Enrichment of low-abundance osteopontin in bovine milk via reciprocating free-flow isoelectric focusing

Osteopontin (OPN) in milk plays an important role in intestinal and brain development in early infancy, and great attention has been focused on OPN isolation to add extra OPN in infant formula. However, large-scale OPN isolation is limited by the low efficiency of sample pretreatment. Herein, we utilized preparative reciprocating free-flow isoelectric focusing (RFFIEF) to showcase the enrichment of low-abundance OPN in bovine milk, which contained an extremely high concentration of unwanted proteins. The reciprocating IEF format and the design of the multi-channel collector allowed us to enrich OPN in 1 L milk within 6 h. We removed 97.5% of unwanted proteins and obtained an enrichment factor of 11. Thus, our RFFIEF method can be applied to the preparative pretreatment of the large-scale milk sample and potentially improve the efficiency of downstream OPN purification.

Identification of pasteurized mare milk and powder adulteration with bovine milk using quantitative proteomics and metabolomics approaches

Adulteration in dairy products presents food safety challenges, driven by economic factors. Processing may change specific biomarkers, thus affecting their effectiveness in detection. In this study, proteomics and metabolomics approaches were to investigate the detection of bovine milk (BM) constituents adulteration in pasteurized mare milk (PMM) and mare milk powder (MMP). Several bovine proteins and metabolites were identified, with their abundances in PMM and MMP increasing upon addition of BM. Proteins like osteopontin (OPN) and serotransferrin (TF) detected adulteration down to 1 % in PMM, whereas these proteins in MMP were utilized to identify 10 % adulteration. Biotin and N6-Me-adenosine were effective in detecting adulteration in PMM as low as 10 % and 1 % respectively, while in MMP, their detection limits extend down to 0.1 %. These findings offer insights for authenticating mare milk products and underscore the influence of processing methods on biomarker levels, stressing the need to consider these effects in milk product authentication.

Entrectinib a Plausible Inhibitor for Osteopontin (SPP1) in Cervical Cancer-Integrated Bioinformatic Approach

Cervical cancer is one of the major causes of death in women, especially in developing countries bearing more than a quarter of the global burden. Secreted phosphoprotein-1, also known as OPN (osteopontin), is an integrin-binding glycophosphoprotein that is overexpressed in a variety of tumors. OPN is a chemokine-like calcified ECM-associated protein that plays a crucial role in evaluating the metastatic potential of various cancers. However, the role of SPP1 in the tumor microenvironment and associated signaling pathways in CC is still unclear. In our study, three CC microarray datasets (GSE9750, GSE46857, and GSE67522) were obtained from the GEO database to identify the differentially expressed genes. Enrichment analysis was carried out by Enrichr and ShinyGO and the PPI interaction network was created by using String and Cytoscape. GEPIA datasets were used to validate the top 10 hub genes, and virtual screening, docking, and dynamic simulation studies were used to identify a suitable inhibitor against the OPN protein using MVD, PyRx, and GROMACS respectively. Our results show that a total of 11 DEGs were common for three datasets and gene ontology pathway enrichment analysis revealed that 2 biological processes i.e. programmed cell death and animal organ development commonly affected mechanisms in all three datasets. Docking and dynamic studies revealed that Entrectinib showed excellent binding affinity against OPN protein. Based on the results, we conclude that OPN is one of the most upregulated genes in cervical cancer and Entrectinib emerges to be a promising potential OPN inhibitor to curtail cervical cancer progression. Schematic representation: The schematic representation of methodology steps is illustrated in the graphical abstract. Schematic representation of methodology.

Analytical Ultracentrifugation-Calibrated Anion-Exchange Chromatography for Sensitive and Intact Determination of Osteopontin in Infant Formula and Dairy Products

Osteopontin is a crucial protein ingredient that has been applied in fortified dairy products and infant formula. It has great significance to infant gut health and brain development. However, current techniques including enzyme-linked immunosorbent assay and liquid chromatography coupled with mass spectrometry are still facing the bottleneck of low sensitivity and indirect quantification. Moreover, the unavailable certified commercial OPN standard hinders its accurate quantification. Herein, a novel method of anion-exchange chromatography was established to determine OPN concentration in several dairy matrices. The polarity-reversed capillary isoelectric focusing was utilized to measure the exact isoelectric point (pI) to support method development for OPN separation. Analytical ultracentrifugation was used to calibrate the purity of intact OPN to develop an in-house reference standard. The method showed the merits of limits of detection to 0.04 mg/100 g, relative standard deviation of reproducibility <5% for 13 out of 14 tested matrices, and an average recovery rate of 101.3%. This method has shown the potential to be adopted as an international standard method for the quantification of intact OPN in infant formula and dairy products.

Milk Osteopontin and Human Health

Osteopontin (OPN) is a multifunctional protein found in all vertebrates. OPN is expressed in many different cell types, and is consequently found in most tissues and physiological secretions. OPN is involved in a multitude of biological processes, such as activation and regulation of the immune system; biomineralization; tissue-transformative processes, including growth and development of the gut and brain; interaction with bacteria; and many more. OPN is found in the highest concentrations in milk, where it is believed to initiate and regulate developmental, immunological and physiological processes in infants who consume milk. Processes for the isolation of bovine OPN for use in infant formula have been developed, and in recent years, many studies have investigated the effects of the intake of milk OPN. The purpose of this article is to review and compare existing knowledge about the structure and function of milk OPN, with a particular focus on the effects of milk OPN on human health and disease.

Peptidomic changes in the milk of water buffaloes (Bubalus bubalis) with intramammary infection by non-aureus staphylococci

Mastitis by non-aureus staphylococci (NAS) is a significant issue in dairy buffalo farming. In a herd with subclinical NAS mastitis, we identified Staphylococcus microti as the predominant species. To assess milk protein integrity and investigate potential disease markers, we characterized 12 NAS-positive and 12 healthy quarter milk samples by shotgun peptidomics combining peptide enrichment and high-performance liquid chromatography/tandem mass spectrometry (LC–MS/MS). We observed significant changes in the milk peptidome. Out of 789 total peptides identified in each group, 49 and 44 were unique or increased in NAS-positive and healthy milk, respectively. In NAS-positive milk, the differential peptides belonged mainly to caseins, followed by milk fat globule membrane proteins (MFGMP) and by the immune defense/antimicrobial proteins osteopontin, lactoperoxidase, and serum amyloid A. In healthy milk, these belonged mainly to MFGMP, followed by caseins. In terms of abundance, peptides from MFGMP and immune defense protein were higher in NAS-positive milk, while peptides from caseins were higher in healthy milk. These findings highlight the impact of NAS on buffalo milk quality and mammary gland health, even when clinical signs are not evident, and underscore the need for clarifying the epidemiology and relevance of the different NAS species in this dairy ruminant.

Safety of bovine milk osteopontin as a Novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on bovine milk osteopontin (bmOPN) as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF concerns OPN derived from bovine whey. The NF is intended to be used at a maximum use level of 151 mg/L, in infant formula (IF), follow-on formula (FoF) and ready-to-eat dairy-based meals for children up to 35 months of age. As compared to the concentrations naturally present in cow's milk and concentrations found in IF on the market reported in the literature, the proposed use level of the NF represents an about 10-fold higher concentration of bmOPN. The intended use levels of the NF would provide bmOPN at a concentration within the range of human milk (hm) OPN. In a 6-month study, 14, 72 and 140 mg bmOPN/L in reconstituted (as consumed) IF were given to 279 infants in order to study possible effects on frequency and severity of adverse events, and growth, formula intake and stool consistency. Despite that a number of inconsistencies and limitations were noted in the study report, the Panel considers that the results obtained from this study do not raise safety concerns. Considering the source of the NF, that neither the toxicological studies nor the provided infant study do raise safety concerns, and the low bmOPN plasma levels in infants resulting from the consumption of the NF, the Panel considers that the margin of exposure (i.e. 36) between the NOAEL of the subchronic toxicity study (1,200 mg/kg bw per day) and the highest P95 estimate for infants (33.4 mg/kg bw per day) is sufficient. The Panel concludes that the NF is safe under the proposed conditions of use.

Analysis and comparison of key proteins in Maiwa yak and bovine milk using high-performance liquid chromatography mass spectrometry

Yak milk is an essential and predominant food resource for Tibetan people for subsistence purposes and to combat altitude-induced challenges. Due to its unique qualities, yak milk has recently been gaining broader attention from consumers across China as well in other parts of the world. One of the key characteristics of yak milk is the protein content, which is about 40 to 60% higher than that of native bovine milk. In this work, a sensitive and reproducible high-throughput analytical method was developed employing both ultra high-performance liquid chromatography Orbitrap (Thermo Fisher Scientific) high-resolution accurate mass spectroscopy (UHPLC-HRAM-MS) and UHPLC coupled with triple quadrupole tandem MS (UHPLC-QqQ-MS) to simultaneously analyze 8 milk proteins. A total of 15 Maiwa yak milk samples and 15 bovine milk samples were qualitatively and quantitatively analyzed using targeted proteomics and compared for α-lactalbumin, β-lactoglobulin, α_S1-casein, α_S2-casein, β-casein, κ-casein, lactoferrin, and osteopontin. Peptides of β-lactoglobulin were used to specifically distinguish yak and bovine milk. The results showed that this novel detection method could quantitatively detect these major and minor milk proteins with >0.99 linear correlation coefficient and a recovery rate between 90 and 120%, with relative standard deviations typically less than 10%. The data revealed that yak milk not only had higher overall milk protein content than bovine milk but higher lactoferrin and osteopontin contents as well. The lactoferrin content of yak milk was about 30% higher than that of bovine milk, and the osteopontin content of yak milk was nearly twice that of bovine milk. The application of this method demonstrates that UHPLC-HRAM-MS and UHPLC-QqQ-MS are suitable for high-throughput qualitative and quantitative analysis of major and minor proteins of yak and bovine milk.

Bovine seminal plasma osteopontin: Structural modelling, recombinant expression and its relationship with semen quality

Osteopontin (OPN) is a multifunctional phosphoprotein that has been linked to fertility in bulls. However, the exact mechanism by which OPN contributes to fertilisation is yet unknown. The biotechnological use of OPN in bovine reproduction is promising but some gaps remain unfilled. The present work aimed: (a) to verify whether the seminal plasma OPN is associated with seminal traits and a standard breeding soundness exam; (b) to predict OPN interactions with integrins, CD44 and glycosaminoglycans through molecular docking; and (c) to develop a protocol for recombinant expression of OPN from vesicular gland cDNA. Ejaculates from top ranked bulls had higher amounts of seminal plasma OPN in comparison with bulls classified as questionable (p < .01). The structural modelling and molecular docking predictions indicated that bovine OPN binds to heparin disaccharide, hyaluronic acid and hyaluronan. In addition, docking studies described the binding complexes of OPN with CD44 and the integrin heterodimers α5β1 and αVβ3. Finally, expression of rOPN-6His was successfully obtained after 3 hr of induction with 0.5 mM IPTG at 37°C and a denaturing purification protocol resulted in efficiently purified recombinant OPN. The present results contribute to the development of biotechnological uses of OPN as a biomarker in bovine reproduction.

Ras-transformation reduce FAM20C expression and osteopontin phosphorylation

Family with sequence similarity 20, member C (FAM20C) is the main kinase of secreted phosphoproteins, including the multifunctional protein and cytokine, osteopontin (OPN). The phosphorylation of OPN varies greatly among cell types, tissues and species, and the different phospho-isoforms contribute to the multifunctionality of the protein. Expression of OPN is increased in human malignancies, and less phosphorylated isoforms of the protein have been associated with this phenotype. Here, we compared OPN from ras-transformed fibroblasts with that from their non-transformed parental cells, and found that OPN was less phosphorylated after ras-transformation. Furthermore, we demonstrated that expression of FAM20C mRNA was reduced five-fold in ras-transformed fibroblasts compared with non-transformed fibroblasts. Transfection with FAM20C of the ras-transformed fibroblasts restored the FAM20C mRNA expression but the phosphorylation of OPN was not increased proportionally. Likewise, the mRNA level of FAM20C was reduced in the malignant ras-transformed mammary cell line MCF10ACA1a compared with its non-transformed parental cell line MCF10A. These results suggest that expression of the FAM20C kinase is reduced after oncogenic ras-transformation, which potentially affects the phosphorylation of secreted phosphoproteins.

In-depth proteome analysis of more than 12,500 proteins in buffalo mammary epithelial cell line identifies protein signatures for active proliferation and lactation

The mature mammary gland is made up of a network of ducts that terminates in alveoli. The innermost layer of alveoli is surrounded by the differentiated mammary epithelial cells (MECs), which are responsible for milk synthesis and secretion during lactation. However, the MECs are in a state of active proliferation during pregnancy, when they give rise to network like structures in the mammary gland. Buffalo (Bubalus bubalis) constitute a major source of milk for human consumption, and the MECs are the major precursor cells which are mainly responsible for their lactation potential. The proteome of MECs defines their functional state and suggests their role in various cellular activities such as proliferation and lactation. To date, the proteome profile of MECs from buffalo origin is not available. In the present study, we have profiled in-depth proteome of in vitro cultured buffalo MECs (BuMECs) during active proliferation using high throughput tandem mass spectrometry (MS). MS analysis identified a total of 8330, 5970, 5289, 4818 proteins in four sub-cellular fractions (SCFs) that included cytosolic (SCF-I), membranous and membranous organelle’s (SCF-II), nuclear (SCF-III), and cytoskeletal (SCF-IV). However, 792 proteins were identified in the conditioned media, which represented the secretome. Altogether, combined analysis of all the five fractions (SCFs- I to IV, and secretome) revealed a total of 12,609 non-redundant proteins. The KEGG analysis suggested that these proteins were associated with 325 molecular pathways. Some of the highly enriched molecular pathways observed were metabolic, MAPK, PI3-AKT, insulin, estrogen, and cGMP-PKG signalling pathway. The newly identified proteins in this study are reported to be involved in NOTCH signalling, transport and secretion processes.

The Use of "Omics" in Lactation Research in Dairy Cows

“Omics” is the application of genomics, transcriptomics, proteomics, and metabolomics in biological research. Over the years, tremendous amounts of biological information has been gathered regarding the changes in gene, mRNA and protein expressions as well as metabolites in different physiological conditions and regulations, which has greatly advanced our understanding of the regulation of many physiological and pathophysiological processes. The aim of this review is to comprehensively describe the advances in our knowledge regarding lactation mainly in dairy cows that were obtained from the “omics” studies. The “omics” technologies have continuously been preferred as the technical tools in lactation research aiming to develop new nutritional, genetic, and management strategies to improve milk production and milk quality in dairy cows.

Characterization of UO2(2+) binding to osteopontin, a highly phosphorylated protein: insights into potential mechanisms of uranyl accumulation in bones

Bones are one of the few organs in which uranyl (UO2(2+)) accumulates. This large dioxo-cation displays affinity for carboxylates, phenolates and phosphorylated functional groups in proteins. The noncollagenous protein osteopontin (OPN) plays an important role in bone homeostasis. It is mainly found in the extracellular matrix of mineralized tissues but also in body fluids such as milk, blood and urine. Furthermore, OPN is an intrinsically disordered protein, which, like other proteins of the SIBLING family, contains a polyaspartic acid sequence and numerous patterns of alternating acidic and phosphorylated residues. All these properties led to the hypothesis that this protein could be prone to UO2(2+) binding. In this work, a simple purification procedure enabling highly purified bovine (bOPN) and human OPN (hOPN) to be obtained was developed. Various biophysical approaches were set up to study the impact of phosphorylations on the affinity of OPN for UO2(2+) as well as the formation of stable complexes originating from structural changes induced by the binding of this metal cation. The results obtained suggest a new mechanism of the interaction of UO2(2+) with bone metabolism and a new role for OPN as a metal transporter.

Milk osteopontin, a nutritional approach to prevent alcohol-induced liver injury

Alcohol consumption is a leading cause of liver disease worldwide; thus, there is an urgent need to develop novel therapeutic interventions. Key events for the onset and progression of alcoholic liver disease result in part from the gut-to-liver interaction. Osteopontin is a cytokine present at high concentration in human milk, umbilical cord, and infants' plasma with beneficial potential. We hypothesized that dietary administration of milk osteopontin could prevent alcohol-induced liver injury perhaps by maintaining gut integrity and averting hepatic inflammation and steatosis. Wild-type mice were fed either the control or the ethanol Lieber-DeCarli diets alone or in combination with milk osteopontin for 3 wk, and parameters of gut and liver damage were measured. Milk osteopontin protected the stomach and the gut by increasing gland height, crypt cell plus enterocyte proliferation, and mucin content in addition to lowering macrophages, plasmacytes, lymphocytes, and neutrophils in the mucosa and submucosa in alcohol-fed mice. Milk osteopontin targeted the gut-liver axis, preserving the expression of tight-junction proteins in alcohol-fed mice thus maintaining intestinal integrity and permeability. There was protection from liver injury since transaminases, the activity scores, triglyceride levels, neutrophil infiltration, 3-nitrotyrosine residues, lipid peroxidation end products, translocation of gram-negative bacteria, lipopolysaccharide levels, and tumor necrosis factor-α were lower in cotreated than in ethanol-fed mice. Furthermore, milk osteopontin diminished ethanol-mediated liver injury in OPN knockout mice. Milk osteopontin could be a simple effective nutritional therapeutic strategy to prevent alcohol hepatotoxicity due, among others, to gut protective, anti-inflammatory, and anti-steatotic actions.

Human osteopontin splicing isoforms: known roles, potential clinical applications and activated signaling pathways

Human osteopontin is subject to alternative splicing, which generates three isoforms, termed OPNa, OPNb and OPNc. These variants show specific expression and roles in different cell contexts. We present an overview of current knowledge of the expression profile of human OPN splicing isoforms (OPN-SIs), their tissue-specific roles, and the pathways mediating their functional properties in different pathophysiological conditions. We also describe their putative application as biomarkers, and their potential use as therapeutic targets by using antibodies, oligonucleotides or siRNA molecules. This synthesis provides new clues for a better understanding of human OPN splice variants, their roles in normal and pathological conditions, and their possible clinical applications.