RESUMO
As chronic inflammation is a hallmark of obesity, pathways that integrate nutrient- and pathogen sensing pathways are of great interest in understanding the mechanisms of insulin resistance, type 2 diabetes, and other chronic metabolic pathologies. Here, we provide evidence that double-stranded RNA-dependent protein kinase (PKR) can respond to nutrient signals as well as endoplasmic reticulum (ER) stress and coordinate the activity of other critical inflammatory kinases such as the c-Jun N-terminal kinase (JNK) to regulate insulin action and metabolism. PKR also directly targets and modifies insulin receptor substrate and hence integrates nutrients and insulin action with a defined pathogen response system. Dietary and genetic obesity features marked activation of PKR in adipose and liver tissues and absence of PKR alleviates metabolic deterioration due to nutrient or energy excess in mice. These findings demonstrate PKR as a critical component of an inflammatory complex that responds to nutrients and organelle dysfunction.
Assuntos
Doenças Metabólicas/metabolismo , eIF-2 Quinase/metabolismo , Animais , Feminino , Humanos , Proteínas Substratos do Receptor de Insulina/metabolismo , MAP Quinase Quinase 4/metabolismo , Masculino , Camundongos , eIF-2 Quinase/genéticaRESUMO
Atherosclerosis and insulin resistance are major components of the cardiometabolic syndrome, a global health threat associated with a systemic inflammatory state. Notch signaling regulates tissue development and participates in innate and adaptive immunity in adults. The role of Notch signaling in cardiometabolic inflammation, however, remains obscure. We noted that a high-fat, high-cholesterol diet increased expression of the Notch ligand Delta-like 4 (Dll4) in atheromata and fat tissue in LDL-receptor-deficient mice. Blockade of Dll4-Notch signaling using neutralizing anti-Dll4 antibody attenuated the development of atherosclerosis, diminished plaque calcification, improved insulin resistance, and decreased fat accumulation. These changes were accompanied by decreased macrophage accumulation, diminished expression of monocyte chemoattractant protein-1 (MCP-1), and lower levels of nuclear factor-κB (NF-κB) activation. In vitro cell culture experiments revealed that Dll4-mediated Notch signaling increases MCP-1 expression via NF-κB, providing a possible mechanism for in vivo effects. Furthermore, Dll4 skewed macrophages toward a proinflammatory phenotype ("M1"). These results suggest that Dll4-Notch signaling plays a central role in the shared mechanism for the pathogenesis of cardiometabolic disorders.
Assuntos
Anticorpos Neutralizantes/farmacologia , Aterosclerose/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/metabolismo , Síndrome Metabólica/metabolismo , Células 3T3-L1 , Proteínas Adaptadoras de Transdução de Sinal , Adipócitos/citologia , Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Animais , Insuficiência da Valva Aórtica/imunologia , Insuficiência da Valva Aórtica/metabolismo , Aterosclerose/imunologia , Aterosclerose/terapia , Proteínas de Ligação ao Cálcio , Quimiocina CCL2/metabolismo , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Humanos , Imunidade Inata/fisiologia , Resistência à Insulina/fisiologia , Peptídeos e Proteínas de Sinalização Intercelular/imunologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/imunologia , Macrófagos/imunologia , Macrófagos/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/imunologia , Síndrome Metabólica/imunologia , Síndrome Metabólica/terapia , Camundongos , Camundongos Obesos , Camundongos Transgênicos , Receptores de LDL/genética , Receptores Notch/metabolismo , Veia Safena/citologia , Transdução de Sinais/fisiologiaRESUMO
Obesity is a major health problem and a risk factor for type 2 diabetes. Leptin, an adipocyte-secreted hormone, acts on the hypothalamus to inhibit food intake and increase energy expenditure. Most obese individuals develop hyperleptinemia and leptin resistance, limiting the therapeutic efficacy of exogenously administered leptin. Mice lacking the tyrosine phosphatase PTP1B are protected from diet-induced obesity and are hypersensitive to leptin, but the site and mechanism for these effects remain controversial. We generated tissue-specific PTP1B knockout (Ptpn1(-/-)) mice. Neuronal Ptpn1(-/-) mice have reduced weight and adiposity, and increased activity and energy expenditure. In contrast, adipose PTP1B deficiency increases body weight, whereas PTP1B deletion in muscle or liver does not affect weight. Neuronal Ptpn1(-/-) mice are hypersensitive to leptin, despite paradoxically elevated leptin levels, and show improved glucose homeostasis. Thus, PTP1B regulates body mass and adiposity primarily through actions in the brain. Furthermore, neuronal PTP1B regulates adipocyte leptin production and probably is essential for the development of leptin resistance.
Assuntos
Tecido Adiposo/metabolismo , Peso Corporal/genética , Regulação Enzimológica da Expressão Gênica , Leptina/administração & dosagem , Neurônios/enzimologia , Proteínas Tirosina Fosfatases/genética , Tecido Adiposo/fisiologia , Animais , Esquema de Medicação , Ingestão de Alimentos , Glucose/metabolismo , Homeostase , Injeções Intraperitoneais , Leptina/metabolismo , Leptina/fisiologia , Masculino , Camundongos , Camundongos Knockout , Proteína Tirosina Fosfatase não Receptora Tipo 1 , Fatores de TempoRESUMO
Adipocyte fatty-acid-binding protein, aP2 (FABP4) is expressed in adipocytes and macrophages, and integrates inflammatory and metabolic responses. Studies in aP2-deficient mice have shown that this lipid chaperone has a significant role in several aspects of metabolic syndrome, including type 2 diabetes and atherosclerosis. Here we demonstrate that an orally active small-molecule inhibitor of aP2 is an effective therapeutic agent against severe atherosclerosis and type 2 diabetes in mouse models. In macrophage and adipocyte cell lines with or without aP2, we also show the target specificity of this chemical intervention and its mechanisms of action on metabolic and inflammatory pathways. Our findings demonstrate that targeting aP2 with small-molecule inhibitors is possible and can lead to a new class of powerful therapeutic agents to prevent and treat metabolic diseases such as type 2 diabetes and atherosclerosis.
Assuntos
Aterosclerose/tratamento farmacológico , Diabetes Mellitus/tratamento farmacológico , Proteínas de Ligação a Ácido Graxo/antagonistas & inibidores , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Tecido Adiposo/citologia , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Aterosclerose/genética , Aterosclerose/metabolismo , Compostos de Bifenilo/metabolismo , Linhagem Celular , Colesterol/metabolismo , Diabetes Mellitus/genética , Diabetes Mellitus/metabolismo , Proteínas de Ligação a Ácido Graxo/metabolismo , Humanos , Inflamação/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Modelos Biológicos , Obesidade/genética , Obesidade/metabolismo , Pirazóis/metabolismoRESUMO
Pharmacological activation of peroxisome proliferator-activated receptor δ/ß (PPARδ/ß) improves glucose handling and insulin sensitivity. The target tissues of drug actions remain unclear. We demonstrate here that adenovirus-mediated liver-restricted PPARδ activation reduces fasting glucose levels in chow- and high fat-fed mice. This effect is accompanied by hepatic glycogen and lipid deposition as well as up-regulation of glucose utilization and de novo lipogenesis pathways. Promoter analyses indicate that PPARδ regulates hepatic metabolic programs through both direct and indirect transcriptional mechanisms partly mediated by its co-activator, PPARγ co-activator-1ß. Assessment of the lipid composition reveals that PPARδ increases the production of monounsaturated fatty acids, which are PPAR activators, and reduces that of saturated FAs. Despite the increased lipid accumulation, adeno-PPARδ-infected livers exhibit less damage and show a reduction in JNK stress signaling, suggesting that PPARδ-regulated lipogenic program may protect against lipotoxicity. The altered substrate utilization by PPARδ also results in a secondary effect on AMP-activated protein kinase activation, which likely contributes to the glucose-lowering activity. Collectively, our data suggest that PPARδ controls hepatic energy substrate homeostasis by coordinated regulation of glucose and fatty acid metabolism, which provide a molecular basis for developing PPARδ agonists to manage hyperglycemia and insulin resistance.
Assuntos
Metabolismo Energético/fisiologia , Hiperglicemia/metabolismo , Resistência à Insulina/fisiologia , Fígado/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Adenilato Quinase/metabolismo , Animais , Glicemia/metabolismo , Ácidos Graxos Monoinsaturados/metabolismo , Regulação da Expressão Gênica/fisiologia , Homeostase/fisiologia , Hiperglicemia/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Receptores Citoplasmáticos e Nucleares/genética , Transcrição Gênica/fisiologiaRESUMO
OBJECTIVE: The adipocyte/macrophage fatty acid-binding proteins aP2 (FABP4) and Mal1 (FABP5) are intracellular lipid chaperones that modulate systemic glucose metabolism, insulin sensitivity, and atherosclerosis. Combined deficiency of aP2 and Mal1 has been shown to reduce the development of atherosclerosis, but the independent role of macrophage Mal1 expression in atherogenesis remains unclear. METHODS AND RESULTS: We transplanted wild-type (WT), Mal1(-/-), or aP2(-/-) bone marrow into low-density lipoprotein receptor-null (LDLR(-/-)) mice and fed them a Western diet for 8 weeks. Mal1(-/-)âLDLR(-/-) mice had significantly reduced (36%) atherosclerosis in the proximal aorta compared with control WTâLDLR(-/-) mice. Interestingly, peritoneal macrophages isolated from Mal1-deficient mice displayed increased peroxisome proliferator-activated receptor-γ (PPARγ) activity and upregulation of a PPARγ-related cholesterol trafficking gene, CD36. Mal1(-/-) macrophages showed suppression of inflammatory genes, such as COX2 and interleukin 6. Mal1(-/-)âLDLR(-/-) mice had significantly decreased macrophage numbers in the aortic atherosclerotic lesions compared with WTâLDLR(-/-) mice, suggesting that monocyte recruitment may be impaired. Indeed, blood monocytes isolated from Mal1(-/-)âLDLR(-/-) mice on a high-fat diet had decreased CC chemokine receptor 2 gene and protein expression levels compared with WT monocytes. CONCLUSION: Taken together, our results demonstrate that Mal1 plays a proatherogenic role by suppressing PPARγ activity, which increases expression of CC chemokine receptor 2 by monocytes, promoting their recruitment to atherosclerotic lesions.
Assuntos
Aterosclerose/prevenção & controle , Proteínas de Ligação a Ácido Graxo/fisiologia , Regulação da Expressão Gênica , Macrófagos/fisiologia , Proteínas de Neoplasias/fisiologia , PPAR gama/fisiologia , Receptores de LDL/fisiologia , Animais , Antígenos CD36/fisiologia , Feminino , Lipídeos/sangue , Camundongos , Receptores CCR2/genéticaRESUMO
Elevated levels of tumor necrosis factor (TNFalpha) are implicated in the development of insulin resistance, but the mechanisms mediating these chronic effects are not completely understood. We demonstrate that TNFalpha signaling through TNF receptor (TNFR) 1 suppresses AMPK activity via transcriptional upregulation of protein phosphatase 2C (PP2C). This in turn reduces ACC phosphorylation, suppressing fatty-acid oxidation, increasing intramuscular diacylglycerol accumulation, and causing insulin resistance in skeletal muscle, effects observed both in vitro and in vivo. Importantly even at pathologically elevated levels of TNFalpha observed in obesity, the suppressive effects of TNFalpha on AMPK signaling are reversed in mice null for both TNFR1 and 2 or following treatment with a TNFalpha neutralizing antibody. Our data demonstrate that AMPK is an important TNFalpha signaling target and is a contributing factor to the suppression of fatty-acid oxidation and the development of lipid-induced insulin resistance in obesity.
Assuntos
Adenilato Quinase/biossíntese , Resistência à Insulina , Músculo Esquelético/enzimologia , Obesidade/enzimologia , Transdução de Sinais , Fator de Necrose Tumoral alfa/metabolismo , Adenilato Quinase/genética , Animais , Resistência à Insulina/genética , Metabolismo dos Lipídeos/genética , Camundongos , Camundongos Mutantes , Músculo Esquelético/patologia , Obesidade/genética , Obesidade/patologia , Oxirredução , Fosfoproteínas Fosfatases/genética , Fosfoproteínas Fosfatases/metabolismo , Proteína Fosfatase 2C , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/metabolismo , Receptores Tipo II do Fator de Necrose Tumoral/genética , Receptores Tipo II do Fator de Necrose Tumoral/metabolismo , Transdução de Sinais/genética , Fator de Necrose Tumoral alfa/genéticaRESUMO
Adipose tissue inflammation is a characteristic of obesity. However, the mechanisms that regulate this inflammatory response and link adipose inflammation to systemic metabolic consequences are not fully understood. In this study, we have taken advantage of the highly restricted coexpression of adipocyte/macrophage fatty acid-binding proteins (FABPs) aP2 (FABP4) and mal1 (FABP5) to examine the contribution of these lipid chaperones in macrophages and adipocytes to local and systemic inflammation and metabolic homeostasis in mice. Deletion of FABPs in adipocytes resulted in reduced expression of inflammatory cytokines in macrophages, whereas the same deletion in macrophages led to enhanced insulin signaling and glucose uptake in adipocytes. Using radiation chimerism through bone marrow transplantation, we generated mice with FABP deficiency in bone marrow and stroma-derived elements in vivo and studied the impact of each cellular target on local and systemic insulin action and glucose metabolism in dietary obesity. The results of these experiments indicated that neither macrophages nor adipocytes individually could account for the total impact of FABPs on systemic metabolism and suggest that interactions between these 2 cell types, particularly in adipose tissue, are critical for the inflammatory basis of metabolic deterioration.
Assuntos
Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Proteínas de Ligação a Ácido Graxo/fisiologia , Inflamação/metabolismo , Macrófagos/metabolismo , Obesidade/metabolismo , Adipócitos/efeitos dos fármacos , Tecido Adiposo/citologia , Animais , Glicemia/metabolismo , Transplante de Medula Óssea , Comunicação Celular/fisiologia , Quimiocina CCL2/metabolismo , Proteínas de Ligação a Ácido Graxo/deficiência , Proteínas de Ligação a Ácido Graxo/genética , Glucose/metabolismo , Insulina/sangue , Insulina/farmacologia , Fígado/citologia , Fígado/metabolismo , Macrófagos/citologia , Macrófagos/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Proteínas de Neoplasias/deficiência , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/fisiologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptor de Insulina/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Fatty acid binding proteins (FABPs) are cytosolic fatty acid chaperones whose biological role and mechanisms of action are not well understood. Here, we developed mice with targeted mutations in two related adipocyte FABPs, aP2 and mal1, to resolve their role in systemic lipid, glucose, and energy metabolism. Mice lacking aP2 and mal1 exhibited a striking phenotype with strong protection from diet-induced obesity, insulin resistance, type 2 diabetes, and fatty liver disease. These mice have altered cellular and systemic lipid transport and composition, leading to enhanced insulin receptor signaling, enhanced muscle AMP-activated kinase (AMP-K) activity, and dramatically reduced liver stearoyl-CoA desaturase-1 (SCD-1) activity underlying their phenotype. Taken together with the previously reported strong protection against atherosclerosis, these results demonstrate that adipocyte/macrophage FABPs have a robust impact on multiple components of metabolic syndrome, integrating metabolic and inflammatory responses in mice and constituting a powerful target for the treatment of these diseases.
Assuntos
Adipócitos/citologia , Proteínas de Transporte/metabolismo , Diabetes Mellitus/metabolismo , Macrófagos/citologia , Obesidade/metabolismo , Proteínas Quinases Ativadas por AMP , Adipócitos/metabolismo , Tecido Adiposo/citologia , Tecido Adiposo/metabolismo , Animais , Arteriosclerose/metabolismo , Peso Corporal , Citocinas/metabolismo , Proteínas de Ligação a Ácido Graxo , Ácidos Graxos/metabolismo , Regulação da Expressão Gênica , Glucose/metabolismo , Immunoblotting , Inflamação , Insulina/metabolismo , Resistência à Insulina , Metabolismo dos Lipídeos , Fígado/metabolismo , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Complexos Multienzimáticos/metabolismo , Mutação , Oxigênio/metabolismo , Fenótipo , Fosforilação , Proteínas Serina-Treonina Quinases/metabolismo , RNA Mensageiro/metabolismo , Receptor de Insulina/metabolismo , Estearoil-CoA Dessaturase/metabolismo , Fatores de Tempo , Distribuição Tecidual , Triglicerídeos/metabolismoRESUMO
The adipocyte fatty acid-binding protein aP2 regulates systemic glucose and lipid metabolism. We report that aP2, in addition to being abundantly expressed by adipocytes, is also expressed by human airway epithelial cells and shows a striking upregulation following stimulation of epithelial cells with the Th2 cytokines IL-4 and IL-13. Regulation of aP2 mRNA expression by Th2 cytokines was highly dependent on STAT6, a transcription factor with a major regulatory role in allergic inflammation. We examined aP2-deficient mice in a model of allergic airway inflammation and found that infiltration of leukocytes, especially eosinophils, into the airways was highly dependent on aP2 function. T cell priming was unaffected by aP2 deficiency, suggesting that aP2 was acting locally within the lung, and analysis of bone marrow chimeras implicated non-hematopoietic cells, most likely bronchial epithelial cells, as the site of action of aP2 in allergic airway inflammation. Thus, aP2 regulates allergic airway inflammation and may provide a link between fatty acid metabolism and asthma.
Assuntos
Adipócitos/fisiologia , Asma/imunologia , Proteínas de Ligação a Ácido Graxo/metabolismo , Hipersensibilidade/imunologia , Inflamação/fisiopatologia , Células 3T3 , Adipócitos/imunologia , Animais , Brônquios/fisiologia , Técnicas de Cultura de Células , Modelos Animais de Doenças , Proteínas de Ligação a Ácido Graxo/deficiência , Proteínas de Ligação a Ácido Graxo/genética , Ácidos Graxos/metabolismo , Interleucina-12/imunologia , Interleucina-4/imunologia , Camundongos , Camundongos Knockout , RNA Mensageiro/genética , Mucosa Respiratória/fisiologia , Células Th2/imunologia , Transcrição GênicaRESUMO
Fatty acid-binding proteins (FABPs) are cytosolic fatty acid chaperones that play a critical role in systemic regulation of lipid and glucose metabolism. In animals lacking the adipocyte/macrophage FABP isoforms aP2 and mal1, there is strong protection against diet-induced obesity, insulin resistance, type 2 diabetes, fatty liver disease, and hypercholesterolemic atherosclerosis. On high-fat diet, FABP-deficient mice also exhibit enhanced muscle AMP-activated kinase (AMPK) and reduced liver stearoyl-CoA desaturase-1 (SCD-1) activities. Here, we performed a cross between aP2(-/-), mal1(-/-), and leptin-deficient (ob/ob) mice to elucidate the role of leptin action on the metabolic phenotype of aP2-mal1 deficiency. The extent of obesity in the ob/ob-aP2-mal1(-/-) mice was comparable with ob/ob mice. However, despite severe obesity, ob/ob-aP2-mal1(-/-) mice remained euglycemic and demonstrated improved peripheral insulin sensitivity. There was also a striking protection from liver fatty infiltration in the ob/ob-aP2-mal1(-/-) mice with strong suppression of SCD-1 activity. On the other hand, the enhanced muscle AMPK activity in aP2-mal1(-/-) mice was lost in the ob/ob background. These results indicated that both decreased body weight and enhanced muscle AMPK activity in aP2-mal1(-/-) mice are potentially leptin dependent but improved systemic insulin sensitivity and protection from liver fatty infiltration are largely unrelated to leptin action and that insulin-sensitizing effects of FABP deficiency are, at least in part, independent of its effects on total-body adiposity.
Assuntos
Adipócitos/metabolismo , Proteínas de Ligação a Ácido Graxo/fisiologia , Leptina/deficiência , Leptina/genética , Macrófagos/metabolismo , Obesidade/genética , Adenilato Quinase/metabolismo , Animais , Camundongos , Camundongos KnockoutRESUMO
The metabolic syndrome is a cluster of metabolic and inflammatory abnormalities including obesity, insulin resistance, type 2 diabetes, hypertension, dyslipidemia, and atherosclerosis. The fatty acid binding proteins aP2 (fatty acid binding protein [FABP]-4) and mal1 (FABP5) are closely related and both are expressed in adipocytes. Previous studies in aP2-deficient mice have indicated a significant role for aP2 in obesity-related insulin resistance, type 2 diabetes, and atherosclerosis. However, the biological functions of mal1 are not known. Here, we report the generation of mice with targeted null mutations in the mal1 gene as well as transgenic mice overexpressing mal1 from the aP2 promoter/enhancer to address the role of this FABP in metabolic regulation in the presence or absence of obesity. To address the role of the second adipocyte FABP in metabolic regulation in the presence and deficiency of obesity, absence of mal1 resulted in increased systemic insulin sensitivity in two models of obesity and insulin resistance. Adipocytes isolated from mal1-deficient mice also exhibited enhanced insulin-stimulated glucose transport capacity. In contrast, mice expressing high levels of mal1 in adipose tissue display reduced systemic insulin sensitivity. Hence, our results demonstrate that mal1 modulates adipose tissue function and contributes to systemic glucose metabolism and constitutes a potential therapeutic target in insulin resistance.
Assuntos
Glicemia/metabolismo , Proteínas de Transporte , Resistência à Insulina/fisiologia , Proteínas de Neoplasias/deficiência , Proteínas de Neoplasias/fisiologia , Obesidade/fisiopatologia , Animais , Clonagem Molecular , Cruzamentos Genéticos , Dieta , Proteínas de Ligação a Ácido Graxo , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Proteínas de Neoplasias/genética , Obesidade/sangue , Obesidade/genética , Regiões Promotoras Genéticas , Isoformas de Proteínas/genéticaRESUMO
Through unknown mechanisms, insulin activates the sterol regulatory element-binding protein (SREBP1c) transcription factor to promote hepatic lipogenesis. We find that this induction is dependent on the mammalian target of rapamycin (mTOR) complex 1 (mTORC1). To further define the role of mTORC1 in the regulation of SREBP1c in the liver, we generated mice with liver-specific deletion of TSC1 (LTsc1KO), which results in insulin-independent activation of mTORC1. Surprisingly, the LTsc1KO mice are protected from age- and diet-induced hepatic steatosis and display hepatocyte-intrinsic defects in SREBP1c activation and de novo lipogenesis. These phenotypes result from attenuation of Akt signaling driven by mTORC1-dependent insulin resistance. Therefore, mTORC1 activation is not sufficient to stimulate hepatic SREBP1c in the absence of Akt signaling, revealing the existence of an additional downstream pathway also required for this induction. We provide evidence that this mTORC1-independent pathway involves Akt-mediated suppression of Insig2a, a liver-specific transcript encoding the SREBP1c inhibitor INSIG2.
Assuntos
Hepatócitos/metabolismo , Proteínas/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteína de Ligação a Elemento Regulador de Esterol 1/metabolismo , Animais , Células Cultivadas , Insulina/metabolismo , Lipogênese , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Complexos Multiproteicos , Proteínas/fisiologia , Transdução de Sinais , Proteína de Ligação a Elemento Regulador de Esterol 1/antagonistas & inibidores , Serina-Treonina Quinases TOR , Proteína 1 do Complexo Esclerose Tuberosa , Proteínas Supressoras de Tumor/deficiência , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismoRESUMO
The transcriptional corepressor SMRT utilizes two major receptor-interacting domains (RID1 and RID2) to mediate nuclear receptor (NR) signaling through epigenetic modification. The physiological significance of such interaction remains unclear. We find SMRT expression and its occupancy on peroxisome proliferator-activated receptor (PPAR) target gene promoters are increased with age in major metabolic tissues. Genetic manipulations to selectively disable RID1 (SMRT(mRID1)) demonstrate that shifting SMRT repression to RID2-associated NRs, notably PPARs, causes premature aging and related metabolic diseases accompanied by reduced mitochondrial function and antioxidant gene expression. SMRT(mRID1) cells exhibit increased susceptibility to oxidative damage, which could be rescued by PPAR activation or antioxidant treatment. In concert, several human Smrt gene polymorphisms are found to nominally associate with type 2 diabetes and adiponectin levels. These data uncover a role for SMRT in mitochondrial oxidative metabolism and the aging process, which may serve as a drug target to improve health span.
Assuntos
Envelhecimento/metabolismo , Epigênese Genética/fisiologia , Correpressor 2 de Receptor Nuclear/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Transdução de Sinais/fisiologia , Adiponectina/genética , Adiponectina/metabolismo , Fatores Etários , Animais , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Perfilação da Expressão Gênica , Humanos , Camundongos , Mitocôndrias/metabolismo , Correpressor 2 de Receptor Nuclear/genética , Receptores Ativados por Proliferador de Peroxissomo/metabolismo , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único/genéticaRESUMO
Although mast cell functions have classically been related to allergic responses, recent studies indicate that these cells contribute to other common diseases such as multiple sclerosis, rheumatoid arthritis, atherosclerosis, aortic aneurysm and cancer. This study presents evidence that mast cells also contribute to diet-induced obesity and diabetes. For example, white adipose tissue (WAT) from obese humans and mice contain more mast cells than WAT from their lean counterparts. Furthermore, in the context of mice on a Western diet, genetically induced deficiency of mast cells, or their pharmacological stabilization, reduces body weight gain and levels of inflammatory cytokines, chemokines and proteases in serum and WAT, in concert with improved glucose homeostasis and energy expenditure. Mechanistic studies reveal that mast cells contribute to WAT and muscle angiogenesis and associated cell apoptosis and cathepsin activity. Adoptive transfer experiments of cytokine-deficient mast cells show that these cells, by producing interleukin-6 (IL-6) and interferon-gamma (IFN-gamma), contribute to mouse adipose tissue cysteine protease cathepsin expression, apoptosis and angiogenesis, thereby promoting diet-induced obesity and glucose intolerance. Our results showing reduced obesity and diabetes in mice treated with clinically available mast cell-stabilizing agents suggest the potential of developing new therapies for these common human metabolic disorders.
Assuntos
Cromolina Sódica/uso terapêutico , Diabetes Mellitus Experimental/etiologia , Mastócitos/efeitos dos fármacos , Obesidade/tratamento farmacológico , Obesidade/genética , Proteínas Proto-Oncogênicas c-kit/genética , Animais , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/imunologia , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/imunologia , Dieta Aterogênica , Avaliação Pré-Clínica de Medicamentos , Feminino , Humanos , Masculino , Mastócitos/metabolismo , Camundongos , Camundongos Transgênicos , Obesidade/complicações , Obesidade/etiologia , Obesidade/imunologia , Especificidade de Órgãos/genética , Proteínas Proto-Oncogênicas c-kit/metabolismoRESUMO
Fatty acid-binding proteins (FABPs) act as intracellular receptors for a variety of hydrophobic compounds, enabling their diffusion within the cytoplasmic compartment. Recent studies have demonstrated the ability of FABPs to simultaneously regulate metabolic and inflammatory pathways. We investigated the role of adipocyte FABP and epithelial FABP in the development of experimental autoimmune encephalomyelitis to test the hypothesis that these FABPs impact adaptive immune responses and contribute to the pathogenesis of autoimmune disease. FABP-deficient mice exhibited a lower incidence of disease, reduced clinical symptoms of experimental autoimmune encephalomyelitis and dramatically lower levels of proinflammatory cytokine mRNA expression in CNS tissue as compared with wild-type mice. In vitro Ag recall responses of myelin oligodendrocyte glycoprotein 35-55-immunized FABP(-/-) mice showed reduced proliferation and impaired IFN-gamma production. Dendritic cells deficient for FABPs were found to be poor producers of proinflammatory cytokines and Ag presentation by FABP(-/-) dendritic cells did not promote proinflammatory T cell responses. This study reveals that metabolic-inflammatory pathway cross-regulation by FABPs contributes to adaptive immune responses and subsequent autoimmune inflammation.
Assuntos
Encefalomielite Autoimune Experimental/metabolismo , Encefalomielite Autoimune Experimental/prevenção & controle , Proteínas de Ligação a Ácido Graxo/deficiência , Sequência de Aminoácidos , Animais , Apresentação de Antígeno/genética , Apresentação de Antígeno/imunologia , Encéfalo/metabolismo , Encéfalo/patologia , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Progressão da Doença , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/patologia , Proteínas de Ligação a Ácido Graxo/biossíntese , Proteínas de Ligação a Ácido Graxo/genética , Glicoproteínas/administração & dosagem , Glicoproteínas/imunologia , Mediadores da Inflamação/antagonistas & inibidores , Mediadores da Inflamação/metabolismo , Ativação Linfocitária/genética , Ativação Linfocitária/imunologia , Macrófagos/imunologia , Macrófagos/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Dados de Sequência Molecular , Glicoproteína Mielina-Oligodendrócito , Fragmentos de Peptídeos/administração & dosagem , Fragmentos de Peptídeos/imunologia , Medula Espinal/metabolismo , Medula Espinal/patologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , Linfócitos T/patologiaRESUMO
Metabolic and inflammatory pathways crosstalk at many levels, and, while required for homeostasis, interaction between these pathways can also lead to metabolic dysregulation under conditions of chronic stress. Thus, we hypothesized that mechanisms might exist to prevent overt inflammatory responses during physiological fluctuations in nutrients or under nutrient-rich conditions, and we identified the six-transmembrane protein STAMP2 as a critical modulator of this integrated response system of inflammation and metabolism in adipocytes. Lack of STAMP2 in adipocytes results in aberrant inflammatory responses to both nutrients and acute inflammatory stimuli. Similarly, in whole animals, visceral adipose tissue of STAMP2(-/-) mice exhibits overt inflammation, and these mice develop spontaneous metabolic disease on a regular diet, manifesting insulin resistance, glucose intolerance, mild hyperglycemia, dyslipidemia, and fatty liver disease. We conclude that STAMP2 participates in integrating inflammatory and metabolic responses and thus plays a key role in systemic metabolic homeostasis.
Assuntos
Adipócitos/metabolismo , Alimentos , Inflamação/metabolismo , Proteínas de Membrana/metabolismo , Redes e Vias Metabólicas , Células 3T3-L1 , Tecido Adiposo/metabolismo , Animais , Células Cultivadas , Feminino , Glucose/metabolismo , Homeostase , Insulina/metabolismo , Resistência à Insulina , Metabolismo dos Lipídeos , Fígado/metabolismo , Masculino , Proteínas de Membrana/genética , Síndrome Metabólica/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , MutaçãoRESUMO
Endoplasmic reticulum (ER) stress is a key link between obesity, insulin resistance, and type 2 diabetes. Here, we provide evidence that this mechanistic link can be exploited for therapeutic purposes with orally active chemical chaperones. 4-Phenyl butyric acid and taurine-conjugated ursodeoxycholic acid alleviated ER stress in cells and whole animals. Treatment of obese and diabetic mice with these compounds resulted in normalization of hyperglycemia, restoration of systemic insulin sensitivity, resolution of fatty liver disease, and enhancement of insulin action in liver, muscle, and adipose tissues. Our results demonstrate that chemical chaperones enhance the adaptive capacity of the ER and act as potent antidiabetic modalities with potential application in the treatment of type 2 diabetes.
Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Retículo Endoplasmático/metabolismo , Glucose/metabolismo , Fenilbutiratos/farmacologia , Ácido Tauroquenodesoxicólico/farmacologia , Tecido Adiposo/metabolismo , Animais , Glicemia/metabolismo , Linhagem Celular Tumoral , Diabetes Mellitus Tipo 2/tratamento farmacológico , Modelos Animais de Doenças , Retículo Endoplasmático/efeitos dos fármacos , Ativação Enzimática , Fator de Iniciação 2 em Eucariotos/metabolismo , Glucose/administração & dosagem , Teste de Tolerância a Glucose , Homeostase , Insulina/sangue , Insulina/farmacologia , Resistência à Insulina , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Fígado/metabolismo , Camundongos , Camundongos Obesos , Fenilbutiratos/uso terapêutico , Fosforilação , Receptor de Insulina/metabolismo , Transdução de Sinais , Ácido Tauroquenodesoxicólico/uso terapêutico , eIF-2 Quinase/metabolismoRESUMO
The fatty acid-binding protein (FABP) family consists of a number of conserved cytoplasmic proteins with roles in intracellular lipid transport, storage, and metabolism. Examination of a comprehensive leukocyte gene expression database revealed strong expression of the adipocyte FABP aP2 in human monocyte-derived dendritic cells (DCs). We isolated bone marrow-derived DC from aP2-deficient mice, and showed that expression of DC cytokines including IL-12 and TNF was significantly impaired in these cells. Degradation of IkappaBalpha was also impaired in aP2-deficient DCs, indicative of reduced signaling through the IkappaB kinase-NF-kappaB pathway. The cytokine defect was selective because there was no effect on Ag uptake or expression of MHC class II, CD40, CD80, or CD86. In an MLR, aP2-deficient DCs stimulated markedly lower T cell proliferation and cytokine production than did wild-type DCs. Moreover, aP2-deficient mice immunized with keyhole limpet hemocyanin/CFA showed reduced production of IFN-gamma by restimulated draining lymph node cells, suggesting a similar defect in DC function in vivo. Similarly, infection of aP2-deficient mice with the natural mouse pathogen ectromelia virus resulted in substantially lower production of IFN-gamma by CD8+ T cells. Thus, FABP aP2 plays an important role in DC function and T cell priming, and provides an additional link between metabolic processes and the regulation of immune responses.