Signaling In Muscle Research Articles

EVALUATION OF NECK FATIGUE CAUSED BY WEARING HELMET IN MOTION: AN ELECTROMYOGRAPHY STUDY

The increased weight of multifunction and intelligent helmet systems can cause an exacerbation of the neck workload. Further, increased weight of the helmet can reduce the wearing comfort, and prolonged use may cause neck fatigue and even neck injury. This study evaluates the fatigue of neck muscles caused by wearing a helmet in motion using electromyography (EMG) measurement. Additionally, a comprehensive evaluation model for neck fatigue was established effectively. Twenty healthy subjects were selected to run for 10[Formula: see text]min continuously in each task by wearing two different helmets, respectively, during which the EMG signals of different neck muscles and subjective scores were recorded and analyzed. Two-way repeated measures analysis of variance (ANOVA) and Pearson correlation analysis were used to obtain indicators of neck fatigue, based on which the support vector machine (SVM) was used to construct a classification model of neck fatigue. By using integral EMG (IEMG) and root mean square (RMS) for assessing the neck injury in sternocleidomastoideus and trapezius muscles, it was observed that the mean power frequency (MPF) and median frequency (MF) in trapezius and splenius capitis could be used as effective evaluation indicators of neck fatigue. The EMG activity in trapezius was the highly sensitivity to fatigue when wearing helmets in motion. The classifier for distinguishing three different neck fatigue levels was 91.67% accurate. This study demonstrates the feasibility of an EMG-based method to evaluate the neck fatigue caused by wearing a helmet in motion, and also provides an evaluation method for the optimal design of helmets in the future.

A-Kinase-Anchoring-Protein Subtypes Differentially Regulate GPCR Signaling and Function in Human Airway Smooth Muscle.

A-kinase-anchoring proteins (AKAPs) act as scaffold proteins that anchor the regulatory subunits of the cAMP-dependent protein kinase A (PKA) to coordinate and compartmentalize signaling elements and signals downstream of Gs-coupled G protein-coupled receptors (GPCRs). The beta-2-adrenoceptor (β2AR), as well as the Gs-coupled EP2 and EP4 receptor subtypes of the E-prostanoid (EP) receptor subfamily, are effective regulators of multiple airway smooth muscle (ASM) cell functions whose dysregulation contributes of asthma pathobiology. Here, we identify specific roles of the AKAPs Ezrin and Gravin, in differentially regulating PKA substrates downstream of the β2AR, EP2 receptor (EP2R) and EP4 receptor (EP4R). Knockdown of Ezrin, Gravin, or both in primary human ASM cells caused differential phosphorylation of the PKA substrates vasodilator-stimulated phosphoprotein (VASP) and heat shock protein 20 (HSP20). Ezrin knockdown, as well as combined Ezrin + Gravin knockdown significantly reduced the induction of phospho-VASP and phospho-HSP20 by β2AR, EP2R, and EP4R agonists. Gravin knockdown inhibited the induction of phospho-HSP20 by β2AR, EP2R, and EP4R agonists. Knockdown of Ezrin, Gravin, or both also attenuated histamine-induced phosphorylation of MLC20. Moreover, knockdown of Ezrin, Gravin or both suppressed the inhibitory effects of Gs-coupled receptor agonists on cell migration in ASM cells. These findings demonstrate the role of AKAPs in regulating Gs-coupled GPCR signaling and function in ASM, and suggest the therapeutic utility of targeting specific AKAP family members in the management of asthma.

Abstract Tu050: Deficiency Of Mitochondrial Disulfide Relay Carrier Leads To Cardiac Hypertrophy

Background: Innate immune activation is critical for cardiac hypertrophy; however, its upstream regulation is less well understood. Coiled-coil-helix-coiled-coil-helix domain 4 (CHCHD4) is an essential carrier for the import of various mitochondrial proteins including TP53 -regulated inhibitor of apoptosis 1 (TRIAP1). CHCHD4 was recently identified as a dysregulated gene in patients with dilated cardiomyopathy and was separately found to mediate innate immune signaling in skeletal muscle. Therefore, we hypothesized that CHCHD4 may play a role in the development of cardiac hypertrophy by regulating innate immunity. Methods: Genetically modified C57BL/6 mice overexpressing CHCHD4 (CHCHD4 Tg) or haploinsufficient in CHCHD4 ( CHCHD4 +/- ) were utilized. Mice were injected either with low dose (2 mg/kg) or high dose (30 mg/kg) isoproterenol (ISO) daily for up to 3 wk to induce hypertrophy. Results: CHCHD4 +/- mice developed cardiac hypertrophy (HW/BW (mg/g): 3.62 ± 0.15 CHCHD4 +/- vs 2.70 ± 0.13 wild-type (WT) or 2.55 ± 0.16 CHCHD4 Tg, p<0.0001) when allowed to age to 28 wk and showed reduced left ventricular ejection fraction (EF) at 1 year when compared with wild-type or CHCHD4 Tg mice (EF (%): 50.94 ± 0.94 CHCHD4 +/- vs 58.33 ± 0.78 wild-type or 57.88 ± 1.32 CHCHD4 Tg, p<0.0001). After low dose ISO treatment, CHCHD4 +/- mice had reduced EF at 2 wk compared to WT or CHCHD4 Tg mice (EF (%): 44.60 ± 1.74 CHCHD4 +/- vs 54.28 ± 0.86 wild-type, p<0.0001; or vs 52.76 ± 1.33 CHCHD4 Tg, p=0.0006). After high dose ISO treatment, WT mice developed cardiac hypertrophy by 1 wk and impaired EF by 3 wk, while CHCHD4 Tg mice remained normal. ISO treatment caused reduction of CHCHD4 levels in both the 24 hr and 1 wk states. This reduction was associated with decreased TRIAP1 and activation of the cGAS-STING-NFkB pathway in wild-type, but not CHCHD4 Tg mice. Further, plasma mitochondrial DNA (mtDNA) was 2.3 times higher in WT mice treated with high dose ISO for 1 wk compared to WT control (n=8-11/group, p=0.011), while that of CHCHD4 Tg mice was not significantly changed by ISO treatment. Conclusions: Our findings suggest that CHCHD4 may be a key upstream regulator of innate immune activation mediating cardiac hypertrophy and that cell-free mtDNA in blood could be a potential biomarker of pathogenesis.

Methylglyoxal reduces resistance exercise-induced protein synthesis and anabolic signaling in rat tibialis anterior muscle.

Resistance exercise provides significant benefits to skeletal muscle, including hypertrophy and metabolic enhancements, supporting overall health and disease management. However, skeletal muscle responsiveness to resistance exercise is significantly reduced in conditions such as aging and diabetes. Recent reports suggest that glycation stress contributes to muscle atrophy and impaired exercise-induced muscle adaptation; however, its role in the muscle response to resistance exercise remains unclear. Therefore, in this study, we investigated whether methylglyoxal (MGO), a key factor in glycation stress, affects the acute responsiveness of skeletal muscles to resistance exercise, focusing on protein synthesis and the key signaling molecules. This study included 12 8-week-old male Sprague-Dawley rats divided into two groups: one received 0.5% MGO-supplemented drinking water (MGO group) and the other received regular water (control group). After 10 weeks, the left tibialis anterior muscle of each rat was subjected to electrical stimulation (ES) to mimic resistance exercise, with the right muscle serving as a non-stimulated control. Muscle protein-synthesis rates were evaluated with SUnSET, and phosphorylation levels of key signaling molecules (p70S6K and S6rp) were quantified using western blotting. In the control group, stimulated muscles exhibited significantly increased muscle protein synthesis and phosphorylation levels of p70S6K and S6rp. In the MGO group, these increases were attenuated, indicating that MGO treatment suppresses the adaptive response to resistance exercise. MGO diminishes the skeletal muscle's adaptive response to ES-simulated resistance exercise, affecting both muscle protein synthesis and key signaling molecules. The potential influence of glycation stress on the effectiveness of resistance exercise or ES emphasizes the need for individualized interventions in conditions of elevated glycation stress, such as diabetes and aging.

Glycogen homeostasis and mtDNA expression require motor neuron to muscle TGFβ/Activin Signaling in Drosophila.

Maintaining metabolic homeostasis requires coordinated nutrient utilization between intracellular organelles and across multiple organ systems. Many organs rely heavily on mitochondria to generate (ATP) from glucose, or stored glycogen. Proteins required for ATP generation are encoded in both nuclear and mitochondrial DNA (mtDNA). We show that motoneuron to muscle signaling by the TGFβ/Activin family member Actβ positively regulates glycogen levels during Drosophila development. Remarkably, we find that levels of stored glycogen are unaffected by altering cytoplasmic glucose catabolism. Instead, Actβ loss reduces levels of mtDNA and nuclearly encoded genes required for mtDNA replication, transcription and translation. Direct RNAi mediated knockdown of these same nuclearly encoded mtDNA expression factors also results in decreased glycogen stores. Lastly, we find that expressing an activated form of the type I receptor Baboon in muscle restores both glycogen and mtDNA levels in actβ mutants, thereby confirming a direct link between Actβ signaling, glycogen homeostasis and mtDNA expression.

The relationship between asymmetry changes in the slope frequency of bioelectrical activity of the gluteus maximus muscles and experience in short track speed skating athletics

BACKGROUND: In short track speed skating, there is asymmetric fatigue of the gluteus maximus (GM) muscle resulting from the technique of skating. Scientific reports confirm the relationship between muscle fatigue and its change in the slope frequency of bioelectrical activity. OBJECTIVE: To investigate whether athletic experience in elite short track speed skating can distinguish the asymmetry change in slope frequency of the raw electromyographic signal (EMG) of the GM muscle, influenced by the disparity in experience between junior and senior athletes. METHODS: In the research, an elite group of short track speed skating national team athletes Junior and Senior, participated. Isometric tension GM muscle was tested using the Biering-Sorensen test. RESULTS: The study confirmed differences in the asymmetry of slope frequences EMG signal in GM muscle between juniors and seniors in short track speed skating (p⩽ 0.001). Senior athletes showed greater slope frequences in the right GM muscle (p⩽ 0.002), while juniors showed greater in the left GM muscle (p⩽ 0.008). Intergroup analysis revealed significantly meaningful differences (p⩽ 0.001) in the level of slope frequences of the right GM muscle (juniors vs. seniors), highlighting the asymmetry resulting from experience. CONCLUSIONS: Statistically significant differences in the level of slope frequences of the right gluteus maximus muscle juniors vs. seniors were demonstrated, suggesting asymmetry due to experience and skating technique.

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.

Hepatokines: unveiling the molecular and cellular mechanisms connecting hepatic tissue to insulin resistance and inflammation.

Insulin resistance arising from Non-Alcoholic Fatty Liver Disease (NAFLD) stands as a prevalent global ailment, a manifestation within societies stemming from individuals' suboptimal dietary habits and lifestyles. This form of insulin resistance emerges as a pivotal factor in the development of type 2 diabetes mellitus (T2DM). Emerging evidence underscores the significant role of hepatokines, as hepatic-secreted hormone-like entities, in the genesis of insulin resistance and eventual onset of type 2 diabetes. Hepatokines exert influence over extrahepatic metabolism regulation. Their principal functions encompass impacting adipocytes, pancreatic cells, muscles, and the brain, thereby playing a crucial role in shaping body metabolism through signaling to target tissues. This review explores the most important hepatokines, each with distinct influences. Our review shows that Fetuin-A promotes lipid-induced insulin resistance by acting as an endogenous ligand for Toll-like receptor 4 (TLR-4). FGF21 reduces inflammation in diabetes by blocking the nuclear translocation of nuclear factor-κB (NF-κB) in adipocytes and adipose tissue, while also improving glucose metabolism. ANGPTL6 enhances AMPK and insulin signaling in muscle, and suppresses gluconeogenesis. Follistatin can influence insulin resistance and inflammation by interacting with members of the TGF-β family. Adropin show a positive correlation with phosphoenolpyruvate carboxykinase 1 (PCK1), a key regulator of gluconeogenesis. This article delves into hepatokines' impact on NAFLD, inflammation, and T2DM, with a specific focus on insulin resistance. The aim is to comprehend the influence of these recently identified hormones on disease development and their underlying physiological and pathological mechanisms.

A Novel MRI-Based Paravertebral Muscle Quality (PVMQ) Score for Evaluating Muscle Quality and Bone Quality: A Comparative Study with the VBQ Score.

This study aims to develop a novel MRI-based paravertebral muscle quality (PVMQ) score for assessing muscle quality and to investigate its correlation with the degree of fat infiltration (DFF) and the vertebral bone quality (VBQ) score of paravertebral muscles. Additionally, the study compares the effectiveness of the PVMQ score and the VBQ score in assessing muscle quality and bone quality. PVMQ scores were derived from the ratio of paravertebral muscle signal intensity (SI) to L3 cerebrospinal fluid SI on T2-weighted MRI. Image J software assessed paravertebral muscle cross-sectional area (CSA) and DFF. Spearman rank correlation analyses explored associations between PVMQ, VBQ scores, DFF, and T-scores in both genders. Receiver operating characteristic (ROC) curves compared PVMQ and VBQ scores' effectiveness in distinguishing osteopenia/osteoporosis and high paraspinal muscle DFF. In this study of 144 patients (94 females), PVMQ scores were significantly higher in osteoporosis and osteopenia groups compared to normals, with variations observed between genders (P < 0.05). PVMQ showed stronger positive correlation with VBQ scores and DFF in females than males (0.584 vs 0.445, 0.579 vs 0.528; P < 0.01). ROC analysis favored PVMQ over VBQ for low muscle mass in both genders (AUC = 0.767 vs 0.718, 0.793 vs 0.718). VBQ was better for bone mass in males (0.737/0.865 vs 0.691/0.858), whereas PVMQ excelled for females (0.808/0.764 vs 0.721/0.718). The novel PVMQ score provides a reliable assessment of paravertebral muscle quality and shows a strong correlation with VBQ scores and DFF, particularly in females. It outperforms VBQ scores in evaluating muscle mass and offers valuable insights for assessing bone mass in females. These findings underscore the potential of the PVMQ score as a dual-purpose tool for evaluating both muscle and bone health, informing future research and clinical practice.

Respiratory SARS-CoV-2 Infection Causes Skeletal Muscle Atrophy and Long-Lasting Energy Metabolism Suppression.

Muscle fatigue represents the most prevalent symptom of long-term COVID, with elusive pathogenic mechanisms. We performed a longitudinal study to characterize histopathological and transcriptional changes in skeletal muscle in a hamster model of respiratory SARS-CoV-2 infection and compared them with influenza A virus (IAV) and mock infections. Histopathological and bulk RNA sequencing analyses of leg muscles derived from infected animals at days 3, 30, and 60 post-infection showed no direct viral invasion but myofiber atrophy in the SARS-CoV-2 group, which was accompanied by persistent downregulation of the genes related to myofibers, ribosomal proteins, fatty acid β-oxidation, tricarboxylic acid cycle, and mitochondrial oxidative phosphorylation complexes. While both SARS-CoV-2 and IAV infections induced acute and transient type I and II interferon responses in muscle, only the SARS-CoV-2 infection upregulated TNF-α/NF-κB but not IL-6 signaling in muscle. Treatment of C2C12 myotubes, a skeletal muscle cell line, with combined IFN-γ and TNF-α but not with IFN-γ or TNF-α alone markedly impaired mitochondrial function. We conclude that a respiratory SARS-CoV-2 infection can cause myofiber atrophy and persistent energy metabolism suppression without direct viral invasion. The effects may be induced by the combined systemic interferon and TNF-α responses at the acute phase and may contribute to post-COVID-19 persistent muscle fatigue.

Effects of hand dominance on myoelectric signal of non‑fatigued lumbar multifidus muscle during single arm lifts.

Some evidence indicates that lower back muscles located at the non‑dominant side of the body are more fatigue resistant than their opposite counterparts presumably due to preferential use of the dominant hand. The aim of the study was to determine if any distinction exists in the surface electromyographic activity of corresponding contralateral non‑fatigued lumbar multifidus (LM) muscles as a function of hand dominance. The relative to maximum root mean square, the median frequency (MdF) and spike shape parameters were computed from the surface myoelectric signals of ipsilateral and contralateral lumbar multifidus muscle of 46 adult healthy subjects (27 right‑handed, 19 left‑handed) during voluntary contractions evoked by the single arm lifts in prone position. Activation of LM as a contralateral muscle to lifted arm was greater than as ipsilateral muscle, independently of handedness. Regardless if LM performed ipsi‑ or contralateral action to the lifted arm, the mean spike amplitude, slope, number of peaks per spike and spike duration were greater and mean spike frequency as well as MdF were smaller in the muscle of dominant than non‑dominant side. Combined changes of spike shape measures indicate increased recruitment, lower firing rates and higher synchronization of motor units in the LM of dominant side as compared to its counterpart.

EMG-based prediction of step direction for a better control of lower limb wearable devices

Background and objectivesLower-limb wearable devices can significantly improve the quality of life of subjects suffering from debilitating conditions, such as amputations, neurodegenerative disorders, and stroke-related impairments. Current control approaches, limited to forward walking, fall short of replicating the complexity of human locomotion in complex environments, such as uneven terrains or crowded places. Here we propose a high-level controller based on two Support Vector Machines exploiting four surface electromyography (EMG) signals of the thigh muscles to detect the onset (Toe-off intention decoder) and the direction (Directional EMG decoder) of the upcoming step. Methods and materialsWe validated a preliminary version of the approach by acquiring EMG signals from ten healthy subjects, performing steps in four directions (forward, backward, right, and left), in three different settings (ground-level walking, stairs, and ramps), and in both steady-state and static conditions. Both the Toe-off intention and Directional EMG decoders have been tested with a 5-fold cross-validation repeated five times, using linear and radial-basis-function kernels, and by changing the classification output timing, from 200 ms before to 50 ms after the toe-off. ResultsThe Toe-off intention decoder reached a median accuracy of 83.34 % (interquartile range (IQR): 6.48) and specificity of 92.72 % (IQR: 3.62) in its radial-basis-function version, while the Directional EMG decoder's median accuracy ranged between 73.92 % (IQR: 5.8), 200 ms before the toe-off, to 92.91 % (IQR: 4.11), 50 ms after the toe-off, with the radial-basis-function kernel implementation. For both the Toe-off intention and Directional EMG decoders the radial-basis-function version achieved better performances than the linear one (Wilcoxon signed rank test, p < 0.05). Conclusions and significanceThe combination of the two decoders proved to be a promising solution to detect the step initiation and classify its direction, paving the way for wearable devices with a broader range of movements and more degrees of freedom, ultimately promoting usability in uncontrolled settings and better reactions to external perturbations. Additionally, the encumbrance of the setup is limited to the thigh of the leg of interest, which simplifies the implementation in compact devices, concurrently limiting the sensors worn by the subject.

How to Optimize the Experimental Protocol for Surface EMG Signal Measurements Using the InterCriteria Decision-Making Approach

The InterCriteria decision-making approach, known as InterCriteria analysis (ICrA), was applied here to optimize the experimental protocol when the surface electromyography (EMG) signals of upper arm human muscles are recorded. Ten healthy subjects performed cycling movements in the sagittal plane with and without added weight for ten, six, two, and one second, respectively, for each active phase. The EMG signals from six muscles, namely m. deltoideus pars clavicularis and pars spinata, m. brachialis, m. anconeus, m. biceps brachii, and m. triceps brachii caput longum, were recorded. ICrA was used on the obtained data to find correlations between the sixteen different phases, eight for elbow flexion and eight for elbow extension. Based on the obtained results, we proposed an optimized experimental protocol (OEP) that omits slower and more difficult tasks while saving crucial data. The optimized protocol consists of seven, instead of ten, tasks and takes three minutes less than the time taken for the full experimental protocol (FEP). The lower number of movements in the OEP could prevent physical and psychical fatigue, discomfort, or even pain in the investigated subjects. In addition, the time to train subjects, as well as the time to process the surface EMG data, can be significantly reduced.

Unveiling the Threat of Maternal Advanced Glycation End Products to Fetal Muscle: Palmitoleic Acid to the Rescue.

Advanced glycation end products (AGEs) accumulate in the plasma of pregnant women with hyperglycemia, potentially inducing oxidative stress and fetal developmental abnormalities. Although intrauterine hyperglycemia has been implicated in excessive fetal growth, the effects of maternal AGEs on fetal development remain unclear. We evaluated the differentiation regulators and cellular signaling in the skeletal muscles of infants born to control mothers (ICM), diabetic mothers (IDM), and diabetic mothers supplemented with either cis-palmitoleic acid (CPA) or trans-palmitoleic acid (TPA). Cell viability, reactive oxygen species levels, and myotube formation were assessed in AGE-exposed C2C12 cells to explore potential mitigation by CPA and TPA. Elevated receptors for AGE expression and decreased Akt and AMPK phosphorylation were evident in rat skeletal muscles in IDM. Maternal palmitoleic acid supplementation alleviated insulin resistance by downregulating RAGE expression and enhancing Akt phosphorylation. The exposure of the C2C12 cells to AGEs reduced cell viability and myotube formation and elevated reactive oxygen species levels, which were attenuated by CPA or TPA supplementation. This suggests that maternal hyperglycemia and plasma AGEs may contribute to skeletal muscle disorders in offspring, which are mitigated by palmitoleic acid supplementation. Hence, the maternal intake of palmitoleic acid during pregnancy may have implications for fetal health.

Combinatorial metabolomic and transcriptomic analysis of muscle growth in hybrid striped bass (female white bass Morone chrysops x male striped bass M. saxatilis)

BackgroundUnderstanding growth regulatory pathways is important in aquaculture, fisheries, and vertebrate physiology generally. Machine learning pattern recognition and sensitivity analysis were employed to examine metabolomic small molecule profiles and transcriptomic gene expression data generated from liver and white skeletal muscle of hybrid striped bass (white bass Morone chrysops x striped bass M. saxatilis) representative of the top and bottom 10 % by body size of a production cohort.ResultsLarger fish (good-growth) had significantly greater weight, total length, hepatosomatic index, and specific growth rate compared to smaller fish (poor-growth) and also had significantly more muscle fibers of smaller diameter (≤ 20 µm diameter), indicating active hyperplasia. Differences in metabolomic pathways included enhanced energetics (glycolysis, citric acid cycle) and amino acid metabolism in good-growth fish, and enhanced stress, muscle inflammation (cortisol, eicosanoids) and dysfunctional liver cholesterol metabolism in poor-growth fish. The majority of gene transcripts identified as differentially expressed between groups were down-regulated in good-growth fish. Several molecules associated with important growth-regulatory pathways were up-regulated in muscle of fish that grew poorly: growth factors including agt and agtr2 (angiotensins), nicotinic acid (which stimulates growth hormone production), gadd45b, rgl1, zfp36, cebpb, and hmgb1; insulin-like growth factor signaling (igfbp1 and igf1); cytokine signaling (socs3, cxcr4); cell signaling (rgs13, rundc3a), and differentiation (rhou, mmp17, cd22, msi1); mitochondrial uncoupling proteins (ucp3, ucp2); and regulators of lipid metabolism (apoa1, ldlr). Growth factors pttg1, egfr, myc, notch1, and sirt1 were notably up-regulated in muscle of good-growing fish.ConclusionA combinatorial pathway analysis using metabolomic and transcriptomic data collectively suggested promotion of cell signaling, proliferation, and differentiation in muscle of good-growth fish, whereas muscle inflammation and apoptosis was observed in poor-growth fish, along with elevated cortisol (an anti-inflammatory hormone), perhaps related to muscle wasting, hypertrophy, and inferior growth. These findings provide important biomarkers and mechanisms by which growth is regulated in fishes and other vertebrates as well.

Epidemiology of thyroid-stimulating immunoglobulin in recent-onset symptomatic thyroid eye disease.

This study aims to report correlations between thyroid-stimulating immunoglobulin (TSI) and both clinical and radiological parameters in recent-onset symptomatic thyroid eye disease (TED) patients. A prospective cohort study of TED patients managed at the Chinese University of Hong Kong from January 2014 to May 2022. Serum TSI levels were determined with the functional assay. Outcomes included the Clinical Activity Score (CAS), marginal reflex distance1 (MRD1), extraocular muscle motility restriction (EOMy), exophthalmos, and diplopia. The radiological assessment included cross-sectional areas and signal of extraocular muscles on STIR-sequence MRI. A total of 255 (197 female) treatment-naive patients, with an average onset age of 50 ± 14 years (mean ± s.d.), were included. Elevated pre-treatment TSI level was observed in 223 (88%) patients. There was a weak positive correlation between TSI and CAS (r = 0.28, P = 0.000031), MRD1 (r = 0.17, P = 0.0080), and the size of the levator palpebrae superioris/superior rectus complex (r = 0.25, P = 0.018). No significant correlation existed between TSI and STIR signals. The AUC and optimal cut-off value for clinical active TED were 0.67 (95% CI: 0.60-0.75) and 284% (specificity: 50%, sensitivity: 85%). In total, 64 patients received intravenous methylprednisolone (IVMP) during the study interval, and they had a higher baseline TSI level than those who did not have IVMP (P = 0.000044). Serial post-IVMP TSI among the 62 patients showed a significant reduction compared to the baseline level (P < 0.001). Both the baseline and post-IVMP TSI levels, and percentages of TSI changes were comparable between patients who responded and did not respond to the first course of IVMP. TSI can be a serum biomarker for the diagnosis, prognosis, and treatment response of TED. Further validation should be warranted.

RONS-mediated redox signaling in skeletal muscle: Impact on glucose uptake through AMPK and AKT pathways

RONS-mediated redox signaling in skeletal muscle: Impact on glucose uptake through AMPK and AKT pathways

DistaNet: grasp-specific distance biofeedback promotes the retention of myoelectric skills

Objective. An active myoelectric interface responds to the user’s muscle signals to enable movements. Machine learning can decode user intentions from myoelectric signals. However, machine learning-based interface control lacks continuous, intuitive feedback about task performance, needed to facilitate the acquisition and retention of myoelectric control skills. Approach. We propose DistaNet as a neural network-based framework that extracts smooth, continuous, and low-dimensional signatures of the hand grasps from multi-channel myoelectric signals and provides grasp-specific biofeedback to the users. Main results. Experimental results show its effectiveness in decoding user gestures and providing biofeedback, helping users retain the acquired motor skills. Significance. We demonstrates myoelectric skill retention in a pattern recognition setting for the first time.

Artificial Neural Network Accuracy Optimization Using Transfer Function Methods on Various Human Gait Walking Environments

A bionic leg with ergonomic functionality can increase the user’s independence. However, an ergonomic bionic leg can be challenged to be developed. One of its challenges is related to functionality, where the bionic leg motor can be rugged to adapt to the user. One of the solutions for the bionic leg challenge is the application of a motor driver controlled by the user’s muscle signal. EMG signal can be utilized as the user’s signal source. The EMG signal is then fed back into the motor device. EMG signals obtained during a natural walking environment can result in smooth and natural movement. This study classifies EMG signals into 8 classes: a controlled walking environment (treadmill walking with various speeds) and a natural walking environment (ground walking, upstairs and downstairs walking). This research aims to optimize the ANN method using transfer function variations. The best method will be used to train EMG-driven motors for future studies related to bionic legs. The best ANN parameter in this research using Levenberg-Marquardt backpropagation as a training algorithm with transfer function pairing of the exponential function: Hyperbolic tangent sigmoid transfer function and SoftMax transfer function with 98.8% accuracy and 0.036 MSE value. The best method from the experiment and ANN classification can be used as a training method for a bionic leg in future research.

Excitation of natural spinal reflex loops in the sensory-motor control of hand prostheses.

Sensory feedback for prosthesis control is typically based on encoding sensory information in specific types of sensory stimuli that the users interpret to adjust the control of the prosthesis. However, in physiological conditions, the afferent feedback received from peripheral nerves is not only processed consciously but also modulates spinal reflex loops that contribute to the neural information driving muscles. Spinal pathways are relevant for sensory-motor integration, but they are commonly not leveraged for prosthesis control. We propose an approach to improve sensory-motor integration for prosthesis control based on modulating the excitability of spinal circuits through the vibration of tendons in a closed loop with muscle activity. We measured muscle signals in healthy participants and amputees during different motor tasks, and we closed the loop by applying vibration on tendons connected to the muscles, which modulated the excitability of motor neurons. The control signals to the prosthesis were thus the combination of voluntary control and additional spinal reflex inputs induced by tendon vibration. Results showed that closed-loop tendon vibration was able to modulate the neural drive to the muscles. When closed-loop tendon vibration was used, participants could achieve similar or better control performance in interfaces using muscle activation than without stimulation. Stimulation could even improve prosthetic grasping in amputees. Overall, our results indicate that closed-loop tendon vibration can integrate spinal reflex pathways in the myocontrol system and open the possibility of incorporating natural feedback loops in prosthesis control.