Loss of TLE3 promotes the mitochondrial program in beige adipocytes and improves glucose metabolism
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ABSTRACT: Prolonged cold exposure stimulates the recruitment of beige adipocytes within white adipose tissue. Beige adipocytes depend on mitochondrial oxidative phosphorylation to drive thermogenesis. The transcriptional mechanisms that promote remodeling in adipose tissue during the cold are not well understood. Here we demonstrate that the transcriptional coregulator transducin-like enhancer of split 3 (TLE3) inhibits mitochondrial gene expression in beige adipocytes. Conditional deletion of TLE3 in adipocytes promotes mitochondrial oxidative metabolism and increases energy expenditure, thereby improving glucose control. Using chromatin immunoprecipitation and deep sequencing, we found that TLE3 occupies distal enhancers in proximity to nuclear-encoded mitochondrial genes and that many of these binding sites are also enriched for early B-cell factor (EBF) transcription factors. TLE3 interacts with EBF2 and blocks its ability to promote the thermogenic transcriptional program. Collectively, these studies demonstrate that TLE3 regulates thermogenic gene expression in beige adipocytes through inhibition of EBF2 transcriptional activity. Inhibition of TLE3 may provide a novel therapeutic approach for obesity and diabetes.
Project description:Prolonged cold exposure stimulates the recruitment of beige adipocytes within white adipose tissue. Beige adipocytes depend on mitochondrial oxidative phosphorylation to drive thermogenesis. The transcriptional coregulator TLE3 inhibits mitochondrial and metabolic gene expression in beige adipocytes.
Project description:Energy-storing white adipocytes maintain their identity by suppressing the gene program defining energy-burning thermogenic brown/beige adipocytes. Here, we reveal that the protein-protein interaction between the transcriptional co-regulator ZFP423 and brown/beige cell determination factor, EBF2, is essential for restraining the thermogenic phenotype of white adipose tissue (WAT). Disruption of the ZFP423-EBF2 protein interaction through CRISPR-Cas9 gene editing triggers widespread “browning” of WAT in adult mice. Mechanistically, adipocyte Zfp423 deficiency induces an EBF2 NuRD-to-BAF co-regulator switch and a shift in PPARgamma occupancy to thermogenic genes. This shift in PPARgamma occupancy increases the anti-diabetic efficacy of the PPARgamma agonist rosiglitazone in obesity while diminishing the unwanted weight-gaining effect of the drug. These data indicate that ZFP423 controls EBF2 co-activator recruitment and PPARgamma occupancy to determine the thermogenic plasticity of adipocytes and raise the concept of targeting transcriptional brakes in adipocyte gene expression as a therapeutic strategy to induce thermogenic adipocyte biogenesis in obesity.
Project description:Energy-storing white adipocytes maintain their identity by suppressing the gene program defining energy-burning thermogenic brown/beige adipocytes. Here, we reveal that the protein-protein interaction between the transcriptional co-regulator ZFP423 and brown/beige cell determination factor, EBF2, is essential for restraining the thermogenic phenotype of white adipose tissue (WAT). Disruption of the ZFP423-EBF2 protein interaction through CRISPR-Cas9 gene editing triggers widespread “browning” of WAT in adult mice. Mechanistically, adipocyte Zfp423 deficiency induces an EBF2 NuRD-to-BAF co-regulator switch and a shift in PPARgamma occupancy to thermogenic genes. This shift in PPARgamma occupancy increases the anti-diabetic efficacy of the PPARgamma agonist rosiglitazone in obesity while diminishing the unwanted weight-gaining effect of the drug. These data indicate that ZFP423 controls EBF2 co-activator recruitment and PPARgamma occupancy to determine the thermogenic plasticity of adipocytes and raise the concept of targeting transcriptional brakes in adipocyte gene expression as a therapeutic strategy to induce thermogenic adipocyte biogenesis in obesity.
Project description:Here we show that synthesis of the mitochondrial phospholipid cardiolipin is an indispensable driver of thermogenic fat function. Cardiolipin biosynthesis is robustly induced in brown and beige adipose upon cold exposure. Mimicking this response by overexpressing cardiolipin synthase (Crls1) enhances energy consumption in mouse and human adipocytes. Crls1 deficiency diminishes mitochondrial uncoupling in brown and beige adipocytes and elicits a nuclear transcriptional response through ER stress-mediated retrograde communication. Cardiolipin depletion in brown and beige fat abolishes adipose thermogenesis and glucose uptake and renders animals strikingly insulin resistant. We further identify a rare human CRLS1 variant associated with insulin resistance and show that adipose CRLS1 levels positively correlate with insulin sensitivity. Thus, adipose cardiolipin is a powerful regulator of organismal energy homeostasis through thermogenic fat bioenergetics.
Project description:Brown and beige fat share a remarkably similar transcriptional program that supports fuel oxidation and thermogenesis. The chromatin-remodeling machinery that governs genome accessibility and renders adipocytes poised for thermogenic activation remains elusive. Here we found that BAF60a, a subunit of the SWI/SNF chromatin-remodeling complexes, serves an indispensible role in cold-induced thermogenesis in brown fat. BAF60a maintains chromatin accessibility for key thermogenic genes in close proximity to PPARg and EBF2 binding sites. Surprisingly, fat-specific BAF60a inactivation triggers more pronounced browning of inguinal white adipose tissue that is linked to induction of MC2R, a receptor for the pituitary hormone ACTH. Elevated MC2R expression sensitizes adipocytes and BAF60a-deficient adipose tissue to thermogenic activation in response to ACTH stimulation. These observations reveal an unexpected dichotomous role of BAF60a-mediated chromatin remodeling in transcriptional control of brown and beige gene programs and illustrate a pituitary-adipose signaling axis in the control of thermogenesis.
Project description:Adipose tissue provides a defense against starvation and environmental cold. These dichotomous functions are performed by three distinct cell types: energy-storing white adipocytes, and thermogenic beige and brown adipocytes. Previous studies have demonstrated that exposure to environmental cold stimulates the recruitment of beige adipocytes in the white adipose tissue (WAT) of mice and humans, a process that has been extensively investigated. However, beige adipose tissue also develops during the peri-weaning period in mice, a developmental program that remains poorly understood. Here, we address this gap in our knowledge using genetic, imaging, physiologic, and genomic approaches. We find that, unlike cold-induced recruitment in adult animals, peri-weaning development of beige adipocytes occurs in a temperature- and sympathetic nerve-independent manner. Instead, the transcription factor B cell leukemia/lymphoma 6 (BCL6) acts in a cell autonomous manner to regulate the commitment but not the maintenance phase of beige adipogenesis. Genome-wide RNA-seq studies reveal that BCL6 regulates a core set of genes involved in fatty acid oxidation and mitochondrial uncoupling, which are necessary for development of functional beige adipocytes. Together, our findings demonstrate that distinct transcriptional and signaling mechanisms control peri-weaning development and cold-induced recruitment of beige adipocytes in mammals.
Project description:Blnc1 is a novel nuclear lncRNA that promotes brown and beige adipocyte differentiation and function. Blnc1 forms a ribonucleoprotein complex with transcription factor EBF2 to stimulate the thermogenic gene program. Further, Blnc1 itself is a target of EBF2, thereby forming a feedforward regulatory loop to drive adipogenesis toward thermogenic phenotype. We used microarrays to elucidate the role of Blnc1 on brown adipocyte differentiation and mitochondrial function. Brown adipocytes expressing Scramble or brown fat lncRNA 1 knockdown (shBlnc1) were differentiated for 6 days and harvested for RNA isolation and microarray using Affymetrix Mouse MG-430 PM Strip arrays. Two replicated samples were included in this study.
Project description:Adipose tissue plays an important role in the regulation of wholebody energy homeostasis, depending on external environments. Upon cold acclimation, brown and beige adipocytes dissipate mitochondrial proton gradient generating heat via uncoupling protein 1. Due to increasing demands for oxygen during thermogenesis, adipose tissue could become hypoxic upon cold exposure. Hypoxia-inducible factors (HIFs) are one of the major transcription factors which are involved in various cellular responses under hypoxic condition. Although HIFs regulate diverse metabolic processes with selective target gene expression, their roles in thermogenic adipocytes are still elusive. In this study, we demonstrate that adipocyte HIF2a regulate thermogenic activity upon cold stimuli. To investigate molecular mechanisms of adipocyte HIF2a upon thermoneutral and cold exposure, we report the transcriptomes of inguinal adipose tissue from WT and adipocyte specific HIF2a knock-out mice.
Project description:Early B Cell Factor 2 (EBF2) is required for brown adipose tissue basal thermogenic gene expression; however, it was unknown whether chronic cold exposure normalized the expression of thermogenic genes in Ebf2 mutant mice. We examined the transcriptome of Ebf2 WT and mutant brown adipose tissue in mice housed at room temperature or one week of cold exposure.
Project description:Blnc1 is a novel nuclear lncRNA that promotes brown and beige adipocyte differentiation and function. Blnc1 forms a ribonucleoprotein complex with transcription factor EBF2 to stimulate the thermogenic gene program. Further, Blnc1 itself is a target of EBF2, thereby forming a feedforward regulatory loop to drive adipogenesis toward thermogenic phenotype. We used microarrays to elucidate the role of Blnc1 on brown adipocyte differentiation and the induction of the thermogenic gene program. Brown adipocytes expressing vector or brown fat lncRNA 1 (blnc1) were differentiated for 6 days and harvested for RNA isolation and microarray using Affymetrix Mouse MG-430 PM Strip arrays. Two replicated samples were included in this study.