Fast Muscle Research Articles

Mechanisms of the modulation of actin-myosin interactions by A1-type myosin light chains

BackgroundThe interaction of N-terminal extension of the myosin A1 essential light chain (A1 ELC) with actin is receiving increasing attention as a target in utilizing synthetic A1 ELC N-terminal-derived peptides in cardiac dysfunction therapy. MethodsTo elucidate the mechanism by which these peptides regulate actin-myosin interaction, here we have investigated their effects on the myosin subfragment 1 (S1)-induced polymerization of G-actin. ResultsThe MLCFpep and MLCSpep peptides spanning the 3–12 of A1 ELC sequences from fast and slow skeletal muscle, respectively, increased the rate of actin polymerization not only by S1(A2) but also the rate of S1(A1)-induced actin polymerization, suggesting that they did not interfere with the direct binding of A1 ELC with actin. The efficiency of actin polymerization in the presence of the N-terminal ELC peptides depended on their sequence. Substitution of aspartic acid for neutral asparagine at position 5 of MLCFpep dramatically enhanced its ability to stimulate S1-induced polymerization and enabled it to initiate polymerization of G-actin in the absence of S1. ConclusionsThese and other results presented in this work suggest that the modulation of myosin motor activity by N-terminal ELC peptides is exerted through a change in actin filament conformation rather than through blocking the A1 ELC-actin interaction. General significanceThe results imply the possibility of enhancing therapeutic effects of these peptides by modifications of their sequence.

Transcriptomic Analysis for Pork Color—The Ham Halo Effect in Biceps Femoris

Pork color is a major indicator of product quality that guides consumer purchasing decisions. Recently, industryhas received an increase in consumer complaints about the lightness and nonuniformity of ham color, primarily lighter colorin the periphery termed “ham halo” that is not caused by manufacturing procedures. This effect is seen in fresh and processed hams and the outer lighter muscle is associated with lower myoglobin concentration, pH, and type I fibers. The objective of this study was to identify differences in gene expression profiles between light and normal-colored portions of the biceps femoris muscle from pork hams. RNA-sequencing (RNA-seq) was performed for paired light and normal-colored muscle samples from 10 animals showing the ham halo effect. Over 50 million paired-end reads (2×75 bp) per library were obtained. An average of 99.74% of trimmed high-quality reads was mapped to the Sscrofa 11.1 genome assembly. Differentially expressed genes (DEGs) were identified using both the DESeq2 and GFOLD software packages. A total of 14,049 genes were expressed in the biceps femoris; 13,907 were expressed in both light and normal muscle, while 56 and 86 genes were only expressed in light and normal muscle, respectively. Analysis with DESeq2 identified 392 DEGs with 359 genes being more highly expressed in normal-colored muscle. A total of 61 DEGs were identified in the DESeq2 analysis and identified in at least 7 of the 10 individual animal analyses. All 61 of these DEGs were up-regulated in normal-colored muscle. Gene Ontology enrichment analysis of DEGs identified the transition between fast and slow fibers and skeletal muscle adaptation and contraction as the most significant biological process terms. The evaluation of gene expression by RNA-seq identified DEGs between regions of the biceps femoris with the ham halo effect that are associated with variation in pork color.

Functional Adaptation of Vocalization Revealed by Morphological and Histochemical Characteristics of Sonic Muscles in Blackmouth Croaker (Atrobucca nibe).

Simple SummarySound production is common in numerous fish species. Some species can emit calls through the contraction of specialized muscles called sonic or drumming muscles. The sonic muscles of fish are among the fastest muscles in vertebrates. Although numerous studies have investigated the mechanism underlying sound production in fish, only the distinct features of the sonic muscles of a few species have been investigated. We demonstrated that the sonic muscles have functionally adapted for fast twitching and fatigue resistance, which support vocalization in the blackmouth croaker (Atrobucca nibe).Sound production in the blackmouth croaker (Atrobucca nibe) was characterized using acoustic, morphological, and histochemical methods. Their calls consisted of a train of two to seven pulses; the frequency ranged from 180 to 3000 Hz, with a dominant frequency of 326 ± 40 Hz. The duration of each call ranged from 80 to 360 ms. Male A. nibe possess a pair of bilaterally symmetric sonic muscles attached to the body wall adjacent to the swim bladder. The average diameter of the sonic muscle fibers was significantly shorter than that of the abdominal muscle fibers. Semithin sections of the sonic muscle fibers revealed a core-like structure (central core) and the radial arrangement of the sarcoplasmic reticulum and myofibrils. Numerous mitochondria were distributed within the central core and around the periphery of the fibers. Most of the fibers were identified as Type IIa on the basis of their myosin adenosine triphosphatase activities, but a few were identified as Type IIc fibers. All sonic muscle fibers exhibited strong oxidative enzyme activity and oxidative and anaerobic capabilities. The features suggest that the sonic muscles of A. nibe are morphologically and physiologically adapted for fast twitching and fatigue resistance, which support fish vocalization.

The effect of Endurance Training on Expression of T3 Receptor-Associated Protein-1 (THRAP-1) in Heart, Slow and Fast Twitch Muscles

The effect of Endurance Training on Expression of T3 Receptor-Associated Protein-1 (THRAP-1) in Heart, Slow and Fast Twitch Muscles

Nitrite Concentration in the Striated Muscles Is Reversely Related to Myoglobin and Mitochondrial Proteins Content in Rats.

Skeletal muscles are an important reservoir of nitric oxide (NO•) stored in the form of nitrite [NO2−] and nitrate [NO3−] (NOx). Nitrite, which can be reduced to NO• under hypoxic and acidotic conditions, is considered a physiologically relevant, direct source of bioactive NO•. The aim of the present study was to determine the basal levels of NOx in striated muscles (including rat heart and locomotory muscles) with varied contents of tissue nitrite reductases, such as myoglobin and mitochondrial electron transport chain proteins (ETC-proteins). Muscle NOx was determined using a high-performance liquid chromatography-based method. Muscle proteins were evaluated using western-immunoblotting. We found that oxidative muscles with a higher content of ETC-proteins and myoglobin (such as the heart and slow-twitch locomotory muscles) have lower [NO2−] compared to fast-twitch muscles with a lower content of those proteins. The muscle type had no observed effect on the [NO3−]. Our results demonstrated that fast-twitch muscles possess greater potential to generate NO• via nitrite reduction than slow-twitch muscles and the heart. This property might be of special importance for fast skeletal muscles during strenuous exercise and/or hypoxia since it might support muscle blood flow via additional NO• provision (acidic/hypoxic vasodilation) and delay muscle fatigue.

MiR-208b Regulates the Conversion of Skeletal Muscle Fiber Types by Inhibiting Mettl8 Expression

Skeletal muscle, the main source of animal meat products, contains muscle fiber as a key unit. It is well known that transformation takes place between different types of muscle fibers, however, the conversion mechanism is not clear. In a previous study, our lab has demonstrated that there is a decrease in type I muscle fibers and an increase in type IIB muscle fibers in skeletal muscle of myostatin gene-edited Meishan pigs. Very interestingly, we observed the down regulation of miR-208b expression and an increase in expression the predicted target gene Mettl8 (Methyltransferase like 8) in skeletal muscle of MSTN gene-edited Meishan pigs. These results reveal that there is a potential connection between the conversion of skeletal muscle fiber types and miR-208b and Mettl8 expression. In this study, we first explored the expression patterns of miR-208b and Mettl8 in skeletal muscle in Meishan pigs; and then C2C12 cells were used to simulate the development and maturation of muscle fibers. Our results indicated that Myh4 expression level decreased and Myh7 expression level increased following overexpression of miR-208b in C2C12 cells. We therefore speculate that miR-208b can promote the conversion of fast-twitch fibers to slow-twitch fibers. The targeting relationship between Mettl8 and miR-208b was confirmed by results obtained using dual luciferase assay, RT-qPCR, and WB analysis. Following the transfection of Mettl8 siRNA into C2C12 cells, we observed that Mettl8 expression decreased significantly while Myh7 expression increased and Myh4 expression decreased, indicating that Mettl8 promotes the conversion of slow muscle fibers to fast muscle fibers. Additionally, changes in skeletal muscle fiber types are observed in those mice where miR-208b and Mettl8 genes are knocked out. The miR-208b knockout inhibits the formation of slow muscle fibers, and the Mettl8 knockout inhibits the formation of fast muscle fibers. In conclusion, our research results show that miR-208b regulates the conversion of different muscle fiber types by inhibiting Mettl8 expression.

Discovery of ultrafast myosin, its amino acid sequence, and structural features

Cytoplasmic streaming with extremely high velocity (∼70 μm s-1) occurs in cells of the characean algae (Chara). Because cytoplasmic streaming is caused by myosin XI, it has been suggested that a myosin XI with a velocity of 70 μm s-1, the fastest myosin measured so far, exists in Chara cells. However, the velocity of the previously cloned Chara corallina myosin XI (CcXI) was about 20 μm s-1, one-third of the cytoplasmic streaming velocity in Chara Recently, the genome sequence of Chara braunii has been published, revealing that this alga has four myosin XI genes. We cloned these four myosin XI (CbXI-1, 2, 3, and 4) and measured their velocities. While the velocities of CbXI-3 and CbXI-4 motor domains (MDs) were similar to that of CcXI MD, the velocities of CbXI-1 and CbXI-2 MDs were 3.2 times and 2.8 times faster than that of CcXI MD, respectively. The velocity of chimeric CbXI-1, a functional, full-length CbXI-1 construct, was 60 μm s-1 These results suggest that CbXI-1 and CbXI-2 would be the main contributors to cytoplasmic streaming in Chara cells and show that these myosins are ultrafast myosins with a velocity 10 times faster than fast skeletal muscle myosins in animals. We also report an atomic structure (2.8-Å resolution) of myosin XI using X-ray crystallography. Based on this crystal structure and the recently published cryo-electron microscopystructure of acto-myosin XI at low resolution (4.3-Å), it appears that the actin-binding region contributes to the fast movement of Chara myosin XI. Mutation experiments of actin-binding surface loops support this hypothesis.

Troponin C mutations alter twitch kinetics and force-frequency relationship of fast and slow twitch skeletal muscle

Troponin C (TnC) is critically involved in the contraction of striated muscle. The role of TnC on the mechanical process of skeletal muscle has been thoroughly investigated. However, the impact of TnC mutations on the force-frequency relationship (FFR) of skeletal muscle is yet to be investigated. The objective of this study is to determine the effect of TnC mutations on the force-frequency relationship and contractile kinetics in fast and slow-twitch skeletal muscle. To investigate this key question, we measured the extensor digitorum longus (EDL) and soleus force-frequency response in a murine model with a TnC mutation (expressed after TnCL48QAAV or TnCD73NAAV injection) that causes increased calcium sensitivity (L48Q) or a decreased calcium sensitivity (D73N) and compared the FFR to the wildtype counterparts.

Definition of the mechanokinetic parameters accounting for the functional diversity of slow and fast isoforms of skeletal muscle myosin with a synthetic nanomachine

The mechanokinetic parameters characterising the force and power produced by fast (psoas) and slow (soleus) skeletal rabbit muscle are defined by feeding to a model simulation the mechanical output of a synthetic nanomachine (Pertici et al., Nat Commun 9:3532, 2018) powered by 8 heavy-mero-myosin fragments (HMM) of myosin II purified from either muscle. Implementation of a length clamp control for the minimization of the trap compliance allows to integrate the measurements of all the relevant steady state parameters (the isometric force (F0), the force-velocity relation and the maximum power (Pmax)) with transient kinetics parameters (rate of isometric force development (r) and force fluctuation due to individual motor attachment-detachment).

Who takes my calcium? Diffusional model and experimental insights on intra- and extra-cellular calcium fluxes in parvalbumin knock-out mice

When fast skeletal muscles are activated, cytosolic [Ca2+]cyto increases while Parvalbumin (PV) acts as a buffer, releasing Mg2+ and binding Ca2+, playing a crucial role in muscle relaxation and plasticity. A recent work on PV knockout (KO) mice elucidated its role also in mitochondrial remodeling and fiber size regulation (Butera et al 2021). Strikingly, in FDB fibers of PV-KO mice, both the [Ca2+]cyto and the sarcoplasmic reticulum [Ca2+]SR levels are not different form the wild-type (WT) mice in basal conditions and during 60Hz stimulations.

The importance of shortening deactivation to different muscle types

Generating high power from a muscle undergoing a cyclical lengthening and shortening contraction pattern requires fast and efficient muscle activation and relaxation. To enhance activation and increase force levels during shortening, some muscle types have evolved stretch activation (SA), a delayed increased in force following rapid muscle lengthening. SA’s complementary phenomenon is shortening deactivation (SD), a delayed decrease in force following muscle shortening, which increases muscle relaxation and results in less resistive force during subsequent muscle lengthening.

Muscle length has a greater effect on the rate of relaxation in slow-twitch rat soleus muscle than fast-twitch EDL muscle

Mammalian skeletal muscle is composed of mixtures of slow-twitch fibers and fast-twitch fibers. We compared the relaxation kinetics of purely fast fiber rat EDL muscle and highly pure slow fiber rat soleus muscle from both intact and permeabilized preparations at different lengths. In the intact muscle study, the muscles were activated at optimal length (Lo), 95% of Lo, and 90% of Lo. After a tetanus, EDL relaxed with a half-time of 65±2 ms at Lo, 64±1 ms at 95% of Lo, and 63±1 ms at 90% of Lo (p< 0.05).

The relationship of dietary total antioxidant capacity with sarcopenia and cardiometabolic biomarkers in type 2 diabetes patients

BackgroundThe aim of this study was to investigate the relationship of dietary total antioxidant capacity (DTAC) with sarcopenia and metabolic biomarkers in people with type 2 diabetes in the Kurdish race.MethodsIn this cross‐sectional study, data of 189 type 2 diabetic patients (35–65 years old) from RaNCD cohort study were evaluated. DTAC, fasting blood sugar, lipid profile, body composition, muscle strength, and sarcopenia were assessed. t and χ2 tests to compare the variables between sarcopenic and non‐sarcopenic patients and one‐way analysis of variance to compare the variables in DTAC tertiles were used. The relationship between DTAC and different variables was evaluated using multiple logistic regression model.ResultsThe mean age and body mass index were 49.7 ± 8.7 years and 27.1 ± 3.9 kg/m2. Body mass index, waist circumference, and hip circumference were significantly different between diabetic patients with and without sarcopenia (p < 0.05). In crude (p = 0.010) and adjusted (p = 0.035) models, there was a significant relationship between DTAC and fasting blood sugar. Also, the relationship between DTAC with waist (p = 0.019) and hip (β = −4.25, p = 0.026) circumference was significant. Sarcopenia was significantly lower in the third tertile in comparison with the first tertile of DTAC (p = 0.016). ConclusionDiet with higher DTAC can be associated with lower fasting blood sugar, abdominal obesity and sarcopenia in type 2 diabetic patients. However, further studies are required to confirm these relationships.

First-in-class drug candidate (MPH-220) efficiently improves spastic gait disorders by selective inhibition of fast skeletal muscle myosin-2

Post-stroke muscle spasticity affects 37% of stroke survivors and disables self-supporting life management and ability to work. Current muscle relaxants are of limited efficiency (less than 40%) and cause serious neurological and cardiovascular side effects due to targeting the nervous system. We have developed a new-generation anti-spastic oral drug candidate, MPH-220, which directly and selectively inhibits fast skeletal myosin 2 isoforms. Brain-damage induced spastic animals showed drastic improvement in gait disorders upon oral MPH-220 treatment in different disease animal models.

Evaluation of Factors Affecting the Reduction in Postpartum Pelvic Floor Muscle Tension and The Therapeutic Effect

Purpose: This study investigated the risk factors associated with reductions in postpartum pel-vic floor muscle tension and evaluated improvements in pelvic floor muscle tension with electrical stimulation combined with biofeedback technology and Kegel exercis-es. Methods: We conducted a case-control study of 170 women with postpartum follow-up at Ningbo Li Huili Hospital from April 2019 to May 2020. According to the Oxford modified scale assessment(MOS), 94 and 76 women were included in the abnormal pelvic floor muscle tension group and control group, respectively. The two groups were trained by pelvic floor training. The changes in pelvic floor muscle tension before and after treatment in the two groups were analyzed to evaluate the effect of postpartum pelvic floor rehabilitation training. Results: The EMG value of the fast muscle contraction stage was negatively correlated with age and neonatal weight (P &lt;0.05). The EMG values of slow muscle contraction and endurance were negatively correlated with weight gain during pregnancy but posi-tively correlated with age and BMI at delivery (P &lt;0.05). The muscle tension of the abnormal muscle tension group was significantly improved and significantly higher than that of the control group (P &lt;0.05) after the two groups received the intervention. Conclusion: The factors affecting postpartum pelvic floor muscle tension include age, delivery times, BMI at delivery and neonatal weight. Electrical stimulation combined with the biofeedback technique and Kegel exercises in the early postpartum period are effec-tive means to reduce the incidence of Pelvic floor disorders.

The Emerging Role of Long Non-Coding RNAs in Development and Function of Gilthead Sea Bream (Sparus aurata) Fast Skeletal Muscle.

Long non-coding RNAs (lncRNAs) are an emerging group of ncRNAs that can modulate gene expression at the transcriptional or translational levels. In the present work, previously published transcriptomic data were used to identify lncRNAs expressed in gilthead sea bream skeletal muscle, and their transcription levels were studied under different physiological conditions. Two hundred and ninety lncRNAs were identified and, based on transcriptomic differences between juveniles and adults, a total of seven lncRNAs showed potential to be important for muscle development. Our data suggest that the downregulation of most of the studied lncRNAs might be linked to increased myoblast proliferation, while their upregulation might be necessary for differentiation. However, with these data, as it is not possible to propose a formal mechanism to explain their effect, bioinformatic analysis suggests two possible mechanisms. First, the lncRNAs may act as sponges of myoblast proliferation inducers microRNAs (miRNAs) such as miR-206, miR-208, and miR-133 (binding energy MEF < −25.0 kcal). Secondly, lncRNA20194 had a strong predicted interaction towards the myod1 mRNA (ndG = −0.17) that, based on the positive correlation between the two genes, might promote its function. Our study represents the first characterization of lncRNAs in gilthead sea bream fast skeletal muscle and provides evidence regarding their involvement in muscle development.

Fine-Tuning of Piezo1 Expression and Activity Ensures Efficient Myoblast Fusion during Skeletal Myogenesis.

Mechanical stimuli, such as stretch and resistance training, are essential in regulating the growth and functioning of skeletal muscles. However, the molecular mechanisms involved in sensing mechanical stress during muscle formation remain unclear. Here, we investigated the role of the mechanosensitive ion channel Piezo1 during myogenic progression of both fast and slow muscle satellite cells. We found that Piezo1 level increases during myogenic differentiation and direct manipulation of Piezo1 in muscle stem cells alters the myogenic progression. Indeed, Piezo1 knockdown suppresses myoblast fusion, leading to smaller myotubes. Such an event is accompanied by significant downregulation of the fusogenic protein Myomaker. In parallel, while Piezo1 knockdown also lowers Ca2+ influx in response to stretch, Piezo1 activation increases Ca2+ influx in response to stretch and enhances myoblasts fusion. These findings may help understand molecular defects present in some muscle diseases. Our study shows that Piezo1 is essential for terminal muscle differentiation acting on myoblast fusion, suggesting that Piezo1 deregulation may have implications in muscle aging and degenerative diseases, including muscular dystrophies and neuromuscular disorders.

Sex differences in semitendinosus muscle fiber-type composition.

Sex differences in muscle fiber-type composition have been documented in several muscle groups while the hamstring muscle fiber-type composition has been poorly characterized. This study aimed to compare the semitendinosus muscle composition between men and women. Biopsy samples were obtained from the semitendinosus muscle of twelve men and twelve women during an anterior cruciate ligament reconstruction. SDH and ATPase activities as well as the size and the proportion of muscle fibers expressing myosin heavy chain (MyHC) isoforms were used to compare muscle composition between men and women. The proportion of SDH-positive muscle fibers was significantly lower (37.4±11.2% vs. 49.3±10.6%, p<0.05), and the percentage of fast muscle fibers (i.e., based on ATPase activity) was significantly higher (65.8±10.1% vs. 54.8±8.3%, p<0.05) in men versus women. Likewise, men muscles exhibited a lower percentage of the area that was occupied by MyHC-I labeling (35.6±10.1% vs. 48.7±8.9%; p<0.05) and a higher percentage of the area that was occupied by MyHC-IIA (38.3±6.7% vs. 32.5±6.5%; p<0.05) and MyHC-IIX labeling (26.1±9.6% vs. 18.8±8.5%; p=0.06) as compared with women muscles. The cross-sectional area of MyHC-I, MyHC-IIA, and MyHC-IIX muscle fibers was 31%, 43%, and 50% larger in men as compared with women, respectively. We identified sex differences in semitendinosus muscle composition as illustrated by a faster phenotype and larger muscle size in men as compared with women. This sexual dimorphism might have functional consequences.

PeMNet for Pectoral Muscle Segmentation.

Simple SummaryDeep learning has become a popular technique in modern computer-aided (CAD) systems. In breast cancer CAD systems, breast pectoral segmentation is an important procedure to remove unwanted pectoral muscle in the images. In recent decades, there are numerous studies aiming at developing efficient and accurate methods for pectoral muscle segmentation. However, some methods heavily rely on manually crafted features that can easily lead to segmentation failure. Moreover, deep learning-based methods are still suffering from poor performance at high computational costs. Therefore, we propose a novel deep learning segmentation framework to provide fast and accurate pectoral muscle segmentation result. In the proposed framework, the novel network architecture enables more useful information to be used and therefore improve the segmentation results. The experimental results using two public datasets validated the effectiveness of the proposed network.As an important imaging modality, mammography is considered to be the global gold standard for early detection of breast cancer. Computer-Aided (CAD) systems have played a crucial role in facilitating quicker diagnostic procedures, which otherwise could take weeks if only radiologists were involved. In some of these CAD systems, breast pectoral segmentation is required for breast region partition from breast pectoral muscle for specific analysis tasks. Therefore, accurate and efficient breast pectoral muscle segmentation frameworks are in high demand. Here, we proposed a novel deep learning framework, which we code-named PeMNet, for breast pectoral muscle segmentation in mammography images. In the proposed PeMNet, we integrated a novel attention module called the Global Channel Attention Module (GCAM), which can effectively improve the segmentation performance of Deeplabv3+ using minimal parameter overheads. In GCAM, channel attention maps (CAMs) are first extracted by concatenating feature maps after paralleled global average pooling and global maximum pooling operation. CAMs are then refined and scaled up by multi-layer perceptron (MLP) for elementwise multiplication with CAMs in next feature level. By iteratively repeating this procedure, the global CAMs (GCAMs) are then formed and multiplied elementwise with final feature maps to lead to final segmentation. By doing so, CAMs in early stages of a deep convolution network can be effectively passed on to later stages of the network and therefore leads to better information usage. The experiments on a merged dataset derived from two datasets, INbreast and OPTIMAM, showed that PeMNet greatly outperformed state-of-the-art methods by achieving an IoU of , global pixel accuracy of , Dice similarity coefficient of , and Jaccard of , respectively.

Comparison of locomotion problems and its economic impact on Cobb and Ross broiler strains

The rapid weight gain and fast muscle growth due to intense genetic selection and improved nutrition for additional breast muscle in broiler commercial strains affect chickens health. In order to compare the main locomotive problems in broilers of Cobb and Ross strains, two pens from a commercial farm in Veracruz, Mexico were used. The first pen housed 16,500 males and 16,500 females of Cobb strain and the second one 16,500 males and 16,500 females of Ross strain. Chicks were checked for locomotion problems from day one until their sale. Animals with problems were recorded and necropsies were performed to identify the pathology. Out of 1406 animals with locomotive problems (2.13% of the total), 58.9% were Cobb and 41.1% Ross (P &lt;0.05). The frequency of locomotive problems was 2.51% for Cobb and 1.75% for Ross. Most common individual lesions were osteochondrosis (38.61%), inflamed joints with purulent contents (37.13%), and valgus (19.65%). Locomotive problems appeared since the first week, but its number increased as birds gained weight, particularly from the fourth week on. Problems occurred more in males than in females and in Cobb birds than in the Ross strain. Economic loss due to locomotion problems was higher for the Cobb strain.