Recovery of muscle mass and muscle oxidative phenotype following disuse does not require GSK-3 inactivation.

BACKGROUND: Physical inactivity contributes to muscle wasting and reductions in mitochondrial oxidative phenotype (OXPHEN), reducing physical performance and quality of life during aging and in chronic disease. Previously, it was shown that inactivation of glycogen synthase kinase (GSK)-3ß stimulates muscle protein accretion, myogenesis, and mitochondrial biogenesis. Additionally, GSK-3ß is inactivated during recovery of disuse-induced muscle atrophy. AIM: Therefore, we hypothesize that GSK-3 inhibition is required for reloading-induced recovery of skeletal muscle mass and OXPHEN. METHODS: Wild-type (WT) and whole-body constitutively active (C.A.) Ser21/9 GSK-3α/ß knock-in mice were subjected to a 14-day hind-limb suspension/14-day reloading protocol. Soleus muscle mass, fiber cross-sectional area (CSA), OXPHEN (abundance of sub-units of oxidative phosphorylation (OXPHOS) complexes and fiber-type composition), as well as expression levels of their main regulators (respectively protein synthesis/degradation, myogenesis and peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) signaling) were monitored. RESULTS: Subtle but consistent differences suggesting suppression of protein turnover signaling and decreased expression of several OXPHOS sub-units and PGC-1α signaling constituents were observed at baseline in C.A. GSK-3 versus WT mice. Although soleus mass recovery during reloading occurred more rapidly in C.A. GSK-3 mice, this was not accompanied by a parallel increased CSA. The OXPHEN response to reloading was not distinct between C.A. GSK-3 and WT mice. No consistent or significant differences in reloading-induced changes in the regulatory steps of protein turnover, myogenesis or muscle OXPHEN were observed in C.A. GSK-3 compared to WT muscle. CONCLUSION: This study indicates that GSK-3 inactivation is dispensable for reloading-induced recovery of muscle mass and OXPHEN.

Economic value and cost-effectiveness of biventricular versus right ventricular pacing: results from the BLOCK-HF study.

Aims: The Biventricular vs Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK-HF) demonstrated that biventricular (BiV) pacing resulted in better clinical and structural outcomes compared to right ventricular (RV) pacing in patients with atrioventricular (AV) block and reduced left ventricular ejection fraction (LVEF; ≤50%). This study investigated the cost-effectiveness of BiV vs RV pacing in the patient population enrolled in the BLOCK-HF trial. Methods: All-cause mortality, New York Heart Association (NYHA) Class distribution over time, and NYHA-specific heart failure (HF)-related healthcare utilization rates were predicted using statistical models based on BLOCK-HF patient data. A proportion-in-state model calculated cost-effectiveness from the Medicare payer perspective. Results: The predicted patient survival was 6.78 years with RV and 7.52 years with BiV pacing, a 10.9% increase over lifetime. BiV pacing resulted in 0.41 more quality-adjusted life years (QALYs) compared to RV pacing, at an additional cost of $12,537. The "base-case" incremental cost-effectiveness ratio (ICER) was $30,860/QALY gained. Within the clinical sub-groups, the highest observed ICER was $43,687 (NYHA Class I). Patients receiving combined BiV pacing and defibrillation (BiV-D) devices were projected to benefit more (0.84 years gained) than BiV pacemaker (BiV-P) recipients (0.49 years gained), compared to dual-chamber pacemakers. Conclusions: BiV pacing in AV block patients improves survival and attenuates HF progression compared to RV pacing. ICERs were consistently below the US acceptability threshold ($50,000/QALY). From a US Medicare perspective, the additional up-front cost associated with offering BiV pacing to the BLOCK-HF patient population appears justified.

Pacemaker complications and costs: a nationwide economic study.

Aims: Novel leadless pacemakers (LPMs) may reduce complications and associated costs related to conventional pacemaker systems. This study sought to estimate the incidence and associated costs of traditional pacemaker complications, in those patients who were eligible for LPM implantation. Methods: A retrospective analysis was conducted on the French National Hospital Database (PMSI), including all patients implanted with a pacemaker in France in 2012, who could have alternatively received an LPM. Complication rates and their associated costs 3 years post-implantation were estimated from the perspective of the French social security system. Results: From a total of 65,553 patients, 11,770 (18%) met the inclusion criteria. Overall, 618 patients (5.3%) had a record of pacemaker complications during follow-up, of which 89% were related to the lead and pocket. Most common were pocket bleeding, lead- or generator-related mechanical complications, and pneumothorax. Overall, the mean cost of pacemaker complications per patient was €6,674 ± 3,867 at 3 years. Specifically, €7,143 ± 2,685 for pocket bleeding, €5,123 ± 2,676 for pneumothorax, and €6,020 ± 3,272 for mechanical complications. Conclusions: Major complications associated with the lead and pocket of conventional pacemaker systems are still common, and these represent a significant burden to healthcare systems as they generate substantial costs.

Real-world geographic variations in the use of cardiac implantable electronic devices-The PANORAMA 2 observational cohort study.

BACKGROUND: Currently, several geographies around the world remain underrepresented in medical device trials. The PANORAMA 2 study was designed to assess contemporary region-specific differences in clinical practice patterns of patients with cardiac implantable electronic devices (CIEDs). METHODS: In this prospective, multicenter, observational, multinational study, baseline and implant data of 4,706 patients receiving Medtronic CIEDs (Medtronic plc, Minneapolis, MN, USA; either de novo device implants, replacements, or upgrades) were analyzed, consisting of: 54% implantable pulse generators (IPGs), 20.3% implantable cardiac defibrillators (ICDs), 15% cardiac resynchronization therapy -defibrillators, and 5.1% cardiac resynchronization therapy -pacemakers, from 117 hospitals in 23 countries across four geographical regions between 2012 and 2016. RESULTS: For all device types, in all regions, there were fewer females than males enrolled, and women were less likely to have ischemic cardiomyopathy. Implant procedure duration differed significantly across the geographies for all device types. Subjects from emerging countries, women, and older patients were less likely to receive a magnetic resonance imaging-compatible device. Defibrillation testing differed significantly between the regions. European patients had the highest rates of atrial fibrillation (AF), and the lowest number of implanted single-chamber IPGs. Evaluation of stroke history suggested that the general embolic risk is more strongly associated with stroke than AF. CONCLUSIONS: We provide comprehensive descriptive data on patients receiving Medtronic CIEDs from several geographies, some of which are understudied in randomized controlled trials. We found significant variations in patient characteristics. Several medical decisions appear to be affected by socioeconomic factors. Long-term follow-up data will help evaluate if these variations require adjustments to outcome expectations.

NF-κB-mediated metabolic remodelling in the inflamed heart in acute viral myocarditis.

Acute viral myocarditis (VM), characterised by leukocyte infiltration and dysfunction of the heart, is an important cause of sudden cardiac death in young adults. Unfortunately, to date, the pathological mechanisms underlying cardiac failure in VM remain incompletely understood. In the current study, we investigated if acute VM leads to cardiac metabolic rewiring and if this process is driven by local inflammation. Transcriptomic analysis of cardiac biopsies from myocarditis patients and a mouse model of VM revealed prominent reductions in the expression of a multitude of genes involved in mitochondrial oxidative energy metabolism. In mice, this coincided with reductions in high-energy phosphate and NAD levels, as determined by Imaging Mass Spectrometry, as well as marked decreases in the activity, protein abundance and mRNA levels of various enzymes and key regulators of cardiac oxidative metabolism. Indicative of fulminant cardiac inflammation, NF-κB signalling and inflammatory cytokine expression were potently induced in the heart during human and mouse VM. In cultured cardiomyocytes, cytokine-mediated NF-κB activation impaired cardiomyocyte oxidative gene expression, likely by interfering with the PGC-1 (peroxisome proliferator-activated receptor (PPAR)-γ co-activator) signalling network, the key regulatory pathway controlling cardiomyocyte oxidative metabolism. In conclusion, we provide evidence that acute VM is associated with extensive cardiac metabolic remodelling and our data support a mechanism whereby cytokines secreted primarily from infiltrating leukocytes activate NF-κB signalling in cardiomyocytes thereby inhibiting the transcriptional activity of the PGC-1 network and consequently modulating myocardial energy metabolism.

Infections and associated costs following cardiovascular implantable electronic device implantations: a nationwide cohort study.

Aims: This study assessed the contemporary occurrence of cardiac device infections (CDIs) following implantation in French hospitals and estimated associated costs. Methods and Results: A retrospective analysis was conducted on the French National Hospital Database (PMSI). Patients with a record of de novo cardiac implantable electronic device (CIED) implantation or replacement interventions in France in 2012 were identified and followed until the end of 2015. Cardiac device infections (CDIs) were identified based on coding using the French classification for procedures [Classification Commune des Actes Médicaux (CCAM)] and International Classification of Diseases (ICD-10). Associated costs were estimated based on direct costs from the perspective of the French social security system. In total 78 267 CIED patients (72% de novo implants) were identified (15% defibrillators; 84% pacemakers). The 36-month infection rate associated with de novo defibrillator-only implants, as well as for cardiac resynchronisation therapy - defibrillators (CRT-Ds) was 1.6%. The CDI risk was 2.9% and 3.9% for replacement ICDs and CRT-Ds. Infection rates were lower for de novo single-chamber pacemaker (SCP)/dual-chamber pacemaker (DCP) (0.5%) and cardiac resynchronisation therapy - pacemaker (CRT-P) implants (1.0%), while for replacement procedures the risk increased to 1.4% (SCP/DCP) and 1.3% (CRT-P). Mean infection-related costs over 24 months were €20 623 and €23 234 for CDIs associated with replacement and de novo procedures, and overall costs were not significantly different between pacemaker and defibrillator patients. Conclusion: Cardiac device infections in France are associated with substantial costs, when considering inpatient hospitalizations. Strategies to minimize the rate of CIED infection should be a priority for health care providers and payers.

Muscle-specific GSK-3ß ablation accelerates regeneration of disuse-atrophied skeletal muscle.

Muscle wasting impairs physical performance, increases mortality and reduces medical intervention efficacy in chronic diseases and cancer. Developing proficient intervention strategies requires improved understanding of the molecular mechanisms governing muscle mass wasting and recovery. Involvement of muscle protein- and myonuclear turnover during recovery from muscle atrophy has received limited attention. The insulin-like growth factor (IGF)-I signaling pathway has been implicated in muscle mass regulation. As glycogen synthase kinase 3 (GSK-3) is inhibited by IGF-I signaling, we hypothesized that muscle-specific GSK-3ß deletion facilitates the recovery of disuse-atrophied skeletal muscle. Wild-type mice and mice lacking muscle GSK-3ß (MGSK-3ß KO) were subjected to a hindlimb suspension model of reversible disuse-induced muscle atrophy and followed during recovery. Indices of muscle mass, protein synthesis and proteolysis, and post-natal myogenesis which contribute to myonuclear accretion, were monitored during the reloading of atrophied muscle. Early muscle mass recovery occurred more rapidly in MGSK-3ß KO muscle. Reloading-associated changes in muscle protein turnover were not affected by GSK-3ß ablation. However, coherent effects were observed in the extent and kinetics of satellite cell activation, proliferation and myogenic differentiation observed during reloading, suggestive of increased myonuclear accretion in regenerating skeletal muscle lacking GSK-3ß. This study demonstrates that muscle mass recovery and post-natal myogenesis from disuse-atrophy are accelerated in the absence of GSK-3ß.

Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy. METHODS: Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors. RESULTS: Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors. CONCLUSIONS: In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.

Regulation of skeletal muscle plasticity by glycogen synthase kinase-3ß: a potential target for the treatment of muscle wasting.

Muscle wasting is a prevalent and disabling condition in chronic disease and cancer and has been associated with increased mortality and impaired efficacy of surgical and medical interventions. Pharmacological therapies to combat muscle wasting are currently limited but considered as an important unmet medical need. Muscle wasting has been attributed to increased muscle proteolysis, and in particular ubiquitin 26S-proteasome system (UPS)-dependent protein breakdown. However, rates of muscle protein synthesis are also subject to extensive (patho) physiological regulation, and the balance between synthesis and degradation ultimately determines net muscle protein turnover. As multinucleated muscle fibers accommodate threshold changes in muscle protein content by the accretion and loss of muscle nuclei, myonuclear turnover may additionally determine muscle mass. Current insights in the mechanisms dictating muscle mass plasticity not only reveal intricate interactions and crosstalk between these processes, but imply the existence of signaling molecules that act as molecular switchboards, which coordinate and integrate cellular responses upon conditions that evoke changes in muscle mass. These "master regulators" of skeletal muscle mass plasticity are preferred targets for pharmacological modulation of skeletal muscle wasting. In this review Glycogen synthase kinase-3ß (GSK-3ß) is highlighted as a master regulator of muscle mass plasticity since, in addition to its role in UPS-mediated muscle protein degradation, it also controls protein synthesis, and influences myonuclear accretion and cell death. Moreover, the regulation of GSK-3ß activity as well as currently available pharmacological inhibitors are described and discussed in the context of multimodal treatment strategies aimed at the inhibition of GSK-3ß, and optimal exploitation of its potential role as a central regulator of skeletal muscle mass plasticity for the treatment of muscle wasting.

Glycogen synthase kinase-3ß is required for the induction of skeletal muscle atrophy.

Skeletal muscle atrophy commonly occurs in acute and chronic disease. The expression of the muscle-specific E3 ligases atrogin-1 (MAFbx) and muscle RING finger 1 (MuRF1) is induced by atrophy stimuli such as glucocorticoids or absence of IGF-I/insulin and subsequent Akt signaling. We investigated whether glycogen synthase kinase-3ß (GSK-3ß), a downstream molecule in IGF-I/Akt signaling, is required for basal and atrophy stimulus-induced expression of atrogin-1 and MuRF1, and myofibrillar protein loss in C(2)C(12) skeletal myotubes. Abrogation of basal IGF-I signaling, using LY294002, resulted in a prominent induction of atrogin-1 and MuRF1 mRNA and was accompanied by a loss of myosin heavy chain fast (MyHC-f) and myosin light chains 1 (MyLC-1) and -3 (MyLC-3). The synthetic glucocorticoid dexamethasone (Dex) also induced the expression of both atrogenes and likewise resulted in the loss of myosin protein abundance. Genetic ablation of GSK-3ß using small interfering RNA resulted in specific sparing of MyHC-f, MyLC-1, and MyLC-3 protein levels after Dex treatment or impaired IGF-I/Akt signaling. Interestingly, loss of endogenous GSK-3ß suppressed both basal and atrophy stimulus-induced atrogin-1 and MuRF1 expression, whereas pharmacological GSK-3ß inhibition, using CHIR99021 or LiCl, only reduced atrogin-1 mRNA levels in response to LY294002 or Dex. In conclusion, our data reveal that myotube atrophy and myofibrillar protein loss are GSK-3ß dependent, and demonstrate for the first time that basal and atrophy stimulus-induced atrogin-1 mRNA expression requires GSK-3ß enzymatic activity, whereas MuRF1 expression depends solely on the physical presence of GSK-3ß.