Resveratrol prevents dexamethasone-induced expression of the muscle atrophy-related ubiquitin ligases atrogin-1 and MuRF1 in cultured myotubes through a SIRT1-dependent mechanism

Synergistic Effects of Korean Mistletoe and Apple Peel Extracts on Muscle Strength and Endurance

Muscular strength and endurance are vital for physical fitness. While mistletoe extract has shown efficacy in significantly increasing muscle strength and endurance, its accessibility is limited. This study explores combining mistletoe and apple peel extracts as an effective muscle health supplement. Analyses of histology, RNA, and protein in the combined extract-treated mouse group demonstrated significant enhancements in muscle strength and endurance, evidenced by larger muscle fibers, improved mitochondrial function, and a higher ratio of type I and IIa muscle fibers. Combining half doses of each extract resulted in greater improvements than using each extract separately, indicating a synergistic effect. Pathway analysis suggests that the observed synergy arises from complementary mechanisms, with a mistletoe extract-induced decrease in myostatin (MSTN) and an apple peel extract-induced increase in IGF1, leading to a sharp rise in AKT, S6K, and MuRF1, which promote myogenesis, along with a significant increase in PGC-1α, TFAM, and MEF2C, which are critical for mitochondrial biogenesis. This research provides practical insights into developing cost-effective, natural supplements to enhance muscle performance and endurance, with potential applications in athletic performance, improving muscle growth and endurance in children, and addressing age-related muscle decline.

SIRT1 signaling pathways in sarcopenia: Novel mechanisms and potential therapeutic targets

Sarcopenia is an aging-related skeletal disease characterized by decreased muscle mass, strength, and physical function, severely affecting the quality of life (QoL) of the elderly population. Sirtuin 1 (SIRT1), as a nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylases, has been reported to participate in various aging-related signaling pathways and exert protective effect on many human diseases. SIRT1 functioned as an important role in the occurrence and progression of sarcopenia through regulating key pathways related to protein homeostasis, apoptosis, mitochondrial dysfunction, insulin resistance and autophagy in skeletal muscle, including SIRT1/Forkhead Box O (FoxO), AMP-activated protein kinase (AMPK)/SIRT1/nuclear factor κB (NF-κB), SIRT1/p53, AMPK/SIRT1/peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), and SIRT1/live kinase B1 (LKB1)/AMPK pathways. However, the specific mechanisms of these processes have not been fully illuminated. Currently, several SIRT1-mediated interventions on sarcopenia have been preliminarily developed, such as SIRT1 activator polyphenolic compounds, exercising and calorie restriction. In this review, we summarized the predominant mechanisms of SIRT1 involved in sarcopenia and therapeutic modalities targeting the SIRT1 signaling pathways for the prevention and prognosis of sarcopenia.

Resveratrol and Vitamin D: Eclectic Molecules Promoting Mitochondrial Health in Sarcopenia

Sarcopenia refers to the progressive loss and atrophy of skeletal muscle function, often associated with aging or secondary to conditions involving systemic inflammation, oxidative stress, and mitochondrial dysfunction. Recent evidence indicates that skeletal muscle function is not only influenced by physical, environmental, and genetic factors but is also significantly impacted by nutritional deficiencies. Natural compounds with antioxidant properties, such as resveratrol and vitamin D, have shown promise in preventing mitochondrial dysfunction in skeletal muscle cells. These antioxidants can slow down muscle atrophy by regulating mitochondrial functions and neuromuscular junctions. This review provides an overview of the molecular mechanisms leading to skeletal muscle atrophy and summarizes recent advances in using resveratrol and vitamin D supplementation for its prevention and treatment. Understanding these molecular mechanisms and implementing combined interventions can optimize treatment outcomes, ensure muscle function recovery, and improve the quality of life for patients.

Jakyak-gamcho-tang, a decoction of Paeoniae Radix and Glycyrrhizae Radix et Rhizoma, ameliorates dexamethasone-induced muscle atrophy and muscle dysfunction

BACKGROUND

Although chronic treatment with glucocorticoids, such as dexamethasone, is frequently associated with muscle atrophy, effective and safe therapeutics for treating muscle atrophy remain elusive. Jakyak-gamcho-tang (JGT), a decoction of Paeoniae Radix and Glycyrrhizae Radix et Rhizoma, has long been used to relieve muscle tension and control muscle cramp-related pain. However, the effects of JGT on glucocorticoid-induced muscle atrophy are yet to be comprehensively clarified.

PURPOSE

The objective of the current study was to validate the protective effect of JGT in dexamethasone-induced muscle atrophy models and elucidate its underlying mechanism through integrated in silico - in vitro - in vivo studies.

STUDY DESIGN AND METHODS

Differential gene expression was preliminarily analyzed using the RNA-seq data to determine the effects of JGT on C2C12 myotubes. The protective effects of JGT were further validated in dexamethasone-treated C2C12 myotubes by assessing cell viability, myotube integrity, and mitochondrial function or in C57BL/6 N male mice with dexamethasone-induced muscle atrophy by evaluating muscle mass and physical performance. Transcriptomic pathway analysis was also performed to elucidate the underlying mechanism.

RESULTS

Based on preliminary gene set enrichment analysis using the RNA-seq data, JGT regulated various pathways related to muscle differentiation and regeneration. Dexamethasone-treated C2C12 myotubes and muscle tissues of atrophic mice displayed substantial muscle protein degradation and muscle loss, respectively, which was efficiently alleviated by JGT treatment. Importantly, JGT-mediated protective effects were associated with observations such as preservation of mitochondrial function, upregulation of myogenic signaling pathways, including protein kinase B/mammalian target of rapamycin/forkhead box O3, inhibition of ubiquitin-mediated muscle protein breakdown, and downregulation of inflammatory and apoptotic pathways induced by dexamethasone.

CONCLUSION

To the best of our knowledge, this is the first report to demonstrate that JGT could be a potential pharmaceutical candidate to prevent muscle atrophy induced by chronic glucocorticoid treatment, highlighting its known effects for relieving muscle spasms and pain. Moreover, transcriptomic pathway analysis can be employed as an efficient in silico tool to predict novel pharmacological candidates and elucidate molecular mechanisms underlying the effects of herbal medications comprising diverse biologically active ingredients.

Resveratrol directly suppresses proteolysis possibly via PKA/CREB signaling in denervated rat skeletal muscle

Although there are reports that polyphenol resveratrol (Rsv) may cause muscle hypertrophy in basal conditions and attenuate muscle wasting in catabolic situations, its mechanism of action is still unclear. Our study evaluated the ex vivo effects of Rsv on protein metabolism and intracellular signaling in innervated (sham-operated; Sham) and 3-day sciatic denervated (Den) rat skeletal muscles. Rsv (10-4 M) reduced total proteolysis (40%) in sham muscles. Den increased total proteolysis (~40%) in muscle, which was accompanied by an increase in the activities of ubiquitin-proteasome (~3-fold) and lysosomal (100%) proteolytic systems. Rsv reduced total proteolysis (59%) in Den muscles by inhibiting the hyperactivation of ubiquitin-proteasome (50%) and lysosomal (~70%) systems. Neither Rsv nor Den altered calcium-dependent proteolysis in muscles. Mechanistically, Rsv stimulated PKA/CREB signaling in Den muscles, and PKA blockage by H89 (50μM) abolished the antiproteolytic action of the polyphenol. Rsv reduced FoxO4 phosphorylation (~60%) in both Sham and Den muscles and Akt phosphorylation (36%) in Den muscles. Rsv also caused a homeostatic effect in Den muscles by returning their protein synthesis rates to levels similar to Sham muscles. These data indicate that Rsv directly inhibits the proteolytic activity of lysosomal and ubiquitin-proteasome systems, mainly in Den muscles through, at least in part, the activation of PKA/CREB signaling.

The Effects of Antioxidants and Pulsed Magnetic Fields on Slow and Fast Skeletal Muscle Atrophy Induced by Streptozotocin: A Preclinical Study

Results

Our findings suggest that antioxidants and PMF may alleviate impaired protein synthesis and degradation pathways in skeletal muscle atrophy. PTS showed a positive effect on the anabolic pathway, while RSV and PMF demonstrated potential for ameliorating the catabolic pathway. Notably, the combination therapy of antioxidants and PMF exhibited a stronger ameliorative effect on skeletal muscle atrophy than either intervention alone.

Conclusion

The present results highlight the benefits of employing a multimodal approach, involving both antioxidant and PMF therapy, for the management of muscle-wasting conditions. These treatments may have potential therapeutic implications for skeletal muscle atrophy.

Cancer cachexia: molecular mechanisms and treatment strategies

Muscle wasting is a consequence of physiological changes or a pathology characterized by increased catabolic activity that leads to progressive loss of skeletal muscle mass and strength. Numerous diseases, including cancer, organ failure, infection, and aging-associated diseases, are associated with muscle wasting. Cancer cachexia is a multifactorial syndrome characterized by loss of skeletal muscle mass, with or without the loss of fat mass, resulting in functional impairment and reduced quality of life. It is caused by the upregulation of systemic inflammation and catabolic stimuli, leading to inhibition of protein synthesis and enhancement of muscle catabolism. Here, we summarize the complex molecular networks that regulate muscle mass and function. Moreover, we describe complex multi-organ roles in cancer cachexia. Although cachexia is one of the main causes of cancer-related deaths, there are still no approved drugs for cancer cachexia. Thus, we compiled recent ongoing pre-clinical and clinical trials and further discussed potential therapeutic approaches for cancer cachexia.

The beneficial therapeutic effects of plant-derived natural products for the treatment of sarcopenia

Sarcopenia is an age-related muscle disorder typically associated with a poor quality of life. Its definition has evolved over time, and several underlying causes of sarcopenia in the elderly have been proposed. However, the exact mechanisms involved in sarcopenia, as well as effective treatments for this condition, are not fully understood. The purpose of this article was to conduct a comprehensive review of previous evidence regarding the definition, diagnosis, risk factors, and efficacy of plant-derived natural products for sarcopenia. The methodological approach for the current narrative review was performed using PubMed, Scopus, and Web of Science databases, as well as Google Scholar (up to March 2021) in order to satisfy our objectives. The substantial beneficial effects along with the safety of some plant-derived natural products including curcumin, resveratrol, catechin, soy protein, and ginseng on sarcopenia are reported in this review. Based on clinical studies, nutraceuticals and functional foods may have beneficial effects on physical performance, including handgrip and knee-extension strength, weight-lifting capacity, time or distance travelled before feeling fatigued, mitochondrial function, muscle fatigue, mean muscle fibre area, and total number of myonuclei. In preclinical studies, supplementation with herbs and natural bioactive compounds resulted in beneficial effects including increased plantaris mass, skeletal muscle mass and strength production, increased expression of anabolic factors myogenin, Myf5 and MyoD, enhanced mitochondrial capacity, and inhibition of muscle atrophy and sarcopenia. We found that several risk factors such as nutritional status, physical inactivity, inflammation, oxidative stress, endocrine system dysfunction, insulin resistance, history of chronic disease, mental health, and genetic factors are linked or associated with sarcopenia. The substantial beneficial effects of some nutraceuticals and functional foods on sarcopenia, including curcumin, resveratrol, catechin, soy protein, and ginseng, without any significant side effects, are reported in this review. Plant-derived natural products might have a beneficial effect on various components of sarcopenia. Nevertheless, due to limited human trials, the clinical benefits of plant-derived natural products remain inconclusive. It is suggested that comprehensive longitudinal clinical studies to better understand risk factors over time, as well as identifying a treatment strategy for sarcopenia that is based on its pathophysiology, be undertaken in future investigations.

Grape Polyphenols in the Treatment of Human Skeletal Muscle Damage Due to Inflammation and Oxidative Stress during Obesity and Aging: Early Outcomes and Promises

Today, inactivity and high-calorie diets contribute to the development of obesity and premature aging. In addition, the population of elderly people is growing due to improvements in healthcare management. Obesity and aging are together key risk factors for non-communicable diseases associated with several co-morbidities and increased mortality, with a major impact on skeletal muscle defect and/or poor muscle mass quality. Skeletal muscles contribute to multiple body functions and play a vital role throughout the day, in all our activities. In our society, limiting skeletal muscle deterioration, frailty and dependence is not only a major public health challenge but also a major socio-economic issue. Specific diet supplementation with natural chemical compounds such as grape polyphenols had shown to play a relevant and direct role in regulating metabolic and molecular pathways involved in the prevention and treatment of obesity and aging and their related muscle comorbidities in cell culture and animal studies. However, clinical studies aiming to restore skeletal muscle mass and function with nutritional grape polyphenols supplementation are still very scarce. There is an urgent need for clinical studies to validate the very encouraging results observed in animal models.

Resveratrol Prevents Skeletal Muscle Atrophy and Senescence via Regulation of Histone Deacetylase 2 in Cigarette Smoke-Induced Mice with Emphysema

Objective

The aim of this study was to investigate the effects of resveratrol (RSV) on cigarette smoke (CS)-induced skeletal muscle atrophy and senescence in mice with emphysema and to explore the underlying mechanisms.

Methods

Gastrocnemius muscle weight and lung and muscular morphology were observed in CS-exposed mice with or without RSV treatment. The expression of atrophy-related markers (MURF1 and MAFbx), senescence-related markers (P53, P21 and SMP30) and NF-κB inflammatory pathways was detected by Western blotting and real-time PCR. The levels of IL-1β and TNF-α were also determined by ELISA, and the number of senescent cells was determined by SA-β gal staining. In addition, the expression of HDAC2 and the effect of HDAC2 on CSE-induced skeletal muscle atrophy and senescence by RSV treatment were investigated.

Results

RSV prevented emphysema and skeletal muscle atrophy in long-term CS-exposed mice. RSV decreased the expression of MURF1, MAFbx, P53, and P21 and inhibited the NF-κB pathway both in vivo and in vitro. Moreover, RSV reversed CS-induced downregulation of HDAC2 expression both in gastrocnemius and in C2C12 cells. Moreover, knockdown of HDAC2 significantly abolished the inhibitory effect of RSV on the expression of MURF1, MAFbx, P53, P21 and inflammatory factors (IL-1β and TNF-α) in C2C12 cells.

Conclusion

RSV prevents CS-induced skeletal muscle atrophy and senescence, and upregulation of HDAC2 expression and suppression of inflammation are involved.

Juzentaihoto Suppresses Muscle Atrophy in KKAy Mice

In obese patients with type 2 diabetes, reduced insulin sensitivity, increased production of inflammatory cytokines, and increased oxidative stress were observed, which lead to decreased protein synthesis and increased proteolysis in the skeletal muscles. Juzentaihoto (JTT) is herbal medicine and we have previously reported that the administration of JTT hot water extract alleviates skeletal muscle atrophy in a mouse model with streptozotocin-induced type 1 diabetes. In this study, we evaluated the inhibitory effects of JTT on muscle atrophy in a mouse model with obesity and type 2 diabetes. JTT was administered to KKAy mice with type 2 diabetic obesity and its effects on the skeletal muscles were evaluated. After JTT administration in KKAy mice, the wet weight and muscle fibre cross-sectional area of gastrocnemius increased and the time duration of exercise in the rotarod test improved. In addition, the serum levels of tumour necrosis factor-α and interleukin-6 decreased, adiponectin levels increased, and homeostasis model assessment for insulin resistance improved. Furthermore, JTT administration decreased the mRNA levels of ubiquitin ligase (atrogin-1, muscle RING-finger protein-1), increased the mRNA levels of Sirtuin1 in gastrocnemius. Our results suggest that JTT improves insulin resistance, suppresses inflammation, and reduces oxidative stress in KKAy mice, thereby suppressing skeletal muscle atrophy. JTT administration in clinical practice is expected to improve muscle atrophy in patients with obesity and type 2 diabetes.

Monotropein Improves Dexamethasone-Induced Muscle Atrophy via the AKT/mTOR/FOXO3a Signaling Pathways

The present study aimed to investigate the effects of monotropein (MON) on improving dexamethasone (DEX)-induced muscle atrophy in mice and C2C12 mouse skeletal muscle cells. The body weights, grip strengths, and muscle weights of mice were assessed. The histological change in the gastrocnemius tissues was also observed through H&E staining. The expression of myosin heavy chain (MyHC), muscle ring finger 1 (MuRF1), and muscle atrophy F-box (Atrogin1) and the phosphorylation of AKT, mTOR, and FOXO3a in the muscle tissues of mice and C2C12 myotubes were analyzed using Western blotting. MON improved muscle atrophy in mice and C2C12 myotubes by regulating catabolic states via the AKT/mTOR/FOXO3a signaling pathways, and enhanced muscle function by the increases of muscle mass and strength in mice. This suggests that MON could be used for the prevention and treatment of muscle atrophy in patients.

Mechanical unloading in 3D-engineered muscle leads to muscle atrophy by suppressing protein synthesis

Three dimensional (3D)-engineered muscle is an useful approach to a more comprehensive understanding of molecular mechanisms underlying unloading-induced muscle atrophy. We investigated the effects of mechanical unloading on molecular muscle protein synthesis (MPS)- and muscle protein breakdown (MPB)-related signaling pathways involved in muscle atrophy in 3D-engineered muscle, and to better understand in vitro model of muscle disuse. The 3D-engineered muscle consisting of C2C12 myoblasts and type-1 collagen gel was allowed to differentiate for 2 weeks and divided into three groups: 0 days of stretched-on control (CON), 2 and/or 7 days of stretched-on (ON), in which both ends of the muscle were fixed with artificial tendons, and the stretched-off group (OFF), in which one side of the artificial tendon was detached. Muscle weight (-38.1 to -48.4%), length (-67.0 to -73.5%), twitch contractile force (-70.5 to -75.0%) and myosin heavy chain expression (-32.5 to -50.5%) in the OFF group were significantly decreased on days 2 and 7 compared with the ON group (P < 0.05, respectively), despite that ON group was stable over time. Although determinative molecular signaling could not be identified, the MPS rate reflected by puromysin labeled protein was significantly decreased following mechanical unloading (P < 0.05, -38.5 to -51.1%). Meanwhile, MPB, particularly the ubiquitin-proteasome pathway, was not impacted. Hence, mechanical unloading of 3D-engineered muscle in vitro leads to muscle atrophy by suppressing MPS, cell differentiation, and cell growth rather than the promotion of MPB.

The Effect of Long-Lasting Swimming on Rats Skeletal Muscles Energy Metabolism after Nine Days of Dexamethasone Treatment

This study investigates the effect of Dexamethasone (Dex) treatment on blood and skeletal muscle metabolites level and skeletal muscle activity of enzymes related to energy metabolism after long-duration swimming. To evaluate whether Dex treatment, swimming, and combining these factors act on analyzed data, rats were randomly divided into four groups: saline treatment non-exercise and exercise and Dex treatment non-exercised and exercised. Animals in both exercised groups underwent long-lasting swimming. The concentration of lipids metabolites, glucose, and lactate were measured in skeletal muscles and blood according to standard colorimetric and fluorimetric methods. Also, activities of enzymes related to aerobic and anaerobic metabolism were measured in skeletal muscles. The results indicated that Dex treatment induced body mass loss and increased lipid metabolites in the rats’ blood but did not alter these changes in skeletal muscles. Interestingly, prolonged swimming applied after 9 days of Dex treatment significantly intensified changes induced by Dex; however, there was no difference in skeletal muscle enzymatic activities. This study shows for the first time the cumulative effect of exercise and Dex on selected elements of lipid metabolism, which seems to be essential for the patient’s health due to the common use of glucocorticoids like Dex.

L-carnitine ameliorates the muscle wasting of cancer cachexia through the AKT/FOXO3a/MaFbx axis

Background

Recent studies suggest potential benefits of applying L-carnitine in the treatment of cancer cachexia, but the precise mechanisms underlying these benefits remain unknown. This study was conducted to determine the mechanism by which L-carnitine reduces cancer cachexia.

Methods

C2C12 cells were differentiated into myotubes by growing them in DMEM for 24 h (hrs) and then changing the media to DMEM supplemented with 2% horse serum. Differentiated myotubes were treated for 2 h with TNF-α to establish a muscle atrophy cell model. After treated with L-carnitine, protein expression of MuRF1, MaFbx, FOXO3, p-FOXO3a, Akt, p-Akt, p70S6K and p-p70S6K was determined by Western blotting. Then siRNA-Akt was used to determine that L-carnitine ameliorated cancer cachexia via the Akt/FOXO3/MaFbx. In vivo, the cancer cachexia model was established by subcutaneously transplanting CT26 cells into the left flanks of the BALB/c nude mice. After treated with L-carnitine, serum levels of IL-1, IL-6 and TNF-α, and the skeletal muscle content of MuRF1, MaFbx, FOXO3, p-FOXO3a, Akt, p-Akt, p70S6K and p-p70S6K were measured.

Results

L-carnitine increased the gastrocnemius muscle (GM) weight in the CT26-bearing cachexia mouse model and the cross-sectional fiber area of the GM and myotube diameters of C2C12 cells treated with TNF-α. Additionally, L-carnitine reduced the protein expression of MuRF1, MaFbx and FOXO3a, and increased the p-FOXO3a level in vivo and in vitro. Inhibition of Akt, upstream of FOXO3a, reversed the effects of L-carnitine on the FOXO3a/MaFbx pathway and myotube diameters, without affecting FOXO3a/MuRF-1. In addition to regulating the ubiquitination of muscle proteins, L-carnitine also increased the levels of p-p70S6K and p70S6K, which are involved in protein synthesis. Akt inhibition did not reverse the effects of L-carnitine on p70S6K and p-p70S6K. Hence, L-carnitine ameliorated cancer cachexia via the Akt/FOXO3/MaFbx and p70S6K pathways. Moreover, L-carnitine reduced the serum levels of IL-1 and IL-6, factors known to induce cancer cachexia. However, there were minimal effects on TNF-α, another inducer of cachexia, in the in vivo model.

Conclusion

These results revealed a novel mechanism by which L-carnitine protects muscle cells and reduces inflammation related to cancer cachexia.

Polyphenols and Their Effects on Muscle Atrophy and Muscle Health

Skeletal muscle atrophy is the decrease in muscle mass and strength caused by reduced protein synthesis/accelerated protein degradation. Various conditions, such as denervation, disuse, aging, chronic diseases, heart disease, obstructive lung disease, diabetes, renal failure, AIDS, sepsis, cancer, and steroidal medications, can cause muscle atrophy. Mechanistically, inflammation, oxidative stress, and mitochondrial dysfunction are among the major contributors to muscle atrophy, by modulating signaling pathways that regulate muscle homeostasis. To prevent muscle catabolism and enhance muscle anabolism, several natural and synthetic compounds have been investigated. Recently, polyphenols (i.e., natural phytochemicals) have received extensive attention regarding their effect on muscle atrophy because of their potent antioxidant and anti-inflammatory properties. Numerous in vitro and in vivo studies have reported polyphenols as strongly effective bioactive molecules that attenuate muscle atrophy and enhance muscle health. This review describes polyphenols as promising bioactive molecules that impede muscle atrophy induced by various proatrophic factors. The effects of each class/subclass of polyphenolic compounds regarding protection against the muscle disorders induced by various pathological/physiological factors are summarized in tabular form and discussed. Although considerable variations in antiatrophic potencies and mechanisms were observed among structurally diverse polyphenolic compounds, they are vital factors to be considered in muscle atrophy prevention strategies.

Control of Skeletal Muscle Atrophy Associated to Cancer or Corticosteroids by Ceramide Kinase

Apart from cytokines and chemokines, sphingolipid mediators, particularly sphingosine-1-phosphate (S1P) and ceramide 1-phosphate (C1P), contribute to cancer and inflammation. Cancer, as well as other inflammatory conditions, are associated with skeletal muscle (SkM) atrophy, which is characterized by the unbalance between protein synthesis and degradation. Although the signaling pathways involved in SkM mass wasting are multiple, the regulatory role of simple sphingolipids is limited. Here, we report the impairment of ceramide kinase (CerK), the enzyme responsible for the phosphorylation of ceramide to C1P, associated with the accomplishment of atrophic phenotype in various experimental models of SkM atrophy: in vivo animal model bearing the C26 adenocarcinoma or Lewis lung carcinoma tumors, in human and murine SkM cells treated with the conditioned medium obtained from cancer cells or with the glucocorticoid dexamethasone. Notably, we demonstrate in all the three experimental approaches a drastic decrease of CerK expression. Gene silencing of CerK promotes the up-regulation of atrogin-1/MAFbx expression, which was also observed after cell treatment with C8-ceramide, a biologically active ceramide analogue. Conversely, C1P treatment significantly reduced the corticosteroid's effects. Altogether, these findings provide evidence that CerK, acting as a molecular modulator, may be a new possible target for SkM mass regulation associated with cancer or corticosteroids.

Fucoxanthin rescues dexamethasone induced C2C12 myotubes atrophy

Muscle atrophy and weakness are the adverse effects of long-term or high dose usage of glucocorticoids. In the present study, we explored the effects of fucoxanthin (10 μM) on dexamethasone (10 μM)-induced atrophy in C2C12 myotubes and investigated its underlying mechanisms. The diameter of myotubes was observed under a light microscope, and the expression of myosin heavy chain (MyHC), proteolysis-related, autophagy-related, apoptosis-related, and mitochondria-related proteins was analyzed by western blots or immunoprecipitation. Fucoxanthin alleviates dexamethasone-induced muscle atrophy in C2C12 myotubes, indicated by increased myotubes diameter and expression of MyHC, decreased expression of muscle atrophy F-box (Atrogin-1) and muscle ring finger 1 (MuRF1). Through activating SIRT1, fucoxanthin inhibits forkhead box O (FoxO) transcriptional activity to reduce protein degradation, induces autophagy to enhance degraded protein clearance, promotes mitochondrial function and diminishes apoptosis. In conclusion, we identified fucoxanthin ameliorates dexamethasone induced C2C12 myotubes atrophy through SIRT1 activation.

Morin attenuates dexamethasone-mediated oxidative stress and atrophy in mouse C2C12 skeletal myotubes

Glucocorticoids are the drugs most commonly used to manage inflammatory diseases. However, they are prone to inducing muscle atrophy by increasing muscle proteolysis and decreasing protein synthesis. Various studies have demonstrated that antioxidants can mitigate glucocorticoid-induced skeletal muscle atrophy. Here, we investigated the effect of a potent antioxidative natural flavonoid, morin, on the muscle atrophy and oxidative stress induced by dexamethasone (Dex) using mouse C2C12 skeletal myotubes. Dex (10 μM) enhanced the production of reactive oxygen species (ROS) in C2C12 myotubes via glucocorticoid receptor. Moreover, Dex administration reduced the diameter and expression levels of the myosin heavy chain protein in C2C12 myotubes, together with the upregulation of muscle atrophy-associated ubiquitin ligases, such as muscle atrophy F-box protein 1/atrogin-1, muscle ring finger protein-1, and casitas B-lineage lymphoma proto-oncogene-b. Dex also significantly decreased phosphorylated Foxo3a and increased total Foxo3a expression. Interestingly, Dex-induced ROS accumulation and Foxo3a expression were inhibited by morin (10 μM) pretreatment. Morin also prevented the Dex-induced reduction of myotube thickness, together with muscle protein degradation and suppression of the upregulation of atrophy-associated ubiquitin ligases. In conclusion, our results suggest that morin effectively prevents glucocorticoid-induced muscle atrophy by reducing oxidative stress.

Nutraceuticals and Exercise against Muscle Wasting during Cancer Cachexia

Cancer cachexia (CC) is a debilitating multifactorial syndrome, involving progressive deterioration and functional impairment of skeletal muscles. It affects about 80% of patients with advanced cancer and causes premature death. No causal therapy is available against CC. In the last few decades, our understanding of the mechanisms contributing to muscle wasting during cancer has markedly increased. Both inflammation and oxidative stress (OS) alter anabolic and catabolic signaling pathways mostly culminating with muscle depletion. Several preclinical studies have emphasized the beneficial roles of several classes of nutraceuticals and modes of physical exercise, but their efficacy in CC patients remains scant. The route of nutraceutical administration is critical to increase its bioavailability and achieve the desired anti-cachexia effects. Accumulating evidence suggests that a single therapy may not be enough, and a bimodal intervention (nutraceuticals plus exercise) may be a more effective treatment for CC. This review focuses on the current state of the field on the role of inflammation and OS in the pathogenesis of muscle atrophy during CC, and how nutraceuticals and physical activity may act synergistically to limit muscle wasting and dysfunction.

PGC-1α-Targeted Therapeutic Approaches to Enhance Muscle Recovery in Aging

Impaired muscle recovery (size and strength) following a disuse period commonly occurs in older adults. Many of these individuals are not able to adequately exercise due to pain and logistic barriers. Thus, nutritional and pharmacological therapeutics, that are translatable, are needed to promote muscle recovery following disuse in older individuals. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) may be a suitable therapeutic target due to pleiotropic regulation of skeletal muscle. This review focuses on nutritional and pharmacological interventions that target PGC-1α and related Sirtuin 1 (SIRT1) and 5' AMP-activated protein kinase (AMPKα) signaling in muscle and thus may be rapidly translated to prevent muscle disuse atrophy and promote recovery. In this review, we present several therapeutics that target PGC-1α in skeletal muscle such as leucine, β-hydroxy-β-methylbuyrate (HMB), arginine, resveratrol, metformin and combination therapies that may have future application to conditions of disuse and recovery in humans.

The Versatility of Sirtuin-1 in Endocrinology and Immunology

Sirtuins belong to the class III family of NAD-dependent histone deacetylases (HDAC) and are involved in diverse physiological processes that range from regulation of metabolism and endocrine function to coordination of immunity and cellular responses to stress. Sirtuin-1 (SIRT1) is the most well-studied family member and has been shown to be critically involved in epigenetics, immunology, and endocrinology. The versatile roles of SIRT1 include regulation of energy sensing metabolic homeostasis, deacetylation of histone and non-histone proteins in numerous tissues, neuro-endocrine regulation via stimulation of hypothalamus-pituitary axes, synthesis and maintenance of reproductive hormones via steroidogenesis, maintenance of innate and adaptive immune system via regulation of T- and B-cell maturation, chronic inflammation and autoimmune diseases. Moreover, SIRT1 is an appealing target in various disease contexts due to the promise of pharmacological and/or natural modulators of SIRT1 activity within the context of endocrine and immune-related disease models. In this review we aim to provide a broad overview on the role of SIRT1 particularly within the context of endocrinology and immunology.

Effect of Quercetin on Dexamethasone-Induced C2C12 Skeletal Muscle Cell Injury

Glucocorticoids are widely used anti-inflammatory drugs in clinical settings. However, they can induce skeletal muscle atrophy by reducing fiber cross-sectional area and myofibrillar protein content. Studies have proven that antioxidants can improve glucocorticoid-induced skeletal muscle atrophy. Quercetin is a potent antioxidant flavonoid widely distributed in fruits and vegetables and has shown protective effects against dexamethasone-induced skeletal muscle atrophy. In this study, we demonstrated that dexamethasone significantly inhibited cell growth and induced cell apoptosis by stimulating hydroxyl free radical production in C2C12 skeletal muscle cells. Our results evidenced that quercetin increased C2C12 skeletal cell viability and exerted antiapoptotic effects on dexamethasone-treated C2C12 cells by regulating mitochondrial membrane potential (ΔΨm) and reducing oxidative species. Quercetin can protect against dexamethasone-induced muscle atrophy by regulating the Bax/Bcl-2 ratio at the protein level and abnormal ΔΨm, which leads to the suppression of apoptosis.

Muscle Disuse Atrophy Caused by Discord of Intracellular Signaling

Significance: Regular contractile activity plays a critical role in maintaining skeletal muscle morphological integrity and physiological function. If the muscle is forced to stop contraction, such as during limb immobilization (IM), the IGF/Akt/mTOR signaling pathway that normally stimulates protein synthesis and inhibits proteolysis will be suppressed, whereas the FoxO-controlled catabolic pathways such as ubiquitin-proteolysis and autophagy/mitophagy will be activated and dominate, resulting in muscle fiber atrophy. Recent Advances: Mitochondria occupy a central position in the regulation of both protein synthesis and degradation through several redox-sensitive pathways, including peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), mitochondrial fusion and fission proteins, mitophagy, and sirtuins. Prolonged IM downregulates PGC-1α due to AMPK (5'-AMP-activated protein kinase) and FoxO activation, thus decreasing mitochondrial biogenesis and causing oxidative damage. Decrease of mitochondrial inner membrane potential and increase of mitochondrial fission can trigger cascades of mitophagy leading to loss of mitochondrial homeostasis (mitostasis), inflammation, and apoptosis. The phenotypic outcomes of these disorders are compromised muscle function and fiber atrophy. Critical Issues: Given the molecular mechanism of the pathogenesis, it is imperative that the integrity of intracellular signaling be restored to prevent the deterioration. So far, overexpression of PGC-1α via transgene and in vivo DNA transfection has been found to be effective in ameliorating mitostasis and reduces IM-induced muscle atrophy. Nutritional supplementation of select amino acids and phytochemicals also provides mechanistic and practical insights into the prevention of muscle disuse atrophy. Future Directions: In light of the importance of mitochondria in regulating the various critical signaling pathways, future work should focus on exploring new epigenetic strategies to restore mitostasis and redox balance.

Resveratrol for protection against statin toxicity in C2C12 and H9c2 cells

Statins are among the most commonly prescribed drugs for the treatment of high blood cholesterol. Myotoxicity of statins in certain individuals is often a severe side effect leading to withdrawal. Using C2C12 and H9c2 cells, both exhibiting characteristics of skeletal muscle cells, we addressed whether resveratrol (RSV) can prevent statin toxicity. Statins decreased cell viability in a dose and time-dependent manner. Among the five statins tested, atorvastatin, simvastatin, lovastatin, pravastatin, and fluvastatin, simvastatin is the most toxic one. Simvastatin at 10 µM caused about 65% loss of metabolic activity as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays in C2C12 cells or H9c2 cells. Inhibition of metabolic activity correlates with an increase in caspase activity. RSV was found to protect H9c2 cells from simvastatin-induced activation of caspase-3/7. However, such protection was not found in C2C12 cells. This cell type-dependent effect of RSV adds to the complexity in muscle cell toxicity of statins.

Resveratrol and metabolic health in COPD: A proof-of-concept randomized controlled trial

BACKGROUND

Patients with COPD are often characterized by disturbed metabolic health which is reflected in altered body composition. Current studies in healthy subjects suggest that resveratrol improves metabolic health by enhancing muscle mitochondrial function and adipose tissue morphology. The primary objective was to investigate the effect of four weeks resveratrol supplementation on muscle mitochondrial function in patients with COPD. Secondary objectives were to investigate the effect of resveratrol on adipose tissue inflammatory and metabolic gene expression, systemic inflammation and body composition in patients with COPD.

METHODS

In a double-blind randomized placebo-controlled proof-of-concept study, 21 COPD patients (FEV₁: 53 ± 15% predicted; age: 67 ± 9 years and BMI: 24.5 ± 3.3 kg/m²) received resveratrol (150 mg/day) or placebo for four weeks. Before and after intervention, blood samples, quadriceps muscle and subcutaneous abdominal fat biopsies were obtained for metabolic and inflammatory profiling. Body composition was assessed by dual energy X-ray absorptiometry.

RESULTS

Muscle mitochondrial biogenesis regulators AMPK, SIRT1 and PGC-1α as well as mitochondrial respiration, Oxphos complexes, oxidative enzyme activities and kynurenine aminotransferases were not improved by resveratrol. Plasma high-sensitive C-reactive protein and kynurenine did not change after resveratrol supplementation. Adipose tissue inflammatory markers were unaffected by resveratrol, while markers of glycolysis and lipolysis were significantly increased compared to placebo supplementation. Body weight decreased after resveratrol supplementation (resveratrol -0.95 ± 1.01 kg vs placebo -0.16 ± 0.66 kg, p = 0.049) due to a reduction in lean mass (resveratrol -1.79 ± 1.67 kg vs 0.37 ± 0.86 kg, p = 0.026).

CONCLUSION

We do not confirm previously reported positive effects of resveratrol on skeletal muscle mitochondrial function in patients with COPD, but show an unexpected decline in lean mass.

CLINICAL TRIAL REGISTRY

Clinicaltrials.gov NCT02245932.

Natural constituents from food sources: potential therapeutic agents against muscle wasting

Skeletal muscle wasting is highly correlated with not only reduced quality of life but also higher morbidity and mortality. Although an increasing number of patients are suffering from various kinds of muscle atrophy and weakness, there is still no effective therapy available, and skeletal muscle is considered as an under-medicated organ. Food provided not only essential macronutrients but also functional substances involved in the modulation of the physiological systems of our body. Natural constituents from commonly consumed dietary plants, either extracts or compounds, have attracted more and more attention to be developed as agents for preventing and treating muscle wasting due to their safety and effectiveness, as well as structural diversity. This review provides an overview of the mechanistic aspects of muscle wasting, and summarizes the extracts and compounds from food sources as potential therapeutic agents against muscle wasting.

Myricanol rescues dexamethasone-induced muscle dysfunction via a sirtuin 1-dependent mechanism

BACKGROUND

Muscle atrophy and weakness are adverse effects of high dose or the sustained usage of glucocorticoids. Loss of mitochondria and degradation of protein are highly correlated with muscle dysfunction. The deacetylase sirtuin 1 (SIRT1) plays a vital role in muscle remodelling. The current study was designed to identify myricanol as a SIRT1 activator, which could protect skeletal muscle against dexamethasone-induced wasting.

METHODS

The dexamethasone-induced atrophy in C2C12 myotubes was evaluated by expression of myosin heavy chain, muscle atrophy F-box (atrogin-1), and muscle ring finger 1 (MuRF1), using western blots. The mitochondrial content and oxygen consumption were assessed by MitoTracker staining and extracellular flux analysis, respectively. Muscle dysfunction was established in male C57BL/6 mice (8-10 weeks old, n = 6) treated with a relatively high dose of dexamethasone (25 mg/kg body weight, i.p., 10 days). Body weight, grip strength, forced swimming capacity, muscle weight, and muscle histology were assessed. The expression of proteolysis-related, autophagy-related, apoptosis-related, and mitochondria-related proteins was analysed by western blots or immunoprecipitation.

RESULTS

Myricanol (10 μM) was found to rescue dexamethasone-induced muscle atrophy and dysfunction in C2C12 myotubes, indicated by increased expression of myosin heavy chain (0.33 ± 0.14 vs. 0.89 ± 0.21, *P < 0.05), decreased expression of atrogin-1 (2.31 ± 0.67 vs. 1.53 ± 0.25, *P < 0.05) and MuRF1 (1.55 ± 0.08 vs. 0.99 ± 0.12, **P < 0.01), and elevated ATP production (3.83 ± 0.46 vs. 5.84 ± 0.79 nM/mg protein, **P < 0.01), mitochondrial content (68.12 ± 10.07% vs. 116.38 ± 5.12%, *P < 0.05), and mitochondrial oxygen consumption (166.59 ± 22.89 vs. 223.77 ± 22.59 pmol/min, **P < 0.01). Myricanol directly binds and activates SIRT1, with binding energy of -5.87 kcal/mol. Through activating SIRT1 deacetylation, myricanol inhibits forkhead box O 3a transcriptional activity to reduce protein degradation, induces autophagy to enhance degraded protein clearance, and increases peroxisome proliferator-activated receptor γ coactivator-1α activity to promote mitochondrial biogenesis. In dexamethasone-induced muscle wasting C57BL/6 mice, 5 mg/kg myricanol treatment reduces the loss of muscle mass; the percentages of quadriceps and gastrocnemius muscle in myricanol-treated mice are 1.36 ± 0.02% and 0.87 ± 0.08%, respectively (cf. 1.18 ± 0.06% and 0.78 ± 0.05% in dexamethasone-treated mice, respectively). Myricanol also rescues dexamethasone-induced muscle weakness, indicated by improved grip strength (70.90 ± 4.59 vs. 120.58 ± 7.93 g, **P < 0.01) and prolonged swimming exhaustive time (48.80 ± 11.43 vs. 83.75 ± 15.19 s, **P < 0.01). Myricanol prevents dexamethasone-induced muscle atrophy and weakness by activating SIRT1, to reduce muscle protein degradation, enhance autophagy, and promote mitochondrial biogenesis and function in mice.

CONCLUSIONS

Myricanol ameliorates dexamethasone-induced skeletal muscle wasting by activating SIRT1, which might be developed as a therapeutic agent for treatment of muscle atrophy and weakness.

Cellular mechanisms promoting cachexia and how they are opposed by sirtuins 1

Many chronic diseases are associated with unintentional loss of body weight, which is termed "cachexia". Cachexia is a complex multifactorial syndrome associated with the underlying primary disease, and characterized by loss of skeletal muscle with or without loss of fat tissue. Patients with cachexia face dire symptoms like dyspnea, fatigue, edema, exercise intolerance, and low responsiveness to medical therapy, which worsen quality of life. Because cachexia is not a stand-alone disorder, treating primary disease - such as cancer - takes precedence for the physician, and it remains mostly a neglected illness. Existing clinical trials have demonstrated limited success mostly because of their monotherapeutic approach and late detection of the syndrome. To conquer cachexia, it is essential to identify as many molecular targets as possible using the latest technologies we have at our disposal. In this review, we have discussed different aspects of cachexia, which include various disease settings, active molecular pathways, and recent novel advances made in this field to understand consequences of this illness. We also discuss roles of the sirtuins, the NAD+-dependent lysine deacetylases, microRNAs, certain dietary options, and epigenetic drugs as potential approaches, which can be used to tackle cachexia as early as possible in its course.

Resveratrol Improves Muscle Atrophy by Modulating Mitochondrial Quality Control in STZ-Induced Diabetic Mice

SCOPE

In this study, we aim to determine the effects of resveratrol (RSV) on muscle atrophy in streptozocin-induced diabetic mice and to explore mitochondrial quality control (MQC) as a possible mechanism.

METHODS AND RESULTS

The experimental mice were fed either a control diet or an identical diet containing 0.04% RSV for 8 weeks. Examinations were subsequently carried out, including the effects of RSV on muscle atrophy and muscle function, as well as on the signaling pathways related to protein degradation and MQC processes. The results show that RSV supplementation improves muscle atrophy and muscle function, attenuates the increase in ubiquitin and muscle RING-finger protein-1 (MuRF-1), and simultaneously attenuates LC3-II and cleaved caspase-3 in the skeletal muscle of diabetic mice. Moreover, RSV treatment of diabetic mice results in an increase in mitochondrial biogenesis and inhibition of the activation of mitophagy in skeletal muscle. RSV also protects skeletal muscle against excess mitochondrial fusion and fission in the diabetic mice.

CONCLUSION

The results suggest that RSV ameliorates diabetes-induced skeletal muscle atrophy by modulating MQC.

Extracellular polysaccharides purified from Aureobasidium pullulans SM‑2001 (Polycan) inhibit dexamethasone‑induced muscle atrophy in mice

The present study assessed the beneficial skeletal muscle‑preserving effects of extracellular polysaccharides from Aureobasidium pullulans SM‑2001 (Polycan) (EAP) on dexamethasone (DEXA)‑induced catabolic muscle atrophy in mice. To investigate whether EAP prevented catabolic DEXA‑induced muscle atrophy, and to examine its mechanisms of action, EAP (100, 200 and 400 mg/kg) was administered orally, once a day for 24 days. EAP treatment was initiated 2 weeks prior to DEXA treatment (1 mg/kg, once a day for 10 days) in mice. Body weight alterations, serum biochemistry, calf thickness, calf muscle strength, gastrocnemius muscle thickness and weight, gastrocnemius muscle antioxidant defense parameters, gastrocnemius muscle mRNA expression, histology and histomorphometry were subsequently assessed. After 24 days, DEXA control mice exhibited muscle atrophy according to all criteria indices. However, these muscle atrophy symptoms were significantly inhibited by oral treatment with all three doses of EAP. Regarding possible mechanisms of action, EAP exhibited favorable ameliorating effects on DEXA‑induced catabolic muscle atrophy via antioxidant and anti‑inflammatory effects; these effects were mediated by modulation of the expression of genes involved in muscle protein synthesis (AKT serine/threonine kinase 1, phosphatidylinositol 3‑kinase, adenosine A1 receptor and transient receptor potential cation channel subfamily V member 4) and degradation (atrogin‑1, muscle RING‑finger protein‑1, myostatin and sirtuin 1). Therefore, these results indicated that EAP may be helpful in improving muscle atrophies of various etiologies. EAP at 400 mg/kg exhibited favorable muscle protective effects against DEXA‑induced catabolic muscle atrophy, comparable with the effects of oxymetholone (50 mg/kg), which has been used to treat various muscle disorders.

Resveratrol for patients with chronic obstructive pulmonary disease: hype or hope?

PURPOSE OF REVIEW

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease with a high prevalence of extrapulmonary manifestations and, frequently, cardiovascular comorbidity. Resveratrol is a food-derived compound with anti-inflammatory, antioxidant, metabolic and cardioprotective potential. Therefore, resveratrol might improve the pulmonary as well as extrapulmonary pathology in COPD. In this review, we will evaluate knowledge on the effects of resveratrol on lung injury, muscle metabolism and cardiovascular risk profile and discuss if resveratrol is a hype or hope for patients with COPD.

RECENT FINDINGS

Experimental models of COPD consistently show decreased inflammation and oxidative stress in the lungs after resveratrol treatment. These beneficial anti-inflammatory and antioxidant properties of resveratrol can indirectly also improve both skeletal and respiratory muscle impairment in COPD. Recent clinical studies in non-COPD populations show improved mitochondrial oxidative metabolism after resveratrol treatment, which could be beneficial for both lung and muscle impairment in COPD. Moreover, preclinical studies suggest cardioprotective effects of resveratrol but results of clinical studies are inconclusive.

SUMMARY

Resveratrol might be an interesting therapeutic candidate to counteract lung and muscle impairments characteristic to COPD. However, there is no convincing evidence that resveratrol will significantly decrease the cardiovascular risk in patients with COPD.

Resveratrol attenuates denervation-induced muscle atrophy due to the blockade of atrogin-1 and p62 accumulation

Decrease in activity stress induces skeletal muscle atrophy. A previous study showed that treatment with resveratrol inhibits muscular atrophy in mdx mice, a model of DMD. However, almost all studies using resveratrol supplementation have only looked at adaptive changes in the muscle weight. The present study was designed to elucidate whether the resveratrol-inducing attenuation of skeletal muscle actually reflects the adaptation of muscle fibers themselves, based on the modulation of atrogin-1- or p62-dependent signaling. Mice were fed either a normal diet or 0.5% resveratrol diet. One week later, the right sciatic nerve was cut. The wet weight, mean fiber area, and amount of atrogin-1 and p62 proteins were examined in the gastrocnemius muscle at 14 days after denervation. The 0.5% resveratrol diet significantly prevented denervation-induced decreases in both the muscle weight and fiber atrophy. In addition, dietary resveratrol suppressed the denervation-induced atrogin-1 and p62 immunoreactivity. In contrast, 0.5% resveratrol supplementation did not significantly modulate the total protein amount of atrogin-1 or p62 in the denervated muscle of mice. Resveratrol supplementation significantly prevents muscle atrophy after denervation in mice, possibly due to the decrease in atrogin-1 and p62-dependent signaling.

The influence of isoflavone for denervation-induced muscle atrophy

PURPOSE

Decrease in activity stress induces skeletal muscle atrophy. A previous study showed that treatment with a high level (20%) of isoflavone inhibits muscle atrophy after short-term denervation (at 4 days) in mice. The present study was designed to elucidate whether the dietary isoflavone aglycone (AglyMax) at a 0.6% prevents denervation-mediated muscle atrophy, based on the modulation of atrogin-1- or apoptosis-dependent signaling.

METHODS

Mice were fed either a normal diet or 0.6% AglyMax diet. One week later, the right sciatic nerve was cut. The wet weight, mean fiber area, amount of atrogin-1 and cleaved caspase-3 proteins, and the percentages of apoptotic nuclei were examined in the gastrocnemius muscle at 14 days after denervation.

RESULTS

The 0.6% AglyMax diet significantly attenuated denervation-induced decreases in fiber atrophy but not the muscle wet weight. In addition, dietary isoflavone suppressed the denervation-induced apoptosis in spite of there being no significant changes in the amount of cleaved caspase-3 protein. In contrast, the 0.6% AglyMax diet did not significantly modulate the protein expression of atrogin-1 in the denervated muscle of mice.

CONCLUSIONS

The isoflavone aglycone (AglyMax) at a 0.6% significantly would modulate muscle atrophy after denervation in mice, probably due to the decrease in apoptosis-dependent signaling.

Dietary resveratrol confers apoptotic resistance to oxidative stress in myoblasts

High levels of reactive oxygen species (ROS) contribute to muscle cell death in aging and disuse. We have previously found that resveratrol can reduce oxidative stress in response to aging and hindlimb unloading in rodents in vivo, but it was not known if resveratrol would protect muscle stem cells during repair or regeneration when oxidative stress is high. To test the protective role of resveratrol on muscle stem cells directly, we treated the C2C12 mouse myoblast cell line with moderate (100 μM) or very high (1 mM) levels of H2O2 in the presence or absence of resveratrol. The p21 promoter activity declined in myoblasts in response to high ROS, and this was accompanied a greater nuclear to cytoplasmic translocation of p21 in a dose-dependent matter in myoblasts as compared to myotubes. Apoptosis, as indicated by TdT-mediated dUTP nick-end labeling, was greater in C2C12 myoblasts as compared to myotubes (P<.05) after treatment with H2O2. Caspase-9, -8 and -3 activities were elevated significantly (P<.05) in myoblasts treated with H2O2. Myoblasts were more susceptible to ROS-induced oxidative stress than myotubes. We treated C2C12 myoblasts with 50 μM of resveratrol for periods up to 48 h to determine if myoblasts could be rescued from high-ROS-induced apoptosis by resveratrol. Resveratrol reduced the apoptotic index and significantly reduced the ROS-induced caspase-9, -8 and -3 activity in myoblasts. Furthermore, Bcl-2 and the Bax/Bcl-2 ratio were partially rescued in myoblasts by resveratrol treatment. Similarly, muscle stem cells isolated from mouse skeletal muscles showed reduced Sirt1 protein abundance with H2O2 treatment, but this could be reversed by resveratrol. Reduced apoptotic susceptibility in myoblasts as compared to myotubes to ROS is regulated, at least in part, by enhanced p21 promoter activity and nuclear p21 location in myotubes. Resveratrol confers further protection against ROS by improving Sirt1 levels and increasing antioxidant production, which reduces mitochondrial associated apoptotic signaling, and cell death in myoblasts.

Resveratrol Enhances Exercise-Induced Cellular and Functional Adaptations of Skeletal Muscle in Older Men and Women

Older men (n = 12) and women (n = 18) 65-80 years of age completed 12 weeks of exercise and took either a placebo or resveratrol (RSV) (500 mg/d) to test the hypothesis that RSV treatment combined with exercise would increase mitochondrial density, muscle fatigue resistance, and cardiovascular function more than exercise alone. Contrary to our hypothesis, aerobic and resistance exercise coupled with RSV treatment did not reduce cardiovascular risk further than exercise alone. However, exercise added to RSV treatment improved the indices of mitochondrial density, and muscle fatigue resistance more than placebo and exercise treatments. In addition, subjects that were treated with RSV had an increase in knee extensor muscle peak torque (8%), average peak torque (14%), and power (14%) after training, whereas exercise did not increase these parameters in the placebo-treated older subjects. Furthermore, exercise combined with RSV significantly improved mean fiber area and total myonuclei by 45.3% and 20%, respectively, in muscle fibers from the vastus lateralis of older subjects. Together, these data indicate a novel anabolic role of RSV in exercise-induced adaptations of older persons and this suggests that RSV combined with exercise might provide a better approach for reversing sarcopenia than exercise alone.

[Effect of resveratrol on forelimb grip strength and myofibril structure in aged rats]

OBJECTIVE

To observe the effect of resveratrol on muscle mass, forelimb grip strength, myofibril structure and AMPK/sirt1 pathway in skeletal muscles of aged rats.

METHODS

Twenty aged (25 months old) SD rats were randomly divided into aged control group and resveratrol treatment group (10 in each group) with 10 young (6 months old) rats served as the young control group. In resveratrol treatment group, the rats were treated with resveratrol (mixed in chow) for 6 weeks. After the treatment, the mass of the gastrocnemius was measured and the sarcopenia index (SI) was calculated as the gastrocnemius mass (mg) to body weight (g) ratio. The forelimb grip strength of the rats was measured using a electronic grip strength meter, and the lengths of the sarcomere, I-band, A-band and H-zone of the myofibrils were determined by transmission electron microscopy.

RESULTS

Compared with the young rats, the aged control rats had significantly lower SI of the gastrocnemius (P<0.05) and grip strength (P<0.05) with increased lengths of the sarcomere, A-band, I-band and H-zone (P<0.05) and lowered expressions of AMPK, P-AMPK, and sirt1 protein (P<0.05). Resveratrol treatment of the aged rats significantly increased the forelimb grip strength, reduced the lengths of sarcomere length, I-band and H-zone (P<0.05) and increased, P-AMPK, sirt1 protein expressions (P<0.05) without significantly affecting the SI (P>0.05) or the A-band length (P>0.05).

CONCLUSION

Resveratrol does not improve the muscle mass but can increase the forelimb grip strength in aged rats possibly by activating AMPK/sirt1 pathway to improve the ultrastructure of the myofibrils.

The effect of exercise, resveratrol or their combination on Sarcopenia in aged rats via regulation of AMPK/Sirt1 pathway

Sarcopenia is an age-related syndrome characterized by progressive loss of muscle mass and function. Exercise is an important strategy to prolong life and increase muscle mass, and resveratrol has been shown a variety beneficial effects on skeletal muscle. In the present study, we investigated the potential efficacy of using short-term exercise (six weeks), resveratrol (150mg/kg/day), or combined exercise+resveratrol (150mg/kg/day) on gastrocnemius muscle mass, grip strength, cross-sectional area and microscopic morphology in aged rats, and explored the potential mechanism at the apoptosis level. Six months old SD rats were used as young control group and 24months old SD rats were adopted as aged group. After six weeks intervention, the data provide evidence that exercise, resveratrol or their combination significantly increase the relative grip strength and muscle mass in aged rats (P<0.05). Electron microscopy discovered a significant increase in sarcomere length, I-band and H-zone in aged rats (P<0.05), and exercise, resveratrol or their combination significantly reduced the increasement (P<0.05). Moreover, light microscopy revealed a significant increase on Feret's diameter and cross-sectional area (CSA) in aged rats (P<0.05), but exercise and resveratrol did not show significant effects on them (P>0.05). Furthermore, exercise, resveratrol or their combination significantly increased the expression of p-AMPK and SIRT1, decreased the expression of acetyl P53 and Bax/Bcl-2 ratio in aged rats (P<0.05). These findings show that aged rats show significant changes in gastrocnemius muscle morphology and ultrastructure, and the protective effects of exercise, resveratrol and their combination are probably associated with anti-apoptotic signaling pathways through activation of AMPK/Sirt1.

Three-Dimensional Culture Model of Skeletal Muscle Tissue with Atrophy Induced by Dexamethasone

Drug screening systems for muscle atrophy based on the contractile force of cultured skeletal muscle tissues are required for the development of preventive or therapeutic drugs for atrophy. This study aims to develop a muscle atrophy model by inducing atrophy in normal muscle tissues constructed on microdevices capable of measuring the contractile force and to verify if this model is suitable for drug screening using the contractile force as an index. Tissue engineered skeletal muscles containing striated myotubes were prepared on the microdevices for the study. The addition of 100 µM dexamethasone (Dex), which is used as a muscle atrophy inducer, for 24 h reduced the contractile force significantly. An increase in the expression of Atrogin-1 and MuRF-1 in the tissues treated with Dex was established. A decrease in the number of striated myotubes was also observed in the tissues treated with Dex. Treatment with 8 ng/mL Insulin-like Growth Factor (IGF-I) for 24 h significantly increased the contractile force of the Dex-induced atrophic tissues. The same treatment, though, had no impact on the force of the normal tissues. Thus, it is envisaged that the atrophic skeletal muscle tissues induced by Dex can be used for drug screening against atrophy.

SIRT1 may play a crucial role in overload-induced hypertrophy of skeletal muscle

KEY POINTS

Silent mating type information regulation 2 homologue 1 (SIRT1) activity and content increased significantly in overload-induced hypertrophy. SIRT1-mediated signalling through Akt, the endothelial nitric oxide synthase mediated pathway, regulates anabolic process in the hypertrophy of skeletal muscle. The regulation of catabolic signalling via forkhead box O 1 and protein ubiquitination is SIRT1 dependent. Overload-induced changes in microRNA levels regulate SIRT1 and insulin-like growth factor 1 signalling.

ABSTRACT

Significant skeletal muscle mass guarantees functional wellbeing and is important for high level performance in many sports. Although the molecular mechanism for skeletal muscle hypertrophy has been well studied, it still is not completely understood. In the present study, we used a functional overload model to induce plantaris muscle hypertrophy by surgically removing the soleus and gastrocnemius muscles in rats. Two weeks of muscle ablation resulted in a 40% increase in muscle mass, which was associated with a significant increase in silent mating type information regulation 2 homologue 1 (SIRT1) content and activity (P < 0.001). SIRT1-regulated Akt, endothelial nitric oxide synthase and GLUT4 levels were also induced in hypertrophied muscles, and SIRT1 levels correlated with muscle mass, paired box protein 7 (Pax7), proliferating cell nuclear antigen (PCNA) and nicotinamide phosphoribosyltransferase (Nampt) levels. Alternatively, decreased forkhead box O 1 (FOXO1) and increased K48 polyubiquitination also suggest that SIRT1 could be involved in the catabolic process of hypertrophy. Furthermore, increased levels of K63 and muscle RING finger 2 (MuRF2) protein could also be important enhancers of muscle mass. We report here that the levels of miR1 and miR133a decrease in hypertrophy and negatively correlate with muscle mass, SIRT1 and Nampt levels. Our results reveal a strong correlation between SIRT1 levels and activity, SIRT1-regulated pathways and overload-induced hypertrophy. These findings, along with the well-known regulatory roles that SIRT1 plays in modulating both anabolic and catabolic pathways, allow us to propose the hypothesis that SIRT1 may actually play a crucial causal role in overload-induced hypertrophy of skeletal muscle. This hypothesis will now require rigorous direct and functional testing.

Resveratrol attenuates skeletal muscle atrophy induced by chronic kidney disease via MuRF1 signaling pathway

Skeletal muscle atrophy is an important clinical characteristic of chronic kidney disease (CKD); however, at present, the therapeutic approaches to muscle atrophy induced by CKD are still at an early stage of development. Resveratrol is used to attenuate muscle atrophy in other experimental models, but the effects on a CKD model are largely unknown. Here, we showed that resveratrol prevented an increase in MuRF1 expression and attenuated muscle atrophy in vivo model of CKD. We also found that phosphorylation of NF-κB was inhibited at the same time. Dexamethasone-induced MuRF1 upregulation was significantly attenuated in C2C12 myotubes by resveratrol in vitro, but this effect on C2C12 myotubes was abrogated by a knockdown of NF-κB, suggesting that the beneficial effect of resveratrol was NF-κB dependent. Our findings provide novel information about the ability of resveratrol to prevent or treat muscle atrophy induced by CKD.

Involvement of the FoxO1/MuRF1/Atrogin-1 Signaling Pathway in the Oxidative Stress-Induced Atrophy of Cultured Chronic Obstructive Pulmonary Disease Myotubes

Oxidative stress is thought to be one of the most important mechanisms implicated in the muscle wasting of chronic obstructive pulmonary disease (COPD) patients, but its role has never been demonstrated. We therefore assessed the effects of both pro-oxidant and antioxidant treatments on the oxidative stress levels and atrophic signaling pathway of cultured COPD myotubes. Treatment of cultured COPD myotubes with the pro-oxidant molecule H₂O₂ resulted in increased ROS production (P = 0.002) and protein carbonylation (P = 0.050), in association with a more pronounced atrophy of the myotubes, as reflected by a reduced diameter (P = 0.003), and the activated expression of atrophic markers MuRF1 and FoxO1 (P = 0.022 and P = 0.030, respectively). Conversely, the antioxidant molecule ascorbic acid induced a reduction in ROS production (P<0.001) and protein carbonylation (P = 0.019), and an increase in the myotube diameter (P<0.001) to a level similar to the diameter of healthy subject myotubes, in association with decreased expression levels of MuRF1, atrogin-1 and FoxO1 (P<0.001, P = 0.002 and P = 0.042, respectively). A significant negative correlation was observed between the variations in myotube diameter and the variations in the expression of MuRF1 after antioxidant treatment (P = 0.047). Moreover, ascorbic acid was able to prevent the H₂O₂-induced atrophy of COPD myotubes. Last, the proteasome inhibitor MG132 restored the basal atrophy level of the COPD myotubes and also suppressed the H₂O₂-induced myotube atrophy. These findings demonstrate for the first time the involvement of oxidative stress in the atrophy of COPD peripheral muscle cells in vitro, via the FoxO1/MuRF1/atrogin-1 signaling pathway of the ubiquitin/proteasome system.

Why so little effort to study anti-oxidant therapy in burns?

Given that oxidative stress is an inherent response to burn injury, it is puzzling as to why investigation into anti-oxidant therapy as an adjunct to burn treatment has been limited. Both the inflammatory response and the stress response to burn injury involve oxidative stress, and there has been some limited success in studies using gamma tocopherol and selenium to improve certain consequences of burns. Much remains to be done to investigate the number, doses and combinations of anti-oxidants, their efficacy, and limitations in improving defined outcomes after burn injury.

Dietary supplementation with shiikuwasha extract attenuates dexamethasone-induced skeletal muscle atrophy in aged rats

Background

Skeletal muscle atrophy is caused by a variety of diseases and conditions. In particular, skeletal muscle atrophy in the elderly contributes to a loss of independence with advanced age and increases the risk of falling. However, the effect of food consumed on a daily basis on skeletal muscle atrophy has been the focus of little research. In this study, the effects of dietary supplementation with shiikuwasha extract or grape extract on dexamethasone-induced skeletal muscle atrophy were evaluated in aged rats.

Methods

Aged male rats (15-month-old) were fed a diet supplemented with either 1 % shiikuwasha extract or 1 % grape extract for 19 days. During the last 5 days of the feeding period, rats were injected with dexamethasone to induce muscle atrophy.

Results

Body weight and hind-limb muscle weight were significantly decreased by dexamethasone treatment. The supplementation of shiikuwasha extract showed no effect on body weight loss, but markedly attenuated tibialis anterior muscle weight loss induced by dexamethasone. On the other hand, grape extract did not affect muscle weight loss. Furthermore, shiikuwasha extract significantly reduced dexamethasone-induced expression of atrogin-1 and MuRF1 mRNA, but did not reduce LC3B-II protein levels.

Conclusion

These results suggest that shiikuwasha extract may partially inhibit the activation of the ubiquitin–proteasome system and may consequently attenuate skeletal muscle atrophy induced by dexamethasone in aged rats.

High-intensity resistance training attenuates dexamethasone-induced muscle atrophy

INTRODUCTION

In this study we investigated the effects of high-intensity resistance training (RT) on dexamethasone (DEX)-induced muscle atrophy in flexor hallucis longus (FHL), tibialis anterior (TA), and soleus (SOL) muscles.

METHODS

Rats underwent either high-intensity RT or were kept sedentary. In the last 10 days they received either DEX (0.5 mg/kg/day, intraperitoneally) or saline.

RESULTS

DEX reduced body weight (-21%), food intake (-28%), FHL and TA muscle mass (-20% and -18%, respectively), and increased muscle-specific ring finger 1 (MuRF-1) protein level (+37% and +45.5%). RT attenuated FHL muscle atrophy through a combination of low increase in MuRF-1 protein level (-3.5%) and significant increases in mammalian target of rapamycin (mTOR) (+63%) and p70S6K (+46% and +49% for control and DEX, respectively) protein levels.

CONCLUSION

RT attenuated DEX-induced muscle atrophy through a combination of increases in mTOR and p70S6K protein levels and a low increase in MuRF-1 protein level.

DJ-1 protects against undernutrition-induced atrophy through inhibition of the MAPK-ubiquitin ligase pathway in myoblasts

AIMS

The purpose of this study is to explore whether antioxidant DJ-1 protein affects the atrophy of skeletal muscle cell induced by undernutrition.

MAIN METHODS

To determine cell atrophic responses, L6 cell line and skeletal primary cells from mouse hind limbs were cultivated under condition of FBS-free and low glucose. Changes of protein expression were analyzed using Western blot. Overexpression and knockdown of DJ-1 was performed in cells to assess its influence on cell atrophic responses.

KEY FINDINGS

Undernutrition decreased cell size and increased the abundance of oxidized form and total form of DJ-1 protein in L6 myoblasts. The undernourished cells revealed an elevation in the expression of muscle-specific RING finger-1 (MuRF-1) and atrogin-1, and in the phosphorylations of p38 mitogen-activated protein kinase (MAPK) and stress-activated protein kinase/c-Jun N-terminal kinase compared with control groups. Moreover, DJ-1-knockout mice showed a decrease in cell size and an enhancement in the expression of MuRF-1 and atrogin-1, as well as in the phosphorylation of MAPKs in gastrocnemius muscles; these changes were also observed in L6 cells transfected with siRNA of DJ-1. On the other hand, L6 cells overexpressing full-length DJ-1 did not exhibit the alterations in cell size and ubiquitin ligases seen after undernourished states of control cells. Myotubes differentiated from L6 cells also showed elevated expression of MuRF-1 and atrogin-1 in response to undernutrition.

SIGNIFICANCE

These results suggest that DJ-1 protein may contribute to undernutrition-induced atrophy via MAPKs/ubiquitin ligase pathway in skeletal muscle cells.