Effects of Cow's Milk Processing on MicroRNA Levels

Characterization of microRNA in cow milk and colostrum

MicroRNAs (miRNAs) are short RNA molecules, typically 21 to 25 nucleotides long, synthesized within eukaryotic cells. They play a crucial role in coordinating complex gene expression regulatory networks. The miRNAs are involved in post-transcriptional regulation, either by degrading target mRNA or suppressing their transcription, thereby influencing protein translation. Additionally, characteristics of farm production systems exert a noticeable influence on miRNA profiles, shaping the functional properties of bovine milk. In this study, milk and colostrum samples of Holstein cows (Bos taurus) were collected for RNA extraction and sequencing. Sequencing data underwent quality controls, and short noncoding RNA reads were analyzed to identify and compare miRNA profiles. The sequencing runs yielded 73,567,661 and 44,283,978 reads for milk and colostrum samples, respectively. Following trimming, 8,335,860 and 7,778,212 reads for milk and colostrum samples were retained. A total of 4.3% milk and 37.8% colostrum reads were identified as miRNAs. Overall, 157 miRNAs were common to milk and colostrum, 2 were unique to milk, and 90 were unique to colostrum. After applying a minimal cutoff of 100 reads per miRNA, 146 miRNAs were considered as expressed. In milk, bta-miR-101 was unique; in colostrum, bta-miR-18a, bta-miR-262-3p, bta-miR-130a, and bta-miR-224 were unique; and 141 miRNAs were common to colostrum and milk. Chromosome distribution of these miRNAs varied, with higher representation on autosome 19 and sexual chromosome X. Overall, colostrum contained a greater number of miRNAs, although specific miRNAs such as miR-11-988b, miR-140, and miR-146b were more abundant in milk. Conversely, miRNAs such as miR-7a-5p, let-7e, and miR-16a were more prevalent in colostrum. Validation through quantitative PCR confirmed the expression levels of selected miRNAs from RNA sequencing, establishing concordance between the methods. Analysis of gene regulation by specific miRNAs identified key miRNAs (e.g., miR-223, miR-181a, and miR-155) involved in regulating various genes. Distinct miRNA profiles in milk and colostrum suggest various functionalities, potentially influencing calf development and immune responses. The study unveils a comprehensive map of miRNAs in milk and colostrum and highlights their potential roles in regulating biological processes, as they play an essential role in calf development, disease resistance, and metabolism.

Expression and characterization of exosomal miRNAs in healthy, sub-clinical mastitis and pasteurized milk of buffaloes

Our research on the expression and characterization of exosomal miRNAs in buffalo milk, particularly in the context of healthy, sub-clinical mastitis and pasteurized milk, is a novel contribution to the field. We are the first to investigate the expressions of miRNAs and the characterization of exosomes in boiled and pasteurized milk. This study is based on clinical signs and CMT, where twenty buffalo milk samples were divided into normal and sub-clinical mastitis and a third group of ten commercial pasteurized milk. The SCC differed significantly (p < 0.001) in all the groups before boiling. The data analysis demonstrated elevated differential expression of miR-148a and miR-186 in sub-clinical mastitis and pasteurized milk compared to normal milk before and after boiling. The positive correlation between SCC and miR-148a and miR-186 expression indicates their potential as robust biomarkers for sub-clinical mastitis in buffaloes. The miR-148a and miR-186, known to play roles in various diseases like cancer, can withstand commercial pasteurization and boiling, raising the intriguing possibility of transferring through milk exosomes. This finding underscores the need for clean milk production and the importance of understanding the mechanisms of miRNA transfer between species, which is crucial for the future of animal health and milk production.

Milk-derived exosome nanovesicles: recent progress and daunting hurdles

Raw milk is the foundation of quality and safety in the dairy industry, and improving milk source management is the fundamental guarantee. Milk-derived exosomes (MDEs) are nanoscale information transfer molecules secreted by mammary cells with unique content and high stability, which can be used not only as potential markers to analyze key traits of lactation, reproduction, nutrition and health of animals, but also help farm managers to take timely interventions to improve animal welfare, milk quality, and functional traits. Our review first outlines the latest advances in MDEs isolation and purification, compositional analysis and characterization tools. We then provide a comprehensive summary of recent applications of MDEs liquid biopsy in breed selection, disease prevention and control, and feeding management. Finally, we evaluate the impact of processing on the stability of MDEs to offer guidance for dairy production and storage. The limitations and challenges in the development and use of MDEs markers are also discussed. As a noninvasive marker with high sensitivity and specificity, the MDEs-mediated assay technology is expected to be a powerful tool for measuring cow health and raw milk quality, enabling dynamic and precise regulation of dairy cows and full traceability of raw milk.