Does NR break down to NAM before NAD+

As we age, our levels of the Co-enzyme Nicotinamide Adenine Dinucleotide NAD+ drop significantly in multiple organs in mice and humans  (5,8,10).

NAD+ decrease is described as a trigger in age-associated decline(23), and perhaps even the key factor in why we age (5).

In 2013, research published by Dr David Sinclair demonstrated that short term supplementation with Nicotinamide MonoNucleotide (NMN) replenished NAD+ and reversed many aspects of aging, making the cells of old mice resemble those of much younger mice, and greatly improving their health (8).

The quotes below are directly from that research:

NMN was able to mitigate most age-associated physiological declines in mice”

“treatment of old mice with NMN reversed all of these biochemical aspects of aging”

Since Dr Sinclairs landmark 2013 study, dozens of others have been published investigating the efficacy of supplementation with NMN and Nicotinamide Riboside (NR) in treatment and prevention of a wide range of disease including cancer, cardiovascular disease, diabetes, Alzheimers, Parkinsons, and more (5,6,7,9,10,11,13,14,15,16).

According to Dr Sinclair:

“enhancing NAD+ biosynthesis by using NAD+ intermediates, such as NMN and NR, is expected to ameliorate age-associated physiological decline”

WHAT IS NR

Nicotinamide Riboside (NR) and NMN are precursors that are used by our bodies to replenish NAD+ levels.

In 2004 Dr Charles Brenner published a paper showing that the enzyme Nrk1 can catalyze NR directly to NMN (100) which might make it a more effective precursor to NAD+ than the previously known NAM, NA, or Tryptophan.

Although NR is unstable by itself, Dartmouth University has patented production methods that combine it with Chloride which makes it stable.

Chromadex has licensed this technology and has been selling NR commercially since 2014 under the brand name “Niagen”.

Tru Niagen is the brand name used by Dr Brenner’s company ProHealthSpan to market their Niagen product.

WHAT IS NAD+

NAD+ is a key co-enzyme that the mitochondria in every cell of our bodies depend on to fuel all basic functions. (3,4)

NAD+ play a key role in communicating between our cells nucleus and the Mitochondria that power all activity in our cells (5,6,7)

NAD+ LEVELS DECREASE WITH AGE

As we age, our bodies produce less NAD+ and the communication between the Mitochondria and cell nucleus is impaired. (5,8,10).

Over time,  decreasing NAD+ impairs the cell’s ability to make energy, which leads to aging and disease (8, 5) and perhaps even the key factor in why we age (5).

NAD+ METABOLISM IN HUMANS

The NAD+ supply is not stagnant – it is constantly being consumed and replenished, with the entire NAD+ pool being turned over 2-4 times per day (14).

NAD+ is synthesized in humans by several different molecules (precursors), thru 2 different pathways:
De Novo Pathway

• Tryptophan
• Nicotinic Acid (NA)

Salvage Pathway

• NAM – Nicotinamide
• NR – Nicotinamide Riboside
• NMN – Nicotinamide MonoNucleotide

This constant recycling of NAD+ is through the salvage pathway, where the enzyme Nampt catalyzes NAM to NMN, which is then metabolized to NAD+.

Nampt is the rate-limiting step in the salvage process (97).

Many studies have confirmed the importance of Nampt in maintaining sufficient NAD+ levels, such as the quote below from a 2016 study that used mice lacking Nampt in muscle fiber:

“NAD content of muscle was decreased by ~85% confirmed the prevailing view that the salvage route of NAD synthesis from NAM sustains the vast majority of the NAD” (97)

These mice exhibited normal muscle strength and endurance while young, but deteriorated rapidly as they aged which confirmed Nampt is critical to maintaining NAD+ levels.

As we age, Nampt enzyme activity is lower, resulting in less NAM recycling, less NAD+, more disease and aging (97,101).

NMN and NR SUPPLEMENTS CAN BYPASS NAMPT

NR had been known for decades, but was not thought to be that important until 2004 when Dr. Charles Brenner discovered the enzyme NRK1 can phosphorylate NR directly to NMN, bypassing the Nampt “bottleneck” (100).

This newly discovered “shortcut” in the NAD+ salvage pathway found that NR can be metabolized directly to NMN to boost NAD+ levels more effectively than NAM.

MOST NR IS FIRST METABOLIZED TO NAM

When taken orally as a supplement, most NR does not make it through the digestive system intact, but is broken down to NAM (97,98,99).

Even when taken at very high dosages, NR has not been detected in the bloodstream in any research (97,98,99).

“This evidence indicates that NR is converted to NAM before absorption occurs and that this reaction is the rate-limiting step ” (98)

“NR has been shown be converted to Nam before being absorbed or reaching tissues” (99)

“oral NR dosing increased circulating NAM ~40-fold while NMN remained unchanged” (97)

“we were surprised to find that NR exerts only a subtle influence on the steady state concentration of NAD in muscles. Our tracer studies suggest that this is largely attributable to breakdown of orally delivered NR into NAM prior to reaching the muscle. ” (97)

Note:NAM does elevate NAD+, but is on the “wrong” side of the Nampt bottleneck, which limits it’s effectiveness

HUMAN STUDY ON NR BIOAVAILABILITY

The following five charts are all from the thesis published by Samuel Alan Trammell in 2016 under supervision by Dr Brenner:

Nicotinamide riboside is uniquely and orally bioavailable in mice and humans

This chart above shows the impact on NAD+ metabolites over time for a 52 year old human after ingesting 1000mg of NR daily for 7 days.

NAD+ levels begin to rise at 4.1 hours, and peak at 8.1 hours.

NAM levels double at .6 hours and have a second peak at 7.7 hours, long before NAD+ levels are elevated.

This chart a left shows impact of NR, NA, and NAM supplementation on blood plasma NAD+ (b), and NAM  (d) levels in 12 human subjects.

The red line at 2 hours shows NR supplementation increases NAM perhaps 3x (d), but has not yet elevated NAD+(b).

The 2 hour mark also is the point at which NAM supplementation begins to increase NAD+ levels (b).

The blue line at 8 hours is when both NR (b) and NAM (d) supplementation reach peak NAD+ increase.

Lastly, the green bar and black bar in chart b show that NAM elevates NAD+ slightly less than NR.

NR elevated NAD+ slightly more than NAM, but is much slower acting

MOUSE STUDIES ON NR BIOAVAILABILITY

The chart above shows the result on NAD+ metabolism of 15 mice fed NR by oral gavage at a dose of 185 mg/kg of bodyweight.

The NR was synthesized with heavy atoms of deuterium at the ribosyl C2 and 13C on the Nam side, to allow tracking.

The measurement at 2 hours shows 54% of the NAD+ has the single heavy molecule (white bar, M+1). This 54% was likely broken down to NAM first, losing the second labelled heavy atom.

At the same time point, 5% of the NAD+ had both labels (Grey bar, M+2).

This 5% of NR made it through the digestive tract intact and was metabolized through the shortcut from NR -> NMN -> NAD+, vs 54% that had been through NR -> NAM -> NMN -> NAD+.

The chart above shows the impact of the same double labeled NR on mouse liver, but this time after IP (Intraperitoneal) Injection.

Note the dramatic difference in the ratio of labelled M+2 over M+1. IP results in much higher levels of intact NR (M+2) being metabolized to NAD+, whereas Oral NR shows far more M+1 labelled NR to NAD+.

This different behavior in IP vs oral NR supplementation also implies oral NR is partially metabolized to NAM before conversion to NAD+.

The above chart shows the resultant increase in select NAD+ metabolites of mice fed NR (unlabeled) at 185 mg/kg of bodyweight.

As noted by the authors, NR and NAR are the only NAD+ precursors tested that did NOT result in elevated levels of the precursor in the liver.

Here is one last quote in discussion section from the Trammell thesis:

“NR has not been detected in the blood cell fraction nor in plasma …NR varied and displayed no response to NR administration … but was detected after IP of double labeled NR in liver (Figure 5.7) and muscle (Figure 5.9), revealing NR does circulate”

They are saying that NR is found in small quantities in the liver, but is not detectable in bloodstream.  Oral supplementation with NR did not show any increase in NR in the body.  However, Injection (IP) of NR does result in a detectable increase of NR in muscle and Liver. So NR does circulate in the bloodstream when injected, but has not yet been detected upon oral supplementation.

The timing and amplitude of the increases in metabolites noted above imply that:

• Oral NR does not result in a detectable increase of NR in the body
• It’s likely a majority of the increase in NAD+ is due to NR->NAM->NAD+.

Note: NAM does elevate NAD+, but is on the “wrong” side of the Nampt bottleneck, which limits it’s effectiveness

NMN QUICKLY RAISES NAD+ IN LIVER AND BLOOD

In this 2016 study, mice were given a single dose of  NMN in water.

NMN  levels in blood showed it is quickly absorbed from the gut into blood circulation within 2–3 min and then cleared from blood circulation into tissues within 15 min

The chart at right shows levels of a double labeled NAD+ (C13-d-nad+) in liver and soleus muscle at 10 and 30 minutes after oral administration of double labeled NMN.

This clearly shows that NMN makes its way through the liver, into muscle, and is metabolized to NAD+ in 30 minutes (23) .

Orally administered NMN is quickly absorbed, efficiently transported into blood circulation, and immediately converted to NAD+in major metabolic tissues (23).

NMN INCREASES NAD+ and SIRT1 DRAMATICALLY IN ORGANS

In this 2017 study, NMN supplementation for 4 days significantly elevated NAD+ and SIRT1, which protected the mice from Kidney damage.

NAD+ and SIRT1 levels were HIGHER in OLD Mice than in YOUNG Mice that did not receive NMN.

LONG TERM SUPPLEMENTATION WITH NMN

In a long-term experiment documented in the 2016 study (23) , mice were given 2 different doses of NMN over 12 months.

Testing revealed that NMN  prevents some aspects of  physiological decline in mice, noting these changes:

• Decreased body weight and fat
• Increased lean muscle mass
• Increased energy and mobility
• Improved visual acuity
• Improved bone density
• Is well-tolerated with no obvious bad side effects
• Increased oxygen consumption and respiratory capacity
• Improved insulin sensitivity and blood plasma lipid profile

Here are some quotes from  the  study:

NMN suppressed age-associated body weight gain, enhanced energy metabolism, promoted physical activity, improved insulin sensitivity and plasma lipid profile, and ameliorated eye function and other pathophysiologies

NMN-administered mice switched their main energy source from glucose to fatty acids

These results strongly suggest that NMN has significant preventive effects against age-associated impairment in energy metabolism

NMN effectively mitigates age-associated physiological decline in mice

LOWER FAT AND INCREASED LEAN MUSCLE MASS

Researchers found that NMN administration suppressed body weight gain by 4% and 9% in the 100 and 300 mg/kg/day groups.

Analyses of  blood chemistry panels and urine did not detect any sign of toxicity from NMN.

Although health span was clearly improved, there was no difference in maximum lifespan observed.

These results suggest that NMN administration can significantly suppress body weight gain without side effects

INCREASED OXYGEN CONSUMPTION AND RESPIRATORY CAPACITY

Oxygen consumption significantly increased in both 100 and 300 mg/kg/day groups during both light and dark periods (Figure 3A).

Energy expenditure also showed significant increases  (Figure 3B).

Respiratory quotient significantly decreased in both groups during both light and dark periods (Figure 3C),

This suggests that NMN-administered mice switched their main energy source from glucose to fatty acids.

The mice that had been receiving NMN for 12 months exhibited energy levels, food and water consumption equivalent to the mice in the control group that were 6 months younger.

NMN administration has significant preventive effects against age associated physical impairment

HUMAN STUDIES – LONG TERM SUPPLEMENTATION WITH NMN

The first clinical trial of NMN in humans is currently underway by an international collaborative team between Keio University School of Medicine in Tokyo and Washington University School of Medicine (33).

Participants are 50 healthy women between 55 and 70 years of age with slightly high blood glucose,BMI and triglyceride levels.

Using a dose of 2 125mg capsules of NMN per day over a period of 8 weeks, researchers are testing for:

• change in insulin sensitivity
• change in beta-cell function
• works to control blood sugar
• blood vessels dilate
• effects of NMN on blood lipids
• effects of NMN on body fat
• markers of cardiovascular and metabolic health

According to the study:

“Data from studies conducted in rodents have shown that NMN supplementation has beneficial effects on cardiovascular and metabolic health, but this has not yet been studied in people”

Testing of metabolic parameter will continue for 2 years after supplementation has ended, so final results will not be published for some time yet, but preliminary results are expected to be announced in early 2018.

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