DEHP and Its Metabolite MEHP Alter the <i>Insr</i> and <i>Glut4</i> Gene Expression by Blunting the Interaction of Transcription Factors in L6 Myotubes

Endocrine-disrupting chemicals (EDCs) play an important role in the incidence of type-2 diabetes. Di-2-ethyl hexyl Phthalate (DEHP) is one of the endocrine-disrupting chemicals used as a plasticizer to impart flexibility and softness to plastic-containing materials. Mono-2-ethylhexyl Phthalate (MEHP), a DEHP's primary metabolite, is preferentially absorbed once metabolized. A previous study from our laboratory showed that DEHP and MEHP altered the key proteins such as insulin receptor (INSR) and glucose transporter-4 (GLUT4) in L6 myotubes. In a sequel to the previous study, the present study hypothesized that DEHP and its metabolite MEHP may alter the <i>Insr</i> and <i>Glut4</i> gene expression in L6 myotubes. Therefore, to find out the molecular mechanism behind the decreased INSR and GLUT4 protein levels in the previous study, the direct effect of DEHP and its metabolite MEHP in regulating <i>Insr</i> and <i>Glut4</i> gene transcription in L6 myotubes was studied. The L6 myotubes were exposed to 50 and 100 μM DEHP and MEHP for 24 h, followed by insulin stimulation for 20 min. We observed decreased <i>Insr</i> and <i>Glut4</i> mRNA levels in DEHP and MEHP-treated groups. Western blot data showed decreased protein levels of MEF2A and MyoD in treated groups. ChIP assay detected a decreased association of MEF2A and MyoD to the <i>Glut4</i> gene promoter and HMGA1 to the <i>Insr</i> gene promoter. The study revealed that DEHP and MEHP diminished the <i>Insr</i> and <i>Glut4</i> gene expression through weakened interaction of their transcription factors on the respective promoter.