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Nicotinamide riboside kinases display redundancy in mediating nicotinamide mononucleotide and nicotinamide riboside metabolism in skeletal muscle cells
Journal article   Open access   Peer reviewed

Nicotinamide riboside kinases display redundancy in mediating nicotinamide mononucleotide and nicotinamide riboside metabolism in skeletal muscle cells

Rachel S Fletcher, Joanna Ratajczak, Craig L Doig, Lucy A Oakey, Rebecca Callingham, Gabriella Da Silva Xavier, Antje Garten, Yasir S Elhassan, Philip Redpath, Marie E Migaud, …
Molecular Metabolism, Vol.6(8), pp.819-832
08/2017
DOI: 10.1016/j.molmet.2017.05.011
PMCID: PMC5518663
PMID: 28752046
url
https://doi.org/10.1016/j.molmet.2017.05.011View
Published (Version of record) Open Access

Abstract

Augmenting nicotinamide adenine dinucleotide (NAD+) availability may protect skeletal muscle from age-related metabolic decline. Dietary supplementation of NAD+ precursors nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) appear efficacious in elevating muscle NAD+. Here we sought to identify the pathways skeletal muscle cells utilize to synthesize NAD+ from NMN and NR and provide insight into mechanisms of muscle metabolic homeostasis. We exploited expression profiling of muscle NAD+ biosynthetic pathways, single and double nicotinamide riboside kinase 1/2 (NRK1/2) loss-of-function mice, and pharmacological inhibition of muscle NAD+ recycling to evaluate NMN and NR utilization. Skeletal muscle cells primarily rely on nicotinamide phosphoribosyltransferase (NAMPT), NRK1, and NRK2 for salvage biosynthesis of NAD+. NAMPT inhibition depletes muscle NAD+ availability and can be rescued by NR and NMN as the preferred precursors for elevating muscle cell NAD+ in a pathway that depends on NRK1 and NRK2. Nrk2 knockout mice develop normally and show subtle alterations to their NAD+ metabolome and expression of related genes. NRK1, NRK2, and double KO myotubes revealed redundancy in the NRK dependent metabolism of NR to NAD+. Significantly, these models revealed that NMN supplementation is also dependent upon NRK activity to enhance NAD+ availability. These results identify skeletal muscle cells as requiring NAMPT to maintain NAD+ availability and reveal that NRK1 and 2 display overlapping function in salvage of exogenous NR and NMN to augment intracellular NAD+ availability. •NRK1 and NRK2 are expressed in skeletal muscle and display redundancy in converting NR and NMN to NAD+.•NRK1 and NRK2 are dispensable for maintaining basal skeletal muscle cell NAD+.•Exogenous NMN salvage to NAD+ is NRK dependent.
Energy Metabolism NAD Nicotinamide riboside Skeletal muscle

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