Extracellular MCT4 is a possible indicator for skeletal muscle MHC fiber type change

Biochemical markers that indicate fiber type rearrangement in myosin heavy chain (MHC) have been used to evaluate the effectiveness of exercise and/or rehabilitation therapy. The aim of this study was to investigate whether measures of extracellular monocarboxylate transporter 4 (MCT4) protein can help in the detection of MHC fiber type variation. Human skeletal muscle cells (HSkMCs) were succumbed to high atmospheric pressure. Immunoblot analyses were performed to evaluate MHC fiber type change, and an enzyme-linked immunosorbent assay system was developed for the quantification of MCT4 concentration. Static pressurization to HSkMCs resulted in an increase in cells of median diameter (18 μm). The proportion of MHC Type I fiber was increased by pressurization, and MCT4 protein concentration in the culture medium was also increased in the pressurized sample. We conclude that the amount of MCT4 in culture medium released from HSkMCs reflects fiber type changes in MHC.