PPARg agonists induce a white-to-brown fat conversion through stabilization of PRDM16 protein
ABSTRACT: Brown adipose tissue dissipates energy through heat and functions as a defense against cold and obesity. PPARγ ligands have been shown to induce the browning of white adipocytes; however, the underlying mechanisms remain unclear. Here we show that PPARγ ligands require full agonism to induce a brown fat gene program preferentially in subcutaneous white adipose. These effects require expression of PRDM16, a factor that controls the development of classical brown fat. Depletion of PRDM16 blunts the effects of the PPARγ agonist rosiglitazone on the induced brown fat gene program. Conversely, PRDM16 and rosiglitazone synergistically activate the brown fat gene program in vivo. This synergy is tightly associated with an increased accumulation of PRDM16 protein, due in large measure to an increase in the half-life of the protein in agonist treated cells. Identifying compounds that stabilize PRDM16 protein may represent a novel therapeutic pathway for the treatment of obesity and diabetes. Microarray analysis of the differentiated inguinal adipocytes expressing sh-scr or sh-PRDM16 in the presence or absence of rosiglitazone (1uM). These samples were profiled using Affymetrix mouse 430A_2 arrays, representing 2 biological replicates for each samples (8 samples in total).
Project description:PRDM16 is a strong activator of brown fat-specific genes, while also a repressor of white fat and muscle-specific genes. We asked what other pathways are regulated by PRDM16 in adipocytes that may be critical for brown and/or beige adipogenesis. Using microarray, we found PRDM16 also represses type I Interferon-stimulated genes (ISGs) in adipocytes. Overall design: We used microarrays to profile changes in gene expression for wildtype and Prdm16 KO adipocytes stimulated with rosiglitazone to induce browning of the adipocytes.
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. Overall design: 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:Here we report, for the first time, the acute effects of the synthetic PPARγ agonist rosiglitazone on the transcriptional network of PPARγ in adipocytes. Treatment with Rosiglitazone for 1 hour leads to acute transcriptional activation as well as repression of a number of genes as determined by genome-wide RNA polymerase II occupancy. Unlike what has been shown for many other nuclear receptors, agonist treatment does not lead to major changes in the occurrence of PPARγ binding sites. However, rosiglitazone promotes PPARγ occupancy at many preexisting sites, and this is paralleled by increased occupancy of the mediator subunit MED1. The increase in PPARγ and MED1 binding is correlated with an increase in transcription of nearby genes indicating that rosiglitazone, in addition to activating the receptor, also promotes its association with DNA, and that this is causally linked to recruitment of mediator and activation of genes. Notably, both Rosiglitazone-activated and -repressed genes are induced during adipogenesis. However, Rosiglitazone-activated genes are markedly more associated with PPARγ than repressed genes and are highly dependent on PPARγ for expression in adipocytes. By contrast, repressed genes are associated with the other key adipocyte transcription factor CCAAT-Enhancer binding protein (C/EBPα), and their expression is more dependent on C/EBPα. This suggests that the relative occupancies of PPARγ and C/EBPα are critical for whether genes will be induced or repressed by PPARγ agonist. Examination of binding of PPARγ, C/EBPα, RNAPII, CBP and MED1 in mature 3T3-L1 adipocytes treated with 1 μM Rosiglitazone and/or 0.1% DMSO for 1 hour.
Project description:Here we have characterized the transcriptional processes underlying the formation of human brown in white (i.e. brite) adipocytes using a genome-wide approach. We show that the browning process is associated with reprogramming of peroxisome proliferator-activated receptor γ (PPARγ) binding to form brite adipocyte-selective PPARγ super-enhancers that appear to play a key role in activation of brite adipocyte-selective genes. We identify the KLF11 gene based on its association with a PPARγ super-enhancer and show that KLF11 is a novel browning factor directly induced by rosiglitazone and required for the activation of brite adipocyte-selective gene program by rosiglitazone. Genome-wide profiling of Dnase I hypersenstive (DHS) sites, epigenomic marks, transcription factor and co-factor binding, and gene expression in hMADS white and brite adipocytes
Project description:This study was undertaken to assess the similarities (or differences) between the well-established PPARγ agonist Rosiglitazone and Non-steroidal anti-inflammatory drugs (NSAIDs) diclofenac, indomethacin and ibuprofen, as well as the partial agonist GQ16 at the transcriptome level. Assessment of NSAID and GQ16 activities in PPARγ-dependent 3T3-L1 cells reveals that NSAIDs and GQ16 display similar effects toward PPARγ-dependent target genes in a manner similar to that of Rosiglitazone. Overall design: Murine 3T3-L1 preadipocytes were differentiated into adipocytes (7 days), then treated with DMSO (control), 100nM rosiglitazone, 25μM sodium diclofenac, 10μM indomethacin, 75μM ibuprofen, or 10μM GQ16 for 24 hours, after which total RNA was isolated.
Project description:Brown adipose tissue (BAT) dissipates chemical energy in the form of heat, as a defense against hypothermia and obesity. Current evidence indicates that brown adipocytes arise from Myf5+-dermotomal precursors through the action of a PRDM16-C/EBP-_ transcriptional complex; however, the underlying mechanisms that determine lineage specification and maintenance of brown adipose cells remain poorly understood. Here we study the role of euchromatic histone-lysine N-methyltransferase 1 (EHMT1), a brown fat-enriched lysine methyltransferase, as an essential enzymatic component of the PRDM16 transcriptional complex and controls brown adipose cell fate. To identify targets and function of EHMT1, we performed genome-wide gene expression profiling of BAT from control mouce (Ehmt1flox/flox), Ehmt1Myf5 KO mouse (Myf5-Cre+/-; Ehmt1flox/flox) and Ehmt1adipo KO mouse (Adipo-Cre+/-; Ehmt1flox/flox). Loss of EHMT1 in Myf5+ lineage causes a near total loss of brown fat characteristics and induces muscle-selective gene program in vivo. In addition, adipose-specific deletion of EHMT1 by Adipo-Cre leads to a marked reduction of the thermogenic and fat oxidation genes.
Project description:PPARγ is a member of the nuclear receptor family for which agonist ligands have anti-growth effects. However, clinical studies using PPARγ ligands as a monotherapy failed to show a beneficial effect. Here we have studied the effects of PPARγ activation with chemotherapeutic agents in current use for specific cancers. We observed a striking synergy between rosiglitazone and platinum-based drugs in several different cancers both in vitro and using transplantable and chemically induced “spontaneous” tumor models. The effect appears to be due in part to PPARγ-mediated downregulation of metallothioneins, proteins that have been shown to be involved in resistance to platinum-based therapy. These data strongly suggest combining PPARγ agonists and platinum-based drugs for the treatment of certain human cancers Experiment Overall Design: Cells were treated with either DMSO/control, rosiglitazone, carboplatin or combination or rosiglitazone and carboplatin in duplicate for 24 hr. RNA was isolated and microarray analysis carried out by the Dana-Farber Cancer Institute Microarray Core.
Project description:Gene expression profile from brown adipose tissues of Prdm16 knockout and wile type mice. Prdm16 is a transcription factor that regulates the thermogenic gene program in brown and beige adipocytes. However, whether Prdm16 is required for the development or physiological function of brown adipose tissue (BAT) in vivo has been unclear. By analyzing mice that selectively lacked Prdm16 in the brown adipose lineage, we found that Prdm16 was dispensable for embryonic BAT development. Brown adipose tissues were collected from Prdm16 knockout and wiletype mice with 4 biological replicates per condition. Experiment was done in two separate batch for 6-week-old and 11-month-old. Extracted RNA was hybridized to Agilent two-color arrays.
Project description:Obesity causes insulin resistance, and PPARγ ligands like rosiglitazone (rosi) are insulin-sensitizing, yet mechanisms remain unclear. High fat diet (HFD) induced obesity has major effects on visceral epididymal adipose tissue (eWAT) of C57BL/6 (B6) mice, and here we report altered activity of gene regulatory elements with changes in PPARγ genome-wide occupancy. Treatment with rosi restored insulin sensitivity, yet surprisingly had little effect on eWAT, leading us to consider the subcutaneous inguinal fat (iWAT). In this depot, rosi markedly induced molecular signatures of brown fat including the key thermogenic gene Ucp1. Obesity-resistant 129S1/SvImJ (129) mice showed this degree of iWAT browning even in the absence of rosi. Remarkably, the 129 Ucp1 locus had increased PPARγ binding and gene expression that was preserved in B6x129 F1 intercross iWAT, with imbalance favoring the 129-derived alleles showing a cis-acting genetic difference. Thus, B6 mice have a genetic defect in Ucp1 expression. However, imbalanced expression favoring 129 over B6 was nearly lost when Ucp1 was activated by rosi, or by iWAT browning in cold-exposed or young mice. These results provide a novel framework for understanding how environmental influences like drugs can rescue genetically determined disease phenotypes by affecting the epigenome. Overall design: C57BL/6J and 129S1/SvlmJ mice were on LFD or HFD; then treated with rosiglitazone