Lipid-Associated Macrophages Reshape BAT Cell Identity in Obesity [CD36_Bulk]
Ontology highlight
ABSTRACT: Obesity and type 2 diabetes cause a loss in brown adipose tissue (BAT) activity in mice and human, but the molecular mechanisms that drive BAT cell remodeling remain largely. Using a multilayered approach, we comprehensively map a deep reorganization in the BAT cells. We uncovered a subset of macrophages as the lipid-associated macrophages (LAM), which were massively increased in genetic and dietary model of BAT expansion. LAM participate in this scenario by capturing extracellular vesicles carrying damaged lipids and mitochondria released from metabolically-stressed brown adipocytes. CD36 scavenger receptor drives LAM phenotype and through * in vitro* and *in vivo* models, we demonstrated that CD36-deficient LAM increased brown fat genes. LAM release Tgfb1 that reduces brown adipocytes identity through Aldh1a1 induction. This study provides the first description of cell dynamics in BAT of obese models identifying LAM as responder to tissue-level metabolic stress and key driver to loss of BAT cell identity.
Project description:Obesity and type 2 diabetes cause a loss in brown adipose tissue (BAT) activity in mice and human, but the molecular mechanisms that drive BAT cell remodeling remain largely. Using a multilayered approach, we comprehensively map a deep reorganization in the BAT cells. We uncovered a subset of macrophages as the lipid-associated macrophages (LAM), which were massively increased in genetic and dietary model of BAT expansion. LAM participate in this scenario by capturing extracellular vesicles carrying damaged lipids and mitochondria released from metabolically-stressed brown adipocytes. CD36 scavenger receptor drives LAM phenotype and through * in vitro* and *in vivo* models, we demonstrated that CD36-deficient LAM increased brown fat genes. LAM release Tgfb1 that reduces brown adipocytes identity through Aldh1a1 induction. This study provides the first description of cell dynamics in BAT of obese models identifying LAM as responder to tissue-level metabolic stress and key driver to loss of BAT cell identity.
Project description:Obesity and type 2 diabetes cause a loss in brown adipose tissue (BAT) activity in mice and human, but the molecular mechanisms that drive BAT cell remodeling remain largely. Using a multilayered approach, we comprehensively map a deep reorganization in the BAT cells. We uncovered a subset of macrophages as the lipid-associated macrophages (LAM), which were massively increased in genetic and dietary model of BAT expansion. LAM participate in this scenario by capturing extracellular vesicles carrying damaged lipids and mitochondria released from metabolically-stressed brown adipocytes. CD36 scavenger receptor drives LAM phenotype and through * in vitro* and *in vivo* models, we demonstrated that CD36-deficient LAM increased brown fat genes. LAM release Tgfb1 that reduces brown adipocytes identity through Aldh1a1 induction. This study provides the first description of cell dynamics in BAT of obese models identifying LAM as responder to tissue-level metabolic stress and key driver to loss of BAT cell identity.
Project description:Obesity and type 2 diabetes cause a loss in brown adipose tissue (BAT) activity in mice and human, but the molecular mechanisms that drive BAT cell remodeling remain largely. Using a multilayered approach, we comprehensively map a deep reorganization in the BAT cells. We uncovered a subset of macrophages as the lipid-associated macrophages (LAM), which were massively increased in genetic and dietary model of BAT expansion. LAM participate in this scenario by capturing extracellular vesicles carrying damaged lipids and mitochondria released from metabolically-stressed brown adipocytes. CD36 scavenger receptor drives LAM phenotype and through * in vitro* and *in vivo* models, we demonstrated that CD36-deficient LAM increased brown fat genes. LAM release Tgfb1 that reduces brown adipocytes identity through Aldh1a1 induction. This study provides the first description of cell dynamics in BAT of obese models identifying LAM as responder to tissue-level metabolic stress and key driver to loss of BAT cell identity.
Project description:Brown adipose tissue (BAT) generates heat via uncoupled respiration, providing mammals with an evolutionary defense against environmental cold. Although the molecular pathways by which cold activates brown adipocytes are well understood, little is known about how BAT maintains its thermogenic capacity during adaptation to environmental warmth. Here, we identify the transcriptional repressor BCL6 as the switch for maintaining brown adipocyte cellular identity under warm conditions. Mice lacking BCL6 in their brown adipocytes display normal thermogenic responses when housed in a cool environment, but fail to maintain thermogenic fitness when housed under warm conditions. In a temperature-dependent manner, BCL6 suppresses apoptosis, fatty acid storage, and coupled respiration to maintain thermogenic competence in brown adipocytes. Enhancer analysis revealed that BCL6 reinforces brown-specific while opposing white-specific enhancers to maintain cellular identity. Thus, unlike other regulators, BCL6 is dispensable for differentiation and activation of brown adipocytes, but specifically required for their maintenance in warmth.
Project description:Brown adipose tissue (BAT) evolved in mammals as a natural defence system against hypothermia and obesity. While existence of BAT in adult humans has been recently appreciated, its cellular origin and molecular identity remain elusive due in large to high cellular heterogeneity within adipose tissues. Here we isolated clonal adipocytes from adult human BAT as well as WAT (control) and critically analyzed their transcriptome to identify bona fide BAT markers and its new functions.
Project description:Brown adipose tissue (BAT) dissipates energy and promotes cardio-metabolic health4. However, loss of BAT during obesity and aging is a principal hurdle for BAT-centered obesity therapies. So far not much is known about BAT apoptosis and signals released by apoptotic brown adipocytes. Here, untargeted metabolomics demonstrated that apoptotic brown adipocytes release a specific pattern of metabolites with purine metabolites being highly enriched. Interestingly, this apoptotic secretome enhances expression of the thermogenic program in healthy adipocytes to maintain tissue functionality. This effect is mediated by the purine inosine which stimulates energy expenditure (EE) in brown adipocytes. Phosphoproteomic analysis demonstrated activation of the cAMP/protein kinase A signaling pathway and of pro-thermogenic transcription factors by inosine.
Project description:Myostatin (MSTN) has been discovered as a critical regulator of muscle mass. Recently, there has been an increasing interest in its functions in metabolism. Here, we specific knocked out MSTN in brown adipose tissue (BAT) (MSTNΔUCP1), and found that the MSTNΔUCP1 mice gained more weight than controls on high-fat diet, with progressive hepatosteatosis, and impaired skeletal muscle activity. RNA-seq analysis indicated signatures of mitochondrial dysfunction and inflammation in MSTN-ablation BAT. Further studies demonstrated that KLF4 is required for the metabolic phenotypes and FGF21 contributes to the microenvironment communication between adipocytes and macrophages induced by loss of MSTN in BAT. Moreover, MSTN-SMAD2/3-p38 signaling pathway mediated the expression of KLF4 and FGF21 in adipocytes. Taken together, brown adipocytes-derived MSTN governs metabolic niche in BAT and regulates systemic energy homeostasis.
Project description:Myostatin (MSTN) has been discovered as a critical regulator of muscle mass. Recently, there has been an increasing interest in its functions in metabolism. Here, we specific knocked out MSTN in brown adipose tissue (BAT) (MSTNΔUCP1), and found that the MSTNΔUCP1 mice gained more weight than controls on high-fat diet, with progressive hepatosteatosis, and impaired skeletal muscle activity. RNA-seq analysis indicated signatures of mitochondrial dysfunction and inflammation in MSTN-ablation BAT. Further studies demonstrated that KLF4 is required for the metabolic phenotypes and FGF21 contributes to the microenvironment communication between adipocytes and macrophages induced by loss of MSTN in BAT. Moreover, MSTN-SMAD2/3-p38 signaling pathway mediated the expression of KLF4 and FGF21 in adipocytes. Taken together, brown adipocytes-derived MSTN governs metabolic niche in BAT and regulates systemic energy homeostasis.
Project description:Obesity and its co-morbidities including type 2 diabetes are increasing at epidemic rates in the U.S. and worldwide. Brown adipose tissue (BAT) is a potential therapeutic to combat obesity and type 2 diabetes. Increasing BAT mass by transplantation improves metabolic health in rodents, but its clinical translation remains a challenge. Here, we investigated if transplantation of 2-4 million differentiated brown pre-adipocytes from mouse BAT stromal fraction (SVF) or human pluripotent stem cells (hPSCs) could improve metabolic health. Transplantation of differentiated brown pre-adipocytes, termed ‘committed pre-adipocytes’ from BAT SVF from mice or derived from hPSCs improves glucose homeostasis and insulin sensitivity in recipient mice under conditions of diet-induced obesity, and this improvement is mediated through the collaborative actions of the liver transcriptome, tissue AKT signaling and FGF21. These data demonstrate that transplantation of a small number of brown adipocytes has significant long-term translational and therapeutic potential to improve glucose metabolism.