Thiamine Depletion Research Articles

Development and Resolution of Brain Lesions Caused by Pyrithiamine- and Dietary-Induced Thiamine Deficiency and Alcohol Exposure in the Alcohol-Preferring Rat: A Longitudinal Magnetic Resonance Imaging and Spectroscopy Study

Wernicke's encephalopathy (WE) is characterized by lesions in thalamus, hypothalamus (including mammillary nuclei), and inferior colliculi, results in serious disabilities, has an etiology of thiamine deficiency, is treatable with thiamine, and occurs most commonly with alcoholism. Despite decades of study, whether alcohol exposure exacerbates the neuropathology or retards its resolution remains controversial. To examine patterns of brain damage and recovery resulting from thiamine deprivation with and without alcohol exposure, we conducted in vivo magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) at 3 T in alcohol-preferring (P) rats, which had voluntarily consumed large amounts of alcohol before thiamine manipulation. A total of 18 adult male P rats (nine alcohol-exposed) received a thiamine-deficient diet for 2 weeks: 10 (five alcohol-exposed) received intraperitoneal (i.p.) pyrithiamine (PT) and eight (four alcohol-exposed) received i.p. thiamine supplementation. Neurological signs developed by day 14. Rats were scanned before thiamine depletion and 18 and 35 days after thiamine repletion. Two-dimensional J-resolved MRS single-voxel spectra with water reference were collected in a voxel subtending the thalamus; metabolite quantification was corrected for voxel tissue content. MRI identified significant enlargement of dorsal ventricles and increase in signal intensities in thalamus, inferior colliculi, and mammillary nuclei of PT compared with thiamine-treated (TT) groups from MRI 1-2, followed by significant normalization from MRI 2-3 in thalamus and colliculi, but not mammillary nuclei and lateral ventricles. Voxel-by-voxel analysis revealed additional hyperintense signal clusters in the dorsal and ventral hippocampus and enlargement of the fourth ventricle. MRS showed a significant decline and then partial recovery in thalamic N-acetylaspartate, a marker of neuronal integrity, in PT compared with TT rats, with no change detected in creatine, choline, or glutamate. PT rats with prior alcohol exposure exhibited attenuated recovery in the thalamus and arrested growth of the corpus callosum; further, two of the five alcohol-exposed PT rats died prematurely. Parenchymal and ventricular changes with thiamine manipulation concur with human radiological signs of WE. The enduring macrostructural and neurochemical abnormalities involving critical nodes of Papez circuit carry liabilities for development of amnesia and incomplete recovery from other cognitive and motor functions subserved by the affected neural systems.

Role of Defective High-Affinity Thiamine Transporter slc19a2 in Marrow from a Mouse Model of Thiamine-Responsive Anemia Syndrome: Evidence for Defective Deoxyribose and Heme Synthesis.

The rare autosomal recessive human disorder, TRMA syndrome (thiamine-responsive anemia with diabetes and deafness, OMIM 249270 ), is caused by mutations in the high affinity vitamin B1 transporter, SLC19A2. In human TRMA, ringed sideroblasts and megaloblastic changes are found in the marrow, suggesting potential defects in heme synthesis or mitochondrial function, and DNA synthesis, respectively. The mechanism whereby defective marrow thiamine transport causes these findings in the marrow was examined in a mouse model for TRMA. We previously demonstrated in fibroblasts from humans with TRMA a defect in the rate and pathway used for de novo ribose synthesis using Stable Isotope Dynamic Metabolic Profiling (SIDMaP analysis - Boros et al, Blood 102: 3556, 2003).To examine whether this fibroblast defect accurately defined the marrow pathophysiology, we have now examined this pathway in detail in mice defective for the orthologous slc19a2 gene by targeted gene disruption (Fleming et al, Mol Genet Metab 80:234, 2003). Slc19a2 mutant (−/−) or wildtype (+/+) mice were subjected to normal mouse chow (22 mg/kg thiamine), or thiamine deficient chow diet. Diets were confirmed thiamine deficient by chemical analysis. To examine heme biosynthesis, we used 55Fe-transferrin, ex vivo, to label marrow from +/+ or −/− mice maintained for 10 days in thiamine replete or deficient chow. Mutant mice had cell surface labeling indistinguishable from +/+ at 0°C (P>0.3), reflecting available transferrin receptors. Total cellular 55Fe uptake at 37 C was equal to or slightly greater than that of +/+ marrow in thiamine depleted state. However, incorporation of 55Fe into heme lagged in −/− cells (7.3 +/− 0.4 pmol/106cells/7 min) compared to +/+ (8.6 +/− 0.5 pmol/106 cells, P =0.018 in triplicate experiments). To examine deoxyribose (dRibose) synthesis, mice were maintained on thiamine replete or depleted chow for 10 days, then [1,2 13C] glucose was administered intraperitoneally overnight and 3 hours before sacrifice and marrow harvest. DNA from whole marrow and from sorted basophilic erythroblasts (CD71+/Ter119+) was isolated, hydrolized, derivatized, and dRibose analyzed by GC-MS. The initial rate of incorporation of 13C into DNA dRibose, reflecting de novo synthetic rate, was reduced 34% in basophilic erythroblasts of −/− mice after thiamine depletion (n=3 in duplicate experiments, P<0.001). dRibose enrichment at position C1 and C2 (m2) compared to C1 onl1 (m1) reflects synthesis via transketolase (thiamine dependent, non-oxidative, m2), vs G6PD (oxidative, non-thiamine dependent, m1). The m2/m1 ratio was 0.73 in +/+ cells, but only 0.36 in −/− erythroblasts, demonstrating defective non-oxidative branch of the pentose phosphate pathway. Thus, defective slc9a2 leads to two distinct erythropoietic defects. De novo DNA dRibose synthesis via transketolase is markedly impaired. Further, while iron uptake by marrow cells is maintained at normal levels, the heme biosynthetic rate is decreased in −/− mice in thiamine-depleted status. This is the first direct demonstration of a role for thiamine in normal erythrocyte heme and DNA metabolism. Together, these defects can account directly for the meglaoblastosis and sideroblasts of human SLC19A2 defects in TRMA.

Thiamine deficiency in the pathogenesis of chronic ethanol-associated cerebellar damage in vitro

Nutritional deficiencies associated with long-term ethanol consumption may cause neuronal damage in ethanol-dependent individuals. Thiamine deficiency, in particular, is thought to contribute to ethanol-associated cerebellar degeneration, although damage may occur in adequately nourished alcoholics. Thus, the present study examined the effects of thiamine depletion and ethanol exposure on cytotoxicity in rat cerebellum. Organotypic cerebellar slice cultures were treated starting at 25 days in vitro with 100mM ethanol for 11 days or 10 days followed by a 24-h withdrawal period. This exposure paradigm has previously been shown in hippocampal slice cultures to result in spontaneous cytotoxicity upon ethanol withdrawal. Additional cerebellar cultures were exposed to the thiamine depleting agent pyrithiamine (10–500μM) for 10 or 11 days, some in the presence of ethanol exposure or withdrawal. Other cultures were co-exposed to thiamine (1–100μM), 500μM pyrithiamine, and ethanol for 10 or 11 days. The results demonstrated that neither 11-day ethanol treatment nor withdrawal from 10-day exposure significantly increased cerebellar cytotoxicity, as measured by propidium iodide fluorescence. The 11-day treatment with 100 or 500μM pyrithiamine significantly increased propidium iodide fluorescence ∼21% above levels observed in control tissue. Cultures treated with both ethanol (11 days or 10 days plus withdrawal) and 500μM pyrithiamine displayed a marked increase in cytotoxicity ∼60–90% above levels observed in control cultures. Pyrithiamine and ethanol-induced cytotoxicity was prevented in cultures co-exposed to thiamine (10–100μM) for the duration of pyrithiamine treatment. Findings from this report suggest that the cerebellum may be more sensitive to the toxic effects of thiamine deficiency, as compared with alcohol withdrawal, associated with alcohol dependence.

High-dose thiamine therapy counters dyslipidaemia in streptozotocin-induced diabetic rats

Cardiovascular disease in diabetes is linked to increased risk of atherosclerosis, increased levels of triglyceride-rich lipoproteins and enhanced hepatic lipogenesis. The hepatic hexosamine pathway has been implicated in signalling for de novo lipogenesis by the liver. In this study, we assessed if decrease of flux through the hexosamine pathway induced by high-dose thiamine therapy counters diabetic dyslipidaemia. The model of diabetes used was the streptozotocin-induced diabetic rat with maintenance insulin therapy. Normal control and diabetic rats were studied for 24 weeks with and without oral high-dose therapy (7 and 70 mg/kg) with thiamine and benfotiamine. Plasma total cholesterol, HDL cholesterol and triglycerides were determined at 6-week intervals and hepatic metabolites and transketolase activity after death of the rats at 24 weeks. We found that thiamine therapy (70 mg/kg) prevented diabetes-induced increases in plasma cholesterol and triglycerides in diabetic rats but did not reverse the diabetes-induced decrease of HDL. This was achieved by prevention of thiamine depletion and decreased transketolase activity in the liver of diabetic rats. There was a concomitant decrease in hepatic UDP-N-acetylglucosamine and fatty acid synthase activity. Thiamine also normalised food intake of diabetic rats. A lower dose of thiamine (7 mg/kg) and the thiamine monophosphate prodrug benfotiamine (7 and 70 mg/kg) were ineffective. High-dose thiamine therapy prevented diabetic dyslipidaemia in experimental diabetes probably by suppression of food intake and hexosamine pathway signalling but other factors may also be involved. Benfotiamine was ineffective.

Thiamine Transporter Gene Expression and Exogenous Thiamine Modulate the Expression of Genes Involved in Drug and Prostaglandin Metabolism in Breast Cancer Cells

In previous studies, we have shown that RNA levels of the thiamine transporter THTR2 were down-regulated in breast cancer tumors in comparison with normal tissues and that THTR2-mediated increases in thiamine uptake activity contributed to increased apoptosis after exposure to ionizing radiation. To further understand the biological effects of the alteration of THTR2 expression, we conducted a DNA microarray study of gene expression in THTR2-transfected breast cancer cells and found that, in addition to increased expression of THTR2 attributable to the transgene, three other genes were up-regulated >2.5-fold in the transfected cells: cytochrome P450 isoform CYP4B1, 15-hydroxyprostaglandin dehydrogenase (15-PGDH), and transcription factor CRIP1. In addition, two genes were confirmed to be down-regulated in THTR2-transfected cells: trefoil factor 1 (TFF1) and Rho-GDP dissociation inhibitor (RGDI). Up-regulation of 15-PGDH and CYP4B1 expression was observed in other breast cancer cell lines transfected with THTR2, and down-regulation was observed after suppression of THTR2 with siRNA vectors. To determine the role of exogenous thiamine in the expression of these genes, we analyzed THTR2-transfected breast cancer cells grown in thiamine-depleted medium by quantitative reverse transcription-PCR and showed that three of these five genes showed evidence of regulation by exogenous thiamine in a manner concordant with the effects of THTR2 overexpression. One of the genes up-regulated by THTR2 transfection was down-regulated by thiamine depletion (CYP4B1), and two genes with decreased expression in THTR2-transfected breast cancer cells were up-regulated by thiamine depletion (TFF1 and RGDI). In summary, these studies show unexpected relationships between thiamine metabolism and genes that may be involved in the oncogenesis of breast and lung cancer.

Copper, selenium, zinc, and thiamine balances during continuous venovenous hemodiafiltration in critically ill patients

Acute renal failure is a serious complication in critically ill patients and frequently requires renal replacement therapy, which alters trace element and vitamin metabolism. The objective was to study trace element balances during continuous renal replacement therapy (CRRT) in intensive care patients. In a prospective randomized crossover trial, patients with acute renal failure received CRRT with either sodium bicarbonate (Bic) or sodium lactate (Lac) as a buffering agent over 2 consecutive 24-h periods. Copper, selenium, zinc, and thiamine were measured with highly sensitive analytic methods in plasma, replacement solutions, and effluent during 8-h periods. Balances were calculated as the difference between fluids administered and effluent losses and were compared with the recommended intakes (RI) from parenteral nutrition. Nineteen sessions were conducted in 11 patients aged 65 +/- 10 y. Baseline plasma concentrations of copper were normal, whereas those of selenium and zinc were below reference ranges; glutathione peroxidase was in the lower range of normal. The replacement solutions contained no detectable copper, 0.01 micromol Se/L (Bic and Lac), and 1.42 (Bic) and 0.85 (Lac) micromol Zn/L. Micronutrients were detectable in all effluents, and losses were stable in each patient; no significant differences were found between the Bic and Lac groups. The 24-h balances were negative for selenium (-0.97 micromol, or 2 times the daily RI), copper (-6.54 micromol, or 0.3 times the daily RI), and thiamine (-4.12 mg, or 1.5 times the RI) and modestly positive for zinc (20.7 micromol, or 0.2 times the RI). CRRT results in significant losses and negative balances of selenium, copper, and thiamine, which contribute to low plasma concentrations. Prolonged CRRT is likely to result in selenium and thiamine depletion despite supplementation at recommended amounts.

Gene-environment interactions in wet beriberi: effects of thiamine depletion in CD36-defect rats.

Selective vulnerability to thiamine deficiency is known to occur between individuals and within different tissues. However, no comprehensive explanation for this has been found, and there are no reports that reproduce the cardiovascular manifestations of human wet beriberi in animals. We hypothesized that the distinction of substrate reliance, namely, the primary dependency on glucose as substrate, could be an underlying factor in the selective vulnerability of thiamine deficiency. In the setting of impaired fatty acid entry, which occurs in CD36-defect rats, substrate reliance shifts from fatty acid to glucose, which would be expected to lead to a susceptibility to thiamine deficiency. Genomic DNA was analyzed for CD36 defects in three cognate strains of rats [spontaneously hypertensive rats (SHR)/NCrj, SHR/Izm, and Wistar-Kyoto (WKY)/NCrj], which identified the presence of a CD36 defect in SHR/NCrj rats but not in SHR/Izm and WKY/NCrj rats. Treatment with 2 wk of thiamine-depleted chow on 4-wk-old rats of each of these strains resulted in increased body and lung weight in the SHR/NCrj rats but not in the SHR/Izm and WKY/NCrj rats. The increased lung weight in the SHR/NCrj rats was accompanied with histological changes of congestive vasculopathy, which were not observed in either the SHR/Izm or the WKY/NCrj rats. Thiamine-deficient 12-wk-old SHR/NCrj rats demonstrated increased body weight (305.6 +/- 6.2 g in thiamine-deficient rats vs. 280.8 +/- 9.1 g in control; P < 0.0001), lactic acidemia (pH, 7.322 +/- 0.026 in thiamine-deficient rats vs. 7.443 +/- 0.016 in control; P < 0.0001; lactate, 2.42 +/- 0.28 mM in thiamine-deficient rats vs. 1.20 +/- 0.11 mM in control; P < 0.0001) and reduced systemic vascular resistance (4.61 +/- 0.42 x 104 dyn.s.cm-5 in thiamine-deficient rats vs. 6.55 +/- 1.36 x 104 dyn.s.cm-5 in control; P < 0.0001) with high cardiac output (186.0 +/- 24.7 ml in thiamine-deficient rats vs. 135.4 +/- 27.2 ml in control; P < 0.0019). In conclusion, SHR/NCrj rats harboring a genetic defect of long-chain fatty acid uptake present the relevant clinical cardiovascular signs of human wet beriberi, strongly indicating a close gene-environment interaction in wet beriberi.

Effects of furazolidone, PCB77, PCB126, Aroclor 1248, paraquat and p, p′-DDE on transketolase activity in embryonal chicken brain

The effect of in ovo exposure to PCBs, DDE and paraquat on transketolase activity was measured in 19-day-old chicken embryos. Furazolidone was used as a positive control for decreased activity of the enzyme. The potency of contaminants to interact with transketolase was also tested in an in vitro system, using control brain 7000× g supernatants containing the enzyme. No effects were found on transketolase activity after in ovo or in vitro exposure to PCB126, Aroclor, DDE or paraquat. PCB77 decreased transketolase activity in vitro, but only at concentrations that, extrapolated to in ovo exposure, would be lethal to the embryo. Furazolidone decreased transketolase activity both in ovo and in vitro. For this contaminant, thiamine residues were analysed in the yolk sacs, but no differences were found between exposed and non-exposed eggs. Transketolase is dependent on thiamine pyrophosphate as a cofactor, and therefore, the decreased enzyme activity could be the result of an interaction between furazolidone and thiamine metabolism. Since thiamine residues were not affected by furazolidone and transketolase inhibition in vitro was similar to the inhibition after in ovo exposure, it was concluded that furazolidone interacted with transketolase on the enzymatic level rather than by a depletion of thiamine.

Thiamine-Responsive Megaloblastic Anemia Syndrome: A Disorder of High-Affinity Thiamine Transport

ABSTRACTThiamine-responsive megaloblastic anemia (TRMA) syndrome (OMIM No. 249270) comprises a distinctive triad of clinical features: megaloblastic anemia with ringed sideroblasts, diabetes mellitus, and progressive sensorineural deafness. The TRMA gene has been mapped and cloned. Designated "SLC19A2" as a member of the solute carrier gene superfamily, this gene is mutated in all TRMA kindreds studied to date. The product of the SLC19A2 gene is a membrane protein which transports thiamine (vitamin B1) with sub-micromolar affinity. Cells from TRMA patients are uniquely sensitive to thiamine depletion to the nanomolar range, while pharmacologic doses of vitamin B1 ameliorate the anemia and diabetes. Here we review the current status of studies aimed at understanding the pathophysiology of this unique transport defect.

JNK1 is inactivated during thiamine deficiency-induced apoptosis in human neuroblastoma cells

Thiamine deficiency results in selective neuronal damage. A number of mechanisms have been proposed to account for brain damage associated with thiamine deficiency and to account for the focal nature of the loss of neurons. One proposed mechanism is programmed cell death. We found efficient induction of apoptosis in human neuroblastoma cells when the cells were deprived of thiamine. Although extensive mitochondrial damage was seen, the release of cytochrome c was not the triggering mechanism for thiamine deficiency-induced apoptosis. Instead, the activity of the cJun amino terminal kinase Jnk1 was lost, and this loss correlated temporally with induction of apoptosis. The loss was specific for Jnk1; Jnk2/3 activity remained unchanged. Loss of Jnk1 activity was not found in lymphoblasts, a cell type that did not undergo apoptosis when deprived of thiamine. These findings suggest that thiamine deficiency results in a cellular stress that brings about the loss of Jnk1 activity and the loss of its function of protecting cells from programmed cell death. We postulate that focal sensitivity to thiamine deficiency results, in part, from specific neuronal cell types being susceptible to the inactivation of Jnk1 in response to depletion of cellular thiamine.

Metabolic aspects of continuous renal replacement therapies

Metabolic aspects of continuous renal replacement therapies

Sensitivity to Thiamine Deficiency in Cultured Human Cells is Dependent on Cell Type and is Enhanced in Cells From Thiamine-Responsive Megaloblastic Anemia Patients

To address tissue-specific variation in sensitivity to thiamine deficiency, three human cell types were grown in medium with various thiamine concentrations. The activity of a cytosolic and a mitochondrial thiamine diphosphate-dependent enzyme was examined. Each cell type displayed a unique response to thiamine depletion with respect to α-ketoglutarate dehydrogenase and transketolase activity and to inhibition of cell growth. Loss of α-ketoglutarate dehydrogenase activity was similar in lymphoblasts and fibroblasts, whereas loss of activity in neuroblastoma cells was significantly more resistant to thiamine depletion. Transketolase activity in neuroblastoma cells was only moderately resistant to thiamine depletion, with the activity in fibroblasts being the most and in lymphoblasts the least resistant. Total transketolase activity was 33% higher in fibroblasts than in lymphoblasts and neuroblastoma cells, indicating a differential requirement for production and maintenance of transketolase activity in this cell type. Compared with normal lymphoblasts, those derived from patients with thiamine-responsive megaloblastic anemia were 100 to 1000 times more sensitive to thiamine depletion. Although fibroblasts from these patients also demonstrated a 1000-fold increase in sensitivity with respect to transketolase activity, α-ketoglutarate dehydrogenase activity demonstrated no enhanced sensitivity. The results indicate a complex, cell-type dependent regulation of intracellular pools of thiamine and its phosphorylated derivatives in response to fluctuating extracellular thiamine levels.

Biochemical evidence of thiamine depletion during the Cuban neuropathy epidemic, 1992–1993

During an epidemic outbreak of neuropathy in Cuba during 1992-1993, blood and urine samples were collected from 107 persons with confirmed neuropathy, from 106 control subjects without clinical abnormality who were broadly matched with the affected persons by age and domicile, and from 537 unmatched subjects, also free from clinical abnormality. The unmatched subjects lived in two locations in Cuba; at each location they were drawn from two age ranges: 11-15-y-old secondary school students and 16-64-y-old adults. Measurements of urinary thiamine and blood transketolase and its activation with thiamine pyrophosphate were made. For the neuropathy subjects, these measurements were repeated after 3 wk of rehabilitation. All groups showed biochemical evidence of thiamine depletion affecting 30-70% of their members, which is a high prevalence. Severity of biochemical depletion was, however, no greater in the neuropathy subjects than in the control subjects (P > 0.05). However, it was greater in Pinar del Rio, where the incidence of disease was higher, than in the city of Havana, where less disease was seen. Although the majority of the affected subjects responded biochemically to a daily oral multivitamin supplement containing thiamine (P < 0.001), in some cases normal biochemical status was not achieved even after 3 wk of intensive treatment. In the affected group, thiamine status was inversely correlated with the amount of alcohol consumed (P = 0.007). Thiamine status at the outset was correlated with clinical outcome after treatment. Although neither thiamine depletion nor alcohol abuse were likely to have been the sole cause of the neuropathy epidemic, they may have been contributory factors. Thiamine supplementation or food fortification may therefore be necessary in Cuba.

Early thiamin assimilation by yeasts under enological conditions: Impact on alcoholic fermentation kinetics

The effect of early must thiamin depletion by wild yeast strains ( i.e. Kloeckera and Saccharomyces species) on alcoholic fermentation kinetics was studied. Experimental conditions affecting thiamin assimilation by yeasts were first determined, using factorial designs. Then sequential and/or mixed cultures simulating wild yeast contamination, as observed during winemaking, were carried out in order to study the influence of early thiamin depletion on fermentation kinetics. The obtained results indicate that biological thiamin depletion leads to slow fermentation and may lead to sluggish or stuck fermentation. Moreover this phenomenon is amplified in media with high assimilable nitrogen contents. No release of thiamin from contaminant yeast and subsequent assimilation by fermentative yeast was observed, indicating that some enological practices (such as centrifugation of musts contaminated early) may lead to stuck fermentation.

The Korsakoff Syndrome

Investigations of the Korsakoff syndrome by researchers from different disciplines have proliferated in recent years, making it apposite to review the various findings. This review is based on the author's knowledge of reports in the major clinical and neuropsychological journals, supplemented by Medline searches to update particular subtopics. The Korsakoff syndrome is defined as a disproportionate impairment in memory, relative to other aspects of cognitive function, resulting from a nutritional (thiamine) depletion. The initial manifestations of the disorder are variable, and a persistent memory impairment can result from a non-alcoholic aetiology, although this seems to happen much less commonly than in the past - presumably because of generally higher standards of nutrition. Although there is agreement on the underlying neuropathology, the critical lesion sites for memory disorder have been debated. Recent evidence suggests that the circuit involving the mammillary bodies, the mammillo-thalamic tract and the anterior thalamus, rather than the medial dorsal nucleus of the thalamus, is particularly critical in the formation of new memories. The relationship of these deficits to thiamine depletion remains a topic of current investigation, as does the purported role of neurotransmitter depletions in the cholinergic, glutamate/GABA and catecholamine and serotonergic systems. Neuro-imaging studies have confirmed autopsy findings of more widespread structural and metabolic abnormalities, particularly involving the frontal lobes. The relationship of these neuropathological, neurochemical, and metabolic abnormalities to cognitive functioning, with particular reference to specific aspects of memory processing, has been considered in some detail. Whereas structural and/or neurochemical abnormalities within the limbic/diencephalic circuits account for anterograde amnesia, some other factor, such as frontal lobe dysfunction, must underlie the severe retrograde memory loss which is characteristically found in this syndrome.

Bioavailability of thiamine in cow milk and curd powders using rat bioassay

The biological availability of thiamine (relative to pure thiamine) in cow milk and curd prepared with mixed starter cultures consisting of Lectococcus lactis subsp lactis and cremoris and Propionibacterium shermanii was assessed using thiamine-depleted young rats. The cow milk and curd samples were freeze-dried. Repletion test diets provided 15 ~g thiamine/d from pasteurized cow milk, curd or pure thiamine for 21 d. Body weight gain, urinary thiamine excretion, hepatic thiamine content, erythrocyte transketolase (ETK) activities with and without added thiamine pyrophosphate (TPP) and TPP effect were determined as the response criteria for this purpose. Twenty-five-d thiamine depletion resulted in a significant (P < 0.01) decrease in body weight gain, decreased thiamine excretion, hepatic thiamine level, ETK activity and increased TPP effect in erythrocyte in comparison to rats receiving standard diet. Repletion with thiamine from different sources brought about a significant (P < 0.01) increase in body weight gain, urinary thiamine excretion, hepatic thiamine and ETK activity. TPP effect for erythrocytes declined significantly (P < 0.01). Restoration was more significant (P < 0.01) in the group receiving curd (CG) than that in the group receiving milk (MG), while it was higher in the MG group than the pure thiamine receiving group (PTG). It was concluded that biological availability of thiamine was greater from curd and milk than from pure thiamine.

Stereological study on the rat heart in chronic alimentary thiamine deficiency—Absence of myocardial changes despite starvation

Young male Wistar rats were fed with a thiamine-free diet for 35 days. The growth of the thiamine-deficient animals was considerably suppressed, as compared to a pair-fed control group (body weights: 140.4 +/- 4.3 g v. 243.1 +/- 4.3 g). A weight-matched control group was therefore evaluated in addition. Histological and ultrastructural investigations of the hearts did not reveal any morphological abnormalities. Stereological analysis was performed on left ventricular papillary muscles. One-way analysis of variance showed significant differences of stereological parameters between the three groups which were not associated with significant linear contrasts between the thiamine-deficient group and the weight-matched control group. Thus, the changes are not to be related to direct effects of thiamine depletion on the myocardium. Conclusively, the data indicate that stereological parameters (ratios) of the myocardium depend on heart weight and body weight, respectively, and are changed during normal growth. Our stereological estimates disclosed alterations of the following parameters: numerical density of myocardial cell nuclei, length density and volume density of capillaries, surface density of outer mitochondrial membranes and surface-to-volume ratio of mitochondria, and volume density of myofibrils. Furthermore, relative heart weights decrease in normal growth. It is concluded that our experimental model of chronic alimentary thiamine deficiency was associated with a normal structure of the myocardium. All significant differences between the thiamine-deficient group and the control group are explained by body weight changes following starvation in chronic thiamine deficiency.

Enhanced sensitivity of cerebellar Purkinje cells to iontophoretically-applied serotonin in thiamine deficiency

Electrophysiological aspects of thiamine depletion in the rat induced by dietary deficiency are described. Behavioral changes as well as qualitative and quantitative alterations in the sensitivity of cerebellar Purkinje cells to iontophoretically-applied 5-hydroxytryptamine (5-HT) were observed. Thiamine-deficient rats were characterized essentially by ataxia, piloerection, paresis, apparent weakness, and hypothermia after 4–6 weeks on a thiamine-free diet. Basal Purkinje cell firing frequency was unaffected by thiamine deficiency. The response of Purkinje cells to iontophoretically-applied 5-HT was solely inhibitory in deficient rats. In control rats, however, responses to 5-HT were excitatory, biphasic, or inhibitory. Neurons in the thiamine-deficient animals were more sensitive to the inhibitory effects of 5-HT, as demonstrated by a significant parallel shift to the left of the dose-response curve. Durations of 5-HT effects were similar in both groups. Dose-response relationships for GABA-induced inhibition of Purkinje cell firing from thiamine deficient and control rats did not differ from one another. These data demonstrate a relatively selective effect of thiamine depletion on cerebellar serotonergic neurotransmission assessed electrophysiologically. We believe there is up-regulation of 5-HT receptors on Purkinje cells caused by thiamine deficiency-induced impairment of indoleamine input to the cerebellum from raphe and related nuclei.

Thiamin depletion after ethanol and acetaldehyde administration to rabbits.

The role of thiamin in the catabolism of ethanol and acetaldehyde has been investigated. When thiamin and subsequently ethanol were administered orally to rabbits, the thiamin concentration in blood increased slightly during the first 3 h and then decreased gradually. After 12 h, it became lower than the value before thiamin administration. Finally, it reached the lowest value after 24 h and then increased slowly to revert to normal in 72 h. It is suggested that thiamin participates in the catabolic pathway of ethanol. An oral administration of pyrazole, an inhibitor of alcohol dehydrogenase, followed by ethanol to rabbits caused a delay in ethanol elimination from blood. When acetaldehyde was injected intravenously to rabbits, thiamin concentration and the transketolase activity in blood decreased gradually and after 12 h the thiamin level reached its lowest value, then increased slowly and normalized in 72 h. Thus, it could be postulated that the decrease in thiamin after an acute ethanol ingestion linked greatly to the acetaldehyde catabolism.

ETHANOL, THIAMINE AND BRAIN DAMAGE

In this paper an attempt has been made to identify important factors governing the supply of thiamine and to examine the relative roles of thiamine and ethanol in the pathogenesis of alcoholic brain damage. Thiamine depletion occurs in alcoholics principally through decreased intake, impaired absorp tion and reduced hepatic storage. The kinetics of thiamine uptake and turnover in brain are such that any fall in circulating levels of the vitamin may significantly impair the supply to the brain. The brain depends on an adequate supply of glucose both as an energy source and as a donor of carbon fragments for protein and lipid biosynthesis. Glucose utilisation is, however, thiamine dependent and it is likely that this is a major factor in the production of thiamine deficient brain damage. Ethanol alone can cause a number of structural alterations in brain tissue and these lesions may be found in alcoholics either in association with or in the absence of thiamine deficient lesions. It is also probable that ethanol and thiamine deficiency act synergistically to produce structural damage. Recurrent deficiences of many different kinds also play a part in the production of cumulative brain damage in the alcoholic.