Determination of the ubiquinol-10 and ubiquinone-10 (coenzyme Q10) in human serum by liquid chromatography tandem mass spectrometry to evaluate the oxidative stress

Gas-Phase Fragmentation of Coenzyme Q10 Radical Anion Generated by APCI: A Study by High/Low-Resolution Tandem/Sequential Mass Spectrometry

Coenzyme Q10 (CoQ10) and closely related compounds with varying isoprenoid tail lengths (CoQn, n = 6-9) are biochemical cofactors involved in many physiological processes, playing important roles in cellular respiration and energy production. Liquid chromatography (LC) coupled with single or tandem mass spectrometry (MS) using electrospray (ESI) or atmospheric pressure chemical ionization (APCI) is considered the gold standard for the identification and quantification of CoQ10 in food and biological samples. However, the characteristic fragmentation exhibited by the CoQ10 radical anion ([M]•-, m/z 862.684), the prevailing ion generated by APCI in negative polarity, has not been studied in detail. In this work, a systematic study was carried out to clarify this issue, using higher collisional energy dissociation (HCD) with high-resolution tandem FTMS and collision-induced dissociation-low-resolution sequential mass spectrometry (CID-MSn, n = 2-4). Various fragmentation pathways were successfully interpreted, with some structures proposed for product ions checked using density functional theory (DFT) calculations. Besides the already-known detachments of methyl radicals occurring directly from the CoQ10 radical anion and leading to ions like [M - CH3]- and [M - 2CH3]•-, the homolytic cleavage of C-C bonds along the oligo-isoprenoid side chain was tentatively proposed to explain some of the observed fragmentations. As a result, the generation of uncommon yet potentially stable distonic biradical anions was hypothesized, with some of them likely undergoing intramolecular cyclization to generate ions without unpaired electrons. Diagnostic product ions emerged from the fragmentation processes of CoQ10 and were found to be common also to the radical anions of other CoQn derivatives (n = 7-9), facilitating their identification in extracts of edible Brassicaceae plant microgreens by reversed-phase liquid chromatography (RPLC)-APCI-FTMS.

Annonaceous acetogenins mimic AA005 targets mitochondrial trifunctional enzyme alpha subunit to treat obesity in male mice

Obesity and related diseases pose a major health risk, yet current anti-obesity drugs inadequately addressing clinical needs. Here we show AA005, an annonaceous acetogenin mimic, resists obesity induced by high-fat diets and leptin mutations at non-toxic doses, with the alpha subunit of the mitochondrial trifunctional protein (HADHA) as a target identified through proteomics and in vitro validation. Pharmacokinetic analysis shows AA005 enriches in adipose tissue, prompting the creation of adipose-specific Hadha-deficient mice. These mice significantly mitigate diet-induced obesity, echoing AA005's anti-obesity effects. AA005 treatment and Hadha deletion in adipose tissues increase body temperature and energy expenditure in high-fat diet-fed mice. The beneficial impact of AA005 on obesity mitigation is ineffective without uncoupling protein 1 (UCP1), essential for thermogenesis regulation. Our investigation shows the interaction between AA005 and HADHA in mitochondria, activating the UCP1-mediated thermogenic pathway. This substantiates AA005 as a promising compound for obesity treatment, targeting HADHA specifically.

Discovery of novel diagnostic biomarkers for Sjögren-Larsson syndrome by untargeted lipidomics

AIM

Sjögren-Larsson syndrome (SLS) is a rare neurometabolic disorder that mainly affects brain, eye and skin and is caused by deficiency of fatty aldehyde dehydrogenase. Our recent finding of a profoundly disturbed brain tissue lipidome in SLS prompted us to search for similar biomarkers in plasma as no functional test in blood is available for SLS.

METHODS AND RESULTS

We performed plasma lipidomics and used a newly developed bioinformatics tool to mine the untargeted part of the SLS plasma and brain lipidome to search for SLS biomarkers. Plasma lipidomics showed disturbed ether lipid metabolism in known lipid classes. Untargeted lipidomics of both plasma and brain (white and grey matter) uncovered two new endogenous lipid classes highly elevated in SLS. The first biomarker group were alkylphosphocholines/ethanolamines containing different lengths of alkyl-chains where some alkylphosphocholines were > 600-fold elevated in SLS plasma. The second group of biomarkers were a set of 5 features of unknown structure. Fragmentation studies suggested that they contain ubiquinol and phosphocholine and one feature was also found as a glucuronide conjugate in plasma. The plasma features were highly distinctive for SLS with levels >100-1000-fold the level in controls, if present at all. We speculate on the origin of the alkylphosphocholines/ethanolamines and the nature of the ubiquinol-containing metabolites.

CONCLUSIONS

The metabolites identified in this study represent novel endogenous lipid classes thus far unknown in humans. They represent the first plasma metabolite SLS-biomarkers and may also yield more insight into SLS pathophysiology.

Coenzyme Q10 mitigates macrophage mediated inflammation in heart following myocardial infarction via the NLRP3/IL1β pathway

BACKGROUND

The protective effect of Coenzyme Q10 (CoQ10) on the cardiovascular system has been reported, however, whether it can promote early recovery of cardiac function and alleviate cardiac remodeling after myocardial infarction (MI) remains to be elucidated. Whether CoQ10 may regulate the macrophage-mediated pro-inflammatory response after MI and its potential mechanism are worth further exploration.

METHODS

To determine the baseline plasma levels of CoQ10 by LC-MS/MS, healthy controls and MI patients (n = 11 each) with age- and gender-matched were randomly enrolled. Additional MI patients were consecutively enrolled and randomized into the blank control (n = 59) or CoQ10 group (n = 61). Follow-ups were performed at 1- and 3-month to assess cardiac function after percutaneous coronary intervention (PCI). In the animal study, mice were orally administered CoQ10/vehicle daily and were subjected to left anterior descending coronary artery (LAD) ligation or sham operation. Echocardiography and serum BNP measured by ELISA were analyzed to evaluate cardiac function. Masson staining and WGA staining were performed to analyze the myocardial fibrosis and cardiomyocyte hypertrophy, respectively. Immunofluorescence staining was performed to assess the infiltration of IL1β/ROS-positive macrophages into the ischemic myocardium. Flow cytometry was employed to analyze the recruitment of myeloid immune cells to the ischemic myocardium post-MI. The expression of inflammatory indicators was assessed through RNA-seq, qPCR, and western blotting (WB).

RESULTS

Compared to controls, MI patients showed a plasma deficiency of CoQ10 (0.76 ± 0.31 vs. 0.46 ± 0.10 µg/ml). CoQ10 supplementation significantly promoted the recovery of cardiac function in MI patients at 1 and 3 months after PCI. In mice study, compared to vehicle-treated MI mice, CoQ10-treated MI mice showed a favorable trend in survival rate (42.85% vs. 61.90%), as well as significantly alleviated cardiac dysfunction, myocardial fibrosis, and cardiac hypertrophy. Notably, CoQ10 administration significantly suppressed the recruitment of pro-inflammatory CCR2+ macrophages into infarct myocardium and their mediated inflammatory response, partially by attenuating the activation of the NLR family pyrin domain containing 3 (NLRP3)/Interleukin-1 beta (IL1β) signaling pathway.

CONCLUSIONS

These findings suggest that CoQ10 can significantly promote early recovery of cardiac function after MI. CoQ10 may function by inhibiting the recruitment of CCR2+ macrophages and suppressing the activation of the NLRP3/IL1β pathway in macrophages.

TRIAL REGISTRATION

Date of registration 09/04/2021 (number: ChiCTR2100045256).

Metabolic flux analysis of coenzyme Q10 synthesized by Rhodobacter sphaeroides under the influence of different pH regulators

Coenzyme Q10 (CoQ10) is crucial for human beings, especially in the fields of biology and medicine. The aim of this experiment was to investigate the conditions for increasing CoQ10 production. At present, microbial fermentation is the main production method of CoQ10, and the production process of microbial CoQ10 metabolism control fermentation is very critical. Metabolic flux is one of the most important determinants of cell physiology in metabolic engineering. Metabolic flux analysis (MFA) is used to estimate the intracellular flux in metabolic networks. In this experiment, Rhodobacter sphaeroides was used as the research object to analyze the effects of aqueous ammonia (NH3·H2O) and calcium carbonate (CaCO3) on the metabolic flux of CoQ10. When CaCO3 was used to adjust the pH, the yield of CoQ10 was 274.43 mg·L-1 (8.71 mg·g-1 DCW), which was higher than that of NH3·H2O adjustment. The results indicated that when CaCO3 was used to adjust pH, more glucose-6-phosphate (G6P) entered the pentose phosphate (HMP) pathway and produced more NADPH, which enhanced the synthesis of CoQ10. At the chorismic acid node, more metabolic fluxes were involved in the synthesis of p-hydroxybenzoic acid (pHBA; the synthetic precursor of CoQ10), enhancing the anabolic flow of CoQ10. In addition, Ca2+ produced by the reaction of CaCO3 with organic acids promotes the synthesis of CoQ10. In summary, the use of CaCO3 adjustment is more favorable for the synthesis of CoQ10 by R. sphaeroides than NH3·H2O adjustment. The migration of metabolic flux caused by the perturbation of culture conditions was analyzed to compare the changes in the distribution of intracellular metabolic fluxes for the synthesis of CoQ10. Thus, the main nodes of the metabolic network were identified as G6P and chorismic acid. This provides a theoretical basis for the modification of genes related to the CoQ10 synthesis pathway.

Traumatic Brain Injury Alters Cerebral Concentrations and Redox States of Coenzymes Q9 and Q10 in the Rat

To date, there is no information on the effect of TBI on the changes in brain CoQ levels and possible variations in its redox state. In this study, we induced graded TBIs (mild TBI, mTBI and severe TBI, sTBI) in male rats, using the weight-drop closed-head impact acceleration model of trauma. At 7 days post-injury, CoQ₉, CoQ₁₀ and α-tocopherol were measured by HPLC in brain extracts of the injured rats, as well as in those of a group of control sham-operated rats. In the controls, about the 69% of total CoQ was in the form of CoQ₉ and the oxidized/reduced ratios of CoQ₉ and CoQ₁₀ were, respectively, 1.05 ± 0.07 and 1.42 ± 0.17. No significant changes in these values were observed in rats experiencing mTBI. Conversely, in the brains of sTBI-injured animals, an increase in reduced and a decrease in oxidized CoQ₉ produced an oxidized/reduced ratio of 0.81 ± 0.1 (p < 0.001 compared with both controls and mTBI). A concomitant decrease in both reduced and oxidized CoQ₁₀ generated a corresponding oxidized/reduced ratio of 1.38 ± 0.23 (p < 0.001 compared with both controls and mTBI). An overall decrease in the concentration of the total CoQ pool was also found in sTBI-injured rats (p < 0.001 compared with both controls and mTBI). Concerning α-tocopherol, whilst no differences compared with the controls were found in mTBI animals, a significant decrease was observed in rats experiencing sTBI (p < 0.01 compared with both controls and mTBI). Besides suggesting potentially different functions and intracellular distributions of CoQ₉ and CoQ₁₀ in rat brain mitochondria, these results demonstrate, for the first time to the best of knowledge, that sTBI alters the levels and redox states of CoQ₉ and CoQ₁₀, thus adding a new explanation to the mitochondrial impairment affecting ETC, OXPHOS, energy supply and antioxidant defenses following sTBI.

A Comparative Study on the Reduction Modes for Quinone to Determine Ubiquinone by HPLC with Luminol Chemiluminescence Detection Based on the Redox Reaction

Ubiquinone (UQ) is considered one of the important biologically active molecules in the human body. Ubiquinone determination in human plasma is important for the investigation of its bioavailability, and also its plasma level is considered an indicator of many illnesses. We have previously developed sensitive and selective chemiluminescence (CL) method for the determination of UQ in human plasma based on its redox cycle with dithiothreitol (DTT) and luminol. However, this method requires an additional pump to deliver DTT as a post-column reagent and has the problems of high DTT consumption and broadening of the UQ peak due to online mixing with DTT. Herein, an HPLC (high-performance liquid chromatography) system equipped with two types of online reduction systems (electrolytic flow cell or platinum catalyst-packed reduction column) that play the role of DTT was constructed to reduce reagent consumption and simplify the system. The newly proposed two methods were carefully optimized and validated, and the analytical performance for UQ determination was compared with that of the conventional DTT method. Among the tested systems, the electrolytic reduction system showed ten times higher sensitivity than the DTT method, with a limit of detection of 3.1 nM. In addition, it showed a better chromatographic performance and the best peak shape with a number of theoretical plates exceeding 6500. Consequently, it was applied to the determination of UQ in healthy human plasma, and it showed good recovery (≥97.9%) and reliable precision (≤6.8%) without any interference from plasma components.

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.

Mitochondrial Coenzyme Q10 Determination Via Isotope Dilution Liquid Chromatography -Tandem Mass Spectrometry

Coenzyme Q10 (CoQ₁₀) is an essential part of the mitochondrial respiratory chain . Here, we describe an accurate and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for determination of mitochondrial CoQ₁₀ in isolated mitochondria . In the assay, mitochondrial suspensions are spiked with CoQ₁₀-[²H₉] internal standard (IS), extracted with organic solvents and CoQ₁₀ quantified by LC-MS/MS using multiple reaction monitoring (MRM).

Is plasma concentration of coenzyme Q10 a predictive marker for left ventricular remodelling after revascularization for ST-segment elevation myocardial infarction?

BACKGROUND

Left ventricular remodelling that frequently occurs after acute myocardial infarction is associated with an increased risk of heart failure and cardiovascular death. Although several risk factors have been identified, there is still no marker in clinical use to predict left ventricular remodelling. Plasma concentration of coenzyme Q10, which plays a key role in mitochondrial energy production and as an antioxidant, seems to be negatively correlated with left ventricular function after acute myocardial infarction.

OBJECTIVE

The goal of our study was to determine whether the plasma coenzyme Q10 baseline concentrations at time of the ST-elevation myocardial infarction (STEMI) could predict left ventricular remodelling at six months' follow-up.

METHODS

Sixty-eight patients who were admitted to hospital for STEMI and successfully revascularized with primary percutaneous coronary intervention were recruited. All patients underwent a 3D-echocardiography examination within the first four days after percutaneous coronary intervention and six months later then divided into two groups based on the presence or not of left ventricular remodelling. Plasma coenzyme Q10 concentration at the time of percutaneous coronary intervention was determined using high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

While we found similar plasma coenzyme Q10 concentrations compared with other studies, no association was evidenced between coenzyme Q10 concentrations and left ventricular remodelling (P = 0.89).

CONCLUSION

We found no evidence for using plasma coenzyme Q10 concentration as an early prediction marker of left ventricular remodelling after STEMI.

Respiratory chain components are required for peptidoglycan recognition protein-induced thiol depletion and killing in Bacillus subtilis and Escherichia coli

Mammalian peptidoglycan recognition proteins (PGRPs or PGLYRPs) kill bacteria through induction of synergistic oxidative, thiol, and metal stress. Tn-seq screening of Bacillus subtilis transposon insertion library revealed that mutants in the shikimate pathway of chorismate synthesis had high survival following PGLYRP4 treatment. Deletion mutants for these genes had decreased amounts of menaquinone (MK), increased resistance to killing, and attenuated depletion of thiols following PGLYRP4 treatment. These effects were reversed by MK or reproduced by inhibiting MK synthesis. Deletion of cytochrome aa₃-600 or NADH dehydrogenase (NDH) genes also increased B. subtilis resistance to PGLYRP4-induced killing and attenuated thiol depletion. PGLYRP4 treatment also inhibited B. subtilis respiration. Similarly in Escherichia coli, deletion of ubiquinone (UQ) synthesis, formate dehydrogenases (FDH), NDH-1, or cytochrome bd-I genes attenuated PGLYRP4-induced thiol depletion. PGLYRP4-induced low level of cytoplasmic membrane depolarization in B. subtilis and E. coli was likely not responsible for thiol depletion. Thus, our results show that the respiratory electron transport chain components, cytochrome aa₃-600, MK, and NDH in B. subtilis, and cytochrome bd-I, UQ, FDH-O, and NDH-1 in E. coli, are required for both PGLYRP4-induced killing and thiol depletion and indicate conservation of the PGLYRP4-induced thiol depletion and killing mechanisms in Gram-positive and Gram-negative bacteria.

Reduced Graphene Oxide Sheets as Inhibitors of the Photochemical Reactions of α-Lipoic Acid in the Presence of Ag and Au Nanoparticles

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of α-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in the presence of trisodium citrate. The presence of excipients did not induce further changes when ALA interacts with Ag and Au nanoparticles with sizes of 5 and 10 nm by exposure to UV light. Compared to the Raman spectrum of ALA powder, changes in Raman lines' position and relative intensities when ALA has interacted with films obtained from Au nanoparticles with sizes between 5 and 50 nm were significant. These changes were explained by considering the chemical mechanism of surface-enhanced Raman scattering (SERS) spectroscopy. The photodegradation of ALA that had interacted with metallic nanoparticles was inhibited in the presence of RGO sheets.

Formate dehydrogenase, ubiquinone, and cytochrome bd-I are required for peptidoglycan recognition protein-induced oxidative stress and killing in Escherichia coli

Mammalian Peptidoglycan Recognition Proteins (PGRPs) kill bacteria through induction of synergistic oxidative, thiol, and metal stress. PGRPs induce oxidative stress in bacteria through a block in the respiratory chain, which results in decreased respiration and incomplete reduction of oxygen (O₂) to hydrogen peroxide (H₂O₂). In this study we identify the site of PGRP-induced generation of H₂O₂ in Escherichia coli. Tn-seq screening of E. coli Tn10 insertion library revealed that mutants in formate dehydrogenase (FDH) genes had the highest survival following PGRP treatment. Mutants lacking functional FDH-O had abolished PGRP-induced H₂O₂ production and the highest resistance to PGRP-induced killing, and formate enhanced PGRP-induced killing and H₂O₂ production in an FDH-dependent manner. Mutants in ubiquinone synthesis (but not menaquinone and demethylmenaquinone) and cytochrome bd-I (but not cytochromes bo₃ and bd-II) also had completely abolished PGRP-induced H₂O₂ production and high resistance to PGRP-induced killing. Because electrons in the respiratory chain flow from dehydrogenases' substrates through quinones and then cytochromes to O₂, these results imply that the site of PGRP-induced incomplete reduction of O₂ to H₂O₂ is downstream from dehydrogenases and ubiquinone at the level of cytochrome bd-I, which results in oxidative stress. These results reveal several essential steps in PGRP-induced bacterial killing.

Short-term ubiquinol-10 supplementation alleviates tissue damage in muscle and fatigue caused by strenuous exercise in male distance runners

Background: Coenzyme Q10 (CoQ10) is the electron transporter in oxidative phosphorylation and an endogenous antioxidant. Recent researches have indicated that doses of 200-300 mg/day are needed to recognize effects to prevent oxidative damage in athletes, and the reduced form of CoQ10, ubiquinol-10, is more bioavailable than its oxidized form. Therefore, we hypothesized that higher doses of ubiquinol-10 could elevate plasma CoQ10 levels rapidly and exert physiological benefits in athletes. Therefore, a placebo controlled, double blinded test was carried out to determine the effects of ubiquinol-10 on the extravasate enzymes and fatigue levels of distance runners. Methods: Sixteen male collegiate distance runners were allocated to two groups receiving 300 mg/day of ubiquinol-10 (19.8 ± 1.7 years) or a placebo (20.1 ± 1.6 years) for 12 days during summer training that comprised 25- and 40-km runs on days 7 and 9, respectively. Results: Ubiquinol-10 elevated plasma CoQ10 concentration to 5.62 μg/mL and significantly decreased activities of the serum extravasate enzymes, CK, ALT, LDH (P < 0.01), and AST (P < 0.05) on day 6. Subjective fatigue status was significantly elevated on day 10 (the day after the 45-km run) in the placebo group (P < 0.001), but did not significantly change in the group given ubiquinol-10. Therefore, ubiquinol-10 could mitigate tissue damage and alleviate fatigue status in distance runners during summer training. Conclusions: Ubiquinol-10 (300 mg/day) supplementation elevated plasma CoQ10 concentrations almost to plateau levels, decreased extravasate enzymes within six days, and suppressed the subjective fatigue in male distance runners.

Evaluation of lipid coverage and high spatial resolution MALDI-imaging capabilities of oversampling combined with laser post-ionisation

Matrix-assisted laser desorption/ionisation-mass spectrometry imaging (MALDI-MSI) is a powerful technique for visualising the spatial locations of lipids in biological tissues. However, a major challenge in interpreting the biological significance of local lipid compositions and distributions detected using MALDI-MSI is the difficulty in associating spectra with cellular lipid metabolism within the tissue. By-and-large this is due to the typically limited spatial resolution of MALDI-MSI (30–100 μm) meaning individual spectra represent the average spectrum acquired from multiple adjacent cells, each potentially possessing a unique lipid composition and biological function. The use of oversampling is one promising approach to decrease the sampling area and improve the spatial resolution in MALDI-MSI, but it can suffer from a dramatically decreased sensitivity. In this work we overcome these challenges through the coupling of oversampling MALDI-MSI with laser post-ionisation (MALDI-2). We demonstrate the ability to acquire rich lipid spectra from pixels as small as 6 μm, equivalent to or smaller than the size of typical mammalian cells. Coupled with an approach for automated lipid identification, it is shown that MALDI-2 combined with oversampling at 6 μm pixel size can detect up to three times more lipids and many more lipid classes than even conventional MALDI at 20 μm resolution in the positive-ion mode. Applying this to mouse kidney and human brain tissue containing active multiple sclerosis lesions, where 74 and 147 unique lipids are identified, respectively, the localisation of lipid signals to individual tubuli within the kidney and lipid droplets with lesion-specific macrophages is demonstrated.

Analytical Method Development for Coq10 Determination in Human Plasma Using HPLC-UV and HPLC/MS/MS

Background:

CoQ10 is a very important compound which is found in every tissue of our organism. It participates in the processes of cellular respiration and ATP production. Also, it acts as a strong antioxidant. In an organism, it is represented in two forms: oxidized (ubiquinone) and reduced (ubiquinol). Its low blood level may be a signal for a list of diseases.

Materials and Methods:

This study developed and compared two methods of CoQ10 determination in order to find the fastest and the most convenient one. The first one involved HPLC-UV with the wavelength of ubiquinone determination equivalent to 290 nm and 275 nm for ubiquinol, respectively. The second one was carried out on an HPLC/MS/MS system utilizing Electrospray Ionization (ESI) and triple quadrupole mass analyzer for quantification in MRM positive mode.

Results:

Two methods of ubiquinol and ubiquinone determination were developed and validated. HPLC-UV included sample preparation based on liquid-liquid extraction. The LLOQ was 0.50 µg/ml. HPLC-MS/MS method sample preparation was based on protein precipitation. The LLOQ was 0.10 µg/ml.

Conclusion:

During the investigation, a conclusion was drawn that the HPLC-UV method is too insensitive for simultaneous determination of ubiquinol and ubiquinone. Furthermore, ubiquinol is very unstable and during exogenous factors’ exposure, it rapidly turns into ubiquinone. While, the HPLCMS/ MS method turned out to be sensitive, selective, rapid as it provides an accurate determination of both forms of CoQ10 in spiked human plasma.

A Simple and Accurate Method for the Determination of Related Substances in Coenzyme Q10 Soft Capsules

As a new dosage form, coenzyme Q10 (Co-Q10) soft capsules are easily absorbed and utilized by the human body. Co-Q10 soft capsules can effectively improve the bioavailability and reduce medical costs for patients. A main concern about Co-Q10 as an active pharmaceutical ingredient (API) is how to control the total quantity of related substances. In this article, according to the degradation pattern of the API, the most easily degradable impurity (impurity X) in the sample was prepared and its chemical structure was determined. Furthermore, a simple and accurate method was developed for the determination of related substances and to avert the interference of excipient ingredients in Co-Q10 soft capsules. The approach was validated adequately and the primary impurity X was confirmed accurately. The limit of total quantity of related substances (less than 1%) could be revised to the level of specific impurity X being no more than 0.5%, in this effective quality control method of Co-Q10 soft capsules. The revised level is suggested to be included in the corresponding standard of the supplement taken from the Pharmacopoeia of the People’s Republic of China (2015 edition). This can provide a feasible method for the relevant enterprises and regulatory authorities to control the related substances of coenzyme Q10 soft capsules.

Coenzyme Q10 Prevents Senescence and Dysfunction Caused by Oxidative Stress in Vascular Endothelial Cells

Oxidative damage in endothelial cells is proposed to play an important role in endothelial dysfunction and atherogenesis. We previously reported that the reduced form of coenzyme Q10 (CoQ₁₀H₂) effectively inhibits oxidative stress and decelerates senescence in senescence-accelerated mice. Here, we treated human umbilical vein endothelial cells (HUVECs) with H₂O₂ and investigated the protective effect of CoQ₁₀H₂ against senescence, oxidative damage, and reduction in cellular functions. We found that CoQ₁₀H₂ markedly reduced the number of senescence-associated β-galactosidase-positive cells and suppressed the expression of senescence-associated secretory phenotype-associated genes in H₂O₂-treated HUVECs. Furthermore, CoQ₁₀H₂ suppressed the generation of intracellular reactive oxygen species (ROS) but promoted NO production that was accompanied by increased eNOS expression. CoQ₁₀H₂ prevented apoptosis and reductions in mitochondrial function and reduced migration and tube formation activity of H₂O₂-treated cells. The present study indicated that CoQ₁₀H₂ protects endothelial cells against senescence by promoting mitochondrial function and thus could delay vascular aging.

Highly sensitive and selective determination of redox states of coenzymes Q9 and Q10 in mice tissues: Application of orbitrap mass spectrometry

Coenzyme Q (CoQ) is a redox active molecule that plays a fundamental role in mitochondrial energy generation and functions as a potent endogenous antioxidant. Redox ratio of CoQ has been suggested as a good marker of mitochondrial dysfunction and oxidative stress. Nevertheless, simultaneous measurement of redox states of CoQ is challenging owing to its hydrophobicity and instability of the reduced form. In order to improve the analytical methodology, paying special attention to this instability, we developed a highly sensitive and selective high-resolution/accurate-mass (HR/AM) UHPLC-MS/MS method for the rapid determination of redox states of CoQ₉ and CoQ₁₀ by ultra-performance liquid chromatography-hybrid quadrupole-Orbitrap mass spectrometry. CoQs were extracted using hexane with the addition of butylated hydroxytoluene to limit oxidation during sample preparation. Chromatographic separation of the analytes was achieved on a Kinetex C₁₈ column with the isocratic elution of 5 mM ammonium formate in 2-propanol/methanol (60:40) within 4 min. A full MS/all ion fragmentation (AIF) acquisition mode with mass accuracy < 5 ppm was used for detection and determination of redox states of CoQ₉ and CoQ₁₀ in healthy mice tissues using reduced and oxidized CoQ₄ as internal standards. The validated method showed good linearity (r² ≥ 0.9991), intraday, inter-day precision (CVs ≤ 11.9%) and accuracy (RE ≤±15.2%). In contrast to existing methods, the current method offers enhanced sensitivity (up to 52 fold) with LOD and LOQ ranged from 0.01 to 0.49 ng mL^-1 and 0.04-1.48 ng mL^-1, respectively. Moreover, we evaluated various diluents to investigate bench top stability (at 4 °C) of targeted analytes in tissue samples during LC-MS assay up to 24 h. Ethanol was determined to be an optimum diluent without any significant oxidation of reduced CoQ up to 24 h. The developed method offers a rapid, highly sensitive and selective strategy for the measurement of redox states of CoQs in clinical studies.

Low-cost and disposable sensors for the simultaneous determination of coenzyme Q10 and α-lipoic acid using manganese (IV) oxide-modified screen-printed graphene electrodes

In this work, for the first time, manganese (IV) oxide-modified screen-printed graphene electrodes (MnO₂/SPGEs) were developed for the simultaneous electrochemical detection of coenzyme Q10 (CoQ10) and α-lipoic acid (ALA). This sensor exhibits attractive benefits such as simplicity, low production costs, and disposability. Cyclic voltammetry (CV) was used to characterize the electrochemical behavior of the analyte and investigate the capacitance and electroactive surface area of the unmodified and modified electrode surfaces. The electrochemical behavior of CoQ10 and ALA on MnO₂/SPGEs was also discussed. Additionally, square wave anodic stripping voltammetry (SWASV) was used for the quantitative determination of CoQ10 and ALA. Under optimal conditions, the obtained signals are linear in the concentration range from 2.0 to 75.0 μg mL^-1 for CoQ10 and 0.3-25.0 μg mL^-1 for ALA. The low limits of detection (LODs) were found to be 0.56 μg mL^-1 and 0.088 μg mL^-1 for CoQ10 and ALA, respectively. Moreover, we demonstrated the utility and applicability of the MnO₂/SPGE sensor through simultaneous measurements of CoQ10 and ALA in dietary supplements. The sensor provides high accuracy measurements, exhibiting its high potential for practical applications.

Serum from postmenopausal women treated with a by-product of olive-oil extraction process stimulates osteoblastogenesis and inhibits adipogenesis in human mesenchymal stem-cells (MSC)

Aging may enhance both oxidative stress and bone-marrow mesenchymal stem-cell (MSC) differentiation into adipocytes. That reduces osteoblastogenesis, thus favoring bone-mass loss and fracture, representing an important worldwide health-issue, mainly in countries with aging populations. Intake of antioxidant products may help to retain bone-mass density. Interestingly, a novel olive-pomace physical treatment to generate olive oil also yields by-products rich in functional antioxidants. Thus, diet of postmenopausal women was supplemented for two months with one of such by-products (distillate 6; D6), being rich in squalene. After treatment, serum from such women showed reduced both lipidic peroxidation and oxidized low-density lipoprotein (LDL). Besides, vitamin E and coenzyme Q10 levels increased. Furthermore, culture medium containing 10% of such serum both increased osteoblastogenesis and reduced adipogenesis in human MSC from bone marrow. Therefore, highly antioxidant by-products like D6 may represent a relevant source for development of functional products, for both prevention and treatment of degenerative pathologies associated with aging, like osteoporosis.

Automated statistical experimental design approach for rapid separation of coenzyme Q10 and identification of its biotechnological process related impurities using UHPLC and UHPLC-APCI-MS

A novel ultra high performance liquid chromatography method development strategy was ameliorated by applying quality by design approach. The developed systematic approach was divided into five steps (i) Analytical Target Profile, (ii) Critical Quality Attributes, (iii) Risk Assessments of Critical parameters using design of experiments (screening and optimization phases), (iv) Generation of design space, and (v) Process Capability Analysis (Cp) for robustness study using Monte Carlo simulation. The complete quality-by-design-based method development was made automated and expedited by employing sub-2 μm particles column with an ultra high performance liquid chromatography system. Successful chromatographic separation of the Coenzyme Q10 from its biotechnological process related impurities was achieved on a Waters Acquity phenyl hexyl (100 mm × 2.1 mm, 1.7 μm) column with gradient elution of 10 mM ammonium acetate buffer (pH 4.0) and a mixture of acetonitrile/2-propanol (1:1) as the mobile phase. Through this study, fast and organized method development workflow was developed and robustness of the method was also demonstrated. The method was validated for specificity, linearity, accuracy, precision, and robustness in compliance to the International Conference on Harmonization, Q2 (R1) guidelines. The impurities were identified by atmospheric pressure chemical ionization-mass spectrometry technique. Further, the in silico toxicity of impurities was analyzed using TOPKAT and DEREK software.

Rapid assessment of the coenzyme Q10 redox state using ultrahigh performance liquid chromatography tandem mass spectrometry

An improved method for accurate and rapid assessment of the coenzyme Q10 (CoQ10) redox state using ultrahigh performance liquid chromatography tandem mass spectrometry was described, with particular attention given to the instability of the reduced form of CoQ10 during sample preparation, chromatographic separation and mass spectrometric detection. As highly lipophilic compounds in complex biological matrices, both reduced and oxidized forms of CoQ10 were extracted simultaneously from the tissue samples by methanol which is superior to ethanol and isopropanol. After centrifugation, the supernatants were immediately separated on a C18 column with isocratic elution using methanol containing 2 mM ammonium acetate as a non-aqueous mobile phase, and detected by positive electrospray ionization tandem mass spectrometry in multiple reaction monitoring (MRM) mode. Ammonium acetate as an additive in methanol provided enhanced mass spectrometric responses for both forms of CoQ10, primarily due to stable formation of adduct ions [M + NH4](+), which served as precursor ions in positive ionization MRM transitions. The assay showed a linear range of 8.6-8585 ng mL(-1) for CoQ10H2 and 8.6-4292 ng mL(-1) for CoQ10. The limits of detection (LODs) were 7.0 and 1.0 ng mL(-1) and limits of quantification (LOQs) were 15.0 and 5.0 ng mL(-1) for CoQ10H2 and CoQ10, respectively. This rapid extractive and analytical method could avoid artificial auto-oxidation of the reduced form of CoQ10, enabling the native redox state assessment. This reliable method was also successfully applied for the measurement of the CoQ10 redox state in liver tissues of mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin, revealing the down-regulated mitochondrial electron transport chain.

Rapid high performance liquid chromatography-high resolution mass spectrometry methodology for multiple prenol lipids analysis in zebrafish embryos

The analysis of lipid molecules in living organism is an important step in deciphering metabolic pathways. Recently, the zebrafish has been adopted as a valuable animal model system to perform in vivo metabolomics studies, however limited methodologies and protocols are currently available to investigate zebrafish lipidome and even fewer to analyze specific classes of lipids. Here we present an HPLC-HRMS based method to rapidly measure multiple prenol lipid molecules from zebrafish tissues. In particular, we have optimized our method for concurrent detection of ubiquinones (Coenzyme Q6, Coenzyme Q9, Coenzyme Q10), cholesterol, vitamin E (α-tocopherol), vitamin K1 and vitamin K2. The purpose of this study was to compare different ionization modes, mobile phases and stationary phases in order to optimize lipid molecules separation. After HPLC-HRMS parameters selection, several extraction conditions from zebrafish embryos were evaluated. We assessed our methodology by quantitation of analytical recovery on zebrafish extracts from wild-type or zebrafish mutants (barolo) affected by impaired biosynthesis of ubiquinones.

Rapid and sensitive analysis of reduced and oxidized coenzyme Q10 in human plasma by ultra performance liquid chromatography-tandem mass spectrometry and application to studies in healthy human subjects

BACKGROUND

Coenzyme Q10 is an endogenous antioxidant as well as a popular dietary supplement. In blood circulation, coenzyme Q10 exists predominantly as its reduced ubiquinol-10 form, which readily oxidizes to ubiquinone-10 ex vivo. Plasma concentrations of coenzyme Q10 reflect net overall metabolic demand, and the ratio of ubiquinol-10:ubiquinone-10 has been established as an important biomarker for oxidative stress. However, the lability of ubiquinol-10 makes accurate determination of both forms of coenzyme Q10 difficult. Ex vivo oxidation of ubiquinol-10 to ubiquinone-10 during sample collection, processing and analysis may obfuscate the in vivo ratio.

METHODS

We developed a rapid and sensitive method for the determination of ubiquinol-10 and ubiquinone-10 in human plasma, using coenzyme Q9 analogues as internal standards. Single-step protein precipitation in 1-propanol, a lipophilic and water-soluble alcohol, allowed for rapid extraction.

RESULTS

Analysis by ultra performance liquid chromatography-tandem mass spectrometry provided rapid run-time and high sensitivity, with lower limits of quantitation for ubiquinol-10 and ubiquinone-10 of 5 μg/L and 10 μg/L, respectively.

CONCLUSIONS

This method is suitable for clinical studies with coenzyme Q10 supplementation in various disease states where this lipid-antioxidant may be beneficial. We have applied this method to >300 plasma samples from coenzyme Q10 research studies in chronic haemodialysis patients and postsurgical patients.

Mitochondrial coenzyme Q10 determination via isotope dilution liquid chromatography tandem mass spectrometry

Coenzyme Q10 (CoQ10) is an essential part of the mitochondrial respiratory chain. Here, we describe an accurate and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for determination of mitochondrial CoQ10 in isolated mitochondria. In the assay, mitochondrial suspensions are spiked with CoQ10-[(2)H6] internal standard, extracted with organic solvents, and CoQ10 quantified by LC-MS/MS using multiple reaction monitoring (MRM).

Coenzyme Q10 treatments influence the lifespan and key biochemical resistance systems in the honeybee, Apis mellifera

Natural bioactive preparations that will boost apian resistance, aid body detoxification, or fight crucial bee diseases are in demand. Therefore, we examined the influence of coenzyme Q10 (CoQ10, 2,3-dimethoxy, 5-methyl, 6-decaprenyl benzoquinone) treatment on honeybee lifespan, Nosema resistance, the activity/concentration of antioxidants, proteases and protease inhibitors, and biomarkers. CoQ10 slows age-related metabolic processes. Workers that consumed CoQ10 lived longer than untreated controls and were less infested with Nosema spp. Relative to controls, the CoQ10-treated workers had higher protein concentrations that increased with age but then they decreased in older bees. CoQ10 treatments increased the activities of antioxidant enzymes (superoxide dismutase, GPx, catalase, glutathione S-transferase), protease inhibitors, biomarkers (aspartate aminotransferase, alkaline phosphatase, alanine aminotransferase), the total antioxidant potential level, and concentrations of uric acid and creatinine. The activities of acidic, neutral, and alkaline proteases, and concentrations of albumin and urea were lower in the bees that were administered CoQ10. CoQ10 could be taken into consideration as a natural diet supplement in early spring before pollen sources become available in the temperate Central European climate. A response to CoQ10 administration that is similar to mammals supports our view that Apis mellifera is a model organism for biochemical gerontology.

A rapid method for the extraction and analysis of carotenoids and other hydrophobic substances suitable for systems biology studies with photosynthetic bacteria

A simple, rapid, and inexpensive extraction method for carotenoids and other non-polar compounds present in phototrophic bacteria has been developed. The method, which has been extensively tested on the phototrophic purple non-sulphur bacterium Rhodospirillum rubrum, is suitable for extracting large numbers of samples, which is common in systems biology studies, and yields material suitable for subsequent analysis using HPLC and mass spectroscopy. The procedure is particularly suitable for carotenoids and other terpenoids, including quinones, bacteriochlorophyll a and bacteriopheophytin a, and is also useful for the analysis of polar phospholipids. The extraction procedure requires only a single step extraction with a hexane/methanol/water mixture, followed by HPLC using a Spherisorb C18 column, with a mobile phase consisting of acetone-water and a non-linear gradient of 50%-100% acetone. The method was employed for examining the carotenoid composition observed during microaerophilic growth of R. rubrum strains, and was able to determine 18 carotenoids, 4 isoprenoid-quinones, bacteriochlorophyll a and bacteriopheophytin a as well as four different phosphatidylglycerol species of different acyl chain compositions. The analytical procedure was used to examine the dynamics of carotenoid biosynthesis in the major and minor pathways operating simultaneously in a carotenoid biosynthesis mutant of R. rubrum.

Analysis of circulating lipid-phase micronutrients in humans by HPLC: review and overview of new developments

Retinol, tocopherols, coenzyme Q10, carotenoids, and vitamin D are lipophilic compounds shown to function as important health-protective agents by mitigating the damaging effects of oxidative and other injury. Scientific interest in evaluating these compounds has resurfaced in recent years, particularly in the nutritional, clinical and epidemiologic fields, and has precipitated the development of a multitude of new analytical techniques. This review considers recent developments in HPLC-based assays since 2007 for the simultaneous determination of these lipid-phase compounds utilizing exclusively serum or plasma as these matrices are mostly used in clinical and epidemiological investigations. We also provide an overview of blood measurements for selected carotenoids, tocopherols, coenzyme Q10 and retinol from the last 15years of healthy umbilical cord blood, children, and adults.

Coenzyme Q10 quantification in muscle, fibroblasts and cerebrospinal fluid by liquid chromatography/tandem mass spectrometry using a novel deuterated internal standard

RATIONALE

Neurological dysfunction is common in primary coenzyme Q10 (2,3-dimethoxy, 5-methyl, 6-polyisoprene parabenzoquinone; CoQ10 ; ubiquinone) deficiencies, the most readily treatable subgroup of mitochondrial disorders. Therapeutic benefit from CoQ10 supplementation has also been noted in other neurodegenerative diseases. CoQ10 can be measured by high-performance liquid chromatography (HPLC) in plasma, muscle or leucocytes; however, there is no reliable method to quantify CoQ10 in cerebrospinal fluid (CSF). Additionally, many methods use CoQ9 , an endogenous ubiquinone in humans, as an internal standard.

METHODS

Deuterated CoQ10 (d6 -CoQ10 ) was synthesised by a novel, simple, method. Total CoQ10 was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using d6 -CoQ10 as internal standard and 5 mM methylamine as an ion-pairing reagent. Chromatography was performed using a Hypsersil GOLD C4 column (150 × 3 mm, 3 µm).

RESULTS

CoQ10 levels were linear over a concentration range of 0-200 nM (R(2) = 0.9995). The lower limit of detection was 2 nM. The inter-assay coefficient of variation (CV) was 3.6% (10 nM) and 4.3% (20 nM), and intra-assay CV 3.4% (10 nM) and 3.6% (20 nM). Reference ranges were established for CoQ10 in CSF (5.7-8.7 nM; n = 17), fibroblasts (57.0-121.6 pmol/mg; n = 50) and muscle (187.3-430.1 pmol/mg; n = 15).

CONCLUSIONS

Use of d6 -CoQ10 internal standard has enabled the development of a sensitive LC/MS/MS method to accurately determine total CoQ10 levels. Clinical applications of CSF CoQ10 determination include identification of patients with cerebral CoQ10 deficiency, and monitoring CSF CoQ10 levels following supplementation.

Mitochondrial coenzyme Q10 determination by isotope-dilution liquid chromatography-tandem mass spectrometry

BACKGROUND

Coenzyme Q10 (CoQ10) is an essential part of the mitochondrial respiratory chain. Unlike most other respiratory chain disorders, CoQ10 deficiency is potentially treatable. We aimed to develop and validate an accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of mitochondrial CoQ10 in clinical samples.

METHODS

We used mitochondria isolated from muscle biopsies of patients (n = 166) suspected to have oxidative phosphorylation deficiency. We also used fibroblast mitochondria from 1 patient with CoQ10 deficiency and 3 healthy individuals. Samples were spiked with nonphysiologic CoQ10-[(2)H6] internal standard, extracted with 1-propanol and with ethanol and hexane (2 mL/5 mL), and CoQ10 quantified by LC-MS/MS. The method and sample stability were validated. A reference interval was established from the patient data.

RESULTS

The method had a limit of quantification of 0.5 nmol/L. The assay range was 0.5-1000 nmol/L and the CVs were 7.5%-8.2%. CoQ10 was stable in concentrated mitochondrial suspensions. In isolated mitochondria, the mean ratio of CoQ10 to citrate synthase (CS) activity (CoQ10/CS) was 1.7 nmol/U (95% CI, 1.6-1.7 nmol/U). We suggest a CoQ10/CS reference interval of 1.1-2.8 nmol/U for both sexes and all ages. The CoQ10/CS ratio was 5-fold decreased in fibroblast mitochondria from a patient with known CoQ10 deficiency due to recessive prenyl (decaprenyl) diphosphate synthase, subunit 2 (PDSS2) mutations.

CONCLUSIONS

Normalization of mitochondrial CoQ10 concentration against citrate synthase activity is likely to reflect most accurately the CoQ10 content available for the respiratory chain. Our assay and the established reference range should facilitate the diagnosis of respiratory chain disorders and treatment of patients with CoQ10 deficiency.

Ubiad1 is an antioxidant enzyme that regulates eNOS activity by CoQ10 synthesis

Protection against oxidative damage caused by excessive reactive oxygen species (ROS) by an antioxidant network is essential for the health of tissues, especially in the cardiovascular system. Here, we identified a gene with important antioxidant features by analyzing a null allele of zebrafish ubiad1, called barolo (bar). bar mutants show specific cardiovascular failure due to oxidative stress and ROS-mediated cellular damage. Human UBIAD1 is a nonmitochondrial prenyltransferase that synthesizes CoQ10 in the Golgi membrane compartment. Loss of UBIAD1 reduces the cytosolic pool of the antioxidant CoQ10 and leads to ROS-mediated lipid peroxidation in vascular cells. Surprisingly, inhibition of eNOS prevents Ubiad1-dependent cardiovascular oxidative damage, suggesting a crucial role for this enzyme and nonmitochondrial CoQ10 in NO signaling. These findings identify UBIAD1 as a nonmitochondrial CoQ10-forming enzyme with specific cardiovascular protective function via the modulation of eNOS activity.

Analytical problems with the determination of coenzyme Q10 in biological samples

The article discusses analytical problems related to the determination of coenzyme Q10 in biological samples. The assaying of coenzyme Q10 in complex samples, such as plasma, tissues, or food items requires meticulous sample preparation prior to final quantification. The process typically consists of the following steps: deproteinization, extraction, and ultimately reduction of extract volumes. At times drying under a gentle stream of neutral gas is applied. In the case of solid samples, a careful homogenization is also required. Each step of the sample preparation process can be a source of analytical errors that may lead to inaccurate results. The main aim of this work is to point to sources of analytical errors in the preparation process and their relation to physicochemical properties of coenzyme Q10. The article also discusses ways of avoiding and reducing the errors.

Assay to measure oxidized and reduced forms of CoQ by LC-MS/MS

The redox status of mitochondrial coenzyme Q (CoQ) is an important marker for oxidative stress associated with several disorders such as Parkinson disease and Alzheimer disease. Altered redox status may be present in mitochondrial electron transport complex disorders. Intracellular CoQ levels reflect the functional status of the mitochondrial electron transport complex better than plasma levels. Here, we describe the method to determine the reduced and oxidized form of CoQ in white blood cells using LC-MS/MS.

Analysis of coenzyme Q10 in bee pollen using online cleanup by accelerated solvent extraction and high performance liquid chromatography

A method for the determination of coenzyme Q10 in bee pollen has been developed applying an online cleanup of accelerated solvent extraction and using environmentally acceptable organic solvents. The extracted samples were analysed by high performance liquid chromatography with diode array detection. The optimised method employed 10 mL extraction cells, 1g sample size, absolute ethanol as extraction solvent, 80°C of extraction temperature, one extraction cycle, 5 min of static time, Cleanert Alumina-N as sorbent and 60% flush volume. The method was validated by means of an evaluation of the matrix effects, linearity, limit of detection (LOD) and quantification (LOQ), trueness, precision and stability. The assay was linear over the concentration range of 0.25-200mg/L and the LOD and LOQ were 0.16 and 0.35 mg/kg, respectively. The recoveries were above 90%. The inter- and intra-day precision was below 6.3%. The method has been successfully applied to the analysis of bee pollen samples. For 20 bee pollen products, the coenzyme Q10 content varied from not detectable to 192.8 mg/kg.

The role of DMQ(9) in the long-lived mutant clk-1

INTRODUCTION

Ubiquinone (UQ) is a redox active lipid that transfers electrons from complex I or II to complex III in the electron transport chain (ETC). The long-lived Caenorhabditis elegans mutant clk-1 is unable to synthesize its native ubiquinone, and accumulates high amounts of its precursor, 5-demethoxyubiquinone-9 (DMQ(9)). In clk-1, complexes I-III activity is inhibited while complexes II-III activity is normal. We asked whether the complexes I-III defect in clk-1 was caused by: (1) a defect in the ETC; (2) an inhibitory effect of DMQ(9); or (3) a decreased amount of ubiquinone.

METHODS

We extracted the endogenous quinones from wildtype (N2) and clk-1 mitochondria, replenished them with exogenous ubiquinones, and measured ETC activities.

RESULTS

Replenishment of extracted mutant and wildtype mitochondria resulted in equal enzymatic activities for complexes I-III and II-III ETC assays. Blue native gels showed that supercomplex formation was indistinguishable between clk-1 and N2. The addition of a pentane extract from clk-1 mitochondria containing DMQ(9) to wildtype mitochondria specifically inhibited complexes I-III activity. UQ in clk-1 mitochondria was oxidized compared to N2.

DISCUSSION

Our results show that no measurable intrinsic ETC defect exists in clk-1 mitochondria. The data indicate that DMQ(9) specifically inhibits electron transfer from complex I to ubiquinone.