Lipolysis regulates major transcriptional programs in brown adipocytes [3Dcultured_eWAs_RNA-seq]
Ontology highlight
ABSTRACT: β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function.
Project description:β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function.
Project description:β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function.
Project description:β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function.
Project description:β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function.
Project description:β-Adrenergic signaling is a core regulator of brown adipocyte function stimulating both lipolysis and transcription of thermogenic genes, thereby expanding the capacity for oxidative metabolism. Here we have used pharmacological inhibitors and a novel direct activator of lipolysis to acutely modulate the activity of lipases, thereby enabling us to uncover lipolysis-dependent signaling pathways downstream of β-adrenergic signaling in brown adipocytes. We show that induction of lipolysis leads to acute induction of several gene programs and is required for transcriptional regulation by β-adrenergic signals. Using machine-learning algorithms to infer causal transcription factors, we show that PPARs are key mediators of lipolysis-induced activation of genes involved in lipid metabolism and thermogenesis. Importantly, lipolysis also activates the unfolded protein response and regulates the core circadian transcriptional machinery independently of PPARs. Our results demonstrate that lipolysis generates important metabolic signals that exert profound pleiotropic effects on brown adipocyte transcription and function.
Project description:Obesity is associated with impaired β-adrenergic receptor (Adrb1-3) signaling and lipolysis, leading to aberrant white adipose tissue (WAT) growth. WAT research has been centered on transcriptional and posttranslational regulations, but posttranscriptional regulation and mRNA modifications are poorly understood. Here, we unveil a METTL14/N6-methyladenosine (m6A) paradigm guiding β-adrenergic signaling and lipolysis. METTL14 complex installs m6A on RNA, regulating mRNA fate and translation. We found that feeding and insulin increased adipose Mettl14 and m6A levels. Adipose Mettl14 and m6A were upregulated in high fat diet (HFD)-induced obesity. Ablation of adipose Mettl14 decreased Adrb2, Adrb3, Atgl (encoding lipase), and Cig-58 (Atgl activator) transcript m6A contents while increasing their translation and protein levels, thereby enhancing adipose β-adrenergic signaling and lipolysis. Consequently, adipocyte-specific Mettl14 knockout mice were resistant to HFD-induced obesity, insulin resistance, glucose intolerance, and NAFLD. These results unravel a METTL14/m6A-based epitranscriptomic mechanism governing β-adrenergic signaling, lipolysis, and adipose growth in health and disease.
Project description:Peroxisome proliferator‑activated receptors (PPARs) have been suggested as the master regulators of adipose tissue formation, however their role in regulating brown fat functionality has not been resolved. To address this question, we generated inducible brown fat specific mouse models for PPARa, b/d and g, respectively. Interestingly, we found that both PPARa and b/d are dispensable for brown fat function. In contrast, we could show that ablation of PPARg in vitro as well in vivo led to a reduced thermogenic capacity accompanied by a loss of inducibility by β-adrenergic signaling, as well as a shift from oxidative fatty acid metabolism to glucose utilization. We identified glycerol kinase (Gyk) as a partial mediator of PPARgfunction, and could show that Gyk expression correlates with brown fat thermogenic capacity in human brown fat biopsies. Thus, Gyk might constitute the link between PPARg mediated regulation of brown fat function and activation by β-adrenergic signaling.
Project description:Increasing energy expenditure through activation of brown adipose tissue (BAT) thermogenesis is an attractive approach to counteract obesity. Thus, it is essential to understand molecular mechanisms that control BAT functions. Here, we describe signal transducer and activator of transcription (STAT) 5 as key regulator of BAT functionality. We found that STAT5 is necessary for acute cold-induced temperature maintenance and stimulated lipid breakdown in BAT using mice that harbour an adipocyte-specific deletion of Stat5a/b genes. In addition, the mitochondrial respiratory capacity of primary differentiated brown adipocytes from STAT5 deficient mice was diminished. We show that increased sensitivity to cold stress upon STAT5 deficiency was associated with reduced expression of thermogenic key player uncoupling protein 1, while decreased stimulated lipolysis of STAT5-deficient BAT explants was linked to decreased protein kinase A activity. In addition, brown remodeling of white fat was diminished following chronic β-adrenergic stimulation. This impairment was linked to a decrease in mitochondrial functionality. We conclude that STAT5 is essential for the β-adrenergic responsiveness of brown adipose tissue and the physiologic function of thermogenic adipose tissue.
Project description:Beyond its thermogenic potential, brown adipose tissue (BAT) performs important endocrine functions that regulate metabolism. However, the BAT microenvironment and the factors involved in BAT homeostasis and adaptation to cold remain poorly characterized. We therefore aimed to study secreted factors from active brown adipocytes that may be involved in adipocyte function and/or may orchestrate inter-cellular communications. For this, mRNA levels in mature adipocytes of brown, beige and white adipose depots from mice exposed to 21 days of cold were evaluated using RNA sequencing, and bioinformatic analysis was used to predict for potentially secreted factors. Cxcl12 was found to be the most cold-induced C-X-C chemokine in BAT, and Cxcl12 mRNA expression analysis by qPCR and fluorescence in-situ hybridization revealed its enrichment in brown adipocytes upon cold. Cold increased CXCL12 secretion from BAT, yet its level in plasma remained unchanged indicating a potential local action. Cxcl12 knockdown in mature brown adipocytes impaired thermogenesis, estimated by norepinephrine (NE)-induced Ucp1 gene expression, glycerol release and mitochondrial respiration despite unaltered β-adrenergic signaling, suggesting Cxcl12 regulates adipocyte function independently from the β-adrenergic pathway. Importantly, unaltered adipocyte characteristics upon Cxcl12 loss may indicate CXCL12 primarily regulates the NE-induced adipocyte activation. Furthermore, CXCL12 might exert inter-cellular crosstalk via its capacity to promote macrophage chemotaxis and neurite outgrowth. Here we present CXCL12 as a novel brown adipocyte, cold-induced secreted factor involved in adipocyte function and inter-cellular crosstalk within BAT.
Project description:Beta-adrenergic stimulation stabilizes ERK3, resulting in the formation of a complex with MK5 and thereby driving lipolysis. A downstream target of the complex is FOXO1, which controls expression of the lipolytic enzyme ATGL. Deletion of ERK3 in mouse adipocytes inhibits lipolysis, but elevates energy dissipation.