Lipoic acid
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Lipoic acid is the trivial name for 6,8-dithiooctanoic acid, ( HSCH2CH2CH(SH)C4H8COOH ) which is regarded as a coenzyme in the oxoglutarate dehydrogenase complex of the citric acid cycle. It is generally involved in oxidative decarboxylations of keto acids and is presented as a growth factor for some organisms.
Lipoic acid exists as two enantiomers, the R-enantiomer and the S-enantiomer. Normally only the R-enantiomer of an amino acid is biologically active, but for lipoic acid the S-enantiomer assists in the reduction of the R-enantiomer when a racemic mixture is given.
Some recent studies have suggested that the S-enantiomer in fact has an inhibiting effect on the R-enantiomer, reducing its biological activity substantially and actually adding to oxidative stress rather than reducing it. Furthermore, the S-enantiomer has been found to reduce the expression of GLUT-4s in cells, responsible for glucose uptake, and hence reduce insulin sensitivity.
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Chelation therapy
Lipoic acid (or α-lipoic acid) is able to pass the blood-brain barrier and is putatively used for detoxification of mercury attached to the brain cells. It can mobilise bound mercury into the blood stream as it is a mercaptan (sulfur compound which readily binds to the mercury). In the blood stream, another chelator such as dimercaptosuccinic acid (DMSA) or methylsulfonylmethane (MSM) is used to transfer mercury safely into the urine for excretion. Neither DMSA nor MSM can cross the blood-brain barrier, which is why both lipoic acid and DMSA are used. It is hypothesized that this treatment—along with carnitine, dimethylglycine (DMG), Vitamin B6, folic acid, and magnesium—could be used to treat autism and amalgam poisoning. In this hypothesis, the reason why autism is difficult to treat is that mercury is attached to the brain cells and most medicines and vitamin supplements do not penetrate the blood-brain barrier. However, α-lipoic acid and perhaps vitamin B12 could making it possible for other chelators to remove mercury safely out of the body and could perhaps one day be used as a treatment for autism.
Because lipoic acid is related to cellular uptake of glucose and it is both soluble in water and fat, it is being used for treatment in diabetes. Studies of rat aging have shown that the use of carnitine and lipoic acid results in improved memory performance and delayed structural mitochondrial decay. As a result, it may be helpful for people with Alzheimer's disease or Parkinson's disease.
Controversy
While there is no doubt that chelation therapy can be beneficial in cases of acute heavy metal poisoning its value is disputed in other cases. Further, conventional medicine does not accept the existence of a link between mercury poisoning and autism [1] (http://www.cbsnews.com/stories/2004/05/18/health/main618142.shtml).
Very large doses of 6,8-dithiooctanoic acid are themselves toxic. The lowest reported dosage to exhibit toxic side-effects (TDLo) was 0.83 mg/kg (total dose less than 1/20 gram). The oral LD50 for experimental rodents was found to be between 500 and 1000 mg/kg.
External links
- Lipoic Acid (http://www.benbest.com/nutrceut/lipoic.html)
References
- Lester Packer et al, 2001, Molecular aspects of Lipoic Acid in the prevention of Diabetes complications. Nutrition 17:888-895.
- Sabine Lijffelhardt et al, 1995, Interaction of a-Lipoic Acid enantiomers and homologues with the enzyme components of the mammalian Pyruvate Dehydrogenase Complex Biochomcal Pharmacology 50:5:637.