Prolonged intake of coenzyme Q10 impairs cognitive functions in mice

Effectiveness of coenzyme Q10 on learning and memory and synaptic plasticity impairment in an aged Aβ-induced rat model of Alzheimer's disease: a behavioral, biochemical, and electrophysiological study

RATIONALE

Aging is the major risk factor for Alzheimer's disease (AD), and cognitive and memory impairments are common among the elderly. Interestingly, coenzyme Q10 (Q10) levels decline in the brain of aging animals. Q10 is a substantial antioxidant substance, which has an important role in the mitochondria.

OBJECTIVE

We assessed the possible effects of Q10 on learning and memory and synaptic plasticity in aged β-amyloid (Aβ)-induced AD rats.

METHODS

In this study, 40 Wistar rats (24-36 months old; 360-450 g) were randomly assigned to four groups (n = 10 rats/group)-group I: control, group II: Aβ, group III: Q10; 50 mg/kg, and group IV: Q10+Aβ. Q10 was administered orally by gavage daily for 4 weeks before the Aβ injection. The cognitive function and learning and memory of the rats were measured by the novel object recognition (NOR), Morris water maze (MWM), and passive avoidance learning (PAL) tests. Finally, malondialdehyde (MDA), total antioxidant capacity (TAC), total thiol group (TTG), and total oxidant status (TOS) were measured.

RESULTS

Q10 improved the Aβ-related decrease in the discrimination index in the NOR test, spatial learning and memory in the MWM test, passive avoidance learning and memory in the PAL test, and long-term potentiation (LTP) impairment in the hippocampal PP-DG pathway in aged rats. In addition, Aβ injection significantly increased serum MDA and TOS levels. Q10, however, significantly reversed these parameters and also increased TAC and TTG levels in the Aβ+Q10 group.

CONCLUSIONS

Our experimental findings suggest that Q10 supplementation can suppress the progression of neurodegeneration that otherwise impairs learning and memory and reduces synaptic plasticity in our experimental animals. Therefore, similar supplemental Q10 treatment given to humans with AD could possibly provide them a better quality of life.

Coenzyme Q10 and Dementia: A Systematic Review

It is well known that coenzyme Q₁₀ (CoQ₁₀) has important antioxidant properties. Because one of the main mechanisms involved in the pathogenesis of Alzheimer's disease (AD) and other neurodegenerative diseases is oxidative stress, analysis of the concentrations of CoQ₁₀ in different tissues of AD patients and with other dementia syndromes and the possible therapeutic role of CoQ₁₀ in AD have been addressed in several studies. We performed a systematic review and a meta-analysis of these studies measuring tissue CoQ₁₀ levels in patients with dementia and controls which showed that, compared with controls, AD patients had similar serum/plasma CoQ₁₀ levels. We also revised the possible therapeutic effects of CoQ₁₀ in experimental models of AD and other dementias (which showed important neuroprotective effects of coenzyme Q₁₀) and in humans with AD, other dementias, and mild cognitive impairment (with inconclusive results). The potential role of CoQ₁₀ treatment in AD and in improving memory in aged rodents shown in experimental models deserves future studies in patients with AD, other causes of dementia, and mild cognitive impairment.

Coenzyme Q10 Levels Associated With Cognitive Functioning and Executive Function in Older Adults

Brain deterioration with age is associated with inflammation and oxidative stress that result in structural and functional changes. Recent studies have indicated that coenzyme Q10 (CoQ10) is associated with neurological oxidative stress and cognitive impairment. Studies with older people have shown a relationship between neurodegenerative diseases and CoQ10 levels. However, no studies have analyzed the relationship between CoQ10 and cognitive functioning in older adults. The aim of this study was to analyze the association between CoQ10 and cognitive functioning in an older adult sample, controlling for other factors that may influence aging, such as the level of physical activity and nutritional status. The sample consisted of 64 older adults aged 65-99 years (76.67 ± 8.16 years), among whom 48 were women (75%). The participants were recruited among those who attended community centers to voluntarily participate in leisure activities. According to previous studies, physical activity and nutritional status are positively associated with cognitive functioning. However, the main finding of this study was that plasma CoQ10, controlling for other measures, was significantly associated with cognitive functioning and executive function. The current findings suggest that a decline in cognitive capacities may be related to reduced antioxidant defenses, as reflected by low CoQ10 levels in older adults.

Sex differences in neurobehavioral consequences of methamphetamine exposure in adult mice

RATIONALE

Recreational and medical use of stimulants is increasing, and their use may increase susceptibility to aging and promote neurobehavioral impairments. The long-term consequences of these psychostimulants and how they interact with age have not been fully studied.

OBJECTIVES

Our study investigated whether chronic exposure to the prototypical psychostimulant, methamphetamine (METH), at doses designed to emulate human therapeutic dosing, would confer a pro-oxidizing redox shift promoting long-lasting neurobehavioral impairments.

METHODS

Groups of 4-month-old male and female C57BL/6 J mice were administered non-contingent intraperitoneal injections of either saline or METH (1.4 mg/kg) twice a day for 4 weeks. Mice were randomly assigned to one experimental group: (i) short-term cognitive assessments (at 5 months), (ii) long-term cognitive assessments (at 9.5 months), and (ii) longitudinal motor assessments (at 5, 7, and 9 months). Brain regions were assessed for oxidative stress and markers of neurotoxicity after behavior testing.

RESULTS

Chronic METH exposure induced short-term effects on associative memory, gait speed, dopamine (DA) signaling, astrogliosis in females, and spatial learning and memory, balance, DA signaling, and excitotoxicity in males. There were no long-term effects of chronic METH on cognition; however, it decreased markers of excitotoxicity in the striatum and exacerbated age-associated motor impairments in males.

CONCLUSION

In conclusion, cognitive and motor functions were differentially and sex-dependently affected by METH exposure, and oxidative stress did not seem to play a role in the observed behavioral outcomes. Future studies are necessary to continue exploring the long-term neurobehavioral consequences of drug use in both sexes and the relationship between aging and drugs.

The Role of Antioxidants in the Interplay between Oxidative Stress and Senescence

Cellular senescence is an irreversible state of cell cycle arrest occurring in response to stressful stimuli, such as telomere attrition, DNA damage, reactive oxygen species, and oncogenic proteins. Although beneficial and protective in several physiological processes, an excessive senescent cell burden has been involved in various pathological conditions including aging, tissue dysfunction and chronic diseases. Oxidative stress (OS) can drive senescence due to a loss of balance between pro-oxidant stimuli and antioxidant defences. Therefore, the identification and characterization of antioxidant compounds capable of preventing or counteracting the senescent phenotype is of major interest. However, despite the considerable number of studies, a comprehensive overview of the main antioxidant molecules capable of counteracting OS-induced senescence is still lacking. Here, besides a brief description of the molecular mechanisms implicated in OS-mediated aging, we review and discuss the role of enzymes, mitochondria-targeting compounds, vitamins, carotenoids, organosulfur compounds, nitrogen non-protein molecules, minerals, flavonoids, and non-flavonoids as antioxidant compounds with an anti-aging potential, therefore offering insights into innovative lifespan-extending approaches.

A Double-Pronged Sword: XJB-5-131 Is a Suppressor of Somatic Instability and Toxicity in Huntington's Disease

Due to large increases in the elderly populations across the world, age-related diseases are expected to expand dramatically in the coming years. Among these, neurodegenerative diseases will be among the most devastating in terms of their emotional and economic impact on patients, their families, and associated subsidized health costs. There is no currently available cure or rescue for dying brain cells. Viable therapeutics for any of these disorders would be a breakthrough and provide relief for the large number of affected patients and their families. Neurodegeneration is accompanied by elevated oxidative damage and inflammation. While natural antioxidants have largely failed in clinical trials, preclinical phenotyping of the unnatural, mitochondrial targeted nitroxide, XJB-5-131, bodes well for further translational development in advanced animal models or in humans. Here we consider the usefulness of synthetic antioxidants for the treatment of Huntington's disease. The mitochondrial targeting properties of XJB-5-131 have great promise. It is both an electron scavenger and an antioxidant, reducing both somatic expansion and toxicity simultaneously through the same redox mechanism. By quenching reactive oxygen species, XJB-5-131 breaks the cycle between the rise in oxidative damage during disease progression and the somatic growth of the CAG repeat which depends on oxidation.

Therapeutic Potential and Immunomodulatory Role of Coenzyme Q10 and Its Analogues in Systemic Autoimmune Diseases

Coenzyme Q₁₀ (CoQ₁₀) is a mitochondrial electron carrier and a powerful lipophilic antioxidant located in membranes and plasma lipoproteins. CoQ₁₀ is endogenously synthesized and obtained from the diet, which has raised interest in its therapeutic potential against pathologies related to mitochondrial dysfunction and enhanced oxidative stress. Novel formulations of solubilized CoQ₁₀ and the stabilization of reduced CoQ₁₀ (ubiquinol) have improved its bioavailability and efficacy. Synthetic analogues with increased solubility, such as idebenone, or accumulated selectively in mitochondria, such as MitoQ, have also demonstrated promising properties. CoQ₁₀ has shown beneficial effects in autoimmune diseases. Leukocytes from antiphospholipid syndrome (APS) patients exhibit an oxidative perturbation closely related to the prothrombotic status. In vivo ubiquinol supplementation in APS modulated the overexpression of inflammatory and thrombotic risk-markers. Mitochondrial abnormalities also contribute to immune dysregulation and organ damage in systemic lupus erythematosus (SLE). Idebenone and MitoQ improved clinical and immunological features of lupus-like disease in mice. Clinical trials and experimental models have further demonstrated a therapeutic role for CoQ₁₀ in Rheumatoid Arthritis, multiple sclerosis and type 1 diabetes. This review summarizes the effects of CoQ₁₀ and its analogs in modulating processes involved in autoimmune disorders, highlighting the potential of these therapeutic approaches for patients with immune-mediated diseases.

Secondary coenzyme Q deficiency in neurological disorders

Coenzyme Q (CoQ) is a ubiquitous lipid serving essential cellular functions. It is the only component of the mitochondrial respiratory chain that can be exogenously absorbed. Here, we provide an overview of current knowledge, controversies, and open questions about CoQ intracellular and tissue distribution, in particular in brain and skeletal muscle. We discuss human neurological diseases and mouse models associated with secondary CoQ deficiency in these tissues and highlight pharmacokinetic and anatomical challenges in exogenous CoQ biodistribution, recent improvements in CoQ formulations and imaging, as well as alternative therapeutical strategies to CoQ supplementation. The last section proposes possible mechanisms underlying secondary CoQ deficiency in human diseases with emphasis on neurological and neuromuscular disorders.

Longevity and Cause of Death in Male Wistar Rats Fed Lifelong Diets Based on Virgin Olive Oil, Sunflower Oil, or Fish Oil

Extending life by delaying the aging process has been proven to be the most effective way to fight multiple chronic diseases in elderly adults. Evidence suggests that longevity is inversely related to unsaturation of membrane phospholipids. This study investigated how different unsaturated dietary fats affect life span and cause of death in male Wistar rats fed diets based on virgin olive oil (V), sunflower oil (S), or fish oil (F), which were supplemented or not with Coenzyme Q10 (CoQ10). Previous results suggest that individual longevity and survival probability at different ages may be modulated by an appropriate dietary fat treatment. Lifelong feeding with V or F diets would reduce death probability compared to feeding with S diet at certain ages, although the effects of V diet would be maintained for most of life. Furthermore, the addition of lower amounts of CoQ10 reduced mortality associated with S diet, but CoQ10 had no effect on survival when combined with virgin olive oil or fish oil. Supplementation with low doses of CoQ10 failed to increase the maximum life span potential of rats fed a V or F diet. No clear evidence showing that monounsaturated fatty acids, n-3 polyunsaturated fatty acids, or CoQ10 exerted the observed effects by modulating the rate of aging has been found.

Preparation of Key Intermediates for the Syntheses of Coenzyme Q10 and Derivatives by Cross-Metathesis Reactions

An alternative catalytic strategy for the preparation of benzylmethacrylate esters, key intermediates in the synthesis of coenzyme Q₁₀ and derivatives, was reported. This strategy avoided undesirable stoichiometric reduction/oxidation processes by utilizing the catalytic formation of allylarenes and then cross-metathesis to selectively form E-benzylmethacrylate esters with good yields (58–64%) and complete E-selectivity. The ester intermediates were reduced to common key benzylallylic alcohols (90–92% yield), which were subsequently used in the formal syntheses of coenzyme Q₁₀ and one derivative.

Effect of coenzyme Q10 supplementation on diabetes induced memory deficits in rats

The main objective of current work was to determine the effects of low and high dose supplementation with coenzyme Q10 (CoQ10) on spatial learning and memory in rats with streptozotocin (STZ)-induced diabetes. Male Wistar rats (weighing 220 ± 10) were randomly divided into six groups: (i) Control (Con, n = 8); (ii) Control+ Low dose of CoQ10 (100 mg/kg) (CLD, n = 10); (iii) Control+ high dose of CoQ10 (600 mg/kg) (CHD, n = 10); (iv) Diabetic (D, n = 10); (v) Diabetic + Low dose of CoQ10 (100 mg/kg) (DLD, n = 10); (vi) Diabetic + high dose of CoQ10 (600 mg/kg) (DHD, n = 10). Diabetes was induced by a single intraperitoneal injection of 50 mg/kg STZ. CoQ10 was administered intragastrically by gavage once a day for 90 days. After 90 days, Morris water maze (MWM) task was used to evaluate the spatial learning and memory in rats. Diabetic animals showed a slower rate of acquisition with respect to the control animals [F (1, 51) = 92.81, P < 0.0001, two-way ANOVA]. High dose (but no low dose) supplementation with CoQ10 could attenuate deteriorative effect of diabetes on memory acquisition. Diabetic animals which received CoQ10 (600 mg/kg) show a considerable decrease in escape latency and traveled distance compared to diabetic animals (p < 0.05, two-way ANOVA,). The present study has shown that low dose supplementation with CoQ10 in diabetic rats failed to improve deficits in cognitive function but high dose supplementation with CoQ10 reversed diabetes-related declines in spatial learning.

Evidence and mechanisms for statin-induced cognitive decline

Introduction

Statin drugs have become the most highly prescribed drugs for cardiovascular disease. However, there is disagreement as to the existence of adverse effects of statin administration on cognitive function. Therefore, it is important to better understand the effects of statins on cognition and possible mechanisms of these effects.

Areas covered

We analyzed relevant studies of the relationship between cognitive performance and statin and usage. We included articles published between 2018 and 1992. We identified three randomized trials, one observational study and 66 case reports that provided credible evidence of statin-induced cognitive impairment. We also identified seven randomized trials and two observational studies reporting no significant evidence of statin-induced cognitive impairment.

Expert opinion

We found methodological differences that may have contributed to the divergence of these results. Evaluation of all these studies indicated that statin-associated cognitive decline is a real entity. Likely mechanisms to explain the adverse effects include 1. Reduction of synthesis of coenzyme Q10 with consequent increasing oxidative stress and reduction of cerebral energy production; 2. Depletion of central nervous system myelin by inhibition of cholesterol synthesis. We conclude that statin-induced cognitive decline does exist, needs to be better recognized and requires more studies of prevention and treatment.

Influence of Chronic Coenzyme Q10 Supplementation on Cognitive Function, Learning, and Memory in Healthy and Diabetic Middle-Aged Rats

Diabetes mellitus can induce impairment in learning and memory. Cognitive and memory deficits are common in older adults and especially in those with diabetes. This is mainly because of hyperglycemia, oxidative stress, and vascular abnormalities. Coenzyme Q10 (CoQ10) can decrease oxidative stress, hyperglycemia, and inflammatory markers, and improve vascular function. Therefore, the aim of the present study was to investigate the possible effects of CoQ10 on cognitive function, learning, and memory in middle-aged healthy and diabetic rats. Adult middle-aged male Wistar rats (390-460 g, 12-13 months old) were divided into 6 experimental groups. Diabetes was induced by a single i.p. injection of streptozotocin (60 mg/kg). CoQ10 (20 or 120 mg/kg, orally by gavage) was administered for 45 days. The cognitive function and learning memory of rats were evaluated using novel object recognition (NOR) and passive avoidance tests. The discrimination index of the NOR test in the diabetic groups receiving CoQ10 (20 or 120 mg/kg) and the healthy group receiving CoQ10 (120 mg/kg) was significantly higher than that in the control group. In addition, the step through latency was significantly longer and the time spent in the dark compartment was significantly shorter in the diabetic groups receiving CoQ10 than in the control group. CoQ10 supplementation can improve learning and memory deficits induced by diabetes in older subjects. In addition, CoQ10 at higher doses can improve cognitive performance in older healthy subjects.

Supplementation with N-Acetyl Cysteine Affects Motor and Cognitive Function in Young but Not Old Mice

BACKGROUND

N-acetyl cysteine (NAC) is a thiolic antioxidant that is thought to increase cellular glutathione (GSH) by augmenting the concentration of available cysteine, an essential precursor to GSH production. Manipulating redox status can affect brain function, and NAC intake has been associated with improving brain function in models of neurodegenerative diseases.

OBJECTIVES

The objective of the study was to determine if short-term dietary supplementation with NAC could ameliorate functional impairment associated with aging.

METHODS

C57BL/6J male mice aged 6, 12, or 24 mo were fed a control diet or the control diet supplemented with 0.3% NAC for a total of 12 wk. After 4 wk of dietary supplementation, mice began a series of behavioral tests to measure spontaneous activity (locomotor activity test), psychomotor performance (bridge-walking and coordinated running), and cognitive capacity (Morris water maze and discriminated active avoidance). The performance of the mice on these tests was analyzed through the use of analyses of variance with Age and Diet as factors.

RESULTS

Supplementation of NAC improved peak motor performance in a coordinated running task by 14% (P < 0.05), and increased the time spent around the platform by 24% in a Morris water maze at age 6 mo. However, the supplementation had no to minimal effect on the motor and cognitive functions of 12- and 24-mo-old mice.

CONCLUSIONS

The findings of this preclinical study support the claim that NAC has nootropic properties in 6-mo-old mice, but suggest that it may not be useful for improving motor and cognitive impairments in older mice.

Protective Effects of Co-Enzyme Q10 on Thioacetamide-Induced Acute Liver Damage and Its Correlation With Behavioral, Biochemical, and Pathological Factors

Background

Acute liver damage may be followed by biochemical, behavioral, and pathological alterations, which can result in serious complications and even death.

Objectives

In this experimental study we determined whether coenzyme Q10 (CoQ10), a common supplementary medicine known to have protective, antioxidative, and anti-inflammatory effects in cells, has any protective effect against thioacetamide (TAA)-induced liver damage and its related neurobehavioral alterations in rats.

Materials and Methods

In this experimental study forty-eight Wistar rats were divided randomly into four groups (n = 12): C1 was the control group; C2 received a single-dose of TAA (350mg/kg; intraperitoneally) without any other treatment; E1 received TAA + 5 mg/kg CoQ10 (intraperitoneally); and E2 received TAA + 10 mg/kg CoQ10. After sacrificing the rats, liver enzymes and plasma-ammonia (NH4) were measured and histopathological analyses of the livers were carried out. Elevated-plus-maze, open-field, and forced-swimming tests were also performed to investigate behavioral correlations.

Results

The serum levels of alanine-aminotransferase (ALT), aspartate-aminotransferase (AST), and NH4 show significant increases (P < 0.05). The groups treated with CoQ10 were shown to have significantly lower clinical grade of encephalopathy (P = 0.001), higher locomotor activity (P = 0.000), and lower levels of depression (P = 0.000). Furthermore, it was also shown that CoQ10 treatment may lead to significant decreases in scores of centrilobular necrosis, apoptosis, inflammatory cell infiltration, vacuolization, and liver necrosis (P < 0.05).

Conclusions

Overall, CoQ10 was determined to have positive effects on liver injury and its related behavioral and biochemical changes.

Coenzyme Q and Its Role in the Dietary Therapy against Aging

Coenzyme Q (CoQ) is a naturally occurring molecule located in the hydrophobic domain of the phospholipid bilayer of all biological membranes. Shortly after being discovered, it was recognized as an essential electron transport chain component in mitochondria where it is particularly abundant. Since then, more additional roles in cell physiology have been reported, including antioxidant, signaling, death prevention, and others. It is known that all cells are able to synthesize functionally sufficient amounts of CoQ under normal physiological conditions. However, CoQ is a molecule found in different dietary sources, which can be taken up and incorporated into biological membranes. It is known that mitochondria have a close relationship with the aging process. Additionally, delaying the aging process through diet has aroused the interest of scientists for many years. These observations have stimulated investigation of the anti-aging potential of CoQ and its possible use in dietary therapies to alleviate the effects of aging. In this context, the present review focus on the current knowledge and evidence the roles of CoQ cells, its relationship with aging, and possible implications of dietary CoQ in relation to aging, lifespan or age-related diseases.

Mitochondrial targeting of XJB-5-131 attenuates or improves pathophysiology in HdhQ150 animals with well-developed disease phenotypes

Oxidative damage to mitochondria (MT) is a major mechanism for aging and neurodegeneration. We have developed a novel synthetic antioxidant, XJB-5-131, which directly targets MT, the primary site and primary target of oxidative damage. XJB-5-131 prevents the onset of motor decline in an HdhQ(150/150) mouse model for Huntington's disease (HD) if treatment starts early. Here, we report that XJB-5-131 attenuates or reverses disease progression if treatment occurs after disease onset. In animals with well-developed pathology, XJB-5-131 promotes weight gain, prevents neuronal death, reduces oxidative damage in neurons, suppresses the decline of motor performance or improves it, and reduces a graying phenotype in treated HdhQ(150/150) animals relative to matched littermate controls. XJB-5-131 holds promise as a clinical candidate for the treatment of HD.

Coenzyme Q10 and α-tocopherol reversed age-associated functional impairments in mice

The purpose of this study was to determine if intake of the antioxidants coenzyme Q10 (CoQ10) or α-tocopherol (Toc), either alone or in combination, could ameliorate cognitive and psychomotor impairments of aged mice, as well as reduce oxidative burden in tissues. For a period of 10 weeks, male C57BL/6J mice (3 or 18 months) were fed either a control diet, or one of three diets supplemented with Toc, CoQ10 or their combination, and were tested for cognitive and psychomotor functions. Old mice on the Toc or Toc/CoQ10 diets showed improved coordinated running performance. Mice on the diet containing Toc/CoQ10 demonstrated improved performance in the discriminated avoidance task. CoQ10 and Toc alone also resulted in improved performance, albeit to a lesser degree. Protein damage was decreased especially when the mice received Toc+CoQ10 combination. Overall, these results suggest that, Toc and CoQ supplementation can ameliorate age-related impairment and reduce protein oxidation. Moreover, concurrent supplementation of CoQ10 and Toc may be more effective than either antioxidant alone.

Exogenous administration of coenzyme Q10 restores mitochondrial oxygen consumption in the aged mouse brain

The level of coenzyme Q (CoQ) has been shown to decrease in an age-dependent manner in several types of animals. However, whether CoQ-dependent mitochondrial function decreases with aging remains unclear. In this study, we found that mitochondrial complexes I and II exhibited significantly reduced oxygen consumption in the brains of aged male mice relative to young male mice, although this decrease in oxygen consumption was not accompanied by a change in the CoQ9 or CoQ10 content. Nevertheless, the administration of exogenous CoQ10 significantly increased the content of CoQ10 and CoQ9 in the brain mitochondria of aged male mice and restored complex I- and II-mediated oxygen consumption to levels comparable to those observed in young mice. These results indicate that mitochondrial oxygen consumption in the brain decreases in aged male mice. Furthermore, these results suggest that exogenous CoQ10 restores mitochondrial oxygen use to levels equivalent to those observed in young mice.

Coenzyme Q(10) supplementation reverses age-related impairments in spatial learning and lowers protein oxidation

Coenzyme Q10 (CoQ) is widely available as a dietary supplement and remains under consideration as a treatment for age-associated neurodegenerative conditions. However, no studies have determined if supplementation, initiated relatively late in life, could have beneficial effects on mild functional impairments associated with normal brain aging. Accordingly, the current study assessed the effect of CoQ intake in older mice for which cognitive and psychomotor impairments were already evident. Separate groups of young (3.5 months) and relatively old mice (17.5 months) were fed a control diet or a diet supplemented with low (0.72 mg/g) or high (2.81 mg/g) concentrations of CoQ for 15 weeks. After 6 weeks, the mice were given tests for spatial learning (Morris water maze), spontaneous locomotor activity, motor coordination, and startle reflex. Age-related impairments in cognitive and psychomotor functions were evident in the 17.5-month-old mice fed the control diet, and the low-CoQ diet failed to affect any aspect of the impaired performance. However, in the Morris water maze test, old mice on the high-CoQ diet swam to the safe platform with greater efficiency than the mice on the control diet. The old mice supplemented with the high-CoQ diet did not show improvement when spatial performance was measured using probe trials and failed to show improvement in other tests of behavioral performance. Protein oxidative damage was decreased in the mitochondria from the heart, liver, and skeletal muscle of the high-CoQ-supplemented mice and, to some extent, in the brain mitochondria. Contrasting with the deleterious effect of long-term CoQ supplementation initiated during young adulthood previously published, this study suggests that CoQ improves spatial learning and attenuates oxidative damage when administered in relatively high doses and delayed until early senescence, after age-related declines have occurred. Thus, in individuals with age-associated symptoms of cognitive decline, high-CoQ intake may be beneficial.

Targeting of XJB-5-131 to mitochondria suppresses oxidative DNA damage and motor decline in a mouse model of Huntington's disease

Oxidative damage and mitochondrial dysfunction are implicated in aging and age-related neurodegenerative diseases, including Huntington's disease (HD). Many naturally occurring antioxidants have been tested for their ability to correct for deleterious effects of reactive oxygen species, but often they lack specificity, are tissue variable, and have marginal efficacy in human clinical trials. To increase specificity and efficacy, we have designed a synthetic antioxidant, XJB-5-131, to target mitochondria. We demonstrate in a mouse model of HD that XJB-5-131 has remarkably beneficial effects. XJB-5-131 reduces oxidative damage to mitochondrial DNA, maintains mitochondrial DNA copy number, suppresses motor decline and weight loss, enhances neuronal survival, and improves mitochondrial function. The findings poise XJB-5-131 as a promising therapeutic compound.

The submitochondrial distribution of ubiquinone affects respiration in long-lived Mclk1+/- mice

MCLK1 and COQ3 are mitochondrial enzymes necessary for ubiquinone biosynthesis, but only MCLK1 also regulates the partitioning of ubiquinone between mitochondrial membranes and affects longevity in mice.

Mclk1 (also known as Coq7) and Coq3 code for mitochondrial enzymes implicated in the biosynthetic pathway of ubiquinone (coenzyme Q or UQ). Mclk1^+/− mice are long-lived but have dysfunctional mitochondria. This phenotype remains unexplained, as no changes in UQ content were observed in these mutants. By producing highly purified submitochondrial fractions, we report here that Mclk1^+/− mice present a unique mitochondrial UQ profile that was characterized by decreased UQ levels in the inner membrane coupled with increased UQ in the outer membrane. Dietary-supplemented UQ₁₀ was actively incorporated in both mitochondrial membranes, and this was sufficient to reverse mutant mitochondrial phenotypes. Further, although homozygous Coq3 mutants die as embryos like Mclk1 homozygous null mice, Coq3^+/− mice had a normal lifespan and were free of detectable defects in mitochondrial function or ubiquinone distribution. These findings indicate that MCLK1 regulates both UQ synthesis and distribution within mitochondrial membranes.

Enhancement of cognitive function in models of brain disease through environmental enrichment and physical activity

This review will provide an overview of the non-drug based approaches that have been demonstrated to enhance cognitive function of the compromised brain, primarily focussed on the two most widely adopted paradigms of environmental enrichment and enhanced physical exercise. Environmental enrichment involves the generation of novelty and complexity in animal housing conditions which facilitates enhanced sensory and cognitive stimulation as well as physical activity. In a wide variety of animal models of brain disorders, environmental enrichment and exercise have been found to have beneficial effects, including cognitive enhancement, delayed disease onset, enhanced cellular plasticity and associated molecular processes. Potential cellular and molecular mechanisms will also be discussed, which have relevance for the future development of 'enviromimetics', drugs which could mimic or enhance the beneficial effects of environmental stimulation. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Protective and restorative effects of a Commiphora mukul gum resin and triheptanoin preparation on the CCL-110 skin fibroblast cell line

Coenzyme Q10 (CoQ10) is a major ingredient in skin care products because of its anti-wrinkle effects, although it has some side effects especially at higher amounts. In this study, we compare the anti-wrinkle related properties of CoQ10 and a proprietary Commiphora mukul gum resin (guggul) and triheptanoin preparation (GU-TC7). GU-TC7 is prepared with a supercritical CO₂-co-solvent extraction with ethanol, standardized to 2% guggulsterones and triheptanoin, a triglyceride composed of three 7-carbon fatty acids. Treatment of CCL-110 skin fibroblasts with GU-TC7 demonstrates a mild proliferative effect compared to CoQ10 and increased type I collagen synthesis. Additionally, GU-TC7 inhibited matrix metalloproteinase-1 (MMP-1) expression in a dose-dependent manner at 20-100 μg mL⁻¹ and inhibited human elastase expression by more than 50% as compared to no elastase inhibition with CoQ10 treatment. These results suggest that GU-TC7 possesses properties that are applicable to the treatment of wrinkles and may be considered for its further evaluation in skin care products.

Reactive oxygen species in the regulation of synaptic plasticity and memory

The brain is a metabolically active organ exhibiting high oxygen consumption and robust production of reactive oxygen species (ROS). The large amounts of ROS are kept in check by an elaborate network of antioxidants, which sometimes fail and lead to neuronal oxidative stress. Thus, ROS are typically categorized as neurotoxic molecules and typically exert their detrimental effects via oxidation of essential macromolecules such as enzymes and cytoskeletal proteins. Most importantly, excessive ROS are associated with decreased performance in cognitive function. However, at physiological concentrations, ROS are involved in functional changes necessary for synaptic plasticity and hence, for normal cognitive function. The fine line of role reversal of ROS from good molecules to bad molecules is far from being fully understood. This review focuses on identifying the multiple sources of ROS in the mammalian nervous system and on presenting evidence for the critical and essential role of ROS in synaptic plasticity and memory. The review also shows that the inability to restrain either age- or pathology-related increases in ROS levels leads to opposite, detrimental effects that are involved in impairments in synaptic plasticity and memory function.

Coenzyme Q plays opposing roles on bacteria/fungi and viruses in Drosophila innate immunity

Coenzyme Q (CoQ or ubiquinone) is a lipid-soluble component of virtually all types of cell membranes and has been shown to play multiple metabolic functions. Several clinical diseases including encephalomyopathy, cerebellar ataxia and isolated myopathy were shown to be associated with CoQ deficiency. However, the role of CoQ in immunity has not been defined. In the present study, we showed that flies defective in CoQ biosynthetic gene coq2 were more susceptible to bacterial and fungal infections, while were more resistant to viruses. We found that Drosophila contained both CoQ9 and CoQ10, and food supplement of CoQ10 could partially rescue the impaired immune functions of coq2 mutants. Surprisingly, wild-type flies fed CoQ10 became more susceptible to viral infection, which suggested that extra caution should be taken when using CoQ10 as a food supplement. We further showed that CoQ was essential for normal induction of anti-microbial peptides and amplification of viruses. Our work determined CoQ content in Drosophila and described its function in immunity for the first time.

Mitochondrial response to controlled nutrition in health and disease

Mitochondria exert crucial physiological functions that create complex links among nutrition, health, and disease. While mitochondrial dysfunction with subsequent impairment of oxidative phosphorylation (OXPHOS) is the hallmark of the rare inherited OXPHOS diseases, OXPHOS dysfunction also plays a central role in the pathophysiology of common conditions such as type 2 diabetes and various neurodegenerative disorders. Dietary interventions, especially calorie restriction, have been shown to improve the course of these diseases and to extend the lifespan. Few data are available on the impact of nutraceuticals (macronutrients, vitamins, and cofactors) on primary inherited OXPHOS diseases. This review presents recent knowledge about the impact of nutritional modulation on mitochondria and lifespan regulation and about the development of potential treatments for mitochondrial dysfunction diseases.

Ageing and neurodegenerative diseases

Ageing, which all creatures must encounter, is a challenge to every living organism. In the human body, it is estimated that cell division and metabolism occurs exuberantly until about 25 years of age. Beyond this age, subsidiary products of metabolism and cell damage accumulate, and the phenotypes of ageing appear, causing disease formation. Among these age-related diseases, neurodegenerative diseases have drawn a lot of attention due to their irreversibility, lack of effective treatment, and accompanied social and economical burdens. In seeking to ameliorate ageing and age-related diseases, the search for anti-ageing drugs has been of much interest. Numerous studies have shown that the plant polyphenol, resveratrol (3,5,4'-trihydroxystilbene), extends the lifespan of several species, prevents age-related diseases, and possesses anti-inflammatory, and anti-cancer properties. The beneficial effects of resveratrol are believed to be associated with the activation of a longevity gene, SirT1. In this review, we discuss the pathogenesis of age-related neurodegenerative diseases including Alzheimer's disease, Parkinson's disease and cerebrovascular disease. The therapeutic potential of resveratrol, diet and the roles of stem cell therapy are discussed to provide a better understanding of the ageing mystery.

Therapeutic use of coenzyme Q10 and coenzyme Q10-related compounds and formulations

IMPORTANCE OF THE FIELD

Coenzyme Q(10) (CoQ(10)) is found in blood and in all organs. CoQ(10) deficiencies are due to autosomal recessive mutations, ageing-related oxidative stress and carcinogenesis processes, and also statin treatment. Many neurodegenerative disorders, diabetes, cancer and muscular and cardiovascular diseases have been associated with low CoQ(10) levels, as well as different ataxias and encephalomyopathies.

AREAS COVERED IN THIS REVIEW

We review the efficacy of a variety of commercial formulations which have been developed to solubilise CoQ(10) and promote its better absorption in vivo, and its use in the therapy of pathologies associated with low CoQ(10) levels, with emphasis in the results of the clinical trials. Also, we review the use of its analogues idebenone and MitoQ.

WHAT THE READER WILL GAIN

This review covers the most relevant aspects related with the therapeutic use of CoQ(10), including existing formulations and their effects on its bioavailability.

TAKE HOME MESSAGE

CoQ(10) does not cause serious adverse effects in humans and new formulations have been developed that increase CoQ(10) absorption. Oral CoQ(10) is a viable antioxidant strategy in many diseases, providing a significant to mild symptomatic benefit. Idebenone and MitoQ are promising substitutive CoQ(10)-related drugs which are well tolerated and safe.