RESUMO
Adaptive induction of thermogenesis in brown adipose tissue (BAT) is essential for the survival of mammals after birth. We show here that G protein-coupled receptor protein 120 (GPR120) expression is dramatically induced after birth in mouse BAT. GPR120 expression in neonatal BAT is the highest among GPR120-expressing tissues in the mouse at any developmental stage tested. The induction of GPR120 in neonatal BAT is caused by postnatal thermal stress rather than by the initiation of suckling. GPR120-null neonates were found to be relatively intolerant to cold: close to one-third did not survive at 21°C, but all such pups survived at 25°C. Heat production in BAT was significantly impaired in GPR120-null pups. Deficiency in GPR120 did not modify brown adipocyte morphology or the anatomical architecture of BAT, as assessed by electron microscopy, but instead impaired the expression of uncoupling protein-1 and the fatty acid oxidation capacity of neonatal BAT. Moreover, GPR120 deficiency impaired fibroblast growth factor 21 (FGF21) gene expression in BAT and reduced plasma FGF21 levels. These results indicate that GPR120 is essential for neonatal adaptive thermogenesis.
Assuntos
Tecido Adiposo Marrom/fisiologia , Animais Recém-Nascidos/fisiologia , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/fisiologia , Termogênese/fisiologia , Animais , Temperatura Baixa , Ácidos Graxos/metabolismo , Feminino , Fatores de Crescimento de Fibroblastos , Glucose/metabolismo , Transtornos de Estresse por Calor/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oxirredução , Palmitatos/metabolismo , Proteína Desacopladora 1/metabolismoRESUMO
Pref-1 (pre-adipocyte factor-1) is known to play a central role in regulating white adipocyte differentiation, but the role of Pref-1 in BAT (brown adipose tissue) has not been analysed. In the present study we found that Pref-1 expression is high in fetal BAT and declines progressively after birth. However, Pref-1-null mice showed unaltered fetal development of BAT, but exhibited signs of over-activation of BAT thermogenesis in the post-natal period. In C/EBP (CCAAT/enhancer-binding protein) α-null mice, a rodent model of impaired fetal BAT differentiation, Pref-1 was dramatically overexpressed, in association with reduced expression of the Ucp1 (uncoupling protein 1) gene, a BAT-specific marker of thermogenic differentiation. In brown adipocyte cell culture models, Pref-1 was mostly expressed in pre-adipocytes and declined with brown adipocyte differentiation. The transcription factor C/EBPδ activated the Pref-1 gene transcription in brown adipocytes, through binding to the proximal promoter region. Accordingly, siRNA (small interfering RNA)-induced C/EBPδ knockdown led to reduced Pref-1 gene expression. This effect is consistent with the observed overexpression of C/EBPδ in C/EBPα-null BAT and high expression of C/EBPδ in brown pre-adipocytes. Dexamethasone treatment of brown pre-adipocytes suppressed Pref-1 down-regulation occurring throughout the brown adipocyte differentiation process, increased the expression of C/EBPδ and strongly impaired expression of the thermogenic markers UCP1 and PGC-1α [PPARγ (peroxisome-proliferator-activated receptor γ) co-activator-α]. However, it did not alter normal fat accumulation or expression of non-BAT-specific genes. Collectively, these results specifically implicate Pref-1 in controlling the thermogenic gene expression program in BAT, and identify C/EBPδ as a novel transcriptional regulator of Pref-1 gene expression that may be related to the specific role of glucocorticoids in BAT differentiation.
Assuntos
Tecido Adiposo Marrom/metabolismo , Proteína delta de Ligação ao Facilitador CCAAT/fisiologia , Diferenciação Celular/fisiologia , Peptídeos e Proteínas de Sinalização Intercelular/fisiologia , Tecido Adiposo Marrom/citologia , Animais , Sequência de Bases , Northern Blotting , Proteína delta de Ligação ao Facilitador CCAAT/genética , Proteínas de Ligação ao Cálcio , Células Cultivadas , Imunoprecipitação da Cromatina , Primers do DNA , Regulação da Expressão Gênica , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Camundongos , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Reação em Cadeia da Polimerase em Tempo RealRESUMO
FGF21 is a novel metabolic regulator involved in the control of glucose homeostasis, insulin sensitivity, and ketogenesis. The liver has been considered the main site of production and release of FGF21 into the blood. Here, we show that, after thermogenic activation, brown adipose tissue becomes a source of systemic FGF21. This is due to a powerful cAMP-mediated pathway of regulation of FGF21 gene transcription. Norepinephrine, acting via ß-adrenergic, cAMP-mediated, mechanisms and subsequent activation of protein kinase A and p38 MAPK, induces FGF21 gene transcription and also FGF21 release in brown adipocytes. ATF2 binding to the FGF21 gene promoter mediates cAMP-dependent induction of FGF21 gene transcription. FGF21 release by brown fat in vivo was assessed directly by analyzing arteriovenous differences in FGF21 concentration across interscapular brown fat, in combination with blood flow to brown adipose tissue and assessment of FGF21 half-life. This analysis demonstrates that exposure of rats to cold induced a marked release of FGF21 by brown fat in vivo, in association with a reduction in systemic FGF21 half-life. The present findings lead to the recognition of a novel pathway of regulation the FGF21 gene and an endocrine role of brown fat, as a source of FGF21 that may be especially relevant in conditions of activation of thermogenic activity.
Assuntos
Tecido Adiposo Marrom/metabolismo , Glândulas Endócrinas/metabolismo , Fatores de Crescimento de Fibroblastos/biossíntese , Regulação da Expressão Gênica/fisiologia , Termogênese/fisiologia , Tecido Adiposo Marrom/citologia , Animais , Células Cultivadas , Temperatura Baixa , AMP Cíclico/genética , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/genética , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Glândulas Endócrinas/citologia , Ativação Enzimática/fisiologia , Fatores de Crescimento de Fibroblastos/genética , Masculino , Camundongos , Camundongos Mutantes , Ratos , Ratos Wistar , Transcrição Gênica/fisiologia , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Peroxisome proliferator activated receptor α (PPARα) is a distinctive marker of the brown fat phenotype that has been proposed to coordinate the transcriptional activation of genes for lipid oxidation and for thermogenic uncoupling protein 1 in brown adipose tissue. Here, we investigated the involvement of PPARα in the transcriptional control of the PPARγ coactivator (PGC)-1α gene. Treatment with PPARα agonists induced PGC-1α mRNA expression in brown fat in vivo and in primary brown adipocytes. This enhancement of PGC-1α transcription was mediated by PPARα binding to a PPAR-responsive element in the distal PGC-1α gene promoter. PGC-1α gene expression was decreased in PPARα-null brown fat, both under basal conditions and in response to thermogenic activation. Moreover, PPARα- and cAMP-mediated pathways interacted to control PGC-1α transcription. PRDM16 (PRD1-BF1-RIZ1 homologous domain-containing 16) promoted PPARα induction of PGC-1α gene transcription, especially under conditions in which protein kinase A pathways were activated. This enhancement was associated with the interaction of PRDM16 with the PGC-1α promoter at the PPARα-binding site. In addition, PPARα promoted the expression of the PRDM16 gene in brown adipocytes, and activation of PPARα in human white adipocytes led to the appearance of a brown adipocyte pattern of gene expression, including induction of PGC-1α and PRDM16. Collectively, these results suggest that PPARα acts as a key component of brown fat thermogenesis by coordinately regulating lipid catabolism and thermogenic gene expression via induction of PGC-1α and PRDM16.
Assuntos
Adipócitos Marrons/metabolismo , Proteínas de Ligação a DNA/metabolismo , PPAR alfa/metabolismo , Termogênese/fisiologia , Transativadores/metabolismo , Fatores de Transcrição/metabolismo , Animais , Western Blotting , Células Cultivadas , Imunoprecipitação da Cromatina , Proteínas de Ligação a DNA/genética , Feminino , Regulação da Expressão Gênica , Masculino , Camundongos , PPAR alfa/genética , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Ligação Proteica , Reação em Cadeia da Polimerase em Tempo Real , Termogênese/genética , Transativadores/genética , Fatores de Transcrição/genéticaRESUMO
Sirt3 (silent mating type information regulation 2, homolog 3), a member of the sirtuin family of protein deacetylases with multiple actions on metabolism and gene expression is expressed in association with brown adipocyte differentiation. Using Sirt3-null brown adipocytes, we determined that Sirt3 is required for an appropriate responsiveness of cells to noradrenergic, cAMP-mediated activation of the expression of brown adipose tissue thermogenic genes. The transcriptional coactivator Pgc-1α (peroxisome proliferator-activated receptor-γ coactivator-1α) induced Sirt3 gene expression in white adipocytes and embryonic fibroblasts as part of its overall induction of a brown adipose tissue-specific pattern of gene expression. In cells lacking Sirt3, Pgc-1α failed to fully induce the expression of brown fat-specific thermogenic genes. Pgc-1α activates Sirt3 gene transcription through coactivation of the orphan nuclear receptor Err (estrogen-related receptor)-α, which bound the proximal Sirt3 gene promoter region. Errα knockdown assays indicated that Errα is required for full induction of Sirt3 gene expression in response to Pgc-1α. The present results indicate that Pgc-1α controls Sirt3 gene expression and this action is an essential component of the overall mechanisms by which Pgc-1α induces the full acquisition of a brown adipocyte differentiated phenotype.
Assuntos
Tecido Adiposo Marrom/metabolismo , Regulação da Expressão Gênica , Sirtuína 3/metabolismo , Fatores de Transcrição/metabolismo , Animais , Núcleo Celular/metabolismo , Clonagem Molecular , AMP Cíclico/metabolismo , Fibroblastos/citologia , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Fenótipo , RNA Mensageiro/metabolismo , Receptores de Estrogênio/metabolismo , Receptor ERRalfa Relacionado ao EstrogênioRESUMO
Genetic modification approaches or pharmacological interventions may be useful for understanding the molecular mechanisms by which nutrient derivatives and metabolites exert their effects in the perinatal period and how they may influence longterm metabolism in adults. Examples for such experimental settings in rodents are targeted disruption of the gene for peroxisome proliferator-activated receptor (PPAR)-a, a lipid sensor and master regulator of lipid catabolism, or maternal treatment with agonists of PPARgamma, a master regulator of adipogenesis and target of insulin sensitizing drugs in adults. All these interventions show differential effects in the perinatal period compared to adults and indicate that altered activity of master regulators of metabolism results in profound metabolic alterations in the perinatal period that may influence adult metabolism.
Assuntos
Modelos Animais de Doenças , Fenômenos Fisiológicos da Nutrição Materna/efeitos dos fármacos , Fenômenos Fisiológicos da Nutrição Materna/genética , Doenças Metabólicas/genética , PPAR alfa/efeitos dos fármacos , PPAR alfa/genética , Tecido Adiposo Marrom , Animais , Animais Recém-Nascidos , Feminino , Regulação da Expressão Gênica/genética , Camundongos , Camundongos Knockout , Leite/metabolismo , Gravidez , RatosRESUMO
The beneficial effects of brown adipose tissue (BAT) are attributed to its capacity to oxidize metabolites and produce heat, but recent data suggest that secretory properties of BAT may also be involved. Here, we identify the chemokine CXCL14 (C-X-C motif chemokine ligand-14) as a novel regulatory factor secreted by BAT in response to thermogenic activation. We found that the CXCL14 released by brown adipocytes recruited alternatively activated (M2) macrophages. Cxcl14-null mice exposed to cold showed impaired BAT activity and low recruitment of macrophages, mainly of the M2 phenotype, into BAT. CXCL14 promoted the browning of white fat and ameliorated glucose/insulin homeostasis in high-fat-diet-induced obese mice. Impairment of type 2 cytokine signaling, as seen in Stat6-null mice, blunts the action of CXCL14, promoting adipose tissue browning. We propose that active BAT is a source of CXCL14, which concertedly promotes adaptive thermogenesis via M2 macrophage recruitment, BAT activation, and the browning of white fat.
Assuntos
Tecido Adiposo Marrom/metabolismo , Quimiocinas CXC/metabolismo , Obesidade/metabolismo , Termogênese , Adipócitos Marrons/metabolismo , Adulto , Animais , Células Cultivadas , Metabolismo Energético , Feminino , Glucose/metabolismo , Humanos , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Células RAW 264.7 , Ratos WistarRESUMO
Thiazolidinediones (TZDs) are insulin-sensitizing drugs currently used to treat type 2 diabetes. They are activators of peroxisome proliferator-activated receptor (PPAR)-gamma, and adipose tissue constitutes a major site for their biological effects. PPAR coactivator (PGC)-1alpha is a transcriptional coactivator of PPARgamma and other transcription factors. It is involved in the control of mitochondrial biogenesis, and its activity has been linked to insulin sensitization. Here we report that PGC-1alpha gene expression in brown and white adipocytes is a direct target of TZDs via PPARgamma activation. Activators of the retinoid X receptor also induce PGC-1alpha gene expression. This is due to the presence of a PPARgamma-responsive element in the distal region of the PGC-1alpha gene promoter that binds PPARgamma/retinoid X receptor heterodimers. Moreover, there is a positive autoregulatory loop of control of the PGC-1alpha gene through coactivation of PPARgamma responsiveness to TZDs by PGC-1alpha itself. These data indicate that some of the effects of TZDs, especially promotion of mitochondrial biogenesis and oxidative pathways in adipose depots, entail PGC-1alpha up-regulation via enhanced transcription of the PGC-1alpha gene.
Assuntos
Adipócitos/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Hipoglicemiantes/farmacologia , PPAR gama/fisiologia , Tiazolidinedionas/farmacologia , Transativadores/genética , Tretinoína/farmacologia , Células 3T3-L1 , Alitretinoína , Animais , Proteínas Quinases Dependentes de AMP Cíclico/fisiologia , Homeostase , Camundongos , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Elementos de Resposta , Rosiglitazona , Fatores de Transcrição , Ativação TranscricionalRESUMO
Uncoupling protein-3 (UCP3) is a member of the mitochondrial carrier family expressed preferentially in skeletal muscle and heart. It appears to be involved in metabolic handling of fatty acids in a way that minimizes excessive production of reactive oxygen species. Fatty acids are powerful regulators of UCP3 gene transcription. We have found that the role of peroxisome proliferator-activated receptor-alpha (PPARalpha) on the control of UCP3 gene expression depends on the tissue and developmental stage. In adults, UCP3 mRNA expression is unaltered in skeletal muscle from PPARalpha-null mice both in basal conditions and under the stimulus of starvation. In contrast, UCP3 mRNA is down-regulated in adult heart both in fed and fasted PPARalpha-null mice. This occurs despite the increased levels of free fatty acids caused by fasting in PPARalpha-null mice. In neonates, PPARalpha-null mice show impaired UCP3 mRNA expression in skeletal muscle in response to milk intake, and this is not a result of reduced free fatty acid levels. The murine UCP3 promoter is activated by fatty acids through either PPARalpha or PPARdelta but not by PPARgamma or retinoid X receptor alone. PPARdelta-dependent activation could be a potential compensatory mechanism to ensure appropriate expression of UCP3 gene in adult skeletal muscle in the absence of PPARalpha. However, among transcripts from other PPARalpha and PPARdelta target genes, only those acutely induced by milk intake in wild-type neonates were altered in muscle or heart from PPARalpha-null neonates. Thus, PPARalpha-dependent regulation is required for appropriate gene regulation of UCP3 as part of the subset of fatty-acid-responsive genes in neonatal muscle and heart.
Assuntos
Canais Iônicos/biossíntese , Canais Iônicos/genética , Proteínas Mitocondriais/biossíntese , Proteínas Mitocondriais/genética , PPAR alfa/fisiologia , Animais , Animais Recém-Nascidos , Células Cultivadas , Cromatina/metabolismo , Ingestão de Alimentos/fisiologia , Ensaio de Desvio de Mobilidade Eletroforética , Ácidos Graxos/fisiologia , Ácidos Graxos não Esterificados/sangue , Feminino , Hipolipemiantes/farmacologia , Immunoblotting , Imunoprecipitação , Camundongos , Camundongos Knockout , Leite/fisiologia , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , PPAR alfa/genética , Gravidez , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transfecção , Proteína Desacopladora 3RESUMO
C/EBPbeta (CCAAT/enhancer-binding protein beta) is a transcriptional regulator of the UCP1 (uncoupling protein-1) gene, the specific marker gene of brown adipocytes that is responsible for their thermogenic capacity. To investigate the role of C/EBPbeta in brown fat, we studied the C/EBPbeta-null mice. When placed in the cold, C/EBPbeta(-/-) mice did not maintain body temperature. This cold-sensitive phenotype occurred, although UCP1 and PGC-1alpha (peroxisome-proliferator-activated receptor gamma co-activator-1alpha) gene expression was unaltered in brown fat of C/EBPbeta(-/-) mice. The UCP1 gene promoter was repressed by the truncated inhibitory C/EBPbeta isoform LIP (liver-enriched transcriptional inhibitory protein, the truncated inhibitory C/EBPbeta isoform). Since C/EBPbeta-null mice lack both C/EBPbeta isoforms, active LAP (liver-enriched transcriptional activatory protein, the active C/EBPbeta isoform) and LIP, the absence of LIP may have a stronger effect than the absence of LAP upon UCP1 gene expression. Gene expression for UCP2 and UCP3 was not impaired in all tissues analysed. In primary brown adipocytes from C/EBPbeta(-/-) mice, induction of gene expression by noradrenaline was preserved. In contrast, the expression of genes related to lipid storage was impaired, as was the amount of triacylglycerol mobilized after acute cold exposure in brown fat from C/EBPbeta(-/-) mice. LPL (lipoprotein lipase) activity was also impaired in brown fat, but not in other tissues of C/EBPbeta(-/-) mice. LPL protein levels were also diminished, but this effect was independent of changes in LPL mRNA, suggesting that C/EBPbeta is involved in the post-transcriptional regulation of LPL gene expression in brown fat. In summary, defective thermoregulation owing to the lack of C/EBPbeta is associated with the reduced capacity to supply fatty acids as fuels to sustain brown fat thermogenesis.
Assuntos
Tecido Adiposo Marrom/efeitos dos fármacos , Tecido Adiposo Marrom/metabolismo , Adrenérgicos/farmacologia , Regulação da Temperatura Corporal/efeitos dos fármacos , Proteína beta Intensificadora de Ligação a CCAAT/fisiologia , Regulação da Expressão Gênica/efeitos dos fármacos , Metabolismo dos Lipídeos/efeitos dos fármacos , Adipócitos/metabolismo , Tecido Adiposo Marrom/enzimologia , Animais , Peso Corporal , Proteína alfa Estimuladora de Ligação a CCAAT/metabolismo , Proteína beta Intensificadora de Ligação a CCAAT/deficiência , Proteína beta Intensificadora de Ligação a CCAAT/genética , Proteína delta de Ligação ao Facilitador CCAAT/metabolismo , Proteínas de Transporte/genética , Células Cultivadas , Temperatura Baixa , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Ácidos Graxos/metabolismo , Deleção de Genes , Marcadores Genéticos/genética , Canais Iônicos , Lipase Lipoproteica/análise , Lipase Lipoproteica/sangue , Lipase Lipoproteica/metabolismo , Proteínas de Membrana/genética , Camundongos , Proteínas Mitocondriais , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Triglicerídeos/metabolismo , Proteína Desacopladora 1RESUMO
The thermogenic activity of brown adipose tissue (BAT) and browning of white adipose tissue are important components of energy expenditure. Here we show that GPR120, a receptor for polyunsaturated fatty acids, promotes brown fat activation. Using RNA-seq to analyse mouse BAT transcriptome, we find that the gene encoding GPR120 is induced by thermogenic activation. We further show that GPR120 activation induces BAT activity and promotes the browning of white fat in mice, whereas GRP120-null mice show impaired cold-induced browning. Omega-3 polyunsaturated fatty acids induce brown and beige adipocyte differentiation and thermogenic activation, and these effects require GPR120. GPR120 activation induces the release of fibroblast growth factor-21 (FGF21) by brown and beige adipocytes, and increases blood FGF21 levels. The effects of GPR120 activation on BAT activation and browning are impaired in FGF21-null mice and cells. Thus, the lipid sensor GPR120 activates brown fat via a mechanism that involves induction of FGF21.
Assuntos
Adipócitos/metabolismo , Tecido Adiposo Marrom/metabolismo , Tecido Adiposo Branco/metabolismo , Fatores de Crescimento de Fibroblastos/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Tecido Adiposo Marrom/efeitos dos fármacos , Tecido Adiposo Branco/efeitos dos fármacos , Animais , Regulação da Temperatura Corporal/fisiologia , Células Cultivadas , Temperatura Baixa , Ácido Eicosapentaenoico , Ácidos Graxos Ômega-3/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/fisiologia , Metilaminas/farmacologia , Camundongos , Camundongos Knockout , Propionatos/farmacologia , Receptores Acoplados a Proteínas G/genética , Regulação para Cima , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Lithium impairs the appearance of the characteristic morphology of brown adipocytes and downregulates the expression of marker genes of brown adipocyte differentiation. These effects are dose-dependent and are more pronounced when exposure of preadipocytes to lithium is initiated at early stages of differentiation. Although lithium reduces the expression of genes common to both white and brown adipocytes [fatty acid binding protein aP2 (aP2/FABP) or peroxisome proliferating activated receptor gamma], genes expressed differentially in brown adipocytes, i.e., uncoupling protein 1, PPAR gamma coactivator-1alpha, and peroxisome proliferating activated receptor alpha, are particularly sensitive to lithium treatment-dependent downregulation. Brown adipocytes appear as preferential targets of the inhibitory action of lithium on adipocyte differentiation.
Assuntos
Adipócitos/efeitos dos fármacos , Tecido Adiposo Marrom/citologia , Lítio/farmacologia , Adipócitos/citologia , Tecido Adiposo Marrom/efeitos dos fármacos , Animais , Biomarcadores/análise , Biomarcadores/metabolismo , Proteínas de Transporte/genética , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Células Cultivadas , Regulação para Baixo , Expressão Gênica/efeitos dos fármacos , Canais Iônicos , Proteínas de Membrana/genética , Camundongos , Proteínas Mitocondriais , Norepinefrina/farmacologia , RNA Mensageiro/análise , RNA Mensageiro/metabolismo , Tretinoína/farmacologia , Proteína Desacopladora 1RESUMO
OBJECTIVE: Human adipose depots contain remnant brown adipocytes interspersed among white adipocytes, and disturbances of brown with respect to white adipocyte biology have been implicated in highly active antiretroviral therapy (HAART)-induced lipomatosis. Brown adipocytes express the uncoupling protein-1 (UCP1) and contain a large number of mitochondria, potential targets of HAART toxicity. The aim of this study was to evaluate the effects of reverse transcriptase inhibitors (RTIs) on primary brown adipocytes differentiated in culture. DESIGN AND METHODS: We analysed the effects of RTIs, nucleoside analogues (NRTIs: stavudine, zidovudine, didanosine and lamivudine) and non-nucleoside analogues (NNRTIs: nevirapine and efavirenz), on differentiation, mitochondrial biogenesis and gene expression in brown adipocytes. RESULTS: None of the NRTIs altered brown adipocyte differentiation whereas NNTRIs had differing effects. Efavirenz blocked lipid deposition and expression of adipose marker genes but nevirapine induced lipid accumulation and adipose gene expression, promoted mitochondrial biogenesis and increased UCP1. Stavudine, zidovudine and didanosine reduced mitochondrial DNA (mtDNA) content. However, mitochondrial genome expression was only impaired in didanosine-treated adipocytes. Stavudine, but not zidovudine, induced expression of the mitochondrial transcription factors and this may explain compensatory mechanisms for the depletion of mtDNA by up-regulating mtDNA transcription. Stavudine caused a specific induction of UCP1 gene expression through direct interaction with a retinoic acid-dependent pathway. CONCLUSIONS: Specific disturbances in brown adipocytes in adipose depots may contribute to HAART-induced lipomatosis. Mitochondrial depletion does not appear to be the only mechanism explaining adverse effects in brown adipocytes because there is evidence of compensatory mechanisms that maintain mtDNA expression, and the expression of the UCP1 gene is specifically altered.
Assuntos
Tecido Adiposo Marrom/efeitos dos fármacos , Tecido Adiposo Marrom/metabolismo , Proteínas de Transporte/biossíntese , Proteínas de Membrana/biossíntese , Mitocôndrias/efeitos dos fármacos , Inibidores da Transcriptase Reversa/farmacologia , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , DNA Mitocondrial/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Canais Iônicos , Mitocôndrias/metabolismo , Proteínas Mitocondriais , Fatores de Transcrição/metabolismo , Proteína Desacopladora 1RESUMO
Uncoupling protein-3 (UCP3) gene is a member of the mitochondrial carrier superfamily preferentially expressed in skeletal muscle and up-regulated by fatty acids. Peroxisome proliferator-activated receptor (PPAR)alpha and PPARdelta (also known as PPARbeta) mediate human UCP3 gene regulation by fatty acids through a direct-repeat (DR-1) element in the promoter. DR-1 mutation renders UCP3 promoter unresponsive to PPAR ligand in vitro and consistently blocks gene induction by fatty acids in vivo. Although they act through separate sites in the promoter, MyoD and PPAR-dependent regulatory pathways are functionally connected: only in the presence of MyoD, does UCP3 become sensitive to PPAR ligand-dependent regulation. MyoD controls UCP3 promoter activity through a noncanonical Ebox site located in the proximal region, close to transcription initiation site. Moreover, acetylation processes play a crucial role in the control of UCP3 gene regulation. The coactivator p300 protein enhances PPAR ligand-mediated regulation whereas a mutant form devoid of histone acetylase activity blocks the response of the promoter to fatty acids. Conversely, histone deacetylase-1 blunts MyoD-dependent expression of the UCP3 promoter and reduces PPAR-dependent responsiveness. A mutated form of MyoD unable to be acetylated has a lower transactivation capacity on the human UCP3 promoter with respect to wild-type MyoD. It is concluded that MyoD and PPAR-dependent pathways mediate human UCP3 gene regulation and that acetylase activity elicited by coregulators is implicated in the functional interaction between these regulatory pathways. Therefore the convergence of MyoD and PPAR-dependent pathways provides a molecular mechanism for skeletal muscle specificity and fatty acid regulation of human UCP3 gene.
Assuntos
Proteínas de Transporte/genética , Músculo Esquelético/fisiologia , Proteína MyoD/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores Citoplasmáticos e Nucleares/fisiologia , Fatores de Transcrição/metabolismo , Animais , Proteínas de Transporte/metabolismo , Ácidos Graxos/farmacologia , Regulação da Expressão Gênica , Humanos , Técnicas In Vitro , Canais Iônicos , Proteínas Mitocondriais , Dados de Sequência Molecular , Proteína MyoD/genética , Receptores Citoplasmáticos e Nucleares/genética , Transdução de Sinais/efeitos dos fármacos , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia , Transcrição Gênica , Ativação Transcricional , Proteína Desacopladora 3RESUMO
FGF21 is a hormonal factor with important functions in the control of metabolism. FGF21 is found in rodent and human milk. Radiolabeled FGF21 administered to lactating dams accumulates in milk and is transferred to neonatal gut. The small intestine of neonatal (but not adult) mice highly expresses ß-Klotho in the luminal area. FGF21-KO pups fed by FGF21-KO dams showed decreased expression and circulating levels of incretins (GIP and GLP-1), reduced gene expression of intestinal lactase and maltase-glucoamylase, and low levels of galactose in plasma, all associated with a mild decrease in body weight. When FGF21-KO pups were nursed by wild-type dams (expressing FGF21 in milk), intestinal peptides and digestive enzymes were up-regulated, lactase enzymatic activity was induced, and galactose levels and body weight were normalized. Neonatal intestine explants were sensitive to FGF21, as evidenced by enhanced ERK1/2 phosphorylation. Oral infusion of FGF21 into neonatal pups induced expression of intestinal hormone factors and digestive enzymes, lactase activity and lactose absorption. These findings reveal a novel role of FGF21 as a hormonal factor contributing to neonatal intestinal function via its presence in maternal milk. Appropriate signaling of FGF21 to neonate is necessary to ensure optimal digestive and endocrine function in developing intestine.
Assuntos
Fatores de Crescimento de Fibroblastos/metabolismo , Mucosa Intestinal/metabolismo , Leite/metabolismo , Administração Oral , Animais , Animais Recém-Nascidos , Peso Corporal , Feminino , Fatores de Crescimento de Fibroblastos/administração & dosagem , Fatores de Crescimento de Fibroblastos/sangue , Galactose/sangue , Regulação da Expressão Gênica no Desenvolvimento , Glucuronidase , Hormônios/genética , Hormônios/metabolismo , Humanos , Incretinas/metabolismo , Absorção Intestinal/efeitos dos fármacos , Intestinos/enzimologia , Proteínas Klotho , Lactase/metabolismo , Lactação , Camundongos Knockout , Leite Humano/metabolismo , Modelos Biológicos , RatosRESUMO
High-fat diet leads to development of cardiac dysfunction through molecular mechanisms poorly known. The aim of this study is to elucidate the early events in cardiac dysfunction caused by a high-fat diet, before massive alterations due to obesity and indirect mechanisms of heart damage take place. Moreover, we analyzed the role of Sirt1, a major mediator of cardiac gene regulation, in these effects. Short-term high-fat feeding (5 weeks) caused a similar mild increase in body weight and triglyceridaemia in wild-type (wt) and Sirt1(+/-) mice. The high-fat diet suppressed the expression of lipid catabolism (PPARα target) gene expression in the hearts of wt mice, but not Sirt1(+/-) mice. Pro-inflammatory genes were induced and estrogen-related receptor-alpha (ERRα) target genes was suppressed in the hearts of wt fed the high-fat diet, but not in Sirt1(+/-) mice. We found the formation of a complex between PPARα and Sirt1 in wt mice under high-fat diet conditions which might account for suppression of the ERRα pathway. Sirt1 haploinsufficiency impairs the formation of this complex and promotes the binding of PPARα to the p65 subunit of NF-κB, thereby mediating inhibition of pro-inflammatory pathways and induction of PPARα target genes. Short-term high-fat diet causes metabolic and inflammatory alterations in heart, and Sirt1 is critical for mediating these cardiac alterations. The capacity of Sirt1 to interact with transcriptional regulators such as NF-κB and PPARα appears to be involved in the cardiac responsiveness to a high-fat diet.
Assuntos
Dieta Hiperlipídica/efeitos adversos , Coração/fisiologia , Sirtuína 1/metabolismo , Animais , Células Cultivadas , Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Transportador de Glucose Tipo 1/genética , Transportador de Glucose Tipo 1/metabolismo , Transportador de Glucose Tipo 4/genética , Transportador de Glucose Tipo 4/metabolismo , Coração/efeitos dos fármacos , Masculino , Camundongos Mutantes , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/fisiologia , NF-kappa B/metabolismo , PPAR alfa , Ratos Sprague-Dawley , Sirtuína 1/genéticaRESUMO
The developmental regulation of peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) gene expression was studied in mice and compared with that of marker genes of liver energy metabolism. The PGC-1alpha gene was highly expressed in fetal liver compared with that in adults and remained high in neonatal liver. The regulation of PGC-1alpha gene expression during the fetal and early neonatal periods was dissociated from that of gluconeogenic genes, i.e. the phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) genes. Only under the effects of starvation was PGC-1alpha gene expression induced in parallel to phosphoenolpyruvate carboxykinase and G6Pase mRNAs during the perinatal period. Furthermore, the PGC-1alpha gene was not regulated as part of the developmental program of gene expression associated with the maturation of hepatic gluconeogenesis, as revealed by the impaired PEPCK and G6Pase gene expression but unaltered PGC-1alpha mRNA levels in CCAAT/enhancer-binding protein-alpha-null fetus and neonates. Regulation of the PGC-1alpha gene and that of mitochondrial 3-hydroxy-3-methyl-glutaryl-coenzyme A synthase, acyl-coenzyme A oxidase, and long-chain acyl-coenzyme dehydrogenase, marker genes of lipid catabolism, were dissociated in fetuses and neonates. The expression of lipid catabolism genes was down-regulated in fasted neonates, whereas PGC-1alpha was oppositely regulated. The independent regulation of PGC-1alpha and lipid catabolism genes was also found in peroxisome proliferator-activated receptor-alpha-null neonates, in which PGC-1alpha mRNA levels were unaffected whereas gene expression for 3-hydroxy-3-methyl-glutaryl-coenzyme A synthase and acyl-coenzyme A oxidase was impaired. Thus, regulation of the PGC-1alpha gene is partially dissociated from the patterns of regulation of hepatic genes encoding enzymes involved in gluconeogenesis and lipid catabolism during fetal ontogeny and in response to the initiation of lactation.
Assuntos
Gluconeogênese/fisiologia , Metabolismo dos Lipídeos , Fígado/metabolismo , Fatores de Transcrição/genética , Animais , Animais Recém-Nascidos , Proteína alfa Estimuladora de Ligação a CCAAT/metabolismo , Jejum , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Lactação/fisiologia , Fígado/embriologia , Fígado/crescimento & desenvolvimento , Camundongos , Oxirredução , Gravidez , RNA Mensageiro/análise , Receptores Citoplasmáticos e Nucleares/metabolismo , Fatores de Transcrição/metabolismo , Regulação para CimaRESUMO
The phytol derivatives phytanic acid and pristanic acid may activate nuclear hormone receptors and influence gene expression and cell differentiation. Phytanic acid induces brown adipocyte differentiation. It was determined that brown fat and brown adipocytes are sites of high gene expression of phytanoyl-CoA hydroxylase, the enzyme required for initiation of peroxisomal alpha-oxidation of phytanic acid. However, the effects of phytanic acid were not mediated by its alpha-oxidation product pristanic acid, which did not promote brown adipocyte differentiation or stimulate transcription of the uncoupling protein-1 gene. Moreover, acute cold exposure of mice caused a dramatic mobilization of the phytanic acid stores in brown adipose tissue thus suggesting that a high local exposure to phytanic acid in brown fat may contribute to signalling adaptive changes in the tissue in response to thermogenic activation.
Assuntos
Adipócitos/efeitos dos fármacos , Tecido Adiposo Marrom/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Ácidos Graxos/farmacologia , Ácido Fitânico/farmacologia , Regiões Promotoras Genéticas/efeitos dos fármacos , Adipócitos/citologia , Adipócitos/metabolismo , Tecido Adiposo Marrom/química , Tecido Adiposo Marrom/metabolismo , Animais , Proteínas de Transporte/genética , Diferenciação Celular/fisiologia , Temperatura Baixa , Ácidos Graxos/metabolismo , Canais Iônicos , Proteínas de Membrana/genética , Camundongos , Proteínas Mitocondriais , Oxigenases de Função Mista/biossíntese , Oxigenases de Função Mista/genética , Ácido Fitânico/metabolismo , Fitol/análogos & derivados , Fitol/metabolismo , Fitol/farmacologia , RNA Mensageiro/biossíntese , Termogênese/efeitos dos fármacos , Termogênese/fisiologia , Proteína Desacopladora 1RESUMO
Fibroblast growth factor 21 (FGF21) is a member of the FGF family that reduces glycemia and ameliorates insulin resistance. Adipose tissue is a main target of FGF21 action. Obesity is associated with a chronic proinflammatory state. Here, we analyzed the role of proinflammatory signals in the FGF21 pathway in adipocytes, evaluating the effects of TNF-α on ß-Klotho and FGF receptor-1 expression and FGF21 action in adipocytes. We also determined the effects of rosiglitazone on ß-Klotho and FGF receptor-1 expression in models of proinflammatory signal induction in vitro and in vivo (high-fat diet-induced obesity). Because c-Jun NH(2)-terminal kinase 1 (JNK1) serves as a sensing juncture for inflammatory status, we also evaluated the involvement of JNK1 in the FGF21 pathway. TNF-α repressed ß-Klotho expression and impaired FGF21 action in adipocytes. Rosiglitazone prevented the reduction in ß-Klotho expression elicited by TNF-α. Moreover, ß-Klotho levels were reduced in adipose tissue from high-fat diet-induced obese mice, whereas rosiglitazone restored ß-Klotho to near-normal levels. ß-Klotho expression was increased in white fat from JNK1(-/-) mice. The absence of JNK1 increased the responsiveness of mouse embryonic fibroblast-derived adipocytes and brown adipocytes to FGF21. In conclusion, we show that proinflammatory signaling impairs ß-Klotho expression and FGF21 responsiveness in adipocytes. We also show that JNK1 activity is involved in modulating FGF21 effects in adipocytes. The impairment in the FGF21 response machinery in adipocytes and the reduction in FGF21 action in response to proinflammatory signals may play important roles in metabolic alterations in obesity and other diseases associated with enhanced inflammation.
Assuntos
Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Fatores de Crescimento de Fibroblastos/metabolismo , Proteínas de Membrana/metabolismo , Proteína Quinase 8 Ativada por Mitógeno/metabolismo , Células 3T3-L1 , Animais , Linhagem Celular , Fatores de Crescimento de Fibroblastos/genética , Humanos , Immunoblotting , Proteínas Klotho , Masculino , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Proteína Quinase 8 Ativada por Mitógeno/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
Retinol binding protein-4 (RBP4) is a serum protein involved in the transport of vitamin A. It is known to be produced by the liver and white adipose tissue. RBP4 release by white fat has been proposed to induce insulin resistance. We analyzed the regulation and production of RBP4 in brown adipose tissue. RBP4 gene expression is induced in brown fat from mice exposed to cold or treated with peroxisome proliferator-activated receptor (PPAR) agonists. In brown adipocytes in culture, norepinephrine, cAMP, and activators of PPARγ and PPARα induced RBP4 gene expression and RBP4 protein release. The induction of RBP4 gene expression by norepinephrine required intact PPAR-dependent pathways, as evidenced by impaired response of the RBP4 gene expression to norepinephrine in PPARα-null brown adipocytes or in the presence of inhibitors of PPARγ and PPARα. PPARγ and norepinephrine can also induce the RBP4 gene in white adipocytes, and overexpression of PPARα confers regulation by this PPAR subtype to white adipocytes. The RBP4 gene promoter transcription is activated by cAMP, PPARα, and PPARγ. This is mediated by a PPAR-responsive element capable of binding PPARα and PPARγ and required also for activation by cAMP. The induction of the RBP4 gene expression by norepinephrine in brown adipocytes is protein synthesis dependent and requires PPARγ-coactivator-1-α, which acts as a norepinephine-induced coactivator of PPAR on the RBP4 gene. We conclude that PPARγ- and PPARα-mediated signaling controls RBP4 gene expression and releases in brown adipose tissue, and thermogenic activation induces RBP4 gene expression in brown fat through mechanisms involving PPARγ-coactivator-1-α coactivation of PPAR signaling.