9 replies to this topic

[Michael]

All:

While emphasizing for the umpteenth time that raising NAD⁺ levels is not, itself, a health benefit and that this study only looks at blood and liver, this a perhaps-surprising study suggests that NMN may be, pharmacodynamically, roughly equivalent to NAM in terms of NAD⁺ elevation — or, at most, might have a kind of 'sustained-release' effect without the concomitant slowing of initial bioavailabiity of sustained-rlease pills, since any sustained action would be due to slower excretion and recycling rather than due to slower absorption.

The investigators (Katsumi Shibata's lab in Japan, who have been investigating NAD⁺ biology for more than 35 years) injected rats with 45 µmol/kg of either NAM or NMN ( ≈5 and 15 mg/kg, respectively) or saline. (For comparison, the rodent "RDA" for NA/NAM is 30 (AIN) or 15 (NRC) mg/kg diet, and weaning Wistar rats consume 0.151 kg chow per kg body weight, which works out to something < 5 mg/kg bw /day. So these are RDAish doses, and if anything the NMN dose is significantly higher than that for NAM). They then tracked levels of "total NAD" (NAD⁺ + NADH) in blood (every half-hour for 6 h), liver (3 h after injection), and urinary NAM metabolites (NAM + NAM N-oxide + N¹-methylnicotinamide + N¹-methyl-4-pyridone-3-carboxamide + N¹-methyl-2-pyridone-5-carboxamide).β-

At these modest doses, neither NAD⁺ precrsor did much of anything to total blood NAD(H) as compared with the background diet (Fig. 3). Similarly, "The concentration of liver total NAD at 3 h after Nam or β-NMN administration also showed no significant differences among the three groups (the values were around 800 nmol/g of liver) [data not shown]."

Despite that, it appears that NMN clearance may take longer than that of NAM: particularly in the 3-6 hour window, and maybe also in the first 3 h, the sum of NAM metabolites flushed out via the urine was lower after NMN administration than NAM (Fig. 2); this was especially true of excreted NAM .
 

This result suggests that β-NMN is retained in the body for longer than Nam is. In addition, this result means that β-NMN has a higher turnover of salvage biosynthesis of NAD⁺ than Nam does.(1)

I think they're really speculating here. For one thing, they didn't look at urinary NMN itself, and some of the difference could be due to an initial rapid release of it: it is notable that a very large amount of NAM is lost in the urine in the first 3 h after injection, suggesting both rapid metabolism of NMN to NAM and that much NAM may be lost without being metabolized to NAD⁺; while you expect a higher percentage of injected NMN to go through NAD⁺ first, since so fewer steps are required to do so (and since, as the authors note, NAMPT is rate-limiting on NAD⁺ synthesis from NAM and is also subject to negative feedback from NAD⁺ production), we don't know absent measurement. Moreover, if there really were higher retention of bioactive members of the "NAD⁺ metabolome" after NMN, hten you ought to see a sustained elevation in NAD⁺ levels — and if there isn't, what's the point?

Actually, the authors do have one answer to the "what's the point?" question (although this isn't what they were addressing at the time):
 

the reaction [converting NAM to NMN] is inhibited by the physiological concentration of NAD⁺ . Therefore, administration of Nam does not contribute to the increased turnover of salvage biosynthesis of NAD⁺ biosynthesis. If β-NMN is administered, it is dephosphorylated and is converted to nicotinamide riboside (NR) ... [which] is transported into liver cells and is re-phosphorylated to form β-NMN. This step (NR + ATP → β-NMN + ADP) should be the rate-limiting step of the conversion of NR to NAD⁺ . Thus, accumulation of NR should be observed in liver cells. The increased concentration of NR may inhibit the reaction of Nam → Nam catabolites. [At minimum, NR and NR-derived NMN are not directly metabolized into these metabolites —MR].The resulting phenomenon accelerates the turnover of salvage biosynthesis of NAD⁺ , which activates the SIRT1 reaction [and also PARPs], because SIRT1 (histone deacetylase) [and PARP] needs NAD⁺.(1)

So, conceivably, even if NAD⁺ levels are not raised, metabolic NAD⁺ flux might be increased, with more of an injected dose being consumed by use by SIRT1 or PARP1 before it is finaly excreted, even if steady-state NAD⁺ levels are similar. Such effects could also happen via effects hypothesized by Frederick and Baur PMID 27508874, in their study of muscle-specific NAMPT knockout mice administered NR or NAM (which found that NR was much more effective at alleviating their phenotype):
 

In light of its potent phenotypic effects in mNKO mice, 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. Nonetheless, our results indicate that NR is more effective than NAM for reversing mNKO phenotypes (Figure S5). The correlation between the NAD content and the respiratory capacity of isolated mitochondria, even in cultured myotubes (Figure 4), supports the model that subtle changes in NAD can disproportionately modulate aerobic metabolism. It is important to note that NAD turnover may vary independently from NAD concentration and that small changes in average tissue concentration might reflect larger changes in specific cells or subcellular compartments. It is also possible that intramuscular conversion of NAD into secondary messengers potently influences calcium homeostasis, which is both essential to muscle contraction and can independently modulate mitochondrial respiration (Ca´rdenas et al., 2010).

 
Well, maybe. I'd want to see more evidence, starting with urinary NMN. Moreover, I strongly question their reasoning that since circulating NMN has to be dephosphorylated into NR before being transported into cells, therefore "accumulation of NR should be observed in liver cells." Rather, if dephosphorylation to NR and then NR uptake is indeed rate-limiting, then there should almost tautologically be nothing slowing its conversion to NAD⁺ after that — and if there's going to be an accumulation, it should be of extracellular NR + NMN.

The study has the possible advantage of bypasssing both simple hydrolysis of NMN in the intestines, and of avoiding it being 'hogged' by the liver. I trust this will discourage Nate from more feverish imaginations about bypassing these processes . That of course also makes it less relevant to oral supplementers. And, they didn't take advantage of this bypass by measuring its effects on NAD⁺ levels in peripheral tissues.

It also bears holding in mind that at substantially higher doses, such as even the very modest megadoses used by most human supplementers (as vs. the heroic levels used in most NR studies), the effects may be quite different, and the possible retention effects of rapid and non-rate-limited NAD⁺ synthesis form NMN followed by reuse of liberated NAM might become more dominant, leading to a more obvious effect on NAD⁺.

But, again, that's quite speculative. On its face, this study strongly suggestss NMN is roughly pharmodynamically equivalent to NAM (and possibly less so, on a milligram-for-milligram basis).


Reference
1: Kawamura T, Mori N, Shibata K. β-Nicotinamide Mononucleotide, an Anti-Aging Candidate Compound, Is Retained in the Body for Longer than Nicotinamide in Rats. J Nutr Sci Vitaminol (Tokyo). 2016;62(4):272-276. PubMed PMID: 27725413.

Edited by Michael, 12 November 2017 - 11:48 PM.

[able]

I don't understand the significance of this.

 

As you say, it's likely not just the NAD+ boost that provides benefit, but signaling involved in the process.

 

But even if we just look at the NAD+ boost - didn't we already know from Trammel study and others that NAM elevates NAD+ in the liver similar to NMN and NR?

 

This study did not use old or sick mice that had a NAD+ deficiency.

 

I thought the benefit of NR and NMN is ability to boost NAD+ in tissues and cells that were deficient, not in elevating NAD+ above "normal" range in liver or blood.  

 

 

Edited by able, 13 November 2017 - 05:08 PM.

[Nate-2004]

The study has the possible advantage of bypasssing both simple hydrolysis of NMN in the intestines, and of avoiding it being 'hogged' by the liver. I trust this will discourage Nate from more feverish imaginations about bypassing these processes

 

Why (to both statements)? I don't fully understand the reasoning.

[warner]

NAM -> Nampt -> NMN -> Nmnat -> NAD

or NR -> Nrk -> NMN -> Nmnat -> NAD

 

As I see it, we have two distinct conditions:

 

(1) Some localized part of body is deficient in B3 (NAD precursors), such as skin, retina, etc.  Supplement with any B3 to fix that, although NAM is least expensive, with fewest side effects.

 

(2) With aging, much of body may become NAD-deficient, in spite of adequate B3 presence.  In this case, supplemental NAM may still be helpful for certain localized conditions, but will not solve the general NAD deficiency.  Other B3s, or associated enzymes, may be needed, but this may be trickier than we think.  Example:  increasing Nampt to increase NMN and NAD likely has negative impact on glaucoma progression (axon degeneration) via increased levels of NMN.

 

So I'm not surprised by results described by Michael.  At the very least, imho, we are getting confused about the general benefits of B3 supplementation to address local deficiencies, and the wider question of addressing age-based decline in NAD levels.

 

I'll return later with a set of references showing the link between Nampt, NMN, and axon degeneration.

[Michael]

Able wrote: I don't understand the significance of this.
 
As you say, it's likely not just the NAD+ boost that provides benefit, but signaling involved in the process.
 
But even if we just look at the NAD+ boost - didn't we already know from Trammel study and others that NAM elevates NAD+ in the liver similar to NMN and NR?

 
No: this is the first study comparing NMN to any other NAD+ precursor of which I'm aware. Trammell & Brenner looked at NR, NA, and NAM. And what exactly T&B show is of course disputed: they argue that it shows that "Nicotinamide riboside is uniquely and orally bioavailable in mice and humans" — a claim that has been met with some justified skepticism (taken in some cases to overconfident assertion of equivalence in the face IMO of insufficient data).
 
If we did have good reason to believe that NAM elevates NAD+ in the liver (and blood) similar to NMN and NR, then (absent some equally-clear superiority on actual health outcomes or other tissues) there'd be no good reason at all for people to shell out for the newfangled version, when NAM is cheap and widely available from suppliers with better track records and facilities that are FDA licensed for OTC drug manufacturing.
 

Able wrote: This study did not use old or sick mice that had a NAD+ deficiency.
 
I thought the benefit of NR and NMN is ability to boost NAD+ in tissues and cells that were deficient, not in elevating NAD+ above "normal" range in liver or blood.

 
That's the most reasonable situation in which to expect a benefit, I agree. Indeed, we've seen a couple of studies where higher-than-RDAish doses in very young animals has apparently led to functional and metabolic deficits instead of improvements. OTOH, clearly a lot of people are hoping that  megadosing will lead to supranormal NAD+ levels and supranormal benefits (super-high DNA repair, unprecedentedly-tight intracellular glucose control, utterly seamless fuel switching, etc); indeed, you were eagerly grasping in that direction yourself the other day.
 

NAM -> Nampt -> NMN -> Nmnat -> NAD
or NR -> Nrk -> NMN -> Nmnat -> NAD

As I see it, we have two distinct conditions:

(1) Some localized part of body is deficient in B3 (NAD precursors), such as skin, retina, etc. Supplement with any B3 to fix that, although NAM is least expensive, with fewest side effects.

(2) With aging, much of body may become NAD-deficient, in spite of adequate B3 presence. In this case, supplemental NAM may still be helpful for certain localized conditions, but will not solve the general NAD deficiency. Other B3s, or associated enzymes, may be needed, but this may be trickier than we think.

I'm not clear why you would think different B3s would behave differently under #1 than #2. I can certainly see that different specific B3s would be better for individual tissues (because of different local availability and expression of different enzymes governing the different metabolic routes (discussed here)), but that argues for preferential use of a particular form for a particular tissue, whereas you seem in general terms to be arguing the converse.
 

Other B3s, or associated enzymes, may be needed, but this may be trickier than we think. Example: increasing Nampt to increase NMN and NAD likely has negative impact on glaucoma progression (axon degeneration) via increased levels of NMN.

As I understand you to now agree, the case for this was weakened by a recent study and seems unlikely.
 

So I'm not surprised by results described by Michael.

It seems to me that this study doesn't actually weigh in on any of these questions — again, can you clarify?
 

At the very least, imho, we are getting confused about the general benefits of B3 supplementation to address local deficiencies, and the wider question of addressing age-based decline in NAD levels.

I certainly agree with this if you eliminate the word "local." Thinking about it, it's not surprising that all NAD+ predursors might yield roughly equivalent elevations in NAD+ in young animals at RDAish levels, as there isn't any homeostatic pushback to using it all to make what is by definition needed NAD+ and nothing is pushing "excessive" consumption; it's as you get to higher doses where you might expect negative feedback and/or room for further increases in the steady-state level because of  "excessive" consumption where particular forms might shine. But for that, as I said, we need more dose-ranging studies using multiple forms and across different age groups (though most especially in normally-aging animals).

Edited by Michael, 22 November 2017 - 09:46 PM.
Fixing attribution per able

[warner]

 

NAM -> Nampt -> NMN -> Nmnat -> NAD
or NR -> Nrk -> NMN -> Nmnat -> NAD

As I see it, we have two distinct conditions:

(1) Some localized part of body is deficient in B3 (NAD precursors), such as skin, retina, etc. Supplement with any B3 to fix that, although NAM is least expensive, with fewest side effects.

(2) With aging, much of body may become NAD-deficient, in spite of adequate B3 presence. In this case, supplemental NAM may still be helpful for certain localized conditions, but will not solve the general NAD deficiency. Other B3s, or associated enzymes, may be needed, but this may be trickier than we think.

I'm not clear why you would think different B3s would behave differently under #1 than #2. I can certainly see that different specific B3s would be better for individual tissues (because of different local availability and expression of different enzymes governing the different metabolic routes (discussed here)), but that argues for preferential use of a particular form for a particular tissue, whereas you seem in general terms to be arguing the converse.

 

At the very least, imho, we are getting confused about the general benefits of B3 supplementation to address local deficiencies, and the wider question of addressing age-based decline in NAD levels.

I certainly agree with this if you eliminate the word "local." Thinking about it, it's not surprising that all NAD+ predursors might yield roughly equivalent elevations in NAD+ in young animals at RDAish levels, as there isn't any homeostatic pushback to using it all to make what is by definition needed NAD+ and nothing is pushing "excessive" consumption; it's as you get to higher doses where you might expect negative feedback and/or room for further increases in the steady-state level because of  "excessive" consumption where particular forms might shine. But for that, as I said, we need more dose-ranging studies using multiple forms and across different age groups (though most especially in normally-aging animals).

 

 

If the enzyme system is intact, an NAD crisis could occur due to either increased NAD consumption, or decreased precursor availability.  This could easily be happening under local conditions, such as skin or retina exposed to UV radiation and/or reduced circulation (accompanying aging).  (I bet in general body surfaces are more vulnerable to this combination of conditions.)  Under such conditions, the NAD limitation can probably be largely addressed by NAM supplementation, as has been shown in prevention of skin cancer and glaucoma.  NR and NMN supplementation will almost certainly also work, perhaps even more efficiently on a molar basis, but you'd want to prove that, and that their added expense was worth it.  (Personally, I'm currently taking 1000 mg of NAM during the night [time of greatest glaucoma risk], split into two 500 mg doses to deal with its one hour half-life, plus 250 mg of NR during day, figuring I'm getting both skin cancer and glaucoma protection from such dosing.)

 

On the other hand, we know that, with aging, the enzyme system does not remain intact (i.e., at youthful operating levels).  To address that, one needs to be more clever than just adding a lot of NAM precursor.  This is where NR and NMN supplementation might get a leg up on NAM, bypassing, for example, a rate-limiting step involving Nampt (and Nrk in the case of NMN)... assuming you can actually get intact NR and NMN to where they need to be.  And this might be a more general solution to reduced NAD levels with aging, rather than simply addressing local precursor deficiency.  (We also have NAM enzyme inhibition effects to consider.)

 

Anyway, that's where I've gotten to after all these years of reviewing NAD-related literature and these threads.  I'm interested, as always, in your take on all of this, especially the relative merits of NAM vs. other NAD precursors.  (btw, I tried taking NR in middle of night instead of NAM, but it kept me awake rest of night, with is bad for glaucoma, raising eye pressure further, while I have no such issue with NAM.)

[Michael]

Your argument makes a lot of sense. I'm skeptical that you could really get a local deficit of precursor availability (the B3s are all water-soluble), but local deficits secondary to local disease processes could certainly occur that would be quite distinct from the apparently global metabolic lowering of NAD+ levels in aging, and if they're independent of NAMPT levels & activity then there would be no need to bypass NAMPT — just to get more precursor.

[warner]

Your argument makes a lot of sense. I'm skeptical that you could really get a local deficit of precursor availability (the B3s are all water-soluble), but local deficits secondary to local disease processes could certainly occur that would be quite distinct from the apparently global metabolic lowering of NAD+ levels in aging, and if they're independent of NAMPT levels & activity then there would be no need to bypass NAMPT — just to get more precursor.

A "local disease process" may have similar effects on reducing NAD bioavailability as does, for example, a non-disease state like UV skin radiation (producing DNA damage, consuming more NAD) combined with reduced circulation related in some way to natural aging.  And regardless of B3 solubility, if circulation/perfusion is reduced enough, the tissue will suffer, not requiring a specific disease process.  So I think speaking of "local" B3/NAD deficits benefiting from (just about any type of) NAD precursor supplementation, whether disease-related or not, is probably a useful addition to our NAD thinking.

 

wrt NAM specifically, I estimated (from literature) its half-life to be about 1 hour, with a peak concentration of about 10 ug/ml at 30 minutes, falling to about 1.25 ug/ml, about 3.5 hours after a 500 mg NAM supplementation.  I then repeat the 500 mg supplementation to get me through the rest of the night.  This 1 gram total over about 7 hours is roughly the human equivalent (about 3g/d) of what the mice were getting (from their water) in the papers that greatly reduced glaucoma progression with NAM.  And since vulnerability to this progression is thought to be highest at night, it makes sense to raise NAM levels during that time.  (I also take 250 mg NR during day, perhaps adding some protection from skin cancer too.)

 

Interestingly, my (normal tension) glaucoma is not really a "disease" as much as it is a genetic predisposition to lower retinal and optic nerve head perfusion.  In other words, under normal conditions, if I eat right, sleep right, etc., then there is no progression since perfusion is adequate.  However, that's an impossible standard to meet, and the purposely elevated NAM is there to protect me from unplanned episodes of reduced perfusion.  Note too that, in a sense, I've always had this glaucoma - I just needed to destroy enough retinal nerve fiber to recognize the vulnerability.  So this is a good example of why it is probably not useful to try to distinguish between "disease" and "non-disease" processes when it comes to local NAD depletion.  I have more of a vulnerability than a disease, and this vulnerability is not reduced by normal levels of B3, regardless of its water solubility.

[Michael]

To anyone who was following the discussioin on NAD+ precursors and glaucoma: these posts have now been moved to this thread.

[Michael]

Slobec: as noted above, posts about NAD+ precursors and glaucoma have now been moved to this thread. The paper you link on this subject is already linked there, so unless you object, I'm going to delete your post.

 

MikeDC: you posted this same material in the NMN thread, and then opened a new thread on "NAD+ increase from oral intake of NR and NMN" with the same information. Accordingly, I'm going to move these redundant posts over there. Please stop posting the same material in multiple threads. If you perseverate, I'm going to just start deleting redundant posts without notice.

 

Anyone with cogent objections to these moves, please chime in promptly.

 

(EDIT: Done, 4 hours later).

Edited by Michael, 26 February 2018 - 07:34 PM.
Done