A randomised, placebo-controlled, double blind study of treatment of Huntington's disease with unsaturated fatty acids

Altered Metabolic Signaling and Potential Therapies in Polyglutamine Diseases

Polyglutamine diseases comprise a cluster of genetic disorders involving neurodegeneration and movement disabilities. In polyglutamine diseases, the target proteins become aberrated due to polyglutamine repeat formation. These aberrant proteins form the root cause of associated complications. The metabolic regulation during polyglutamine diseases is not well studied and needs more attention. We have brought to light the significance of regulating glutamine metabolism during polyglutamine diseases, which could help in decreasing the neuronal damage associated with excess glutamate and nucleotide generation. Most polyglutamine diseases are accompanied by symptoms that occur due to excess glutamate and nucleotide accumulation. Along with a dysregulated glutamine metabolism, the Nicotinamide adenine dinucleotide (NAD+) levels drop down, and, under these conditions, NAD+ supplementation is the only achievable strategy. NAD+ is a major co-factor in the glutamine metabolic pathway, and it helps in maintaining neuronal homeostasis. Thus, strategies to decrease excess glutamate and nucleotide generation, as well as channelizing glutamine toward the generation of ATP and the maintenance of NAD+ homeostasis, could aid in neuronal health. Along with understanding the metabolic dysregulation that occurs during polyglutamine diseases, we have also focused on potential therapeutic strategies that could provide direct benefits or could restore metabolic homeostasis. Our review will shed light into unique metabolic causes and into ideal therapeutic strategies for treating complications associated with polyglutamine diseases.

Cell Rearrangement and Oxidant/Antioxidant Imbalance in Huntington's Disease

Huntington's Disease (HD) is a hereditary neurodegenerative disorder caused by the expansion of a CAG triplet repeat in the HTT gene, resulting in the production of an aberrant huntingtin (Htt) protein. The mutant protein accumulation is responsible for neuronal dysfunction and cell death. This is due to the involvement of oxidative damage, excitotoxicity, inflammation, and mitochondrial impairment. Neurons naturally adapt to bioenergetic alteration and oxidative stress in physiological conditions. However, this dynamic system is compromised when a neurodegenerative disorder occurs, resulting in changes in metabolism, alteration in calcium signaling, and impaired substrates transport. Thus, the aim of this review is to provide an overview of the cell's answer to the stress induced by HD, focusing on the role of oxidative stress and its balance with the antioxidant system.

Site-specific mitochondrial dysfunction in neurodegeneration

Mitochondria are essential for neuronal survival and mitochondrial dysfunction is a hallmark of neurodegeneration. The loss in mitochondrial energy production, oxidative stress, and changes in calcium handling are associated with neurodegenerative diseases; however, different sites and types of mitochondrial dysfunction are linked to distinct neuropathologies. Understanding the causal or correlative relationship between changes in mitochondria and neuropathology will lead to new therapeutic strategies. Here, we summarize the evidence of site-specific mitochondrial dysfunction and mitochondrial-related clinical trials for neurodegenerative diseases. We further discuss potential therapeutic approaches, such as mitochondrial transplantation, restoration of mitochondrial function, and pharmacological alleviation of mitochondrial dysfunction.

Oxidative Stress and Neurodegeneration: Interconnected Processes in PolyQ Diseases

Neurodegenerative polyglutamine (polyQ) disorders are caused by trinucleotide repeat expansions within the coding region of disease-causing genes. PolyQ-expanded proteins undergo conformational changes leading to the formation of protein inclusions which are associated with selective neuronal degeneration. Several lines of evidence indicate that these mutant proteins are associated with oxidative stress, proteasome impairment and microglia activation. These events may correlate with the induction of inflammation in the nervous system and disease progression. Here, we review the effect of polyQ-induced oxidative stress in cellular and animal models of polyQ diseases. Furthermore, we discuss the interplay between oxidative stress, neurodegeneration and neuroinflammation using as an example the well-known neuroinflammatory disease, Multiple Sclerosis. Finally, we review some of the pharmaceutical interventions which may delay the onset and progression of polyQ disorders by targeting disease-associated mechanisms.

Reactive Species in Huntington Disease: Are They Really the Radicals You Want to Catch?

Huntington disease (HD) is a neurodegenerative condition and one of the so-called rare or minority diseases, due to its low prevalence (affecting 1–10 of every 100,000 people in western countries). The causative gene, HTT, encodes huntingtin, a protein with a yet unknown function. Mutant huntingtin causes a range of phenotypes, including oxidative stress and the activation of microglia and astrocytes, which leads to chronic inflammation of the brain. Although substantial efforts have been made to find a cure for HD, there is currently no medical intervention able to stop or even delay progression of the disease. Among the many targets of therapeutic intervention, oxidative stress and inflammation have been extensively studied and some clinical trials have been promoted to target them. In the present work, we review the basic research on oxidative stress in HD and the strategies used to fight it. Many of the strategies to reduce the phenotypes associated with oxidative stress have produced positive results, yet no substantial functional recovery has been observed in animal models or patients with the disease. We discuss possible explanations for this and suggest potential ways to overcome it.

Exercise, diet and stress as modulators of gut microbiota: Implications for neurodegenerative diseases

The last decade has witnessed an exponentially growing interest in gut microbiota and the gut-brain axis in health and disease. Accumulating evidence from preclinical and clinical research indicate that gut microbiota, and their associated microbiomes, may influence pathogenic processes and thus the onset and progression of various diseases, including neurological and psychiatric disorders. In fact, gut dysbiosis (microbiota dysregulation) has been associated with a range of neurodegenerative diseases, including Alzheimer's, Parkinson's, Huntington's and motor neuron disease, as well as multiple sclerosis. The gut microbiota constitutes a dynamic microbial system constantly challenged by many biological variables, including environmental factors. Since the gut microbiota constitute a changeable and experience-dependent ecosystem, they provide potential therapeutic targets that can be modulated as new interventions for dysbiosis-related disorders, including neurodegenerative diseases. This article reviews the evidence for environmental modulation of gut microbiota and its relevance to brain disorders, exploring in particular the implications for neurodegenerative diseases. We will focus on three major environmental factors that are known to influence the onset and progression of those diseases, namely exercise, diet and stress. Further exploration of environmental modulation, acting via both peripheral (e.g. gut microbiota and associated metabolic dysfunction or 'metabolopathy') and central (e.g. direct effects on CNS neurons and glia) mechanisms, may lead to the development of novel therapeutic approaches, such as enviromimetics, for a wide range of neurological and psychiatric disorders.

Are immunotherapies for Huntington's disease a realistic option?

There is compelling evidence that the pathophysiology of many neurodegenerative diseases includes dysregulation of the immune system, with some elements that precede disease onset. However, if these alterations are prominent, why have clinical trials targeting this system failed to translate into long-lasting meaningful benefits for patients? This review focuses on Huntington's disease, a genetic disorder marked by notable cerebral and peripheral inflammation. We summarize ongoing and completed clinical trials that have involved pharmacological approaches to inhibit various components of the immune system and their pre-clinical correlates. We then discuss new putative treatment strategies using more targeted immunotherapies such as vaccination and intrabodies and how these may offer new hope in the treatment of Huntington's disease as well as other neurodegenerative diseases.

Rating Scales and Performance-based Measures for Assessment of Functional Ability in Huntington's Disease: Critique and Recommendations

Limitation of functional ability is a major feature of Huntington's disease (HD). The International Parkinson and Movement Disorder Society (MDS) commissioned the appraisal of the use and clinimetric properties of clinical measures of functional ability that have been applied in HD studies and trials to date, to make recommendations regarding their use based on standardized criteria. After a systematic literature search, we included a total of 29 clinical measures grouped into two categories: (1) performance-based measures (e.g., balance, walking, and reaching/grasping), and (2) rating scales. Three performance-based measures are rated as "recommended": the Tinetti Mobility Test for screening of fall risk and for severity assessment of mobility in patients with manifest HD (up to stage III); the Berg Balance Scale for severity of balance impairment; and the Six-Minute Walk Test for assessment of walking endurance (severity) in HD subjects with preserved ambulation. No rating scale targeting functional ability reached a "recommended" status either for screening or severity measurement. The main challenges identified in this review include applying widely accepted conceptual frameworks to the identified measures, the lack of validation of clinical measures to detect change over time, and absence of validated measures for upper limb function. Furthermore, measures of capacity or ability to perform activities of daily living had ceiling effects in people with early and pre-manifest HD. We recommend that the MDS prioritize the development of new scales that capture small, but meaningful changes in function over time for outcome assessment in clinical trials, particularly in earlier stages of HD.

Miscellaneous treatments for antipsychotic-induced tardive dyskinesia

BACKGROUND

Antipsychotic (neuroleptic) medication is used extensively to treat people with chronic mental illnesses. Its use, however, is associated with adverse effects, including movement disorders such as tardive dyskinesia (TD) - a problem often seen as repetitive involuntary movements around the mouth and face. This review, one in a series examining the treatment of TD, covers miscellaneous treatments not covered elsewhere.

OBJECTIVES

To determine whether drugs, hormone-, dietary-, or herb-supplements not covered in other Cochrane reviews on TD treatments, surgical interventions, electroconvulsive therapy, and mind-body therapies were effective and safe for people with antipsychotic-induced TD.

SEARCH METHODS

We searched the Cochrane Schizophrenia Group's Study-Based Register of Trials including trial registers (16 July 2015 and 26 April 2017), inspected references of all identified studies for further trials and contacted authors of trials for additional information.

SELECTION CRITERIA

We included reports if they were randomised controlled trials (RCTs) dealing with people with antipsychotic-induced TD and schizophrenia or other chronic mental illnesses who remained on their antipsychotic medication and had been randomly allocated to the interventions listed above versus placebo, no intervention, or any other intervention.

DATA COLLECTION AND ANALYSIS

We independently extracted data from these trials and we estimated risk ratios (RR) or mean differences (MD), with 95% confidence intervals (CIs). We assumed that people who left early had no improvement. We assessed risk of bias and created 'Summary of findings' tables using GRADE.

MAIN RESULTS

We included 31 RCTs of 24 interventions with 1278 participants; 22 of these trials were newly included in this 2017 update. Five trials are awaiting classification and seven trials are ongoing. All participants were adults with chronic psychiatric disorders, mostly schizophrenia, and antipsychotic-induced TD. Studies were primarily of short (three to six6 weeks) duration with small samples size (10 to 157 participants), and most (61%) were published more than 20 years ago. The overall risk of bias in these studies was unclear, mainly due to poor reporting of allocation concealment, generation of the sequence, and blinding.Nineteen of the 31 included studies reported on the primary outcome 'No clinically important improvement in TD symptoms'. Two studies found moderate-quality evidence of a benefit of the intervention compared with placebo: valbenazine (RR 0.63, 95% CI 0.46 to 0.86, 1 RCT, n = 92) and extract of Ginkgo biloba (RR 0.88, 95% CI 0.81 to 0.96, 1 RCT, n = 157), respectively. However, due to small sample sizes we cannot be certain of these effects.We consider the results for the remaining interventions to be inconclusive: Low- to very low-quality evidence of a benefit was found for buspirone (RR 0.53, 95% CI 0.33 to 0.84, 1 RCT, n = 42), dihydrogenated ergot alkaloids (RR 0.45, 95% CI 0.21 to 0.97, 1 RCT, n = 28), hypnosis or relaxation, (RR 0.45, 95% CI 0.21 to 0.94, 1 study, n = 15), pemoline (RR 0.48, 95% CI 0.29 to 0.77, 1 RCT, n = 46), promethazine (RR 0.24, 95% CI 0.11 to 0.55, 1 RCT, n = 34), insulin (RR 0.52, 95% CI 0.29 to 0.96, 1 RCT, n = 20), branched chain amino acids (RR 0.79, 95% CI 0.63 to 1.00, 1 RCT, n = 52), and isocarboxazid (RR 0.24, 95% CI 0.08 to 0.71, 1 RCT, n = 20). There was low- to very low-certainty evidence of no difference between intervention and placebo or no treatment for the following interventions: melatonin (RR 0.89, 95% CI 0.71 to 1.12, 2 RCTs, n = 32), lithium (RR 1.59, 95% CI 0.79 to 3.23, 1 RCT, n = 11), ritanserin (RR 1.00, 95% CI 0.70 to 1.43, 1 RCT, n = 10), selegiline (RR 1.37, 95% CI 0.96 to 1.94, 1 RCT, n = 33), oestrogen (RR 1.18, 95% CI 0.76 to 1.83, 1 RCT, n = 12), and gamma-linolenic acid (RR 1.00, 95% CI 0.69 to 1.45, 1 RCT, n = 16).None of the included studies reported on the other primary outcome, 'no clinically significant extrapyramidal adverse effects'.

AUTHORS' CONCLUSIONS

This review has found that the use of valbenazine or extract of Ginkgo biloba may be effective in relieving the symptoms of tardive dyskinesia. However, since only one RCT has investigated each one of these compounds, we are awaiting results from ongoing trials to confirm these results. Results for the remaining interventions covered in this review must be considered inconclusive and these compounds probably should only be used within the context of a well-designed evaluative study.

Therapy development in Huntington disease: From current strategies to emerging opportunities

Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder in which patients typically present with uncontrolled involuntary movements and subsequent cognitive decline. In 1993, a CAG trinucleotide repeat expansion in the coding region of the huntingtin (HTT) gene was identified as the cause of this disorder. This extended CAG repeat results in production of HTT protein with an expanded polyglutamine tract, leading to pathogenic HTT protein conformers that are resistant to protein turnover, culminating in cellular toxicity and neurodegeneration. Research into the mechanistic basis of HD has highlighted a role for bioenergetics abnormalities stemming from mitochondrial dysfunction, and for synaptic defects, including impaired neurotransmission and excitotoxicity. Interference with transcription regulation may underlie the mitochondrial dysfunction. Current therapies for HD are directed at treating symptoms, as there are no disease-modifying therapies. Commonly prescribed drugs for involuntary movement control include tetrabenazine, a potent and selective inhibitor of vesicular monoamine transporter 2 that depletes synaptic monoamines, and olanzapine, an atypical neuroleptic that blocks the dopamine D2 receptor. Various drugs are used to treat non-motor features. The HD therapeutic pipeline is robust, as numerous efforts are underway to identify disease-modifying treatments, with some small compounds and biological agents moving into clinical trials. Especially encouraging are dosage reduction strategies, including antisense oligonucleotides, and molecules directed at transcription dysregulation. Given the depth and breadth of current HD drug development efforts, there is reason to believe that disease-modifying therapies for HD will emerge, and this achievement will have profound implications for the entire neurotherapeutics field.

Huntington's Disease: Pathological Mechanisms and Therapeutic Strategies

Huntington's disease (HD) is a devastating neurodegenerative disorder that occurs in patients with a mutation in the huntingtin or IT15 gene. Patients are plagued by early cognitive signs, motor deficits, and psychiatric disturbances. Symptoms are attributed to cell death in the striatum and disruption of cortical–striatal circuitry. Mechanisms of cell death are unclear, but processes involving mitochondrial abnormalities, excitotoxicity, and abnormal protein degradation have been implicated. Many factors likely contribute to neuron death and dysfunction, and this has made it difficult to systematically address the pathology in HD. Pharmaceutical therapies are commonly used in patients to treat disease symptoms. These have limited benefit and do not address the inexorable disease progression. Several neuroprotective therapies are being evaluated in animal models of HD as well as in clinical trials. Similarly, cell replacement strategies such as fetal transplantation have been used in the clinic with minimal success, making future cell replacement strategies such as stem cell therapy uncertain. This review describes the disease pathology in HD and addresses many of the past and emerging therapeutic strategies.

Toward therapeutic targets for SCA3: Insight into the role of Machado-Joseph disease protein ataxin-3 in misfolded proteins clearance

Machado-Joseph disease (MJD, also known as spinocerebellar ataxia type 3, SCA3), an autosomal dominant neurological disorder, is caused by an abnormal expanded polyglutamine (polyQ) repeat in the ataxin-3 protein. The length of the expanded polyQ stretch correlates positively with the severity of the disease and inversely with the age at onset. To date, we cannot fully explain the mechanism underlying neurobiological abnormalities of this disease. Yet, accumulating reports have demonstrated the functions of ataxin-3 protein in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, all of which suggest a role of ataxin-3 in the clearance of misfolded proteins. Notably, the SCA3 pathogenic form of ataxin-3 (ataxin-3(exp)) impairs the misfolded protein clearance via mechanisms that are either dependent or independent of its deubiquitinase (DUB) activity, resulting in the accumulation of misfolded proteins and the progressive loss of neurons in SCA3. Some drugs, which have been used as activators/inducers in the chaperone system, ubiquitin-proteasome system, and aggregation-autophagy, have been demonstrated to be efficacious in the relief of neurodegeneration diseases like Huntington's disease (HD), Parkinson's (PD), Alzheimer's (AD) as well as SCA3 in animal models and clinical trials, putting misfolded protein clearance on the list of potential therapeutic targets. Here, we undertake a comprehensive review of the progress in understanding the physiological functions of ataxin-3 in misfolded protein clearance and how the polyQ expansion impairs misfolded protein clearance. We then detail the preclinical studies targeting the elimination of misfolded proteins for SCA3 treatment. We close with future considerations for translating these pre-clinical results into therapies for SCA3 patients.

Animal models of Huntington's disease for translation to the clinic: best practices

Mouse models of Huntington's disease (HD) recapitulate many aspects of the human disease. These genetically modified mice are powerful tools that are used not only to examine the pathogenesis of the disease, but also to assess the efficacy of potential new treatments. Disappointingly, in the past few years we have seen the success of potential therapies in animal studies, subsequently followed by failure in clinical trials. We discuss here a number of factors that influence the translatability of findings from the preclinical to the clinical realm. In particular, we discuss issues related to sample size, reporting of information regarding experimental protocols and mouse models, assignment to experimental groups, incorporation of cognitive measures for early phases of the disease, environmental enrichment, surrogate measures for survival, and the use of more than one HD mouse model. Although it is reasonable to question the appropriateness of the animal models used, we argue that it is more parsimonious to assume that improvements in experimental design and publication of negative results will lead to improved translatability to the clinic and insights about HD pathophysiology.

Omega-3 fatty acids in neurodegenerative diseases: focus on mitochondria

Mitochondrial dysfunction represents a common early pathological event in brain aging and in neurodegenerative diseases, e.g., in Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD), as well as in ischemic stroke. In vivo and ex vivo experiments using animal models of aging and AD, PD, and HD mainly showed improvement of mitochondrial function after treatment with polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA). Thereby, PUFA are particular beneficial in animals treated with mitochondria targeting toxins. However, DHA showed adverse effects in a transgenic PD mouse model and it is not clear if a diet high or low in PUFA might provide neuroprotective effects in PD. Post-treatment with PUFA revealed conflicting results in ischemic animal models, but intravenous administered DHA provided neuroprotective efficacy after acute occlusion of the middle cerebral artery. In summary, the majority of preclinical data indicate beneficial effects of n-3 PUFA in neurodegenerative diseases, whereas most controlled clinical trials did not meet the expectations. Because of the high half-life of DHA in the human brain clinical studies may have to be initiated much earlier and have to last much longer to be more efficacious.

Endogenous neuroprotection in chronic neurodegenerative disorders: with particular regard to the kynurenines

Parkinson's disease (PD) and Huntington's disease (HD) are progressive chronic neurodegenerative disorders that are accompanied by a considerable impairment of the motor functions. PD may develop for familial or sporadic reasons, whereas HD is based on a definite genetic mutation. Nevertheless, the pathological processes involve oxidative stress and glutamate excitotoxicity in both cases. A number of metabolic routes are affected in these disorders. The decrease in antioxidant capacity and alterations in the kynurenine pathway, the main pathway of the tryptophan metabolism, are features that deserve particular interest, because the changes in levels of neuroactive kynurenine pathway compounds appear to be strongly related to the oxidative stress and glutamate excitotoxicity involved in the disease pathogenesis. Increase of the antioxidant capacity and pharmacological manipulation of the kynurenine pathway are therefore promising therapeutic targets in these devastating disorders.

Emerging drug therapies in Huntington's disease

Huntington's disease (HD) is a relentless neurodegenerative disease that results in profound disability through a triad of motor, cognitive and neuropsychiatric symptoms. At present, there are very few therapeutic interventions available with the exception of a limited number of drugs that offer mild symptomatic relief. Although the genetic basis of the disease has been identified, the mechanisms behind the cellular pathogenesis are still not clear and as a result no candidate drugs with the potential for disease modification have been found clinically until now. One of the major limitations in assessing the usefulness of drug treatments in HD is the lack of well-designed, double-blind, placebo-controlled clinical trials. Most studies have been open-label, using a small number of patients and tend to concentrate on the motor features of the disease, primarily the chorea. This review discusses the treatments now used for HD before evaluating the newer drugs at present being explored in both the clinic and in the laboratory in mouse models of the disease.

Therapeutic interventions for symptomatic treatment in Huntington's disease

BACKGROUND

Huntington's disease (HD) is an orphan autosomal dominant neurodegenerative disorder caused by the amplification of a nucleic acids triplet repeat. It is characterised by core symptoms of chorea, progressive dementia and psychiatric manifestations such as depression, irritability, apathy and psychosis. In current clinical practice, drugs exist that seem to improve symptoms for HD patients. However, their effectiveness has not been fully measured.

OBJECTIVES

To evaluate the effectiveness of the available interventions for the symptomatic treatment of HD.

SEARCH STRATEGY

The search strategy developed for the Movement Disorders Group was undertaken. Cochrane Controlled Trials Register, Medline, EMBASE and Clinical Trials Database of the United States National Institute of Health were thoroughly searched up until December 2007.

SELECTION CRITERIA

All randomised, double-blinded, placebo-controlled clinical trials conducted on any symptomatic therapy used for HD with at least ten participants were included. Participants should have HD clinical features and a confirmatory genetic diagnosis or a compatible family history. All disease variants and ages of disease onset were included. Cross-over studies were included. All pharmacological and non-pharmacological interventions aimed at the control of signs and symptoms associated with HD were to be selected.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the identified trials for eligibility. In the selected trials, the assessment of their methodological quality was done according to the Cochrane Collaboration handbook, and eligible data were registered onto standardised forms. If possible, an intention-to-treat analysis was conducted. When data were not available in the original publication, the principal investigator of the trial was contacted. A meta-analysis was conducted when possible and otherwise the descriptive summary of the results was provided. The software Revman 5.0.15 was used for statistical analysis.

MAIN RESULTS

22 trials (1254 participants) were included. Nine trials had a cross-over design and 13 were conducted in parallel. Study duration ranged from 2 to 80 weeks. Various pharmacological interventions were studied, mostly, they were anti-dopaminergic drugs (n = 5), glutamate receptor antagonists (n = 5) and energy metabolites (n = 5). Only tetrabenazine showed a clear efficacy for the control of chorea. The remaining pharmacological interventions revealed no clear effectiveness.

AUTHORS' CONCLUSIONS

No intervention proved to have a consistent symptomatic control in HD. Tetrabenazine is the anti-choreic drug with the best quality data available. Other symptomatic areas should be explored by well-designed randomised placebo-controlled studies.

Exercise contributes to the effects of DHA dietary supplementation by acting on membrane-related synaptic systems

Dietary omega-3 fatty acid (i.e. docosohexaenoic acid (DHA)) and exercise are gaining recognition for supporting brain function under normal and challenging conditions. Here we evaluate the possibility that the interaction of DHA and exercise can involve specific elements of the synaptic plasma membrane. We found that voluntary exercise potentiated the effects of a 12-day DHA dietary supplementation regimen on increasing the levels of syntaxin 3 (STX-3) and the growth-associated protein (GAP-43) in the adult rat hippocampus region. STX-3 is a synaptic membrane-bound protein involved in the effects of DHA on membrane expansion. The DHA diet and exercise also elevated levels of the NMDA receptor subunit NR2B, which is important for synaptic function underlying learning and memory. The actions of exercise and DHA dietary supplementation reflected on enhanced learning performance in the Morris water maze as learning ability was associated with higher levels of STX-3 and NR2B. The overall findings reveal a mechanism by which exercise can interact with the function of DHA dietary enrichment to elevate the capacity of the adult brain for axonal growth, synaptic plasticity, and cognitive function.

Reduction in Cerebral Atrophy Associated with Ethyl-Eicosapentaenoic Acid Treatment in Patients with Huntington's Disease

Ultra-pure ethyl-eicosapentaenoic acid (ethyl-EPA), a semi-synthetic ethyl ester of eicosapentaenoic acid, is associated with clinical improvement in motor functioning in Huntington's disease. The aim was to determine the extent to which it might reduce the rate of progress of cerebral atrophy. High-resolution cerebral magnetic resonance imaging scans were acquired at baseline, 6 months and 1 year in up to 34 patients with stage I or II Huntington's disease who took part in a randomized, double-blind, placebo-controlled trial of ethyl-EPA. For each subject and each pair of structural images, the two-timepoint brain volume change was calculated in a double-blind manner. Significant group-level reductions in brain atrophy were observed in the head of the caudate nucleus and the posterior thalamus. These findings show that treatment with ethyl-EPA is associated with significant reduction in brain atrophy, particularly in the caudate and thalamus. No other drug tested in Huntington's disease has shown this effect.

Neurological benefits of omega-3 fatty acids

The central nervous system is highly enriched in long-chain polyunsaturated fatty acid (PUFA) of the omega-6 and omega-3 series. The presence of these fatty acids as structural components of neuronal membranes influences cellular function both directly, through effects on membrane properties, and also by acting as a precursor pool for lipid-derived messengers. An adequate intake of omega-3 PUFA is essential for optimal visual function and neural development. Furthermore, there is increasing evidence that increased intake of the long-chain omega-3 PUFA, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may confer benefits in a variety of psychiatric and neurological disorders, and in particular neurodegenerative conditions. However, the mechanisms underlying these beneficial effects are still poorly understood. Recent evidence also indicates that in addition to the positive effects seen in chronic neurodegenerative conditions, omega-3 PUFA may also have significant neuroprotective potential in acute neurological injury. Thus, these compounds offer an intriguing prospect as potentially new therapeutic approaches in both chronic and acute conditions. The purpose of this article is to review the current evidence of the neurological benefits of omega-3 PUFA, looking specifically at neurodegenerative conditions and acute neurological injury.

RAR/RXR and PPAR/RXR signaling in neurological and psychiatric diseases

Retinoids are important signals in brain development. They regulate gene transcription by binding to retinoic acid receptors (RAR) and, as was discovered recently, a peroxisome proliferator-activated receptor (PPAR). Traditional ligands of PPAR are best known for their functions in lipid metabolism and inflammation. RAR and PPAR are ligand-activated transcription factors, which share members of the retinoid X receptor (RXR) family as heterodimeric partners. Both signal transduction pathways have recently been implicated in the progression of neurodegenerative and psychiatric diseases. Since inflammatory processes contribute to various neurodegenerative diseases, the anti-inflammatory activity of retinoids and PPARgamma agonists recommends them as potential therapeutic targets. In addition, genetic linkage studies, transgenic mouse models and experiments with vitamin A deprivation provide evidence that retinoic acid signaling is directly involved in physiology and pathology of motoneurons, of the basal ganglia and of cognitive functions. The activation of PPAR/RXR and RAR/RXR transcription factors has therefore been proposed as a therapeutic strategy in disorders of the central nervous system.

Therapeutic perspectives for the treatment of Huntington's disease: treating the whole body

Huntington's disease (HD) is a tremendously debilitating disorder that strikes relatively young individuals and progresses rapidly over the next ten to fifteen years inducing a loss of cognitive and motor skills and eventually death occurs. The primary locus of the disorder is a polyglutamine expansion of the protein product of the huntingtin (htt) gene. The htt protein appears to be a scaffolding protein that orchestrates the complex assembly of multiple intracellular proteins involved in multiple processes, including vesicular movement and cell metabolism. The htt protein is ubiquitously expressed in human tissues but the predominance of the interest in the pathology lies in its effects on the central nervous system (CNS). Most of the current therapeutics for HD thus have been targeted at preventing neuronal damage in the CNS, however, a considerable body of evidence has been accumulating to suggest that the maintenance of a healthy nervous system is tightly linked with peripheral physiological health. Therefore treatment of both the peripheral and central pathophysiologies of HD could form the basis of a more effective HD therapeutic strategy.

Hypothalamic dysfunction and neuroendocrine and metabolic alterations in Huntington's disease: clinical consequences and therapeutic implications

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by cognitive, psychiatric, behavioural and motor disturbances. Although the course of HD is also frequently complicated by unintended weight loss, sleep disturbances and autonomic nervous system dysfunction, the aetiology of these signs and symptoms remains largely unknown. In recent years, many novel findings from both animal and human studies have emerged that indicate considerable hypothalamic, endocrine and metabolic alterations in HD. However, a comprehensive overview of these findings is lacking and their precise clinical significance is far from clear. Therefore, in this review we attempt to put these recent developments in the field into perspective by integrating them with previous findings in a comprehensible manner, and by discussing their clinical relevance, with a special focus on body weight, sleep and autonomic functions in HD, which will also allow for the identification of future lines of research in this area.

A systematic review of the treatment studies in Huntington's disease since 1990

Huntington's disease (HD) is an autosomal dominant, inherited, neuropsychiatric disease that gives rise to progressive motor, cognitive and behavioural symptoms. Current drug therapy has no effect on the progression of disability, and the need for any pharmacological treatment should be carefully considered. Hyperkinesias and psychiatric symptoms may respond well to pharmacotherapy, but neuropsychological deficits and dementia remain untreatable. Pharmacological intervention in the treatment of the movement disorder of HD is aimed at restoring the balance of neurotransmitters in the basal ganglia. A surprising amount of current drug therapy of HD in clinical practice is based on studies published before 1990. The authors conducted a systematic review of pharmacological therapy in HD using the available papers that were published between 1990 and 2006.

Ethyl-EPA in Huntington disease: potentially relevant mechanism of action

The pathomechanisms involved in the neuronal dysfunction in Huntington disease (HD) are still unresolved and may be heterogeneous. One potential mechanism might be related to the induction of mitochondrial dysfunction in the CNS. This might lead firstly to neuronal dysfunction and finally to the activation of apoptotic pathways. Several compounds, which should alleviate mitochondrial dysfunction, have been tested in preclinical models as well as in clinical trials of different scale. Recently we reported the efficacy of Ethyl-eicosapentaenoic acid (Ethyl-EPA) in patients with HD. Ethyl-EPA is a polyunsaturated fatty acid from the n-3 group, which is in clinical development for HD and melancholic depression. In our trial with Ethyl-EPA in HD responding patients could be characterized by either a lower CAG repeat number or a chorea-predominant clinical expression of the disease. Here we would like to describe some evidence on the potential mechanism of action of Ethyl-EPA in HD. We specifically focus on pathways, which are known to be influenced in HD and are modified by Ethyl-EPA and which points to an involvement of mitochondrial function as a common target. Some attention is given to the NF-kappa B pathway and the c-Jun amino-terminal kinases (JNK) pathway, which both may lead to an activation of the antiproliferative factor p53 and consequently mitochondrial dysfunction. Further the effects of EPA or Ethyl-EPA in preclinical models of HD are described. The evidence from these studies led to the design of phase III clinical trials, which are ongoing.

Tardive dyskinesia and essential fatty acids

Tardive dyskinesia (TD) is a movement disorder described in individuals who have been treated with anti-dopaminergic agents. The pathophysiology of this condition remains to be fully elucidated. Several mechanisms like dopaminergic supersensitivity, dysfunction of striatonigral, GABAergic neurons and disturbed balance between dopaminergic and cholinergic systems have been described. Essential fatty acids (EFAs) are important components of neuronal membrane and the EFA content of these membranes can significantly influence neuronal functioning. Lower levels of EFAs have been reported in red blood cells (RBC) and plasma of individuals with moderate to severe TD. Supplementation with EFAs (omega-3 and omega-6 and ethyl-EPA) have been tried to alleviate TD in open and double-blind clinical trials and in some animal models of TD. In addition, antioxidants (Vitamin E) and melatonin have been tried. However, smaller numbers of patients and shortened length of clinical studies make it difficult to draw any definitive conclusions. Large multi-centre studies with sound methodology of both EFAs and antioxidants are needed.

Bioactive lipids in schizophrenia

Bioactive lipids, in particular arachidonic acid (AA), are vital for monoaminergic neurotransmission, brain development and synaptic plasticity. Phospholipases A2 (PLA2) are key-enzymes in AA metabolism and are activated during monoaminergic neurotransmission. Reduced membrane AA levels, and an altered activity of PLA2 have been found in peripheral membranes of drug-naïve patients with schizophrenia with some conflicting results in more chronic patient populations. Furthermore, in vivo brain phosphorus-31 magnetic resonance spectroscopy suggests reduced lipid membrane precursors (phosphomonoesters) and increased membrane breakdown products (phosphodiesters) in drug-naïve or early treated first-episode schizophrenia patients compared to age-matched controls or chronic populations and these changes were correlated with peripheral red blood cell membrane AA levels. We postulate that processes modulating membrane lipid metabolism are associated with psychotic illnesses and might partially explain the mechanism of action of antipsychotic agents, as well as experimental agents such as purified ethyl-eicosapentaenoic acid (E-EPA). Recent supplementation trials suggest that E-EPA is a modestly effective augmentation treatment resulting in reduced doses of antipsychotic medication in acutely ill patients with schizophrenia (but not in residual-type schizophrenia). This review investigates the role of bioactive lipids in schizophrenia and its treatment, as well as its potential use in prevention.

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.

Ethyl-EPA treatment improves motor dysfunction, but not neurodegeneration in the YAC128 mouse model of Huntington disease

Huntington disease (HD) is an adult-onset neurodegenerative disorder that is characterized by selective degeneration in the striatum. There are currently no treatments that can prevent the progressive decline of motor and cognitive function in HD. In parallel with a human clinical trial, we examined the efficacy of ethyl-EPA treatment in the YAC128 mouse model of HD. Oral delivery of ethyl-EPA to symptomatic YAC128 mice beginning at 7 months of age increased membrane EPA levels 3-fold (P < 0.001) and resulted in a modest but significant improvement in motor dysfunction by 12 months of age as measured by open-field activity (P = 0.01) and performance on the rotarod (P = 0.05). At this age, ethyl-EPA-treated YAC128 mice showed no improvement in striatal volume, striatal neuron counts, striatal neuronal cross-sectional area, or striatal DARPP-32 expression compared to untreated YAC128 mice, thereby indicating no reduction of striatal neuropathology. This result is congruent with modest motor benefits observed in HD patients treated with ethyl-EPA. Overall, this work demonstrates the feasibility of experimental therapeutics in the YAC128 mouse model and suggests that experiments in these mice may be predictive for future human clinical trials.

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.

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.

Essential fatty acids in Huntington's disease

Huntington's disease is an inherited neurodegenerative disorder due to a mutation in exon 1 of the Huntingtin gene that encodes a stretch of polyglutamine (polyQ) residues close to the N-terminus of the huntingtin protein. Aggregated polyQ residues are highly toxic to the neuronal cells when they enter the cell nucleus. The mechanisms by which aggregated polyQ induces neurodegeneration include the binding of abnormal huntingtin to cyclic adenosine monophosphate response element binding protein, which hampers its ability to turn on transcription of other genes; mutant huntingtin binding to the active site on the cyclic adenosine monophosphate response element binding protein, which is essential for its acetyltransferase activity and, hence, the drugs that inhibit histone deacetylase arrest polyQ-dependent neurodegeneration; and/or disrupting the ubiquitin-proteasome system. Transgenic R6/1 mice that incorporate a human genomic fragment containing promoter elements exon 1 and a portion of intron 2 of the huntingtin gene responsible for Huntington's disease develop late-onset neurologic deficits in a manner similar to the motor abnormalities of Huntington's disease and show increased survival rates and decreased neurologic deficits when supplemented with essential fatty acids throughout life. A randomized, placebo-controlled, double-blind study has shown that highly unsaturated fatty acids are beneficial to patients with Huntington's disease. These results raise the possibility that unsaturated fatty acids may prevent or arrest polyQ aggregation, inhibit histone deacetylase, and/or activate the ubiquitin-proteasome system. In view of the encouraging results with essential fatty acids in Huntington's disease, it is proposed that their possible use in other neurodegenerative conditions need to be explored.

A review of the treatment options for Huntington's disease

Huntington's disease (HD) is an autosomal dominant, inherited, neuropsychiatric disease which gives rise to progressive motor, cognitive and behavioural symptoms. Its core pathology involves degeneration of the basal ganglia, in particular, the caudate and putamen, and is caused by a single autosomal gene coding for a mutated form of the protein, huntingtin. At the present time, the only treatment options available in HD are symptomatic. There are several substances available today for the treatment of chorea. Other neurological symptoms, such as dystonia, can be treated, but treatment is associated with a high risk of adverse events. Psychiatric symptoms, on the other hand, are often amenable to treatment and relief of these symptoms may provide significant improvement in quality of life.

Huntington's disease: present treatments and future therapeutic modalities

Huntington's disease (HD) is a devastating neuropsychiatric disorder for which therapeutic interventions have been rather fruitless to date, except in a slight symptomatic relief. Even the discovery of the gene related to HD in 1993 has not effectively advanced treatments. This article is essentially a review of available double-blind, placebo-controlled trials of therapy for this condition which also includes relevant open label trials. Unfortunately, HD research has tended to concentrate on the motor aspects of the disorder, whereas the major problems are behavioural (e.g. dementia, depression, psychosis), and the chorea is often least relevant in terms of management. We conclude that there is definitely poor evidence in management of HD. The analysis of the 24 best studies fails to result in a treatment recommendation of clinical relevance. Based on data of open-label studies, or even case reports, we recommend riluzole, olanzapine and amantadine for the treatment of the movement disorders associated with HD, selective serotonin reuptake inhibitors and mirtazapine for the treatment of depression, and atypical antipsychotic drugs for HD psychosis and behavioural problems. Moreover, adjuvant psychotherapy, physiotherapy and speech therapy should be applied to supply the optimal management. Finally, some cellular mechanisms are discussed in this paper because they are essential for future neuroprotective modalities, such as minocycline, unsaturated fatty acids or riluzole.

Gait and Balance Dysfunction in Adults

Determining the precise cause of gait dysfunction in adults is often difficult because of the multifactorial nature of the disorder. Additionally, elderly patients have other comorbidities that further complicate their diagnosis. A proper history and physical examination, however, often allow the clinician to arrive at the correct diagnosis. Once a diagnosis is reached, appropriate therapeutic decisions can be made. Patients presenting with Parkinsonism need a thorough evaluation to rule out potentially reversible conditions, such as normal pressure hydrocephalus. Patients with idiopathic Parkinson's disease usually develop gait difficulty and freezing episodes late in the course of the illness. Another important cause of gait disturbance in adults is the cerebellar ataxias. Among the sporadic forms, gluten sensitivity is an important consideration. Identification of this entity is important, because the disease process can be halted with a gluten-free diet. Another group is the paraneoplastic ataxias, which can often be diagnosed in the proper clinical setting. Most of the adult-onset hereditary ataxias are autosomal dominant conditions. Except for the episodic ataxias, treatment of these conditions has been disappointing. Mixed results have been obtained with the use of amantadine, buspirone, and 5-hydroxytryptophan. Physical therapy plays an important role in the gait rehabilitation of these patients. Over the past several years, researchers have developed a greater understanding of motor control and how it relates to freezing. Clinicians can now train patients to use external cues to overcome their motor blocks. Another important advance has been the development of subthalamic nucleus deep brain stimulation in the treatment of patients with troublesome peak dose dyskinesia and other motor fluctuations. Subthalamic nucleus deep brain stimulation should be considered when best medical treatment fails. Cortical myoclonus can be treated with levetiracetam, which has US Food and Drug Administration approval as an antiepileptic agent. It has been quite effective in the treatment of myoclonus and should be considered when other medications fail.

A new category of psychotropic drugs: neuroactive lipids as exemplified by ethyl eicosapentaenoate (E-E)

New treatments for psychiatric disorders are urgently required. Recent reviews show that there have been no improvements in efficacy of drugs for either affective disorders or schizophrenia since the first compounds were introduced over 40 years ago. Neuroactive lipids represent an entirely novel class of psychotropic compounds. Ethyl eicosapentaenoate is the first example of this group. Placebo-controlled studies have found it to be effective in depression, in treatment-unresponsive schizophrenia and in tardive dyskinesia. It is extremely well tolerated with none of the usual side-effects of either antidepressants or neuroleptics. It probably works by modulating postreceptor signal transduction processes.