Cofactors needed for proper neurotransmitter production
The generic protocol developed for management of neurotransmitter dysfunction relating to the catecholamine system and/or serotonin system was developed by Marty Hinz, MD and involves the use of the amino acids tyrosine, 5-HTP, and cysteine along with the cofactors needed for neurotransmitter synthesis, including vitamin C, vitamin B6, calcium, selenium and folic acid. Results do not appear to be dependent on taking the amino acids with or without food; however, taking amino acids on an empty stomach should improve absorption and uptake and is therefore preferred.
The use of cysteine, selenium and folic acid are used to prevent depletion of the methionine-homocysteine cycle by L-dopa (and presumably by L-tyrosine as it is the immediate precursor of L-dopa). Administration of L-dopa leads to depletion of S-adenosyl-methionine (SAMe) which acts as a methyl donor in many important reactions and is part of the methionine-homocysteine cycle (which, amongst other things, helps maintain healthy homocysteine levels).
In addition, proper levels of SAMe are needed in order for norepinephrine to be converted into epinephrine. Therefore, long-term use of L-dopa without proper administration of cysteine and folic acid can lead to the depletion of epinephrineas well as a loss of SAMe. (2)
Therefore all people taking L-dopa and/or L-tyrosine need to be supplemented with adequate levels of sulfur amino acids to prevent depletion of the methionine-homocysteine cycle, depletion of glutathione, depletion of epinephrine, and the other components dependent on the methionine-homocysteine cycle. While administration of any of the sulfur amino acids in the cycle is adequate if the dosing is high enough, cysteine is chosen because it is the most cost effective.
Selenium needs to be administered with cysteine to prevent cysteine (or any sulfur amino acids) from creating an environment that contributes to central nervous system neurotoxicity from methylmercury.
Methylmercury is formed in the body if body stores of mercury come into contact with a methyl donor, such as SAMe or cysteine. Methylmercury is a much more toxic and dangerous substances than elemental mercury, as it can cross the blood-brain-barrier and studies have shown that administration of sulfur-containing amino acids can potentially facilitate the concentration of methylmercury in the brain. (5) However, selenium irreversibly binds to methylmercury in the central nervous system rendering the methylmercury biologically inactive and non-toxic.(6) Therefore, by providing the body with sufficient selenium along with adequate sulfur amino acids, such as cysteine, the potential danger of methylmercury exposure is avoided.
Folic acid is required in order to provide optimal function of the folic acid cycle which keeps the methionine-homocysteine cycle functioning properly. Folic acid also plays a vital role in keeping homocysteine levels in check.
High levels of homocysteine can increase the risk of cardiovascular disease, Alzheimer’s disease and bone fracture. It can take 3 to 6 months for high homocysteine levels to return to normal once proper levels of folic acid, B6 and B12 are established. As noted previously, without proper administration of amino acids of the methionine-homocysteine cycle epinephrine is depleted. It appears to be no coincidence that it can take 3 to 6 months for epinephrine levels to return to normal, a fact that appears to parallel proper balance in the methionine-homocysteine cycle with corresponding homocysteine improvement.