Organelles coordinate milk production and secretion during lactation: Insights into mammary pathologies

Profiling several key milk miRNAs and analysing their signalling pathways in dairy sheep breeds during peak and late lactation

BACKGROUND

The comprehensive understanding of microRNAs (miRNAs) in sheep milk during various lactation periods and their impact on milk yield and composition remains limited.

OBJECTIVES

This study aimed to investigate the expression patterns of four highly expressed miRNAs in sheep milk and their association with milk composition and yield parameters during peak and late lactation stages.

METHODS

A total of 40 healthy 4-year-old Akkaraman (n = 20) and Awassi (n = 20) ewes registered with the Ministry of Agriculture and Forestry of the Republic of Türkiye were used in the present study. For miRNA isolation from milk, the Qiagen miRNeasy Serum/Plasma Advanced Kit was utilised following the manufacturer's instructions. The expression levels of miRNAs were assessed using Qiagen miRNA PCR Assays.

RESULTS

The significant fold changes in the expression levels of oar-miR-30a-5p, oar-miR-148a and oar-miR-181a were observed between peak and late lactation periods in the Awassi sheep breed. Conversely, only oar-miR-30a-5p and oar-miR-148a exhibited statistically significant changes in the Akkaraman sheep breed during the same lactation periods. Furthermore, oar-miR-21-5p demonstrated a significant fold change exclusively in peak lactation compared to Akkaraman and Awassi ewes.

CONCLUSIONS

The findings suggest that the expression of the analysed miRNAs is influenced by both the lactation stage and different sheep breeds. This study offers valuable insights into the relationship between key miRNA expressions in sheep milk and milk composition and yield parameters during peak and late lactation, contributing to the existing knowledge in this field.

Microproteomic-Based Analysis of the Goat Milk Protein Synthesis Network and Casein Production Evaluation

Goat milk has been consumed by humans since ancient times and is highly nutritious. Its quality is mainly determined by its casein content. Milk protein synthesis is controlled by a complex network with many signal pathways. Therefore, the aim of our study is to clearly depict the signal pathways involved in milk protein synthesis in goat mammary epithelial cells (GMECs) using state-of-the-art microproteomic techniques and to identify the key genes involved in the signal pathway. The microproteomic analysis identified more than 2253 proteins, with 323 pathways annotated from the identified proteins. Knockdown of IRS1 expression significantly influenced goat casein composition (α, β, and κ); therefore, this study also examined the insulin receptor substrate 1 (IRS1) gene more closely. A total of 12 differential expression proteins (DEPs) were characterized as upregulated or downregulated in the IRS1-silenced sample compared to the negative control. The enrichment and signal pathways of these DEPs in GMECs were identified using GO annotation and KEGG, as well as KOG analysis. Our findings expand our understanding of the functional genes involved in milk protein synthesis in goats, paving the way for new approaches for modifying casein content for the dairy goat industry and milk product development.

Simple methods for measuring milk exosomes using fluorescent compound GIF-2250/2276

Exosomes are small extracellular vesicles (EVs) found in culture supernatants, blood, and breast milk. The size of these nanocomplexes limits the methods of EV analyses. In this study, nitrobenzoxadiazole (NBD), a fluorophore, conjugated endosome-lysosome imager, GIF-2250 and its derivative, GIF-2276, were evaluated for exosome analyses. A correlation was established between GIF-2250 intensity and protein maker levels in bovine milk exosomes. We found that high-temperature sterilization milk may not contain intact exosomes. For precise analysis, we synthesized GIF-2276, which allows for the covalent attachment of NBD to the Lys residue of exosome proteins, and labeled milk exosomes were separated using a gel filtration system. GIF-2276 showed chromatographic peaks of milk exosomes containing >3 ng protein. The area (quantity) and retention time (size) of the exosome peaks were correlated to biological activity (NO synthesis suppression in RAW264.7 murine macrophages). Heat denaturation of purified milk-derived exosomes disrupted these indicators. Proteome analyses revealed GIF-2276-labeled immunomodulators, such as butyrophilin subfamily 1 member A1 and polymeric immunoglobulin receptor. The immunogenicity and quantity of these factors decreased by heat denaturation. When milk exosomes were purified from market-sourced milk we found that raw and low-temperature sterilization milk samples, contained exosomes (none in high-temperature sterilization milk). These results were also supported by transmission electron microscopy analyses. We also found that GIF-2276 could monitor exosome transportation into HEK293 cells. These results suggested that GIF-2250/2276 may be helpful to evaluate milk exosomes.

Milk fat globule size: Unraveling the intricate relationship between metabolism, homeostasis, and stress signaling

Fat is an important component of milk which delivers energy, nutrients, and bioactive molecules from the lactating mother to the suckling neonate. Milk fat consists of a complex mixture of different types of lipids; hundreds of fatty acids, triglycerides, phospholipids, sphingolipids, cholesterol and cholesteryl ester, and glycoconjugates, secreted by the mammary gland epithelial cells (MEC) in the form of a lipid-protein assembly termed the milk fat globule (MFG). The mammary gland in general, and specifically that of modern dairy cows, faces metabolic stress once lactation commences, which changes the lipogenic capacity of MECs directly by reducing available energy and reducing factors required for both lipid synthesis and secretion or indirectly by activating a proinflammatory response. Both processes have the capacity to change the morphometric features (e.g., number and size) of the secreted MFG and its precursor-the intracellular lipid droplet (LD). The MFG size is tightly associated with its lipidome and proteome and also affects the bioavailability of milk fat and protein. Thus, MFG size has the potential to regulate the bioactivity of milk and dairy products. MFG size also plays a central role in the functional properties of milk and dairy products such as texture and stability. To understand how stress affects the structure-function of the MFG, we cover: (i) The mechanism of production and secretion of the MFG and the implications of MFG size, (ii) How the response mechanisms to stress can change the morphometric features of MFGs, and (iii) The possible consequences of such modifications.

Supplementation of dietary semen vaccariae extracts to lactating sow diets: effects on the production performance, milk components, and gene expression related to mammogenesis

This study aimed to investigate the effects of dietary semen vaccariae extracts (SVE) on the production performance, colostrum components, and relative gene expression related to mammogenesis of lactating sows. 48 pregnant sows were selected and randomly allocated into four groups, with six replicates and two sows per replicate. The first group was the control (CON), while the other groups received the same diet further supplemented with 1.5, 3.0 and 4.5 g SVE per kg (SV1, SV2 and SV3, respectively). Compared with the control group, (1) the average daily gain was increased (p < 0.05) in SV1, SV2, and SV3 during the 11-21 days and 1-21 days of lactation; (2) the serum insulin-like growth factor-1, insulin, prolactin, and estrogen contents in SV1, SV2, and SV3 were increased (p < 0.05) on the 1st and 21st day of lactation; (3) The plasma Lysine, Threonine, and Tryptophan concentrations were also higher (p < 0.05) in SV1, SV2, and SV3 on the 1st and 21st day of lactation; (4) The milk Lysine, Methionine, Threonine, and Tryptophan concentrations were higher (p < 0.05) in SV1, SV2, and SV3 on the 1st and 21st day of lactation; (5) The milk lactose ratio and milk protein content were increased (p < 0.05) in the groups treated with semen vaccariae on the 1st day of lactation, while the milkfat ratio and milk protein content were increased (p < 0.05) in SV2 and SV3 on the 21st day of lactation; (6) the immunoglobulin M, A, and G contents were increased (p < 0.05) in the groups treated with the semen vaccariae on the first day of lactation; and (7) the relative PRLR, STAT5a, FcRn, CSN2, and LALBA expressions were higher (p < 0.05) in the groups treated with the semen vaccariae on the 1st and 21st day of lactation. In this study, the optimum dosage was 3.0 g/kg semen vaccariae, which increased the average daily gain of piglets, total lactation yield, and serum hormone levels, improved the amino acid levels in plasma, and facilitated the milk quality, up-regulated the relative gene expressions in the mammogenesis.

Proteomics and Peptidomics As a Tool to Compare the Proteins and Endogenous Peptides in Human, Cow, and Donkey Milk

Cow's milk is the most widely used ingredient in infant formulas. However, its specific protein composition can cause allergic reactions. Finding alternatives to replace cow's milk and fill the nutritional gap with human milk is essential for the health of infants. Proteomic and peptidomic techniques have supported the elucidation of milk's nutritional ingredients. Recently, omics approaches have attracted increasing interest in the investigation of milk because of their high throughput, precision, sensitivity, and reproducibility. This review offers a significant overview of recent developments in proteomics and peptidomics used to study the differences in human, cow, and donkey milk. All three types of milks were identified to have critical biological functions in human health, particularly in infants. Donkey milk proteins were closer in composition to human milk, were less likely to cause allergic reactions, and may be developed as novel raw materials for formula milk powders.

Mammary lipid secretion: a reassessment

Mammary lipid secretion is generally held to be unique and remarkably uniform between the many different orders of mammals. It produces a unit membrane-bounded milk fat globule (MFG). The unit membrane is separated from the lipoprotein boundary of what was the cytoplasmic lipid droplet (CLD) boundary by a uniform layer of cytoplasmic proteins. In 3-8% of the MFG in all species examined this cytoplasmic layer widens to include cytoplasmic organelles which are referred to as 'crescents'. This defines the MFG secretion as apocrine indicating a closely regulated process which minimises the loss of mammary epithelial cell (MEC) cytoplasm. The apocrine nature of the secretion might be expected since the evolution of the mammary gland is considered to be from an apocrine secreting skin gland. This short Research Reflection review is designed to investigate the exact cytoplasmic interactions which allow such efficient lipid secretion. There are two main scenarios: one which assumes that the observed close association between CLD and GV results in the CLD being released as a consequence of sequential exocytosis of the content of the associated GV. The second assumes that the CLD and the MEC apical plasmalemma interact in some way which causes the CLD to rise out of the cytoplasm enveloped in the plasmalemma. Here I present the evidence for the two possibilities. The first scenario is favoured, but the second cannot be ruled out.

ARID3A plays a key regulatory role in palmitic acid-stimulated milk fat synthesis in mouse mammary epithelial cells

Palmitic acid (PA) can stimulate milk fat synthesis in mammary gland, but the specific mechanism is still unclear. In our research, we aim to explore the role and corresponding mechanism of AT-rich interaction domain 3A (ARID3A) in milk fat synthesis stimulated by PA. We found that ARID3A protein level in mouse mammary gland tissues during lactation was much higher than that during puberty and involution. ARID3A knockdown and gene activation showed that ARID3A stimulated the synthesis of triglycerides and cholesterol in HC11 cells, secretion of free fatty acids from cells and lipid droplet formation in cells. ARID3A also promoted the expression and maturation of SREBP1 in HC11 cells. PA stimulated ARID3A protein expression and SREBP1 expression and maturation in a dose-dependent manner, and the PI3K specific inhibitor LY294002 blocked the stimulation of PA on ARID3A expression. ARID3A knockdown blocked the stimulation of PA on SREBP1 protein expression and maturation. We further showed that ARID3A was localized in the nucleus and PA stimulated this localization, and ARID3A knockdown blocked the stimulation of PA on the mRNA expression of SREBP1. To sum up, our data reveal that ARID3A is a key mediator for PA to promote SREBP1 mRNA expression and stimulate milk fat synthesis in mammary epithelial cells.

KRAS Affects the Lipid Composition by Regulating Mitochondrial Functions and MAPK Activation in Bovine Mammary Epithelial Cells

Kirsten rat sarcoma viral oncogene homolog (KRAS), or guanosine triphosphatase KRAS, is a proto-oncogene that encodes the small guanosine triphosphatase transductor protein. Previous studies have found that KRAS can promote cytokine secretion, cell chemotaxis, and survival. However, its effects on milk fat synthesis in bovine mammary epithelial cells are unclear. In this study, the effects of KRAS inhibition on cell metabolism, autophagy, oxidative stress, endoplasmic reticulum stress, mitochondrial function, and lipid composition as well as the potential mechanisms were detected in an immortalized dairy cow mammary epithelial cell line (MAC-T). The results showed that inhibition of KRAS changed the lipid composition (especially the triglyceride level), mitochondrial functions, autophagy, and endoplasmic reticulum stress in cells. Moreover, KRAS inhibition regulated the levels of the mammalian target of rapamycin and mitogen-activated protein kinase (extracellular regulated protein kinases, c-Jun N-terminal kinases, p38) activation. These results indicated that regulation of KRAS would affect the synthesis and composition of milk fat. These results are also helpful for exploring the synthesis and secretion of milk fat at the molecular level and provide a theoretical basis for improving the percentage of fat in milk and the yield of milk from cows.

Emerging innovations on exosome-based onco-therapeutics

Exosomes, nano-sized extracellular vesicles for intercellular communications, are gaining rapid momentum as a novel strategy for the diagnosis and therapeutics of a spectrum of diseases including cancers. Secreted by various cell sources, exosomes pertain numerous functionalities from their parental cells and have enhanced stability that enable them with many features favorable for clinical use and commercialization. This paper focuses on the possible roles of exosomes in cancer therapeutics and reviews current exosome-based innovations toward enhanced cancer management and challenges that limit their clinical translation. Importantly, this paper casts insights on how cold atmospheric plasma, an emerging anticancer strategy, may aid in innovations on exosome-based onco-therapeutics toward improved control over cancers.