Skeletal muscle is the tissue directly involved in insulin-stimulated glucose
uptake. Glucose is the primary energy substrate for contracting muscles, and
proper metabolism of glucose is essential for health. Contractile activity and
the associated Ca2+signaling regulate functional capacity and
muscle mass. A high concentration of Ca2+and the presence of
calmodulin (CaM) leads to the activation of calcineurin (CaN), a protein with
serine-threonine phosphatase activity. The signaling pathway linked with CaN and
transcription factors like the nuclear factor of activated T cells (NFAT) is
essential for skeletal muscle development and reprogramming of fast-twitch to
slow-twitch fibers. CaN activation may promote metabolic adaptations in muscle
cells, resulting in better insulin-stimulated glucose transport. The molecular
mechanisms underlying the altered insulin response remain unclear. The role of
the CaN/NFAT pathway in regulating skeletal muscle hypertrophy is better
described than its involvement in the pathogenesis of insulin resistance. Thus,
there are opportunities for future research in that field. This review presents
the role of CaN/NFAT signaling and suggests the relationship with
insulin-resistant muscles.