Comparative aspects of milk caseins

Chemerin Stimulates the Secretory Activity of BME-UV1 Bovine Mammary Epithelial Cells

Adipose tissue is an active endocrine gland, synthesizing and secreting multiple signaling molecules termed adipokines. Following the detection of adipokines and their receptors in the mammary tissue of various species, it is indicated that adipokines play a role in the development of the mammary gland. The aim of the present study was to determine the concentration-dependent influence of three adipokines, leptin, adiponectin, and chemerin, on the viability, apoptosis, and secretory activity of BME-UV1 bovine mammary epithelial cells. The study confirmed that BME-UV1 cells contain the leptin receptor (Ob-R) protein, and express transcripts of adiponectin (ADIPOR1 and ADIPOR2) and chemerin (CMLKR1 and GPR1) receptors. Regardless of the administered dose, none of the three tested adipokines had an effect on the viability of BME-UV1 cells, and the number of apoptotic cells remained unchanged. However, chemerin (100 ng/mL) stimulated BME-UV1 cells to synthesize and secrete αS1-casein, the major protein component of milk. These results indicate that chemerin may be a potent regulator of the bovine mammary epithelial cells' functional differentiation, contributing, along with the major systemic hormones and local growth factors, to the development of the bovine mammary gland.

Evolution, diversification and function of the maternal-infant dyad in mammalian feeding

The evolution of the mother/infant dyad providing a source of nutrition for infants is essential for the origin and subsequent diversification of mammals. Despite the importance of this dyad, research on maternal and infant function is often treated independently. Our goal is to synthesize the work on maternal and infant function, discuss our own studies of suckling, and compare the origins of lactation and suckling with their ensuing diversification. Our central premise is that while extensive work has demonstrated variation across mammals in the maternal aspect of this system, very little has been done to address how this relates to infant function. We start with a discussion of the fundamental anatomy and physiology of both mother and infant. We next discuss the origin of mammary glands and milk, and infant suckling, which is distinct from their subsequent diversification. We then discuss the diversification of maternal and infant function, highlighting the evolutionary diversity present in maternal function (both anatomically and physiologically), before arguing that the diversity of infant function is unexplored, and needs to be better studied in the future. We end by discussing some of the holes in our understanding, and suggestions for future work that can address these lacunae. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Comparative Label-Free Liquid Chromatography-Mass Spectrometry Milk Proteomic Profiles Highlight Putative Differences between the Autochthon Teramana and Saanen Goat Breeds

Goat's milk is an excellent source of nutrients, with greater benefits compared to cow's milk. Limited information is available on autochthon goat breeds, which are important for biodiversity preservation. In this study, the aim of using label-free quantification was to investigate the milk proteome of two goat breeds, the autochthon Teramana and Saanen breeds, which are commonly used by the industry. Utilising label-free proteomic analysis, 749 and 666 proteins, respectively were identified and quantified from the Teramana and Saanen goat milk. Moreover, utilising statistical analysis, 29 proteins were able to discriminate the two goat breeds, with many of the identified proteins involved in complement and coagulation cascades. This work enhances our understanding of the goat milk proteome and shows differences between the two breeds, leading to an important contribution toward a more detailed molecular-view of this unique substrate. Additionally, charactersation of the milk proteins can help in guiding genetic improvements in the goat herds, and thus increasing its use in human nutrition.

Effects of Ultra-High-Pressure Jet Processing on Casein Structure and Curdling Properties of Skimmed Bovine Milk

Ultra-high-pressure jet processing (UHPJ) is a new non-thermal processing technique that can be employed for the homogenization and the sterilization of dairy products. However, the effects on dairy products are unknown when using UHPJ for homogenization and sterilization. Thus, this study aimed to investigate the effects of UHPJ on the sensory and curdling properties of skimmed milk and the casein structure in skimmed milk. Skimmed bovine milk was treated with UHPJ using different pressures (100, 150, 200, 250, 300 MPa) and casein was extracted by isoelectric precipitation. Subsequently, the average particle size, Zeta potential, contents of free sulfhydryl and disulfide bonds, secondary structure, and surface micromorphology were all used as evaluation indicators to explore the effects of UHPJ on the structure of casein. The results showed that with an increase of pressure, the free sulfhydryl group content changed irregularly, while the disulfide bond content increased from 1.085 to 3.0944 μmol/g. The content of α-helix and random coil in the casein decreased, while the β-sheet content increased at 100, 150, 200 MPa pressure. However, treatment with higher pressures of 250 and 300 MPa had the opposite effect. The average particle size of the casein micelles first decreased to 167.47 nm and then increased up to 174.63 nm; the absolute value of Zeta potential decreased from 28.33 to 23.77 mV. Scanning electron microscopy analysis revealed that the casein micelles had fractured into flat, loose, porous structures under pressure instead of into large clusters. After being ultra-high-pressure jet-processed, the sensory properties of skimmed milk and its fermented curd were analyzed concurrently. The results demonstrated that UHPJ could alter the viscosity and color of skimmed milk, shortening curdling time from 4.5 h to 2.67 h, and that the texture of the curd fermented with this skimmed milk could be improved to varying degrees by changing the structure of casein. Thus, UHPJ has a promising application in the manufacture of fermented milk due to its ability to enhance the curdling efficiency of skimmed milk and improve the texture of fermented milk.

Nutritional Parameters in Colostrum of Different Mammalian Species

Colostrum (or first milk) is the food produced by all the mothers in all specific mammalian species, ruminants, monogastric and marine mammalians for their newborns during the first 24–48 h post-partum. Colostrum provides to the neonate all essential nutrients necessary for the first week of life, but the effect of colostrum shows a long-term effect not limited to these first days. Colostrum is considered to be a safe and essential food for human consumption. Some young children can show at the beginning of their colostrum-based diet some side effects, such as nausea and flatulence, but they disappear quickly. In human colostrum, the immunoglobulins and lactoferrin determined show the ability to create natural immunity in newborns, reducing greatly the mortality rate in children. Recent studies suggest that bovine colostrum (BC) may be an interesting nutraceutical food, due to its ability in preventing and/or mitigating several diseases in newborns and adults. This review aims to show the nutraceutical and functional properties of colostrum produced by several mammalian species, describing the different colostrum bio-active molecules and reporting the clinical trials aimed to determine colostrum nutraceutical and therapeutic characteristics in human nutrition.

Distribution and variation in proteins of casein micellar fractions response to heat-treatment from five dairy species

Casein micelles (CMs) contribute to the physicochemical properties and stability of milk. However, how the proteome of CMs changes following heat treatment has not been elucidated. Here, changes in the proteins of CMs in samples of Holstein, buffalo, yak, goat, and camel milk following heat treatment were investigated using a LC-MS/MS approach. According to the hierarchical clustering results, Holstein, yak, and buffalo milk samples had similar CMs protein components, followed by goat and camel milk samples. Changes in lipoprotein lipase and α-lactalbumin in CMs were dependent on the intensity of heat treatment and were similar among the studied species, whereas changes in κ-casein, lactoferrin, and apolipoprotein A-I differed among different types of milk. These results provide information on the distribution and variations of the proteomes of CMs following heat treatment, which will assist in the identification of proteins that are dissociated and attached to CMs from different dairy species during heat treatment.

Bovine Colostrum: Its Constituents and Uses

Colostrum is the milk produced during the first few days after birth and contains high levels of immunoglobulins, antimicrobial peptides, and growth factors. Colostrum is important for supporting the growth, development, and immunologic defence of neonates. Colostrum is naturally packaged in a combination that helps prevent its destruction and maintain bioactivity until it reaches more distal gut regions and enables synergistic responses between protective and reparative agents present within it. Bovine colostrum been used for hundreds of years as a traditional or complementary therapy for a wide variety of ailments and in veterinary practice. Partly due to concerns about the side effects of standard Western medicines, there is interest in the use of natural-based products of which colostrum is a prime example. Numerous preclinical and clinical studies have demonstrated therapeutic benefits of bovine colostrum for a wide range of indications, including maintenance of wellbeing, treatment of medical conditions and for animal husbandry. Articles within this Special Issue of Nutrients cover the effects and use bovine colostrum and in this introductory article, we describe the main constituents, quality control and an overview of the use of bovine colostrum in health and disease.

Circulating Branched Chain Amino Acid Concentrations Are Higher in Dairy-Avoiding Females Following an Equal Volume of Sheep Milk Relative to Cow Milk: A Randomized Controlled Trial

Background: Intolerances to bovine dairy are a motivating factor in consumers seeking alternate-or replacement-dairy beverages and foods. Sheep milk (SM) is an alternate dairy source, with greater protein, although similar amino acid composition compared to cow milk (CM). Studies are yet to address the appearance of circulating amino acids following consumption of SM, relative to CM, in humans. Objective: To clinically determine the appearance of branched chain amino acids, and other amino acids, in circulation in response to equal servings of SM and CM, in females who avoid dairy products. Design: In a double-blinded, randomized, cross-over trial, 30 self-described dairy avoiding females (20-40 years) drank 650 mL of SM or CM that were reconstituted from the spray dried powders (30 and 25 g in 180 mL water, respectively) on separate occasions, following an overnight fast. After reconstitution, the energy and protein provided by SM was higher than for CM (2,140 vs. 1,649 kJ; 29.9 vs. 19.4 g protein); content of branched chain amino acids (BCAAs) were 10.5 and 6.5 mg·mL-1, respectively. Blood samples were collected at fasting and at regular intervals over 5 h after milk consumption. Plasma amino acids were measured by HPLC. Results: 80% of subjects self-identified as lactose intolerant, and the majority (47%) "avoided drinking milk" "most of the time". SM resulted in greater plasma appearance of BCAAs at 60 min (641.1 ± 16.3 vs. 563.5 ± 14.4 μmol·L-1; p < 0.001) compared with CM. SM similarly resulted in elevated postprandial concentrations of the amino acids lysine, methionine, and proline, particularly at 240 min (time × milk interactions p = 0.011, 0.017, and p = 0.002, respectively). Postprandial increases in plasma alanine concentrations were sustained to 120 min after CM (time × milk interaction p = 0.001) but not after SM, despite greater quantities provided by SM. Conclusions: SM is a rich source of protein, and relative to CM, provides a greater quantity of BCAAs, with a corresponding elevation of the postprandial circulating BCAA response. SM is therefore a possible dairy alternative of benefit to those who need to increase total protein intake or for individuals with heightened protein requirements. Unique Identifier and Registry: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=375324, identifier U1111-1209-7768.

Associations between maternal milk protein genotypes with preweaning calf growth traits in beef cattle

The objectives of this study were to investigate milk casein polymorphisms in dams and to determine the impacts of maternal casein genotypes on growth traits of their sucking calves. Milk samples from 433 dams of the breeds German Angus (GA) and German Simmental (GS) were typed at the milk protein loci α s1-casein (αs1-CN), β-casein (β-CN), α s2-casein (αs2-CN), and κ-casein (κ-CN) via isoelectric focusing. Associations between casein genotypes in maternal milk with growth traits of their 1,872 calves were analyzed until the age of weaning using linear mixed models, considering either genotypes of individual casein loci (model 1) or composite α s1-β-α s2-κ-CN genotypes within the casein cluster (model 2). Besides environmental effects such as sex, age of the dam, and calving year-season, genetic effects (breed group and maternal and paternal effects) were considered in statistical models. The composite casein genotype BBǀA2A2ǀAAǀAB (order of genes on bovine chromosome 6: α s1-ǀβ-ǀα s2-ǀκ-CN) was associated with greater average daily weight gains (ADG) and heavier age-adjusted weaning weights (WW) of calves (P < 0.05). The effects of composite genotypes on birth weight of calves were similar (P > 0.05; model 2). With regard to individual casein loci, greater ADG and WW were observed for calves from dams with the genotypes κ-CN BB and α s1-CN BB, respectively (P < 0.05; model 1). Age-adjusted WW was largest for calves from dams carrying the κ-CN genotype BB (215 kg) compared with calves representing the maternal AB and AA genotypes (both 204 kg). Results from the present study suggested selectable casein genotypes due to their nutritional value of milk (value in terms of offspring performances), offering new perspectives for breeding strategies in beef cattle to improve preweaning calf performance.

Expression of a recombinant anti-programed cell death 1 antibody in the mammary gland of transgenic mice

Nivolumab, a fully human IgG4 anti-programed cell death 1（PD-1）antibody, is recently one of the most popular and successful therapeutic monoclonal antibodies in clinical use. With the increasing demands for Nivolumab and other therapeutic monoclonal antibodies, the mammary gland bioreactor has been regarded as another choice for the production of recombinant monoclonal antibodies besides mammalian cell culture. Here, we expressed a recombinant human anti-PD-1 antibody in the mammary glands of transgenic mice. Two expression vectors were constructed bearing the heavy and light chains of anti-PD-1 antibody respectively under the control of bovine α_s1-casein promoter. Transgenic mice were then generated by co-microinjection of the two expression cassettes. Three F0 founders with both heavy chain and light chain positive were obtained. Transgenes of both chains were detected to be stably transmitted to the offspring. The recombinant antibody was detected in the milk of transgenic mice with the highest expression level up to 80.52 ± 0.82 mg/L and could specifically binds to the human PD-1 antigen. Therefore, our results suggest the feasibility of anti-PD-1 antibody production in the milk of transgenic animals.

Marsupial and monotreme milk-a review of its nutrient and immune properties

All mammals are characterized by the ability of females to produce milk. Marsupial (metatherian) and monotreme (prototherian) young are born in a highly altricial state and rely on their mother’s milk for the first part of their life. Here we review the role and importance of milk in marsupial and monotreme development. Milk is the primary source of sustenance for young marsupials and monotremes and its composition varies at different stages of development. We applied nutritional geometry techniques to a limited number of species with values available to analyze changes in macronutrient composition of milk at different stages. Macronutrient energy composition of marsupial milk varies between species and changes concentration during the course of lactation. As well as nourishment, marsupial and monotreme milk supplies growth and immune factors. Neonates are unable to mount a specific immune response shortly after birth and therefore rely on immunoglobulins, immunological cells and other immunologically important molecules transferred through milk. Milk is also essential to the development of the maternal-young bond and is achieved through feedback systems and odor preferences in eutherian mammals. However, we have much to learn about the role of milk in marsupial and monotreme mother-young bonding. Further research is warranted in gaining a better understanding of the role of milk as a source of nutrition, developmental factors and immunity, in a broader range of marsupial species, and monotremes.

Polymorphisms of the kappa casein (CSN3) gene and inference of its variants in water buffalo (Bubalus bubalis)

Kappa casein plays a crucial role in the formation of stable casein micelles and has a key influence on milk-clotting properties. However, current understanding of buffalo CSN3 gene polymorphisms is not sufficient. In this study, the polymorphisms in the complete coding sequence (CDS) of the buffalo CSN3 were detected using PCR product direct sequencing. The CDS of CSN3 for river and swamp buffalo was the same in length, which contained an open reading frame of 573 nucleotides encoding a peptide containing 190 amino acid residues. A total of eight single nucleotide polymorphisms (SNPs) was identified in two types of buffalo. Among them, c.86C>T, c.252G>C, c.445G>A, c.467C>T and c.516A>C were non-synonymous, which leads to p.Pro8Leu, p.Lys63Asn, p.Val128Ile, p.Thr135Ile and p.Glu151Asp substitutions in buffalo kappa casein ( κ -CN), respectively. The substitution of p.Thr135Ile may exert a vital effect on the function of buffalo κ -CN. Eleven haplotypes were defined based on the SNPs found in buffalo, and accordingly, seven protein variants and four synonymous variants of buffalo κ -CN were inferred, called variants A, B, B 1 , C, C 1 , C 2 , D, E, F, F 1 and G. The variants observed in water buffalo did not exist in the Bos genus. In addition, 14 amino acid differential sites of κ -CN between buffalo and the Bos genus were identified, of which 3 were located at glycosylation sites (80S, 96T, 141S) and 4 at phosphorylation sites (19S, 80S, 96T, 141S). It is speculated that they may lead to differences in the physicochemical properties of κ -CN between buffalo and the Bos genus. This study will lay a foundation for exploring the association between the variation in the CSN3 gene and the lactation traits of buffalo.

The effect of heparan sulfate on promoting amyloid fibril formation by β-casein and their binding research with multi-spectroscopic approaches

As a molecular chaperone, β-casein is difficult to form amyloid fibrils under physiological conditions due to its chaperone activity. Heparan sulfate (HS) has drawn attention of technologists all over the word because of its relation to amyloid deposits in some amyloidosis diseases. For better understanding the relationship between the β-casein and HS, the multi-spectroscopic studies were employed. The data of thioflavin T (ThT) binding assay, transmission electron microscopy (TEM) and circular dichroism (CD) demonstrated that HS promoted fibril formation by β-casein in the amount and the growth speed. The results of steady-state UV-vis absorption spectra, fluorescence spectroscopy and fluorescence lifetime revealed that the β-casein-HS complexes were formed and HS quenched the fluorescence of β-casein by a static quenching mechanism. On the basis of fluorescence analysis, the value of binding constant was equal to 1.17 × 10⁷ L mol^-1 at 338.15 K and there was about one binding site between them. According to thermodynamic parameters obtained, it was deduced that a spontaneous reaction happened, and protein-ligand complex was stabilized by hydrogen bonds and hydrophobic interaction. Furthermore, using fluorescence resonance energy transfer (FRET) assay, the value of binding distance between HS and Trp143 of β-casein was calculated to be 0.93 nm. Finally, on the basis of synchronous fluorescence experiment, the polarity increasing and hydrophobicity decreasing around Trp143 occurred during the period of fibril formation by β-casein.

Comparative genomics of casein genes

This research paper addresses the hypothesis that comparative genomics can give a new insight into the functionality of casein genes with respect to the casein micelle. Comparative genomics is a rapidly emerging field in computational biology whereby two or more genomes are compared in order to obtain a global view on genomes as well as assigning previously unknown functions for genes. Casein genes are among the most rapidly evolving mammalian genes, with the gene products mainly grouped into four types (αs1-, αs2-, β- and κ-casein). Functionally, casein genes are central to the casein micelle, the exact structure of which is still a subject of intense debate. Moreover, and adding to this complexity, some mammals lack some of the casein genes, although casein micelles have been observed in their milk. This observation has prompted an investigation into the distribution of casein genes across a host of mammalian species. It was apparent from this study that casein gene sequences are very diverse from each other and we confirmed that many mammalian species lack one or more of the casein genes. The genes encoding β- and κ-caseins are present in most mammals whereas α-casein encoding genes are less represented. This suggests different mechanisms for casein micelle formation in different species as well as the functions that are assigned to each individual casein.

Effect of calorific intake on proteomic composition of colostrum in dairy cows

The amount of concentrated feed supplied to a dairy cow affects milk yield. However, there is no evidence of a relationship between the colostrum proteomic composition and energy intake. We supplied 30 heifers (4–24 months old, two groups of 15 heifers each) with either a normal diet and high-energy diet to investigate the correlation between energy intake and colostrum protein composition. Colostrum milk proteins were analysed on the day of calving and on the third day following calving using two-dimensional gel electrophoresis (2-DE) and peptide mass fingerprinting (PMF). Five proteins were identified as differentially expressed between the two feeding groups in the colostrum on the day of calving. The levels of αS2-casein precursor and β-casein was higher in the colostrum from the high-energy diet group (HEG), whereas the levels of IgG3 heavy chain constant region, non-classical MHC class I antigen isoform X2, and β-casein A2 variant were higher in the normal-diet group (NEG) colostrum. Twelve differential proteins were identified on the third day: β-lactoglobulin, αS2-casein, zinc-α2-glycoprotein, lactoferrin, fibrinogen gamma-B chain isoform X1, non-classical MHC class I antigen isoform X2, complement C3, gelsolin isoform A precursor, vitamin D-binding protein isoform X1, immunoglobulin gamma 1 heavy chain constant region, IgG3 heavy chain constant region and polymeric immunoglobulin receptor. All were present at higher levels in the normal-diet group colostrum than in the high-energy diet group colostrum, although the milk yield from mature cows was lower in the normal-diet group. In conclusion, a high-energy diet can enhance milk production; however, the levels of immune-related factors are higher in the colostrum of cows fed a normal diet.

Rapid autophagic regression of the milk gland during involution is critical for maximizing tsetse viviparous reproductive output

Tsetse flies are important vectors of human and animal trypanosomiasis. Ability to reduce tsetse populations is an effective means of disease control. Lactation is an essential component of tsetse’s viviparous reproductive physiology and requires a dramatic increase in the expression and synthesis of milk proteins by the milk gland organ in order to nurture larval growth. In between each gonotrophic cycle, tsetse ceases milk production and milk gland tubules undergo a nearly two-fold reduction in width (involution). In this study, we examined the role autophagy plays during tsetse fly milk gland involution and reproductive output. Autophagy genes show elevated expression in tissues associated with lactation, immediately before or within two hours post-parturition, and decline at 24-48h post-parturition. This expression pattern is inversely correlated with that of the milk gland proteins (lactation-specific protein coding genes) and the autophagy inhibitor fk506-bp1. Increased expression of Drosophila inhibitor of apoptosis 1, diap1, was also observed in the milk gland during involution, when it likely prevents apoptosis of milk gland cells. RNAi-mediated knockdown of autophagy related gene 8a (atg8a) prevented rapid milk gland autophagy during involution, prolonging gestation, and reducing fecundity in the subsequent gonotrophic cycle. The resultant inhibition of autophagy reduced the recovery of stored lipids during the dry (non-lactating) periods by 15–20%. Ecdysone application, similar to levels that occur immediately before birth, induced autophagy, and increased milk gland involution even before abortion. This suggests that the ecdysteroid peak immediately preceding parturition likely triggers milk gland autophagy. Population modeling reveals that a delay in involution would yield a negative population growth rate. This study indicates that milk gland autophagy during involution is critical to restore nutrient reserves and allow efficient transition between pregnancy cycles. Targeting post-birth phases of reproduction could be utilized as a novel mechanism to suppress tsetse populations and reduce trypanosomiasis.

Tsetse flies are vectors for trypanosomes that cause both African sleeping sickness in humans and Nagana in animals. The reduction of tsetse populations is the most efficient way to reduce the prevalence of this economically important disease with current control methods including pesticide application, traps, and sterile insect techniques. Tsetse pregnancy and milk production represent a species-specific target for population control and milk gland transition during each larval growth cycle could represent a novel target for tsetse control. Within one day after birth, the milk gland organ, essential for provisioning nutrients to the intrauterine larva, undergoes involution marked by an ecdysone driven increase in autophagy that allows breakdown of this gland. Inhibiting the process of autophagy prevents the timely transition from the lactation phase to the dry phase, triggering a delay in subsequent pregnancy cycle. This misregulation of milk gland involution leads to an overall decrease in the number of offspring that each female can produce per lifetime. This study has determined the molecular components of this process, and reveals new targets of interference for vector control.

Production of angiotensin I converting enzyme inhibitory (ACE-I) peptides during milk fermentation and their role in reducing hypertension

Fermented milk is a potential source of various biologically active peptides with specific health benefits. Angiotensin converting enzyme inhibitory (ACE-I) peptides are one of the most studied bioactive peptides produced during milk fermentation. The presence of these peptides is reported in various fermented milk products such as, yoghurt, cheese, sour milk, etc., which are also available as commercial products. Many of the ACE-I peptides formed during milk fermentation are resistant to gastrointestinal digestion and inhibit angiotensin converting enzyme (ACE) in the rennin angiotension system (RAS). There are various factors, which affect the formation ACE-I peptides and their ability to reach the target tissue in active form, which includes type of starters (lactic acid bacteria (LAB), yeast, etc.), substrate composition (casein type, whey protein, etc.), composition of ACE-I peptide, pre and post-fermentation treatments, and its stability during gastrointestinal digestion. The antihypertensive effect of fermented milk products has also been proved by various in vitro and in vivo (animal and human trials) experiments. This paper reviews the literature on fermented milk products as a source of ACE-I peptides and various factors affecting the production and activity of ACE-I peptides.

Proteomic analysis and cross species comparison of casein fractions from the milk of dairy animals

Casein micelles contribute to the physicochemical properties of milk and may also influence its functionality. At present, however, there is an incomplete understanding of the casein micelle associated proteins and its diversity among the milk obtained from different species. Therefore, milk samples were collected from seven dairy animals groups, casein fractions were prepared by ultracentrifugation and their constituent proteins were identified by liquid chromatography tandem mass spectrometry. A total of 193 distinct proteins were identified among all the casein micelle preparations. Protein interaction analysis indicated that caseins could interact with major whey proteins, including β-lactoglobulin, α-lactalbumin, lactoferrin, and serum albumin, and then whey proteins interacted with other proteins. Pathway analysis found that the peroxisome proliferator-activated receptor signaling pathway is shared among the studied animals. Additionally, galactose metabolism pathway is also found to be commonly involved for proteins derived from camel and horse milk. According to the similarity of casein micelle proteomes, two major sample clusters were classified into ruminant animals (Holstein and Jersey cows, buffaloes, yaks, and goats) and non-ruminants (camels and horses). Our results provide new insights into the protein profile associated with casein micelles and the functionality of the casein micelle from the studied animals.

Mammary alveolar cell as in vitro evaluation system for casein gene expression involved in glucose level

Objective

Glucose is an essential fuel in the energy metabolism and synthesis pathways of all mammalian cells. In lactating animals, glucose is the major precursor for lactose and is a substrate for the synthesis of milk proteins and fat in mammary secretory (alveolar) epithelial cells. However, clear utilization of glucose in mammary cells during lactogenesis is still unknown, due to the lack of in vitro analyzing models. Therefore, the objective of this study was to test the reliability of the mammary alveolar (MAC-T) cell as an in vitro study model for glucose metabolism and lactating system.

Methods

Undifferentiated MAC-T cells were cultured in three types of Dulbecco’s modified Eagle’s medium with varying levels of glucose (no-glucose: 0 g/L, low-glucose: 1 g/L, and high-glucose: 4.5 g/L) for 8 d, after which differentiation to casein secretion was induced. Cell proliferation and expression levels of apoptotic genes, Insulin like growth factor-1 (IGF1) receptor, oxytocin receptor, αS1, αS2, and β casein genes were analyzed at 1, 2, 4, and 8 d after differentiation.

Results

The proliferation of MAC-T cells with high-glucose treatment was seen to be significantly higher. Expression of apoptotic genes was not affected in any group. However, expression levels of the mammary development related gene (IGF1 receptor) and lactation related gene (oxytocin receptor) were significantly higher in the low-glucose group. Expressions of αS1-casein, αS2-casein, and β-casein were also higher in the low-glucose treated group as compared to that in the no-glucose and high-glucose groups.

Conclusion

The results demonstrated that although a high-glucose environment increases cell proliferation in MAC-T cells, a low-glucose treatment to MAC-T cells induces higher expression of casein genes. Our results suggest that the MAC-T cells may be used as an in vitro model to analyze mammary cell development and lactation connected with precise biological effects.

Investigating the genetic polymorphism of sheep milk proteins: a useful tool for dairy production

Sheep is the second most important dairy species after cow worldwide, and especially in the Mediterranean and Middle East regions. In some countries, the difficult environmental conditions require a peculiar adaptation and, in these contexts, sheep are able to provide higher quality protein than cattle. In the least-developed countries, the amount of dairy sheep and ovine milk production is progressively increasing. In order to improve dairy productions, in particular those with local connotations, it is necessary to obtain in-depth information regarding milk quality and rheological properties. The genetic polymorphisms of milk proteins are often associated with quantitative and qualitative parameters in milk and are potential candidate markers that should be included in breeding strategies similar to those already available for cattle. Due to the current and growing interest in this topic and considering the large amount of new information, the aim of this study was to review the literature on sheep milk protein polymorphisms with a particular emphasis on recent findings in order to give scientists useful support. Moreover, the effects of different protein variants on milk yield and composition are discussed.

Analysis of genetic variations across regulatory and coding regions of kappa-casein gene of Indian native cattle (Bos indicus) and buffalo (Bubalus bubalis)

The promoter region of kappa-casein (κ-CN) gene in Indian native cattle and buffalo breeds was sequenced and analyzed for nucleotide variations. Sequence comparison across breeds of Indian cattle revealed a total of 7 variations in the promoter region, of which − 515 G/T, − 427 C/T, − 385 C/T, − 283 A/G and − 251 C/T were located within consensus binding sites for octamer-binding protein (OCT1)/pregnancy specific mammary nuclear factor (PMF), activator protein-2 (AP2), hepatocyte nuclear factor (HNF-1) and GAL4 transcription factors (TFs), respectively. These variations might be involved in gain or loss of potential transcription factor binding sites (TFBSs). Unlike the other 4 variants, the − 283 (A/G) variant located within HNF-1 TFBS was specific to Indian cattle as this change has not been observed in the Bos taurus sequence. Other TFBSs viz., MGF, TBP, NF-1, milk box and C/EBP were conserved across species. For the Indian native buffalo breeds, only 3 changes were identified in the promoter region; − 305 (A/C), − 160 (T/C) and − 141 (A/G) and most of the TFBSs were found to be conserved. However, deletion of two adjacent nucleotides located in and around binding site for C/EBP TF was identified in buffalo when compared with promoter sequence of bovine κ-CN. For κ-CN of Indian native cattle, a strong linkage disequilibrium (LD) was observed for variations 515 G/T, − 427 C/T and − 385 C/T in the promoter region; and for variations at codons 136 and 148 of exon-IV. Further, among intragenic haplotypes, variation − 427 C/T was found to be in LD with variations at codons 136 and 148. The information generated in the present work provides comprehensive characterization of κ-CN gene promoter and coding regions in Indian cattle and buffaloes and reported variations could become important candidates for carrying out further research in dairy traits.

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The κ-casein gene (κ-CN) and its promoter region was sequence characterized in 15 Indian native cattle and 8 buffalo breeds.

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Among the identified variations, four were located within TFBSs in Indian cattle, while all TFBSs were conserved in buffaloes.

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The κ-CN CDS was highly conserved with only 3 and 2 non-synonymous changes for Indian cattle and buffaloes, respectively.

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Across promoter and CDS, − 427 C/T was found to be in LD with variation at codons 136 and 148.

A novel highly divergent protein family identified from a viviparous insect by RNA-seq analysis: a potential target for tsetse fly-specific abortifacients

In tsetse flies, nutrients for intrauterine larval development are synthesized by the modified accessory gland (milk gland) and provided in mother's milk during lactation. Interference with at least two milk proteins has been shown to extend larval development and reduce fecundity. The goal of this study was to perform a comprehensive characterization of tsetse milk proteins using lactation-specific transcriptome/milk proteome analyses and to define functional role(s) for the milk proteins during lactation. Differential analysis of RNA-seq data from lactating and dry (non-lactating) females revealed enrichment of transcripts coding for protein synthesis machinery, lipid metabolism and secretory proteins during lactation. Among the genes induced during lactation were those encoding the previously identified milk proteins (milk gland proteins 1-3, transferrin and acid sphingomyelinase 1) and seven new genes (mgp4-10). The genes encoding mgp2-10 are organized on a 40 kb syntenic block in the tsetse genome, have similar exon-intron arrangements, and share regions of amino acid sequence similarity. Expression of mgp2-10 is female-specific and high during milk secretion. While knockdown of a single mgp failed to reduce fecundity, simultaneous knockdown of multiple variants reduced milk protein levels and lowered fecundity. The genomic localization, gene structure similarities, and functional redundancy of MGP2-10 suggest that they constitute a novel highly divergent protein family. Our data indicates that MGP2-10 function both as the primary amino acid resource for the developing larva and in the maintenance of milk homeostasis, similar to the function of the mammalian casein family of milk proteins. This study underscores the dynamic nature of the lactation cycle and identifies a novel family of lactation-specific proteins, unique to Glossina sp., that are essential to larval development. The specificity of MGP2-10 to tsetse and their critical role during lactation suggests that these proteins may be an excellent target for tsetse-specific population control approaches.

Amelioration of reproduction-associated oxidative stress in a viviparous insect is critical to prevent reproductive senescence

Impact of reproductive processes upon female health has yielded conflicting results; particularly in relation to the role of reproduction-associated stress. We used the viviparous tsetse fly to determine if lactation, birth and involution lead to damage from oxidative stress (OS) that impairs subsequent reproductive cycles. Tsetse females carry an intrauterine larva to full term at each pregnancy cycle, and lactate to nourish them with milk secretions produced by the accessory gland ( = milk gland) organ. Unlike most K-strategists, tsetse females lack an apparent period of reproductive senescence allowing the production of 8-10 progeny over their entire life span. In a lactating female, over 47% of the maternal transcriptome is associated with the generation of milk proteins. The resulting single larval offspring weighs as much as the mother at birth. In studying this process we noted an increase in specific antioxidant enzyme (AOE) transcripts and enzymatic activity at critical times during lactation, birth and involution in the milk gland/fat body organ and the uterus. Suppression of superoxide dismutase (sod) decreased fecundity in subsequent reproductive cycles in young mothers and nearly abolished fecundity in geriatric females. Loss of fecundity was in part due to the inability of the mother to produce adequate milk to support larval growth. Longevity was also impaired after sod knockdown. Generation of OS in virgin females through exogenous treatment with hydrogen peroxide at times corresponding to pregnancy intervals reduced survival, which was exacerbated by sod knockdown. AOE expression may prevent oxidative damage associated with the generation of nutrients by the milk gland, parturition and milk gland breakdown. Our results indicate that prevention of OS is essential for females to meet the growing nutritional demands of juveniles during pregnancy and to repair the damage that occurs at birth. This process is particularly important for females to remain fecund during the latter portion of their lifetime.

Update of the WHO/IUIS Allergen Nomenclature Database based on analysis of allergen sequences

The IUIS Allergen Nomenclature Sub-Committee, under the auspices of the World Health Organization and the International Union of Immunological Societies, maintains the systematic nomenclature of allergenic proteins and publishes a database of approved allergen names on its Web site, www.allergen.org. In this paper, we summarize updates of allergen names approved at the meetings of the committee in 2011 through 2013. These changes reflect recent progress in identification, cloning, and sequencing of allergens. The goals of this update were to increase consistency in the classification of allergens, isoallergens, and variants and in the incorporation of the evolutionary classification of proteins into allergen nomenclature, while keeping changes of established names to a minimum in the interest of continuity. Allergens for which names have been updated include respiratory allergens from birch and ragweed pollen, midge larvae, and horse dander; food allergens from peanut, cow's milk, and tomato; and cereal grain allergens. The IUIS Allergen Nomenclature Sub-Committee encourages researchers to use these updated allergen names in future publications.

Nutrient transport in the mammary gland: calcium, trace minerals and water soluble vitamins

Milk nutrients are secreted by epithelial cells in the alveoli of the mammary gland by several complex and highly coordinated systems. Many of these nutrients are transported from the blood to the milk via transcellular pathways that involve the concerted activity of transport proteins on the apical and basolateral membranes of mammary epithelial cells. In this review, we focus on transport mechanisms that contribute to the secretion of calcium, trace minerals and water soluble vitamins into milk with particular focus on the role of transporters of the SLC series as well as calcium transport proteins (ion channels and pumps). Numerous members of the SLC family are involved in the regulation of essential nutrients in the milk, such as the divalent metal transporter-1 (SLC11A2), ferroportin-1 (SLC40A1) and the copper transporter CTR1 (SLC31A1). A deeper understanding of the physiology and pathophysiology of these transporters will be of great value for drug discovery and treatment of breast diseases.

Strategies for a direct characterization of phosphoproteins on hydroxyapatite surfaces

We show in this work how systems formed by phosphoproteins on calcium phosphate surfaces can be directly characterized, in real time, in liquid medium, without the need for elution or labeling. Specifically, we show how this is possible by applying three different techniques: ellipsometry, quartz crystal microbalance with dissipation, and atomic force microscopy-based friction force spectroscopy. We apply these techniques to study two different model systems, i.e. those formed upon the adsorption of two model phosphoproteins (κ- and β-casein) on hydroxyapatite (HA) surfaces. Information on the kinetics of adsorption, surface excess, viscoelasticity, water content, thickness of the layers, and protein-surface interaction is provided. Results indicate that both phosphoproteins form homogeneous elastic highly hydrated monolayers on the HA surfaces, the strength of β-casein layers being higher by approximately a factor of 4. Based on the experimental results, models for the conformation of κ- and β-casein molecules adsorbed on HA surfaces are proposed.

Detection of casein phosphopeptides in goat milk

The aims of this study were to profile casein phosphopeptides in goat milk, to accurately determine the site of phosphorylation, and to evaluate whether or not any of the casein phosphorylation patterns were specific to a given physiological condition. Goat milk, collected before and after experimental induction of endotoxin mastitis, was separated by SDS-PAGE. Casein bands were digested with trypsin and the resulting peptides were analyzed by nLC-MS/MS. Eight out of nine predicted tryptic phosphopeptides corresponding to 18 different phosphorylation sites were detected in αS1-, αS2-, and β-casein. Characterization of the phosphorylation sites illustrated the capability of tandem MS to accurately localize phosphorylated residues among a number of other putative sites. Despite an apparent lower abundance, almost all of the phosphopeptides were also detected in milk samples obtained from the goats following experimental induction of endotoxin mastitis. However, a tetra-phosphopeptide in αS2-casein was only observed in the milk samples obtained from healthy animals. The absence of this multiphosphopeptide in the mastitic goat milk samples could indicate changes in phosphorylation as a result of disease and potentially be used as a marker for milk quality. This study represents the first comprehensive analysis of casein phosphoproteome and reveals a much higher level of phosphorylation than previously demonstrated in goat milk.

Short communication: retinoic acid plus prolactin to synergistically increase specific casein gene expression in MAC-T cells

Mammary alveolar (MAC-T) cells, an established bovine mammary epithelial cell line, are frequently used to investigate differentiation. A lactogenic phenotype in these cells is induced by treatment with a combination of hydrocortisone, insulin, and prolactin (PRL). The effect of the vitamin A derivative retinoic acid (RA), which induces differentiation in many cells, has not been studied in MAC-T cells. The objective of this study was to evaluate the differentiation potential of RA (1 μM) in MAC-T cells and to examine the effect of combined treatment with RA (1 μM) and PRL (5 μg/mL). Although RA treatment alone inhibited MAC-T cell proliferation, co-treatment of RA with PRL increased cell growth compared with the control group (treated with 1 μg/mL hydrocortisone and 5 μg/mL insulin). The ratio of Bcl to Bax mRNA was decreased in the RA treatment compared with RA+PRL or control. Retinoic acid-induced differentiation of MAC-T cells was associated with an increase in the mRNA expression of αS1-casein (3.9-fold), αS2-casein (4.5-fold), and β-casein (4.4-fold) compared with the control group. Expression of αS1-casein, αS2-casein, and β-casein was increased 12.9-fold, 11.9-fold, and 19.3-fold, respectively, following treatment with RA and PRL combined compared with the control group. These results demonstrate that RA induces differentiation of MAC-T cells and acts synergistically with PRL to increase specific casein gene expression.

Farm animal milk proteomics

Milk is one of the most important nutrients for humans during lifetime. Farm animal milk in all its products like cheese and other fermentation and transformation products is a widespread nutrient for the entire life of humans. Proteins are key molecules of the milk functional component repertoire and their investigation represents a major challenge. Proteins in milk, such as caseins, contribute to the formation of micelles that are different from species to species in dimension and casein-type composition; they are an integral part of the MFGM (Milk Fat Globule Membrane) that has being exhaustively studied in recent years. Milk proteins can act as enzymes or have an antimicrobial activity; they could act as hormones and, last but not least, they have a latent physiological activity encoded in their primary structure that turns active when the protein is cleaved by fermentation or digestion processes. In this review we report the last progress in proteomics, peptidomics and bioinformatics. These new approaches allow us to better characterize the milk proteome of farm animal species, to highlight specific PTMs, the peptidomic profile and even to predict the potential nutraceutical properties of the analyzed proteins.