Muscle Contraction Research Articles

Acute high-intensity muscle contraction moderates AChR gene expression independent of rapamycin-sensitive mTORC1 pathway in rat skeletal muscle.

The relationship between mechanistic target of rapamycin complex 1 (mTORC1) activation after resistance exercise and acetylcholine receptor (AChR) subunit gene expression remains largely unknown. Therefore, we aimed to investigate the effect of electrical stimulation-induced intense muscle contraction, which mimics acute resistance exercise, on the mRNA expression of AChR genes and the signalling pathways involved in neuromuscular junction (NMJ) maintenance, such as mTORC1 and muscle-specific kinase (MuSK). The gastrocnemius muscle of male adult Sprague-Dawley rats was isometrically exercised. Upon completion of muscle contraction, the rats were euthanized in the early (after 0, 1, 3, 6 or 24h) and late (after 48 or 72h) recovery phases and the gastrocnemius muscles were removed. Non-exercised control animals were euthanized in the basal state (control group). In the early recovery phase, Agrn gene expression increased whereas LRP4 decreased without any change in the protein and gene expression of AChR gene subunits. In the late recovery phase, Agrn, Musk, Chrnb1, Chrnd and Chrne gene expression were altered and agrin and MuSK protein expression increased. Moreover, mTORC1 and protein kinase B/Akt-histone deacetylase 4 (HDAC) were activated in the early phase but not in the late recovery phase. Furthermore, rapamycin, an inhibitor of mTORC1, did not disturb changes in AChR subunit gene expression after muscle contraction. However, rapamycin addition slightly increased AChR gene expression, while insulin did not impact it in rat L6 myotube. These results suggest that changes in the AChR subunits after muscle contraction are independent of the rapamycin-sensitive mTORC1 pathway.

Stable oxidative posttranslational modifications alter the gating properties of RyR1.

The ryanodine receptor type 1 (RyR1) is a Ca2+ release channel that regulates skeletal muscle contraction by controlling Ca2+ release from the sarcoplasmic reticulum (SR). Posttranslational modifications (PTMs) of RyR1, such as phosphorylation, S-nitrosylation, and carbonylation are known to increase RyR1 open probability (Po), contributing to SR Ca2+ leak and skeletal muscle dysfunction. PTMs on RyR1 have been linked to muscle dysfunction in diseases like breast cancer, rheumatoid arthritis, Duchenne muscle dystrophy, and aging. While reactive oxygen species (ROS) and oxidative stress induce PTMs, the impact of stable oxidative modifications like 3-nitrotyrosine (3-NT) and malondialdehyde adducts (MDA) on RyR1 gating remains unclear. Mass spectrometry and single-channel recordings were used to study how 3-NT and MDA modify RyR1 and affect Po. Both modifications increased Po in a dose-dependent manner, with mass spectrometry identifying 30 modified residues out of 5035 amino acids per RyR1 monomer. Key modifications were found in domains critical for protein interaction and channel activation, including Y808/3NT in SPRY1, Y1081/3NT and H1254/MDA in SPRY2&3, and Q2107/MDA and Y2128/3NT in JSol, near the binding site of FKBP12. Though these modifications did not directly overlap with FKBP12 binding residues, they promoted FKBP12 dissociation from RyR1. These findings provide detailed insights into how stable oxidative PTMs on RyR1 residues alter channel gating, advancing our understanding of RyR1-mediated Ca2+ release in conditions associated with oxidative stress and muscle weakness.

Correlations Between Mandibular Kinematics and Electromyography During the Masticatory Cycle: An Observational Study by Digital Analysis

The analysis of the masticatory cycle plays a fundamental role in studying the functions of the stomatognathic system and evaluating temporomandibular dysfunctions (TMD). The primary objective of this study is to investigate the complex interplay between mandibular kinematics and surface electromyography (sEMG) activity during the masticatory cycle using advanced 4D dentistry technology in 22 healthy subjects (without TMD). By employing electromyography, it becomes feasible to capture the electrical activity of the masticatory muscles throughout the chewing process. The BTS TMJOINT (© 2023 BTS Bioengineering, Garbagnate Milanese, MI, Italy) electromyograph was utilized in this study. Mandibular tracking, on the other hand, allows for recording the movements of the mandible during chewing and condylar slopes. This latest technology (ModJaw®, Tech in motion™, Villeurbanne, France) utilizes motion sensors placed on the jaw to accurately track three-dimensional movements, including jaw opening, closing, and lateral movements. Nowadays, in clinical gnathology, it is common practice to examine masticatory function by analyzing mandibular kinematics and muscle contraction as distinct entities. Similarly, the results obtained from these analyses are typically assessed independently. The investigation of a correlation between electromyography data and mandibular kinematics during the masticatory cycle could provide several advantages for clinicians in diagnosis and lead to a combined analysis of muscle activities and intraarticular dynamics. In conclusion, it can be inferred from the results obtained in the present study that the chewing cycle with a greater vertical movement results in increased masseter muscular activity, and condylar slopes are positively correlated to an increase in temporalis muscle activation. This comprehensive approach can provide valuable insights into the relationship between muscle activity and mandibular movement, enabling clinicians to gain a deeper understanding of the functional dynamics of the stomatognathic system.

A genetically encoded actuator boosts L-type calcium channel function in diverse physiological settings.

L-type Ca2+ channels (CaV1.2/1.3) convey influx of calcium ions that orchestrate a bevy of biological responses including muscle contraction, neuronal function, and gene transcription. Deficits in CaV1 function play a vital role in cardiac and neurodevelopmental disorders. Here, we develop a genetically encoded enhancer of CaV1.2/1.3 channels (GeeCL) to manipulate Ca2+ entry in distinct physiological settings. We functionalized a nanobody that targets the CaV complex by attaching a minimal effector domain from an endogenous CaV modulator-leucine-rich repeat containing protein 10 (Lrrc10). In cardiomyocytes, GeeCL selectively increased L-type current amplitude. In neurons in vitro and in vivo, GeeCL augmented excitation-transcription (E-T) coupling. In all, GeeCL represents a powerful strategy to boost CaV1.2/1.3 function and lays the groundwork to illuminate insights on neuronal and cardiac physiology and disease.

Stable pelvic floor muscle training improves urinary incontinence in women with gestational diabetes mellitus

Background Gestational diabetes mellitus (GDM) is a common metabolic disease that contributes to urinary incontinence (UI) in pregnant women. The aim of this study was to investigate the therapeutic potential of stable pelvic floor muscle (PFM) training with transverse abdominal muscle for pregnancy-specific UI in patients with GDM. Methods This was a randomised controlled trial. A total of 73 pregnant women with GDM and pregnancy-specific UI were screened, 35 of whom received stable PFM training with transverse abdominal muscle in the second trimester. After six weeks of training, UI status was assessed by the quantity of fluid loss and the International Consultation on Incontinence Questionnaire short form (ICI-Q-SF), and the quality of life was evaluated by the Incontinence Quality of Life Questionnaire score. Additionally, the thickness of the transverse abdominal muscle was measured by ultrasonography. Results At 6 weeks later, the quantity of fluid loss and ICI-Q-SF score were significantly lower, and the overall healing rate was significantly higher in the training group than those in the control group. The training also significantly improved the quality of life, especially in terms of behavioural limitation and psychosocial impact. Additionally, the thickness of transverse abdominal muscle under the status of maximal contractions of transverse abdominal muscle and PFM was significantly higher in the training group than in the control group after 6 weeks. Conclusions Stable PMF training with transverse abdominal muscle alleviated UI and improved the quality of life in patients with GDM. The thickening of transverse abdominal muscle induced by the training contributes to the remission of UI through the cooperation of PMF.

Inter-rater and Intra-rater Reliability of Het’s MMT in Pelvic Floor Assessment

Abstract Objective: Pelvic floor dysfunctions (pfds) such as urinary incontinence, pelvic organ prolapse, and vaginismus are very common and are affecting the quality of life of the female suffering through it. The pelvic floor muscles can be in spasm, thus resulting in the inability to relax or the pelvic floor muscles can be extremely weak or loose, resulting in the inability to contract strongly and completely. The spasmodic pelvic floor can result in vaginismus, dyspareunia, chronic pelvic pain, constipation, etc., Moreover, a weak pelvic floor can lead to issues such as urinary incontinence, pelvic organ prolapse, and sexual dysfunction. There is a scarcity of a valid and reliable scale that assesses both the components of pfd. Subjects and Methods: The present study was conducted on 1349 participants which were divided into three groups on the basis of their symptoms. Group A – No symptoms (n = 439), Group B – Hypotonus pfd (n = 658), and Group C – Hypertonus pfd (n = 252). Examination: Vaginal examination to assess the pelvic floor muscles relaxation and contraction was done by Het’s Manual Muscle Testing (MMT). Inter rater reliability was assessed by comparing the data of two independent examiners on the same day. The intra rater reliability was assessed by comparing the data of test and retest at an interval of 1 week. Results: The intra rater reliability at 95% confidence interval (CI) was 0.92 – Normal pelvic floor function, 0.96 – Hypotonus pfd, and 0.97 – Hypertonus pfd. Moreover, inter rater reliability at 95% CI was 0.93 – normal pelvic floor function, 0.95 for hypotonus pfd, and 0.98 – hypertonus pfd. Conclusions: This study concludes Het’s MMT is a highly reliable manual muscle testing tool to assess the pelvic floor muscles.

Segregation of the COL6A2 Variant (c.1817-3C>G) in a Consanguineous Saudi Family with Bethlem Myopathy

Introduction: Bethlem myopathy is a rare genetic disease caused by a variant mapped to 21q22, which harbors the collagen type VI alpha 2 chain (COL6A2) and collagen type VI alpha 1 chain (COL6A1) genes, and 2q37, which harbors the collagen type VI alpha 3 chain (COL6A3) gene. Disease onset can occur at any age, and the symptoms are related to those of muscular dystrophy. Since Bethlem myopathy is a rare disease, no previous studies have been conducted in Arab countries, including Saudi Arabia. Its variable presentation of nonspecific muscular contractions and severity represents a diagnostic dilemma. Case presentation: Here, we report a Saudi pediatric patient, who is 9 years old (proband), brought to the pediatric clinic of King Saud’s Hospital by his mother. The boy presented with difficulty standing, walking, and running with his classmates and unaffected siblings. He has a younger sibling, aged 6 years old, who reported having a limping gait and difficulty bending his right knee. Laboratory results for the proband were unremarkable except for a slight increase in creatine kinase (CK). Whole-exome sequencing (WES) was performed for five family members, including the proband and his symptomatic brother, their mother and two asymptomatic siblings. A very rare 3′ splice site acceptor intronic variant, NM_001849.4: c.1817-3C>G, located three nucleotides before exon 25, was identified in COL6A2. Bioinformatics tools (SpliceAI, dbscSNV, FATHMM-MKL, and MaxEntScan) predicted this variant as pathogenic. The proband and his 6-year-old sibling presented a homozygous genotype for the variant, whereas the mother and one asymptomatic sibling were heterozygous, and the other sibling carried homozygous wild-type alleles. Conclusions: This is the first study to report a case of Bethlem myopathy confirmed by WES in Saudi Arabia and all Arab nations. The identified variant is rare, and its segregation pattern suggests autosomal recessive inheritance. The segregation pattern and bioinformatics tool results may qualify this variant to be annotated as pathogenic, addressing the reported uncertainty of its classification. Our findings contribute to linking and filling the knowledge gap of diagnosing and managing patients with collagen VI-related myopathies, providing greater clinical and genetic understanding to the existing knowledge.

Whole-body-electro-myostimulation for the care of inclusion body myositis-A case report.

External muscle stimulation, possibly combined with active muscle contraction, could improve physical functioning and performance in inclusion body myositis. Inclusion body myositis (IBM) is a chronic, progressive inflammatory muscle disease with largely unknown causes. It typically affects men more than women, usually beginning in the latter half of life. IBM leads to muscle weakness and wasting, especially in the arms and legs, which significantly impairs daily functioning and complicates participation in exercise training. Few studies have examined the impact of physical training on fitness, inflammation markers, and quality of life in IBM patients. The patient, a Caucasian male (78.3 kg, 174.0 cm, born October 1948), was diagnosed with IBM in October 2011. From October 2017 to September 2019, he underwent exercise training focused on external muscle stimulation combined with active muscle contractions. Regular assessments included cardiopulmonary exercise testing, functional tests (6-min walking test, modified timed up and go test, modified chair rise test), lung function exams, blood parameters, body composition, and quality of life questionnaires. The decline in physical fitness may have been slowed during the intervention period, as indicated by some improvements like peak oxygen uptake and the functional test results while other parameters remained unchanged or declined like peak power output, fat-free mass or lung functioning. However, a recurrence of his prostate cancer after treatment with androgen deprivation therapy may have led to further declines and thus increased muscle wasting. The data may suggest that supportive exercise programs focusing on external muscle stimulation, possibly combined with active muscle contraction, might improve physical functioning, exercise performance, and quality of life in IBM management.

Troponin I and Its Clinical Significance

Troponin I is one of the regulatory proteins of the troponin complex (troponin I, troponin C and troponin T) found in both cardiac and skeletal muscle. The letter I stands for its inhibitory character as binding is prevented between actin and myosin in relaxed muscle. It plays a significant role in holding actin-tropomyosin complex in place by binding actin in thin myofilaments. Binding of calcium to troponin C causes certain conformational changes, leading to troponin I dislocation and thus exposing binding site of myosin on actin, which leads to muscle contraction. It is frequently used in the diagnosis of acute coronary syndrome and myocardial infarction, and also serves as a prognostic marker in their management (1). There are three distinct forms of troponin I with tissue-specific expression patterns: 1. Slow-twitch skeletal muscle isoform troponin I, 2. Fast-twitch skeletal muscle isoform troponin I and 3. Cardiac troponin I.

Quantification of Sarcoplasmic Reticulum Ca2+ Release in Primary Ventricular Cardiomyocytes.

In the heart, ion channels generate electrical currents that signal muscle contraction through changes in intracellular calcium concentration, i.e., [Ca2+]. The cardiac ryanodine receptor type 2 (RyR2) is the predominant ion channel responsible for increasing intracellular [Ca2+] by releasing Ca2+ from the sarcoplasmic reticulum (SR). Timely Ca2+ release is necessary for appropriate cardiac function, and dysfunction can cause or contribute to life-threatening diseases such as arrhythmia. Quantification of SR-Ca2+ release in the form of sparks and waves can provide valuable insight into RyR2 opening, and factors that influence or regulate channel function. Here, we provide a series of protocols that outline processes for (1) obtaining high-quality isolated cardiomyocytes, (2) preparing samples for experimentally investigating factors that influence RyR2 function, and (3) data acquisition and analysis. Notably, our protocols leverage the potency of the recently developed myosin ATPase inhibitor, Mavacamten. This affords the opportunity to characterize the effects of small molecules or reconstituted proteins/enzymes on RyR2-Ca2+ release events across a range of [Ca2+]. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Cardiomyocyte isolation from mouse Basic Protocol 2: Preparation of cardiomyocytes for Ca2+ imaging Basic Protocol 3: Confocal microscopy and quantitative Ca2+ analysis using SparkMaster 2.

Age-related increase in the excitability of mouse layer V pyramidal neurons in the primary motor cortex is accompanied by an increased persistent inward current.

Sarcopenia, or pathological age-related loss of muscle strength and mass, contributes to physical function impairment in older adults. While current understanding of sarcopenia is centered mostly on neuromuscular mechanisms, mounting evidence supports that deficits at the level of the primary motor cortex (PMC) play a significant role. Despite the importance of the PMC to initiate movement, understanding of how age affects the excitability of layer V pyramidal neurons (LVPNs) of the PMC is limited. To address this, we used the whole-cell patch clamp technique to measure the excitability of LVPNs of the PMC in young, late adulthood, and old mice. Old LVPNs had increased firing frequency and membrane input resistance, but no differences in action potential kinetics versus young and late adulthood mice. Since changes in the persistent inward current (PIC) are known to contribute to changes in motor neuron excitability, we measured LVPN PICs as a putative contributor to LVPN excitability. The PIC amplitude was increased in old LVPN via increases in Na+ and Ca2+ PICs, in addition to being active across a wider voltage range. Given that LVPN function is integral to initiation of voluntary muscle contraction, altered LVPN excitability likely contributes to age-related impairment of physical function.

Improving Neck and Jawline Aesthetics With OnabotulinumtoxinA by Minimizing Platysma Muscle Contraction Effects: Efficacy and Safety Results in a Phase 3 Randomized, Placebo-Controlled Study.

Platysma prominence (PP) describes the noticeable appearance of the platysma muscle upon contraction, causing less defined jawline contour and vertical neck bands. To assess safety and efficacy of onabotulinumtoxinA for improvement of PP in adults. Participants with moderate-to-severe (Grade 3 to 4) PP at maximum contraction received onabotulinumtoxinA or placebo on Day 1 and were monitored for 120 days. OnabotulinumtoxinA dosage (26, 31, or 36 U) was customized based on baseline PP severity on each side of the neck. Efficacy analyses were conducted in the intent-to-treat (ITT) population (all randomized participants), and modified ITT population (mITT; psychosocially impacted by PP appearance). Results from ITT and mITT populations were comparable. As assessed by investigators, 76.7% of onabotulinumtoxinA mITT participants achieved ≥1-grade improvement versus 21.2% in the placebo group, and 41.0% versus 2.2% (P < 0.0001) achieved ≥2-grade improvement at Day 14. As assessed by participants, 79.9% of onabotulinumtoxinA mITT participants versus 21.8% in the placebo group and 40.8% versus 3.9% (P < 0.0001) achieved ≥1- or ≥2-grade improvement, respectively, at Day 14. OnabotulinumtoxinA responder rates remained higher than placebo through Day 120, gradually declining over time. OnabotulinumtoxinA participants reported significantly higher satisfaction with treatment effect, lower bother from jawline and vertical neck bands, and lower psychosocial impact from PP than placebo at Day 14 (P < 0.0001). OnabotulinumtoxinA effectively improved self-perceived jawline definition and was well tolerated. OnabotulinumtoxinA was well tolerated and effective in improving moderate-to-severe PP, including neck bands and jawline definition.

OPTIMIZING THE PHYSICAL DEVELOPMENT OF ADULTS BY USING EMS FITNESS TECHNOLOGY IN LEISURE TIME MOTOR ACTIVITIES

EMS Fitness is an electrical muscle stimulation, a full-body training method that offers the combination of strength training and cardio training through a machine that uses electrical impulses to stimulate muscle contraction. The aim of the study was to follow the effects of electrostimulation training on body composition, weight loss and muscle strength increase. Ten people, women and men, aged between 25 and 50, were studied. We want to demonstrate the hypothesis that the use of the EMS Fitness technique over a period of 90 days will lead to a decrease in body weight, optimisation of body mass index and increase in muscle strength. Participants in the exercise group performed 12 weeks of high-intensity training using specific EMS equipment in an Xbody. The objective of the experiment was to identify whether the use of EMS technology contributed to changes in body mass, skeletal muscle mass, body fat and visceral fat. All exercise sessions were constantly supervised; in addition, exercise intensity, volume and frequency were recorded in training logs. A body composition scale was used for testing, which provides accurate body analysis using BIA technology. The training scheme was used for 12 weeks, changing the dosage and intensity for each subject, with the first signs of weight loss appearing after the first week. Methods used in the research: experimental method, graph-tabel method, observation method, bibliographic study method. Our results support the hypothesis, as the use of the EMS Fitness technique over a period of 90 days led to decreased body mass, optimized body mass index and increased muscle strength. In conclusion, I believe that people in Romania should have a wider openness in practicing physical exercise in their free time in order to develop a healthy generation and decrease the possibility of reaching the stage of obesity and stopping diseases, and a good help in achieving this goal is presented by training using EMS Fitness technology.

Atrial fibrillation and atrial flutter in the practice of the emergency medical team in Poland

Background: Atrial Fibrillation (AF) is one of the most common heart arrhythmias globally. It is characterized by irregular, chaotic contractions of the atrial muscle, leading to an irregular and often rapid heart rhythm. The prevalence of this arrhythmia increases with age, which is associated with both the aging population and cardiovascular risk factors such as hypertension, coronary artery disease, and diabetes. Atrial Flutter (AFL) represents a less common variant of atrial fibrillation, occurring significantly less frequently - in relation to atrial fibrillation (AF), it is estimated to account for less than one-tenth of cases. The aim of the study was to analyze emergency medical services delivered to patients diagnosed with atrial fibrillation (AF) and atrial flutter (AFL) in the Voivodeship of Warmia and Mazury (Poland). The patients were classified according to the 10th Revision of the International Classification of Diseases (ICD-10 )[1]. Methods: The study was based on a retrospective data analysis. From a total population of 400,251 subjects (n= 400,251), 4715 patients were selected for the study. The majority of the patients were women (n=2941; 62.38%), whereas men accounted for 37.62% of the examined sample (n=1774). The analysis relied on a database administered by the Governor of the Voivodeship of Warmia and Mazury in Olsztyn [2]. The analyzed data included the area of intervention, the patient's age and sex, and the diagnoses made by physicians, paramedics, and emergency nurses. Three research hypotheses postulating the presence of relationships between the patient's sex and the diagnosis (1), the patient's age and the diagnosis (2), and a life-threatening emergency and the patient's age (3) were formulated. Results: The results of the study suggest that the patient's sex affects the medical diagnosis. In particular, women were more frequently diagnosed with chest pain, whereas the probability of the remaining diagnoses was similar in both sexes. The patient's age does not significantly influence the diagnosis. The patient's sex is not a significant predictor of a life-threatening emergency. Conclusion: The conducted study on the dataset from the Warmian-Masurian Voivodeship revealed significant correlations between demographic variables and the diagnosis of atrial fibrillation (AF) and atrial flutter (AFL) in patients. Analyzing this data may have significant implications for emergency medical systems, enabling the adaptation of intervention strategies to different patient categories.

Proteomic profiling of extracellular vesicles in takotsubo syndrome

Abstract Background/Purpose Takotsubo syndrome (TS) is an acute form of heart failure characterized by transient regional wall motion abnormalities triggered by a stressful event. The mechanisms underlying its development and recovery are poorly understood, resulting in a lack of disease-specific treatments and diagnostic markers. Extracellular vesicles (EVs) play a significant role in cellular communication and have been shown to be important in various diseases. Their involvement in cardiac conditions like TS is an emerging area of research. The primary objective of this study is to isolate and characterize EVs, as well as profile their proteomic profile, from the heart tissue of rats induced with TS. Methods Rats underwent TS induction through the infusion of 1 mg/kg isoprenaline over 15 minutes (TS24h), or were given saline (control). High-resolution echocardiography verified apical ballooning at 6 hours. After 24 hours, heart tissues from apical and basal segments were collected and processed. EV isolation involved tissue slicing, enzymatic digestion, and differential centrifugation steps, including a final iodixanol cushion separation for large and small EVs (Figure 1). Tandem mass tags and mass spectrometry were utilized for global proteomics and any differentially expressed proteins (DEPs) were identified. Analytical techniques such as volcano plots, heatmaps, enrichment analysis, and protein clustering/networks were employed. The strongest clusters (lowest False Discovery Rate and highest intensity) were selected, and their Gene Ontology (GO) terms/pathways were identified. Results Pure, cup-shaped, vesicles ranging from 50-800nm were successfully isolated (figure 1). EVs from apex of control and TS24h hearts had lower protein concentrations compared to their corresponding basal segments. Global proteomic analysis revealed a distinct protein profile in EVs from the apical segment of TS hearts at 24 hours. A total of 256 (TS24h-apex vs control-apex) and 561 proteins (TS24h-apex vs TS24h-base) were differentially expressed. No DEPs were observed when comparing the basal segments of TS24h and control hearts. Functional enrichment analysis of the DEPs showed an abundant change of biological processes related to metabolic lipid processes, inflammatory response, complement activation, reorganization of extracellular matrix. A downregulation was seen for biological processes related to mitochondrial ATP synthesis coupled electron transport and muscle contraction. Conclusion This study demonstrates a distinct EV protein profile in the apical segments of TS hearts, with marked changes in proteins related to metabolic lipid processes, inflammation, and mitochondrial activity. This extensive catalogue of novel proteins sets the stage for future research aimed at identifying potential therapeutic targets and diagnostic biomarkers, and enabling proof-of-concept studies in TS.

Muscle RING-finger proteins (MuRF) regulate protein kinase A activity via retrograde vesicular transport of PKA RI-alpha

Abstract Background Muscle RING finger (MuRF) proteins are muscle-restricted E3 ubiquitin ligases that control protein degradation in striated muscles. MuRF proteins have coordinate functions for maintenance of striated muscle structure and function that depends on their target proteins. MuRF1 is a key enzyme in muscle atrophy. MuRF2 and MuRF3 bind to and stabilize microtubules which affects striated muscle differentiation and contraction. Although some MuRF-interaction partners have been described only few have been proven to be targeted for proteasomal degradation. To better understand the function of MuRF proteins, we set out to identify and functionally characterize novel MuRF target proteins. Methods and Results Stable isotope labeling of amino acids in cell culture followed by affinity purification and quantitative mass spectrometry analysis (SILAC-AP-MS) was used to identify the interactome of MuRF proteins. We identified the mammalian retromer subunit sorting nexin 5 (SNX5) that is involved in subcellular trafficking as a novel MuRF2 and MuRF3 interaction partner. Coimmunoprecipitation experiments and immunocytochemistry confirmed physical interaction and colocalization between SNX5 and MuRF2 or MuRF3. The interaction domains were mapped. MuRF2, MuRF3 and SNX5 were colocalized to early endosomes at microtubules in myocytes. MuRF2 mediated the ubiquitin proteasome system-dependent degradation of SNX5 in a RING-finger dependent manner, whereas MuRF3 stabilized SNX5. Using mass spectrometry, we identified the regulatory subunit of protein kinase A (PKA-RI-α) as a cargo of SNX5 coated early endosomes in myocytes. CRISPR-Cas9 and siRNA experiments showed that SNX5 regulates PKA activity by stabilizing PKA-RI-α in myocytes. Deletion of SNX5 resulted in PKA activation and inhibition of the HDAC5-MEF2 axis that disturbed myogenic differentiation. Conclusion MuRF2 and MuRF3 play opposing roles in SNX5-mediated retrograde transport of early endosomes along microtubules in myocytes. This mechanism is involved in regulation of PKA catalytic activity via stabilization of PKA-RI-α and controls differentiation of striated muscles.

Impact of SGLT2 inhibitor dapagliflozin on myocardial protein profile in rats with long-standing Type 1 diabetes mellitus

Abstract Background Sodium-glucose cotransporter 2 (SGLT2) inhibitors have beneficial effects on the cardiovascular system in diabetes mellitus (DM) patients. However, as most trials have focused on Type 2 DM, the impact of SGLT2 inhibitors on Type 1 DM remains unclear. Objective To investigate the effects of long-term treatment with SGLT2 inhibitor dapagliflozin on the left ventricular (LV) proteome in Type 1 DM rats. Methods Male Wistar rats were divided into three groups: Control (C, n=7); Diabetes (DM, n=6); and Diabetes treated with Dapagliflozin (DM+DAPA, n=8) for 30 weeks. Diabetes was induced by streptozotocin (40 mg/kg). Dapagliflozin was added to chow at 5 mg/kg/day. Label-free mass spectrometry was used to assess LV proteome using a nanoAcquity UPLC-Xevo QTof MS system and ProteinLynx Global Server (PLGS) software. Cytoscape software, Cluster Marker, and Cluego plugins were used for bioinformatic analysis. Statistical analysis: ANOVA and Tukey or Kruskal-Wallis and Dunn. Results Dapagliflozin increased body weight (C 574±43; DM 339±31*; DM+DAPA 413±30*# g; p&amp;lt;0.05: * vs C; # vs DM) and reduced glycemia [C 108 (101–111); DM 554 (529–562)*; DM+DAPA 343 (237–416)*# mg/dL; p&amp;lt;0.05: * vs C; # vs DM]. One rat died in C and two in DM+DAPA. A total of 252 differentially expressed proteins were identified. Most proteins identified in the networks were downregulated in DM vs C and upregulated in DM+DAPA vs DM. Six proteins related to energy metabolism (Atp5j, P21571; CKm, P00564; Ak1, P39069; Atp5h, P31399; Mdh1, O88989; and Idh2, P56574), four involved in myocyte excitation-contraction (Act1, P68065; Casq2, P51868; SERCA1, Q64578; and SERCA2a, P11507), and two associated with oxidative stress (Sod1, P07632; and Sod2, P07895) were upregulated in DM+DAPA x DM. Comparing DM with C, the KEEG Pathway with the highest percentage of gene associations for upregulated proteins was related to gap junction (25.6%), necroptosis (25.6%), and fatty acid degradation (25.6%), and for downregulated proteins was related to Alzheimer disease (27.3%), cardiac muscle contraction (25%) and glycolysis/gluconeogenesis (13.6%). Comparing DM+DAPA with DM, the KEEG Pathway with the highest percentage of gene associations for upregulated proteins was related to Parkinson disease (18.3%), cardiac muscle contraction (14.2%), citrate acid cycle (9.47%), necroptosis (8.88%), and cGMP-PKG signaling (7.10 %), and for downregulated proteins was related to ketone bodies synthesis and degradation (100%). Conclusion Dapagliflozin is safe and prevents changes in the expression of proteins related to energy metabolism, cardiac muscle contraction, and oxidative stress in Type 1 diabetes mellitus rats. These results offer new insights into the cardioprotective mechanisms of dapagliflozin in Type 1 diabetes mellitus.

The importance of analysing a single common window of a concentric and eccentric dynamic muscle contraction: unveiling the components of EMG data and motor unit pool

This study proposes a method for analysing decomposed electromyographic signals to enhance the characterization of motor units (MU). It involves two steps: (i) clustering groups of motor units based on firing rate (FR), recruitment threshold, and MU action potential amplitude, and (ii) segmentation of data at the time of interest. Such method, capable of distinguishing different groups of MU, could help understanding muscle force production. FR of MU in Vastus Lateralis and Rectus Femoris during knee extension was investigated. The findings distinguish MU groups and reveals differences in: FR between both contractions types; clustered groups; and segmented MU data in both contraction types.

Impact of spilanthol supplementation with balance training on neuromuscular performance

Abstract Background Age-related reductions in muscle mass, muscle contraction power, force, and coordination contribute to an elevated risk of falls and associated consequences. Research suggests that the enhancement of neuromuscular function is attainable through a regimen of targeted exercises and the strategic inclusion of certain supplements like spilanthol. This randomized controlled trial investigated the effect of resistance exercise with either spilanthol plus coordination/ balance training (BAL) or BAL-alone on neuromuscular function (countermovement jump, multiple one-leg hopping, and sit-to-stand test). Materials and methods In the course of this study, a cohort of 68 healthy male participants, aged 40 to 50 years, completed a rigorous 6-month intervention, from the initial 75 recruits. In the spilanthol-plus-BAL group, participants engaged in 30 minutes of resistance exercise sessions four times a week, complemented by daily supplementation of 17.5 mg of spilanthol. Results The analysis of the results showed significant improvements in the spilanthol-plus-BAL group, particularly evident in the peak countermovement power (p &amp;lt; 0.01). The mean effect size for this parameter was a + 1.5[0.9 to 2.1] W/kg greater change in spilanthol-plus-BAL group than BAL-alone group after six months. Moreover, multiple one-leg hopping performance showed significant enhancement in the spilanthol-plus-BAL group post-intervention. The parameters of sit-to-stand duration (1.04 s vs. 1.95 s; p = 0.03) and average acceleration (1.54 g vs. 1.06 g; p = 0.04) both exhibited substantial improvements in the spilanthol-plus-BAL group compared to the BAL-alone group. Conclusions The findings of this investigation contribute empirical evidence supporting the proposition that spilanthol supplementation, when integrated with BAL training, can exert a more pronounced impact on select facets of neuromuscular function. Key messages • Spilanthol supplementation with balance training can exert a pronounced impact on neuromuscular function. • Spilanthol supplementation with balance training demonstrates potential in mitigating sarcopenia and other degenerative conditions.

MANEJO DO SORRISO GENGIVAL ATRAVÉS DO USO DA TOXINA BOTULÍNICA TIPO A

An aesthetically pleasing smile results from the combination of several factors, such as the position, size, shape, and color of the teeth, as well as the exposure and characteristics of the gingival tissue. When evaluating the gingival tissue in a smile, several important factors must be considered: excessive vertical growth of the maxilla, reduced length of the upper lip, excessive contraction of the upper lip, and disproportion between the length and width of the clinical crown of the anterior teeth. A minimally invasive approach that can be used as a complement to dental treatment is the application of botulinum toxin, a neurotoxin produced by the anaerobic bacterium Clostridium botulinum. This toxin blocks the release of acetylcholine in the presynaptic vesicles of neuromuscular junctions, inhibiting muscle contraction. The aim of this literature review was to analyze the use of botulinum toxin type A (BTX-A) in the management of gummy smile. The search was conducted in the databases Google Scholar, PubMed, Latin American and Caribbean Health Sciences Literature (LILACS), and Scientific Electronic Library Online (SciELO). The descriptors used for the search were "botulinum toxin," "gingiva," "periodontology," and "dental aesthetics," combined using the boolean operators AND and OR. Although the evidence demonstrates favorable results, the use of botulinum toxin to correct gummy smile has limitations. It is a temporary solution, and patients should be informed about the need for periodic reapplications and the potential side effects, such as facial asymmetries. The reviewed studies indicate that this technique is particularly effective in cases of gummy smile resulting from hyperactivity of the upper lip elevator muscle, providing a significant reduction in gingival exposure, with results lasting up to 12 weeks. The combination of different therapeutic approaches, along with a careful evaluation of the causes of gummy smile, allows dental professionals to offer more integrated and personalized solutions for each patient.