miR-182 attenuates atrophy-related gene expression by targeting FoxO3 in skeletal muscle

Epigenetics of Skeletal Muscle Atrophy

Skeletal muscle atrophy, characterized by diminished muscle strength and mass, arises from various causes, including malnutrition, aging, nerve damage, and disease-related secondary atrophy. Aging markedly escalates the prevalence of sarcopenia. Concurrently, the incidence of muscle atrophy significantly rises among patients with chronic ailments such as heart failure, diabetes, and chronic obstructive pulmonary disease (COPD). Epigenetics plays a pivotal role in skeletal muscle atrophy. Aging elevates methylation levels in the promoter regions of specific genes within muscle tissues. This aberrant methylation is similarly observed in conditions like diabetes, neurological disorders, and cardiovascular diseases. This study aims to explore the relationship between epigenetics and skeletal muscle atrophy, thereby enhancing the understanding of its pathogenesis and uncovering novel therapeutic strategies.

Restoration of epigenetic impairment in the skeletal muscle and chronic inflammation resolution as a therapeutic approach in sarcopenia

Sarcopenia is an age-associated loss of skeletal muscle mass, strength, and function, accompanied by severe adverse health outcomes, such as falls and fractures, functional decline, high health costs, and mortality. Hence, its prevention and treatment have become increasingly urgent. However, despite the wide prevalence and extensive research on sarcopenia, no FDA-approved disease-modifying drugs exist. This is probably due to a poor understanding of the mechanisms underlying its pathophysiology. Recent evidence demonstrate that sarcopenia development is characterized by two key elements: (i) epigenetic dysregulation of multiple molecular pathways associated with sarcopenia pathogenesis, such as protein remodeling, insulin resistance, mitochondria impairments, and (ii) the creation of a systemic, chronic, low-grade inflammation (SCLGI). In this review, we focus on the epigenetic regulators that have been implicated in skeletal muscle deterioration, their individual roles, and possible crosstalk. We also discuss epidrugs, which are the pharmaceuticals with the potential to restore the epigenetic mechanisms deregulated in sarcopenia. In addition, we discuss the mechanisms underlying failed SCLGI resolution in sarcopenia and the potential application of pro-resolving molecules, comprising specialized pro-resolving mediators (SPMs) and their stable mimetics and receptor agonists. These compounds, as well as epidrugs, reveal beneficial effects in preclinical studies related to sarcopenia. Based on these encouraging observations, we propose the combination of epidrugs with SCLI-resolving agents as a new therapeutic approach for sarcopenia that can effectively attenuate of its manifestations.

Synovia tissue-specific exosomes participate in the dual variation of the osteoarthritis microenvironment via miR-182

Osteoarthritis (OA) is the most common type of joint disease and the leading cause of chronic disability among older adults. As an important component of the joint, synovium influences the inflammatory and degenerative process of OA. This study found that miRNA 182 (miR-182) in synovium-specific exosomes can modulate inflammation and apoptotic signaling. It also regulated different biological functions to promote the progression of OA. Experiments based on rat OA model and synovium samples from OA patients, we found that synovium-derived miR-182 regulates inflammatory response in the early stage of OA by regulating the expression level of forkhead box O-3 (FOXO3). However, the expression of miR-182 was significantly increased in synovial tissue of advanced OA, which was involved in the apoptotic signal of severe OA. These findings suggest that miR-182 may directly regulate OA progression by modulating FOXO3 production inflammation, and apoptosis.

MicroRNAs-associated with FOXO3 in cellular senescence and other stress responses

FOXO3 is a member of the FOXO transcription factor family and is known for regulating cellular survival in response to stress caused by various external and biological stimuli. FOXO3 decides cell fate by modulating cellular senescence, apoptosis and autophagy by transcriptional regulation of genes involved in DNA damage response and oxidative stress resistance. These cellular processes are tightly regulated physiologically, with FOXO3 acting as the hub that integrates signalling networks controlling them. The activity of FOXO3 is influenced by post-translational modifications, altering its subcellular localisation. In addition, FOXO3 can also be regulated directly or indirectly by microRNAs (miRNAs) or vice versa. This review discusses the involvement of various miRNAs in FOXO3-driven cellular responses such as senescence, apoptosis, autophagy, redox and inflammation defence. Given that these responses are linked and influence cell fate, a thorough understanding of the complex regulation by miRNAs would provide key information for developing therapeutic strategy and avoid unintended consequences caused by off-site targeting of FOXO3.

Nanocarriers for gene delivery to the cardiovascular system

Cardiovascular diseases have posed a great threat to human health. Fortunately, gene therapy holds great promise in the fight against cardiovascular disease (CVD). In gene therapy, it is necessary to select the appropriate carriers to deliver the genes to the target cells of the target organs. There are usually two types of carriers, viral carriers and non-viral carriers. However, problems such as high immunogenicity, inflammatory response, and limited loading capacity have arisen with the use of viral carriers. Therefore, scholars turned their attention to non-viral carriers. Among them, nanocarriers are highly valued because of their easy modification, targeting, and low toxicity. Despite the many successes of gene therapy in the treatment of human diseases, it is worth noting that there are still many problems to be solved in the field of gene therapy for the treatment of cardiovascular diseases. In this review, we give a brief introduction to the common nanocarriers and several common cardiovascular diseases (arteriosclerosis, myocardial infarction, myocardial hypertrophy). On this basis, the application of gene delivery nanocarriers in the treatment of these diseases is introduced in detail.

Effect of miR-182-5p on apoptosis in myocardial infarction

Objective

This study aimed to delineate the diagnostic significance of miR-182-5p by investigating its influence on myocardial apoptosis and function, employing both in vivo and in vitro myocardial infarction models.

Methods

A rat myocardial infarction model was established. Myocardial infarction area was detected using the 2,3,5-chlorotriphenyltetrazolium (TTC) method, myocardial enzyme spectrums were measured using enzyme-linked immunosorbent assay (ELISA), myocardial structure was detected by hematoxylin and eosin (HE) staining, myocardial apoptosis was detected using the TUNEL method, and expression levels of miR-182-5p and apoptosis-related molecules were detected using real-time fluorescence quantitative PCR (qPCR) and Western blot. miR-182-5p mimics and inhibitor were transfected into rat H9C2 cardiomyocytes and mouse HL-1 cardiomyocytes to establish a hypoxia model. Cardiomyocyte viability was detected using the CCK-8 method, expression levels of apoptosis-related indicators were detected using Western blot, and caspase-3/7 activity was detected using a caspase-3/7 activity detection kit. AAV9 adeno-associated virus was used to construct an miR-182-5p overexpression virus, which was injected into mice through the tail vein to create a mouse myocardial infarction model. TTC, ELISA, HE staining, echocardiography, real-time fluorescence qPCR, and Western blot methods were used to detect the effects of AAV9-miR-182-5p on myocardial injury, myocardial function, and myocardial apoptosis levels in myocardial infarction.

Results

The rat model displayed reduced miR-182-5p expression concurrent with an increase in apoptosis. The in vitro H9C2 and HL-1 hypoxia models revealed that miR-182-5p augmented the hypoxia-induced decrease in myocardial cell viability, suppressed Bcl-2 expression, and increased Bax, Bnip3, and caspase-3/7 activity levels. The injection of AAV9-miR-182-5p significantly exacerbated myocardial tissue damage, impaired myocardial function, and enhanced apoptosis.

Conclusion

miR-182-5p escalates myocardial injury during myocardial infarction by fostering apoptosis. Interventions that aim to reduce miR-182-5p levels might be crucial in halting the progression of myocardial infarction.

Muscle-derived exosomes and exercise in cancer prevention

There are a lot of evidences on the beneficial effects mediated by exercise on the prevention of not communicable diseases (NCDs) including different type of cancer. The production of circulating exerkines transported in exosomes represents a novel pathway activated by exercise. However, the biological mechanisms that could explain the role of exosomes in cancer prevention have been not fully elucidated. The aim of this mini-review is to provide an update on the biological mechanisms bringing the release of muscle-derived exosomes during exercise and cancer prevention.

Organ Crosstalk Contributes to Muscle Wasting in Chronic Kidney Disease

Muscle wasting (ie, atrophy) is a serious consequence of chronic kidney disease (CKD) that reduces muscle strength and function. It reduces the quality of life for CKD patients and increases the risks of comorbidities and mortality. Current treatment strategies to prevent or reverse skeletal muscle loss are limited owing to the broad and systemic nature of the initiating signals and the multifaceted catabolic mechanisms that accelerate muscle protein degradation and impair protein synthesis and repair pathways. Recent evidence has shown how organs such as muscle, adipose, and kidney communicate with each other through interorgan exchange of proteins and RNAs during CKD. This crosstalk changes cell functions in the recipient organs and represents an added dimension in the complex processes that are responsible for muscle atrophy in CKD. This complexity creates challenges for the development of effective therapies to ameliorate muscle wasting and weakness in patients with CKD.

Indirect regulation of HIPPO pathway by miRNA mediates high-intensity intermittent exercise to ameliorate aging skeletal muscle function

Exercise-induced microRNA (miRNA) and HIPPO pathways participate in the regulation of skeletal muscle plasticity but their underlying mechanisms remain unclear. We aimed to investigate the effect of high-intensity interval training (HIIT) on miRNA expression and the HIPPO pathway in the skeletal muscle of aging rats to determine its role in the amelioration of muscle aging. Thirty-six 18-month-old female rats were randomly divided into sedentary control (SED, n = 12), moderate-intensity continuous training (MICT, n = 12), and HIIT (n = 12) groups, with continuous exercise for 8 months. Quantitative reverse transcription-polymerase chain reaction, immunoblotting, KEGG enrichment, and dual-luciferase assays were performed on the target skeletal muscle. Compared with the SED group, the MICT and HIIT groups showed a significant trend of improvement in Lee's index and grip strength and a marked increase in skeletal muscle mitochondrial function, apoptosis, antioxidant, and lipolysis-related protein expression. They also exhibited PI3K/AKT pathway activation and a decrease in expression of HIPPO pathway-related proteins; 20 miRNAs were differentially expressed and enriched in the exercise group compared with the SED group, including the HIPPO pathway and metabolic pathways. Further analysis of L6 cells confirmed that miR-182 may target PTEN, which indirectly regulates HIPPO signaling, but not Mob1. the combined application of HIIT and MICT increased the antioxidant and lipolytic capacities of skeletal muscle and improved atrophy of aging skeletal muscle; HIIT was more effective than MICT. This may be related to HIIT-mediated AKT pathway activation and HIPPO pathway inhibition by miRNAs (miR-486 and miR-182).

FoxO3 and oxidative stress: a multifaceted role in cellular adaptation

Oxidative stress is a major cause of morbidity and mortality in human health and disease. In this review, we focus on the Forkhead Box (Fox) subclass O3 (FoxO3), an extensively studied transcription factor that plays a pleiotropic role in a wide range of physiological and pathological processes by regulating multiple gene regulatory networks involved in the modulation of numerous aspects of cellular metabolism, including fuel metabolism, cell death, and stress resistance. This review will also focus on regulatory mechanisms of FoxO3 expression and activity, such as crucial post-translational modifications and non-coding RNAs. Moreover, this work discusses and evidences some pathways to how this transcription factor and reactive oxygen species regulate each other, which may lead to the pathogenesis of various types of diseases. Therefore, in addition to being a promising therapeutic target, the FoxO3-regulated signaling pathways can also be used as reliable diagnostic and prognostic biomarkers and indicators for drug responsiveness.

Forkhead Box O Signaling Pathway in Skeletal Muscle Atrophy

Skeletal muscle atrophy is the consequence of protein degradation exceeding protein synthesis because of disease, aging, and physical inactivity. Patients with skeletal muscle atrophy have decreased muscle mass and fiber cross-sectional area, and experience reduced survival quality and motor function. The forkhead box O (FOXO) signaling pathway plays an important role in the pathogenesis of skeletal muscle atrophy by regulating E3 ubiquitin ligases and some autophagy factors. However, the mechanism of FOXO signaling pathway leading to skeletal muscle atrophy is still unclear. The development of treatment strategies for skeletal muscle atrophy has been a thorny clinical problem. FOXO-targeted therapy to treat skeletal muscle atrophy is a promising approach, and an increasing number of relevant studies have been reported. This article reviews the mechanism and therapeutic targets of the FOXO signaling pathway mediating skeletal muscle atrophy, and provides ideas for the clinical treatment of this condition.

Role of exosomes and exosomal microRNA in muscle–Kidney crosstalk in chronic kidney disease

Chronic kidney disease (CKD) is a progressive damage of kidneys that can no longer serve the blood-filtering function, and is a life-threatening condition. Skeletal muscle wasting is a common complication of CKD. Yet the relationship between kidney and skeletal muscle in CKD remains unclear. Exosomes, a type of small membrane-bound vesicles released from cells to the extracellular environment, have increasingly received attention due to their potential as mediators of crosstalk between kidneys and different organs, including skeletal muscle. This mini-review summarizes the recent findings that point to the role of exosomes in the cross-talk between kidney and skeletal muscle in CKD. Understanding of the contents and the mechanism of exosome release may prone exosomes be the potential therapeutic targets for CKD.

Non-Coding RNAs in the Therapeutic Landscape of Pathological Cardiac Hypertrophy

Cardiovascular diseases are a major health problem, and long-term survival for people diagnosed with heart failure is, still, unrealistic. Pathological cardiac hypertrophy largely contributes to morbidity and mortality, as effective therapeutic approaches are lacking. Non-coding RNAs (ncRNAs) arise as active regulators of the signaling pathways and mechanisms that govern this pathology, and their therapeutic potential has received great attention in the last decades. Preclinical studies in large animal models have been successful in ameliorating cardiac hypertrophy, and an antisense drug for the treatment of heart failure has, already, entered clinical trials. In this review, we provide an overview of the molecular mechanisms underlying cardiac hypertrophy, the involvement of ncRNAs, and the current therapeutic landscape of oligonucleotides targeting these regulators. Strategies to improve the delivery of such therapeutics and overcome the actual challenges are, also, defined and discussed. With the fast advance in the improvement of oligonucleotide drug delivery, the inclusion of ncRNAs-targeting therapies for cardiac hypertrophy seems, increasingly, a closer reality.

Pathophysiological mechanisms leading to muscle loss in chronic kidney disease

Loss of muscle proteins is a deleterious consequence of chronic kidney disease (CKD) that causes a decrease in muscle strength and function, and can lead to a reduction in quality of life and increased risk of morbidity and mortality. The effectiveness of current treatment strategies in preventing or reversing muscle protein losses is limited. The limitations largely stem from the systemic nature of diseases such as CKD, which stimulate skeletal muscle protein degradation pathways while simultaneously activating mechanisms that impair muscle protein synthesis and repair. Stimuli that initiate muscle protein loss include metabolic acidosis, insulin and IGF1 resistance, changes in hormones, cytokines, inflammatory processes and decreased appetite. A growing body of evidence suggests that signalling molecules secreted from muscle can enter the circulation and subsequently interact with recipient organs, including the kidneys, while conversely, pathological events in the kidney can adversely influence protein metabolism in skeletal muscle, demonstrating the existence of crosstalk between kidney and muscle. Together, these signals, whether direct or indirect, induce changes in the levels of regulatory and effector proteins via alterations in mRNAs, microRNAs and chromatin epigenetic responses. Advances in our understanding of the signals and processes that mediate muscle loss in CKD and other muscle wasting conditions will support the future development of therapeutic strategies to reduce muscle loss.

Circular RNA, microRNA and Protein Profiles of the Longissimus Dorsi of Germany ZIKA and Sichuan White Rabbits

Due to the dietetic properties and remarkable nutritive value of rabbit meat, its industry is increasing rapidly. However, the association between circular RNAs, microRNAs, and proteins and muscle fiber type, and meat quality of rabbit is still unknown. Here, using deep sequencing and iTRAQ proteomics technologies we first identified 3159 circRNAs, 356 miRNAs, and 755 proteins in the longissimus dorsi tissues from Sichuan white (SCWrabs) and Germany great line ZIKA rabbits (ZIKArabs). Next, we identified 267 circRNAs, 3 miRNAs, and 29 proteins differentially expressed in the muscle tissues of SCWrabs and ZIKArabs. Interaction network analysis revealed some key regulation relationships between noncoding RNAs and proteins that might be associated with the muscle fiber type and meat quality of rabbit. Further, miRNA isoforms and gene variants identified in SCWrabs and ZIKArabs revealed some pathways and biological processes related to the muscle development. This is the first study of noncoding RNA and protein profiles for the two rabbit breeds. It provides a valuable resource for future studies in rabbits and will improve our understanding of the molecular regulation mechanisms in the muscle development of livestock. More importantly, the output of our study will benefit the researchers and producers in the rabbit breeding program.

Melatonin-based therapeutics for atherosclerotic lesions and beyond: Focusing on macrophage mitophagy

Atherosclerosis refers to a unique form of chronic proinflammatory anomaly of the vasculature, presented as rupture-prone or occlusive lesions in arteries. In advanced stages, atherosclerosis leads to the onset and development of multiple cardiovascular diseases with lethal consequences. Inflammatory cytokines in atherosclerotic lesions contribute to the exacerbation of atherosclerosis. Pharmacotherapies targeting dyslipidemia, hypercholesterolemia, and neutralizing inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-17, and IL-12/23) have displayed proven promises although contradictory results. Moreover, adjuvants such as melatonin, a pluripotent agent with proven anti-inflammatory, anti-oxidative and neuroprotective properties, also display potentials in alleviating cytokine secretion in macrophages through mitophagy activation. Here, we share our perspectives on this concept and present melatonin-based therapeutics as a means to modulate mitophagy in macrophages and, thereby, ameliorate atherosclerosis.

MicroRNAs associated with signaling pathways and exercise adaptation in sarcopenia

Considering the expansion of human life-span over the past few decades; sarcopenia, a physiological consequence of aging process characterized with a diminution in mass and strength of skeletal muscle, has become more frequent. Thus, there is a growing need for expanding our knowledge on the molecular mechanisms of muscle atrophy in sarcopenia which are complex and involve many signaling pathways associated with protein degradation and synthesis. MicroRNAs (miRNAs) as evolutionary conserved small RNAs, could complementarily bind to their target mRNAs and post-transcriptionally inhibit their translation. Aberrant expression of miRNAs contributes to the development of sarcopenia by regulating the expression of critical genes involved in age-related skeletal muscle mass loss. Here we have a review on the signaling pathways along with the miRNAs controlling their components expression and subsequently we provide a brief overview on the effects of exercise on expression pattern of miRNAs in sarcopenia.

Altered expression of microRNAs in the rat diaphragm in a model of ventilator-induced diaphragm dysfunction after controlled mechanical ventilation

BACKGROUND

Ventilator-induced diaphragm dysfunction (VIDD) is a common complication of life support by mechanical ventilation observed in critical patients in clinical practice and may predispose patients to severe complications such as ventilator-associated pneumonia or ventilator discontinuation failure. To date, the alterations in microRNA (miRNA) expression in the rat diaphragm in a VIDD model have not been elucidated. This study was designed to identify these alterations in expression.

RESULTS

Adult male Wistar rats received conventional controlled mechanical ventilation (CMV) or breathed spontaneously for 12 h. Then, their diaphragm tissues were collected for RNA extraction. The miRNA expression alterations in diaphragm tissue were investigated by high-throughput microRNA-sequencing (miRNA-seq). For targeted mRNA functional analysis, gene ontology (GO) analyses and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were subsequently conducted. qRT-PCR validation and luciferase reporter assays were performed. We successfully constructed a model of ventilator-induced diaphragm dysfunction and identified 38 significantly differentially expressed (DE) miRNAs, among which 22 miRNAs were upregulated and 16 were downregulated. GO analyses identified functional genes, and KEGG pathway analyses revealed the signaling pathways that were most highly correlated, which were the MAPK pathway, FoxO pathway and Autophagy-animal. Luciferase reporter assays showed that STAT3 was a direct target of both miR-92a-1-5p and miR-874-3p and that Trim63 was a direct target of miR-3571.

CONCLUSIONS

The current research supplied novel perspectives on miRNAs in the diaphragm, which may not only be implicated in diaphragm dysfunction pathogenesis but could also be considered as therapeutic targets in diaphragm dysfunction.

Ellagic acid protects rats from chronic renal failure via MiR-182/FOXO3a axis

Studies showed that ellagic acid (EA) can significantly improve kidney function, but the renal-protective effects of EA and the potential mechanism require adequate elucidation. This study investigated the mechanisms of EA in chronic renal failure (CRF) injury. A rat model of CRF was established by 5/6 nephrectomy. The body weight, urine volume and urine protein content of the rat model of CRF with EA treatment (0/20/40 mg/kg/day) were recorded. Hematoxylin&eosin (H&E) staining, Masson staining and TUNEL were used for histopathological observation. Serum levels of creatinine value, blood urea nitrogen, superoxide dismutase, glutathione, malondialdehyde, tumor necrosis factor-α, interleukin-6 and intercellular cell adhesion molecule-1 were determined using enzyme-linked immunosorbent assay (ELISA) kits. The expressions of genes involved in CRF damage were detected by quantitative real-time PCR (qRT-PCR) and western blot. The relationships among EA, miR-182 and FOXO3a were verified by TargetScan 7.2, dual-luciferase assay and rescue experiments. In this study, EA treatment significantly increased the body weight, but reduced urination and urine protein content, renal tissue damage, collagen deposition, inflammation and the contents of serum creatinine (Scr), blood urea nitrogen (BUN), and malondialdehyde (MDA), and improved the antioxidant capacity of CRF rats. Moreover, EA treatment inhibited miR-182, TGF-β1, fibronectin and Bax levels, and promoted those of FOXO3a and Bcl-2 in CRF rats. Additionally, miR-182 specifically targeted FOXO3a, and effectively reduced the renal-protective effect of EA. Further research found that overexpressed FOXO3a partially reversed the inhibitory effect of miR-182 on CRF rats. Our results suggest that EA might reduce CRF injury in rats via miR-182/FOXO3a.

Liquid Biopsy for Cancer Cachexia: Focus on Muscle-Derived microRNAs

Cancer cachexia displays a complex nature in which systemic inflammation, impaired energy metabolism, loss of muscle and adipose tissues result in unintentional body weight loss. Cachectic patients have a poor prognosis and the presence of cachexia reduces the tolerability of chemo/radio-therapy treatments and it is frequently the primary cause of death in advanced cancer patients. Early detection of this condition could make treatments more effective. However, early diagnostic biomarkers of cachexia are currently lacking. In recent years, although solid biopsy still remains the "gold standard" for diagnosis of cancer, liquid biopsy is gaining increasing interest as a source of easily accessible potential biomarkers. Moreover, the growing interest in circulating microRNAs (miRNAs), has made these molecules attractive for the diagnosis of several diseases, including cancer. Some muscle-derived circulating miRNA might play a pivotal role in the onset/progression of cancer cachexia. This topic is of great interest since circulating miRNAs might be easily detectable by means of liquid biopsies and might allow an early diagnosis of this syndrome. We here summarize the current knowledge on circulating muscular miRNAs involved in muscle atrophy, since they might represent easily accessible and promising biomarkers of cachexia.

miRNA Landscape in Pathogenesis and Treatment of Vogt-Koyanagi-Harada Disease

miRNAs, one of the members of the noncoding RNA family, are regulators of gene expression in inflammatory and autoimmune diseases. Changes in miRNA pool expression have been associated with differentiation of CD4⁺ T cells toward an inflammatory phenotype and with loss of self-tolerance in autoimmune diseases. Vogt–Koyanagi–Harada (VKH) disease is a chronic multisystemic pathology, affecting the uvea, inner ear, central nervous system, and skin. Several lines of evidence support an autoimmune etiology for VKH, with loss of tolerance against retinal pigmented epithelium-related self-antigens. This deleterious reaction is characterized by exacerbated inflammation, due to an aberrant T_H1 and T_H17 polarization and secretion of their proinflammatory hallmark cytokines interleukin 6 (IL-6), IL-17, interferon γ, and tumor necrosis factor α, and an impaired CD4⁺ CD25^high FoxP3⁺ regulatory T cell function. To restrain inflammation, VKH is pharmacologically treated with corticosteroids and immunosuppressive drugs as first and second line of therapy, respectively. Changes in the expression of miRNAs related to immunoregulatory pathways have been associated with VKH development, whereas some genetic variants of miRNAs have been found to be risk modifiers of VKH. Furthermore, the drugs commonly used in VKH treatment have great influence on miRNA expression, including those miRNAs associated to VKH disease. This relationship between response to therapy and miRNA regulation suggests that these small noncoding molecules might be therapeutic targets for the development of more effective and specific pharmacological therapy for VKH. In this review, we discuss the latest evidence regarding regulation and alteration of miRNA associated with VKH disease and its treatment.

The mechanism by which noncoding RNAs regulate muscle wasting in cancer cachexia

Cancer cachexia (CC) is a complex metabolic syndrome that accelerates muscle wasting and affects up to 80% of patients with cancer; however, timely diagnostic methods and effective cures are lacking. Although a considerable number of studies have focused on the mechanism of CC-induced muscle atrophy, few novel therapies have been applied in the last decade. In recent years, noncoding RNAs (ncRNAs) have attracted great attention as many differentially expressed ncRNAs in cancer cachectic muscles have been reported to participate in the inhibition of myogenesis and activation of proteolysis. In addition, extracellular vesicles (EVs), which function as ncRNA carriers in intercellular communication, are closely involved in changing ncRNA expression profiles in muscle and promoting the development of muscle wasting; thus, EV-related ncRNAs may represent potential therapeutic targets. This review comprehensively describes the process of ncRNA transmission through EVs and summarizes the pathways and targets of ncRNAs that lead to CC-induced muscle atrophy.

Effects of purposeful soccer heading on circulating small extracellular vesicle concentration and cargo

BACKGROUND

Considering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure.

METHODS

Healthy adult (aged 18-35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells.

RESULTS

Plasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3β (GSK3β), and mitogen-activated protein kinase 8 (MAPK8).

CONCLUSION

Collectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease.

Exosomal microRNAs in cancer-related sarcopenia: Tumor-derived exosomal microRNAs in muscle atrophy

Cancer-associated sarcopenia is a complex metabolic syndrome marked by muscle mass wasting. Muscle wasting is a serious complication that is a primary contributor to cancer-related mortality. The underlying molecular mechanisms of cancer-associated sarcopenia have not been completely described to date. In general, evidence shows that the main pathophysiological alterations in sarcopenia are associated with the degradation of cellular components, an exceptional inflammatory secretome and mitochondrial dysfunction. Importantly, we highlight the prospect that several miRNAs carried by tumor-derived exosomes that have shown the ability to promote inflammatory secretion, activate catabolism, and even participate in the regulation of cellular degradation pathways can be delivered to and exert effects on muscle cells. In this review, we aim to describe the current knowledge about the functions of exosomal miRNAs in the induction of cancer-associated muscle wasting and propose potential treatment strategies.

Extracellular Vesicles and Exosomes: Insights From Exercise Science

The benefits of exercise on health and longevity are well-established, and evidence suggests that these effects are partially driven by a spectrum of bioactive molecules released into circulation during exercise (e.g., exercise factors or 'exerkines'). Recently, extracellular vesicles (EVs), including microvesicles (MVs) and exosomes or exosome-like vesicles (ELVs), were shown to be secreted concomitantly with exerkines. These EVs have therefore been proposed to act as cargo carriers or 'mediators' of intercellular communication. Given these findings, there has been a rapidly growing interest in the role of EVs in the multi-systemic, adaptive response to exercise. This review aims to summarize our current understanding of the effects of exercise on MVs and ELVs, examine their role in the exercise response and long-term adaptations, and highlight the main methodological hurdles related to blood collection, purification, and characterization of ELVs.

circFOXO3: Going around the mechanistic networks in cancer by interfering with miRNAs regulatory networks

Circular RNAs (circRNA) have gained recent interest due to their functional versatility due to their interactions with other RNA species and proteins, all of which underline complex regulatory networks involved in pathogenic mechanisms. As a result, recent insights in circRNA biology are investigating their biomarker and therapeutic potential. One such circRNA is CircFOXO3, which consists of the circularized second exon of the FOXO3 mRNA, a member of the forkhead box transcription factor family involved in the regulation of developmental programs. Recent research focused on the role of circFOXO3 in the context of cancer has highlighted several implications in key tumorigenesis mechanisms, thus consolidating its relevance among other identified circRNAs. In this paper, we will focus on the currently identified case-specific implications of circFOXO3 in cancer, with a focus on the circFOXO3-miRNA-mRNA regulatory networks, its interactions with different proteins, and their cumulated biological effects upon tumor development. Therefore, we aim to provide an integrated perspective of the mechanistic implications of circFOXO3 in different cancers while also highlighting its biomarker or therapeutic potential based on the current evidence.

Muscle Stem Cell-Derived Extracellular Vesicles Reverse Hydrogen Peroxide-Induced Mitochondrial Dysfunction in Mouse Myotubes

Muscle stem cells (MuSCs) hold great potential as a regenerative therapeutic but have met numerous challenges in treating systemic muscle diseases. Muscle stem cell-derived extracellular vesicles (MuSC-EVs) may overcome these limitations. We assessed the number and size distribution of extracellular vesicles (EVs) released by MuSCs ex vivo, determined the extent to which MuSC-EVs deliver molecular cargo to myotubes in vitro, and quantified MuSC-EV-mediated restoration of mitochondrial function following oxidative injury. MuSCs released an abundance of EVs in culture. MuSC-EVs delivered protein cargo into myotubes within 2 h of incubation. Fluorescent labeling of intracellular mitochondria showed co-localization of delivered protein and mitochondria. Oxidatively injured myotubes demonstrated a significant decline in maximal oxygen consumption rate and spare respiratory capacity relative to untreated myotubes. Remarkably, subsequent treatment with MuSC-EVs significantly improved maximal oxygen consumption rate and spare respiratory capacity relative to the myotubes that were damaged but received no subsequent treatment. Surprisingly, MuSC-EVs did not affect mitochondrial function in undamaged myotubes, suggesting the cargo delivered is able to repair but does not expand the existing mitochondrial network. These data demonstrate that MuSC-EVs rapidly deliver proteins into myotubes, a portion of which co-localizes with mitochondria, and reverses mitochondria dysfunction in oxidatively-damaged myotubes.

Role of microRNA in muscle regeneration and diseases related to muscle dysfunction in atrophy, cachexia, osteoporosis, and osteoarthritis

MicroRNAs (miRNAs) are a class of small non-coding RNAs that have emerged as potential predictive, prognostic, and therapeutic biomarkers, relevant to many pathophysiological conditions including limb immobilization, osteoarthritis, sarcopenia, and cachexia. Impaired musculoskeletal homeostasis leads to distinct muscle atrophies. Understanding miRNA involvement in the molecular mechanisms underpinning conditions such as muscle wasting may be critical to developing new strategies to improve patient management. MicroRNAs are powerful post-transcriptional regulators of gene expression in muscle and, importantly, are also detectable in the circulation. MicroRNAs are established modulators of muscle satellite stem cell activation, proliferation, and differentiation, however, there have been limited human studies that investigate miRNAs in muscle wasting. This narrative review summarizes the current knowledge as to the role of miRNAs in the skeletal muscle differentiation and atrophy, synthesizing the findings of published data. Cite this article: Bone Joint Res 2020;9(11):798-807.

Regulation of Skeletal Muscle Atrophy in Cachexia by MicroRNAs and Long Non-coding RNAs

Skeletal muscle atrophy is a common complication of cachexia, characterized by progressive bodyweight loss and decreased muscle strength, and it significantly increases the risks of morbidity and mortality in the population with atrophy. Numerous complications associated with decreased muscle function can activate catabolism, reduce anabolism, and impair muscle regeneration, leading to muscle wasting. microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), types of non-coding RNAs, are important for regulation of skeletal muscle development. Few studies have specifically identified the roles of miRNAs and lncRNAs in cellular or animal models of muscular atrophy during cachexia, and the pathogenesis of skeletal muscle wasting in cachexia is not entirely understood. To develop potential approaches to improve skeletal muscle mass, strength, and function, a more comprehensive understanding of the known key pathophysiological processes leading to muscular atrophy is needed. In this review, we summarize the known miRNAs, lncRNAs, and corresponding signaling pathways involved in regulating skeletal muscle atrophy in cachexia and other diseases. A comprehensive understanding of the functions and mechanisms of miRNAs and lncRNAs during skeletal muscle wasting in cachexia and other diseases will, therefore, promote therapeutic treatments for muscle atrophy.

MIR-190B Alleviates Cell Autophagy and Burn-Induced Skeletal Muscle Wasting via Modulating PHLPP1/Akt/FoxO3A Signaling Pathway

INTRODUCTION

Cell autophagy is an important material recycling process and is involved in regulating many vital activities under both physiological and pathological conditions. However, the mechanism of autophagy regulating burn-induced skeletal muscle wasting still needs to be elucidated.

METHODS

The rat burn model with 30% total body surface area and L6 cell line were used in this study. An immunofluorescence assay was used to detect autophagic levels. MicroRNA array and real-time PCR were employed to measure miR-190b levels, and its influence on PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1) protein translation was estimated using luciferase reporter assay. The expression levels of autophagy-related proteins were analyzed by Western blot. Skeletal muscle wasting was evaluated by the ratio of tibias anterior muscle weight to body weight.

RESULTS

Our study demonstrates that burn injury promotes expression of the autophagy-related proteins light chain 3 (LC3) and Beclin-1, suppresses expression of Akt and Forkhead box O (FoxO) 3a protein phosphorylation, and increases PHLPP1 protein level which is required for Akt dephosphorylation. miR-190b, the regulator of PHLPP1 protein translation, also significantly decreases after burn injury. Ectopic expression of miR-190b in L6 myoblast cell downregulates PHLPP1 protein expression, elevates Akt and FoxO3a phosphorylation, and subsequently reduces cell autophagy. Finally, suppressing autophagy with 3-methyladenine represses the protein expression of LC3 and Beclin-1 and mitigates burn-induced skeletal muscle wasting.

CONCLUSION

Burn injury induced skeletal muscle cell autophagy and subsequently resulted in skeletal muscle wasting via regulating miR-190b/PHLPP1/Akt/FoxO3a signaling pathway.

Signaling Pathways That Control Muscle Mass

The loss of skeletal muscle mass under a wide range of acute and chronic maladies is associated with poor prognosis, reduced quality of life, and increased mortality. Decades of research indicate the importance of skeletal muscle for whole body metabolism, glucose homeostasis, as well as overall health and wellbeing. This tissue’s remarkable ability to rapidly and effectively adapt to changing environmental cues is a double-edged sword. Physiological adaptations that are beneficial throughout life become maladaptive during atrophic conditions. The atrophic program can be activated by mechanical, oxidative, and energetic distress, and is influenced by the availability of nutrients, growth factors, and cytokines. Largely governed by a transcription-dependent mechanism, this program impinges on multiple protein networks including various organelles as well as biosynthetic and quality control systems. Although modulating muscle function to prevent and treat disease is an enticing concept that has intrigued research teams for decades, a lack of thorough understanding of the molecular mechanisms and signaling pathways that control muscle mass, in addition to poor transferability of findings from rodents to humans, has obstructed efforts to develop effective treatments. Here, we review the progress made in unraveling the molecular mechanisms responsible for the regulation of muscle mass, as this continues to be an intensive area of research.

Imoxin prevents dexamethasone-induced promotion of muscle-specific E3 ubiquitin ligases and stimulates anabolic signaling in C2C12 myotubes

Muscle atrophy is the loss of skeletal muscle mass during several pathological conditions such as long-term fasting, aging, cancer, diabetes, sepsis and immune disorders. Glucocorticoids are known to trigger skeletal muscle atrophy. Dexamethasone (DEX), a synthetic glucocorticoid, induces skeletal muscle atrophy by suppression of protein synthesis and promotion of protein degradation. The double-stranded RNA (dsRNA)-activated protein kinase R (PKR) plays a significant role in mediating lipopolysaccharide-induced inflammation. However, pathological roles of PKR in muscle atrophy are not fully understood. The current study aimed to investigate the effect of imoxin, a PKR inhibitor, on DEX-induced muscle atrophy in C2C12 myotubes. Myotubes were incubated with imoxin at different concentrations with or without 5 μM DEX for 24 h. In the current study, imoxin treatment significantly reduced protein levels of MuRF1 and MAFbx induced by DEX by 88 ± 2% and MAFbx by 99 ± 0%, respectively. Moreover, 5 μM imoxin treatment reduced protein ubiquitination by 42 ± 4% and protein content of nuclear FoxO3α (77 ± 4%) in presence of DEX. Furthermore, 5 μM imoxin treatment stimulated Akt phosphorylation (195 ± 5%), mTOR phosphorylation (171 ± 21 %) and p70S6K1 phosphorylation (314 ± 31 %) under DEX-treated condition even though DEX treatment did not suppressed Akt/mTOR/p70S6K1 axis. These findings suggest that imoxin may protect against DEX-induced skeletal muscle atrophy by alleviating muscle specific E3 ubiquitin ligases and imoxin alone may promote protein synthesis via Akt/mTOR/S6K1 axis in muscle cells.

Blood flow-restricted resistance exercise alters the surface profile, miRNA cargo and functional impact of circulating extracellular vesicles

Ischemic exercise conducted as low-load blood flow restricted resistance exercise (BFRE) can lead to muscle remodelling and promote muscle growth, possibly through activation of muscle precursor cells. Cell activation can be triggered by blood borne extracellular vesicles (EVs) as these nano-sized particles are involved in long distance signalling. In this study, EVs isolated from plasma of healthy human subjects performing a single bout of BFRE were investigated for their change in EV surface profiles and miRNA cargos as well as their impact on skeletal muscle precursor cell proliferation. We found that after BFRE, five EV surface markers and 12 miRNAs were significantly altered. Furthermore, target prediction and functional enrichment analysis of the miRNAs revealed several target genes that are associated to biological pathways involved in skeletal muscle protein turnover. Interestingly, EVs from BFRE plasma increased the proliferation of muscle precursor cells. In addition, alterations in surface markers and miRNAs indicated that the combination of exercise and ischemic conditioning during BFRE can stimulate blood cells to release EVs. These results support that BFRE promotes EV release to engage in muscle remodelling and/or growth processes.

MicroRNAs as major regulators of the autophagy pathway

Autophagy is a cellular stress response mechanism activation of which leads to degradation of cellular components, including proteins as well as damaged organelles in lysosomes. Defects in autophagy mechanisms were associated with several pathologies (e.g. cancer, neurodegenerative diseases, and rare genetic diseases). Therefore, autophagy regulation is under strict control. Transcriptional and post-translational mechanisms that control autophagy in cells and organisms studied in detail. Recent studies introduced non-coding small RNAs, and especially microRNAs (miRNAs) in the post-translational orchestration of the autophagic activity. In this review article, we analyzed in detail the current status of autophagy-miRNA connections. Comprehensive documentation of miRNAs that were directly involved in autophagy regulation resulted in the emergence of common themes and concepts governing these complex and intricate interactions. Hence, a better and systematic understanding of these interactions reveals a central role for miRNAs in the regulation of autophagy.

miR-183-96-182 Cluster Is Involved in Invariant NKT Cell Development, Maturation, and Effector Function

The development, differentiation and function of invariant NKT (iNKT) cells require a well-defined set of transcription factors, but how these factors are integrated to each other and the detailed signaling networks remain poorly understood. Using a Dicer-deletion mouse model, our previous studies have demonstrated the critical involvement of microRNAs (miRNAs) in iNKT cell development and function, but the role played by individual miRNAs in iNKT cell development and function is still not clear. In this study, we show the dynamic changes of miRNA 183 cluster (miR-183C) expression during iNKT cell development. Mice with miR-183C deletion showed a defective iNKT cell development, sublineage differentiation, and cytokine secretion function. miRNA target identification assays indicate the involvement of multiple target molecules. Our study not only confirmed the role of miR-183C in iNKT cell development and function but also demonstrated that miR-183C achieved the regulation of iNKT cells through integrated targeting of multiple signaling molecules and pathways.

Skeletal muscle wasting in chronic kidney disease: the emerging role of microRNAs

Skeletal muscle wasting is a common complication of chronic kidney disease (CKD), characterized by the loss of muscle mass, strength and function, which significantly increases the risk of morbidity and mortality in this population. Numerous complications associated with declining renal function and lifestyle activate catabolic pathways and impair muscle regeneration, resulting in substantial protein wasting. Evidence suggests that increasing skeletal muscle mass improves outcomes in CKD, making this a clinically important research focus. Despite extensive research, the pathogenesis of skeletal muscle wasting is not completely understood. It is widely recognized that microRNAs (miRNAs), a family of short non-coding RNAs, are pivotal in the regulation of skeletal muscle homoeostasis, with significant roles in regulating muscle growth, regeneration and metabolism. The abnormal expression of miRNAs in skeletal muscle during disease has been well described in cellular and animal models of muscle atrophy, and in recent years, the involvement of miRNAs in the regulation of muscle atrophy in CKD has been demonstrated. As this exciting field evolves, there is emerging evidence for the involvement of miRNAs in a beneficial crosstalk system between skeletal muscle and other organs that may potentially limit the progression of CKD. In this article, we describe the pathophysiological mechanisms of muscle wasting and explore the contribution of miRNAs to the development of muscle wasting in CKD. We also discuss advances in our understanding of miRNAs in muscle–organ crosstalk and summarize miRNA-based therapeutics currently in clinical trials.

MicroRNA-182-3p negatively regulates cytokines expression by targeting TLR5M in orange-spotted grouper, Epinephelus coioides

Toll-like receptors (TLRs) as essential pattern recognition receptors in innate immunity, can recognize pathogens and trigger immune response to eliminate invading pathogens. MicroRNAs regulates multiple biological processes by suppressing mRNA translation or resulting in mRNA degradation. MiR-182 has previously been implicated in DNA repair, disease and cancer aspects. The potential role of miR-182-3p in TLR signaling pathway against pathogens is unclear. In this study, we found that the expression of miR-182-3p was up-regulated after Vibrio parahaemolyticus flagellin stimulation in grouper spleen (GS) cells, and negatively correlated with the expression of orange-spotted grouper (Epinephelus coioides) TLR5M (EcTLR5M). Then we found that miR-182-3p could directly target EcTLR5M by using bioinformatic analysis and dual-luciferase reporter assay. Dual-luciferase reporter assay also showed that miR-182-3p down-regulated the wild-type EcTLR5M 3'UTR in luciferase activity rather than the mutant group in HEK 293T cells. We further verified the effect of miR-182-3p on the activation of Nuclear factor-κB (NF-κB) signaling pathway, and found that miR-182-3p inhibitors significantly augmented flagellin-induced NF-κB phosphorylation. Additionally, we also demonstrated that the increased expression of miR-182-3p significantly suppressed the flagellin-induced EcTLR5M, pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) mRNA expression. And the endogenous miR-182-3p knockdown experiments reversely verified the regulatory effect of miR-182-3p. These results suggested that miR-182-3p post-transcriptionally controls EcTLR5M expression and thereby suppresses the expression of pro-inflammatory cytokines. This study is the first to demonstrate that miR-182-3p suppresses pro-inflammatory cytokines expression by regulating the TLR signaling pathway.

Exosomes: Revisiting their role as "garbage bags"

In recent years, the term "extracellular vesicle" (EV) has been used to define different types of vesicles released by various cells. It includes plasma membrane-derived vesicles (ectosomes/microvesicles) and endosome-derived vesicles (exosomes). Although it remains difficult to evaluate the compartment of origin of the two kinds of vesicles once released, it is critical to discriminate these vesicles because their mode of biogenesis is probably directly related to their physiologic function and/or to the physio-pathologic state of the producing cell. The purpose of this review is to specifically consider exosome secretion and its consequences in terms of a material loss for producing cells, rather than on the effects of exosomes once they are taken up by recipient cells. I especially describe one putative basic function of exosomes, that is, to convey material out of cells for off-site degradation by recipient cells. As illustrated by some examples, these components could be evacuated from cells for various reasons, for example, to promote "differentiation" or enhance homeostatic responses. This basic function might explain why so many diseases have made use of the exosomal pathway during pathogenesis.

miR-125b-5p targeting TRAF6 relieves skeletal muscle atrophy induced by fasting or denervation

Background

Skeletal muscle atrophy, characterized by accelerated protein degradation, occurs in such conditions as unloading, immobilization, fasting, and denervation. Effective treatments for skeletal muscle atrophy are not yet available. Considering that microRNAs (miRs) may play an important role in the regulation of muscle atrophy, in the present study, we aimed to examine the effect of miR-125b-5p-based therapeutic strategies on skeletal muscle atrophy, and to explore the underlying mechanisms.

Methods

Fasting-induced atrophic mouse C2C12 myotubes and denervated rat tibialis anterior (TA) muscles were used as in vitro and in vivo models of skeletal muscle atrophy, respectively. The morphological parameters of skeletal muscle were measured by immunostaining-based quantification. The interaction between miR-125b-5p and TRAF6 3'-UTR was detected by luciferase reporter analysis. The mRNA and protein expressions were determined by real-time qPCR and Western blot analysis respectively. The miR mimics/agomir and miR inhibitor/antagomir were transfected into C2C12 myotubes and TA muscles respectively to alter the expression of miR-125b-5p.

Results

The expression of miR-125b-5p was down-regulated in both atrophic C2C12 myotubes and denervated TA muscles. The interaction between miR-125b-5p and TRAF6 3'-UTR was identified. Overexpression of miR-125b-5p protected skeletal muscle samples from atrophy in vitro and in vivo by targeting TRAF6 through inactivation of several ubiquitin-proteasome system (UPS)- and autophagy-lysosome system (ALS)-related proteins.

Conclusions

Overexpression of miR-125b-5p may provide a promising therapeutic approach to treat muscle atrophy.

Skeletal muscle atrogenes: From rodent models to human pathologies

Skeletal muscle atrophy is a common side effect of most human diseases. Muscle loss is not only detrimental for the quality of life but it also dramatically impairs physiological processes of the organism and decreases the efficiency of medical treatments. While hypothesized for years, the existence of an atrophying programme common to all pathologies is still incompletely solved despite the discovery of several actors and key regulators of muscle atrophy. More than a decade ago, the discovery of a set of genes, whose expression at the mRNA levels were similarly altered in different catabolic situations, opened the way of a new concept: the presence of atrogenes, i.e. atrophy-related genes. Importantly, the atrogenes are referred as such on the basis of their mRNA content in atrophying muscles, the regulation at the protein level being sometimes more complicate to elucidate. It should be noticed that the atrogenes are markers of atrophy and that their implication as active inducers of atrophy is still an open question for most of them. While the atrogene family has grown over the years, it has mostly been incremented based on data coming from rodent models. Whether the rodent atrogenes are valid for humans still remain to be established. An "atrogene" was originally defined as a gene systematically up- or down-regulated in several catabolic situations. Even if recent works often restrict this notion to the up-regulation of a limited number of proteolytic enzymes, it is important to keep in mind the big picture view. In this review, we provide an update of the validated and potential rodent atrogenes and the metabolic pathways they belong, and based on recent work, their relevance in human physio-pathological situations. We also propose a more precise definition of the atrogenes that integrates rapid recovery when catabolic stimuli are stopped or replaced by anabolic ones.

Effective Delivery of Hypertrophic miRNA Inhibitor by Cholesterol-Containing Nanocarriers for Preventing Pressure Overload Induced Cardiac Hypertrophy

Persistent cardiac hypertrophy causes heart failure and sudden death. Gene therapy is a promising intervention for this disease, but is limited by the lack of effective delivery systems. Herein, it is reported that CHO-PGEA (cholesterol (CHO)-terminated ethanolamine-aminated poly(glycidyl methacrylate)) can efficiently condense small RNAs into nanosystems for preventing cardiac hypertrophy. CHO-PGEA contains two features: 1) lipophilic cholesterol groups enhance transfection efficiency in cardiomyocytes, 2) abundant hydrophilic hydroxyl groups benefit biocompatibility. miR-182, which is known to downregulate forkhead box O3, is selected as an intervention target and can be blocked by synthetic small RNA inhibitor of miR-182 (miR-182-in). CHO-PGEA can efficiently deliver miR-182-in into hearts. In the mice with aortic coarctation, CHO-PEGA/miR-182-in significantly suppresses cardiac hypertrophy without organ injury. This work demonstrates that CHO-PGEA/miRNA nanosystems are very promising for RNA-based therapeutics to treat heart diseases.

Characterization of MicroRNAs Regulating FOXO Expression

MicroRNAs are critical post-transcriptional regulators of a majority of genes, of which the FOXO family of transcription factors is no exception. Here, we describe generalizable methods, including 3' UTR reporter assays and western blotting after microRNA manipulation, to test if a candidate miRNA (miR-182) directly targets a candidate (FOXO3) gene product. We also provide guidance on candidate miRNA selection and unbiased miRNA-target identification methods.

da Silva F, Larina‐Neto R, Chadi G, Zanoteli E. Omega-3 multiple effects increasing glucocorticoid-induced muscle atrophy: autophagic, AMPK and UPS mechanisms

Muscle atrophy occurs in many conditions, including use of glucocorticoids. N-3 (omega-3) is widely consumed due its healthy properties; however, concomitant use with glucocorticoids can increase its side effects. We evaluated the influences of N-3 on glucocorticoid atrophy considering IGF-1, Myostatin, MEK/ERK, AMPK pathways besides the ubiquitin-proteasome system (UPS) and autophagic/lysosomal systems. Sixty animals constituted six groups: CT, N-3 (EPA 100 mg/kg/day for 40 days), DEXA 1.25 (DEXA 1.25 mg/kg/day for 10 days), DEXA 1.25 + N3 (EPA for 40 days + DEXA 1.25 mg/kg/day for the last 10 days), DEXA 2.5 (DEXA 2.5 mg/kg/day for 10 days), and DEXA 2.5 + N3 (EPA for 40 days + DEXA 2.5 mg/kg/day for 10 days). Results: N-3 associated with DEXA increases atrophy (fibers 1 and 2A), FOXO3a, P-SMAD2/3, Atrogin-1/MAFbx (mRNA) expression, and autophagic protein markers (LC3II, LC3II/LC3I, LAMP-1 and acid phosphatase). Additionally, N-3 supplementation alone decreased P-FOXO3a, PGC1-alpha, and type 1 muscle fiber area. Conclusion: N-3 supplementation increases muscle atrophy caused by DEXA in an autophagic, AMPK and UPS process.

Mechanisms and Modulation of Oxidative/Nitrative Stress in Type 4 Cardio-Renal Syndrome and Renal Sarcopenia

Chronic kidney disease (CKD) is a public health problem and a recognized risk factor for cardiovascular diseases (CVD). CKD could amplify the progression of chronic heart failure leading to the development of type 4 cardio-renal syndrome (T4CRS). The severity and persistence of heart failure are strongly associated with mortality risk in T4CRS. CKD is also a catabolic state leading to renal sarcopenia which is characterized by the loss of skeletal muscle strength and physical function. Renal sarcopenia also promotes the development of CVD and increases the mortality in CKD patients. In turn, heart failure developed in T4CRS could result in chronic muscle hypoperfusion and metabolic disturbances leading to or aggravating the renal sarcopenia. The interplay of multiple factors (e.g., comorbidities, over-activated renin-angiotensin-aldosterone system [RAAS], sympathetic nervous system [SNS], oxidative/nitrative stress, inflammation, etc.) may result in the progression of T4CRS and renal sarcopenia. Among these factors, oxidative/nitrative stress plays a crucial role in the complex pathomechanism and interrelationship between T4CRS and renal sarcopenia. In the heart and skeletal muscle, mitochondria, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, uncoupled nitric oxide synthase (NOS) and xanthine oxidase are major ROS sources producing superoxide anion (O2^·−) and/or hydrogen peroxide (H₂O₂). O2^·− reacts with nitric oxide (NO) forming peroxynitrite (ONOO⁻) which is a highly reactive nitrogen species (RNS). High levels of ROS/RNS cause lipid peroxidation, DNA damage, interacts with both DNA repair enzymes and transcription factors, leads to the oxidation/nitration of key proteins involved in contractility, calcium handling, metabolism, antioxidant defense mechanisms, etc. It also activates the inflammatory response, stress signals inducing cardiac hypertrophy, fibrosis, or cell death via different mechanisms (e.g., apoptosis, necrosis) and dysregulates autophagy. Therefore, the thorough understanding of the mechanisms which lead to perturbations in oxidative/nitrative metabolism and its relationship with pro-inflammatory, hypertrophic, fibrotic, cell death and other pathways would help to develop strategies to counteract systemic and tissue oxidative/nitrative stress in T4CRS and renal sarcopenia. In this review, we also focus on the effects of some well-known and novel pharmaceuticals, nutraceuticals, and physical exercise on cardiac and skeletal muscle oxidative/nitrative stress in T4CRS and renal sarcopenia.

Intestinal bile acid sequestration improves glucose control by stimulating hepatic miR-182-5p in type 2 diabetes

Colesevelam is a bile acid sequestrant approved to treat both hyperlipidemia and type 2 diabetes, but the mechanism for its glucose-lowering effects is not fully understood. The aim of this study was to investigate the role of hepatic microRNAs (miRNAs) as regulators of metabolic disease and to investigate the link between the cholesterol and glucose-lowering effects of colesevelam. To quantify the impact of colesevelam treatment in rodent models of diabetes, metabolic studies were performed in Zucker diabetic fatty (ZDF) rats and db/db mice. Colesevelam treatments significantly decreased plasma glucose levels and increased glycolysis in the absence of changes to insulin levels in ZDF rats and db/db mice. High-throughput sequencing and real-time PCR were used to quantify hepatic miRNA and mRNA changes, and the cholesterol-sensitive miR-96/182/183 cluster was found to be significantly increased in livers from ZDF rats treated with colesevelam compared with vehicle controls. Inhibition of miR-182 in vivo attenuated colesevelam-mediated improvements to glycemic control in db/db mice. Hepatic expression of mediator complex subunit 1 (MED1), a nuclear receptor coactivator, was significantly decreased with colesevelam treatments in db/db mice, and MED1 was experimentally validated to be a direct target of miR-96/182/183 in humans and mice. In summary, these results support that colesevelam likely improves glycemic control through hepatic miR-182-5p, a mechanism that directly links cholesterol and glucose metabolism. NEW & NOTEWORTHY Colesevelam lowers systemic glucose levels in Zucker diabetic fatty rats and db/db mice and increases hepatic levels of the sterol response element binding protein 2-responsive microRNA cluster miR-96/182/183. Inhibition of miR-182 in vivo reverses the glucose-lowering effects of colesevelam in db/db mice. Mediator complex subunit 1 (MED1) is a novel, direct target of the miR-96/182/183 cluster in mice and humans.

Recent advances in understanding the role of FOXO3

The forkhead box O3 (FOXO3, or FKHRL1) protein is a member of the FOXO subclass of transcription factors. FOXO proteins were originally identified as regulators of insulin-related genes; however, they are now established regulators of genes involved in vital biological processes, including substrate metabolism, protein turnover, cell survival, and cell death. FOXO3 is one of the rare genes that have been consistently linked to longevity in in vivo models. This review provides an update of the most recent research pertaining to the role of FOXO3 in (i) the regulation of protein turnover in skeletal muscle, the largest protein pool of the body, and (ii) the genetic basis of longevity. Finally, it examines (iii) the role of microRNAs in the regulation of FOXO3 and its impact on the regulation of the cell cycle.

Exploratory Profiling of Urine MicroRNAs in the dy2J/dy2J Mouse Model of LAMA2-CMD: Relation to Disease Progression

Circulating microRNAs (miRNAs) are being considered as non-invasive biomarkers for disease progression and clinical trials. Congenital muscular dystrophy with deficiency of laminin α2 chain (LAMA2-CMD) is a very severe form of muscular dystrophy, for which no treatment is available. In order to identify LAMA2-CMD biomarkers we have profiled miRNAs in urine from the dy^2J /dy^2J mouse model of LAMA2-CMD at three distinct time points (representing asymptomatic, initial and established disease). We demonstrate that unique groups of miRNAs are differentially expressed at each time point. We suggest that urine miRNAs can be sensitive biomarkers for different stages of LAMA2-CMD.

Memory Decline and Its Reversal in Aging and Neurodegeneration Involve miR-183/96/182 Biogenesis

Aging is characterized by progressive memory decline that can lead to dementia when associated with neurodegeneration. Here, we show in mice that aging-related memory decline involves defective biogenesis of microRNAs (miRNAs), in particular miR-183/96/182 cluster, resulting from increased protein phosphatase 1 (PP1) and altered receptor SMAD (R-SMAD) signaling. Correction of the defect by miR-183/96/182 overexpression in hippocampus or by environmental enrichment that normalizes PP1 activity restores memory in aged animals. Regulation of miR-183/96/182 biogenesis is shown to involve the neurodegeneration-related RNA-binding proteins TDP-43 and FUS. Similar alterations in miR-183/96/182, PP1, and R-SMADs are observed in the brains of patients with amyotrophic lateral sclerosis (ALS) or frontotemporal lobar degeneration (FTLD), two neurodegenerative diseases with pathological aggregation of TDP-43. Overall, these results identify new mechanistic links between miR-183/96/182, PP1, TDP-43, and FUS in age-related memory deficits and their reversal.