Expression Of Atrophy-related Genes Research Articles

Circulating myomiRNAs as biomarkers in patients with Cushing’s syndrome

PurposeImpairment of skeletal muscle mass and strength affects 40–70% of patients with active Cushing’s syndrome (CS). Glucocorticoid excess sustains muscle atrophy and weakness, while muscle-specific microRNAs (myomiRs) level changes were associated with muscle organization and function perturbation. The aim of the current study is to explore changes in circulating myomiRs in CS patients compared to healthy controls and their involvement in IGFI/PI3K/Akt/mTOR pathway regulation in skeletal muscle.MethodsC2C12, mouse myocytes, were exposed to hydrocortisone (HC), and atrophy-related gene expression was investigated by RT-qPCR, WB and IF to assess HC-mediated atrophic signalling. miRNAs were evaluated in HC-treated C2C12 by PCR Arrays. MyomiRs significantly overexpressed in C2C12 were investigated in 37 CS patients and 24 healthy controls serum by RT-qPCR. The anti-anabolic role of circulating miRNAs significantly upregulated in CS patients was explored in C2C12 by investigating the IGFI/PI3K/Akt/mTOR pathway regulation.ResultsHC induced higher expression of atrophy-related genes, miR-133a-3p, miR-122-5p and miR-200b-3p in C2C12 compared to untreated cells. Conversely, the anabolic IGFI/PI3K/Akt/mTOR signalling was reduced and this effect was mediated by miR-133a-3p. In CS patients miR-133a-3p and miR-200b-3p revealed higher circulating levels (p < 0.0001, respectively) compared to controls. ROC curves for miR-133a-3p (AUC 0.823, p < 0.0001) and miR-200b-3p (AUC 0.850, p < 0.0001) demonstrated that both myomiRs represent potential biomarkers to discriminate between CS and healthy subjects. Pearson’s correlation analysis revealed that circulating levels of miR-133a-3p are directly correlated with 24 h urinary-free cortisol level (r = 0.468, p = 0.004) in CS patients.ConclusionsHC induces atrophic signals by miR-133a-3p overexpression in mouse myocytes and humans. Circulating miR-133a-3p is promising biomarkers of hypercortisolism.

The role of circulatory chemokines in sepsis-induced myopathy in mice

BACKGROUND: Sepsis is a condition of life-threatening organ dysfunction caused by a dysregulated host response to infection and carries a high risk of mortality. A rapidly growing number of “sepsis survivors” experience persistent and severe skeletal muscle weakness and atrophy (i.e., sepsis-induced myopathy). The myopathy is triggered by the interaction of circulating pathogens, inflammatory factors (e.g., cytokines and chemokines), and myofibers. Currently, there are no treatments for sepsis-induced myopathy partially due to a lack of therapeutic targets. Chemokines are peptides that possess chemo attractant properties and are released by immune cells during infection insult. Circulating levels of chemokines in septic patients are known to be high. However, the role these chemokines play in context of sepsis-induced myopathy is currently unknown. Our goal in this study was to identify the role of circulating chemokines on sepsis-induced myopathy. METHODS: We induced sepsis via cecal ligation and puncture (CLP) or sham control surgeries in a group of young adults (5 mo) male C57BL6 mice. Seven days after surgery, serum was collected from sham and CLP mice. The serum samples were pooled for cell culture experiments. In a subset of healthy mice, we isolated primary myoblasts. The myoblasts were co-cultured in conditioned media containing pooled serum samples collected from sham and CLP mice. We performed a multiplex assay to identify the levels of chemokines on the pooled serum samples. We measured myoblast proliferation, myotube area, and fusion index. In follow-up experiments, we exposed C2C12 myotubes to a selected group of chemokine peptides previously identified in serum samples. RESULTS: Exposure to septic serum attenuated the proliferative capacity of healthy myoblasts by 46% (p &lt; 0.05). In addition, myoblasts exposed to septic serum did not differentiate into healthy myotubes. Multiplex analyses of pooled sham and septic serum revealed a marked elevation of the following chemokines: CXCL-1 (healthy = 173.4 ± 0.1, septic = 69,630 ± 13,732 pg/ml), CXCL-2 (healthy = 1,078 ± 0.1, septic = 3,907 ± 259 pg/ml), CXCL-10 (healthy = 366 ± 0.1, septic = 3,961 ± 293 pg/ml), CCL-2 (healthy = 276 ± 0.1, septic = 1672 ± 362 pg/ml). Exposure of mature C2C12 myotubes to the chemokine peptides for 24 h increased the mRNA expression of atrophy-related genes ( FOXO1, GABARAP, BNIP3, TRIM63, MAP11A3B, FOXO32, FOXO30). CONCLUSION: Circulating chemokines play a regulatory role in sepsis-induced myopathy via attenuation of the proliferative capacity of myoblasts and by altering myotube morphology and the expression of atrophy related genes. Chemokines are potential therapeutic targets to treat sepsis-induced myopathy. Funded by NIH R21AG072011-03 to OL This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The effect of metformin along with high-intensity interval training on gene expression of FoxO1 and Atrogin-1 in type 2 diabetic mice

Background and aims: Muscle atrophy is a complication of type 2 diabetes, in which the expression of atrophy-related genes is increased. The present study aimed to investigate the effect of high-intensity interval training (HIIT) and metformin on gene expression of two atrophy-related genes (i.e., FoxO1 and Atrogin-1) in the skeletal muscle of diabetic mice. Methods: A total of 30 mice (C57BL/6) were assigned to two groups: control (n=6), and high-fat diet (HFD) (n=24). The mice in the HFD group were fed a HDF for 16 weeks. Then, diabetes was induced in mice by HFD. Then, they were divided into 4 groups as follows: (i) diabetic control, (ii) diabetes + metformin (DM), (iii) diabetes + HIIT (DH), and (iv) diabetes + metformin + HIIT (DMH). The DM group took metformin, the HIIT group performed a HIIT program, and the DMH group had both HIIT and metformin. The real-time PCR methods were used to measure the mRNA expression of FoxO1 and Atrogin-1. Results: The findings showed that HFD-induced diabetes caused increases in the expression of FoxO1 (P=0.0006) and Atrogin-1 (P=0.0008), and HIIT could restrain these increments (P=0.086, P=0.041). However, the decreasing effect of metformin on the expression of these genes was not significant (P=0.15) and the combined effect of HIIT and metformin on the expression of these genes was not greater than the individual effect of HIIT (P=0.64). Conclusion: These results indicated that HIIT (but not metformin) may prevent type 2 diabetes-induced downregulation of FoxO1 and Atrogin-1 in skeletal muscle, and metformin could not affect the impact of the training on these atrophy-related genes.

Low-Carbohydrate Diet Modulates Glucose–Lipid Utilization in Skeletal Muscle of Diabetic Mice

Type 2 diabetes is associated with many complications, including skeletal muscle atrophy. Ketogenic diets and low-carbohydrate diets (LCD) have recently been introduced as dietary interventions in patients with diabetes, but their effects on glucose and lipid metabolism in skeletal muscle have not been studied. In the current study, we compared the effects of LCD and ketogenic diet on glucose and lipid metabolism in skeletal muscle of diabetic mice. C57BL/6J mice with type 2 diabetes, constructed by a high-fat diet combined with streptozotocin, were fed a standard diet, a high-fat diet, an LCD, or a ketogenic diet for 14 weeks, respectively. Here, we found that the LCD, rather than the ketogenic diet, retained skeletal muscle weight and suppressed the expression of atrophy-related genes in diabetic mice. In addition, the LCD had more glycolytic/type IIb myofiber content and inhibited forkhead box O1 and pyruvate dehydrogenase kinase 4 expression, leading to improved glucose utilization. However, the ketogenic diet maintained more oxidative/type I myofibers. Moreover, compared with the ketogenic diet, the LCD decreased intramuscular triglycerides content and muscle lipolysis, suggesting improvement in lipid metabolism. Taken together, these data suggested that the LCD improved glucose utilization, and inhibited lipolysis and atrophy in skeletal muscle of diabetic mice, while the ketogenic diet showed metabolic disorders in skeletal muscle.

Effect of Long-Term Supplementation with Acetic Acid on the Skeletal Muscle of Aging Sprague Dawley Rats

Mitochondrial function in skeletal muscle, which plays an essential role in oxidative capacity and physical activity, declines with aging. Acetic acid activates AMP-activated protein kinase (AMPK), which plays a key role in the regulation of whole-body energy by phosphorylating key metabolic enzymes in both biosynthetic and oxidative pathways and stimulates gene expression associated with slow-twitch fibers and mitochondria in skeletal muscle cells. In this study, we investigate whether long-term supplementation with acetic acid improves age-related changes in the skeletal muscle of aging rats in association with the activation of AMPK. Male Sprague Dawley (SD) rats were administered acetic acid orally from 37 to 56 weeks of age. Long-term supplementation with acetic acid decreased the expression of atrophy-related genes, such as atrogin-1, muscle RING-finger protein-1 (MuRF1), and transforming growth factor beta (TGF-β), activated AMPK, and affected the proliferation of mitochondria and type I fiber-related molecules in muscles. The findings suggest that acetic acid exhibits an anti-aging function in the skeletal muscles of aging rats.

VDR regulates simulated microgravity-induced atrophy in C2C12 myotubes

Muscle wasting is a major problem leading to reduced quality of life and higher risks of mortality and various diseases. Muscle atrophy is caused by multiple conditions in which protein degradation exceeds its synthesis, including disuse, malnutrition, and microgravity. While Vitamin D receptor (VDR) is well known to regulate calcium and phosphate metabolism to maintain bone, recent studies have shown that VDR also plays roles in skeletal muscle development and homeostasis. Moreover, its expression is upregulated in muscle undergoing atrophy as well as after muscle injury. Here we show that VDR regulates simulated microgravity-induced atrophy in C2C12 myotubes in vitro. After 8 h of microgravity simulated using 3D-clinorotation, the VDR-binding motif was associated with chromatin regions closed by the simulated microgravity and enhancer regions inactivated by it, which suggests VDR mediates repression of enhancers. In addition, VDR was induced and translocated into the nuclei in response to simulated microgravity. VDR-deficient C2C12 myotubes showed resistance to simulated microgravity-induced atrophy and reduced induction of FBXO32, an atrophy-associated ubiquitin ligase. These results demonstrate that VDR contributes to the regulation of simulated microgravity-induced atrophy at least in part by controlling expression of atrophy-related genes.

Activating the Protein Synthesis Signaling by HIIT Concomitant with the Suppression of Protein Degradation in Wistar Rats’ Skeletal Muscle

Background: Muscle loss occurs in some conditions such as aging, sarcopenia, and cancer. The interaction between protein synthesis and degradation signaling components induced by high-intensity interval training (HIIT) is not well studied. Objectives: The purpose of the present study was to simultaneously examine the effect of eight-week HIIT on the gene expression of both signaling components. Methods: Sixteen male Wistar rats were randomly assigned to HIIT and non-exercise control groups. The HIIT group ran on a treadmill, five days/week for eight weeks, with 0º slope, including five interval sets of high and low intensity. Forty-eight hours after the last exercise session, dissected soleus muscles were stored at -80°C for later analyses. Results: The gene expression of Akt1, mTORC1, and S6K1 were increased in the HIIT group compared with the control group (All P ≤ 0.031) concomitant with the suppression of eIF4EBP1. The results of the S6K1 and eIF4EBP1 mRNA were also confirmed by the Western blotting. According to the inhibitory effect of Akt1, the gene expressions of FoxO3a and, consequently, MuRF1 and LC3A were significantly inhibited (All P ≤ 0.003). Western blot analysis did not confirm the LC3A protein expression, which may underline the role of LC3A in autophagy to promote cell survival. Conclusions: The intensities and durations of the exercise training protocol are sufficient to increase protein synthesis signaling components and especially inhibit the atrophy-related gene expression, which may lead to attenuating muscle loss and increasing muscle mass. Accordingly, it may be considered for rehabilitation and/or prevention of some conditions such as sarcopenia and cachexia.

Ovarian cancer ascites induces skeletal muscle wasting in vitro and reflects sarcopenia in patients.

BackgroundCachexia‐associated skeletal muscle wasting or ‘sarcopenia’ is highly prevalent in ovarian cancer and contributes to poor outcome. Drivers of cachexia‐associated sarcopenia in ovarian cancer remain elusive, underscoring the need for novel and better models to identify tumour factors inducing sarcopenia. We aimed to assess whether factors present in ascites of sarcopenic vs. non‐sarcopenic ovarian cancer patients differentially affect protein metabolism in skeletal muscle cells and to determine if these effects are correlated to cachexia‐related patient characteristics.MethodsFifteen patients with an ovarian mass and ascites underwent extensive physical screening focusing on cachexia‐related parameters. Based on computed tomography‐based body composition imaging, six cancer patients were classified as sarcopenic and six were not; three patients with a benign condition served as an additional non‐sarcopenic control group. Ascites was collected, and concentrations of cachexia‐associated factors were assessed by enzyme‐linked immunosorbent assay. Subsequently, ascites was used for in vitro exposure of C2C12 myotubes followed by measurements of protein synthesis and breakdown by radioactive isotope tracing, qPCR‐based analysis of atrophy‐related gene expression, and NF‐κB activity reporter assays.ResultsC2C12 protein synthesis was lower after exposure to ascites from sarcopenic patients (sarcopenia 3.1 ± 0.1 nmol/h/mg protein vs. non‐sarcopenia 5.5 ± 0.2 nmol/h/mg protein, P < 0.01), and protein breakdown rates tended to be higher (sarcopenia 31.2 ± 5.2% vs. non‐sarcopenia 20.9 ± 1.9%, P = 0.08). Ascites did not affect MuRF1, Atrogin‐1, or REDD1 expression of C2C12 myotubes, but NF‐κB activity was specifically increased in cells exposed to ascites from sarcopenic patients (sarcopenia 2.2 ± 0.4‐fold compared with control vs. non‐sarcopenia 1.2 ± 0.2‐fold compared with control, P = 0.01). Protein synthesis and breakdown correlated with NF‐κB activity (r s = −0.60, P = 0.03 and r s = 0.67, P = 0.01, respectively). The skeletal muscle index of the ascites donors was also correlated to both in vitro protein synthesis (r s = 0.70, P = 0.005) and protein breakdown rates (r s = −0.57, P = 0.04).ConclusionsAscites of sarcopenic ovarian cancer patients induces pronounced skeletal muscle protein metabolism changes in C2C12 cells that correlate with clinical muscle measures of the patient and that are characteristic of cachexia. The use of ascites offers a new experimental tool to study the impact of both tumour‐derived and systemic factors in various cachexia model systems, enabling identification of novel drivers of tissue wasting in ovarian cancer.

Emerging Treatment Options for Sarcopenia in Chronic Liver Disease.

Sarcopenia is characterized by a skeletal muscle disorder with progressive and generalized loss of muscle mass and function, and it increases the risk of adverse outcomes with considerable prevalence in patients with chronic liver disease. Sarcopenia in chronic liver disease underlies complicated and multifactorial mechanisms for pathogenesis, including alterations in protein turnover, hyperammonemia, energy disposal, hormonal changes, and chronic inflammation. The key contribution to sarcopenia in patients with chronic liver diseases can be the hyperammonemia-induced upregulation of myostatin, which causes muscle atrophy via the expression of atrophy-related genes. Several clinical studies on emerging treatment options for sarcopenia have been reported, but only a few have focused on patients with chronic liver diseases, with mostly nutritional and behavioral interventions being carried out. The inhibition of the myostatin-activin receptor signaling pathway and hormonal therapy might be the most promising therapeutic options in combination with an ammonia-lowering approach in sarcopenic patients with chronic liver diseases. This review focuses on current and emerging treatment options for sarcopenia in chronic liver diseases with underlying mechanisms to counteract this condition.

Plectin regulates Wnt signaling mediated-skeletal muscle development by interacting with Dishevelled-2 and antagonizing autophagy.

Skeletal muscle is the most abundant tissue in the human and animal body, loss of its function can lead to muscle aging and various myogenic diseases. The skeletal muscle development is a complex and tightly regulated process, which is driven by a variety of many factors, signaling pathways and regulatory mechanisms. Plectin (Plec), a cytolinker protein, is ubiquitously expressed in various tissues such as skin, muscle, plasma membrane, and most types of cells. Although known isoforms of Plec is well-characterized in muscle dystrophy, very little is known on the function of Plec in the skeletal muscle development. Here, we found that Plec plays a vital role in promoting C2C12 myoblasts differentiation and proliferation, but inhibits their apoptosis. Also, Plec regulates the expression of atrophy-related genes (atrogin-1 and muRF-1) to rescue muscle atrophy. Furthermore, we have demonstrated that Plec binds to Dishevelled-2 (Dvl-2) and forms a protein complex, which is then activate the canonical Wnt signaling. We also observed that Plec resists ubiquitination by stabilizing Dvl-2 and reduces the level of LC3-labeled Dvl-2 and antagonizes the autophagy system. In conclusion, our findings suggest that Plec regulates canonical Wnt signaling mediated skeletal development by stabilizing Dvl-2 and downregulating the cellular autophagic degradation system.

Isolation and Characterization of Compounds from Glycyrrhiza uralensis as Therapeutic Agents for the Muscle Disorders

Skeletal muscle is the most abundant tissue and constitutes about 40% of total body mass. Herein, we report that crude water extract (CWE) of G. uralensis enhanced myoblast proliferation and differentiation. Pretreatment of mice with the CWE of G. uralensis prior to cardiotoxin-induced muscle injury was found to enhance muscle regeneration by inducing myogenic gene expression and downregulating myostatin expression. Furthermore, this extract reduced nitrotyrosine protein levels and atrophy-related gene expression. Of the five different fractions of the CWE of G. uralensis obtained, the ethyl acetate (EtOAc) fraction more significantly enhanced myoblast proliferation and differentiation than the other fractions. Ten bioactive compounds were isolated from the EtOAc fraction and characterized by GC-MS and NMR. Of these compounds (4-hydroxybenzoic acid, liquiritigenin, (R)-(-)-vestitol, isoliquiritigenin, medicarpin, tetrahydroxymethoxychalcone, licochalcone B, liquiritin, liquiritinapioside, and ononin), liquiritigenin, tetrahydroxymethoxychalcone, and licochalcone B were found to enhance myoblast proliferation and differentiation, and myofiber diameters in injured muscles were wider with the liquiritigenin than the non-treated one. Computational analysis showed these compounds are non-toxic and possess good drug-likeness properties. These findings suggest that G. uralensis-extracted components might be useful therapeutic agents for the management of muscle-associated diseases.

Fibromodulin Modulates Chicken Skeletal Muscle Development via the Transforming Growth Factor-β Signaling Pathway.

Simple SummaryFibromodulin (Fmod) plays critical roles in skeletal muscle development and maintenance, but the roles of Fmod in skeletal muscle atrophy and development in chickens are unclear. Here, we demonstrate that Fmod plays important roles in the differentiation and atrophy of chicken skeletal muscle by regulating the transforming growth factor-β signaling pathway. These results suggest that Fmod plays important roles in skeletal muscle growth and development in chickens.Fibromodulin (Fmod), which is an extracellular matrix protein, belongs to the extracellular matrix small-leucine-rich proteoglycan family. Fmod is abundantly expressed in muscles and connective tissues and is involved in biological regulation processes, including cell apoptosis, cell adhesion, and modulation of cytokine activity. Fmod is the main regulator of myostatin, which controls the development of muscle cells, but its regulatory path is unknown. Chicken models are ideal for studying embryonic skeletal muscle development; therefore, to investigate the mechanism of Fmod in muscle development, Fmod-silenced and Fmod-overexpressed chicken myoblasts were constructed. The results showed that Fmod plays a positive role in differentiation by detecting the expression of myogenic differentiation markers, immunofluorescence of MyHC protein, and myotube formation in myoblasts. Fmod regulates expression of atrophy-related genes to alleviate muscle atrophy, which was confirmed by histological analysis of breast muscles in Fmod-modulated chicks in vivo. Additionally, genes differentially expressed between Fmod knockdown and normal myoblasts were enriched in the signaling pathway of transforming growth factor β (TGF-β). Both Fmod-silenced and Fmod-overexpressed myoblasts regulated the expression of TGFBR1 and p-Smad3. Thus, Fmod can promote differentiation but not proliferation of myoblasts by regulating the TGF-β signaling pathway, which may serve a function in muscular atrophy.

ISLR regulates skeletal muscle atrophy via IGF1-PI3K/Akt-Foxo signaling pathway.

Immunoglobulin superfamily containing leucine-rich repeat (Islr) contains an Ig-like domain, an LRR motif, and a transmembrane domain and is highly expressed in various chicken tissues. Although Islr has known roles in muscle regeneration, its role in the regulation of muscle atrophy has not been studied. In this study, we constructed Islr-silenced or Islr-overexpressed myoblasts to investigate its role during the differentiation of myoblasts into myotubes. The results showed that Islr was highly expressed in chicken skeletal muscle tissue and regulated myoblast differentiation, but not proliferation. Islr regulated the expression of atrophy-related genes including atrogin-1 and MuRF-1, and could rescue dexamethasone-induced atrophy in myoblasts and myotubes. Western blot analysis indicated that Islr participates in myoblast atrophy through IGF/PI3K/AKT-FOXO signaling. Meanwhile, the expression of caspase-8 and caspase-9 increased in Islr-silenced groups, indicating its role in cell viability. Taken together, these data suggested that Islr plays an important role in myoblasts differentiation, and which can alleviate skeletal muscle atrophy and prevents muscle cell apoptosis via IGF/PI3K/AKT-FOXO signaling pathway.

Myoferlin Regulates Wnt/β-Catenin Signaling-Mediated Skeletal Muscle Development by Stabilizing Dishevelled-2 Against Autophagy.

Myoferlin (MyoF), which is a calcium/phospholipid-binding protein expressed in cardiac and muscle tissues, belongs to the ferlin family. While MyoF promotes myoblast differentiation, the underlying mechanisms remain poorly understood. Here, we found that MyoF not only promotes C2C12 myoblast differentiation, but also inhibits muscle atrophy and autophagy. In the present study, we found that myoblasts fail to develop into mature myotubes due to defective differentiation in the absence of MyoF. Meanwhile, MyoF regulates the expression of atrophy-related genes (Atrogin-1 and MuRF1) to rescue muscle atrophy. Furthermore, MyoF interacts with Dishevelled-2 (Dvl-2) to activate canonical Wnt signaling. MyoF facilitates Dvl-2 ubiquitination resistance by reducing LC3-labeled Dvl-2 levels and antagonizing the autophagy system. In conclusion, we found that MyoF plays an important role in myoblast differentiation during skeletal muscle atrophy. At the molecular level, MyoF protects Dvl-2 against autophagy-mediated degradation, thus promoting activation of the Wnt/β-catenin signaling pathway. Together, our findings suggest that MyoF, through stabilizing Dvl-2 and preventing autophagy, regulates Wnt/β-catenin signaling-mediated skeletal muscle development.

4-Aminopyridine attenuates muscle atrophy after sciatic nerve crush injury in mice.

We recently demonstrated the beneficial effects of 4-aminopyridine (4-AP), a potassium channel blocker, in enhancing remyelination and recovery of nerve conduction velocity and motor function after sciatic nerve crush injury in mice. Although muscle atrophy occurs very rapidly after nerve injury, the effect of 4-AP on muscle atrophy and intrinsic muscle contractile function is largely unknown. Mice were assigned to sciatic nerve crush injury and no-injury groups and were followed for 3, 7, and 14 days with/without 4-AP or saline treatment. Morphological, functional, and transcriptional properties of skeletal muscle were assessed. In addition to improving in vivo function, 4-AP significantly reduced muscle atrophy with increased muscle fiber diameter and contractile force. Reduced muscle atrophy was associated with attenuated expression of atrophy-related genes and increased expression of proliferating stem cells. These findings provide new insights into the potential therapeutic benefits of 4-AP against nerve injury-induced muscle atrophy and dysfunction. Muscle Nerve 60: 192-201, 2019.

D-Methionine Ameliorates Cisplatin-Induced Muscle Atrophy via Inhibition of Muscle Degradation Pathway.

Cisplatin induces anorexia, weight loss, loss of adipose tissue, skeletal muscle atrophy, and serious adverse effects that can cause premature termination of chemotherapy. The aim of this study was to use an animal model to assess cisplatin therapy (3 cycles) with and without d-methionine to investigate its protective effects on cisplatin-induced anorexia and skeletal muscle wasting. Wistar rats were divided into 3 groups and treated as follows: saline as control (group 1), intraperitoneal cisplatin once a week for 3 weeks (group 2), and intraperitoneal cisplatin once a week for 3 weeks plus oral administration of d-methionine (group 3). Tissue somatic index (TSI), gastric emptying index (GEI), and feeding efficiency were measured. Both hepatic lipid metabolism and muscle atrophy-related gene expressions and C2C12 myotubes were determined by polymerase chain reaction. Micro–computed tomography (micro-CT) was used to conduct assessment of bone microarchitecture indices. Pathological changes of the gastric mucosa were assessed by hematoxylin and eosin staining after euthanizing the animals. d-Methionine increased food intake, weight gain, gastric emptying, and feeding efficiency, as well as decrease stomach contents, after cisplatin injections. Cisplatin caused shortening of myofibers. Cisplatin-induced muscle mass wasting was mediated by the elevation of mRNA expressions of MAFbx and MuRF-1 in ubiquitin ligases in muscle tissue homogenate. The mRNA expressions of MyoD and myogenin, markers of muscle differentiation, declined following cisplatin administration. The administration of d-methionine not only led to significant improvements in myofiber diameter and cross-sectional fiber areas but also reversed muscle atrophy-related gene expression. However, there were no significant changes in stomach histology or microarchitecture of trabecular bone among the study groups. The results indicate that d-methionine has an appetite-enhancing effect and ameliorates cisplatin-induced adipose and muscle tissue loss during cisplatin-based chemotherapy.

CARM1 contributes to skeletal muscle wasting by mediating FoxO3 activity and promoting myofiber autophagy

Coactivator-associated arginine methyltransferase 1 (CARM1) is involved in a variety of biological processes in different cell types and disease conditions, including myogenesis. However, the specific function of CARM1 in skeletal muscle wasting under pathologic conditions remains unclear. Here, we identify CARM1 as a novel participant in muscular atrophy. Increases in CARM1 protein levels correlated positively with the loss of muscle mass upon denervation in mice. Notably, the knockdown of CARM1 represses the progression of muscle wasting and the expression of the atrophy-related genes Atrogin-1 and MuRF1 in vivo and in vitro. With respect to the underlying mechanism, we show that CARM1 interacts with and asymmetrically dimethylates FoxO3 (a specific transcription factor that controls atrophy-related gene expression). This methylation modification by CARM1 is required for FoxO3-dependent transcription. Accordingly, a CARM1 methyltransferase inhibitor also restrains the expression of Atrogin-1 and MuRF1 and myotube atrophy. Furthermore, CARM1 knockdown induces a remarkable myofiber autophagic deficit during the atrophy process. Altogether, our study identifies a crucial regulator of skeletal muscle atrophy and suggests that CARM1 is a potential target for the prevention of muscle atrophy.

Concurrent treatment with ursolic acid and low-intensity treadmill exercise improves muscle atrophy and related outcomes in rats.

The objective of this study was to analyze the concurrent treatment effects of ursolic acid (UA) and low-intensity treadmill exercise and to confirm the effectiveness of UA as an exercise mimetic to safely improve muscle atrophy-related diseases using Sprague-Dawley (SD) rats with skeletal muscle atrophy. Significant muscle atrophy was induced in male SD rats through hind limb immobilization using casting for 10 days. The muscle atrophy-induced SD rats were group into four: SED, sedentary; UA, daily intraperitoneal UA injection, 5 mg/kg; EX, low-intensity (10–12 m/min, 0° grade) treadmill exercise; and UEX, daily intraperitoneal UA injection, 5 mg/kg, and low-intensity (10–12 m/min, 0° grade) treadmill exercise. After 8 weeks of treatment, endurance capacity was analyzed using a treadmill, and tissues were extracted for analysis of visceral fat mass, body weight, muscle mass, expression of muscle atrophy- and hypertrophy-related genes, and endurance capacity. Although the effects of body weight gain control, muscle mass increase, and endurance capacity improvement were inadequate in the UA group, significant results were confirmed in the UEX group. The UEX group had significantly reduced body weight and visceral fat, significantly improved mass of tibialis anterior and gastrocnemius muscles, and significantly decreased atrophy-related gene expression of MuRF1 and atrogin-1, but did not have significant change in hypertrophy-related gene expression of Akt and mTOR. The endurance capacity was significantly improved in the EX and UEX groups. These data suggest that concurrent treatment with low-intensity exercise and UA is effective for atrophy-related physical dysfunctions.

Long-term thermal manipulation in the late incubation period can inhibit breast muscle development by activating endoplasmic reticulum stress in duck (Anasplatyrhynchos domestica)

Poultry embryos are easily affected by environmental changings during incubation, thereinto, the temperature modification is the most important one, but the mechanism of temperature effects on bird eggs is not clear. By using RNA-seq, we have previously found that endoplasmic reticulum stress (ERS) may involve in regulating embryonic muscle development of duck under the influence of temperature alteration. To further clarify the role of ERS in the effect, in the present study, we detected the impact of increasing the incubation temperature by 1℃ during embryonic days 10–27 (E10-27) on the development of duck embryos, and investigated the changes in mRNA and protein expression of ERS marker genes and muscle-related genes under the thermal manipulation (TM). The results of relative weight comparison showed that only the relative weight of breast muscle was steadily decreased by TM from E10 to the first day after hatching (W0). Meanwhile, the real-time PCR and western-blot analysis revealed that raising the incubation temperature stimulated the expression of ERS marker genes in breast muscle at E20. The mRNA expressions of muscle hypertrophy and atrophy-related genes were also detected, and were not changed regularly, however, the protein expressions of hypertrophy-related genes were all decreased at both E20 and W0, and the protein expression of atrophy-related genes were up-regulated at E20. The protein expression of muscle proliferation-related genes were also decreased at E20. Additionally, these results were the same as that in the ERS positive control groups. Taken together, these results indicated that long-term TM during late embryonic period could block the development of duck breast muscle by inhibiting muscle hypertrophy and proliferation, and promoting muscle atrophy at a post-transcriptional level via the activation of ERS.

Glucocorticoids Induce Bone and Muscle Atrophy by Tissue-Specific Mechanisms Upstream of E3 Ubiquitin Ligases.

Glucocorticoid excess, either endogenous with diseases of the adrenal gland, stress, or aging or when administered for immunosuppression, induces bone and muscle loss, leading to osteopenia and sarcopenia. Muscle weakness increases the propensity for falling, which, combined with the lower bone mass, increases the fracture risk. The mechanisms underlying glucocorticoid-induced bone and muscle atrophy are not completely understood. We have demonstrated that the loss of bone and muscle mass, decreased bone formation, and reduced muscle strength, hallmarks of glucocorticoid excess, are accompanied by upregulation in both tissues in vivo of the atrophy-related genes atrogin1, MuRF1, and MUSA1. These are E3 ubiquitin ligases traditionally considered muscle-specific. Glucocorticoids also upregulated atrophy genes in cultured osteoblastic/osteocytic cells, in ex vivo bone organ cultures, and in muscle organ cultures and C2C12 myoblasts/myotubes. Furthermore, glucocorticoids markedly increased the expression of components of the Notch signaling pathway in muscle in vivo, ex vivo, and in vitro. In contrast, glucocorticoids did not increase Notch signaling in bone or bone cells. Moreover, the increased expression of atrophy-related genes in muscle, but not in bone, and the decreased myotube diameter induced by glucocorticoids were prevented by inhibiting Notch signaling. Thus, glucocorticoids activate different mechanisms in bone and muscle that upregulate atrophy-related genes. However, the role of these genes in the effects of glucocorticoids in bone is unknown. Nevertheless, these findings advance our knowledge of the mechanism of action of glucocorticoids in the musculoskeletal system and provide the basis for novel therapies to prevent glucocorticoid-induced atrophy of bone and muscle.