RESUMO
Mammalian transcriptomes display complex circadian rhythms with multiple phases of gene expression that cannot be accounted for by current models of the molecular clock. We have determined the underlying mechanisms by measuring nascent RNA transcription around the clock in mouse liver. Unbiased examination of enhancer RNAs (eRNAs) that cluster in specific circadian phases identified functional enhancers driven by distinct transcription factors (TFs). We further identify on a global scale the components of the TF cistromes that function to orchestrate circadian gene expression. Integrated genomic analyses also revealed mechanisms by which a single circadian factor controls opposing transcriptional phases. These findings shed light on the diversity and specificity of TF function in the generation of multiple phases of circadian gene transcription in a mammalian organ.
Assuntos
Ritmo Circadiano , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica , Transcrição Gênica , Animais , Fatores de Transcrição de Zíper de Leucina Básica/genética , Relógios Circadianos , Fígado/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Membro 1 do Grupo D da Subfamília 1 de Receptores Nucleares/genéticaRESUMO
Molecular clocks in the periphery coordinate tissue-specific daily biorhythms by integrating input from the hypothalamic master clock and intracellular metabolic signals. One such key metabolic signal is the cellular concentration of NAD+, which oscillates along with its biosynthetic enzyme, nicotinamide phosphoribosyltransferase (NAMPT). NAD+ levels feed back into the clock to influence rhythmicity of biological functions, yet whether this metabolic fine-tuning occurs ubiquitously across cell types and is a core clock feature is unknown. Here, we show that NAMPT-dependent control over the molecular clock varies substantially between tissues. Brown adipose tissue (BAT) requires NAMPT to sustain the amplitude of the core clock, whereas rhythmicity in white adipose tissue (WAT) is only moderately dependent on NAD+ biosynthesis, and the skeletal muscle clock is completely refractory to loss of NAMPT. In BAT and WAT, NAMPT differentially orchestrates oscillation of clock-controlled gene networks and the diurnality of metabolite levels. NAMPT coordinates the rhythmicity of TCA cycle intermediates in BAT, but not in WAT, and loss of NAD+ abolishes these oscillations similarly to high-fat diet-induced circadian disruption. Moreover, adipose NAMPT depletion improved the ability of animals to defend body temperature during cold stress but in a time-of-day-independent manner. Thus, our findings reveal that peripheral molecular clocks and metabolic biorhythms are shaped in a highly tissue-specific manner by NAMPT-dependent NAD+ synthesis.
Assuntos
NAD , Nicotinamida Fosforribosiltransferase , Animais , NAD/metabolismo , Nicotinamida Fosforribosiltransferase/genética , Nicotinamida Fosforribosiltransferase/metabolismo , Ritmo Circadiano/fisiologia , Tecido Adiposo Marrom/metabolismo , Obesidade/metabolismo , Citocinas/metabolismoRESUMO
Brown adipose tissue is a thermogenic organ that dissipates chemical energy as heat to protect animals against hypothermia and to counteract metabolic disease. However, the transcriptional mechanisms that determine the thermogenic capacity of brown adipose tissue before environmental cold are unknown. Here we show that histone deacetylase 3 (HDAC3) is required to activate brown adipose tissue enhancers to ensure thermogenic aptitude. Mice with brown adipose tissue-specific genetic ablation of HDAC3 become severely hypothermic and succumb to acute cold exposure. Uncoupling protein 1 (UCP1) is nearly absent in brown adipose tissue lacking HDAC3, and there is also marked downregulation of mitochondrial oxidative phosphorylation genes resulting in diminished mitochondrial respiration. Remarkably, although HDAC3 acts canonically as a transcriptional corepressor, it functions as a coactivator of oestrogen-related receptor α (ERRα) in brown adipose tissue. HDAC3 coactivation of ERRα is mediated by deacetylation of PGC-1α and is required for the transcription of Ucp1, Ppargc1a (encoding PGC-1α), and oxidative phosphorylation genes. Importantly, HDAC3 promotes the basal transcription of these genes independently of adrenergic stimulation. Thus, HDAC3 uniquely primes Ucp1 and the thermogenic transcriptional program to maintain a critical capacity for thermogenesis in brown adipose tissue that can be rapidly engaged upon exposure to dangerously cold temperature.
Assuntos
Tecido Adiposo Marrom/metabolismo , Regulação da Expressão Gênica , Histona Desacetilases/metabolismo , Termogênese , Animais , Respiração Celular , Temperatura Baixa , Elementos Facilitadores Genéticos/genética , Temperatura Alta , Humanos , Masculino , Camundongos , Mitocôndrias/metabolismo , Fosforilação Oxidativa , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/genética , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Receptores de Estrogênio/metabolismo , Termogênese/genética , Proteína Desacopladora 1/genética , Proteína Desacopladora 1/metabolismo , Receptor ERRalfa Relacionado ao EstrogênioRESUMO
Thyroid hormones are important for homeostatic control of energy metabolism and body temperature. Although skeletal muscle is considered a key site for thyroid action, the contribution of thyroid hormone receptor signaling in muscle to whole-body energy metabolism and body temperature has not been resolved. Here, we show that T3-induced increase in energy expenditure requires thyroid hormone receptor alpha 1 (TRα1 ) in skeletal muscle, but that T3-mediated elevation in body temperature is achieved in the absence of muscle-TRα1 . In slow-twitch soleus muscle, loss-of-function of TRα1 (TRαHSACre ) alters the fiber-type composition toward a more oxidative phenotype. The change in fiber-type composition, however, does not influence the running capacity or motivation to run. RNA-sequencing of soleus muscle from WT mice and TRαHSACre mice revealed differentiated transcriptional regulation of genes associated with muscle thermogenesis, such as sarcolipin and UCP3, providing molecular clues pertaining to the mechanistic underpinnings of TRα1 -linked control of whole-body metabolic rate. Together, this work establishes a fundamental role for skeletal muscle in T3-stimulated increase in whole-body energy expenditure.
Assuntos
Metabolismo Energético/efeitos dos fármacos , Fibras Musculares de Contração Rápida/fisiologia , Fibras Musculares de Contração Lenta/fisiologia , Músculo Esquelético/fisiologia , Receptores alfa dos Hormônios Tireóideos/fisiologia , Hormônios Tireóideos/farmacologia , Animais , Masculino , Camundongos , Camundongos Knockout , Fibras Musculares de Contração Rápida/citologia , Fibras Musculares de Contração Rápida/efeitos dos fármacos , Fibras Musculares de Contração Lenta/citologia , Fibras Musculares de Contração Lenta/efeitos dos fármacos , Músculo Esquelético/citologia , Músculo Esquelético/efeitos dos fármacos , Condicionamento Físico Animal , TranscriptomaRESUMO
Insulin orchestrates metabolic homeostasis through a complex signaling network for which the precise mechanisms controlling its fine-tuning are not completely understood. Here, we report that Afadin, a scaffold protein, is phosphorylated on S1795 (S1718 in humans) in response to insulin in adipocytes, and this phosphorylation is impaired with obesity and insulin resistance. In turn, loss of Afadin enhances the response to insulin in adipose tissues via upregulation of the insulin receptor protein levels. This happens in a cell-autonomous and phosphorylation-dependent manner. Insulin-stimulated Afadin-S1795 phosphorylation modulates Afadin binding with interaction partners in adipocytes, among which HDAC6 preferentially interacts with phosphorylated Afadin and acts as a key intermediate to suppress insulin receptor protein levels. Adipose tissue-specific Afadin depletion protects against insulin resistance and improves glucose homeostasis in diet-induced obese mice, independently of adiposity. Altogether, we uncover a novel insulin-induced cellular feedback mechanism governed by the interaction of Afadin with HDAC6 to negatively control insulin action in adipocytes, which may offer new strategies to alleviate insulin resistance.
Assuntos
Tecido Adiposo/metabolismo , Antígenos CD/genética , Desacetilase 6 de Histona/genética , Insulina/genética , Proteínas dos Microfilamentos/genética , Obesidade/genética , Processamento de Proteína Pós-Traducional , Receptor de Insulina/genética , Células 3T3-L1 , Adipócitos/metabolismo , Adipócitos/patologia , Tecido Adiposo/patologia , Animais , Antígenos CD/metabolismo , Dieta Hiperlipídica/efeitos adversos , Glucose/metabolismo , Desacetilase 6 de Histona/metabolismo , Homeostase/genética , Humanos , Insulina/metabolismo , Insulina/farmacologia , Resistência à Insulina , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas dos Microfilamentos/metabolismo , Obesidade/etiologia , Obesidade/metabolismo , Obesidade/patologia , Fosforilação , Cultura Primária de Células , Receptor de Insulina/metabolismoRESUMO
Circadian oscillation of body temperature is a basic, evolutionarily conserved feature of mammalian biology. In addition, homeostatic pathways allow organisms to protect their core temperatures in response to cold exposure. However, the mechanism responsible for coordinating daily body temperature rhythm and adaptability to environmental challenges is unknown. Here we show that the nuclear receptor Rev-erbα (also known as Nr1d1), a powerful transcriptional repressor, links circadian and thermogenic networks through the regulation of brown adipose tissue (BAT) function. Mice exposed to cold fare considerably better at 05:00 (Zeitgeber time 22) when Rev-erbα is barely expressed than at 17:00 (Zeitgeber time 10) when Rev-erbα is abundant. Deletion of Rev-erbα markedly improves cold tolerance at 17:00, indicating that overcoming Rev-erbα-dependent repression is a fundamental feature of the thermogenic response to cold. Physiological induction of uncoupling protein 1 (Ucp1) by cold temperatures is preceded by rapid downregulation of Rev-erbα in BAT. Rev-erbα represses Ucp1 in a brown-adipose-cell-autonomous manner and BAT Ucp1 levels are high in Rev-erbα-null mice, even at thermoneutrality. Genetic loss of Rev-erbα also abolishes normal rhythms of body temperature and BAT activity. Thus, Rev-erbα acts as a thermogenic focal point required for establishing and maintaining body temperature rhythm in a manner that is adaptable to environmental demands.
Assuntos
Regulação da Temperatura Corporal/fisiologia , Ritmo Circadiano/fisiologia , Membro 1 do Grupo D da Subfamília 1 de Receptores Nucleares/metabolismo , Aclimatação/genética , Aclimatação/fisiologia , Tecido Adiposo Marrom/metabolismo , Animais , Regulação da Temperatura Corporal/genética , Ritmo Circadiano/genética , Temperatura Baixa , Regulação para Baixo , Canais Iônicos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Mitocondriais/metabolismo , Membro 1 do Grupo D da Subfamília 1 de Receptores Nucleares/deficiência , Membro 1 do Grupo D da Subfamília 1 de Receptores Nucleares/genética , Termogênese/genética , Termogênese/fisiologia , Fatores de Tempo , Proteína Desacopladora 1RESUMO
The NAD(+)-dependent deacetylase SIRT1 is an evolutionarily conserved metabolic sensor of the Sirtuin family that mediates homeostatic responses to certain physiological stresses such as nutrient restriction. Previous reports have implicated fluctuations in intracellular NAD(+) concentrations as the principal regulator of SIRT1 activity. However, here we have identified a cAMP-induced phosphorylation of a highly conserved serine (S434) located in the SIRT1 catalytic domain that rapidly enhanced intrinsic deacetylase activity independently of changes in NAD(+) levels. Attenuation of SIRT1 expression or the use of a nonphosphorylatable SIRT1 mutant prevented cAMP-mediated stimulation of fatty acid oxidation and gene expression linked to this pathway. Overexpression of SIRT1 in mice significantly potentiated the increases in fatty acid oxidation and energy expenditure caused by either pharmacological ß-adrenergic agonism or cold exposure. These studies support a mechanism of Sirtuin enzymatic control through the cAMP/PKA pathway with important implications for stress responses and maintenance of energy homeostasis.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Ácidos Graxos/metabolismo , NAD/metabolismo , Transdução de Sinais , Sirtuína 1/metabolismo , Acetilação , Sequência de Aminoácidos , Animais , Células Cultivadas , Humanos , Masculino , Camundongos , Camundongos Transgênicos , Dados de Sequência Molecular , Oxirredução , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação , Fosfosserina/metabolismo , Transativadores/metabolismo , Fatores de TranscriçãoRESUMO
Circadian clocks harmonize processes ranging from intracellular biochemistry to whole-body physiology in accordance with the Earth's 24h rotation. These intrinsic oscillators are based on an interlocked transcriptional-translational feedback loop comprised from a set of core clock factors. In addition to maintaining rhythmicity in nearly every cell of the body, these clock factors also mediate tissue specific metabolic functions. In this review, we will explore how the molecular clock shapes the unique features of different adipose depots.
Assuntos
Tecido Adiposo/fisiologia , Ritmo Circadiano/fisiologia , Animais , HumanosRESUMO
Normal epithelial cells require matrix attachment for survival, and the ability of tumour cells to survive outside their natural extracellular matrix (ECM) niches is dependent on acquisition of anchorage independence. Although apoptosis is the most rapid mechanism for eliminating cells lacking appropriate ECM attachment, recent reports suggest that non-apoptotic death processes prevent survival when apoptosis is inhibited in matrix-deprived cells. Here we demonstrate that detachment of mammary epithelial cells from ECM causes an ATP deficiency owing to the loss of glucose transport. Overexpression of ERBB2 rescues the ATP deficiency by restoring glucose uptake through stabilization of EGFR and phosphatidylinositol-3-OH kinase (PI(3)K) activation, and this rescue is dependent on glucose-stimulated flux through the antioxidant-generating pentose phosphate pathway. Notably, we found that the ATP deficiency could be rescued by antioxidant treatment without rescue of glucose uptake. This rescue was found to be dependent on stimulation of fatty acid oxidation, which is inhibited by detachment-induced reactive oxygen species (ROS). The significance of these findings was supported by evidence of an increase in ROS in matrix-deprived cells in the luminal space of mammary acini, and the discovery that antioxidants facilitate the survival of these cells and enhance anchorage-independent colony formation. These results show both the importance of matrix attachment in regulating metabolic activity and an unanticipated mechanism for cell survival in altered matrix environments by antioxidant restoration of ATP generation.
Assuntos
Antioxidantes/metabolismo , Células Epiteliais/metabolismo , Matriz Extracelular/metabolismo , Oncogenes/fisiologia , Receptor ErbB-2/metabolismo , Trifosfato de Adenosina/metabolismo , Anoikis/fisiologia , Mama/citologia , Mama/metabolismo , Mama/patologia , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Adesão Celular , Linhagem Celular , Sobrevivência Celular , Ativação Enzimática , Células Epiteliais/citologia , Células Epiteliais/patologia , Receptores ErbB/metabolismo , Ácidos Graxos/metabolismo , Glucose/metabolismo , Humanos , Oncogenes/genética , Via de Pentose Fosfato/fisiologia , Fosfatidilinositol 3-Quinases/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Receptor ErbB-2/genéticaRESUMO
AMP-activated protein kinase (AMPK) is a metabolic fuel gauge conserved along the evolutionary scale in eukaryotes that senses changes in the intracellular AMP/ATP ratio. Recent evidence indicated an important role for AMPK in the therapeutic benefits of metformin, thiazolidinediones and exercise, which form the cornerstones of the clinical management of type 2 diabetes and associated metabolic disorders. In general, activation of AMPK acts to maintain cellular energy stores, switching on catabolic pathways that produce ATP, mostly by enhancing oxidative metabolism and mitochondrial biogenesis, while switching off anabolic pathways that consume ATP. This regulation can take place acutely, through the regulation of fast post-translational events, but also by transcriptionally reprogramming the cell to meet energetic needs. Here we demonstrate that AMPK controls the expression of genes involved in energy metabolism in mouse skeletal muscle by acting in coordination with another metabolic sensor, the NAD+-dependent type III deacetylase SIRT1. AMPK enhances SIRT1 activity by increasing cellular NAD+ levels, resulting in the deacetylation and modulation of the activity of downstream SIRT1 targets that include the peroxisome proliferator-activated receptor-gamma coactivator 1alpha and the forkhead box O1 (FOXO1) and O3 (FOXO3a) transcription factors. The AMPK-induced SIRT1-mediated deacetylation of these targets explains many of the convergent biological effects of AMPK and SIRT1 on energy metabolism.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Metabolismo Energético , NAD/metabolismo , Sirtuínas/metabolismo , Acetilação , Aminoimidazol Carboxamida/análogos & derivados , Animais , Linhagem Celular , Metabolismo Energético/genética , Ativação Enzimática , Proteína Forkhead Box O1 , Proteína Forkhead Box O3 , Fatores de Transcrição Forkhead/genética , Regulação da Expressão Gênica , Genes Mitocondriais/genética , Masculino , Camundongos , Músculo Esquelético/citologia , Músculo Esquelético/enzimologia , Músculo Esquelético/metabolismo , Mutação , Consumo de Oxigênio , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação , Ribonucleotídeos , Sirtuína 1 , Transativadores/genética , Transativadores/metabolismo , Fatores de Transcrição , Transcrição GênicaRESUMO
Fatty acids are essential components of the dynamic lipid metabolism in cells. Fatty acids can also signal to intracellular pathways to trigger a broad range of cellular responses. Oleic acid is an abundant monounsaturated omega-9 fatty acid that impinges on different biological processes, but the mechanisms of action are not completely understood. Here, we report that oleic acid stimulates the cAMP/protein kinase A pathway and activates the SIRT1-PGC1α transcriptional complex to modulate rates of fatty acid oxidation. In skeletal muscle cells, oleic acid treatment increased intracellular levels of cyclic adenosine monophosphate (cAMP) that turned on protein kinase A activity. This resulted in SIRT1 phosphorylation at Ser-434 and elevation of its catalytic deacetylase activity. A direct SIRT1 substrate is the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α), which became deacetylated and hyperactive after oleic acid treatment. Importantly, oleic acid, but not other long chain fatty acids such as palmitate, increased the expression of genes linked to fatty acid oxidation pathway in a SIRT1-PGC1α-dependent mechanism. As a result, oleic acid potently accelerated rates of complete fatty acid oxidation in skeletal muscle cells. These results illustrate how a single long chain fatty acid specifically controls lipid oxidation through a signaling/transcriptional pathway. Pharmacological manipulation of this lipid signaling pathway might provide therapeutic possibilities to treat metabolic diseases associated with lipid dysregulation.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Ácidos Graxos/metabolismo , Ácido Oleico/farmacologia , Sirtuína 1/metabolismo , Transativadores/metabolismo , Acetilação/efeitos dos fármacos , Animais , Western Blotting , Linhagem Celular , Células Cultivadas , Transferência Ressonante de Energia de Fluorescência , Camundongos , Camundongos Endogâmicos C57BL , Complexos Multiproteicos/metabolismo , Músculo Esquelético/citologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Mutação , Oxirredução/efeitos dos fármacos , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo , Fosforilação/efeitos dos fármacos , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Serina/genética , Serina/metabolismo , Sirtuína 1/genética , Transativadores/genética , Fatores de Transcrição , Ativação Transcricional/efeitos dos fármacosRESUMO
CONTEXT: Housing temperature is a critical regulator of mouse metabolism and thermoneutral housing can improve model translation to humans. However, the impact of housing temperature on the ability of wheel running exercise training to rescue the detrimental effect of diet-induced obese mice is currently not fully understood. OBJECTIVE: To investigate how housing temperature affects muscle metabolism in obese mice with regard to calcium handling and exercise training (ET) adaptations in skeletal muscle, and benefits of ET on adiposity and glucometabolic parameters. METHODS: Lean or obese female mice were housed at standard ambient temperature (22 °C) or thermoneutrality (30 °C) with/without access to running wheels. The metabolic phenotype was investigated using glucose tolerance tests, indirect calorimetry, and body composition. Molecular muscle adaptations were measured using immunoblotting, qPCR, and spectrophotometric/fluorescent assays. RESULTS: Obese female mice housed at 22 °C showed lower adiposity, lower circulating insulin levels, improved glucose tolerance, and elevated basal metabolic rate compared to 30 °C housing. Mice exposed to voluntary wheel running exhibited a larger fat loss and higher metabolic rate at 22 °C housing compared to thermoneutrality. In obese female mice, glucose tolerance improved after ET independent of housing temperature. Independent of diet and training, 22 °C housing increased skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) activity. Additionally, housing at 22 °C elevated the induction of training-responsive muscle proteins in obese mice. CONCLUSION: Our findings highlight that housing temperature significantly influences adiposity, insulin sensitivity, muscle physiology, and exercise adaptations in diet-induced obese female mice.
Assuntos
Adaptação Fisiológica , Cálcio , Músculo Esquelético , Obesidade , Condicionamento Físico Animal , Animais , Feminino , Condicionamento Físico Animal/fisiologia , Músculo Esquelético/metabolismo , Camundongos , Obesidade/metabolismo , Obesidade/fisiopatologia , Cálcio/metabolismo , Adaptação Fisiológica/fisiologia , Camundongos Endogâmicos C57BL , Resposta ao Choque Frio/fisiologia , Camundongos Obesos , Temperatura Baixa , Adiposidade/fisiologiaRESUMO
BACKGROUND: Statin therapy has shown pleiotropic effects affecting both mitochondrial function and inflammatory status. However, few studies have investigated the concurrent effects of statin exposure on mitochondrial function and inflammatory status in human subcutaneous white adipose tissue. OBJECTIVES: In a cross-sectional study, we investigated the effects of simvastatin on mitochondrial function and inflammatory status in subcutaneous white adipose tissue of 55 human participants: 38 patients (19 females/19 males) in primary prevention with simvastatin (> 40 mg/d, > 3 mo) and 17 controls (9 females/8 males) with elevated plasma cholesterol. The 2 groups were matched on age, body mass index, and maximal oxygen consumption. METHODS: Anthropometrics and fasting biochemical characteristics were measured. Mitochondrial respiratory capacity was assessed in white adipose tissue by high-resolution respirometry. Subcutaneous white adipose tissue expression of the inflammatory markers IL-6, chemokine (C-C motif) ligand 2 (CCL2), CCL-5, tumor necrosis factor-α, IL-10, and IL-4 was analyzed by quantitative PCR. RESULTS: Simvastatin-treated patients showed lower plasma cholesterol (P < .0001), low-density lipoprotein (P < .0001), and triglyceride levels (P = .0116) than controls. Simvastatin-treated patients had a lower oxidative phosphorylation capacity of mitochondrial complex II (P = .0001 when normalized to wet weight, P < .0001 when normalized to citrate synthase activity [intrinsic]), and a lower intrinsic mitochondrial electron transport system capacity (P = .0004). Simvastatin-treated patients showed higher IL-6 expression than controls (P = .0202). CONCLUSION: Simvastatin treatment was linked to mitochondrial respiratory capacity in human subcutaneous white adipose tissue, but no clear link was found between statin exposure, respiratory changes, and inflammatory status of adipose tissue.
Assuntos
Inibidores de Hidroximetilglutaril-CoA Redutases , Sinvastatina , Masculino , Feminino , Humanos , Sinvastatina/efeitos adversos , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Interleucina-6/metabolismo , Estudos Transversais , Mitocôndrias/metabolismo , Tecido Adiposo Branco/metabolismo , Colesterol/metabolismo , Tecido Adiposo/metabolismoRESUMO
Exploring mechanisms responsible for brown adipose tissue's (BAT) high metabolic activity is crucial to exploit its energy-dissipating ability for therapeutic purposes. Basigin (Bsg), a multifunctional highly glycosylated transmembrane protein, was recently proposed as one of the 98 critical markers allowing to distinguish 'white' and 'brown' adipocytes, yet its function in thermogenic brown adipocytes is unknown. Here, we report that Bsg is negatively associated with obesity in mice. By contrast, Bsg expression increased in the mature adipocyte fraction of BAT upon cold acclimation. Additionally, Bsg levels were highly induced during brown adipocyte maturation in vitro and were further increased upon ß-adrenergic stimulation in a HIF-1α-dependent manner. siRNA-mediated Bsg gene silencing in cultured brown adipocytes did not impact adipogenesis nor mitochondrial function. However, a significant decrease in mitochondrial respiration, lipolysis and Ucp1 transcription was observed in adipocytes lacking Bsg, when activated by norepinephrine. Furthermore, using gas chromatography/mass spectrometry-time-of-flight analysis to assess the composition of cellular metabolites, we demonstrate that brown adipocytes lacking Bsg have lower levels of intracellular lactate and acetoacetate. Bsg was additionally required to regulate intracellular AcAc and tricarboxylic acid cycle intermediate levels in NE-stimulated adipocytes. Our study highlights the critical role of Bsg in active brown adipocytes, possibly by controlling cellular metabolism.
Assuntos
Adipócitos Marrons , Tecido Adiposo Marrom , Camundongos , Animais , Adipócitos Marrons/metabolismo , Tecido Adiposo Marrom/metabolismo , Basigina/metabolismo , Lipólise , Obesidade/metabolismo , Termogênese/genética , Proteína Desacopladora 1/genética , Proteína Desacopladora 1/metabolismoRESUMO
Thermogenesis by uncoupling protein 1 (UCP1) is one of the primary mechanisms by which brown adipose tissue (BAT) increases energy expenditure. UCP1 resides in the inner mitochondrial membrane (IMM), where it dissipates membrane potential independent of adenosine triphosphate (ATP) synthase. Here, we provide evidence that phosphatidylethanolamine (PE) modulates UCP1-dependent proton conductance across the IMM to modulate thermogenesis. Mitochondrial lipidomic analyses revealed PE as a signature molecule whose abundance bidirectionally responds to changes in thermogenic burden. Reduction in mitochondrial PE by deletion of phosphatidylserine decarboxylase (PSD) made mice cold intolerant and insensitive to ß3 adrenergic receptor agonist-induced increase in whole-body oxygen consumption. High-resolution respirometry and fluorometry of BAT mitochondria showed that loss of mitochondrial PE specifically lowers UCP1-dependent respiration without compromising electron transfer efficiency or ATP synthesis. These findings were confirmed by a reduction in UCP1 proton current in PE-deficient mitoplasts. Thus, PE performs a previously unknown role as a temperature-responsive rheostat that regulates UCP1-dependent thermogenesis.
Assuntos
Fosfatidiletanolaminas , Prótons , Camundongos , Animais , Proteína Desacopladora 1/metabolismo , Fosfatidiletanolaminas/metabolismo , Mitocôndrias/metabolismo , Termogênese , Obesidade/metabolismo , Trifosfato de Adenosina/metabolismo , Camundongos KnockoutRESUMO
Obesity and type 2 diabetes (T2D) are growing health challenges with unmet treatment needs. Traf2- and NCK-interacting protein kinase (TNIK) is a recently identified obesity- and T2D-associated gene with unknown functions. We show that TNIK governs lipid and glucose homeostasis in Drosophila and mice. Loss of the Drosophila ortholog of TNIK, misshapen, altered the metabolite profiles and impaired de novo lipogenesis in high sugar-fed larvae. Tnik knockout mice exhibited hyperlocomotor activity and were protected against diet-induced fat expansion, insulin resistance, and hepatic steatosis. The improved lipid profile of Tnik knockout mice was accompanied by enhanced skeletal muscle and adipose tissue insulin-stimulated glucose uptake and glucose and lipid handling. Using the T2D Knowledge Portal and the UK Biobank, we observed associations of TNIK variants with blood glucose, HbA1c, body mass index, body fat percentage, and feeding behavior. These results define an untapped paradigm of TNIK-controlled glucose and lipid metabolism.
Assuntos
Resistência à Insulina , Metabolismo dos Lipídeos , Obesidade , Proteínas Serina-Treonina Quinases , Animais , Camundongos , Diabetes Mellitus Tipo 2/genética , Glucose/metabolismo , Lipídeos , Fígado/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/genética , Obesidade/metabolismo , Proteínas Serina-Treonina Quinases/metabolismoRESUMO
Lactate is a circulating metabolite and a signalling molecule with pleiotropic physiological effects. Studies suggest that lactate modulates energy balance by lowering food intake, inducing adipose browning and increasing whole-body thermogenesis. Yet, like many other metabolites, lactate is often commercially produced as a counterion-bound salt and typically administered in vivo through hypertonic aqueous solutions of sodium L-lactate. Most studies have not controlled for injection osmolarity and the co-injected sodium ions. Here, we show that the anorectic and thermogenic effects of exogenous sodium L-lactate in male mice are confounded by the hypertonicity of the injected solutions. Our data reveal that this is in contrast to the antiobesity effect of orally administered disodium succinate, which is uncoupled from these confounders. Further, our studies with other counterions indicate that counterions can have confounding effects beyond lactate pharmacology. Together, these findings underscore the importance of controlling for osmotic load and counterions in metabolite research.
Assuntos
Depressores do Apetite , Camundongos , Masculino , Animais , Depressores do Apetite/farmacologia , Ácido Láctico , Termogênese/fisiologia , Sódio , Concentração OsmolarRESUMO
Specialized fat tissue generates heat and holds the potential to counter metabolic diseases.
Assuntos
Adipócitos Bege/metabolismo , Adipócitos Marrons/metabolismo , Termogênese , Adipócitos Brancos/metabolismo , Animais , Metabolismo Energético , Humanos , Doenças Metabólicas/metabolismo , Doenças Metabólicas/terapia , Camundongos , Mitocôndrias/metabolismo , Nutrientes/metabolismoRESUMO
BACKGROUND: Thermogenic brown and beige adipocytes are recognized for their unique capacity to consume extraordinary levels of metabolites and lipids from the blood to fuel heat-producing catabolic processes [1-7]. In humans, the functions of thermogenic adipocytes are associated with cardiometabolic protection and improved glycemic control [8-13]. Consequently, engaging these macronutrient-consuming and energy-dissipating activities has gained attention as a promising therapeutic strategy for counteracting metabolic diseases, such as obesity and diabetes. SCOPE OF REVIEW: In this review, we highlight new advances in our understanding of the physiological role of G protein-coupled receptors (GPCRs) in controlling thermogenic adipocyte biology. We further extend our discussion to the opportunities and challenges posed by pharmacologically targeting different elements of GPCR signaling in these highly specialized fat cells. MAJOR CONCLUSIONS: GPCRs represent appealing candidates through which to harness adipose thermogenesis. Yet safely and effectively targeting these druggable receptors on brown and beige adipocytes has thus far proven challenging. Therefore, continued interrogation across the GPCR landscape is necessary for future leaps within the field of thermogenic fat biology to unlock the therapeutic potential of adipocyte catabolism.