The effect of BPA exposure on insulin resistance and type 2 diabetes - The impact of muscle contraction.

Type 2 diabetes (T2D) is considered one of the leading causes of death worldwide. In addition to physical inactivity and obesity, established risk factors for T2D, chemical contaminants consumed in industrialized food such as BPA might also be a contributor to the development of T2D. Epidemiological studies have shown that BPA concentrations are higher in human specimens of T2D when compared to healthy subjects, while experimental studies suggested that bisphenol A (BPA) impairs the pathway by which insulin stimulates glucose uptake. In skeletal muscle and adipocytes, insulin resistance is developed by the impairment of the insulin pathway to stimulate the translocation of glucose transporter, GLUT4, to the cell membrane. Recent results demonstrated that BPA impairs several components of insulin-induced glucose uptake pathway and affect the expression of GLUT4. Regular physical exercise delays or inhibits the development of T2D due to the physiologic processes taking place during muscle contraction, and the fact that skeletal muscle is the site for almost 80% of the glucose transported under insulin stimulation. In fact, the mechanism by which contraction induces glucose uptake in skeletal muscle is partially independent of the insulin pathway, therefore, the effect of BPA on this mechanism is unknown. We hypothesize that during the development of insulin resistance, BPA contributes to the impairment of the molecular pathway by which insulin induces glucose uptake while contraction-induced glucose uptake is not impaired. At the late stages of T2D, BPA may affect GLUT4 expression that will decrease the ability of muscle contraction to induce glucose uptake.