Tobias Wollersheim

Critical illness myopathy and GLUT4 - significance of insulin and muscle contraction

RATIONALE Critical illness myopathy (CIM) has no known cause and no treatment. Immobilization and impaired glucose metabolism are implicated. OBJECTIVES We assessed signal transduction in skeletal muscle of patients at risk for CIM. We also investigated the effects of evoked muscle contraction. METHODS In a prospective observational and interventional pilot study, we screened 874 mechanically ventilated patients with a sepsis-related organ-failure assessment score greater than or equal to 8 for 3 consecutive days in the first 5 days of intensive care unit stay. Thirty patients at risk for CIM underwent euglycemic-hyperinsulinemic clamp, muscle microdialysis studies, and muscle biopsies. Control subjects were healthy. In five additional patients at risk for CIM, we performed corresponding analyses after 12-day, daily, unilateral electrical muscle stimulation with the contralateral leg as control. MEASUREMENTS AND MAIN RESULTS We performed successive muscle biopsies and assessed systemic insulin sensitivity and signal transduction pathways of glucose utilization at the mRNA and protein level and glucose transporter-4 (GLUT4) localization in skeletal muscle tissue. Skeletal muscle GLUT4 was trapped at perinuclear spaces, most pronounced in patients with CIM, but resided at the sarcolemma in control subjects. Glucose metabolism was not stimulated during euglycemic-hyperinsulinergic clamp. Insulin signal transduction was competent up to p-Akt activation; however, p-adenosine monophosphate-activated protein kinase (p-AMPK) was not detectable in CIM muscle. Electrical muscle stimulation increased p-AMPK, repositioned GLUT4, locally improved glucose metabolism, and prevented type-2 fiber atrophy. CONCLUSIONS Insufficient GLUT4 translocation results in decreased glucose supply in patients with CIM. Failed AMPK activation is involved. Evoked muscle contraction may prevent muscle-specific AMPK failure, restore GLUT4 disposition, and diminish protein breakdown. Clinical trial registered with http://www.controlled-trials.com (registration number ISRCTN77569430).

Long-term recovery In critical illness myopathy is complete, contrary to polyneuropathy.

Introduction: Muscle weakness in critically ill patients after discharge varies. It is not known whether the electrophysiological distinction between critical illness myopathy (CIM) and critical illness polyneuropathy (CIP) during the early part of a patients stay in the intensive care unit (ICU) predicts long‐term prognosis. Methods: This was a prospective cohort study of mechanically ventilated ICU patients undergoing conventional nerve conduction studies and direct muscle stimulation in addition to neurological examination during their ICU stay and 1 year after ICU discharge. Results: Twenty‐six patients (7 ICU controls, 8 CIM patients, and 11 CIM/CIP patients) were evaluated 1 year after discharge from the ICU. Eighty‐eight percent (n = 7) of CIM patients recovered within 1 year compared with 55% (n = 6) of CIM/CIP patients. Thirty‐six percent (n = 4) of CIM/CIP patients still needed assistance during their daily routine (P = 0.005). Conclusions: Early electrophysiological testing predicts long‐term outcome in ICU survivors. CIM has a significantly better prognosis than CIM/CIP. Muscle Nerve 50: 431–436, 2014

Inflammation-Induced Acute Phase Response in Skeletal Muscle and Critical Illness Myopathy

Objectives Systemic inflammation is a major risk factor for critical-illness myopathy (CIM) but its pathogenic role in muscle is uncertain. We observed that interleukin 6 (IL-6) and serum amyloid A1 (SAA1) expression was upregulated in muscle of critically ill patients. To test the relevance of these responses we assessed inflammation and acute-phase response at early and late time points in muscle of patients at risk for CIM. Design Prospective observational clinical study and prospective animal trial. Setting Two intensive care units (ICU) and research laboratory. Patients/Subjects 33 patients with Sequential Organ Failure Assessment scores ≥8 on 3 consecutive days within 5 days in ICU were investigated. A subgroup analysis of 12 patients with, and 18 patients without CIM (non-CIM) was performed. Two consecutive biopsies from vastus lateralis were obtained at median days 5 and 15, early and late time points. Controls were 5 healthy subjects undergoing elective orthopedic surgery. A septic mouse model and cultured myoblasts were used for mechanistic analyses. Measurements and Main Results Early SAA1 expression was significantly higher in skeletal muscle of CIM compared to non-CIM patients. Immunohistochemistry showed SAA1 accumulations in muscle of CIM patients at the early time point, which resolved later. SAA1 expression was induced by IL-6 and tumor necrosis factor-alpha in human and mouse myocytes in vitro. Inflammation-induced muscular SAA1 accumulation was reproduced in a sepsis mouse model. Conclusions Skeletal muscle contributes to general inflammation and acute-phase response in CIM patients. Muscular SAA1 could be important for CIM pathogenesis. Trial Registration ISRCTN77569430.

The E3 ubiquitin ligase TRIM62 and inflammation-induced skeletal muscle atrophy

IntroductionICU-acquired weakness (ICUAW) complicates the disease course of critically ill patients. Inflammation and acute-phase response occur directly within myocytes and contribute to ICUAW. We observed that tripartite motif-containing 62 (TRIM62), an E3 ubiquitin ligase and modifier of inflammation, is increased in the skeletal muscle of ICUAW patients. We investigated the regulation and function of muscular TRIM62 in critical illness.MethodsTwenty-six critically ill patients with Sequential Organ Failure Assessment scores ≥8 underwent two skeletal muscle biopsies from the vastus lateralis at median days 5 and 15 in the ICU. Four patients undergoing elective orthopedic surgery served as controls. TRIM62 expression and protein content were analyzed in these biopsies. The kinetics of Trim62, Atrogin1 and MuRF1 expression were determined in the gastrocnemius/plantaris and tibialis anterior muscles from mouse models of inflammation-, denervation- and starvation-induced muscle atrophy to differentiate between these contributors to ICUAW. Cultured myocytes were used for mechanistic analyses.ResultsTRIM62 expression and protein content were increased early and remained elevated in muscles from critically ill patients. In all three animal models, muscular Trim62 expression was early and continuously increased. Trim62 was expressed in myocytes, and its overexpression activated the atrophy-inducing activator protein 1 signal transduction pathway. Knockdown of Trim62 by small interfering RNA inhibited lipopolysaccharide-induced interleukin 6 expression.ConclusionsTRIM62 is activated in the muscles of critically ill patients. It could play a role in the pathogenesis of ICUAW by activating and maintaining inflammation in myocytes.Trial registrationCurrent Controlled Trials ID: http://www.controlled-trials.com/ISRCTN77569430 (registered 13 February 2008)

CARbon DIoxide for the treatment of Febrile seizures: rationale, feasibility, and design of the CARDIF-study

Background2-8% of all children aged between 6 months and 5 years have febrile seizures. Often these seizures cease spontaneously, however depending on different national guidelines, 20-40% of the patients would need therapeutic intervention. For seizures longer than 3-5 minutes application of rectal diazepam, buccal midazolam or sublingual lorazepam is recommended. Benzodiazepines may be ineffective in some patients or cause prolonged sedation and fatigue. Preclinical investigations in a rat model provided evidence that febrile seizures may be triggered by respiratory alkalosis, which was subsequently confirmed by a retrospective clinical observation. Further, individual therapeutic interventions demonstrated that a pCO2-elevation via re-breathing or inhalation of 5% CO2 instantly stopped the febrile seizures. Here, we present the protocol for an interventional clinical trial to test the hypothesis that the application of 5% CO2 is effective and safe to suppress febrile seizures in children.MethodsThe CARDIF (CAR bon DI oxide against F ebrile seizures) trial is a monocentric, prospective, double-blind, placebo-controlled, randomized study. A total of 288 patients with a life history of at least one febrile seizure will be randomized to receive either carbogen (5% CO2 plus 95% O2) or placebo (100% O2). As recurrences of febrile seizures mainly occur at home, the study medication will be administered by the parents through a low-pressure can fitted with a respiratory mask. The primary outcome measure is the efficacy of carbogen to interrupt febrile seizures. As secondary outcome parameters we assess safety, practicability to use the can, quality of life, contentedness, anxiousness and mobility of the parents.ProspectThe CARDIF trial has the potential to develop a new therapy for the suppression of febrile seizures by redressing the normal physiological state. This would offer an alternative to the currently suggested treatment with benzodiazepines. This study is an example of academic translational research from the study of animal physiology to a new therapy.Trial registrationClinicalTrials.gov identifier: NCT01370044

Secreted Frizzled-Related Protein 2 and Inflammation-Induced Skeletal Muscle Atrophy.

Objective: In sepsis, the disease course of critically ill patients is often complicated by muscle failure leading to ICU-acquired weakness. The myokine transforming growth factor-&bgr;1 increases during inflammation and mediates muscle atrophy in vivo. We observed that the transforming growth factor-&bgr;1 inhibitor, secreted frizzled-related protein 2, was down-regulated in skeletal muscle of ICU-acquired weakness patients. We hypothesized that secreted frizzled-related protein 2 reduction enhances transforming growth factor-&bgr;1-mediated effects and investigated the interrelationship between transforming growth factor-&bgr;1 and secreted frizzled-related protein 2 in inflammation-induced atrophy. Design: Observational study and prospective animal trial. Setting: Two ICUs and research laboratory. Patients/Subjects: Twenty-six critically ill patients with Sequential Organ Failure Assessment scores greater than or equal to 8 underwent a skeletal muscle biopsy from the vastus lateralis at median day 5 in ICU. Four patients undergoing elective orthopedic surgery served as controls. To search for signaling pathways enriched in muscle of ICU-acquired weakness patients, a gene set enrichment analysis of our recently published gene expression profiles was performed. Quantitative reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemistry were used to analyze secreted frizzled-related protein 2 expression and protein content. A mouse model of inflammation-induced skeletal muscle atrophy due to polymicrobial sepsis and cultured myocytes were used for mechanistic analyses. Interventions: None. Measurements and Main Results: Gene set enrichment analysis uncovered transforming growth factor-&bgr;1 signaling activation in vastus lateralis from ICU-acquired weakness patients. Muscular secreted frizzled-related protein 2 expression was reduced after 5 days in ICU. Likewise, muscular secreted frizzled-related protein 2 expression was decreased early and continuously in mice with inflammation-induced atrophy. In muscle, secreted frizzled-related protein 2 was predominantly contained in fast twitch/type II myofibers. Secreted frizzled-related protein 2 physically interacted and colocalized with transforming growth factor-&bgr;1 through its cysteine-rich domain. Finally, secreted frizzled-related protein 2 prevented transforming growth factor-&bgr;1-induced atrophy in C2C12 myotubes. Conclusions: Muscular secreted frizzled-related protein 2 is down-regulated in ICU-acquired weakness patients and mice with inflammation-induced muscle atrophy. Decreased secreted frizzled-related protein 2 possibly establishes a positive feedback loop enhancing transforming growth factor-&bgr;1-mediated atrophic effects in inflammation-induced atrophy.

Relation of Resting Membrane Polarization and Insulin Resistance in Critically Ill Patients

Critically ill patients feature depolarization of the resting membrane potential and reduced membrane excitability in motor nerve and muscle [1, 2], which is correlated to ICU-acquired weakness and an increased insulin resistance [3].

Accuracy of a subcutaneous continuous glucose management system in critically ill patients

Continuous glucose management (CGM) has not yet been implemented to daily routine in the intensive care unit (ICU) setting. CGM systems aim to improve glycemic control, and consequently patient outcome.

Reply: To PMID 24415656.

than patients with either critical illness polyneuropathy (CIP) or CIM/CIP. The authors diagnosed CIM if the amplitude of compound muscle action potentials after direct muscle stimulation (dmCMAPs) or the duration of motor unit action potentials on electromyographic (EMG) examination were reduced. The sole indicator for CIP was reduced sensory nerve action potential (SNAP) amplitudes. dmCMAP amplitudes are reduced in both myopathy and motor neuropathy. On the other hand, quantitative needle EMG can only be done in conscious patients who are able to cooperate. Therefore, CIM will be overdiagnosed in all sedated patients, in whom quantitative EMG is unavailable. Similarly, motor neuropathy will be underdiagnosed if reduced SNAP amplitudes are the sole criterion for CIP. As a result, it seems likely that several patients were misclassified as CIM-only in the study by Koch et al. Based on these considerations and our own observations we disagree with their conclusion that CIM patients enjoy complete recovery, and we offer an alternative explanation for the findings. We previously studied the pattern of electrophysiological abnormalities prospectively in 30 patients with sepsis/systemic inflammatory response syndrome. Motor (median and ulnar unilaterally, and common fibular and tibial bilaterally) and sensory (median and ulnar unilaterally, and sural bilaterally) nerve conduction studies were performed weekly from admission until discharge, and after 6 months. Differences from reference values of compound muscle action potentials (CMAPs), SNAPs, and motor and sensory nerve conduction velocities (NCVs) were subject to cluster analysis. We were able to delineate 4 different topographical patterns of neuromuscular injury (Table 1), which reflect different levels of severity and were associated with clinical outcome. Although cluster 1 contained patients and controls with normal electrophysiological values, cluster 2 included only patients with abnormal CMAPs in the lower extremities. Cluster 3 contained patients with moderately abnormal CMAPs, SNAPs, and sensory NCVs in the extremities and motor NCVs in the lower extremities. Finally, cluster 4 was comprised of patients with severely abnormal CMAPs, SNAPs, and NCVs in all extremities. Thus, decreased CMAP amplitude was the most benign abnormality, whereas SNAP and sensory NCV were affected only in more severe patterns. Importantly, because the abnormalities in cluster 2 were restricted to the lower extremities, a lengthdependent pathophysiology was suggested, implicating the (co-)presence of CIP. Therefore, although the electrophysiological signature of cluster 2 was broadly similar to that of patients classified as CIM by Koch et al., a more parsimonious explanation is less severe neuromuscular injury, rather than an exclusive myopathic pathology. From these observations we conclude that, if electrophysiological investigation is employed for prognostication in critically ill patients, it may be more favorable to assess the load of neuromuscular injury rather than attempt to differentiate CIM from CIP.

Critically Ill Patients With Icu-Acquired Weakness Show Reduced Density of Myosin in Electron Microscope Early After Onset of Critical Illness

Recently we showed increased expression of atrophy genes MuRF-1 and Atrogin-1 during early course of critical illness resulting in MyHC loss and finally the clinical presentation of ICU-acquired weakness. Appropriate studies of systematic electron microscope investigations from this early time in critical illness do not exist yet.