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I updated my above post, and added the entire list of drugs and supplements I compiled that protect against quinolinic acid-induced neurotoxicity.
Yes, I did see that link, thanks @Wayne (in fact it was @dannybex's post about quinolinic acid that promoted me think of this thread and brain lesions, as quinolinic acid can cause such lesions).
But I could not find any references about niacin reducing quinolinic acid neurotoxicity, and I can't see from the reference cited how niacin can inhibit quinolinic acid neurotoxicity, unless I am missing an important point.
Although interestingly, picolinic acid has been found to block the neurotoxic (but not the neuroexcitant) effects of quinolinic acid. 1 Picolinic acid is an isomer of nicotinic acid (niacin).
I think picolinic acid can be found in supplements such as zinc picolinate.
That's correct that niacin may not directly reduce QA neurotoxicity, but it's my understanding that if one gets sufficient amounts of niacin, then tryptophan won't be broken down, resulting in lower levels of quinolinic acid.
Tryptophan may not be needed for NAD + synthesis as long as the supply of niacin in the diet is sufficient. Niacin poor diets lead to increased dependence on tryptophan breakdown for NAD + synthesis.
I think you are alluding to the following statement from the study:
However, I am not entirely sure (because I really don't know much about it), but I don't think NAD+ synthesis is the same pathway as the pathway in microglia which during inflammation creates quinolinic acid from tryptophan via the action of the enzyme IDO (indoleamine-2-3-dioxygenase).
With the appropriate vitamin B6, quinolinic acid is not the final product of tryptophan catabolism, NAD+ or niacin is, and any damage initiated by quinolinic acid as a natural by-product within this pathway is offset by two neuroprotective factors, kynurenine and picolinic acid.
This paper found that "Serum quinolinic acid was increased only in the cobalamin-deficient rats."
Many of us have high B12 levels, but perhaps there's a functional deficiency?
Also, this study found 'folic acid' protected 'susceptible retinal neurons from the neurotoxic effects' of quinolinic acid in chick retinas.
I appreciate your reply.
This is what so frustrating about this whole situation. Dr. Marrs says B6 prevents it, while Yasko and others say the exact opposite. And since I've been unable to tolerate B6 (I used to get 'stocking-glove' neuropathy, but in the last 8-9 months, stronger myoclonic-like jerks in my feet in bed -- QA's been shown to induce convulsions) it makes me wonder if that's due to B6 causing increased levels of QA.
It's even more frustrating because it seems like 99% of studies done (especially on humans) from any nutritional perspective are typically pre-1975 and thus the full papers are extremely difficult to pull up. But I've seen a case study with 2 siblings where QA excretion decreased when they were given B6, and then the opposite in an older study.
Of course I can't find Yasko's paper when I need it, but here's @aquariusgirl 's post which quotes it:
"I’ve noted that in certain instances, the use of high dose B6 or P5P is not always helpful, and may cause overstimulatory or OCD type behaviors. While kynurenic acid is a calming neurotransmitter, it’s converted by B6 or P5P into quinolinic acid, which is an excitotoxin that can aggravate the nervous system."
But then again, if niacin lowers quinolinate levels, then why don't I just take it and shut the ____ up? Well, I've tried it off and on for a couple months, but it seems to increase histamine levels, and so I end up w/watery eyes, strained eyesight, and (sorry) more frustration.
Would be really interested to hear from others with elevated quinolinic on their OAT.
Did niacin help? Did B6? Or did B6 make things worse?
Do you suffer from b6/p5p intolerance symptoms and have high quinolinic?
Anyway, thanks @Hip. I've tried cucurmin but it's really constipating for me. Maybe could try a tiny dose.