Muscle Protein Degradation Research Articles

Muscle and Metabolic Genes Are Differentially Expressed During Thermal Acclimation by the Brook Trout Myotome.

Cold-water fishes, such as Brook trout (Salvelinus fontinalis), are being challenged by the consequences of climate change. The ability of these fish to acclimate to warmer environmental conditions is vital to their survival. Acclimation to warmer water may allow brook trout to reduce the metabolic costs of higher temperatures. Previous work has shown that brook trout display a significant thermal acclimation response in their myotomal muscle, with slower contractile properties observed in warm acclimated fish. In this study, gene expression was examined in hatchery brook trout acclimated to a range in temperatures (4, 10 or 20°C). Brook trout displayed variations in gene expression in their myotomal muscle in accordance with acclimation temperature. Genes important for muscle function, cellular metabolism, protein degradation, and stress response showed variation to both warm (20°C) and cold (4°C) acclimation. The warm acclimated fish also showed decreased expression of genes associated with aerobic metabolism and increased expression of genes for heat shock proteins, while the cold acclimated fish showed increased expression of genes associated with lipid metabolism and protein turnover. α-tubulin displayed a close association with thermal acclimation, increasing in expression with acclimation temperature. The patterns of muscle gene expression were the opposite of what was expected. Although warm acclimated fish have previously been shown to display slow muscle contractile properties, this study found that warm acclimation is associated with increased expression of genes for kinetically faster isoforms of important muscle proteins. Collectively, the results demonstrate a robust response to elevated temperature in the hatchery fish greater than 10,000 genes showing differential expression with temperature. These results provide a roadmap for the analysis of the acclimation response of native populations of brook trout encountering climate change.

Developing a ceRNA-based lncRNA-miRNA-mRNA regulatory network to uncover roles in skeletal muscle development

The precise role of lncRNAs in skeletal muscle development and atrophy remain elusive. We conducted a bioinformatic analysis of 26 GEO datasets from mouse studies, encompassing embryonic development, postnatal growth, regeneration, cell proliferation, and differentiation, using R and relevant packages (limma et al.). LncRNA-miRNA relationships were predicted using miRcode and lncBaseV2, with miRNA-mRNA pairs identified via miRcode, miRDB, and Targetscan7. Based on the ceRNA theory, we constructed and visualized the lncRNA-miRNA-mRNA regulatory network using ggalluvial among other R packages. GO, Reactome, KEGG, and GSEA explored interactions in muscle development and regeneration. We identified five candidate lncRNAs (Xist, Gas5, Pvt1, Airn, and Meg3) as potential mediators in these processes and microgravity-induced muscle wasting. Additionally, we created a detailed lncRNA-miRNA-mRNA regulatory network, including interactions such as lncRNA Xist/miR-126/IRS1, lncRNA Xist/miR-486-5p/GAB2, lncRNA Pvt1/miR-148/RAB34, and lncRNA Gas5/miR-455-5p/SOCS3. Significant signaling pathway changes (PI3K/Akt, MAPK, NF-κB, cell cycle, AMPK, Hippo, and cAMP) were observed during muscle development, regeneration, and atrophy. Despite bioinformatics challenges, our research underscores the significant roles of lncRNAs in muscle protein synthesis, degradation, cell proliferation, differentiation, function, and metabolism under both normal and microgravity conditions. This study offers new insights into the molecular mechanisms governing skeletal muscle development and regeneration.

Feruloylacetone and Its Analog Demethoxyferuloylacetone Mitigate Obesity-Related Muscle Atrophy and Insulin Resistance in Mice.

Obesity-induced muscle alterations, such as inflammation, metabolic dysregulation, and myosteatosis, lead to a decline in muscle mass and function, often resulting in sarcopenic obesity. Currently, there are no definitive treatments for sarcopenic obesity beyond lifestyle changes and dietary supplementation. Feruloylacetone (FER), a thermal degradation product of curcumin, and its analog demethoxyferuloylacetone (DFER), derived from the thermal degradation of bisdemethoxycurcumin, have shown potential antiobesity effects in previous studies. This study investigates the impact of FER and DFER on obesity-related glucose intolerance and muscle atrophy. High-fat diet (HFD) feeding resulted in muscle mass reduction and increased intramuscular triglyceride accumulation, both of which were mitigated by FER and DFER supplementation. The supplements activated the PI3K/Akt/mTOR signaling pathway, enhanced muscle protein synthesis, and decreased markers of muscle protein degradation. Additionally, FER and DFER supplementation improved glucose homeostasis in HFD-fed mice. The supplements also promoted the formation of a gut microbial consortium comprising Blautia intestinalis, Dubosiella newyorkensis, Faecalicatena fissicatena, Waltera intestinalis, Clostridium viride, and Caproiciproducens galactitolivorans, which contributed to the reduction of obesity-induced chronic inflammation. These findings suggest, for the first time, that FER and DFER may prevent obesity-related complications, including muscle atrophy and insulin resistance, thereby warranting further research into their long-term efficacy and safety.

Potential Effect of Defatted Mealworm Hydrolysate on Muscle Protein Synthesis in C2C12 Cells and Rats

(1) Background: the objective of this study was to examine the impact of defatted mealworm hydrolysate (DMH), formulated through protein hydrolysis, on muscle protein synthesis in C2C12 cells and rats; (2) Methods: C2C12 cells were treated with dexamethasone and DMH, and cell viability was quantified using the MTT assay. Twenty-four Sprague–Dawley rats were divided into three groups (control, DEX, and DEX + DMH) and treated for 8 weeks. The DEX and DEX + DMH groups were administered intraperitoneal injections of DEX at a concentration of 2.25 mg/kg over a 3-d period. The control and DEX groups were fed a control diet, whereas the DMH group had part of the protein composition of the control diet replaced with 3.5% of DMH. The impact of DMH on muscle protein synthesis was evaluated through the measurement of grip strength, gastrocnemius and tibialis anterior muscle weights, and the investigation of muscle protein synthesis and degradation factor mRNA expression utilising the real-time PCR method; (3) Results: in vitro experiments demonstrated that treatment with DMH at concentrations greater than 5 mg/mL markedly alleviated DEX-induced injury in C2C12 cells. In vivo experiments demonstrated that the mRNA expression levels of myogenin and myoblast determination proteins, which promote muscle protein synthesis, were significantly increased. Furthermore, rats fed DMH exhibited significantly enhanced grip strength and tibialis anterior weight; (4) Conclusions: these findings indicate that DMH may serve as a functional material capable of promoting muscle protein synthesis and that the utilization of proteolytic enzymes is advantageous for the effective utilization of mealworms.

Identification of Gene‐Therapy Responsive Blood Biomarkers in mdx Mouse Model

ABSTRACTIntroductionIdentifying serum biomarkers that reflect the restoration of dystrophin in skeletal muscle is important for evaluating the effect of dystrophin‐restoring therapies in preclinical and clinical trials. Many potential blood biomarkers have been identified in Duchenne muscular dystrophy (DMD) patients, which change with disease progression or respond to pharmacological treatment. In this study, it was suggested that a panel of such blood biomarker candidates could be used to monitor dystrophin rescue in mdx mice treated with microdystrophin based therapies.MethodsPlasma samples from mdx mice treated with the microdystrophin therapy SGT‐001 were analysed with an antibody suspension bead array consisting of 87 antibodies. The array targets 83 unique proteins previously identified as biomarker candidates for DMD. Each sample was assayed at two different plasma dilutions to cover a broader concentration range. Protein concentrations estimated as Median fluorescent intensities (MFI) were correlated to dystrophin expression in muscle tissue, as measured by immunohistochemistry and Western blot. Thirteen of the targets were selected and analysed in a DMD and Becker muscular dystrophy (BMD) longitudinal natural history cohort using a suspension bead array.ResultsTen proteins were found to be significantly elevated in untreated mdx mice compared with C57 wild‐type mice and to correlate with dystrophin expression (Spearman's correlation, FDR < 0.05) upon gene transfer in mdx mice. Translatability of these biomarkers from animal models to patients was evaluated by exploring abundance trajectories over time in both DMD and BMD patients and association with dystrophin expression in BMD patients. Consistent with the observations in mouse, six of these biomarker candidates were more abundant in DMD patients compared with controls, and six were also differentially abundant between BMD and DMD patients. Among them, serum titin was shown to be associated with dystrophin expression in BMD patients, having a steeper decline over time in patients with low dystrophin expression in tibialis anterior compared with patients with high expression. Myosine light chain 3 had a steeper decline with time in DMD patients compared with BMD patients.ConclusionsThe 10 biomarker candidates identified in mouse plasma are related to muscle contraction, glycolysis, microtubule formation and protein degradation. Human titin and myosine light chain 3 were the most interesting candidates as explorative biomarkers to monitor microdystrophin expression in gene therapies. If confirmed, these biomarkers could be used to detect restoration of dystrophin expression per se, monitor changes in dystrophin expression over time and potentially confirm disease phenotype changes from severe to mild disease forms.

Evaluation of Alternative Dietary Ingredients as a Sustainable and Ecological Solution for Meagre (Argyrosomus regius) Production in Earthen Ponds

The aquaculture sector is developing sustainability measures to address resource limitations and environmental concerns. A key strategy is replacing fishmeal and fish oil with alternatives that can equally sustain fish health, growth, and water quality. This study compared a standard diet (STD) to an alternative diet (ALT) containing sustainable ingredients, such as plant-based proteins and animal by-products, for meagre raised in earthen ponds within a polyculture system. Over 150 days, 5400 meagre juveniles (174.9 ± 32.8 g) were fed these diets. Fish on the ALT diet showed superior growth, likely due to higher dietary protein content and reduced protein degradation in liver and muscle, leading to increased protein content and reduced levels of dry matter, lipid, ash, energy, and phosphorous. While muscle cohesiveness was affected, fiber area and density were unchanged. ALT-fed fish exhibited higher saturated (SFA) and polyunsaturated (PUFA) fatty acids, reflecting the diet. Water quality indicators, including ammonia, nitrites, nitrates, and phosphates, were similar across diets, though chlorophyll a was higher in ponds with STD-fed fish. Overall, the ALT diet emerges as a sustainable alternative to the STD diet, maintaining or enhancing protein levels while reducing fishmeal usage. This approach effectively supports meagre growth and fillet quality without significant additional environmental impact.

Fucosterol, a Phytosterol of Marine Algae, Attenuates Immobilization-Induced Skeletal Muscle Atrophy in C57BL/6J Mice.

The objective of this study was to examine whether fucosterol, a phytosterol of marine algae, could ameliorate skeletal muscle atrophy in tumor necrosis factor-alpha (TNF-α)-treated C2C12 myotubes and in immobilization-induced C57BL/6J mice. Male C57BL6J mice were immobilized for 1 week to induce skeletal muscle atrophy. Following immobilization, the mice were administrated orally with saline or fucosterol (10 or 30 mg/kg/day) for 1 week. Fucosterol significantly attenuated immobilization-induced muscle atrophy by enhancing muscle strength, with a concomitant increase in muscle volume, mass, and myofiber cross-sectional area in the tibialis anterior (TA) muscle in mice. In both the TNF-α-treated C2C12 myotubes and the TA muscle of immobilized mice, fucosterol significantly prevented muscle protein degradation, which was attributed to a reduction in atrogin-1 and muscle ring finger 1 gene expression through an increase in forkhead box O3α (FoxO3α) phosphorylation. Continuously, fucosterol stimulated muscle protein synthesis by increasing the phosphorylation of the mammalian target of the rapamycin (mTOR), 70 kDa ribosomal protein S6 kinase, and 4E binding protein 1, which was mediated through the stimulation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Thus, fucosterol alleviated skeletal muscle atrophy in TNF-α-treated C2C12 myotubes and immobilized C57BL/6J mice through the regulation of the Akt/mTOR/FoxO3α signaling pathway.

Effects of Alnus japonica Hot Water Extract and Oregonin on Muscle Loss and Muscle Atrophy in C2C12 Murine Skeletal Muscle Cells.

Background/Objectives: Sarcopenia is characterized by the loss of muscle mass and function, increases in mortality rate, and risk of comorbidities in the elderly. This study evaluated the effects of Alnus japonica hot water extract (AJHW) and its active compound, oregonin, on muscle atrophy and apoptosis in vitro. Methods: AJHW underwent phytochemical analysis. C2C12 cells were subjected to H2O2 and dexamethasone to induce oxidative stress and muscle loss, after which AJHW and oregonin were administered to assess their impacts on cell viability, apoptosis, muscle protein synthesis stimulation, and muscle protein degradation inhibition. Cell viability was assessed via an MTT assay, and apoptosis was analyzed by measuring Bcl-2, Bax, cleaved caspase-3, and cleaved PARP through Western blotting. Western blotting and RT-PCR were utilized to analyze MyoD, Myogenin, Atrogin-1, and MuRF1 protein and gene expression in a muscle atrophy model, as well as the Akt/mTOR and FoxO3α pathways. Results: AJHW was confirmed to contain oregonin, an active compound. AJHW and oregonin significantly increased cell viability and reduced apoptosis by upregulating Bcl-2 and downregulating Bax, cleaved caspase-3, and cleaved PARP. They significantly enhanced muscle protein synthesis through the upregulation of MyoD and Myogenin, while diminishing muscle degradation by downregulating Atrogin-1 and MuRF1. The activation of the Akt/mTOR pathway and inhibition of the FoxO3α pathway were also observed. Conclusions: AJHW and oregonin effectively prevented muscle cell apoptosis, promoted muscle protein synthesis, and inhibited muscle protein degradation in vitro. These results suggest that AJHW and oregonin could serve as therapeutic agents to prevent and treat sarcopenia.

Fish collagen peptides supplementation ameliorates skeletal muscle injury in high-fat diet mice associated with thyroid function recovery

This study aims to explore the effects of fish collagen peptides (FCP) supplementation on skeletal muscle injury in high-fat (HF) diet mice and their possible mechanisms. Experimental mice were fed a normal diet (4 % fat), HF diet (20 % fat), or FCP diet (20 % fat and 1 % FCPs) for 22 consecutive weeks. Results show that FCP supplementation improves skeletal muscle motor function and histomorphology, and lipid levels; promotes protein synthesis, and inhibits protein degradation in skeletal muscle. Moreover, FCP supplementation also improves mitochondrial biogenesis, promotes energy metabolism and ATP production. Furthermore, FCP supplementation increases antioxidant defenses in the thyroid and skeletal muscle, improves thyroid morphological structure, promotes the synthesis and secretion of thyroid hormones, and enhances the actions of thyroid hormones on its receptor organ skeletal muscle. Cumulatively, these findings indicate that FCP supplementation can alleviate skeletal muscle injury induced by an HF diet associated with thyroid function recovery.

Importance of proteins and mitochondrial changes as freshness indicators in fish muscle post-mortem.

Evaluating protein and mitochondrial alterations post-mortem can contribute to determining correlations between fish-processing parameters and ultimate fish muscle quality. The myofibrillar protein alteration during rigor mortis directly affects the texture of fish muscle. To identify the mechanisms behind post-mortem softness and quality deterioration, it is crucial to understand the conditions linked to the breakdown of myofibrillar proteins in fish skeletal muscle. Therefore, monitoring protein breakdown at the molecular level and finding target proteins would be considered a marker for fish freshness. Mitochondria play an important role in executing and regulating cell death processes, including apoptosis and necrosis. The mitochondria are the seat of cellular respiration and experience significant alterations in post-mortem tissues. Processes used to reduce protein degradation, such as optimizing chilling and handling practices, would also minimize mitochondrial changes in fillet quality. Moreover, pH fluctuations are considered a critical point that influences both protein and mitochondrial changes. This review considered the implications of protein and mitochondrial alteration during post-mortem storage in fish fillets and the possible pathways of their interaction on fillet quality. Mitochondrial characteristics, such as membrane integrity, pH, and ATP levels, are important for post-mortem muscle cell changes, serving as an early indicator of fish freshness. Understanding the mechanisms behind protein degradation in fish muscle led to maintaining fillet quality and requires further experiments. Label-free proteomics combined with bioinformatics is crucial for comprehending protein degradation mechanisms to provide customers with safe and fresh fish products while minimizing economic losses associated with fillet deterioration. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Changes in the freshness of freshwater Japanese icefish (Salangichthys microdon) during chilled and super‐chilled storage

AbstractBackgroundThe Japanese icefish (Salangichthys microdon) is a valuable food resource in Japan; however, its freshness rapidly diminishes during transport and cold storage. In this study, the freshness change during chilled (5°C) and super‐chilled (−1 and −2°C) of S. microdon samples collected from Kasumigaura lake in October and December was assessed by observing their surface structure and determining their drip loss, K values, and free amino acid content.ResultsThe results revealed that more wrinkles formed on the surface of S. microdon samples with increasing storage time. More drip loss occurred in fall than in winter. Higher K values and increased degradation of muscle proteins were observed in winter. Moreover, their free amino acid content increased with storage time at all temperatures.ConclusionThis study suggested that seasonal differences and storage temperature should be considered in selecting the appropriate fishing, handling, and storage methods to maintain the freshness and quality of S. microdon.

Glycyrrhiza uralensis extract improves dexamethasone-induced sarcopenia via regulating myostatin- and FoxO3a-mediated E3 ubiquitin ligase

Sarcopenia affects the skeletal muscle system and impairs physical activity. This study investigated the effects of Glycyrrhiza uralensis (GU) extract on ameliorating dexamethasone (DEX)-induced sarcopenia in C2C12 myoblasts and C57BL/6J mice. Initially, network pharmacology analysis determined the association between GU and DEX-induced sarcopenia and predicted potentially related signaling pathways. Subsequently, the protective effects of different GU extracts on DEX-induced damage in C2C12 myotubes were evaluated by cell viability assays and Jenner and Giemsa (J&G) staining. Finally, the GU extract screened in vitro was evaluated by body composition analysis, grip strength and endurance tests, serum analysis, histological analysis, and protein expression level analysis in DEX-induced C57BL/6J mice. Network pharmacology confirmed the correlation between GU and DEX-induced sarcopenia involving TNF, MSTN, and FoxO signaling pathways. In DEX-induced damaged myotubes, only GU water extract (GW) dose-dependently increased cell viability. J&G staining of GW-treated myotubes revealed that GW increased the cell fusion index, maturation index and myotube diameter, attenuating DEX-induced cell damage. Oral administration of GW at doses above 300 mg/kg/day restored lean body mass lost due to DEX and subsequently reduced body fat. GW also enhanced grip strength and endurance, reduced muscle tissue injury, and increased the cross-sectional area of muscle fibers in DEX-induced mice. GW reduced the inflammatory response by alleviating serum TNF-α levels and ultimately decreased E3 ubiquitin ligase (MAFbx and MuRF-1) by downregulating myostatin and promoting FoxO3a phosphorylation. These results suggest that GU inhibits muscle protein degradation and is a potential food and medicinal homolog for preventing or treating sarcopenia.

Chrysanthemum indicum L. ameliorates muscle atrophy by improving glucose tolerance in CT26-induced cancer cachexia.

Cancer cachexia is associated with various metabolic mechanisms such as inflammatory response, insulin resistance, and increased muscle proteolysis. However, effective treatment methods have not yet been standardized. Chrysanthemum indicum L. (CI) is a perennial plant belonging to the Asteraceae family, and its flowers have been used for the treatment of headaches, colds, and rhinitis in Asia. This study investigated the effect of CI on cancer cachexia. We subcutaneously injected CT26 colon cancer cells (5 × 105 cells/mouse) into the right flank of BALB/c mice. After 1week, the mice were orally administered vehicle, CI (100mg/kg), or Celecoxib (50mg/kg) for 3weeks. CI improved loss of body weight and impaired glucose tolerance, but celecoxib did not recover the body weight and glucose intolerance. CI not only improved the decreased myofiber diameters but also inhibited muscle protein degradation factors, MAFbx and MuRF1. CI also increased cellular membrane GLUT4 in CT26 conditioned medium-treated C2C12 myofibers and cancer cachexia-induced mice. Furthermore, we found that linarin, a constituent of CI, was responsible for the improvement of muscle atrophy. Our findings indicate that CI can ameliorate muscle atrophy by improving glucose uptake, suggesting that CI could be a therapeutic agent for cancer cachexia.

Tanshinone IIA alleviates inflammation-induced skeletal muscle atrophy by regulating mitochondrial dysfunction

Skeletal muscle atrophy, characterized by loss of muscle mass and function, is often linked to systemic inflammation. Tanshinone IIA (Tan IIA), a major active constituent of Salvia miltiorrhiza, has anti-inflammatory and antioxidant properties. However, the effect of Tan IIA on inflammation-induced skeletal muscle atrophy remains unclear. Here, a mice model of the inflammatory muscle atrophy was established using lipopolysaccharide (LPS). Tan IIA intervention significantly increased muscle mass and strength, improved muscle fiber size, and maintained the integrity of skeletal muscle mitochondrial morphology in LPS-treated mice. Myotubes derived from myosatellite cells (MUSCs) were exposed to LPS in vitro. Tan IIA treatment inhibited LPS-induced muscle protein degradation and increased myotube diameter. Notably, Tan IIA attenuated LPS-induced inflammatory response and hyperactive mitophagy both in vivo and in vitro. In addition, Tan IIA treatment effectively diminished oxidative stress, inhibited the accumulation of mitochondrial reactive oxygen species (mtROS), and attenuated mitochondrial fission in LPS-treated myotubes. Reducing mtROS production helped to inhibit LPS-induced excessive mitophagy and myotubes atrophy. Together, our results reveal that Tan IIA can protect against inflammation-induced skeletal muscle atrophy by regulating mitochondrial dysfunction, presenting innovative potential therapeutics for skeletal muscle atrophy.

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.

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

Recently, feeding a fungal mycelium from Pleurotus sapidus was found to reduce relative breast muscle weight of broilers. The present study tested the hypothesis that dietary inclusion of P. sapidus mycelium modulates the expression of genes involved in protein anabolic and protein catabolic pathways in breast muscle of broilers. The study included 72 male, 1-day-old Cobb 500 broilers which were randomly assigned to three groups fed three different diets containing either 0 (PSA-0), 25 (PSA-25) and 50 (PSA-50) g/kg diet P. sapidus mycelium in a three-phase feeding system for 35 days. Within the somatropic axis, the mRNA level of GHR was higher and that of IGF1R was lower in group PSA-25 than in group PSA-0 (P < 0.05). Within the mTOR signaling pathway, the mRNA level of S6K1 was higher in group PSA-25 than in group PSA-0 (P < 0.05). Within muscle growth-related genes, the mRNA level of MYOG was lower in groups PSA-25 and PSA-50 than in group PSA-0 (P < 0.05). The relative phosphorylation of proteins involved in protein anabolic pathways (S6K1, RPS6, eIF2a, AKT) did not differ across the three groups. The mRNA of most genes involved in molecular pathways of protein degradation and inhibition of protein synthesis, such as the GCN/eIF2a pathway, the ubiquitin-proteasome pathway, and the autophagy-lysosomal pathway, showed no differences across the three groups. Only the mRNA level of ATG9A was higher in group PSA-25 compared to group PSA-0 (P < 0.05). These observations suggest that a modulation of these signaling pathways is unlikely to explain the reduced relative breast muscle weight in broilers. Nevertheless, future studies are necessary to exclude an effect of feeding P. sapidus mycelium on other less prominent pathways affecting skeletal muscle mass.

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.