Muscle Protein Degradation Research Articles

GABA Prevents Sarcopenia by Regulation of Muscle Protein Degradation and Inflammaging in 23- to 25-Month-Old Female Mice.

Sarcopenia is the gradual decrease in skeletal muscle mass, strength and function in elderly individuals. Gamma-aminobutyric acid (GABA) is a neurotransmitter naturally produced from glutamate by the enzyme glutamic acid decarboxylase. Age-related decline in GABA is linked to age-related motor and sensory decline and seems to affect sarcopenia, yet no detailed study has been conducted. In this study, we aimed to investigate the effect of GABA on improving sarcopenia by suppressing muscle protein degradation through supplementing decreased GABA in old mice. GABA (10 or 30 mg/kg/day) was orally administered daily to young (3 months) and old (21-23 months) C57BL/6 mice for 7 weeks. The body weight and grip strength of the mice were measured weekly at the same time. After sacrificing the mice, the quadriceps and gastrocnemius muscles were excised from their hind limbs, and the spleen and serum were collected. Histological, biochemical and molecular analyses were conducted in various experiments. The administration of GABA increased muscle strength (+41%, +70% compared to the aged mouse control group, GABA at doses of 10 or 30 mg/kg/day respectively, p < 0.05) and muscle mass (quadriceps: +28%, +46%; gastrocnemius: +12%, +19%, p < 0.05) in old mice. This increase was accompanied by a cross-sectional area (CSA) increase in the quadriceps and gastrocnemius muscle (p < 0.05). The administration of GABA increased IGF-1 levels in serum (p < 0.05), leading to the activation of muscle protein synthesis. We found that GABA inhibits sarcopenia by regulating muscle protein degradation through the activation of Akt/mTOR/FoxO3a signalling pathways. GABA also regulates inflammaging, which is a hallmark of age-related muscle atrophy. There was a significant increase in the F4/80 + CD11b + total macrophage ratio in gastrocnemius and spleen, especially the M1 macrophage ratio increased in old mice. However, GABA administration was effective in suppressing M1 macrophages (gastrocnemius: -40%, - 53%; spleen: -22%, -26%, p < 0.05). Pro-inflammatory cytokines such as TNF-α and IL-6, primarily secreted by M1 macrophages, are also decreased by treatment with GABA (TNF-α: -24%, -27%; IL-6: -45%, -59%, p < 0.05). Together, this study demonstrates the importance of GABA in maintaining muscle and low-chronic inflammation during ageing. We suggest that GABA shows potential as a substance that can effectively address sarcopenia and enhance the overall lifespan and well-being of older individuals.

Aquo-ethanolic extract of Lilii Bulbus attenuates dexamethasone-induced muscle loss and enhances muscle strength in experimental mice

Traditionally, Lilium lancifolium bulb is known for its ability to nourish yin, nourish the lungs, clear the heart, soothe coughs, reduce irritability, and calm the mind. In Oriental Medicine, it is categorized as a tonic remedy for alleviating symptoms of fatigue and enhancing the strength of bones and muscles.In this study, we aimed to validate the effectiveness of the aquo-ethanolic extract of Lilli Bulbus (LBE) in a dexamethasone (DEX)-induced muscle atrophy model, both in vitro and in vivo, and elucidate its mechanism of action through muscle transcriptome analysis. The effects of LBE on the viability and myotube density of C2C12 myoblasts and differentiated C2C12 myotubes with and without DEX treatment were investigated. LBE pretreatment protected C2C12 myoblast cells and increased the muscle density of C2C12 myotubes in response to DEX. LBE showed potent free radical scavenging activities in cell-free biochemical assays as well as antioxidant activity in C2C12 myoblasts. LBE also exhibited protective effects in an experimental animal model of DEX-induced muscle atrophy, showing muscular function and motor coordination recovery. Transcriptomic analysis of three different muscle tissues from mice with DEX-induced muscle atrophy showed that the regulation of the extracellular matrix was perturbed by glucocorticoid treatment, and this perturbation was reversed by LBE treatment.Collectively, LBE alleviated skeletal muscle loss and maintained muscle function from the chronic toxicity of DEX by protecting muscle cells from various stressful conditions, as well as DEX itself, inhibiting muscle protein degradation, and preserving the muscle tissue microenvironment.

Skeletal myocyte-specific knockout of Ptpn1 and Ptpn2 enhances inflammatory response in muscle and increases mortality in polymicrobial sepsis

Abstract Background Critically ill patients often suffer from heart and skeletal muscle atrophy and failure (intensive care unit acquired weakness; ICUAW). Inflammation and sepsis are major risk factors for ICUAW. Critically ill patients with sepsis frequently develop insulin resistance that decreases protein synthesis and increases protein degradation in muscle eventually leading to ICUAW. The link between inflammation and insulin resistance is not well understood, but protein tyrosine phosphatases (PTP), that inhibit insulin signaling via insulin receptor (INSR) dephosphorylation as well as inflammation-associated pathways, are implicated. Hypothesis: We hypothesized that PTP1B and TC-PTP mediate inflammation-induced insulin resistance and muscle atrophy in heart and skeletal muscle. Methods and Results qRT-PCR analyses showed that the proinflammatory cytokines tumor necrosis factor (TNF), interleukin (IL)-1β, and IL-6 caused a ~2-fold increase in Ptpn1/PTP1B and Ptpn2/TC-PTP mRNA expression in C2C12 myocytes as well as in neonatal rat ventricular cardiomyocytes. Inhibition of the IL-6/GP130 pathway by siRNA and inhibitors in myocytes in vitro and skeletal muscle specific gp130 knockout mice in vivo attenuated IL-6-induced Ptpn1/PTP1B and Ptpn2/TC-PTP mRNA expression. CLP-induced polymicrobial sepsis was associated with a significant increase in gene expression and protein content of pro-inflammatory cytokines (Tnf, Il1b, Ifng) and leukocyte markers (CD68, CD11c, F4/80) in muscle of skeletal myocyte specific double knockout (Ptpn1+Ptpn2loxP/loxP, MCK cre, dKO) compared to wildtype (Ptpn1+Ptpn2loxP/loxP) mice in sepsis. This also resulted in a lower survival rate of dKO mice in sepsis (42% WT vs. 23% dKO). Immunohistological analyses revealed centralized nuclei, macrophage/monocyte infiltration and enhanced regeneration (Myh3, Pax7, Ki67) in tibialis anterior muscle of septic dKO mice. A strong activation of the NLRP3-inflammasome, as indicated by cleavage of caspase 1, GSDMD, GSDME and caspase 8, indicative for a pronounced inflammation and activated cell death pathways was observed in muscle of septic dKO mice. Conclusion The proinflammatory cytokine IL-6 increases the expression of Ptpn1 and Ptpn2 and enhances overall PTP activity. Selective inhibition of the IL-6R/GP130 signaling pathway by JAK2- and STAT3-inhibition as well as Gp130 deletion in myocytes in vivo attenuates those effects. Muscle-specific deletion of Ptpn1 and Ptpn2 in skeletal muscle leads to increased mortality, enhanced pro-inflammatory response and induced inflammatory, programmed cell death pathways in sepsis. Our data show that Ptpn1 and Ptpn2 play a key anti-inflammatory role in skeletal muscle.

6′-sialyllactose prevents dexamethasone-induced muscle atrophy by controlling the muscle protein degradation pathway

Sarcopenia is associated with various geriatric diseases, such as gait disorders, falls, malnutrition, and osteoporosis. Accordingly, interest in the prevention and treatment of sarcopenia has grown over the years. The human milk oligosaccharide (HMO) 6′-sialyllactose (6′-SL) is known to improve exercise performance, reduce muscle fatigue, and improve GNE myopathy; however, its effect on sarcopenia has not yet been reported. In this study, we aimed to investigate the efficacy of 6′-SL in dexamethasone-induced muscle atrophy, which is a widely used model for the study of sarcopenia. The effects of 6′-SL on differentiated C2C12 skeletal muscle cells and on mice were examined by treatment with 6′-SL in the presence or absence of dexamethasone. 6′-SL was found to inhibit the dexamethasone-induced decrease of MHC expression, as well as to prevent reduction in the number, length, and width of myotubes. Furthermore, the dexamethasone-induced upregulation of myostatin, muscle RING-finger protein-1 (MuRF1), and atrogin-1 were also inhibited by 6′-SL treatment. In mice, intraperitoneal administration of dexamethasone caused decreases in muscle fiber diameter, muscle weight, and exercise performance, most of which were significantly inhibited by oral treatment with 6′-SL. Therefore, utilization of 6′-SL could contribute to the prevention and treatment of muscle atrophy and sarcopenia.

HouShiHeiSan attenuates sarcopenia in middle cerebral artery occlusion (MCAO) rats

Ethnopharmacological relevancePhysical therapy is the main clinical treatment for limb symptoms after ischemic stroke, and there is a lack of reliable drug intervention programs. HouShiHeiSan (HS)comes from “Synopsis of the Golden Chamber”, where it is recorded: “seauelae of wind stroke and heaviness of limbs”, indicating this formulae is a promising opion for clinical practice. Aim of the studyThe aim of this study is to explore the therapeutic effect of HS on sarcopenia after ischemic stroke (ISS) by using the middle cerebral artery occlusion (MCAO) rats. Materials and methodsAfter 7 days of adaptive feeding Sprague-Dawley (SD) rats were randomly divided into sham and MCAO surgery groups. After MCAO operation, the agreement of the models was evaluated with a laser speckle instrument, and then, treatment groups were administered HS and related solvent. During the 7 days treatment period, the Zea-Longa score was used to assess the neural function, the treadmill for exercise capacity and traction instrument for grip strength. Besides, the physiological electrical signal system was used to record muscular electrical signals, while the muscle thickness was measured by ultrasound. After data acquisition on the 7th day after MCAO operation, the soleus muscle was dissected, and the indexes of length, weight of whole muscle tissue and cross-sectional area of muscular cells by H&E were recorded. Subsequently, mechanistic indicators were examined. MuRF1 and MAFbx expression was detected by immunohistochemistry (IHC). Furthermore, the expression level of more related indicators of muscular differentiation and cellular proterin balance, including mTOR, p-mTOR, AKT, p-AKT, p70s6k, p-p70s6, FOXO1, p-FOXO1, MyoD1, Myostatin, MuRF1 and MAFbx, were tested via Western blot. ResultsHS improved motor performance and promoted muscle regeneration in MCAO rats. In terms of motor ability, HS mixed with alcohol significantly improved the neurological function damage, reduce the weight loss, increase the running distance per unit time and increase the grip strength. The postoperative muscle electrical signal intensity increased, and muscle thickness, weight, and length were maintained. The HS with alcohol group significantly maintained the cross-sectional size of muscle cells and reduced the number of MyoD1 and myostatin-positive cells in the muscle tissue. It simultaneously promoted the expression of p-mTOR, p-AKT, p-p70s6k, and MyoD1 to promote the synthesis of muscle proteins and inhibited the expression of p-FOXO1, myostatin, MAFbx, and MuRF1 to reduce muscle protein degradation. ConclusionHS can enhance muscle protein synthesis and decrease protein breakdown by activating the AKT/mTOR/FOXO1 pathway, thereby preserving muscle health and enhancing motor performance following stroke in rats.

Ameliorative Effects of Fermented Red Ginseng Extract on Muscle Atrophy in Dexamethasone-Induced C2C12 Cell And Hind Limb-Immobilized C57BL/6J Mice.

Fermented red ginseng (FRG) enhances the bioactivity and bioavailability of ginsenosides, which possess various immunomodulatory, antiaging, anti-obesity, and antidiabetic properties. However, the effects of FRG extract on muscle atrophy and the underlying molecular mechanisms remain unclear. This study aimed to elucidate the effects of FRG extract on muscle atrophy using both in vitro and invivo models. In vitro experiments used dexamethasone (DEX)-induced C2C12 myotubes to assess cell viability, myotube diameter, and fusion index. In vivo experiments were conducted on hind limb immobilization (HI)-induced mice to evaluate grip strength, muscle mass, and fiber cross-sectional area (CSA) of the gastrocnemius (GAS), quadriceps (QUA), and soleus (SOL) muscles. Molecular mechanisms were investigated through the analysis of key signaling pathways associated with muscle protein synthesis, energy metabolism, and protein degradation. FRG extract treatment enhanced viability of DEX-induced C2C12 myotubes and restored myotube diameter and fusion index. In HI-induced mice, FRG extract improved grip strength, increased muscle mass and CSA of GAS, QUA, and SOL muscles. Mechanistic studies revealed that FRG extract activated the insulin-like growth factor 1/protein kinase B (Akt)/mammalian target of rapamycin signaling pathway, promoted muscle energy metabolism via the sirtuin 1/peroxisome proliferator-activated receptor gamma-coactivator-1α pathway, and inhibited muscle protein degradation by suppressing the forkhead box O3a, muscle ring-finger 1, and F-box protein (Fbx32) signaling pathways. FRG extract shows promise for ameliorating muscle atrophy by modulating key molecular pathways associated with muscle protein synthesis, energy metabolism, and protein degradation, offering insights for future drug development.

Mechanism of denervation muscle atrophy mediated by Ach/p38/MAPK pathway in rats with erectile dysfunction caused by nerve injury

BackgroundPeripheral nerve injury can result in penile cavernosal denervation muscle atrophy, a primary factor in nerve injury erectile dysfunction (NED). While acetylcholine (Ach) is integral to erectile function, its role and mechanisms in NED need further exploration. ObjectiveTo investigate the inhibition of CCMSCs Apoptosis and Protein Degradation Pathway by Ach in NED rat model. MethodsWe investigated changes in Ach secretion and receptor expression in an NED rat model, followed by the evaluation of apoptosis and ubiquitin proteasome activation in hypoxic Cavernous smooth muscle cells (CCMSCs) and their co-cultures with Schwann cells (SWCs), under Ach influence. Further, key pathways in NED were identified via high-throughput sequencing, focusing on the p38/MAPK signaling pathway. We examined gene alterations related to this pathway using hypoxic cell models and employed p38 inhibitors to verify protein changes. Our findings in vitro were then confirmed in the NED rat model. ResultsNerve injury led to reduced Ach receptors and associated gene expression. Experimentally, Ach was shown to counteract CCMSC apoptosis and muscle protein degradation via the p38/MAPK pathway. Inhibition of the Ach degradation pathway demonstrated a capacity to slow NED progression in vivo. Discussion and conclusionActivation of Ach receptors may decelerate denervation-induced cavernosal muscle atrophy, suggesting a potential therapeutic approach for NED. This study highlights the crucial role of the Ach/p38/MAPK axis in the pathophysiology of penis smooth muscle atrophy and its broader implications in managing NED and male erectile dysfunction.

Research note: Effect of a biotechnologically produced Pleurotus sapidus mycelium on expression of genes involved in protein synthesis and degradation in breast muscle of broilers

Research note: Effect of a biotechnologically produced Pleurotus sapidus mycelium on expression of genes involved in protein synthesis and degradation in breast muscle of broilers

High-Intensity Interval Training Mitigates Sarcopenia and Suppresses the Myoblast Senescence Regulator EEF1E1.

The optimal exercise regimen for alleviating sarcopenia remains uncertain. This study aimed to investigate the efficacy of high-intensity interval training (HIIT) over moderate-intensity continuous training (MICT) in ameliorating sarcopenia. We conducted a randomized crossover trial to evaluate plasma proteomic reactions to acute HIIT (four 4-min high-intensity intervals at 70% maximal capacity alternating with 4 min at 30%) versus MICT (constant 50% maximal capacity) in inactive adults. We explored the relationship between a HIIT-specific protein relative to MICT, identified via comparative proteomic analysis, eukaryotic translation elongation factor 1 epsilon 1 (EEF1E1) and sarcopenia in a paired case-control study of elderly individuals (aged over 65). Young (3 months old) and aged (20 months old) mice were randomized to sedentary, HIIT and MICT groups (five sessions/week for 4 weeks; n = 8 for each group). Measurements included skeletal muscle index, hand grip strength, expression of atrophic markers Atrogin1 and MuRF1 and differentiation markers MyoD, myogenin and MyHC-II via western blotting. We examined the impact of EEF1E1 siRNA and recombinant protein on D-galactose-induced myoblast senescence, measuring senescence-associated β-galactosidase and markers like p21 and p53. The crossover trial, including 10 sedentary adults (32 years old, IQR 31-32) demonstrated significant alterations in the abundance of 21 plasma proteins after HIIT compared with MICT. In the paired case-control study of 84 older adults (84 years old, IQR 69-81; 52% female), EEF1E1 was significantly increased in those with sarcopenia compared to those without (14.68 [95%CI, 2.02-27.34] pg/mL, p = 0.03) and was associated with skeletal muscle index (R2 = 0.51, p < 0.001) and hand grip strength (R2 = 0.54, p < 0.001). In the preclinical study, aged mice exhibited higher EEF1E1 mRNA and protein levels in skeletal muscle compared to young mice, accompanied by a lower muscle mass and strength, increased cellular senescence and protein degradation markers and reduced muscle differentiation efficiency (all p < 0.05). HIIT reduced EEF1E1 expression and mitigated age-related muscle decline and atrophy in aged mice more effectively than MICT. Notably, EEF1E1 downregulation via siRNA significantly counteracted D-galactose-induced myoblast senescence as evidenced by reduced markers of muscle protein degradation and improved muscle differentiation efficiency (all p < 0.05). Conversely, treatments that increased EEF1E1 levels accelerated the senescence process (p < 0.05). Further exploration indicated that the decrease in EEF1E1 was associated with increased SIRT1 level and enhanced autophagy. This study highlights the potential of HIIT as a promising approach to prevent and treat sarcopenia while also highlighting EEF1E1 as a potential intervention target.

352 Supplementing bovine satellite cells with anabolic hormones and/or zinc at differentiation impacts abundance of mRNA involved in growth, mineral transport, and oxidative stress

Abstract Zinc (Zn) is the most utilized metal in biological processes and supports growth through critical roles in protein turnover. The Zn requirements of skeletal muscle may be augmented when growth promoting technologies, such as anabolic hormones are being utilized. Both anabolic hormones and Zn affect protein synthesis and degradation in skeletal muscle. However, the molecular mechanisms through which Zn may interact with anabolic hormones to support skeletal muscle growth remains unknown. The objective of this study was to determine whether trenbolone acetate (TBA), estradiol (E2) and Zn interact to promote differentiation of bovine satellite cell (BSC) cultures by assessing abundance of mRNA involved in growth, mineral transport, differentiation, protein turnover and oxidative stress. To do this, primary BSC cultures were isolated from three different steers and grown to 80% confluency and induced to differentiate in 3% horse serum, at which time a factorial design was employed to assess the impact of Zn (0, 10, 20 or 40 μM) as ZnCl2 and/or the impact of hormone (10 nM TBA,10 nM E2, 10 nM TBA and 10 nM E2). Zinc concentrations represent physiologically relevant plasma Zn concentrations. Total mRNA was isolated from the treated cultures at 4 h, 12 h and 24 h post-treatment. Assays utilizing cultures from each steer were run in duplicate (n = 6). The mRNA abundance of 45 genes were examined and analyzed using the PROC MIXED procedure of SAS with time as a repeated measure to evaluate the fixed effects of hormone, mineral, time, and all interactions. No effects (P ≥ 0.19) of hormone x mineral x time, hormone x time, hormone x mineral or hormone were noted. A mineral x time effect (P ≤ 0.04) was noted for the igf1r, slc39a7, mapk1, mmp2, and G6pd. A mineral effect was found for hormone receptors (ir, ar, esr1, esr2, and gper; P ≤ 0.03), mRNA involved in mineral transport (slc30a10, slc30a7, sod1, sod2, slc2a4, and slc39a8; P ≤ 0.009), and genes related to skeletal muscle differentiation (pax7, myf5, myf6, spry1, myog, mef2a, and myod; P ≤ 0.02) and protein turnover (akt1, fox01, fox04, mstn,fbox32, fox03, mtor, trim63, and CKM; P ≤ 0.03). These differences are generally driven by abundance being increased (P ≤ 0.05) in cultures treated with 40 or 20 μM Zn compared with cultures receiving 0 or 10 μM Zn. These results indicate that while Zn and hormone do not appear to interact to influence gene expression of differentiating primary BSC cultures at the time points measured, increased concentrations of Zn appear to increase mRNA abundance of hormone receptors, mineral transporters, and genes involved in skeletal muscle differentiation and protein turnover.

Artificial neural network inference analysis identified novel genes and gene interactions associated with skeletal muscle aging.

Sarcopenia is an age-related muscle disease that increases the risk of falls, disabilities, and death. It is associated with increased muscle protein degradation driven by molecular signalling pathways including Akt and FOXO1. This study aims to identify genes, gene interactions, and molecular pathways and processes associated with muscle aging and exercise in older adults that remained undiscovered until now leveraging on an artificial intelligence approach called artificial neural network inference (ANNi). Four datasets reporting the profile of muscle transcriptome obtained by RNA-seq of young (21-43years) and older adults (63-79years) were selected and retrieved from the Gene Expression Omnibus (GEO) data repository. Two datasets contained the transcriptome profiles associated to muscle aging and two the transcriptome linked to resistant exercise in older adults, the latter before and after 6months of exercise training. Each dataset was individually analysed by ANNi based on a swarm neural network approach integrated into a deep learning model (Intelligent Omics). This allowed us to identify top 200 genes influencing (drivers) or being influenced (targets) by aging or exercise and the strongest interactions between such genes. Downstream gene ontology (GO) analysis of these 200 genes was performed using Metacore (Clarivate™) and the open-source software, Metascape. To confirm the differential expression of the genes showing the strongest interactions, real-time quantitative PCR (RT-qPCR) was employed on human muscle biopsies obtained from eight young (25±4years) and eight older men (78±7.6years), partaking in a 6-month resistance exercise training programme. CHAD, ZDBF2, USP54, and JAK2 were identified as the genes with the strongest interactions predicting aging, while SCFD1, KDM5D, EIF4A2, and NIPAL3 were the main interacting genes associated with long-term exercise in older adults. RT-qPCR confirmed significant upregulation of USP54 (P=0.005), CHAD (P=0.03), and ZDBF2 (P=0.008) in the aging muscle, while exercise-related genes were not differentially expressed (EIF4A2 P=0.99, NIPAL3 P=0.94, SCFD1 P=0.94, and KDM5D P=0.64). GO analysis related to skeletal muscle aging suggests enrichment of pathways linked to bone development (adj P-value 0.006), immune response (adj P-value <0.001), and apoptosis (adj P-value 0.01). In older exercising adults, these were ECM remodelling (adj P-value <0.001), protein folding (adj P-value <0.001), and proteolysis (adj P-value <0.001). Using ANNi and RT-qPCR, we identified three strongly interacting genes predicting muscle aging, ZDBF2, USP54, and CHAD. These findings can help to inform the design of nonpharmacological and pharmacological interventions that prevent or mitigate sarcopenia.

Proteomic Profiling of Hindlimb Skeletal Muscle Disuse in a Murine Model of Sepsis.

Sepsis leads to multiple organ dysfunction and negatively impacts patient outcomes. Skeletal muscle disuse is a significant comorbidity in septic patients during their ICU stay due to prolonged immobilization. Combination of sepsis and muscle disuse will promote a unique proteomic signature in skeletal muscle in comparison to disuse and sepsis separately. Following cecal ligation and puncture (CLP) or Sham surgeries, mice were subjected to hindlimb suspension (HLS) or maintained normal ambulation (NA). Tibialis anterior muscles from 24 C57BL6/J male mice were harvested for proteomic analysis. Proteomic profiles were assessed using nano-liquid chromatography with tandem mass spectrometry, followed by data analysis including Partial Least Squares Discriminant Analysis (PLS-DA), to compare the differential protein expression across groups. A total of 2876 differentially expressed proteins were identified, with marked differences between groups. In mice subjected to CLP and HLS combined, there was a distinctive proteomic signature characterized by a significant decrease in the expression of proteins involved in mitochondrial function and muscle metabolism, alongside a marked increase in proteins related to muscle degradation pathways. The PLS-DA demonstrated a clear separation among experimental groups, highlighting the unique profile of the CLP/HLS group. This suggests an important interaction between sepsis-induced inflammation and disuse atrophy mechanisms in sepsis-induced myopathy. Our findings reveal a complex proteomic landscape in skeletal muscle exposed to sepsis and disuse, consistent with an exacerbation of muscle protein degradation under these combined stressors. The identified proteins and their roles in cellular stress responses and muscle pathology provide potential targets for intervention to mitigate muscle dysfunction in septic conditions, highlighting the importance of addressing both sepsis and disuse concurrently in clinical and experimental settings.

Effects of Ulmus macrocarpa Extract and Catechin 7-O-β-D-apiofuranoside on Muscle Loss and Muscle Atrophy in C2C12 Murine Skeletal Muscle Cells.

Muscle atrophy is known to be one of the symptoms leading to sarcopenia, which significantly impacts the quality of life, mortality, and morbidity. Therefore, the development of therapeutics for muscle atrophy is essential. This study focuses on addressing muscle loss and atrophy using Ulmus macrocarpa extract and its marker compound, catechin 7-O-β-D-apiofuranoside, by investigating their effects on biomarkers associated with muscle cell apoptosis. Additionally, protein and gene expression in a muscle atrophy model were examined using Western blotting and RT-PCR. Ulmus macrocarpa has been used as food or medicine due to its safety, including its roots, barks, and fruit. Catechin 7-O-β-D apiofuranoside is an indicator substance of plants of the Ulmus genus and has been reported to have various effects such as antioxidant and anti-inflammatory effects. The experimental results demonstrated that catechin glycoside and Ulmus macrocarpa extract decreased the expression of the muscle-degradation-related proteins Atrogin-1 and Muscle RING-Finger protein-1 (MuRF1) while increasing the expression of the muscle-synthesis-related proteins Myoblast determination (MyoD) and Myogenin. Gene expression confirmation experiments validated a decrease in the expression of Atrogin and MuRF1 mRNA and an increase in the expression of MyoD and Myogenin mRNA. Furthermore, an examination of muscle protein expression associated with the protein kinase B (Akt)/forkhead box O (FoxO) signaling pathway confirmed a decrease in the expression of FoxO, a regulator of muscle protein degradation. These results confirm the potential of Ulmus macrocarpa extract to inhibit muscle apoptosis, prevent muscle decomposition, and promote the development of functional materials for muscle synthesis, health-functional foods, and natural-product-derived medicines.

A single, maximal dose of celecoxib, ibuprofen, or flurbiprofen does not reduce the muscle signalling response to plyometric exercise in young healthy adults.

Non-steroidal anti-inflammatory drugs (NSAIDs) possess analgesic and anti-inflammatory properties by inhibiting cyclooxygenase (COX) enzymes. Conflicting evidence exists on whether NSAIDs influence signaling related to muscle adaptations and exercise with some research finding a reduction in muscle protein synthesis signaling via the AKT-mTOR pathway, changes in satellite cell signaling, reductions in muscle protein degradation, and reductions in cell proliferation. In this study, we determined if a single maximal dose of flurbiprofen (FLU), celecoxib (CEL), ibuprofen (IBU), or a placebo (PLA) affects the short-term muscle signaling responses to plyometric exercise. This was a block randomized, double-masked, crossover design, where 12 participants performed four plyometric exercise bouts consisting of 10 sets of 10 plyometric jumps at 40% 1RM. Two hours before exercise, participants consumed a single dose of celecoxib (CEL 200mg), IBU (800mg), FLU (100mg) or PLA with food. Muscle biopsy samples were collected before and 3-h after exercise from the vastus lateralis. Data were analyzed using a repeated measures (RM) ANOVA, ANOVA, or a Friedman test. Significance was considered at p < 0.05. We found no treatment effects on the mRNA expression of PTSG1, PTSG2, MYC, TBP, RPLOP, MYOD1, Pax7, MYOG, Atrogin-1, or MURF1 (all, p > 0.05). We also found no treatment effects on AKT-mTOR signaling or MAPK signaling measured through the phosphorylation status of mTORS2441, mTORS2448, RPS6 235/236, RPS 240/244, 4EBP1, ERK1/2, p38 T180/182 normalized to their respective total abundance (all, p > 0.05). However, we did find a significant difference between MNK1 T197/202 in PLA compared to FLU (p < .05). A single, maximal dose of IBU, CEL, or FLU taken prior to exercise did not affect the signaling of muscle protein synthesis, protein degradation, or ribosome biogenesis three hours after a plyometric training bout.

A randomized translational study on protein- and glucose metabolism in skeletal muscles evaluated by gene-ontology, following preoperative oral carbohydrate loading compared to overnight peripheral parenteral nutrition (PPN) before major cancer surgery

BackgroundEffects of preoperative drinks on muscle metabolism are unclear despite general recommendations. The aim of the present study was therefore to compare metabolic effects of a preoperative oral nutrition drink, recommended by protocols for enhanced recovery after surgery (ERAS), compared to overnight preoperative peripheral total parenteral nutrition (PPN) on skeletal muscle metabolism in patients aimed at major gastrointestinal cancer surgery.MethodsPatients were randomized, based on diagnosis and clinical characteristics, to receive either a commercial carbohydrate-rich nutrition drink (Drink); or overnight (12 h) peripheral parenteral nutrition (PPN) as study regimens; compared to isotone Ringer-acetate as Control regimen. Arterial blood- and abdominal muscle tissue specimens were collected at start of surgery. Blood chemistry included substrate- and hormone concentrations. Muscle mRNA transcript analyses were performed by microarray and evaluated for changes in gene activities by Gene Ontology algorithms.ResultsPatient groups were comparable in all measured preoperative assessments. The Nutrition Drink had significant metabolic alterations on muscle glucose metabolism (p < 0.05), without any significant effects on amino acid- and protein metabolism. PPN showed similar significant effects on glucose metabolism as Drinks (p < 0.05), but indicated also major positive effects on amino acid- (p < 0.001) and protein anabolism (p < 0.05), particularly by inhibition of muscle protein degradation, related to both ubiquitination of proteins and autophagy/lysosome pathways (p < 0.05).ConclusionConventional overnight preoperative PPN seems effective to induce and support improved muscle protein metabolism in patients aimed at major cancer surgery while preoperative oral carbohydrate loading, according to ERAS-protocols, was ineffective to improve skeletal muscle catabolism and should therefore not be recommended before major cancer surgery.Trial registration Clinical trials.gov: NCT05080816, Registered June 10th 2021- Retrospectively registered. https://clinicaltrials.gov/study/NCT05080816

Correction to “α‐Ketoglutarate prevents skeletal muscle protein degradation and muscle atrophy through PHD3/ADRB2 pathway”

Correction to “α‐Ketoglutarate prevents skeletal muscle protein degradation and muscle atrophy through <scp>PHD3</scp>/<scp>ADRB2</scp> pathway”

Sunitinib-mediated inhibition of STAT3 in skeletal muscle and spinal cord does not affect the disease in a mouse model of ALS

Variability in disease onset and progression is a hallmark of amyotrophic lateral sclerosis (ALS), both in sporadic and genetic forms. Recently, we found that SOD1-G93A transgenic mice expressing the same amount of mutant SOD1 but with different genetic backgrounds, C57BL/6JOlaHsd and 129S2/SvHsd, show slow and rapid muscle wasting and disease progression, respectively. Here, we investigated the different molecular mechanisms underlying muscle atrophy. Although both strains showed similar denervation-induced degradation of muscle proteins, only the rapidly progressing mice exhibited early and sustained STAT3 activation that preceded atrophy in gastrocnemius muscle. We therefore investigated the therapeutic potential of sunitinib, a tyrosine kinase inhibitor known to inhibit STAT3 and prevent cancer-induced muscle wasting. Although sunitinib treatment reduced STAT3 activation in the gastrocnemius muscle and lumbar spinal cord, it did not preserve spinal motor neurons, improve neuromuscular impairment, muscle atrophy and disease progression in the rapidly progressing SOD1-G93A mice. Thus, the effect of sunitinib is not equally positive in different diseases associated with muscle wasting. Moreover, given the complex role of STAT3 in the peripheral and central compartments of the neuromuscular system, the present study suggests that its broad inhibition may lead to opposing effects, ultimately preventing a potential positive therapeutic action in ALS.

Myogenic microRNAs as Therapeutic Targets for Skeletal Muscle Mass Wasting in Breast Cancer Models.

Breast cancer is the type of cancer with the highest prevalence in women worldwide. Skeletal muscle atrophy is an important prognostic factor in women diagnosed with breast cancer. This atrophy stems from disrupted skeletal muscle homeostasis, triggered by diminished anabolic signalling and heightened inflammatory conditions, culminating in an upregulation of skeletal muscle proteolysis gene expression. The importance of delving into research on modulators of skeletal muscle atrophy, such as microRNAs (miRNAs), which play a crucial role in regulating cellular signalling pathways involved in skeletal muscle protein synthesis and degradation, has been recognised. This holds true for conditions of homeostasis as well as pathologies like cancer. However, the determination of specific miRNAs that modulate skeletal muscle atrophy in breast cancer conditions has not yet been explored. In this narrative review, we aim to identify miRNAs that could directly or indirectly influence skeletal muscle atrophy in breast cancer models to gain an updated perspective on potential therapeutic targets that could be modulated through resistance exercise training, aiming to mitigate the loss of skeletal muscle mass in breast cancer patients.

Correction to “α‐Ketoglutarate prevents skeletal muscle protein degradation and muscle atrophy through PHD3/ADRB2 pathway”

Correction to “α‐Ketoglutarate prevents skeletal muscle protein degradation and muscle atrophy through <scp>PHD3</scp>/<scp>ADRB2</scp> pathway”

Skeletal muscle preservation in arctic ground squirrels during hibernation season

Reduced skeletal loading leads to muscle atrophy in humans and most mammals. By contrast, hibernating mammals demonstrate limited loss of skeletal muscle mass and strength by the end of winter after being physically inactive for several months. The present study objective was to establish potential underlying processes for the lack of muscle loss during the hibernation season of arctic ground squirrels (AGS). Our hypothesis was that early in the the hibernation season, protective mechanisms of AGS are not yet mobilized and muscles show signs of atrophy, while compensatory processes for preventing muscle loss appear at a later time point. Quadriceps muscles of juvenile male AGS were collected shortly before hibernation, and on 2, 6, 10-12 and 16-22 weeks during hibernation. Pre-hibernating animals were used as controls. Fiber cross-sectional area (CSA) and fiber type composition were determined with immunohistochemistry. Amount of total RNA, ribosomal RNA content and expression levels of genes involved in 2 pathways of protein degradation, ubiquitination and autophagy, were analyzed by real-time PCR, to evaluate molecular mechanisms of muscle maintenance. One-Way ANOVA was used to statistically analyze the group differences. We found that CSA was not different between the groups (P &gt; 0.05). CSA frequency distribution curves did not reveal any shift to a smaller or larger size range. No difference was detected in myofiber composition between the hibernation groups compared to the control. Total RNA and ribosomal RNA content were not significantly different between the groups during hibernation. Muscle atrophy marker FBXO32 (Atrogin-1, MAFBX) and autophagy related genes MAP1LC3A and BECN1 did not show different level of expression between the groups. Only another muscle atrophy marker TRIM63 (MURF-1, Iris Ring Finger Protein) was significantly over-expressed at the time point of 2 weeks of hibernation. These results indicate that throughout the hibernation season, AGS preserve muscle fiber CSA showing limited signs of muscle atrophy only during the first weeks of hibernation, and yet-to-be determined processes exist to suppress protein degradation in AGS muscles during hibernation. The work was supported by Center of Biomedical Research Excellence under grant number [P20GM130443]. This is the full abstract presented at the American Physiology Summit 2024 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.