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Effects of Elevated Circulating Hormones on Resistance Exercise-Induced Akt Signaling

SPIERING, BARRY A.1; KRAEMER, WILLIAM J.1; ANDERSON, JEFFREY M.1; ARMSTRONG, LAWRENCE E.1; NINDL, BRADLEY C.2; VOLEK, JEFF S.1; JUDELSON, DANIEL A.3; JOSEPH, MICHAEL1; VINGREN, JAKOB L.1; HATFIELD, DISA L.1; FRAGALA, MAREN S.1; HO, JEN-YU1; MARESH, CARL M.1

Medicine & Science in Sports & Exercise: June 2008 - Volume 40 - Issue 6 - p 1039-1048
doi: 10.1249/MSS.0b013e31816722bd
BASIC SCIENCES: Original Investigations

Purpose: Hormones and muscle contraction alter protein kinase B (Akt) signaling via distinct mechanisms. Therefore, the purpose of this study was to determine whether physiologically elevated circulating hormones modulate resistance exercise (RE)-induced signaling of Akt and its downstream targets. We hypothesized that elevated circulating hormones would potentiate the signaling response.

Methods: Seven healthy men (mean ± SD age, 27 ± 4 yr; body mass, 79.1 ± 13.6 kg; body fat, 16% ± 7%) performed two identical lower-body RE protocols (five sets of five maximal repetitions of knee extensions) in a randomized order and separated by 1-3 wk: one protocol was preceded by rest [low-circulating hormonal concentration (LHC) trial], and the other was preceded by a bout of high-volume upper-body RE using short rest periods designed to elicit a large increase in circulating hormones [high-circulating hormonal concentration (HHC) trial].

Results: The HHC trial invoked significantly (P ≤ 0.05) greater growth hormone (GH) and cortisol concentrations compared with the LHC trial. There were minimal differences between trials in insulin and insulin-like growth factor-I (IGF-I) concentrations. Contrary to our hypothesis, 70-kDa ribosomal protein S6 kinase (p70 S6K) threonine (Thr) 389 phosphorylation within the vastus lateralis was attenuated at 180 min post-RE during the HHC trial. RE did not affect Akt or glycogen synthase kinase-3β (GSK-3β) phosphorylation nor were there differences between trials. Immediately post-RE, eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1) phosphorylation declined, and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation increased; however, there were no differences between trials in these variables.

Conclusion: p70 S6K Thr 389 phosphorylation was attenuated during the HHC trial despite dramatically greater (>2.5-fold) circulating GH concentrations; this was potentially due to cortisol-induced inhibition of p70 S6K Thr 389 phosphorylation.

1Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT; 2Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA; and 3Department of Kinesiology, California State University-Fullerton, Fullerton, CA

Address for correspondence: William J. Kraemer, Ph.D., Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269; E-mail: William.Kraemer@uconn.edu.

Submitted for publication December 2007.

Accepted for publication January 2008.

©2008The American College of Sports Medicine