1α,25(OH)2-Vitamin D3 and 17β-Estradiol: Two Steroid Partners Acting in Skeletal Muscle

1α,25(OH)2-vitamin D3 and 17β-estradiol regulate skeletal muscle cell proliferation, differentiation, apoptosis and contractility through receptor-mediated transcriptional and non-genomic mechanisms. This review focuses on recent advances on signal transduction pathways activated by both steroid hormones. Data are given on the participation of the VDR and ERs (α and β) in activation of MAPKs in muscle cells. Likewise, we describe novel evidence supporting non-classical localizations of the VDR in the plasma membrane and ER β in mitochondria. 1α,25(OH)2D3 promotes DNA synthesis in skeletal muscle cells implicating c-Src/ERK1/2, whereas 17β-estradiol inhibits apoptosis through ERK2 and p38 MAPKs. This study provides basis for the understanding of vitamin D- and estrogen-dependent myopathies.