Early changes of muscle IGF-1 and myostatin gene expression in gastric cancer patients

Introduction: Cachexia increases morbidity and mortality of cancer patients. The progressive loss of muscle mass negatively affects physical function and quality of life. We previously showed reduced muscle insulin-like growth factor-1 (IGF-1) expression and enhanced myostatin signaling in tumor-bearing animals. This study was aimed at investigating whether similar perturbations occur in gastric cancer patients. Methods: Early perturbations of myostatin and IGF-1 signaling (including the expression of muscle-specific ubiquitin ligases) were investigated in 16 gastric cancer patients and in 6 controls by analyzing muscle mRNA expression with semiquantitative reverse transcriptase polymerase chain reaction (PCR) and real-time PCR. Results: In gastric cancer patients, muscle mRNA levels for IGF-1, myostatin, and atrogin-1 were reduced irrespective of weight loss (≤5% or >5%), whereas MuRF1 expression was unchanged. Conclusions: IGF-1 and myostatin mRNA levels are downregulated in gastric cancer patients who have minimal or no weight loss. These early alterations are particularly relevant in order to devise preventive and therapeutic strategies for cancer cachexia. © 2013 Wiley Periodicals, Inc

The role of myostatin in muscle wasting: an overview

Myostatin is an extracellular cytokine mostly expressed in skeletal muscles and known to play a crucial role in the negative regulation of muscle mass. Upon the binding to activin type IIB receptor, myostatin can initiate several different signalling cascades resulting in the upregulation of the atrogenes and downregulation of the important for myogenesis genes. Muscle size is regulated via a complex interplay of myostatin signalling with the insulin-like growth factor 1/phosphatidylinositol 3-kinase/Akt pathway responsible for increase in protein synthesis in muscle. Therefore, the regulation of muscle weight is a process in which myostatin plays a central role but the mechanism of its action and signalling cascades are not fully understood. Myostatin upregulation was observed in the pathogenesis of muscle wasting during cachexia associated with different diseases (i.e. cancer, heart failure, HIV). Characterisation of myostatin signalling is therefore a perspective direction in the treatment development for cachexia. The current review covers the present knowledge about myostatin signalling pathways leading to muscle wasting and the state of therapy approaches via the regulation of myostatin and/or its downstream targets in cachexia

Depletion of stromal cells expressing fibroblast activation protein-α from skeletal muscle and bone marrow results in cachexia and anemia.

Fibroblast activation protein-α (FAP) identifies stromal cells of mesenchymal origin in human cancers and chronic inflammatory lesions. In mouse models of cancer, they have been shown to be immune suppressive, but studies of their occurrence and function in normal tissues have been limited. With a transgenic mouse line permitting the bioluminescent imaging of FAP(+) cells, we find that they reside in most tissues of the adult mouse. FAP(+) cells from three sites, skeletal muscle, adipose tissue, and pancreas, have highly similar transcriptomes, suggesting a shared lineage. FAP(+) cells of skeletal muscle are the major local source of follistatin, and in bone marrow they express Cxcl12 and KitL. Experimental ablation of these cells causes loss of muscle mass and a reduction of B-lymphopoiesis and erythropoiesis, revealing their essential functions in maintaining normal muscle mass and hematopoiesis, respectively. Remarkably, these cells are altered at these sites in transplantable and spontaneous mouse models of cancer-induced cachexia and anemia. Thus, the FAP(+) stromal cell may have roles in two adverse consequences of cancer: their acquisition by tumors may cause failure of immunosurveillance, and their alteration in normal tissues contributes to the paraneoplastic syndromes of cachexia and anemia

Molecular pathways leading to loss of skeletal muscle mass in cancer cachexia can findings from animal models be translated to humans?

Background: Cachexia is a multi-factorial, systemic syndrome that especially affects patients with cancer of the gastrointestinal tract, and leads to reduced treatment response, survival and quality of life. The most important clinical feature of cachexia is the excessive wasting of skeletal muscle mass. Currently, an effective treatment is still lacking and the search for therapeutic targets continues. Even though a substantial number of animal studies have contributed to a better understanding of the underlying mechanisms of the loss of skeletal muscle mass, subsequent clinical trials of potential new drugs have not yet yielded any effective treatment for cancer cachexia. Therefore, we questioned to which degree findings from animal studies can be translated to humans in clinical practice and research. Discussion: A substantial amount of animal studies on the molecular mechanisms of muscle wasting in cancer cachexia has been conducted in recent years. This extensive review of the literature showed that most of their observations could not be consistently reproduced in studies on human skeletal muscle samples. However, studies on human material are scarce and limited in patient numbers and homogeneity. Therefore, their results have to be interpreted critically. Summary: More research is needed on human tissue samples to clarify the signaling pathways that lead to skeletal muscle loss, and to confirm pre-selected drug targets from animal models in clinical trials. In addition, improved diagnostic tools and standardized clinical criteria for cancer cachexia are needed to conduct standardized, randomized controlled trials of potential drug candidates in the future

Molecular Mechanisms of Heart Valve and Skeletal Muscle Development and Disease

Heart valves function to provide unidirectional blood flow during each cardiac cycle. The development of the heart valves from embryonic stages is a highly regulated process involving many signaling pathways in order to provide the proper extracellular matrix components in the trilaminar structure. When these processes are dysregulated, disease can persist in the valves. Here we examined additional levels of regulation in the heart valves at the level of miRNAs and phosphate homeostasis. There are many studies examining miRNA regulation in the heart, however, there is little knowledge about which miRNAs are expressed in the heart valves during development, maturation, homeostasis and disease. To address this gap and determine miRNA regulators of valve development and disease, RNA was extracted from mouse atrioventricular (AV) heart valves at mE11.5 (endocardial cushion), mE15.5 (remodeling), postnatal (maturing), and 4 months (4m) of age (maintained). The mechanism of miR-101 binding to the 3’UTR of Sox9, a SRY transcription factor required for proper valve development, was analyzed and the results suggest Sox9 may be regulated in the valves by miR-101 during development. In addition to the miRNA valve studies, although elevated FGF23 and phosphate serum levels have been demonstrated to be associated with vascular calcification in patients with chronic kidney disease (CKD), the direct effect on the heart valves remains unknown. Here we show evidence for phosphate, but not FGF23 promoting calcification in heart valve explants, valve interstitial cells and in mouse aortic smooth muscle cells. Sodium phosphate (NaPh) Co-transporters are required for this calcification and their expression is altered by phosphate and FGF23. Lastly, the data presented here also shows a mechanism by which skeletal muscle wasting or cachexia can be prevented in mouse models of cancer cachexia. These studies specifically look at inhibiting myostatin-family ligands in order to protect skeletal muscles from cancer induced wasting. Taken together, these studies provide evidence as to examine both heart valve and skeletal muscle signaling pathways further in order to understand the developmental processes that have gone awry in diseases associated with these tissues. (Revised 7/2014 CREC)</p

Effect of the IL-1 Receptor Antagonist Kineret® on Disease Phenotype in mdx Mice.

Duchenne muscular dystrophy (DMD) is an X-linked muscle disease caused by mutations in the dystrophin gene. The pathology of DMD manifests in patients with progressive muscle weakness, loss of ambulation and ultimately death. One of the characteristics of DMD is muscle inflammation, and dystrophin-deficient skeletal muscles produce higher levels of the pro-inflammatory cytokine interleukin 1β (IL-1β) in response to toll like receptor (TLR) stimulation compared to controls; therefore, blocking the IL-1β pathway could improve the disease phenotype in mdx mice, a mouse model of DMD. Kineret® or IL-1Ra is a recombinant IL-1 receptor antagonist approved by the FDA for treating rheumatoid arthritis. To determine the efficacy of IL-1Ra in a DMD model, we administered subcutaneous injections of saline control or IL-1Ra (25 mg/kg/day) to mdx mice daily for 45 days beginning at 5 weeks of age. Functional and histological parameters were measured at the conclusion of the study. IL-1Ra only partially inhibited this signaling pathway in this study; however, there were still interesting observations to be noted. For example, although not significantly changed, splenocytes from the IL-1Ra-treated group secreted less IL-1β after LPS stimulation compared to control mice indicating a blunted response and incomplete inhibition of the pathway (37% decrease). In addition, normalized forelimb grip strength was significantly increased in IL-1Ra-treated mice. There were no changes in EDL muscle-specific force measurements, histological parameters, or motor coordination assessments in the dystrophic mice after IL-1Ra treatment. There was a significant 27% decrease in the movement time and total distance traveled by the IL-1Ra treated mice, correlating with previous studies examining effects of IL-1 on behavior. Our studies indicate partial blocking of IL-1β with IL-1Ra significantly altered only a few behavioral and strength related disease parameters; however, treatment with inhibitors that completely block IL-1β, pathways upstream of IL-1β production or combining various inhibitors may produce more favorable outcomes

IL-1Ra blunted the effect of LPS on IL-1 secretion in splenocytes from <i>mdx</i> mice.

<p>Enzyme-linked immunosorbent assay (ELISA) was performed on medium from primary splenocytes isolated from <i>mdx</i> mice that had been treated with IL-1Ra or saline. Splenocytes from IL-1Ra- and saline-treated mice were isolated and stimulated with lipopolysaccharide (LPS). Medium was collected after 24 h to quantify the levels of IL-1 secreted into the medium by the splenocytes. LPS treatment significantly increased the IL-1 production in the splenocytes from control mice (groups 1–2) and from the IL-1Ra-treated mice (groups 3–4). Although not significant, this increase was blunted in the IL-1Ra and was 36% lower than the amount of secreted IL-1 in group 2. Values in the graphs represent mean ± SEM. Statistically significant differences were determined by using parametric, unpaired, two-tailed, t-tests with a p≤0.05 being significant (n = 4 for each group tested).</p