Low-frequency electroacupuncture activates mTORC1 signaling in mouse tibialis anterior muscle independent of the time of day

<title>Abstract</title> <p>Electroacupuncture (EA) has been reported to improve muscle function and attenuate skeletal muscle atrophy. Although activation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway is a key regulator of skeletal muscle protein synthesis, it remains unclear whether the anabolic response to EA depends on the time of day. This study investigated the effects of EA at four different times of day on mTORC1 signaling in the mouse tibialis anterior muscle. EA significantly increased the phosphorylation of p70S6 kinase (Thr389) and ribosomal protein S6 (Ser240/244), indicating activation of the mTORC1/S6K1 pathway regardless of treatment time. In contrast, 4E-BP1 phosphorylation was slightly decreased, whereas the abundance of the activated γ/4E-BP1 form remained unchanged. Total mTOR protein abundance was modestly decreased, whereas Raptor expression and PRAS40 abundance and phosphorylation were unchanged, suggesting that EA-induced mTORC1 activation was not mediated by major changes in upstream regulators. EA also reduced the expression of regulated in development and DNA damage responses 1 (REDD1), consistent with enhanced mTORC1 activity. Despite mTORC1 activation, Atrogin-1 and MuRF1 protein abundance and puromycin incorporation were unchanged. These findings demonstrate that EA activates mTORC1 signaling in skeletal muscle independently of the time of day. Although this activation was not accompanied by increased global protein synthesis, EA may promote a molecular environment that enhances responsiveness to subsequent anabolic stimuli. Further studies are needed to determine its physiological significance.</p>