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Nauka => Tekstovi => Topic started by: Bred on 24-08-2006, 15:35:45

Title: Thiamine
Post by: Bred on 24-08-2006, 15:35:45
For the similarly-spelled nucleic acid, see Thymine
Thiamine or thiamin, also known as vitamin B1, is a colorless compound with chemical formula C12H17N4OS. It is soluble in water and insoluble in alcohol. Thiamine decomposes if heated. Thiamine was first discovered in 1910 by Umetaro Suzuki of Japan when researching how rice bran cured patients of Beriberi. He named it aberic acid.

Contents [hide]
1 Biological roles
2 Nutrition
2.1 Deficiency
2.2 Diagnostic Testing for B1 Deficiency
2.3 Overdose
2.4 Genetic diseases
2.5 Good sources
3 References
4 External links
 


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Biological roles
 
Thiamine pyrophosphate (TPP)Thiamine pyrophosphate (TPP) is a coenzyme for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and transketolase. The first two of these enzymes function in the metabolism of carbohydrates, while transketolase functions in the pentose phosphate pathway to synthesize NADPH and the pentose sugars deoxyribose and ribose. TPP is synthesized by the enzyme thiamine pyrophosphokinase, which requires free thiamine, magnesium, and adenosine triphosphate.

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Nutrition
Also known as vitamin B1, thiamine plays an important role in helping the body convert carbohydrates and fat into 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.

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Deficiency
Systemic thiamine deficiency can lead to myriad problems including neurodegeneration, wasting, and death. A lack of thiamine can be caused by malnutrition, 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) [1].

Well-known syndromes caused by thiamine deficiency include Wernicke-Korsakoff syndrome and beriberi, diseases also common in chronic abusers of alcohol.

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Diagnostic Testing for B1 Deficiency
A positive diagnosis test for Thiamine deficiency can be assertained by measuring erythrocyte levels of transketolase in serum.

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Overdose
The only known cases of thiamine overdose occurred with thiamine injections. Thiamine injection may result in anaphylactic reactions.

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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.

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Good sources
Thiamine is found naturally in the following foods, each of which contains at least 0.1mg of the vitamin per 28-100g (1-3.5oz): - Green peas - Spinach - Liver - Beef - Pork - Navy beans - Nuts - Pinto beans - Soybeans

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References
Jane Higdon, "Thiamin", Micronutrient Information Center, Linus Pauling Institute

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