Thiamine Status in Humans and Content of Phosphorylated Thiamine Derivatives in Biopsies and Cultured Cells

in PLoS ONE (2010), 5(10), 13616

Background Thiamine (vitamin B1) is an essential molecule for all life forms because thiamine diphosphate (ThDP) is an indispensable cofactor for oxidative energy metabolism. The less abundant thiamine ... [more ▼]

Background Thiamine (vitamin B1) is an essential molecule for all life forms because thiamine diphosphate (ThDP) is an indispensable cofactor for oxidative energy metabolism. The less abundant thiamine monophosphate (ThMP), thiamine triphosphate (ThTP) and adenosine thiamine triphosphate (AThTP), present in many organisms, may have still unidentified physiological functions. Diseases linked to thiamine deficiency (polyneuritis, Wernicke-Korsakoff syndrome) remain frequent among alcohol abusers and other risk populations. This is the first comprehensive study on the distribution of thiamine derivatives in human biopsies, body fluids and cell lines. Methodology and Principal Findings Thiamine derivatives were determined by HPLC. In human tissues, the total thiamine content is lower than in other animal species. ThDP is the major thiamine compound and tissue levels decrease at high age. In semen, ThDP content correlates with the concentration of spermatozoa but not with their motility. The proportion of ThTP is higher in humans than in rodents, probably because of a lower 25-kDa ThTPase activity. The expression and activity of this enzyme seems to correlate with the degree of cell differentiation. ThTP was present in nearly all brain and muscle samples and in ~60% of other tissue samples, in particular fetal tissue and cultured cells. A low ([ThTP]+[ThMP])/([Thiamine]+[ThMP]) ratio was found in cardiovascular tissues of patients with cardiac insufficiency. AThTP was detected only sporadically in adult tissues but was found more consistently in fetal tissues and cell lines. Conclusions and Significance The high sensitivity of humans to thiamine deficiency is probably linked to low circulating thiamine concentrations and low ThDP tissue contents. ThTP levels are relatively high in many human tissues, as a result of low expression of the 25-kDa ThTPase. Another novel finding is the presence of ThTP and AThTP in poorly differentiated fast-growing cells, suggesting a hitherto unsuspected link between these compounds and cell division or differentiation. [less ▲]

Synthesis of thiamine triphosphate in brain mitochondria and E. coli: possible role of FoF1-ATPase

Scientific conference (2010)

Thiaminylated adenine nucleotides — chemical synthesis, structural characterization and natural occurrence

in FEBS Journal (2009), 276(12), 32563268

Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine ... [more ▼]

Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate (AThTP), produced in E. coli in response to carbon starvation. Here, we show that the chemical synthesis of AThTP leads to another new compound, adenosine thiamine diphosphate (thiaminylated ADP, AThDP), as a side product. The structure of both compounds was confirmed by mass spectrometry and 1H-, 13C- and 31P-NMR and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared to the conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a through-space interaction with the adenosine moiety, suggesting an U-shaped folding of adenosine thiamine derivatives. Such a structure where the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, AThTP may account for 15% of total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and in some cell lines. Using a HPLC method, we show for the first time that AThDP may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate. [less ▲]

Thiamin diphosphate in biological chemistry: new aspects of thiamin metabolism, especially triphosphate derivatives acting other than as cofactors

in FEBS Journal (2009), 276(11), 2917-2925

Prokaryotes, yeasts and plants synthesize thiamine (vitamin B1) via complex pathways. Animal cells capture the vitamin through specific high-affinity transporters essential for internal thiamine ... [more ▼]

Prokaryotes, yeasts and plants synthesize thiamine (vitamin B1) via complex pathways. Animal cells capture the vitamin through specific high-affinity transporters essential for internal thiamine homeostasis. Inside the cells, thiamine is phosphorylated to higher phosphate derivatives. Thiamine diphosphate (ThDP) is the best-known thiamine compound for its role as an enzymatic cofactor. However, besides ThDP, at least three other thiamine phosphates occur naturally in most cells: thiamine monophosphate (ThMP), thiamine triphosphate (ThTP) and the recently discovered adenosine thiamine triphosphate (AThTP). It was suggested that ThTP has a specific neurophysiological role, but recent data are in favor of a much more basic metabolic function. During amino acid starvation, Escherichia coli accumulate ThTP possibly acting as a signal involved in the adaptation of the bacteria to changing nutritional conditions. In animal cells, ThTP can phosphorylate some proteins, but the physiological significance of this mechanism remains unknown. AThTP, recently discovered in E. coli, accumulates during carbon starvation and might act as an alarmone. Among the proteins involved in thiamine metabolism, thiamine transporters, thiamine pyrophosphokinase and a soluble 25-kDa thiamine triphosphatase have been characterized at the molecular level, in contrast to thiamine mono- and diphosphatases whose specificities remain to be proven. A soluble enzyme catalyzing the synthesis of AThTP from ThDP and ADP or ATP has been partially characterized in E. coli, but the mechanism of ThTP synthesis remains elusive. The data reviewed here illustrate the complexity of thiamine biochemistry, which is not restricted to the cofactor role of ThDP. [less ▲]

Thiamine phosphate derivatives at the interface of cell bioenergetics and nucleotide metabolism: potential implications in aging and neurodegeneration

Scientific conference (2008)

Overexpression of airway CD39 in transgenic mice enhances lipopolysaccharide-induced inflammation.

in Purinergic Signalling (2008), 4

Adenylate Kinase-Independent Thiamine Triphosphate Accumulation under Severe Energy Stress in Escherichia Coli

in BMC Microbiology (2008), 8

BACKGROUND: Thiamine triphosphate (ThTP) exists in most organisms and might play a role in cellular stress responses. In E. coli, ThTP is accumulated in response to amino acid starvation but the mechanism ... [more ▼]

BACKGROUND: Thiamine triphosphate (ThTP) exists in most organisms and might play a role in cellular stress responses. In E. coli, ThTP is accumulated in response to amino acid starvation but the mechanism of its synthesis is still a matter of controversy. It has been suggested that ThTP is synthesized by an ATP-dependent specific thiamine diphosphate kinase. However, it is also known that vertebrate adenylate kinase 1 catalyzes ThTP synthesis at a very low rate and it has been postulated that this enzyme is responsible for ThTP synthesis in vivo. RESULTS: Here we show that bacterial, as vertebrate adenylate kinases are able to catalyze ThTP synthesis, but at a rate more than 106-fold lower than ATP synthesis. This activity is too low to explain the high rate of ThTP accumulation observed in E. coli during amino acid starvation. Moreover, bacteria from the heat-sensitive CV2 strain accumulate high amounts of ThTP (>50% of total thiamine) at 37 degrees C despite complete inactivation of adenylate kinase and a subsequent drop in cellular ATP. CONCLUSION: These results clearly demonstrate that adenylate kinase is not responsible for ThTP synthesis in vivo. Furthermore, they show that E. coli accumulate large amounts of ThTP under severe energy stress when ATP levels are very low, an observation not in favor of an ATP-dependent mechanisms for ThTP synthesis. [less ▲]

Thiamine triphosphate and adenosine thiamine triphosphate: New signals in bacterial stress response ?

Conference (2007)

At the crossroad of thiamine degradation and biosynthesis

in Nature Chemical Biology (2007), 3(8), 454-455

The physiological significance of thiaminase II has escaped our understanding for many years. The recent discovery of a new thiamine salvage pathway shows that this enzyme is involved in the regeneration ... [more ▼]

The physiological significance of thiaminase II has escaped our understanding for many years. The recent discovery of a new thiamine salvage pathway shows that this enzyme is involved in the regeneration of precursors for thiamine biosynthesis. [less ▲]

The antitrypanosomal drug melarsoprol competitively inhibits thiamin uptake in mouse neuroblastoma cells

in Cell Biology and Toxicology (2006), 22(3), 183-187

Melarsoprol is the main drug used for the treatment of late-stage sleeping sickness, although it causes severe side-effects such as encephalopathy and polyneuropathy leading to death in some patients ... [more ▼]

Melarsoprol is the main drug used for the treatment of late-stage sleeping sickness, although it causes severe side-effects such as encephalopathy and polyneuropathy leading to death in some patients. Recent data suggest that melarsoprol and its active metabolite melarsenoxide interfere with thiamin transport and metabolism in E. coli and yeast, but there are no data concerning their possible effects on thiamin metabolism in mammalian cells. We tested both drugs on thiamin transport in cultured mouse neuroblastoma cells using C-14-labeled thiamin. Melarsoprol, competitively inhibits high-affinity thiamin transport in mouse neuroblastoma cells with a K-i of 44 mu mol/L. However, the active compound melarsenoxide has no inhibitory effect. This suggests that the side effects of melarsoprol treatment are unlikely to be due to inhibition of thiamin transport by melarsenoxide, its main metabolite in the brain. [less ▲]