Researchers use supplementation with NMN, NR and NAD+ to restore levels of NAD+ in mice, making them look and behave like they did when young and extending their lifespan.

Although they have similar effect in some organs, it seems there are differences in the effect they have in other tissues throughout the body.

We cover some results from research comparing with NMN vs NR here, and debunk some of the claims that Chromadex makes about NR vs NMN here.

NAD+ not effective in drinking water or in capsule form
The NAD+ molecule is twice as large as NR or NMN, and is totally degraded in the Gastro-Intestinal tract, so researchers do not use NAD+ in drinking water of mice and it is not sold in capsule form for humans.

NAD+ in IV or IP injections
Research has been successful using NAD+ injections in mice.

In humans, clinics that provide NAD+ by IV are exploding in popularity, even though they charge over $1,000 a day and require the patient to be hooked up to a drip IV for 8 hours.

NMN and NR poor bioavailability in capsules
NMN and NR capsules are only partially digested in the stomach, but are almost totally metabolized in the liver and excreted as NAM (Liu, 2018).

Sublingual delivery solves the bioavailability problem

Molecules like NMN, NR and NAD+ that have low molecular weight and are hydrophilic can be absorbed through the capillaries under the tongue directly into the bloodstream. This is called Sublingual (under the tongue) delivery.

Sublingual delivery can bypass the stomach and liver.

This solves the bioavailability problem of capsules that get digested in the stomach, so NAD+ can be used instead of NAD+ precursors. It also greatly improves the effectiveness of NMN.

Why no sublingual NR?

NR is not stable by itself (see below) , so Chromadex adds Chloride to make it stable.
ALL NR sold is actually Nicotinamide Riboside CHLORIDE
Unfortunately, the taste is not acceptable for sublingual use.

So NR is only available in capsule form, which much pass through the stomach and liver where it is metabolized to the less effective Nicotinamide (Liu, 2018) .

NAD+ SUPPLEMENTATION

The hypothalamus is the master regulator of energy metabolism which impacts the entire body.NAD+ crosses the blood brain barrier to increase NAD+ in the hypothalamus to increase energy expenditure and decrease hunger. (more below).

Below are some of the disease and illnesses that we believe NAD+ supplementation is more effective for than NMN.
  • Chronic fatigue
  • Weight control
  • Mood disorders
  • Alcohol and drug addiction
Research has also shown NAD+ supplementation to be effective for the following conditions (more here).
  • Protects against liver damage
  • Multiple Sclerosis autoimmune-related neurodegeneration
  • Heart disease
  • Heart damage from stroke
  • Brain damage from injury
Does NAD+ enter cells directly?

 

NAD+ DOES CROSS THE BLOOD BRAIN BARRIER AND ENTERS CELLS INTACT

 

There are claims that both NMN and NAD+ are “TOO LARGE”, and cannot enter cells directly, but must first be broken down to NR.

We recently wrote this article refuting that theory.

On September 1 2018, more proof was published proving that NAD+ crosses the blood brain barrier, enters the hypothalamus INTACT, and raises NAD+ levels.

Even better, just 1 Mg/kg a day decreased hunger, increased energy expenditure and fat burning for up to 24 hours after dosage.

For reference, most research providing mice with NMN or NR in drinking water uses 300 to 400 Mg/kg a day.

This study found both IV and IP injections had similar results. The results with 1-3 Mg/Kg by IP is extremely promising, as we note that sublingual delivery can be even more effective than IP delivery.

Restores NAD+ in brain, Increases Metabolism
<!–– NAD+ REACHES THE BRAIN MORE THAN NMN OR NR ––>

Once in the bloodstream NAD+ was thought to be too large to cross the cell membrane, making it ineffective at restoring the NAD+ contents inside the cells of many tissues. In this article we show that is not true for heart and brain, and perhaps other tissues.

In fact, this research published in March 2018 shows NAD+ is able to cross the blood brain barrier and quickly increases levels of NAD+ in the hypothalamus, while NR and NMN do not.

Administration of 1 mg/kg of NAD+ reduced hunger and weight gain, and increases energy expenditure and fat burning in mice (r).

Elevating NAD+ levels the hypothalamus has great impact throughout the body, as it regulates hunger and energy expenditure.

Restoring NAD+ levels in the hypothalamus to those of a young animal is very likely to have a positive impact on organs and tissues throughout the body.

(more about the importance of hypothalamus as master regulator of metabolism below)

Even more tantalizing are the possible implications for aging itself.
That the hypothalamus as master aging clock, is a credible theory on aging.

Hypothalamus controls energy metabolism <!–– Hypothalamus controls energy metabolism template ––>

Hypothalamic circuits regulating appetite and energy homeostasis:  pathways to obesity

The hypothalamus in particular has emerged as an integrating, superordinate master regulator of whole-body energy homeostasis.

In summary, the hypothalamus plays a key role in the regulation of appetite and food intake both in humans and rodents.

Hypothalamic inflammation impairs the effects of insulin and leptin, contributing not only to hyperphagia and obesity development but also to the associated dysregulation of glucose homeostasis.

Brain regulation of appetite and satiety

Energy homeostasis is controlled mainly by neuronal circuits in the hypothalamus and brainstem.

Brain Regulation of Energy Metabolism (Roh, 2016)

The hypothalamus is the region of the brain that controls food intake and body weight.

Leptin and insulin signal the status of body energy stores to the hypothalamus.

Hypothalamic regulation of energy homeostasis (Sainsbury, 2002)

These peripheral hormones influence their effects on energy homeostasis either by activating or inhibiting the activity of the orexigenic or anorexic peptides within the hypothalamus.

Research and Benefits of NAD+ Supplementation

NMN and NAD+ enter tissues directly

Exogenous nicotinamide adenine dinucleotide regulates energy metabolism via hypothalamic Connexin 43 (Roh, 2018)

In conclusion, our results demonstrate that exogenous NAD is effectively imported into the hypothalamus and increases hypothalamic NAD content. Therefore, NAD supplement can constitute a therapeutic method for metabolic disorders characterized by hypothalamic NAD depletion in humans.

In this study published in September 2018, administration of LABELED NAD+ by IP and IV injection demonstrated that exogenous NAD+ crosses the blood brain barrier to enter the hypothalamus INTACT, reduces hunger and weight gain, and increases energy expenditure and fat burning in mice.

This study also shows that NR and NMN can not utilize the cd43 gap to cross the blood brain barrier!

This might explain why NAD+ clinics have found success treating addictions and other brain imbalances, but NR and NMN have not been used in similar fashion.

Exogenous NAD Blocks Cardiac Hypertrophic Response via Activation of the SIRT3-LKB1-AMP-activated Kinase Pathway (Pillai, 2009)

Bruzzone et al. (21) have shown that connexin 43 (Cx43) channels are permeable to extracellular NAD

Pharmacological effects of exogenous NAD on mitochondrial bioenergetics, DNA repair, and apoptosis.

“Taken together, our findings strengthen the hypothesis that eNAD crosses the plasma membrane intact”

“In the present study we report that exposure to eNAD substantially increases the dinucleotide cellular pool, suggesting plasma membrane permeability”

Nicotinamide adenine dinucleotide is transported into mammalian mitochondria (Baur, 2018)

Here we present evidence that mitochondria directly import NAD

Taken together, our experiments confirm that despite the lack of any recognized transporter, mammalian mitochondria, like their yeast and plant counterparts, are capable of importing NAD

at least two studies have previously reported evidence for uptake of NAD, leading the authors to propose that intact NAD crosses the plasma membrane and subsequently enters the mitochondria directly

This observation suggests that a mitochondrial transporter for NMN may also await discovery

In summary, we show that mammalian mitochondria are capable of directly importing NAD (or NADH). This finding strongly suggests the existence of an undiscovered transporter in mammalian mitochondria

Detection and pharmacological modulation of nicotinamide mononucleotide (NMN) in vitro and in vivo (Fermenting, 2009)

evidence that intracellular NMN contents promptly increase when the nucleotide is added to the culture media indicates that plasma membrane is permeable to this nucleotide

Pharmacological Effects of Exogenous NAD on Mitochondrial Bioenergetics, DNA Repair and Apoptosis

Although the canonical view considers NAD unable to permeates lipid bilayers (Di Lisa and Ziegler, 2001), several studies report evidence for exogenous NAD (eNAD) uptake by different cells “

These findings are at odds with the hypothesis that eNAD increase iNAD contents because of extracellularly-formed NAD precursors

Nicotinamide adenine dinucleotide is transported into mammalian mitochondria

mitochondria do not synthesize NAD at all, but rather take it up intact from the cytosol, which in turn, can take up NAD from the extracellular space 
While mammalian mitochondria are generally considered to be impermeable to pyridine nucleotides (32,33), at least two studies have previously reported evidence for uptake of NAD

leading the authors to propose that intact NAD crosses the plasma membrane and subsequently enters the mitochondria directly

Increases energy and metabolism

Exogenous nicotinamide adenine dinucleotide regulates energy metabolism via hypothalamic Connexin 43

In this study, administration of LABELED NAD+ by IP and IV injection demonstrated that exogenous NAD+ crosses the blood brain barrier to enter the hypothalamus INTACT, reduces hunger and weight gain, and increases energy expenditure and fat burning in mice.

This study shows that NAD+ levels in the blood have a direct effect on the levels of metabolic activity in the body.

They also show that NR and NMN can not utilize the cd43 gap to cross the blood brain barrier.

This might explain why NAD+ clinics have found success treating addictions and other brain imbalances, but NR and NMN have not been used in similar fashion.

In mice, exogenous NAD may be transported to the hypothalamus via Cx43 at the blood-brain barrier [48] thereby increasing hypothalamic NAD content and decreasing food intake and weight gain.

Protects against age-related damage

Increased NAD+ levels protects against mitochondrial and age-related disorders (Srivastava,2016)

Reduced NAD+/NADH ratio is strongly implicated in mitochondrial disorders and, age-related disorders including diabetes, obesity, neurodegeneration and cancer [26, 53, 60, 71].

NAD+ levels also decline during aging in multiple models including worms, rodents and human tissue [17, 45, 67, 72].

Increasing evidence suggests that boosting NAD+ levels could be clinically beneficial, as it activates the NAD+/sirtuin pathway which yields beneficial effects on multiple metabolic pathways

Protects against  liver damage

NAD+ administration decreases doxorubicin-induced liver damage of mice by enhancing antioxidation capacity and decreasing DNA damage.

NAD+ at the doses of 100 or 200 mg/kg was also injected intraperitoneally 1 h before the DOX administration.

NAD(+) is capable of increasing the antioxidation capacity of tissues.

NAD(+) can significantly decrease DOX-induced liver damage

can also selectively decrease tumor cell survival, NAD(+)

 

Multiple Sclerosis autoimmune neurodegeneration

Treatment with NAD(+) inhibited experimental autoimmune encephalomyelitis by activating AMPK/SIRT1 signaling pathway and modulating Th1/Th17 immune responses in mice (Wang, 2016)

NAD(+) could be an effective and promising agent to treat multiple sclerosis

Prevents heart disease

Exogenous NAD Blocks Cardiac Hypertrophic Response via Activation of the SIRT3-LKB1-AMP-activated Kinase Pathway (Pillai, 2009)

Mice were simultaneously treated with NAD at 1 mg/kg/day for 2 weeks 

NAD treatment was capable of maintaining cellular NAD levels 

Exogenous supplementation of NAD restores the intracellular levels of NAD and blocks the cardiac hypertrophic response. 

These results indicated that NAD treatment prevented the development of cardiomyocyte hypertrophy 

NAD treatment restored the cellular NAD levels 

NAD treatment may become a panacea for prevention and cure of many diseases in the future

 

Prevents heart damage from Stroke

Exogenous NAD+ administration significantly protects against myocardial ischemia/reperfusion injury in rat model (Zhang, 2016)

NAD+ produced 85% decrease in the infarct size

NAD+ is one of the drugs that have greatest capacity to decrease myocardial ischemia

NAD+ dose dependently decreased infarct formation

 

Decreased brain damage

Intranasal administration with NAD+ profoundly decreases brain injury in a rat model of transient focal ischemia (Ying,2007)

The profound protective effects of the intranasal NAD+ administration were also observed at 72 hrs after ischemia.

intranasal administration with 10 mg / kg NAD+, but not with 5 mg / kg NAD+, significantly attenuated the ischemia / reperfusion-produced neurological deficits

NAD+ administration can profoundly decrease brain damage under certain pathological conditions

 

Not limited by homeostasis

Supplying NAD+ direct to the bloodstream bypasses the liver, temporarily enabling a greater increase in NAD+ levels.

Any NAD+ (or NMN) in the bloodstream will get filtered out by the liver in 30-60 minutes.

So after an initial spike in NAD+, the same limits imposed by homeostasis in the liver will likely take effect.

This is why NAD+ clinics use slow IV drips to constantly supply NAD+ to the bloodstream rather than a single large daily injection of NAD+.

Frequent dosages throughout the day of our NAD+ sublingual tablets provide a steady supply of NAD+ direct to the bloodstream, avoiding the limits imposed by homeostasis in the liver.

What about NAD+ Injections?

NAD+ IV clinics have been treating patients for decades.

IV Injections avoid the digestion problem that limits the effectiveness of NAD+ Booster capsules.

They have found that an IV drip which provides a slow, constant supply of NAD+ directly to the bloodstream over a long period of time is the most effective delivery method.

Treatment plans are often 8-14 days, cost $1,000-$1,300 a day, and require the patient to sit for 8 hours or more hooked up to an IV drip.

In the last ten years, NAD+ has been more widely used to help detoxify from other types of chemical dependencies, including benzodiazepines, methadone, suboxone, methamphetamines and stimulants.

NAD+ Clinics

Below are some of the most well known clinics:

springfieldwellnesscenter.com

BR+ NAD Minimizes the Cravings and Withdrawal Symptoms of Addiction Detox through Brain Restoration

Our proprietary BR+ NAD IV treatment restores brain function while minimizing withdrawal symptoms and reducing or eliminating cravings. It further enhances brain function by improving clarity, well-being, and impulse control: your life is your own again.

Improves Brain Function

We are the leading provider of this breakthrough treatment in the US. We provide treatment for a growing list of conditions, beginning with addiction recovery and extending to Parkinson’s, Alzheimer’s & other degenerative diseases.

nadtreatmentcenter.com

NAD Treatment Center™ is a provider of Brain Restoration Therapy, using intravenous NAD+. The therapy assists in alleviating brain-destroying diseases of alcoholism, addiction, chronic stress, depression and anxiety. Combining innovation and compassion, our medical team provides healing and hope for people who are affected by substance abuse and addiction. NAD+ supports the detoxification process and brain function to help your ongoing treatment and aftercare

ANTI-AGING
Researchers investigating brain health and longevity have found NAD+ is an essential coenzyme that promotes cellular regeneration. Studies have found replenishing cellular levels of NAD+ can repair DNA, protect brain cells from damage, reduce inflammation and turn on enzymes that help prevent aging.

ADDICTION
Intravenous NAD+ has been used since the 1960s to help individuals detoxify from alcohol and opioid dependencies. In the last ten years, NAD+ has been more widely used to help detoxify from other types of chemical dependencies, including benzodiazepines, methadone, suboxone, methamphetamines and stimulants.

CHRONIC CONDITIONS
Many chronic conditions, including chronic fatigue syndrome, neurodegenerative disease and mental health disorders have been linked to cellular dysfunction and dysregulation. NAD+ therapy may help reduce the symptoms of many chronic conditions, and may help individuals suffering from chronic conditions regain their vitality and strength.

ivforlife.com


What if there was a compound that could turn back time, restore energy, improve athletic performance, bring back clarity of thought, reverse depression and help cure cravings for alcohol and drugs even in the most addicted individuals?

There is such a substance. It is called NAD+, and it occurs naturally in every cell in your body.

Compelling research has shown that supplementing with NAD+ may help you withdraw from addictive substances safely, overcome anxiety and depression, handle acute and chronic stress more effectively, and cope better with PTSD.

In fact, clinics across the US are starting to use IV infusions of NAD+ to help people withdraw from drug and alcohol addiction with minimal symptoms in as little as 7-14 days of treatment. These individuals report feeling calm and content and say they lost their “cravings” after a full course of treatment.

And NAD+ may actually prolong life, protect DNA, slow down aging and help restore function in neurodegenerative illness due to its effects on the genes that govern aging.

kenstarrmd.com

Dr. Starr prescribes Nicotinamide Adenine Dinucleotide (NAD+) for intravenous administration under the supervision of our trained registered nurses. NAD+ treatments are performed in our outpatient infusion rooms. While each infusion session typically takes a full 6-8 hours, the duration of NAD+ treatment typically requires 10 (or more) sessions to ensure complete results. For treatment for a non-addiction disorder, such as stress or anxiety, your treatment course may be shorter, and is ultimately determined during your medical assessment with Dr. Starr.

NAD+ Therapy involves a high dose intravenous infusion of NAD+ that goes straight into the bloodstream. IV therapy allows NAD+ to bypass the digestive system for better absorption. NAD+ works rapidly to repair cells throughout the body and neurons in the brain. When your NAD+ levels are increased, your cells produce more energy, your good genes are “turned on”, DNA is repaired, and many other functions are optimized. Since NAD+ is such a powerful and prolific molecule in the body, high dose IV therapy can be helpful for many different conditions.

CONDITIONS SUCCESSFULLY TREATED WITH NAD OR BRAIN RESTORATION THERAPY BR+

Reflex Sympathetic Dystrophy
Parkinson’s Disease
Dementia
Chronic Migraine Headaches
PTSD
Interstitial Cystitis
Depression / Anxiety
Opiate Dependence
Alcohol Dependence
Stimulant Dependence

theholisticsanctuary.com

NAD is short for Nicotinamide Adenine Dinucleotide. NAD is a coenzyme of Niacin, which is vitamin B3. Niacin produces energy in the body which is needed for its proper function and well-being. However, people that are involved in drug and alcohol abuse are deficient in NAD making it hard for them to get over their addictions. It is no wonder high-end drug rehabs used it to detox heavily addicted patients from tranquilizers, alcohol and stimulants among others.

NAD IV Drips Brain Restoration Therapy

A majority of people that are addicted to alcohol and other harmful drugs usually suffer from a severe form of neurotransmitter imbalance. This imbalance results in them experiencing insomnia, depression and anxiety among others. Apart from this imbalance, their bodies also absorb nutrients poorly leading to other mineral imbalances and their capability in forming neurotransmitters is also negatively affected. However, when amino acids are introduced into the body along other vitamins and coenzymes the proper levels are re-established and neurotransmitters begin to be properly circulated in the body, thus eliminating or at least reducing the withdrawal effects a drug addict would have otherwise experienced.

NAD IV Drips Brain Restoration Therapy is based on the supplementing of amino acids in the body so that it can be able to produce its own neurotransmitters and utilize them properly as well. When the production and utilization are done well through exercise and proper nutrition, the drug addict begins to get closer to being completely cured other than the suppression of symptoms as other conventional therapies have been known to do.

In general, the use of NAD amino acid IV drips to repair the brain of drug addicts has been quite successful. For those considering signing up for the treatment in any of the drug rehab centers run by professionals, it is important to note that:

The treatment only works when followed as described by a health worker at an accredited facility. Also, the length of treatment varies from one person to another thus making it important to exercise patient while seeking this kind of treatment for addiction. For example, alcohol addiction can be overcome much faster when compared to other hard drugs. Patients interested in NAD amino acid IV Drips should expect to be discouraged by medical experts on the use of this addiction treatment but with the proper administration, the results are likely to be successful. Finally, NAD IV Drips for Addiction Treatment can be a bit costly but the benefits are worth it in the long run.

addictioncenter.com

How is NAD Therapy Used?

NAD Therapy Requires The Use Of An IV DripIn NAD Therapy, the co-enzyme is placed in an IV and slowly dripped into the blood stream. This allows the substance to bypass the stomach (where analgesic medication breaks down) and travel directly to the brain. This provides the individual with a boost of energy, providing enhanced mood and awareness, as the energy they get is now from their natural sources, not other substances. It has also been claimed to slow the aging process. These benefits have opened the door for clinics to use it as a luxury, like a spa treatment.

Advertising it as an all-natural, mood-elevating, no-crash, anti-aging energy booster, clinics are selling to people who have not suffered an addiction of any kind. It is advertised as a therapeutic treatment to give them more energy and reverse aging. This procedure isn’t as lengthy as someone looking for rehabilitation and can be sold as a regular treatment appointment, receiving a “top off” every 6 to 8 weeks.

Why Use NAD Therapy to Treat Addiction?

It has been determined that the excessive use of drugs and alcohol will deplete the body’s natural stores of NAD. Because of this, the brain cannot receive the same energy it usually would from breaking down food. NAD Therapy floods the brain with the co-enzyme to replenish its stores, providing three key effects.

It flushes out all of the drugs that are still in the user’s system.
It curbs the cravings for alcohol and Opioids and lessens the pain of withdrawal, making recovery easier physically and mentally.
It allows the body to produce energy more naturally, without a crash or jitters like caffeine and sugar or the negative effects that come with other substances.
Length of sessions vary depending on severity of the addiction and what the clinic recommends. After the initial session, follow ups will be scheduled 1 to 2 months later. These sessions can continue at the discretion of the prescribing clinic.

Importance of Hypothalamus for Energy Metabolism

Hypothalamic circuits regulating appetite and energy homeostasis:  pathways to obesity

The hypothalamus in particular has emerged as an integrating, superordinate master regulator of whole-body energy homeostasis.

In summary, the hypothalamus plays a key role in the regulation of appetite and food intake both in humans and rodents.

Hypothalamic inflammation impairs the effects of insulin and leptin, contributing not only to hyperphagia and obesity development but also to the associated dysregulation of glucose homeostasis.

Brain regulation of appetite and satiety

Energy homeostasis is controlled mainly by neuronal circuits in the hypothalamus and brainstem.

Brain Regulation of Energy Metabolism (Roh, 2016)

The hypothalamus is the region of the brain that controls food intake and body weight.

Leptin and insulin signal the status of body energy stores to the hypothalamus.

Hypothalamic regulation of energy homeostasis (Sainsbury, 2002)

These peripheral hormones influence their effects on energy homeostasis either by activating or inhibiting the activity of the orexigenic or anorexic peptides within the hypothalamus.

Hypothalamus as master aging clock

Building the Case that Aging is Controlled from the Brain

Is there an Aging Clock in the Hypothalamus?

Hypothalamic programming of systemic ageing involving IKK-b, NF-kB and GnRH (Zhang, 2014)

Nutrition to boost NAD+

OTHER WAYS TO INCREASE NAD+

There are a number of lifestyle changes you can make  to increase NAD+ in you body.

It’s well known that Calorie Restriction  (CR) can extend longevity by 30–50% in many mammals (32)

CR has also been shown to increase NAD+ levels in the body , thru these pathways:

  • Lowering blood glucose levels minimizes inflammation, which consumes NAD+.
  • The ketone body BHB signals to increase AMPK to produce more NAD+
  • Burning Ketones for fuel instead of glucose requires 1/2 as much NAD+

– Ketone bodies mimic the life span extending properties of caloric restriction (veech,2017)

 KETOSIS BOOSTS NAD+

Ketosis is a metabolic state in which fat provides most of the fuel for the body. It occurs when there is limited access to glucose (blood sugar), which is the preferred fuel source for many cells in the body.

Ketosis can occur in many different diet plans whenever carb intake is low, but is most often associated the Ketogenic Diet, as that is a much easier method for restricting carbs (3, 4, 5, 6).

Recent research now shows  Ketosis  provides the benefit in life extension, lowering inflammation and boosting NAD+ (3,9).

Intermittent or Periodic Ketosis is also effective at extending lifespan and likely achieves much of the benefit (36,37).

Some research even shows more benefit from a cyclical rather than a full time Ketogenic Diet (71).

Ketogenic Diet Reduces Midlife Mortality and Improves Memory in Aging Mice (Newman, 2017)

The Red bars in the chart at left show the increased levels of the Ketone Body BHB produced from a cyclical Keto diet, resulting in Increased NAD+ and greatly improved neurological function and health.

Exercise to boost NAD+

EXERCISE THAT BOOSTS NAD+

Researchers are finding that 2-3  short bouts of High Intensity Interval Training  (HIIT) per week is far more effective at lowering inflammation (and increasing NAD+), especially among older adults (55)

Exercise is very effective at boosting AMPK and NAD+, especially when performed at times of low blood glucose levels  ( more about HIIT ).

Short bouts of HIIT accomplishes the goal, while avoiding overtraining from endurance workouts  which increases inflammation and consumes NAD+ (55).

NAD+ and aging

Decline of NAD+ during Aging, Age-Related Diseases, and Cancer

Several evidences suggest a decline in NAD+ levels while we age, connecting NAD+ deficits to age-related diseases and cancer.

Inflammation increases during the aging process possibly due to the presence of senescent cells [1].

CD38 and bone marrow stromal cell antigen-1 (BST- 1) may provide explanations to NAD+ decline during aging.

CD38 is a membrane-bound hydrolase implicated in immune responses and metabolism. NAD+ can be degraded through its hydrolysis, deacetylation, or by NAD+ nucleosidases (also called NAD+ hydrolases or NADases) such as CD38.

Expression and activity of CD38 increase in older mice, promoting NMN degradation in vivo, responsible for NAD+ decline and mitochondrial dysfunctions [2].

Interestingly, loss of CD38 inhibits glioma progression and extends the survival of glioma- bearing mice.

Targeting CD38 in the tumor microenvironment may clearly serve as a novel therapeutic approach to treat glioma [3].

 

Daratumumab, a CD38 monoclonal antibody, rep- resents a first-in-class drug for the treatment of multiple myeloma. It promotes T cell expansion through inhibition of CD38+ immunosuppressive cells, improving patients’ responses [4].

These findings suggest that NAD+ boosters should be combined with CD38 inhibitors for a more efficient antiaging therapy.

 

NAD+ Biosynthesis Decreases during Aging, Age-Related Diseases, and Cancer 

NAD+ increases can also occur independently of the Preiss–Handler route. NAM and NR are important NAD+ precursors first converted to nicotinamide mononucleotide (NMN) by nicotinamide phosphoribosyltransferase (NAMPT) and NR kinase (NRK), respectively. NMN is then transformed into NAD+ by NMN adenylyltransferase [36].

As we age, our bodies undergo changes in metabolism, and a key part of these processes may affect de novo NAD+ synthesis, also called the L-tryptophan/kynurenine pathway (see Figure IB in Box 1). In mammals, the use of the de novo NAD+ biosynthetic pathway is limited to a few specific organs.

Finally, dysregulation of the kynurenine pathway is also linked to genetic disorders and age-related diseases such as obesity and cancer [14,15]. These age-associated changes in de novo NAD+ biosynthesis may have the potential to impact several biological processes, and thus contribute to age-related diseases and cancer in the elderly.

Animal models mimicking downregulation of NAD+ biosyn-thesis are needed to modulate its activity and understand its pathophysiological relevance in age-related pathologies and cancer.

Boosting NAD+ with Niacin in Age-Related Diseases and Cancer 

In humans, a lack of nicotinic acid (NA, also called niacin) in the diet causes the vitamin B3 deficiency disease pellagra, characterized by changes in the skin with very characteristic  pigmented sunburn-like rashes developing in areas that are exposed to sunlight. Likewise, people with chronic L-tryptophan-poor diets or malnutrition develop pellagra.

Furthermore, several epidemiologic studies in human reported an association between incidence of certain types of cancers and niacin deficiency [27].

In this regard, low dietary niacin has also been associated with an increased frequency of oral, gastric, and colon cancers, as well as esophageal dysplasia.

In some populations, it was shown that daily supplementation of niacin decreased esophageal cancer incidence and mortality. Although the molecular mechanisms of niacin deprivation and cancer incidence are not well understood, it has been recently reported that NAD+ depletion leads to DNA damage and increased tumorigenesis, and boosting NAD+ levels is shown to play a role in the prevention of liver and pancreatic cancers in mice [19,28,29].

Thus, malnutrition through inadequate amounts and/or diversity of food may affect the intra- cellular pools of nicotinamide and NAD+ thereby influencing cellular responses to genotoxic damage, which can lead to mutagenesis and cancer formation [19,27]. NAD+ boosters are therefore essential in patients at risk of exposure to genotoxic and mutagenic agents, including ionizing or UV radiations or, DNA damaging chemicals.

In addition, niacin deficiency in combination with carcinogenic agents was described to induce and increase tumorigenesis in rats and mice.

For instance, in rats, the lack of niacin together with carcinogen treatment increased tumorigenesis and death of rats [30,31]. Additionally, in mice, the incidence of skin tumours induced by UV was significantly reduced by local application of NAM or by niacin supplementation in the diet [32].

Boosting NAD+ with NAM in Age-Related Diseases and Cancer 

Recent research has focused on uncovering the consequences of a decrease in NAD+ during aging using age-related disease models. In PGC1a knockout mouse, a model of kidney failure, NAD+ levels are reportedly decreased, and boosting NAD+ by NAM improves kidney function [33].

NAM injections during four days re-establish local NAD+ levels via nicotinamide phos- phoribosyltransferase (NAmPRTase or NAMPT) activation and improve renal function in postischaemic PGC1a knockout mice [33].

Surgical resection of small renal tumors can induce kidney ischemia severely affecting the renal function. Therefore, NAD+ boosters can be beneficial to protect the organ from severe injury.

Moreover, in a model of muscular dystrophy in zebrafish, NAD+ increases, which functions as an agonist of muscle fiber–extracellular matrix adhesion, and corrects dystrophic phenotype recovering muscle architecture [34].

Boosting NAD+ with NR in Age-Related Diseases and Cancer 

Further research has extensively used NR to ameliorate the effects of NAD+ deficits in pleiotropic disorders. NR naturally occurs in milk [35,36]. NR is converted to NAD+ in two step reactions by nicotinamide riboside kinases (NRKs)-dependent phosphorylation and adenylylation by nicotinamide mononucleotide adenylyl transferases (NMNATs) [36].

It is considered to be a relevant NAD+ precursor in vivo. Evidences demonstrate the beneficial effect of NR in skeletal muscle aging [37,38] and mitochondrial-associated disorders, such as myopathies [39,40] or those characterized by impaired cytochrome c oxidase biogenesis affecting the respiratory chain [41].

In line of these findings, a mouse model of Duchenne muscular dystrophy present significant reductions in muscle NAD+ levels accompanied with increased poly-ADP-ribose polymerases (PARP) activity, and reduced expression of NAMPT [42].

Replenishing NAD+ stores with dietary NR supplementation improved muscle function in these mice through better mitochondrial function [42].

Additionally, enhanced NAD+ concen- trations by NR are apparently beneficial for some neurodegenerative diseases [43], as well as in noise-induced hearing loss [44].

NR-mediated NAD+ repletion is also protective, and even therapeutic, in certain metabolic disorders associated with cancer, such as fatty liver disease [28,45] and type 2 diabetes [28,46]. Metabolic disorders characterized by defective mitochon- drial function could also benefit from an increase in NAD+ levels.

Indeed, stimulation of the  oxidative metabolism in liver, muscle, and brown adipose tissue potentially protects against obesity [47]. Interestingly, NAMPT protein levels are not affected in chow- and high fat diet (HFD)-treated mice fed with NR, arguing that in models of obesity, NR directly increases NAD+ levels without affecting other salvage reactions [47].

Recently, diabetic mice with insulin resistance and sensory neuropathy treated with NR reportedly show a better glucose toler- ance, reduced weight gain and liver damage, and protection against hepatic steatosis and sensory and diabetic neuropathy [48].

 

Boosting NAD+ with NMN in Age-Related Diseases and Cancer 

NMN is also a key biosynthetic intermediate enhancing NAD+ synthesis and ameliorates various pathologies in mouse disease models [49,50].

Very recent research demonstrate that a 12- month-long NMN administration to regular chow-fed wild-type C57BL/6 mice during normal aging rapidly increases NAD+ levels in numerous tissues and blunts age-associated physio- logical decline in treated mice without any toxic effects [49]. NMN is also beneficial in treating age- and diet-induced diabetes, and vascular dysfunction associated with aging in mice [51,52].

Administration of NMN also protects the heart of mice from ischemia-reperfusion injury [53] and restores mitochondrial function in muscles of aged mice [37,54].

It has been speculated that NMN is a circulating NAD+ precursor, due to the extracellular activity of NAMPT [55]. However, the mechanisms by which extracellular NMN is converted to cellular NAD+ still remain elusive.

On the one hand, it is reported that NMN is directly trans- ported into hepatocytes [51]. On the other hand, NMN can be dephosphorylated to NR to support elevated NAD+ synthesis [56–59].

It is recently shown that NAM can be metabolized extracellularly into NMN by extracellular NAMPT. NMN is then converted into NR by CD73 [60]. Hence, NR is taken up by the cells and intracellularly phosphorylated firstly into NMN by NRKs and then, converted into NAD+ by NMNATs [60] (Figure 3).

Thus, mammalian cells require conversion of extracellular NMN to NR for cellular uptake and NAD+ synthesis. Consistent with these findings, in murine skeletal muscle specifically depleted for NAMPT, administration of NR rapidly restored muscle mass by entering the muscles and replenishing the pools of NAD+ through its conversion to NMN [38].

Interestingly, mice injected with NMN had increased NAM in their plasma that may come after initial conversion of NMN into NR [60]. However, degradation of NR into NAM could only be observed when cells were cultured in media supplementing with 10% FBS [60].

Finally, it is important to note that NR is stably associated with protein fractions in milk with a lifetime of weeks [35].

Notably, as reported above, NMN may be degraded by CD38 in older mice promoting NAD+ decline and mitochondrial dysfunctions [2], suggesting that NR may be more efficient than NMN in elderly.

Yet, the beneficial synergistic activation of sirtuins and metabolic pathways to replenish NAD+ pools cannot be excluded. However, given its efficient assimilation and high tolerance, NR represents still the most convenient and efficient NAD+ booster.

Overall, these findings suggest that NAD+ decrease in disease models and NAD+ precursors (NAM, NR or NMN) may circumvent NAD+ decline to generate adequate levels of NAD+ during aging and thus be used as preventive and therapeutic antiaging supplements.

NMN and NR  supplementations may be equivalent strategies to enhance NAD+ biosynthesis with their own limitations.

Side-Effects of Some NAD+ Boosters 

Clearly, several intermediates of the salvage pathway can be considered to boost NAD+ levels but some have contraindications. High doses of NA given to rats are needed to robustly increase NAD+ levels [61].

Additionally, relevant and unpleasant side effects through NA-induced prostaglandin- mediated cutaneous vasodilation (flushing) affecting patient compliance are due to the activation of the G-protein-coupled receptor GPR109A (HM74A) and represent a limitation in the pharma- cological use of NA [62].

NAM is much less efficient than NA as a lipid lowering agent and has also several side effects; in particular, it causes hepatic toxicity through NAM-mediated inhibition of sirtuins [63].

The metabolism of these conventional compounds to NAD+ is also different, as NA is converted via the three-step Preiss–Handler pathway, whereas NAM is metabolized into NMN via NAMPT and then to NAD+ by NMNATs [64]

Manipulating NAD+ by Manipulating Enzyme Activity of Salvage Reactions 

Enhancing the activity of enzymes that participate in salvage reactions can also be a strategic intervention to increase NAD+ concentrations. Different studies have addressed the importance of regulating the activity of NAMPT during disease, including metabolic disorders and cancer.

NAMPT is necessary in boosting NAD+ pools via the salvage pathway.

Consequently, NAMPT deletion provokes obesity-related insulin resistance, a phenotype rescued by boosting NAD+ levels in the white adipose tissue by giving NMN in drinking water [67].

Conversely, in a mouse model for atherosclerosis, NAMPT depletion promotes macro- phage reversal cholesterol transport, a key process for peripheral cholesterol efflux during atherosclerosis reversion [68].

Other recent reports suggest that NAMPT downregulation could be beneficial in treating pancreatic ductal adenocarcinoma [69,70] and colorectal cancer [71].

Recent findings show that Duchenne muscular dystrophy was accompanied by reduced levels of NAMPT in mice [42]. Moreover, NAMPT knockout mice exhibit a dramatic decline in intramuscular NAD+ content, accompanied by fiber degeneration and progressive loss of both muscle strength and treadmill endurance.

NR treatment induced a modest increase in intra- muscular NAD+ pools but sufficient to rapidly restore muscle mass. Importantly, overexpres- sion of NAMPT preserves muscle NAD+ levels and exercise capacity in aged mice [38].

Inhibitors against NAMPT are being used in several phase II clinical trials as anticancer therapy.

Given that NAMPT activation is important to boost NAD+ levels, therapy involving NAMPT inhibition should be considered with caution. Although levels of NAD+ remain to be determined in models with NAMPT depletion, further investigation on the effects of NAMPT modulation is clearly required.

The specific mechanisms and actual benefits of regulation of NAMPT activity remain elusive, evidencing the need of more specific disease models.

 

Can Dietary Restriction and Protein Catabolism Maintain NAD+ Levels?
Among the questions that still remain not well understood is why DR profoundly increases lifespan? Can DR affect NAD+ levels?

It is well established that overfeeding and obesity are important risk factors for cancer in humans [129] and obesity-induced liver and colorectal cancer, among others, can shorten lifespan.

Earlier research has also shown that both increased physical activity and reduction in caloric intake (without suffering malnourishment) can extend lifespan in yeasts, flies, worms, fish, rodents, and primates [3–8].

Furthermore, a recent study pointed to the importance of the ratio of macronutrients more than the caloric intake as the determinant factor in nutrition-mediated health status and lifespan extension [9].

Although in humans it is difficult to measure the beneficial effects of DR and currently there is no reliable data that describe the consequences of significantly limiting food intake, some studies have assessed how DR affects health status.

People practicing DR seem to be healthier, at least based on risk parameters such as LDL cholesterol, triglycerides, and blood pressure [130].

Activation of the salvage pathways during DR could be turned on and glucose restriction can stimulate SIRT1 through activation of the AMPK-NAMPT pathway resulting in inhibition of skeletal myoblast differentiation [131].

Interestingly, effects of NMN supplementation and exercise on glucose tolerance in HFD-treated mice are very similar [132].

Even though these effects are tissue-specific since exercise predominantly affects muscle, whereas NMN shows major effects in liver, and that mechanism of action can be different, exercise and NMN predominantly affect mitochondrial functions and may both contribute to the boost of NAD+.

It is thus tempting to speculate that L-tryptophan concentrations and thus the de novo NAD+ biosynthesis could fluctuate during DR ameliorating the aging process.

Recent studies in humans and mice suggest that moderate exercise can increase blood NAD+ levels and decrease L-tryptophan levels [137].

A possible explanation for this phenomenon is that DR,  and/or exercise, can induce autophagy and promote the release of several metabolites and essential amino acids [138].

 

Conclusion

 

Aging is proposed to be responsible for diverse pathologies, however, it should be considered as a disease among other diseases that appear in time while individuals age.

Although some questions still remain unclear, NAD+ precursors may present possible therapeutic solutions for the maintenance of NAD+ levels during aging and thus may provide prophylaxis to live longer and better.

Although more research is needed to understand the efficacy as well as potential adverse side effects of NAD+ Replacement Therapies in humans, recent studies already provided some pharmacological properties, showing low toxicity and high effectiveness.

SUMMARY

    • Sublingual delivery is required for all NAD+ metabolites and precursors to avoid digestion in the stomach and liver.
    • NAD+ clinics use slow drip IV of NAD+ to avoid the stomach and liver. They are exploding in popularity, but the extreme cost and time required for treatment severely limit their application for the general public.
    • Sublingual NAD+ delivery solves the bioavailability problem and mimics the slow drip delivery used successfully by NAD+ IV clinics.
    • Sublingual NAD+ is not subject to the homeostasis that limits NAD+ increase with NR (and perhaps NMN), as it is supplied directly to the bloodstream.
    • We believe the ability of NAD+ to increase metabolism through the hypothalamus has a great impact on the entire body. This is accomplished directly from increased NAD+ circulating in blood plasma, and not from NMN or NR.
    • Other organs such as heart, liver, kidney, and lungs also clearly benefit from increased circulating NAD+, but there is evidence NR an NMN may have similar effectiveness.
    • Exogenous NR increases circulating NAD+ levels, but after several weeks, that increase is severely limited by homeostasis.
    • Exogenous NMN elevates NAD+ levels similar to NR, but seems to be less limited by homeostasis. Publication of recently completed research should shed more light on that question.

NMN demonstrates a remarkable ability to rapidly restore vascular growth that has not been shown with use of NR or NAD+.

 

Sublingual NAD+ will lead to a greater increase in circulating NAD+ than NR or NMN supplements.