Project description:Opsin3 (Opn3) is a transmembrane heptahelical G-protein-coupled receptor (GPCR) with the potential to produce a non-visual photoreceptive effect. Interestingly, anatomical profiling of GPCRs reveals that Opn3 mRNA is highly expressed in adipose tissue. The photosensitive functions of Opn3 in mammals are poorly understood, and whether Opn3 has a function in fat is entirely unknown. In this study, we found that Opn3-knockout (Opn3-KO) mice were prone to diet-induced obesity and insulin-resistance. At the cellular level, Opn3-KO brown adipocytes cultured in darkness had decreased glucose uptake and lower nutrient-induced mitochondrial respiration than wild-type (WT) cells. Light exposure promoted mitochondrial activity and glucose uptake in WT adipocytes but not in Opn3-KO cells. Using RNA sequencing, we identified several novel light-sensitive and Opn3-dependent molecular signatures in brown adipocytes. Importantly, direct exposure of BAT to light in living mice significantly enhanced thermogenic capacity of BAT, and this effect was diminished in Opn3-KO animals. These results uncover a previously unrecognized cell-autonomous, light-sensing mechanism in brown adipocytes via Opn3-GPCR signaling that can regulate fuel metabolism and mitochondrial respiration in vitro and thermogenesis in vivo. Our work also provides a molecular basis for developing light-based treatments for obesity and its related metabolic disorders.
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:Cre recombinase activity was induced in differentiating brown adipocytes from CreERT2 Sykflox/flox mice in vitro, which resulted in a partial loss of Syk protein in mature brown adipocytes. Such cells were viable, morphologically normal and displayed largely normal gene expression as indicated by mRNA sequencing and qPCR analysis, suggesting that Syk is not required for survival and gene expression of terminally differentiated brown adipocytes. mRNA sequencing of Syk depleted brown adipocytes treated with 0.1 microM isoproterenol for 6 h showed that 2460 genes were not induced or suppressed upon stimulation. Gene set enrichment analysis revealed a great enrichment for genes essential for mitochondrial respiration and biogenesis, for genes associated with and required for adipogenesis, as well as for genes responsive to various stimuli in adipocytes among genes highly ranked by reduced fold changes in response to isoproterenol in the Syk deficient brown adipocytes.
Project description:The adipose organ, including white and brown adipose tissues, is an important player in systemic energy homeostasis, storing excess energy in form of lipids while releasing energy upon various energy demands. Recent studies have demonstrated that white and brown adipocytes also function as endocrine cells and regulate systemic metabolism by secreting factors that act locally and systemically. However, a comparative proteomic analysis of secreted factors from white and brown adipocytes and their responsiveness to adrenergic stimulation has not been reported yet. Therefore, we studied and compared the secretome of white and brown adipocytes, with and without norepinephrine (NE) stimulation. Our results reveal that in the absence of NE, carbohydrate metabolism-regulating proteins are preferably secreted from white adipocytes, while brown adipocytes predominantly secrete integrin signaling proteins. Upon NE stimulation, white adipocytes secrete more proteins involved in lipid metabolism, while brown adipocytes secrete more proteins with specific anti-inflammatory properties. In conclusion, our study provides a comprehensive catalogue of novel adipokine candidates secreted from white and brown adipocytes with many of them responsive to NE.
Project description:We have identified a population of adipocytes in fat tissue that arise from bone marrow-derived progenitor cells. We used microarrays to compare the global gene expression patterns of the bone marrow progenitor-derived adipocytes as well as conventional white and brown adipocytes to evaluate the relationship between these adipocyte subpopulations. Gonadal fat tissue (for white adipocytes) and intrascapular fat tissue (for brown adipocytes) was digested with collagenase and adipocytes were recovered by centrifugation/flotation. Bone marrow derived adipocytes were isolated from the adipocyte fraction of gonadal fat tissue from mice receiving bone marrow tranplants from donors expressing either green fluorescent protein (GFP) or beta-galactosidase (LacZ) by flow cytometry.
Project description:Purpose: To test if there is a heterogeneity within brown adipocytes, we performed single cell RNA-sequencing of primary brown adipocytes isolated from mouse brown adipose tissue. Methods: Brown adipocytes from 10-week-old C57BL/6J male mice were freshly collected and resuspended in PBS containing 0.04% BSA at a concentration of 700~1200 cells/µl. Cell number and viability were measured using a TC20 Automated Cell Counter (BioRad). Single-cell RNA libraries were prepared according to the Chromium™ Single Cell 3' Reagent Kits v2 User Guide (10x Genomics). Approximately 10,000 cells were loaded on a Chromium single cell Controller instrument (10x Genomics) to generate single cell gel beads in emulsion (GEMs). The barcoded sequencing libraries were constructed using the Chromium Single-Cell 3′ Library Kit (10x Genomics) for enzymatic fragmentation, end-repair, A-tailing, adaptor ligation, ligation cleanup, sample index PCR, and PCR cleanup. Libraries were sequenced with a Hiseq 2500 instrument (Illumina) with a depth of 50k-100k reads per cell. Raw sequencing data were processed using the 10x Genomics Cell Ranger pipeline (version 2.0) to generate FASTQ files and aligned to mm10 genome to gene expression count. The subsequent data analysis was performed using “Seurat” package and R scripts. Cells with mitochondrial read rate > 50% and < 200 detectable genes were considered as low-quality and filtered out. Normalized and scaled data were clustered using the top significant principal components of highly variable genes. The t-distributed stochastic neighbor embedding (t-SNE) algorithm was used to visualize the resulting clusters. Cluster-specific markers were identified to generate heatmap and feature plots in the identified cell clusters. Genes were compared between different clusters using Bioconductor package “Limma” on normalized data. Gene Set Enrichment Analysis (GSEA) v3 was performed using genes ranked by the fold changes between different clusters to evaluate the significant activation of the C2 KEGG gene sets in MSigDb (http://software.broadinstitute.org/gsea/msigdb/collections.jsp). Results: Two major brown adipocyte subpopulations were clustered as brown adipocytes with high thermogenic activity (BA-H, 2,352 cells) and brown adipocytes with low thermogenic activity (BA-L, 1,250 cells). Conclusions: In summary, the brown adipocyte single cell transcriptomic reveals a unique subpopulation of brown adipocytes with low thermogenic activity. These cells hold a unique metabolic status, and the function of these cells is fundamentally different from the cells within the BA-H subpopulation.
Project description:The rising incidence of obesity and related disorders such as diabetes and heart disease has focused considerable attention on the discovery of novel therapeutics. One promising approach has been to increase the number or activity of brown-like adipocytes in white adipose depots, as this has been shown to prevent diet-induced obesity and reduce the incidence and severity of type 2 diabetes. Thus, the conversion of fat-storing cells into metabolically active thermogenic cells has become an appealing therapeutic strategy to combat obesity. Here, we report a screening platform for the identification of small molecules capable of promoting a white-to-brown metabolic conversion in human adipocytes. We identified two inhibitors of Janus Kinase (JAK) activity with no precedent in adipose tissue biology that permanently confer brown-like metabolic activity to white adipocytes. Importantly, these metabolically converted adipocytes exhibit elevated UCP1 expression and increased mitochondrial activity. We further found that repression of interferon signalling and activation of hedgehog signalling in JAK-inactivated adipocytes contributes to the metabolic conversion observed in these cells. Our findings highlight a novel role for the JAK/STAT pathway in the control of adipocyte function and establish a platform to identify compounds for the treatment of obesity. Human pluripotent stem-cell derived mesenchymal progenitor cells (PSC-MPCs), white adipose cells (PSC-WA), and brown adipose cells (PSC-BA) were treated with DMSO (as control), a JAK3-inhibitor compound, and a SYK-inhibitor compound respectively. Transcriptomic expression profiling was performed at 24 hours and 7 days respectively. Three biological replicates are available for each condition defined by cell type, compound, and time.
Project description:The rising incidence of obesity and related disorders such as diabetes and heart disease has focused considerable attention on the discovery of novel therapeutics. One promising approach has been to increase the number or activity of brown-like adipocytes in white adipose depots, as this has been shown to prevent diet-induced obesity and reduce the incidence and severity of type 2 diabetes. Thus, the conversion of fat-storing cells into metabolically active thermogenic cells has become an appealing therapeutic strategy to combat obesity. Here, we report a screening platform for the identification of small molecules capable of promoting a white-to-brown metabolic conversion in human adipocytes. We identified two inhibitors of Janus Kinase (JAK) activity with no precedent in adipose tissue biology that permanently confer brown-like metabolic activity to white adipocytes. Importantly, these metabolically converted adipocytes exhibit elevated UCP1 expression and increased mitochondrial activity. We further found that repression of interferon signalling and activation of hedgehog signalling in JAK-inactivated adipocytes contributes to the metabolic conversion observed in these cells. Our findings highlight a novel role for the JAK/STAT pathway in the control of adipocyte function and establish a platform to identify compounds for the treatment of obesity.
Project description:We have identified a population of adipocytes in fat tissue that arise from bone marrow-derived progenitor cells. We used microarrays to compare the global gene expression patterns of the bone marrow progenitor-derived adipocytes as well as conventional white and brown adipocytes to evaluate the relationship between these adipocyte subpopulations.
Project description:To investigate the function of YBX1 in the regulation of brown adipose aging, differentiated C3H10T1/2 brown adipocytes were transfected with specific siRNAs targeting YBX1 or control siRNA. Total RNA was extracted at 48h after transfection to performed gene expression profiling analysis by high throughput RNA-seq.