MicroRNA-26a/b and their host genes synergistically regulate triacylglycerol synthesis by targeting the INSIG1 gene

MiR-26a Inhibits Porcine Adipogenesis by Regulating ACADM and ACSL1 Genes and Cell Cycle Progression

MicroRNAs play essential roles in biological processes by regulating gene expression at the post-transcriptional level. Our previous studies suggested the role of miR-26a in porcine fat accumulation. Here, through gain- and loss-of-function analyses, we first showed that miR-26a increased the proliferation of porcine preadipocytes by promoting cell division and that miR-26a inhibited the preadipocyte differentiation. Next, acyl-CoA dehydrogenase, medium chain (ACADM) was revealed to promote the proliferation and differentiation of preadipocytes for the first time. Then, it was revealed that miR-26a regulates adipogenesis by directly binding to the 3' untranslated region of ACADM and the long-chain acyl-Co A synthetase 1 (ACSL1) gene, a previously known regulator of adipogenesis. Finally, RNA-sequencing, performed on preadipocytes overexpressing miR-26a, identified 337 differentially expressed genes in the early stage of adipogenesis; among them, nine genes were characterized as potential targets of miR-26a. The 337 genes were mainly involved in Gene Ontology terms related to cell division, indicating that cell cycle progression was also a major event regulated by miR-26a during adipogenesis. We provide novel data for understanding the molecular mechanisms underlying adipogenesis, which will contribute to controlling fat accumulation in animals.

MiR-2284b regulation of α-s1 casein synthesis in mammary epithelial cells of dairy goats

The lactation character of dairy goats is the most important characteristic, and milk protein is an important index to evaluate milk quality. Casein accounts for more than 80% of the total milk protein in goat milk and is the main component of milk protein. Using GMECs (goat mammary epithelial cells) as the research object, the CHECK2 vector of the CSN1S1 gene and the overexpression vector of pcDNA 3.1 were constructed, and the mimics of miR-2284b and the interfering RNA of CSN1S1 were synthesized. Using PCR, RT-qPCR, a dual luciferase activity detection system, EdU, CCK8, cell apoptosis detection and ELISA detection, we explored the regulatory mechanism and molecular mechanism of miR-2284b regulation of αs1-casein synthesis in GMECs. miR-2284b negatively regulates proliferation and apoptosis of GMECs and αs1-casein synthesis. Two new gene sequences of CSN1S1 were discovered. CSN1S1-1/-2 promoted the proliferation of GMECs and inhibited cell apoptosis. However, it had no effect on αs1-casein synthesis. MiR-2284b negatively regulates αs1-casein synthesis in GMECs by inhibiting the CSN1S1 gene. These results all indicated that miR-2284b could regulate αs1-casein synthesis, thus playing a theoretical guiding role in the future breeding process of dairy goats and accelerating the development of dairy goat breeding.

MicroRNA-148a Targets DNMT1 and PPARGC1A to Regulate the Viability, Proliferation, and Milk Fat Synthesis of Ovine Mammary Epithelial Cells

In this study, the expression profiles of miR-148a were constructed in eight different ovine tissues, including mammary gland tissue, during six different developmental periods. The effect of miR-148a on the viability, proliferation, and milk fat synthesis of ovine mammary epithelial cells (OMECs) was investigated, and the target relationship of miR-148a with two predicted target genes was verified. The expression of miR-148a exhibited obvious tissue-specific and temporal-specific patterns. miR-148a was expressed in all eight ovine tissues investigated, with the highest expression level in mammary gland tissue (p < 0.05). Additionally, miR-148a was expressed in ovine mammary gland tissue during each of the six developmental periods studied, with its highest level at peak lactation (p < 0.05). The overexpression of miR-148a increased the viability of OMECs, the number and percentage of Edu-labeled positive OMECs, and the expression levels of two cell-proliferation marker genes. miR-148a also increased the percentage of OMECs in the S phase. In contrast, transfection with an miR-148a inhibitor produced the opposite effect compared to the miR-148a mimic. These results indicate that miR-148a promotes the viability and proliferation of OMECs in Small-tailed Han sheep. The miR-148a mimic increased the triglyceride content by 37.78% (p < 0.01) and the expression levels of three milk fat synthesis marker genes in OMECs. However, the miR-148a inhibitor reduced the triglyceride level by 87.11% (p < 0.01). These results suggest that miR-148a promotes milk fat synthesis in OMECs. The dual-luciferase reporter assay showed that miR-148a reduced the luciferase activities of DNA methyltransferase 1 (DNMT1) and peroxisome proliferator-activated receptor gamma coactivator 1-A (PPARGC1A) in wild-type vectors, suggesting that they are target genes of miR-148a. The expression of miR-148a was highly negatively correlated with PPARGC1A (r = -0.789, p < 0.001) in ovine mammary gland tissue, while it had a moderate negative correlation with DNMT1 (r = -0.515, p = 0.029). This is the first study to reveal the molecular mechanisms of miR-148a underlying the viability, proliferation, and milk fat synthesis of OMECs in sheep.

MiR-103-5p deficiency suppresses lipid accumulation via upregulating PLSCR4 and its host gene PANK3 in goat mammary epithelial cells

Lipids are intimately related to the unique flavor and nutritional values of goat milk. MicroRNAs (miRNA) participate in the regulation of various biological functions, including the synthesis and degradation of lipids. Several studies have shown that miR-103 is involved in the regulation of lipid metabolism, however, the molecular mechanism by which miR-103 regulates lipid metabolism in goat mammary gland is poorly understood. In this study, miR-103 was knocked out in goat mammary epithelial cells (GMECs) by CRISPR/Cas9, and the accumulation of lipid droplets, triglycerides, and cholesterol in the cells was suppressed subsequently. Overexpression or knockdown of miR-103-5p and miR-103-3p in GMECs revealed that it was miR-103-5p that promoted lipid accumulation but not miR-103-3p. In addition, Pantothenate Kinase 3 (PANK3), the host gene of miR-103, and Phospholipid Scramblase 4 (PLSCR4) were identified as the target genes of miR-103-5p by dual fluorescein and miRNA pulldown. Furthermore, we identified that cellular lipid levels were negatively regulated by PANK3 and PLSCR4. Lastly, in miR-103 knockout GMECs, the knockdown of PANK and PLSCR4 rescued the lipid accumulation. These findings suggest that miR-103-5p promotes lipid accumulation by targeting PLSCR4 and the host gene PANK3 in GMECs, providing new insights for the regulation of goat milk lipids via miRNAs.

Genome-Wide Association Study of Milk Composition in Karachai Goats

This study is first to perform a genome-wide association study (GWAS) to investigate the milk quality traits in Karachai goats. The objective of the study was to identify candidate genes associated with milk composition traits based on the identification and subsequent analysis of all possible SNPs, both genome-wide (high-confidence) and suggestive (subthreshold significance). To estimate the milk components, 22 traits were determined, including several types of fatty acids. DNA was extracted from ear tissue or blood samples. A total of 167 Karachai goats were genotyped using an Illumina GoatSNP53K BeadChip panel (Illumina Inc., San Diego, CA, USA). Overall, we identified 167 highly significant and subthreshold SNPs associated with the milk components of Karachai goats. A total of 10 SNPs were located within protein-coding genes and 33 SNPs in close proximity to them (±0.2 Mb). The largest number of genome-wide significant SNPs was found on chromosomes 2 and 8 and some of them were associated with several traits. The greatest number of genome-wide significant SNPs was identified for crude protein and lactose (6), and the smallest number-only 1 SNP-for freezing point depression. No SNPs were identified for monounsaturated and polyunsaturated fatty acids. Functional annotation of all 43 SNPs allowed us to identify 66 significant candidate genes on chromosomes 1, 2, 3, 4, 5, 8, 10, 13, 16, 18, 21, 23, 25, 26, and 27. We considered these genes potential DNA markers of the fatty acid composition of Karachai goat milk. Also, we found 12 genes that had a polygenic effect: most of them were simultaneously associated with the dry matter content and fatty acids (METTL, SLC1A 8, PHACTR1, FMO2, ECI1, PGP, ABCA3, AMDHD2). Our results suggest that the genes identified in our study affecting the milk components in Karachai goats differed from those identified in other breeds of dairy goats.

miR-26a-5p Regulates Adipocyte Differentiation via Directly Targeting ACSL3 in Adipocytes

Preadipocytes become mature adipocytes after proliferation and differentiation, and although many genes and microRNAs have been identified in intramuscular fat, their physiological function and regulatory mechanisms remain largely unexplored. miR-26a-5p has been reported to be related to fat deposition, but its effect on porcine preadipocyte differentiation has not been explored. In this study, bioinformatics analysis and luciferase reporter assay identified that miR-26a-5p binds to the 3'UTR of Acyl-CoA synthetase long-chain family member 3 (ACSL3) mRNA. The model for porcine intramuscular preadipocyte differentiation was established to explore the function of miR-6a-5p-ACSL3 on adipocyte differentiation. ACSL3 knockdown markedly reduced the triglycerides (TG) content of cells, as well as the mRNA levels of adipogenic marker genes (PPAR-γ and SREBP-1c). The number of lipid droplets in cells transfected with a miR-26a-5p mimic is significantly reduced, consistent with ACSL3 knockdown results, while the miR-26a-5p inhibitor resulted in opposite results. Taken together, miR-26a-5p is a repressor of porcine preadipocyte differentiation and plays a vital role in ACSL3-mediated adipogenesis.

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.

Fatty Acid Desaturation Is Suppressed in Mir-26a/b Knockout Goat Mammary Epithelial Cells by Upregulating INSIG1

MicroRNA-26 (miR-26a and miR-26b) plays a critical role in lipid metabolism, but its endogenous regulatory mechanism in fatty acid metabolism is not clear in goat mammary epithelial cells (GMECs). GMECs with the simultaneous knockout of miR-26a and miR-26b were obtained using the CRISPR/Cas9 system with four sgRNAs. In knockout GMECs, the contents of triglyceride, cholesterol, lipid droplets, and unsaturated fatty acid (UFA) were significantly reduced, and the expression of genes related to fatty acid metabolism was decreased, but the expression level of miR-26 target insulin-induced gene 1 (INSIG1) was significantly increased. Interestingly, the content of UFA in miR-26a and miR-26b simultaneous knockout GMECs was significantly lower than that in wild-type GMECs and miR-26a- and miR-26b-alone knockout cells. After decreasing INSIG1 expression in knockout cells, the contents of triglycerides, cholesterol, lipid droplets, and UFAs were restored, respectively. Our studies demonstrate that the knockout of miR-26a/b suppressed fatty acid desaturation by upregulating the target INSIG1. This provides reference methods and data for studying the functions of miRNA families and using miRNAs to regulate mammary fatty acid synthesis.

A novel regulatory facet for hypertriglyceridemia: The role of microRNAs in the regulation of triglyceride-rich lipoprotein biosynthesis

Atherosclerotic cardiovascular disease (ASCVD) is one of the major leading global causes of death. Genetic and epidemiological studies strongly support the causal association between triacylglycerol-rich lipoproteins (TAGRL) and atherogenesis, even in statin-treated patients. Recent genetic evidence has clarified that variants in several key genes implicated in TAGRL metabolism are strongly linked to the increased ASCVD risk. There are several triacylglycerol-lowering agents; however, new therapeutic options are in development, among which are miRNA-based therapeutic approaches. MicroRNAs (miRNAs) are small non-coding RNAs (18-25 nucleotides) that negatively modulate gene expression through translational repression or degradation of target mRNAs, thereby reducing the levels of functional genes. MiRNAs play a crucial role in the development of hypertriglyceridemia as several miRNAs are dysregulated in both synthesis and clearance of TAGRL particles. MiRNA-based therapies in ASCVD have not yet been applied in human trials but are attractive. This review provides a concise overview of current interventions for hypertriglyceridemia and the development of novel miRNA and siRNA-based drugs. We summarize the miRNAs involved in the regulation of key genes in the TAGRLs synthesis pathway, which has gained attention as a novel target for therapeutic applications in CVD.

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.

Functional and miRNA regulatory characteristics of INSIG genes highlight the key role of lipid synthesis in the liver of chicken (Gallus gallus)

The insulin-induced genes (INSIG1 and INSIG2) have been demonstrated to play a vital role in regulating lipid metabolism in mammals, however the function and regulation mechanism of them remains unknown in poultry. In this study, firstly the phylogenetic trees of INSIGs among various species were constructed and their subcellular locations were mapped in chicken LMH. Then the spatiotemporal expression profiles, over-expression and knockdown assays of chicken INSIGs were conducted. Furthermore, conservation of potential miRNA binding sites in INSIGs among species were analyzed, and the miRNA biological function and regulatory role were verified. The results showed that chicken INSIGs located in cellular endoplasmic reticulum, and were originated from the common ancestors of their mammalian counterparts. The INSIGs were widely expressed in all detected tissues, and their expression levels in the liver of chicken at 30 wk were significantly higher than that at 20 wk (P < 0.01). Over-expression of INSIGs led no significant increase in mRNA abundance of lipid metabolism-related genes and the contents of triacylglycerol (TG) and cholesterol (TC) in LMH cells. Knockdown of INSIG1 led to the decreased expressions of ACSL1, MTTP-L, ApoB, ApoVLDLII genes and TG, TC contents (P < 0.05). Knockdown of INSIG2 could significantly decrease the contents of TG and TC, and expressions of key genes related to the lipid metabolism (P < 0.05). Moreover, INSIG1 was directly targeted by both miR-130b-3p and miR-218-5p, and INSIG2 was directly targeted by miR-130b-3p. MiR-130b-3p mimic and miR-218-5p mimic treatment could significant decrease the mRNA and protein levels of INSIGs, mRNA levels of genes related to lipid metabolism, and the contents of TG and TC in LMH cells. The inhibition of miR-130b-3p and miR-218-5p on TG and TC contents could be restored by the overexpression of INSIGs, respectively. No significant alteration in expressions of sterol regulatory element binding protein (SREBPs) and SREBP cleavage-activating protein (SCAP) were observed when INSIGs were over-expressed. SCAP was down-regulated when INSIG1 was knocked down, while SREBP1 was down-regulated when INSIG2 was knocked down. Taken together, these results highlight the role of INSIG1 and INSIG2 in lipid metabolism and their regulatory mechanism in chicken.

An Integrated Analysis of Lactation-Related miRNA and mRNA Expression Profiles in Donkey Mammary Glands

Donkey milk is consumed by humans for its nutritional and therapeutic properties. MicroRNAs (miRNAs) and messenger RNAs (mRNAs) have been implicated in the regulation of milk component synthesis and mammary gland development. However, the regulatory profile of the miRNAs and mRNAs involved in lactation in donkeys is unclear. We performed mRNA-seq and miRNA-seq and constructed coexpression regulatory networks for the mammary glands during the lactating and nonlactating period of jennies. We identified 3144 differentially expressed (DE) mRNAs (987 upregulated mRNAs and 2157 downregulated mRNAs) and 293 DE miRNAs (231 upregulated miRNAs and 62 downregulated miRNAs) in the lactating group compared to the nonlactating group. The DE miRNA target mRNA were significantly associated with pathways related to RNA polymerase, glycosphingolipid biosynthesis, mRNA surveillance, ribosome biogenesis in eukaryotes, glycerophospholipid metabolism, Ras signaling, and the fly hippo signaling pathway. The mRNA–miRNA coregulation analysis showed that novel-m0032-3p, miR-195, miR-26-5p, miR-23-3p, miR-674-3p, and miR-874-3p are key miRNAs that target mRNAs involved in immunity and milk lipid, protein, and vitamin metabolism in the jenny mammary gland. Our results improve the current knowledge of the molecular mechanisms regulating bioactive milk component metabolism in the mammary glands and could be used to improve milk production in donkeys.

MicroRNA-199a-3p regulates proliferation and milk fat synthesis of ovine mammary epithelial cells by targeting VLDLR

In our previous study, microRNA (miR)-199a-3p was found to be the most upregulated miRNA in mammary gland tissue during the non-lactation period compared with the peak-lactation period. However, there have been no reports describing the function of miR-199a-3p in ovine mammary epithelial cells (OMECs) and the biological mechanisms by which the miRNA affects cell proliferation and milk fat synthesis in sheep. In this study, the effect of miR-199a-3p on viability, proliferation, and milk fat synthesis of OMECs was investigated, and the target relationship of the miRNA with very low-density lipoprotein receptor (VLDLR) was also verified. Transfection with a miR-199a-3p mimic increased the viability of OMECs and the number of Edu-labeled positive OMECs. In contrast, a miR-199-3p inhibitor had the opposite effect with the miR-199a-3p mimic. The expression levels of three marker genes were also regulated by both the miR-199a-3p mimic and miR-199-3p inhibitor in OMECs. Together, these results suggest that miR-199a-3p promotes the viability and proliferation of OMECs. A dual luciferase assay confirmed that miR-199a-3p can target VLDLR by binding to the 3′-untranslated regions (3'UTR) of the gene. Further studies found a negative correlation in the expression of miR-199a-3p with VLDLR. The miR-199a-3p mimic decreased the content of triglycerides, as well as the expression levels of six milk fat synthesis marker genes in OMECs, namely, lipoprotein lipase gene (LPL), acetyl-CoA carboxylase alpha gene (ACACA), fatty acid binding protein 3 gene (FABP3), CD36, stearoyl-CoA desaturase gene (SCD), and fatty acid synthase gene (FASN). The inhibition of miR-199a-3p increased the level of triglycerides and the expression of LPL, ACACA, FABP3, SCD, and FASN in OMECs. These findings suggest that miR-199a-3p inhibited milk fat synthesis of OMECs. This is the first study to reveal the molecular mechanisms by which miR-199a-3p regulates the proliferation and milk fat synthesis of OMECs in sheep.

Dietary Improvement during Lactation Normalizes miR-26a, miR-222 and miR-484 Levels in the Mammary Gland, but Not in Milk, of Diet-Induced Obese Rats

We aimed to evaluate in rats whether the levels of specific miRNA are altered in the mammary gland (MG) and milk of diet-induced obese dams, and whether improving maternal nutrition during lactation attenuates such alterations. Dams fed with a standard diet (SD) (control group), with a Western diet (WD) prior to and during gestation and lactation (WD group), or with WD prior to and during gestation but moved to SD during lactation (Rev group) were followed. The WD group showed higher miR-26a, miR-222 and miR-484 levels than the controls in the MG, but the miRNA profile in Rev animals was not different from those of the controls. The WD group also displayed higher miR-125a levels than the Rev group. Dams of the WD group, but not the Rev group, displayed lower mRNA expression levels of Rb1 (miR-26a’s target) and Elovl6 (miR-125a’s target) than the controls in the MG. The WD group also presented lower expression of Insig1 (miR-26a’s target) and Cxcr4 (miR-222’s target) than the Rev group. However, both WD and Rev animals displayed lower expression of Vegfa (miR-484’s target) than the controls. WD animals also showed greater miR-26a, miR-125a and miR-222 levels in the milk than the controls, but no differences were found between the WD and Rev groups. Thus, implementation of a healthy diet during lactation normalizes the expression levels of specific miRNAs and some target genes in the MG of diet-induced obese dams but not in milk.

Characterization of the microRNA Expression Profiles in the Goat Kid Liver

The liver is the largest digestive gland in goats with an important role in early metabolic function development. MicroRNAs (miRNA) are crucial for regulating the development and metabolism in the goat liver. In the study, we sequenced the miRNAs in the liver tissues of the goat kid to further research their regulation roles in early liver development. The liver tissues were procured at 5-time points from the Laiwu black goats of 1 day (D1), 2 weeks (W2), 4 weeks (W4), 8 weeks (W8), and 12 weeks (W12) after birth, respectively with five goats per time point, for a total of 25 goats. Our study identified 214 differential expression miRNAs, and the expression patterns of 15 randomly selected miRNAs were examined among all five age groups. The Gene ontology annotation results showed that differential expression miRNA (DE miRNA) target genes were significantly enriched in the fatty acid synthase activity, toxin metabolic process, cell surface, and antibiotic metabolic process. The KEGG analysis result was significantly enriched in steroid hormone synthesis and retinol metabolism pathways. Further miRNA-mRNA regulation network analysis reveals 9 differently expressed miRNA with important regulation roles. Overall, the DE miRNAs were mainly involved in liver development, lipid metabolism, toxin related metabolism-related biological process, and pathways. Our results provide new information about the molecular mechanisms and pathways in the goat kid liver development.

Characterization of RNA Editome in the Mammary Gland of Yaks during the Lactation and Dry Periods

Simple Summary

In order to study the influence of RNA editing sites on lactation and mammary gland development process in yaks, we comprehensively characterized the RNA editome of the yak mammary gland during the lactation period and dry period by using the transcriptome and genome sequencing data. The results revealed 82,872 nonredundant RNA editing sites, 14,159 of which were differentially edited between the lactation period and dry period. Enrichment analysis showed that the genes harboring differential editing sites were mainly associated with mammary gland development-related pathways, such as MAPK pathway, PI3K-Akt pathway, FoxO signaling pathway, GnRH signaling pathway, and focal adhesion pathway. Our findings offer some novel insights into the RNA editing function in the mammary gland of yaks.

Abstract

The mammary gland is a complicated organ comprising several types of cells, and it undergoes extensive morphogenetic and metabolic changes during the female reproductive cycle. RNA editing is a posttranscriptional modification event occurring at the RNA nucleotide level, and it drives transcriptomic and proteomic diversities, with potential functional consequences. RNA editing in the mammary gland of yaks, however, remains poorly understood. Here, we used REDItools to identify RNA editing sites in mammary gland tissues in yaks during the lactation period (LP, n = 2) and dry period (DP, n = 3). Totally, 82,872 unique RNA editing sites were identified, most of which were detected in the noncoding regions with a low editing degree. In the coding regions (CDS), we detected 5235 editing sites, among which 1884 caused nonsynonymous amino acid changes. Of these RNA editing sites, 486 were found to generate novel possible miRNA target sites or interfere with the initial miRNA binding sites, indicating that RNA editing was related to gene regulation mediated by miRNA. A total of 14,159 RNA editing sites (involving 3238 common genes) showed a significant differential editing level in the LP when compared with that in the DP through Tukey’s Honest Significant Difference method (p < 0.05). According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, genes that showed different RNA editing levels mainly participated in pathways highly related to mammary gland development, including MAPK, PI3K-Akt, FoxO, and GnRH signaling pathways. Collectively, this work demonstrated for the first time the dynamic RNA editome profiles in the mammary gland of yaks and shed more light on the mechanism that regulates lactation together with mammary gland development.

Cadmium promotes apoptosis and inflammation via the circ08409/miR-133a/TGFB2 axis in bovine mammary epithelial cells and mouse mammary gland

Cadmium is a common environmental heavy metal pollutant that can accumulate over long periods of time and cause disease. Thus, analysis of the molecular mechanisms affected by cadmium in the body could be of great significance for the prevention and treatment of cadmium-related diseases. In this study, flow cytometry, immunofluorescence, transmission electron microscopy, H&E (Hematoxylin Eosin) staining and TUNEL (TdT-mediated dUTP Nick-End Labeling) assays were used to verify that cadmium induced apoptosis and immune responses in bovine mammary epithelial cells (BMECs) and in mouse mammary gland. Isolated BMECs cultured with or without cadmium were collected to screen miRNA (microRNA) using high-throughput sequencing. There were 42 differentially-expressed miRNAs among which 27 were upregulated and 15 downregulated including bta-miR-133a, bta-miR-23b-5p, bta-miR-29e, bta-miR-365-5p, bta-miR-615, bta-miR-7, bta-miR-11975, bta-miR-127, and bta-miR-411a. Among those, miR-133a (which can specifically target TGFB2 (Recombinant Transforming Growth Factor Beta 2) was the most significantly downregulated with a fold-change of 5.27 in BMECs cultured with cadmium. Application of the double luciferase reporter system, western blotting, and qRT-PCR (Quantitative Real-time PCR) revealed that circ08409 can directly bind to miR-133a. Experiments demonstrated that circRNA-08409 could adsorb bta-miR-133a. Both circ08409 and TGFB2 significantly increased apoptosis and altered expression level of a series of inflammatory factors in BMECs. In contrast, miR-133a decreased significantly apoptosis and inflammation in the cells. Compared with cultures receiving only cadmium, the miR-133a+cadmium cultures exhibited significant reductions in the occurrence of late apoptosis. Overall, results indicated that circ08409 could relieve the inhibitory effect of miR-133a on TGFB2 expression by combining with miR-133a and subsequently modulating cell proliferation, apoptosis and inflammation. Overall, the data suggested that the circ08409/miR-133a/TGFB2 axis might play a role in mediating the effect of cadmium on BMECs. As such, data provide novel insights into controlling hazards that cadmium could induce in the mammary gland.

microRNA-26a-5p Prevents Retinal Neuronal Cell Death in Diabetic Mice by Targeting PTEN

AIM

To explore the role of microRNA-26a-5p (miR-26a) in early diabetic retinal neuronal cell death and reveal the underlying mechanism(s).

METHODS

A streptozotocin (STZ)-induced diabetic mouse model was established using C57BL/6 J mice. Control or miR-26a mimic was intravitreally injected. Hematoxylin-eosin (H&E) and transmission electron microscopy (TEM) were used to observe the morphologic alterations in the retinal structure and ultrastructure, respectively. The expression of miR-26a and phosphatase and tensin homolog (PTEN) was assayed using qRT-PCR and western blotting, respectively. An immunofluorescence assay was used to investigate the distribution of PTEN expression in the retina. The expression of glial fibrillary acidic protein (GFAP) was measured to identify glial cell activation. The mRNA levels of IL-1β, NF-κB, and VEGF were examined to assess diabetic retinal inflammation.

RESULTS

miR-26a expression was decreased in retinal tissues of diabetic mice, and injection of miR-26a mimic restored the miR-26a level. Diabetic mice had significantly reduced neuroretinal thickness and ganglion cell number; miR-26a mimic delayed the thinning of neuroretinal layers and the loss of ganglion numbers. TEM showed damaged ultrastructure of retinal ganglions in diabetic mice, while miR-26a mitigated the damages. PTEN expression was increased mainly in the inner and outer nuclear layer of the retina in diabetic mice; miR-26a mimics lowered PTEN expression. GFAP, IL-1β, NF-κB, and VEGF expression were significantly increased in the diabetic mice, and intravitreal delivery of miR-26a resulted in a down-regulated expression of these factors.

CONCLUSION

miR-26a can protect against retinal neuronal impairment in diabetic mice by down-regulating PTEN, highlighting the potential of miR-26a as a target for DR treatment.

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.

MicroRNA regulation of cholesterol metabolism

MicroRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level. Since many microRNAs have multiple mRNA targets, they are uniquely positioned to regulate the expression of several molecules and pathways simultaneously. For example, the multiple stages of cholesterol metabolism are heavily influenced by microRNA activity. Understanding the scope of microRNAs that control this pathway is highly relevant to diseases of perturbed cholesterol metabolism, most notably cardiovascular disease (CVD). Atherosclerosis is a common cause of CVD that involves inflammation and the accumulation of cholesterol-laden cells in the arterial wall. However, several different cell types participate in atherosclerosis, and perturbations in cholesterol homeostasis may have unique effects on the specialized functions of these various cell types. Therefore, our review discusses the current knowledge of microRNA-mediated control of cholesterol homeostasis, followed by speculation as to how these microRNA-mRNA target interactions might have distinctive effects on different cell types that participate in atherosclerosis.

MicroRNA-193a-5p Regulates the Synthesis of Polyunsaturated Fatty Acids by Targeting Fatty Acid Desaturase 1 (FADS1) in Bovine Mammary Epithelial Cells

Cardiovascular diseases (CVDs) are seriously threatening to human life and health. Polyunsaturated fatty acids (PUFAs) are known for their role in preventing CVDs. It is beneficial to population health to promote the content of PUFAs in bovine milk. In recent years, limited research based on molecular mechanisms has focused on this field. The biological roles of numerous microRNAs (miRNAs) remain unknown. In this study, a promising and negatively correlated pair of the miRNA (miRNA-193a-5p) and a fatty acid desaturase 1 (FADS1) gene are identified and screened to explore whether they are potential factors of PUFAs’ synthesis in bovine milk. The targeted relationship between miRNA-193a-5p and FADS1 in bovine mammary epithelial cells (BMECs) is demonstrated by dual luciferase reporter assays. qRT-PCR and western blot assays indicate that both the expression of mRNA and the protein FADS1 show a negative correlation with miRNA-193a-5p expression in BMECs. Also, miR-193a-5p expression is positively correlated with the expression of genes associated with milk fatty acid metabolism, including ELOVL fatty acid elongase 6 (ELOVL6) and diacylglycerol O-acyltransferase 2 (DGAT2). The expression of fatty acid desaturase 2 (FADS2) is negatively correlated with miR-193a-5p expression in BMECs. The contents of triglycerides (TAG), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) have a significant positive correlation with the expression of FADS1 and a significant negative correlation with the expression of miR-193a-5p in BMECs. For the first time, this study confirms that miRNA-193a-5p regulates PUFAs metabolism in BMECs by targeting FADS1, indicating that miRNA-193a-5p and FADS1 are underlying factors that improve PUFAs content in bovine milk.

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.

MiR-204-5p promotes lipid synthesis in mammary epithelial cells by targeting SIRT1

OBJECTIVES

Understanding the molecular mechanisms of lipid synthesis in the mammary gland is crucial for regulating the level and composition of lipids in milk. This study aimed to investigate the functional and molecular mechanisms of miR-204-5p in mammary epithelial cells to provide a theoretical basis for milk lipid synthesis.

METHODS

Real-time quantitative PCR was performed to detect the transcriptional levels of miR-204-5p and related mRNA abundance in mammary epithelial cells. Western blotting was conducted to determine protein expression. Cell proliferation was assessed by Cell Counting Kit-8. A dual-luciferase reporter assay was conducted to verify the targeting relationship between miR-204-5p and SIRT1. siRNA and overexpression plasmids were transfected into mouse HC11 mammary epithelial cells.

RESULTS

The abundance of miR-204-5p was much higher in lactating mouse mammary glands than in other tissues, which indicated that miR-204-5p may be involved in regulating milk production. MiR-204-5p affected the expression of β-casein and milk lipid synthesis in HC11 mouse mammary epithelial cells but did not influence the proliferation of HC11 cells. Overexpression of miR-204-5p significantly increased the number of Oil Red O⁺ cells, triglyceride accumulation and the expression of markers associated with lipid synthesis, including FASN and PPARγ, whereas inhibition of miR-204-5p had the opposite effect. miR-204-5p promotes lipid synthesis by negatively regulating SIRT1. Overexpression of SIRT1 can repress the promotion of miR-204-5p on lipid synthesis.

CONCLUSION

Our findings showed that miR-204-5p can promote the synthesis of milk lipids in mammary epithelial cells by targeting SIRT1.

Small RNA deep sequencing reveals the expressions of microRNAs in ovine mammary gland development at peak-lactation and during the non-lactating period

MicroRNAs (miRNAs) are small non-coding RNAs that are involved in mammary gland development and lactation in livestock. Little is known about the roles of miRNAs in ovine mammary gland development, hence in this study the expression profiles of miRNAs of the mammary gland tissues of ewes at peak-lactation and during the non-lactating period were investigated using RNA sequencing. A total of 147 mature miRNAs were expressed in the two periods. Compared with peak-lactation, eight miRNAs in the non-lactating ewe mammary gland were significantly up-regulated, whereas fifteen miRNAs were down-regulated. A KEGG analysis revealed that the target genes of the up-regulated miRNAs were significantly enriched in lysosome, Wnt and MAPK signaling pathways, while the target genes of down-regulated miRNAs were significantly enriched in the PI3K-Akt signaling pathway, protein processing in endoplasmic reticulum and axon guidance. These results suggest that further study of the differentially expressed miRNAs could provide a better understanding of the molecular mechanisms of mammary development and lactation in sheep.

Circ09863 Regulates Unsaturated Fatty Acid Metabolism by Adsorbing miR-27a-3p in Bovine Mammary Epithelial Cells

Fatty acid composition plays a key role in regulating flavor and quality of milk. Therefore, in order to improve milk quality, it is particularly important to investigate regulatory mechanisms of milk fatty acid metabolism. Circular RNAs (circRNAs) regulate expression genes associated with several biological processes including fatty acid metabolism. In this study, high-throughput sequencing was used to detect differentially expressed genes in bovine mammary tissue at early lactation and peak lactation. Circ09863 profiles were influenced by the lactation stage. Functional studies in bovine mammary epithelial cells (BMECs) revealed that circ09863 promotes triglyceride (TAG) synthesis together with increased content of unsaturated fatty acids (C16:1 and C18:1). These results suggested that circ09863 is partly responsible for modulating fatty acid metabolism. Additionally, software prediction identified a miR-27a-3p binding site in the circ09863 sequence. Overexpression of miR-27a-3p in BMECs led to decreased TAG synthesis. However, overexpression of circ09863 (pcDNA-circ09863) in BMECs significantly reduced expression of miR-27a-3p and enhanced gene expression of fatty acid synthase (FASN), a target of miR-27a-3p. Overall, data suggest that circ09863 relieves the inhibitory effect of miR-27a-3p on FASN expression by binding miR-27a-3p and subsequently regulating TAG synthesis and fatty acid composition. Together, these mechanisms provide new research avenues and theoretical bases to improve milk quality.

miR-26a mediates LC-PUFA biosynthesis by targeting the Lxrα-Srebp1 pathway in the marine teleost Siganus canaliculatus

MicroRNAs have been recently shown to be important regulators of lipid metabolism. However, the mechanisms of microRNA-mediated regulation of long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis in vertebrates remain largely unknown. Herein, we for the first time addressed the role of miR-26a in LC-PUFA biosynthesis in the marine rabbitfish Siganus canaliculatus The results showed that miR-26a was significantly down-regulated in liver of rabbitfish reared in brackish water and in S. canaliculatus hepatocyte line (SCHL) incubated with the LC-PUFA precursor α-linolenic acid, suggesting that miR-26a may be involved in LC-PUFA biosynthesis because of its abundance being regulated by factors affecting LC-PUFA biosynthesis. Opposite patterns were observed in the expression of liver X receptor α (lxrα) and sterol regulatory element-binding protein-1 (srebp1), as well as the LC-PUFA biosynthesis-related genes (Δ4 fads2, Δ6Δ5 fads2, and elovl5) in SCHL cells incubated with α-linolenic acid. Luciferase reporter assays revealed rabbitfish lxrα as a target of miR-26a, and overexpression of miR-26a in SCHL cells markedly reduced protein levels of Lxrα, Srebp1, and Δ6Δ5 Fads2 induced by the agonist T0901317. Moreover, increasing endogenous Lxrα by knockdown of miR-26a facilitated Srebp1 activation and concomitant increased expression of genes involved in LC-PUFA biosynthesis and consequently promoted LC-PUFA biosynthesis both in vitro and in vivo These results indicate a critical role of miR-26a in regulating LC-PUFA biosynthesis through targeting the Lxrα-Srebp1 pathway and provide new insights into the regulatory network controlling LC-PUFA biosynthesis and accumulation in vertebrates.

microRNAs targeting cellular cholesterol: implications for combating anticancer drug resistance

Over sixty percent of all mammalian protein-coding genes are estimated to be regulated by microRNAs (miRNAs), and unsurprisingly miRNA dysregulation has been linked with cancer. Aberrant miRNA expression in cancer cells has been linked with tumourigenesis and drug resistance. In the past decade, increasing number of studies have demonstrated that cholesterol accumulation fuels tumour growth and contributes to drug resistance, therefore, miRNAs controlling cholesterol metabolism and homeostasis are obvious hypothetical targets for investigating their role in cholesterol-mediated drug resistance in cancer. In this review, we have collated published evidences to consolidate this hypothesis and have scrutinized it by utilizing computational tools to explore the role of miRNAs in cholesterol-mediated drug resistance in breast cancer cells. We found that hsa-miR-128 and hsa-miR-223 regulate genes mediating lipid signalling and cholesterol metabolism, cancer drug resistance and breast cancer genes. The analysis demonstrates that targeting these miRNAs in cancer cells presents an opportunity for developing new strategies to combat anticancer drug resistance.

Multi-population GWAS and enrichment analyses reveal novel genomic regions and promising candidate genes underlying bovine milk fatty acid composition

Background

The power of genome-wide association studies (GWAS) is often limited by the sample size available for the analysis. Milk fatty acid (FA) traits are scarcely recorded due to expensive and time-consuming analytical techniques. Combining multi-population datasets can enhance the power of GWAS enabling detection of genomic region explaining medium to low proportions of the genetic variation. GWAS often detect broader genomic regions containing several positional candidate genes making it difficult to untangle the causative candidates. Post-GWAS analyses with data on pathways, ontology and tissue-specific gene expression status might allow prioritization among positional candidate genes.

Results

Multi-population GWAS for 16 FA traits quantified using gas chromatography (GC) in sample populations of the Chinese, Danish and Dutch Holstein with high-density (HD) genotypes detects 56 genomic regions significantly associated to at least one of the studied FAs; some of which have not been previously reported. Pathways and gene ontology (GO) analyses suggest promising candidate genes on the novel regions including OSBPL6 and AGPS on Bos taurus autosome (BTA) 2, PRLH on BTA 3, SLC51B on BTA 10, ABCG5/8 on BTA 11 and ALG5 on BTA 12. Novel genes in previously known regions, such as FABP4 on BTA 14, APOA1/5/7 on BTA 15 and MGST2 on BTA 17, are also linked to important FA metabolic processes.

Conclusion

Integration of multi-population GWAS and enrichment analyses enabled detection of several novel genomic regions, explaining relatively smaller fractions of the genetic variation, and revealed highly likely candidate genes underlying the effects. Detection of such regions and candidate genes will be crucial in understanding the complex genetic control of FA metabolism. The findings can also be used to augment genomic prediction models with regions collectively capturing most of the genetic variation in the milk FA traits.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5573-9) contains supplementary material, which is available to authorized users.

Effect of diets supplemented with starch and corn oil, marine algae, or hydrogenated palm oil on mammary lipogenic gene expression in cows and goats: A comparative study

A direct comparison of cow and goat performance and milk fatty acid (FA) responses to diets that either induce milk fat depression or increase milk fat content in cows suggests species-specific regulation of lipid metabolism, including mammary lipogenesis. This experiment was conducted to highlight potential mechanisms responsible for the differences in mammary lipogenesis due to diet and ruminant species. Twelve Holstein cows and 12 Alpine goats were fed a basal diet containing no additional lipid (CTL) or a similar diet supplemented with corn oil [5% dry matter intake (DMI)] and wheat starch (COS), marine algae powder (MAP; 1.5% DMI), or hydrogenated palm oil (HPO; 3% DMI), according to a 4 × 4 Latin square design with 28-d experimental periods. Milk yield, milk composition, FA profile, and secretions were measured. On d 27 of each experimental period, the mRNA abundance of 21 genes involved in lipid metabolism or enzyme activities or both were measured in mammary tissue sampled by biopsy. The results showed significant differences in the milk fat response of cows and goats to the dietary treatments. In cows, fat content was lowered by COS (-45%) and MAP (-22%) and increased by HPO (+13%) compared with CTL, and in goats only MAP had an effect compared with CTL, with a decrease of 15%. In both species, COS and MAP lowered the yields (mmol/d per kilogram of body weight) of <C16 and C16 FA. With COS, this decrease was compensated by an increase of >C16 FA in goats but not in cows, and the >C16 FA yield decreased with MAP in both species. Supplementation of HPO increased the yield of milk C16 FA (mmol/d per kilogram of body weight) in cows. These variations in milk fat content and FA secretion were not associated with modifications in the mammary expression of 21 genes involved in major lipid pathways, except for 3 transcription factors: PPARA, INSIG1, and SP1. This absence of large changes might be due to post-transcriptional regulation of these genes and related to the time of sampling of the mammary tissue relative to the previous meal and milking or to differences in the availability of substrate for the corresponding proteins. However, the abundance of 14 mRNA among the 21 encoding for genes studied in the mammary gland was significantly different among species, with 5 more abundant in cows (FADS3, ACSL1, PPARA, LXRA, and PPARG1) and 10 more abundant in goats (FASN, CD36, FABP3, LPL, GPAM, LPIN1, CSN2, MFGE8, and INSIG1). These species specificities of mammary lipid metabolism require further investigation.

Association between the expression of miR-26 and goat milk fatty acids

microRNA (miRNA) are small noncoding RNA that regulate protein abundance and are involved in diverse aspects of cellular function including aspects of lipid metabolism in mammary gland of ruminants. Although our previous studies showed that the miR-26 family and its host genes control components of the cellular fatty acid metabolic machinery in goat mammary epithelial cells, a direct relationship between the miR-26 family and milk fatty acids remains unknown. Bioinformatics analysis in this study indicated that the miR-26 family targets belong to the PI3K-Akt signalling pathway, MAPK signalling pathway, and fatty acid biosynthesis pathway. Studies on the relationship of miR-26 family and their host genes with milk composition during mid-lactation revealed that the expression of the miR-26 family and their host genes were associated with total fat yield and short-chain, medium-chain and long-chain fatty acid content, but not lactose or milk protein content. In addition, a significant positive correlation was detected for the expression of the miR-26 family with C16:1 and C18:3 in milk fat. Taken together, our findings demonstrate that the expression of miR-26 is directly related to milk fatty acid composition and underscores the significance of miRNAs in milk fat synthesis regulation.

Critical Roles of microRNAs in the Pathogenesis of Fatty Liver: New Advances, Challenges, and Potential Directions

In this review, we summarize the current understanding of microRNA (miRNA)-mediated modulation of the gene expression in the fatty liver as well as related signaling pathways. Because of the breadth and diversity of miRNAs, miRNAs may have a very wide variety of biological functions, and much evidence has confirmed that miRNAs are involved in the pathogenesis of fatty liver. In the pathophysiological mechanism of fatty liver, miRNAs may be regulated by upstream regulators, and have their own regulatory targets. miRNAs display important roles in the pathological mechanisms of alcoholic liver disease and non-alcoholic fatty liver disease. At present, most of the miRNA studies are focused on cell and tissue levels, and in vivo studies will help us elucidate the regulation of miRNAs and help us evaluate the potential of miRNAs as diagnostic markers and therapeutic targets. Furthermore, there is evidence that miRNAs are involved in the mechanism of natural medicine treatment in fatty liver. Given the important roles of miRNAs in the pathogenesis of fatty liver, we predict that studies of miRNAs in the pathogenesis of fatty liver will contribute to the elucidation of fatty liver pathology and the treatment of fatty liver patients.

miR-25 modulates triacylglycerol and lipid accumulation in goat mammary epithelial cells by repressing PGC-1beta

Background

The goat (Caprahircus) is one of the most important livestock animals. Goat milk fat is an important component in the nutritional quality of goat milk. Growing evidence points to the critical roles of microRNAs (miRNAs) in lipid metabolism.

Results

Using a highly sensitive method of S-poly(T) plus for miRNAs detection, we analyze the expression patterns of 715 miRNAs in goat mammary gland tissues at different stages of lactation. We observed that miR-25 expression had an inverse relationship with milk production. Overexpression of miR-25 significantly repressed triacylglycerol synthesis and lipid droplet accumulation. To explore the regulatory mechanism of miR-25 in milk lipid metabolism, we analyzed its putative target genes with bioinformatics analysis followed by 3′-UTR assays. Peroxisome proliferative activated receptor gamma coactivator 1 beta (PGC-1beta), a key regulator of lipogenics was identified as a direct target of miR-25 with three specific sites within its 3′-UTR. In addition, miR-25 mimics in goat mammary epithelial cells reduced the expressions of genes involved in lipid metabolism.

Conclusions

Taken together, our results show miR-25 is potentially involved in lipid metabolism and we reveal the function of the miR-25/PGC-1beta regulatory axis during lactation.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0262-0) contains supplementary material, which is available to authorized users.

Cohesive Regulation of Neural Progenitor Development by microRNA miR-26, Its Host Gene Ctdsp and Target Gene Emx2 in the Mouse Embryonic Cerebral Cortex

Proper proliferation and differentiation of neural progenitors (NPs) in the developing cerebral cortex are critical for normal brain formation and function. Emerging evidence has shown the importance of microRNAs (miRNAs) in regulating cortical development and the etiology of neurological disorders. Here we show that miR-26 is co-expressed with its host gene Ctdsp in the mouse embryonic cortex. We demonstrate that similar to its host gene Ctdsp2, miR-26 positively regulates proliferation of NPs through controlling the cell-cycle progression, by using miR-26 overexpression and sponge approaches. On the contrary, miR-26 target gene Emx2 limits expansion of cortical NPs, and promotes transcription of miR-26 host gene Ctdsp. Our study suggests that miR-26, its target Emx2 and its host gene Ctdsp cohesively regulate proliferation of NPs during the mouse cortical development.

Sunflower oil supplementation affects the expression of miR-20a-5p and miR-142-5p in the lactating bovine mammary gland

Oil supplementation in dairy cattle diets is used to modulate milk fat composition, as well as the expression of mammary lipogenic genes, whose regulation remains unclear. MiRNAs are small non-coding RNA considered as crucial regulators of gene expression, offering clues to explain the mechanism underlying gene nutriregulation. The present study was designed to identify miRNAs whose expression in the cow mammary gland is modulated by sunflower oil supplementation. MiRNomes were obtained using RNAseq technology from the mammary gland of lactating cows receiving a low forage diet, supplemented or not with 4% sunflower oil. Among the 272 miRNAs characterized, eight were selected for RT-qPCR validations, showing the significant down-regulation of miR-142-5p and miR-20a-5p by sunflower supplementation. These two miRNAs are predicted to target genes whose expression was reported as differentially expressed by sunflower supplementation. Among their putative targets, ELOVL6 gene involved in lipid metabolism has been studied. However, a first analysis did not show its significant down-regulation, in response to the over-expression of miR-142-5p, of miR-20a-5p, or both, in a bovine mammary epithelial cell line. However, a clearer understanding of the miRNA expression by lipid supplementation would help to decipher the regulation of lactating cow mammary gland in response to nutrition.

miR-26b Promotes 3T3-L1 Adipocyte Differentiation Through Targeting PTEN

microRNAs (miRNAs) play important roles in adipogenesis that is closely linked to obesity and energy homeostasis. Thus far, only a few miRNAs have been identified to regulate adipocyte development, arousing interest in the detailed function of miRNAs during adipogenesis. In this study, we found that the miR-26b expression showed an increasing trend during 3T3-L1 cells differentiation. To investigate the role of miR-26b in adipogenesis, the synthetic miR-26b agomirs and antagomirs were used to perform overexpression and knockdown experiment, respectively. Our data revealed that overexpression of miR-26b significantly accelerated the mRNA expression of the adipogenic markers, peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FAS), CCAAT/enhancer binding protein alpha (C/EBPα), and lipoprotein lipase, and the protein level of PPARγ and FAS. miR-26b overexpression also resulted in a significant increase in lipid accumulation. In contrast, inhibition of miR-26b expression decreased differentiation of 3T3-L1 cells. By target gene prediction and luciferase reporter assay, we demonstrated that miR-26b may directly bind to the 3' UTR of phosphatase and tensin homolog (PTEN). Taken together, these results demonstrate that miR-26b might participate in regulating adipogenic differentiation in 3T3-L1 cells by inhibiting the PTEN expression, further highlighting the importance of miRNA in adipogenesis.

MicroRNA roles in signalling during lactation: an insight from differential expression, time course and pathway analyses of deep sequence data

The study examined microRNA (miRNA) expression and regulatory patterns during an entire bovine lactation cycle. Total RNA from milk fat samples collected at the lactogenesis (LAC, day1 [D1] and D7), galactopoiesis (GAL, D30, D70, D130, D170 and D230) and involution (INV, D290 and when milk production dropped to 5 kg/day) stages from 9 cows was used for miRNA sequencing. A total of 475 known and 238 novel miRNAs were identified. Fifteen abundantly expressed miRNAs across lactation stages play regulatory roles in basic metabolic, cellular and immunological functions. About 344, 366 and 209 miRNAs were significantly differentially expressed (DE) between GAL and LAC, INV and GAL, and INV and LAC stages, respectively. MiR-29b/miR-363 and miR-874/miR-6254 are important mediators for transition signals from LAC to GAL and from GAL to INV, respectively. Moreover, 58 miRNAs were dynamically DE in all lactation stages and 19 miRNAs were significantly time-dependently DE throughout lactation. Relevant signalling pathways for transition between lactation stages are involved in apoptosis (PTEN and SAPK/JNK), intracellular signalling (protein kinase A, TGF-β and ERK5), cell cycle regulation (STAT3), cytokines, hormones and growth factors (prolactin, growth hormone and glucocorticoid receptor). Overall, our data suggest diverse, temporal and physiological signal-dependent regulatory and mediator functions for miRNAs during lactation.

Donor Graft MicroRNAs: A Newly Identified Player in the Development of New-onset Diabetes After Liver Transplantation

New-onset diabetes after liver transplantation (NODALT) is a frequent complication with an unfavorable outcome. We previously demonstrated a crucial link between donor graft genetics and the risk of NODALT. We selected 15 matched pairs of NODALT and non-NODALT liver recipients using propensity score matching analysis. The donor liver tissues were tested for the expression of 10 microRNAs (miRNAs) regulating human hepatic glucose homeostasis. The biological functions of potential target genes were predicted using gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Both miR-103 and miR-181a were significantly highly expressed in the NODALT group as compared to the non-NODALT group. The predicted target genes (e.g. Irs2, Pik3r1, Akt2, and Gsk3b) were involved in glucose import and the insulin signaling pathway. We also observed dysregulation of miRNAs (e.g. let-7, miR-26b, miR-145, and miR-183) in cultured human hepatocytes treated with tacrolimus or high glucose, the two independent risk factors of NODALT identified in this cohort. The hepatic miRNA profiles altered by tacrolimus or hyperglycemia were associated with insulin resistance and glucose homeostatic imbalance as revealed by enrichment analysis. The disease susceptibility miRNA expressive pattern could be imported directly from the donor and consolidated by the transplant factors.

Comparative analysis of hepatic miRNA levels in male marathon mice reveals a link between obesity and endurance exercise capacities

Dummerstorf marathon mice (DUhTP) are characterized by increased accretion of peripheral body fat with fast mobilization in response to mild physical activity if running wheels were included in their home cages. The obese phenotype coincides with elevated hepatic lipogenesis if compared to unselected controls. We now asked, if microRNA (miRNA) species present in the liver may contribute to the obese phenotype of DUhTP mice and if miRNAs respond to mild physical activity in our mouse model. Total RNA was extracted from livers of sedentary or physically active marathon mice and controls and analyzed by array hybridization or real-time PCR using locked nucleic acid probes. Pathway analysis of altered miRNA concentrations identified fatty acid biosynthesis as the most important target for the effects of miRNAs in the liver. A miRNA signature consisting of miR-21, 27, 33, 122, and 143 was present at higher abundance (p < 0.01) in the liver of sedentary or active DUhTP mice indicating involvement of miRNAs with hepatic lipogenesis. Furthermore, in protein lysates from the liver of DUhTP mice, significantly reduced concentrations of total and phosphorylated AKT and lower levels of phosphorylated AMPK were found (p < 0.05). Our results indicate active involvement of miRNAs in the control of hepatic energy metabolism and discuss effects on signal transduction as a potentially direct effect of miR-143 in the liver of DUhTP mice.

The role of miRNAs in cardiovascular disease risk factors

Coronary artery disease and atherosclerosis are complex pathologies that develop over time due to genetic and environmental factors. Differential expression of miRNAs has been identified in patients with coronary artery disease and atherosclerosis, however, their association with cardiovascular disease risk factors, including hyperlipidemia, hypertension, obesity, diabetes, lack of physical activity and smoking, remains unclear. This review examines the role of miRNAs as either biomarkers or potential contributors to the pathophysiology of these aforementioned risk factors. It is intended to provide an overview of the published literature which describes alterations in miRNA levels in both human and animal studies of cardiovascular risk factors and when known, the possible mechanism by which these miRNAs may exert either beneficial or deleterious effects. The intent of this review is engage clinical, translational, and basic scientists to design future collaborative studies to further elucidate the potential role of miRNAs in cardiovascular diseases.