Oakey, L. A. et al. (2018) Metabolic tracing reveals novel adaptations to skeletal muscle cell energy production pathways in response to NAD+ depletion. Wellcome Open Research, 3, 147. (doi: 10.12688/wellcomeopenres.14898.2) (PMID:30607371) (PMCID:PMC6305244)
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Abstract
Background: Skeletal muscle is central to whole body metabolic homeostasis, with age and disease impairing its ability to function appropriately to maintain health. Inadequate NAD+ availability is proposed to contribute to pathophysiology by impairing metabolic energy pathway use. Despite the importance of NAD+ as a vital redox cofactor in energy production pathways being well-established, the wider impact of disrupted NAD+ homeostasis on these pathways is unknown. Methods: We utilised skeletal muscle myotube models to induce NAD+ depletion, repletion and excess and conducted metabolic tracing to provide comprehensive and detailed analysis of the consequences of altered NAD+ metabolism on central carbon metabolic pathways. We used stable isotope tracers, [1,2-13C] D-glucose and [U-13C] glutamine, and conducted combined 2D-1H,13C-heteronuclear single quantum coherence (HSQC) NMR spectroscopy and GC-MS analysis. Results: NAD+ excess driven by nicotinamide riboside (NR) supplementation within skeletal muscle cells results in enhanced nicotinamide clearance, but had no effect on energy homeostasis or central carbon metabolism. Nicotinamide phosphoribosyltransferase (NAMPT) inhibition induced NAD+ depletion and resulted in equilibration of metabolites upstream of glyceraldehyde phosphate dehydrogenase (GAPDH). Aspartate production through glycolysis and TCA cycle activity is increased in response to low NAD+, which is rapidly reversed with repletion of the NAD+ pool using NR. NAD+ depletion reversibly inhibits cytosolic GAPDH activity, but retains mitochondrial oxidative metabolism, suggesting differential effects of this treatment on sub-cellular pyridine pools. When supplemented, NR efficiently reverses these metabolic consequences. However, the functional relevance of increased aspartate levels after NAD+ depletion remains unclear, and requires further investigation.
| Item Type: | Articles |
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| Additional Information: | This work was supported by a PhD studentship funded by the University of Birmingham and a Wellcome Trust Senior Fellowship (GGL-104612/Z/14/Z). Metabolic tracing was performed through the University of Birmingham Metabolic Tracing Analysis Core (MTAC). We thank ChromaDex (Irvine, California) for nicotinamide riboside and helpful discussions. TZ and ODKM are funded by Cancer Research UK Career Development Fellowship (C53309/A19702). |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Tennant, Mr Daniel and Maddocks, Professor Oliver and Zhang, Mr Tong |
| Creator Roles: | |
| Authors: | Oakey, L. A., Fletcher, R. S., Elhassan, Y. S., Cartwright, D. M., Doig, C. L., Garten, A., Thakker, A., Maddocks, O. D.K., Zhang, T., Tennant, D. A., Ludwig, C., and Lavery, G. G. |
| College/School: | College of Medical Veterinary and Life Sciences > School of Cancer Sciences |
| Journal Name: | Wellcome Open Research |
| Publisher: | F1000Research |
| ISSN: | 2398-502X |
| ISSN (Online): | 2398-502X |
| Copyright Holders: | Copyright © 2018 Oakey LA et al. |
| First Published: | First published in Wellcome Open Research 3: 147 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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