Uncoupling Protein 3 Promoter Research Articles

Genistein-mediated thermogenesis and white-to-beige adipocyte differentiation involve transcriptional activation of cAMP response elements in the Ucp1 promoter.

Genistein is an isoflavone present in soybeans and is considered a bioactive compound due to its widely reported biological activity. We have previously shown that intraperitoneal genistein administration and diet supplementation activates the thermogenic program in rats and mice subcutaneous white adipose tissue (scWAT) under multiple environmental cues, including cold exposure and high-fat diet feeding. However, the mechanistic insights of this process were not previously unveiled. Uncoupling protein 1 (UCP1), a mitochondrial membrane polypeptide responsible for dissipating energy into heat, is considered the most relevant thermogenic marker; thus, we aimed to evaluate whether genistein regulates UCP1 transcription. Here we show that genistein administration to thermoneutral-housed mice leads to the appearance of beige adipocyte markers, including a sharp upregulation of UCP1 expression and protein abundance in scWAT. Reporter assays showed an increase in UCP1 promoter activity after genistein stimulation, and in silico analysis revealed the presence of estrogen (ERE) and cAMP (CRE) response elements as putative candidates of genistein activation. Mutation of the CRE but not the ERE reduced genistein-induced promoter activity by 51%. Additionally, in vitro and in vivo ChIP assays demonstrated the binding of CREB to the UCP1 promoter after acute genistein administration. Taken together, these data elucidate the mechanism of genistein-mediated UCP1 induction and confirm its potential applications in managing metabolic disorders.

GATA3 induces the upregulation of UCP-1 by directly binding to PGC-1α during adipose tissue browning

ObjectiveObesity is recognized as the cause of multiple metabolic diseases and is rapidly increasing worldwide. As obesity is due to an imbalance in energy homeostasis, the promotion of energy consumption through browning of white adipose tissue (WAT) has emerged as a promising therapeutic strategy to counter the obesity epidemic. However, the molecular mechanisms of the browning process are not well understood. In this study, we investigated the effects of the GATA family of transcription factors on the browning process. MethodsWe used qPCR to analyze the expression of GATA family members during WAT browning. In order to investigate the function of GATA3 in the browning process, we used the lentivirus system for the ectopic expression and knockdown of GATA3. Western blot and real-time qPCR analyses revealed the regulation of thermogenic genes upon ectopic expression and knockdown of GATA3. Luciferase reporter assays, co-immunoprecipitation, and chromatin immunoprecipitation were performed to demonstrate that GATA3 interacts with proliferator-activated receptor-γ co-activator-1α (PGC-1α) to regulate the promoter activity of uncoupling protein-1 (UCP-1). Enhanced energy expenditure by GATA3 was confirmed using oxygen consumption assays, and the mitochondrial content was assessed using MitoTracker. Furthermore, we examined the in vivo effects of lentiviral GATA3 overexpression and knockdown in inguinal adipose tissue of mice. ResultsGata3 expression levels were significantly elevated in the inguinal adipose tissue of mice exposed to cold conditions. Ectopic expression of GATA3 enhanced the expression of UCP-1 and thermogenic genes upon treatment with norepinephrine whereas GATA3 knockdown had the opposite effect. Luciferase reporter assays using the UCP-1 promoter region showed that UCP-1 expression was increased in a dose-dependent manner by GATA3 regardless of norepinephrine treatment. GATA3 was found to directly bind to the promoter region of UCP-1. Furthermore, our results indicated that GATA3 interacts with the transcriptional coactivator PGC-1α to increase the expression of UCP-1. Taken together, we demonstrate that GATA3 has an important role in enhancing energy expenditure by increasing the expression of thermogenic genes both in vitro and in vivo. ConclusionGATA3 may represent a promising target for the prevention and treatment of obesity by regulating thermogenic capacity.

Essential role of the PGC-1α/PPARβ axis in Ucp3 gene induction.

We report that the peroxisome proliferator-activated receptor (PPAR)γ coactivator 1-α (PGC-1α)/PPARβ axis is a crucial mediator of uncoupling protein 3 (UCP3) expression in skeletal muscle cells via the transactivativation of a distal PPAR response element at the Ucp3 gene promoter. This mechanism is activated during the myogenic process and by high concentrations of fatty acids independent of PGC-1α protein levels. Ucp3 is essential for PGC-1α-induced oxidative capacity and the adaptive mitochondrial response to fatty acid exposure. These findings provide further evidence for the broad spectrum of the coactivator action in mitochondrial homeostasis, positioning the PGC-1ɑ/PPARβ axis as an essential component of the molecular regulation of Ucp3 gene in skeletal muscle cells. Uncoupling protein 3 (UCP3) has an essential role in fatty acid metabolism and mitochondrial redox regulation in skeletal muscle. However, the molecular mechanisms involved in the expression of Ucp3 are poorly known. In the present study, we show that the peroxisome proliferator-activated receptor (PPAR)γ coactivator 1-α (PGC-1α)/PPARβ axis is a crucial mediator of Ucp3 expression in skeletal muscle cells. In silico analysis of the UCP3 promoter and quantitative chromatin immunoprecipitation experiments revealed that the induction of the UCP3 transcript is mediated by the transactivation of a distal PPAR response element at the Ucp3 gene promoter by the coactivator PGC-1α. This mechanism is activated during myogenesis and during metabolic stress induced by fatty acids independent of PGC-1α protein levels. We also provide evidence that Ucp3 is essential for PGC-1α-induced oxidative capacity. Taken together, our results highlight PGC-1ɑ/PPARβ as an essential component of the molecular regulation of Ucp3 gene in skeletal muscle cells.

1999-P: Cysteine-Rich Protein 2 (CRIP2) Is a Novel Transcriptional Regulator of Uncoupling Protein 1

Since traditional weight loss strategies have been unsuccessful at slowing the increasing rate of obesity, alternative strategies are in high demand. Brown adipose tissue (BAT) is a thermogenic tissue that efficiently expends energy. Thermogenesis in BAT occurs through the action of uncoupling protein 1 (UCP1). Identifying novel transcriptional regulators of UCP1 may lead to potential targets to increase BAT activity since its expression is under tight transcriptional control. Engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) is a modified CRISPR/Cas9 methodology that identifies novel transcriptional regulators. EnChIP uses dCas9 (lacks endonuclease activity) and guide RNAs (gRNAs) targeting a specific promoter region. The DNA-bound dCas9 can be immunoprecipitated, and the associated promoter region/transcriptional machinery can be sent for proteomic analysis to identify novel transcriptional regulators. Following β-adrenergic stimulation, which activates UCP1 gene transcription in brown adipocytes, we performed enChIP by using five gRNAs targeting the UCP1 promoter. EnChIP analysis of the UCP1 promoter revealed cysteine-rich protein 2 (CRIP2) as a putative transcriptional regulator of UCP1, which was validated by ChIP-PCR. We demonstrated that knocking down CRIP2 in brown adipocytes significantly decreased β-adrenergic-induced UCP1 expression and heat production. Mechanistically, we demonstrated that following β-adrenergic stimulation, CRIP2 was phosphorylated and translocated from the cytosol to the nucleus, where it interacted with peroxisomal proliferator-activated receptor gamma (PPARγ). Taken together, using the unbiased CRISPR-based enChIP approach, we identify CRIP2 as a novel transcriptional regulator that modulates UCP1 expression in response to β-adrenergic stimulation. These findings pave the foundation for developing new anti-obesity and antidiabetes therapies. Disclosure J. Darcy: None. C. Wang: None. M. Lundh: Employee; Self; Gubra. F. Shamsi: None. M. Lynes: None. T. d'Aprigny: None. B. Emanuelli: None. Y. Tseng: Other Relationship; Self; Chugai Pharmaceutical Co., Ltd. Funding National Institutes of Health (R01DK077097, R01DK102898, T32DK007260)

Insulin-like growth factor-1 directly mediates expression of mitochondrial uncoupling protein 3 via forkhead box O4

ObjectiveThe objective of our study was to examine the direct action of insulin-like growth factor-1(IGF-1) signaling on energy homeostasis in myocytes. DesignWe studied the IGF-1 stimulation of mitochondrial uncoupling protein 3 (UCP3) expression in the HEK 293 derived cell line TSA201, murine C2C12 skeletal muscle myoblasts, and rat L6 skeletal myoblasts. We also investigated the direct effect of IGF-1 on the Insulin/IGF-1 receptor (IGF-1R)/phosphatidylinositol 3 (PI3)-Akt/forkhead box O4 (FOXO4) pathway using a combination of a reporter assay, semi-quantitative polymerase chain reaction, western blotting, and animal experiments. ResultsWe demonstrated that IGF-1 regulates UCP3 expression via phosphorylation of FOXO4, which is a downstream signal transducer of IGF-1. UCP3 expression increased with activated FOXO4 in a dose-dependent manner. We also examined the functional FOXO4 binding site consensus sequences and identified it as the −1922 bp site in the UCP3 promoter region. UCP3 was also found to be concomitantly expressed with IGF-1 during differentiation of C2C12 myoblasts. Our animal experiments showed that high fat diet induced IGF-1 levels which likely influenced UCP3 expression in the skeletal muscle. ConclusionOur findings demonstrate that that IGF-1 directly stimulates UCP3 expression via the IGF-1/IGF-1R/PI3-Akt/FOXO4 pathway.

Identification of a G-quadruplex forming sequence in the promoter of UCP1.

G-quadruplexes are higher-order nucleic acid structures formed in G-rich sequences in DNA or RNA. G-quadruplexes are distributed in many locations in the human genome, including promoter regions, and are viewed as promising therapeutic targets. Uncoupling protein-1 (UCP1) is a mitochondrial thermogenic gene critical for energy expenditure in the form of heat in the brown adipose tissue. UCP1 is only expressed during brown fat cell differentiation and is a candidate target for treating obesity. However, the regulation of UCP1 expression is not clear. We reported here that a G-quadruplex forming sequence exists in the promoter of UCP1. The 5,10,15,20-tetra(N-methyl-4-pyridyl) porphyrin (TMPyP4) enhanced cellular expression of UCP1 and destabilized the G-quadruplex formed by the sequence from the promoter of UCP1. Mutations in the G-quadruplex regulated the cellular activity of UCP1 promoter as evidenced by a UCP1-promoter luciferase assay. These results suggest that G-quadruplex structure is a potential target to regulate the expression of UCP1.

Effects of growth hormone on uncoupling protein 1 in white adipose tissues in obese mice

ObjectiveThe transition of white adipocytes to beige cells (a phenomenon referred to as browning or beigeing) during obesity has been previously reported. Our study aimed to examine the mechanisms through which obesity induced by a high fat diet (HFD) affects uncoupling protein 1 (UCP1) expression via signal transduction and activator of transcription 5 (STAT5s). DesignSeven-week-old male C57BL/6J mice were fed a normal or HFD for 11weeks. Body weight, white adipose tissue weight, and blood lipid and glucose levels were measured. To unveil the molecular mechanisms of UCP1 expression in adipose tissue, we performed further studying 3T3-L1 cells using qRT-PCR. We also measured UCP1 promoter activity in the TSA201 cell line using a dual luciferase assay. In addition, we analyzed the predicted consensus sequences for STAT5 binding in the UCP1 promoter region. ResultsMice fed an HFD had higher body weight and intra-abdominal adipose tissues weight and a higher expression of UCP1, GH receptor (GHR), STATs, suppressors of cytokine signaling (SOCSs), and cytokine-inducible SH2-containing protein (CISH) compared to control mice. In 3T3-L1 cell studies, GH induced phosphorylation of the STAT5, SOCSs, CISH and UCP1 expressions. UCP1 promoter activity was associated with constitutively active STAT5 in a dose-dependent manner. We confirmed functional STAT5 binding sites at −425, −279, and −178bp of the UCP1 promoter. ConclusionWe suggest that endogenous GH induces UCP1 expression in adipose tissue via STAT5.

Vitamin D3/VDR resists diet-induced obesity by modulating UCP3 expression in muscles.

BackgroundThe impact of vitamin D3 (VD3) on obesity has been reported in the past. Our study was aimed at investigating the possible mechanisms by which VD3 affects obesity induced by a high fat diet.MethodsEight-week-old C57BL/6 J male mice were fed a normal- or high-fat diet for 9 weeks and were treated with a gavage of vehicle (corn oil) or cholecalciferol (50 μg/kg, daily). Body weight, white adipose tissue weight, blood lipid and glucose levels were measured. In addition, we investigated the expression of 1,25(OH)2D3 (calcitriol)/VDR-regulated genes involved in energy and lipid metabolism, such as of uncoupling protein 3 (UCP3), by using qRT-PCR in the liver, adipose tissue, skeletal muscle and C2C12, L6, and H-EMC-SS cells. We also measured UCP3 promoter transcription in the same cell lines using a Dual Luciferase Assay. Furthermore, we analyzed the binding site consensus sequences of VDR on the UCP3 promoter.ResultsMice consuming a high-fat diet treated with cholecalciferol had lower body weight and adipose tissue weight and higher expression of UCP3 compared to the other treatment groups. Changes in the expression of genes correlated with calcitriol/VDR. Luciferase activity was dose-dependently associated with calcitriol/VDR levels. We confirmed the functional VDR binding site consensus sequences at -2200, -1561, -634, and +314 bp in the UCP3 promoter region.ConclusionWe suggest that VD3/VDR inhibits weight gain by activating UCP3 in the muscles.Electronic supplementary materialThe online version of this article (doi:10.1186/s12929-016-0271-2) contains supplementary material, which is available to authorized users.

A novel thermoregulatory role for PDE10A in mouse and human adipocytes.

Phosphodiesterase type 10A (PDE10A) is highly enriched in striatum and is under evaluation as a drug target for several psychiatric/neurodegenerative diseases. Preclinical studies implicate PDE10A in the regulation of energy homeostasis, but the mechanisms remain unclear. By utilizing small‐animal PET/MRI and the novel radioligand [18F]‐AQ28A, we found marked levels of PDE10A in interscapular brown adipose tissue (BAT) of mice. Pharmacological inactivation of PDE10A with the highly selective inhibitor MP‐10 recruited BAT and potentiated thermogenesis in vivo. In diet‐induced obese mice, chronic administration of MP‐10 caused weight loss associated with increased energy expenditure, browning of white adipose tissue, and improved insulin sensitivity. Analysis of human PET data further revealed marked levels of PDE10A in the supraclavicular region where brown/beige adipocytes are clustered in adults. Finally, the inhibition of PDE10A with MP‐10 stimulated thermogenic gene expression in human brown adipocytes and induced browning of human white adipocytes. Collectively, our findings highlight a novel thermoregulatory role for PDE10A in mouse and human adipocytes and promote PDE10A inhibitors as promising candidates for the treatment of obesity and diabetes.

Functional and Activity Analysis of Cattle UCP3 Promoter with MRFs-Related Factors.

Uncoupling protein 3 (UCP3) is mainly expressed in muscle. It plays an important role in muscle, but less research on the regulation of cattle UCP3 has been performed. In order to elucidate whether cattle UCP3 can be regulated by muscle-related factors, deletion of cattle UCP3 promoter was amplified and cloned into pGL3-basic, pGL3-promoter and PEGFP-N3 vector, respectively, then transfected into C2C12 myoblasts cells and UCP3 promoter activity was measured using the dual-Luciferase reporter assay system. The results showed that there is some negative-regulatory element from −620 to −433 bp, and there is some positive-regulatory element between −433 and −385 bp. The fragment (1.08 kb) of UCP3 promoter was cotransfected with muscle-related transcription factor myogenic regulatory factors (MRFs) and myocyte-specific enhancer factor 2A (MEF2A). We found that UCP3 promoter could be upregulated by Myf5, Myf6 and MyoD and downregulated by MyoG and MEF2A.

Effect of -55CT Polymorphism of UCP3 on Insulin Resistance and Cardiovascular Risk Factors after a High Protein/Low Carbohydrate versus a Standard Hypocaloric Diet

Background: The C/C genotype of a polymorphism in the uncoupling protein3 (UCP3) promoter (-55C->T) (rs1800849) is associated with an increased body mass index. Objective: The aim of our study was to investigate the effect of polymorphism on the UCP3 promoter (-55C->T) on insulin resistance and cardiovascular risk factors secondary to a high protein/low carbohydrate vs. a standard hypocaloric diets (1,000 kcal/day). Design: A population of 283 obese subjects was analyzed in a randomized trial. A nutritional evaluation was performed at the beginning and at the end of a 9-month period in which subjects received 1 of 2 diets (diet HP: high protein/low carbohydrate vs. diet S: standard diet). Results: Weight improvement was higher in non-T carriers. With both diets and only in wild genotype (diet HP vs. diet S), total cholesterol (-9.7 ± 4.0 vs. -11.1 ± 2.0 mg/dl; p > 0.05) and low density lipoprotein (LDL) cholesterol (-8.3 ± 3.0 vs. -5.5 ± 2.7 mg/dl; p > 0.05) decreased. The improvement in these parameters was similar in subjects with diet HP than HS. With diet HP and only in wild genotype, glucose (-5.2 ± 2.2 mg/dl; p < 0.05), triglycerides (-15.5 ± 3.9 mg/dl; p < 0.05), insulin levels (-3.9 ± 3.1 UI/l; p < 0.05) and homeostasis model assessment (HOMA-R; -0.6 ± 0.1 units; p < 0.05) decreased. Conclusion: Carriers of T allele have a different response than non-carrier subjects, with a lack of decrease of LDL cholesterol, glucose, insulin levels and HOMA-R. The weight loss was lower in T carriers. HP diet showed a better metabolic response than S diet in 55CC homozygous.

Proinflammatory cytokine interleukin-1β suppresses cold-induced thermogenesis in adipocytes

In this study, we investigated the effects of interleukin-1β (IL-1β), a typical proinflammatory cytokine on the β-adrenoreceptor-stimulated induction of uncoupling protein 1 (UCP1) expression in adipocytes. IL-1β mRNA expression levels were upregulated in white adipose tissues of obese mice and in RAW264.7 macrophages under conditions designed to mimic obese adipose tissue. Isoproterenol-stimulated induction of UCP1 mRNA expression was significantly inhibited in C3H10T1/2 adipocytes by conditioned medium from lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in comparison with control conditioned medium. This inhibition was significantly attenuated in the presence of recombinant IL-1 receptor antagonist and IL-1β antibody, suggesting that activated macrophage-derived IL-1β is an important cytokine for inhibition of β-adrenoreceptor-stimulated UCP1 induction in adipocytes. IL-1β suppressed isoproterenol-induced UCP1 mRNA expression in C3H10T1/2 adipocytes, and this effect was partially but significantly abrogated by inhibition of extracellular signal-regulated kinase (ERK). IL-1β also suppressed the isoproterenol-induced activation of the UCP1 promoter and transcription factors binding to the cAMP response element. Moreover, intraperitoneal administration of IL-1β suppressed cold-induced UCP1 expression in adipose tissues. These findings suggest that IL-1β upregulated in obese adipose tissues suppresses β-adrenoreceptor-stimulated induction of UCP1 expression through ERK activation in adipocytes.

Cold-Inducible Zfp516 Activates UCP1 Transcription to Promote Browning of White Fat and Development of Brown Fat

Uncoupling protein 1 (UCP1) mediates nonshivering thermogenesis and, upon cold exposure, is induced in brown adipose tissue (BAT) and subcutaneous white adipose tissue (iWAT). Here, by high-throughput screening using the UCP1 promoter, we identify Zfp516 as a transcriptional activator of UCP1 as wellas PGC1α, thereby promoting a BAT program. Zfp516 itself is induced by cold and sympathetic stimulation through the cAMP-CREB/ATF2 pathway. Zfp516 directly binds to the proximal region of the UCP1 promoter, not to the enhancer region where other transcription factors bind, and interacts with PRDM16 to activate the UCP1 promoter. Although ablation of Zfp516 causes embryonic lethality, knockout embryos still show drastically reduced BAT mass. Overexpression of Zfp516 in adipose tissue promotes browning of iWAT even at room temperature, increasing body temperature and energy expenditure and preventing diet-induced obesity. Zfp516 may represent a future target for obesity therapeutics.

Histone deacetylase 1 plays an important role in brown adipogenesis (817.4)

Induction of brown adipocytes in white fat plays an important role in the regulation of energy homeostasis. Here, we have investigated the role of HDAC1 in brown adipogenesis. The RNA and protein levels of HDAC1 are lower in mice brown compared to white adipose tissue, in brown adipose tissue of mice exposed to cold compared to that of mice residing in room temperature, and reduced during brown adipocyte differentiation. Overexpression of HDAC1 inhibits, whereas genetic deletion of HDAC1 results in further enhancement of isoproterenol‐stimulated expression of uncoupling protein 1 (UCP1) and other BAT‐specific genes, including peroxisome proliferative activated receptor γ coactivator 1α (PGC1α), PGC1β, PR domain containing 16 (PRDM16), type 2 deiodinase (DIO2), fibroblast growth factor 21 (FGF21) and myelin protein zero‐like 2 (Eva1) in brown adipocyte cell lines BAT‐1 and HIB1B. Chromatin immunoprecipitation assay indicates that histone H3 and H4 acetylation is significantly increased at the UCP1 promoter in β‐adrenergic stimulated brown adipocytes, which is also associated with increased active histone markers H3 lysine 4 tri‐methylation, and H3 lysine 27 acetylation. Thus, our data suggest that epigenetics plays an important role in brown adipogenesis and thermogenesis, and identify HDAC1 as an important regulator during this process.Grant Funding Source: NIHR01HL107500

Activation of pattern recognition receptors in brown adipocytes induces inflammation and suppresses uncoupling protein 1 expression and mitochondrial respiration

Pattern recognition receptors (PRR), Toll-like receptors (TLR), and nucleotide-oligomerization domain-containing proteins (NOD) play critical roles in mediating inflammation and modulating functions in white adipocytes in obesity. However, the role of PRR activation in brown adipocytes, which are recently found to be present in adult humans, has not been studied. Here we report that mRNA of TLR4, TLR2, NOD1, and NOD2 is upregulated, paralleled with upregulated mRNA of inflammatory cytokines and chemokines in the brown adipose tissue (BAT) of the obese mice. During brown adipocyte differentiation, mRNA and protein expression of NOD1 and TLR4, but not TLR2 and NOD2, is also increased. Activation of TLR4, TLR2, or NOD1 in brown adipocytes induces activation of NF-κB and MAPK signaling pathways, leading to inflammatory cytokine/chemokine mRNA expression and/or protein secretion. Moreover, activation of TLR4, TLR2, or NOD1 attenuates both basal and isoproterenol-induced uncoupling protein 1 (UCP-1) expression without affecting mitochondrial biogenesis and lipid accumulation in brown adipocytes. Cellular bioenergetics measurements confirm that attenuation of UCP-1 expression by PRR activation is accompanied by suppression of both basal and isoproterenol-stimulated oxygen consumption rates and isoproterenol-induced uncoupled respiration from proton leak; however, maximal respiration and ATP-coupled respiration are not changed. Further, the attenuation of UCP-1 by PRR activation appears to be mediated through downregulation of the UCP-1 promoter activities. Taken together, our results demonstrate the role of selected PRR activation in inducing inflammation and downregulation of UCP-1 expression and mitochondrial respiration in brown adipocytes. Our results uncover novel targets in BAT for obesity treatment and prevention.

Effects of Eicosapentaenoic Acid and Docosahexaenoic Acid on Uncoupling Protein 3 Gene Expression in C2C12 Muscle Cells

Uncoupling protein 3 (UCP3) is a mitochondrial membrane transporter that is expressed mainly in skeletal muscle where it plays an important role in energy expenditure and fat oxidation. In this study, we investigated the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on UCP3 gene expression in C2C12 muscle cells. EPA and DHA up-regulated UCP3 mRNA level in a dose-dependent manner and similarly increased UCP3 promoter activity in C2C12 muscle cells. To determine whether AMP-activated protein kinase (AMPK) signaling may also directly regulate UCP3 expression, 5′-amino-4-imidazolecarboxamide-ribonucleoside (AICAR), an AMP analog that activates AMPK, was treated in C2C12 muscle cells. AICAR showed additive effects with EPA or DHA on the UCP3 promoter activation. These results indicate that EPA and DHA directly regulate the gene expression of UCP3, potentially through AMPK-mediated pathway in C2C12 muscle cells.

The transcription factor Nrf2 promotes survival by enhancing the expression of uncoupling protein 3 under conditions of oxidative stress

Uncoupling protein 3 (UCP3) is a member of the mitochondrial inner membrane carrier superfamily that modulates energy efficiency by catalyzing proton conductance and thus decreasing the production of superoxide anion. However, its role during oxidative stress and the underlying regulatory and molecular mechanisms remain poorly understood. We sought to investigate how UCP3 expression is regulated by oxidative stress and to evaluate the putative antioxidant role of this protein. H2O2 treatment increased UCP3 expression and the nuclear accumulation of the transcription factor Nrf2 in C2C12 and HL-1 cells. Nrf2 siRNA prevented H2O2-induced UCP3 expression, increasing oxidative stress and cell death. ChIP assays identified an antioxidant-response element (ARE) within the UCP3 promoter that bound Nrf2 after exposure to H2O2. Luciferase reporter experiments confirmed increased ARE activity in H2O2-treated HL-1 cells. Importantly, H2O2 increased the UCP3-mediated proton leak, suggesting a role for this protein in attenuating ROS-induced damage. Nrf2 nuclear accumulation and increased UCP3 protein were also detected in intact mouse heart subjected to a condition known to increase ROS generation. This is the first study to demonstrate that H2O2 augments UCP3 expression and it provides the first evidence of Nrf2 binding to the UCP3 promoter in response to oxidative challenge. These findings suggest that UCP3 functions as a member of the cellular antioxidant defense system that protects against oxidative stress in vivo. In conclusion, we have identified a novel regulatory process induced by an oxidative insult whereby the expression of the mitochondrial protein UCP3 is driven by the Nrf2 transcription factor, which decreases ROS production and prevents cell death.

Inflammation induced by RAW macrophages suppresses UCP1 mRNA induction via ERK activation in 10T1/2 adipocytes

Recently, it has been demonstrated that uncoupling protein-1 (UCP1)-expressing white adipocytes (brown-like adipocytes) are important for energy expenditure in white adipose tissue (WAT), in which energy expenditure decreases under obese conditions. However, the relationship between the induction of brown-like adipocytes and the decrease in energy expenditure in obese WAT remains to be elucidated. Here, we show that proinflammatory cytokines derived from activated macrophages suppress the induction of UCP1 promoter activity and mRNA expression via an extracellular signal-related kinase (ERK) in white adipocytes. The coculture with RAW264.7 (RAW) macrophages suppressed the induction of UCP1 mRNA expression by isoproterenol (ISO), a typical β-adrenergic receptor agonist, in C3H10T1/2 (10T1/2) adipocytes. A conditioned medium derived from lipopolysaccharide (LPS)-activated macrophages and tumor necrosis factor-α (TNF-α) also suppressed the induction of UCP1 mRNA but did not affect its mRNA stability. By using a luciferase reporter assay system, the conditioned medium and TNF-α also suppressed the activity of the UCP1 promoter and transcriptional factors binding to the cAMP response element (CRE). Importantly, PD98059, an ERK inhibitor, partially abrogated the suppression of UCP1 promoter activation and mRNA induction. These results indicate that ERK is an important factor in the suppression of UCP1 transcriptional activation in the interaction between white adipocytes and activated macrophages. This report suggests a possible mechanism of the UCP1 transcriptional suppression in white adipocytes associated with obese and diabetic conditions.

Synergism between cAMP and PPARγSignalling in the Initiation of UCP1 Gene Expression in HIB1B Brown Adipocytes

Expression of the brown adipocyte-specific gene, uncoupling protein 1 (UCP1), is increased by both PPARγ stimulation and cAMP activation through their ability to stimulate the expression of the PPAR coactivator PGC1α. In HIB1B brown preadipocytes, combination of the PPARγ agonist, rosiglitazone, and the cAMP stimulator forskolin synergistically increased UCP1 mRNA expression, but PGC1α expression was only increased additively by the two drugs. The PPARγ antagonist, GW9662, and the PKA inhibitor, H89, both inhibited UCP1 expression stimulated by rosiglitazone and forskolin but PGC1α expression was not altered to the same extent. Reporter studies demonstrated that combined rosiglitazone and forskolin synergistically activated transcription from a full length 3.1 kbp UCP1 luciferase promoter construct, but the response was only additive and much reduced when a minimal 260 bp proximal UCP1 promoter was examined. Rosiglitazone and forskolin in combination were able to synergistically stimulate promoters comprising of tandem repeats of either PPREs or CREs. We conclude that rosiglitazone and forskolin act together to synergistically activate the UCP1 promoter directly rather than by increasing PGC1α expression and by a mechanism involving cross-talk between the signalling systems regulating the CRE and PPRE on the promoters.

Association of the UCP-1 single nucleotide polymorphism A-3826G with the dampness-phlegm pattern among Korean stroke patients

BackgroundPatients with stroke have various syndromes and symptoms. Through pattern identification (PI), traditional Korean medicine (TKM) classifies the several syndromes and symptoms of stroke patients into five categories: Fire-heat (FH), Dampness-phlegm (DP), Yin-deficiency (YD), Qi-deficiency (QD) and Blood-stasis (BS). DP has been associated with obesity and hyperlipidemia. Uncoupling protein-1 (UCP-1), which plays a major role in thermogenesis and energy expenditure can increase the risk of obesity and can be related metabolic disorders. In this study, we elucidated the association of three polymorphisms located in the UCP-1 promoter and coding region with DP among Korean stroke patients.Methods1,593 patients with cerebral infarction (583/DP, 1,010/non-DP) and 587 normal subjects were enrolled. The genotypes A-3826G, G-1766A and Ala64Thr (G+1068A) for each subject were determined by polymerase chain reaction with TaqMan probes and five percent of subjects were re-genotyped by sequencing method to confirm the accuracy of genotyping. The results were analyzed using a multiple logistic regression model to evaluate the genetic associations: the UCP-1polymorphisms of normal versus those of DP subjects and those of normal versus those of non-DP subjects.ResultsA significantly higher percentage of subjects in the DP group possessed the A-3826G G allele than the A allele (OR=1.508, p=0.006). Furthermore, the number of subjects with the GG type of A-1766G was significantly lower in the non-DP group than the normal group in the recessive model (OR=0.606, p=0.042). In addition, an analysis of the relationship among 2 SNPs of UCP-1 and lipid serum concentration showed that the serum level of HDL cholesterol was significantly higher in subjects with the A-3826G G allele in the normal group (p=0.032). Serum triglyceride and HDL cholesterol were also associated with the A-1766G variant in the recessive model (p=0.002, p=0.046).ConclusionsThese results suggest that that the A-3826G and A-1766G UCP-1 polymorphisms, which are related to obesity, might be candidate genetic markers for the DP pattern in the TKM diagnosis system.