TRB3 regulates skeletal muscle mass in food deprivation-induced atrophy.
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ABSTRACT:
SUBMITTER: Choi RH
PROVIDER: S-EPMC6436654 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:When reducing activity and using stored energy during seasonal food shortages, animals risk degradation of skeletal muscles, although some species avoid or minimize the resulting atrophy while experiencing these conditions during hibernation. Polar bears may be food deprived and relatively inactive during winter (when pregnant females hibernate and hunting success declines for other demographic groups) as well as summer (when sea ice retreats from key foraging habitats). We investigated muscle atrophy in samples of biceps femoris collected from free-ranging polar bears in the Southern Beaufort Sea (SBS) throughout their annual cycle. Atrophy was most pronounced in April-May as a result of food deprivation during the previous winter, with muscles exhibiting reduced protein concentration, increased water content, and lower creatine kinase mRNA. These animals increased feeding and activity in spring (when seal prey becomes more available), initiating a period of muscle recovery. During the following ice melt of late summer, ~30% of SBS bears abandon retreating sea ice for land; in August, these 'shore' bears exhibited no muscle atrophy, indicating that they had fully recovered from winter food deprivation. These individuals subsequently scavenged whale carcasses deposited by humans and by October, had retained good muscle condition. In contrast, ~70% of SBS bears follow the ice north in late summer, into deep water with less prey. These 'ice' bears fast; by October, they exhibited muscle protein loss and rapid changes in myosin heavy-chain isoforms in response to reduced activity. These findings indicate that, unlike other bears during winter hibernation, polar bears without food in summer cannot mitigate atrophy. Consequently, prolonged summer fasting resulting from climate change-induced ice loss creates a risk of greater muscle atrophy and reduced abilities to travel and hunt.
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Project description:Skeletal muscle mass is regulated by a complex array of signaling pathways. TGF-β-activated kinase 1 (TAK1) is an important signaling protein, which regulates context-dependent activation of multiple intracellular pathways. However, the role of TAK1 in the regulation of skeletal muscle mass remains unknown. Here, we report that inducible inactivation of TAK1 causes severe muscle wasting, leading to kyphosis, in both young and adult mice.. Inactivation of TAK1 inhibits protein synthesis and induces proteolysis, potentially through upregulating the activity of the ubiquitin-proteasome system and autophagy. Phosphorylation and enzymatic activity of AMPK are increased, whereas levels of phosphorylated mTOR and p38 MAPK are diminished upon inducible inactivation of TAK1 in skeletal muscle. In addition, targeted inactivation of TAK1 leads to the accumulation of dysfunctional mitochondria and oxidative stress in skeletal muscle of adult mice. Inhibition of TAK1 does not attenuate denervation-induced muscle wasting in adult mice. Finally, TAK1 activity is highly upregulated during overload-induced skeletal muscle growth, and inactivation of TAK1 prevents myofiber hypertrophy in response to functional overload. Overall, our study demonstrates that TAK1 is a key regulator of skeletal muscle mass and oxidative metabolism.
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Project description:Diverse stresses including starvation and muscle disuse cause skeletal muscle atrophy. However, the molecular mechanisms of muscle atrophy are complex and not well understood. Here, we demonstrate that growth arrest and DNA damage-inducible 45a protein (Gadd45a) is a critical mediator of muscle atrophy. We identified Gadd45a through an unbiased search for potential downstream mediators of the stress-inducible, pro-atrophy transcription factor ATF4. We show that Gadd45a is required for skeletal muscle atrophy induced by three distinct skeletal muscle stresses: fasting, muscle immobilization, and muscle denervation. Conversely, forced expression of Gadd45a in muscle or cultured myotubes induces atrophy in the absence of upstream stress. We show that muscle-specific ATF4 knock-out mice have a reduced capacity to induce Gadd45a mRNA in response to stress, and as a result, they undergo less atrophy in response to fasting or muscle immobilization. Interestingly, Gadd45a is a myonuclear protein that induces myonuclear remodeling and a comprehensive program for muscle atrophy. Gadd45a represses genes involved in anabolic signaling and energy production, and it induces pro-atrophy genes. As a result, Gadd45a reduces multiple barriers to muscle atrophy (including PGC-1?, Akt activity, and protein synthesis) and stimulates pro-atrophy mechanisms (including autophagy and caspase-mediated proteolysis). These results elucidate a critical stress-induced pathway that reprograms muscle gene expression to cause atrophy.
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Project description:AimLoss of skeletal muscle mass is a common clinical finding in cancer patients. The purpose of this meta-analysis and systematic review was to quantify the effect of doxorubicin on skeletal muscle and report on the proposed molecular pathways possibly leading to doxorubicin-induced muscle atrophy in both human and animal models.MethodsA systematic search of the literature was conducted in PubMed, EMBASE, Web of Science and CENTRAL databases. The internal validity of included studies was assessed using SYRCLE's risk of bias tool.ResultsTwenty eligible articles were identified. No human studies were identified as being eligible for inclusion. Doxorubicin significantly reduced skeletal muscle weight (ie EDL, TA, gastrocnemius and soleus) by 14% (95% CI: 9.9; 19.3) and muscle fibre cross-sectional area by 17% (95% CI: 9.0; 26.0) when compared to vehicle controls. Parallel to negative changes in muscle mass, muscle strength was even more decreased in response to doxorubicin administration. This review suggests that mitochondrial dysfunction plays a central role in doxorubicin-induced skeletal muscle atrophy. The increased production of ROS plays a key role within this process. Furthermore, doxorubicin activated all major proteolytic systems (ie calpains, the ubiquitin-proteasome pathway and autophagy) in the skeletal muscle. Although each of these proteolytic pathways contributes to doxorubicin-induced muscle atrophy, the activation of the ubiquitin-proteasome pathway is hypothesized to play a key role. Finally, a limited number of studies found that doxorubicin decreases protein synthesis by a disruption in the insulin signalling pathway.ConclusionThe results of the meta-analysis show that doxorubicin induces skeletal muscle atrophy in preclinical models. This effect may be explained by various interacting molecular pathways. Results from preclinical studies provide a robust setting to investigate a possible dose-response, separate the effects of doxorubicin from tumour-induced atrophy and to examine underlying molecular pathways. More research is needed to confirm the proposed signalling pathways in humans, paving the way for potential therapeutic approaches.
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Project description:BackgroundCritically ill patients develop atrophic muscle failure, which increases morbidity and mortality. Interleukin-1β (IL-1β) is activated early in sepsis. Whether IL-1β acts directly on muscle cells and whether its inhibition prevents atrophy is unknown. We aimed to investigate if IL-1β activation via the Nlrp3 inflammasome is involved in inflammation-induced atrophy.MethodsWe performed an experimental study and prospective animal trial. The effect of IL-1β on differentiated C2C12 muscle cells was investigated by analyzing gene-and-protein expression, and atrophy response. Polymicrobial sepsis was induced by cecum ligation and puncture surgery in Nlrp3 knockout and wild type mice. Skeletal muscle morphology, gene and protein expression, and atrophy markers were used to analyze the atrophy response. Immunostaining and reporter-gene assays showed that IL-1β signaling is contained and active in myocytes.ResultsImmunostaining and reporter gene assays showed that IL-1β signaling is contained and active in myocytes. IL-1β increased Il6 and atrogene gene expression resulting in myocyte atrophy. Nlrp3 knockout mice showed reduced IL-1β serum levels in sepsis. As determined by muscle morphology, organ weights, gene expression, and protein content, muscle atrophy was attenuated in septic Nlrp3 knockout mice, compared to septic wild-type mice 96 h after surgery.ConclusionsIL-1β directly acts on myocytes to cause atrophy in sepsis. Inhibition of IL-1β activation by targeting Nlrp3 could be useful to prevent inflammation-induced muscle failure in critically ill patients.
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Project description:Skeletal muscle is the metabolic powerhouse of the body, however, dysregulation of the mechanisms involved in skeletal muscle mass maintenance can have devastating effects leading to many metabolic and physiological diseases. The lack of effective solutions makes finding a validated nutritional intervention an urgent unmet medical need. In vitro testing in murine skeletal muscle cells and human macrophages was carried out to determine the effect of a hydrolysate derived from vicia faba (PeptiStrong: NPN_1) against phosphorylated S6, atrophy gene expression, and tumour necrosis factor alpha (TNF-α) secretion, respectively. Finally, the efficacy of NPN_1 on attenuating muscle waste in vivo was assessed in an atrophy murine model. Treatment of NPN_1 significantly increased the phosphorylation of S6, downregulated muscle atrophy related genes, and reduced lipopolysaccharide-induced TNF-α release in vitro. In a disuse atrophy murine model, following 18 days of NPN_1 treatment, mice exhibited a significant attenuation of muscle loss in the soleus muscle and increased the integrated expression of Type I and Type IIa fibres. At the RNA level, a significant upregulation of protein synthesis-related genes was observed in the soleus muscle following NPN_1 treatment. In vitro and preclinical results suggest that NPN_1 is an effective bioactive ingredient with great potential to prolong muscle health.
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Project description:BackgroundSodium-glucose cotransporter 2 inhibitors (SGLT2i) are commonly used in the management of type 2 diabetes mellitus (T2DM) and have been found to worsen the reduction of skeletal muscle mass in individuals with T2DM. This study aims to examine the potential of exercise in mitigating the skeletal muscle atrophy induced by SGLT2i treatment.MethodsA rat model of T2DM (40 male Sprague-Dawley rats; T2DM induced by a combination of high-fat diet and streptozotocin) was used to examine the effects of six-week treatment with Dapagliflozin (DAPA, SGLT2i) in combination with either aerobic exercise (AE) or resistance training (RT) on skeletal muscle. T2DM-eligible rats were randomized into the T2DM control group (CON, n = 6), DAPA treatment group (DAPA, n = 6), DAPA combined with aerobic exercise intervention group (DAPA + AE, n = 6), and DAPA combined with resistance training intervention group (DAPA + RT, n = 6). To assess the morphological changes in skeletal muscle, myosin ATPase and HE staining were performed. mRNA expression levels of Atrogin-1, MuRF1, and Myostatin were determined using quantitative PCR. Furthermore, protein expression levels of AKT, p70S6K, mTOR, FoXO1/3A, NF-κB, and MuRF1 were examined through western blotting.ResultsBoth the administration of DAPA alone and the combined exercise intervention with DAPA resulted in significant reductions in blood glucose levels and body weight in rats. However, DAPA alone administration led to a decrease in skeletal muscle mass, whereas RT significantly increased skeletal muscle mass and muscle fiber cross-sectional area. The DAPA + RT group exhibited notable increases in both total protein levels and phosphorylation levels of AKT and p70S6K in skeletal muscle. Moreover, the DAPA, DAPA + AE, and DAPA + RT groups demonstrated downregulation of protein expression (FoXO1/3A) and mRNA levels (Atrogin-1, MuRF1, and Myostatin) associated with muscle atrophy.ConclusionsOur findings provide support for the notion that dapagliflozin may induce skeletal muscle atrophy through mechanisms unrelated to protein metabolism impairment in skeletal muscle, as it does not hinder protein metabolic pathways while reduces muscle atrophy-related genes. Additionally, our observations reveal that RT proves more effective than AE in enhancing skeletal muscle mass and muscle fiber cross-sectional area in rats with T2DM by stimulating protein anabolism within the skeletal muscle.
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Project description:Skeletal muscle atrophy is a common and debilitating condition that lacks a pharmacologic therapy. To develop a potential therapy, we identified 63 mRNAs that were regulated by fasting in both human and mouse muscle, and 29 mRNAs that were regulated by both fasting and spinal cord injury in human muscle. We used these two unbiased mRNA expression signatures of muscle atrophy to query the Connectivity Map, which singled out ursolic acid as a compound whose signature was opposite to those of atrophy-inducing stresses. A natural compound enriched in apples, ursolic acid reduced muscle atrophy and stimulated muscle hypertrophy in mice. It did so by enhancing skeletal muscle insulin/IGF-I signaling and inhibiting atrophy-associated skeletal muscle mRNA expression. Importantly, ursolic acid's effects on muscle were accompanied by reductions in adiposity, fasting blood glucose, and plasma cholesterol and triglycerides. These findings identify a potential therapy for muscle atrophy and perhaps other metabolic diseases.
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