Authors: Mallat J, Lemyze M, Thevenin D
PMID: 27293820 PMCID: PMC4885988 DOI: 10.21037/jtd.2016.04.32
Abstract
Thiamine was the first B vitamin to be identified and is also referred to as vitamin B1. It is a water-soluble vitamin that is an indispensable constituent of cellular metabolism. A lack of this vitamin can, therefore, be potentially life-threatening. Thiamine is present in the human body as free thiamine and as various phosphorylated forms: thiamine monophosphate, thiamine diphosphate, also known as thiamine pyrophosphate (TPP), which is the most important and active form of this vitamin, and thiamine triphosphate. Thiamin pyrophosphate is an intracellular compound, which is why it can be considered as the best marker of thiamine nutritional status. It acts in concomitance with magnesium to expedite various mitochondrial oxidative decarboxylation reactions. Thiamin pyrophosphate is necessary as a cofactor for branched-chain ketoacid dehydrogenase complex essential for the metabolism of the branched-chain amino acids and for two critical complexes required for the mitochondrial synthesis of adenosine triphosphate (ATP): pyruvate and 2-oxoglutarate dehydrogenase (α-ketoglutarate) complexes. Specifically, TPP is a catalyst in the reactions of pyruvate to acetyl-Coenzyme A and α-ketoglutarate to succinyl-Coenzyme A in the Krebs cycle. Also, TPP serves as a coenzyme for transketolase, a cytosolic enzyme implicated in the pentose phosphate pathway, that functions in maintaining cell redox status through the production of NADPH (reduced nicotinamide adenine dinucleotide phosphate) and glutathione. Thus, thiamine is an essential source of energy generation from glucose, via the conversion of pyruvate from glucose into acetyl-Coenzyme A for access to the tricarboxylic acid cycle, and lack of thiamine leads to alterations in intermediate metabolism that end-up in lactic acidosis.
Keywords: thiamine, septic shock, vitamin B
