Viswanathan Mangala Priya, Mullainadhan Vigneswari, Chinnaiyan Mayilvanan, Karundevi Balasubramanian
Department of Endocrinology, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai 600 113, India.
Department of Endocrinology, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai 600 113, India.
Toxicology. 2017 Jul 1;386:60-71. doi: 10.1016/j.tox.2017.05.005. Epub 2017 May 17.
Di-(2-ethyl hexyl) phthalate (DEHP) is the plasticizer used in variety of medical and consumer products to impart structural flexibility. DEHP and its primary metabolite mono-(2-ethyl hexyl)phthalate (MEHP) posed a considerable interest because of their contribution to insulin resistance, type-2 diabetes and obesity. Experimental and epidemiological data have shown that DEHP affects blood glucose homeostasis. However, direct effect of DEHP and its metabolite MEHP on insulin signal transduction and glucose transporter 4 (GLUT4) translocation remain obscure. The present study was delineated to decipher the direct effects of DEHP and MEHP on insulin signal transduction and proteins involved in GLUT4 translocation in cultured L6 myotubes, the rat skeletal muscle model. For this study we have exposed cells with 50 and 100μM DEHP and MEHP for 24h followed by insulin stimulation for 20min. GLUT4 level in both cytosol and plasma membrane fractions were analysed by western blot analysis and found to be significantly decreased. Further, DEHP and MEHP treatment significantly altered the insulin signalling molecules and proteins involved in GLUT4 translocation (Rab8A (Ras related proteins in skeletal muscle), insulin - regulated amino peptidase (IRAP), synaptosomal - associated protein 23 (SNAP23), Syntaxin4, Munc18c) from cytosol to plasma membrane. Impaired GLUT4 in the plasma membrane resulted in decreased C-deoxy glucose uptake. C-glucose oxidation and glycogen content were also significantly decreased in treated groups. In essence, the present study is first of its kind to show the direct adverse effects of DEHP and MEHP on insulin signal transduction and GLUT4 translocation in cultured L6 myotubes. Further, MEHP is found to be more effective than DEHP as a result of its differential structure and physico-chemical properties.
邻苯二甲酸二（2-乙基己基）酯（DEHP）是一种增塑剂，用于多种医疗和消费产品中以赋予结构柔韧性。由于DEHP及其主要代谢产物单（2-乙基己基）邻苯二甲酸酯（MEHP）会导致胰岛素抵抗、2型糖尿病和肥胖，因此备受关注。实验和流行病学数据表明，DEHP会影响血糖稳态。然而，DEHP及其代谢产物MEHP对胰岛素信号转导和葡萄糖转运蛋白4（GLUT4）转位的直接影响仍不清楚。本研究旨在阐明DEHP和MEHP对培养的L6肌管（大鼠骨骼肌模型）中胰岛素信号转导以及参与GLUT4转位的蛋白质的直接影响。在本研究中，我们用50和100μM的DEHP和MEHP处理细胞24小时，然后用胰岛素刺激20分钟。通过蛋白质免疫印迹分析对细胞质和质膜部分中的GLUT4水平进行分析，发现其显著降低。此外，DEHP和MEHP处理显著改变了参与GLUT4转位的胰岛素信号分子和蛋白质（Rab8A（骨骼肌中的Ras相关蛋白）、胰岛素调节氨肽酶（IRAP）、突触体相关蛋白23（SNAP23）、Syntaxin4、Munc18c）从细胞质到质膜的转位。质膜中GLUT4受损导致2-脱氧葡萄糖摄取减少。处理组中的2-葡萄糖氧化和糖原含量也显著降低。本质上，本研究首次表明DEHP和MEHP对培养的L6肌管中的胰岛素信号转导和GLUT4转位具有直接不利影响。此外，由于MEHP的结构和物理化学性质不同，发现其比DEHP更有效。
