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PubMed1989

Identity of soluble thiamine-binding protein with thiamine repressible acid phosphatase in Saccharomyces cerevisiae.

Two secretory glycoproteins of S. cerevisiae, a soluble thiamine-binding protein and a thiamine-repressible acid phosphatase, were shown to be repressed to a similar extent by excess thiamine in the growth medium. Thiamine-repressible acid phosphatase was co-purified throughout the purification of the soluble thiamine-binding protein. Purified and deglycosylated soluble thiamine-binding proteins exhibited both thiamine-binding and acid phosphatase activities on non-denaturing polyacrylamide gel electrophoresis. Heat treatment of the purified soluble thiamine-binding protein caused a decrease in both activities with a similar inactivation profile. Two thiamine-repressible acid phosphatase-defective mutants isolated were found to be also defective in soluble thiamine-binding activity. The uptake of [14C]thiamine phosphate esters, such as thiamine monophosphate and thiamine pyrophsphate, was remarkably impaired in the mutant cells, whereas the uptake of [14C]thiamine by the mutant was almost the same with that by the parent strain. From these results, it was concluded that the soluble thiamine-binding protein is identical to the thiamine-repressible acid phosphatase in S. cerevisiae, which is involved in the hydrolysis of exogenous thiamine phosphate esters in the periplasmic space prior to the uptake of their thiamine moiety by yeast cells.

Acid Phosphatase↗
PubMed1987

The relationship between blood thiamine levels and dietary thiamine content in diabetic outpatients and healthy subjects.

Forty-six diabetic outpatients consumed (1,533 +/- 308 kcal (mean +/- SD) per day, 205 +/- 42 g of carbohydrates, 73 +/- 18 g of protein, 49 +/- 18 g of fat, and 0.05 +/- 0.34 mg of thiamine. No significant correlation was found in 46 diabetic between blood thiamine level and the intake of dietary energy, carbohydrate or thiamine. In 13 healthy subjects given prepared diets, a significant correlation was found between blood thiamine level and dietary thiamine content, thiamine content per 1,000 kcal, and 24-h urinary thiamine amount divided by urinary creatinine. When 9 healthy subjects (6 males, 3 females) consumed 1,600 kcal with 0.6 mg of thiamine for two days, their blood thiamine level was 47 +/- 29.1 ng/ml before and 29.7 +/- 7.1 ng/ml after eating the diet, showing low blood thiamine levels due to the low content of dietary thiamine. When 5 or 6 healthy female subjects consumed 1,400 kcal with 1.6 mg of thiamine or 2,000 kcal with 1.9 mg of thiamine for two days, their blood thiamine level was 45.3 +/- 4.8 ng/ml or 57.7 +/- 8.4 ng/ml before and 51.5 +/- 11.7 ng/ml or 56.4 +/- 11.7 ng/ml after eating the diets, respectively. In both diabetic outpatients and healthy subjects, a significant positive correlation was found between blood thiamine levels and dietary thiamine concentrations per 1,000 kcal, and a significant positive correlation was also found between erythrocyte transketolase activity and dietary thiamine content.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1976

Thiamine transport in thiamine-deficient rats. Role of the unstirred water layer.

As part of a systematic study of alcoholism and thiamine absorption, the effect of diet-induced thiamine deficiency and the role of the unstirred water layer on the thiamine transport were investigated. Using 3H-labeled dextran as a marker of adherent mucosal volume, jejunal uptake of 14C-labeled thiamine hydrochloride was measured, in vitro, in thiamine-deficient rats and pair-fed controls. Uptake of low thiamine concentrations (0.2 and 0.5 muM) was greater in the thiamine-deficient rats than in the controls. In contrast, uptake rates for high thiamine concentrations (20 and 50 muM) were similar in both groups. While Jmax was unaltered, Km was decreased in thiamine deficiency, suggesting a decrease in unstirred water layer thickness. Accordingly, the thickness of the water layer was measured in both groups of animals and correlated with Jmax and Km under unstirred and stirred conditions. Without stirring, there was no difference in Jmax between the two groups. In contrast, both Km and the water layer were reduced in the thiamine-deficient rats. With stirring, Jmax was not affected, but both Km and the water layer thickness were reduced to similar values in both groups. Reversal of thiamine deficiency resulted in the return of thiamine uptake and the unstirred water layer thickness to control values. These data support the concept of a dual system of thiamine transport and emphasize the role of the unstirred water layer as an important determinant of transport kinetics not only under physiologic situations but also in diet-induced rat thiamine deficiency, a model for a clinical patholigical state. The decrease in the unstirred water layer thickness in thiamine deficiency may be also viewed as a possible adaptive mechanism to facilitate absorption of meager supplies of thiamine.

Animals↗
PubMed1992

Thiamine transport by erythrocytes and ghosts in thiamine-responsive megaloblastic anaemia.

A 9-year study of thiamine metabolism and cellular transport was performed in two patients with thiamine-responsive megaloblastic anaemia associated with diabetes mellitus and sensorineural deafness, in their relatives, and in age-matched controls from the same area. The ratios between the content of thiamine and that of its phosphoesters in erythrocytes were within the normal range, whereas the absolute values of thiamine and thiamine compounds were reduced by about 40% as compared to controls. Thiamine pyrophosphokinase activity was about 30% lower than in controls. Thiamine treatment restored the levels of thiamine and thiamine compounds to normal values, whereas kinase was unaffected. Both the saturable (specific, predominant at low, less than 2 mumol/L, physiological concentrations of thiamine) and the non-saturable component of thiamine transport were investigated. Erythrocytes and ghosts from patients exhibited no saturable component, this abnormality being specific for the patients and not shared by their parents. It is concluded that the cells from thiamine-responsive megaloblastic anaemia patients contain low levels of thiamine compounds, probably due to their inability to take up and retain physiological concentrations of thiamine, as a result of the lack of the saturable, specific component of transport and reduced thiamine pyrophosphokinase.

Anemia, Megaloblastic↗
PubMed1992

The concentration of thiamin and thiamin phosphate esters in patients with alcoholic liver cirrhosis.

The blood and plasma concentrations of thiamin and thiamin phosphate esters were determined concomitantly by high-performance liquid chromatography (HPLC) in 22 patients with alcoholic liver cirrhosis, and also in 10 of them 24 hr after a 100 mg thiamin i.m. injection. Sixteen patients were abstaining from alcohol at the time of the study, 6 were currently misusing alcohol. The control group included 30 healthy volunteers, of whom 10 were given the same thiamin injection as the patients. Blood thiamin diphosphate was the only compound decreased in the abstaining patients compared to controls (70.9 +/- 21.9 nmol/l vs. 84.4 +/- 19.0 nmol/l), but all thiamin compounds in blood and plasma were decreased in the misusing patients. All thiamin compounds (except blood monophosphate) were also significantly lower in the misusing than in the abstaining patients (plasma thiamin: 5.3 +/- 1.3 vs. 11.7 +/- 8.3 nmol/l; plasma monophosphate: 1.0 +/- 1.1 vs. 4.1 +/- 2.9 nmol/l; blood diphosphate: 45.7 +/- 18.3 vs. 70.9 +/- 21.9 nmol/l). Thiamin phosphorylation ratio was decreased in the patients after thiamin administration compared to controls (2.83 +/- 0.74 vs. 3.68 +/- 0.58). Plasma thiamin was higher in the abstaining patients than in the controls (11.7 +/- 8.4 nmol/l vs. 7.3 +/- 2.5 nmol/l), and above the mean + 2 SD of the controls in 31% of the abstaining patients. In conclusion, current ethanol misuse is associated with low thiamin concentrations, and liver cirrhosis is associated with a decreased thiamin diphosphate concentration and thiamin phosphorylation.

Adult↗
PubMed1997

Dietary thiamin supply during gestation effects thiamin status of lactating rats and their suckling offspring.

This investigation was designed to examine the effect of dietary thiamin supply during gestation on body thiamin status of lactating rats and their suckling offspring, and thiamin in milk from 1 to 13 days postpartum. Therefore, a study over two generations was conducted feeding 2, 6.7 and 20 mg/kg thiamin during gestation and 8 mg/kg thiamin during lactation. Rat dams receiving inadequate thiamin during gestation and their offspring were thiamin-deficient on the basis of reduced activity of transketolase in blood and erythrocytes, which did not reach completely the control level even two weeks postpartum. The thiamin intake during gestation influenced significantly the thiamin levels in tissues of the dams and their offspring. However, the observed dose-dependence remained only for the first days of lactation. The thiamin concentration in milk two days postpartum also reflected the nutritional thiamin status from the pregnant rats, in which the thiamin concentration raised continuously with the duration of the lactation cycle. The data indicate that an adequate thiamin supply during lactation can not completely compensate for an inadequate thiamin supply during gestation, and that necessitates a constant thiamin intake.

Animals↗
PubMed1984

Blood thiamine and thiamine phosphate ester concentrations in alcoholic and non-alcoholic liver diseases.

Thiamine state was investigated in patients with alcoholic liver disease, patients with various non-alcoholic liver diseases, and controls using a direct technique (thiochrome assay) to measure thiamine, thiamine monophospate, and the active coenzyme thiamine pyrophosphate in whole blood after isolating the fractions by ion exchange chromatography. Overall nutrition was similar in all groups as assessed by anthropometry, and no patient had clinical evidence of thiamine deficiency. There was no significant difference among the groups in mean concentration of any form of thiamine. The scatter was much greater in patients with alcoholic liver disease but only 8.7% had biochemical thiamine deficiency (defined as a blood concentration of the active coenzyme greater than 2 SD below the mean control value). An unexpected finding was of abnormally high total thiamine concentrations (greater than 2 SD above the mean control value) in 17.4% of patients with alcoholic liver disease, the highest concentrations being found in two patients with severe alcoholic hepatitis and cirrhosis. The ratio of phosphorylated to unphosphorylated thiamine was calculated as an index of phosphorylation and, although the mean did not differ significantly among the groups, the range was greatest in alcoholic liver disease. The lowest ratios occurred in the two patients with severe alcoholic hepatitis, but neither had evidence of thiamine pyrophosphate deficiency. Contrary to studies using indirect assay techniques, these results suggest that thiamine deficiency is unusual in well nourished patients with alcoholic liver disease. The new finding of unexpectedly high thiamine concentrations in some patients may be due to abnormalities of hepatic storage or release in liver disease, particularly in severe alcoholic hepatitis. There was no convincing evidence of impaired thiamine phosphorylation in any patients with liver disease. Conclusions from studies using indirect assays on the prevalence and mechanisms of thiamine deficiency in liver diseases may not be valid.

Adult↗
PubMed1993

Thiamin and thiamin phosphate ester deficiency assessed by high performance liquid chromatography in four clinical cases of Wernicke encephalopathy.

The concentrations of thiamin and thiamin phosphate esters were determined by high performance liquid chromatography in four patients with clinical Wernicke encephalopathy. Three were alcohol abusers, and one had prolonged vomiting and anorexia. Thiamin and thiamin monophosphate were assessed in plasma and whole blood (four patients) and in cerebrospinal fluid (two patients) before and during thiamin treatment. Thiamin diphosphate was also assessed in whole blood in the four patients. Before treatment, thiamin monophosphate was significantly decreased in all patients, and thiamin diphosphate in three. A poor increase in thiamin mono- and diphosphate was paralleled by a slow clinical improvement in one patient, while an increase in all thiamin compounds was observed in two patients with a rapid recovery. Thiamin monophosphate was a more sensitive marker of deficiency than thiamin diphosphate and unphosphorylated thiamin.

Adult↗
PubMed1987

Thiamine triphosphate and membrane-associated thiamine phosphatases in the electric organ of Electrophorus electricus.

The main electric organ of Electrophorus electricus is particularly rich in thiamine triphosphate, which represents 87% of the total thiamine content in this tissue. The thiamine pyrophosphate concentration, however, is very low in the eel electric organ and skeletal muscle as compared with other eel or rat tissues. Furthermore, electroplax membranes contain a whole set of enzymes responsible for the dephosphorylation of thiamine tri-, pyro- and monophosphate. Thiamine triphosphatase has a pH optimum of 6.8 and is dependent on Mg2+. The real substrate of the enzyme is probably a 1:1 complex of Mg2+ and thiamine triphosphate. Thiamine pyrophosphatase is activated by Ca2+. The apparent Km for thiamine triphosphate and Vmax are found to be, respectively, 1.76 mM and 5.95 nmol/mg of protein/min. Thiamine triphosphatase activity is inhibited at physiological K+ concentrations (up to 90 mM) and increasing Na+ concentrations (50% inhibition at 300 mM). ZnCl2 (10 mM) inhibits 90% of the enzyme activity. ATP and ITP are also strongly inhibitory. No significant effect of neurotoxins is seen. Membrane-associated thiamine triphosphatase is affected differently by proteolytic enzymes and is partially inactivated by pretreatment with phospholipase C and neuraminidase. The physiological significance of thiamine triphosphatase is discussed in relation to a specific role of thiamine in the nervous system.

Animals↗
PubMed1994

Further studies on erythrocyte thiamin transport and phosphorylation in seven patients with thiamin-responsive megaloblastic anaemia.

Erythrocyte thiamin metabolism and transport were investigated in 7 patients from Brazil, Israel and Italy suffering from thiamin-responsive megaloblastic anaemia (TRMA) associated with diabetes mellitus and sensorineural deafness. All patients discontinued thiamin therapy for 4-7 days before the investigation. TRMA patients showed invariably reduced total thiamin levels in erythrocytes (percentage reduction compared with healthy controls, -46.8 +/- 3%; mean +/- SEM). The proportions of individual thiamin compounds, expressed as a percentage of total thiamin content, were within the normal range, whereas their absolute amounts were significantly decreased in the following order: thiamin monophosphate > thiamin pyrophosphate > thiamin. Thiamin pyrophosphokinase activity was also reduced as compared with controls (mean reduction +/- SEM, -25.9 +/- 1%). The saturable, specific component of thiamin uptake, which normally prevails at physiological concentrations of thiamin (< 2 mumol/L), was absent in erythrocytes obtained from TRMA patients, while the non-saturable (diffusive) component of uptake was normally present. These results confirm observations made previously in two patients and demonstrate that TRMA is consistently associated with a state of thiamin deficiency, which is presumably secondary to reduced thiamin cellular transport and absorption (caused by lack of a membrane-specific carrier), and to impaired intracellular pyrophosphorylation.

Anemia, Megaloblastic↗
PubMed1990

Blood thiamine and thiamine phosphate concentrations in excessive drinkers with or without peripheral neuropathy.

The aim of our study was to answer the following questions: (1) is thiamine deficient in chronic excessive drinkers; and (2) is peripheral neuropathy associated with thiamine deficiency or with alcohol intake itself? We performed direct assays of blood concentrations of free thiamine and thiamine phosphate in excessive drinkers with or without peripheral neuropathy and in control subjects. We found no difference in free thiamine concentrations between excessive drinkers with and without neuropathy, and no difference in free thiamine concentrations between the two groups of excessive drinkers and the control group. By contrast, a deficiency in thiamine phosphate was observed in each group of excessive drinkers compared to the control group. This was reflected in blood concentrations of total thiamine which were also lower in excessive drinkers than in controls. Finally, the thiamine phosphate: free thiamine ratio was slightly but significantly lower in the two groups of excessive drinkers than in the control group. Both groups of excessive drinkers showed typical moderate liver disease of alcoholic origin. In conclusion, the free thiamine fraction was not diminished in this group of alcoholic hospital inpatients. Thiamine deficiency would not therefore appear to play a determining role in the onset of peripheral neuropathy. In contrast, the phosphorylated fraction was slightly reduced, probably owing to the liver disease in these subjects. Contrary to studies using indirect assay techniques, our results suggest that thiamine deficiency is either slight or absent in chronic drinkers.

Adult↗
PubMed1995

Comparison of erythrocyte transketolase activity with thiamine and thiamine phosphate ester levels in chronic alcoholic patients.

The effect of chronic alcoholism on biochemical evaluation of thiamine status was studied by the concomitant determination of erythrocyte transketolase (ETK) activity, its relative increase by in vitro addition of thiamine diphosphate (TDP effect) and the direct measurement of thiamine and its phosphate esters by high performance liquid chromatography. Thirty-eight percent of alcoholic subjects showed a thiamine deficiency with decreased thiamine diphosphate concentrations compared with healthy subjects (90.8 +/- 25.7 nmol/l vs. 176 +/- 28.0 nmol/l, respectively, mean +/- S.D., P < 0.001). Thiamine diphosphate concentrations were highly correlated with total thiamine concentrations and TDP effect (respectively r = 0.99 and 0.79, n = 85, P < 0.001). No abnormality in thiamine phosphorylation related to chronic alcoholism was noted. Finally, 47% of these deficient alcoholic patients had normal ETK activity. We concluded that, if indirect evaluation of thiamine status is to be chosen, the determination of ETK activity should be associated with TDP effect since the latter has been shown to be highly linked to total thiamine and thiamine diphosphate in erythrocytes. Furthermore, the direct measurement of thiamine and its phosphate esters was a more sensitive and specific index of thiamine nutrition.

Adult↗
PubMed2003

Effect of intravenous infusions of thiamine on the disposition kinetics of thiamine and its pyrophosphate.

BACKGROUND: Thiamine supplementation is necessary in patients with thiamine deficiency syndromes. Experimental evidence suggests that tissue uptake and the elimination of thiamine are dose-dependent. AIM: The aim of the present study was to investigate the effect of different i.v. infusion rates of thiamine on blood concentrations of thiamine and its active metabolite thiamine pyrophosphate (TPP) and on renal excretion of thiamine. METHODS: Twelve healthy subjects received in a two-period block randomized study 150 mg thiamine intravenously over either 1 or 24 h. RESULTS: The maximum blood concentrations (Cmax) of thiamine were significantly higher after the more rapid infusion (RI; 2300 ng/mL) than after the slower infusion (SI; 177 ng/mL). The AUC of thiamine was identical after both infusion protocols. There was a slightly (10%) increased AUC of TPP (P < 0.08) after SI, whereas C(max) values were comparable. Urinary excretion of thiamine was significantly decreased from 83.6% of the applied dose after RI to 57.6% after the SI. CONCLUSIONS: Our data suggest an increased tissue uptake of thiamine when it is given as an SI compared with a RI of the same dose. It is concluded, therefore, that an SI of thiamine may be superior to RI or bolus injections to treat severe deficiency syndromes.

Adult↗
PubMed1983

Enzyme system involved in the synthesis of thiamin triphosphate. I. Purification and characterization of protein-bound thiamin diphosphate: ATP phosphoryltransferase.

An enzyme system catalyzing the synthesis of thiamin triphosphate consists of an enzyme (protein-bound thiamin diphosphate:ATP phosphoryltransferase), thiamin diphosphate bound to a macromolecule as substrate, ATP, Mg2+, and a low molecular weight cofactor. This system was established by combining a purified enzyme and an essentially pure, macromolecule-bound substrate prepared from rat livers. This macromolecule was found to be a protein, and the transphosphorylation of thiamin diphosphate to thiamin triphosphate with ATP and enzyme was shown to occur on this macromolecule which binds thiamin diphosphate. Free thiamin, thiamin monophosphate, thiamin diphosphate, and thiamin triphosphate have no effect on this reaction. Thus, the overall reaction is: thiamin diphosphate-protein + ATP in equilibrium thiamin triphosphate-protein + ADP. So-called thiamin diphosphate:ATP phosphoryltransferase (EC 2.7.4.15) activity was not detected in rat brain or liver. The enzyme was extracted from acetone powder of a crude mitochondrial fraction of bovine brain cortex and purified to homogeneity with a 0.6% yield after DEAE-cellulose chromatography, a first gel filtration, hydroxylapatite chromatography, chromatofocusing, and a second gel filtration. The purified enzyme showed a single protein band on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Its molecular weight was estimated to be 103,000. The pH optimum was 7.5, and the Km was determined to be 6 X 10(-4) M for ATP. ATP was found to be the most effective phosphate donor among the nucleoside triphosphates. Amino acid analysis of the purified enzyme revealed an abundance of glutaminyl, glutamyl, and aspartyl residues. Sulfhydryl reagents inhibited the enzyme reaction. Metals such as Fe2+, Zn2+, Pb2+, and Cu2+ strongly inhibited the activity. The enzyme was unstable, and glycerol (20%) and dithiothreitol (1.0 mM) were found to preserve the enzyme activity.

Amino Acids↗