Muscle Dysfunction Research Articles

Three-dimensional tissue engineered skeletal muscle modelling facioscapulohumeral muscular dystrophy

Abstract Facioscapulohumeral muscular dystrophy (FSHD) is caused by sporadic misexpression of the transcription factor double homeobox 4 (DUX4) in skeletal muscles. So far, monolayer cultures and animal models have been used to study the FSHD disease mechanism and for FSHD therapy development, but these models do not fully recapitulate the disease and there is a lack of knowledge on how DUX4 misexpression leads to skeletal muscle dysfunction. To overcome these barriers, we have developed a three-dimensional tissue engineered skeletal muscle (3D-TESM) model by generating genetically matched myogenic progenitors (MPs) from human induced pluripotent stem cells of three mosaic FSHD patients. 3D-TESMs derived from genetically affected MPs recapitulate pathological features including DUX4 and DUX4 target gene expression, smaller myofiber diameters, and reduced absolute forces upon electrical stimulation. RNA sequencing data illustrates increased expression of DUX4 target genes in 3D-TESMs compared to two-dimensional (2D) myotubes, and cellular differentiation was improved by 3D culture conditions. Treatment of 3D-TESMs with three different small molecules identified in drug development screens in 2D muscle cultures showed no improvements, and sometimes even declines, in contractile force and sarcomere organization. These results suggest that these compounds either have a detrimental effect on the formation of 3D-TESMs, an effect that might have been overlooked or was challenging to detect in 2D cultures and in vivo models, and/or that further development of the 3D-TESM model is needed. In conclusion, we have developed a 3D skeletal muscle model for FSHD that can be employed for preclinical research focusing on DUX4 expression and downstream pathways of FSHD in relation to contractile properties. In the future, we expect that this model can also be used for preclinical drug screening.

Endurance exercise attenuates Gαq-RNAi induced hereditary obesity and skeletal muscle dysfunction via improving skeletal muscle Srl/MRCC-I pathway in Drosophila.

G protein alpha q subunit (Gαq) can binds to the G protein-coupled receptor (GPCR) for signaling and is closely related to lipid metabolism. Endurance exercise is an effective means of combating acquired obesity and its complications, but the mechanisms by which endurance exercise modulates hereditary obesity and its complications are unknown. In this study, we achieved knockdown of Gαq in drosophila adipose tissue and skeletal muscle by constructing the Gαq-UAS-RNAi/Ppl-Gal4 and Gαq-UAS-RNAi/Mef2-GAl4 systems. Drosophila were subjected a three-week endurance exercise intervention, and changes in relevant indicators were detected and observed by RT-PCR, ELISA, oil red staining, immunofluorescence staining, and transmission electron microscopy. The results showed that knockdown of Gαq in both adipose tissue and skeletal muscle induced a significant increase in triglycerides accompanied by a decrease in rapid climbing ability, a decrease in Superoxide Dismutase (SOD) activity level, and a decrease in Mitochondrial respiratory chain complexI (MRCC I) content in Drosophila whole body and skeletal muscle, and down-regulated the expression of the G protein alpha q subunit (Gαq), the skeletal muscle myosin heavy chain expression gene (Mhc), mitochondrial biogenesis gene Spargal(the PGC-1alpha homologue in Drosophila). Endurance exercise significantly improved the triglyceride levels in the whole body and skeletal muscle of drosophila with Gαq knockdown in adipose tissue and skeletal muscle, as well as their ability to climb, increased SOD activity level and MRCCI content level, and up-regulated the expression of Gαq, Mhc, and Spargal(Srl). Thus, the present findings suggest that genetic defects in the Gαq gene in adipose and skeletal muscle tissues induce hereditary obesity and skeletal muscle dysfunction, and that endurance exercise attenuates this hereditary obesity and concomitant skeletal muscle dysfunction in drosophila by improving skeletal muscle fiber contractile proteins, mitochondrial function and function, and antioxidant capacity via mediating the Gαq/Mhc, Gαq/Srl/MRCC-I, and Gαq/SOD pathways.

Abstract 4124039: Aging-Associated Protein Medin Induces Human Coronary Artery Endothelial Proinflammatory and Prothrombotic Activation

Background: Age is the most important risk factor for coronary artery disease (CAD), independent of traditional risk factors such as hypertension, diabetes (DM), hyperlipidemia and smoking, through poorly understood mechanisms. Medin, a cleavage product of MFGE8 protein that forms the most common human amyloid, accumulates in the vasculature with age, including the coronary arteries. Although medin amyloid has been implicated in various diseases such as Alzheimer’s disease, vascular dementia and aortic aneurysms, its role in CAD remains unknown. Medin was shown to induce changes characteristic of vascular aging, such as endothelial and smooth muscle dysfunction in human donor cerebral arteries. Medin also induced proinflammatory activation of human brain microvascular endothelial cells through NFκB activation . Aims: To determine the effects of medin on pro-inflammatory and prothrombotic activation of human coronary artery endothelial cells (HCAECs). Methods: Primary HCAECs (passages 6-8) were exposed for 20 hours to physiologic doses of recombinant medin (0.5, 1 and 5 µM) and gene expression of pro-inflammatory proteins (IL-6, IL-8, IL-1b and intercellular adhesion molecule (ICAM)-1), prothrombotic protein (plasminogen activator inhibitor (PAI)-1) and anticoagulant membrane protein thrombomodulin were quantified using rtPCR and compared. Separately, HCAECs were exposed to medin (0.5, 1 and 5 µM) with or without small molecule specific inhibitor of NFκB (RO106-9920, 10 uM) for 20 hours and protein expression of IL-6 in conditioned media was measured using ELISA. Results: Medin caused dose-dependent increases in gene expressions of pro-inflammatory cytokines IL-6, IL-8, IL-1b, ICAM-1 (Figure 1 A-D). Medin caused a dose-dependent increase in PAI-1 and a dose-dependent decrease in thrombomodulin (Fig. 1 E-F). Co-treatment with RO106-9920 prevented medin-induced increase in IL-6 protein expression (Fig. 1G). Conclusions: Medin induces pro-inflammatory and prothrombotic activation of human coronary artery endothelial cells. The proinflammatory activation is likely NFκB-dependent. Medin is a promising potential novel mediator of CAD and vascular aging.

Abstract 4119913: Aging-Associate Peptide Medin Induces Proinflammatory Activation in Human Brain Vascular Smooth Muscle Cells

Background: Medin is one of the most common amyloidogenic proteins and accumulates in the vasculature with aging. Vascular medin accumulation is associated with Alzheimer's disease, vascular dementia and aortic aneurysms. In vitro , medin has been shown to induce endothelial proinflammatory activation and in ex vivo human cerebral arterial tissue, medin induces both endothelial and smooth muscle dysfunction. The role of medin in vascular smooth muscle (VSMC) activation remains unknown. Aim: The aim of the study is to determine using gene transcription assay whether medin induces VSMC activation and phenotypic transformation. Methods: Human brain vascular smooth muscle cells (HBVSMCs, passages 6-10) were exposed to medin at doses observed in human tissues (0, 0.5, 1 and 5 υM) for 20 hours and reverse transcription polymerase chain reaction (rtPCR) was used to quantify gene expression of proinflammatory factors (interleukin (IL)-6, IL-8, IL-1b) and structural and enzyme proteins associated with VSMC phenotypic transformation (ACTA2, MYH11 and NOX4). In separate experiments, HBVSMCs were exposed to vehicle, medin 5 υM without or with small molecule NFκB inhibitor RO106-9920 (10 υM) or NLGM1 nanoliposome (70% phosphatidylcholine, 25% cholesterol, 5% monosialoganglioside, 100 υg/mL, agent shown to reverse medin-induced endothelial dysfunction and proinflammatory activation). Results: Medin induced a dose-dependent increase in gene expression of IL-6, IL-8 and IL-1b but did not alter gene expression of ACTA2, MYH11 and NOX4 (Fig. 1). Co-treatment of medin with RO106-9920 and NLGM1 showed a trend (not statistically significant) of reduced IL-6 and IL-8 (Fig. 2). Conclusions: Physiologic doses of medin induced pro-inflammatory activation of HBVSMCs but did not affect gene expression of structural proteins (ACTA2 and MYH11) and enzyme (NOX4) involved in VSMC phenotypic transformation. Although the mechanisms behind this effect remains to be explored, results suggest that medin may be an important mediator of aging-associated vascular inflammation.

Lipin1 as a therapeutic target for respiratory insufficiency of duchenne muscular dystrophy

In Duchenne muscular dystrophy (DMD), diaphragm muscle dysfunction results in respiratory insufficiency which is a leading cause of death in patients. Mutations to the dystrophin gene result in myocyte membrane instability, contributing to the structural deterioration of the diaphragm muscle tissues. With previous works suggesting the importance of lipin1 for maintaining skeletal muscle membrane integrity, we explored the roles of lipin1 in the dystrophic diaphragm. We found that the protein expression levels of lipin1 were reduced by 60% in the dystrophic diaphragm. While further knockdown of lipin1 in the dystrophic diaphragm leads to increased necroptosis, restoration of lipin1 in the dystrophic diaphragm results in reduced inflammation and fibrosis, decreased myofiber death, and improved respiratory function. Our results demonstrated that lipin1 restoration improved respiratory function by enhancing membrane integrity and suggested that lipin1 could be a potential therapeutic target for preventing respiratory insufficiency and respiratory failure in DMD. Continued investigation is required to better understand the mechanisms behind these findings, and to determine the role of lipin1 in maintaining muscle membrane stability.

EFFECTIVENESS OF HYPOPRESSIVE EXERCISES ON POSTNATAL MOTHERS WITH URINARY INCONTINENCE-A PILOT STUDY.

Background: Pelvic Floor Muscle Dysfunctions can lead to Urinary Incontinence, a condition which often affects women both during pregnancy and after childbirth. As a result of this, certain exercises are recommended during and after pregnancy to prevent and treat this incontinence. Hypopressive Exercise is one of these methods used to prevent Urinary Incontinence. Objective: The purpose of the study is to find the Effectiveness of Hypopressive Exercises on Postnatal Mothers with Urinary Incontinence. Methods: 30 Mothers (between the age group of 25 – 35 years) clinically pre diagnosed with urinary incontinence with PERFECT score were included in the study. with informed consent, the protocol was explained to the subjects. Mothers were given Hypopressive Exercises for 3 sessions per week for 4 weeks. This session lasted between 30 to 40 minutes. The outcome measure of the Exercises was measured using UI – QUID and PERFECT test. Results were tabulated using statistical analysis. Result: The analysis shows that the mothers who underwent Hypopressive exercises have significant reduction in urinary incontinence (p-value) P<0.0001. Conclusion: This study concluded that the mothers underwent Hypopressive exercises have significant reduction in Urinary Incontinence and increase in Pelvic Floor Muscle Strength Implications: The Hypopressive Exercises strengthens the Deep Core Muscles which increases body awareness by training the Pelvic Floor Muscles in women and reduces Urinary Incontinence. These Exercises not only pay attention to maintaining proper body posture and Pelvic Floor Muscles activation. But also had a positive impact on the Quality of Life and reduction of incidents of urine leakage among mothers.

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.

Neurovascular dysregulation in systemic sclerosis: novel insights into pathophysiology, diagnosis, and treatment utilizing invasive cardiopulmonary exercise testing.

Pathologic abnormalities in skeletal muscle and the systemic vasculature are common in patients with systemic sclerosis (SSc). These abnormalities may lead to impaired systemic peripheral oxygen extraction (EO2), known as neurovascular dysregulation, which may be because of abnormal blood flow distribution in the vasculature, microvascular shunting, and/or skeletal muscle mitochondrial dysfunction. Findings from invasive cardiopulmonary exercising testing (iCPET) provide important insights and enable diagnosis and treatment of this SSc disease manifestation. Recent findings from noninvasive cardiopulmonary exercise testing (niCPET) support the existence of neurovascular dysregulation in patients with SSc. Invasive cardiopulmonary exercise testing (iCPET) has pointed to reduced systemic vascular distensibility as a possible mechanism for neurovascular dysregulation in patients with connective tissue diseases, including SSc. Neurovascular dysregulation is likely an underappreciated cause of exercise impairment and dyspnea in patients with SSc in the presence or absence of underlying cardiopulmonary disease. It is posited to be related to microcirculatory and muscle dysfunction. Further studies are needed to clarify the pathophysiology of neurovascular dysregulation in SSc and to identify novel treatment targets and additional therapies.

Angiopoietin 1 Attenuates Dysregulated Angiogenesis in the Gastrocnemius of DMD Mice.

Duchenne muscular dystrophy (DMD) is a degenerative neuromuscular disease caused by a lack of functional dystrophin. Ang 1 paracrine signalling maintains the endothelial barrier of blood vessels, preventing plasma leakage. Chronic inflammation, a consequence of DMD, causes endothelial barrier dysfunction in skeletal muscle. We aim to elucidate changes in the DMD mouse's gastrocnemius microvascular niche following local administration of Ang 1. Gastrocnemii were collected from eight-week-old mdx/utrn+/- and healthy mice. Additional DMD cohort received an intramuscular injection of Ang 1 to gastrocnemius and contralateral control. Gastrocnemii were collected for analysis after two weeks. Using immunohistochemistry and real-time quantitative reverse transcription, we demonstrated an abundance of endothelial cells in DMD mouse's gastrocnemius, but morphology and gene expression were altered. Myofiber perimeters were shorter in DMD mice. Following Ang 1 treatment, fewer endothelial cells were present, and microvessels were more circular. Vegfr1, Vegfr2, and Vegfa expression in Ang 1-treated gastronemii increased, while myofiber size distribution was consistent with vehicle-only gastrocnemii. These results suggest robust angiogenesis in DMD mice, but essential genes were underexpressed-furthermore, exogenous Ang 1 attenuated angiogenesis. Consequentially, gene expression increased. The impact must be investigated further, as Ang 1 therapy may be pivotal in restoring the skeletal muscle microvascular niche.

A PROSPECTIVE STUDY ON MANAGEMENT OF CARDIOGENIC SHOCK WITH PERCUTANEOUS CORONARY INTERVENTION

Cardiogenic shock following acute myocardial infarction (AMI) is a critical condition with high mortality rates. Percutaneous coronary intervention (PCI) has emerged as a key intervention, but the outcomes and associated risk factors, including comorbidities such as hypertension, diabetes, and smoking, remain essential to understand for optimizing treatment and improving prognosis. Objective: To evaluate outcomes and identify risk factors in patients with cardiogenic shock secondary to acute myocardial infarction managed with percutaneous coronary intervention. Methods: A prospective observational study was conducted at a tertiary care hospital involving 70 patients aged 60 years and above who presented with cardiogenic shock due to AMI within 24 hours of symptom onset. Data were collected on demographics, clinical indicators of shock severity, and mechanical complications, including pump failure, papillary muscle rupture, ventricular septal rupture (VSR), and free wall rupture. The incidence of comorbidities, such as hypertension, diabetes, and smoking status, was documented. Mortality and recovery patterns were assessed during hospitalization and post-discharge. Statistical analysis was performed to examine associations between comorbidities and adverse outcomes. Results: The mean age of the cohort was 68.8 ± 4.5 years, with a male predominance of 57.1%. Key complications included pump failure in 31.4%, papillary muscle rupture in 11.4%, papillary muscle dysfunction in 34.3%, VSR in 7.1%, and free wall rupture in 4.3% of patients. Overall mortality was 12.9%. Hypertension was present in 67.1% of patients, diabetes in 61.4%, and smoking in 21.4%, all of which correlated with higher complication rates and adverse outcomes. Conclusion: Early PCI management in patients with cardiogenic shock secondary to AMI is associated with favorable survival rates. However, comorbidities such as hypertension and diabetes significantly increase complication rates. These findings underscore the importance of timely intervention and risk-targeted management to improve survival outcomes in high-risk patients.

Sex-dependent interplay of phosphate and inflammation on muscle strength irrespective of muscle mass in middle-aged and older adults

BackgroundElevated circulatory phosphate levels are linked to age-related muscle dysfunction, yet the mechanisms remain unclear. This study investigated the hypothesis that inflammation plays a role in connecting elevated phosphate levels to muscular dysfunction in middle-aged and older individuals and explored potential sex-based differences in these associations. MethodsThe study, based on the I-Lan Longitudinal Aging Study Cohort, analyzed individuals' serum phosphate and hsCRP levels. Sex-specific analyses explored links between circulatory phosphate, inflammation, and muscle profiles (mass, handgrip strength, and walking speed). The study also examined potential mediation or synergistic effects of inflammation in the circulatory phosphate-muscle relationship. ResultsThe study included 2006 participants (mean age: 65.5 ± 6.5 years; 49.8 % men). Women exhibited higher circulatory phosphate levels than men. Linear analyses revealed that higher phosphate levels were significantly associated with weaker handgrip strength but not with reduced muscle mass in both men and women. In women, circulatory phosphate was not associated with inflammation (hsCRP levels), while in men, higher phosphate levels were significantly associated with higher hsCRP levels. In men, a synergistic effect was observed, where the combination of high hsCRP and elevated phosphate levels had a more pronounced impact on reducing handgrip strength than either factor alone. ConclusionsThis study highlights a sex-specific association of inflammation in the mechanisms of hyperphosphatemia-related muscle weakness. The findings emphasize the importance of managing both hyperphosphatemia and chronic inflammation to mitigate their collective impact on muscle function, particularly in older men. Addressing these factors is crucial for promoting muscle health in later life.

JAK inhibition with tofacitinib rapidly increases contractile force in human skeletal muscle.

Reduction in muscle contractile force associated with many clinical conditions incurs serious morbidity and increased mortality. Here, we report the first evidence that JAK inhibition impacts contractile force in normal human muscle. Muscle biopsies were taken from patients who were randomized to receive tofacitinib (n = 16) or placebo (n = 17) for 48 h. Single-fiber contractile force and molecular studies were carried out. The contractile force of individual diaphragm myofibers pooled from the tofacitinib group (n = 248 fibers) was significantly higher than those from the placebo group (n = 238 fibers), with a 15.7% greater mean maximum specific force (P = 0.0016). Tofacitinib treatment similarly increased fiber force in the serratus anterior muscle. The increased force was associated with reduced muscle protein oxidation and FoxO-ubiquitination-proteasome signaling, and increased levels of smooth muscle MYLK. Inhibition of MYLK attenuated the tofacitinib-dependent increase in fiber force. These data demonstrate that tofacitinib increases the contractile force of skeletal muscle and offers several underlying mechanisms. Inhibition of the JAK-STAT pathway is thus a potential new therapy for the muscle dysfunction that occurs in many clinical conditions.

Short-chain fatty acids enhance muscle mass and function through the activation of mTOR signalling pathways in sarcopenic mice.

Sarcopenia is a prevalent muscle disorder in old people leading to higher fracture rate, mortality, and other adverse clinical outcomes. Evidence indicates that short-chain fatty acids (SCFAs), which are beneficial gut microbial metabolites, were reduced in old people with sarcopenia. This study aimed to determine whether the use of SCFAs as a supplement can be a therapeutic strategy of sarcopenia in a pre-clinical model. Seven-month-old pre-sarcopenic senescent accelerated mouse prone 8 (SAMP8) mice received daily SCFAs cocktail (acetate, butyrate, and propionate) for 3months. Age-matched senescence accelerated mouse resistant 1 (SAMR1) and SAMP8 mice receiving sodium-matched drinking water were control groups. The gut microbiota composition analysis of aged mice with or without sarcopenia was conducted by 16S rDNA sequencing. Gut barrier-related proteins and lipopolysaccharide (LPS) concentration were biomarkers of gut permeability. Colon inflammation levels, circulatory SCFAs concentration, muscle quality, function, and underlying pathways were detected by cell number counting, RT-qPCR, gas chromatography-mass spectrometry, measurements of muscle wet weight and grip strength, ex vivo functional test, treadmill endurance test, transcriptomic sequencing, morphological and immunofluorescent staining, as well as western blot. To investigate the role of mTOR signalling pathways in SCFAs treatment, C2C12 myotubes were treated with rapamycin. Aged SAMP8 mice had different microbiota composition, and lower serum butyric acid compared with SAMR1 mice (P<0.05). SCFAs treatment reversed the increment of colon inflammation (2.8-fold lower of il-1β) and gut barrier permeability (1.7-fold lower of LPS) in SAMP8 mice. Increased muscle mass, myofibre cross-sectional area, grip strength, twitch and tetanic force were found in SCFAs-treated mice compared with control SAMP8 mice (P<0.05). Anti-fatigue capacity (1.6-fold) and muscle glycogen (2-fold) also improved after SCFAs treatment (P<0.05). Transcriptomic analysis showed that AMPK, insulin, and mTOR pathways were involved in SCFAs treatment (P<0.05). Regulation of AKT/mTOR/S6K1 and AMPK/PGC1α pathways were found. SCFAs attenuated fat infiltration and improved mitochondria biogenesis of atrophic muscle. In vitro studies indicated that SCFAs inhibited FoxO3a/Atrogin1 and activated mTOR pathways to improve myotube growth (P<0.05), and rapamycin attenuated the effect of SCFAs through the inhibition of mTOR pathways. This study demonstrated that bacterial metabolites SCFAs could attenuate age-related muscle loss and dysfunction, and protein synthesis-related mTOR signalling pathways were involved both in vivo and in vitro.

Elucidating the roles of SOD3 correlated genes and reactive oxygen species in rare human diseases using a bioinformatic-ontology approach.

Superoxide Dismutase 3 (SOD3) scavenges extracellular superoxide giving a hydrogen peroxide metabolite. Both Reactive Oxygen Species diffuse through aquaporins causing oxidative stress and biomolecular damage. SOD3 is differentially expressed in cancer and this research utilises Gene Expression Omnibus data series GSE2109 with 2,158 cancer samples. Genome-wide expression correlation analysis was conducted with SOD3 as the seed gene. Categorical SOD3 Pearson Correlation gene lists incrementing in correlation strength by 0.01 from ρ≥|0.34| to ρ≥|0.41| were extracted from the data. Positively and negatively SOD3 correlated genes were separated for each list and checked for significance against disease overlapping genes in the ClinVar and Orphanet databases via Enrichr. Disease causal genes were added to the relevant gene list and checked against Gene Ontology, Phenotype Ontology, and Elsevier Pathways via Enrichr before the significant ontologies containing causal and non-overlapping genes were reviewed with a literature search for possible disease and oxidative stress associations. 12 significant individually discriminated disorders were identified: Autosomal Dominant Cutis Laxa (p = 6.05x10-7), Renal Tubular Dysgenesis of Genetic Origin (p = 6.05x10-7), Lethal Arteriopathy Syndrome due to Fibulin-4 Deficiency (p = 6.54x10-9), EMILIN-1-related Connective Tissue Disease (p = 6.54x10-9), Holt-Oram Syndrome (p = 7.72x10-10), Multisystemic Smooth Muscle Dysfunction Syndrome (p = 9.95x10-15), Distal Hereditary Motor Neuropathy type 2 (p = 4.48x10-7), Congenital Glaucoma (p = 5.24x210-9), Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome (p = 3.77x10-16), Classical-like Ehlers-Danlos Syndrome type 1 (p = 3.77x10-16), Retinoblastoma (p = 1.9x10-8), and Lynch Syndrome (p = 5.04x10-9). 35 novel (21 unique) genes across 12 disorders were identified: ADNP, AOC3, CDC42EP2, CHTOP, CNN1, DES, FOXF1, FXR1, HLTF, KCNMB1, MTF2, MYH11, PLN, PNPLA2, REST, SGCA, SORBS1, SYNPO2, TAGLN, WAPL, and ZMYM4. These genes are proffered as potential biomarkers or therapeutic targets for the corresponding rare diseases discussed.

Skeletal muscle metabolic characteristics and fresh meat quality defects associated with wooden breast.

Wooden breast (WB) is a myopathy that occurs in pectoralis major (PM) muscles, predominately affecting large, fast-growing broilers. Severe myodegeneration, increased hypoxia, reduced blood flow, and increased collagen deposition are hallmark characteristics of WB that culminate in unsatisfactory fresh meat quality attributes, such as poor water-holding capacity, tenderness, and processing characteristics. Therefore, WB meat is often downgraded resulting in economic losses for the United States poultry industry. Although WB has been well characterized, its etiology remains undefined. As the scientific community continues to resolve mechanisms responsible for WB onset, understanding biochemical changes associated with WB may facilitate solutions to negate its poor meat quality attributes. Given changes in metabolism of living muscle can alter biochemical processes during the conversion of muscle to meat, this review aims to summarize and discuss the current knowledge of WB muscle and meat biochemistry. For example, it appears metabolic pathways that support combating stress are upregulated in WB muscle at the expense of glycolytic flux, which presumably contributes to the high ultimate pH of WB meat. Further, perturbed function of WB mitochondria, such as altered calcium handling, impacts aspects of postmortem metabolism and proteolysis. Collectively, metabolic dysfunction of WB muscle alters the biochemical processes that occur during the conversion of muscle to meat, and thus contributes to the poor WB meat quality.

Stress Granule Assembly in Pulmonary Arterial Hypertension.

The role of stress granules (SGs) in pulmonary arterial hypertension (PAH) is unknown. We hypothesized that SG formation contributes to abnormal vascular phenotypes, and cardiac and skeletal muscle dysfunction in PAH. Using the rat Sugen/hypoxia (SU/Hx) model of PAH, we demonstrate the formation of SG puncta and increased expression of SG proteins compared to control animals in lungs, right ventricles, and soleus muscles. Acetazolamide (ACTZ) treatment ameliorated the disease and reduced SG formation in all of these tissues. Primary pulmonary artery smooth muscle cells (PASMCs) from diseased animals had increased SG protein expression and SG number after acute oxidative stress and this was ameliorated by ACTZ. Pharmacologic inhibition of SG formation or genetic ablation of the SG assembly protein (G3BP1) altered the SU/Hx-PASMC phenotype by decreasing proliferation, increasing apoptosis and modulating synthetic and contractile marker expression. In human PAH lungs, we found increased SG puncta in pulmonary arteries compared to control lungs and in human PAH-PASMCs we found increased SGs after acute oxidative stress compared to healthy PASMCs. Genetic ablation of G3BP1 in human PAH-PASMCs resulted in a phenotypic switch to a less synthetic and more contractile phenotype. We conclude that increased SG formation in PASMCs and other tissues may contribute to PAH pathogenesis.

Heat exposure promotes sarcopenia via gut microbiota-derived metabolites.

The unprecedented rise in global ambient temperatures in the last decade has significantly impacted human health, yet how heat exposure affects the development of sarcopenia remains enigmatic. Here, we demonstrate that chronic heat exposure induces skeletal muscle volume loss, leading to muscle strength and functional decline in mice. The microbiota composition of heat-exposed mice was analyzed using 16S ribosomal DNA analysis. Liquid chromatography-mass spectrometry (LC-MS) was used to explore the effects of heat exposure on the blood metabolome and to further analyze the correlation between blood metabolism and gut microbiota. Transplantation of microbiota from heat-exposed mice to germ-free mice was sufficient to increase adverse effects on skeletal muscle function in the host. Mechanistically, using an untargeted metabolomics strategy, we reveal that altered gut microbiota due to high temperatures is associated with elevated serum levels of homocitrulline. Homocitrulline causes mitochondrial dysfunction in myocytes by exacerbating ferroptosis levels. And Nrf2 activator (Oltipraz) supplementation alleviates muscle atrophy and dysfunction induced by heat exposure. Our findings reveal the detrimental effects of heat exposure on muscle function and provide new strategies for treating sarcopenia.

Honokiol and Nicotinamide Adenine Dinucleotide Improve Exercise Endurance in Pulmonary Hypertensive Rats Through Increasing SIRT3 Function in Skeletal Muscle.

Pulmonary hypertension (PH) significantly impairs exercise capacity and the quality of life in patients, which is influenced by dysfunctions in multiple organ systems, including the right ventricle, lungs, and skeletal muscles. Recent research has identified metabolic reprogramming and mitochondrial dysfunction as contributing factors to reduced exercise tolerance in PH patients. In this study, we investigated the therapeutic potential of enhancing mitochondrial function through the activation of the mitochondrial deacetylase SIRT3, using SIRT3 activator Honokiol combined with the SIRT3 co-factor nicotinamide adenine dinucleotide (NAD), in a Sugen/Hypoxia-induced PH rat model. Our results show that Sugen/Hypoxia-induced PH significantly impairs RV, lung, and skeletal muscle function, leading to reduced exercise capacity. Treatment with Honokiol and NAD notably improved exercise endurance, primarily by restoring SIRT3 levels in skeletal muscles, reducing proteolysis and atrophy in the gastrocnemius, and enhancing mitochondrial complex I levels in the soleus. These effects were independent of changes in cardiopulmonary hemodynamics. We concluded that targeting skeletal muscle dysfunction may be a promising approach to improving exercise capacity and overall quality of life in PH patients.

Spinal muscle characteristics during three different types of locomotion activities among college students with idiopathic scoliosis

Background contextPhysical activities such as walking and climbing stairs are pervasive in human daily life. Individuals with scoliosis frequently encounter dysfunction in their muscle recruitment. Multiple studies have corroborated the presence of muscle dysfunction in individuals diagnosed with scoliosis. However, there is currently a noteworthy research gap regarding the exploration of changes in muscle characteristics and disparities from those observed in individuals without scoliosis during everyday activities, specifically stair climbing.PurposeThis study aims to examine the unique patterns of muscle activity during daily life in individuals with scoliosis and distinguish the specific differences between scoliosis patients and the healthy controls. The findings of this study are significantly important for the future accurate assessment of scoliosis and the development of rehabilitation treatment plans.Study designCase–control study.Sample sizeTwenty eight idiopathic scoliosis patients and twenty eight controls.Outcome measuresRoot Mean Square(RMS), Maximum Voluntary Isometric Contraction(MVIC)%, RMS ratio(RMS convex / RMS concave).MethodsThe surface electromyography (sEMG) device used in this study was the Delsys Trigno, with a sampling frequency of 1500 Hz. It recorded the activation level, peak contraction, and average activation level of the erector spinae (at T6, T10, and L3 levels), gluteus maximus, gluteus medius, external oblique, and rectus abdominis muscles during three different types of locomotion for both the 28 individuals with idiopathic scoliosis and the 28 control participants.ResultsThe movement patterns of the idiopathic scoliosis patients significantly differ from those of the normal population during level walking and ascending or descending stairs. In level walking, there is an asymmetry in the activation levels of the T6 and L3 erector spinae muscles, with lower activation on the convex side compared to the concave side. Similarly, during stair ascent, the activation of the T6 and T10 erector spinae muscles is asymmetric, with higher activation on the convex side than the concave side. Moreover, during stair descent, the activation of the T6 erector spinae muscle is asymmetric, with higher activation on the convex side than the concave side.ConclusionsDuring level walking and stair activities, idiopathic scoliosis patients exhibit pronounced abnormal movement patterns that significantly differ from those of the control group. Under different activity conditions such as level walking, ascending and descending stairs, idiopathic scoliosis patients demonstrate abnormal muscle activation in different segments of the spine. It is crucial for clinicians to prioritize the symmetry of muscle activation in the spinal region of idiopathic scoliosis patients and consider incorporating symmetry training for these muscles.

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

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