Creatine in Huntington disease is safe, tolerable, bioavailable in brain and reduces serum 8OH2'dG

Creatine for treating muscle disorders

BACKGROUND

Progressive muscle weakness is a main symptom of most hereditary and acquired muscle diseases. Creatine improves muscle performance in healthy individuals. This is an update of our 2007 Cochrane review that evaluated creatine treatment in muscle disorders.

OBJECTIVES

To evaluate the efficacy of creatine compared to placebo for the treatment of muscle weakness in muscle diseases.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Specialized Register (4 October 2010), the Cochrane Central Register of Controlled Trials (11 October 2010, Issue 4, 2010 in The Cochrane Library), MEDLINE (January 1966 to September 2010) and EMBASE (January 1980 to September 2010) for randomised controlled trials (RCT) of creatine used to treat muscle diseases.

SELECTION CRITERIA

RCTs or quasi-RCTs of creatine treatment compared to placebo in hereditary muscle diseases or idiopathic inflammatory myopathies.

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

The updated searches identified two new studies. A total of 14 trials, including 364 randomised participants, met the selection criteria. Meta-analysis of six trials in muscular dystrophies including 192 participants revealed a significant increase in muscle strength in the creatine group compared to placebo, with a weighted mean difference of 8.47%; (95% confidence intervals (CI) 3.55 to 13.38). Pooled data of four trials including 115 participants showed that a significantly higher number of patients felt better during creatine treatment compared to placebo with a risk ratio of 4.51 (95% CI 2.33 to 8.74). One trial in 37 participants with idiopathic inflammatory myopathies also showed a significant improvement in functional performance. No trial reported any clinically relevant adverse event. In metabolic myopathies, meta-analyses of three cross-over trials including 33 participants revealed no significant difference in muscle strength. One trial reported a significant deterioration of ADL (mean difference 0.54 on a 1 to 10 scale; 95% CI 0.14 to 0.93) and an increase in muscle pain during high-dose creatine treatment in McArdle disease.

AUTHORS' CONCLUSIONS

High quality evidence from RCTs shows that short- and medium-term creatine treatment increases muscle strength in muscular dystrophies. There is also evidence that creatine improves functional performance in muscular dystrophy and idiopathic inflammatory myopathy. Creatine is well tolerated in these people. High quality but limited evidence from RCTs does not show significant improvement in muscle strength in metabolic myopathies. High-dose creatine treatment impaired ADL and increased muscle pain in McArdle disease.

Energy deficit in Huntington disease: why it matters

Huntington disease (HD) is an autosomal dominant neurodegenerative disease with complete penetrance. Although the understanding of the cellular mechanisms that drive neurodegeneration in HD and account for the characteristic pattern of neuronal vulnerability is incomplete, defects in energy metabolism, particularly mitochondrial function, represent a common thread in studies of HD pathogenesis in humans and animal models. Here we review the clinical, biochemical, and molecular evidence of an energy deficit in HD and discuss the mechanisms underlying mitochondrial and related alterations.

Nrf2-ARE stress response mechanism: a control point in oxidative stress-mediated dysfunctions and chronic inflammatory diseases

Nrf2, a redox sensitive transcription factor, plays a pivotal role in redox homeostasis during oxidative stress. Nrf2 is sequestered in cytosol by an inhibitory protein Keap1 which causes its proteasomal degradation. In response to electrophilic and oxidative stress, Nrf2 is activated, translocates to nucleus, binds to antioxidant response element (ARE), thus upregulates a battery of antioxidant and detoxifying genes. This function of Nrf2 can be significant in the treatment of diseases, such as cancer, neurodegenerative, cardiovascular and pulmonary complications, where oxidative stress causes Nrf2 derangement. Nrf2 upregulating potential of phytochemicals has been explored, in facilitating cure for various ailments while, in cancer cells, Nrf2 upregulation causes chemoresistance. Therefore, Nrf2 emerges as a key regulator in oxidative stress-mediated diseases and Nrf2 silencing can open avenues in cancer treatment. This review summarizes Nrf2-ARE stress response mechanism and its role as a control point in oxidative stress-induced cellular dysfunctions including chronic inflammatory diseases.

Huntington's disease: from molecular pathogenesis to clinical treatment

Huntington's disease is a progressive, fatal, neurodegenerative disorder caused by an expanded CAG repeat in the huntingtin gene, which encodes an abnormally long polyglutamine repeat in the huntingtin protein. Huntington's disease has served as a model for the study of other more common neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease. These disorders all share features including: delayed onset; selective neuronal vulnerability, despite widespread expression of disease-related proteins during the whole lifetime; abnormal protein processing and aggregation; and cellular toxic effects involving both cell autonomous and cell-cell interaction mechanisms. Pathogenic pathways of Huntington's disease are beginning to be unravelled, offering targets for treatments. Additionally, predictive genetic testing and findings of neuroimaging studies show that, as in some other neurodegenerative disorders, neurodegeneration in affected individuals begins many years before onset of diagnosable signs and symptoms of Huntington's disease, and it is accompanied by subtle cognitive, motor, and psychiatric changes (so-called prodromal disease). Thus, Huntington's disease is also emerging as a model for strategies to develop therapeutic interventions, not only to slow progression of manifest disease but also to delay, or ideally prevent, its onset.

Molecular biology of Huntington's disease

It has been more than 17 years since the causative mutation for Huntington's disease was discovered as the expansion of the triplet repeat in the N-terminal portion of the Huntingtin (HTT) gene. In the intervening time, researchers have discovered a great deal about Huntingtin's involvement in a number of cellular processes. However, the role of Huntingtin in the key pathogenic mechanism leading to neurodegeneration in the disease process has yet to be discovered. Here, we review the body of knowledge that has been uncovered since gene discovery and include discussions of the HTT gene, CAG triplet repeat expansion, HTT expression, protein features, posttranslational modifications, and many of its known protein functions and interactions. We also highlight potential pathogenic mechanisms that have come to light in recent years.

The clinical and genetic features of Huntington disease

Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that usually presents in adulthood with characteristic motor and cognitive features and with variable and diverse psychiatric disturbances. Following the discovery of the causative defect in the HTT gene in 1993, great advances in understanding the pathogenesis of HD have been made, yet no effective disease-modifying therapy has been identified. In this new era of HD research, we have seen the emergence of a number of large clinical trials, the systematic search for novel biomarkers and the recent initiation of the first pre-manifest HD clinical studies. In this review, we seek to provide an overview of the clinical and genetic features of HD together with a summary of clinical research at this time.

Mitochondrial therapy for Parkinson's disease: neuroprotective pharmaconutrition may be disease-modifying

Progressive destruction of neurons that produce dopamine in the basal ganglia of the brain, particularly the substantia nigra, is a hallmark of Parkinson's disease. The syndrome of the Parkinsonian phenotype is caused by many etiologies, involving multiple contributing mechanisms. Characteristic findings are pathologic inclusions called Lewy bodies, which are protein aggregates inside nerve cells. Environmental insults are linked with the disease, and a number of associated genes have also been identified. Neuroinflammation, microglia activation, oxidative stress, and mitochondrial dysfunction are central processes producing nerve damage. In addition, protein misfolding, driven by accumulation and condensation of α-synuclein, compounded by inadequate elimination of defective protein through the ubiquitin- proteasome system, promote apoptosis. Current pharmacologic therapy is palliative rather than disease- modifying, and typically becomes unsatisfactory over time. Coenzyme Q10 and creatine, two agents involved in energy production, may be disease-modifying, and able to produce sufficient beneficial pathophysiologic changes in preclinical studies to warrant large studies now in progress. Use of long-chain omega-3 fatty acids and vitamin D in PD are also topics of current interest.

Creatine prevents the inhibition of energy metabolism and lipid peroxidation in rats subjected to GAA administration

Guanidinoacetate methyltransferase (GAMT) deficiency is an inherited neurometabolic disorder, biochemically characterized by the tissue accumulation of guanidinoacetate (GAA). Affected patients present epilepsy and mental retardation whose etiopathogeny is unclear. Previous reports have shown that GAA alters brain energy metabolism and that creatine, which is depleted in patients with GAMT deficiency, can act as a neuroprotector; as such, in the present study we investigated the effect of creatine administration on some of the altered parameters of energy metabolism (complex II, Na(+),K(+)-ATPase and creatine kinase) and lipid peroxidation caused by intrastriatal administration of GAA in adult rats. Animals were pretreated for 7 days with daily intraperitonial administrations of creatine. Subsequently, these animals were divided into two groups: Group 1 (sham group), rats that suffered surgery and received saline; and group 2 (GAA-treated). Thirty min after GAA or saline, the animals were sacrificed and the striatum dissected out. Results showed that the administration of creatine was able to reverse the activities of complex II, Na(+),K(+)-ATPase and creatine kinase, as well as, the levels of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation. These findings indicate that the energy metabolism deficit caused by GAA may be prevented by creatine, which probably acts as an antioxidant since it was able to prevent lipid peroxidation. These data may contribute, at least in part, to a better understanding of the mechanisms related to the energy deficit and oxidative stress observed in GAMT deficiency.

Triterpenoids CDDO-ethyl amide and CDDO-trifluoroethyl amide improve the behavioral phenotype and brain pathology in a transgenic mouse model of Huntington's disease

Oxidative stress is a prominent feature of Huntington's disease (HD) due to mitochondrial dysfunction and the ensuing overproduction of reactive oxygen species (ROS). This phenomenon ultimately contributes to cognitive and motor impairment, as well as brain pathology, especially in the striatum. Targeting the transcription of the endogenous antioxidant machinery could be a promising therapeutic approach. The NF-E2-related factor-2 (Nrf2)/antioxidant response element (ARE) signaling pathway is an important pathway involved in antioxidant and anti-inflammatory responses. Synthetic triterpenoids, which are derived from 2-Cyano-3,12-Dioxooleana-1,9-Dien-28-Oic acid (CDDO) activate the Nrf2/ARE pathway and reduce oxidative stress in animal models of neurodegenerative diseases. We investigated the effects of CDDO-ethyl amide (CDDO-EA) and CDDO-trifluoroethyl amide (CDDO-TFEA) in N171-82Q mice, a transgenic mouse model of HD. CDDO-EA or CDDO-TFEA were administered in the diet at various concentrations, starting at 30days of age. CDDO-EA and CDDO-TFEA upregulated Nrf2/ARE induced genes in the brain and peripheral tissues, reduced oxidative stress, improved motor impairment and increased longevity. They also rescued striatal atrophy in the brain and vacuolation in the brown adipose tissue. Therefore compounds targeting the Nrf2/ARE pathway show great promise for the treatment of HD.

Reduced creatine kinase as a central and peripheral biomarker in Huntington's disease

A major goal of current clinical research in Huntington's disease (HD) has been to identify preclinical and manifest disease biomarkers, as these may improve both diagnosis and the power for therapeutic trials. Although the underlying biochemical alterations and the mechanisms of neuronal degeneration remain unknown, energy metabolism defects in HD have been chronicled for many years. We report that the brain isoenzyme of creatine kinase (CK-BB), an enzyme important in buffering energy stores, was significantly reduced in presymptomatic and manifest disease in brain and blood buffy coat specimens in HD mice and HD patients. Brain CK-BB levels were significantly reduced in R6/2 mice by approximately 18% to approximately 68% from 21 to 91 days of age, while blood CK-BB levels were decreased by approximately 14% to approximately 44% during the same disease duration. Similar findings in CK-BB levels were observed in the 140 CAG mice from 4 to 12 months of age, but not at the earliest time point, 2 months of age. Consistent with the HD mice, there was a grade-dependent loss of brain CK-BB that worsened with disease severity in HD patients from approximately 28% to approximately 63%, as compared to non-diseased control patients. In addition, CK-BB blood buffy coat levels were significantly reduced in both premanifest and symptomatic HD patients by approximately 23% and approximately 39%, respectively. The correlation of CK-BB as a disease biomarker in both CNS and peripheral tissues from HD mice and HD patients may provide a powerful means to assess disease progression and to predict the potential magnitude of therapeutic benefit in this disorder.

Molecular Mechanisms and Potential Therapeutical Targets in Huntington's Disease

Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the gene encoding for huntingtin protein. A lot has been learned about this disease since its first description in 1872 and the identification of its causative gene and mutation in 1993. We now know that the disease is characterized by several molecular and cellular abnormalities whose precise timing and relative roles in pathogenesis have yet to be understood. HD is triggered by the mutant protein, and both gain-of-function (of the mutant protein) and loss-of-function (of the normal protein) mechanisms are involved. Here we review the data that describe the emergence of the ancient huntingtin gene and of the polyglutamine trait during the last 800 million years of evolution. We focus on the known functions of wild-type huntingtin that are fundamental for the survival and functioning of the brain neurons that predominantly degenerate in HD. We summarize data indicating how the loss of these beneficial activities reduces the ability of these neurons to survive. We also review the different mechanisms by which the mutation in huntingtin causes toxicity. This may arise both from cell-autonomous processes and dysfunction of neuronal circuitries. We then focus on novel therapeutical targets and pathways and on the attractive option to counteract HD at its primary source, i.e., by blocking the production of the mutant protein. Strategies and technologies used to screen for candidate HD biomarkers and their potential application are presented. Furthermore, we discuss the opportunities offered by intracerebral cell transplantation and the likely need for these multiple routes into therapies to converge at some point as, ideally, one would wish to stop the disease process and, at the same time, possibly replace the damaged neurons.

Uridine ameliorates the pathological phenotype in transgenic G93A-ALS mice

There is strong evidence from studies in humans and animal models to suggest the involvement of energy metabolism defects in neurodegenerative diseases. Uridine, a pyrimidine nucleoside, has been suggested to be neuroprotective in neurological disorders by improving bioenergetic effects, increasing ATP levels and enhancing glycolytic energy production. We assessed whether uridine treatment extended survival and improved the behavioral and neuropathological phenotype observed in G93A-ALS mice. In vitro and in vivo pharmacokinetic analyses in mutant SOD models provided optimal dose and assurance that uridine entered the brain. A dose-ranging efficacy trial in G93A mice was performed using survival, body weight, open-field analysis, and neuropathology as outcome measures. Urinary levels of 8-hydroxy-2'-deoxyguanosine, identifying DNA oxidative damage, were measured and used as a pharmacodynamic biomarker. Uridine administration significantly extended survival in a dose-dependent manner in G93A mice, while improving the behavioral and neuropathological phenotype. Uridine increased survival by 17.4%, ameliorated body weight loss, enhanced motor performance, reduced gross lumbar and ventral horn atrophy, attenuated lumbar ventral horn neuronal cell death, and decreased reactive astrogliosis. Consistent with a therapeutic effect, uridine significantly reduced urinary 8-hydroxy-2'-deoxyguanosine in G93A mice. These data suggest that uridine may be a therapeutic candidate in ALS patients.

Impairment of PGC-1alpha expression, neuropathology and hepatic steatosis in a transgenic mouse model of Huntington's disease following chronic energy deprivation

We investigated the ability of AMP-activated protein kinase (AMPK) to activate PPARgamma coactivator-1alpha (PGC-1alpha) in the brain, liver and brown adipose tissue (BAT) of the NLS-N171-82Q transgenic mouse model of Huntington's disease (HD). In the striatum of the HD mice, the baseline levels of PGC-1alpha, NRF1, NRF2, Tfam, COX-II, PPARdelta, CREB and ERRalpha mRNA and mitochondrial DNA (mtDNA), were significantly reduced. Administration of the creatine analog beta guanidinopropionic acid (GPA) reduced ATP and PCr levels and increased AMPK mRNA in both the cerebral cortex and striatum. Treatment with GPA significantly increased expression of PGC-1alpha, NRF1, Tfam and downstream genes in the striatum and cerebral cortex of wild-type (WT) mice, but there was no effect on these genes in the HD mice. The striatum of the untreated HD mice showed microvacuolation in the neuropil, as well as gliosis and huntingtin aggregates, which were exacerbated by treatment with GPA. GPA treatment produced a significant increase in mtDNA in the cerebral cortex and striatum of WT mice, but not in HD mice. The HD mice treated with GPA had impaired activation of liver PGC-1alpha and developed hepatic steatosis with accumulation of lipids, degeneration of hepatocytes and impaired activation of gluconeogenesis. The BAT in the HD mice showed vacuolation due to accumulation of neutral lipids, and age-dependent impairment of UCP-1 activation and temperature regulation. Impaired activation of PGC-1alpha, therefore, plays an important role in the behavioral phenotype, metabolic disturbances and pathology of HD, which suggests the possibility that agents that enhance PGC-1alpha function will exert therapeutic benefits in HD patients.

Therapeutic approaches to mitochondrial dysfunction in Parkinson's disease

A large body of evidence from postmortem brain tissue and genetic analysis in humans, as well as biochemical and pathological studies in animal models of neurodegeneration suggest that mitochondrial dysfunction is a key pathological mechanism in Parkinson's Disease (PD). Mitochondrial dysfunction leads to oxidative stress, damage to mitochondrial DNA, mitochondrial DNA deletions, altered mitochondrial morphology, alterations in mitochondrial fission and fusion and ultimately neuronal demise. Therapeutic approaches targeting mitochondrial dysfunction and oxidative damage, therefore, hold great promise in PD. A number of agents, which target energy metabolism, are presently in therapeutic trials in PD. Both creatine and Coenzyme Q10 (CoQ10) are being tested in phase III clinical trials. In addition, preclinical studies in animal models have shown efficacy of mitochondrial-targeted antioxidants and the SS peptides. A promising approach for increasing antioxidant defenses is to transcriptionally increase the activity of the Nrf2/ARE pathway, which activates transcription of anti-inflammatory and antioxidant genes. A number of agents including sulforaphane, curcumin and triterpenoids have been shown to activate this pathway and to produce neuroprotective effects. Lastly, newly identified therapeutic targets include peroxisomal proliferator activated receptor gamma-coactivator (PGC-1alpha) and sirtuins. These pathways provide promise for future therapeutic developments in the treatment of PD.

Huntington disease: pathogenesis, biomarkers, and approaches to experimental therapeutics

Huntington disease (HD) is characterized by motor, cognitive and behavioral abnormalities that typically emerge in adulthood in persons who have inherited the mutant gene. HD has a single genetic cause, a well-defined neuropathology, and informative pre-manifest predictive genetic testing. Thus, it has been possible to develop imaging biomarkers of HD progression, not just in the period of manifest illness, but also in the prodromal or "premanifest" period. Striatal atrophy is the most studied, and shows steady progression beginning in the prodromal period beginning up to 15 years before predicted onset, and continuing through the period of manifest illness. Therapeutic targets for HD include the huntingtin protein itself, either by reducing its levels with antisense oligonucleotides or siRNA, or potentially by intervening via posttranslational modifications such as phosphorylation, acetylation, SUMOylation, or proteolytic cleavage. Other strategies involve bolstering the cell's ability to deal with abnormal proteins, either via chaperones or protein degradation machinery. It may be possible to counteract the abnormal transcription caused by mutant huntingtin, with histone deacetylase inhibitors, or to enhance relevant gene products such as Brain Derived Neurotrophic Factor (BDNF). Another tactic is to enhance cellular metabolic defenses, such as with creatine or Coenzyme Q10. Strategies are being devised to use biomarkers, and administer therapeutic agents which can be given safely for long periods of time during the proodromal period, with a goal not just to slow progression, but to delay, or conceivably even prevent, the onset of clinical HD.

Identification of phenylbutyrate-generated metabolites in Huntington disease patients using parallel liquid chromatography/electrochemical array/mass spectrometry and off-line tandem mass spectrometry

Oral sodium phenylbutyrate (SPB) is currently under investigation as a histone deacetylation (HDAC) inhibitor in Huntington disease (HD). Ongoing studies indicate that symptoms related to HD genetic abnormalities decrease with SPB therapy. In a recently reported safety and tolerability study of SPB in HD, we analyzed overall chromatographic patterns from a method that employs gradient liquid chromatography with series electrochemical array, ultraviolet (UV), and fluorescence (LCECA/UV/F) for measuring SPB and its metabolite phenylacetate (PA). We found that plasma and urine from SPB-treated patients yielded individual-specific patterns of approximately 20 metabolites that may provide a means for the selection of subjects for extended trials of SPB. The structural identification of these metabolites is of critical importance because their characterization will facilitate understanding the mechanisms of drug action and possible side effects. We have now developed an iterative process with LCECA, parallel LCECA/LCMS, and high-performance tandem MS for metabolite characterization. Here we report the details of this method and its use for identification of 10 plasma and urinary metabolites in treated subjects, including indole species in urine that are not themselves metabolites of SPB. Thus, this approach contributes to understanding metabolic pathways that differ among HD patients being treated with SPB.

Ammonia toxicity to the brain: effects on creatine metabolism and transport and protective roles of creatine

Hyperammonemia can provoke irreversible damage to the developing brain, with the formation of cortical atrophy, ventricular enlargement, demyelination or gray and white matter hypodensities. Among the various pathogenic mechanisms involved, alterations in cerebral energy have been demonstrated. In particular, we could show that ammonia exposure generates a secondary deficiency in creatine in brain cells, by altering the brain expression and activity of the genes allowing creatine synthesis (AGAT and GAMT) and transport (SLC6A8). On the other hand, it is known that creatine administration can exert protective effects in various neurodegenerative processes. We could also show that creatine co-treatment under ammonia exposure can protect developing brain cells from some of the deleterious effects of ammonia, in particular axonal growth impairment. This article focuses on the effects of ammonia exposure on creatine metabolism and transport in developing brain cells, and on the potential neuroprotective properties of creatine in the brain exposed to ammonium.

The spinocerebellar ataxias

Slowly progressive ataxia accompanied by cerebellar degeneration is often genetic in origin. The past 15 years have witnessed a revolution in our understanding of the causes of dominantly inherited ataxias, now known as the spinocerebellar ataxias (SCAs). Nearly 30 distinct genetic causes of SCA are known, numbered chronologically in order of discovery. All SCAs display classic cerebellar signs, and many display disabling noncerebellar features, most commonly brainstem dysfunction. Eye movement abnormalities are common, reflecting cerebellar and brainstem degeneration. Visual loss from retinal degeneration is rare in SCA, occurring most commonly and profoundly in SCA7. Although the SCAs are relentlessly progressive and currently untreatable, recent scientific advances have begun to shed light on various disease mechanisms that may lead to preventive therapies.

Magnetic resonance spectroscopy of regional brain metabolite markers in FALS mice and the effects of dietary creatine supplementation

We investigated the effects of disease progression on brain regional neurochemistry in a mutant mouse model of familial amyotrophic lateral sclerosis (FALS; the G93A model) using in vivo and in vitro magnetic resonance spectroscopy (MRS). There were numerous changes in the brain spectra that were brain region dependent. At early time points starting around 80 days of age there were increases in brain glutamate. At later time points there were more extensive changes including decreased N-acetyl aspartate and glutamate and increased glutamine, taurine and myo-inositol. The effects of the disease were most severe in spinal cord followed by medulla and then sensorimotor cortex. There were no changes noted in cerebellum as a control region. The effects of creatine supplementation in the diet (2%) were measured in wild-type and FALS animals in medulla, cerebellum and cortex. The increase in brain creatine was largest in cerebellum (25%) followed by medulla (11%) and then cortex (4%), reflecting the ordering of creatine kinase activity. There was a protective effect of creatine on N-acetyl aspartate loss in the medulla at late stages. Creatine supplementation had a positive effect on weight retention, leading to a 13% increase in weight between 120 and 130 days. MRS shows promise in monitoring multiple facets of neuroprotective strategies in ALS and ALS models.

Mitochondria: a therapeutic target in neurodegeneration

Mitochondrial dysfunction has long been associated with neurodegenerative disease. Therefore, mitochondrial protective agents represent a unique direction for the development of drug candidates that can modify the pathogenesis of neurodegeneration. This review discusses evidence showing that mitochondrial dysfunction has a central role in the pathogenesis of Alzheimer's, Parkinson's and Huntington's diseases and amyotrophic lateral sclerosis. We also debate the potential therapeutic efficacy of metabolic antioxidants, mitochondria-directed antioxidants and Szeto-Schiller (SS) peptides. Since these compounds preferentially target mitochondria, a major source of oxidative damage, they are promising therapeutic candidates for neurodegenerative diseases. Furthermore, we will briefly discuss the novel action of the antihistamine drug Dimebon on mitochondria.

Heterolytic reduction of fatty acid hydroperoxides by cytochrome c/cardiolipin complexes: antioxidant function in mitochondria

Cytochrome c (cyt c), a mitochondrial intermembrane electron shuttle between complexes III and IV, can, upon binding with an anionic phospholipid, cardiolipin (CL), act as a peroxidase that catalyzes cardiolipin oxidation. H(2)O(2) was considered as a source of oxidative equivalents for this reaction, which is essential for programmed cell death. Here we report that peroxidase cyt c/CL complexes can utilize free fatty acid hydroperoxides (FFA-OOH) at exceptionally high rates that are approximately 3 orders of magnitude higher than for H(2)O(2). Similarly, peroxidase activity of murine liver mitochondria was high with FFA-OOH. Using EPR spin trapping and LC-MS techniques, we have demonstrated that cyt c/CL complexes split FFA-OOH predominantly via a heterolytic mechanism, yielding hydroxy-fatty acids, whereas H(2)O(2) (and tert-butyl hydroperoxide, t-BuOOH) undergo homolytic cleavage. Computer simulations have revealed that Arg(38) and His(33) are important for the heterolytic mechanism at potential FFA-OOH binding sites of cyt c (but not for H(2)O(2) or t-BuOOH). Regulation of FFA-OOH metabolism may be an important function of cyt c that is associated with elimination of toxic FFA-OOH and synthesis of physiologically active hydroxy-fatty acids in mitochondria.

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.

Mouse models of Huntington's disease and methodological considerations for therapeutic trials

Huntington's disease (HD) is an autosomal dominant, progressive, and fatal neurodegenerative disorder caused by an expanded polyglutamine cytosine-adenine-guanine repeat in the gene coding for the protein huntingtin. Despite great progress, a direct causative pathway from the HD gene mutation to neuronal dysfunction and death has not yet been established. One important advance in understanding the pathogenic mechanisms of this disease has been the development of multiple murine models that replicate many of the clinical, neuropathological, and molecular events in HD patients. These models have played an important role in providing accurate and experimentally accessible systems to study multiple aspects of disease pathogenesis and to test potential therapeutic treatment strategies. Understanding how disease processes interrelate has become important in identifying a pharmacotherapy in HD and in the design of clinical trials. A review of the current state of HD mouse models and their successes in elucidating disease pathogenesis are discussed. There is no clinically proven treatment for HD that can halt or ameliorate the inexorable disease progression. As such, a guide to assessing studies in mouse models and salient issues related to translation from mice to humans are included.

Impaired PGC-1alpha function in muscle in Huntington's disease

We investigated the role of PPAR gamma coactivator 1alpha (PGC-1alpha) in muscle dysfunction in Huntington's disease (HD). We observed reduced PGC-1alpha and target genes expression in muscle of HD transgenic mice. We produced chronic energy deprivation in HD mice by administering the catabolic stressor beta-guanidinopropionic acid (GPA), a creatine analogue that reduces ATP levels, activates AMP-activated protein kinase (AMPK), which in turn activates PGC-1alpha. Treatment with GPA resulted in increased expression of AMPK, PGC-1alpha target genes, genes for oxidative phosphorylation, electron transport chain and mitochondrial biogenesis, increased oxidative muscle fibers, numbers of mitochondria and motor performance in wild-type, but not in HD mice. In muscle biopsies from HD patients, there was decreased PGC-1alpha, PGC-1beta and oxidative fibers. Oxygen consumption, PGC-1alpha, NRF1 and response to GPA were significantly reduced in myoblasts from HD patients. Knockdown of mutant huntingtin resulted in increased PGC-1alpha expression in HD myoblast. Lastly, adenoviral-mediated delivery of PGC-1alpha resulted increased expression of PGC-1alpha and markers for oxidative muscle fibers and reversal of blunted response for GPA in HD mice. These findings show that impaired function of PGC-1alpha plays a critical role in muscle dysfunction in HD, and that treatment with agents to enhance PGC-1alpha function could exert therapeutic benefits. Furthermore, muscle may provide a readily accessible tissue in which to monitor therapeutic interventions.

Accumulation of oxidative stress around the stroke-like lesions of MELAS patients

To investigate the relationship between oxidative stress and progressive spread of the stroke-like lesions in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with 3243A>G mutation, we retrospectively analyzed the spread frequency in patients with and without treatment with the radical scavenger edaravone. Oxidative damage and defensive enzymes were histologically evaluated. Spread was significantly less frequent in the patients treated with edaravone. Although 8-hydroxy-2'-deoxyguanosine, a marker for oxidative damage of DNA, was obviously accumulated in peri-lesional surviving neurons, manganese superoxide dismutase and 8-oxoguanine glycosylase 1 were not up-regulated in those neurons. Increased oxidative stress and insufficient defense could be involved in the pathogenesis of the spreading lesions in MELAS.

Combination therapy with coenzyme Q10 and creatine produces additive neuroprotective effects in models of Parkinson's and Huntington's diseases

Coenzyme Q(10) (CoQ(10)) and creatine are promising agents for neuroprotection in neurodegenerative diseases via their effects on improving mitochondrial function and cellular bioenergetics and their properties as antioxidants. We examined whether a combination of CoQ(10) with creatine can exert additive neuroprotective effects in a MPTP mouse model of Parkinson's disease, a 3-NP rat model of Huntington's disease (HD) and the R6/2 transgenic mouse model of HD. The combination of the two agents produced additive neuroprotective effects against dopamine depletion in the striatum and loss of tyrosine hydroxylase neurons in the substantia nigra pars compacta (SNpc) following chronic subcutaneous administration of MPTP. The combination treatment resulted in significant reduction in lipid peroxidation and pathologic alpha-synuclein accumulation in the SNpc neurons of the MPTP-treated mice. We also observed additive neuroprotective effects in reducing striatal lesion volumes produced by chronic subcutaneous administration of 3-NP to rats. The combination treatment showed significant effects on blocking 3-NP-induced impairment of glutathione homeostasis and reducing lipid peroxidation and DNA oxidative damage in the striatum. Lastly, the combination of CoQ(10) and creatine produced additive neuroprotective effects on improving motor performance and extending survival in the transgenic R6/2 HD mice. These findings suggest that combination therapy using CoQ(10) and creatine may be useful in the treatment of neurodegenerative diseases such as Parkinson's disease and HD.

Exploring the therapeutic role of creatine supplementation

Creatine (Cr) plays a central role in energy provision through a reaction catalyzed by phosphorylcreatine kinase. Furthermore, this amine enhances both gene expression and satellite cell activation involved in hypertrophic response. Recent findings have indicated that Cr supplementation has a therapeutic role in several diseases characterized by atrophic conditions, weakness, and metabolic disturbances (i.e., in the muscle, bone, lung, and brain). Accordingly, there has been an evidence indicating that Cr supplementation is capable of attenuating the degenerative state in some muscle disorders (i.e., Duchenne and inflammatory myopathies), central nervous diseases (i.e., Parkinson's, Huntington's, and Alzheimer's), and bone and metabolic disturbances (i.e., osteoporosis and type II diabetes). In light of this, Cr supplementation could be used as a therapeutic tool for the elderly. The aim of this review is to summarize the main studies conducted in this field and to highlight the scientific and clinical perspectives of this promising therapeutic supplement.

Complexity and heterogeneity: what drives the ever-changing brain in Huntington's disease?

Significant advances are being made in our understanding of basic pathophyiological and biochemical mechanisms that cause Huntington's disease (HD). There is increasing reason to believe that pathologic alterations occur in the brain for years before symptoms manifest. The "classic" hallmark of neuropathology in HD is selective neurodegeneration in which vulnerable populations of neurons degenerate while less vulnerable populations are spared. While the earliest and most striking neuropathologic changes have been found in the neostriatum, neuronal loss has been identified in many other regions of the brain. We report topologically selective, early, and progressive changes in the cortex, striatum, extrastriatal brain structures, and white matter throughout the spectrum of disease. Our growing understanding of HD underscores the reality that points to the complexity of HD. A single, well-defined, genetic mutation causes a cascade of events whose final result is an aggregate insult of the homeostatic process. We explore possible explanations for the selective vulnerability of the brain in HD. The ultimate goal in HD is to develop disease-modifying therapies that will prevent the onset of clinical symptoms in those individuals who are at risk and slow the progression of symptoms in those individuals already affected with symptoms. Understanding changes in brain morphometry and their relationship to clinical symptoms may provide important and new insights into basic pathophysiological mechanisms at play in the disease.

Mitochondrial approaches for neuroprotection

A large body of evidence from postmortem brain tissue and genetic analysis in humans and biochemical and pathological studies in animal models (transgenic and toxin) of neurodegeneration suggest that mitochondrial dysfunction is a common pathological mechanism. Mitochondrial dysfunction from oxidative stress, mitochondrial DNA deletions, pathological mutations, altered mitochondrial morphology, and interaction of pathogenic proteins with mitochondria leads to neuronal demise. Therefore, therapeutic approaches targeting mitochondrial dysfunction and oxidative damage hold great promise in neurodegenerative diseases. This review discusses the potential therapeutic efficacy of creatine, coenzyme Q10, idebenone, synthetic triterpenoids, and mitochondrial targeted antioxidants (MitoQ) and peptides (SS-31) in in vitro studies and in animal models of Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. We have also reviewed the current status of clinical trials of creatine, coenzyme Q10, idebenone, and MitoQ in neurodegenerative disorders. Further, we discuss newly identified therapeutic targets, including peroxisome proliferator-activated receptor-gamma-coactivator and sirtuins, which provide promise for future therapeutic developments in neurodegenerative disorders.

Nrf2-induced antioxidant protection: a promising target to counteract ROS-mediated damage in neurodegenerative disease?

Neurodegenerative diseases share various pathological features, such as accumulation of aberrant protein aggregates, microglial activation, and mitochondrial dysfunction. These pathological processes are associated with generation of reactive oxygen species (ROS), which cause oxidative stress and subsequent damage to essential molecules, such as lipids, proteins, and DNA. Hence, enhanced ROS production and oxidative injury play a cardinal role in the onset and progression of neurodegenerative disorders. To maintain a proper redox balance, the central nervous system is endowed with an antioxidant defense mechanism consisting of endogenous antioxidant enzymes. Expression of most antioxidant enzymes is tightly controlled by the antioxidant response element (ARE) and is activated by nuclear factor E2-related factor 2 (Nrf2). In past years reports have highlighted the protective effects of Nrf2 activation in reducing oxidative stress in both in vitro and in vivo models of neurodegenerative disorders. Here we provide an overview of the involvement of ROS-induced oxidative damage in Alzheimer's disease, Parkinson's disease, and Huntington's disease and we discuss the potential therapeutic effects of antioxidant enzymes and compounds that activate the Nrf2-ARE pathway.

Creatine and its potential therapeutic value for targeting cellular energy impairment in neurodegenerative diseases

Substantial evidence indicates bioenergetic dysfunction and mitochondrial impairment contribute either directly and/or indirectly to the pathogenesis of numerous neurodegenerative disorders. Treatment paradigms aimed at ameliorating this cellular energy deficit and/or improving mitochondrial function in these neurodegenerative disorders may prove to be useful as a therapeutic intervention. Creatine is a molecule that is produced both endogenously, and acquired exogenously through diet, and is an extremely important molecule that participates in buffering intracellular energy stores. Once creatine is transported into cells, creatine kinase catalyzes the reversible transphosphorylation of creatine via ATP to enhance the phosphocreatine energy pool. Creatine kinase enzymes are located at strategic intracellular sites to couple areas of high energy expenditure to the efficient regeneration of ATP. Thus, the creatine kinase/phosphocreatine system plays an integral role in energy buffering and overall cellular bioenergetics. Originally, exogenous creatine supplementation was widely used only as an ergogenic aid to increase the phosphocreatine pool within muscle to bolster athletic performance. However, the potential therapeutic value of creatine supplementation has recently been investigated with respect to various neurodegenerative disorders that have been associated with bioenergetic deficits as playing a role in disease etiology and/or progression which include; Alzheimer's, Parkinson's, amyotrophic lateral sclerosis (ALS), and Huntington's disease. This review discusses the contribution of mitochondria and bioenergetics to the progression of these neurodegenerative diseases and investigates the potential neuroprotective value of creatine supplementation in each of these neurological diseases. In summary, current literature suggests that exogenous creatine supplementation is most efficacious as a treatment paradigm in Huntington's and Parkinson's disease but appears to be less effective for ALS and Alzheimer's disease.

Bioenergetic-based neuroprotection and glaucoma

Primary open-angle glaucoma (POAG) is a pressure-sensitive optic neuropathy which results in the death of retinal ganglion cells and causes associated loss of vision. Presently, the only accepted treatment strategy is to lower the intraocular pressure; however, for some patients this is insufficient to prevent progressive disease. Although the pathogenesis of POAG remains unclear, there is considerable evidence that energy failure at the optic nerve head may be involved. Neuroprotection, a strategy which directly enhances the survival of neurons, is desirable, but remains clinically elusive. One particular form of neuroprotection involves the notion of enhancing the energy supply of neurons. These 'bioenergetic' methods of neuroprotection have proven successful in animal models of other neurodegenerative diseases and conditions, including Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis and traumatic brain injury, but have been relatively unexplored in glaucoma models. This review focuses on some of the potential approaches for bioenergetic neuroprotection in the retina, including increasing the energy buffering capacity of damaged cells, decreasing the permeability of the mitochondrial membrane pore and free radical scavenging.

A novel, efficient, randomized selection trial comparing combinations of drug therapy for ALS

Combining agents with different mechanisms of action may be necessary for meaningful results in treating ALS. The combinations of minocycline-creatine and celecoxib-creatine have additive effects in the murine model. New trial designs are needed to efficiently screen the growing number of potential neuroprotective agents. Our objective was to assess two drug combinations in ALS using a novel phase II trial design. We conducted a randomized, double-blind selection trial in sequential pools of 60 patients. Participants received minocycline (100 mg)-creatine (10 g) twice daily or celecoxib (400 mg)-creatine (10 g) twice daily for six months. The primary objective was treatment selection based on which combination best slowed deterioration in the ALS Functional Rating Scale-Revised (ALSFRS-R); the trial could be stopped after one pool if the difference between the two arms was adequately large. At trial conclusion, each arm was compared to a historical control group in a futility analysis. Safety measures were also examined. After the first patient pool, the mean six-month decline in ALSFRS-R was 5.27 (SD=5.54) in the celecoxib-creatine group and 6.47 (SD=9.14) in the minocycline-creatine group. The corresponding decline was 5.82 (SD=6.77) in the historical controls. The difference between the two sample means exceeded the stopping criterion. The null hypothesis of superiority was not rejected in the futility analysis. Skin rash occurred more frequently in the celecoxib-creatine group. In conclusion, the celecoxib-creatine combination was selected as preferable to the minocycline-creatine combination for further evaluation. This phase II design was efficient, leading to treatment selection after just 60 patients, and can be used in other phase II trials to assess different agents.

A novel pathogenic pathway of immune activation detectable before clinical onset in Huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by both neurological and systemic abnormalities. We examined the peripheral immune system and found widespread evidence of innate immune activation detectable in plasma throughout the course of HD. Interleukin 6 levels were increased in HD gene carriers with a mean of 16 years before the predicted onset of clinical symptoms. To our knowledge, this is the earliest plasma abnormality identified in HD. Monocytes from HD subjects expressed mutant huntingtin and were pathologically hyperactive in response to stimulation, suggesting that the mutant protein triggers a cell-autonomous immune activation. A similar pattern was seen in macrophages and microglia from HD mouse models, and the cerebrospinal fluid and striatum of HD patients exhibited abnormal immune activation, suggesting that immune dysfunction plays a role in brain pathology. Collectively, our data suggest parallel central nervous system and peripheral pathogenic pathways of immune activation in HD.

Oxidative stress biomarkers in sporadic ALS

We aimed to investigate oxidative stress biomarkers in a cross-sectional pilot study of 50 participants with sporadic ALS (SALS) compared to 46 control subjects. We measured urinary 8-oxodeoxyguanosine (8-oxodG), urinary 15-F(2t)-isoprostane (IsoP), and plasma protein carbonyl by ELISA methods. We also determined if ELISA measurement of 8-oxodG could be validated against measures from high-pressure liquid chromatography coupled with electrochemical detection, the current standard method. We found that 8-oxodG and IsoP levels adjusted for creatinine were significantly elevated in SALS participants. These differences persisted after age and gender were controlled in regression analyses. These markers are highly and positively correlated with each other. 8-oxodG measured by the two techniques from the same urine sample were positively correlated (p<.0001). Protein carbonyl was not different between SALS participants and controls. In conclusion, using ELISA, we confirmed that certain oxidative stress biomarkers were elevated in SALS participants. ELISA may be reliable and thus useful in epidemiology studies requiring large numbers of samples to determine the significance of increased oxidative stress markers in SALS. Further studies are required.

Neuroprotection for Huntington's disease: ready, set, slow

The ultimate goal for Huntington's disease (HD) therapeutics is to develop disease-modifying neuroprotective therapies that can delay or prevent illness in those who are at genetic risk and can slow progression in those who are affected clinically. Neuroprotection is the preservation of neuronal structure, function, and viability, and neuroprotective therapy is thus targeted at the underlying pathology of HD, rather than at its specific symptoms. Preclinical target discovery research in HD is identifying numerous distinct targets, along with options for modulating them, with some proceeding into large-scale efficacy studies in early symptomatic HD subjects. The first pilot studies of neuroprotective compounds in premanifest HD are also soon to begin. This review discusses the opportunities for neuroprotection in HD, clinical methodology in premanifest and manifest HD, the clinical assessment of neuroprotection, molecular targets and therapeutic leads, and the current state of clinical development.

Maternal creatine: does it reach the fetus and improve survival after an acute hypoxic episode in the spiny mouse (Acomys cahirinus)?

OBJECTIVE

We hypothesized that elevating creatine in the maternal diet would reach fetal and placental tissues and improve fetal survival after acute hypoxia at birth.

STUDY DESIGN

Pregnant spiny mice were fed a control or 5% creatine-supplemented diet from day 20 of gestation (term, approximately 39 days). On days 37-38, intrauterine hypoxia was induced by placement of the isolated uterus in a saline solution bath for 7.5-8 minutes, after which fetuses were expelled from the uterus and resuscitation was attempted by manual palpation of the chest. Total creatine content (creatine + phosphocreatine) of placental, fetal, and maternal organs was measured.

RESULTS

The maternal creatine diet significantly increased total creatine content in the placenta, fetal brain, heart, liver, and kidney and increased the capacity of offspring to survive birth hypoxia. Maternal creatine improved postnatal growth after birth hypoxia.

CONCLUSION

This study provides evidence that creatine has potential as a prophylactic therapy for pregnancies that are classified as high risk for fetal hypoxia.

The neuroprotective role of creatine

Significant progress has been made in identifying neuroprotective agents and their translation to patients with neurological disorders. While the direct causative pathways of neurodegeneration remain unclear, they are under great clinical and experimental investigation. There are a number of interrelated pathogenic mechanisms triggering molecular events that lead to neuronal death. One putative mechanism reported to play a prominent role in the pathogenesis of neurological diseases is impaired energy metabolism. If reduced energy stores play a role in neuronal loss, then therapeutic strategies that buffer intracellular energy levels may prevent or impede the neurodegenerative process. Recent studies suggest that impaired energy production promotes neurological disease onset and progression. Sustained ATP levels are critical to cellular homeostasis and may have both direct and indirect influence on pathogenic mechanisms associated with neurological disorders. Creatine is a critical component in maintaining cellular energy homeostasis, and its administration has been reported to be neuroprotective in a wide number of both acute and chronic experimental models of neurological disease. In the context of this chapter, we will review the experimental evidence for creatine supplementation as a neurotherapeutic strategy in patients with neurological disorders, including Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease, as well as in ischemic stroke, brain and spinal cord trauma, and epilepsy.