Variants of β-casofensin, a bioactive milk peptide, differently modulate the intestinal barrier: In vivo and ex vivo studies in rats.

β-Casofensin is a bioactive milk peptide that modulates the intestinal barrier, particularly through its action on goblet cells. β-Casofensin corresponds to fragment (f) 94-123 of the bovine β-casein (β-CN) A2 variant. Fifteen genetic variants of bovine β-CN (A1-3, B-G, H1-2, I-L) are known, of which the A2, A1, and B forms are the most common.

Protective effects of β-casofensin, a bioactive peptide from bovine β-casein, against indomethacin-induced intestinal lesions in rats.

Scope: β-casofensin, also known as peptide β-CN(94-123), is a milk bioactive peptide that modulates the intestinal barrier through its action on goblet cells. Here, we evaluated whether oral administration of β-casofensin can prevent indomethacin-induced injury of the jejunum in rats.

Methods And Results: Rats received β-casofensin (0.

The membrane-associated form of α(s1)-casein interacts with cholesterol-rich detergent-resistant microdomains.

Caseins, the main milk proteins, interact with colloidal calcium phosphate to form the casein micelle. The mesostructure of this supramolecular assembly markedly influences its nutritional and technological functionalities. However, its detailed molecular organization and the cellular mechanisms involved in its biogenesis have been only partially established.

β-Casein(94-123)-derived peptides differently modulate production of mucins in intestinal goblet cells.

We recently reported the identification of a peptide from yoghurts with promising potential for intestinal health: the sequence (94-123) of bovine β-casein. This peptide, composed of 30 amino acid residues, maintains intestinal homoeostasis through production of the secreted mucin MUC2 and of the transmembrane-associated mucin MUC4. Our study aimed to search for the minimal sequence responsible for the biological activity of β-CN(94-123) by using several strategies based on (i) known bioactive peptides encrypted in β-CN(94-123), (ii) in silico prediction of peptides reactivity and (iii) digestion of β-CN(94-123) by enzymes of intestinal brush border membranes.

Milk protein fractions moderately extend the duration of satiety compared with carbohydrates independently of their digestive kinetics in overweight subjects.

Digestive kinetics are believed to modulate satiety through the modulation of nutrient delivery. We hypothesised that the duration of satiety could be extended by modulating the kinetics of dietary amino acid delivery in overweight subjects, using snacks containing casein and whey protein. In the present study, eighty-two subjects underwent a first satiety test where they received a control snack containing 60 g maltodextrin.

Sequential release of milk protein-derived bioactive peptides in the jejunum in healthy humans.

Background: The digestive hydrolysis of dietary proteins leads to the release of peptides in the intestinal tract, where they may exert a variety of functions, but their characterization and quantification are difficult.

Objectives: We aimed to characterize and determine kinetics of the formation of peptides present in the jejunum of humans who ingested casein or whey proteins by using mass spectrometry and to look for and quantify bioactive peptides.

Design: Subjects were equipped with a double-lumen nasogastric tube that migrated to the proximal jejunum.

A novel bioactive peptide from yoghurts modulates expression of the gel-forming MUC2 mucin as well as population of goblet cells and Paneth cells along the small intestine.

Several studies demonstrated that fermented milks may provide a large number of bioactive peptides into the gastrointestinal tract. We previously showed that beta-casomorphin-7, an opioid-like peptide produced from bovine β-casein, strongly stimulates intestinal mucin production in ex vivo and in vitro models, suggesting the potential benefit of milk bioactive peptides on intestinal protection. In the present study, we tested the hypothesis that the total peptide pool (TPP) from a fermented milk (yoghurt) may act on human intestinal mucus-producing cells (HT29-MTX) to induce mucin expression.

Glucose slows down the heat-induced aggregation of β-lactoglobulin at neutral pH.

The behavior of β-lactoglobulin (β-Lg) during heat treatments depends on the environmental conditions. The influence of the presence or absence of a reducing sugar, namely, glucose, on the modification of the protein during heating has been studied using fluorescence, polyacrylamide gel electrophoresis (PAGE), size-exclusion chromatography (SEC), and transmission electron microscopy. Glycated products were formed during heating 24 h at 90 °C and pH 7.

Topography of the casein micelle surface by surface plasmon resonance (SPR) using a selection of specific monoclonal antibodies.

Several theoretical models of the casein micelle structure have been proposed in the past, but the exact organization of the four individual caseins (α(s1), α(s2), β, and κ) within this supramolecular structure remains unknown. The present study aims at determining the topography of the casein micelle surface by following the interaction between 44 monoclonal antibodies specific for different epitopes of α(s1)-, α(s2)-, β-, and κ-casein and the casein micelle in real time and no labeling using a surface plasmon resonance (SPR)-based biosensor. Although the four individual caseins were found to be accessible for antibody binding, data confirmed that the C-terminal extremity of κ-casein was highly accessible and located at the periphery of the structure.

AlphaS1-casein, which is essential for efficient ER-to-Golgi casein transport, is also present in a tightly membrane-associated form.

Background: Caseins, the main milk proteins, aggregate in the secretory pathway of mammary epithelial cells into large supramolecular structures, casein micelles. The role of individual caseins in this process and the mesostructure of the casein micelle are poorly known.

Results: In this study, we investigate primary steps of casein micelle formation in rough endoplasmic reticulum-derived vesicles prepared from rat or goat mammary tissues.

Food processing increases casein resistance to simulated infant digestion.

The objective of this study was to determine whether processing could modify the resistance of casein (CN) to digestion in infants. A range of different dairy matrices was manufactured from raw milk in a pilot plant and subjected to in vitro digestion using an infant gut model. Digestion products were identified using MS and immunochemical techniques.

Phosphorylation and coordination bond of mineral inhibit the hydrolysis of the beta-casein (1-25) peptide by intestinal brush-border membrane enzymes.

Caseinophosphopeptides (CPP) are food mineral-rich components that may resist intestinal enzyme hydrolysis. We wondered whether phosphorylation and/or mineral binding induces resistance of CPP to intestinal hydrolysis. We used intestinal brush-border membrane vesicles to digest different forms of the beta-casein (1-25) peptide: unphosphorylated and phosphorylated carrier of varied cations.

The (193-209) 17-residues peptide of bovine β-casein is transported through Caco-2 monolayer.

Although the bioavailability of large peptides with biological activity is of great interest, the intestinal transport has been described for peptides up to only nine residues. β-casein (β-CN, 193-209) is a long and hydrophobic peptide composed of 17 amino acid residues (molecular mass 1881 Da) with immunomodulatory activity. The present work examined the transport of the β-CN (193-209) peptide across Caco-2 cell monolayer.

Comparative resistance of food proteins to adult and infant in vitro digestion models.

IgE-mediated allergy to milk and egg is widespread in industrialised countries and mainly affects infants and young children. It may be connected to an incomplete digestion of dietary proteins causing an inappropriate immune response in the gut. In order to study this, a biochemical model of infant gastroduodenal digestion has been developed, which has reduced levels of protease (eightfold for pepsin and tenfold for trypsin and chymotrypsin), phosphatidylcholine and bile salts, compared with the adult model.

Comparison of electrospray and matrix-assisted laser desorption ionization on the same hybrid quadrupole time-of-flight tandem mass spectrometer: application to bidimensional liquid chromatography of proteins from bovine milk fraction.

Recently, two ionization sources, electrospray (ESI) and matrix-assisted laser desorption (MALDI) have been used in parallel to exploit their complementary nature and to increase proteome coverage. In this study, a method using bidimensional (2D) nanoLC coupled online with ESI quadrupole time-of-flight (Q-TOF) with the simultaneous collection of fractions for analyses by LC-MALDI Q-TOF-MS/MS was developed. A total of 39 bovine proteins were identified to a high degree of confidence.

Identification in milk of a serum amyloid A peptide chemoattractant for B lymphoblasts.

Background: Normal mammary gland contains an extravascular population of B lymphoblasts, precursors of the immunoglobulin plasma cells that play a key role in the passive protection of neonates by secreting immunoglobulins to colostrum and milk. We investigated the presence of chemoattractants in the milk by analysing the chemoattractant activity of various fractions of this secretion. Milk chemoattractants are potentially involved in the recruitment of lymphocytes from the maternal bloodstream in lactating mammary glands.

Ultra high temperature treatment, but not pasteurization, affects the postprandial kinetics of milk proteins in humans.

Although the chemical and physical modifications to milk proteins induced by technological treatments have been characterized extensively, their nutritional consequences have rarely been assessed in humans. We measured the effect of 2 technological treatments on the postprandial utilization of milk nitrogen (N), pasteurization (PAST) and ultra high temperature (UHT), compared with microfiltration (MF), using a sensitive method based on the use of milk proteins intrinsically labeled with (15)N. Twenty-five subjects were studied after a 1-wk standardization of their diet.

Epitope characterization of a supramolecular protein assembly with a collection of monoclonal antibodies: the case of casein micelle.

In milk, kappa-, beta-, alphas(1)- and alphas(2)-casein (CN) are associated into a supramolecular assembly, the micelle. In this work, CN micelles contained in fresh skim milk were used to produce over 100 monoclonal antibodies. The specificity of these probes was determined using libraries of synthetic peptides and peptides fractionated from tryptic hydrolysis of purified CNs.

Glycosylations of kappa-casein-derived caseinomacropeptide reduce its accessibility to endo- but not exointestinal brush border membrane peptidases.

Caseinomacropeptide (CMP) is a peptide obtained from kappa-casein hydrolysis by gastric proteinases and which exhibits various biological activities. The aim of this study was to analyze the intestinal processing of CMP at the brush border membrane (BBM) level. Intestinal BBM vesicles (BBMV) were used to digest glycosylated and unglycosylated CMP.

Kinetics of fibril formation of bovine kappa-casein indicate a conformational rearrangement as a critical step in the process.

S-carboxymethylated (SCM) kappa-casein forms in vitro fibrils that display several characteristics of amyloid fibrils, although the protein is unrelated to amyloid diseases. In order to get insight into the processes that prevent the formation of amyloid fibrils made of kappa-caseins in milk, we have characterized in detail the reaction and the roles of its possible effectors: glycosylation and other caseins. Given that native kappa-casein occurs as a heterogeneous mixture of carbohydrate-free and carbohydrate-containing chains, kinetics of fibril formation were performed on purified glycosylated and unglycosylated SCM kappa-caseins using the fluorescent dye thioflavin T in conjunction with transmission electron microscopy and Fourier transform infrared spectroscopy for morphological and structural analyses.

Effects of the environmental factors on the casein micelle structure studied by cryo transmission electron microscopy and small-angle x-ray scattering/ultrasmall-angle x-ray scattering.

Casein micelles are colloidal protein-calcium-transport complexes whose structure has not been unequivocally elucidated. This study used small-angle x-ray scattering (SAXS) and ultrasmall angle x-ray scattering (USAXS) as well as cryo transmission electron microscopy (cryo-TEM) to provide fine structural details on their structure. Cryo-TEM observations of native casein micelles fractionated by differential centrifugation showed that colloidal calcium phosphate appeared as nanoclusters with a diameter of about 2.

Compared with casein or total milk protein, digestion of milk soluble proteins is too rapid to sustain the anabolic postprandial amino acid requirement.

Background: The in vivo quality of milk protein fractions has seldom been studied in humans.

Objective: Our objective was to compare the postprandial utilization of dietary nitrogen from 3 [(15)N]-labeled milk products: micellar caseins (MC), milk soluble protein isolate (MSPI), and total milk protein (TMP).

Design: The macronutrient intakes of 23 healthy volunteers were standardized for 1 wk, after which time the subjects ingested a meal containing MC (n = 8), MSPI (n = 7), or TMP (n = 8).