The Emergence of the Nicotinamide Riboside Kinases in the regulation of NAD+ Metabolism.

The concept of replenishing or elevating nicotinamide adenine dinucleotide (NAD+) availability to combat metabolic disease and ageing (described extensively in recent reviews [1, 2]) is an area of intense research. This has led to a need to define the endogenous regulatory pathways and mechanisms cell and tissues utilise to maximise NAD+ availability such that strategies to intervene in the clinical setting are able to be fully realised. This review discusses the importance of different salvage pathways involved in metabolising the vitamin B3 class of NAD+ precursor molecules, with a particular focus on the recently identified nicotinamide riboside kinase (NRK) pathway at both a tissue-specific and systemic level.