Antioxidant effect of exercise: Exploring the role of the mitochondrial complex I superassembly

The Impact of Physical Exercise on Oxidative and Nitrosative Stress: Balancing the Benefits and Risks

This review comprehensively evaluates the effects of physical exercise on oxidative and nitrosative stress, mainly focusing on the role of antioxidants. Using a narrative synthesis approach, data from empirical studies, reviews, systematic reviews, and meta-analyses published between 2004 and 2024 were collated from databases like PubMed, EBSCO (EDS), and Google Scholar, culminating in the inclusion of 41 studies. The quality of these studies was rigorously assessed to ensure the clarity of objectives, coherence in arguments, comprehensive literature coverage, and depth of critical analysis. Findings revealed that moderate exercise enhances antioxidant defenses through hormesis, while excessive exercise may exacerbate oxidative stress. The review also highlights that while natural dietary antioxidants are beneficial, high-dose supplements could impede the positive adaptations to exercise. In conclusion, the review calls for more focused research on tailored exercise and nutrition plans to further understand these complex interactions and optimize the health outcomes for athletes and the general population.

Early heart and skeletal muscle mitochondrial response to a moderate hypobaric hypoxia environment

In eukaryotic cells, aerobic energy is produced by mitochondria through oxygen uptake. However, little is known about the early mitochondrial responses to moderate hypobaric hypoxia (MHH) in highly metabolic active tissues. Here, we describe the mitochondrial responses to acute MHH in the heart and skeletal muscle. Rats were randomly allocated into a normoxia control group (n = 10) and a hypoxia group (n = 30), divided into three groups (0, 6, and 24 h post-MHH). The normoxia situation was recapitulated at the University of Granada, at 662 m above sea level. The MHH situation was performed at the High-Performance Altitude Training Centre of Sierra Nevada located in Granada at 2320 m above sea level. We found a significant increase in mitochondrial supercomplex assembly in the heart as soon as the animals reached 2320 m above sea level and their levels are maintained 24 h post-exposure, but not in skeletal muscle. Furthermore, in skeletal muscle, at 0 and 6 h, there was increased dynamin-related protein 1 (Drp1) expression and a significant reduction in Mitofusin 2. In conclusion, mitochondria from the muscle and heart respond differently to MHH: mitochondrial supercomplexes increase in the heart, whereas, in skeletal muscle, the mitochondrial pro-fission response is trigged. Considering that skeletal muscle was not actively involved in the ascent when the heart was beating faster to compensate for the hypobaric, hypoxic conditions, we speculate that the different responses to MHH are a result of the different energetic requirements of the tissues upon MHH. KEY POINTS: The heart and the skeletal muscle showed different mitochondrial responses to moderate hypobaric hypoxia. Moderate hypobaric hypoxia increases the assembly of the electron transport chain complexes into supercomplexes in the heart. Skeletal muscle shows an early mitochondrial pro-fission response following exposure to moderate hypobaric hypoxia.

SCAF1 drives the compositional diversity of mammalian respirasomes

Supercomplexes of the respiratory chain are established constituents of the oxidative phosphorylation system, but their role in mammalian metabolism has been hotly debated. Although recent studies have shown that different tissues/organs are equipped with specific sets of supercomplexes, depending on their metabolic needs, the notion that supercomplexes have a role in the regulation of metabolism has been challenged. However, irrespective of the mechanistic conclusions, the composition of various high molecular weight supercomplexes remains uncertain. Here, using cryogenic electron microscopy, we demonstrate that mammalian (mouse) tissues contain three defined types of 'respirasome', supercomplexes made of CI, CIII2 and CIV. The stoichiometry and position of CIV differs in the three respirasomes, of which only one contains the supercomplex-associated factor SCAF1, whose involvement in respirasome formation has long been contended. Our structures confirm that the 'canonical' respirasome (the C-respirasome, CICIII2CIV) does not contain SCAF1, which is instead associated to a different respirasome (the CS-respirasome), containing a second copy of CIV. We also identify an alternative respirasome (A-respirasome), with CIV bound to the 'back' of CI, instead of the 'toe'. This structural characterization of mouse mitochondrial supercomplexes allows us to hypothesize a mechanistic basis for their specific role in different metabolic conditions.

Preserved respiratory chain capacity and physiology in mice with profoundly reduced levels of mitochondrial respirasomes

The mammalian respiratory chain complexes I, III2, and IV (CI, CIII2, and CIV) are critical for cellular bioenergetics and form a stable assembly, the respirasome (CI-CIII2-CIV), that is biochemically and structurally well documented. The role of the respirasome in bioenergetics and the regulation of metabolism is subject to intense debate and is difficult to study because the individual respiratory chain complexes coexist together with high levels of respirasomes. To critically investigate the in vivo role of the respirasome, we generated homozygous knockin mice that have normal levels of respiratory chain complexes but profoundly decreased levels of respirasomes. Surprisingly, the mutant mice are healthy, with preserved respiratory chain capacity and normal exercise performance. Our findings show that high levels of respirasomes are dispensable for maintaining bioenergetics and physiology in mice but raise questions about their alternate functions, such as those relating to the regulation of protein stability and prevention of age-associated protein aggregation.

Mitochondrial DNA-targeted therapy: A novel approach to combat cancer

Mitochondrial DNA (mtDNA) encodes proteins and RNAs that are essential for mitochondrial function and cellular homeostasis, and participates in important processes of cellular bioenergetics and metabolism. Alterations in mtDNA are associated with various diseases, especially cancers, and are considered as biomarkers for some types of tumors. Moreover, mtDNA alterations have been found to affect the proliferation, progression and metastasis of cancer cells, as well as their interactions with the immune system and the tumor microenvironment (TME). The important role of mtDNA in cancer development makes it a significant target for cancer treatment. In recent years, many novel therapeutic methods targeting mtDNA have emerged. In this study, we first discussed how cancerogenesis is triggered by mtDNA mutations, including alterations in gene copy number, aberrant gene expression and epigenetic modifications. Then, we described in detail the mechanisms underlying the interactions between mtDNA and the extramitochondrial environment, which are crucial for understanding the efficacy and safety of mtDNA-targeted therapy. Next, we provided a comprehensive overview of the recent progress in cancer therapy strategies that target mtDNA. We classified them into two categories based on their mechanisms of action: indirect and direct targeting strategies. Indirect targeting strategies aimed to induce mtDNA damage and dysfunction by modulating pathways that are involved in mtDNA stability and integrity, while direct targeting strategies utilized molecules that can selectively bind to or cleave mtDNA to achieve the therapeutic efficacy. This study highlights the importance of mtDNA-targeted therapy in cancer treatment, and will provide insights for future research and development of targeted drugs and therapeutic strategies.

Mitochondrial adaptations to calorie restriction and bariatric surgery in human skeletal muscle: a systematic review with meta-analysis

OBJECTIVE

We performed a meta-analysis to determine the changes induced by calorie restriction (CR) and bariatric surgery on human skeletal muscle mitochondria.

METHODS

A systematic search of Medline and Web of Science was conducted. Controlled trials exploring CR (≥14 days) and mitochondrial function and/or content assessment were included. Moreover, studies analyzing weight loss following gastric surgery were included for comparison purposes. Human muscle data from 28 studies assessing CR (520 muscle samples) and from 10 studies assessing bariatric surgery (155 muscle samples) were analyzed in a random effect meta-analysis with three a priori chosen covariates.

MAIN RESULTS

We report a decrease (p < 0.05) (mean (95 % CI)) in maximal mitochondrial state 3 respiration in response to CR (-0.44 (-0.85, -0.03)) but not in response to surgery (-0.33 (-1.18, 0.52)). No changes in mitochondrial content were reported after CR (-0.05 (-0.12, 0.13)) or in response to surgery (0.23 (-0.05, 0.52)). Moreover, data from CR subjects showed a reduction in complex IV (CIV) activity (-0.29 (-0.56, -0.03)) but not in CIV content (-0.21 (-0.63, 0.22)). Similar results were obtained when the length of the protocol, the initial body mass index, and the estimated energy deficit were included in the model as covariates.

CONCLUSION

The observation of reduced maximal mitochondrial state 3, uncoupled respiration, and CIV activity without altering mitochondrial content suggests that, in human skeletal muscle, CR mainly modulates intrinsic mitochondrial function.

Leisure-time regular exercise and prevention of the side effects of immune system activity in middle-aged healthy subjects

Regular exercise is recommended to improve immune system function and antioxidant activity, while conversely, it may cause inflammation by increasing neutrophil-derived main enzyme, myeloperoxidase, which produces reactive oxygen species. The present study aimed to investigate changes in myeloperoxidase level, its influence on total oxidant status, and the capacity of the antioxidant defence system to counteract oxidative stress in middle-aged men participating in leisure-time regular exercise compared to untrained peer subjects. Twenty trained (age 53.58±2.94 years, body mass index (BMI) 25.47±1.6) and 17 untrained (age 54.17±2.83 years, BMI 27.83±1.12) healthy middle-aged men participated in this study [Rasht, Gilan, Iran]. Participants performed a modified Bruce treadmill test as a model of progressive exercise training. Blood samples were taken before, immediately after, and one hour after the end of the test. A mixed ANOVA and Bonferroni post hoc test was used for the analysis of variables. A significant difference was observed in myeloperoxidase levels between groups, while the trained group showed a significantly lower concentration than the untrained group (P<0.018). This result was also consistent with the lower total oxidant status in this group (P<0.001). Total antioxidant capacity changed significantly in both groups with higher concentration in the trained group (P<0.001). The leisure-time regular exercise can reduce myeloperoxidase concentration and total oxidant status in healthy middle-aged men while increasing the total antioxidant capacity, which may potentially protect them from the side effects of immune system activity induced by exercise training.

Effect of 8 Weeks Aerobic Training and Saffron Supplementation on Inflammation and Metabolism in Middle-Aged Obese Women with Type 2 Diabetes Mellitus

Background: This study aimed to investigate the effects of 8-week aerobic training (AT) and saffron supplementation on inflammation and metabolism in middle-aged obese women with type 2 diabetes mellitus (T2DM). Methods: Thirty-two obese women with T2DM were randomly divided into four groups (n = 8 in all groups): saffron + training (ST), placebo + training (PT), saffron supplementation (SS), and placebo (P). The ST and PT groups performed eight weeks of aerobic training (AT) (three sessions/week at 60−75% HRmax). A daily dose of 400 mg saffron powder was consumed by the ST and SS groups for 8 weeks. Blood samples were taken after 12 h of fasting, 48 h before the first AT session, 48 h and two weeks after the last AT session. Results: AT, saffron supplementation, and their combination affected body mass index (BMI), homeostatic model assessment for insulin resistance (HOMA-IR), and serum levels of insulin, adiponectin, interleukin-6 (IL-6), high-density lipoprotein cholesterol (HDL-C), cholesterol, and triglyceride (TG) (p < 0.05). However, body weight, body fat percentage, and serum levels of glucose, resistin, tumor necrosis factor-alpha (TNF-α), irisin, and low-density lipoprotein cholesterol (LDL-C) showed significant changes in the ST group only (p < 0.05). In addition, a significant difference was seen between all factors in post-training and follow-up in the ST group (p < 0.05). Conclusions: Saffron supplementation at a dose of 400 mg/day, when combined with AT, could improve inflammation, metabolism, glycemic status, and lipid profile in T2DM patients, and these changes are sustainable at up to 2 weeks of detraining.

Düzenli olarak uygulanan orta şiddetteki egzersiz programının tiyol/disülfid homeostazı ve iskemi modifiye albümin üzerine etkisi

Amaç: Tiyol/disülfid homeostazı, oksidatif stresin ve antioksidan kapasitenin bir göstergesidir. İskemi-modifiye albümin (İMA), hem oksidatif stres hem de iskemi için önemli bir belirteçtir. Düzenli olarak uygulanan orta şiddetteki egzersizin tiyol/disülfid homeostazı ve IMA seviyeleri üzerine olası etkilerini değerlendirmeyi amaçladık. 
Metot: Sprague-Dawley sıçanlar kullanıldı. Çalışma, Egzersiz grubu (EG, n=9) ve Kontrol grubundan (KG, n=6) oluşturuldu. 10 haftalık bir yüzme egzersizi yaptırıldı. Bu çalışmada tiyol/disülfid homeostazı ölçüm yöntemi kullanıldı. IMA seviyeleri, bir kobalt-albümin bağlama yöntemiyle ölçüldü. 
Bulgular: EG'de, total tiyol seviyeleri KG ile karşılaştırıldığında anlamlı derecede daha yüksekti (p

Impact of exercise training on muscle mitochondria modifications in older adults: a systematic review of randomized controlled trials

BACKGROUND

Previous evidence showed that cellular aging is a multifactorial process that is associated with decline in mitochondrial function. Physical exercise has been proposed as an effective and safe therapeutical intervention to improve the mitochondria network in the adult myocytes.

AIMS

The aim of this systematic review of randomized controlled trials (RCTs) was to assess the exercise-induced muscle mitochondria modifications in older adults, underlining the differences related to different exercise modalities.

METHODS

On November 28th, 2021, five databases (PubMed, Scopus, Web of Science, Cochrane, and PEDro) were systematically searched for RCTs to include articles with: healthy older people as participants; physical exercise (endurance training (ET), resistance training (RT), and combined training (CT)) as intervention; other different exercise modalities or physical inactivity as comparator; mitochondrial modifications (quality, density and dynamics, oxidative, and antioxidant capacity) as outcomes. The quality assessment was performed according to the PEDro scale; the bias risk was evaluated by Cochrane risk-of-bias assessment tool.

RESULTS

Out of 2940 records, 6 studies were included (2 assessing ET, 2 RT, 1 CT, and 1 both ET and RT). Taken together, 164 elderly subjects were included in the present systematic review. Significant positive effects were reported in terms of mitochondrial quality, density, dynamics, oxidative and antioxidant capacity, even though with different degrees according to the exercise type. The quality assessment reported one good-quality study, whereas the other five studies had a fair quality.

DISCUSSION

The overall low quality of the studies on this topic indicate that further research is needed.

CONCLUSION

RT seems to be the most studied physical exercise modality improving mitochondrial density and dynamics, while ET have been related to mitochondrial antioxidant capacity improvements. However, these exercise-induced specific effects should be better explored in older people.

Physiological Doses of Hydroxytyrosol Modulate Gene Expression in Skeletal Muscle of Exercised Rats

We tested whether physiological doses of hydroxytyrosol (HT) may alter the mRNA transcription of key metabolic genes in exercised skeletal muscle. Two groups of exercise-trained Wistar rats, HTlow and HTmid, were supplemented with 0.31 and 4.61 mg/kg/d of HT, respectively, for 10 weeks. Another two groups of rats were not supplemented with HT; one remained sedentary and the other one was exercised. After the experimental period, the soleus muscle was removed for qRT-PCR and western blot analysis. The consumption of 4.61 mg/kg/d of HT during exercise increased the mRNA expression of important metabolic proteins. Specifically, 4.61 mg/kg/d of HT may upregulate long-chain fatty acid oxidation, lactate, and glucose oxidation as well as mitochondrial Krebs cycle in trained skeletal muscle. However, a 4.61 mg/kg/d of HT may alter protein translation, as in spite of the increment showed by CD36 and GLUT4 at the mRNA level this was not translated to higher protein content.

Oxidative stress response to different exercise intensity with an automated assay: thiol/disulphide homeostasis

The aim of this study was to investigate the effect of different intensity treadmill exercises on the thiol disulphide homeostasis which is a new marker of oxidative stress in rats. Male albino Wistar rats were randomly divided into four groups as follows: control (CNT), low (LEx), moderate (MEx) and high-intensity exercise (HEx) group. Exercise was performed for 4 weeks. Following completion of the experimental protocol, serum total thiol, native thiol and disulphide concentrations were determined using a novel automated measurement method. Additionally, dynamic disulphide status, reduced thiol, oxidised thiol and thiol oxidation reduction percentage ratios were compared among the groups. Disulphide levels were significantly lower in MEx group and highest in CNT group (p = .047). The lowest oxidised thiol and the highest reduced thiol were determined in CNT group (p = .086; p = .083). These findings indicate that moderate-intensity exercise is more effective in reducing oxidative stress than low and high-intensity exercise.

Effects of high-intensity interval training on mitochondrial supercomplex assembly and biogenesis, mitophagy, and the AMP-activated protein kinase pathway in the soleus muscle of aged female rats

PURPOSE

Exercise helps improve mitochondrial function to combat sarcopenia. Certain parts of the mitochondrial respiratory chain complex can form a higher-order structure called "supercomplex" to reduce the production of reactive oxygen species and improve muscle mass. The effect of exercise on the assembly of the mitochondrial supercomplex is still unclear. The aim of this study was to investigate the effects of long-term high-intensity interval training (HIIT) on mitochondrial biogenesis, mitophagy, and mitochondrial supercomplexes (mitoSCs) assembly in aging soleus muscle.

METHODS

Female Sprague-Dawley rats (n = 36) were randomly divided into four groups: young sedentary (Y-SED, 8 months old, n = 12), old sedentary (O-SED, 26 months old, n = 12), moderate-intensity continuous training (MICT, from 18 to 26 months old, n = 12), and HIIT (from 18 to 26 months old, n = 12). Rats in the MICT and HIIT groups were subjected to an 8-month training program. Real-time fluorescent quantitative polymerase chain reaction was used to measure the expression of the antioxidative factors, inflammatory factors, and mitochondrial fusion- and division-related genes. Western blotting was used to detect the expression of mitochondrial biogenesis and mitophagy markers and AMP-activated protein kinase (AMPK) pathway proteins. Enzyme-linked immunosorbent assays were used to determine serum irisin contents. Blue native polyacrylamide gel electrophoresis was used to assess the formation of mitochondrial supercomplexes.

RESULTS

Compared with the Y-SED group, the soleus muscle and mitochondria in the O-SED group showed reduced expression of mitophagy- and mitochondrial biogenesis-related proteins. In the HIIT group, the expression of autophagy-related proteins in the soleus muscle and mitochondria was significantly increased compared with that in the MICT group. Serum irisin and mitochondrial fusion protein levels significantly decreased with age. Superoxide dismutase 2 protein levels and AMPK pathway protein expression were significantly increased in the HIIT group compared with those in the other groups. Additionally, the expression levels of mitoSCs and the mRNA levels of interleukin-15 and optical atrophy 1 increased in the HIIT group compared with that in the MICT group.

CONCLUSION

Compared with MICT, HIIT activated the AMPK pathway to upregulate mitochondrial biogenesis- and mitophagy-related proteins, and promote the assembly and formation of mitoSCs to improve the mitochondrial function of aging soleus muscles.

Effects of Simultaneous Exposure to a Western Diet and Wheel-Running Training on Brain Energy Metabolism in Female Rats

BACKGROUND

In the pathogenesis of central nervous system disorders (e.g., neurodegenerative), an important role is attributed to an unhealthy lifestyle affecting brain energy metabolism. Physical activity in the prevention and treatment of lifestyle-related diseases is getting increasing attention.

METHODS

We performed a series of assessments in adult female Long Evans rats subjected to 6 weeks of Western diet feeding and wheel-running training. A control group of lean rats was fed with a standard diet. In all experimental groups, we measured physiological parameters (animal weights, body composition, serum metabolic parameters). We assessed the impact of simultaneous exposure to a Western diet and wheel-running on the cerebrocortical protein expression (global proteomic profiling), and in the second part of the experiment, we measured the cortical levels of protein related to brain metabolism (Western blot).

RESULTS

Western diet led to an obese phenotype and induced changes in the serum metabolic parameters. Wheel-running did not reduce animal weights or fat mass but significantly decreased serum glucose level. The global proteome analysis revealed that the altered proteins were functionally annotated as they were involved mostly in metabolic pathways. Western blot analysis showed the downregulation of the mitochondrial protein-Acyl-CoA dehydrogenase family member 9, hexokinase 1 (HK1)-enzyme involved in principal glucose metabolism pathways and monocarboxylate transporter 2 (MCT2). Wheel-running reversed this decline in the cortical levels of HK1 and MCT2.

CONCLUSION

The cerebrocortical proteome is affected by a combination of physical activity and Western diet in female rats. An analysis of the cortical proteins involved in brain energy metabolism provides a valuable basis for the deeper investigation of changes in the brain structure and function induced by simultaneous exposure to a Western diet and physical activity.

Regulation and functional role of the electron transport chain supercomplexes

Mitochondria are one of the most exhaustively investigated organelles in the cell and most attention has been paid to the components of the mitochondrial electron transport chain (ETC) in the last 100 years. The ETC collects electrons from NADH or FADH₂ and transfers them through a series of electron carriers within multiprotein respiratory complexes (complex I to IV) to oxygen, therefore generating an electrochemical gradient that can be used by the F₁-F₀-ATP synthase (also named complex V) in the mitochondrial inner membrane to synthesize ATP. The organization and function of the ETC is a continuous source of surprises. One of the latest is the discovery that the respiratory complexes can assemble to form a variety of larger structures called super-complexes (SCs). This opened an unexpected level of complexity in this well-known and fundamental biological process. This review will focus on the current evidence for the formation of different SCs and will explore how they modulate the ETC organization according to the metabolic state. Since the field is rapidly growing, we also comment on the experimental techniques used to describe these SC and hope that this overview may inspire new technologies that will help to advance the field.

Proteomic Analysis of Cardiac Adaptation to Exercise by High Resolution Mass Spectrometry

Regular exercise has many health benefits, among which is a significant reduction of cardiovascular risk. Although many beneficial effects of exercise are well described, the exact mechanisms by which exercise confers cardiovascular benefits are yet to be fully understood. In the current study, we have used high resolution mass spectrometry to determine the proteomic responses of the heart to exercise training in mice. The impact of exercise-induced oxidative stress on modifications of cardiomyocyte proteins with lipid peroxidation biomarker 4-hydroxynonenal (4-HNE) was examined as well. Fourteen male mice were randomized into the control (sedentary) group and the exercise group that was subjected to a swim exercise training program for 5 days a week for 5 months. Proteins were isolated from the left ventricular tissue, fractionated and digested for shotgun proteomics. Peptides were separated by nanoliquid chromatography and analyzed on an Orbitrap Fusion mass spectrometer using high-energy collision–induced dissociation and electron transfer dissociation fragmentation. We identified distinct ventricular protein signatures established in response to exercise training. Comparative proteomics identified 23 proteins that were upregulated and 37 proteins that were downregulated with exercise, in addition to 65 proteins that were identified only in ventricular tissue samples of exercised mice. Most of the proteins specific to exercised mice are involved in respiratory electron transport and/or implicated in glutathione conjugation. Additionally, 10 proteins were found to be modified with 4-HNE. This study provides new data on the effects of exercise on the cardiac proteome and contributes to our understanding of the molecular mechanisms underlying the beneficial effects of exercise on the heart.

The influence of aerobic exercise on mitochondrial quality control in skeletal muscle

Mitochondria are dynamic organelles, intricately designed to meet cellular energy requirements. To accommodate alterations in energy demand, mitochondria have a high degree of plasticity, changing in response to transient activation of numerous stress-related pathways. This adaptive response is particularly relevant in highly metabolic tissues such as skeletal muscle, where mitochondria support numerous biological processes related to metabolism, growth and regeneration. Aerobic exercise is a potent stimulus for skeletal muscle remodelling, leading to alterations in substrate utilisation, fibre-type composition and performance. Underlying these physiological responses is a change in mitochondrial quality control (MQC), a term encompassing the co-ordination of mitochondrial synthesis (biogenesis), remodelling (dynamics) and degradation (mitophagy) pathways. Understanding of MQC in skeletal muscle and the regulatory role of aerobic exercise of this process are rapidly advancing, as are the molecular techniques allowing the study of MQC in vivo. Given the emerging link between MQC and the onset of numerous non-communicable diseases, understanding the molecular regulation of MQC, and the role of aerobic exercise in this process, will have substantial future impact on therapeutic approaches to manipulate MQC and maintain mitochondrial function across health span.

Molecular and Supramolecular Structure of the Mitochondrial Oxidative Phosphorylation System: Implications for Pathology

Under aerobic conditions, mitochondrial oxidative phosphorylation (OXPHOS) converts the energy released by nutrient oxidation into ATP, the currency of living organisms. The whole biochemical machinery is hosted by the inner mitochondrial membrane (mtIM) where the protonmotive force built by respiratory complexes, dynamically assembled as super-complexes, allows the F1FO-ATP synthase to make ATP from ADP + Pi. Recently mitochondria emerged not only as cell powerhouses, but also as signaling hubs by way of reactive oxygen species (ROS) production. However, when ROS removal systems and/or OXPHOS constituents are defective, the physiological ROS generation can cause ROS imbalance and oxidative stress, which in turn damages cell components. Moreover, the morphology of mitochondria rules cell fate and the formation of the mitochondrial permeability transition pore in the mtIM, which, most likely with the F1FO-ATP synthase contribution, permeabilizes mitochondria and leads to cell death. As the multiple mitochondrial functions are mutually interconnected, changes in protein composition by mutations or in supercomplex assembly and/or in membrane structures often generate a dysfunctional cascade and lead to life-incompatible diseases or severe syndromes. The known structural/functional changes in mitochondrial proteins and structures, which impact mitochondrial bioenergetics because of an impaired or defective energy transduction system, here reviewed, constitute the main biochemical damage in a variety of genetic and age-related diseases.

Mitochondrial Functionality in Inflammatory Pathology-Modulatory Role of Physical Activity

The incidence and severity of metabolic diseases can be reduced by introducing healthy lifestyle habits including moderate exercise. A common observation in age-related metabolic diseases is an increment in systemic inflammation (the so-called inflammaging) where mitochondrial reactive oxygen species (ROS) production may have a key role. Exercise prevents these metabolic pathologies, at least in part, due to its ability to alter immunometabolism, e.g., reducing systemic inflammation and by improving immune cell metabolism. Here, we review how exercise regulates immunometabolism within contracting muscles. In fact, we discuss how circulating and resident macrophages alter their function due to mitochondrial signaling, and we propose how these effects can be triggered within skeletal muscle in response to exercise. Finally, we also describe how exercise-induced mitochondrial adaptations can help to fight against virus infection. Moreover, the fact that moderate exercise increases circulating immune cells must be taken into account by public health agencies, as it may help prevent virus spread. This is of interest in order to face not only acute respiratory-related coronavirus (SARS-CoV) responsible for the COVID-19 pandemic but also for future virus infection challenges.

Clinical Therapeutic Management of Human Mitochondrial Disorders

Despite recent advances in the elucidation of etiology and pathogenesis of mitochondrial disorders, their therapeutic management remains challenging. This review focuses on currently available therapeutic options for human mitochondrial disorders. Current treatment of mitochondrial disorders relies on symptomatic, multidisciplinary therapies of various manifestations in organs such as the brain, muscle, nerves, eyes, ears, endocrine organs, heart, intestines, kidneys, lungs, bones, bone marrow, cartilage, immune system, and skin. If respiratory chain functions are primarily or secondarily impaired, antioxidants or cofactors should be additionally given one by one. All patients with mitochondrial disorders should be offered an individually tailored diet and physical training program. Irrespective of the pathogenesis, all patients with mitochondrial disorders should avoid exposure to mitochondrion-toxic agents and environments. Specific treatment can be offered for stroke-like episodes, mitochondrial epilepsy, mitochondrial neurogastrointestinal encephalopathy, Leber hereditary optic neuropathy, thiamine-responsive Leigh syndrome, primary coenzyme Q deficiency, primary carnitine deficiency, Friedreich ataxia, ethylmalonic encephalopathy, acyl-CoA dehydrogenase deficiency, pyruvate dehydrogenase deficiency, and hereditary vitamin E deficiency. Preventing the transmission of mitochondrial DNA-related mitochondrial disorders can be achieved by mitochondrion replacement therapy (spindle transfer, pronuclear transfer). In conclusion, specific and nonspecific therapies for human mitochondrial disorders are available, and beneficial effects have been anecdotally reported. However, double-blind, placebo-controlled studies to confirm effectiveness are lacking for the majority of the measures applied to mitochondrial disorders. Transmission of certain mitochondrial disorders can be prevented by mitochondrion replacement therapy. A multidisciplinary approach is required to meet the therapeutic challenges of patients with mitochondrial disorders.

Domesticated and optimized mitochondria: Mitochondrial modifications based on energetic status and cellular stress

Mitochondria are the main source of energy and play an important role in coupling intracellular and intercellular metabolic cooperation. Cellular stress and energetic status can affect various mitochondrial behaviors, including mitochondrial biogenesis, mitophagy, assembly of respiratory chain supercomplexes and mitochondrial distribution. These modifications usually result in adaptive adjustment of mitochondrial output and resistance to cellular stress. However, when the pro-death signals triggered by excessive damage converge to mitochondria, mitochondrial reserve and functional status can profoundly determine the direction of cell death, and even affect the survival and death of surrounding or distant tissues. In this review, we discuss multiple mitochondrial modifications in eukaryotes based on metabolic status and cellular stress, and review the emerging knowledge about the effects of mitochondrial dysfunction on the fate of cells and surrounding tissues.

Digitonin concentration is determinant for mitochondrial supercomplexes analysis by BlueNative page

The BlueNative page (BNGE) gel has been the reference technique for studying the electron transport chain organization since it was established 20 years ago. Although the migration of supercomplexes has been demonstrated being real, there are still several concerns about its ability to reveal genuine interactions between respiratory complexes. Moreover, the use of different solubilization conditions generates conflicting interpretations. Here, we thoroughly compare the impact of different digitonin concentrations on the liquid dispersions' physical properties and correlate with the respiratory complexes' migration pattern and supercomplexes. Our results demonstrate that digitonin concentration generates liquid dispersions with specific size and variability critical to distinguish between a real association of complexes from being trapped in the same micelle.

Scaf1 promotes respiratory supercomplexes and metabolic efficiency in zebrafish

The oxidative phosphorylation (OXPHOS) system is a dynamic system in which the respiratory complexes coexist with super-assembled quaternary structures called supercomplexes (SCs). The physiological role of SCs is still disputed. Here, we used zebrafish to study the relevance of respiratory SCs. We combined immunodetection analysis and deep data-independent proteomics to characterize these structures and found similar SCs to those described in mice, as well as novel SCs including III2  + IV2 , I + IV, and I + III2  + IV2 . To study the physiological role of SCs, we generated two null allele zebrafish lines for supercomplex assembly factor 1 (scaf1). scaf1-/- fish displayed altered OXPHOS activity due to the disrupted interaction of complexes III and IV. scaf1-/- fish were smaller in size and showed abnormal fat deposition and decreased female fertility. These physiological phenotypes were rescued by doubling the food supply, which correlated with improved bioenergetics and alterations in the metabolic gene expression program. These results reveal that SC assembly by Scaf1 modulates OXPHOS efficiency and allows the optimization of metabolic resources.

Functional role of respiratory supercomplexes in mice: SCAF1 relevance and segmentation of the Qpool

Mitochondrial respiratory complexes assemble into supercomplexes (SC). Q-respirasome (III2 + IV) requires the supercomplex assembly factor (SCAF1) protein. The role of this factor in the N-respirasome (I + III2 + IV) and the physiological role of SCs are controversial. Here, we study C57BL/6J mice harboring nonfunctional SCAF1, the full knockout for SCAF1, or the wild-type version of the protein and found that exercise performance is SCAF1 dependent. By combining quantitative data-independent proteomics, 2D Blue native gel electrophoresis, and functional analysis of enriched respirasome fractions, we show that SCAF1 confers structural attachment between III2 and IV within the N-respirasome, increases NADH-dependent respiration, and reduces reactive oxygen species (ROS). Furthermore, the expression of AOX in cells and mice confirms that CI-CIII superassembly segments the CoQ in two pools and modulates CI-NADH oxidative capacity.

Exercise training protects the heart against ischemia-reperfusion injury: A central role for mitochondria?

Ischemic heart disease is one of the main causes of morbidity and mortality worldwide. Physical exercise is an effective lifestyle intervention to reduce the risk factors for cardiovascular disease and also to improve cardiac function and survival in patients with ischemic heart disease. Among the strategies that contribute to reduce heart damages during ischemia and reperfusion, regular physical exercise is efficient both in rodent experimental models and in humans. However, the cellular and molecular mechanisms of the cardioprotective effects of exercise remain unclear. During ischemia and reperfusion, mitochondria are crucial players in cell death, but also in cell survival. Although exercise training can influence mitochondrial function, the consequences on heart sensitivity to ischemic insults remain elusive. In this review, we describe the effects of physical activity on cardiac mitochondria and their potential key role in exercise-induced cardioprotection against ischemia-reperfusion damage. Based on recent scientific data, we discuss the role of different pathways that might help to explain why mitochondria are a key target of exercise-induced cardioprotection.

The emerging role of skeletal muscle mitochondrial dynamics in exercise and ageing

Mitochondria are the hub for energy production within living cells. They can undergo morphological changes in response to nutrient availability and cellular stress. Here, we review how exercise chronically and acutely affects mitochondrial dynamics. Moreover, we discuss whether mitochondrial dysfunction observed in elderly subjects is due to the ageing process per se or due to the associated sedentary state. Finally, we study how endurance exercise can improve mitochondrial dynamics in older subjects, thereby improving their overall health and likely limiting muscle waste.

Mitochondrial respiratory chain composition and organization in response to changing oxygen levels

Mitochondria are the major consumer of oxygen in eukaryotic cells, owing to the requirement of oxygen to generate ATP through the mitochondrial respiratory chain (MRC) and the oxidative phosphorylation system (OXPHOS). This aerobic energy transduction is more efficient than anaerobic processes such as glycolysis. Hypoxia, a condition in which environmental or intracellular oxygen levels are below the standard range, triggers an adaptive signaling pathway within the cell. When oxygen concentrations are low, hypoxia-inducible factors (HIFs) become stabilized and activated to mount a transcriptional response that triggers modulation of cellular metabolism to adjust to hypoxic conditions. Mitochondrial aerobic metabolism is one of the main targets of the hypoxic response to regulate its functioning and efficiency in the presence of decreased oxygen levels. During evolution, eukaryotic cells and tissues have increased the plasticity of their mitochondrial OXPHOS system to cope with metabolic needs in different oxygen contexts. In mammalian mitochondria, two factors contribute to this plasticity. First, several subunits of the multimeric MRC complexes I and IV exist in multiple tissue-specific and condition-specific isoforms. Second, the MRC enzymes can coexist organized as individual entities or forming supramolecular structures known as supercomplexes, perhaps in a dynamic manner to respond to environmental conditions and cellular metabolic demands. In this review, we will summarize the information currently available on oxygen-related changes in MRC composition and organization and will discuss gaps of knowledge and research opportunities in the field.

Human muscular mitochondrial fusion in athletes during exercise

The main objective of this work was to investigate whether mitochondrial fusion occurs in the skeletal muscle of well-trained athletes in response to high-intensity exercise. Well-trained swimmers (n = 9) performed a duration-matched sprint interval training (SIT) and high-intensity high-volume training (HIHVT) session on separate days. Muscle samples from triceps brachii were taken before, immediately after, and 3 h after the training sessions. Transmission electron microscopy (TEM) was applied to assess mitochondrial morphology. Moreover, expression of genes coding for regulators of mitochondrial fusion and fission were assessed by real-time quantitative PCR. In addition, mitofusin (MFN)2 and optic atrophy 1 (OPA1) were quantified by Western blot analysis. TEM analyses showed that mitochondrial morphology remained altered for 3 h after HIHVT, whereas SIT-induced changes were only evident immediately after exercise. Only SIT increased MFN1 and MFN2 mRNA expression, whereas SIT and HIHVT both increased MFN2 protein content 3 h after exercise. Notably, only HIHVT increased OPA1 protein content. Mitochondrial morphologic changes that suggest fusion occurs in well-adapted athletes during exercise. However, HIHVT appears as a more robust inducer of mitochondrial fusion events than SIT. Indeed, SIT induces a rapid and transient change in mitochondrial morphology.-Huertas, J. R., Ruiz-Ojeda, F. J., Plaza-Díaz, J., Nordsborg, N. B., Martín-Albo, J., Rueda-Robles, A., Casuso, R. A. Human muscular mitochondrial fusion in athletes during exercise.

Muscle wasting: A review of exercise, classical and non-classical RAS axes

This review identifies how the classical/non‐classical renin‐angiotensin system (RAS) and exercise influence muscle wasting. The classical RAS axis enhances muscle loss through the interaction with NADPH oxidase (NOX), ubiquitin proteasome system (UPS), protein synthesis and fibrosis pathways. The mainstream hypothesis identifies reactive oxygen species (ROS) as the key pathway in muscle, this review recognizes alternative pathways that lead to an increase in muscle wasting through the classical RAS axis. In addition, pathways in which the non‐classical RAS axis and exercise inhibit the classical RAS axis are also explored. The non‐classical RAS axis and exercise have a significant negative impact on ROS production and protein synthesis. The non‐classical RAS axis has been identified in this review to directly affect protein synthesis pathways not by altering the pre‐existing intracellular ROS level, further supporting the idea that muscle wasting caused by the classical RAS system is not entirely due to ROS production. Exercise has been identified to modify the RAS axes making it a therapeutic option.

Mitochondrial disorders and drugs: what every physician should know

Mitochondrial disorders are a group of metabolic conditions caused by impairment of the oxidative phosphorylation system. There is currently no clear evidence supporting any pharmacological interventions for most mitochondrial disorders, except for coenzyme Q10 deficiencies, Leber hereditary optic neuropathy, and mitochondrial neurogastrointestinal encephalomyopathy. Furthermore, some drugs may potentially have detrimental effects on mitochondrial dysfunction. Drugs known to be toxic for mitochondrial functions should be avoided whenever possible. Mitochondrial patients needing one of these treatments should be carefully monitored, clinically and by laboratory exams, including creatine kinase and lactate. In the era of molecular and ‘personalized’ medicine, many different physicians (not only neurologists) should be aware of the basic principles of mitochondrial medicine and its therapeutic implications. Multicenter collaboration is essential for the advancement of therapy for mitochondrial disorders. Whenever possible, randomized clinical trials are necessary to establish efficacy and safety of drugs. In this review we discuss in an accessible way the therapeutic approaches and perspectives in mitochondrial disorders. We will also provide an overview of the drugs that should be used with caution in these patients.

Stay Fit, Stay Young: Mitochondria in Movement: The Role of Exercise in the New Mitochondrial Paradigm

Skeletal muscles require the proper production and distribution of energy to sustain their work. To ensure this requirement is met, mitochondria form large networks within skeletal muscle cells, and during exercise, they can enhance their functions. In the present review, we discuss recent findings on exercise-induced mitochondrial adaptations. We emphasize the importance of mitochondrial biogenesis, morphological changes, and increases in respiratory supercomplex formation as mechanisms triggered by exercise that may increase the function of skeletal muscles. Finally, we highlight the possible effects of nutraceutical compounds on mitochondrial performance during exercise and outline the use of exercise as a therapeutic tool in noncommunicable disease prevention. The resulting picture shows that the modulation of mitochondrial activity by exercise is not only fundamental for physical performance but also a key point for whole-organism well-being.

Postinfarction exercise training alleviates cardiac dysfunction and adverse remodeling via mitochondrial biogenesis and SIRT1/PGC-1α/PI3K/Akt signaling

Exercise training mitigates cardiac pathological remodeling and dysfunction caused by myocardial infarction (MI), but its underlying cellular and molecular mechanisms remain elusive. Our present study in an in vivo rat model of MI determined the impact of post-MI exercise training on myocardial fibrosis, mitochondrial biogenesis, antioxidant capacity, and ventricular function. Adult male rats were randomized into: (a) Sedentary control group; (b) 4-week treadmill exercise training group; (c) Sham surgery group; (d) MI group with permanent ligation of left anterior descending coronary artery and kept sedentary during post-MI period; and (e) post-MI 4-week exercise training group. Results indicated that exercise training significantly improved post-MI left ventricular function and reduced markers of cardiac fibrosis. Exercise training also significantly attenuated MI-induced mitochondrial damage and oxidative stress, which were associated with enhanced antioxidant enzyme expression and/or activity and total antioxidant capacity in the heart. Interestingly, the adaptive activation of the SIRT1/PGC-1α/PI3K/Akt signaling following MI was further enhanced by post-MI exercise training, which is likely responsible for exercise-induced cardioprotection and mitochondrial biogenesis. In conclusion, this study has provided novel evidence on the activation of SIRT1/PGC-1α/PI3K/Akt pathway, which may mediate exercise-induced cardioprotection through reduction of cardiac fibrosis and oxidative stress, as well as improvement of mitochondrial integrity and biogenesis in post-MI myocardium.

Exercise training increases the S-Klotho plasma levels in sedentary middle-aged adults: A randomised controlled trial. The FIT-AGEING study

This study aimed to investigate the effects of different training modalities on the soluble Klotho (S-Klotho) plasma levels in sedentary middle-aged adults. A total of 74 middle-aged adults (53.4 ± 5.0 years old; 52.7% women) were enrolled in the FIT-AGEING study. We conducted a 12-week randomised controlled trial. The participants were randomly assigned to 4 different groups: (i) a control group (no exercise), (ii) a physical activity recommendation from the World Health Organization group (PAR), (iii) a high intensity interval training group (HIIT), and (iv) a high intensity interval training group adding whole-body electromyostimulation training group (HIIT-EMS). S-Klotho plasma levels, anthropometric measurements, and body composition variables were measured before and after the intervention programme. All exercise training modalities induced an increase in the S-Klotho plasma levels (all P ≤ 0.019) without statistical differences between them (all P ≥ 0.696). We found a positive association between changes in lean mass index and changes in the S-Klotho plasma levels, whereas a negative association was reported between changes in fat mass outcomes and changes in the S-Klotho plasma levels after our intervention study. In conclusion, our results suggest that the link between exercise training and the increase in S-Klotho plasma levels could be mediated by a decrease of fat mass and an increase of lean mass.

Hydroxytyrosol influences exercise-induced mitochondrial respiratory complex assembly into supercomplexes in rats

Hydroxytyrosol (HT) has been demonstrated to improve mitochondrial function, both in sedentary and in exercised animals. Herein, we assessed the effects of two different doses of HT on exercise-induced mitochondrial respiratory complex (C) assembly into supercomplexes (SCs) and the relation of the potential results to OPA1 levels and oxidative stress. Wistar rats were allocated into six groups: sedentary (SED), sedentary consuming 20 mg/kg/d of HT (SED-20), sedentary consuming 300 mg/kg/d of HT (SED-300); exercised (EXE), exercised consuming 20 mg/kg/d of HT (EXE-20) and exercised consuming 300 mg/kg/d of HT (EXE-300). Animals were exercised and/or supplemented for 10 weeks, and assembly of SCs, mitochondrial oxidative status and expression of OPA1 were quantified in the gastrocnemius muscle. Both EXE and EXE-20 animals exhibited increased assembly of CI into SCs, but this effect was absent in EXE-300 animals. Levels of CIII₂ assembled into SCs were only increased in EXE-20 animals. Notably EXE-300 animals showed a decreased relative expression of s-OPA1 isoforms. Therefore, HT exerted dose-dependent effects on SC assembly in exercised animals. Although the mechanisms leading to SCs assembly in response to exercise and HT are unclear, it seems that a high HT dose can prevent SCs assembly during exercise by decreasing the expression of the s-OPA1 isoforms.

Mitochondrial targeting as a novel therapy for stroke

Stroke is a main cause of mortality and morbidity worldwide. Despite the increasing development of innovative treatments for stroke, most are unsuccessful in clinical trials. In recent years, an encouraging strategy for stroke therapy has been identified in stem cells transplantation. In particular, grafting cells and their secretion products are leading with functional recovery in stroke patients by promoting the growth and function of the neurovascular unit – a communication framework between neurons, their supply microvessels along with glial cells – underlying stroke pathology and recovery. Mitochondrial dysfunction has been recently recognized as a hallmark in ischemia/reperfusion neural damage. Emerging evidence of mitochondria transfer from stem cells to ischemic-injured cells points to transfer of healthy mitochondria as a viable novel therapeutic strategy for ischemic diseases. Hence, a more in-depth understanding of the cellular and molecular mechanisms involved in mitochondrial impairment may lead to new tools for stroke treatment. In this review, we focus on the current evidence of mitochondrial dysfunction in stroke, investigating favorable approaches of healthy mitochondria transfer in ischemic neurons, and exploring the potential of mitochondria-based cellular therapy for clinical applications. This paper is a review article. Referred literature in this paper has been listed in the references section. The data sets supporting the conclusions of this article are available online by searching various databases, including PubMed.

Understanding the Role of Dysfunctional and Healthy Mitochondria in Stroke Pathology and Its Treatment

Stroke remains a major cause of death and disability in the United States and around the world. Solid safety and efficacy profiles of novel stroke therapeutics have been generated in the laboratory, but most failed in clinical trials. Investigations into the pathology and treatment of the disease remain a key research endeavor in advancing scientific understanding and clinical applications. In particular, cell-based regenerative medicine, specifically stem cell transplantation, may hold promise as a stroke therapy, because grafted cells and their components may recapitulate the growth and function of the neurovascular unit, which arguably represents the alpha and omega of stroke brain pathology and recovery. Recent evidence has implicated mitochondria, organelles with a central role in energy metabolism and stress response, in stroke progression. Recognizing that stem cells offer a source of healthy mitochondria—one that is potentially transferrable into ischemic cells—may provide a new therapeutic tool. To this end, deciphering cellular and molecular processes underlying dysfunctional mitochondria may reveal innovative strategies for stroke therapy. Here, we review recent studies capturing the intimate participation of mitochondrial impairment in stroke pathology, and showcase promising methods of healthy mitochondria transfer into ischemic cells to critically evaluate the potential of mitochondria-based stem cell therapy for stroke patients.

Effects of hydroxytyrosol dose on the redox status of exercised rats: the role of hydroxytyrosol in exercise performance

Background

Hydroxytyrosol (HT) is a polyphenol found in olive oil that is known for its antioxidant effects. Here, we aimed to describe the effects of a low and high HT dose on the physical running capacity and redox state in both sedentary and exercised rats.

Methods

Male Wistar rats were allocated into 6 groups: sedentary (SED; n = 10); SED consuming 20 mg/kg/d HT (SED20; n = 7); SED consuming 300 mg/kg/d HT (SED300; n = 7); exercised (EXE; n = 10); EXE consuming 20 mg/kg/d HT (EXE20; n = 10) and EXE consuming 300 mg/kg/d HT (EXE300; n = 10). All the interventions lasted 10 weeks; the maximal running velocity was assessed throughout the study, whereas daily physical work was monitored during each training session. At the end of the study, the rats were sacrificed by bleeding. Hemoglobin (HGB) and hematocrit (HCT) were measured in the terminal blood sample. Moreover, plasma hydroperoxide (HPx) concentrations were quantified as markers of lipid peroxidation.

Results

In sedentary rats, HT induced an antioxidant effect in a dose-dependent manner without implications on running performance. However, if combined with exercise, the 300 mg/kg/d HT dosage exhibited a pro-oxidant effect in the EXE300 group compared with the EXE and EXE20 groups. The EXE20 rats showed a reduction in daily physical work and a lower maximal velocity than the EXE and EXE300 rats. The higher physical capacity exhibited by the EXE300 group was achieved despite the EXE300 rats expressing lower HGB levels and a lower HCT than the EXE20 rats.

Conclusions

Our results suggest that a high HT dose induces a systemic pro-oxidant effect and may prevent the loss of performance that was observed with the low HT dose.