Selective response of various brain cell types during neurodegeneration induced by mild impairment of oxidative metabolism

Thiamine and benfotiamine: Focus on their therapeutic potential

Thiamine, also known as vitamin B1, is an essential nutrient that plays a crucial role in energy metabolism and overall health. It is a water-soluble vitamin that plays an important role in the conversion of carbohydrates into energy in the body. Thiamine is essential for the proper functioning of the nervous system, heart and muscles. Thiamine deficiency is a life-threatening disease that leads to various disorders and lesions in the nerves and brain, at least in vertebrates. Several thiamine precursors with higher bioavailability have been developed to compensate for thiamine deficiency, including benfotiamine. Benfotiamine is more bioavailable and has higher tissue penetration than thiamine. Studies have shown its antioxidant and anti-inflammatory potential in activated immune and glial cells. It also improves complications observed in type 2 diabetes and has beneficial effects in mouse models of neurodegenerative disease. Benfotiamine represents an off-the-shelf agent used to support nerve health, promote healthy aging and support glucose metabolism. Accordingly, the present review aimed to provide an overview of the neuroprotective effects of thiamine/benfotiamine in the context of inflammation and oxidative stress.

The importance of thiamine (vitamin B1) in humans

Thiamine (thiamin, B1) is a vitamin necessary for proper cell function. It exists in a free form as a thiamine, or as a mono-, di- or triphosphate. Thiamine plays a special role in the body as a coenzyme necessary for the metabolism of carbohydrates, fats and proteins. In addition, it participates in the cellular respiration and oxidation of fatty acids: in malnourished people, high doses of glucose result in acute thiamine deficiency. It also participates in energy production in the mitochondria and protein synthesis. In addition, it is also needed to ensure the proper functioning of the central and peripheral nervous system, where it is involved in neurotransmitter synthesis. Its deficiency leads to mitochondrial dysfunction, lactate and pyruvate accumulation, and consequently to focal thalamic degeneration, manifested as Wernicke's encephalopathy or Wernicke-Korsakoff syndrome. It can also lead to severe or even fatal neurologic and cardiovascular complications, including heart failure, neuropathy leading to ataxia and paralysis, confusion, or delirium. The most common risk factor for thiamine deficiency is alcohol abuse. This paper presents current knowledge of the biological functions of thiamine, its antioxidant properties, and the effects of its deficiency in the body.

Dietary inflammation index is associated with dyslipidemia: evidence from national health and nutrition examination survey, 1999-2019

BACKGROUND AND AIMS

This study aimed to investigate the association between the Dietary Inflammatory Index (DII) and dyslipidemia, as well as to evaluate the mortality risk associated with DII in participants with dyslipidemia.

METHODS

Data from the National Health and Nutrition Examination Survey database were divided into dyslipidemia and non-dyslipidemia groups. The association between DII and dyslipidemia was investigated using the weighted chi-square test, weighted t-test, and weighted logistic regression. Weighted Cox proportional hazards models were used to estimate the hazard ratios and 95% confidence intervals for all-cause and cardiovascular disease-related mortality within the dyslipidemia group.

RESULTS

A total of 17,820 participants, including 4,839 without and 12,981 with dyslipidemia were analyzed in this study. The results showed that DII was higher in the dyslipidemia group compared to the non-dyslipidemia group (1.42 ± 0.03 vs. 1.23 ± 0.04, P < 0.01). However, for energy, protein, carbohydrates, total fat, saturated fat, and iron, DII was lower in participants with dyslipidemia. Logistic regression analysis revealed a strong positive association between DII and dyslipidemia. The odds ratios for dyslipidemia from Q1 to Q4 were 1.00 (reference), 1.12 (0.96-1.31), 1.23 (1.04-1.44), and 1.33 (1.11-1.59), respectively. In participants with dyslipidemia, a high DII was associated with high all-cause and cardiovascular mortality.

CONCLUSION

DII was closely associated with dyslipidemia. A pro-inflammatory diet may play a role in unfavorable consequences and is linked to both all-cause mortality and cardiovascular death in patients with dyslipidemia. Participants with dyslipidemia should pay attention to their anti-inflammatory dietary patterns.

Pharmacological thiamine levels as a therapeutic approach in Alzheimer's disease

of the study.

Activation of the Hepcidin-Ferroportin1 pathway in the brain and astrocytic-neuronal crosstalk to counteract iron dyshomeostasis during aging

During physiological aging, iron accumulates in the brain with a preferential distribution in regions that are more vulnerable to age-dependent neurodegeneration such as the cerebral cortex and hippocampus. In the brain of aged wild-type mice, alteration of the Brain Blood Barrier integrity, together with a marked inflammatory and oxidative state lead to increased permeability and deregulation of brain-iron homeostasis. In this context, we found that iron accumulation drives Hepcidin upregulation in the brain and the inhibition of the iron exporter Ferroportin1. We also observed the transcription and the increase of NCOA4 levels in the aged brain together with the increase of light-chain enriched ferritin heteropolymers, more efficient as iron chelators. Interestingly, in cerebral cortex and hippocampus, Ferroportin1 is mainly expressed by astrocytes, while the iron storage protein ferritin light-chain by neurons. This differential distribution suggests that astrocytes mediate iron shuttling in the nervous tissue and that neurons are unable to metabolize it. Our findings highlight for the first time that Hepcidin/Ferroportin1 axis and NCOA4 are directly involved in iron metabolism in mice brain during physiological aging as a response to a higher brain iron influx.

Aerobic Fitness, B-Vitamins, and Weight Status Are Related to Selective Attention in Children

There is an increasing prevalence of poor health behaviors during childhood, particularly in terms of physical activity and nutrition. This trend has occurred alongside a growing body of evidence linking these behaviors to cognitive function. B-vitamins are thought to be particularly important in the neural development that occurs during pregnancy, as well as in healthy cognitive aging. However, much less is known regarding the role of B-vitamins during childhood. Given that preadolescent childhood is a critical period for cognitive development, this study investigated the relationship between specific aspects of nutrition, particularly B-vitamins, and related health factors (e.g., body mass, fitness) on selective attention in children. Children (n = 85; 8-11 years) completed a selective attention task to assess inhibition. Participant's dietary intake was collected using the Automated Self-Administered 24-h dietary assessment tool. Correlations between specific nutrients, BMI, fitness, and task performance were investigated. After accounting for demographic variables and total caloric intake, increased B-vitamin intake (i.e., thiamin and folic acid) was associated with shorter reaction times (p's < 0.05), fitness was associated with greater response accuracy (p < 0.05), and increased BMI was related to increased variability in reaction times (p < 0.05). Together, these findings suggest that aspects of health may have unique contributions on cognitive performance. Proper physical health and nutrition are imperative for effective cognitive functioning in preadolescent children. Targeted efforts aimed at health education amongst this population could ensure proper cognitive development during school-age years, providing a strong foundation throughout life.

The Inferior Colliculus in Alcoholism and Beyond

Post-mortem neuropathological and in vivo neuroimaging methods have demonstrated the vulnerability of the inferior colliculus to the sequelae of thiamine deficiency as occurs in Wernicke-Korsakoff Syndrome (WKS). A rich literature in animal models ranging from mice to monkeys-including our neuroimaging studies in rats-has shown involvement of the inferior colliculi in the neural response to thiamine depletion, frequently accomplished with pyrithiamine, an inhibitor of thiamine metabolism. In uncomplicated alcoholism (i.e., absent diagnosable neurological concomitants), the literature citing involvement of the inferior colliculus is scarce, has nearly all been accomplished in preclinical models, and is predominately discussed in the context of ethanol withdrawal. Our recent work using novel, voxel-based analysis of structural Magnetic Resonance Imaging (MRI) has demonstrated significant, persistent shrinkage of the inferior colliculus using acute and chronic ethanol exposure paradigms in two strains of rats. We speculate that these consistent findings should be considered from the perspective of the inferior colliculi having a relatively high CNS metabolic rate. As such, they are especially vulnerable to hypoxic injury and may be provide a common anatomical link among a variety of disparate insults. An argument will be made that the inferior colliculi have functions, possibly related to auditory gating, necessary for awareness of the external environment. Multimodal imaging including diffusion methods to provide more accurate in vivo visualization and quantification of the inferior colliculi may clarify the roles of brain stem nuclei such as the inferior colliculi in alcoholism and other neuropathologies marked by altered metabolism.

The Relevance of Thiamine Evaluation in a Practical Setting

Thiamine is a crucial cofactor involved in the maintenance of carbohydrate metabolism and participates in multiple cellular metabolic processes. Although thiamine can be obtained from various food sources, some common food groups are deficient in thiamine, and it can be denatured by high temperature and pH. Additionally, different drugs can alter thiamine metabolism. In addition, the half-life of thiamine in the body is between 1 and 3 weeks. All these factors could provide an explanation for the relatively short period needed to develop thiamine deficiency and observe the consequent clinical symptoms. Thiamine deficiency could lead to neurological and cardiological problems. These clinical conditions could be severe or even fatal. Marginal deficiency too may promote weaker symptoms that might be overlooked. Patients undergoing upper gastrointestinal or pancreatic surgery could have or develop thiamine deficiency for many different reasons. To achieve the best outcome for these patients, we strongly recommend the execution of both an adequate preoperative nutritional assessment, which includes thiamine evaluation, and a close nutritional follow up to avoid a nutrient deficit in the postoperative period.

Thiamine Deficiency Causes Long-Lasting Neurobehavioral Deficits in Mice

Thiamine deficiency (TD) has detrimental effects on brain health and neurobehavioral development, and it is associated with many aging-related neurological disorders. To facilitate TD-related neuropsychological studies, we generated a TD mouse model by feeding a thiamine-deficient diet for 30 days, followed by re-feeding the control diet for either one week or 16 weeks as recovery treatment. We then performed neurobehavioral tests in these two cohorts: cohort of one week post TD treatment (1 wk-PTDT) and 16 weeks post TD treatment (16 wks-PTDT). The TD mice showed no significant difference from control in any tests in the 1 wk-PTDT cohort at the age of 13-14 weeks. The tests for the 16 wks-PTDT cohort at the age of 28-29 weeks, however, demonstrated anxiety and reduced locomotion in TD animals in open field and elevated plus maze. In comparison, rotor rod and water maze revealed no differences between TD and control mice. The current findings of the differential effects of the same TD treatment on locomotion and anxiety at different ages may reflect the progressive and moderate change of TD-induced neurobehavioral effects. The study suggests that, even though the immediate neurobehavioral impact of TD is modest or negligible at a young age, the impact could develop and become severe during the aging process.

Axonopathy Likely Initiates Neuropathological Processes Via a Mechanism of Axonal Leakage in Alzheimer's Mouse Models

BACKGROUND

The formation of hyperphosphorylated tau and the production of β-amyloid are thought to be critical steps contributing to the pathological mechanisms in Alzheimer's disease (AD). However, there has been a long-lasting debate over their importance in the onset of AD. Recent studies have demonstrated that axonopathy is considered as an early neuropathological change of AD. However, the exact relationship between the development of axonopathy and the classic neuropathological changes such as senile plaques (SPs) and neurofibrillary tangles (NFTs) is unclear.

OBJECTIVE

The aim of this study was to investigate whether the formation of SPs and NFTs is associated with the development of axonal leakage.

METHOD AND RESULTS

Here we show that the formation and development of axonal leakage - a novel axonopathy is an age-dependent process, accompanied by swellings of axons and varicosities and associated with chronic oxidative stress induced by thiamine deficient (TD) diet in Kunming mice. In an APP/PS1 transgenic mouse model of AD, axonal leakage appears at 3 months, becomes more obvious at 6 months and severe, beyond 1 year. We also show that slight axonal leakage is related to the formation of hyperphosphorylated tau, but not plaques, and that only severe axonal leakage accompanied by the extensive swollen axons and varicosities, and overproduction of β-amyloid leads to the formation of SPs and hyperphosphorylated tau.

CONCLUSION

These data provide an explanation of the common origin and development of SPs and NFTs, and suggest that axonal leakage might be a key event in the development of the neuropathological processes in AD.

Protective Effects of Citicoline and Benfotiamine Each Alone and in Combination on Streptozotocin-induced Memory Impairment in Mice

Objective

Diabetes mellitus is associated with cognitive disorders such as Alzheimer’s disease. Studies have shown that citicoline and benfotiamine can improve memory and learning through different mechanism of actions. The aim of this study was to compare the individual effects of benfotiamine (100, 200, 300 mg/kg) and citicoline (50, 100, 250, 500 mg/kg, gavage) and their co-administration on memory impairments in diabetic mice.

Methods

Diabetes was induced by a single dose of streptozotocin (STZ, 140 mg/kg, intraperitoneal) and benfotiamine and/or citicoline were administered for three weeks. Memory was evaluated using the object recognition task (ORT) and passive avoidance test (PAT).

Results

Results from ORT shows that citicoline at 50, 100, 250, and 500 mg/kg and benfotiamine at 100, 200, and 300 mg/kg and their combination (benfotiamine at 100 mg/kg added to citicoline at 50, 100, and 250 mg/kg) are equally effective in reversing the memory loss induced by STZ (p < 0.001). PAT results demonstrate that citicoline at 100, 250, and 500 mg/kg and benfotiamine at above doses did not improve the latency time when administered separately, but benfotiamine at a fixed dose of 100 mg/kg in the presence of citicoline at 50, 100, and 250 mg/kg increased the latency time and improved memory significantly.

Conclusion

In conclusion, in PAT, co-administration of benfotiamine and citicoline was more effective than either alone in improving memory. Regarding ORT, although benfotiamine added to citicoline improved memory notably, the difference between combination therapy and single-drug therapy was not considerable.

Metabolic responses of BV-2 cells to puerarin on its polarization using ultra-performance liquid chromatography-mass spectrometry

Microglia are the primary immune cells in the central nervous system with functional plasticity. They can be activated into M1 and M2 phenotypes when neuroinflammation-related diseases occur. M1 phenotype cells produce pro-inflammatory mediators that cause neuroinflammation and the M2 phenotype can secrete anti-inflammatory cytokines that protect neurons from damage. Therefore, inhibiting the M1 phenotype while stimulating the M2 phenotype has been suggested as a potential therapeutic approach for treating neuroinflammation-related diseases. Puerarin has been demonstrated to exert anti-inflammatory and neuroprotective effects. However, the role of puerarin in regulating microglia polarization and its reaction mechanism has not been fully elucidated. In this paper, a metabolomics approach with ultra-performance liquid chromatography-mass spectrometry was performed to investigate the metabolic changes of BV-2 cells in different phenotypes and test the effects of puerarin on polarization. Thirty-nine metabolites were identified as the biomarkers related to the polarization of BV-2 cells and puerarin intervention reverted the content of most of the biomarkers. Our study demonstrated that puerarin could play a key role in M1/M2 polarization of BV-2 cells from a perspective of metabolomics, and it could regulate the balance between promotion and suppression of inflammation.

Systemic Mitochondrial Oxidative Phosphorylation Protein Levels Correlate with Neuroimaging Measures in Chronically HIV-Infected Individuals

Few studies have examined systemic mitochondrial function in conjunction with brain imaging in human immunodeficiency virus (HIV) disease. Oxidative phosphorylation enzyme protein levels of peripheral blood mononuclear cells were measured in association with neuroimaging indices in 28 HIV+ individuals. T1-weighted magnetic resonance imaging yielded volumes of seven brain regions of interest; diffusion tensor imaging determined fractional anisotropy (FA) and mean diffusivity (MD) in the corpus callosum (CC). Higher nicotinamide adenine dinucleotide dehydrogenase levels correlated with lower volumes of thalamus (p = .005) and cerebral white matter (p = .049) and, in the CC, with lower FA (p = .011, body; p = .005, genu; p = .009, total CC) and higher MD (p = .023, body; p = .035, genu; p = .019, splenium; p = .014, total CC). Greater cytochrome c oxidase levels correlated with lower thalamic (p = .034) and cerebellar gray matter (p = .021) volumes. The results indicate that systemic mitochondrial cellular bioenergetics are associated with brain health in HIV.

Benfotiamine treatment activates the Nrf2/ARE pathway and is neuroprotective in a transgenic mouse model of tauopathy

Impaired glucose metabolism, decreased levels of thiamine and its phosphate esters, and reduced activity of thiamine-dependent enzymes, such as pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and transketolase occur in Alzheimer's disease (AD). Thiamine deficiency exacerbates amyloid beta (Aβ) deposition, tau hyperphosphorylation and oxidative stress. Benfotiamine (BFT) rescued cognitive deficits and reduced Aβ burden in amyloid precursor protein (APP)/PS1 mice. In this study, we examined whether BFT confers neuroprotection against tau phosphorylation and the generation of neurofibrillary tangles (NFTs) in the P301S mouse model of tauopathy. Chronic dietary treatment with BFT increased lifespan, improved behavior, reduced glycated tau, decreased NFTs and prevented death of motor neurons. BFT administration significantly ameliorated mitochondrial dysfunction and attenuated oxidative damage and inflammation. We found that BFT and its metabolites (but not thiamine) trigger the expression of Nrf2/antioxidant response element (ARE)-dependent genes in mouse brain as well as in wild-type but not Nrf2-deficient fibroblasts. Active metabolites were more potent in activating the Nrf2 target genes than the parent molecule BFT. Docking studies showed that BFT and its metabolites (but not thiamine) bind to Keap1 with high affinity. These findings demonstrate that BFT activates the Nrf2/ARE pathway and is a promising therapeutic agent for the treatment of diseases with tau pathology, such as AD, frontotemporal dementia and progressive supranuclear palsy.

Thiamine for preventing dementia development among patients with alcohol use disorder: A nationwide population-based cohort study

OBJECTIVE OF STUDY

Alcohol use disorder is one of the most important factors contributing to dementia. This study examined the protective effect of thiamine administration on the incidence of dementia among patients with alcohol use disorder in Taiwan by evaluating a nationwide database.

METHODS

We retrieved data for this retrospective cohort study from the Longitudinal Health Insurance Database 1995-2000. Patients receiving thiamine therapy after the diagnosis of alcohol use disorder were recruited as the thiamine therapy (TT) group, and the comparison group without TT (NTT group) included randomly assigned and age-, sex-, and index year-matched individuals with alcohol use disorder. Demographic data, comorbid medical disorders, and psychotropic medication use were evaluated and controlled. The cumulative defined daily dose (DDD) was analyzed to demonstrate the dose effect.

RESULTS

Each group had 5059 patients. The TT group had a lower crude hazard ratio (0.76; 95% confidence interval: 0.60-0.96) of dementia than the NTT group. After adjusting for demographic data, comorbidity, and psychotropic medication use, the adjusted hazard ratio was 0.54 (95% confidence interval: 0.43-0.69). The significance existed among TT subjects with cumulative DDD higher than 23. The Kaplan-Meier analysis demonstrated a lower cumulative incidence of dementia in the TT group than in the NTT group.

CONCLUSION

The results indicated that thiamine therapy could be a protective factor for dementia development in patients with alcohol use disorder. Thiamine therapy should be a crucial part of the treatment plan and health policies to prevent dementia development or progression among patients with alcohol use disorder.

Comparative effects of EtOH consumption and thiamine deficiency on cognitive impairment, oxidative damage, and β-amyloid peptide overproduction in the brain

The effects of chronic EtOH consumption, associated or not with thiamine deficiency (TD), on cognitive impairment, oxidative damage, and β-amyloid (Aβ) peptide accumulation in the brain were investigated in male C57BL/6 mice. We established an alcoholic mouse model by feeding an EtOH liquid diet, a TD mouse model by feeding a thiamine-depleted liquid diet, and an EtOH treatment associated with TD mouse model by feeding a thiamine-depleted EtOH liquid diet for 7 weeks. The learning and memory functions of the mice were detected through the Y-maze test. Biochemical parameters were measured using corresponding commercial kits. The Aβ expression in the hippocampus was observed by immunohistochemical staining. Several results were obtained. First, EtOH significantly reduced cognitive function by significantly decreasing the Glu content in the hippocampus; increasing the AChE activity in the cortex; and reducing the thiamine level, and superoxide dismutase (SOD), glutathione peroxidase (GPx), and choline acetyltransferase (ChAT) activities in both the hippocampus and cortex. The treatment also increased the levels of malondialdehyde (MDA), protein carbonyl, 8-hydroxydeoxyguanosine (8-OHdG), and nitric oxide (NO) and the activities of total nitric oxide synthase (tNOS), inducible nitric oxide synthase (iNOS), and monoamine oxidase B (MAO-B). Furthermore, EtOH enhanced the expression levels of Aβ_1-42 and Aβ_1-40 in the hippocampus. Second, TD induced the same dysfunctions caused by EtOH in the biochemical parameters, except for learning ability, 8-OHdG content, and GPx, tNOS, and AChE activities in the cortex. Third, the modification of MDA, protein carbonyl and NO levels, and GPx, iNOS, ChAT, and MAO-B activities in the brain induced by chronic EtOH treatment associated with TD was greater than that induced by EtOH or TD alone. The synergistic effects of EtOH and TD on Aβ_1-40 and Glu release, as well as on SOD activity, depended on their actions on the hippocampus or cortex. These findings suggest that chronic EtOH consumption can induce TD, cognitive impairment, Aβ accumulation, oxidative stress injury, and neurotransmitter metabolic abnormalities. Furthermore, the association of chronic EtOH consumption with TD causes dramatic brain dysfunctions with a severe effect on the brain.

Thiamine deficiency induces endoplasmic reticulum stress and oxidative stress in human neurons derived from induced pluripotent stem cells

Thiamine (vitamin B1) deficiency (TD) plays a major role in the etiology of Wernicke's encephalopathy (WE) which is a severe neurological disorder. TD induces selective neuronal cell death, neuroinflammation, endoplasmic reticulum (ER) stress and oxidative stress in the brain which are commonly observed in many aging-related neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and progressive supranuclear palsy (PSP). However, the underlying cellular and molecular mechanisms remain unclear. The progress in this line of research is hindered due to the lack of appropriate in vitro models. The neurons derived for the human induced pluripotent stem cells (hiPSCs) provide a relevant and powerful tool for the research in pharmaceutical and environmental neurotoxicity. In this study, we for the first time used human induced pluripotent stem cells (hiPSCs)-derived neurons (iCell neurons) to investigate the mechanisms of TD-induced neurodegeneration. We showed that TD caused a concentration- and duration-dependent death of iCell neurons. TD induced ER stress which was evident by the increase in ER stress markers, such as GRP78, XBP-1, CHOP, ATF-6, phosphorylated eIF2α, and cleaved caspase-12. TD also triggered oxidative stress which was shown by the increase in the expression 2,4-dinitrophenyl (DNP) and 4-hydroxynonenal (HNE). ER stress inhibitors (STF-083010 and salubrinal) and antioxidant N-acetyl cysteine (NAC) were effective in alleviating TD-induced death of iCell neurons, supporting the involvement of ER stress and oxidative stress. It establishes that the iCell neurons are a novel tool to investigate cellular and molecular mechanisms for TD-induced neurodegeneration.

Adjuvant thiamine improved standard treatment in patients with major depressive disorder: results from a randomized, double-blind, and placebo-controlled clinical trial

Given that antidepressants (ADs) work slowly, there is interest in means to accelerate their therapeutic effect and to reduce side effects. In this regard, thiamine (vitamin B₁) is attracting growing interest. Thiamine is an essential nutrient, while thiamine deficiency leads to a broad variety of disorders including irritability and symptoms of depression. Here, we tested the hypothesis that adjuvant thiamine would reduce depression, compared to placebo. A total of 51 inpatients (mean age: 35.2 years; 53 % females) with MDD (Hamilton Depression Rating Scale score (HDRS) at baseline: >24) took part in the study. A standardized treatment with SSRI was introduced and kept at therapeutic levels throughout the study. Patients were randomly assigned either to the thiamine or the placebo condition. Experts rated (HDRS) symptoms of depression at baseline, and after 3, 6, and 12 weeks (end of the study). Between baseline and the end of the study, depression had reduced in both groups. Compared to placebo, adjuvant thiamine improved symptoms of depression after 6 week of treatment, and improvements remained fairly stable until the end of the study, though mean differences at week 12 were not statistically significant anymore. No adverse side effects were reported in either group. Results suggest that among younger patients with MDD adjuvant thiamine alleviated symptoms of depression faster compared to placebo. Importantly, improvements were observed within 6 weeks of initiation of treatment. Thus, thiamine might have the potential to counteract the time lag in the antidepressant effects of ADs.

Vitamin B1 (thiamine) and dementia

The earliest and perhaps best example of an interaction between nutrition and dementia is related to thiamine (vitamin B1). Throughout the last century, research showed that thiamine deficiency is associated with neurological problems, including cognitive deficits and encephalopathy. Multiple similarities exist between classical thiamine deficiency and Alzheimer's disease (AD) in that both are associated with cognitive deficits and reductions in brain glucose metabolism. Thiamine-dependent enzymes are critical components of glucose metabolism that are reduced in the brains of AD patients and by thiamine decline, and a decrease in their levels could account for the reduction in glucose metabolism. In preclinical models, reduced thiamine can drive AD-like abnormalities, including memory deficits, neuritic plaques, and hyperphosphorylation of tau. Furthermore, excess thiamine diminishes AD-like pathologies. In addition to dietary deficits, drugs or other manipulations that interfere with thiamine absorption can cause thiamine deficiency. Elucidating the reasons why the brains of AD patients are functionally thiamine deficient and determining the effects of thiamine restoration may provide critical information to help treat patients with AD.

PKR downregulation prevents neurodegeneration and β-amyloid production in a thiamine-deficient model

Brain thiamine homeostasis has an important role in energy metabolism and displays reduced activity in Alzheimer's disease (AD). Thiamine deficiency (TD) induces regionally specific neuronal death in the animal and human brains associated with a mild chronic impairment of oxidative metabolism. These features make the TD model amenable to investigate the cellular mechanisms of neurodegeneration. Once activated by various cellular stresses, including oxidative stress, PKR acts as a pro-apoptotic kinase and negatively controls the protein translation leading to an increase of BACE1 translation. In this study, we used a mouse TD model to assess the involvement of PKR in neuronal death and the molecular mechanisms of AD. Our results showed that the TD model activates the PKR-eIF2α pathway, increases the BACE1 expression levels of Aβ in specific thalamus nuclei and induces motor deficits and neurodegeneration. These effects are reversed by PKR downregulation (using a specific inhibitor or in PKR knockout mice).

Excessive α-tocopherol exacerbates microglial activation and brain injury caused by acute ischemic stroke

The vitamin E family includes both tocopherols and tocotrienols, where α-tocopherol (αTOC) is the most bioavailable form. Clinical trials testing the therapeutic efficacy of high-dose αTOC against stroke have largely failed or reported negative outcomes when a "more is better" approach to supplementation (>400 IU/d) was used. This work addresses mechanisms by which supraphysiologic αTOC may contribute to stroke-induced brain injury. Ischemic stroke injury and the neuroinflammatory response were studied in tocopherol transfer protein-deficient mice maintained on a diet containing αTOC vitamin E at the equivalent human dose of 1680 IU/d. Ischemic stroke-induced brain injury was exacerbated in the presence of supraphysiologic brain αTOC levels. At 48 h after stroke, S100B and RAGE expression was increased in stroke-affected cortex of mice with elevated brain αTOC levels. Such increases were concomitant with aggravated microglial activation and neuroinflammatory signaling. A poststroke increase in markers of oxidative injury and neurodegeneration in the presence of elevated brain αTOC establish that at supraphysiologic levels, αTOC potentiates neuroinflammatory responses to acute ischemic stroke. Exacerbation of microglial activation by excessive αTOC likely depends on its unique cell signaling regulatory properties independent of antioxidant function. Against the background of clinical failure for high-dose αTOC, outcomes of this work identify risk for exacerbating stroke-induced brain injury as a result of supplementing diet with excessive levels of αTOC.

Associations between in vivo neuroimaging and postmortem brain cytokine markers in a rodent model of Wernicke's encephalopathy

Thiamine (vitamin B1) deficiency, associated with a variety of conditions, including chronic alcoholism and bariatric surgery for morbid obesity, can result in the neurological disorder Wernicke's encephalopathy (WE). Recent work building upon early observations in animal models of thiamine deficiency has demonstrated an inflammatory component to the neuropathology observed in thiamine deficiency. The present, multilevel study including in vivo magnetic resonance imaging (MRI) and spectroscopy (MRS) and postmortem quantification of chemokine and cytokine proteins sought to determine whether a combination of these in vivo neuroimaging tools could be used to characterize an in vivo MR signature for neuroinflammation. Thiamine deficiency for 12days was used to model neuroinflammation; glucose loading in thiamine deficiency was used to accelerate neurodegeneration. Among 38 animals with regional brain tissue assayed postmortem for cytokine/chemokine protein levels, three groups of rats (controls+glucose, n=6; pyrithiamine+saline, n=5; pyrithiamine+glucose, n=13) underwent MRI/MRS at baseline (time 1), after 12days of treatment (time 2), and 3h after challenge (glucose or saline, time 3). In the thalamus of glucose-challenged, thiamine deficient animals, correlations between in vivo measures of pathology (lower levels of N-acetyle aspartate and higher levels of lactate) and postmortem levels of monocyte chemotactic protein-1 (MCP-1, also known as chemokine ligand 2, CCL2) support a role for this chemokine in thiamine deficiency-related neurodegeneration, but do not provide a unique in vivo signature for neuroinflammation.

Thiamine deficiency promotes T cell infiltration in experimental autoimmune encephalomyelitis: the involvement of CCL2

Multiple sclerosis (MS) is a complex multifactorial disease that results from the interplay between environmental factors and a susceptible genetic background. Experimental autoimmune encephalomyelitis (EAE) has been widely used to investigate the mechanisms underlying MS pathogenesis. Chemokines, such as CCL2, are involved in the development of EAE. We have previously shown that thiamine deficiency (TD) induced CCL2 in neurons. We hypothesized that TD may affect the pathogenesis of EAE. In this study, EAE was induced in C57BL/6J mice by the injection of myelin oligodendroglial glycoprotein (MOG) peptides 35-55 with or without TD. TD aggravated the development of EAE, which was indicated by clinical scores and pathologic alterations in the spinal cord. TD also accelerated the development of EAE in an adoptive transfer EAE model. TD caused microglial activation and a drastic increase (up 140%) in leukocyte infiltration in the spinal cord of the EAE mice; specifically, TD increased Th1 and Th17 cells. TD upregulated the expression of CCL2 and its receptor CCR2 in the spinal cord of EAE mice. Cells in peripheral lymph node and spleen isolated from MOG-primed TD mice showed much stronger proliferative responses to MOG. CCL2 stimulated the proliferation and migration of T lymphocytes in vitro. Our results suggested that TD exacerbated the development of EAE through activating CCL2 and inducing pathologic inflammation.

Autophagy alleviates neurodegeneration caused by mild impairment of oxidative metabolism

Thiamine deficiency (TD) causes mild impairment of oxidative metabolism and region-selective neuronal loss in the brain, which may be mediated by neuronal oxidative stress, endoplasmic reticulum (ER) stress, and neuroinflammation. TD-induced brain damage is used to model neurodegenerative disorders, and the mechanism for the neuronal death is still unclear. We hypothesized that autophagy might be activated in the TD brain and play a protective role in TD-induced neuronal death. Our results demonstrated that TD induced the accumulation of autophagosomes in thalamic neurons measured by transmission electron microscopy, and the up-regulation of autophagic markers LC3-II, Atg5, and Beclin1 as measured with western blotting. TD also increased the expression of autophagic markers and induced LC3 puncta in SH-SY5Y neuroblastoma cells. TD-induced expression of autophagic markers was reversed once thiamine was re-administered. Both inhibition of autophagy by wortmannin and Beclin1 siRNA potentiated TD-induced death of SH-SY5Y cells. In contrast, activation of autophagy by rapamycin alleviated cell death induced by TD. Intraperitoneal injection of rapamycin stimulated neuronal autophagy and attenuated TD-induced neuronal death and microglia activation in the submedial thalamus nucleus (SmTN). TD inhibited the phosphorylation of p70S6 kinase, suggesting mTOR/p70S6 kinase pathway was involved in the TD-induced autophagy. These results suggest that autophagy is neuroprotective in response to TD-induced neuronal death in the central nervous system. This opens a potential therapeutic avenue for neurodegenerative diseases caused by mild impairment of oxidative metabolism. Autophagy is neuroprotective in response to thiamine deficiency (TD)-induced neuronal death. TD caused neuronal damage and induced the formation of autophagosome, and increased the expression of autophagy-related proteins. Autophagy sequestered damaged and dysfunctional organelles/protein, and transported them to lysosomes for degradation/recycling. This process provided nutrients for injured neurons. Wortmannin and knockdown of Beclin1 inhibited autophagy, and exacerbated TD-induced cell death, while activation of autophagy by rapamycin offered protection against TD neurotoxicity.

Thiamine nutritional status and depressive symptoms are inversely associated among older Chinese adults

Thiamine has been hypothesized to play an important role in mental health; however, few studies have investigated the association between thiamine nutritional status and depression in the general population. Concentrations of free thiamine and its phosphate esters [thiamine monophosphate (TMP) and thiamine diphosphate (TDP)] in erythrocytes were measured by HPLC among 1587 Chinese men and women aged 50-70 y. The presence of depressive symptoms was defined as a Center for Epidemiological Studies Depression Scale score of ≥16. The median erythrocyte concentration (nmol/L) was 3.73 for free thiamine, 3.74 for TMP, and 169 for TDP. The overall prevalence of depressive symptoms was 11.3%. Lower concentrations of all 3 erythrocyte thiamine biomarkers were monotonically associated with a higher prevalence of depressive symptoms: the multivariable adjusted ORs comparing the lowest with the highest quartiles were 2.97 (95% CI = 1.87, 4.72; P-trend < 0.001) for free thiamine, 3.46 (95% CI = 1.99, 6.02; P-trend < 0.001) for TMP, and 1.98 (95% CI = 1.22, 3.21; P-trend = 0.002) for TDP. In conclusion, poorer thiamine nutritional status and higher odds of depressive symptoms were associated among older Chinese adults. This finding should be further investigated in prospective or interventional studies.

Abnormal thiamine-dependent processes in Alzheimer's Disease. Lessons from diabetes

Reduced glucose metabolism is an invariant feature of Alzheimer's Disease (AD) and an outstanding biomarker of disease progression. Glucose metabolism may be an attractive therapeutic target, whether the decline initiates AD pathophysiology or is a critical component of a cascade. The cause of cerebral regional glucose hypometabolism remains unclear. Thiamine-dependent processes are critical in glucose metabolism and are diminished in brains of AD patients at autopsy. Further, the reductions in thiamine-dependent processes are highly correlated to the decline in clinical dementia rating scales. In animal models, thiamine deficiency exacerbates plaque formation, promotes phosphorylation of tau and impairs memory. In contrast, treatment of mouse models of AD with the thiamine derivative benfotiamine diminishes plaques, decreases phosphorylation of tau and reverses memory deficits. Diabetes predisposes to AD, which suggests they may share some common mechanisms. Benfotiamine diminishes peripheral neuropathy in diabetic humans and animals. In diabetes, benfotiamine induces key thiamine-dependent enzymes of the pentose shunt to reduce accumulation of toxic metabolites including advanced glycation end products (AGE). Related mechanisms may lead to reversal of plaque formation by benfotiamine in animals. If so, the use of benfotiamine could provide a safe intervention to reverse biological and clinical processes of AD progression. This article is part of a Special Issue entitled 'Mitochondrial function and dysfunction in neurodegeneration'.

Role of thiamine in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia in elderly individuals and is associated with progressive neurodegeneration of the human neocortex. Thiamine levels and the activity of thiamine-dependent enzymes are reduced in the brains and peripheral tissues of patients with AD. Genetic studies have provided the opportunity to determine what proteins link thiamine to AD pathology (ie, transketolase, apolipoprotein E, α-1-antitrypsin, pyruvate dehydrogenase complex, p53, glycogen synthetase kinase-3β, c-Fos gene, the Sp1 promoter gene, and the poly(ADP-ribosyl) polymerase-1 gene). We reviewed the association between histopathogenesis and neurotransmitters to understand the relationship between thiamine and AD pathology. Oral thiamine trials have been shown to improve the cognitive function of patients with AD; however, absorption of thiamine is poor in elderly individuals. In the early stage of thiamine-deficient encephalopathy (Wernicke's encephalopathy), however, parental thiamine has been used successfully. Therefore, further studies are needed to determine the benefits of using parental thiamine as a treatment for AD.

Research advances at the Institute for Nutritional Sciences at Shanghai, China

Nutrition-related health issues have emerged as a major threat to public health since the rebirth of the economy in China starting in the 1980s. To meet this challenge, the Chinese Academy of Sciences established the Institute for Nutritional Sciences (INS) at Shanghai, China ≈ 8 y ago. The mission of the INS is to apply modern technologies and concepts in nutritional research to understand the molecular mechanism and provide means of intervention in the combat against nutrition-related diseases, including type 2 diabetes, metabolic syndrome, obesity, cardiovascular diseases, and many types of cancers. Through diligent and orchestrated efforts by INS scientists, graduate students, and research staff in the past few years, the INS has become the leading institution in China in the areas of basic nutritional research and metabolic regulation. Scientists at the INS have made important progress in many areas, including the characterization of genetic and nutritional properties of the Chinese population, metabolic control associated with nutrient sensing, molecular mechanisms underlying glucose and lipid metabolism, regulation of metabolism by adipokines and inflammatory pathways, disease intervention using functional foods or extracts of Chinese herbs, and many biological studies related to carcinogenesis. The INS will continue its efforts in understanding the optimal nutritional needs for Chinese people and the molecular causes associated with metabolic diseases, thus paving the way for effective and individualized intervention in the future. This review highlights the major research endeavors undertaken by INS scientists in recent years.

Nutritional Status Driving Infection by Trypanosoma cruzi: Lessons from Experimental Animals

This paper reviews the scientific knowledge about protein-energy and micronutrient malnutrition in the context of Chagas disease, especially in experimental models. The search of articles was conducted using the electronic databases of SciELO (Scientific Electronic Library Online), PubMed and MEDLINE published between 1960 and March 2010. It was possible to verify that nutritional deficiencies (protein-energy malnutrition and micronutrient malnutrition) exert a direct effect on the infection by T. cruzi. However, little is known about the immunological mechanisms involved in the relationship "nutritional deficiencies and infection by T. cruzi". A hundred years after the discovery of Chagas disease many aspects of this illness still require clarification, including the effects of nutritional deficiencies on immune and pathological mechanisms of T. cruzi infection.

ADAR2-dependent RNA editing of GluR2 is involved in thiamine deficiency-induced alteration of calcium dynamics

BACKGROUND

Thiamine (vitamin B1) deficiency (TD) causes mild impairment of oxidative metabolism and region-selective neuronal loss in the central nervous system (CNS). TD in animals has been used to model aging-associated neurodegeneration in the brain. The mechanisms of TD-induced neuron death are complex, and it is likely multiple mechanisms interplay and contribute to the action of TD. In this study, we demonstrated that TD significantly increased intracellular calcium concentrations [Ca2+]i in cultured cortical neurons.

RESULTS

TD drastically potentiated AMPA-triggered calcium influx and inhibited pre-mRNA editing of GluR2, a Ca2+-permeable subtype of AMPA receptors. The Ca2+ permeability of GluR2 is regulated by RNA editing at the Q/R site. Edited GluR2 (R) subunits form Ca2+-impermeable channels, whereas unedited GluR2 (Q) channels are permeable to Ca2+ flow. TD inhibited Q/R editing of GluR2 and increased the ratio of unedited GluR2. The Q/R editing of GluR2 is mediated by adenosine deaminase acting on RNA 2 (ADAR2). TD selectively decreased ADAR2 expression and its self-editing ability without affecting ADAR1 in cultured neurons and in the brain tissue. Over-expression of ADAR2 reduced AMPA-mediated rise of [Ca2+]i and protected cortical neurons against TD-induced cytotoxicity, whereas down-regulation of ADAR2 increased AMPA-elicited Ca2+ influx and exacerbated TD-induced death of cortical neurons.

CONCLUSIONS

Our findings suggest that TD-induced neuronal damage may be mediated by the modulation of ADAR2-dependent RNA Editing of GluR2.

Neuronal MCP-1 mediates microglia recruitment and neurodegeneration induced by the mild impairment of oxidative metabolism

Chemokines are implicated in the neuroinflammation of several chronic neurodegenerative disorders. However, the precise role of chemokines in neurodegeneration is unknown. Thiamine deficiency (TD) causes abnormal oxidative metabolism in the brain as well as a well-defined microglia activation and neurodegeneration in the submedial thalamus nucleus (SmTN), which are common features of neurodegenerative diseases. We evaluated the role of chemokines in neurodegeneration and the underlying mechanism in a TD model. Among the chemokines examined, TD selectively induced neuronal expression of monocyte chemoattractant protein-1 (MCP-1) in the SmTN prior to microglia activation and neurodegeneration. The conditioned medium collected from TD-induced neurons caused microglia activation. With a neuron/microglia co-culture system, we showed that MCP-1-induced neurotoxicity required the presence of microglia, and exogenous MCP-1 was able to activate microglia and stimulated microglia to produce cytokines. A MCP-1 neutralizing antibody inhibited MCP-1-induced microglia activation and neuronal death in culture and in the thalamus. MCP-1 knockout mice were resistant to TD-induced neuronal death in SmTN. TD selectively induced the accumulation of reactive oxygen species in neurons, and antioxidants blocked TD-induced MCP-1 expression. Together, our results indicated an induction of neuronal MCP-1 during mild impairment of oxidative metabolism caused by microglia recruitment/activation, which exacerbated neurodegeneration.

A mitocentric view of Alzheimer's disease suggests multi-faceted treatments

Alzheimer's disease (AD) is defined by senile plaques made of amyloid-beta peptide (Abeta), neurofibrillary tangles made of hyperphosphorylated tau proteins, and memory deficits. Thus, the events initiating the cascade leading to these end points may be more effective therapeutic targets than treating each facet individually. In the small percentage of cases of AD that are genetic (or animal models that reflect this form of AD), the factor initiating AD is clear (e.g., genetic mutations lead to high Abeta1-42 or hyperphosphorylated tau proteins). In the vast majority of AD cases, the cause is unknown. Substantial evidence now suggests that abnormalities in glucose metabolism/mitochondrial function/oxidative stress (GMO) are an invariant feature of AD and occur at an early stage of the disease process in both genetic and non-genetic forms of AD. Indeed, decreases in brain glucose utilization are diagnostic for AD. Changes in calcium homeostasis also precede clinical manifestations of AD. Abnormal GMO can lead to plaques, tangles, and the calcium abnormalities that accompany AD. Abnormalities in GMO diminish the ability of the brain to adapt. Therapies targeting mitochondria may ameliorate abnormalities in plaques, tangles, calcium homeostasis, and cognition that comprise AD.

Association of SOD2, a mitochondrial antioxidant enzyme, with gray matter volume shrinkage in alcoholics

Chronic alcoholism leads to gray matter shrinkage and induces the formation of superoxide anions (O(2)(-)) that can cause neuronal cell death. The mitochondrial superoxide dismutase 2 (SOD2) enzyme is critical in the metabolism of superoxide. An Ala16Val polymorphism putatively affects SOD2 enzyme activity in vivo. Brain volumes of 76 treatment-seeking alcohol-dependent individuals were measured with a 1.5T MRI. Intracranial tissue margins were manually outlined on coronal sections. Gray matter, white matter, sulcal, and ventricular CSF volumes were estimated using intensity-based K-means clustering. Ala16Val (rs4880) and a second haplotype tagging SNP, rs10370, were genotyped. The q-value package was used to correct for multiple comparisons. In the alcoholics, cerebrospinal fluid and intra-cranial volumes showed significant differences across the six diplotype categories. The homozygous Ala16-containing diplotype rs10370TT-rs4880GG was associated with lowest gray matter ratio (greater shrinkage; p=0.005). Presence of one or two copies of the low activity Ala16 allele was a risk factor for lower gray matter volume in alcoholics below the median alcohol consumption (p=0.03) but not in alcoholics above this level. White matter ratio was associated with sex (p=0.002) and lifetime total alcohol consumption (p=0.01) but not with diplotypes. In this exploratory analysis, a putative functional missense variant of SOD2 appears to influence gray matter loss in alcoholics. This may be due to impaired clearance of reactive oxygen species formed as a result of alcohol exposure. The risk/protective effect was observed in alcoholics with lower levels of lifetime alcohol consumption. Highest levels of exposure may overwhelm the protective action of the SOD2 enzyme.

Vitamin-regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF-kappaB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B(12). However, the vitamin-induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood-brain barrier. As cytokines are essential to CNS-immune and CNS-hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin-mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.

Amyloid beta peptides trigger CD47-dependent mast cell secretory and phagocytic responses

Mast cells are found in the brain, where they contribute to immune responses. They have been implicated in multiple sclerosis, but their potential role in Alzheimers disease (AD), another inflammatory disease of the central nervous system, remains elusive. In the present study, we examined mast cell responses to amyloid beta (Abeta) peptides 1-40 and 1-42, the major components of the Alzheimer amyloid plaques. Rat peritoneal mast cells were used as experimental model for human brain serosal mast cells. Fibrillar Abeta1-40 and Ami1-42 peptides induced concentration-dependent exocytosis, as assessed by measurement of histamine secretion; exocytosis was reduced by pre-treatment with pertussis toxin and with antibodies against the CD47 receptor and the beta1-integrin subunit. Fibrillar Abeta1-40 and Abeta1- 42 peptides coated on heat-inactivated yeast particles and soluble fibrillar Abeta1-40 and Abeta1-42 peptides were also recognized and phagocyted by mast cells. Uptake of the peptides was decreased in the presence of 4N1, a peptide agonist of the CD47 receptor, but remained unchanged in the presence of 4NGG, a peptide derived from 4N1 which does not bind to CD47. Non-fibrillar forms of Abeta1-40 and 1-42 peptides were unable to elicit mast cell responses. These results show that fibrillar Abeta peptides can trigger mast cells and elicit exocytosis and phagocytosis. The Abeta-induced activation of mast cells operates through a CD47/beta1-integrin membrane complex coupled with Gi-protein. The present data support the hypothesis that mast cells, similarly to microglial cells, could play a major role in AD pathogenesis.

Altered expression of tight junction proteins and matrix metalloproteinases in thiamine-deficient mouse brain

Wernicke's encephalopathy (WE) in humans is a metabolic disorder caused by thiamine deficiency (TD). In both humans and experimental animals, TD leads to selective neuronal cell death in diencephalic and brainstem structures. Neuropathologic features of WE include petechial hemorrhagic lesions, and blood-brain barrier (BBB) breakdown has been suggested to play an important role in the pathogenesis of TD. The goal of the present study was to examine expression of the tight junction (TJ) protein occludin, its associated scaffolding proteins zona occludens (ZO-1 and ZO-2), and to measure matrix metalloproteinase (MMP) levels as a function of regional BBB permeability changes in thiamine-deficient mice. TD was induced in 12-week-old male C57Bl/6 mice by feeding a thiamine-deficient diet and administration of the central thiamine antagonist pyrithiamine. BBB permeability was measured by IgG extravasation; expression of occludin, ZO-1 and ZO-2 was measured by Western blot analysis and RT-PCR, structural integrity of the BBB was assessed using occludin and ZO-1 immunostaining, and MMPs levels were measured by gelatin zymography and immunohistochemistry. Studies were performed in vulnerable (medial thalamus) versus spared (frontal cortex) regions of the brain. Hemorrhagic lesions, selective increases in brain IgG extravasation, a concomitant loss in protein expression of occludin, ZO-1 and ZO-2, as well as decreased and disrupted patterns of occludin and ZO-1 immunostaining were observed in the medial thalamus of thiamine-deficient mice. MMP-9 levels were also selectively increased in the medial thalamus of these animals, and were found to be localized in the vascular endothelium, as well as in cells with an apparent polymorphonuclear morphology. No changes of TJ gene expression were observed. These results indicate that alterations in TJ proteins occur in TD, and offer a plausible explanation for the selective increase in BBB permeability in thiamine-deficient animals. They also suggest a role for MMP-9 in the initiation of changes to BBB integrity in TD.

Ethanol promotes thiamine deficiency-induced neuronal death: involvement of double-stranded RNA-activated protein kinase

BACKGROUND

Heavy alcohol consumption causes cerebellar degeneration, and the underlying mechanism is unclear. Chronic alcoholism is usually associated with thiamine deficiency (TD) which is known to induce selective neurodegeneration in the brain. However, the role of TD in alcohol-induced cerebellar degeneration remains to be elucidated. The double-stranded RNA-activated protein kinase (PKR) is a potent antiviral protein. Viral infection or binding to dsRNA causes PKR autophosphorylation and subsequent phosphorylation of the alpha-subunit of eukaryotic translation factor-2alpha, leading to inhibition of translation or apoptosis. PKR can also be activated by cellular stresses.

METHODS

In this study, we used an in vitro model, cultured cerebellar granule neurons (CGNs), to investigate the interaction between TD and ethanol and evaluate the contribution of their interaction to neuronal loss. TD was induced by treatment with amprolium in association with ethanol. Cell viability was determined by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide assay. PKR expression/phosphorylation and subcellular distribution was analyzed with immunoblotting and immunocytochemistry.

RESULTS

Thiamine deficiency caused death of CGNs but ethanol did not. However, TD plus ethanol induced a much greater cell loss than TD alone. TD-induced PKR phosphorylation and ethanol exposure significantly promoted TD-induced PKR phosphorylation as well as its nuclear translocation. A selective PKR inhibitor not only protected CGNs against TD toxicity, but also abolished ethanol potentiation of TD-induced loss of CGNs.

CONCLUSIONS

Ethanol promoted TD-induced PKR activation and neuronal death. PKR may be a convergent protein that mediates the interaction between TD and ethanol.

Senescence accelerated mouse strain is sensitive to neurodegeneration induced by mild impairment of oxidative metabolism

Neuronal loss and impairment of oxidative metabolism are frequently observed in aging associated neurodegenerative diseases. Thiamine deficiency (TD) induces the region selective neuronal loss in the brain, which has been used to model neurodegeneration, accompanied by mild impairment of oxidative metabolism. C57BL/6 mice were commonly used animals for TD experiments; however, the individual variations among C57BL/6 mice in response to TD limited the consistence of brain pathology. The senescence accelerated prone 8 (SAMP8) mouse strain exhibits age-related morphological changes in the brain and deficits in learning and memory. In this study, we compared the effects of TD on SAMP8 mice, senescence accelerated resistant 1 (SAMR1) mice and C57BL/6 mice. TD-induced body weight loss in SAMP8 mice was much greater than in SAMR1 and C57BL/6 mice. In addition, earlier and more severe loss of neurons in the submedial thalamic nucleus (SmTN) of the thalamus was detected in the SAMP8 mice. After 8 days of TD (TD8), the loss of NeuN-positive neurons in the SmTN of SAMP8, SAMR1 and C57BL/6 mice was 65%, 50%, and 36%, respectively. TD also caused accumulation of amyloid precursor protein (APP) in the thalamus. After TD10, APP immunoreactivity in the thalamus of SAMP8 was much more intense than that of SAMR1 and C57BL/6 mice. These results suggest that SAMP8 mice are sensitive to TD and therefore offer a useful model for studying aging related neurodegeneration caused by the impairment of oxidative metabolism.

Oxidant-induced changes in mitochondria and calcium dynamics in the pathophysiology of Alzheimer's disease

Considerable data support the hypothesis that mitochondrial abnormalities link gene defects and/or environmental insults to the neurodegenerative process. The interaction of oxidants with calcium and the mitochondrial enzymes of the tricarboxylic acid cycle are central to that relationship. Abnormalities that were discovered in brains or fibroblasts from patients with Alzheimer's disease (AD) have been modeled in vitro and in vivo to assess their pathophysiological importance and to determine how they might be reversed. The conclusions are consistent with the hypothesis that the AD-related abnormalities result from oxidative stress. The selection of compounds for reversal is complex because the actions of the relevant compounds vary under different conditions, such as cell redox states and acute versus chronic changes. However, the models that have been developed are useful for testing the effectiveness of the potential medications. The results suggest that the reversal of mitochondrial deficits and a reduction in oxidative stress will reduce clinical and pathological changes and benefit patients.

Possible relation of hemin-induced HO-1 expression to the upregulation of VEGF and BDNF mRNA levels in rat C6 glioma cells

Glial cells are generally considered to contribute to retaining the integrity of neural function through the protection of neuronal cells against neurodegenerative insults and also expected to play a potential role in the protection of cerebrovascular systems from various toxic insults of hemorrhaged blood, thus proposing a possible implication of glial cells in the recovery of brain function from the damage caused by cerebral hemorrhage. Based on this hypothetical idea, the direct effect of hemin on the expression of genes encoding heme oxygenase-1 (HO-1), vascular endothelial growth factor (VEGF), and brain-derived neurotrophic factor (BDNF) in glial cells was examined using rat C6 glioma cells as an in vitro model system. Hemin elevated both HO-1 and VEGF mRNA levels in the glioma cells at the concentration causing no critical damage to the cells, and the elevation of BDNF mRNA levels was also observed by exposing the cells to hemin under the same conditions. Furthermore, the elevation of VEGF and BDNF mRNA levels induced by hemin was blocked by pretreatment of the cells with the agents inhibiting not only HO-1 gene expression but also its enzymatic activity. These pharmacological studies indicate that hemin can induce the enhancement of VEGF and BDNF gene expression probably through the mechanism mediated by HO-1 activity in the glioma cells, proposing the possibility that glial cells are capable of contributing to the recovery of brain function from the damage caused by cerebral hemorrhage through the production of neurogenic and angiogenic factors.

Metabolic and structural role of thiamine in nervous tissues

In the literature, previous descriptions of the role of thiamine (B1 vitamin) focused mostly on its biochemical functions as a coenzyme precursor of some key enzymes of the carbohydrate metabolism. This report reviews recent developments on the metabolic and structural role of thiamine, e.g., the coenzyme and noncoenzyme functions of the vitamin. Taking into account analysis of our experimental data relating to the effects of thiamine deficiency on developing central nervous system (CNS) and data available in literature, we seek to establish a clear difference between the metabolic and structural role of thiamine. Our experimental data indicate that the specific and nonspecific effects express two diametrically diverse functions of thiamine in development: the nonspecific effects show up the metabolic consequences of thiamine deficiency resulting in apoptosis and severe cellular deficit; inversely, the specific effects announced the structural consequences of thiamine deficiency, described as cellular membrane damage, irregular and ectopic cells. The review highlights the existence of noncoenzyme functions of this vitamin through its interactions with biological membranes.

Thiamine deficiency induces oxidative stress and exacerbates the plaque pathology in Alzheimer's mouse model

Mitochondrial dysfunction, oxidative stress and reductions in thiamine-dependent enzymes have been implicated in multiple neurological disorders including Alzheimer's disease (AD). Experimental thiamine deficiency (TD) is an established model for reducing the activities of thiamine-dependent enzymes in brain. TD diminishes thiamine-dependent enzymes throughout the brain, but produces a time-dependent selective neuronal loss, glial activation, inflammation, abnormalities in oxidative metabolism and clusters of degenerating neurites in only specific thalamic regions. The present studies tested how TD alters brain pathology in Tg19959 transgenic mice over expressing a double mutant form of the amyloid precursor protein (APP). TD exacerbated amyloid plaque pathology in transgenic mice and enlarged the area occupied by plaques in cortex, hippocampus and thalamus by 50%, 200% and 200%, respectively. TD increased Abeta(1-42) levels by about three fold, beta-CTF (C99) levels by 33% and beta-secretase (BACE1) protein levels by 43%. TD-induced inflammation in areas of plaque formation. Thus, the induction of mild impairment of oxidative metabolism, oxidative stress and inflammation induced by TD alters metabolism of APP and/or Abeta and promotes accumulation of plaques independent of neuron loss or neuritic clusters.

Translocation of amyloid precursor protein C-terminal fragment(s) to the nucleus precedes neuronal death due to thiamine deficiency-induced mild impairment of oxidative metabolism

Thiamine deficiency (TD) is a model of neurodegeneration induced by mild impairment of oxidative metabolism. TD produces time-dependent glial activation, inflammation, oxidative stress, altered metabolism of amyloid precursor protein (APP), exacerbation of plaque formation from APP, and finally, selective neuron death in specific brain regions. The sub-medial thalamic nucleus (SmTN) is the most sensitive region to TD. Alteration in APP metabolism and nuclear translocation of carboxy-terminal fragments (CTF) of APP has been implicated in neuron death in other models of neurodegeneration. These experiments tested whether TD causes translocation of CTF into the nucleus of neurons in the SmTN that are destined to die after 9 days of TD by examining overlapping immunoreactivity (IR) of antibody APP 369 with either Alz90, 6E10 or 4G8 epitopes in the nuclei of the neurons in the SmTN. TD caused the accumulation of the CTF of APP in nuclei of SmTN neurons within 3 days of TD. These changes did not occur in the cortex which is spared in TD. Western blot analysis of nuclear fractions revealed a significant (61%; P < 0.026) increase in CTF 12 levels in TD SmTN (2.08 +/- 0.56) compared to control SmTN (1.29 +/- 0.41). Although TD increased CTF 15 levels in TD SmTN (1.95 +/- 0.73) compared to control SmTN (0.62 +/- 0.52) by 214%; P < 0.665 and decreased the full-length holo-APP levels in TD SmTN (0.32 +/- 0.30) compared to control SmTN (0.47 +/- 0.18) by 34%; P < 0.753, the differences were statistically insignificant. TD did not alter CTF 15 or CTF 12 levels in cortex. These findings demonstrate that changes in APP metabolism occur in early stages of TD, and they may play an important role in TD-induced selective neuronal loss.

Activation of double-stranded RNA-activated protein kinase by mild impairment of oxidative metabolism in neurons

Thiamine (vitamin B1) deficiency (TD) causes mild and chronic impairment of oxidative metabolism and induces neuronal death in specific brain regions. The mechanisms underlying TD-induced cell death, however, remain unclear. The double-stranded RNA-activated protein kinase (PKR), has been well known for its anti-viral function. Upon activation by viral infection or double-stranded RNA, PKR phosphorylates its substrate, the alpha-subunit of eukaryotic initiation factor-2 (eIF2alpha), leading to inhibition of translation. In response to various cellular stresses, PKR can also be stimulated by its protein activators, or its mouse homologue, PKR activator (RAX). We demonstrated that TD in mice induced phosphorylation of PKR at Thr446 and Thr451 and phosphorylation of eIF2alpha at Ser51 in the cerebellum and the thalamus. TD caused phosphorylation of PKR and eIF2alpha, as well as nuclear translocation of PKR in primary cultures of cerebellar granule neurons. PKR phosphorylation is necessary for its nuclear translocation because TD failed to induce nuclear translocation of a T446A/T451A PKR mutant. Both PKR inhibitor and dominant-negative PKR mutant protected cerebellar granule neurons against TD-induced cell death. TD promoted the association between RAX and PKR. Antioxidant vitamin E dramatically decreased the RAX/PKR association and ameliorated TD-induced cell death. Our results indicate that TD-induced neuronal death is at least partially mediated by the activation of PKR.