Tassone Eliezer J, Cimellaro Antonio, Perticone Maria, Hribal Marta L, Sciacqua Angela, Andreozzi Francesco, Sesti Giorgio, Perticone Francesco
Department of Medical and Surgical Sciences, Magna Græcia University, Catanzaro, Italy.
Department of Experimental and Clinical Medicine, Magna Græcia University, Catanzaro, Italy.
Front Endocrinol (Lausanne). 2018 Mar 26;9:98. doi: 10.3389/fendo.2018.00098. eCollection 2018.
High levels of uric acid (UA) are associated with type-2 diabetes and cardiovascular disease. Recent pieces of evidence attributed to UA a causative role in the appearance of diabetes and vascular damage. However, the molecular mechanisms by which UA induces these alterations have not been completely elucidated so far. Among the mechanisms underlying insulin resistance, it was reported the role of a transmembrane glycoprotein, named either ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) or plasma cell antigen 1, which is able to inhibit the function of insulin receptor (I) and it is overexpressed in insulin-resistant subjects. In keeping with this, we stimulated human umbilical vein endothelial cells (HUVECs) with insulin and UA to investigate the effects of UA on insulin signaling pathway, testing the hypothesis that UA can interfere with insulin signaling by the activation of ENPP1. Cultures of HUVECs were stimulated with insulin, UA and the urate transporter SLC22A12 (URAT1) inhibitor probenecid. Akt and endothelial nitric oxide synthase (eNOS) phosphorylation levels were investigated by immunoblotting. ENPP1 binding to I and its tyrosine phosphorylation levels were tested by immunoprecipitation and immunoblotting. UA inhibited insulin-induced Akt/eNOS axis. Moreover, UA induced ENPP1 binding to I that resulted in an impairment of insulin signaling cascade. Probenecid reverted UA effects, suggesting that UA intracellular uptake is required for its action. In endothelial cells, UA directly interferes with insulin signaling pathway at receptor level, through ENPP1 recruitment. This evidence suggests a new molecular model of UA-induced insulin resistance and vascular damage.
高尿酸（UA）水平与2型糖尿病和心血管疾病相关。最近的证据表明UA在糖尿病的发生和血管损伤中起因果作用。然而，迄今为止，UA诱导这些改变的分子机制尚未完全阐明。在胰岛素抵抗的潜在机制中，有报道称一种跨膜糖蛋白发挥作用，该蛋白名为胞外核苷酸焦磷酸酶/磷酸二酯酶1（ENPP1）或浆细胞抗原1，它能够抑制胰岛素受体（I）的功能，并且在胰岛素抵抗的受试者中过表达。与此一致的是，我们用胰岛素和UA刺激人脐静脉内皮细胞（HUVECs），以研究UA对胰岛素信号通路的影响，检验UA可通过激活ENPP1干扰胰岛素信号的假说。用胰岛素、UA和尿酸转运体SLC22A12（URAT1）抑制剂丙磺舒刺激HUVECs培养物。通过免疫印迹法研究Akt和内皮型一氧化氮合酶（eNOS）的磷酸化水平。通过免疫沉淀和免疫印迹法检测ENPP1与I的结合及其酪氨酸磷酸化水平。UA抑制胰岛素诱导的Akt/eNOS轴。此外，UA诱导ENPP1与I结合，导致胰岛素信号级联受损。丙磺舒可逆转UA的作用，提示UA的细胞内摄取是其发挥作用所必需的。在内皮细胞中，UA通过招募ENPP1在受体水平直接干扰胰岛素信号通路。这一证据提示了UA诱导胰岛素抵抗和血管损伤的新分子模型。
