Project description:Differentiation of brown adipocytes is a crucial process for adaptive thermogenesis, which is stimulated by various factors. We found robust browning of inguinal white adipose tissue in UCP1/ApoE-DKO mice, but not in ApoE-KO mice, under high-fat diet condition. We used microarray to determine the genes specifically regulated in the browning white adipose tissue in UCP1/ApoE-DKO mice.
Project description:Abstract
Brown and brite adipocytes are the key cells performing uncoupling protein 1 (UCP1) dependent non-shivering thermogenesis (NST) induced by cold exposure. Several lipid species are associated to NST in brown and white adipose tissue. Studies investigating the association of the lipid profile with NST rely on the analysis of whole organ homogenates or on the differentiation of pre-adipocytes in vitro. These approaches have so far not addressed the heterogeneity of white adipose tissue. Aim of this study was to characterize the lipid composition of white adipose tissue on a region-specific level in an in vivo context.
We applied MALDI mass spectrometry imaging (MALDI-MSI) in combination with immunohistochemistry and high-resolution mass spectrometry on sections of inguinal white adipose tissue of 129S6/SvEvTac and C57BL6/N-UCP1 knockout and wildtype mice acclimatized to cold to identify lipids specific to areas of UCP1 expression.
Based on the analysis of cold exposed 129S6/SvEvTac mice we identified cardiolipins (CL) and diacylglycerols (DG) species to be specific for areas expressing UCP1 and triacylglycerols (TG) to be the main lipid class characteristic for UCP1 negative regions within inguinal white adipose tissue. Investigation of C57BL6/N-UCP1 knockout and wildtype mice housed at either room temperature or acclimatized to cold, demonstrated that CL content in white adipose tissue is increased upon cold stimulation, independent of UCP1.
We introduce a MALDI-MSI based approach to identify lipids associated to thermogenic adipocytes in adipose tissues demonstrating a clear regional cold dependent upregulation of CL independent of UCP1.
Project description:We analyzed transcript abundance in interscapular brown and inguinal white adipose tissue of wildtype and UCP1-KO mice either adpated to 20°C or 30°C and fed a high fat or control diet.
Project description:Selective ablation of Hdac3 in adipose tissue switches the metabolic signature of white adipose tissue by potentiating oxidative capacity and boosting browning. To investigate the genome-wide consequences of the lack of Hdac3 in adipose tissue, we used RNA-seq to profile the gene expression program of inguinal adipose tissue from mice with selective ablation of Hdac3 in adipose tissue (H3atKO) and their respective control (floxed).
Project description:Two types of UCP1 positive cells-brown and beige adipocytes exist in mammals. Beige adipocytes are very plastic, and can be dynamically regulated by environment.Beige adipocytes formed postnatally in subcutaneous inguinal white adipose tissue (iWAT) lost thermogenic gene expression and multilocular morphology at adult stage, but cold could restore their “beigeing” characteristics, a phenomenon termed as beige adipocyte renaissance. Our results showed that beige cell maintenance and renaissance in adult mice were regulated by cAMP and HDAC4 signaling in white adipocytes non-cell autonomously. Genetic modulations of various components of this cAMP-HDAC4 cascade (e.g. LKB1) led to persistent browning and reduced adiposity independent of thermogenesis. To further study the mechanisms of beige adipocytes maintenance, we performed RNA-seq with samples from inguinal white adipose tissues of WT, AdipoqCre LKB1 F/F, and AdipoqCre LKB1 F/F; HDAC4 F/F mice.Our studies will move the beige adipocyte field forward and attract clinical applications to target beige adipocyte renaissance.
Project description:The adipocytes functions as a central organ in the regulation of metabolic homeostasis. Factors which contribute to the adipocyte differentiation and function would be the promising targets to combat the obesity and associated metabolic disorders. The activating transcription factor 7 (ATF7), a stress-responsive chromatin regulator, has recently been shown to be involved in the energy metabolism; however, the underlying mechanisms are still unknown. Here, we show that ATF7 is required for adipocyte differentiation and it interacts with histone dimethyltransferase G9a in adipocyte to repress the interferon-stimulated genes (ISGs) expression, which suppresses adipogenesis. Ablation of ATF7 promotes the beige biogenesis and browning of inguinal white adipose tissue (iWAT). ATF7 binds to the transcription regulatory regions of Ucp1 gene, and silences it by maintaining the histone H3K9 dimethylation level. These results establish the multifunction of ATF7 in adipocyte and provide molecular insights into the epigenetic control of development and function of adipose tissues. We used microarrays to identify the differentatial expression genes in the inguinal white adipose tissue of ATF7 KO mice.
Project description:The adipose tissue is a key site regulating energy metabolism. One of the contributing factors behind this is browning of white adipose tissue (WAT), however, knowledge of the intracellular determinants of browning process remains incomplete. By generating adipocyte-specific Senp2 knockout (Senp2-aKO) mice, here we showed that SENP2 negatively regulates browning by de-conjugating SUMO from C/EBPβ. Senp2-aKO mice were resistant to diet-induced obesity and insulin resistance due to increased energy expenditure and heat production. Senp2 knockout promoted beige adipocyte accumulation in inguinal WAT by upregulation of thermogenic gene expression. In addition, SENP2 knockdown promoted thermogenic adipocyte differentiation of precursor cells isolated from inguinal and epididymal WATs. Mechanistically, sumoylated C/EBPβ, a target of SENP2, suppressed expression of HOXC10, a browning inhibitor, by recruiting a transcriptional repressor DAXX. These findings indicate that a SENP2-C/EBPβ-HOXC10 axis operates for the control of beige adipogenesis in inguinal WAT.
Project description:The adipose tissue is a key site regulating energy metabolism. One of the contributing factors behind this is browning of white adipose tissue (WAT), however, knowledge of the intracellular determinants of browning process remains incomplete. By generating adipocyte-specific Senp2 knockout (Senp2-aKO) mice, here we showed that SENP2 negatively regulates browning by de-conjugating SUMO from C/EBPβ. Senp2-aKO mice were resistant to diet-induced obesity and insulin resistance due to increased energy expenditure and heat production. Senp2 knockout promoted beige adipocyte accumulation in inguinal WAT by upregulation of thermogenic gene expression. In addition, SENP2 knockdown promoted thermogenic adipocyte differentiation of precursor cells isolated from inguinal and epididymal WATs. Mechanistically, sumoylated C/EBPβ, a target of SENP2, suppressed expression of HOXC10, a browning inhibitor, by recruiting a transcriptional repressor DAXX. These findings indicate that a SENP2-C/EBPβ-HOXC10 axis operates for the control of beige adipogenesis in inguinal WAT.
Project description:Chronic cold exposure causes white adipose tissue (WAT) to adopt features of brown adipose tissue, a process known as browning. Previous studies have hinted at a possible role for the transcription factor Peroxisome Proliferator-Activated Receptor alpha (PPARα) in cold-induced browning. Here we aimed to investigate the importance of PPARα in driving transcriptional changes during cold-induced browning in mice. Male wildtype and PPARα−/− mice were housed at thermoneutrality (28 °C) or cold (5 °C) for 10 days. Whole genome expression analysis was performed on inguinal WAT. In addition, other analyses were carried out. Whole genome expression data of livers of wildtype and PPARα−/− mice fasted for 24 h served as positive control for PPARα-dependent gene regulation.Cold exposure increased food intake and decreased weight of BAT and WAT to a similar extent in wildtype and PPARα−/− mice. Except for plasma non-esterified fatty acids, none of the cold-induced changes in plasma metabolites were dependent on PPARα genotype. Histological analysis of inguinal WAT showed clear browning upon cold exposure but did not reveal any morphological differences between wildtype and PPARα−/− mice. Transcriptomics analysis of inguinal WAT showed a marked effect of cold on overall gene expression, as revealed by principle component analysis and hierarchical clustering. However, wildtype and PPARα−/− mice clustered together, even after cold exposure, indicating a similar overall gene expression profile in the two genotypes. Pathway analysis revealed that cold upregulated pathways involved in energy usage, oxidative phosphorylation, and fatty acid β-oxidation to a similar extent in wildtype and PPARα−/− mice. Furthermore, cold-mediated induction of genes related to thermogenesis such as Ucp1, Elovl3, Cox7a1, Cox8, and Cidea, as well as many PPAR target genes, was similar in wildtype and PPARα−/− mice. Finally, pharmacological PPARα activation had a minimal effect on expression of cold-induced genes in murine WAT.Cold-induced changes in gene expression in inguinal WAT are unaltered in mice lacking PPARα, indicating that PPARα is dispensable for cold-induced browning.
Project description:To determine the function of miR-203 in white fat browning upon cold exposure, we injected miR-203 inhibitors and negative control into inguinal white adipose tissue, followed by cold exposure (4oC) for 24 hours. Total RNA were harvested for RNA-seq.