Overactivity of CBS causes low glutathione, high ammonia and overproduction of sulfur compounds. This is very common, especially in autistics. CBS* is the critical enzyme in converting homocysteine to cystathionine (see Methionine cycle, step 4, lower half of diagram).
* Cystathionine beta synthase.
Thus, with upregulation of CBS:
Homocysteine + B6 (as P5P) + Mg + CBS yields overabundant Cystine (instead of cysteine) + excess Ammonia + AKG
Accumulating sulfur metabolites promote formation of cystine rather than cysteine (and then, hydrogen sulfide and thiosulfates.) Lacking cysteine, glutathione cannot be formed. Oxidative stress becomes profound. Methyl cannot attach to B12, impeding the transformation of homocysteine to methionine. Formation of homocysteine from SAH is also suppressed.
The ammonia creates brain fog. In part, because ammonia inhibits axonal electrical potentials, decreases brain ATP, causes astrocyte inflammation. And also because it depletes BH4, which is used in forming tyrosine, dopamine, norepinephrine and serotonin.
In summary, CBS upregulation leads to: Severe oxidative stress. Failure to form methionine and glutathione. Low SAM. SAH and perhaps some HCY accumulation. Toxic sulfur compounds. Ammonia overload. Brain fog.
Elevated urinary sulfurs. (Check ammonia and sulfur periodically. The individual can do this themselves with urinary test strips.)
Homocysteine on the low side.
Diets high in sulfur foods worsen the accumulation of detrimental sulfurs. Animal proteins, and sulfur in foods, nutrients and meds often need to be restricted (perhaps even NAC and glutathione), at least until sulfurs start to normalize.
GABA may be indicated, if anxiety or overstimulation is developing. (Roberts)
Toxic metal accumulation and metal metabolism dysfunction may have some association with CBS overactivity. (Roberts, See section on CBS.)
Yucca to help detox ammonia.
RNA support to help neutralize ammonia.
Activated charcoal to neutralize ammonia (at night, with magnesium citrate to insure removal).
Carnitine / CoQ10/ and or NADH if needed to support energy levels.
Countering oxidative stress.
NAC and selenium foster creation of glutathione. Reduced glutathione can be taken. Relatively absorbable forms include sublinguals, creams, sprays (as liposomal preparations), IVs, or suppositories.
Reduce factors worsening oxidative stress, such as, toxicity, illness, poor diet, stress, overexertion and metal metabolism dysfunction. Also, avoid excitotoxins.
Mercury levels may need attention, as mercury will readily bind to the abundant sulfhydryl (thiol) groups and, via the bloodstream, gain greater access to body tissues (Cutler).
Methylation cycle issues.
The sulfur pathway may need to be dealt with first to prevent draining out of precursors, as well to encourage enough glutathione to methylate B12. (Roberts)
To support methylation, glutathione and methyl-B12 may need to be provided directly. (Walsh)
Betaine may help create some methionine, if the betaine pathway is working effectively. But usually, methionine and/or SAM is needed. (Walsh)
Reminder: This information is presented for educational purposes only, and is not intended as diagnosis or treatment recommendations for the individual. Even within the histadelic subgroup, each person's biochemical requirements tend to be unique. So if you need treatment for depression, mania, bipolar, or any other medical condition, please consult a knowledgeable physician.
Next posts: Sulfites, sulfates. Salicylates and phenols.
For info on the role of histadelia in bipolar disorder, see my book, Natural Healing for Bipolar Disorder