid phase of the chyme were not as extensively coalesced as those remaining within the curd. These phenomena were observed to be similar for the raw and pasteurized whole milk of all species. The pasteurized whole milks from all species formed relatively less structured coagula compared with their raw milk counterparts, leading to a greater extent of protein breakdown and, thus, higher proportions of fat release from the pasteurized milk curds. This study provides a deeper understanding of how the curd-forming properties of different mammalian milks in the gastric environment provide controlled delivery of nutrients (such as protein and fat).

Milk Fat Globule Membrane Proteome and Micronutrients in the Milk Lipid Fraction: Insights into Milk Bioactive Compounds

Milk lipids are composed of milk fat globules (MFGs) surrounded by the milk fat globule membrane (MFGM). MFGM protects MFGs from coalescence and enzymatic degradation. The milk lipid fraction is a “natural solvent” for macronutrients such as phospholipids, proteins and cholesterol, and micronutrients such as minerals and vitamins. The research focused largely on the polar lipids of MFGM, given their wide bioactive properties. In this review we discussed (i) the composition of MFGM proteome and its variations among species and phases of lactation and (ii) the micronutrient content of human and cow’s milk lipid fraction. The major MFGM proteins are shared among species, but the molecular function and protein expression of MFGM proteins vary among species and phases of lactation. The main minerals in the milk lipid fraction are iron, zinc, copper and calcium, whereas the major vitamins are vitamin A, β-carotene, riboflavin and α-tocopherol. The update and the combination of this knowledge could lead to the exploitation of the MFGM proteome and the milk lipid fraction at nutritional, biological or technological levels. An example is the design of innovative and value-added products, such as MFGM-supplemented infant formulas.

Nature-Assembled Structures for Delivery of Bioactive Compounds and Their Potential in Functional Foods

Consumers are demanding more natural, healthy, and high-quality products. The addition of health-promoting substances, such as bioactive compounds, to foods can boost their therapeutic effect. However, the incorporation of bioactive substances into food products involves several technological challenges. They may have low solubility in water or poor stability in the food environment and/or during digestion, resulting in a loss of their therapeutic properties. Over recent years, the encapsulation of bioactive compounds into laboratory-engineered colloidal structures has been successful in overcoming some of these hurdles. However, several nature-assembled colloidal structures could be employed for this purpose and may offer many advantages over laboratory-engineered colloidal structures. For example, the casein micelles and milk fat globules from milk and the oil bodies from seeds were designed by nature to deliver biological material or for storage purposes. These biological functional properties make them good candidates for the encapsulation of bioactive compounds to aid in their addition into foods. This review discusses the structure and biological function of different nature-assembled carriers, preparation/isolation methods, some of the advantages and challenges in their use as bioactive compound delivery systems, and their behavior during digestion.

Shifts in the Holstein dairy cow milk fat globule membrane proteome that occur during the first week of lactation are affected by parity

Background

The milk fat globule membrane (MFGM) proteomes of colostrum and transition milk are rich sources of proteins that are likely important for neonatal calf health. In addition, characterization of these proteomes could also yield valuable information regarding mammary gland physiology of the early postpartum lactating cow. The objectives of this research were to characterize the MFGM proteomes of colostrum and transition milk through sample collections at four timepoints postpartum, including the first milking (M1, colostrum), second milking (M2, transition milk), fourth milking (M4, transition milk), and fourteenth milking (M14, mature milk), and compare these proteomes between multiparous (MP; n = 10) and primiparous (PP; n = 10) Holstein dairy cows. Isolated MFGM proteins were labeled using Tandem Mass tagging and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Protein identification was completed using MASCOT and Sequest in Proteome Discoverer 2.2. The scaled abundance values were analyzed using PROC MIXED in SAS to determine the effects of milking (MIL), parity (PAR), and MIL × PAR. The adaptive false-discovery rate (FDR)-adjusted P values were determined using PROC MULTTEST. Protein characterization and bioinformatic analysis were completed using a combination of PANTHER, Blast, and Uniprot.

Results

A total of 104 common proteins were identified in each of the MFGM samples. Statistical analysis revealed that 70.2% of identified proteins were affected by MIL. Of these, 78.1% were lower in M14 compared with M1, including immune-related proteins lactotransferrin, lactadherin and hemopexin. Parity affected 44.2% of proteins. Of the proteins affected by PAR, 84.8% were higher in MP cows compared with PP cows, including apolipoprotein E and histones 2A, 2B, 3, and 4 b. Butyrophilin subfamily 1 member 1A and annexin 5 were higher in samples from PP cows. Milking × parity affected 32.7% of identified proteins, including lactotransferrin, gelsolin, vitamin D binding protein, and S100 proteins.

Conclusions

This research supports previous findings that the Holstein MFGM proteome changes rapidly during the first week of lactation. In addition, this research identifies the impact of parity on the colostrum and transition milk MFGM proteomes, which may be important for milk-fed calf health or for the identification of protein biomarkers for mammary functionality.

In vitro Fermentation of Digested Milk Fat Globule Membrane From Ruminant Milk Modulates Piglet Ileal and Caecal Microbiota

Lipids in milk are secreted as a triacylglycerol core surrounded by a trilayer membrane, the milk fat globule membrane (MFGM). This membrane, known to have important roles in infant brain and intestinal development, is composed of proteins, glycoproteins, and complex lipids. We hypothesized that some of the beneficial properties of MFGM are due to its effects on the gastrointestinal microbiota. This study aimed to determine the effect of a commercial phospholipid concentrate (PC) and enriched bovine, caprine, and ovine MFGM fractions on ileal and hindgut microbiota in vitro. Digestion of PC and MFGMs was conducted using an in vitro model based on infant gastric and small intestine conditions. The recovered material was then in vitro fermented with ileal and caecal inocula prepared from five piglets fed a commercial formula for 20 days before ileal and caecal digesta were collected. After each fermentation, samples were collected to determine organic acid production and microbiota composition using 16S rRNA sequencing. All substrates, except PC (5%), were primarily fermented by the ileal microbiota (8–14%) (P < 0.05). PC and caprine MFGM reduced ileal microbiota alpha diversity compared to ileal inoculum. Caprine MFGM increased and PC reduced the ileal ratio of firmicutes:proteobacteria (P < 0.05), respectively, compared to the ileal inoculum. Bovine and ovine MFGMs increased ileal production of acetic, butyric, and caproic acids compared to other substrates and reduced the proportions of ileal proteobacteria (P < 0.0001). There was a limited fermentation of bovine (3%), caprine (2%), and ovine (2%) MFGMs by the caecal microbiota compared to PC (14%). In general, PC and all MFGMs had a reduced effect on caecal microbiota at a phylum level although MFG source-specific effects were observed at the genus level. These indicate that the main effects of the MFGM in the intestinal microbial population appears to occur in the ileum.

Effects of Chemical Composition and Microstructure in Human Milk and Infant Formulas on Lipid Digestion

Infant formula (IF) is an important substitute for infants when human milk (HM) is unavailable; however, it was often observed with "insufficient fat" and showed different metabolic phenotypes, which may affect the growth and brain development of the infant. Considering that the milk fat digestion rate may affect the fat absorption and metabolism and further influence the metabolic phenotype, it is valuable to study the fat digestive behaviors of IF and HM. In the current study, we investigated the in vitro fat digestive properties of HM in comparison to four formulas (IF1, 2, 3, 4) including IFs enriched in OPO lipids (IF1 and IF3) and IFs with common mixed plant oils (IF2 and IF4). Results showed that the extent of eventual lipid hydrolysis of HM (98.9 ± 2.70%) was higher than those of IF1 and IF3 (90.4 ± 3.39 and 91.1 ± 1.67%, respectively) (p < 0.05) and IF2 and IF4 (81.9 ± 1.64 and 79.9 ± 1.05% respectively) (p < 0.01). Native fat globules and protein aggregation were observed at the end of HM gastric digestion, and the aggregates became smaller and then resolved from 60 to 120 min in intestinal digestion, while a large number of aggregates were observed in IF, which may slow the lipid digestion. The absorption differences between HM and IFs in lipid digestion need further study to elucidate the nutritional relevance to infant development and growth.

Protein digestion properties of Xinong Saanen goat colostrum and mature milk using in vitro digestion model

BACKGROUND

Xinong Saanen goat milk is a raw material for goat milk-based infant formula production. This study aims to analyze digestion properties of Xinong Saanen goat colostrum and mature milk by simulating infant gastrointestinal digestion. Zeta potential, particles size, protein profile and peptides composition of these two kinds of milk during the digestion process were studied.

RESULTS

Zeta-potential values of the digested colostrum were lower than those of mature milk through the whole digestion. Absolute zeta potential of colostrum duodenal digestion samples showed a decrease from 16.63 ± 2.08 to 11.80 ± 2.03 mV while that of mature milk decreased sharply and then increased (P < 0.05). Colostrum had a larger particle size than mature milk and both milks showed decreased particle size with increasing digestion time but an increase for the last 30 min. Colostrum showed more high molecular weight (MW) proteins which cannot be hydrolyzed completely compared with mature milk. Digested peptides (< 10 kDa) were characterized using liquid chromatography combined with tandem mass spectrometry (LC-MS/MS). The casein-derived peptides identified in digested colostrum and mature milk accounted for 76.67% and 59.53%, respectively. β-Casein was the most abundant in colostrum while that in mature milk was α_s1 -casein. Enterotoxin-binding glycoprotein PP20K, butyrophilin subfamily 1 member A1 (BTN1A1) and perilipin (PLIN) were only detected in digested mature milk.

CONCLUSION

Differences in digestion properties between goat colostrum and mature milk were mainly shown in duodenal digestion phase. Data may provide useful information about utilization of goat milk for infant formula formulation. © 2019 Society of Chemical Industry.

Characterization of difference in structure and function of fresh and mastitic bovine milk fat globules

Characterization of milk fat globule (MFG) was performed to investigate the difference in MFG membrane (MFGM) between fresh and mastitis Holstein Friesian cow milk. Lipid distribution investigated by exogenous phospholipids using microscopy showed higher phospholipid content in fresh compared to mastitic MFGM. Xanthine oxidase assay indicative of membrane impairment revealed lower activity in mastitic samples compared to fresh globules. Of note, significantly higher roughness of globule surface and zeta potential was observed in mastitis compared to fresh globules. Influence of globule membrane on the interaction with L. fermentum demonstrated preferential adhesion of bacteria to fresh compared to mastitic globules including enhanced extent of binding. Results of the present study provides an insight of the interfacial changes occurring at the globule surface as well as highlighting the importance of selective bacterial interaction with milk components for the potential development of functional food with relevance to human health.

Free fatty acid release from vegetable and bovine milk fat-based infant formulas and human milk during two-phase in vitro digestion

The profile of fatty acids released during in vitro digestion of vegetable and bovine milk fat-based infant formula differ.

Evaluation of Dietary Bovine Milk Fat Globule Membrane Supplementation on Growth, Serum Cholesterol and Lipoproteins, and Neurodevelopment in the Young Pig

Introduction: Milk fat globule membrane (MFGM) is a protein- and phospholipid-rich membrane that surrounds the lipid droplet in milk. We have previously reported that a diet composed of a combination of prebiotics, bovine MFGM (bMFGM), and lactoferrin (bLf) supported brain development in young pigs. Due to the growing interest of its potential benefits in neurodevelopment, the present study focused on the effects of dietary bMFGM alone using the pig as a translational model. Methods: Male pigs were provided ad libitum access to milk replacer with added whey protein-lipid concentrate (source of bMFGM) at 0 (CONT), 2.5 (MFGM-2.5), or 5 (MFGM-5.0) g/L from postnatal day (PND) 2 to 31. Blood was collected from pigs at PND 15 and 31, and pigs underwent behavioral testing using the novel object recognition task starting at PND 25. At PND 31, magnetic resonance imaging was conducted and animals were subsequently euthanized for tissue collection. Results: No group differences in body weight gain or milk intake were observed. At PND 31, few group differences were detected in absolute and relative brain volumes, brain water diffusivity outcomes, or behavioral parameters using the novel object recognition task. Serum lipoprotein was higher in pigs receiving diets with added dietary bMFGM compared with the CONT group. Serum cholesterol and high-density lipoprotein significantly higher (all P < 0.05) in the MFGM-2.5 compared with the CONT group. However, cholesterol concentrations within the brain prefrontal cortex and hippocampus did not differ among dietary groups. Conclusion: In this pig model, dietary supplementation with bMFGM was well-tolerated and supported growth and dietary intake similar to the control formula. Added dietary bMFGM was associated with increased serum lipoprotein, but no group differences in early brain cholesterol concentrations, macrostructure, microstructure, or recognition memory pigs at 31 days of age. Further examination of longitudinal brain development and myelination in the pig, particularly at later ages/maturation, is warranted.

Compositional Dynamics of the Milk Fat Globule and Its Role in Infant Development

Human milk is uniquely optimized for the needs of the developing infant. Its composition is complex and dynamic, driven primarily by maternal genetics, and to a lesser extent by diet and environment. One important component that is gaining attention is the milk fat globule (MFG). The MFG is composed of a triglyceride-rich core surrounded by a tri-layer membrane, also known as the milk fat globule membrane (MFGM) that originates from mammary gland epithelia. The MFGM is enriched with glycerophospholipids, sphingolipids, cholesterol, and proteins, some of which are glycosylated, and are known to exert numerous biological roles. Mounting evidence suggests that the structure of the MFG and bioactive components of the MFGM may benefit the infant by aiding in the structural and functional maturation of the gut through the provision of essential nutrients and/or regulating various cellular events during infant growth and immune education. Further, antimicrobial peptides and surface carbohydrate moieties surrounding the MFG might have a pivotal role in shaping gut microbial populations, which in turn may promote protection against immune and inflammatory diseases early in life. This review seeks to: (1) understand the components of the MFG, as well as maternal factors including genetic and lifestyle factors that influence its characteristics; (2) examine the potential role of this milk component on the intestinal immune system; and (3) delineate the mechanistic roles of the MFG in infant intestinal maturation and establishment of the microbiota in the alimentary canal.

A subset of extracellular vesicles carries the bulk of microRNAs in commercial dairy cow's milk

MicroRNAs are small gene-regulatory RNAs that are found in various biological fluids, including milk, where they are often contained inside extracellular vesicles (EVs), like exosomes. In a previous study, we reported that commercial dairy cow's milk microRNAs resisted simulated digestion and were not exclusively associated with canonical exosomes. Here, we report the characterization of a milk EV subset that sediments at lower ultracentrifugation speeds and that contains the bulk of microRNAs. Milk EVs were isolated by differential ultracentrifugation and Iodixanol density gradient (IDG), and analysed for (1) microRNA enrichment by reverse transcription and quantitative polymerase chain reaction (RT-qPCR), and (2) EV-associated proteins by Western blot. Milk EVs were characterized further by dynamic light scattering (DLS), density measurements, fluorescent DiR and RNA labelling, high-sensitivity flow cytometry (HS-FCM), transmission electron microscopy (TEM), proteinase K and RNase A assay, and liquid chromatography tandem-mass spectrometry (LC-MS/MS). We found that the bulk of milk microRNAs (e.g., bta-miR-125b, bta-miR-148a, etc.) sediment at 12,000 g and 35,000 g. Their distribution pattern was different from that of exosome-enriched proteins, but similar to that of several proteins commonly found in milk fat globule membranes (MFGM), including xanthine dehydrogenase (XDH). These low-speed ultracentrifugation pellets contained cytoplasm-enclosing phospholipid bilayered membrane vesicles of a density comprised between 1.11 and 1.14 g/mL in Iodixanol. This milk EV subset of ~100 nm in diameter/~200 nm hydrodynamic size resisted to proteinase K digestion and protected their microRNA content from RNase A digestion. Our results support the existence of a milk EV subset pelleting at low ultracentrifugations speeds, with a protein coating comparable with MFGM, which contains and protects the bulk of milk microRNAs from degradation. This milk EV subset may represent a new EV population of interest, whose content in microRNAs and proteins supports its potential bioactivity.

Determination of lactadherin concentration in dairy by-products by ELISA: Effect of heat treatment and hydrolysis

Lactadherin is a peripheral glycoprotein of the milk fat globule membrane with several attributed biological activities. In this study, we developed an indirect competitive ELISA to determine lactadherin concentration by using a rabbit polyclonal antiserum. The ELISA was applied to quantify lactadherin in several dairy by-products. Of the products tested, raw and commercial buttermilk had the highest concentrations of lactadherin (6.79 and 5.27 mg/g of product, respectively), followed by commercial butter serum (4.86 mg/g), commercial skim milk (4.84 mg/g), and raw whey (1.20 mg/g). The concentration of immunoreactive lactadherin was also determined in dairy by-products after they were subjected to different technological treatments. Thus, raw products were heat treated at combinations of temperature and time typically used in the dairy industry, and commercial products were hydrolyzed using 3 proteolytic enzyme preparations. Heat treatments of whey and buttermilk resulted in a smaller decrease in lactadherin concentration than did hydrolysis as determined by ELISA and electrophoresis. At high temperatures for long durations, the loss of lactadherin was higher in whey than in buttermilk, with the maximal reduction of around 48% found after treating whey at 72°C for 60 min. Hydrolysis of commercial products with proteolytic enzymes resulted in a marked decrease of immunoreactivity within the first 5 min of treatment, which thereafter was constant throughout 4 h of hydrolysis. These results demonstrate that dairy by-products from milk fat processing are good natural sources of lactadherin, although technological processes have to be considered, because they have different effects on lactadherin content.

The composition and functional properties of whey protein concentrates produced from buttermilk are comparable with those of whey protein concentrates produced from skimmed milk

The demand for whey protein is increasing in the food industry. Traditionally, whey protein concentrates (WPC) and isolates are produced from cheese whey. At present, microfiltration (MF) enables the utilization of whey from skim milk (SM) through milk protein fractionation. This study demonstrates that buttermilk (BM) can be a potential source for the production of a WPC with a comparable composition and functional properties to a WPC obtained by MF of SM. Through the production of WPC powder and a casein- and phospholipid (PL)-rich fraction by the MF of BM, sweet BM may be used in a more optimal and economical way. Sweet cream BM from industrial churning was skimmed before MF with 0.2-µm ceramic membranes at 55 to 58°C. The fractionations of BM and SM were performed under the same conditions using the same process, and the whey protein fractions from BM and SM were concentrated by ultrafiltration and diafiltration. The ultrafiltration and diafiltration was performed at 50°C using pasteurized tap water and a membrane with a 20-kDa cut-off to retain as little lactose as possible in the final WPC powders. The ultrafiltrates were subsequently spray dried, and their functional properties and chemical compositions were compared. The amounts of whey protein and PL in the WPC powder from BM (BMWPC) were comparable to the amounts found in the WPC from SM (SMWPC); however, the composition of the PL classes differed. The BMWPC contained less total protein, casein, and lactose compared with SMWPC, as well as higher contents of fat and citric acid. No difference in protein solubility was observed at pH values of 4.6 and 7.0, and the overrun was the same for BMWPC and SMWPC; however, the BMWPC made less stable foam than SMWPC.

Molecular characterization of whey protein hydrolysate fractions with ferrous chelating and enhanced iron solubility capabilities

The ferrous (Fe2+) chelating capabilities of WPI hydrolysate fractions produced via cascade membrane filtration were investigated, specifically 1 kDa permeate (P) and 30 kDa retentate (R) fractions. The 1 kDa-P possessed a Fe2+ chelating capability at 1 g L(-1) equivalent to 84.4 μM EDTA (for 30 kDa-R the value was 8.7 μM EDTA). Fourier transformed infrared (FTIR) spectroscopy was utilized to investigate the structural characteristics of hydrolysates and molecular interactions with Fe2+. Solid-phase extraction was employed to enrich for chelating activity; the most potent chelating fraction was enriched in histidine and lysine. The solubility of ferrous sulfate solutions (10 mM) over a range of pH values was significantly (P<0.05) improved in dispersions of hydrolysate fraction solutions (10 g protein L(-1)). Total iron solubility was improved by 72% in the presence of the 1 kDa-P fraction following simulated gastrointestinal digestion (SGID) compared to control FeSO4·7H2O solutions.

Exosomes from breast milk inhibit HIV-1 infection of dendritic cells and subsequent viral transfer to CD4+ T cells

OBJECTIVE

To investigate whether exosomes derived from human breast milk or plasma confer protection against HIV-1 infection of monocyte-derived dendritic cells (MDDCs) and subsequent viral transfer to CD4 T cells.

DESIGN

MDDCs were generated and milk and plasma-derived exosomes were isolated from healthy donors. To determine the capacity of exosomes to inhibit HIV-1 infection, MDDCs were preincubated with exosomes before exposure to HIV-1BaL. To investigate transfer of HIV-1 from MDDCs to CD4 T cells, MDDCs preincubated with exosomes and HIV-1BaL were cocultured with allogeneic CD4 T cells. To explore receptors used by MDDCs for binding of exosomes, blocking experiments were performed.

METHODS

Productive HIV-1 infection was analysed in MDDCs and CD4 T cells by determining p24 expression by flow cytometry. Confocal microscopy and flow cytometry was used to investigate uptake of fluorescently labelled exosomes by MDDCs.

RESULTS

Milk exosomes, but not plasma exosomes, bind MDDCs via DC-SIGN inhibiting HIV-1 infection of MDDCs and subsequent viral transfer to CD4 T cells.

CONCLUSION

We propose that milk exosomes act as a novel protective factor against vertical transmission of HIV-1 by competing with HIV-1 for binding to DC-SIGN on MDDCs.

In vivo digestion of bovine milk fat globules: effect of processing and interfacial structural changes. I. Gastric digestion

The aim was to study the in vivo gastric digestion of fat globules in bovine cream from raw, pasteurised or pasteurised and homogenised milk. Fasted rats were gavaged once and chyme samples were collected after 30, 120 and 180 min post-gavage. Proteins from raw (RC) and pasteurised (PC) creams appeared to be digested faster and to a greater extent. Free fatty acids (FAs) increased throughout the 3h postprandial period. Short and medium chain FAs were released more rapidly than long chain FAs which were hydrolysed to a greater degree from PC. The size of the fat globules of all creams increased in the stomach. Protein aggregates were observed in pasteurised and homogenised cream chyme. Protrusions, probably caused by the accumulation of insoluble lipolytic products, appeared at the surface of the globules in RC and PC chyme. Overall, PC proteins and lipids appeared to be digested to a greater extent.

In vivo digestion of bovine milk fat globules: effect of processing and interfacial structural changes. II. Upper digestive tract digestion

The aim of this research was to study the effect of milk processing on the in vivo upper digestive tract digestion of milk fat globules. Fasted rats were serially gavaged over a 5h period with cream from raw, pasteurised, or pasteurised and homogenised milk. Only a few intact dietary proteins and peptides were present in the small intestinal digesta. Significantly (P<0.05) more longer chain (C≥10) fatty acids were present in the digesta of rats gavaged with raw (448 mg g(-1) digesta dry matter (DDM)) and homogenised creams (528 mg g(-1) DDM), as compared to pasteurised and homogenised cream (249 mg g(-1) DDM). Microscopy techniques were used to investigate the structural changes during digestion. Liquid-crystalline lamellar phases surrounding the fat globules, fatty acid soap crystals and lipid-mucin interactions were evident in all small intestinal digesta. Overall, the pasteurised and homogenised cream appeared to be digested to a greater extent.

Consumption of human milk glycoconjugates by infant-associated bifidobacteria: mechanisms and implications

Human milk is a rich source of nutrients and energy, shaped by mammalian evolution to provide all the nutritive requirements of the newborn. In addition, several molecules in breast milk act as bioactive agents, playing an important role in infant protection and guiding a proper development. While major breast milk nutrients such as lactose, lipids and proteins are readily digested and consumed by the infant, other molecules, such as human milk oligosaccharides and glycosylated proteins and lipids, can escape intestinal digestion and transit through the gastrointestinal tract. In this environment, these molecules guide the composition of the developing infant intestinal microbiota by preventing the colonization of enteric pathogens and providing carbon and nitrogen sources for other colonic commensals. Only a few bacteria, in particular Bifidobacterium species, can gain access to the energetic content of milk as it is displayed in the colon, probably contributing to their predominance in the intestinal microbiota in the first year of life. Bifidobacteria deploy exquisite molecular mechanisms to utilize human milk oligosaccharides, and recent evidence indicates that their activities also target other human milk glycoconjugates. Here, we review advances in our understanding of how these microbes have been shaped by breast milk components and the strategies associated with their consumption of milk glycoconjugates.