Thiamine

For the similarly spelled nucleic acid, see Thymine

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Thiamine or thiamin, also known as vitamin B₁ and aneurine hydrochloride, is one of the B vitamins. It is a colorless compound with chemical formula C₁₂H₁₇N₄OS. It is soluble in water and insoluble in alcohol. Thiamine decomposes if heated. Its chemical structure contains a pyrimidine ring and a thiazole ring.

History

Thiamine was first discovered in 1910 by Umetaro Suzuki in Japan when researching how rice bran cured patients of beriberi. He named it aberic acid (later orizanin). He did not determine its chemical composition, nor that it was an amine.

It was first crystallized by Jansen and Donath in 1926 (they named it aneurin, for antineuritic vitamin).

Its chemical composition and synthesis was finally reported by Robert R. Williams in 1935. He also coined the name for it, thiamine.

Thiamine phosphate derivatives

There are four known natural thiamine phosphate derivatives: thiamine monophosphate (ThMP), thiamine diphosphate (ThDP) or thiamine pyrophosphate (TPP), thiamine triphosphate (ThTP), and the recently discovered adenosine thiamine triphosphate (AThTP).

Thiamine pyrophosphate

Thiamine pyrophosphate (TPP), also known as thiamine diphosphate (ThDP), is a coenzyme for several enzymes that catalyze the dehydrogenation (decarboxylation and subsequent conjugation to Coenzyme A) of alpha-keto acids. Examples include:

• In mammals:
  • pyruvate dehydrogenase and α-ketoglutarate dehydrogenase (metabolism of carbohydrates)
  • branched-chain alpha-keto acid dehydrogenase
  • 2-hydroxyphytanoyl-CoA lyase
  • transketolase (functions in the pentose phosphate pathway to synthesize NADPH and the pentose sugars deoxyribose and ribose)

• In other species:
  • pyruvate decarboxylase (in yeast)
  • several additional bacterial enzymes

TPP is synthesized by the enzyme thiamine pyrophosphokinase, which requires free thiamine, magnesium, and adenosine triphosphate.

Thiamine triphosphate

Thiamine triphosphate (ThTP) was long considered a specific neuroactive form of thiamine.

However, recently it was shown that ThTP exists in bacteria, fungi, plants and animals suggesting a much more general cellular role. In particular in E. coli it seems to play a role in response to amino acid starvation.

Adenosine thiamine triphosphate

Adenosine thiamine triphosphate (AThTP) or thiaminylated adenosine triphosphate has recently been discovered in Escherichia coli where it accumulates as a result of carbon starvation. In E. coli, AThTP may account for up to 20 % of total thiamine.

It also exists in lesser amounts in yeast, roots of higher plants and animal tissues.

Nutrition

Thiamine plays an important role in helping the body metabolize carbohydrates and fat to produce energy. It is essential for normal growth and development and helps to maintain proper functioning of the heart and the nervous and digestive systems. Thiamine is water-soluble and cannot be stored in the body; however, once absorbed, the vitamin is concentrated in muscle tissue.

Good sources

Thiamine is found naturally in the following foods, each of which contains at least 0.1 mg of the vitamin per 28-100 g (1-3.5 oz): Green peas, Spinach, Liver, Beef, Pork, Navy beans, Nuts, Pinto beans, Bananas, Soybeans, Goji berries, Whole-grains, Breads, Yeast,the aleurone layer of unpolished rice, and Legumes.

Deficiency

Systemic thiamine deficiency can lead to myriad problems including neurodegeneration, wasting and death. A lack of thiamine can be caused by malnutrition, alcoholism, a diet high in thiaminase-rich foods (raw freshwater fish, raw shellfish, ferns) and/or foods high in anti-thiamine factors (tea, coffee, betel nuts).

Well-known syndromes caused by thiamine deficiency include Wernicke-Korsakoff syndrome and beriberi, diseases also common with chronic alcoholism.

It is thought that many people with diabetes have a deficiency of thiamine [2] and that this may be linked to some of the complications that can occur.

Diagnostic testing for B1 deficiency

A positive diagnosis test for Thiamine deficiency can be ascertained by measuring the activity of transketolase in erythrocyte . Thiamine can also be seen directly in whole blood following the conversion of thiamine to a fluorescent thiochrome derivative.

August 10, 2007 article states deficiency of Vitamin B1 not revealed by above tests. See http://www2.warwick.ac.uk/newsandevents/pressreleases/researchers_find_vitamin/ for complete information regarding diabetic neuropathy and Vitamin B1 Deficiency.

Genetic diseases

Genetic diseases of thiamine transport are rare but serious. Thiamine Responsive Megaloblastic Anemia with diabetes mellitus and sensorineural deafness (TRMA) is an autosomal recessive disorder caused by mutations in the gene SLC19A2, a high affinity thiamine transporter. TRMA patients do not show signs of systemic thiamine deficiency, suggesting redundancy in the thiamine transport system. This has led to the discovery of a second high affinity thiamine transporter, SLC19A3.

Online Mendelian Inheritance in Man (OMIM) 249270

Research

High doses

The RDA in most countries is set at about 1.4 mg. However, tests on volunteers at daily doses of about 50 mg have claimed an increase in mental acuity.

Thiamine as an insect repellent

Some studies suggest that taking thiamine (vitamin B1) 25 mg to 50 mg three times per day is effective in reducing mosquito bites. A large intake of Thiamine produces a skin odor that is not detectable by humans, but is disagreeable to female mosquitoes. Thiamine takes more than 2 weeks before the odor fully saturates the skin. With the advances in topical preparations there is an increasing number of Thiamine based repellent products. Whilst there is considerable anecdotal evidence of Thiamine products being effective in the field (Australia, US and Canada), there have yet to be any clinical trials run to demonstrate the efficacy of these products.

Autism

A 2002 pilot study administered thiamine tetrahydrofurfuryl disulfide (TTFD) rectally to ten autism spectrum children, and found beneficial clinical effect in eight. This study has not been replicated and a 2006 review of thiamine by the same author did not mention thiamine's possible effect on autism.

External links

• "Branched-Chain Amino Acid Metabolism" at ncbi.nlm.nih.gov