RESUMEN
Signaling pathways that promote adipose tissue thermogenesis are well characterized, but the limiters of energy expenditure are largely unknown. Here, we show that ablation of the anti-inflammatory cytokine IL-10 improves insulin sensitivity, protects against diet-induced obesity, and elicits the browning of white adipose tissue. Mechanistic studies define bone marrow cells as the source of the IL-10 signal and adipocytes as the target cell type mediating these effects. IL-10 receptor alpha is highly enriched in mature adipocytes and is induced in response to differentiation, obesity, and aging. Assay for transposase-accessible chromatin sequencing (ATAC-seq), ChIP-seq, and RNA-seq reveal that IL-10 represses the transcription of thermogenic genes in adipocytes by altering chromatin accessibility and inhibiting ATF and C/EBPß recruitment to key enhancer regions. These findings expand our understanding of the relationship between inflammatory signaling pathways and adipose tissue function and provide insight into the physiological control of thermogenesis that could inform future therapy.
Asunto(s)
Adipocitos/metabolismo , Ensamble y Desensamble de Cromatina , Metabolismo Energético , Interleucina-10/metabolismo , Termogénesis , Factores de Transcripción Activadores/metabolismo , Animales , Proteína beta Potenciadora de Unión a CCAAT/metabolismo , Línea Celular , Células Cultivadas , Interleucina-10/genética , Masculino , Ratones , Ratones Endogámicos C57BL , Transducción de SeñalRESUMEN
Cellular lipid requirements are achieved through a combination of biosynthesis and import programs. Using isotope tracer analysis, we show that type I interferon (IFN) signaling shifts the balance of these programs by decreasing synthesis and increasing import of cholesterol and long chain fatty acids. Genetically enforcing this metabolic shift in macrophages is sufficient to render mice resistant to viral challenge, demonstrating the importance of reprogramming the balance of these two metabolic pathways in vivo. Unexpectedly, mechanistic studies reveal that limiting flux through the cholesterol biosynthetic pathway spontaneously engages a type I IFN response in a STING-dependent manner. The upregulation of type I IFNs was traced to a decrease in the pool size of synthesized cholesterol and could be inhibited by replenishing cells with free cholesterol. Taken together, these studies delineate a metabolic-inflammatory circuit that links perturbations in cholesterol biosynthesis with activation of innate immunity.
Asunto(s)
Colesterol/metabolismo , Inmunidad Innata , Interferón gamma/metabolismo , Transducción de Señal , Animales , Línea Celular Tumoral , Humanos , Interferon beta-1b , Proteínas de la Membrana/metabolismo , Ácido Mevalónico/metabolismo , Ratones , Ratones Endogámicos C57BL , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Proteína 2 de Unión a Elementos Reguladores de Esteroles/metabolismoRESUMEN
Multilocular adipocytes are a hallmark of thermogenic adipose tissue1,2, but the factors that enforce this cellular phenotype are largely unknown. Here, we show that an adipocyte-selective product of the Clstn3 locus (CLSTN3ß) present in only placental mammals facilitates the efficient use of stored triglyceride by limiting lipid droplet (LD) expansion. CLSTN3ß is an integral endoplasmic reticulum (ER) membrane protein that localizes to ER-LD contact sites through a conserved hairpin-like domain. Mice lacking CLSTN3ß have abnormal LD morphology and altered substrate use in brown adipose tissue, and are more susceptible to cold-induced hypothermia despite having no defect in adrenergic signalling. Conversely, forced expression of CLSTN3ß is sufficient to enforce a multilocular LD phenotype in cultured cells and adipose tissue. CLSTN3ß associates with cell death-inducing DFFA-like effector proteins and impairs their ability to transfer lipid between LDs, thereby restricting LD fusion and expansion. Functionally, increased LD surface area in CLSTN3ß-expressing adipocytes promotes engagement of the lipolytic machinery and facilitates fatty acid oxidation. In human fat, CLSTN3B is a selective marker of multilocular adipocytes. These findings define a molecular mechanism that regulates LD form and function to facilitate lipid utilization in thermogenic adipocytes.
Asunto(s)
Adipocitos , Proteínas de Unión al Calcio , Metabolismo de los Lípidos , Proteínas de la Membrana , Animales , Femenino , Humanos , Ratones , Adipocitos/citología , Adipocitos/metabolismo , Tejido Adiposo Pardo/citología , Tejido Adiposo Pardo/metabolismo , Proteínas de Unión al Calcio/deficiencia , Proteínas de Unión al Calcio/metabolismo , Proteínas de la Membrana/deficiencia , Proteínas de la Membrana/metabolismo , Placenta , Triglicéridos/metabolismo , Retículo Endoplásmico/metabolismo , Gotas Lipídicas/metabolismo , Ácidos Grasos/metabolismo , Hipotermia/metabolismo , TermogénesisRESUMEN
Obesity increases the risk of mortality because of metabolic sequelae such as type 2 diabetes and cardiovascular disease1. Thermogenesis by adipocytes can counteract obesity and metabolic diseases2,3. In thermogenic fat, creatine liberates a molar excess of mitochondrial ADP-purportedly via a phosphorylation cycle4-to drive thermogenic respiration. However, the proteins that control this futile creatine cycle are unknown. Here we show that creatine kinase B (CKB) is indispensable for thermogenesis resulting from the futile creatine cycle, during which it traffics to mitochondria using an internal mitochondrial targeting sequence. CKB is powerfully induced by thermogenic stimuli in both mouse and human adipocytes. Adipocyte-selective inactivation of Ckb in mice diminishes thermogenic capacity, increases predisposition to obesity, and disrupts glucose homeostasis. CKB is therefore a key effector of the futile creatine cycle.
Asunto(s)
Tejido Adiposo/metabolismo , Forma BB de la Creatina-Quinasa/metabolismo , Creatina/metabolismo , Termogénesis , Adipocitos/metabolismo , Tejido Adiposo/citología , Tejido Adiposo/enzimología , Animales , Forma BB de la Creatina-Quinasa/deficiencia , Forma BB de la Creatina-Quinasa/genética , AMP Cíclico/metabolismo , Metabolismo Energético/genética , Femenino , Glucosa/metabolismo , Homeostasis , Humanos , Masculino , Ratones , Mitocondrias/metabolismo , Obesidad/enzimología , Obesidad/genética , Obesidad/metabolismo , Transducción de SeñalRESUMEN
Elevated levels of branched chain amino acids (BCAAs) and branched-chain α-ketoacids are associated with cardiovascular and metabolic disease, but the molecular mechanisms underlying a putative causal relationship remain unclear. The branched-chain ketoacid dehydrogenase kinase (BCKDK) inhibitor BT2 (3,6-dichlorobenzo[b]thiophene-2-carboxylic acid) is often used in preclinical models to increase BCAA oxidation and restore steady-state BCAA and branched-chain α-ketoacid levels. BT2 administration is protective in various rodent models of heart failure and metabolic disease, but confoundingly, targeted ablation of Bckdk in specific tissues does not reproduce the beneficial effects conferred by pharmacologic inhibition. Here, we demonstrate that BT2, a lipophilic weak acid, can act as a mitochondrial uncoupler. Measurements of oxygen consumption, mitochondrial membrane potential, and patch-clamp electrophysiology show that BT2 increases proton conductance across the mitochondrial inner membrane independently of its inhibitory effect on BCKDK. BT2 is roughly sixfold less potent than the prototypical uncoupler 2,4-dinitrophenol and phenocopies 2,4-dinitrophenol in lowering de novo lipogenesis and mitochondrial superoxide production. The data suggest that the therapeutic efficacy of BT2 may be attributable to the well-documented effects of mitochondrial uncoupling in alleviating cardiovascular and metabolic disease.
Asunto(s)
Lipogénesis , Enfermedades Metabólicas , Membranas Mitocondriales , Inhibidores de Proteínas Quinasas , Especies Reactivas de Oxígeno , Humanos , 2,4-Dinitrofenol/farmacología , 3-Metil-2-Oxobutanoato Deshidrogenasa (Lipoamida)/metabolismo , Aminoácidos de Cadena Ramificada/metabolismo , Lipogénesis/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Especies Reactivas de Oxígeno/metabolismo , Animales , Ratones , Ratas , Línea Celular , Membranas Mitocondriales/efectos de los fármacos , Células CultivadasRESUMEN
Sex differences in physiology and disease in mammals result from the effects of three classes of factors that are inherently unequal in males and females: reversible (activational) effects of gonadal hormones, permanent (organizational) effects of gonadal hormones, and cell-autonomous effects of sex chromosomes, as well as genes driven by these classes of factors. Often, these factors act together to cause sex differences in specific phenotypes, but the relative contribution of each and the interactions among them remain unclear. Here, we used the four core genotypes (FCG) mouse model with or without hormone replacement to distinguish the effects of each class of sex-biasing factors on transcriptome regulation in liver and adipose tissues. We found that the activational hormone levels have the strongest influence on gene expression, followed by the organizational gonadal sex effect, and last, sex chromosomal effect, along with interactions among the three factors. Tissue specificity was prominent, with a major impact of estradiol on adipose tissue gene regulation and of testosterone on the liver transcriptome. The networks affected by the three sex-biasing factors include development, immunity and metabolism, and tissue-specific regulators were identified for these networks. Furthermore, the genes affected by individual sex-biasing factors and interactions among factors are associated with human disease traits such as coronary artery disease, diabetes, and inflammatory bowel disease. Our study offers a tissue-specific account of the individual and interactive contributions of major sex-biasing factors to gene regulation that have broad impact on systemic metabolic, endocrine, and immune functions.
Asunto(s)
Caracteres Sexuales , Cromosomas Sexuales , Animales , Femenino , Hormonas Gonadales/metabolismo , Hormonas Gonadales/farmacología , Hormonas Esteroides Gonadales/metabolismo , Gónadas/metabolismo , Masculino , Mamíferos/genética , Ratones , Cromosomas Sexuales/genéticaRESUMEN
Newly activated CD8(+) T cells reprogram their metabolism to meet the extraordinary biosynthetic demands of clonal expansion; however, the signals that mediate metabolic reprogramming remain poorly defined. Here we demonstrate an essential role for sterol regulatory element-binding proteins (SREBPs) in the acquisition of effector-cell metabolism. Without SREBP signaling, CD8(+) T cells were unable to blast, which resulted in attenuated clonal expansion during viral infection. Mechanistic studies indicated that SREBPs were essential for meeting the heightened lipid requirements of membrane synthesis during blastogenesis. SREBPs were dispensable for homeostatic proliferation, which indicated a context-specific requirement for SREBPs in effector responses. Our studies provide insights into the molecular signals that underlie the metabolic reprogramming of CD8(+) T cells during the transition from quiescence to activation.
Asunto(s)
Linfocitos T CD8-positivos/metabolismo , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Proteína 2 de Unión a Elementos Reguladores de Esteroles/metabolismo , Inmunidad Adaptativa/genética , Animales , Linfocitos T CD8-positivos/inmunología , Diferenciación Celular/genética , Proliferación Celular , Células Cultivadas , Activación de Linfocitos/genética , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , ARN Interferente Pequeño/genética , Transducción de Señal/genética , Transducción de Señal/inmunología , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/genética , Proteína 2 de Unión a Elementos Reguladores de Esteroles/genética , Transgenes/genéticaRESUMEN
Respirometry is the gold standard measurement of mitochondrial oxidative function, as it reflects the activity of the electron transport chain complexes working together. However, the requirement for freshly isolated mitochondria hinders the feasibility of respirometry in multi-site clinical studies and retrospective studies. Here, we describe a novel respirometry approach suited for frozen samples by restoring electron transfer components lost during freeze/thaw and correcting for variable permeabilization of mitochondrial membranes. This approach preserves 90-95% of the maximal respiratory capacity in frozen samples and can be applied to isolated mitochondria, permeabilized cells, and tissue homogenates with high sensitivity. We find that primary changes in mitochondrial function, detected in fresh tissue, are preserved in frozen samples years after collection. This approach will enable analysis of the integrated function of mitochondrial Complexes I to IV in one measurement, collected at remote sites or retrospectively in samples residing in tissue biobanks.
Asunto(s)
Criopreservación , Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Mitocondrias/metabolismo , Consumo de Oxígeno , Proteínas de Pez Cebra/metabolismo , Pez Cebra/metabolismo , Animales , Masculino , RatonesRESUMEN
Sex is a key risk factor for many types of cardiovascular disease. It is imperative to understand the mechanisms underlying sex differences to devise optimal preventive and therapeutic approaches for all individuals. Both biological sex (determined by sex chromosomes and gonadal hormones) and gender (social and cultural behaviors associated with femininity or masculinity) influence differences between men and women in disease susceptibility and pathology. Here, we focus on the application of experimental mouse models that elucidate the influence of 2 components of biological sex-sex chromosome complement (XX or XY) and gonad type (ovaries or testes). These models have revealed that in addition to well-known effects of gonadal hormones, sex chromosome complement influences cardiovascular risk factors, such as plasma cholesterol levels and adiposity, as well as the development of atherosclerosis and pulmonary hypertension. One mechanism by which sex chromosome dosage influences cardiometabolic traits is through sex-biased expression of X chromosome genes that escape X inactivation. These include chromatin-modifying enzymes that regulate gene expression throughout the genome. The identification of factors that determine sex-biased gene expression and cardiometabolic traits will expand our mechanistic understanding of cardiovascular disease processes and provide insight into sex differences that remain throughout the lifespan as gonadal hormone levels alter with age.
Asunto(s)
Enfermedades Cardiovasculares , Caracteres Sexuales , Adiposidad , Animales , Enfermedades Cardiovasculares/genética , Femenino , Hormonas Gonadales/metabolismo , Humanos , Masculino , Ratones , Cromosomas Sexuales/genética , Cromosomas Sexuales/metabolismo , Cromosoma X/genética , Cromosoma X/metabolismoRESUMEN
In humans, the combination of all sex-specific genetic, epigenetic, and hormonal influences of biologic sex produces different in vivo environments for male and female cells. We dissect how these influences of sex modify the pharmacokinetics and pharmacodynamics of multiple drugs and provide examples for common drugs acting on specific organ systems. We also discuss how gender of physicians and patients may influence the therapeutic response to drugs. We aim to highlight sex as a genetic modifier of the pharmacological response to drugs, which should be considered as a necessary step toward precision medicine that will benefit men and women. SIGNIFICANCE STATEMENT: This study discusses the influences of biologic sex on the pharmacokinetics and pharmacodynamics of drugs and provides examples for common drugs acting on specific organ systems. This study also discusses how gender of physicians and patients influence the therapeutic response to drugs.
Asunto(s)
Preparaciones Farmacéuticas , Caracteres Sexuales , Femenino , Humanos , Masculino , Medicina de PrecisiónRESUMEN
To elucidate the contributions of specific lipid species to metabolic traits, we integrated global hepatic lipid data with other omics measures and genetic data from a cohort of about 100 diverse inbred strains of mice fed a high-fat/high-sucrose diet for 8 weeks. Association mapping, correlation, structure analyses, and network modeling revealed pathways and genes underlying these interactions. In particular, our studies lead to the identification of Ifi203 and Map2k6 as regulators of hepatic phosphatidylcholine homeostasis and triacylglycerol accumulation, respectively. Our analyses highlight mechanisms for how genetic variation in hepatic lipidome can be linked to physiological and molecular phenotypes, such as microbiota composition.
Asunto(s)
Dieta Alta en Grasa/efectos adversos , Hígado Graso/genética , Glucosa/efectos adversos , Resistencia a la Insulina/genética , MAP Quinasa Quinasa 6/genética , Proteínas Nucleares/genética , Animales , Modelos Animales de Enfermedad , Hígado Graso/inducido químicamente , Hígado Graso/metabolismo , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Variación Genética , Lipidómica , Masculino , Ratones , Fosfatidilcolinas/metabolismo , Triglicéridos/metabolismoRESUMEN
Strategies to increase energy expenditure are an attractive approach to reduce excess fat storage and body weight to improve metabolic health. In mammals, uncoupling protein-1 (UCP1) in brown and beige adipocytes uncouples fatty acid oxidation from ATP generation in mitochondria and promotes energy dissipation as heat. We set out to identify small molecules that enhance UCP1 levels and activity using a high-throughput screen of nearly 12,000 compounds in mouse brown adipocytes. We identified a family of compounds that increase Ucp1 expression and mitochondrial activity (including un-coupled respiration) in mouse brown adipocytes and human brown and white adipocytes. The mechanism of action may be through compound binding to A kinase anchoring protein (AKAP) 1, modulating its localization to mitochondria and its interaction with protein kinase A (PKA), a known node in the ß-adrenergic signaling pathway. In mice, the hit compound increased body temperature, UCP1 protein levels, and thermogenic gene expression. Some of the compound effects on mitochondrial function were UCP1- or AKAP1-independent, suggesting compound effects on multiple nodes of energy regulation. Overall, our results highlight a role for AKAP1 in thermogenesis, uncoupled respiration, and regulation energy balance.
Asunto(s)
Proteínas de Anclaje a la Quinasa A/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Bibliotecas de Moléculas Pequeñas/farmacología , Termogénesis/efectos de los fármacos , Proteína Desacopladora 1/biosíntesis , Adipocitos Marrones/enzimología , Adipocitos Marrones/metabolismo , Adipocitos Blancos/enzimología , Adipocitos Blancos/metabolismo , Animales , Células Cultivadas , Metabolismo Energético , Activación Enzimática , Perfilación de la Expresión Génica , Ensayos Analíticos de Alto Rendimiento , Humanos , Ratones , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Reproducibilidad de los Resultados , Transducción de SeñalRESUMEN
Although significant progress has been made in understanding epigenetic regulation of in vitro adipogenesis, the physiological functions of epigenetic regulators in metabolism and their roles in obesity remain largely elusive. Here, we report that KDM4B (lysine demethylase 4B) in adipose tissues plays a critical role in energy balance, oxidation, lipolysis, and thermogenesis. Loss of KDM4B in mice resulted in obesity associated with reduced energy expenditure and impaired adaptive thermogenesis. Obesity in KDM4B-deficient mice was accompanied by hyperlipidemia, insulin resistance, and pathological changes in the liver and pancreas. Adipocyte-specific deletion of Kdm4b revealed that the adipose tissues were the main sites for KDM4B antiobesity effects. KDM4B directly controlled the expression of multiple metabolic genes, including Ppargc1a and Ppara Collectively, our studies identify KDM4B as an essential epigenetic factor for the regulation of metabolic health and maintaining normal body weight in mice. KDM4B may provide a therapeutic target for treatment of obesity.
Asunto(s)
Histona Demetilasas con Dominio de Jumonji/metabolismo , Enfermedades Metabólicas/metabolismo , Obesidad/metabolismo , Adipocitos/metabolismo , Adipogénesis/fisiología , Tejido Adiposo/metabolismo , Animales , Peso Corporal/fisiología , Dieta Alta en Grasa/efectos adversos , Metabolismo Energético/fisiología , Epigénesis Genética/fisiología , Resistencia a la Insulina/fisiología , Lipólisis/fisiología , Ratones , Ratones Endogámicos C57BL , Oxidación-Reducción , Termogénesis/fisiologíaRESUMEN
Zinc metallopeptidase STE24 (ZMPSTE24) is essential for the conversion of farnesyl-prelamin A to mature lamin A, a key component of the nuclear lamina. In the absence of ZMPSTE24, farnesyl-prelamin A accumulates in the nucleus and exerts toxicity, causing a variety of disease phenotypes. By â¼4 months of age, both male and female Zmpste24-/- mice manifest a near-complete loss of adipose tissue, but it has never been clear whether this phenotype is a direct consequence of farnesyl-prelamin A toxicity in adipocytes. To address this question, we generated a conditional knockout Zmpste24 allele and used it to create adipocyte-specific Zmpste24-knockout mice. To boost farnesyl-prelamin A levels, we bred in the "prelamin A-only" Lmna allele. Gene expression, immunoblotting, and immunohistochemistry experiments revealed that adipose tissue in these mice had decreased Zmpste24 expression along with strikingly increased accumulation of prelamin A. In male mice, Zmpste24 deficiency in adipocytes was accompanied by modest changes in adipose stores (an 11% decrease in body weight, a 23% decrease in body fat mass, and significantly smaller gonadal and inguinal white adipose depots). No changes in adipose stores were detected in female mice, likely because prelamin A expression in adipose tissue is lower in female mice. Zmpste24 deficiency in adipocytes did not alter the number of macrophages in adipose tissue, nor did it alter plasma levels of glucose, triglycerides, or fatty acids. We conclude that ZMPSTE24 deficiency in adipocytes, and the accompanying accumulation of farnesyl-prelamin A, reduces adipose tissue stores, but only modestly and only in male mice.
Asunto(s)
Tejido Adiposo/metabolismo , Lamina Tipo A/metabolismo , Proteínas de la Membrana/metabolismo , Metaloendopeptidasas/metabolismo , Tejido Adiposo/química , Alelos , Animales , Núcleo Celular/química , Núcleo Celular/metabolismo , Femenino , Masculino , Proteínas de la Membrana/deficiencia , Proteínas de la Membrana/genética , Metaloendopeptidasas/deficiencia , Metaloendopeptidasas/genética , Ratones , Ratones Noqueados , Ratones TransgénicosRESUMEN
BACKGROUND: A protein that is expressed on capillary endothelial cells, called GPIHBP1 (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1), binds lipoprotein lipase and shuttles it to its site of action in the capillary lumen. A deficiency in GPIHBP1 prevents lipoprotein lipase from reaching the capillary lumen. Patients with GPIHBP1 deficiency have low plasma levels of lipoprotein lipase, impaired intravascular hydrolysis of triglycerides, and severe hypertriglyceridemia (chylomicronemia). During the characterization of a monoclonal antibody-based immunoassay for GPIHBP1, we encountered two plasma samples (both from patients with chylomicronemia) that contained an interfering substance that made it impossible to measure GPIHBP1. That finding raised the possibility that those samples might contain GPIHBP1 autoantibodies. METHODS: Using a combination of immunoassays, Western blot analyses, and immunocytochemical studies, we tested the two plasma samples (as well as samples from other patients with chylomicronemia) for the presence of GPIHBP1 autoantibodies. We also tested the ability of GPIHBP1 autoantibodies to block the binding of lipoprotein lipase to GPIHBP1. RESULTS: We identified GPIHBP1 autoantibodies in six patients with chylomicronemia and found that these autoantibodies blocked the binding of lipoprotein lipase to GPIHBP1. As in patients with GPIHBP1 deficiency, those with GPIHBP1 autoantibodies had low plasma levels of lipoprotein lipase. Three of the six patients had systemic lupus erythematosus. One of these patients who had GPIHBP1 autoantibodies delivered a baby with plasma containing maternal GPIHBP1 autoantibodies; the infant had severe but transient chylomicronemia. Two of the patients with chylomicronemia and GPIHBP1 autoantibodies had a response to treatment with immunosuppressive agents. CONCLUSIONS: In six patients with chylomicronemia, GPIHBP1 autoantibodies blocked the ability of GPIHBP1 to bind and transport lipoprotein lipase, thereby interfering with lipoprotein lipase-mediated processing of triglyceride-rich lipoproteins and causing severe hypertriglyceridemia. (Funded by the National Heart, Lung, and Blood Institute and the Leducq Foundation.).
Asunto(s)
Autoanticuerpos/sangre , Hiperlipoproteinemia Tipo I/inmunología , Lipoproteína Lipasa/metabolismo , Receptores de Lipoproteína/inmunología , Adulto , Autoanticuerpos/fisiología , Femenino , Humanos , Hiperlipoproteinemia Tipo I/sangre , Inmunoensayo , Lipólisis , Lipoproteína Lipasa/sangre , Masculino , Persona de Mediana Edad , Unión Proteica , Transporte de Proteínas , Receptores de Lipoproteína/metabolismoRESUMEN
OBJECTIVE: Air pollution is associated with increased cardiovascular morbidity and mortality, as well as dyslipidemia and metabolic syndrome. Our goal was to dissect the mechanisms involved. Approach and Results: We assessed the effects of exposure to air pollution on lipid metabolism in mice through assessment of plasma lipids and lipoproteins, oxidized fatty acids 9-HODE (9-hydroxyoctadecadienoic) and 13-HODE (13-hydroxyoctadecadienoic), lipid, and carbohydrate metabolism. Findings were corroborated, and mechanisms were further assessed in HepG2 hepatocytes in culture. ApoE knockout mice exposed to inhaled diesel exhaust (DE, 6 h/d, 5 days/wk for 16 weeks) exhibited elevated plasma cholesterol and triglyceride levels, increased hepatic triglyceride content, and higher hepatic levels of 9-HODE and 13-HODE, as compared to control mice exposed to filtered air. A direct effect of DE exposure on hepatocytes was demonstrated by treatment of HepG2 cells with a methanol extract of DE particles followed by loading with oleic acid. As observed in vivo, this led to increased triglyceride content and significant downregulation of ACAD9 mRNA expression. Treatment of HepG2 cells with DE particles and oleic acid did not alter de novo lipogenesis but inhibited total, mitochondrial, and ATP-linked oxygen consumption rate, indicative of mitochondrial dysfunction. Treatment of isolated mitochondria, prepared from mouse liver, with DE particles and oleic acid also inhibited mitochondrial complex activity and ß-oxidation. CONCLUSIONS: DE exposure leads to dyslipidemia and liver steatosis in ApoE knockout mice, likely due to mitochondrial dysfunction and decreased lipid catabolism.
Asunto(s)
Hígado Graso/inducido químicamente , Hiperlipidemias/inducido químicamente , Mitocondrias/metabolismo , Emisiones de Vehículos/toxicidad , Animales , Células Hep G2 , Humanos , Metabolismo de los Lípidos/efectos de los fármacos , Masculino , Ratones , Triglicéridos/metabolismoRESUMEN
Metabolism and ageing are intimately linked. Compared with ad libitum feeding, dietary restriction consistently extends lifespan and delays age-related diseases in evolutionarily diverse organisms. Similar conditions of nutrient limitation and genetic or pharmacological perturbations of nutrient or energy metabolism also have longevity benefits. Recently, several metabolites have been identified that modulate ageing; however, the molecular mechanisms underlying this are largely undefined. Here we show that α-ketoglutarate (α-KG), a tricarboxylic acid cycle intermediate, extends the lifespan of adult Caenorhabditis elegans. ATP synthase subunit ß is identified as a novel binding protein of α-KG using a small-molecule target identification strategy termed drug affinity responsive target stability (DARTS). The ATP synthase, also known as complex V of the mitochondrial electron transport chain, is the main cellular energy-generating machinery and is highly conserved throughout evolution. Although complete loss of mitochondrial function is detrimental, partial suppression of the electron transport chain has been shown to extend C. elegans lifespan. We show that α-KG inhibits ATP synthase and, similar to ATP synthase knockdown, inhibition by α-KG leads to reduced ATP content, decreased oxygen consumption, and increased autophagy in both C. elegans and mammalian cells. We provide evidence that the lifespan increase by α-KG requires ATP synthase subunit ß and is dependent on target of rapamycin (TOR) downstream. Endogenous α-KG levels are increased on starvation and α-KG does not extend the lifespan of dietary-restricted animals, indicating that α-KG is a key metabolite that mediates longevity by dietary restriction. Our analyses uncover new molecular links between a common metabolite, a universal cellular energy generator and dietary restriction in the regulation of organismal lifespan, thus suggesting new strategies for the prevention and treatment of ageing and age-related diseases.
Asunto(s)
Caenorhabditis elegans/efectos de los fármacos , Ácidos Cetoglutáricos/farmacología , Longevidad/fisiología , ATPasas de Translocación de Protón Mitocondriales/metabolismo , Serina-Treonina Quinasas TOR/metabolismo , Animales , Línea Celular , Activación Enzimática/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Técnicas de Silenciamiento del Gen , Células HEK293 , Humanos , Células Jurkat , Longevidad/efectos de los fármacos , Longevidad/genética , Ratones , ATPasas de Translocación de Protón Mitocondriales/genética , Unión ProteicaRESUMEN
The regulation of cellular lipid storage and membrane lipid composition plays a critical role in metabolic homeostasis, and dysregulation may contribute to disorders such as obesity, fatty liver, type 2 diabetes, and cardiovascular disease. The mammalian lipin proteins (lipin 1, lipin 2, and lipin 3) are phosphatidic acid phosphatase (PAP) enzymes that modulate levels of cellular triacylglycerols and phospholipids, and also regulate lipid intermediates in cellular signaling pathways. Lipin proteins also have the ability to coactivate/corepress transcription. In humans and mice, lipin gene mutations cause severe metabolic phenotypes including rhabdomyolysis (lipin 1), autoinflammatory disease (lipin 2), and impaired intestinal lipoprotein assembly (lipin 2/lipin 3). Characterization of these diseases has revealed roles for lipin PAP activity in fundamental cellular processes such as autophagy, inflammasome activation, and lipoprotein assembly. Lipin protein activity is regulated at pre- and posttranscriptional levels, which suggests a need for their ordered response to specific physiological stimuli. Challenges for the future include better elucidation of the unique biochemical and physiological properties of individual lipin family members and determination of lipin protein structure-function relationships. Further research may propel exploration of lipin proteins as viable therapeutic targets in metabolic or inflammatory disorders.
Asunto(s)
Inflamación/metabolismo , Lípidos/biosíntesis , Síndrome Metabólico/metabolismo , Fosfatidato Fosfatasa/metabolismo , Animales , Autofagia , Humanos , Inflamación/patología , Síndrome Metabólico/patología , Compuestos Orgánicos/metabolismoRESUMEN
Estrogen receptor α (ERα) action plays an important role in pancreatic ß-cell function and survival; thus, it is considered a potential therapeutic target for the treatment of type 2 diabetes in women. However, the mechanisms underlying the protective effects of ERα remain unclear. Because ERα regulates mitochondrial metabolism in other cell types, we hypothesized that ERα may act to preserve insulin secretion and promote ß-cell survival by regulating mitochondrial-endoplasmic reticulum (EndoRetic) function. We tested this hypothesis using pancreatic islet-specific ERα knockout (PERαKO) mice and Min6 ß-cells in culture with Esr1 knockdown (KD). We found that Esr1-KD promoted reactive oxygen species production that associated with reduced fission/fusion dynamics and impaired mitophagy. Electron microscopy showed mitochondrial enlargement and a pro-fusion phenotype. Mitochondrial cristae and endoplasmic reticulum were dilated in Esr1-KD compared with ERα replete Min6 ß-cells. Increased expression of Oma1 and Chop was paralleled by increased oxygen consumption and apoptosis susceptibility in ERα-KD cells. In contrast, ERα overexpression and ligand activation reduced both Chop and Oma1 expression, likely by ERα binding to consensus estrogen-response element sites in the Oma1 and Chop promoters. Together, our findings suggest that ERα promotes ß-cell survival and insulin secretion through maintenance of mitochondrial fission/fusion-mitophagy dynamics and EndoRetic function, in part by Oma1 and Chop repression.
Asunto(s)
Apoptosis , Estrés del Retículo Endoplásmico , Receptor alfa de Estrógeno/metabolismo , Células Secretoras de Insulina/metabolismo , Mitocondrias/metabolismo , Mitofagia , Animales , Supervivencia Celular , Receptor alfa de Estrógeno/genética , Femenino , Insulina/genética , Insulina/metabolismo , Metaloproteasas/biosíntesis , Metaloproteasas/genética , Ratones , Ratones Noqueados , Mitocondrias/genética , Proteínas Mitocondriales/biosíntesis , Proteínas Mitocondriales/genética , Especies Reactivas de Oxígeno/metabolismo , Factor de Transcripción CHOP/biosíntesis , Factor de Transcripción CHOP/genéticaRESUMEN
Lipid droplets (LDs) are distinct and dynamic organelles that affect the health of cells and organs. Much progress has been made in understanding how these structures are formed, how they interact with other cellular organelles, how they are used for storage of triacylglycerol in adipose tissue, and how they regulate lipolysis. Our understanding of the biology of LDs in the heart and vascular tissue is relatively primitive in comparison with LDs in adipose tissue and liver. The National Heart, Lung, and Blood Institute convened a working group to discuss how LDs affect cardiovascular diseases. The goal of the working group was to examine the current state of knowledge on the cell biology of LDs, including current methods to study them in cells and organs and reflect on how LDs influence the development and progression of cardiovascular diseases. This review summarizes the working group discussion and recommendations on research areas ripe for future investigation that will likely improve our understanding of atherosclerosis and heart function.