Polymorphism of bovine beta-casein and its potential effect on human health

Beyond the gut: Investigating the mechanism of formation of β-casomorphins in human blood

To evaluate the potential differences in the propensity of β-casein A1 (β-CNA1) and A2 (β-CNA2) from bovine milk to release health-relevant β-casomorphins (BCMs), food-derived peptides were monitored over time in the blood of eight human volunteers who consumed milk containing both protein variants. Liquid chromatography coupled with high resolution tandem mass spectrometry revealed interindividual variability of milk peptidomic profiles in human blood. BCMs were not detected, whereas BCM precursors originating from both β-CNA1 and β-CNA2 were ascertained, with β-CNA2-derived peptides showing a slightly greater susceptibility to proteolysis. Ten synthetic peptides mimicking circulating BCM precursors from β-CNA1 and β-CNA2, which were incubated ex vivo with the blood of two volunteers, showed comparable potential to generate BCMs. The formation of BCMs seemed to depend mainly on the size of the BCM precursors and less on the presence of His67 or Pro67. These findings challenge the belief that BCMs are released exclusively from β-CNA1 and support the nutritional safety of conventional milk, informing health policies regarding milk consumption.

The A1/A2 β-casein genotype of cows, but not their horn status, influences peptide generation during simulated digestion of milk

The effect of the horn status of cows on their milk composition and quality is a controversial research topic. In this study, 128 milk samples from 64 horned and 64 disbudded Brown Swiss and Original Braunvieh cows were collected from alpine farms where both horned and disbudded cows were grazing on mountain pastures. The samples were analyzed for their detailed composition and protein digestion in a simulated in vitro digestion (INFOGEST). To exclude probable influences on digestion, the β-CN genotype with its variants A1 and A2 was also included in the study. The effects of horn status and β-CN genotype were investigated in linear mixed models, which included additional influencing random factors such as Original Braunvieh blood proportion, stage of lactation, and farm. Horn status did not have any effect on milk composition or digestion. In contrast, milk from A1A1 cows showed a different protein digestion than milk of A1A2 and A2A2 cows in the gastric phase, including smaller amounts of β-casomorphin(BCM)21-associated peptides and larger amounts of BCM11-associated peptides. Abundances of BCM7 did not differ between β-CN genotypes. At the end of the intestinal phase, the digested milk of A1A1 and A2A2 β-CN genotypes did not differ.

Effect of bovine beta-casomorphins on rat pancreatic beta cells (RIN-5F) under glucotoxic stress

Beta-casomorphins (BCMs) are the bio-active peptides having opioid properties which are formed by the proteolytic digestion of β-caseins in milk. BCM-7 forms when A1 milk is digested in the small intestine due to a histidine at the 67th position in β-casein, unlike A2 milk, which has proline at this position and produces BCM-9. BCM-7 has further degraded into BCM-5 by the dipeptidyl peptidase-IV (DPP-IV) enzyme in the intestine. The opioid-like activity of BCM-7 is responsible for eliciting signaling pathways which enable a wide range of physiological effects. The aim of our study was to find out the differential role of BCMs (BCM-7, BCM-9 and BCM-5) on pancreatic β-cell proliferation, insulin secretion, and opioid peptide binding receptors from β-cells (RIN-5F cell line) in normal (5.5 mM) and high glucose (27.5 mM) concentrations. Our results showed that BCM-7/9/5 did not affect β-cell viability, proliferation, and insulin secretion at normal glucose level. However, at higher glucose concentration, BCMs significantly protected β-cells from glucotoxicity but did not affect the insulin secretion. Interestingly, in the presence of Mu-opioid peptide receptor antagonist CTOP, BCMs did not protect β-cells from glucotoxicity. The results suggest that BCMs protect β-cells from glucotoxicity via non-opioid mediated pathways because BCMs did not modulate the gene expression of the mu, kappa and delta opioid peptide receptors.

Exploring the binding behavior mechanism of vitamin B12 to α-Casein and β-Casein: multi-spectroscopy and molecular dynamic approaches

The aim of this study was to investigate the behavior interaction of α-Casein-B12 and β-Casein-B12 complexes as binary systems through the methods of multiple spectroscopic, zeta potential, calorimetric, and molecular dynamics (MD) simulation. Fluorescence spectroscopy denoted the role ofB12as a quencher in both cases of α-Casein and β-Casein fluorescence intensities, which also verifies the existence of interactions. The quenching constants of α-Casein-B12 and β-Casein-B12 complexes at 298 K in the first set of binding sites were 2.89 × 104 and 4.41 × 104 M-1, while the constants of second set of binding sites were 8.56 × 104 and 1.58 × 105 M-1, respectively. The data of synchronized fluorescence spectroscopy at Δλ = 60 nm were indicative of the closer location of β-Casein-B12 complex to the Tyr residues. Additionally, the binding distance between B12 and the Trp residues of α-Casein and β-Casein were obtained in accordance to the Förster's theory of nonradioactive energy transfer to be 1.95 nm and 1.85 nm, respectively. Relatively, the RLS results demonstrated the production of larger particles in both systems, while the outcomes of zeta potential confirmed the formation of α-Casein-B12 and β-Casein-B12 complexes and approved the existence of electrostatic interactions. We also evaluated the thermodynamic parameters by considering the fluorescence data at three varying temperatures. According to the nonlinear Stern-Volmer plots of α-Casein and β-Casein in the presence of B12 in binary systems, the two sets of binding sites indicated the detection of two types of interaction behaviors. Time-resolved fluorescence results revealed that the fluorescence quenching of complexes are static mechanism. Furthermore, the outcomes of circular dichroism (CD) represented the occurrence of conformational changes in α-Casein and β-Casein upon their binding to B12 as the binary system. The experimental results that were obtained throughout the binding of α-Casein-B12 and β-Casein-B12 complexes were confirmed by molecular modeling.Communicated by Ramaswamy H. Sarma.

Effects of Different Cow-Milk Beta-Caseins on the Gut-Brain Axis: A Narrative Review of Preclinical, Animal, and Human Studies

The gut and brain communicate through bidirectional neural, endocrine, and immune signals to coordinate central nervous system activity with gastrointestinal function. Dysregulated inflammation can promote immune cell activation and increase entero-endocrine signaling and intestinal permeability; hence, a functional gut-brain axis is necessary for a healthy digestive system. The consumption of milk products can lead to gut discomfort via effects on gastrointestinal tract function and the inflammatory state, which, in turn, affect the brain. A1 β-casein and A2 β-casein are major components of bovine-milk protein, and their digestion may result in different physiological effects following the consumption of milk products. Peptides derived from A1 β-casein, such as β-casomorphins, may increase gut dysfunction and inflammation, thereby modulating the availability of bioactive metabolites in the bloodstream and contribute to changes in cognitive function. This narrative review examines the functional interrelationships between the consumption of cow-milk-derived β-caseins and their effect on the brain, immune system, and the gut, which together comprise the gut-brain axis.

Anti-cancer potential of casein and its derivatives: novel strategies for cancer treatment

Cancer is one of the leading causes of death worldwide, with over 10 million fatalities annually. While tumors can be surgically removed and treated with chemotherapy, radiotherapy, immunotherapy, hormonal therapy, or combined therapies, current treatments often result in toxic side effects in normal tissue. Therefore, researchers are actively seeking ways to selectively eliminate cancerous cells, minimizing the toxic side effects in normal tissue. Caseins and its derivatives have shown promising anti-cancer potential, demonstrating antitumor and cytotoxic effects on cells from various tumor types without causing harm to normal cells. Collectively, these data reveals advancements in the study of caseins and their derivative peptides, particularly providing a comprehensive understanding of the molecular mechanism of action in cancer therapy. These mechanisms occur through various signaling pathways, including (i) the increase of interferon-associated STAT1 signaling, (ii) the suppression of stemness-related markers such as CD44, (iii) the attenuation of the STAT3/HIF1-α signaling, (iv) the down-expression of uPAR and PAI-1, (v) the loss of mitochondrial membrane potential and reduced intracellular ATP production, (vi) the increase of caspase-3 activity, and (vii) the suppression of TLR4/NF-кB signaling. Therefore, we conclude that casein could be an effective adjuvant for cancer treatment.

Release of CM-12 from A2-type casein by the cleavage of Ser-Leu-Xaa at the C-terminus using Aspergillus oryzae alkaline protease

BACKGROUND

Aspergillus oryzae protease can release the opioid peptide β-casomorphin-10 (CM-10, YPFPGPIPNS, 60-69) from A2-type casein. However, not only is the yield of the active peptide low, but the key enzyme involved in processing has yet to be identified.

RESULTS

A significant amount of the opioid peptide 60YPFPGPIPNSLP71 (CM-12) was produced from the A2-type casein peptide 53AQTQSLVYPFPGPIPNSLPQNIPPLTQTPV82 when the active protease in A. oryzae protease extract was fractionated with DEAE-Sepharose. The fractionated enzyme produced CM-12 from bovine A2-type casein but not from bovine A1 casein. A major protein of 34 kDa was purified and identified as an alkaline protease (Alp). Motif prediction of the Alp cleavage site using Multiple EM for Motif Elicitation analysis revealed preferable cleavage at the C-terminal end of Ser-Leu-Xaa for the release of CM-12. A2-type casein hydrolysate by Alp exhibited similar levels of opioid activity to that of synthetic CM-12 in cAMP-Glo assays with μ-opioid receptor-expressing HEK293 cells. These results suggest that CM-12 is a major opioid peptide in the casein hydrolysate.

CONCLUSION

Our findings showed that Alp fractionated from A. oryzae protease extract produced the opioid peptide CM-12 from A2-type casein as a result of preferential cleavage at the C-terminal end of Ser-Leu-Xaa and the removal of coexisting enzymes. Moreover, docking predictions suggested a stable interaction between CM-12 and the 3D structure of Alp. Casein hydrolysate with Alp-containing CM-12 has the potential for use as a bioactive peptide material with opioid activity. © 2024 Society of Chemical Industry.

The Effect of A2 Milk on Gastrointestinal Symptoms in Comparison to A1/A2 Milk: A Single-center, Randomized, Double-blind, Cross-over Study

β-Casein, a major protein in cow's milk, is divided into the A1 and A2 type variants. Digestion of A1 β-casein yields the peptide β-casomorphin-7 which could cause gastrointestinal (GI) discomfort but A2 milk containing only A2 β-casein might be more beneficial than A1/A2 (regular) milk. The aim of this study was to evaluate the differences in GI discomfort after ingestion of A2 milk and A1/A2 milk. A randomized, double-blind, cross-over human trial was performed with 40 subjects who experienced GI discomfort following milk consumption. For each intervention period, either A2 milk first (A2→A1/A2) or A1/A2 milk was first consumed for 2 weeks (A1/A2→A2) following a 2-week washout period. GI symptom rating scale (GSRS) scores, questionnaire for digestive symptoms, and laboratory tests including fecal calprotectin were evaluated. For symptom analysis, generalized estimating equations gamma model was used. A2 milk increased bloating (P = 0.041) and loose stools (P = 0.026) compared to A1/A2 milk in GSRS. However, A2 milk caused less abdominal pain (P = 0.050), fecal urgency (P < 0.001) and borborygmus (P = 0.007) compared to A1/A2 milk in questionnaire for digestive symptoms. In addition, fecal calprotectin also decreased or less increased after consumption of A2 milk compared to A1/A2 milk (P = 0.030), and this change was more pronounced in males (P = 0.005) than in females. There were no significant adverse reactions during the trial. A2 milk alleviated digestive discomfort in Koreans following A2 milk consumption (ClinicalTrials.gov NCT06252636 and CRIS KCT0009301).

BCM-7: Opioid-like Peptide with Potential Role in Disease Mechanisms

Bovine milk is an essential supplement due to its rich energy- and nutrient-rich qualities. Caseins constitute the vast majority of the proteins in milk. Among these, β-casein comprises around 37% of all caseins, and it is an important type of casein with several different variants. The A1 and A2 variants of β-casein are the most researched genotypes due to the changes in their composition. It is accepted that the A2 variant is ancestral, while a point mutation in the 67th amino acid created the A1 variant. The digestion derived of both A1 and A2 milk is BCM-7. Digestion of A2 milk in the human intestine also forms BCM-9 peptide molecule. The opioid-like characteristics of BCM-7 are highlighted for their potential triggering effect on several diseases. Most research has been focused on gastrointestinal-related diseases; however other metabolic and nervous system-based diseases are also potentially triggered. By manipulating the mechanisms of these diseases, BCM-7 can induce certain situations, such as conformational changes, reduction in protein activity, and the creation of undesired activity in the biological system. Furthermore, the genotype of casein can also play a role in bone health, such as altering fracture rates, and calcium contents can change the characteristics of dietary products. The context between opioid molecules and BCM-7 points to a potential triggering mechanism for the central nervous system and other metabolic diseases discussed.

Bovine milk β-casein: Structure, properties, isolation, and targeted application of isolated products

β-Casein, an important protein found in bovine milk, has significant potential for application in the food, pharmaceutical, and other related industries. This review first introduces the composition, structure, and functional properties of β-casein. It then reviews the techniques for isolating β-casein. Chemical and enzymatic isolation methods result in inactivity of β-casein and other components in the milk, and it is difficult to control the production conditions, limiting the utilization range of products. Physical technology not only achieves high product purity and activity but also effectively preserves the biological activity of the components. The isolated β-casein needs to be utilized effectively and efficiently for various purity products in order to achieve optimal targeted application. Bovine β-casein, which has a purity higher than or close to that of breast β-casein, can be used in infant formulas. This is achieved by modifying its structure through dephosphorylation, resulting in a formula that closely mimics the composition of breast milk. Bovine β-casein, which is lower in purity than breast β-casein, can be maximized for the preparation of functional peptides and for use as natural carriers. The remaining byproducts can be utilized as food ingredients, emulsifiers, and carriers for encapsulating and delivering active substances. Thus, realizing the intensive processing and utilization of bovine β-casein isolation. This review can promote the industrial production process of β-casein, which is beneficial for the sustainable development of β-casein as a food and material. It also provides valuable insights for the development of other active substances in milk.

A2 milk consumption and its health benefits: an update

Milk is a widely consumed nutrient-rich food containing protein variants such as casein A2 and A1. A1 differs from A2 in an amino acid at position 67 (Pro67 to His67). The breakdown of β-casein yields β-casomorphins (BCM), among which BCM-7 is extensively studied for its effects on the human body. Animal studies have shown that A1 β-casein milk increases digestive transit time and enhances myeloperoxidase activity. Individuals with lactose intolerance prefer A2 milk to conventional A1 milk, as BCM-7 in A1 milk can lead to inflammation and discomfort in sensitive individuals. A2 milk, which contains A2 β-casein, is believed to be more easily digestible than A1 β-casein. Its popularity has grown owing to reports linking A1 casein to diseases such as type 1 diabetes, heart disease, and autism. A2 milk has gained popularity as an alternative to A1 milk, primarily because of its potential benefits for individuals with certain diseases. This review aims to provide an updated understanding of A2 milk consumption and its health benefits. This review aims to provide an updated understanding of A2 milk consumption and its health benefits.

Genome sequencing and de novo and reference-based genome assemblies of Bos indicus breeds

BACKGROUND

Indian cattle breeds (Bos indicus) are known for their remarkable adaptability to hot and humid climates, higher nutritious quality of milk, better disease tolerance, and greater ability to perform in poor feed compared to taurine cattle (Bos taurus). Distinct phenotypic differences are observed among the B. indicus breeds; however, the whole genome sequences were unavailable for these indigenous breeds.

OBJECTIVE

We aimed to perform whole genome sequencing to construct the draft genome assemblies of four B. indicus breeds; Ongole, Kasargod Dwarf, Kasargod Kapila, and Vechur (the smallest cattle of the world).

METHODS

We sequenced the whole genomes using Illumina short-read technology, and constructed de novo and reference-based genome assemblies of these native B. indicus breeds for the first time.

RESULTS

The draft de novo genome assemblies of B. indicus breeds ranged from 1.98 to 3.42 Gbp. We also constructed the mitochondrial genome assemblies (~ 16.3 Kbp), and yet unavailable 18S rRNA marker gene sequences of these B. indicus breeds. The genome assemblies helped to identify the bovine genes related to distinct phenotypic characteristics and other biological processes for this species compared to B. taurus, which are plausibly responsible for providing better adaptive traits. We also identified the genes that showed sequence variation in dwarf and non-dwarf breeds of B. indicus compared to B. taurus.

CONCLUSIONS

The genome assemblies of these Indian cattle breeds, the 18S rRNA marker genes, and identification of the distinct genes in B. indicus breeds compared to B. taurus will help in future studies on these cattle species.

Detection of A2A2 genotype of beta casein protein (CSN2) gene in local, exotic and cross bred cattle in Pakistan

Genetic variants of bovine Beta-casein protein (CSN2) gene especially A1 and A2 are the most important variants in dairy cattle. A1 milk protein is considered as risk factor for different disease and milk intolerance which release Beta-Casomorphin-7 during digestion which is a bioactive opioid but not released from A2 milk protein. This opioid is responsible for several human health problems like Coronary Heart disease, type 1 diabetics, milk intolerance and other neurological disorders. In present study, 360 blood sample were collected from Lohani, Achai, jersey, Holstein Friesian, Achai x jersey, Friesian x Sahiwal and Sahiwal x Friesian from different region of Khyber Pakhtunkhwa (KP) province. The polymerase chain reaction (PCR) amplicons were sequenced for the identification of polymorphism in exon 7 of Beta-casein protein (CSN2) gene. Sequencing analysis explored CSN2 genotype in exon 7 using the Genomic sequence from GenBank (X.71104) g.8101 C > A at codon 67. The allelic and genotypic frequencies of CSN2 gene were analyzed and observed that Holstein Friesian cattle exhibited A1A2 33%, A1A1 50% and A2A2 17%, Jersey cattle show 68% A1A1, 18% A1A2 and 14% A2A2, Sahiwal x Friesian 56% A1A1, 26% A1A2 and 18% A2A2, Jersey × Achai 78% A2A2, 15% A1A2 and 7% A1A1, Achai 100% A2A2 Lohani 100% A2A2. This is a preliminary study, conducted with meager resources, therefore, it is very difficult to make conclusion that which particular breed possess harmful alleles and which breed possess useful alleles of beta-casein gene. Therefore, a comprehensive molecular work is needed to be performed with greater number of samples sequencing.

An update on the effects of food-derived active peptides on the intestinal microecology

The intestinal microecology is a research hotspot, and neologisms related to the gut such as gut-brain axis, gut-lung axis, gut-bone axis, gut-skin axis, gut-renal axis, and gut-liver axis have emerged from recent research. Meticulous investigation has discovered that food-derived active peptides (FDAPs) are bioactive substances that optimize the structure of the gut microbiota to improve human health. However, few reviews have summarized and emphasized the nutritional value of FDAPs and their mechanisms of action in regulating the composition of the gut microbiota. We aim to provide an update on the latest research on FDAPs by comparing, summarizing, and discussing the potential food sources of FDAPs, their physiological functions, and regulatory effects on the intestinal microecology. The key findings are that few studies have analyzed the potential mechanisms and molecular pathways through which FDAPs maintain intestinal microecological homeostasis. We found that an imbalance in the ratio of Bacteroidetes and Firmicutes in the gut microbiota and abnormal production of short-chain fatty acids are key to the occurrence and development of various diseases. This review provides theoretical support for future comprehensive research on the digestion, distribution, metabolism, and excretion of FDAPs and the mechanisms underlying the interactions between FDAPs and the intestinal microecology.

Worldwide research on the health effects of bovine milk containing A1 and A2 β-casein: Unraveling the current scenario and future trends through bibliometrics and text mining

The possible adverse effect of consuming bovine milk with A1 β-casein (but not with A2 β-casein) on health aspects due to the release of β-casomorphin-7 (BCM-7) is currently under debate. The aim of this study was to perform a bibliometric analysis of studies extracted from Scopus to explore the relationship between BCM-7, A1 or A2 bovine milk with different aspects of health. Over time, several research groups were formed that are no longer active and although some authors have returned to the field of study, they have focused their efforts mainly on conducting reviews that show the same imprecise conclusions due to the few original articles. Research is concentrated in Europe and Asia, where New Zealand, China and Germany are the countries with the most publications, records and citations on the subject, respectively. On the other hand, no country in Africa or South America has scientific production, which opens the possibility of building collaborations between countries and exploring areas that lack scientific studies. Based on conflicting information from primarily in vitro and animal studies, and limited clinical trials with poor designs, A1 milk presents pro-inflammatory and oxidative activity, but the evidence is insufficient to associate its consumption with negative health effects. However, A2 milk may be better tolerated by the digestive system of some individuals, suggesting its possible modulating role in the intestinal microbiota. Stronger scientific evidence is needed to reach a consensus on whether the presence of β-casein A1 can significantly negatively affect health. The information shown will allow a better understanding of the subject and consumers will be able to make their own decisions regarding A1 or A2 milk.

Difficulties in Establishing the Adverse Effects of β-Casomorphin-7 Released from β-Casein Variants-A Review

β-Casomorphin-7 (BCM-7) is a peptide released through the proteolysis of β-casein (β-CN), which is considered a bioactive peptide displaying evidence of promoting the binding and activation of the μ-opioid receptor located in various body parts, such as the gastrointestinal tract, the immune system and potentially the central nervous system. The possible effects of BCM-7 on health are a theme rising in popularity due to evidence found in several studies on the modulation of gastrointestinal proinflammatory responses that can trigger digestive symptoms, such as abdominal discomfort. With the advancement of studies, the hypothesis that there is a correlation of the possible effects of BCM-7 with the microbiota-gut-brain axis has been established. However, some studies have suggested the possibility that these adverse effects are restricted to a portion of the population, and the topic is controversial due to the small number of in vivo studies, which makes it difficult to obtain more conclusive results. In addition, a threshold of exposure to BCM-7 has not yet been established to clarify the potential of this peptide to trigger physiological responses at gastrointestinal and systemic levels. The proportion of the population that can be considered more susceptible to the effects of BCM-7 are evidenced in the literature review. The challenges of establishing the adverse effects of BCM-7 are discussed, including the importance of quantifying the BCM-7 release in the different β-CN genotypes. In summary, the reviewed literature provides plausible indications of the hypothesis of a relationship between β-CN A1/BCM-7 and adverse health effects; however, there is need for further, especially in vivo studies, to better understand and confirm the physiological effects of this peptide.

Caseins: Versatility of Their Micellar Organization in Relation to the Functional and Nutritional Properties of Milk

The milk of mammals is a complex fluid mixture of various proteins, minerals, lipids, and other micronutrients that play a critical role in providing nutrition and immunity to newborns. Casein proteins together with calcium phosphate form large colloidal particles, called casein micelles. Caseins and their micelles have received great scientific interest, but their versatility and role in the functional and nutritional properties of milk from different animal species are not fully understood. Caseins belong to a class of proteins that exhibit open and flexible conformations. Here, we discuss the key features that maintain the structures of the protein sequences in four selected animal species: cow, camel, human, and African elephant. The primary sequences of these proteins and their posttranslational modifications (phosphorylation and glycosylation) that determine their secondary structures have distinctively evolved in these different animal species, leading to differences in their structural, functional, and nutritional properties. The variability in the structures of milk caseins influence the properties of their dairy products, such as cheese and yogurt, as well as their digestibility and allergic properties. Such differences are beneficial to the development of different functionally improved casein molecules with variable biological and industrial utilities.

Gastric Emptying of New-World Milk Containing A1 and A2 Β-Casein Is More Rapid as Compared to Milk Containing Only A2 Β-Casein in Lactose Maldigesters: A Randomized, Cross-Over Trial Using Magnetic Resonance Imaging

Lactose maldigesters report an increase in abdominal pain due to the consumption of milk containing a mixture of A1 and A2 β-casein as compared to milk containing only A2 β-casein. Gastric transit affects gastrointestinal symptoms and rapid transit has been associated with an increase in abdominal pain. We conducted a double-blinded, randomized, crossover trial in 10 lactose maldigesters. Subjects consumed each of the two types of milk: conventional milk containing 75% A1 β-casein and 25% A2 β-casein and A2 milk containing 100% A2 β-casein. Magnetic resonance images were acquired, and abdominal pain was rated and recorded at 0, 10, 30, 60 and 120 min after milk consumption. The volume of milk in the stomach was calculated using FSL software. The volume of milk in the stomach after consuming milk with 75% A1 β-casein and 25% A2 β-casein was significantly lower at 30 (p = 0.01), 60 (p = 0.002) and 120 (p < 0.001) minutes as compared to milk with 100% A2 β-casein in the 10 lactose maldigesters. The transit of New-World milk containing A1 and A2 β-casein was more rapid as compared to Old-World milk containing only A2 β-casein. This difference in transit may mediate symptoms of lactose intolerance.

Identification of stably expressed Internal Control Genes (ICGs) for normalization of expression data in liver of C57BL/6 mice injected with beta casomorphins

In recent years, beta-casomorphin peptides (BCM7/BCM9) derived from the digestion of cow milk have drawn a lot of attention world over because of their proposed impact on human health. In order to evaluate the transcriptional modulation of target genes through RT-qPCR in response to these peptides, availability of appropriate reference or internal control genes (ICGs) will be the key. The present study was planned to identify a panel of stable ICGs in the liver tissue of C57BL/6 mice injected with BCM7/BCM9 cow milk peptides for 3 weeks. A total of ten candidate genes were evaluated as potential ICGs by assessing their expression stability using software suites; geNorm, NormFinder and BestKeeper. The suitability of the identified ICGs was validated by assessing the relative expression levels of target genes, HP and Cu/Zn SOD. Based on geNorm, PPIA and SDHA gene pair was identified to be most stably expressed in liver tissue during the animal trials. Similarly, NormFinder analysis also identified PPIA as the most stable gene. BestKeeper analysis showed crossing point SD value for all the genes in the acceptable range that is closer to 1. Overall, the study identified a panel of stable ICGs for reliable normalization of target genes expression data in mice liver tissues during BCM7/9 peptides trial.

Does a Little Difference Make a Big Difference? Bovine β-Casein A1 and A2 Variants and Human Health-An Update

For over 20 years, bovine beta-casein has been a subject of increasing scientific interest because its genetic A1 variant during gastrointestinal digestion releases opioid-like peptide β-casomorphin-7 (β-CM-7). Since β-CM-7 is involved in the dysregulation of many physiological processes, there is a growing discussion of whether the consumption of the β-casein A1 variant has an influence on human health. In the last decade, the number of papers dealing with this problem has substantially increased. The newest clinical studies on humans showed a negative effect of variant A1 on serum glutathione level, digestive well-being, cognitive performance score in children, and mood score in women. Scientific reports in this field can affect the policies of dairy cattle breeders and the milk industry, leading to the elimination of allele A1 in dairy cattle populations and promoting milk products based on milk from cows with the A2A2 genotype. More scientific proof, especially in well-designed clinical studies, is necessary to determine whether a little difference in the β-casein amino acid sequence negatively affects the health of milk consumers.

Investigation of genetic polymorphism at β-casein A1/A2 loci and association analysis with production & reproduction traits in Vrindavani crossbred cows

Casein constitutes approximately 80% of the total protein in bovine milk and is regarded as a high-quality dietary protein embracing all the nine essential amino acids. However, the contested physiological effect of a bioactive peptide released upon digestion of a β-casein milk protein variant originating from a cow of a particular genetic makeup has evoked wide interest in research and industry. Present investigations were carried out to genotype the polymorphism in milk β-casein gene, delineate the seasonal, periodic, and parity variations in production and reproduction traits, and examine the genetic association between β-casein genotypes and production, and reproduction traits in Vrindavani crossbred cows. The study revealed that all three types of genotypes viz. A1A1, A2A2 and A1A2 were present in the Vrindavani crossbred population with genotypic frequencies of 12.3%, 39.6% and 48.1% respectively. The least-squares analysis revealed that the season of calving, period of calving, and parity affected several production and reproduction traits of Vrindavani cows significantly. It was found that β-Casein A1/A2 genotype had a significant effect on economic traits viz. LL (p ≤ 0.05), MY/LL (p ≤ 0.05), and Fat% (p ≤ 0.05) in Vrindavani crossbreds. The findings uncover the genetic constitution of the crossbreds for β-casein locus and emphasize its relationship with important economic traits that can aid in devising selection goals.

Acid and Rennet Coagulation Properties of A2 Milk

This study investigated the acid and rennet milk coagulation properties of A2 milk (β-casein (CN) A2A2 genotype), in comparison to a control milk (blend of A2A1/A1A1/A2A2 genotypes). Acid and rennet coagulation were evaluated using the Optigraph^® system, measuring the coagulation time, aggregation rate, and gel density or curd firmness. The acidification kinetics were monitored using a CINAC^® system, evaluating the time to reach pH 4.6, the acidification rate, the maximum acidification rate, the time required to reach it, and the latency time. The water-holding capacity of acid milk gels and the potential yield, total solids, and syneresis of enzymatic gels were also evaluated. Some variables were highly influenced by the farm factor, showing the importance of the effect of extrinsic parameters. Acid and enzymatic coagulation times were not affected in either milk. The A2 milk presented higher acid gel density and latency time than the control milk. Although the differences in water-holding capacity were not statistically significant, the A2 milk presented lower values, related with the higher gel density. The A2 milk also showed higher rennet aggregation rate and curd firmness than the control milk. Potential yield and syneresis were higher in the A2 milk, which is in accordance with the higher firmness of curd. Coagulation results and gel and curd properties indicate that it is possible to manufacture acid and rennet coagulation dairy products from A2 milk with no major differences when compared with a control milk.

Immune mechanisms, resistance genes, and their roles in the prevention of mastitis in dairy cows

Mastitis is one of the most important diseases of the mammary gland. The increased incidence of this disease in cows is due to the breeding of dairy cattle for higher yields, which is accompanied by an increased susceptibility to mastitis. Therefore, the difficulty involved with preventing this disease has increased. An integral part of current research is the elimination of mastitis in order to reduce the consumption of antibiotic drugs, thereby reducing the resistance of microorganisms and decreasing companies' economic losses due to mastitis (i.e. decreased milk yield, increased drug costs, and reduced milk supply). Susceptibility to mastitis is based on dairy cows' immunity, health, nutrition, and welfare. Thus, it is important to understand the immune processes in the body in order to increase the resistance of animals. Recently, various studies have focused on the selection of mastitis resistance genes. An important point is also the prevention of mastitis. This publication aims to describe the physiology of the mammary gland along with its immune mechanisms and to approximate their connection with potential mastitis resistance genes. This work describes various options for mastitis elimination and focuses on genetic selection and a closer specification of resistance genes to mastitis. Among the most promising resistance genes for mastitis, we consider CD14, CXCR1, lactoferrin, and lactoglobulin.

Separation and characterization of bovine milk proteins by capillary electrophoresis-mass spectrometry

Protein profiling of major bovine milk proteins (i.e., whey and casein proteins) is of great interest in food science and technology. This complex set of protein proteoforms may vary with breed, genetics, lactation stage, health, and nutritional status of the animal. Current routine methods for bovine milk protein profiling at the intact level are typically based on capillary electrophoresis-ultraviolet, which does not allow confirming unequivocally the identity of the separated proteins. As an alternative, in this study, we describe for the first time a novel and simple capillary electrophoresis-mass spectrometry method in positive electrospray ionization mode. Under the optimized conditions, capillary electrophoresis-mass spectrometry allowed the separation and identification at the intact level of major bovine milk whey and casein proteins in less than 15 min. Furthermore, high-resolution mass spectrometry confirmed its importance in the reliable characterization of bovine milk protein proteoforms, especially those with slight molecular mass differences, such as β-casein A1 and A2, which are relevant to unequivocally identify milk with specific β-casein compositions (e.g., A2A2 milk, which is widely known as A2 milk). This differentiation was not possible by matrix-assisted laser desorption/ionization mass spectrometry, which provided rapidly and easily a rich but less accurate fingerprint of bovine milk proteins due to the lower mass resolution.

Frequency of β-Casein Gene Polymorphisms in Jersey Cows in Western Japan

Simple Summary

Reports presenting survey results for β-casein gene polymorphisms have increased, but none have been about Jersey cows in Asia. This study examined the CSN2 gene variants for 590 Jersey cows in Okayama Prefecture, located in the western region of Japan. Blood samples were collected at eight farms, and nucleotide substitutions were determined by sequencing exon 7 regions of chromosome 6 of the CSN2 gene. Blood biochemical analyses were also performed to clarify if A1A1, A1A2, and A2A2 cows differ in their metabolic profiles. The frequency of the A2 allele found in this study was numerically higher than those reported for Holsteins, crossbreeds, and Mexican and Danish Jerseys. The β-casein genotypes did not affect the metabolism of the major nutrients.

Abstract

This study aimed to investigate β-casein gene polymorphisms in Jersey cows in Japan. Blood samples were collected from 590 cows from eight Jersey farms in Okayama Prefecture, western Japan. Sequence analysis of exon 7 regions in chromosome 6 of the CSN2 gene revealed the genotype and allele frequencies of the β-casein variants. Considering that variant B belongs to the A1 group and variant I to the A2 group, plasma metabolite concentrations were compared among the A1A1, A1A2, and A2A2 group-based genotypes. The most frequent genotype was A2A2 (0.558), followed by A2B (0.190) and A2I (0.103). No variants of A3, F, G, H1, or H2 were found. The frequencies of group-based genotypes were A1A1 (0.032), A1A2 (0.303), and A2A2 (0.665). Although farm-to-farm differences were observed in the plasma concentrations of urea nitrogen, calcium, and phosphorus, no differences were found between the A1A1, A1A2, and A2A2 group-based genotypes; hence, the β-casein genotypes did not affect the metabolism of major nutrients. Owing to the high frequency of the A2 variant, Jersey cows can be considered an attractive breed for marker-assisted selection to create A2A2 herds.

Demographic pattern of A1/A2 beta casein variants indicates conservation of A2 type haplotype across native cattle breeds (Bos indicus) of India

Genetic variations of the beta casein gene hold importance because of their probable association with human health. Comparative sequence analysis of β-casein gene across Indian native, crossbred and exotic breeds in India revealed 15 SNPs and 4 INDELs corresponding to 14 haplotypes. The frequency of A2 type haplotype was maximum (0.941) across all Indian native breeds. Among the 15 variants reported for taurine breeds, only three (A1, A2 and B) were observed in analysed populations. Allelic profiling of A1/A2 β-casein variants in ~ 4000 animals belonging to three cattle types and breeding bulls also revealed the predominance of A2 allele (0.95) in Indian cattle. The high proportion of A2 allele/haplotype indicates that Indian native cattle are the best suited to meet the demands for A2 milk globally. However, a higher percentage of heterozygous genotype (A1A2) in breeding bulls warrants the need to screen sire lines so as to drift the herd towards A2.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03232-0.

Worldwide Research Trends on Milk Containing Only A2 β-Casein: A Bibliometric Study

Simple Summary

A1 β-casein has been correlated with adverse health outcomes, and, as a consequence, milk containing only A2 β-casein has emerged on the market. There has been a relevant increase in publications in this area since 2010. Food Science Technology and Agriculture were the main research areas of this topic. The term β-casomorphin was the most frequently used. The USA, New Zealand, and Australia were the most productive countries, though the most productive research institutions were, in absolute terms, from India, France, and Germany. The majority of the most cited studies that refer to A2 β-casein and health were reviews, and a few clinical trials have also been published.

Abstract

The protein fraction of β-casein may play a key role in the manifestation of a new intolerance: milk protein intolerance. The most common forms of β-casein among dairy cattle breeds are A1 and A2 β-casein. During gastrointestinal digestion of A1 β-casein, an opioid called peptide β-casomorphin-7 (BCM-7) is more frequently released, which can lead to adverse health outcomes. For that reason, novel products labelled as “A2 milk” or “A1-free dairy products” have appeared on the market. In this context, a bibliometric analysis on A2 β-casein research was carried out through the Web of Science (WoS) database. The main objective of this work was to provide an overview of the state of the art in the field of β-casein A2 by analyzing the number of publications per year, trends in thematic content, the most frequently used terms, and the most important institutions and countries in the field. This bibliometric study showed that a greater effort is needed to determine the possible implications of this novel product for human health and the market.

Benefits of A2 Milk for Sports Nutrition, Health and Performance

Bovine milk is one of the best pre-and pro-workout sources for athletes owing to its rich nutritional content. Even though bovine milk consumption significantly benefits athletes' health and performance, many athletes cannot consume bovine milk since they struggle with gastrointestinal problems caused after milk consumption. Especially, the consumption of regular milk, which contains A1 β-casein, is associated with a variety of diseases ranging from gastrointestinal discomfort to ischemic heart diseases. The main reason behind this is related to β-casomorphine 7 (BCM-7), which is derived from A1 β-casein during the digestion of A1 milk. A1 β-casein is formed as a result of a point mutation in the position of 67th in the amino acid sequence A2 β-casein by changing proline to histidine. Therefore, this mutated form of β-casein in regular milk cannot easily be digested by the human-associated digestion enzymes. A2 milk, which includes A2 β-casein instead of A1 β-casein, is the best substitute for regular milk with the same nutritional content. This natural form of milk positively affects the athlete's health as well as performance without causing any gastrointestinal discomfort or more serious problems which are seen in the consumption of regular milk. In this review, A2 milk and its potential health effects in comparison to diseases related to A1 milk consumption are discussed.

A2 Milk and BCM-7 Peptide as Emerging Parameters of Milk Quality

Beta-casein makes up about 30% of the total protein contained in milk and can be present in cows' milk in two distinct forms (A1 or A2) or as a combination of the two. The only difference between these two variants of β-casein (β-CN) is a single amino acid substitution. This results in a different behavior of the protein upon enzymatic cleavage, following human consumption or due to microbial action. In most of the commercially available milk containing A1 or A1/A2 β-CN variants, the β-casomorphin-7 peptide (BCM-7) is released upon digestion and during cheese manufacturing/ripening, while this does not happen with A2 milk. BCM-7 is a known μ-opioid receptor agonist that may influence the gastro-intestinal physiology directly and may also exert effects elsewhere in the body, such as on the cardiovascular, neurological and endocrine systems. The present article is aimed at a revision of prior review papers on the topic, with a focus on the impact of ingestion of A1 β-CN milk and A2 β-CN milk on any health-related outcomes and on the impact of A1 or A2 β-CN variant on technological properties of cows' milk. When systematic reviews were considered, it was possible to conclude that A2 β-CN exerts beneficial effects at the gastrointestinal level compared with A1 β-CN, but that there is no evidence of A1 β-CN having negative effects on human health. Physicochemical differences among cows' milk containing either β-CN A2 or β-CN A1 and their effects on technological properties are discussed.

Role of CSN2, CSN3, and BLG genes and the polygenic background in the cattle milk protein profile

To devise better selection strategies in dairy cattle breeding programs, a deeper knowledge of the role of the major genes encoding for milk protein fractions is required. The aim of the present study was to assess the effect of the CSN2, CSN3, and BLG genotypes on individual protein fractions (α_S1-CN, α_S2-CN, β-CN, κ-CN, β-LG, α-LA) expressed qualitatively as percentages of total nitrogen content (% N), quantitatively as contents in milk (g/L), and as daily production levels (g/d). Individual milk samples were collected from 1,264 Brown Swiss cows reared in 85 commercial herds in Trento Province (northeast Italy). A total of 989 cows were successfully genotyped using the Illumina Bovine SNP50 v.2 BeadChip (Illumina Inc.), and a genomic relationship matrix was constructed using the 37,519 SNP markers obtained. Milk protein fractions were quantified and the β-CN, κ-CN, and β-LG genetic variants were identified by reversed-phase HPLC (RP-HPLC). All protein fractions were analyzed through a Bayesian multitrait animal model implemented via Gibbs sampling. The effects of days in milk, parity order, and the CSN2, CSN3, and BLG genotypes were assigned flat priors in this model, whereas the effects of herd and animal additive genetic were assigned Gaussian prior distributions, and inverse Wishart distributions were assumed for the respective co-variance matrices. Marginal posterior distributions of the parameters of interest were compared before and after the inclusion of the effects of the 3 major genes in the model. The results showed that a high portion of the genetic variance was controlled by the major genes. This was particularly apparent in the qualitative protein profile, which was found to have a higher heritability than the protein fraction contents in milk and their daily yields. When the genes were included individually in the model, CSN2 was the major gene controlling all the casein fractions except for κ-CN, which was controlled directly by the CSN3 gene. The BLG gene had the most influence on the 2 whey proteins. The genetic correlations showed the major genes had only a small effect on the relationships between the protein fractions, but through comparison of the correlation coefficients of the proteins expressed in different ways they revealed potential mechanisms of regulation and competitive synthesis in the mammary gland. The estimates for the effects of the CSN2 and CSN3 genes on protein profiles showed overexpression of protein synthesis in the presence of the B allele in the genotype. Conversely, the β-LG B variant was associated with a lower concentration of β-LG compared with the β-LG A variant, independently of how the protein fractions were expressed, and it was followed by downregulation (or upregulation in the case of the β-LG B) of all other protein fractions. These results should be borne in mind when seeking to design more efficient selection programs aimed at improving milk quality for the efficiency of dairy industry and the effect of dairy products on human health.

A Survey to Identify the Current Management of Cow’s Milk Disorders and the Role of Goat Milk-Based Formulas in the Middle East and North Africa Region

Background: Cow’s milk allergy (CMA) and cow’s milk intolerance (CMI) are the major cow’s milk disorders observed in infants and young children. This study investigates, for the first time, physician knowledge regarding CMA and CMI prevalence, diagnosis, and management in the Middle East and North Africa (MENA) region. In addition, we explore the role of goat milk-based formula as an alternative in infants suffering from CMI. Method: This cross-sectional survey was conducted from December 2020 to February 2021. A convenience sample of 2500 MENA-based physicians received the questionnaire, developed by a working group of pediatric experts. Results: 1868 physicians completed the questionnaire, including pediatric specialists (80.8%), training physicians (0.2%), dermatologists (0.1%), family/general physicians (12.9%), neonatologists (3.6%), neurosurgeons (0.2%), allergy nurse specialists (0.3%), pharmacists (2.1%), and public health workers (0.1%). Differentiation between CMA and CMI was recognized by the majority of respondents (80.7%), for which the majority of respondents (35.4%) identified that the elimination and challenge test was the best test to differentiate CMA from CMI, whereas 30.7% and 5.4% preferred the immunoglobulin E (IgE) test and skin prick test, respectively. In addition, 28.5% of respondents reported that there is no confirmatory test to differentiate CMA from CMI. The majority of respondents (47.3%) reported that amino acid-based formula (AAF)/ extensively hydrolyzed formula (EHF) is the cornerstone for the management of CMA. However, most respondents (33.7%) reported that lactose avoidance was best for the management of CMI. Overall, 65% of the respondents were aware of nutritionally adapted goat’s milk formula as an alternative to cow’s milk products and 37% would recommend its routine use in infants (≤2 years of age). Conclusion: The results of this survey demonstrate that the majority of physicians are aware of the underlying pathophysiology and management of CMA and CMI. However, a significant proportion of physicians do not follow the clinical guidelines concerning CMA/CMI diagnosis and management. Notably, this survey identified that goat’s milk formulas may offer a suitable alternative to AAF/EHF in infants with CMI as they contain β-casein protein which is easily digestible. In addition, goat’s milk formulas contain higher levels of oligosaccharides and medium-chained fatty acids compared with standard cow’s milk formulas, yet further clinical trials are warranted to support the inclusion of goat’s milk formulas in clinical guidelines.

Assessment of A1 and A2 variants in the CNS2 gene of some cattle breeds by using ACRS-PCR method

The aim of this study is to reveal β-casein polymorphism of some cattle breeds and also the potential to produce A2 milk from existing animals and to develop strategies in this area. Therefore, a total of 400 cattle, 100 animals from each breed of Holstein, Brown Swiss, Jersey and Simmental raised commonly in Turkey, were obtained, and C > A polymorphism in 67th amino acid in the 7th exons of β-casein gene was determined by TaqI enzyme with PCR-ACRS method. Blood samples were collected from dairy cattle farms raising Holstein, Brown Swiss and Jersey breeds from Konya province and Simmental breed from Kütahya province in Turkey. A1 and A2 allele frequencies in Holstein, Brown Swiss, Jersey and Simmental cattle breeds were determined as 0.475/0.525, 0.370/0.630, 0.215/0.785 and 0.440/0.560, respectively. The highest A2 allele frequency (0.785) was found in Jersey breed. A1A1 genotypes in Holstein, Brown Swiss, Jersey and Simmental breeds were 0.240, 0.150, 0.030 and 0.160, respectively; A1A2 genotypes were 0.470, 0.440, 0.370 and 0.560, respectively; A2A2 genotypes were determined as 0.290, 0.410, 0.600 and 0.280, respectively. In these breeds, the highest A2A2 genotype frequency was found in Jersey (0.600), the lowest A1A1 genotype frequency (0.030) was found in Jersey and the highest A1A2 genotype frequency (0.560) was found in Simmental. Holstein, Brown Swiss, Simmental and Jersey populations were at the level of Hardy-Weinberg in terms of β-casein gene (p > 0.05). The average H_o, H_e and PIC values were calculated as 0.460, 0.469 and 0.605, respectively. In conclusion, the frequency of commonly reared cattles in Turkey especially Brown Swiss, and Jersey breeds in A2A2 genotype are satisfactory, but it can be said that the use of animals with A2 allele in selection is extremely important for increasing A2 milk producing potential in the future.

Leaky gut biomarkers in casein- and gluten-rich diet fed rat model of autism

It is proposed that gluten- and casein-rich diets (GRD and CRD) can synergistically exacerbate dysbiosis as comorbidity in autism by worsening leaky gut that affects the brain through the gut–brain axis. In this study, 35 young male rats were divided into 7 groups, Group 1 serves as control; Group 2, clindamycin (CL)-treated; and Group 3, propionic acid (PPA)-induced rodent model of autism. These three groups were fed standard diet until the end of the experiment. Groups 4–7 are rats treated similarly with CL and PPA, then fed on CRD or GRD until the end of the experiment. Serum zonulin, glutathione (GSH), lipid peroxides, and gut microbial composition were measured in the seven studied groups. Data demonstrate the significant increase in serum zonulin as marker of leaky gut in the CL-treated groups fed on CRD or GRD. Lipid peroxides were significantly higher in the serum of GRD-fed rats compared to CRD-fed or normal diet-fed rats. GSH was much lower in CL-treated groups fed on CRD or GRD compared to PPA-treated rats fed on both diets. Both diets differentially affected the diversity of the gut microbiota. This study demonstrates that CRD and GRD exacerbates leaky gut, according to serum zonulin, which was used as marker for increased gut permeability.

The Moo'D Study: protocol for a randomised controlled trial of A2 beta-casein only versus conventional dairy products in women with low mood

Background

Beta-casein is a major protein in cow’s milk, of which A1 and A2 are the most frequent variants. Recent evidence implicates A1 beta-casein consumption in mechanisms that are of potential importance to mental health, yet its possible effects on psychological endpoints remains unknown. The primary aim of the study is to evaluate the comparative effects of consumption of dairy products containing A2 beta-casein versus conventional dairy (i.e. containing both A1 and A2 beta-casein) on symptoms of psychological distress in women with low mood.

Methods

‘The Moo’D Study’ is a 16-week, superiority, 1:1 parallel group, triple-blinded, randomised controlled trial. Ninety women with low mood (Patient Health Questionnaire score ≥ 5) will be randomised to consume either A2 beta-casein only or conventional dairy products. The primary outcome, symptoms of psychological distress, will be measured by the 21-item Depression, Anxiety and Stress Scale. Secondary outcomes will include symptoms of depression, anxiety and stress, severity of low mood, cognition, gut microbiota composition, gut symptomatology, markers of immune function, gut inflammation, systemic metabolites, endothelial integrity and oxidative stress, body composition, perceived wellbeing, sleep, quality of life, resource use and cost-effectiveness.

Discussion

This study will advance our understanding of the possible impact of milk proteins on psychological distress in women as well as elucidate mechanisms underpinning any association. Given dairy products form a substantial component of traditional and Western diets, the implications of these findings are likely to be of clinical and public health importance.

Trial registration

The trial protocol has been prospectively registered with the Australia and New Zealand Clinical Trials Registry, ACTRN12618002023235. Registered on 17 December 2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05812-6.

Novel LNA probe-based assay for the A1 and A2 identification of β-casein gene in milk samples

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A novel LNA probe-based qPCR allowed the detection of A1 and A2 alleles from β -casein gene in bovine samples.

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100% of agreement between results obtained by rHamp and LNA qPCR assays.

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The limit of detection of A1 in A2 samples was 1% or 7.5 DNA copies.

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This method is a highly sensitive and specific tool for detecting A1 and A2 alleles directly in milk.

The rising consumption of A2 milk and its derivatives in recent years has garnered attention from both consumers and producers, mainly due its possible health benefits, such as enhanced digestion and easier absorption. Thus, a novel real-time PCR using a combination of locked nucleic acid modified (LNA) conjugated probes was developed to genotype A1 and A2 alleles of β-casein gene (CSN2) and to detect and quantify the A1 presence in A2 samples. The limit of detection for each probe (A1 and A2) was evaluated using decreasing serial dilutions. Besides, the sensitivity of A1 allele detection in the A2 samples was also tested. The limits of detection of A1 and A2 alleles were 6 copies, while for A1 allele detection in A2 samples was 7.5 copies (1%). The LNA-probe based method was found to be rapid, robust, highly sensitive, cost effective, and can be employed as screening test to certificate the A2 dairy products.

Polymorphism of the beta-casein gene and adaptability of Sindhi cows to semiarid conditions

This study aimed to investigate the effect of beta-casein genotypes (A1A2 and A2A2) in three different thermal comfort conditions on the adaptability of Sindhi cows and as a tool for selecting thermotolerant cattle. Twelve Sindhi cows were used in a completely randomized design in a 2 × 3 factorial arrangement, with six replicates, with two genotypes, and three thermal comfort conditions. The climatic variables were recorded, while black globe temperature, humidity index, and radiant heat load were calculated. We measured respiratory rate, surface temperature, and rectal temperature while the heat tolerance coefficient was calculated. Genotype had no significant effect (p > 0.05) on any of the parameters measured. However, there was a thermal comfort condition effect (p < 0.05) on rectal temperature, surface temperature, and thermal gradients. The respiratory rate and heat tolerance coefficient were not significantly affected (p > 0.05). Therefore, although the results indicate substantial adaptability of Sindhi cows under any thermal conditions, the tested genotypes should not be used as a tool for selecting thermotolerant Sindhi cows.

Identification and in silico characterization of structural and functional impacts of genetic variants in milk protein genes in the Zebu breeds Guzerat and Gyr

Whole genome sequencing of bovine breeds has allowed identification of genetic variants in milk protein genes. However, functional repercussion of such variants at a molecular level has seldom been investigated. Here, the results of a multistep Bioinformatic analysis for functional characterization of recently identified genetic variants in Brazilian Gyr and Guzerat breeds is described, including predicted effects on the following: (i) evolutionary conserved nucleotide positions/regions; (ii) protein function, stability, and interactions; (iii) splicing, branching, and miRNA binding sites; (iv) promoters and transcription factor binding sites; and (v) collocation with QTL. Seventy-one genetic variants were identified in the caseins (CSN1S1, CSN2, CSN1S2, and CSN3), LALBA, LGB, and LTF genes. Eleven potentially regulatory variants and two missense mutations were identified. LALBA Ile60Val was predicted to affect protein stability and flexibility, by reducing the number the disulfide bonds established. LTF Thr546Asn is predicted to generate steric clashes, which could mildly affect iron coordination. In addition, LALBA Ile60Val and LTF Thr546Asn affect exonic splicing enhancers and silencers. Consequently, both mutations have the potential of affecting immune response at individual level, not only in the mammary gland. Although laborious, this multistep procedure for classifying variants allowed the identification of potentially functional variants for milk protein genes.

Effect of Protein Genotypes on Physicochemical Properties and Protein Functionality of Bovine Milk: A Review

Milk protein comprises caseins (CNs) and whey proteins, each of which has different genetic variants. Several studies have reported the frequencies of these genetic variants and the effects of variants on milk physicochemical properties and functionality. For example, the C variant and the BC haplotype of αS1-casein (αS1-CN), β-casein (β-CN) B and A1 variants, and κ-casein (κ-CN) B variant, are favourable for rennet coagulation, as well as the B variant of β-lactoglobulin (β-lg). κ-CN is reported to be the only protein influencing acid gel formation, with the AA variant contributing to a firmer acid curd. For heat stability, κ-CN B variant improves the heat resistance of milk at natural pH, and the order of heat stability between phenotypes is BB > AB > AA. The A2 variant of β-CN is more efficient in emulsion formation, but the emulsion stability is lower than the A1 and B variants. Foaming properties of milk with β-lg variant B are better than A, but the differences between β-CN A1 and A2 variants are controversial. Genetic variants of milk proteins also influence milk yield, composition, quality and processability; thus, study of such relationships offers guidance for the selection of targeted genetic variants.

Genetic polymorphism of bovine beta-casein gene in Japanese dairy farm herds

The aim of this study was to investigate beta‐casein polymorphism among 320 Japanese cows sampled from eight dairy farms. We used a newly‐developed genotyping method that involved collecting DNA from hairs and a Cycleave polymerase chain reaction (PCR) assay to detect the A1, A2, and B variants. Results revealed the presence of five genotypes (A1A1, A2A2, A1A2, A1B, and A2B). We found that the most common genotype was A2A2 (0.42), followed by A1A2 (0.39) and A1A1 (0.11). The A1B and A2B genotypes were less frequent (<0.05). The frequencies of alleles A1, A2, and B were calculated to be 0.32, 0.64, and 0.04, respectively. Our study is the first to show the current status of beta‐casein polymorphisms in Japanese dairy farms. Given the adverse effects of A1 beta‐casein on human health, attempts have been made to develop herds consisting solely of A2A2 cows. Our study provides a reference for improving cow populations in Japanese dairy farms. The Cycleave PCR‐based assay we developed here can be used for rapid and reliable genotyping of bovine beta‐casein.

Post-weaning A1/A2 β-casein milk intake modulates depressive-like behavior, brain μ-opioid receptors, and the metabolome of rats

The postnatal period is critical for brain and behavioral development and is sensitive to environmental stimuli, such as nutrition. Prevention of weaning from maternal milk was previously shown to cause depressive-like behavior in rats. Additionally, loss of dietary casein was found to act as a developmental trigger for a population of brain opioid receptors. Here, we explore the effect of exposure to milk containing A1 and A2 β-casein beyond weaning. A1 but not A2 β-casein milk significantly increased stress-induced immobility in rats, concomitant with an increased abundance of Clostridium histolyticum bacterial group in the caecum and colon of A1 β-casein fed animals, brain region-specific alterations of μ-opioid and oxytocin receptors, and modifications in urinary biochemical profiles. Moreover, urinary gut microbial metabolites strongly correlated with altered brain metabolites. These findings suggest that consumption of milk containing A1 β-casein beyond weaning age may affect mood via a possible gut-brain axis mechanism.

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Postnatal brain development is sensitive to nutritional exposures

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Consumption of A1 but not A2 β-casein milk post-weaning affects mood in rats

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Gut microbial, biochemical, and neurochemical changes accompany mood alterations

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Urinary gut microbial metabolites correlate with brain metabolites

Análisis genético de cinco polimorfismos de nucleótido simple de caseínas lácteas obtenidos con chips genómicos en ganado Holstein de Antioquia, Colombia

Los polimorfismos genéticos asociados con las caseínas de la leche son de gran importancia, ya que pueden ser usados como marcadores genéticos para mejorar el rendimiento productivo en los hatos lecheros. El objetivo de este estudio fue evaluar la diversidad y estructura genética de 5 SNP de caseínas de la leche, obtenidos con chips genómicos en vacas y toros de raza Holstein en Antioquia (Colombia). Fueron muestreados 113 animales de raza Holstein en 3 regiones del departamento de Antioquia (norte, centro y oriente) y un cuarto grupo de sementales comerciales. Los animales fueron genotipificados con chips genómicos de alta densidad (Illumina BovineHD e Illumina SNP50 v2), a partir de los cuales se identificaron 5 SNP (ARS-BFGL-NGS-8140, BTA-77380-no-rs, BTA-32346-no-rs, BTB-00821654 y ARS-BFGL-NGS-15809). Para cada SNP se realizó un análisis genético mediante un análisis de varianza molecular (Amova) usando el software GenAIEx 6.501. Los SNP con mayor heterocigosidad total (HT) fueron ARS-BFGL-NGS-8140 y BTA-32346-no-rs, con resultados cercanos al 45%; sin embargo, la HT para ARS-BFGL-NGS-15809, BTA-77380-no-rs y BTB-00821654 estuvo por debajo del 15%. El SNP con mayor diversidad genética fue BTA-32346-no-rs (Ho – He = 0,06; p < 0,05). En esta investigación se evaluó una subpoblación de toros comerciales extranjeros, en la cual se obtuvieron frecuencias alélicas y genotípicas similares a las obtenidas para las subpoblaciones locales, sugiriendo que los alelos de los toros muy posiblemente están fijados en dichas subpoblaciones, por lo que la estructura y diversidad genética tienden a ser bajas en la muestra de estudio.