Interactions between reactive oxygen species generated by contractile activity and aging in skeletal muscle?

Oxidative stress, mitochondrial dysfunction, and respiratory chain enzyme defects in inflammatory myopathies

We investigated the relationship between oxidative stress and inflammatory myopathies. We searched in the current literature the role of mitochondria and respiratory chain defects as sources of oxidative stress and reactive oxygen species production that led to muscle weakness and fatigue. Different molecules and pathways contribute to redox milieu, reactive oxygen species generation, accumulation of misfolded and carbonylated proteins that lose their ability to fulfil cellular activities. Small peptides and physical techniques proved, in mice models, to reduce oxidative stress. We focused on inclusion body myositis, as a major expression of myopathy related to oxidative stress, where mitochondrial abnormalities are causative agents as well. We described the effect of physical exercise in inclusion body myositis that showed to increase strength and to reduce beta amyloid accumulation with subsequent improvement of the mitochondrial functions. We illustrated the influence of epigenetic control on the immune system by non-coding genetic material in the interaction between oxidative stress and inflammatory myopathies.

Mitochondrial Dysfunction Is a Common Denominator Linking Skeletal Muscle Wasting Due to Disease, Aging, and Prolonged Inactivity

Skeletal muscle is the most abundant tissue in the body and is required for numerous vital functions, including breathing and locomotion. Notably, deterioration of skeletal muscle mass is also highly correlated to mortality in patients suffering from chronic diseases (e.g., cancer). Numerous conditions can promote skeletal muscle wasting, including several chronic diseases, cancer chemotherapy, aging, and prolonged inactivity. Although the mechanisms responsible for this loss of muscle mass is multifactorial, mitochondrial dysfunction is predicted to be a major contributor to muscle wasting in various conditions. This systematic review will highlight the biochemical pathways that have been shown to link mitochondrial dysfunction to skeletal muscle wasting. Importantly, we will discuss the experimental evidence that connects mitochondrial dysfunction to muscle wasting in specific diseases (i.e., cancer and sepsis), aging, cancer chemotherapy, and prolonged muscle inactivity (e.g., limb immobilization). Finally, in hopes of stimulating future research, we conclude with a discussion of important future directions for research in the field of muscle wasting.

Chrysanthemi Zawadskii var. Latilobum Attenuates Obesity-Induced Skeletal Muscle Atrophy via Regulation of PRMTs in Skeletal Muscle of Mice

As obesity promotes ectopic fat accumulation in skeletal muscle, resulting in impaired skeletal muscle and mitochondria function, it is associated with skeletal muscle loss and dysfunction. This study investigated whether Chrysanthemi zawadskii var. latilobum (CZH) protected mice against obesity-induced skeletal muscle atrophy and the underlying molecular mechanisms. High-fat diet (HFD)-induced obese mice were orally administered either distilled water, low-dose CZH (125 mg/kg), or high-dose CZH (250 mg/kg) for 8 w. CZH reduced obesity-induced increases in inflammatory cytokines levels and skeletal muscle atrophy, which is induced by expression of atrophic genes such as muscle RING-finger protein 1 and muscle atrophy F-box. CZH also improved muscle function according to treadmill running results and increased the muscle fiber size in skeletal muscle. Furthermore, CZH upregulated mRNA and protein levels of protein arginine methyltransferases (PRMT)1 and PRMT7, which subsequently attenuated mitochondrial dysfunction in the skeletal muscle of obese mice. We also observed that CZH significantly decreased PRMT6 mRNA and protein expression, which resulted in decreased muscle atrophy. These results suggest that CZH ameliorated obesity-induced skeletal muscle atrophy in mice via regulation of PRMTs in skeletal muscle.

A cross-sectional study: Associations between sarcopenia and clinical characteristics of patients with type 2 diabetes

Sarcopenia is a geriatric syndrome and it impairs physical function. Patients with type 2 diabetes mellitus (T2DM) are at a higher risk of sarcopenia. The purpose of this study is to explore characteristics of general information and metabolic factors of sarcopenia in patients with T2DM in the northeast of China, and provide information for the prevention and treatment of sarcopenia in clinical practice.Patients with T2DM aged ≥65 were recruited in Changchun from March 2017 to February 2018. Questionnaires of general information, physical examination, laboratory and imaging examination were conducted. The patients were assigned into sarcopenia group and non-sarcopenia group according to the diagnostic criteria proposed by Asian working group for sarcopenia (AWGS), and the differences between 2 groups were analyzed.A total of 132 participants were included in this study, of which, 38 (28.8%) were diagnosed with sarcopenia. 94 (71.2%) were with no sarcopenia. Logistic regression analysis showed that age (OR: 1.182, 95%CI: 1.038-1.346), trunk fat mass (TFM) (OR: 1.499, 95%CI: 1.146-1.960) and free thyroxine (FT4) (OR: 1.342, 95%CI: 1.102-1.635) were independent risk factors for sarcopenia. BMI (body mass index) (OR: 0.365, 95%CI: 0.236-0.661), exercise (OR: 0.016, 95%CI: 0.001-0.169), female (OR: 0.000, 95%CI: 0.00-0.012), metformin (OR: 0.159, 95%CI: 0.026-0.967) and TSM (trunk skeletal muscle mass) (OR: 0.395, 95%CI: 0.236-0.661) were protective factors for sarcopenia.Sarcopenia in patients with T2DM is associated with increased age, increased TFM and increased FT4 level. Regular exercise, female, metformin administrations, high BMI and increased TSM are associated with lower risk of sarcopenia.

Fatiguing contractions increase protein S-glutathionylation occupancy in mouse skeletal muscle

Protein S-glutathionylation is an important reversible post-translational modification implicated in redox signaling. Oxidative modifications to protein thiols can alter the activity of metabolic enzymes, transcription factors, kinases, phosphatases, and the function of contractile proteins. However, the extent to which muscle contraction induces oxidative modifications in redox sensitive thiols is not known. The purpose of this study was to determine the targets of S-glutathionylation redox signaling following fatiguing contractions. Anesthetized adult male CB6F1 (BALB/cBy × C57BL/6) mice were subjected to acute fatiguing contractions for 15 min using in vivo stimulations. The right (stimulated) and left (unstimulated) gastrocnemius muscleswere collected 60 min after the last stimulation and processed for redox proteomics assay of S-glutathionylation. Using selective reduction with a glutaredoxin enzyme cocktail and resin-assisted enrichment technique, we quantified the levels of site-specific protein S-glutathionylation at rest and following fatiguing contractions. Redox proteomics revealed over 2200 sites of S-glutathionylation modifications, of which 1290 were significantly increased after fatiguing contractions. Muscle contraction leads to the greatest increase in S-glutathionylation in the mitochondria (1.03%) and the smallest increase in the nucleus (0.47%). Regulatory cysteines were significantly S-glutathionylated on mitochondrial complex I and II, GAPDH, MDH1, ACO2, and mitochondrial complex V among others. Similarly, S-glutathionylation of RYR1, SERCA1, titin, and troponin I2 are known to regulate muscle contractility and were significantly S-glutathionylated after just 15 min of fatiguing contractions. The largest fold changes (> 1.6) in the S-glutathionylated proteome after fatigue occurred on signaling proteins such as 14-3-3 protein gamma and MAP2K4, as well as proteins like SERCA1, and NDUV2 of mitochondrial complex I, at previously unknown glutathionylation sites. These findings highlight the important role of redox control over muscle physiology, metabolism, and the exercise adaptive response. This study lays the groundwork for future investigation into the altered exercise adaptation associated with chronic conditions, such as sarcopenia.

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A single bout of fatiguing contractions increase muscle protein S-glutathionylation.

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Mitochondrial proteins are sensitive to oxidative modifications following fatigue.

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The glutathionylated proteome includes cysteines of known functional importance.

Long-Term Exercise Protects against Cellular Stresses in Aged Mice

The current study examined the effect of aging and long-term wheel-running on the expression of heat shock protein (HSP), redox regulation, and endoplasmic reticulum (ER) stress markers in tibialis anterior (T.A.) and soleus muscle of mice. Male mice were divided into young (Y, 3-month-old), old-sedentary (OS, 24-month-old), and old-exercise (OE, 24-month-old) groups. The OE group started voluntary wheel-running at 3 months and continued until 24 months of age. Aging was associated with a higher thioredoxin-interacting protein (TxNiP) level, lower thioredoxin-1 (TRX-1) to TxNiP ratio—a determinant of redox regulation and increased CHOP, an indicator of ER stress-related apoptosis signaling in both muscles. Notably, GRP78, a key indicator of ER stress, was selectively elevated in T.A. Long-term exercise decreased TxNiP in T.A. and soleus muscles and increased the TRX-1/TxNiP ratio in soleus muscle of aged mice. Inducible HSP70 and constituent HSC70 were upregulated, whereas CHOP was reduced after exercise in soleus muscle. Thus, our data demonstrated that aging induced oxidative stress and activated ER stress-related apoptosis signaling in skeletal muscle, whereas long-term wheel-running improved redox regulation, ER stress adaptation and attenuated ER stress-related apoptosis signaling. These findings suggest that life-long exercise can protect against age-related cellular stress.

Skeletal muscle bioenergetics in aging and heart failure

Changes in mitochondrial capacity and quality play a critical role in skeletal and cardiac muscle dysfunction. In vivo measurements of mitochondrial capacity provide a clear link between physical activity and mitochondrial function in aging and heart failure, although the cause and effect relationship remains unclear. Age-related decline in mitochondrial quality leads to mitochondrial defects that affect redox, calcium, and energy-sensitive signaling by altering the cellular environment that can result in skeletal muscle dysfunction independent of reduced mitochondrial capacity. This reduced mitochondrial quality with age is also likely to sensitize skeletal muscle mitochondria to elevated angiotensin or beta-adrenergic signaling associated with heart failure. This synergy between aging and heart failure could further disrupt cell energy and redox homeostasis and contribute to exercise intolerance in this patient population. Therefore, the interaction between aging and heart failure, particularly with respect to mitochondrial dysfunction, should be a consideration when developing strategies to improve quality of life in heart failure patients. Given the central role of the mitochondria in skeletal and cardiac muscle dysfunction, mitochondrial quality may provide a common link for targeted interventions in these populations.

Advanced aging causes diaphragm functional abnormalities, global proteome remodeling, and loss of mitochondrial cysteine redox flexibility in mice

AIM

Inspiratory muscle (diaphragm) function declines with age, contributing to exercise intolerance and impaired airway clearance. Studies of diaphragm dysfunction in rodents have focused on moderate aging (~24months); thus, the impact of advanced age on the diaphragm and potential mechanisms of dysfunction are less clear. Therefore, we aimed to define the effects of advanced age on the mechanics, morphology, and global and redox proteome of the diaphragm.

METHODS

We studied diaphragm from young (6months) and very old male mice (30months). Diaphragm function was evaluated using isolated muscle bundles. Proteome analyses followed LC-MS/MS processing of diaphragm muscle.

RESULTS

Advanced aging decreased diaphragm peak power by ~35% and maximal isometric specific force by ~15%, and prolonged time to peak twitch tension by ~30% (P<0.05). These changes in contractile properties were accompanied, and might be caused by, decreases in abundance of calsequestrin, sarcoplasmic reticulum C^a2+-ATPase, sarcalumenin, and parvalbumin that were revealed by our label-free proteomics data. Advanced aging also increased passive stiffness (P<0.05), which might be a consequence of an upregulation of cytoskeletal and extracellular matrix proteins identified by proteomics. Analyses of cysteine redox state indicated that the main diaphragm abnormalities with advanced aging are in metabolic enzymes and mitochondrial proteins.

CONCLUSION

Our novel findings are that the most pronounced impact of advanced aging on the diaphragm is loss of peak power and disrupted cysteine redox homeostasis in metabolic enzymes and mitochondrial proteins.

Redox homeostasis and age-related deficits in neuromuscular integrity and function

Skeletal muscle is a major site of metabolic activity and is the most abundant tissue in the human body. Age-related muscle atrophy (sarcopenia) and weakness, characterized by progressive loss of lean muscle mass and function, is a major contributor to morbidity and has a profound effect on the quality of life of older people. With a continuously growing older population (estimated 2 billion of people aged >60 by 2050), demand for medical and social care due to functional deficits, associated with neuromuscular ageing, will inevitably increase. Despite the importance of this 'epidemic' problem, the primary biochemical and molecular mechanisms underlying age-related deficits in neuromuscular integrity and function have not been fully determined. Skeletal muscle generates reactive oxygen and nitrogen species (RONS) from a variety of subcellular sources, and age-associated oxidative damage has been suggested to be a major factor contributing to the initiation and progression of muscle atrophy inherent with ageing. RONS can modulate a variety of intracellular signal transduction processes, and disruption of these events over time due to altered redox control has been proposed as an underlying mechanism of ageing. The role of oxidants in ageing has been extensively examined in different model organisms that have undergone genetic manipulations with inconsistent findings. Transgenic and knockout rodent studies have provided insight into the function of RONS regulatory systems in neuromuscular ageing. This review summarizes almost 30 years of research in the field of redox homeostasis and muscle ageing, providing a detailed discussion of the experimental approaches that have been undertaken in murine models to examine the role of redox regulation in age-related muscle atrophy and weakness.

Aging-associated metabolic disorder induces Nox2 activation and oxidative damage of endothelial function

Oxidative stress attributable to the activation of a Nox2-containing NADPH oxidase is involved in the development of vascular diseases and in aging. However, the mechanism of Nox2 activation in normal aging remains unclear. In this study, we used age-matched wild-type (WT) and Nox2 knockout (KO) mice at 3-4 months (young); 11-12 months (middle-aged) and 21-22 months (aging) to investigate age-related metabolic disorders, Nox2 activation and endothelial dysfunction. Compared to young mice, middle-aged and aging WT mice had significant hyperglycaemia, hyperinsulinaemia, increased systemic oxidative stress and higher blood pressure. Endothelium-dependent vessel relaxation to acetylcholine was significantly impaired in WT aging aortas, and this was accompanied by increased Nox2 and ICAM-1 expressions, MAPK activation and decreased insulin receptor expression and signaling. However, these aging-associated disorders were significantly reduced or absent in Nox2KO aging mice. The effect of metabolic disorder on Nox2 activation and endothelial dysfunction was further confirmed using high-fat diet-induced obesity and insulin resistance in middle-aged WT mice treated with apocynin (a Nox2 inhibitor). In vitro experiments showed that in response to high glucose plus high insulin challenge, WT coronary microvascular endothelial cells increased significantly the levels of Nox2 expression, activation of stress signaling pathways and the cells were senescent, e.g. increased p53 and β-galactosidase activity. However, these changes were absent in Nox2KO cells. In conclusion, Nox2 activation in response to aging-associated hyperglycaemia and hyperinsulinaemia plays a key role in the oxidative damage of vascular function. Inhibition or knockout of Nox2 preserves endothelial function and improves global metabolism in old age.

Improved muscle function and quality after diet intervention with leucine-enriched whey and antioxidants in antioxidant deficient aged mice

Antioxidant (AOX) deficiencies are commonly observed in older adults and oxidative stress has been suggested to contribute to sarcopenia. Here we investigate if 1) low levels of dietary antioxidants had a negative impact on parameters of muscle mass, function and quality, and 2) to study if nutritional interventions with AOX and/or leucine-enriched whey protein could improve these muscle parameters in aged mice. 18-months-old mice were fed a casein-based antioxidant-deficient (lowox) diet or a casein-based control-diet (CTRL) for 7 months. During the last 3 months, lowox-mice were subjected to either: a) continued lowox, b) supplementation with vitamin A/E, Selenium and Zinc (AOX), c) substitution of casein with leucine-enriched whey protein (PROT) or d) a combination of both AOX and PROT (TOTAL). After 7 months lowox-mice displayed lower muscle strength and more muscle fatigue compared to CTRL. Compared to lowox-mice, PROT-mice showed improved muscle power, grip strength and less muscle fatigue. AOX-mice showed improved oxidative status, less muscle fatigue, improved grip strength and mitochondrial dynamics compared to lowox-mice. The TOTAL-mice showed the combined effects of both interventions compared to lowox-mice. In conclusion, nutritional intervention with AOX and/or leucine-enriched whey protein can play a role in improving muscle health in a AOX-deficient mouse model.

Mitochondrial ROS regulate oxidative damage and mitophagy but not age-related muscle fiber atrophy

Age-related loss of skeletal muscle mass and function is a major contributor to morbidity and has a profound effect on the quality of life of older people. The potential role of age-dependent mitochondrial dysfunction and cumulative oxidative stress as the underlying cause of muscle aging remains a controversial topic. Here we show that the pharmacological attenuation of age-related mitochondrial redox changes in muscle with SS31 is associated with some improvements in oxidative damage and mitophagy in muscles of old mice. However, this treatment failed to rescue the age-related muscle fiber atrophy associated with muscle atrophy and weakness. Collectively, these data imply that the muscle mitochondrial redox environment is not a key regulator of muscle fiber atrophy during sarcopenia but may play a key role in the decline of mitochondrial organelle integrity that occurs with muscle aging.

Long-term administration of the mitochondria-targeted antioxidant mitoquinone mesylate fails to attenuate age-related oxidative damage or rescue the loss of muscle mass and function associated with aging of skeletal muscle

Age-related skeletal muscle dysfunction is the underlying cause of morbidity that affects up to half the population aged 80 and over. Considerable evidence indicates that oxidative damage and mitochondrial dysfunction contribute to the sarcopenic phenotype that occurs with aging. To examine this, we administered the mitochondria-targeted antioxidant mitoquinone mesylate {[10-(4,5-dimethoxy-2-methyl-3,6-dioxo-1,4-cyclohexadien-1-yl)decyl] triphenylphosphonium; 100 μM} to wild-type C57BL/6 mice for 15 wk (from 24 to 28 mo of age) and investigated the effects on age-related loss of muscle mass and function, changes in redox homeostasis, and mitochondrial organelle integrity and function. We found that mitoquinone mesylate treatment failed to prevent age-dependent loss of skeletal muscle mass associated with myofiber atrophy or alter a variety of in situ and ex vivo muscle function analyses, including maximum isometric tetanic force, decline in force after a tetanic fatiguing protocol, and single-fiber-specific force. We also found evidence that long-term mitoquinone mesylate administration did not reduce mitochondrial reactive oxygen species or induce significant changes in muscle redox homeostasis, as assessed by changes in 4-hydroxynonenal protein adducts, protein carbonyl content, protein nitration, and DNA damage determined by the content of 8-hydroxydeoxyguanosine. Mitochondrial membrane potential, abundance, and respiration assessed in permeabilized myofibers were not significantly altered in response to mitoquinone mesylate treatment. Collectively, these findings demonstrate that long-term mitochondria-targeted mitoquinone mesylate administration failed to attenuate age-related oxidative damage in skeletal muscle of old mice or provide any protective effect in the context of muscle aging.—Sakellariou, G. K., Pearson, T., Lightfoot, A. P., Nye, G. A., Wells, N., Giakoumaki, I. I., Griffiths, R. D., McArdle, A., Jackson, M. J. Long-term administration of the mitochondria-targeted antioxidant mitoquinone mesylate fails to attenuate age-related oxidative damage or rescue the loss of muscle mass and function associated with aging of skeletal muscle.

In the idiopathic inflammatory myopathies (IIM), do reactive oxygen species (ROS) contribute to muscle weakness?

The idiopathic inflammatory myopathies (IIMs) are a group of rare autoimmune disorders, collectively known as myositis. Affected patients present with proximal muscle weakness, which usually improves following treatment with immunosuppressants, but often incompletely so, thus many patients remain weak. IIMs are characterised histologically by inflammatory cell infiltrates into skeletal muscle and overexpression of major histocompatibility complex I on muscle cell surfaces. Although inflammatory cell infiltrates represent a major feature of myositis there is growing evidence that muscle weakness correlates only poorly with the degree of cellular infiltration, while weakness may in fact precede such infiltrations. The mechanisms underpinning such non-immune cell mediated weakness in IIM are poorly understood. Activation of the endoplasmic reticulum stress pathways appears to be a potential contributor. Data from non-muscle cells indicate that endoplasmic reticulum stress results in altered redox homeostasis capable of causing oxidative damage. In myopathological situations other than IIM, as seen in ageing and sepsis, evidence supports an important role for reactive oxygen species (ROS). Modified ROS generation is associated with mitochondrial dysfunction, depressed force generation and activation of muscle catabolic and autophagy pathways. Despite the growing evidence demonstrating a key role for ROS in skeletal muscle dysfunction in myopathologies other than IIM, no research has yet investigated the role of modified generation of ROS in inducing the weakness characteristic of IIM. This article reviews current knowledge regarding muscle weakness in the absence of immune cells in IIM, and provides a background to the potential role of modified ROS generation as a mechanism of muscle dysfunction. The authors suggest that ROS-mediated mechanisms are potentially involved in non-immune cell mediated weakness seen in IIM and outline how these mechanisms might be investigated in this context. This appears a timely strategy, given recent developments in targeted therapies which specifically modify ROS generation.

Synopsis on the linkage of Alzheimer's and Parkinson's disease with chronic diseases

Neurodegeneration is the progressive loss of neuronal structure and function, which ultimately leads to neurological disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis, and Huntington's disease. Even after the recent significant advances in neurobiology, the above-mentioned disorders continue to haunt the global population. Several studies have suggested the role of specific environmental and genetic risk factors associated with these disorders. However, the exact mechanism associated with the progression of these disorders still needs to be elucidated. In the recent years, sophisticated research has revealed interesting association of prominent neurodegenerative disorders such as AD and PD with chronic diseases such as cancer, diabetes, and cardiovascular diseases. Several common molecular mechanisms such as generation of free radicals, oxidative DNA damage, aberrations in mitochondrial DNA, and dysregulation of apoptosis have been highlighted as possible points of connection. The present review summarizes the possible mechanism of coexistence of AD and PD with other chronic diseases.

Application of redox proteomics to skeletal muscle aging and exercise

Skeletal muscle represents a physiologically relevant model for the application of redox proteomic techniques to dissect its response to exercise and aging. Contracting skeletal muscles generate ROS (reactive oxygen species) and RNS (reactive nitrogen species) necessary for the regulation of many proteins involved in excitation–contraction coupling. The magnitude and species of ROS/RNS generated by contracting muscles will have downstream effects on specific protein targets and cellular redox signalling. Redox modifications on specific proteins are essential for the adaptive response to exercise and skeletal muscle can develop a dysregulated redox response during aging. In the present article, we discuss how redox proteomics can be applied to identify and quantify the reversible modifications on susceptible cysteine residues within those redox-sensitive proteins, and the integration of oxidative and non-oxidative protein modifications in relation to the functional proteome.

Molecular characterization of argininosuccinate synthase and argininosuccinate lyase from the liver of the African lungfish Protopterus annectens, and their mRNA expression levels in the liver, kidney, brain and skeletal muscle during aestivation

Argininosuccinate synthase (Ass) and argininosuccinate lyase (Asl) are involved in arginine synthesis for various purposes. The complete cDNA coding sequences of ass and asl from the liver of Protopterus annectens consisted of 1,296 and 1,398 bp, respectively. Phylogenetic analyses revealed that the deduced Ass and Asl of P. annectens had close relationship with that of the cartilaginous fish Callorhinchus milii. Besides being strongly expressed in the liver, ass and asl expression were detectable in many tissues/organs. In the liver, mRNA expression levels of ass and asl increased significantly during the induction phase of aestivation, probably to increase arginine production to support increased urea synthesis. The increases in ass and asl mRNA expression levels during the prolonged maintenance phase and early arousal phase of aestivation could reflect increased demand on arginine for nitric oxide (NO) production in the liver. In the kidney, there was a significant decrease in ass mRNA expression level after 6 months of aestivation, indicating possible decreases in the synthesis and supply of arginine to other tissues/organs. In the brain, changes in ass and asl mRNA expression levels during the three phases of aestivation could be related to the supply of arginine for NO synthesis in response to conditions that resemble ischaemia and ischaemia-reperfusion during the maintenance and arousal phase of aestivation, respectively. The decrease in ass mRNA expression level, accompanied with decreases in the concentrations of arginine and NO, in the skeletal muscle of aestivating P. annectens might ameliorate the potential of disuse muscle atrophy.