leptin and Neointima

Obesity is associated with elevated circulating leptin levels and hypothalamic leptin resistance. Leptin receptors (LepRs) are expressed on endothelial cells, and leptin promotes neointima formation in a receptor-dependent manner. Our aim was to examine the importance of endothelial LepR (End.LepR) signaling during vascular remodeling and to determine whether the cardiovascular consequences of obesity are because of hyperleptinemia or endothelial leptin resistance.. Mice with loxP-flanked LepR alleles were mated with mice expressing Cre recombinase controlled by the inducible endothelial receptor tyrosine kinase promoter. Obesity was induced with high-fat diet. Neointima formation was examined after chemical carotid artery injury. Morphometric quantification revealed significantly greater intimal hyperplasia, neointimal cellularity, and proliferation in End.LepR knockout mice, and similar findings were obtained in obese, hyperleptinemic End.LepR wild-type animals. Analysis of primary endothelial cells confirmed abrogated signal transducer and activator of transcription-3 phosphorylation in response to leptin in LepR knockout and obese LepR wild-type mice. Quantitative PCR, ELISA, and immunofluorescence analyses revealed increased expression and release of endothelin-1 in End.LepR-deficient and LepR-resistant cells, and ET receptor A/B antagonists abrogated their paracrine effects on murine aortic smooth muscle cell proliferation. Reduced expression of peroxisome proliferator-activated receptor-γ and increased nuclear activator protein-1 staining was observed in End.LepR-deficient and LepR-resistant cells, and peroxisome proliferator-activated receptor-γ antagonization increased endothelial endothelin-1 expression.. Our findings suggest that intact endothelial leptin signaling limits neointima formation and that obesity represents a state of endothelial leptin resistance. These observations and the identification of endothelin-1 as soluble mediator of the cardiovascular risk factor obesity may have relevant therapeutic implications.

Topics: Animals; Carotid Arteries; Carotid Artery Injuries; Cell Movement; Cell Proliferation; Cells, Cultured; Diet, High-Fat; Disease Models, Animal; Endothelial Cells; Endothelin-1; Female; Genotype; Integrases; Leptin; Male; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Neointima; Obesity; Paracrine Communication; Phenotype; Phosphorylation; PPAR gamma; Promoter Regions, Genetic; Receptor, TIE-2; Receptors, Endothelin; Receptors, Leptin; Signal Transduction; STAT3 Transcription Factor; Vascular Remodeling

Obesity is a strong risk factor for the development of cardiovascular diseases and is associated with a marked increase in circulating leptin concentration. Leptin is a peptide hormone mainly produced by adipose tissue and is regulated by energy level, hormones and various inflammatory mediators. Genistein is an isoflavone that exhibits diverse health-promoting effects. Here, we investigated whether genistein suppressed the atherogenic effect induced by leptin. The A10 cells were treated with leptin and/or genistein, and then the cell proliferation and migration were analysed. The reactive oxygen species (ROS) and proteins levels were also measured, such as p44/42MAPK, cell cycle-related protein (cyclin D1 and p21) and matrix metalloproteinase-2 (MMP-2). Immunohistochemistry and morphometric analysis were used for the neointima formation in a rat carotid artery injury model. Genistein (5 μM) significantly inhibited both the proliferation and migration of leptin (10 ng/ml)-stimulated A10 cells. In accordance with these finding, genistein decreased the leptin-stimulated ROS production and phosphorylation of the p44/42MAPK signal transduction pathway. Meanwhile, genistein reversed the leptin-induced expression of cyclin D1, and cyclin-dependent kinase inhibitor, p21. Genistein attenuated leptin-induced A10 cell migration by inhibiting MMP-2 activity. Furthermore, the leptin (0.25 mg/kg)-augmented neointima formation in a rat carotid artery injury model was attenuated in the genistein (5 mg/kg body weight)-treated group when compared with the balloon injury plus leptin group. Genistein was capable of suppressing the atherogenic effects of leptin in vitro and in vivo, and may be a promising candidate drug in the clinical setting.

Topics: Animals; Carotid Artery Injuries; Cell Movement; Cell Proliferation; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Genistein; Leptin; Male; Matrix Metalloproteinase 2; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Neointima; Phosphorylation; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Signal Transduction

Sulforaphane (SFN), a dietary phase-2 enzyme inducer that mitigates cellular oxidative stress through nuclear factor erythroid 2-related factor 2 (Nrf2) activation, is known to exhibit beneficial effects in the vessel wall. For instance, it inhibits vascular smooth muscle cell (VSMC) proliferation, a major event in atherosclerosis and restenosis after angioplasty. In particular, SFN attenuates the mitogenic and pro-inflammatory actions of platelet-derived growth factor (PDGF) and tumor necrosis factor-α (TNFα), respectively, in VSMCs. Nevertheless, the vasoprotective role of SFN has not been examined in the setting of obesity characterized by hyperleptinemia and insulin resistance. Using the mouse model of western diet-induced obesity, the present study demonstrates for the first time that subcutaneous delivery of SFN (0.5mg/Kg/day) for~3weeks significantly attenuates neointima formation in the injured femoral artery [↓ (decrease) neointima/media ratio by~60%; n=5-8]. This was associated with significant improvements in metabolic parameters, including ↓ weight gain by~52%, ↓ plasma leptin by~42%, ↓ plasma insulin by~63%, insulin resistance [↓ homeostasis model assessment of insulin resistance (HOMA-IR) index by~73%], glucose tolerance (↓ AUCGTT by~24%), and plasma lipid profile (e.g., ↓ triglycerides). Under in vitro conditions, SFN significantly decreased leptin-induced VSMC proliferation by~23% (n=5) with associated diminutions in leptin-induced cyclin D1 expression and the phosphorylation of p70S6kinase and ribosomal S6 protein (n=3-4). The present findings reveal that, in addition to improving systemic metabolic parameters, SFN inhibits leptin-induced VSMC proliferative signaling that may contribute in part to the suppression of injury-induced neointima formation in diet-induced obesity.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Anti-Obesity Agents; Anticarcinogenic Agents; Antioxidants; Aorta; Cell Proliferation; Cells, Cultured; Diet, Western; Femoral Artery; Humans; Injections, Subcutaneous; Insulin Resistance; Isothiocyanates; Leptin; Male; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Neointima; Obesity; Oxidative Stress; Sulfoxides; Weight Gain

Leptin contributes to the pathogenesis of vascular repair and cardiovascular events. This study evaluated the molecular mechanism of EGCG in balloon injury-induced leptin expression. According to immunohistochemical and confocal analyses, leptin expression was increased and the aortic lumen exhibited narrowing after balloon injury. EGCG treatment attenuated leptin expression and diminished neointimal formation. The in vitro study showed that angiotensin II (Ang II) induced the migration and proliferation of cultured vascular smooth muscle cells (VSMCs), whereas treatment with EGCG, leptin siRNA, and c-Jun siRNA inhibited the migration and proliferation of VSMCs significantly. The EMSA shows that balloon injury increased AP-1-binding activity, and EGCG and c-Jun siRNA inhibited the AP-1-binding activity. Western blot and real-time RT-PCR analyses revealed similar results in intimal tissue samples. In summary, balloon injury induces leptin expression in the carotid artery of rats, and EGCG inhibits leptin expression through the JNK/AP-1 pathway and also attenuates neointimal formation.

Topics: Angioplasty, Balloon; Angiotensin II; Animals; Aorta, Thoracic; Carotid Arteries; Carotid Artery Injuries; Catechin; Cell Movement; Cells, Cultured; Leptin; Male; Muscle, Smooth, Vascular; Neointima; Rats; Rats, Wistar; RNA, Small Interfering

Clinical and experimental evidence suggests that periadventitial adipose tissue may modulate vascular lesion formation. The aim of this study was to determine the role of perivascular leptin expression on neointima formation and to differentiate it from local inflammation and systemically elevated leptin levels.. Increased neointima formation after carotid artery injury was observed in hyperleptinemic, diet-induced obese wild-type mice, but not in leptin-deficient ob/ob mice. High-fat diet was associated with increased leptin expression in visceral adipose tissue (VAT) as well as in perivascular adipose tissue. Perivascular leptin overexpression achieved by adenoviral vectors enhanced intimal cell proliferation and neointima formation in wild-type mice, but not in leptin receptor-deficient mice. Perivascular transplantation of VAT from high-fat diet-induced obese wild-type mice around the carotid artery of immunodeficient mice also promoted neointima formation, without affecting body weight or systemic leptin levels, and this effect was absent, if VAT from ob/ob mice was used. On the contrary, perivascular transplantation of VAT from ob/ob mice fed high-fat diet, characterized by marked immune cell accumulation, promoted neointimal hyperplasia also in the absence of leptin. In vitro, recombinant leptin and VAT-conditioned medium increased human arterial smooth muscle cell proliferation in a (partly) leptin-dependent manner.. Our findings suggest that locally elevated leptin levels may promote neointima formation, independent of obesity and systemic hyperleptinemia, but also underline the importance of perivascular inflammation in mediating the increased cardiovascular risk in obesity.

Topics: Animals; Cell Proliferation; Diet, High-Fat; Humans; Intra-Abdominal Fat; Leptin; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Myocytes, Smooth Muscle; Neointima; Obesity

Apolipoprotein E (apoE) may act as a vasculoprotective factor by promoting plasma lipid clearance and cholesterol efflux. Moreover, apoE accumulates at sites of vascular injury and modulates the effect of growth factors on smooth muscle cells (SMCs). Experimental data suggested that hypothalamic apoE expression is reduced in obesity and associated with leptin resistance. In this study, we examined the role of apoE in mediating the effects of leptin on vascular lesion formation.. Leptin was administered to apoE knockout (apoE-/-) mice via osmotic pumps to increase its circulating levels. Morphometric analysis revealed that leptin did not alter neointima formation and failed to increase α-actin- or PCNA-immunopositive SMCs after vascular injury. Similar findings were obtained after analysis of atherosclerotic lesions. Comparison of apoE-/-, wild-type, or LDL receptor-/- mice and functional analyses in aortic SMCs from WT or apoE-/- mice or human arterial SMCs after treatment with small interfering (si)RNA or heparinase revealed that leptin requires the presence of apoE, expressed, secreted and bound to the cell surface, to fully activate leptin receptor signalling and to promote SMC proliferation and neointima formation. Mechanistically, leptin induced the phosphorylation and membrane translocation of caveolin (cav)-1, and apoE down-regulation or caveolae disruption inhibited the leptin-induced p47phox activation, ROS formation and SMC proliferation. Finally, leptin failed to increase neointima formation in mice lacking cav-1.. Our findings suggest that apoE mediates the effects of leptin on vascular lesion formation by stabilizing cav-1-enriched cell membrane microdomains in SMCs, thus allowing NADPH oxidase assembly and ROS-mediated mitogenic signalling.

Topics: Animals; Apolipoproteins E; Caveolin 1; Cell Proliferation; Cells, Cultured; Humans; Leptin; Male; Membrane Microdomains; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocytes, Smooth Muscle; NADPH Oxidases; Neointima; Reactive Oxygen Species; Receptors, LDL; RNA, Small Interfering; Signal Transduction