RESUMEN
A variety of studies have suggested that vitamin D may play a palliative role in improving insulin secretion and glucose tolerance. Endothelial cells of the microcirculation are thought to play an important role in regulating both insulin secretion and insulin sensitivity in target tissues. We have selectively deleted the vitamin D receptor (VDR) gene in endothelial cells of the murine vasculature. These mice demonstrate improved glucose tolerance, improved insulin sensitivity in skeletal muscle, but not in liver, and a reduction in expression and secretion of insulin in the pancreatic islets. Collectively, these data, taken within the context of recent publications in this field, suggest that the endothelial cell VDR plays a tonic inhibitory role in regulating glucose disposal and could prove to be a factor in controlling glucose homeostasis in the intact organism.
Asunto(s)
Células Endoteliales/metabolismo , Glucosa/metabolismo , Insulina/metabolismo , Músculo Esquelético/metabolismo , Receptores de Calcitriol/genética , Vitamina D/metabolismo , Animales , Regulación de la Expresión Génica , Prueba de Tolerancia a la Glucosa , Homeostasis , Resistencia a la Insulina , Islotes Pancreáticos/metabolismo , Hígado/metabolismo , Ratones , Ratones Noqueados , Receptores de Calcitriol/deficienciaRESUMEN
Previous studies demonstrated that the liganded vitamin D receptor (VDR) plays an important role in controlling cardiovascular homeostasis. Both the whole animal VDR gene knockout (VDR-/-) and the myocyte-specific VDR gene deletion result in changes in cardiac structure and function. Clinical states associated with cardiac steatosis (obesity and diabetes mellitus) are also associated with low circulating 25 OH vitamin D levels. We, therefore, examined the effects of VDR deficiency (VDR-/- mouse) in a murine model of cardiac steatosis that expresses the terminal enzyme involved in triglyceride synthesis, diacylglycerol acyltransferase 1 (DGAT1), selectively in the cardiac myocyte. These mice display early cardiac dysfunction and late cardiomyopathy and heart failure. In the present study, we demonstrate that mice harboring both genetic modifications (i.e., MHC-DGAT1 Tg and VDR-/-) exhibit an increase in myocyte size, heart weight/body weight ratio and natriuretic peptide gene expression, all markers of cardiac hypertrophy, that exceed that seen in either VDR-/- or the MHC-DGAT1 Tg mice alone. This was accompanied by a dramatic increase in interstitial fibrosis and increased expression of collagen 1a1 and collagen 3a1, as well as the osteopontin and matrix metalloproteinase 2, genes. At a functional level, this resulted in a 37% reduction in ejection fraction and 55% reduction in fractional shortening in the DGAT1; VDR-/- mice relative to the controls. Collectively, these data demonstrate that deficiency in the vitamin D signaling system enhances the pathological phenotype in this experimental cardiomyopathy and suggest an important role for vitamin D in modulating disease severity in common cardiovascular disorders.
Asunto(s)
Cardiomiopatías/genética , Diacilglicerol O-Acetiltransferasa/genética , Insuficiencia Cardíaca/genética , Miocitos Cardíacos/metabolismo , Receptores de Calcitriol/genética , Animales , Peso Corporal , Cardiomiopatías/metabolismo , Cardiomiopatías/patología , Tamaño de la Célula , Colágeno Tipo I/genética , Colágeno Tipo I/metabolismo , Colágeno Tipo III/genética , Colágeno Tipo III/metabolismo , Diacilglicerol O-Acetiltransferasa/metabolismo , Venenos Elapídicos/genética , Venenos Elapídicos/metabolismo , Fibrosis , Insuficiencia Cardíaca/metabolismo , Insuficiencia Cardíaca/patología , Masculino , Metaloproteinasa 2 de la Matriz/genética , Metaloproteinasa 2 de la Matriz/metabolismo , Ratones , Ratones Noqueados , Miocitos Cardíacos/patología , Péptido Natriurético Tipo-C/genética , Péptido Natriurético Tipo-C/metabolismo , Osteopontina/genética , Osteopontina/metabolismo , Receptores de Calcitriol/deficiencia , Volumen SistólicoRESUMEN
Lipid accumulation in the heart is associated with obesity and diabetes and may play an important role in the pathogenesis of heart failure. The renin-angiotensin system is also thought to contribute to cardiovascular morbidity in obese and diabetic patients. We hypothesized that the presence of lipid within the myocyte might potentiate the cardiomyopathic effects of ANG II in the cardiac diacylglycerol acyl transferase 1 (DGAT1) transgenic mouse model of myocyte steatosis. Treatment with ANG II resulted in a similar increase in blood pressure in both nontransgenic and DGAT1 transgenic mice. However, ANG II in DGAT1 transgenic mice resulted in a marked increase in interstitial fibrosis and a reduction in systolic function compared with nontransgenic littermates. Lipidomic analysis revealed that >20% of lipid species were significantly altered between nontransgenic and DGAT1 transgenic animals, whereas 3% were responsive to ANG II administration. ROS were also increased by ANG II in DGAT1 transgenic hearts. ANG II treatment resulted in increased expression of transforming growth factor (TGF)-ß2 and the type I TGF-ß receptor as well as increased phosphorylation of Smad2 in DGAT1 transgenic hearts. Injection of neutralizing antibodies to TGF-ß resulted in a reduction in fibrosis in DGAT1 transgenic hearts treated with ANG II. These results suggest that myocyte steatosis amplifies the fibrotic effects of ANG II through mechanisms that involve activation of TGF-ß signaling and increased production of ROS.
Asunto(s)
Angiotensina II/farmacología , Cardiomiopatías/metabolismo , Metabolismo de los Lípidos , Miocitos Cardíacos/metabolismo , Animales , Cardiomiopatías/fisiopatología , Células Cultivadas , Diacilglicerol O-Acetiltransferasa/genética , Diacilglicerol O-Acetiltransferasa/metabolismo , Fibrosis/metabolismo , Ventrículos Cardíacos/metabolismo , Ventrículos Cardíacos/patología , Ventrículos Cardíacos/fisiopatología , Ratones , Ratones Endogámicos DBA , Miocitos Cardíacos/efectos de los fármacos , Especies Reactivas de Oxígeno/metabolismo , Receptores de Factores de Crecimiento Transformadores beta/metabolismo , Factor de Crecimiento Transformador beta2/metabolismo , Triglicéridos/metabolismoRESUMEN
Vitamin D deficiency has been associated with cardiovascular dysfunction. We evaluated the role of the vitamin D receptor (VDR) in vascular endothelial function, a marker of cardiovascular health, at baseline and in the presence of angiotensin II, using an endothelial-specific knockout of the murine VDR gene. In the absence of endothelial VDR, acetylcholine-induced aortic relaxation was significantly impaired (maximal relaxation, endothelial-specific VDR knockout=58% versus control=73%; P<0.05). This was accompanied by a reduction in endothelial NO synthase expression and phospho-vasodilator-stimulated phosphoprotein levels in aortae from the endothelial-specific VDR knockout versus control mice. Although blood pressure levels at baseline were comparable at 12 and 24 weeks of age, the endothelial VDR knockout mice demonstrated increased sensitivity to the hypertensive effects of angiotensin II compared with control mice (after 1-week infusion: knockout=155±15 mm Hg versus control=133±7 mm Hg; P<0.01; after 2-week infusion: knockout=164±9 mm Hg versus control=152±13 mm Hg; P<0.05). By the end of 2 weeks, angiotensin II infusion-induced, hypertrophy-sensitive myocardial gene expression was higher in endothelial-specific VDR knockout mice (fold change compared with saline-infused control mice, type-A natriuretic peptide: knockout mice=3.12 versus control=1.7; P<0.05; type-B natriuretic peptide: knockout mice=4.72 versus control=2.68; P<0.05). These results suggest that endothelial VDR plays an important role in endothelial cell function and blood pressure control and imply a potential role for VDR agonists in the management of cardiovascular disease associated with endothelial dysfunction.
Asunto(s)
Endotelio Vascular/fisiopatología , Hipertensión/tratamiento farmacológico , Receptores de Calcitriol/antagonistas & inhibidores , Vasodilatación/efectos de los fármacos , Acetilcolina/farmacología , Angiotensina II/farmacología , Animales , Aorta/metabolismo , Presión Sanguínea/efectos de los fármacos , Western Blotting , ADN/genética , Modelos Animales de Enfermedad , Células Endoteliales/metabolismo , Células Endoteliales/patología , Endotelio Vascular/metabolismo , Endotelio Vascular/patología , Regulación de la Expresión Génica , Humanos , Hipertensión/genética , Hipertensión/fisiopatología , Inmunohistoquímica , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Péptido Natriurético Encefálico/metabolismo , Ratas , Receptores de Calcitriol/biosíntesis , Receptores de Calcitriol/genéticaRESUMEN
Vitamin D receptors (VDR) are found in cells throughout the cardiovascular system. A variety of experimental studies indicate that the liganded VDR may play an important role in controlling cardiac hypertrophy and fibrosis, regulating blood pressure, and suppressing the development of atherosclerosis. Some, but not all, observational studies in humans provide support for these experimental findings, raising the possibility that vitamin D or its analogs might prove useful therapeutically in the prevention or treatment of cardiovascular disease.
Asunto(s)
Enfermedades Cardiovasculares/tratamiento farmacológico , Miocardio/metabolismo , Receptores de Calcitriol/agonistas , Vitamina D/uso terapéutico , Animales , Enfermedades Cardiovasculares/metabolismo , Enfermedades Cardiovasculares/patología , Enfermedades Cardiovasculares/fisiopatología , Humanos , Ligandos , Miocardio/patología , Receptores de Calcitriol/metabolismo , Transducción de Señal/efectos de los fármacos , Vitamina D/metabolismoRESUMEN
Angiotensin-converting enzyme (ACE) inhibitors ameliorate the progression of renal disease. In combination with vitamin D receptor activators, they provide additional benefits. In the present study, uremic (U) rats were treated as follows: U+vehicle (UC), U+enalapril (UE; 25 mg/l in drinking water), U+paricalcitol (UP; 0.8 µg/kg ip, 3 × wk), or U+enalapril+paricalcitol (UEP). Despite hypertension in UP rats, proteinuria decreased by 32% vs. UC rats. Enalapril alone, or in combination with paricalcitol, further decreased proteinuria (≈70%). Glomerulosclerosis and interstitial infiltration increased in UC rats. Paricalcitol and enalapril inhibited this. The increase in cardiac atrial natriuretic peptide (ANP) seen in UC rats was significantly decreased by paricalcitol. Enalapril produced a more dramatic reduction in ANP. Renal oxidative stress plays a critical role in inflammation and progression of sclerosis. The marked increase in p22(phox), a subunit of NADPH oxidase, and decrease in endothelial nitric oxide synthase were inhibited in all treated groups. Cotreatment with both compounds inhibited the uremia-induced increase in proinflammatory inducible nitric oxide synthase (iNOS) and glutathione peroxidase activity better than either compound alone. Glutathione reductase was also increased in UE and UP rats vs. UC. Kidney 4-hydroxynonenal was significantly increased in the UC group compared with the normal group. Combined treatment with both compounds significantly blunted this increase, P < 0.05, while either compound alone had no effect. Additionally, the expression of Mn-SOD was increased and CuZn-SOD decreased by uremia. This was ameliorated in all treatment groups. Cotreatment with enalapril and paricalcitol had an additive effect in increasing CuZn-SOD expression. In conclusion, like enalapril, paricalcitol alone can improve proteinuria, glomerulosclerosis, and interstitial infiltration and reduce renal oxidative stress. The effects of paricalcitol may be amplified when an ACE inhibitor is added since cotreatment with both compounds seems to have an additive effect on ameliorating uremia-induced changes in iNOS and CuZn-SOD expression, peroxidase activity, and renal histomorphometry.
Asunto(s)
Enalapril/uso terapéutico , Ergocalciferoles/uso terapéutico , Glomerulonefritis/tratamiento farmacológico , Proteinuria/tratamiento farmacológico , Receptores de Calcitriol/efectos de los fármacos , Aldehídos/metabolismo , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Animales , Factor Natriurético Atrial/efectos de los fármacos , Femenino , Riñón/efectos de los fármacos , NADPH Oxidasas/metabolismo , Óxido Nítrico Sintasa de Tipo II/metabolismo , Estrés Oxidativo/efectos de los fármacos , Proteinuria/metabolismo , Ratas , Superóxido Dismutasa/metabolismo , Uremia/metabolismoRESUMEN
Lipid accumulation in the heart is associated with obesity and diabetes mellitus and may play an important role in the pathogenesis of heart failure seen in this patient population. Stored triglycerides are synthesized by the enzyme diacylglycerol acyl transferase (DGAT). We hypothesized that forced expression of DGAT1 in the cardiac myocyte would result in increased lipid accumulation and heart dysfunction. A cardiac myocyte-selective DGAT1 transgenic mouse was created and demonstrated increased lipid accumulation in the absence of hyperglycemia, plasma dyslipidemia or differences in body weight. Over time, expression of DGAT1 in the heart resulted in the development of a significant cardiomyopathy. Echocardiography revealed diastolic dysfunction with increased early mitral inflow velocity to late mitral inflow velocity ratio and decreased deceleration time, suggesting a restrictive pattern in the transgenic mice. Moderate systolic dysfunction was also seen at 52 weeks. Histological analysis showed increased cardiac fibrosis and increased expression of procollagen type 1A, matrix metalloproteinase 2, and tissue inhibitor of matrix metalloproteinase 2 in the transgenic mice. Mitochondrial biogenesis was reduced in the transgenic hearts, as was expression of cytochrome c oxidase 1 and cytochrome c. Expression of key transcription factors important in the regulation of mitochondrial biogenesis were reduced. These findings suggest that triglyceride accumulation, in the absence of systemic metabolic derangement, results in cardiac dysfunction and decreased mitochondrial biogenesis.
Asunto(s)
Cardiomiopatías/metabolismo , Diacilglicerol O-Acetiltransferasa/metabolismo , Ácidos Grasos/metabolismo , Miocardio/metabolismo , Animales , Animales Recién Nacidos , Western Blotting , Cardiomiopatías/patología , Cardiomiopatías/fisiopatología , Células Cultivadas , Citocromos c/metabolismo , Diacilglicerol O-Acetiltransferasa/genética , Modelos Animales de Enfermedad , Femenino , Fibrosis , Expresión Génica , Metabolismo de los Lípidos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Ratones Transgénicos , Mitocondrias/metabolismo , Miocardio/patología , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/patología , Ratas , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Tiempo , Triglicéridos/metabolismoRESUMEN
AIMS: Atrial natriuretic peptide (ANP) is a hormone that has both antihypertrophic and antifibrotic properties in the heart. We hypothesized that myocyte-derived ANP inhibits endothelin (ET) gene expression in fibroblasts. METHODS AND RESULTS: We have investigated the mechanism(s) involved in the antiproliferative effect of ANP on cardiac fibroblasts in a cell culture model. We found that cardiac myocytes inhibited DNA synthesis in co-cultured cardiac fibroblasts as did treatment with the ET-1 antagonist BQ610. The effect of co-culture was reversed by antibody directed against ANP or the ANP receptor antagonist HS-142-1. ANP inhibited the expression of the ET-1 gene and ET-1 gene promoter activity in cultured fibroblasts. The site of the inhibition was localized to a GATA-binding site positioned between -132 and -135 upstream from the transcription start site. GATA4 expression was demonstrated in cardiac fibroblasts, GATA4 bound the ET-1 promoter both in vitro and in vivo, and siRNA-mediated knockdown of GATA4 inhibited ET-1 expression. ET-1 treatment resulted in increased levels of phospho-serine(105) GATA4 in cardiac fibroblasts and this induction was partially suppressed by co-treatment with ANP. CONCLUSION: Collectively, these findings suggest that locally produced ET-1 serves as an autocrine stimulator of fibroblast proliferation, that ANP produced in neighbouring myocytes serves as a paracrine inhibitor of this proliferation, and that the latter effect operates through a reduction in GATA4 phosphorylation and coincident reduction in GATA4-dependent transcriptional activity.
Asunto(s)
Factor Natriurético Atrial/metabolismo , Proliferación Celular , Endotelina-1/metabolismo , Fibroblastos/metabolismo , Factor de Transcripción GATA4/metabolismo , Miocitos Cardíacos/metabolismo , Animales , Animales Recién Nacidos , Comunicación Autocrina , Sitios de Unión , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Técnicas de Cocultivo , Replicación del ADN , Relación Dosis-Respuesta a Droga , Regulación hacia Abajo , Endotelina-1/antagonistas & inhibidores , Endotelina-1/genética , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Fibroblastos/efectos de los fármacos , Factor de Transcripción GATA4/genética , Ventrículos Cardíacos/citología , Ventrículos Cardíacos/metabolismo , Oligopéptidos/farmacología , Comunicación Paracrina , Fosforilación , Polisacáridos/farmacología , Regiones Promotoras Genéticas , Interferencia de ARN , Ratas , Ratas Sprague-Dawley , Receptores del Factor Natriurético Atrial/antagonistas & inhibidores , Receptores del Factor Natriurético Atrial/metabolismo , Serina , Transducción de Señal , Activación Transcripcional , TransfecciónRESUMEN
Increased B-type natriuretic peptide (BNP) gene expression is regarded as one of the hallmarks of cardiac myocyte hypertrophy. Here we demonstrate that both basal- and endothelin-1-dependent stimulation of human (h) BNP gene transcription requires the presence of an intact Yin Yang 1 (YY1) binding site positioned at -62 bp relative to the transcription start site. Mutation of this site reduced both basal and stimulated hBNP promoter activity. This site was shown to bind YY1 both in vitro and within the context of the intact cell. The latter interaction increased after endothelin-1 treatment. Exposure to endothelin-1 also resulted in increased nuclear localization of YY1 and a reduction in acetylation of the YY1 protein. Overexpression of wild-type YY1 increased both basal and endothelin-stimulated hBNP promoter activity, whereas a carboxy-terminal deletion mutant of YY1 was devoid of activity. Treatment with the histone deacetylase inhibitor trichostatin A resulted in decreased hBNP reporter activity. YY1 was shown to associate with histone deacetylase 2, and histone deacetylase 2 was shown to associate directly with the hBNP promoter in the intact cell. Collectively these findings demonstrate that YY1 plays an important role in regulating the transcriptional activity of the hBNP gene promoter. These data suggest a model in which YY1 activates hBNP transcription through interaction with histone deacetylase 2.
Asunto(s)
Endotelina-1/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Histona Desacetilasas/metabolismo , Miocitos Cardíacos/metabolismo , Péptido Natriurético Encefálico/genética , Péptido Natriurético Encefálico/metabolismo , Proteínas Represoras/metabolismo , Factor de Transcripción YY1/metabolismo , Animales , Núcleo Celular/metabolismo , Células Cultivadas , Inhibidores Enzimáticos/farmacología , Histona Desacetilasa 2 , Inhibidores de Histona Desacetilasas , Humanos , Ácidos Hidroxámicos/farmacología , Miocitos Cardíacos/citología , Miocitos Cardíacos/efectos de los fármacos , Regiones Promotoras Genéticas/genética , Ratas , Ratas Sprague-Dawley , Proteínas Represoras/antagonistas & inhibidores , TransfecciónRESUMEN
The liganded vitamin D receptor (VDR) is thought to play an important role in controlling cardiac function. Specifically, this system has been implicated as playing an antihypertrophic role in the heart. Despite this, studies of VDR in the heart have been limited in number and scope. In the present study, we used a combination of real-time polymerase chain reaction, Western blot analysis, immunofluorescence, and transient transfection analysis to document the presence of functional VDR in both the myocytes and fibroblasts of the heart, as well as in the intact ventricular myocardium. We also demonstrated the presence of 1-alpha-hydroxylase and 24-hydroxylase in the heart, 2 enzymes involved in the synthesis and metabolism of 1,25 dihydroxyvitamin D. VDR is shown to interact directly with the human B-type natriuretic peptide gene promoter, a surrogate marker of the transcriptional response to hypertrophy. Of note, induction of myocyte hypertrophy either in vitro or in vivo leads to an increase in VDR mRNA and protein levels. Collectively, these findings suggest that the key components required for a functional 1,25 dihydroxyvitamin D-dependent signaling system are present in the heart and that this putatively antihypertrophic system is amplified in the setting of cardiac hypertrophy.