Coenzyme Q10 serum levels in Huntington's disease

Role of Mitochondrial Dysfunctions in Neurodegenerative Disorders: Advances in Mitochondrial Biology

Mitochondria, essential organelles responsible for cellular energy production, emerge as a key factor in the pathogenesis of neurodegenerative disorders. This review explores advancements in mitochondrial biology studies that highlight the pivotal connection between mitochondrial dysfunctions and neurological conditions such as Alzheimer's, Parkinson's, Huntington's, ischemic stroke, and vascular dementia. Mitochondrial DNA mutations, impaired dynamics, and disruptions in the ETC contribute to compromised energy production and heightened oxidative stress. These factors, in turn, lead to neuronal damage and cell death. Recent research has unveiled potential therapeutic strategies targeting mitochondrial dysfunction, including mitochondria targeted therapies and antioxidants. Furthermore, the identification of reliable biomarkers for assessing mitochondrial dysfunction opens new avenues for early diagnosis and monitoring of disease progression. By delving into these advancements, this review underscores the significance of understanding mitochondrial biology in unraveling the mechanisms underlying neurodegenerative disorders. It lays the groundwork for developing targeted treatments to combat these devastating neurological conditions.

Ferroptosis: underlying mechanisms and involvement in neurodegenerative diseases

Ferroptosis, a mode of cell death that was recently identified in 2012, is driven by iron-dependent lipid peroxidation and distinct from other mechanisms of cell death such as autophagy and apoptosis. Ferroptosis has the unique features of disruptions in iron equilibrium, iron-induced lipid peroxidation, and the accumulation of glutamate-induced cellular toxicity. The regulation of ferroptosis mainly involves the iron, lipid, and amino acid metabolic pathways, which are controlled by system Xc-, voltage-dependent anion channels, p53 and other pathways. Neurodegenerative diseases involve gradual neuronal loss predominantly within the central nervous system and are categorized into both sporadic and rare hereditary disorders. These diseases result in the progressive decline of specific neuron populations and their interconnections. Recent investigations have revealed a strong correlation between the manifestation and progression of neurodegenerative diseases and ferroptosis. The pharmacological modulation of ferroptosis, whether by induction or inhibition, exhibits promising prospects for therapeutic interventions for these diseases. This review aims to examine the literature on ferroptosis and its implications in various neurodegenerative diseases. We hope to offer novel insights into the potential therapies targeting ferroptosis in central nervous system neurodegenerative diseases. However, there are still limitations of this review. First, despite our efforts to maintain objectivity during our analysis, this review does not cover all the studies on ferroptosis and neurodegenerative diseases. Second, cell death in neurodegenerative diseases is not solely caused by ferroptosis. Future research should focus on the interplay of different cell death mechanisms to better elucidate the specific disease pathogenesis.

Coenzyme Q10: Role in Less Common Age-Related Disorders

In this article we have reviewed the potential role of coenzyme Q10 (CoQ10) in the pathogenesis and treatment of a number of less common age-related disorders, for many of which effective therapies are not currently available. For most of these disorders, mitochondrial dysfunction, oxidative stress and inflammation have been implicated in the disease process, providing a rationale for the potential therapeutic use of CoQ10, because of its key roles in mitochondrial function, as an antioxidant, and as an anti-inflammatory agent. Disorders reviewed in the article include multi system atrophy, progressive supranuclear palsy, sporadic adult onset ataxia, and pulmonary fibrosis, together with late onset versions of Huntington’s disease, Alexander disease, lupus, anti-phospholipid syndrome, lysosomal storage disorders, fibromyalgia, Machado-Joseph disease, acyl-CoA dehydrogenase deficiency, and Leber’s optic neuropathy.

Free radical biology in neurological manifestations: mechanisms to therapeutics interventions

Recent advancements and growing attention about free radicals (ROS) and redox signaling enable the scientific fraternity to consider their involvement in the pathophysiology of inflammatory diseases, metabolic disorders, and neurological defects. Free radicals increase the concentration of reactive oxygen and nitrogen species in the biological system through different endogenous sources and thus increased the overall oxidative stress. An increase in oxidative stress causes cell death through different signaling mechanisms such as mitochondrial impairment, cell-cycle arrest, DNA damage response, inflammation, negative regulation of protein, and lipid peroxidation. Thus, an appropriate balance between free radicals and antioxidants becomes crucial to maintain physiological function. Since the 1brain requires high oxygen for its functioning, it is highly vulnerable to free radical generation and enhanced ROS in the brain adversely affects axonal regeneration and synaptic plasticity, which results in neuronal cell death. In addition, increased ROS in the brain alters various signaling pathways such as apoptosis, autophagy, inflammation and microglial activation, DNA damage response, and cell-cycle arrest, leading to memory and learning defects. Mounting evidence suggests the potential involvement of micro-RNAs, circular-RNAs, natural and dietary compounds, synthetic inhibitors, and heat-shock proteins as therapeutic agents to combat neurological diseases. Herein, we explain the mechanism of free radical generation and its role in mitochondrial, protein, and lipid peroxidation biology. Further, we discuss the negative role of free radicals in synaptic plasticity and axonal regeneration through the modulation of various signaling molecules and also in the involvement of free radicals in various neurological diseases and their potential therapeutic approaches. The primary cause of free radical generation is drug overdosing, industrial air pollution, toxic heavy metals, ionizing radiation, smoking, alcohol, pesticides, and ultraviolet radiation. Excessive generation of free radicals inside the cell R1Q1 increases reactive oxygen and nitrogen species, which causes oxidative damage. An increase in oxidative damage alters different cellular pathways and processes such as mitochondrial impairment, DNA damage response, cell cycle arrest, and inflammatory response, leading to pathogenesis and progression of neurodegenerative disease other neurological defects.

Mechanisms of Ferroptosis and Emerging Links to the Pathology of Neurodegenerative Diseases

Neurodegenerative diseases are a diverse class of diseases attributed to chronic progressive neuronal degeneration and synaptic loss in the brain and/or spinal cord, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis and multiple sclerosis. The pathogenesis of neurodegenerative diseases is complex and diverse, often involving mitochondrial dysfunction, neuroinflammation, and epigenetic changes. However, the pathogenesis of neurodegenerative diseases has not been fully elucidated. Recently, accumulating evidence revealed that ferroptosis, a newly discovered iron-dependent and lipid peroxidation-driven type of programmed cell death, provides another explanation for the occurrence and progression of neurodegenerative diseases. Here, we provide an overview of the process and regulation mechanisms of ferroptosis, and summarize current research progresses that support the contribution of ferroptosis to the pathogenesis of neurodegenerative diseases. A comprehensive understanding of the emerging roles of ferroptosis in neurodegenerative diseases will shed light on the development of novel therapeutic technologies and strategies for slowing down the progression of these diseases.

Signaling Overlap between the Golgi Stress Response and Cysteine Metabolism in Huntington's Disease

Huntington's disease (HD) is caused by expansion of polyglutamine repeats in the protein huntingtin, which affects the corpus striatum of the brain. The polyglutamine repeats in mutant huntingtin cause its aggregation and elicit toxicity by affecting several cellular processes, which include dysregulated organellar stress responses. The Golgi apparatus not only plays key roles in the transport, processing, and targeting of proteins, but also functions as a sensor of stress, signaling through the Golgi stress response. Unlike the endoplasmic reticulum (ER) stress response, the Golgi stress response is relatively unexplored. This review focuses on the molecular mechanisms underlying the Golgi stress response and its intersection with cysteine metabolism in HD.

Therapeutic Advances for Huntington's Disease

Huntington’s disease (HD) is a progressive neurological disease that is inherited in an autosomal fashion. The cause of disease pathology is an expansion of cytosine-adenine-guanine (CAG) repeats within the huntingtin gene (HTT) on chromosome 4 (4p16.3), which codes the huntingtin protein (mHTT). The common symptoms of HD include motor and cognitive impairment of psychiatric functions. Patients exhibit a representative phenotype of involuntary movement (chorea) of limbs, impaired cognition, and severe psychiatric disturbances (mood swings, depression, and personality changes). A variety of symptomatic treatments (which target glutamate and dopamine pathways, caspases, inhibition of aggregation, mitochondrial dysfunction, transcriptional dysregulation, and fetal neural transplants, etc.) are available and some are in the pipeline. Advancement in novel therapeutic approaches include targeting the mutant huntingtin (mHTT) protein and the HTT gene. New gene editing techniques will reduce the CAG repeats. More appropriate and readily tractable treatment goals, coupled with advances in analytical tools will help to assess the clinical outcomes of HD treatments. This will not only improve the quality of life and life span of HD patients, but it will also provide a beneficial role in other inherited and neurological disorders. In this review, we aim to discuss current therapeutic research approaches and their possible uses for HD.

Impaired Redox Signaling in Huntington's Disease: Therapeutic Implications

Huntington's disease (HD) is a neurodegenerative disease triggered by expansion of polyglutamine repeats in the protein huntingtin. Mutant huntingtin (mHtt) aggregates and elicits toxicity by multiple mechanisms which range from dysregulated transcription to disturbances in several metabolic pathways in both the brain and peripheral tissues. Hallmarks of HD include elevated oxidative stress and imbalanced redox signaling. Disruption of antioxidant defense mechanisms, involving antioxidant molecules and enzymes involved in scavenging or reversing oxidative damage, have been linked to the pathophysiology of HD. In addition, mitochondrial function is compromised in HD leading to impaired bioenergetics and elevated production of free radicals in cells. However, the exact mechanisms linking redox imbalance to neurodegeneration are still elusive. This review will focus on the current understanding of aberrant redox homeostasis in HD and potential therapeutic interventions.

Coenzyme Q10 and neuropsychiatric and neurological disorders: relevance for schizophrenia

Objective: Mitochondrial dysfunction has been implicated in the pathophysiology of schizophrenia and other neuropsychiatric disorders. Though the exact mechanisms and clinical implications for this dysfunction are not fully determined, there is a hypothesis that deficiency in coenzyme Q10 (CoQ10) may contribute to mitochondrial impairments and be reflected in cognitive, affective, and energy disturbances in the disorders. CoQ10 is a critical component of the mitochondrial respiratory chain and an essential free radical scavenger, necessary for mitochondrial function. Here, we review the results of CoQ10 supplementation interventions for adults with various neurological and neuropsychiatric disorders and consider the therapeutic potential of CoQ10 supplementation for schizophrenia in light of these studies. Methods: A literature review of randomised controlled trials and open-label studies investigating the effect of CoQ10 as a single intervention in adults with neurological and neuropsychiatric disorders was conducted. Results: CoQ10 supplementation has some positive effects on fatigue, cognitive impairment and affective difficulties in several neurological and neuropsychiatric conditions with associated mitochondrial dysfunction. Discussion: CoQ10 may be of therapeutic value to schizophrenia given evidence of mitochondrial dysfunction in the disorder.

Molecular diagnosis of coenzyme Q10 deficiency: an update

INTRODUCTION

Coenzyme Q₁₀ (CoQ) deficiency syndromes comprise a growing number of genetic disorders. While primary CoQ deficiency syndromes are rare diseases, secondary deficiencies have been related to both genetic and environmental conditions, which are the main causes of biochemical CoQ deficiency. The diagnosis is the essential first step for planning future treatment strategies, as the potential treatability of CoQ deficiency is the most critical issue for the patients. Areas covered: While the quickest and most effective tool to define a CoQ-deficient status is its biochemical determination in biological fluids or tissues, this quantification does not provide a definite diagnosis of a CoQ-deficient status nor insight about the genetic etiology of the disease. The different laboratory tests to check for CoQ deficiency are evaluated in order to choose the best diagnostic pathway for the patient. Expert commentary: New insights are being discovered about the implication of new proteins in the intricate CoQ biosynthetic pathway. These insights reinforce the idea that next generation sequencing diagnostic strategies are the unique alternative in terms of rapid and accurate molecular diagnosis of CoQ deficiency.

The chicken or the egg: mitochondrial dysfunction as a cause or consequence of toxicity in Huntington's disease

Mitochondrial dysfunction and ensuing oxidative damage is typically thought to be a primary cause of Huntington's disease, Alzheimer's disease, and Parkinson disease. There is little doubt that mitochondria (MT) become defective as neurons die, yet whether MT defects are the primary cause or a detrimental consequence of toxicity remains unanswered. Oxygen consumption rate (OCR) and glycolysis provide sensitive and informative measures of the functional status MT and the cells metabolic regulation, yet these measures differ depending on the sample source; species, tissue type, age at measurement, and whether MT are measured in purified form or in a cell. The effects of these various parameters are difficult to quantify and not fully understood, but clearly have an impact on interpreting the bioenergetics of MT or their failure in disease states. A major goal of the review is to discuss issues and coalesce detailed information into a reference table to help in assessing mitochondrial dysfunction as a cause or consequence of Huntington's disease.

Coenzyme Q10 depletion in medical and neuropsychiatric disorders: potential repercussions and therapeutic implications

Coenzyme Q10 (CoQ10) is an antioxidant, a membrane stabilizer, and a vital cofactor in the mitochondrial electron transport chain, enabling the generation of adenosine triphosphate. It additionally regulates gene expression and apoptosis; is an essential cofactor of uncoupling proteins; and has anti-inflammatory, redox modulatory, and neuroprotective effects. This paper reviews the known physiological role of CoQ10 in cellular metabolism, cell death, differentiation and gene regulation, and examines the potential repercussions of CoQ10 depletion including its role in illnesses such as Parkinson's disease, depression, myalgic encephalomyelitis/chronic fatigue syndrome, and fibromyalgia. CoQ10 depletion may play a role in the pathophysiology of these disorders by modulating cellular processes including hydrogen peroxide formation, gene regulation, cytoprotection, bioenegetic performance, and regulation of cellular metabolism. CoQ10 treatment improves quality of life in patients with Parkinson's disease and may play a role in delaying the progression of that disorder. Administration of CoQ10 has antidepressive effects. CoQ10 treatment significantly reduces fatigue and improves ergonomic performance during exercise and thus may have potential in alleviating the exercise intolerance and exhaustion displayed by people with myalgic encepholamyletis/chronic fatigue syndrome. Administration of CoQ10 improves hyperalgesia and quality of life in patients with fibromyalgia. The evidence base for the effectiveness of treatment with CoQ10 may be explained via its ability to ameliorate oxidative stress and protect mitochondria.

Coenzyme Q10 deficiency in patients with Parkinson's disease

Reactive oxygen species (ROS) are well known to contribute to the pathophysiology of Parkinson's disease (PD). Clinical trials of antioxidants are currently underway in PD patients, however, antioxidant research has been hindered by a lack of peripheral biomarkers.

METHODS

Twenty-two patients with PD elected to have a novel antioxidant assessment (Functional Intracellular Assay (FIA), SpectraCell Lab, Houston, TX) performed between 2004 and 2008. Each PD case was compared to four age- and gender-matched controls (n=88) in four separate, random iterations using laboratory data submitted during the same time period. Logistic regression was used to determine the odds of functional deficiency in antioxidant nutrients (i.e., glutathione, coenzyme Q10, selenium, vitamin E and alpha-lipoic acid) by case-control status. The proportion of cases with functional deficiency was also compared to that for controls by chi(2) test.

RESULTS

Compared to cases, PD patients had a significantly greater odds of deficiency in coenzyme Q10 status (OR: 4.7-5.4; 95% CI: 1.5-17.7; P=0.003-0.009) based on FIA results, but not of vitamin E, selenium, lipoic acid, or glutathione (all P>0.05). The proportion of cases with coenzyme Q10 deficiency was also significantly greater in cases than in controls (32-36% vs. 8-9%; P=0.0012-0.006).

CONCLUSIONS

Deficiency of coenzyme Q10 assessed via FIA should be explored as a potential peripheral biomarker of antioxidant status in PD.

Evidence for behavioral benefits of early dietary supplementation with CoEnzymeQ10 in a slowly progressing mouse model of Huntington's disease

Controversies surround the usefulness of Coenzyme Q10 (CoQ10) in Huntington's disease (HD), an autosomal dominant, fatal, neurodegenerative disease with no cure or disease modifying treatment. CoQ10, an endogenous substrate for electron transport and an anti-oxidant, has been shown in some but not all studies to improve symptoms and survival in mouse models of HD. Previous studies have been conducted in fast-progressing models that better mimic the juvenile forms of HD than the much more common middle-age onset form, possibly accounting for mixed results. Establishing the usefulness of CoQ10 to alter HD disease course in a model that better recapitulates the progressive features of the human disorder is important because clinical trials of CoQ10, which is safe and well tolerated, are being planned in patients. The CAG140 knock-in (KI) mouse model of HD in which an expanded (approximately 120) CAG repeat is inserted in the mouse gene provides a model of the mutation in the proper genomic and protein context. These mice display progressive motor, cognitive and emotional anomalies, transcriptional disturbances and late striatal degeneration. Homozygote mutant CAG140 KI mice and wild-type littermates were fed CoQ10 (0.2%, 0.6%) in chow, and behavioral and pathological markers of disease were examined. CoQ10 improved early behavioral deficits and normalized some transcriptional deficits without altering huntingtin aggregates in striatum. The lower dose (0.2%) was more beneficial than 0.6%. Similar to previous studies, this low dose also induced deleterious effects in open field and rotarod in WT mice, however these effects are of unclear clinical significance in view of the excellent safety profile of CoQ10 in humans. These data confirm that CoQ10 may be beneficial in HD but suggest that maximum benefit may be observed when treatment is begun at early stages of the disease and that dosage may be critical.

Coenzyme Q10 and its effects in the treatment of neurodegenerative diseases

According to clinical and pre-clinical studies, oxidative stress and its consequences may be the cause or, at least, a contributing factor, to a large number of neurodegenerative diseases. These diseases include common and debilitating disorders, characterized by progressive and irreversible loss of neurons in specific regions of the brain. The most common neurodegenerative diseases are Parkinson's disease, Huntington's disease, Alzheimer's disease and amyotrophic lateral sclerosis. Coenzyme Q10 (CoQ10) has been extensively studied since its discovery in 1957. It is a component of the electron transportation chain and participates in aerobic cellular respiration, generating energy in the form of adenosine triphosphate (ATP). The property of CoQ10 to act as an antioxidant or a pro-oxidant, suggests that it also plays an important role in the modulation of redox cellular status under physiological and pathological conditions, also performing a role in the ageing process. In several animal models of neurodegenerative diseases, CoQ10 has shown beneficial effects in reducing disease progression. However, further studies are needed to assess the outcome and effectiveness of CoQ10 before exposing patients to unnecessary health risks at significant costs.

Coenzyme Q10 effects in neurodegenerative disease

Coenzyme Q10 (CoQ10) is an essential cofactor in the mitochondrial respiratory chain, and as a dietary supplement it has recently gained attention for its potential role in the treatment of neurodegenerative disease. Evidence for mitochondrial dysfunction in neurodegenerative disorders derives from animal models, studies of mitochondria from patients, identification of genetic defects in patients with neurodegenerative disease, and measurements of markers of oxidative stress. Studies of in vitro models of neuronal toxicity and animal models of neurodegenerative disorders have demonstrated potential neuroprotective effects of CoQ10. With this data in mind, several clinical trials of CoQ10 have been performed in Parkinson's disease and atypical Parkinson's syndromes, Huntington's disease, Alzheimer disease, Friedreich's ataxia, and amyotrophic lateral sclerosis, with equivocal findings. CoQ10 is widely available in multiple formulations and is very well tolerated with minimal adverse effects, making it an attractive potential therapy. Phase III trials of high-dose CoQ10 in large sample sizes are needed to further ascertain the effects of CoQ10 in neurodegenerative diseases.

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.

Mitochondrial NAD+-linked State 3 respiration and complex-I activity are compromised in the cerebral cortex of 3-nitropropionic acid-induced rat model of Huntington's disease

Mitochondrial complex-I dysfunction has been observed in patients of Huntington's disease (HD). We assessed whether such a defect is present in the 3-nitropropionic acid (3-NP) model of HD. Rats treated with 3-NP (10-20 mg/kg i.p., for 4 days) exhibited weight loss, gait abnormalities, and striatal lesions with increased glial fibrillary acidic protein immunostaining on fifth and ninth days, while increase in striatal dopamine and loss of tyrosine hydroxylase immunoreactivity were observed on fifth day following treatment. We report for the first time a dose-dependent reduction in complex-I activity in the cerebral cortex when analyzed spectrophotometrically and by blue native-polyacrylamide gel electrophoresis following 3-NP treatment. The citrate synthase normalized activities of mitochondrial complex-I, -II, -(I + III) and -IV were decreased in the cortex of 3-NP treated rats. In addition, succinate driven State 3 respiration was also significantly inhibited in vivo and in the isolated mitochondria. These findings taken together with the observation of a significant decrease in vivo but not in vitro of State 3 respiration with NAD(+)-linked substrates, suggest complex-I dysfunction in addition to irreversible inhibition of complex-II and succinate dehydrogenase activity as a contributing factor in 3-NP-induced cortico-striatal lesion.

Oxidative Stress in Skin Fibroblasts Cultures of Patients with Huntington’s Disease

Oxidative stress and mitochondrial dysfunction should play a role in the neurodegeneration in Huntington's disease (HD). The most consistent finding is decreased activity of the mitochondrial complexes II/III and IV of the respiratory chain in the striatum. We assessed enzymatic activities of respiratory chain enzymes and other enzymes involved in oxidative processes in skin fibroblasts cultures of patients with HD. We studied respiratory chain enzyme activities, activities of total, Cu/Zn- and Mn-superoxide-dismutase, glutathione-peroxidase (GPx) and catalase, and coenzyme Q(10) (CoQ(10)) levels in skin fibroblasts cultures from 13 HD patients and 13 age- and sex-matched healthy controls. When compared with controls, HD patients showed significantly lower specific activities for catalase corrected by protein concentrations (P < 0.01). Oxidized, reduced and total CoQ(10) levels (both corrected by citrate synthase (CS) and protein concentrations), and activities of total, Cu/Zn- and Mn-superoxide-dismutase, and gluthatione-peroxidase, did not differ significantly between HD-patients and control groups. Values for enzyme activities in the HD group did not correlate with age at onset and of the disease and with the CAG triplet repeats. The primary finding of this study was the decreased activity of catalase in HD patients, suggesting a possible contribution of catalase, but not of other enzymes related with oxidative stress, to the pathogenesis of this disease.

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

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

Effect of coenzyme Q10 and vitamin E on brain energy metabolism in the animal model of Huntington's disease

The neuropathological and clinical symptoms of Huntington's disease (HD) can be simulated in animal model with systemic administration of 3-nitropropionic acid (3-NP). Energy defects in HD could be ameliorated by administration of coenzyme Q(10) (CoQ(10)), creatine, or nicotinamid. We studied the activity of creatine kinase (CK) and the function of mitochondrial respiratory chain in the brain of aged rats administered with 3-NP with and without previous application of antioxidants CoQ(10)+vitamin E. We used dynamic and steady-state methods of in vivo phosphorus magnetic resonance spectroscopy ((31)P MRS) for determination of the pseudo-first order rate constant (k(for)) of the forward CK reaction, the phosphocreatine (PCr) to adenosinetriphosphate (ATP) ratio, intracellular pH(i) and Mg(i)(2+) content in the brain. The respiratory chain function of isolated mitochondria was assessed polarographically; the concentration of CoQ(10) and alpha-tocopherol by HPLC. We found significant elevation of k(for) in brains of 3-NP rats, reflecting increased rate of CK reaction in cytosol. The function of respiratory chain in the presence of succinate was severely diminished. The activity of cytochromeoxidase and mitochondrial concentration of CoQ(10) was unaltered; tissue content of CoQ(10) was decreased in 3-NP rats. Antioxidants CoQ(10)+vitamin E prevented increase of k(for) and the decrease of CoQ(10) content in brain tissue, but were ineffective to prevent the decline of respiratory chain function. We suppose that increased activity of CK system could be compensatory to decreased mitochondrial ATP production, and CoQ(10)+vitamin E could prevent the increase of k(for) after 3-NP treatment likely by activity of CoQ(10) outside the mitochondria. Results of our experiments contributed to elucidation of mechanism of beneficial effect of CoQ(10) administration in HD and showed that the rate constant of CK is a sensitive indicator of brain energy disorder reflecting therapeutic effect of drugs that could be used as a new in vivo biomarker of neurodegenerative diseases.