The impact of bisphenol AF on skeletal muscle function and differentiation in vitro

Various environmental chemicals have been identified as contributors to metabolic diseases. Bisphenol AF (BPAF), a substitute for bisphenol A, has been associated with changes in glucose metabolism and incidence of type 2 diabetes mellitus in humans. However, its mode of action remains unclear. Considering that skeletal muscle is the primary tissue for glucose utilization and the development of insulin resistance, yet largely neglected in toxicological assessments, we investigated the impact of BPAF on skeletal muscle function and differentiation. We examined the effects of BPAF (0.01-10 μM) on glucose uptake, response to insulin, production of reactive oxygen species (ROS), intracellular calcium, and myocyte differentiation, during hyperglycemia, insulin stimulation, and muscle contraction. We used the rat myoblast cell line L6 differentiated into myotubes, and murine primary isolated muscle fibers. In myotubes and contracting adult fibers, BPAF increased mitochondrial ROS. Basal glucose uptake was increased in myotubes while cells' ability to respond to insulin was decreased. Additionally, in developing myotubes, differentiation markers were downregulated with BPAF, along with impaired formation of tube structures. These effects were primarily observed at 10 μM concentration, which is markedly higher than reported human exposure concentrations. The results provide an insight into potential hazards associated with BPAF in terms of metabolic disruption in skeletal muscle. The developed in vitro methods show promise for future usage in assessments of new chemicals and their mixtures.