Effects of growth hormone on muscle and bone in female mice: role of follistatin

The interactions between muscle and bone are noted for the clinical relationships between sarcopenia and osteoporosis. Myokines secreted from the skeletal muscles play roles in the muscle-bone interactions related to various physiological and pathophysiological states. Although numerous evidence suggested that growth hormone (GH) influences both muscle and bone, the effects of GH on the muscle-bone interactions have remained unknown. We therefore investigated the influences of GH administration for 8 weeks on muscle and bone, including myokine expression, in mice with or without ovariectomy (OVX). GH administration significantly increased muscle mass in the whole body and lower limbs, as well as tissue weights of the extensor digitorum longus (EDL) and soleus muscles, in mice with or without OVX. Moreover, it markedly increased grip strength in both mice. As for femurs, GH administration significantly increased cortical thickness and area in mice with or without OVX. Moreover, GH significantly blunted the decrease in the ratio of bone volume to tissue volume at trabecular bone in mice with OVX. GH administration significantly decreased follistatin mRNA levels in the EDL, but not the soleus, muscles in mice with or without OVX, although it did not affect the other myokines examined. However, GH administration significantly elevated serum follistatin levels in mice. In conclusion, our study indicated that GH administration increases skeletal muscle mass and grip strength, as well as cortical and trabecular bone-related parameters obtained by µCT analyses, in mice. However, myokine regulation might not be critical for the effects of GH on muscle and bone.