Induction of the nicotinamide riboside kinase NAD+ salvage pathway in skeletal myopathy of H6PDH KO mice

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Doig, C ORCID: https://orcid.org/0000-0001-9694-4230, Zielinska, A, Fletcher, R, Oakey, L, Elhassan, Y, Garten, A, Cartwright, D, Heising, S, Alsheri, A, Watson, D, Adamski, J, Tennant, D and Lavery, G, 2020. Induction of the nicotinamide riboside kinase NAD+ salvage pathway in skeletal myopathy of H6PDH KO mice. Skeletal Muscle, 10: 5. ISSN 2044-5040

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Official URL: https://doi.org/10.1186/s13395-019-0216-z

Abstract

Background: Hexose-6-Phosphate Dehydrogenase (H6PD) is a generator of NADPH in the Endoplasmic/Sarcoplasmic Reticulum (ER/SR). Interaction of H6PD with 11β-hydroxysteroid dehydrogenase type 1 provides NADPH to support oxo-reduction of inactive to active glucocorticoids, but the wider understanding of H6PD in ER/SR NAD(P)(H) homeostasis is incomplete. Lack of H6PD results in a deteriorating skeletal myopathy, altered glucose homeostasis, ER stress and activation of the unfolded protein response. Here we further assess muscle responses to H6PD deficiency to delineate pathways that may underpin myopathy and link SR redox status to muscle wide metabolic adaptation.

Methods: We analysed skeletal muscle from H6PD knockout (H6PDKO), H6PD and NRK2 double knockout (DKO) and wild-type (WT) mice. H6PDKO mice were supplemented with the NAD+ precursor nicotinamide riboside. Skeletal muscle samples were subjected to biochemical analysis including NAD(H) measurement, LC-MS based metabolomics, Western blotting, and high resolution mitochondrial respirometry. Genetic and supplement models were assessed for degree of myopathy compared to H6PDKO.

Results: H6PDKO skeletal muscle showed adaptations in the routes regulating nicotinamide and NAD+ biosynthesis, with significant activation of the Nicotinamide Riboside Kinase 2 (NRK2) pathway. Associated with changes in NAD+ biosynthesis, H6PDKO muscle had impaired mitochondrial respiratory capacity with altered mitochondrial acylcarnitine and acetyl-CoA metabolism. Boosting NAD+ levels through the NRK2 pathway using the precursor nicotinamide riboside elevated NAD+/NADH but had no effect to mitigate ER stress and dysfunctional mitochondrial respiratory capacity or acetyl-CoA metabolism. Similarly, H6PDKO/NRK2 double KO mice did not display an exaggerated timing or severity of myopathy or overt change in mitochondrial metabolism despite depression of NAD+ availability.

Conclusions: These findings suggest a complex metabolic response to changes in muscle SR NADP(H) redox status that result in impaired mitochondrial energy metabolism and activation of cellular NAD+ salvage pathways. It is possible that SR can sense and signal perturbation in NAD(P)(H) that cannot be rectified in the absence of H6PD. Whether NRK2 pathway activation is a direct response to changes in SR NAD(P)(H) availability or adaptation to deficits in metabolic energy availability remains to be resolved.

Item Type:	Journal article
Publication Title:	Skeletal Muscle
Creators:	Doig, C., Zielinska, A., Fletcher, R., Oakey, L., Elhassan, Y., Garten, A., Cartwright, D., Heising, S., Alsheri, A., Watson, D., Adamski, J., Tennant, D. and Lavery, G.
Publisher:	BioMed Central Ltd.
Date:	19 February 2020
Volume:	10
ISSN:	2044-5040
Identifiers:	Number Type 1215237 Other 10.1186/s13395-019-0216-z DOI
Rights:	This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Divisions:	Schools > School of Science and Technology
Record created by:	Jonathan Gallacher
Date Added:	26 Nov 2019 11:01
Last Modified:	31 May 2021 15:07
URI:	https://irep.ntu.ac.uk/id/eprint/38510