miR-27a is an important adipogenesis regulator associated with differential lipid accumulation between intramuscular and subcutaneous adipose tissues of sheep

Functional differentiation of the ovine preadipocytes -insights from gene expression profiling

The preadipocytes differentiation is a vital process of lipogenesis; exploring the molecular mechanisms of lipogenesis contributes to improve the meat quality and final commercial income. Lipogenesis has been widely reported in other livestock, but little is known about the gene expression profiles at different stages during preadipocytes differentiation in sheep. In this study, ovine preadipocytes were cultured in vitro and then induced to begin differentiation. Then, the gene expression profiles of preadipocytes collected on day 0 (D0), day 2 (D2), and day 8 (D8) of differentiation were analyzed by RNA-seq technology. According to the findings, 2254 differentially expressed genes (DEGs) were found in D2 vs D0; 1817 DEGs and 1902 DEGs were found in D8 vs D0 and D8 vs D2, respectively. The DEGs were found to be enriched in several biological processes, including focal adhesion, ECM-receptor interaction, PI3K-Akt signaling pathway, steroid biosynthesis, and MAPK signaling pathway, according to Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The regulatory network of the DEGs related to ovine preadipocytes differentiation was systematically constructed, which showed that hub genes might modulate ovine preadipocytes differentiation. In summary, preadipocyte differentiation is regulated by several key genes, including ACACB, CXCL6, SREBF1, INSIG1, APOE, GJA1, CDH11, SYNE1, PCSK1, S100A4, FN1, PLIN2, CXCL6, FN1, PTX3, and FABP3. This study provides a deeper knowledge of the roles of genes in sheep lipogenesis by revealing global gene expression profiles during preadipocyte differentiation.

MiRNA-Seq reveals key MicroRNAs involved in fat metabolism of sheep liver

There is a genetic difference between Hu sheep (short/fat-tailed sheep) and Tibetan sheep (short/thin-tailed sheep) in tail type, because of fat metabolism. Previous studies have mainly focused directly on sheep tail fat, which is not the main organ of fat metabolism. The function of miRNAs in sheep liver fat metabolism has not been thoroughly elucidated. In this study, miRNA-Seq was used to identify miRNAs in the liver tissue of three Hu sheep (short/fat-tailed sheep) and three Tibetan sheep (short/thin-tailed sheep) to characterize the differences in fat metabolism of sheep. In our study, Hu sheep was in a control group, we identified 11 differentially expressed miRNAs (DE miRNAs), including six up-regulated miRNAs and five down-regulated miRNAs. Miranda and RNAhybrid were used to predict the target genes of DE miRNAs, obtaining 3,404 target genes. A total of 115 and 67 GO terms as well as 54 and 5 KEGG pathways were significantly (padj < 0.05) enriched for predicted 3,109 target genes of up-regulated and 295 target genes of down-regulated miRNAs, respectively. oar-miR-432 was one of the most up-regulated miRNAs between Hu sheep and Tibetan sheep. And SIRT1 is one of the potential target genes of oar-miR-432. Furthermore, functional validation using the dual-luciferase reporter assay indicated that the up-regulated miRNA; oar-miR-432 potentially targeted sirtuin 1 (SIRT1) expression. Then, the oar-miR-432 mimic transfected into preadipocytes resulted in inhibited expression of SIRT1. This is the first time reported that the expression of SIRT1 gene was regulated by oar-miR-432 in fat metabolism of sheep liver. These results could provide a meaningful theoretical basis for studying the fat metabolism of sheep.

The Duck RXRA Gene Promotes Adipogenesis and Correlates with Feed Efficiency

BACKGROUND

The accumulation of fat in ducks is the main cause of low feed efficiency and metabolic diseases in ducks. Retinoic acid X receptor alpha (RXRA) is a member of the nuclear receptor superfamily involved in lipid, glucose, energy, and hormone metabolism. The effect of the RXRA gene on lipid metabolism in duck preadipocytes (DPACs) and the relationship between SNPs and the feed efficiency traits of ducks are unclear.

METHODS

qRT-PCR and Western blotting analyses were used to detect changes in mRNA and protein in cells. Intracellular triglycerides (TGs) were detected using an ELISA kit. A general linear model analysis was used to determine the association between RXRA SNPs and feed efficiency.

RESULTS

The duck RXRA gene was highly expressed on the fourth day of DPAC differentiation. The RXRA gene increased the content of fat and TG in DPACs and promoted the expression of cell differentiation genes; g.5,952,667 correlated with average daily feed intake (ADFI), residual feed intake (RFI), and feed conversion ratio (FCR).

CONCLUSIONS

Duck RXRA can accelerate fat accumulation, and the polymorphism of the RXRA gene is closely related to feed efficiency, which provides basic data for breeding high feed efficiency ducks.

Effects of propylene glycol used at different doses in Akkaraman lambs rations on metabolism-related parameters and liver gene and protein expression during different feeding periods

This study aimed to investigate the metabolic effects of propylene glycol (PG) over 60, 90, and 120 days in lambs. Seventy-two weaned male lambs were allocated into three groups: control (Con), PG1.5 (1.5 mL/kg live weight0.75 ), and PG3 (3 mL/kg live weight0.75 ). Blood samples were collected at the beginning and slaughter days. Biochemical parameters (glucose, triglycerides, ALT, AST, LDH, BUN, and insulin) and gene and protein levels of peroxisome proliferator activated receptor gamma (PPARγ), diacylglycerol o-acyltransferase 1 (DGAT1), carbohydrate responsive element binding protein (ChREBP), and sterol regulatory element binding transcription factor 1c (SREBP-1c) in the liver were determined. Glucose in PG1.5 was increased on Day 60, while significant differences were observed in biochemical parameters except for insulin on the 60, 90, and 120 days. Biochemical parameters such as ALT, AST, LDH, and BUN increased over time, while triglycerides decreased. DGAT1 gene and protein levels were lower, while SREBP-1c and PPARγ were higher in PG groups on Day 60. While SREBP-1c was lower in PG1.5, ChREBP was higher in PG3 on Day 90. PPARγ, DGAT1, and ChREBP were upregulated in PG3 on Day 120. Positive correlations were found between proteins. The long-term use of PG in lambs did not have detrimental effects on metabolism. The study provides valuable insights into the molecular mechanisms underlying the metabolic effects of PG in lambs, shedding light on its potential applications in lamb production.

MiR-27a as a diagnostic biomarker and potential therapeutic target in systemic sclerosis

Systemic sclerosis (SSc) or scleroderma is a multiorgan rheumatoid disease characterized by skin tightening or organ dysfunction due to fibrosis, vascular damage, and autoimmunity. No specific cause has been discovered for this illness, and hence no effective treatment exists for it. On the other hand, due to the lack of diagnostic biomarkers capable of effectively and specifically differentiating the patients, early diagnosis has not been possible. Due to their potent regulatory roles in molecular pathways, microRNAs are among the novel candidates for the diagnosis and treatment of diseases like SSc. MiR-27a is a microRNA known for its role in the pathogenesis of fibrosis and cancer, both of which employ similar signaling pathways; hence we hypothesized that Mir-27a could be dysregulated in the blood of individuals affected by SSc and it might be useful in the diagnosis or treatment of this disease. Blood was collected from 60 SSc patients (30 limited and 30 diffuse) diagnosed by a rheumatologist according to ACR/AULAR criteria; following RNA isolation and cDNA synthesis; real-time qPCR was performed on the samples using Taq-Man probes and data were analyzed by the ΔΔCT method. Also, potential targets of miR-27a were evaluated using bioinformatics. It was revealed that miR-27a was significantly down-regulated in SSc patients in comparison to healthy individuals, but there was no difference in miR-27 expression between limited and diffused SSc patients. Besides, miR-27a was found to target several contributing factors to SSc. It seems that miR-27a has a protective role in SSc, and its downregulation could result in the disease's onset. Based on bioinformatics analyses, it is speculated that miR-27a likely targets factors contributing to the pathogenesis of SSc, which are elevated upon the downregulation of miR-27a; hence, miR-27a mimics could be considered as potential therapeutic agents for the treatment of SSc in future studies. Since no difference was observed between limited and diffuse patient groups, it is unlikely that this microRNA has a role in disease progression. According to ROC analysis of qPCR data, miR-27a could be employed as a valuable diagnostic biomarker for SSc.

MicroRNA and circular RNA profiling in the deposited fat tissue of Sunite sheep

As the most typical deposited fat, tail fat is an important energy reservoir for sheep adapted to harsh environments and plays an important role as a raw material in daily life. However, the regulatory mechanisms of microRNA (miRNA) and circular RNA (circRNA) in tail fat development remain unclear. In this study, we characterized the miRNA and circRNA expression profiles in the tail fat of sheep at the ages of 6, 18, and 30 months. We identified 219 differentially expressed (DE) miRNAs (including 12 novel miRNAs), which exhibited a major tendency to be downregulated, and 198 DE circRNAs, which exhibited a tendency to be upregulated. Target gene prediction analysis was performed for the DE miRNAs. Functional analysis revealed that their target genes were mainly involved in cellular interactions, while the host genes of DE circRNAs were implicated in lipid and fatty acid metabolism. Subsequently, we established a competing endogenous RNA (ceRNA) network based on the negative regulatory relationship between miRNAs and target genes. The network revealed that upregulated miRNAs play a leading role in the development of tail fat. Finally, the ceRNA relationship network with oar-miR-27a_R-1 and oar-miR-29a as the core was validated, suggesting possible involvement of these interactions in tail fat development. In summary, DE miRNAs were negatively correlated with DE circRNAs during sheep tail fat development. The multiple ceRNA regulatory network dominated by upregulated DE miRNAs may play a key role in this developmental process.

Transcriptional analysis of microRNAs related to unsaturated fatty acid synthesis by interfering bovine adipocyte ACSL1 gene

Long-chain fatty acyl-CoA synthase 1 (ACSL1) plays a vital role in the synthesis and metabolism of fatty acids. The proportion of highly unsaturated fatty acids in beef not only affects the flavor and improves the meat’s nutritional value. In this study, si-ACSL1 and NC-ACSL1 were transfected in bovine preadipocytes, respectively, collected cells were isolated on the fourth day of induction, and then RNA-Seq technology was used to screen miRNAs related to unsaturated fatty acid synthesis. A total of 1,075 miRNAs were characterized as differentially expressed miRNAs (DE-miRNAs), of which the expressions of 16 miRNAs were upregulated, and that of 12 were downregulated. Gene ontology analysis indicated that the target genes of DE-miRNAs were mainly involved in biological regulation and metabolic processes. Additionally, KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis identified that the target genes of DE-miRNAs were mainly enriched in metabolic pathways, fatty acid metabolism, PI3K-Akt signaling pathway, glycerophospholipid metabolism, fatty acid elongation, and glucagon signaling pathway. Combined with the previous mRNA sequencing results, several key miRNA-mRNA targeting relationship pairs, i.e., novel-m0035-5p—ACSL1, novel-m0035-5p—ELOVL4, miR-9-X—ACSL1, bta-miR-677—ACSL1, miR-129-X—ELOVL4, and bta-miR-485—FADS2 were screened via the miRNA-mRNA interaction network. Thus, the results of this study provide a theoretical basis for further research on miRNA regulation of unsaturated fatty acid synthesis in bovine adipocytes.

Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes

BACKGROUND

After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits.

REVIEW

Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation.

CONCLUSIONS

Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.

Identification of key miRNAs regulating fat metabolism based on RNA-seq from fat-tailed sheep and F2 of wild Argali

The evolution mechanism of sheep tail fat has not yet been clear, many researches focus on this issue, yet there still many gaps to be filled in the targets and non-coding RNA regulation. In our study, the differential expression mRNAs and miRNAs were detected by RNA-seq and constructed a mRNA-miRNA network related to the lipid deposition in tail of fat-tailed sheep and F2 of Argali with domestic sheep (thin-tailed). Then 6 kinds of tissues from thin-tailed and control group were extracted for function validation of candidate genes and its regulator miRNAs. 125 differentially expressed miRNAs were identified by RNA-seq, and enrichment analysis of their target genes revealed 10 significantly enriched pathways related to lipid metabolism. In these pathways, 126 DE-miRNA target genes were also differentially expression in the same tissues in our previous transcriptomic data. In PPI network, 6 hubgenes (SCD, ACACA, GPD2, ELOVL6, ELOVL5, GPAM) were extracted using the cytoHubba application, and they may be target genes for 3 candidate DE-miRNAs (miR-320d, miR-151b, miR-6715). The validation results of RT-qPCR show: the expression trend of miR-320d is opposite to the target gene SCD, and that of miR-151b and the target gene ACACA are also opposite in 6 tissues, implying that they may have direct targeting relationships. Moreover, the expression of miR-320d in F2 tail fat was significantly higher than that in fat-tailed sheep (P < 0.05), and the expression of SCD in F2 tail fat was extremely significantly lower than that in fat-tailed sheep (P < 0.01). The expression of miR-151b in F2 tail fat and subcutaneous fat was significantly higher than that in fat-tailed sheep (P < 0.05), and the expression of ACACA in F2 subcutaneous fat was significantly lower than that in fat-tailed sheep. miR-320d may directly and negatively regulate tail fat deposition by targeting SCD, while miR-151b may indirectly and negatively regulate tail fat deposition by targeting ACACA.

MiR-128-1-5p regulates differentiation of ovine stromal vascular fraction by targeting the KLF11 5'-UTR

Fat content is an important index to evaluate the individual performance of livestock animals such as sheep for meat production purposes. Reducing the subcutaneous and visceral fat while increasing the intramuscular fat is a valuable goal to achieve for the meat production industry. Here, we investigated the effect of miR-128-1-5p on adipogenesis of subcutaneous fat by targeting 5'-UTR in KLF11, a rare mechanism where most miRNAs bind the 3'-UTR of mRNAs. A dual fluorescence reporter assay was conducted to validate the binding sites of miR-128-1-5p on 5'-UTR of KLF11 mRNA. Roles of miR-128-1-5p in KLF11 expression were measured through co-transfecting miRNA mimics with KLF11-expressing vectors (CDSs together with or without the 5'-UTR) into ovine stromal vascular fractions (SVF). Additionally, functional roles of miR-128-1-5p, and KLF11 in adipogenesis of ovine subcutaneous fat were investigated. Results showed that miR-128-1-5p targeted KLF11 5'-UTR, reduced the fluorescence activity of the dual fluorescent reporter vector, as well as KLF11 mRNA, and protein expression levels. During the differentiation of SVF, disturbing the expression of miR-128-1-5p and KLF11 changed the adipogenic differentiation of SVF as observed in the lipid formation, and adipogenic marker genes. This study indicates that miR-128-1-5p promotes the expression of lipogenic marker genes and the formation of lipid droplets by targeting KLF11 5'-UTR. Furthermore, overexpression, and inhibition of KLF11 indicate that KLF11 inhibited SVF differentiation. In summary, the 5'-UTR binding mechanism discovered in this study extends the understanding of miRNA functions. Key roles of miR-128-1-5p and KLF11 in the adipogenesis of sheep subcutaneous fat have potential values for improving the meat and/or fat ratio of domestic animals.

The miR-23-27-24 cluster: an emerging target in NAFLD pathogenesis

The incidence of non-alcoholic fatty liver disease (NAFLD) is increasing globally, being the most widespread form of chronic liver disease in the west. NAFLD includes a variety of disease states, the mildest being non-alcoholic fatty liver that gradually progresses to non-alcoholic steatohepatitis, fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Small non-coding single-stranded microRNAs (miRNAs) regulate gene expression at the miRNA or translational level. Numerous miRNAs have been shown to promote NAFLD pathogenesis and progression through increasing lipid accumulation, oxidative stress, mitochondrial damage, and inflammation. The miR-23-27-24 clusters, composed of miR-23a-27a-24-2 and miR-23b-27b-24-1, have been implicated in various biological processes as well as many diseases. Herein, we review the current knowledge on miR-27, miR-24, and miR-23 in NAFLD pathogenesis and discuss their potential significance in NAFLD diagnosis and therapy.

Bone Marrow Adiposity in Models of Radiation- and Aging-Related Bone Loss Is Dependent on Cellular Senescence

Oxidative stress-induced reactive oxygen species, DNA damage, apoptosis, and cellular senescence have been associated with reduced osteoprogenitors in a reciprocal fashion to bone marrow adipocyte tissue (BMAT); however, a direct (causal) link between cellular senescence and BMAT is still elusive. Accumulation of senescent cells occur in naturally aged and in focally radiated bone tissue, but despite amelioration of age- and radiation-associated bone loss after senescent cell clearance, molecular events that precede BMAT accrual are largely unknown. Here we show by RNA-Sequencing data that BMAT-related genes were the most upregulated gene subset in radiated bones of C57BL/6 mice. Using focal radiation as a model to understand age-associated changes in bone, we performed a longitudinal assessment of cellular senescence and BMAT. Using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), RNA in situ hybridization of p21 transcripts and histological assessment of telomere dysfunction as a marker of senescence, we observed an increase in senescent cell burden of bone cells from day 1 postradiation, without the presence of BMAT. BMAT was significantly elevated in radiated bones at day 7, confirming the qRT-PCR data in which most BMAT-related genes were elevated by day 7, and the trend continued until day 42 postradiation. Similarly, elevation in BMAT-related genes was observed in bones of aged mice. The senolytic cocktail of Dasatinib (D) plus Quercetin (Q) (ie, D + Q), which clears senescent cells, reduced BMAT in aged and radiated bones. MicroRNAs (miRNAs or miRs) linked with senescence marker p21 were downregulated in radiated and aged bones, whereas miR-27a, a miR that is associated with increased BMAT, was elevated both in radiated and aged bones. D + Q downregulated miR-27a in radiated bones at 42 days postradiation. Overall, our study provides evidence that BMAT occurrence in oxidatively stressed bone environments, such as radiation and aging, is induced following a common pathway and is dependent on the presence of senescent cells. © 2022 American Society for Bone and Mineral Research (ASBMR).

miR-27a Regulates Sheep Adipocyte Differentiation by Targeting CPT1B Gene

Simple Summary

The content of intramuscular fat (IMF) is the main determinant of the nutritional and economic value of sheep meat. Therefore, lipid synthesis in sheep longissimus lumborum (LL) has become an important research focus. MicroRNA-27a (miR-27a) has been shown to play a crucial role in the proliferation and differentiation of adipocyte progenitor cells. In this study, we revealed that miR-27a significantly inhibited the formation of lipid droplets by targeting CPT1B to inhibit genes involved in lipid synthesis including PPAR γ, SCD, LPL, and FABP4. Here, we constructed a miR-27a-CPT1B regulatory network map, which revealed the interaction between miR-27a and CPT1B in lipid synthesis in ovine preadipocytes.

Abstract

MiRNAs are vital regulators and play a major role in cell differentiation, biological development, and disease occurrence. In recent years, many studies have found that miRNAs are involved in the proliferation and differentiation of adipocytes. The objective of this study was to evaluate the effect of miR-27a and its target gene CPT1B on ovine preadipocytes differentiation in Small-tailed Han sheep (Ovis aries). Down-regulation of miR-27a significantly promoted the production of lipid droplets, while overexpression of miR-27a led to a reduction in lipid droplet production. In addition, inhibition of miR-27a led to a significant increase in the expression of genes involved in lipid synthesis, including PPAR γ, SCD, LPL, and FABP4. Target Scan software predicted that CPT1B is a new potential target gene of miR-27a. Further experiments revealed that CPT1B gene expression and protein levels were negatively correlated with miR-27a expression. Overexpression of miR-27a led to a significant decrease in CPT1B mRNA levels and inhibited the accumulation of lipid droplets and vice versa. Moreover, overexpression of CPT1B promoted the synthesis of lipid droplets in ovine preadipocytes. Furthermore, luciferase reporter assays confirmed CPT1B to be a miR-27a direct target gene. This study confirmed that miR-27a increases the expression of genes related to lipid synthesis in ovine preadipocytes by targeting CPT1B, thereby promoting the synthesis of lipid droplets. The results of this study can be used to be exploited in devising novel approaches for improving the IMF content of sheep.

miR-301a inhibits adipogenic differentiation of adipose-derived stromal vascular fractions by targeting HOXC8 in sheep

MicroRNAs (miRNAs) regulate adipogenic differentiation in stromal vascular fractions (SVFs) through post-transcriptional regulation of transcription factors and other functional genes. miR-301 and the homeobox C8 (HOXC8) gene are involved in lipid homeostasis; however, their roles in the adipogenic differentiation of ovine SVFs are unknown. Here, we explored the effects of miR-301 and HOXC8 on adipogenic differentiation in ovine SVFs and the regulatory role of miR-301a in HOXC8 expression. Additionally, we evaluated the effect of miR-301a and HOXC8 on the mRNA abundance of adipogenic markers and the ability of ovine SVFs to accumulate lipids. We found that miR-301a regulates adipogenic differentiation in ovine SVFs by directly targeting the 3'-untranslated region of HOXC8, resulting in significant downregulation of the HOXC8 mRNA and protein. Moreover, miR-301a overexpression suppressed adipogenic differentiation in ovine SVFs and significantly inhibited the expression of adipogenesis-related genes-including adiponectin, C/EBPα, PPARγ, and FABP4. Conversely, HOXC8 overexpression in ovine SVFs increased the accumulation of lipid droplets and remarkably promoted the expression of adipogenic markers. Taken together, our results indicate that miR-301a attenuates the adipogenic differentiation of ovine SVFs by targeting HOXC8. These findings improve our understanding of the mechanism of lipid accumulation and metabolism in sheep.

C-type natriuretic peptide promotes adipogenic differentiation of goat adipose-derived stem cells via cGMP/PKG/ p38 MAPK signal pathway

C-type natriuretic peptide (CNP) is a member of natriuretic peptide family, which plays unique roles in cardiovascular system. Once CNP binds to natriuretic peptide receptor B (NPR-B), NPR-B induces the production of cGMP, thereby activating PKG and downstream targets. The expression of NPR-B in adipose tissue led to a hypothesis that CNP could have roles involving in regulation of adipogenesis. However, there are few studies on the relationship between CNP and adipogenesis in goat. In the present study, goat adipose-derived stem cells (ADSCs) were isolated and employed to investigate the effect of CNP on adipogenesis in goat. The results showed that CNP significantly promoted adipogenic differentiation of goat ADSCs and also up-regulated the expression of brown adipose genes including uncoupling protein 1 (UCP-1) and peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α). Furthermore, treatment with CNP increased the cGMP production and the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), MAPK activated protein kinase 2 (MK2), and activating transcription factor 2 (ATF2) during adipogenic differentiation. Conversely, PKG inhibitor Rp-8-CPT-cGMP or p38 MAPK specific inhibitor SB203580 abolished stimulative effect of CNP on adipogenic differentiation. Collectively, it is proved that CNP promoted adipogenic differentiation of goat ADSCs depending on the cGMP/PKG/p38 MAPK signal pathway.

microRNA-27a-3p but Not -5p Is a Crucial Mediator of Human Adipogenesis

MicroRNAs (miRNAs), a class of small, non-coding RNA molecules, play an important role in the posttranscriptional regulation of gene expression, thereby influencing important cellular functions. In adipocytes, miRNAs show import regulatory features and are described to influence differentiation as well as metabolic, endocrine, and inflammatory functions. We previously identified miR-27a being upregulated under inflammatory conditions in human adipocytes and aimed to elucidate its function in adipocyte biology. Both strands of miR-27a, miR-27a-3p and -5p, were downregulated during the adipogenic differentiation of Simpson–Golabi–Behmel syndrome (SGBS) cells, human multipotent adipose-derived stem cells (hMADS), and human primary adipose-derived stromal cells (hASCs). Using miRNA-mimic transfection, we observed that miR-27a-3p is a crucial regulator of adipogenesis, while miR-27a-5p did not alter the differentiation capacity in SGBS cells. In silico screening predicted lipoprotein lipase (LPL) and peroxisome proliferator activated receptor γ (PPARγ) as potential targets of miR-27a-3p. The downregulation of both genes was verified in vitro, and the interaction of miR-27-3p with target sites in the 3′ UTRs of both genes was confirmed via a miRNA-reporter-gene assay. Here, the knockdown of LPL did not interfere with adipogenic differentiation, while PPARγ knockdown decreased adipogenesis significantly, suggesting that miR-27-3p exerts its inhibitory effect on adipogenesis by repressing PPARγ. Taken together, we identified and validated a crucial role for miR-27a-3p in human adipogenesis played by targeting the essential adipogenic transcription factor PPARγ. Though we confirmed LPL as an additional target of miR-27a-3p, it does not appear to be involved in regulating human adipogenesis. Thereby, our findings call the conclusions drawn from previous studies, which identified LPL as a crucial regulator for murine and human adipogenesis, into question.

Regulation of cholesterol biosynthesis and lipid metabolism: A microRNA management perspective

Cellular disruption of lipid and cholesterol metabolism results in pathological processes linked to metabolic and cardiovascular diseases. Classically, at the transcription stages, the Cholesterol levels are controlled by two cellular pathways. First, the SREBP transcription factor family controls Cholesterol biosynthesis via transcriptional regulation of critical rate-limiting cholesterogenic and lipogenic proteins. Secondly, The LXR/RXR transcription factor family controls cholesterol shuttling via transcriptional regulation of cholesterol transport proteins. In addition, the posttranscriptional control of gene expression of various enzymes and proteins of cholesterol biosynthesis pathways is mediated by small non-coding microRNAs. Regulatory noncoding miRNAs are critical regulators of biological processes, including developmental and metabolic functions. miRNAs function to fine-tune lipid and cholesterol metabolism pathways by controlling the mRNA levels and translation of critical molecules in each pathway. This review discusses the regulatory roles of miRNAs in cholesterol and lipid metabolism via direct and indirect effects on their target genes, including SREBP, LXR, HDL, LDL, and ABCA transporters. We also discuss the therapeutic implications of miRNA functions and their purported role in the potentiation of small molecule therapies.

Whole-Transcriptome Analysis of Preadipocyte and Adipocyte and Construction of Regulatory Networks to Investigate Lipid Metabolism in Sheep

Many local sheep breeds in China have poor meat quality. Increasing intramuscular fat (IMF) content can significantly improve the quality of mutton. However, the molecular mechanisms of intramuscular adipocyte formation and differentiation remain unclear. This study compared differences between preadipocytes and mature adipocytes by whole-transcriptome sequencing and constructed systematically regulatory networks according to the relationship predicted among the differentially expressed RNAs (DERs). Sequencing results showed that in this process, there were 1,196, 754, 100, and 17 differentially expressed messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), respectively. Gene Ontology analysis showed that most DERs enriched in Cell Part, Cellular Process, Biological Regulation, and Binding terms. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis found that the DERs primarily focused on Focal adhesion, phosphoinositide 3-kinase (PI3K)-Akt, mitogen-activated protein kinase (MAPK), peroxisome proliferator-activated receptor (PPAR) signaling pathways. Forty (40) DERs were randomly selected from the core regulatory network to verify the accuracy of the sequence data. The results of qPCR showed that the DER expression trend was consistent with sequence data. Four novel promising candidate miRNAs (miR-336, miR-422, miR-578, and miR-722) played crucial roles in adipocyte differentiation, and they also participated in multiple and important regulatory networks. We verified the expression pattern of the miRNAs and related pathways’ members at five time points in the adipocyte differentiation process (0, 2, 4, 6, 8, 10 days) by qPCR, including miR-336/ACSL4/LncRNA-MSTRG71379/circRNA0002331, miR-422/FOXO4/LncRNA-MSTRG54995/circRNA0000520, miR-578/IGF1/LncRNA-MSTRG102235/circRNA0002971, and miR-722/PDK4/LncRNA-MSTRG107440/circ RNA0002909. In this study, our data provided plenty of valuable candidate DERs and regulatory networks for researching the molecular mechanisms of sheep adipocyte differentiation and will assist studies in improving the IMF.

Identification of miRNA in Sheep Intramuscular Fat and the Role of miR-193a-5p in Proliferation and Differentiation of 3T3-L1

Intramuscular fat (IMF) is one of the most critical parameters affecting meat quality and mainly affected by genetic factors. MicroRNA as an important regulatory factor, which is still a lack of research in the development of sheep IMF deposition. We used RNA sequencing (RNA-seq) and cell-level validation to explore the role of miRNA in IMF deposition. As for this purpose, longissimus thoracis et lumborum (LTL) samples of 2 month-old (Mth-2) and 12 months-old (Mth-12) Aohan fine-wool sheep (AFWS) were used to identified miRNAs expression. We found 59 differentially expressed miRNAs (DE-miRNA) between these age groups and predicted their 1,796 target genes. KEGG functional enrichment analysis revealed eight pathways involved in lipid metabolism-related processes, including fatty acid elongation and the AMPK signaling pathway. A highly expressed DE-miRNA, miR-193a-5p, was found to serve a function in 3T3-L1 preadipocyte differentiation. Luciferase assay demonstrated that miR-193a-5p directly binds to the 3′-UTR region of ACAA2. By constructing mimics and inhibitor vector transfecting into 3T3-L1 cells to explore the effect of miR-193a-5p on cell proliferation and differentiation, we demonstrated that overexpression of miR-193a-5p inhibited 3T3-L1 preadipocyte proliferation, as evidenced by decreased mRNA and protein expression of CDK4 and CyclinB. CCK-8 assay showed that miR-193a-5p significantly inhibited cell proliferation. Similarly, the overexpression of miR-193a-5p inhibited 3T3-L1 preadipocyte differentiation and adipocyte-specific molecular markers’ expression, leading to a decrease in PPARγ and C/EBPα and ACAA2. Inhibition of miR-193a-5p had the opposite effects. Our study lists the miRNAs associated with intramuscular lipid deposition in sheep and their potential targets, striving to improve sheep meat quality.

MiR-33a inhibits the adipogenic differentiation of ovine adipose-derived stromal vascular fraction cells by targeting SIRT6

Adipose tissue is important for the regulation of energy balance through its metabolic, cellular, and endocrine functions. Furthermore, the excessive storage of subcutaneous fat can seriously affect the health and carcass traits of domestic animals. Stromal vascular fraction (SVF) cell adipogenic differentiation increases the number of differentiated adipocytes and plays a role in lipid deposition. The adipogenic differentiation of SVF cells is regulated by various factors, including microRNAs and cytokines. Sirt6 and miR-33a are known to be involved in metabolism and adipogenesis, respectively; however, their effects on the adipogenic differentiation of ovine SVF cells were previously unknown. Thus, the aim of this study was to investigate this. The results showed that SIRT6 is a binding target for miR-33a. Moreover, overexpression or inhibition of miR-33a was found to change the expression of SIRT6 messenger RNA and protein. Furthermore, modulating SIRT6 altered the expression of adipogenic marker genes. In addition, miR-33a and SIRT6 were found to play opposing roles in adipogenesis. Specifically, we demonstrated that miR-33a is involved in the negative regulation of ovine SVF cell adipogenic differentiation by inhibiting the expression of SIRT6. These findings reveal a key role for miR-33a and SIRT6 in adipogenesis, which will enrich our understanding of the regulatory factors associated with SVF cell adipogenic differentiation and provide a basis for further study on this process.