thiamines

Thiamines are a class of compounds that contain a thiazolium ring linked to a pyrimidine ring. The most nutritionally significant member is thiamine, commonly known as vitamin B1. In humans, thiamine is rapidly phosphorylated to thiamine pyrophosphate (TPP, also called thiamine diphosphate), the main catalytic cofactor, and to a lesser extent to thiamine triphosphate. TPP serves as a coenzyme for several enzymes involved in carbohydrate metabolism, including pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and branched-chain ketoacid dehydrogenase, as well as transketolase in the pentose phosphate pathway.

Thiamine’s biological role centers on energy production. As a cofactor, TPP enables decarboxylation and transfer reactions essential for aerobic respiration and for maintaining cellular energy. Thiamine phosphate esters are required for the proper function of enzymes in sugar metabolism, amino acid catabolism, and nucleotide synthesis. The precise role of thiamine triphosphate is less clear but is thought to involve signaling and specific neural processes.

Dietary intake and metabolism: humans cannot synthesize thiamine and must obtain it from the diet. Good sources include pork, whole grains and fortified cereals, legumes, nuts, and enriched foods. Thiamine is absorbed primarily in the small intestine via specific transporters and, once inside cells, is phosphorylated to TPP by thiamine pyrophosphokinase. The body stores only small amounts, and excess is excreted in urine.

Deficiency of thiamine impairs energy metabolism and can cause beriberi (dry or wet) and Wernicke–Korsakoff syndrome, particularly in cases of chronic alcohol use, malnutrition, or malabsorption. Diagnosis involves clinical assessment, thiamine status testing, and sometimes erythrocyte transketolase activity. Treatment is rapid thiamine replacement, with prevention through adequate dietary intake and, in high-risk populations, fortification and supplementation.