Bta-miR-152 affects intracellular triglyceride content by targeting the UCP3 gene

MicroRNA-2285f regulates milk fat metabolism by targeting MAP2K2 in bovine mammary epithelial cells

In this study, Holstein dairy cows raised in Ningxia were selected as the research object. Mammary epithelial cells (BMECs) were extracted from the milk of eight Holstein cows with significantly different milk fat expression rates and transcribed for sequencing. Bioinformatics analysis was used to analyse the correlation of fat milk percentage, and the critical miR-2285f regulating milk fat was screened out. The target gene binding sites were predicted, and 293T cells and mammary epithelial cells were used as miRNA and target gene models for functional verification in vitro. The tissue difference of miR-2285f Holstein cows was quantitatively analysed by transfecting miR-2285f mimic and inhibitor. Assay (dual luciferase reporter gene assay) and quantitative real-time PCR (quantitative real-time PCR, qRT-PCR), triglyceride (TAG) detection, oil red O detection of lipid droplets, Western Blot assay, Edu and Flow cytometry, The molecular regulatory effects of miR-2285f and target gene MAP2K2 on milk fat metabolism of Holstein dairy cows were studied. The wild-type vector and mutant vector of map2k2-3'utr were constructed, and double luciferase reporting experiments were conducted to verify that MAP2K2 was one of the target genes of miR-2285f. According to qRT-PCR and Western Blot analysis, miR-2285f mainly regulates the expression of MAP2K2 protein in BMECs at the translation level. Bta-miR-2285f can promote cell proliferation and slow cell apoptosis by regulating MAP2K2. Bta-miR-2285f can promote triglyceride (TAG) and lipid droplet accumulation in mammary epithelial cells by targeting MAP2K2. Bta-miR-2285f can regulate protein levels of fat milk marker gene PPARG by targeting MAP2K2. In conclusion, miR-2285f can target the expression of the MAP2K2 gene, promote the proliferation of dairy mammary epithelial cells, inhibit cell apoptosis and regulate the milk fat metabolism in dairy mammary epithelial cells. The results of this study revealed the function of miR-2285f in regulating the differential expression of fat milk in Holstein dairy cows at the cellular level. They provided a theoretical and experimental basis for analysing the regulation network of milk fat synthesis of Holstein dairy cows and the molecular breeding of dairy cows.

Progress in epigenetic regulation of milk synthesis, with particular emphasis on mRNA regulation and DNA methylation

Inadequate milk secretion and a lack of nutrients in humans and mammals are serious problems. It is of great significance to clarify the mechanisms of milk synthesis and treatment methods. Epigenetic modification, represented by RNA methylation, is an important way of gene expression regulation that profoundly affects human gene expression and participates in various physiological and pathological mechanisms. Epigenetic disorders also have an important impact on the production and secretion of milk. This review systematically summarized the research results of epigenetics in the process of lactation in PubMed, Web of Science, NSTL, and other databases and reviewed the effects of epigenetics on human and mammalian lactation, including miRNAs, circRNAs, lncRNAs, DNA methylations, and RNA methylations. The abnormal expression of miRNAs was closely related to the synthesis and secretion of milk fat, milk protein, and other nutrients in the milk of cattle, sheep, and other mammals. MiRNAs are also involved in the synthesis of human milk and the secretion of nutrients. CircRNAs and lncRNAs mainly target miRNAs and regulate the synthesis of nutrients in milk by ceRNA mechanisms. The abnormal expression of DNA and RNA methylation also has an important impact on milk synthesis. Epigenetic modification has the potential to regulate the milk synthesis of breast epithelial cells. Analyzing the mechanisms of human and mammalian milk secretion deficiency and nutrient deficiency from the perspective of epigenetics will provide a new perspective for the treatment of postpartum milk deficiency in pregnant women and mammalian milk secretion deficiency.

MicroRNA-200c Affects Milk Fat Synthesis by Targeting PANK3 in Ovine Mammary Epithelial Cells

Milk fat is the foremost nutrient of milk and a vital indicator in evaluating milk quality. Accumulating evidence suggests that microRNAs (miRNAs) are involved in the synthesis of milk fat. The miR-200c is closely related to lipid metabolism, but little is known about its effect on the synthesis of milk fat in MECs of ewes. Herein, the effect of miR-200c on the proliferation of ovine mammary epithelial cells (MECs) and its target relationship with a predicted target gene were investigated. The regulatory effects of miR-200c on the expression of the target genes and the content of triglycerides in ovine MECs were further analyzed. The results revealed that the expression level of miR-200c was differentially expressed in both eight tissues selected during lactation and in mammary gland tissues at different physiological periods. Overexpression of miR-200c inhibited the viability and proliferation of ovine MECs, while inhibition of miR-200c increased cell viability and promoted the proliferation of ovine MECs. Target gene prediction results indicated that miR-200c would bind the 3'UTR region of pantothenate kinase 3 (PANK3). Overexpression of miR-200c reduced the luciferase activity of PANK3, while inhibition of miR-200c increased its luciferase activity. These findings illustrated that miR-200c could directly interact with the target site of the PANK3. It was further found that overexpression of miR-200c reduced the expression levels of PANK3 and, thus, accelerated the synthesis of triglycerides. In contrary, the inhibitor of miR-200c promoted the expression of PANK3 that, thus, inhibited the synthesis of triglycerides in ovine MECs. Together, these findings revealed that miR-200c promotes the triglycerides synthesis in ovine MECs via increasing the lipid synthesis related genes expression by targeting PANK3.

Regulation of Key Genes for Milk Fat Synthesis in Ruminants

Milk fat is the most important and energy-rich substance in milk and plays an important role in the metabolism of nutrients during human growth and development. It is mainly used in the production of butter and yogurt. Milk fat not only affects the flavor and nutritional value of milk, but also is the main target trait of ruminant breeding. There are many key genes involve in ruminant milk fat synthesis, including ACSS2, FASN, ACACA, CD36, ACSL, SLC27A, FABP3, SCD, GPAM, AGPAT, LPIN, DGAT1, PLIN2, XDH, and BTN1A1. Taking the de novo synthesis of fatty acids (FA) and intaking of long-chain fatty acids (LCFA) in blood to the end of lipid droplet secretion as the mainline, this manuscript elucidates the complex regulation model of key genes in mammary epithelial cells (MECs) in ruminant milk fat synthesis, and constructs the whole regulatory network of milk fat synthesis, to provide valuable theoretical basis and research ideas for the study of milk fat regulation mechanism of ruminants.

Progress on the Regulation of Ruminant Milk Fat by Noncoding RNAs and ceRNAs

Milk fat is not only a key factor affecting the quality of fresh milk but also a major target trait forbreeding. The regulation of milk fat involves multiple genes, network regulation and signal transduction. To explore recent discoveries of pathway regulation, we reviewed the published literature with a focus on functional noncoding RNAs and epigenetic regulation in ruminants. Results indicate that miRNAs play key roles in the regulation of milk fat synthesis and catabolism in ruminants. Although few data are available, merging evidence indicates that lncRNAs and circRNAs act on milk fat related genes through indirect action with microRNAs or RNAs in the ceRNA network to elicit positive effects on transcription. Although precise regulatory mechanisms remain unclear, most studies have focused on the regulation of the function of target genes through functional noncoding RNAs. Data to help identify factors that can regulate their own expression and function or to determine whether self-regulation involves positive and/or negative feedback are needed. Despite the growing body of research on the role of functional noncoding RNA in the control of ruminant milk fat, most data are still not translatable for field applications. Overall, the understanding of mechanisms whereby miRNA, lncRNA, circRNA, and ceRNA regulate ruminant milk fat remains an exciting area of research.

MicroRNA-432 inhibits milk fat synthesis by targeting SCD and LPL in ovine mammary epithelial cells

The microRNA (miR)-432 is differentially expressed in the mammary gland of two breeds of lactating sheep with different milk production traits, and between the non-lactating and peak-lactation periods, but there have been no reports describing the molecular mechanisms involved. In this study, the effect of miR-432 on the proliferation of ovine mammary epithelial cells (OMECs) and the target genes of miR-432 were investigated. The effects of miR-432 on the expression of the target genes and the content of triglycerides in the OMECs were also analyzed. Transfection with a miR-432 mimic was found using CCK8 and Edu assays, to inhibit the viability of OMECs and reduce the number of proliferated OMECs. In contrast, a miR-432 inhibitor had the opposite effect to the miR-432 mimic, and together these results suggest that miR-432 inhibits the proliferation of OMECs. A dual luciferase assay revealed that the genes for stearoyl-CoA desaturase (SCD) and lipoprotein lipase (LPL) are targeted by miR-432. The transfection of miR-432 mimic into OMECs resulted in decreases in the expression of SCD and LPL, and three other milk fat synthesis marker genes; FABP4, LPIN1 and ACACA. The mimic also decreased the content of triglycerides. The miR-432 inhibitor had the opposite effect to the mimic on the expression of these genes and the level of triglycerides. This is the first study to reveal the biological mechanisms by which miR-432 inhibits milk fat synthesis in sheep.

Circ11103 Interacts with miR-128/PPARGC1A to Regulate Milk Fat Metabolism in Dairy Cows

The quality of milk is inseparable from its milk components, and fatty acid content is a key factor affecting the quality of milk. In this study, the miRNA and mRNA profiles of the bovine mammary gland tissue during the dry period and the peak lactation period were determined through high-throughput sequencing. In total, 72 miRNA-mRNA regulatory pathways were screened, including miR-128/PPARGC1A regulatory pathways. miR-128 can directly target PPARGC1A and inhibit its expression. In addition, the study also observed that there was a miR-128 binding site in the sequence of the circular RNA circ11103, and circ11103 significantly reduced the expression of miR-128. circ11103 upregulated the triglyceride levels in bovine mammary epithelial cells (BMECs) and increased the contents of unsaturated fatty acids. However, miR-128 decreased triglyceride and cholesterol levels in BMECs. This study aims to analyze the mechanism governing the regulatory effect of circ11103 on milk fat metabolism, which provides new insights into improving milk quality.

Epigenetics: New Insights into Mammary Gland Biology

The mammary gland undergoes important anatomical and physiological changes from embryogenesis through puberty, pregnancy, lactation and involution. These steps are under the control of a complex network of molecular factors, in which epigenetic mechanisms play a role that is increasingly well described. Recently, studies investigating epigenetic modifications and their impacts on gene expression in the mammary gland have been performed at different physiological stages and in different mammary cell types. This has led to the establishment of a role for epigenetic marks in milk component biosynthesis. This review aims to summarize the available knowledge regarding the involvement of the four main molecular mechanisms in epigenetics: DNA methylation, histone modifications, polycomb protein activity and non-coding RNA functions.

Deep small RNA-Seq reveals microRNAs expression profiles in lactating mammary gland of 2 sheep breeds with different milk performance

Micro ribonucleic acid (miRNA) is a type of noncoding RNA, and it has been revealed to play important roles in the activity of the mammary gland (MG) in some species. However, the function of miRNAs in MG of sheep is poorly understood. In the study, Gansu Alpine Merino (GAM; n = 9) and Small-tailed Han sheep (STH; n = 9) with different milk production traits were investigated. Microstructures and the expression profile of miRNAs of MG tissues at peak lactation were studied. Mature alveolar lumens of MG in appearance were larger in STH than GAM. The expression levels of CSN2 and the content of rough endoplasmic reticulum were also higher in STH ewes than GAM ewes. A total of 124 mature miRNAs were expressed, and 18 of these were differentially expressed between the 2 breeds. The KEGG analysis results showed that the targeted genes of differentially expressed miRNAs were mainly involved in some metabolic pathways and signaling pathways related to MG development, milk protein, and fat synthesis. The findings in the study can improve our understanding of the roles of miRNAs in the development and lactation of MG in sheep.

RNA-Seq Reveals the Expression Profiles of Long Non-Coding RNAs in Lactating Mammary Gland from Two Sheep Breeds with Divergent Milk Phenotype

Simple Summary

Long non-coding RNAs (lncRNAs) play a key role in regulating the expression level of mRNAs. The expression profiles of ovine mammary gland were investigated in two sheep breeds with divergent milk phenotype using RNA-Seq. A total of 1894 lncRNAs were found to be expressed and 68 of these were differentially expressed between the two breeds. Some important Gene Ontogeny (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that were related to lactation and mammary gland morphogenesis were found for the target genes of differentially expressed lncRNAs. This study can improve our understanding of the functions of lncRNAs in the regulation of lactation, milk yield, and milk components in sheep.

Abstract

Long non-coding RNAs (lncRNAs) are a kind of non-coding RNA with >200 nucleotides in length. Some lncRNAs have been proven to have clear regulatory functions in many biological processes of mammals. However, there have been no reports on the roles of lncRNAs in ovine mammary gland tissues. In the study, the expression profiles of lncRNAs were studied using RNA-Seq in mammary gland tissues from lactating Small-Tailed Han (STH) ewes and Gansu Alpine Merino (GAM) ewes with different milk yield and ingredients. A total of 1894 lncRNAs were found to be expressed. Compared with the GAM ewes, the expression levels of 31 lncRNAs were significantly up-regulated in the mammary gland tissues of STH ewes, while 37 lncRNAs were remarkably down-regulated. Gene Ontogeny (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis found that the target genes of differentially expressed lncRNAs were enriched in the development and proliferation of mammary epithelial cells, morphogenesis of mammary gland, ErbB signaling pathway, and Wnt signaling pathway. Some miRNA sponges of differentially expressed lncRNAs, reported to be associated with lactation and mammary gland morphogenesis, were found in a lncRNA-miRNA network. This study reveals comprehensive lncRNAs expression profiles in ovine mammary gland tissues, thereby providing a further understanding of the functions of lncRNAs in the lactation and mammary gland development of sheep.

Mechanism of miR-98 inhibiting tumor proliferation and invasion by targeting IGF1R in diabetic patients combined with colon cancer

Expression level of miR-98 in diabetic colon cancer (CRC) tissues and the regulation mechanism of colon cancer cell proliferation and invasion ability were studied. Forty patients with type 2 diabetes mellitus complicated with colon cancer, 40 colon cancer patients, and 40 patients with diabetic colonoscopy were enrolled between January 2017 and January 2018. Real-time quantitative PCR was used to detect the expression level of miR-98. After SW480 cells were transfected with miR-98 mimics or control simulants, the proliferation of cancer cells was detected by MTT assay, and the invasion ability of cancer cells was detected by Transwell cell invasion assay. The dual luciferase assay was used to detect the binding relationship between miR-98 and IGF1R. Western blot analysis was used to detect the expression of IGF1R protein in tumor tissues of patients with diabetes mellitus and colon cancer. Compared with diabetic patients, the expression level of miR-98 was decreased in colon cancer patients. Compared with tumor tissues of colon cancer patients, the expression level of miR-98 was significantly decreased in diabetic colon cancer tissues. Compared with the commonly cultured colon cancer SW480 cells, the expression level of miR-98 was significantly decreased in SW480 cells cultured under high glucose conditions. Increased expression of miR-98 inhibits colon cancer cell proliferation and invasion. miR-98 can target and bind to IGF1R and inhibit its expression level. IGF1R is upregulated in diabetic colon cancer tissue. miR-98 inhibits proliferation and invasion of diabetic colon cancer by targeting IGF1R. The expression level of miR-98 in diabetic colon cancer tissues is lower than that in colon cancer tissues. miR-98 can inhibit the proliferation and invasion of colon cancer cells by targeting the target gene IGF1R. miR-98 may be a potential biological target for the treatment of patients with diabetes and colon cancer.