I don't have a grip on it, either, and it's pretty important with our illness. When people ask, "Do we want to raise it or lower it?", I think the answer is probably "It depends". Some papers I've seen claim we have low basal levels of NO, and we need more, as that would attenuate the high peaks, when they happen. Others hypothesize that our iNOS is high, but eNOS and nNOS may be depressed.
Yes, the info about NO and NOS, (nitric oxide synthase), in ME/CFS is equivocal. From reading about it, elevated NO can cause numerous problems in the body. Elevated NO from iNOS, (induced NOS), is caused by infections, and can be much much higher than the other forms.
I believe elevated NO from iNOS may be common in ME/CFS because we can have 'occult' infections that aren't easily detected in typical blood tests.
NO can be elevated from increased LPS from overgrowth of strains of e. coli, staph., or even lactic acid bacteria, such as L. Plantarum. These bacteria are considered to be normal and commensal, true, but can over produce metabolites if overgrown : lactic acid, nitric oxide, etc.
Lactic acid and nitric oxide are important and useful, until, like everything else, they are in excess.
These past two weeks, I've been stricken with migraines, again. Driven by pain, I researched and found a correlation between elevated NO and migraine. ( various causes for folks)
I also have a history of polyuria and dehydration.
I took the antibiotic, rifaximin, low dose, to rid some possible NO producing bacteria. The migraines are gone, but, I'd rather try something else.
Reishi mushrooms look to be a possibility. They might could lower blood glucose a little, so probably best taken with meals. ( I think some studies use very high doses.)
@Violeta , would you mind describing your trials with Reishi mushrooms? ( brand, dosage, etc.)
Thanks.