Project description:MicroRNAs (miRNAs) constitute a class of short noncoding RNAs which regulate gene expression by targeting messenger RNA, inducing translational repression and messenger RNA degradation. This regulation of gene expression by miRNAs in adipose tissue (AT) can impact on the regulation of metabolism and energy homeostasis, particularly considering the different types of adipocytes which exist in mammals, i.e., white adipocytes (white AT; WAT), brown adipocytes (brown AT; BAT), and inducible brown adipocytes in WAT (beige or brite or brown-in-white adipocytes). Indeed, an increasing number of miRNAs has been identified to regulate key signaling pathways of adipogenesis in BAT, brite AT, and WAT by acting on transcription factors that promote or inhibit adipocyte differentiation. For example, MiR-328, MiR-378, MiR-30b/c, MiR-455, MiR-32, and MiR-193b-365 activate brown adipogenesis, whereas MiR-34a, MiR-133, MiR-155, and MiR-27b are brown adipogenesis inhibitors. Given that WAT mainly stores energy as lipids, whilst BAT mainly dissipates energy as heat, clarifying the effects of miRNAs in different types of AT has recently attracted significant research interest, aiming to also develop novel miRNA-based therapies against obesity, diabetes, and other obesity-related diseases. Therefore, this review presents an up-to-date comprehensive overview of the role of key regulatory miRNAs in BAT, brite AT, and WAT.
Project description:Cold exposure imposes a metabolic challenge to mammals that is met by a coordinated response in different tissues to prevent hypothermia. This study reports a transcriptomic analysis in brown adipose tissue (BAT), white adipose (WAT) and liver of mice in response to 24 h cold exposure at 8°C. Expression of 1895 genes were significantly (P<0.05) up- or down-regulated more than two fold by cold exposure in all tissues but only 5 of these genes were shared by all three tissues, and only 19, 14 and 134 genes were common between WAT and BAT, WAT and liver, and BAT and liver, respectively. We confirmed using qRT-PCR, the increased expression of a number of characteristic BAT genes during cold exposure. In both BAT and the liver, the most common direction of change in gene expression was suppression (496 genes in BAT and 590 genes in liver). Gene ontology analysis revealed for the first time significant (P<0.05) down regulation in response to cold, of genes involved in oxidoreductase activity, lipid metabolic processes and protease inhibitor activity, in both BAT and liver, but not WAT. The results reveal an unexpected importance of down regulation of cytochrome P450 gene expression and apolipoprotein, in both BAT and liver, but not WAT, in response to cold exposure. Pathway analysis suggests a model in which down regulation of the nuclear transcription factors HNF4α and PPARα in both BAT and liver may orchestrate the down regulation of genes involved in lipoprotein and steroid metabolism as well as Phase I enzymes belonging to the cytochrome P450 group in response to cold stress in mice. We propose that the response to cold stress involves decreased gene expression in a range of cellular processes in order to maximise pathways involved in heat production.
Project description:ObjectiveMaresin 1 (MaR1) is a docosahexaenoic acid-derived proresolving lipid mediator with insulin-sensitizing and anti-steatosis properties. Here, we aim to unravel MaR1 actions on brown adipose tissue (BAT) activation and white adipose tissue (WAT) browning.MethodsMaR1 actions were tested in cultured murine brown adipocytes and in human mesenchymal stem cells (hMSC)-derived adipocytes. In vivo effects of MaR1 were tested in diet-induced obese (DIO) mice and lean WT and Il6 knockout (Il6-/-) mice.ResultsIn cultured differentiated murine brown adipocytes, MaR1 reduces the expression of inflammatory genes, while stimulates glucose uptake, fatty acid utilization and oxygen consumption rate, along with the upregulation of mitochondrial mass and genes involved in mitochondrial biogenesis and function and the thermogenic program. In Leucine Rich Repeat Containing G Protein-Coupled Receptor 6 (LGR6)-depleted brown adipocytes using siRNA, the stimulatory effect of MaR1 on thermogenic genes was abrogated. In DIO mice, MaR1 promotes BAT remodeling, characterized by higher expression of genes encoding for master regulators of mitochondrial biogenesis and function and iBAT thermogenic activation, together with increased M2 macrophage markers. In addition, MaR1-treated DIO mice exhibit a better response to cold-induced BAT activation. Moreover, MaR1 induces a beige adipocyte signature in inguinal WAT of DIO mice and in hMSC-derived adipocytes. MaR1 potentiates Il6 expression in brown adipocytes and BAT of cold exposed lean WT mice. Interestingly, the thermogenic properties of MaR1 were abrogated in Il6-/- mice.ConclusionsThese data reveal MaR1 as a novel agent that promotes BAT activation and WAT browning by regulating thermogenic program in adipocytes and M2 polarization of macrophages. Moreover, our data suggest that LGR6 receptor is mediating MaR1 actions on brown adipocytes, and that IL-6 is required for the thermogenic effects of MaR1.
Project description:There are still questions about whether macrophage differentiation is predetermined or is induced in response to tissue microenvironments. C2D macrophage cells reside early in the macrophage lineage in vitro, but differentiate to a more mature phenotype after adoptive transfer to the peritoneal cavity (PEC-C2D). Since C2D macrophage cells also traffic to adipose tissue after adoptive transfer, we explored the impact of white adipose tissue (WAT), brown adipose tissue (BAT) and in vitro cultured adipocytes on C2D macrophage cells. When PEC-C2D macrophage cells were cultured with preadipocytes the cells stretched out and CD11b and Mac-2 expression was lower compared to PEC-C2D macrophage cells placed in vitro alone. In contrast, PEC-C2D cells co-cultured with adipocytes maintained smaller, round morphology and more cells expressed Mac-2 compared to PEC-C2D co-cultured with preadipocytes. After intraperitoneal injection, C2D macrophage cells migrated into both WAT and BAT. A higher percentage of C2D macrophage cells isolated from WAT (WAT-C2D) expressed Ly-6C (33%), CD11b (11%), Mac-2 (11%) and F4/80 (29%) compared to C2D macrophage cells isolated from BAT (BAT-C2D). Overall, BAT-C2D macrophage cells had reduced expression of many cytokine, chemokine and receptor gene transcripts when compared to in vitro grown C2D macrophages, while WAT-C2D macrophage cells and PEC-C2D up-regulated many of these gene transcripts. These data suggest that the C2D macrophage phenotype can change rapidly and distinct phenotypes are induced by different microenvironments.
Project description:Brown adipose tissue (BAT) has a unique capacity to expend calories by decoupling energy expenditure from ATP production, therefore BAT could realize therapeutic potential to treat metabolic diseases such as obesity and type 2 diabetes. Recent studies have investigated markers and function of native BAT, however, successful therapies will rely on methods that supplement the small existing pool of brown adipocytes in adult humans. In this study, we engineered BAT from both human and rat adipose precursors and determined whether these ex vivo constructs could mimic in vivo tissue form and metabolic function. Adipose-derived stem cells (ASCs) were isolated from several sources, human white adipose tissue (WAT), rat WAT, and rat BAT, then differentiated toward both white and brown adipogenic lineages in two-dimensional and three-dimensional (3D) culture conditions. ASCs derived from WAT were successfully differentiated in 3D poly(ethylene glycol) hydrogels into mature adipocytes with BAT phenotype and function, including high uncoupling protein 1 (UCP1) mRNA and protein expression and increased metabolic activity (basal oxygen consumption, proton leak, and maximum respiration). By utilizing this "browning" process, the abundant and accessible WAT stem cell population can be engineered into 3D tissue constructs with the metabolic capacity of native BAT, ultimately for therapeutic intervention in vivo and as a tool for studying BAT and its metabolic properties.
Project description:BackgroundAlthough the accumulation of white adipose tissue (WAT) is a risk factor for disease, brown adipose tissue (BAT) has been suggested to have a protective role against obesity.ObjectiveWe studied whether changes in BAT were related to changes in the amounts of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) in children treated for malignancy.DesignWe examined the effect of BAT activity on weight, SAT, and VAT in 32 pediatric patients with cancer whose positron emission tomography-computed tomography (PET-CT) scans at diagnosis showed no BAT activity. Changes in weight, SAT, and VAT from diagnosis to remission for children with metabolically active BAT at disease-free follow-up (BAT+) were compared with those in children without visualized BAT when free of disease (BAT-).ResultsFollow-up PET-CT studies (4.7 ± 2.4 mo later) after successful treatment of the cancer showed BAT+ in 19 patients but no active BAT (BAT-) in 13 patients. BAT+ patients, in comparison with BAT- patients, gained significantly less weight (3.3 ± 6.6% compared with 11.0 ± 11.6%; P = 0.02) and had significantly less SAT (18.2 ± 26.5% compared with 67.4 ± 71.7%; P = 0.01) and VAT (22.6 ± 33.5% compared with 131.6 ± 171.8%; P = 0.01) during treatment. Multiple regression analysis indicated that the inverse relations between BAT activation and measures of weight, SAT, and VAT persisted even after age, glucocorticoid treatment, and the season when the PET-CT scans were obtained were accounted for.ConclusionThe activation of BAT in pediatric patients undergoing treatment of malignancy is associated with significantly less adipose accumulation. This trial was registered at clinicaltrials.gov as NCT01517581.
Project description:A cellular compartment from brown adipose tissue (BAT) of newborn rats was isolated by Percoll-density-gradient centrifugation and was shown to proliferate and to undergo adipose conversion in vitro in primary culture. The features of the effector requirement for adipose conversion as well as the differentiated morphological and biochemical phenotype are almost identical with that of a compartment designated HCF, from white adipose tissue (WAT). A possible role for these precursors from BAT and WAT in the involution of BAT into WAT, on the one hand, and in the development of brown adipose cells among typical WAT deposits, on the other, is discussed.
Project description:ObjectiveA potential strategy to treat obesity - and the associated metabolic consequences - is to increase energy expenditure. This could be achieved by stimulating thermogenesis through activation of brown adipose tissue (BAT) and/or the induction of browning of white adipose tissue (WAT). Over the last years, it has become clear that several metalloproteinases play an important role in adipocyte biology. Here, we investigated the potential role of ADAMTS5.MethodsMice deficient in ADAMTS5 (Adamts5-/-) and wild-type (Adamts5+/+) littermates were kept on a standard of Western-type diet for 15 weeks. Energy expenditure and heat production was followed by indirect calorimetry. To activate thermogenesis, mice were treated with the β3-adrenergic receptor (β3-AR) agonist CL-316,243 or alternatively, exposed to cold for 2 weeks.ResultsCompared to Adamts5+/+ mice, Adamts5-/- mice have significantly more interscapular BAT and marked browning of their subcutaneous (SC) WAT. Thermogenic pathway analysis indicated, in the absence of ADAMTS5, enhanced β3-AR signaling via activation of the cAMP response element-binding protein (CREB). Additional β3-AR stimulation with CL-316,243 promoted browning of WAT in Adamts5+/+ mice but had no additive effect in Adamts5-/- mice. However, cold exposure induced more pronounced browning of WAT in Adamts5-/- mice.ConclusionsThese data indicate that ADAMTS5 plays a functional role in development of BAT and browning of WAT. Hence, selective targeting of ADAMTS5 could provide a novel therapeutic strategy for treatment/prevention of obesity and metabolic diseases.
Project description:PR (PRD1-BF1-RIZ1 homologous) domain-containing 16 (PRDM16) drives a brown fat differentiation program, but the mechanisms by which PRDM16 activates brown fat-selective genes have been unclear. Through chromatin immunoprecipitation (ChIP) followed by deep sequencing (ChIP-seq) analyses in brown adipose tissue (BAT), we reveal that PRDM16 binding is highly enriched at a broad set of brown fat-selective genes. Importantly, we found that PRDM16 physically binds to MED1, a component of the Mediator complex, and recruits it to superenhancers at brown fat-selective genes. PRDM16 deficiency in BAT reduces MED1 binding at PRDM16 target sites and causes a fundamental change in chromatin architecture at key brown fat-selective genes. Together, these data indicate that PRDM16 controls chromatin architecture and superenhancer activity in BAT.
Project description:The aim of this study was to identify genes expressed selectively in brown adipose tissue as compared to white adipose tissue from the same animals. This analysis provides a gene set that is brown and white adipose selective. Keywords: tissue comparison from mice