Tibialis Anterior Research Articles

Forces experienced at different levels of the musculoskeletal system during horizontal decelerations

ABSTRACT Horizontal decelerations are frequently performed during team sports and are closely linked to sports performance and injury. This study aims to provide a comprehensive description of the kinetic demands of decelerations at the whole-body, structural, and tissue-specific levels of the musculoskeletal system. Team-sports athletes performed maximal-effort horizontal decelerations whilst full-body kinematics and ground reaction forces (GRFs) were recorded. A musculoskeletal model was used to determine whole-body (GRFs), structural (ankle, knee, and hip joint moments and contact forces), and tissue (twelve lower-limb muscle forces) loads. External GRFs in this study, especially in the horizontal direction, were up to six times those experienced during accelerated or constant-speed running reported in the literature. To cope with these high external forces, large joint moments (hip immediately after touchdown; ankle and knee during mid and late stance) and contact forces (ankle, knee, hip immediately after touchdown) were observed. Furthermore, eccentric force requirements of the tibialis anterior, soleus, quadriceps, and gluteal muscles were particularly high. The presented loading patterns provide the first empirical explanations for why decelerating movements are amongst the most challenging in team sports and can help inform deceleration-specific training prescription to target horizontal deceleration performance, or fatigue and injury resistance in team-sports athletes.

In vivo intracellular Ca2+ profiles after eccentric rat muscle contractions: Addressing the mechanistic bases for repeated bout protection.

Eccentric contractions (ECC) are accompanied by accumulation of intracellular calcium ions ([Ca2+]i) and induce skeletal muscle damage. Suppressed muscle damage in repeated bouts of ECC is well characterized, however, whether it is mediated by altered Ca2+ profiles remains unknown. PURPOSE: We tested the hypothesis that repeated ECC suppresses Ca2+ accumulation via adaptions in Ca2+ regulation. METHODS: Male Wistar rats were divided into two groups: ECC single bout (ECC-SB) and repeated bout (ECC-RB). Tibialis anterior (TA) muscles were subjected to ECC (40 times, 5 sets) once (ECC-SB), or twice 14 days apart (ECC-RB). Under anesthesia, the TA muscle was loaded with Ca2+ indicator Fura-2 AM and the 340/380 nm ratio was evaluated as [Ca2+]i. Ca2+ handling proteins were measured by western blots. RESULTS: ECC induced [Ca2+]i increase in both groups, but ECC-RB evinced a markedly suppressed [Ca2+]i (Time: P < 0.01, Group: P = 0.0357). 5 hours post-ECC, in contrast to the localized [Ca2+]i accumulation in ECC-SB, ECC-RB exhibited lower and more uniform [Ca2+]i (P < 0.01). In ECC-RB mitochondria Ca2+ uniporter complex components, MCU and MICU2, were significantly increased pre-second ECC bout (P < 0.01) and both SERCA1 and MICU1 were better preserved after contractions (P < 0.01). CONCLUSION: 14 days after novel ECC skeletal muscle mitochondrial Ca2+ regulating proteins were elevated. Following subsequent ECC [Ca2+]i accumulation and muscle damage were suppressed and SERCA1 and MICU1 preserved. These findings suggest that tolerance to a subsequent ECC bout is driven, at least in part, by enhanced mitochondrial and SR Ca2+ regulation.

Time-series transcriptomics reveals distinctive mRNA expression dynamics associated with gene ontology specificity and protein expression in skeletal muscle after electrical stimulation-induced resistance exercise.

Resistance exercise upregulates and downregulates the expression of a wide range of genes in skeletal muscle. However, detailed analysis of mRNA dynamics such as response rates and temporal patterns of the transcriptome after resistance exercise has not been performed. We aimed to clarify the dynamics of time-series transcriptomics after resistance exercise. We used electrical stimulation-induced muscle contraction as a resistance exercise model (5 sets × 10 times of 3 s of 100-Hz electrical stimulation) on the tibialis anterior muscle of rats and measured the transcriptome in the muscle before and at 0, 1, 3, 6, and 12 h after muscle contractions by RNA sequencing. We also examined the relationship between the parameters of mRNA dynamics and the increase in protein expression at 12 h after muscle contractions. We found that the function of the upregulated genes differed after muscle contractions depending on their response rate. Genes related to muscle differentiation and response to mechanical stimulus were enriched in the sustainedly upregulated genes. Furthermore, there was a positive correlation between the magnitude of upregulated mRNA expression and the corresponding protein expression level at 12 h after muscle contractions. Although it has been theoretically suggested, this study experimentally demonstrated that the magnitude of the mRNA response after electrical stimulation-induced resistance exercise contributes to skeletal muscle adaptation via increases in protein expression. These findings suggest that mRNA expression dynamics such as response rate, a sustained upregulated expression pattern, and the magnitude of the response contribute to mechanisms underlying adaptation to resistance exercise.

Treatment with tofacitinib attenuates muscle loss through myogenin activation in the collagen-induced arthritis.

Sarcopenia is a muscle disease characterized by reduction of muscle strength and muscle mass. In RA, 25.9 to 43.3% of the patients present sarcopenia. The loss of muscle mass observed in RA patients occurs either by activation of catabolic pathways or by inhibition of anabolic pathways. Despite having a list of drugs capable of treating RA inflammation, their effect on muscle is unclear. Our objective was to evaluate the tofacitinib effect on the muscle mass of collagen-induced arthritis (CIA) mice. CIA was induced in male DBA/1J mice by subcutaneous injection of Type 2 Collagen plus Freund Adjuvant. Animals were randomized into 3 groups: CIA + tofacitinib; CIA + vehicle; and healthy controls. Treatment was administered twice a day, between days 18 and 45 after induction. Clinical score, edema, and body weight were evaluated during the experimental period. After euthanasia, tibiotarsal joints were collected for assessment of disease histopathological score, and tibialis anterior (TA) and gastrocnemius (GA) muscles were weighed to assess muscle mass. Muscle atrophy was evaluated by measurement of TA myofiber cross-sectional area (CSA). Protein expression was evaluated by western blot using GA homogenates. Serum inflammatory markers were evaluated by ELISA. Statistical analysis included ANOVA followed by Tukey's or with Kruskal-Wallis. The statistical difference was assumed for p < 0.05. Tofacitinib treatment decreased arthritis severity by reducing clinical score, and hind paw edema in comparison with the vehicle group. Tofacitinib showed weight gain, higher TA and GA weights, and increased CSA compared to the vehicle group. On day 45, Tofacitinib presented increased muscle strength compared to the vehicle group, however, no difference was found in muscle fatigue. Pax7 expression was unchanged, while MyoD expression showed an increasing trend, and myogenin expression was significantly increased in Tofacitinib compared to vehicle and control groups. The treatment didn't modify Murf-1 expression. Tofacitinib mice showed decreased serum levels of TNF and increased IL-6 serum levels. Tofacitinib attenuated muscle loss in arthritic mice, increased muscle weight and muscle CSA. Activation of satellite cell regeneration, based on the increased expression of myogenin, is a potential mechanism involved in tofacitinib action against muscle loss.

Effects of Raised Heel Insole on Muscle Activity during ankle Sudden Inversion in Normal Adults

Raised heel insoles increase the plantar flexion angle of the ankle and cause ankle inversion sprain. The purpose of this study was to artificially create an ankle sudden inversion situation, which is a mechanical situation of actual ankle joint damage, and investigate the effect of the raised heel insole on ankle joint muscle activity. The subjects of this study were forty subjects with normal adults. The subjects performed sudden ankle inversion on the trapdoor with no raised heel insole, insole heights of 3cm, and insole heights of 7cm. The application of the raised heel insole was conducted randomly. The subjects performed the trapdoor test three times using dominant feet with a 60-second rest period between tests. This study assessed muscle activity during sudden ankle inversion three times. Raised heel insoles showed a significant decrease in Tibialis Anterior, Peroneus Longus, and Peroneus Brevis muscle activity than no raised heel insole (p&lt;.05). Raised heel insoles showed a significant increase in Gastrocnemius muscle activity than no raised heel insole (p&lt;.05). Raised heel insoles increase the risk of ankle sprain injury by reducing tibialis anterior and peroneus muscle activity during sudden ankle inversion.

Curcumin Mitigates Muscle Atrophy Potentially by Attenuating Calcium Signaling and Inflammation in a Spinal Nerve Ligation Model

Denervation-induced calcium/calmodulin-dependent protein kinase II (CaMKII) activation and inflammation can result in muscle atrophy. Curcumin and bisdemethoxycurcumin are well known to exhibit an anti-inflammatory effect. In addition, curcumin has been shown to attenuate CaMKII activation in neuronal cells. This study aimed to examine the effect of curcumin or bisdemethoxycurcumin on CaMKII activation, inflammation, and muscle cross-sectional area (CSA) in spinal nerve ligated rats. Sixteen female rats were assigned to sham (CON), spinal nerve ligation (SNL), SNL+ curcumin 100 mg/kg BW (100CUR), and SNL+ bisdemethoxycurcumin 50 mg/kg BW (50CMO) for 4 weeks. Ipsilateral (surgical) soleus and tibialis anterior (TA) muscles was stained for dystrophin to measure CSA. Ipsilateral and contralateral (non-surgical) plantaris muscles were analyzed for protein content for acetylcholine receptor (AChR), CaMKII, CaMKIIThr286, nuclear factor-κB (NF-κB), NF-κBSer536, and interleukin-1β (IL-1β) and normalized to α-tubulin and then CON. A significant (p &lt; 0.050) group effect was observed for TA CSA where CON (11,082.25 ± 1617.68 μm2; p &lt; 0.001) and 100CUR (9931.04 ± 2060.87 μm2; p = 0.018) were larger than SNL (4062.25 ± 151.86 μm2). In the ipsilateral plantaris, the SNL (4.49 ± 0.69) group had greater CaMKII activation compared to CON (1.00 ± 0.25; p = 0.010), 100CUR (1.12 ± 0.45; p = 0.017), and 50CMO (0.78 ± 0.19; p = 0.009). The ipsilateral plantaris (2.11 ± 0.66) had greater IL-1β protein content than the contralateral leg (0.65 ± 0.14; p = 0.041) in the SNL group. In plantaris, the SNL (1.65 ± 0.51) group had greater NF-κB activation compared to CON (1.00 ± 0.29; p = 0.021), 100CUR (0.61 ± 0.10; p = 0.003), 50CMO (0.77 ± 0.25; p = 0.009) groups. The observed reduction in Ca2+ signaling and inflammation in type II plantaris muscle fibers might reflect the changes within the type II TA muscle fibers which may contribute to the mitigation of TA mass loss with curcumin supplementation.

Utilizing Multiple Triboelectric Nanogenerator Sensors and Signal Processing Technology for Monitoring Periodic Leg Movements of Sleep

High-quality sleep is essential for both physiological and cognitive functions. However, periodic leg movements of sleep (PLMS), an involuntary phenomenon during sleep, affects millions of people worldwide, contributing to sleep fragmentation and functional impairments. The accurate monitoring of PLMS is important for identifying and addressing these issues. Traditional methods, such as polysomnography (PSG), which monitor the bare tibialis muscle movements in clinical environments, may not adequately reflect the natural sleep patterns at home. They are costly and unsuitable for long-term studies. In recent years, there has been growing interest in using flexible sensors for sleep monitoring. Previous studies have applied triboelectric nanogenerators (TENGs) as flexible sensors to detect muscle movements during sleep. However, distinguishing true PLMS from false signals caused by external factors, such as blankets, remains a challenge. This study proposes a method using three TENG sensors placed on the dorsum, ankle, and tibialis, respectively, along with signal processing techniques to enhance the accuracy of PLMS detection. This study provides a cost-effective, comfortable method for PLMS monitoring, with the potential for widespread use in home-based sleep studies and long-term care in the future.

A wearable hip exoskeleton for anaerobic exercise in healthy adults

Guidelines encouraging social distancing, limited outings, and remote work due to COVID-19 have increased sedentary periods and reduced levels of physical activity. These habits increase the risk of metabolic diseases, obesity, cardiovascular disease, and diabetes mellitus. The World Health Organization recommends muscle-strengthening exercises as well as regular physical activity to promote overall health. This study investigates the effect of a wearable hip exoskeleton on muscle activity and heart rate during anaerobic exercise in 40 healthy adults (mean age of 40.00 ± 11.51 years; n = 20 females). Bot Fit, a wearable hip-type robotic exoskeleton, was developed by Samsung Electronics Co., Ltd. (Suwon, Republic of Korea) to enhance the effects of both aerobic and anaerobic exercise. All study participants performed a fitness exercise protocol, including knee-ups, good mornings, squats, mountain climbs, kick-backs, reverse lunges, and split jacks, with and without a Bot Fit. To evaluate the effect of anaerobic exercise with the Bot Fit, muscle activity and heart rate were measured during fitness exercises with and without a Bot Fit. Measured muscles were the rectus abdominis (RA), erector spinae (ES), rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), tibialis anterior (TA), gastrocnemius medialis (GCM), and gluteus maximus (GM). During anaerobic exercises with the Bot Fit, there was a significant increase in muscle activity compared to exercising without the Bot Fit. Muscle activity increased significantly in the RA, RF, VL, BF and TA muscles during knee-ups; in the ES, BF, and GM during good mornings; in the RF, VL, VM, BF, and GM during squats; in RA, RF, VL, VM, and GM during mountain climbs; in the RA and BF during kick-backs; in the RF, BF, and GCM during reverse lunges; and in the RF and VL during split jacks (p < 0.05). Heart rates showed a statistically significant increase during good mornings, mountain climbs, and reverse lunge exercises while wearing the Bot Fit (p < 0.05). This study demonstrated that anaerobic exercises by healthy adults using a Bot Fit led to enhanced activation of abdominal and lower-limb muscles as well as an improved heart rate, maximizing the effect of anaerobic exercise compared with the same exercise protocol without a Bot Fit. This suggests that use of a Bot Fit can increase the effectiveness of anaerobic exercise in healthy adults.

Extracellular matrix-mimicking cryogels composed of methacrylated fucoidan enhance vascularized skeletal muscle regeneration following volumetric muscle loss

Volumetric muscle loss (VML) significantly impairs the inherent regenerative ability of skeletal muscle and results in chronic functional impairment. Polysaccharides in the muscle extracellular matrix are crucial for regulating cell proliferation and differentiation. Recent studies indicate that fucoidan has beneficial effects on musculoskeletal conditions. However, the impact of fucoidan on skeletal muscle regeneration remains poorly understood. In this study, methacrylated fucoidan (FuMA) was synthesized through chemical grafting of the methacryloyl group onto fucoidan. In vitro experiments demonstrated that treatment with FuMA significantly up-regulated the expression of myogenic markers and promoted the formation of myotubes in C2C12 myoblast cells. Importantly, FuMA treatment led to a significant enhancement in mitochondrial energy metabolism of myoblasts via activation of the NRF2 antioxidant signaling pathway. To further investigate the regenerative properties in repairing skeletal muscle defects, we fabricated a dual crosslinked cryogel consisting of FuMA and methacrylated gelatin (GelMA) with a porous and interconnected structure. In a rat tibialis anterior muscle VML model, implantation of the FuMA/GelMA cryogel effectively promoted the regeneration of muscle fibers, reduced collagen deposition, and facilitated the formation of new blood vessels. Hence, polysaccharide-based cryogels represent a promising implantable biomimetic scaffold for facilitating skeletal muscle regeneration following severe injuries.

Contractile regulation of the glucocorticoid-sensitive transcriptome in young and aged skeletal muscle.

Elevated glucocorticoids alter the skeletal muscle transcriptome to induce a myopathy characterized by muscle atrophy, muscle weakness, and decreased metabolic function. These effects are more likely to occur and be more severe in aged muscles. Resistance exercise can blunt the development of glucocorticoid myopathy in young muscle, but the potential to oppose the signals initiating myopathy in aged muscle is unknown. To answer this, young (4-mo-old) and aged (24-to 25-mo-old) male C57BL/6 mice were randomized to receive either an intraperitoneal (IP) injection of dexamethasone (DEX; 2 mg/kg) or saline as a control. Two hours postinjections, the tibialis anterior (TA) muscles of mice were subjected to unilateral high-force contractions. Muscles were harvested 4 h later. The glucocorticoid- and contraction-sensitive genes were determined by RNA sequencing. The number of glucocorticoid-sensitive genes was similar between young and aged muscle. Contractions opposed changes to more glucocorticoid-sensitive genes in aged muscle, with this outcome primarily occurring when hormone levels were elevated. Glucocorticoid-sensitive gene programs opposed by contractions were primarily related to metabolism in young mice and muscle size regulation and inflammation in aged mice. In silico analysis implied peroxisome proliferator-activated receptor gamma-1 (PPARG) contributed to the contraction-induced opposition of glucocorticoid-sensitive genes in aged muscle. Increasing PPARG expression in the TA of aged mice using adeno-associated virus serotype 9 partially counteracted the glucocorticoid-induced reduction in runt-related transcription factor 1 (Runx1) mRNA content, recapitulating the effects observed by contractions. Overall, these data contribute to our understanding of the contractile regulation of the glucocorticoid transcriptome in aged skeletal muscle.NEW & NOTEWORTHY We establish the extent to which muscle contractions oppose changes to the glucocorticoid-sensitive transcriptome in both young and aged muscle. We also identify peroxisome proliferator-activated receptor gamma (PPARG) as a transcription factor likely contributing to contraction-induced opposition to the glucocorticoid transcriptome in aged muscle. Overall, these data contribute to our understanding of the contractile regulation of the glucocorticoid transcriptome.

Comprehensive corrective exercise program improves ankle function in female athletes with limited weight-bearing ankle dorsiflexion: A randomized controlled trial.

Limited ankle dorsiflexion range of motion is one of the most important risk factors for lower limb injury, which changes the biomechanics and the neuromuscular control of the lower limb muscles. This study aims to test the effectiveness of a comprehensive corrective exercise program (CCEP) on the range of motion, proprioception, dynamic balance, and muscle activation in female athletes with limited weight-bearing lunge ankle dorsiflexion range of motion. 30 female athletes aged 15 to 25 years with dorsiflexion under 34° were randomized to two groups. The intervention group (n = 15) received eight weeks of CCEP including soft tissue mobilization, joint mobilization, stretching, and strengthening, and the control (n = 15) group did not receive any intervention. range of motion, proprioception, dynamic balance, and muscle activation were assessed before and after the intervention. The training group showed clinically acceptable and statistically significant changes in ankle dorsiflexion range of motion (ES = 0.714), balance (ES = 0.423), and proprioception (ES = 0.253; P < 0.05). There were significant changes in the activity of the tibialis anterior and soleus muscles in the dynamic overhead squat test (descending and ascending phases) and the activity of the medial gastrocnemius in the descending phase decreased significantly (P < 0.05). No significant change was observed in the activity of the peroneus longus muscle (P > 0.05). The findings show that CCEP appears to be beneficial in increasing dorsiflexion range of motion, proprioception, balance, and decreasing ankle muscle activity among individuals with limited ankle dorsiflexion. Improving the dorsiflexion range of motion may be promising for reducing ankle sprain injury.

Astragaloside IV Improves Muscle Atrophy by Modulating the Activity of UPS and ALP via Suppressing Oxidative Stress and Inflammation in Denervated Mice.

Peripheral nerve injury is common clinically and can lead to neuronal degeneration and atrophy and fibrosis of the target muscle. The molecular mechanisms of muscle atrophy induced by denervation are complex and not fully understood. Inflammation and oxidative stress play an important triggering role in denervated muscle atrophy. Astragaloside IV (ASIV), a monomeric compound purified from astragalus membranaceus, has antioxidant and anti-inflammatory properties. The aim of this study was to investigate the effect of ASIV on denervated muscle atrophy and its molecular mechanism, so as to provide a new potential therapeutic target for the prevention and treatment of denervated muscle atrophy. In this study, an ICR mouse model of muscle atrophy was generated through sciatic nerve dissection. We found that ASIV significantly inhibited the reduction of tibialis anterior muscle mass and muscle fiber cross-sectional area in denervated mice, reducing ROS and oxidative stress-related protein levels. Furthermore, ASIV inhibits the increase in inflammation-associated proteins and infiltration of inflammatory cells, protecting the denervated microvessels in skeletal muscle. We also found that ASIV reduced the expression levels of MAFbx, MuRF1 and FoxO3a, while decreasing the expression levels of autophagy-related proteins, it inhibited the activation of ubiquitin-proteasome and autophagy-lysosome hydrolysis systems and the slow-to-fast myofiber shift. Our results show that ASIV inhibits oxidative stress and inflammatory responses in skeletal muscle due to denervation, inhibits mitophagy and proteolysis, improves microvascular circulation and reverses the transition of muscle fiber types; Therefore, the process of skeletal muscle atrophy caused by denervation can be effectively delayed.

Kinetic changes of gait initiation in individuals with chronic ankle instability: A systematic review.

Gait initiation (GI) in individuals with chronic ankle instability (CAI) has shown differences in the center of pressure (COP) and muscular measures compared to healthy controls. Some studies reported that these alterations appeared when GI was with the affected leg, while others indicated that they occurred when GI was with the non-affected leg. This systematic review aimed to understand kinetic and muscular differences between individuals with CAI, healthy controls, and the affected and non-affected legs of individuals with CAI. PubMed, Science Direct, Web of Science, Google Scholar, and Scopus databases (1990-2023) were searched using the Population, Exposure, Comparator, and Outcome measure. The PRISMA guidelines were followed. The outcome measures were the peak and rate of COP displacement in the medial-lateral and anterior-posterior directions, and resultant plane during phases 1, 2, and 3 of COP trace during GI and the duration of each phase. The other measures included the onset time of the tibialis anterior and soleus muscle activity between individuals with CAI, healthy controls, and the affected and non-affected legs of the individuals with CAI. The studies' quality assessment was conducted based on the Strengthening the Reporting of Observational Studies in Epidemiology checklist. Five studies were included in the final evaluation. The results of included studies showed, individuals with CAI spent less time during phases 1 and 2, as well as a shorter peak of COP displacement in the lateral direction during phase 1 compared to healthy controls, regardless of whether the GI was with the affected or non-affected leg. Individuals with CAI have probably adopted a strategy involving adjusting the peak of COP displacement to manage internal sway while in a single-leg stance. Overall, there was no comprehensive conclusion about differences between the two legs in individuals with CAI.

Spiny mice are primed but fail to regenerate volumetric skeletal muscle loss injuries

BackgroundIn recent years, the African spiny mouse Acomys cahirinus has been shown to regenerate a remarkable array of severe internal and external injuries in the absence of a fibrotic response, including the ability to regenerate full-thickness skin excisions, ear punches, severe kidney injuries, and complete transection of the spinal cord. While skeletal muscle is highly regenerative in adult mammals, Acomys displays superior muscle regeneration properties compared with standard laboratory mice following several injuries, including serial cardiotoxin injections of skeletal muscle and volumetric muscle loss (VML) of the panniculus carnosus muscle following full-thickness excision injuries. VML is an extreme muscle injury defined as the irrecoverable ablation of muscle mass, most commonly resulting from combat injuries or surgical debridement. Barriers to the treatment of VML injury include early and prolonged inflammatory responses that promote fibrotic repair and the loss of structural and mechanical cues that promote muscle regeneration. While the regeneration of the panniculus carnosus in Acomys is impressive, its direct relevance to the study of VML in patients is less clear as this muscle has largely been lost in humans, and, while striated, is not a true skeletal muscle. We therefore sought to test the ability of Acomys to regenerate a skeletal muscle more commonly used in VML injury models.MethodsWe performed two different VML injuries of the Acomys tibialis anterior muscle and compared the regenerative response to a standard laboratory mouse strain, Mus C57BL6/J.ResultsNeither Acomys nor Mus recovered lost muscle mass or myofiber number within three months following VML injury, and Acomys also failed to recover force production better than Mus. In contrast, Acomys continued to express eMHC within the injured area even three months following injury, whereas Mus ceased expressing eMHC less than one-month post-injury, suggesting that Acomys muscle was primed, but failed, to regenerate.ConclusionsWhile the panniculus carnosus muscle in Acomys regenerates following VML injury in the context of full-thickness skin excision, this regenerative ability does not translate to regenerative repair of a skeletal muscle.

Transcriptional Analysis of Cancer Cachexia: Conserved and Unique Features Across Pre-Clinical Models and Biological Sex.

Studies suggest heterogeneity in cancer cachexia (CC) among models and biological sexes, yet examinations comparing models and sexes are scarce. We compared the transcriptional landscape of skeletal muscle across murine CC models and biological sexes during early and late CC. Global gene expression analyses were performed on gastrocnemius (LLC-Lewis Lung Carcinoma), quadriceps (KPC-pancreatic), and tibialis anterior (C26-colorectal and ApcMin/+) muscles across biological sexes. Differentially expressed genes (DEGs) were identified using an adj-p-value of <0.05, followed by pathway and computational cistrome analyses. Integrating all controls, early, and late-stage of all models and sexes revealed up to 68% of DEGs and pathways were enriched at early and late CC, indicating a conserved transcriptional profile during CC development. Comparing DEGs and pathways within sexes and across models, in early-CC, the transcriptional response was highly heterogeneous. At late-stage, 11.5% of upregulated and 10% of downregulated genes were shared between models in males, while 18.9% of upregulated and 7% of downregulated DEGs were shared in females. Shared DEGs were enriched in proteasome and mitophagy/autophagy pathways (upregulated), and downregulation of energy metabolism pathways in males only. Between sexes, though proportion of shared DEGs was low (<16%), similar pathway enrichment was observed, including proteasome and mitophagy at late-stage CC. In early-CC, Osmr upregulation was the only commonality across all models and sexes, while CLOCK and ARNTL/BMAL1 were predicted transcriptional factors associated with dysregulations in all three male models. This study highlights sex and model differences in CC progression and suggests conserved transcriptional changes as potential therapeutic targets.

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.

Titin hyper-phosphorylation in the peripheral skeletal muscle but not the diaphragm of HFpEF: association with muscle atrophy and dysfunction

Abstract Background Titin hypo-phosphorylation is an important regulatory mechanism for myocardial stiffness in heart failure with preserved ejection fraction (HFpEF). In contrast, a hyper-phosphorylation of titin in the peripheral skeletal muscle (SKM) was reported in mouse models exhibiting muscle atrophy. In former studies it, was shown that SKM atrophy occurs in HFpEF and is associated with muscle dysfunction and a fiber type shift from type I, towards type II fibers. However, these alterations were not seen in the diaphragm muscle (Dia) and a fiber type shift towards type I was documented. So far, no information about the phosphorylation status of titin is available for SKM and the Dia and its association with muscle dysfunction in HFpEF. Purpose To assess titin phosphorylation in SKM and Dia of a HFpEF animal model and to relate it to muscle function and atrophy. Methods To confirm the development of HFpEF echocardiography was performed in female ZSF1-lean (con, n=18) and ZSF1-obese rats (HFpEF, n=18) at the age of 32 weeks. Skeletal muscle function (soleus) was measured in an organ bath setting after the animals were sacrificed. Tissue of the tibialis anterior muscle (TA) and the diaphragm (Dia) was collected and fixed in formalin or snap frozen in liquid nitrogen. To detect titin expression homogenized TA and Dia tissue samples were resolved on a vertical agarose gel. Phosphorylated titin was detected by staining the gel with Pro-Q Diamond, whereas total titin was visualized using Sypro Ruby. Cross sectional area (CSA) of TA and Dia was quantified after Hematoxylin/eosin staining of tissue section. Myosin heavy chain (MHC) ubiquitination was assessed by western blot. Results Assessment of SKM function revealed significantly reduced maximal absolute (-12 %) and maximal specific force (-22 %) in HFpEF animals when compared to controls. In the TA a significantly reduced CSA was evident in HFpEF (1911±103 vs. 1394±103 µm2, p=0.002), whereas in the diaphragm an increased CSA was noted (438±11 vs. 560±18 µm2, p&amp;lt;0.001). In TA of HFpEF animals, the proportion of phosphorylated titin was significantly elevated whereas the total amount of titin was reduced (Fig. 1A, C). In addition, a significantly higher proportion of ubiquitinated MHC was detected (Figure 1E). However in the Dia these alterations were not observed, even a higher amount of total titin was seen (Fig. 1B, D, F). Furthermore, a significant negative correlation between phosphorylated titin and absolute force (r=-0.461, p=0.035, Fig. 2A) as well as specific force (r=-0.693, p=0.0005, Fig. 2B) was evident. Conclusion In contrast to the heart, the TA showed a titin hyper-phosphorylation in HFpEF, going along with a degradation of total titin. This hyper-phosphorylation could be correlated with a loss of force in the SKM. Additionally a higher ubiquitination of MHC was prevalent in the TA, which may be connected to molecular remodeling and fiber type shift towards a more glycolytic type.

MYH7-related myopathies: clinical, myopathological and genotypic spectrum in a multicentre French cohort

BackgroundMyosin heavy chain 7 (MYH7)-related myopathies (MYH7-RMs) are a group of muscle disorders linked to pathogenic variants in the MYH7 gene, encoding the slow/beta-cardiac myosin heavy chain, which is highly...

Molecular, Histological, and Functional Changes in Acta1-MCM;FLExDUX4/+ Mice.

DUX4 is the major gene responsible for facioscapulohumeral dystrophy (FSHD). Several mouse models expressing DUX4 have been developed, the most commonly used by academic laboratories being ACTA1-MCM/FLExDUX4. In this study, molecular and histological modifications in the tibialis anterior and quadriceps muscles were investigated in this model at different time points. We investigated several changes that could be used as markers of therapeutic efficacy. Our results confirm the progressive muscular dystrophy previously described but also highlight biases associated with tamoxifen injections and the complexity of choosing the genes used to calculate a DUX4-pathway gene composite score. We also developed a comprehensive force test that better reflects the movements made in everyday life. This functional force-velocity-endurance model, which describes the force production capacities at all velocity and fatigue levels, was applied on 12-13-week-old animals without tamoxifen. Our data highlight that previously unsuspected muscle properties are also affected by the expression of DUX4, leading to a weaker muscle with a lower initial muscle force but with preserved power and endurance capacity. Importantly, this force-velocity-endurance approach can be used in humans for clinical evaluations.

Effects of Maturation on Plantar Flexor Activity and Achilles Tendon Stiffness in Vertical Jumping: Sex Differences.

The aim of this study was to investigate the effect of maturation on vertical jumping performance, in adolescent boys and girls, concerning plantar flexor activity and Achilles tendon (AT) stiffness. Thirty-nine adolescents were tested in a counter-movement jump (CMJ) at three different time points: 18 and 9 months before peak height velocity (PHV) and at PHV. The EMG activity of the medialis gastrocnemius (MG) and tibialis anterior (TA) muscles was evaluated, in relation to jump height. Boys showed higher jumping ability and AT stiffness than girls. Additionally, boys revealed increased eccentric (ecc) and concentric (con) MG activity, along with decreased ecc and con TA activity, near PHV. On the other hand, girls showed increased ecc and con TA/MG co-contraction compared to boys, mainly near PHV. In conclusion, a different mechanism of vertical jumping performance is adopted between early adolescent boys and girls. Nevertheless, no notable alterations in jumping capability were detected over time, indicating that the maturation process does not influence stretch-shortening cycle (SSC) performance.