RESUMEN
Adipose tissue secrets adipokines and fatty acids, which may contribute to obesity-associated vascular dysfunction and cardiovascular risk. This study investigated which factors are responsible for the synergistic effect of adipokine and oleic acid- (OA-) induced proliferation of human vascular smooth muscle cells (VSMC). Adipocyte-conditioned medium (CM) from human adipocytes induces proliferation of VSMC in correlation to its vascular endothelial growth factor (VEGF) content. CM increases VEGF-receptor (VEGF-R) 1 and 2 expression and VEGF secretion of VSMC, while OA only stimulates VEGF secretion. VEGF neutralization abrogates CM- and OA-induced proliferation and considerably reduces proliferation induced by CM and OA in combination. VEGF release is higher from visceral adipose tissue (VAT) of obese subjects compared to subcutaneous adipose tissue (SAT) and VAT from lean controls. Furthermore, VEGF release from VAT correlates with its proliferative effect. Perivascular adipose tissue (PAT) from type 2 diabetic patients releases significantly higher amounts of VEGF and induces stronger proliferation of VSMC as compared to SAT and SAT/PAT of nondiabetics. In conclusion, VEGF is mediating CM-induced proliferation of VSMC. As this adipokine is released in high amounts from VAT of obese patients and PAT of diabetic patients, VEGF might link adipose tissue inflammation to increased VSMC proliferation.
Asunto(s)
Adipocitos/citología , Tejido Adiposo/metabolismo , Grasa Intraabdominal/metabolismo , Miocitos del Músculo Liso/citología , Factor A de Crecimiento Endotelial Vascular/metabolismo , Adipoquinas/metabolismo , Adulto , Biopsia , Proliferación Celular , Células Cultivadas , Vasos Coronarios/patología , Diabetes Mellitus Tipo 2/metabolismo , Femenino , Regulación de la Expresión Génica , Humanos , Inflamación , Masculino , Persona de Mediana Edad , Músculo Liso Vascular/citología , Obesidad/metabolismo , Ácido Oléico/química , Sobrepeso , Adulto JovenRESUMEN
Abdominal obesity is a major risk factor for cardiovascular disease, and recent studies highlight a key role of adipose tissue dysfunction, inflammation, and aberrant adipokine release in this process. An increased demand for lipid storage results in both hyperplasia and hypertrophy, finally leading to chronic inflammation, hypoxia, and a phenotypic change of the cellular components of adipose tissue, collectively leading to a substantially altered secretory output of adipose tissue. In this review we have assessed the adipo-vascular axis, and an overview of adipokines associated with cardiovascular disease is provided. This resulted in a first list of more than 30 adipokines. A deeper analysis only considered adipokines that have been reported to impact on inflammation and NF-κB activation in the vasculature. Out of these, the most prominent link to cardiovascular disease was found for leptin, TNF-α, adipocyte fatty acid-binding protein, interleukins, and several novel adipokines such as lipocalin-2 and pigment epithelium-derived factor. Future work will need to address the potential role of these molecules as biomarkers and/or drug targets.
Asunto(s)
Adipoquinas/fisiología , Enfermedades Cardiovasculares/fisiopatología , Inflamación/fisiopatología , Enfermedades Metabólicas/fisiopatología , Tejido Adiposo/fisiopatología , Animales , Humanos , Modelos Animales , FN-kappa B/fisiología , Obesidad/fisiopatología , RatasRESUMEN
In the context of obesity, perivascular fat produces various adipokines and releases free fatty acids, which may induce inflammation and proliferation in the vascular wall. In this study we investigated how adipokines, oleic acid (OA) and the combined treatment regulate human vascular smooth muscle cell (hVSMC) proliferation and migration and the underlying signalling pathways. Adipocyte-conditioned media (CM) generated from human adipocytes induces a prominent proliferation and migration of hVSMC. Autocrine action of adiponectin totally abolishes CM-induced proliferation. Furthermore, OA but not palmitic acid induces proliferation of hVSMC. CM itself does not contain fatty acids, but CM in combination with OA markedly enhances proliferation of hVSMC in a synergistic way. Both the nuclear factor (NF)-κB and the mammalian target of rapamycin (mTOR) pathway were synergistically activated under these conditions and found to be essential for hVSMC proliferation. Expression of iNOS and production of nitric oxide was only enhanced by combined treatment inducing a marked release of VEGF. Combination of OA and VEGF induces an additive increase of hVSMC proliferation. We could show that the combination of CM and OA led to a synergistic proliferation of hVSMC. Expression of iNOS and production of nitric oxide were only enhanced under these conditions and were paralleled by a marked release of VEGF. These results suggest that the combined elevated release of fatty acids and adipokines by adipose tissue in obesity might be critically related to hVSMC dysfunction, vascular inflammation and the development of atherosclerosis.
Asunto(s)
Adipoquinas/farmacología , Proliferación Celular/efectos de los fármacos , Músculo Liso Vascular/efectos de los fármacos , Ácido Oléico/farmacología , Transducción de Señal/efectos de los fármacos , Adiponectina/metabolismo , Adulto , Movimiento Celular/efectos de los fármacos , Células Cultivadas , Femenino , Humanos , Inflamación/metabolismo , Músculo Liso Vascular/citología , Músculo Liso Vascular/metabolismo , FN-kappa B/metabolismo , Óxido Nítrico/biosíntesis , Óxido Nítrico Sintasa de Tipo II/biosíntesis , Óxido Nítrico Sintasa de Tipo II/genética , Serina-Treonina Quinasas TOR/metabolismo , Factor A de Crecimiento Endotelial Vascular/biosíntesis , Factor A de Crecimiento Endotelial Vascular/genéticaRESUMEN
Adipose tissue is not only releasing lipids but also various adipokines that are both dysregulated in the obese state and may contribute to obesity-associated vascular dysfunction and cardiovascular risk. We have previously shown that the combination of adipocyte-conditioned medium (CM) and oleic acid (OA) increases proliferation of human vascular smooth muscle cells (VSMC) in a synergistic way. We identified vascular endothelial growth factor (VEGF) as a component within CM that is responsible for most of the observed effects. In this study, we investigate novel mechanisms that underlie the combined effects of adipokine and oleic acid-induced proliferation of VSMC. Oleic acid leads to significant lipid accumulation in VSMC that is further enhanced by the combined treatment with CM. Accordingly CM stimulates CD36 expression in VSMC while OA is not affecting CD36. Silencing of CD36 was established and prevents lipid accumulation in all tested conditions. CD36 silencing also abrogates CM- and OA-induced proliferation and considerably reduces proliferation induced by the combination of CM and OA. At the same time, VEGF secretion and VEGF-receptor 1 (VEGF-R1) by VSMC was not affected by CD36 silencing. However, VEGF was not able to induce any proliferation in VSMC after CD36 silencing that also blunted VEGF-induced extracellular signal-regulated kinase (ERK) activation. Finally, combined silencing of CD36 together with a blocking antibody against VEGF prevented most of CMOA-induced proliferation. In conclusion, our results demonstrate that CD36 is mediating CM-induced proliferation of VSMC. Induction of CD36 by adipokines enhances the response of VSMC towards VEGF and OA.
Asunto(s)
Adipoquinas/farmacología , Antígenos CD36/genética , Proliferación Celular/efectos de los fármacos , Medios de Cultivo Condicionados/farmacología , Miocitos del Músculo Liso/efectos de los fármacos , Ácido Oléico/farmacología , Adipocitos/citología , Adipocitos/metabolismo , Adipoquinas/metabolismo , Tejido Adiposo/citología , Tejido Adiposo/metabolismo , Adulto , Anticuerpos Neutralizantes/farmacología , Antígenos CD36/antagonistas & inhibidores , Antígenos CD36/metabolismo , Vasos Coronarios/citología , Vasos Coronarios/efectos de los fármacos , Vasos Coronarios/metabolismo , Medios de Cultivo Condicionados/química , Femenino , Regulación de la Expresión Génica , Humanos , Masculino , Persona de Mediana Edad , Proteína Quinasa 1 Activada por Mitógenos/genética , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/genética , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Músculo Liso Vascular/citología , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/metabolismo , Miocitos del Músculo Liso/citología , Miocitos del Músculo Liso/metabolismo , Cultivo Primario de Células , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Transducción de Señal , Factor A de Crecimiento Endotelial Vascular/antagonistas & inhibidores , Factor A de Crecimiento Endotelial Vascular/genética , Factor A de Crecimiento Endotelial Vascular/metabolismo , Receptor 1 de Factores de Crecimiento Endotelial Vascular/genética , Receptor 1 de Factores de Crecimiento Endotelial Vascular/metabolismoRESUMEN
OBJECTIVE: To study expression of the recently identified adipokine dipeptidyl peptidase-4 (DPP4) in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) of patients with various BMIs and insulin sensitivities, as well as to assess circulating DPP4 in relation to obesity and insulin sensitivity. RESEARCH DESIGN AND METHODS: DPP4 expression was measured in SAT and VAT from 196 subjects with a wide range of BMIs and insulin sensitivities. DPP4 release was measured ex vivo in paired biopsies from SAT and VAT as well as in vivo from SAT of lean and obese patients. Circulating DPP4 was measured in insulin-sensitive and insulin-resistant BMI-matched obese patients. RESULTS: DPP4 expression was positively correlated with BMI in both SAT and VAT, with VAT consistently displaying higher expression than SAT. Ex vivo release of DPP4 from adipose tissue explants was higher in VAT than in SAT in both lean and obese patients, with obese patients displaying higher DPP4 release than lean controls. Net release of DPP4 from adipose tissue was also demonstrated in vivo with greater release in obese subjects than in lean subjects and in women than in men. Insulin-sensitive obese patients had significantly lower circulating DPP4 than did obesity-matched insulin-resistant patients. In this experiment, DPP4 positively correlated with the amount of VAT, adipocyte size, and adipose tissue inflammation. CONCLUSIONS: DPP4, a novel adipokine, has a higher release from VAT that is particularly pronounced in obese and insulin-resistant patients. Our data suggest that DPP4 may be a marker for visceral obesity, insulin resistance, and the metabolic syndrome.
Asunto(s)
Dipeptidil Peptidasa 4/genética , Regulación de la Expresión Génica , Resistencia a la Insulina/genética , Grasa Intraabdominal/enzimología , Obesidad/genética , ARN Mensajero/genética , Grasa Subcutánea/enzimología , Adipocitos/enzimología , Adipocitos/patología , Adulto , Anciano , Anciano de 80 o más Años , Biopsia , Índice de Masa Corporal , Células Cultivadas , Dipeptidil Peptidasa 4/biosíntesis , Femenino , Humanos , Insulina/metabolismo , Grasa Intraabdominal/patología , Masculino , Persona de Mediana Edad , Obesidad/metabolismo , Obesidad/patología , Reacción en Cadena en Tiempo Real de la Polimerasa , Grasa Subcutánea/patología , Adulto JovenRESUMEN
Adipose tissue (AT) hypoxia occurs in obese humans and mice. Acute hypoxia in adipocytes causes dysregulation of adipokine secretion with an increase in inflammatory factors and diminished adiponectin release. O2 levels in humans range between 3 and 11% revealing that conventional in vitro culturing at ambient air and acute hypoxia treatment (1% O2) are performed under non-physiological conditions. In this study, we mimicked physiological conditions by differentiating human primary adipocytes under 10% or 5% O2 in comparison to 21% O2. Induction of differentiation markers was comparable between all three conditions. Adipokine release by adipocytes differentiated at lower oxygen levels was altered, with a marked upregulation of adiponectin, IL-6 and DPP4 secretion, and reduced leptin levels compared with adipocytes differentiated at 21% O2. Isoproterenol-induced lipolysis was significantly elevated in adipocytes differentiated at 10% and 5% compared with 21% O2. This effect was accompanied by increased protein expression of ß-1 and -2 adrenergic receptor, HSL and perilipin. Conditioned medium (CM) of adipocytes differentiated at the three different conditions was generated for stimulation of human skeletal muscle cells (SkMC) or smooth muscle cells (SMC). CM-induced insulin resistance in SkMC was comparable for the different CMs. However, the SMC proliferative effect of CM from adipocytes differentiated at 10% O2 was significantly reduced compared with 21% O2. This study demonstrates that oxygen levels during adipogenesis are important factors altering adipocyte functionality such as adipokine release, in particular adiponectin secretion, as well as the hormone-induced lipolytic pathway.
RESUMEN
It is widely accepted that obesity is a major risk factor for the development of atherosclerosis. In this context, adipose tissue produces a variety of adipokines and releases free fatty acids, contributing to a chronic-low grade inflammation state implicated in vascular complications. In this study, we investigated the role of adipokines, oleic acid (OA), palmitic acid (PA), and the combinations on activation of NF-κB target genes in human vascular smooth muscle cells (SMC) to assess the hypothesis of synergistic interactions between these molecules. Adipocyte-conditioned medium (CM), generated from human adipocytes, in combination with low concentrations of OA, but not PA, induces SMC proliferation and activation of the transcription factor NF-κB in a synergistic way. Combined treatment of CM and OA further regulates a set of downstream NF-κB target genes including angiopoietin-1, activin A, and MMP-1, all critically involved in SMC dysfunction. This suggests that the lipotoxic potential of fatty acids is substantially enhanced by the presence of adipocyte-derived factors.