Effect of moderate acute exercise on expression of mRNA involved in the calcineurin signaling pathway in human skeletal muscle

Calcineurin, a calcium-regulated protein phosphatase, activates gene expression specific to slow muscle fibers by dephosphorylating a family of the nuclear factor of activated T cells (NFAT), which cooperates with myocyte enhancer factor-2 (MEF2) and AP-1. However, it remains unknown how acute exercise influences this signaling pathway and leads to the development of slow muscle fibers. In the present study, we investigated the effect of moderate acute exercise on mRNA expression of genes in the calcineurin signaling pathway in human skeletal muscle. Five healthy volunteers underwent 1 h bicycle ergometer at 50% VO(2)max, and vastus lateralis muscle biopsies were collected before and after exercise. Four hours after exercise, alterations in mRNA expression of NFAT 1-3 were observed with a wide variety among subjects, while c-fos mRNA was significantly induced in all subjects. By contrast, the expression of calcineurin, MEF2, and myocyte-enriched calcineurin-interacting protein 1 (MCIP1) remained unchanged. These results suggest that even moderate acute exercise may change mRNA expression of genes in the calcineurin-signaling pathway.