Inhibitory Effect of Kori-tofu Protein on Denervation-Induced Atrogene Expression in Mouse Skeletal Muscle

Soy glycinin contains a functional inhibitory sequence, DIpYNP, against muscle-atrophy-associated ubiquitin ligase Cbl-b. It inhibited the binding of Cbl-b and IRS-1 (called Cblin-like peptide) and improved denervation-induced muscle atrophy in mice. In the present study, we evaluated the anti-muscle atrophy effect by feeding Kori-tofu to a mouse model of muscle atrophy induced by sciatic nerve transection, because Kori-tofu is a freeze-dried tofu made mainly from soy proteins. In the mice fed with Kori-tofu for one week, no significant inhibition in the reduction of the tibialis anterior (TA), gastrocnemius (GA) or soleus (SOL) muscle due to denervation was observed, compared with those of mice fed a soy protein isolate (SPI) or casein. However, in the TA muscle of the Kori-tofu-fed group, a significant suppression of the increased expression levels of muscle atrophy-related genes, MAFbx/atrogin-1 and MuRF-1, induced by denervation was observed similarly as that of mice fed a SPI. Additionally, the denervation-mediated decrease in the fast-twitch type myosin heavy chain (MyHC) level was suppressed in the TA of the Kori-tofu-fed group. Thus, our results suggest that Kori-tofu could be a useful and perishable functional space food against unloading-mediated muscle atrophy.