Does NAD+ In Fact Decline With Age Sufficiently to be a Useful Target for Interventions?
Nicotinamide adenine dinucleotide (NAD) is an important part of the mechanisms by which mitochondria produce chemical energy store molecules to power cellular processes. NAD levels fall with age, concurrent with growing mitochondrial dysfunction. There is some enthusiasm for approaches - such as supplementation with vitamin B3 derivatives - that might compensate for this issue and thereby improve mitochondrial function in later life.
Researchers here suggest that in fact the quality and quantity of evidence for NAD+ levels to decline with age doesn't rise to the level that the scientific community should by using as a basis to proceed towards the development of interventions. I think it most likely that more rigorous work will confirm the existing evidence. More pertinent objections to sizable investment in NAD upregulation are that (a) exercise increases NAD levels to a greater degree than any of the other approaches assessed to date, and (b) the results of clinical trials of NAD upregulation are decidedly mediocre.
Nicotinamide adenine dinucleotide (NAD+) is an essential molecule involved in various metabolic reactions, acting as an electron donor in the electron transport chain and as a co-factor for NAD+-dependent enzymes. In the early 2000s, reports that NAD+ declines with aging introduced the notion that NAD+ metabolism is globally and progressively impaired with age. Since then, NAD+ became an attractive target for potential pharmacological therapies aiming to increase NAD+ levels to promote vitality and protect against age-related diseases.
This review summarizes and discusses a collection of studies that report the levels of NAD+ with aging in different species (i.e., yeast, C. elegans, rat, mouse, monkey, and human), to determine whether the notion that overall NAD+ levels decrease with aging stands true. We find that, despite systematic claims of overall changes in NAD+ levels with aging, the evidence to support such claims is very limited and often restricted to a single tissue or cell type. This is particularly true in humans, where the development of NAD+ levels during aging is still poorly characterized. There is a need for much larger, preferably longitudinal, studies to assess how NAD+ levels develop with aging in various tissues. This will strengthen our conclusions on NAD metabolism during aging and should provide a foundation for better pharmacological targeting of relevant tissues.