Ingestion of soy protein isolate attenuates eccentric contraction-induced force depression and muscle proteolysis via inhibition of calpain-1 activation in rat fast-twitch skeletal muscle Academic Article uri icon


  • OBJECTIVE:Eccentric contraction (ECC) is a contraction in which skeletal muscles are stretched while contracting. The aim of this study was to determine how ingestion of soy protein isolate (SPI) or animal-based proteins affect force deficit, calpain activation, and proteolysis of calcium ion (Ca2+)-regulatory proteins in rat fast-twitch muscles subjected to ECC. METHODS:In the first experiment, male Wistar rats were randomly assigned to a control and an SPI group, which were fed a 20% casein and a 20% SPI diet, respectively, for 28 d before the ECC protocol. Anterior crural muscles underwent 200 repeated ECCs and were excised 3 d later. In the second experiment, half of the SPI rats were given water containing NG-nitro-l-arginine-methyl ester (L-NAME), an inhibitor of nitric oxide synthase, for 3 d of recovery after ECC. RESULTS:SPI ingestion attenuated ECC-induced force deficit, proteolysis of Ca2+-regulatory proteins, and autolysis of calpain-1. Co-ingestion of L-NAME inhibited SPI-associated increases in nitrite and nitrate levels and negated the force recovery effects of SPI. CONCLUSION:These results suggest that SPI ingestion inhibits ECC-elicited force deficit and proteolysis of Ca2+ regulatory proteins, which is caused by inhibited activation of calpain-1 via increased nitric oxide production.


  • Kanzaki, Keita
  • Watanabe, Daiki
  • Aibara, Chihiro
  • Kawakami, Yuki
  • Yamada, Takashi
  • Takahashi, Yoshitaka
  • Wada, Masanobu

publication date

  • 2019