Molecular mechanism underlying muscle mass retention in hibernating bats: Role of periodic arousal
Article first published online: 21 OCT 2009
Copyright © 2009 Wiley-Liss, Inc.
Journal of Cellular Physiology
Volume 222, Issue 2, pages 313–319, February 2010
How to Cite
Lee, K., So, H., Gwag, T., Ju, H., Lee, J.-W., Yamashita, M. and Choi, I. (2010), Molecular mechanism underlying muscle mass retention in hibernating bats: Role of periodic arousal. J. Cell. Physiol., 222: 313–319. doi: 10.1002/jcp.21952
- Issue published online: 26 NOV 2009
- Article first published online: 21 OCT 2009
- Manuscript Accepted: 2 SEP 2009
- Manuscript Received: 6 JUL 2009
- National Space Laboratory Program (Korea Science and Engineering Foundation). Grant Number: 2008-03190
Hibernators like bats show only marginal muscle atrophy during prolonged hibernation. The current study was designed to test the hypothesis that hibernators use periodic arousal to increase protein anabolism that compensates for the continuous muscle proteolysis during disuse. To test this hypothesis, we investigated the effects of 3-month hibernation (HB) and 7-day post-arousal torpor (TP) followed by re-arousal (RA) on signaling activities in the pectoral muscles of summer-active (SA) and dormant Murina leucogaster bats. The bats did not lose muscle mass relative to body mass during the HB or TP-to-RA period. For the first 30-min following arousal, the peak amplitude and frequency of electromyographic spikes increased 3.1- and 1.4-fold, respectively, indicating massive myofiber recruitment and elevated motor signaling during shivering. Immunoblot analyses of whole-tissue lysates revealed several principal outcomes: (1) for the 3-month HB, the phosphorylation levels of Akt1 (p-Akt1) and p-mTOR decreased significantly compared to SA bats, but p-FoxO1 levels remained unaltered; (2) for the TP-to-RA period, p-Akt1 and p-FoxO1 varied little, while p-mTOR showed biphasic oscillation; (3) proteolytic signals (i.e., atrogin-1, MuRF1, Skp2 and calpain-1) remained constant during the HB and TP-to-RA period. These results suggest that the resistive properties of torpid bat muscle against atrophy might be attained primarily by relatively constant proteolysis in combination with oscillatory anabolic activity (e.g., p-mTOR) corresponding to the frequency of arousals occurring throughout hibernation. J. Cell. Physiol. 222: 313–319, 2010. © 2009 Wiley-Liss, Inc.