VITAMIN B1 Thiamine

Thiamine mononitrate

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 by Umetaro Suzuki in Japan when researching how rice bran cured patients of Beriberi. He named it aberic acid.

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.

Roles in disease

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).

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

Overdose

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

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.