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      Understanding sex differences in the regulation of cancer-induced muscle wasting

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          Abstract

          <div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d141086e103">Purpose:</h5> <p id="P1">We highlight evidence for sexual dimorphism in preclinical and clinical studies investigating the etiology and treatment of cancer cachexia. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d141086e108">Recent Findings:</h5> <p id="P2">Cancer cachexia is unintended bodyweight loss occurring with cancer, and skeletal muscle wasting is a critical predictor of negative outcomes in the cancer patient. Skeletal muscle exhibits sexual dimorphism in fiber type, function, and regeneration capacity. Sex differences have been implicated in skeletal muscle metabolism, mitochondrial function, immune response to injury, and myogenic stem cell regulation. All of these processes have the potential to be involved in cancer-induced muscle wasting. Unfortunately, the vast majority of published studies examining cancer cachexia in preclinical models or cancer patients either have not accounted for sex in their design or have exclusively studied males. Preclinical studies have established that ovarian function and estradiol can affect skeletal muscle function, metabolism and mass; ovarian function has also been implicated in the sensitivity of circulating inflammatory cytokines and the progression of cachexia. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d141086e113">Summary:</h5> <p id="P3">Females and males have unique characteristics that effect skeletal muscle’s microenvironment and intrinsic signaling. These differences provide a strong rationale for distinct etiologies for cancer cachexia development and treatment in males and females. </p> </div>

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          Most cited references115

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          Definition and classification of cancer cachexia: an international consensus.

          To develop a framework for the definition and classification of cancer cachexia a panel of experts participated in a formal consensus process, including focus groups and two Delphi rounds. Cancer cachexia was defined as a multifactorial syndrome defined by an ongoing loss of skeletal muscle mass (with or without loss of fat mass) that cannot be fully reversed by conventional nutritional support and leads to progressive functional impairment. Its pathophysiology is characterised by a negative protein and energy balance driven by a variable combination of reduced food intake and abnormal metabolism. The agreed diagnostic criterion for cachexia was weight loss greater than 5%, or weight loss greater than 2% in individuals already showing depletion according to current bodyweight and height (body-mass index [BMI] <20 kg/m(2)) or skeletal muscle mass (sarcopenia). An agreement was made that the cachexia syndrome can develop progressively through various stages--precachexia to cachexia to refractory cachexia. Severity can be classified according to degree of depletion of energy stores and body protein (BMI) in combination with degree of ongoing weight loss. Assessment for classification and clinical management should include the following domains: anorexia or reduced food intake, catabolic drive, muscle mass and strength, functional and psychosocial impairment. Consensus exists on a framework for the definition and classification of cancer cachexia. After validation, this should aid clinical trial design, development of practice guidelines, and, eventually, routine clinical management. Copyright © 2011 Elsevier Ltd. All rights reserved.
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            Mitophagy and Quality Control Mechanisms in Mitochondrial Maintenance.

            The maintenance of a healthy and functional mitochondrial network is critical during development as well as throughout life in the response to physiological adaptations and stress conditions. Owing to their role in energy production, mitochondria are exposed to high levels of reactive oxygen species, making them particularly vulnerable to mitochondrial DNA mutations and protein misfolding. Given that mitochondria are formed from proteins encoded by both nuclear and mitochondrial genomes, an additional layer of complexity is inherent in the coordination of protein synthesis and the mitochondrial import of nuclear-encoded proteins. For these reasons, mitochondria have evolved multiple systems of quality control to ensure that the requisite number of functional mitochondria are present to meet the demands of the cell. These pathways work to eliminate damaged mitochondrial proteins or parts of the mitochondrial network by mitophagy and renew components by adding protein and lipids through biogenesis, collectively resulting in mitochondrial turnover. Mitochondrial quality control mechanisms are multi-tiered, operating at the protein, organelle and cell levels. Herein, we discuss mitophagy in different physiological contexts and then relate it to other quality control pathways, including the unfolded protein response, shedding of vesicles, proteolysis, and degradation by the ubiquitin-proteasome system. Understanding how these pathways contribute to the maintenance of mitochondrial homeostasis could provide insights into the development of targeted treatments when these systems fail in disease.
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              Fiber types in mammalian skeletal muscles.

              Mammalian skeletal muscle comprises different fiber types, whose identity is first established during embryonic development by intrinsic myogenic control mechanisms and is later modulated by neural and hormonal factors. The relative proportion of the different fiber types varies strikingly between species, and in humans shows significant variability between individuals. Myosin heavy chain isoforms, whose complete inventory and expression pattern are now available, provide a useful marker for fiber types, both for the four major forms present in trunk and limb muscles and the minor forms present in head and neck muscles. However, muscle fiber diversity involves all functional muscle cell compartments, including membrane excitation, excitation-contraction coupling, contractile machinery, cytoskeleton scaffold, and energy supply systems. Variations within each compartment are limited by the need of matching fiber type properties between different compartments. Nerve activity is a major control mechanism of the fiber type profile, and multiple signaling pathways are implicated in activity-dependent changes of muscle fibers. The characterization of these pathways is raising increasing interest in clinical medicine, given the potentially beneficial effects of muscle fiber type switching in the prevention and treatment of metabolic diseases.
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                Author and article information

                Journal
                Current Opinion in Supportive and Palliative Care
                Current Opinion in Supportive and Palliative Care
                Ovid Technologies (Wolters Kluwer Health)
                1751-4258
                2018
                December 2018
                : 12
                : 4
                : 394-403
                Article
                10.1097/SPC.0000000000000380
                6239206
                30102621
                fcb64ffb-0eae-4838-b4dd-f45474e1208e
                © 2018
                History

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