Brown Preadipocytes Research Articles

Glucocorticoid Receptor Accelerates, but Is Dispensable for, Adipogenesis.

Dexamethasone (DEX), a synthetic ligand for glucocorticoid receptor (GR), is routinely used to stimulate adipogenesis in culture. GR-depleted preadipocytes show adipogenesis defects 1 week after induction of differentiation. However, it has remained unclear whether GR is required for adipogenesis in vivo By deleting GR in precursors of brown adipocytes, we found unexpectedly that GR is dispensable for brown adipose tissue development in mice. In culture, GR-deficient primary or immortalized white and brown preadipocytes showed severely delayed adipogenesis 1 week after induction of differentiation. However, when differentiation was extended to 3 weeks, GR-deficient preadipocytes showed levels of adipogenesis marker expression and lipid accumulation similar to those of the wild-type cells, indicating that DEX-bound GR accelerates, but is dispensable for, adipogenesis. Consistently, DEX accelerates, but is dispensable for, adipogenesis in culture. We show that DEX-bound GR accelerates adipogenesis by directly promoting the expression of adipogenic transcription factors CCAAT/enhancer-binding protein alpha (C/EBPα), C/EBPβ, C/EBPδ, KLF5, KLF9, and peroxisome proliferator-activated receptor γ (PPARγ) in the early phase of differentiation. Mechanistically, DEX-bound GR recruits histone H3K27 acetyltransferase CBP to promote activation of C/EBPβ-primed enhancers of adipogenic genes. These results clarify the role of GR in adipogenesis in vivo and demonstrate that DEX-mediated activation of GR accelerates, but is dispensable for, adipogenesis.

Bi-directional regulation of brown fat adipogenesis by the insulin receptor.

Insulin is a potent inducer of adipogenesis, and differentiation of adipocytes requires many components of the insulin signaling pathway, including the insulin receptor substrate IRS-1 and phosphatidylinositol 3-kinase (PI3K). Brown pre-adipocytes in culture exhibit low levels of insulin receptor (IR), and during differentiation there is both an increase in total IR levels and a shift in the alternatively spliced forms of IR from the A isoform (–exon 11) to the B isoform (+exon 11). Brown pre-adipocyte cell lines from insulin receptor-deficient mice exhibit dramatically impaired differentiation and an inability to regulate alternative splicing of the insulin receptor. Surprisingly, re-expression of either splice isoform of IR in the IR-deficient cells fails to rescue differentiation in these cells. Likewise, overexpression of IR in control IRlox cells also results in inhibition of differentiation and a failure to accumulate expression of the adipogenic markers peroxisome proliferator-activated receptor gamma, Glut4, and fatty acid synthase, although cells overexpressing IR retain the ability to activate PI3K and down-regulate mitogen-activated protein kinase (MAPK) phosphorylation. Thus, differentiation of brown adipocytes requires a timed and regulated expression of IR, and either the absence or overabundance of insulin receptors in these cells dramatically inhibits differentiation.

Modulation of brown adipocyte activity by milk by-products: Stimulation of brown adipogenesis by buttermilk.

Brown adipocytes dissipate chemical energy in the form of heat through the expression of mitochondrial uncoupling protein 1 (Ucp1); Ucp1 expression is further upregulated by the stimulation of β-adrenergic receptors in brown adipocytes. An increase in energy expenditure by activated brown adipocytes potentially contributes to the prevention of or therapeutics for obesity. The present study examined the effects of milk by-products, buttermilk and butter oil, on brown adipogenesis and the function of brown adipocytes. The treatment with buttermilk modulated brown adipogenesis, depending on the product tested; during brown adipogenesis, buttermilk 1 inhibited the differentiation of HB2 brown preadipocytes. In contrast, buttermilk 3 and 5 increased the expression of Ucp1 in the absence of isoproterenol (Iso), a β-adrenergic receptor agonist, suggesting the stimulation of brown adipogenesis. In addition, the Iso-induced expression of Ucp1 was enhanced by buttermilk 2 and 3. The treatment with buttermilk did not affect the basal or induced expression of Ucp1 by Iso in HB2 brown adipocytes, except for buttermilk 5, which increased the basal expression of Ucp1. Conversely, butter oil did not significantly affect the expression of Ucp1, irrespective of the cell phase of HB2 cells, ie, treatment during brown adipogenesis or of brown adipocytes. The results of the present study indicate that buttermilk is a regulator of brown adipogenesis and suggest its usefulness as a potential food material for antiobesity.

The KDM5 family is required for activation of pro-proliferative cell cycle genes during adipocyte differentiation.

The KDM5 family of histone demethylases removes the H3K4 tri-methylation (H3K4me3) mark frequently found at promoter regions of actively transcribed genes and is therefore generally considered to contribute to corepression. In this study, we show that knockdown (KD) of all expressed members of the KDM5 family in white and brown preadipocytes leads to deregulated gene expression and blocks differentiation to mature adipocytes. KDM5 KD leads to a considerable increase in H3K4me3 at promoter regions; however, these changes in H3K4me3 have a limited effect on gene expression per se. By contrast, genome-wide analyses demonstrate that KDM5A is strongly enriched at KDM5-activated promoters, which generally have high levels of H3K4me3 and are associated with highly expressed genes. We show that KDM5-activated genes include a large set of cell cycle regulators and that the KDM5s are necessary for mitotic clonal expansion in 3T3-L1 cells, indicating that KDM5 KD may interfere with differentiation in part by impairing proliferation. Notably, the demethylase activity of KDM5A is required for activation of at least a subset of pro-proliferative cell cycle genes. In conclusion, the KDM5 family acts as dual modulators of gene expression in preadipocytes and is required for early stage differentiation and activation of pro-proliferative cell cycle genes.

Kinase Inactive Tyrosine Kinase (Tyk2) Supports Differentiation of Brown Fat Cells.

It has been known for decades that brown adipose tissue (BAT) plays a central role in maintaining body temperature in hibernating animals and human infants. Recently, it has become evident that there are also depots of brown fat in adult humans, and the mass of brown fat is inversely correlated with body weight. There are a variety of transcription factors implicated in the differentiation of classical Myf5+ brown preadipocytes, one of the most important of which is PRDM16. We have recently identified that in addition to PRDM16, the tyrosine kinase Tyk2 and the STAT3 transcription factor are required for the differentiation of Myf5 positive brown preadipocytes both in cell culture and in mice. Tyk2 is a member of the Jak family of tyrosine kinases, which are activated by exposure of cells to different cytokines and growth factors. In this study we report the surprising observation that a mutated form of Tyk2, which lacks tyrosine kinase activity (Tyk2KD) restores differentiation of brown preadipocytes in vitro as well as in Tyk2-/- mice. Furthermore, expression of the Tyk2KD transgene in brown fat reverses the obese phenotype of Tyk2-/- animals. Treatment of cells with Jak-selective inhibitors suggests that the mechanism by which Tyk2KD functions to restore BAT differentiation is by dimerizing with kinase active Jak1 or Jak2. These results indicate that there are redundant mechanisms by which members of the Jak family can contribute to differentiation of BAT.

427 - Reduced Mitochondrial Oxidative Stress Impairs Brown Adipose Tissue-Mediated Thermogenesis in Mice

Our recent work identified oxidative stress in adipocyte as a prerequisite for diet-induced thermogenesis and uncoupling protein 1 (UCP1) induction in white and brown adipose tissue of mice. To further confirm this observation, we used mice that overexpressed human catalase targeted to mitochondria (mCAT mice). Similar to the heart, catalase activity was significantly increased in brown adipose tissue (BAT) of mCAT mice compared to wild-type (WT) mice. WT and mCAT mice were fed high fat diet (HFD, 45% calories from fat) or normal chow diet (NCD, 4% calories from fat) for 20 weeks. Oxidative stress markers such as 4-hydroxynonenal and nitrotyrosine were only elevated in BAT of WT mice fed HFD. HFD induced similar weight gain and adiposity in WT and mCAT mice but mCAT mice produced less heat especially when housed at colder temperatures (15°C) or when given a beta-adrenergic agonist to activate thermogenesis. UCP1 expression in BAT was similarly induced by HFD in both WT and mCAT. However, mitochondrial uncoupling, as assessed by proton leak, was reduced in brown preadipocytes isolated from HFD-fed mCAT mice compared to those isolated from WT mice on HFD. To determine if the changes in BAT function affected whole body glucose and insulin homeostasis, we performed glucose and insulin tolerance tests. HFD similarly impaired glucose and insulin tolerance in WT and mCAT mice but induced adipose tissue inflammation only in WT mice. Taken together, these data suggest that oxidative stress is required for diet and cold-induced thermogenesis in mice.

Changes in expression levels of brown adipocyte differentiation associated with key genes and reference controls during adipogenesis

Objective To investigate the expression changes in the key differentiation-associated genes and reference genes during the progress of primary brown phagocyte adipocytes. Methods Twenty 4-week-old male C57BL/6J mice were selected randomly and brown adipose tissues were extracted from interscapular area.These brown preadipocytes were cultured in high glucose dulbecco′s modified eagle media, and induced in cocktail culture media (containing 0.5 mmol/L isobutylmethylxanthine, 5 mmol/L Dexamethasone, insulin 320 nmol/L, 1 nmol/L three iodine thyroid original amino acid, and 0.125 mmol/L Indomethacin). The total RNA of brown fat cells in the differentiation process(0, 2, 4, 6 day) were extracted by Trizol RNA isolation assay respectively.And then the RNA quality was verified by agarose gel electrophoresis.Oil red O staining was conducted to detect the maturation of brown fat cells.UCP1, the maker of mature brown fat cells, was detected by immunofluorescence assay.The expression of reference (GAPDH, β-actin, 18S and PPIA) and brown adipocyte differentiation associated genes(UCP1, PRDM16, PGC-1α, EBF2, PPARγ and Cidea) were detected by real-time quantitative PCR(RT-qPCR) method. Results (1)On day 6 of introduction, brown adipocytes were filled with small lipid droplets, and the protein expression of UCP1 increased significantly detected by immunofluorescence.(2)Agarose gel electrophoresis showed 3 bright bands, suggesting a fine RNA quality.(3)The relative gene expression levels of GAPDH, 18S and β-actin existed variations, wheras the expression level of PPIA maintained stable, indicating that PPIA could be used as a reference for differentiation of brown adipose tissues in mouse models during adipogenesis.(4)The expression of brown adipocyte differentiation-associated genes (UCP1, PRDM16, PGC-1α, EBF2, PPARγ and Cidea) increased gradually as time passed(0, 2, 4, 6 day) significantly(all P<0.05). Conclusions PPIA is a suitable reference gene for brown adipocyte differentiation.Brown differen-tiation key genes, such as UCP1, PRDM16, PGC-1α, EBF2, PPARγ and cidea, Could be used as suitable mature marker genes during adipogenesis. Key words: Brown adipocyte; Adipogenesis; Real-time quantitative PCR; Marker gene of brown adipocyte

Differential roles of the insulin and insulin-like growth factor-I (IGF-I) receptors in response to insulin and IGF-I.

Insulin and insulin-like growth factor-I (IGF-I) receptors are highly homologous tyrosine kinase receptors that share many common steps in their signaling pathways and have ligands that can bind to either receptor with differing affinities. To define precisely the signaling specific to the insulin receptor (IR) or the IGF-I receptor, we have generated brown preadipocyte cell lines that lack either receptor (insulin receptor knockout (IRKO) or insulin-like growth factor receptor knockout (IGFRKO)). Control preadipocytes expressed fewer insulin receptors than IGF-I receptors (20,000 versus 60,000), but during differentiation, insulin receptor levels increased so that mature adipocytes expressed slightly more insulin receptors than IGF-I receptors (120,000 versus 100,000). In these cells, insulin stimulated IR homodimer phosphorylation, whereas IGF-I activated both IGF-I receptor homodimers and hybrid receptors. Insulin-stimulated IRS-1 phosphorylation was significantly impaired in IRKO cells but was surprisingly elevated in IGFRKO cells. IRS-2 phosphorylation was unchanged in either cell line upon insulin stimulation. IGF-I-dependent phosphorylation of IRS-1 and IRS-2 was ablated in IGFRKO cells but not in IRKO cells. In control cells, both insulin and IGF-I produced a dose-dependent increase in phosphorylated Akt and MAPK, although IGF-I elicited a stronger response at an equivalent dose. In IRKO cells, the insulin-dependent increase in phospho-Akt was completely abolished at the lowest dose and reached only 20% of the control stimulation at 10 nm. Most interestingly, the response to IGF-I was also impaired at low doses, suggesting that IR is required for both insulin- and IGF-I-dependent phosphorylation of Akt. Most surprisingly, insulin- or IGF-I-dependent phosphorylation of MAPK was unaltered in either receptor-deficient cell line. Taken together, these results indicate that the insulin and IGF-I receptors contribute distinct signals to common downstream components in response to both insulin and IGF-I.

RNA-Seq Analysis Reveals a Negative Role of KLF16 in Adipogenesis.

In this study, we performed high throughput RNA sequencing at the preadipocyte (D0) and differentiated adipocyte (D7) stages of primary brown preadipocyte differentiation in order to characterize the transcriptional events regulating differentiation and function. Compared to the preadipocyte stage (D0), 6,668 genes were identified as differentially expressed genes (DEGs) with a fold change of ≥ 2.0 at the differentiated adipocyte stage (D7). Several adipogenic genes including peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer-binding protein-α (C/EBPα), and Krüppel-like factor (KLF) family genes were differentially expressed at D0 and D7. Since KLF16 gene expression was downregulated at day 7 and its adipogenic function has not been characterized, we investigated its role in adipogenesis. Knockdown of KLF16 stimulated the differentiation of both brown and 3T3-L1 preadipocytes, and led to increased PPARγ expression. However, overexpression of KLF16 had opposite effects. Furthermore, KLF16 downregulated PPARγ expression in brown adipocytes and inhibited its promoter activity. These results indicate that KLF16 inhibits adipogenesis through downregulation of PPARγ expression.

Eicosapentaenoic Acid Potentiates Brown Thermogenesis through FFAR4-dependent Up-regulation of miR-30b and miR-378

Emerging evidence suggests that n-3 polyunsaturated fatty acids (PUFA) promote brown adipose tissue thermogenesis. However, the underlying mechanisms remain elusive. Here, we hypothesize that n-3 PUFA promotes brown adipogenesis by modulating miRNAs. To test this hypothesis, murine brown preadipocytes were induced to differentiate the fatty acids of palmitic, oleate, or eicosapentaenoic acid (EPA). The increases of brown-specific signature genes and oxygen consumption rate by EPA were concurrent with up-regulation of miR-30b and 378 but not by oleate or palmitic acid. Next, we hypothesize that free fatty acid receptor 4 (Ffar4), a functional receptor for n-3 PUFA, modulates miR-30b and 378. Treatment of Ffar4 agonist (GW9508) recapitulated the thermogenic activation of EPA by increasing oxygen consumption rate, brown-specific marker genes, and miR-30b and 378, which were abrogated in Ffar4-silenced cells. Intriguingly, addition of the miR-30b mimic was unable to restore EPA-induced Ucp1 expression in Ffar4-depleted cells, implicating that Ffar4 signaling activity is required for up-regulating the brown adipogenic program. Moreover, blockage of miR-30b or 378 by locked nucleic acid inhibitors significantly attenuated Ffar4 as well as brown-specific signature gene expression, suggesting the signaling interplay between Ffar4 and miR-30b/378. The association between miR-30b/378 and brown thermogenesis was also confirmed in fish oil-fed C57/BL6 mice. Interestingly, the Ffar4 agonism-mediated signaling axis of Ffar4-miR-30b/378-Ucp1 was linked with an elevation of cAMP in brown adipocytes, similar to cold-exposed or fish oil-fed brown fat. Taken together, our work identifies a novel function of Ffar4 in modulating brown adipogenesis partly through a mechanism involving cAMP activation and up-regulation of miR-30b and miR-378.

MiR-34a(-/-) mice are susceptible to diet-induced obesity.

ObjectiveMicroRNA (miR)−34a regulates inflammatory pathways, and increased transcripts have been observed in serum and subcutaneous adipose of subjects who have obesity and type 2 diabetes. Therefore, the role of miR‐34a in adipose tissue inflammation and lipid metabolism in murine diet‐induced obesity was investigated.MethodsWild‐type (WT) and miR‐34a−/− mice were fed chow or high‐fat diet (HFD) for 24 weeks. WT and miR‐34a−/− bone marrow‐derived macrophages were cultured in vitro with macrophage colony‐stimulating factor (M‐CSF). Brown and white preadipocytes were cultured from the stromal vascular fraction (SVF) of intrascapular brown and epididymal white adipose tissue (eWAT), with rosiglitazone.ResultsHFD‐fed miR‐34a−/− mice were significantly heavier with a greater increase in eWAT weight than WT. miR‐34a−/− eWAT had a smaller adipocyte area, which significantly increased with HFD. miR‐34a−/− eWAT showed basal increases in Cd36, Hmgcr, Lxrα, Pgc1α, and Fasn. miR‐34a−/− intrascapular brown adipose tissue had basal reductions in c/ebpα and c/ebpβ, with in vitro miR‐34a−/− white adipocytes showing increased lipid content. An F4/80high macrophage population was present in HFD miR‐34a−/− eWAT, with increased IL‐10 transcripts and serum IL‐5 protein. Finally, miR‐34a−/− bone marrow‐derived macrophages showed an ablated CXCL1 response to tumor necrosis factor‐α.ConclusionsThese findings suggest a multifactorial role of miR‐34a in controlling susceptibility to obesity, by regulating inflammatory and metabolic pathways.

Comparison of Anti‐obesity Effects of Onion Peels by Different Extraction Methods Using 3T3‐L1 and Primary Brown Adipocytes In Vitro

Obesity, indicated by excess body fat accumulation, is a serious health problem. Various functional foods have been attracted for improving obese condition. Onion peel, a by‐product of onion has shown possible benefits in obesity studies. Since onion peel is not the edible part of onion, it is important to select a relevant extraction method to obtain beneficial compounds from onion peel for a targeted purpose. Different extracting process causes the distinct selectivity of functional compounds which may have different biological effects. Here, we utilized two onion peel extracts obtained through 60% ethanol extraction (OPE) and boiling water extraction (OPW). The purpose of this study was to compare anti‐obesity effect of OPE and OPW in white and brown adipocytes which are related to energy storage and utilization, respectively. Briefly, 3T3‐L1, fibroblasts that mimic white preadipocytes and primary brown preadipocytes isolated from interscapular brown adipose tissue of 4 week‐old male C57BL/6 mice were cultured and differentiated into mature adipocytes. Various concentrations of OPE and OPW were treated to the cells during differentiation and then gene expression was measured using real‐time PCR. In 3T3‐L1 cells, OPE decreased the expression of proliferator‐activated receptor γ (PPARγ), fatty acid synthase, and acetyl‐CoA carboxylase genes which are involved in adipogenesis and lipogenesis respectively whereas OPW did not. Interestingly, both OPE and OPW significantly increased the expression of carnitine palmitoyltransferase 1 α and PPARγ coactivator 1 α (PGC1α) genes which are related to the regulation of fatty acid oxidation. In brown adipocytes, PPARγ was significantly decreased by both OPE and OPW treatment. Only OPE significantly increased uncoupling protein 1 (UCP1) gene which is associated with a non‐shivering thermogenesis, increasing energy expenditure by utilizing fatty acids. However UCP1 gene was not altered by OPW treatment. This was not correlated with the expression of PGC1α gene and other downstream genes of PGC1α. Collectively, onion peel extracts exhibited anti‐obesity effects in both white and brown adipocytes. However, the effects and mechanisms were affected by the different extraction methods.Support or Funding InformationSupported by USDA

Dicer1-miR-328-Bace1 signalling controls brown adipose tissue differentiation and function.

Activation of brown adipose tissue (BAT) controls energy homeostasis in rodents and humans and has emerged as an innovative strategy for the treatment of obesity and type 2 diabetes mellitus. Here we show that ageing- and obesity-associated dysfunction of brown fat coincides with global microRNA downregulation due to reduced expression of the microRNA-processing node Dicer1. Consequently, heterozygosity of Dicer1 in BAT aggravated diet-induced-obesity (DIO)-evoked deterioration of glucose metabolism. Analyses of differential microRNA expression during preadipocyte commitment and mouse models of progeria, longevity and DIO identified miR-328 as a regulator of BAT differentiation. Reducing miR-328 blocked preadipocyte commitment, whereas miR-328 overexpression instigated BAT differentiation and impaired muscle progenitor commitment-partly through silencing of the β-secretase Bace1. Loss of Bace1 enhanced brown preadipocyte specification in vitro and was overexpressed in BAT of obese and progeroid mice. In vivo Bace1 inhibition delayed DIO-induced weight gain and improved glucose tolerance and insulin sensitivity. These experiments reveal Dicer1-miR-328-Bace1 signalling as a determinant of BAT function, and highlight the potential of Bace1 inhibition as a therapeutic approach to improve not only neurodegenerative diseases but also ageing- and obesity-associated impairments of BAT function.

Src family kinases suppress differentiation of brown adipocytes and browning of white adipocytes.

Brown adipocytes and beige adipocytes can expend energy, generate heat, and increase whole-body energy expenditure. The detailed mechanisms of adipogenesis and thermogenesis of these cells are still obscure. Here, we show that Src family kinases (SFKs) regulate both brown adipogenesis and browning of white adipocytes. To identify factors involved in brown adipogenesis, we first examined the effect of several chemical inhibitors on the differentiation of brown preadipocytes isolated from mouse brown adipose tissue (BAT) and found that treatment with PP2, the specific inhibitor of SFKs, promoted the differentiation. Another inhibitor of SFKs, PP1, also promoted the brown adipogenesis, whereas an inactive analogue of PP2, PP3, did not. Moreover, over-expression of C-terminal Src kinase (CSK), the negative regulator of SFKs, also promoted brown adipogenesis. Next, we examined the effect of inhibition of SFKs on the differentiation of white preadipocytes isolated from white adipose tissue (WAT). Our results showed that either PP2 treatment or CSK-over-expression generated Ucp1-positive beige adipocytes, thus inducing browning of white adipocytes. Finally, our analysis showed that the expression levels and activity of SFKs in WAT were much higher than in BAT. These results taken together suggest that SFKs regulate differentiation and browning of fat cells in vivo.

Tribbles 3 inhibits brown adipocyte differentiation and function by suppressing insulin signaling

Recent studies have demonstrated that adult humans have substantial amounts of functioning brown adipose tissue (BAT). Since BAT has been implicated as an anti-obese and anti-diabetic tissue, it is important to understand the signaling molecules that regulate BAT function. There has been a link between insulin signaling and BAT metabolism as deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function. Tribbles 3 (TRB3) is a pseudo kinase that has been shown to regulate metabolism and insulin signaling in multiple tissues but the role of TRB3 in BAT has not been studied. In this study, we found that TRB3 expression was present in BAT and overexpression of TRB3 in brown preadipocytes impaired differentiation and decreased expression of BAT markers. Furthermore, TRB3 overexpression resulted in significantly lower oxygen consumption rates for basal and proton leakage, indicating decreased BAT activity. Based on previous studies showing that deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function, we assessed insulin signaling in brown preadipocytes and BAT in vivo. Overexpression of TRB3 in cells impaired insulin-stimulated IRS1 and Akt phosphorylation, whereas TRB3KO mice displayed improved IRS1 and Akt phosphorylation. Finally, deletion of IRS1 abolished the function of TRB3 to regulate BAT differentiation and metabolism. These data demonstrate that TRB3 inhibits insulin signaling in BAT, resulting in impaired differentiation and function.

Direct action of capsaicin in brown adipogenesis and activation of brown adipocytes.

The ingestion of capsaicin, the principle pungent component of red and chili peppers, induces thermogenesis, in part, through the activation of brown adipocytes expressing genes related to mitochondrial biogenesis and uncoupling such as peroxisome proliferator-activated receptor (Ppar) γ coactivator-1α (Pgc-1α) and uncoupling protein 1 (Ucp1). Capsaicin has been suggested to induce the activation of brown adipocytes, which is mediated by the stimulation of sympathetic nerves. However, capsaicin may directly affect the differentiation of brown preadipocytes, brown adipocyte function, or both, through its significant absorption. We herein demonstrated that Trpv1, a capsaicin receptor, is expressed in brown adipose tissue, and that its expression level is increased during the differentiation of HB2 brown preadipocytes. Furthermore, capsaicin induced calcium influx in brown preadipocytes. A treatment with capsaicin in the early stage of brown adipogenesis did not affect lipid accumulation or the expression levels of Fabp4 (a gene expressed in mature adipocytes), Pparγ2 (a master regulator of adipogenesis) or brown adipocyte-selective genes. In contrast, a treatment with capsaicin in the late stage of brown adipogenesis slightly increased the expression levels of Fabp4, Pparγ2 and Pgc-1α. Although capsaicin did not affect the basal expression level of Ucp1, Ucp1 induction by forskolin was partially inhibited by capsaicin, irrespective of the dose of capsaicin. The results of the present study suggest the direct effects of capsaicin on brown adipocytes or in the late stage of brown adipogenesis.

The Effects of High Fat Diet and Resveratrol on Mitochondrial Activity of Brown Adipocytes

BackgroundResveratrol (RSV) is a polyphenolic phytoalexin that has many effects on metabolic diseases such as diabetes and obesity. Given the importance of brown adipose tissue (BAT) for energy expenditure, we investigated the effects of RSV on brown adipocytes.MethodsFor the in vitro study, interscapular BAT was isolated from 7-week-old male Sprague Dawley rats. For the in vivo study, 7-week-old male Otsuka Long Evans Tokushima Fatty (OLETF) rats were divided into four groups and treated for 27 weeks with: standard diet (SD); SD+RSV (10 mg/kg body weight, daily); high fat diet (HFD); HFD+RSV. RSV was provided via oral gavage once daily during the in vivo experiments.ResultsRSV treatment of primary cultured brown preadipocytes promoted mitochondrial activity, along with over-expression of estrogen receptor α (ER-α). In OLETF rats, both HFD and RSV treatment increased the weight of BAT and the differentiation of BAT. However, only RSV increased the mitochondrial activity and ER-α expression of BAT in the HFD-fed group. Finally, RSV improved the insulin sensitivity of OLETF rats by increasing the mitochondrial activity of BAT, despite having no effects on white adipocytes and muscles in either diet group.ConclusionRSV could improve insulin resistance, which might be associated with mitochondrial activity of brown adipocyte. Further studies evaluating the activity of RSV for both the differentiation and mitochondrial activity of BAT could be helpful in investigating the effects of RSV on metabolic parameters.

Jmjd3-Mediated H3K27me3 Dynamics Orchestrate Brown Fat Development and Regulate White Fat Plasticity

Progression from brown preadipocytes to adipocytes engages two transcriptional programs: the expression of adipogenic genes common to both brown fat (BAT) and white fat (WAT), and the expression of BAT-selective genes. However, the dynamics of chromatin states and epigenetic enzymes involved remain poorly understood. Here we show that BAT development is selectively marked and guided by repressive H3K27me3 and is executed by its demethylase Jmjd3. We find that a significant subset of BAT-selective genes, but not common fat genes or WAT-selective genes, are demarcated by H3K27me3 in both brown and white preadipocytes. Jmjd3-catalyzed removal of H3K27me3, in part through Rreb1-mediated recruitment, is required for expression of BAT-selective genes and for development of beige adipocytes both in vitro and in vivo. Moreover, gain- and loss-of-function Jmjd3 transgenic mice show age-dependent body weight reduction and cold intolerance, respectively. Together, we identify an epigenetic mechanism governing BAT fate determination and WAT plasticity.

3D brown adipogenesis to create “Brown-Fat-in-Microstrands”

The ability of brown adipocytes (fat cells) to dissipate energy as heat shows great promise for the treatment of obesity and other metabolic disorders. Employing pluripotent stem cells, with an emphasis on directed differentiation, may overcome many issues currently associated with primary fat cell cultures. In addition, three-dimensional (3D) cell culture systems are needed to better understand the role of brown adipocytes in energy balance and treating obesity. To address this need, we created 3D “Brown-Fat-in-Microstrands” by microfluidic synthesis of alginate hydrogel microstrands that encapsulated cells and directly induced cell differentiation into brown adipocytes, using mouse embryonic stem cells (ESCs) as a model of pluripotent stem cells, and brown preadipocytes as a positive control. Brown adipocyte differentiation within microstrands was confirmed by immunocytochemistry and qPCR analysis of the expression of the brown adipocyte-defining marker uncoupling protein 1 (UCP1), as well as other general adipocyte markers. Cells within microstrands were responsive to a β-adrenergic agonist with an increase in gene expression of thermogenic UCP1, indicating that these “Brown-Fat-in-Microstrands” are functional. The ability to create “Brown-Fat-in-Microstrands” from pluripotent stem cells opens up a new arena to understanding brown adipogenesis and its implications in obesity and metabolic disorders.

Effects of ethyl acetate extract of Kaempferia parviflora on brown adipose tissue.

We have previously reported the effects of Kaempferia parviflora (KP), including anti-obesity, preventing various metabolic diseases, and regulating differentiation of white adipose cells. In this study we used Tsumura, Suzuki, Obese Diabetes (TSOD) mice--an animal model of spontaneous obese type II diabetes--and primary brown preadipocytes to examine the effects of the ethyl acetate extract of KP (KPE) on brown adipose tissue, which is one of the energy expenditure organs. TSOD mice were fed with MF mixed with either KPE 0.3 or 1% for 8 weeks. Computed tomography images showed that whitening of brown adipocytes was suppressed in the interscapular tissue of the KPE group. We also examined mRNA expression of uncoupling protein 1 (UCP-1) and β3-adrenalin receptor (β3AR) in brown adipose tissue. As a result, mRNA expression of UCP-1 significantly increased in the KPE 1% treatment group, indicating that KPE activated brown adipose tissue. We then evaluated the direct effects of KPE on brown adipocytes using primary brown preadipocytes isolated from interscapular brown adipocytes in ICR mice. Triacylglycerol (TG) accumulation in primary brown preadipocytes was increased by KPE in a dose-dependent manner. Each mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ), UCP-1, and β3AR exhibited an upward trend compared with the control group. Moreover, some polymethoxyflavonoids (PMFs), the main compound in KP, also increased TG accumulation. This study therefore showed that KPE enhanced the thermogenesis effect of brown adipocytes as well as promoted the differentiation of brown adipocyte cells.