title: Sex- and tissue-specific changes in mTOR signaling with age in C57BL/6J mice.
abstract: Inhibition of the mTOR (mechanistic Target Of Rapamycin) signaling pathway robustly extends the lifespan of model organisms including mice. The precise molecular mechanisms and physiological effects that underlie the beneficial effects of rapamycin are an exciting area of research. Surprisingly, while some data suggest that mTOR signaling normally increases with age in mice, the effect of age on mTOR signaling has never been comprehensively assessed. Here, we determine the age-associated changes in mTORC1 (mTOR complex 1) and mTORC2 (mTOR complex 2) signaling in the liver, muscle, adipose, and heart of C57BL/6J.Nia mice, the lifespan of which can be extended by rapamycin treatment. We find that the effect of age on several different readouts of mTORC1 and mTORC2 activity varies by tissue and sex in C57BL/6J.Nia mice. Intriguingly, we observed increased mTORC1 activity in the liver and heart tissue of young female mice compared to male mice of the same age. Tissue and substrate-specific results were observed in the livers of HET3 and DBA/2 mouse strains, and in liver, muscle and adipose tissue of F344 rats. Our results demonstrate that aging does not result in increased mTOR signaling in most tissues and suggest that rapamycin does not promote lifespan by reversing or blunting such an effect.
authors.affiliation: Department of Medicine, University of Wisconsin-Madison, Madison, WI, USA.|William S. Middleton Memorial Veterans Hospital, Madison, WI, USA.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Baar
authors.affiliation: Department of Medicine, University of Wisconsin-Madison, Madison, WI, USA.|William S. Middleton Memorial Veterans Hospital, Madison, WI, USA.
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Carbajal
authors.affiliation: Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, WI, USA.|University of Wisconsin Carbone Comprehensive Cancer Center, University of Wisconsin, Madison, WI, USA.
authors.forename: Irene M
authors.initials: IM
authors.lastname: Ong
authors.affiliation: Department of Medicine, University of Wisconsin-Madison, Madison, WI, USA.|William S. Middleton Memorial Veterans Hospital, Madison, WI, USA.|University of Wisconsin Carbone Comprehensive Cancer Center, University of Wisconsin, Madison, WI, USA.
authors.forename: Dudley W
authors.identifier: http://orcid.org/0000-0002-0079-4467
authors.initials: DW
authors.lastname: Lamming
mesh_terms: D000375:Aging; D000818:Animals; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008810:Mice, Inbred C57BL; D011916:Rats, Inbred F344; D012727:Sex Characteristics; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: C546843:mTOR protein, mouse; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus
keywords: aging; mTOR; mTORC1; mTORC2; mice; rapamycin; sexual dimorphism