| First Author | White JP | Year | 2013 |
| Journal | Am J Physiol Endocrinol Metab | Volume | 304 |
| Issue | 10 | Pages | E1042-52 |
| PubMed ID | 23531613 | Mgi Jnum | J:198215 |
| Mgi Id | MGI:5495866 | Doi | 10.1152/ajpendo.00410.2012 |
| Citation | White JP, et al. (2013) Muscle mTORC1 suppression by IL-6 during cancer cachexia: a role for AMPK. Am J Physiol Endocrinol Metab 304(10):E1042-52 |
| abstractText | Although catabolic signaling has a well-established role in muscle wasting during cancer cachexia, the suppression of anabolic signaling also warrants further investigation. In cachectic tumor-bearing mice, circulating IL-6 levels are associated with suppressed muscle protein synthesis and mTORC1 signaling. We have found AMPK and IGF-I/insulin signaling, two well-known regulators of the mammalian target of rapamycin (mTOR), are altered with the progression of cachexia. How IL-6 can induce suppression of mTORC1 signaling remains to be established. The purpose of this study was to examine mTOR complex 1 (mTORC1) activation and regulation by IL-6 during cancer cachexia. IL-6 effects on mTOR activation were examined in Apc(Min/+) mouse skeletal muscle and C2C12 myotubes. Systemic IL-6 overexpression in Apc(Min/+) mice produced a dose-dependent suppression of mTOR signaling that corresponded to induction of STAT3 and AMPK phosphorylation. This result was also evident in IL-6-treated myotubes. Basal mTOR activation and mTOR responsiveness to glucose administration were suppressed in cachectic skeletal muscle. However, insulin induction of mTOR activity was maintained in IL-6-treated myotubes. Whereas IL-6 suppression of myotube mTOR activity was rescued by AMPK inhibition, inhibition of STAT3 signaling was not sufficient to rescue IL-6 suppression of mTOR activity. Last, treadmill exercise training was able to prevent IL-6-induced inhibition of mTOR signaling in Apc(Min/+) mice independently of activated STAT. In conclusion, we report dose-dependent suppression of mTOR activity by IL-6 and suppressed mTOR responsiveness to glucose administration in Apc(Min/+) mice. IL-6 suppression of mTOR activity was dependent on AMPK activation and independent of STAT signaling in myotubes. |
