Leucine and mTORc1 act independently to regulate 2-deoxyglucose uptake in L6 myotubes

Yin, Qiong; Brameld, John M.; Parr, Tim; Murton, Andrew J.

Abstract

© 2020, The Author(s). Chronic mTORc1 hyperactivation via obesity-induced hyperleucinaemia has been implicated in the development of insulin resistance, yet the direct impact of leucine on insulin-stimulated glucose uptake in muscle cells remains unclear. To address this, differentiated L6 myotubes were subjected to various compounds designed to either inhibit mTORc1 activity (rapamycin), blunt leucine intracellular import (BCH), or activate mTORc1 signalling (3BDO), prior to the determination of the uptake of the glucose analogue, 2-deoxyglucose (2-DG), in response to 1mM insulin. In separate experiments, L6 myotubes were subject to various media concentrations of leucine (0–0.8mM) for 24h before 2-DG uptake in response to insulin was assessed. Both rapamycin and BCH blunted 2-DG uptake, irrespective of insulin administration, and this occurred in parallel with a decline in mTOR, 4E-BP1, and p70S6K phosphorylation status, but little effect on AKT phosphorylation. In contrast, reducing leucine media concentrations suppressed 2-DG uptake, both under insulin- and non-insulin-stimulated conditions, but did not alter the phosphorylation state of AKT-mTORc1 components examined. Unexpectedly, 3BDO failed to stimulate mTORc1 signalling, but, nonetheless, caused a significant increase in 2-DG uptake under non-insulin-stimulated conditions. Both leucine and mTORc1 influence glucose uptake in muscle cells independent of insulin administration, and this likely occurs via distinct but overlapping mechanisms.

Citation

Yin, Q., Brameld, J. M., Parr, T., & Murton, A. J. (2020). Leucine and mTORc1 act independently to regulate 2-deoxyglucose uptake in L6 myotubes. Amino Acids, 52, 477–486. https://doi.org/10.1007/s00726-020-02829-0

• Journal Article Type: Article
• Acceptance Date: Feb 8, 2020
• Online Publication Date: Feb 27, 2020
• Publication Date: 2020-03
• Deposit Date: Feb 28, 2020
• Publicly Available Date: Mar 3, 2020
• Journal: Amino Acids
• Print ISSN: 0939-4451
• Electronic ISSN: 1438-2199
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 52
• Pages: 477–486
• DOI: https://doi.org/10.1007/s00726-020-02829-0
• Keywords: Insulin resistance, Obesity, Muscle, Glucose uptake, Leucine, Branched chain amino acids
• Public URL: https://nottingham-repository.worktribe.com/output/4049540
• Publisher URL: https://link.springer.com/article/10.1007%2Fs00726-020-02829-0
• Additional Information: Received: 5 September 2019; Accepted: 8 February 2020; First Online: 27 February 2020; : ; : The authors declare that they have no conflict of interest.