Inhibitory effects of statins on human monocarboxylate transporter 4.

Human MCT4 (SLC16A3) is responsible for the efflux of L-lactic acid from skeletal muscle cells and is essential for muscle homeostasis. However, the effects of monocarboxylate drugs, such as statins on the MCT4-mediated transport of L-lactic acid have not been elucidated. Inhibition of L-lactic acid transport mediated by MCT4 might to lead to collapse of muscle homeostasis. The aim of this study was to establish an MCT4 transfected cell line and to clarify the transport mechanism of L-lactic acid and the effects of statins on this transport system. Results of Western blot analyses and immunohistochemistry studies indicated that the expression of CD147 and MCT4-FLAG protein were observed and was displayed clear plasma membrane localization in CD147 and MCT4-FLAG co-transfected cell line (cm cells). Uptake of L-lactic acid in cm cells was significantly greater than that in cells transfected with a vector alone. L-lactic acid uptake was concentration-dependent with a K(m) value of 28.43+/-3.87 mM. The results of a previous study showing a K(m) value of 28.5 mM in hMCT4-expressed oocytes. Lipophilic statins significantly inhibited [(14)C] L-lactic acid uptake in a concentration-dependent manner. In contrast, the inhibitory effects of hydrophilic statins were very weak.