Neuroprotective effects of creatine in a transgenic mouse model of Huntington's disease

Oxidative stress and mitochondrial dysfunction in neurodegenerative diseases

In recent years, it has become increasingly clear that mitochondrial dysfunction and oxidative damage are major contributors to neuronal loss. Free radicals, typically generated from mitochondrial respiration, cause oxidative damage of nucleic acids, lipids, carbohydrates and proteins. Despite enormous amount of effort, however, the mechanism by which oxidative damage causes neuronal death is not well understood. Emerging data from a number of neurodegenerative diseases suggest that there may be common features of toxicity that are related to oxidative damage. In this review, while focusing on Huntington's disease (HD), we discuss similarities among HD, Friedreich ataxia and xeroderma pigmentosum, which provide insight into shared mechanisms of neuronal death.

Resistência à insulina com a suplementação de creatina em animais de experimentação

INTRODUÇÃO E OBJETIVO: A suplementação de creatina tem sido usada para melhorar o desempenho muscular. Esta afeta o metabolismo da glicose e estimula a secreção de insulina in vitro e in vivo. No entanto, a hipersecreção de insulina em longo prazo pode induzir também resistência à insulina. O presente trabalho analisou os efeitos da suplementação oral de creatina para avaliar a possibilidade da ocorrência de resistência à insulina in vivo. MÉTODOS: Quarenta e oito ratos Wistar (24 fêmeas/24 machos) foram divididos em dois grupos de 24 (controle e estudo) e subdivididos em seis grupos de oito. Por quatro semanas, foram alimentados com ração padrão, tendo livre acesso a água. Além disso, o grupo de estudo recebeu dieta suplementar de creatina (0,4g de creatina para 30mL de água por rato/dia). Nos 7º, 14º, 21º e 28º dias do experimento, 12 ratos foram anestesiados (tiopental sódico 0,15mL/100g), após jejum de seis horas, sendo submetidos ao teste intravenoso de tolerância à insulina (0,5mL de uma solução de 30% de insulina humana regular e 70% de salina). As amostras de sangue foram coletadas das veias dos rabos dos ratos, nos tempos basal, três, seis, nove, 12 e 15 minutos após a administração da insulina. A mensuração da glicose foi feita pelo método da glicose-oxidase. O trabalho foi previamente aprovado pelo Comitê de Ética em Pesquisa do CCMB- PUCSP. RESULTADOS: A média da constante de decaimento da glicose (K ITT) foi calculada pela fórmula 0,693/T1/2. O grupo de estudo, quando comparado com o grupo controle, apresentou resistência insulínica no 21º dia (p < 0,0004) e 28º dia (p < 0,0001). CONCLUSÃO: Este trabalho mostra que a suplementação prolongada de creatina pode levar à resistência à insulina e que deveria ser usada com cautela em indivíduos com distúrbios do metabolismo da glicose.

Creatine for treating muscle disorders

BACKGROUND

Progressive muscle weakness is a main symptom of most hereditary muscle diseases. Creatine is a popular nutritional supplement among athletes. It improves muscle performance in healthy individuals and might be helpful for treating myopathies.

OBJECTIVES

To evaluate the efficacy of oral creatine supplementation in muscle diseases.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Register in May 2004 for randomised trials using the search term 'creatine'. We also searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2005) using the same search term. We adapted this strategy to search MEDLINE (PubMed, from January 1966 to September 2005) and EMBASE (from January 1980 to May 2004). We reviewed the bibliographies of the randomised trials identified, contacted the authors and known experts in the field and approached pharmaceutical companies to identify additional published or unpublished data.

SELECTION CRITERIA

Types of studies: randomised or quasi-randomised controlled trials.

TYPES OF PARTICIPANTS

people of all ages with hereditary muscle disease. Types of intervention: any creatine supplementation of at least 0.03 g/kg body weight/day.

PRIMARY OUTCOME MEASURE

change in muscle strength measured by quantitative muscle testing.

SECONDARY OUTCOME MEASURES

change in muscle strength measured by manual muscle testing, change in energy parameters assessed by 31 phosphorous spectroscopy, change in muscle mass or a surrogate for muscle mass, adverse events.

DATA COLLECTION AND ANALYSIS

Two authors independently applied the selection criteria, assessed trial quality and extracted data. Some missing data were obtained from investigators.

MAIN RESULTS

Twelve trials, including 266 participants, met the selection criteria. One trial compared creatine and glutamine treatment with placebo. In trials with 138 participants with muscular dystrophies treated with creatine, there was a significant increase in maximum voluntary contraction in the creatine group compared to placebo, with a weighted mean difference of 8.47% (95% confidence intervals 3.55 to 13.38). There was also an increase in lean body mass during creatine treatment compared to placebo (weighted mean difference 0.63 kg, 95% confidence intervals 0.02 to 1.25). No trial reported any clinically relevant adverse event. In trials with 33 participants with metabolic myopathies treated with creatine, there was no significant difference in maximum voluntary contraction between the creatine and placebo group (weighted mean difference -2.26%, confidence intervals -6.29 to 1.78). One trial reported a significant increase in muscle pain during high-dose creatine treatment (150 mg/kg body weight) in glycogen storage disease type V.

AUTHORS' CONCLUSIONS

Evidence from randomised controlled trials shows that short- and medium-term creatine treatment improves muscle strength in people with muscular dystrophies, and is well-tolerated. Evidence from randomised controlled trials does not show significant improvement in muscle strength in metabolic myopathies. High-dose creatine in glycogenosis type V increased muscle pain.

Transcriptional repression of PGC-1alpha by mutant huntingtin leads to mitochondrial dysfunction and neurodegeneration

Huntington's disease (HD) is an inherited neurodegenerative disease caused by a glutamine repeat expansion in huntingtin protein. Transcriptional deregulation and altered energy metabolism have been implicated in HD pathogenesis. We report here that mutant huntingtin causes disruption of mitochondrial function by inhibiting expression of PGC-1alpha, a transcriptional coactivator that regulates several metabolic processes, including mitochondrial biogenesis and respiration. Mutant huntingtin represses PGC-1alpha gene transcription by associating with the promoter and interfering with the CREB/TAF4-dependent transcriptional pathway critical for the regulation of PGC-1alpha gene expression. Crossbreeding of PGC-1alpha knockout (KO) mice with HD knockin (KI) mice leads to increased neurodegeneration of striatal neurons and motor abnormalities in the HD mice. Importantly, expression of PGC-1alpha partially reverses the toxic effects of mutant huntingtin in cultured striatal neurons. Moreover, lentiviral-mediated delivery of PGC-1alpha in the striatum provides neuroprotection in the transgenic HD mice. These studies suggest a key role for PGC-1alpha in the control of energy metabolism in the early stages of HD pathogenesis.

Influência da suplementação aguda e crônica de creatina sobre as concentrações sanguíneas de glicose e lactato de ratos Wistar

Estudos recentes sugerem que a suplementação de creatina pode interferir com a captação de glicose e a produção de lactato durante a atividade física. O objetivo deste estudo foi investigar os efeitos da suplementação aguda (5g.kg¹ durante uma semana) e crônica (1g.kg¹ durante oito semanas) de creatina sobre as concentrações sanguíneas de glicose e lactato de ratos sedentários e exercitados (natação a 80% da carga máxima tolerada). Setenta e dois ratos Wistar machos (240 ± 10g) foram utilizados e divididos igualmente em quatro grupos experimentais (n = 18): CON - ratos sedentários não suplementados; NAT - ratos exercitados não suplementados; CRE - ratos sedentários e suplementados; CRE + NAT - ratos exercitados e suplementados. As amostras sanguíneas foram obtidas antes e após o teste de determinação da carga máxima realizado semanalmente durante todo o experimento. Antes do teste de carga máxima, com exceção do grupo CRE-NAT (3-5 semanas), que apresentou concentrações plasmáticas de glicose inferiores em relação os demais grupos, todos os outros resultados foram semelhantes entre os grupos experimentais. Após o teste de carga máxima todos os grupos experimentais apresentaram redução das concentrações plasmáticas de glicose e aumento das concentrações plasmáticas de lactato. Contudo, em relação à glicose, esta redução foi significativamente (p < 0,05) pronunciada nos grupos CRE (1-4 semanas) e CRE + NAT (1-8 semanas) e, em relação ao lactato, o aumento foi significativamente (p < 0,05) menor nos grupos CRE (1-2 semanas) e CRE + NAT (1-8 semanas). Os achados deste estudo sugerem que o regime adotado de suplementação influenciou o perfil metabólico glicêmico, minimizou o acúmulo de lactato e potencializou a máxima carga suportada nos animais suplementados.

Cardiac dysfunction in the R6/2 mouse model of Huntington's disease

Recent evidence suggests that mutant huntingtin protein-induced energetic perturbations contribute to neuronal dysfunction in Huntington's disease (HD). Given the ubiquitous expression of huntingtin, other cell types with high energetic burden may be at risk for HD-related dysfunction. Early-onset cardiovascular disease is the second leading cause of death in HD patients; a direct role for mutant huntingtin in this phenomenon remains unevaluated. Here we tested the hypothesis that expression of mutant huntingtin is sufficient to induce cardiac dysfunction, using a well-described transgenic model of HD (line R6/2). R6/2 mice developed cardiac dysfunction by 8 weeks of age, progressing to severe failure at 12 weeks, assessed by echocardiography. Limited evidence of cardiac remodeling (e.g. hypertrophy, fibrosis, apoptosis, beta(1) adrenergic receptor downregulation) was observed. Immunogold electron microscopy demonstrated significant elevations in nuclear and mitochondrial polyglutamine presence in the R6/2 myocyte. Significant alterations in mitochondrial ultrastructure were seen, consistent with metabolic stress. Increased cardiac lysine acetylation and protein nitration were observed and were each significantly associated with impairments in cardiac performance. These data demonstrate that mutant huntingtin expression has potent cardiotoxic effects; cardiac failure may be a significant complication of this important experimental model of HD. Investigation of the potential cardiotropic effects of mutant huntingtin in humans may be warranted.

Metformin therapy in a transgenic mouse model of Huntington's disease

Huntington's disease (HD) is a hereditary neurodegenerative disease that leads to striatal degeneration and a severe movement disorder. We used a transgenic mouse model of HD (the R6/2 line with approximately 150 glutamine repeats) to test a new therapy for this disease. We treated HD mice with metformin, a widely used anti-diabetes drug, in the drinking water (0, 2 or 5mg/ml) starting at 5 weeks of age. Metformin treatment significantly prolonged the survival time of male HD mice at the 2mg/ml dose (20.1% increase in lifespan) without affecting fasting blood glucose levels. This dose of metformin also decreased hind limb clasping time in 11-week-old mice. The higher dose did not prolong survival, and neither dose of metformin was effective in female HD mice. Collectively, our results suggest that metformin may be worth further investigation in additional HD models.

Neuronal life-and-death signaling, apoptosis, and neurodegenerative disorders

When subjected to excessive oxidative stress, neurons may respond adaptively to overcome the stress, or they may activate a programmed cell death pathway called apoptosis. Apoptosis is characterized by alterations in mitochondria and the endoplasmic reticulum and activation of cysteine proteases called caspases. Increasing evidence suggests that apoptotic biochemical cascades are involved in the dysfunction and death of neurons in neurodegenerative disorders such as Alzheimer's, Parkinson, and Huntington's diseases. Studies of normal aging, of genetic mutations that cause disease, and of environmental factors that affect disease risk are revealing cellular and molecular alterations that may cause excessive oxidative stress and trigger neuronal apoptosis. Accumulation of self-aggregating proteins such as amyloid beta-peptide, tau, alpha-synuclein, and huntingtin may be involved in apoptosis both upstream and downstream of oxidative stress. Membrane-associated oxidative stress resulting in perturbed lipid metabolism and disruption of cellular calcium homeostasis may trigger apoptosis in several different neurodegenerative disorders. Counteracting neurodegenerative processes are an array of mechanisms including neurotrophic factor signaling, antioxidant enzymes, protein chaperones, antiapoptotic proteins, and ionostatic systems. Emerging findings suggest that the resistance of neurons to death during aging can be enhanced by modifications of diet and lifestyle.

Oral uridine pro-drug PN401 is neuroprotective in the R6/2 and N171-82Q mouse models of Huntington's disease

Previously, uridine pro-drug 2',3',5'-tri-O-acetyluridine (PN401) was shown to be protective in the mitochondrial complex II inhibitor 3-nitropropionic acid model of Huntington's disease (HD). In this study, PN401 increased survival and improved motor function on the rotarod in both R6/2 and N171-82Q polyglutamine repeat mouse models of HD. PN401 significantly decreased neurodegeneration in both the piriform cortex and striatum although PN401 decreased huntingtin protein aggregates only in the striatum. Cortical and striatal brain-derived neurotrophic factor (BDNF) protein levels were reduced in the +/- compared to the -/- N171-82Q mice and PN401 treatment significantly increased cortical BDNF in both +/- and -/- mice, but PN401 did not affect striatal BDNF. These results suggest that PN401 may have beneficial effects in the treatment of neurodegenerative diseases such as HD.

Hyperammonemia induces transport of taurine and creatine and suppresses claudin-12 gene expression in brain capillary endothelial cells in vitro

Ammonia is a key neurotoxin involved in the neurological complications of acute liver failure. The present study was undertaken to study the effects of exposure to pathophysiologically relevant concentrations of ammonium chloride on cultured brain capillary endothelial cells in order to identify mechanisms by which ammonia may alter blood-brain barrier function. Conditionally immortalized mouse brain capillary endothelial cells (TM-BBB) were used as an in vitro model of the blood-brain barrier. Gene expression of a series of blood-brain barrier transporters and tight junction proteins was assessed by quantitative real time PCR analysis. Exposure to ammonia (5mM for 72h) resulted in significant increases in mRNA levels of taurine transporter (TAUT; 2.0-fold increase) as well as creatine transporter (CRT; 1.9-fold increase) whereas claudin-12 mRNA expression was significantly reduced to 67.7% of control levels. Furthermore, [(3)H]taurine and [(14)C]creatine uptake were concomitantly increased following exposure to ammonia, suggesting that up-regulation of both TAUT and CRT under hyperammonemic conditions results in an increased function of these two transporters in TM-BBB cells. TAUT and CRT are respectively involved in osmoregulation and energy buffering in the brain, two systems that are thought to be affected in acute liver failure. Furthermore, claudin-12 down-regulation suggests that hyperammonemia may also affect tight junction integrity. Our results provide evidence that ammonia can alter brain capillary endothelial cell gene expression and transporter function. These findings may be relevant to pathological situations involving hyperammonemia, such as liver disease.

RNAi: a potential therapy for the dominantly inherited nucleotide repeat diseases

Genetic diseases that are accompanied by central nervous system involvement are often fatal. Among these are the autosomal dominant neurogenetic diseases caused by nucleotide repeat expansion. For example, Huntington's disease (HD) and spinal cerebellar ataxia are caused by expansion of a tract of CAGs encoding glutamine. In HD and the other CAG-repeat expansion diseases, the expansion is in the coding region. Myotonic dystrophy is caused by repeat expansions of CUG or CCTG in noncoding regions, and the mutant RNA is disease causing. Treatments for these disorders are limited to symptomatic intervention. RNA interference (RNAi), which is a method for inhibiting target gene expression, provides a unique tool for therapy by attacking the fundamental problem directly. In this review, we describe briefly several representative disorders and their respective molecular targets, and methods to accomplish therapeutic RNAi. Finally, we summarize studies performed to date.

Viral delivery of glial cell line-derived neurotrophic factor improves behavior and protects striatal neurons in a mouse model of Huntington's disease

Huntington's disease (HD) is a fatal, genetic, neurological disorder resulting from a trinucleotide repeat expansion in the gene that encodes for the protein huntingtin. These excessive repeats confer a toxic gain of function on huntingtin, which leads to the degeneration of striatal and cortical neurons and a devastating motor, cognitive, and psychological disorder. Trophic factor administration has emerged as a compelling potential therapy for a variety of neurodegenerative disorders, including HD. We previously demonstrated that viral delivery of glial cell line-derived neurotrophic factor (GDNF) provides structural and functional neuroprotection in a rat neurotoxin model of HD. In this report we demonstrate that viral delivery of GDNF into the striatum of presymptomatic mice ameliorates behavioral deficits on the accelerating rotorod and hind limb clasping tests in transgenic HD mice. Behavioral neuroprotection was associated with anatomical preservation of the number and size of striatal neurons from cell death and cell atrophy. Additionally, GDNF-treated mice had a lower percentage of neurons containing mutant huntingtin-stained inclusion bodies, a hallmark of HD pathology. These data further support the concept that viral vector delivery of GDNF may be a viable treatment for patients suffering from HD.

Changes in Expression of N-Methyl-D-Aspartate Receptor Subunits Occur Early in the R6/2 Mouse Model of Huntington’s Disease

A leading hypothesis of the cause of neuronal death in Huntington's disease (HD) is excitotoxicity, in which subpopulations of striatal neurons are hypersensitive to glutamate release due to changes in postsynaptic N-methyl-D-aspartate receptors (NMDARs). In the present study we used RT-PCR methods on single cells and tissue to compare the expression of NMDAR subunits, NR1, NR2A and NR2B, in the striatum of R6/2 transgenic mice with their wild-type (WT) littermates at three different age groups corresponding to different symptomatic milestones (19-25 days showing no overt evidence of abnormal behavior, 38-45 days at the onset of the overt phenotype and 78-90 days displaying the full behavioral phenotype). Single-cell RT-PCR studies also examined neurons for the expression of substance P and enkephalin to define different subpopulations of medium-sized projection neurons of the striatum. The results showed a significant decrease in the percentage of cells expressing NR2A at all ages examined. The decrease in expression was not associated with any significant change in expression of NR1 or NR2B. Cells that did not express NR2A contained both enkephalin and substance P, but proportionately more cells containing enkephalin displayed decreases in NR2A. Semi-quantitative RT-PCR studies on striatal tissue in the oldest age group confirmed the significant decrease in NR2A and also showed a decrease in NR2B. These results support the hypothesis that changes in the composition of postsynaptic NMDARs occur in the R6/2 model of HD and this effect occurs early in the expression of the phenotype.

DNA microarray analysis of striatal gene expression in symptomatic transgenic Huntington's mice (R6/2) reveals neuroinflammation and insulin associations

Huntington's disease (HD) is an inherited, progressive neurodegenerative disorder caused by CAG repeat expansion in the gene that codes for the protein huntingtin. The underlying neuropathological events leading to the selectivity of striatal neuronal loss are unknown. However, the huntingtin mutation interferes at several levels of normal cell function. The complexity of this disease makes microarray analysis an appealing technique to begin the identification of common pathways that may contribute to the pathology. In this study, striatal tissue was extracted for gene expression profiling from wild-type and symptomatic transgenic Huntington mice (R6/2) expressing part of the human Huntington's disease gene. We interrogated a 15 K high-density mouse EST array not previously used for HD and identified 170 significantly differentially expressed ESTs in symptomatic R6/2 mice. Of the 80 genes with known function, 9 genes had previously been identified as altered in HD. 71 known genes were associated with HD for the first time. The data obtained from this study confirm and extend previous observations using DNA microarray techniques on genetic models for HD, revealing novel changes in expression in a number of genes not previously associated with HD. Further bioinformatic analysis, using software to construct biological association maps, focused attention on proteins such as insulin and TH1-mediated cytokines, suggesting that they may be important regulators of affected genes. These results may provide insight into the regulation and interaction of genes that contribute to adaptive and pathological processes involved in HD.

Dose ranging and efficacy study of high-dose coenzyme Q10 formulations in Huntington's disease mice

There is substantial evidence that a bioenergetic defect may play a role in the pathogenesis of Huntington's Disease (HD). A potential therapy for remediating defective energy metabolism is the mitochondrial cofactor, coenzyme Q10 (CoQ10). We have reported that CoQ10 is neuroprotective in the R6/2 transgenic mouse model of HD. Based upon the encouraging results of the CARE-HD trial and recent evidence that high-dose CoQ10 slows the progressive functional decline in Parkinson's disease, we performed a dose ranging study administering high levels of CoQ10 from two commercial sources in R6/2 mice to determine enhanced efficacy. High dose CoQ10 significantly extended survival in R6/2 mice, the degree of which was dose- and source-dependent. CoQ10 resulted in a marked improvement in motor performance and grip strength, with a reduction in weight loss, brain atrophy, and huntingtin inclusions in treated R6/2 mice. Brain levels of CoQ10 and CoQ9 were significantly lower in R6/2 mice, in comparison to wild type littermate control mice. Oral administration of CoQ10 elevated CoQ10 plasma levels and significantly increased brain levels of CoQ9, CoQ10, and ATP in R6/2 mice, while reducing 8-hydroxy-2-deoxyguanosine concentrations, a marker of oxidative damage. We demonstrate that high-dose administration of CoQ10 exerts a greater therapeutic benefit in a dose dependent manner in R6/2 mice than previously reported and suggest that clinical trials using high dose CoQ10 in HD patients are warranted.

Emerging chemotherapeutic strategies for Huntington's disease

Huntington's disease (HD) is a progressive and fatal neurological disorder caused by an expanded CAG repeat in the gene coding for the protein, huntingtin. There is no clinically proven treatment for HD. Although the exact cause of neuronal death in HD remains unknown, it has been postulated that the abnormal aggregation of the mutant huntingtin protein may cause toxic effects in neurons, leading to a cascade of pathogenic mechanisms associated with transcriptional dysfunction, oxidative stress, mitochondrial alterations, apoptosis, bioenergetic defects and subsequent excitotoxicity. Understanding how these processes interrelate has become important in identifying a pharmacotherapy in HD and in the design of clinical trials. A number of drug compounds that separately target these mechanisms have significantly improved the clinical and neuropathological phenotype of HD transgenic mice and, as such, are immediate candidates for human clinical trials in HD patients. These compounds are discussed herein.

rAAV-mediated shRNA ameliorated neuropathology in Huntington disease model mouse

Huntington disease (HD) is a fatal progressive neurodegenerative disorder associated with expansion of a CAG repeat in the first exon of the gene coding the protein huntingtin (htt). Although the feasibility of RNA interference (RNAi)-mediated reduction of htt expression to attenuate HD-associated symptoms is suggested, the effects of post-symptomatic RNAi treatment in the HD model mice have not yet been certified. Here we show the effects of recombinant adeno-associated virus (rAAV)-mediated delivery of RNAi into the HD model mouse striatum after the onset of disease. Neuropathological abnormalities associated with HD, such as insoluble protein accumulation and down-regulation of DARPP-32 expression, were successfully ameliorated by the RNAi transduction. Importantly, neuronal aggregates in the striatum were reduced after RNAi transduction in the animals comparing to those at the time point of RNAi transduction. These results suggest that the direct inhibition of mutant gene expression by rAVV would be promising for post-symptomatic HD therapy.

Creatine and neurotrophin-4/5 promote survival of nitric oxide synthase-expressing interneurons in striatal cultures

Nitric oxide (NO) mediates a variety of physiological functions in the central nervous system and acts as an important developmental regulator. Striatal interneurons expressing neuronal nitric oxide synthase (nNOS) have been described to be relatively spared from the progressive cell loss in Huntington's disease (HD). We have recently shown that creatine, which supports the phosphagen energy system, induces the differentiation of GABAergic cells in cultured striatal tissue. Moreover, neurotrophin-4/5 (NT-4/5) has been found to promote the survival and differentiation of cultured striatal neurons. In the present study, we assessed the effects of creatine and NT-4/5 on nNOS-immunoreactive (-ir) neurons of E14 rat ganglionic eminences grown for 1 week in culture. Chronic administration of creatine [5mM], NT-4/5 [10ng/ml], or a combination of both factors significantly increased numbers of nNOS-ir neurons. NT-4/5 exposure also robustly increased levels of nNOS protein. Interestingly, only NT-4/5 and combined treatment significantly increased general viability but no effects were seen for creatine supplementation alone. In addition, NT-4/5 and combined treatment resulted in a significant larger soma size and number of primary neurites of nNOS-ir neurons while creatine administration alone exerted no effects. Double-immunolabeling studies revealed that all nNOS-ir cells co-localized with GABA. In summary, our findings suggest that creatine and NT-4/5 affect differentiation and/or survival of striatal nNOS-ir GABAergic interneurons. These findings provide novel insights into the biology of developing striatal neurons and highlight the potential of both creatine and NT-4/5 as therapeutics for HD.

The use of the R6 transgenic mouse models of Huntington's disease in attempts to develop novel therapeutic strategies

Huntington's disease (HD) is a genetic neurodegenerative disorder. Since identification of the disease-causing gene in 1993, a number of genetically modified animal models of HD have been generated. The first transgenic mouse models, R6/1 and R6/2 lines, were established 8 years ago. The R6/2 mice have been the best characterized and the most widely used model to study pathogenesis of HD and therapeutic interventions. In the present review, we especially focus on the characteristics of R6 transgenic mouse models and, in greater detail, describe the different therapeutic strategies that have been tested in these mice. We also, at the end, critically assess the relevance of the HD mouse models compared with the human disease and discuss how they can be best used in the future.

Pharmaceutical, cellular and genetic therapies for Huntington's disease

HD (Huntington's disease) is a devastating neurodegenerative disorder caused by a polyglutamine expansion in the gene encoding the huntingtin protein. Presently, there is no known cure for HD and existing symptomatic treatments are limited. However, recent advances have identified multiple pathological mechanisms involved in HD, some of which have now become the focus of therapeutic intervention. In this review, we consider progress made towards developing safe and effective pharmaceutical-, cell- and genetic-based therapies, and discuss the extent to which some of these therapies have been successfully translated into clinical trials. These new prospects offer hope for delaying and possibly halting this debilitating disease.

Effectiveness of creatine monohydrate on seizures and oxidative damage induced by methylmalonate

Methylmalonic acidemias are metabolic disorders caused by a severe deficiency of methylmalonyl CoA mutase activity, which are characterized by neurological dysfunction, including convulsions. It has been reported that methylmalonic acid (MMA) accumulation inhibits succinate dehydrogenase (SDH) and beta-hydroxybutyrate dehydrogenase activity and respiratory chain complexes in vitro, leading to decreased CO2 production, O2 consumption and increased lactate production. Acute intrastriatal administration of MMA also induces convulsions and reactive species production. Though creatine has been reported to decrease MMA-induced convulsions and lactate production, it is not known whether it also protects against MMA-induced oxidative damage. In the present study we investigated the effects of creatine (1.2-12 mg/kg, i.p.) and MK-801 (3 nmol/striatum) on the convulsions, striatal content of thiobarbituric acid reactive substances (TBARS) and on protein carbonylation induced by MMA. Moreover, we investigated the effect of creatine (12 mg/kg, i.p.) on the MMA-induced striatal creatine and phosphocreatine depletion. Low doses of creatine (1.2 and 3.6 mg/kg) protected against MMA-induced oxidative damage, but did not protect against MMA-induced convulsions. A high dose of creatine (12 mg/kg, i.p.) and MK-801 (3 nmol/striatum) protected against MMA-induced seizures (evidenced by electrographic recording), protein carbonylation and TBARS production ex vivo. Furthermore, acute creatine administration increased the striatal creatine and phosphocreatine content and protected against MMA-induced creatine and phosphocreatine depletion. Our results suggest that an increase of the striatal high-energy phosphates elicited by creatine protects not only against MMA-induced convulsions, but also against MMA-induced oxidative damage. Therefore, since NMDA antagonists are limited value in the clinics, the present results indicate that creatine may be useful as an adjuvant therapy for methylmalonic acidemic patients.

Reduced transglutaminase-catalyzed protein aggregation is observed in the presence of creatine using sedimentation velocity

Transglutaminases (TGases) are enzymes that catalyze covalent isopeptide crosslinks between reactive lysine and glutamine residues in proteins. Higher than normal local concentrations of TGase have been correlated with increased protein aggregation in vivo. These insoluble protein aggregates are the hallmark of several neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, although each aggregating protein involved is disease specific. Because TGase is implicated in protein aggregation, there is evidence that its regulation may retard disease progression. Here we report on a laser light transmission technique as an in vitro tool to gauge the efficacy of creatine, a candidate inhibitor, to regulate aggregation. Sedimentation velocities of protein-coated particles in TGase-containing water-glycerol solutions were tracked with different levels of creatine. Sedimentation velocities were converted to apparent aggregate sizes using Stoke's law of sedimentation. The results indicated that creatine promoted up to a 20% reduction in protein aggregation in vitro. This technique may prove to be useful in identifying other functional TGase inhibitors.

The therapeutic role of creatine in Huntington's disease

Huntington's disease (HD) is an autosomal dominant and fatal neurological disorder characterized by a clinical triad of progressive choreiform movements, psychiatric symptoms, and cognitive decline. HD is caused by an expanded trinucleotide CAG repeat in the gene coding for the protein huntingtin. No proven treatment to prevent the onset or to delay the progression of HD currently exists. While a direct causative pathway from the gene mutation to the selective neostriatal neurodegeneration remains unclear, it has been hypothesized that interactions of the mutant huntingtin protein or its fragments may result in a number of interrelated pathogenic mechanisms triggering a cascade of molecular events that lead to the untimely neuronal death observed in HD. One putative pathological mechanism reported to play a prominent role in the pathogenesis of HD is mitochondrial dysfunction and the subsequent reduction of cellular energy. Indeed, if mitochondrial impairment and reduced energy stores play roles in the neuronal loss in HD, then a therapeutic strategy that buffers intracellular energy levels may ameliorate the neurodegenerative process. Sustained ATP levels may have both direct and indirect importance in ameliorating the severity of many of the pathogenic mechanisms associated with HD. Creatine, a guanidino compound produced endogenously and acquired exogenously through diet, is a critical component in maintaining much needed cellular energy. As such, creatine is one of a number of ergogens that may provide a relatively safe and immediately available therapeutic strategy to HD patients that may be the cornerstone of a combined treatment necessary to delay the relentless progression of HD.

Effects of CAG repeat length, HTT protein length and protein context on cerebral metabolism measured using magnetic resonance spectroscopy in transgenic mouse models of Huntington's disease

Huntington's disease is a neurodegenerative illness caused by expansion of CAG repeats at the N-terminal end of the protein huntingtin. We examined longitudinal changes in brain metabolite levels using in vivo magnetic resonance spectroscopy in five different mouse models. There was a large (>50%) exponential decrease in N-acetyl aspartate (NAA) with time in both striatum and cortex in mice with 150 CAG repeats (R6/2 strain). There was a linear decrease restricted to striatum in N171-82Q mice with 82 CAG repeats. Both the exponential and linear decreases of NAA were paralleled in time by decreases in neuronal area measured histologically. Yeast artificial chromosome transgenic mice with 72 CAG repeats, but low expression levels, had less striatal NAA loss than the N171-82Q mice (15% vs. 43%). We evaluated the effect of gene context in mice with an approximate 146 CAG repeat on the hypoxanthine phosphoribosyltransferase gene (HPRT). HPRT mice developed an obese phenotype in contrast to weight loss in the R6/2 and N171-82Q mice. These mice showed a small striatal NAA loss (21%), and a possible increase in brain lipids detectable by magnetic resonance (MR) spectroscopy and decreased brain water T1. Our results indicate profound metabolic defects that are strongly affected by CAG repeat length, as well as gene expression levels and protein context.

Mitochondrial dysfunction in bipolar disorder: evidence from magnetic resonance spectroscopy research

Magnetic resonance spectroscopy (MRS) affords a noninvasive window on in vivo brain chemistry and, as such, provides a unique opportunity to gain insight into the biochemical pathology of bipolar disorder. Studies utilizing proton ((1)H) MRS have identified changes in cerebral concentrations of N-acetyl aspartate, glutamate/glutamine, choline-containing compounds, myo-inositol, and lactate in bipolar subjects compared to normal controls, while studies using phosphorus ((31)P) MRS have examined additional alterations in levels of phosphocreatine, phosphomonoesters, and intracellular pH. We hypothesize that the majority of MRS findings in bipolar subjects can be fit into a more cohesive bioenergetic and neurochemical model of bipolar illness that is both novel and yet in concordance with findings from complementary methodological approaches. In this review, we propose a hypothesis of mitochondrial dysfunction in bipolar disorder that involves impaired oxidative phosphorylation, a resultant shift toward glycolytic energy production, a decrease in total energy production and/or substrate availability, and altered phospholipid metabolism.

Translating therapies for Huntington's disease from genetic animal models to clinical trials

Genetic animal models of inherited neurological diseases provide an opportunity to test potential treatments and explore their promise for translation to humans experiencing these diseases. Therapeutic trials conducted in mouse models of Huntington's disease have identified a growing number of potential therapies that are candidates for clinical trials. Although it is very exciting to have these candidates, there has been increasing concern about the feasibility and desirability of taking all of the compounds that may work in mice and testing them in patients with HD. There is a need to begin to prioritize leads emerging from transgenic mouse studies; however, it is difficult to compare results between compounds and laboratories, and there are also many additional factors that can affect translation to humans. Among the important issues are what constitutes an informative genetic model, what principals should be followed in designing and conducting experiments using genetic animal models, how can results from different laboratories and in different models be compared, what body of evidence is desirable to fully inform clinical decision making, and what factors contribute to the equipoise in determining whether preclinical information about a therapy makes clinical study warranted. In the context of Huntington's disease, we will review the current state of genetic models and their successes in putting forward therapeutic leads, provide a guide to assessing studies in mouse models, and discuss some of the salient issues related to translation from mice to humans.

The paradigm of Huntington's disease: therapeutic opportunities in neurodegeneration

Despite a relatively small number of affected patients, Huntington's disease (HD) has been a historically important disease, embodying many of the major themes in modern neuroscience, including molecular genetics, selective neuronal vulnerability, excitotoxicity, mitochondrial dysfunction, apoptosis, and transcriptional dysregulation. The discovery of the HD gene in 1993 opened the door to the mechanisms of HD pathogenesis. Multiple pathologic mechanisms have been discovered, each one serving as a potential therapeutic target. HD thus continues to serve as a paradigmatic disorder, with basic bench research generating clinically relevant insights and stimulating the development of therapeutic human trials.

Novel therapeutic targets for Huntington’s disease

Huntington's disease (HD) is a fatal autosomal-dominant disorder involving progressive motor, cognitive and psychiatric symptoms. HD is one of a large family of neurodegenerative diseases caused by a trinucleotide (CAG) repeat mutation, encoding an expanded tract of glutamines in the disease protein. HD was one of the first neurological disorders for which accurate transgenic models were created, allowing mechanisms of pathogenesis to be explored at molecular, cellular and behavioural levels. In the last decade, the understanding of molecular and cellular changes which occur in HD prior to onset of symptoms, and at early and late stages of disease progression, has been greatly expanded. A wide range of potential molecular targets for therapeutic intervention have been identified, associated with a variety of cellular processes including gene transcription, protein trafficking, protein degradation, protein-protein interactions, glutamatergic synaptic transmission, presynaptic signalling, postsynaptic signalling, synaptic plasticity, dopaminergic and neurotrophic modulation of synaptic function, experience-dependent neurogenesis, mitochondrial function and oxidative metabolism. Presymptomatic testing for the HD gene mutation necessitates future development of novel therapeutics aimed at delaying onset of symptoms, as well as slowing or reversing disease progression.

Atypical diabetes associated with inclusion formation in the R6/2 mouse model of Huntington's disease is not improved by treatment with hypoglycaemic agents

The R6/2 transgenic mouse model of Huntington's disease (HD) develops a progressive neurological phenotype that involves severe motor and cognitive dysfunctions. Although not a cardinal sign, diabetes has been described in R6/2 mice. It is not clear, however, whether the diabetes contributes to the HD-like phenotype of R6/2 mice. In our study we found that the severity of diabetes in R6/2 mice was associated with the progressive formation of ubiquinated inclusions in pancreatic beta cells. Diabetes is dissociated from early motor and cognitive dysfunctions and did not correlate with motor impairment and survival of R6/2 mice. However, chronic behavioural testing (at a level higher than that which is reported to improve several aspects of the R6/2 phenotype) exacerbated the onset of diabetes. Pharmacological treatment of the diabetes was attempted using two oral hypoglycaemic agents commonly used by diabetics. The mice responded acutely to glibenclamide (which induces exocytosis of insulin) but not to rosiglitazone (which induces sensitization to insulin). This supports the suggestion that the diabetes in R6/2 mice is caused by an impairment in insulin release rather than insulin insensitivity. However, chronic treatment with these hypoglycaemic agents had no effect on either the course of the diabetes or the disease in R6/2 mice.

Effects of creatine treatment on survival and differentiation of GABA-ergic neurons in cultured striatal tissue

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder, characterized by a prominent loss of GABA-ergic medium-sized spiny neurons in the caudate putamen. There is evidence that impaired energy metabolism contributes to neuronal death in HD. Creatine is an endogenous substrate for creatine kinases and thereby supports cellular ATP levels. This study investigated the effects of creatine supplementation (5 mm) on cell survival and neuronal differentiation in striatal cultures. Chronic creatine treatment resulted in significant increased densities of GABA-immunoreactive (-ir) neurons, although total neuronal cell number and general viability were not affected. Similar effects were seen after short-term treatment, suggesting that creatine acted as a differentiation factor. Inhibitors of transcription or translation did not abolish the creatine-mediated effects, nor did omission of extracellular calcium, whereas inhibition of mitogen-activated protein kinase and phosphatidylinositol-3-kinase significantly attenuated the creatine induced increase in GABA-ir cell densities. Creatine exhibited significant neuroprotection against toxicity instigated either by glucose- and serum deprivation or addition of 3-nitropropionic acid. In sum, the neuroprotective properties in combination with promotion of neuronal differentiation suggest that creatine has potential as a therapeutic drug in the treatment of neurodegenerative diseases, like HD.

Oxidative enhancement of insulin receptor signaling: experimental findings and clinical implications

Signaling through the insulin receptor and several other receptor tyrosine kinases is subject to redox regulation. Prolonged exposure to hydrogen peroxide impairs the action of insulin, and may account to some extent for the decreased insulin responsiveness in hyperglycemic diabetic patients. However, insulin receptor kinase (IRK) autophosphorylation and/or kinase activity were found to be markedly enhanced by a more limited exposure to hydrogen peroxide or by an oxidative shift in the thiol/disulfide redox status. Oxidative enhancement of IRK function may be mediated by two different mechanisms with similar effects, i.e., by direct oxidative activation of IRK activity or by oxidative inactivation of a protein tyrosine phosphatase, which otherwise down-regulates IRK-mediated signaling. As both mechanisms enhance IRK activity in the absence of insulin, there is a strong possibility that the background IRK activity in the postabsorptive period may be abnormally increased in certain oxidative conditions and thereby disturb the metabolism of glucose and other energy substrates. This remains to be tested. In line with the oxidative enhancement of IRK activity, clinical studies have shown that treatment with a thiol-containing antioxidant increases the postabsorptive glucose and/or insulin concentrations (i.e., the HOMA-R index) at least under certain conditions. This effect may have therapeutic implications.

A novel therapeutic strategy for polyglutamine diseases by stabilizing aggregation-prone proteins with small molecules

Polyglutamine diseases, such as Huntington disease (HD) and spinocerebellar ataxia 1 and 3, are autosomal dominant neurodegenerative disorders. They are caused by CAG trinucleotide repeat expansions that are translated into abnormally long polyglutamine tracts. One of the pathological hallmarks in polyglutamine diseases is the formation of intranuclear inclusions of polyglutamine-containing proteins in the brain. Although causal relationships between polyglutamine aggregation and cellular toxicity are much debated, inhibition of the polyglutamine-mediated protein aggregation may provide treatment options for polyglutamine diseases. However, the extreme insolubility of expanded polyglutamines makes it difficult to prepare polyglutamine-containing proteins on a large scale and to search for aggregation inhibitors by in vitro high-throughput screening. To overcome this we developed a novel in vitro model system for polyglutamine diseases using myoglobin as a host protein. We searched for small molecules that inhibit polyglutamine-mediated aggregation by in vitro screening with a mutant myoglobin containing a 35 polyglutamine repeat. The screening assay revealed that disaccharides have a potential to inhibit polyglutamine-induced protein aggregation and to increase survival in a cellular model of HD. Oral administration of trehalose, the most effective disaccharide in vitro, decreased polyglutamine aggregates in the cerebrum and liver, improved motor dysfunction and extended life span in a transgenic mouse model of HD. In vitro experiments suggest that the beneficial effects of trehalose result from its ability to bind and stabilize polyglutamine-containing proteins. The lack of toxicity and high solubility, coupled with its efficacy upon oral administration, make trehalose promising as a therapeutic drug or lead compound for the treatment of polyglutamine diseases. The stabilization of aggregation-prone proteins with small molecules is an attractive strategy because it can block the initial stage of the disease cascade. In addition, this therapeutic approach could be applied not only to polyglutamine diseases but also to a wide variety of misfolding-induced diseases.

A combination drug therapy improves cognition and reverses gene expression changes in a mouse model of Huntington's disease

Huntington's disease is a genetic disease caused by a single mutation. It is characterized by progressive movement, emotional and cognitive deficits. R6/2 mice transgenic for exon 1 of the HD gene with 150+ CAG repeats have a progressive neurological phenotype, including deterioration in cognitive function. The mechanism underlying the cognitive deficits in R6/2 mice is unknown, but dysregulated gene expression, reduced neurotransmitter levels and abnormal synaptic function are present before the cognitive decline becomes pronounced. Our goal here was to ameliorate the cognitive phenotype in R6/2 mice using a combination drug therapy (tacrine, moclobemide and creatine) aimed at boosting neurotransmitter levels in the brain. Treatment from 5 weeks of age prevented deterioration in two different cognitive tasks until at least 12 weeks. However, motor deterioration continued unabated. Microarray analysis of global gene expression revealed that many genes significantly up- or down-regulated in untreated R6/2 mice had returned towards normal levels after treatment, though a minority were further dysregulated. Thus dysregulated gene expression was reversed by the combination treatment in the R6/2 mice and probably underlies the observed improvements in cognitive function. Our study shows that cognitive decline caused by a genetic mutation can be slowed by a combination drug treatment, and gives hope that cognitive symptoms in HD can be treated.

Targeting cellular energy production in neurological disorders

The concepts of energy dysregulation and oxidative stress and their complicated interdependence have rapidly evolved to assume primary importance in understanding the pathophysiology of numerous neurological disorders. Therefore, neuroprotective strategies addressing specific bioenergetic defects hold particular promise in the treatment of these conditions (i.e., amyotrophic lateral sclerosis, Huntington's disease, Parkinson's disease, Friedreich's ataxia, mitochondrial cytopathies and other neuromuscular diseases), all of which, to some extent, share 'the final common pathway' leading to cell death through either necrosis or apoptosis. Compounds such as creatine monohydrate and coenzyme Q(10) offer substantial neuroprotection against ischaemia, trauma, oxidative damage and neurotoxins. Miscellaneous agents, including alpha-lipoic acid, beta-OH-beta-methylbutyrate, riboflavin and nicotinamide, have also been shown to improve various metabolic parameters in brain and/or muscle. This review will highlight the biological function of each of the above mentioned compounds followed by a discussion of their utility in animal models and human neurological disease. The balance of this work will be comprised of discussions on the therapeutic applications of creatine and coenzyme Q(10).

CGS21680 attenuates symptoms of Huntington's disease in a transgenic mouse model

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by a CAG trinucleotide expansion in exon 1 of the Huntingtin (Htt) gene. We show herein that in an HD transgenic mouse model (R6/2), daily administration of CGS21680 (CGS), an A(2A) adenosine receptor (A(2A)-R)-selective agonist, delayed the progressive deterioration of motor performance and prevented a reduction in brain weight. 3D-microMRI analysis revealed that CGS reversed the enlarged ventricle-to-brain ratio of R6/2 mice, with particular improvements in the left and right ventricles. (1)H-MRS showed that CGS significantly reduced the increased choline levels in the striatum. Immunohistochemical analyses further demonstrated that CGS reduced the size of ubiquitin-positive neuronal intranuclear inclusions (NIIs) in the striatum of R6/2 mice and ameliorated mutant Htt aggregation in a striatal progenitor cell line overexpressing mutant Htt with expanded polyQ. Moreover, chronic CGS treatment normalized the elevated blood glucose levels and reduced the overactivation of a major metabolic sensor [5'AMP-activated protein kinase (AMPK)] in the striatum of R6/2 mice. Since AMPK is a master switch for energy metabolism, modulation of energy dysfunction caused by the mutant Htt might contribute to the beneficial effects of CGS. Collectively, CGS is a potential drug candidate for the treatment of HD.

Creatine feeding increases GLUT4 expression in rat skeletal muscle

The purpose of this study was to investigate the potential role of creatine in GLUT4 gene expression in rat skeletal muscle. Female Wistar rats were fed normal rat chow (controls) or chow containing 2% creatine monohydrate ad libitum for 3 wk. GLUT4 protein levels of creatine-fed rats were significantly increased in extensor digitorum longus (EDL), triceps, and epitrochlearis muscles compared with muscles from controls (P < 0.05), and triceps GLUT4 mRNA levels were approximately 100% greater in triceps muscles from creatine-fed rats than in muscles from controls (P < 0.05). In epitrochlearis muscles from creatine-fed animals, glycogen content was approximately 40% greater (P < 0.05), and insulin-stimulated glucose transport rates were higher (P < 0.05) than in epitrochlearis muscles from controls. Despite no changes in [ATP], [creatine], [phosphocreatine], or [AMP], creatine feeding increased AMP-activated protein kinase (AMPK) phosphorylation by 50% in rat EDL muscle (P < 0.05). Creatinine content of EDL muscle was almost twofold higher for creatine-fed animals than for controls (P < 0.05). Creatine feeding increased protein levels of myocyte enhancer factor 2 (MEF2) isoforms MEF2A ( approximately 70%, P < 0.05), MEF2C ( approximately 60%, P < 0.05), and MEF2D ( approximately 90%, P < 0.05), which are transcription factors that regulate GLUT4 expression, in creatine-fed rat EDL muscle nuclear extracts. Electrophoretic mobility shift assay showed that DNA binding activity of MEF2 was increased by approximately 40% (P < 0.05) in creatine-fed rat EDL compared with controls. Our data suggest that creatine feeding enhances the nuclear content and DNA binding activity of MEF2 isoforms, which is concomitant with an increase in GLUT4 gene expression.

Creatine protects against 3-nitropropionic acid-induced cell death in murine corticostriatal slice cultures

In murine corticostriatal slice cultures, we studied the protective effects of the bioenergetic compound creatine on neuronal cell death induced by the mitochondrial toxin 3-nitropropionic acid (3-NP). 3-NP caused a dose-dependent neuronal degeneration accompanied by an increased lactate dehydrogenase (LDH) activity in the cell culture medium. An increased ratio of lactate to pyruvate concentration in the medium suggested that metabolic activity shifted to anaerobic energy metabolism. These effects were predominantly observed in the 24-h recovery period after 3-NP exposure. Creatine protected against 3-NP neurotoxicity: LDH activity was reduced and aerobic respiration of pyruvate was stimulated, which resulted in lower lactate levels and less cell death. In both striatum and cortex, apoptosis in 3-NP-exposed slices was demonstrated by increased activation of the pro-apoptotic protein caspase-3 and by numerous cells exhibiting DNA fragmentation detected by the terminal transferase-mediated biotinylated-UTP nick end-labeling (TUNEL) technique. Creatine administration to the 3-NP-exposed corticostriatal slices resulted in a reduced number of TUNEL-positive cells in the recovery period. However, in the striatum, an unexpected increase of both TUNEL-positive cells and caspase-3-immunostained cells was observed in the exposure phase in the presence of creatine. In the recovery phase, caspase-3-immunostaining decreased to basal levels in both striatum and cortex. These findings suggest that 3-NP-induced neuronal degeneration in corticostriatal slices results from apoptosis that in the cortex can be prevented by creatine, while in the more vulnerable striatal cells it may lead to an accelerated and increased execution of apoptotic cell death, preventing further necrosis-related damage in this region.

Nutritional therapy improves function and complements corticosteroid intervention inmdx mice

Corticosteroid therapy for Duchenne muscular dystrophy is effective but associated with long-term side effects. To determine the potential therapeutic benefit from four nutritional compounds (creatine monohydrate, conjugated linoleic acid, alpha-lipoic acid, and beta-hydroxy-beta-methylbutyrate) alone, in combination, and with corticosteroids (prednisolone), we evaluated the effects on several variables in exercising mdx mice. Outcome measures included grip strength, rotarod performance, serum creatine kinase levels, muscle metabolites, internalized myonuclei, and retroperitoneal fat pad weight. In isolation, each nutritional treatment showed some benefit, with the combination therapy showing the most consistent benefits. Prednisolone and the combination therapy together provided the most consistent evidence of efficacy; increased peak grip strength (P < 0.05), decreased grip strength fatigue (P < 0.05), decreased number of internalized myonuclei (P < 0.01), and smaller retroperitoneal fat pad stores (P < 0.001). This study provided evidence for therapeutic benefit from a four-compound combination therapy alone, and in conjunction with corticosteroids in the mdx model of DMD.

Creatine supplementation lowers brain glutamate levels in Huntington?s disease

There is evidence from in vitro and animal experiments that oral creatine (Cr) supplementation might prevent or slow down neurodegeneration in Huntington's disease (HD). However, this neuroprotective effect could not be replicated in clinical trials, possibly owing to treatment periods being too short to impact on clinical endpoints. We used proton magnetic resonance spectroscopy ((1)H-MRS) as a surrogate marker to evaluate the effect of Cr supplementation on brain metabolite levels in HD.Twenty patients (age 46+/-7.3 years, mean duration of symptoms 4.0+/-2.1 years, number of CAG repeats 44.5+/-2.7) were included. The primary endpoint was metabolic alteration as measured by (1)H-MRS in the parieto-occipital cortex before (t1) and after 8-10 weeks (t2) of Cr administration. Secondary measures comprised the motor section of the Unified Huntington's Disease Rating Scale and the Mini Mental State Examination. (1)H-MRS showed a 15.6% decrease of unresolved glutamate (Glu)+glutamine (Gln; Glu+Gln=Glx; p<0.001) and a 7.8% decrease of Glu (p<0.027) after Cr treatment. N-acetylaspartate trended to fall (p=0.073) whereas total Cr, choline-containing compounds, glucose, and lactate remained unchanged. There was no effect on clinical rating scales. This cortical Glx and Glu decrease may be explained by Cr enhancing the energy-dependent conversion of Glu to Gln via the Glu-Gln cycle, a pathway known to be impaired in HD. Since Glu-mediated excitotoxicity is presumably pivotal in HD pathogenesis, these results indicate a therapeutic potential of Cr in HD. Thus, longterm clinical trials are warranted.

Chronology of behavioral symptoms and neuropathological sequela in R6/2 Huntington's disease transgenic mice

Genetic murine models play an important role in the study of human neurological disorders by providing accurate and experimentally accessible systems to study pathogenesis and to test potential therapeutic treatments. One of the most widely employed models of Huntington's disease (HD) is the R6/2 transgenic mouse. To characterize this model further, we have performed behavioral and neuropathological analyses that provide a foundation for the use of R6/2 mice in preclinical therapeutic trials. Behavioral analyses of the R6/2 mouse reveal age-related impairments in dystonic movements, motor performance, grip strength, and body weight that progressively worsen until death. Significant neuropathological sequela, identified as increasing marked reductions in brain weight, are present from 30 days, whereas decreased brain volume is present from 60 days and decreased neostriatal volume and striatal neuron area, with a concomitant reduction in striatal neuron number, are present at 90 days of age. Huntingtin-positive aggregates are present at postnatal day 1 and increase in number and size with age. Our findings suggest that the R6/2 HD model exhibits a progressive HD-like behavioral and neuropathological phenotype that more closely corresponds to human HD than previously believed, providing further assurance that the R6/2 mouse is an appropriate model for testing potential therapies for HD.

Heterogeneity in 1H-MRS profiles of presymptomatic and early manifest Huntington's disease

OBJECTIVE

To evaluate (1)H-MRS profiles of the putamen in presymptomatic and manifest Huntington's disease (HD) patients for spectroscopic markers that are reliable, consistent signs of early pathology and to look for hemispheric differences as signs of use activation in an accelerated degradative process of the dominant hemisphere.

METHODS

A short echo time Point RESolved Spectroscopy (PRESS) spectroscopic imaging study was performed at low field (0.5 Tesla, T) on 27 right-handed patients (17 presymptomatic gene carriers and 10 manifest patients of less than 3 years from clinical onset) and 10 right-handed normal volunteers. Spectra from individual voxels (0.56 cm(3)) in the putamen were selected for analysis. Resonance areas of peaks were normalized to water as a concentration standard. Interhemispheric comparisons were made in individuals in all three groups to look for hemispheric differences.

RESULTS

Two presymptomatic patients showed normal spectra but all other HD patients displayed some combination of reduced N-acetylaspartate (NAA), enhanced glutamate/glutamine (Glx) activity, and lactate (Lac) elevations or reduced creatine (Cr). Rather than showing any one metabolite as pathognomonic of early change, spectroscopic profiles showed heterogeneity between HD patients. Low creatine was common in the presymptomatic but not in the manifest group. Hemispheric ratios of abnormal metabolites showed lower values of NAA and Glx in the dominant hemisphere in all three groups but values of creatine were selectively lower in the dominant hemisphere of only the presymptomatic patients. Lac was elevated in both hemispheres but less so in the dominant hemisphere in all HD patients.

CONCLUSIONS

(1)H-MRS profiles from the putamen of presymptomatic and manifest patients reflect heterogeneity in pathophysiology. With the possible exception of low creatine in presymptomatic patients (1)H-MRS spectra are not suggestive of hemispheric differences supportive of an overall accelerated degradative process in the dominant hemisphere.

Effects of creatine treatment on the survival of dopaminergic neurons in cultured fetal ventral mesencephalic tissue

Parkinson's disease is a disabling neurodegenerative disorder of unknown etiology characterized by a predominant and progressive loss of dopaminergic neurons in the substantia nigra. Recent findings suggest that impaired energy metabolism plays an important role in the pathogenesis of this disorder. The endogenously occurring guanidino compound creatine is a substrate for mitochondrial and cytosolic creatine kinases. Creatine supplementation improves the function of the creatine kinase/phosphocreatine system by increasing cellular creatine and phosphocreatine levels and the rate of ATP resynthesis. In addition, mitochondrial creatine kinase together with high cytoplasmic creatine levels inhibit mitochondrial permeability transition, a major step in early apoptosis. In the present study, we analyzed the effects of externally added creatine on the survival and morphology of dopaminergic neurons and also addressed its neuroprotective properties in primary cultures of E14 rat ventral mesencephalon. Chronic administration of creatine [5 mM] for 7 days significantly increased survival (by 1.32-fold) and soma size (by 1.12-fold) of dopaminergic neurons, while having no effect on other investigated morphological parameters. Most importantly, concurrent creatine exerted significant neuroprotection for dopaminergic neurons against neurotoxic insults induced by serum and glucose deprivation (P < 0.01), 1-methyl-4-phenyl pyridinium ion (MPP+) [15 microM] and 6-hydroxydopamine (6-OHDA) [90 microM] exposure (P < 0.01). In addition, creatine treatment significantly protected dopaminergic cells facing MPP+-induced deterioration of neuronal morphology including overall process length/neuron (by 60%), number of branching points/neuron (by 80%) and area of influence per individual neuron (by 60%). Less pronounced effects on overall process length/neuron and number of branching points/neuron were also found after 6-OHDA exposure (P < 0.05) and serum/glucose deprivation (P < 0.05). In conclusion, our findings identify creatine as a rather potent natural survival- and neuroprotective factor for developing nigral dopaminergic neurons, which is of relevance for therapeutic approaches in Parkinson's disease and for the improvement of cell replacement strategies.

The role of creatine in the management of amyotrophic lateral sclerosis and other neurodegenerative disorders

Creatine is consumed in the diet and endogenously synthesised in the body. Over the past decade, the ergogenic benefits of synthetic creatine monohydrate have made it a popular dietary supplement, particularly among athletes. The anabolic properties of creatine also offer hope for the treatment of diseases characterised by weakness and muscle atrophy. Moreover, because of its cellular mechanisms of action, creatine offers potential benefits for diseases involving mitochondrial dysfunction. Recent data also support the hypothesis that creatine may have a neuroprotective effect. Amyotrophic lateral sclerosis (ALS) is characterised by progressive degeneration of motor neurons, resulting in weakening and atrophy of skeletal muscles. In patients with this condition, creatine offers potential benefits in terms of facilitating residual muscle contractility as well as improving neuronal function. It may also help stabilise mitochondrial dysfunction, which plays a key role in the pathogenesis of ALS. Indeed, the likely multifactorial aetiology of ALS means the combined pharmacodynamic properties of creatine offer promise for the treatment of this condition. Evidence from available animal models of ALS supports the utility of treatment with creatine in this setting. Limited data available in other neuromuscular and neurodegenerative diseases further support the potential benefit of creatine monohydrate in ALS. However, few randomised, controlled trials have been conducted. To date, two clinical trials of creatine monohydrate in ALS have been completed without demonstration of significant improvements in overall survival or a composite measure of muscle strength. These trials have also posed unanswered questions about the optimal dosage of creatine and its beneficial effects on muscle fatigue, a measure distinct from muscle strength. A large, multicentre, clinical trial is currently underway to further investigate the efficacy of creatine monohydrate in ALS and address these unresolved issues. Evidence to date shows that creatine supplementation has a good safety profile and is well tolerated by ALS patients. The purpose of this article is to provide a short, balanced review of the literature concerning creatine monohydrate in the treatment of ALS and related neurodegenerative diseases. The pharmacokinetics and rationale for the use of creatine are described along with available evidence from animal models and clinical trials for ALS and related neurodegenerative or neuromuscular diseases.

Protection from mitochondrial complex II inhibition in vitro and in vivo by Nrf2-mediated transcription

Complex II inhibitors 3-nitropropionic acid (3NP) and malonate cause striatal damage reminiscent of Huntington's disease and have been shown to involve oxidative stress in their pathogenesis. Because nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent transcriptional activation by means of the antioxidant response element is known to coordinate the up-regulation of cytoprotective genes involved in combating oxidative stress, we investigated the significance of Nrf2 in complex II-induced toxicity. We found that Nrf2-deficient cells and Nrf2 knockout mice are significantly more vulnerable to malonate and 3NP and demonstrate increased antioxidant response element (ARE)-regulated transcription mediated by astrocytes. Furthermore, ARE preactivation by means of intrastriatal transplantation of Nrf2-overexpressing astrocytes before lesioning conferred dramatic protection against complex II inhibition. These observations implicate Nrf2 as an essential inducible factor in the protection against complex II inhibitor-mediated neurotoxicity. These data also introduce Nrf2-mediated ARE transcription as a potential target of preventative therapy in neurodegenerative disorders such as Huntington's disease.

A Creatine Transporter Is Operative at the Brush Border Level of the Rat Jejunal Enterocyte

Although ergogenic effects and health benefits have been reported for creatine used as nutritional supplement, to date little is known about the mechanism of creatine absorption in the small intestine. Thus the current study was undertaken to elucidate the mechanism of creatine intake in rat jejunum with the use of well-purified brush border membrane vesicles, isolated from jejunal enterocyte. Creatine uptake was found markedly stimulated by inwardly directed Na(+) and Cl(- )gradients, potential-sensitive, strongly reduced by the substitution of Na(+) and Cl(-) with various cations and anions and positively affected by intravesicular K(+). Moreover, creatine uptake is: 1) significantly inhibited by creatine structural analogs, 2) abolished by low concentrations of 2-aminoethyl methanethiosulfonate hydrobromide (MTSEA), 3) saturable as a function of creatine concentration with an apparent Michaelis-Menten constant of 24.08 +/- 0.80 muM and a maximal velocity of 391.30 +/- 6.19 pmoles mg protein(-1) 30 s(-1). The transport is electrogenic since at least two Na(+) and one Cl(-) are required to transport one creatine molecule. Western blot analysis showed the same amount of creatine transport protein in the jejunal apical membrane when compared to ileum. Thus, these data demonstrate the existence of a Na(+)- and Cl(-)-dependent, membrane potential-sensitive, electrogenic carrier-mediated mechanism for creatine absorption in rat jejunal apical membrane vesicles, which is biochemically and pharmacologically similar to those observed in other tissues. However, in other cell types the stimulatory effect of intravesicular K(+) was never detected.