Inhibiting myostatin signaling partially mitigates structural and functional adaptations to hindlimb suspension in mice.

Novel treatments for muscle wasting are of significant value to patients with disease states that result in muscle weakness, injury recovery after immobilization and bed rest, and for astronauts participating in long-duration spaceflight. We utilized an anti-myostatin peptibody to evaluate how myostatin signaling contributes to muscle loss in hindlimb suspension. Male C57BL/6 mice were left non-suspended (NS) or were hindlimb suspended (HS) for 14 days and treated with a placebo vehicle (P) or anti-myostatin peptibody (D). Hindlimb suspension (HS-P) resulted in rapid and significantly decreased body mass (-5.6% by day 13) with hindlimb skeletal muscle mass losses between -11.2% and -22.5% and treatment with myostatin inhibitor (HS-D) partially attenuated these losses. Myostatin inhibition increased hindlimb strength with no effect on soleus tetanic strength. Soleus mass and fiber CSA were reduced with suspension and did not increase with myostatin inhibition. In contrast, the gastrocnemius showed histological evidence of wasting with suspension that was partially mitigated with myostatin inhibition. While expression of genes related to protein degradation (Atrogin-1 and Murf-1) in the tibialis anterior increased with suspension, these atrogenes were not significantly reduced by myostatin inhibition despite a modest activation of the Akt/mTOR pathway. Taken together, these findings suggest that myostatin is important in hindlimb suspension but also motivates the study of other factors that contribute to disuse muscle wasting. Myostatin inhibition benefitted skeletal muscle size and function, which suggests therapeutic potential for both spaceflight and terrestrial applications.

[Application value of urinary IGFBP7 and TIMP-2 in acute kidney injury with decompensated hepatitis B virus-related liver cirrhosis].

Objective: To investigate the application value of new urinary biomarkers insulin-like growth factor binding protein 7 (IGFBP7) and tissue matrix metalloproteinase inhibitor-2 (TIMP-2) in acute kidney injury with decompensated hepatitis B virus-related liver cirrhosis. Methods: 45 newly hospitalized cases with decompensated hepatitis B virus-related liver cirrhosis were selected. Among them, 19 cases were combined with AKI on admission (cirrhosis-AKI group), 26 cases without AKI (cirrhosis-non-AKI group), and 12 healthy cases (normal control group). First-morning urine samples were collected and IGFBP7 and TIMP-2 were detected by enzyme-linked immunosorbent assay (ELISA). Urinary IGFBP7 and serum creatinine (SCr) were dynamically monitored after hospitalization in cirrhosis-non-AKI group. Normally distributed measurement data were compared by t-test, and non-normally distributed measurement data were compared by rank sum test. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to evaluate the diagnostic accuracy of the indicators. Results: Urinary IGFBP7, IGFBP7 with TIMP-2 (IGFBP7×TIMP-2) in cirrhosis-AKI group (n = 19) were equally higher than that of the cirrhosis-non-AKI group (P < 0.05). Urinary IGFBP7, TIMP-2 and IGFBP7×TIMP-2 in cirrhosis-AKI group or cirrhosis-non-AKI group were significantly higher than those of the normal control group (P < 0.01). The AUC of urinary IGFBP7 and urinary IGFBP7×TIMP-2 for diagnosis of AKI were 0.703 (95% CI 0.547-0.860) and 0.700 (95% CI 0.541-0.859), respectively. In the liver cirrhosis-non-AKI group (n = 26), 5 cases of AKI were newly diagnosed according to the changes in SCr during hospitalization (progressive group). Urinary IGFBP7 was significantly increased 2 days before the diagnosis of AKI. The concentration of urinary IGFBP7 at admission in the progressive group (n = 5) was higher than that of the non-progressive group (n = 21) (P < 0.05). Conclusion: Urinary IGFBP7 and TIMP-2 concentrations were significantly increased in patients with decompensated hepatitis B virus-related liver cirrhosis. When AKI occurred, urinary IGFBP7 and IGFBP7×TIMP-2 was further increased. Urinary IGFBP7 is valuable for early AKI diagnosis, and may play a role in predicting AKI occurrence.

[Application of MOAS for Evaluating of Violence Risk in the Inpatients with Mental Disorders].

OBJECTIVES: To explore the value of Modified Overt Aggression Scale （MOAS） on predicting serious aggressive behavior in the inpatients with mental disorders and to provide theoretical basis for violence risk assessments in the inpatients with mental disorders. METHODS: Total 918 inpatients in a psychiatric hospital were evaluated by trained medical workers using MOAS in September 2009, and their serious violent behavior were followed up for 2 years. The value of MOAS on predicting violence in the inpatients with mental disorders was analyzed by SPSS 21.0. RESULTS: （1） Compared to the patients without serious aggressive behaviors, the patients with serious aggressive behavior within 2 years showed significantly higher scores （P＜0.05） on verbal aggression, aggression against property, physical aggression and total weighted score of MOAS; （2） Significant correlation was found between the score of verbal aggression and the serious acts of violence within 2 years （P＜0.05）; （3） Scores of verbal aggression, physical aggression and total weighted score of MOAS had predictive value on serious aggressive behaviors within 2 years. CONCLUSIONS: MOAS has certain value on predicting the serious aggressive behaviors of patients with mental disorders within 2 years.

Complete reversal of muscle wasting in experimental cancer cachexia: Additive effects of activin type II receptor inhibition and ß-2 agonist.

Formoterol is a highly potent ß2-adrenoceptor-selective agonist, which is a muscle growth promoter in many animal species. Myostatin/activin inhibition reverses skeletal muscle loss and prolongs survival of tumor-bearing animals. The aim of this investigation was to evaluate the effects of a combination of the soluble myostatin receptor ActRIIB (sActRIIB) and the ß2-agonist formoterol in the cachectic Lewis lung carcinoma model. The combination of formoterol and sActRIIB was extremely effective in reversing muscle wasting associated with experimental cancer cachexia in mice. Muscle weights from tumor-bearing animals were completely recovered following treatment and this was also reflected in the measured grip strength. This combination increased food intake in both control and tumor-bearing animals. The double treatment also prolonged survival significantly without affecting the weight and growth of the primary tumor. In addition, it significantly reduced the number of metastasis. Concerning the mechanisms for the preservation of muscle mass during cachexia, the effects of formoterol and sActRIIB seemed to be additive, since formoterol reduced the rate of protein degradation (as measured in vitro as tyrosine release, using incubated isolated individual muscles) while sActRIIB only affected protein synthesis (as measured in vivo using tritiated phenylalanine). Formoterol also increased the rate of protein synthesis and this seemed to be favored by the presence of sActRIIB. Combining formoterol and sActRIIB seemed to be a very promising treatment for experimental cancer cachexia. Further studies in human patients are necessary and may lead to a highly effective treatment option for muscle wasting associated with cancer.

Identification and expression analysis of YABBY family genes associated with fruit shape in tomato (Solanum lycopersicum L.).

YABBY family genes play important roles in the development of leaf, flower, and fruit. The purpose of this research was to integrate all the YABBY genes and analyze the correlation between gene expression and fruit shape in tomato. Scanning of 24 genomes of sequenced species demonstrated that YABBY genes were very normal and stable in flowering plants except the seedless plants. Nine YABBY genes in tomato were computationally and experimentally characterized. The phylogeny was constructed based on whole proteins or the YABBY domain, and five distinct clades were observed as described in other angiosperms. A comparison of the expression patterns in tomatoes with large differences in fruit shape and/or size suggested that during the fruit development, YABBY genes had both negative and positive functions. The obtained information could provide a deeper understanding of the evolution of YABBY genes and can also be useful for tomato yield and shape breeding.

Simple sequence repeat-based association analysis of fruit traits in eggplant (Solanum melongena).

Association mapping based on linkage disequilibrium (LD) provides a promising tool to identify quantitative trait loci (QTLs) in plant resources. A total of 141 eggplant (Solanum melongena L.) accessions were selected to detect simple sequence repeat (SSR) markers associated with nine fruit traits. Population structure analysis was performed with 105 SSR markers, which revealed that two subgroups were present in this population. LD analysis exhibited an extensive long-range LD of approximately 11 cM. A total of 49 marker associations related to eight phenotypic traits were identified to involve 24 different markers, although no association was found with the trait of fruit glossiness. To our knowledge, this is the 1st approach to use a genome-wide association study in eggplant with SSR markers. These results suggest that the association analysis approach could be a useful alternative to traditional linkage mapping to detect putative QTLs in eggplant.

Myostatin/activin pathway antagonism: molecular basis and therapeutic potential.

Muscle wasting is associated with a wide range of catabolic diseases. This debilitating loss of muscle mass and functional capacity reduces the quality of life and increases the risks of morbidity and mortality. Major progress has been made in understanding the biochemical mechanisms and signaling pathways regulating muscle protein balance under normal conditions and the enhanced protein loss in atrophying muscles. It is now clear that activation of myostatin/activin signaling is critical in triggering the accelerated muscle catabolism that causes muscle loss in multiple disease states. Binding of myostatin and activin to the ActRIIB receptor complex on muscle cell membrane leads to activation of Smad2/3-mediated transcription, which in turn stimulates FoxO-dependent transcription and enhanced muscle protein breakdown via ubiquitin-proteasome system and autophagy. In addition, Smad activation inhibits muscle protein synthesis by suppressing Akt signaling. Pharmacological blockade of the myostatin/activin-ActRIIB pathway has been shown to prevent or reverse the loss of muscle mass and strength in various disease models including cancer cachexia and renal failure. Moreover, it can markedly prolong the lifespan of animals with cancer-associated muscle loss. Furthermore, inhibiting myostatin/activin actions also improves insulin sensitivity, reduces excessive adiposity, attenuates systemic inflammation, and accelerates bone fracture healing in disease models. Based on these exciting advances, the potential therapeutic benefits of myostatin/activin antagonism are now being tested in multiple clinical settings. This article is part of a Directed Issue entitled: Molecular basis of muscle wasting.

Myostatin blockage using actRIIB antagonism in mice bearing the Lewis lung carcinoma results in the improvement of muscle wasting and physical performance.

BACKGROUND: Cachexia is a multiorganic syndrome associated with cancer, characterized by body weight loss, muscle and adipose tissue wasting and inflammation. METHODS: The aim of this investigation was to examine the effect of the soluble receptor antagonist of myostatin (sActRIIB) in cachectic tumor-bearing animals analyzing changes in muscle proteolysis and in quality of life. RESULTS: Administration of sActRIIB resulted in an improvement in body and muscle weights. Administration of the soluble receptor antagonist of myostatin also resulted in an improvement in the muscle force. CONCLUSIONS: These results suggest that blocking myostatin pathway could be a promising therapeutic strategy for the treatment of cancer cachexia.

Targeting the myostatin signaling pathway to treat muscle wasting diseases.

PURPOSE OF REVIEW: To understand the mechanisms of muscle wasting and how inhibiting myostatin signaling affects them. RECENT FINDINGS: Myostatin signaling is critical for the understanding of the pathogenesis of muscle wasting as blocking signaling mitigates muscle losses in rodent models of catabolic diseases including cancer, chronic kidney, or heart failure. SUMMARY: Muscle wasting increases the risks of morbidity and mortality. But, the reliability of estimates of the degree of muscle wasting is controversial as are definitions of terms like cachexia. Much information has been learnt about the pathophysiology of muscle wasting, including the major role of the ubiquitin-proteasome system (UPS) which along with other proteases degrades protein and limits protein synthesis. In contrast, few successful strategies for reversing muscle loss have been tested. Several catabolic conditions are characterized by inflammation, increased glucocorticoid production, and impaired intracellular signaling in response to insulin and IGF-1. These characteristics lead to activation of the UPS and other proteases producing muscle wasting. Another potential initiator of muscle wasting is myostatin and its expression is increased in muscles of animal models and patients with certain catabolic conditions. Myostatin is a member of the TGF-ß family; it suppresses muscle growth and its absence stimulates muscle growth substantially. Recently, pharmacologic suppression of myostatin was found to counteract inflammation, increased glucocorticoids and impaired insulin/IGF-1 signaling and most importantly, prevents muscle wasting in rodent models of cancer and kidney failure. Myostatin antagonism as a therapy for patients with muscle wasting should become a topic of clinical investigation.

Pharmacological inhibition of myostatin suppresses systemic inflammation and muscle atrophy in mice with chronic kidney disease.

Chronic kidney disease (CKD) and several other catabolic conditions are characterized by increased circulating inflammatory cytokines, defects in IGF-1 signaling, abnormal muscle protein metabolism, and progressive muscle atrophy. In these conditions, no reliable treatments successfully block the development of muscle atrophy. In mice with CKD, we found a 2- to 3-fold increase in myostatin expression in muscle. Its pharmacological inhibition by subcutaneous injections of an anti-myostatin peptibody into CKD mice (IC(50) ∼1.2 nM) reversed the loss of body weight (≈5-7% increase in body mass) and muscle mass (∼10% increase in muscle mass) and suppressed circulating inflammatory cytokines vs. results from CKD mice injected with PBS. Pharmacological myostatin inhibition also decreased the rate of protein degradation (16.38 ± 1.29%; P<0.05), increased protein synthesis in extensor digitorum longus muscles (13.21 ± 1.09%; P<0.05), markedly enhanced satellite cell function, and improved IGF-1 intracellular signaling. In cultured muscle cells, TNF-α increased myostatin expression via a NF-κB-dependent pathway, whereas muscle cells exposed to myostatin stimulated IL-6 production via p38 MAPK and MEK1 pathways. Because IL-6 stimulates muscle protein breakdown, we conclude that CKD increases myostatin through cytokine-activated pathways, leading to muscle atrophy. Myostatin antagonism might become a therapeutic strategy for improving muscle growth in CKD and other conditions with similar characteristics.

Reversal of cancer cachexia and muscle wasting by ActRIIB antagonism leads to prolonged survival.

Muscle wasting and cachexia have long been postulated to be key determinants of cancer-related death, but there has been no direct experimental evidence to substantiate this hypothesis. Here, we show that in several cancer cachexia models, pharmacological blockade of ActRIIB pathway not only prevents further muscle wasting but also completely reverses prior loss of skeletal muscle and cancer-induced cardiac atrophy. This treatment dramatically prolongs survival, even of animals in which tumor growth is not inhibited and fat loss and production of proinflammatory cytokines are not reduced. ActRIIB pathway blockade abolished the activation of the ubiquitin-proteasome system and the induction of atrophy-specific ubiquitin ligases in muscles and also markedly stimulated muscle stem cell growth. These findings establish a crucial link between activation of the ActRIIB pathway and the development of cancer cachexia. Thus ActRIIB antagonism is a promising new approach for treating cancer cachexia, whose inhibition per se prolongs survival.

Regulation of protein catabolism by muscle-specific and cytokine-inducible ubiquitin ligase E3alpha-II during cancer cachexia.

The progressive depletion of skeletal muscle is a hallmark of many types of advanced cancer and frequently is associated with debility, morbidity, and mortality. Muscle wasting is primarily mediated by the activation of the ubiquitin-proteasome system, which is responsible for degrading the bulk of intracellular proteins. E3 ubiquitin ligases control polyubiquitination, a rate-limiting step in the ubiquitin-proteasome system, but their direct involvement in muscle protein catabolism in cancer remains obscure. Here, we report the full-length cloning of E3alpha-II, a novel "N-end rule" ubiquitin ligase, and its functional involvement in cancer cachexia. E3alpha-II is highly enriched in skeletal muscle, and its expression is regulated by proinflammatory cytokines. In two different animal models of cancer cachexia, E3alpha-II was significantly induced at the onset and during the progression of muscle wasting. The E3alpha-II activation in skeletal muscle was accompanied by a sharp increase in protein ubiquitination, which could be blocked by arginine methylester, an E3alpha-selective inhibitor. Treatment of myotubes with tumor necrosis factor alpha or interleukin 6 elicited marked increases in E3alpha-II but not E3alpha-I expression and ubiquitin conjugation activity in parallel. E3alpha-II transfection markedly accelerated ubiquitin conjugation to endogenous cellular proteins in muscle cultures. These findings show that E3alpha-II plays an important role in muscle protein catabolism during cancer cachexia and suggest that E3alpha-II is a potential therapeutic target for muscle wasting.

Suppression of synapsin II inhibits the formation and maintenance of synapses in hippocampal culture.

Numerous synaptic proteins, including several integral membrane proteins, have been assigned roles in synaptic vesicle fusion with or retrieval from the presynaptic plasma membrane. In contrast, the synapsins, neuron-specific phosphoproteins associated with the cytoplasmic surface of synaptic vesicles, appear to play a much broader role, being involved in the regulation of neurotransmitter release and in the organization of the nerve terminal. Here we have administered antisense synapsin II oligonucleotides to dissociated hippocampal neurons, either before the onset of synaptogenesis or 1 week after the onset of synaptogenesis. In both cases, synapsin II was no longer detectable within 24-48 h of treatment. After 5 days of treatment, cultures were analyzed for the presence of synapses by synapsin I and synaptophysin antibody labeling and by electron microscopy. Cultures in which synapsin II was suppressed after axon elongation, but before synapse formation, did not develop synapses. Cultures in which synapsin II was suppressed after the development of synapses lost most of their synapses. Remarkably, with the removal of the antisense oligonucleotides, neurons and their synaptic connections recovered. These studies lead us to conclude that synapsin II is involved in the formation and maintenance of synapses in hippocampal neurons.

Laminin and neuropeptide Y are increased by synapsin transfection in cultured NG108-15 neuroblastoma/glioma hybrid cells.

We have investigated the presence and expression of laminin and neuropeptide Y (NPY) in several NG108-15 cell lines transfected with synapsin Ib, IIa, or IIb. The content of laminin, a basal membrane glycoprotein that promotes adhesion and induces neurite out-growth and neuronal differentiation, was increased in all transfected cell lines examined. In cells that were chemically differentiated with prostaglandin E1 plus 3-isobutyl-1-methylxanthine, laminin levels were increased even further. The content of NPY, suggested to be a neurotransmitter/neuromodulator in peripheral sympathetic neurons as well as in central neurons, was also increased in all transfected cell lines examined. Immunohistochemical analysis combined with confocal laser microscopy showed that NPY staining was granular and very often enriched in neuritic varicosities. The distribution and the staining pattern of NPY were consistent with storage of NPY in large dense-cored vesicles. The results indicate that, in differentiated neurons, the synapsins increase the levels of a neuropeptide transmitter stored in large dense-cored vesicles and of an extracellular matrix protein associated with neuronal maturation.

Increase in synaptic vesicle proteins in synapsin-transfected NG108-15 cells: a subcellular fractionation study.

We have examined the subcellular distribution of synapsins and synaptophysin in density gradients from synapsin- and vector-transfected NG108-15 cells, since we recently found that transfection of synapsin IIb cDNA into neuroblastoma x glioma hybrid cells (NG108-15) resulted in cell lines that had a more neuronal phenotype than controls. The increase in synapsins and synaptophysin in the transfected cells was maximal in the region of the gradient containing small synaptic vesicles. The transferrin receptor, a marker for early endosomes, did not increase in the synapsin-containing fractions in the transfected cells. Secretogranin I, a soluble protein stored in and secreted from large dense cored vesicles, showed a very pronounced increase in the dense regions of gradients from transfected cells. These subcellular fractionation data suggest a possible role for the synapsins in the regulation of synaptic vesicle function.

Remodeling of cytoskeletal architecture of nonneuronal cells induced by synapsin.

The synapsins, a family of neuron-specific phosphoproteins, have been implicated in the functional and structural maturation of synapses. The cell biological basis for these effects is unknown. In vitro, the synapsins interact with cytoskeletal elements including actin. To examine, in vivo, the possible effect of the synapsins on cytoskeletal organization and cell morphology, we have transfected each of the four known members of the synapsin family into nonneuronal cells. We report here that synapsin expression in fibroblast cells gives rise to an alteration in cell morphology that is associated with formation of highly elongated processes. This morphological change is accompanied by a reorganization of filamentous actin (F-actin) characterized by disruption of existing stress fibers and formation of bundles of actin cables in the elongated processes. These results suggest that interactions of the synapsins with actin, and possibly with other cytoskeletal elements, may play a role in the morphological differentiation of neurons.

Aberrant neurites and synaptic vesicle protein deficiency in synapsin II-depleted neurons.

Synapsin I and synapsin II are neuron-specific phosphoproteins that have a role in the regulation of neurotransmitter release and in the formation of nerve terminals. After depletion of synapsin II by antisense oligonucleotides, rat hippocampal neurons in culture were unable to consolidate their minor processes and did not elongate axons. These aberrant morphological changes were accompanied by an abnormal distribution of intracellular filamentous actin (F-actin). In addition, synapsin II suppression resulted in a selective decrease in the amounts of several synaptic vesicle-associated proteins. These data suggest that synapsin II participates in cytoskeletal organization during the early stages of nerve cell development.

Induction of formation of presynaptic terminals in neuroblastoma cells by synapsin IIb.

The synapsins are a family of closely related phosphoproteins (termed synapsins Ia, Ib, IIa and IIb) associated with synaptic vesicles and implicated in the short-term regulation of neurotransmitter release from nerve endings. During development, expression of the synapsins correlates temporally with synapse formation, but there has been no direct evidence that they are involved in synaptogenesis. Here we report that overexpression of synapsin IIb in the neuroblastoma x glioma hybrid clonal cell line NG108-15 leads, during cell differentiation, to marked increases in the number of neuritic varicosities and in the numbers of small clear vesicles and large dense core vesicles per varicosity, as well as to the appearance of synapse-like cell-cell contacts. Thus, synapsin IIb may be involved in the regulation of synapse formation and, as a result, in long-term neuronal signalling.