RESUMEN
The X-linked inhibitor of apoptosis protein (XIAP) is a potent caspase inhibitor, best known for its anti-apoptotic function in cancer. During apoptosis, XIAP is antagonized by SMAC, which is released from the mitochondria upon caspase-mediated activation of BID. Recent studies suggest that XIAP is involved in immune signaling. Here, we explore XIAP as an important mediator of an immune response against the enteroinvasive bacterium Shigella flexneri, both in vitro and in vivo. Our data demonstrate for the first time that Shigella evades the XIAP-mediated immune response by inducing the BID-dependent release of SMAC from the mitochondria. Unlike apoptotic stimuli, Shigella activates the calpain-dependent cleavage of BID to trigger the release of SMAC, which antagonizes the inflammatory action of XIAP without inducing apoptosis. Our results demonstrate how the cellular death machinery can be subverted by an invasive pathogen to ensure bacterial colonization.
Asunto(s)
Proteína Proapoptótica que Interacciona Mediante Dominios BH3/fisiología , Proteínas Portadoras/metabolismo , Disentería Bacilar/inmunología , Mitocondrias/inmunología , Proteínas Mitocondriales/metabolismo , Shigella/inmunología , Proteína Inhibidora de la Apoptosis Ligada a X/fisiología , Animales , Apoptosis , Proteínas Reguladoras de la Apoptosis , Western Blotting , Caspasas/metabolismo , Proliferación Celular , Células Cultivadas , Disentería Bacilar/microbiología , Disentería Bacilar/patología , Femenino , Hepatocitos/inmunología , Hepatocitos/metabolismo , Hepatocitos/patología , Técnicas para Inmunoenzimas , Integrasas/metabolismo , Masculino , Potencial de la Membrana Mitocondrial , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias/metabolismo , Mitocondrias/patología , Proteínas Mitocondriales/inmunología , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Shigella/patogenicidad , Transducción de Señal , Espectrometría de Masa por Ionización de Electrospray , Espectrometría de Masas en TándemRESUMEN
BACKGROUND: Coronin proteins are known as regulators of actin-based cellular processes, and some of them are associated with the malignant progression of human cancer. Here, we show that expression of coronin 2A is up-regulated in human colon carcinoma. METHODS: This study included 26 human colon tumour specimens and 9 normal controls. Expression and localisation of coronin 2A was studied by immunohistochemistry, immunofluorescence imaging, cell fractionation, and immunoblotting. Functional roles of coronin 2A were analysed by over-expression and knock-down of the protein. Protein interactions were studied by co-immunoprecipitation and pull-down experiments, mass spectrometry analyses, and in vitro kinase and methylation assays. RESULTS: Histopathological investigation revealed that the expression of coronin 2A in colon tumour cells is up-regulated during the adenoma-adenocarcinoma progression. At the subcellular level, coronin 2A localised to multiple compartments, i.e. F-actin stress fibres, the front of lamellipodia, focal adhesions, and the nuclei. Over-expression of coronin 2A led to a reduction of F-actin stress fibres and elevated cell migration velocity. We identified two novel direct coronin 2A interaction partners. The interaction of coronin 2A with MAPK14 (mitogen activated protein kinase 14 or MAP kinase p38α) led to phosphorylation of coronin 2A and also to activation of the MAPK14 pathway. Moreover, coronin 2A interacted with PRMT5 (protein arginine N-methyltransferase 5), which modulates the sensitivity of tumour cells to TRAIL-induced cell death. CONCLUSIONS: We show that increased expression of coronin 2A is associated with the malignant phenotype of human colon carcinoma. Moreover, we linked coronin 2A to MAPK14 and PRMT5 signalling pathways involved in tumour progression.
Asunto(s)
Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Adenoma/genética , Adenoma/metabolismo , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/metabolismo , Regulación Neoplásica de la Expresión Génica , Proteínas de Microfilamentos/genética , Transducción de Señal , Adenocarcinoma/patología , Adenoma/patología , Línea Celular Tumoral , Movimiento Celular/genética , Neoplasias del Colon/genética , Neoplasias del Colon/metabolismo , Neoplasias del Colon/patología , Neoplasias Colorrectales/patología , Humanos , Proteínas de Microfilamentos/metabolismo , Proteína Quinasa 14 Activada por Mitógenos/metabolismo , Fosforilación , Transporte de Proteínas , Proteína-Arginina N-Metiltransferasas/metabolismo , Seudópodos/metabolismo , Receptores del Ligando Inductor de Apoptosis Relacionado con TNF/metabolismo , Fibras de Estrés/metabolismo , Especificidad por SustratoRESUMEN
Circulating IL-6 levels correlate with the severity of blood-stage malaria in humans and mouse models, but the impact of IL-6 classic signaling through membrane IL-6Rα, as well as IL-6 trans-signaling through soluble IL-6Rα, on the outcome of malaria has remained unknown. In this study, we created IL-6Rα-deficient mice that exhibit a 50% survival of otherwise lethal blood-stage malaria of the genus Plasmodium chabaudi. Inducing IL-6 trans-signaling by injection of mouse recombinant soluble IL-6Rα in IL-6Rα-deficient mice restores the lethal outcome to malaria infection. In contrast, inhibition of IL-6 trans-signaling via injection of recombinant sGP130Fc protein in control mice results in a 40% survival rate. Our data demonstrate that IL-6 trans-signaling, rather than classic IL-6 signaling, contributes to malaria-induced lethality in mice, preceded by an increased inflammatory response. Therefore, inhibition of IL-6 trans-signaling may serve as a novel promising therapeutic basis to combat malaria.
Asunto(s)
Interleucina-6/inmunología , Malaria/inmunología , Plasmodium chabaudi/inmunología , Transducción de Señal/inmunología , Animales , Receptor gp130 de Citocinas/genética , Receptor gp130 de Citocinas/inmunología , Receptor gp130 de Citocinas/farmacología , Interleucina-6/genética , Subunidad alfa del Receptor de Interleucina-6/genética , Subunidad alfa del Receptor de Interleucina-6/inmunología , Malaria/genética , Ratones , Ratones Noqueados , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/inmunología , Proteínas Recombinantes de Fusión/farmacología , Proteínas Recombinantes/genética , Proteínas Recombinantes/inmunología , Proteínas Recombinantes/farmacocinética , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genéticaRESUMEN
Liver mitochondria play a central role in metabolic adaptations to changing nutritional states, yet their dynamic regulation upon anticipated changes in nutrient availability has remained unaddressed. Here, we found that sensory food perception rapidly induced mitochondrial fragmentation in the liver through protein kinase B/AKT (AKT)-dependent phosphorylation of serine 131 of the mitochondrial fission factor (MFFS131). This response was mediated by activation of hypothalamic pro-opiomelanocortin (POMC)-expressing neurons. A nonphosphorylatable MFFS131G knock-in mutation abrogated AKT-induced mitochondrial fragmentation in vitro. In vivo, MFFS131G knock-in mice displayed altered liver mitochondrial dynamics and impaired insulin-stimulated suppression of hepatic glucose production. Thus, rapid activation of a hypothalamus-liver axis can adapt mitochondrial function to anticipated changes of nutritional state in control of hepatic glucose metabolism.
Asunto(s)
Alimentos , Gluconeogénesis , Glucosa , Hígado , Proteínas de la Membrana , Mitocondrias Hepáticas , Dinámicas Mitocondriales , Proteínas Mitocondriales , Percepción , Animales , Masculino , Ratones , Técnicas de Sustitución del Gen , Glucosa/metabolismo , Hipotálamo/metabolismo , Insulina/metabolismo , Hígado/metabolismo , Ratones Endogámicos C57BL , Mitocondrias Hepáticas/metabolismo , Proteínas Mitocondriales/metabolismo , Proteínas Mitocondriales/genética , Neuronas/metabolismo , Fosforilación , Proopiomelanocortina/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones TransgénicosRESUMEN
Pro-opiomelanocortin (POMC)-expressing neurons in the arcuate nucleus of the hypothalamus represent key regulators of metabolic homeostasis. Electrophysiological and single-cell sequencing experiments have revealed a remarkable degree of heterogeneity of these neurons. However, the exact molecular basis and functional consequences of this heterogeneity have not yet been addressed. Here, we have developed new mouse models in which intersectional Cre/Dre-dependent recombination allowed for successful labeling, translational profiling and functional characterization of distinct POMC neurons expressing the leptin receptor (Lepr) and glucagon like peptide 1 receptor (Glp1r). Our experiments reveal that POMCLepr+ and POMCGlp1r+ neurons represent largely nonoverlapping subpopulations with distinct basic electrophysiological properties. They exhibit a specific anatomical distribution within the arcuate nucleus and differentially express receptors for energy-state communicating hormones and neurotransmitters. Finally, we identify a differential ability of these subpopulations to suppress feeding. Collectively, we reveal a notably distinct functional microarchitecture of critical metabolism-regulatory neurons.
Asunto(s)
Conducta Alimentaria/fisiología , Hipotálamo/fisiología , Neuronas/fisiología , Proopiomelanocortina/metabolismo , Animales , Metabolismo Energético/fisiología , Homeostasis/fisiología , Hipotálamo/citología , Ratones , Ratones Transgénicos , Neuronas/citologíaRESUMEN
Leptin-stimulated Stat3 activation in proopiomelanocortin (POMC)-expressing neurons of the hypothalamus plays an important role in maintenance of energy homeostasis. While Stat3 activation in POMC neurons is required for POMC expression, the role of elevated basal Stat3 activation as present in the development of obesity has not been directly addressed. Here, we have generated and characterized mice expressing a constitutively active version of Stat3 (Stat3-C) in POMC neurons (Stat3-C(POMC) mice). On normal chow diet, these animals develop obesity as a result of hyperphagia and decreased POMC expression accompanied by central leptin and insulin resistance. This unexpected finding coincides with POMC-cell-specific, Stat3-mediated upregulation of SOCS3 expression inhibiting both leptin and insulin signaling as insulin-stimulated PIP(3) (phosphatidylinositol-3,4,5 triphosphate) formation and protein kinase B (AKT) activation in POMC neurons as well as with the fact that insulin's ability to hyperpolarize POMC neurons is largely reduced in POMC cells of Stat3-C(POMC) mice. These data indicate that constitutive Stat3 activation is not sufficient to promote POMC expression but requires simultaneous PI3K (phosphoinositide 3-kinase)-dependent release of FOXO1 repression. In contrast, upon exposure to a high-fat diet, food intake and body weight were unaltered in Stat3-C(POMC) mice compared with control mice. Taken together, these experiments directly demonstrate that enhanced basal Stat3 activation in POMC neurons as present in control mice upon high-fat feeding contributes to the development of hypothalamic leptin and insulin resistance.
Asunto(s)
Insulina/metabolismo , Leptina/metabolismo , Proteínas de la Membrana/metabolismo , Inhibición Neural/fisiología , Neuronas/fisiología , Obesidad/fisiopatología , Proopiomelanocortina/metabolismo , Proteína Relacionada con Agouti/genética , Proteína Relacionada con Agouti/metabolismo , Animales , Composición Corporal/genética , Peso Corporal/genética , Modelos Animales de Enfermedad , Ingestión de Alimentos/genética , Ensayo de Cambio de Movilidad Electroforética , Ensayo de Inmunoadsorción Enzimática/métodos , Retroalimentación/fisiología , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Prueba de Tolerancia a la Glucosa , Proteínas Fluorescentes Verdes/genética , Hipotálamo/patología , Técnicas In Vitro , Resistencia a la Insulina/genética , Factor Inhibidor de Leucemia/farmacología , Proteínas de la Membrana/genética , Ratones , Ratones Transgénicos , Inhibición Neural/efectos de los fármacos , Inhibición Neural/genética , Neuropéptido Y/genética , Neuropéptido Y/metabolismo , Obesidad/genética , Obesidad/metabolismo , Técnicas de Placa-Clamp/métodos , Fosfatidilinositol 3-Quinasas/metabolismo , Transducción de Señal/genética , Proteína 3 Supresora de la Señalización de Citocinas , Proteínas Supresoras de la Señalización de Citocinas/genética , Proteínas Supresoras de la Señalización de Citocinas/metabolismo , TransfecciónRESUMEN
OBJECTIVE: The current obesity pandemic represents a major health burden, given that it predisposes to the development of numerous obesity-associated disorders. The obesity-derived adipokines not only impair systemic insulin action but also increase the incidence of hepatocellular carcinoma (HCC), a highly prevalent cancer with poor prognosis. Thus, worldwide incidences of HCC are expected to further increase, and defining the molecular as well as cellular mechanisms will allow for establishing new potential treatment options. The adipose tissue of obese individuals increases circulating leptin and interleukin-6 (IL-6) levels, which both share similar signaling capacities such as Signal Transducer and Activator of Transcription 3 (STAT3) and Phosphoinositide 3-kinase (PI3K)/Akt activation. While mouse models with deficient IL-6 signaling show an ameliorated but not absent Diethylnitrosamine (DEN)-induced HCC development, the morbid obesity in mice with mutant leptin signaling complicates the dissection of hepatic leptin receptor (LEPR) and IL-6 signaling in HCC development. Here we have investigated the function of compensating hepatic LEPR expression in HCC development of IL-6Rα-deficient mice. METHODS: We generated and characterized a mouse model of hepatic LEPR deficiency that was intercrossed with IL-6Rα-deficient mice. Cohorts of single and double knockout mice were subjected to the DEN-HCC model to ascertain liver cancer development and characterize metabolic alterations. RESULTS: We demonstrate that both high-fat diet (HFD)-induced obesity and IL-6Rα deficiency induce hepatic Lepr expression. Consistently, double knockout mice show a further reduction in tumor burden in DEN-induced HCC when compared to control and single LepRL-KO/IL-6Rα knock out mice, whereas metabolism remained largely unaltered between the genotypes. CONCLUSIONS: Our findings reveal a compensatory role for hepatic LEPR in HCC development of IL-6Rα-deficient mice and suggest hepatocyte-specific leptin signaling as promoter of HCC under obese conditions.
Asunto(s)
Subunidad alfa del Receptor de Interleucina-6/deficiencia , Neoplasias Hepáticas Experimentales/metabolismo , Receptores de Leptina/biosíntesis , Animales , Proliferación Celular/fisiología , Dieta Alta en Grasa , Dietilnitrosamina , Modelos Animales de Enfermedad , Femenino , Expresión Génica , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Hepatocitos/patología , Subunidad alfa del Receptor de Interleucina-6/genética , Subunidad alfa del Receptor de Interleucina-6/metabolismo , Leptina/metabolismo , Metabolismo de los Lípidos , Neoplasias Hepáticas Experimentales/inducido químicamente , Neoplasias Hepáticas Experimentales/genética , Neoplasias Hepáticas Experimentales/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Fosfatidilinositol 3-Quinasas/metabolismo , Fosforilación , Receptores de Leptina/genética , Receptores de Leptina/metabolismo , Factor de Transcripción STAT3/metabolismo , Transducción de SeñalRESUMEN
Anorexigenic pro-opiomelanocortin (Pomc)/alpha-melanocyte stimulating hormone (αMSH) neurons of the hypothalamic melanocortin system function as key regulators of energy homeostasis, also controlling somatic growth across different species. However, the mechanisms of melanocortin-dependent growth control still remain ill-defined. Here, we reveal a thus-far-unrecognized structural and functional connection between Pomc neurons and the somatotropic hypothalamo-pituitary axis. Excessive feeding of larval zebrafish causes leptin resistance and reduced levels of the hypothalamic satiety mediator pomca. In turn, this leads to reduced activation of hypophysiotropic somatostatin (Sst)-neurons that express the melanocortin receptor Mc4r, elevated growth hormone (GH) expression in the pituitary, and enhanced somatic growth. Mc4r expression and αMSH responsiveness are conserved in Sst-expressing hypothalamic neurons of mice. Thus, acquired leptin resistance and attenuation of pomca transcription in response to excessive caloric intake may represent an ancient mechanism to promote somatic growth when food resources are plentiful.
Asunto(s)
Dieta , Hormona del Crecimiento/metabolismo , Crecimiento y Desarrollo/efectos de los fármacos , Leptina/farmacología , Proopiomelanocortina/metabolismo , Somatostatina/metabolismo , Animales , Axones/efectos de los fármacos , Axones/metabolismo , Humanos , Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Larva/efectos de los fármacos , Larva/fisiología , Metabolismo de los Lípidos/efectos de los fármacos , Ratones Endogámicos C57BL , Ratones Transgénicos , Inhibición Neural/efectos de los fármacos , Adenohipófisis/efectos de los fármacos , Adenohipófisis/metabolismo , Pez Cebra , alfa-MSH/metabolismoRESUMEN
Colorectal cancer (CRC) is one of the most lethal cancers worldwide in which the vast majority of cases exhibit little genetic risk but are associated with a sedentary lifestyle and obesity. Although the mechanisms underlying CRC and colitis-associated colorectal cancer (CAC) remain unclear, we hypothesised that obesity-induced inflammation predisposes to CAC development. Here, we show that diet-induced obesity accelerates chemically-induced CAC in mice via increased inflammation and immune cell recruitment. Obesity-induced interleukin-6 (IL-6) shifts macrophage polarisation towards tumour-promoting macrophages that produce the chemokine CC-chemokine-ligand-20 (CCL-20) in the CAC microenvironment. CCL-20 promotes CAC progression by recruiting CC-chemokine-receptor-6 (CCR-6)-expressing B cells and γδ T cells via chemotaxis. Compromised cell recruitment as well as inhibition of B and γδ T cells protects against CAC progression. Collectively, our data reveal a function for IL-6 in the CAC microenvironment via lymphocyte recruitment through the CCL-20/CCR-6 axis, thereby implicating a potential therapeutic intervention for human patients.
Asunto(s)
Quimiocina CCL20/metabolismo , Colitis Ulcerosa/patología , Neoplasias Colorrectales/inmunología , Interleucina-6/metabolismo , Obesidad/inmunología , Receptores CCR6/metabolismo , Animales , Transformación Celular Neoplásica/inmunología , Transformación Celular Neoplásica/patología , Quimiocina CCL20/inmunología , Quimiotaxis/inmunología , Colitis Ulcerosa/inducido químicamente , Colitis Ulcerosa/inmunología , Colon/efectos de los fármacos , Colon/inmunología , Colon/patología , Neoplasias Colorrectales/patología , Dieta Alta en Grasa/efectos adversos , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Femenino , Humanos , Subunidad alfa del Receptor de Interleucina-6/genética , Subunidad alfa del Receptor de Interleucina-6/metabolismo , Mucosa Intestinal/efectos de los fármacos , Mucosa Intestinal/inmunología , Mucosa Intestinal/patología , Linfocitos/inmunología , Linfocitos/metabolismo , Macrófagos/inmunología , Macrófagos/metabolismo , Ratones , Ratones Noqueados , Obesidad/etiología , Receptores CCR6/genética , Transducción de Señal/inmunología , Microambiente Tumoral/inmunologíaRESUMEN
Chronic alterations in calcium (Ca2+) signalling in podocytes have been shown to cause proteinuria and progressive glomerular diseases. However, it is unclear whether short Ca2+ peaks influence glomerular biology and cause podocyte injury. Here we generated a DREADD (Designer Receptor Exclusively Activated by a Designer Drug) knock-in mouse line to manipulate intracellular Ca2+ levels. By mating to a podocyte-specific Cre driver we are able to investigate the impact of Ca2+ peaks on podocyte biology in living animals. Activation of the engineered G-protein coupled receptor with the synthetic compound clozapine-N-oxide (CNO) evoked a short and transient Ca2+ peak in podocytes immediately after CNO administration in vivo. Interestingly, this Ca2+ peak did neither affect glomerular perfusion nor filtration in the animals. Moreover, no obvious alterations in the glomerular morphology could be observed. Taken together, these in vivo findings suggest that chronic alterations and calcium overload rather than an induction of transient Ca2+ peaks contribute to podocyte disease.
RESUMEN
Aging is a progressive decline of body function, during which many tissues accumulate few cells with high levels of deleted mitochondrial DNA (mtDNA), leading to a defect of mitochondrial functions. Whether this mosaic mitochondrial deficiency contributes to organ dysfunction is unknown. To investigate this, we generated mice with an accelerated accumulation of mtDNA deletions in the myocardium, by expressing a dominant-negative mutant mitochondrial helicase. These animals accumulated few randomly distributed cardiomyocytes with compromised mitochondrial function, which led to spontaneous ventricular premature contractions and AV blocks at 18 months. These symptoms were not caused by a general mitochondrial dysfunction in the entire myocardium, and were not observed in mice at 12 months with significantly lower numbers of dysfunctional cells. Therefore, our results suggest that the disposition to arrhythmia typically found in the aged human heart might be due to the random accumulation of mtDNA deletions and the subsequent mosaic respiratory chain deficiency.
Asunto(s)
Envejecimiento , Arritmias Cardíacas/etiología , ADN Mitocondrial/genética , Mitocondrias/genética , Enfermedades Mitocondriales/complicaciones , Enfermedades Mitocondriales/genética , Oxígeno/metabolismo , Animales , Arritmias Cardíacas/genética , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/patología , Respiración de la Célula , Complejo IV de Transporte de Electrones/genética , Complejo IV de Transporte de Electrones/metabolismo , Eliminación de Gen , Ratones , Mitocondrias/metabolismo , Mitocondrias/patología , Enfermedades Mitocondriales/metabolismo , Enfermedades Mitocondriales/patología , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/patologíaRESUMEN
Dysregulation of hypothalamic-pituitary-adrenal (HPA) axis activity leads to debilitating neuroendocrine or metabolic disorders such as Cushing's syndrome (CS). Glucocorticoids control HPA axis activity through negative feedback to the pituitary gland and the central nervous system (CNS). However, the cellular mechanisms involved are poorly understood, particularly in the CNS. Here we show that, in mice, selective loss of TrkB signalling in cholecystokinin (CCK)-GABAergic neurons induces glucocorticoid resistance, resulting in increased corticotrophin-releasing hormone expression, chronic hypercortisolism, adrenocortical hyperplasia, glucose intolerance and mature-onset obesity, reminiscent of the human CS phenotype. Interestingly, obesity is not due to hyperphagia or decreased energy expenditure, but is associated with increased de novo lipogenesis in the liver. Our study therefore identifies CCK neurons as a novel and critical cellular component of the HPA axis, and demonstrates the requirement of TrkB for the transmission of glucocorticoid signalling.
Asunto(s)
Colecistoquinina/metabolismo , Síndrome de Cushing/metabolismo , Neuronas GABAérgicas/metabolismo , Glicoproteínas de Membrana/metabolismo , Obesidad/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Animales , Composición Corporal/efectos de los fármacos , Calorimetría Indirecta , Colecistoquinina/genética , Síndrome de Cushing/genética , Ingestión de Alimentos/efectos de los fármacos , Femenino , Neuronas GABAérgicas/efectos de los fármacos , Immunoblotting , Hibridación in Situ , Masculino , Glicoproteínas de Membrana/genética , Ratones , Mifepristona/farmacología , Obesidad/genética , Proteínas Tirosina Quinasas/genéticaRESUMEN
Activation of c-Jun N-terminal kinase 1 (JNK1)- and inhibitor of nuclear factor kappa-B kinase 2 (IKK2)-dependent signaling plays a crucial role in the development of obesity-associated insulin and leptin resistance not only in peripheral tissues but also in the CNS. Here, we demonstrate that constitutive JNK activation in agouti-related peptide (AgRP)-expressing neurons of the hypothalamus is sufficient to induce weight gain and adiposity in mice as a consequence of hyperphagia. JNK activation increases spontaneous action potential firing of AgRP cells and causes both neuronal and systemic leptin resistance. Similarly, activation of IKK2 signaling in AgRP neurons also increases firing of these cells but fails to cause obesity and leptin resistance. In contrast to JNK activation, IKK2 activation blunts insulin signaling in AgRP neurons and impairs systemic glucose homeostasis. Collectively, these experiments reveal both overlapping and nonredundant effects of JNK- and IKK-dependent signaling in AgRP neurons, which cooperate in the manifestation of the metabolic syndrome.
Asunto(s)
Proteína Relacionada con Agouti/metabolismo , Quinasa I-kappa B/metabolismo , Resistencia a la Insulina , Proteínas Quinasas JNK Activadas por Mitógenos/metabolismo , Neuronas/enzimología , Obesidad/enzimología , Potenciales de Acción/efectos de los fármacos , Adiposidad/efectos de los fármacos , Animales , Peso Corporal/efectos de los fármacos , Activación Enzimática/efectos de los fármacos , Glucosa/metabolismo , Homeostasis/efectos de los fármacos , Insulina/metabolismo , Leptina/farmacología , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Masculino , Ratones Endogámicos C57BL , Proteínas Mutantes/metabolismo , Neuronas/efectos de los fármacosRESUMEN
Ceramides increase during obesity and promote insulin resistance. Ceramides vary in acyl-chain lengths from C14:0 to C30:0 and are synthesized by six ceramide synthase enzymes (CerS1-6). It remains unresolved whether obesity-associated alterations of specific CerSs and their defined acyl-chain length ceramides contribute to the manifestation of metabolic diseases. Here we reveal that CERS6 mRNA expression and C16:0 ceramides are elevated in adipose tissue of obese humans, and increased CERS6 expression correlates with insulin resistance. Conversely, CerS6-deficient (CerS6(Δ/Δ)) mice exhibit reduced C16:0 ceramides and are protected from high-fat-diet-induced obesity and glucose intolerance. CerS6 deletion increases energy expenditure and improves glucose tolerance, not only in CerS6(Δ/Δ) mice, but also in brown adipose tissue- (CerS6(ΔBAT)) and liver-specific (CerS6(ΔLIVER)) CerS6 knockout mice. CerS6 deficiency increases lipid utilization in BAT and liver. These experiments highlight CerS6 inhibition as a specific approach for the treatment of obesity and type 2 diabetes mellitus, circumventing the side effects of global ceramide synthesis inhibition.
Asunto(s)
Ceramidas/metabolismo , Intolerancia a la Glucosa , Esfingosina N-Aciltransferasa/metabolismo , Tejido Adiposo Pardo/metabolismo , Animales , Índice de Masa Corporal , Dieta Alta en Grasa , Femenino , Humanos , Peroxidación de Lípido , Hígado/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Obesidad/metabolismo , Obesidad/patología , PPAR gamma/genética , PPAR gamma/metabolismo , Esfingosina N-Aciltransferasa/deficiencia , Esfingosina N-Aciltransferasa/genética , Aumento de PesoRESUMEN
Janus kinase (JAK)-signal transducers and activators of transcription (STAT) signaling pathways are critical for the maintenance of homeostatic and developmental processes; however, deregulation and chronic activation of JAK-STAT3 results in numerous diseases. Among others, obesity is currently being intensively studied. In obesity, chronic JAK-STAT3 is activated by the CNS by increased circulating leptin levels leading to the development of leptin resistance, whereas in the peripheral organs chronic IL-6-induced JAK-STAT3 impairs insulin action. We report the consequences of chronic JAK-STAT3 induced signaling as present under obese conditions in the main metabolic organs.
RESUMEN
Obesity and associated metabolic disturbances, such as increased circulating fatty acids cause prolonged low grade activation of inflammatory signaling pathways in liver, skeletal muscle, adipose tissue and even in the CNS. Activation of inflammatory pathways in turn impairs insulin signaling, ultimately leading to obesity-associated type 2 diabetes mellitus. Conventional JNK-1 knock out mice are protected from high fat diet-induced insulin resistance, characterizing JNK-1-inhibition as a potential approach to improve glucose metabolism in obese patients. However, the cell type-specific role of elevated JNK-1 signaling as present during the course of obesity has not been fully elucidated yet. To investigate the functional contribution of altered JNK-1 activation in skeletal muscle, we have generated a ROSA26 insertion mouse strain allowing for Cre-activatable expression of a JNK-1 constitutive active construct (JNK(C)). To examine the consequence of skeletal muscle-restricted JNK-1 overactivation in the development of insulin resistance and glucose metabolism, JNK(C) mice were crossed to Mck-Cre mice yielding JNK(SM-C) mice. However, despite increased muscle-specific JNK activation, energy homeostasis and glucose metabolism in JNK(SM-C) mice remained largely unaltered compared to controls. In line with these findings, obese mice with skeletal muscle specific disruption of JNK-1, did not affect energy and glucose homeostasis. These experiments indicate that JNK-1 activation in skeletal muscle does not account for the major effects on diet-induced, JNK-1-mediated deterioration of insulin action and points towards a so far underappreciated role of JNK-1 in other tissues than skeletal muscle during the development of obesity-associated insulin resistance.
Asunto(s)
Glucosa/metabolismo , Homeostasis , Resistencia a la Insulina , Proteína Quinasa 8 Activada por Mitógenos/metabolismo , Músculo Esquelético/metabolismo , Obesidad/metabolismo , Animales , Western Blotting , Composición Corporal , Dieta Alta en Grasa/efectos adversos , Metabolismo Energético , Femenino , Expresión Génica , Sistema de Señalización de MAP Quinasas , Masculino , Ratones , Ratones Noqueados , Ratones Transgénicos , Proteína Quinasa 8 Activada por Mitógenos/genética , Obesidad/etiología , Obesidad/genética , Fosforilación , Proteínas/genética , Proteínas/metabolismo , Proteínas Proto-Oncogénicas c-jun/metabolismo , ARN no Traducido , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Obesity increases the incidence of hepatocellular carcinoma (HCC) development in part through the activation of obesity-associated proinflammatory signaling. Here, we show that in lean mice, abrogation of IL-6Rα signaling protects against diethylnitrosamine (DEN)-induced HCC development. HCC protection occurs via Mcl-1 destabilization, thus promoting hepatocyte apoptosis. IL-6 regulates Mcl-1 stability via the inhibition of PP-1α expression, promoting GSK-3ß inactivation. In addition, IL-6 suppresses expression of the Mcl-1 E3 ligase (Mule). Consequently, IL-6Rα deficiency activates PP-1α and Mule expression, resulting in increased Mcl-1 turnover and protection against HCC development. In contrast, in obesity, inhibition of PP-1α and Mule expression, leading to Mcl-1 stabilization, occurs independently of IL-6 signaling. Collectively, this study provides evidence that obesity inhibits hepatocyte apoptosis through Mcl-1 stabilization independent of IL-6 signaling, thus promoting liver carcinogenesis.