Coenzyme Q deficiency triggers mitochondria degradation by mitophagy

Idebenone ameliorates statin-induced myotoxicity in atherosclerotic ApoE-/- mice by reducing oxidative stress and improving mitochondrial function

Statins are the first line of choice for the treatment for atherosclerosis, but their use can cause myotoxicity, a common side effect that may require dosage reduction or discontinuation. The exact mechanism of statin-induced myotoxicity is unknown. Previous research has demonstrated that the combination of idebenone and statin yielded superior anti-atherosclerotic outcomes. Here, we investigated the mechanism of statin-induced myotoxicity in atherosclerotic ApoE-/- mice and whether idebenone could counteract it. After administering simvastatin to ApoE-/- mice, we observed a reduction in plaque formation as well as a decrease in their exercise capacity. We observed elevated levels of lactic acid and creatine kinase, along with a reduction in the cross-sectional area of muscle fibers, an increased presence of ragged red fibers, heightened mitochondrial crista lysis, impaired mitochondrial complex activity, and decreased levels of CoQ9 and CoQ10. Two-photon fluorescence imaging revealed elevated H2O2 levels in the quadriceps, indicating increased oxidative stress. Proteomic analysis indicated that simvastatin inhibited the tricarboxylic acid cycle. Idebenone treatment not only further reduced plaque formation but also ameliorated the impaired exercise capacity caused by simvastatin. Our study represents the inaugural comprehensive investigation into the mechanisms underlying statin-induced myotoxicity. We have demonstrated that statins inhibit CoQ synthesis, impair mitochondrial complex functionality, and elevate oxidative stress, ultimately resulting in myotoxic effects. Furthermore, our research marks the pioneering identification of idebenone's capability to mitigate statin-induced myotoxicity by attenuating oxidative stress, thereby safeguarding mitochondrial complex functionality. The synergistic use of idebenone and statin not only enhances the effectiveness against atherosclerosis but also mitigates statin-induced myotoxicity.

Traditional Chinese medicine and mitophagy: A novel approach for cardiovascular disease management

BACKGROUND

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality worldwide, imposing an enormous economic burden on individuals and human society. Laboratory studies have identified several drugs that target mitophagy for the prevention and treatment of CVD. Only a few of these drugs have been successful in clinical trials, and most studies have been limited to animal and cellular models. Furthermore, conventional drugs used to treat CVD, such as antiplatelet agents, statins, and diuretics, often result in adverse effects on patients' cardiovascular, metabolic, and respiratory systems. In contrast, traditional Chinese medicine (TCM) has gained significant attention for its unique theoretical basis and clinical efficacy in treating CVD.

PURPOSE

This paper systematically summarizes all the herbal compounds, extracts, and active monomers used to target mitophagy for the treatment of CVD in the last five years. It provides valuable information for researchers in the field of basic cardiovascular research, pharmacologists, and clinicians developing herbal medicines with fewer side effects, as well as a useful reference for future mitophagy research.

METHODS

The search terms "cardiovascular disease," "mitophagy," "herbal preparations," "active monomers," and "cardiac disease pathogenesis" in combination with "natural products" and "diseases" were used to search for studies published in the past five years until January 2024.

RESULTS

Studies have shown that mitophagy plays a significant role in the progression and development of CVD, such as atherosclerosis (AS), heart failure (HF), myocardial infarction (MI), myocardial ischemia/reperfusion injury (MI/RI), cardiac hypertrophy, cardiomyopathy, and arrhythmia. Herbal compound preparations, crude extracts, and active monomers have shown potential as effective treatments for these conditions. These substances protect cardiomyocytes by inducing mitophagy, scavenging damaged mitochondria, and maintaining mitochondrial homeostasis. They display notable efficacy in combating CVD.

CONCLUSION

TCM (including herbal compound preparations, extracts, and active monomers) can treat CVD through various pharmacological mechanisms and signaling pathways by inducing mitophagy. They represent a hotspot for future cardiovascular basic research and a promising candidate for the development of future cardiovascular drugs with fewer side effects and better therapeutic efficacy.

Identification of potential biomarkers and pathways for asthenozoospermia by bioinformatics analysis and experiments

Background

Asthenozoospermia, a type of male infertility, is primarily caused by dysfunctional sperm mitochondria. Despite previous bioinformatics analysis identifying potential key lncRNAs, miRNAs, hub genes, and pathways associated with asthenospermia, there is still a need to explore additional molecular mechanisms and potential biomarkers for this condition.

Methods

We integrated data from Gene Expression Omnibus (GEO) (GSE22331, GSE34514, and GSE160749) and performed bioinformatics analysis to identify differentially expressed genes (DEGs) between normozoospermia and asthenozoospermia. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to gain insights into biological processes and signaling pathways. Weighted Gene Co-expression Network Analysis (WGCNA) identified gene modules associated with asthenozoospermia. Expression levels of key genes were assessed using datasets and experimental data. Gene Set Enrichment Analysis (GSEA) and correlation analysis identified pathways associated with the hub gene and explore the relationship between the ZNF764 and COQ9 and mitochondrial autophagy-related genes. Competitive endogenous RNA (ceRNA) networks were constructed, and in vitro experiments using exosome samples were conducted to validate this finding.

Results

COQ9 was identified as a marker gene in asthenozoospermia, involved in autophagy, ATP-dependent chromatin remodeling, endocytosis, and cell cycle, etc. The ceRNA regulatory network (LINC00893/miR-125a-5p/COQ9) was constructed, and PCR demonstrated that LINC00893 and COQ9 were downregulated in asthenozoospermia, while miR-125a-5p and m6A methylation level of LINC00893 were upregulated in asthenozoospermia compared to normozoospermic individuals.

Conclusion

The ceRNA regulatory network (LINC00893/miR-125a-5p/COQ9) likely plays a crucial role in the mechanism of asthenozoospermia. However, further functional experiments are needed to fully understand its significance.

Hydrogen sulfide supplementation as a potential treatment for primary mitochondrial diseases

Primary mitochondrial diseases (PMD) are amongst the most common inborn errors of metabolism causing fatal outcomes within the first decade of life. With marked heterogeneity in both inheritance patterns and physiological manifestations, these conditions present distinct challenges for targeted drug therapy, where effective therapeutic countermeasures remain elusive within the clinic. Hydrogen sulfide (H2S)-based therapeutics may offer a new option for patient treatment, having been proposed as a conserved mitochondrial substrate and post-translational regulator across species, displaying therapeutic effects in age-related mitochondrial dysfunction and neurodegenerative models of mitochondrial disease. H2S can stimulate mitochondrial respiration at sites downstream of common PMD-defective subunits, augmenting energy production, mitochondrial function and reducing cell death. Here, we highlight the primary signalling mechanisms of H2S in mitochondria relevant for PMD and outline key cytoprotective proteins/pathways amenable to post-translational restoration via H2S-mediated persulfidation. The mechanisms proposed here, combined with the advent of potent mitochondria-targeted sulfide delivery molecules, could provide a framework for H2S as a countermeasure for PMD disease progression.

Ferulago angulata extract alleviates testicular toxicity in male mice exposed to diazinon and lead

In this study, we investigated the protective effects of Ferulago angulata extract (FAE) against the reproductive toxicants Diazinon (DZN) and Lead (Pb) in mice. These pollutants are known to induce oxidative stress (OS), while FAE acts as a natural antioxidant. Adult male NMRI mice were exposed to DZN, Pb, and DZN+Pb, with or without FAE treatment for six weeks. We evaluated OS markers, testicular histology, and expression of mRNA related to enzymatic antioxidants. Exposure to DZN and Pb led to increased levels of thiobarbituric acid reactive substance (TBARS) and nitric oxide (NO) in the testes, along with a decrease in the total antioxidant capacity (TAC). Furthermore, the mRNA expression of antioxidant enzymes such as superoxide dismutase 1 (SOD1) and glutathione peroxidase 4 (GPX4) was altered. However, when FAE was administered concurrently, it restored the biochemical parameters to normal levels, reduced the toxic effects of DZN and Pb, and provided protection against testicular histopathological injury. These findings suggest that FAE has the potential to serve as a protective agent against oxidative damage caused by contaminants in reproductive organs, specifically in the testes.

ANT-dependent MPTP underlies necrotic myofiber death in muscular dystrophy

Mitochondrial permeability transition pore (MPTP) formation contributes to ischemia-reperfusion injury in the heart and several degenerative diseases, including muscular dystrophy (MD). MD is a family of genetic disorders characterized by progressive muscle necrosis and premature death. It has been proposed that the MPTP has two molecular components, the adenine nucleotide translocase (ANT) family of proteins and an unknown component that requires the chaperone cyclophilin D (CypD) to activate. This model was examined in vivo by deleting the gene encoding ANT1 (Slc25a4) or CypD (Ppif) in a δ-sarcoglycan (Sgcd) gene-deleted mouse model of MD, revealing that dystrophic mice lacking Slc25a4 were partially protected from cell death and MD pathology. Dystrophic mice lacking both Slc25a4 and Ppif together were almost completely protected from necrotic cell death and MD disease. This study provides direct evidence that ANT1 and CypD are required MPTP components governing in vivo cell death, suggesting a previously unrecognized therapeutic approach in MD and other necrotic diseases.

The Role of Mitophagy in Glaucomatous Neurodegeneration

This review aims to provide a better understanding of the emerging role of mitophagy in glaucomatous neurodegeneration, which is the primary cause of irreversible blindness worldwide. Increasing evidence from genetic and other experimental studies suggests that mitophagy-related genes are implicated in the pathogenesis of glaucoma in various populations. The association between polymorphisms in these genes and increased risk of glaucoma is presented. Reduction in intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma, while clinical trials highlight the inadequacy of IOP-lowering therapeutic approaches to prevent sight loss in many glaucoma patients. Mitochondrial dysfunction is thought to increase the susceptibility of retinal ganglion cells (RGCs) to other risk factors and is implicated in glaucomatous degeneration. Mitophagy holds a vital role in mitochondrial quality control processes, and the current review explores the mitophagy-related pathways which may be linked to glaucoma and their therapeutic potential.

Is Disrupted Mitophagy a Central Player to Parkinson's Disease Pathology?

Whilst the pathophysiology at a cellular level has been defined, the cause of Parkinson's disease (PD) remains poorly understood. This neurodegenerative disorder is associated with impaired dopamine transmission in the substantia nigra, and protein accumulations known as Lewy bodies are visible in affected neurons. Cell culture models of PD have indicated impaired mitochondrial function, so the focus of this paper is on the quality control processes involved in and around mitochondria. Mitochondrial autophagy (mitophagy) is the process through which defective mitochondria are removed from the cell by internalisation into autophagosomes which fuse with a lysosome. This process involves many proteins, notably including PINK1 and parkin, both of which are known to be coded on genes associated with PD. Normally in healthy individuals, PINK1 associates with the outer mitochondrial membrane, which then recruits parkin, activating it to attach ubiquitin proteins to the mitochondrial membrane. PINK1, parkin, and ubiquitin cooperate to form a positive feedback system which accelerates the deposition of ubiquitin on dysfunctional mitochondria, resulting in mitophagy. However, in hereditary PD, the genes encoding PINK1 and parkin are mutated, resulting in proteins that are less efficient at removing poorly performing mitochondria, leaving cells more vulnerable to oxidative stress and ubiquitinated inclusion bodies, such as Lewy bodies. Current research that looks into the connection between mitophagy and PD is promising, already yielding potentially therapeutic compounds; until now, pharmacological support for the mitophagy process has not been part of the therapeutic arsenal. Continued research in this area is warranted.

Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome

Mutations in several genes involved in the epigenetic regulation of gene expression have been considered risk alterations to different intellectual disability (ID) syndromes associated with features of autism spectrum disorder (ASD). Among them are the pathogenic variants of the lysine-acetyltransferase 6A (KAT6A) gene, which causes KAT6A syndrome. The KAT6A enzyme participates in a wide range of critical cellular functions, such as chromatin remodeling, gene expression, protein synthesis, cell metabolism, and replication. In this manuscript, we examined the pathophysiological alterations in fibroblasts derived from three patients harboring KAT6A mutations. We addressed survival in a stress medium, histone acetylation, protein expression patterns, and transcriptome analysis, as well as cell bioenergetics. In addition, we evaluated the therapeutic effectiveness of epigenetic modulators and mitochondrial boosting agents, such as pantothenate and L-carnitine, in correcting the mutant phenotype. Pantothenate and L-carnitine treatment increased histone acetylation and partially corrected protein and transcriptomic expression patterns in mutant KAT6A cells. Furthermore, the cell bioenergetics of mutant cells was significantly improved. Our results suggest that pantothenate and L-carnitine can significantly improve the mutant phenotype in cellular models of KAT6A syndrome.

Modulatory effect of exogenous Coenzyme Q10 on redox and inflammatory biomarkers during aging in rats

An impaired redox homeostasis is an important hallmark of biological aging. Coenzyme Q₁₀ is an endogenous lipophilic antioxidant that decreases with age and has been linked to oxidative stress. The purpose of this study was to evaluate the effect of CoQ₁₀ supplementation on redox homeostasis and levels of inflammatory cytokines in young and old rats. Male Wistar rats (young and old) were randomly divided into four groups (n = 6). Group I: young control, Group II: young rats treated with CoQ₁₀, Group III: old control, Group IV: old rats treated with CoQ₁₀. CoQ₁₀ (20 mg/kg) was administered daily to Group II and IV via oral gavage. After 28 days of treatment, rats were sacrificed and biomarkers of oxidative stress and inflammatory cytokines were evaluated. Results demonstrated a significant (p ≤ 0.05) increase in malondialdehyde, protein carbonyl oxidation, advanced oxidation protein products, inflammatory cytokines: CRP, IL-6, TNF-α, and a decline in levels of superoxide dismutase, catalase, reduced glutathione, ferric reducing antioxidant potential in plasma and plasma membrane redox system in old rats when compared to young rats. After treatment with CoQ₁₀ significant decrease in the level of MDA, PCO, AOPP, CRP, IL-6, and TNF-α was observed. Also, significant up-regulation of SOD, CAT, GSH, FRAP, and PMRS was observed. The results show that supplementing rats with CoQ₁₀ aids in the maintenance of redox equilibrium with replenishment of antioxidant reserves and down-regulation of inflammatory biomarkers. Thus CoQ₁₀ supplementation could be a potential anti-aging therapy.

Data-independent acquisition-based quantitative proteomic analysis of m.3243A>G MELAS reveals novel potential pathogenesis and therapeutic targets

The pathogenesis of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS) syndrome has not been fully elucidated. The m.3243A > G mutation which is responsible for 80% MELAS patients affects proteins with undetermined functions. Therefore, we performed quantitative proteomic analysis on skeletal muscle specimens from MELAS patients. We recruited 10 patients with definitive MELAS and 10 age- and gender- matched controls. Proteomic analysis based on nanospray liquid chromatography-mass spectrometry (LC-MS) was performed using data-independent acquisition (DIA) method and differentially expressed proteins were revealed by bioinformatics analysis. We identified 128 differential proteins between MELAS and controls, including 68 down-regulated proteins and 60 up-regulated proteins. The differential proteins involved in oxidative stress were identified, including heat shock protein beta-1 (HSPB1), alpha-crystallin B chain (CRYAB), heme oxygenase 1 (HMOX1), glucose-6-phosphate dehydrogenase (G6PD) and selenoprotein P. Gene ontology and kyoto encyclopedia of genes and genomes pathway analysis showed significant enrichment in phagosome, ribosome and peroxisome proliferator-activated receptors (PPAR) signaling pathway. The imbalance between oxidative stress and antioxidant defense, the activation of autophagosomes, and the abnormal metabolism of mitochondrial ribosome proteins (MRPs) might play an important role in m.3243A > G MELAS. The combination of proteomic and bioinformatics analysis could contribute potential molecular networks to the pathogenesis of MELAS in a comprehensive manner.

The impacts of vorinostat on NADPH oxidase and mitochondrial biogenesis gene expression in the heart of mice model of depression

The comorbidity of depression and high risk of cardiovascular diseases (CVD) have been reported as major health problems. Our previous study confirmed that fluoxetine (FLX) therapy had a significant influence on brain function but not on the heart in depression. In the present study, suberoyanilide hydroxamic acid (SAHA) was proposed as another therapeutic candidate for treatment of depression comorbid CVD in maternal separation model, following behavioral analyses and gene expression level in the heart. Our data demonstrated that SAHA significantly attenuates the NOX-4 gene expression level in treated mice with SAHA and FLX without significant change in NOX-2 expression level. SAHA decreased the gene expression level of peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) and nuclear respiratory factors (Nrf2) in heart tissues of maternally separated mice. It supposed that non-effectiveness of FLX on mitochondrial biogenesis and NOX gene expression level in the heart of depressed patient can be related to recurrence of depression. It revealed that SAHA not only reversed the depressive-like behavior similar to our previous data but also recovered the heart mitochondrial function via effect on NOX-2, NOX-4, and mitochondrial biogenesis genes' (PGC-1α, Nrf-2, and peroxisome proliferator-activated receptor-α (PPAR-α)) expression levels. We suggest performing more studies to confirm SAHA as a therapeutic candidate in depression comorbid CVD.

Correlation between coenzyme Q10 content and the nutrient sensors in AKI induced by Hemiscorpius lepturus envenomation

Introduction: Acute kidney injury (AKI) may have a negative effect on mitochondrial hemostasis and bioenergetics as well as coenzyme Q₁₀ (CoQ₁₀) content. PGC-1α, AMPK, sirtuin 1 (Sirt1), and Sirt3, as the key metabolic regulators under nutritional stress, stimulate energy production via mitochondrial biogenesis during AKI. However, no report is available on the relationship between CoQ₁₀ level and nutrient sensors in the pathophysiology of AKI caused by Hemiscorpius lepturus scorpion envenomation. Methods: Three doses of venoms (1, 5, and 10 mg/kg) were administered by subcutaneous (SC) injection to male albino mice. The animals were sacrificed 1 day or 7 days after administration of venom and their kidneys were collected to analyze gene expression involved in AKI, nutrient sensors, and apoptosis signaling activation by real-time polymerase chain reaction (PCR) and the measurement of CoQ₁₀ level using the High-performance liquid chromatography (HPLC) method. Results: The data indicated a significant decrease in CoQ₁₀ level after the administration of venom in 5 and 10 mg/kg. In addition, 1 day after the treatment, a significant over-expression of Sirt1 (5 and 10 mg/kg) was observed compared with normal mice. Overexpression of Sirt3 occurred 1 day and 7 days after treatment only at the dose of 5.0 mg/kg of venom. Furthermore, over-expression of AMPK as an important mitochondrial energetic sensor happened 1 day and 7 days after the injection of venom (5 mg/kg) (P < 0.01). The significant increase in the gene expression of caspase-9 and 3 after the injection of venom (5 and 10 mg/kg) confirmed the role of cell death signaling. Conclusion: The venom-induced energy-sensing pathways have a key role in gene expression of PGC-1α, AMPK, Sirt3, and CoQ₁₀ content after venom-induced AKI.

Nutraceuticals as Modulators of Autophagy: Relevance in Parkinson’s Disease

Dietary supplements and nutraceuticals have entered the mainstream. Especially in the media, they are strongly advertised as safe and even recommended for certain diseases. Although they may support conventional therapy, sometimes these substances can have unexpected side effects. This review is particularly focused on the modulation of autophagy by selected vitamins and nutraceuticals, and their relevance in the treatment of neurodegenerative diseases, especially Parkinson’s disease (PD). Autophagy is crucial in PD; thus, the induction of autophagy may alleviate the course of the disease by reducing the so-called Lewy bodies. Hence, we believe that those substances could be used in prevention and support of conventional therapy of neurodegenerative diseases. This review will shed some light on their ability to modulate the autophagy.

Coenzyme Q10 deficiency can be expected to compromise Sirt1 activity

For reasons that remain unclear, endogenous synthesis and tissue levels of coenzyme Q10 (CoQ10) tend to decline with increasing age in at least some tissues. When CoQ10 levels are sufficiently low, this compromises the efficiency of the mitochondrial electron transport chain, such that production of superoxide by site 2 increases and the rate of adenosine triphosphate production declines. Moreover, CoQ10 deficiency can be expected to decrease activities of Sirt1 and Sirt3 deacetylases, believed to be key determinants of health span. Reduction of the cytoplasmic and mitochondrial NAD⁺/NADH ratio consequent to CoQ10 deficit can be expected to decrease the activity of these deacetylases by lessening availability of their obligate substrate NAD⁺. The increased oxidant production induced by CoQ10 deficiency can decrease the stability of Sirt1 protein by complementary mechanisms. And CoQ10 deficiency has also been found to lower mRNA expression of Sirt1. An analysis of the roles of Sirt1/Sirt3 in modulation of cellular function helps to rationalise clinical benefits of CoQ10 supplementation reported in heart failure, hypertension, non-alcoholic fatty liver disease, metabolic syndrome and periodontal disease. Hence, correction of CoQ10 deficiency joins a growing list of measures that have potential for amplifying health protective Sirt1/Sirt3 activities.

Vitamin E prevents lipid peroxidation and iron accumulation in PLA2G6-Associated Neurodegeneration

BACKGROUND

PLA2G6-Associated Neurodegeneration (PLAN) is a rare neurodegenerative disease with autosomal recessive inheritance, which belongs to the NBIA (Neurodegeneration with Brain Iron Accumulation) group. Although the pathogenesis of the disease remains largely unclear, lipid peroxidation seems to play a central role in the pathogenesis. Currently, there is no cure for the disease.

OBJECTIVE

In this work, we examined the presence of lipid peroxidation, iron accumulation and mitochondrial dysfunction in two cellular models of PLAN, patients-derived fibroblasts and induced neurons, and assessed the effects of α-tocopherol (vitamin E) in correcting the pathophysiological alterations in PLAN cell cultures.

METHODS

Pathophysiological alterations were examined in fibroblasts and induced neurons generated by direct reprograming. Iron and lipofuscin accumulation were assessed using light and electron microscopy, as well as biochemical analysis techniques. Reactive Oxygen species production, lipid peroxidation and mitochondrial dysfunction were measured using specific fluorescent probes analysed by fluorescence microscopy and flow cytometry.

RESULTS

PLAN fibroblasts and induced neurons clearly showed increased lipid peroxidation, iron accumulation and altered mitochondrial membrane potential. All these pathological features were reverted with vitamin E treatment.

CONCLUSIONS

PLAN fibroblasts and induced neurons reproduce the main pathological alterations of the disease and provide useful tools for disease modelling. The main pathological alterations were corrected by Vitamin E supplementation in both models, suggesting that blocking lipid peroxidation progression is a critical therapeutic target.

The role of mitochondrial reactive oxygen species in insulin resistance

Insulin resistance is one of the earliest pathological features of a suite of diseases including type 2 diabetes collectively referred to as metabolic syndrome. There is a growing body of evidence from both pre-clinical studies and human cohorts indicating that reactive oxygen species, such as the superoxide radical anion and hydrogen peroxide are key players in the development of insulin resistance. Here we review the evidence linking mitochondrial reactive oxygen species generated within mitochondria with insulin resistance in adipose tissue and skeletal muscle, two major insulin sensitive tissues. We outline the relevant mitochondria-derived reactive species, how the mitochondrial redox state is regulated, and methodologies available to measure mitochondrial reactive oxygen species. Importantly, we highlight key experimental issues to be considered when studying the role of mitochondrial reactive oxygen species in insulin resistance. Evaluating the available literature on both mitochondrial reactive oxygen species/redox state and insulin resistance in a variety of biological systems, we conclude that the weight of evidence suggests a likely role for mitochondrial reactive oxygen species in the etiology of insulin resistance in adipose tissue and skeletal muscle. However, major limitations in the methods used to study reactive oxygen species in insulin resistance as well as the lack of data linking mitochondrial reactive oxygen species and cytosolic insulin signaling pathways are significant obstacles in proving the mechanistic link between these two processes. We provide a framework to guide future studies to provide stronger mechanistic information on the link between mitochondrial reactive oxygen species and insulin resistance as understanding the source, localization, nature, and quantity of mitochondrial reactive oxygen species, their targets and downstream signaling pathways may pave the way for important new therapeutic strategies.

Epigenome-wide association study of mitochondrial genome copy number

We conducted cohort- and race-specific epigenome-wide association analyses of mitochondrial deoxyribonucleic acid (mtDNA) copy number (mtDNA CN) measured in whole blood from participants of African and European origins in five cohorts (n = 6182, mean age = 57-67 years, 65% women). In the meta-analysis of all the participants, we discovered 21 mtDNA CN-associated DNA methylation sites (CpG) (P < 1 × 10-7), with a 0.7-3.0 standard deviation increase (3 CpGs) or decrease (18 CpGs) in mtDNA CN corresponding to a 1% increase in DNA methylation. Several significant CpGs have been reported to be associated with at least two risk factors (e.g. chronological age or smoking) for cardiovascular disease (CVD). Five genes [PR/SET domain 16, nuclear receptor subfamily 1 group H member 3 (NR1H3), DNA repair protein, DNA polymerase kappa and decaprenyl-diphosphate synthase subunit 2], which harbor nine significant CpGs, are known to be involved in mitochondrial biosynthesis and functions. For example, NR1H3 encodes a transcription factor that is differentially expressed during an adipose tissue transition. The methylation level of cg09548275 in NR1H3 was negatively associated with mtDNA CN (effect size = -1.71, P = 4 × 10-8) and was positively associated with the NR1H3 expression level (effect size = 0.43, P = 0.0003), which indicates that the methylation level in NR1H3 may underlie the relationship between mtDNA CN, the NR1H3 transcription factor and energy expenditure. In summary, the study results suggest that mtDNA CN variation in whole blood is associated with DNA methylation levels in genes that are involved in a wide range of mitochondrial activities. These findings will help reveal molecular mechanisms between mtDNA CN and CVD.

Autophagy-Lysosomal Pathway as Potential Therapeutic Target in Parkinson's Disease

Cellular quality control systems have gained much attention in recent decades. Among these, autophagy is a natural self-preservation mechanism that continuously eliminates toxic cellular components and acts as an anti-ageing process. It is vital for cell survival and to preserve homeostasis. Several cell-type-dependent canonical or non-canonical autophagy pathways have been reported showing varying degrees of selectivity with regard to the substrates targeted. Here, we provide an updated review of the autophagy machinery and discuss the role of various forms of autophagy in neurodegenerative diseases, with a particular focus on Parkinson's disease. We describe recent findings that have led to the proposal of therapeutic strategies targeting autophagy to alter the course of Parkinson's disease progression.

Coenzyme Q at the Hinge of Health and Metabolic Diseases

Coenzyme Q is a unique lipidic molecule highly conserved in evolution and essential to maintaining aerobic metabolism. It is endogenously synthesized in all cells by a very complex pathway involving a group of nuclear genes that share high homology among species. This pathway is tightly regulated at transcription and translation, but also by environment and energy requirements. Here, we review how coenzyme Q reacts within mitochondria to promote ATP synthesis and also integrates a plethora of metabolic pathways and regulates mitochondrial oxidative stress. Coenzyme Q is also located in all cellular membranes and plasma lipoproteins in which it exerts antioxidant function, and its reaction with different extramitochondrial oxidoreductases contributes to regulate the cellular redox homeostasis and cytosolic oxidative stress, providing a key factor in controlling various apoptosis mechanisms. Coenzyme Q levels can be decreased in humans by defects in the biosynthesis pathway or by mitochondrial or cytosolic dysfunctions, leading to a highly heterogeneous group of mitochondrial diseases included in the coenzyme Q deficiency syndrome. We also review the importance of coenzyme Q levels and its reactions involved in aging and age-associated metabolic disorders, and how the strategy of its supplementation has had benefits for combating these diseases and for physical performance in aging.

The multifaceted regulation of mitophagy by endogenous metabolites

Owing to the dominant functions of mitochondria in multiple cellular metabolisms and distinct types of regulated cell death, maintaining a functional mitochondrial network is fundamental for the cellular homeostasis and body fitness in response to physiological adaptations and stressed conditions. The process of mitophagy, in which the dysfunctional or superfluous mitochondria are selectively engulfed by autophagosome and subsequently degraded in lysosome, has been well formulated as one of the major mechanisms for mitochondrial quality control. To date, the PINK1-PRKN-dependent and receptors (including proteins and lipids)-dependent pathways have been characterized to determine the mitophagy in mammalian cells. The mitophagy is highly responsive to the dynamics of endogenous metabolites, including iron-, calcium-, glycolysis-TCA-, NAD⁺-, amino acids-, fatty acids-, and cAMP-associated metabolites. Herein, we summarize the recent advances toward the molecular details of mitophagy regulation in mammalian cells. We also highlight the key regulations of mammalian mitophagy by endogenous metabolites, shed new light on the bidirectional interplay between mitophagy and cellular metabolisms, with attempting to provide a perspective insight into the nutritional intervention of metabolic disorders with mitophagy deficit.Abbreviations: acetyl-CoA: acetyl-coenzyme A; ACO1: aconitase 1; ADCYs: adenylate cyclases; AMPK: AMP-activated protein kinase; ATM: ATM serine/threonine kinase; BCL2L1: BCL2 like 1; BCL2L13: BCL2 like 13; BNIP3: BCL2 interacting protein 3; BNIP3L: BCL2 interacting protein 3 like; Ca²⁺: calcium ion; CALCOCO2: calcium binding and coiled-coil domain 2; CANX: calnexin; CO: carbon monoxide; CYCS: cytochrome c, somatic; DFP: deferiprone; DNM1L: dynamin 1 like; ER: endoplasmic reticulum; FKBP8: FKBP prolyl isomerase 8; FOXO3: forkhead box O3; FTMT: ferritin mitochondrial; FUNDC1: FUN14 domain containing 1; GABA: γ-aminobutyric acid; GSH: glutathione; HIF1A: hypoxia inducible factor 1 subunit alpha; IMMT: inner membrane mitochondrial protein; IRP1: iron regulatory protein 1; ISC: iron-sulfur cluster; ITPR2: inositol 1,4,5-trisphosphate type 2 receptor; KMO: kynurenine 3-monooxygenase; LIR: LC3 interacting region; MAM: mitochondria-associated membrane; MAP1LC3: microtubule associated protein 1 light chain 3; MFNs: mitofusins; mitophagy: mitochondrial autophagy; mPTP: mitochondrial permeability transition pore; MTOR: mechanistic target of rapamycin kinase; NAD⁺: nicotinamide adenine dinucleotide; NAM: nicotinamide; NMN: nicotinamide mononucleotide; NO: nitric oxide; NPA: Niemann-Pick type A; NR: nicotinamide riboside; NR4A1: nuclear receptor subfamily 4 group A member 1; NRF1: nuclear respiratory factor 1; OPA1: OPA1 mitochondrial dynamin like GTPase; OPTN: optineurin; PARL: presenilin associated rhomboid like; PARPs: poly(ADP-ribose) polymerases; PC: phosphatidylcholine; PHB2: prohibitin 2; PINK1: PTEN induced kinase 1; PPARG: peroxisome proliferator activated receptor gamma; PPARGC1A: PPARG coactivator 1 alpha; PRKA: protein kinase AMP-activated; PRKDC: protein kinase, DNA-activated, catalytic subunit; PRKN: parkin RBR E3 ubiquitin protein ligase; RHOT: ras homolog family member T; ROS: reactive oxygen species; SIRTs: sirtuins; STK11: serine/threonine kinase 11; TCA: tricarboxylic acid; TP53: tumor protein p53; ULK1: unc-51 like autophagy activating kinase 1; VDAC1: voltage dependent anion channel 1.

Effect of coenzyme Q10 supplementation on oxidative stress and clinical outcomes in patients with low levels of coenzyme Q10 admitted to the intensive care unit

Today, trauma is known to be the third leading cause of death in most countries. Studies have demonstrated below-normal plasma levels of antioxidants in trauma patients. The present study aimed to assess the efficacy of Coenzyme Q10 (CoQ10) on oxidative stress, clinical outcomes and anthropometrical parameters in traumatic mechanical ventilated patients admitted to the intensive care unit. Patients were randomised to receive sublingual CoQ10 (400 mg/d) or placebo for 7 d. Primary and secondary outcomes were measured at the baseline and end of the study. We enrolled forty patients for this trial: twenty in the CoQ10 group and twenty in the placebo group. There was not any significant difference in the baseline variables (P > 0⋅05). At the end of the study, CoQ10 administration caused a considerable reduction in the Malondialdehyde (MDA) and Interleukin 6 (IL-6) concentrations (P < 0⋅001), Glasgow Coma Score (GCS; P = 0⋅02), ICU and hospital length of stay and mechanical ventilation (MV) duration (P < 0⋅001). We found that CoQ10 administration could increase Fat-Free Mass (P < 0⋅001) (FFM; P = 0⋅04), Skeletal Muscle Mass (SMM; P = 0⋅04) and Body Cell Mass (BCM) percent (P = 0⋅03). There was not any significant difference in other factors between the two groups (P > 0⋅05). CoQ10 administration has beneficial effects on patients with traumatic injury and has no side effects. However, since the possibility of the type II error was high, the outcomes on the duration of MV, ICU stay and hospital stay, and GCS may very well be false positives.

Prevalence of Hypovitaminosis C and its Relationship with Frailty in Older Hospitalised Patients: A Cross-Sectional Study

Frailty is common in older hospitalised patients and may be associated with micronutrient malnutrition. Only limited studies have explored the relationship between frailty and vitamin C deficiency. This study investigated the prevalence of vitamin C deficiency and its association with frailty severity in patients ≥75 years admitted under a geriatric unit. Patients (n = 160) with a mean age of 84.4 ± 6.4 years were recruited and underwent frailty assessment by use of the Edmonton Frail Scale (EFS). Patients with an EFS score <10 were classified as non-frail/vulnerable/mildly frail and those with ≥10 as moderate–severely frail. Patients with vitamin C levels between 11–28 μmol/L were classified as vitamin C depleted while those with levels <11 μmol/L were classified as vitamin C deficient. A multivariate logistic regression model determined the relationship between vitamin C deficiency and frailty severity after adjustment for various co-variates. Fifty-seven (35.6%) patients were vitamin C depleted, while 42 (26.3%) had vitamin C deficiency. Vitamin C levels were significantly lower among patients who were moderate–severely frail when compared to those who were non-frail/vulnerable/mildly frail (p < 0.05). After adjusted analysis, vitamin C deficiency was 4.3-fold more likely to be associated with moderate–severe frailty (aOR 4.30, 95% CI 1.33-13.86, p = 0.015). Vitamin C deficiency is common and is associated with a greater severity of frailty in older hospitalised patients.

Down regulation of the expression of mitochondrial phosphopantetheinyl-proteins in pantothenate kinase-associated neurodegeneration: pathophysiological consequences and therapeutic perspectives

Background

Neurodegeneration with brain iron accumulation (NBIA) is a group of genetic neurological disorders frequently associated with iron accumulation in the basal nuclei of the brain characterized by progressive spasticity, dystonia, muscle rigidity, neuropsychiatric symptoms, and retinal degeneration or optic nerve atrophy. Pantothenate kinase-associated neurodegeneration (PKAN) is the most widespread NBIA disorder. It is caused by mutations in the gene of pantothenate kinase 2 (PANK2) which catalyzes the first reaction of coenzyme A (CoA) biosynthesis. Thus, altered PANK2 activity is expected to induce CoA deficiency as well as low levels of essential metabolic intermediates such as 4′-phosphopantetheine which is a necessary cofactor for critical proteins involved in cytosolic and mitochondrial pathways such as fatty acid biosynthesis, mitochondrial respiratory complex I assembly and lysine and tetrahydrofolate metabolism, among other metabolic processes.

Methods

In this manuscript, we examined the effect of PANK2 mutations on the expression levels of proteins with phosphopantetheine cofactors in fibroblast derived from PKAN patients. These proteins include cytosolic acyl carrier protein (ACP), which is integrated within the multifunctional polypeptide chain of the fatty acid synthase involved in cytosolic fatty acid biosynthesis type I (FASI); mitochondrial ACP (mtACP) associated with mitocondrial fatty acid biosynthesis type II (FASII); mitochondrial alpha-aminoadipic semialdehyde synthase (AASS); and 10-formyltetrahydrofolate dehydrogenases (cytosolic, ALD1L1, and mitochondrial, ALD1L2).

Results

In PKAN fibroblasts the expression levels of cytosolic FAS and ALD1L1 were not affected while the expression levels of mtACP, AASS and ALD1L2 were markedly reduced, suggesting that 4′-phosphopantetheinylation of mitochondrial but no cytosolic proteins were markedly affected in PKAN patients. Furthermore, the correction of PANK2 expression levels by treatment with pantothenate in selected mutations with residual enzyme content was able to correct the expression levels of mitochondrial phosphopantetheinyl-proteins and restore the affected pathways. The positive effects of pantothenate in particular mutations were also corroborated in induced neurons obtained by direct reprograming of mutant PANK2 fibroblasts.

Conclusions

Our results suggest that the expression levels of mitochondrial phosphopantetheinyl-proteins are severely reduced in PKAN cells and that in selected mutations pantothenate increases the expression levels of both PANK2 and mitochondrial phosphopantetheinyl-proteins associated with remarkable improvement of cell pathophysiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01823-3.

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.

The multiple roles of coenzyme Q in cellular homeostasis and their relevance for the pathogenesis of coenzyme Q deficiency

Coenzyme Q (CoQ) is a redox active lipid that plays a central role in cellular homeostasis. It was discovered more than 60 years ago because of its role as electron transporter in the mitochondrial respiratory chain. Since then it has become evident that CoQ has many other functions, not directly related to bioenergetics. It is a cofactor of several mitochondrial dehydrogenases involved in the metabolism of lipids, amino acids, and nucleotides, and in sulfide detoxification. It is a powerful antioxidant and it is involved in the control of programmed cell death by modulating both apoptosis and ferroptosis. CoQ deficiency is a clinically and genetically heterogeneous group of disorders characterized by the impairment of CoQ biosynthesis. CoQ deficient patients display defects in cellular bioenergetics, but also in the other pathways in which CoQ is involved. In this review we will focus on the functions of CoQ not directly related to the respiratory chain, and on how their impairment is relevant for the pathophysiology of CoQ deficiency. A better understanding of the complex set of events triggered by CoQ deficiency will allow to design novel approaches for the treatment of this condition.

Pituitary Adenylate Cyclase-Activating Polypeptide: A Potent Therapeutic Agent in Oxidative Stress

Stroke is a life-threatening condition that is characterized by secondary cell death processes that occur after the initial disruption of blood flow to the brain. The inability of endogenous repair mechanisms to sufficiently support functional recovery in stroke patients and the inadequate treatment options available are cause for concern. The pathology behind oxidative stress in stroke is of particular interest due to its detrimental effects on the brain. The oxidative stress caused by ischemic stroke overwhelms the neutralization capacity of the body's endogenous antioxidant system, which leads to an overproduction of reactive oxygen species (ROS) and reactive nitrogen species (RNS) and eventually results in cell death. The overproduction of ROS compromises the functional and structural integrity of brain tissue. Therefore, it is essential to investigate the mechanisms involved in oxidative stress to help obtain adequate treatment options for stroke. Here, we focus on the latest preclinical research that details the mechanisms behind secondary cell death processes that cause many central nervous system (CNS) disorders, as well as research that relates to how the neuroprotective molecular mechanisms of pituitary adenylate cyclase-activating polypeptides (PACAPs) could make these molecules an ideal candidate for the treatment of stroke.

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.

The Mitochondrial Permeability Transition: Nexus of Aging, Disease and Longevity

The activity of the mitochondrial permeability transition pore, mPTP, a highly regulated multi-component mega-channel, is enhanced in aging and in aging-driven degenerative diseases. mPTP activity accelerates aging by releasing large amounts of cell-damaging reactive oxygen species, Ca²⁺ and NAD⁺. The various pathways that control the channel activity, directly or indirectly, can therefore either inhibit or accelerate aging or retard or enhance the progression of aging-driven degenerative diseases and determine lifespan and healthspan. Autophagy, a catabolic process that removes and digests damaged proteins and organelles, protects the cell against aging and disease. However, the protective effect of autophagy depends on mTORC2/SKG1 inhibition of mPTP. Autophagy is inhibited in aging cells. Mitophagy, a specialized form of autophagy, which retards aging by removing mitochondrial fragments with activated mPTP, is also inhibited in aging cells, and this inhibition leads to increased mPTP activation, which is a major contributor to neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. The increased activity of mPTP in aging turns autophagy/mitophagy into a destructive process leading to cell aging and death. Several drugs and lifestyle modifications that enhance healthspan and lifespan enhance autophagy and inhibit the activation of mPTP. Therefore, elucidating the intricate connections between pathways that activate and inhibit mPTP, in the context of aging and degenerative diseases, could enhance the discovery of new drugs and lifestyle modifications that slow aging and degenerative disease.

Not all mitochondrial DNAs are made equal and the nucleus knows it

The oxidative phosphorylation (OXPHOS) system is the only structure in animal cells with components encoded by two genomes, maternally transmitted mitochondrial DNA (mtDNA), and biparentally transmitted nuclear DNA (nDNA). MtDNA‐encoded genes have to physically assemble with their counterparts encoded in the nucleus to build together the functional respiratory complexes. Therefore, structural and functional matching requirements between the protein subunits of these molecular complexes are rigorous. The crosstalk between nDNA and mtDNA needs to overcome some challenges, as the nuclear‐encoded factors have to be imported into the mitochondria in a correct quantity and match the high number of organelles and genomes per mitochondria that encode and synthesize their own components locally. The cell is able to sense the mito‐nuclear match through changes in the activity of the OXPHOS system, modulation of the mitochondrial biogenesis, or reactive oxygen species production. This implies that a complex signaling cascade should optimize OXPHOS performance to the cellular‐specific requirements, which will depend on cell type, environmental conditions, and life stage. Therefore, the mitochondria would function as a cellular metabolic information hub integrating critical information that would feedback the nucleus for it to respond accordingly. Here, we review the current understanding of the complex interaction between mtDNA and nDNA.

Coenzyme Q10 modulates sulfide metabolism and links the mitochondrial respiratory chain to pathways associated to one carbon metabolism

Abnormalities of one carbon, glutathione and sulfide metabolisms have recently emerged as novel pathomechanisms in diseases with mitochondrial dysfunction. However, the mechanisms underlying these abnormalities are not clear. Also, we recently showed that sulfide oxidation is impaired in Coenzyme Q10 (CoQ10) deficiency. This finding leads us to hypothesize that the therapeutic effects of CoQ10, frequently administered to patients with primary or secondary mitochondrial dysfunction, might be due to its function as cofactor for sulfide:quinone oxidoreductase (SQOR), the first enzyme in the sulfide oxidation pathway. Here, using biased and unbiased approaches, we show that supraphysiological levels of CoQ10 induces an increase in the expression of SQOR in skin fibroblasts from control subjects and patients with mutations in Complex I subunits genes or CoQ biosynthetic genes. This increase of SQOR induces the downregulation of the cystathionine β-synthase and cystathionine γ-lyase, two enzymes of the transsulfuration pathway, the subsequent downregulation of serine biosynthesis and the adaptation of other sulfide linked pathways, such as folate cycle, nucleotides metabolism and glutathione system. These metabolic changes are independent of the presence of sulfur aminoacids, are confirmed in mouse models, and are recapitulated by overexpression of SQOR, further proving that the metabolic effects of CoQ10 supplementation are mediated by the overexpression of SQOR. Our results contribute to a better understanding of how sulfide metabolism is integrated in one carbon metabolism and may explain some of the benefits of CoQ10 supplementation observed in mitochondrial diseases.

Coenzyme Q10: Novel Formulations and Medical Trends

The aim of this review is to shed light over the most recent advances in Coenzyme Q10 (CoQ10) applications as well as to provide detailed information about the functions of this versatile molecule, which have proven to be of great interest in the medical field. Traditionally, CoQ10 clinical use was based on its antioxidant properties; however, a wide range of highly interesting alternative functions have recently been discovered. In this line, CoQ10 has shown pain-alleviating properties in fibromyalgia patients, a membrane-stabilizing function, immune system enhancing ability, or a fundamental role for insulin sensitivity, apart from potentially beneficial properties for familial hypercholesterolemia patients. In brief, it shows a remarkable amount of functions in addition to those yet to be discovered. Despite its multiple therapeutic applications, CoQ10 is not commonly prescribed as a drug because of its low oral bioavailability, which compromises its efficacy. Hence, several formulations have been developed to face such inconvenience. These were initially designed as lipid nanoparticles for CoQ10 encapsulation and distribution through biological membranes and eventually evolved towards chemical modifications of the molecule to decrease its hydrophobicity. Some of the most promising formulations will also be discussed in this review.

Hydrogen Sulfide Switch Phenomenon Regulating Autophagy in Cardiovascular Diseases

Hydrogen sulfide (H₂S), a novel gaseous signaling molecule, is a vital physiological signal in mammals. H₂S protects the cardiovascular system via modulation of vasodilation, vascular remodeling, and inhibition of vascular calcification, and also has anti-atherosclerosis properties. Autophagy is a lysosomal-mediated intracellular degradation mechanism for excessive or abnormal proteins and lipids. The contribution of autophagy to normal and disease-state cell physiology is extremely complicated. Autophagy acts as a double-edged sword in the cardiovascular system. It can defend against damage to cells caused by environmental changes and it can also induce active cell death under certain conditions. In recent years, accumulating evidence indicates that H₂S can up- or downregulate autophagy in many pathological processes, thereby switching from a harmful to a beneficial role. In this review, we summarize progress on understanding the mechanism by which H₂S regulates autophagy in cardiovascular disease. We also discuss a H₂S switch phenomenon that regulates autophagy and provides protection in cardiovascular diseases.

<p>Mitochondrial Imbalance as a New Approach to the Study of Fibromyalgia</p>

Background

Fibromyalgia (FM) is a common chronic pain disease, whose pathogenic mechanism still remains elusive. Oxidative stress markers and impaired bioenergetics homeostasis have been proposed as relevant events in the pathogenesis of the disease. Hence, the aim of the study is to analyse the potential biomarkers of mitochondrial imbalance in FM patients along with coenzyme Q10 (CoQ10) as a possible treatment.

Methods

The symptomatology of patients was recorded with an adaption of the Fibromyalgia Impact Questionnaire (FIQ). Mitochondrial imbalance was tested from blood extraction and serum isolation in 33 patients diagnosed with FM and 30 healthy controls. Western blot and HPLC techniques were performed to study the different parameters. Finally, bioinformatic analysis of machine learning was performed to predict possible associations of results.

Results

CoQ10 parameter did not show evidence to be a good marker of the disease, as the values are not significantly different between control and patient groups (Student’s t-test, CI 95%). For this reason, the focus of the study changed into the ratio between mitochondrial mass and autophagy levels. The bioinformatics analysis showed a possible association between this ratio and patients’ symptomatology. Finally, the effects of coenzyme Q10 as a potential treatment for the disease were different within patients, and its efficacy may be related to the initial mitochondrial status. However, there is no statistical significance due to limitations within the sample size.

Conclusion

Our study supports the hypothesis that an imbalance in mitochondrial homeostasis is involved in the FM pathogenesis. However, whether the increase in oxidative stress is the result of mitochondrial imbalance or the cause of this disease remains an open question. The measurement of this imbalance might be used as a preliminary biomarker for the diagnosis and follow-up of patients with FM, and even for the evaluation of the effects of the different antioxidants therapies.

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.

Mitochondrial Dysfunction and Calcium Dysregulation in Leigh Syndrome Induced Pluripotent Stem Cell Derived Neurons

Leigh syndrome (LS) is the most frequent infantile mitochondrial disorder (MD) and is characterized by neurodegeneration and astrogliosis in the basal ganglia or the brain stem. At present, there is no cure or treatment for this disease, partly due to scarcity of LS models. Current models generally fail to recapitulate important traits of the disease. Therefore, there is an urgent need to develop new human in vitro models. Establishment of induced pluripotent stem cells (iPSCs) followed by differentiation into neurons is a powerful tool to obtain an in vitro model for LS. Here, we describe the generation and characterization of iPSCs, neural stem cells (NSCs) and iPSC-derived neurons harboring the mtDNA mutation m.13513G>A in heteroplasmy. We have performed mitochondrial characterization, analysis of electrophysiological properties and calcium imaging of LS neurons. Here, we show a clearly compromised oxidative phosphorylation (OXPHOS) function in LS patient neurons. This is also the first report of electrophysiological studies performed on iPSC-derived neurons harboring an mtDNA mutation, which revealed that, in spite of having identical electrical properties, diseased neurons manifested mitochondrial dysfunction together with a diminished calcium buffering capacity. This could lead to an overload of cytoplasmic calcium concentration and the consequent cell death observed in patients. Importantly, our results highlight the importance of calcium homeostasis in LS pathology.

Assessing Autophagy in Archived Tissue or How to Capture Autophagic Flux from a Tissue Snapshot

Autophagy is a highly conserved degradation mechanism that is essential for maintaining cellular homeostasis. In human disease, autophagy pathways are frequently deregulated and there is immense interest in targeting autophagy for therapeutic approaches. Accordingly, there is a need to determine autophagic activity in human tissues, an endeavor that is hampered by the fact that autophagy is characterized by the flux of substrates whereas histology informs only about amounts and localization of substrates and regulators at a single timepoint. Despite this challenging task, considerable progress in establishing markers of autophagy has been made in recent years. The importance of establishing clear-cut autophagy markers that can be used for tissue analysis cannot be underestimated. In this review, we attempt to summarize known techniques to quantify autophagy in human tissue and their drawbacks. Furthermore, we provide some recommendations that should be taken into consideration to improve the reliability and the interpretation of autophagy biomarkers in human tissue samples.

Arsenic-induced autophagic alterations and mitochondrial impairments in HPG-S axis of mature male mice offspring (F1-generation): A persistent toxicity study

Arsenic (As) has been implicated in causing reproductive toxicity, but the precise cellular pathway through which the As toxicity in mature F1- male mice hypothalamic-pituitary- gonadal- sperm (HPG-S) axis is induced has not well been documented. Hence, parental mice were treated to As₂O₃ (0, 0.2, 2, and 20 ppm in deionized water) from five weeks before mating until weaning, and the male pups from weaning to maturity. Afterward, the markers of oxidative stress, mitochondrial impairment, and autophagy as fundamental mechanisms of cytotoxicity and organ injury were evaluated. Higher As₂O₃ doses (2 and 20 ppm) were a potent inducer of oxidative stress, mitochondrial dysfunction, and autophagy in HPG-S axis. Concomitant with a dose-dependent increase in the number of MDC-labeled autophagic vacuoles in the HPG axis, an adverse dose-dependent effect was observed on the mean body weight, litter size, organ coefficient, and spermatogenesis. Transmission electron microscopy also revealed more autophagosomes at high As₂O₃ dosage. Concomitant with a dose-dependent increment in gene expression of PI3K, Atg5, Atg12, as well as protein expression of Beclin1, LC3- I, II, P62 in HPG axis tissues and Atg12 in the pituitary; a dose-dependent decrease in mTOR gene expression was recorded in the HPG tissues of mature F₁-males. These observations provide direct evidence that oxidative stress-induced mitochondrial impairments and autophagic cell death, through AMPK/TSC/mTOR and LC3 related pathways, are fundamental mechanisms for As₂O₃- induced toxicity on the reproductive system in mature male mice offspring.

Parkin-mediated mitophagy and autophagy flux disruption in cellular models of MERRF syndrome

Mitochondrial diseases are considered rare genetic disorders characterized by defects in oxidative phosphorylation (OXPHOS). They can be provoked by mutations in nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). MERRF (Myoclonic Epilepsy with Ragged-Red Fibers) syndrome is one of the most frequent mitochondrial diseases, principally caused by the m.8344A>G mutation in mtDNA, which affects the translation of all mtDNA-encoded proteins and therefore impairs mitochondrial function. In the present work, we evaluated autophagy and mitophagy flux in transmitochondrial cybrids and fibroblasts derived from a MERRF patient, reporting that Parkin-mediated mitophagy is increased in MERRF cell cultures. Our results suggest that supplementation with coenzyme Q₁₀ (CoQ), a component of the electron transport chain (ETC) and lipid antioxidant, prevents Parkin translocation to the mitochondria. In addition, CoQ acts as an enhancer of autophagy and mitophagy flux, which partially improves cell pathophysiology. The significance of Parkin-mediated mitophagy in cell survival was evaluated by silencing the expression of Parkin in MERRF cybrids. Our results show that mitophagy acts as a cell survival mechanism in mutant cells. To confirm these results in one of the main affected cell types in MERRF syndrome, mutant induced neurons (iNs) were generated by direct reprogramming of patients-derived skin fibroblasts. The treatment of MERRF iNs with Guttaquinon CoQ₁₀ (GuttaQ), a water-soluble derivative of CoQ, revealed a significant improvement in cell bioenergetics. These results indicate that iNs, along with fibroblasts and cybrids, can be utilized as reliable cellular models to shed light on disease pathomechanisms as well as for drug screening.

Autophagy and Mitochondrial Encephalomyopathies

Mitochondrial encephalomyopathies are a group of disorders affecting skeletal muscles and brain. Although the symptoms vary among these disorders, mitochondrial DNA mutation or loss is the common characteristic. The abnormality of mitochondrial genome usually causes the dysfunction of mitochondrial respiratory and even mitochondrial damage. As a critical way of degradation, attention has been paid to the involvement of autophagy in encephalomyopathies. Autophagy is found activated in these encephalomyopathies-relevant cells as a compensatory manner to eliminate these damaged and dysfunctional mitochondria. However, accumulating evidences indicate that autophagy is incompetent to clear them. The insufficient mitophagy may ultimately accelerate cell death. Here we discuss the involvement of autophagy in encephalomyopathies based on the current evidence. We further look into the future to rescue encephalomyopathies by regulating autophagy. Only five encephalomyopathies are included in this chapter due to the availability of evidence. Nevertheless, these encephalomyopathies share a variety of common features and autophagy may also be regulated in the other encephalomyopathies.

Important Role of Mitochondria and the Effect of Mood Stabilizers on Mitochondrial Function

Mitochondria primarily serve as source of cellular energy through the Krebs cycle and β-oxidation to generate substrates for oxidative phosphorylation. Redox reactions are used to transfer electrons through a gradient to their final acceptor, oxygen, and to pump hydrogen protons into the intermembrane space. Then, ATP synthase uses the electrochemical gradient to generate adenosine triphosphate (ATP). During these processes, reactive oxygen species (ROS) are generated. ROS are highly reactive molecules with important physiological functions in cellular signaling. Mitochondria play a crucial role in intracellular calcium homeostasis and serve as transient calcium stores. High levels of both, ROS and free cytosolic calcium, can damage mitochondrial and cellular structures and trigger apoptosis. Impaired mitochondrial function has been described in many psychiatric diseases, including mood disorders, in terms of lowered mitochondrial membrane potential, suppressed ATP formation, imbalanced Ca2+ levels and increased ROS levels. In vitro models have indicated that mood stabilizers affect mitochondrial respiratory chain complexes, ROS production, ATP formation, Ca2+ buffering and the antioxidant system. Most studies support the hypothesis that mitochondrial dysfunction is a primary feature of mood disorders. The precise mechanism of action of mood stabilizers remains unknown, but new mitochondrial targets have been proposed for use as mood stabilizers and mitochondrial biomarkers in the evaluation of therapy effectiveness.

Liensinine Inhibits Beige Adipocytes Recovering to white Adipocytes through Blocking Mitophagy Flux In Vitro and In Vivo

Promoting white-to-beige adipocyte transition is a promising approach for obesity treatment. Although Liensinine (Lie), a kind of isoquinoline alkaloid, has been reported to affect white-to-beige adipocyte transition, its effects on inhibiting beige adipocytes recovering to white adipocytes and maintaining the characteristics of beige adipocyte remain unclear. Therefore, we explored the effects and underlying mechanism of Lie on beige adipocyte maintenance in vitro and in vivo. Here, we first demonstrated that after white adipocytes turned to beige adipocytes by rosiglitazone (Rosi) stimuli, beige adipocytes gradually lost their characteristics and returned to white adipocytes again once Rosi was withdrawn. We found that Lie retained high levels of uncoupling protein 1 (UCP1) and mitochondrial oxidative phosphorylation complex I, II, III, IV and V (COX I-V), oxygen consumption rate (OCR) after Rosi withdrawal. In addition, after Rosi withdrawal, the beige-to-white adipocyte transition was coupled to mitophagy, while Lie inhibited mitophagy flux by promoting the accumulation of pro-cathepsin B (pro-CTSB), pro-cathepsin D (pro-CTSD) and pro-cathepsin L (pro-CTSL), ultimately maintaining the beige adipocytes characteristics in vitro. Moreover, through blocking mitophagy flux, Lie significantly retained the molecular characteristics of beige adipocyte, reduced body weight gain rate and enhanced energy expenditure after stimuli withdrawal in vivo. Together, our data showed that Lie inhibited lysosomal cathepsin activity by promoting the accumulation of pro-CTSB, pro-CTSD and pro-CTSL, which subsequently inhibited mitophagy flux, and ultimately inhibited the beige adipocytes recovering to white adipocytes and maintained the characteristics of beige adipocyte after stimuli withdrawal. In conclusion, by blocking lysosome-mediated mitophagy, Lie inhibits beige adipocytes recovering to white adipocytes and may be a potential candidate for preventing high fat diet induced obesity.

Vitamin C deficiency causes muscle atrophy and a deterioration in physical performance

L-Ascorbic acid (AsA) is a water-soluble antioxidant. We examined the effect of AsA deficiency on skeletal muscle using senescence marker protein-30 (SMP30)-knockout (KO) mice that are defective in AsA biosynthesis, which makes this mouse model similar to humans, to clarify the function of AsA in skeletal muscle. Eight-week-old female SMP30-KO mice were divided into the following two groups: an AsA-sufficient group [AsA(+)] that was administered 1.5 g/L AsA and an AsA-deficient group [AsA(−)] that was administered tap (AsA-free) water. At 4 weeks, the AsA content in the gastrocnemius muscle of AsA(−) mice was 0.7% compared to that in the gastrocnemius muscle of AsA(+) mice. Significantly lower weights of all muscles were observed in AsA(−) mice than those in AsA(+) mice at 12 and 16 weeks. The cross-sectional area of the soleus was significantly smaller in AsA(−) mice at 16 weeks than that in AsA(+) mice. The physical performance of AsA(−) mice was significantly less than that of AsA(+) mice at 12 weeks. Following AsA deficiency for 12 weeks, the expression of ubiquitin ligases, such as atrogin1/muscle atrophy F-box (MAFbx) and muscle RING-finger protein 1 (MuRF1), was upregulated. Furthermore, all detected effects of AsA deficiency on muscles of the AsA(−) group at 12 weeks were restored following AsA supplementation for 12 weeks. Thus, longer-term AsA deficiency is associated with muscle wasting, that this can be reversed by restoring AsA levels.

Rapamycin administration is not a valid therapeutic strategy for every case of mitochondrial disease

Background

The vast majority of mitochondrial disorders have limited the clinical management to palliative care. Rapamycin has emerged as a potential therapeutic drug for mitochondrial diseases since it has shown therapeutic benefits in a few mouse models of mitochondrial disorders. However, the underlying therapeutic mechanism is unclear, the minimal effective dose needs to be defined and whether this therapy can be generally used is unknown.

Methods

We have evaluated whether low and high doses of rapamycin administration may result in therapeutic effects in a mouse model (Coq9^R239X) of mitochondrial encephalopathy due to CoQ deficiency. The evaluation involved phenotypic, molecular, image (histopathology and MRI), metabolomics, transcriptomics and bioenergetics analyses.

Findings

Low dose of rapamycin induces metabolic changes in liver and transcriptomics modifications in midbrain. The high dose of rapamycin induces further changes in the transcriptomics profile in midbrain due to the general inhibition of mTORC1. However, neither low nor high dose of rapamycin were able to improve the mitochondrial bioenergetics, the brain injuries and the phenotypic characteristics of Coq9^R239X mice, resulting in the lack of efficacy for increasing the survival.

Interpretation

These results may be due to the lack of microgliosis-derived neuroinflammation, the limitation to induce autophagy, or the need of a functional CoQ-junction. Therefore, the translation of rapamycin therapy into the clinic for patients with mitochondrial disorders requires, at least, the consideration of the particularities of each mitochondrial disease.

Fund

Supported by the grants from “Fundación Isabel Gemio - Federación Española de Enfermedades Neuromusculares – Federación FEDER” (TSR-1), the NIH (P01HD080642) and the ERC (Stg-337327).

Pathophysiological characterization of MERRF patient-specific induced neurons generated by direct reprogramming

Mitochondrial diseases are a group of rare heterogeneous genetic disorders caused by total or partial mitochondrial dysfunction. They can be caused by mutations in nuclear or mitochondrial DNA (mtDNA). MERRF (Myoclonic Epilepsy with Ragged-Red Fibers) syndrome is one of the most common mitochondrial disorders caused by point mutations in mtDNA. It is mainly caused by the m.8344A > G mutation in the tRNA^Lys (UUR) gene of mtDNA (MT-TK gene). This mutation affects the translation of mtDNA encoded proteins; therefore, the assembly of the electron transport chain (ETC) complexes is disrupted, leading to a reduced mitochondrial respiratory function. However, the molecular pathogenesis of MERRF syndrome remains poorly understood due to the lack of appropriate cell models, particularly in those cell types most affected in the disease such as neurons. Patient-specific induced neurons (iNs) are originated from dermal fibroblasts derived from different individuals carrying the particular mutation causing the disease. Therefore, patient-specific iNs can be used as an excellent cell model to elucidate the mechanisms underlying MERRF syndrome. Here we present for the first time the generation of iNs from MERRF dermal fibroblasts by direct reprograming, as well as a series of pathophysiological characterizations which can be used for testing the impact of a specific mtDNA mutation on neurons and screening for drugs that can correct the phenotype.

Intracellular cholesterol accumulation and coenzyme Q10 deficiency in Familial Hypercholesterolemia

Familial Hypercholesterolemia (FH) is an autosomal co-dominant genetic disorder characterized by elevated low-density lipoprotein (LDL) cholesterol levels and increased risk for premature cardiovascular disease. Here, we examined FH pathophysiology in skin fibroblasts derived from FH patients harboring heterozygous mutations in the LDL-receptor. Fibroblasts from FH patients showed a reduced LDL-uptake associated with increased intracellular cholesterol levels and coenzyme Q₁₀ (CoQ₁₀) deficiency, suggesting dysregulation of the mevalonate pathway. Secondary CoQ₁₀ deficiency was associated with mitochondrial depolarization and mitophagy activation in FH fibroblasts. Persistent mitophagy altered autophagy flux and induced inflammasome activation accompanied by increased production of cytokines by mutant cells. All the pathological alterations in FH fibroblasts were also reproduced in a human endothelial cell line by LDL-receptor gene silencing. Both increased intracellular cholesterol and mitochondrial dysfunction in FH fibroblasts were partially restored by CoQ₁₀ supplementation. Dysregulated mevalonate pathway in FH, including increased expression of cholesterogenic enzymes and decreased expression of CoQ₁₀ biosynthetic enzymes, was also corrected by CoQ₁₀ treatment. Reduced CoQ₁₀ content and mitochondrial dysfunction may play an important role in the pathophysiology of early atherosclerosis in FH. The diagnosis of CoQ₁₀ deficiency and mitochondrial impairment in FH patients may also be important to establish early treatment with CoQ₁₀.

CoQ10 supplementation rescues nephrotic syndrome through normalization of H2S oxidation pathway

Nephrotic syndrome (NS), a frequent chronic kidney disease in children and young adults, is the most common phenotype associated with primary coenzyme Q₁₀ (CoQ₁₀) deficiency and is very responsive to CoQ₁₀ supplementation, although the pathomechanism is not clear. Here, using a mouse model of CoQ deficiency-associated NS, we show that long-term oral CoQ₁₀ supplementation prevents kidney failure by rescuing defects of sulfides oxidation and ameliorating oxidative stress, despite only incomplete normalization of kidney CoQ levels and lack of rescue of CoQ-dependent respiratory enzymes activities. Liver and kidney lipidomics, and urine metabolomics analyses, did not show CoQ metabolites. To further demonstrate that sulfides metabolism defects cause oxidative stress in CoQ deficiency, we show that silencing of sulfide quinone oxido-reductase (SQOR) in wild-type HeLa cells leads to similar increases of reactive oxygen species (ROS) observed in HeLa cells depleted of the CoQ biosynthesis regulatory protein COQ8A. While CoQ₁₀ supplementation of COQ8A depleted cells decreases ROS and increases SQOR protein levels, knock-down of SQOR prevents CoQ₁₀ antioxidant effects. We conclude that kidney failure in CoQ deficiency-associated NS is caused by oxidative stress mediated by impaired sulfides oxidation and propose that CoQ supplementation does not significantly increase the kidney pool of CoQ bound to the respiratory supercomplexes, but rather enhances the free pool of CoQ, which stabilizes SQOR protein levels rescuing oxidative stress.

Clinical syndromes associated with Coenzyme Q10 deficiency

Primary Coenzyme Q deficiencies represent a group of rare conditions caused by mutations in one of the genes required in its biosynthetic pathway at the enzymatic or regulatory level. The associated clinical manifestations are highly heterogeneous and mainly affect central and peripheral nervous system, kidney, skeletal muscle and heart. Genotype–phenotype correlations are difficult to establish, mainly because of the reduced number of patients and the large variety of symptoms. In addition, mutations in the same COQ gene can cause different clinical pictures. Here, we present an updated and comprehensive review of the clinical manifestations associated with each of the pathogenic variants causing primary CoQ deficiencies.

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.

Mitochondrial CoQ deficiency is a common driver of mitochondrial oxidants and insulin resistance

Insulin resistance in muscle, adipocytes and liver is a gateway to a number of metabolic diseases. Here, we show a selective deficiency in mitochondrial coenzyme Q (CoQ) in insulin-resistant adipose and muscle tissue. This defect was observed in a range of in vitro insulin resistance models and adipose tissue from insulin-resistant humans and was concomitant with lower expression of mevalonate/CoQ biosynthesis pathway proteins in most models. Pharmacologic or genetic manipulations that decreased mitochondrial CoQ triggered mitochondrial oxidants and insulin resistance while CoQ supplementation in either insulin-resistant cell models or mice restored normal insulin sensitivity. Specifically, lowering of mitochondrial CoQ caused insulin resistance in adipocytes as a result of increased superoxide/hydrogen peroxide production via complex II. These data suggest that mitochondrial CoQ is a proximal driver of mitochondrial oxidants and insulin resistance, and that mechanisms that restore mitochondrial CoQ may be effective therapeutic targets for treating insulin resistance.

After we eat, our blood sugar levels increase. To counteract this, the pancreas releases a hormone called insulin. Part of insulin’s effect is to promote the uptake of sugar from the blood into muscle and fat tissue for storage. Under certain conditions, such as obesity, this process can become defective, leading to a condition known as insulin resistance. This condition makes a number of human diseases more likely to develop, including type 2 diabetes. Working out how insulin resistance develops could therefore unveil new treatment strategies for these diseases.

Mitochondria – structures that produce most of a cell’s energy supply – appear to play a role in the development of insulin resistance. Mitochondria convert nutrients such as fats and sugars into molecules called ATP that fuel the many processes required for life. However, ATP production can also generate potentially harmful intermediates often referred to as ‘reactive oxygen species’ or ‘oxidants’. Previous studies have suggested that an increase in the amount of oxidants produced in mitochondria can cause insulin resistance.

Fazakerley et al. therefore set out to identify the reason for increased oxidants in mitochondria, and did so by analysing the levels of proteins and oxidants found in cells grown in the laboratory, and mouse and human tissue samples. This led them to find that concentrations of a molecule called coenzyme Q (CoQ), an essential component of mitochondria that helps to produce ATP, were lower in mitochondria from insulin-resistant fat and muscle tissue. Further experiments suggested a link between the lower levels of CoQ and the higher levels of oxidants in the mitochondria. Replenishing the mitochondria of the lab-grown cells and insulin-resistant mice with CoQ restored ‘normal’ oxidant levels and prevented the development of insulin resistance.

Strategies that aim to increase mitochondria CoQ levels may therefore prevent or reverse insulin resistance. Although CoQ supplements are readily available, swallowing CoQ does not efficiently deliver CoQ to mitochondria in humans, so alternative treatment methods must be found. It is also of interest that statins, common drugs taken by millions of people around the world to lower cholesterol, also lower CoQ and have been reported to increase the risk of developing type 2 diabetes. Further research is therefore needed to investigate whether CoQ might provide the link between statins and type 2 diabetes.