The TWEAK–Fn14 system is a critical regulator of denervation-induced skeletal muscle atrophy in mice

The TNF-related cytokine TWEAK promotes skeletal muscle atrophy that is associated with classical disuse syndromes

Pharmacological characterization of a novel 5-hydroxybenzothiazolone-derived b2-adrenoceptor agonist with functional selectivity for anabolic effects on skeletal muscle resulting in a wider cardiovascular safety window in preclinical studies

Copyright ª 2019 by The Author(s) The anabolic effects of b2-adrenoceptor (b2-AR) agonists on skeletal muscle have been demonstrated in various species. However, the clinical use of b2-AR agonists for skeletal muscle wasting conditions has been limited by their undesired cardiovascular effects. Here, we describe the preclinical pharmacological profile of a novel 5-hydroxybenzothiazolone (5-HOB) derived b2-AR agonist in comparison with formoterol as a representative b2-AR agonist that have been well characterized. In vitro, 5-HOB has nanomolar affinity for the human b2-AR and selectivity over the b1-AR and b3-AR. 5-HOB also shows potent agonistic activity at the b2-AR in primary skeletal muscle myotubes and induces hypertrophy of skeletal muscle myotubes. Compared with formoterol, 5-HOB demonstrates comparable full-agonist activity on cAMP production in skeletal muscle cells and skeletal muscle tissue–derived membranes. In contrast, a greatly reduced intrinsic activity was determined in cardiomyocytes and cell membranes prepared from the rat heart. In addition, 5-HOB shows weak effects on chronotropy, inotropy, and vascular relaxation compared with formoterol. In vivo, 5-HOB significantly increases hind limb muscle weight in rats with attenuated effects on heart weight and ejection fraction, unlike formoterol. Furthermore, changes in cardiovascular parameters after bolus subcutaneous treatment in rats and rhesus monkeys are significantly lower with 5-HOB compared with formoterol. In conclusion, the pharmacological profile of 5-HOB indicates superior tissue selectivity compared with the conventional b2-AR agonist formoterol in preclinical studies and supports the notion that such tissue-selective agonists should be investigated for the safe treatment of muscle-wasting conditions without cardiovascular limiting effects

Genomic profiling reveals that transient adipogenic activation is a hallmark of mouse models of skeletal muscle regeneration.

The marbling of skeletal muscle by ectopic adipose tissue is a hallmark of many muscle diseases, including sarcopenia and muscular dystrophies, and generally associates with impaired muscle regeneration. Although the etiology and the molecular mechanisms of ectopic adipogenesis are poorly understood, fatty regeneration can be modeled in mice using glycerol-induced muscle damage. Using comprehensive molecular and histological profiling, we compared glycerol-induced fatty regeneration to the classical cardiotoxin (CTX)-induced regeneration model previously believed to lack an adipogenic response in muscle. Surprisingly, ectopic adipogenesis was detected in both models, but was stronger and more persistent in response to glycerol. Importantly, extensive differential transcriptomic profiling demonstrated that glycerol induces a stronger inflammatory response, and promotes adipogenic regulatory networks while reducing fatty acid β-oxidation. Altogether, these results provide a comprehensive repository of gene expression changes during the time course of two muscle regeneration models, and strongly suggest that adipogenic commitment is a hallmark of muscle regeneration, which can lead to ectopic adipocyte accumulation in response to specific physiopathological challenge

ActRII blockade protects mice from cancer cachexia and prolongs survival in the presence of anti-cancer treatments

Background Cachexia affects the majority of patients with advanced cancer and is associated with reduced treatment tolerance, response to therapy, quality of life and life expectancy. Cachectic patients with advanced cancer often receive anti-cancer therapies against their specific cancer type as a standard of care, and whether specific ActRII inhibition is efficacious when combined with anti-cancer agents has not been elucidated yet. Methods In this study, we evaluated interactions between ActRII blockade and anti-cancer agents in CT-26 mouse colon cancer-induced cachexia model. CDD866 (murinized version of bimagrumab) is a neutralizing antibody against the Activin receptor type II (ActRII) preventing binding of ligands such as myostatin and Activin A, which are involved in cancer cachexia. CDD866 was evaluated in association with cisplatin as a standard cytotoxic agent or with everolimus, a molecular-targeted agent against mammalian Target of Rapamycin (mTOR). In the early studies, the treatment effect on cachexia was investigated, and in the additional studies the treatment effect on progression of cancer and the associated cachexia was evaluated using body weight loss or tumor volume as interruption criteria. Results Cisplatin accelerated body weight loss and tended to exacerbate skeletal muscle loss in cachectic animals, likely due to some toxicity of this anti-cancer agent. Administration of CDD866 alone or in combination with cisplatin protected from skeletal muscle weight loss compared to animals receiving only cisplatin, corroborating that ActRII inhibition remains fully efficacious under cisplatin treatment. In contrast, everolimus treatment alone significantly protected the tumor-bearing mice against skeletal muscle weight loss caused by CT-26 tumor. CDD866 not only remains efficacious in the presence of everolimus but also showed a non-significant trend for an additive effect on reversing skeletal muscle weight loss. Importantly, both combination therapies slowed down time-to-progression. Conclusions Anti ActRII blockade is an effective intervention against cancer cachexia providing benefit even in the presence of anti-cancer therapies. Co-treatment comprising chemotherapies and ActRII inhibitors might constitute a promising new approach to alleviate chemotherapy- and cancer-related wasting conditions and extend survival rates in cachectic cancer patients

Genomic Profiling Reveals That Transient Adipogenic Activation Is a Hallmark of Mouse Models of Skeletal Muscle Regeneration

<div><p>The marbling of skeletal muscle by ectopic adipose tissue is a hallmark of many muscle diseases, including sarcopenia and muscular dystrophies, and generally associates with impaired muscle regeneration. Although the etiology and the molecular mechanisms of ectopic adipogenesis are poorly understood, fatty regeneration can be modeled in mice using glycerol-induced muscle damage. Using comprehensive molecular and histological profiling, we compared glycerol-induced fatty regeneration to the classical cardiotoxin (CTX)-induced regeneration model previously believed to lack an adipogenic response in muscle. Surprisingly, ectopic adipogenesis was detected in both models, but was stronger and more persistent in response to glycerol. Importantly, extensive differential transcriptomic profiling demonstrated that glycerol induces a stronger inflammatory response and promotes adipogenic regulatory networks while reducing fatty acid β-oxidation. Altogether, these results provide a comprehensive mapping of gene expression changes during the time course of two muscle regeneration models, and strongly suggest that adipogenic commitment is a hallmark of muscle regeneration, which can lead to ectopic adipocyte accumulation in response to specific physio-pathological challenges.</p></div

Treatment of Sarcopenia with Bimagrumab: Results from a Phase II, Randomized, Controlled, Proof-of-Concept Study

Objectives: To assess the effects of bimagrumab on skeletal muscle mass and function in older adults with sarcopenia and mobility limitations. Design: A 24-week, randomized, double-blind, placebo-controlled, parallel-arm, proof-of-concept study. Setting: Five centers in the United States. Participants: Community-dwelling adults (N = 40) aged 65 and older with gait speed between 0.4 and 1.0 m/s over 4 m and an appendicular skeletal muscle index of 7.25 kg/m2 or less for men and 5.67 kg/m2 or less for women. Intervention: Intravenous bimagrumab 30 mg/kg (n = 19) or placebo (n = 21). Measurements: Change from baseline in thigh muscle volume (TMV), subcutaneous and intermuscular fat, appendicular and total lean body mass, grip strength, gait speed, and 6-minute walk distance (6MWD). Results: Thirty-two (80%) participants completed the study. TMV increased by Week 2, was sustained throughout the treatment period, and remained above baseline at the end of study in bimagrumab-treated participants, whereas there was no change with placebo treatment (Week 2: 5.15 ± 2.19% vs −0.34 ± 2.59%, P <.001; Week 4: 6.12 ± 2.56% vs 0.16 ± 3.42%, P <.001; Week 8: 8.01 ± 3.70% vs 0.35 ± 3.32%, P <.001; Week 16: 7.72 ± 5.31% vs 0.42 ± 5.14%, P <.001; Week 24: 4.80 ± 5.81% vs −1.01 ± 4.43%, P =.002). Participants with slower walking speed at baseline receiving bimagrumab had clinically meaningful and statistically significantly greater improvements in gait speed (mean 0.15 m/s, P =.009) and 6MWD (mean 82 m, P =.022) than those receiving placebo at Week 16. Adverse events in the bimagrumab group included muscle-related symptoms, acne, and diarrhea, most of which were mild in severity and resolved by the end of study. Conclusion: Treatment with bimagrumab over 16 weeks increased muscle mass and strength in older adults with sarcopenia and improved mobility in those with slow walking speed

Ectopic adipogenesis occurs in both glycerol- and CTX-induced muscle regeneration.

<p>(A) qPCR analysis of the mRNA level of the platelet-derived growth factor receptor alpha (PDGFRα). (B) Cryosections were performed at the mid-belly part of TA and subjected to H&E and perilipin staining at each time points after injection. Representative perilipin (green) /DAPI (blue) fluorescent stainings at 21 dpi are shown next to an H&E staining of the same region. Scale bars, 50 μm. (C), Quantitative analysis of perilipin expression assessed by counting and measuring the area of all perilipin expressing cells per section. Data are expressed as mean ± s.e.m., n = 5–6/group. * p-value <0.05 <i>vs</i>. control, # p-value <0.05 in Glycerol <i>vs</i>. CTX at same time points.</p

Gene set enrichment mapping of glycerol- <i>vs.</i> CTX-injected muscle.

<p>Gene set enrichment analysis was performed on glycerol-injected compared to CTX-injected muscles 3 and 7 days after injection, and clustered according to gene set ontology. The size of nodes is proportional to the number of genes contained in the gene set. Red nodes: gene sets upregulated in glycerol <i>vs</i>. CTX model, blue nodes: gene sest downregulated in glycerol <i>vs</i>. CTX model, green bar: link between two gene sets sharing regulated genes.</p

Adipogenesis and β-oxidation are differentially regulated in muscle after glycerol or CTX injection.

<p>qPCR analysis of the mRNA levels of different adipogenic (A), or in fatty-acid oxidation (B) regulators. Data are expressed as mean ± s.e.m., n = 5–6/group. * p-value <0.05 <i>vs</i>. control, # p-value <0.05 in Glycerol <i>vs</i>. CTX at same time points. Acadm, acyl-CoA dehydrogenase medium; Acs/l, acyl-CoA synthesase short-/long-chain; Acss, Acetyl-coenzyme A synthetase; Acox, Acyl-coenzyme A oxidase, Palmitoyl; C/EBP: CCAAT/ Enhancer binding protein; Cpt, carnitine palmitoyltransferase; Hadh, hydroxyacyl-CoA dehydrogenase; PPAR, peroxisome proliferator activated receptor.</p

Glycerol and CTX induce similar kinetics of degeneration and regeneration.

<p>Control uninjured tibialis anterior muscle, and tibialis anterior muscles injected with either 25 µl of 50% (v/v) glycerol or 10 µM CTX were sectioned and stained with laminin and DAPI 3, 7, 14 or 21 days after injection (dpi) (A), or with hematoxylin-eosin at 21 dpi (B). Cryosections were performed at the mid-belly part of tibialis anterior. Scale bars, 100 μm. Yellow arrow: immune cell nuclei, white arrow: central nuclei, red circle: fat cell-like structure. (C) Quantitative analysis of total myofibers and of myofibers with at least one central nuclei from laminin/DAPI stained sections. (D) qPCR analysis of the mRNA levels of different markers of muscle regeneration. Data are expressed as mean ± s.e.m., n = 5–6/group. * p-value <0.05 <i>vs</i>. control. MYH, Myosin Heavy Chain.</p