:Taurine:

Function: antiseizure, antioxidant.

Taurine is a sulfur-bearing amino acid like methionine, cystine, cysteine and homocysteine. It is a lesser-known amino acid because it is not incorporated into the structural building blocks of protein. Yet taurine is an essential amino acid in pre-term and newborn infants of humans and many other species. Adults can synthesize their own taurine, yet are probably dependent in part on dietary taurine. Taurine is abundant in the brain, heart, breast, gallbladder and kidney and has important roles in health and disease in these organs.

Taurine has many diverse biological functions serving as a neurotransmitter in the brain, a stabilizer of cell membranes and a facilitator in the transport of ions such as sodium, potassium, calcium and magnesium. Taurine is highly concentrated in animal and fish protein, which are good sources of dietary taurine. It can be synthesized by the body from cysteine when vitamin B6 is present. Deficiency of taurine occurs in premature infants and neonates fed formula milk, and in various disease states.

Inborn errors of taurine metabolism have been described, With, low blood taurine resulting in early signs of depression, lethargy, fatigability, sleep disturbances, progressive weight loss and depth perception impairment. Later, a Parkinson's syndrome developed and progressed to coma and then death.

Another inborn error of taurine metabolism has been described, with mitral valve prolapse associated with a rapidly progressive form of congestive cardiomyopathy. These patents have elevated urinary taurine levels and depressed levels of myocardial (heart muscle) taurine. There may be a subcategory of taurine-responsive mitral valve prolapse patients.

Taurine, after GABA, is the second most important inhibitory neurotransmitter in the brain. Its inhibitory effect is one source of taurine's anticonvulsant and antianxiety properties. It also lowers glutamic acid in the brain, and preliminary clinical trials suggest taurine may be useful in some forms of epilepsy. Taurine in the brain is usually associated with zinc or manganese. The amino acids alanine and glutamic acid, as well as pantothenic acid, inhibit taurine metabolism while vitamins A and B6, zinc and manganese help build taurine. Cysteine and B6 are the nutrients most directly involved in taurine synthesis. Taurine levels have been found to decrease significantly in many depressed patients.

One reason that the findings are not entirely clear is because taurine is often elevated in the blood of epileptics who need it. It is often difficult to distinguish compensatory changes in human biochemistry from true metabolic or deficiency disease.

Low levels of taurine are found in retinitis pigmentosa. Taurine deficiency in experimental animals produces degeneration of light-sensitive cells. Taurine has potential for herapeutic applications in eye diseases, especially of the retina.

Taurine has many important metabolic roles. Supplements can stimulate prolactin and insulin release. The parathyroid gland makes a peptide hormone called glutataurine (glutamic acid-taurine), which further demonstrates taurine's role in endocrinology. Taurine increases bilirubin and cholesterol excretion in bile, critical to normal gallbladder function. It seems to inhibit the effect of morphine and potentiate the effects of opiate antagonists.

Low plasma taurine levels have been found in a variety of conditions, i.e., depression, hypertension, hypothyroidism, gout, institutionalized patients, infertility, obesity, kidney failure and others.

Megataurine therapy has been proven to be useful in many patient groups, i.e., those with post myocardial infarction, congestive heart failure, elevated cholesterol or preventricular arrhythmias. Dying heart muscle quickly becomes depleted of taurine. Taurine may prove to be useful in patients with epilepsy, gallstones, mitral valve prolapse, hypertension, hyperbilirubinemia, retinitis pigmentosa, photosensitivity and diabetes. Effective supplements range from 500 mg to 5 g orally. Therapy can be guided by plasma amino acid determination. Taurine is usually well absorbed, and taurine levels can increase to five times normal during therapy without ill effects.