Project description:Brown Adipose YY1 Deficiency Activates Expression of Secreted Proteins Linked to Energy Expenditure and Prevents Diet-Induced Obesity [BAT]
Project description:Brown Adipose YY1 Deficiency Activates Expression of Secreted Proteins Linked to Energy Expenditure and Prevents Diet-Induced Obesity [IWAT]
Project description:Brown Adipose YY1 Deficiency Activates Expression of Secreted Proteins Linked to Energy Expenditure and Prevents Diet-Induced Obesity
Project description:Brown Adipose YY1 Deficiency Activates Expression of Secreted Proteins Linked to Energy Expenditure and Prevents Diet-Induced Obesity [IWAT]
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:Coenzyme Q is an essential component of mitochondrial function and required for thermogenic activity in brown adipose tissues (BAT). BAT CoQ deficiency (50-75%) by genetic or pharmacological means does not interfere with basal or maximal mitochondrial respiration in brown adipocytes but increases mitochondrial oxidants and induces UPRmt, ISR, and repression of UCP1 expression. ATF4, the master regulator of ISR, is required for UCP1 suppression in BAT CoQ deficiency. In animals, BAT CoQ deficiency causes cold intolerance but activates compensatory thermogenic mechanisms in BAT and other tissues via greatly induced BAT FGF21 expression resulting in paradoxically upregulated whole-body respiration rates and protection from obesity at room temperature and thermoneutrality. BAT-specific loss of either ATF4 or FGF21 abolishes these metabolic benefits demonstrating a central role for CoQ in the modulation of whole-body energy expenditure and thus for the etiology of primary and secondary CoQ deficiencies.
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:Obesity has become a global health problem. Brown adipose tissue (BAT), specialized for energy expenditure through thermogenesis, potently counteracts obesity. Recently, BAT is also identified in human adults. We found that Lgr4 homozygous mutant (Lgr4m/m) mice display reduced adiposity and exhibit brown-like adipocytes in their WAT depots with higher expression of uncoupling protein 1 (Ucp1). Furthermore, Lgr4 ablation potentiates brown adipocyte differentiation from stromal vascular fraction (SVF) of epididymal WAT (eWAT) in vitro. We used microarrays to emxamine the gene expression profiles of the brown-like adipocytes differentiated from SVF of wild-type and Lgr4 mutant mice. We identified distinct gene expression profiles of these two groups.
Project description:Brown adipose tissue (BAT) functions in energy expenditure in part due its role in thermoregulation. The prominent capacity of BAT to enhance fuel utilization and energy expenditure makes it an attractive target for treating obesity and metabolic disorders. Prolonged cold exposure induces de novo recruitment of brown adipocytes and activates their thermogenic activity. However, the exact source of cold-induced brown adipocytes is not completely understood. In this study, we sought to investigate the cellular origin of cold-induced brown adipocytes using single-cell RNA sequencing. We identified two distinct types of adipocyte progenitors that contribute to de novo recruitment of brown adipocytes in response to cold challenge. One is the previously known Pdgfra-expressing mesenchymal progenitors and the other is a vascular smooth muscle-derived adipocyte progenitor (VSM-APC) population, which expresses the temperature-sensitive ion channel transient receptor potential cation channel subfamily V member 1 (Trpv1). Using flow cytometry and lineage tracing, we demonstrated that the Trpv1pos VSM-APCs were indeed distinct from the Pdgfrapos progenitors and could contribute to brown adipocytes with greater thermogenic potential. Together, these findings illustrate a landscape of thermogenic adipose niche at the single cell resolution and identify a new cellular origin for the development of brown adipocytes.
Project description:Obesity results from a caloric imbalance between energy intake, absorption and expenditure. In both rodents and humans, diet-induced thermogenesis contributes to energy expenditure and involves the activation of brown adipose tissue (BAT). We hypothesized that environmental toxicants commonly used as food additives or pesticides might reduce BAT thermogenesis through suppression of uncoupling protein 1 (UCP1) and this may contribute to the development of obesity. Using a step-wise screening approach, we discovered that the organophosphate insecticide chlorpyrifos suppresses UCP1 and mitochondrial respiration in BAT at concentrations as low as 1 pM. In mice housed at thermoneutrality and fed a high-fat diet, chlorpyrifos impaired BAT mitochondrial function and diet-induced thermogenesis, promoting greater obesity, non-alcoholic fatty liver disease (NAFLD) and insulin resistance. This was associated with reductions in cAMP; activation of p38MAPK and AMPK; protein kinases critical for maintaining UCP1 and mitophagy, respectively in BAT. These data indicate that the commonly used pesticide chlorpyrifos, suppresses diet-induced thermogenesis and the activation of BAT, suggesting its use may contribute to the obesity epidemic.