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AICAR suppresses p70S6k and eEF2 signaling after eccentric resistance exercise
Author(s) -
Thomson David M.,
Fick Christopher A.,
Gordon Scott E.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a819-a
Subject(s) - ampk , p70 s6 kinase 1 , phosphorylation , endocrinology , medicine , amp activated protein kinase , skeletal muscle , muscle hypertrophy , chemistry , signal transduction , protein kinase a , protein kinase b , biology , biochemistry
p70S6k (S6k) and eukaryotic elongation factor 2 (eEF2) are key signaling proteins involved in skeletal muscle hypertrophy and can be inhibited by activation of 5′‐AMP‐activated protein kinase (AMPK). To study the effect of AMPK activity on S6k and eEF2 signaling after eccentric resistance exercise, EDL muscles (n=8/group) from Fischer 344 x Brown Norway male rats were subjected to a 20‐min bout of in‐vivo eccentric resistance exercise by sciatic nerve electrical stimulation. 40 min prior to exercise, rats received a subcutaneous injection of saline (SAL) or AICAR (AIC; 1 mg/g BW), an AMPK activator. Exercised (EX) and contralateral control (CTR) muscles were removed at 0, 20 and 40 min post‐exercise, and phosphorylation of AMPK (Thr172), S6k (Thr389), and eEF2 (Thr56) was assessed by western blot. AMPK phosphorylation was not different in EX vs. CTR at any time‐point. With SAL, S6k phosphorylation (indicative of activity) was elevated (p ≤ 0.05) in EX vs. CTR at 0, 20 and 40 min, but AIC attenuated this increase. With SAL, eEF2 phosphorylation (indicative of decreased activity) was suppressed in EX vs. CTR at 20 and 40, but not 0, min. AIC generally increased eEF2 phosphorylation vs. SAL regardless of exercise. In conclusion, eccentric resistance exercise may not stimulate AMPK in fast‐twitch muscle. Signaling through S6k and eEF2 appears to be enhanced in response to such exercise. However, this signaling is inhibited by AICAR, suggesting that AMPK could act as a negative regulator of exercise‐induced translational signaling. Supported by NIH AG025101 and NIA Animal Allocation Dissertation Support.