Benfotiamine in the treatment of diabetic polyneuropathy--a three-week randomized, controlled pilot study (BEDIP study)

OBJECTIVE

The aim of the study was to evaluate the efficacy of benfotiamine administered over three weeks (allithiamine; a lipid-soluble vitamin B1 prodrug with high bioavailability) to patients with diabetic polyneuropathy in a randomized, placebo-controlled, double-blind, two-center pilot study.

MATERIAL AND METHODS

Forty inpatients (23 male, 18 female, age range 18 - 70 years) with a history of type 1 or 2 diabetes and polyneuropathy of not longer than two years, were included in the study. Twenty Patients received two 50 mg benfotiamine tablets four times daily and 20 patients received placebo over the three-week study period. Two clinical units were involved with 10 patients receiving placebo and 10 patients benfotiamine in each. The neuropathy score according to Katzenwadel et al. [1987] was used to evaluate symptoms of polyneuropathy, vibration perception threshold and both the physician's and the patient's own assessment were documented.

RESULTS

A statistically significant (p = 0.0287) improvement in the neuropathy score was observed in the group given active drug when compared to the placebo-treated controls. There was no statistically significant change observed in the tuning fork test. The most pronounced effect on complaints was a decrease in pain (p = 0.0414). More patients in the benfotiamine-treated group than in the placebo group considered their clinical condition to have improved (p = 0.052). No side effects attributable to benfotiamine were observed. The differences between the groups cannot be attributed to a change in metabolic parameters since there were no significant alterations in the HbA1 levels and blood sugar profiles. The body mass index of the two groups did not differ.

CONCLUSION

This pilot investigation (BEDIP Study) has confirmed the results of two earlier randomized controlled trials and has provided further evidence for the beneficial effects of benfotiamine in patients with diabetic neuropathy.

Thiamine and vasculopathies

After peroxynitrite addition to aqueous solutions of thiamine at neutral and alkaline pH formation of thiamine disulfide and fluorescent products was observed. The fluorescent compounds were identified as thiochrome (TChr) and oxodihydrothiochrome (ODTChr) using spectral and fluorescent methods as well as paper chromatography and mass spectrometry. TChr and ODTChr are not the end products of thiamine oxidation and in neutral medium are unstable to peroxynitrite action and degrade rapidly to form non-fluorescent products. Thiamine, TChr, and ODTChr protects tyrosine from its modification by peroxynitrite. In the presence of TChr and ODTChr modification of tyrosinyl residues in human serum albumin and cytocrome c decreased. The prolonged thiamine incubation with glucose, amino acids and nitrite was accompanied by oxidative transformation of thiamine and formation of fluorescent products. We have shown that thiamine is also oxidized into TChr and ODTChr, i.e., it forms the same products as after thiamine oxidation by peroxynitrite. Moreover, thiamine (or its derivatives) appears as peroxynitrite scavenger leading to toxic effects lowering at diabetes mellitus.

Determination of thiamine and its phosphate esters in rat tissues analyzed as thiochromes on a RP-amide C16 column

A new reversed-phase chromatographic method is described for the separation and quantification of thiamine (T), thiamine monophosphate (TMP) and diphosphate (TDP) in rat tissues. Sample extraction with perchloric acid (HClO(4)) was found more suitable than extraction with trichloroacetic acid (TCA), as regards convenience and background fluorescence. Derivatization of thiamine vitamers to thiochromes was optimized and complete separation of TDP and TMP thiochromes was obtained on a RP-amide C16 column in isocratic elution, with T thiochrome eluting in less than 10 min. The precision and the accuracy of the HPLC procedure were assessed: ranging from 0.5 to 7.7% for intra-day and from 2.0 to 9.4% for inter-day precision, a recovery average of 101% was determined (range 90-111%). Mean values of recovery for TDP, TMP or T were 91, 96 and 90% for liver extracts, respectively. Analysis of vitamers in tissues of rat submitted to 8 days thiamin deficiency, followed by a 14 days repletion, showed a significant reduction of TPP after 8 days of depletion in liver (-67%), brains (-50%), kidneys (-60%), followed by a complete recovery upon repletion.

[Clinical efficacy of the drug enerion in the treatment of patients with psychogenic (functional) erectile dysfunction]

Twenty patients with psychogenic erectile dysfunction received the drug enerion (Hungary). After a 30-day course of enerion erectile function improved in 16 of the above patients. A mean value of the international index of erectile function (IIEF) increased in them from 17.5 to 24.8 points. Improvement of cavernous arterial blood flow after the treatment was seen in 3 of 6 patients with arterial disorders. As shown by electromyographic examinations, cavernous electric activity normalized in 8 patients. Thus, psychogenic erectile dysfunction can be effectively treated with enerion.

Fluorimetric Determination of Peroxynitrite Based on an Enzymatic Reaction

A novel fluorimetric method for the determination of peroxynitrite (ONOO-) using hemoglobin (Hb) as a catalyst is described. The method employs the reaction of ONOO with thiamine (TM), a colorless, non-fluorescent reagent in a glycine-NaCl-NaOH buffer solution (pH 12.7), to generate a highly fluorescent product, thiochrome (TC). The fluorescent product was monitored by fluorimetry. A linear calibration graph was obtained over an ONOO- concentration range from 4.95 x 10(-7) mol L(-1) to 2.97 x 10(-5) mol L(-1), with a detection limit of 9.78 x 10(-9) mol L(-1) ONOO-. The relative standard deviation at an ONOO- concentration of 2.11 x 10(-6) mol L(-1) was 4.15% (n = 9).

Thiamine tetrahydrofurfuryl disulfide: a little known therapeutic agent

Thiamine tetrahydrofurfuryl disulfide (TTFD) is the synthetic counterpart of allithiamine, occurring naturally in garlic. Allithiamine was discovered in Japan in 1951. Its extensive research was reported by a group known as the Vitamin B Research Committee of Japan, and given this name because of its existence in the bulbs of many of the allium species of plants. It was found to be a disulfide derivative of thiamine, produced as a result of enzymatic action on the thiamine molecule in garlic bulbs when the bulb is cut or crushed. Subsequent experimental work in both animals and human subjects revealed that its metabolic effect was much more powerful than the thiamine from which it was derived. Japanese investigators created a number of synthetic forms and investigated their use in a number of human disease conditions. Although some derivatives have been synthesized without a disulfide bond in the molecule, these investigators emphasized that the disulfide was an extremely important part of its biologic action and TTFD is the most modern of the disulfide derivatives. Because at least part of its beneficial effects are the same as water soluble thiamine salts, this review deals first with the clinical uses of thiamine (vitamin B1) in medicine.

Potential oscillation elicited by i.v. olfaction and its applicability as an objective clinical olfaction test

OBJECTIVE

Alinamin has long been applied in Japan for testing i.v. olfaction and to diagnose olfactory disorders. The test is subjective, each subject being asked about the presence or absence of olfaction. The credibility of the answers is highly questionable in some cases; as a result, the reliability of the test is poor. Recent studies demonstrated an induced electric potential in the scalp during i.v. olfactory testing. Some patients complain of the pain of the injection during i.v. olfactory testing; therefore, the effect of this pain must be considered with respect to measurement of the i.v. olfaction-elicited potential (IVOP).

MATERIAL AND METHODS

This investigation involved 179 subjects with various olfaction levels. Each subject received an Alinamin injection; the elicited potential amplitude was compared before and after the injection and the increasing ratio (IR) was computed. Gender, age, level of olfactory disorder, the presence or absence of olfaction and the presence or absence of the pain of injection were considered as factors affecting IR.

RESULTS

IR showed significant increases in groups characterized by the presence of olfaction as well as in groups reporting pain of injection. The test subjects were further divided into four groups based on their olfaction and pain of injection patterns as follows: Group A, no smell and no pain; Group B, smell and no pain; Group C, no smell and pain; and Group D, smell and pain. Subjects exhibiting no recognizable olfaction or pain of injection (Group A) revealed no increase in IVOP following injection. Subjects with either recognizable olfaction or pain of injection (Groups B and C) exhibited a slight increase in IVOP following injection. Subjects with both noticeable olfaction and pain of injection (Group D) demonstrated a significant increase in IVOP following the injection with a very high value of IR (>2). Furthermore, there were significant differences between the four groups in terms of IR level, with the exception of Groups B and C.

CONCLUSIONS

Olfaction is largely involved with the generation of IVOP. However, pain resulting from injection of Alinamin is considered to be a significant factor. IVOP showed significant effectiveness for diagnosing olfactory disorders in cases who did not experience pain of injection.

Thiamine and benfotiamine prevent increased apoptosis in endothelial cells and pericytes cultured in high glucose

BACKGROUND

High glucose induces pathological alterations in small and large vessels, possibly through increased formation of AGE, activation of aldose reductase and protein kinase C, and increased flux through the hexosamine pathway. We showed previously that thiamine and benfotiamine correct delayed replication and increase lactate production in endothelial cells subjected to high glucose. We now aim at verifying the effects of thiamine and benfotiamine on cell cycle, apoptosis, and expression of adhesion molecules in endothelial cells and pericytes, under high ambient glucose.

METHODS

Human umbilical vein endothelial cells and bovine retinal pericytes were cultured in normal (5.6 mmol/L) or high (28 mmol/L) glucose, with or without thiamine or benfotiamine, 50 or 100 micro mol/L. Apoptosis was determined by two separate ELISA methods, measuring DNA fragmentation and caspase-3 activity, respectively. Cell cycle and integrin subunits alpha3, alpha5, and beta1 concentration were measured by flow cytometry.

RESULTS

Apoptosis was increased in high glucose after 3 days of culture, both in endothelium and pericytes. Thiamine and benfotiamine reversed such effects. Neither cell cycle traversal nor integrin concentrations were modified in these experimental conditions.

CONCLUSIONS

Thiamine and benfotiamine correct increased apoptosis due to high glucose in cultured vascular cells. Further elucidations of the mechanisms through which they work could help set the basis for clinical use of this vitamin in the prevention and/or treatment of diabetic microangiopathy.

Hemodynamic Response of the Frontal Cortex Elicited by Intravenous Thiamine Propyldisulphide Administration

The intravenous olfaction (IVO) test is a unique type of clinical olfactometry and is widely used in Japan. However, it is difficult to distinguish actual olfactory disturbance from feigned disturbance because the IVO test is a psychophysical test. To resolve this problem, we investigated the possibility of an objective IVO test assisted with near infrared spectroscopy (NIRS). IVO testing was performed according to the usual protocol with thiamine propyldisulphide (alinamin) administration. The relative oxy- and deoxyhemoglobin levels of the orbitofrontal area during olfactory stimulation by IVO test were measured by NIRS. Pairs of NIRS emitters and detectors were positioned on the bilateral frontal scalp. After administration of alinamin, oxyhemoglobin levels increased, though deoxyhemoglobin levels did not change. An increase in oxyhemoglobin levels was observed bilaterally. Administration of saline did not elicit any change in the oxy- or deoxyhemoglobin levels and concentration of the administered alinamin related increasing of the oxyhemoglobin level was observed. Oxyhemoglobin remained unchanged in anosmic subjects despite administration of alinamin. The latency of oxyhemoglobin increase on each side and smelling latency showed significant correlation. Latencies of oxyhemoglobin increases between the right and left sides also showed significant correlation. Oxyhemoglobin response appears to be linked to olfactory related response. NIRS is a useful technique for the development of an objective form of IVO testing.

Thiamine biosynthesis in Escherichia coli: in vitro reconstitution of the thiazole synthase activity

The biosynthesis of thiamine in Escherichia coli requires the formation of an intermediate thiazole from tyrosine, 1-deoxy-d-xylulose-5-phosphate (Dxp), and cysteine using at least six structural proteins, ThiFSGH, IscS, and ThiI. We describe for the first time the reconstitution of thiazole synthase activity using cell-free extracts and proteins derived from adenosine-treated E. coli 83-1 cells. The addition of adenosine or adenine to growing cultures of Aerobacter aerogenes, Salmonella typhimurium, and E. coli has been shown previously to relieve the repression by thiamine of its own biosynthesis and increase the expression levels of the thiamine biosynthetic enzymes. By exploiting this effect, we show that the in vitro thiazole synthase activity of cleared lysates or desalted proteins from E. coli 83-1 cells is dependent upon the addition of purified ThiGH-His complex, tyrosine (but not cysteine or 1-deoxy-d-xylulose-5-phosphate), and an as yet unidentified intermediate present in the protein fraction from these cells. The activity is strongly stimulated by the addition of S-adenosylmethionine and NADPH.

Thiochrome Enhances Acetylcholine Affinity at Muscarinic M4 Receptors: Receptor Subtype Selectivity via Cooperativity Rather than Affinity

Thiochrome (2,7-dimethyl-5H-thiachromine-8-ethanol), an oxidation product and metabolite of thiamine, has little effect on the equilibrium binding of l-[3H]N-methyl scopolamine ([3H]NMS) to the five human muscarinic receptor subtypes (M1-M5) at concentrations up to 0.3 mM. In contrast, it inhibits [3H]NMS dissociation from M1 to M4 receptors at submillimolar concentrations and from M5 receptors at 1 mM. These results suggest that thiochrome binds allosterically to muscarinic receptors and has approximately neutral cooperativity with [3H]NMS at M1 to M4 and possibly M5 receptors. Thiochrome increases the affinity of acetylcholine (ACh) 3- to 5-fold for inhibiting [3H]NMS binding to M4 receptors but has no effect on ACh affinity at M1 to M3 or M5 receptors. Thiochrome (0.1 mM) also increases the direct binding of [3H]ACh to M4 receptors but decreases it slightly at M2 receptors. In agreement with the binding data, thiochrome does not affect the potency of ACh for stimulating the binding of guanosine 5'-O-(3-[35S]thiotriphosphate) ([35S]GTPgammaS) to membranes containing M1 to M3 receptors, but it increases ACh potency 3.5-fold at M4 receptors. It also selectively reduces the release of [3H]ACh from potassium-stimulated slices of rat striatum, which contain autoinhibitory presynaptic M4 receptors, but not from hippocampal slices, which contain presynaptic M2 receptors. We conclude that thiochrome is a selective M4 muscarinic receptor enhancer of ACh affinity and has neutral cooperativity with ACh at M1 to M3 receptors; it therefore demonstrates a powerful new form of selectivity, "absolute subtype selectivity", which is derived from cooperativity rather than from affinity.

Fragmentation of the Conjugate Base of 2-(1-Hydroxybenzyl)thiamin: Does Benzoylformate Decarboxylase Prevent Orbital Overlap To Avoid It?

The base-catalyzed addition of thiamin to benzaldehyde produces 2-(1-hydroxybenzyl)thiamin (HBnT), but in neutral solution HBnT undergoes base-catalyzed irreversible fragmentation into pyrimidine and thiazole derivatives. The fragmentation (rather than elimination) occurs in proportion to the extent that N1' is protonated or alkylated. Generating the conjugate base of HBnT by decarboxylation surprisingly leads to fragmentation independent of the state of N1'. Therefore, a cationic state at N1' specifically promotes removal of the C2alpha proton rather than the fragmentation process itself. It is suggested that benzoylformate decarboxylase, which generates a similar intermediate, exerts stereoelectronic control of the conformation of the carbanion, blocking fragmentation and facilitating protonation.

Three thiamine analogues differently alter thiamine transport and metabolism in nervous tissue: an in vivo kinetic study using rats

Thiamine (T) analogues pyrithiamine, oxythiamine or amprolium in amounts 10-1000 times higher than labelled T, were i.p. injected into rats together with 14C-T (30 microg; 46.25 KBq). The radioactivity associated with T and its phosphoesters in the plasma and cerebral cortex, brainstem, cerebellum, and sciatic nerve were determined at time intervals from 0.25 to 240 h from injection. The experimental data obtained were processed with a mathematical compartmental model that calculated the fractional rate constants. These are the amount of content in a given compartment that is replaced in 1 h and expressed in per hour. The results showed that all three analogues inhibited thiamine entry from plasma. Instead, oxythiamine enhanced T phosphorylation to T pyrophosphate (TPP); amprolium and oxythiamine enhanced TPP dephosphorylation to monophosphate (TMP); pyrithiamine reduced TPP dephosphorylation and TMP formation, while none of the analogues modified TMP dephosphorylation to T. In conclusion, in living rats, the action of T analogues was much more complex than could be expected from their structure and action in vitro.

Silver-Induced Enhancement of Thiochrome-Based Peroxide Measurements

Thiamine is presently one of the most attractive substrates used for sensitive fluorometric measurements of peroxides. Thiochrome (TC), a highly fluorescent product, is formed in enzyme-mediated oxidations. It is assumed that H(2)O(2) is nearly quantitatively converted to TC. The reaction cannot differentiate H(2)O(2) from many other peroxides such as methylhydroperoxide (MHP); to perform differential measurements, H(2)O(2) can first be selectively destroyed by a suitable catalyst such as MnO(2). In substituting Ag(2)O for MnO(2) to accomplish the selective destruction of H(2)O(2), we achieved the stated objective but were puzzled by a 3-fold increase in the MHP response in the presence of Ag(2)O. It was soon discovered that traces of dissolved Ag(+) and Hg(2+) can dramatically increase the yield of TC in this reaction from either H(2)O(2) or MHP; the normal yield in fact is only 20%. We present here a reaction scheme and kinetic model that adequately describes this behavior and should provide a path to substantially increase the sensitivity of this important assay method.

Adjuvant role of vitamin B analogue (sulbutiamine) with anti-infective treatment in infection associated asthenia

AIMS OF THE STUDY

Asthenic symptoms such as weakness accompany illness. This study investigates whether the centrally acting cholinergic agent, vitamin B analogue (sulbutiamine), is effective and acceptable in relieving these symptoms in infectious disease when combined with specific anti-infective treatment.

METHODOLOGY

In a prospective uncontrolled, non-randomised, commercial, observational study, 1772 patients with an infectious disease and asthenic symptoms, drawn from the practice of 350 randomly selected physicians throughout India, received vitamin B analogue (sulbutiamine) in addition to specific anti-infective treatment for 15 days. The primary outcome variable was complete resolution of asthenic symptoms with treatment.

RESULTS

The number (%, 95% confidence interval) of patients with complete resolution of all asthenic symptoms was 916 (51.7, 49.4-54). In the remaining patients, severe asthenia was reduced but persisted in 11 (0.6, 0-26); and moderate asthenia in 94 (5.3, 0-17.6). The response was greater in patients with acute infection and symptoms more related to cerebral function. Side effects occurred in 10 (0.6%), patients and well being improved significantly.

CONCLUSIONS

Vitamin B analogue (sulbutiamine) may be a useful adjunct to specific anti-infective treatment.

Prevention of incipient diabetic nephropathy by high-dose thiamine and benfotiamine

Accumulation of triosephosphates arising from high cytosolic glucose concentrations in hyperglycemia is the trigger for biochemical dysfunction leading to the development of diabetic nephropathy-a common complication of diabetes associated with a high risk of cardiovascular disease and mortality. Here we report that stimulation of the reductive pentosephosphate pathway by high-dose therapy with thiamine and the thiamine monophosphate derivative benfotiamine countered the accumulation of triosephosphates in experimental diabetes and inhibited the development of incipient nephropathy. High-dose thiamine and benfotiamine therapy increased transketolase expression in renal glomeruli, increased the conversion of triosephosphates to ribose-5-phosphate, and strongly inhibited the development of microalbuminuria. This was associated with decreased activation of protein kinase C and decreased protein glycation and oxidative stress-three major pathways of biochemical dysfunction in hyperglycemia. Benfotiamine also inhibited diabetes-induced hyperfiltration. This was achieved without change in elevated plasma glucose concentration and glycated hemoglobin in the diabetic state. High-dose thiamine and benfotiamine therapy is a potential novel strategy for the prevention of clinical diabetic nephropathy.

Down-regulation of thiamine transporter THTR2 gene expression in breast cancer and its association with resistance to apoptosis

The recent molecular identification of two thiamine transporters, SLC19A2 (THTR1) and SLC19A3 (THTR2), has provided the opportunity to study thiamine transporter gene expression in human malignancies. We compared RNA levels of both THTR1 and THTR2 in a panel of human breast tumors and corresponding normal tissues. THTR2 RNA levels were down-regulated in breast cancer to 14% of the level found in corresponding normal tissues, while THTR1 levels were unchanged. Both thiamine transport genes were cloned and expressed in a breast cancer cell line to examine the impact of reconstituted thiamine transport gene expression on drug and radiation sensitivity and on resistance to apoptosis. THTR2-transfected breast cancer cells showed a 2.5-fold increase in specific THTR2 activity and a 3-fold increase in cytotoxicity against a bromoacetyl ester derivative of thiamine. Surprisingly, these cells also showed a 3-fold increase in sensitivity to doxorubicin and an increase in sensitivity to ionizing radiation, but no change in sensitivity to methotrexate or paclitaxel. TUNEL assays demonstrate an increase in apoptosis in THTR2-transfected cells exposed to doxorubicin and radiation, and Western blot analysis suggests that apoptosis associated with these cytotoxic stresses is mediated at least in part by a caspase-3-dependent pathway. Therefore, thiamine transporter THTR2 gene expression is down-regulated in breast cancer, which may contribute to resistance to apoptosis in these tumors.

Vitamin B1 blocks damage caused by hyperglycemia

Diabetes accelerates the aging process and leads to complications that include blindness, renal failure, nerve damage, stroke, and cardiovascular disease. It has been hypothesized that high plasma glucose concentrations are responsible for increased mitochondrial free radical production and subsequent inactivation of glyceraldehyde phosphate dehydrogenase (GAPDH) in vascular endothelial cells and other cells implicated in these complications. As a result of the decreased ability of GAPDH to process upstream metabolites, three pathways of metabolic damage are activated, which include the advanced glycation end-product formation pathway, the protein kinase C pathway, and the hexosamine pathway. All three pathways have been implicated in abnormal cell signaling in diabetes. A group of German and U.S. scientists has now found that treating diabetic rats with high doses of benfotiamine, a lipid-soluble form of vitamin B1, can prevent diabetic retinopathy and all three forms of metabolic damage by stimulating transketolase activity and thus diverting excess metabolites toward the pentose pathway. Although vitamin B1 is available over the counter, the researchers at this time do not advocate self-treatment without further clinical data.

Benfotiamine blocks three major pathways of hyperglycemic damage and prevents experimental diabetic retinopathy

Three of the major biochemical pathways implicated in the pathogenesis of hyperglycemia induced vascular damage (the hexosamine pathway, the advanced glycation end product (AGE) formation pathway and the diacylglycerol (DAG)-protein kinase C (PKC) pathway) are activated by increased availability of the glycolytic metabolites glyceraldehyde-3-phosphate and fructose-6-phosphate. We have discovered that the lipid-soluble thiamine derivative benfotiamine can inhibit these three pathways, as well as hyperglycemia-associated NF-kappaB activation, by activating the pentose phosphate pathway enzyme transketolase, which converts glyceraldehyde-3-phosphate and fructose-6-phosphate into pentose-5-phosphates and other sugars. In retinas of diabetic animals, benfotiamine treatment inhibited these three pathways and NF-kappaB activation by activating transketolase, and also prevented experimental diabetic retinopathy. The ability of benfotiamine to inhibit three major pathways simultaneously might be clinically useful in preventing the development and progression of diabetic complications.

The coenzyme thiamine pyrophosphate inhibits the self-splicing of the group I intron

Effects of the coenzyme thiamine pyrophosphate and its analogs on the inhibition of self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td) were investigated. Of all compounds tested, the coenzyme thiamine pyrophosphate was the most potent inhibitor and the order of inhibitory efficiency for compounds tested was as follows: thiamine pyrophosphate>thiamine monophosphate>thiamine>thiochrome. Increasing guanosine concentration overcame the suppression of self-splicing by thiamine pyrophosphate close to the level of normal splicing. Kinetic analysis demonstrated that thiamine pyrophosphate acts as a competitive inhibitor for the td intron RNA with a Ki of 2.2mM. The splicing specificity inhibition by thiamine pyrophosphate is predominantly due to changes in Km.

Polypeptide components of oligomeric legumin-like thiamin-binding protein from buckwheat seeds characterized by partial amino acid sequencing and photoaffinity labeling

Among thiamin-binding proteins that ubiquitously occur in plant seeds, that of common buckwheat became a model of extensive studies of the chemical mechanism of ligand-protein interaction. In this work, the polypeptide components of buckwheat seed thiamin-binding protein (BSTBP) are identified and characterized. We suggest that BSTBP is probably a fraction of major storage 13 S globulin (legumin), has an average molecular mass of 235 kDa and comprises hexamers of 57-kDa and 38-kDa subunits in variable combinations. Each subunit is a pair of disulfide-linked polypeptide chains, 36 kDa plus 24 kDa and two-times 22 kDa, respectively. The N-terminal sequences of 22-kDa and 24-kDa components show strict homology with those reported for "basic subunits" of buckwheat legumin. By photoaffinity labeling of BSTBP with 4-azido-2-nitrobenzoylthiamine, it is shown that the 36-kDa chain plays the major role in thiamin binding, but the other chains may also be variably involved. Putative thiamin-binding fragments are identified and sequenced.

Determination of thiamine in pharmaceutical preparations by sequential injection renewable surface solid-phase spectrofluorometry

Fluorometric determination of thiamine requires the conversion of the analyte to fluorescent thiochrome by hexacyanoferrate(III) oxidation in alkaline solution and the isolation of the produced thiochrome from the reaction medium by solvent extraction. It was observed that thiochrome could be concentrated and separated from the reaction medium by solid-phase extraction. The thiochrome sorpted on the surface of octadecyl-alklylated poly[styrene/divinylbenzene] (C18-PS/DP) microbeads emitted strong fluorescence upon excitation, the maximum excitation and emission wavelengths being 385 nm and 433 nm, respectively. Based on this observation, a sequential injection renewable surface solid-phase spectrofluorometry was developed for the determination of thiamine. A sequential injection system on-line coupled to a chip-based flow-through cell was employed to handle the chemical reaction, bead injection and discharging, and adsorption of thiochrome. Solid-phase fluorometric detection was realized by coupling the chip-based flow-through cell to a spectrofluorometer with a multistrand bifurcated optical fiber. Under the optimized condition, a detection limit of 0.03 microg ml(-1) was achieved at the sample throughput of 30 h(-1) and consumption of 1 mg C18-PS/DP microbeads for each run. Eleven runs of a 2 microg ml(-1) thiamine standard solution gave a relative standard deviation of 1.0%. The developed approach was successfully applied for the determination of thiamine contents in pharmaceutical preparations.

Bioavailability of Theophylline and Thiamine Disulfide Incorporated into Mucoadhesive Microspheres Consisting of Dextran Derivatives and Cellulose Acetate Butyrate

Mucoadhesive microspheres made of oppositely charged dextran derivatives and cellulose acetate butyrate (Ad-MS) were evaluated for their ability to improve the bioavailability of theophylline (TH) and thiamine disulfide (TDS). A drug suspension (or solution) and non-adhesive microspheres (MS) were used as references. In vitro drug release profiles from MS and Ad-MS were similar for each drug, whereas their gastrointestinal transits differed. The plasma concentration after oral administration of drug suspension (or solution), MS and Ad-MS was investigated in rats. In the case of TH, sustained plasma level profiles were observed after MS or Ad-MS administration, with similar C(max), T(max) and MRT( infinity ) values. AUC( infinity ) values of the suspension, MS and Ad-MS were statistically equivalence. These indicated that Ad-MS achieved a sustained plasma level profile without a decrease of AUC. In the case of TDS, MRT( infinity ) and AUC( infinity ) of Ad-MS were significantly larger than those of the solution and MS, indicating that the plasma level was sustained and the extent of bioavailability was increased. These results suggested that Ad-MS is a promising device for improvement of bioavailability of drugs those absorption windows are limited to upper part of the gastrointestinal tract.

[Use of enerion in psychovegetative syndrome with pronounced asthenia]

Enerion was used in the treatment of 40 patients with psychovegetative syndrome and asthenia. Before treatment, the patients have pronounced asthenia appearances, anxiety disorders, relevant autonomic disorders, mild depression and decrease of working capacity, attention concentration and memory. The treatment was conducted as monotherapy during 28 days with enerion dosage 400 mg/day. After treatment, expression of autonomic and asthenic disorders was reduced significantly, along with improvement of psychometric and neurophysiological indices. High efficacy of the medication was detected in 75% of the patients and moderate one--in 25%. The drug was well-tolerated.

Reactivity of intermediates in benzoylformate decarboxylase: avoiding the path to destruction

Benzoylformate decarboxylase forms a covalent intermediate from thiamin diphosphate (TDP) and benzoylformate, alpha-mandelylTDP. This loses carbon dioxide to form a carbanion (enamine). Protonation of the carbanion and elimination of benzaldehyde regenerate enzyme-bound TDP. We synthesized alpha-mandelylthiamin and found that the rate of the loss of carbon dioxide is one-millionth that of the enzymic reaction. Thus, the enzyme provides an environment that facilitates the unimolecular decarboxylation process. However, the resulting nonenzymic carbanion reacts very rapidly to give products that lead to the irreversible destruction of the cofactor. This contrasts with the normal process on the enzyme. Brønsted acids on the enzyme may divert the reaction to the benzaldehyde precursor, or the enzyme may block access to the pathway that leads to destruction of the cofactor.

Thiamine derivatives bind messenger RNAs directly to regulate bacterial gene expression

Although proteins fulfil most of the requirements that biology has for structural and functional components such as enzymes and receptors, RNA can also serve in these capacities. For example, RNA has sufficient structural plasticity to form ribozyme and receptor elements that exhibit considerable enzymatic power and binding specificity. Moreover, these activities can be combined to create allosteric ribozymes that are modulated by effector molecules. It has also been proposed that certain messenger RNAs might use allosteric mechanisms to mediate regulatory responses depending on specific metabolites. We report here that mRNAs encoding enzymes involved in thiamine (vitamin B(1)) biosynthesis in Escherichia coli can bind thiamine or its pyrophosphate derivative without the need for protein cofactors. The mRNA-effector complex adopts a distinct structure that sequesters the ribosome-binding site and leads to a reduction in gene expression. This metabolite-sensing regulatory system provides an example of a 'riboswitch' whose evolutionary origin might pre-date the emergence of proteins.

Potential changes with gamma-band oscillation at the frontal scalp elicited by intravenous olfactory stimulation in humans

Intravenous olfaction is a unique stimulation method often used in Japan to diagnose olfactory disturbances. Odorant is injected into a vein and transported by blood flow and respiration to the upper air tract. The intravenous olfaction might allow the potential at the frontal scalp to be recorded without contamination from electromyograms, such as those caused by sniffing. We injected Alinamin (thiamine propyldisulphide) into healthy subjects according to a standard protocol for clinical intravenous olfaction testing and we simultaneously recorded potential changes at the frontal scalp. When Alinamin was injected into the right median cubital vein over a 20 s period, the potential changes with gamma-band oscillations were detected 17.6 +/- 6.7 s (mean +/- SD) after the start of the injection. The main frequency component of this gamma-band oscillation is 30-160 Hz. The gamma-band oscillation elicited by intravenous olfactory stimulation (VOP) was similar to the induced wave of the olfactory bulb. Mapping the VOPs on the frontal scalp of a subject with less developed frontal sinuses and the relation between the thickness of the frontal sinuses and VOP amplitude suggest an intracranial source, possibly the olfactory bulb. The gamma-band potential at the frontal scalp is a useful measure of central disturbance.

Electroencephalographic changes during intravenous olfactory stimulation in humans

The intravenous olfaction test with thiamin propyl disulfide (TPD) is a simple procedure widely used in Japan. An olfactory stimulus is provided by intravenous injection of TPD (2 ml) over the course of 20 sec. The subject smells n-propyl mercaptan (a decomposition product of TPD discharged from the blood into alveoli) in expired air after treatment. In this preliminary study we recorded electroencephalograms (EEGs) in normal subjects during three stages: 1) eyes-closed rest (prestimulus), 2) olfactory sensation after TPD injection, and 3) disappearance of sensation. In each of these stages, we calculated and compared EEG powers according to the band components of each electrode position. This study was designed a) to evaluate by frequency analysis EEG changes during olfactory sensation after TPD injection, and b) to identify the most significant changes in EEG power according to frequency band and electrode location. During the intravenous olfactory stimulation, alpha 2 and beta 2 waves were activated over the frontal and temporal regions. After disappearance of olfactory sensation, these waves decreased in the same regions. EEG powers returned to prestimulus levels.

[The immunometaboic effects of benfotiamine and riboxine on hemolytic anemia]

Single (80 mg/kg) or multiply repeated (30 mg/kg) intramuscular injections of phenylhydrazine decrease the functional activity of mononuclear blood cells and the reduces immunological reactivity of the organism. Benfotiamine and riboxin decrease the extent of changes in the immunological response to a single administration of phenylhydrazine but do not significantly influence the immunological functions impaired by repeated injections of the hemolytic toxin.

[Bendotiamine efficacy in alcoholic polyneuropathy therapy]

Benfogamma efficacy in alcoholic polyneuropathy therapy with pain syndrome and other sensor disorders has been studied. Fourteen males with stage II-III chronic alcoholism (mean age 41.2 +/- 9 years, mean alcoholism duration 20.6 +/- 6 years, mean alcoholic polyneuropathy therapy duration 6.8 +/- 4.9 years) have been examined, 93% of the cases having positive family history of alcoholism. Clinical neurophysiological examination was conducted at the beginning and at the end of 6-week therapy, 450 mg/day (2 weeks) and 300 mg/day (4 weeks). During the treatment the regress of algic, other sensor and movement disorders, as well as some neuropathy symptoms has been observed. The evidence of positive dynamics at peripheral and segmental nerve system level was supported by neurophysiological data.

Stereocontrolled synthesis of (-)-macrolactin A

The total synthesis of (-)-macrolactin A, a 24-membered macrolide, has been achieved using a newly developed 1,3-diol synthon for the introduction of two key stereogenic centers. The synthon was derived from sequential use of the Noyori asymmetric reduction followed by chiral sulfoxide methodology. Tellurium-derived cuprate organometallics offered an efficient and highly stereoselective means for installation of the C8 Z/E-diene, while the C15 E/E-segment was derived from a Julia-Lythgoe olefination. Yamaguchi lactonization was used to secure the macrocycle in a convergent approach with the longest linear sequence of 19 steps from Noyori alcohol 6.

Substituent effects in carbon-nitrogen cleavage of thiamin derivatives. Fragmentation pathways and enzymic avoidance of cofactor destruction

The combination of thiamin and benzaldehyde can produce benzoin but also destroys thiamin. The destruction comes from fragmentation of the conjugate of thiamin and benzaldehyde undergoing a process that produces a phenyl thiazole ketone and pyrimidine. The key step in this process is cleavage of the C-N bond between the heterocycles, which occurs by an unknown mechanism. Enzymes that utilize similar intermediates do not fragment the cofactor although fragmentation is inherent to the structure. To analyze the nature of the C-N cleavage step, the rates of fragmentation of a series of phenyl-substituted N1'-methyl-2-(1-hydroxybenzyl)thiamin derivatives were determined under two sets of conditions: (1) where proton transfer in the step prior to C-N bond breaking is rate-determining and (2) where C-N bond breaking is rate-determining. The resulting rho values are 1.6 and 1.8, respectively, leading to the conclusion that C-N cleavage is insensitive to substituent effects. On the basis of these results, we conclude that cleavage occurs by a facile process that resembles the outcome of a [1,5] sigmatropic rearrangement. An enzyme may avoid the fragmentation by holding the intermediate in a conformation that prevents such a process, allowing the normal catalytic process to proceed.

Efficacy of benfotiamine versus thiamine on function and glycation products of peripheral nerves in diabetic rats

In rats with streptozotocin (STZ) induced diabetes the effect of (watersoluble) thiamine nitrate and of (lipidsoluble) benfotiamine on peripheral nerve function (motor nerve conduction velocity) as well as on the formation of advanced glycation end-products in peripheral nerve tissue was studied. In one group of animals drug administration was started immediately after diabetes induction (prevention study) and in another group two months after diabetes induction (treatment study). Motor nerve conduction velocity (NCV) dropped by 10.5% in diabetic animals, carboxymethyl-lysine (CML) rose to a 3.5fold concentration, deoxyglucosone (3DG)-type AGE formation was increased 5.1fold compared with controls. After three months preventive administration of both vitamin B(1) preparations NCV had increased substantially compared with results in diabetic controls. It was nearly normal after six months with benfotiamine, while the administration of thiamine nitrate resulted in no further amelioration. NCV was nearly normalized after six months of benfotiamine application but not with thiamine. Furthermore, benfotiamine induced a major inhibition of neural imidazole-type AGE formation and completely prevented diabetes induced glycoxidation products (CML). Treatment with thiamine did not significantly affect AGE or cmL levels. Unlike treatment with water-soluble thiamine nitrate timely administration of liposoluble prodrug benfotiamine was effective in the prevention of functional damage and of AGE and cmL formation in nerves of diabetic rats.

Host-guest-like thiamine-anion complexation in thiaminium bis(tetrafluoroborate)

In the title compound, 3-[(4-amino-2-methyl-5-pyrimidin-1-io)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium(2+) bis(tetrafluoroborate), C(12)H(18)N(4)OS(2+).2BF(4)(-), the divalent thiamine cation (in the F conformation) is associated with BF(4)(-) anions via two characteristic bridging interactions between the thiazolium and pyrimidinium rings, i.e. C-H...BF(4)(-)...pyrimidinium and N-H...BF(4)(-)...thiazolium interactions. Thiamine molecules are linked by N-H...O hydrogen bonds to form a helical chain structure.

Impact of the reduced folate carrier on the accumulation of active thiamin metabolites in murine leukemia cells

The thiamin transporter encoded by SLC19A2 and the reduced folate carrier (RFC1) share 40% homology at the protein level, but the thiamin transporter does not mediate transport of folates. By using murine leukemia cell lines that express no, normal, or high levels of RFC1, we demonstrate that RFC1 does not mediate thiamin influx. However, high level RFC1 expression substantially reduced accumulation of the active thiamin coenzyme, thiamin pyrophosphate (TPP). This decreased level of TPP, synthesized intracellularly from imported thiamin, resulted from RFC1-mediated efflux of TPP. This conclusion was supported by the following observations. (i) Efflux of intracellular TPP was increased in cells with high expression of RFC1. (ii) Methotrexate inhibits TPP influx. (iii) TPP competitively inhibits methotrexate influx. (iv) Loading cells, which overexpress RFC1 to high levels of methotrexate to inhibit competitively RFC1-mediated TPP efflux, augment TPP accumulation. (v) There was an inverse correlation between thiamin accumulation and RFC1 activity in cells grown at a physiological concentration of thiamin. The modulation of thiamin accumulation by RFC1 in murine leukemia cells suggests that this carrier may play a role in thiamin homeostasis and could serve as a modifying factor in thiamin nutritional deficiency as well as when the high affinity thiamin transporter is mutated.

Benfotiamine is similar to thiamine in correcting endothelial cell defects induced by high glucose

We investigated the hypothesis that benfotiamine, a lipophilic derivative of thiamine, affects replication delay and generation of advanced glycosylation end-products (AGE) in human umbilical vein endothelial cells cultured in the presence of high glucose. Cells were grown in physiological (5.6 mM) and high (28.0 mM) concentrations of D-glucose, with and without 150 microM thiamine or benfotiamine. Cell proliferation was measured by mitochondrial dehydrogenase activity. AGE generation after 20 days was assessed fluorimetrically. Cell replication was impaired by high glucose (72.3%+/-5.1% of that in physiological glucose, p=0.001). This was corrected by the addition of either thiamine (80.6%+/-2.4%, p=0.005) or benfotiamine (87.5%+/-8.9%, p=0.006), although it not was completely normalized (p=0.001 and p=0.008, respectively) to that in physiological glucose. Increased AGE production in high glucose (159.7%+/-38.9% of fluorescence in physiological glucose, p=0.003) was reduced by thiamine (113.2%+/-16.3%, p=0.008 vs. high glucose alone) or benfotiamine (135.6%+/-49.8%, p=0.03 vs. high glucose alone) to levels similar to those observed in physiological glucose. Benfotiamine, a derivative of thiamine with better bioavailability, corrects defective replication and increased AGE generation in endothelial cells cultured in high glucose, to a similar extent as thiamine. These effects may result from normalization of accelerated glycolysis and the consequent decrease in metabolites that are extremely active in generating nonenzymatic protein glycation. The potential role of thiamine administration in the prevention or treatment of vascular complications of diabetes deserves further investigation.

Bioavailability of water- and lipid-soluble thiamin compounds in broiler chickens

The bioavailability of thiamin mononitrate, thiamin chloride-hydrochloride and benfotiamin was compared in broiler chickens. A thiamin-deficient diet was supplemented with either 1.8 and 1.5 mg/kg thiamin equivalent as water-soluble salts, or with 1.5 and 1.2 mg/kg thiamin equivalent as benfotiamin, respectively, and fed to 3 replicate groups/treatment for 21 days. Weight gain, feed consumption and feed conversion rate were not significantly affected by solubility or dietary level of thiamin. Likewise, using biochemical indices of thiamin status (erythrocyte transketolase activation coefficient, and thiamin concentrations in blood and liver), no differences were found between the water-soluble thiamin salts, indicating that they have identical potency. In contrast, biochemical indices of thiamin status showed a significantly higher bioavailability for benfotiamin than for the water-soluble sources.

Evidence for a modulatory effect of sulbutiamine on glutamatergic and dopaminergic cortical transmissions in the rat brain

Chronic treatment of rats by sulbutiamine induced no change in density of N-methyl-D-aspartate (NMDA) and (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors in the cingular cortex, but a significant decrease of the kainate binding sites, as measured by quantitative autoradiography. In the same treated animals, an increase of D1 dopaminergic (DA) binding sites was measured both in the prefrontal and the cingular cortex, while no modification of the D2 binding sites was detected. Furthermore, an acute sulbutiamine administration induced a decrease of kainate binding sites but no change of the density of D1 and D2 DA receptors. Acute sulbutiamine injection led to a decrease of the DA levels in the prefrontal cortex and 3,4-dihydroxyphenylacetic acid levels in both the cingular and the prefrontal cortex. These observations are discussed in terms of a modulatory effect of sulbutiamine on both dopaminergic and glutamatergic cortical transmissions.

Thiamine intestinal transport and related issues: recent aspects

In the intestinal lumen thiamine is in free form and very low concentrations. Absorption takes place primarily in the proximal part of the small intestine by means of a dual mechanism, which is saturable at low (physiological) concentrations and diffusive at higher. Thiamine undergoes intracellular phosphorylation mainly to thiamine pyrophosphate, while at the serosal side only free thiamine is present. Thiamine uptake is enhanced by thiamine deficiency, and reduced by thyroid hormone and diabetes. The entry of thiamine into the enterocyte, as evaluated in brush border membrane vesicles of rat small intestine in the absence of H+ gradient, is Na+- and biotransformation-independent, completely inhibited by thiamine analogs and reduced by ethanol administration and aging. The transport involves a saturable mechanism at low concentrations of vitamin and simple diffusion at higher. Outwardly oriented H+ gradients enhance thiamine transport, whose saturable component is a Na+-independent electroneutral uphill process utilizing energy supplied by the H+ gradient, and involving a thiamine/ H+ 1:1 stoichiometric exchange. The exit of thiamine from the enterocyte, as evaluated in basolateral membrane vesicles, is Na+-dependent, directly coupled to ATP hydrolysis by Na+-K+-ATPase, and inhibited by thiamine analogs. Transport of thiamine by renal brush border membrane vesicles is similar to the intestinal as far as both H+ gradient influence and specificity are concerned. In the erythrocyte thiamine transport is a Na+-independent, electroneutral process yet with two components: saturable, prevailing at low thiamine concentrations, and diffusive at higher. The saturable (specific) component is missing in patients of the rare disease known as thiamine-responsive megaloblastic anaemia (TRMA), producing a general disturbance of thiamine transport up to thiamine deficiency. The TRMA gene is located in chromosome 1q23.3. Recently, the thiamine transporter has been cloned: it is a protein of 497 amino acid residues with high homology with the reduced-folate transporter.