Hubert Astrid, Bochenek Magdalena L, Schütz Eva, Gogiraju Rajinikanth, Münzel Thomas, Schäfer Katrin
From the Center for Cardiology, Cardiology I (A.H., M.L.B., E.S., R.G., T.M., K.S.) and Center for Thrombosis and Hemostasis (M.L.B.), University Medical Center Mainz, Germany.
Arterioscler Thromb Vasc Biol. 2017 Sep;37(9):1683-1697. doi: 10.1161/ATVBAHA.117.309798. Epub 2017 Jul 13.
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.
肥胖与循环瘦素水平升高及下丘脑瘦素抵抗有关。瘦素受体（LepRs）在内皮细胞上表达，且瘦素以受体依赖的方式促进新生内膜形成。我们的目的是研究内皮LepR（End.LepR）信号在血管重塑过程中的重要性，并确定肥胖的心血管后果是由于高瘦素血症还是内皮瘦素抵抗。
将带有侧翼loxP序列的LepR等位基因的小鼠与表达由诱导型内皮受体酪氨酸激酶启动子控制的Cre重组酶的小鼠交配。用高脂饮食诱导肥胖。在化学性颈动脉损伤后检查新生内膜形成情况。形态计量学定量分析显示，End.LepR基因敲除小鼠的内膜增生、新生内膜细胞密度和增殖明显更严重，在肥胖、高瘦素血症的End.LepR野生型动物中也得到了类似的结果。对原代内皮细胞的分析证实，在LepR基因敲除和肥胖的LepR野生型小鼠中，瘦素刺激下信号转导子和转录激活子3的磷酸化被消除。定量PCR、ELISA和免疫荧光分析显示，End.LepR缺陷和LepR抵抗细胞中内皮素-1的表达和释放增加，ET受体A/B拮抗剂消除了它们对小鼠主动脉平滑肌细胞增殖的旁分泌作用。在End.LepR缺陷和LepR抵抗细胞中观察到过氧化物酶体增殖物激活受体-γ表达降低和核激活蛋白-1染色增加，过氧化物酶体增殖物激活受体-γ拮抗作用增加了内皮细胞内皮素-1的表达。
我们的研究结果表明，完整的内皮瘦素信号限制新生内膜形成，肥胖代表一种内皮瘦素抵抗状态。这些观察结果以及将内皮素-1鉴定为肥胖心血管危险因素的可溶性介质可能具有相关的治疗意义。
