Phytoecdysteroids Enhance Skeletal Muscle Function Recovery Following In Vivo Eccentric Contraction‐Induced Injury in Old Mice

Abstract

Listen

Translate article

Phytoecdysteroids are natural plant steroids synthesized by a variety of hardy plants. Previous work by our group has shown that administration of phytoecdysteroids, such as 20‐hydroxyecdysone (20E), in old mice results in an increase in protein synthesis signaling and skeletal muscle fiber size. The effect of phytoecdysteroids on recovery from eccentric contraction‐induced skeletal muscle damage is unknown. Therefore, the purpose of this study was to investigate the degree to which 7 days of 20E supplementation, in old male mice, improves recovery of isometric skeletal muscle function following injurious eccentric muscle contractions (EC), compared to placebo (PLA). Old male mice (mean age 27.5 ± 0.5 months) were assigned to either EC+20E or EC+PLA treatment groups. Mice were anesthetized with isoflurane and then in vivo isometric contractions (Aurora Scientific, 1300A) were performed to obtain optimal electrode placement for stimulation of the anterior crural muscle group. Following electrode placement, the isometric torque‐frequency relationship was established (PRE). Then, 150 EC were performed to induce injury in the anterior crural muscle group. Upon completion, the torque‐frequency relationship was re‐measured to confirm damage (POST). Following recovery from anesthesia, the mice received either 20E (50 mg•kg−1 BW) in liquid diet (BioServ, AIN‐76) or PLA (liquid diet only) by oral gavage. Mice were gavaged daily for 6 days. On day 7, mice were anesthetized with isoflurane and the torque‐frequency relationship was re‐assessed (7‐day). Repeated measures ANOVA revealed that EC in EC+PLA led to a depression in the torque‐frequency relationship, as measured at 7‐day (p<0.01). Conversely, 7 days of 20E supplementation led to recovery of the torque‐frequency relationship to PRE levels (p=0.461). Additionally, maximal (250 Hz) and submaximal (40 Hz) isometric torques remained depressed in EC+PLA (p=0.014 and p=0.004, respectively), while EC+20E showed no change (p=0.559, p=0.632, respectively) from PRE to 7‐day. In conclusion, these findings suggest that 20E exerts anabolic or ergogenic effects in old male mice that aid in recovery of isometric skeletal muscle function following EC‐induced injury.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.