ABSTRACT: Attainment of a brown adipocyte cell phenotype in white adipocytes, with their abundant mitochondria and increased energy expenditure potential, is a legitimate strategy for combating obesity. The unique transcriptional regulators of the primary brown adipocyte phenotype are unknown, limiting our ability to promote brown adipogenesis over white. In the present work, we used microarray analysis strategies to study primary preadipocytes, and we made the striking discovery that brown preadipocytes demonstrate a myogenic transcriptional signature, whereas both brown and white primary preadipocytes demonstrate signatures distinct from those found in immortalized adipogenic models. We found a plausible SIRT1-related transcriptional signature during brown adipocyte differentiation that may contribute to silencing the myogenic signature. In contrast to brown preadipocytes or skeletal muscle cells, white preadipocytes express Tcf21, a transcription factor that has been shown to suppress myogenesis and nuclear receptor activity. In addition, we identified a number of developmental genes that are differentially expressed between brown and white preadipocytes and that have recently been implicated in human obesity. The interlinkage between the myocyte and the brown preadipocyte confirms the distinct origin for brown versus white adipose tissue and also represents a plausible explanation as to why brown adipocytes ultimately specialize in lipid catabolism rather than storage, much like oxidative skeletal muscle tissue. Keywords: In vitro differentiation
Project description:Attainment of a brown adipocyte cell phenotype in white adipocytes, with their abundant mitochondria and increased energy expenditure potential, is a legitimate strategy for combating obesity. The unique transcriptional regulators of the primary brown adipocyte phenotype are unknown, limiting our ability to promote brown adipogenesis over white. In the present work, we used microarray analysis strategies to study primary preadipocytes, and we made the striking discovery that brown preadipocytes demonstrate a myogenic transcriptional signature, whereas both brown and white primary preadipocytes demonstrate signatures distinct from those found in immortalized adipogenic models. We found a plausible SIRT1-related transcriptional signature during brown adipocyte differentiation that may contribute to silencing the myogenic signature. In contrast to brown preadipocytes or skeletal muscle cells, white preadipocytes express Tcf21, a transcription factor that has been shown to suppress myogenesis and nuclear receptor activity. In addition, we identified a number of developmental genes that are differentially expressed between brown and white preadipocytes and that have recently been implicated in human obesity. The interlinkage between the myocyte and the brown preadipocyte confirms the distinct origin for brown versus white adipose tissue and also represents a plausible explanation as to why brown adipocytes ultimately specialize in lipid catabolism rather than storage, much like oxidative skeletal muscle tissue. Experiment Overall Design: Comparisons of white and brown pre- and mature-adiposytes
Project description:Brown adipocytes are specialized for heat generation and energy expenditure as a defense against cold and obesity. Recent studies demonstrate that brown adipocytes arise in vivo from a Myf5-positive, myoblastic progenitor by the action of PRDM16. Here, we identified a brown fat-enriched miRNA cluster mir-193b-365 as a key regulator of brown fat development. Blocking miR-193b and/or miR-365 in primary brown preadipocytes dramatically impaired brown adipocyte adipogenesis whereas myogenic markers were significantly induced. Forced expression of miR-193b and/or miR-365 in C2C12 myoblasts blocked the entire program of myogenesis, and miR-193b induced myoblasts to differentiate into brown adipocytes. Mir-193b-365 was upregulated by PRDM16. Our results demonstrate that mir-193b-365 serves as an essential regulator for brown fat differentiation, in part by repressing myogenesis. To study if miR-193b-365 is required for brown adipocyte adipogenesis, mRNAs from cultured primary brown adipocytes (Day 4) transfected with each locked nucleic acid (LNA) miRNA inhibitor or Control inhibitor were analyzed by microarray analysis.
Project description:Brown adipocytes are specialized for heat generation and energy expenditure as a defense against cold and obesity. Recent studies demonstrate that brown adipocytes arise in vivo from a Myf5-positive, myoblastic progenitor by the action of PRDM16. Here, we identified a brown fat-enriched miRNA cluster mir-193b-365 as a key regulator of brown fat development. Blocking miR-193b and/or miR-365 in primary brown preadipocytes dramatically impaired brown adipocyte adipogenesis whereas myogenic markers were significantly induced. Forced expression of miR-193b and/or miR-365 in C2C12 myoblasts blocked the entire program of myogenesis, and miR-193b induced myoblasts to differentiate into brown adipocytes. Mir-193b-365 was upregulated by PRDM16. Our results demonstrate that mir-193b-365 serves as an essential regulator for brown fat differentiation, in part by repressing myogenesis.
Project description:The marker genes associated with white adipocytes and brown adipocytes have been previously identified; however, these markers have not been updated in several years, and the differentiation process of preadipocytes remains relatively fixed. Consequently, there has been a lack of exploration into alternative differentiation schemes. In this particular study, we present a transcriptional signature specific to brown adipocytes and white adipocytes. Notably, our findings reveal that ZNF497, ZIC1, ZFY, UTY, USP9Y, TXLNGY, TTTY14, TNNT3, TNNT2, TNNT1, TNNI1, TNNC1, TDRD15, SOX11, SLN, SFRP2, PRKY, PAX3KLHL40, PAX3, INKA2-AS1, SOX11, and TDRD15 exhibit high expression levels in brown adipocytes. XIST, HOXA10, PCAT19, HOXA7, PLSCR3, and AVPR1A exhibited high expression levels in white adipocytes, suggesting their potential as novel marker genes for the transition from white to brown adipocytes. Furthermore, our analysis revealed the coordinated activation of several pathways, including the PPAR signaling pathway, focal adhesion, retrograde endocannabinoid signaling, oxidative phosphorylation, PI3K-Akt signaling pathway, and thermogenesis pathways, in brown adipocytes. Moreover, in contrast to prevailing culture techniques, we conducted a comparative analysis of the differentiation protocols for white preadipocytes and brown preadipocytes, revealing that the differentiation outcome remained unaffected by the diverse culture schemes employed. However, the expression levels of certain marker genes in both adipocyte types were found to be altered. This investigation not only identified potential novel marker genes for adipocytes but also examined the impact of different differentiation methods on preadipocyte maturation. Consequently, these findings offer significant insights for further research on the differentiation processes of diverse adipocyte subtypes.
Project description:Brown adipose tissue (BAT) is a central thermogenic organ that enhances energy expenditure (EE) and cardiometabolic health. However, regulators that specifically increase the number of thermogenic adipocytes are still an unmet need. Here, we show by phosphoproteomics that cAMP activates distinct signaling pathways in brown progenitors, with the cAMP-EPAC1 axis enhancing proliferation and differentiation of thermogenic but not white adipocytes. Further analysis revealed that a specific subpopulation of preadipocytes that are PDGFRα-positive express EPAC1. In vivo, pharmacological activation of EPAC1 enhances BAT growth and browning of white fat, leading to increased EE and reduced diet-induced adiposity. In contrast, mice lacking EPAC1 in PDGFRα-positive preadipocytes show the opposite phenotype. Importantly, EPAC1 activation enhances proliferation and differentiation of human brown adipocytes and human brown fat organoids. Interestingly, a coding variant in EPAC1 that positively correlates with BMI abolishes norepinephrine-induced proliferation of brown adipocytes. Thus, EPAC1 might be an attractive target to enhance thermogenic adipocyte number and EE to combat metabolic diseases.
Project description:Adipocytes are key players in maintaining energy homeostasis and are classified into two different categories: white and brown adipocyte. While white adipocytes store energy as triacylglycerols in lipid droplets, brown adipocytes combust excess chemical energy and release in the form of heat through uncoupled respiration. This characteristic phenomenon of brown fat attracts researchers and pharmacological industries to view brown fat as one of the potential therapeutic targets for obesity and associated metabolic disease. In the current study, we investigated the effect of a small molecule, sesaminol (SML) on brown fat activity and found that SML induces thermogenic program in primary white adipocytes as well as chow diet fed mice. In particular, SML treatment to mice elevated mitochondrial complex proteins and the rate oxygen consumption in brown and white fat. Administration of SML to high fat diet (HFD) challenged mice decreased weight gain, adiposity and cholesterol levels along with an increase of brown fat gene program in brown and white fat. Mechanistically, SML repressed the myogenic gene program in C2C12 myoblasts and increased all mitochondrial marker genes as appeared in brown adipose cells. Together, our results demonstrate that SML stimulates brown adipose function and protects mice against diet induced weight gain.
Project description:Adipose tissue is the major depot for energy storage. Recent studies have shown that at least three types of adipocytes can be distinguished depending on their anatomical locations : 1) The classic brown adipocytes, i.e., brown adipose tissue (BAT); 2) The 'brite' (brown-in-white) adipocytes, i.e. inguinal white adipose tissue (iWAT); 3) The 'true' white adipocytes, i.e., epididymal white adipose tissue (eWAT). Two strains of mice (SV129 and C57BL/6J) were used in this study. SV strain is resistant to obesity and latter is prone to obesity. Pre-adipocyte cells were isolated from subcutaneous tissue (iWAT) to create four groups of cell cultures per strain of mouse.
Project description:Brown adipose tissue is specialized to burn lipids for heat generation as a natural defense against cold and obesity. Previous studies established microRNAs as essential regulators of brown adipocyte differentiation, but it remains unknown whether microRNAs are required for the feature maintenance of mature brown adipocytes. To address this question, we ablated Dgcr8, a key regulator of the microRNA biogenesis pathway, in mature brown as well as white adipocytes. The adipose tissue -specific Dgcr8 knockout mice displayed enlarged but pale interscapular brown fat with decreased expression of genes characteristic of brown fat, and the mice were intolerant to cold exposure. In vitro primary brown adipocyte cultures confirmed that microRNAs are required for marker gene expression in mature brown adipocytes. We also demonstrated that microRNAs are essential for the browning of subcutaneous white adipocyte both in vitro and in vivo. Using this animal model, we performed microRNA expression profiling analysis and identified a set of BAT-specific microRNAs that are up-regulated during brown adipocyte differentiation and enriched in brown fat compared to other organs. We identified miR-182 and miR-203 as new regulators of brown adipocyte development. Taken together, our study demonstrates an essential role of microRNAs in the maintenance as well as the differentiation of brown adipocytes.
Project description:Brown adipose tissue (BAT) holds therapeutic potential for obesity and metabolic syndrome via increasing energy expenditure. Both inter- and intra-individual differences contribute to heterogeneity in human BAT and potentially to differential thermogenic capacity in human populations. Here, we demonstrated the generation of brown and white preadipocyte clones from human neck fat and characterized their adipogenic differentiation and thermogenic function. Combining a UCP1 reporter system and gene expression profiling, we defined novel sets of gene signatures in human preadipocytes that could predict the thermogenic potential of mature adipocytes. Knocking out the positive UCP1 regulators, PREX1 and EDNRB, in brown preadipocytes by CRISPRs markedly abolished the high level of UCP1 in mature brown adipocytes. Finally, we showed the ability to prospectively isolate adipose progenitors with great thermogenic potential. These data provide new insights into the cellular heterogeneity in human fat and offer clinically relevant gene targets that mark thermogenically competent preadipocytes. Highly adipogenic clonal white and brown cell lines
Project description:Brown adipose tissue is specialized to burn lipids for heat generation as a natural defense against cold and obesity. Previous studies established microRNAs as essential regulators of brown adipocyte differentiation, but it remains unknown whether microRNAs are required for the feature maintenance of mature brown adipocytes. To address this question, we ablated Dgcr8, a key regulator of the microRNA biogenesis pathway, in mature brown as well as white adipocytes. The adipose tissue -specific Dgcr8 knockout mice displayed enlarged but pale interscapular brown fat with decreased expression of genes characteristic of brown fat, and the mice were intolerant to cold exposure. In vitro primary brown adipocyte cultures confirmed that microRNAs are required for marker gene expression in mature brown adipocytes. We also demonstrated that microRNAs are essential for the browning of subcutaneous white adipocyte both in vitro and in vivo. Using this animal model, we performed microRNA expression profiling analysis and identified a set of BAT-specific microRNAs that are up-regulated during brown adipocyte differentiation and enriched in brown fat compared to other organs. We identified miR-182 and miR-203 as new regulators of brown adipocyte development. Taken together, our study demonstrates an essential role of microRNAs in the maintenance as well as the differentiation of brown adipocytes. TotalRNAs were extracted using a Qiagen kit, and 5 M-NM-<g of total RNAs for each sample were used to prepare the mRNA- Seq library according to the manufacturerM-bM-^@M-^Ys instruction (NEB). cDNA libraries were prepared and sequenced by Hi-seq in Whitehead Genome Core. 2 replicates of each treatment were analyzed.