NAD+ Reversing Aging? Overview of NR and NMN

NAD+ article including human studies on NR and NMN

Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are two supplements that have taken the longevity and anti-aging world by storm. With animal studies showing exciting results including reversal of age-related diseases, these supplements are an exciting glimpse into the future of reversing aging.

Just a heads up, so you aren’t disappointed:  There is little research, as of yet, into the ways that genetic differences impact NR or NMN. Instead, I will dig into the science of how NR and NMN work, the research that has been done on NR and NMN, and then explain the connections with sirtuins, PARPs, and aging. I will also dig into genetic variants that impact the body’s production of NAD+ and the relation to sirtuin gene variants. But… I can’t tell you, based on your genes, whether you should take NR or NMN :-)

What is NAD+

NAD+ (nicotinamide adenine dinucleotide) is an important molecule that all plants and animals produce and use. It is a niacin derivative used in all living cells for a bunch of different purposes.  It is one of those ‘can’t live without’ type of molecules!

NAD+ is important in a number of cellular processes

NAD+ in cellular energy production:

A quick overview of cellular energy production for those for whom high school biology is but a distant memory…

In cellular metabolism, NAD+ is an essential part of energy production. When you eat food, your body converts it into the components needed by the cells for producing energy. For example, carbohydrates break down into their simple components such as glucose. The glucose can then be directly used in the cells to produce ATP, which is the molecule your body uses for energy.

During cellular energy production, glycolysis uses glucose to produce a little ATP (net of 2 molecules) and acetyl-CoA. Then, the acetyl-CoA can be used in the mitochondria to produce more ATP via the citric acid cycle (aka Krebs cycle). Additionally, your body can convert fatty acids into acetyl-CoA when it is in ketosis.

NAD+ comes into play within the citric acid cycle, shuttling electrons between the NAD+ and NADH. The net result from the citric acid cycle is three NADH molecules (and one ATP).

Next up in energy production within the mitochondria is oxidative phosphorylation (electron transport chain). Within the inner membrane of the mitochondria, oxidative phosphorylation takes those intermediates of the citric acid cycle and cranks out a bunch of ATP (energy molecule). This is your body’s main way of producing energy when there is enough oxygen present.  In fact, it is the main way that all aerobic organisms with mitochondria produce energy.

An essential step in this process uses NAD+ for the transfer of electrons.

Electron transport chain showing the process of producing energy in a cell. Image credit: public domain

Other roles of NAD+

While the use of NAD+ for cellular energy production is fundamental to life as we know it, this molecule is also used in numerous other reactions in the body.

ADP-ribose transfer reactions consume NAD+. Examples of this include processes such as the repair of DNA and in the maintenance of telomeres, the end caps of DNA that are important in cellular aging.

Reactions involving sirtuins also use NAD+. Sirtuins are a family of proteins (SIRT1 through SIRT7) that are essential for turning on and off the translation of genes within a cell. This is foundational for the control of cellular functions. (More on sirtuins to come…)

Additionally, NAD+ is involved in cell signaling processes both within and outside of cells.

Yep – I’ve used the words essential, foundational, and fundamental here, but these seem like a weak way to explain the necessity of NAD+ in your body.

Let me dive into all of these a bit further…

NAD+ and Aging:

As we age, there are a number of physiological changes that take place. You all know this — you lose your hearing and your hair, muscle mass declines, wrinkles increase, weight tends to rise, along with blood glucose levels. Eventually, you end up with heart problems or diabetes, and then everything goes downhill from there.

NAD+ levels decrease with aging and could be at the heart of some of the age-related declines we face. For example, NAD+ is important in DNA repair, and this process is so important for preventing cellular death – or cancer.[ref] Mitochondrial energy production decreasing as we age is another big part of why everything goes downhill.

Sirtuins and Aging:

I mentioned above that sirtuins rely on NAD+, and that this is important in gene expression. Let me explain this further…

Sirtuins, SIRT1 through SIRT7, are a family of genes. Their functions haven’t been fully understood yet.

The regulation of gene expression involves sirtuins. Meaning, the sirtuins must cause the DNA in the cell nucleus to either be accessible or inaccessible for a gene to be transcribed. The ability for the regulation of genes transcribed into proteins is fundamental to cell function. Every cell nucleus contains the same DNA. The differences between a liver cell and a muscle cell are due to the regulation of which genes are transcribed. Thus, disrupting the sirtuins can lead to mucked up cell function and the symptoms of aging.

In the initial studies on the sirtuin genes in yeast, it was found adding in additional copies of the gene increased lifespan by 30%. [ref] Think about what that could mean for humans — regularly living to 110 instead of 80? In the genetics section below, I’ve listed a couple of the sirtuin genetic variants with links to an increased human lifespan.

SIRT1 codes for the sirtuin 1 protein. It involves sensing nutrient availability and thus linked to problems with insulin resistance. Studies show animals with insulin resistance have decreased SIRT1 levels. When researchers increase SIRT1 in animals, they are resistant to the problems of obesity and insulin resistance that a high-fat diet induces in them. [ref][ref]  Researchers recently discovered that SIRT1 is also important in the development of the egg cell. [ref]

SIRT2 codes for the sirtuin 2 protein that is located in the cytosol of the cell. This important enzyme arranges the chromosomes for cell division in mitosis.

Sirtuins use NAD+ to complete their cellular activity, and through that, the NAD+  levels may be a sensor for how much energy is available in an organism. [ref]

SIRT3, 4, and 5, found in the mitochondria, are important for oxidative stress and fat metabolism. [ref]

SIRT6 is important in the gene expression for metabolic regulation, telomere maintenance, and mitochondrial respiration. Reducing Sirt6 in the liver causes animals to develop fatty liver disease, and knocking out Sirt6 all together causes animals to die within a few weeks due to severely accelerated aging.[ref]

PARPs and NAD+

Another group of enzymes that consume NAD+ in their reactions is PARPs, which stands for poly(ADP-ribose) polymerase. PARPs are another family of proteins that are important in DNA repair and genomic stability. They detect broken DNA and signal for it to be repaired. Also, when the DNA isn’t repaired cell death is initiated. Again – vital cellular functions, especially in aging. [ref]

PPAR1 uses up a lot of NAD+ in the process, causing a decrease in ATP production for the cell. When a cell hasn’t replicated the DNA properly, the DNA damage signaling response is enacted. [ref]  Cell death is necessary, in the right context, but excessive cell death, especially in the brain, is not good.

Excessive DNA breakage can lead to a lot of PARP activation, thus depleting NAD+. What causes DNA breakage? UV light, reactive oxygen species (oxidative stress), lipid peroxidation, and a number of different environmental toxicants. DNA damage occurs all the time in the normal course of cell replication. Thus the importance of DNA damage repair systems in the body.

PARP1 can initiate cellular repair for single-strand DNA breaks. This is important in longevity.

Inhibiting PARP is a way to mitigate the decreased NAD+ and ATP levels and decrease cell death. It doesn’t fix the cause (DNA breakage), but it puts a bandaid on the downstream effects of PARP activation. Atherosclerosis and congestive heart failure are two diseases in which PARP inhibitors might be used. The inflammation within the vascular cells causes PARP1 activation and the subsequent decrease in NAD+ and cellular energy. Inhibiting PARP then slows the inflammatory response and preserves the ATP and NAD+ in the cells of the heart. [ref]

The flip side of inhibiting PARP would be to have plenty of NAD+ available for the rest of the heart cells. Animal studies using a mouse model of sepsis show that, indeed, giving nicotinamide riboside, which increases NAD+, protected the heart and lungs from injury and decreased death due to sepsis. [ref]

Creating NAD+ in the body:

Precursors of NAD+ include different forms of niacin (vitamin B3) and tryptophan. The different forms of niacin, whether from food or from supplements, are nicotinamide (aka niacinamide) and nicotinic acid (niacin). The nicotinic acid form (niacin) is the one that can cause flushing when taken in larger doses.

Foods that are high in niacin include tuna, chicken, beef liver, salmon, and pork. Non-meat sources of niacin include brown rice, peanuts, and potatoes.  What doesn’t have niacin? Corn that hasn’t been nixtamalized (processed with lime water). A lack of niacin causes a disease state known as pellagra. Thus, in the late 1800s and early 1900s when people in the US South were dependent on corn for most of their calories, there was an epidemic of pellagra. Symptoms of pellagra include dementia, diarrhea, and a skin rash.

Tryptophan, found in a lot of protein-containing foods, is an essential amino acid. Your body can also convert tryptophan into niacin through the kynurenine pathway. However, this pathway to form niacin isn’t utilized by the body as much as obtaining niacin from foods that contain it.

Another way to create more NAD+ is by converting nicotinic acid. The first step converting nicotinic acid to NA mononucleotide uses the NAPRT enzyme coded for by the NAPRT gene. [ref][ref]

creating NAD+ from NMN and NR and tryptophan

NR and NMN:

Both nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are important in the creation and recycling of NAD+.

NMN, synthesized from nicotinamide (niacinamide) and PRPP (5’-phosphoribosyl-pyrophosphate), uses the enzyme NAMPT. [ref]  (More on NAMPT in the Genetic Variants section below.)

NR is another precursor of NAD+. It can be found at low levels in foods, particularly in milk.

NAD+ doesn’t have to be synthesized continually from the precursors — it can be recycled through the “NAD Salvage Pathways”. Reusing the components of NAD+, specifically, nicotinamide is your body’s main way of having enough NAD+ available in all cells. This salvage pathway uses the supplemental NR and NMN in the body.

 


Studies on NR and NMN:

Enough background science – let’s get into the interesting research on supplemental nicotinamide riboside and nicotinamide mononucleotide.

Animal studies on NR and NMN:

Here are some of the animal studies on NAD+ precursors that are exciting:

Alzheimer’s: In a mouse model of Alzheimer’s disease, NMN shows the restoration of mitochondrial function in the brain. The oxygen consumption deficits in the brain mitochondria, found in Alzheimer’s, showed a reversal. Again, this is a mouse study… but pretty cool. [ref]

Fertility: There have been several studies showing that NMN or NAD+ precursors restore fertility at the end of an animal’s normal reproductive age. It seems to do this through rejuvenating egg quality.[ref][ref]

Hemorrhagic shock: In a rodent model of hemorrhagic shock, those receiving NMN had less inflammation and better cellular metabolism. Both of which increase survival in hemorrhagic shock.[ref]

Aging: Nicotinamide riboside (NR) was fed to old mice for three months. The NR decreased several of the signs of aging in the mice such as altered fat mass, cholesterol levels, and liver enzymes. [ref]

Fatty Liver Disease: Quite a few studies show that NR can reverse fatty liver disease. [ref][ref][ref]

Cognitive Function: Another mouse study showed that NR could improve cognitive function in a mouse model of diabetes. Not only was cognitive function improved, but inflammatory markers in the brain were reduced, as was amyloid-beta. [ref]

Hearing Loss: NR was shown to protect mice from age-related noise-induced hearing loss. This was through increasing SIRT3 expression. [ref]

Offspring: For postpartum mouse moms, NR was beneficial. It increased lactation, nursing behavior, and transmission of micronutrients to the mouse babies. Those offspring grew up to have advantages “in physical performance, anti-anxiety, spatial memory, delayed onset of behavioral immobility, and promotion of adult hippocampal neurogenesis”. [ref]

Mitochondrial Function: A mouse study also found that NMN could dampen the DNA damage response and improve mitochondrial function. It also helped with liver damage. [ref]

Increased Lifespan: A small increase in lifespan (about 4%) has been shown in mice that were fed NR starting in old age. [ref]

Restored SIRT1 Levels: Middle-aged mice fed NMN showed increased Sirt1 levels, similar to younger mice. [ref]

Human studies on NR and NMN:

Safety first: A study looked at the safety of NR (Niagen brand) in healthy men and women over a course of 8 weeks. They used doses ranging from 100 to 1000 mg. All doses increase NAD+ metabolites within 2 weeks, and it was dose-dependent (high doses= high NAD+). Most importantly, there were no differences in adverse events between the NR groups and the placebo group.  This study also noted that the NR did not mess up methylation. [ref]

Another trial of 2,000 mg/day of NR in obese, sedentary men aged 40 – 70 was found to be safe (12-week study). But it didn’t show any miraculous effects on insulin sensitivity, glucose disposal, or resting energy expenditure. [ref] In other words, the fabulous metabolic results seen in mice didn’t happen in obese, older men. Or at least the markers that they were looking at (HbA1C, glucose, cholesterol, triglycerides) didn’t change much.

Boosting NAD+: A short, small study examined the effects of NR on healthy volunteers for 9 days. The study participants took 250 mg for the first two days and then titrated up to 1000 mg. On day 9, NAD+ levels had increased by 100%. No side effects were reported for the NR supplement. Interestingly, most of the individual response curves were similar in the percentage increase, but there were a couple of participants that had a much bigger response. [ref – open access]

Decreased Inflammation: A study of ‘aged men’ looked at the effects of supplementing with 1,000 mg of NR per day for 3 weeks. The results showed an elevation of NAD+  in the muscles and a decrease in inflammatory cytokines levels. [ref]

Heart health: A study that included 30 middle-aged and older men and women looked at the effect of NR vs placebo for six weeks. Oral NR supplementation (1,000mg/day ) raised NAD+ levels by 60% compared to placebo. NR lowered blood pressure and aortic stiffness (a little). Notably, the participants who had stage one hypertension, to begin with, had a 10 point drop in systolic blood pressure. One drawback, in my mind, for this study, is that it had participants take the placebo or NR for six weeks – and then swap for the next six weeks. Then the comparison of the data was done for the placebo vs. NR. It seems like there should have been lasting benefits from the group initially taking NR and then switching to the placebo group, thus masking some of the statistical differences. [ref]

Human studies are nice, but more studies are needed on larger groups for longer time periods. Several clinical trials are in the works right now, so hopefully, we will have more answers soon!

Niacin/NR/NMN from food:

Some studies indicate that 20mg of niacin can meet our need for NAD+ biosynthesis. The US government’s daily requirement for niacin is 12 mg, which seems to be the amount needed to prevent pellagra, and it sets the RDA at 16mg/day. [ref]

Broccoli and cabbage contain up to around 1mg/ 100 gm of NMN. Avocados and tomatoes have also shown to contain NMN in the .36 to 1.6 mg/100 grams range. So, while food can be a minor source of NMN, it is mainly synthesized in the body.

Tryptophan can also eventually end up as NAD+. But, it takes 60-times the amount of tryptophan compared to niacin to get to nicotinic acid mononucleotide (NAMN). Tryptophan can help to prevent pellagra (niacin deficiency), but it isn’t the main source for most people today. [ref]  (Read about tryptophan and the kynurenine pathway genes)

Methylation cycle and nicotinamide:

Not all nicotinamide converts back to NAD+. Some of it can degrade through a methylation-dependent pathway. The NNMT (nicotinamide N-methyltransferase) enzyme is key to the reaction between nicotinamide and SAMe.

A mouse model created with too much of the NNMT enzyme was used to test the link with fatty liver disease. Mice that produce extra NNMT were fed a high-fat diet and nicotinamide. They had accelerated fatty liver disease. [ref]


Circadian Rhythm and NAD+

I’m sure that most of you who have read a few of my articles have noticed that circadian rhythm is a theme that runs throughout genetics and health. There’s no escaping the fact that circadian rhythm controls so much of what goes on in our body.  Kind of like the cycle of sunlight and darkness governs all living organisms….. 

The core molecular circadian clock is driven by the rising and falling levels of four genes: CLOCK and BMAL1 rise and then are suppressed as PER and CRY accumulate. The CLOCK gene expression is controlled by a sirtuin (SIRT1), which, in turn, is dependent on NAD+ levels. [ref]

I know – you all are thinking, “holy crap! mind blown!”  right now. Or you are wondering how deep in the weeds this article will wander:-)

Let me connect a few dots…  NAD+ levels are needed for the sirtuins to work. The sirtuin family of proteins controls whether a portion of the DNA is available to be transcribed – or not. Like a light switch turning on or off.

SIRT1, important for the core circadian clock gene (aptly named CLOCK) to function correctly, rises and falls over the course of 24 hours.

A connection exists between the disruption of the core clock genes and the various chronic disease states associated with aging, such as diabetes, heart disease, obesity, metabolic syndrome, and Alzheimer’s disease.

Thus, one mechanism by which low NAD+ levels impact us as we age is through altered CLOCK gene expression.

SIRT6 has also shown to control the liver’s clock – separately from SIRT1. This leads to the control of lipid metabolism in the liver. [ref]


Genetic variants:

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NRK1 gene:

A mouse study found knocking out the NRK1 gene impairs mitochondrial function. When the NRK1 deficient mice were fed a high-fat diet (equivalent to humans eating fast food/ junk food), the mice developed insulin resistance and fatty liver disease. [ref]

None of the NRK1 variants included in 23andMe have shown to affect the function of that gene.

NAMPT gene:

NAMOT gene codes for an enzyme used in the synthesis of NMN by the body. NAMPT is also called visfatin in studies.

Check your genetic data for rs61330082 (23andMe v5; AncestryDNA):

  • G/G: typical NAMPT production
  • A/G: decreased NAMPT production
  • A/A: decreased NAMPT production [ref]

Members: Your genotype for rs61330082 is .

Check your genetic data for rs9770242 (23andMe v4; AncestryDNA):

  • A/A: most common genotype,
  • A/C: typical
  • C/C: lower risk of heart disease [ref], lower fasting glucose levels and lower fasting plasma insulin levels [ref]

Members: Your genotype for rs9770242 is .

 

SIRTUINS: The sirtuins use up NAD+ in the cells. Genetic variants in this family of genes impact disease risk for a number of diseases associated with aging and low NAD+. The genetic variants listed here are just a few of the SIRT gene variants. They were chosen because they are included in common genetic testing, but they aren’t necessarily the most important SIRT variants.

SIRT1 gene:

Sirtuins linked with longevity, important for the CLOCK gene, requires NAD+

Check your genetic data for rs3758391(23andMe v5; AncestryDNA):

  • C/C: typical
  • C/T: lower cardiovascular disease mortality, better cognitive function in aging
  • T/T: lower cardiovascular disease mortality, better cognitive function in aging [ref], elevated SIRT1 expression [ref]

Members: Your genotype for rs3758391 is .

Check your genetic data for rs12778366 (23andMe v4, v5; AncestryDNA):

  • C/C: reduced risk of diabetes complications [ref] 30% reduced mortality risk in aging population, better glucose tolerance [ref]
  • C/T: reduced risk of diabetes complications, somewhat reduced mortality risk
  • T/T: typical

Members: Your genotype for rs12778366 is .

SIRT3 gene:

Check your genetic data for rs511744 (23andMe v4; AncestryDNA):

  • T/T: increased lifespan (avg. of 1.3 years in this study)[ref]
  • C/T: typical lifespan
  • C/C: typical lifespan

Members: Your genotype for rs511744 is .

SIRT6 gene:

It is important in metabolic regulation, telomere maintenance, and mitochondrial respiration.

Check your genetic data for rs352493 (23andMe v4, v5; AncestryDNA):

  • T/T: typical
  • C/T: risk of increased severity in CAD
  • C/C: increased risk of more severe coronary artery disease [ref]

Members: Your genotype for rs352493 is .


Lifehacks

Supplements to boost NAD+

Nicotinamide riboside (NR) is patented and made by ChromaDex in the US. It is called (Niagen) and sold as TRU Niagen.  Also included in Thorne ReveraCel (coupled with resveratrol and quercetin) and in the Life Extension formula NAD+ Cell Regeneration (which seems to be way overpriced online – check around for better prices!).

NR, also found in the supplement called Basis, is made by Elysium. It now contains a formulation of NR that is proprietary to Basis. Lots of research (and marketing…) has been done by the developer of Basis, so it may be worthwhile to check out. You have to order directly through the company.

NMN is also available as a supplement. There are several options available, including GeneX NMN and Mastermind NMN.

Resveratrol is an activator of SIRT1. [ref] Some people stack resveratrol with NR to boost the effects of SIRT1. Resveratrol is available at any local health food store (or grocery store).

Pterostilbene, a polyphenol found in blueberries and an analog of resveratrol, is an activator of SIRT1.[ref][ref] The nicotinamide riboside supplement BASIS includes pterostilbene. It is also available as a stand-alone supplement or you can eat a lot of delicious blueberries.

Tryptophan is a precursor, albeit a minor one, for the synthesis of NAD+. Even though it is a minor player, it is important to get enough tryptophan in your diet. Most foods that contain protein also contain tryptophan, so people generally get plenty of tryptophan if they eat a varied diet. Foods that contain a lot of tryptophan include cheese, chicken, fish, eggs, beef, pork, beans and lentils.

Don’t want to take supplements?

There may be other ways to reap the NAD+ benefits:

Exercise… It seems that everyone (including me) always recommends exercise for pretty much every health topic.  A recent study showed that one way that exercise is beneficial in aging is that it stops the decline in the enzymes needed for NAD+ production. In older people (age 55+), aerobic exercise increased NAMPT. [ref]

Fasting has shown to increase NAD+ levels. [ref]

Methylation cycle worries?

Some clinicians seem worried about supplemental NR decreasing methyl groups in the body. One small human study did not find an effect on methyl groups [ref], but individual genetic differences may make this an issue for some people. If this is a problem for you, increasing your methyl donors may help.  Choline (from eggs, liver, sunflower lecithin) and folate (from broccoli, legumes, leafy greens) can help increase your supply of methyl groups. Supplements that increase methylation include SAMe, TMG, and methylfolate.


Related Genes and Topics:

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A decades-old diabetes drug now holds promise for increasing healthspan. Research shows that metformin may reduce the risk of some of the diseases of aging, thus increasing the number of years someone is healthy.



Author Information:   Debbie Moon
Debbie Moon is the founder of Genetic Lifehacks. She holds a Master of Science in Biological Sciences from Clemson University. Debbie is a science communicator who is passionate about explaining evidence-based health information. Her goal with Genetic Lifehacks is to bridge the gap between scientific research and the lay person's ability to utilize that information. To contact Debbie, visit the contact page.