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Functional Assessment of Urinary Neuro-biogenic Amines—A COMPREHENSIVE GUIDE

119

transport chain within the mitochondria

and inhibits the generation of reactive

oxygen species. Oxidative stress (the

production of radical oxygen species)

is associated with many neurologic dis-

orders. Taurine does not cross the blood

brain barrier (BBB) easily and must be

synthesized within the CNS.

Effects:

Decreased

taurine levels may occur

due to dietary insufficiency or digestion

and absorption issues in the gastrointes-

tinal tract. Decreased CNS taurine syn-

thesis has been reported in individuals

with autoimmune and neurodegenera-

tive diseases, including rheumatoid ar-

thritis, Parkinson’s disease, Alzheimer’s

disease, and motor neuron diseases such

as amyotrophic lateral sclerosis (ALS).

Low levels of taurine during develop-

ment may result in abnormal brain de-

velopment. A low urinary taurine due

to a renal clearance disorder may occa-

sionally mask an elevated plasma taurine

level.

Excess

urinary taurine levels may re-

sult from inherited renal defects, liver

disease, heart disease or radiation injury.

High plasma taurine may be associat-

ed with stress reactions, depression and

psychosis. Plasma and urinary taurine

may increase due to liver inflammation

or disease. Oral supplementation may

raise taurine levels. Taurine is an ingre-

dient in many “energy drinks” and tau-

rine supplements may be used by ath-

letes. Taurine supplements may be used

to treat seizure disorders, autism and

attention deficit-hyperactivity disorder

(ADHD). Patients with Cushing’s dis-

ease may have elevated urinary taurine

levels, but low plasma levels. Patients

with autism may have elevated urine

taurine, glycine and alanine with low

glutamate.

Synthesis and Metabolism:

Taurine

BHMT

Methionine

SAMe

CBS

AHCY

MTR

Homocysteine

DNA

RNA

Protein

Lipids

SAH

TMG

methyltransferases

MTRR

Cystathionine

Cysteine

Sulfite

CTH CDO CSAD

Hypotaurine

dehydrogenase

adenosine

DMG

B12

Taurine synthesis from cysteine.

The methylation pathway (as it is commonly known) synthesizes cysteine behind the blood-brain barrier, and is a

precursor for the antioxidants taurine and glutathione.

Legend

: AHCY = adenosylhomocysteinase; BHMT = betaine-homocysteine methyltransferase; CBS; CTH = Cystathionine gamma-lyase;

CDO = Cysteine dioxygenase; CSAD = cysteine sulfinate decarboxylase; MTR = methionine synthase; MTRR = methionine synthase reductase;

MTHFR = methylenetetrahydrofolate reductase; SUOX