The Biochemist's Stone: NAD+

Posted by Nicholas A. Nelson on March 5, 2020 in Uncategorized | Leave a comment

NAD+ (pronounced “N-A-D Plus”) is one of the most fundamental, crucial molecules in metabolism throughout all life on Earth. Life without NAD+ is hard to imagine: it holds irreplaceable roles in nearly every cellular process, from handling oxidative stress, DNA repair, and protein folding through to the generation of cellular energy (ATP). How does one molecule have a hand in so many functions? And why have most of us never heard of it?

NAD+ — A Humble Hand in Everything

NAD+ is the common abbreviation of nicotinamide adenine dinucleotide – a relatively small molecule built by linking nicotinamides (processed vitamin B3) and adenine (the “A” in DNA’s A’s, T’s, C’s, and Gs). The “+” denotation comes from its positive electrical charge: at the molecular level, it is an electron short of happy, and will gladly take an electron from a willing donor (of which there are many). Normally this turns NAD+ into its molecular sibling, NADH, which is identical in structure except for the addition of two electrons and hydrogen (H). NADH will readily donate its hydrogen (and two electrons) to a willing recipient to convert itself back to NAD+, and does so regularly.

Note: NAD+ and NADH are so intricately tied together, they are often referred to by others and within this article as NAD+/NADH in tandem, or simply as just NAD+.

At the molecular level, both of these events are forms of moving energy from one molecule to another, allowing latent molecules to become active or active molecules to calm down. Molecules in the cell work by changing their shapes to fill different functions, and changing the energy state of a molecule by, say, the loss or gain of an electron, can cause dramatic changes in how a protein likes to fold. So NAD+/NADH may have seemingly humble-sounding roles: the donation or reception of electrons. But the movement of electrons changes how much energy a molecule has, and how much energy a molecule has changes its shape, and what shape a molecule has changes its function. 

This form of moving energy, exchanging electrons to change molecular shape and function, regulates the activity of thousands of proteins in the cell. Each protein has a unique shape, with different targets and different actions, but many need a “cofactor” to act. NAD+ fills this role, for numerous proteins in every cell and species on Earth.

It is thus through an absolutely fundamental role in the molecular machinery of life that NAD+ can play a role in countless processes within the cell. And perhaps it is the tendency for people’s eyes to roll into the back of their head when confronted with upper-division biochemistry, which you may have just experienced in the preceding paragraphs, that explains why nobody really talks about NAD+. Regardless, I hope we’re better off for having read the above, and ready to move on to ask:

What happens when we don’t have enough NAD+?

A lot can go wrong in the absence of NAD+. Vitamin B3 is a precursor to NAD+ synthesis, which most of us get through our diet. Otherwise, the disease pellagra develops, characterized by tearing skin, sensitivity to sunlight, mental confusion, aggression, and eventual dementia, colitis, or diarrhea. It is as if the entire body starts shutting down – failing to perform even its most basic functions, not making enough energy, accumulating stressors and mutations, and dying.

It might be said that every disease has some aspect of the above: basically, a failure to perform critical functions gets worse over time, eventually leading to pathology and potentially progressing to death. Pellagra develops because not enough Vitamin B3 is consumed, so not enough NAD+ can be synthesized. Is it possible then that a “side effect” of every disease could include some dysregulation of NAD+?

It turns out the answer to this question is, to some extent, yes: almost all diseases show some form of abnormal NAD+ levels. At first this may seem perplexing – it seems impossible for most of biology that one molecule could always show up, given the wide range of different ailments we see, each with different causes and prognoses. But upon further reflection, many scientists have landed near the opposite conclusion: of course nearly every disease involves abnormal NAD+. If nearly every cell process involves NAD+ at some basic level, then maybe every disease could impact NAD+’s ability to function, regardless of its primary cause.

So it seems some effects associated with insufficient NAD+ are present in nearly every disease, and it stands to reason (and research!) that NAD+ function could be perturbed in every disease. Could every disease then have some side effects alleviated by restoring NAD+ levels?  

What happens when we supplement lab animals’ NAD+ supply?

The last decade has been a renaissance of NAD+ supplementation research, many of which try to address the questions posed above in rodents. The findings have been interesting and, uncharacteristically for pharmaceutical research, nearly universally positive. 

Supplemented with NAD+ precursors, if you’re a healthy mouse, you live 30% longer. You’re a mouse injected with cancer? That cancer takes longer to grow. High-fat diets induce less weight gain. Painful loud noise causes less hearing loss. Kidney, heart, muscle, and pancreas function improve. Dozens of markers of well-being, in healthy and experimental mice, benefit from NAD+ supplementation^[1]. 

Nervous system function has of course been an area of particular interest. And following brain or spinal cord injuries, fewer neurons die when supplemented with some form of B3 vitamins. In other experiments, neuropathic pain is reduced. Models of Alzheimer’s and Parkinson’s disease are slower to develop, or even partially reversed, as are ALS and glaucoma^[1]. NAD+ supplements may not be a total panacea but (not for the first time in science research) we seem to be part-way there.

Still, unfortunately, in all of these cases you’re still a mouse. And history has shown us, findings in mice do not always pan out the same for humans trying to reap the potential benefits of cutting-edge research. Let us ask then:

What do we know about human NAD+ supplementation?

This is the part of the article where I tell you not all studies in humans are as promising as those in mice. For NAD+ supplements, most studies on humans actually show slim to no effect. One potential explanation given being that because they are conducted over relatively short durations for a human life, on the order of 4-12 weeks, the benefits from NAD+ supplementation simply did not have time to take hold. 

What is touted as a partial-success, though, is that many studies show humans can at least tolerate NAD+ supplements well – that is, while the studies show few-to-no positive effects, they also show no more side effects than treatment with placebo, even at higher doses. Maybe it will take more than a few weeks of NAD+ supplements to be beneficial for human health, it seems hopeful the side effects could still be minimal.

While the studies in humans have not shown huge changes in disease state, traditional markers used in mouse studies are showing up positive. In two studies, supplementation has shown a 40% or greater increase in NAD+ in the blood after 8 weeks^[4][5]. But similar increase in blood circulating NAD+ did not correlate as predicted with improved markers of metabolism in obese patients, even after 12 weeks of NAD+ supplementation^[6]. Another study in 70-80 year old patients^[7] did find that muscle metabolism, which declines with age, increased to more youthful levels with NAD+ supplementation, and that the cytokines (main components of immune system activation) circulating in the blood decreased. And these two markers have been associated with better outcomes in mouse healthspan through stronger muscles later in life^[8] and longer lifespan by calming down the hectic, “exhausted” immune system typical of old age.

These are not the only studies conducted in humans, but are a pretty representative sample of what is seen in the couple dozen that are available.

Trials in human patients are thus limited in effect, but suggest we may recapture at least some of the myriad of benefits NAD+ supplements have bestowed upon mice. Research into NAD+ supplementation in humans is still in its infancy, and the next few years promise to really break open the field and set the bar for what we can and cannot expect from NAD+ supplements.

Supplements, You and Me, and the United States

In the USA, supplements are a largely unregulated industry. There is no board overseeing supplement quality control, the FDA does not have to approve claims made by manufacturers, and there is a ton of money to be made. 

When there is no regulation and huge potential benefits to, say, cutting supplements with fillers instead of active ingredients, making pills look larger or even lying outright about the ingredients, there is reason to distrust the content and claims made by supplement vendors. Third party laboratories offer services to test supplement purity, and thus validate at least the contents of what is sold by vendors willing to pay for it. But many supplements don’t have controlled scientific studies backing their effects, and indeed are not even required to.

In the case of NAD+ supplements there is at least some excellent research, the data for which is growing by the week and trying to get an honest, objective look at effects in laboratory animals and humans. Unlike many supplements available on the market, some academic scientists even own patents and companies associated with NAD+ supplementation^[9]. This may be a good thing and a bad thing – good that scientists are personally invested in NAD+ supplements and actively pushing for research. But this can arouse suspicion, as it increases the monetary motivation specific researchers may have to “prove” positive effects of the supplements they want to sell.

The research is still growing, but certainly promising. I am not a medical doctor, and I can’t give advice to the Internet community to take or not take any one pill or another. But I am more interested in NAD+ supplements than I have been in any other. Of course, as friend and fellow Neuwriter Drew Schreiner remarked to me – we tend to find a new way to “cure cancer” in mice almost monthly. Maybe we’ll soon find we’ve improved “all” diseases, or “cured aging” in mice with NAD+, but have little to show for human health. For now, however, I am cautiously enthralled; even with all the caveats I’ve given above, the future of NAD+ looks as exciting to me as it is intriguing.

References

1. Katsyuba E, Romani M, Hofer D, Auwerx J. NAD+ homeostasis in health and disease. Nat Metab. 2020;2(1):9-31. doi:10.1038/s42255-019-0161-5He Mickey! by ismaelalvarez on DeviantArt. https://www.deviantart.com/ismaelalvarez/art/He-Mickey–572368559. Accessed March 4, 2020.
   
2. Mickey Mouse Job Redux – Teaessare Illustration Design – Clip Art Library. http://clipart-library.com/clipart/8cAaMdkca.htm. Accessed March 4, 2020.
   
3. ismaelalvarez on DeviantArt. He Mickey! https://www.deviantart.com/ismaelalvarez/art/He-Mickey–572368559
   
4. Dellinger RW, Santos SR, Morris M, et al. ARTICLE Repeat dose NRPT (nicotinamide riboside and pterostilbene) increases NAD + levels in humans safely and sustainably: a randomized, double-blind, placebo-controlled study. doi:10.1038/s41514-017-0016-9
   
5. Conze D, Brenner C, Kruger CL. safety and Metabolism of Long-term Administration of NIAGeN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, placebo-controlled Clinical trial of Healthy overweight Adults. doi:10.1038/s41598-019-46120-z
   
6. Dollerup OL, Christensen B, Svart M, et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. 2018. doi:10.1093/ajcn/nqy132
   
7. Elhassan YS, Kluckova K, Fletcher RS, Brenner C, Philp A, Lavery Correspondence GG. Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD + Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures. Cell Rep. 2019;28. doi:10.1016/j.celrep.2019.07.043
   
8. Frederick DW, Loro E, Liu L, et al. Loss of NAD Homeostasis Leads to Progressive and Reversible Degeneration of Skeletal Muscle. Cell Metab. 2016;24(2):269-282. doi:10.1016/j.cmet.2016.07.005
   
9. Bomgardner, Melody M. Firms feud over purported age-fighting molecule. https://cen.acs.org/business/consumer-products/Firms-feud-over-Niagen-purported/96/i33. Accessed March 5, 2020.
   
10. Bogan KL, Brenner C. Nicotinic Acid, Nicotinamide, and Nicotinamide Riboside: A Molecular Evaluation of NAD + Precursor Vitamins in Human Nutrition. doi:10.1146/annurev.nutr.28.061807.155443
    
11. Yang N-C, Cho Y-H, Lee I. The Lifespan Extension Ability of Nicotinic Acid Depends on Whether the Intracellular NAD + Level Is Lower than the Sirtuin-Saturating Concentrations. Int J Mol Sci Artic. doi:10.3390/ijms21010142
    
12. Rajman L, Chwalek K, Sinclair DA. Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence. Cell Metab. 2018;27(3):529-547. doi:10.1016/j.cmet.2018.02.011
    
13. FightAging Reason. Poor Results from an Initial Human Trial of Nicotinamide Mononucleotide – Fight Aging! https://www.fightaging.org/archives/2019/11/poor-results-from-an-initial-human-trial-of-nicotinamide-mononucleotide/. Accessed February 21, 2020.
    
14. Study explores emerging role of NAD+ in innate and adaptive immune responses | EurekAlert! Science News. https://www.eurekalert.org/pub_releases/2018-02/bawh-see022318.php. Accessed February 21, 2020.
    
15. Massudi H, Grant R, Guillemin GJ, Braidy N. NAD + metabolism and oxidative stress: the golden nucleotide on a crown of thorns. Redox Rep. 2012;17(1):28-46. doi:10.1179/1351000212Y.0000000001