Project description:Brown adipose tissue (BAT) and brown adipocytes differentiated in vitro from preadipocytes of PKGI-/- mice vs. WT were compared on a whole genome DNA array
Project description:To identify transcriptomic differences in interscapular brown adipose tissue depots from HFD-challenged wild-type (WT) vs. Axl KO (whole-body Axl Receptor knockout) mice
Project description:Brown adipose tissue (BAT) has in recent times been rediscovered in adult humans, and together with work from preclinical models, shown to have the potential of providing a variety of positive metabolic benefits. These include improved insulin sensitivity and reduced susceptibility to obesity and its various co-morbidities. As such, its continued study could offer insights to therapeutically modulate this tissue to improve metabolic health. It has been reported that adipose-specific deletion of the gene for protein kinase D1 (Prkd1) enhances mitochondrial respiration and improves whole-body glucose homeostasis. We sought to determine whether these effects were mediated specifically through brown adipocytes using a Prkd1 brown adipose tissue (BAT) Ucp1-Cre-specific knockout mouse model, Prkd1BKO. We unexpectedly observed that upon both cold exposure and beta-3-AR agonist administration, Prkd1 loss in BAT did not alter canonical thermogenic gene expression or adipocyte morphology. We took an unbiased approach to assess whether other signaling pathways were altered. RNAs from cold-exposed control and Prkd1BKO were subjected to RNA-Seq analysis. These studies revealed that myogenic gene expression is altered in Prkd1BKO BAT after both acute (8 hr) and extended (4 day) cold exposure. Given that brown adipocytes and skeletal myocytes share a common precursor cell lineage expressing myogenic factor 5 (Myf5), these data suggest that loss of Prkd1 in BAT may alter the biology of preadipocytes in this depot. The data presented herein clarify the role of Prkd1 in BAT thermogenesis and present new avenues for the further study of Prkd1 function in BAT.
Project description:We analyzed coding transcript abundance in fully differentiated, primary brown adipocytes from murine, interscapular brown adipose tissue of wildtype and UCP1-KO mice.
Project description:To investigate the specific role of PGC-1 coactivators in brown fat cells, we generated immortal preadipocyte lines from the brown adipose tissue of mice lacking PGC-1alpha. We could then efficiently knockdown PGC-1beta expression by shRNA expression. Loss of PGC-1alpha did not alter brown fat differentiation but severly reduced the induction of thermogenic genes. In order to assess the specific requirement for PGC-1± in the global transcriptional response to cAMP, we used Affymetrix arrays to compare the sets of genes induced in response to a 4 hr dbcAMP treatment in differentiated wt and KO cells. This analysis revealed that 88 genes were induced more than 3-fold in the wt cells; of these, 54 (61% of total) were similarly increased in both wt and KO. However, 28 genes (32% of total) were decreased by at least 50% in the KO cells compared to wt cells. These data were confirmed by quantitative PCR for a subset of genes. These data indicate that PGC-1± is required for proper expression of approximately one third of the genes induced in response to cAMP in brown fat cells, but this set of sensitive genes is enriched in those involved in adaptative thermogenesis. Experiment Overall Design: WT and PGC-1alpha KO brown preadipocytes were differentiated into mature brown adipocytes for seven days. Cells were then treated with dibutyryl cAMP for four hours. Two replicates were made for each condition: WT non treated, WT treated with cAMP, KO non treated, KO treated with cAMP. Transcription profiling of wild type and PGC-1 alpha knockout mouse mature brown adipocytes treated with dibutyryl cAMP to investigate the specific role of PGC-1 coactivators in brown fat cells
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:Mitochondria play an essential role in the ability of brown fat to generate heat, and the PGC-1 coactivators control several aspects of mitochondrial biogenesis. To investigate their specific roles in brown fat cells, we generated immortal preadipocyte lines from the brown adipose tissue of mice lacking PGC-1±. We could then efficiently knockdown PGC-1β expression by shRNA expression. Loss of PGC-1± did not alter brown fat differentiation but severely reduced the induction of thermogenic genes. Cells deficient in either PGC-1α or PGC-1β coactivators showed a small decrease in the differentiation-dependant program of mitochondrial biogenesis and respiration; however, this increase in mitochondrial number and function was totally abolished during brown fat differentiation when both PGC-1± and PGC-1 were deficient. These data show that PGC-1± is essential for brown fat thermogenesis but not brown fat differentiation, and the PGC-1 coactivators play an absolutely essential but complementary function in differentiation-induced mitochondrial biogenesis. Affymetrix microarray analysis of total RNA from wt, PGC-1± KO and PGC-1± KO; cells expressing an RNAi specific for PGC-1 knockdown was performed. Of the 461; mitochondrial genes analyzed, 181 were found to be at least 20% different between wt; and defective PGC-1± and β adipocytes (p < 0.05). More than 85% of these genes were downregulated in cells deficient for PGC-1alpha and PGC-1beta. Experiment Overall Design: Brown preadipocytes that were either WT, KO for PGC-1alpha, or KO for PGC-1alpha and deficient for PGC-1beta (knockdown through siRNA expression) were differentiated for seven days. RNA was made from biological replicates of the three different types of brown adipocytes (WT, KO expressing a control siRNA, KO expressing a siRNA specific for PGC-1beta knockdown).
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:The experiment was designed to determine the gene expression changes cultured brown adipocytes in response to the inflammatory stimulus of LPS treatment. Both wild type and TLR4 knockout cells were applied to enable assessment of the contribution of TLR4 to the response.