Research Paper Volume 5, Issue 7 pp 539—550
Rapamycin doses sufficient to extend lifespan do not compromise muscle mitochondrial content or endurance
- 1 State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, China
- 2 Institute for Diabetes, Obesity, and Metabolism and Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia PA 19104, USA
- 3 Department of Science, Systems and Models, Roskilde University, Roskilde, Denmark
- 4 Division of Trauma, Critical Care, and Emergency Surgery, University of Pennsylvania, Philadelphia PA 19104, USA
- 5 Whitehead Institute for Biomedical Research, Cambridge MA 02142; Department of Biology, MIT, Cambridge, MA 02139; Howard Hughes Medical Institute, MIT, Cambridge, MA 02139; Broad Institute of Harvard and MIT, Seven Cambridge Center, Cambridge, MA 02142; The David H. Koch Institute for Integrative Cancer Research at MIT, Cambridge, MA 02139, USA
- 6 The Jackson Laboratory, Bar Harbor, ME 04609, USA
Received: May 29, 2013 Accepted: July 12, 2013 Published: July 16, 2013
https://doi.org/10.18632/aging.100576How to Cite
Abstract
Rapamycin extends lifespan in mice, but can have a number of undesirable effects that may ultimately limit its utility in humans. The canonical target of rapamycin, and the one thought to account for its effects on lifespan, is the mammalian/mechanistic target of rapamycin, complex 1 (mTORC1). We have previously shown that at least some of the detrimental side effects of rapamycin are due to “off target” disruption of mTORC2, suggesting they could be avoided by more specific targeting of mTORC1. However, mTORC1 inhibition per se can reduce the mRNA expression of mitochondrial genes and compromise the function of mitochondria in cultured muscle cells, implying that defects in bioenergetics might be an unavoidable consequence of targeting mTORC1 in vivo. Therefore, we tested whether rapamycin, at the same doses used to extend lifespan, affects mitochondrial function in skeletal muscle. While mitochondrial transcripts were decreased, particularly in the highly oxidative soleus muscle, we found no consistent change in mitochondrial DNA or protein levels. In agreement with the lack of change in mitochondrial components, rapamycin-treated mice had endurance equivalent to that of untreated controls, and isolated, permeabilized muscle fibers displayed similar rates of oxygen consumption. We conclude that the doses of rapamycin required to extend life do not cause overt mitochondrial dysfunction in skeletal muscle.