A dietary supplement to slow aging

This is great news if you are a mouse!

Here's the summary of the paper:

NAD+ repletion improves mitochondrial and stem cell function and enhances life span in mice, by
Hongbo Zhang, Dongryeol Ryu, Yibo Wu, Karim Gariani, Xu Wang, Peiling Luan, Davide D’Amico, Eduardo R. Ropelle, Matthias P. Lutolf, Ruedi Aebersold, Kristina Schoonjans, Keir J. Menzies, Johan Auwerx, (here, if you subscribe to Science.)

The oxidized form of cellular nicotinamide adenine dinucleotide (NAD+) is critical for mitochondrial function, and its supplementation can lead to increased longevity. Zhang et al. found that feeding the NAD+ precursor nicotinamide riboside (NR) to aging mice protected them from muscle degeneration... NR treatment enhanced muscle function and also protected mice from the loss of muscle stem cells. The treatment was similarly protective of neural and melanocyte stem cells, which may have contributed to the extended life span of the NR-treated animals.

Writing in Science, Leonard Guarente notes:

NAD was discovered over a century ago, and its role in cells as a redox conduit in metabolism was subsequently established. More recently, its oxidized form, NAD+, resurfaced as a key molecule in aging in organisms ranging from yeast to mammals by the finding that the antiaging proteins, sirtuins, are NAD+-dependent deacylases. These proteins play a key role in mitochondrial function. Indeed, aging is also associated with loss of sirtuin and mitochondrial function.

As to whether NAD+ replenishment can improve health maintenance in humans, it has been reported that cellular NAD+ amounts decline during human aging (11). Also, the strict conservation in the relevant pathways of NAD+ synthesis, sirtuins, and PARPs suggests that NAD+ replenishment may also provide health benefits in people. Still, it will be important to test in humans whether dietary supplementation with NAD+ precursors will raise cellular NAD+ concentrations sufficiently to compensate for the loss due to aging. If so, it will also be necessary to test, in rigorously controlled trials, whether raising NAD+ concentrations improves health parameters, such as blood glucose and lipid profile, as well as inflammation. More expanded trials could measure effects on bone density, endothelial cell function, muscle mass, or even cognition. If NAD+ precursors can positively affect health parameters, it is reasonable to anticipate their place at the table alongside more traditional pharmaceutical drugs in the treatment of diseases.

And yes, you can buy this stuff.

But before you do that you may want to check out some of the writing that comes up from the Skeptical Search Engine.

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Here's the thing about mice--they don't have the same energy metabolism as humans. Mice are geared to reproduce quickly--if you give mice enough food, you don't get fat mice, you get more little mice. Mice are terrestrial tribbles.

Since mice have not been optimized for long life, there are a lot of tweaks that can be made to increase their lifespan. Humans are much better optimized for longevity, and it is unlikely that things which improve the lifespan of a mouse will have much effect on humans.

Problem is, of course, that testing with more relevant model systems (long-lived primates like us) just takes too much time. Guarante is already in his 60s and can't wait. (He looks it too, makes me wonder.....) His statement above is ironic given that he founded Elysium health, which is going the "promote it for quick bucks" supplement route for an NAD precursor, not the clinical trials route--at least, there's no mention of trials on Elysium's website.

Indeed, mice are way different. On the other hand, this supplement seems, at least, not too expensive and seems not dangerous, so maybe it won't be too hard to get some reasonable data in testing.