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Mitochondrial biology is integral to our fundamental understanding of human health and many diseases. They exist in every human cell type except for red blood cells and have critical functions in metabolism, oxidative phosphorylation, oxidation-reduction, and as signaling hubs responsible for mediating protective mechanisms. Rare mitochondrial diseases (RMDs) are devastating and complex, affect multiple organ systems, and disproportionately impact young children. Despite copious existing knowledge and increased public interest, the knowledge is fragmented and difficult to access. Clinical case reports (CCRs) on RMDs contain valuable clinical insights, but they are scarce and lack the metadata necessary to facilitate their discovery among the two million CCRs on PubMed. The unstructured text data of CCRs is also ill-suited to computational approaches, limiting our ability to derive the knowledge contained within.To address these issues, I assembled all available informatics tools and resources with mitochondrial components and used them to contribute to Gene Wiki pages that enable easy access to mitochondrial knowledge for researchers, students, clinicians, and patients. Through these efforts, I made mitochondrial gene, protein, and disease knowledge widely accessible with contributions of over 4MB of content across 541 Gene Wiki pages. Concurrently, I used Gene Wiki as an educational platform to train over 50 students in the biosciences and pre-medical studies in mitochondrial biology and disease, as well as instilling effective research and writing methods in biomedicine.To impose structure on CCRs and render them FAIR (Findable, Accessible, Interoperable, Reusable), I developed and applied a standardized metadata template to RMD CCRs and codified patient symptomology with the International Statistical Classification of Disease and Related Health Problems (ICD) system. I created the open-source, cloud-based MitoCases RMD Knowledge Platform (http://mitocases.org/) to house data on 384 RMD CCRs, including 4,561 instances of 952 unique ICD codes. Supplementing CCRs with structured metadata amplifies machine-readable information content and provides a distinct improvement in searching for CCRs as compared to indexing by title and abstract. Finally, I employed these resources to conduct a thorough review of Barth syndrome and characterized the diversity of presentations, range of genetic etiologies, and treatment paradigms.

Cristae membrane state plays a central role in regulating mitochondrial function and cellular metabolism. The protein Optic atrophy 1 (Opa1) is an important crista remodeler that exists as two forms in the mitochondrion, a membrane-anchored long form (l-Opa1) and a processed short form (s-Opa1). The mechanisms for how Opa1 influences cristae shape have remained unclear due to lack of native three-dimensional views of cristae. We perform in situ cryo-electron tomography of cryo-focused ion beam milled mouse embryonic fibroblasts with defined Opa1 states to understand how each form of Opa1 influences cristae architecture. In our tomograms, we observe a variety of cristae shapes with distinct trends dependent on s-Opa1:l-Opa1 balance. Increased l-Opa1 levels promote cristae stacking and elongated mitochondria while increased s-Opa1 levels correlated with irregular cristae packing and round mitochondria shape. Functional assays indicate a role for l-Opa1 in wild-type apoptotic and calcium handling responses, and compromised respiratory function under Opa1 imbalance. In summary, we provide three-dimensional visualization of cristae architecture to reveal relationships between mitochondrial ultrastructure and cellular function dependent on Opa1-mediated membrane remodeling., Competing Interests: Declaration of Interests B.P.K is an inventor on patents and/or patent applications filed by Mass General Brigham that describe genome engineering technologies. B.P.K. is a consultant for EcoR1 capital, and is an advisor to Acrigen Biosciences, Life Edit Therapeutics, and Prime Medicine. L.H.C. is an advisor for Stealth Biotherapeutics. The remaining authors declare that there are no competing financial interests.

The ancient, dynamic, and multifaceted functions of the mitochondrial network are essential for organismal homeostasis and contribute to numerous human diseases. As central hubs for metabolism, ion transport, and multiple macromolecular synthesis pathways, mitochondria establish and control extensive signaling networks to ensure cellular survival. In this review, we explore how these same mitochondrial functions also participate in the control of regulated cell death (RCD). We discuss the complementary essential mito-chondrial functions as compartments that participate in the production and presentation of key molecules and platforms that actively enable, initiate, and execute RCD.

We reviewed the status of interventional clinical trials for primary mitochondrial diseases. Using national and international search engines, we found 48 randomized controlled trials (RCTs) registered as of May 15, 2019. Consilience between lay and professional mitochondrial disease communities to engage in RCTs has increased, as has progress in developing new disease and treatment biomarkers and potential therapies. The continued advancement of general knowledge of mitochondrial biology has fostered appreciation for the fundamental role mitochondria play in the etiopathology of other rare and common illnesses, emphasizing the therapeutic potential of mitochondrially-targeted small molecules for an increasing spectrum of human diseases.

It is increasingly being postulated that among-individual variation in mitochondrial function underlies variation in individual performance (e.g. growth rate) and state of health. It has been suggested (but not adequately tested) that environmental conditions experienced before birth have been suggested to programme postnatal mitochondrial function, with persistent effects potentially lasting into adulthood. We tested this hypothesis in an avian model by experimentally manipulating prenatal conditions (incubation temperature and stability), then measuring mitochondrial aerobic metabolism in blood cells from the same individuals during the middle of the growth period and at adulthood. Mitochondrial aerobic metabolism changed markedly across life stages, and part of these age-related changes were influenced by the prenatal temperature conditions. A high incubation temperature induced a consistent and long-lasting increase in mitochondrial aerobic metabolism. Postnatal mitochondrial aerobic metabolism was positively associated with oxidative damage on DNA but not telomere length. While we detected significant within-individual consistency in mitochondrial aerobic metabolism across life-stages, the prenatal temperature regime only accounted for a relatively small proportion (

Mitochondria are crucial components of eukaryotic cells and exchange signalling molecules, metabolites, proteins and lipids with the rest of the cell. The organelle is key for energy metabolism as they provide most of the cellular ATP through oxidative phosphorylation and regulate intermediate metabolism. Mitochondria are also a major source of reactive oxygen species (ROS), which are by-products of aerobic respiration and recently recognised as important signalling molecules that control various cellular functions. To avoid the potential damaging effects of ROS, mitochondria contain protein antioxidant systems to help maintain thiol homeostasis. Mitochondria are emerging as an important redox signalling node and are involved in a myriad of signalling pathways, which have a redox component, either through a response to a particular ROS or the shift of the redox state of a responsive group. It is not surprising that mitochondria are therefore heavily regulated by retrograde signalling of the master regulator of cellular antioxidant defence, nuclear factor erythroid-derived 2-related factor 2 (Nrf2). Until now it has not been possible to disentangle the overlapping effects of mitochondrial ROS signalling compared to a redox signal stemming from disruption of mitochondrial thiol homeostasis. Furthermore, it is important to distinguish between disturbing the cytosolic and mitochondrial protein antioxidant systems. I characterised the effects of mitochondrial thiol homeostasis disruption on mitochondrial physiology with MitoCDNB, showing mitochondrial fission. I found that selective disruption of the mitochondrial glutathione pool and inhibition of its thioredoxin system led to Nrf2 activation, while using MitoPQ to enhance production of mitochondrial superoxide and hydrogen peroxide alone did not. To further our understanding of how mitochondrial redox homeostasis is sensed in the cytoplasm and signalled to the nucleus I used an RNAseq approach to investigate the intricacies of early mitochondrial retrograde signalling.

Mitochondria are maternally inherited organelles that play critical tissue-specific roles, including hormone synthesis and energy production, that influence development, health, and aging. However, whether mitochondria from women and men exhibit consistent biological differences remains unclear, representing a major gap in biomedical knowledge. This meta-analysis systematically examined 4 domains and 6 subdomains of mitochondrial biology (total 39 measures), including mitochondrial content, respiratory capacity, reactive oxygen species (ROS) production, morphometry, and mitochondrial DNA copy number. Standardized effect sizes (Hedge’s g) of sex differences were computed for each measure using data in 2,258 participants (51.5% women) from 50 studies. Only two measures demonstrated aggregate binary sex differences: higher mitochondrial content in women (g = 0.20, χ2p = 0.01), and higher ROS production in skeletal muscle in men (g = 0.49, χ2p < 0.0001). differences showed weak to Sex no correlation with age or BMI. Studies with small sample sizes tended to overestimate effect sizes (r = -0.17, p < 0.001), and sex differences varied by tissue examined. Our findings point to a wide variability of findings in the literature concerning possible binary sex differences in mitochondrial biology. Studies specifically designed to capture sex- and gender-related differences in mitochondrial biology are needed, including detailed considerations of physical activity and sex hormones.

The role and nature of mitochondrial dysfunction in diabetic kidney disease (DKD) has been extensively studied. Yet, the molecular drivers of mitochondrial remodeling in DKD are poorly understood. Diabetic kidney cells exhibit a cascade of mitochondrial dysfunction ranging from changes in mitochondrial morphology to significant alterations in mitochondrial biogenesis, biosynthetic, bioenergetics and production of reactive oxygen species (ROS). How these changes individually or in aggregate contribute to progression of DKD remain to be fully elucidated. Nevertheless, because of the remarkable progress in our basic understanding of the role of mitochondrial biology and its dysfunction in DKD, there is great excitement on future targeted therapies based on improving mitochondrial function in DKD. This review will highlight the latest advances in understanding the nature of mitochondria dysfunction and its role in progression of DKD, and the development of mitochondrial targets that could be potentially used to prevent its progression.

Current knowledge of mitochondrial biology and function has provided with tools and technologies that helped a better understanding of the molecular etiology of complex mitochondrial disorders. Dual genetic control of this subcellular organelle function regulates various signaling mechanisms which are essential for metabolism, bioenergetics, fatty acid biosynthesis, and DNA replication & repair. Understanding nuclear mitochondrial crosstalk through advanced genomics as well as clinical perspectives is the overall basis of mitochondrial research and medicine, also the sole objective of Society for Mitochondrial Medicine and Research (SMRM) - India. The eighth virtual international conference on 'Advances in Mitochondrial Medicine and Translational Research' was organized at the Manipal School of Life Sciences, MAHE, Manipal, India, during 6 - 7 November 2020. The aim of the virtual conference was to highlight the recent advances and future perspectives that represent comprehensive clinical and fundamental research interests in the area of mitochondrial biology of human diseases. To systematically present the various findings in mitochondrial biology, the meeting was themed with specific aspects comprising (a) mitochondrial disorders: clinical & genomic perspectives, (b) mitochondria in cancer, (c) mitochondrial metabolism & disorders, and (d) mitochondrial diseases & therapy. This report provides an overview of the recent advancements in the area of mitochondrial biology and medicine that was discussed at the conference.

Mitochondria are important sub-cellular organelles in eukaryotes. Defects in mitochondrial system lead to a variety of disease. Therefore, detailed knowledge of mitochondrial proteome is vital to understand mitochondrial system and their function. Sequence databases contain large number of mitochondrial proteins but they are mostly not annotated. In this study, we developed a support vector machine approach, SubmitoLoc, to predict mitochondrial sub cellular locations of proteins based on various sequence derived properties. We evaluated the predictor using 10-fold cross validation. Our method achieved 88.56 % accuracy using all features. Average sensitivity and specificity for four-subclass prediction is 85.37% and 87.25% respectively. High prediction accuracy suggests that SubmitoLoc will be useful for researchers studying mitochondrial biology and drug discovery.

The concept that mitochondria are highly dynamic is as widely accepted as it is untrue for a number of important contexts. Healthy mitochondria of the most energy-dependent and mitochondrial-rich mammalian organ, the heart, only rarely undergo fusion or fission and are seemingly static within cardiac myocytes. Here, we revisit mitochondrial dynamism with a fresh perspective developed from the recently discovered multifunctionality of mitochondrial fusion proteins and newly defined mechanisms for direct cross talk between mitochondrial dynamics, biogenesis, quality control, and trafficking pathways. Insights gained from comparing static mitochondrial biology in cardiac myocytes and dynamic mitochondrial biology in neurons are reviewed with the goal of understanding contextual fallacies of overly generalized characterizations of these essential and intriguing organelles.

Mutations in OPA1 cause autosomal dominant optic atrophy (DOA) as well as DOA+, a phenotype characterized by more severe neurological deficits. OPA1 deficiency causes mitochondrial fragmentation and also disrupts cristae, respiration, mitochondrial DNA (mtDNA) maintenance, and cell viability. It has not yet been established whether phenotypic severity can be modulated by genetic modifiers of OPA1. We screened the entire known mitochondrial proteome (1,531 genes) to identify genes that control mitochondrial morphology using a first‐in‐kind imaging pipeline. We identified 145 known and novel candidate genes whose depletion promoted elongation or fragmentation of the mitochondrial network in control fibroblasts and 91 in DOA+ patient fibroblasts that prevented mitochondrial fragmentation, including phosphatidyl glycerophosphate synthase (PGS1). PGS1 depletion reduces CL content in mitochondria and rebalances mitochondrial dynamics in OPA1‐deficient fibroblasts by inhibiting mitochondrial fission, which improves defective respiration, but does not rescue mtDNA depletion, cristae dysmorphology, or apoptotic sensitivity. Our data reveal that the multifaceted roles of OPA1 in mitochondria can be functionally uncoupled by modulating mitochondrial lipid metabolism, providing novel insights into the cellular relevance of mitochondrial fragmentation., Phenotypic screening of OPA1 patient fibroblasts identifies multiple genetic suppressors of mitochondrial fragmentation including PGS1, a key enzyme in cardiolipin biosynthesis. PGS1 depletion reduces mitochondrial fission and restores normal mitochondrial morphology to OPA1‐deficient fibroblasts.

Mitochondria undergo structural and functional remodeling to meet the cell demand in response to the intracellular and extracellular stimulations, playing an essential role in maintaining normal cellular function. Merging evidence demonstrated that dysregulation of mitochondrial remodeling is a fundamental driving force of complex human diseases, highlighting its crucial pathophysiological roles and therapeutic potential. In this review, we outlined the progress of the molecular basis of mitochondrial structural and functional remodeling and their regulatory network. In particular, we summarized the latest evidence of the fundamental association of impaired mitochondrial remodeling in developing diverse cardiac diseases and the underlying mechanisms. We also explored the therapeutic potential related to mitochondrial remodeling and future research direction. This updated information would improve our knowledge of mitochondrial biology and cardiac diseases’ pathogenesis, which would inspire new potential strategies for treating these diseases by targeting mitochondria remodeling.

No abstract available

Introduction. Aging is a natural time-dependent process characterized by the accumulation of damage in cellular structures that compromises cellular and tissue function leading ultimately to the death of the organism. Furthermore, aging is the most significant risk factor for chronic diseases including cancer, cardiovascular disease (CVDs) and neurodegeneration. Nine candidates have been proposed as the main features of aging. These candidates which have been regarded as "The Hallmarks of Aging" are: telomere attrition, genomic instability, epigenetic alterations, loss of proteostasis, mitochondrial dysfunction, deregulated nutrient sensing, cellular senescence, stem cell exhaustion, and altered intercellular communication. Given the great complexity of the changes that participate in the establishment of the aging phenotype, numerous theories have been proposed to explain its aetiology, but neither of them appears to be capable of fully explaining the origin of this process, and they often contradict each other. Among them, the Free Radical Theory of Aging proposes that oxidative stress and redox imbalance are factors directly related with aging. The general idea of this theory is to consider reactive oxygen species (ROS) and other reactive species, that are continuously generated in the organism, as the main cause of aging. Therefore, cellular aging is associated with chronic oxidative stress. ROS are products of normal cellular metabolism in mitochondrial respiration and can be also produced in defensive responses of cells against infectious agents, upon exposure to xenobiotics, cytokines, redox stress, and in a several of intracellular signaling pathways. Mitochondria are both the main source and a major target of ROS. Mitochondria are one of the most important organelles in aerobic organisms, as the sites where aerobic respiration takes place to produce the energy that is necessary to sustain most cellular processes. Mitochondria also participate in additional cellular processes of great relevance, including β-oxidation of fatty acids, calcium signaling, and apoptosis. However, ROS and free radicals are generated as by-products of mitochondrial metabolism that attack nucleic acids, proteins, and membrane phospholipids. Among phospholipids, those containing polyunsaturated fatty acids (PUFAs) are more susceptible to oxidation by free radicals, leading to lipid peroxidation that causes a loss of membrane fluidity and impairs many cell functions. Additionally, with age, mitochondrial enzymes, ATP production, and respiratory capacity decline and, at the same time, ROS and mitochondrial mutations increase, being these changes accompanied by alterations in morphology and abundance of these organelles. Mutations in mtDNA result in a loss of mitochondrial function and turnover. This leads to the autophagic digestion of defective mitochondria which, if not accompanied by efficient mitochondrial biogenesis, may lead to the consequent decrease in the synthesis of ATP and bioenergetic dysfunction. Mitochondria are generated by growth and division of pre-existing organelles. In addition, they are highly dynamic structures that undergo continuous changes in size, shape, number, and distribution, which is highly controlled by a balance between fusion and fission. Their dynamics is determined by mitochondrial turnover, biogenesis, and a balance between the frequency of fusion and fission events. These events are critical for the normal function of cells, allowing the replacement of old or damaged mitochondria which are continuously removed from the cell. All these mechanisms allow the maintenance and distribution of mtDNA, the quality control of the organelle, and the regulation of apoptosis. Imbalanced mitochondria dynamics contributes to the loss of mitochondrial homeostasis, leading to alterations in mitochondrial function, metabolism, and signaling. Progressive mitocondrial dysfunction is considered a hallmark of aging, and it has been involved in a wide range of pathological conditions whose incidence increases with aging, as neurodegenerative diseases, diabetes, CVDs, muscle atrophy and cancer, and it is also related with several processes of embryonic development. Mitochondria are eliminated when they are damaged or dysfunctional through a process regulated called mitophagy. Nutritional and genetic interventions are among the strategies currently followed by researchers to delay or even reverse the deleterious consequences of aging. Caloric restriction (CR) without malnutrition is the most effective nongenetic intervention that delays aging and increases lifespan in numerous organisms. Beneficial effects of CR on longevity are mainly due to an improvement in mitochondrial function. Furthermore, there is an important metabolic adaptation to CR, causing substantial changes in numerous signaling pathways that regulate growth, metabolism, repair of damage, oxidative stress, autophagy and inflammatory processes. Among these changes, CR increases the amount of monounsaturated fatty acids (MUFAs) in membranes while decreasing PUFAs without any observed changes in saturated fatty acids (SFA), which is in accordance with the Theory of Membranes in Aging that proposes that lifespan is inversely related to the level of unsaturation, particularly the level of n-3 PUFA, in membrane phospholipids. Moreover, CR modulates key molecules involved in the regulation of autophagy and increases NAD+ levels activating enzymatic activity of the sirtuins (SIRTs). Homeostasis of NAD+ is important for the maintenance of many functions and protection against aging and age-related diseases. NAD+ is a metabolic regulator and its efficacy has been reported in metabolic diseases such as insulin resistance, fatty liver or hypertension. The overexpression of enzymes capable of generating NAD+ from the oxidation of NADH, as NADH-cytochrome b5 reductase-3 (CYB5R3), is another strategy that is currently under evaluation. CYB5R3 is a flavoprotein that participates in the elongation and desaturation of fatty acids, which seems to be an excellent candidate as a novel effector for the regulation of metabolism, mainly at mitochondrial level. CYB5R3 plays an important role in the regulation of metabolic pathways associated with healthspan and aging through mechanisms that appear to be related with protection against oxidative stress, production of cellular NAD+ and alterations in fatty acids composition. Although CYB5R3 shows a constitutive basal expression in many tissues, its expression can be also induced in response to environmental stress and nutrient deprivation. Constitutive expression of the Cyb5r3 gene is controlled by SP1 transcription factor, which can be further upregulated through pathways involving forkhead box O3 (FOXO3a) and nuclear factor erythroid 2-related factor 2 (NFE2L2) transcription factors. Mice overexpressing this protein showed increased longevity and displayed greater protection against diseases associated with aging. At the metabolic level, CYB5R3 overexpression increases insulin sensitivity, decreases inflammation and oxidative stress, and protects mice against cancer induction. Therefore, this enzyme plays a fundamental role in the regulation of lipid metabolism that allows to increase lifespan, suggesting that strategies aimed at incrementing CYB5R3 expression and/or activity may constitute viable interventions to confer protection against metabolic pathologies and to improve healthspan. Dietary fats are essential components to generate energy. Fatty acids (FAs) can be categorized as saturated (SFAs), monounsaturated (MUFAs), or polyunsaturated (PUFAs) and most of them can be synthesized by the organisms excepting the socalled essential fatty acids that must be ingested through the diet. In addition, FAs are an important source of energy due to their ability to be efficiently stored as triglycerides (TGs). Several studies have reported the relationship between dietary fat and the risk of metabolic and CVDs, among other disorders. Diets rich in MUFAs and PUFAs have cardioprotective effects, while the relationship between SFA and the risk of coronary heart disease is still controversial. Fatty acids can undergo autoxidation reactions generating lipid peroxides that affect the properties of biological membranes. Additionally, the toxic products derived from peroxidation can damage proteins, DNA, and other biomolecules. Since lipids are prone to oxidation, which exerts negative effects in health, the use of antioxidants in foods has become extensive to prevent lipid oxidation. The liver and heart are closely related in health and in disease. Deregulated hepatic lipid metabolism and many metabolic diseases, such as diabetes and obesity, are ultimately detrimental to cardiac function. The liver is the main organ in the regulation of energy metabolism. It performs three essential functions: the metabolic processing of proteins, carbohydrates and lipids after their absorption in the intestine, the detoxification of toxic agents and substances, and the storage of energy in form of glycogen. In spite of some changes occurring during aging (see below), the liver ages fairly well. Although in normal conditions hepatocyte turnover rate is low, the liver shows a relatively high rate of regeneration. That is why this organ has been widely used as a model to study the effects of diets, CR and other anti-aging interventions. Aging-related changes in liver include a reduction of weight and volume, a decline in the rate of hepatic regeneration, increased size of hepatocytes, polyploid nuclei, decreased area of smooth endoplasmic reticulum, decreased clearance of free radicals, and a decrease in the number and function of mitochondria, resulting in a decline in the ATP production. Aging is also associated with redistribution of fat in the body characterized by increased fat deposition in non-adipose tissues, including liver. All these structural and functional alterations could contribute to the development of liver disease with age. The heart is the main organ of the circulatory system and one of the first organs to be formed during the embryonic development. The heart is a complex organ containing different cell types that contribute to the structural, biochemical, mechanical, and electrical properties of the organ. Among the cell types, cardiomyocytes, responsible for the contractile function of the myocardium, are well differentiated cells without regeneration capacity. The most drastic changes in heart function occurring with age are: left ventricular hypertrophy, alterations in the diastolic function, aortic valve calcification, arrhythmia and heart failure. These alterations are, at least in part, due to a decrease in the number of cardiomyocytes, as well to hypertrophy and fibrosis due to an increased collagen and alterations in the extracellular matrix. As postmitotic cells, cardiomyocytes are highly susceptible to age-related mitochondrial damage and ROS production which results in an overall enhancement in the rate of cardiomyocyte death with age. The progressive decline of cardiomyocyte mitochondrial function is considered the major mechanism underlying heart aging, in addition to the accumulation of cholesterol and fatty acids in tissues which lead to the production of inflammatory cytokines as well as ROS that further contribute to CVDs prevalence and mortality. Starting hypothesis and objectives. Previous studies developed in our group were focused on NADH-cytochrome b5 reductase-3 (Cyb5r3) as a new pro-longevity gene. Mice overexpressing CYB5R3 contain higher levels of polyunsaturated fatty acids in hepatic membranes, which resembles, at least partially, the effects of the consumption of a diet containing fish oil or the overexpression of the Fat-1 gene of C. elegans. Unsaturated fatty acids show high susceptibility to peroxidation. However, CYB5R3 transgenic mice exhibited a significant reduction in lipid peroxidation. The specific changes in FA composition that take place in mice overexpressing CYB5R3 may be the result of a metabolic reprogramming, and could be indicative of an improvement in mitochondrial function, leading to a lower generation of ROS and the prevention of the oxidative damage accumulation, which partially mimics the effects observed in animals subjected to CR. These mice showed increased insulin sensitivity and improved regulation of glucose homeostasis, less inflammation and decreased oxidative damage, and were protected against induced cancer. However, mice over- expressing CYB5R3 fed a standard diet ad libitum were fatter than wild-type controls, and preferentially use carbohydrate to meet their energy needs. This differs from studies with CR as antiaging intervention that showed an improvement in healthspan and lifespan due to the enhancement of β-oxidation as a preferential source of energy. Thus, CYB5R3 overexpression could contribute to extend lifespan in mice by mechanisms that may be independent of those described for CR. Since CYB5R3 increase has been reported in long-term CR intervention, it has been hypothesized that the beneficial effects of CR could be mediated, at least partially, by a such increase of CYB5R3. However, it has not yet been studied how the CYB5R3 overexpression affects mitochondrial processes that are relevant to determine the aging pattern, and how the alterations in fatty acid composition and CR can interact with the changes elicited by CYB5R3 overexpression in transgenic mice. The working hypothesis of this PhD is that mitochondrial efficiency is optimized in CYB5R3 transgenic mice, which leads to an improvement in energy production and better preservation of mitochondria during aging. For this reason, our main objective has been to study several mitochondrial function markers in liver and heart tissues of CYB5R3-overexpressing mice submitted to nutritional interventions (CR and alterations in fat composition of the diet) and aging. To this end, we have pursued the following 5 specific aims: 1. To study the physiological effects of CYB5R3 overexpression, dietary fats, CR and aging on body composition and biochemical profile. 2. To characterize the CYB5R3 overexpression in liver and heart in the three proposed interventions. 3. To determine the combined effect of CYB5R3 overexpression and CR on key markers of mitochondrial function. 4. To determine dietary conditions that maximize mitochondrial preservation in mice overexpressing CYB5R3. 5. To determine the effects of aging on the mitochondria parameters studied in the previously indicated aims in CYB5R3 overexpressing mice. The results of this PhD can help identify healthy lifestyles and nutritional patterns that can modulate healthy aging and extend longevity, as well as to identify new mitochondrial targets that allow the preservation of mitochondrial physiology and aid in the prevention of metabolic diseases associated with age. Introducción. El envejecimiento se define como el declive funcional dependiente del tiempo que se caracteriza por la acumulación de daños en las estructuras celulares, comprometiendo la función celular y tisular dando lugar, en último término, a la muerte del organismo. El envejecimiento es el principal factor de riesgo de las enfermedades crónicas incluyendo cáncer, enfermedades cardiovasculares (CVDs) y neurodegenerativas. Se han propuesto nueve causas principales por las que se produce el envejecimiento: las denominadas “marcas distintivas del envejecimiento”, que son las siguientes: acortamiento telomérico, inestabilidad genómica, modificaciones epigenéticas, pérdida de la proteostasis, disfunción mitocondrial, desregulación de la detección del estado nutricional, senescencia celular, alteración de la comunicación intercelular y perdida de células madre. Para tratar de explicar los cambios celulares que dan lugar el fenotipo del envejecimiento se han propuesto numerosas teorías, pero, debido a la complejidad de este proceso, ninguna de ellas puede explicar completamente el origen del envejecimiento. De estas teorías, la llamada Teoría de los Radicales Libres propone que el estrés oxidativo y el desajuste en el estado redox del organismo dan lugar al envejecimiento. Esta teoría considera que las especies reactivas de oxígeno (ROS) y otras especies reactivas (que están continuamente generándose en el organismo) son la principal causa del envejecimiento. Por lo tanto, el envejecimiento celular estaría provocado por un estrés oxidativo crónico. Las ROS son productos del metabolismo celular producidos por la respiración mitocondrial, respuesta defensiva de las células frente a agentes infecciosos, exposición a xenobióticos, respuesta a citoquinas y estrés redox. Además, actúan como moléculas de señalización celular. Las mitocondrias son la mayor fuente de ROS y las principales afectadas por el daño oxidativo que estas moléculas pueden llegar a causar. Además, son uno de los orgánulos más importantes en los organismos aeróbicos, que se encargan de la respiración celular y producen la energía necesaria para las funciones vitales de la célula. Las mitocondrias también participan en otros procesos celulares de gran importancia como la β-oxidación de ácidos grasos, homeostasis de calcio y apoptosis. Sin embargo, las ROS y los radicales libres son productos del metabolismo mitocondrial que, debido a su alta reactividad, interaccionan con los ácidos nucleicos, proteínas y fosfolípidos de membranas, dañando sus estructuras. Los fosfolípidos de membrana que contienen ácidos grasos poliinsaturados (PUFA) son los más susceptibles de ser oxidados por los radicales libres, dando lugar a la peroxidación lipídica, que altera las características de las membranas biológicas y afecta considerablemente a la función celular. Por otro lado, con el envejecimiento, las enzimas mitocondriales, la producción de ATP y la capacidad respiratoria de la célula disminuyen, a la vez que aumenta la producción de ROS. Los daños producidos en las mitocondrias dan lugar a mutaciones y alteraciones en la morfología y abundancia de estos orgánulos. Las mutaciones en el DNA mitocondrial (mtDNA) dan lugar a una pérdida de la función mitocondrial y a una desregulación de su recambio en la célula. El recambio mitocondrial se produce mediante la eliminación de mitocondrias dañadas por el proceso de autofagia, y la síntesis de nuevas mitocondrias a través de la biogénesis mitocondrial. Alteraciones en alguno de esos procesos dan lugar a una disminución de la síntesis de ATP y disfunción bioenergética. La biogénesis mitocondrial se produce por el crecimiento y división de mitocondrias preexistentes. Además, estos orgánulos son altamente dinámicos y están constantemente cambiando de forma, tamaño, número y distribución en la célula. Esta dinámica está controlada por un balance entre los procesos fusión y fisión mitocondrial, siendo estos eventos críticos para el correcto funcionamiento de las células que, a su vez, permiten el reemplazo de las mitocondrias viejas o dañadas. Todos esos mecanismos, además, participan en la distribución del DNA mitocondrial, en el mantenimiento del orgánulo en condiciones óptimas y en la regulación de la apoptosis. Un desajuste en la dinámica mitocondrial da lugar a la perdida de la homeostasis del orgánulo, provocando alteraciones en su funcionamiento, metabolismo y señalización. La disfunción mitocondrial progresiva está considerada una marca distintiva del envejecimiento e involucra una gran variedad de condiciones patológicas que aumentan con el envejecimiento como son las enfermedades neurodegenerativas, diabetes, CVDs, atrofia muscular y cáncer. También están implicadas en numerosos procesos del desarrollo embrionario. La eliminación mitocondrial por autofagia es un proceso altamente regulado llamado mitofagia. Con el fin de retrasar o revertir los efectos deletéreos del envejecimiento, numerosas intervenciones nutricionales y genéticas están siendo estudiadas. Entre ellas, la restricción calórica (CR) sin malnutrición es la intervención no genética más efectiva que retrasa el envejecimiento e incrementa la vida máxima en numerosos organismos. Los efectos beneficiosos de la CR sobre la longevidad se deben en gran parte a una mejora en la función mitocondrial. Además, la CR produce adaptaciones metabólicas muy importantes dando lugar a cambios en numerosas rutas de señalización que participan en el crecimiento, metabolismo, mecanismos de reparación de daños, estrés oxidativo, autofagia y procesos inflamatorios. Entre esos cambios, la CR aumenta el contenido de ácidos grasos monoinsaturados (MUFA), disminuye el contenido de PUFA y no provoca cambios en la cantidad de ácidos grasos saturados (SFA) en las membranas biológicas, lo que apoya la Teoría de las Membranas en el envejecimiento que establece que la longevidad máxima esta inversamente relacionada con el nivel de insaturación de las membranas biológicas, particularmente con los niveles de PUFA n-3. Por otro lado, la CR modula moléculas clave que participan en la regulación de la autofagia e incrementa los niveles de NAD+ resultando en la activación de enzimas como las sirtuinas. La homeostasis de NAD+ es importante para el mantenimiento de muchas funciones y protección frente al envejecimiento y de las enfermedades relacionadas con éste. El NAD+ es un regulador metabólico y su eficacia ha sido probada en enfermedades metabólicas como la resistencia a insulina, hígado graso o hipertensión. La sobreexpresión de enzimas capaces de generar NAD+, como la NADH citocromo b5 reductasa 3 (CYB5R3), es una estrategia que está siendo estudiada actualmente. La CYB5R3 es una flavoproteína que participa en la elongación y desaturación de ácidos grasos, lo que la hace una excelente candidata para la regulación del metabolismo, principalmente a nivel mitocondrial. La CYB5R3 tiene un rol fundamental en la regulación de rutas metabólicas asociadas con la prolongación de la vida saludable y el envejecimiento a través de mecanismos que parecen estar relacionados con la protección frente a estrés oxidativo, la producción de NAD+ celular y las alteraciones en la composición de ácidos grasos. A pesar de que esta proteína tiene una expresión basal constitutiva en muchos tejidos, puede ser también inducida en respuesta a estrés ambiental y deprivación de nutrientes. La expresión constitutiva del gen Cyb5r3 está controlada por el factor de transcripción SP1, siendo además regulada por los factores de transcripción FOXO3a y NFE2L2. Los ratones que sobrexpresan CYB5R3 muestran una mayor longevidad y una mayor protección frente enfermedades asociadas con el envejecimiento. A nivel metabólico, la sobreexpresión de esta enzima aumenta la sensibilidad a insulina, disminuye la inflamación y el estrés oxidativo y protege a los ratones frente a la inducción de cáncer. Además, esta enzima tiene un papel fundamental en la regulación del metabolismo lipídico, lo que permite aumentar la esperanza de vida, sugiriendo que aquellas estrategias centradas en aumentar su expresión y/o actividad pueden constituir intervenciones viables que confieran protección frente a patologías metabólicas y prolonguen la vida saludable. Los ácidos grasos son componentes de la dieta esenciales para generar energía. Los ácidos grasos pueden ser categorizados como saturados (SFA), monoinsaturados (MUFA) y poliinsaturados (PUFA) y la mayoría de ellos pueden ser sintetizados por el organismo, a excepción de los llamados ácidos grasos esenciales, que solamente pueden ser obtenidos a través de la ingesta. Además, los ácidos grasos son fuentes importantes de energía que pueden ser almacenados en forma de triglicéridos. Numerosos estudios han informado de la relación de los ácidos grasos de la dieta con el riesgo de enfermedades metabólicas y cardiovasculares, así como con otros trastornos. Las dietas ricas en MUFA y PUFA tienen efectos cardioprotectores, mientras que la relación entre SFA y el riesgo de sufrir enfermedades cardiovasculares sigue en debate. Los ácidos grasos pueden dar lugar a reacciones de autooxidación provocando peroxidación lipídica, lo que afecta a las propiedades de las membranas biológicas. Además, los productos tóxicos derivados de la peroxidación lipídica pueden dañar proteínas, DNA y otras biomoléculas. Debido a que los lípidos son propensos a la oxidación y causar efectos negativos en la salud, se ha extendido el uso de antioxidantes en los alimentos para prevenir su oxidación. El hígado y el corazón son dos órganos estrechamente relacionados en la salud y enfermedad. La desregulación del metabolismo lipídico hepático y muchas enfermedades metabólicas como la diabetes y la obesidad son, en última instancia, perjudiciales para la función cardíaca. El hígado es el principal órgano que regula el metabolismo energético desempeñando tres funciones fundamentales: el procesamiento metabólico de proteínas, carbohidratos y lípidos tras su absorción en el intestino, la detoxificación de agentes tóxicos y fármacos, y el almacenamiento de energía en forma de glucógeno. El hígado envejece relativamente bien a pesar de algunos cambios que ocurren con el envejecimiento. En condiciones normales el hígado tiene una tasa de regeneración bastante alta, a pesar de que el recambio de sus hepatocitos es relativamente bajo. Es por ello que el hígado ha sido muy utilizado por los investigadores como modelo de estudio del efecto de las dietas, la CR y otras intervenciones antienvejecimiento. Los cambios relacionados con la edad que experimenta el hígado incluyen una reducción del peso y volumen del órgano, el aumento del tamaño de los hepatocitos, la aparición de núcleos poliploides, una disminución del área del retículo endoplásmico liso, una menor capacidad de eliminación de ROS y la disminución en el número y función de las mitocondrias, procesos que tienen como resultado un declive de la producción de ATP. El envejecimiento ha sido asociado con la redistribución de la grasa del cuerpo, caracterizado por un incremento en la deposición de grasa visceral, incluido el hígado. Todos esos cambios estructurales y funcionales pueden contribuir a desarrollar enfermedades hepáticas con la edad. El corazón es el órgano principal del sistema circulatorio y, debido a su importancia, es uno de los órganos que se forman en primer lugar durante el desarrollo embrionario. El corazón es un órgano complejo formado por diferentes tipos celulares que dan lugar a sus distintivas propiedades estructurales, bioquímicas, mecánicas y eléctricas. Los cardiomiocitos son las células responsables de la función contráctil del miocardio y son células altamente diferenciadas sin capacidad de regeneración. Los cambios más drásticos que se producen en la función cardiaca con el envejecimiento son: hipertrofia del ventrículo izquierdo, alteraciones de la función diastólica, calcificación de la válvula aórtica, arritmia y fallo cardiaco. Esas alteraciones son, en parte, debido a una disminución en el número de cardiomiocitos, así como la hipertrofia y fibrosis provocadas por un incremento en el colágeno y por las alteraciones de la matriz extracelular. Como células postmitóticas, los cardiomiocitos son altamente susceptibles a los daños mitocondriales relacionados con el envejecimiento y producción de ROS, lo que potencia su muerte con la edad. El declive progresivo de la función mitocondrial de los cardiomiocitos es considerado la señal más clara de envejecimiento en el corazón. Por otra parte, la acumulación de colesterol y ácidos grasos en los tejidos da lugar a la producción de citoquinas inflamatorias, así como a ROS, que contribuyen a la prevalencia y mortalidad de las CVDs. Hipótesis inicial y objetivos. Estudios previos desarrollados en nuestro grupo se han centrado en como un nuevo gen con efectos pro-longevidad. Los ratones que sobre-expresan CYB5R3 presentan un número elevado de PUFA en las membranas hepáticas, efecto que se asemeja (al menos parcialmente) a los producidos por el consumo de una dieta rica en aceite de pescado o por sobreexpresión de la desaturasa Fat-1 de C.elegans. Los ácidos grasos insaturados son altamente susceptibles a la peroxidación. Sin embargo, los ratones transgénicos que sobre-expresan CYB5R3 muestran una reducción significativa en la peroxidación lipídica. Los cambios específicos en la composición de ácidos grasos que tiene lugar con la sobreexpresión de esta proteína pueden ser el resultado de un reajuste en el metabolismo, lo que además podría indicar una mejora en la función mitocondrial dando lugar a menos generación de ROS y la prevención de acumulación de daño oxidativo, efectos que mimetizan parcialmente a los observados en los animales sometidos a CR. Esos ratones transgénicos muestran una mayor sensibilidad a la insulina y una mejora en la homeostasis de la glucosa, menor inflamación, disminución del daño por estrés oxidativo y mayor prevención frente a la inducción de cáncer. Sin embargo, los ratones que sobre-expresan CYB5R3 alimentados ad libitum con una dieta estándar presentaron mayor peso corporal que sus controles y preferentemente obtenían energía del metabolismo de los carbohidratos. Por el contrario, los estudios centrados en la CR como intervención antienvejecimiento han mostrado una mejora en la prolongación de la vida saludable y de la longevidad máxima debido a una mayor utilización de la β-oxidación de ácidos grasos como fuente principal de energía, lo que difiere de los mecanismos por los que actúa la sobreexpresión de CYB5R3. Por lo tanto, la sobreexpresión de CYB5R3 puede contribuir a prolongar la vida máxima en ratones por mecanismos independientes de los descritos por la CR. Por otra parte, se ha informado que una intervención de CR a largo plazo induce la sobreexpresión de CYB5R3, por lo que se piensa que el efecto beneficioso de la CR podría estar mediado, al menos en parte, por el incremento de CYB5R3. Sin embargo, no ha sido estudiado aún cómo la sobreexpresión de CYB5R3 afecta a los procesos mitocondriales que son relevantes para determinar la pauta de envejecimiento. Tampoco se ha descrito cómo las alteraciones en la composición de ácidos grasos y la CR podrían interaccionar con los cambios provocados por la sobreexpresión de CYB5R3 en ratones transgénicos. La hipótesis de trabajo de esta Tesis Doctoral es que la eficiencia mitocondrial está optimizada en ratones transgénicos que sobre-expresan CYB5R3, lo que da lugar a una mejora en la producción de energía y una mayor preservación de la mitocondria durante el envejecimiento. Por esto mismo, nuestro principal objetivo ha sido estudiar marcadores mitocondriales en hígado y corazón de ratones que sobreexpresan esta proteína, sometidos a diferentes intervenciones nutricionales (CR y alteraciones en la composición de ácidos grasos de la dieta), así como estudiar cómo se ven afectados estos factores por el envejecimiento. Para lograr este fin, hemos planteado 5 objetivos específicos: 1. Estudiar el efecto fisiológico de la sobreexpresión de CYB5R3, los ácidos grasos de la dieta, la CR y el envejecimiento sobre el peso corporal y el perfil bioquímico. 2. Caracterizar la sobreexpresión de CYB5R3 en hígado y corazón en las tres intervenciones propuestas. 3. Determinar los efectos combinados de la sobrexpresión de CYB5R3 y de la CR sobre marcadores clave de la función mitocondrial. 4. Determinar los patrones nutricionales que maximizan la preservación mitocondrial en ratones que sobreexpresan CYB5R3. 5. Determinar los efectos del envejecimiento sobre los parámetros mitocondriales estudiados en los objetivos previamente citados, en ratones sobre-expresantes de CYB5R3. Los resultados de esta Tesis Doctoral podrían ayudar a identificar estilos de vida saludables y patrones nutricionales que pueden modular el envejecimiento saludable y la extensión de la vida máxima. También servirán para identificar nuevas dianas que permitan la preservación de la fisiología mitocondrial con el objetivo de prevenir enfermedades metabólicas asociadas con el envejecimiento.

In this review, we summarize current knowledge of perhaps one of the most intriguing phenomena in cell biology: the mitochondrial permeability transition pore (mPTP). This phenomenon, which was initially observed as a sudden loss of inner mitochondrial membrane impermeability caused by excessive calcium, has been studied for almost 50 years, and still no definitive answer has been provided regarding its mechanisms. From its initial consideration as an in vitro artifact to the current notion that the mPTP is a phenomenon with physiological and pathological implications, a long road has been travelled. We here summarize the role of mitochondria in cytosolic calcium control and the evolving concepts regarding the mitochondrial permeability transition (mPT) and the mPTP. We show how the evolving mPTP models and mechanisms, which involve many proposed mitochondrial protein components, have arisen from methodological advances and more complex biological models. We describe how scientific progress and methodological advances have allowed milestone discoveries on mPTP regulation and composition and its recognition as a valid target for drug development and a critical component of mitochondrial biology.

Mitochondrial dysfunction is associated with ageing, but the detailed causal relationship between the two is still unclear. We review the major phenomenological manifestations of mitochondrial age-related dysfunction including biochemical, regulatory and energetic features. We conclude that the complexity of these processes and their inter-relationships are still not fully understood and at this point it seems unlikely that a single linear cause and effect relationship between any specific aspect of mitochondrial biology and ageing can be established in either direction.

Mitochondrial biology has seen a surge in popularity in the past 5 years, with the emergence of numerous new avenues of exciting mitochondria-related research including immunometabolism, mitochondrial transplantation and mitochondria-microbe biology. Since the early 1960s mitochondrial dysfunction has been observed in cells of the lung in individuals and in experimental models of chronic and acute respiratory diseases. However, it is only in the past decade with the emergence of more sophisticated tools and methodologies that we are beginning to understand how this enigmatic organelle regulates cellular homeostasis and contributes to disease processes in the lung. In this review, we highlight the diverse role of mitochondria in individual lung cell populations and what happens when these essential organelles become dysfunctional with ageing and in acute and chronic lung disease. Although much remains to be uncovered, we also discuss potential targeted therapeutics for mitochondrial dysfunction in the ageing and diseased lung.

Disruption of mitochondrial biosynthesis or dynamics, or loss of control over mitochondrial regulation leads to a significant alteration in fuel preference and metabolic shifts that potentially affect the health of kidney cells. Mitochondria regulate metabolic networks which affect multiple cellular processes. Indeed, mitochondria have established themselves as therapeutic targets in several diseases. The importance of mitochondria in regulating the pathogenesis of several diseases has been recognized, however, there is limited understanding of mitochondrial biology in the kidney. This review provides an overview of mitochondrial dysfunction in kidney diseases. We describe the importance of mitochondria and mitochondrial sirtuins in the regulation of renal metabolic shifts in diverse cells types, and review this loss of control leads to increased cell-to-cell transdifferentiation processes and myofibroblast-metabolic shifts, which affect the pathophysiology of several kidney diseases. In addition, we examine mitochondrial-targeted therapeutic agents that offer potential leads in combating kidney diseases.

Tafazzin, which is encoded by the TAZ gene, catalyzes transacylation to form mature cardiolipin and shows preference for the transfer of a linoleic acid (LA) group from phosphatidylcholine (PC) to monolysocardiolipin (MLCL) with influence from mitochondrial membrane curvature. The protein contains domains and motifs involved in targeting, anchoring, and an active site for transacylase activity. Tafazzin activity affects many aspects of mitochondrial structure and function, including that of the electron transport chain, fission-fusion, as well as apoptotic signaling. TAZ mutations are implicated in Barth syndrome, an underdiagnosed and devastating disease that primarily affects male pediatric patients with a broad spectrum of disease pathologies that impact the cardiovascular, neuromuscular, metabolic, and hematologic systems.

The Manila clam, Ruditapes philippinarum (Adams & Reeve, 1850), is a widespread and commercially important bivalve species showing a peculiar way of mitochon- drial inheritance known as Doubly Uniparental Inheritance (DUI), which is different from the strict maternal inheritance found in the broad majority of metazoans. DUI in R. philippinarum was discovered later than in mytilids and unionids. Nevertheless, this case keeps providing interesting data pertinent to the mechanism of this inherit- ance system. In this review, we discuss the contribution of this species, both in the context of the available knowledge on DUI and in the broader context of metazoan mitochondrial biology. Indeed, thanks to its unusual features, DUI can shed light on mitochondrial inheritance and biogenesis and, above all, on the relationship between mitochondria and germ line. Moreover, DUI is a unique experimental system for studying mitochondrial heteroplasmy, and two processes that shape genome evolu- tion: genomic conflicts and mito-nuclear coevolution, which are at the very root of eukaryotic life.

Summary: TRAP1 is the mitochondrial paralog of the heat shock protein 90 (HSP90) chaperone family. Its activity as an energy metabolism regulator has important implications in cancer, neurodegeneration, and ischemia. Selective inhibitors of TRAP1 could inform on its mechanisms of action and set the stage for targeted drug development, but their identification was hampered by the similarity among active sites in HSP90 homologs. We use a dynamics-based approach to identify a TRAP1 allosteric pocket distal to its active site that can host drug-like molecules, and we select small molecules with optimal stereochemical features to target the pocket. These leads inhibit TRAP1, but not HSP90, ATPase activity and revert TRAP1-dependent downregulation of succinate dehydrogenase activity in cancer cells and in zebrafish larvae. TRAP1 inhibitors are not toxic per se, but they abolish tumorigenic growth of neoplastic cells. Our results indicate that exploiting conformational dynamics can expand the chemical space of chaperone antagonists to TRAP1-specific inhibitors with wide therapeutic opportunities. : The molecular chaperone TRAP1 regulates energy metabolism, and its activity is relevant in cancer and degenerative diseases. Here, Sanchez-Martin et al. identify highly selective allosteric inhibitors of TRAP1. These compounds revert biochemical and pro-neoplastic effects of TRAP1 and could both enlighten its mode of action and disclose novel therapeutic strategies. Keywords: chaperone inhibitors, anticancer compound, molecular dynamics, allosteric ligands, TRAP1, HSP90, mitochondria, mitochondrial biology, zebrafish, cancer cells, neurofibroma

In recent years, cytosine methylation in mammalian mitochondrial DNA is one of the intensely studied topics in mitochondrial biology and medicine. It could profoundly impact gene expression, replication and maintenance of mitochondrial DNA, and abnormalities in mitochondrial DNA methylation might cause diseases with mitochondrial dysfunction. Therefore, elucidating whether mitochondrial DNA is methylated or not is of pivotal importance. However, despite a number of studies suggesting the occurrence of mitochondrial DNA methylation, it appears that no conclusive landscape or role of the methylation comes to consensus. On the other hand, our recent investigation revealed challenging points in studying methylation on mitochondrial DNA. This chapter will discuss these points and propose accurate estimation of the status of 5-methylcytosine in mitochondrial DNA.

Background Quantitative analysis of mitochondrial morphology plays important roles in studies of mitochondrial biology. The analysis depends critically on segmentation of mitochondria, the image analysis process of extracting mitochondrial morphology from images. The main goal of this study is to characterize the performance of convolutional neural networks (CNNs) in segmentation of mitochondria from fluorescence microscopy images. Recently, CNNs have achieved remarkable success in challenging image segmentation tasks in several disciplines. So far, however, our knowledge of their performance in segmenting biological images remains limited. In particular, we know little about their robustness, which defines their capability of segmenting biological images of different conditions, and their sensitivity, which defines their capability of detecting subtle morphological changes of biological objects.

Physiology and behavior in mammals is predominantly under circadian clock control. Circadian clocks are present in nearly every cell of the body and oscillate with a frequency of about 24 h in a self-sustained and cell autonomous manner. These clocks not only play a principal role in metabolic control but concurrently respond to a wide variety of metabolic cues. While various aspects of circadian regulation of metabolic functions have been extensively studied, our knowledge regarding circadian mitochondrial biology is just emerging. We review herein the current literature addressing circadian mitochondrial biology: from diurnal changes in mitochondrial make-up, through dynamics and functions. We will discuss as well potential mechanisms that are implicated in circadian control of mitochondrial biology in mammals.

The biological basis of human aging remains one of the greatest unanswered scientific questions. Increasing evidence, however, points to a role for alterations in mitochondrial function as a potential central regulator of the aging process. Here, we focus primarily on three aspects of mitochondrial biology that link this ancient organelle to how and why we age. In particular, we discuss the role of mitochondria in regulating the innate immune system, the mechanisms linking mitochondrial quality control to age-dependent pathology, and the possibility that mitochondrial-to-nuclear signaling might regulate the rate of aging.

Mitochondrial disease originates from genetic changes that impact human bodily functions by disrupting the mitochondrial oxidative phosphorylation system. MitoCarta is a curated and published inventory that sheds light on the mitochondrial proteome, but the function of some mitochondrially-localised proteins remains poorly characterised. Consequently, various gene editing systems have been employed to uncover the involvement of these proteins in mitochondrial biology and disease. CRISPR/Cas9 is an efficient, versatile, and highly accurate genome editing tool that was first introduced over a decade ago and has since become an indispensable tool for targeted genetic manipulation in biological research. The broad spectrum of CRISPR/Cas9 applications serves as an attractive and tractable system to study genes and pathways that are essential for the regulation and maintenance of mitochondrial health. It has opened possibilities of generating reliable cell and animal models of human disease, and with further exploitation of the technology, large-scale genomic screenings have uncovered a wealth of fundamental mechanistic insights. In this review, we describe the applications of CRISPR/Cas9 system as a genome editing tool to uncover new insights into pathomechanisms of mitochondrial diseases and/or biological processes involved in mitochondrial function.

Mitochondria play important roles in diverse cellular processes such as energy production, cellular metabolism, and apoptosis to promote cell death. To investigate mitochondria-associated biological processes such as structure, dynamics, morphological change, metabolism, and mitophagy, there exists a continuous demand for visualizing and monitoring techniques elucidating mitochondrial biology and disease-relevancy. Due to the advantages of high sensitivity and practicality, fluorescence phenomena have been most widely used as scientific techniques for the visualization of biological phenomena and systems. In this review, we briefly overview the different types of fluorescent materials such as chemical probes, peptide- or protein-based probes, and nanomaterials for monitoring mitochondrial biology.