Hitomi Hirofumi, Kiyomoto Hideyasu, Nishiyama Akira, Hara Taiga, Moriwaki Kumiko, Kaifu Kumiko, Ihara Genei, Fujita Yoshiko, Ugawa Toyomu, Kohno Masakazu
Department of Cardiorenal and Cerebrovascular Medicine, Faculty of Medicine, Kagawa University, Kita-gun, Japan.
Hypertension. 2007 Oct;50(4):750-5. doi: 10.1161/HYPERTENSIONAHA.107.093955. Epub 2007 Jul 23.
Clinical reports indicate that patients with primary aldosteronism commonly have impaired glucose tolerance; however, the relationship between aldosterone and insulin signaling pathway has not been clarified. In this study, we examined the effects of aldosterone treatment on insulin receptor substrate-1 expression and insulin signaling pathway including Akt phosphorylation and glucose uptake in rat vascular smooth muscle cells. Insulin receptor substrate-1 protein expression and Akt phosphorylation were determined by Western blot analysis with anti-insulin receptor substrate-1 and phosphorylated-Akt antibodies, respectively. Glucose metabolism was evaluated using (3)H-labeled 2-deoxy-d-glucose uptake. Aldosterone (1-100 nmol/L) dose-dependently decreased insulin receptor substrate-1 protein expression with a peak at 18 hours (n=4). Aldosterone-induced degradation of insulin receptor substrate-1 was markedly attenuated by treatment with the selective mineralocorticoid receptor antagonist eplerenone (10 micromol/L; n=4). Furthermore, degradation was blocked by the Src inhibitor PP1 (20 micromol/L; n=4). Treatment with antioxidants, N-acetylcysteine (10 mmol/L), or ebselen (40 micromol/L) also attenuated aldosterone-induced insulin receptor substrate-1 degradation (n=4). In addition, proteasome inhibitor MG132 (1 micromol/L) prevented insulin receptor substrate-1 degradation (n=4). Aldosterone treatment abolished insulin-induced Akt phosphorylation (100 nmol/L; 5 minutes; n=4). Furthermore, aldosterone pretreatment decreased insulin-stimulated (100 nmol/L; 60 minutes; n=4) glucose uptake by 50%, which was reversed by eplerenone (10 micromol/L; n=4). These data indicate that aldosterone decreases insulin receptor substrate-1 expression via Src and reactive oxygen species stimulation by proteasome-dependent degradation in vascular smooth muscle cells; thus, aldosterone may be involved in the pathogenesis of vascular insulin resistance via oxidative stress.
临床报告表明，原发性醛固酮增多症患者通常存在糖耐量受损的情况；然而，醛固酮与胰岛素信号通路之间的关系尚未阐明。在本研究中，我们检测了醛固酮处理对大鼠血管平滑肌细胞中胰岛素受体底物-1表达以及包括Akt磷酸化和葡萄糖摄取在内的胰岛素信号通路的影响。分别使用抗胰岛素受体底物-1抗体和磷酸化-Akt抗体，通过蛋白质印迹分析来测定胰岛素受体底物-1蛋白表达和Akt磷酸化。使用（3）H标记的2-脱氧-D-葡萄糖摄取来评估葡萄糖代谢。醛固酮（1-100 nmol/L）呈剂量依赖性降低胰岛素受体底物-1蛋白表达，在18小时时达到峰值（n = 4）。用选择性盐皮质激素受体拮抗剂依普利酮（10 μmol/L；n = 4）处理可显著减弱醛固酮诱导的胰岛素受体底物-1降解。此外，Src抑制剂PP1（20 μmol/L；n = 4）可阻断降解。用抗氧化剂N-乙酰半胱氨酸（10 mmol/L）或依布硒仑（40 μmol/L）处理也可减弱醛固酮诱导的胰岛素受体底物-1降解（n = 4）。此外，蛋白酶体抑制剂MG132（1 μmol/L）可防止胰岛素受体底物-1降解（n = 4）。醛固酮处理消除了胰岛素诱导的Akt磷酸化（100 nmol/L；5分钟；n = 4）。此外,醛固酮预处理使胰岛素刺激（100 nmol/L；60分钟；n = 4）后的葡萄糖摄取降低了50%，依普利酮（10 μmol/L；n =4）可使其恢复正常。这些数据表明，醛固酮通过Src和活性氧刺激在血管平滑肌细胞中通过蛋白酶体依赖性降解降低胰岛素受体底物-1的表达；因此，醛固酮可能通过氧化应激参与血管胰岛素抵抗的发病机制。
