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Objectives: The aim of the study was to study the Janus kinase/tyrosine kinase-activated transduction factor (JAK/STAT) signaling pathway and myogenesis on the masseter muscle after sleep deprivation and to investigate the role of stress in this scenario. Subjects and Methods: A total of 18 male Wistar rats were divided into the following groups: control (n = 6): animals were not submitted to any procedures, and paradoxical sleep deprivation and vehicle (PSD + V; n = 6): animals were subjected to PSD for 96 h and (PSD + MET; n = 6): animals were subjected to PSD for 96 h with administration of metyrapone. Paradoxical sleep deprivation was performed by the modified multiple platforms method. Histopathological analysis, histomorphometry, and immunohistochemistry were performed. Results: The results showed the presence of inflammatory infiltrate in the PSD + V and PSD + MET groups and atrophy. Histomorphometry showed that the cellular profile area decreased, while cellular density increased in both experimental groups. Expression of p-STAT 3, MyoD, and MyoG increased in the PSD + V group, while the PSD + MET group showed increased expression of IL-6 and p-STAT 3. Conclusion: Our results suggest that sleep deprivation induces an inflammatory response and atrophy in the masseter muscle of rats.

Background Patients with critical illness can lose more than 15% of muscle mass in one week, and this can have long-term detrimental effects. However, there is currently no synthesis of the data of intensive care unit (ICU) muscle wasting studies, so the true mean rate of muscle loss across all studies is unknown. The aim of this project was therefore to systematically synthetise data on the rate of muscle loss and to identify the methods used to measure muscle size and to synthetise data on the prevalence of ICU-acquired weakness in critically ill patients. Methods We conducted a systematic literature search of MEDLINE, PubMed, AMED, BNI, CINAHL, and EMCARE until January 2022 (International Prospective Register of Systematic Reviews [PROSPERO] registration: CRD420222989540. We included studies with at least 20 adult critically ill patients where the investigators measured a muscle mass-related variable at two time points during the ICU stay. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and assessed the study quality using the Newcastle–Ottawa Scale. Results Fifty-two studies that included 3251 patients fulfilled the selection criteria. These studies investigated the rate of muscle wasting in 1773 (55%) patients and assessed ICU-acquired muscle weakness in 1478 (45%) patients. The methods used to assess muscle mass were ultrasound in 85% ( n  = 28/33) of the studies and computed tomography in the rest 15% ( n  = 5/33). During the first week of critical illness, patients lost every day −1.75% (95% CI −2.05, −1.45) of their rectus femoris thickness or −2.10% (95% CI −3.17, −1.02) of rectus femoris cross-sectional area. The overall prevalence of ICU-acquired weakness was 48% (95% CI 39%, 56%). Conclusion On average, critically ill patients lose nearly 2% of skeletal muscle per day during the first week of ICU admission.

Multiple-system atrophy is a neurodegenerative disease characterized by progressive autonomic failure, parkinsonism, and cerebellar and pyramidal tract symptoms. Glial cytoplasmic inclusions of α-synuclein are a defining histologic feature. There is no curative treatment. Multiple-system atrophy is an adult-onset, fatal neurodegenerative disease characterized by progressive autonomic failure, parkinsonian features, and cerebellar and pyramidal features in various combinations. It is classified as the parkinsonian subtype if parkinsonism is the predominant feature and as the cerebellar subtype if cerebellar features predominate. With its variable clinical presentations, multiple-system atrophy presents a major diagnostic challenge not only in neurology but also in other specialties, including cardiology, gastroenterology, urology, otolaryngology, and sleep medicine. Despite having faster motor progression, multiple-system atrophy may masquerade as Parkinson’s disease or idiopathic late-onset cerebellar ataxia until advanced stages of the disease. The history of . . .

Skeletal muscle atrophy is a hallmark of the cachexia syndrome that is associated with poor survival and reduced quality of life in patients with cancer 1 . Muscle atrophy involves excessive protein catabolism and loss of muscle mass and strength 2 . An effective therapy against muscle wasting is currently lacking because mechanisms driving the atrophy process remain incompletely understood. Our gene expression analysis in muscle tissues indicated upregulation of ectodysplasin A2 receptor (EDA2R) in tumour-bearing mice and patients with cachectic cancer. Here we show that activation of EDA2R signalling promotes skeletal muscle atrophy. Stimulation of primary myotubes with the EDA2R ligand EDA-A2 triggered pronounced cellular atrophy by induction of the expression of muscle atrophy-related genes Atrogin1 and MuRF1 . EDA-A2-driven myotube atrophy involved activation of the non-canonical NFĸB pathway and was dependent on NFκB-inducing kinase (NIK) activity. Whereas EDA-A2 overexpression promoted muscle wasting in mice, deletion of either EDA2R or muscle NIK protected tumour-bearing mice from loss of muscle mass and function. Tumour-induced oncostatin M (OSM) upregulated muscle EDA2R expression, and muscle-specific oncostatin M receptor (OSMR)-knockout mice were resistant to tumour-induced muscle wasting. Our results demonstrate that EDA2R–NIK signalling mediates cancer-associated muscle atrophy in an OSM–OSMR-dependent manner. Thus, therapeutic targeting of these pathways may be beneficial in prevention of muscle loss. Gene expression analysis in muscle tissues showed upregulation of ectodysplasin A2 receptor in tumour-bearing mice and patients with cachectic cancer, and thus therapeutic targeting of relevant pathways may be beneficial in prevention of muscle loss.

Sarcopenia (severe muscle depletion) is a prevalent muscle abnormality in patients with cirrhosis that confers poor prognosis both pre- and post-liver transplantation. The pathogenesis of sarcopenia is multifactorial and results from an imbalance between protein synthesis and breakdown. Nutritional, metabolic, and biochemical abnormalities seen in chronic liver disease alter whole body protein homeostasis. Hyperammonemia, increased autophagy, proteasomal activity, lower protein synthesis, and impaired mitochondrial function play an important role in muscle depletion in cirrhosis. Factors including cellular energy status, availability of metabolic substrates (e.g., branched-chain amino acids), alterations in the endocrine system (insulin resistance, circulating levels of insulin, insulin-like growth factor-1, corticosteroids, and testosterone), cytokines, myostatin, and exercise are involved in regulating muscle mass. A favored atrophy of type II fast-twitch glycolytic fibers seems to occur in patients with cirrhosis and sarcopenia. Identification of muscle biological abnormalities and underlying mechanisms is required to plan clinical trials to reverse sarcopenia through modulation of specific mechanisms. Accordingly, a combination of nutritional, physical, and pharmacological interventions might be necessary to reverse sarcopenia in cirrhosis. Moderate exercise should be combined with appropriate energy and protein intake, in accordance with clinical guidelines. Interventions with branched chain amino acids, testosterone, carnitine, or ammonia-lowering therapies should be considered individually. Various factors such as dose, type, duration of supplementations, etiology of cirrhosis, amount of dietary protein intake, and compliance with supplementation and exercise should be the focus of future large randomized controlled trials investigating both prevention and treatment of sarcopenia in this patient population.

Background/ObjectivesTo assess the safety and efficacy of avacincaptad pegol (ACP), a C5 inhibitor, for geographic atrophy (GA) secondary to age-related macular degeneration (AMD) over an 18-month treatment course.Subjects/MethodsThis study was an international, prospective, randomized, double-masked, sham-controlled, phase 2/3 clinical trial that consisted of 2 parts. In part 1, 77 participants were randomized 1:1:1 to receive monthly intravitreal injections of ACP 1 mg, ACP 2 mg, or sham. In part 2, 209 participants were randomized 1:2:2 to receive monthly ACP 2 mg, ACP 4 mg, or sham. The mean rate of change of GA over 18 months was measured by fundus autofluorescence.ResultsCompared with their respective sham cohorts, monthly ACP treatment reduced the mean GA growth (square root transformation) over 18 months by 28.1% (0.168 mm, 95% CI [0.066, 0.271]) for the 2 mg cohort and 30.0% (0.167 mm, 95% CI [0.062, 0.273]) for the 4 mg cohort. ACP treatment was generally well tolerated over 18 months, with most ocular adverse events (AEs) related to the injection procedure. Macular neovascularization (MNV) was more frequent in both 2 mg (11.9%) and 4 mg (15.7%) cohorts than their respective sham control groups (2.7% and 2.4%).ConclusionsOver this 18-month study, ACP 2 mg and 4 mg showed continued reductions in the progression of GA growth compared to sham and continued to be generally well tolerated. A pivotal phase 3 GATHER2 trial is currently underway to support the efficacy and safety of ACP as a potential treatment for GA.

Exercise induces expression of the myokine irisin, which is known to promote browning of white adipose tissue and has been shown to mediate beneficial effects following exercise. Here we show that irisin induces expression of a number of pro-myogenic and exercise response genes in myotubes. Irisin increases myogenic differentiation and myoblast fusion via activation of IL6 signaling. Injection of irisin in mice induces significant hypertrophy and enhances grip strength of uninjured muscle. Following skeletal muscle injury, irisin injection improves regeneration and induces hypertrophy. The effects of irisin on hypertrophy are due to activation of satellite cells and enhanced protein synthesis. In addition, irisin injection rescues loss of skeletal muscle mass following denervation by enhancing satellite cell activation and reducing protein degradation. These data suggest that irisin functions as a pro-myogenic factor in mice. Exercise induces expression of the myokine Irisin. Here the authors show that Irisin promotes muscle hypertrophy and regeneration following injury or denervation in mice, by activating satellite cells and modulating protein synthesis and degradation.

Intensive care unit-acquired weakness (ICUAW) occurs in critically ill patients stemming from the critical illness itself, and results in sustained disability long after the ICU stay. Weakness can be attributed to muscle wasting, impaired contractility, neuropathy, and major pathways associated with muscle protein degradation such as the ubiquitin proteasome system and dysregulated autophagy. Furthermore, it is characterized by the preferential loss of myosin, a distinct feature of the condition. While many risk factors for ICUAW have been identified, effective interventions to offset these changes remain elusive. In addition, our understanding of the mechanisms underlying the long-term, sustained weakness observed in a subset of patients after discharge is minimal. Herein, we discuss the various proposed pathways involved in the pathophysiology of ICUAW, with a focus on the mechanisms underpinning skeletal muscle wasting and impaired contractility, and the animal models used to study them. Furthermore, we will explore the contributions of inflammation, steroid use, and paralysis to the development of ICUAW and how it pertains to those with the corona virus disease of 2019 (COVID-19). We then elaborate on interventions tested as a means to offset these decrements in muscle function that occur as a result of critical illness, and we propose new strategies to explore the molecular mechanisms of ICUAW, including serum-related biomarkers and 3D human skeletal muscle culture models.

Diaphragm weakness is highly prevalent in critically ill patients. It may exist prior to ICU admission and may precipitate the need for mechanical ventilation but it also frequently develops during the ICU stay. Several risk factors for diaphragm weakness have been identified; among them sepsis and mechanical ventilation play central roles. We employ the term critical illness-associated diaphragm weakness to refer to the collective effects of all mechanisms of diaphragm injury and weakness occurring in critically ill patients. Critical illness-associated diaphragm weakness is consistently associated with poor outcomes including increased ICU mortality, difficult weaning, and prolonged duration of mechanical ventilation. Bedside techniques for assessing the respiratory muscles promise to improve detection of diaphragm weakness and enable preventive or curative strategies. Inspiratory muscle training and pharmacological interventions may improve respiratory muscle function but data on clinical outcomes remain limited.

Skeletal muscle is a plastic organ that is maintained by multiple pathways regulating cell and protein turnover. During muscle atrophy, proteolytic systems are activated, and contractile proteins and organelles are removed, resulting in the shrinkage of muscle fibers. Excessive loss of muscle mass is associated with poor prognosis in several diseases, including myopathies and muscular dystrophies, as well as in systemic disorders such as cancer, diabetes, sepsis and heart failure. Muscle loss also occurs during aging. In this paper, we review the key mechanisms that regulate the turnover of contractile proteins and organelles in muscle tissue, and discuss how impairments in these mechanisms can contribute to muscle atrophy. We also discuss how protein synthesis and degradation are coordinately regulated by signaling pathways that are influenced by mechanical stress, physical activity, and the availability of nutrients and growth factors. Understanding how these pathways regulate muscle mass will provide new therapeutic targets for the prevention and treatment of muscle atrophy in metabolic and neuromuscular diseases.