Multimodal Action of Mas Activation for Systemic Cancer Cachexia Therapy

Cancer cachexia remains a largely intractable, deadly condition for patients with no approved, effective therapies. However, research progress over the past few decades demonstrates that cachexia is a disease with specific, targetable mechanisms. New work by Murphy and colleagues in this issue of Cancer Research suggests that activation of the alternative renin–angiotensin system with the nonpeptide Mas receptor agonist AVE 0991 holds promise for reducing muscle wasting in cancer. Their cell studies demonstrate on-target activity in skeletal muscle cells, whereas their mouse results suggest potentially more important systemic effects

Structure and Mechanics of Mammalian Prehensile Tail Vertebrae

abstractPrehensile tails (PTs) – capable of suspending the body weight of the animal – evolved independently as many as 14 times among 40 extant mammalian genera. The structure of the mammalian PT is well studied in New World monkeys, where it evolved twice: once in the atelines (Ateles, Lagothrix, Brachyteles, and Lagothrix) and once in the genus Cebus. Recently, we have expanded our studies to nonprimate taxa such as carnivoran procyonids (raccoons and relatives) and didelphid marsupials (opossums and relatives). Adult PTs share musculoskeletal features that distinguish them from nonprehensile tails, which are thought to be adaptive to the mechanical demands of suspension and/or prehension incurred with locomotion, posture, and manipulation: 1) craniocaudally expanded sacroiliac joint and more proximal region vertebrae, which increase joint and tail stability; 2) more expansive transverse and hemal processes (proximal and distal attachments for primary tail flexors, respectively); and 3) tail vertebrae that are estimated to be structurally stronger and more rigid. Yet, our understanding of the broader adaptive significance of the PT has been hampered by two major deficits. First, structural data are largely limited to cortical and trabecular geometric assessments, which only provide estimates of mechanical properties and therefore limit the mechanical conclusions we can draw. Second, our studies have concentrated solely on the features of the adults, even while we know anecdotally that tail-use behavior changes ontogenetically, and it would be expected that these changes would be reflected in the mechanical properties of the tail vertebrae. The present study demonstrates that cortical geometric assessments correlate with structural mechanical properties of tail vertebrae in an ontogenetic series of squirrel monkeys, and both sets of data reveal a trend of increasing structural strength of the vertebrae with increasing body size (i.e, age)

The Colon-26 Carcinoma Tumor-bearing Mouse as a Model for the Study of Cancer Cachexia

Cancer cachexia is the progressive loss of skeletal muscle mass and adipose tissue, negative nitrogen balance, anorexia, fatigue, inflammation, and activation of lipolysis and proteolysis systems. Cancer patients with cachexia benefit less from anti-neoplastic therapies and show increased mortality1. Several animal models have been established in order to investigate the molecular causes responsible for body and muscle wasting as a result of tumor growth. Here, we describe methodologies pertaining to a well-characterized model of cancer cachexia: mice bearing the C26 carcinoma2-4. Although this model is heavily used in cachexia research, different approaches make reproducibility a potential issue. The growth of the C26 tumor causes a marked and progressive loss of body and skeletal muscle mass, accompanied by reduced muscle cross-sectional area and muscle strength3-5. Adipose tissue is also lost. Wasting is coincident with elevated circulating levels of pro-inflammatory cytokines, particularly Interleukin-6 (IL-6)3, which is directly, although not entirely, responsible for C26 cachexia. It is well-accepted that a primary mechanism by which the C26 tumor induces muscle tissue depletion is the activation of skeletal muscle proteolytic systems. Thus, expression of muscle-specific ubiquitin ligases, such as atrogin-1/MAFbx and MuRF-1, represent an accepted method for the evaluation of the ongoing muscle catabolism2. Here, we present how to execute this model in a reproducible manner and how to excise several tissues and organs (the liver, spleen, and heart), as well as fat and skeletal muscles (the gastrocnemius, tibialis anterior, and quadriceps). We also provide useful protocols that describe how to perform muscle freezing, sectioning, and fiber size quantification

In Vitro, In Vivo, and In Silico Methods for Assessment of Muscle Size and Muscle Growth Regulation

Trauma, burn injury, sepsis, and ischemia lead to acute and chronic loss of skeletal muscle mass and function. Healthy muscle is essential for eating, posture, respiration, reproduction, and mobility, as well as for appropriate function of the senses including taste, vision, and hearing. Beyond providing support and contraction, skeletal muscle also exerts essential roles in temperature regulation, metabolism, and overall health. As the primary reservoir for amino acids, skeletal muscle regulates whole-body protein and glucose metabolism by providing substrate for protein synthesis and supporting hepatic gluconeogenesis during illness and starvation. Overall, greater muscle mass is linked to greater insulin sensitivity and glucose disposal, strength, power, and longevity. In contrast, low muscle mass correlates with dysmetabolism, dysmobility, and poor survival. Muscle mass is highly plastic, appropriate to its role as reservoir, and subject to striking genetic control. Defining mechanisms of muscle growth regulation holds significant promise to find interventions that promote health and diminish morbidity and mortality after trauma, sepsis, inflammation, and other systemic insults. In this invited review, we summarize techniques and methods to assess and manipulate muscle size and muscle mass in experimental systems, including cell culture and rodent models. These approaches have utility for studies of myopenia, sarcopenia, cachexia, and acute muscle growth or atrophy in the setting of health or injury

Mouse Hind Limb Skeletal Muscle Functional Adaptation in a Simulated Fine Branch Arboreal Habitat

The musculoskeletal system is remarkably plastic during growth. The purpose of this study was to examine the muscular plasticity in functional and structural properties in a model known to result in significant developmental plasticity of the postcranial skeleton. Fifteen weanling C57BL/6 mice were raised to 16 weeks of age in one of two enclosures: a climbing enclosure that simulates a fine branch arboreal habitat and is traversed by steel wires crossing at 45° relative to horizontal at multiple intersections, and a control enclosure that resembles a parking deck with no wires but the same volume of habitable space. At killing, ex vivo contractility properties of the soleus (SOL) and extensor digitorum longus (EDL) muscles were examined. Our results demonstrate that EDL muscles of climbing mice contracted with higher specific forces and were comprised of muscle fibers with slower myosin heavy chain isoforms. EDL muscles also fatigued at a higher rate in climbing mice compared to controls. SOL muscle function is not affected by the climbing environment. Likewise, mass and architecture of both EDL and SOL muscles were not different between climbing and control mice. Our data demonstrate that functional adaptation does not require concomitant architectural adaptation in order to increase contractile force

Evidence for similarity in symptoms and mechanism: The extra‐pulmonary symptoms of severe asthma and the polysymptomatic presentation of fibromyalgia

Background Asthma is a disease of the lung and a systemic disease. Functional disorders are associated with multiple systemic abnormalities that have been explained by complexity models. The aim was to test the similarity in type and aetiology between the extra‐pulmonary symptoms of severe asthma and the symptoms of fibromyalgia. Methods One Hundred patients recruited from a specialist severe asthma clinic and 1751 people reporting different functional disorder diagnoses recruited via the internet completed the same 60‐item questionnaire. Symptom patterns were compared between groups using a new measure, the symptom pattern similarity index where 0 = no relationship, 1 = identical patterns between groups. Results Severe asthma patients report numerous extra‐pulmonary symptoms. The similarity index between the symptom pattern of the asthma patients with other groups was irritable bowel syndrome = 0.54, chronic fatigue syndrome = 0.69, and fibromyalgia = 0.75. The index between fibromyalgia and asthma patients with the most and least frequent extra‐pulmonary symptoms was 0.81 and 0.55 respectively. Conclusions Patients with severe asthma have numerous extra‐pulmonary symptoms similar in type and pattern to the symptoms of fibromyalgia. The similarity of the symptom pattern between asthma and fibromyalgia increases as the number of extra‐pulmonary symptoms increases as predicted by network theory and previously shown to be the case with other functional disorders. These findings support the hypothesis that functional disorders and extra‐pulmonary asthma symptoms have a common complexity or network aetiology. Evidence based behavioural interventions for fibromyalgia may be helpful for patients with severe asthma reporting extra‐pulmonary symptoms

Mechanical Effects of Fine-Wire Climbing on the Hindlimb Skeleton of Mice

poster abstractHigh-impact exercise (running/jumping) can stimulate multiple anabolic responses (increased trabecular bone volume, BV/TV) in the skeleton, but is also linked to an increased incidence of skeletal fracture. Thus, it is not an appropriate treatment for patients with elevated fracture risks. However, multi-directional offaxis mechanical loading can also elicit anabolic responses, even when magnitudes are relatively low. This represents a potential alternative to high-impact exercise for improving skeletal mechanical properties. To test this hypothesis, we raised twelve weanling female C57BL/6 mice to 4 months of age in custom enclosures that prevent (control) or require (experimental) manual and pedal grasping while balancing and climbing above narrow wire substrates. At sacrifice, we measured whole mouse bone density (DEXA) and performed architectural (μCT) and mechanical (4-pt bending) analyses of the femur and tibia. Body mass was similar between groups, although exercised mice were leaner (-35% fat mass). Bone mineral density was also similar, while bone mineral content was increased (+7%) in the exercised mice. Femoral midshaft polar moment of inertia was similar between groups, but exercised mice had lower BV/TV (-46%) of the distal femur and greater trabecular spacing (+21%). Exercised femora showed more total displacement (+58%) and post yield displacement (+115%) in bending than controls, and increased material toughness (+40%). Patterns were similar for the tibia. Mechanical data are consistent with high-impact exercise studies, but architectural data are not. Together they suggest that our exercise model may improve bone mechanical properties by redistributing mineral within the skeleton, and not by increasing net bone formation

Exogenous GDF11 Induces Cardiac and Skeletal Muscle Dysfunction and Wasting

Growth differentiation factor 11 (GDF11), a TGF-beta superfamily member, is highly homologous to myostatin and essential for embryonic patterning and organogenesis. Reports of GDF11 effects on adult tissues are conflicting, with some describing anti-aging and pro-regenerative activities on the heart and skeletal muscle while others opposite or no effects. Herein, we sought to determine the in vivo cardiac and skeletal muscle effects of excess GDF11. Mice were injected with GDF11 secreting cells, an identical model to that used to initially identify the in vivo effects of myostatin. GDF11 exposure in mice induced whole body wasting and profound loss of function in cardiac and skeletal muscle over a 14-day period. Loss of cardiac mass preceded skeletal muscle loss. Cardiac histologic and echocardiographic evaluation demonstrated loss of ventricular muscle wall thickness, decreased cardiomyocyte size, and decreased cardiac function 10 days following initiation of GDF11 exposure. Changes in skeletal muscle after GDF11 exposure were manifest at day 13 and were associated with wasting, decreased fiber size, and reduced strength. Changes in cardiomyocytes and skeletal muscle fibers were associated with activation of SMAD2, the ubiquitin–proteasome pathway and autophagy. Thus, GDF11 over administration in vivo results in cardiac and skeletal muscle loss, dysfunction, and death. Here, serum levels of GDF11 by Western blotting were 1.5-fold increased over controls. Although GDF11 effects in vivo are likely dose, route, and duration dependent, its physiologic changes are similar to myostatin and other Activin receptors ligands. These data support that GDF11, like its other closely related TGF-beta family members, induces loss of cardiac and skeletal muscle mass and function

Forelimb muscle architecture and myosin isoform composition in the groundhog (Marmota monax)

Scratch-digging mammals are commonly described as having large, powerful forelimb muscles for applying high force to excavate earth, yet studies quantifying the architectural properties of the musculature are largely unavailable. To further test hypotheses about traits that represent specializations for scratch-digging, we quantified muscle architectural properties and myosin expression in the forelimb of the groundhog (Marmota monax), a digger that constructs semi-complex burrows. Architectural properties measured were muscle moment arm, muscle mass (MM), belly length (ML), fascicle length (lF), pennation angle and physiological cross-sectional area (PCSA), and these metrics were used to estimate maximum isometric force, joint torque and power. Myosin heavy chain (MHC) isoform composition was determined in selected forelimb muscles by SDS-PAGE and densitometry analysis. Groundhogs have large limb retractors and elbow extensors that are capable of applying moderately high torque at the shoulder and elbow joints, respectively. Most of these muscles (e.g. latissimus dorsi and pectoralis superficialis) have high lF/ML ratios, indicating substantial shortening ability and moderate power. The unipennate triceps brachii long head has the largest PCSA and is capable of the highest joint torque at both the shoulder and elbow joints. The carpal and digital flexors show greater pennation and shorter fascicle lengths than the limb retractors and elbow extensors, resulting in higher PCSA/MM ratios and force production capacity. Moreover, the digital flexors have the capacity for both appreciable fascicle shortening and force production, indicating high muscle work potential. Overall, the forelimb musculature of the groundhog is capable of relatively low sustained force and power, and these properties are consistent with the findings of a predominant expression of the MHC-2A isoform. Aside from the apparent modifications to the digital flexors, the collective muscle properties observed are consistent with its behavioral classification as a less-specialized burrower and these may be more representative of traits common to numerous rodents with burrowing habits or mammals with some fossorial ability