Anabolic steroids activate calcineurin-NFAT signaling and thereby increase myotube size and reduce denervation atrophy

Identification and verification of atrial fibrillation hub genes caused by primary mitral regurgitation

In the clinic, atrial fibrillation (AF) is a common arrhythmia. Despite constant innovation in treatments for AF, they remain limited by a lack of knowledge of the underlying mechanism responsible for AF. In this study, we examined the molecular mechanisms associated with primary mitral regurgitation (MR) in AF using several bioinformatics techniques. Limma was used to identify differentially expressed genes (DEGs) associated with AF using microarray data from the GSE115574 dataset. WGCNA was used to identify significant module genes. A functional enrichment analysis for overlapping genes between the DEGs and module genes was done and several AF hub genes were identified from a protein-protein interaction (PPI) network. Receiver operating characteristic (ROC) curves were generated to evaluate the validity of the hub genes. We examined 306 DEGs and 147 were upregulated and 159 were downregulated. WGCNA analysis revealed black and ivory modules that contained genes associated with AF. Functional enrichment analysis revealed various biological process terms related to AF. The AUCs for the 8 hub genes screened by the PPI network analysis were > 0.7, indicating satisfactory diagnostic accuracy. The 8 AF-related hub genes included SYT13, VSNL1, GNAO1, RGS4, RALYL, CPLX1, CHGB, and CPLX3. Our findings provide novel insight into the molecular mechanisms of AF and may lead to the development of new treatments.

Activation of androgen receptors alters hippocampal synaptic plasticity and memory retention through modulation of L-type calcium channels

AIMS

It has been revealed that membrane androgen receptor activation modulates avoidance memory and synaptic plasticity. In a previous study, we showed that Calcineurin, a calcium dependent phosphatase, could be a potential mediator of these AR effects. Also, it is reported that AR activation leads to L-type calcium channel activation. The aim of the current study is to test whether L-type calcium channels are downstream of AR and whether this signal pathway mediates the impairment effect of androgenic steroids on passive avoidance memory and synaptic plasticity.

MATERIALS AND METHODS

We measured the effect of Nandrolone Decanoate (AR agonist), AR antagonist (Nilutamide) plus ND or L-type calcium channel inhibitor (Nifedipine) plus ND on passive avoidance performance of adolescent male rats. For extracellular field potential recordings hippocampal slices were perfused with ND, Nilutamide-ND or Nifedipine-ND.

KEY FINDINGS

Our results clarified that AR activation by ND could impair avoidance behavior as step through latency decreased in ND-treated group while application of both Nilutamide and Nifedipine reestablished normal avoidance behavior. Also, LTP induction in the CA1 area of hippocampus was diminished by ND perfusion and both AR antagonist and L-type calcium channel inhibitor application lead to normal LTP. These findings support our hypothesis that activation of L-type calcium channels are involved in ARs mechanism effects on both avoidance behavior and hippocampal synaptic plasticity.

SIGNIFICANCE

Understanding the biological effects of AR agonists on cognitive processes and its cellular mechanism may be a new/supplementary way to treating fear-related disorders.

The Overexpression of miR-377 Aggravates Sepsis-Induced Myocardial Hypertrophy by Binding to Rcan2 and Mediating CaN Activity

Sepsis remains a complicated and incompletely understood syndrome, and myocardial dysfunction is one of the main complications contributing to poor clinical outcomes. Accumulating evidence has revealed the critical involvement of the deregulated expression of specific microRNAs (miRNAs) in cardiac pathologies caused by sepsis. Intriguingly, miR-377 has been correlated with cardiomyocyte apoptosis, whereas its effect on myocardial hypertrophy remains to be illustrated. Thus, the current study sets out to explore the impact and underlying mechanism of miR-377 on myocardial hypertrophy induced by sepsis. The expression pattern of miR-377 was detected in myocardial tissues of septic mice induced by cecal ligation-perforation (CLP). We found that miR-377 was highly expressed in myocardial tissues of CLP-induced septic mice with cardiomyocyte hypertrophy. Besides, miR-377 inhibition could relieve cardiomyocyte hypertrophy and reduce inflammation in septic mice. Further, mechanistic studies found that miR-377 could target Rcan2 and then regulate calcineurin (CaN) activity via Ca2+/CaN signaling pathway. Collectively, our findings illuminate that miR-377 enhances myocardial hypertrophy caused by sepsis, by targeting Rcan2 and further regulating the Ca2+/CaN signaling pathway. This work highlights downregulation of miR-377 as a novel target for the management of sepsis-induced myocardial hypertrophy.

Calpain 6 inhibits autophagy in inflammatory environments: A preliminary study on myoblasts and a chronic kidney disease rat model

A non-classical calpain, calpain 6 (CAPN6), can inhibit skeletal muscle differentiation and regeneration. In the present study, the role of CAPN6 in the regulation of the autophagy of myoblasts in vitro was investigated. The underlying molecular events and the CAPN6 level in atrophic skeletal muscle in a rat model of chronic kidney disease (CKD) were also investigated. In vitro, CAPN6 was overexpressed, or knocked down, in rat L6 myoblasts to assess autophagy and related gene expression and co-localization. Subsequently, myoblasts were treated with a mixture of cytokines, and relative gene expression and autophagy were assessed. A rat model of CKD for muscle atrophy was established, and blood chemical level and the expression of CAPN6 in muscle were assessed. The data revealed that the knockdown of CAPN6 in rat myoblasts resulted in increased microtubule-associated protein 1 light chain 3 (LC3) levels, while its overexpression decreased LC3 levels and impaired autophagy. Additionally, it was observed that the co-localization of mammalian target of rapamycin (mTOR) and lysosomal-associated membrane protein 1 (LAMP1), a lysosomal marker, proteins was increased. In addition, mTOR, Raptor and α-tubulin (a marker of microtubules) increased in the CAPN6 overexpression group. However, inflammatory cytokines, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, interferon (INF)-γ and lipopolysaccharides upregulated CAPN6 expression, inhibited L6 myoblast autophagy and stabilized mTOR activity. Furthermore, the animal model successfully mimicked human disease as regards an increase in body weight, and a reduction in muscle mass, cross-sectional area and blood biomarker concentrations; a slight increase in CAPN6 mRNA and protein levels in muscles was observed. Finally, the data of the present study suggested that CAPN6 reduced autophagy via the maintenance of mTOR signaling, which may play a role in CKD-related muscle atrophy. However, future studies are required to determine whether CAPN6 may be used as an intervention target for CKD-related skeletal muscle atrophy.

Nandrolone decanoate relieves joint pain in hypogonadal men: a novel prospective pilot study and review of the literature

Testosterone is an archetypal androgenic-anabolic steroid (AAS), while its exogenous administration is considered to be the gold standard for the treatment of male hypogonadism. The benefits are not due to its intrinsic nature alone but are due to the result of its interactions with the androgen receptor (AR). As the management of hypogonadism continues to advance into the modern era, it would be preferable for modern andrologists to have multiple tools at their disposal to influence AR activity. Nandrolone, or 19-nortestosterone, is one such compound. In the following review of the literature, we examine the history, pharmacology, and clinical applications of this medication. We also present the results of our novel pilot study examining the favorable effects of nandrolone on joint pain for hypogonadal men.

Calcineurin is involved in retrieval of passive avoidance memory and synaptic plasticity impairment induced by Nandrolone administration in adolescent male rats

In spite of evidence about negative effects of Nandrolone Decanoate (ND) on cognitive and memory performance, the underlying mechanisms are complex and have remained unclear. This research examines the role of Calcineurin in synaptic plasticity and memory storage impairment in ND administrated adolescent male rats. For behavioral study by passive avoidance learning and memory (PAL), adolescent male rats were treated with ND or ND plus selective Calcineurin antagonist (Tacrolimus), before retention test. ND significantly decreased the retrieval of PAL, whereas Tacrolimus plus ND had no significant effect on PAL. For electrophysiological study hippocampal slices were perfused by ND or ND plus Tacrolimus. The magnitude of fEPSP-LTP of ND perfused slices was less than the control and a reduction of fEPSP-PS (E-S) coupling was observed, while pre-administration of Tacrolimus abolished the ND impairment effect on fEPSP-LTP and E-S coupling. This study showed that ND may induce impairing effects on hippocampal area CA1 activity and plasticity and PAL memory storage through changes in the function of the Calcineurin.

Nandrolone decanoate administration does not attenuate muscle atrophy during a short period of disuse

BACKGROUND

A few days of bed rest or immobilization following injury, disease, or surgery can lead to considerable loss of skeletal muscle mass and strength. It has been speculated that such short, successive periods of muscle disuse may be largely responsible for the age-related loss of muscle mass throughout the lifespan.

OBJECTIVE

To assess whether a single intramuscular injection of nandrolone decanoate prior to immobilization can attenuate the loss of muscle mass and strength in vivo in humans.

DESIGN, SETTING AND PARTICIPANTS

Thirty healthy (22 ± 1 years) men were subjected to 7 days of one-legged knee immobilization by means of a full leg cast with (NAD, n = 15) or without (CON, n = 15) prior intramuscular nandrolone decanoate injection (200 mg).

MEASURES

Before and immediately after immobilization, quadriceps muscle cross-sectional area (CSA) (by means of single-slice computed tomography (CT) scans of the upper leg) and one-legged knee extension strength (one-repetition maximum [1-RM]) were assessed for both legs. Furthermore, muscle biopsies from the immobilized leg were taken before and after immobilization to assess type I and type II muscle fiber cross-sectional area.

RESULTS

Quadriceps muscle CSA decreased during immobilization in both CON and NAD (-6 ± 1% and -6 ± 1%, respectively; main effect of time P<0.01), with no differences between the groups (time × treatment interaction, P = 0.59). Leg muscle strength declined following immobilization (-6 ± 2% in CON and -7 ± 3% in NAD; main effect of time, P<0.05), with no differences between groups (time × treatment interaction, P = 0.55).

CONCLUSIONS

This is the first study to report that nandrolone decanoate administration does not preserve skeletal muscle mass and strength during a short period of leg immobilization in vivo in humans.

Phosphate stimulates myotube atrophy through autophagy activation: evidence of hyperphosphatemia contributing to skeletal muscle wasting in chronic kidney disease

Background

Accelerated muscle atrophy is associated with a three-fold increase in mortality in chronic kidney disease (CKD) patients. It is suggested that hyperphosphatemia might contribute to muscle wasting, but the underlying mechanisms remain unclear. Although evidence indicates that autophagy is involved in the maintenance of muscle homeostasis, it is not known if high phosphate levels can result in activation of autophagy, leading to muscle protein loss.

Methods

Immortalized rat L6 myotubes were exposed to a high concentration of phosphate, with or without autophagy inhibition. Myotube atrophy was examined by phase contrast microscopy. Autophagic activity was assessed by measuring the expression of microtubule-associated protein 1 light chain 3 (LC3) and p62 using quantitative real-time polymerase chain reaction and western blot.

Results

Phosphate induced cell atrophy in L6 myotubes in a dose- and time-dependent manner, and these responses were not associated with calcification or osteogenesis. Phosphate also dose- and time-dependently increased the LC3-II/LC3-I ratio. Inhibition of autophagy with wortmannin or knockdown of Atg5 significantly suppressed myotube atrophy caused by high phosphate concentration.

Conclusions

High phosphate concentration induces muscle cell atrophy through the activation of autophagy. Targeting autophagy could be a therapeutic strategy for preventing muscle wasting caused by hyperphosphatemia.

The influence of isoflavone for denervation-induced muscle atrophy

PURPOSE

Decrease in activity stress induces skeletal muscle atrophy. A previous study showed that treatment with a high level (20%) of isoflavone inhibits muscle atrophy after short-term denervation (at 4 days) in mice. The present study was designed to elucidate whether the dietary isoflavone aglycone (AglyMax) at a 0.6% prevents denervation-mediated muscle atrophy, based on the modulation of atrogin-1- or apoptosis-dependent signaling.

METHODS

Mice were fed either a normal diet or 0.6% AglyMax diet. One week later, the right sciatic nerve was cut. The wet weight, mean fiber area, amount of atrogin-1 and cleaved caspase-3 proteins, and the percentages of apoptotic nuclei were examined in the gastrocnemius muscle at 14 days after denervation.

RESULTS

The 0.6% AglyMax diet significantly attenuated denervation-induced decreases in fiber atrophy but not the muscle wet weight. In addition, dietary isoflavone suppressed the denervation-induced apoptosis in spite of there being no significant changes in the amount of cleaved caspase-3 protein. In contrast, the 0.6% AglyMax diet did not significantly modulate the protein expression of atrogin-1 in the denervated muscle of mice.

CONCLUSIONS

The isoflavone aglycone (AglyMax) at a 0.6% significantly would modulate muscle atrophy after denervation in mice, probably due to the decrease in apoptosis-dependent signaling.

GSK-3β/NFAT Signaling Is Involved in Testosterone-Induced Cardiac Myocyte Hypertrophy

Testosterone induces cardiac hypertrophy through a mechanism that involves a concerted crosstalk between cytosolic and nuclear signaling pathways. Nuclear factor of activated T-cells (NFAT) is associated with the promotion of cardiac hypertrophy, glycogen synthase kinase-3β (GSK-3β) is considered to function as a negative regulator, mainly by modulating NFAT activity. However, the role played by calcineurin-NFAT and GSK-3β signaling in testosterone-induced cardiac hypertrophy has remained unknown. Here, we determined that testosterone stimulates cardiac myocyte hypertrophy through NFAT activation and GSK-3β inhibition. Testosterone increased the activity of NFAT-luciferase (NFAT-Luc) in a time- and dose-dependent manner, with the activity peaking after 24 h of stimulation with 100 nM testosterone. NFAT-Luc activity induced by testosterone was blocked by the calcineurin inhibitors FK506 and cyclosporine A and by 11R-VIVIT, a specific peptide inhibitor of NFAT. Conversely, testosterone inhibited GSK-3β activity as determined by increased GSK-3β phosphorylation at Ser9 and β-catenin protein accumulation, and also by reduction in β-catenin phosphorylation at residues Ser33, Ser37, and Thr41. GSK-3β inhibition with 1-azakenpaullone or a GSK-3β-targeting siRNA increased NFAT-Luc activity, whereas overexpression of a constitutively active GSK-3β mutant (GSK-3βS9A) inhibited NFAT-Luc activation mediated by testosterone. Testosterone-induced cardiac myocyte hypertrophy was established by increased cardiac myocyte size and [³H]-leucine incorporation (as a measurement of cellular protein synthesis). Calcineurin-NFAT inhibition abolished and GSK-3β inhibition promoted the hypertrophy stimulated by testosterone. GSK-3β activation by GSK-3βS9A blocked the increase of hypertrophic markers induced by testosterone. Moreover, inhibition of intracellular androgen receptor prevented testosterone-induced NFAT-Luc activation. Collectively, these results suggest that cardiac myocyte hypertrophy induced by testosterone involves a cooperative mechanism that links androgen signaling with the recruitment of NFAT through calcineurin activation and GSK-3β inhibition.

Muscle-bone interactions: From experimental models to the clinic? A critical update

Bone is a biomechanical tissue shaped by forces from muscles and gravitation. Simultaneous bone and muscle decay and dysfunction (osteosarcopenia or sarco-osteoporosis) is seen in ageing, numerous clinical situations including after stroke or paralysis, in neuromuscular dystrophies, glucocorticoid excess, or in association with vitamin D, growth hormone/insulin like growth factor or sex steroid deficiency, as well as in spaceflight. Physical exercise may be beneficial in these situations, but further work is still needed to translate acceptable and effective biomechanical interventions like vibration therapy from animal models to humans. Novel antiresorptive and anabolic therapies are emerging for osteoporosis as well as drugs for sarcopenia, cancer cachexia or muscle wasting disorders, including antibodies against myostatin or activin receptor type IIA and IIB (e.g. bimagrumab). Ideally, increasing muscle mass would increase muscle strength and restore bone loss from disuse. However, the classical view that muscle is unidirectionally dominant over bone via mechanical loading is overly simplistic. Indeed, recent studies indicate a role for neuronal regulation of not only muscle but also bone metabolism, bone signaling pathways like receptor activator of nuclear factor kappa-B ligand (RANKL) implicated in muscle biology, myokines affecting bone and possible bone-to-muscle communication. Moreover, pharmacological strategies inducing isolated myocyte hypertrophy may not translate into increased muscle power because tendons, connective tissue, neurons and energy metabolism need to adapt as well. We aim here to critically review key musculoskeletal molecular pathways involved in mechanoregulation and their effect on the bone-muscle unit as a whole, as well as preclinical and emerging clinical evidence regarding the effects of sarcopenia therapies on osteoporosis and vice versa.

Muscle Decline in Aging and Neuromuscular Disorders - Mechanisms and Countermeasures: Terme Euganee, Padova (Italy), April 13-16, 2016

Not available.

Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation

Calcineurin (CN) is a Ca(2+)/calmodulin (CaM) activated serine/threonine phosphatase, and its regulatory region (CNRR) plays a critical role in the coupling of Ca(2+) signals to cellular responses. Ca(2+)/CaM binds to the CNRR, resulting in a conformational change that removes an autoinhibitory domain (CN467-486) from the active site of the phosphatase and activates the enzyme. However, almost the entire regulatory region (CN374-521) is not visible in the electron density maps of reported structures. In this study, we produced separate CN fragments corresponding to the CNRR (CNRR381-521, CN residues 381-521) and determined the binding affinity of CNRR381-521 for Ca(2+)/CaM using isothermal titration calorimetry (ITC). The structural change in CNRR381-521 induced by Ca(2+)/CaM binding was also investigated by Fourier transform infrared spectroscopy (FT-IR). The results indicate that Ca(2+)/CaM binding to CNRR381-521 is an exothermic reaction with a dissociation constant of 2.0×10(-6) M. Binding of calmodulin changes the calcineurin regulatory region to a less dynamic conformation.