Immunoenhancing effects of bovine glycomacropeptide and its derivatives on the proliferative response and phagocytic activities of human macrophagelike cells, U937

Glycomacropeptide: A comprehensive understanding of its major biological characteristics and purification methodologies

Glycomacropeptide (GMP) is a bioactive peptide derived from whey protein, consisting of 64 amino acids. It is a phenylalanine-free peptide, making it a beneficial dietary option for individuals dealing with phenylketonuria (PKU). PKU is an inherited metabolic disorder characterized by high levels of phenylalanine in the bloodstream, resulting from a deficiency of phenylalanine dehydrogenase in affected individuals. Consequently, patients with PKU require lifelong adherence to a low-phenylalanine diet, wherein a significant portion of their protein intake is typically sourced from a phenylalanine-free amino acid formula. GMP has several nutritional values, numerous bioactivity properties, and therapeutic effects in various inflammatory disorders. Despite all these features, the purification of GMP is an imperative requirement; however, there are no unique methods for achieving this goal. Traditionally, several methods have been used for GMP purification, such as thermal or acid treatment, alcoholic precipitation, ultrafiltration (UF), gel filtration, and membrane separation techniques. However, these methods have poor specificity, and the presence of large amounts of impurities can interfere with the analysis of GMP. More efficient and highly specific GMP purification methods need to be developed. In this review, we have highlighted and summarized the current research progress on the major biological features and purification methodologies associated with GMP, as well as providing an extensive overview of the recent developments in using charged UF membranes for GMP purification and the influential factors.

Peptidome comparison on the immune regulation effects of different casein fractions in a cyclophosphamide mouse model

The protein composition of human milk plays a crucial role in infant formula milk powder formulation. Notably, significant differences exist between bovine casein and human milk casein. Previous studies have shown that casein hydrolysates could enhance immune function; however, gastrointestinal dyspepsia in infants affects the type and function of peptides. Therefore, the present study used peptidomics to sequence and analyze hydrolyzed peptides from different casein fractions. Additionally, animal experiments were conducted to assess the functionality of these casein fractions and elucidate their differences. The results revealed variations in peptide composition among the different casein fractions of formula milk powder. Interestingly, milk powder formulated with both β- and κ-casein (BK) exhibited significant enrichment of peptides related to the immune system. Moreover, the BK group significantly alleviated immune organ damage in cyclophosphamide-treated mice and regulated serum levels of pro-inflammatory and anti-inflammatory factors. Furthermore, feeding different casein fractions influenced the intestinal microflora of cyclophosphamide-treated mice, with the BK group mitigating the changes caused by cyclophosphamide. In conclusion, the findings suggest that BK formula in milk powder has the potential to positively enhance immunity. This study provides a robust theoretical basis for human-emulsified formula milk powder development.

Macrophage-Immunomodulatory Actions of Bovine Whey Protein Isolate, Glycomacropeptide, and Their In Vitro and In Vivo Digests

Whey protein isolate (WPI) consists of an array of proteins and peptides obtained as a byproduct of the cheesemaking process. Research suggests that WPI, along with its peptides such as glycomacropeptide (GMP), possesses immunomodulatory properties. These properties hold potential for alleviating the adverse effects of inflammatory conditions such as inflammatory bowel disease. Although promising, the immunoregulatory properties of the digested forms of WPI and GMP-those most likely to interact with the gut immune system-remain under-investigated. To address this knowledge gap, the current study examined the effects of in vitro-digested WPI and GMP, in vivo-digested WPI, and undigested WPI and GMP on the secretion of pro-inflammatory cytokines (TNF-α and IL-1β) in lipopolysaccharide-stimulated macrophage-like cells. Our results indicate that digested WPI and GMP reduced the expression of TNF-α and IL-1β, two pro-inflammatory cytokines. Whole WPI had no effect on TNF-α but reduced IL-1β levels. In contrast, in vivo-digested WPI reduced TNF-α but increased IL-1β. Undigested GMP, on the other hand, increased the secretion of both cytokines. These results demonstrate that digestion greatly modifies the effects of WPI and GMP on macrophages and suggest that digested WPI and GMP could help mitigate gastrointestinal inflammation. Further clinical studies are necessary to determine the biological relevance of WPI and GMP digestion products within the gut and their capacity to influence gut inflammation.

Preventative and therapeutic potential of animal milk components against COVID-19: A comprehensive review

The global pandemic of COVID-19 is considered one of the most catastrophic events on earth. During the pandemic, food ingredients may play crucial roles in preventing infectious diseases and sustaining people's general health and well-being. Animal milk acts as a super food since it has the capacity to minimize the occurrence of viral infections due to inherent antiviral properties of its ingredients. SARS-CoV-2 virus infection can be prevented by immune-enhancing and antiviral properties of caseins, α-lactalbumin, β-lactoglobulin, mucin, lactoferrin, lysozyme, lactoperoxidase, oligosaccharides, glycosaminoglycans, and glycerol monolaurate. Some of the milk proteins (i.e., lactoferrin) may work synergistically with antiviral medications (e.g., remdesivir), and enhance the effectiveness of treatment in this disease. Cytokine storm during COVID-19 can be managed by casein hydrolyzates, lactoferrin, lysozyme, and lactoperoxidase. Thrombus formation can be prevented by casoplatelins as these can inhibit human platelet aggregation. Milk vitamins (i.e., A, D, E, and B complexes) and minerals (i.e., Ca, P, Mg, Zn, and Se) can have significantly positive effects on boosting the immunity and health status of individuals. In addition, certain vitamins and minerals can also act as antioxidants, anti-inflammatory, and antivirals. Thus, the overall effect of milk might be a result of synergistic antiviral effects and host immunomodulator activities from multiple components. Due to multiple overlapping functions of milk ingredients, they can play vital and synergistic roles in prevention as well as supportive agents during principle therapy of COVID-19.

Protective Effect of Glycomacropeptide on the Inflammatory Response of U937 Macrophages

Macrophages play crucial roles in inflammation and oxidative stress associated with noncommunicable diseases, such as cardiovascular diseases, diabetes, and cancer. Glycomacropeptide (GMP) is a bioactive peptide derived from milk κ-casein that contains abundant sialic acid and has shown anti-inflammatory, antioxidative, anti-obesity, and anti-diabetic properties when is orally administered. The aim of this study was to evaluate the effect of GMP on the regulation of the inflammatory response in human macrophages and the participation of sialic acid in this activity. GMP pretreatment decreased by 35%, 35%, and 49% the production of nitrites, interleukin (IL)-1β, and tumor necrosis factor (TNF)-α, respectively, in activated human macrophages U937. The same effect was obtained when cells were pretreated with asialo GMP, and no change on the gene expression of the lectins associated with the recognition of sialic acids, SIGLEC5, 7, and 9, was induced by GMP on macrophages, which suggests that sialic acid might not be involved in this immunoregulatory effect. Interestingly, GMP increased 8.9- and 3.5-fold the gene expression of the canonical anti-inflammatory protein SOCS3 and the antioxidant enzyme HMOX1, respectively, in U937 cells. Thus, GMP exerts anti-inflammatory and antioxidative activities on activated macrophages in a sialic acid-independent manner, which might be related to its in vivo reported bioactivity.

Lactose and Casein Cause Changes on Biomarkers of Oxidative Damage and Dysbiosis in an Experimental Model of Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Experimental Autoimmune Encephalomyelitis (EAE) in rats closely reproduces Multiple Sclerosis (MS), a disease characterized by neuroinflammation and oxidative stress that also appears to extend to other organs and their compartments. The origin of MS is a matter for discussion, but it would seem that altering certain bacterial populations present in the gut may lead to a proinflammatory condition due to the bacterial Lipopolysaccharides (LPS) in the so-called brain-gut axis. The casein and lactose in milk confer anti-inflammatory properties and immunomodulatory effects. The objectives of this study were to evaluate the effects of administration of casein and lactose on the oxidative damage and the clinical status caused by EAE and to verify whether both casein and lactose had any effect on the LPS and its transport protein -LBP-.

METHODS

Twenty male Dark Agouti rats were divided into control rats (control), EAE rats, and EAE rats, to which casein and lactose, EAE+casein, and EAE+lactose, respectively, were administered. Fifty-one days after casein and lactose administration, the rats were sacrificed, and different organs were studied (brain, spinal cord, blood, heart, liver, kidney, small, and large intestine). In the latter, products derived from oxidative stress were studied (lipid peroxides and carbonylated proteins) as well as the glutathione redox system, various inflammation factors (total nitrite, Nuclear Factor-kappa B p65, the Rat Tumour Necrosis Factor-α), and the LPS and LBP values.

RESULTS AND CONCLUSION

Casein and lactose administration improved the clinical aspect of the disease at the same time as reducing inflammation and oxidative stress, exerting its action on the glutathione redox system, or increasing GPx levels.

Top-Down Glycopeptidomics Reveals Intact Glycomacropeptide Is Digested to a Wide Array of Peptides in Human Jejunum

BACKGROUND

Bovine milk κ-casein-derived caseinomacropeptide (CMP) is produced in large quantities during cheese-making and has various biological activities demonstrated via in vitro and in vivo experiments. Previous studies examined protein degradation and peptide release after casein or whey protein consumption. However, whether purified intact CMP that is partially glycosylated survives intact to its presumed site of bioactivity within the gut remains unknown.

OBJECTIVES

The aim of this study was to determine the extent to which purified intact CMP (including glycosylated forms) is digested into peptide fragments within the jejunum of healthy human adults after consumption.

METHODS

Jejunal fluids were collected from 3 adult participants (2 men and 1 woman, age: 27 ± 7 y; BMI: 23 ± 1 kg/m2) for 3 h after consuming 37.5 g of purified intact CMP. CMP and CMP-derived peptides were isolated from the collected jejunal fluids by ethanol precipitation and solid-phase extraction and identified by MS-based top-down glycopeptidomics. Relative abundances of CMP and CMP-derived peptides were compared qualitatively between the feed and the jejunal fluids.

RESULTS

Intact CMP was dominant in feeding material, accounting for 90% of the total ion abundance of detected peptides, and in very low abundance (<2%) in the jejunal fluids. CMP-derived fragment peptides ranging from 11 to 20 amino acids in length were predominant (accounting for 68-88% of the total peptide ion abundance) in jejunal fluids during 1-3 h post consumption.

CONCLUSIONS

This study demonstrates that intact CMP (including glycosylated forms) is mostly digested in the human jejunum, releasing a wide array of CMP-derived peptide fragments. Some of the CMP-derived peptides with high homology to known bioactive peptides consistently survived across 3 h of digestion. Therefore, future research should examine the biological effects of the partially digested form-the CMP-derived fragments-rather than those of intact CMP.

Glycomacropeptide Prevents Iron/Ascorbate-Induced Oxidative Stress, Inflammation and Insulin Sensitivity with an Impact on Lipoprotein Production in Intestinal Caco-2/15 Cells

Background. Metabolic Syndrome (MetS), a major worldwide concern for the public health system, refers to a cluster of key metabolic components, and represents a risk factor for diabetes and cardiovascular diseases. As oxidative stress (OxS) and inflammation are the major triggers of insulin sensitivity (IS), a cardinal MetS feature, the principal aim of the present work is to determine whether glycomacropeptide (GMP), a milk-derived bioactive peptide, exerts beneficial effects on their expression. Methods. Fully differentiated intestinal Caco-2/15 cells are used to evaluate the preventive action of 2 mg/mL GMP against OxS and inflammation induced by the mixture iron-ascorbate (Fe/Asc) (200 μM:2 mM). The potency of GMP of decreasing the production of lipoproteins, including chylomicrons (CM), very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) is also assessed. Results. The administration of GMP significantly reduces malondialdehyde, a biomarker of lipid peroxidation, and raises superoxide dismutase 2 and glutathione peroxidase via the induction of the nuclear factor erythroid 2–related factor 2, a transcription factor, which orchestrates cellular antioxidant defenses. Similarly, GMP markedly lowers the inflammatory agents tumor necrosis factor-α and cyclooxygenase-2 via abrogation of the nuclear transcription factor-kB. Moreover, GMP-treated cells show a down-regulation of Fe/Asc-induced mitogen activated protein kinase pathway, suggesting greater IS. Finally, GMP decreases the production of CM, VLDL, and LDL. Conclusions. Our results highlight the effectiveness of GMP in attenuating OxS, inflammation and lipoprotein biogenesis, as well as improving IS, the key components of MetS. Further investigation is needed to elucidate the mechanisms mediating the preventive action of GMP.

Immunomodulatory significance of natural peptides in mammalians: Promising agents for medical application

Modulation of immune responses by immunoregulatory agents, such as the natural or synthetic immunomodulatory peptides, has been suggested as a potential strategy to modulate immune system against infection and other immune-related diseases. These compositionally simple peptides have attracted much attention for many drug developers, due to their high activity, low toxicity and clear target specificity. Host defence peptides and milk-derived peptides are two kinds of natural immunomodulatory peptides which have been widely studied in mammalians. They could participate at the interface of innate and adaptive immunity by regulating immune effector cells. This review summarizes the recent advances in host defence peptides and milk-derived peptides as well as their general characteristics, immunomodulatory functions and possible applications.

Bovine κ-Casein Fragment Induces Hypo-Responsive M2-Like Macrophage Phenotype

Immunomodulatory nutraceuticals have garnered special attention due to their therapeutic potential for the amelioration of many chronic inflammatory conditions. Macrophages are key players in the induction, propagation and resolution of inflammation, actively contributing to the pathogenesis and resolution of inflammatory disorders. As such, this study aimed to investigate the possible therapeutic effects bovine casein derived nutraceuticals exert on macrophage immunological function. Initial studies demonstrated that sodium caseinate induced a M2-like macrophage phenotype that was attributed to the kappa-casein subunit. Kappa-casein primed macrophages acquired a M2-like phenotype that expressed CD206, CD54, OX40L, CD40 on the cell surface and gene expression of Arg-1, RELM-α and YM1, archetypical M2 markers. Macrophages stimulated with kappa-casein secreted significantly reduced TNF-α and IL-10 in response to TLR stimulation through a mechanism that targeted the nuclear factor-κB signal transduction pathway. Macrophage proteolytic processing of kappa-casein was required to elicit these suppressive effects, indicating that a fragment other than C-terminal fragment, glycomacropeptide, induced these modulatory effects. Kappa-casein treated macrophages also impaired T-cell responses. Given the powerful immuno-modulatory effects exhibited by kappa-casein and our understanding of immunopathology associated with inflammatory diseases, this fragment has the potential as an oral nutraceutical and therefore warrants further investigation.

Glycomacropeptide Bioactivity and Health: A Review Highlighting Action Mechanisms and Signaling Pathways

Food-derived bioactive peptides are reported as beneficial and safe for human health. Glycomacropeptide (GMP) is a milk-protein-derived peptide that, in addition to its nutritional value, retains many biological properties and has therapeutic effects in several inflammatory disorders. GMP was shown under in vitro and in vivo conditions to exert a number of activities that regulate the physiology of important body systems, namely the gastrointestinal, endocrine, and immune systems. This review represents a comprehensive compilation summarizing the current knowledge and updated information on the major biological properties associated with GMP. GMP bioactivity is addressed with special attention on mechanisms of action, signaling pathways involved, and structural characteristics implicated. In addition, the results of various studies dealing with the effects of GMP on models of inflammatory diseases are reviewed and discussed.

Novel Mechanisms Underlying the Therapeutic Effect of Glycomacropeptide on Allergy: Change in Gut Microbiota, Upregulation of TGF-β, and Inhibition of Mast Cells

BACKGROUND

The prevalence of allergic diseases is globally increasing. We have previously described that glycomacropeptide (GMP), a bioactive milk peptide, has therapeutic value in experimental models of skin hypersensitivity, anaphylaxis, and asthma, as it prevents an excessive T helper type 2 cell immune response. The aim of this study was to analyze the effect of GMP on key elements directly involved in the development or control of allergy, in order to improve the precise knowledge about its mechanism of action.

METHODS

Rats were systemically sensitized with ovalbumin and orally treated with GMP. Levels of Lactobacillus, Bifidobacterium, and Bacteroides were analyzed in their feces. Splenocytes were isolated and the production of transforming growth factor (TGF)-β by allergens was measured. Intradermal skin reactions were developed to evaluate in vivo activation of mast cells. Peritoneal mast cells were isolated and activated by the allergen, and histamine secretion was determined.

RESULTS

GMP administration increased the amount of intestinal Lactobacillus and Bifidobacterium of allergen-sensitized animals after 3 days of treatment. The increase in Bacteroides was also significant, but only after 17 days of GMP administration. Ten days after treatment cessation, Lactobacillus and Bacteroides were still elevated. GMP intake also elevated the production of TGF-β in the splenocytes of sensitized animals. In addition, treatment with GMP attenuated mast cell activation by the allergen and inhibited histamine secretion, without affecting the number of mast cells.

CONCLUSIONS

The prebiotic action of GMP on allergy-protective microbiota, an increase in TGF-β production, and a reduction in mast cell response to allergens are novel mechanisms that explain the antiallergic activity of GMP.

Food-derived immunomodulatory peptides

Food proteins contain specific amino acid sequences within their structures that may positively impact bodily functions and have multiple immunomodulatory effects. The functional properties of these specific sequences, also referred to as bioactive peptides, are revealed only after the degradation of native proteins during digestion processes. Currently, milk proteins have been the most explored source of bioactive peptides, which presents an interesting opportunity for the dairy industry. However, plant- and animal-derived proteins have also been shown to be important sources of bioactive peptides. This review summarizes the in vitro and in vivo evidence of the role of various food proteins as sources of immunomodulatory peptides and discusses the possible pathways involving these properties. © 2016 Society of Chemical Industry.

Casein glycomacropeptide for active distal ulcerative colitis: a randomized pilot study

BACKGROUND

In ulcerative colitis (UC), dietary supplements may have anti-inflammatory properties and improve disease course. We investigated the effects of casein glycomacropeptide (CGMP), a fraction of bovine whey protein, in active UC.

MATERIALS AND METHODS

In a randomized open-label intervention study, 24 patients with active UC involving 10-40 cm of the distal colon were randomized in a 2 : 1 ratio into two groups. The first group was administered their usual treatment plus a daily supplement of CGMP 30 g, and the second group was administered a dose escalation to 4800 mg oral mesalamine daily (standard treatment) for 4 weeks. Clinical, endoscopic, mucosal and circulating disease activity markers were monitored. Acceptance of and adherence to CGMP up to 8 weeks were documented.

RESULTS

After 4 weeks of treatment, 10 of 16 (63%) patients who received CGMP had an unchanged or decreased Simple Clinical Colitis Activity Index (SCCAI), which was similar to the four of eight (50%) (P = 0·67) patients on the standard treatment. The number of patients in which SCCAI decreased by three or more did not differ between the two groups: nine of 16 (56%) in the CGMP group vs. four of eight (50%) in the standard treatment group (P = 0·77). Changes in disease extent and severity were similar between the two groups. CGMP was well tolerated and accepted by the patients.

CONCLUSIONS

The addition of CGMP as a nutritional therapy to standard treatment was safe and accepted by patients with active distal UC. The disease-modifying effect of CGMP was similar to that of the mesalamine dose escalation.

Structure Characterization and Immunomodulating Effects of Polysaccharides Isolated from Dendrobium officinale

A crude polysaccharide fraction (cDOP) has been determined to be the characteristic marker of Dendrobium officinale, an expensive tea material in Asia, but its chemistry and bioactivity have not been studied. In work reported here, cDOP was destarched (DOP, 90% yield) and separated into two subfraction polysaccharides, DOPa and DOPb, which were characterized by monosaccharide composition and methylation analyses and spectral analyses (FT-IR and (1)H and (13)C NMR). Both are composed of mannose and glucose at similar ratios and have a similar structure with a backbone of 1,4-linked β-D-mannopyranosyl and β-D-glucopyranosyl residues. Significant differences were observed only in their molecular weights. Bioassay using mouse macrophage cell line RAW264.7 indicated that DOP and its two subfractions enhance cell proliferation, TNF-α secretion, and phagocytosis in a dose-dependent manner. They also induced the proliferation of lymphocytes alone and with mitogens. DOPa and DOPb are thus proven to be major, active polysaccharide markers of D. officinale.

Food derived bioactive peptides and intestinal barrier function

A wide range of food-derived bioactive peptides have been shown to exert health-promoting actions and are therefore considered functional foods or nutraceuticals. Some of these actions are related to the maintenance, reinforcement or repairment of the intestinal barrier function (IBF) whose role is to selectively allow the absorption of water, nutrients and ions while preventing the influx of microorganisms from the intestinal lumen. Alterations in the IBF have been related to many disorders, such as inflammatory bowel disease or metabolic syndrome. Components of IBF are the intestinal epithelium, the mucus layer, secretory immunoglobulin A and cells of the innate and adaptive immune systems. Here we review the effects of food derived bioactive peptides on these IBF components. In vitro and in vivo effects, both in healthy and disease states, have been reviewed. Although limited, the available information indicates a potential for food-derived peptides to modify IBF and to contribute to disease treatment, but further research is needed to better isolate responsible peptides, and to help define their mode of action.

Structural and functional characteristics of bovine milk protein glycosylation

Most secreted and cell membrane proteins in mammals are glycosylated. Many of these glycoproteins are also prevalent in milk and play key roles in the biomodulatory properties of milk and ultimately in determining milk's nutritional quality. Although a significant amount of information exists on the types and roles of free oligosaccharides in milk, very little is known about the glycans associated with milk glycoproteins, in particular, the biological properties that are linked to their presence. The main glycoproteins found in bovine milk are lactoferrin, the immunoglobulins, glycomacropeptide, a glycopeptide derived from κ-casein, and the glycoproteins of the milk fat globule membrane. Here, we review the glycoproteins present in bovine milk, the information currently available on their glycosylation and the biological significance of their oligosaccharide chains.

Pressurized whey protein can limit bacterial burden and protein oxidation in Pseudomonas aeruginosa lung infection

BACKGROUND

Lung infection caused by Pseudomonas aeruginosa is associated with an exuberant inflammatory response, oxidative stress, and lung damage. Whey protein is a rich source of cysteine, and anti-inflammatory and immune-enhancing peptides. Anti-inflammatory and antioxidant properties of whey are augmented by hyperbaric pressure treatment. In this study, we tested whether dietary supplementation with pressurized whey protein enhances the host ability to clear P. aeruginosa infection compared with native (i.e., unpressurized) whey.

METHODS

Using a minimally invasive, non-lethal model of murine (female C57Bl/6) model of P. aeruginosa infection (mucoid strain embedded in agar beads), we studied kinetics of infection, inflammation, and oxidative stress at d 1, 3, and 7 postinfection. A parallel set of mice were fed for 4 wk a semipurified diet containing either native or pressurized whey and subsequently infected with P. aeruginosa. In these mice, the parameters mentioned previously were studied at d 1 and 3 postinfection.

RESULTS

Infection with P. aeruginosa resulted in inflammation and protein oxidation sustained beyond bacterial clearance. Animals that were fed pressurized whey had fewer bacteria at day 3 than mice on native whey. Weight loss or broncho-alveolar lavage cell content were comparable. Airway protein oxidation was attenuated, whereas airway leukocyte bacterial killing ability and oxidative burst in response to opsonized bacteria were increased in the pressurized whey-fed animals.

CONCLUSIONS

Use of nutritionally derived substances with anti-inflammatory and antioxidant properties, such as pressurized whey, aids in limiting airway bacterial infection, particularly, under conditions of ongoing oxidative stress.

Glycomacropeptide, a low-phenylalanine protein isolated from cheese whey, supports growth and attenuates metabolic stress in the murine model of phenylketonuria

Phenylketonuria (PKU) is caused by a mutation in the phenylalanine (phe) hydroxylase gene and requires a low-phe diet plus amino acid (AA) formula to prevent cognitive impairment. Glycomacropeptide (GMP) contains minimal phe and provides a palatable alternative to AA formula. Our objective was to compare growth, body composition, and energy balance in Pah(enu2) (PKU) and wild-type mice fed low-phe GMP, low-phe AA, or high-phe casein diets from 3-23 wk of age. The 2 × 2 × 3 design included main effects of genotype, sex, and diet. Fat and lean mass were assessed by dual-energy X-ray absorptiometry, and acute energy balance was assessed by indirect calorimetry. PKU mice showed growth and lean mass similar to wild-type littermates fed the GMP or AA diets; however, they exhibited a 3-15% increase in energy expenditure, as reflected in oxygen consumption, and a 3-30% increase in food intake. The GMP diet significantly reduced energy expenditure, food intake, and plasma phe concentration in PKU mice compared with the casein diet. The high-phe casein diet or the low-phe AA diet induced metabolic stress in PKU mice, as reflected in increased energy expenditure and intake of food and water, increased renal and spleen mass, and elevated plasma cytokine concentrations consistent with systemic inflammation. The low-phe GMP diet significantly attenuated these adverse effects. Moreover, total fat mass, %body fat, and the respiratory exchange ratio (CO(2) produced/O(2) consumed) were significantly lower in PKU mice fed GMP compared with AA diets. In summary, GMP provides a physiological source of low-phe dietary protein that promotes growth and attenuates the metabolic stress induced by a high-phe casein or low-phe AA diet in PKU mice.

Possible role of milk-derived bioactive peptides in the treatment and prevention of metabolic syndrome

The growing prevalence of metabolic syndrome as well as its impact on public health has garnered increased attention in recent years. As a result, metabolic syndrome is now considered one of the world's leading public health problems. Bioactive peptides deriving from milk proteins may play an important role in the prevention and treatment of metabolic syndrome and its complications via several mechanisms, such as the satiety response, the regulation of insulinemia levels and blood pressure, the uptake of free radicals, and alteration of the lipid profile. These peptides can be incorporated into functional foods or administered via nutraceuticals to decrease the risk of obesity, atherogenesis, arterial hypertension, and type 2 diabetes. Recent findings have generated considerable scientific and commercial interest in milk-derived bioactive peptides, leading to numerous publications on the effectiveness of these substances. This review summarizes the current knowledge on bioactive peptides derived from milk proteins and examines the potential value of these peptides in the treatment and prevention of metabolic syndrome and its complications.

Review: Production and functionality of active peptides from milk

In recent years, research on the production of active peptides obtained from milk and their potential functionality has grown, to a great extent. Bioactive peptides have been defined as specific protein fragments that have a positive impact on body functions or conditions, and they may ultimately have an influence on health. Individual proteins of casein or milk-derived products such as cheese and yogurt have been used as a protein source to study the isolation and activity of peptides with several applications. Currently, the milk whey waste obtained in the production of cheese also represents a protein source from which active peptides could be isolated with potential industrial applications. The active properties of milk peptides and the results found with regard to their physiological effects have led to the classification of peptides as belonging to the group of ingredients of protein nature, appropriate for use in functional foods or pharmaceutical formulations. In this study, the main peptides obtained from milk protein and the past research studies about its production and biological activities will be explained. Second, an analysis will be made on the methods to determinate the biological activities, the separation of bioactive peptides and its structure identification. All of these form the base required to obtain synthetic peptides. Finally, we explain the experimental animal and human trials done in the past years. Nevertheless, more research is required on the design and implementation of equipment for the industrial production and separation of peptides. In addition, different authors suggest that more emphasis should therefore be given to preclinical studies, proving that results are consistent and that effects are demonstrated repeatedly by several research human groups.

Proteomic characterization of specific minor proteins in the human milk casein fraction

Human milk contains many bioactive proteins that are likely to support the early development of the newborn. The aim of this study was to identify whether there are specific minor proteins associated with the human milk casein micelle prepared by the acid precipitation method. Protein identification was performed by liquid chromatography tandem mass spectrometry analysis. Eighty-two proteins were identified in the casein micelle, 18 of which are not present in their whey compartment. Thirty-two of these proteins specifically associated with the casein micelle have not previously been identified in human milk or colostrum. Proteins involved in immune function comprised the major part (28%) of total proteins, and another significant part is involved in metabolism/energy production (22%). Most of the proteins were of extracellular or cytoplasmic origin (accounting for 50 and 29%, respectively). This study indicates that various soluble proteins should be considered as part of the casein compartment, prepared by the acid precipitation method. The data provide new insight not only into the proteomic profile of the human milk casein micelle and its physiological significance, but also into the proper proportion of casein and casein-associated proteins to use in infant formula.

New insights into the immunological effects of food bioactive peptides in animal models of intestinal inflammation

Bioactive peptides have proven to be active in several conditions, including inflammatory bowel disease (IBD). This is a chronic and relapsing condition of unknown aetiology that comprises chiefly ulcerative colitis and Crohn's disease. Although there are treatments for IBD, they have frequent side effects and they are not always effective; therefore there is a need for new therapies that could alleviate this condition. Two bioactive peptides present in milk (transforming growth factor-beta (TGF-beta) and casein macropeptide, also named glycomacropeptide) have been shown to have intestinal anti-inflammatory activities. In fact, TGF-beta is currently added to formulas intended for patients with IBD, and several studies indicate that these formulas could induce clinical remission. In this paper, evidence supporting the anti-inflammatory effect of TGF-beta and bovine glycomacropeptide, as well as their mechanisms of action, is reviewed, focusing on the evidence obtained in animal models.

Invited review: physiological properties of bioactive peptides obtained from whey proteins

Processing of whey proteins yields several bioactive peptides that can trigger physiological effects in the human body: on the nervous system via their opiate and ileum-contracting activities; on the cardiovascular system via their antithrombotic and antihypertensive activities; on the immune system via their antimicrobial and antiviral activities; and on the nutrition system via their digestibility and hypocholesterolemic effects. The specific physiological effects, as well the mechanisms by which they are achieved and the stabilities of the peptides obtained from various whey fractions during their gastrointestinal route, are specifically discussed in this review.

The intestinal antiinflammatory agent glycomacropeptide has immunomodulatory actions on rat splenocytes

Bovine glycomacropeptide (GMP) is an immunologically active milk peptide that is a part of the normal human diet. GMP has therapeutic value in preclinical models of intestinal inflammation, and its mechanism may be related to effects on lymphocytes. This study focuses on the actions of GMP on rat splenocytes in vitro and in vivo. Bovine serum albumin and lactoferrin were used for comparative purposes. GMP (0.01-0.1mgmL(-1)) enhanced Concanavalin A (ConA) evoked but not basal splenocyte proliferation. At 1mgmL(-1) GMP lost this effect but augmented basal TNF-alpha secretion and also iNOS and COX2 expression. IFN-gamma, IL-2 and IL-17 were not affected by GMP in quiescent splenocytes, but IL-10 was augmented at all concentrations tested. On the other hand, GMP produced a marked inhibitory effect (70%) on IFN-gamma secretion and to a lower extent (50%) also on TNF-alpha. GMP was shown to block STAT4 but not IkappaB-alpha phosphorylation. The Treg marker Foxp3 was markedly upregulated by GMP. Bovine serum albumin had some effects on splenocyte function which were of lower magnitude and not entirely coincidental, while lactoferrin had a strong antiproliferative effect, as expected, indicating a specific effect of GMP. When administered for 3 days to normal Wistar rats, GMP reproduced the Foxp3 induction effect observed previously in vitro. This was observed in splenocytes but not in thymocytes, and only when administered by the oral rather than the intraperitoneal route. Thus our results support the hypothesis that GMP may limit intestinal inflammation acting at least in part on lymphocytes.

Bovine glycomacropeptide induces cytokine production in human monocytes through the stimulation of the MAPK and the NF-kappaB signal transduction pathways

BACKGROUND AND PURPOSE

Bovine glycomacropeptide (BGMP) is a natural milk peptide that is produced naturally in the gastrointestinal tract during digestion. Glycomacropepide has intestinal anti-inflammatory activity, but the mechanism of action is unknown. Here we have characterized the effects of BGMP on monocytes.

EXPERIMENTAL APPROACH

We have used human THP-1 cells as an in vitro monocyte model. The effect of BGMP on the secretion of tumour necrosis factor (TNF), interleukin (IL)-1beta and IL-8 was assessed, as well as the involvement of the NF-kappaB and MAP kinase signalling pathways. The stimulatory effect of BGMP was also tested in human peripheral blood monocytes.

KEY RESULTS

BGMP up-regulated the secretion of TNF, IL-1beta and IL-8 in a concentration-dependent fashion. The biological activity was exerted by the intact peptide, because cytokine secretion was not affected by protease inhibitors. The secretion of IL-8 and specially TNF and IL-1beta was blocked by PD98059, SP600125, SB203580 and Bay11-7082, suggesting the involvement of the MAP kinases p38, c-Jun N-terminal kinase and ERK and particularly the NF-kappaB pathway, although IL-8 secretion was independent of p38. BGMP was shown to elicit the phosphorylation of IkappaB-alpha and the nuclear translocation of the NF-kappaB subunits p50 and p65. The effect of BGMP on cytokine secretion was validated in human primary blood monocytes.

CONCLUSIONS AND IMPLICATIONS

BGMP stimulates human monocytes, operating via MAP kinase and NF-kappaB pathways. BGMP may exert an indirect intestinal anti-inflammatory effect by potentiating host defences against invading microorganisms.

A bovine whey protein extract can enhance innate immunity by priming normal human blood neutrophils

Bovine milk-derived products, in particular whey proteins, exhibit beneficial properties for human health, including the acquired immune response. However, their effects on innate immunity have received little attention. Neutrophils are key cells of innate defenses through their primary functions of chemotaxis, phagocytosis, oxidative burst, and degranulation. A whey protein extract (WPE) purified from bovine lactoserum was evaluated for its direct and indirect effects on these primary functions of normal human blood neutrophils in vitro. Although WPE had no direct effects on primary functions, a 24-h pretreatment of neutrophils with WPE was associated with a significant and dose-dependent increase of their chemotaxis, superoxide production, and degranulation in response to N-formyl-methionine-leucine-phenylalanine, as well as of their phagocytosis of bioparticles. The pretreatment increased the surface expression of CD11b, CD16B, and CD32A receptors. The major WPE protein components beta-lactoglobulin (beta-LG) and alpha-lactalbumin (alpha-LA) were the main active fractions having an additive effect on human neutrophils that became more responsive to a subsequent stimulation. This effect on NADPH oxidase activity was associated with translocation of p47(phox) to plasma membrane. Glycomacropeptide, a peptide present in measurable amounts in WPE products, was able to enhance the individual effect of beta-LG or alpha-LA on neutrophils. The present data suggest that WPE, through beta-LG and alpha-LA, has the capacity to enhance or "prime" human neutrophil responses to a subsequent stimulation, an effect that could be associated with increased innate defenses in vivo.

Enzymatic preparation of immunomodulating hydrolysates from soy proteins

Soy protein hydrolysates with lower molecular weight were enzymatically prepared by several commercially available proteases (Alcalase 2.4L, Flavourzyme, Trypsin, Papain, Protease A and Peptidase R) with protein recovery varied from 42.59% to 79.87%. Relative content of positively charged peptides was determined on SP Sephadex C-25 using gradient sodium chloride solution as eluents. Immunomodulating properties were evaluated by measuring their effect on in vitro proliferation of murine spleen lymphocytes and phagocytic activity of peritoneal macrophages. The results showed that soy protein hydrolysates (SPHs) prepared with Alcalase and insoluble soy protein (InSP), preferable to other enzymes and soy proteins, have the highest immunomodulating activity and the optimum conditions were determined as follows: E/S=2% (Alcalase), 60 degrees C, pH 8.0, InSP concentration 6% and 225min. Positive correlations were obtained between the immunomodulating activity and content of positively charged peptides. The results suggested that lower molecular weight and positively charged peptides released from soy protein were effective in stimulating immunomodulating activity, thus provided insights into the preparation of potent immunomodulating products.

Bovine glycomacropeptide ameliorates experimental rat ileitis by mechanisms involving downregulation of interleukin 17

BACKGROUND AND PURPOSE

Bovine glycomacropeptide (BGMP) is an inexpensive, non-toxic milk peptide with anti-inflammatory effects in rat experimental colitis but its mechanism of action is unclear. It is also unknown whether BGMP can ameliorate inflammation in proximal regions of the intestine. Our aim was therefore two-fold: first, to determine the anti-inflammatory activity of BGMP in the ileum; second, to characterise its mechanism of action.

EXPERIMENTAL APPROACH

We used a model of ileitis induced by trinitrobenzenesulphonic acid in rats. Rats were treated orally with BGMP and its efficacy compared with that of oral 5-aminosalicylic acid or vehicle, starting 2 days before ileitis induction.

KEY RESULTS

BGMP pretreatment (500 mg kg(-1) day(-1)) resulted in marked reduction of inflammatory injury, as assessed by lower extension of necrosis and damage score, myeloperoxidase, alkaline phosphatase, inducible nitric oxide synthase, interleukin 1beta, tumour necrosis factor and interleukin 17. These effects were generally comparable to those of 5-aminosalicylic acid (200 mg kg(-1) day(-1)). Neither compound affected the production of interferon gamma, tumour necrosis factor and interleukin 2 by mesenteric lymph node cells isolated from animals with ileitis. The expression of Foxp3 was increased in ileitis and not reduced significantly by BGMP or aminosalicylate treatment.

CONCLUSIONS AND IMPLICATIONS

These results demonstrate that BGMP has anti-inflammatory activity in the ileum with similar efficacy to 5-aminosalicylic acid. The mechanism of action may involve Th17 and regulatory T cells and perhaps macrophages but probably not Th1 lymphocytes. Patients with Crohn's ileitis may benefit from treatment with BGMP.

Effects of alpha-lactalbumin-enriched formula containing different concentrations of glycomacropeptide on infant nutrition

BACKGROUND

Formula-fed infants have growth and plasma amino acid patterns different from those of breastfed infants.

OBJECTIVE

alpha-Lactalbumin is a major protein in human milk, and the addition of bovine alpha-lactalbumin to infant formula has been proposed to modify the plasma amino acid pattern of the recipient infant, possibly allowing a reduction in the protein content of the formula, which may affect growth.

DESIGN

We compared breastfed infants and infants fed standard formula or alpha-lactalbumin-enriched formulas (25% of protein) with glycomacropeptide accounting for 15% or 10% of the protein. The protein content of each formula was 13.1 g/L. Ninety-six infants aged 6 +/- 2 wk were recruited. Anthropometric measures were recorded, and interviews were conducted at enrollment and monthly until 6 mo of age. Blood samples were collected at enrollment and at 4 and 6 mo.

RESULTS

Formula intake did not differ between groups, and weight gain in the alpha-lactalbumin-enriched formula groups were similar to that of the breastfed infants. The standard formula group gained significantly more weight than did the breastfed infants. All formula-fed infants had significantly higher plasma concentrations of most essential amino acids at 4 and 6 mo than did the breastfed infants, and serum urea nitrogen was also higher in the formula-fed infants. Insulin and leptin concentrations did not differ between groups.

CONCLUSIONS

Compared with standard formula-fed infants, infants fed formula with a modified protein composition had growth patterns more similar to those of breastfed infants. All formula-fed groups had plasma amino acid concentrations similar to or higher than those of breastfed infants. This indicates that the protein content of alpha-lactalbumin-enriched formula can be further reduced, which should be evaluated.

Emerging health properties of whey proteins and their clinical implications

The nursery rhyme "Little Miss Muffet sat on a tuffet (small stool) eating her curds and whey. ..." is recognition of the fact that over the centuries "curds and whey", the two major components of cow's milk, have been widely accepted as part of a healthy diet. Milk provides complete nourishment for the neonate for six months from birth, containing factors that help develop various organ systems including the brain, immune system, and the intestine. Importantly it provides immune protection at a time when the neonates own immune system, though fully developed, is albeit immature. Many adult consumers include cow's milk as part of a healthy diet as it provides protein and essential nutrients, vitamins, and minerals, in particular calcium for strong bones. There is a growing appreciation that milk, and in particular whey, contains components that not only provide nutrition, but can also prevent and attenuate disease, or augment conventional therapies, when delivered in amounts that exceed normal dietary intakes. This paper reviews the emerging health properties of whey proteins and their clinical implications.

On the role of breastfeeding in health promotion and the prevention of allergic diseases

Based on animal models, we specify the major role of different bioactive milk components known to participate significantly in neonatal health promotion and in protection against a large number of infectious diseases and the development of allergies and asthma.