Analysis of Coenzyme Q10 in muscle and fibroblasts for the diagnosis of CoQ10 deficiency syndromes

Metabolic, Mitochondrial, and Inflammatory Effects of Efavirenz, Emtricitabine, and Tenofovir Disoproxil Fumarate in Asymptomatic Antiretroviral-Naïve People with HIV

This study aimed to comprehensively assess the metabolic, mitochondrial, and inflammatory effects of first-line efavirenz, emtricitabine, and tenofovir disoproxil fumarate (EFV/FTC/TDF) single-tablet regimen (STR) relative to untreated asymptomatic HIV infection. To this end, we analyzed 29 people with HIV (PWH) treated for at least one year with this regimen vs. 33 antiretroviral-naïve PWH. Excellent therapeutic activity was accompanied by significant alterations in metabolic parameters. The treatment group showed increased plasmatic levels of glucose, total cholesterol and its fractions (LDL and HDL), triglycerides, and hepatic enzymes (GGT, ALP); conversely, bilirubin levels (total and indirect fraction) decreased in the treated cohort. Mitochondrial performance was preserved overall and treatment administration even promoted the recovery of mitochondrial DNA (mtDNA) content depleted by the virus, although this was not accompanied by the recovery in some of their encoded proteins (since cytochrome c oxidase II was significantly decreased). Inflammatory profile (TNFα, IL-6), ameliorated after treatment in accordance with viral reduction and the recovery of TNFα levels correlated to mtDNA cell restoration. Thus, although this regimen causes subclinical metabolic alterations, its antiviral and anti-inflammatory properties may be associated with partial improvement in mitochondrial function.

Primary Coenzyme Q10 Deficiency-Related Ataxias

Cerebellar ataxia is a neurological syndrome characterized by the imbalance (e.g., truncal ataxia, gait ataxia) and incoordination of limbs while executing a task (dysmetria), caused by the dysfunction of the cerebellum or its connections. It is frequently associated with other signs of cerebellar dysfunction, including abnormal eye movements, dysmetria, kinetic tremor, dysarthria, and/or dysphagia. Among the so-termed mitochondrial ataxias, variants in genes encoding steps of the coenzyme Q10 biosynthetic pathway represent a common cause of autosomal recessive primary coenzyme Q10 deficiencies (PCoQD)s. PCoQD is a potentially treatable condition; therefore, a correct and timely diagnosis is essential. After a brief presentation of the illustrative case of an Italian woman with this condition (due to a novel homozygous nonsense mutation in COQ8A), this article will review ataxias due to PCoQD.

Mutations of GEMIN5 are associated with coenzyme Q10 deficiency: long-term follow-up after treatment

GEMIN5 exerts key biological functions regulating pre-mRNAs intron removal to generate mature mRNAs. A series of patients were reported harboring mutations in GEMIN5. No treatments are currently available for this disease. We treated two of these patients with oral Coenzyme Q10 (CoQ10), which resulted in neurological improvements, although MRI abnormalities remained. Whole Exome Sequencing demonstrated compound heterozygosity at the GEMIN5 gene in both cases: Case one: p.Lys742* and p.Arg1016Cys; Case two: p.Arg1016Cys and p.Ser411Hisfs*6. Functional studies in fibroblasts revealed a decrease in CoQ10 biosynthesis compared to controls. Supplementation with exogenous CoQ10 restored it to control intracellular CoQ10 levels. Mitochondrial function was compromised, as indicated by the decrease in oxygen consumption, restored by CoQ10 supplementation. Transcriptomic analysis of GEMIN5 patients compared with controls showed general repression of genes involved in CoQ10 biosynthesis. In the rigor mortis defective flies, CoQ10 levels were decreased, and CoQ10 supplementation led to an improvement in the adult climbing assay performance, a reduction in the number of motionless flies, and partial restoration of survival. Overall, we report the association between GEMIN5 dysfunction and CoQ10 deficiency for the first time. This association opens the possibility of oral CoQ10 therapy, which is safe and has no observed side effects after long-term therapy.

Total and reduced/oxidized forms of coenzyme Q10 in fibroblasts of patients with mitochondrial disease

Coenzyme Q₁₀ (CoQ₁₀) is involved in ATP production through electron transfer in the mitochondrial respiratory chain complex. CoQ₁₀ receives electrons from respiratory chain complex I and II to become the reduced form, and then transfers electrons at complex III to become the oxidized form. The redox state of CoQ₁₀ has been reported to be a marker of the mitochondrial metabolic state, but to our knowledge, no reports have focused on the individual quantification of reduced and oxidized CoQ₁₀ or the ratio of reduced to total CoQ₁₀ (reduced/total CoQ₁₀) in patients with mitochondrial diseases. We measured reduced and oxidized CoQ₁₀ in skin fibroblasts from 24 mitochondrial disease patients, including 5 primary CoQ₁₀ deficiency patients and 10 respiratory chain complex deficiency patients, and determined the reduced/total CoQ₁₀ ratio. In primary CoQ₁₀ deficiency patients, total CoQ₁₀ levels were significantly decreased, however, the reduced/total CoQ₁₀ ratio was not changed. On the other hand, in mitochondrial disease patients other than primary CoQ₁₀ deficiency patients, total CoQ₁₀ levels did not decrease. However, the reduced/total CoQ₁₀ ratio in patients with respiratory chain complex IV and V deficiency was higher in comparison to those with respiratory chain complex I deficiency. Measurement of CoQ₁₀ in fibroblasts proved useful for the diagnosis of primary CoQ₁₀ deficiency. In addition, the reduced/total CoQ₁₀ ratio may reflect the metabolic status of mitochondrial disease.

Assessing Cellular Uptake of Exogenous Coenzyme Q10 into Human Skin Cells by X-ray Fluorescence Imaging

X-ray fluorescence (XRF) imaging is a highly sensitive non-invasive imaging method for detection of small element quantities in objects, from human-sized scales down to single-cell organelles, using various X-ray beam sizes. Our aim was to investigate the cellular uptake and distribution of Q₁₀, a highly conserved coenzyme with antioxidant and bioenergetic properties. Q₁₀ was labeled with iodine (I₂-Q₁₀) and individual primary human skin cells were scanned with nano-focused beams. Distribution of I₂-Q₁₀ molecules taken up inside the screened individual skin cells was measured, with a clear correlation between individual Q₁₀ uptake and cell size. Experiments revealed that labeling Q₁₀ with iodine causes no artificial side effects as a result of the labeling procedure itself, and thus is a perfect means of investigating bioavailability and distribution of Q₁₀ in cells. In summary, individual cellular Q₁₀ uptake was demonstrated by XRF, opening the path towards Q₁₀ multi-scale tracking for biodistribution studies.

A novel COQ7 mutation causing primarily neuromuscular pathology and its treatment options

Coenzyme Q₁₀ (CoQ₁₀) is necessary as electron transporter in mitochondrial respiration and other cellular functions. CoQ₁₀ is synthesized by all cells and defects in the synthesis pathway result in primary CoQ₁₀ deficiency that frequently leads to severe mitochondrial disease syndrome. CoQ₁₀ is exceedingly hydrophobic, insoluble, and poorly bioavailable, with the result that dietary CoQ₁₀ supplementation produces no or only minimal relief for patients. We studied a patient from Turkey and identified and characterized a new mutation in the CoQ₁₀ biosynthetic gene COQ7 (c.161G > A; p.Arg54Gln). We find that unexpected neuromuscular pathology can accompany CoQ₁₀ deficiency caused by a COQ7 mutation. We also show that by-passing the need for COQ7 by providing the unnatural precursor 2,4-dihydroxybenzoic acid, as has been proposed, is unlikely to be an effective and safe therapeutic option. In contrast, we show for the first time in human patient cells that the respiratory defect resulting from CoQ₁₀ deficiency is rescued by providing CoQ₁₀ formulated with caspofungin (CF/CoQ). Caspofungin is a clinically approved intravenous fungicide whose surfactant properties lead to CoQ₁₀ micellization, complete water solubilization, and efficient uptake by cells and organs in animal studies. These findings reinforce the possibility of using CF/CoQ in the clinical treatment of CoQ₁₀-deficient patients.

Technical Aspects of Coenzyme Q10 Analysis: Validation of a New HPLC-ED Method

The biochemical measurement of the CoQ status in different tissues can be performed using HPLC with electrochemical detection (ED). Because the production of the electrochemical cells used with the Coulochem series detectors was discontinued, we aimed to standardize a new HPLC-ED method with new equipment. We report all technical aspects, troubleshooting and its performance in different biological samples, including plasma, skeletal muscle homogenates, urine and cultured skin fibroblasts. Analytical variables (intra- and inter-assay precision, linearity, analytical measurement range, limit of quantification, limit of detection and accuracy) were validated in calibrators and plasma samples and displayed adequate results. The comparison of the results of a new ERNDIM external quality control (EQC) scheme for the plasma CoQ determination between HPLC-ED (Lab 1) and LC-MS/MS (Lab 2) methods shows that the results of the latter were slightly higher in most cases, although a good consistency was generally observed. In conclusion, the new method reported here showed a good analytical performance. The global quality of the EQC scheme results among different participants can be improved with the contribution of more laboratories.

Primary Coenzyme Q10 Deficiency-7 and Pathogenic COQ4 Variants: Clinical Presentation, Biochemical Analyses, and Treatment

Primary Coenzyme Q10 Deficiency-7 (COQ10D7) is a rare mitochondrial disorder caused by pathogenic COQ4 variants. In this review, we discuss the correlation of COQ4 genotypes, particularly the East Asian-specific c.370G > A variant, with the clinical presentations and therapeutic effectiveness of coenzyme Q10 supplementation from an exon-dependent perspective. Pathogenic COQ4 variants in exons 1–4 are associated with less life-threating presentations, late onset, responsiveness to CoQ10 therapy, and a relatively long lifespan. In contrast, pathogenic COQ4 variants in exons 5–7 are associated with early onset, unresponsiveness to CoQ10 therapy, and early death and are more fatal. Patients with the East Asian-specific c.370G > A variant displays intermediate disease severity with multi-systemic dysfunction, which is between that of the patients with variants in exons 1–4 and 5–7. The mechanism underlying this exon-dependent genotype-phenotype correlation may be associated with the structure and function of COQ4. Sex is shown unlikely to be associated with disease severity. While point-of-care high-throughput sequencing would be useful for the rapid diagnosis of pathogenic COQ4 variants, whereas biochemical analyses of the characteristic impairments in CoQ10 biosynthesis and mitochondrial respiratory chain activity, as well as the phenotypic rescue of the CoQ10 treatment, are necessary to confirm the pathogenicity of suspicious variants. In addition to CoQ10 derivatives, targeted drugs and gene therapy could be useful treatments for COQ10D7 depending on the in-depth functional investigations and the development of gene editing technologies. This review provides a fundamental reference for the sub-classification of COQ10D7 and aim to advance our knowledge of the pathogenesis, clinical diagnosis, and prognosis of this disease and possible interventions.

The Role of Nutrient Supplementation in the Management of Chronic Pain in Fibromyalgia: A Narrative Review

INTRODUCTION

The multifaceted clinical presentation of fibromyalgia (FM) supports the modern understanding of the disorder as a more global condition than one simply affecting pain sensation. The main pharmacologic therapies used clinically include anti-epileptics and anti-depressants. Conservative treatment options include exercise, myofascial release, psychotherapy, and nutrient supplementation.

METHODS

Narrative review.

RESULTS

Nutrient supplementation is a broadly investigated treatment modality as numerous deficiencies have been linked to FM. Additionally, a proposed link between gut microbiome patterns and chronic pain syndromes has led to studies investigating probiotics as a possible treatment. Despite positive results, much of the current evidence regarding this topic is of poor quality, with variable study designs, limited sample sizes, and lack of control groups.

CONCLUSIONS

The etiology of FM is complex, and has shown to be multi-factorial with genetics and environmental exposures lending influence into its development. Preliminary results are promising, however, much of the existing evidence regarding diet supplementation is of poor quality. Further, more robust studies are needed to fully elucidate the potential of this alternative therapeutic option.

The Impact of N-Acetyl Cysteine and Coenzyme Q10 Supplementation on Skeletal Muscle Antioxidants and Proteome in Fit Thoroughbred Horses

Horses have one of the highest skeletal muscle oxidative capacities amongst mammals, which, combined with a high glycolytic capacity, could perturb redox status during maximal exercise. We determined the effect of 30 d of oral coenzyme Q10 and N-acetyl-cysteine supplementation (NACQ) on muscle glutathione (GSH), cysteine, ROS, and coenzyme Q10 concentrations, and the muscle proteome, in seven maximally exercising Thoroughbred horses using a placebo and randomized cross-over design. Gluteal muscle biopsies were obtained the day before and 1 h after maximal exercise. Concentrations of GSH, cysteine, coenzyme Q10, and ROS were measured, and citrate synthase, glutathione peroxidase, and superoxide dismutase activities analyzed. GSH increased significantly 1 h post-exercise in the NACQ group (p = 0.022), whereas other antioxidant concentrations/activities were unchanged. TMT proteomic analysis revealed 40 differentially expressed proteins with NACQ out of 387 identified, including upregulation of 13 mitochondrial proteins (TCA cycle and NADPH production), 4 Z-disc proteins, and down regulation of 9 glycolytic proteins. NACQ supplementation significantly impacted muscle redox capacity after intense exercise by enhancing muscle glutathione concentrations and increasing expression of proteins involved in the uptake of glutathione into mitochondria and the NAPDH-associated reduction of oxidized glutathione, without any evident detrimental effects on performance.

Primary Coenzyme Q deficiencies: A literature review and online platform of clinical features to uncover genotype-phenotype correlations

Primary Coenzyme Q (CoQ) deficiencies are clinically heterogeneous conditions and lack clear genotype-phenotype correlations, complicating diagnosis and prognostic assessment. Here we present a compilation of all the symptoms and patients with primary CoQ deficiency described in the literature so far and analyse the most common clinical manifestations associated with pathogenic variants identified in the different COQ genes. In addition, we identified new associations between the age of onset of symptoms and different pathogenic variants, which could help to a better diagnosis and guided treatment. To make these results useable for clinicians, we created an online platform (https://coenzymeQbiology.github.io/clinic-CoQ-deficiency) about clinical manifestations of primary CoQ deficiency that will be periodically updated to incorporate new information published in the literature. Since CoQ primary deficiency is a rare disease, the available data are still limited, but as new patients are added over time, this tool could become a key resource for a more efficient diagnosis of this pathology.

CoQ10 protects against acetaminophen-induced liver injury by enhancing mitophagy

Coenzyme Q10 (CoQ10), which is a key cofactor of the electron transport chain in the mitochondria has shown many beneficial effects on liver diseases. However, the mechanisms of CoQ10 protective role on the acetaminophen (APAP)-induced liver injury are elusive and unclear. In this study, we further investigated the CoQ10 therapeutic effects on APAP-overdose liver injury. C57BL/6 J mice were intraperitoneally treated with APAP to induce liver injury. CoQ10 (5 mg/kg) was given to mice at 1.5 h after APAP treatment. The results showed that hepatic CoQ10 levels were decreased during the APAP-induced hepatotoxicity and preceded serum ALT elevation. Treatment of CoQ10 significantly improved the liver injury induced by APAP. Moreover, CoQ10 treatment decreased the ROS levels and promoted the antioxidative related gene expression in APAP overdose mice. Importantly, results showed that even though CoQ10 had no effects on the mtDNA copy number and the expression of genes related to mitochondrial biogenesis, it significantly improved the mitochondrial complex I and V activities and promoted the mitophagy in APAP-overdose mice. To further authenticate mitophagy role in CoQ10-mediated improved liver injury in vivo, we administrated APAP-overdose mice with chloroquine 1 h prior to APAP treatment and found that chloroquine treatment functionally abrogated the CoQ10 protective role on APAP overdose mice. To conclude, this study provides evidence that CoQ10 activates mitophagy to protect against APAP-induced liver injury. Therefore, CoQ10 may represent a novel therapeutic option for the prevention and treatment of drug-induced liver injury.

Coenzyme Q10 Treatment Monitoring in Different Human Biological Samples

Coenzyme Q₁₀ (CoQ) treatment monitoring is a matter of debate since CoQ distribution from plasma to blood cells and tissues is not fully understood. We aimed to analyze the CoQ levels in a wide set of human biological samples (plasma, blood mononuclear cells (BMCs), platelets, urinary cells, and skeletal muscle) from a group of 11 healthy male runners before and after CoQ supplementation. The CoQ content in the different samples was analyzed by HPLC coupled to electrochemical detection. No significant differences were observed in the CoQ levels measured in the BMCs, platelets, and urine after the one-month treatment period. Plasma CoQ (expressed in absolute values and values relative to total cholesterol) significantly increased after CoQ supplementation (p = 0.003 in both cases), and the increase in CoQ in muscle approached significance (p = 0.074). CoQ levels were increased in the plasma of all supplemented subjects, and muscle CoQ levels were increased in 8 out of 10 supplemented subjects. In conclusion, the analysis of CoQ in plasma samples seems to be the best surrogate biomarker for CoQ treatment monitoring. Moreover, oral CoQ administration was effective for increasing muscle CoQ concentrations in most subjects.

Modulation of Coenzyme Q10 content and oxidative status in human dermal fibroblasts using HMG-CoA reductase inhibitor over a broad range of concentrations. From mitohormesis to mitochondrial dysfunction and accelerated aging

Coenzyme Q₁₀ (CoQ₁₀) is an endogenous lipophilic quinone, ubiquitous in biological membranes and endowed with antioxidant and bioenergetic properties, both crucial to the aging process. In fact, coenzyme Q₁₀ synthesis is known to decrease with age in different tissues including skin. Moreover, synthesis can be inhibited by 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors such as statins, that are widely used hypocholesterolemic drugs. They target a key enzymatic step along the mevalonate pathway, involved in the synthesis of both cholesterol and isoprenylated compounds including CoQ₁₀.In the present study, we show that pharmacological CoQ₁₀ deprivation at concentrations of statins > 10000 nM triggers intracellular oxidative stress, mitochondrial dysfunction and generates cell death in human dermal fibroblasts (HDF). On the contrary, at lower statin concentrations, cells and mainly mitochondria, are able to partially adapt and prevent oxidative imbalance and overt mitochondrial toxicity. Importantly, our data demonstrate that CoQ₁₀ decrease promotes mitochondrial permeability transition and bioenergetic dysfunction leading to premature aging of human dermal fibroblasts in vitro.

A fatal case of COQ7-associated primary coenzyme Q10 deficiency

BACKGROUND

Primary coenzyme Q10 (CoQ10) deficiencies are clinically and genetically heterogeneous group of disorders associated with defects of genes involved in the CoQ10 biosynthesis pathway. COQ7-associated CoQ10 deficiency is very rare and only two cases have been reported.

METHODS AND RESULTS

We report a patient with encephalo-myo-nephro-cardiopathy, persistent lactic acidosis, and basal ganglia lesions resulting in early infantile death. Using whole exome sequencing, we identified compound heterozygous variants in the COQ7 gene consisting of a deletion insertion resulting in frameshift [c.599_600delinsTAATGCATC, p.(Lys200Ilefs*56)] and a missense substitution [c.319C>T, p.(Arg107Trp), NM_016138.4]. Skin fibroblast studies showed decreased combined complex II + III activity and reduction in CoQ10 level.

CONCLUSION

This third patient presenting with lethal encephalo-myo-nephro-cardiopathy represents the severe end of this ultra-rare mitochondrial disease caused by biallelic COQ7 mutations. The response to CoQ10 supplement is poor and alternative treatment strategies should be developed for a more effective management of this disorder.

Vitamin K2 cannot substitute Coenzyme Q10 as electron carrier in the mitochondrial respiratory chain of mammalian cells

Coenzyme Q₁₀ (CoQ₁₀) deficiencies are a group of heterogeneous conditions that respond to ubiquinone administration if treated soon after the onset of symptoms. However, this treatment is only partially effective due to its poor bioavailability. We tested whether vitamin K2, which was reported to act as a mitochondrial electron carrier in D. melanogaster, could mimic ubiquinone function in human CoQ₁₀ deficient cell lines, and in yeast carrying mutations in genes required for coenzyme Q₆ (CoQ₆) biosynthesis. We found that vitamin K2, despite entering into mitochondria, restored neither electron flow in the respiratory chain, nor ATP synthesis. Conversely, coenzyme Q₄ (CoQ₄), an analog of CoQ₁₀ with a shorter isoprenoid side chain, could efficiently substitute its function. Given its better solubility, CoQ₄ could represent an alternative to CoQ₁₀ in patients with both primary and secondary CoQ₁₀ deficiencies.

Plasma coenzyme Q10 status is impaired in selected genetic conditions

Identifying diseases displaying chronic low plasma Coenzyme Q₁₀ (CoQ) values may be important to prevent possible cardiovascular dysfunction. The aim of this study was to retrospectively evaluate plasma CoQ concentrations in a large cohort of pediatric and young adult patients. We evaluated plasma CoQ values in 597 individuals (age range 1 month to 43 years, average 11 years), studied during the period 2005–2016. Patients were classified into 6 different groups: control group of healthy participants, phenylketonuric patients (PKU), patients with mucopolysaccharidoses (MPS), patients with other inborn errors of metabolism (IEM), patients with neurogenetic diseases, and individuals with neurological diseases with no genetic diagnosis. Plasma total CoQ was measured by reverse-phase high-performance liquid chromatography with electrochemical detection and ultraviolet detection at 275 nm. ANOVA with Bonferroni correction showed that plasma CoQ values were significantly lower in the PKU and MPS groups than in controls and neurological patients. The IEM group showed intermediate values that were not significantly different from those of the controls. In PKU patients, the Chi-Square test showed a significant association between having low plasma CoQ values and being classic PKU patients. The percentage of neurogenetic and other neurological patients with low CoQ values was low (below 8%). In conclusión, plasma CoQ monitoring in selected groups of patients with different IEM (especially in PKU and MPS patients, but also in IEM under protein-restricted diets) seems advisable to prevent the possibility of a chronic blood CoQ suboptimal status in such groups of patients.

Clinical phenotype, in silico and biomedical analyses, and intervention for an East Asian population-specific c.370G>A (p.G124S) COQ4 mutation in a Chinese family with CoQ10 deficiency-associated Leigh syndrome

COQ4 mutations have recently been shown to cause a broad spectrum of mitochondrial disorders in association with CoQ10 deficiency. Herein, we report the clinical phenotype, in silico and biochemical analyses, and intervention for a novel c.370 G > A (p.G124S) COQ4 mutation in a Chinese family. This mutation is exclusively present in the East Asian population (allele frequency of ~0.001). The homozygous mutation caused CoQ10 deficiency-associated Leigh syndrome with an onset at 1-2 months of age, presenting as respiratory distress, lactic acidosis, dystonia, seizures, failure to thrive, and detectable lesions in the midbrain and basal ganglia. No renal impairment was involved. The levels of CoQ10 and mitochondrial respiratory chain complex (C) II + III activity were clearly lower in cultured fibroblasts derived from the patient than in those from unaffected carriers; the decreased CII + III activity could be increased by CoQ10 treatment. Follow-up studies suggested that our patient benefitted from the oral supplementation of CoQ10, which allowed her to maintain a relatively stable health status. Based on the genetic testing, preimplantation and prenatal diagnoses were performed, confirming that the next offspring of this family was unaffected. Our cases expand the phenotypic spectrum of COQ4 mutations and the genotypic spectrum of Leigh syndrome.

The dilemma of diagnosing coenzyme Q10 deficiency in muscle

BACKGROUND

Coenzyme Q₁₀ (CoQ₁₀) is an important component of the mitochondrial respiratory chain (RC) and is critical for energy production. Although the prevalence of CoQ₁₀ deficiency is still unknown, the general consensus is that the condition is under-diagnosed. The aim of this study was to retrospectively investigate CoQ₁₀ deficiency in frozen muscle specimens in a cohort of ethnically diverse patients who received muscle biopsies for the investigation of a possible RC deficiency (RCD).

METHODS

Muscle samples were homogenized whereby 600 ×g supernatants were used to analyze RC enzyme activities, followed by quantification of CoQ₁₀ by stable isotope dilution liquid chromatography tandem mass spectrometry. The experimental group consisted of 156 patients of which 76 had enzymatically confirmed RCDs. To further assist in the diagnosis of CoQ₁₀ deficiency in this cohort, we included sequencing of 18 selected nuclear genes involved with CoQ₁₀ biogenesis in 26 patients with low CoQ₁₀ concentration in muscle samples.

RESULTS

Central 95% reference intervals (RI) were established for CoQ₁₀ normalized to citrate synthase (CS) or protein. Nine patients were considered CoQ₁₀ deficient when expressed against CS, while 12 were considered deficient when expressed against protein. In two of these patients the molecular genetic cause could be confirmed, of which one would not have been identified as CoQ₁₀ deficient if expressed only against protein content.

CONCLUSION

In this retrospective study, we report a central 95% reference interval for 600 ×g muscle supernatants prepared from frozen samples. The study reiterates the importance of including CoQ₁₀ quantification as part of a diagnostic approach to study mitochondrial disease as it may complement respiratory chain enzyme assays with the possible identification of patients that may benefit from CoQ₁₀ supplementation. However, the anomaly that only a few patients were identified as CoQ₁₀ deficient against both markers (CS and protein), while the majority of patients where only CoQ₁₀ deficient against one of the markers (and not the other), remains problematic. We therefore conclude from our data that, to prevent possibly not diagnosing a potential CoQ₁₀ deficiency, the expression of CoQ₁₀ levels in muscle on both CS as well as protein content should be considered.

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.

Genetic Rescue of Mitochondrial and Skeletal Muscle Impairment in an Induced Pluripotent Stem Cells Model of Coenzyme Q10 Deficiency

Coenzyme Q₁₀ (CoQ₁₀ ) plays a crucial role in mitochondria as an electron carrier within the mitochondrial respiratory chain (MRC) and is an essential antioxidant. Mutations in genes responsible for CoQ₁₀ biosynthesis (COQ genes) cause primary CoQ₁₀ deficiency, a rare and heterogeneous mitochondrial disorder with no clear genotype-phenotype association, mainly affecting tissues with high-energy demand including brain and skeletal muscle (SkM). Here, we report a four-year-old girl diagnosed with minor mental retardation and lethal rhabdomyolysis harboring a heterozygous mutation (c.483G > C (E161D)) in COQ4. The patient's fibroblasts showed a decrease in [CoQ₁₀ ], CoQ₁₀ biosynthesis, MRC activity affecting complexes I/II + III, and respiration defects. Bona fide induced pluripotent stem cell (iPSCs) lines carrying the COQ4 mutation (CQ4-iPSCs) were generated, characterized and genetically edited using the CRISPR-Cas9 system (CQ4^ed -iPSCs). Extensive differentiation and metabolic assays of control-iPSCs, CQ4-iPSCs and CQ4^ed -iPSCs demonstrated a genotype association, reproducing the disease phenotype. The COQ4 mutation in iPSC was associated with CoQ₁₀ deficiency, metabolic dysfunction, and respiration defects. iPSC differentiation into SkM was compromised, and the resulting SkM also displayed respiration defects. Remarkably, iPSC differentiation in dopaminergic or motor neurons was unaffected. This study offers an unprecedented iPSC model recapitulating CoQ₁₀ deficiency-associated functional and metabolic phenotypes caused by COQ4 mutation. Stem Cells 2017;35:1687-1703.

The Value of Coenzyme Q10 Determination in Mitochondrial Patients

Coenzyme Q₁₀ (CoQ) is a lipid that is ubiquitously synthesized in tissues and has a key role in mitochondrial oxidative phosphorylation. Its biochemical determination provides insight into the CoQ status of tissues and may detect CoQ deficiency that can result from either an inherited primary deficiency of CoQ metabolism or may be secondary to different genetic and environmental conditions. Rapid identification of CoQ deficiency can also allow potentially beneficial treatment to be initiated as early as possible. CoQ may be measured in different specimens, including plasma, blood mononuclear cells, platelets, urine, muscle, and cultured skin fibroblasts. Blood and urinary CoQ also have good utility for CoQ treatment monitoring.

A statistical algorithm showing coenzyme Q10 and citrate synthase as biomarkers for mitochondrial respiratory chain enzyme activities

Laboratory data interpretation for the assessment of complex biological systems remains a great challenge, as occurs in mitochondrial function research studies. The classical biochemical data interpretation of patients versus reference values may be insufficient, and in fact the current classifications of mitochondrial patients are still done on basis of probability criteria. We have developed and applied a mathematic agglomerative algorithm to search for correlations among the different biochemical variables of the mitochondrial respiratory chain in order to identify populations displaying correlation coefficients >0.95. We demonstrated that coenzyme Q10 may be a better biomarker of mitochondrial respiratory chain enzyme activities than the citrate synthase activity. Furthermore, the application of this algorithm may be useful to re-classify mitochondrial patients or to explore associations among other biochemical variables from different biological systems.

Mitochondrial dysfunction in inherited renal disease and acute kidney injury

Mitochondria are increasingly recognized as key players in genetic and acquired renal diseases. Most mitochondrial cytopathies that cause renal symptoms are characterized by tubular defects, but glomerular, tubulointerstitial and cystic diseases have also been described. For example, defects in coenzyme Q10 (CoQ10) biosynthesis and the mitochondrial DNA 3243 A>G mutation are important causes of focal segmental glomerulosclerosis in children and in adults, respectively. Although they sometimes present with isolated renal findings, mitochondrial diseases are frequently associated with symptoms related to central nervous system and neuromuscular involvement. They can result from mutations in nuclear genes that are inherited according to classic Mendelian rules or from mutations in mitochondrial DNA, which are transmitted according to more complex rules of mitochondrial genetics. Diagnosis of mitochondrial disorders involves clinical characterization of patients in combination with biochemical and genetic analyses. In particular, prompt diagnosis of CoQ10 biosynthesis defects is imperative because of their potentially reversible nature. In acute kidney injury (AKI), mitochondrial dysfunction contributes to the physiopathology of tissue injury, whereas mitochondrial biogenesis has an important role in the recovery of renal function. Potential therapies that target mitochondrial dysfunction or promote mitochondrial regeneration are being developed to limit renal damage during AKI and promote repair of injured tissue.

Serum Levels of Coenzyme Q10 in Patients with Multiple System Atrophy

The COQ2 gene encodes an essential enzyme for biogenesis, coenzyme Q10 (CoQ10). Recessive mutations in this gene have recently been identified in families with multiple system atrophy (MSA). Moreover, specific heterozygous variants in the COQ2 gene have also been reported to confer susceptibility to sporadic MSA in Japanese cohorts. These findings have suggested the potential usefulness of CoQ10 as a blood-based biomarker for diagnosing MSA. This study measured serum levels of CoQ10 in 18 patients with MSA, 20 patients with Parkinson's disease and 18 control participants. Although differences in total CoQ10 (i.e., total levels of serum CoQ10 and its reduced form) among the three groups were not significant, total CoQ10 level corrected by serum cholesterol was significantly lower in the MSA group than in the Control group. Our findings suggest that serum CoQ10 can be used as a biomarker in the diagnosis of MSA and to provide supportive evidence for the hypothesis that decreased levels of CoQ10 in brain tissue lead to an increased risk of MSA.

Determination of urinary coenzyme Q10 by HPLC with electrochemical detection: Reference values for a paediatric population

Kidney dysfunction is being increasingly associated with mitochondrial diseases and coenzyme Q10 (CoQ) deficiency. The assessment of CoQ status requires the biochemical determination of CoQ in biological fluids and different cell types, but no methods have been developed as yet for the analysis of CoQ in excretory systems. The aim of this study was to standardize a new procedure for urinary CoQ determination and to establish reference values for a paediatric population. Urinary CoQ was analyzed by HPLC with electrochemical detection. Reference values (n = 43) were stratified into two age groups (2-10 years: range 24-109 nmol CoQ/gram of pellet protein; 11-17 years: range 43-139 nmol CoQ/gram of pellet protein). In conclusion, urinary CoQ analysis is a noninvasive, reliable, and reproducible method to determine urinary tract CoQ status.

Molecular diagnosis of coenzyme Q10 deficiency

Coenzyme Q10 (CoQ) deficiency syndromes comprise a growing number of neurological and extraneurological disorders. Primary-genetic but also secondary CoQ deficiencies have been reported. The biochemical determination of CoQ is a good tool for the rapid identification of CoQ deficiencies but does not allow the selection of candidate genes for molecular diagnosis. Moreover, the metabolic pathway for CoQ synthesis is an intricate and not well-understood process, where a large number of genes are implicated. Thus, only next-generation sequencing techniques (either genetic panels of whole-exome and -genome sequencing) are at present appropriate for a rapid and realistic molecular diagnosis of these syndromes. The potential treatability of CoQ deficiency strongly supports the necessity of a rapid molecular characterization of patients, since primary CoQ deficiencies may respond well to CoQ treatment.

Severe encephalopathy associated to pyruvate dehydrogenase mutations and unbalanced coenzyme Q10 content

Coenzyme Q10 (CoQ10) deficiency is associated to a variety of clinical phenotypes including neuromuscular and nephrotic disorders. We report two unrelated boys presenting encephalopathy, ataxia, and lactic acidosis, who died with necrotic lesions in different areas of brain. Levels of CoQ10 and complex II+III activity were increased in both skeletal muscle and fibroblasts, but it was a consequence of higher mitochondria mass measured as citrate synthase. In fibroblasts, oxygen consumption was also increased, whereas steady state ATP levels were decreased. Antioxidant enzymes such as NQO1 and MnSOD and mitochondrial marker VDAC were overexpressed. Mitochondria recycling markers Fis1 and mitofusin, and mtDNA regulatory Tfam were reduced. Exome sequencing showed mutations in PDHA1 in the first patient and in PDHB in the second. These genes encode subunits of pyruvate dehydrogenase complex (PDH) that could explain the compensatory increase of CoQ10 and a defect of mitochondrial homeostasis. These two cases describe, for the first time, a mitochondrial disease caused by PDH defects associated with unbalanced of both CoQ10 content and mitochondria homeostasis, which severely affects the brain. Both CoQ10 and mitochondria homeostasis appears as new markers for PDH associated mitochondrial disorders.

Mutation loads in different tissues from six pathogenic mtDNA point mutations

In this work, we studied the mtDNA mutations m.3243A>G, m.3252A>G, m.15923A>G, m.13513G>A, m.8993T>G and m.9176T>C in the blood, urine and buccal mucosa of a cohort of 27 subjects. Urine cells had the highest mutation load for all of the mtDNA mutations studied. The mutation loads in the blood, urine and the buccal mucosa were significantly higher in the mitochondrial disorder group that manifested clinical signs than in the asymptomatic subjects. In conclusion, urine is a suitable biological sample for molecular diagnosis of mtDNA mutations and for the study of the attendant risk of recurrence in the offspring of asymptomatic mothers identified as non-carriers after mutation analysis in blood.

Primary coenzyme Q10 deficiency presenting as fatal neonatal multiorgan failure

Coenzyme Q10 deficiency is a clinically and genetically heterogeneous disorder, with manifestations that may range from fatal neonatal multisystem failure, to adult-onset encephalopathy. We report a patient who presented at birth with severe lactic acidosis, proteinuria, dicarboxylic aciduria, and hepatic insufficiency. She also had dilation of left ventricle on echocardiography. Her neurological condition rapidly worsened and despite aggressive care she died at 23 h of life. Muscle histology displayed lipid accumulation. Electron microscopy showed markedly swollen mitochondria with fragmented cristae. Respiratory-chain enzymatic assays showed a reduction of combined activities of complex I+III and II+III with normal activities of isolated complexes. The defect was confirmed in fibroblasts, where it could be rescued by supplementing the culture medium with 10 μM coenzyme Q10. Coenzyme Q10 levels were reduced (28% of controls) in these cells. We performed exome sequencing and focused the analysis on genes involved in coenzyme Q10 biosynthesis. The patient harbored a homozygous c.545T>G, p.(Met182Arg) alteration in COQ2, which was validated by functional complementation in yeast. In this case the biochemical and morphological features were essential to direct the genetic diagnosis. The parents had another pregnancy after the biochemical diagnosis was established, but before the identification of the genetic defect. Because of the potentially high recurrence risk, and given the importance of early CoQ10 supplementation, we decided to treat with CoQ10 the newborn child pending the results of the biochemical assays. Clinicians should consider a similar management in siblings of patients with CoQ10 deficiency without a genetic diagnosis.

Genetic bases and clinical manifestations of coenzyme Q10 (CoQ 10) deficiency

Coenzyme Q(10) is a remarkable lipid involved in many cellular processes such as energy production through the mitochondrial respiratory chain (RC), beta-oxidation of fatty acids, and pyrimidine biosynthesis, but it is also one of the main cellular antioxidants. Its biosynthesis is still incompletely characterized and requires at least 15 genes. Mutations in eight of them (PDSS1, PDSS2, COQ2, COQ4, COQ6, ADCK3, ADCK4, and COQ9) cause primary CoQ(10) deficiency, a heterogeneous group of disorders with variable age of onset (from birth to the seventh decade) and associated clinical phenotypes, ranging from a fatal multisystem disease to isolated steroid resistant nephrotic syndrome (SRNS) or isolated central nervous system disease. The pathogenesis is complex and related to the different functions of CoQ(10). It involves defective ATP production and oxidative stress, but also an impairment of pyrimidine biosynthesis and increased apoptosis. CoQ(10) deficiency can also be observed in patients with defects unrelated to CoQ(10) biosynthesis, such as RC defects, multiple acyl-CoA dehydrogenase deficiency, and ataxia and oculomotor apraxia.Patients with both primary and secondary deficiencies benefit from high-dose oral supplementation with CoQ(10). In primary forms treatment can stop the progression of both SRNS and encephalopathy, hence the critical importance of a prompt diagnosis. Treatment may be beneficial also for secondary forms, although with less striking results.In this review we will focus on CoQ(10) biosynthesis in humans, on the genetic defects and the specific clinical phenotypes associated with CoQ(10) deficiency, and on the diagnostic strategies for these conditions.

Association between coenzyme Q10 and glucose transporter (GLUT1) deficiency

Background

It has been demonstrated that glucose transporter (GLUT1) deficiency in a mouse model causes a diminished cerebral lipid synthesis. This deficient lipid biosynthesis could contribute to secondary CoQ deficiency. We report here, for the first time an association between GLUT1 and coenzyme Q₁₀ deficiency in a pediatric patient.

Case presentation

We report a 15 year-old girl with truncal ataxia, nystagmus, dysarthria and myoclonic epilepsy as the main clinical features. Blood lactate and alanine values were increased, and coenzyme Q₁₀ was deficient both in muscle and fibroblasts. Coenzyme Q₁₀ supplementation was initiated, improving ataxia and nystagmus. Since dysarthria and myoclonic epilepsy persisted, a lumbar puncture was performed at 12 years of age disclosing diminished cerebrospinal glucose concentrations. Diagnosis of GLUT1 deficiency was confirmed by the presence of a de novo heterozygous variant (c.18+2T>G) in the SLC2A1 gene. No mutations were found in coenzyme Q₁₀ biosynthesis related genes. A ketogenic diet was initiated with an excellent clinical outcome. Functional studies in fibroblasts supported the potential pathogenicity of coenzyme Q₁₀ deficiency in GLUT1 mutant cells when compared with controls.

Conclusion

Our results suggest that coenzyme Q₁₀ deficiency might be a new factor in the pathogenesis of G1D, although this deficiency needs to be confirmed in a larger group of G1D patients as well as in animal models. Although ketogenic diet seems to correct the clinical consequences of CoQ deficiency, adjuvant treatment with CoQ could be trialled in this condition if our findings are confirmed in further G1D patients.

Biochemical diagnosis of coenzyme q10 deficiency

Coenzyme Q10 (CoQ10) deficiency appears to have a particularly heterogeneous clinical presentation. However, there appear to be 5 recognisable clinical phenotypes: encephalomyopathy, severe infantile multisystemic disease, nephropathy, cerebellar ataxia, and isolated myopathy. However, although useful, clinical symptoms alone are insufficient for the definitive diagnosis of CoQ10 deficiency which relies upon biochemical assessment of tissue CoQ10 status. In this article, we review the biochemical methods used in the diagnosis of human CoQ10 deficiency and indicate the most appropriate tissues for this evaluation.

Invertebrate models for coenzyme q10 deficiency

The human syndrome of coenzyme Q (CoQ) deficiency is a heterogeneous mitochondrial disease characterized by a diminution of CoQ content in cells and tissues that affects all the electron transport processes CoQ is responsible for, like the electron transference in mitochondria for respiration and ATP production and the antioxidant capacity that it exerts in membranes and lipoproteins. Supplementation with external CoQ is the main attempt to address these pathologies, but quite variable results have been obtained ranging from little response to a dramatic recovery. Here, we present the importance of modeling human CoQ deficiencies in animal models to understand the genetics and the pathology of this disease, although the election of an organism is crucial and can sometimes be controversial. Bacteria and yeast harboring mutations that lead to CoQ deficiency are unable to grow if they have to respire but develop without any problems on media with fermentable carbon sources. The complete lack of CoQ in mammals causes embryonic lethality, whereas other mutations produce tissue-specific diseases as in humans. However, working with transgenic mammals is time and cost intensive, with no assurance of obtaining results. Caenorhabditis elegans and Drosophila melanogaster have been used for years as organisms to study embryonic development, biogenesis, degenerative pathologies, and aging because of the genetic facilities and the speed of working with these animal models. In this review, we summarize several attempts to model reliable human CoQ deficiencies in invertebrates, focusing on mutant phenotypes pretty similar to those observed in human patients.

Successful reversal of propionic acidaemia associated cardiomyopathy: evidence for low myocardial coenzyme Q10 status and secondary mitochondrial dysfunction as an underlying pathophysiological mechanism

Dilated cardiomyopathy is a rare complication in propionic acidaemia (PA). Underlying pathophysiological mechanisms are poorly understood. We present a child of Pakistani consanguineous parents, diagnosed with late-onset PA at 18months of age. He presented a mild phenotype, showed no severe further decompensations, normal growth and psychomotor development on a low protein diet and carnitine supplementation. At 15years, a mildly dilated left ventricle was noticed. At 17years he presented after a 2-3month history of lethargy and weight loss with severe decompensated dilated cardiomyopathy. He was stabilised on inotropic support and continuous haemofiltration; a Berlin Heart biventricular assist device was implanted. He received d,l-hydroxybutyrate 200mg/kg/day, riboflavin and thiamine 200mg/day each and coenzyme Q10 (CoQ10). Myocardial biopsy showed endocardial fibrosis, enlarged mitochondria, with atypical cristae and slightly low respiratory chain (RC) complex IV activity relative to citrate synthase (0.012, reference range 0.014-0.034). Myocardial CoQ10 was markedly decreased (224pmol/mg, reference range 942-2738), with a marginally decreased white blood cell level (34pmol/mg reference range 37-133). The dose of CoQ10 was increased from 1.5 to 25mg/kg/day. Cardiomyopathy slowly improved allowing removal of the external mechanical cardiac support after 67days. We demonstrate for the first time low myocardial CoQ10 in cardiomyopathy in PA, highlighting secondary mitochondrial impairment as a relevant causative mechanism. According to these findings, a high-dose CoQ10 supplementation could be a potential adjuvant therapeutic to be considered in PA-related cardiomyopathy.

NLRP3 inflammasome is activated in fibromyalgia: the effect of coenzyme Q10

AIMS

Fibromyalgia (FM) is a prevalent chronic pain syndrome characterized by generalized hyperalgesia associated with a wide spectrum of symptoms such as fatigue and joint stiffness. Diagnosis of FM is difficult due to the lack of reliable diagnostic biomarkers, while treatment is largely inadequate. We have investigated the role of coenzyme Q10 (CoQ10) deficiency and mitochondrial dysfunction in inflammasome activation in blood cells from FM patients, and in vitro and in vivo CoQ10 deficiency models.

RESULTS

Mitochondrial dysfunction was accompanied by increased protein expression of interleukin (IL)-1β, NLRP3 (NOD-like receptor family, pyrin domain containing 3) and caspase-1 activation, and an increase of serum levels of proinflammatory cytokines (IL-1β and IL-18). CoQ10 deficiency induced by p-aminobenzoate treatment in blood mononuclear cells and mice showed NLRP3 inflammasome activation with marked algesia. A placebo-controlled trial of CoQ10 in FM patients has shown a reduced NLRP3 inflammasome activation and IL-1β and IL-18 serum levels.

INNOVATION

These results show an important role for the NLRP3 inflammasome in the pathogenesis of FM, and the capacity of CoQ10 in the control of inflammasome.

CONCLUSION

These findings provide new insights into the pathogenesis of FM and suggest that NLRP3 inflammasome inhibition represents a new therapeutic intervention for the disease.

Effect of Coenzyme Q10 supplementation on mitochondrial electron transport chain activity and mitochondrial oxidative stress in Coenzyme Q10 deficient human neuronal cells

Primary Coenzyme Q10 (CoQ10) deficiency is an autosomal recessive disorder with a heterogeneous clinical presentation. Common presenting features include both muscle and neurological dysfunction. Muscle abnormalities can improve, both clinically and biochemically following CoQ10 supplementation, however neurological symptoms are only partially ameliorated. At present, the reasons for the refractory nature of the neurological dysfunction remain unknown. In order to investigate this at the biochemical level we evaluated the effect of CoQ10 treatment upon a previously established neuronal cell model of CoQ10 deficiency. This model was established by treatment of human SH-SY5Y neuronal cells with 1 mM para-aminobenzoic acid (PABA) which induced a 54% decrease in cellular CoQ10 status. CoQ10 treatment (2.5 μM) for 5 days significantly (p<0.0005) decreased the level of mitochondrial superoxide in the CoQ10 deficient neurons. In addition, CoQ10 treatment (5 μM) restored mitochondrial membrane potential to 90% of the control level. However, CoQ10 treatment (10 μM) was only partially effective at restoring mitochondrial electron transport chain (ETC) enzyme activities. ETC complexes II/III activity was significantly (p<0.05) increased to 82.5% of control levels. ETC complexes I and IV activities were restored to 71.1% and 77.7%, respectively of control levels. In conclusion, the results of this study have indicated that although mitochondrial oxidative stress can be attenuated in CoQ10 deficient neurons following CoQ10 supplementation, ETC enzyme activities appear partially refractory to treatment. Accordingly, treatment with >10 μM CoQ10 may be required to restore ETC enzyme activities to control level. Accordingly, these results have important implication for the treatment of the neurological presentations of CoQ10 deficiency and indicate that high doses of CoQ10 may be required to elicit therapeutic efficacy.

Coenzyme Q10 as a therapy for mitochondrial disease

Treatment of mitochondrial respiratory chain (MRC) disorders is extremely difficult, however, coenzyme Q10 (CoQ10) and its synthetic analogues are the only agents which have shown some therapeutic benefit to patients. CoQ10 serves as an electron carrier in the MRC as well as functioning as a potent lipid soluble antioxidant. CoQ10 supplementation is fundamental to the treatment of patients with primary defects in the CoQ10 biosynthetic pathway. The efficacy of CoQ10 and its analogues in the treatment of patients with MRC disorders not associated with a CoQ10 deficiency indicates their ability to restore electron flow in the MRC and/or increase mitochondrial antioxidant capacity may also be important contributory factors to their therapeutic potential.

Characterization of CoQ₁₀ biosynthesis in fibroblasts of patients with primary and secondary CoQ₁₀ deficiency

Primary coenzyme Q₁₀ (CoQ₁₀) deficiencies are associated with mutations in genes encoding enzymes important for its biosynthesis and patients are responsive to CoQ₁₀ supplementation. Early treatment allows better prognosis of the disease and therefore, early diagnosis is desirable. The complex phenotype and genotype and the frequent secondary CoQ₁₀ deficiencies make it difficult to achieve a definitive diagnosis by direct quantification of CoQ₁₀. We developed a non-radioactive methodology for the quantification of CoQ₁₀ biosynthesis in fibroblasts that allows the identification of primary deficiencies. Fibroblasts were incubated 72 h with 28 μmol/L (2)H₃-mevalonate or 1.65 mmol/L (13)C₆-p-hydroxybenzoate. The newly synthesized (2)H₃- and (13)C₆- labelled CoQ₁₀ were analysed by high performance liquid chromatography-tandem mass spectrometry. The mean and the reference range for (13)C₆-CoQ₁₀ and (2)H₃-CoQ₁₀ biosynthesis were 0.97 (0.83-1.1) and 0.13 (0.09-0.17) nmol/Unit of citrate synthase, respectively. We validated the methodology through the study of one patient with COQ2 mutations and six patients with CoQ₁₀ deficiency secondary to other inborn errors of metabolism. Afterwards we investigated 16 patients' fibroblasts and nine showed decreased CoQ₁₀ biosynthesis. Therefore, the next step is to study the COQ genes in order to reach a definitive diagnosis in these nine patients. In the patients with normal rates the deficiency is probably secondary. In conclusion, we have developed a non-invasive non-radioactive method suitable for the detection of defects in CoQ₁₀ biosynthesis, which offers a good tool for the stratification of patients with these treatable mitochondrial diseases.

Survival transcriptome in the coenzyme Q10 deficiency syndrome is acquired by epigenetic modifications: a modelling study for human coenzyme Q10 deficiencies

OBJECTIVES

Coenzyme Q10 (CoQ10) deficiency syndrome is a rare condition that causes mitochondrial dysfunction and includes a variety of clinical presentations as encephalomyopathy, ataxia and renal failure. First, we sought to set up what all have in common, and then investigate why CoQ10 supplementation reverses the bioenergetics alterations in cultured cells but not all the cellular phenotypes. DESIGN MODELLING STUDY: This work models the transcriptome of human CoQ10 deficiency syndrome in primary fibroblast from patients and study the genetic response to CoQ10 treatment in these cells.

SETTING

Four hospitals and medical centres from Spain, Italy and the USA, and two research laboratories from Spain and the USA.

PARTICIPANTS

Primary cells were collected from patients in the above centres.

MEASUREMENTS

We characterised by microarray analysis the expression profile of fibroblasts from seven CoQ10-deficient patients (three had primary deficiency and four had a secondary form) and aged-matched controls, before and after CoQ10 supplementation. Results were validated by Q-RT-PCR. The profile of DNA (CpG) methylation was evaluated for a subset of gene with displayed altered expression.

RESULTS

CoQ10-deficient fibroblasts (independently from the aetiology) showed a common transcriptomic profile that promotes cell survival by activating cell cycle and growth, cell stress responses and inhibiting cell death and immune responses. Energy production was supported mainly by glycolysis while CoQ10 supplementation restored oxidative phosphorylation. Expression of genes involved in cell death pathways was partially restored by treatment, while genes involved in differentiation, cell cycle and growth were not affected. Stably demethylated genes were unaffected by treatment whereas we observed restored gene expression in either non-methylated genes or those with an unchanged methylation pattern.

CONCLUSIONS

CoQ10 deficiency induces a specific transcriptomic profile that promotes cell survival, which is only partially rescued by CoQ10 supplementation.

Analysis of coenzyme Q(10) in lymphocytes by HPLC-MS/MS

Coenzyme Q(10) (CoQ(10)) deficiency syndromes are potentially treatable disorders. Skeletal muscle is the most widely accepted tissue for their study, but sampling is an invasive procedure. Cultured skin fibroblasts seem to improve the biochemical diagnosis, but their growth requires a certain period of time. Our aim was to set up a minimally invasive, fast and reliable analytical procedure to measure CoQ(10) in lymphocytes, to prevent any delay in diagnosing primary CoQ(10) deficiency. HPLC-MS/MS analysis of CoQ(10) showed high sensitivity and specificity. The reference range was established in apparently healthy volunteers (n=33); the mean of CoQ(10) in lymphocytes was 107nmol/g protein (95% confidence interval: 105-120) and 2.0nmol/UCS (95% confidence interval: 2.06-2.46). Therefore, the range was narrower when normalized to units of citrate synthase (UCS) than when normalized to grams of protein. The method was linear from 0.01 to 1μM with a good precision and sensitivity (limit of quantification 0.01μM). Intra-assay and inter-assay coefficients of variation were lower than 13%. Recovery was higher than 95%. In our hands, lymphocytes seem to be a reliable matrix as they reflect intracellular content of CoQ(10). In addition, they can be obtained by a minimally invasive procedure (venipuncture).

New mitochondrial DNA mutations in tRNA associated with three severe encephalopamyopathic phenotypes: neonatal, infantile, and childhood onset

The reported cases showed clinical, biochemical, histopathological, and molecular features lending support to the hypothesis of a pathogenic effect of the detected mutations. Case 1 was a neonatal presentation who showed multiple mitochondrial respiratory chain enzyme defects in muscle associated with a new homoplasmic m.5514A > G transition in the tRNA(Trp) gene. Case 2 was a late infantile presentation who also showed mitochondrial respiratory chain enzyme deficiencies in muscle together with a new m.1643A > G tRNA(Val) mutation in homoplasmy. Case 3 showed a MERRF phenotype presented in childhood associated with the once previously reported m.15923A > G mutation in heteroplasmy in all the tissues studied.

Copper and bezafibrate cooperate to rescue cytochrome c oxidase deficiency in cells of patients with SCO2 mutations

BACKGROUND

Mutations in SCO2 cause cytochrome c oxidase deficiency (COX) and a fatal infantile cardioencephalomyopathy. SCO2 encodes a protein involved in COX copper metabolism; supplementation with copper salts rescues the defect in patients' cells. Bezafibrate (BZF), an approved hypolipidemic agent, ameliorates the COX deficiency in mice with mutations in COX10, another COX-assembly gene.

METHODS

We have investigated the effect of BZF and copper in cells with SCO2 mutations using spectrophotometric methods to analyse respiratory chain activities and a luciferase assay to measure ATP production..

RESULTS

Individual mitochondrial enzymes displayed different responses to BZF. COX activity increased by about 40% above basal levels (both in controls and patients), with SCO2 cells reaching 75-80% COX activity compared to untreated controls. The increase in COX was paralleled by an increase in ATP production. The effect was dose-dependent: it was negligible with 100 μM BZF, and peaked at 400 μM BZF. Higher BZF concentrations were associated with a relative decline of COX activity, indicating that the therapeutic range of this drug is very narrow. Combined treatment with 100 μM CuCl2 and 200 μM BZF (which are only marginally effective when administered individually) achieved complete rescue of COX activity in SCO2 cells.

CONCLUSIONS

These data are crucial to design therapeutic trials for this otherwise fatal disorder. The additive effect of copper and BZF will allow to employ lower doses of each drug and to reduce their potential toxic effects. The exact mechanism of action of BZF remains to be determined.

Renal involvement in mitochondrial cytopathies

Mitochondrial cytopathies constitute a group of rare diseases that are characterized by their frequent multisystemic involvement, extreme variability of phenotype and complex genetics. In children, renal involvement is frequent and probably underestimated. The most frequent renal symptom is a tubular defect that, in most severe forms, corresponds to a complete De Toni-Debré-Fanconi syndrome. Incomplete proximal tubular defects and other tubular diseases have also been reported. In rare cases, patients present with chronic tubulo-interstitial nephritis or cystic renal diseases. Finally, a group of patients develop primarily a glomerular disease. These patients correspond to sporadic case reports or can be classified into two major defects, namely 3243 A>G tRNA(LEU) mutations and coenzyme Q10 biosynthesis defects. The latter group is particularly important because it represents the only treatable renal mitochondrial defect. In this Educational Review, the principal characteristics of these diseases and the main diagnostic approaches are summarized.

Coenzyme Q deficiency in muscle

PURPOSE OF REVIEW

Coenzyme Q (CoQ) is a vital component of the mitochondrial respiratory chain. A number of patients with CoQ deficiency presented with different clinical phenotypes, often affecting skeletal muscle, and responded well to CoQ supplementation. We discuss recent advances in this field with special attention to muscle involvement.

RECENT FINDINGS

The identification of genetic defects causing CoQ deficiency has allowed to distinguish primary forms, due to mutations in biosynthetic genes, from secondary defects caused either by mutations in genes unrelated to CoQ biosynthesis or by nongenetic factors. To date, none of the patients with genetically proven primary deficiency presented with an exclusively (or prominently) myopathic phenotype. Most patients with myopathy were found to harbor other genetic defects (mutations in electron-transferring-flavoprotein dehydrogenase or mitochondrial DNA). The majority of patients with CoQ deficiency still lack a genetic diagnosis. The pathogenesis of CoQ deficiency cannot be attributed solely to the bioenergetic defect, suggesting that other roles of CoQ, including its antioxidant properties or its role in pyrimidine metabolism, may also play crucial roles.

SUMMARY

Early recognition of CoQ deficiency is essential to institute appropriate and timely treatment, thus avoiding irreversible tissue damage.

Measurement of oxidized and reduced coenzyme Q in biological fluids, cells, and tissues: an HPLC-EC method

Direct measure of coenzyme Q (CoQ) in biological specimens may provide important advantages. Precise and selective high-performance liquid chromatography (HPLC) methods with electrochemical (EC) detection have been developed for the measurement of reduced (ubiquinol) and oxidized (ubiquinone) CoQ in biological fluids, cells, and tissues. EC detection is preferred for measurement of CoQ because of its high sensitivity. Reduced and oxidized CoQ are first extracted from biological specimens using 1-propanol. After centrifugation, the 1-propanol supernatant is directly injected into HPLC and monitored at a dual-electrode. The EC reactions occur at the electrode surface. The first electrode transforms ubiquinone into ubiquinol, and the second electrode measures the current produced by the oxidation of the hydroquinone group of ubiquinol. The methods described provide rapid, precise, and simple procedures for determination of reduced and oxidized CoQ in biological fluids, cells, and tissues. The methods have been successfully adapted to meet regulatory requirements for clinical laboratories, and have been proven reliable for analysis of clinical and research samples for clinical trials and animal studies involving large numbers of specimens.

Renal mitochondrial cytopathies

Renal diseases in mitochondrial cytopathies are a group of rare diseases that are characterized by frequent multisystemic involvement and extreme variability of phenotype. Most frequently patients present a tubular defect that is consistent with complete De Toni-Debré-Fanconi syndrome in most severe forms. More rarely, patients present with chronic tubulointerstitial nephritis, cystic renal diseases, or primary glomerular involvement. In recent years, two clearly defined entities, namely 3243 A > G tRNA(LEU) mutations and coenzyme Q10 biosynthesis defects, have been described. The latter group is particularly important because it represents the only treatable renal mitochondrial defect. In this paper, the physiopathologic bases of mitochondrial cytopathies, the diagnostic approaches, and main characteristics of related renal diseases are summarized.