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1.
J Lipid Res ; 54(7): 1848-59, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23585690

RESUMO

Peroxisome proliferator-activated receptor (PPAR)α is a nuclear receptor that coordinates liver metabolism during fasting. Fatty acid synthase (FAS) is an enzyme that stores excess calories as fat during feeding, but it also activates hepatic PPARα by promoting synthesis of an endogenous ligand. Here we show that the mechanism underlying this paradoxical relationship involves the differential regulation of FAS in at least two distinct subcellular pools: cytoplasmic and membrane-associated. In mouse liver and cultured hepatoma cells, the ratio of cytoplasmic to membrane FAS-specific activity was increased with fasting, indicating higher cytoplasmic FAS activity under conditions associated with PPARα activation. This effect was due to a nutrient-dependent and compartment-selective covalent modification of FAS. Cytoplasmic FAS was preferentially phosphorylated during feeding or insulin treatment at Thr-1029 and Thr-1033, which flank a dehydratase domain catalytic residue. Mutating these sites to alanines promoted PPARα target gene expression. Rapamycin-induced inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1), a mediator of the feeding/insulin signal to induce lipogenesis, reduced FAS phosphorylation, increased cytoplasmic FAS enzyme activity, and increased PPARα target gene expression. Rapamycin-mediated induction of the same gene was abrogated with FAS knockdown. These findings suggest that hepatic FAS channels lipid synthesis through specific subcellular compartments that allow differential gene expression based on nutritional status.


Assuntos
Ácido Graxo Sintases/metabolismo , Alimentos , Lipídeos/biossíntese , PPAR alfa/metabolismo , Animais , Células Cultivadas , Citoplasma/enzimologia , Ácido Graxo Sintases/antagonistas & inibidores , Ácido Graxo Sintases/genética , Células HEK293 , Humanos , Insulina/metabolismo , Fígado/enzimologia , Masculino , Alvo Mecanístico do Complexo 1 de Rapamicina , Camundongos , Camundongos Endogâmicos C57BL , Complexos Multiproteicos/metabolismo , PPAR alfa/antagonistas & inibidores , PPAR alfa/genética , Fosforilação/efeitos dos fármacos , Sirolimo/farmacologia , Serina-Treonina Quinases TOR/metabolismo
2.
Cell Metab ; 6(6): 497-505, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18054318

RESUMO

Age-related disease, not aging per se, causes most morbidity in older humans. Here we report that skeletal muscle respiratory uncoupling due to UCP1 expression diminishes age-related disease in three mouse models. In a longevity study, median survival was increased in UCP mice (animals with skeletal muscle-specific UCP1 expression), and lymphoma was detected less frequently in UCP female mice. In apoE null mice, a vascular disease model, diet-induced atherosclerosis was decreased in UCP animals. In agouti yellow mice, a genetic obesity model, diabetes and hypertension were reversed by induction of UCP1 in skeletal muscle. Uncoupled mice had decreased adiposity, increased temperature and metabolic rate, elevated muscle SIRT and AMP kinase, and serum characterized by increased adiponectin and decreased IGF-1 and fibrinogen. Accelerating metabolism in skeletal muscle does not appear to impact aging but may delay age-related disease.


Assuntos
Envelhecimento/metabolismo , Transporte de Elétrons/fisiologia , Músculo Esquelético/metabolismo , Envelhecimento/genética , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Aterosclerose/genética , Aterosclerose/metabolismo , Aterosclerose/prevenção & controle , Dieta Aterogênica , Feminino , Humanos , Canais Iônicos/deficiência , Canais Iônicos/genética , Canais Iônicos/metabolismo , Longevidade/genética , Longevidade/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Knockout , Camundongos Transgênicos , Proteínas Mitocondriais/deficiência , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Desacopladores/metabolismo , Proteína Desacopladora 1
3.
Cell Metab ; 5(2): 91-102, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17276352

RESUMO

Glucocorticoid excess causes insulin resistance and hypertension. Hepatic expression of PPARalpha (Ppara) is required for glucocorticoid-induced insulin resistance. Here we demonstrate that afferent fibers of the vagus nerve interface with hepatic Ppara expression to disrupt blood pressure and glucose homeostasis in response to glucocorticoids. Selective hepatic vagotomy decreased hyperglycemia, hyperinsulinemia, hepatic insulin resistance, Ppara expression, and phosphoenolpyruvate carboxykinase (PEPCK) enzyme activity in dexamethasone-treated Ppara(+/+) mice. Selective vagotomy also decreased blood pressure, adrenergic tone, renin activity, and urinary sodium retention in these mice. Hepatic reconstitution of Ppara in nondiabetic, normotensive dexamethasone-treated PPARalpha null mice increased glucose, insulin, hepatic PEPCK enzyme activity, blood pressure, and renin activity in sham-operated animals but not hepatic-vagotomized animals. Disruption of vagal afferent fibers by chemical or surgical means prevented glucocorticoid-induced metabolic derangements. We conclude that a dynamic interaction between hepatic Ppara expression and a vagal afferent pathway is essential for glucocorticoid induction of diabetes and hypertension.


Assuntos
Dexametasona/farmacologia , Hipertensão/induzido quimicamente , Resistência à Insulina/fisiologia , Fígado/inervação , Fígado/metabolismo , PPAR alfa/metabolismo , Nervo Vago/fisiologia , Vias Aferentes/efeitos dos fármacos , Vias Aferentes/metabolismo , Vias Aferentes/cirurgia , Vias Aferentes/ultraestrutura , Animais , Pressão Sanguínea/efeitos dos fármacos , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Glucose/biossíntese , Fígado/efeitos dos fármacos , Fígado/ultraestrutura , Camundongos , Camundongos Endogâmicos C57BL , PPAR alfa/deficiência , PPAR alfa/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Vagotomia , Nervo Vago/efeitos dos fármacos , Nervo Vago/cirurgia , Nervo Vago/ultraestrutura
4.
J Biol Chem ; 286(35): 30949-30961, 2011 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-21757749

RESUMO

Fatty acid synthase (FAS) promotes energy storage through de novo lipogenesis and participates in signaling by the nuclear receptor PPARα in noncardiac tissues. To determine if de novo lipogenesis is relevant to cardiac physiology, we generated and characterized FAS knockout in the myocardium (FASKard) mice. FASKard mice develop normally, manifest normal resting heart function, and have normal cardiac PPARα signaling as well as fatty acid oxidation. However, they decompensate with stress. Most die within 1 h of transverse aortic constriction, probably due to arrhythmia. Voltage clamp measurements of FASKard cardiomyocytes show hyperactivation of L-type calcium channel current that could not be reversed with palmitate supplementation. Of the classic regulators of this current, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) but not protein kinase A signaling is activated in FASKard hearts, and knockdown of FAS in cultured cells activates CaMKII. In addition to being intolerant of the stress of acute pressure, FASKard hearts were also intolerant of the stress of aging, reflected as persistent CaMKII hyperactivation, progression to dilatation, and premature death by ∼1 year of age. CaMKII signaling appears to be pathogenic in FASKard hearts because inhibition of its signaling in vivo rescues mice from early mortality after transverse aortic constriction. FAS was also increased in two mechanistically distinct mouse models of heart failure and in the hearts of humans with end stage cardiomyopathy. These data implicate a novel relationship between FAS and calcium signaling in the heart and suggest that FAS induction in stressed myocardium represents a compensatory response to protect cardiomyocytes from pathological calcium flux.


Assuntos
Ácido Graxo Sintases/metabolismo , Miocárdio/patologia , Miócitos Cardíacos/metabolismo , Animais , Aorta/metabolismo , Aorta/patologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Cruzamentos Genéticos , Ecocardiografia/métodos , Feminino , Genótipo , Lipogênese , Masculino , Camundongos , Modelos Biológicos , Miocárdio/metabolismo , Especificidade por Substrato
5.
J Clin Invest ; 118(6): 2281-90, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18483620

RESUMO

Niemann-Pick C1 (NPC1) is a key participant in cellular cholesterol trafficking. Loss of NPC1 function leads to defective suppression of SREBP-dependent gene expression and failure to appropriately activate liver X receptor-mediated (LXR-mediated) pathways, ultimately resulting in intracellular cholesterol accumulation. To determine whether NPC1 contributes to regulation of macrophage sterol homeostasis in vivo, we examined the effect of NPC1 deletion in BM-derived cells on atherosclerotic lesion development in the Ldlr-/- mouse model of atherosclerosis. High-fat diet-fed chimeric Npc1-/- mice reconstituted with Ldlr-/-Npc1-/- macrophages exhibited accelerated atherosclerosis despite lower serum cholesterol compared with mice reconstituted with wild-type macrophages. The discordance between the low serum lipoprotein levels and the presence of aortic atherosclerosis suggested that intrinsic alterations in macrophage sterol metabolism in the chimeric Npc1-/- mice played a greater role in atherosclerotic lesion formation than did serum lipoprotein levels. Macrophages from chimeric Npc1-/- mice showed decreased synthesis of 27-hydroxycholesterol (27-HC), an endogenous LXR ligand; decreased expression of LXR-regulated cholesterol transporters; and impaired cholesterol efflux. Lower 27-HC levels were associated with elevated cholesterol oxidation products in macrophages and plasma of chimeric Npc1-/- mice and with increased oxidative stress. Our results demonstrate that NPC1 serves an atheroprotective role in mice through regulation of LXR-dependent cholesterol efflux and mitigation of cholesterol-induced oxidative stress in macrophages.


Assuntos
Aterosclerose/metabolismo , Colesterol/metabolismo , Macrófagos/metabolismo , Proteínas/genética , Proteínas/fisiologia , Ração Animal , Animais , Aorta/patologia , Transporte Biológico , Colesterol/sangue , Hidroxicolesteróis/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Transgênicos , Modelos Biológicos , Proteína C1 de Niemann-Pick , Estresse Oxidativo , Esteróis/metabolismo , Fatores de Tempo
6.
Nat Med ; 9(8): 1069-75, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12847522

RESUMO

Hypertension and diabetes are common side effects of glucocorticoid treatment. To determine whether peroxisome proliferator-activated receptor-alpha (PPAR-alpha) mediates these sequelae, mice deficient in low-density lipoprotein receptor (Ldlr-/-), with (Ppara+/+) or without (Ppara-/-) PPAR-alpha, were treated chronically with dexamethasone. Ppara+/+, but not Ppara-/-, mice developed hyperglycemia, hyperinsulinemia and hypertension. Similar effects on glucose metabolism were seen in a different model using C57BL/6 mice. Hepatic gluconeogenic gene expression was increased and insulin-mediated suppression of endogenous glucose production was less effective in dexamethasone-treated Ppara+/+ mice. Adenoviral reconstitution of PPAR-alpha in the livers of nondiabetic, normotensive, dexamethasone-treated Ppara-/- mice induced hyperglycemia, hyperinsulinemia and increased gluconeogenic gene expression. It also increased blood pressure, renin activity, sympathetic nervous activity and renal sodium retention. Human hepatocytes treated with dexamethasone and the PPAR-alpha agonist Wy14,643 induced PPARA and gluconeogenic gene expression. These results identify hepatic activation of PPAR-alpha as a mechanism underlying glucocorticoid-induced insulin resistance.


Assuntos
Dexametasona/farmacologia , Diabetes Mellitus/metabolismo , Glucocorticoides/farmacologia , Hipertensão/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores de LDL/metabolismo , Fatores de Transcrição/metabolismo , Animais , Linhagem Celular , HDL-Colesterol/metabolismo , Glucose/metabolismo , Hepatócitos/citologia , Hepatócitos/fisiologia , Humanos , Insulina/metabolismo , Rim/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de LDL/genética , Sódio/metabolismo
7.
Nature ; 435(7041): 502-6, 2005 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-15917810

RESUMO

The observations that atherosclerosis often occurs in non-smokers without elevated levels of low-density lipoprotein cholesterol, and that most atherosclerosis loci so far identified in mice do not affect systemic risk factors associated with atherosclerosis, suggest that as-yet-unidentified mechanisms must contribute to vascular disease. Arterial walls undergo regional disturbances of metabolism that include the uncoupling of respiration and oxidative phosphorylation, a process that occurs to some extent in all cells and may be characteristic of blood vessels being predisposed to the development of atherosclerosis. To test the hypothesis that inefficient metabolism in blood vessels promotes vascular disease, we generated mice with doxycycline-inducible expression of uncoupling protein-1 (UCP1) in the artery wall. Here we show that UCP1 expression in aortic smooth muscle cells causes hypertension and increases dietary atherosclerosis without affecting cholesterol levels. UCP1 expression also increases superoxide production and decreases the availability of nitric oxide, evidence of oxidative stress. These results provide proof of principle that inefficient metabolism in blood vessels can cause vascular disease.


Assuntos
Aorta/citologia , Arteriosclerose/fisiopatologia , Pressão Sanguínea/fisiologia , Proteínas de Transporte/metabolismo , Respiração Celular/fisiologia , Proteínas de Membrana/metabolismo , Músculo Liso Vascular/metabolismo , Desacopladores/metabolismo , Aconitato Hidratase/metabolismo , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Arteriosclerose/genética , Proteínas de Transporte/genética , Colesterol/sangue , Dieta , Doxiciclina/farmacologia , Expressão Gênica/efeitos dos fármacos , Canais Iônicos , Proteínas de Membrana/genética , Camundongos , Camundongos Transgênicos , Proteínas Mitocondriais , Músculo Liso Vascular/citologia , Estresse Oxidativo , Fenótipo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Renina/sangue , Sódio/urina , Superóxidos/metabolismo , Transgenes/genética , Proteína Desacopladora 1
8.
Cell Metab ; 1(5): 309-22, 2005 May.
Artigo em Inglês | MEDLINE | ID: mdl-16054078

RESUMO

De novo lipogenesis is an energy-expensive process whose role in adult mammals is poorly understood. We generated mice with liver-specific inactivation of fatty-acid synthase (FAS), a key lipogenic enzyme. On a zero-fat diet, FASKOL (FAS knockout in liver) mice developed hypoglycemia and fatty liver, which were reversed with dietary fat. These phenotypes were also observed after prolonged fasting, similarly to fasted PPARalpha-deficiency mice. Hypoglycemia, fatty liver, and defects in expression of PPARalpha target genes in FASKOL mice were corrected with a PPARalpha agonist. On either zero-fat or chow diet, FASKOL mice had low serum and hepatic cholesterol levels with elevated SREBP-2, decreased HMG-CoA reductase expression, and decreased cholesterol biosynthesis; these were also corrected with a PPARalpha agonist. These results suggest that products of the FAS reaction regulate glucose, lipid, and cholesterol metabolism by serving as endogenous activators of distinct physiological pools of PPARalpha in adult liver.


Assuntos
Colesterol/metabolismo , Ácido Graxo Sintases/metabolismo , Glucose/metabolismo , Metabolismo dos Lipídeos , Fígado/metabolismo , PPAR alfa/metabolismo , Animais , Colesterol/genética , Proteínas de Ligação a DNA/genética , Gorduras na Dieta/administração & dosagem , Ácido Graxo Sintases/biossíntese , Ácidos Graxos/genética , Ácidos Graxos/metabolismo , Fígado Gorduroso/metabolismo , Regulação Enzimológica da Expressão Gênica , Homeostase/fisiologia , Hidroximetilglutaril-CoA Redutases/genética , Hipoglicemia/metabolismo , Fígado/enzimologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Biológicos , PPAR alfa/agonistas , PPAR alfa/genética , Proteína de Ligação a Elemento Regulador de Esterol 2 , Fatores de Transcrição/genética
9.
Cell Metab ; 1(2): 133-44, 2005 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16054054

RESUMO

The role of the peroxisome proliferator-activated receptor-alpha (PPARalpha) in the development of insulin-resistant diabetes was evaluated using gain- and loss-of-function approaches. Transgenic mice overexpressing PPARalpha in muscle (MCK-PPARalpha mice) developed glucose intolerance despite being protected from diet-induced obesity. Conversely, PPARalpha null mice were protected from diet-induced insulin resistance in the context of obesity. In skeletal muscle, MCK-PPARalpha mice exhibited increased fatty acid oxidation rates, diminished AMP-activated protein kinase activity, and reduced insulin-stimulated glucose uptake without alterations in the phosphorylation status of key insulin-signaling proteins. These effects on muscle glucose uptake involved transcriptional repression of the GLUT4 gene. Pharmacologic inhibition of fatty acid oxidation or mitochondrial respiratory coupling prevented the effects of PPARalpha on GLUT4 expression and glucose homeostasis. These results identify PPARalpha-driven alterations in muscle fatty acid oxidation and energetics as a potential link between obesity and the development of glucose intolerance and insulin resistance.


Assuntos
Diabetes Mellitus/metabolismo , Músculos/metabolismo , Obesidade/metabolismo , PPAR alfa/metabolismo , Animais , Northern Blotting , Western Blotting , DNA Complementar/metabolismo , Ácidos Graxos/metabolismo , Regulação da Expressão Gênica , Glucose/metabolismo , Glucose/farmacocinética , Insulina/metabolismo , Resistência à Insulina , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Músculo Esquelético/metabolismo , Músculos/citologia , Análise de Sequência com Séries de Oligonucleotídeos , Oxigênio/metabolismo , Fenótipo , Fosfatidilinositol 3-Quinases , Fosforilação , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Fatores de Tempo , Transcrição Gênica
10.
J Clin Invest ; 117(9): 2539-52, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17694178

RESUMO

Central nervous system control of energy balance affects susceptibility to obesity and diabetes, but how fatty acids, malonyl-CoA, and other metabolites act at this site to alter metabolism is poorly understood. Pharmacological inhibition of fatty acid synthase (FAS), rate limiting for de novo lipogenesis, decreases appetite independently of leptin but also promotes weight loss through activities unrelated to FAS inhibition. Here we report that the conditional genetic inactivation of FAS in pancreatic beta cells and hypothalamus produced lean, hypophagic mice with increased physical activity and impaired hypothalamic PPARalpha signaling. Administration of a PPARalpha agonist into the hypothalamus increased PPARalpha target genes and normalized food intake. Inactivation of beta cell FAS enzyme activity had no effect on islet function in culture or in vivo. These results suggest a critical role for brain FAS in the regulation of not only feeding, but also physical activity, effects that appear to be mediated through the provision of ligands generated by FAS to PPARalpha. Thus, 2 diametrically opposed proteins, FAS (induced by feeding) and PPARalpha (induced by starvation), unexpectedly form an integrative sensory module in the central nervous system to orchestrate energy balance.


Assuntos
Ácido Graxo Sintases/metabolismo , Homeostase , PPAR alfa/metabolismo , Animais , Comportamento Apetitivo , Peso Corporal , Diferenciação Celular , Ativação Enzimática , Ácido Graxo Sintases/deficiência , Ácido Graxo Sintases/genética , Feminino , Hormônios/sangue , Doenças Hipotalâmicas/enzimologia , Doenças Hipotalâmicas/patologia , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/enzimologia , Masculino , Camundongos , Camundongos Knockout , PPAR alfa/agonistas , Transdução de Sinais/efeitos dos fármacos
11.
J Nutr ; 140(11): 1907-14, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20861213

RESUMO

After loss of intestinal surface area, the remaining bowel undergoes a morphometric and functional adaptive response. Enterocytic expression of the transcriptional coregulator tetradecanoyl phorbol acetate induced sequence 7 (Tis7) is markedly increased in a murine model of intestinal adaptation. Mice overexpressing Tis7 in intestine have greater triglyceride absorption and weight gain when fed a high-fat diet (42% energy) than their wild-type (WT) littermates fed the same diet. These and other data suggest that Tis7 has a unique role in nutrient absorptive and metabolic adaptation. Herein, male Tis7(-/-) and WT mice were fed a high-fat diet (42% energy) for 8 wk. Weight was monitored and metabolic analyses and hepatic and intestinal lipid concentrations were compared after 8 wk. Intestinal lipid absorption and metabolism studies and intestinal resection surgeries were performed in separate groups of Tis7(-/-) and WT mice. At 8 wk, weight gain was less and jejunal mucosal and hepatic triglyceride and cholesterol concentrations were lower in Tis7(-/-) mice than in the WT controls. Following corn oil gavage, serum cholesterol, triglyceride, and FFA concentrations were lower in the Tis7(-/-) mice than in the WT mice. Incorporation of oral (3)[H] triolein into intestinal mucosal cholesterol ester and FFA was less in Tis7(-/-) compared with WT mice. Following resection, crypt cell proliferation rates and villus heights were lower in Tis7(-/-) than in WT mice, indicating a blunted adaptive response. Our results suggest a novel physiologic function for Tis7 in the gut as a global regulator of lipid absorption and metabolism and epithelial cell proliferation.


Assuntos
Adaptação Fisiológica/genética , Gorduras na Dieta/efeitos adversos , Proteínas Imediatamente Precoces/genética , Intestinos/fisiopatologia , Metabolismo dos Lipídeos/genética , Proteínas de Membrana/genética , Síndrome do Intestino Curto/fisiopatologia , Aumento de Peso/genética , Animais , Proliferação de Células , Fígado Gorduroso/genética , Fígado Gorduroso/metabolismo , Fígado Gorduroso/patologia , Regulação da Expressão Gênica/genética , Absorção Intestinal/genética , Mucosa Intestinal/metabolismo , Mucosa Intestinal/patologia , Intestino Delgado/cirurgia , Intestinos/patologia , Lipídeos/análise , Lipídeos/sangue , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , RNA Mensageiro/metabolismo , Síndrome do Intestino Curto/metabolismo , Síndrome do Intestino Curto/patologia , Fatores de Tempo , Triglicerídeos/metabolismo
12.
Mini Rev Med Chem ; 8(6): 619-27, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18537717

RESUMO

Endothelial Lipase (EL) is a newly identified member of the triacylglycerol lipase family. Recent studies suggested that EL may be an important determinant of HDL-metabolism and inflammation acting at the level of the vessel wall. The aim of this review is to summarize important facts derived from experimental approaches and from epidemiologic human studies to provide a comprehensive view on the role of EL in inflammation and atherogenesis as well as target for potential pharmaceutical interventions.


Assuntos
Aterosclerose/fisiopatologia , Endotélio/enzimologia , Inflamação/fisiopatologia , Lipase/fisiologia , Lipoproteínas HDL/metabolismo , Animais , Humanos , Fatores de Risco
13.
Arterioscler Thromb Vasc Biol ; 27(12): 2699-706, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17951320

RESUMO

OBJECTIVE: High-fat, cholesterol-containing diets contribute to hyperlipidemia. Both high-fat diets and hyperlipidemia are associated with chronic inflammatory diseases like atherosclerosis. Integrins, heterodimeric mediators of inflammatory cell recruitment, are not generally thought to be affected by diet. However, high-fat feeding promotes inflammation, atherosclerosis, and death in hyperlipidemic mice with beta3 integrin deficiency, and treatment of humans from Western populations with oral beta3 integrin inhibitors increases mortality. The mechanisms responsible for these beta3 integrin-associated events are unknown. METHODS AND RESULTS: Here we show that diet-induced death in beta3 integrin-deficient mice is a TNFalpha-dependent process mediated by bone marrow-derived cells. In 2 different hyperlipidemic models, apoE-null and LDL receptor-null mice, beta3-replete animals transplanted with beta3-deficient marrow died with Western-type high-fat feeding whereas beta3-deficient animals transplanted with beta3-replete marrow were rescued from diet-induced death. Transplantation with beta3-deficient marrow also increased atherosclerosis. TNFalpha [corrected] expression was increased in beta3-deficient macrophages and normalized by either retroviral or adenoviral reconstitution of beta3 integrin expression. Treatment with the anti-TNFalpha antibody infliximab rescued beta3 integrin-deficient mice from Western diet-induced death, directly implicating TNFalpha in the pathophysiology triggered by diet-induced hyperlipidemia. CONCLUSIONS: These findings suggest that macrophage beta3 integrin, acting through TNFalpha, suppresses inflammation caused by hyperlipidemia attributable to high-fat feeding.


Assuntos
Aterosclerose/prevenção & controle , Hiperlipidemias/complicações , Inflamação/prevenção & controle , Integrina beta3/metabolismo , Macrófagos/metabolismo , Transdução de Sinais , Fator de Necrose Tumoral alfa/metabolismo , Animais , Anti-Inflamatórios/farmacologia , Anti-Inflamatórios/uso terapêutico , Anticorpos Monoclonais/farmacologia , Anticorpos Monoclonais/uso terapêutico , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Aterosclerose/etiologia , Aterosclerose/metabolismo , Transplante de Medula Óssea , Linhagem Celular , Células Cultivadas , Gorduras na Dieta/administração & dosagem , Modelos Animais de Doenças , Progressão da Doença , Genótipo , Humanos , Hiperlipidemias/tratamento farmacológico , Hiperlipidemias/genética , Hiperlipidemias/metabolismo , Hiperlipidemias/cirurgia , Inflamação/etiologia , Inflamação/metabolismo , Infliximab , Integrina beta3/genética , Lipopolissacarídeos/farmacologia , Macrófagos/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fenótipo , RNA Mensageiro/metabolismo , Receptores de LDL/deficiência , Receptores de LDL/genética , Receptores de LDL/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fatores de Tempo , Transfecção , Fator de Necrose Tumoral alfa/antagonistas & inibidores , Fator de Necrose Tumoral alfa/genética
14.
Arterioscler Thromb Vasc Biol ; 27(6): 1361-7, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17363695

RESUMO

OBJECTIVE: Grb2 is a ubiquitously expressed linker protein that couples growth factor receptor activation to downstream mitogen-activated protein kinase (MAPK) cascades. Macrophage proliferation and uptake of modified lipoproteins are critical components of atherogenesis which require MAPK activation. However, the precise role of upstream signaling factors and the interrelationship of various MAPK cascades in the pathogenesis of atherosclerosis remains uncertain. Complete deletion of Grb2 in mice results in early embryonic lethality. However, Grb2 heterozygous mice appear normal at birth. To test the role of the Grb2 adapter protein in atherosclerotic lesion formation, we generated Grb2+/- mice in the apoE-/- genetic background. METHODS AND RESULTS: Grb2+/- apoE-/- and apoE-/- mice exhibited similar body weight and serum lipid profiles. However, Grb2+/- apoE-/- mice on a Western diet had reduced lesion formation compared with apoE-/- mice by aortic sinus and en face assays. Transplantation of apoE-/- mice with Grb2+/- apoE-/- or apoE-/- bone marrow indicated that Grb2 haploinsufficiency in blood-borne cells confers resistance to Western diet-induced atherosclerosis. Cell culture experiments with bone marrow-derived macrophages showed that Grb2 is required for oxidized low density lipoprotein (oxLDL)-induced MAPK activation and foam cell formation. CONCLUSIONS: Grb2 is required for atherosclerotic lesion formation and uptake of oxidized LDL by macrophages.


Assuntos
Apolipoproteínas E/metabolismo , Aterosclerose/metabolismo , Proteína Adaptadora GRB2/metabolismo , Lipoproteínas LDL/metabolismo , Macrófagos/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/genética , Aterosclerose/induzido quimicamente , Aterosclerose/genética , Aterosclerose/patologia , Glicemia/metabolismo , Células da Medula Óssea/metabolismo , Transplante de Medula Óssea , Células Cultivadas , Gorduras na Dieta , Modelos Animais de Doenças , Ativação Enzimática , Células Espumosas/metabolismo , Proteína Adaptadora GRB2/deficiência , Proteína Adaptadora GRB2/genética , Lipídeos/sangue , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos
15.
Arterioscler Thromb Vasc Biol ; 23(11): 2104-9, 2003 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-14512368

RESUMO

OBJECTIVE: The alpha2beta1 integrin serves as a collagen or collagen/laminin receptor on many cell types, including endothelial cells and platelets. Many studies indicate that the alpha2beta1 integrin is a critical mediator of platelet adhesion to collagen. Epidemiologic studies suggest a direct correlation between the genetically determined platelet surface density of the alpha2beta1 integrin and the risk of thrombotic diseases, such as myocardial infarction and stroke, in the young, which are well-established complications of atherosclerosis. We have now used the alpha2beta1 integrin-deficient mouse to evaluate the contributions of the alpha2beta1 integrin to the development of atherosclerosis. METHODS AND RESULTS: We generated wild-type (alpha2+/+) or alpha2beta1 integrin-deficient (alpha2-/-) mice that were also deficient in the apolipoprotein E (ApoE) gene (ApoE-/-) and compared atherosclerotic lesion development in alpha2+/+ ApoE-/- and alpha2-/- ApoE-/- mice that were fed a high-fat, cholesterol-containing diet for 6 or 15 weeks. Total lesional area did not differ significantly between the alpha2-null animals and the wild-type animals at either 6 or 15 weeks. CONCLUSIONS: Our results suggest that risk for arterial thrombotic disease associated with high-level alpha2beta1 integrin expression is not attributable to enhanced development of atherosclerosis per se but may rather be a consequence of thrombotic complications at the plaques.


Assuntos
Arteriosclerose/metabolismo , Integrina alfa2beta1/deficiência , Integrina alfa2beta1/metabolismo , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/metabolismo , Arteriosclerose/patologia , Modelos Animais de Doenças , Células Espumosas/metabolismo , Células Espumosas/patologia , Imuno-Histoquímica , Lipoproteínas/sangue , Camundongos , Fatores de Risco , Seio Aórtico/metabolismo , Seio Aórtico/patologia
16.
Arterioscler Thromb Vasc Biol ; 22(6): 961-8, 2002 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-12067905

RESUMO

Insulin resistance is commonly associated with hypertension, a condition that causes vascular disease in people with obesity and type 2 diabetes. The mechanisms linking hypertension and insulin resistance are poorly understood. To determine whether respiratory uncoupling can prevent insulin resistance-related hypertension, we crossed transgenic mice expressing uncoupling protein 1 (UCP1) in skeletal muscle with lethal yellow (A(y)/a) mice, genetically obese animals known to have elevated blood pressure. Despite increased food intake, UCP-A(y)/a mice weighed less than their A(y)/a littermates. The metabolic rate was higher in UCP-A(y)/a mice than in A(y)/a mice and did not impair their ability to alter oxygen consumption in response to temperature changes, an adaptation involving sympathetic nervous system activity. Compared with their nontransgenic littermates, UCP-A(y)/a mice had lower fasting insulin, glucose, triglyceride, and cholesterol levels and were more insulin sensitive. Blood pressure, serum leptin, and urinary catecholamine levels were also lower in uncoupled mice. Independent of sympathetic nervous system activity, low-dose peripheral leptin infusion increased blood pressure in UCP-A(y)/a mice but not in their A(y)/a littermates. These data indicate that skeletal muscle respiratory uncoupling reverses insulin resistance and lowers blood pressure in genetic obesity without affecting thermoregulation. The data also suggest that uncoupling could decrease the risk of atherosclerosis in type 2 diabetes.


Assuntos
Pressão Sanguínea/fisiologia , Proteínas de Transporte/fisiologia , Leptina/fisiologia , Proteínas de Membrana/fisiologia , Animais , Pressão Sanguínea/genética , Composição Corporal/genética , Composição Corporal/fisiologia , Peso Corporal/genética , Peso Corporal/fisiologia , Cruzamento , Proteínas de Transporte/biossíntese , Dieta , Metabolismo Energético/genética , Metabolismo Energético/fisiologia , Feminino , Glucose/metabolismo , Infusões Parenterais , Canais Iônicos , Leptina/administração & dosagem , Leptina/sangue , Proteínas de Membrana/biossíntese , Camundongos , Camundongos Transgênicos , Proteínas Mitocondriais , Músculo Esquelético/química , Músculo Esquelético/metabolismo , Obesidade/sangue , Obesidade/genética , Consumo de Oxigênio/genética , Consumo de Oxigênio/fisiologia , Proteína Desacopladora 1
17.
Biochem J ; 379(Pt 2): 461-9, 2004 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-14705966

RESUMO

The lysosomal storage disease MPS VII (mucopolysaccharidosis type VII) is caused by a deficiency in beta-glucuronidase activity, and results in the accumulation of partially degraded glycosaminoglycans in many cell types. Although MPS VII is a simple monogenetic disorder, the clinical presentation is complex and incompletely understood. ERT (enzyme replacement therapy) is relatively effective at improving the clinical course of the disease; however, some pathologies persist. In order to clarify the molecular events contributing to the disease phenotype and how ERT might impact upon them, we analysed liver tissue from untreated and treated MPS VII mice at both 2 and 5 months of age using biochemical assays and microarray analysis. Overall, as the disease progresses, more genes have altered expression and, at either age, numerous transcriptional changes in multiple pathways appear to be refractory to therapy. With respect to the primary site of disease, both transcriptional and post-transcriptional mechanisms are involved in the regulation of lysosomal enzymes and other lysosome-associated proteins. Many of the changes observed in both lysosome-associated mRNAs and proteins are normalized by enzyme replacement. In addition, gene expression changes in seemingly unrelated pathways may account for the complex metabolic phenotype of the MPS VII mouse. In particular, beta-glucuronidase deficiency appears to induce physiological malnutrition in MPS VII mice. Malnutrition may account for the pronounced adipose storage deficiency observed in this animal. Studying the molecular response to lysosomal storage, especially those changes recalcitrant to therapy, has revealed additional targets that may improve the efficacy of existing therapies.


Assuntos
Glucuronidase/uso terapêutico , Fígado/metabolismo , Mucopolissacaridose VII/tratamento farmacológico , Transcrição Gênica , Animais , Perfilação da Expressão Gênica , Fígado/química , Fígado/patologia , Lisossomos/química , Masculino , Camundongos , Camundongos Mutantes , Mucopolissacaridose VII/genética , Mucopolissacaridose VII/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Proteínas/metabolismo , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa
18.
Diabetes ; 63(6): 1920-32, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24458361

RESUMO

Microfibril-associated glycoprotein 1 (MAGP1) is a component of extracellular matrix microfibrils. Here we show that MAGP1 expression is significantly altered in obese humans, and inactivation of the MAGP1 gene (Mfap2(-/-)) in mice results in adipocyte hypertrophy and predisposition to metabolic dysfunction. Impaired thermoregulation was evident in Mfap2(-/-) mice prior to changes in adiposity, suggesting a causative role for MAGP1 in the increased adiposity and predisposition to diabetes. By 5 weeks of age, Mfap2(-/-) mice were maladaptive to cold challenge, uncoupling protein-1 expression was attenuated in the brown adipose tissue, and there was reduced browning of the subcutaneous white adipose tissue. Levels of transforming growth factor-ß (TGF-ß) activity were elevated in Mfap2(-/-) adipose tissue, and the treatment of Mfap2(-/-) mice with a TGF-ß-neutralizing antibody improved their body temperature and prevented the increased adiposity phenotype. Together, these findings indicate that the regulation of TGF-ß by MAGP1 is protective against the effects of metabolic stress, and its absence predisposes individuals to metabolic dysfunction.


Assuntos
Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Proteínas Contráteis/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Obesidade/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Animais , Proteínas Contráteis/deficiência , Diabetes Mellitus Tipo 2/genética , Proteínas da Matriz Extracelular/deficiência , Pleiotropia Genética , Predisposição Genética para Doença , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Obesidade/genética , Fenótipo , Fatores de Processamento de RNA , Transdução de Sinais , Termogênese/genética
19.
J Clin Invest ; 123(3): 1229-40, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23376793

RESUMO

Exogenous dietary fat can induce obesity and promote diabetes, but endogenous fat production is not thought to affect skeletal muscle insulin resistance, an antecedent of metabolic disease. Unexpectedly, the lipogenic enzyme fatty acid synthase (FAS) was increased in the skeletal muscle of mice with diet-induced obesity and insulin resistance. Skeletal muscle-specific inactivation of FAS protected mice from insulin resistance without altering adiposity, specific inflammatory mediators of insulin signaling, or skeletal muscle levels of diacylglycerol or ceramide. Increased insulin sensitivity despite high-fat feeding was driven by activation of AMPK without affecting AMP content or the AMP/ATP ratio in resting skeletal muscle. AMPK was induced by elevated cytosolic calcium caused by impaired sarco/endoplasmic reticulum calcium ATPase (SERCA) activity due to altered phospholipid composition of the sarcoplasmic reticulum (SR), but came at the expense of decreased muscle strength. Thus, inhibition of skeletal muscle FAS prevents obesity-associated diabetes in mice, but also causes muscle weakness, which suggests that mammals have retained the capacity for lipogenesis in muscle to preserve physical performance in the setting of disrupted metabolic homeostasis.


Assuntos
Sinalização do Cálcio , Resistência à Insulina , Lipogênese , Músculo Esquelético/metabolismo , Adenilato Quinase/metabolismo , Animais , Quinase da Proteína Quinase Dependente de Cálcio-Calmodulina/metabolismo , Linhagem Celular , Dieta Hiperlipídica/efeitos adversos , Ativação Enzimática , Indução Enzimática , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/metabolismo , Humanos , Técnicas In Vitro , Membranas Intracelulares/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fibras Musculares Esqueléticas/enzimologia , Relaxamento Muscular , Força Muscular , Músculo Esquelético/enzimologia , Obesidade/enzimologia , Obesidade/etiologia , Obesidade/metabolismo , PPAR alfa/agonistas , PPAR alfa/metabolismo , Fenótipo , Fosfolipídeos/metabolismo , Pirimidinas/farmacologia , Retículo Sarcoplasmático/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Ativação Transcricional
20.
Cell Metab ; 15(4): 534-44, 2012 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-22440612

RESUMO

We investigated the role of autophagy in atherosclerosis. During plaque formation in mice, autophagic markers colocalized predominantly with macrophages (mφ). Atherosclerotic aortas had elevated levels of p62, suggesting that dysfunctional autophagy is characteristic of plaques. To determine whether autophagy directly influences atherogenesis, we characterized Beclin-1 heterozygous-null and mφ-specific ATG5-null (ATG5-mφKO) mice, commonly used models of autophagy haploinsufficiency and deficiency, respectively. Haploinsufficent Beclin-1 mice had no atherosclerotic phenotype, but ATG5-mφKO mice had increased plaques, suggesting an essential role for basal levels of autophagy in atheroprotection. Defective autophagy is associated with proatherogenic inflammasome activation. Classic inflammasome markers were robustly induced in ATG5-null mφ, especially when coincubated with cholesterol crystals. Moreover, cholesterol crystals appear to be increased in ATG5-mφKO plaques, suggesting a potentially vicious cycle of crystal formation and inflammasome activation in autophagy-deficient plaques. These results show that autophagy becomes dysfunctional in atherosclerosis and its deficiency promotes atherosclerosis in part through inflammasome hyperactivation.


Assuntos
Aterosclerose/metabolismo , Aterosclerose/patologia , Autofagia , Progressão da Doença , Inflamassomos/metabolismo , Animais , Proteínas Reguladoras de Apoptose/metabolismo , Autofagia/efeitos dos fármacos , Proteína Beclina-1 , Colesterol/farmacologia , Modelos Animais de Doenças , Haploinsuficiência/efeitos dos fármacos , Heterozigoto , Inflamação/patologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Macrófagos/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Biológicos , Placa Aterosclerótica/metabolismo , Placa Aterosclerótica/patologia
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