The Glutathione System: A New Drug Target in Neuroimmune Disorders

Glutathione (GSH) has a crucial role in cellular signaling and antioxidant defenses either by reacting directly with reactive oxygen or nitrogen species or by acting as an essential cofactor for GSH S-transferases and glutathione peroxidases. GSH acting in concert with its dependent enzymes, known as the glutathione system, is responsible for the detoxification of reactive oxygen and nitrogen species (ROS/RNS) and electrophiles produced by xenobiotics. Adequate levels of GSH are essential for the optimal functioning of the immune system in general and T cell activation and differentiation in particular. GSH is a ubiquitous regulator of the cell cycle per se. GSH also has crucial functions in the brain as an antioxidant, neuromodulator, neurotransmitter, and enabler of neuron survival. Depletion of GSH leads to exacerbation of damage by oxidative and nitrosative stress; hypernitrosylation; increased levels of proinflammatory mediators and inflammatory potential; dysfunctions of intracellular signaling networks, e.g., p53, nuclear factor-κB, and Janus kinases; decreased cell proliferation and DNA synthesis; inactivation of complex I of the electron transport chain; activation of cytochrome c and the apoptotic machinery; blockade of the methionine cycle; and compromised epigenetic regulation of gene expression. As such, GSH depletion has marked consequences for the homeostatic control of the immune system, oxidative and nitrosative stress (O&NS) pathways, regulation of energy production, and mitochondrial survival as well. GSH depletion and concomitant increase in O&NS and mitochondrial dysfunctions play a role in the pathophysiology of diverse neuroimmune disorders, including depression, myalgic encephalomyelitis/chronic fatigue syndrome and Parkinson’s disease, suggesting that depleted GSH is an integral part of these diseases. Therapeutical interventions that aim to increase GSH concentrations in vivo include N-acetyl cysteine; Nrf-2 activation via hyperbaric oxygen therapy; dimethyl fumarate; phytochemicals, including curcumin, resveratrol, and cinnamon; and folate supplementation.     

Coenzyme Q biochemistry and biosynthesis

Coenzyme Q (CoQ) is a remarkably hydrophobic, redox-active lipid that empowers diverse cellular processes. Although most known for shuttling electrons between mitochondrial electron transport chain (ETC) complexes, the roles for CoQ are far more wide-reaching and ever-expanding. CoQ serves as a conduit for electrons from myriad pathways to enter the ETC, acts as a cofactor for biosynthetic and catabolic reactions, detoxifies damaging lipid species, and engages in cellular signaling and oxygen sensing. Many open questions remain regarding the biosynthesis, transport, and metabolism of CoQ, which hinders our ability to treat human CoQ deficiency. Here, we recount progress in filling these knowledge gaps, highlight unanswered questions, and underscore the need for novel tools to enable discoveries and improve the treatment of CoQ-related diseases.     

Overview on coenzyme Q10 as adjunctive therapy in chronic heart failure. Rationale, design and end-points of "Q-symbio"--a multinational trial

Energy starvation of the myocardium is probably a dominant feature of heart failure and attention has been directed towards agents which may stabilize myocardial metabolism and maintain adequate energy stores. A reduced myocardial tissue content of the essential redox-component and natural antioxidant Coenzyme Q10 (CoQ10) has been detected in patients with heart failure and the observed level of CoQ10 deficiency was correlated to the severity of heart failure. CoQ10 fulfills various criteria of an obvious adjunct in patients with symptomatic heart failure: it is devoid of significant side effects and it improves symptoms and quality of life. Till this date, several double-blind placebo-controlled trials with CoQ10 supplementation in more than 1000 patients have been positive and statistically significant with respect to various clinical parameters, e.g. improvement in NYHA Class, exercise capacity and reduced hospitalisation frequency. Also treatment with CoQ10 led to a significant improvement of relevant hemodynamic parameters. In only 3 out of 13 double-blind studies comprising 10% of the total number of patients treated the results were neutral. Thus, based on the available controlled data CoQ10 is a promising, effective and safe approach in chronic heart failure. This is why a double-blind multicenter trial with focus on morbidity and mortality has been planned to start in 2003: Q-SYMBIO. Patients in NYHA classes III to IV (N=550) receiving standard therapy are being randomized to treatment with CoQ10 100 mg t.i.d. or placebo in parallel groups. End-points in a short-term evaluation phase of 3 months include symptoms, functional capacity and biomarker status (BNP). The aim of a subsequent 2-year follow-up study is to test the hypothesis that CoQ10 may reduce cardiovascular morbidity (unplanned cardiovascular hospitalisation due to worsening heart failure) and mortality as a composite endpoint. This trial should help to establish the future role of CoQ10 as part of a maintenance therapy in patients with chronic heart failure.     

Book review

In this paper, we report results obtained from a continuing clinical trial on the effect of coenzyme Q 10 (CoQ 10 ) administration on human vastus lateralis (quadriceps) skeletal muscle. Muscle samples, obtained from aged individuals receiving placebo or CoQ 10 supplementation (300 mg per day for four weeks prior to hip replacement surgery) were analysed for changes in gene and protein expression and in muscle fibre type composition. Microarray analysis (Affymetrix U95A human oligonucleotide array) using a change in gene expression of 1.8-fold or greater as a cutoff point, demonstrated that a total of 115 genes were differentially expressed in six subject comparisons. In the CoQ 10 -treated subjects, 47 genes were up-regulated and 68 down-regulated in comparison with placebo-treated subjects. Restriction fragment differential display analysis showed that over 600 fragments were differentially expressed using a 2.0-fold or greater change in expression as a cutoff point. Proteome analysis revealed that, of the high abundance muscle proteins detected (2086 &;#45 115), the expression of 174 proteins was induced by CoQ 10 while 77 proteins were repressed by CoQ 10 supplementation. Muscle fibre types were also affected by CoQ 10 treatment; CoQ 10 -treated individuals showed a lower proportion of type I (slow twitch) fibres and a higher proportion of type IIb (fast twitch) fibres, compared to age-matched placebo-treated subjects. The data suggests that CoQ 10 treatment can act to influence the fibre type composition towards the fibre type profile generally found in younger individuals. Our results led us to the conclusion that coenzyme Q 10 is a gene regulator and consequently has wide-ranging effects on over-all tissue metabolism. We develop a comprehensive hypothesis that CoQ 10 plays a major role in the determination of membrane potential of many, if not all, sub-cellular membrane systems and that H 2 O 2 arising from the activities of CoQ 10 acts as a second messenger for the modulation of gene expression and cellular metabolism.     

Cellular redox activity of coenzyme Q10: effect of CoQ10 supplementation on human skeletal muscle

In this paper, we report results obtained from a continuing clinical trial on the effect of coenzyme Q 10 (CoQ 10 ) administration on human vastus lateralis (quadriceps) skeletal muscle. Muscle samples, obtained from aged individuals receiving placebo or CoQ 10 supplementation (300 mg per day for four weeks prior to hip replacement surgery) were analysed for changes in gene and protein expression and in muscle fibre type composition. Microarray analysis (Affymetrix U95A human oligonucleotide array) using a change in gene expression of 1.8-fold or greater as a cutoff point, demonstrated that a total of 115 genes were differentially expressed in six subject comparisons. In the CoQ 10 -treated subjects, 47 genes were up-regulated and 68 down-regulated in comparison with placebo-treated subjects. Restriction fragment differential display analysis showed that over 600 fragments were differentially expressed using a 2.0-fold or greater change in expression as a cutoff point. Proteome analysis revealed that, of the high abundance muscle proteins detected (2086 ±115), the expression of 174 proteins was induced by CoQ 10 while 77 proteins were repressed by CoQ 10 supplementation. Muscle fibre types were also affected by CoQ 10 treatment; CoQ 10 -treated individuals showed a lower proportion of type I (slow twitch) fibres and a higher proportion of type IIb (fast twitch) fibres, compared to age-matched placebo-treated subjects. The data suggests that CoQ 10 treatment can act to influence the fibre type composition towards the fibre type profile generally found in younger individuals. Our results led us to the conclusion that coenzyme Q 10 is a gene regulator and consequently has wide-ranging effects on over-all tissue metabolism. We develop a comprehensive hypothesis that CoQ 10 plays a major role in the determination of membrane potential of many, if not all, sub-cellular membrane systems and that H 2 O 2 arising from the activities of CoQ 10 acts as a second messenger for the modulation of gene expression and cellular metabolism.     

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.     

Mitochondrial dysfunction and Down's syndrome: is there a role for coenzyme Q(10) ?

Structural changes and abnormal function of mitochondria have been documented in Down's syndrome (DS) cells, patients, and animal models. DS cells in culture exhibit a wide array of functional mitochondrial abnormalities including reduced mitochondrial membrane potential, reduced ATP production, and decreased oxido-reductase activity. New research has also brought to central stage the prominent role of oxidative stress in this condition. This review focuses on recent advances in the field with a particular emphasis on novel translational approaches involving the utilization of coenzyme Q(10) (CoQ(10) ) to treat a variety of clinical phenotypes associated with DS that are linked to increased oxidative stress and energy deficits. CoQ(10) has already provided promising results in several different conditions associated with altered energy metabolism and oxidative stress in the CNS. Two studies conducted in Ancona investigated the effect of CoQ(10) treatment on DNA damage in DS patients. Although the effect of CoQ(10) was evidenced only at single cell level, the treatment affected the distribution of cells according to their content in oxidized bases. In fact, it produced a strong negative correlation linking cellular CoQ(10) content and the amount of oxidized purines. Results suggest that the effect of CoQ(10) treatment in DS not only reflects antioxidant efficacy, but likely modulates DNA repair mechanisms.     

Coenzyme Q10, a cutaneous antioxidant and energizer.

The processes of aging and photoaging are associated with an increase in cellular oxidation. This may be in part due to a decline in the levels of the endogenous cellular antioxidant coenzyme Q10 (ubiquinone, CoQ10). Therefore, we have investigated whether topical application of CoQ10 has the beneficial effect of preventing photoaging. We were able to demonstrate that CoQ10 penetrated into the viable layers of the epidermis and reduce the level of oxidation measured by weak photon emission. Furthermore, a reduction in wrinkle depth following CoQ10 application was also shown. CoQ10 was determined to be effective against UVA mediated oxidative stress in human keratinocytes in terms of thiol depletion, activation of specific phosphotyrosine kinases and prevention of oxidative DNA damage. CoQ10 was also able to significantly suppress the expression of collagenase in human dermal fibroblasts following UVA irradiation. These results indicate that CoQ10 has the efficacy to prevent many of the detrimental effects of photoaging.     

Systematic review of effect of coenzyme Q10 in physical exercise, hypertension and heart failure

COENZYME Q10 IN PHYSICAL EXERCISE. We identified eleven studies in which CoQ10 was tested for an effect on exercise capacity, six showed a modest improvement in exercise capacity with CoQ10 supplementation but five showed no effect. CoQ10 IN HYPERTENSION. We identified eight published trials of CoQ10 in hypertension. Altogether in the eight studies the mean decrease in systolic blood pressure was 16 mm Hg and in diastolic blood pressure, 10 mm Hg. Being devoid of significant side effects CoQ10 may have a role as an adjunct or alternative to conventional agents in the treatment of hypertension. CoQ10 IN HEART FAILURE. We performed a randomised double blind placebo-controlled pilot trial of CoQ10 therapy in 35 patients with heart failure. Over 3 months, in the CoQ10 patients but not in the placebo patients there were significant improvements in symptom class and a trend towards improvements in exercise time. META-ANALYSIS OF RANDOMISED TRIALS OF COENZYME Q10 IN HEART FAILURE. In nine randomised trials of CoQ10 in heart failure published up to 2003 there were non-significant trends towards increased ejection fraction and reduced mortality. There were insufficient numbers of patients for meaningful results. To make more definitive conclusions regarding the effect of CoQ10 in cardiac failure we recommend a prospective, randomised trial with 200-300 patients per study group. Further trials of CoQ10 in physical exercise and in hypertension are recommended.     

Coenzyme Q10 administration and its potential for treatment of neurodegenerative diseases.

Coenzyme Q10 (CoQ10) is an essential cofactor of the electron transport chain as well as an important antioxidant. Previous studies have suggested that it may exert therapeutic effects in patients with known mitochondrial disorders. We investigated whether it can exert neuroprotective effects in a variety of animal models. We have demonstrated that CoQ10 can protect against striatal lesions produced by both malonate and 3-nitropropionic acid. It also protects against MPTP toxicity in mice. It extended survival in a transgenic mouse model of amyotrophic lateral sclerosis. We demonstrated that oral administration can increase plasma levels in patients with Parkinson's disease. Oral administration of CoQ10 significantly decreased elevated lactate levels in patients with Huntington's disease. These studies therefore raise the prospect that administration of CoQ10 may be useful for the treatment of neurodegenerative diseases.     

Coenzyme Q10: absorption, tissue uptake, metabolism and pharmacokinetics

Available data on the absorption, metabolism and pharmacokinetics of coenzyme Q10 (CoQ10) are reviewed in this paper. CoQ10 has a fundamental role in cellular bioenergetics. CoQ10 is also an important antioxidant. Because of its hydrophobicity and large molecular weight, absorption of dietary CoQ10 is slow and limited. In the case of dietary supplements, solubilized CoQ10 formulations show enhanced bioavailability. The T_max is around 6 h, with an elimination half-life of about 33 h. The reference intervals for plasma CoQ10 range from 0.40 to 1.91 μmol/l in healthy adults. With CoQ10 supplements there is reasonable correlation between increase in plasma CoQ10 and ingested dose up to a certain point. Animal data show that CoQ10 in large doses is taken up by all tissues including heart and brain mitochondria. This has implications for therapeutic applications in human diseases, and there is evidence for its beneficial effect in cardiovascular and neurodegenerative diseases. CoQ10 has an excellent safety record.     

Coenzyme Q(10) in male infertility: physiopathology and therapy

Both the bioenergetic and the antioxidant role of CoQ(10) suggest a possible involvement in sperm biochemistry and male infertility. CoQ(10) can be quantified in seminal fluid, where its concentration correlates with sperm count and motility. It was found that distribution of CoQ(10) between sperm cells and seminal plasma was altered in varicocele patients, who also presented a higher level of oxidative stress and lower total antioxidant capacity. The effect of vericocelectomy on partially reversing these biochemical abnormalities is discussed. The redox status of coenzyme Q(10) in seminal fluid was also determined: an inverse correlation was found between ubiquinol/ubiquinone ratio and hydroperoxide levels and between this ratio and the percentage of abnormal sperm forms. After the first in vitro observations CoQ(10) was administered to infertile patients affected by idiopathic asthenozoospermia, originally in an open label study and then in three randomized placebo-controlled trials; doses were around 200-300 mg/day and treatment lasted 6 months. A significant increase in the concentration of CoQ(10) was found, both in seminal plasma and sperm cells. Treatment also led to a certain improvement in sperm motility. In one of the studies there was also a decrease in plasma levels of follicle stimulating horhone (FSH) and luteinizine horhone (LH). Administration of CoQ(10) may play a positive role in the treatment of asthenozoospermia, possibly related to not only to its function in the mitochondrial respiratory chain but also to its antioxidant properties. Further studies are needed in order to determine whether there is also an effect on fertility rate.     

MitoQ10 induces adipogenesis and oxidative metabolism in myotube cultures

Coenzyme Q(10) (CoQ(10)) plays an essential role in determination of mitochondrial membrane potential and substrate utilization in all metabolically important tissues. The objective of the present study was to investigate the effect of Coenzyme Q analog (MitoQ(10)) on oxidative phenotype and adipogenesis in myotubes derived from fast-glycolytic Pectoralis major (PM) and slow-oxidative Anterior latissimus dorsi (ALD) muscles of the turkey (Meleagris gallopavo). The myotubes were subjected to the following treatments: fusion media alone, fusion media+125 nM MitoQ(10), and 500 nM MitoQ(10). Lipid accumulation was visualized by Oil Red O staining and quantified by measuring optical density of extracted lipid at 500 nm. Quantitative Real-Time PCR was utilized to quantify the expression levels of peroxisome proliferator-activated receptor (PPARγ) and PPARγ co-activator-1α (PGC-1α). MitoQ(10) treatment resulted in the highest (P<0.05) lipid accumulation in PM myotubes. MitoQ(10) up-regulated genes controlling oxidative mitochondrial biogenesis and adipogenesis in PM myotube cultures. In contrast, MitoQ(10) had a limited effect on adipogenesis and down-regulated oxidative metabolism in ALD myotube cultures. Differential response to MitoQ(10) treatment may be dependent on the cellular redox state. MitoQ(10) likely controls a range of metabolic pathways through its differential regulation of gene expression levels in myotubes derived from fast-glycolytic and slow-oxidative muscles.     

Effect of coenzyme Q10 on catalase activity and other antioxidant parameters in streptozotocin-induced diabetic rats

Although coenzyme Q10 (CoQ10) is a component of the oxidative phosphorylation process in mitochondria that converts the energy in carbohydrates and fatty acids into ATP to drive cellular machinery and synthesis, its effect in type I diabetes is not clear. We have studied the effect of 4 wk of treatment with CoQ10 (10 mg/kg, ip, daily) in streptozotocin (STZ)-induced (40 mg/kg, iv in adult rats) type I diabetes rat models. Treatment with CoQ10 produced a significant decrease in elevated levels of glucose, cholesterol, triglycerides, very-low-density lipoprotein, lowdensity lipoprotein, and atherogenic index and increased high-density lipoprotein cholesterol levels in diabetic rats. CoQ10 treatment significantly decreased the area under the curve over 120 min for glucose in diabetic rats, without affecting serum insulin levels and the area under the curve over 120 min for insulin in diabetic rats. CoQ10 treatment also reduced lipid peroxidation and increased antioxidant parameters like superoxide dismutase, catalase, and glutathione in the liver homogenates of diabetic rats. CoQ10 also lowered the elevated blood pressure in diabetic rats. In conclusion, CoQ10 treatment significantly improved deranged carbohydrate and lipid metabolism of experimental chemically induced diabetes in rats. The mechanism of its beneficial effect appears to be its antioxidant property.     

Coenzyme Q10 reduces the toxicity of rotenone in neuronal cultures by preserving the mitochondrial membrane potential

Defects in mitochondrial energy metabolism due to respiratory chain disorders lead to a decrease in mitochondrial membrane potential (DeltaPsim) and induce apoptosis. Since coenzyme Q10 (CoQ10) plays a dual role as an antioxidant and bioenergetic agent in the respiratory chain, it has attracted increasing attention concerning the prevention of apoptosis in mitochondrial diseases. In this study the potential of CoQ10 to antagonize the apoptosis-inducing effects of the respiratory chain inhibitor rotenone was explored by video-enhanced microscopy in SH-SY5Y neuroblastoma cells. The cationic fluorescent dye JC-1 which exhibits potential-dependent accumulation in mitochondria was used as an indicator to monitor changes in DeltaPsim. The relative changes in fluorescence intensity after incubation with rotenone for 15 minutes were calculated. Pre-treatment with CoQ10 (10 or 100 microM) for 48 h led to a significant reduction of rotenone-induced loss of DeltaPsim. These results suggest, that cytoprotection by CoQ10 may be mediated by raising cellular resistance against the initiating steps of apoptosis, namely the decrease of DeltaPsim. Whether these data may provide new directions for the development of neuroprotective strategies has to be investigated in future studies.     

Characterization of cellular uptake and distribution of coenzyme Q10 and vitamin E in PC12 cells

Coenzyme Q (CoQ) is a well-known electron transporter in the mitochondrial respiratory chain. Furthermore, ubiquinol (UQH(2))--a reduced form of ubiquinone (UQ)--has been shown to act as a radical-scavenging antioxidant. Some studies have reported the beneficial effect of CoQ addition to cultured cells; however, the cellular uptake and distribution of CoQ have not been elucidated. In the present study, we used rat pheochromocytoma PC12 cells to investigate and compare the cellular uptake and distribution of CoQ(10) and alpha-tocopherol (alphaT). UQ(10) or UQ(10)H(2) treatment resulted in an increase in the cellular content of both CoQ(10) in a time- and concentration-dependent manner. A subcellular fractionation study revealed that the added UQ(10) as well as UQ(10)H(2) mainly localized in the mitochondrial fraction, which is similar to the localization of endogenous CoQ but different from that of alphaT. The cellular distribution of alphaT directly corresponded to the lipid distribution, while the CoQ distribution did not show any relationship with the lipid distribution, particularly in the mitochondrial and microsomal fractions. These results indicate that the cellular distribution of CoQ is completely different from that of alphaT; moreover, a certain system which accumulates CoQ preferentially in mitochondria may be suggested.     

Improved brain and muscle mitochondrial respiration with CoQ. An in vivo study by 31P-MR spectroscopy in patients with mitochondrial cytopathies.

We used in vivo phosphorus magnetic resonance spectroscopy (31P-MRS) to study the effect of CoQ10 on the efficiency of brain and skeletal muscle mitochondrial respiration in ten patients with mitochondrial cytopathies. Before CoQ, brain [PCr] was remarkably lower in patients than in controls, while [Pi] and [ADP] were higher. Brain cytosolic free [Mg2+] and delta G of ATP hydrolysis were also abnormal in all patients. MRS also revealed abnormal mitochondrial function in the skeletal muscles of all patients, as shown by a decreased rate of PCr recovery from exercise. After six-months of treatment with CoQ (150 mg/day), all brain MRS-measurable variables as well as the rate of muscle mitochondrial respiration were remarkably improved in all patients. These in vivo findings show that treatment with CoQ in patients with mitochondrial cytopathies improves mitochondrial respiration in both brain and skeletal muscles, and are consistent with Lenaz's view that increased CoQ concentration in the mitochondrial membrane increases the efficiency of oxidative phosphorylation independently of enzyme deficit.     

Autophagy in obesity and atherosclerosis: Interrelationships between cholesterol homeostasis,lipoprotein metabolism and autophagy in macrophages and other systems

The incidence of diseases characterized by a dysregulation of lipid metabolism such as obesity, diabetes and atherosclerosis is rising at alarming rates, driving research to uncover new therapies to manage dyslipidemias and resolve the metabolic syndrome conundrum. Autophagy and lipid homeostasis – both ancient cellular pathways – have seemingly co-evolved to share common regulatory elements, and autophagy has emerged as a prominent mechanism involved in the regulation of lipid metabolism. This review highlights recent findings on the role of autophagy in the regulation of cellular cholesterol homeostasis and lipoprotein metabolism, with special emphasis on macrophages. From modulation of inflammation to regulation of cellular cholesterol levels, a protective role for autophagy in atherosclerosis is emerging. The manipulation of autophagic activity represents a new possible therapeutic approach for the treatment complex metabolic disorders such as obesity and the metabolic syndrome.     

Coenzyme Q10 as a possible treatment for neurodegenerative diseases

Coenzyme Q 10 (CoQ 10 ) is an essential cofactor of the electron transport gene as well as an important antioxidant, which is particularly effective within mitochondria. A number of prior studies have shown that it can exert efficacy in treating patients with known mitochondrial disorders. We investigated the potential usefulness of coenzyme Q 10 in animal models of Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD). It has been demonstrated that CoQ 10 can protect against striatal lesions produced by the mitochondrial toxins malonate and 3-nitropropionic acid. These toxins have been utilized to model the striatal pathology, which occurs in HD. It also protects against 1-methyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity in mice. CoQ 10 significantly extended survival in a transgenic mouse model of ALS. CoQ 10 can significantly extend survival, delay motor deficits and delay weight loss and attenuate the development of striatal atrophy in a transgenic mouse model of HD. In this mouse model, it showed additive efficacy when combined with the N -methyl- d -aspartate (NMDA) receptor antagonist, remacemide. CoQ 10 is presently being studied as a potential treatment for early PD as well as in combination with remacemide as a potential treatment for HD.