Matrine improves skeletal muscle atrophy by inhibiting E3 ubiquitin ligases and activating the Akt/mTOR/FoxO3α signaling pathway in C2C12 myotubes and mice

Involvement of ionomic metabolism of both the cerebrospinal fluid and the spinal cord in the analgesic efficacy of matrine in rats

CONTEXT

Matrine has antinociceptive properties, and spinal cord ionomic changes are involved in bone cancer pain.

OBJECTIVE

To investigate the relationship between ionomic metabolism in cerebrospinal fluid (CSF) and spinal cord and matrine's analgesic efficacy.

MATERIALS AND METHODS

The antinociceptive effects of matrine were identified in rats via intraperitoneal (i.p.) injection using the tail-immersion and formalin tests. Pharmacodynamic parameters for matrine against formalin-induced pain were calculated with nonlinear regression analysis. Inductively coupled plasma mass spectrometry (ICP-MS) technology was utilized to detect contents of the ionome in CSF and spinal cord. Variations in ionomic metabolism in different treated groups were examined using Pearson's correlation coefficients and principal component analysis (PCA).

RESULTS

In the tail-immersion test, matrine significantly prolonged tail-flick latency in rats. Matrine also dose-dependently yielded analgesia against formalin-induced biphasic pain, with an onset at around 10 min post-injection and a duration of 100 min. The ED50 and Emax values were 19.01 mg/kg and 71.86% for phase I and 40.30 mg/kg and 81.51% for phase II, respectively. Pearson's correlation coefficient study and PCA revealed significant reprogramming of ionomic metabolism in the CSF and the spinal cord in the NM (normal saline + matrine), NF (normal saline + formalin), and FM (formalin + matrine) groups, compared to the NN (normal saline + normal saline) group.

DISCUSSION AND CONCLUSIONS

These findings broaden the known analgesic spectrum of matrine and provide novel insights into the involvement of ionomic metabolism in its analgesic efficacy.

XLOC_015548 Mitigates Skeletal Muscle Atrophy via the Gadd45g/MEK/ERK Pathway and Redox Regulation

BACKGROUND

Skeletal muscle atrophy is a common musculoskeletal disorder that significantly reduces patient quality of life. Long non-coding RNA (lncRNA) XLOC_015548 has been identified as a pivotal regulator of C2C12 myoblast proliferation and differentiation. However, its role in mitigating denervation-induced muscle atrophy and the underlying mechanisms remain unclear.

METHODS

We employed lentiviral-mediated stable expression of XLOC_015548 in C2C12 myoblasts and skeletal muscle-specific XLOC_015548-edited mouse models to investigate the function of this lncRNA. Muscle atrophy models were established in vitro by glucocorticoid-induced atrophy with dexamethasone (DEX) and in vivo by sciatic nerve transection-induced denervation. The MEK inhibitor U0126 was used to assess the role of the growth arrest and DNA damage-inducible 45 gamma/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (Gadd45g/MEK/ERK) signaling pathway.

RESULTS

Overexpression of XLOC_015548 significantly activated the MEK/ERK signaling pathway (p < 0.05) by downregulating Gadd45g expression (p < 0.05) and promoting its cytoplasmic localization, thereby enhancing cell proliferation and myotube formation. Furthermore, XLOC_015548 reduced the level of reactive oxygen species (ROS) (p < 0.01), stabilized the mitochondrial membrane potential, and alleviated DEX-induced oxidative stress. These protective effects were partially reversed by U0126, confirming the involvement of the MEK/ERK pathway. Skeletal muscle-specific overexpression of XLOC_015548 in vivo significantly reduced denervation-induced muscle atrophy (q < 0.05) and increased the muscle fiber cross-sectional area.

CONCLUSION

XLOC_015548 plays a critical role in promoting myogenic differentiation and protecting against muscle atrophy by regulating Gadd45g expression, activating the MEK/ERK signaling pathway, and reducing oxidative stress. These findings underscore the therapeutic potential of XLOC_015548 in skeletal muscle atrophy, and provide a foundation for lncRNA-based treatment strategies.

The Molecular Mechanisms and Treatment of Cancer-Related Cachexia

Cancer cachexia is a multifactorial syndrome characterized by persistent skeletal muscle loss, with or without fat loss, which cannot be completely reversed by traditional nutritional support and leads to impaired organ function. Cachexia seriously reduces the quality of life of (QOL) patients, affects the therapeutic effect against cancers, increases the incidence of complications, and is an important cause of death for patients with advanced cancers. To date, no effective medical intervention has completely reversed cachexia, and no medication has been agreed upon. Here, we describe recent advances in the diagnosis, molecular mechanism and treatment of cancer-related cachexia.

Irisin alters D-galactose-induced apoptosis by increasing caveolin-1 expression in C2C12 myoblasts and skeletal muscle fibroblasts

Muscle atrophy and skeletal muscle fibrosis are significant pathological manifestations of primary sarcopenia. The regulation of C2C12 myoblast and skeletal muscle fibroblast apoptosis is associated with these pathological changes. Previous studies have indicated that irisin, the cleaved form of fibronectin type III domain-containing protein 5 (FNDC5), can alleviate primary sarcopenia. However, the mechanisms of the effect of irisin in age-related apoptosis remain unknown. Our present research aimed to explore the effect of irisin and the underlying mechanism of D-galactose (D-gal)-induced apoptosis in skeletal muscle fibroblasts and C2C12 myoblasts. We found the opposite effects of D-gal on C2C12 myoblasts and fibroblasts. We also found that irisin suppressed C2C12 cell apoptosis and promoted fibroblast apoptosis. Mechanistically, irisin altered D-gal-induced apoptosis by increasing caveolin-1 expression. Taken together, these findings further demonstrated that irisin is a potential agent that can treat aged-relative muscle atrophy and fibrosis.

EIF4A3-Induced Circular RNA CircDdb1 Promotes Muscle Atrophy through Encoding a Novel Protein CircDdb1-867aa

Little is known about if and how circular RNAs (circRNAs) are involved in skeletal muscle atrophy. Here a conserved circular RNA Damage-specific DNA binding protein 1 (circDdb1), derived from the host gene encoding Damage-specific DNA binding protein 1 (DDB1), as a mechanism of muscle atrophy is identified. circDdb1 expression is markedly increased in a variety of muscle atrophy types in vivo and in vitro, and human aging muscle. Both in vivo and in vitro, ectopic expression of circDdb1 causes muscle atrophy. In contrast, multiple forms of muscle atrophy caused by dexamethasone, tumor necrosis factor-alpha (TNF-α), or angiotensin II (Ang II) in myotube cells, as well as by denervation, angiotensin II, and immobility in mice, are prevented by circDdb1 inhibition. Eukaryotic initiation factor 4A3 (EIF4A3) is identified as a regulator of circDdb1 expression in muscle atrophy, whereas circDdb1 encodes a novel protein, circDdb1-867aa. circDdb1-867aa binds with and increases the phosphorylation level of eukaryotic elongation factor 2 (eEF2) at Thr56 to reduce protein translation and promote muscle atrophy. In summary, these findings establish circDdb1 as a shared regulator of muscle atrophy across multiple diseases and a potential therapeutic target.

Amelioration of Cancer Cachexia by Dalbergia odorifera Extract Through AKT Signaling Pathway Regulation

Background/Objectives: Cancer cachexia is a multifactorial syndrome characterized by the progressive loss of skeletal muscle mass and adipose tissue. Dalbergia odorifer is widely used in traditional medicine in Korea and China to treat various diseases. However, its exact role and underlying mechanism in regulating cancer cachexia have not been elucidated yet. This research was conducted to investigate the effect of D. odorifer extract (DOE) in preventing the development of cancer-induced cachexia symptoms and figure out the relevant mechanisms. Methods: A cancer cachexia model was established in Balb/c mice using the CT26 colon carcinoma cell line. To evaluate the anti-cachexia effect of Dalbergia odorifer extract (DOE), CT26-bearing mice were orally administered with DOE at concentrations of 50 and 100 mg/kg BW for 14 days. C2C12 myotubes and 3T3L1 adipocytes were treated with 80% CT26 conditioned medium, DOE, and wortmannin, a particular AKT inhibitor to determine the influence of DOE in the AKT signaling pathway. Mice body weight, food intake, myofiber cross-sectional area, adipocyte size, myotube diameter, lipid accumulation, and relevant gene expression were analyzed. Results: The oral administration of DOE at doses of 50 and 100 mg/kg body weight to CT26 tumor-bearing mice resulted in a significant reduction in body weight loss, an increase in food intake, and a decrease in serum glycerol levels. Furthermore, DOE treatment led to an increase in muscle mass, larger muscle fiber diameter, and elevated expression levels of MyH2 and Igf1, while simultaneously reducing the expression of Atrogin1 and MuRF1. DOE also attenuated adipose tissue wasting, as evidenced by increased epididymal fat mass, enlarged adipocyte size, and upregulated Pparγ expression, alongside a reduction in Ucp1 and IL6 levels. In cachectic C2C12 myotubes and 3T3-L1 adipocytes induced by the CT26 conditioned medium, DOE significantly inhibited muscle wasting and lipolysis by activating the AKT signaling pathway. The treatment of wortmannin, a specific AKT inhibitor, effectively neutralized DOE's impact on the AKT pathway, myotube diameter, and lipid accumulation. Conclusions: DOE ameliorates cancer cachexia through the expression of genes involved in protein synthesis and lipogenesis, while suppressing those related to protein degradation, suggesting its potential as a plant-derived therapeutic agent in combating cancer cachexia.

Targeting MuRF1 to Combat Skeletal Muscle Wasting in Cardiac Cachexia: Mechanisms and Therapeutic Prospects

Cardiac cachexia, the terminal stage of chronic heart failure, is characterized by severe systemic metabolic imbalances and significant weight loss, primarily resulting from skeletal muscle mass depletion. Despite the detrimental consequences, there is no standardized and clinically-approved intervention currently available for cardiac cachexia. In the context of cardiac cachexia, accelerated protein turnover, that is, inhibited protein synthesis and enhanced protein degradation, plays a crucial role in skeletal muscle wasting. This process is primarily mediated by various proteins encoded by atrogenes. Among them, the atrogene Trim63 (tripartite motif family 63) and its encoded protein MuRF1 have been extensively studied. This review article aims to elucidate the pathogenic mechanisms underlying skeletal muscle wasting in cardiac cachexia, describe the biochemical characteristics of MuRF1, and provide an overview of the investigation into MuRF1-targeting inhibitors. The ultimate goal is to offer novel strategies for the clinical treatment for skeletal muscle wasting associated with cardiac cachexia.

Photobiomodulation therapy moderates cancer cachexia-associated muscle wasting through activating PI3K/AKT/FoxO3a pathway

Cancer cachexia-associated muscle wasting as a multifactorial wasting syndrome, is an important factor affecting the long-term survival rate of tumor patients. Photobiomodulation therapy (PBMT) has emerged as a promising tool to cure and prevent many diseases. However, the effect of PBMT on skeletal muscle atrophy during cancer progression has not been fully demonstrated yet. Here, we found PBMT alleviated the atrophy of myotube diameter induced by cancer cells in vitro, and prevented cancer-associated muscle atrophy in mice bearing tumor. Mechanistically, the alleviation of muscle wasting by PBMT was found to be involved in inhibiting E3 ubiquitin ligases MAFbx and MuRF-1. In addition, transcriptomic analysis using RNA-seq and GSEA revealed that PI3K/AKT pathway might be involved in PBMT-prevented muscle cachexia. Next, we showed the protective effect of PBMT against muscle cachexia was totally blocked by AKT inhibitor in vitro and in vivo. Moreover, PBMT-activated AKT promoted FoxO3a phosphorylation and thus inhibiting the nucleus entry of FoxO3a. Lastly, in cisplatin-treated muscle cachexia model, PBMT had also been shown to ameliorate muscle atrophy through enhancing PI3K/AKT pathway to suppress MAFbx and MuRF-1 expression. These novel findings revealed that PBMT could be a promising therapeutic approach in treating muscle cachexia induced by cancer.

Jianpi Decoction Combined with Medroxyprogesterone Acetate Alleviates Cancer Cachexia and Prevents Muscle Atrophy by Directly Inhibiting E3 Ubiquitin Ligase

OBJECTIVE

To provide comprehensive evidence for the anti-cancer cachexia effect of Jianpi Decoction (JP) and to explore its mechanism of anti-cancer cachexia.

METHODS

A mouse model of colon cancer (CT26)-induced cancer cachexia (CC) was used to investigate the anti-CC effect of JP combined with medroxyprogesterone acetate (MPA). Thirty-six mice were equally divided into 6 groups: normal control, CC, MPA (100 mg•kg-1•d-1), MPA + low-dose (20 mg•kg-1•d-1) JP (L-JP), MPA + medium-dose (30 mg•kg-1•d-1) JP (M-JP), and MPA + high-dose (40 mg•kg-1•d-1) JP (H-JP) groups. After successful modeling, the mice were administered by gavage for 11 d. The body weight and tumor volume were measured and recorded every 2 d starting on the 8th day after implantation. The liver, heart, spleen, lung, kidney, tumor and gastrocnemius muscle of mice were collected and weighed. The pathological changes of the tumor was observed, and the cross-sectional area of the gastrocnemius muscle was calculated. The protein expressions of STAT3 and E3 ubiquitinase in the gastrocnemius muscle were measured by Western blot. In addition, an in vitro C2C12 myotube formation model was established to investigate the role of JP in hindering dexamethasone-induced muscle atrophy. In vitro experiments were divided into control, model, and JP serum groups. After 2-d administration, microscopic photographs were taken and myotube diameters were calculated. Western blot was performed to measure the protein expressions of STAT3 and E3 ubiquitinase.

RESULTS

JP combined with MPA restored tumor-induced weight loss (P<0.05, vs. CC) and muscle fiber size (P<0.01, vs. CC). Mechanistically, JP reduced the expression of atrophy-related proteins MuRF1 and MAFbx in tumor-induced muscle atrophy in vivo (P<0.05, vs. CC). In addition, JP reduced the expression of atrophy-related proteins MuRF1 and MAFbx and p-STAT3 phosphorylation (P<0.05 or P<0.01 vs. model group) in C2C12 myotubes treated with dexamethasone in vitro.

CONCLUSIONS

Administration of JP combined with MPA restores tumor-induced cachexia conditions. In addition, the profound effect of JP combined with MPA on tumor-induced cachexia may be due to its inhibition of muscle proteolysis (E3 ubiquitinase system).

Pharmacological Activity of Matrine in Inhibiting Colon Cancer Cells VM Formation, Proliferation, and Invasion by Downregulating Claudin-9 Mediated EMT Process and MAPK Signaling Pathway

Purpose

Matrine (Mat), the main active ingredient of traditional Chinese herbal plant Sophora flavescens Ait, has significant antitumor effects, but its pharmacological mechanism on colon cancer (CC) remains unclear. This study aimed to investigate the therapeutic effect of Mat on CC as well as the potential mechanism.

Methods

The vasculogenic mimicry (VM) of CC cells was observed by three-dimensional (3D) Matrigel cell culture. Cell proliferation, apoptosis, migration, invasion, and actin filament integrity were detected by CCK8, flow cytometry, wound healing, Transwell and Phalloidin staining assays. qRT-PCR and Western blotting were applied to detect the expression of EMT factors. RNA-sequencing was conducted to screen differentially expressed genes (DEGs), and the GO and KEGG pathway enrichment analyses were performed. Then, the expression of the key MAPK pathway genes and the target gene Claudin-9 (Cldn9) were analyzed. RNA interference was used to silence Cldn9 expression, and the effects of Cldn9 silencing and simultaneous treatment with Mat on VM formation, proliferation, apoptosis, invasion, and migration were investigated. Finally, the expression of EMT factors and MAPK pathway key genes was detected.

Results

CT26 cells formed the most typical VM structure. Mat disrupted the VM of CT26 cells, significantly suppressed their proliferation, migration, invasion, actin filament integrity, induced apoptosis, and inhibited EMT process. RNA-sequencing revealed 163 upregulated genes and 333 downregulated genes in Mat-treated CT26 cells, and the DEGs were significantly enriched in cell adhesion molecules and MAPK signaling pathways. Further confirmed that Mat significantly inhibited the phosphorylation levels of JNK and ERK, and the target gene Cldn9 was significantly upregulated in human CC tissues. Silencing Cldn9 markedly inhibited the VM, proliferative activity, invasiveness, and actin filament integrity of CT26 cells, blocked the EMT process, and downregulated the phosphorylation of JNK and ERK, whereas Mat intervention further strengthened the above trends.

Conclusion

This study indicated that Mat may synergistically inhibit the EMT process and MAPK signaling pathway through downregulation Cldn9, thereby exerting pharmacological effects on inhibiting VM formation, proliferation, and invasion of CC cells.

Weight bearing training alleviates muscle atrophy and pyroptosis of middle-aged rats

Background

Age-related muscle atrophy and adipose accumulation begin to occur in young and middle-aged individuals, and exercise at an early age improves body composition. Pyroptosis may play an essential role in age-related low-grade inflammation. This study aimed to explore the alleviation of muscle atrophy by weight-bearing training with increasing age via inhibition of pyroptosis.

Methods

Ninety 8-month-old male SD rats were randomly divided into three groups: (1) normal baseline group (N group, n = 10), sacrificed after adaptive feeding; control group (C group, n = 40); and weight-bearing running group (R group, n = 40). Blood samples, adipose tissue (AT), and extensor digitorum longus (EDL) were collected after 8, 16, 24, and 32-weeks intervention.

Results

The body weight, muscle mass, fat mass, plasma lipid, AT wet weight, adipocyte cross-sectional area (CSA), and apoptosis rates of AT and EDL were increased, while the muscle mass, wet weight, and fiber CSA of EDL were decreased by aging, which were reversed by exercise. Weight-bearing training promoted protein synthesis in EDL, inhibited protein degradation in EDL, and expression of pyroptotic key proteins in EDL and AT in rats.

Conclusion

Weight-bearing training improves body composition and alleviates age-related muscle atrophy in rats, and its mechanism may be related to the inhibition of pyroptosis in the EDL and AT and the improvement of muscle protein metabolism.

CircRNAs Related to Breast Muscle Development and Their Interaction Regulatory Network in Gushi Chicken

Circular RNAs (circRNAs) play a significant regulatory role during skeletal muscle development. To identify circRNAs during postnatal skeletal muscle development in chickens, we constructed 12 cDNA libraries from breast muscle tissues of Chinese Gushi chickens at 6, 14, 22, and 30 weeks and performed RNA sequencing. In total, 2112 circRNAs were identified, and among them 79.92% were derived from exons. CircRNAs are distributed on all chromosomes of chickens, especially chromosomes 1-9 and Z. Bioinformatics analysis showed that each circRNA had an average of 38 miRNA binding sites, 61.32% of which have internal ribosomal entry site (IRES) elements. Furthermore, in total 543 differentially expressed circRNAs (DE-circRNAs) were identified. Functional enrichment analysis revealed that DE-circRNAs source genes are engaged in biological processes and muscle development-related pathways; for example, cell differentiation, sarcomere, and myofibril formation, mTOR signaling pathway, and TGF-β signaling pathway, etc. We also established a competitive endogenous RNA (ceRNA) regulatory network associated with skeletal muscle development. The results in this report indicate that circRNAs can mediate the development of chicken skeletal muscle by means of a complex ceRNA network among circRNAs, miRNAs, genes, and pathways. The findings of this study might help increase the number of known circRNAs in skeletal muscle tissue and offer a worthwhile resource to further investigate the function of circRNAs in chicken skeletal muscle development.

Identification of Body Size Determination Related Candidate Genes in Domestic Pig Using Genome-Wide Selection Signal Analysis

This study aimed to identify the genes related to the body size of pigs by conducting genome-wide selection analysis (GWSA). We performed a GWSA scan on 50 pigs belonging to four small-bodied pig populations (Diannan small-eared pig, Bama Xiang pig, Wuzhishan pig, and Jeju black pig from South Korea) and 124 large-bodied pigs. We used the genetic parameters of the pairwise fixation index (FST) and π ratio (case/control) to screen candidate genome regions and genes related to body size. The results revealed 47,339,509 high-quality SNPs obtained from 174 individuals, while 280 interacting candidate regions were obtained from the top 1% signal windows of both parameters, along with 187 genes (e.g., ADCK4, AMDHD2, ASPN, ASS1, and ATP6V0C). The results of the candidate gene (CG) annotation showed that a series of CGs (e.g., MSTN, LTBP4, PDPK1, PKMYT1, ASS1, and STAT6) was enriched into the gene ontology terms. Moreover, molecular pathways, such as the PI3K-Akt, HIF-1, and AMPK signaling pathways, were verified to be related to body development. Overall, we identified a series of key genes that may be closely related to the body size of pigs, further elucidating the heredity basis of body shape determination in pigs and providing a theoretical reference for molecular breeding.

Matrine Exerts Pharmacological Effects Through Multiple Signaling Pathways: A Comprehensive Review

As The main effective monomer of the traditional Chinese medicine Sophora flavescens Ait, matrine has a broad scope of pharmacological activities such as anti-tumor, anti-inflammatory, analgesic, anti-fibrotic, anti-viral, anti-arrhythmia, and improving immune function. These actions explain its therapeutic effects in various types of tumors, cardiopathy, encephalomyelitis, allergic asthma, rheumatoid arthritis (RA), osteoporosis, and central nervous system (CNS) inflammation. Evidence has shown that the mechanism responsible for the pharmacological actions of matrine may be via the activation or inhibition of certain key molecules in several cellular signaling pathways including the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR), transforming growth factor-β/mothers against decapentaplegic homolog (TGF-β/Smad), nuclear factor kappa B (NF-κB), Wnt (wingless/ integration 1)/β-catenin, mitogen-activated protein kinases (MAPKs), and Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathways. This review comprehensively summarizes recent studies on the pharmacological mechanisms of matrine to provide a theoretical basis for molecular targeted therapies and further development and utilization of matrine.

Genus Sophora: a comprehensive review on secondary chemical metabolites and their biological aspects from past achievements to future perspectives

Sophora is deemed as one of the most remarkable genera of Fabaceae, and the third largest family of flowering plants. The genus Sophora comprises approximately 52 species, 19 varieties, and 7 forms that are widely distributed in Asia and mildly in Africa. Sophora species are recognized to be substantial sources of broad spectrum biopertinent secondary metabolites namely flavonoids, isoflavonoids, chalcones, chromones, pterocarpans, coumarins, benzofuran derivatives, sterols, saponins (mainly triterpene glycosides), oligostilbenes, and mainly alkaloids. Meanwhile, extracts and isolated compounds from Sophora have been identified to possess several health-promising effects including anti-inflammatory, anti-arthritic, antiplatelets, antipyretic, anticancer, antiviral, antimicrobial, antioxidant, anti-osteoporosis, anti-ulcerative colitis, antidiabetic, anti-obesity, antidiarrheal, and insecticidal activities. Herein, the present review aims to provide comprehensive details about the phytochemicals and biological effects of Sophora species. The review spotlighted on the promising phytonutrients extracted from Sophora and their plethora of bioactivities. The review also clarifies the remaining gaps and thus qualifies and supplies a platform for further investigations of these compounds.

Skeletal Muscle Deconditioning in Breast Cancer Patients Undergoing Chemotherapy: Current Knowledge and Insights From Other Cancers

Breast cancer represents the most commonly diagnosed cancer while neoadjuvant and adjuvant chemotherapies are extensively used in order to reduce tumor development and improve disease-free survival. However, chemotherapy also leads to severe off-target side-effects resulting, together with the tumor itself, in major skeletal muscle deconditioning. This review first focuses on recent advances in both macroscopic changes and cellular mechanisms implicated in skeletal muscle deconditioning of breast cancer patients, particularly as a consequence of the chemotherapy treatment. To date, only six clinical studies used muscle biopsies in breast cancer patients and highlighted several important aspects of muscle deconditioning such as a decrease in muscle fibers cross-sectional area, a dysregulation of protein turnover balance and mitochondrial alterations. However, in comparison with the knowledge accumulated through decades of intensive research with many different animal and human models of muscle atrophy, more studies are necessary to obtain a comprehensive understanding of the cellular processes implicated in breast cancer-mediated muscle deconditioning. This understanding is indeed essential to ultimately lead to the implementation of efficient preventive strategies such as exercise, nutrition or pharmacological treatments. We therefore also discuss potential mechanisms implicated in muscle deconditioning by drawing a parallel with other cancer cachexia models of muscle wasting, both at the pre-clinical and clinical levels.

Nutraceuticals in the Prevention and Treatment of the Muscle Atrophy

Imbalance of protein homeostasis, with excessive protein degradation compared with protein synthesis, leads to the development of muscle atrophy resulting in a decrease in muscle mass and consequent muscle weakness and disability. Potential triggers of muscle atrophy include inflammation, malnutrition, aging, cancer, and an unhealthy lifestyle such as sedentariness and high fat diet. Nutraceuticals with preventive and therapeutic effects against muscle atrophy have recently received increasing attention since they are potentially more suitable for long-term use. The implementation of nutraceutical intervention might aid in the development and design of precision medicine strategies to reduce the burden of muscle atrophy. In this review, we will summarize the current knowledge on the importance of nutraceuticals in the prevention of skeletal muscle mass loss and recovery of muscle function. We also highlight the cellular and molecular mechanisms of these nutraceuticals and their possible pharmacological use, which is of great importance for the prevention and treatment of muscle atrophy.

Ubiquitin Ligases at the Heart of Skeletal Muscle Atrophy Control

Skeletal muscle loss is a detrimental side-effect of numerous chronic diseases that dramatically increases mortality and morbidity. The alteration of protein homeostasis is generally due to increased protein breakdown while, protein synthesis may also be down-regulated. The ubiquitin proteasome system (UPS) is a master regulator of skeletal muscle that impacts muscle contractile properties and metabolism through multiple levers like signaling pathways, contractile apparatus degradation, etc. Among the different actors of the UPS, the E3 ubiquitin ligases specifically target key proteins for either degradation or activity modulation, thus controlling both pro-anabolic or pro-catabolic factors. The atrogenes MuRF1/TRIM63 and MAFbx/Atrogin-1 encode for key E3 ligases that target contractile proteins and key actors of protein synthesis respectively. However, several other E3 ligases are involved upstream in the atrophy program, from signal transduction control to modulation of energy balance. Controlling E3 ligases activity is thus a tempting approach for preserving muscle mass. While indirect modulation of E3 ligases may prove beneficial in some situations of muscle atrophy, some drugs directly inhibiting their activity have started to appear. This review summarizes the main signaling pathways involved in muscle atrophy and the E3 ligases implicated, but also the molecules potentially usable for future therapies.

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.

Emerging Role for Linear and Circular Spermine Oxidase RNAs in Skeletal Muscle Physiopathology

Skeletal muscle atrophy is a pathological condition so far without effective treatment and poorly understood at a molecular level. Emerging evidence suggest a key role for circular RNAs (circRNA) during myogenesis and their deregulation has been reported to be associated with muscle diseases. Spermine oxidase (SMOX), a polyamine catabolic enzyme plays a critical role in muscle differentiation and the existence of a circRNA arising from SMOX gene has been recently identified. In this study, we evaluated the expression profile of circular and linear SMOX in both C2C12 differentiation and dexamethasone-induced myotubes atrophy. To validate our findings in vivo their expression levels were also tested in two murine models of amyotrophic lateral sclerosis: SOD1G93A and hFUS+/+, characterized by progressive muscle atrophy. During C2C12 differentiation, linear and circular SMOX show the same trend of expression. Interestingly, in atrophy circSMOX levels significantly increased compared to the physiological state, in both in vitro and in vivo models. Our study demonstrates that SMOX represents a new player in muscle physiopathology and provides a scientific basis for further investigation on circSMOX RNA as a possible new therapeutic target for the treatment of muscle atrophy.

Emerging Strategies Targeting Catabolic Muscle Stress Relief

Skeletal muscle wasting represents a common trait in many conditions, including aging, cancer, heart failure, immobilization, and critical illness. Loss of muscle mass leads to impaired functional mobility and severely impedes the quality of life. At present, exercise training remains the only proven treatment for muscle atrophy, yet many patients are too ill, frail, bedridden, or neurologically impaired to perform physical exertion. The development of novel therapeutic strategies that can be applied to an in vivo context and attenuate secondary myopathies represents an unmet medical need. This review discusses recent progress in understanding the molecular pathways involved in regulating skeletal muscle wasting with a focus on pro-catabolic factors, in particular, the ubiquitin-proteasome system and its activating muscle-specific E3 ligase RING-finger protein 1 (MuRF1). Mechanistic progress has provided the opportunity to design experimental therapeutic concepts that may affect the ubiquitin-proteasome system and prevent subsequent muscle wasting, with novel advances made in regards to nutritional supplements, nuclear factor kappa-light-chain-enhancer of activated B cells (NFB) inhibitors, myostatin antibodies, β2 adrenergic agonists, and small-molecules interfering with MuRF1, which all emerge as a novel in vivo treatment strategies for muscle wasting.

Matrine: A Promising Natural Product With Various Pharmacological Activities

Matrine is an alkaloid isolated from the traditional Chinese medicine Sophora flavescens Aiton. At present, a large number of studies have proved that matrine has an anticancer effect can inhibit cancer cell proliferation, arrest cell cycle, induce apoptosis, and inhibit cancer cell metastasis. It also has the effect of reversing anticancer drug resistance and reducing the toxicity of anticancer drugs. In addition, studies have reported that matrine has a therapeutic effect on Alzheimer's syndrome, encephalomyelitis, asthma, myocardial ischemia, rheumatoid arthritis, osteoporosis, and the like, and its mechanism is mainly related to the inhibition of inflammatory response and apoptosis. Its treatable disease spectrum spans multiple systems such as the nervous system, circulatory system, and immune system. The antidisease effect and mechanism of matrine are diverse, so it has high research value. This review summarizes recent studies on the pharmacological mechanism of matrine, with a view to providing reference for subsequent research.

Preventive Effects of Schisandrin A, A Bioactive Component of Schisandra chinensis, on Dexamethasone-Induced Muscle Atrophy

Muscle wasting is caused by various factors, such as aging, cancer, diabetes, and chronic kidney disease, and significantly decreases the quality of life. However, therapeutic interventions for muscle atrophy have not yet been well-developed. In this study, we investigated the effects of schisandrin A (SNA), a component extracted from the fruits of Schisandra chinensis, on dexamethasone (DEX)-induced muscle atrophy in mice and studied the underlying mechanisms. DEX+SNA-treated mice had significantly increased grip strength, muscle weight, and muscle fiber size compared with DEX+vehicle-treated mice. In addition, SNA treatment significantly reduced the expression of muscle degradation factors such as myostatin, MAFbx (atrogin1), and muscle RING-finger protein-1 (MuRF1) and enhanced the expression of myosin heavy chain (MyHC) compared to the vehicle. In vitro studies using differentiated C2C12 myotubes also showed that SNA treatment decreased the expression of muscle degradation factors induced by dexamethasone and increased protein synthesis and expression of MyHCs by regulation of Akt/FoxO and Akt/70S6K pathways, respectively. These results suggest that SNA reduces protein degradation and increases protein synthesis in the muscle, contributing to the amelioration of dexamethasone-induced muscle atrophy and may be a potential candidate for the prevention and treatment of muscle atrophy.