Thiamine deficiency in rats affects thiamine metabolism possibly through the formation of oxidized thiamine pyrophosphate

Biochemical and medical aspects of vitamin B1 research

Vitamin B1 is an indispensable food factor for the human and animal body. In animals, vitamin B1 is found in the form of thiamine and its phosphate esters - thiamine mono-, di- and triphosphate, as well as an adenylated derivative - adenosine thiamine triphosphate. At present, the only vitamin B1 form with biochemical functions being elucidated is thiamine diphosphate, which serves as a coenzyme for several important enzymes involved in carbohydrate, amino acid, fatty acid and energy metabolism. Here we review the latest developments in the field of vitamin B1 research in animals. Transport, metabolism and biological role of thiamine and its derivatives are considered as well as the involvement of vitamin B1-dependent processes in human diseases and its therapeutic issues, a field that has gained momentum with several important recent developments.

Thiamine disulfide derivatives in thiol redox regulation: Role of thioredoxin and glutathione systems

Thiamine (vitamin B1), under the proper conditions, is able to reversibly open the thiazole ring, forming a thiol-bearing molecule that can be further oxidized to the corresponding disulfide. To improve the bioavailability of the vitamin, several derivatives of thiamine in the thioester or disulfide form were developed and extensively studied over time, as apparent from the literature. We have examined three thiamine-derived disulfides: thiamine disulfide, sulbutiamine, and fursultiamine with reference to their intervention in modulating the thiol redox state. First, we observed that both glutathione and thioredoxin (Trx) systems were able to reduce the three disulfides. In particular, thioredoxin reductase (TrxR) reduced these disulfides either directly or in the presence of Trx. In Caco-2 cells, the thiamine disulfide derivatives did not modify the total thiol content, which, however, was significantly decreased by the concomitant inhibition of TrxR. When oxidative stress was induced by tert-butyl hydroperoxide, the thiamine disulfides exerted a protective effect, indicating that the thiol form deriving from the reduction of the disulfides might be the active species. Further, the thiamine disulfides examined were shown to increase the nuclear levels of the transcription factor nuclear factor erythroid 2 related factor 2 and to stimulate both expression and activity of NAD(P)H quinone dehydrogenase 1 and TrxR. However, other enzymes of the glutathione and Trx systems were scarcely affected. As the thiol redox balance plays a critical role in oxidative stress and inflammation, the information presented can be of interest for further research, considering the potential favorable effect exerted in the cell by many sulfur compounds, including the thiamine-derived disulfides.

Synthetic Thioesters of Thiamine: Promising Tools for Slowing Progression of Neurodegenerative Diseases

Thiamine (vitamin B1) is essential for the brain. This is attributed to the coenzyme role of thiamine diphosphate (ThDP) in glucose and energy metabolism. The synthetic thiamine prodrug, the thioester benfotiamine (BFT), has been extensively studied and has beneficial effects both in rodent models of neurodegeneration and in human clinical studies. BFT has no known adverse effects and improves cognitive outcomes in patients with mild Alzheimer's disease. In cell culture and animal models, BFT has antioxidant and anti-inflammatory properties that seem to be mediated by a mechanism independent of the coenzyme function of ThDP. Recent in vitro studies show that another thiamine thioester, O,S-dibenzoylthiamine (DBT), is even more efficient than BFT, especially with respect to its anti-inflammatory potency, and is effective at lower concentrations. Thiamine thioesters have pleiotropic properties linked to an increase in circulating thiamine concentrations and possibly in hitherto unidentified open thiazole ring derivatives. The identification of the active neuroprotective metabolites and the clarification of their mechanism of action open extremely promising perspectives in the field of neurodegenerative, neurodevelopmental, and psychiatric conditions. The present review aims to summarize existing data on the neuroprotective effects of thiamine thioesters and give a comprehensive account.

Reduced Nucleotides, Thiols and O2 in Cellular Redox Balance: A Biochemist's View

In the present review, which is aimed at researchers, teachers and students in life sciences, we try to show how the physicochemical properties of the elements and molecules define the concept of redox balance. Living organism are open systems traversed by fluxes of energy and matter. During catabolic oxidative metabolism, matter-mostly hydrogenated organic molecules-is oxidized and ultimately released as CO₂. Electrons are passed over to coupling molecules, such as NAD+ and FAD, whose reduced forms serve as electrons donors in anabolic reactions. Early photosynthetic activity led to the accumulation of O₂ and the transformation of the reduction to an oxidizing atmosphere, favoring the development of oxidative metabolism in living organisms. We focus on the specific properties of O₂ that provide the chemical energy for the combustion reactions occurring in living cells. We explain the concepts of redox potential and redox balance in complex systems such as living cells, we present the main redox couples involved in cellular redox balance and we discuss the chemical properties underlying their cellular roles and, in particular, their antioxidant properties in the defense against reactive oxygen species (ROS). Finally, we try to provide an integrative view emphasizing the interplay between metabolism, oxidative stress and metabolic compartmentation in mammalian cells.