RESUMO
The microvascular system consists of two cell types: endothelial and mural (pericytes and vascular smooth muscle cells; VSMCs) cells. Communication between endothelial and mural cells plays a pivotal role in the maintenance of vascular homeostasis; however, in vivo molecular and cellular mechanisms underlying mural cell development remain unclear. In this study, we found that macrophages played a crucial role in TGFß-dependent pericyte-to-VSMC differentiation during retinal vasculature development. In mice with constitutively-active Foxo1-overexpression, substantial accumulation of TGFß1-producing macrophages and pericytes around the angiogenic front region was observed. Additionally, the TGFß-SMAD pathway was activated in pericytes adjacent to macrophages, resulting in an excess ectopic α-smooth muscle actin-positive VSMCs. Furthermore, we identified endothelial SEMA3C as an attractant for macrophages. In vivo neutralization of SEMA3C rescued macrophage accumulation and ectopic VSMC phenotypes in the mice, as well as drug-induced macrophage depletion. Therefore, macrophages play an important physiological role in VSMC development via the FOXO1-SEMA3C pathway.
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Intraluminal lymphatic valves (LVs) contribute to the prevention of lymph backflow and maintain circulatory homeostasis. Several reports have investigated the molecular mechanisms which promote LV formation; however, the way in which they are suppressed is not completely clear. We show that the forkhead transcription factor FOXO1 is a suppressor of LV formation and maintenance in lymphatic endothelial cells. Oscillatory shear stress by bidirectional flow inactivates FOXO1 via Akt phosphorylation, resulting in the upregulation of a subset of LV-specific genes mediated by downregulation of a transcriptional repressor, PRDM1. Mice with an endothelial-specific Foxo1 deletion have an increase in LVs, and overexpression of Foxo1 in mice produces a decrease in LVs. Genetic reduction of PRDM1 rescues the decrease in LV by Foxo1 overexpression. In conclusion, FOXO1 plays a critical role in lymph flow homeostasis by preventing excess LV formation. This gene might be a therapeutic target for lymphatic circulatory abnormalities.
Assuntos
Proteína Forkhead Box O1/fisiologia , Linfangiogênese , Vasos Linfáticos/patologia , Fator 1 de Ligação ao Domínio I Regulador Positivo/metabolismo , Animais , Feminino , Humanos , Vasos Linfáticos/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosforilação , Fator 1 de Ligação ao Domínio I Regulador Positivo/genética , Transdução de SinaisRESUMO
Progesterone receptor membrane associated component 1 (PGRMC1) exhibits haem-dependent dimerization on cell membrane and binds to EGF receptor and cytochromes P450 to regulate cancer proliferation and chemoresistance. However, its physiological functions remain unknown. Herein, we demonstrate that PGRMC1 is required for adipogenesis, and its expression is significantly enhanced by insulin or thiazolidine, an agonist for PPARγ. The haem-dimerized PGRMC1 interacts with low-density lipoprotein receptors (VLDL-R and LDL-R) or GLUT4 to regulate their translocation to the plasma membrane, facilitating lipid uptake and accumulation, and de-novo fatty acid synthesis in adipocytes. These events are cancelled by CO through interfering with PGRMC1 dimerization. PGRMC1 expression in mouse adipose tissues is enhanced during obesity induced by a high fat diet. Furthermore, adipose tissue-specific PGRMC1 knockout in mice dramatically suppressed high-fat-diet induced adipocyte hypertrophy. Our results indicate a pivotal role of PGRMC1 in developing obesity through its metabolic regulation of lipids and carbohydrates in adipocytes.
Assuntos
Adipócitos/metabolismo , Progressão da Doença , Metabolismo dos Lipídeos , Proteínas de Membrana/metabolismo , Obesidade/patologia , Receptores de Progesterona/metabolismo , Células 3T3-L1 , Adipócitos/efeitos dos fármacos , Animais , Monóxido de Carbono/farmacologia , Diferenciação Celular/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Glucose/metabolismo , Transportador de Glucose Tipo 4/metabolismo , Hipertrofia , Metabolismo dos Lipídeos/efeitos dos fármacos , Lipoproteínas LDL/metabolismo , Lipoproteínas VLDL/metabolismo , Camundongos , Modelos Biológicos , Obesidade/sangue , Transporte Proteico/efeitos dos fármacos , Receptores de LDL/metabolismoRESUMO
Although adipocytes are major targets of insulin, the influence of impaired insulin action in adipocytes on metabolic homeostasis remains unclear. We here show that adipocyte-specific PDK1 (3'-phosphoinositide-dependent kinase 1)-deficient (A-PDK1KO) mice manifest impaired metabolic actions of insulin in adipose tissue and reduction of adipose tissue mass. A-PDK1KO mice developed insulin resistance, glucose intolerance, and hepatic steatosis, and this phenotype was suppressed by additional ablation of FoxO1 specifically in adipocytes (A-PDK1/FoxO1KO mice) without an effect on adipose tissue mass. Neither circulating levels of adiponectin and leptin nor inflammatory markers in adipose tissue differed between A-PDK1KO and A-PDK1/FoxO1KO mice. Lipidomics and microarray analyses revealed that leukotriene B4 (LTB4) levels in plasma and in adipose tissue as well as the expression of 5-lipoxygenase (5-LO) in adipose tissue were increased and restored in A-PDK1KO mice and A-PDK1/FoxO1KO mice, respectively. Genetic deletion of the LTB4 receptor BLT1 as well as pharmacological intervention to 5-LO or BLT1 ameliorated insulin resistance in A-PDK1KO mice. Furthermore, insulin was found to inhibit LTB4 production through down-regulation of 5-LO expression via the PDK1-FoxO1 pathway in isolated adipocytes. Our results indicate that insulin signaling in adipocytes negatively regulates the production of LTB4 via the PDK1-FoxO1 pathway and thereby maintains systemic insulin sensitivity.
Assuntos
Proteínas Quinases Dependentes de 3-Fosfoinositídeo , Adipócitos/metabolismo , Araquidonato 5-Lipoxigenase/metabolismo , Proteína Forkhead Box O1 , Resistência à Insulina , Proteínas Quinases Dependentes de 3-Fosfoinositídeo/genética , Proteínas Quinases Dependentes de 3-Fosfoinositídeo/metabolismo , Animais , Células Cultivadas , Proteína Forkhead Box O1/genética , Proteína Forkhead Box O1/metabolismo , Resistência à Insulina/genética , Resistência à Insulina/fisiologia , Leucotrieno B4/metabolismo , Masculino , Camundongos , Camundongos Knockout , Transdução de Sinais/genéticaRESUMO
The transcription factor forkhead box (FOXO) controls important biological responses, including proliferation, apoptosis, differentiation, metabolism, and oxidative stress resistance. The transcriptional activity of FOXO is tightly regulated in a variety of cellular processes. FOXO can convert the external stimuli of insulin, growth factors, nutrients, cytokines, and oxidative stress into cell-specific biological responses by regulating the transcriptional activity of target genes. However, how a single transcription factor regulates a large set of target genes in various tissues in response to a variety of external stimuli remains to be clarified. Evidence indicates that FOXO-binding proteins synergistically function to achieve tightly controlled processes. Here, we review the elaborate mechanism of FOXO-binding proteins, focusing on adipogenesis, glucose homeostasis, and other metabolic regulations in order to deepen our understanding and to identify a novel therapeutic target for the prevention and treatment of metabolic disorders.
Assuntos
Fatores de Transcrição Forkhead/metabolismo , Processamento de Proteína Pós-Traducional , Proteínas 14-3-3/metabolismo , Proteína de Ligação a CREB/metabolismo , Insulina/metabolismo , Especificidade de Órgãos , Ligação Proteica , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Quinases Associadas a Fase S/metabolismo , Sirtuínas/metabolismoRESUMO
Pancreatic endocrine cell development into differentiated α- and ß-cells is highly regulated and involves multiple transcription factors. However, the mechanisms behind the determination of α- and ß-cell masses remains unclear. We previously identified Foxo1 CoRepressor (FCoR), which inhibits Foxo1 by acetylation. Here we demonstrate that Fcor-knockout mice (FcorKO) exhibit significantly increased α-cell mass, expression of the master α-cell regulatory transcription factor Aristaless-related homeobox (Arx), which can be normalized by ß-cell-specific FCoR overexpression (FcorKO-ßFcor), and exhibit ß-to-α-cell conversion. Compared with FcorKO, ß-cell-specific Foxo1 knockout in the FcorKO (DKO) led to decreased Arx expression and α-cell mass. Foxo1 binding to Arx promoter led to DNA methyltransferase 3a (Dnmt3a) dissociation, Arx promoter hypomethylation, and increased Arx expression. In contrast, FCoR suppressed Arx through Foxo1 inhibition and Dnmt3a recruitment to Arx promoter and increased Arx promoter methylation. Our findings suggest that the FCoR-Foxo1 axis regulates pancreatic α-cell mass by suppressing Arx expression.
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Crosstalk between immunity and the thermogenic program has provided insight into metabolic energy regulation. Here, we generated thermogenic program-accelerating mice (T-QKO), in which Foxo1 is knockout and Foxo3 is hetero-knockout in CD4+ T cells. T-QKO exhibit lean phenotype under HFD due to increased energy expenditure. Cold exposure significantly increased expression of the thermogenic genes (Ppargc1a and Ucp1), Th2 cytokines (Il4 and Il13), and Th2 marker gene (Gata3) in subcutaneous adipose tissue (SC) of T-QKO. Furthermore, Ccr4 expression was significantly increased in Th2 cells of T-QKO, and cold exposure induced Ccl22 expression in SC, leading to increased accumulation of Th2 cell population in SC of T-QKO. These data reveal a mechanism by which cold exposure induces selective recruitment of Th2 cells into SC, leading to regulation of energy expenditure by generating beige adipocyte and suggest that inhibition of Foxo in T cells may support a strategy to prevent and treat obesity.
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Nesfatin-1 is a hypothalamic anorexigenic peptide processed from nucleobindin 2 (NUCB2). Central and peripheral administration of NUCB2/nesfatin-1 enhances glucose metabolism and insulin release. NUCB2/nesfatin-1 is also localized in pancreatic islets, while its function remains unknown. To explore the role of pancreatic ß-cell-produced NUCB2/nesfatin-1, we developed pancreatic ß-cell-specific NUCB2 knockout (ßNUCB2 KO) mice and NUCB2 gene knockdown (shNUCB2) MIN6 ß-cell line. In ßNUCB2 KO mice, casual blood glucose was elevated from 12 weeks of age. In a glucose tolerance test at 12 weeks, insulin secretion at 15 min was reduced and blood glucose at 2 h increased in ßNUCB2 KO mice fasted 8 h. In islets isolated from ßNUCB2 KO mice, high glucose-stimulated insulin secretion (GSIS) was impaired. In shNUCB2 MIN6 cells, GSIS was reduced and UCP-2 mRNA expression was elevated. These results show impaired GSIS possibly associated with UCP-2 overexpression in NUCB2-silenced ß-cells, suggesting that ß-cell-produced NUCB2/nesfatin-1 maintains GSIS and thereby glycemia.
Assuntos
Glicemia/metabolismo , Índice Glicêmico/fisiologia , Secreção de Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Nucleobindinas/metabolismo , Proteína Desacopladora 2/metabolismo , Animais , Linhagem Celular , Glucose/metabolismo , Teste de Tolerância a Glucose/métodos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , RatosRESUMO
Obesity has become an explicit public health concern because of its relevance to metabolic syndrome. Evidence points to the significance of beige adipocytes in regulating energy expenditure. Here, using yeast two-hybrid screening, we show that Zfp238 is a Foxo1 co-repressor and that adipose-tissue-specific ablation of Zfp238 (Adipo-Zfp238KO) in mice leads to obesity, decreased energy expenditure, and insulin resistance under normal chow diet. Adipo-Zfp238KO inhibits induction of Ucp1 expression in subcutaneous adipose tissue upon cold exposure or CL316243, but not in brown adipose tissue. Furthermore, knockdown of Zfp238 in 3T3-L1 cells decreases Ucp1 expression in response to cool incubation or forskolin significantly compared with control cells. In contrast, overexpression of Zfp238 in 3T3-L1 cells significantly increases Ucp1 expression in response to forskolin. Finally, double knockdown of both Zfp238 and Foxo1 normalizes Ucp1 induction. These data suggest that Zfp238 in adipose tissue regulates the thermogenic program in cooperation with Foxo1.
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Oxytocin neurons in the paraventricular nucleus (PVN) of hypothalamus regulate energy metabolism and reproduction. Plasma oxytocin concentration is reduced in obese subjects with insulin resistance. These findings prompted us to hypothesize that insulin serves to promote oxytocin release. This study examined whether insulin activates oxytocin neurons in the PVN, and explored the underlying signaling. We generated the mice deficient of 3-phosphoinositide-dependent protein kinase-1 (PDK1), a major signaling molecule particularly for insulin, specifically in oxytocin neurons (Oxy Pdk1 KO). Insulin increased cytosolic calcium concentration ([Ca2+]i) in oxytocin neurons with larger (â§25 µm) and smaller (<25 µm) diameters isolated from PVN in C57BL/6 mice. In PDK1 Oxy Pdk1 KO mice, in contrast, this effect of insulin to increase [Ca2+]i was markedly diminished in the larger-sized oxytocin neurons, while it was intact in the smaller-sized oxytocin neurons. Furthermore, intracerebroventricular insulin administration induced oxytocin release into plasma in Oxy Cre but not Oxy Pdk1 KO mice. These results demonstrate that insulin PDK1-dependently preferentially activates PVN magnocellular oxytocin neurons to release oxytocin into circulation, possibly serving as a mechanism for the interaction between metabolism and perinatal functions.
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Proteínas Quinases Dependentes de 3-Fosfoinositídeo/genética , Metabolismo Energético/genética , Insulina/administração & dosagem , Ocitocina/genética , Animais , Sinalização do Cálcio/genética , Hipotálamo/metabolismo , Insulina/sangue , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Ocitocina/sangue , Núcleo Hipotalâmico Paraventricular/metabolismoRESUMO
In the hypothalamic arcuate nucleus (ARC), orexigenic agouti-related peptide (AgRP) neurons regulate feeding behavior and energy homeostasis. The 3-phosphoinositide-dependent protein kinase-1 (PDK1) in AgRP neurons serves as a major signaling molecule for leptin and insulin, the hormones regulating feeding behavior, energy homeostasis and circulation. However, it is unclear whether PDK1 in AGRP neurons is also involved in regulation of blood pressure. This study explored it by generating and analyzing AgRP neuron-specific PDK1 knockout (Agrp-Pdk1flox/flox) mice and effect of high salt diet on blood pressure in KO and WT mice was analyzed. Under high salt diet feeding, systolic blood pressure (SBP) of Agrp-Pdk1flox/flox mice was significantly elevated compared to Agrp-Cre mice. When the high salt diet was switched to control low salt diet, SBP of Agrp-Pdk1flox/flox mice returned to the basal level observed in Agrp-Cre mice within 1 week. In Agrp-Pdk1flox/flox mice, urinary noradrenalin excretion and NUCB2 mRNA expression in hypothalamic paraventricular nucleus (PVN) were markedly upregulated. Moreover, silencing of NUCB2 in the PVN counteracted the rises in urinary noradrenalin excretions and SBP. These results demonstrate a novel role of PDK1 in AgRP neurons to counteract the high salt diet-induced hypertension by preventing hyperactivation of PVN nesfatin-1 neurons.
Assuntos
Proteína Relacionada com Agouti/genética , Núcleo Arqueado do Hipotálamo/metabolismo , Hipertensão/genética , Neurônios/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteína Relacionada com Agouti/deficiência , Animais , Núcleo Arqueado do Hipotálamo/efeitos dos fármacos , Núcleo Arqueado do Hipotálamo/fisiopatologia , Pressão Sanguínea , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Modelos Animais de Doenças , Ingestão de Energia/efeitos dos fármacos , Comportamento Alimentar/efeitos dos fármacos , Regulação da Expressão Gênica , Hipertensão/induzido quimicamente , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Insulina/genética , Insulina/metabolismo , Leptina/genética , Leptina/metabolismo , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/patologia , Norepinefrina/urina , Nucleobindinas , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/fisiopatologia , Proteínas Serina-Treonina Quinases/deficiência , Piruvato Desidrogenase Quinase de Transferência de Acetil , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais , Cloreto de Sódio na Dieta/efeitos adversosRESUMO
OBJECTIVE: In the hypothalamic arcuate nucleus (ARC), orexigenic agouti-related peptide (AgRP) neurons regulate feeding behavior and energy homeostasis, functions connected to bone metabolism. The 3-phosphoinositide-dependent protein kinase-1 (PDK1) serves as a major signaling molecule particularly for leptin and insulin in AgRP neurons. We asked whether PDK1 in AGRP neurons also contributes to bone metabolism. METHODS: We generated AgRP neuron-specific PDK1 knockout (Agrp Pdk1-/- ) mice and those with additional AgRP neuron-specific expression of transactivation-defective FoxO1 (Agrp Pdk1-/-Δ256Foxo1). Bone metabolism in KO and WT mice was analyzed by quantitative computed tomography (QCT), bone histomorphometry, measurement of plasma biomarkers, and qPCR analysis of peptides. RESULTS: In Agrp Pdk1-/- female mice aged 6 weeks, compared with Agrp Cre mice, both stature and femur length were shorter while body weight was unchanged. Cortical bone mineral density (BMD) and cancellous BMD in the femur decreased, and bone formation was delayed. Furthermore, plasma GH and IGF-1 levels were reduced in parallel with decreased mRNA expressions for GH in pituitary and GHRH in ARC. Osteoblast activity was suppressed and osteoclast activity was enhanced. These changes in stature, BMD and GH level were rescued in Agrp Pdk1-/-Δ256Foxo1 mice, suggesting that the bone abnormalities and impaired GH release were mediated by enhanced Foxo1 due to deletion of PDK1. CONCLUSIONS: This study reveals a novel role of PDK1-Foxo1 pathway of AgRP neurons in controlling bone metabolism primarily via GHRH-GH-IGF-1 axis.
Assuntos
Núcleo Arqueado do Hipotálamo/metabolismo , Densidade Óssea , Hormônio do Crescimento/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Osteogênese , Proteínas Serina-Treonina Quinases/metabolismo , Proteína Relacionada com Agouti/genética , Proteína Relacionada com Agouti/metabolismo , Animais , Núcleo Arqueado do Hipotálamo/citologia , Feminino , Proteína Forkhead Box O1/metabolismo , Hormônio Liberador de Hormônio do Crescimento/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Proteínas Serina-Treonina Quinases/genética , Piruvato Desidrogenase Quinase de Transferência de AcetilRESUMO
High-fat diet (HFD) induces low-grade chronic inflammation and insulin resistance. However, little is known about the mechanism underlying HFD-induced chronic inflammation in peripheral insulin-responsive tissues. Here, we show that colonic pro-inflammatory macrophages regulate insulin sensitivity under HFD conditions. To investigate the pathophysiological role of colonic macrophages, we generated macrophage-specific chemokine (C-C Motif) receptor 2 (Ccr2) knockout (M-Ccr2KO) and intestinal epithelial cell-specific tamoxifen-inducible Ccl2 knockout (Vil-Ccl2KO) mice. Both strains exhibited similar body weight to control under HFD. However, they exhibited decreased infiltration of colonic pro-inflammatory macrophages, decreased intestinal permeability, and inactivation of the colonic inflammasome. Interestingly, they showed significantly improved glucose tolerance and insulin sensitivity with decreased chronic inflammation of adipose tissue. Therefore, inhibition of pro-inflammatory macrophage infiltration prevents HFD-induced insulin resistance and could be a novel therapeutic approach for type 2 diabetes.
Assuntos
Quimiocina CCL2/metabolismo , Colo/patologia , Inflamação/patologia , Resistência à Insulina , Macrófagos/metabolismo , Macrófagos/patologia , Receptores CCR2/metabolismo , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Animais , Dieta Hiperlipídica , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Microbioma Gastrointestinal/efeitos dos fármacos , Deleção de Genes , Inflamassomos/metabolismo , Insulina/farmacologia , Macrófagos/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Especificidade de Órgãos/efeitos dos fármacos , PermeabilidadeRESUMO
Salt-inducible kinase 3 (SIK3), an AMP-activated protein kinase-related kinase, is induced in the murine liver after the consumption of a diet rich in fat, sucrose, and cholesterol. To examine whether SIK3 can modulate glucose and lipid metabolism in the liver, we analyzed phenotypes of SIK3-deficent mice. Sik3(-/-) mice have a malnourished the phenotype (i.e., lipodystrophy, hypolipidemia, hypoglycemia, and hyper-insulin sensitivity) accompanied by cholestasis and cholelithiasis. The hypoglycemic and hyper-insulin-sensitive phenotypes may be due to reduced energy storage, which is represented by the low expression levels of mRNA for components of the fatty acid synthesis pathways in the liver. The biliary disorders in Sik3(-/-) mice are associated with the dysregulation of gene expression programs that respond to nutritional stresses and are probably regulated by nuclear receptors. Retinoic acid plays a role in cholesterol and bile acid homeostasis, wheras ALDH1a which produces retinoic acid, is expressed at low levels in Sik3(-/-) mice. Lipid metabolism disorders in Sik3(-/-) mice are ameliorated by the treatment with 9-cis-retinoic acid. In conclusion, SIK3 is a novel energy regulator that modulates cholesterol and bile acid metabolism by coupling with retinoid metabolism, and may alter the size of energy storage in mice.
Assuntos
Glucose/metabolismo , Metabolismo dos Lipídeos , Proteínas Serina-Treonina Quinases/genética , Animais , Ácidos e Sais Biliares/metabolismo , Colesterol/metabolismo , Ácido Cólico/metabolismo , Dieta Hiperlipídica , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Homeostase/genética , Hipoglicemia/genética , Hipoglicemia/metabolismo , Metabolismo dos Lipídeos/genética , Lipodistrofia/genética , Lipodistrofia/metabolismo , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fenótipo , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de SinaisRESUMO
Chronic inflammation in adipose tissue contributes to obesity-related insulin resistance. The 3-phosphoinositide-dependent protein kinase 1 (Pdk1)/forkhead transcription factor (Foxo1) pathway is important in regulating glucose and energy homeostasis, but little is known about this pathway in adipose tissue macrophages (ATMs). To investigate this, we generated transgenic mice that carried macrophage/granulocyte-specific mutations, including a Pdk1 knockout (LysMPdk1(-/-)), a Pdk1 knockout with transactivation-defective Foxo1 (Δ256LysMPdk1(-/-)), a constitutively active nuclear (CN) Foxo1 (CNFoxo1(LysM)), or a transactivation-defective Foxo1 (Δ256Foxo1(LysM)). We analyzed glucose metabolism and gene expression in ATM populations isolated with fluorescence-activated cell sorting. The LysMPdk1(-/-) mice exhibited elevated M1 macrophages in adipose tissue and insulin resistance. Overexpression of transactivation-defective Foxo1 rescued these phenotypes. CNFoxo1(LysM) promoted transcription of the C-C motif chemokine receptor 2 (Ccr2) in ATMs and increased M1 macrophages in adipose tissue. On a high-fat diet, CNFoxo1(LysM) mice exhibited insulin resistance. Pdk1 deletion or Foxo1 activation in bone marrow-derived macrophages abolished insulin and interleukin-4 induction of genes involved in alternative macrophage activation. Thus, Pdk1 regulated macrophage infiltration by inhibiting Foxo1-induced Ccr2 expression. This shows that the macrophage Pdk1/Foxo1 pathway is important in regulating insulin sensitivity in vivo.
Assuntos
Fatores de Transcrição Forkhead/genética , Resistência à Insulina/fisiologia , Paniculite/etiologia , Proteínas Serina-Treonina Quinases/genética , Proteínas Quinases Dependentes de 3-Fosfoinositídeo , Tecido Adiposo/patologia , Tecido Adiposo/fisiologia , Animais , Dieta Hiperlipídica , Proteína Forkhead Box O1 , Interleucina-4/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Paniculite/fisiopatologia , Receptores CCR2/biossínteseRESUMO
Forkhead box-containing protein o (Foxo) 1 is a key transcription factor in insulin and glucose metabolism. We identified a Foxo1-CoRepressor (FCoR) protein in mouse adipose tissue that inhibits Foxo1's activity by enhancing acetylation via impairment of the interaction between Foxo1 and the deacetylase Sirt1 and via direct acetylation. FCoR is phosphorylated at Threonine 93 by catalytic subunit of protein kinase A and is translocated into nucleus, making it possible to bind to Foxo1 in both cytosol and nucleus. Knockdown of FCoR in 3T3-F442A cells enhanced expression of Foxo target and inhibited adipocyte differentiation. Overexpression of FCoR in white adipose tissue decreased expression of Foxo-target genes and adipocyte size and increased insulin sensitivity in Lepr(db/db) mice and in mice fed a high-fat diet. In contrast, Fcor knockout mice were lean, glucose intolerant, and had decreased insulin sensitivity that was accompanied by increased expression levels of Foxo-target genes and enlarged adipocytes. Taken together, these data suggest that FCoR is a novel repressor that regulates insulin sensitivity and energy metabolism in adipose tissue by acting to fine-tune Foxo1 activity.
Assuntos
Proteínas Correpressoras/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Regulação da Expressão Gênica , Resistência à Insulina , Acetilação , Tecido Adiposo/metabolismo , Animais , Proteínas Correpressoras/genética , Proteína Forkhead Box O1 , Expressão Gênica , Técnicas de Silenciamento de Genes , Camundongos , Camundongos Knockout , Sirtuína 1/metabolismoRESUMO
Recent studies have revealed that insulin signaling in pancreatic ß-cells and the hypothalamus is critical for maintaining nutrient and energy homeostasis, the failure of which are hallmarks of metabolic syndrome. We previously reported that forkhead transcription factor forkhead box-containing protein of the O subfamily (FoxO)1, a downstream effector of insulin signaling, plays important roles in ß-cells and the hypothalamus when we investigated the roles of FoxO1 independently in the pancreas and hypothalamus. However, because metabolic syndrome is caused by the combined disorders in hypothalamus and pancreas, to elucidate the combined implications of FoxO1 in these organs, we generated constitutively active FoxO1 knockin (KI) mice with specific activation in both the hypothalamus and pancreas. The KI mice developed obesity, insulin resistance, glucose intolerance, and hypertriglyceridemia due to increased food intake, decreased energy expenditure, and impaired insulin secretion, which characterize metabolic syndrome. The KI mice also had increased hypothalamic Agouti-related protein and neuropeptide Y levels and decreased uncoupling protein 1 and peroxisome proliferator-activated receptor γ coactivator 1α levels in adipose tissue and skeletal muscle. Impaired insulin secretion was associated with decreased expression of pancreatic and duodenum homeobox 1 (Pdx1), muscyloaponeurotic fibrosarcoma oncogene homolog A (MafA), and neurogenic differentiation 1 (NeuroD) in islets, although ß-cell mass was paradoxically increased in KI mice. Based on these results, we propose that uncontrolled FoxO1 activation in the hypothalamus and pancreas accounts for the development of obesity and glucose intolerance, hallmarks of metabolic syndrome.
Assuntos
Fatores de Transcrição Forkhead/metabolismo , Regulação da Expressão Gênica/fisiologia , Intolerância à Glucose/metabolismo , Hipotálamo/metabolismo , Obesidade/metabolismo , Pâncreas/metabolismo , Animais , Proliferação de Células , Ingestão de Alimentos , Metabolismo Energético/genética , Metabolismo Energético/fisiologia , Proteína Forkhead Box O1 , Fatores de Transcrição Forkhead/genética , Intolerância à Glucose/genética , Insulina/metabolismo , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/fisiologia , Camundongos , Obesidade/genética , Consumo de Oxigênio , Fatores de TempoRESUMO
Insulin-like growth factors (IGFs) are well known to play essential roles in enhancement of myogenic differentiation. In this report we showed that initial IGF-I signal activation but long-term IGF-1 signal termination are required for myogenic differentiation. L6 myoblast stably transfected with myc-epitope tagged insulin receptor substrate-1, myc-IRS-1 (L6-mIRS1) was unable to differentiate into myotubes, indicating that IRS-1 constitutive expression inhibited myogenesis. To elucidate the molecular mechanisms underlying myogenic inhibition, IGF-I signaling was examined. IGF-I treatment of control L6 cells for 18 h resulted in a marked suppression of IGF-I stimulated IRS-1 association with the p85 PI 3-kinase and suppression of activation of Akt that correlated with a down regulation of IRS-1 protein. L6-mIRS1 cells, in contrast, had sustained high levels of IRS-1 protein following 18 h of IGF-I treatment with persistent p85 PI 3-kinase association with IRS-1, Akt phosphorylation and phosphorylation of the downstream Akt substrate, Foxo1. Consistent with Foxo1 phosphorylation, Foxo1 protein was excluded from the nuclei in L6-mIRS1 cells, whereas Foxo1 was localized in the nuclei in control L6 cells during induction of differentiation. In addition, L6 cells stably expressing a dominant-interfering form of Foxo1, Δ256Foxo1 (L6-Δ256Foxo1) were unable to differentiate into myotubes. Together, these data demonstrate that IGF-I regulation of Foxo1 nuclear localization is essential for the myogenic program in L6 cells but that persistent activation of IGF-1 signaling pathways results in a negative feedback to prevent myogenesis.
Assuntos
Diferenciação Celular , Núcleo Celular/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Proteínas Substratos do Receptor de Insulina/metabolismo , Desenvolvimento Muscular , Mioblastos/citologia , Mioblastos/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Animais , Diferenciação Celular/efeitos dos fármacos , Núcleo Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Genes Dominantes/genética , Fator de Crescimento Insulin-Like I/farmacologia , Desenvolvimento Muscular/efeitos dos fármacos , Mutação/genética , Mioblastos/efeitos dos fármacos , Transporte Proteico/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos , Células Satélites de Músculo Esquelético/citologia , Células Satélites de Músculo Esquelético/efeitos dos fármacos , Células Satélites de Músculo Esquelético/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Insulin and leptin intracellular signaling pathways converge and act synergistically on the hypothalamic phosphatidylinositol-3-OH kinase/3-phosphoinositide-dependent protein kinase 1 (PDK1). However, little is known about whether PDK1 in agouti-related peptide (AGRP) neurons contributes to energy homeostasis. We generated AGRP neuron-specific PDK1 knockout (AGRPPdk1(-/-)) mice and mice with selective expression of transactivation-defective Foxo1 (Δ256Foxo1(AGRP)Pdk1(-/-)). The AGRPPdk1(-/-) mice showed reductions in food intake, body length, and body weight. The Δ256Foxo1(AGRP)Pdk1(-/-) mice showed increased body weight, food intake, and reduced locomotor activity. After four weeks of calorie-restricted feeding, oxygen consumption and locomotor activity were elevated in AGRPPdk1(-/-) mice and reduced in Δ256Foxo1(AGRP)Pdk1(-/-) mice. In vitro, ghrelin-induced changes in [Ca(2+)](i) and inhibition of ghrelin by leptin were significantly attenuated in AGRPPdk1(-/-) neurons compared to control neurons. However, ghrelin-induced [Ca(2+)](i) changes and leptin inhibition were restored in Δ256Foxo1(AGRP)Pdk1(-/-) mice. These results suggested that PDK1 and Foxo1 signaling pathways play important roles in the control of energy homeostasis through AGRP-independent mechanisms.