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 (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 much more effective precursor to NAD+. 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+ 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).
NAD+ METABOLISM IN HUMANS
NAD+ is synthesized in humans by several different molecules (precursors), thru 2 different pathways:
De Novo Pathway
- Nicotinic Acid (NA)
- NAM – Nicotinamide
- NR – Nicotinamide Riboside
- NMN – Nicotinamide MonoNucleotide
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).
This recycling 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.
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 NAM and the Nampt limiting step (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 the already well known precursors NA, NAM or Tryptophan.
SOME NR IS 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)
“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)
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:
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 at right shows metabolites found in urine of the subject from the same experiment as above.
The red box shows NAM is elevated more than 10x baseline at the same time point that NAD+ is elevated, which implies that NR has elevated NAM to such an extent that excess NAM is excreted in urine.
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 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+.
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 large increase of NR, and that a significant fraction of the increase in NAD+ is due to NR->NAM->NAD+.
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 effectively mitigates age-associated physiological decline in mice
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
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
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 (37).